Atomic Layer Deposition for Coating of High Aspect Ratio TiO2 Nanotube Layers

PubMed Central

2016-01-01

We present an optimized approach for the deposition of Al2O3 (as a model secondary material) coating into high aspect ratio (≈180) anodic TiO2 nanotube layers using the atomic layer deposition (ALD) process. In order to study the influence of the diffusion of the Al2O3 precursors on the resulting coating thickness, ALD processes with different exposure times (i.e., 0.5, 2, 5, and 10 s) of the trimethylaluminum (TMA) precursor were performed. Uniform coating of the nanotube interiors was achieved with longer exposure times (5 and 10 s), as verified by detailed scanning electron microscopy analysis. Quartz crystal microbalance measurements were used to monitor the deposition process and its particular features due to the tube diameter gradient. Finally, theoretical calculations were performed to calculate the minimum precursor exposure time to attain uniform coating. Theoretical values on the diffusion regime matched with the experimental results and helped to obtain valuable information for further optimization of ALD coating processes. The presented approach provides a straightforward solution toward the development of many novel devices, based on a high surface area interface between TiO2 nanotubes and a secondary material (such as Al2O3). PMID:27643411

Methods for improved growth of group III nitride semiconductor compounds

DOEpatents

Melnik, Yuriy; Chen, Lu; Kojiri, Hidehiro

2015-03-17

Methods are disclosed for growing group III-nitride semiconductor compounds with advanced buffer layer technique. In an embodiment, a method includes providing a suitable substrate in a processing chamber of a hydride vapor phase epitaxy processing system. The method includes forming an AlN buffer layer by flowing an ammonia gas into a growth zone of the processing chamber, flowing an aluminum halide containing precursor to the growth zone and at the same time flowing additional hydrogen halide or halogen gas into the growth zone of the processing chamber. The additional hydrogen halide or halogen gas that is flowed into the growth zone during buffer layer deposition suppresses homogeneous AlN particle formation. The hydrogen halide or halogen gas may continue flowing for a time period while the flow of the aluminum halide containing precursor is turned off.

Process of producing a ceramic matrix composite article and article formed thereby

DOE Office of Scientific and Technical Information (OSTI.GOV)

Corman, Gregory Scot; McGuigan, Henry Charles; Brun, Milivoj Konstantin

A CMC article and process for producing the article to have a layer on its surface that protects a reinforcement material within the article from damage. The method entails providing a body containing a ceramic reinforcement material in a matrix material that contains a precursor of a ceramic matrix material. A fraction of the reinforcement material is present and possibly exposed at a surface of the body. The body surface is then provided with a surface layer formed of a slurry containing a particulate material but lacking the reinforcement material of the body. The body and surface layer are heatedmore » to form the article by converting the precursor within the body to form the ceramic matrix material in which the reinforcement material is contained, and by converting the surface layer to form the protective layer that covers any fraction of the reinforcement material exposed at the body surface.« less

Process of producing a ceramic matrix composite article and article formed thereby

DOEpatents

Corman, Gregory Scot [Ballston Lake, NY; McGuigan, Henry Charles [Duanesburg, NY; Brun, Milivoj Konstantin [Ballston Lake, NY

2011-10-25

A CMC article and process for producing the article to have a layer on its surface that protects a reinforcement material within the article from damage. The method entails providing a body containing a ceramic reinforcement material in a matrix material that contains a precursor of a ceramic matrix material. A fraction of the reinforcement material is present and possibly exposed at a surface of the body. The body surface is then provided with a surface layer formed of a slurry containing a particulate material but lacking the reinforcement material of the body. The body and surface layer are heated to form the article by converting the precursor within the body to form the ceramic matrix material in which the reinforcement material is contained, and by converting the surface layer to form the protective layer that covers any fraction of the reinforcement material exposed at the body surface.

Atomic Layer Deposition of the Solid Electrolyte LiPON

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kozen, Alexander C.; Pearse, Alexander J.; Lin, Chuan -Fu

We demonstrate an atomic layer deposition (ALD) process for the solid electrolyte lithium phosphorousoxynitride (LiPON) using lithium tert-butoxide (LiO tBu), H 2O, trimethylphosphate (TMP), and plasma N 2 ( PN 2) as precursors. We use in-situ spectroscopic ellipsometry to determine growth rates for process optimization to design a rational, quaternary precursor ALD process where only certain substrate–precursor chemical reactions are favorable. We demonstrate via in-situ XPS tunable nitrogen incorporation into the films by variation of the PN 2 dose and find that ALD films over approximately 4.5% nitrogen are amorphous, whereas LiPON ALD films with less than 4.5% nitrogen aremore » polycrystalline. Lastly, we characterize the ionic conductivity of the ALD films as a function of nitrogen content and demonstrate their functionality on a model battery electrode—a Si anode on a Cu current collector.« less

Atomic Layer Deposition of the Solid Electrolyte LiPON

DOE PAGES

Kozen, Alexander C.; Pearse, Alexander J.; Lin, Chuan -Fu; ...

2015-07-09

We demonstrate an atomic layer deposition (ALD) process for the solid electrolyte lithium phosphorousoxynitride (LiPON) using lithium tert-butoxide (LiO tBu), H 2O, trimethylphosphate (TMP), and plasma N 2 ( PN 2) as precursors. We use in-situ spectroscopic ellipsometry to determine growth rates for process optimization to design a rational, quaternary precursor ALD process where only certain substrate–precursor chemical reactions are favorable. We demonstrate via in-situ XPS tunable nitrogen incorporation into the films by variation of the PN 2 dose and find that ALD films over approximately 4.5% nitrogen are amorphous, whereas LiPON ALD films with less than 4.5% nitrogen aremore » polycrystalline. Lastly, we characterize the ionic conductivity of the ALD films as a function of nitrogen content and demonstrate their functionality on a model battery electrode—a Si anode on a Cu current collector.« less

Using ALD To Bond CNTs to Substrates and Matrices

NASA Technical Reports Server (NTRS)

Wong, Eric W.; Bronikowski, Michael J.; Kowalczyk, Robert S.

2008-01-01

Atomic-layer deposition (ALD) has been shown to be effective as a means of coating carbon nanotubes (CNTs) with layers of Al2O3 that form strong bonds between the CNTs and the substrates on which the CNTs are grown. ALD is a previously developed vaporphase thin-film-growth technique. ALD differs from conventional chemical vapor deposition, in which material is deposited continually by thermal decomposition of a precursor gas. In ALD, material is deposited one layer of atoms at a time because the deposition process is self-limiting and driven by chemical reactions between the precursor gas and the surface of the substrate or the previously deposited layer.

Double-Layer Gadolinium Zirconate/Yttria-Stabilized Zirconia Thermal Barrier Coatings Deposited by the Solution Precursor Plasma Spray Process

NASA Astrophysics Data System (ADS)

Jiang, Chen; Jordan, Eric H.; Harris, Alan B.; Gell, Maurice; Roth, Jeffrey

2015-08-01

Advanced thermal barrier coatings (TBCs) with lower thermal conductivity, increased resistance to calcium-magnesium-aluminosilicate (CMAS), and improved high-temperature capability, compared to traditional yttria-stabilized zirconia (YSZ) TBCs, are essential to higher efficiency in next generation gas turbine engines. Double-layer rare-earth zirconate/YSZ TBCs are a promising solution. From a processing perspective, solution precursor plasma spray (SPPS) process with its unique and beneficial microstructural features can be an effective approach to obtaining the double-layer microstructure. Previously durable low-thermal-conductivity YSZ TBCs with optimized layered porosity, called the inter-pass boundaries (IPBs) were produced using the SPPS process. In this study, an SPPS gadolinium zirconate (GZO) protective surface layer was successfully added. These SPPS double-layer TBCs not only retained good cyclic durability and low thermal conductivity, but also demonstrated favorable phase stability and increased surface temperature capabilities. The CMAS resistance was evaluated with both accumulative and single applications of simulated CMAS in isothermal furnaces. The double-layer YSZ/GZO exhibited dramatic improvement in the single application, but not in the continuous one. In addition, to explore their potential application in integrated gasification combined cycle environments, double-layer TBCs were tested under high-temperature humidity and encouraging performance was recorded.

Automated Rapid Prototyping of 3D Ceramic Parts

NASA Technical Reports Server (NTRS)

McMillin, Scott G.; Griffin, Eugene A.; Griffin, Curtis W.; Coles, Peter W. H.; Engle, James D.

2005-01-01

An automated system of manufacturing equipment produces three-dimensional (3D) ceramic parts specified by computational models of the parts. The system implements an advanced, automated version of a generic rapid-prototyping process in which the fabrication of an object having a possibly complex 3D shape includes stacking of thin sheets, the outlines of which closely approximate the horizontal cross sections of the object at their respective heights. In this process, the thin sheets are made of a ceramic precursor material, and the stack is subsequently heated to transform it into a unitary ceramic object. In addition to the computer used to generate the computational model of the part to be fabricated, the equipment used in this process includes: 1) A commercially available laminated-object-manufacturing machine that was originally designed for building woodlike 3D objects from paper and was modified to accept sheets of ceramic precursor material, and 2) A machine designed specifically to feed single sheets of ceramic precursor material to the laminated-object-manufacturing machine. Like other rapid-prototyping processes that utilize stacking of thin sheets, this process begins with generation of the computational model of the part to be fabricated, followed by computational sectioning of the part into layers of predetermined thickness that collectively define the shape of the part. Information about each layer is transmitted to rapid-prototyping equipment, where the part is built layer by layer. What distinguishes this process from other rapid-prototyping processes that utilize stacking of thin sheets are the details of the machines and the actions that they perform. In this process, flexible sheets of ceramic precursor material (called "green" ceramic sheets) suitable for lamination are produced by tape casting. The binder used in the tape casting is specially formulated to enable lamination of layers with little or no applied heat or pressure. The tape is cut into individual sheets, which are stacked in the sheet-feeding machine until used. The sheet-feeding machine can hold enough sheets for about 8 hours of continuous operation.

Fused filament 3D printing of ionic polymer-metal composites (IPMCs)

NASA Astrophysics Data System (ADS)

Carrico, James D.; Traeden, Nicklaus W.; Aureli, Matteo; Leang, Kam K.

2015-12-01

This paper describes a new three-dimensional (3D) fused filament additive manufacturing (AM) technique in which electroactive polymer filament material is used to build soft active 3D structures, layer by layer. Specifically, the unique actuation and sensing properties of ionic polymer-metal composites (IPMCs) are exploited in 3D printing to create electroactive polymer structures for application in soft robotics and bio-inspired systems. The process begins with extruding a precursor material (non-acid Nafion precursor resin) into a thermoplastic filament for 3D printing. The filament is then used by a custom-designed 3D printer to manufacture the desired soft polymer structures, layer by layer. Since at this stage the 3D-printed samples are not yet electroactive, a chemical functionalization process follows, consisting in hydrolyzing the precursor samples in an aqueous solution of potassium hydroxide and dimethyl sulfoxide. Upon functionalization, metal electrodes are applied on the samples through an electroless plating process, which enables the 3D-printed IPMC structures to be controlled by voltage signals for actuation (or to act as sensors). This innovative AM process is described in detail and the performance of 3D printed IPMC actuators is compared to an IPMC actuator fabricated from commercially available Nafion sheet material. The experimental results show comparable performance between the two types of actuators, demonstrating the potential and feasibility of creating functional 3D-printed IPMCs.

Graphitic carbon stabilized silver nanoparticles synthesized by a simple chemical precursor method

NASA Astrophysics Data System (ADS)

Soni, Bhasker; Biswas, Somnath

2018-04-01

Monodispersed graphitic carbon stabilized silver nanoparticles (AgNPs) were synthesized following a simple chemical precursor method. The precursor was obtained by a controlled reduction of Ag+ in aqueous solution of poly-vinyl alcohol (PVA) and sucrose. The process allows precise control over the morphology of the AgNPs along with in situ formation of a surface stabilization layer of graphitic carbon.

Method of making molecularly doped composite polymer material

DOEpatents

Affinito, John D [Tucson, AZ; Martin, Peter M [Kennewick, WA; Graff, Gordon L [West Richland, WA; Burrows, Paul E [Kennewick, WA; Gross, Mark E. , Sapochak, Linda S.

2005-06-21

A method of making a composite polymer of a molecularly doped polymer. The method includes mixing a liquid polymer precursor with molecular dopant forming a molecularly doped polymer precursor mixture. The molecularly doped polymer precursor mixture is flash evaporated forming a composite vapor. The composite vapor is cryocondensed on a cool substrate forming a composite molecularly doped polymer precursor layer, and the cryocondensed composite molecularly doped polymer precursor layer is cross linked thereby forming a layer of the composite polymer layer of the molecularly doped polymer.

Influence of atomic layer deposition valve temperature on ZrN plasma enhanced atomic layer deposition growth

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muneshwar, Triratna, E-mail: muneshwa@ualberta.ca; Cadien, Ken

2015-11-15

Atomic layer deposition (ALD) relies on a sequence of self-limiting surface reactions for thin film growth. The effect of non-ALD side reactions, from insufficient purging between pulses and from precursor self-decomposition, on film growth is well known. In this article, precursor condensation within an ALD valve is described, and the effect of the continuous precursor source from condensate evaporation on ALD growth is discussed. The influence of the ALD valve temperature on growth and electrical resistivity of ZrN plasma enhanced ALD (PEALD) films is reported. Increasing ALD valve temperature from 75 to 95 °C, with other process parameters being identical, decreasedmore » both the growth per cycle and electrical resistivity (ρ) of ZrN PEALD films from 0.10 to 0.07 nm/cycle and from 560 to 350 μΩ cm, respectively. Our results show that the non-ALD growth resulting from condensate accumulation is eliminated at valve temperatures close to the pressure corrected boiling point of precursor.« less

Process for forming epitaxial perovskite thin film layers using halide precursors

DOEpatents

Clem, Paul G.; Rodriguez, Mark A.; Voigt, James A.; Ashley, Carol S.

2001-01-01

A process for forming an epitaxial perovskite-phase thin film on a substrate. This thin film can act as a buffer layer between a Ni substrate and a YBa.sub.2 Cu.sub.3 O.sub.7-x superconductor layer. The process utilizes alkali or alkaline metal acetates dissolved in halogenated organic acid along with titanium isopropoxide to dip or spin-coat the substrate which is then heated to about 700.degree. C. in an inert gas atmosphere to form the epitaxial film on the substrate. The YBCO superconductor can then be deposited on the layer formed by this invention.

Fabricating Large-Area Sheets of Single-Layer Graphene by CVD

NASA Technical Reports Server (NTRS)

Bronikowski, Michael; Manohara, Harish

2008-01-01

This innovation consists of a set of methodologies for preparing large area (greater than 1 cm(exp 2)) domains of single-atomic-layer graphite, also called graphene, in single (two-dimensional) crystal form. To fabricate a single graphene layer using chemical vapor deposition (CVD), the process begins with an atomically flat surface of an appropriate substrate and an appropriate precursor molecule containing carbon atoms attached to substituent atoms or groups. These molecules will be brought into contact with the substrate surface by being flowed over, or sprayed onto, the substrate, under CVD conditions of low pressure and elevated temperature. Upon contact with the surface, the precursor molecules will decompose. The substituent groups detach from the carbon atoms and form gas-phase species, leaving the unfunctionalized carbon atoms attached to the substrate surface. These carbon atoms will diffuse upon this surface and encounter and bond to other carbon atoms. If conditions are chosen carefully, the surface carbon atoms will arrange to form the lowest energy single-layer structure available, which is the graphene lattice that is sought. Another method for creating the graphene lattice includes metal-catalyzed CVD, in which the decomposition of the precursor molecules is initiated by the catalytic action of a catalytic metal upon the substrate surface. Another type of metal-catalyzed CVD has the entire substrate composed of catalytic metal, or other material, either as a bulk crystal or as a think layer of catalyst deposited upon another surface. In this case, the precursor molecules decompose directly upon contact with the substrate, releasing their atoms and forming the graphene sheet. Atomic layer deposition (ALD) can also be used. In this method, a substrate surface at low temperature is covered with exactly one monolayer of precursor molecules (which may be of more than one type). This is heated up so that the precursor molecules decompose and form one monolayer of the target material.

Low-Temperature Molecular Layer Deposition Using Monofunctional Aromatic Precursors and Ozone-Based Ring-Opening Reactions.

PubMed

Svärd, Laura; Putkonen, Matti; Kenttä, Eija; Sajavaara, Timo; Krahl, Fabian; Karppinen, Maarit; Van de Kerckhove, Kevin; Detavernier, Christophe; Simell, Pekka

2017-09-26

Molecular layer deposition (MLD) is an increasingly used deposition technique for producing thin coatings consisting of purely organic or hybrid inorganic-organic materials. When organic materials are prepared, low deposition temperatures are often required to avoid decomposition, thus causing problems with low vapor pressure precursors. Monofunctional compounds have higher vapor pressures than traditional bi- or trifunctional MLD precursors, but do not offer the required functional groups for continuing the MLD growth in subsequent deposition cycles. In this study, we have used high vapor pressure monofunctional aromatic precursors in combination with ozone-triggered ring-opening reactions to achieve sustained sequential growth. MLD depositions were carried out by using three different aromatic precursors in an ABC sequence, namely with TMA + phenol + O 3 , TMA + 3-(trifluoromethyl)phenol + O 3 , and TMA + 2-fluoro-4-(trifluoromethyl)benzaldehyde + O 3 . Furthermore, the effect of hydrogen peroxide as a fourth step was evaluated for all studied processes resulting in a four-precursor ABCD sequence. According to the characterization results by ellipsometry, infrared spectroscopy, and X-ray reflectivity, self-limiting MLD processes could be obtained between 75 and 150 °C with each of the three aromatic precursors. In all cases, the GPC (growth per cycle) decreased with increasing temperature. In situ infrared spectroscopy indicated that ring-opening reactions occurred in each ABC sequence. Compositional analysis using time-of-flight elastic recoil detection indicated that fluorine could be incorporated into the film when 3-(trifluoromethyl)phenol and 2-fluoro-4-(trifluoromethyl)benzaldehyde were used as precursors.

Supported mesoporous carbon ultrafiltration membrane and process for making the same

DOEpatents

Strano, Michael; Foley, Henry C.; Agarwal, Hans

2004-04-13

A novel supported mesoporous carbon ultrafiltration membrane and process for producing the same. The membranes comprise a mesoporous carbon layer that exists both within and external to the porous support. A liquid polymer precursor composition comprising both carbonizing and noncarbonizing templating polymers is deposited on the porous metal support. The coated support is then heated in an inert-gas atmosphere to pyrolyze the polymeric precursor and form a mesoporous carbon layer on and within the support. The pore-size of the membranes is dependent on the molecular weight of the noncarbonizing templating polymer precursor. The mesoporous carbon layer is stable and can withstand high temperatures and exposure to organic chemicals. Additionally, the porous metal support provides excellent strength properties. The composite structure of the membrane provides novel structural properties and allows for increased operating pressures allowing for greater membrane flow rates. The invention also relates to the use of the novel ultrafiltration membrane to separate macromolecules from solution. An example is shown separating bovine serum albumin from water. The membrane functions by separating and by selective adsorption. Because of the membrane's porous metal support, it is well suited to industrial applications. The unique properties of the supported mesoporous carbon membrane also allow the membrane to be used in transient pressure or temperature swing separations processes. Such processes were not previously possible with existing mesoporous membranes. The present invention, however, possesses the requisite physical properties to perform such novel ultrafiltration processes.

Deposition of ultra thin CuInS₂ absorber layers by ALD for thin film solar cells at low temperature (down to 150 °C).

PubMed

Schneider, Nathanaelle; Bouttemy, Muriel; Genevée, Pascal; Lincot, Daniel; Donsanti, Frédérique

2015-02-06

Two new processes for the atomic layer deposition of copper indium sulfide (CuInS₂) based on the use of two different sets of precursors are reported. Metal chloride precursors (CuCl, InCl₃) in combination with H2S imply relatively high deposition temperature (Tdep = 380 °C), and due to exchange reactions, CuInS₂ stoechiometry was only achieved by depositing In₂S3 layers on a CuxS film. However, the use of acac- metal precursors (Cu(acac)₂, In(acac)₃) allows the direct deposition of CuInS₂ at temperature as low as 150 °C, involving in situ copper-reduction, exchange reaction and diffusion processes. The morphology, crystallographic structure, chemical composition and optical band gap of thin films were investigated using scanning electronic microscope, x-ray diffraction under grazing incidence conditions, x-ray fluorescence, energy dispersive spectrometry, secondary ion mass spectrometry, x-ray photoelectron spectroscopy and UV-vis spectroscopy. Films were implemented as ultra-thin absorbers in a typical CIS-solar cell architecture and allowed conversion efficiencies up to 2.8%.

Method for depositing high-quality microcrystalline semiconductor materials

DOEpatents

Guha, Subhendu [Bloomfield Hills, MI; Yang, Chi C [Troy, MI; Yan, Baojie [Rochester Hills, MI

2011-03-08

A process for the plasma deposition of a layer of a microcrystalline semiconductor material is carried out by energizing a process gas which includes a precursor of the semiconductor material and a diluent with electromagnetic energy so as to create a plasma therefrom. The plasma deposits a layer of the microcrystalline semiconductor material onto the substrate. The concentration of the diluent in the process gas is varied as a function of the thickness of the layer of microcrystalline semiconductor material which has been deposited. Also disclosed is the use of the process for the preparation of an N-I-P type photovoltaic device.

Cu2ZnSnSe4 Thin Film Solar Cell with Depth Gradient Composition Prepared by Selenization of Sputtered Novel Precursors.

PubMed

Lai, Fang-I; Yang, Jui-Fu; Chen, Wei-Chun; Kuo, Shou-Yi

2017-11-22

In this study, we proposed a new method for the synthesis of the target material used in a two stage process for preparation of a high quality CZTSe thin film. The target material consisting of a mixture of Cu x Se and Zn x Sn 1-x alloy was synthesized, providing a quality CZTSe precursor layer for highly efficient CZTSe thin film solar cells. The CZTSe thin film can be obtained by annealing the precursor layers through a 30 min selenization process under a selenium atmosphere at 550 °C. The CZTSe thin films prepared by using the new precursor thin film were investigated and characterized using X-ray diffraction, Raman scattering, and photoluminescence spectroscopy. It was found that diffusion of Sn occurred and formed the CTSe phase and Cu x Se phase in the resultant CZTSe thin film. By selective area electron diffraction transmission electron microscopy images, the crystallinity of the CZTSe thin film was verified to be single crystal. By secondary ion mass spectroscopy measurements, it was confirmed that a double-gradient band gap profile across the CZTSe absorber layer was successfully achieved. The CZTSe solar cell with the CZTSe absorber layer consisting of the precursor stack exhibited a high efficiency of 5.46%, high short circuit current (J SC ) of 37.47 mA/cm 2 , open circuit voltage (V OC ) of 0.31 V, and fill factor (F.F.) of 47%, at a device area of 0.28 cm 2 . No crossover of the light and dark current-voltage (I-V) curves of the CZTSe solar cell was observed, and also, no red kink was observed under red light illumination, indicating a low defect concentration in the CZTSe absorber layer. Shunt leakage current with a characteristic metal/CZTSe/metal leakage current model was observed by temperature-dependent I-V curves, which led to the discovery of metal incursion through the CdS buffer layer on the CZTSe absorber layer. This leakage current, also known as space charge-limited current, grew larger as the measurement temperature increased and completely overwhelmed the diode current at a measurement temperature of 200 °C. This is due to interlayer diffusion of metal that increases the shunt leakage current and decreases the efficiency of the CZTSe thin film solar cells.

The Low Temperature Epitaxy of Strained GeSn Layers Using RTCVD System

NASA Astrophysics Data System (ADS)

Kil, Yeon-Ho; Yuk, Sim-Hoon; Jang, Han-Soo; Lee, Sang-Geul; Choi, Chel-Jong; Shim, Kyu-Hwan

2018-03-01

We have investigated the low temperature (LT) growth of GeSn-Ge-Si structures using rapid thermal chemical vapor deposition system utilizing Ge2H6 and SnCl4 as the reactive precursors. Due to inappropriate phenomena, such as, Ge etch and Sn segregation, it was hard to achieve high quality GeSn epitaxy at the temperature > 350 °C. On the contrary, we found that the SnCl4 promoted the reaction of Ge2H6 precursors in a certain process condition of LT, 240-360 °C. In return, we could perform the growth of GeSn epi layer with 7.7% of Sn and its remaining compressive strain of 71.7%. The surface propagated defects were increased with increasing the Sn content in the GeSn layer confirmed by TEM analysis. And we could calculate the activation energies at lower GeSn growth temperature regime using by Ge2H6 and SnCl4 precursors about 0.43 eV.

Highly Strong and Elastic Graphene Fibres Prepared from Universal Graphene Oxide Precursors

PubMed Central

Huang, Guoji; Hou, Chengyi; Shao, Yuanlong; Wang, Hongzhi; Zhang, Qinghong; Li, Yaogang; Zhu, Meifang

2014-01-01

Graphene fibres are continuously prepared from universal graphene oxide precursors by a novel hydrogel-assisted spinning method. With assistance of a rolling process, meters of ribbon-like GFs, or GRs with improved conductivity, tensile strength, and a long-range ordered compact layer structure are successfully obtained. Furthermore, we refined our spinning process to obtained elastic GRs with a mixing microstructure and exceptional elasticity, which may provide a platform for electronic skins and wearable electronics, sensors, and energy devices. PMID:24576869

Novel Cyclosilazane-Type Silicon Precursor and Two-Step Plasma for Plasma-Enhanced Atomic Layer Deposition of Silicon Nitride.

PubMed

Park, Jae-Min; Jang, Se Jin; Lee, Sang-Ick; Lee, Won-Jun

2018-03-14

We designed cyclosilazane-type silicon precursors and proposed a three-step plasma-enhanced atomic layer deposition (PEALD) process to prepare silicon nitride films with high quality and excellent step coverage. The cyclosilazane-type precursor, 1,3-di-isopropylamino-2,4-dimethylcyclosilazane (CSN-2), has a closed ring structure for good thermal stability and high reactivity. CSN-2 showed thermal stability up to 450 °C and a sufficient vapor pressure of 4 Torr at 60 °C. The energy for the chemisorption of CSN-2 on the undercoordinated silicon nitride surface as calculated by density functional theory method was -7.38 eV. The PEALD process window was between 200 and 500 °C, with a growth rate of 0.43 Å/cycle. The best film quality was obtained at 500 °C, with hydrogen impurity of ∼7 atom %, oxygen impurity less than 2 atom %, low wet etching rate, and excellent step coverage of ∼95%. At 300 °C and lower temperatures, the wet etching rate was high especially at the lower sidewall of the trench pattern. We introduced the three-step PEALD process to improve the film quality and the step coverage on the lower sidewall. The sequence of the three-step PEALD process consists of the CSN-2 feeding step, the NH 3 /N 2 plasma step, and the N 2 plasma step. The H radicals in NH 3 /N 2 plasma efficiently remove the ligands from the precursor, and the N 2 plasma after the NH 3 plasma removes the surface hydrogen atoms to activate the adsorption of the precursor. The films deposited at 300 °C using the novel precursor and the three-step PEALD process showed a significantly improved step coverage of ∼95% and an excellent wet etching resistance at the lower sidewall, which is only twice as high as that of the blanket film prepared by low-pressure chemical vapor deposition.

Electro-deposition of superconductor oxide films

DOEpatents

Bhattacharya, Raghu N.

2001-01-01

Methods for preparing high quality superconducting oxide precursors which are well suited for further oxidation and annealing to form superconducting oxide films. The method comprises forming a multilayered superconducting precursor on a substrate by providing an electrodeposition bath comprising an electrolyte medium and a substrate electrode, and providing to the bath a plurality of precursor metal salts which are capable of exhibiting superconducting properties upon subsequent treatment. The superconducting precursor is then formed by electrodepositing a first electrodeposited (ED) layer onto the substrate electrode, followed by depositing a layer of silver onto the first electrodeposited (ED) layer, and then electrodepositing a second electrodeposited (ED) layer onto the Ag layer. The multilayered superconducting precursor is suitable for oxidation at a sufficient annealing temperature in air or an oxygen-containing atmosphere to form a crystalline superconducting oxide film.

New CVD-based method for the growth of high-quality crystalline zinc oxide layers

NASA Astrophysics Data System (ADS)

Huber, Florian; Madel, Manfred; Reiser, Anton; Bauer, Sebastian; Thonke, Klaus

2016-07-01

High-quality zinc oxide (ZnO) layers were grown using a new chemical vapour deposition (CVD)-based low-cost growth method. The process is characterized by total simplicity, high growth rates, and cheap, less hazardous precursors. To produce elementary zinc vapour, methane (CH4) is used to reduce a ZnO powder. By re-oxidizing the zinc with pure oxygen, highly crystalline ZnO layers were grown on gallium nitride (GaN) layers and on sapphire substrates with an aluminum nitride (AlN) nucleation layer. Using simple CH4 as precursor has the big advantage of good controllability and the avoidance of highly toxic gases like nitrogen oxides. In photoluminescence (PL) measurements the samples show a strong near-band-edge emission and a sharp line width at 5 K. The good crystal quality has been confirmed in high resolution X-ray diffraction (HRXRD) measurements. This new growth method has great potential for industrial large-scale production of high-quality single crystal ZnO layers.

Real-time observation of Cu2ZnSn(S,Se)4 solar cell absorber layer formation from nanoparticle precursors.

PubMed

Mainz, Roland; Walker, Bryce C; Schmidt, Sebastian S; Zander, Ole; Weber, Alfons; Rodriguez-Alvarez, Humberto; Just, Justus; Klaus, Manuela; Agrawal, Rakesh; Unold, Thomas

2013-11-07

The selenization of Cu-Zn-Sn-S nanocrystals is a promising route for the fabrication of low-cost thin film solar cells. However, the reaction pathway of this process is not completely understood. Here, the evolution of phase formation, grain size, and elemental distributions is investigated during the selenization of Cu-Zn-Sn-S nanoparticle precursor thin films by synchrotron-based in situ energy-dispersive X-ray diffraction and fluorescence analysis as well as by ex situ electron microscopy. The precursor films are heated in a closed volume inside a vacuum chamber in the presence of selenium vapor while diffraction and fluorescence signals are recorded. The presented results reveal that during the selenization the cations diffuse to the surface to form large grains on top of the nanoparticle layer and the selenization of the film takes place through two simultaneous reactions: (1) a direct and fast formation of large grained selenides, starting with copper selenide which is subsequently transformed into Cu2ZnSnSe4; and (2) a slower selenization of the remaining nanoparticles. As a consequence of the initial formation of copper selenides at the surface, the subsequent formation of CZTSe starts under Cu-rich conditions despite an overall Cu-poor composition of the film. The implications of this process path for the film quality are discussed. Additionally, the proposed growth model provides an explanation for the previously observed accumulation of carbon from the nanoparticle precursor beneath the large grained layer.

MicroRNAs Promote Granule Cell Expansion in the Cerebellum Through Gli2.

PubMed

Constantin, Lena; Wainwright, Brandon J

2015-12-01

MicroRNAs (miRNAs) are important regulators of cerebellar function and homeostasis. Their deregulation results in cerebellar neuronal degeneration and spinocerebellar ataxia type 1 and contributes to medulloblastoma. Canonical miRNA processing involves Dicer, which cleaves precursor miRNAs into mature double-stranded RNA duplexes. In order to address the role of miRNAs in cerebellar granule cell precursor development, loxP-flanked exons of Dicer1 were conditionally inactivated using the granule cell precursor-specific Atoh1-Cre recombinase. A reduction of 87% in Dicer1 transcript was achieved in this conditional Dicer knockdown model. Although knockdown resulted in normal survival, mice had disruptions to the cortical layering of the anterior cerebellum, which resulted from the premature differentiation of granule cell precursors in this region during neonatal development. This defect manifested as a thinner external granular layer with ectopic mature granule cells, and a depleted internal granular layer. We found that expression of the activator components of the Hedgehog-Patched pathway, the Gli family of transcription factors, was perturbed in conditional Dicer knockdown mice. We propose that loss of Gli2 mRNA mediated the anterior-restricted defect in conditional Dicer knockdown mice and, as proof of principle, were able to show that miR-106b positively regulated Gli2 mRNA expression. These findings confirm the importance of miRNAs as positive mediators of Hedgehog-Patched signalling during granule cell precursor development.

Structural and dielectric properties of thin ZrO2 films on silicon grown by atomic layer deposition from cyclopentadienyl precursor

NASA Astrophysics Data System (ADS)

Niinistö, J.; Putkonen, M.; Niinistö, L.; Kukli, K.; Ritala, M.; Leskelä, M.

2004-01-01

ZrO2 thin films with thicknesses below 20 nm were deposited by the atomic layer deposition process on Si(100) substrates at 350 °C. An organometallic precursor, Cp2Zr(CH3)2 (Cp=cyclopentadienyl, C5H5) was used as the zirconium source and water or ozone as oxygen source. The influence of oxygen source and substrate pretreatment on the dielectric properties of ZrO2 films was investigated. Structural characterization with high-resolution transmission electron microscopy was performed to films grown onto HF-etched or native oxide covered silicon. Strong inhibition of ZrO2 film growth was observed with the water process on HF-etched Si. Ozone process on HF-etched Si resulted in interfacial SiO2 formation between the dense and uniform film and the substrate while water process produced interfacial layer with intermixing of SiO2 and ZrO2. The effective permittivity of ZrO2 in Al/ZrO2/Si/Al capacitor structures was dependent on the ZrO2 layer thickness and oxygen source used. The interfacial layer formation increased the capacitance equivalent oxide thickness (CET). CET of 2.0 nm was achieved with 5.9 nm ZrO2 film deposited with the H2O process on HF-stripped Si. The ozone-processed films showed good dielectric properties such as low hysteresis and nearly ideal flatband voltage. The leakage current density was lower and breakdown field higher for the ozone-processed ZrO2 films.

Selective growth of titanium dioxide by low-temperature chemical vapor deposition.

PubMed

Reinke, Michael; Kuzminykh, Yury; Hoffmann, Patrik

2015-05-13

A key factor in engineering integrated optical devices such as electro-optic switches or waveguides is the patterning of thin films into specific geometries. In particular for functional oxides, etching processes are usually developed to a much lower extent than for silicon or silicon dioxide; therefore, selective area deposition techniques are of high interest for these materials. We report the selective area deposition of titanium dioxide using titanium isopropoxide and water in a high-vacuum chemical vapor deposition (HV-CVD) process at a substrate temperature of 225 °C. Here—contrary to conventional thermal CVD processes—only hydrolysis of the precursor on the surface drives the film growth as the thermal energy is not sufficient to thermally decompose the precursor. Local modification of the substrate surface energy by perfluoroalkylsilanization leads to a reduced surface residence time of the precursors and, consequently, to lower reaction rate and a prolonged incubation period before nucleation occurs, hence, enabling selective area growth. We discuss the dependence of the incubation time and the selectivity of the deposition process on the presence of the perfluoroalkylsilanization layer and on the precursor impinging rates—with selectivity, we refer to the difference of desired material deposition, before nucleation occurs in the undesired regions. The highest measured selectivity reached (99 ± 5) nm, a factor of 3 superior than previously reported in an atomic layer deposition process using the same chemistry. Furthermore, resolution of the obtained patterns will be discussed and illustrated.

Methods for producing thin film charge selective transport layers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hammond, Scott Ryan; Olson, Dana C.; van Hest, Marinus Franciscus Antonius Maria

Methods for producing thin film charge selective transport layers are provided. In one embodiment, a method for forming a thin film charge selective transport layer comprises: providing a precursor solution comprising a metal containing reactive precursor material dissolved into a complexing solvent; depositing the precursor solution onto a surface of a substrate to form a film; and forming a charge selective transport layer on the substrate by annealing the film.

Detailed Visualization of Phase Evolution during Rapid Formation of Cu(InGa)Se2 Photovoltaic Absorber from Mo/CuGa/In/Se Precursors.

PubMed

Koo, Jaseok; Kim, Sammi; Cheon, Taehoon; Kim, Soo-Hyun; Kim, Woo Kyoung

2018-03-02

Amongst several processes which have been developed for the production of reliable chalcopyrite Cu(InGa)Se 2 photovoltaic absorbers, the 2-step metallization-selenization process is widely accepted as being suitable for industrial-scale application. Here we visualize the detailed thermal behavior and reaction pathways of constituent elements during commercially attractive rapid thermal processing of glass/Mo/CuGa/In/Se precursors on the basis of the results of systematic characterization of samples obtained from a series of quenching experiments with set-temperatures between 25 and 550 °C. It was confirmed that the Se layer crystallized and then melted between 250 and 350 °C, completely disappearing at 500 °C. The formation of CuInSe 2 and Cu(InGa)Se 2 was initiated at around 450 °C and 550 °C, respectively. It is suggested that pre-heat treatment to control crystallization of Se layer should be designed at 250-350 °C and Cu(InGa)Se 2 formation from CuGa/In/Se precursors can be completed within a timeframe of 6 min.

Atomic Layer Deposition of Electron Selective SnOx and ZnO Films on Mixed Halide Perovskite: Compatibility and Performance.

PubMed

Hultqvist, Adam; Aitola, Kerttu; Sveinbjörnsson, Kári; Saki, Zahra; Larsson, Fredrik; Törndahl, Tobias; Johansson, Erik; Boschloo, Gerrit; Edoff, Marika

2017-09-06

The compatibility of atomic layer deposition directly onto the mixed halide perovskite formamidinium lead iodide:methylammonium lead bromide (CH(NH 2 ) 2 , CH 3 NH 3 )Pb(I,Br) 3 (FAPbI 3 :MAPbBr 3 ) perovskite films is investigated by exposing the perovskite films to the full or partial atomic layer deposition processes for the electron selective layer candidates ZnO and SnO x . Exposing the samples to the heat, the vacuum, and even the counter reactant of H 2 O of the atomic layer deposition processes does not appear to alter the perovskite films in terms of crystallinity, but the choice of metal precursor is found to be critical. The Zn precursor Zn(C 2 H 5 ) 2 either by itself or in combination with H 2 O during the ZnO atomic layer deposition (ALD) process is found to enhance the decomposition of the bulk of the perovskite film into PbI 2 without even forming ZnO. In contrast, the Sn precursor Sn(N(CH 3 ) 2 ) 4 does not seem to degrade the bulk of the perovskite film, and conformal SnO x films can successfully be grown on top of it using atomic layer deposition. Using this SnO x film as the electron selective layer in inverted perovskite solar cells results in a lower power conversion efficiency of 3.4% than the 8.4% for the reference devices using phenyl-C 70 -butyric acid methyl ester. However, the devices with SnO x show strong hysteresis and can be pushed to an efficiency of 7.8% after biasing treatments. Still, these cells lacks both open circuit voltage and fill factor compared to the references, especially when thicker SnO x films are used. Upon further investigation, a possible cause of these losses could be that the perovskite/SnO x interface is not ideal and more specifically found to be rich in Sn, O, and halides, which is probably a result of the nucleation during the SnO x growth and which might introduce barriers or alter the band alignment for the transport of charge carriers.

Steering the Properties of MoOx Hole Transporting Layers in OPVs and OLEDs: Interface Morphology vs. Electronic Structure

PubMed Central

Marchal, Wouter; Verboven, Inge; Kesters, Jurgen; Moeremans, Boaz; De Dobbelaere, Christopher; Bonneux, Gilles; Elen, Ken; Conings, Bert; Maes, Wouter; Boyen, Hans Gerd; Deferme, Wim; Van Bael, Marlies; Hardy, An

2017-01-01

The identification, fine-tuning, and process optimization of appropriate hole transporting layers (HTLs) for organic solar cells is indispensable for the production of efficient and sustainable functional devices. In this study, the optimization of a solution-processed molybdenum oxide (MoOx) layer fabricated from a combustion precursor is carried out via the introduction of zirconium and tin additives. The evaluation of the output characteristics of both organic photovoltaic (OPV) and organic light emitting diode (OLED) devices demonstrates the beneficial influence upon the addition of the Zr and Sn ions compared to the generic MoOx precursor. A dopant effect in which the heteroatoms and the molybdenum oxide form a chemical identity with fundamentally different structural properties could not be observed, as the additives do not affect the molybdenum oxide composition or electronic band structure. An improved surface roughness due to a reduced crystallinity was found to be a key parameter leading to the superior performance of the devices employing modified HTLs. PMID:28772483

Steering the Properties of MoOx Hole Transporting Layers in OPVs and OLEDs: Interface Morphology vs. Electronic Structure.

PubMed

Marchal, Wouter; Verboven, Inge; Kesters, Jurgen; Moeremans, Boaz; De Dobbelaere, Christopher; Bonneux, Gilles; Elen, Ken; Conings, Bert; Maes, Wouter; Boyen, Hans Gerd; Deferme, Wim; Van Bael, Marlies; Hardy, An

2017-01-30

The identification, fine-tuning, and process optimization of appropriate hole transporting layers (HTLs) for organic solar cells is indispensable for the production of efficient and sustainable functional devices. In this study, the optimization of a solution-processed molybdenum oxide (MoOx) layer fabricated from a combustion precursor is carried out via the introduction of zirconium and tin additives. The evaluation of the output characteristics of both organic photovoltaic (OPV) and organic light emitting diode (OLED) devices demonstrates the beneficial influence upon the addition of the Zr and Sn ions compared to the generic MoOx precursor. A dopant effect in which the heteroatoms and the molybdenum oxide form a chemical identity with fundamentally different structural properties could not be observed, as the additives do not affect the molybdenum oxide composition or electronic band structure. An improved surface roughness due to a reduced crystallinity was found to be a key parameter leading to the superior performance of the devices employing modified HTLs.

Experimental characterization and modeling for the growth rate of oxide coatings from liquid solutions of metalorganic precursors by ultrasonic pulsed injection in a cold-wall low-pressure reactor

NASA Astrophysics Data System (ADS)

Krumdieck, Susan Pran

Several years ago, a method for depositing ceramic coatings called the Pulsed-MOCVD system was developed by the Raj group at Cornell University in association with Dr. Harvey Berger and Sono-Tek Corporation. The process was used to produce epitaxial thin films of TiO2 on sapphire substrates under conditions of low pressure, relatively high temperature, and very low growth rate. The system came to CU-Boulder when Professor Raj moved here in 1997. It is quite a simple technique and has several advantages over typical CVD systems. The purpose of this dissertation is two-fold; (1) understand the chemical processes, thermodynamics, and kinetics of the Pulsed-MOCVD technique, and (2) determine the possible applications by studying the film structure and morphology over the entire range of deposition conditions. Polycrystalline coatings of ceramic materials were deposited on nickel in the low-pressure, cold-wall reactor from metalorganic precursors, titanium isopropoxide, and a mixture of zirconium isopropoxide and yttria isopropoxide. The process utilized pulsed liquid injection of a dilute precursor solution with atomization by ultrasonic nozzle. Thin films (less than 1mum) with fine-grained microstructure and thick coatings (up to 1mum) with columnar-microstructure were deposited on heated metal substrates by thermal decomposition of a single liquid precursor. The influence of each of the primary deposition parameters, substrate temperature, total flow rate, and precursor concentration on growth rate, conversion efficiency and morphology were investigated. The operating conditions were determined for kinetic, mass transfer, and evaporation process control regimes. Kinetic controlled deposition was found to produce equiaxed morphology while mass transfer controlled deposition produced columnar morphology. A kinetic model of the deposition process was developed and compared to data for deposition of TiO2 from Ti(OC3H7) 4 precursor. The results demonstrate that growth rate and morphology over the range of process operating conditions would make the Pulsed-MOCVD system suitable for application of thermal barrier coatings, electrical insulating layers, corrosion protection coatings, and the electrolyte layers in solid oxide fuel cells.

An efficient copper phthalocyanine additive of perovskite precursor for improving the photovoltaic performance of planar perovskite solar cells

NASA Astrophysics Data System (ADS)

Wu, Shufang; Liu, Qingwei; Zheng, Ya; Li, Renjie; Peng, Tianyou

2017-08-01

Solution processable planar heterojunction perovskite solar cell has drawn much attention as a promising low-cost photovoltaic device, and much effort has been made to improve its power conversion efficiency by choosing appropriate additives for the perovskite precursor solution. Different to those additives reported, a soluble and thermal stable tert-butyl substituted copper phthalocyanine (CuPc(tBu)4) as additive is first introduced into the perovskite precursor solution of a planar perovskite solar cell that is fabricated via the one-step solution process. It is found that the pristine device without CuPc(tBu)4 additive exhibits a power conversion efficiency of 15.3%, while an extremely low concentration (4.4 × 10-3 mM) of CuPc(tBu)4 in the precursor solution leads to the corresponding device achieving an enhanced power conversion efficiency of 17.3%. CuPc(tBu)4 as an additive can improve the quality of perovskite layer with higher crystallinity and surface coverage, then resulting in enhanced light absorption and reduced charge recombination, and thus the better power conversion efficiency. The finding presented here provides a new choice for improving the quality of perovskite layer and the photovoltaic performance of the planar heterojunction perovskite solar cells.

Method of deforming a biaxially textured buffer layer on a textured metallic substrate and articles therefrom

DOEpatents

Lee, Dominic F.; Kroeger, Donald M.; Goyal, Amit

2000-01-01

The present invention provides methods and biaxially textured articles having a deformed epitaxial layer formed therefrom for use with high temperature superconductors, photovoltaic, ferroelectric, or optical devices. A buffer layer is epitaxially deposited onto biaxially-textured substrates and then mechanically deformed. The deformation process minimizes or eliminates grooves, or other irregularities, formed on the buffer layer while maintaining the biaxial texture of the buffer layer. Advantageously, the biaxial texture of the buffer layer is not altered during subsequent heat treatments of the deformed buffer. The present invention provides mechanical densification procedures which can be incorporated into the processing of superconducting films through the powder deposit or precursor approaches without incurring unfavorable high-angle grain boundaries.

Organic and inorganic–organic thin film structures by molecular layer deposition: A review

PubMed Central

Sundberg, Pia

2014-01-01

Summary The possibility to deposit purely organic and hybrid inorganic–organic materials in a way parallel to the state-of-the-art gas-phase deposition method of inorganic thin films, i.e., atomic layer deposition (ALD), is currently experiencing a strongly growing interest. Like ALD in case of the inorganics, the emerging molecular layer deposition (MLD) technique for organic constituents can be employed to fabricate high-quality thin films and coatings with thickness and composition control on the molecular scale, even on complex three-dimensional structures. Moreover, by combining the two techniques, ALD and MLD, fundamentally new types of inorganic–organic hybrid materials can be produced. In this review article, we first describe the basic concepts regarding the MLD and ALD/MLD processes, followed by a comprehensive review of the various precursors and precursor pairs so far employed in these processes. Finally, we discuss the first proof-of-concept experiments in which the newly developed MLD and ALD/MLD processes are exploited to fabricate novel multilayer and nanostructure architectures by combining different inorganic, organic and hybrid material layers into on-demand designed mixtures, superlattices and nanolaminates, and employing new innovative nanotemplates or post-deposition treatments to, e.g., selectively decompose parts of the structure. Such layer-engineered and/or nanostructured hybrid materials with exciting combinations of functional properties hold great promise for high-end technological applications. PMID:25161845

Rapid preparation of solution-processed InGaZnO thin films by microwave annealing and photoirradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheong, Heajeong; Ogura, Shintaro; Ushijima, Hirobumi

We fabricated solution-processed indium–gallium–zinc oxide (IGZO) thin-film transistors (TFTs) by microwave (MW) annealing an IGZO precursor film followed by irradiating with vacuum ultraviolet (VUV) light. MW annealing allows more rapid heating of the precursor film than conventional annealing processes using a hot plate or electric oven and promotes the crystallization of IGZO. VUV irradiation was used to reduce the duration and temperature of the post-annealing step. Consequently, the IGZO TFTs fabricated through MW annealing for 5 min and VUV irradiation for 1 min exhibited an on/off current ratio of 10{sup 8} and a field-effect mobility of 0.3 cm{sup 2} V{sup −1} s{supmore » −1}. These results indicate that MW annealing and photoirradiation is an effective combination for annealing solution processed IGZO precursor films to prepare the semiconductor layers of TFTs.« less

Fabrication of nanostructured ZnO film as a hole-conducting layer of organic photovoltaic cell

PubMed Central

2013-01-01

We have investigated the effect of fibrous nanostructured ZnO film as a hole-conducting layer on the performance of polymer photovoltaic cells. By increasing the concentration of zinc acetate dihydrate, the changes of performance characteristics were evaluated. Fibrous nanostructured ZnO film was prepared by sol-gel process and annealed on a hot plate. As the concentration of zinc acetate dihydrate increased, ZnO fibrous nanostructure grew from 300 to 600 nm. The obtained ZnO nanostructured fibrous films have taken the shape of a maze-like structure and were characterized by UV-visible absorption, scanning electron microscopy, and X-ray diffraction techniques. The intensity of absorption bands in the ultraviolet region was increased with increasing precursor concentration. The X-ray diffraction studies show that the ZnO fibrous nanostructures became strongly (002)-oriented with increasing concentration of precursor. The bulk heterojunction photovoltaic cells were fabricated using poly(3-hexylthiophene-2,5-diyl) and indene-C60 bisadduct as active layer, and their electrical properties were investigated. The external quantum efficiency of the fabricated device increased with increasing precursor concentration. PMID:23680100

Fabrication of nanostructured ZnO film as a hole-conducting layer of organic photovoltaic cell

NASA Astrophysics Data System (ADS)

Kim, Hyomin; Kwon, Yiseul; Choe, Youngson

2013-05-01

We have investigated the effect of fibrous nanostructured ZnO film as a hole-conducting layer on the performance of polymer photovoltaic cells. By increasing the concentration of zinc acetate dihydrate, the changes of performance characteristics were evaluated. Fibrous nanostructured ZnO film was prepared by sol-gel process and annealed on a hot plate. As the concentration of zinc acetate dihydrate increased, ZnO fibrous nanostructure grew from 300 to 600 nm. The obtained ZnO nanostructured fibrous films have taken the shape of a maze-like structure and were characterized by UV-visible absorption, scanning electron microscopy, and X-ray diffraction techniques. The intensity of absorption bands in the ultraviolet region was increased with increasing precursor concentration. The X-ray diffraction studies show that the ZnO fibrous nanostructures became strongly (002)-oriented with increasing concentration of precursor. The bulk heterojunction photovoltaic cells were fabricated using poly(3-hexylthiophene-2,5-diyl) and indene-C60 bisadduct as active layer, and their electrical properties were investigated. The external quantum efficiency of the fabricated device increased with increasing precursor concentration.

Process stability and morphology optimization of very thick 4H-SiC epitaxial layers grown by chloride-based CVD

NASA Astrophysics Data System (ADS)

Yazdanfar, M.; Stenberg, P.; Booker, I. D.; Ivanov, I. G.; Kordina, O.; Pedersen, H.; Janzén, E.

2013-10-01

The development of a chemical vapor deposition (CVD) process for very thick silicon carbide (SiC) epitaxial layers suitable for high power devices is demonstrated by epitaxial growth of 200 μm thick, low doped 4H-SiC layers with excellent morphology at growth rates exceeding 100 μm/h. The process development was done in a hot wall CVD reactor without rotation using both SiCl4 and SiH4+HCl precursor approaches to chloride based growth chemistry. A C/Si ratio <1 and an optimized in-situ etch are shown to be the key parameters to achieve 200 μm thick, low doped epitaxial layers with excellent morphology.

Continuous lengths of oxide superconductors

DOEpatents

Kroeger, Donald M.; List, III, Frederick A.

2000-01-01

A layered oxide superconductor prepared by depositing a superconductor precursor powder on a continuous length of a first substrate ribbon. A continuous length of a second substrate ribbon is overlaid on the first substrate ribbon. Sufficient pressure is applied to form a bound layered superconductor precursor powder between the first substrate ribbon and the second substrate ribbon. The layered superconductor precursor is then heat treated to establish the oxide superconducting phase. The layered oxide superconductor has a smooth interface between the substrate and the oxide superconductor.

Method for fabrication of ceramic dielectric films on copper foils

DOEpatents

Ma, Beihai; Narayanan, Manoj; Dorris, Stephen E.; Balachandran, Uthamalingam

2015-03-10

The present invention provides a method for fabricating a ceramic film on a copper foil. The method comprises applying a layer of a sol-gel composition onto a copper foil. The sol-gel composition comprises a precursor of a ceramic material suspended in 2-methoxyethanol. The layer of sol-gel is then dried at a temperature up to about 250.degree. C. The dried layer is then pyrolyzed at a temperature in the range of about 300 to about 450.degree. C. to form a ceramic film from the ceramic precursor. The ceramic film is then crystallized at a temperature in the range of about 600 to about 750.degree. C. The drying, pyrolyzing and crystallizing are performed under a flowing stream of an inert gas. In some embodiments an additional layer of the sol-gel composition is applied onto the ceramic film and the drying, pyrolyzing and crystallizing steps are repeated for the additional layer to build up a thicker ceramic layer on the copper foil. The process can be repeated one or more times if desired.

Functionalized graphene-Pt composites for fuel cells and photoelectrochemical cells

DOEpatents

Diankov, Georgi; An, Jihwan; Park, Joonsuk; Goldhaber, David J. K.; Prinz, Friedrich B.

2017-08-29

A method of growing crystals on two-dimensional layered material is provided that includes reversibly hydrogenating a two-dimensional layered material, using a controlled radio-frequency hydrogen plasma, depositing Pt atoms on the reversibly hydrogenated two-dimensional layered material, using Atomic Layer Deposition (ALD), where the reversibly hydrogenated two-dimensional layered material promotes loss of methyl groups in an ALD Pt precursor, and forming Pt-O on the reversibly hydrogenated two-dimensional layered material, using combustion by O.sub.2, where the Pt-O is used for subsequent Pt half-cycles of the ALD process, where growth of Pt crystals occurs.

Selective epitaxial growth of Ge1-xSnx on Si by using metal-organic chemical vapor deposition

NASA Astrophysics Data System (ADS)

Washizu, Tomoya; Ike, Shinichi; Inuzuka, Yuki; Takeuchi, Wakana; Nakatsuka, Osamu; Zaima, Shigeaki

2017-06-01

Selective epitaxial growth of Ge and Ge1-xSnx layers on Si substrates was performed by using metal-organic chemical vapor deposition (MOCVD) with precursors of tertiary-butyl-germane (t-BGe) and tri-butyl-vinyl-tin (TBVSn). We investigated the effects of growth temperature and total pressure during growth on the selectivity and the crystallinity of the Ge and Ge1-xSnx epitaxial layers. Under low total pressure growth conditions, the dominant mechanism of the selective growth of Ge epitaxial layers is the desorption of the Ge precursors. At a high total pressure case, it is needed to control the surface migration of precursors to realize the selectivity because the desorption of Ge precursors was suppressed. The selectivity of Ge growth was improved by diffusion of the Ge precursors on the SiO2 surfaces when patterned substrates were used at a high total pressure. The selective epitaxial growth of Ge1-xSnx layer was also realized using MOCVD. We found that the Sn precursors less likely to desorb from the SiO2 surfaces than the Ge precursors.

Pd-Pt and Fe-Ni nanoparticles formed by covalent molecular assembly in supercritical carbon dioxide.

PubMed

Puniredd, Sreenivasa Reddy; Weiyi, Seah; Srinivasan, M P

2008-04-01

We report the formation of Pd-Pt nanoparticles within a dendrimer-laden ultrathin film matrix immobilized on a solid support and constructed by covalent layer-by-layer (LbL) assembly using supercritical carbon dioxide (SCCO2) as the processing medium. Particle size distribution and composition were controlled by precursor composition. The precursor compositions are optimized for Pd-Pt nanoparticles and later extended to the formation of Fe-Ni nanoparticles. As an example of the application of nanoparticles in tribology, Fe-Ni nanoparticle-laden films were observed to exhibit better tribological properties than those containing the monometallic species, thereby suggesting that combination of nanoparticles can be used to derive greater benefits.

Surface Surgery of the Nickel-Rich Cathode Material LiNi0.815Co0.15Al0.035O2: Toward a Complete and Ordered Surface Layered Structure and Better Electrochemical Properties.

PubMed

Tang, Zhongfeng; Bao, Junjie; Du, Qingxia; Shao, Yu; Gao, Minghao; Zou, Bangkun; Chen, Chunhua

2016-12-21

A complete and ordered layered structure on the surface of LiNi 0.815 Co 0.15 Al 0.035 O 2 (NCA) has been achieved via a facile surface-oxidation method with Na 2 S 2 O 8 . The field-emission transmission electron microscopy images clearly show that preoxidation of the hydroxide precursor can eliminate the crystal defects and convert Ni(OH) 2 into layered β-NiOOH, which leads to a highly ordered crystalline NCA, with its (006) planes perpendicular to the surface in the sintering process. X-ray photoelectron spectroscopy and Raman shift results demonstrate that the contents of Ni 2+ and Co 2+ ions are reduced with preoxidization on the surface of the hydroxide precursor. The level of Li + /Ni 2+ disordering in the modified NCA determined by the peak intensity ratio I (003) /I (104) in X-ray diffraction patterns decreases. Thanks to the complete and ordered layered structure on the surface of secondary particles, lithium ions can easily intercalate/extract in the discharging-charging process, leading to greatly improved electrochemical properties.

Amorphous surface layer versus transient amorphous precursor phase in bone - A case study investigated by solid-state NMR spectroscopy.

PubMed

Von Euw, Stanislas; Ajili, Widad; Chan-Chang, Tsou-Hsi-Camille; Delices, Annette; Laurent, Guillaume; Babonneau, Florence; Nassif, Nadine; Azaïs, Thierry

2017-09-01

The presence of an amorphous surface layer that coats a crystalline core has been proposed for many biominerals, including bone mineral. In parallel, transient amorphous precursor phases have been proposed in various biomineralization processes, including bone biomineralization. Here we propose a methodology to investigate the origin of these amorphous environments taking the bone tissue as a key example. This study relies on the investigation of a bone tissue sample and its comparison with synthetic calcium phosphate samples, including a stoichiometric apatite, an amorphous calcium phosphate sample, and two different biomimetic apatites. To reveal if the amorphous environments in bone originate from an amorphous surface layer or a transient amorphous precursor phase, a combined solid-state nuclear magnetic resonance (NMR) experiment has been used. The latter consists of a double cross polarization 1 H→ 31 P→ 1 H pulse sequence followed by a 1 H magnetization exchange pulse sequence. The presence of an amorphous surface layer has been investigated through the study of the biomimetic apatites; while the presence of a transient amorphous precursor phase in the form of amorphous calcium phosphate particles has been mimicked with the help of a physical mixture of stoichiometric apatite and amorphous calcium phosphate. The NMR results show that the amorphous and the crystalline environments detected in our bone tissue sample belong to the same particle. The presence of an amorphous surface layer that coats the apatitic core of bone apatite particles has been unambiguously confirmed, and it is certain that this amorphous surface layer has strong implication on bone tissue biogenesis and regeneration. Questions still persist on the structural organization of bone and biomimetic apatites. The existing model proposes a core/shell structure, with an amorphous surface layer coating a crystalline bulk. The accuracy of this model is still debated because amorphous calcium phosphate (ACP) environments could also arise from a transient amorphous precursor phase of apatite. Here, we provide an NMR spectroscopy methodology to reveal the origin of these ACP environments in bone mineral or in biomimetic apatite. The 1 H magnetization exchange between protons arising from amorphous and crystalline domains shows unambiguously that an ACP layer coats the apatitic crystalline core of bone et biomimetic apatite platelets. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Processing of SiO2 protective layer using HMDS precursor by combustion CVD.

PubMed

Park, Kyoung-Soo; Kim, Youngman

2011-08-01

Hexamethyldisilazane (HMDS, [(CH3)3Si]2NH) was used as a precursor to form SiO2 protective coatings on IN738LC alloys by combustion chemical vapor deposition (CCVD). SEM and XPS showed that the processed coatings were composed mainly of SiO2. The amount of HMDS had the largest effect on the size of the SiO2 agglomerates and the thickness of the deposited coatings. The specimens coated with SiO2 using the 0.05 mol/l HMDS solution showed a significantly higher temperature oxidation resistance than those deposited under other conditions.

A pressure tuned stop-flow atomic layer deposition process for MoS2 on high porous nanostructure and fabrication of TiO2/MoS2 core/shell inverse opal structure

NASA Astrophysics Data System (ADS)

Li, Xianglin; Puttaswamy, Manjunath; Wang, Zhiwei; Kei Tan, Chiew; Grimsdale, Andrew C.; Kherani, Nazir P.; Tok, Alfred Iing Yoong

2017-11-01

MoS2 thin films are obtained by atomic layer deposition (ALD) in the temperature range of 120-150 °C using Mo(CO)6 and dimethyl disulfide (DMDS) as precursors. A pressure tuned stop-flow ALD process facilitates the precursor adsorption and enables the deposition of MoS2 on high porous three dimensional (3D) nanostructures. As a demonstration, a TiO2/MoS2 core/shell inverse opal (TiO2/MoS2-IO) structure has been fabricated through ALD of TiO2 and MoS2 on a self-assembled multilayer polystyrene (PS) structure template. Due to the self-limiting surface reaction mechanism of ALD and the utilization of pressure tuned stop-flow ALD processes, the as fabricated TiO2/MoS2-IO structure has a high uniformity, reflected by FESEM and FIB-SEM characterization. A crystallized TiO2/MoS2-IO structure can be obtained through a post annealing process. As a 3D photonic crystal, the TiO2/MoS2-IO exhibits obvious stopband reflecting peaks, which can be adjusted through changing the opal diameters as well as the thickness of MoS2 layer.

Opportunities offered by the interaction of plasma and droplets to elaborate nanostructured oxide materials

NASA Astrophysics Data System (ADS)

Nikravech, Mehrdad; Rahmani, Abdelkader

2016-09-01

The association of plasma and spray will permit to process materials where organometallic precursors are not available or economically non-reliable. The injection of aerosols in low pressure plasma results in the rapid evaporation of solvent and the rapid transformation of small amounts of precursors contained in each droplet leading to form nanoscale oxide particles. We developed two configurations of this technique: one is Spray Plasma that permits to deposit this layers on flat substrates; the second one is Fluidized Spray Plasma that permits to deposit thin layers on the surface of solid beads. The aim of this presentation is to describe the principles of this new technique together with several applications. The influence of experimental parameters to deposit various mixed metal oxides will be demonstrated: thin dense layers of nanostructured ZnO for photovoltaic applications, porous layers of LaxSr1-x MnO3 as the cathode for fuel cells, ZnO-Cu, NiO layers on solid pellets in fluidized bed for catalysis applications. Aknowledgement to Programme interdisciplinaire SPC Énergies de Demain.

Comparison of precursor infiltration into polymer thin films via atomic layer deposition and sequential vapor infiltration using in-situ quartz crystal microgravimetry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Padbury, Richard P.; Jur, Jesse S., E-mail: jsjur@ncsu.edu

Previous research exploring inorganic materials nucleation behavior on polymers via atomic layer deposition indicates the formation of hybrid organic–inorganic materials that form within the subsurface of the polymer. This has inspired adaptations to the process, such as sequential vapor infiltration, which enhances the diffusion of organometallic precursors into the subsurface of the polymer to promote the formation of a hybrid organic–inorganic coating. This work highlights the fundamental difference in mass uptake behavior between atomic layer deposition and sequential vapor infiltration using in-situ methods. In particular, in-situ quartz crystal microgravimetry is used to compare the mass uptake behavior of trimethyl aluminummore » in poly(butylene terephthalate) and polyamide-6 polymer thin films. The importance of trimethyl aluminum diffusion into the polymer subsurface and the subsequent chemical reactions with polymer functional groups are discussed.« less

Representation of ocean-atmosphere processes associated with extended monsoon episodes over South Asia in CFSv2

NASA Astrophysics Data System (ADS)

Mohan, T. S.; Annamalai, H.; Marx, Larry; Huang, Bohua; Kinter, James

2018-02-01

In the present study, we analyze 30-years output from free run solutions of CFSv2 coupled model to assess the model’s representation of extended (>7 days) active and break monsoon episodes over south Asia. Process based diagnostics is applied to the individual and composite events to identify precursor signals in both ocean and atmospheric variables. Our examination suggests that CFSv2, like most coupled models, depict systematic biases in variables important for ocean-atmosphere interactions. Nevertheless, model solutions capture many aspects of monsoon extended break and active episodes realistically, encouraging us to apply process-based diagnostics. Diagnostics reveal that sea surface temperature (SST) variations over the northern Bay of Bengal where the climatological mixed-layer is thin, lead the in-situ precipitation anomalies by about 8 (10) days during extended active (break) episodes, and the precipitation anomalies over central India by 10-14 days. Mixed-layer heat budget analysis indicates for a close correspondence between SST tendency and net surface heat flux (Q_net). MSE budgets indicate that horizontal moisture advection to be a coherent precursor signal ( 10 days) during both extended break (dry advection) and active (moist advection) events. The lead timings in these precursor signals in CFSv2 solutions will be of potential use to monitor and predict extended monsoon episodes. Diagnostics, however, also indicate that for about 1/3 of the identified extended break and active episodes, inconsistencies in budget terms suggest precursor signals could lead to false alarms. Apart from false alarms, compared to observations, CFSv2 systematically simulates a greater number of extended monsoon active episodes.

Structure for HTS composite conductors and the manufacture of same

DOEpatents

Cotton, J.D.; Riley, G.N. Jr.

1999-06-01

A superconducting oxide composite structure including a superconducting oxide member, a metal layer surrounding the superconducting oxide member, and an insulating layer of a complex oxide formed in situ adjacent to the superconducting oxide member and the metal layer is provided together with a method of forming such a superconducting oxide composite structure including encapsulating a superconducting oxide member or precursor within a metal matrix layer from the group of: (1) a reactive metal sheath adjacent to the superconducting oxide member or precursor, the reactive metal sheath surrounded by a second metal layer or (2) an alloy containing a reactive metal; to form an intermediate product, and, heating the intermediate product at temperatures and for time sufficient to form an insulating layer of a complex oxide in situ, the insulating layer to the superconducting oxide member or precursor and the metal matrix layer. 10 figs.

Structure for hts composite conductors and the manufacture of same

DOEpatents

Cotton, James D.; Riley, Jr., Gilbert Neal

1999-01-01

A superconducting oxide composite structure including a superconducting oxide member, a metal layer surrounding the superconducting oxide member, and an insulating layer of a complex oxide formed in situ adjacent to the superconducting oxide member and the metal layer is provided together with a method of forming such a superconducting oxide composite structure including encapsulating a superconducting oxide member or precursor within a metal matrix layer from the group of: (i) a reactive metal sheath adjacent to the superconducting oxide member or precursor, the reactive metal sheath surrounded by a second metal layer or (ii) an alloy containing a reactive metal; to form an intermediate product, and, heating the intermediate product at temperatures and for time sufficient to form an insulating layer of a complex oxide in situ, the insulating layer to the superconducting oxide member or precursor and the metal matrix layer.

Hybrid inorganic–organic superlattice structures with atomic layer deposition/molecular layer deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tynell, Tommi; Yamauchi, Hisao; Karppinen, Maarit, E-mail: maarit.karppinen@aalto.fi

2014-01-15

A combination of the atomic layer deposition (ALD) and molecular layer deposition (MLD) techniques is successfully employed to fabricate thin films incorporating superlattice structures that consist of single layers of organic molecules between thicker layers of ZnO. Diethyl zinc and water are used as precursors for the deposition of ZnO by ALD, while three different organic precursors are investigated for the MLD part: hydroquinone, 4-aminophenol and 4,4′-oxydianiline. The successful superlattice formation with all the organic precursors is verified through x-ray reflectivity studies. The effects of the interspersed organic layers/superlattice structure on the electrical and thermoelectric properties of ZnO are investigatedmore » through resistivity and Seebeck coefficient measurements at room temperature. The results suggest an increase in carrier concentration for small concentrations of organic layers, while higher concentrations seem to lead to rather large reductions in carrier concentration.« less

AxBAxB… pulsed atomic layer deposition: Numerical growth model and experiments

NASA Astrophysics Data System (ADS)

Muneshwar, Triratna; Cadien, Ken

2016-02-01

Atomic layer deposition (ALD) is widely used for the fabrication of advanced semiconductor devices and related nanoscale structures. During ALD, large precursor doses (>1000 L per pulse) are often required to achieve surface saturation, of which only a small fraction is utilized in film growth while the rest is pumped from the system. Since the metal precursor constitutes a significant cost of ALD, strategies to enhance precursor utilization are essential for the scaling of ALD processes. In the precursor reaction step, precursor physisorption is restricted by steric hindrance (mA1) from ligands on the precursor molecules. On reaction, some of these ligands are removed as by-products resulting in chemisorbed species with reduced steric hindrance (mA1 → mA2, where mA2 < mA1) and some of the initially hindered surface reaction sites becoming accessible for further precursor physisorption. To utilize these additional reaction sites, we propose a generalized AxBAxB… pulsed deposition where the total precursor dose (ΦA) is introduced as multiple x (x > 1, x ∈ I) short-pulses rather than a single pulse. A numerical first-order surface reaction kinetics growth model is presented and applied to study the effect of AxBAxB… pulsed ALD on the growth per cycle (GPC). The model calculations predict higher GPC for AxBAxB… pulsing than with ABAB… deposition. In agreement with the model predictions, with AxBAxB… pulsed deposition, the GPC was found to increase by ˜46% for ZrN plasma enhanced ALD (PEALD), ˜49% for HfO2 PEALD, and ˜8% for thermal Al2O3 ALD with respect to conventional ABAB… pulsed growth.

Dynamic integration of splicing within gene regulatory pathways

PubMed Central

Braunschweig, Ulrich; Gueroussov, Serge; Plocik, Alex; Graveley, Brenton R.; Blencowe, Benjamin J.

2013-01-01

Precursor mRNA splicing is one of the most highly regulated processes in metazoan species. In addition to generating vast repertoires of RNAs and proteins, splicing has a profound impact on other gene regulatory layers, including mRNA transcription, turnover, transport and translation. Conversely, factors regulating chromatin and transcription complexes impact the splicing process. This extensive cross-talk between gene regulatory layers takes advantage of dynamic spatial, physical and temporal organizational properties of the cell nucleus, and further emphasizes the importance of developing a multidimensional understanding of splicing control. PMID:23498935

Efficient Planar Structured Perovskite Solar Cells with Enhanced Open-Circuit Voltage and Suppressed Charge Recombination Based on a Slow Grown Perovskite Layer from Lead Acetate Precursor.

PubMed

Li, Cong; Guo, Qiang; Wang, Zhibin; Bai, Yiming; Liu, Lin; Wang, Fuzhi; Zhou, Erjun; Hayat, Tasawar; Alsaedi, Ahmed; Tan, Zhan'ao

2017-12-06

For planar structured organic-inorganic hybrid perovskite solar cells (PerSCs) with the poly(3,4-ethylenedioxythiophene:polystyrene sulfonate) (PEDOT:PSS) hole transport layer, the open-circuit voltage (V oc ) of the device is limited to be about 1.0 V, resulting in inferior performance in comparison with TiO 2 -based planar counterparts. Therefore, increasing V oc of the PEDOT:PSS-based planar device is an important way to enhance the efficiency of the PerSCs. Herein, we demonstrate a novel approach for perovskite film formation and the film is formed by slow growth from lead acetate precursor via a one-step spin-coating process without the thermal annealing (TA) process. Because the perovskite layer grows slowly and naturally, high-quality perovskite film can be achieved with larger crystalline particles, less defects, and smoother surface morphology. Ultraviolet absorption, X-ray diffraction, scanning electron microscopy, steady-state fluorescence spectroscopy (photoluminescence), and time-resolved fluorescence spectroscopy are used to clarify the crystallinity, morphology, and internal defects of perovskite thin films. The power conversion efficiency of p-i-n PerSCs based on slow-grown film (16.33%) shows greatly enhanced performance compared to that of the control device based on traditional thermally annealed perovskite film (14.33%). Furthermore, the V oc of the slow-growing device reaches 1.12 V, which is 0.1 V higher than that of the TA device. These findings indicate that slow growth of the perovskite layer from lead acetate precursor is a promising approach to achieve high-quality perovskite film for high-performance PerSCs.

Fine line structures of ceramic films formed by patterning of metalorganic precursors using photolithography and ion beams

NASA Astrophysics Data System (ADS)

Hung, L. S.; Zheng, L. R.

1992-05-01

Fine line structures of ceramic thin films were fabricated by patterning of metalorganic precursors using photolithography and ion beams. A trilevel structure was developed with an outer resist layer to transfer patterns, a silver delineated layer as an implantation mask, and a planar resist layer protecting the precursor film from chemical attacking and sputtering. Ion irradiation through the Ag stencil rendered metal carboxylates insoluble in 2-ethylhexanoic acid, permitting patterning of the precursor film with patterning features on micron scales. The potential of this technique was demonstrated in patterning of Bi2Sr2CaCu2O(8+x) and Pb(Zr(0.53)Ti(0.47) thin films.

Fused filament 3D printing of ionic polymer-metal composites for soft robotics

NASA Astrophysics Data System (ADS)

Carrico, James D.; Leang, Kam K.

2017-04-01

Additive manufacturing techniques are used to create three-dimensional structures with complex shapes and features from polymer and/or metal materials. For example, fused filament three-dimensional (3D) printing utilizes non-electroactive polymers, such as acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA), to build structures and components in a layer-by-layer fashion for a wide variety of applications. Presented here is a summary of recent work on a fused filament 3D-printing technique to create 3D ionic polymer-metal composite (IPMC) structures for applications in soft robotics. The 3D printing technique overcomes some of the limitations of existing manufacturing processes for creating IPMCs, such as limited shapes and sizes and time-consuming manufacturing steps. In the process described, first a precursor material (non-acid Nafion precursor resin) is extruded into a thermoplastic filament for 3D printing. Then, a custom-designed 3D printer is described that utilizes the precursor filament to manufacture custom-shaped structures. Finally, the 3D-printed samples are functionalized by hydrolyzing them in an aqueous solution of potassium hydroxide and dimethyl sulfoxide, followed by application of platinum electrodes. Presented are example 3D-printed single and multi-degree-of-freedom IPMC actuators and characterization results, as well as example soft-robotic devices to demonstrate the potential of this process.

The Au(111)/IL interfacial nanostructure in the presence of precursors and its influence on the electrodeposition process.

PubMed

Borisenko, Natalia; Lahiri, Abhishek; Pulletikurthi, Giridhar; Cui, Tong; Carstens, Timo; Zahlbach, Janine; Atkin, Rob; Endres, Frank

2018-01-01

Ionic liquids have attracted significant interest as electrolytes for the electrodeposition of metals and semiconductors, but the details of the deposition processes are not yet well understood. In this paper, we give an overview of how the addition of various precursors (TaF 5 , SiCl 4 , and GaCl 3 ) affects the solid/IL interfacial structure. In situ Atomic Force Microscopy (AFM) and vibrational spectroscopy have been employed to study the changes of the Au(111)/IL interface and in the electrolytes, respectively. Ionic liquids with the 1-butyl-1-methylpyrrolidinium ([Py 1,4 ] + ) cation and bis(trifluoromethylsulfonyl)amide ([TFSA] - ), trifluoromethylsulfonate ([TfO] - ) and tris(pentafluoroethyl)trifluorophosphate ([FAP] - ) as anions were chosen for this purpose. In situ AFM force-distance measurements reveal that both the anion of the IL and the solutes (TaF 5 or GaCl 3 ) influence the Electrical Double Layer (EDL) structure of the Au(111)/IL interface, which can affect the deposition process of Ta and the morphology of the Ga electrodeposits, respectively. Furthermore, the concentration of the precursor can significantly alter the Au(111)/[Py 1,4 ][FAP]-SiCl 4 interfacial structure wherein the presence of 0.25 M SiCl 4 a double layer structure forms that facilitates Si deposition. This study may provide some critical insights into the structure of the electrode/IL interface for specific applications.

Effect of Group-III precursors on unintentional gallium incorporation during epitaxial growth of InAlN layers by metalorganic chemical vapor deposition

NASA Astrophysics Data System (ADS)

Kim, Jeomoh; Ji, Mi-Hee; Detchprohm, Theeradetch; Dupuis, Russell D.; Fischer, Alec M.; Ponce, Fernando A.; Ryou, Jae-Hyun

2015-09-01

Unintentional incorporation of gallium (Ga) in InAlN layers grown with different molar flow rates of Group-III precursors by metalorganic chemical vapor deposition has been experimentally investigated. The Ga mole fraction in the InAl(Ga)N layer was increased significantly with the trimethylindium (TMIn) flow rate, while the trimethylaluminum flow rate controls the Al mole fraction. The evaporation of metallic Ga from the liquid phase eutectic system between the pyrolized In from injected TMIn and pre-deposited metallic Ga was responsible for the Ga auto-incorporation into the InAl(Ga)N layer. The theoretical calculation on the equilibrium vapor pressure of liquid phase Ga and the effective partial pressure of Group-III precursors based on growth parameters used in this study confirms the influence of Group-III precursors on Ga auto-incorporation. More Ga atoms can be evaporated from the liquid phase Ga on the surrounding surfaces in the growth chamber and then significant Ga auto-incorporation can occur due to the high equilibrium vapor pressure of Ga comparable to effective partial pressure of input Group-III precursors during the growth of InAl(Ga)N layer.

Single Source Precursors for Thin Film Solar Cells

NASA Technical Reports Server (NTRS)

Banger, Kulbinder K.; Hollingsworth, Jennifer A.; Harris, Jerry D.; Cowen, Jonathan; Buhro, William E.; Hepp, Aloysius F.

2002-01-01

The development of thin film solar cells on flexible, lightweight, space-qualified substrates provides an attractive cost solution to fabricating solar arrays with high specific power, (W/kg). The use of a polycrystalline chalcopyrite absorber layer for thin film solar cells is considered as the next generation photovoltaic devices. At NASA GRC we have focused on the development of new single source precursors (SSP) and their utility to deposit the chalcopyrite semi-conducting layer (CIS) onto flexible substrates for solar cell fabrication. The syntheses and thermal modulation of SSPs via molecular engineering is described. Thin-film fabrication studies demonstrate the SSPs can be used in a spray CVD (chemical vapor deposition) process, for depositing CIS at reduced temperatures, which display good electrical properties, suitable for PV (photovoltaic) devices.

Materials Design Through Chemical Control of Precursors

DTIC Science & Technology

2008-08-22

Ligand Sets,” H. M. El-Kaderi, M.J. Heeg, and C.H. Winter, Polyhedron 2006, 25, 224-234. 7. “Atomic Layer Deposition of Ga2O3 Films from a...poster presentation. 4. “Atomic Layer Deposition (ALD) of High Quality Ga2O3 Thin Films from a Dimeric Dialkylamido-Bridged Gallium Complex,” C. L...growth of Ga2O3 films from a new metalorganic precursor (“Atomic Layer Deposition of Ga2O3 Films from a 4 Dialkylamido-Based Precursor,” C. L

Sensor-based atomic layer deposition for rapid process learning and enhanced manufacturability

NASA Astrophysics Data System (ADS)

Lei, Wei

In the search for sensor based atomic layer deposition (ALD) process to accelerate process learning and enhance manufacturability, we have explored new reactor designs and applied in-situ process sensing to W and HfO 2 ALD processes. A novel wafer scale ALD reactor, which features fast gas switching, good process sensing compatibility and significant similarity to the real manufacturing environment, is constructed. The reactor has a unique movable reactor cap design that allows two possible operation modes: (1) steady-state flow with alternating gas species; or (2) fill-and-pump-out cycling of each gas, accelerating the pump-out by lifting the cap to employ the large chamber volume as ballast. Downstream quadrupole mass spectrometry (QMS) sampling is applied for in-situ process sensing of tungsten ALD process. The QMS reveals essential surface reaction dynamics through real-time signals associated with byproduct generation as well as precursor introduction and depletion for each ALD half cycle, which are then used for process learning and optimization. More subtle interactions such as imperfect surface saturation and reactant dose interaction are also directly observed by QMS, indicating that ALD process is more complicated than the suggested layer-by-layer growth. By integrating in real-time the byproduct QMS signals over each exposure and plotting it against process cycle number, the deposition kinetics on the wafer is directly measured. For continuous ALD runs, the total integrated byproduct QMS signal in each ALD run is also linear to ALD film thickness, and therefore can be used for ALD film thickness metrology. The in-situ process sensing is also applied to HfO2 ALD process that is carried out in a furnace type ALD reactor. Precursor dose end-point control is applied to precisely control the precursor dose in each half cycle. Multiple process sensors, including quartz crystal microbalance (QCM) and QMS are used to provide real time process information. The sensing results confirm the proposed surface reaction path and once again reveal the complexity of ALD processes. The impact of this work includes: (1) It explores new ALD reactor designs which enable the implementation of in-situ process sensors for rapid process learning and enhanced manufacturability; (2) It demonstrates in the first time that in-situ QMS can reveal detailed process dynamics and film growth kinetics in wafer-scale ALD process, and thus can be used for ALD film thickness metrology. (3) Based on results from two different processes carried out in two different reactors, it is clear that ALD is a more complicated process than normally believed or advertised, but real-time observation of the operational chemistries in ALD by in-situ sensors provides critical insight to the process and the basis for more effective process control for ALD applications.

Process development for waveguide chemical sensors with integrated polymeric sensitive layers

NASA Astrophysics Data System (ADS)

Amberkar, Raghu; Gao, Zhan; Park, Jongwon; Henthorn, David B.; Kim, Chang-Soo

2008-02-01

Due to the proper optical property and flexibility in the process development, an epoxy-based, high-aspect ratio photoresist SU-8 is now attracting attention in optical sensing applications. Manipulation of the surface properties of SU-8 waveguides is critical to attach functional films such as chemically-sensitive layers. We describe a new integration process to immobilize fluorescence molecules on SU-8 waveguide surface for application to intensity-based optical chemical sensors. We use two polymers for this application. Spin-on, hydrophobic, photopatternable silicone is a convenient material to contain fluorophore molecules and to pattern a photolithographically defined thin layer on the surface of SU-8. We use fumed silica powders as an additive to uniformly disperse the fluorophores in the silicone precursor. In general, additional processes are not critically required to promote the adhesion between the SU-8 and silicone. The other material is polyethylene glycol diacrylate (PEGDA). Recently we demonstrated a novel photografting method to modify the surface of SU-8 using a surface bound initiator to control its wettability. The activated surface is then coated with a monomer precursor solution. Polymerization follows when the sample is exposed to UV irradiation, resulting in a grafted PEGDA layer incorporating fluorophores within the hydrogel matrix. Since this method is based the UV-based photografting reaction, it is possible to grow off photolithographically defined hydrogel patterns on the waveguide structures. The resulting films will be viable integrated components in optical bioanalytical sensors. This is a promising technique for integrated chemical sensors both for planar type waveguide and vertical type waveguide chemical sensors.

Achieving composition-controlled Cu2ZnSnS4 films by sulfur-free annealing process

NASA Astrophysics Data System (ADS)

Jiang, Hailong; Wei, Xiaoqing; Huang, Yongliang; Wang, Xian; Han, Anjun; Liu, Xiaohui; Liu, Zhengxin; Meng, Fanying

2017-06-01

Cu2ZnSnS4 (CZTS) films were firstly prepared by the nonvacuum spin-coating method, and then annealed at 550 °C in N2 atmosphere. A graphite box was used to inhibit the volatilization of gaseous SnS and S2 to suppress the CZTS decomposition and generation of MoS2 during annealing. The sulfur supplementation carried out in a conventional annealing process was not applied in this work. It was found that Sn loss was overcome and the compositions of postannealed films were close to that of precursor solution. Thus, by this method, the compositions of CZTS films can be controlled by adjusting the elemental ratios of the precursor solution. Besides, the increase in inert atmosphere pressure could further minimize the Sn loss and improve the crystallinity of CZTS films. Furthermore, the resistive MoS2 layer between the CZTS film and the Mo layer was suppressed because sulfur was not used and CZTS decomposition was suppressed.

Direct selective growth of ZnO nanowire arrays from inkjet-printed zinc acetate precursor on a heated substrate

PubMed Central

2013-01-01

Inkjet printing of functional materials has drawn tremendous interest as an alternative to the conventional photolithography-based microelectronics fabrication process development. We introduce direct selective nanowire array growth by inkjet printing of Zn acetate precursor ink patterning and subsequent hydrothermal ZnO local growth without nozzle clogging problem which frequently happens in nanoparticle inkjet printing. The proposed process can directly grow ZnO nanowires in any arbitrary patterned shape, and it is basically very fast, low cost, environmentally benign, and low temperature. Therefore, Zn acetate precursor inkjet printing-based direct nanowire local growth is expected to give extremely high flexibility in nanomaterial patterning for high-performance electronics fabrication especially at the development stage. As a proof of concept of the proposed method, ZnO nanowire network-based field effect transistors and ultraviolet photo-detectors were demonstrated by direct patterned grown ZnO nanowires as active layer. PMID:24252130

Method and system for continuous atomic layer deposition

DOEpatents

Elam, Jeffrey W.; Yanguas-Gil, Angel; Libera, Joseph A.

2017-03-21

A system and method for continuous atomic layer deposition. The system and method includes a housing, a moving bed which passes through the housing, a plurality of precursor gases and associated input ports and the amount of precursor gases, position of the input ports, and relative velocity of the moving bed and carrier gases enabling exhaustion of the precursor gases at available reaction sites.

Metallorganic chemical vapor deposition and atomic layer deposition approaches for the growth of hafnium-based thin films from dialkylamide precursors for advanced CMOS gate stack applications

NASA Astrophysics Data System (ADS)

Consiglio, Steven P.

To continue the rapid progress of the semiconductor industry as described by Moore's Law, the feasibility of new material systems for front end of the line (FEOL) process technologies needs to be investigated, since the currently employed polysilicon/SiO2-based transistor system is reaching its fundamental scaling limits. Revolutionary breakthroughs in complementary-metal-oxide-semiconductor (CMOS) technology were recently announced by Intel Corporation and International Business Machines Corporation (IBM), with both organizations revealing significant progress in the implementation of hafnium-based high-k dielectrics along with metal gates. This announcement was heralded by Gordon Moore as "...the biggest change in transistor technology since the introduction of polysilicon gate MOS transistors in the late 1960s." Accordingly, the study described herein focuses on the growth of Hf-based dielectrics and Hf-based metal gates using chemical vapor-based deposition methods, specifically metallorganic chemical vapor deposition (MOCVD) and atomic layer deposition (ALD). A family of Hf source complexes that has received much attention recently due to their desirable properties for implementation in wafer scale manufacturing is the Hf dialkylamide precursors. These precursors are room temperature liquids and possess sufficient volatility and desirable decomposition characteristics for both MOCVD and ALD processing. Another benefit of using these sources is the existence of chemically compatible Si dialkylamide sources as co-precursors for use in Hf silicate growth. The first part of this study investigates properties of MOCVD-deposited HfO2 and HfSixOy using dimethylamido Hf and Si precursor sources using a customized MOCVD reactor. The second part of this study involves a study of wet and dry surface pre-treatments for ALD growth of HfO2 using tetrakis(ethylmethylamido)hafnium in a wafer scale manufacturing environment. The third part of this study is an investigation of the properties of conductive HfN grown via plasma-assisted atomic layer deposition (PA-ALD) using tetrakis(ethylmethylamido)hafnium on a modified commercially available wafer processing tool. Key properties of these materials for use as gate stack replacement materials are addressed and future directions for further characterization and novel material investigations are proposed.

Mesoporous-silica films, fibers, and powders by evaporation

DOEpatents

Bruinsma, Paul J.; Baskaran, Suresh; Bontha, Jagannadha R.; Liu, Jun

2008-05-06

This invention pertains to surfactant-templated nanometer-scale porosity of a silica precursor solution and forming a mesoporous material by first forming the silica precursor solution into a preform having a high surface area to volume ratio, then rapid drying or evaporating a solvent from the silica precursor solution. The mesoporous material may be in any geometric form, but is preferably in the form of a film, fiber, powder or combinations thereof. The rapid drying or evaporation of solvent from the solution is accomplished by layer thinning, for example spin casting, liquid drawing, and liquid spraying respectively. Production of a film is by layer thinning, wherein a layer of the silica precursor solution is formed on a surface followed by removal of an amount of the silica precursor solution and leaving a geometrically thinner layer of the silica precursor solution from which the solvent quickly escapes via evaporation. Layer thinning may be by any method including but not limited to squeegeeing and/or spin casting. In powder formation by spray drying, the same conditions of fast drying exists as in spin-casting (as well as in fiber spinning) because of the high surface-area to volume ratio of the product. When a powder is produced by liquid spraying, the particles or micro-bubbles within the powder are hollow spheres with walls composed of mesoporous silica. Mesoporous fiber formation starts with a similar silica precursor solution but with an added pre-polymer making a pituitous mixture that is drawn into a thin strand from which solvent is evaporated leaving the mesoporous fiber(s).

Mesoporous-silica films, fibers, and powders by evaporation

DOEpatents

Bruinsma, Paul J.; Baskaran, Suresh; Bontha, Jagannadha R.; Liu, Jun

1999-01-01

This invention pertains to surfactant-templated nanometer-scale porosity of a silica precursor solution and forming a mesoporous material by first forming the silica precursor solution into a preform having a high surface area to volume ratio, then rapid drying or evaporating a solvent from the silica precursor solution. The mesoporous material may be in any geometric form, but is preferably in the form of a film, fiber, powder or combinations thereof. The rapid drying or evaporation of solvent from the solution is accomplished by layer thinning, for example spin casting, liquid drawing, and liquid spraying respectively. Production of a film is by layer thinning, wherein a layer of the silica precursor solution is formed on a surface followed by removal of an amount of the silica precursor solution and leaving a geometrically thinner layer of the silica precursor solution from which the solvent quickly escapes via evaporation. Layer thinning may be by any method including but not limited to squeegeeing and/or spin casting. In powder formation by spray drying, the same conditions of fast drying exists as in spin-casting (as well as in fiber spinning) because of the high surface-area to volume ratio of the product. When a powder is produced by liquid spraying, the particles or micro-bubbles within the powder are hollow spheres with walls composed of mesoporous silica. Mesoporous fiber formation starts with a similar silica precursor solution but with an added pre-polymer making a pituitous mixture that is drawn into a thin strand from which solvent is evaporated leaving the mesoporous fiber(s).

Mesoporous-silica films, fibers, and powders by evaporation

DOEpatents

Bruinsma, P.J.; Baskaran, S.; Bontha, J.R.; Liu, J.

1999-07-13

This invention pertains to surfactant-templated nanometer-scale porosity of a silica precursor solution and forming a mesoporous material by first forming the silica precursor solution into a preform having a high surface area to volume ratio, then rapid drying or evaporating a solvent from the silica precursor solution. The mesoporous material may be in any geometric form, but is preferably in the form of a film, fiber, powder or combinations thereof. The rapid drying or evaporation of solvent from the solution is accomplished by layer thinning, for example spin casting, liquid drawing, and liquid spraying respectively. Production of a film is by layer thinning, wherein a layer of the silica precursor solution is formed on a surface followed by removal of an amount of the silica precursor solution and leaving a geometrically thinner layer of the silica precursor solution from which the solvent quickly escapes via evaporation. Layer thinning may be by any method including but not limited to squeegeeing and/or spin casting. In powder formation by spray drying, the same conditions of fast drying exists as in spin-casting (as well as in fiber spinning) because of the high surface-area to volume ratio of the product. When a powder is produced by liquid spraying, the particles or micro-bubbles within the powder are hollow spheres with walls composed of mesoporous silica. Mesoporous fiber formation starts with a similar silica precursor solution but with an added pre-polymer making a pituitous mixture that is drawn into a thin strand from which solvent is evaporated leaving the mesoporous fiber(s). 24 figs.

Comparison of trimethylgallium and triethylgallium as “Ga” source materials for the growth of ultrathin GaN films on Si (100) substrates via hollow-cathode plasma-assisted atomic layer deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alevli, Mustafa, E-mail: mustafaalevli@marmara.edu.tr; Haider, Ali; Kizir, Seda

2016-01-15

GaN films grown by hollow cathode plasma-assisted atomic layer deposition using trimethylgallium (TMG) and triethylgallium (TEG) as gallium precursors are compared. Optimized and saturated TMG/TEG pulse widths were used in order to study the effect of group-III precursors. The films were characterized by grazing incidence x-ray diffraction, atomic force microscopy, x-ray photoelectron spectroscopy, and spectroscopic ellipsometry. Refractive index follows the same trend of crystalline quality, mean grain, and crystallite sizes. GaN layers grown using TMG precursor exhibited improved structural and optical properties when compared to GaN films grown with TEG precursor.

Control of the Structure of Diffusion Layer in Carbon Steels Under Nitriding with Preliminary Deposition of Copper Oxide Catalytic Films

NASA Astrophysics Data System (ADS)

Petrova, L. G.; Aleksandrov, V. A.; Malakhov, A. Yu.

2017-07-01

The effect of thin films of copper oxide deposited before nitriding on the phase composition and the kinetics of growth of diffusion layers in carbon steels is considered. The process of formation of an oxide film involves chemical reduction of pure copper on the surface of steel specimens from a salt solution and subsequent oxidation under air heating. The oxide film exerts a catalytic action in nitriding of low- and medium-carbon steels, which consists in accelerated growth of the diffusion layer, the nitride zone in the first turn. The kinetics of the nitriding process and the phase composition of the layer are controlled by the thickness of the copper oxide precursor, i.e., the deposited copper film.

Atomic layer deposition of a high-k dielectric on MoS2 using trimethylaluminum and ozone.

PubMed

Cheng, Lanxia; Qin, Xiaoye; Lucero, Antonio T; Azcatl, Angelica; Huang, Jie; Wallace, Robert M; Cho, Kyeongjae; Kim, Jiyoung

2014-08-13

We present an Al2O3 dielectric layer on molybdenum disulfide (MoS2), deposited using atomic layer deposition (ALD) with ozone/trimethylaluminum (TMA) and water/TMA as precursors. The results of atomic force microscopy and low-energy ion scattering spectroscopy show that using TMA and ozone as precursors leads to the formation of uniform Al2O3 layers, in contrast to the incomplete coverage we observe when using TMA/H2O as precursors. Our Raman and X-ray photoelectron spectroscopy measurements indicate minimal variations in the MoS2 structure after ozone treatment at 200 °C, suggesting its excellent chemical resistance to ozone.

Microstructural study of brass matrix internal tin multifilamentary Nb3Sn superconductors

NASA Astrophysics Data System (ADS)

Banno, Nobuya; Miyamoto, Yasuo; Tachikawa, Kyoji

2018-03-01

Zn addition to the Cu matrix in internal-tin-processed Nb3Sn superconductors is attractive in terms of the growth kinetics of the Nb3Sn layers. Sn activity is enhanced in the Cu-Zn (brass) matrix, which accelerates Nb3Sn layer formation. Here, we prepared multifilamentary wires using a brass matrix with a Nb core diameter of less than 10 μm and investigated the potential for further Jc improvement through microstructural and microchemical studies. Ti was added into the Sn cores in the precursor wire. Microchemical analysis showed that Ti accumulates between subelements consisting of Nb cores, which blocks Sn diffusion through this region when the spacing between the subelements in the precursor wire is a few microns. The average grain size was found to be about 230 nm through image analysis. To date, matrix Jc values of 1470 and 640 A/mm-2 have been obtained at 12 and 16 T, respectively. The area fraction of Nb cores in the filamentary region of the precursor wire was about 36.3%. There was still some unreacted Nb core area after heat treatment. Insufficient Ti diffusion into the Nb3Sn layers was identified in the outer subelements. These findings suggest that there is still room for improvement in Jc.

Electrical properties of GaN-based metal-insulator-semiconductor structures with Al2O3 deposited by atomic layer deposition using water and ozone as the oxygen precursors

NASA Astrophysics Data System (ADS)

Kubo, Toshiharu; Freedsman, Joseph J.; Iwata, Yasuhiro; Egawa, Takashi

2014-04-01

Al2O3 deposited by atomic layer deposition (ALD) was used as an insulator in metal-insulator-semiconductor (MIS) structures for GaN-based MIS-devices. As the oxygen precursors for the ALD process, water (H2O), ozone (O3), and both H2O and O3 were used. The chemical characteristics of the ALD-Al2O3 surfaces were investigated by x-ray photoelectron spectroscopy. After fabrication of MIS-diodes and MIS-high-electron-mobility transistors (MIS-HEMTs) with the ALD-Al2O3, their electrical properties were evaluated by current-voltage (I-V) and capacitance-voltage (C-V) measurements. The threshold voltage of the C-V curves for MIS-diodes indicated that the fixed charge in the Al2O3 layer is decreased when using both H2O and O3 as the oxygen precursors. Furthermore, MIS-HEMTs with the H2O + O3-based Al2O3 showed good dc I-V characteristics without post-deposition annealing of the ALD-Al2O3, and the drain leakage current in the off-state region was suppressed by seven orders of magnitude.

Electric Pulse Discharge Activated Carbon Supercapacitors for Transportation Application

NASA Astrophysics Data System (ADS)

Nayak, Subhadarshi; Agrawal, Jyoti

2012-03-01

ScienceTomorrow is developing a high-speed, low-cost process for synthesizing high-porosity electrodes for electrochemical double-layer capacitors. Four types of coal (lignite, subbituminous, bituminous, and anthracite) were used as precursor materials for spark discharge activation with multiscale porous structure. The final porosity and pore distribution depended, among other factors, on precursor type. The high gas content in low-grade carbon resulted in mechanical disintegration, whereas high capacitance was attained in higher-grade coal. The properties, including capacitance, mechanical robustness, and internal conductivity, were excellent when the cost is taken into consideration.

Purification of carbon nanotubes via selective heating

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rogers, John A.; Wilson, William L.; Jin, Sung Hun

The present invention provides methods for purifying a layer of carbon nanotubes comprising providing a precursor layer of substantially aligned carbon nanotubes supported by a substrate, wherein the precursor layer comprises a mixture of first carbon nanotubes and second carbon nanotubes; selectively heating the first carbon nanotubes; and separating the first carbon nanotubes from the second carbon nanotubes, thereby generating a purified layer of carbon nanotubes. Devices benefiting from enhanced electrical properties enabled by the purified layer of carbon nanotubes are also described.

Chemical solution-deposited PbZr 0.53 Ti 0.47 O3 on La 0.5 Sr 0.5 Co O3. SIMS investigation of the effect of different precursor additives on the layer structure.

PubMed

Pollak, C; Malic, B; Kosec, M; Javoric, S; Hutter, H

2002-10-01

Chemical solution-deposited thin films of PbZr(0.53)Ti(0.47)O(3)/La(0.5)Sr(0.5)CoO(3) on Pt/TiO(2)/SiO(2)/Si substrates have been investigated by dynamic SIMS. The PbZr(0.53)Ti(0.47)O(3) (PZT) is intended to serve as a ferroelectric layer for microelectronic or microelectromechanical applications; conducting La(0.5)Sr(0.5)CoO(3) (LSCO) is a buffer layer intended to eliminate fatigue effects which usually occur at the Pt/PZT interface. Depth profiles of the main components were obtained and revealed that significant diffusion occurred during the deposition and crystallisation processes. Two types of sample, with different thickness of PZT and different types of poly(vinyl alcohol) (PVA) added to the LSCO precursor, were investigated.

Effect of Group-III precursors on unintentional gallium incorporation during epitaxial growth of InAlN layers by metalorganic chemical vapor deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Jeomoh, E-mail: jkim610@gatech.edu; Ji, Mi-Hee; Detchprohm, Theeradetch

2015-09-28

Unintentional incorporation of gallium (Ga) in InAlN layers grown with different molar flow rates of Group-III precursors by metalorganic chemical vapor deposition has been experimentally investigated. The Ga mole fraction in the InAl(Ga)N layer was increased significantly with the trimethylindium (TMIn) flow rate, while the trimethylaluminum flow rate controls the Al mole fraction. The evaporation of metallic Ga from the liquid phase eutectic system between the pyrolized In from injected TMIn and pre-deposited metallic Ga was responsible for the Ga auto-incorporation into the InAl(Ga)N layer. The theoretical calculation on the equilibrium vapor pressure of liquid phase Ga and the effectivemore » partial pressure of Group-III precursors based on growth parameters used in this study confirms the influence of Group-III precursors on Ga auto-incorporation. More Ga atoms can be evaporated from the liquid phase Ga on the surrounding surfaces in the growth chamber and then significant Ga auto-incorporation can occur due to the high equilibrium vapor pressure of Ga comparable to effective partial pressure of input Group-III precursors during the growth of InAl(Ga)N layer.« less

Synthesis of Hexagonal Boron Nitride Mono layer: Control of Nucleation and Crystal Morphology

DOE PAGES

Stehle, Yijing Y.; Meyer, III, Harry M.; Unocic, Raymond R.; ...

2015-11-10

Mono layer hexagonal boron nitride (hBN) attracts significant attention due to the potential to be used as a complementary two-dimensional dielectric in fabrication of functional 2D heterostructures. Here we investigate the growth stages of the hBN single crystals and show that hBN crystals change their shape from triangular to truncated triangular and further to hexagonal depending on copper substrate distance from the precursor. We suggest that the observed hBN crystal shape variation is affected by the ratio of boron to nitrogen active species concentrations on the copper surface inside the CVD reactor. Strong temperature dependence reveals the activation energies formore » the hBN nucleation process of similar to 5 eV and crystal growth of similar to 3.5 eV. We also show that the resulting h-BN film morphology is strongly affected by the heating method of borazane precursor and the buffer gas. Elucidation of these details facilitated synthesis of high quality large area monolayer hexagonal boron nitride by atmospheric pressure chemical vapor deposition on copper using borazane as a precursor.« less

Atomic layer deposition of TiO{sub 2} from tetrakis-dimethyl-amido titanium or Ti isopropoxide precursors and H{sub 2}O

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xie Qi; Jiang Yulong; Detavernier, Christophe

2007-10-15

Atomic layer deposition (ALD) of TiO{sub 2} thin films using Ti isopropoxide and tetrakis-dimethyl-amido titanium (TDMAT) as two kinds of Ti precursors and water as another reactant was investigated. TiO{sub 2} films with high purity can be grown in a self-limited ALD growth mode by using either Ti isopropoxide or TDMAT as Ti precursors. Different growth behaviors as a function of deposition temperature were observed. A typical growth rate curve-increased growth rate per cycle (GPC) with increasing temperatures was observed for the TiO{sub 2} film deposited by Ti isopropoxide and H{sub 2}O, while surprisingly high GPC was observed at lowmore » temperatures for the TiO{sub 2} film deposited by TDMAT and H{sub 2}O. An energetic model was proposed to explain the different growth behaviors with different precursors. Density functional theory (DFT) calculation was made. The GPC in the low temperature region is determined by the reaction energy barrier. From the experimental results and DFT calculation, we found that the intermediate product stability after the ligand exchange is determined by the desorption behavior, which has a huge effect on the width of the ALD process window.« less

Atomic Layer Deposition of L-Alanine Polypeptide

DOE PAGES

Fu, Yaqin; Li, Binsong; Jiang, Ying-Bing; ...

2014-10-30

L-Alanine polypeptide thin films were synthesized via atomic layer deposition (ALD). Rather, instead of using an amino acid monomer as the precursor, an L-alanine amino acid derivatized with a protecting group was used to prevent self-polymerization, increase the vapor pressure, and allow linear cycle-by-cycle growth emblematic of ALD. Moreover, the successful deposition of a conformal polypeptide film has been confirmed by FTIR, TEM, and Mass Spectrometry, and the ALD process has been extended to polyvaline.

Lithosphere-Atmosphere-Ionosphere Coupling (LAIC) Model - An Unified Concept for Earthquake Precursors Validation

NASA Technical Reports Server (NTRS)

Pulinets, S.; Ouzounov, D.

2010-01-01

The paper presents a conception of complex multidisciplinary approach to the problem of clarification the nature of short-term earthquake precursors observed in atmosphere, atmospheric electricity and in ionosphere and magnetosphere. Our approach is based on the most fundamental principles of tectonics giving understanding that earthquake is an ultimate result of relative movement of tectonic plates and blocks of different sizes. Different kind of gases: methane, helium, hydrogen, and carbon dioxide leaking from the crust can serve as carrier gases for radon including underwater seismically active faults. Radon action on atmospheric gases is similar to the cosmic rays effects in upper layers of atmosphere: it is the air ionization and formation by ions the nucleus of water condensation. Condensation of water vapor is accompanied by the latent heat exhalation is the main cause for observing atmospheric thermal anomalies. Formation of large ion clusters changes the conductivity of boundary layer of atmosphere and parameters of the global electric circuit over the active tectonic faults. Variations of atmospheric electricity are the main source of ionospheric anomalies over seismically active areas. Lithosphere-Atmosphere-Ionosphere Coupling (LAIC) model can explain most of these events as a synergy between different ground surface, atmosphere and ionosphere processes and anomalous variations which are usually named as short-term earthquake precursors. A newly developed approach of Interdisciplinary Space-Terrestrial Framework (ISTF) can provide also a verification of these precursory processes in seismically active regions. The main outcome of this paper is the unified concept for systematic validation of different types of earthquake precursors united by physical basis in one common theory.

TOPICAL REVIEW: Review of a chemical approach to YBa2Cu3O7-x-coated superconductors—metalorganic deposition using trifluoroacetates

NASA Astrophysics Data System (ADS)

Araki, Takeshi; Hirabayashi, Izumi

2003-11-01

Large-area, uniform, high critical current density (Jc) YBa2Cu3O7-x (YBCO) superconductor films are now routinely obtained by metalorganic deposition using trifluoroacetates (TFA-MOD). This method does not require any expensive vacuum apparatus at any time during the whole process. Thus, TFA-MOD is regarded as one of the most suitable candidates for fabricating a YBCO tape for many high-power applications. This method originated from an electron beam process using BaF2 developed by Mankiewich et al. Afterwards, Gupta et al reported using TFA-MOD to prepare a similar precursor film. These two ex situ processes used fluorides instead of BaCO3 to avoid the fatal deterioration in Jc, which is caused in the resulting films through metal carboxylic groups. Fluorides not only avoid such deterioration but also lead to perfectly c-axis-oriented epitaxial crystal growth. In conventional metalorganic deposition, nucleation in the precursor film causes random orientation in the resulting film. However, in TFA-MOD, nanocrystallites in the precursor film never cause such disorder. Furthermore, during the firing process of TFA-MOD, water and HF gas diffuse quickly between the film surface and growth front of the YBCO layer. This diffusion never limits the growth rate of YBCO. What distinguishes TFA-MOD from conventional metalorganic deposition? What happens during heat treatment? In this paper, we discuss all the TFA-MOD processes and the peculiar growth scheme of the YBCO layer in TFA-MOD using the model of a quasi-liquid network. In addition, we review the history of TFA-MOD and recent results and discuss the prospects of future applications.

Spray CVD for Making Solar-Cell Absorber Layers

NASA Technical Reports Server (NTRS)

Banger, Kulbinder K.; Harris, Jerry; Jin, Michael H.; Hepp, Aloysius

2007-01-01

Spray chemical vapor deposition (spray CVD) processes of a special type have been investigated for use in making CuInS2 absorber layers of thin-film solar photovoltaic cells from either of two subclasses of precursor compounds: [(PBu3) 2Cu(SEt)2In(SEt)2] or [(PPh3)2Cu(SEt)2 In(SEt)2]. The CuInS2 films produced in the experiments have been characterized by x-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, and four-point-probe electrical tests.

Atomic layer deposition of Al{sub 2}O{sub 3} for single electron transistors utilizing Pt oxidation and reduction

DOE Office of Scientific and Technical Information (OSTI.GOV)

McConnell, Michael S., E-mail: mmcconn5@nd.edu; Schneider, Louisa C.; Karbasian, Golnaz

This work describes the fabrication of single electron transistors using electron beam lithography and atomic layer deposition to form nanoscale tunnel transparent junctions of alumina (Al{sub 2}O{sub 3}) on platinum nanowires using either water or ozone as the oxygen precursor and trimethylaluminum as the aluminum precursor. Using room temperature, low frequency conductance measurements between the source and drain, it was found that devices fabricated using water had higher conductance than devices fabricated with ozone. Subsequent annealing caused both water- and ozone-based devices to increase in conductance by more than 2 orders of magnitude. Furthermore, comparison of devices at low temperaturesmore » (∼4 K) showed that annealed devices displayed much closer to the ideal behavior (i.e., constant differential conductance) outside of the Coulomb blockade region and that untreated devices showed nonlinear behavior outside of the Coulomb blockade region (i.e., an increase in differential conductance with source-drain voltage bias). Transmission electron microscopy cross-sectional images showed that annealing did not significantly change device geometry, but energy dispersive x-ray spectroscopy showed an unusually large amount of oxygen in the bottom platinum layer. This suggests that the atomic layer deposition process results in the formation of a thin platinum surface oxide, which either decomposes or is reduced during the anneal step, resulting in a tunnel barrier without the in-series native oxide contribution. Furthermore, the difference between ozone- and water-based devices suggests that ozone promotes atomic layer deposition nucleation by oxidizing the surface but that water relies on physisorption of the precursors. To test this theory, devices were exposed to forming gas at room temperature, which also reduces platinum oxide, and a decrease in resistance was observed, as expected.« less

Self-Functionalization Behind a Solution-Processed NiOx Film Used As Hole Transporting Layer for Efficient Perovskite Solar Cells.

PubMed

Ciro, John; Ramírez, Daniel; Mejía Escobar, Mario Alejandro; Montoya, Juan Felipe; Mesa, Santiago; Betancur, Rafael; Jaramillo, Franklin

2017-04-12

Fabrication of solution-processed perovskite solar cells (PSCs) requires the deposition of high quality films from precursor inks. Frequently, buffer layers of PSCs are formed from dispersions of metal oxide nanoparticles (NPs). Therefore, the development of trustable methods for the preparation of stable colloidal NPs dispersions is crucial. In this work, a novel approach to form very compact semiconducting buffer layers with suitable optoelectronic properties is presented through a self-functionalization process of the nanocrystalline particles by their own amorphous phase and without adding any other inorganic or organic functionalization component or surfactant. Such interconnecting amorphous phase composed by residual nitrate, hydroxide, and sodium ions, proved to be fundamental to reach stable colloidal dispersions and contribute to assemble the separate crystalline nickel oxide NPs in the final film, resulting in a very homogeneous and compact layer. A proposed mechanism behind the great stabilization of the nanoparticles is exposed. At the end, the self-functionalized nickel oxide layer exhibited high optoelectronic properties enabling perovskite p-i-n solar cells as efficient as 16.6% demonstrating the pertinence of the presented strategy to obtain high quality buffer layers processed in solution at room temperature.

A novel precursor system and its application to produce tin doped indium oxide.

PubMed

Veith, M; Bubel, C; Zimmer, M

2011-06-14

A new type of precursor has been developed by molecular design and synthesised to produce tin doped indium oxide (ITO). The precursor consists of a newly developed bimetallic indium tin alkoxide, Me(2)In(O(t)Bu)(3)Sn (Me = CH(3), O(t)Bu = OC(CH(3))(3)), which is in equilibrium with an excess of Me(2)In(O(t)Bu). This quasi single-source precursor is applied in a sol-gel process to produce powders and coatings of ITO using a one-step heat treatment process under an inert atmosphere. The main advantage of this system is the simple heat treatment that leads to the disproportionation of the bivalent Sn(II) precursor into Sn(IV) and metallic tin, resulting in an overall reduced state of the metal in the final tin doped indium oxide (ITO) material, hence avoiding the usually necessary reduction step. Solid state (119)Sn-NMR measurements of powder samples confirm the appearance of Sn(II) in an amorphous gel state and of metallic tin after annealing under nitrogen. The corresponding preparation of ITO coatings by spin coating on glass leads to transparent conductive layers with a high transmittance of visible light and a low electrical resistivity without the necessity of a reduction step.

Confined-plume chemical deposition: rapid synthesis of crystalline coatings of known hard or superhard materials on inorganic or organic supports by resonant IR decomposition of molecular precursors.

PubMed

Ivanov, Borislav L; Wellons, Matthew S; Lukehart, Charles M

2009-08-26

A one-step process for preparing microcrystalline coatings of known superhard, very hard, or ultraincompressible ceramic compositions on either inorganic or organic supports is reported. Midinfrared pulsed-laser irradiation of preceramic chemical precursors layered between IR-transmissive hard/soft supports under temporal and spatial confinement at a laser wavelength resonant with a precursor vibrational band gives one-step deposition of crystalline ceramic coatings without incurring noticeable collateral thermal damage to the support material. Reaction plume formation at the precursor/laser beam interface initiates confined-plume, chemical deposition (CPCD) of crystalline ceramic product. Continuous ceramic coatings are produced by rastering the laser beam over a sample specimen. CPCD processing of the Re-B single-source precursor, (B(3)H(8))Re(CO)(4), the dual-source mixtures, Ru(3)(CO)(12)/B(10)H(14) or W(CO)(6)/B(10)H(14), and the boron/carbon single-source precursor, o-B(10)C(2)H(12), confined between Si wafer or NaCl plates gives microcrystalline deposits of ReB(2), RuB(2), WB(4), or B(4)C, respectively. CPCD processing of Kevlar fabric wetted by (B(3)H(8))Re(CO)(4) produces an oriented, microcrystalline coating of ReB(2) on the Kevlar fabric without incurring noticeable thermal damage of the polymer support. Similarly, microcrystalline coatings of ReB(2) can be formed on IR-transmissive IR2, Teflon, or Ultralene polymer films.

Fibrous selective emitter structures from sol-gel process

NASA Astrophysics Data System (ADS)

Chen, K. C.

1999-03-01

Selective emitters have the potential benefit of high efficiency due to the matching of emission spectra to the response of photovoltaic (PV) cells. Continuous uniform rare-earth oxide selective emitter fibers were successfully fabricated using a viscous solution made from metal organic precursors. Cylindrical- and planar configuration emitter structures were made by direct cross-winding or stacking of precursor fiber layers. The combustion and optical performance of the planar emitter structures were tested. The results indicates that both the designing of the fiber packing density and the thickness is critical for high photon and power output.

Fluidized bed coupled rotary reactor for nanoparticles coating via atomic layer deposition

NASA Astrophysics Data System (ADS)

Duan, Chen-Long; Liu, Xiao; Shan, Bin; Chen, Rong

2015-07-01

A fluidized bed coupled rotary reactor has been designed for coating on nanoparticles (NPs) via atomic layer deposition. It consists of five major parts: reaction chamber, dosing and fluidizing section, pumping section, rotary manipulator components, as well as a double-layer cartridge for the storage of particles. In the deposition procedure, continuous fluidization of particles enlarges and homogenizes the void fraction in the particle bed, while rotation enhances the gas-solid interactions to stabilize fluidization. The particle cartridge presented here enables both the fluidization and rotation acting on the particle bed, demonstrated by the analysis of pressure drop. Moreover, enlarged interstitials and intense gas-solid contact under sufficient fluidizing velocity and proper rotation speed facilitate the precursor delivery throughout the particle bed and consequently provide a fast coating process. The cartridge can ensure precursors flowing through the particle bed exclusively to achieve high utilization without static exposure operation. By optimizing superficial gas velocities and rotation speeds, minimum pulse time for complete coating has been shortened in experiment, and in situ mass spectrometry showed the precursor usage can reach 90%. Inductively coupled plasma-optical emission spectroscopy results suggested a saturated growth of nanoscale Al2O3 films on spherical SiO2 NPs. Finally, the uniformity and composition of the shells were characterized by high angle annular dark field-transmission electron microscopy and energy dispersive X-ray spectroscopy.

TiO2/WO3 photoactive bilayers in the UV-Vis light region

NASA Astrophysics Data System (ADS)

Vasilaki, E.; Vernardou, D.; Kenanakis, G.; Vamvakaki, M.; Katsarakis, N.

2017-04-01

In this work, photoactive bilayered films consisting of anatase TiO2 and monoclinic WO3 were synthesized by a sol-gel route. Titanium isopropoxide and tungsten hexachloride were used as metal precursors and deposition was achieved by spin-coating on Corning glass substrates. The samples were characterized by X-ray diffraction, photoluminescence, UV-Vis, and Raman spectroscopy, as well as field emission scanning electron microscopy. The prepared immobilized catalysts were tested for their photocatalytic performance by the decolorization of methylene blue in aqueous matrices, under UV-Vis light irradiation. The annealing process influenced the crystallinity of the bilayered films, while the concentration of the tungsten precursor solution and the position of the tungsten trioxide layer further affected their photocatalytic performance. In particular, the photocatalytic performance of the bilayered films was optimized at a concentration of 0.1 M of the WO3 precursor solution, when deposited as an overlying layer on TiO2 by two annealing steps ( 76% methylene blue decolorization in 300 min of irradiation versus 59% in the case of a bare TiO2 film). In general, the coupled layer catalysts exhibited superior photoactivity compared to that of bare TiO2 films with WO3 acting as an electron trap, resulting, therefore, in a more efficient electron-hole separation and inhibiting their recombination.

Three-dimensional bioprinting of rat embryonic neural cells.

PubMed

Lee, Wonhye; Pinckney, Jason; Lee, Vivian; Lee, Jong-Hwan; Fischer, Krisztina; Polio, Samuel; Park, Je-Kyun; Yoo, Seung-Schik

2009-05-27

We present a direct cell printing technique to pattern neural cells in a three-dimensional (3D) multilayered collagen gel. A layer of collagen precursor was printed to provide a scaffold for the cells, and the rat embryonic neurons and astrocytes were subsequently printed on the layer. A solution of sodium bicarbonate was applied to the cell containing collagen layer as nebulized aerosols, which allowed the gelation of the collagen. This process was repeated layer-by-layer to construct the 3D cell-hydrogel composites. Upon characterizing the relationship between printing resolutions and the growth of printed neural cells, single/multiple layers of neural cell-hydrogel composites were constructed and cultured. The on-demand capability to print neural cells in a multilayered hydrogel scaffold offers flexibility in generating artificial 3D neural tissue composites.

Silicone Resin Applications for Ceramic Precursors and Composites

PubMed Central

Narisawa, Masaki

2010-01-01

This article reviews the applications of silicone resins as ceramic precursors. The historical background of silicone synthesis chemistry is introduced to explain the production costs and supply availability of various silicones. Thermal degradation processes of silicones are classified in terms of the main chain structure and cyclic oligomer expulsion process, which determine the resulting ceramic yield and the chemical composition. The high temperature decomposition of Si-O-C beyond 1,400 °C in an inert atmosphere and formation of a protective silica layer on material surfaces beyond 1,200 °C in an oxidative atmosphere are discussed from the viewpoints of the wide chemical composition of the Si-O-C materials. Applications of the resins for binding agents, as starting materials for porous ceramics, matrix sources with impregnation, fiber spinning and ceramic adhesions are introduced. The recent development of the process of filler or cross-linking agent additions to resin compounds is also introduced. Such resin compounds are useful for obtaining thick coatings, MEMS parts and bulk ceramics, which are difficult to obtain by pyrolysis of simple organometallic precursors without additives.

Facile preparation in two steps of highly hydrophobic coatings on polypropylene surface

NASA Astrophysics Data System (ADS)

Petcu, Cristian; Nistor, Cristina Lavinia; Purcar, Violeta; Cinteză, Ludmila Otilia; Spătaru, Cătălin-Ilie; Ghiurea, Marius; Ianchiş, Raluca; Anastasescu, Mihai; Stoica, Mihai

2015-08-01

Monolayer and bilayer coatings deposited on polypropylene (PP) surface were prepared by sol-gel process at room temperature. Monolayer coatings were produced from sol-gel acidic solutions, containing tetraethylorthosilicate (TEOS) and different co-precursors such as phenyltriethoxysilane (PhTES), octylmethyldimethoxysilane (OMDMS) and dodecyltriethoxysilane (DOTES). Bilayer coatings consist of one layer prepared in a similar way described for monolayer coatings, followed by a second layer, obtained from fluorinated silica nanoparticles dispersion. The fluorinated group has been confirmed by the presence of Csbnd F bonds along with network Sisbnd Osbnd Si vibrational mode. Water contact angle values registered for bilayer-coated polypropylene are higher, comparing with the reference (pristine PP) and with the monolayer-coated substrate, and varies as a function of the hydrophobic functional groups of the silica co-precursors: phenyl < octyl < dodecyl. The fluorooctyl functions lead to a significant decrease in the surface energy values for bilayer coating, with very small values of polar component.

Giving Bigger Satellites a Boost

NASA Technical Reports Server (NTRS)

2000-01-01

Ultramet, Inc. has spurred a new process for producing rocket engine thrust chambers, through SBIR funding and the Glenn Research Center. High-temperature oxidation-resistant thruster materials are being produced in order to achieve high-temperature capability without sacrificing reliability. These thruster materials lead to an estimated three-percent improvement in propulsion system performance. To develop this material, Ultramet used a process called chemical vapor deposition (CVD). CVD involves heating precursors for metals, like iridium and rhenium, to temperatures at which they become gaseous. They are then deposited onto a mandrel, or spindle, layer-by-layer to produce high-density, highly resistant materials from the inside out.

Plasma characterization studies for materials processing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pfender, E.; Heberlein, J.

New applications for plasma processing of materials require a more detailed understanding of the fundamental processes occurring in the processing reactors. We have developed reactors offering specific advantages for materials processing, and we are using modeling and diagnostic techniques for the characterization of these reactors. The emphasis is in part set by the interest shown by industry pursuing specific plasma processing applications. In this paper we report on the modeling of radio frequency plasma reactors for use in materials synthesis, and on the characterization of the high rate diamond deposition process using liquid precursors. In the radio frequency plasma torchmore » model, the influence of specific design changes such as the location of the excitation coil on the enthalpy flow distribution is investigated for oxygen and air as plasma gases. The diamond deposition with liquid precursors has identified the efficient mass transport in form of liquid droplets into the boundary layer as responsible for high growth, and the chemical properties of the liquid for the film morphology.« less

Chemical solution deposition method of fabricating highly aligned MgO templates

DOEpatents

Paranthaman, Mariappan Parans [Knoxville, TN; Sathyamurthy, Srivatsan [Knoxville, TN; Aytug, Tolga [Knoxville, TN; Arendt, Paul N [Los Alamos, NM; Stan, Liliana [Los Alamos, NM; Foltyn, Stephen R [Los Alamos, NM

2012-01-03

A superconducting article includes a substrate having an untextured metal surface; an untextured barrier layer of La.sub.2Zr.sub.2O.sub.7 or Gd.sub.2Zr.sub.2O.sub.7 supported by and in contact with the surface of the substrate; a biaxially textured buffer layer supported by the untextured barrier layer; and a biaxially textured superconducting layer supported by the biaxially textured buffer layer. Moreover, a method of forming a buffer layer on a metal substrate includes the steps of: providing a substrate having an untextured metal surface; coating the surface of the substrate with a barrier layer precursor; converting the precursor to an untextured barrier layer; and depositing a biaxially textured buffer layer above and supported by the untextured barrier layer.

P-polarized reflectance spectroscopy: A high sensitive real-time monitoring technique to study surface kinetics under steady state epitaxial deposition conditions

NASA Technical Reports Server (NTRS)

Dietz, Nikolaus; Bachmann, Klaus J.

1995-01-01

This paper describes the results of real-time optical monitoring of epitaxial growth processes by p-polarized reflectance spectroscopy (PRS) using a single wavelength application under pulsed chemical beam epitaxy (PCBE) condition. The high surface sensitivity of PRS allows the monitoring of submonolayer precursors coverage on the surface as shown for GaP homoepitaxy and GaP on Si heteroepitaxy as examples. In the case of heteroepitaxy, the growth rate and optical properties are revealed by PRS using interference oscillations as they occur during growth. Super-imposed on these interference oscillations, the PRS signal exhibits a fine structure caused by the periodic alteration of the surface chemistry by the pulsed supply of chemical precursors. This fine structure is modeled under conditions where the surface chemistry cycles between phosphorus supersaturated and phosphorus depleted surfaces. The mathematical model describes the fine structure using a surface layer that increases during the tertiarybutyl phosphine (TBP) supply and decreases during and after the triethylgallium (TEG) pulse, which increases the growing GaP film thickness. The imaginary part of the dielectric function of the surface layer is revealed from the turning points in the fine structure, where the optical response to the first precursor pulse in the cycle sequence changes sign. The amplitude of the fine structure is determined by the surface layer thickness and the complex dielectric functions for the surface layer with the underlying bulk film. Surface kinetic data can be obtained by analyzing the rise and decay transients of the fine structure.

Self-cleaning and surface chemical reactions during hafnium dioxide atomic layer deposition on indium arsenide.

PubMed

Timm, Rainer; Head, Ashley R; Yngman, Sofie; Knutsson, Johan V; Hjort, Martin; McKibbin, Sarah R; Troian, Andrea; Persson, Olof; Urpelainen, Samuli; Knudsen, Jan; Schnadt, Joachim; Mikkelsen, Anders

2018-04-12

Atomic layer deposition (ALD) enables the ultrathin high-quality oxide layers that are central to all modern metal-oxide-semiconductor circuits. Crucial to achieving superior device performance are the chemical reactions during the first deposition cycle, which could ultimately result in atomic-scale perfection of the semiconductor-oxide interface. Here, we directly observe the chemical reactions at the surface during the first cycle of hafnium dioxide deposition on indium arsenide under realistic synthesis conditions using photoelectron spectroscopy. We find that the widely used ligand exchange model of the ALD process for the removal of native oxide on the semiconductor and the simultaneous formation of the first hafnium dioxide layer must be significantly revised. Our study provides substantial evidence that the efficiency of the self-cleaning process and the quality of the resulting semiconductor-oxide interface can be controlled by the molecular adsorption process of the ALD precursors, rather than the subsequent oxide formation.

Novel Chemical Process for Producing Chrome Coated Metal

PubMed Central

Pelar, Christopher; Greenaway, Karima; Zea, Hugo; Wu, Chun-Hsien

2018-01-01

This work demonstrates that a version of the Reduction Expansion Synthesis (RES) process, Cr-RES, can create a micron scale Cr coating on an iron wire. The process involves three steps. I. A paste consisting of a physical mix of urea, chrome nitrate or chrome oxide, and water is prepared. II. An iron wire is coated by dipping. III. The coated, and dried, wire is heated to ~800 °C for 10 min in a tube furnace under a slow flow of nitrogen gas. The processed wires were then polished and characterized, primarily with scanning electron microscopy (SEM). SEM indicates the chrome layer is uneven, but only on the scale of a fraction of a micron. The evidence of porosity is ambiguous. Elemental mapping using SEM electron microprobe that confirmed the process led to the formation of a chrome metal layer, with no evidence of alloy formation. Additionally, it was found that thickness of the final Cr layer correlated with the thickness of the precursor layer that was applied prior to the heating step. Potentially, this technique could replace electrolytic processing, a process that generates carcinogenic hexavalent chrome, but further study and development is needed. PMID:29303977

Novel Chemical Process for Producing Chrome Coated Metal.

PubMed

Pelar, Christopher; Greenaway, Karima; Zea, Hugo; Wu, Chun-Hsien; Luhrs, Claudia C; Phillips, Jonathan

2018-01-05

This work demonstrates that a version of the Reduction Expansion Synthesis (RES) process, Cr-RES, can create a micron scale Cr coating on an iron wire. The process involves three steps. I. A paste consisting of a physical mix of urea, chrome nitrate or chrome oxide, and water is prepared. II. An iron wire is coated by dipping. III. The coated, and dried, wire is heated to ~800 °C for 10 min in a tube furnace under a slow flow of nitrogen gas. The processed wires were then polished and characterized, primarily with scanning electron microscopy (SEM). SEM indicates the chrome layer is uneven, but only on the scale of a fraction of a micron. The evidence of porosity is ambiguous. Elemental mapping using SEM electron microprobe that confirmed the process led to the formation of a chrome metal layer, with no evidence of alloy formation. Additionally, it was found that thickness of the final Cr layer correlated with the thickness of the precursor layer that was applied prior to the heating step. Potentially, this technique could replace electrolytic processing, a process that generates carcinogenic hexavalent chrome, but further study and development is needed.

"Nickel Nanoflowers" with Surface-Attached Fluoropolymer Networks by C,H Insertion for the Generation of Metallic Superhydrophobic Surfaces.

PubMed

Hönes, Roland; Rühe, Jürgen

2018-05-08

Metallic superhydrophobic surfaces (SHSs) combine the attractive properties of metals, such as ductility, hardness, and conductivity, with the favorable wetting properties of nanostructured surfaces. Moreover, they promise additional benefits with respect to corrosion protection. For the modification of the intrinsically polar and hydrophilic surfaces of metals, a new method has been developed to deposit a long-term stable, highly hydrophobic coating, using nanostructured Ni surfaces as an example. Such substrates were chosen because the deposition of a thin Ni layer is a common choice for enhancing corrosion resistance of other metals. As the hydrophobic coating, we propose a thin film of an extremely hydrophobic fluoropolymer network. To form this network, a thin layer of a fluoropolymer precursor is deposited on the Ni substrate which includes a comonomer that is capable of C,H insertion cross-linking (CHic). Upon UV irradiation or heating, the cross-linker units become activated and the thin glassy film of the precursor is transformed into a polymer network that coats the surface conformally and permanently, as shown by extensive extraction experiments. To achieve an even higher stability, the same precursor film can also be transformed into a chemically surface-attached network by depositing a self-assembled monolayer of an alkane phosphonic acid on the Ni before coating with the precursor. During cross-linking, by the same chemical process, the growing polymer network will simultaneously attach to the alkane phosphonic acid layer at the surface of the metal. This strategy has been used to turn fractal Ni "nanoflower" surfaces grown by anisotropic electroplating into SHSs. The wetting characteristics of the obtained nanostructured metallic surfaces are studied. Additionally, the corrosion protection effect and the significant mechanical durability are demonstrated.

Simultaneous growth of self-patterned carbon nanotube forests with dual height scales

NASA Astrophysics Data System (ADS)

Sam, Ebru Devrim; Kucukayan-Dogu, Gokce; Baykal, Beril; Dalkilic, Zeynep; Rana, Kuldeep; Bengu, Erman

2012-05-01

In this study, we report on a unique, one-step fabrication technique enabling the simultaneous synthesis of vertically aligned multi-walled carbon nanotubes (VA-MWCNTs) with dual height scales through alcohol catalyzed chemical vapor deposition (ACCVD). Regions of VA-MWCNTs with different heights were well separated from each other leading to a self-patterning on the surface. We devised a unique layer-by-layer process for application of catalyst and inhibitor precursors on oxidized Si (100) surfaces before the ACCVD step to achieve a hierarchical arrangement. Patterning could be controlled by adjusting the molarity and application sequence of precursors. Contact angle measurements on these self-patterned surfaces indicated that manipulation of these hierarchical arrays resulted in a wide range of hydrophobic behavior changing from that of a sticky rose petal to a lotus leaf.In this study, we report on a unique, one-step fabrication technique enabling the simultaneous synthesis of vertically aligned multi-walled carbon nanotubes (VA-MWCNTs) with dual height scales through alcohol catalyzed chemical vapor deposition (ACCVD). Regions of VA-MWCNTs with different heights were well separated from each other leading to a self-patterning on the surface. We devised a unique layer-by-layer process for application of catalyst and inhibitor precursors on oxidized Si (100) surfaces before the ACCVD step to achieve a hierarchical arrangement. Patterning could be controlled by adjusting the molarity and application sequence of precursors. Contact angle measurements on these self-patterned surfaces indicated that manipulation of these hierarchical arrays resulted in a wide range of hydrophobic behavior changing from that of a sticky rose petal to a lotus leaf. Electronic supplementary information (ESI) available: Fig. S1; AFM image of the Co-O layer which was first dried at 40 °C and then oxidized at 200 °C. Fig. S2; graph relative to the area of CNT islands for different catalyst configurations. Fig. S3; representative XPS spectra of (a) Si 2p, (b) Al 2p, (c) Fe 2p and (d) Co 2p for a reduced Al/Fe/Al/Co (20/20/20/20) catalyst film (grey line in all figures shows the peak backgrounds and orange line shows the curve fitted). Contact angle movies, Video S1 and Video S2, of Al/Fe/Al/Co samples 40/20/20/20 and 20/40/20/20, respectively. See DOI: 10.1039/c2nr30258f

Understanding the Mechanism of SiC Plasma-Enhanced Chemical Vapor Deposition (PECVD) and Developing Routes toward SiC Atomic Layer Deposition (ALD) with Density Functional Theory.

PubMed

Filatova, Ekaterina A; Hausmann, Dennis; Elliott, Simon D

2018-05-02

Understanding the mechanism of SiC chemical vapor deposition (CVD) is an important step in investigating the routes toward future atomic layer deposition (ALD) of SiC. The energetics of various silicon and carbon precursors reacting with bare and H-terminated 3C-SiC (011) are analyzed using ab initio density functional theory (DFT). Bare SiC is found to be reactive to silicon and carbon precursors, while H-terminated SiC is found to be not reactive with these precursors at 0 K. Furthermore, the reaction pathways of silane plasma fragments SiH 3 and SiH 2 are calculated along with the energetics for the methane plasma fragments CH 3 and CH 2 . SiH 3 and SiH 2 fragments follow different mechanisms toward Si growth, of which the SiH 3 mechanism is found to be more thermodynamically favorable. Moreover, both of the fragments were found to show selectivity toward the Si-H bond and not C-H bond of the surface. On the basis of this, a selective Si deposition process is suggested for silicon versus carbon-doped silicon oxide surfaces.

Parameter Space of Atomic Layer Deposition of Ultrathin Oxides on Graphene

PubMed Central

2016-01-01

Atomic layer deposition (ALD) of ultrathin aluminum oxide (AlOx) films was systematically studied on supported chemical vapor deposition (CVD) graphene. We show that by extending the precursor residence time, using either a multiple-pulse sequence or a soaking period, ultrathin continuous AlOx films can be achieved directly on graphene using standard H2O and trimethylaluminum (TMA) precursors even at a high deposition temperature of 200 °C, without the use of surfactants or other additional graphene surface modifications. To obtain conformal nucleation, a precursor residence time of >2s is needed, which is not prohibitively long but sufficient to account for the slow adsorption kinetics of the graphene surface. In contrast, a shorter residence time results in heterogeneous nucleation that is preferential to defect/selective sites on the graphene. These findings demonstrate that careful control of the ALD parameter space is imperative in governing the nucleation behavior of AlOx on CVD graphene. We consider our results to have model system character for rational two-dimensional (2D)/non-2D material process integration, relevant also to the interfacing and device integration of the many other emerging 2D materials. PMID:27723305

Russian Doll Genes and Complex Chromosome Rearrangements in Oxytricha trifallax

PubMed Central

Braun, Jasper; Nabergall, Lukas; Neme, Rafik; Landweber, Laura F.; Saito, Masahico; Jonoska, Nataša

2018-01-01

Ciliates have two different types of nuclei per cell, with one acting as a somatic, transcriptionally active nucleus (macronucleus; abbr. MAC) and another serving as a germline nucleus (micronucleus; abbr. MIC). Furthermore, Oxytricha trifallax undergoes extensive genome rearrangements during sexual conjugation and post-zygotic development of daughter cells. These rearrangements are necessary because the precursor MIC loci are often both fragmented and scrambled, with respect to the corresponding MAC loci. Such genome architectures are remarkably tolerant of encrypted MIC loci, because RNA-guided processes during MAC development reorganize the gene fragments in the correct order to resemble the parental MAC sequence. Here, we describe the germline organization of several nested and highly scrambled genes in Oxytricha trifallax. These include cases with multiple layers of nesting, plus highly interleaved or tangled precursor loci that appear to deviate from previously described patterns. We present mathematical methods to measure the degree of nesting between precursor MIC loci, and revisit a method for a mathematical description of scrambling. After applying these methods to the chromosome rearrangement maps of O. trifallax we describe cases of nested arrangements with up to five layers of embedded genes, as well as the most scrambled loci in O. trifallax. PMID:29545465

Chemical routes to nanocrystalline and thin-film III-VI and I-III-VI semiconductors

NASA Astrophysics Data System (ADS)

Hollingsworth, Jennifer Ann

1999-11-01

The work encompasses: (1) catalyzed low-temperature, solution-based routes to nano- and microcrystalline III-VI semiconductor powders and (2) spray chemical vapor deposition (spray CVD) of I-III-VI semiconductor thin films. Prior to this work, few, if any, examples existed of chemical catalysis applied to the synthesis of nonmolecular, covalent solids. New crystallization strategies employing catalysts were developed for the regioselective syntheses of orthorhombic InS (beta-InS), the thermodynamic phase, and rhombohedral InS (R-InS), a new, metastable structural isomer. Growth of beta-InS was facilitated by a solvent-suspended, molten-metal flux in a process similar to the SolutionLiquid-Solid (SLS) growth of InP and GaAs fibers and single-crystal whiskers. In contrast, metastable R-InS, having a pseudo-graphitic layered structure, was prepared selectively when the molecular catalyst, benzenethiol, was present in solution and the inorganic "catalyst" (metal flux) was not present. In the absence of any crystal-growth facilitator, metal flux or benzenethiol, amorphous product was obtained under the mild reaction conditions employed (T ≤ 203°C). The inorganic and organic catalysts permitted the regio-selective syntheses of InS and were also successfully applied to the growth of network and layered InxSey compounds, respectively, as well as nanocrystalline In2S3. Extensive microstructural characterization demonstrated that the layered compounds grew as fullerene-like nanostructures and large, colloidal single crystals. Films of the I-III-VI compounds, CuInS2, CuGaS2, and Cu(In,Ga)S 2, were deposited by spray CVD using the known single-source metalorganic precursor, (Ph3P)2CuIn(SEt)4, a new precursor, (Ph3P)2CuGa(SEt)3, and a mixture of the two precursors, respectively. The CulnS2 films exhibited a variety of microstructures from dense and faceted or platelet-like to porous and dendritic. Crystallographic orientations ranged from strongly [112] to strongly [220] oriented. Microstructure, orientation, and growth kinetics were controlled by changing processing parameters: carrier-gas flow rate, substrate temperature, and precursor-solution concentration. Low resistivities (<50 O cm) were associated with [220]-oriented films. All CuInS2 films were approximately stoichiometric and had the desired bandgap (Eg ≅ 1.4 eV) for application as the absorber layer in thin-film photovoltaic devices.

Low-temperature fabrication of an HfO2 passivation layer for amorphous indium-gallium-zinc oxide thin film transistors using a solution process.

PubMed

Hong, Seonghwan; Park, Sung Pyo; Kim, Yeong-Gyu; Kang, Byung Ha; Na, Jae Won; Kim, Hyun Jae

2017-11-24

We report low-temperature solution processing of hafnium oxide (HfO 2 ) passivation layers for amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistors (TFTs). At 150 °C, the hafnium chloride (HfCl 4 ) precursor readily hydrolyzed in deionized (DI) water and transformed into an HfO 2 film. The fabricated HfO 2 passivation layer prevented any interaction between the back surface of an a-IGZO TFT and ambient gas. Moreover, diffused Hf 4+ in the back-channel layer of the a-IGZO TFT reduced the oxygen vacancy, which is the origin of the electrical instability in a-IGZO TFTs. Consequently, the a-IGZO TFT with the HfO 2 passivation layer exhibited improved stability, showing a decrease in the threshold voltage shift from 4.83 to 1.68 V under a positive bias stress test conducted over 10,000 s.

In situ spectroscopic ellipsometry study of low-temperature epitaxial silicon growth

NASA Astrophysics Data System (ADS)

Halagačka, L.; Foldyna, M.; Leal, R.; Roca i Cabarrocas, P.

2018-07-01

Low-temperature growth of doped epitaxial silicon layers is a promising way to reduce the cost of p-n junction formation in c-Si solar cells. In this work, we study process of highly doped epitaxial silicon layer growth using in situ spectroscopic ellipsometry. The film was deposited by plasma-enhanced chemical vapor deposition (PECVD) on a crystalline silicon substrate at a low substrate temperature of 200 °C. In the deposition process, SiF4 was used as a precursor, B2H6 as doping gas, and a hydrogen/argon mixture as carrier gas. A spectroscopic ellipsometer with a wide spectral range was used for in situ spectroscopic measurements. Since the temperature during process is 200 °C, the optical functions of silicon differ from these at room temperature and have to be adjusted. Thickness of the epitaxial silicon layer was fitted on in situ ellipsometric data. As a result we were able to determine the dynamics of epitaxial layer growth, namely initial layer formation time and epitaxial growth rate. This study opens new perspectives in understanding and monitoring the epitaxial silicon deposition processes as the model fitting can be applied directly during the growth.

Improved high temperature integration of Al{sub 2}O{sub 3} on MoS{sub 2} by using a metal oxide buffer layer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Son, Seokki; Choi, Moonseok; Kim, Dohyung

2015-01-12

We deposited a metal oxide buffer layer before atomic layer deposition (ALD) of Al{sub 2}O{sub 3} onto exfoliated molybdenum disulfide (MoS{sub 2}) in order to accomplish enhanced integration. We demonstrate that even at a high temperature, functionalization of MoS{sub 2} by means of a metal oxide buffer layer can effectively provide nucleation sites for ALD precursors, enabling much better surface coverage of Al{sub 2}O{sub 3}. It is shown that using a metal oxide buffer layer not only allows high temperature ALD process, resulting in highly improved quality of Al{sub 2}O{sub 3}/MoS{sub 2} interface, but also leaves MoS{sub 2} intact.

p57KIP2 regulates radial glia and intermediate precursor cell cycle dynamics and lower layer neurogenesis in developing cerebral cortex

PubMed Central

Mairet-Coello, Georges; Tury, Anna; Van Buskirk, Elise; Robinson, Kelsey; Genestine, Matthieu; DiCicco-Bloom, Emanuel

2012-01-01

During cerebral cortex development, precise control of precursor cell cycle length and cell cycle exit is required for balanced precursor pool expansion and layer-specific neurogenesis. Here, we defined the roles of cyclin-dependent kinase inhibitor (CKI) p57KIP2, an important regulator of G1 phase, using deletion mutant mice. Mutant mice displayed macroencephaly associated with cortical hyperplasia during late embryogenesis and postnatal development. Embryonically, proliferation of radial glial cells (RGC) and intermediate precursors (IPC) was increased, expanding both populations, with greater effect on IPCs. Furthermore, cell cycle re-entry was increased during early corticogenesis, whereas cell cycle exit was augmented at middle stage. Consequently, neurogenesis was reduced early, whereas it was enhanced during later development. In agreement, the timetable of early neurogenesis, indicated by birthdating analysis, was delayed. Cell cycle dynamics analyses in mutants indicated that p57KIP2 regulates cell cycle length in both RGCs and IPCs. By contrast, related CKI p27KIP1 controlled IPC proliferation exclusively. Furthermore, p57KIP2 deficiency markedly increased RGC and IPC divisions at E14.5, whereas p27KIP1 increased IPC proliferation at E16.5. Consequently, loss of p57KIP2 increased primarily layer 5-6 neuron production, whereas loss of p27KIP1 increased neurons specifically in layers 2-5. In conclusion, our observations suggest that p57KIP2 and p27KIP1 control neuronal output for distinct cortical layers by regulating different stages of precursor proliferation, and support a model in which IPCs contribute to both lower and upper layer neuron generation. PMID:22223678

Synthesis of Cu2ZnSnS4 thin films by a precursor solution paste for thin film solar cell applications.

PubMed

Cho, Jin Woo; Ismail, Agus; Park, Se Jin; Kim, Woong; Yoon, Sungho; Min, Byoung Koun

2013-05-22

Cu2ZnSnS4 (CZTS) is a very promising semiconductor material when used for the absorber layer of thin film solar cells because it consists of only abundant and inexpensive elements. In addition, a low-cost solution process is applicable to the preparation of CZTS absorber films, which reduces the cost when this film is used for the production of thin film solar cells. To fabricate solution-processed CZTS thin film using an easily scalable and relatively safe method, we suggest a precursor solution paste coating method with a two-step heating process (oxidation and sulfurization). The synthesized CZTS film was observed to be composed of grains of a size of ~300 nm, showing an overall densely packed morphology with some pores and voids. A solar cell device with this film as an absorber layer showed the highest efficiency of 3.02% with an open circuit voltage of 556 mV, a short current density of 13.5 mA/cm(2), and a fill factor of 40.3%. We also noted the existence of Cd moieties and an inhomogeneous Zn distribution in the CZTS film, which may have been triggered by the presence of pores and voids in the CZTS film.

Improved performance of low cost CuInS2 superstrate-type solar cells using Zinc assisted spray pyrolysis processing

NASA Astrophysics Data System (ADS)

Cheshme Khavar, Amir Hossein; Mahjoub, Ali Reza; Taghavinia, Nima

2017-12-01

Superstrate configuration CuInS2 (CIS) solar cells are fabricated using a spray pyrolysis method. We avoided selenization process, cyanide etching and CdS buffer layer, to keep the process ‘green’. CIS layers are formed by spray pyrolysis of an aqueous precursor ink containing metal chloride salts and thiourea at 350 °C. We investigated the effect of intentional Zn doping on structural, morphological and photovoltaic response of the fabricated CIS films by dissolving ZnCl2 in aqueous precursor solution. At a zinc doping level ranging between 0.25 and 1.00 mol%, Zn doping is found to improve the CIS crystal growth and surface morphology of CIS films. Compared with the performance of the non-doped CIS cell, the Zn-doped CIS solar cell displayed a remarkable efficiency enhancement of 58-97% and the maximum enhancement was obtained at a Zn content of 0.5 mol%. The device structure consists of    and show promising PCE of 4.29 % without any anti-reflection coating. Over the course of 300 d under ambient condition, the fabricated device showed only 1% loss in efficiency.

Multiscale modeling for SiO2 atomic layer deposition for high-aspect-ratio hole patterns

NASA Astrophysics Data System (ADS)

Miyano, Yumiko; Narasaki, Ryota; Ichikawa, Takashi; Fukumoto, Atsushi; Aiso, Fumiki; Tamaoki, Naoki

2018-06-01

A multiscale simulation model is developed for optimizing the parameters of SiO2 plasma-enhanced atomic layer deposition of high-aspect-ratio hole patterns in three-dimensional (3D) stacked memory. This model takes into account the diffusion of a precursor in a reactor, that in holes, and the adsorption onto the wafer. It is found that the change in the aperture ratio of the holes on the wafer affects the concentration of the precursor near the top of the wafer surface, hence the deposition profile in the hole. The simulation results reproduced well the experimental results of the deposition thickness for the various hole aperture ratios. By this multiscale simulation, we can predict the deposition profile in a high-aspect-ratio hole pattern in 3D stacked memory. The atomic layer deposition parameters for conformal deposition such as precursor feeding time and partial pressure of precursor for wafers with various hole aperture ratios can be estimated.

Role of defects in laser-induced modifications of silica coatings and fused silica using picosecond pulses at 1053 nm: II Scaling laws and the density of precursors

DOE PAGES

Laurence, T. A.; Negres, R. A.; Ly, S.; ...

2017-06-22

Here, we investigate the role of defects in laser-induced damage of fused silica and of silica coatings produced by e-beam and PIAD processes which are used in damage resistant, multi-layer dielectric, reflective optics. We perform experiments using 1053 nm, 1–60 ps laser pulses with varying beam size, number of shots, and pulse widths in order to understand the characteristics of defects leading to laser-induced damage. This pulse width range spans a transition in mechanisms from intrinsic material ablation for short pulses to defect-dominated damage for longer pulses. We show that for pulse widths as short as 10 ps, laser-induced damagemore » properties of fused silica and silica films are dominated by isolated absorbers. The density of these precursors and their fluence dependence of damage initiation suggest a single photon process for initial energy absorption in these precursors. Higher density precursors that initiate close to the ablation threshold at shorter pulse widths are also observed in fused silica, whose fluence and pulse width scaling suggest a multiphoton initiation process. We also show that these initiated damage sites grow with subsequent laser pulses. We show that scaling laws obtained in more conventional ways depend on the beam size and on the definition of damage for ps pulses. For this reason, coupling scaling laws with the density of precursors are critical to understanding the damage limitations of optics in the ps regime.« less

Role of defects in laser-induced modifications of silica coatings and fused silica using picosecond pulses at 1053 nm: II Scaling laws and the density of precursors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Laurence, T. A.; Negres, R. A.; Ly, S.

Here, we investigate the role of defects in laser-induced damage of fused silica and of silica coatings produced by e-beam and PIAD processes which are used in damage resistant, multi-layer dielectric, reflective optics. We perform experiments using 1053 nm, 1–60 ps laser pulses with varying beam size, number of shots, and pulse widths in order to understand the characteristics of defects leading to laser-induced damage. This pulse width range spans a transition in mechanisms from intrinsic material ablation for short pulses to defect-dominated damage for longer pulses. We show that for pulse widths as short as 10 ps, laser-induced damagemore » properties of fused silica and silica films are dominated by isolated absorbers. The density of these precursors and their fluence dependence of damage initiation suggest a single photon process for initial energy absorption in these precursors. Higher density precursors that initiate close to the ablation threshold at shorter pulse widths are also observed in fused silica, whose fluence and pulse width scaling suggest a multiphoton initiation process. We also show that these initiated damage sites grow with subsequent laser pulses. We show that scaling laws obtained in more conventional ways depend on the beam size and on the definition of damage for ps pulses. For this reason, coupling scaling laws with the density of precursors are critical to understanding the damage limitations of optics in the ps regime.« less

Low-temperature atomic layer deposition of SiO2/Al2O3 multilayer structures constructed on self-standing films of cellulose nanofibrils.

PubMed

Putkonen, Matti; Sippola, Perttu; Svärd, Laura; Sajavaara, Timo; Vartiainen, Jari; Buchanan, Iain; Forsström, Ulla; Simell, Pekka; Tammelin, Tekla

2018-02-13

In this paper, we have optimized a low-temperature atomic layer deposition (ALD) of SiO 2 using AP-LTO® 330 and ozone (O 3 ) as precursors, and demonstrated its suitability to surface-modify temperature-sensitive bio-based films of cellulose nanofibrils (CNFs). The lowest temperature for the thermal ALD process was 80°C when the silicon precursor residence time was increased by the stop-flow mode. The SiO 2 film deposition rate was dependent on the temperature varying within 1.5-2.2 Å cycle -1 in the temperature range of 80-350°C, respectively. The low-temperature SiO 2 process that resulted was combined with the conventional trimethyl aluminium + H 2 O process in order to prepare thin multilayer nanolaminates on self-standing CNF films. One to six stacks of SiO 2 /Al 2 O 3 were deposited on the CNF films, with individual layer thicknesses of 3.7 nm and 2.6 nm, respectively, combined with a 5 nm protective SiO 2 layer as the top layer. The performance of the multilayer hybrid nanolaminate structures was evaluated with respect to the oxygen and water vapour transmission rates. Six stacks of SiO 2 /Al 2 O with a total thickness of approximately 35 nm efficiently prevented oxygen and water molecules from interacting with the CNF film. The oxygen transmission rates analysed at 80% RH decreased from the value for plain CNF film of 130 ml m -2  d -1 to 0.15 ml m -2  d -1 , whereas the water transmission rates lowered from 630 ± 50 g m -2  d -1 down to 90 ± 40 g m -2  d -1 This article is part of a discussion meeting issue 'New horizons for cellulose nanotechnology'. © 2017 The Author(s).

Low-temperature atomic layer deposition of SiO2/Al2O3 multilayer structures constructed on self-standing films of cellulose nanofibrils

NASA Astrophysics Data System (ADS)

Putkonen, Matti; Sippola, Perttu; Svärd, Laura; Sajavaara, Timo; Vartiainen, Jari; Buchanan, Iain; Forsström, Ulla; Simell, Pekka; Tammelin, Tekla

2017-12-01

In this paper, we have optimized a low-temperature atomic layer deposition (ALD) of SiO2 using AP-LTO® 330 and ozone (O3) as precursors, and demonstrated its suitability to surface-modify temperature-sensitive bio-based films of cellulose nanofibrils (CNFs). The lowest temperature for the thermal ALD process was 80°C when the silicon precursor residence time was increased by the stop-flow mode. The SiO2 film deposition rate was dependent on the temperature varying within 1.5-2.2 Å cycle-1 in the temperature range of 80-350°C, respectively. The low-temperature SiO2 process that resulted was combined with the conventional trimethyl aluminium + H2O process in order to prepare thin multilayer nanolaminates on self-standing CNF films. One to six stacks of SiO2/Al2O3 were deposited on the CNF films, with individual layer thicknesses of 3.7 nm and 2.6 nm, respectively, combined with a 5 nm protective SiO2 layer as the top layer. The performance of the multilayer hybrid nanolaminate structures was evaluated with respect to the oxygen and water vapour transmission rates. Six stacks of SiO2/Al2O with a total thickness of approximately 35 nm efficiently prevented oxygen and water molecules from interacting with the CNF film. The oxygen transmission rates analysed at 80% RH decreased from the value for plain CNF film of 130 ml m-2 d-1 to 0.15 ml m-2 d-1, whereas the water transmission rates lowered from 630 ± 50 g m-2 d-1 down to 90 ± 40 g m-2 d-1. This article is part of a discussion meeting issue `New horizons for cellulose nanotechnology'.

Supramolecular structure formation of Langmuir-Blodgett films of comblike precursor and polyimide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goloudina, S. I., E-mail: goloudina@mail.ru; Luchinin, V. V.; Rozanov, V. V.

2013-03-15

The surface structure of Langmuir-Blodgett films of a comblike polyimide precursor-a rigid-chain polyamic acid alkylamine salt bearing multichains of tertiary amine-and films of the corresponding polyimide were studied by atomic force microscopy (AFM). An analysis of the images of the surface of three-layer films revealed a domain structure. It was found that the Langmuir-Blodgett film formation of the precursor occurs as a result of the layer-by-layer deposition of two-dimensional domains (composed of polyamic acid salt molecules on the water surface) onto a substrate. The formation of domains in a monolayer is associated with the chemical structure of the precursor, tomore » be more precise, with the rigidity of the main chain and the presence of closely spaced aliphatic side chains in the polymer chain, whose total cross-section area is close to the surface area of the projection onto the plane of the repeating unit of the main chain. Polyimide films inherit the domain structure of the precursor films; the inhomogeneity of the film thickness substantially decreases, whereas the domain size and character of their distribution in the film remain unchanged.« less

Method for synthesizing thin film electrodes

DOEpatents

Boyle, Timothy J [Albuquerque, NM

2007-03-13

A method for making a thin-film electrode, either an anode or a cathode, by preparing a precursor solution using an alkoxide reactant, depositing multiple thin film layers with each layer approximately 500 1000 .ANG. in thickness, and heating the layers to above 600.degree. C. to achieve a material with electrochemical properties suitable for use in a thin film battery. The preparation of the anode precursor solution uses Sn(OCH.sub.2C(CH.sub.3).sub.3).sub.2 dissolved in a solvent in the presence of HO.sub.2CCH.sub.3 and the cathode precursor solution is formed by dissolving a mixture of (Li(OCH.sub.2C(CH.sub.3).sub.3)).sub.8 and Co(O.sub.2CCH.sub.3).H.sub.2O in at least one polar solvent.

Surface Acidity and Properties of TiO2/SiO2 Catalysts Prepared by Atomic Layer Deposition: UV-visible Diffuse Reflectance, DRIFTS, and Visible Raman Spectroscopy Studies

DTIC Science & Technology

2009-06-15

titanium isopropoxide (TTIP) as metal precursors. The deposition rate of titania films from TiCl4 was found to be stable in the 150-300 °C...tetrachloride (TiCl4) and titanium isopropoxide (TTIP) are widely used as metal precursors and water or hydrogen peroxide are used as oxygen precursors.29-36... titanium dioxide supported on high surface area silica gel have been synthesized by atomic layer deposition (ALD) using titanium tetrachloride (TiCl4) and

The competition of densification and structure ordering during crystallization of HCP-Mg in the framework of layering

NASA Astrophysics Data System (ADS)

Luo, Jie; Jiang, Yewei; Yu, Ronggang; Wu, Yongquan

2017-06-01

In this paper, we performed an NPT molecular dynamics simulation of crystallization process of HCP-Mg to probe the competition between densification and structural ordering. Two opposite layering patterns, i.e. outward and inward, were designed for analysis. From the perspective of solid-like cluster (SLC) itself, structural ordering always precedes densification; but from the perspective of SLC's precursor, structural ordering always lags behind densification; the reversion occurs at the closest two liquid layers around SLC. We call it dip-rebound phenomenon. This phenomenon is a completely new finding. It resolves, to some extent, recent debate about whether densification or structural ordering triggers crystallization.

Modified Back Contact Interface of CZTSe Thin Film Solar Cells: Elimination of Double Layer Distribution in Absorber Layer

PubMed Central

Zhang, Zhaojing; Yao, Liyong; Bi, Jinlian; Gao, Shoushuai; Gao, Qing; Jeng, Ming‐Jer; Sun, Guozhong; Zhou, Zhiqiang; He, Qing; Sun, Yun

2017-01-01

Abstract Double layer distribution exists in Cu2SnZnSe4 (CZTSe) thin films prepared by selenizing the metallic precursors, which will degrade the back contact of Mo substrate to absorber layer and thus suppressing the performance of solar cell. In this work, the double‐layer distribution of CZTSe film is eliminated entirely and the formation of MoSe2 interfacial layer is inhibited successfully. CZTSe film is prepared by selenizing the precursor deposited by electrodeposition method under Se and SnSex mixed atmosphere. It is found that the insufficient reaction between ZnSe and Cu‐Sn‐Se phases in the bottom of the film is the reason why the double layer distribution of CZTSe film is formed. By increasing Sn content in the metallic precursor, thus making up the loss of Sn because of the decomposition of CZTSe and facilitate the diffusion of liquid Cu2Se, the double layer distribution is eliminated entirely. The crystallization of the formed thin film is dense and the grains go through the entire film without voids. And there is no obvious MoSe2 layer formed between CZTSe and Mo. As a consequence, the series resistance of the solar cell reduces significantly to 0.14 Ω cm2 and a CZTSe solar cell with efficiency of 7.2% is fabricated. PMID:29610727

Modified Back Contact Interface of CZTSe Thin Film Solar Cells: Elimination of Double Layer Distribution in Absorber Layer.

PubMed

Zhang, Zhaojing; Yao, Liyong; Zhang, Yi; Ao, Jianping; Bi, Jinlian; Gao, Shoushuai; Gao, Qing; Jeng, Ming-Jer; Sun, Guozhong; Zhou, Zhiqiang; He, Qing; Sun, Yun

2018-02-01

Double layer distribution exists in Cu 2 SnZnSe 4 (CZTSe) thin films prepared by selenizing the metallic precursors, which will degrade the back contact of Mo substrate to absorber layer and thus suppressing the performance of solar cell. In this work, the double-layer distribution of CZTSe film is eliminated entirely and the formation of MoSe 2 interfacial layer is inhibited successfully. CZTSe film is prepared by selenizing the precursor deposited by electrodeposition method under Se and SnSe x mixed atmosphere. It is found that the insufficient reaction between ZnSe and Cu-Sn-Se phases in the bottom of the film is the reason why the double layer distribution of CZTSe film is formed. By increasing Sn content in the metallic precursor, thus making up the loss of Sn because of the decomposition of CZTSe and facilitate the diffusion of liquid Cu 2 Se, the double layer distribution is eliminated entirely. The crystallization of the formed thin film is dense and the grains go through the entire film without voids. And there is no obvious MoSe 2 layer formed between CZTSe and Mo. As a consequence, the series resistance of the solar cell reduces significantly to 0.14 Ω cm 2 and a CZTSe solar cell with efficiency of 7.2% is fabricated.

Chemical vapor deposition of mesoporous graphene nanoballs for supercapacitor.

PubMed

Lee, Jung-Soo; Kim, Sun-I; Yoon, Jong-Chul; Jang, Ji-Hyun

2013-07-23

A mass-producible mesoporous graphene nanoball (MGB) was fabricated via a precursor-assisted chemical vapor deposition (CVD) technique for supercapacitor application. Polystyrene balls and reduced iron created under high temperature and a hydrogen gas environment provide a solid carbon source and a catalyst for graphene growth during the precursor-assisted CVD process, respectively. Carboxylic acid and sulfonic acid functionalization of the polystyrene ball facilitates homogeneous dispersion of the hydrophobic polymer template in the metal precursor solution, thus, resulting in a MGB with a uniform number of graphene layers. The MGB is shown to have a specific surface area of 508 m(2)/g and is mesoporous with a mean mesopore diameter of 4.27 nm. Mesopores are generated by the removal of agglomerated iron domains, permeating down through the soft polystyrene spheres and providing the surface for subsequent graphene growth during the heating process in a hydrogen environment. This technique requires only drop-casting of the precursor/polystyrene solution, allowing for mass-production of multilayer MGBs. The supercapacitor fabricated by the use of the MGB as an electrode demonstrates a specific capacitance of 206 F/g and more than 96% retention of capacitance after 10,000 cycles. The outstanding characteristics of the MGB as an electrode for supercapacitors verify the strong potential for use in energy-related areas.

Sodium bromide additive improved film morphology and performance in perovskite light-emitting diodes

NASA Astrophysics Data System (ADS)

Li, Jinghai; Cai, Feilong; Yang, Liyan; Ye, Fanghao; Zhang, Jinghui; Gurney, Robert S.; Liu, Dan; Wang, Tao

2017-07-01

Organometal halide perovskite is a promising material to fabricate light-emitting diodes (LEDs) via solution processing due to its exceptional optoelectronic properties. However, incomplete precursor conversion and various defect states in the perovskite light-emitting layer lead to low luminance and external quantum efficiency of perovskite LEDs. We show here the addition of an optimum amount of sodium bromide in the methylammonium lead bromide (MAPbBr3) precursor during a one-step perovskite solution casting process can effectively improve the film coverage, enhance the crystallinity, and passivate ionic defects on the surface of MAPbBr3 crystal grains, resulting in LEDs with a reduced turn-on voltage from 2.8 to 2.3 V and an enhanced maximum luminance from 1059 to 6942 Cd/m2 when comparing with the pristine perovskite-based device.

Modular injector integrated linear apparatus with motion profile optimization for spatial atomic layer deposition.

PubMed

Wang, Xiaolei; Li, Yun; Lin, Jilong; Shan, Bin; Chen, Rong

2017-11-01

A spatial atomic layer deposition apparatus integrated with a modular injector and a linear motor has been designed. It consists of four parts: a precursor delivery manifold, a modular injector, a reaction zone, and a driving unit. An injector with multi-layer structured channels is designed to help improve precursor distribution homogeneity. During the back and forth movement of the substrate at high speed, the inertial impact caused by jerk and sudden changes of acceleration will degrade the film deposition quality. Such residual vibration caused by inertial impact will aggravate the fluctuation of the gap distance between the injector and the substrate in the deposition process. Thus, an S-curve motion profile is implemented to reduce the large inertial impact, and the maximum position error could be reduced by 84%. The microstructure of the film under the S-curve motion profile shows smaller root-mean-square and scanning voltage amplitude under an atomic force microscope, which verifies the effectiveness of the S-curve motion profile in reducing the residual vibration and stabilizing the gap distance between the injector and the substrate. The film deposition rate could reach 100 nm/min while maintaining good uniformity without obvious periodic patterns on the surface.

Modular injector integrated linear apparatus with motion profile optimization for spatial atomic layer deposition

NASA Astrophysics Data System (ADS)

Wang, Xiaolei; Li, Yun; Lin, Jilong; Shan, Bin; Chen, Rong

2017-11-01

A spatial atomic layer deposition apparatus integrated with a modular injector and a linear motor has been designed. It consists of four parts: a precursor delivery manifold, a modular injector, a reaction zone, and a driving unit. An injector with multi-layer structured channels is designed to help improve precursor distribution homogeneity. During the back and forth movement of the substrate at high speed, the inertial impact caused by jerk and sudden changes of acceleration will degrade the film deposition quality. Such residual vibration caused by inertial impact will aggravate the fluctuation of the gap distance between the injector and the substrate in the deposition process. Thus, an S-curve motion profile is implemented to reduce the large inertial impact, and the maximum position error could be reduced by 84%. The microstructure of the film under the S-curve motion profile shows smaller root-mean-square and scanning voltage amplitude under an atomic force microscope, which verifies the effectiveness of the S-curve motion profile in reducing the residual vibration and stabilizing the gap distance between the injector and the substrate. The film deposition rate could reach 100 nm/min while maintaining good uniformity without obvious periodic patterns on the surface.

Flexible and High-Performance Amorphous Indium Zinc Oxide Thin-Film Transistor Using Low-Temperature Atomic Layer Deposition.

PubMed

Sheng, Jiazhen; Lee, Hwan-Jae; Oh, Saeroonter; Park, Jin-Seong

2016-12-14

Amorphous indium zinc oxide (IZO) thin films were deposited at different temperatures, by atomic layer deposition (ALD) using [1,1,1-trimethyl-N-(trimethylsilyl)silanaminato]indium (INCA-1) as the indium precursor, diethlzinc (DEZ) as the zinc precursor, and hydrogen peroxide (H 2 O 2 ) as the reactant. The ALD process of IZO deposition was carried by repeated supercycles, including one cycle of indium oxide (In 2 O 3 ) and one cycle of zinc oxide (ZnO). The IZO growth rate deviates from the sum of the respective In 2 O 3 and ZnO growth rates at ALD growth temperatures of 150, 175, and 200 °C. We propose growth temperature-dependent surface reactions during the In 2 O 3 cycle that correspond with the growth-rate results. Thin-film transistors (TFTs) were fabricated with the ALD-grown IZO thin films as the active layer. The amorphous IZO TFTs exhibited high mobility of 42.1 cm 2 V -1 s -1 and good positive bias temperature stress stability. Finally, flexible IZO TFT was successfully fabricated on a polyimide substrate without performance degradation, showing the great potential of ALD-grown TFTs for flexible display applications.

Fabrication of hierarchical flower-like porous ZnO nanostructures from layered ZnC2O4·3Zn(OH)2 and gas sensing properties

NASA Astrophysics Data System (ADS)

Cui, Jiashan; Sun, Jianbo; Liu, Xin; Li, Jinwei; Ma, Xinzhi; Chen, Tingting

2014-07-01

ZnO materials with porous and hierarchical flower-like structure were synthesized through mild hydrothermal and simple calcination approach, in which the flower-like layered zinc oxalate hydroxide (ZnC2O4·3Zn(OH)2) precursor was first synthesized and then calcined at 600 °C. The obtained products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopic (TEM), Brunauer-Emmett-Teller (BET) and thermogravimetric (TG) analysis. We proposed the possible growth mechanism of the material via studying the time evolution experiment results. In the process of reaction, oxalic acid as a structure-directing agent hydrolyzed and then formed primarily sheets-like intermediate ZnC2O4·2H2O. Hexamethylenetetramine (HMT) as surfactant, with directional adsorption, leads to the formation of layered zinc oxalate hydroxide precursor. Furthermore, the gas sensitivity also can be characterized, whose results indicated that the synthesized materials had a preferable selectivity to ethanol gas. The fast response rate and reversible performance can be attributed to the produced greater specific surface area produced, which was caused by the porous and hierarchical flower-like structure.

Melanin as an active layer in biosensors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Piacenti da Silva, Marina, E-mail: marinaness@yahoo.com; Congiu, Mirko, E-mail: congiumat@gmail.com; Oliveira Graeff, Carlos Frederico de, E-mail: graeff@fc.unesp.br

2014-03-15

The development of pH sensors is of great interest due to its extensive application in several areas such as industrial processes, biochemistry and particularly medical diagnostics. In this study, the pH sensing properties of an extended gate field effect transistor (EGFET) based on melanin thin films as active layer are investigated and the physical mechanisms related to the device operation are discussed. Thin films were produced from different melanin precursors on indium tin oxide (ITO) and gold substrates and were investigated by Atomic Force Microscopy and Electrochemical Impedance Spectroscopy. Experiments were performed in the pH range from 2 to 12.more » EGFETs with melanin deposited on ITO and on gold substrates showed sensitivities ranging from 31.3 mV/pH to 48.9 mV/pH, depending on the melanin precursor and the substrate used. The pH detection is associated with specific binding sites in its structure, hydroxyl groups and quinone imine.« less

Atomic layer deposition of magnesium fluoride via bis(ethylcyclopentadienyl)magnesium and anhydrous hydrogen fluoride

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hennessy, John, E-mail: hennessy@caltech.edu; Jewell, April D.; Greer, Frank

2015-01-15

A new process has been developed to deposit magnesium fluoride (MgF{sub 2}) thin films via atomic layer deposition (ALD) for use as optical coatings in the ultraviolet. MgF{sub 2} was deposited in a showerhead style ALD reactor using bis(ethylcyclopentadienyl)magnesium and anhydrous hydrogen fluoride (HF) as precursors at substrate temperatures from 100 to 250 °C. The use of HF was observed to result in improved morphology and reduced impurity content compared to other reported MgF{sub 2} ALD approaches that use metal fluoride precursors as the fluorine-containing chemistry. Characterization of these films has been performed using spectroscopic ellipsometry, atomic force microscopy, and x-raymore » photoelectron spectroscopy for material deposited on silicon substrates. Films at all substrate temperatures were transparent at wavelengths down to 190 nm and the low deposition temperature combined with low surface roughness makes these coatings good candidates for a variety of optical applications in the far ultraviolet.« less

A versatile single molecular precursor for the synthesis of layered oxide cathode materials for Li-ion batteries.

PubMed

Li, Maofan; Liu, Jiajie; Liu, Tongchao; Zhang, Mingjian; Pan, Feng

2018-02-01

A carbonyl-bridged single molecular precursor LiTM(acac) 3 [transition metal (TM) = cobalt/manganese/nickel (Co/Mn/Ni), acac = acetylacetone], featuring a one-dimensional chain structure, was designed and applied to achieve the layered oxide cathode materials: LiTMO 2 (TM = Ni/Mn/Co, NMC). As examples, layered oxides, primary LiCoO 2 , binary LiNi 0.8 Co 0.2 O 2 and ternary LiNi 0.5 Mn 0.3 Co 0.2 O 2 were successfully prepared to be used as cathode materials. When they are applied to lithium-ion batteries (LIBs), all exhibit good electrochemical performance because of their unique morphology and great uniformity of element distribution. This versatile precursor is predicted to accommodate many other metal cations, such as aluminum (Al 3+ ), iron (Fe 2+ ), and sodium (Na + ), because of the flexibility of organic ligand, which not only facilitates the doping-modification of the NMC system, but also enables synthesis of Na-ion layered oxides. This opens a new direction of research for the synthesis of high-performance layered oxide cathode materials for LIBs.

Sol-Gel Deposited Double Layer TiO₂ and Al₂O₃ Anti-Reflection Coating for Silicon Solar Cell.

PubMed

Jung, Jinsu; Jannat, Azmira; Akhtar, M Shaheer; Yang, O-Bong

2018-02-01

In this work, the deposition of double layer ARC on p-type Si solar cells was carried out by simple spin coating using sol-gel derived Al2O3 and TiO2 precursors for the fabrication of crystalline Si solar cells. The first ARC layer was created by freshly prepared sol-gel derived Al2O3 precursor using spin coating technique and then second ARC layer of TiO2 was deposited with sol-gel derived TiO2 precursor, which was finally annealed at 400 °C. The double layer Al2O3/TiO2 ARC on Si wafer exhibited the low average reflectance of 4.74% in the wavelength range of 400 and 1000 nm. The fabricated solar cells based on double TiO2/Al2O3 ARC attained the conversion efficiency of ~13.95% with short circuit current (JSC) of 35.27 mA/cm2, open circuit voltage (VOC) of 593.35 mV and fill factor (FF) of 66.67%. Moreover, the fabricated solar cells presented relatively low series resistance (Rs) as compared to single layer ARCs, resulting in the high VOC and FF.

Microstructures of BN/SiC coatings on nicalon fibers

NASA Technical Reports Server (NTRS)

Dickerson, R. M.; Singh, M.

1995-01-01

The microstructures of Nicalon silicon carbide (SiC) fibers and layered coatings of boron nitride (BN) followed by chemical vapor infiltrated silicon carbide (CVI-SiC) were characterized using optical and electron microscopy. Two different precursors and reactions were used to produce the BN layers while the deposition of CVI silicon carbide was nearly identical. Coated tows were examined in cross-section to characterize the chemistry and structures of the constituents and the interfaces. One BN precursor yielded three sublayers while the other gave a relatively homogeneous nanocrystalline layer.

Wafer-scale two-dimensional semiconductors from printed oxide skin of liquid metals

NASA Astrophysics Data System (ADS)

Carey, Benjamin J.; Ou, Jian Zhen; Clark, Rhiannon M.; Berean, Kyle J.; Zavabeti, Ali; Chesman, Anthony S. R.; Russo, Salvy P.; Lau, Desmond W. M.; Xu, Zai-Quan; Bao, Qiaoliang; Kevehei, Omid; Gibson, Brant C.; Dickey, Michael D.; Kaner, Richard B.; Daeneke, Torben; Kalantar-Zadeh, Kourosh

2017-02-01

A variety of deposition methods for two-dimensional crystals have been demonstrated; however, their wafer-scale deposition remains a challenge. Here we introduce a technique for depositing and patterning of wafer-scale two-dimensional metal chalcogenide compounds by transforming the native interfacial metal oxide layer of low melting point metal precursors (group III and IV) in liquid form. In an oxygen-containing atmosphere, these metals establish an atomically thin oxide layer in a self-limiting reaction. The layer increases the wettability of the liquid metal placed on oxygen-terminated substrates, leaving the thin oxide layer behind. In the case of liquid gallium, the oxide skin attaches exclusively to a substrate and is then sulfurized via a relatively low temperature process. By controlling the surface chemistry of the substrate, we produce large area two-dimensional semiconducting GaS of unit cell thickness (~1.5 nm). The presented deposition and patterning method offers great commercial potential for wafer-scale processes.

Wafer-scale two-dimensional semiconductors from printed oxide skin of liquid metals.

PubMed

Carey, Benjamin J; Ou, Jian Zhen; Clark, Rhiannon M; Berean, Kyle J; Zavabeti, Ali; Chesman, Anthony S R; Russo, Salvy P; Lau, Desmond W M; Xu, Zai-Quan; Bao, Qiaoliang; Kevehei, Omid; Gibson, Brant C; Dickey, Michael D; Kaner, Richard B; Daeneke, Torben; Kalantar-Zadeh, Kourosh

2017-02-17

A variety of deposition methods for two-dimensional crystals have been demonstrated; however, their wafer-scale deposition remains a challenge. Here we introduce a technique for depositing and patterning of wafer-scale two-dimensional metal chalcogenide compounds by transforming the native interfacial metal oxide layer of low melting point metal precursors (group III and IV) in liquid form. In an oxygen-containing atmosphere, these metals establish an atomically thin oxide layer in a self-limiting reaction. The layer increases the wettability of the liquid metal placed on oxygen-terminated substrates, leaving the thin oxide layer behind. In the case of liquid gallium, the oxide skin attaches exclusively to a substrate and is then sulfurized via a relatively low temperature process. By controlling the surface chemistry of the substrate, we produce large area two-dimensional semiconducting GaS of unit cell thickness (∼1.5 nm). The presented deposition and patterning method offers great commercial potential for wafer-scale processes.

Wafer-scale two-dimensional semiconductors from printed oxide skin of liquid metals

PubMed Central

Carey, Benjamin J.; Ou, Jian Zhen; Clark, Rhiannon M.; Berean, Kyle J.; Zavabeti, Ali; Chesman, Anthony S. R.; Russo, Salvy P.; Lau, Desmond W. M.; Xu, Zai-Quan; Bao, Qiaoliang; Kavehei, Omid; Gibson, Brant C.; Dickey, Michael D.; Kaner, Richard B.; Daeneke, Torben; Kalantar-Zadeh, Kourosh

2017-01-01

A variety of deposition methods for two-dimensional crystals have been demonstrated; however, their wafer-scale deposition remains a challenge. Here we introduce a technique for depositing and patterning of wafer-scale two-dimensional metal chalcogenide compounds by transforming the native interfacial metal oxide layer of low melting point metal precursors (group III and IV) in liquid form. In an oxygen-containing atmosphere, these metals establish an atomically thin oxide layer in a self-limiting reaction. The layer increases the wettability of the liquid metal placed on oxygen-terminated substrates, leaving the thin oxide layer behind. In the case of liquid gallium, the oxide skin attaches exclusively to a substrate and is then sulfurized via a relatively low temperature process. By controlling the surface chemistry of the substrate, we produce large area two-dimensional semiconducting GaS of unit cell thickness (∼1.5 nm). The presented deposition and patterning method offers great commercial potential for wafer-scale processes. PMID:28211538

Amyloid precursor protein expression and processing are differentially regulated during cortical neuron differentiation.

PubMed

Bergström, Petra; Agholme, Lotta; Nazir, Faisal Hayat; Satir, Tugce Munise; Toombs, Jamie; Wellington, Henrietta; Strandberg, Joakim; Bontell, Thomas Olsson; Kvartsberg, Hlin; Holmström, Maria; Boreström, Cecilia; Simonsson, Stina; Kunath, Tilo; Lindahl, Anders; Blennow, Kaj; Hanse, Eric; Portelius, Erik; Wray, Selina; Zetterberg, Henrik

2016-07-07

Amyloid precursor protein (APP) and its cleavage product amyloid β (Aβ) have been thoroughly studied in Alzheimer's disease. However, APP also appears to be important for neuronal development. Differentiation of induced pluripotent stem cells (iPSCs) towards cortical neurons enables in vitro mechanistic studies on human neuronal development. Here, we investigated expression and proteolytic processing of APP during differentiation of human iPSCs towards cortical neurons over a 100-day period. APP expression remained stable during neuronal differentiation, whereas APP processing changed. α-Cleaved soluble APP (sAPPα) was secreted early during differentiation, from neuronal progenitors, while β-cleaved soluble APP (sAPPβ) was first secreted after deep-layer neurons had formed. Short Aβ peptides, including Aβ1-15/16, peaked during the progenitor stage, while processing shifted towards longer peptides, such as Aβ1-40/42, when post-mitotic neurons appeared. This indicates that APP processing is regulated throughout differentiation of cortical neurons and that amyloidogenic APP processing, as reflected by Aβ1-40/42, is associated with mature neuronal phenotypes.

Superconducting Mercury-Based Cuprate Films with a Zero-Resistance Transition Temperature of 124 Kelvin

NASA Astrophysics Data System (ADS)

Tsuei, C. C.; Gupta, A.; Trafas, G.; Mitzi, D.

1994-03-01

The synthesis of high-quality films of the recently discovered mercury-based cuprate films with high transition temperatures has been plagued by problems such as the air sensitivity of the cuprate precursor and the volatility of Hg and HgO. These processing difficulties have been circumvented by a technique of atomic-scale mixing of the HgO and cuprate precursors, use of a protective cap layer, and annealing in an appropriate Hg and O_2 environment. With this procedure, a zero-resistance transition temperature as high as 124 kelvin in c axis-oriented epitaxial HgBa_2CaCu_2O6+δ films has been achieved.

Superconducting mercury-based cuprate films with a zero-resistance transition temperature of 124 Kelvin.

PubMed

Tsuei, C C; Gupta, A; Trafas, G; Mitzi, D

1994-03-04

The synthesis of high-quality films of the recently discovered mercury-based cuprate films with high transition temperatures has been plagued by problems such as the air sensitivity of the cuprate precursor and the volatility of Hg and HgO. These processing difficulties have been circumvented by a technique of atomic-scale mixing of the HgO and cuprate precursors, use of a protective cap layer, and annealing in an appropriate Hg and O(2) environment. With this procedure, a zero-resistance transition temperature as high as 124 kelvin in c axis-oriented epitaxial HgBa(2)CaCu(2)O(6+delta) films has been achieved.

Facile fabrication of luminescent organic dots by thermolysis of citric acid in urea melt, and their use for cell staining and polyelectrolyte microcapsule labelling.

PubMed

Zholobak, Nadezhda M; Popov, Anton L; Shcherbakov, Alexander B; Popova, Nelly R; Guzyk, Mykhailo M; Antonovich, Valeriy P; Yegorova, Alla V; Scrypynets, Yuliya V; Leonenko, Inna I; Baranchikov, Alexander Ye; Ivanov, Vladimir K

2016-01-01

Luminescent organic dots (O-dots) were synthesized via a one-pot, solvent-free thermolysis of citric acid in urea melt. The influence of the ratio of the precursors and the duration of the process on the properties of the O-dots was established and a mechanism of their formation was hypothesized. The multicolour luminescence tunability and toxicity of synthesized O-dots were extensively studied. The possible applications of O-dots for alive/fixed cell staining and labelling of layer-by-layer polyelectrolyte microcapsules were evaluated.

Facile fabrication of luminescent organic dots by thermolysis of citric acid in urea melt, and their use for cell staining and polyelectrolyte microcapsule labelling

PubMed Central

Zholobak, Nadezhda M; Popov, Anton L; Shcherbakov, Alexander B; Popova, Nelly R; Guzyk, Mykhailo M; Antonovich, Valeriy P; Yegorova, Alla V; Scrypynets, Yuliya V; Leonenko, Inna I; Baranchikov, Alexander Ye

2016-01-01

Luminescent organic dots (O-dots) were synthesized via a one-pot, solvent-free thermolysis of citric acid in urea melt. The influence of the ratio of the precursors and the duration of the process on the properties of the O-dots was established and a mechanism of their formation was hypothesized. The multicolour luminescence tunability and toxicity of synthesized O-dots were extensively studied. The possible applications of O-dots for alive/fixed cell staining and labelling of layer-by-layer polyelectrolyte microcapsules were evaluated. PMID:28144539

Postgrowth tuning of the bandgap of single-layer molybdenum disulfide films by sulfur/selenium exchange.

PubMed

Ma, Quan; Isarraraz, Miguel; Wang, Chen S; Preciado, Edwin; Klee, Velveth; Bobek, Sarah; Yamaguchi, Koichi; Li, Emily; Odenthal, Patrick Michael; Nguyen, Ariana; Barroso, David; Sun, Dezheng; von Son Palacio, Gretel; Gomez, Michael; Nguyen, Andrew; Le, Duy; Pawin, Greg; Mann, John; Heinz, Tony F; Rahman, Talat Shahnaz; Bartels, Ludwig

2014-05-27

We demonstrate bandgap tuning of a single-layer MoS2 film on SiO2/Si via substitution of its sulfur atoms by selenium through a process of gentle sputtering, exposure to a selenium precursor, and annealing. We characterize the substitution process both for S/S and S/Se replacement. Photoluminescence and, in the latter case, X-ray photoelectron spectroscopy provide direct evidence of optical band gap shift and selenium incorporation, respectively. We discuss our experimental observations, including the limit of the achievable bandgap shift, in terms of the role of stress in the film as elucidated by computational studies, based on density functional theory. The resultant films are stable in vacuum, but deteriorate under optical excitation in air.

Influence of ZnO seed layer precursor molar ratio on the density of interface defects in low temperature aqueous chemically synthesized ZnO nanorods/GaN light-emitting diodes

NASA Astrophysics Data System (ADS)

Alnoor, Hatim; Pozina, Galia; Khranovskyy, Volodymyr; Liu, Xianjie; Iandolo, Donata; Willander, Magnus; Nur, Omer

2016-04-01

Low temperature aqueous chemical synthesis (LT-ACS) of zinc oxide (ZnO) nanorods (NRs) has been attracting considerable research interest due to its great potential in the development of light-emitting diodes (LEDs). The influence of the molar ratio of the zinc acetate (ZnAc): KOH as a ZnO seed layer precursor on the density of interface defects and hence the presence of non-radiative recombination centers in LT-ACS of ZnO NRs/GaN LEDs has been systematically investigated. The material quality of the as-prepared seed layer as quantitatively deduced by the X-ray photoelectron spectroscopy is found to be influenced by the molar ratio. It is revealed by spatially resolved cathodoluminescence that the seed layer molar ratio plays a significant role in the formation and the density of defects at the n-ZnO NRs/p-GaN heterostructure interface. Consequently, LED devices processed using ZnO NRs synthesized with molar ratio of 1:5 M exhibit stronger yellow emission (˜575 nm) compared to those based on 1:1 and 1:3 M ratios as measured by the electroluminescence. Furthermore, seed layer molar ratio shows a quantitative dependence of the non-radiative defect densities as deduced from light-output current characteristics analysis. These results have implications on the development of high-efficiency ZnO-based LEDs and may also be helpful in understanding the effects of the ZnO seed layer on defect-related non-radiative recombination.

V6O13 films by control of the oxidation state from aqueous precursor to crystalline phase.

PubMed

Peys, Nick; Ling, Yun; Dewulf, Daan; Gielis, Sven; De Dobbelaere, Christopher; Cuypers, Daniel; Adriaensens, Peter; Van Doorslaer, Sabine; De Gendt, Stefan; Hardy, An; Van Bael, Marlies K

2013-01-28

An aqueous deposition process for V(6)O(13) films is developed whereby the vanadium oxidation state is continuously controlled throughout the entire process. In the precursor stage, a controlled wet chemical reduction of the vanadium(V) source with oxalic acid is achieved and monitored by (51)Vanadium Nuclear Magnetic Resonance ((51)V-NMR) and Ultraviolet-Visible (UV-Vis) spectroscopy. The resulting vanadium(IV) species in the aqueous solution are identified as mononuclear citrato-oxovanadate(IV) complexes by Electron Paramagnetic Resonance (EPR) and Fourier Transform Infra-Red (FTIR) spectroscopy. This precursor is successfully employed for the deposition of uniform, thin films. The optimal deposition and annealing conditions for the formation of crystalline V(6)O(13), including the control of the vanadium oxidation state, are determined through an elaborate study of processing temperature and O(2) partial pressure. To ensure a sub 100 nm adjustable film thickness, a non-oxidative intermediate thermal treatment is carried out at the end of each deposition cycle, allowing maximal precursor decomposition while still avoiding V(IV) oxidation. The resulting surface hydrophilicity, indispensable for the homogeneous deposition of the next layer, is explained by an increased surface roughness and the increased availability of surface vanadyl groups. Crystalline V(6)O(13) with a preferential (002) orientation is obtained after a post deposition annealing in a 0.1% O(2) ambient for thin films with a thickness of 20 nm.

Reliable solution processed planar perovskite hybrid solar cells with large-area uniformity by chloroform soaking and spin rinsing induced surface precipitation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chern, Yann-Cherng; Wu, Hung-Ruei; Chen, Yen-Chu

2015-08-15

A solvent soaking and rinsing method, in which the solvent was allowed to soak all over the surface followed by a spinning for solvent draining, was found to produce perovskite layers with high uniformity on a centimeter scale and with much improved reliability. Besides the enhanced crystallinity and surface morphology due to the rinsing induced surface precipitation that constrains the grain growth underneath in the precursor films, large-area uniformity with film thickness determined exclusively by the rotational speed of rinsing spinning for solvent draining was observed. With chloroform as rinsing solvent, highly uniform and mirror-like perovskite layers of area asmore » large as 8 cm × 8 cm were produced and highly uniform planar perovskite solar cells with power conversion efficiency of 10.6 ± 0.2% as well as much prolonged lifetime were obtained. The high uniformity and reliability observed with this solvent soaking and rinsing method were ascribed to the low viscosity of chloroform as well as its feasibility of mixing with the solvent used in the precursor solution. Moreover, since the surface precipitation forms before the solvent draining, this solvent soaking and rinsing method may be adapted to spinless process and be compatible with large-area and continuous production. With the large-area uniformity and reliability for the resultant perovskite layers, this chloroform soaking and rinsing approach may thus be promising for the mass production and commercialization of large-area perovskite solar cells.« less

Method for fabrication of crack-free ceramic dielectric films

DOEpatents

Ma, Beihai; Narayanan, Manoj; Balachandran, Uthamalingam; Chao, Sheng; Liu, Shanshan

2016-05-31

The invention provides a process for forming crack-free dielectric films on a substrate. The process comprises the application of a dielectric precursor layer of a thickness from about 0.3 .mu.m to about 1.0 .mu.m to a substrate. The deposition is followed by low temperature heat pretreatment, prepyrolysis, pyrolysis and crystallization step for each layer. The deposition, heat pretreatment, prepyrolysis, pyrolysis and crystallization are repeated until the dielectric film forms an overall thickness of from about 1.5 .mu.m to about 20.0 .mu.m and providing a final crystallization treatment to form a thick dielectric film. The process provides a thick crack-free dielectric film on a substrate, the dielectric forming a dense thick crack-free dielectric having an overall dielectric thickness of from about 1.5 .mu.m to about 20.0 .mu.m.

Morphological evolution of carbon nanofibers encapsulating SnCo alloys and its effect on growth of the solid electrolyte interphase layer.

PubMed

Shin, Jungwoo; Ryu, Won-Hee; Park, Kyu-Sung; Kim, Il-Doo

2013-08-27

Two distinctive one-dimensional (1-D) carbon nanofibers (CNFs) encapsulating irregularly and homogeneously segregated SnCo nanoparticles were synthesized via electrospinning of polyvinylpyrrolidone (PVP) and polyacrylonitrile (PAN) polymers containing Sn-Co acetate precursors and subsequent calcination in reducing atmosphere. CNFs synthesized with PVP, which undergoes structural degradation of the polymer during carbonization processes, exhibited irregular segregation of heterogeneous alloy particles composed of SnCo, Co3Sn2, and SnO with a size distribution of 30-100 nm. Large and exposed multiphase SnCo particles in PVP-driven amorphous CNFs (SnCo/PVP-CNFs) kept decomposing liquid electrolyte and were partly detached from CNFs during cycling, leading to a capacity fading at the earlier cycles. The closer study of solid electrolyte interphase (SEI) layers formed on the CNFs reveals that the gradual growth of fiber radius due to continuous increment of SEI layer thickness led to capacity fading. In contrast, SnCo particles in PAN-driven CNFs (SnCo/PAN-CNFs) showed dramatically reduced crystallite sizes (<10 nm) of single phase SnCo nanoparticles which were entirely embedded in dense, semicrystalline, and highly conducting 1-D carbon matrix. The growth of SEI layer was limited and saturated during cycling. As a result, SnCo/PAN-CNFs showed much improved cyclability (97.9% capacity retention) and lower SEI layer thickness (86 nm) after 100 cycles compared to SnCo/PVP-CNFs (capacity retention, 71.9%; SEI layer thickness, 593 nm). This work verifies that the thermal behavior of carbon precursor is highly responsible for the growth mechanism of SEI layer accompanied with particles detachment and cyclability of alloy particle embedded CNFs.

Factors dominating 3-dimensional ozone distribution during high tropospheric ozone period.

PubMed

Chen, Xiaoyang; Liu, Yiming; Lai, Anqi; Han, Shuangshuang; Fan, Qi; Wang, Xuemei; Ling, Zhenhao; Huang, Fuxiang; Fan, Shaojia

2018-01-01

Data from an in situ monitoring network and five ozone sondes are analysed during August of 2012, and a high tropospheric ozone episode is observed around the 8th of AUG. The Community Multi-scale Air Quality (CMAQ) model and its process analysis tool were used to study factors and mechanisms for high ozone mixing ratio at different levels of ozone vertical profiles. A sensitive scenario without chemical initial and boundary conditions (ICBCs) from MOZART4-GEOS5 was applied to study the impact of stratosphere-troposphere exchange (STE) on vertical ozone. The simulation results indicated that the first high ozone peak near the tropopause was dominated by STE. Results from process analysis showed that: in the urban area, the second peak at approximately 2 km above ground height was mainly caused by local photochemical production. The third peak (near surface) was mainly caused by the upwind transportation from the suburban/rural areas; in the suburban/rural areas, local photochemical production of ozone dominated the high ozone mixing ratio from the surface to approximately 3 km height. Furthermore, the capability of indicators to distinguish O 3 -precursor sensitivity along the vertical O 3 profiles was investigated. Two sensitive scenarios, which had cut 30% anthropogenic NO X or VOC emissions, showed that O 3 -precursor indicators, specifically the ratios of O 3 /NOy, H 2 O 2 /HNO 3 or H 2 O 2 /NO Z , could partly distinguish the O 3 -precursor sensitivity between VOCs-sensitive and NOx-sensitive along the vertical profiles. In urban area, the O 3 -precursor relationship transferred from VOCs-sensitive within the boundary layer to NOx-sensitive at approximately 1-3 km above ground height, further confirming the dominant roles of transportation and photochemical production in high O 3 peaks at the near-ground layer and 2 km above ground height, respectively. Copyright © 2017 Elsevier Ltd. All rights reserved.

Oxygen-free atomic layer deposition of indium sulfide

DOEpatents

Martinson, Alex B.; Hock, Adam S.; McCarthy, Robert; Weimer, Matthew S.

2016-07-05

A method for synthesizing an In(III) N,N'-diisopropylacetamidinate precursor including cooling a mixture comprised of diisopropylcarbodiimide and diethyl ether to approximately -30.degree. C., adding methyllithium drop-wise into the mixture, allowing the mixture to warm to room temperature, adding indium(III) chloride as a solid to the mixture to produce a white solid, dissolving the white solid in pentane to form a clear and colorless solution, filtering the mixture over a celite plug, and evaporating the solution under reduced pressure to obtain a solid In(III) N,N'-diisopropylacetamidinate precursor. This precursor has been further used to develop a novel atomic layer deposition technique for indium sulfide by dosing a reactor with the precursor, purging with nitrogen, dosing with dilute hydrogen sulfide, purging again with nitrogen, and repeating these steps to increase growth.

Solution-Processed Cu2ZnSn(S,Se) 4 Thin-Film Solar Cells Using Elemental Cu, Zn, Sn, S, and Se Powders as Source.

PubMed

Guo, Jing; Pei, Yingli; Zhou, Zhengji; Zhou, Wenhui; Kou, Dongxing; Wu, Sixin

2015-12-01

Solution-processed approach for the deposition of Cu2ZnSn (S,Se)4 (CZTSSe) absorbing layer offers a route for fabricating thin film solar cell that is appealing because of simplified and low-cost manufacturing, large-area coverage, and better compatibility with flexible substrates. In this work, we present a simple solution-based approach for simultaneously dissolving the low-cost elemental Cu, Zn, Sn, S, and Se powder, forming a homogeneous CZTSSe precursor solution in a short time. Dense and compact kesterite CZTSSe thin film with high crystallinity and uniform composition was obtained by selenizing the low-temperature annealed spin-coated precursor film. Standard CZTSSe thin film solar cell based on the selenized CZTSSe thin film was fabricated and an efficiency of 6.4 % was achieved.

N-halamine biocidal coatings via a layer-by-layer assembly technique.

PubMed

Cerkez, Idris; Kocer, Hasan B; Worley, S D; Broughton, R M; Huang, T S

2011-04-05

Two N-halamine copolymer precursors, poly(2,2,6,6-tetramethyl-4-piperidyl methacrylate-co-acrylic acid potassium salt) and poly(2,2,6,6-tetramethyl-4-piperidyl methacrylate-co-trimethyl-2-methacryloxyethylammonium chloride) have been synthesized and successfully coated onto cotton fabric via a layer-by-layer (LbL) assembly technique. A multilayer thin film was deposited onto the fiber surfaces by alternative exposure to polyelectrolyte solutions. The coating was rendered biocidal by a dilute household bleach treatment. The biocidal efficacies of tested swatches composed of treated fibers were evaluated against Staphylococcus aureus and Escherichia coli. It was determined that chlorinated samples inactivated both S. aureus and E. coli O157:H7 within 15 min of contact time, whereas the unchlorinated control samples did not exhibit significant biocidal activities. Stabilities of the coatings toward washing and ultraviolet light exposure have also been studied. It was found that the stability toward washing was superior, whereas the UVA light stability was moderate compared to previously studied N-halamine moieties. The layer-by-layer assembly technique can be used to attach N-halamine precursor polymers onto cellulose surfaces without using covalently bonding tethering groups which limit the structure designs. In addition, ionic precursors are very soluble in water, thus promising for biocidal coatings without the use of organic solvents.

Carbon reactivation kinetics in GaAs: Its dependence on dopant precursor, doping level, and layer thickness

NASA Astrophysics Data System (ADS)

Mimila-Arroyo, J.; Bland, S.; Barbé, M.

2002-05-01

The reactivation kinetics of the acceptor behavior of carbon, its dependence on dopant precursors, doping level, layer thickness, and annealing temperature, as well as the behavior of carbon-hydrogen complexes in GaAs grown by metalorganic chemical vapor deposition are studied. Independent of the carbon source, in the "as grown" material, systematically carbon hydrogen complexes are present and the hole concentration is lower than the corresponding carbon concentration. The carbon reactivation kinetics was achieved by ex situ rapid thermal annealing through a series of multistage annealing experiments and assessed at each annealing stage by infrared absorption, hydrogen secondary ion mass spectroscopy profiling, and hole concentration measurements. Carbon reactivation occurs solely by the debonding of hydrogen from the isolated carbon acceptor and its out-diffusion from the sample. The carbon reactivation kinetics can be treated as a first order one with an activation energy, Ea=1.42±0.01 eV, independent of doping precursors, doping level, and layer thickness. The reactivation constant results to decrease as doping level and layer thickness increase. An empirical formula has been obtained that allows one to calculate the reactivation constant as a function of the carbon doping, layer thickness, and annealing temperature, allowing one to determine the optimal carbon reactivation conditions for any C:GaAs layer.

Selective growth of Ge1- x Sn x epitaxial layer on patterned SiO2/Si substrate by metal-organic chemical vapor deposition

NASA Astrophysics Data System (ADS)

Takeuchi, Wakana; Washizu, Tomoya; Ike, Shinichi; Nakatsuka, Osamu; Zaima, Shigeaki

2018-01-01

We have investigated the selective growth of a Ge1- x Sn x epitaxial layer on a line/space-patterned SiO2/Si substrate by metal-organic chemical vapor deposition. We examined the behavior of a Sn precursor of tributyl(vinyl)tin (TBVSn) during the growth on Si and SiO2 substrates and investigated the effect of the Sn precursor on the selective growth. The selective growth of the Ge1- x Sn x epitaxial layer was performed under various total pressures and growth temperatures of 300 and 350 °C. The selective growth of the Ge1- x Sn x epitaxial layer on the patterned Si region is achieved at a low total pressure without Ge1- x Sn x growth on the SiO2 region. In addition, we found that the Sn content in the Ge1- x Sn x epitaxial layer increases with width of the SiO2 region for a fixed Si width even with low total pressure. To control the Sn content in the selective growth of the Ge1- x Sn x epitaxial layer, it is important to suppress the decomposition and migration of Sn and Ge precursors.

Patterned growth of p-type MoS 2 atomic layers using sol-gel as precursor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, Wei; Lin, Junhao; Feng, Wei

2D layered MoS 2 has drawn intense attention for its applications in flexible electronic, optoelectronic, and spintronic devices. Most of the MoS 2 atomic layers grown by conventional chemical vapor deposition techniques are n-type due to the abundant sulfur vacancies. Facile production of MoS 2 atomic layers with p-type behavior, however, remains challenging. Here, a novel one-step growth has been developed to attain p-type MoS 2 layers in large scale by using Mo-containing sol–gel, including 1% tungsten (W). Atomic-resolution electron microscopy characterization reveals that small tungsten oxide clusters are commonly present on the as-grown MoS 2 film due to themore » incomplete reduction of W precursor at the reaction temperature. These omnipresent small tungsten oxide clusters contribute to the p-type behavior, as verified by density functional theory calculations, while preserving the crystallinity of the MoS 2 atomic layers. The Mo containing sol–gel precursor is compatible with the soft-lithography techniques, which enables patterned growth of p-type MoS 2 atomic layers into regular arrays with different shapes, holding great promise for highly integrated device applications. Lastly, an atomically thin p–n junction is fabricated by the as-prepared MoS 2, which shows strong rectifying behavior.« less

Patterned growth of p-type MoS 2 atomic layers using sol-gel as precursor

DOE PAGES

Zheng, Wei; Lin, Junhao; Feng, Wei; ...

2016-07-19

2D layered MoS 2 has drawn intense attention for its applications in flexible electronic, optoelectronic, and spintronic devices. Most of the MoS 2 atomic layers grown by conventional chemical vapor deposition techniques are n-type due to the abundant sulfur vacancies. Facile production of MoS 2 atomic layers with p-type behavior, however, remains challenging. Here, a novel one-step growth has been developed to attain p-type MoS 2 layers in large scale by using Mo-containing sol–gel, including 1% tungsten (W). Atomic-resolution electron microscopy characterization reveals that small tungsten oxide clusters are commonly present on the as-grown MoS 2 film due to themore » incomplete reduction of W precursor at the reaction temperature. These omnipresent small tungsten oxide clusters contribute to the p-type behavior, as verified by density functional theory calculations, while preserving the crystallinity of the MoS 2 atomic layers. The Mo containing sol–gel precursor is compatible with the soft-lithography techniques, which enables patterned growth of p-type MoS 2 atomic layers into regular arrays with different shapes, holding great promise for highly integrated device applications. Lastly, an atomically thin p–n junction is fabricated by the as-prepared MoS 2, which shows strong rectifying behavior.« less

High crystalline Cu2ZnSnS4 semiconductor prepared from low toxicity ethanol-based precursors

NASA Astrophysics Data System (ADS)

Munir, Badrul; Prastyo, Bayu Eko; Nurjaya, Dwi Marta; Muslih, Ersan Yudhapratama; Alfauzan, Sahri Karim

2017-01-01

At this moment, we present a new, cost-effective, and environmentally friendly method of preparing a high crystalline Cu2ZnSnS4 (CZTS) absorber layer for thin film solar cells using ethanol-based solutions. Ethanolamine (ETA) and 2-mercaptopropionic acid (MPA) were studied as a stabilizer and to improve wetting ability of the precursors during the deposition process. Cu2ZnSnS4 precursors are deposited onto soda lime glass using spin coater in different molar of cations in the precursor. The effects of a precursor system, ethanol-ETA-MPA, and ethanol-MPA, on the structure, morphology, composition and optical properties of CZTS thin films have been investigated in details. X-ray diffraction and energy-dispersive X-ray spectroscopy analyses confirmed the successful fabrication of high crystalline Cu2ZnSnS4 kesterite phase. The crystallinity of CZTS is continue increasing before reaching 2.2 molar cations of the ethanol-MPA precursors. The crystallinity of ethanol-ETA-MPA precursors remains similar in the experiment using 1.2 molar and 1.6 molars. The highest crystallinity was achieved using 2 molar cations of the ethanol-MPA precursor. Its band gap energy is found to be around 1.4 eV. The SEM micrographs of CZTS film shows the average grain size around 1.5 µm and some porosity which indicated the room of improvement. The high-crystallinity CZTS achieved in the present study brings a low-cost absorber semiconductor one step closer to practical use.

Design of Polymers with Semiconductor, NLO and Structural Properties.

DTIC Science & Technology

1991-04-22

polymer thin films. + 14 KV Needle electrod Polymer layer ITO electrode Substrate Heater and temperature control unit The second harmonic coefficients of...the solubily and processability through utilization of derivitization and precursor routes we have been able to form the first optical quality films...ethylene spacer, and therefore 14 possesses a great degree of solubility in organic solvents, necessary for the fabrication of optical quality thin films

Surface passivation of Fe{sub 3}O{sub 4} nanoparticles with Al{sub 2}O{sub 3} via atomic layer deposition in a rotating fluidized bed reactor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Duan, Chen-Long; Deng, Zhang; Cao, Kun

2016-07-15

Iron(II,III) oxide (Fe{sub 3}O{sub 4}) nanoparticles have shown great promise in many magnetic-related applications such as magnetic resonance imaging, hyperthermia treatment, and targeted drug delivery. Nevertheless, these nanoparticles are vulnerable to oxidation and magnetization loss under ambient conditions, and passivation is usually required for practical applications. In this work, a home-built rotating fluidized bed (RFB) atomic layer deposition (ALD) reactor was employed to form dense and uniform nanoscale Al{sub 2}O{sub 3} passivation layers on Fe{sub 3}O{sub 4} nanoparticles. The RFB reactor facilitated the precursor diffusion in the particle bed and intensified the dynamic dismantling of soft agglomerates, exposing every surfacemore » reactive site to precursor gases. With the aid of in situ mass spectroscopy, it was found that a thicker fluidization bed formed by larger amount of particles increased the residence time of precursors. The prolonged residence time allowed more thorough interactions between the particle surfaces and the precursor gas, resulting in an improvement of the precursor utilization from 78% to nearly 100%, even under a high precursor feeding rate. Uniform passivation layers around the magnetic cores were demonstrated by both transmission electron microscopy and the statistical analysis of Al mass concentrations. Individual particles were coated instead of the soft agglomerates, as was validated by the specific surface area analysis and particle size distribution. The results of thermogravimetric analysis suggested that 5 nm-thick ultrathin Al{sub 2}O{sub 3} coatings could effectively protect the Fe{sub 3}O{sub 4} nanoparticles from oxidation. The x-ray diffraction patterns also showed that the magnetic core crystallinity of such passivated nanoparticles could be well preserved under accelerated oxidation conditions. The precise thickness control via ALD maintained the saturation magnetization at 66.7 emu/g with a 5 nm-thick Al{sub 2}O{sub 3} passivation layer. This good preservation of the magnetic properties with superior oxidation resistance will be beneficial for practical magnetic-based applications.« less

Process for forming a metal compound coating on a substrate

DOEpatents

Sharp, D.J.; Vernon, M.E.; Wright, S.A.

1988-06-29

A method of coating a substrate with a thin layer of a metal compound by forming a dispersion of an electrophoretically active organic colloid and a precursor of the metal compound in an electrolytic cell in which the substrate is an electrode. Upon application of an electric potential, the electrode is coated with a mixture of the organic colloid and the precursor to the metal compound, and the coated substrate is then heated in the presence of an atmosphere or vacuum to decompose the organic colloid and form a coating of either a combination of metal compound and carbon, or optionally forming a porous metal compound coating by heating to a temperature high enough to chemically react the carbon.

Fabrication of contacts for silicon solar cells including printing burn through layers

DOEpatents

Ginley, David S; Kaydanova, Tatiana; Miedaner, Alexander; Curtis, Calvin J; Van Hest, Marinus Franciscus Antonius Maria

2014-06-24

A method for fabricating a contact (240) for a solar cell (200). The method includes providing a solar cell substrate (210) with a surface that is covered or includes an antireflective coating (220). For example, the substrate (210) may be positioned adjacent or proximate to an outlet of an inkjet printer (712) or other deposition device. The method continues with forming a burn through layer (230) on the coating (220) by depositing a metal oxide precursor (e.g., using an inkjet or other non-contact printing method to print or apply a volume of liquid or solution containing the precursor). The method includes forming a contact layer (240) comprising silver over or on the burn through layer (230), and then annealing is performed to electrically connect the contact layer (240) to the surface of the solar cell substrate (210) through a portion of the burn through layer (230) and the coating (220).

Electron-beam Induced Processes and their Applicability to Mask Repair

NASA Astrophysics Data System (ADS)

Boegli, Volker A.; Koops, Hans W. P.; Budach, Michael; Edinger, Klaus; Hoinkis, Ottmar; Weyrauch, Bernd; Becker, Rainer; Schmidt, Rudolf; Kaya, Alexander; Reinhardt, Andreas; Braeuer, Stephan; Honold, Heinz; Bihr, Johannes; Greiser, Jens; Eisenmann, Michael

2002-12-01

The applicability of electron-beam induced chemical reactions to mask repair is investigated. To achieve deposition and chemical etching with a focused electron-beam system, it is required to disperse chemicals in a molecular beam to the area of interest with a well-defined amount of molecules and monolayers per second. For repair of opaque defects the precursor gas reacts with the absorber material of the mask and forms a volatile reaction product, which leaves the surface. In this way the surface atoms are removed layer by layer. For clear defect repair, additional material, which is light absorbing in the UV, is deposited onto the defect area. This material is rendered as a nanocrystalline deposit from metal containing precursors. An experimental electron-beam mask repair system is developed and used to perform exploratory work applicable to photo mask, EUV mask, EPL and LEEPL stencil mask repair. The tool is described and specific repair actions are demonstrated. Platinum deposited features with lateral dimensions down to 20 nm demonstrate the high resolution obtainable with electron beam induced processes, while AFM and AIMS measurements indicate, that specifications for mask repair at the 70 nm device node can be met. In addition, examples of etching quartz and TaN are given.

Theoretical modeling and experimental observations of the atomic layer deposition of SrO using a cyclopentadienyl Sr precursor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fredrickson, Kurt D.; Slepko, Alex; Demkov, Alexander A., E-mail: demkov@physics.utexas.edu

2016-08-14

First-principle calculations are used to model the adsorption and hydration of strontium bis(cyclopentadienyl) [Sr(Cp){sub 2}] on TiO{sub 2}-terminated strontium titanate, SrTiO{sub 3} (STO), for the deposition of strontium oxide, SrO, by atomic layer deposition (ALD). The Sr(Cp){sub 2} precursor is shown to adsorb on the TiO{sub 2}-terminated surface, with the Sr atom assuming essentially the bulk position in STO. The C–Sr bonds are weaker than in the free molecule, with a Ti atom at the surface bonding to one of the C atoms in the cyclopentadienyl rings. The surface does not need to be hydrogenated for precursor adsorption. The calculationsmore » are compared with experimental observations for a related Sr cyclopentadienyl precursor, strontium bis(triisopropylcyclopentadienyl) [Sr({sup i}Pr{sub 3}Cp){sub 2}], adsorbed on TiO{sub 2}-terminated STO. High-resolution x-ray photoelectron spectroscopy and low-energy ion scattering spectroscopy show adsorption of the Sr precursor on the TiO{sub 2}-terminated STO after a single precursor dose. This study suggests that ALD growth from the strontium precursors featuring cyclopentadienyl ligands, such as Sr(Cp){sub 2}, may initiate film growth on non-hydroxylated surfaces.« less

Superpixel guided active contour segmentation of retinal layers in OCT volumes

NASA Astrophysics Data System (ADS)

Bai, Fangliang; Gibson, Stuart J.; Marques, Manuel J.; Podoleanu, Adrian

2018-03-01

Retinal OCT image segmentation is a precursor to subsequent medical diagnosis by a clinician or machine learning algorithm. In the last decade, many algorithms have been proposed to detect retinal layer boundaries and simplify the image representation. Inspired by the recent success of superpixel methods for pre-processing natural images, we present a novel framework for segmentation of retinal layers in OCT volume data. In our framework, the region of interest (e.g. the fovea) is located using an adaptive-curve method. The cell layer boundaries are then robustly detected firstly using 1D superpixels, applied to A-scans, and then fitting active contours in B-scan images. Thereafter the 3D cell layer surfaces are efficiently segmented from the volume data. The framework was tested on healthy eye data and we show that it is capable of segmenting up to 12 layers. The experimental results imply the effectiveness of proposed method and indicate its robustness to low image resolution and intrinsic speckle noise.

Partitioning Tungsten between Matrix Precursors and Chondrule Precursors through Relative Settling

NASA Astrophysics Data System (ADS)

Hubbard, Alexander

2016-08-01

Recent studies of chondrites have found a tungsten isotopic anomaly between chondrules and matrix. Given the refractory nature of tungsten, this implies that W was carried into the solar nebula by at least two distinct families of pre-solar grains. The observed chondrule/matrix split requires that the distinct families were kept separate during the dust coagulation process, and that the two families of grain interacted with the chondrule formation mechanism differently. We take the co-existence of different families of solids in the same general orbital region at the chondrule-precursor size as given, and explore the requirements for them to have interacted with the chondrule formation process at significantly different rates. We show that this sorting of families of solids into chondrule- and matrix-destined dust had to have been at least as powerful a sorting mechanism as the relative settling of aerodynamically distinct grains at least two scale heights above the midplane. The requirement that the chondrule formation mechanism was correlated in some fashion with a dust-grain sorting mechanism argues strongly for spatially localized chondrule formation mechanisms such as turbulent dissipation in non-thermally ionized disk surface layers, and argues against volume-filling mechanisms such as planetesimal bow shocks.

Growth of organic crystals via attachment and transformation of nanoscopic precursors

NASA Astrophysics Data System (ADS)

Jiang, Yuan; Kellermeier, Matthias; Gebaue, Denis; Lu, Zihao; Rosenberg, Rose; Moise, Adrian; Przybylski, Michael; Cölfen, Helmut

2017-06-01

A key requirement for the understanding of crystal growth is to detect how new layers form and grow at the nanoscale. Multistage crystallization pathways involving liquid-like, amorphous or metastable crystalline precursors have been predicted by theoretical work and have been observed experimentally. Nevertheless, there is no clear evidence that any of these precursors can also be relevant for the growth of crystals of organic compounds. Herein, we present a new growth mode for crystals of DL-glutamic acid monohydrate that proceeds through the attachment of preformed nanoscopic species from solution, their subsequent decrease in height at the surface and final transformation into crystalline 2D nuclei that eventually build new molecular layers by further monomer incorporation. This alternative mechanism provides a direct proof for the existence of multistage pathways in the crystallization of molecular compounds and the relevance of precursor units larger than the monomeric constituents in the actual stage of growth.

New insights into earthquake precursors from InSAR.

PubMed

Moro, Marco; Saroli, Michele; Stramondo, Salvatore; Bignami, Christian; Albano, Matteo; Falcucci, Emanuela; Gori, Stefano; Doglioni, Carlo; Polcari, Marco; Tallini, Marco; Macerola, Luca; Novali, Fabrizio; Costantini, Mario; Malvarosa, Fabio; Wegmüller, Urs

2017-09-20

We measured ground displacements before and after the 2009 L'Aquila earthquake using multi-temporal InSAR techniques to identify seismic precursor signals. We estimated the ground deformation and its temporal evolution by exploiting a large dataset of SAR imagery that spans seventy-two months before and sixteen months after the mainshock. These satellite data show that up to 15 mm of subsidence occurred beginning three years before the mainshock. This deformation occurred within two Quaternary basins that are located close to the epicentral area and are filled with sediments hosting multi-layer aquifers. After the earthquake, the same basins experienced up to 12 mm of uplift over approximately nine months. Before the earthquake, the rocks at depth dilated, and fractures opened. Consequently, fluids migrated into the dilated volume, thereby lowering the groundwater table in the carbonate hydrostructures and in the hydrologically connected multi-layer aquifers within the basins. This process caused the elastic consolidation of the fine-grained sediments within the basins, resulting in the detected subsidence. After the earthquake, the fractures closed, and the deep fluids were squeezed out. The pre-seismic ground displacements were then recovered because the groundwater table rose and natural recharge of the shallow multi-layer aquifers occurred, which caused the observed uplift.

Probing platinum degradation in polymer electrolyte membrane fuel cells by synchrotron X-ray microscopy.

PubMed

Berejnov, Viatcheslav; Martin, Zulima; West, Marcia; Kundu, Sumit; Bessarabov, Dmitri; Stumper, Jürgen; Susac, Darija; Hitchcock, Adam P

2012-04-14

Synchrotron-based scanning transmission X-ray spectromicroscopy (STXM) was used to characterize the local chemical environment at and around the platinum particles in the membrane (PTIM) which form in operationally tested (end-of-life, EOL) catalyst coated membranes (CCMs) of polymer electrolyte membrane fuel cells (PEM-FC). The band of metallic Pt particles in operationally tested CCM membranes was imaged using transmission electron microscopy (TEM). The cathode catalyst layer in the beginning-of-life (BOL) CCMs was fabricated using commercially available catalysts created from Pt precursors with and without nitrogen containing ligands. The surface composition of these catalyst powders was measured by X-ray Photoelectron Spectroscopy (XPS). The local chemical environment of the PTIM in EOL CCMs was found to be directly related to the Pt precursor used in CCM fabrication. STXM chemical mapping at the N 1s edge revealed a characteristic spectrum at and around the dendritic Pt particles in CCMs fabricated with nitrogen containing Pt-precursors. This N 1s spectrum was identical to that of the cathode and different from the membrane. For CCM samples fabricated without nitrogen containing Pt-precursors the N 1s spectrum at the Pt particles was indistinguishable from that of the adjacent membrane. We interpret these observations to indicate that nitrogenous ligands in the nitrogen containing precursors, or decomposition product(s) from that source, are transported together with the dissolved Pt from the cathode into the membrane as a result of the catalyst degradation process. This places constraints on possible mechanisms for the PTIM band formation process.

Synthesis of transparent conducting oxide coatings

DOEpatents

Elam, Jeffrey W.; Martinson, Alex B. F.; Pellin, Michael J.; Hupp, Joseph T.

2010-05-04

A method and system for preparing a light transmitting and electrically conductive oxide film. The method and system includes providing an atomic layer deposition system, providing a first precursor selected from the group of cyclopentadienyl indium, tetrakis (dimethylamino) tin and mixtures thereof, inputting to the deposition system the first precursor for reaction for a first selected time, providing a purge gas for a selected time, providing a second precursor comprised of an oxidizer, and optionally inputting a second precursor into the deposition system for reaction and alternating for a predetermined number of cycles each of the first precursor, the purge gas and the second precursor to produce the oxide film.

Corundum ceramic materials modified with silica nanopowders: structure and mechanical properties

NASA Astrophysics Data System (ADS)

Kostytsyn, M. A.; Muratov, D. S.; Lysov, D. V.; Chuprunov, K. O.; Yudin, A. G.; Leybo, D. V.

2016-01-01

Filtering elements are often used in the metallurgy of rare earth metals. Corundum ceramic is one of the most suitable materials for this purpose. The process of formation and the properties of nanomodified ceramic materials, which are proposed as filtering materials with tunable effective porosity, are described. A silica nanopowder is used as a porosity-increasing agent. Vortex layer apparatus is used for mixing of precursor materials. The obtained results show that nanomodification with the vortex layer apparatus using 0.04 wt. % silica nanopowder as a modifying agent leads to an increase in the compression strength of corundum ceramic by the factor of 1.5.

Fabrication of CIS Absorber Layers with Different Thicknesses Using A Non-Vacuum Spray Coating Method.

PubMed

Diao, Chien-Chen; Kuo, Hsin-Hui; Tzou, Wen-Cheng; Chen, Yen-Lin; Yang, Cheng-Fu

2014-01-03

In this study, a new thin-film deposition process, spray coating method (SPM), was investigated to deposit the high-densified CuInSe₂ absorber layers. The spray coating method developed in this study was a non-vacuum process, based on dispersed nano-scale CuInSe₂ precursor and could offer a simple, inexpensive, and alternative formation technology for CuInSe₂ absorber layers. After spraying on Mo/glass substrates, the CuInSe₂ thin films were annealed at 550 °C by changing the annealing time from 5 min to 30 min in a selenization furnace, using N₂ as atmosphere. When the CuInSe₂ thin films were annealed, without extra Se or H₂Se gas used as the compensation source during the annealing process. The aim of this project was to investigate the influence of annealing time on the densification and crystallization of the CuInSe₂ absorber layers to optimize the quality for cost effective solar cell production. The thickness of the CuInSe₂ absorber layers could be controlled as the volume of used dispersed CuInSe₂-isopropyl alcohol solution was controlled. In this work, X-ray diffraction patterns, field emission scanning electron microscopy, and Hall parameter measurements were performed in order to verify the quality of the CuInSe₂ absorber layers obtained by the Spray Coating Method.

Optical in situ monitoring of plasma-enhanced atomic layer deposition process

NASA Astrophysics Data System (ADS)

Zeeshan Arshad, Muhammad; Jo, Kyung Jae; Kim, Hyun Gi; Jeen Hong, Sang

2018-06-01

An optical in situ process monitoring method for the early detection of anomalies in plasma process equipment is presented. Cyclic process steps of precursor treatment and plasma reaction for the deposition of an angstrom-scale film increase their complexity to ensure the process quality. However, a small deviation in process parameters, for instance, gas flow rate, process temperature, or RF power, may jeopardize the deposited film quality. As a test vehicle for the process monitoring, we have investigated the aluminum-oxide (Al2O3) encapsulation process in plasma-enhanced atomic layer deposition (PEALD) to form a moisture and oxygen diffusion barrier in organic-light emitting diodes (OLEDs). By optical in situ monitoring, we successfully identified the reduction in oxygen flow rates in the reaction steps, which resulted in a 2.67 times increase in the water vapor transmission ratio (WVTR) of the deposited Al2O3 films. Therefore, we are convinced that the suggested in situ monitoring method is useful for the detection of process shifts or drifts that adversely affect PEALD film quality.

Highly conductive, multi-layer composite precursor composition to fuel cell flow field plate or bipolar plate

DOEpatents

Jang, Bor Z [Centerville, OH; Zhamu, Aruna [Centerville, OH; Guo, Jiusheng [Centerville, OH

2011-02-15

This invention provides a moldable, multiple-layer composite composition, which is a precursor to an electrically conductive composite flow field plate or bipolar plate. In one preferred embodiment, the composition comprises a plurality of conductive sheets and a plurality of mixture layers of a curable resin and conductive fillers, wherein (A) each conductive sheet is attached to at least one resin-filler mixture layer; (B) at least one of the conductive sheets comprises flexible graphite; and (C) at least one resin-filler mixture layer comprises a thermosetting resin and conductive fillers with the fillers being present in a sufficient quantity to render the resulting flow field plate or bipolar plate electrically conductive with a conductivity no less than 100 S/cm and thickness-direction areal conductivity no less than 200 S/cm.sup.2.

Large-Scale Precise Printing of Ultrathin Sol-Gel Oxide Dielectrics for Directly Patterned Solution-Processed Metal Oxide Transistor Arrays.

PubMed

Lee, Won-June; Park, Won-Tae; Park, Sungjun; Sung, Sujin; Noh, Yong-Young; Yoon, Myung-Han

2015-09-09

Ultrathin and dense metal oxide gate di-electric layers are reported by a simple printing of AlOx and HfOx sol-gel precursors. Large-area printed indium gallium zinc oxide (IGZO) thin-film transistor arrays, which exhibit mobilities >5 cm(2) V(-1) s(-1) and gate leakage current of 10(-9) A cm(-2) at a very low operation voltage of 2 V, are demonstrated by continuous simple bar-coated processes. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Influence of ZnO seed layer precursor molar ratio on the density of interface defects in low temperature aqueous chemically synthesized ZnO nanorods/GaN light-emitting diodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alnoor, Hatim, E-mail: hatim.alnoor@liu.se; Iandolo, Donata; Willander, Magnus

Low temperature aqueous chemical synthesis (LT-ACS) of zinc oxide (ZnO) nanorods (NRs) has been attracting considerable research interest due to its great potential in the development of light-emitting diodes (LEDs). The influence of the molar ratio of the zinc acetate (ZnAc): KOH as a ZnO seed layer precursor on the density of interface defects and hence the presence of non-radiative recombination centers in LT-ACS of ZnO NRs/GaN LEDs has been systematically investigated. The material quality of the as-prepared seed layer as quantitatively deduced by the X-ray photoelectron spectroscopy is found to be influenced by the molar ratio. It is revealedmore » by spatially resolved cathodoluminescence that the seed layer molar ratio plays a significant role in the formation and the density of defects at the n-ZnO NRs/p-GaN heterostructure interface. Consequently, LED devices processed using ZnO NRs synthesized with molar ratio of 1:5 M exhibit stronger yellow emission (∼575 nm) compared to those based on 1:1 and 1:3 M ratios as measured by the electroluminescence. Furthermore, seed layer molar ratio shows a quantitative dependence of the non-radiative defect densities as deduced from light-output current characteristics analysis. These results have implications on the development of high-efficiency ZnO-based LEDs and may also be helpful in understanding the effects of the ZnO seed layer on defect-related non-radiative recombination.« less

Plasma-enhanced atomic layer deposition of titanium oxynitrides films: A comparative spectroscopic and electrical study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sowińska, Małgorzata, E-mail: malgorzata.sowinska@b-tu.de; Henkel, Karsten; Schmeißer, Dieter

2016-01-15

The process parameters' impact of the plasma-enhanced atomic layer deposition (PE-ALD) method on the oxygen to nitrogen (O/N) ratio in titanium oxynitride (TiO{sub x}N{sub y}) films was studied. Titanium(IV)isopropoxide in combination with NH{sub 3} plasma and tetrakis(dimethylamino)titanium by applying N{sub 2} plasma processes were investigated. Samples were characterized by the in situ spectroscopic ellipsometry, x-ray photoelectron spectroscopy, and electrical characterization (current–voltage: I-V and capacitance–voltage: C-V) methods. The O/N ratio in the TiO{sub x}N{sub y} films is found to be very sensitive for their electric properties such as conductivity, dielectric breakdown, and permittivity. Our results indicate that these PE-ALD film propertiesmore » can be tuned, via the O/N ratio, by the selection of the process parameters and precursor/coreactant combination.« less

Method for fabrication of crack-free ceramic dielectric films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ma, Beihai; Narayanan, Manoj; Balachandran, Uthamalingam

The invention provides a process for forming crack-free dielectric films on a substrate. The process comprises the application of a dielectric precursor layer of a thickness from about 0.3 .mu.m to about 1.0 .mu.m to a substrate. The deposition is followed by low temperature heat pretreatment, prepyrolysis, pyrolysis and crystallization step for each layer. The deposition, heat pretreatment, prepyrolysis, pyrolysis and crystallization are repeated until the dielectric film forms an overall thickness of from about 1.5 .mu.m to about 20.0 .mu.m and providing a final crystallization treatment to form a thick dielectric film. The process provides a thick crack-free dielectricmore » film on a substrate, the dielectric forming a dense thick crack-free dielectric having an overall dielectric thickness of from about 1.5 .mu.m to about 20.0 .mu.m.« less

Investigation of nucleation and growth processes of diamond films by atomic force microscopy

NASA Technical Reports Server (NTRS)

George, M. A.; Burger, A.; Collins, W. E.; Davidson, J. L.; Barnes, A. V.; Tolk, N. H.

1994-01-01

The nucleation and growth of plasma-enhanced chemical-vapor deposited polycrystalline diamond films were studied using atomic force microscopy (AFM). AFM images were obtained for (1) nucleated diamond films produced from depositions that were terminated during the initial stages of growth, (2) the silicon substrate-diamond film interface side of diamond films (1-4 micrometers thick) removed from the original surface of the substrate, and (3) the cross-sectional fracture surface of the film, including the Si/diamond interface. Pronounced tip effects were observed for early-stage diamond nucleation attributed to tip convolution in the AFM images. AFM images of the film's cross section and interface, however, were not highly affected by tip convolution, and the images indicate that the surface of the silicon substrate is initially covered by a small grained polycrystalline-like film and the formation of this precursor film is followed by nucleation of the diamond film on top of this layer. X-ray photoelectron spectroscopy spectra indicate that some silicon carbide is present in the precursor layer.

Analytic expressions for Atomic Layer Deposition: coverage, throughput, and materials utilization in cross-flow, particle coating, and spatial ALD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yanguas-Gil, Angel; Elam, Jeffrey W.

2014-05-01

In this work, the authors present analytic models for atomic layer deposition (ALD) in three common experimental configurations: cross-flow, particle coating, and spatial ALD. These models, based on the plug-flow and well-mixed approximations, allow us to determine the minimum dose times and materials utilization for all three configurations. A comparison between the three models shows that throughput and precursor utilization can each be expressed by universal equations, in which the particularity of the experimental system is contained in a single parameter related to the residence time of the precursor in the reactor. For the case of cross-flow reactors, the authorsmore » show how simple analytic expressions for the reactor saturation profiles agree well with experimental results. Consequently, the analytic model can be used to extract information about the ALD surface chemistry (e. g., the reaction probability) by comparing the analytic and experimental saturation profiles, providing a useful tool for characterizing new and existing ALD processes. (C) 2014 American Vacuum Society« less

High throughput two-step ultrasonic spray deposited CH3NH3PbI3 thin film layer for solar cell application

NASA Astrophysics Data System (ADS)

Lan, Ding-Hung; Hong, Shao-Huan; Chou, Li-Hui; Wang, Xiao-Feng; Liu, Cheng-Liang

2018-06-01

Organometal halide perovskite materials have demonstrated tremendous advances in the photovoltaic field recently because of their advantageous features of simple fabrication and high power conversion efficiency. To meet the high demand for high throughput and cost-effective, we present a wet process method that enables the probing of the parameters for perovskite layer deposition through two-step sequential ultrasonic spray-coating. This paper describes a detailed investigation on the effects of modification of spray precursor solution (PbI2 and CH3NH3I precursor concentration and solvents used) and post-annealing condition (temperature and time), which can be performed to create optimal film quality as well as improve device efficiency. Through the systematic optimization, the inverted planar perovskite solar cells show the reproducible photovoltaic properties with best power conversion efficiency (PCE) of 10.40% and average PCE of 9.70 ± 0.40%. A continuous spray-coating technique for rapid fabrication of total 16 pieces of perovskite films was demonstrated for providing a viable alternative for the high throughput production of the perovskite solar cells.

Single-step ambient-air synthesis of graphene from renewable precursors as electrochemical genosensor.

PubMed

Seo, Dong Han; Pineda, Shafique; Fang, Jinghua; Gozukara, Yesim; Yick, Samuel; Bendavid, Avi; Lam, Simon Kwai Hung; Murdock, Adrian T; Murphy, Anthony B; Han, Zhao Jun; Ostrikov, Kostya Ken

2017-01-30

Thermal chemical vapour deposition techniques for graphene fabrication, while promising, are thus far limited by resource-consuming and energy-intensive principles. In particular, purified gases and extensive vacuum processing are necessary for creating a highly controlled environment, isolated from ambient air, to enable the growth of graphene films. Here we exploit the ambient-air environment to enable the growth of graphene films, without the need for compressed gases. A renewable natural precursor, soybean oil, is transformed into continuous graphene films, composed of single-to-few layers, in a single step. The enabling parameters for controlled synthesis and tailored properties of the graphene film are discussed, and a mechanism for the ambient-air growth is proposed. Furthermore, the functionality of the graphene is demonstrated through direct utilization as an electrode to realize an effective electrochemical genosensor. Our method is applicable to other types of renewable precursors and may open a new avenue for low-cost synthesis of graphene films.

Single-step ambient-air synthesis of graphene from renewable precursors as electrochemical genosensor

NASA Astrophysics Data System (ADS)

Seo, Dong Han; Pineda, Shafique; Fang, Jinghua; Gozukara, Yesim; Yick, Samuel; Bendavid, Avi; Lam, Simon Kwai Hung; Murdock, Adrian T.; Murphy, Anthony B.; Han, Zhao Jun; Ostrikov, Kostya (Ken)

2017-01-01

Thermal chemical vapour deposition techniques for graphene fabrication, while promising, are thus far limited by resource-consuming and energy-intensive principles. In particular, purified gases and extensive vacuum processing are necessary for creating a highly controlled environment, isolated from ambient air, to enable the growth of graphene films. Here we exploit the ambient-air environment to enable the growth of graphene films, without the need for compressed gases. A renewable natural precursor, soybean oil, is transformed into continuous graphene films, composed of single-to-few layers, in a single step. The enabling parameters for controlled synthesis and tailored properties of the graphene film are discussed, and a mechanism for the ambient-air growth is proposed. Furthermore, the functionality of the graphene is demonstrated through direct utilization as an electrode to realize an effective electrochemical genosensor. Our method is applicable to other types of renewable precursors and may open a new avenue for low-cost synthesis of graphene films.

Improvement of J(sc) in a Cu2ZnSnS4 Solar Cell by Using a Thin Carbon Intermediate Layer at the Cu2ZnSnS4/Mo Interface.

PubMed

Zhou, Fangzhou; Zeng, Fangqin; Liu, Xu; Liu, Fangyang; Song, Ning; Yan, Chang; Pu, Aobo; Park, Jongsung; Sun, Kaiwen; Hao, Xiaojing

2015-10-21

Back contact modification plays an important role in improving energy conversion efficiency of Cu2ZnSnS4 (CZTS) thin film solar cells. In this paper, an ultrathin carbon layer is introduced on molybdenum (Mo)-coated soda lime glass (SLG) prior to the deposition of CZTS precursor to improve the back contact and therefore enhance CZTS solar cell efficiency. By introducing this layer, the short circuit current (Jsc) and device conversion efficiency increase for both nonvacuum (sol-gel) and vacuum (sputtering) methods. Specifically, for the sol-gel based process, Jsc increases from 13.60 to 16.96 mA/cm(2) and efficiency from 4.47% to 5.52%, while for the sputtering based process, Jsc increases from 17.50 to 20.50 mA/cm(2) and efficiency from 4.10% to 5.20%. Furthermore, introduction of this layer does not lead to any deterioration of either open circuit voltage (Voc) or fill factor (FF).

Sulfurization effect on optical properties of Cu2SNS3 thin films grown by two-stage process

NASA Astrophysics Data System (ADS)

Reddy, G. Phaneendra; Reddy, K. T. Ramakrishna

2017-05-01

A good phase controlled and impurity free two stage process was used to prepare Cu2SnS3 layers on glass substrates. The layers were prepared by sulfurization of sputtered Cu-Sn metallic precursors by varying the sulfurization temperature (Ts) in the range, 150-450°C, keeping the other deposition parameters constant. A complete investigation of the optical properties of the layers with sulfurization temperature was made by using the optical transmittance and reflectance measurements versus wavelength. The absorption coefficient α, was evaluated using the optical data that showed a α > 104 cm-1 for all the as-grown films. The optical bandgap of the as grown layers was determined from the second derivative diffused reflectance spectra that varied from 1.96 eV to 0.99 eV. Consequently, refractive index and extinction coefficient were calculated from Pankov's relations. In addition, the other optical parameters such as the dielectric constants, dissipation factor and also optical conductivity calculated. A detailed analysis of the dependence of all the above parameters on Ts is reported and discussed.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Chen; Metzler, Dominik; Oehrlein, Gottlieb S., E-mail: oehrlein@umd.edu

Angstrom-level plasma etching precision is required for semiconductor manufacturing of sub-10 nm critical dimension features. Atomic layer etching (ALE), achieved by a series of self-limited cycles, can precisely control etching depths by limiting the amount of chemical reactant available at the surface. Recently, SiO{sub 2} ALE has been achieved by deposition of a thin (several Angstroms) reactive fluorocarbon (FC) layer on the material surface using controlled FC precursor flow and subsequent low energy Ar{sup +} ion bombardment in a cyclic fashion. Low energy ion bombardment is used to remove the FC layer along with a limited amount of SiO{sub 2} frommore » the surface. In the present article, the authors describe controlled etching of Si{sub 3}N{sub 4} and SiO{sub 2} layers of one to several Angstroms using this cyclic ALE approach. Si{sub 3}N{sub 4} etching and etching selectivity of SiO{sub 2} over Si{sub 3}N{sub 4} were studied and evaluated with regard to the dependence on maximum ion energy, etching step length (ESL), FC surface coverage, and precursor selection. Surface chemistries of Si{sub 3}N{sub 4} were investigated by x-ray photoelectron spectroscopy (XPS) after vacuum transfer at each stage of the ALE process. Since Si{sub 3}N{sub 4} has a lower physical sputtering energy threshold than SiO{sub 2}, Si{sub 3}N{sub 4} physical sputtering can take place after removal of chemical etchant at the end of each cycle for relatively high ion energies. Si{sub 3}N{sub 4} to SiO{sub 2} ALE etching selectivity was observed for these FC depleted conditions. By optimization of the ALE process parameters, e.g., low ion energies, short ESLs, and/or high FC film deposition per cycle, highly selective SiO{sub 2} to Si{sub 3}N{sub 4} etching can be achieved for FC accumulation conditions, where FC can be selectively accumulated on Si{sub 3}N{sub 4} surfaces. This highly selective etching is explained by a lower carbon consumption of Si{sub 3}N{sub 4} as compared to SiO{sub 2}. The comparison of C{sub 4}F{sub 8} and CHF{sub 3} only showed a difference in etching selectivity for FC depleted conditions. For FC accumulation conditions, precursor chemistry has a weak impact on etching selectivity. Surface chemistry analysis shows that surface fluorination and FC reduction take place during a single ALE cycle for FC depleted conditions. A fluorine rich carbon layer was observed on the Si{sub 3}N{sub 4} surface after ALE processes for which FC accumulation takes place. The angle resolved-XPS thickness calculations confirmed the results of the ellipsometry measurements in all cases.« less

Global tropospheric ozone modeling: Quantifying errors due to grid resolution

NASA Astrophysics Data System (ADS)

Wild, Oliver; Prather, Michael J.

2006-06-01

Ozone production in global chemical models is dependent on model resolution because ozone chemistry is inherently nonlinear, the timescales for chemical production are short, and precursors are artificially distributed over the spatial scale of the model grid. In this study we examine the sensitivity of ozone, its precursors, and its production to resolution by running a global chemical transport model at four different resolutions between T21 (5.6° × 5.6°) and T106 (1.1° × 1.1°) and by quantifying the errors in regional and global budgets. The sensitivity to vertical mixing through the parameterization of boundary layer turbulence is also examined. We find less ozone production in the boundary layer at higher resolution, consistent with slower chemical production in polluted emission regions and greater export of precursors. Agreement with ozonesonde and aircraft measurements made during the NASA TRACE-P campaign over the western Pacific in spring 2001 is consistently better at higher resolution. We demonstrate that the numerical errors in transport processes on a given resolution converge geometrically for a tracer at successively higher resolutions. The convergence in ozone production on progressing from T21 to T42, T63, and T106 resolution is likewise monotonic but indicates that there are still large errors at 120 km scales, suggesting that T106 resolution is too coarse to resolve regional ozone production. Diagnosing the ozone production and precursor transport that follow a short pulse of emissions over east Asia in springtime allows us to quantify the impacts of resolution on both regional and global ozone. Production close to continental emission regions is overestimated by 27% at T21 resolution, by 13% at T42 resolution, and by 5% at T106 resolution. However, subsequent ozone production in the free troposphere is not greatly affected. We find that the export of short-lived precursors such as NOx by convection is overestimated at coarse resolution.

Plasma enhanced atomic layer deposition of ZnO with diethyl zinc and oxygen plasma: Effect of precursor decomposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muneshwar, Triratna, E-mail: muneshwa@ualberta.ca; Cadien, Ken; Shoute, Gem

2016-09-15

Although atomic layer deposition (ALD) of ZnO using diethyl zinc (DEZ) precursor has been extensively reported, variation in growth-per-cycle (GPC) values and the range of substrate temperature (T{sub sub}) for ALD growth between related studies remain unexplained. For identical processes, GPC for the characteristic self-limiting ALD growth is expected to be comparable. Hence, a significant variation in GPC among published ZnO ALD studies strongly suggests a concealed non-ALD growth component. To investigate this, the authors report plasma-enhanced ALD growth of ZnO using DEZ precursor and O{sub 2} inductively coupled plasma. The effect of T{sub sub} on ZnO GPC was studiedmore » with deposition cycles (1) 0.02 s–15 s–6 s–15 s, (2) 0.10 s–15 s–15 s–15 s, and (3) 0.20 s–15 s–30 s–15 s, where the cycle parameters t{sub 1}–t{sub 2}–t{sub 3}–t{sub 4} denote duration of DEZ pulse, post-DEZ purge, plasma exposure, and postplasma purge, respectively. The non-ALD growth characteristics observed at T{sub sub} ≥ 60 °C are discussed and attributed to DEZ precursor decomposition. The authors demonstrate ZnO growth at T{sub sub} = 50 °C to be self-limiting with respect to both t{sub 1} and t{sub 3} giving GPC of 0.101 ± 0.001 nm/cycle. The effect of precursor decomposition related (non-ALD) growth at T{sub sub} ≥ 60 °C is illustrated from comparison of optical dielectric function, electrical resistivity, and surface roughness of ZnO films deposited at T{sub sub} = 50, 125, and 200 °C.« less

Porous nC-Si/SiOx nanostructured layer on Si substrate with tunable photoluminescent properties fabricated by direct, precursor-free microplasma irradiation in air

NASA Astrophysics Data System (ADS)

Wang, Tao; Hu, Mingshan; Yang, Bin; Wang, Xiaolin; Liu, Jingquan

2018-03-01

Porous nC-Si/SiOx photoluminescent nanostructured layer is fabricated by direct, precursor-free microplasma irradiation on Si substrate in air. It is confirmed that the deposited layer has porous and cluster-like structures by scanning electron microscopy (SEM) and profile scanning. Fourier transform infrared transmission (FTIR), X-ray diffraction (XRD) and X-ray photoelectron spectrum (XPS) results indicate the produced layer is actually composed of nanocrystalline silicon (nC-Si) embedded in SiOx matrix. Transmission electron microscopy (TEM) and Raman results show the mean particle size of nC-Si is mainly between 2 and 4 nm and the highest crystalline volume fraction reaches 86.9%. The photoluminescence (PL) measurement of nC-Si/SiOx layer exhibited a broad band centered at 1.7-1.9 eV, ranging from 1.2-2.4 eV, and could be tuned by varying the applied voltage. The synthetical mechanisms are discussed to explain the PL properties of the layers. We propose that the energetic ions bombing induced by high compressed electric field near the Si surface is the main reason for porous nC-Si/SiOx formation. Maskless deposition of the line pattern of nC-Si/SiOx layer was also successfully fabricated. This simple, maskless, vacuum-free and precursor-free technique could be used in various potential optoelectronics and biological applications in the future.

Improving the electrical properties of lanthanum silicate films on ge metal oxide semiconductor capacitors by adopting interfacial barrier and capping layers.

PubMed

Choi, Yu Jin; Lim, Hajin; Lee, Suhyeong; Suh, Sungin; Kim, Joon Rae; Jung, Hyung-Suk; Park, Sanghyun; Lee, Jong Ho; Kim, Seong Gyeong; Hwang, Cheol Seong; Kim, HyeongJoon

2014-05-28

The electrical properties of La-silicate films grown by atomic layer deposition (ALD) on Ge substrates with different film configurations, such as various Si concentrations, Al2O3 interfacial passivation layers, and SiO2 capping layers, were examined. La-silicate thin films were deposited using alternating injections of the La[N{Si(CH3)3}2]3 precursor with O3 as the La and O precursors, respectively, at a substrate temperature of 310 °C. The Si concentration in the La-silicate films was further controlled by adding ALD cycles of SiO2. For comparison, La2O3 films were also grown using [La((i)PrCp)3] and O3 as the La precursor and oxygen source, respectively, at the identical substrate temperature. The capacitance-voltage (C-V) hysteresis decreased with an increasing Si concentration in the La-silicate films, although the films showed a slight increase in the capacitance equivalent oxide thickness. The adoption of Al2O3 at the interface as a passivation layer resulted in lower C-V hysteresis and a low leakage current density. The C-V hysteresis voltages of the La-silicate films with Al2O3 passivation and SiO2 capping layers was significantly decreased to ∼0.1 V, whereas the single layer La-silicate film showed a hysteresis voltage as large as ∼1.0 V.

Single-source precursors for ternary chalcopyrite materials, and methods of making and using the same

NASA Technical Reports Server (NTRS)

Banger, Kulbinder K. (Inventor); Hepp, Aloysius F. (Inventor); Harris, Jerry D. (Inventor); Jin, Michael Hyun-Chul (Inventor); Castro, Stephanie L. (Inventor)

2006-01-01

A single source precursor for depositing ternary I-III-VI.sub.2 chalcopyrite materials useful as semiconductors. The single source precursor has the I-III-VI.sub.2 stoichiometry built into a single precursor molecular structure which degrades on heating or pyrolysis to yield the desired I-III-VI.sub.2 ternary chalcopyrite. The single source precursors effectively degrade to yield the ternary chalcopyrite at low temperature, e.g. below 500.degree. C., and are useful to deposit thin film ternary chalcopyrite layers via a spray CVD technique. The ternary single source precursors according to the invention can be used to provide nanocrystallite structures useful as quantum dots. A method of making the ternary single source precursors is also provided.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Kuaibing, E-mail: wangkb@njau.edu.cn; State Key Laboratory of Coordination Chemistry, Coordination Chemistry Institute, Nanjing University, Nanjing 210093; Lv, Bo

Hollow CuO/Co{sub 3}O{sub 4} hybrids, which inherited from its coordination polymer precursor consisting of sheets layer and nanoparticles layer composites, were synthesized and characterized by SEM, EDX, XRD and XPS. To assess its electrochemical capacitive performances, cyclic voltammetry, galvanostatic charging-discharging measurements and A.C. impedance tests were performed successively. The CuO/Co{sub 3}O{sub 4} hybrids had higher capacitance and lower charge transfer resistance than bare Co{sub 3}O{sub 4} nanostructures, revealing that it provided a protection layer and produced a synergistic effect due to the existence of CuO layer. The distinct synergistic effect could be further confirmed by endurance cycling tests. The capacitancemore » of the CuO/Co{sub 3}O{sub 4} hybrids was 111% retained after 500 cycles at a charging rate of 1.0 A g{sup −1} and remained an intense growth trend after 2000 cycles at scan rate of 200 mV s{sup −1}. - Graphical abstract: Hollow CuO/Co{sub 3}O{sub 4} hybrids are synthesized and display a peculiar synergetic effect on the resulting performances, which can further be evaluated and confirmed by series of electrochemical measurements. - Highlights: • Hollow CuO/Co{sub 3}O{sub 4} hybrids are synthesized from bimetallic-Schiff base polymer precursors. • The capacitance of the CuO/Co{sub 3}O{sub 4} hybrids keeps a growth tendency after 2000 cycles. • A synergetic effect is found for the hybrids in electrochemical energy storage process.« less

Improved Single-Source Precursors for Solar-Cell Absorbers

NASA Technical Reports Server (NTRS)

Banger, Kulbinder K.; Harris, Jerry; Hepp, Aloysius

2007-01-01

Improved single-source precursor compounds have been invented for use in spray chemical vapor deposition (spray CVD) of chalcopyrite semiconductor absorber layers of thin-film cells. A "single-source precursor compound" is a single molecular compound that contains all the required elements, which when used under the spray CVD conditions, thermally decomposes to form CuIn(x)Ga(1-x)S(y)Se(2-y).

The processes of formation and epitaxial alignment of SrTiO3 thin films prepared by metallo-organic decomposition

NASA Astrophysics Data System (ADS)

Braunstein, G.; Paz-Pujalt, G. R.; Mason, M. G.; Blanton, T.; Barnes, C. L.; Margevich, D.

1993-01-01

The processes of formation and crystallization of thin films of SrTiO3 prepared by the method of metallo-organic decomposition have been studied with particular emphasis on the relationship between the thermal decomposition of the metallo-organic precursors and the eventual epitaxial alignment of the crystallized films. The films are deposited by spin coating onto single-crystalline silicon and SrTiO3 substrates, pyrolyzed on a hot plate at temperatures ranging from 200 to 450 °C, and subsequently heat treated in a quartz tube furnace at temperatures ranging from 300 to 1200 °C. Heat treatment at temperatures up to 450-500 °C results in the evaporation of solvents and other organic addenda, thermal decomposition of the metallo-organic (primarily metal-carboxylates) precursors, and formation of a carbonate species. This carbonate appears to be an intermediate phase in the reaction of SrCO3 and TiO2 to form SrTiO3. Relevant to this work is the fact that the carbonate species exhibits diffraction lines, indicating the formation of grains that can serve as seeds for the nucleation and growth of randomly oriented SrTiO3 crystallites, thereby leading to a polycrystalline film. Deposition on silicon substrates indeed results in the formation of polycrystalline SrTiO3. However, when the precursor solution is deposited on single-crystalline SrTiO3 substrates, the crystallization process involves a competition between two mechanisms: the random nucleation and growth of crystallites just described, and layer-by-layer solid phase epitaxy. Epitaxial alignment on SrTiO3 substrates can be achieved when the samples are heat treated at temperatures of 1100-1200 °C or at temperatures as low as 600-650 °C when the substrate is heated to about 1100 °C before spin coating.

Photochemical CVD of Ru on functionalized self-assembled monolayers from organometallic precursors

NASA Astrophysics Data System (ADS)

Johnson, Kelsea R.; Arevalo Rodriguez, Paul; Brewer, Christopher R.; Brannaka, Joseph A.; Shi, Zhiwei; Yang, Jing; Salazar, Bryan; McElwee-White, Lisa; Walker, Amy V.

2017-02-01

Chemical vapor deposition (CVD) is an attractive technique for the metallization of organic thin films because it is selective and the thickness of the deposited film can easily be controlled. However, thermal CVD processes often require high temperatures which are generally incompatible with organic films. In this paper, we perform proof-of-concept studies of photochemical CVD to metallize organic thin films. In this method, a precursor undergoes photolytic decomposition to generate thermally labile intermediates prior to adsorption on the sample. Three readily available Ru precursors, CpRu(CO)2Me, (η3-allyl)Ru(CO)3Br, and (COT)Ru(CO)3, were employed to investigate the role of precursor quantum yield, ligand chemistry, and the Ru oxidation state on the deposition. To investigate the role of the substrate chemistry on deposition, carboxylic acid-, hydroxyl-, and methyl-terminated self-assembled monolayers were used. The data indicate that moderate quantum yields for ligand loss (φ ≥ 0.4) are required for ruthenium deposition, and the deposition is wavelength dependent. Second, anionic polyhapto ligands such as cyclopentadienyl and allyl are more difficult to remove than carbonyls, halides, and alkyls. Third, in contrast to the atomic layer deposition, acid-base reactions between the precursor and the substrate are more effective for deposition than nucleophilic reactions. Finally, the data suggest that selective deposition can be achieved on organic thin films by judicious choice of precursor and functional groups present on the substrate. These studies thus provide guidelines for the rational design of new precursors specifically for selective photochemical CVD on organic substrates.

Fluorocarbon assisted atomic layer etching of SiO 2 and Si using cyclic Ar/C 4F 8 and Ar/CHF 3 plasma

DOE PAGES

Metzler, Dominik; Li, Chen; Engelmann, Sebastian; ...

2015-11-11

The need for atomic layer etching (ALE) is steadily increasing as smaller critical dimensions and pitches are required in device patterning. A flux-control based cyclic Ar/C 4F 8 ALE based on steady-state Ar plasma in conjunction with periodic, precise C 4F 8 injection and synchronized plasma-based low energy Ar + ion bombardment has been established for SiO 2. 1 In this work, the cyclic process is further characterized and extended to ALE of silicon under similar process conditions. The use of CHF 3 as a precursor is examined and compared to C 4F 8. CHF 3 is shown to enablemore » selective SiO 2/Si etching using a fluorocarbon (FC) film build up. Other critical process parameters investigated are the FC film thickness deposited per cycle, the ion energy, and the etch step length. Etching behavior and mechanisms are studied using in situ real time ellipsometry and X-ray photoelectron spectroscopy. Silicon ALE shows less self-limitation than silicon oxide due to higher physical sputtering rates for the maximum ion energies used in this work, ranged from 20 to 30 eV. The surface chemistry is found to contain fluorinated silicon oxide during the etching of silicon. As a result, plasma parameters during ALE are studied using a Langmuir probe and establish the impact of precursor addition on plasma properties.« less

Growth and characterization of Al2O3 films on fluorine functionalized epitaxial graphene

NASA Astrophysics Data System (ADS)

Robinson, Zachary R.; Jernigan, Glenn G.; Wheeler, Virginia D.; Hernández, Sandra C.; Eddy, Charles R.; Mowll, Tyler R.; Ong, Eng Wen; Ventrice, Carl A.; Geisler, Heike; Pletikosic, Ivo; Yang, Hongbo; Valla, Tonica

2016-08-01

Intelligent engineering of graphene-based electronic devices on SiC(0001) requires a better understanding of processes used to deposit gate-dielectric materials on graphene. Recently, Al2O3 dielectrics have been shown to form conformal, pinhole-free thin films by functionalizing the top surface of the graphene with fluorine prior to atomic layer deposition (ALD) of the Al2O3 using a trimethylaluminum (TMA) precursor. In this work, the functionalization and ALD-precursor adsorption processes have been studied with angle-resolved photoelectron spectroscopy, low energy electron diffraction, and X-ray photoelectron spectroscopy. It has been found that the functionalization process has a negligible effect on the electronic structure of the graphene, and that it results in a twofold increase in the adsorption of the ALD-precursor. In situ TMA-dosing and XPS studies were also performed on three different Si(100) substrates that were terminated with H, OH, or dangling Si-bonds. This dosing experiment revealed that OH is required for TMA adsorption. Based on those data along with supportive in situ measurements that showed F-functionalization increases the amount of oxygen (in the form of adsorbed H2O) on the surface of the graphene, a model for TMA-adsorption on graphene is proposed that is based on a reaction of a TMA molecule with OH.

Atomic Layer Deposition of the Metal Pyrites FeS2 , CoS2 , and NiS2.

PubMed

Guo, Zheng; Wang, Xinwei

2018-05-14

Atomic layer deposition (ALD) of the pyrite-type metal disulfides FeS 2 , CoS 2 , and NiS 2 is reported for the first time. The deposition processes use iron, cobalt, and nickel amidinate compounds as the corresponding metal precursors and the H 2 S plasma as the sulfur source. All the processes are demonstrated to follow ideal self-limiting ALD growth behavior to produce fairly pure, smooth, well-crystallized, stoichiometric pyrite FeS 2 , CoS 2 , and NiS 2 films. By these processes, the FeS 2 , CoS 2 , and NiS 2 films can also be uniformly and conformally deposited into deep narrow trenches with aspect ratios as high as 10:1, which thereby highlights the broad and promising applicability of these ALD processes for conformal film coatings on complex high-aspect-ratio 3D architectures in general. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Method for fabrication of crack-free ceramic dielectric films

DOEpatents

Ma, Beihai; Balachandran, Uthamalingam; Chao, Sheng; Liu, Shanshan; Narayanan, Manoj

2014-02-11

The invention provides a process for forming crack-free dielectric films on a substrate. The process comprise the application of a dielectric precursor layer of a thickness from about 0.3 .mu.m to about 1.0 .mu.m to a substrate. The deposition is followed by low temperature heat pretreatment, prepyrolysis, pyrolysis and crystallization step for each layer. The deposition, heat pretreatment, prepyrolysis, pyrolysis and crystallization are repeated until the dielectric film forms an overall thickness of from about 1.5 .mu.m to about 20.0 .mu.m and providing a final crystallization treatment to form a thick dielectric film. Also provided was a thick crack-free dielectric film on a substrate, the dielectric forming a dense thick crack-free dielectric having an overall dielectric thickness of from about 1.5 .mu.m to about 20.0 .mu.m.

Thermal Exfoliation of Natural Cellulosic Material for Graphene Synthesis

NASA Astrophysics Data System (ADS)

Ray, Ajoy Kumar; Chatterjee, Somenath; Singh, Jitendra Kumar; Bapari, Himangshu

2015-01-01

Hibiscus flower petals have been used as a cheap natural resource precursor for cost-effective synthesis of high quality graphene by thermal exfoliation process. In order to compare the quality of graphene obtained from the flower petals directly with the flower petals pretreated with nickel(II) chloride, Raman spectroscopic technique has been used as the structural probe. The role of temperature and the effect of nickel on thermal exfoliation process have been examined. It has been observed that graphene obtained via nickel incorporation is of better quality because NI2+ ions that get dispersed in the layered-structured cellulose at elevated temperatures get reduced to the metallic state, which in turn push the graphitic layers during thermal exfoliation to produce good quality graphene. In contrast, no such driving force is present in cellulose and hemi-cellulose of flower petals that contain lignin.

High-efficiency perovskite solar cells prepared by using a sandwich structure MAI-PbI2-MAI precursor film.

PubMed

Zhang, Xuhui; Ye, Jiajiu; Zhu, Liangzheng; Zheng, Haiying; Liu, Guozhen; Liu, Xuepeng; Duan, Bin; Pan, Xu; Dai, Songyuan

2017-04-06

Two-step deposition has been widely used in the perovskite layer preparation for perovskite solar cells due to its attractive morphology controllability. However, the limited diffusivity of CH 3 NH 3 I (MAI) might cause some PbI 2 to remain in the perovskite film. The residual PbI 2 in the perovskite film would lead to inferior performance of devices, such as, low power conversion efficiency (PCE), poor reproducibility and weak air stability. In this work, we developed a sandwich structure MAI-PbI 2 -MAI precursor film to prepare a PbI 2 -free CH 3 NH 3 PbI 3 perovskite film. In comparison to the two-step approach, the MAI-PbI 2 -MAI precursor film with a typical sandwich structure formed a uniform and pinhole-free perovskite film without any PbI 2 residue, which could significantly improve the performance of the devices. Moreover, the bottom MAI layer of the MAI-PbI 2 -MAI precursor film could improve the interfacial contact of the porous TiO 2 layer, leading to the promotion of the charge transfer and reduction of the recombination rate. Therefore, the devices fabricated from the sandwich structure MAI-PbI 2 -MAI precursor films showed dramatic improvements of open-circuit voltage (V oc ), short-circuit current density (J sc ), fill factor (FF) and PCE. As a result, a promising PCE of 17.8% with good long-term air stability was achieved for the MAI-PbI 2 -MAI precursor film based PSC, which is better than that prepared by a two-step approach.

First principles calculations of interactions of ZrCl4 precursors with the bare and hydroxylated ZrO2 surfaces

NASA Astrophysics Data System (ADS)

Iskandarova, I. M.; Knizhnik, A. A.; Bagatur'yants, A. A.; Potapkin, B. V.; Korkin, A. A.

2004-05-01

First-principles calculations have been performed to determine the structures and relative energies of different zirconium chloride groups chemisorbed on the tetragonal ZrO2(001) surface and to study the effects of the surface coverage with metal chloride groups and the degree of hydroxylation on the adsorption energies of metal precursors. It is shown that the molecular and dissociative adsorption energies of the ZrCl4 precursor on the bare t-ZrO2(001) surface are too small to hold ZrCl4 molecules on the surface during an atomic layer deposition (ALD) cycle at temperatures higher than 300°C. On the contrary, it has been found that molecular adsorption on the fully hydroxylated zirconia surface leads to the formation of a stable adsorbed complex. This strong adsorption of ZrCl4 molecules can lead to a decrease in the film growth rate of the ALD process at lower temperatures (<200°C). The energies of interaction between adsorbed ZrCl4 groups at a 50% surface coverage has been found to be relatively small, which explains the maximum film growth rate observed in the ZrCl4:H2O ALD process. Moreover, we found that the adsorbed ZrCl4 precursors after hydrolysis give rise to very stable hydroxyl groups, which can be responsible for film growth at high temperatures (up to 900°C).

Atmospheric new particle formation at the research station Melpitz, Germany: connection with gaseous precursors and meteorological parameters

NASA Astrophysics Data System (ADS)

Größ, Johannes; Hamed, Amar; Sonntag, André; Spindler, Gerald; Elina Manninen, Hanna; Nieminen, Tuomo; Kulmala, Markku; Hõrrak, Urmas; Plass-Dülmer, Christian; Wiedensohler, Alfred; Birmili, Wolfram

2018-02-01

This paper revisits the atmospheric new particle formation (NPF) process in the polluted Central European troposphere, focusing on the connection with gas-phase precursors and meteorological parameters. Observations were made at the research station Melpitz (former East Germany) between 2008 and 2011 involving a neutral cluster and air ion spectrometer (NAIS). Particle formation events were classified by a new automated method based on the convolution integral of particle number concentration in the diameter interval 2-20 nm. To study the relevance of gaseous sulfuric acid as a precursor for nucleation, a proxy was derived on the basis of direct measurements during a 1-month campaign in May 2008. As a major result, the number concentration of freshly produced particles correlated significantly with the concentration of sulfur dioxide as the main precursor of sulfuric acid. The condensation sink, a factor potentially inhibiting NPF events, played a subordinate role only. The same held for experimentally determined ammonia concentrations. The analysis of meteorological parameters confirmed the absolute need for solar radiation to induce NPF events and demonstrated the presence of significant turbulence during those events. Due to its tight correlation with solar radiation, however, an independent effect of turbulence for NPF could not be established. Based on the diurnal evolution of aerosol, gas-phase, and meteorological parameters near the ground, we further conclude that the particle formation process is likely to start in elevated parts of the boundary layer rather than near ground level.

Ozone pollution in China: A review of concentrations, meteorological influences, chemical precursors, and effects.

PubMed

Wang, Tao; Xue, Likun; Brimblecombe, Peter; Lam, Yun Fat; Li, Li; Zhang, Li

2017-01-01

High concentrations of ozone in urban and industrial regions worldwide have long been a major air quality issue. With the rapid increase in fossil fuel consumption in China over the past three decades, the emission of chemical precursors to ozone-nitrogen oxides and volatile organic compounds-has increased sharply, surpassing that of North America and Europe and raising concerns about worsening ozone pollution in China. Historically, research and control have prioritized acid rain, particulate matter, and more recently fine particulate matter (PM 2.5 ). In contrast, less is known about ozone pollution, partly due to a lack of monitoring of atmospheric ozone and its precursors until recently. This review summarizes the main findings from published papers on the characteristics and sources and processes of ozone and ozone precursors in the boundary layer of urban and rural areas of China, including concentration levels, seasonal variation, meteorology conducive to photochemistry and pollution transport, key production and loss processes, ozone dependence on nitrogen oxides and volatile organic compounds, and the effects of ozone on crops and human health. Ozone concentrations exceeding the ambient air quality standard by 100-200% have been observed in China's major urban centers such as Jing-Jin-Ji, the Yangtze River delta, and the Pearl River delta, and limited studies suggest harmful effect of ozone on human health and agricultural corps; key chemical precursors and meteorological conditions conductive to ozone pollution have been investigated, and inter-city/region transport of ozone is significant. Several recommendations are given for future research and policy development on ground-level ozone. Copyright © 2016 Elsevier B.V. All rights reserved.

Enhancing the platinum atomic layer deposition infiltration depth inside anodic alumina nanoporous membrane

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vaish, Amit, E-mail: anv@udel.edu; Krueger, Susan; Dimitriou, Michael

Nanoporous platinum membranes can be straightforwardly fabricated by forming a Pt coating inside the nanopores of anodic alumina membranes (AAO) using atomic layer deposition (ALD). However, the high-aspect-ratio of AAO makes Pt ALD very challenging. By tuning the process deposition temperature and precursor exposure time, enhanced infiltration depth along with conformal coating was achieved for Pt ALD inside the AAO templates. Cross-sectional scanning electron microscopy/energy dispersive x-ray spectroscopy and small angle neutron scattering were employed to analyze the Pt coverage and thickness inside the AAO nanopores. Additionally, one application of platinum-coated membrane was demonstrated by creating a high-density protein-functionalized interface.

Roll-to-Roll Processing of Inverted Polymer Solar Cells using Hydrated Vanadium(V)Oxide as a PEDOT:PSS Replacement

PubMed Central

Espinosa, Nieves; Dam, Henrik Friis; Tanenbaum, David M.; Andreasen, Jens W.; Jørgensen, Mikkel; Krebs, Frederik C.

2011-01-01

The use of hydrated vanadium(V)oxide as a replacement of the commonly employed hole transporting material PEDOT:PSS was explored in this work. Polymer solar cells were prepared by spin coating on glass. Polymer solar cells and modules comprising 16 serially connected cells were prepared using full roll-to-roll (R2R) processing of all layers. The devices were prepared on flexible polyethyleneterphthalate (PET) and had the structure PET/ITO/ZnO/P3HT:PCBM/V2O5·(H2O)n/Ag. The ITO and silver electrodes were processed and patterned by use of screen printing. The zinc oxide, P3HT:PCBM and vanadium(V)oxide layers were processed by slot-die coating. The hydrated vanadium(V)oxide layer was slot-die coated using an isopropanol solution of vanadyl-triisopropoxide (VTIP). Coating experiments were carried out to establish the critical thickness of the hydrated vanadium(V)oxide layer by varying the concentration of the VTIP precursor over two orders of magnitude. Hydrated vanadium(V)oxide layers were characterized by profilometry, scanning electron microscopy, energy dispersive X-ray spectroscopy, and grazing incidence wide angle X-ray scattering. The power conversion efficiency (PCE) for completed modules was up to 0.18%, in contrast to single cells where efficiencies of 0.4% were achieved. Stability tests under indoor and outdoor conditions were accomplished over three weeks on a solar tracker. PMID:28879984

Roll-to-Roll Processing of Inverted Polymer Solar Cells using Hydrated Vanadium(V)Oxide as a PEDOT:PSS Replacement.

PubMed

Espinosa, Nieves; Dam, Henrik Friis; Tanenbaum, David M; Andreasen, Jens W; Jørgensen, Mikkel; Krebs, Frederik C

2011-01-11

The use of hydrated vanadium(V)oxide as a replacement of the commonly employed hole transporting material PEDOT:PSS was explored in this work. Polymer solar cells were prepared by spin coating on glass. Polymer solar cells and modules comprising 16 serially connected cells were prepared using full roll-to-roll (R2R) processing of all layers. The devices were prepared on flexible polyethyleneterphthalate (PET) and had the structure PET/ITO/ZnO/P3HT:PCBM/V₂O₅·(H₂O) n /Ag. The ITO and silver electrodes were processed and patterned by use of screen printing. The zinc oxide, P3HT:PCBM and vanadium(V)oxide layers were processed by slot-die coating. The hydrated vanadium(V)oxide layer was slot-die coated using an isopropanol solution of vanadyl-triisopropoxide (VTIP). Coating experiments were carried out to establish the critical thickness of the hydrated vanadium(V)oxide layer by varying the concentration of the VTIP precursor over two orders of magnitude. Hydrated vanadium(V)oxide layers were characterized by profilometry, scanning electron microscopy, energy dispersive X-ray spectroscopy, and grazing incidence wide angle X-ray scattering. The power conversion efficiency (PCE) for completed modules was up to 0.18%, in contrast to single cells where efficiencies of 0.4% were achieved. Stability tests under indoor and outdoor conditions were accomplished over three weeks on a solar tracker.

Liquid Feedstock Plasma Spraying: An Emerging Process for Advanced Thermal Barrier Coatings

NASA Astrophysics Data System (ADS)

Markocsan, Nicolaie; Gupta, Mohit; Joshi, Shrikant; Nylén, Per; Li, Xin-Hai; Wigren, Jan

2017-08-01

Liquid feedstock plasma spraying (LFPS) involves deposition of ultrafine droplets of suspensions or solution precursors (typically ranging from nano- to submicron size) and permits production of coatings with unique microstructures that are promising for advanced thermal barrier coating (TBC) applications. This paper reviews the recent progress arising from efforts devoted to development of high-performance TBCs using the LFPS approach. Advancements in both suspension plasma spraying and solution precursor plasma spraying, which constitute the two main variants of LFPS, are presented. Results illustrating the different types of the microstructures that can be realized in LFPS through appropriate process parameter control, model-assisted assessment of influence of coating defects on thermo-mechanical properties and the complex interplay between pore coarsening, sintering and crystallite growth in governing thermal conductivity are summarized. The enhancement in functional performances/lifetime possible in LFPS TBCs with multilayered architectures and by incorporating new pyrochlore chemistries such as gadolinium zirconate, besides the conventional single 8 wt.% yttria-stabilized zirconia insulating ceramic layer, is specifically highlighted.

Effect of preparation conditions on the properties of Cu3BiS3 thin films grown by a two - step process

NASA Astrophysics Data System (ADS)

Mesa, F.; Gordillo, G.

2009-05-01

Cu3BiS3 thin films were prepared on soda-lime glass substrates by co-evaporation of the precursors in a two-step process; for that, the metallic precursors were evaporated from a tungsten boat in presence of elemental sulfur evaporated from a tantalum effusion cell. The films were characterized by spectral transmittance, atomic force microscopy AFM and x-ray diffraction (XRD) measurements to investigate the effect of the growth conditions on the optical, morphological and structural properties. The results revealed that, independently of the deposition conditions, the films grow only in the orthorhombic Cu3BiS3 phase. It was also found that the Cu3BiS3 films present p-type conductivity, a high absorption coefficient (greater than 104 cm-1) and an energy band gap Eg of about 1.41 eV, indicating that this compound has good properties to perform as absorbent layer in thin film solar cells.

Rational growth of Bi2S3 nanotubes from quasi-two-dimensional precursors.

PubMed

Ye, Changhui; Meng, Guowen; Jiang, Zhi; Wang, Yinhai; Wang, Guozhong; Zhang, Lide

2002-12-25

Synthesis of Bi2S3 nanotubes from rolling of the quasi-two-dimensional (2-D) layered precursor represents new progress in the synthetic approach and adds new members to the present inorganic fullerene family. These nanotubes display multiwalled structures that resemble that of a multiwalled carbon nanotube. The successful synthesis of Bi2S3 nanotubes highlights the feasibility of inorganic fullerene-like structures from other chemicals that possess layered crystalline structures, not only the well-known 2-D family, but possibly also those quasi-2-D members.

Fabrication of CIS Absorber Layers with Different Thicknesses Using A Non-Vacuum Spray Coating Method

PubMed Central

Diao, Chien-Chen; Kuo, Hsin-Hui; Tzou, Wen-Cheng; Chen, Yen-Lin; Yang, Cheng-Fu

2014-01-01

In this study, a new thin-film deposition process, spray coating method (SPM), was investigated to deposit the high-densified CuInSe2 absorber layers. The spray coating method developed in this study was a non-vacuum process, based on dispersed nano-scale CuInSe2 precursor and could offer a simple, inexpensive, and alternative formation technology for CuInSe2 absorber layers. After spraying on Mo/glass substrates, the CuInSe2 thin films were annealed at 550 °C by changing the annealing time from 5 min to 30 min in a selenization furnace, using N2 as atmosphere. When the CuInSe2 thin films were annealed, without extra Se or H2Se gas used as the compensation source during the annealing process. The aim of this project was to investigate the influence of annealing time on the densification and crystallization of the CuInSe2 absorber layers to optimize the quality for cost effective solar cell production. The thickness of the CuInSe2 absorber layers could be controlled as the volume of used dispersed CuInSe2-isopropyl alcohol solution was controlled. In this work, X-ray diffraction patterns, field emission scanning electron microscopy, and Hall parameter measurements were performed in order to verify the quality of the CuInSe2 absorber layers obtained by the Spray Coating Method. PMID:28788451

DOE Office of Scientific and Technical Information (OSTI.GOV)

J. M. Rafi; Lynn, D.; Pellegrini, G.

The radiation hardness and thermal stability of the electrical characteristics of atomic layer deposited Al 2O 3 layers to be used as passivation films for silicon radiation detectors with slim edges are investigated. To directly measure the interface charge and to evaluate its change with the ionizing dose, metal-oxide-silicon (MOS) capacitors implementing differently processed Al 2O 3 layers were fabricated on p-type silicon substrates. Qualitatively similar results are obtained for degradation of capacitance–voltage and current–voltage characteristics under gamma and proton irradiations up to equivalent doses of 30 Mrad and 21.07 Mrad, respectively. While similar negative charge densities are initially extractedmore » for all non-irradiated capacitors, superior radiation hardness is obtained for MOS structures with alumina layers grown with H 2O instead of O 3 as oxidant precursor. Competing effects between radiation-induced positive charge trapping and hydrogen release from the H 2O-grown Al 2O 3 layers may explain their higher radiation resistance. Finally, irradiated and non-irradiated MOS capacitors with differently processed Al 2O 3 layers have been subjected to thermal treatments in air at temperatures ranging between 100 °C and 200 °C and the thermal stability of their electrical characteristics has been evaluated. Partial recovery of the gamma-induced degradation has been noticed for O 3-grown MOS structures. Lastly, this can be explained by a trapped holes emission process, for which an activation energy of 1.38 ± 0.15 eV has been extracted.« less

Atomic Layer Deposition of HfO2 and Si Nitride on Ge Substrates

NASA Astrophysics Data System (ADS)

Zhu, Shiyang; Nakajima, Anri

2007-12-01

Hafnium oxide (HfO2) thin films were deposited on Ge substrates at 300 °C using atomic layer deposition (ALD) with tetrakis(diethylamino)hafnium (termed as TDEAH) as a precursor and water as an oxidant. The deposition rate was estimated to be 0.09 nm/cycle and the deposited HfO2 films have a smooth surface and an almost stoichiometric composition, indicating that the growth follows a layer-by-layer kinetics, similarly to that on Si substrates. Si nitride thin films were also deposited on Ge by ALD using SiCl4 as a precursor and NH3 as an oxidant. Si nitride has a smaller deposition rate of about 0.055 nm/cycle and a larger gate leakage current than HfO2 deposited on Ge by ALD.

Hollow Cathode Plasma-Enhanced Atomic Layer Deposition of Silicon Nitride Using Pentachlorodisilane.

PubMed

Meng, Xin; Kim, Harrison Sejoon; Lucero, Antonio T; Hwang, Su Min; Lee, Joy S; Byun, Young-Chul; Kim, Jiyoung; Hwang, Byung Keun; Zhou, Xiaobing; Young, Jeanette; Telgenhoff, Michael

2018-04-25

In this work, a novel chlorodisilane precursor, pentachlorodisilane (PCDS, HSi 2 Cl 5 ), was investigated for the growth of silicon nitride (SiN x ) via hollow cathode plasma-enhanced atomic layer deposition (PEALD). A well-defined self-limiting growth behavior was successfully demonstrated over the growth temperature range of 270-360 °C. At identical process conditions, PCDS not only demonstrated approximately >20% higher growth per cycle than that of a commercially available chlorodisilane precursor, hexachlorodisilane (Si 2 Cl 6 ), but also delivered a better or at least comparable film quality determined by characterizing the refractive index, wet etch rate, and density of the films. The composition of the SiN x films grown at 360 °C using PCDS, as determined by X-ray photoelectron spectroscopy, showed low O content (∼2 at. %) and Cl content (<1 at. %; below the detection limit). Fourier transform infrared spectroscopy spectra suggested that N-H bonds were the dominant hydrogen-containing bonds in the SiN x films without a significant amount of Si-H bonds originating from the precursor molecules. The possible surface reaction pathways of the PEALD SiN x using PCDS on the surface terminated with amine groups (-NH 2 and -NH-) are proposed. The PEALD SiN x films grown using PCDS also exhibited a leakage current density as low as 1-2 nA/cm 2 at 2 MV/cm and a breakdown electric field as high as ∼12 MV/cm.

Achieving High Current Density of Perovskite Solar Cells by Modulating the Dominated Facets of Room-Temperature DC Magnetron Sputtered TiO2 Electron Extraction Layer.

PubMed

Huang, Aibin; Lei, Lei; Zhu, Jingting; Yu, Yu; Liu, Yan; Yang, Songwang; Bao, Shanhu; Cao, Xun; Jin, Ping

2017-01-25

The short circuit current density of perovskite solar cell (PSC) was boosted by modulating the dominated plane facets of TiO 2 electron transport layer (ETL). Under optimized condition, TiO 2 with dominant {001} facets showed (i) low incident light loss, (ii) highly smooth surface and excellent wettability for precursor solution, (iii) efficient electron extraction, and (iv) high conductivity in perovskite photovoltaic application. A current density of 24.19 mA cm -2 was achieved as a value near the maximum limit. The power conversion efficiency was improved to 17.25%, which was the record value of PSCs with DC magnetron sputtered carrier transport layer. What is more, the room-temperature process had a great significance for the cost reduction and flexible application of PSCs.

Aerosol-Jet-Printing silicone layers and electrodes for stacked dielectric elastomer actuators in one processing device

NASA Astrophysics Data System (ADS)

Reitelshöfer, Sebastian; Göttler, Michael; Schmidt, Philip; Treffer, Philipp; Landgraf, Maximilian; Franke, Jörg

2016-04-01

In this contribution we present recent findings of our efforts to qualify the so called Aerosol-Jet-Printing process as an additive manufacturing approach for stacked dielectric elastomer actuators (DEA). With the presented system we are able to print the two essential structural elements dielectric layer and electrode in one machine. The system is capable of generating RTV-2 silicone layers made of Wacker Elastosil P 7670. Therefore, two aerosol streams of both precursor components A and B are generated in parallel and mixed in one printing nozzle that is attached to a 4-axis kinematic. At maximum speed the printing of one circular Elastosil layer with a calculated thickness of 10 μm and a diameter of 1 cm takes 12 seconds while the process keeps stable for 4.5 hours allowing a quite high overall material output and the generation of numerous silicone layers. By adding a second printing nozzle and the infrastructure to generate a third aerosol, the system is also capable of printing inks with conductive particles in parallel to the silicone. We have printed a reduced graphene oxide (rGO) ink prepared in our lab to generate electrodes on VHB 4905, Elastosil foils and finally on Aerosol-Jet-Printed Elastosil layers. With rGO ink printed on Elastosil foil, layers with a 4-point measured sheet resistance as low as 4 kΩ can be realized leaving room for improving the electrode printing time, which at the moment is not as good as the quite good time-frame for printing the silicone layers. Up to now we have used the system to print a fully functional two-layer stacked DEA to demonstrate the principle of continuously 3D printing actuators.

Tuning the morphology of silver nanostructures photochemically coated on glass substrates: an effective approach to large-scale functional surfaces

NASA Astrophysics Data System (ADS)

Zaier, Mohamed; Vidal, Loic; Hajjar-Garreau, Samar; Bubendorff, Jean-Luc; Balan, Lavinia

2017-03-01

This paper reports on a simple and environmentally friendly photochemical process capable of generating nano-layers (8-22 nm) of silver nanostructures directly onto glass surfaces. This approach opens the way to large-scale functionalized surfaces with plasmonic properties through a single light-induced processing. Thus, Ag nanostructures top-coated were obtained through photo-reduction, at room temperature, of a photosensitive formulation containing a metal precursor, free from extra toxic stabilizers or reducing agents. The reactive formulation was confined between two glass slides and exposed to a continuous near-UV source. In this way, stable silver nano-layers can be generated directly on the substrate with a very good control of the morphology of as-synthesized nanostructures that allows tailoring the optical properties of the coated layers. The position and width of the corresponding surface plasmon resonance bands can be adjusted over a broad spectral window. By extension, this low-cost and easy-to-apply process can also be used to coat ultra thin layers of metal nanostructures on a variety of substrates. The possibility of controlling of nanostructures shape should achieve valuable developments in many fields, as diverse as plasmonics, surface enhanced Raman scattering, nano-electronic circuitry, or medical devices.

Hybrid layers deposited by an atmospheric pressure plasma process for corrosion protection of galvanized steel.

PubMed

Del Frari, D; Bour, J; Bardon, J; Buchheit, O; Arnoult, C; Ruch, D

2010-04-01

Finding alternative treatments to reproduce anticorrosion properties of chromated coatings is challenging since both physical barrier and self-healing effects are needed. Siloxane based treatments are known to be a promising way to achieve physical barrier coatings, mainly plasma polymerized hexamethyldisiloxane (ppHMDSO). In addition, it is known that cerium-based coatings can also provide corrosion protection of metals by means of self-healing effect. In this frame, innovative nanoAlCeO3/ppHMDSO layers have thus been deposited and studied. These combinations allow to afford a good physical barrier effect and active properties. Liquid siloxane and cerium-based particles mixture is atomized and introduced as precursors into a carrier gas. Gas mixture is then injected into an atmospheric pressure dielectric barrier discharge (DBD) where plasma polymerization of the siloxane precursor occurs. The influence of cerium concentration on the coating properties is investigated: coating structure and topography have been studied by scanning electron microscopy (SEM) and interferometry, and corrosion resistance of these different coatings is compared by electrochemistry techniques: polarization curves and electrochemical impedance spectroscopy (EIS). Potential self-healing property afforded by cerium in the layer was studied by associating EIS measurements and nanoscratch controlled damaging. Among the different combinations investigated, mixing of plasma polymerized HMDSO and AICeO3 nanoparticles seems to give promising results with a good physical barrier and interesting electroactive properties. Indeed, corrosion currents measured on such coatings are almost as low as those measured with the chromated film. Combination of nanoscratch damaging of layers with EIS experiments to investigate self-healing also allow to measure the active protection property of such layers.

Sol-gel preparation of self-cleaning SiO2-TiO2/SiO2-TiO2 double-layer antireflective coating for solar glass

NASA Astrophysics Data System (ADS)

Lin, Wensheng; Zheng, Jiaxian; Yan, Lianghong; Zhang, Xinxiang

2018-03-01

Self-cleaning SiO2-TiO2/SiO2-TiO2 double-layer antireflective (AR) coating is prepared by sol-gel process. SiO2 sol is prepared by using tetraethyl orthosilicate (TEOS) as precursor and ammonia as catalyst, while TiO2 sol was prepared by using tetrabutyl orthotitanate (TBOT) as precursor and hydrochloric acid as catalyst. The effect of TiO2 content on refractive index, abrasion-resistance and photo-catalytic activity of SiO2-TiO2 hybrid thin films or powders is systematically investigated. It is found that the refractive index of SiO2-TiO2 hybrid thin films increases gradually from 1.18 to 1.53 as the weight ratio of TiO2 to SiO2 increased from 0 to 1.0. The SiO2-TiO2 hybrid thin film and powder possesses good abrasion-resistance and photo-catalytic activity, respectively, as the weight ratio of TiO2 to SiO2 is 0.4. The degradation degree of Rhodamine B by SiO2-TiO2 hybrid powder is 88.3%. Finally, SiO2-TiO2/SiO2-TiO2 double-layer AR coating with high transmittance, abrasion-resistance and self-cleaning property is realized.

Correlation of film density and wet etch rate in hydrofluoric acid of plasma enhanced atomic layer deposited silicon nitride

DOE Office of Scientific and Technical Information (OSTI.GOV)

Provine, J., E-mail: jprovine@stanford.edu; Schindler, Peter; Kim, Yongmin

2016-06-15

The continued scaling in transistors and memory elements has necessitated the development of atomic layer deposition (ALD) of silicon nitride (SiN{sub x}), particularly for use a low k dielectric spacer. One of the key material properties needed for SiN{sub x} films is a low wet etch rate (WER) in hydrofluoric (HF) acid. In this work, we report on the evaluation of multiple precursors for plasma enhanced atomic layer deposition (PEALD) of SiN{sub x} and evaluate the film’s WER in 100:1 dilutions of HF in H{sub 2}O. The remote plasma capability available in PEALD, enabled controlling the density of the SiN{submore » x} film. Namely, prolonged plasma exposure made films denser which corresponded to lower WER in a systematic fashion. We determined that there is a strong correlation between WER and the density of the film that extends across multiple precursors, PEALD reactors, and a variety of process conditions. Limiting all steps in the deposition to a maximum temperature of 350 °C, it was shown to be possible to achieve a WER in PEALD SiN{sub x} of 6.1 Å/min, which is similar to WER of SiN{sub x} from LPCVD reactions at 850 °C.« less

Free tropospheric ozone production following entrainment of urban plumes into deep convection

NASA Technical Reports Server (NTRS)

Pickering, Kenneth E.; Thompson, Anne M.; Scala, John R.; Tao, Wei-Kuo; Dickerson, Russell R.; Simpson, Joanne

1992-01-01

It is shown that rapid vertical transport of air from urban plumes through deep convective clouds can cause substantial enhancement of the rate of O3 production in the free troposphere. Simulation of convective redistribution and subsequent photochemistry of an urban plume from Oklahoma City during the 1985 PRESTORM campaign shows enhancement of O3 production in the free tropospheric cloud outflow layer by a factor of almost 4. In contrast, simulation of convective transport of an urban plume from Manaus, Brazil, into a prestine free troposphere during GTE/ABLE 2B (1987), followed by a photochemical simulation, showed enhancement of O3 production by a factor of 35. The reasons for the different enhancements are (1) intensity of cloud vertical motion; (2) initial boundary layer O3 precursor concentrations; and (3) initial amount of background free tropospheric NO(x). Convective transport of ozone precursors to the middle and upper troposphere allows the resulting O3 to spread over large geographic regions, rather than being confined to the lower troposphere where loss processes are much more rapid. Conversely, as air with lower NO descends and replaces more polluted air, there is greater O3 production efficiency per molecule of NO in the boundary layer following convective transport. As a result, over 30 percent more ozone could be produced in the entire tropospheric column in the first 24 hours following convective transport of urban plumes.

Effects of Residual Solvent Molecules Facilitating the Infiltration Synthesis of ZnO in a Nonreactive Polymer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ye, Xinyi; Kestell, John; Kisslinger, Kim

Infiltration synthesis, the atomic-layer-deposition-based organic–inorganic material hybridization technique that enables unique hybrid composites with improved material properties and inorganic nanostructures replicated from polymer templates, is shown to be driven by the binding reaction between reactive chemical groups of polymers and perfusing vapor-phase material precursors. Here in this paper, we discover that residual solvent molecules from polymer processing can react with infiltrating material precursors to enable the infiltration synthesis of metal oxides in a nonreactive polymer. The systematic study, which combines in situ quartz crystal microgravimetry, polarization-modulated infrared reflection–absorption spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy, shows that the ZnOmore » infiltration synthesis in nominally nonreactive SU-8 polymer is mediated by residual processing solvent cyclopentanone, a cyclic ketone whose Lewis-basic terminal carbonyl group can react with the infiltrating Lewis-acidic Zn precursor diethylzinc (DEZ). In addition, we find favorable roles of residual epoxy rings in the SU-8 film in further assisting the infiltration synthesis of ZnO. Lastly, the discovered rationale not only improves the understanding of infiltration synthesis mechanism, but also potentially expands its application to more diverse polymer systems for the generation of unique functional organic–inorganic hybrids and inorganic nanostructures.« less

PARTITIONING TUNGSTEN BETWEEN MATRIX PRECURSORS AND CHONDRULE PRECURSORS THROUGH RELATIVE SETTLING

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hubbard, Alexander, E-mail: ahubbard@amnh.org

2016-08-01

Recent studies of chondrites have found a tungsten isotopic anomaly between chondrules and matrix. Given the refractory nature of tungsten, this implies that W was carried into the solar nebula by at least two distinct families of pre-solar grains. The observed chondrule/matrix split requires that the distinct families were kept separate during the dust coagulation process, and that the two families of grain interacted with the chondrule formation mechanism differently. We take the co-existence of different families of solids in the same general orbital region at the chondrule-precursor size as given, and explore the requirements for them to have interactedmore » with the chondrule formation process at significantly different rates. We show that this sorting of families of solids into chondrule- and matrix-destined dust had to have been at least as powerful a sorting mechanism as the relative settling of aerodynamically distinct grains at least two scale heights above the midplane. The requirement that the chondrule formation mechanism was correlated in some fashion with a dust-grain sorting mechanism argues strongly for spatially localized chondrule formation mechanisms such as turbulent dissipation in non-thermally ionized disk surface layers, and argues against volume-filling mechanisms such as planetesimal bow shocks.« less

Effects of Residual Solvent Molecules Facilitating the Infiltration Synthesis of ZnO in a Nonreactive Polymer

DOE PAGES

Ye, Xinyi; Kestell, John; Kisslinger, Kim; ...

2017-05-04

Infiltration synthesis, the atomic-layer-deposition-based organic–inorganic material hybridization technique that enables unique hybrid composites with improved material properties and inorganic nanostructures replicated from polymer templates, is shown to be driven by the binding reaction between reactive chemical groups of polymers and perfusing vapor-phase material precursors. Here in this paper, we discover that residual solvent molecules from polymer processing can react with infiltrating material precursors to enable the infiltration synthesis of metal oxides in a nonreactive polymer. The systematic study, which combines in situ quartz crystal microgravimetry, polarization-modulated infrared reflection–absorption spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy, shows that the ZnOmore » infiltration synthesis in nominally nonreactive SU-8 polymer is mediated by residual processing solvent cyclopentanone, a cyclic ketone whose Lewis-basic terminal carbonyl group can react with the infiltrating Lewis-acidic Zn precursor diethylzinc (DEZ). In addition, we find favorable roles of residual epoxy rings in the SU-8 film in further assisting the infiltration synthesis of ZnO. Lastly, the discovered rationale not only improves the understanding of infiltration synthesis mechanism, but also potentially expands its application to more diverse polymer systems for the generation of unique functional organic–inorganic hybrids and inorganic nanostructures.« less

Method of making a layered composite electrode/electrolyte

DOEpatents

Visco, Steven J.; Jacobson, Craig P.; DeJonghe, Lutgard C.

2005-01-25

An electrode/electrolyte structure is prepared by a plurality of methods. An unsintered (possibly bisque fired) moderately catalytic electronically-conductive or homogeneous mixed ionic electronic conductive electrode material is deposited on a layer composed of a sintered or unsintered ionically-conductive electrolyte material prior to being sintered. A layer of particulate electrode material is deposited on an unsintered ("green") layer of electrolyte material and the electrode and electrolyte layers are sintered simultaneously, sometimes referred to as "co-firing," under conditions suitable to fully densify the electrolyte while the electrode retains porosity. Or, the layer of particulate electrode material is deposited on a previously sintered layer of electrolyte, and then sintered. Subsequently, a catalytic material is added to the electrode structure by infiltration of an electrolcatalyst precursor (e.g., a metal salt such as a transition metal nitrate). This may be followed by low temperature firing to convert the precursor to catalyst. The invention allows for an electrode with high electronic conductivity and sufficient catalytic activity to achieve high power density in an ionic (electrochemical) device such as fuel cells and electrolytic gas separation systems.

Low Pressure Vapor-assisted Solution Process for Tunable Band Gap Pinhole-free Methylammonium Lead Halide Perovskite Films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sutter-Fella, Carolin M.; Li, Yanbo; Cefarin, Nicola

Organo-lead halide perovskites have recently attracted great interest for potential applications in thin-film photovoltaics and optoelectronics. Herein, we present a protocol for the fabrication of this material via the low-pressure vapor assisted solution process (LP-VASP) method, which yields ~19% power conversion efficiency in planar heterojunction perovskite solar cells. First, we report the synthesis of methylammonium iodide (CH 3NH 3I) and methylammonium bromide (CH 3NH 3Br) from methylamine and the corresponding halide acid (HI or HBr). Then, we describe the fabrication of pinhole-free, continuous methylammonium-lead halide perovskite (CH 3NH 3PbX 3 with X = I, Br, Cl and their mixture) filmsmore » with the LP-VASP. This process is based on two steps: i) spin-coating of a homogenous layer of lead halide precursor onto a substrate, and ii) conversion of this layer to CH 3NH 3PbI 3-xBr x by exposing the substrate to vapors of a mixture of CH 3NH 3I and CH 3NH 3Br at reduced pressure and 120 °C. Through slow diffusion of the methylammonium halide vapor into the lead halide precursor, we achieve slow and controlled growth of a continuous, pinhole-free perovskite film. The LP-VASP allows synthetic access to the full halide composition space in CH 3NH 3PbI 3-xBr x with 0 ≤ x ≤ 3. Depending on the composition of the vapor phase, the bandgap can be tuned between 1.6 eV ≤ E g ≤ 2.3 eV. In addition, by varying the composition of the halide precursor and of the vapor phase, we can also obtain CH 3NH 3PbI 3-xCl x. Films obtained from the LP-VASP are reproducible, phase pure as confirmed by X-ray diffraction measurements, and show high photoluminescence quantum yield. The process does not require the use of a glovebox.« less

Low Pressure Vapor-assisted Solution Process for Tunable Band Gap Pinhole-free Methylammonium Lead Halide Perovskite Films

DOE PAGES

Sutter-Fella, Carolin M.; Li, Yanbo; Cefarin, Nicola; ...

2017-09-08

Organo-lead halide perovskites have recently attracted great interest for potential applications in thin-film photovoltaics and optoelectronics. Herein, we present a protocol for the fabrication of this material via the low-pressure vapor assisted solution process (LP-VASP) method, which yields ~19% power conversion efficiency in planar heterojunction perovskite solar cells. First, we report the synthesis of methylammonium iodide (CH 3NH 3I) and methylammonium bromide (CH 3NH 3Br) from methylamine and the corresponding halide acid (HI or HBr). Then, we describe the fabrication of pinhole-free, continuous methylammonium-lead halide perovskite (CH 3NH 3PbX 3 with X = I, Br, Cl and their mixture) filmsmore » with the LP-VASP. This process is based on two steps: i) spin-coating of a homogenous layer of lead halide precursor onto a substrate, and ii) conversion of this layer to CH 3NH 3PbI 3-xBr x by exposing the substrate to vapors of a mixture of CH 3NH 3I and CH 3NH 3Br at reduced pressure and 120 °C. Through slow diffusion of the methylammonium halide vapor into the lead halide precursor, we achieve slow and controlled growth of a continuous, pinhole-free perovskite film. The LP-VASP allows synthetic access to the full halide composition space in CH 3NH 3PbI 3-xBr x with 0 ≤ x ≤ 3. Depending on the composition of the vapor phase, the bandgap can be tuned between 1.6 eV ≤ E g ≤ 2.3 eV. In addition, by varying the composition of the halide precursor and of the vapor phase, we can also obtain CH 3NH 3PbI 3-xCl x. Films obtained from the LP-VASP are reproducible, phase pure as confirmed by X-ray diffraction measurements, and show high photoluminescence quantum yield. The process does not require the use of a glovebox.« less

Layer-by-layer introduction of poly(phenylenevinylene) onto microspheres and probing the influence from the weak/strong polyanion spacer-layers.

PubMed

Song, Jing; Qiu, Tian; Chen, Yun; Zhang, Wei; Fan, Li-Juan

2015-08-15

The layer-by-layer (LBL) technique was employed for preparing fluorescent microspheres with a core-shell structure by the alternating adsorption of positively charged poly(p-phenylenevinylene) precursor (pre-PPV) and the polyanions onto polymer substrate spheres, followed by the thermal elimination to convert pre-PPV into fluorescent poly(p-phenylenevinylene) (PPV). Weak polyelectrolytes poly(acrylic acid) (PAA) (usually in a partly ionized form) and strong polyelectrolytes poly(sodium-p-styrenesulfonate) (PSS) were used as the anions to space the PPV layers and reduce the fluorescence self-quenching. Flow cytometry, combined with spectroscopy and microscopy, were used to study the structure and photophysical properties of the resulting microspheres. Optimization of the processing factors was carried out. PAA and PSS as weak and strong polyelectrolytes, respectively, displayed very different influence on the final emission of the spheres. Such difference was attributed to different inherent characteristics of PAA and PSS after detailed investigation in many aspects. In addition, the fluorescent spheres were found to have excellent photostability and thermal stability. Copyright © 2015 Elsevier Inc. All rights reserved.

Process to make structured particles

DOEpatents

Knapp, Angela Michelle; Richard, Monique N; Luhrs, Claudia; Blada, Timothy; Phillips, Jonathan

2014-02-04

Disclosed is a process for making a composite material that contains structured particles. The process includes providing a first precursor in the form of a dry precursor powder, a precursor liquid, a precursor vapor of a liquid and/or a precursor gas. The process also includes providing a plasma that has a high field zone and passing the first precursor through the high field zone of the plasma. As the first precursor passes through the high field zone of the plasma, at least part of the first precursor is decomposed. An aerosol having a second precursor is provided downstream of the high field zone of the plasma and the decomposed first material is allowed to condense onto the second precursor to from structured particles.

Atomic layer deposition of quaternary chalcogenides

DOEpatents

Thimsen, Elijah J; Riha, Shannon C; Martinson, Alex B.F.; Elam, Jeffrey W; Pellin, Michael J

2014-06-03

Methods and systems are provided for synthesis and deposition of chalcogenides (including Cu.sub.2ZnSnS.sub.4). Binary compounds, such as metal sulfides, can be deposited by alternating exposures of the substrate to a metal cation precursor and a chalcogen anion precursor with purge steps between.

Pulsed photoinitiated fabrication of inkjet printed titanium dioxide/reduced graphene oxide nanocomposite thin films.

PubMed

Bourgeois, Briley; Luo, Sijun; Riggs, Brian; Ji, Yaping; Adireddy, Shiva; Schroder, Kurt; Farnsworth, Stan; Chrisey, Douglas; Escarra, Matthew

2018-08-03

This work reports a new technique for scalable and low-temperature processing of nanostructured TiO 2 thin films, allowing for practical manufacturing of TiO 2 -based devices such as perovskite solar cells at low-temperature or on flexible substrates. Dual layers of dense and mesoporous TiO 2 /graphitic oxide nanocomposite films are synthesized simultaneously using inkjet printing and pulsed photonic irradiation. Investigation of process parameters including precursor concentration (10-20 wt%) and exposure fluence (4.5-8.5 J cm -2 ) reveals control over crystalline quality, graphitic oxide phase, film thickness, dendrite density, and optical properties. Raman spectroscopy shows the E g peak, characteristic of anatase phase titania, increases in intensity with higher photonic irradiation fluence, suggesting increased crystallinity through higher fluence processing. Film thickness and dendrite density is shown to increase with precursor concentration in the printed ink. The dense base layer thickness was controlled between 20 and 80 nm. The refractive index of the films is determined by ellipsometry to be 1.92 ± 0.08 at 650 nm. Films exhibit an energy weighted optical transparency of 91.1%, in comparison to 91.3% of a thermally processed film, when in situ carbon materials were removed. Transmission and diffuse reflectance are used to determine optical band gaps of the films ranging from 2.98 to 3.38 eV in accordance with the photonic irradiation fluence and suggests tunability of TiO 2 phase composition. The sheet resistance of the synthesized films is measured to be 14.54 ± 1.11 Ω/□ and 28.90 ± 2.24 Ω/□ for films as-processed and after carbon removal, respectively, which is comparable to high temperature processed TiO 2 thin films. The studied electrical and optical properties of the light processed films show comparable results to traditionally processed TiO 2 while offering the distinct advantages of scalable manufacturing, low-temperature processing, simultaneous bilayer fabrication, and in situ formation of removable carbon nanocomposites.

Chemical precursor impact on the properties of Cu{sub 2}ZnSnS{sub 4} absorber layer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vashistha, Indu B., E-mail: indu-139@yahoo.com; Sharma, S. K.; Sharma, Mahesh C.

2016-04-13

In present work impact of different chemical precursor on the deposition of solar absorber layer Cu{sub 2}ZnSnS{sub 4} (CZTS) were studied by Chemical Bath Deposition (CBD) method without using expensive vacuum facilities and followed by annealing. As compared to the other deposition methods, CBD method is interesting one because it is simple, reproducible, non-hazardous, cost effective and well suited for producing large-area thin films at low temperatures, although effect of precursors and concentration plays a vital role in the deposition. So, the central theme of this work is optimizing and controlling of chemical reactions for different chemical precursors. Further Effectmore » of different chemical precursors i.e. sulphate and chloride is analyzed by structural, morphological, optical and electrical properties. The X-ray diffraction (XRD) of annealed CZTS thin film revealed that films were polycrystalline in nature with kestarite tetragonal crystal structure. The Atomic Force micrographs (AFM) images indicated total coverage compact film and as well as growth of crystals. The band gap of annealed CZTS films was found in the range of optimal band gap by absorption spectroscopy.« less

Synthesis, Processing and Properties of Calcium- and Nickel-Doped Yttrium Chromates(III) Y0.8Ca0.2Cr1-x Ni x O3 (x = 0-0.3) and Studies on Their Potential Application as Coatings for SOFC Interconnects

NASA Astrophysics Data System (ADS)

Stygar, M.; Tejchman, W.; Dąbrowa, J.; Kruk, A.; Brylewski, T.

2018-05-01

In the present study, a calcium- and nickel-doped yttrium chromates (YCCN)-based, conductive-protective layers for metallic interconnects used in the intermediate-temperature solid oxide fuel cells (IT-SOFCs) were investigated. Synthesis of Y0.8Ca0.2Cr1-x Ni x O3 (x = 0; 0.15 and 0.3) powders was performed using a wet chemistry method with two different complexing agents: ethylenediaminetetraacetic acid and glycine. Based on the result of thermal analysis of obtained precursors, optimal conditions of the calcination process were determined. Powders were then milled, compacted and sintered at different temperatures using free sintering method, into series of dense, polycrystalline sinters. The use of glycine precursor allowed obtaining a single-phase material in all cases. Based on the electrical and sintering properties, the Y0.8Ca0.2Cr0.85Ni0.15O3 material was selected for further studies. It was deposited using cost-effective screen-printing method on the Crofer 22APU ferritic stainless steel. To investigate properties and suitability of the resulting layer/steel system for IT-SOFCs applications, the high-temperature, dual-atmosphere studies were carried out for the first time for ceramic/metallic system, in conditions as close as possible to actual working conditions of the fuel cell. The layer exhibited high stability and good protective properties. The area-specific resistance of the studied ceramic layer/metallic substrate composite was determined, with the obtained value of 0.0366 Ω cm2 being within the arbitrary limit set for these materials (0.1 Ω cm2). The results show that the investigated materials are suitable for the projected application.

Chemical processes related to net ozone tendencies in the free troposphere

NASA Astrophysics Data System (ADS)

Bozem, Heiko; Butler, Tim M.; Lawrence, Mark G.; Harder, Hartwig; Martinez, Monica; Kubistin, Dagmar; Lelieveld, Jos; Fischer, Horst

2017-09-01

Ozone (O3) is an important atmospheric oxidant, a greenhouse gas, and a hazard to human health and agriculture. Here we describe airborne in situ measurements and model simulations of O3 and its precursors during tropical and extratropical field campaigns over South America and Europe, respectively. Using the measurements, net ozone formation/destruction tendencies are calculated and compared to 3-D chemistry-transport model simulations. In general, observation-based net ozone tendencies are positive in the continental boundary layer and the upper troposphere at altitudes above ˜ 6 km in both environments. On the other hand, in the marine boundary layer and the middle troposphere, from the top of the boundary layer to about 6-8 km altitude, net O3 destruction prevails. The ozone tendencies are controlled by ambient concentrations of nitrogen oxides (NOx). In regions with net ozone destruction the available NOx is below the threshold value at which production and destruction of O3 balance. While threshold NO values increase with altitude, in the upper troposphere NOx concentrations are generally higher due to the integral effect of convective precursor transport from the boundary layer, downward transport from the stratosphere and NOx produced by lightning. Two case studies indicate that in fresh convective outflow of electrified thunderstorms net ozone production is enhanced by a factor 5-6 compared to the undisturbed upper tropospheric background. The chemistry-transport model MATCH-MPIC generally reproduces the pattern of observation-based net ozone tendencies but mostly underestimates the magnitude of the net tendency (for both net ozone production and destruction).

Preparation and Layer-by-Layer Solution Deposition of Cu(In,Ga)O2 Nanoparticles with Conversion to Cu(In,Ga)S2 Films

PubMed Central

Dressick, Walter J.; Soto, Carissa M.; Fontana, Jake; Baker, Colin C.; Myers, Jason D.; Frantz, Jesse A.; Kim, Woohong

2014-01-01

We present a method of Cu(In,Ga)S2 (CIGS) thin film formation via conversion of layer-by-layer (LbL) assembled Cu-In-Ga oxide (CIGO) nanoparticles and polyelectrolytes. CIGO nanoparticles were created via a novel flame-spray pyrolysis method using metal nitrate precursors, subsequently coated with polyallylamine (PAH), and dispersed in aqueous solution. Multilayer films were assembled by alternately dipping quartz, Si, and/or Mo substrates into a solution of either polydopamine (PDA) or polystyrenesulfonate (PSS) and then in the CIGO-PAH dispersion to fabricate films as thick as 1–2 microns. PSS/CIGO-PAH films were found to be inadequate due to weak adhesion to the Si and Mo substrates, excessive particle diffusion during sulfurization, and mechanical softness ill-suited to further processing. PDA/CIGO-PAH films, in contrast, were more mechanically robust and more tolerant of high temperature processing. After LbL deposition, films were oxidized to remove polymer and sulfurized at high temperature under flowing hydrogen sulfide to convert CIGO to CIGS. Complete film conversion from the oxide to the sulfide is confirmed by X-ray diffraction characterization. PMID:24941104

Coffee-Ring Defined Short Channels for Inkjet-Printed Metal Oxide Thin-Film Transistors.

PubMed

Li, Yuzhi; Lan, Linfeng; Xiao, Peng; Sun, Sheng; Lin, Zhenguo; Song, Wei; Song, Erlong; Gao, Peixiong; Wu, Weijing; Peng, Junbiao

2016-08-03

Short-channel electronic devices several micrometers in length are difficult to implement by direct inkjet printing due to the limitation of position accuracy of the common inkjet printer system and the spread of functional ink on substrates. In this report, metal oxide thin-film transistors (TFTs) with channel lengths of 3.5 ± 0.7 μm were successfully fabricated with a common inkjet printer without any photolithography steps. Hydrophobic CYTOP coffee stripes, made by inkjet-printing and plasma-treating processes, were utilized to define the channel area of TFTs with channel lengths as short as ∼3.5 μm by dewetting the inks of the source/drain (S/D) precursors. Furthermore, by introduction of an ultrathin layer of PVA to modify the S/D surfaces, the spreading of precursor ink of the InOx semiconductor layer was well-controlled. The inkjet-printed short-channel TFTs exhibited a maximum mobility of 4.9 cm(2) V(-1) s(-1) and an on/off ratio of larger than 10(9). This approach of fabricating short-channel TFTs by inkjet printing will promote the large-area fabrication of short-channel TFTs in a cost-effective manner.

Tuning dipolar magnetic interactions by controlling individual silica coating of iron oxide nanoparticles

NASA Astrophysics Data System (ADS)

Rivas Rojas, P. C.; Tancredi, P.; Moscoso Londoño, O.; Knobel, M.; Socolovsky, L. M.

2018-04-01

Single and fixed size core, core-shell nanoparticles of iron oxides coated with a silica layer of tunable thickness were prepared by chemical routes, aiming to generate a frame of study of magnetic nanoparticles with controlled dipolar interactions. The batch of iron oxides nanoparticles of 4.5 nm radii, were employed as cores for all the coated samples. The latter was obtained via thermal decomposition of organic precursors, resulting on nanoparticles covered with an organic layer that was subsequently used to promote the ligand exchange in the inverse microemulsion process, employed to coat each nanoparticle with silica. The amount of precursor and times of reaction was varied to obtain different silica shell thicknesses, ranging from 0.5 nm to 19 nm. The formation of the desired structures was corroborated by TEM and SAXS measurements, the core single-phase spinel structure was confirmed by XRD, and superparamagnetic features with gradual change related to dipolar interaction effects were obtained by the study of the applied field and temperature dependence of the magnetization. To illustrate that dipolar interactions are consistently controlled, the main magnetic properties are presented and analyzed as a function of center to center minimum distance between the magnetic cores.

Electrospinning of calcium carbonate fibers and their conversion to nanocrystalline hydroxyapatite.

PubMed

Holopainen, Jani; Santala, Eero; Heikkilä, Mikko; Ritala, Mikko

2014-12-01

Calcium carbonate (CaCO3) fibers were prepared by electrospinning followed by annealing. Solutions consisting of calcium nitrate tetrahydrate (Ca(NO3)2·4H2O) and polyvinylpyrrolidone (PVP) dissolved in ethanol or 2-methoxyethanol were used for the fiber preparation. By varying the precursor concentrations in the electrospinning solutions CaCO3 fibers with average diameters from 140 to 290 nm were obtained. After calcination the fibers were identified as calcite by X-ray diffraction (XRD). The calcination process was studied in detail with high temperature X-ray diffraction (HTXRD) and thermogravimetric analysis (TGA). The initially weak fiber-to-substrate adhesion was improved by adding a strengthening CaCO3 layer by spin or dip coating Ca(NO3)2/PVP precursor solution on the CaCO3 fibers followed by annealing of the gel formed inside the fiber layer. The CaCO3 fibers were converted to nanocrystalline hydroxyapatite (HA) fibers by treatment in a dilute phosphate solution. The resulting hydroxyapatite had a plate-like crystal structure with resemblance to bone mineral. The calcium carbonate and hydroxyapatite fibers are interesting materials for bone scaffolds and bioactive coatings. Copyright © 2014 Elsevier B.V. All rights reserved.

Development of the intrinsic and extrinsic innervation of the gut.

PubMed

Uesaka, Toshihiro; Young, Heather M; Pachnis, Vassilis; Enomoto, Hideki

2016-09-15

The gastrointestinal (GI) tract is innervated by intrinsic enteric neurons and by extrinsic efferent and afferent nerves. The enteric (intrinsic) nervous system (ENS) in most regions of the gut consists of two main ganglionated layers; myenteric and submucosal ganglia, containing numerous types of enteric neurons and glial cells. Axons arising from the ENS and from extrinsic neurons innervate most layers of the gut wall and regulate many gut functions. The majority of ENS cells are derived from vagal neural crest cells (NCCs), which proliferate, colonize the entire gut, and first populate the myenteric region. After gut colonization by vagal NCCs, the extrinsic nerve fibers reach the GI tract, and Schwann cell precursors (SCPs) enter the gut along the extrinsic nerves. Furthermore, a subpopulation of cells in myenteric ganglia undergoes a radial (inward) migration to form the submucosal plexus, and the intrinsic and extrinsic innervation to the mucosal region develops. Here, we focus on recent progress in understanding the developmental processes that occur after the gut is colonized by vagal ENS precursors, and provide an up-to-date overview of molecular mechanisms regulating the development of the intrinsic and extrinsic innervation of the GI tract. Copyright © 2016 Elsevier Inc. All rights reserved.

Growth of ferroelectric Ba{sub 0.8}Sr{sub 0.2}TiO{sub 3} epitaxial films by ultraviolet pulsed laser irradiation of chemical solution derived precursor layers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Queraltó, A.; Pérez del Pino, A., E-mail: aperez@icmab.es; Mata, M. de la

2015-06-29

Highly crystalline epitaxial Ba{sub 0.8}Sr{sub 0.2}TiO{sub 3} (BST) thin-films are grown on (001)-oriented LaNiO{sub 3}-buffered LaAlO{sub 3} substrates by pulsed laser irradiation of solution derived barium-zirconium-titanium precursor layers using a UV Nd:YAG laser source at atmospheric conditions. The structural analyses of the obtained films, studied by X-ray diffractometry and transmission electron microscopy, demonstrate that laser processing allows the growth of tens of nm-thick BST epitaxial films with crystalline structure similar to that of films obtained through conventional thermal annealing methods. However, the fast pulsed nature of the laser employed leads to crystallization kinetic evolution orders of magnitude faster than inmore » thermal treatments. The combination of specific photothermal and photochemical mechanisms is the main responsible for the ultrafast epitaxial laser-induced crystallization. Piezoresponse microscopy measurements demonstrate equivalent ferroelectric behavior in laser and thermally annealed films, being the piezoelectric constant ∼25 pm V{sup −1}.« less

Low Temperature ABC-Type Ru Atomic Layer Deposition through Consecutive Dissociative Chemisorption, Combustion, and Reduction Steps

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Junling; Elam, Jeffrey W.

Thermal atomic layer deposition (ALD) of noble metals is frequently performed using molecular oxygen as the nonmetal precursor to effect a combustion-type chemistry at relatively high temperatures of 300 °C. Bis(ethylcyclopentadienyl)ruthenium (Ru(EtCp)2) is one of the common used metal precursors for Ru ALD. Using Ru(EtCp)2 and oxygen as reactants, Ru ALD was acheived at near 300 °C. Here, we demonstrate that Ru ALD can proceed at as low as 150 °C by using successive exposures to oxygen and hydrogen as the co-reactants. In situ quartz crystal microbalance (QCM) and quadrupole mass spectroscopy (QMS) measurements both suggest that this ABC-type ALDmore » occurs through dissociative chemisorption, combustion, and reduction for the Ru(EtCp)2, oxygen and hydrogen steps, respectively, in a similar manner to processes using ozone and hydrogen as co-reactants reported previously. Moreover, we believe this molecular O2 and H2 based ABC-type ALD could be exploited for the ALD of other noble metals to decrease the deposition temperature and reduce oxygen impurities.« less

Inhibiting Metal Oxide Atomic Layer Deposition: Beyond Zinc Oxide

DOE PAGES

Sampson, Matthew D.; Emery, Jonathan D.; Pellin, Michael J.; ...

2017-04-05

The atomic layer deposition (ALD) of several metal oxides is selectivity inhibited on alkanethiol self-assembled monolayers (SAMs) on Au and the eventual nucleation mechanism is investigated. The inhibition ability of the SAM is significantly improved by the in situ H 2-plasma pretreatment of the Au substrate prior to gas-phase deposition of a long-chain alkanethiol, 1-dodecanethiol (DDT). This more rigorous surface preparation inhibits even aggressive oxide ALD precursors, including trimethylaluminum and water, for at least 20 cycles. We study the effect that ALD precursor purge times, growth temperature, alkanethiol chain length, alkanethiol deposition time, and plasma treatment time have on Almore » 2O 3 ALD inhibition. This is the first example of Al 2O 3 ALD inhibition from a vapor-deposited SAM. Inhibition of Al 2O 3, ZnO, and MnO ALD processes are compared, revealing the versatility of this selective surface treatment. As a result, atomic force microscopy (AFM) and grazing incidence x-ray fluorescence (GIXRF) further reveals insight into the mechanism by which the well-defined surface chemistry of ALD may eventually be circumvented to allow metal oxide nucleation and growth on SAM-modified surfaces.« less

Inhibiting Metal Oxide Atomic Layer Deposition: Beyond Zinc Oxide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sampson, Matthew D.; Emery, Jonathan D.; Pellin, Michael J.

The atomic layer deposition (ALD) of several metal oxides is selectivity inhibited on alkanethiol self-assembled monolayers (SAMs) on Au and the eventual nucleation mechanism is investigated. The inhibition ability of the SAM is significantly improved by the in situ H 2-plasma pretreatment of the Au substrate prior to gas-phase deposition of a long-chain alkanethiol, 1-dodecanethiol (DDT). This more rigorous surface preparation inhibits even aggressive oxide ALD precursors, including trimethylaluminum and water, for at least 20 cycles. We study the effect that ALD precursor purge times, growth temperature, alkanethiol chain length, alkanethiol deposition time, and plasma treatment time have on Almore » 2O 3 ALD inhibition. This is the first example of Al 2O 3 ALD inhibition from a vapor-deposited SAM. Inhibition of Al 2O 3, ZnO, and MnO ALD processes are compared, revealing the versatility of this selective surface treatment. As a result, atomic force microscopy (AFM) and grazing incidence x-ray fluorescence (GIXRF) further reveals insight into the mechanism by which the well-defined surface chemistry of ALD may eventually be circumvented to allow metal oxide nucleation and growth on SAM-modified surfaces.« less

Chemical Evolution of Ozone and Its Precursors in Asian Pacific Rim Outflow During TRACE-P

NASA Astrophysics Data System (ADS)

Hamlin, A.; Crawford, J.; Olson, J.; Pippin, M.; Avery, M.; Sachse, G.; Barrick, J.; Blake, D.; Tan, D.; Sandholm, S.; Kondo, Y.; Singh, H.; Eisele, F.; Zondlo, M.; Flocke, F.; Talbot, R.

2002-12-01

During NASA's GTE/TRACE-P (Transport and Chemical Evolution over the Pacific) mission, a widespread stagnant pollution layer was observed between 2 and 4 km over the central Pacific. In this region, high levels of O3 (70~ppbv), CO (210~ppbv), and NOx (130~pptv) were observed. Back trajectories suggest this airmass had been rapidly transported from the Asian coast near the Yellow Sea to the central Pacific where it underwent subsidence. The chemical evolution of ozone and its precursors for this airmass is examined using lagrangian photochemical box model calculations. Simulations are conducted along trajectories which intersect the flight path where predicted mixing ratios are compared to measurements. An analysis of the photochemical processes controlling the cycling of nitrogen oxides and ozone production and destruction during transport will be presented.

Mechanochemical approach for synthesis of layered double hydroxides

NASA Astrophysics Data System (ADS)

Zhang, Xiaoqing; Li, Shuping

2013-06-01

In this paper, a mechanochemical approach is used to prepare layered double hydroxides (LDHs). This approach involves manually grinding the precursor, nitrates and then the hydrothermal treatment. The study indicates that grinding leads to the incomplete formation of LDHs phase, LDHs-M. The reaction degree of precursor salts to LDHs after grinding depends on the melting points of the precursors. As expected, hydrothermal treatment is beneficial for the good crystallization and regularity of LDHs. Especially, the effect of hydrothermal treatment has been emphatically explored. The hydration of LDHs-M, increment of zeta potentials and the complete exchange of NO3- by CO32- anions occur successively or in parallel during the hydrothermal treatment. It can be found that combination of grinding and hydrothermal treatment gives rise to the formation of uniform and monodispersed particles of LDHs.

Precursor of transition to turbulence: spatiotemporal wave front.

PubMed

Bhaumik, S; Sengupta, T K

2014-04-01

To understand transition to turbulence via 3D disturbance growth, we report here results obtained from the solution of Navier-Stokes equation (NSE) to reproduce experimental results obtained by minimizing background disturbances and imposing deterministic excitation inside the shear layer. A similar approach was adopted in Sengupta and Bhaumik [Phys. Rev. Lett. 107, 154501 (2011)], where a route of transition from receptivity to fully developed turbulent stage was explained for 2D flow in terms of the spatio-temporal wave-front (STWF). The STWF was identified as the unit process of 2D turbulence creation for low amplitude wall excitation. Theoretical prediction of STWF for boundary layer was established earlier in Sengupta, Rao, and Venkatasubbaiah [Phys. Rev. Lett. 96, 224504 (2006)] from the Orr-Sommerfeld equation as due to spatiotemporal instability. Here, the same unit process of the STWF during transition is shown to be present for 3D disturbance field from the solution of governing NSE.

Precursor preparation for Ca-Al layered double hydroxide to remove hexavalent chromium coexisting with calcium and magnesium chlorides

NASA Astrophysics Data System (ADS)

Zhong, Lihua; He, Xiaoman; Qu, Jun; Li, Xuewei; Lei, Zhiwu; Zhang, Qiwu; Liu, Xinzhong

2017-01-01

Al(OH)3 and Ca(OH)2 powders are co-ground to prepare a precursor which hydrates into a layered double hydroxide (LDH) phase by agitation in aqueous solution with target hexavalent chromium (Cr(VI)) at room temperature, to achieve an obvious improvement in removal efficiency of Cr(VI) through an easy incorporation into the structure. Although the prepared precursor transforms into LDH phases also when agitated in the solutions of calcium and magnesium chlorides, it incorporates Cr(VI) preferentially to the chloride salts when they coexist. The adsorption isotherm and kinetic studies show that the phenomena occurring on the Al-Ca precursor fit a pseudo-second-order kinetics with a Langmuir adsorption capacity of 59.45 mg/g. Besides, characterizations of the prepared precursor and the samples after adsorption are also performed by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Transmission electron microscope (TEM) to understand the reason of the preferential incorporation of Cr(VI) to the coexisting chloride salts during the LDH phase formation. Ca-Al precursor (C3A) was agitated in a hexavalent chromium (Cr(VI)) solution to form Al-Ca-CrO4 LDH product. Ca-Al-CrO4 LDH phase occurred preferentially to Ca-Al-MCl2 LDH phases in the solutions of calcium and magnesium chlorides, it incorporates Cr(VI) preferentially to the chloride salts when they coexist.

Ceramic impregnated superabrasives

DOEpatents

Radtke, Robert P.; Sherman, Andrew

2009-02-10

A superabrasive fracture resistant compact is formed by depositing successive layers of ceramic throughout the network of open pores in a thermally stable self-bonded polycrystalline diamond or cubic boron nitride preform. The void volume in the preform is from approximately 2 to 10 percent of the volume of the preform, and the average pore size is below approximately 3000 nanometers. The preform is evacuated and infiltrated under at least about 1500 pounds per square inch pressure with a liquid pre-ceramic polymerizable precursor. The precursor is infiltrated into the preform at or below the boiling point of the precursor. The precursor is polymerized into a solid phase material. The excess is removed from the outside of the preform, and the polymer is pyrolized to form a ceramic. The process is repeated at least once more so as to achieve upwards of 90 percent filling of the original void volume. When the remaining void volume drops below about 1 percent the physical properties of the compact, such as fracture resistance, improve substantially. Multiple infiltration cycles result in the deposition of sufficient ceramic to reduce the void volume to below 0.5 percent. The fracture resistance of the compacts in which the pores are lined with formed in situ ceramic is generally at least one and one-half times that of the starting preforms.

Tunable hydrogel composite with two-step processing in combination with innovative hardware upgrade for cell-based three-dimensional bioprinting.

PubMed

Wüst, Silke; Godla, Marie E; Müller, Ralph; Hofmann, Sandra

2014-02-01

Three-dimensional (3-D) bioprinting is the layer-by-layer deposition of biological material with the aim of achieving stable 3-D constructs for application in tissue engineering. It is a powerful tool for the spatially directed placement of multiple materials and/or cells within the 3-D sample. Encapsulated cells are protected by the bioink during the printing process. Very few materials are available that fulfill requirements for bioprinting as well as provide adequate properties for cell encapsulation during and after the printing process. A hydrogel composite including alginate and gelatin precursors was tuned with different concentrations of hydroxyapatite (HA) and characterized in terms of rheology, swelling behavior and mechanical properties to assess the versatility of the system. Instantaneous as well as long-term structural integrity of the printed hydrogel was achieved with a two-step mechanism combining the thermosensitive properties of gelatin with chemical crosslinking of alginate. Novel syringe tip heaters were developed for improved temperature control of the bioink to avoid clogging. Human mesenchymal stem cells mixed into the hydrogel precursor survived the printing process and showed high cell viability of 85% living cells after 3 days of subsequent in vitro culture. HA enabled the visualization of the printed structures with micro-computed tomography. The inclusion of HA also favors the use of the bioink for bone tissue engineering applications. By adding factors other than HA, the composite could be used as a bioink for applications in drug delivery, microsphere deposition or soft tissue engineering. Copyright © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Effects of humidity during formation of zinc oxide electron contact layers from a diethylzinc precursor solution

DOE PAGES

Mauger, Scott A.; Steirer, K. Xerxes; Boe, Jonas; ...

2016-01-19

Here, this work focuses on the role of humidity in the formation of ZnO thin films from a reactive diethylzinc precursor solution for use as the electron contact layer (ECL) in organic photovoltaic (OPV) devices. This method is well suited for flexible devices because the films are annealed at 120 °C, making the process compatible with polymer substrates. ZnO films were prepared by spin coating and annealing at different relative humidity (RH) levels. It is found that RH during coating and annealing affects the chemical and physical properties of the ZnO films. Using x-ray photoelectron spectroscopy it is found thatmore » increasing RH during the formation steps produces a more stoichiometric oxide and a higher Zn/O ratio. Spectroscopic ellipsometry data shows a small decrease in the optical band gap with increased humidity, consistent with a more stoichiometric oxide. Kelvin probe measurements show that increased RH during formation results in a larger work function (i.e. further from vacuum). Consistent with these data, but counter to what might be expected, when these ZnO films are used as ECLs in OPV devices those with ZnO ECLs processed in low RH (less stoichiometric) had higher power conversion efficiency than those with high-RH processed ZnO due to improved open-circuit voltage. The increase in open-circuit voltage with decreasing humidity was observed with two different donor polymers and fullerene acceptors, which shows the trend is due to changes in ZnO. The observed changes in open-circuit voltage follow the same trend as the ZnO work function indicating that the increase in open-circuit voltage with decreasing humidity is the result of improved energetics at the interface between the bulk-heterojunction and the ZnO layer due to a vacuum level shift.« less

Methods for using atomic layer deposition to produce a film for solid state electrolytes and protective electrode coatings for lithium batteries

DOEpatents

Elam, Jeffrey W.; Meng, Xiangbo

2018-03-13

A method for using atomic layer deposition to produce a film configured for use in an anode, cathode, or solid state electrolyte of a lithium-ion battery or a lithium-sulfur battery. The method includes repeating a cycle for a predetermined number of times in an inert atmosphere. The cycle includes exposing a substrate to a first precursor, purging the substrate with inert gas, exposing the substrate to a second precursor, and purging the substrate with inert gas. The film is a metal sulfide.

The interactive role of subsynoptic scale jet sreak and planetary boundary layer adjustments in organizing an apparently isolated convective complex

NASA Technical Reports Server (NTRS)

Kaplan, M. L.; Zack, J. W.; Wong, V. C.; Tuccillo, J. J.; Coats, G. D.

1982-01-01

A mesoscale atmospheric simulation system is described that is being developed in order to improve the simulation of subsynoptic and mesoscale adjustments associated with cyclogenesis, severe storm development, and significant atmospheric transport processes. Present emphasis in model development is in the parameterization of physical processes, time-dependent boundary conditions, sophisticated initialization and analysis procedures, nested grid solutions, and applications software development. Basic characteristics of the system as of March 1982 are listed. In a case study, the Grand Island tornado outbreak of 3 June 1980 is considered in substantial detail. Results of simulations with a mesoscale atmospheric simulation system indicate that over the high plains subtle interactions between existing jet streaks and deep well mixed boundary layers can lead to well organized patterns of mesoscale divergence and pressure falls. The amplitude and positioning of these mesoscale features is a function of the subtle nonlinear interaction between the pre-existing jet-streak and deep well mixed boundary layers. Model results for the case study indicate that the model has the potential for forecasting the precursor mesoscale convective environment.

Equilibrium chemical vapor deposition growth of Bernal-stacked bilayer graphene.

PubMed

Zhao, Pei; Kim, Sungjin; Chen, Xiao; Einarsson, Erik; Wang, Miao; Song, Yenan; Wang, Hongtao; Chiashi, Shohei; Xiang, Rong; Maruyama, Shigeo

2014-11-25

Using ethanol as the carbon source, self-limiting growth of AB-stacked bilayer graphene (BLG) has been achieved on Cu via an equilibrium chemical vapor deposition (CVD) process. We found that during this alcohol catalytic CVD (ACCVD) a source-gas pressure range exists to break the self-limitation of monolayer graphene on Cu, and at a certain equilibrium state it prefers to form uniform BLG with a high surface coverage of ∼94% and AB-stacking ratio of nearly 100%. More importantly, once the BLG is completed, this growth shows a self-limiting manner, and an extended ethanol flow time does not result in additional layers. We investigate the mechanism of this equilibrium BLG growth using isotopically labeled (13)C-ethanol and selective surface aryl functionalization, and results reveal that during the equilibrium ACCVD process a continuous substitution of graphene flakes occurs to the as-formed graphene and the BLG growth follows a layer-by-layer epitaxy mechanism. These phenomena are significantly in contrast to those observed for previously reported BLG growth using methane as precursor.

Physical and Electrical Properties of SiO2 Layer Synthesized by Eco-Friendly Method

NASA Astrophysics Data System (ADS)

Jong-Woong Kim,; Young-Seok Kim,; Sung-Jei Hong,; Tae-Hwan Hong,; Jeong-In Han,

2010-05-01

SiO2 thin film has a wide range of applications, including insulation layers in microelectronic devices, such as semiconductors and flat panel displays, due to its advantageous characteristics. Herein, we developed a new eco-friendly method for manufacturing SiO2 nanoparticles and, thereby, SiO2 paste to be used in the digital printing process for the fabrication of SiO2 film. By excluding harmful Cl- and NO3- elements from the SiO2 nanoparticle synthetic process, we were able to lower the heat treatment temperature for the SiO2 precursor from 600 to 300 °C and the diameter of the final SiO2 nanoparticles to about 14 nm. The synthesized SiO2 nanoparticles were dispersed in an organic solvent with additives to make a SiO2 paste for feasibility testing. The SiO2 paste was printed onto a glass substrate to test the feasibility of using it for digital printing. The insulation resistance of the printed film was high enough for it to be used as an insulation layer for passivation.

Degradation processes of reinforced concretes by combined sulfate–phosphate attack

DOE Office of Scientific and Technical Information (OSTI.GOV)

Secco, Michele, E-mail: michele.secco@unipd.it; Department of Civil, Environmental and Architectural Engineering; Lampronti, Giulio Isacco, E-mail: gil21@cam.ac.uk

2015-02-15

A novel form of alteration due to the interaction between hydrated cement phases and sulfate and phosphate-based pollutants is described, through the characterization of concrete samples from an industrial reinforced concrete building. Decalcification of the cement matrices was observed, with secondary sulfate and phosphate-based mineral formation, according to a marked mineralogical and textural zoning. Five alteration layers may be detected: the two outermost layers are characterized by the presence of gypsum–brushite solid solution phases associated with anhydrous calcium sulfates and phosphates, respectively, while a progressive increase in apatite and ammonium magnesium phosphates is observable in the three innermost layers, associatedmore » with specific apatite precursors (brushite, octacalcium phosphate and amorphous calcium phosphate, respectively). The heterogeneous microstructural development of secondary phases is related to the chemical, pH and thermal gradients in the attacked cementitious systems, caused by different sources of pollutants and the exposure to the sun's radiation.« less

Stabilized CdSe-CoPi composite photoanode for light-assisted water oxidation by transformation of a CdSe/cobalt metal thin film.

PubMed

Costi, Ronny; Young, Elizabeth R; Bulović, Vladimir; Nocera, Daniel G

2013-04-10

Integration of water splitting catalysts with visible-light-absorbing semiconductors would enable direct solar-energy-to-fuel conversion schemes such as those based on water splitting. A disadvantage of some common semiconductors that possess desirable optical bandgaps is their chemical instability under the conditions needed for oxygen evolution reaction (OER). In this study, we demonstrate the dual benefits gained from using a cobalt metal thin-film as the precursor for the preparation of cobalt-phosphate (CoPi) OER catalyst on cadmium chalcogenide photoanodes. The cobalt layer protects the underlying semiconductor from oxidation and degradation while forming the catalyst and simultaneously facilitates the advantageous incorporation of the cadmium chalcogenide layer into the CoPi layer during continued processing of the electrode. The resulting hybrid material forms a stable photoactive anode for light-assisted water splitting.

An improved biofilter to control the dissolved organic nitrogen concentration during drinking water treatment.

PubMed

Zhang, Huining; Gu, Li; Liu, Bing; Gan, Huihui; Zhang, Kefeng; Jin, Huixia; Yu, Xin

2016-09-01

Dissolved organic nitrogen (DON) is a key precursor of numerous disinfection by-products (DBPs), especially nitrogenous DBPs (N-DBPs) formed during disinfection in drinking water treatment. To effectively control DBPs, reduction of the DON concentration before the disinfection process is critical. Traditional biofilters can increase the DON concentration in the effluent, so an improved biofilter is needed. In this study, an improved biofilter was set up with two-layer columns using activated carbon and quartz sand under different influent patterns. Compared with the single-layer filter, the two-layer biofilter controlled the DON concentration more efficiently. The two-point influent biofilter controlled the DON concentration more effectively than the single-point influent biofilter. The improved biofilter resulted in an environment (including matrix, DO, and pH) suitable for microbial growth. Along the depth of the biofilter column, the environment affected the microbial biomass and microbial activity and thus affected the DON concentration.

Electrochemical synthesis of a surface-porous Mg70.5Al29.5 eutectic alloy in a neutral aqueous NaCl solution

NASA Astrophysics Data System (ADS)

Yang, Feng; Li, Yong-gang; Wei, Ying-hui; Wei, Huan; Yan, Ze-ying; Hou, Li-feng

2018-03-01

A surface-porous Mg-Al eutectic alloy was fabricated at room temperature via electrochemical dealloying in a neutral, aqueous 0.6 M NaCl solution by controlling the applied potential and processing duration. Selective dissolution occurred on the alloy surface. The surface-porous formation mechanism is governed by the selective dissolution of the α-Mg phase, which leaves the Mg17Al12 phase as the porous layer framework. The pore characteristics (morphology, size, and distribution) of the dealloyed samples are inherited from the α-Mg phases of the precursor Mg70.5Al29.5 (at.%) alloy. Size control in the porous layer can be achieved by regulating the synthesis parameters.

Effect of annealing time on optical and electrical properties of CdS thin films

NASA Astrophysics Data System (ADS)

Soliya, Vanshika; Tandel, Digisha; Patel, Chandani; Patel, Kinjal

2018-05-01

Cadmium sulphide (CdS) is semiconductor compound of II-VI group. Thin film of CdS widely used in the applications such as, a buffer layer in copper indium diselenide (CIS) hetrojunction based solar cells, transistors, photo detectors and light emitting diodes. Because of the ease of making like chemical bath deposition (CBD), screen printing and thermal evaporation. It is extensively used in the CIS based solar cells as a buffer layers. The buffer layers usually used for reducing the interface recombination of the photo generated carriers by means of improving the lattice mismatch between the layers. The optimum thickness and the optoelectronics properties of CdS thin films like, optical band gap, electrical resistivity, structure, and composition etc., are to be considering for its use as a buffer layer. In the present study the CdS thin film were grown by simple dip coating method. In this method we had prepared 0.1M Cadmium-thiourea precursor solution. Before the deposition process of CdS, glass substrate has been cleaned using Methanol, Acetone, Trichloroethylene and De-ionized (DI) water. After coating of precursor layer, it was heated at 200 °C for themolysis. Then after CdS films were annealed at 200 °C for different time and studied its influence on the optical transmission, band gap, XRD, raman and the electrical resistivity. As increasing the annealing time we had observed the average transmission of the films was reduce after the absorption edge. In addition to the blue shift of absorption edge was observed. The observed optimum band gap was around 2.50 eV. XRD and raman analysis confirms the cubuc phase of CdS. Hot probe method confirms the n-type conductivity of the CdS film. Hall probe data shows the resistivity of the films was in the order of 103 Ωcm. Observed data signifies its future use in the many optoelectronics devices.

Density functional theory study of HfCl4, ZrCl4, and Al(CH3)3 decomposition on hydroxylated SiO2: Initial stage of high-k atomic layer deposition

NASA Astrophysics Data System (ADS)

Jeloaica, L.; Estève, A.; Djafari Rouhani, M.; Estève, D.

2003-07-01

The initial stage of atomic layer deposition of HfO2, ZrO2, and Al2O3 high-k films, i.e., the decomposition of HfCl4, ZrCl4, and Al(CH3)3 precursor molecules on an OH-terminated SiO2 surface, is investigated within density functional theory. The energy barriers are determined using artificial activation of vibrational normal modes. For all precursors, reaction proceeds through the formation of intermediate complexes that have equivalent formation energies (˜-0.45 eV), and results in HCl and CH4 formation with activation energies of 0.88, 0.91, and 1.04 eV for Hf, Zr, and Al based precursors, respectively. The reaction product of Al(CH3)3 decomposition is found to be more stable (by -1.45 eV) than the chemisorbed intermediate complex compared to the endothermic decomposition of HfCl4 and ZrCl4 chemisorbed precursors (0.26 and 0.29 eV, respectively).

Synthesis and optical properties of Mg-Al layered double hydroxides precursor powders

NASA Astrophysics Data System (ADS)

Lin, Chia-Hsuan; Chu, Hsueh-Liang; Hwang, Weng-Sing; Wang, Moo-Chin; Ko, Horng-Huey

2017-12-01

The synthesis and optical properties of Mg-Al layered double hydroxide (LDH) precursor powders were investigated using X-ray diffraction (XRD), Fourier transform-infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), selected area electron diffraction (SAED), high-resolution TEM (HRTEM), UV-transmission spectrometer, and fluorescence spectrophotometer. The FT-IR results show that the intense absorption at around 1363-1377 cm-1 can be assigned to the antisymmetric ν3 mode of interlayer carbonate anions because the LDH phase contains some CO32-. The XRD results show that all of the Mg-Al LDH precursor powders contain only a single phase of [Mg0.833Al0.167(OH)2](CO3)0.083.(H2O)0.75 but have broad and weak intensities of peaks. All of Mg-Al LDHs precursor powders before calcination have the same photoluminescence (PL) spectra. Moreover, these spectra were excited at λex = 235 nm, and the broad emission band was in the range 325-650 nm. In the range, there were relatively strong intensity at around 360, 407 and 510 nm, respectively.

Effect of pores formation process and oxygen plasma treatment to hydroxyapatite formation on bioactive PEEK prepared by incorporation of precursor of apatite.

PubMed

Yabutsuka, Takeshi; Fukushima, Keito; Hiruta, Tomoko; Takai, Shigeomi; Yao, Takeshi

2017-12-01

When bioinert substrates with fine-sized pores are immersed in a simulated body fluid (SBF) and the pH value or the temperature is increased, fine particles of calcium phosphate, which the authors denoted as 'precursor of apatite' (PrA), are formed in the pores. By this method, hydroxyapatite formation ability can be provided to various kinds of bioinert materials. In this study, the authors studied fabrication methods of bioactive PEEK by using the above-mentioned process. First, the fine-sized pores were formed on the surface of the PEEK substrate by H 2 SO 4 treatment. Next, to provide hydrophilic property to the PEEK, the surfaces of the PEEK were treated with O 2 plasma. Finally, PrA were formed in the pores by the above-mentioned process, which is denoted as 'Alkaline SBF' treatment, and the bioactive PEEK was obtained. By immersing in SBF with the physiological condition, hydroxyapatite formation was induced on the whole surface of the substrate within 1day. The formation of PrA directly contributed to hydroxyapatite formation ability. By applying the O 2 plasma treatment, hydroxyapatite formation was uniformly performed on the whole surface of the substrate. The H 2 SO 4 treatment contributed to a considerable enhancement of adhesive strength of the formed hydroxyapatite layer formed in SBF because of the increase of surface areas of the substrate. As a comparative study, the sandblasting method was applied as the pores formation process instead of the H 2 SO 4 treatment. Although hydroxyapatite formation was provided also in this case, however, the adhesion of the formed hydroxyapatite layer to the substrate was not sufficient even if the O 2 plasma treatment was conducted. This result indicates that the fine-sized pores should be formed on the whole surface of the substrate uniformly to achieve high adhesive strength of the hydroxyapatite layer. Therefore, it is considered that the H 2 SO 4 treatment before the O 2 plasma and the 'Alkaline SBF' treatment is an important factor to achieve high adhesive strength of hydroxyapatite layer to the PEEK substrate. This material is expected to be a candidate for next-generation implant materials with high bioactivity. Copyright © 2017 Elsevier B.V. All rights reserved.

Characterizing fluorocarbon assisted atomic layer etching of Si using cyclic Ar/C4F8 and Ar/CHF3 plasma

NASA Astrophysics Data System (ADS)

Metzler, Dominik; Li, Chen; Engelmann, Sebastian; Bruce, Robert L.; Joseph, Eric A.; Oehrlein, Gottlieb S.

2017-02-01

With the increasing interest in establishing directional etching methods capable of atomic scale resolution for fabricating highly scaled electronic devices, the need for development and characterization of atomic layer etching processes, or generally etch processes with atomic layer precision, is growing. In this work, a flux-controlled cyclic plasma process is used for etching of SiO2 and Si at the Angstrom-level. This is based on steady-state Ar plasma, with periodic, precise injection of a fluorocarbon (FC) precursor (C4F8 and CHF3) and synchronized, plasma-based Ar+ ion bombardment [D. Metzler et al., J. Vac. Sci. Technol., A 32, 020603 (2014) and D. Metzler et al., J. Vac. Sci. Technol., A 34, 01B101 (2016)]. For low energy Ar+ ion bombardment conditions, physical sputter rates are minimized, whereas material can be etched when FC reactants are present at the surface. This cyclic approach offers a large parameter space for process optimization. Etch depth per cycle, removal rates, and self-limitation of removal, along with material dependence of these aspects, were examined as a function of FC surface coverage, ion energy, and etch step length using in situ real time ellipsometry. The deposited FC thickness per cycle is found to have a strong impact on etch depth per cycle of SiO2 and Si but is limited with regard to control over material etching selectivity. Ion energy over the 20-30 eV range strongly impacts material selectivity. The choice of precursor can have a significant impact on the surface chemistry and chemically enhanced etching. CHF3 has a lower FC deposition yield for both SiO2 and Si and also exhibits a strong substrate dependence of FC deposition yield, in contrast to C4F8. The thickness of deposited FC layers using CHF3 is found to be greater for Si than for SiO2. X-ray photoelectron spectroscopy was used to study surface chemistry. When thicker FC films of 11 Å are employed, strong changes of FC film chemistry during a cycle are seen whereas the chemical state of the substrate varies much less. On the other hand, for FC film deposition of 5 Å for each cycle, strong substrate surface chemical changes are seen during an etching cycle. The nature of this cyclic etching with periodic deposition of thin FC films differs significantly from conventional etching with steady-state FC layers since surface conditions change strongly throughout each cycle.

Passivation of InGaAs(001)-(2 × 4) by Self-Limiting Chemical Vapor Deposition of a Silicon Hydride Control Layer.

PubMed

Edmonds, Mary; Kent, Tyler; Chagarov, Evgueni; Sardashti, Kasra; Droopad, Ravi; Chang, Mei; Kachian, Jessica; Park, Jun Hong; Kummel, Andrew

2015-07-08

A saturated Si-Hx seed layer for gate oxide or contact conductor ALD has been deposited via two separate self-limiting and saturating CVD processes on InGaAs(001)-(2 × 4) at substrate temperatures of 250 and 350 °C. For the first self-limiting process, a single silicon precursor, Si3H8, was dosed at a substrate temperature of 250 °C, and XPS results show the deposited silicon hydride layer saturated at about 4 monolayers of silicon coverage with hydrogen termination. STS results show the surface Fermi level remains unpinned following the deposition of the saturated silicon hydride layer, indicating the InGaAs surface dangling bonds are electrically passivated by Si-Hx. For the second self-limiting process, Si2Cl6 was dosed at a substrate temperature of 350 °C, and XPS results show the deposited silicon chloride layer saturated at about 2.5 monolayers of silicon coverage with chlorine termination. Atomic hydrogen produced by a thermal gas cracker was subsequently dosed at 350 °C to remove the Si-Cl termination by replacing with Si-H termination as confirmed by XPS, and STS results confirm the saturated Si-Hx bilayer leaves the InGaAs(001)-(2 × 4) surface Fermi level unpinned. Density function theory modeling of silicon hydride surface passivation shows an Si-Hx monolayer can remove all the dangling bonds and leave a charge balanced surface on InGaAs.

Method for fabrication of ceramic dielectric films on copper foils

DOEpatents

Ma, Beihai; Narayanan, Manoj; Dorris, Stephen E.; Balachandran, Uthamalingam

2017-06-14

The present invention provides copper substrate coated with a lead-lanthanum-zirconium-titanium (PLZT) ceramic film, which is prepared by a method comprising applying a layer of a sol-gel composition onto a copper foil. The sol-gel composition comprises a precursor of a ceramic material suspended in 2-methoxyethanol. The layer of sol-gel is then dried at a temperature up to about 250.degree. C. The dried layer is then pyrolyzed at a temperature in the range of about 300 to about 450.degree. C. to form a ceramic film from the ceramic precursor. The ceramic film is then crystallized at a temperature in the range of about 600 to about 750.degree. C. The drying, pyrolyzing and crystallizing are performed under a flowing stream of an inert gas.

Towards deriving Ni-rich cathode and oxide-based anode materials from hydroxides by sharing a facile co-precipitation method.

PubMed

Qiu, Haifa; Du, Tengfei; Wu, Junfeng; Wang, Yonglong; Liu, Jian; Ye, Shihai; Liu, Sheng

2018-05-22

Although intensive studies have been conducted on layered transition metal oxide(TMO)-based cathode materials and metal oxide-based anode materials for Li-ion batteries, their precursors generally follow different or even complex synthesis routes. To share one route for preparing precursors of the cathode and anode materials, herein, we demonstrate a facile co-precipitation method to fabricate Ni-rich hydroxide precursors of Ni0.8Co0.1Mn0.1(OH)2. Ni-rich layered oxide of LiNi0.8Co0.1Mn0.1O2 is obtained by lithiation of the precursor in air. An NiO-based anode material is prepared by calcining the precursor or multi-walled carbon nanotubes (MWCNTs) incorporated precursors. The pre-addition of ammonia solution can simplify the co-precipitation procedures and the use of an air atmosphere can also make the heat treatment facile. LiNi0.8Co0.1Mn0.1O2 as the cathode material delivers a reversible capacity of 194 mA h g-1 at 40 mA g-1 and a notable cycling retention of 88.8% after 100 cycles at 200 mA g-1. This noticeable performance of the cathode arises from a decent particle morphology and high crystallinity of the layered oxides. As the anode material, the MWCNTs-incorporated oxides deliver a much higher reversible capacity of 811.1 mA h g-1 after 200 cycles compared to the pristine oxides without MWCNTs. The improvement on electrochemical performance can be attributed to synergistic effects from MWCNTs incorporation, including reinforced electronic conductivity, rich meso-pores and an alleviated volume effect. This facile and sharing method may offer an integrated and economical approach for commercial production of Ni-rich electrode materials for Li-ion batteries.

Superconductive wire

DOEpatents

Korzekwa, David A.; Bingert, John F.; Peterson, Dean E.; Sheinberg, Haskell

1995-01-01

A superconductive article is made by inserting a rigid mandrel into an internal cavity of a first metallic tube, said tube having an interior surface and an exterior surface, said interior surface defining the interior cavity, forming a layer of a superconductive material or superconductive precursor upon the exterior surface of said first metallic tube, machining the layer of superconductive material or superconductive precursor to a predetermined diameter to form an intermediate article configured for insertion into a second metallic tube having an interior diameter corresponding to the predetermined diameter, inserting the machined intermediate article into a second metallic tube having an internal diameter corresponding to the predetermined diameter of the intermediate article to form a composite intermediate article, reducing or ironing the composite intermediate article to a predetermined cross-sectional diameter, and sintering the reduced or ironed composite intermediate article at temperatures and for time sufficient for the superconductive material or superconductive precursor to exhibit superconductivity.

Superconductive wire

DOEpatents

Korzekwa, D.A.; Bingert, J.F.; Peterson, D.E.; Sheinberg, H.

1995-07-18

A superconductive article is made by inserting a rigid mandrel into an internal cavity of a first metallic tube, said tube having an interior surface and an exterior surface, said interior surface defining the interior cavity, forming a layer of a superconductive material or superconductive precursor upon the exterior surface of said first metallic tube, machining the layer of superconductive material or superconductive precursor to a predetermined diameter to form an intermediate article configured for insertion into a second metallic tube having an interior diameter corresponding to the predetermined diameter, inserting the machined intermediate article into a second metallic tube having an internal diameter corresponding to the predetermined diameter of the intermediate article to form a composite intermediate article, reducing or ironing the composite intermediate article to a predetermined cross-sectional diameter, and sintering the reduced or ironed composite intermediate article at temperatures and for time sufficient for the superconductive material or superconductive precursor to exhibit superconductivity. 2 figs.

Atomic layer deposition for fabrication of HfO2/Al2O3 thin films with high laser-induced damage thresholds.

PubMed

Wei, Yaowei; Pan, Feng; Zhang, Qinghua; Ma, Ping

2015-01-01

Previous research on the laser damage resistance of thin films deposited by atomic layer deposition (ALD) is rare. In this work, the ALD process for thin film generation was investigated using different process parameters such as various precursor types and pulse duration. The laser-induced damage threshold (LIDT) was measured as a key property for thin films used as laser system components. Reasons for film damaged were also investigated. The LIDTs for thin films deposited by improved process parameters reached a higher level than previously measured. Specifically, the LIDT of the Al2O3 thin film reached 40 J/cm(2). The LIDT of the HfO2/Al2O3 anti-reflector film reached 18 J/cm(2), the highest value reported for ALD single and anti-reflect films. In addition, it was shown that the LIDT could be improved by further altering the process parameters. All results show that ALD is an effective film deposition technique for fabrication of thin film components for high-power laser systems.

Gamma and proton irradiation effects and thermal stability of electrical characteristics of metal-oxide-silicon capacitors with atomic layer deposited Al 2O 3 dielectric

DOE PAGES

J. M. Rafi; Lynn, D.; Pellegrini, G.; ...

2015-12-11

The radiation hardness and thermal stability of the electrical characteristics of atomic layer deposited Al 2O 3 layers to be used as passivation films for silicon radiation detectors with slim edges are investigated. To directly measure the interface charge and to evaluate its change with the ionizing dose, metal-oxide-silicon (MOS) capacitors implementing differently processed Al 2O 3 layers were fabricated on p-type silicon substrates. Qualitatively similar results are obtained for degradation of capacitance–voltage and current–voltage characteristics under gamma and proton irradiations up to equivalent doses of 30 Mrad and 21.07 Mrad, respectively. While similar negative charge densities are initially extractedmore » for all non-irradiated capacitors, superior radiation hardness is obtained for MOS structures with alumina layers grown with H 2O instead of O 3 as oxidant precursor. Competing effects between radiation-induced positive charge trapping and hydrogen release from the H 2O-grown Al 2O 3 layers may explain their higher radiation resistance. Finally, irradiated and non-irradiated MOS capacitors with differently processed Al 2O 3 layers have been subjected to thermal treatments in air at temperatures ranging between 100 °C and 200 °C and the thermal stability of their electrical characteristics has been evaluated. Partial recovery of the gamma-induced degradation has been noticed for O 3-grown MOS structures. Lastly, this can be explained by a trapped holes emission process, for which an activation energy of 1.38 ± 0.15 eV has been extracted.« less

Fabrication of textured SnO2 transparent conductive films using self-assembled Sn nanospheres

NASA Astrophysics Data System (ADS)

Fukumoto, Michitaka; Nakao, Shoichiro; Hirose, Yasushi; Hasegawa, Tetsuya

2018-06-01

We present a novel method to fabricate textured surfaces on transparent conductive SnO2 films by processing substrates through a bottom-up technique with potential for industrially scalable production. The substrate processing consists of three steps: deposition of precursor Sn films on glass substrates, formation of a self-assembled Sn nanosphere layer with reductive annealing, and conversion of Sn to SnO2 by oxidative annealing. Ta-doped SnO2 films conformally deposited on the self-assembled nanospherical SnO2 templates exhibited attractive optical and electrical properties, namely, enhanced haze values and low sheet resistances, for applications as transparent electrodes in photovoltaics.

High Efficiency Inverted Planar Perovskite Solar Cells with Solution-Processed NiOx Hole Contact.

PubMed

Yin, Xuewen; Yao, Zhibo; Luo, Qiang; Dai, Xuezeng; Zhou, Yu; Zhang, Ye; Zhou, Yangying; Luo, Songping; Li, Jianbao; Wang, Ning; Lin, Hong

2017-01-25

NiO x is a promising hole-transporting material for perovskite solar cells due to its high hole mobility, good stability, and easy processability. In this work, we employed a simple solution-processed NiO x film as the hole-transporting layer in perovskite solar cells. When the thickness of the perovskite layer increased from 270 to 380 nm, the light absorption and photogenerated carrier density were enhanced and the transporting distance of electron and hole would also increase at the same time, resulting in a large charge transfer resistance and a long hole-extracted process in the device, characterized by the UV-vis, photoluminescence, and electrochemical impedance spectroscopy spectra. Combining both of these factors, an optimal thickness of 334.2 nm was prepared with the perovskite precursor concentration of 1.35 M. Moreover, the optimal device fabrication conditions were further achieved by optimizing the thickness of NiO x hole-transporting layer and PCBM electron selective layer. As a result, the best power conversion efficiency of 15.71% was obtained with a J sc of 20.51 mA·cm -2 , a V oc of 988 mV, and a FF of 77.51% with almost no hysteresis. A stable efficiency of 15.10% was caught at the maximum power point. This work provides a promising route to achieve higher efficiency perovskite solar cells based on NiO or other inorganic hole-transporting materials.

A high ozone episode in winter 2013 in the Uinta Basin oil and gas region characterized by aircraft measurements

NASA Astrophysics Data System (ADS)

Oltmans, S. J.; Karion, A.; Schnell, R. C.; Pétron, G.; Sweeney, C.; Wolter, S.; Neff, D.; Montzka, S. A.; Miller, B. R.; Helmig, D.; Johnson, B. J.; Hueber, J.

2014-08-01

During the winter of 2012-2013 atmospheric surface ozone mole fractions exceeded the US 8 h standard of 75 ppb on 39 days in the Uinta Basin of Utah. As part of the Uinta Basin Winter Ozone Study (UBWOS) aircraft flights were conducted throughout the basin with continuous measurements of ozone (O3), methane (CH4), carbon dioxide (CO2), carbon monoxide (CO), nitrogen dioxide (NO2), and discrete whole air flask samples for determination of ∼50 trace gases including a number of non-methane hydrocarbons (NMHCs). During the course of seven flights conducted between 31 January and 7 February 2013, coinciding with strong, multi-day temperature inversions, O3 levels gradually built up in the shallow boundary layer from ∼45 ppb to ∼140 ppb. Near-surface CH4 mole fractions increased during the episode from near background levels of ∼2 ppm to over 10 ppm. Based on elevated levels of CH4 across the basin and high correlations of CH4 with NMHCs from the discrete air samples, O3 precursor NMHCs were also inferred to be elevated throughout the basin. Discrete plumes of high NO2 were observed in the gas production region of the basin suggesting that gas processing plants and compressor facilities were important point sources of reactive nitrogen oxides (NOx). Vertical profiles obtained during the flights showed that the high O3 mole fractions (as well as other elevated constituents) were confined to a shallow layer from near the ground to 300-400 m above ground level (m a.g.l.) capped by a strong temperature inversion. The highest mole fractions of the measured constituents during the study period were in an isothermal cold layer that varied from ∼300 m depth on 4 February to ∼150 m on 5 February. A gradient layer with declining mole fractions with altitude extended above the isothermal layer to ∼1900 m a.s.l. (300-400 m a.g.l.) indicative of some mixing of air out of the boundary layer. O3 mole fractions continued to increase within the basin as the high O3 episode developed over the course of a week. CH4 mole fractions, on the other hand, leveled off after several days. On several flights, the aircraft sampled the plume of a coal-fired power plant (located east of the main gas field) flowing above the inversion layer. These measurements ruled out the effluents of the power plant as a significant source of NOx for O3 production beneath the temperature inversion in the basin. The presence of elevated O3 precursors within the basin and the rapid daytime production of O3 in the atmosphere beneath the temperature inversion both indicated that O3 was being produced from precursors emitted within the basin beneath the temperature inversion. Although observations show that horizontal winds in the surface layer were relatively light during the high ozone event, they were sufficient to disperse precursors up to 80 km from primary sources in the main gas field in the southeast quadrant to the balance of the Uinta Basin.

Supramolecular self-assembly of graphene oxide and metal nanoparticles into stacked multilayers by means of a multitasking protein ring

NASA Astrophysics Data System (ADS)

Ardini, Matteo; Golia, Giordana; Passaretti, Paolo; Cimini, Annamaria; Pitari, Giuseppina; Giansanti, Francesco; Leandro, Luana Di; Ottaviano, Luca; Perrozzi, Francesco; Santucci, Sandro; Morandi, Vittorio; Ortolani, Luca; Christian, Meganne; Treossi, Emanuele; Palermo, Vincenzo; Angelucci, Francesco; Ippoliti, Rodolfo

2016-03-01

Graphene oxide (GO) is rapidly emerging worldwide as a breakthrough precursor material for next-generation devices. However, this requires the transition of its two-dimensional layered structure into more accessible three-dimensional (3D) arrays. Peroxiredoxins (Prx) are a family of multitasking redox enzymes, self-assembling into ring-like architectures. Taking advantage of both their symmetric structure and function, 3D reduced GO-based composites are hereby built up. Results reveal that the ``double-faced'' Prx rings can adhere flat on single GO layers and partially reduce them by their sulfur-containing amino acids, driving their stacking into 3D multi-layer reduced GO-Prx composites. This process occurs in aqueous solution at a very low GO concentration, i.e. 0.2 mg ml-1. Further, protein engineering allows the Prx ring to be enriched with metal binding sites inside its lumen. This feature is exploited to both capture presynthesized gold nanoparticles and grow in situ palladium nanoparticles paving the way to straightforward and ``green'' routes to 3D reduced GO-metal composite materials.Graphene oxide (GO) is rapidly emerging worldwide as a breakthrough precursor material for next-generation devices. However, this requires the transition of its two-dimensional layered structure into more accessible three-dimensional (3D) arrays. Peroxiredoxins (Prx) are a family of multitasking redox enzymes, self-assembling into ring-like architectures. Taking advantage of both their symmetric structure and function, 3D reduced GO-based composites are hereby built up. Results reveal that the ``double-faced'' Prx rings can adhere flat on single GO layers and partially reduce them by their sulfur-containing amino acids, driving their stacking into 3D multi-layer reduced GO-Prx composites. This process occurs in aqueous solution at a very low GO concentration, i.e. 0.2 mg ml-1. Further, protein engineering allows the Prx ring to be enriched with metal binding sites inside its lumen. This feature is exploited to both capture presynthesized gold nanoparticles and grow in situ palladium nanoparticles paving the way to straightforward and ``green'' routes to 3D reduced GO-metal composite materials. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr08632a

High-efficiency near-infrared enabled planar perovskite solar cells by embedding upconversion nanocrystals.

PubMed

Meng, Fan-Li; Wu, Jiao-Jiao; Zhao, Er-Fei; Zheng, Yan-Zhen; Huang, Mei-Lan; Dai, Li-Ming; Tao, Xia; Chen, Jian-Feng

2017-11-30

Integration of the upconversion effect in perovskite solar cells (PSCs) is a facile approach towards extending the spectral absorption from the visible to the near infrared (NIR) range and reducing the non-absorption loss of solar photons. However, the big challenge for practical application of UCNCs in planar PSCs is the poor compatibility between UCNCs and the perovskite precursor. Herein, we have subtly overcome the tough compatibility issue using a ligand-exchange strategy. For the first time, β-NaYF 4 :Yb,Er UCNCs have been embedded in situ into a CH 3 NH 3 PbI 3 layer to fabricate NIR-enabled planar PSCs. The CH 3 NH 3 I-capped UCNCs generated from the ligand-exchange were mixed with the perovskite precursor and served as nucleation sites for the UCNC-mediated heteroepitaxial growth of perovskite; moreover, the in situ embedding of UCNCs into the perovskite layer was realized during a spin-coating process. The resulting UCNC-embedded perovskite layer attained a uniform pinhole-free morphology with enlarged crystal grains and enabled NIR absorption. It also contributed to the energy transfer from the UCNCs to the perovskite and electron transport to the collecting electrode surface. The device fabricated using the UCNC-embedded perovskite film achieved an average power-conversion efficiency of 18.60% (19.70% for the best) under AM 1.5G and 0.37% under 980 nm laser, corresponding to 54% and 740-fold increase as compared to that of its counterpart without UCNCs.

Synthesis and Characterization of Transition Metal Oxides and Dichalcogenides and Their Application in Organic Photovoltaics

NASA Astrophysics Data System (ADS)

Mendez, Diego Barrera

This Ph.D. research focused on the development of new materials for alternative renewable energy using organic photovoltaics (OPVs). The first step was to established reliable fabrication and characterization methods of organic photovoltaic devices. The reproducibility of organic photovoltaic cell performance is one of the essential issues that must be achieved before engaging serious investigations of the applications of creative and challenging ideas. Secondly, we thoroughly studied the surface chemistry of the underlying layer and its critical role on the morphology of the BHJ active layer. We showed that when the active layer (which consists of blends of poly(3-hexylthiophene) (P3HT) and phenyl-C60-butyric acid methyl ester (PCBM)) is deposited and annealed over a sol-gel ZnO electron transport layer surface made from monoethanolamine (MEA) containing precursor, PCBM clusters form during annealing and this phase segregation leads to a drastic reduction of OPV parameters due to both low charge generation and high bimolecular recombination. Rinsing the pyrolyzed ZnO films with solvents or using a ZnO recipe without MEA significantly reduced the formation of PCBM clusters and produced devices with good performance. Third, we developed new materials suitable for low-temperature processing and large-area deposition methods to be used as transport layer on OPVs. We achieved the synthesis of MoOx suspensions suitable for large area deposition, with controlled size, stoichiometry, and electronic properties using controlled oxidative dissolution of organometallic powders with H2O2 in n-butanol. The small nanoparticle diameters of ˜ 2 nm enabled solution processing of nanoparticle films on ITO with electronic properties comparable to solution processed and vacuum deposited counterparts, without the need for any post processing. We also accomplished the synthesis of transition metal dichalcogenides (TMDs) directly from precursors in solution using a versatile synthesis method. We demonstrate the ability to synthesize few-layer (˜ 2 nm) MoS2 , MoSe2, WS2, and WSe2 flakes with relatively large lateral sizes (> 2 mum) using a solvothermal method. We demonstrate that the reducing agent, 1,2-hexadecanediol is critical to ensure TMD formation and eliminate corresponding metal oxide. TEM, Raman, PESA, and Kelvin Probe measurements confirmed that all TMDs are p-type, highly crystalline, exhibit 2H phase and present hexagonal crystalline structure. In addition, thickness for all TMDs was consistent with a few-layer flakes. Finally, we studied the use of films spray casted from liquid-exfoliated MoS2 suspensions as hole transport layer for OPVs. Electrical measurements on the devices showed that FF achieved using MoS2 is identical to that using spin-coated polymeric reference material. Calculations showed that the lower Jsc observed in MoS2 devices is explained by reduced light absorption in the active layer region due to less back-reflected light in MoS2 devices. With all these results we have contributed to enable a route towards low-cost OPV and other electronics fabrication.

Spray Chemical Vapor Deposition of Single-Source Precursors for Chalcopyrite I-III-VI2 Thin-Film Materials

NASA Technical Reports Server (NTRS)

Hepp, Aloysius F.; Banger, Kulbinder K.; Jin, Michael H.-C.; Harris, Jerry D.; McNatt, Jeremiah S.; Dickman, John E.

2008-01-01

Thin-film solar cells on flexible, lightweight, space-qualified substrates provide an attractive approach to fabricating solar arrays with high mass-specific power. A polycrystalline chalcopyrite absorber layer is among the new generation of photovoltaic device technologies for thin film solar cells. At NASA Glenn Research Center we have focused on the development of new single-source precursors (SSPs) for deposition of semiconducting chalcopyrite materials onto lightweight, flexible substrates. We describe the syntheses and thermal modulation of SSPs via molecular engineering. Copper indium disulfide and related thin-film materials were deposited via aerosol-assisted chemical vapor deposition using SSPs. Processing and post-processing parameters were varied in order to modify morphology, stoichiometry, crystallography, electrical properties, and optical properties to optimize device quality. Growth at atmospheric pressure in a horizontal hotwall reactor at 395 C yielded the best device films. Placing the susceptor closer to the evaporation zone and flowing a more precursor-rich carrier gas through the reactor yielded shinier-, smoother-, and denser-looking films. Growth of (112)-oriented films yielded more Cu-rich films with fewer secondary phases than growth of (204)/(220)-oriented films. Post-deposition sulfur-vapor annealing enhanced stoichiometry and crystallinity of the films. Photoluminescence studies revealed four major emission bands and a broad band associated with deep defects. The highest device efficiency for an aerosol-assisted chemical vapor deposited cell was one percent.

Ozone Production in Global Tropospheric Models: Quantifying Errors due to Grid Resolution

NASA Astrophysics Data System (ADS)

Wild, O.; Prather, M. J.

2005-12-01

Ozone production in global chemical models is dependent on model resolution because ozone chemistry is inherently nonlinear, the timescales for chemical production are short, and precursors are artificially distributed over the spatial scale of the model grid. In this study we examine the sensitivity of ozone, its precursors, and its production to resolution by running a global chemical transport model at four different resolutions between T21 (5.6° × 5.6°) and T106 (1.1° × 1.1°) and by quantifying the errors in regional and global budgets. The sensitivity to vertical mixing through the parameterization of boundary layer turbulence is also examined. We find less ozone production in the boundary layer at higher resolution, consistent with slower chemical production in polluted emission regions and greater export of precursors. Agreement with ozonesonde and aircraft measurements made during the NASA TRACE-P campaign over the Western Pacific in spring 2001 is consistently better at higher resolution. We demonstrate that the numerical errors in transport processes at a given resolution converge geometrically for a tracer at successively higher resolutions. The convergence in ozone production on progressing from T21 to T42, T63 and T106 resolution is likewise monotonic but still indicates large errors at 120~km scales, suggesting that T106 resolution is still too coarse to resolve regional ozone production. Diagnosing the ozone production and precursor transport that follow a short pulse of emissions over East Asia in springtime allows us to quantify the impacts of resolution on both regional and global ozone. Production close to continental emission regions is overestimated by 27% at T21 resolution, by 13% at T42 resolution, and by 5% at T106 resolution, but subsequent ozone production in the free troposphere is less significantly affected.

A Novel and Facile Route to Synthesize Atomic-Layered MoS2 Film for Large-Area Electronics.

PubMed

Boandoh, Stephen; Choi, Soo Ho; Park, Ji-Hoon; Park, So Young; Bang, Seungho; Jeong, Mun Seok; Lee, Joo Song; Kim, Hyeong Jin; Yang, Woochul; Choi, Jae-Young; Kim, Soo Min; Kim, Ki Kang

2017-10-01

High-quality and large-area molybdenum disulfide (MoS 2 ) thin film is highly desirable for applications in large-area electronics. However, there remains a challenge in attaining MoS 2 film of reasonable crystallinity due to the absence of appropriate choice and control of precursors, as well as choice of suitable growth substrates. Herein, a novel and facile route is reported for synthesizing few-layered MoS 2 film with new precursors via chemical vapor deposition. Prior to growth, an aqueous solution of sodium molybdate as the molybdenum precursor is spun onto the growth substrate and dimethyl disulfide as the liquid sulfur precursor is supplied with a bubbling system during growth. To supplement the limiting effect of Mo (sodium molybdate), a supplementary Mo is supplied by dissolving molybdenum hexacarbonyl (Mo(CO) 6 ) in the liquid sulfur precursor delivered by the bubbler. By precisely controlling the amounts of precursors and hydrogen flow, full coverage of MoS 2 film is readily achievable in 20 min. Large-area MoS 2 field effect transistors (FETs) fabricated with a conventional photolithography have a carrier mobility as high as 18.9 cm 2 V -1 s -1 , which is the highest reported for bottom-gated MoS 2 -FETs fabricated via photolithography with an on/off ratio of ≈10 5 at room temperature. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Novel Solvent-free Perovskite Deposition in Fabrication of Normal and Inverted Architectures of Perovskite Solar Cells

PubMed Central

Nejand, Bahram Abdollahi; Gharibzadeh, Saba; Ahmadi, Vahid; Shahverdi, H. Reza

2016-01-01

We introduced a new approach to deposit perovskite layer with no need for dissolving perovskite precursors. Deposition of Solution-free perovskite (SFP) layer is a key method for deposition of perovskite layer on the hole or electron transport layers that are strongly sensitive to perovskite precursors. Using deposition of SFP layer in the perovskite solar cells would extend possibility of using many electron and hole transport materials in both normal and invert architectures of perovskite solar cells. In the present work, we synthesized crystalline perovskite powder followed by successful deposition on TiO2 and cuprous iodide as the non-sensitve and sensitive charge transport layers to PbI2 and CH3NH3I solution in DMF. The post compressing step enhanced the efficiency of the devices by increasing the interface area between perovskite and charge transport layers. The 9.07% and 7.71% cell efficiencies of the device prepared by SFP layer was achieved in respective normal (using TiO2 as a deposition substrate) and inverted structure (using CuI as deposition substrate) of perovskite solar cell. This method can be efficient in large-scale and low cost fabrication of new generation perovskite solar cells. PMID:27640991

A comparative study on the direct deposition of μc-Si:H and plasma-induced recrystallization of a-Si:H: Insight into Si crystallization in a high-density plasma

NASA Astrophysics Data System (ADS)

Zhou, H. P.; Xu, M.; Xu, S.; Feng, Y. Y.; Xu, L. X.; Wei, D. Y.; Xiao, S. Q.

2018-03-01

Deep insight into the crystallization mechanism of amorphous silicon is of theoretical and technological significance for the preparation of high-quality microcrystalline/polycrystalline silicon. In this work, we intensively compare the present two plasma-involved routes, i.e., the direct deposition and recrystallization of precursor amorphous silicon (a-Si) films, to fabricate microcrystalline silicon. Both the directly deposited and recrystallized samples show multi-layered structures as revealed by electronic microscopy. High-density hydrogen plasma involved recrystallization process, which is mediated by the hydrogen diffusion into the deep region of the precursor a-Si film, displays significantly different nucleation configuration, interface properties, and crystallite shape. The underlying mechanisms are analyzed in combination with the interplay of high-density plasma and growing or treated surface.

Femtosecond-laser hyperdoping silicon in an SF{sub 6} atmosphere: Dopant incorporation mechanism

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sher, Meng-Ju, E-mail: msher@stanford.edu; Mangan, Niall M.; Lin, Yu-Ting

2015-03-28

In this paper, we examine the fundamental processes that occur during femtosecond-laser hyperdoping of silicon with a gas-phase dopant precursor. We probe the dopant concentration profile as a function of the number of laser pulses and pressure of the dopant precursor (sulfur hexafluoride). In contrast to previous studies, we show the hyperdoped layer is single crystalline. From the dose dependence on pressure, we conclude that surface adsorbed molecules are the dominant source of the dopant atoms. Using numerical simulation, we estimate the change in flux with increasing number of laser pulses to fit the concentration profiles. We hypothesize that themore » native oxide plays an important role in setting the surface boundary condition. As a result of the removal of the native oxide by successive laser pulses, dopant incorporation is more efficient during the later stage of laser irradiation.« less

Small angle neutron and X-ray studies of carbon structures with metal atoms

NASA Astrophysics Data System (ADS)

Lebedev, V. T.; Szhogina, A. A.; Bairamukov, V. Yu

2017-05-01

Encapsulation of metal atoms inside carbon single-wall cages or within multi-layer cells has been realized using molecular precursors and high temperature processes transforming them into desirable structures. Endohedral fullerenols Fe@C60(OH)X with 3d-metal (iron) have been studied by SANS in aqueous solutions where they form stable globular clusters with radii R C ∼ 10-12 nm and aggregation numbers N C ∼ 104. This self-assembly is a crucial feature of paramagnetic fullerenols as perspective contrast agents for Magneto-Resonance Imaging in medicine. Cellular carbon-metal structures have been created by the pyrolysis of diphthalocyanines of lanthanides and actinides. It was established that these ultra porous matrices consist of globular cells of molecular precursor size (∼ 1 nm) which are aggregated into superstructures. This provides retain of metal atoms inside matrices which may serve for safety storage of spent fuel of nuclear power plants.

Versatile Tri(pyrazolyl)phosphanes as Phosphorus Precursors for the Synthesis of Highly Emitting InP/ZnS Quantum Dots.

PubMed

Panzer, René; Guhrenz, Chris; Haubold, Danny; Hübner, René; Gaponik, Nikolai; Eychmüller, Alexander; Weigand, Jan J

2017-11-13

Tri(pyrazolyl)phosphanes (5 R1,R2 ) are utilized as an alternative, cheap and low-toxic phosphorus source for the convenient synthesis of InP/ZnS quantum dots (QDs). From these precursors, remarkably long-term stable stock solutions (>6 months) of P(OLA) 3 (OLAH=oleylamine) are generated from which the respective pyrazoles are conveniently recovered. P(OLA) 3 acts simultaneously as phosphorus source and reducing agent in the synthesis of highly emitting InP/ZnS core/shell QDs. These QDs are characterized by a spectral range between 530-620 nm and photoluminescence quantum yields (PL QYs) between 51-62 %. A proof-of-concept white light-emitting diode (LED) applying the InP/ZnS QDs as a color-conversion layer was built to demonstrate their applicability and processibility. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Shadowgraphic investigations into the laser-induced forward transfer of different SnO2 precursor films

NASA Astrophysics Data System (ADS)

Mattle, Thomas; Shaw-Stewart, James; Hintennach, Andreas; Schneider, Christof W.; Lippert, Thomas; Wokaun, Alexander

2013-08-01

Laser-induced forward transfer of different SnO2 precursor films for sensor applications were investigated using time resolved imaging, from 0 to 2 μs after the onset of the ablation process. Transfers of SnCl2(acac)2 and SnO2 nano-particles, both with and without a triazene polymer dynamic release layer (DRL), were investigated and compared to transfers of aluminum films with a triazene polymer DRL. Shockwave speed and flyer speeds at high laser fluences of Φ = 650 mJ/cm2 and at the lower fluences, suitable for the transfer of functional and well defined pixels were analyzed. No influence of the use of a triazene polymer DRL on shockwave and flyer speed was observed. Material ejected under transfer condition showed a velocity of around 200 m/s with a weak shockwave.

Surface engineering of zirconium particles by molecular layer deposition: Significantly enhanced electrostatic safety at minimum loss of the energy density

NASA Astrophysics Data System (ADS)

Qin, Lijun; Yan, Ning; Hao, Haixia; An, Ting; Zhao, Fengqi; Feng, Hao

2018-04-01

Because of its high volumetric heat of oxidation, Zr powder is a promising high energy fuel/additive for rocket propellants. However, the application of Zr powder is restricted by its ultra-high electrostatic discharge sensitivity, which poses great hazards for handling, transportation and utilization of this material. By performing molecular layer deposition of polyimide using 1,2,4,5-benzenetetracarboxylic anhydride and ethylenediamine as the precursors, Zr particles can be uniformly encapsulated by thin layers of the polymer. The thicknesses of the encapsulation layers can be precisely controlled by adjusting the number of deposition cycle. High temperature annealing converts the polymer layer into a carbon coating. Results of thermal analyses reveal that the polymer or carbon coatings have little negative effect on the energy release process of the Zr powder. By varying the thickness of the polyimide or carbon coating, electrostatic discharge sensitivity of the Zr powder can be tuned in a wide range and its uncontrolled ignition hazard can be virtually eliminated. This research demonstrates the great potential of molecular layer deposition in effectively modifying the surface properties of highly reactive metal based energetic materials with minimum sacrifices of their energy densities.

Entropy Production of Emerging Turbulent Scales in a Temporal Supercritical N-Neptane/Nitrogen Three-Dimensional Mixing Layer

NASA Technical Reports Server (NTRS)

Bellan, J.; Okongo, N.

2000-01-01

A study of emerging turbulent scales entropy production is conducted for a supercritical shear layer as a precursor to the eventual modeling of Subgrid Scales (from a turbulent state) leading to Large Eddy Simulations.

Oxidation precursor dependence of atomic layer deposited Al2O3 films in a-Si:H(i)/Al2O3 surface passivation stacks.

PubMed

Xiang, Yuren; Zhou, Chunlan; Jia, Endong; Wang, Wenjing

2015-01-01

In order to obtain a good passivation of a silicon surface, more and more stack passivation schemes have been used in high-efficiency silicon solar cell fabrication. In this work, we prepared a-Si:H(i)/Al2O3 stacks on KOH solution-polished n-type solar grade mono-silicon(100) wafers. For the Al2O3 film deposition, both thermal atomic layer deposition (T-ALD) and plasma enhanced atomic layer deposition (PE-ALD) were used. Interface trap density spectra were obtained for Si passivation with a-Si films and a-Si:H(i)/Al2O3 stacks by a non-contact corona C-V technique. After the fabrication of a-Si:H(i)/Al2O3 stacks, the minimum interface trap density was reduced from original 3 × 10(12) to 1 × 10(12) cm(-2) eV(-1), the surface total charge density increased by nearly one order of magnitude for PE-ALD samples and about 0.4 × 10(12) cm(-2) for a T-ALD sample, and the carrier lifetimes increased by a factor of three (from about 10 μs to about 30 μs). Combining these results with an X-ray photoelectron spectroscopy analysis, we discussed the influence of an oxidation precursor for ALD Al2O3 deposition on Al2O3 single layers and a-Si:H(i)/Al2O3 stack surface passivation from field-effect passivation and chemical passivation perspectives. In addition, the influence of the stack fabrication process on the a-Si film structure was also discussed in this study.

Epitaxial growth of hexagonal boron nitride monolayers by a three-step boration-oxidation-nitration process

NASA Astrophysics Data System (ADS)

Müller, Frank; Hüfner, Stefan; Sachdev, Hermann; Gsell, Stefan; Schreck, Matthias

2010-08-01

The formation of well-ordered monolayers of hexagonal boron nitride on the surface of a Rh/YSZ/Si(111) multilayer substrate via a three-step boration-oxidation-nitration process was investigated by x-ray photoelectron spectroscopy (XPS), x-ray photoelectron diffraction (XPD) and low-energy electron diffraction (LEED). The chemical vapor deposition (CVD) of trimethylborate B(OCH3)3 results in a selective decomposition of the precursor, leading to a dilute distribution of boron within the interstitials of the Rh lattice. After oxidation, the layer of a boron oxygen species of about 1 nm thickness can be transformed into a hexagonal monolayer of BN by annealing in NH3 atmosphere. The results of the present study clearly show that the formation of BN monolayers is also possible when boron and nitrogen are provided successively from separate sources. This procedure represents an alternative routine for the preparation of well-ordered BN monolayers, which benefits from a strong reduction of hazardous potential and economic costs compared to the use of borazine as the current standard precursor.

Engineering Particle Surface Chemistry and Electrochemistry with Atomic Layer Deposition

NASA Astrophysics Data System (ADS)

Jackson, David Hyman Kentaro

Atomic layer deposition (ALD) is a vapor phase thin film coating technique that relies on sequential pulsing of precursors that undergo self-limited surface reactions. The self- limiting reactions and gas phase diffusion of the precursors together enable the conformal coating of microstructured particles with a high degree of thickness and compositional control. ALD may be used to deposit thin films that introduce new functionalities to a particle surface. Examples of new functionalities include: chemical reactivity, a mechanically strong protective coating, and an electrically resistive layer. The coatings properties are often dependent on the bulk properties and microstructure of the particle substrate, though they usually do not affect its bulk properties or microstructure. Particle ALD finds utility in the ability to synthesize well controlled, model systems, though it is expensive due to the need for costly metal precursors that are dangerous and require special handling. Enhanced properties due to ALD coating of particles in various applications are frequently described empirically, while the details of their enhancement mechanisms often remain the focus of ongoing research in the field. This study covers the various types of particle ALD and attempts to describe them from the unifying perspective of surface science.

Application of Deep Learning to Detect Precursors of Tropical Cyclone

NASA Astrophysics Data System (ADS)

Matsuoka, D.; Nakano, M.; Sugiyama, D.; Uchida, S.

2017-12-01

Tropical cyclones (TCs) affect significant damage to human society. Predicting TC generation as soon as possible is important issue in both academic and social perspectives. In the present work, we investigate the probability of predicting TCs seven days prior using deep neural networks. The training data is produced from 30-year cloud resolving global atmospheric simulation (NICAM) with 14 km horizontal resolution (Kodama et al., 2015). We employed a TCs tracking algorithm (Sugi et al., 2002; Nakano et al., 2015) to NICAM simulation data in order to generate supervised cloud images (horizontal sizes are 800-1,000km). We generate approximately one million images of "TCs (include their precursors)" and "not TCs (low pressure clouds)". We generate ten types of image classifier based on 2-dimensional convolutional neural network, includes four convolutional layers, three pooling layers and two fully connected layers. The final predicted results are obtained by these ensemble mean values. Generated classifiers are applied to untrained global simulation data (four million test images). As a result, we succeeded in predicting the precursors of TCs seven and five days before their formation with a Recall of 88.6% and 89.6% (Precision is 11.4%), respectively.

Chemical bath deposited ZnS buffer layer for Cu(In,Ga)Se2 thin film solar cell

NASA Astrophysics Data System (ADS)

Hong, Jiyeon; Lim, Donghwan; Eo, Young-Joo; Choi, Changhwan

2018-02-01

The dependence of Zn precursors using zinc sulfate (ZnSO4), zinc acetate (Zn(CH3COO)2), and zinc chloride (ZnCl2) on the characteristics of the chemical bath deposited ZnS thin film used as a buffer layer of Cu(In,Ga)Se2 (CIGS) thin film solar cell was studied. It is found that the ZnS film deposition rate increases with higher stability constant during decomplexation reaction of zinc ligands, which affects the crack formation and the amount of sulfur and oxygen contents within the film. The band gap energies of all deposited films are in the range of 3.40-3.49 eV, which is lower than that of the bulk ZnS film due to oxygen contents within the films. Among the CIGS solar cells having ZnS buffer layers prepared by different Zn precursors, the best cell efficiency with 9.4% was attained using Zn(CH3COO)2 precursor due to increased Voc mainly. This result suggests that [Zn(NH3)4]2+ complex formation should be well controlled to attain the high quality ZnS thin films.

High Performance, Low Temperature Solution-Processed Barium and Strontium Doped Oxide Thin Film Transistors.

PubMed

Banger, Kulbinder K; Peterson, Rebecca L; Mori, Kiyotaka; Yamashita, Yoshihisa; Leedham, Timothy; Sirringhaus, Henning

2014-01-28

Amorphous mixed metal oxides are emerging as high performance semiconductors for thin film transistor (TFT) applications, with indium gallium zinc oxide, InGaZnO (IGZO), being one of the most widely studied and best performing systems. Here, we investigate alkaline earth (barium or strontium) doped InBa(Sr)ZnO as alternative, semiconducting channel layers and compare their performance of the electrical stress stability with IGZO. In films fabricated by solution-processing from metal alkoxide precursors and annealed to 450 °C we achieve high field-effect electron mobility up to 26 cm 2 V -1 s -1 . We show that it is possible to solution-process these materials at low process temperature (225-200 °C yielding mobilities up to 4.4 cm 2 V -1 s -1 ) and demonstrate a facile "ink-on-demand" process for these materials which utilizes the alcoholysis reaction of alkyl metal precursors to negate the need for complex synthesis and purification protocols. Electrical bias stress measurements which can serve as a figure of merit for performance stability for a TFT device reveal Sr- and Ba-doped semiconductors to exhibit enhanced electrical stability and reduced threshold voltage shift compared to IGZO irrespective of the process temperature and preparation method. This enhancement in stability can be attributed to the higher Gibbs energy of oxidation of barium and strontium compared to gallium.

High Performance, Low Temperature Solution-Processed Barium and Strontium Doped Oxide Thin Film Transistors

PubMed Central

2013-01-01

Amorphous mixed metal oxides are emerging as high performance semiconductors for thin film transistor (TFT) applications, with indium gallium zinc oxide, InGaZnO (IGZO), being one of the most widely studied and best performing systems. Here, we investigate alkaline earth (barium or strontium) doped InBa(Sr)ZnO as alternative, semiconducting channel layers and compare their performance of the electrical stress stability with IGZO. In films fabricated by solution-processing from metal alkoxide precursors and annealed to 450 °C we achieve high field-effect electron mobility up to 26 cm2 V–1 s–1. We show that it is possible to solution-process these materials at low process temperature (225–200 °C yielding mobilities up to 4.4 cm2 V–1 s–1) and demonstrate a facile “ink-on-demand” process for these materials which utilizes the alcoholysis reaction of alkyl metal precursors to negate the need for complex synthesis and purification protocols. Electrical bias stress measurements which can serve as a figure of merit for performance stability for a TFT device reveal Sr- and Ba-doped semiconductors to exhibit enhanced electrical stability and reduced threshold voltage shift compared to IGZO irrespective of the process temperature and preparation method. This enhancement in stability can be attributed to the higher Gibbs energy of oxidation of barium and strontium compared to gallium. PMID:24511184

Recent Advances in Interface Engineering for Planar Heterojunction Perovskite Solar Cells.

PubMed

Yin, Wei; Pan, Lijia; Yang, Tingbin; Liang, Yongye

2016-06-25

Organic-inorganic hybrid perovskite solar cells are considered as one of the most promising next-generation solar cells due to their advantages of low-cost precursors, high power conversion efficiency (PCE) and easy of processing. In the past few years, the PCEs have climbed from a few to over 20% for perovskite solar cells. Recent developments demonstrate that perovskite exhibits ambipolar semiconducting characteristics, which allows for the construction of planar heterojunction (PHJ) perovskite solar cells. PHJ perovskite solar cells can avoid the use of high-temperature sintered mesoporous metal oxides, enabling simple processing and the fabrication of flexible and tandem perovskite solar cells. In planar heterojunction materials, hole/electron transport layers are introduced between a perovskite film and the anode/cathode. The hole and electron transporting layers are expected to enhance exciton separation, charge transportation and collection. Further, the supporting layer for the perovskite film not only plays an important role in energy-level alignment, but also affects perovskite film morphology, which have a great effect on device performance. In addition, interfacial layers also affect device stability. In this review, recent progress in interfacial engineering for PHJ perovskite solar cells will be reviewed, especially with the molecular interfacial materials. The supporting interfacial layers for the optimization of perovskite films will be systematically reviewed. Finally, the challenges remaining in perovskite solar cells research will be discussed.

Atomic layer deposition of metal sulfide thin films using non-halogenated precursors

DOEpatents

Martinson, Alex B. F.; Elam, Jeffrey W.; Pellin, Michael J.

2015-05-26

A method for preparing a metal sulfide thin film using ALD and structures incorporating the metal sulfide thin film. The method includes providing an ALD reactor, a substrate, a first precursor comprising a metal and a second precursor comprising a sulfur compound. The first and the second precursors are reacted in the ALD precursor to form a metal sulfide thin film on the substrate. In a particular embodiment, the metal compound comprises Bis(N,N'-di-sec-butylacetamidinato)dicopper(I) and the sulfur compound comprises hydrogen sulfide (H.sub.2S) to prepare a Cu.sub.2S film. The resulting metal sulfide thin film may be used in among other devices, photovoltaic devices, including interdigitated photovoltaic devices that may use relatively abundant materials for electrical energy production.

Methods for forming particles

DOEpatents

Fox, Robert V.; Zhang, Fengyan; Rodriguez, Rene G.; Pak, Joshua J.; Sun, Chivin

2016-06-21

Single source precursors or pre-copolymers of single source precursors are subjected to microwave radiation to form particles of a I-III-VI.sub.2 material. Such particles may be formed in a wurtzite phase and may be converted to a chalcopyrite phase by, for example, exposure to heat. The particles in the wurtzite phase may have a substantially hexagonal shape that enables stacking into ordered layers. The particles in the wurtzite phase may be mixed with particles in the chalcopyrite phase (i.e., chalcopyrite nanoparticles) that may fill voids within the ordered layers of the particles in the wurtzite phase thus produce films with good coverage. In some embodiments, the methods are used to form layers of semiconductor materials comprising a I-III-VI.sub.2 material. Devices such as, for example, thin-film solar cells may be fabricated using such methods.

Improved oxidation resistance of organic/inorganic composite atomic layer deposition coated cellulose nanocrystal aerogels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, Sean W.; Matthews, David J.; Conley, John F., E-mail: jconley@eecs.oregonstate.edu

2014-07-01

Cellulose nanocrystal (CNC) aerogels are coated with thin conformal layers of Al{sub 2}O{sub 3} using atomic layer deposition to form hybrid organic/inorganic nanocomposites. Electron probe microanalysis and scanning electron microscopy analysis indicated the Al{sub 2}O{sub 3} penetrated more than 1500 μm into the aerogel for extended precursor pulse and exposure/purge times. The measured profile of coated fiber radius versus depth from the aerogel surface agrees well with simulations of precursor penetration depth in modeled aerogel structures. Thermogravimetric analysis shows that Al{sub 2}O{sub 3} coated CNC aerogel nanocomposites do not show significant thermal degradation below 295 °C as compared with 175 °C for uncoatedmore » CNC aerogels, an improvement of over 100 °C.« less

Sol-gel applications for ceramic membrane preparation

NASA Astrophysics Data System (ADS)

Erdem, I.

2017-02-01

Ceramic membranes possessing superior properties compared to polymeric membranes are more durable under severe working conditions and therefore their service life is longer. The ceramic membranes are composed of some layers. The support is the layer composed of coarser ceramic structure and responsible for mechanical durability under filtration pressure and it is prepared by consolidation of ceramic powders. The top layer is composed of a finer ceramic micro-structure mainly responsible for the separation of components present in the fluid to be filtered and sol-gel method is a versatile tool to prepare such a tailor-made ceramic filtration structure with finer pores. Depending on the type of filtration (e.g. micro-filtration, ultra-filtration, nano-filtration) aiming separation of components with different sizes, sols with different particulate sizes should be prepared and consolidated with varying precursors and preparation conditions. The coating of sol on the support layer and heat treatment application to have a stable ceramic micro-structure are also important steps determining the final properties of the top layer. Sol-gel method with various controllable parameters (e.g. precursor type, sol formation kinetics, heat treatment conditions) is a practical tool for the preparation of top layers of ceramic composite membranes with desired physicochemical properties.

Ultrathin TiO2 layer coated-CdS spheres core-shell nanocomposite with enhanced visible-light photoactivity.

PubMed

Chen, Zhang; Xu, Yi-Jun

2013-12-26

Development of various strategies for controllable fabrication of core-shell nanocomposites (CSNs) with highly active photocatalytic performance has been attracting ever-increasing research attention. In particular, control of the ultrathin layer TiO2 shell in constructing CSNs in an aqueous phase is a significant but technologically challenging issue. Here, this paper demonstrates the interface assembly synthesis of CdS nanospheres@TiO2 core-shell photocatalyst via the electrostatic interaction of negatively charged water-stable titania precursor with positively charged CdS nanospheres (CdS NSPs), followed by the formation of the ultrathin-layer TiO2 shell through a facile refluxing process in aqueous phase. The as-formed CdS NSPs@TiO2 core-shell nanohybrid exhibits a high visible-light-driven photoactivity for selective transformation and reduction of heavy metal ions. The ultrathin TiO2 layer coated on CdS NSPs results in excellent light transmission property, enhanced adsorption capacity, and improved transfer of charge carriers and lifespan of photoinduced electron-hole pairs, which would prominently contribute to the significant photoactivity enhancement. It is anticipated that this facile aqueous-phase synthesis strategy could be extended to design a variety of more efficient CSN photocatalysts with controllable morphology toward target applications in diverse photoredox processes.

Controllable Growth of Perovskite Films by Room-Temperature Air Exposure for Efficient Planar Heterojunction Photovoltaic Cells

DOE PAGES

Yang, Bin; Dyck, Ondrej; Poplawsky, Jonathan; ...

2015-12-01

A two-step-solution-processing approach has been established to grow void-free perovskite films for low-cost and high-performance planar heterojunction photovoltaic devices. We generally applied a high-temperature thermal annealing treatment in order to drive the diffusion of CH 3NH 3I precursor molecules into the compact PbI 2 layer to form perovskite films. But, thermal annealing for extended periods would lead to degraded device performance due to the defects generated by decomposition of perovskite into PbI 2. In this work, we explored a controllable layer-by-layer spin-coating method to grow bilayer CH 3NH 3I/PbI 2 films, and then drive the interdiffusion between PbI 2 andmore » CH 3NH 3I layers by a simple room-temperature-air-exposure for making well-oriented, highly-crystalline perovskite films without thermal annealing. This high degree of crystallinity resulted in a carrier diffusion length of ~ 800 nm and high device efficiency of 15.6%, which is comparable to the reported values from thermally-annealed perovskite films based counterparts. Finally, the simplicity and high device performance of this processing approach is highly promising for direct integration into industrial-scale device manufacture.« less

The optimum titanium precursor of fabricating TiO2 compact layer for perovskite solar cells.

PubMed

Qin, Jianqiang; Zhang, Zhenlong; Shi, Wenjia; Liu, Yuefeng; Gao, Huiping; Mao, Yanli

2017-12-29

Perovskite solar cells (PSCs) have attracted tremendous attentions due to its high performance and rapid efficiency promotion. Compact layer plays a crucial role in transferring electrons and blocking charge recombination between the perovskite layer and fluorine-doped tin oxide (FTO) in PSCs. In this study, compact TiO 2 layers were synthesized by spin-coating method with three different titanium precursors, titanium diisopropoxide bis (acetylacetonate) (c-TTDB), titanium isopropoxide (c-TTIP), and tetrabutyl titanate (c-TBOT), respectively. Compared with the PSCs based on the widely used c-TTDB and c-TTIP, the device based on c-TBOT has significantly enhanced performance, including open-circuit voltage, short-circuit current density, fill factor, and hysteresis. The significant enhancement is ascribed to its excellent morphology, high conductivity and optical properties, fast charge transfer, and large recombination resistance. Thus, a power conversion efficiency (PCE) of 17.03% has been achieved for the solar cells based on c-TBOT.

The optimum titanium precursor of fabricating TiO2 compact layer for perovskite solar cells

NASA Astrophysics Data System (ADS)

Qin, Jianqiang; Zhang, Zhenlong; Shi, Wenjia; Liu, Yuefeng; Gao, Huiping; Mao, Yanli

2017-12-01

Perovskite solar cells (PSCs) have attracted tremendous attentions due to its high performance and rapid efficiency promotion. Compact layer plays a crucial role in transferring electrons and blocking charge recombination between the perovskite layer and fluorine-doped tin oxide (FTO) in PSCs. In this study, compact TiO2 layers were synthesized by spin-coating method with three different titanium precursors, titanium diisopropoxide bis (acetylacetonate) (c-TTDB), titanium isopropoxide (c-TTIP), and tetrabutyl titanate (c-TBOT), respectively. Compared with the PSCs based on the widely used c-TTDB and c-TTIP, the device based on c-TBOT has significantly enhanced performance, including open-circuit voltage, short-circuit current density, fill factor, and hysteresis. The significant enhancement is ascribed to its excellent morphology, high conductivity and optical properties, fast charge transfer, and large recombination resistance. Thus, a power conversion efficiency (PCE) of 17.03% has been achieved for the solar cells based on c-TBOT.

Leveraging Subsidence in Permafrost with Remotely Sensed Active Layer Thickness (ReSALT) Products

NASA Astrophysics Data System (ADS)

Schaefer, K. M.; Chen, A.; Chen, J.; Chen, R. H.; Liu, L.; Michaelides, R. J.; Moghaddam, M.; Parsekian, A.; Tabatabaeenejad, A.; Thompson, J. A.; Zebker, H. A.; Meyer, F. J.

2017-12-01

The Remotely Sensed Active Layer Thickness (ReSALT) product uses the Interferometric Synthetic Aperture Radar (InSAR) technique to measure ground subsidence in permafrost regions. Seasonal subsidence results from the expansion of soil water into ice as the surface soil or active layer freezes and thaws each year. Subsidence trends result from large-scale thaw of permafrost and from the melting and subsequent drainage of excess ground ice in permafrost-affected soils. The attached figure shows the 2006-2010 average seasonal subsidence from ReSALT around Barrow, Alaska. The average active layer thickness (the maximum surface thaw depth during summer) is 30-40 cm, resulting in an average seasonal subsidence of 1-3 cm. Analysis of the seasonal subsidence and subsidence trends provides valuable insights into important permafrost processes, such as the freeze/thaw of the active layer, large-scale thawing due to climate change, the impact of fire, and infrastructure vulnerability. ReSALT supports the Arctic-Boreal Vulnerability Experiment (ABoVE) field campaign in Alaska and northwest Canada and is a precursor for a potential NASA-ISRO Synthetic Aperture Radar (NISAR) product. ReSALT includes uncertainties for all parameters and is validated against in situ measurements from the Circumpolar Active Layer Monitoring (CALM) network, Ground Penetrating Radar and mechanical probe measurements. Here we present examples of ReSALT products in Alaska to highlight the untapped potential of the InSAR technique to understand permafrost dynamics, with a strong emphasis on the underlying processes that drive the subsidence.

In-Situ Grown P-N Junctions in MERCURY(1-X) Cadmium(x) Telluride for IR Detectors.

NASA Astrophysics Data System (ADS)

Rao, Vithal Rajaram

In-situ grown p-n junctions in mercury cadmium telluride (Hg_{1-x}Cd _{x}Te with x between 0.2-0.3) were fabricated and characterized in this study. Fabrication of these junctions involved the growth of p-n structures at 370^circC on CdTe substrates by Organometallic Vapor Phase Epitaxy. P-type doping with arsenic was achieved by using tertiarybutylarsine as the precursor. N-type doping was obtained either with indium, using trimethylindium as the precursor or by leaving the layer undoped. These p-n structures were processed to fabricate photodiodes. Their electrical performance was evaluated and conclusions regarding current mechanisms which determine their behavior were drawn. By varying the Hg pressure between 0.07-0.13 atm, p-type doping level in the 10^{16 }/cm^3-rm2times10 ^{17}/cm^3 range was achieved. At higher values of Hg pressure, the arsenic doping level in the layer increased significantly. This is possibly due to an increase in Te vacancies, allowing arsenic to occupy more group VI sites where they behave as acceptors. The activation efficiency of arsenic in the layers was measured to be equal to 50%. A high temperature anneal at 415 ^circC for 15 minutes did not result in any increase in the activation efficiency, possibly indicating the presence of stable As-complexes in the layer. Growth of p^+n structures was carried out in a single run. The acceptor concentration in the p-type cap layer was 5-rm10times10 ^{16}/cm^3. Indium doped n-type base layers had a carrier concentration of 1- rm2times10^{16}/cm^3 , while undoped layers had a n-type background carrier concentration of 4-rm6times10^ {14}/cm^3. The cap layer was 3 μm thick with x = 0.30, while the base layer was 8mum thick with x = 0.26. Under the growth conditions, arsenic showed a diffusion coefficient of rm2times10 ^{13}cm^2/s, which was higher than the interdiffusion coefficient of the alloy junction. This resulted in placement of the p-n junction in the lower bandgap base layer, which is necessary for high quantum efficiency devices. Photodiodes showed a cutoff wavelength of 7.5 mum, which correlates with the alloy composition of the base layer. Measured R_0 A of these diodes varied between 1-100 ohm-cm ^2. In the lower R_0A diodes, reverse bias was dominated by surface currents, possibly due to degradation of the passivating layer. Diodes with higher R_0A showed under reverse bias that trap assisted tunneling current dominated their performance. The origin of these traps is process related and could correspond to the presence of inactivated arsenic close to the p-n junction. Forward bias was dominated by diffusion and recombination currents, while the presence of additional leakage currents was evident.

Layer-by-layer deposition of nanostructured CsPbBr3 perovskite thin films

NASA Astrophysics Data System (ADS)

Reshetnikova, A. A.; Matyushkin, L. B.; Andronov, A. A.; Sokolov, V. S.; Aleksandrova, O. A.; Moshnikov, V. A.

2017-11-01

Layer-by-layer deposition of nanostructured perovskites cesium lead halide thin films is described. The method of deposition is based on alternate immersion of the substrate in the precursor solutions or colloidal solution of nanocrystals and methyl acetate/lead nitrate solution using the device for deposition of films by SILAR and dip-coating techniques. An example of obtaining a photosensitive structure based on nanostructures of ZnO nanowires and layers of CsBbBr3 nanocrystals is also shown.

Microstructure and Mechanics of Superconductor Epitaxy via the Chemical Solution Deposition Method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Frederick F. Lange

2006-11-30

Executive Summary: Initially the funds were sufficient funds were awarded to support one graduate student and one post-doc. Lange, though other funds, also supported a graduate intern from ETH Zurich, Switzerland for a period of 6 months. The initial direction was to study the chemical solution deposition method to understand the microstructural and mechanical phenomena that currently limit the production of thick film, reliable superconductor wires. The study was focused on producing thicker buffer layer(s) on Ni-alloy substrates produced by the RABiTS method. It focused on the development of the microstructure during epitaxy, and the mechanical phenomena that produce cracksmore » during dip-coating, pyrolysis (decomposition of precursors during heating), crystallization and epitaxy. The initial direction of producing thicker layers of a know buffer layer material was redirected by co-workers at ORNL, in an attempt to epitaxially synthesize a potential buffer layer material, LaMnO3, via the solution route. After a more than a period of 6 months that showed that the LaMnO3 reacted with the Ni-W substrate at temperatures that could produce epitaxy, reviewers at the annual program review strongly recommended that the research was not yielding positive results. The only positive result presented at the meeting was that much thicker films could be produce by incorporating a polymer into the precursor that appeared to increase the precursor’s resistance to crack growth. Thus, to continue the program, the objectives were changed to find compositions with the perovskite structure that would be a) chemically compatible with either the Ni-W RABiTS or the MgO IBAD Ni-alloy substrates, and produce a better lattice parameter fit between either of the two substrates. At the start of the second year, the funding was reduced to 2/3’s of the first year level, which required the termination of the post-doc after approximately 5 months into the second year. From then on, further funding was intermittent to say the least, and funding to support the student and the research expenses has to be supplemented by Lange’s gift funds. During the first part of the second year, strontium zirconate was identified as an alternative to lanthanum manganite as a buffer layer for use on the IBAD MgO superconducting wire. A lattice parameter of 4.101 Angstroms offers a reduced lattice mismatch between the MgO and SrZrO3. Studies were focused on investigating hybrid precursor routes, combining Sr acetate with a number of different Zr alkoxides. Initial results from heat treating precursors to form powders are positive with the formation of orthorhombic SrZrO3 at temperatures between 800°C and 1100°C under a reducing atmosphere of Ar – 5% H2. Buffer layer research on RABiTS substrates were centered on GdAlO3 (3.71 Å) and YAlO3 (3.68 Å) buffer layer materials. Powder experiments in YAlO3 have shown the perovskite phase to be metastable at processing temperatures below 1500 °C. Experiments involving spin coating of YAlO3 precursors have found significant problems involved with wettability of the YAlO3 precursor (Yttrium acetate, Aluminum tri-sec butoxide, DI water and Formic Acid) on RABiTS substrates; this, and the demise of the funds precluded further research using YAlO3. The diminished funds for the second year, and the small, tricked funds during the third year lead to a redirection of the student to another research area., and a stop to any experimental achievements that were much too ambition relative to the available funds. The only positive results obtained during this latter period was the understanding why two dissimilar structures could result in an epitaxial relation. It was shown that two rules of crystal chemistry, cation/anion coordination and charge balance, could be applied to understand the epitaxy of SrTiO3 on Ni c(2 X 2)S, TiO2 (anatase) on LaAlO3, TiO2 (rutile) on r-plane Al2O3, and Zr1-x(Yx)O2 on (0001) Al2O3. This new understanding of the interface between two dissimilar structures has important implications that include the buffer layers used for the superconductor program, namely, the epitaxy of perovskites such as the epitaxy of SrTiO3 on the Ni c(2 X 2)S wire. This discovery is the major part of the finial report that follows.« less

Chlorine mobility during annealing in N2 in ZrO2 and HfO2 films grown by atomic layer deposition

NASA Astrophysics Data System (ADS)

Ferrari, S.; Scarel, G.; Wiemer, C.; Fanciulli, M.

2002-12-01

Atomic layer deposition (ALD) growth of high-κ dielectric films (ZrO2 and HfO2) was performed using ZrCl4, HfCl4, and H2O as precursors. In this work, we use time of flight secondary ion mass spectrometry to investigate the chlorine distribution in ALD grown ZrO2 and HfO2 films, and its evolution during rapid thermal processes in nitrogen atmosphere. Chlorine outdiffusion is found to depend strongly upon annealing temperature and weakly upon the annealing time. While in ZrO2 chlorine concentration is significantly decreased already at 900 °C, in HfO2 it is extremely stable, even at temperatures as high as 1050 °C.

Lanthanum aluminum oxide thin-film dielectrics from aqueous solution.

PubMed

Plassmeyer, Paul N; Archila, Kevin; Wager, John F; Page, Catherine J

2015-01-28

Amorphous LaAlO3 dielectric thin films were fabricated via solution processing from inorganic nitrate precursors. Precursor solutions contained soluble oligomeric metal-hydroxyl and/or -oxo species as evidenced by dynamic light scattering (DLS) and Raman spectroscopy. Thin-film formation was characterized as a function of annealing temperature using Fourier transform infrared (FTIR), X-ray diffraction (XRD), X-ray reflectivity (XRR), scanning electron microscopy (SEM), and an array of electrical measurements. Annealing temperatures ≥500 °C result in thin films with low leakage-current densities (∼1 × 10(-8) A·cm(-2)) and dielectric constants ranging from 11.0 to 11.5. When incorporated as the gate dielectric layer in a-IGZO thin-film transistors (TFTs), LaAlO3 thin films annealed at 600 °C in air yielded TFTs with relatively low average mobilities (∼4.5 cm(2)·V(-1)·s(-1)) and high turn-on voltages (∼26 V). Interestingly, reannealing the LaAlO3 in 5%H2/95%N2 at 300 °C before deposition of a-IGZO channel layers resulted in TFTs with increased average mobilities (11.1 cm(2)·V(-1)·s(-1)) and lower turn-on voltages (∼6 V).

Self-limiting atomic layer deposition of conformal nanostructured silver films

NASA Astrophysics Data System (ADS)

Golrokhi, Zahra; Chalker, Sophia; Sutcliffe, Christopher J.; Potter, Richard J.

2016-02-01

The controlled deposition of ultra-thin conformal silver nanoparticle films is of interest for applications including anti-microbial surfaces, plasmonics, catalysts and sensors. While numerous techniques can produce silver nanoparticles, few are able to produce highly conformal coatings on high aspect ratio surfaces, together with sub-nanometre control and scalability. Here we develop a self-limiting atomic layer deposition (ALD) process for the deposition of conformal metallic silver nanoparticle films. The films have been deposited using direct liquid injection ALD with ((hexafluoroacetylacetonato)silver(I)(1,5-cyclooctadiene)) and propan-1-ol. An ALD temperature window between 123 and 128 °C is identified and within this range self-limiting growth is confirmed with a mass deposition rate of ∼17.5 ng/cm2/cycle. The effects of temperature, precursor dose, co-reactant dose and cycle number on the deposition rate and on the properties of the films have been systematically investigated. Under self-limiting conditions, films are metallic silver with a nano-textured surface topography and nanoparticle size is dependent on the number of ALD cycles. The ALD reaction mechanisms have been elucidated using in-situ quartz crystal microbalance (QCM) measurements, showing chemisorption of the silver precursor, followed by heterogeneous catalytic dehydrogenation of the alcohol to form metallic silver and an aldehyde.

Pulsed deposition of silicate films

NASA Astrophysics Data System (ADS)

He, W.; Solanki, R.; Conley, J. F.; Ono, Y.

2003-09-01

A sequential pulsed process is utilized for deposition of nonstoichiometric silicate films without employing an oxidizing agent. The metal precursors were HfCl4, AlCl3, and ZrCl4, as well as Hf(NO3)4 and the silicon source was tris(tert-butoxy)silanol. Unlike atomic layer deposition, the growth per cycle was several monolayers thick, where the enhancement in growth was due to a catalytic reaction. The bulk and electrical properties of these films are similar to those of silicon dioxide. Silicon carbide devices coated with these films show good insulating characteristics.

Process for microwave sintering boron carbide

DOEpatents

Holcombe, C.E.; Morrow, M.S.

1993-10-12

A method of microwave sintering boron carbide comprises leaching boron carbide powder with an aqueous solution of nitric acid to form a leached boron carbide powder. The leached boron carbide powder is coated with a glassy carbon precursor to form a coated boron carbide powder. The coated boron carbide powder is consolidated in an enclosure of boron nitride particles coated with a layer of glassy carbon within a container for microwave heating to form an enclosed coated boron carbide powder. The enclosed coated boron carbide powder is sintered within the container for microwave heating with microwave energy.

Process for microwave sintering boron carbide

DOEpatents

Holcombe, Cressie E.; Morrow, Marvin S.

1993-01-01

A method of microwave sintering boron carbide comprises leaching boron carbide powder with an aqueous solution of nitric acid to form a leached boron carbide powder. The leached boron carbide powder is coated with a glassy carbon precursor to form a coated boron carbide powder. The coated boron carbide powder is consolidated in an enclosure of boron nitride particles coated with a layer of glassy carbon within a container for microwave heating to form an enclosed coated boron carbide powder. The enclosed coated boron carbide powder is sintered within the container for microwave heating with microwave energy.

Synthesis of Highly Dispersed and Highly Stable Supported Au–Pt Bimetallic Catalysts by a Two-Step Method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Xiaofeng; Zhao, Haiyan; Wu, Tianpin

2016-11-01

Highly dispersed and highly stable supported bimetallic catalysts were prepared using a two-step process. Pt nanoparticles (NPs) were first deposited on porous γ-Al2O3 particles by atomic layer deposition (ALD). Au NPs were synthesized by using gold(III) chloride as the Au precursor, and then immobilized on ALD Pt/γ-Al2O3 particles. The Au–Pt bimetallic catalysts were highly active and highly stable in a vigorously stirred liquid phase reaction of glucose oxidation.

Hydrothermal Synthesis of Nanostructured Vanadium Oxides

PubMed Central

Livage, Jacques

2010-01-01

A wide range of vanadium oxides have been obtained via the hydrothermal treatment of aqueous V(V) solutions. They exhibit a large variety of nanostructures ranging from molecular clusters to 1D and 2D layered compounds. Nanotubes are obtained via a self-rolling process while amazing morphologies such as nano-spheres, nano-flowers and even nano-urchins are formed via the self-assembling of nano-particles. This paper provides some correlation between the molecular structure of precursors in the solution and the nanostructure of the solid phases obtained by hydrothermal treatment. PMID:28883325

Effect of precursor solutions on ZnO film via solution precursor plasma spray and corresponding gas sensing performances

NASA Astrophysics Data System (ADS)

Yu, Z. X.; Ma, Y. Z.; Zhao, Y. L.; Huang, J. B.; Wang, W. Z.; Moliere, M.; Liao, H. L.

2017-08-01

Solution precursor plasma spraying (SPPS) as a novel thermal spray method was employed to deposit nano-structured ZnO thin film using different formulations of the precursor solution. This article focuses on the influence of the solution composition on the preferential orientation of crystal growth, on crystal size and surface morphology of the resulting ZnO films. The trend of preferential growth along (002) lattice plane of ZnO film was studied by slow scanning X-ray diffraction using a specific coefficient P(002). It appears that the thermal spray process promotes the buildup of ZnO films preferentially oriented along the c-axis. The shape of single particle tends to change from round shaped beads to hexagonal plates by increasing the volume ratio of ethanol in the solvent. Both cauliflower and honeycomb-like surface morphologies featuring high specific surface area and roughness were obtained through the SPPS process by varying solution composition. These ZnO films are hydrophobic with contact angle as high as 136°, which is seemingly associated with micro reliefs developing high surface specific area. Then the gas sensing performances of ZnO films preferentially oriented along (002) face were tentatively predicted using the "first principle calculation method" and were compared with those of conventional films that are mainly oriented along the (101) face. The (002) face displays better hydrogen adsorption capability than the (101) face with much larger resulting changes in electrical resistance. In conclusion, the c-axis oriented ZnO films obtained through SSPS have favorable performances to be used as sensitive layer in gas sensing applications.

Process for the enhanced capture of heavy metal emissions

DOEpatents

Biswas, Pratim; Wu, Chang-Yu

2001-01-01

This invention is directed to a process for forming a sorbent-metal complex. The process includes oxidizing a sorbent precursor and contacting the sorbent precursor with a metallic species. The process further includes chemically reacting the sorbent precursor and the metallic species, thereby forming a sorbent-metal complex. In one particular aspect of the invention, at least a portion of the sorbent precursor is transformed into sorbent particles during the oxidation step. These sorbent particles then are contacted with the metallic species and chemically reacted with the metallic species, thereby forming a sorbent-metal complex. Another aspect of the invention is directed to a process for forming a sorbent metal complex in a combustion system. The process includes introducing a sorbent precursor into a combustion system and subjecting the sorbent precursor to an elevated temperature sufficient to oxidize the sorbent precursor and transform the sorbent precursor into sorbent particles. The process further includes contacting the sorbent particles with a metallic species and exposing the sorbent particles and the metallic species to a complex-forming temperature whereby the metallic species reacts with the sorbent particles thereby forming a sorbent-metal complex under UV irradiation.

Low-temperature ({<=}200 Degree-Sign C) plasma enhanced atomic layer deposition of dense titanium nitride thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Samal, Nigamananda; Du Hui; Luberoff, Russell

Titanium nitride (TiN) has been widely used in the semiconductor industry for its diffusion barrier and seed layer properties. However, it has seen limited adoption in other industries in which low temperature (<200 Degree-Sign C) deposition is a requirement. Examples of applications which require low temperature deposition are seed layers for magnetic materials in the data storage (DS) industry and seed and diffusion barrier layers for through-silicon-vias (TSV) in the MEMS industry. This paper describes a low temperature TiN process with appropriate electrical, chemical, and structural properties based on plasma enhanced atomic layer deposition method that is suitable for themore » DS and MEMS industries. It uses tetrakis-(dimethylamino)-titanium as an organometallic precursor and hydrogen (H{sub 2}) as co-reactant. This process was developed in a Veeco NEXUS Trade-Mark-Sign chemical vapor deposition tool. The tool uses a substrate rf-biased configuration with a grounded gas shower head. In this paper, the complimentary and self-limiting character of this process is demonstrated. The effects of key processing parameters including temperature, pulse time, and plasma power are investigated in terms of growth rate, stress, crystal morphology, chemical, electrical, and optical properties. Stoichiometric thin films with growth rates of 0.4-0.5 A/cycle were achieved. Low electrical resistivity (<300 {mu}{Omega} cm), high mass density (>4 g/cm{sup 3}), low stress (<250 MPa), and >85% step coverage for aspect ratio of 10:1 were realized. Wet chemical etch data show robust chemical stability of the film. The properties of the film have been optimized to satisfy industrial viability as a Ruthenium (Ru) preseed liner in potential data storage and TSV applications.« less

Mild solution-processed metal-doped TiO2 compact layers for hysteresis-less and performance-enhanced perovskite solar cells

NASA Astrophysics Data System (ADS)

Liang, Chao; Li, Pengwei; Zhang, Yiqiang; Gu, Hao; Cai, Qingbin; Liu, Xiaotao; Wang, Jiefei; Wen, Hua; Shao, Guosheng

2017-12-01

TiO2 is extensively used as electron-transporting material on perovskite solar cells (PSCs). However, traditional TiO2 processing method needs high annealing temperature (>450 °C) and pure TiO2 suffers from low electrical mobility and poor conductivity. In this study, a general one-pot solution-processed method is devised to grow uniform crystallized metal-doped TiO2 thin film as large as 15 × 15 cm2. The doping process can be controlled effectively via a series of doping precursors from niobium (V), tin (IV), tantalum (V) to tungsten (VI) chloride. As far as we know, this is so far the lowest processing temperature for metal-doped TiO2 compact layers, as low as 70 °C. The overall performance of PSCs employing the metal-doped TiO2 layers is significantly improved in term of hysteresis effect, short circuit current, open-circuit voltage, fill factor, power conversion efficiency, and device stability. With the insertion of metal ions into TiO2 lattice, the corresponding CH3NH3PbI3 PSC leads to a ∼25% improved PCE of over 16% under irradiance of 100 mW cm-2 AM1.5G sunlight, compared with control device. The results indicate that this mild solution-processed metal-doped TiO2 is an effective industry-scale way for fabricating hysteresis-less and high-performance PSCs.

Engineering Defect-Free Nanoporous Pd from Optimized Pd-Ni Precursor Alloy by Understanding Palladium-Hydrogen Interactions During Dealloying

NASA Astrophysics Data System (ADS)

Schoop, Julius; Balk, T. John

2014-04-01

Thin films of nanoporous palladium (np-Pd) were produced from binary palladium-nickel (Pd-Ni) precursor alloys. A suitable precursor alloy and a method of dealloying to yield optimum nanoporosity (average pore/ligament size of 7 nm) were developed by studying the effects of various processing parameters on final microstructure. To obtain crack-free np-Pd, a 100 nm thin film of 20 at. pct Pd (80 at. pct Ni) can be dealloyed for ~5 hours in a 1 M solution of sulfuric acid, with oleic acid and oleylamine added as surfactants. Both shorter and longer dealloying times, as well as heating, inhibit the formation of crack-free np-Pd. Stress measurements at different stages of dealloying revealed that the necessary dealloying time is determined by the diffusion-controlled corrosion reaction occurring within the thin film during dealloying. Strong interaction between hydrogen and np-Pd was reflected in the stress evolution during dealloying. A mechanism is proposed for the formation of a Ni-rich dense top layer that results from H-induced swelling during initial dealloying and permits the development of defect-free np-Pd beneath, by limiting the speed of dealloying.

Bi-layer sandwich film for antibacterial catheters

PubMed Central

Schamberger, Florian; Zare, Hamideh Heidari; Bröskamp, Sara Felicitas; Jocham, Dieter

2017-01-01

Background: Approximately one quarter of all nosocomial infections can be attributed to the urinary tract. The infections are supposed to be mainly caused by implantations of urethral catheters and stents. A new catheter design is introduced with the aim to lower the high number of nosocomial urethral infections. In order to avoid limitations to use, the design is first applied to conventional commercially available balloon catheters. Results: The main feature of the design is a sandwich layer on both sides of the catheter wall, which is composed of a fragmented base layer of silver capped by a thin film of poly(p-xylylene). This top layer is mainly designed to release a controlled amount of Ag+ ions, which is bactericidal, but not toxic to humans. Simultaneously, the lifetime is prolonged to at least one year. The base layer is electrolessly deposited applying Tollens’ reagens, the cap layer is deposited by using chemical vapor deposition. Conclusion: The three main problems of this process, electroless deposition of a fragmented silver film on the surface of an electrically insulating organic polymer, irreproducible evaporation during heating of the precursor, and exponential decrease of the layer thickness along the capillary, have been solved trough the application of a simple electrochemical reaction and two standard principles of physics: Papin’s pot and the principle of Le Chatelier. PMID:29046846

Bi-layer sandwich film for antibacterial catheters.

PubMed

Franz, Gerhard; Schamberger, Florian; Zare, Hamideh Heidari; Bröskamp, Sara Felicitas; Jocham, Dieter

2017-01-01

Background: Approximately one quarter of all nosocomial infections can be attributed to the urinary tract. The infections are supposed to be mainly caused by implantations of urethral catheters and stents. A new catheter design is introduced with the aim to lower the high number of nosocomial urethral infections. In order to avoid limitations to use, the design is first applied to conventional commercially available balloon catheters. Results: The main feature of the design is a sandwich layer on both sides of the catheter wall, which is composed of a fragmented base layer of silver capped by a thin film of poly( p -xylylene). This top layer is mainly designed to release a controlled amount of Ag + ions, which is bactericidal, but not toxic to humans. Simultaneously, the lifetime is prolonged to at least one year. The base layer is electrolessly deposited applying Tollens' reagens, the cap layer is deposited by using chemical vapor deposition. Conclusion: The three main problems of this process, electroless deposition of a fragmented silver film on the surface of an electrically insulating organic polymer, irreproducible evaporation during heating of the precursor, and exponential decrease of the layer thickness along the capillary, have been solved trough the application of a simple electrochemical reaction and two standard principles of physics: Papin's pot and the principle of Le Chatelier.

Insertion and assembly of the precursor of subunit II into the photosystem I complex may precede its processing.

PubMed Central

Cohen, Y; Steppuhn, J; Herrmann, R G; Yalovsky, S; Nechushtai, R

1992-01-01

The biogenesis and assembly of subunit II of photosystem I (PSI) (psaD gene product) were studied and characterized. The precursor and the mature form were produced in vitro and incubated with intact plastids or isolated thylakoids. Following import of the precursor into isolated plastids, mostly the mature form of subunit II was found in the thylakoids. However, when the processing activity was inhibited only the precursor form was present in the membranes. The precursor was processed by a stromal peptidase and processing could occur before or after insertion of the precursor into the thylakoids. Following insertion into isolated thylakoids, both the precursor and the mature form of subunit II were confined to the PSI complex. Insertion of the mature form of subunit II was much less efficient than that of the precursor. Kinetic studies showed that the precursor was inserted into the membrane. Only at a later stage, the mature form began to accumulate. These results suggest that in vivo the precursor of subunit II is inserted and embedded in the thylakoids, as part of the PSI complex. Only later, it is processed to the mature form through the action of a stromal peptidase. Images PMID:1740118

Optimization of a Solution-Processed SiO2 Gate Insulator by Plasma Treatment for Zinc Oxide Thin Film Transistors.

PubMed

Jeong, Yesul; Pearson, Christopher; Kim, Hyun-Gwan; Park, Man-Young; Kim, Hongdoo; Do, Lee-Mi; Petty, Michael C

2016-01-27

We report on the optimization of the plasma treatment conditions for a solution-processed silicon dioxide gate insulator for application in zinc oxide thin film transistors (TFTs). The SiO2 layer was formed by spin coating a perhydropolysilazane (PHPS) precursor. This thin film was subsequently thermally annealed, followed by exposure to an oxygen plasma, to form an insulating (leakage current density of ∼10(-7) A/cm(2)) SiO2 layer. Optimized ZnO TFTs (40 W plasma treatment of the gate insulator for 10 s) possessed a carrier mobility of 3.2 cm(2)/(V s), an on/off ratio of ∼10(7), a threshold voltage of -1.3 V, and a subthreshold swing of 0.2 V/decade. In addition, long-term exposure (150 min) of the pre-annealed PHPS to the oxygen plasma enabled the maximum processing temperature to be reduced from 180 to 150 °C. The resulting ZnO TFT exhibited a carrier mobility of 1.3 cm(2)/(V s) and on/off ratio of ∼10(7).

Room temperature synthesis of protonated layered titanate sheets using peroxo titanium carbonate complex solution.

PubMed

Sutradhar, Narottam; Sinhamahapatra, Apurba; Pahari, Sandip Kumar; Bajaj, Hari C; Panda, Asit Baran

2011-07-21

We report the synthesis of peroxo titanium carbonate complex solution as a novel water-soluble precursor for the direct synthesis of layered protonated titanate at room temperature. The synthesized titanates showed excellent removal capacity for Pb(2+) and methylene blue. Based on experimental observations, a probable mechanism for the formation of protonated layered dititanate sheets is also discussed.

Controllable Growth of Perovskite Films by Room-Temperature Air Exposure for Efficient Planar Heterojunction Photovoltaic Cells.

PubMed

Yang, Bin; Dyck, Ondrej; Poplawsky, Jonathan; Keum, Jong; Das, Sanjib; Puretzky, Alexander; Aytug, Tolga; Joshi, Pooran C; Rouleau, Christopher M; Duscher, Gerd; Geohegan, David B; Xiao, Kai

2015-12-01

A two-step solution processing approach has been established to grow void-free perovskite films for low-cost high-performance planar heterojunction photovoltaic devices. A high-temperature thermal annealing treatment was applied to drive the diffusion of CH3NH3I precursor molecules into a compact PbI2 layer to form perovskite films. However, thermal annealing for extended periods led to degraded device performance owing to the defects generated by decomposition of perovskite into PbI2. A controllable layer-by-layer spin-coating method was used to grow "bilayer" CH3NH3I/PbI2 films, and then drive the interdiffusion between PbI2 and CH3NH3I layers by a simple air exposure at room temperature for making well-oriented, highly crystalline perovskite films without thermal annealing. This high degree of crystallinity resulted in a carrier diffusion length of ca. 800 nm and a high device efficiency of 15.6%, which is comparable to values reported for thermally annealed perovskite films. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Optimization of rotational speed for growing BaFe12O19 thin films using spin coating

NASA Astrophysics Data System (ADS)

Budiawanti, S.; Soegijono, B.; Mudzakir, I.; Suharno, Fadillah, L.

2017-07-01

Barium ferrite (BaFe12O19, BaM) thin films were fabricated by the spin coating of precursors obtained by using a sol-gel method. The effects of the rotational speed on the spin-coating process for growing a BaM thin film were investigated in this study. Coated films were heat-deposited at different rotational speeds ranging from 2000 to 4000 rpm, while the number of layers was set to nine. Further, the effect of the number of layers on the growth of BaM thin films was discussed. For this purpose, we take the layers number 1 to 12 and take the constant rotational speed of 3000 rpm. All the film were characterized using X-Ray diffraction, Scanning Electron microscope, and Energy-dispersive X-Ray spectroscopy and Vibrating Sample Magnetometer. It was found that by increasing the rotational speed the amount of material deposited on the Si substrate decreased. The measured grain size of the BaM thin film was nearly similar for three three different rotational speeds. However, the grain size was found to increase the number of layers.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martinson, A. B. F.; DeVries, M. J.; Libera, J. A.

Growing interest in Fe{sub 2}O{sub 3} as a light harvesting layer in solar energy conversion devices stems from its unique combination of stability, nontoxicity, and exceptionally low material cost. Unfortunately, the known methods for conformally coating high aspect ratio structures with Fe{sub 2}O{sub 3} leave a glaring gap in the technologically relevant temperature range of 170-350 C. Here, we elucidate a self-limiting atomic layer deposition (ALD) process for the growth of hematite, {alpha}-Fe{sub 2}O{sub 3}, over a moderate temperature window using ferrocene and ozone. At 200 C, the self-limiting growth of Fe{sub 2}O{sub 3} is observed at rates up tomore » 1.4 {angstrom}/cycle. Dense and robust thin films grown on both fused quartz and silicon exhibit the expected optical bandgap (2.1 eV). In situ mass spectrometric analysis reveals the evolution of two distinct cyclic reaction products during the layer-by-layer growth. The readily available and relatively high vapor pressure iron precursor is utilized to uniformly coat a high surface area template with aspect ratio 150.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martinson, Alex B.F.; DeVries, Michael J.; Libera, J. A.

Growing interest in Fe 2O 3 as a light harvesting layer in solar energy conversion devices stems from its unique combination of stability, nontoxicity, and exceptionally low material cost. Unfortunately, the known methods for conformally coating high aspect ratio structures with Fe 2O 3 leave a glaring gap in the technologically relevant temperature range of 170-350 °C. Here, we elucidate a self-limiting atomic layer deposition (ALD) process for the growth of hematite, α-Fe 2O 3, over a moderate temperature window using ferrocene and ozone. At 200 °C, the self-limiting growth of Fe 2O 3 is observed at rates up tomore » 1.4 Å/cycle. Dense and robust thin films grown on both fused quartz and silicon exhibit the expected optical bandgap (2.1 eV). In situ mass spectrometric analysis reveals the evolution of two distinct cyclic reaction products during the layer-by-layer growth. The readily available and relatively high vapor pressure iron precursor is utilized to uniformly coat a high surface area template with aspect ratio ~150.« less

QCM gas phase detection with ceramic materials--VOCs and oil vapors.

PubMed

Latif, Usman; Rohrer, Andreas; Lieberzeit, Peter A; Dickert, Franz L

2011-06-01

Titanate sol-gel layers imprinted with carbonic acids were used as sensitive layers on quartz crystal microbalance. These functionalized ceramics enable us detection of volatile organic compounds such as ethanol, n-propanol, n-butanol, n-hexane, n-heptane, n-/iso-octane, and n-decane. Variation of the precursors (i.e., tetrabutoxy titanium, tetrapropoxy titanium, tetraethoxy titanium) allows us to tune the sensitivity of the material by a factor of 7. Sensitivity as a function of precursors leads to selective inclusion of n-butanol vapors down to 1 ppm. The selectivity of materials is optimized to differentiate between isomers, e.g., n- and iso-octane. The results can be rationalized by correlating the sensor effects of hydrocarbons with the Wiener index. A mass-sensitive sensor based on titanate layer was also developed for monitoring emanation of degraded engine oil. Heating the sensor by a meander avoids vapor condensation. Thus, a continuously working oil quality sensor was designed.

Nanostructures produced by phase-separation during growth of (III-V).sub.1-x(IV.sub.2).sub.x alloys

DOEpatents

Norman, Andrew G [Evergreen, CO; Olson, Jerry M [Lakewood, CO

2007-06-12

Nanostructures (18) and methods for production thereof by phase separation during metal organic vapor-phase epitaxy (MOVPE). An embodiment of one of the methods may comprise providing a growth surface in a reaction chamber and introducing a first mixture of precursor materials into the reaction chamber to form a buffer layer (12) thereon. A second mixture of precursor materials may be provided into the reaction chamber to form an active region (14) on the buffer layer (12), wherein the nanostructure (18) is embedded in a matrix (16) in the active region (14). Additional steps are also disclosed for preparing the nanostructure (18) product for various applications.

76 FR 15945 - Application(s) for Duty-Free Entry of Scientific Instruments

Federal Register 2010, 2011, 2012, 2013, 2014

2011-03-22

.... 9700 South Cass Ave., Lemont, IL 60439. Instrument: TFS500 Atomic Layer Deposition System. Manufacturer: Beneq OY, Finland. Intended Use: The instrument will be used in experiments on atomic layer deposition... and precursor combinations. For the research the instrument is required to have a modular deposition...

Radiation induced precursor flow field ahead of a Jovian entry body

NASA Technical Reports Server (NTRS)

Tiwari, S.; Szema, K. Y.

1977-01-01

The change in flow properties ahead of the bow shock of a Jovian entry body, resulting from absorption of radiation from the shock layer, is investigated. Ultraviolet radiation is absorbed by the free stream gases, causing dissociation, ionization, and an increase in enthalpy of flow ahead of the shock wave. As a result of increased fluid enthalpy, the entire flow field in the precursor region is perturbed. The variation in flow properties is determined by employing the small perturbation technique of classical aerodynamics as well as the thin layer approximation for the preheating zone. By employing physically realistic models of radiative transfer, solutions are obtained for velocity, pressure, density, temperature, and enthalpy variations. The results indicate that the precursor flow effects, in general, are greater at higher altitudes. Just ahead of the shock, however, the effects are larger at lower altitudes. Pre-heating of the gas significantly increases the static pressure and temperature ahead of the shock for velocities exceeding 36 km/sec.

Spontaneous Synthesis of Highly Crystalline TiO2 Compact/Mesoporous Stacked Films by a Low-Temperature Steam-Annealing Method for Efficient Perovskite Solar Cells.

PubMed

Sanehira, Yoshitaka; Numata, Youhei; Ikegami, Masashi; Miyasaka, Tsutomu

2018-05-23

Highly crystalline TiO 2 nanostructured films were synthesized by a simple steam treatment of a TiCl 4 precursor film under a saturated water vapor atmosphere at 125 °C, here referred to as the steam-annealing method. In a single TiO 2 film preparation step, a bilayer structure comprising a compact bottom layer and a mesoporous surface layer was formed. The mesoporous layer was occupied by bipyramidal nanoparticles, with a composite phase of anatase and brookite crystals. Despite the low-temperature treatment process, the crystallinity of the TiO 2 film was high, comparable with that of the TiO 2 film sintered at 500 °C. The compact double-layered TiO 2 film was applied to perovskite solar cells (PSCs) as an electron-collecting layer. The PSC exhibited a maximum power conversion efficiency (PCE) of 18.9% with an open-circuit voltage ( V OC ) of 1.15 V. The PCE and V OC were higher than those of PSCs using a TiO 2 film formed by 500 °C sintering.

Combinatorial investigation of the effects of sodium on Cu 2ZnSnSe4 polycrystalline thin films

NASA Astrophysics Data System (ADS)

Gibbs, Alex Hilton

Cu2ZnSnSe4 (CZTSe) possess highly suitable optical and electronic properties for use as an absorber layer in thin film solar cells. CZTSe also has potential to achieve terawatt level solar energy production due to its inexpensive and abundant material constituents. Currently, fabricating CZTSe devices with the expected theoretical performance has not been achieved, making the growth and formation of CZTSe an interesting topic of research. In this work, a two-step vacuum fabrication process consisting of RF co-sputtering followed by reactive annealing was explored as a viable technique for synthesizing CZTSe thin films. Furthermore, the enhancement of the fabrication process by the incorporation of sodium during annealing was studied using a combinatorial approach. Film composition was analyzed using electron dispersive spectroscopy. Structure, phase morphology, and formation were determined using scanning electron microscopy, x-ray diffraction, atomic force microscopy and raman spectroscopy. Optical and electronic properties were characterized using UV-Vis and Voc were measurements under a one sun solar simulator. RF co-sputtering CuSe, ZnSe, and SnSe precursors produced films with good thickness uniformity, adhesion and stoichiometry control over 3 x 3 in 2 substrates. Composition measurements showed that the precursor films maintained stability during an annealing process of 580° C for 20 minutes producing near stoichiometric CZTSe. However, grain size was small with an average diameter of 350 nm. The CZTSe film produced by this process exhibited a suitable absorption coefficient of > 104 cm-1 and aband gap near 1.0 eV. The film also produced an XRD pattern consistent with tetragonal CZTSe with no secondary phase formation with the exception of approximately 12.5 nm of interfacial MoSe2 formation at the back contact. The combinatorial investigation of the influence of sodium on CZTSe growth and morphology was achieved using a custom built constant withdraw shutter to evaporate NaF with a 0-60 nm thickness spread on the substrate prior to precursor sputtering. This experiment showed that the incorporation of NaF did enhance grain size; however, there was little correlation with initial NaF composition observed. It is concluded that NaF undergoes high degree of vapor transport and readily distributes nonuniformly throughout the film during the annealing process and also potentially escapes the annealing environment if not properly contained. An experiment on achieving Na incorporation by diffusion from a soda lime glass substrate resulted in a far more uniform enhancement of grain growth. The experiment also revealed that NaF greatly reduced precursor film adhesion to the substrate due to the hygroscopic nature of NaF. X-ray diffraction measurements also showed that the addition of the NaF layer was could potentially suppress the formation of MoSe2.

Phreatic eruptions and deformation of Ioto Island (Iwo-jima), Japan, triggered by deep magma injection

NASA Astrophysics Data System (ADS)

Ueda, Hideki; Nagai, Masashi; Tanada, Toshikazu

2018-03-01

On Ioto Island (Iwo-jima), 44 phreatic eruptions have been recorded since 1889, when people began to settle there. Four of these eruptions, after the beginning of continuous observation by seismometers in 1976, were accompanied by intense seismic activity and rapid crustal deformation beforehand. Other eruptions on Ioto were without obvious crustal activities. In this paper, we discuss the mechanisms of phreatic eruptions on Ioto. Regular geodetic surveys and continuous GNSS observations show that Ioto intermittently uplifts at an abnormally high rate. All of the four eruptions accompanied by the precursors took place during intermittent uplifts. The crustal deformation before and after one of these eruptions revealed that a sill-like deformation source in the shallow part of Motoyama rapidly inflated before and deflated after the beginning of the eruption. From the results of a seismic array and a borehole survey, it is estimated that there is a layer of lava at a depth of about 100-200 m, and there is a tuff layer about 200-500 m beneath it. The eruptions accompanied by the precursors probably occurred due to abrupt boiling of hot water in hydrothermal reservoirs in the tuff layer, sealed by the lava layer and triggered by intermittent uplift. For the eruptions without precursors, the hydrothermal systems are weakly sealed by clay or probably occurred on the same principle as a geyser because phreatic eruptions had occurred beforehand and hydrostatic pressure is applied to the hydrothermal reservoirs.

Crystalline oxides on semiconductors: A structural transition of the interface phase

NASA Astrophysics Data System (ADS)

Walker, F. J.; Buongiorno-Nardelli, Marco; Billman, C. A.; McKee, R. A.

2004-03-01

The growth of crystalline oxides on silicon is facilitated by the preparation of a surface phase of alkaline earth silicide. We describe how the surface phase serves as a precursor of the final interface phase using reflection high energy electron diffraction (RHEED) and density functional theory (DFT). RHEED intensity oscillations of the growth of BaSrO show layer-by-layer build up of the oxide on the interface. The 2x1 symmetry of the surface precursor persists up to 3 ML BaSrO coverage at which point a 1x1 pattern characteristic of the rock-salt structure of BaSrO is observed. Prior to 3 ML growth of alkaline earth oxide, DFT calculations and RHEED show that the surface precursor persists as the interface phase and induces large displacements in the growing oxide layer away from the rock-salt structure and having a 2x1 symmetry. These distortions of the rock-salt structure are energetically unfavorable and become more unfavorable as the oxide thickness increases. At 3 ML, the stability of the rock-salt structure drives a structural transformation of the film and the interface phase to a structure that is distinct from the surface precursor. Research sponsored jointly by the Division of Materials Sciences and Engineering, Office of Basic Energy Sciences, U.S. Department of Energy at Oak Ridge National Laboratory under contract DE-AC05-00OR22725 with UT-Battelle, LLC and at the University of Tennessee under contract DE-FG02-01ER45937. Calculations have been performed on CCS supercomputers at Oak Ridge National Laboratory.

Synthesis of ZrO 2 thin films by atomic layer deposition: growth kinetics, structural and electrical properties

NASA Astrophysics Data System (ADS)

Cassir, Michel; Goubin, Fabrice; Bernay, Cécile; Vernoux, Philippe; Lincot, Daniel

2002-06-01

Ultra thin films of ZrO 2 were synthesized on soda lime glass and SnO 2-coated glass, using ZrCl 4 and H 2O precursors by atomic layer deposition (ALD), a sequential CVD technique allowing the formation of dense and homogeneous films. The effect of temperature on the film growth kinetics shows a first temperature window for ALD processing between 280 and 350 °C and a second regime or "pseudo-window" between 380 and 400 °C, with a growth speed of about one monolayer per cycle. The structure and morphology of films of less than 1 μm were characterized by XRD and SEM. From 275 °C, the ZrO 2 film is crystallized in a tetragonal form while a mixture of tetragonal and monoclinic phases appears at 375 °C. Impedance spectroscopy measurements confirmed the electrical properties of ZrO 2 and the very low porosity of the deposited layer.

Characterizing Fluorocarbon Assisted Atomic Layer Etching of Si Using Cyclic Ar/C 4F 8 and Ar/CHF 3 Plasma

DOE PAGES

Metzler, Dominik; Li, Chen; Engelmann, Sebastian; ...

2016-09-08

With the increasing interest in establishing directional etching methods capable of atomic scale resolution for fabricating highly scaled electronic devices, the need for development and characterization of atomic layer etching (ALE) processes, or generally etch processes with atomic layer precision, is growing. In this work, a flux-controlled cyclic plasma process is used for etching of SiO 2 and Si at the Angstrom-level. This is based on steady-state Ar plasma, with periodic, precise injection of a fluorocarbon (FC) precursor (C 4F 8 and CHF 3), and synchronized, plasma-based Ar+ ion bombardment [D. Metzler et al., J Vac Sci Technol A 32,more » 020603 (2014), and D. Metzler et al., J Vac Sci Technol A 34, 01B101 (2016)]. For low energy Ar+ ion bombardment conditions, physical sputter rates are minimized, whereas material can be etched when FC reactants are present at the surface. This cyclic approach offers a large parameter space for process optimization. Etch depth per cycle, removal rates, and self-limitation of removal, along with material dependence of these aspects, were examined as a function of FC surface coverage, ion energy, and etch step length using in situ real time ellipsometry. The deposited FC thickness per cycle is found to have a strong impact on etch depth per cycle of SiO 2 and Si, but is limited with regard to control over material etching selectivity. Ion energy over the 20 to 30 eV range strongly impacts material selectivity. The choice of precursor can have a significant impact on the surface chemistry and chemically enhanced etching. CHF 3 has a lower FC deposition yield for both SiO 2 and Si, and also exhibits a strong substrate dependence of FC deposition yield, in contrast to C4F 8. The thickness of deposited FC layers using CHF 3 is found to be greater for Si than for SiO 2. X-ray photoelectron spectroscopy was used to study surface chemistry. When thicker FC films of 11 Å are employed, strong changes of FC film chemistry during a cycle are seen whereas the chemical state of the substrate varies much less. On the other hand, for FC film deposition of 5 Å for each cycle, strong substrate surface chemical changes are seen during an etching cycle. The nature of this cyclic etching with periodic deposition of thin FC films differs significantly from conventional etching with steady-state FC layers since surface conditions change strongly throughout each cycle.« less

Dry Process for Manufacturing Hybridized Boron Fiber/Carbon Fiber Thermoplastic Composite Materials from a Solution Coated Precursor

NASA Technical Reports Server (NTRS)

Belvin, Harry L. (Inventor); Cano, Roberto J. (Inventor)

2003-01-01

An apparatus for producing a hybrid boron reinforced polymer matrix composite from precursor tape and a linear array of boron fibers. The boron fibers are applied onto the precursor tapes and the precursor tape processed within a processing component having an impregnation bar assembly. After passing through variable-dimension forming nip-rollers, the precursor tape with the boron fibers becomes a hybrid boron reinforced polymer matrix composite. A driving mechanism is used to pulled the precursor tape through the method and a take-up spool is used to collect the formed hybrid boron reinforced polymer matrix composite.

Carbon-based composite electrocatalysts for low temperature fuel cells

DOEpatents

Popov, Branko N [Columbia, SC; Lee, Jog-Won [Columbia, SC; Subramanian, Nalini P [Kennesaw, GA; Kumaraguru, Swaminatha P [Honeoye Falls, NY; Colon-Mercado, Hector R [Columbia, SC; Nallathambi, Vijayadurga [T-Nagar, IN; Li, Xuguang [Columbia, SC; Wu, Gang [West Columbia, SC

2009-12-08

A process for synthesis of a catalyst is provided. The process includes providing a carbon precursor material, oxidizing the carbon precursor material whereby an oxygen functional group is introduced into the carbon precursor material, and adding a nitrogen functional group into the oxidized carbon precursor material.

Chemical vapor deposition growth of boron-carbon-nitrogen layers from methylamine borane thermolysis products

NASA Astrophysics Data System (ADS)

Leardini, Fabrice; Flores, Eduardo; Galvis E, Andrés R.; Ferrer, Isabel J.; Ramón Ares, José; Sánchez, Carlos; Molina, Pablo; van der Meulen, Herko P.; Gómez Navarro, Cristina; López Polin, Guillermo; Urbanos, Fernando J.; Granados, Daniel; García-García, F. Javier; Demirci, Umit B.; Yot, Pascal G.; Mastrangelo, Filippo; Grazia Betti, Maria; Mariani, Carlo

2018-01-01

This work investigates the growth of B-C-N layers by chemical vapor deposition using methylamine borane (MeAB) as the single-source precursor. MeAB has been synthesized and characterized, paying particular attention to the analysis of its thermolysis products, which are the gaseous precursors for B-C-N growth. Samples have been grown on Cu foils and transferred onto different substrates for their morphological, structural, chemical, electronic and optical characterizations. The results of these characterizations indicate a segregation of h-BN and graphene-like (Gr) domains. However, there is an important presence of B and N interactions with C at the Gr borders, and of C interacting at the h-BN-edges, respectively, in the obtained nano-layers. In particular, there is a significant presence of C-N bonds, at Gr/h-BN borders and in the form of N doping of Gr domains. The overall B:C:N contents in the layers is close to 1:3:1.5. A careful analysis of the optical bandgap determination of the obtained B-C-N layers is presented, discussed and compared with previous seminal works with samples of similar composition.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Metzler, Dominik; Li, Chen; Engelmann, Sebastian

With the increasing interest in establishing directional etching methods capable of atomic scale resolution for fabricating highly scaled electronic devices, the need for development and characterization of atomic layer etching (ALE) processes, or generally etch processes with atomic layer precision, is growing. In this work, a flux-controlled cyclic plasma process is used for etching of SiO 2 and Si at the Angstrom-level. This is based on steady-state Ar plasma, with periodic, precise injection of a fluorocarbon (FC) precursor (C 4F 8 and CHF 3), and synchronized, plasma-based Ar+ ion bombardment [D. Metzler et al., J Vac Sci Technol A 32,more » 020603 (2014), and D. Metzler et al., J Vac Sci Technol A 34, 01B101 (2016)]. For low energy Ar+ ion bombardment conditions, physical sputter rates are minimized, whereas material can be etched when FC reactants are present at the surface. This cyclic approach offers a large parameter space for process optimization. Etch depth per cycle, removal rates, and self-limitation of removal, along with material dependence of these aspects, were examined as a function of FC surface coverage, ion energy, and etch step length using in situ real time ellipsometry. The deposited FC thickness per cycle is found to have a strong impact on etch depth per cycle of SiO 2 and Si, but is limited with regard to control over material etching selectivity. Ion energy over the 20 to 30 eV range strongly impacts material selectivity. The choice of precursor can have a significant impact on the surface chemistry and chemically enhanced etching. CHF 3 has a lower FC deposition yield for both SiO 2 and Si, and also exhibits a strong substrate dependence of FC deposition yield, in contrast to C4F 8. The thickness of deposited FC layers using CHF 3 is found to be greater for Si than for SiO 2. X-ray photoelectron spectroscopy was used to study surface chemistry. When thicker FC films of 11 Å are employed, strong changes of FC film chemistry during a cycle are seen whereas the chemical state of the substrate varies much less. On the other hand, for FC film deposition of 5 Å for each cycle, strong substrate surface chemical changes are seen during an etching cycle. The nature of this cyclic etching with periodic deposition of thin FC films differs significantly from conventional etching with steady-state FC layers since surface conditions change strongly throughout each cycle.« less

Method for producing highly conformal transparent conducting oxides

DOEpatents

Elam, Jeffrey W.; Mane, Anil U.

2016-07-26

A method for forming a transparent conducting oxide product layer. The method includes use of precursors, such as tetrakis-(dimethylamino) tin and trimethyl indium, and selected use of dopants, such as SnO and ZnO for obtaining desired optical, electrical and structural properties for a highly conformal layer coating on a substrate. Ozone was also input as a reactive gas which enabled rapid production of the desired product layer.

Mitotic position and morphology of committed precursor cells in the zebrafish retina adapt to architectural changes upon tissue maturation.

PubMed

Weber, Isabell P; Ramos, Ana P; Strzyz, Paulina J; Leung, Louis C; Young, Stephen; Norden, Caren

2014-04-24

The development of complex neuronal tissues like the vertebrate retina requires the tight orchestration of cell proliferation and differentiation. Although the complexity of transcription factors and signaling pathways involved in retinogenesis has been studied extensively, the influence of tissue maturation itself has not yet been systematically explored. Here, we present a quantitative analysis of mitotic events during zebrafish retinogenesis that reveals three types of committed neuronal precursors in addition to the previously known apical progenitors. The identified precursor types present at distinct developmental stages and exhibit different mitotic location (apical versus nonapical), cleavage plane orientation, and morphology. Interestingly, the emergence of nonapically dividing committed bipolar cell precursors can be linked to an increase in apical crowding caused by the developing photoreceptor cell layer. Furthermore, genetic interference with neuronal subset specification induces ectopic divisions of committed precursors, underlining the finding that progressing morphogenesis can effect precursor division position. Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.

Structural and morphological characterization of anatase TiO 2 coating on χ-Alumina scale fiber fabricated by sol-gel dip-coating method

NASA Astrophysics Data System (ADS)

Nguyen, Hue Thi; Miao, Lei; Tanemura, Sakae; Tanemura, Masaki; Toh, Shoichi; Kaneko, Kenji; Kawasaki, Masahiro

2004-10-01

Anatase TiO 2 coatings 0.4 μm thick have been successfully fabricated by sol-gel dip-coating process on χ-Al 2O 3 fibers 100 μm by 10 cm long with a surface fish-scale. This was achieved by adjustment of the sol-gel parameters such as molar ratio of the precursors in TiO 2-sols, dip-coating time, drying duration in air, heating processes and number of cyclical repetitions of the process. Two samples were prepared using two sols containing different molar ratios of precursors. XRD, TEM, EDS and SEM characterization confirmed: (1) the similarity of the growth of anatase-TiO 2 from two sols under the optimal sol-gel parameters, (2) that the coatings are composed of aggregated crystallites of 10-25 nm in diameter, (3) the good compositional uniformity of Ti in the fabricated anatase-TiO 2 crystallites, (4) a surface covering ratio of anatase-TiO 2 around the fiber of at least 90%, and (5) that there is a good adherence of the fabricated anatase-TiO 2 layer on alumina fiber as evidenced by the lack of cracking and peeling off traces around the boundary between the coating and the fiber.

Facile preparation of robust microcapsules by manipulating metal-coordination interaction between biomineral layer and bioadhesive layer.

PubMed

Zhang, Lei; Shi, Jiafu; Jiang, Zhongyi; Jiang, Yanjun; Meng, Ruijie; Zhu, Yuanyuan; Liang, Yanpeng; Zheng, Yang

2011-02-01

A novel approach combining biomimetic mineralization and bioadhesion is proposed to prepare robust and versatile organic-inorganic hybrid microcapsules. More specifically, these microcapsules are fabricated by sequential deposition of inorganic layer and organic layer on the surface of CaCO(3) microparticles, followed by the dissolution of CaCO(3) microparticles using EDTA. During the preparation process, protamine induces the hydrolysis and condensation of titania or silica precursor to form the inorganic layer or the biomineral layer. The organic layer or bioadhesive layer was formed through the rapid, spontaneous oxidative polymerization of dopamine into polydopamine (PDA) on the surface of the biomineral layer. There exist multiple interactions between the inorganic layer and the organic layer. Thus, the as-prepared organic-inorganic hybrid microcapsules acquire much higher mechanical stability and surface reactivity than pure titania or pure silica microcapsules. Furthermore, protamine/titania/polydopamine hybrid microcapsules display superior mechanical stability to protamine/silica/polydopamine hybrid microcapsules because of the formation of Ti(IV)-catechol coordination complex between the biomineral layer and the bioadhesive layer. As an example of application, three enzymes are respectively immobilized through physical encapsulation in the lumen, in situ entrapment within the wall and chemical attachment on the out surface of the hybrid microcapsules. The as-constructed multienzyme system displays higher catalytic activity and operational stability. Hopefully, the approach developed in this study will evolve as a generic platform for facile and controllable preparation of organic-inorganic hybrid materials with different compositions and shapes for a variety of applications in catalysis, sensor, drug/gene delivery.

Atomic Layer Deposition of Wet-Etch Resistant Silicon Nitride Using Di(sec-butylamino)silane and N2 Plasma on Planar and 3D Substrate Topographies.

PubMed

Faraz, Tahsin; van Drunen, Maarten; Knoops, Harm C M; Mallikarjunan, Anupama; Buchanan, Iain; Hausmann, Dennis M; Henri, Jon; Kessels, Wilhelmus M M

2017-01-18

The advent of three-dimensional (3D) finFET transistors and emergence of novel memory technologies place stringent requirements on the processing of silicon nitride (SiN x ) films used for a variety of applications in device manufacturing. In many cases, a low temperature (<400 °C) deposition process is desired that yields high quality SiN x films that are etch resistant and also conformal when grown on 3D substrate topographies. In this work, we developed a novel plasma-enhanced atomic layer deposition (PEALD) process for SiN x using a mono-aminosilane precursor, di(sec-butylamino)silane (DSBAS, SiH 3 N( s Bu) 2 ), and N 2 plasma. Material properties have been analyzed over a wide stage temperature range (100-500 °C) and compared with those obtained in our previous work for SiN x deposited using a bis-aminosilane precursor, bis(tert-butylamino)silane (BTBAS, SiH 2 (NH t Bu) 2 ), and N 2 plasma. Dense films (∼3.1 g/cm 3 ) with low C, O, and H contents at low substrate temperatures (<400 °C) were obtained on planar substrates for this process when compared to other processes reported in the literature. The developed process was also used for depositing SiN x films on high aspect ratio (4.5:1) 3D trench nanostructures to investigate film conformality and wet-etch resistance (in dilute hydrofluoric acid, HF/H 2 O = 1:100) relevant for state-of-the-art device architectures. Film conformality was below the desired levels of >95% and attributed to the combined role played by nitrogen plasma soft saturation, radical species recombination, and ion directionality during SiN x deposition on 3D substrates. Yet, very low wet-etch rates (WER ≤ 2 nm/min) were observed at the top, sidewall, and bottom trench regions of the most conformal film deposited at low substrate temperature (<400 °C), which confirmed that the process is applicable for depositing high quality SiN x films on both planar and 3D substrate topographies.

A chlorine precursor route (CPR) to poly(p-phenylene vinylene) light emitting diodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heieh, B.R.; Antoniadis, H.; Bland, D.C.

1995-12-01

We use a chlorine precursor route (CPR) to fabricate PPV based electroluminescent (EL) devices. 1,4- Bis(chloromethyl)-2,3-diphenylbenzene was polymerized with one equivalent amount of potassium t-butoxide (t-BuOK) to give the corresponding chlorine precursor polymer with very high molecular weights. This polymer is soluble in common organic solvents and is highly stable in the solid state and in solution. Thin films of the precursor polymer were spin cast on indiumtin-oxide (ITO) coated glass substrates followed by thermal conversion at 300{degrees}C for 2 h to give DP-PPV thin films. We found that CPR is more convenient and reliable than sulfonium precursor route formore » the fabrication of PPV thin film EL devices. Efficient emission of green light (500 nm) was observed for Mg/DP-PPV/ITO and Al/DP-PPV/ITO single layer devices.« less

Electrodeposition of NiO films from various solvent electrolytic solutions for dye sensitized solar cell application

NASA Astrophysics Data System (ADS)

Koussi-Daoud, S.; Pellegrin, Y.; Odobel, F.; Viana, B.; Pauporté, T.

2017-02-01

We have investigated the preparation of NiO layers by cathodic electrodeposition in various organic-based solvents, namely ethanol, dimethyl sulfoxide (DMSO), DMSO/2 vol.% H2O and DMSO/25 vol.% H2O mixtures. The layers were formed from the electrochemical reduction of nickel nitrate precursor. We show that, depending on the solvent used, various nickel compounds were deposited. In the case of ethanol, a transparent precursor layer was obtained that was transformed into NiO after an annealing treatment at 300°C. For DMSO and DMSO with 2 volume % of H2O, adherent, well-covering, mesoporous and rather thick NiO layers were obtained after an annealing treatment at 450°C. These layers, after growth, contained nickel oxide or hydroxide, metallic nickel and DMSO. The solvent acted as a blowing agent, being included in the deposit and giving rise to a mesoporous film after its elimination by thermal annealing. These porous layers of p-type oxide have been successfully sensitized by a push-pull dye (P1 dye) and showed photocurrent generation and an open circuit voltage (Voc) up to 167 mV in p-type dye-sensitized solar cells (p-DSSCs). For DMSO with 25 volume % of H2O, the deposited layers contained more metallic nickel and were dense even after annealing. They were unsuitable in p-DSSCs.

Layered Manufacturing: Challenges and Opportunities

DTIC Science & Technology

2003-04-01

quality of the surface finish, eliminating residual stress , controlling local composition and microstructure, achieving fine feature size and...applications. Some methods have achieved commercial status, having graduated from the university level, others are in various stages of research. However...Road * Sintering * Co-firing * Shrinkage * Gas dimensions + Powder or + Resin * Residual stress precursors * Layer wire feeding infiltration * Distortion

Possible Short-Term Precursors of Strong Crustal Earthquakes in Japan based on Data from the Ground Stations of Vertical Ionospheric Sounding

NASA Astrophysics Data System (ADS)

Korsunova, L. P.; Khegai, V. V.

2018-01-01

We have studied changes in the ionosphere prior to strong crustal earthquakes with magnitudes of M ≥ 6.5 based on the data from the ground-based stations of vertical ionospheric sounding Kokobunji, Akita, and Wakkanai for the period 1968-2004. The data are analyzed based on hourly measurements of the virtual height and frequency parameters of the sporadic E layer and critical frequency of the regular F2 layer over the course of three days prior to the earthquakes. In the studied intervals of time before all earthquakes, anomalous changes were discovered both in the frequency parameters of the Es and F2 ionospheric layers and in the virtual height of the sporadic E layer; the changes were observed on the same day at stations spaced apart by several hundred kilometers. A high degree of correlation is found between the lead-time of these ionospheric anomalies preceding the seismic impact and the magnitude of the subsequent earthquakes. It is concluded that such ionospheric disturbances can be short-term ionospheric precursors of earthquakes.

Room-temperature Electrochemical Synthesis of Carbide-derived Carbons and Related Materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gogotsi, Yury

2015-02-28

This project addresses room-temperature electrochemical etching as an energy-efficient route to synthesis of 3D nanoporous carbon networks and layered 2D carbons and related structures, as well as provides fundamental understanding of structure and properties of materials produced by this method. Carbide-derived-carbons (CDCs) are a growing class of nanostructured carbon materials with properties that are desirable for many applications, such as electrical energy and gas storage. The structure of these functional materials is tunable by the choice of the starting carbide precursor, synthesis method, and process parameters. Moving from high-temperature synthesis of CDCs through vacuum decomposition above 1400°C and chlorination abovemore » 400°C, our studies under the previous DOE BES support led to identification of precursor materials and processing conditions for CDC synthesis at temperatures as low as 200°C, resulting in amorphous and highly reactive porous carbons. We also investigated synthesis of monolithic CDC films from carbide films at 250-1200°C. The results of our early studies provided new insights into CDC formation, led to development of materials for capacitive energy storage, and enabled fundamental understanding of the electrolyte ions confinement in nanoporous carbons.« less

High-performance thin-film transistors with solution-processed ScInO channel layer based on environmental friendly precursor

NASA Astrophysics Data System (ADS)

Song, Wei; Lan, Linfeng; Li, Meiling; Wang, Lei; Lin, Zhenguo; Sun, Sheng; Li, Yuzhi; Song, Erlong; Gao, Peixiong; Li, Yan; Peng, Junbiao

2017-09-01

Thin-film transistors (TFTs) with solution-processed scandium (Sc) substituted indium oxide (Sc x In1-x O3, ScInO) thin films based on environmental friendly water-induced precursor were fabricated. As the Sc concentration increases from 0% to 10%, the mobility decreases from 23.7 cm2 V-1 s-1 to 6.4 cm2 V-1 s-1, which is attributed to the non-overlapping of the Sc3+ electron orbit. However, the off current decreases and the turn-ON voltage (V ON) shifts towards the positive direction as the Sc content increases, which indicates lower carrier density after incorporation of Sc into In2O3. More interestingly, the incorporation of Sc into In2O3 can effectively improve the electrical stability of the TFT devices under gate bias stress, which is attributed to the reduction of the number of oxygen vacancies due to the relatively low standard electrode potential (-2.36) of Sc and strong bonding strength of Sc-O (680 kJ mol-1). The reduction of oxygen vacancies is confirmed by the x-ray photoelectron spectroscopy (XPS) experiments.

Atomic layer deposition of hafnium oxide: A detailed reaction mechanism from first principles

NASA Astrophysics Data System (ADS)

Widjaja, Yuniarto; Musgrave, Charles B.

2002-08-01

Atomic layer deposition (ALD) of hafnium oxide (HfO2) using HfCl4 and H2O as precursors is studied using density functional theory. The mechanism consists of two deposition half-reactions: (1) HfCl4 with Hf-OH sites, and (2) H2O with Hf-Cl sites. Both half-reactions exhibit stable intermediates with energies lower than those of the final products. We show that increasing the temperature reduces the stability of the complex. However, increasing temperature also increases the dissociation free-energy barrier, which in turn results in increased desorption of adsorbed precursors. Both half-reactions are qualitatively similar to the corresponding reactions of ZrO2 ALD using ZrCl4 and H2O.

Microstructure and texture dependence of the dielectric anomalies and dc conductivity of Bi3TiNbO9 ferroelectric ceramics

NASA Astrophysics Data System (ADS)

Moure, A.; Pardo, L.

2005-04-01

Ceramics of composition Bi3TiNbO9 (BTN) and perovskite-layered structure (Aurivillius type) [B. Aurivillius, Ark. Kemi 1, 463 (1949)] were processed by natural sintering and hot pressing from amorphous precursors. Precursors were obtained by mechanochemical activation of stoichiometric mixtures of oxides. These materials are in general interesting for their use as high-temperature piezoelectrics. Among them, BTN possesses the highest ferroparaelectric phase-transition temperature (>900°C). The transition temperature establishes the working limit of the ceramic and the electric properties, especially the dc conductivity, affect on its polarizability. In this work, dielectric studies of BTN ceramics with controlled texture and microstructure have been made at 1, 100KHz, and 1MHZ and in the temperature range from 200°C up to the ferroparaelectric transition temperature. Values of ɛ'˜250 at 200°C are achieved in ceramics hot pressed at temperatures as low as 700°C for 1h.

Functionalization of SiO2 Surfaces for Si Monolayer Doping with Minimal Carbon Contamination.

PubMed

van Druenen, Maart; Collins, Gillian; Glynn, Colm; O'Dwyer, Colm; Holmes, Justin D

2018-01-17

Monolayer doping (MLD) involves the functionalization of semiconductor surfaces followed by an annealing step to diffuse the dopant into the substrate. We report an alternative doping method, oxide-MLD, where ultrathin SiO 2 overlayers are functionalized with phosphonic acids for doping Si. Similar peak carrier concentrations were achieved when compared with hydrosilylated surfaces (∼2 × 10 20 atoms/cm 3 ). Oxide-MLD offers several advantages over conventional MLD, such as ease of sample processing, superior ambient stability, and minimal carbon contamination. The incorporation of an oxide layer minimizes carbon contamination by facilitating attachment of carbon-free precursors or by impeding carbon diffusion. The oxide-MLD strategy allows selection of many inexpensive precursors and therefore allows application to both p- and n-doping. The phosphonic acid-functionalized SiO 2 surfaces were investigated using X-ray photoelectron spectroscopy and attenuated total reflectance Fourier transform infrared spectroscopy, whereas doping was assessed using electrochemical capacitance voltage and Hall measurements.

Optical devices featuring nonpolar textured semiconductor layers

DOEpatents

Moustakas, Theodore D; Moldawer, Adam; Bhattacharyya, Anirban; Abell, Joshua

2013-11-26

A semiconductor emitter, or precursor therefor, has a substrate and one or more textured semiconductor layers deposited onto the substrate in a nonpolar orientation. The textured layers enhance light extraction, and the use of nonpolar orientation greatly enhances internal quantum efficiency compared to conventional devices. Both the internal and external quantum efficiencies of emitters of the invention can be 70-80% or higher. The invention provides highly efficient light emitting diodes suitable for solid state lighting.

Nonequilibrium radiation and chemistry models for aerocapture vehicle flowfields, volume 2

NASA Technical Reports Server (NTRS)

Carlson, Leland A.

1991-01-01

A technique was developed for predicting the character and magnitude of the shock wave precursor ahead of an entry vehicle and the effect of this precursor on the vehicle flow field was ascertained. A computational method and program were developed to properly model this precursor. Expressions were developed for the mass production rates of each species due to photodissociation and photoionization reactions. Also, consideration was given to the absorption and emission of radiation and how it affects the energy in each of the energy modes of both the atomic and diatomic species. A series of parametric studies were conducted covering a range of entry conditions in order to predict the effects of the precursor on the shock layer and the radiative heat transfer to the body.

Facile and green synthesis of (La0.95Eu0.05)2O2S red phosphors with sulfate-ion pillared layered hydroxides as a new type of precursor: controlled hydrothermal processing, phase evolution and photoluminescence

PubMed Central

Wang, Xuejiao; Li, Ji-Guang; Zhu, Qi; Li, Xiaodong; Sun, Xudong; Sakka, Yoshio

2014-01-01

This study presents a facile and green route for the synthesis of (La0.95Eu0.05)2O2S red phosphors of controllable morphologies, with the sulfate-type layered hydroxides of Ln2(OH)4SO4·2H2O (Ln = La and Eu) as a new type of precursor. The technique takes advantage of the fact that the precursor has had the exact Ln:S molar ratio of the targeted phosphor, thus saving the hazardous sulfurization reagents indispensable to traditional synthesis. Controlled hydrothermal processing at 120 °C yielded phase-pure Ln2(OH)4SO4·2H2O crystallites in the form of either nanoplates or microprisms, which can both be converted into Ln2O2S phosphor via a Ln2O2SO4 intermediate upon annealing in flowing H2 at a minimum temperature of ∼ 700 °C. The nanoplates collapse into relatively rounded Ln2O2S particles while the microprisms retain well their initial morphologies at 1 200 °C, thus yielding two types of red phosphors. Photoluminescence excitation (PLE) studies found two distinct charge transfer (CT) excitation bands of O2− → Eu3+ at ∼ 270 nm and S2− → Eu3+ at ∼ 340 nm for the Ln2O2S phosphors, with the latter being stronger and both significantly stronger than the intrinsic intra-f transitions of Eu3+. The two types of phosphors share high similarities in the positions of PLE/PL (photoluminescence) bands and both show the strongest red emission at 627 nm (5D0 → 7F2 transition of Eu3+) under S2− → Eu3+ CT excitation at 340 nm. The PLE/PL intensities show clear dependence on particle morphology and calcination temperature, which were investigated in detail. Fluorescence decay analysis reveals that the 627 nm red emission has a lifetime of ∼ 0.5 ms for both types of the phosphors. PMID:27877631

Atomic layer deposition of metal sulfide materials

DOE PAGES

Dasgupta, Neil P.; Meng, Xiangbo; Elam, Jeffrey W.; ...

2015-01-12

The field of nanoscience is delivering increasingly intricate yet elegant geometric structures incorporating an ever-expanding palette of materials. Atomic layer deposition (ALD) is a powerful driver of this field, providing exceptionally conformal coatings spanning the periodic table and atomic-scale precision independent of substrate geometry. This versatility is intrinsic to ALD and results from sequential and self-limiting surface reactions. This characteristic facilitates digital synthesis, in which the film grows linearly with the number of reaction cycles. While the majority of ALD processes identified to date produce metal oxides, novel applications in areas such as energy storage, catalysis, and nanophotonics are motivatingmore » interest in sulfide materials. Recent progress in ALD of sulfides has expanded the diversity of accessible materials as well as a more complete understanding of the unique chalcogenide surface chemistry. ALD of sulfide materials typically uses metalorganic precursors and hydrogen sulfide (H 2S). As in oxide ALD, the precursor chemistry is critical to controlling both the film growth and properties including roughness, crystallinity, and impurity levels. By modification of the precursor sequence, multicomponent sulfides have been deposited, although challenges remain because of the higher propensity for cation exchange reactions, greater diffusion rates, and unintentional annealing of this more labile class of materials. A deeper understanding of these surface chemical reactions has been achieved through a combination of in situ studies and quantum-chemical calculations. As this understanding matures, so does our ability to deterministically tailor film properties to new applications and more sophisticated devices. This Account highlights the attributes of ALD chemistry that are unique to metal sulfides and surveys recent applications of these materials in photovoltaics, energy storage, and photonics. Within each application space, the benefits and challenges of novel ALD processes are emphasized and common trends are summarized. We conclude with a perspective on potential future directions for metal chalcogenide ALD as well as untapped opportunities. As a result, we consider challenges that must be addressed prior to implementing ALD metal sulfides into future device architectures.« less

Effect of sodium acetate additive in successive ionic layer adsorption and reaction on the performance of CdS quantum-dot-sensitized solar cells

NASA Astrophysics Data System (ADS)

Liu, I.-Ping; Chen, Liang-Yih; Lee, Yuh-Lang

2016-09-01

Sodium acetate (NaAc) is utilized as an additive in cationic precursors of the successive ionic layer adsorption and reaction (SILAR) process to fabricate CdS quantum-dot (QD)-sensitized photoelectrodes. The effects of the NaAc concentration on the deposition rate and distribution of QDs in mesoporous TiO2 films, as well as on the performance of CdS-sensitized solar cells are studied. The experimental results show that the presence of NaAc can significantly accelerate the deposition of CdS, improve the QD distribution across photoelectrodes, and thereby, increase the performance of solar cells. These results are mainly attributed to the pH-elevation effect of NaAc to the cationic precursors which increases the electrostatic interaction of the TiO2 film to cadmium ions. The light-to-energy conversion efficiency of the CdS-sensitized solar cell increases with increasing concentration of the NaAc and approaches a maximum value (3.11%) at 0.05 M NaAc. Additionally, an ionic exchange is carried out on the photoelectrode to transform the deposited CdS into CdS1-xSex ternary QDs. The light-absorption range of the photoelectrode is extended and an exceptional power conversion efficiency of 4.51% is achieved due to this treatment.

Exploitation of the UV Aerosol Index scattering angle dependence: Properties of Siberian smoke plumes

NASA Astrophysics Data System (ADS)

Penning de Vries, Marloes; Beirle, Steffen; Sihler, Holger; Wagner, Thomas

2017-04-01

The UV Aerosol Index (UVAI) is a simple measure of aerosols from satellite that is particularly sensitive to elevated layers of absorbing particles. It has been determined from a range of instruments including TOMS, GOME-2, and OMI, for almost four decades and will be continued in the upcoming Sentinel missions S5-precursor, S4, and S5. Despite its apparent simplicity, the interpretation of UVAI is not straightforward, as it depends on aerosol abundance, absorption, and altitude in a non-linear way. In addition, UVAI depends on the geometry of the measurement (viewing angle, solar zenith and relative azimuth angles), particularly if viewing angles exceed 45 degrees, as is the case for OMI and TROPOMI (on S5-precursor). The dependence on scattering angle complicates the interpretation and further processing (e.g., averaging) of UVAI. In certain favorable cases, however, independent information on aerosol altitude and absorption may become available. We present a detailed study of the scatter angle dependence using SCIATRAN radiative transfer calculations. The model results were compared to observations of an extensive Siberian smoke plume, of which parts reached 10-12 km altitude. Due to its large extent and the high latitude, OMI observed the complete plume in five consecutive orbits under a wide range of scattering angles. This allowed us to deduce aerosol characteristics (absorption and layer height) that were compared with collocated CALIOP lidar measurements.

Delicate Structural Control of Si-SiOx-C Composite via High-Speed Spray Pyrolysis for Li-Ion Battery Anodes.

PubMed

Lee, Seung Jong; Kim, Hye Jin; Hwang, Tae Hoon; Choi, Sunghun; Park, Sung Hyeon; Deniz, Erhan; Jung, Dae Soo; Choi, Jang Wook

2017-03-08

Despite the high theoretical capacity, silicon (Si) anodes in lithium-ion batteries have difficulty in meeting the commercial standards in various aspects. In particular, the huge volume change of Si makes it very challenging to simultaneously achieve high initial Coulombic efficiency (ICE) and long-term cycle life. Herein, we report spray pyrolysis to prepare Si-SiO x composite using an aqueous precursor solution containing Si nanoparticles, citric acid, and sodium hydroxide (NaOH). In the precursor solution, Si nanoparticles are etched by NaOH with the production of [SiO 4 ] 4- . During the dynamic course of spray pyrolysis, [SiO 4 ] 4- transforms to SiO x matrix and citric acid decomposes to carbon surface layer with the assistance of NaOH that serves as a decomposition catalyst. As a result, a Si-SiO x composite, in which Si nanodomains are homogeneously embedded in the SiO x matrix with carbon surface layer, is generated by a one-pot process with a residence time of only 3.5 s in a flow reactor. The optimal composite structure in terms of Si domain size and Si-to-O ratio exhibited excellent electrochemical performance, such as reversible capacity of 1561.9 mAh g -1 at 0.06C rate and ICE of 80.2% and 87.9% capacity retention after 100 cycles at 1C rate.

Fine-scale structure of the mid-mantle characterised by global stacks of PP precursors

NASA Astrophysics Data System (ADS)

Bentham, H. L. M.; Rost, S.; Thorne, M. S.

2017-08-01

Subduction zones are likely a major source of compositional heterogeneities in the mantle, which may preserve a record of the subduction history and mantle convection processes. The fine-scale structure associated with mantle heterogeneities can be studied using the scattered seismic wavefield that arrives as coda to or as energy preceding many body wave arrivals. In this study we analyse precursors to PP by creating stacks recorded at globally distributed stations. We create stacks aligned on the PP arrival in 5° distance bins (with range 70-120°) from 600 earthquakes recorded at 193 stations stacking a total of 7320 seismic records. As the energy trailing the direct P arrival, the P coda, interferes with the PP precursors, we suppress the P coda by subtracting a best fitting exponential curve to this energy. The resultant stacks show that PP precursors related to scattering from heterogeneities in the mantle are present for all distances. Lateral variations are explored by producing two regional stacks across the Atlantic and Pacific hemispheres, but we find only negligible differences in the precursory signature between these two regions. The similarity of these two regions suggests that well mixed subducted material can survive at upper and mid-mantle depth. To describe the scattered wavefield in the mantle, we compare the global stacks to synthetic seismograms generated using a Monte Carlo phonon scattering technique. We propose a best-fitting layered heterogeneity model, BRT2017, characterised by a three layer mantle with a background heterogeneity strength (ɛ = 0.8%) and a depth-interval of increased heterogeneity strength (ɛ = 1%) between 1000 km and 1800 km. The scalelength of heterogeneity is found to be 8 km throughout the mantle. Since mantle heterogeneity of 8 km scale may be linked to subducted oceanic crust, the detection of increased heterogeneity at mid-mantle depths could be associated with stalled slabs due to increases in viscosity, supporting recent observations of mantle viscosity increases due to the iron spin transition at depths of ∼1000 km.

Sol-gel type synthesis of Bi.sub.2 (Sr,Ta.sub.2)O.sub.9 using an acetate based system

DOEpatents

Boyle, Timothy J.

1997-01-01

A method of forming a layered-perovskite bismuth-strontium-tantalum oxide (SBT) ferroelectric material is performed by dissolving a bismuth compound in a first solvent to form a first solution, mixing a strontium compound and a tantalum compound to form a binary mixture, dissolving the binary mixture in a second solvent to form a second solution, mixing the first solution with the second solution to form a SBT precursor solution, evaporating the first and second solvents to form a SBT precursor material and subsequently sintering said SBT precursor material in the presence of oxygen.

Sol-gel type synthesis of Bi{sub 2}(Sr,Ta{sub 2})O{sub 9} using an acetate based system

DOEpatents

Boyle, T.J.

1997-11-04

A method of forming a layered-perovskite bismuth-strontium-tantalum oxide (SBT) ferroelectric material is performed by dissolving a bismuth compound in a first solvent to form a first solution, mixing a strontium compound and a tantalum compound to form a binary mixture, dissolving the binary mixture in a second solvent to form a second solution, mixing the first solution with the second solution to form a SBT precursor solution, evaporating the first and second solvents to form a SBT precursor material and subsequently sintering said SBT precursor material in the presence of oxygen. 6 figs.

Method of making organic light emitting devices

DOEpatents

Shiang, Joseph John [Niskayuna, NY; Janora, Kevin Henry [Schenectady, NY; Parthasarathy, Gautam [Saratoga Springs, NY; Cella, James Anthony [Clifton Park, NY; Chichak, Kelly Scott [Clifton Park, NY

2011-03-22

The present invention provides a method for the preparation of organic light-emitting devices comprising a bilayer structure made by forming a first film layer comprising an electroactive material and an INP precursor material, and exposing the first film layer to a radiation source under an inert atmosphere to generate an interpenetrating network polymer composition comprising the electroactive material. At least one additional layer is disposed on the reacted first film layer to complete the bilayer structure. The bilayer structure is comprised within an organic light-emitting device comprising standard features such as electrodes and optionally one or more additional layers serving as a bipolar emission layer, a hole injection layer, an electron injection layer, an electron transport layer, a hole transport layer, exciton-hole transporting layer, exciton-electron transporting layer, a hole transporting emission layer, or an electron transporting emission layer.

Ribonucleoprotein organization of eukaryotic RNA. XXXII. U2 small nuclear RNA precursors and their accurate 3' processing in vitro as ribonucleoprotein particles.

PubMed

Wieben, E D; Nenninger, J M; Pederson, T

1985-05-05

Biosynthetic precursors of U2 small nuclear RNA have been identified in cultured human cells by hybrid-selection of pulse-labeled RNA with cloned U2 DNA. These precursor molecules are one to approximately 16 nucleotides longer than mature U2 RNA and contain 2,2,7-trimethylguanosine "caps". The U2 RNA precursors are associated with proteins that react with a monoclonal antibody for antigens characteristic of small nuclear ribonucleoprotein particles. Like previously described precursors of U1 and U4 small nuclear RNAs, the pre-U2 RNAs are recovered in cytoplasmic fractions, although it is not known if this is their location in vivo. The precursors are processed to mature-size U2 RNA when cytoplasmic extracts are incubated in vitro at 37 degrees C. Mg2+ is required but ATP is not. The ribonucleoprotein structure of the pre-U2 RNA is maintained during the processing reaction in vitro, as are the 2,2,7-trimethylguanosine caps. The ribonucleoprotein organization is of major importance, as exogenous, protein-free U2 RNA precursors are degraded rapidly in the in vitro system. Two lines of evidence indicate that the conversion of U2 precursors to mature-size U2 RNA involves a 3' processing reaction. First, the reaction is unaffected by a large excess of mature U2 small nuclear RNP, whose 5' trimethylguanosine caps would be expected to compete for a 5' processing activity. Second, when pre-U2 RNA precursors are first stoichiometrically decorated with an antibody specific for 2,2,7-trimethylguanosine, the extent of subsequent processing in vitro is unaffected. These results provide the first demonstration of a eukaryotic RNA processing reaction in vitro occurring within a ribonucleoprotein particle.

Microstructures and Properties of the C/Zr-O-Si-C Composites Fabricated by Polymer Infiltration and Pyrolysis

NASA Astrophysics Data System (ADS)

Ma, Yan; Chen, Zhaohui

2013-09-01

A way to improve the ablation properties of the C/SiC composites in an oxyacetylene torch environment was investigated by the precursor infiltration and pyrolysis route using three organic precursors (zirconium butoxide, polycarbosilane, and divinylbenzene). The ceramic matrix derived from the precursors at 1200 °C was mainly a mixture of SiC, ZrO2, and C. After annealing at 1600 °C for 1 h, ZrO2 partly transformed to ZrC because of the carbothermic reductions and completely transformed to ZrC at 1800 °C in 1 h. The mechanical properties of the composites decreased with increasing temperature, while the ablation resistance increased due to the increasing content of ZrC. Compared with C/SiC composites, the ablation resistance of the C/Zr-O-Si-C composites overwhelms because of the oxide films which formed on the ablation surfaces. And, the films were composed of two layers: the porous surface layer (the mixture of ZrO2 and SiO2) and the dense underlayer (SiO2).

Linking Horizontal And Vertical Transports of Biomass Fire Emissions to the Tropical Atlantic Ozone Paradox during the Northern Hemisphere Winter Season: II. 1998-1999.

NASA Technical Reports Server (NTRS)

Jenkins, Gregory S.; Ryu, Jung-Hee; Thompson, Anne M.; Witte, Jacquelyn C.

2002-01-01

The horizontal and vertical transport of biomass fire emissions in West Africa during November 1998 through February 1999, are examined using all available data including wind, fire, aerosol, precipitation, lightning and outgoing longwave radiation. Ozonesonde data from the Aerosols99 Trans-Atlantic cruise are also included with rain and wind analyses. The results here support earlier studies that ozone and ozone precursors associated with biomass burning are confined to the lower troposphere primarily due to the lack of deep convection over land areas. Ozone and its precursors are horizontally transported equatorward or towards the west by winds in the 1000-700 hPa layers. However, rising adiabatic motions associated with the diurnal evolution of the West African n can transport ozone and its precursors vertically into the free troposphere above the marine boundary layer. Moreover, lightning from South America, Central Africa and mesoscale convective systems in the Gulf of Guinea can lead to elevated ozone mixing ratios in the middle and upper troposphere.

AVIRIS and TIMS data processing and distribution at the land processes distributed active archive center

NASA Technical Reports Server (NTRS)

Mah, G. R.; Myers, J.

1993-01-01

The U.S. Government has initiated the Global Change Research program, a systematic study of the Earth as a complete system. NASA's contribution of the Global Change Research Program is the Earth Observing System (EOS), a series of orbital sensor platforms and an associated data processing and distribution system. The EOS Data and Information System (EOSDIS) is the archiving, production, and distribution system for data collected by the EOS space segment and uses a multilayer architecture for processing, archiving, and distributing EOS data. The first layer consists of the spacecraft ground stations and processing facilities that receive the raw data from the orbiting platforms and then separate the data by individual sensors. The second layer consists of Distributed Active Archive Centers (DAAC) that process, distribute, and archive the sensor data. The third layer consists of a user science processing network. The EOSDIS is being developed in a phased implementation. The initial phase, Version 0, is a prototype of the operational system. Version 0 activities are based upon existing systems and are designed to provide an EOSDIS-like capability for information management and distribution. An important science support task is the creation of simulated data sets for EOS instruments from precursor aircraft or satellite data. The Land Processes DAAC, at the EROS Data Center (EDC), is responsible for archiving and processing EOS precursor data from airborne instruments such as the Thermal Infrared Multispectral Scanner (TIMS), the Thematic Mapper Simulator (TMS), and Airborne Visible and Infrared Imaging Spectrometer (AVIRIS). AVIRIS, TIMS, and TMS are flown by the NASA-Ames Research Center ARC) on an ER-2. The ER-2 flies at 65000 feet and can carry up to three sensors simultaneously. Most jointly collected data sets are somewhat boresighted and roughly registered. The instrument data are being used to construct data sets that simulate the spectral and spatial characteristics of the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument scheduled to be flown on the first EOS-AM spacecraft. The ASTER is designed to acquire 14 channels of land science data in the visible and near-IR (VNIR), shortwave-IR (SWIR), and thermal-IR (TIR) regions from 0.52 micron to 11.65 micron at high spatial resolutions of 15 m to 90 m. Stereo data will also be acquired in the VNIR region in a single band. The AVIRIS and TMS cover the ASTER VNIR and SWIR bands, and the TIMS covers the TIR bands. Simulated ASTER data sets have been generated over Death Valley, California, Cuprite, Nevada, and the Drum Mountains, Utah using a combination of AVIRIS, TIMS, amd TMS data, and existing digital elevation models (DEM) for the topographic information.

Pore radius fine tuning of a silica matrix (MCM-41) based on the synthesis of alumina nanolayers with different thicknesses by atomic layer deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zemtsova, Elena G., E-mail: ezimtsova@yandex.ru; Arbenin, Andrei Yu.; Plotnikov, Alexander F.

2015-03-15

The authors investigated a new approach to modify the surface of the mesoporous silica matrix MCM-41. This approach is based on manipulating the chemical composition of the porous surface layer and also on fine tuning the pore radius by applying the atomic layer deposition (ALD) technique. The synthesis of alumina nanolayers was performed on the planar and the porous matrix (MCM-41) by the ALD technique using aluminum tri-sec-butoxide and water as precursors. The authors show that one cycle on silicon, using aluminum tri-sec-butoxide and water as precursors, results in a 1–1.2 Å increase in alumina nanolayer thickness. This is comparable tomore » the increase in thickness per cycle for other precursors such as trimethylaluminum and aluminum chloride. The authors show that the synthesis of an Al{sub 2}O{sub 3} nanolayer on the pore surface of the mesoporous silica matrix MCM-41 by the ALD technique results in a regular change in the porous structure of the samples. The specific porosity (ml/g) of the MCM-41 was 0.95 and that of MCM-41 after 5 ALD cycles was 0.39. The pore diameter (nm) of MCM-41 was 3.3 and that of MCM-41 after 5 ALD cycles was 2.3.« less

Modeling and in Situ Probing of Surface Reactions in Atomic Layer Deposition.

PubMed

Zheng, Yuanxia; Hong, Sungwook; Psofogiannakis, George; Rayner, G Bruce; Datta, Suman; van Duin, Adri C T; Engel-Herbert, Roman

2017-05-10

Atomic layer deposition (ALD) has matured into a preeminent thin film deposition technique by offering a highly scalable and economic route to integrate chemically dissimilar materials with excellent thickness control down to the subnanometer regime. Contrary to its extensive applications, a quantitative and comprehensive understanding of the reaction processes seems intangible. Complex and manifold reaction pathways are possible, which are strongly affected by the surface chemical state. Here, we report a combined modeling and experimental approach utilizing ReaxFF reactive force field simulation and in situ real-time spectroscopic ellipsometry to gain insights into the ALD process of Al 2 O 3 from trimethylaluminum and water on hydrogenated and oxidized Ge(100) surfaces. We deciphered the origin for the different peculiarities during initial ALD cycles for the deposition on both surfaces. While the simulations predicted a nucleation delay for hydrogenated Ge(100), a self-cleaning effect was discovered on oxidized Ge(100) surfaces and resulted in an intermixed Al 2 O 3 /GeO x layer that effectively suppressed oxygen diffusion into Ge. In situ spectroscopic ellipsometry in combination with ex situ atomic force microscopy and X-ray photoelectron spectroscopy confirmed these simulation results. Electrical impedance characterizations evidenced the critical role of the intermixed Al 2 O 3 /GeO x layer to achieve electrically well-behaved dielectric/Ge interfaces with low interface trap density. The combined approach can be generalized to comprehend the deposition and reaction kinetics of other ALD precursors and surface chemistry, which offers a path toward a theory-aided rational design of ALD processes at a molecular level.

Catalyst containing oxygen transport membrane

DOEpatents

Christie, Gervase Maxwell; Wilson, Jamie Robyn; van Hassel, Bart Antonie

2012-12-04

A composite oxygen transport membrane having a dense layer, a porous support layer and an intermediate porous layer located between the dense layer and the porous support layer. Both the dense layer and the intermediate porous layer are formed from an ionic conductive material to conduct oxygen ions and an electrically conductive material to conduct electrons. The porous support layer has a high permeability, high porosity, and a high average pore diameter and the intermediate porous layer has a lower permeability and lower pore diameter than the porous support layer. Catalyst particles selected to promote oxidation of a combustible substance are located in the intermediate porous layer and in the porous support adjacent to the intermediate porous layer. The catalyst particles can be formed by wicking a solution of catalyst precursors through the porous support toward the intermediate porous layer.

Advanced Precursor Reaction Processing for Cu(InGa)(SeS)2 Solar Cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shafarman, William N.

This project “Advanced Precursor Reaction Processing for Cu(InGa)(SeS)2 Solar Cells”, completed by the Institute of Energy Conversion (IEC) at the University of Delaware in collaboration with the Department of Chemical Engineering at the University of Florida, developed the fundamental understanding and technology to increase module efficiency and improve the manufacturability of Cu(InGa)(SeS)2 films using the precursor reaction approach currently being developed by a number of companies. Key results included: (1) development of a three-step H2Se/Ar/H2S reaction process to control Ga distribution through the film and minimizes back contact MoSe2 formation; (2) Ag-alloying to improve precursor homogeneity by avoiding In phasemore » agglomeration, faster reaction and improved adhesion to allow wider reaction process window; (3) addition of Sb, Bi, and Te interlayers at the Mo/precursor junction to produce more uniform precursor morphology and improve adhesion with reduced void formation in reacted films; (4) a precursor structure containing Se and a reaction process to reduce processing time to 5 minutes and eliminate H2Se usage, thereby increasing throughput and reducing costs. All these results were supported by detailed characterization of the film growth, reaction pathways, thermodynamic assessment and device behavior.« less

Assembly of Layered Monetite-Chitosan Nanocomposite and Its Transition to Organized Hydroxyapatite.

PubMed

Ruan, Qichao; Liberman, David; Zhang, Yuzheng; Ren, Dongni; Zhang, Yunpeng; Nutt, Steven; Moradian-Oldak, Janet

2016-06-13

Bioinspired synthesis of hierarchically structured calcium phosphate (CaP) material is a highly promising strategy for developing improved bone substitute materials. However, synthesis of CaP materials with outstanding mechanical properties still remains an ongoing challenge. Inspired by the formation of lamellar structure in nacre, we designed an organic matrix composed of chitosan and cis-butenediolic acid (maleic acid, MAc) that could assemble into a layered complex and further guide the mineralization of monetite crystals, resulting in the formation of organized and parallel arrays of monetite platelets with a brick-and-mortar structure. Using the layered monetite-chitosan composite as a precursor, we were able to synthesize hydroxyapatite (HAp) with multiscale hierarchically ordered structure via a topotactic phase transformation process. On the nanoscale, needlelike HAp crystallites assembled into organized bundles that aligned to form highly oriented plates on the microscale. On the large-scale level, these plates with different crystal orientations were stacked together to form a layered structure. The organized structures and composite feature yielded CaP materials with improved mechanical properties close to those of bone. Our study introduces a biomimetic approach that may be practical for the design of advanced, mechanically robust materials for biomedical applications.

Design and fabrication of metal-insulator-metal diode for high frequency applications

NASA Astrophysics Data System (ADS)

Azad, Ibrahim; Ram, Manoj K.; Goswami, D. Yogi; Stefanakos, Elias

2017-02-01

Metal-insulator-metal (MIM) diodes play significant role in high speed electronics where high frequency rectification is needed. Quantum based tunneling mechanism helps MIM diodes to rectify at high frequency signals. Rectenna, antenna coupled MIM diodes are becoming popular due to their potential use as IR detectors and energy harvesters. Because of small active area, MIM diodes could easily be incorporated into integrated circuits (IC's). The objective of the work is to design and develop MIM diodes for high frequency rectification. In this work, thin insulating layer of ZnO was fabricated using Langmuir-Blodgett (LB) technique which facilitates ultrathin thin, uniform and pinhole free fabrication of insulating layer. The ZnO layer was synthesized from organic precursor of zinc acetate layer. The optimization in the LB technique of fabrication process led to fabricate MIM diodes with high non-linearity and sensitivity. Moreover, the top and bottom electrodes as well as active area of the diodes were patterned using UV-tunneling conduction mechanism. The highest sensitivity of the diode was measured around 37 (A/W), and the rectification ratio was found around 36 under low applied bias at +/-100 mV.

Amazon boundary layer aerosol concentration sustained by vertical transport during rainfall

DOE PAGES

Wang, Jian; Krejci, Radovan; Giangrande, Scott; ...

2016-10-24

The nucleation of atmospheric vapours is an important source of new aerosol particles that can subsequently grow to form cloud condensation nuclei in the atmosphere. Most field studies of atmospheric aerosols over continents are influenced by atmospheric vapours of anthropogenic origin and, in consequence, aerosol processes in pristine, terrestrial environments remain poorly understood. The Amazon rainforest is one of the few continental regions where aerosol particles and their precursors can be studied under near-natural conditions, but the origin of small aerosol particles that grow into cloud condensation nuclei in the Amazon boundary layer remains unclear. Here we present aircraft- andmore » ground-based measurements under clean conditions during the wet season in the central Amazon basin. We find that high concentrations of small aerosol particles (with diameters of less than 50 nanometres) in the lower free troposphere are transported from the free troposphere into the boundary layer during precipitation events by strong convective downdrafts and weaker downward motions in the trailing stratiform region. Lastly, this rapid vertical transport can help to maintain the population of particles in the pristine Amazon boundary layer, and may therefore influence cloud properties and climate under natural conditions.« less

Amazon boundary layer aerosol concentration sustained by vertical transport during rainfall

NASA Astrophysics Data System (ADS)

Wang, Jian; Krejci, Radovan; Giangrande, Scott; Kuang, Chongai; Barbosa, Henrique M. J.; Brito, Joel; Carbone, Samara; Chi, Xuguang; Comstock, Jennifer; Ditas, Florian; Lavric, Jost; Manninen, Hanna E.; Mei, Fan; Moran-Zuloaga, Daniel; Pöhlker, Christopher; Pöhlker, Mira L.; Saturno, Jorge; Schmid, Beat; Souza, Rodrigo A. F.; Springston, Stephen R.; Tomlinson, Jason M.; Toto, Tami; Walter, David; Wimmer, Daniela; Smith, James N.; Kulmala, Markku; Machado, Luiz A. T.; Artaxo, Paulo; Andreae, Meinrat O.; Petäjä, Tuukka; Martin, Scot T.

2016-11-01

The nucleation of atmospheric vapours is an important source of new aerosol particles that can subsequently grow to form cloud condensation nuclei in the atmosphere. Most field studies of atmospheric aerosols over continents are influenced by atmospheric vapours of anthropogenic origin (for example, ref. 2) and, in consequence, aerosol processes in pristine, terrestrial environments remain poorly understood. The Amazon rainforest is one of the few continental regions where aerosol particles and their precursors can be studied under near-natural conditions, but the origin of small aerosol particles that grow into cloud condensation nuclei in the Amazon boundary layer remains unclear. Here we present aircraft- and ground-based measurements under clean conditions during the wet season in the central Amazon basin. We find that high concentrations of small aerosol particles (with diameters of less than 50 nanometres) in the lower free troposphere are transported from the free troposphere into the boundary layer during precipitation events by strong convective downdrafts and weaker downward motions in the trailing stratiform region. This rapid vertical transport can help to maintain the population of particles in the pristine Amazon boundary layer, and may therefore influence cloud properties and climate under natural conditions.

Amazon boundary layer aerosol concentration sustained by vertical transport during rainfall.

PubMed

Wang, Jian; Krejci, Radovan; Giangrande, Scott; Kuang, Chongai; Barbosa, Henrique M J; Brito, Joel; Carbone, Samara; Chi, Xuguang; Comstock, Jennifer; Ditas, Florian; Lavric, Jost; Manninen, Hanna E; Mei, Fan; Moran-Zuloaga, Daniel; Pöhlker, Christopher; Pöhlker, Mira L; Saturno, Jorge; Schmid, Beat; Souza, Rodrigo A F; Springston, Stephen R; Tomlinson, Jason M; Toto, Tami; Walter, David; Wimmer, Daniela; Smith, James N; Kulmala, Markku; Machado, Luiz A T; Artaxo, Paulo; Andreae, Meinrat O; Petäjä, Tuukka; Martin, Scot T

2016-11-17

The nucleation of atmospheric vapours is an important source of new aerosol particles that can subsequently grow to form cloud condensation nuclei in the atmosphere. Most field studies of atmospheric aerosols over continents are influenced by atmospheric vapours of anthropogenic origin (for example, ref. 2) and, in consequence, aerosol processes in pristine, terrestrial environments remain poorly understood. The Amazon rainforest is one of the few continental regions where aerosol particles and their precursors can be studied under near-natural conditions, but the origin of small aerosol particles that grow into cloud condensation nuclei in the Amazon boundary layer remains unclear. Here we present aircraft- and ground-based measurements under clean conditions during the wet season in the central Amazon basin. We find that high concentrations of small aerosol particles (with diameters of less than 50 nanometres) in the lower free troposphere are transported from the free troposphere into the boundary layer during precipitation events by strong convective downdrafts and weaker downward motions in the trailing stratiform region. This rapid vertical transport can help to maintain the population of particles in the pristine Amazon boundary layer, and may therefore influence cloud properties and climate under natural conditions.

Characteristics of layered tin disulfide deposited by atomic layer deposition with H2S annealing

NASA Astrophysics Data System (ADS)

Lee, Seungjin; Shin, Seokyoon; Ham, Giyul; Lee, Juhyun; Choi, Hyeongsu; Park, Hyunwoo; Jeon, Hyeongtag

2017-04-01

Tin disulfide (SnS2) has attracted much attention as a two-dimensional (2D) material. A high-quality, low-temperature process for producing 2D materials is required for future electronic devices. Here, we investigate tin disulfide (SnS2) layers deposited via atomic layer deposition (ALD) using tetrakis(dimethylamino)tin (TDMASn) as a Sn precursor and H2S gas as a sulfur source at low temperature (150° C). The crystallinity of SnS2 was improved by H2S gas annealing. We carried out H2S gas annealing at various conditions (250° C, 300° C, 350° C, and using a three-step method). Angle-resolved X-ray photoelectron spectroscopy (ARXPS) results revealed the valence state corresponding to Sn4+ and S2- in the SnS2 annealed with H2S gas. The SnS2 annealed with H2S gas had a hexagonal structure, as measured via X-ray diffraction (XRD) and the clearly out-of-plane (A1g) mode in Raman spectroscopy. The crystallinity of SnS2 was improved after H2S annealing and was confirmed using the XRD full-width at half-maximum (FWHM). In addition, high-resolution transmission electron microscopy (HR-TEM) images indicated a clear layered structure.

Synthesis and characterization of Zn(O,OH)S and AgInS2 layers to be used in thin film solar cells

NASA Astrophysics Data System (ADS)

Vallejo, W.; Arredondo, C. A.; Gordillo, G.

2010-11-01

In this paper AgInS2 and Zn(O,OH)S thin films were synthesized and characterized. AgInS2 layers were grown by co-evaporation from metal precursors in a two-step process, and, Zn(O,OH)S thin films were deposited from chemical bath containing thiourea, zinc acetate, sodium citrate and ammonia. X-ray diffraction measurements indicated that AgInS2 thin films grown with chalcopyrite structure, and the as-grown Zn(O,OH)S thin films were polycrystalline. It was also found that the AgInS2 films presented p-type conductivity, a high absorption coefficient (greater than 104 cm-1) and energy band-gap Eg of about 1.95 eV, Zn(O,OH),S thin films presented Eg of about 3.89 eV. Morphological analysis showed that under this synthesis conditions Zn(O,OH),S thin films coated uniformly the absorber layer. Additionally, the Zn(O,OH)S kinetic growth on AgInS2 layer was studied also. Finally, the results suggest that these layers possibly could be used in one-junction solar cells and/or as top cell in a tandem solar cell.

Strain-balanced InAs/GaSb type-II superlattice structures and photodiodes grown on InAs substrates by metalorganic chemical vapor deposition

NASA Astrophysics Data System (ADS)

Huang, Yong; Ryou, Jae-Hyun; Dupuis, Russell D.; Zuo, Daniel; Kesler, Benjamin; Chuang, Shun-Lien; Hu, Hefei; Kim, Kyou-Hyun; Ting Lu, Yen; Hsieh, K. C.; Zuo, Jian-Min

2011-07-01

We propose and demonstrate strain-balanced InAs/GaSb type-II superlattices (T2SLs) grown on InAs substrates employing GaAs-like interfacial (IF) layers by metalorganic chemical vapor deposition (MOCVD) for effective strain management, simplified growth scheme, improved materials crystalline quality, and reduced substrate absorption. The in-plane compressive strain from the GaSb layers in the T2SLs on the InAs was completely balanced by the GaAs-like IF layers formed by controlled precursor carry-over and anion exchange effects, avoiding the use of complicated IF layers and precursor switching schemes that were used for the MOCVD growth of T2SLs on GaSb. An infrared (IR) p-i-n photodiode structure with 320-period InAs/GaSb T2SLs on InAs was grown and the fabricated devices show improved performance characteristics with a peak responsivity of ˜1.9 A/W and a detectivity of ˜6.78 × 109 Jones at 8 μm at 78 K. In addition, the InAs buffer layer and substrate show a lower IR absorption coefficient than GaSb substrates in most of the mid- and long-IR spectral range.

Tungstocobaltate-pillared layered double hydroxides: Preparation, characterization, magnetic and catalytic properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wei Xiaocui; Baicheng College of Higher Medicine, Baicheng 137000; Fu Youzhi

2008-06-15

A new polyoxometalate anion-pillared layered double hydroxide (LDH) was prepared by aqueous ion exchange of a Mg-Al LDH precursor in nitrate form with the tungstocobaltate anions [CoW{sub 12}O{sub 40}]{sup 5-}. The physicochemical properties of the product were characterized by the methods of powder X-ray diffraction, elemental analysis, infrared spectroscopy, thermogravimetric analysis and cyclic voltammetry. It was confirmed that [CoW{sub 12}O{sub 40}]{sup 5-} was intercalated between the brucite-type layers of the LDHs without a change in the structure. Magnetic measurement shows the occurrence of antiferromagnetic interactions between the magnetic centers. The investigation of catalytic performance for this sample exhibits high activitymore » for the oxidation of benzaldehyde by hydrogen peroxide. - Graphical abstract: A tungstocobaltate anion [CoW{sub 12}O{sub 40}]{sup 5-} pillared layered double hydroxide (LDH) was prepared by aqueous ion exchange with a Mg-Al LDH precursor in nitrate form, demonstrating that [CoW{sub 12}O{sub 40}]{sup 5-} was intercalated between the brucite-type layers of the LDHs without change in structure. Magnetic measurement shows the occurrence of antiferromagnetic interactions between the magnetic centers. The investigation of catalytic performance for this sample exhibits high activity for the oxidation of benzaldehyde by hydrogen peroxide.« less

Catalyst-free one step synthesis of large area vertically stacked N-doped graphene-boron nitride heterostructures from biomass source.

PubMed

Esteve-Adell, Ivan; He, Jinbao; Ramiro, Fernando; Atienzar, Pedro; Primo, Ana; García, Hermenegildo

2018-03-01

A procedure for the one-step preparation of films of few-layer N-doped graphene on top of nanometric hexagonal boron nitride sheets ((N)graphene/h-BN) based on the pyrolysis at 900 °C under an inert atmosphere of a film of chitosan containing about 20 wt% of ammonium borate salt as a precursor is reported. During the pyrolysis a spontaneous segregation of (N)graphene and boron nitride layers takes place. The films were characterized by optical microscopy that shows a thin graphene overlayer covering the boron nitride layer, the latter showing characteristic cracks, and by XPS measurements at different monitoring angles from 0° to 50° where an increase in the proportion of C vs. B and N was observed. The resulting (N)graphene/h-BN films were also characterized by Raman, HRTEM, SEM, FIB-SEM and AFM. The thickness of the (N)graphene and h-BN layers can be controlled by varying the concentration of precursors and the spin coating rate and is typically below 5 nm. Electrical conductivity measurements using microelectrodes can cause the burning of the graphene layer at high intensities, while lower intensities show that (N)graphene/h-BN films behave as capacitors in the range of positive voltages.

Thermochemical and kinetic aspects of the sulfurization of Cu-Sb and Cu-Bi thin films

NASA Astrophysics Data System (ADS)

Colombara, Diego; Peter, Laurence M.; Rogers, Keith D.; Hutchings, Kyle

2012-02-01

CuSbS2 and Cu3BiS3 are being investigated as part of a search for new absorber materials for photovoltaic devices. Thin films of these chalcogenides were produced by conversion of stacked and co-electroplated metal precursor layers in the presence of elemental sulfur vapour. Ex-situ XRD and SEM/EDS analyses of the processed samples were employed to study the reaction sequence with the aim of achieving compact layer morphologies. A new “Time-Temperature-Reaction” (TTR) diagram and modified Pilling-Bedworth coefficients have been introduced for the description and interpretation of the reaction kinetics. For equal processing times, the minimum temperature required for CuSbS2 to appear is substantially lower than for Cu3BiS3, suggesting that interdiffusion across the interfaces between the binary sulfides is a key step in the formation of the ternary compounds. The effects of the heating rate and sulfur partial pressure on the phase evolution as well as the potential losses of Sb and Bi during the processes have been investigated experimentally and the results related to the equilibrium pressure diagrams obtained via thermochemical computation.

Reverse micelle synthesis of nanoscale metal containing catalysts. [Nickel metal (with a nickel oxide surface layer) and iron oxyhydroxide nanoscale powders

DOE Office of Scientific and Technical Information (OSTI.GOV)

Darab, J.G.; Fulton, J.L.; Linehan, J.C.

1993-03-01

The need for morphological control during the synthesis of catalyst precursor powders is generally accepted to be important. In the liquefaction of coal, for example, iron-bearing catalyst precursor particles containing individual crystallites with diameters in the 1-100 nanometer range are believed to achieve good dispersion through out the coal-solvent slurry during liquefaction 2 runs and to undergo chemical transformations to catalytically active iron sulfide phases. The production of the nanoscale powders described here employs the confining spherical microdomains comprising the aqueous phase of a modified reverse micelle (MRM) microemulsion system as nanoscale reaction vessels in which polymerization, electrochemical reduction andmore » precipitation of solvated salts can occur. The goal is to take advantage of the confining nature of micelles to kinetically hinder transformation processes which readily occur in bulk aqueous solution in order to control the morphology and phase of the resulting powder. We have prepared a variety of metal, alloy, and metal- and mixed metal-oxide nanoscale powders from appropriate MRM systems. Examples of nanoscale powders produced include Co, Mo-Co, Ni[sub 3]Fe, Ni, and various oxides and oxyhydroxides of iron. Here, we discuss the preparation and characterization of nickel metal (with a nickel oxide surface layer) and iron oxyhydroxide MRM nanoscale powders. We have used extended x-ray absorption fine structure (EXAFS) spectroscopy to study the chemical polymerization process in situ, x-ray diffraction (XRD), scanning and transmission electron microcroscopies (SEM and TEM), elemental analysis and structural modelling to characterize the nanoscale powders produced. The catalytic activity of these powders is currently being studied.« less

Wintertime vertical variations in particulate matter (PM) and precursor concentrations in the San Joaquin Valley during the California Regional Coarse PM/Fine PM Air Quality Study.

PubMed

Brown, Steven G; Roberts, Paul T; McCarthy, Michael C; Lurmann, Frederick W; Hyslop, Nicole P

2006-09-01

Air quality monitoring was conducted at a rural site with a tower in the middle of California's San Joaquin Valley (SJV) and at elevated sites in the foothills and mountains surrounding the SJV for the California Regional PM10/ PM2.5 Air Quality Study. Measurements at the surface and n a tower at 90 m were collected in Angiola, CA, from December 2000 through February 2001 and included hourly black carbon (BC), particle counts from optical particle counters, nitric oxide, ozone, temperature, relative humidity, wind speed, and direction. Boundary site measurements were made primarily using 24-hr integrated particulate matter (PM) samples. These measurements were used to understand the vertical variations of PM and PM precursors, the effect of stratification in the winter on concentrations and chemistry aloft and at the surface, and the impact of aloft-versus-surface transport on PM concentrations. Vertical variations of concentrations differed among individual species. The stratification may be important to atmospheric chemistry processes, particularly nighttime nitrate formation aloft, because NO2 appeared to be oxidized by ozone in the stratified aloft layer. Additionally, increases in accumulation-mode particle concentrations in the aloft layer during a fine PM (PM2.5) episode corresponded with increases in aloft nitrate, demonstrating the likelihood of an aloft nighttime nitrate formation mechanism. Evidence of local transport at the surface and regional transport aloft was found; transport processes also varied among the species. The distribution of BC appeared to be regional, and BC was often uniformly mixed vertically. Overall, the combination of time-resolved tower and surface measurements provided important insight into PM stratification, formation, and transport.

Chelant Enhanced Solution Processing for Wafer Scale Synthesis of Transition Metal Dichalcogenide Thin Films.

PubMed

Ionescu, Robert; Campbell, Brennan; Wu, Ryan; Aytan, Ece; Patalano, Andrew; Ruiz, Isaac; Howell, Stephen W; McDonald, Anthony E; Beechem, Thomas E; Mkhoyan, K Andre; Ozkan, Mihrimah; Ozkan, Cengiz S

2017-07-25

It is of paramount importance to improve the control over large area growth of high quality molybdenum disulfide (MoS 2 ) and other types of 2D dichalcogenides. Such atomically thin materials have great potential for use in electronics, and are thought to make possible the first real applications of spintronics. Here in, a facile and reproducible method of producing wafer scale atomically thin MoS 2 layers has been developed using the incorporation of a chelating agent in a common organic solvent, dimethyl sulfoxide (DMSO). Previously, solution processing of a MoS 2 precursor, ammonium tetrathiomolybdate ((NH 4 ) 2 MoS 4 ), and subsequent thermolysis was used to produce large area MoS 2 layers. Our work here shows that the use of ethylenediaminetetraacetic acid (EDTA) in DMSO exerts superior control over wafer coverage and film thickness, and the results demonstrate that the chelating action and dispersing effect of EDTA is critical in growing uniform films. Raman spectroscopy, photoluminescence (PL), x-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM) and high-resolution scanning transmission electron microscopy (HR-STEM) indicate the formation of homogenous few layer MoS 2 films at the wafer scale, resulting from the novel chelant-in-solution method.

Regulation of the membrane mucin Muc4 in corneal epithelial cells by proteosomal degradation and TGF-beta.

PubMed

Lomako, Joseph; Lomako, Wieslawa M; Carothers Carraway, Coralie A; Carraway, Kermit L

2010-04-01

MUC4 is a heterodimeric membrane mucin, composed of a mucin subunit ASGP-1 (MUC4alpha) and a transmembrane subunit ASGP-2 (MUC4beta), which has been implicated in the protection of epithelial cell surfaces. In the rat stratified corneal epithelium Muc4 is found predominantly in the most superficial cell layers. Since previous studies in other tissues have shown that Muc4 is regulated by TGF-beta via a proteosomal degradation mechanism, we investigated the regulation of corneal Muc4 in stratified cultures of corneal epithelial cells. Application of proteosome or processing inhibitors led to increases in levels of Muc4, particularly in the basal and intermediate levels of the stratified cultures. These changes were accompanied by increases in Muc4 ubiquitination, chaperone association and incorporation into intracellular aggresomes. In contrast, treatment with TGF-beta resulted in reduced levels of Muc4, which were reversed by proteosome inhibition. The results support a model in which Muc4 precursor is synthesized in all layers of the corneal epithelium, but Muc4 is degraded in basal and intermediate layers by a proteosomal mechanism at least partly dependent on TGF-beta inhibition of Muc4 processing. J. Cell. Physiol. 223: 209-214, 2010. (c) 2009 Wiley-Liss, Inc.

Deformation sensor based on polymer-supported discontinuous graphene multi-layer coatings

NASA Astrophysics Data System (ADS)

Carotenuto, G.; Schiavo, L.; Romeo, V.; Nicolais, L.

2014-05-01

Graphene can be conveniently used in the modification of polymer surfaces. Graphene macromolecules are perfectly transparent to the visible light and electrically conductive, consequently these two properties can be simultaneously provided to polymeric substrates by surface coating with thin graphene layers. In addition, such coating process provides the substrates of: water-repellence, higher surface hardness, low-friction, self-lubrication, gas-barrier properties, and many other functionalities. Polyolefins have a non-polar nature and therefore graphene strongly sticks on their surface. Nano-crystalline graphite can be used as graphene precursor in some chemical processes (e.g., graphite oxide synthesis by the Hummer method), in addition it can be directly applied to the surface of a polyolefin substrate (e.g., polyethylene) to cover it by a thin graphene multilayer. In particular, the nano-crystalline graphite perfectly exfoliate under the application of a combination of shear and friction forces and the produced graphene single-layers perfectly spread and adhere on the polyethylene substrate surface. Such polymeric materials can be used as ITO (indium-tin oxide) substitute and in the fabrication of different electronic devices. Here the fabrication of transparent resistive deformation sensors based on low-density polyethylene films coated by graphene multilayers is described. Such devices are very sensible and show a high reversible and reproducible behavior.

Inkjet-printed p-type nickel oxide thin-film transistor

NASA Astrophysics Data System (ADS)

Hu, Hailong; Zhu, Jingguang; Chen, Maosheng; Guo, Tailiang; Li, Fushan

2018-05-01

High-performance inkjet-printed nickel oxide thin-film transistors (TFTs) with Al2O3 high-k dielectric have been fabricated using a sol-gel precursor ink. The "coffee ring" effect during the printing process was facilely restrained by modifying the viscosity of the ink to control the outward capillary flow. The impacts on the device performance was studied in detail in consideration of annealing temperature of the nickel oxide film and the properties of dielectric layer. The optimized switching ability of the device were achieved at an annealing temperature of 280 °C on a 50-nm-thick Al2O3 dielectric layer, with a hole mobility of 0.78 cm2/V·s, threshold voltage of -0.6 V and on/off current ratio of 5.3 × 104. The as-printed p-type oxide TFTs show potential application in low-cost, large-area complementary electronic devices.

Chemical Vapor Deposition for Ultra-lightweight Thin-film Solar Arrays for Space

NASA Technical Reports Server (NTRS)

Hepp, Aloysius F.; Raffaelle, Ryne P.; Banger, Kulbinder K.; Jin, Michael H.; Lau, Janice E.; Harris, Jerry D.; Cowen, Jonathan E.; Duraj, Stan A.

2002-01-01

The development of thin-film solar cells on flexible, lightweight, space-qualified substrates provides an attractive cost solution to fabricating solar arrays with high specific power, (W/kg). The use of a polycrystalline chalcopyrite absorber layer for thin film solar cells is considered as the next generation photovoltaic devices. A key technical issues outlined in the 2001 U.S. Photovoltaic Roadmap, is the need to develop low cost, high throughput manufacturing for high-efficiency thin film solar cells. At NASA GRC we have focused on the development of new single-source-precursors (SSPs) and their utility to deposit the chalcopyrite semi-conducting layer (CIS) onto flexible substrates for solar cell fabrication. The syntheses and thermal modulation of SSPs via molecular engineering is described. Thin-film fabrication studies demonstrate the SSPs can be used in a spray CVD process, for depositing CIS at reduced temperatures, which display good electrical properties, suitable for PV devices.

Chemical lift-off and direct wafer bonding of GaN/InGaN P-I-N structures grown on ZnO

NASA Astrophysics Data System (ADS)

Pantzas, K.; Rogers, D. J.; Bove, P.; Sandana, V. E.; Teherani, F. H.; El Gmili, Y.; Molinari, M.; Patriarche, G.; Largeau, L.; Mauguin, O.; Suresh, S.; Voss, P. L.; Razeghi, M.; Ougazzaden, A.

2016-02-01

p-GaN/i-InGaN/n-GaN (PIN) structures were grown epitaxially on ZnO-buffered c-sapphire substrates by metal organic vapor phase epitaxy using the industry standard ammonia precursor for nitrogen. Scanning electron microscopy revealed continuous layers with a smooth interface between GaN and ZnO and no evidence of ZnO back-etching. Energy Dispersive X-ray Spectroscopy revealed a peak indium content of just under 5 at% in the active layers. The PIN structure was lifted off the sapphire by selectively etching away the ZnO buffer in an acid and then direct bonded onto a glass substrate. Detailed high resolution transmission electron microscoy and grazing incidence X-ray diffraction studies revealed that the structural quality of the PIN structures was preserved during the transfer process.

Superparamagnetic magnetite nanocrystals-graphene oxide nanocomposites: facile synthesis and their enhanced electric double-layer capacitor performance.

PubMed

Wang, Qihua; Wang, Dewei; Li, Yuqi; Wang, Tingmei

2012-06-01

Superparamagnetic magnetite nanocrystals-graphene oxide (FGO) nanocomposites were successfully synthesized through a simple yet versatile one-step solution-processed approach at ambient conditions. Magnetite (Fe3O4) nanocrystals (NCs) with a size of 10-50 nm were uniformly deposited on the surfaces of graphene oxide (GO) sheets, which were confirmed by transmission electron microscopy (TEM) and high-angle annular dark field scanning transmission election microscopy (HAADF-STEM) studies. FGO with different Fe3O4 loadings could be controlled by simply manipulating the initial weight ratio of the precursors. The M-H measurements suggested that the as-prepared FGO nanocomposites have a large saturation magnetizations that made them can move regularly under an external magnetic field. Significantly, FGO nanocomposites also exhibit enhanced electric double-layer capacitor (EDLC) activity compared with pure Fe3O4 NCs and GO in terms of specific capacitance and high-rate charge-discharge.

Atomic configurations in AP-MOVPE grown lattice-mismatched InGaAsN films unravelled by X-ray photoelectron spectroscopy combined with bulk and surface characterization techniques

NASA Astrophysics Data System (ADS)

López-Escalante, M. C.; Ściana, B.; Dawidowski, W.; Bielak, K.; Gabás, M.

2018-03-01

This work presents the results of X-ray photoelectron spectroscopy studies on the bonding N configuration in InGaAsN epilayers grown by atmospheric pressure metal organic vapour phase epitaxy. Growth temperature has been tuned in order to obtain both, relaxed and strained layers. The studies were concentrated on analysing the influence of the growth temperature, post growth thermal annealing process and surface quality on the formation of Ga-N and In-N bonds as well as N-related defects. The contamination of InGaAsN films by growth precursor residues and oxides has also been addressed. The growth temperature stands out as a decisive factor boosting In-N bonds formation, while the thermal annealing seems to affect the N-related defects density in the layers.

Laser-induced atomic assembling of periodic layered nanostructures of silver nanoparticles in fluoro-polymer film matrix

NASA Astrophysics Data System (ADS)

Bagratashvili, V. N.; Rybaltovsky, A. O.; Minaev, N. V.; Timashev, P. S.; Firsov, V. V.; Yusupov, V. I.

2010-05-01

Fluorinated acrylic polymer (FAP) films have been impregnated with silver precursor (Ag(hfac)COD) by supercritical fluid technique and next irradiated with laser (λ = 532 nm). Laser-chemically reduced Ag atoms have been assembled into massifs of Ag nanoparticles (3 - 8 nm) in FAP/Ag(hfac)COD films matrix in the form of periodic layered nanostructures (horizontal to film surface) with unexpectedly short period (90 - 180 nm). The wavelet analysis of TEM images reveals the existence of even shorter-period structures in such films. Photolysis with non-coherent light or pyrolysis of FAP/Ag(hfac)COD film results in formation of Ag nanoparticles massifs but free of any periodic nanoparticle assemblies. Our interpretation of the observed effect of laser formation of short-period nano-sized Ag nanoparticle assemblies is based on self-enhanced interference process in the course of modification of optical properties of film.

Regularly arranged indium islands on glass/molybdenum substrates upon femtosecond laser and physical vapor deposition processing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ringleb, F.; Eylers, K.; Teubner, Th.

2016-03-14

A bottom-up approach is presented for the production of arrays of indium islands on a molybdenum layer on glass, which can serve as micro-sized precursors for indium compounds such as copper-indium-gallium-diselenide used in photovoltaics. Femtosecond laser ablation of glass and a subsequent deposition of a molybdenum film or direct laser processing of the molybdenum film both allow the preferential nucleation and growth of indium islands at the predefined locations in a following indium-based physical vapor deposition (PVD) process. A proper choice of laser and deposition parameters ensures the controlled growth of indium islands exclusively at the laser ablated spots. Basedmore » on a statistical analysis, these results are compared to the non-structured molybdenum surface, leading to randomly grown indium islands after PVD.« less

Structural comparison of nickel electrodes and precursor phases

NASA Technical Reports Server (NTRS)

Cornilsen, Bahne C.; Shan, Xiaoyin; Loyselle, Patricia

1989-01-01

A summary of previous Raman spectroscopic results and a discussion of important structural differences in the various phases of active mass and active mass precurors are presented. Raman spectra provide unique signatures for these phases, and allow one to distinguish each phase, even when the compound is amorphous to X-rays (i.e., does not scatter X-rays because of a lack of order and/or small particle size). The structural changes incurred during formation, charge and discharge, cobalt addition, and aging will be discussed and related to electrode properties. Important structural differences include NiO2 layer stacking, nonstoichiometry (especially cation-deficit nonstoichiometry), disorder, dopant content, and water content. The results indicate that optimal nickel active mass is non-close packed and nonstoichiometric. The formation process transforms precursor phases into this structure. Therefore, the precursor disorder, or lack thereof, influences this final active mass structure and the rate of formation. Aging processes induce structural change which is believed to be detrimental. The role of cobalt addition can be appreciated in terms of structures favored or stabilized by the dopant. In recent work, the in situ Raman technique to characterize the critical structural parameters was developed. An in situ method relates structure, electrochemistry, and preparation. In situ Raman spectra of cells during charge and discharge, either during cyclic voltammetry or under constant current conditions were collected. With the structure-preparation knowledge and the in situ Raman tool, it will be possible to define the structure-property-preparation relations in more detail. This instrumentation has application to a variety of electrode systems.

Iron-Terephthalate Coordination Network Thin Films Through In-Situ Atomic/Molecular Layer Deposition.

PubMed

Tanskanen, A; Karppinen, M

2018-06-12

Iron terephthalate coordination network thin films can be fabricated using the state-of-the-art gas-phase atomic/molecular layer deposition (ALD/MLD) technique in a highly controlled manner. Iron is an Earth-abundant and nonhazardous transition metal, and with its rich variety of potential applications an interesting metal constituent for the inorganic-organic coordination network films. Our work underlines the role of the metal precursor used when aiming at in-situ ALD/MLD growth of crystalline inorganic-organic thin films. We obtain crystalline iron terephthalate films when FeCl 3 is employed as the iron source whereas depositions based on the bulkier Fe(acac) 3 precursor yield amorphous films. The chemical composition and structure of the films are investigated with GIXRD, XRR, FTIR and XPS.

The effects of shock wave precursors ahead of hypersonic entry vehicles

NASA Technical Reports Server (NTRS)

Stanley, Scott A.; Carlson, Leland A.

1991-01-01

A model has been developed to predict the magnitude and characteristics of the shock wave precursor ahead of a hypervelocity vehicle. This model includes both chemical and thermal nonequilibrium, utilizes detailed mass production rates for the photodissociation and photoionization reactions, and accounts for the effects of radiative absorption and emission on the individual internal energy modes of both atomic and diatomic species. Comparison of the present results with shock tube data indicates that the model is reasonably accurate. A series of test cases representing earth aerocapture return from Mars indicate that there is significant production of atoms, ions and electrons ahead of the shock front due to radiative absorption and that the precursor is characterized by an enhanced electron/electronic temperature and molecular ionization. However, the precursor has a negligible effect on the shock layer flow field.

Structural characterization of layered Na0.5Co0.5Mn0.5O2 material as a promising cathode for sodium-ion batteries

NASA Astrophysics Data System (ADS)

Manikandan, Palanisamy; Heo, Seongwoo; Kim, Hyun Woo; Jeong, Hu Young; Lee, Eungje; Kim, Youngsik

2017-09-01

Layered Na0.5Co0.5Mn0.5O2 material is synthesized through a facile mixed hydroxy-carbonate route using (Co0.5Mn0.5)2(OH)2CO3 precursor and well characterized as a hexagonal layered structure under P63/mmc space group. The lattice parameters and unit cell volume (a = 2.8363 Å, c = 11.3152 Å and V = 78.83 Å3) are calculated by Rietveld refinement analysis. A flaky-bundle morphology is obtained to the layered Na0.5Co0.5Mn0.5O2 material with the hexagonal flake size ∼30 nm. Advanced transmission electron microscopic images are revealed the local structure of the layered Na0.5Co0.5Mn0.5O2 material with contrasting bright dots and faint dark dots corresponding to the Co/Mn and Na atoms. Two oxidation and reduction peaks are occurred in a cyclic voltammetric analysis corresponding to Co3+/Co4+ and Mn3+/Mn4+ redox processes. These reversible processes are attributed to the intercalation/de-intercalation of Na+ ions into the host structure of layered Na0.5Co0.5Mn0.5O2 material. Accordingly, the sodium cell is delivered the initial charge-discharge capacity 53/144 mAh g-1 at 0.5 C, which cycling studies are extended to rate capability test at 1 C, 3 C and 5C. Eventually, the Na-ion full-cell is yielded cathode charge-discharge capacity 55/52 mAh g-1 at 0.212 mA and exhibited as a high voltage cathode for Na-ion batteries.

Characterisation of well-adhered ZrO2 layers produced on structured reactors using the sonochemical sol-gel method

NASA Astrophysics Data System (ADS)

Jodłowski, Przemysław J.; Chlebda, Damian K.; Jędrzejczyk, Roman J.; Dziedzicka, Anna; Kuterasiński, Łukasz; Sitarz, Maciej

2018-01-01

The aim of this study was to obtain thin zirconium dioxide coatings on structured reactors using the sonochemical sol-gel method. The preparation method of metal oxide layers on metallic structures was based on the synergistic combination of three approaches: the application of ultrasonic irradiation during the synthesis of Zr sol-gel based on a precursor solution containing zirconium(IV) n-propoxide, the addition of stabilszing agents, and the deposition of ZrO2 on the metallic structures using the dip-coating method. As a result, dense, uniform zirconium dioxide films were obtained on the FeCrAlloy supports. The structured reactors were characterised by various physicochemical methods, such as BET, AFM, EDX, XRF, XRD, XPS and in situ Raman spectroscopy. The results of the structural analysis by Raman and XPS spectroscopy confirmed that the metallic surface was covered by a ZrO2 layer without any impurities. SEM/EDX mapping revealed that the deposited ZrO2 covered the metallic support uniformly. The mechanical and high temperature tests showed that the developed ultrasound assisted sol-gel method is an efficient way to obtain thin, well-adhered zirconium dioxide layers on the structured reactors. The prepared metallic supports covered with thin ZrO2 layers may be a good alternative to layered structured reactors in several dynamics flow processes, for example for gas exhaust abatement.

Growth behavior and properties of atomic layer deposited tin oxide on silicon from novel tin(II)acetylacetonate precursor and ozone

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kannan Selvaraj, Sathees; Feinerman, Alan; Takoudis, Christos G., E-mail: takoudis@uic.edu

In this work, a novel liquid tin(II) precursor, tin(II)acetylacetonate [Sn(acac){sub 2}], was used to deposit tin oxide films on Si(100) substrate, using a custom-built hot wall atomic layer deposition (ALD) reactor. Three different oxidizers, water, oxygen, and ozone, were tried. Resulting growth rates were studied as a function of precursor dosage, oxidizer dosage, reactor temperature, and number of ALD cycles. The film growth rate was found to be 0.1 ± 0.01 nm/cycle within the wide ALD temperature window of 175–300 °C using ozone; no film growth was observed with water or oxygen. Characterization methods were used to study the composition, interface quality, crystallinity, microstructure,more » refractive index, surface morphology, and resistivity of the resulting films. X-ray photoelectron spectra showed the formation of a clean SnO{sub x}–Si interface. The resistivity of the SnO{sub x} films was calculated to be 0.3 Ω cm. Results of this work demonstrate the possibility of introducing Sn(acac){sub 2} as tin precursor to deposit conducting ALD SnO{sub x} thin films on a silicon surface, with clean interface and no formation of undesired SiO{sub 2} or other interfacial reaction products, for transparent conducting oxide applications.« less

Surface chemistry of copper metal and copper oxide atomic layer deposition from copper(ii) acetylacetonate: a combined first-principles and reactive molecular dynamics study.

PubMed

Hu, Xiao; Schuster, Jörg; Schulz, Stefan E; Gessner, Thomas

2015-10-28

Atomistic mechanisms for the atomic layer deposition using the Cu(acac)2 (acac = acetylacetonate) precursor are studied using first-principles calculations and reactive molecular dynamics simulations. The results show that Cu(acac)2 chemisorbs on the hollow site of the Cu(110) surface and decomposes easily into a Cu atom and the acac-ligands. A sequential dissociation and reduction of the Cu precursor [Cu(acac)2 → Cu(acac) → Cu] are observed. Further decomposition of the acac-ligand is unfavorable on the Cu surface. Thus additional adsorption of the precursors may be blocked by adsorbed ligands. Molecular hydrogen is found to be nonreactive towards Cu(acac)2 on Cu(110), whereas individual H atoms easily lead to bond breaking in the Cu precursor upon impact, and thus release the surface ligands into the gas-phase. On the other hand, water reacts with Cu(acac)2 on a Cu2O substrate through a ligand-exchange reaction, which produces gaseous H(acac) and surface OH species. Combustion reactions with the main by-products CO2 and H2O are observed during the reaction between Cu(acac)2 and ozone on the CuO surface. The reactivity of different co-reactants toward Cu(acac)2 follows the order H > O3 > H2O.

Different processing of CAPA and pyrokinin precursors in the giant mealworm beetle Zophobas atratus (Tenebrionidae) and the boll weevil Anthonomus grandis grandis (Curculionidae).

PubMed

Neupert, Susanne; Marciniak, Pawel; Köhler, Rene; Nachman, Ronald J; Suh, Charles P-C; Predel, Reinhard

2018-03-01

Capa and pyrokinin (pk) genes in hexapods share a common evolutionary origin. Using transcriptomics and peptidomics, we analyzed products of these genes in two beetles, the giant mealworm beetle (Zophobas atratus; Tenebrionidae) and the boll weevil (Anthonomus grandis grandis; Curculionidae). Our data revealed that even within Coleoptera, which represents a very well-defined group of insects, highly different evolutionary developments occurred in the neuropeptidergic system. These differences, however, primarily affect the general structure of the precursors and differential processing of mature peptides and, to a lesser degree, the sequences of the active core motifs. With the differential processing of the CAPA-precursor in Z. atratus we found a perfect example of completely different products cleaved from a single neuropeptide precursor in different cells. The CAPA precursor in abdominal ganglia of this species yields primarily periviscerokinins (PVKs) whereas processing of the same precursor in neurosecretory cells of the subesophageal ganglion results in CAPA-tryptoPK and a novel CAPA-PK. Particularly important was the detection of that CAPA-PK which has never been observed in the CNS of insects before. The three different types of CAPA peptides (CAPA-tryptoPK, CAPA-PK, PVK) each represent potential ligands which activate different receptors. In contrast to the processing of the CAPA precursor from Z. atratus, no indications of a differential processing of the CAPA precursor were found in A. g. grandis. These data suggest that rapid evolutionary changes regarding the processing of CAPA precursors were still going on when the different beetle lineages diverged. The sequence of the single known PVK of A. g. grandis occupies a special position within the known PVKs of insects and might serve asa basis to develop lineage-specific peptidomimetics capable of disrupting physiological processes regulated by PVKs. Copyright © 2017 Elsevier Inc. All rights reserved.

Hybrid gas-to-particle conversion and chemical vapor deposition for production of high-surface area films

NASA Astrophysics Data System (ADS)

Nguyen, Quynh Tan

A hybrid process, based upon gas-to-particle conversion and chemical vapor deposition, is presented as an alternative technique for producing porous films with the main advantages of solvent-free, low-substrate temperature operation. Starting from solid precursors, nanoparticles were produced in the vapor phase. Downstream of this reaction zone, these nanoparticles were collected via thermophoresis onto a cooled substrate forming a porous film. Initially, alumina (Al2O3) films were produced. Later, multi-component processing was explored by incorporating platinum (Pt) nanoparticles into the Al2O3 matrix leading to the production of Pt/Al 2O3 films by two routes: simultaneous precursor injection processing or by a layer-by-layer approach. In single component processing, the formation of nanoparticle aggregates was evident within the amorphous Al2O3 films. Aggregates, composed of these particles, are likely held together by relatively weak van der Waals forces leading to the observed poor physical cohesion. In multi-component processing, reasonable control of composition and distribution of species is possible with Pt nanoparticles appearing to be co-agglomerated with alumina. Deposited crystalline Pt nanoparticles may encourage the crystallization of the amorphous Al2O3. Finally, from chemisorption results, the produced sample appears to have potentially greater catalytic activity than a commercially available standard. A model is in development to study nanoparticle interactions with a gas and deposition occurring in stagnation flow onto the cooled horizontal substrate within the tubular reactor. Using velocity and temperature fields generated from numerical solutions to the Navier-Stokes and energy equations, particle trajectories were calculated from the summation of drag, gravitational, thermophoretic, and Brownian forces. In rectangular coordinates, cooling stage width to reactor diameter ratio, deposition stage temperature, and initial velocity were the primary parameters varied in this study. An optimum balance between thermophoretic and drag forces appears to be the key factor in obtaining high yield and surface uniformity in the films. The results also suggest that Brownian motion is not a significant contributor to deposition under conditions in this study.

Thin-film copper indium gallium selenide solar cell based on low-temperature all-printing process.

PubMed

Singh, Manjeet; Jiu, Jinting; Sugahara, Tohru; Suganuma, Katsuaki

2014-09-24

In the solar cell field, development of simple, low-cost, and low-temperature fabrication processes has become an important trend for energy-saving and environmental issues. Copper indium gallium selenide (CIGS) solar cells have attracted much attention due to the high absorption coefficient, tunable band gap energy, and high efficiency. However, vacuum and high-temperature processing in fabrication of solar cells have limited the applications. There is a strong need to develop simple and scalable methods. In this work, a CIGS solar cell based on all printing steps and low-temperature annealing is developed. CIGS absorber thin film is deposited by using dodecylamine-stabilized CIGS nanoparticle ink followed by printing buffer layer. Silver nanowire (AgNW) ink and sol-gel-derived ZnO precursor solution are used to prepare a highly conductive window layer ZnO/[AgNW/ZnO] electrode with a printing method that achieves 16 Ω/sq sheet resistance and 94% transparency. A CIGS solar cell based on all printing processes exhibits efficiency of 1.6% with open circuit voltage of 0.48 V, short circuit current density of 9.7 mA/cm(2), and fill factor of 0.34 for 200 nm thick CIGS film, fabricated under ambient conditions and annealed at 250 °C.

The Chemistry of Inorganic Precursors during the Chemical Deposition of Films on Solid Surfaces.

PubMed

Barry, Seán T; Teplyakov, Andrew V; Zaera, Francisco

2018-03-20

The deposition of thin solid films is central to many industrial applications, and chemical vapor deposition (CVD) methods are particularly useful for this task. For one, the isotropic nature of the adsorption of chemical species affords even coverages on surfaces with rough topographies, an increasingly common requirement in microelectronics. Furthermore, by splitting the overall film-depositing reactions into two or more complementary and self-limiting steps, as it is done in atomic layer depositions (ALD), film thicknesses can be controlled down to the sub-monolayer level. Thanks to the availability of a vast array of inorganic and metalorganic precursors, CVD and ALD are quite versatile and can be engineered to deposit virtually any type of solid material. On the negative side, the surface chemistry that takes place in these processes is often complex, and can include undesirable side reactions leading to the incorporation of impurities in the growing films. Appropriate precursors and deposition conditions need to be chosen to minimize these problems, and that requires a proper understanding of the underlying surface chemistry. The precursors for CVD and ALD are often designed and chosen based on their known thermal chemistry from inorganic chemistry studies, taking advantage of the vast knowledge developed in that field over the years. Although a good first approximation, however, this approach can lead to wrong choices, because the reactions of these precursors at gas-solid interfaces can be quite different from what is seen in solution. For one, solvents often aid in the displacement of ligands in metalorganic compounds, providing the right dielectric environment, temporarily coordinating to the metal, or facilitating multiple ligand-complex interactions to increase reaction probabilities; these options are not available in the gas-solid reactions associated with CVD and ALD. Moreover, solid surfaces act as unique "ligands", if these reactions are to be viewed from the point of view of the metalorganic complexes used as precursors: they are bulky and rigid, can provide multiple binding sites for a single reaction, and can promote unique bonding modes, especially on metals, which have delocalized electronic structures. The differences between the molecular and surface chemistry of CVD and ALD precursors can result in significant variations in their reactivity, ultimately leading to unpredictable properties in the newly grown films. In this Account, we discuss some of the main similarities and differences in chemistry that CVD/ALD precursors follow on surfaces when contrasted against their known behavior in solution, with emphasis on our own work but also referencing other key contributions. Our approach is unique in that it combines expertise from the inorganic, surface science, and quantum-mechanics fields to better understand the mechanistic details of the chemistry of CVD and ALD processes and to identify new criteria to consider when designing CVD/ALD precursors.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Metzler, Dominik; Li, Chen; Engelmann, Sebastian

The need for atomic layer etching (ALE) is steadily increasing as smaller critical dimensions and pitches are required in device patterning. A flux-control based cyclic Ar/C 4F 8 ALE based on steady-state Ar plasma in conjunction with periodic, precise C 4F 8 injection and synchronized plasma-based low energy Ar + ion bombardment has been established for SiO 2. 1 In this work, the cyclic process is further characterized and extended to ALE of silicon under similar process conditions. The use of CHF 3 as a precursor is examined and compared to C 4F 8. CHF 3 is shown to enablemore » selective SiO 2/Si etching using a fluorocarbon (FC) film build up. Other critical process parameters investigated are the FC film thickness deposited per cycle, the ion energy, and the etch step length. Etching behavior and mechanisms are studied using in situ real time ellipsometry and X-ray photoelectron spectroscopy. Silicon ALE shows less self-limitation than silicon oxide due to higher physical sputtering rates for the maximum ion energies used in this work, ranged from 20 to 30 eV. The surface chemistry is found to contain fluorinated silicon oxide during the etching of silicon. As a result, plasma parameters during ALE are studied using a Langmuir probe and establish the impact of precursor addition on plasma properties.« less

Methods for and products of processing nanostructure nitride, carbonitride and oxycarbonitride electrode power materials by utilizing sol gel technology for supercapacitor applications

DOEpatents

Huang, Yuhong; Wei, Oiang; Chu, Chung-tse; Zheng, Haixing

2001-01-01

Metal nitride, carbonitride, and oxycarbonitride powder with high surface area (up to 150 m.sup.2 /g) is prepared by using sol-gel process. The metal organic precursor, alkoxides or amides, is synthesized firstly. The metal organic precursor is modified by using unhydrolyzable organic ligands or templates. A wet gel is formed then by hydrolysis and condensation process. The solvent in the wet gel is then be removed supercritically to form porous amorphous hydroxide. This porous hydroxide materials is sintered to 725.degree. C. under the ammonia flow and porous nitride powder is formed. The other way to obtain high surface area nitride, carbonitride, and oxycarbonitride powder is to pyrolyze polymerized templated metal amides aerogel in an inert atmosphere. The electrochemical capacitors are prepared by using sol-gel prepared nitride, carbonitride, and oxycarbonitride powder. Two methods are used to assemble the capacitors. Electrode is formed either by pressing the mixture of nitride powder and binder to a foil, or by depositing electrode coating onto metal current collector. The binder or coating is converted into a continuous network of electrode material after thermal treatment to provide enhanced energy and power density. Liquid electrolyte is soaked into porous electrode. The electrochemical capacitor assembly further has a porous separator layer between two electrodes/electrolyte and forming a unit cell.

Optical devices featuring textured semiconductor layers

DOEpatents

Moustakas, Theodore D [Dover, MA; Cabalu, Jasper S [Cary, NC

2011-10-11

A semiconductor sensor, solar cell or emitter, or a precursor therefor, has a substrate and one or more textured semiconductor layers deposited onto the substrate. The textured layers enhance light extraction or absorption. Texturing in the region of multiple quantum wells greatly enhances internal quantum efficiency if the semiconductor is polar and the quantum wells are grown along the polar direction. Electroluminescence of LEDs of the invention is dichromatic, and results in variable color LEDs, including white LEDs, without the use of phosphor.

Optical devices featuring textured semiconductor layers

DOEpatents

Moustakas, Theodore D [Dover, MA; Cabalu, Jasper S [Cary, NC

2012-08-07

A semiconductor sensor, solar cell or emitter, or a precursor therefor, has a substrate and one or more textured semiconductor layers deposited onto the substrate. The textured layers enhance light extraction or absorption. Texturing in the region of multiple quantum wells greatly enhances internal quantum efficiency if the semiconductor is polar and the quantum wells are grown along the polar direction. Electroluminescence of LEDs of the invention is dichromatic, and results in variable color LEDs, including white LEDs, without the use of phosphor.

Supramolecular self-assembly of graphene oxide and metal nanoparticles into stacked multilayers by means of a multitasking protein ring.

PubMed

Ardini, Matteo; Golia, Giordana; Passaretti, Paolo; Cimini, Annamaria; Pitari, Giuseppina; Giansanti, Francesco; Di Leandro, Luana; Ottaviano, Luca; Perrozzi, Francesco; Santucci, Sandro; Morandi, Vittorio; Ortolani, Luca; Christian, Meganne; Treossi, Emanuele; Palermo, Vincenzo; Angelucci, Francesco; Ippoliti, Rodolfo

2016-03-28

Graphene oxide (GO) is rapidly emerging worldwide as a breakthrough precursor material for next-generation devices. However, this requires the transition of its two-dimensional layered structure into more accessible three-dimensional (3D) arrays. Peroxiredoxins (Prx) are a family of multitasking redox enzymes, self-assembling into ring-like architectures. Taking advantage of both their symmetric structure and function, 3D reduced GO-based composites are hereby built up. Results reveal that the "double-faced" Prx rings can adhere flat on single GO layers and partially reduce them by their sulfur-containing amino acids, driving their stacking into 3D multi-layer reduced GO-Prx composites. This process occurs in aqueous solution at a very low GO concentration, i.e. 0.2 mg ml(-1). Further, protein engineering allows the Prx ring to be enriched with metal binding sites inside its lumen. This feature is exploited to both capture presynthesized gold nanoparticles and grow in situ palladium nanoparticles paving the way to straightforward and "green" routes to 3D reduced GO-metal composite materials.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Jian; Krejci, Radovan; Giangrande, Scott

The nucleation of atmospheric vapours is an important source of new aerosol particles that can subsequently grow to form cloud condensation nuclei in the atmosphere. Most field studies of atmospheric aerosols over continents are influenced by atmospheric vapours of anthropogenic origin and, in consequence, aerosol processes in pristine, terrestrial environments remain poorly understood. The Amazon rainforest is one of the few continental regions where aerosol particles and their precursors can be studied under near-natural conditions, but the origin of small aerosol particles that grow into cloud condensation nuclei in the Amazon boundary layer remains unclear. Here we present aircraft- andmore » ground-based measurements under clean conditions during the wet season in the central Amazon basin. We find that high concentrations of small aerosol particles (with diameters of less than 50 nanometres) in the lower free troposphere are transported from the free troposphere into the boundary layer during precipitation events by strong convective downdrafts and weaker downward motions in the trailing stratiform region. Lastly, this rapid vertical transport can help to maintain the population of particles in the pristine Amazon boundary layer, and may therefore influence cloud properties and climate under natural conditions.« less

Selection of an anti-solvent for efficient and stable cesium-containing triple cation planar perovskite solar cells.

PubMed

Xiao, Meng; Zhao, Li; Geng, Min; Li, Yanyan; Dong, Binghai; Xu, Zuxun; Wan, Li; Li, Wenlu; Wang, Shimin

2018-06-19

The perovskite layer is a crucial component influencing high-performance perovskite solar cells (PSCs). In the one-step solution method, anti-solvents are important for obtaining smooth and uniform perovskite active layers. This work explored the effect of various anti-solvents on the preparation of triple cation perovskite active layers. In general, anti-solvents with low dielectric constants, low polarity, and low boiling point are suitable for the preparation of perovskite films. Microstructural and elemental analyses of the perovskite films were systematically conducted by scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The photoelectric properties, carrier transfer, and recombination process in the PSCs were investigated using photocurrent-voltage characteristic curves and electrochemical impedance spectroscopy. Optimum performance was obtained when the anti-solvent was diethyl ether (DEE) and the ratio of the optimum amount of DEE to the volume of the precursor was 1 : 10. Meanwhile, we found that the partial replacement of formamidinium/methylammonium by cesium could increase the stability of the PSCs and enhance the power conversion efficiency from 15.49% to over 17.38%.

Initial stage of atomic layer deposition of 2D-MoS2 on a SiO2 surface: a DFT study.

PubMed

Shirazi, M; Kessels, W M M; Bol, A A

2018-06-20

In this study, we investigate the reactions involving Atomic Layer Deposition (ALD) of 2D-MoS2 from the heteroleptic precursor Mo(NMe2)2(NtBu)2 and H2S as the co-reagent on a SiO2(0001) surface by means of density functional theory (DFT). All dominant reaction pathways from the early stage of adsorption of each ALD reagent to the formation of bulk-like Mo and S at the surface are identified. In the metal pulse, proton transfer from terminal OH groups on the SiO2 to the physisorbed metal precursor increases the Lewis acidity of Mo and Lewis basicity of O, which gives rise to the chemical adsorption of the metal precursor. Proton transfer from the surface to the dimethylamido ligands leads to the formation and desorption of dimethylamine. In contrast, the formation and desorption of tert-butylamine is not energetically favorable. The tert-butylimido ligand can only be partially protonated in the metal pulse. In the sulphur pulse, co-adsorption and dissociation of H2S molecules give rise to the formation and desorption of tert-butylamine. Through the calculated activation energies, the cooperation between H2S molecules ('cooperative' mechanism) is shown to have a profound influence on the formation and desorption of tert-butylamine, which are crucial steps in the initial ALD deposition of 2D-MoS2 on SiO2. The cyclic ALD reactions give rise to the formation of a buffer layer which might have important consequences for the electrical and optical properties on the 2D layer formed in the subsequent homodeposition.

Process for making silver metal filaments

DOEpatents

Bamberger, Carlos E.

1997-01-01

A process for making silver metal particles from silver salt particles having the same morphology. Precursor silver salt particles selected from the group consisting of silver acetate and silver sulfide having a selected morphology are contained in a reactor vessel having means for supporting the particles in an air suspension to prevent the agglomeration of the particles. Air is flowed through the reactor vessel at a flow rate sufficient to suspend the particles in the reactor vessel. The suspended precursor silver salt particles are heated to a processing temperature and at a heating rate below which the physical deterioration of the suspended precursor silver salt particles takes place. The suspended precursor silver salt particles are maintained at the processing temperature for a period of time sufficient to convert the particles into silver metal particles having the same morphology as the precursor silver salt particles.

Initial stages of growth and the influence of temperature during chemical vapor deposition of sp{sup 2}-BN films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chubarov, Mikhail; Pedersen, Henrik; Högberg, Hans

2015-11-15

Knowledge of the structural evolution of thin films, starting by the initial stages of growth, is important to control the quality and properties of the film. The authors present a study on the initial stages of growth and the temperature influence on the structural evolution of sp{sup 2} hybridized boron nitride (BN) thin films during chemical vapor deposition (CVD) with triethyl boron and ammonia as precursors. Nucleation of hexagonal BN (h-BN) occurs at 1200 °C on α-Al{sub 2}O{sub 3} with an AlN buffer layer (AlN/α-Al{sub 2}O{sub 3}). At 1500 °C, h-BN grows with a layer-by-layer growth mode on AlN/α-Al{sub 2}O{sub 3} upmore » to ∼4 nm after which the film structure changes to rhombohedral BN (r-BN). Then, r-BN growth proceeds with a mixed layer-by-layer and island growth mode. h-BN does not grow on 6H-SiC substrates; instead, r-BN nucleates and grows directly with a mixed layer-by-layer and island growth mode. These differences may be caused by differences in substrate surface temperature due to different thermal conductivities of the substrate materials. These results add to the understanding of the growth process of sp{sup 2}-BN employing CVD.« less

Optimization of formaldehyde concentration on electroless copper deposition on alumina surface

NASA Astrophysics Data System (ADS)

Shahidin, S. A. M.; Fadil, N. A.; Yusop, M. Zamri; Tamin, M. N.; Osman, S. A.

2018-05-01

The effect of formaldehyde concentration on electroless copper plating on alumina wafer was studied. The main composition of plating bath was copper sulphate (CuSO4) as precursor and formaldehyde as a reducing agent. The copper deposition films were assessed by varying the ratio of CuSO4 and formaldehyde. The plating rate was calculated from the weight gained after plating process whilst the surface morphology was observed by field emission scanning electron microscopy (FESEM). The results show that 1:3 ratio of copper to formaldehyde is an optimum ratio to produce most uniform coating with good adhesion between copper layer and alumina wafer substrate.

Electrodeposition of biaxially textured layers on a substrate

DOEpatents

Bhattacharya, Raghu N; Phok, Sovannary; Spagnol, Priscila; Chaudhuri, Tapas

2013-11-19

Methods of producing one or more biaxially textured layer on a substrate, and articles produced by the methods, are disclosed. An exemplary method may comprise electrodepositing on the substrate a precursor material selected from the group consisting of rare earths, transition metals, actinide, lanthanides, and oxides thereof. An exemplary article (150) may comprise a biaxially textured base material (130), and at least one biaxially textured layer (110) selected from the group consisting of rare earths, transition metals, actinides, lanthanides, and oxides thereof. The at least one biaxially textured layer (110) is formed by electrodeposition on the biaxially textured base material (130).

Catalyst containing oxygen transport membrane

DOEpatents

Lane, Jonathan A.; Wilson, Jamie R.; Christie, Gervase Maxwell; Petigny, Nathalie; Sarantopoulos, Christos

2017-02-07

A composite oxygen transport membrane having a dense layer, a porous support layer and an intermediate porous layer located between the dense layer and the porous support layer. Both the dense layer and the intermediate porous layer are formed from an ionic conductive material to conduct oxygen ions and an electrically conductive material to conduct electrons. The porous support layer has a high permeability, high porosity, and a microstructure exhibiting substantially uniform pore size distribution as a result of using PMMA pore forming materials or a bi-modal particle size distribution of the porous support layer materials. Catalyst particles selected to promote oxidation of a combustible substance are located in the intermediate porous layer and in the porous support adjacent to the intermediate porous layer. The catalyst particles can be formed by wicking a solution of catalyst precursors through the porous support toward the intermediate porous layer.

Low-temperature liquid precursors of crystalline metal oxides assisted by heterogeneous photocatalysis.

PubMed

Bretos, Iñigo; Jiménez, Ricardo; Pérez-Mezcua, Dulce; Salazar, Norberto; Ricote, Jesús; Calzada, M Lourdes

2015-04-24

The photocatalytically assisted decomposition of liquid precursors of metal oxides incorporating TiO2 particles enables the preparation of functional layers from the ferroelectric Pb(Zr,Ti)O3 and multiferroic BiFeO3 perovskite systems at temperatures not exceeding 350 ºC. This enables direct deposition on flexible plastic, where the multifunctionality provided by these complex-oxide materials guarantees their potential use in next-generation flexible electronics. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Transition Metal Dichalcogenide Growth via Close Proximity Precursor Supply

NASA Astrophysics Data System (ADS)

O'Brien, Maria; McEvoy, Niall; Hallam, Toby; Kim, Hye-Young; Berner, Nina C.; Hanlon, Damien; Lee, Kangho; Coleman, Jonathan N.; Duesberg, Georg S.

2014-12-01

Reliable chemical vapour deposition (CVD) of transition metal dichalcogenides (TMDs) is currently a highly pressing research field, as numerous potential applications rely on the production of high quality films on a macroscopic scale. Here, we show the use of liquid phase exfoliated nanosheets and patterned sputter deposited layers as solid precursors for chemical vapour deposition. TMD monolayers were realized using a close proximity precursor supply in a CVD microreactor setup. A model describing the growth mechanism, which is capable of producing TMD monolayers on arbitrary substrates, is presented. Raman spectroscopy, photoluminescence, X-ray photoelectron spectroscopy, atomic force microscopy, transmission electron microscopy, scanning electron microscopy and electrical transport measurements reveal the high quality of the TMD samples produced. Furthermore, through patterning of the precursor supply, we achieve patterned growth of monolayer TMDs in defined locations, which could be adapted for the facile production of electronic device components.

Nanoscale Transforming Mineral Phases in Fresh Nacre.

PubMed

DeVol, Ross T; Sun, Chang-Yu; Marcus, Matthew A; Coppersmith, Susan N; Myneni, Satish C B; Gilbert, Pupa U P A

2015-10-21

Nacre, or mother-of-pearl, the iridescent inner layer of many mollusk shells, is a biomineral lamellar composite of aragonite (CaCO3) and organic sheets. Biomineralization frequently occurs via transient amorphous precursor phases, crystallizing into the final stable biomineral. In nacre, despite extensive attempts, amorphous calcium carbonate (ACC) precursors have remained elusive. They were inferred from non-nacre-forming larval shells, or from a residue of amorphous material surrounding mature gastropod nacre tablets, and have only once been observed in bivalve nacre. Here we present the first direct observation of ACC precursors to nacre formation, obtained from the growth front of nacre in gastropod shells from red abalone (Haliotis rufescens), using synchrotron spectromicroscopy. Surprisingly, the abalone nacre data show the same ACC phases that are precursors to calcite (CaCO3) formation in sea urchin spicules, and not proto-aragonite or poorly crystalline aragonite (pAra), as expected for aragonitic nacre. In contrast, we find pAra in coral.

DOE Office of Scientific and Technical Information (OSTI.GOV)

DeVol, Ross T.; Sun, Chang-Yu; Marcus, Matthew A.

Nacre, or mother-of-pearl, the iridescent inner layer of many mollusk shells, is a biomineral lamellar composite of aragonite (CaCO 3) and organic sheets. Biomineralization frequently occurs via transient amorphous precursor phases, crystallizing into the final stable biomineral. In nacre, despite extensive attempts, amorphous calcium carbonate (ACC) precursors have remained elusive. They were inferred from non-nacre-forming larval shells, or from a residue of amorphous material surrounding mature gastropod nacre tablets, and have only once been observed in bivalve nacre. Here we present the first direct observation of ACC precursors to nacre formation, obtained from the growth front of nacre in gastropodmore » shells from red abalone (Haliotis rufescens), using synchrotron spectromicroscopy. Surprisingly, the abalone nacre data show the same ACC phases that are precursors to calcite (CaCO 3) formation in sea urchin spicules, and not proto-aragonite or poorly crystalline aragonite (pAra), as expected for aragonitic nacre. In contrast, we find pAra in coral.« less

Semi-automatic spray pyrolysis deposition of thin, transparent, titania films as blocking layers for dye-sensitized and perovskite solar cells.

PubMed

Krýsová, Hana; Krýsa, Josef; Kavan, Ladislav

2018-01-01

For proper function of the negative electrode of dye-sensitized and perovskite solar cells, the deposition of a nonporous blocking film is required on the surface of F-doped SnO 2 (FTO) glass substrates. Such a blocking film can minimise undesirable parasitic processes, for example, the back reaction of photoinjected electrons with the oxidized form of the redox mediator or with the hole-transporting medium can be avoided. In the present work, thin, transparent, blocking TiO 2 films are prepared by semi-automatic spray pyrolysis of precursors consisting of titanium diisopropoxide bis(acetylacetonate) as the main component. The variation in the layer thickness of the sprayed films is achieved by varying the number of spray cycles. The parameters investigated in this work were deposition temperature (150, 300 and 450 °C), number of spray cycles (20-200), precursor composition (with/without deliberately added acetylacetone), concentration (0.05 and 0.2 M) and subsequent post-calcination at 500 °C. The photo-electrochemical properties were evaluated in aqueous electrolyte solution under UV irradiation. The blocking properties were tested by cyclic voltammetry with a model redox probe with a simple one-electron-transfer reaction. Semi-automatic spraying resulted in the formation of transparent, homogeneous, TiO 2 films, and the technique allows for easy upscaling to large electrode areas. The deposition temperature of 450 °C was necessary for the fabrication of highly photoactive TiO 2 films. The blocking properties of the as-deposited TiO 2 films (at 450 °C) were impaired by post-calcination at 500 °C, but this problem could be addressed by increasing the number of spray cycles. The modification of the precursor by adding acetylacetone resulted in the fabrication of TiO 2 films exhibiting perfect blocking properties that were not influenced by post-calcination. These results will surely find use in the fabrication of large-scale dye-sensitized and perovskite solar cells.

Precursor preparation for Ca-Al layered double hydroxide to remove hexavalent chromium coexisting with calcium and magnesium chlorides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhong, Lihua; He, Xiaoman; Qu, Jun

Al(OH){sub 3} and Ca(OH){sub 2} powders are co-ground to prepare a precursor which hydrates into a layered double hydroxide (LDH) phase by agitation in aqueous solution with target hexavalent chromium (Cr(VI)) at room temperature, to achieve an obvious improvement in removal efficiency of Cr(VI) through an easy incorporation into the structure. Although the prepared precursor transforms into LDH phases also when agitated in the solutions of calcium and magnesium chlorides, it incorporates Cr(VI) preferentially to the chloride salts when they coexist. The adsorption isotherm and kinetic studies show that the phenomena occurring on the Al-Ca precursor fit a pseudo-second-order kineticsmore » with a Langmuir adsorption capacity of 59.45 mg/g. Besides, characterizations of the prepared precursor and the samples after adsorption are also performed by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Transmission electron microscope (TEM) to understand the reason of the preferential incorporation of Cr(VI) to the coexisting chloride salts during the LDH phase formation. - Graphical abstract: Activated Ca-Al hydroxides (C{sub 3}A) transformed into Ca-Al-OH compound when agitated in water. Ca-Al precursor (C{sub 3}A) was agitated in a hexavalent chromium (Cr(VI)) solution to form Al-Ca-CrO{sub 4} LDH product. Ca-Al-CrO{sub 4} LDH phase occurred preferentially to Ca-Al-MCl{sub 2} LDH phases in the solutions of calcium and magnesium chlorides, it incorporates Cr(VI) preferentially to the chloride salts when they coexist. - Highlights: • Activated Ca-Al hydroxides transformed into LDH when agitated in water with some inorganic substances. • Hexavalent Cr was incorporated in the LDH structure at high adsorption capacity. • Ca-Al-Cr LDH phase occurred preferentially to Ca-Al-MCl{sub 2} LDH phases with coexistence. • The prepared Ca-Al hydroxides had high performance as adsorbent even with high salinity of the solution.« less

Enabling Desktop Nanofabrication with the Targeted Use of Soft Materials

NASA Astrophysics Data System (ADS)

Eichelsdoerfer, Daniel James

This thesis focuses on the application of soft materials to scanning probe-based molecular printing techniques, such as dip-pen nanolithography (DPN). The selective incorporation of soft materials in place of hard materials in traditional cantilever-based scanning probe lithography (SPL) systems not only enables the deposition of a broader range of materials, but also dramatically lowers the cost while simultaneously increasing the throughput of SPL. Chapter 1 introduces SPL and DPN, and highlights a few recent advances in using DPN to control surface chemical functionality at the nanoscale. In addition to introducing the material deposition capabilities of DPN, Chapter 1 introduces the development of the cantilever-free architecture, a relatively recent paradigm shift in high-throughput SPL. Furthermore, an in-depth synthetic methodology for making the most widely used cantilever-free tip arrays, consisting of elastomeric nanoscale pens adhered to an elastomeric backing layer on a glass slide, is included as an appendix. Chapter 2 discusses the synthesis of metal and metal oxide nanoparticles at specified locations by using DPN to deposit the precursors dispersed in a polymer matrix; after deposition, the precursors are annealed to form single nanoparticles. This work builds on previous soft material-based advances in DPN by utilizing the polymer as a "nanoreactor" to synthesize the desired nanoparticles, where the precursors can diffuse and coalesce into a single nanoparticle within each spot. The process of precursor aggregation and single nanoparticle formation is studied, and it is found that metal precursors follow one of three pathways based upon their reduction potential. Chapter 3 is the first of three chapters that highlights the power of soft materials in the cantilever-free architecture. In particular, Chapter 3 examines the role of the elastomeric backing layer as a compliant spring whose stiffness (as measured by the spring constant, k) can be tuned with a simple chemical change to the composition of the elastomer. In particular, the extent of cross-linking within the elastomer is found to dictate the k the backing layer, and arrays with spring constants tuned from 7 to 150 N/m are described. Furthermore, a simple geometric model is developed that explains the low variation of k within each cantilever-free array; this stands in contrast to arrays of cantilevers, which typically show large variations of k within an array. Chapter 4 addresses the problem of individual actuation in SPL by embedding resistive heaters directly beneath the elastomeric backing layer. This actuation scheme was chosen because the elastomer used in the cantilever-free tip arrays has extraordinary thermal expansion properties, and thorough exploration of their actuation behavior shows that the heater arrays are fast (> 100 microm/s) and powerful (> 4 microm) enough for actuation. After implementing several corrections for the tip height -- a problem that is intractable without the heaters, and has never been addressed before -- printing of alkanethiols onto Au is demonstrated with a 2D array of individually actuated probes. Chapter 5 examines the hypothesis that elastomeric tips can absorb solvent and be used to transport materials in the absence of environmental solvent. This is evaluated by first using tip arrays soaked in a nonpolar solvent to pattern a hydrophobic block copolymer that cannot be patterned by traditional DPN, and is subsequently explored for the case of water uptake into the pen arrays. Surprisingly, despite their poor water retention ability, the tip arrays can store enough water to pattern hydrophilic polymers in dry environments for over 2 hours. The dynamics of the solvent absorption are captured by a simple calculation that accounts for the dynamical behavior of water retention and the backing layer thickness, thereby allowing these results to be generalized to other solvents. This exploration of the subtle and dynamic role of absorbed solvent in cantilever-free pen arrays shows that proper pre-treatment of the arrays can be used to obviate the need for an environmental chamber in molecular printing. (Abstract shortened by UMI.)

Microwave assisted synthesis and characterisation of a zinc oxide/tobacco mosaic virus hybrid material. An active hybrid semiconductor in a field-effect transistor device.

PubMed

Sanctis, Shawn; Hoffmann, Rudolf C; Eiben, Sabine; Schneider, Jörg J

2015-01-01

Tobacco mosaic virus (TMV) has been employed as a robust functional template for the fabrication of a TMV/zinc oxide field effect transistor (FET). A microwave based approach, under mild conditions was employed to synthesize stable zinc oxide (ZnO) nanoparticles, employing a molecular precursor. Insightful studies of the decomposition of the precursor were done using NMR spectroscopy and material characterization of the hybrid material derived from the decomposition was achieved using dynamic light scattering (DLS), transmission electron microscopy (TEM), grazing incidence X-ray diffractometry (GI-XRD) and atomic force microscopy (AFM). TEM and DLS data confirm the formation of crystalline ZnO nanoparticles tethered on top of the virus template. GI-XRD investigations exhibit an orientated nature of the deposited ZnO film along the c-axis. FET devices fabricated using the zinc oxide mineralized virus template material demonstrates an operational transistor performance which was achieved without any high-temperature post-processing steps. Moreover, a further improvement in FET performance was observed by adjusting an optimal layer thickness of the deposited ZnO on top of the TMV. Such a bio-inorganic nanocomposite semiconductor material accessible using a mild and straightforward microwave processing technique could open up new future avenues within the field of bio-electronics.

Characteristics of zinc oxide nanorod array/titanium oxide film heterojunction prepared by aqueous solution deposition

NASA Astrophysics Data System (ADS)

Lee, Ming-Kwei; Hong, Min-Hsuan; Li, Bo-Wei

2016-07-01

The characteristics of a ZnO nanorod array/TiO2 film heterojunction were investigated. A TiO2 film was prepared on glass by aqueous solution deposition with precursors of ammonium hexafluorotitanate and boric acid at 40 °C. Then, a ZnO seed layer was prepared on a TiO2 film/glass substrate by RF sputtering. A vertically oriented ZnO nanorod array was grown on a ZnO seed layer/TiO2 film/glass substrate by aqueous solution deposition with precursors of zinc nitrate and hexamethylenetetramine (HMT) at 70 °C. After thermal annealing in N2O ambient at 300 °C, this heterojunction used as an oxygen gas sensor shows much better rise time, decay time, and on/off current ratio than as-grown and annealed ZnO nanorods.

Msx genes define a population of mural cell precursors required for head blood vessel maturation.

PubMed

Lopes, Miguel; Goupille, Olivier; Saint Cloment, Cécile; Lallemand, Yvan; Cumano, Ana; Robert, Benoît

2011-07-01

Vessels are primarily formed from an inner endothelial layer that is secondarily covered by mural cells, namely vascular smooth muscle cells (VSMCs) in arteries and veins and pericytes in capillaries and veinules. We previously showed that, in the mouse embryo, Msx1(lacZ) and Msx2(lacZ) are expressed in mural cells and in a few endothelial cells. To unravel the role of Msx genes in vascular development, we have inactivated the two Msx genes specifically in mural cells by combining the Msx1(lacZ), Msx2(lox) and Sm22α-Cre alleles. Optical projection tomography demonstrated abnormal branching of the cephalic vessels in E11.5 mutant embryos. The carotid and vertebral arteries showed an increase in caliber that was related to reduced vascular smooth muscle coverage. Taking advantage of a newly constructed Msx1(CreERT2) allele, we demonstrated by lineage tracing that the primary defect lies in a population of VSMC precursors. The abnormal phenotype that ensues is a consequence of impaired BMP signaling in the VSMC precursors that leads to downregulation of the metalloprotease 2 (Mmp2) and Mmp9 genes, which are essential for cell migration and integration into the mural layer. Improper coverage by VSMCs secondarily leads to incomplete maturation of the endothelial layer. Our results demonstrate that both Msx1 and Msx2 are required for the recruitment of a population of neural crest-derived VSMCs.

Fabrication and characterization of novel multilayered structures by stereocomplexion of poly(D-lactic acid)/poly(L-lactic acid) and self-assembly of polyelectrolytes.

PubMed

Dellacasa, Elena; Zhao, Li; Yang, Gesheng; Pastorino, Laura; Sukhorukov, Gleb B

2016-01-01

The enantiomers poly(D-lactic acid) (PDLA) and poly(L-lactic acid) (PLLA) were alternately adsorbed directly on calcium carbonate (CaCO3) templates and on poly(styrene sulfonate) (PSS) and poly(allylamine hydrochloride) (PAH) multilayer precursors in order to fabricate a novel layer-by-layer (LBL) assembly. A single layer of poly(L-lysine) (PLL) was used as a linker between the (PDLA/PLLA) n stereocomplex and the cores with and without the polymeric (PSS/PAH) n /PLL multilayer precursor (PEM). Nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC) were used to characterize the chemical composition and molecular weight of poly(lactic acid) polymers. Both multilayer structures, with and without polymeric precursor, were firstly fabricated and characterized on planar supports. A quartz crystal microbalance (QCM), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and ellipsometry were used to evaluate the thickness and mass of the multilayers. Then, hollow, spherical microcapsules were obtained by the removal of the CaCO3 sacrificial template. The chemical composition of the obtained microcapsules was confirmed by differential scanning calorimetry (DSC) and wide X-ray diffraction (WXRD) analyses. The microcapsule morphology was evaluated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) measurements. The experimental results confirm the successful fabrication of this innovative system, and its full biocompatibility makes it worthy of further characterization as a promising drug carrier for sustained release.

Fabrication and characterization of novel multilayered structures by stereocomplexion of poly(D-lactic acid)/poly(L-lactic acid) and self-assembly of polyelectrolytes

PubMed Central

Yang, Gesheng; Pastorino, Laura

2016-01-01

Summary The enantiomers poly(D-lactic acid) (PDLA) and poly(L-lactic acid) (PLLA) were alternately adsorbed directly on calcium carbonate (CaCO3) templates and on poly(styrene sulfonate) (PSS) and poly(allylamine hydrochloride) (PAH) multilayer precursors in order to fabricate a novel layer-by-layer (LBL) assembly. A single layer of poly(L-lysine) (PLL) was used as a linker between the (PDLA/PLLA)n stereocomplex and the cores with and without the polymeric (PSS/PAH)n/PLL multilayer precursor (PEM). Nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC) were used to characterize the chemical composition and molecular weight of poly(lactic acid) polymers. Both multilayer structures, with and without polymeric precursor, were firstly fabricated and characterized on planar supports. A quartz crystal microbalance (QCM), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and ellipsometry were used to evaluate the thickness and mass of the multilayers. Then, hollow, spherical microcapsules were obtained by the removal of the CaCO3 sacrificial template. The chemical composition of the obtained microcapsules was confirmed by differential scanning calorimetry (DSC) and wide X-ray diffraction (WXRD) analyses. The microcapsule morphology was evaluated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) measurements. The experimental results confirm the successful fabrication of this innovative system, and its full biocompatibility makes it worthy of further characterization as a promising drug carrier for sustained release. PMID:26925356

Low temperature thin films formed from nanocrystal precursors

DOEpatents

Alivisatos, A. Paul; Goldstein, Avery N.

1993-01-01

Nanocrystals of semiconductor compounds are produced. When they are applied as a contiguous layer onto a substrate and heated they fuse into a continuous layer at temperatures as much as 250, 500, 750 or even 1000.degree. K below their bulk melting point. This allows continuous semiconductor films in the 0.25 to 25 nm thickness range to be formed with minimal thermal exposure.

Low temperature thin films formed from nanocrystal precursors

DOEpatents

Alivisatos, A.P.; Goldstein, A.N.

1993-11-16

Nanocrystals of semiconductor compounds are produced. When they are applied as a contiguous layer onto a substrate and heated they fuse into a continuous layer at temperatures as much as 250, 500, 750 or even 1000 K below their bulk melting point. This allows continuous semiconductor films in the 0.25 to 25 nm thickness range to be formed with minimal thermal exposure. 9 figures.

Fabrication and Properties of Carbon Fibers

PubMed Central

Huang, Xiaosong

2009-01-01

This paper reviews the research and development activities conducted over the past few decades on carbon fibers. The two most important precursors in the carbon fiber industry are polyacrylonitrile (PAN) and mesophase pitch (MP). The structure and composition of the precursor affect the properties of the resultant carbon fibers significantly. Although the essential processes for carbon fiber production are similar, different precursors require different processing conditions in order to achieve improved performance. The research efforts on process optimization are discussed in this review. The review also attempts to cover the research on other precursor materials developed mainly for the purpose of cost reduction.

Effect of Precursors on Key Opto-electrical Properties of Successive Ion Layer Adsorption and Reaction-Prepared Al:ZnO Thin Films

NASA Astrophysics Data System (ADS)

Kumar, K. Deva Arun; Valanarasu, S.; Ganesh, V.; Shkir, Mohd.; Kathalingam, A.; AlFaify, S.

2018-02-01

Aluminum-doped zinc oxide (Al:ZnO) thin films were deposited on glass substrates by successive ion layer adsorption and reaction (SILAR) method using different precursors. This inexpensive SILAR method involves dipping of substrate sequentially in zinc solution, de-ionized water and ethylene glycol in multiple cycles. Prepared films were investigated by x-ray diffraction (XRD), scanning electron microscope (SEM), atomic force microscope (AFM), optical absorption, photoluminescence (PL), Raman spectroscopy and electrical studies. XRD study confirmed incorporation of aluminum in ZnO lattice with a polycrystalline hexagonal wurtzite structure of the films. The crystallite size determined by the Scherrer equation showed an increase from 28 nm to 35 nm for samples S1 to S4, respectively. SEM study showed smooth morphology with homogeneous distribution of particles. From the AFM images, the surface roughness was found to change according to precursors. For the optical analysis, the zinc chloride precursor showed high optical transmittance of about 90% in the visible range with a band gap value 3.15 eV. The room-temperature PL spectra exhibited a stronger violet emission peak at 420 nm for all the prepared samples. The Raman spectra showed a peak around 435 cm-1 which could be assigned to non-polar optical phonons (E2-high) mode AZO films of a ZnO wurtzite structure. Hall effect measurements showed n-type conductivity with low resistivity ( ρ) and high carrier concentrations ( n) of 2.39 × 10-3 Ω-cm and 8.96 × 1020 cm-3, respectively, for the film deposited using zinc chloride as precursor. The above properties make the prepared AZO film to be regarded as a very promising electrode material for fabrication of optoelectronic devices.

Obtaining a Low and Wide Atomic Layer Deposition Window (150-275 °C) for In2 O3 Films Using an InIII Amidinate and H2 O.

PubMed

Kim, Sang Bok; Jayaraman, Ashwin; Chua, Danny; Davis, Luke M; Zheng, Shao-Liang; Zhao, Xizhu; Lee, Sunghwan; Gordon, Roy G

2018-06-05

Indium oxide is a major component of many technologically important thin films, most notably the transparent conductor indium tin oxide (ITO). Despite being pyrophoric, homoleptic indium(III) alkyls do not allow atomic layer deposition (ALD) of In 2 O 3 using water as a co-precursor at substrate temperatures below 200 °C. Several alternative indium sources have been developed, but none allows ALD at lower temperatures except in the presence of oxidants such as O 2 or O 3 , which are not compatible with some substrates or alloying processes. We have synthesized a new indium precursor, tris(N,N'-diisopropylformamidinato)indium(III), compound 1, which allows ALD of pure, carbon-free In 2 O 3 films using H 2 O as the only co-reactant, on substrates in the temperature range 150-275 °C. In contrast, replacing just the H of the anionic iPrNC(H)NiPr ligand with a methyl group (affording the known tris(N,N'-diisopropylacetamidinato)indium(III), compound 2) results in a considerably higher and narrower ALD window in the analogous reaction with H 2 O (225-300 °C). Kinetic studies demonstrate that a higher rate of surface reactions in both parts of the ALD cycle gives rise to this difference in the ALD windows. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

DDR-type zeolite membrane synthesis, modification and gas permeation studies

DOE PAGES

Yang, Shaowei; Cao, Zishu; Arvanitis, Antonios; ...

2016-01-22

DDR-type zeolite membrane was synthesized on porous α-alumina substrate by hydrothermal treatment of a ball-milled Sigmal-1 crystal seed layer in an aluminum-free precursor solution containing 1-Adamantylamine as the structure directing agent (SDA). The as-synthesized DDR zeolite membranes were defect-free but the supported zeolite layers were susceptible to crack development during the subsequent high-temperature SDA removal process. The cracks were effectively eliminated by the liquid phase chemical deposition method using tetramethoxysilane as the precursor for silica deposits. The modified membrane was extensively studied for H 2, He, O 2, N 2, CO 2, CH 4, and i-C 4H 10 pure gasmore » permeation and CO 2/CH 4 mixture separation. At 297 K and 2-bar feed gas pressure, the membrane achieved a CO 2/CH 4 separation factor of ~92 for a feed containing 90% CO 2, which decreased to 62 for a feed containing 10% CO 2 with the CO 2 permeance virtually unchanged at ~1.8×10 –7 mol/m• sup>2 s • Pa regardless of the feed composition. It also exhibited an O 2/N 2 permselectivity of 1.8 at 297 K. Furthermore, the gas permeation behaviors of the current aluminum-containing DDR type zeolite membrane are generally in good agreement with the findings in both experimental and theoretical studies on the pure-silica DDR membranes in recent literature.« less

Reduction of nitrogen compounds in oceanic basement and its implications for HCN formation and abiotic organic synthesis

PubMed Central

2009-01-01

Hydrogen cyanide is an excellent organic reagent and is central to most of the reaction pathways leading to abiotic formation of simple organic compounds containing nitrogen, such as amino acids, purines and pyrimidines. Reduced carbon and nitrogen precursor compounds for the synthesis of HCN may be formed under off-axis hydrothermal conditions in oceanic lithosphere in the presence of native Fe and Ni and are adsorbed on authigenic layer silicates and zeolites. The native metals as well as the molecular hydrogen reducing CO2 to CO/CH4 and NO3-/NO2- to NH3/NH4+ are a result of serpentinization of mafic rocks. Oceanic plates are conveyor belts of reduced carbon and nitrogen compounds from the off-axis hydrothermal environments to the subduction zones, where compaction, dehydration, desiccation and diagenetic reactions affect the organic precursors. CO/CH4 and NH3/NH4+ in fluids distilled out of layer silicates and zeolites in the subducting plate at an early stage of subduction will react upon heating and form HCN, which is then available for further organic reactions to, for instance, carbohydrates, nucleosides or even nucleotides, under alkaline conditions in hydrated mantle rocks of the overriding plate. Convergent margins in the initial phase of subduction must, therefore, be considered the most potent sites for prebiotic reactions on Earth. This means that origin of life processes are, perhaps, only possible on planets where some kind of plate tectonics occur. PMID:19849830

Reduction of nitrogen compounds in oceanic basement and its implications for HCN formation and abiotic organic synthesis.

PubMed

Holm, Nils G; Neubeck, Anna

2009-10-22

Hydrogen cyanide is an excellent organic reagent and is central to most of the reaction pathways leading to abiotic formation of simple organic compounds containing nitrogen, such as amino acids, purines and pyrimidines. Reduced carbon and nitrogen precursor compounds for the synthesis of HCN may be formed under off-axis hydrothermal conditions in oceanic lithosphere in the presence of native Fe and Ni and are adsorbed on authigenic layer silicates and zeolites. The native metals as well as the molecular hydrogen reducing CO2 to CO/CH4 and NO3-/NO2- to NH3/NH4+ are a result of serpentinization of mafic rocks. Oceanic plates are conveyor belts of reduced carbon and nitrogen compounds from the off-axis hydrothermal environments to the subduction zones, where compaction, dehydration, desiccation and diagenetic reactions affect the organic precursors. CO/CH4 and NH3/NH4+ in fluids distilled out of layer silicates and zeolites in the subducting plate at an early stage of subduction will react upon heating and form HCN, which is then available for further organic reactions to, for instance, carbohydrates, nucleosides or even nucleotides, under alkaline conditions in hydrated mantle rocks of the overriding plate. Convergent margins in the initial phase of subduction must, therefore, be considered the most potent sites for prebiotic reactions on Earth. This means that origin of life processes are, perhaps, only possible on planets where some kind of plate tectonics occur.

Pyrolytic synthesis and characterization of N-doped carbon nanoflakes for electrochemical applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Savilov, S.V., E-mail: savilov@chem.msu.ru; N.S. Kurnakov Institute of General and Inorganic Chemistry Of Russian Academy of Sciences, Leninsky avenue, 31, Moscow 119991; Arkhipova, E.A.

2015-09-15

Highlights: • Carbon nanoflakes doped with nitrogen were produced by a pyrolytic technique. • Quarternary, pyrrolic and pyridinic types of nitrogen are confirmed by XPS. • Nitrogen content depends on precursor used and temperature processed. • Specific surface area values decrease with increasing of synthesis duration. • N-doped carbon nanoflakes may be suitable for electrochemical applications. - Abstract: Nitrogen doped carbon nanoflakes, which are very important for many electrochemical applications, were synthesized by pyrolysis of nitrogen containing organic compounds over metal oxide template. Acetonitrile, pyridine and butylamine, which are of different volatility were tested as N-containing precursors. Morphology, structure andmore » chemical composition of the as-synthesized materials were investigated by scanning electron microscopy (SEM), high resolution transmission electron microscopy (TEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). It was found that materials are highly defective and consist of a few malformed graphene layers. X-ray photoelectron spectra reflect the dominant graphitic and pyridinic N-bonding configuration. It was also noted that specific surface area depends on the duration and temperature of the reaction. Increase in duration and temperature led to decrease of the specific surface area from 1000 to 160 m{sup 2}/g, 1170 to 210 m{sup 2}/g and 1180 to 480 m{sup 2}/g for acetonitrile, butylamine and pyridine precursors, respectively.« less

Low temperature stabilization process for production of carbon fiber having structural order

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rios, Orlando; McGuire, Michael Alan; More, Karren Leslie

A method for producing a carbon fiber, the method comprising: (i) subjecting a continuous carbon fiber precursor having a polymeric matrix in which strength-enhancing particles are incorporated to a stabilization process during which the carbon fiber precursor is heated to within a temperature range ranging from the glass transition temperature to no less than 20.degree. C. below the glass transition temperature of the polymeric matrix, wherein the maximum temperature employed in the stabilization process is below 400.degree. C., for a processing time within said temperature range of at least 1 hour in the presence of oxygen and in the presencemore » of a magnetic field of at least 1 Tesla, while said carbon fiber precursor is held under an applied axial tension; and (ii) subjecting the stabilized carbon fiber precursor, following step (i), to a carbonization process. The stabilized carbon fiber precursor, resulting carbon fiber, and articles made thereof are also described.« less

Synthesis of Monolayer MoS2 by Chemical Vapor Deposition

NASA Astrophysics Data System (ADS)

Withanage, Sajeevi; Lopez, Mike; Dumas, Kenneth; Jung, Yeonwoong; Khondaker, Saiful

Finite and layer-tunable band gap of transition metal dichalcogenides (TMDs) including molybdenum disulfide (MoS2) are highlighted over the zero band gap graphene in various semiconductor applications. Weak interlayer Van der Waal bonding of bulk MoS2 allows to cleave few to single layer MoS2 using top-down methods such as mechanical and chemical exfoliation, however few micron size of these flakes limit MoS2 applications to fundamental research. Bottom-up approaches including the sulfurization of molybdenum (Mo) thin films and co-evaporation of Mo and sulfur precursors received the attention due to their potential to synthesize large area. We synthesized monolayer MoS2 on Si/SiO2 substrates by atmospheric pressure Chemical Vapor Deposition (CVD) methods using sulfur and molybdenum trioxide (MoO3) as precursors. Several growth conditions were tested including precursor amounts, growth temperature, growth time and flow rate. Raman, photoluminescence (PL) and atomic force microscopy (AFM) confirmed monolayer islands merging to create large area were observed with grain sizes up to 70 μm without using any seeds or seeding promoters. These studies provide in-depth knowledge to synthesize high quality large area MoS2 for prospective electronics applications.

Quality Control Pathways for Nucleus-Encoded Eukaryotic tRNA Biosynthesis and Subcellular Trafficking

PubMed Central

Huang, Hsiao-Yun

2015-01-01

tRNAs perform an essential role in translating the genetic code. They are long-lived RNAs that are generated via numerous posttranscriptional steps. Eukaryotic cells have evolved numerous layers of quality control mechanisms to ensure that the tRNAs are appropriately structured, processed, and modified. We describe the known tRNA quality control processes that check tRNAs and correct or destroy aberrant tRNAs. These mechanisms employ two types of exonucleases, CCA end addition, tRNA nuclear aminoacylation, and tRNA subcellular traffic. We arrange these processes in order of the steps that occur from generation of precursor tRNAs by RNA polymerase (Pol) III transcription to end maturation and modification in the nucleus to splicing and additional modifications in the cytoplasm. Finally, we discuss the tRNA retrograde pathway, which allows tRNA reimport into the nucleus for degradation or repair. PMID:25848089

Forming high efficiency silicon solar cells using density-graded anti-reflection surfaces

DOEpatents

Yuan, Hao-Chih; Branz, Howard M.; Page, Matthew R.

2014-09-09

A method (50) is provided for processing a graded-density AR silicon surface (14) to provide effective surface passivation. The method (50) includes positioning a substrate or wafer (12) with a silicon surface (14) in a reaction or processing chamber (42). The silicon surface (14) has been processed (52) to be an AR surface with a density gradient or region of black silicon. The method (50) continues with heating (54) the chamber (42) to a high temperature for both doping and surface passivation. The method (50) includes forming (58), with a dopant-containing precursor in contact with the silicon surface (14) of the substrate (12), an emitter junction (16) proximate to the silicon surface (14) by doping the substrate (12). The method (50) further includes, while the chamber is maintained at the high or raised temperature, forming (62) a passivation layer (19) on the graded-density silicon anti-reflection surface (14).

Forming high-efficiency silicon solar cells using density-graded anti-reflection surfaces

DOEpatents

Yuan, Hao-Chih; Branz, Howard M.; Page, Matthew R.

2015-07-07

A method (50) is provided for processing a graded-density AR silicon surface (14) to provide effective surface passivation. The method (50) includes positioning a substrate or wafer (12) with a silicon surface (14) in a reaction or processing chamber (42). The silicon surface (14) has been processed (52) to be an AR surface with a density gradient or region of black silicon. The method (50) continues with heating (54) the chamber (42) to a high temperature for both doping and surface passivation. The method (50) includes forming (58), with a dopant-containing precursor in contact with the silicon surface (14) of the substrate (12), an emitter junction (16) proximate to the silicon surface (14) by doping the substrate (12). The method (50) further includes, while the chamber is maintained at the high or raised temperature, forming (62) a passivation layer (19) on the graded-density silicon anti-reflection surface (14).

Metal-organic chemical vapor deposition of cerium oxide, gallium-indium-oxide, and magnesium oxide thin films: Precursor design, film growth, and film characterization

NASA Astrophysics Data System (ADS)

Edleman, Nikki Lynn

A new class of volatile, low-melting, fluorine-free lanthanide metal-organic chemical vapor deposition (MOCVD) precursors has been developed. The neutral, monomeric cerium, neodymium, gadolinium, and erbium complexes are coordinatively saturated by a versatile, multidentate, ether-functionalized beta-ketoiminate ligand, and complex melting point and volatility characteristics can be tuned by altering the alkyl substituents on the ligand periphery. Direct comparison with lanthanide beta-diketonate complexes reveals that the present precursor class is a superior choice for lanthanide oxide MOCVD. Epitaxial CeO 2 buffer layer films have been grown on (001) YSZ substrates by MOCVD at significantly lower temperatures than previously reported using one of the newly developed cerium precursors. High-quality YBCO films grown on these CeO2 buffer layers by POMBE exhibit very good electrical transport properties. The cerium complex has therefore been explicitly demonstrated to be a stable and volatile precursor and is attractive for low-temperature growth of coated conductor multilayer structures by MOCVD. Gallium-indium-oxide thin films (GaxIn2-xO 3), x = 0.0˜1.1, have been grown by MOCVD using the volatile metal-organic precursors In(dpm)3 and Ga(dpm)3. The films have a homogeneously Ga-substituted, cubic In2O3 microstructure randomly oriented on quartz or heteroepitaxial on (100) YSZ single-crystal substrates. The highest conductivity of the as-grown films is found at x = 0.12. The optical transmission window and absolute transparency of the films rivals or exceeds that of the most transparent conductive oxides known. Reductive annealing results in improved charge transport characteristics with little loss of optical transparency. No significant difference in electrical properties is observed between randomly oriented and heteroepitaxial films, thus arguing that carrier scattering effects at high-angle grain boundaries play a minor role in the film conductivity mechanism. The synthesis and characterization of a new magnesium MOCVD precursor, Mg(dpm)2(TMEDA) is detailed. It is shown that the donating ligand TMEDA prevents oligomerization and subsequent volatility depression as observed in the commonly used [Mg(dpm)2]2. The superiority of Mg(dpm)2(TMEDA) as an MOCVD precursor is explicitly demonstrated by growth of epitaxial MgO thin films on single-crystal SrTiO3 substrates.

Large eddy simulation for atmospheric boundary layer flow over flat and complex terrains

NASA Astrophysics Data System (ADS)

Han, Yi; Stoellinger, Michael; Naughton, Jonathan

2016-09-01

In this work, we present Large Eddy Simulation (LES) results of atmospheric boundary layer (ABL) flow over complex terrain with neutral stratification using the OpenFOAM-based simulator for on/offshore wind farm applications (SOWFA). The complete work flow to investigate the LES for the ABL over real complex terrain is described including meteorological-tower data analysis, mesh generation and case set-up. New boundary conditions for the lateral and top boundaries are developed and validated to allow inflow and outflow as required in complex terrain simulations. The turbulent inflow data for the terrain simulation is generated using a precursor simulation of a flat and neutral ABL. Conditionally averaged met-tower data is used to specify the conditions for the flat precursor simulation and is also used for comparison with the simulation results of the terrain LES. A qualitative analysis of the simulation results reveals boundary layer separation and recirculation downstream of a prominent ridge that runs across the simulation domain. Comparisons of mean wind speed, standard deviation and direction between the computed results and the conditionally averaged tower data show a reasonable agreement.

Synthesis of (cinnamate-zinc layered hydroxide) intercalation compound for sunscreen application

PubMed Central

2013-01-01

Background Zinc layered hydroxide (ZLH) intercalated with cinnamate, an anionic form of cinnamic acid (CA), an efficient UVA and UVB absorber, have been synthesized by direct method using zinc oxide (ZnO) and cinnamic acid as the precursor. Results The resulting obtained intercalation compound, ZCA, showed a basal spacing of 23.9 Å as a result of cinnamate intercalated in a bilayer arrangement between the interlayer spaces of ZLH with estimated percentage loading of cinnamate of about 40.4 % w/w. The UV–vis absorption spectrum of the intercalation compound showed excellent UVA and UVB absorption ability. Retention of cinnamate in ZLH interlayers was tested against media usually came across with sunscreen usage to show low release over an extended period of time. MTT assay of the intercalation compound on human dermal fibroblast (HDF) cells showed cytotoxicity of ZCA to be concentration dependent and is overall less toxic than its precursor, ZnO. Conclusions (Cinnamate-zinc layered hydroxide) intercalation compound is suitable to be used as a safe and effective sunscreen with long UV protection effect. PMID:23383738

Aqueous solution-chemical derived Nisbnd Al2O3 solar selective absorbing coatings. 2. Wetting agents and spreading of aqueous solutions on aluminum substrate

NASA Astrophysics Data System (ADS)

Li, Zhenxiang; Zhao, Jianxi

2013-03-01

Wettability of aluminum substrate by the aqueous solutions containing ethoxylated alcohol nonionic surfactants C12En- or Triton X-series was studied using dynamic contact angle measurements. The efficiency of wetting was found to strongly depend on the length of polyoxyethylene (POE) chain of C12En- or Triton X surfactants. For C12E4 that has a very short POE chain, it hardly made the aqueous solution spreading over aluminum. The others with a long POE chain were indeed very efficient in promoting the solution spreading. Moreover, all the spreading process could be completed within 10 s. The single-layer Nisbnd Al2O3 coatings were fabricated from the precursor solutions containing C12En- or Triton X surfactants and the reflectance spectra were measured by a UV/vis spectrophotometer equipped with an integrating sphere. The results indicated that the precursor solution with a long POE chain surfactant as wetting agent favored to fabricate a uniform film on the aluminum substrate and therefore to get a high solar absorptance.

Thermal Protective Coating for High Temperature Polymer Composites

NASA Technical Reports Server (NTRS)

Barron, Andrew R.

1999-01-01

The central theme of this research is the application of carboxylate-alumoxane nanoparticles as precursors to thermally protective coatings for high temperature polymer composites. In addition, we will investigate the application of carboxylate-alumoxane nanoparticle as a component to polymer composites. The objective of this research was the high temperature protection of polymer composites via novel chemistry. The significance of this research is the development of a low cost and highly flexible synthetic methodology, with a compatible processing technique, for the fabrication of high temperature polymer composites. We proposed to accomplish this broad goal through the use of a class of ceramic precursor material, alumoxanes. Alumoxanes are nano-particles with a boehmite-like structure and an organic periphery. The technical goals of this program are to prepare and evaluate water soluble carboxylate-alumoxane for the preparation of ceramic coatings on polymer substrates. Our proposed approach is attractive since proof of concept has been demonstrated under the NRA 96-LeRC-1 Technology for Advanced High Temperature Gas Turbine Engines, HITEMP Program. For example, carbon and Kevlar(tm) fibers and matting have been successfully coated with ceramic thermally protective layers.

The Influence of Water Vapor on the Stability and Processing of Hybrid Perovskite Solar Cells Made from Non-Stoichiometric Precursor Mixtures.

PubMed

Petrus, Michiel L; Hu, Yinghong; Moia, Davide; Calado, Philip; Leguy, Aurélien M A; Barnes, Piers R F; Docampo, Pablo

2016-09-22

We investigated the influence of moisture on methylammonium lead iodide perovskite (MAPbI 3 ) films and solar cells derived from non-stoichiometric precursor mixtures. We followed both the structural changes under controlled air humidity through in situ X-ray diffraction, and the electronic behavior of devices prepared from these films. A small PbI 2 excess in the films improved the stability of the perovskite compared to stoichiometric samples. We assign this to excess PbI 2 layers at the perovskite grain boundaries or to the termination of the perovskite crystals with Pb and I. In contrast, the MAI-excess films composed of smaller perovskite crystals showed increased electronic disorder and reduced device performance owing to poor charge collection. Upon exposure to moisture followed by dehydration (so-called solvent annealing), these films recrystallized to form larger, highly oriented crystals with fewer electronic defects and a remarkable improvement in photocurrent and photovoltaic efficiency. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Performance improvement for solution-processed high-mobility ZnO thin-film transistors

NASA Astrophysics Data System (ADS)

Sha Li, Chen; Li, Yu Ning; Wu, Yi Liang; Ong, Beng S.; Loutfy, Rafik O.

2008-06-01

The fabrication technology of stable, non-toxic, transparent, high performance zinc oxide (ZnO) thin-film semiconductors via the solution process was investigated. Two methods, which were, respectively, annealing a spin-coated precursor solution and annealing a drop-coated precursor solution, were compared. The prepared ZnO thin-film semiconductor transistors have well-controlled, preferential crystal orientation and exhibit superior field-effect performance characteristics. But the ZnO thin-film transistor (TFT) fabricated by annealing a drop-coated precursor solution has a distinctly elevated linear mobility, which further approaches the saturated mobility, compared with that fabricated by annealing a spin-coated precursor solution. The performance of the solution-processed ZnO TFT was further improved when substituting the spin-coating process by the drop-coating process.

Low temperature fabrication of metal oxide thin film transistors formed by a heated aqueous precursor solution

NASA Astrophysics Data System (ADS)

Lee, Keun Ho; Han, Sun Woong; Park, Jee Ho; Yoo, Young Bum; Jong Lee, Se; Baik, Hong Koo; Song, Kie Moon

2016-01-01

We introduce an easy process for the fabrication of solution-processed indium oxide (InO) thin film transistors (TFTs) by heating a precursor solution. InO TFTs fabricated from solutions of an InO precursor heated at 90 °C had the highest mobility of 4.61 cm2 V-1 s-1 after being annealed at 200 °C. When the InO precursor solution is heated, HNO3 may be thermally evaporated in the InO precursor solution. Nitrogen atoms can disrupt hydrolysis and condensation reactions. An InO thin film deposited from a solution of the heated InO precursor is advantageous for hydrolysis and condensation reactions due to the absence of nitrogen atoms.

Photochemical metal organic deposition of metal oxides

NASA Astrophysics Data System (ADS)

Law, Wai Lung (Simon)

This thesis pertains to the study of the deposition of metal oxide thin films via the process of Photochemical Metal Organic Deposition (PMOD). In this process, an amorphous metal organic precursor thin film is subjected to irradiation under ambient conditions. Fragmentation of the metal precursor results from the photoreaction, leading to the formation of metal oxide thin films in the presence of oxygen. The advantage of PMOD lies in its ability to perform lithography of metal oxide thin film without the application of photoresist. The metal organic precursor can be imaged directly by photolysis through a lithography mask under ambient conditions. Thus the PMOD process provides an attractive alternative to the conventional VLSI fabrication process. Metal carboxylates and metal acetylacetonates complexes were used as the precursors for PMOD process in this thesis. Transition metal carboxylate and metal acetylacetonate complexes have shown previously that when deposited as amorphous thin films, they will undergo fragmentation upon photolysis, leading to the formation of metal oxide thin films under ambient conditions. In this thesis, the formation of main group metal oxides of aluminum, indium and tin, as well as the formation of rare-earth metal oxides of cerium and europium by PMOD from its corresponding metal organic precursor will be presented. The nature of the photoreactions as well as the properties of the thin films deposited by PMOD will be investigated. Doped metal oxide thin films can also be prepared using the PMOD process. By mixing the metal precursors prior to deposition in the desired ratio, precursor films containing more than one metal precursor can be obtained. Mixed metal oxide thin films corresponding to the original metal ratio, in the precursor mixture, can be obtained upon photolysis under ambient conditions. In this thesis, the properties of doped metal oxide thin films of europium doped aluminum oxide as well as tin doped indium oxide thin films will also be presented.

Solid-Solution Sulfides Derived from Tunable Layered Double Hydroxide Precursors/Graphene Aerogel for Pseudocapacitors and Sodium-Ion Batteries.

PubMed

Song, Yajie; Li, Hui; Yang, Lan; Bai, Daxun; Zhang, Fazhi; Xu, Sailong

2017-12-13

Transition-metal sulfides (TMSs) are suggested as promising electrode materials for electrochemical pseudocapacitors and lithium- and sodium-ion batteries; however, they typically involve mixed composites or conventionally stoichiometric TMSs (such as NiCo 2 S 4 and Ni 2 CoS 4 ). Herein we demonstrate a preparation of solid-solution sulfide (Ni 0.7 Co 0.3 )S 2 supported on three-dimensional graphene aerogel (3DGA) via a sulfuration of NiCo-layered double hydroxide (NiCo-LDH) precursor/3DGA. The electrochemical tests show that the (Ni 0.7 Co 0.3 )S 2 /3DGA electrode exhibits a capacitance of 2165 F g -1 at 1 A g -1 , 2055 F g -1 at 2 A g -1 , and 1478 F g -1 at 10 A g -1 ; preserves 78.5% capacitance retention upon 1000 cycles for pseudocapacitors; and in particular, possesses a relatively high charge capacity of 388.7 mA h g -1 after 50 cycles at 100 mA g -1 as anode nanomaterials for sodium-ion batteries. Furthermore, the electrochemical performances are readily tuned by varying the cationic type of the tunable LDH precursors to prepare different solid-solution sulfides, such as (Ni 0.7 Fe 0.3 )S 2 /3DGA and (Co 0.7 Fe 0.3 )S 2 /3DGA. Our results show that engineering LDH precursors can offer an alternative for preparing diverse transition-metal sulfides for energy storage.

Tissue Motion and Assembly During Early Cardiovascular Morphogenesis

NASA Astrophysics Data System (ADS)

Rongish, Brenda

2010-03-01

Conventional dogma in the field of cardiovascular developmental biology suggests that cardiac precursor cells migrate to the embryonic midline to form a tubular heart. These progenitors are believed to move relative to their extracellular matrix (ECM); responding to stimulatory and inhibitory cues in their environment. The tubular heart that is formed by 30 hours post fertilization is comprised of two concentric layers: the muscular myocardium and the endothelial-like endocardium, which are separated by a thick layer of ECM believed to be secreted predominantly by the myocardial cells. Here we describe the origin and motility of fluorescently tagged endocardial precursors in transgenic (Tie1-YFP) quail embryos (R. Lansford, Caltech) using epifluorescence time-lapse imaging. To visualize the environment of migrating endocardial progenitors, we labeled two ECM components, fibronectin and fibrillin-2, via in vivo microinjection of fluorochrome-conjugated monoclonal antibodies. Dynamic imaging was performed at stages encompassing tubular heart assembly and early looping. We established the motion of endocardial precursor cells and presumptive cardiac ECM fibrils using both object tracking and particle image velocimetry (image cross correlation). We determined the relative importance of directed cell autonomous motility versus passive tissue movements in endocardial morphogenesis. The data show presumptive endocardial cells and cardiac ECM fibrils are swept passively into the anterior and posterior poles of the elongating tubular heart. These quantitative data indicate the contribution of cell autonomous motility displayed by endocardial precursors is limited. Thus, tissue motion drives most of the cell displacements during endocardial morphogenesis.

Functional characterization and molecular mechanism exploration of three granulin epithelin precursor splice variants in biomineralization of the pearl oyster Pinctada fucata.

PubMed

Zhao, Mi; He, Maoxian; Huang, Xiande; Wang, Qi; Shi, Yu

2016-02-01

The granulin/epithelin precursor (GEP) encodes a glycoprotein precursor which exhibits pleiotropic tissue growth factor activity with multiple functions. Here, GEP was isolated and its role in the shell biomineralization process of the pearl oyster Pinctada fucata was investigated. Three forms of GEP mRNA were isolated from the pearl oyster (designated PfGEP-1, PfGEP-2 and PfGEP-3). Genomic DNA flanking the splicing region of the PfGEP variants was sequenced and it was found that PfGEP-2 splices out Exon 4, whereas PfGEP-3 splices out Exon 3 compared to PfGEP-1. PfGEP-1 (1505 amino acids) consists of 18 granulin domains, whereas PfGEP-2 (1459 amino acids) and PfGEP-3 (1471 amino acids) consist of 17.5 granulin domains, respectively. Analyses of PfGEP-1 and PfGEP-3 mRNA showed differential patterns in the tissues and developmental stages. Western blotting results showed that the three splice variants can translate to proteins in HEK293T cells. A knockdown experiment using PfGEP dsRNA showed decreased PfGEP-1/PfGEP-3 and PfMSX mRNA, and irregular crystallization of the nacreous layer using scanning electron microscopy. In luciferase assays, co-transfection of PfGEP-1 could activate as well as repress luciferase expression of the reporter plasmid driven by the PfMSX promoter, whereas PfGEP-3 stimulated the expression, elucidating the molecular mechanisms involved in the correlation between PfGEP and PfMSX. These results suggested that GEP variants might function differently during the biomineralization process, which provides new knowledge on the mechanism regulating nacre formation.

High-Quality Hollow Closed-Pore Silica Antireflection Coatings Based on Styrene-Acrylate Emulsion @ Organic-Inorganic Silica Precursor.

PubMed

Guo, Zhaolong; Zhao, Haixin; Zhao, Wei; Wang, Tao; Kong, Depeng; Chen, Taojing; Zhang, Xiaoyan

2016-05-11

Making use of a facile and low-cost way for the preparation of a hierarchically organized novel hollow closed-pore silica antireflective coating (CHAR) with tailored optical properties and a mechanical reliability is of great interest in the field of solar photovoltaic technology. The process mainly contains two aspects: (1) a styrene-acrylate emulsion @ organic-inorganic silica precursor (SA@OISP) core/shell hierarchical nanostructure, consisting of a sacrificial styrene-acrylate (SA) primary template, was fabricated using a sol-gel method; (2) the self-assembly of the nanostructures leads to SA@OISP nanospheres forming the high-quality hollow closed-pore silica antireflection coating (CHAR) by a dip-coating process and a subsequent calcination treatment. The resulting SA@OISP nanospheres have a mean diameter of 65.2 nm and contained a SA soft core with a mean diameter of approximately 54.8 nm and an organic-inorganic silica precursor (OISP) shell with a thickness of approximately 6-10 nm. Furthermore, the prepared CHAR film exhibited a high transmittance and good ruggedness. An average transmittance (TAV) of 97.64% was obtained, and the value is close to the ideal single-layered antireflection coating (98.09%) over a broad range of wavelengths (from 380 to 1100 nm). The CHAR film showed a stable TAV, with attenuation values of less than 0.8% and 0.43% after the abrasion test and the damp heat test, respectively. The conversion efficiency of the CHAR coating cover solar modules tends to be increased by 3.75%. The promising results obtained in this study suggest that the CHAR film was considered as an essential component of the solar module and were expected to provide additional solar energy harvest under extreme outdoor climates.

Deposition of single and layered amorphous fluorocarbon films by C8F18 PECVD

NASA Astrophysics Data System (ADS)

Yamauchi, Tatsuya; Mizuno, Kouichiro; Sugawara, Hirotake

2008-10-01

Amorphous fluorocarbon films were deposited by plasma-enhanced chemical vapor deposition (PECVD) using C8F18 in closed system at C8F18 pressures 0.1--0.3 Torr, deposition times 1--30 min and plasma powers 20--200 W@. The layered films were composed by repeated PECVD processes. We compared `two-layered' and `intermittently deposited' films, which were made by the PECVD, respectively, with and without renewal of the gas after the deposition of the first layer. The interlayer boundary was observed in the layered films, and that of the intermittently deposited films showed a tendency to be clearer when the deposition time until the interruption of the PECVD was shorter. The film thickness increased linearly in the beginning of the PECVD and it turned down after 10--15 min, that was similar between the single and intermittently deposited films. It was considered that large precursors made at a low decomposition degree of C8F18 contributed to the film deposition in the early phase and that the downturn was due to the development of the C8F18 decomposition. This explanation on the deposition mechanism agrees qualitatively with our experimental data of pressure change and optical emission spectra during the deposition. This work is supported by Grant-in-Aid from Japan Society for the Promotion of Science.

Spatial atomic layer deposition for coating flexible porous Li-ion battery electrodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yersak, Alexander S.; Sharma, Kashish; Wallas, Jasmine M.

Ultrathin atomic layer deposition (ALD) coatings on the electrodes of Li-ion batteries can enhance the capacity stability of the Li-ion batteries. To commercialize ALD for Li-ion battery production, spatial ALD is needed to decrease coating times and provide a coating process compatible with continuous roll-to-roll (R2R) processing. The porous electrodes of Li-ion batteries provide a special challenge because higher reactant exposures are needed for spatial ALD in porous substrates. This work utilized a modular rotating cylinder spatial ALD reactor operating at rotation speeds up to 200 revolutions/min (RPM) and substrate speeds up to 200 m/min. The conditions for spatial ALDmore » were adjusted to coat flexible porous substrates. The reactor was initially used to characterize spatial Al2O3 and ZnO ALD on flat, flexible metalized polyethylene terephthalate foils. These studies showed that slower rotation speeds and spacers between the precursor module and the two adjacent pumping modules could significantly increase the reactant exposure. The modular rotating cylinder reactor was then used to coat flexible, model porous anodic aluminum oxide (AAO) membranes. The uniformity of the ZnO ALD coatings on the porous AAO membranes was dependent on the aspect ratio of the pores and the reactant exposures. Larger reactant exposures led to better uniformity in the pores with higher aspect ratios. The reactant exposures were increased by adding spacers between the precursor module and the two adjacent pumping modules. The modular rotating cylinder reactor was also employed for Al2O3 ALD on porous LiCoO2 (LCO) battery electrodes. Uniform Al coverages were obtained using spacers between the precursor module and the two adjacent pumping modules at rotation speeds of 25 and 50 RPM. The LCO electrodes had a thickness of ~49 um and pores with aspect ratios of ~12-25. Coin cells were then constructed using the ALD-coated LCO electrodes and were tested to determine their battery performance. The capacity of the Al2O3 ALD-coated LCO battery electrodes was measured versus the number of charge-discharge cycles. Both temporal and spatial ALD processing methods led to higher capacity stability compared with uncoated LCO battery electrodes. The results for improved battery performance were comparable for temporal and spatial ALD-coated electrodes. The next steps are also presented for scale-up to R2R spatial ALD using the modular rotating cylinder reactor.« less

Metallic Nanowire Interconnections for Integrated Circuit Fabrication

NASA Technical Reports Server (NTRS)

Ng, Hou Tee (Inventor); Li, Jun (Inventor); Meyyappan, Meyya (Inventor)

2007-01-01

A method for fabricating an electrical interconnect between two or more electrical components. A conductive layer is provided on a substarte and a thin, patterned catalyst array is deposited on an exposed surface of the conductive layer. A gas or vapor of a metallic precursor of a metal nanowire (MeNW) is provided around the catalyst array, and MeNWs grow between the conductive layer and the catalyst array. The catalyst array and a portion of each of the MeNWs are removed to provide exposed ends of the MeNWs.

Precursors for the polymer-assisted deposition of films

DOEpatents

McCleskey, Thomas M.; Burrell, Anthony K.; Jia, Quanxi; Lin, Yuan

2013-09-10

A polymer assisted deposition process for deposition of metal oxide films is presented. The process includes solutions of one or more metal precursor and soluble polymers having binding properties for the one or more metal precursor. After a coating operation, the resultant coating is heated at high temperatures to yield metal oxide films. Such films can be epitaxial in structure and can be of optical quality. The process can be organic solvent-free.

Facile synthesis of a conjugation-grafted-TiO2 nanohybrid with enhanced visible-light photocatalytic properties from nanotube titanic acid precursors

NASA Astrophysics Data System (ADS)

Guo, Yanru; Zhang, Min; Zhang, Zhihua; Li, Qiuye; Yang, Jianjun

2016-08-01

A conjugation-grafted-TiO2 nanohybrid was synthesized by chemically grafting conjugated structures on the surface of nanotube titanic acid (NTA) precursor-based TiO2 through the controlled thermal degradation of a coacervated polymer layer of polyvinyl alcohol (PVA). The interfacial interactions between the NTA precursor-based TiO2 and conjugated structures were characterized using Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Moreover, the effects of the NTA's pretreatment temperature and the weight ratio of NTA to PVA on the photocatalytic degradation of methyl orange were also investigated. A higher NTA pretreatment temperature and a lower NTA to PVA weight ratio were found to enhance photogenerated electron-hole separation efficiency and photocatalytic activity. Moreover, the conjugation-grafted-TiO2 nanohybrid synthesized from the NTA precursor displayed a much higher visible-light photocatalytic activity than that of the sample obtained from the P25 precursor. The origin of the enhanced photocatalytic activity under visible-light irradiation is also discussed in detail.

Nazca-South America Subduction Zone Reflectivity from P'P' Precursors

NASA Astrophysics Data System (ADS)

Gu, Y. J.; Schultz, R.

2012-12-01

Much of what is known about mantle owes to the interpretation of its reflectivity structure. On the global scale mantle stratifications have been attributed to mineralogical phase changes of olivine; two widely observed examples are the 410 and 660 km discontinuities. Among the various seismological tools, results from longer-period SS/PP precursors and high frequency receiver functions are routinely compared to increase the confidence of the recovered mantle stratifications. The former are lower frequency approaches with complex Fresnel zones, while constraints on receiver distribution hinder analysis in oceanic regions for the latter. P'P' precursors are a promising high frequency alternative, capable of resolving small-scale structures (resolution of ~5 km vertically, 200 km laterally) in the mantle, owing to its short-period nature (~1Hz), shallow angle of incidence and nearly symmetric Fresnel zone. However, P'P' precursors are known for several complications: phase triplication (PKiKPPKiKP, PKIKPPKIKP, PKPPKPab and PKPPKPbc) and the maximum-phase Fresnel zones result in strong scattering and asymmetric arrivals. Much of these concerns are alleviated through revamped processing techniques involving stacking, deconvolution, Radon transform and migration. We utilize P'P' precursors to constrain the mantle structure and layering beneath the Nazca-South America subduction zone. Our migration profiles reveal both olivine (e.g., 410, 520, 660) and garnet related transitions in the mantle, with constraints on the sharpness of these transitions. Observations of a depressed 660 are attributed to thermal variations, showing the spatial extent of the impinging Nazca slab. Prominent 520 arrivals near subducted slab material suggest this transition is sharpened to a thickness resonant with P'P' (~10km). The possibility of chemical heterogeneity is evidenced near the top of the mantle transition zone through complicated 410 amplitudes. The existence, depth, sharpness and strength of these reflectors/discontinuities offer new constraints on the dynamics and mineralogy of the mantle.

An Introduction to Atomic Layer Deposition with Thermal Applications

NASA Technical Reports Server (NTRS)

Dwivedi, Vivek H.

2015-01-01

Atomic Layer Deposition (ALD) is a cost effective nano-manufacturing technique that allows for the conformal coating of substrates with atomic control in a benign temperature and pressure environment. Through the introduction of paired precursor gases thin films can be deposited on a myriad of substrates ranging from glass, polymers, aerogels, and metals to high aspect ratio geometries. This talk will focus on the utilization of ALD for engineering applications.

Active Materials for Photonic Systems (AMPS)

DTIC Science & Technology

1998-04-13

titanium isopropoxide were used as metalorganic precursors. The PZT films grown on the (101) oriented Ru02 electrode layers are highly (001) oriented...fabrication it was noted mat adhesion loss occurred at the platinum/ titanium interface. This loss occurred during stripping of the photoresist layer used to...reveal that the titanium was present as titanium dioxide rather than as the original metal. This indicated that oxygen had diffused through the platinum

Synthesis and study of photovoltaic performance on various photoelectrode materials for DSSCs: Optimization of compact layer on nanometer thickness

NASA Astrophysics Data System (ADS)

Surya, Subramanian; Thangamuthu, Rangasamy; Senthil Kumar, Sakkarapalayam Murugesan; Murugadoss, Govindhasamy

2017-02-01

Dye-sensitized solar cells (DSSCs) have gained widespread attention in recent years because of their low production costs, ease of fabrication process and tuneable optical properties, such as colour and transparency. In this work, we explored a strategy wherein nanoparticles of pure TiO2, TiO2sbnd SnO2 nanocomposite, Sn (10%) doped TiO2 and SnO2 synthesized by the simple chemical precipitation method were employed as photoelectrodes to enhance the photovoltaic conversion efficiency of solar cells. The nanoparticles were characterized by different characterization techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM with EDX), transmission electron microscopy (TEM), high resolution electron microscopy (HR-TEM), UV-Visible absorbance (UV-vis), photoluminescence (PL), thermal gravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS) measurements. Moreover, we also demonstrated the effect of thin compact layer in DSSCs by architecture with various precursor materials of different concentrations. We found that the optimized compact layer material TDIP (titanium diisopropoxide) with a concentration of 0.3 M % is produced the highest efficiency of 2.25% for Sn (10%) doped TiO2 electron transport material (ETM) and 4.38% was achieved for pure TiO2 ETM using SnCl2 compact layer with 0.1 M concentrations.

Nacre-Templated Synthesis of Highly Dispersible Carbon Nanomeshes for Layered Membranes with High-Flux Filtration and Sensing Properties.

PubMed

Kong, Meng; Li, Mingjie; Shang, Ruoxu; Wu, Jingyu; Yan, Peisong; Xu, Dongmei; Li, Chaoxu

2018-01-24

Marine shells not only represent a rapidly accumulating type of fishery wastes but also offer a unique sort of hybrid nanomaterials produced greenly and massively in nature. The elaborate "brick and mortar" structures of nacre enabled the synthesis of carbon nanomeshes with <1 nm thickness, hierarchical porosity, and high specific surface area through pyrolysis, in which two-dimensional (2D) organic layers served as the carbonaceous precursor and aragonite platelets as the hard template. Mineral bridges within 2D organic layers templated the formation of mesh pores of 20-70 nm. In contrast to other hydrophobic carbon nanomaterials, these carbon nanomeshes showed super dispersibility in diverse solvents and thus processability for membranes through filtration, patterning, spray-coating, and ink-writing. The carbon membranes with layered structures were capable of serving not only for high-flux filtration and continuous flow absorption but also for electrochemical and strain sensing with high sensitivity. Thus, utilization of marine shells, on one hand, relieves the environmental concern of shellfish waste, on the other hand, offers a facile, green, low-cost, and massive approach to synthesize unique carbon nanomeshes alternative to graphene nanomeshes and applicable in environmental adsorption, filtration, wearable sensors, and flexible microelectronics.

Suppressing the Photocatalytic Activity of TiO2 Nanoparticles by Extremely Thin Al2O3 Films Grown by Gas-Phase Deposition at Ambient Conditions

PubMed Central

Guo, Jing; Valdesueiro, David; Yuan, Shaojun; Liang, Bin; van Ommen, J. Ruud

2018-01-01

This work investigated the suppression of photocatalytic activity of titanium dioxide (TiO2) pigment powders by extremely thin aluminum oxide (Al2O3) films deposited via an atomic-layer-deposition-type process using trimethylaluminum (TMA) and H2O as precursors. The deposition was performed on multiple grams of TiO2 powder at room temperature and atmospheric pressure in a fluidized bed reactor, resulting in the growth of uniform and conformal Al2O3 films with thickness control at sub-nanometer level. The as-deposited Al2O3 films exhibited excellent photocatalytic suppression ability. Accordingly, an Al2O3 layer with a thickness of 1 nm could efficiently suppress the photocatalytic activities of rutile, anatase, and P25 TiO2 nanoparticles without affecting their bulk optical properties. In addition, the influence of high-temperature annealing on the properties of the Al2O3 layers was investigated, revealing the possibility of achieving porous Al2O3 layers. Our approach demonstrated a fast, efficient, and simple route to coating Al2O3 films on TiO2 pigment powders at the multigram scale, and showed great potential for large-scale production development. PMID:29364840

Low cost sol-gel derived SiC-SiO2 nanocomposite as anti reflection layer for enhanced performance of crystalline silicon solar cells

NASA Astrophysics Data System (ADS)

Jannat, Azmira; Lee, Woojin; Akhtar, M. Shaheer; Li, Zhen Yu; Yang, O.-Bong

2016-04-01

This paper describes the preparation, characterizations and the antireflection (AR) coating application in crystalline silicon solar cells of sol-gel derived SiC-SiO2 nanocomposite. The prepared SiC-SiO2 nanocomposite was effectively applied as AR layer on p-type Si-wafer via two step processes, where the sol-gel of precursor solution was first coated on p-type Si-wafer using spin coating at 2000 rpm and then subjected to annealing at 450 °C for 1 h. The crystalline, and structural observations revealed the existence of SiC and SiO2 phases, which noticeably confirmed the formation of SiC-SiO2 nanocomposite. The SiC-SiO2 layer on Si solar cells was found to be an excellent AR coating, exhibiting the low reflectance of 7.08% at wavelengths ranging from 400 to 1000 nm. The fabricated crystalline Si solar cell with SiC-SiO2 nanocomposite AR coating showed comparable power conversion efficiency of 16.99% to the conventional SixNx AR coated Si solar cell. New and effective sol-gel derived SiC-SiO2 AR layer would offer a promising technique to produce high performance Si solar cells with low-cost.