Science.gov

Sample records for molecular materials thin-film

  1. Preface: Thin films of molecular organic materials

    NASA Astrophysics Data System (ADS)

    Fraxedas, J.

    2008-03-01

    This special issue is devoted to thin films of molecular organic materials and its aim is to assemble numerous different aspects of this topic in order to reach a wide scientific audience. Under the term 'thin films', structures with thicknesses spanning from one monolayer or less up to several micrometers are included. In order to narrow down this relaxed definition (how thin is thin?) I suggest joining the stream that makes a distinction according to the length scale involved, separating nanometer-thick films from micrometer-thick films. While the physical properties of micrometer-thick films tend to mimic those of bulk materials, in the low nanometer regime new structures (e.g., crystallographic and substrate-induced phases) and properties are found. However, one has to bear in mind that some properties of micrometer-thick films are really confined to the film/substrate interface (e.g. charge injection), and are thus of nanometer nature. Supported in this dimensionality framework, this issue covers the most ideal and model 0D case, a single molecule on a surface, through to the more application-oriented 3D case, placing special emphasis on the fascinating 2D domain that is monolayer assembly. Thus, many aspects will be reviewed, such as single molecules, self-organization, monolayer regime, chirality, growth, physical properties and applications. This issue has been intentionally restricted to small molecules, thus leaving out polymers and biomolecules, because for small molecules it is easier to establish structure--property relationships. Traditionally, the preparation of thin films of molecular organic materials has been considered as a secondary, lower-ranked part of the more general field of this class of materials. The coating of diverse surfaces such as silicon, inorganic and organic single crystals, chemically modified substrates, polymers, etc., with interesting molecules was driven by the potential applications of such molecular materials

  2. Thin films for material engineering

    NASA Astrophysics Data System (ADS)

    Wasa, Kiyotaka

    2016-07-01

    Thin films are defined as two-dimensional materials formed by condensing one by one atomic/molecular/ionic species of matter in contrast to bulk three-dimensional sintered ceramics. They are grown through atomic collisional chemical reaction on a substrate surface. Thin film growth processes are fascinating for developing innovative exotic materials. On the basis of my long research on sputtering deposition, this paper firstly describes the kinetic energy effect of sputtered adatoms on thin film growth and discusses on a possibility of room-temperature growth of cubic diamond crystallites and the perovskite thin films of binary compound PbTiO3. Secondly, high-performance sputtered ferroelectric thin films with extraordinary excellent crystallinity compatible with MBE deposited thin films are described in relation to a possible application for thin-film MEMS. Finally, the present thin-film technologies are discussed in terms of a future material science and engineering.

  3. Thin film dielectric composite materials

    DOEpatents

    Jia, Quanxi; Gibbons, Brady J.; Findikoglu, Alp T.; Park, Bae Ho

    2002-01-01

    A dielectric composite material comprising at least two crystal phases of different components with TiO.sub.2 as a first component and a material selected from the group consisting of Ba.sub.1-x Sr.sub.x TiO.sub.3 where x is from 0.3 to 0.7, Pb.sub.1-x Ca.sub.x TiO.sub.3 where x is from 0.4 to 0.7, Sr.sub.1-x Pb.sub.x TiO.sub.3 where x is from 0.2 to 0.4, Ba.sub.1-x Cd.sub.x TiO.sub.3 where x is from 0.02 to 0.1, BaTi.sub.1-x Zr.sub.x O.sub.3 where x is from 0.2 to 0.3, BaTi.sub.1-x Sn.sub.x O.sub.3 where x is from 0.15 to 0.3, BaTi.sub.1-x Hf.sub.x O.sub.3 where x is from 0.24 to 0.3, Pb.sub.1-1.3x La.sub.x TiO.sub.3+0.2x where x is from 0.23 to 0.3, (BaTiO.sub.3).sub.x (PbFeo.sub.0.5 Nb.sub.0.5 O.sub.3).sub.1-x where x is from 0.75 to 0.9, (PbTiO.sub.3).sub.- (PbCo.sub.0.5 W.sub.0.5 O.sub.3).sub.1-x where x is from 0.1 to 0.45, (PbTiO.sub.3).sub.x (PbMg.sub.0.5 W.sub.0.5 O.sub.3).sub.1-x where x is from 0.2 to 0.4, and (PbTiO.sub.3).sub.x (PbFe.sub.0.5 Ta.sub.0.5 O.sub.3).sub.1-x where x is from 0 to 0.2, as the second component is described. The dielectric composite material can be formed as a thin film upon suitable substrates.

  4. Tungsten-doped thin film materials

    DOEpatents

    Xiang, Xiao-Dong; Chang, Hauyee; Gao, Chen; Takeuchi, Ichiro; Schultz, Peter G.

    2003-12-09

    A dielectric thin film material for high frequency use, including use as a capacitor, and having a low dielectric loss factor is provided, the film comprising a composition of tungsten-doped barium strontium titanate of the general formula (Ba.sub.x Sr.sub.1-x)TiO.sub.3, where X is between about 0.5 and about 1.0. Also provided is a method for making a dielectric thin film of the general formula (Ba.sub.x Sr.sub.1-x)TiO.sub.3 and doped with W, where X is between about 0.5 and about 1.0, a substrate is provided, TiO.sub.2, the W dopant, Ba, and optionally Sr are deposited on the substrate, and the substrate containing TiO.sub.2, the W dopant, Ba, and optionally Sr is heated to form a low loss dielectric thin film.

  5. Molecular theory of liquid crystal thin films

    NASA Astrophysics Data System (ADS)

    Meng, Shihong

    A molecular theory has been developed to describe the isotropic-nematic transitoon of model nematogens in bulk and in thin films. The surfaces of thin films can be hard surfaces or coated with surfactant monolayers. The theory only includes hard body interactions between all molecule species: solvent, nematogens and surfactants. We have studied the influence of the separation between confining walls, concentration of nematogens, as well as the surface anchoring and areal density of surfactant at the interface upon the phases of nematogens. We have explained the possible existence of planar degenerate phase through entropic pictures and have confirmed close to the bulk isotropic-nematic transition point, the order of the phases of nematogens from isotropic to nematic then back to isotropic when varying the areal density of surfactant monolayers at interfaces. From the results obtained, we believe that we have captured the main competing interactions between surfactants and nematogens and our molecular level theory is capable of describing these two interactions of different natures. Our results can provide a guideline for molecular design of biosensors. We have modeled the molecular systems with as much simplification as possible while retaining the main features. The thesis is arranged into introduction, results on bulk, thin films confined between hard walls and between surfactant monolayers.

  6. Formation of Organic Thin Films of Nonlinear Optical Materials by Molecular Layer Epitaxy

    NASA Astrophysics Data System (ADS)

    Burtman, V.; Kopylova, T. N.; Van Der Boom, M.; Gadirov, R. M.; Tel'minov, E. N.; Nikonov, S. Yu.; Nikonova, E. N.

    2016-03-01

    Conditions are described under which films of [(aminophenyl)azo]pyridine are formed by molecular layer epitaxy, and their optical absorption and x-ray photoelectron spectra are investigated. The nonlinear properties of such structures are described with the help of measurements of the intensity of second harmonic generation as a function of the angle of incidence.

  7. Thin film phase transition materials development program

    NASA Astrophysics Data System (ADS)

    Case, W. E.

    1985-04-01

    A number of application concepts have emerged based on the idea that a phase transition thin film such as vanadium dioxide provides a high resolution, two-dimensional format for switching, recording, and processing optical signals. These applications range from high density optical disk recording systems and optical data processing to laser protection devices, infrared FLIRS and seekers, laser radar systems and IR scene simulators. All application candidates have a potential for providing either a totally new capability, an improved performance, a lower cost, or combinations of the three. Probably of greatest significance is the emergence of agile sensor concepts arising out of some of the film's special properties. These are represented by the above FLIRs, seekers and laser radar systems. A three year research program has been completed to advance the state-of-the-art in the preparation and characterization of selected thin film phase transition materials. The objectives of the program were: (1) to expand the data base and improve operational characteristics of Vought prepared vanadium dioxide thin films, (2) to evolve process chemistry and subsequently characterize several new program materials, including rare-earth chalcogenides, organic semiconductor charge complexes, alloys of transition metal oxides, and metal-insulator cermets, and (3) to spin-off new applications and concepts.

  8. Porous Organic Cage Thin Films and Molecular-Sieving Membranes.

    PubMed

    Song, Qilei; Jiang, Shan; Hasell, Tom; Liu, Ming; Sun, Shijing; Cheetham, Anthony K; Sivaniah, Easan; Cooper, Andrew I

    2016-04-01

    Porous organic cage molecules are fabricated into thin films and molecular-sieving membranes. Cage molecules are solution cast on various substrates to form amorphous thin films, with the structures tuned by tailoring the cage chemistry and processing conditions. For the first time, uniform and pinhole-free microporous cage thin films are formed and demonstrated as molecular-sieving membranes for selective gas separation. PMID:26800019

  9. Growth and physical properties of molecular organic thin films

    NASA Astrophysics Data System (ADS)

    Fraxedas, J.

    2004-04-01

    Highly-oriented polycrystalline thin films of molecular organic materials consisting of small molecules can be easily obtained by physical and chemical vapour deposition methods. The crystallographic phase, orientation and morphology of the films critically depend on the interface and on the kinetics of growth and can be controlled, to a certain extent, by a judicious selection of the substrates and of the growth parameters. This article shortly explores the formation of organic-inorganic heterostructures as a function of coverage: from the most fundamental case, a single molecule on a surface, to thick films (thickness ˜ 1 μ m). The case of high-quality thick TTF-TCNQ films exemplifies the fact that the derived physical properties are essentially identical to those obtained from single crystals. Key words. Molecular organic materials thin films interfaces.

  10. Polycrystalline thin film materials and devices

    SciTech Connect

    Baron, B.N.; Birkmire, R.W.; Phillips, J.E.; Shafarman, W.N.; Hegedus, S.S.; McCandless, B.E. . Inst. of Energy Conversion)

    1992-10-01

    Results of Phase II of a research program on polycrystalline thin film heterojunction solar cells are presented. Relations between processing, materials properties and device performance were studied. The analysis of these solar cells explains how minority carrier recombination at the interface and at grain boundaries can be reduced by doping of windows and absorber layers, such as in high efficiency CdTe and CuInSe{sub 2} based solar cells. The additional geometric dimension introduced by the polycrystallinity must be taken into consideration. The solar cells are limited by the diode current, caused by recombination in the space charge region. J-V characteristics of CuInSe{sub 2}/(CdZn)S cells were analyzed. Current-voltage and spectral response measurements were also made on high efficiency CdTe/CdS thin film solar cells prepared by vacuum evaporation. Cu-In bilayers were reacted with Se and H{sub 2}Se gas to form CuInSe{sub 2} films; the reaction pathways and the precursor were studied. Several approaches to fabrication of these thin film solar cells in a superstrate configuration were explored. A self-consistent picture of the effects of processing on the evolution of CdTe cells was developed.

  11. Synthesis of thin films and materials utilizing a gaseous catalyst

    SciTech Connect

    Morse, Daniel E; Schwenzer, Birgit; Gomm, John R; Roth, Kristian M; Heiken, Brandon; Brutchey, Richard

    2013-10-29

    A method for the fabrication of nanostructured semiconducting, photoconductive, photovoltaic, optoelectronic and electrical battery thin films and materials at low temperature, with no molecular template and no organic contaminants. High-quality metal oxide semiconductor, photovoltaic and optoelectronic materials can be fabricated with nanometer-scale dimensions and high dopant densities through the use of low-temperature biologically inspired synthesis routes, without the use of any biological or biochemical templates.

  12. Materials availability for thin film solar cells

    NASA Astrophysics Data System (ADS)

    Makita, Yunosuke

    1997-04-01

    Materials availability is one of the most important factors when we consider the mass-production of next generation photovoltaic devices. "In (indium)" is a vital element to produce high efficient thin film solar cells such as InP and CuIn(Ga)Se2 but its lifetime as a natural resource is suggested to be of order of 10˜15 years. The lifetime of a specific natural resource as an element to produce useful device substances is directly related with its abundance in the earth's crust, consumption rate and recycling rate (if recycling is economically meaningful). The chemical elements having long lifetime as a natural resource are those existing in the atmosphere such as N (nitrogen) and O (oxygen); the rich elements in the earth's crust such as Si, Ca, Sr and Ba; the mass-used metals such as Fe (iron), Al (aluminum) and Cu (copper) that reached the stage of large-scale recycling. We here propose a new paradigm of semiconductor material-science for the future generation thin film solar cells in which only abundant chemical elements are used. It is important to remark that these abundant chemical elements are normally not toxic and are fairly friendly to the environment. β-FeSi2 is composed of two most abundant and nontoxic chemical elements. This material is one of the most promising device materials for future generation energy devices (solar cells and thermoelectric device that is most efficient at temperature range of 700-900 °C). One should remind of the versatility of β-FeSi2 that this material can be used not only as energy devices but also as photodetector, light emitting diode and/or laser diode at the wavelength of 1.5 μm that can be monolithically integrated on Si substrates due to the relatively small lattice mismatch.

  13. Optical Properties of Thin Film Molecular Mixtures

    NASA Technical Reports Server (NTRS)

    Jaworske, Donald A.; Shumway, Dean A.; Lyons, Valerie (Technical Monitor)

    2002-01-01

    Thin films composed of molecular mixtures of metal and dielectric are being considered for use as solar selective coatings for a variety of space power applications. By controlling the degree of molecular mixing, the solar selective coatings can be tailored to have the combined properties of high solar absorptance, alpha, and low infrared emittance, epsilon. On orbit, these combined properties would simultaneously maximize the amount of solar energy captured by the coating and minimize the amount of thermal energy radiated. Mini-satellites equipped with solar collectors coated with these cermet coatings may utilize the captured heat energy to power a heat engine to generate electricity, or to power a thermal bus that directs heat to remote regions of the spacecraft. Early work in this area identified the theoretical boundary conditions needed to operate a Carnot cycle in space, including the need for a solar concentrator, a solar selective coating at the heat inlet of the engine, and a radiator. A solar concentrator that can concentrate sunlight by a factor of 100 is ideal. At lower values, the temperature of the solar absorbing surface becomes too low for efficient heat engine operation, and at higher values, cavity type heat receivers become attractive. In designing the solar selective coating, the wavelength region yielding high solar absorptance must be separated from the wavelength region yielding low infrared emittance by establishing a sharp transition in optical properties. In particular, a sharp transition in reflectance is desired in the infrared to achieve the desired optical performance. For a heat engine operating at 450C, a sharp transition at 1.8 micrometers is desired. The radiator completes the heat flow through the Carnot cycle. Additional work has been done supporting the use of molecular mixtures for terrestrial applications. Sputter deposition provides a means to apply coatings to the tubes that carry a working fluid at the focus of trough

  14. Optical Properties of Thin Film Molecular Mixtures

    NASA Technical Reports Server (NTRS)

    Jaworske, Donald A.; Shumway, Dean A.

    2003-01-01

    Thin films composed of molecular mixtures of metal and dielectric are being considered for use as solar selective coatings for a variety of space power applications. By controlling the degree of molecular mixing, the solar selective coatings can be tailored to have the combined properties of high solar absorptance, , and low infrared emittance, . On orbit, these combined properties would simultaneously maximize the amount of solar energy captured by the coating and minimize the amount of thermal energy radiated. Mini-satellites equipped with solar collectors coated with these cermet coatings may utilize the captured heat energy to power a heat engine to generate electricity, or to power a thermal bus that directs heat to remote regions of the spacecraft. Early work in this area identified the theoretical boundary conditions needed to operate a Carnot cycle in space, including the need for a solar concentrator, a solar selective coating at the heat inlet of the engine, and a radiator.1 A solar concentrator that can concentrate sunlight by a factor of 100 is ideal. At lower values, the temperature of the solar absorbing surface becomes too low for efficient heat engine operation, and at higher values, cavity type heat receivers become attractive. In designing the solar selective coating, the wavelength region yielding high solar absorptance must be separated from the wavelength region yielding low infrared emittance by establishing a sharp transition in optical properties. In particular, a sharp transition in reflectance is desired in the infrared to achieve the desired optical performance. For a heat engine operating at 450 C, a sharp transition at 1.8 micrometers is desired.2 The radiator completes the heat flow through the Carnot cycle.

  15. Patterns and conformations in molecularly thin films

    NASA Astrophysics Data System (ADS)

    Basnet, Prem B.

    Molecularly thin films have been a subject of great interest for the last several years because of their large variety of industrial applications ranging from micro-electronics to bio-medicine. Additionally, molecularly thin films can be used as good models for biomembrane and other systems where surfaces are critical. Many different kinds of molecules can make stable films. My research has considered three such molecules: a polymerizable phospholipid, a bent-core molecules, and a polymer. One common theme of these three molecules is chirality. The phospolipid molecules studied here are strongly chiral, which can be due to intrinsically chiral centers on the molecules and also due to chiral conformations. We find that these molecules give rise to chiral patterns. Bent-core molecules are not intrinsically chiral, but individual molecules and groups of molecules can show chiral structures, which can be changed by surface interactions. One major, unconfirmed hypothesis for the polymer conformation at surface is that it forms helices, which would be chiral. Most experiments were carried out at the air/water interface, in what are called Langmuir films. Our major tools for studying these films are Brewster Angle Microscopy (BAM) coupled with the thermodynamic information that can be deduced from surface pressure isotherms. Phospholipids are one of the important constituents of liposomes -- a spherical vesicle com-posed of a bilayer membrane, typically composed of a phospholipid and cholesterol bilayer. The application of liposomes in drug delivery is well-known. Crumpling of vesicles of polymerizable phospholipids has been observed. With BAM, on Langmuir films of such phospholipids, we see novel spiral/target patterns during compression. We have found that both the patterns and the critical pressure at which they formed depend on temperature (below the transition to a i¬‘uid layer). Bent-core liquid crystals, sometimes knows as banana liquid crystals, have drawn

  16. Fluorination of amorphous thin-film materials with xenon fluoride

    DOEpatents

    Weil, R.B.

    1987-05-01

    A method is disclosed for producing fluorine-containing amorphous semiconductor material, preferably comprising amorphous silicon. The method includes depositing amorphous thin-film material onto a substrate while introducing xenon fluoride during the film deposition process.

  17. Fluorination of amorphous thin-film materials with xenon fluoride

    DOEpatents

    Weil, Raoul B.

    1988-01-01

    A method is disclosed for producing fluorine-containing amorphous semiconductor material, preferably comprising amorphous silicon. The method includes depositing amorphous thin-film material onto a substrate while introducing xenon fluoride during the film deposition process.

  18. Dynamic Characterization of Thin Film Magnetic Materials

    NASA Astrophysics Data System (ADS)

    Gu, Wei

    A broadband dynamic method for characterizing thin film magnetic material is presented. The method is designed to extract the permeability and linewidth of thin magnetic films from measuring the reflection coefficient (S11) of a house-made and short-circuited strip line testing fixture with or without samples loaded. An adaptive de-embedding method is applied to remove the parasitic noise of the housing. The measurements were carried out with frequency up to 10GHz and biasing magnetic fields up to 600 Gauss. Particular measurement setup and 3-step experimental procedures are described in detail. The complex permeability of a 330nm thick continuous FeGaB, 435nm thick laminated FeGaB film and a 100nm thick NiFe film will be induced dynamically in frequency-biasing magnetic field spectra and compared with a theoretical model based on Landau-Lifshitz-Gilbert (LLG) equations and eddy current theories. The ferromagnetic resonance (FMR) phenomenon can be observed among these three magnetic materials investigated in this thesis.

  19. Molecular tailoring of interfaces for thin film on substrate systems

    NASA Astrophysics Data System (ADS)

    Grady, Martha Elizabeth

    Thin film on substrate systems appear most prevalently within the microelectronics industry, which demands that devices operate in smaller and smaller packages with greater reliability. The reliability of these multilayer film systems is strongly influenced by the adhesion of each of the bimaterial interfaces. During use, microelectronic components undergo thermo-mechanical cycling, which induces interfacial delaminations leading to failure of the overall device. The ability to tailor interfacial properties at the molecular level provides a mechanism to improve thin film adhesion, reliability and performance. This dissertation presents the investigation of molecular level control of interface properties in three thin film-substrate systems: photodefinable polyimide films on passivated silicon substrates, self-assembled monolayers at the interface of Au films and dielectric substrates, and mechanochemically active materials on rigid substrates. For all three materials systems, the effect of interfacial modifications on adhesion is assessed using a laser-spallation technique. Laser-induced stress waves are chosen because they dynamically load the thin film interface in a precise, noncontacting manner at high strain rates and are suitable for both weak and strong interfaces. Photodefinable polyimide films are used as dielectrics in flip chip integrated circuit packages to reduce the stress between silicon passivation layers and mold compound. The influence of processing parameters on adhesion is examined for photodefinable polyimide films on silicon (Si) substrates with three different passivation layers: silicon nitride (SiNx), silicon oxynitride (SiOxNy), and the native silicon oxide (SiO2). Interfacial strength increases when films are processed with an exposure step as well as a longer cure cycle. Additionally, the interfacial fracture energy is assessed using a dynamic delamination protocol. The high toughness of this interface (ca. 100 J/m2) makes it difficult

  20. Physical Properties of Thin Film Semiconducting Materials

    NASA Astrophysics Data System (ADS)

    Bouras, N.; Djebbouri, M.; Outemzabet, R.; Sali, S.; Zerrouki, H.; Zouaoui, A.; Kesri, N.

    2005-10-01

    The physics and chemistry of semiconducting materials is a continuous question of debate. We can find a large stock of well-known properties but at the same time, many things are not understood. In recent years, porous silicon (PS-Si), diselenide of copper and indium (CuInSe2 or CIS) and metal oxide semiconductors like tin oxide (SnO2) and zinc oxide (ZnO) have been subjected to extensive studies because of the rising interest their potential applications in fields such as electronic components, solar panels, catalysis, gas sensors, in biocompatible materials, in Li-based batteries, in new generation of MOSFETS. Bulk structure and surface and interface properties play important roles in all of these applications. A deeper understanding of these fundamental properties would impact largely on technological application performances. In our laboratory, thin films of undoped and antimony-doped films of tin oxide have been deposited by chemical vapor deposition. Spray pyrolysis was used for ZnO. CIS was prepared by flash evaporation or close-space vapor transport. Some of the deposition parameters have been varied, such as substrate temperature, time of deposition (or anodization), and molar concentration of bath preparation. For some samples, thermal annealing was carried out under oxygen (or air), under nitrogen gas and under vacuum. Deposition and post-deposition parameters are known to strongly influence film structure and electrical resistivity. We investigated the influence of film thickness and thermal annealing on structural optical and electrical properties of the films. Examination of SnO2 by x-ray diffraction showed that the main films are polycrystalline with rutile structure. The x-ray spectra of ZnO indicated a hexagonal wurtzite structure. Characterizations of CIS films with compositional analysis, x-ray diffraction, scanning microscopy, spectrophotometry, and photoluminescence were carried out.

  1. Thin-film perovskites-ferroelectric materials for integrated optics

    SciTech Connect

    Walker, F.J. |; McKee, R.A.

    1995-12-31

    Optical guided wave (OGW) devices, based on LiNbO{sub 3} or GaAs. are commercially available products with established markets and applications. While LiNbO{sub 3} presently dominates the commercial applications, there are several drivers for the development of improved electro-optic (EO) materials. If the appropriate crystal quality could be obtained for thin-film BaTiO{sub 3} supported on MgO for example, or for an integrated BaTiO{sub 3}/Mg0 structure on silicon or GaAs, then the optimum OGW device structure might be realized. We report on our results for the growth of optical quality, epitaxial BaTiO{sub 3} and SrTiO{sub 3} on single-crystal MgO substrates using source shuttering molecular beam epitaxy (MBE) techniques. We also discuss how these materials can be integrated onto silicon. Our MBE studies show that, for this important class of perovskite oxides, heteroepitaxy between the perovskites and alkaline earth oxides is dominated by interfacial electrostatics at the first atomic layers. We have been able to demonstrate that a layer-by-layer energy minimization associated with interfacial electrostatics leads to the growth of high quality thin films of these materials. We have fabricated waveguides from these materials, and the optical clarity and loss coefficients have been characterized and found to be comparable to in-diffused waveguide structures typically represented by Ti drifted LiNbO{sub 3}.

  2. Packaging material for thin film lithium batteries

    DOEpatents

    Bates, John B.; Dudney, Nancy J.; Weatherspoon, Kim A.

    1996-01-01

    A thin film battery including components which are capable of reacting upon exposure to air and water vapor incorporates a packaging system which provides a barrier against the penetration of air and water vapor. The packaging system includes a protective sheath overlying and coating the battery components and can be comprised of an overlayer including metal, ceramic, a ceramic-metal combination, a parylene-metal combination, a parylene-ceramic combination or a parylene-metal-ceramic combination.

  3. Research on polycrystalline thin-film materials, cells, and modules

    NASA Astrophysics Data System (ADS)

    Mitchell, R. L.; Zweibel, K.; Ullal, H. S.

    1990-11-01

    DOE supports research activities in polycrystalline thin films through the Polycrystalline Thin Film Program. This program includes includes R and D in both copper indium diselenide and cadmium telluride thin films for photovoltaic applications. The objective is to support R and D of photovoltaic cells and modules that meet the DOE long term goals of high efficiency (15 to 20 percent), low cost ($50/sq cm), and reliability (30-year life time). Research carried out in this area is receiving increased recognition due to important advances in polycrystalline thin film CuInSe2 and CdTe solar cells and modules. These have become the leading thin film materials for photovoltaics in terms of efficiency and stability. DOE has recognized this potential through a competitive initiative for the development of CuInSe(sub 2) and CdTe modules. The recent progress and future directions are studied of the Polycrystalline Thin Film Program and the status of the subcontracted research on these promising photovoltaic materials.

  4. Research on polycrystalline thin-film materials, cells, and modules

    SciTech Connect

    Mitchell, R.L.; Zweibel, K.; Ullal, H.S.

    1990-11-01

    The US Department of Energy (DOE) supports research activities in polycrystalline thin films through the Polycrystalline Thin-Film Program at the Solar Energy Research Institute (SERI). This program includes research and development (R D) in both copper indium diselenide and cadmium telluride thin films for photovoltaic applications. The objective of this program is to support R D of photovoltaic cells and modules that meet the DOE long-term goals of high efficiency (15%--20%), low cost ($50/m{sup 2}), and reliability (30-year life time). Research carried out in this area is receiving increased recognition due to important advances in polycrystalline thin-film CuInSe{sub 2} and CdTe solar cells and modules. These have become the leading thin-film materials for photovoltaics in terms of efficiency and stability. DOE has recognized this potential through a competitive initiative for the development of CuInSe{sub 2} and CdTe modules. This paper focuses on the recent progress and future directions of the Polycrystalline Thin-Film Program and the status of the subcontracted research on these promising photovoltaic materials. 26 refs., 12 figs, 1 tab.

  5. Polycrystalline thin film materials and devices

    NASA Astrophysics Data System (ADS)

    Baron, B. N.; Birkmire, R. W.; Phillips, J. E.; Shafarman, W. N.; Hegedus, S. S.; McCandless, B. E.

    1991-11-01

    Results and conclusions of Phase 1 of a multi-year research program on polycrystalline thin film solar cells are presented. The research comprised investigation of the relationships among processing, materials properties and device performance of both CuInSe2 and CdTe solar cells. The kinetics of the formation of CuInSe2 by selenization with hydrogen selenide was investigated and a CuInSe2/Cds solar cell was fabricated. An alternative process involving the reaction of deposited copper-indium-selenium layers was used to obtain single phase CuInSe2 films and a cell efficiency of 7 percent. Detailed investigations of the open circuit voltage of CuInSe2 solar cells showed that a simple Shockley-Read-Hall recombination mechanism can not account for the limitations in open circuit voltage. Examination of the influence of CuInSe2 thickness on cell performance indicated that the back contact behavior has a significant effect when the CuInSe2 is less than 1 micron thick. CdTe/CdS solar cells with efficiencies approaching 10 percent can be repeatedly fabricated using physical vapor deposition and serial post deposition processing. The absence of moisture during post deposition was found to be critical. Improvements in short circuit current of CdTe solar cells to levels approaching 25 mA/cm(exp 2) are achievable by making the CdS window layer thinner. Further reductions in the CdS window layer thickness are presently limited by interdiffusion between the CdS and the CdTe. CdTe/CdS cells stored without protection from the atmosphere were found to degrade. The degradation was attributed to the metal contact. CdTe cells with ZnTe:Cu contacts to the CdTe were found to be more stable than cells with metal contacts. Analysis of current-voltage and spectral response of CdTe/CdS cells indicates the cell operates as a p-n heterojunction with the diode current dominated by SRH recombination in the junction region of the CdTe.

  6. High throughput growth and characterization of thin film materials

    NASA Astrophysics Data System (ADS)

    Mao, Samuel S.

    2013-09-01

    It usually takes more than 10 years for a new material from initial research to its first commercial application. Therefore, accelerating the pace of discovery of new materials is critical to tackling challenges in areas ranging from clean energy to national security. As discovery of new materials has not kept pace with the product design cycles in many sectors of industry, there is a pressing need to develop and utilize high throughput screening and discovery technologies for the growth and characterization of new materials. This article presents two distinctive types of high throughput thin film material growth approaches, along with a number of high throughput characterization techniques, established in the author's group. These approaches include a second-generation "discrete" combinatorial semiconductor discovery technology that enables the creation of arrays of individually separated thin film semiconductor materials of different compositions, and a "continuous" high throughput thin film material screening technology that enables the realization of ternary alloy libraries with continuously varying elemental ratios.

  7. Molecularly Oriented Polymeric Thin Films for Space Applications

    NASA Technical Reports Server (NTRS)

    Fay, Catharine C.; Stoakley, Diane M.; St.Clair, Anne K.

    1997-01-01

    The increased commitment from NASA and private industry to the exploration of outer space and the use of orbital instrumentation to monitor the earth has focused attention on organic polymeric materials for a variety of applications in space. Some polymeric materials have exhibited short-term (3-5 yr) space environmental durability; however, future spacecraft are being designed with lifetimes projected to be 10-30 years. This gives rise to concern that material property change brought about during operation may result in unpredicted spacecraft performance. Because of their inherent toughness and flexibility, low density, thermal stability, radiation resistance and mechanical strength, aromatic polyimides have excellent potential use as advanced materials on large space structures. Also, there exists a need for high temperature (200-300 C) stable, flexible polymeric films that have high optical transparency in the 300-600nm range of the electromagnetic spectrum. Polymers suitable for these space applications were fabricated and characterized. Additionally, these polymers were molecularly oriented to further enhance their dimensional stability, stiffness, elongation and strength. Both unoriented and oriented polymeric thin films were also cryogenically treated to temperatures below -184 C to show their stability in cold environments and determine any changes in material properties.

  8. Bulk and Thin Film Contact Resistance with Dissimilar Materials

    NASA Astrophysics Data System (ADS)

    Lau, Y. Y.; Zhang, P.; Tang, W.; Gomez, M. R.; French, D. M.; Zier, J. C.; Gilgenbach, R. M.

    2011-10-01

    Contact resistance is important to integrated circuits, thin film devices, carbon nanotube based cathodes, MEMS relays and interconnectors, wire-array z-pinches, metal-insulator-vacuum junctions, and high power microwave sources, etc. This paper summarizes the recent modeling efforts at U of M, addressing the effect of dissimilar materials and of finite dimensions on the contact resistance of both bulk contacts and thin film contacts. Accurate analytical scaling laws are constructed for the contact resistance of both bulk and thin film contacts over a large range of resistivity ratios and aspect ratios in Cartesian and cylindrical geometries. They were validated against known limiting cases; and spot-checks with numerical simulations and experiments. Supported by AFOSR, AFRL, L-3, and Northrop-Grumman.

  9. Molecular solution processing of metal chalcogenide thin film solar cells

    NASA Astrophysics Data System (ADS)

    Yang, Wenbing

    The barrier to utilize solar generated electricity mainly comes from their higher cost relative to fossil fuels. However, innovations with new materials and processing techniques can potentially make cost effective photovoltaics. One such strategy is to develop solution processed photovoltaics which avoid the expensive vacuum processing required by traditional solar cells. The dissertation is mainly focused on two absorber material system for thin film solar cells: chalcopyrite CuIn(S,Se)2 (CISS) and kesterite Cu2ZnSn(S,Se) 4 organized in chronological order. Chalcopyrite CISS is a very promising material. It has been demonstrated to achieve the highest efficiency among thin film solar cells. Scaled-up industry production at present has reached the giga-watt per year level. The process however mainly relies on vacuum systems which account for a significant percentage of the manufacturing cost. In the first section of this dissertation, hydrazine based solution processed CISS has been explored. The focus of the research involves the procedures to fabricate devices from solution. The topics covered in Chapter 2 include: precursor solution synthesis with a focus on understanding the solution chemistry, CISS absorber formation from precursor, properties modification toward favorable device performance, and device structure innovation toward tandem device. For photovoltaics to have a significant impact toward meeting energy demands, the annual production capability needs to be on TW-level. On such a level, raw materials supply of rare elements (indium for CIS or tellurium for CdTe) will be the bottleneck limiting the scalability. Replacing indium with zinc and tin, earth abundant kesterite CZTS exhibits great potential to reach the goal of TW-level with no limitations on raw material availability. Chapter 3 shows pioneering work towards solution processing of CZTS film at low temperature. The solution processed devices show performances which rival vacuum

  10. Organic thin film transistors: from active materials to novel applications

    NASA Astrophysics Data System (ADS)

    Torsi, L.; Cioffi, N.; Di Franco, C.; Sabbatini, L.; Zambonin, P. G.; Bleve-Zacheo, T.

    2001-08-01

    In this paper, a bird's eye view of most of the organic materials employed as n-channel and p-channel transistor active layers is given along with the relevant device performances; organic thin film transistors (OTFT) operation regimes are discussed and an interesting perspective application of OTFT as multi-parameter gas sensor is proposed.

  11. Chloroaluminum phthalocyanine thin films: chemical reaction and molecular orientation.

    PubMed

    Latteyer, Florian; Peisert, Heiko; Uihlein, Johannes; Basova, Tamara; Nagel, Peter; Merz, Michael; Schuppler, Stefan; Chassé, Thomas

    2013-05-01

    The chemical transformation of the polar chloroaluminum phthalocyanine, AlClPc, to μ-(oxo)bis(phthalocyaninato)aluminum(III), (PcAl)2O, in thin films on indium tin oxide is studied and its influence on the molecular orientation is discussed. The studies were conducted using complementary spectroscopic techniques: Raman spectroscopy, X-ray photoelectron spectroscopy, and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. In addition, density functional theory calculations were performed in order to identify specific vibrations and to monitor the product formation. The thin films of AlClPc were annealed in controlled environmental conditions to obtain (PcAl)2O. It is shown that the chemical transformation in the thin films can proceed only in the presence of water. The influence of the reaction and the annealing on the molecular orientation was studied with Raman spectroscopy and NEXAFS spectroscopy in total electron yield and partial electron yield modes. The comparison of the results obtained from these techniques allows the determination of the molecular orientation of the film as a function of the probing depth. PMID:23494276

  12. Supercritical fluid molecular spray thin films and fine powders

    DOEpatents

    Smith, Richard D.

    1988-01-01

    Solid films are deposited, or fine powders formed, by dissolving a solid material into a supercritical fluid solution at an elevated pressure and then rapidly expanding the solution through a short orifice into a region of relatively low pressure. This produces a molecular spray which is directed against a substrate to deposit a solid thin film thereon, or discharged into a collection chamber to collect a fine powder. The solvent is vaporized and pumped away. Solution pressure is varied to determine, together with flow rate, the rate of deposition and to control in part whether a film or powder is produced and the granularity of each. Solution temperature is varied in relation to formation of a two-phase system during expansion to control porosity of the film or powder. A wide variety of film textures and powder shapes are produced of both organic and inorganic compounds. Films are produced with regular textural feature dimensions of 1.0-2.0 .mu.m down to a range of 0.01 to 0.1 .mu.m. Powders are formed in very narrow size distributions, with average sizes in the range of 0.02 to 5 .mu.m.

  13. Growth of thin films of organic nonlinear optical materials by vapor growth processes - An overview and examination of shortfalls

    NASA Technical Reports Server (NTRS)

    Frazier, D. O.; Penn, B. G.; Witherow, W. K.; Paley, M. S.

    1991-01-01

    Research on the growth of second- and third-order nonlinear optical (NLO) organic thin film by vapor deposition is reviewed. Particular attention is given to the experimental methods for growing thin films of p-chlorophenylurea, diacetylenes, and phthalocyanines; characteristics of the resulting films; and approaches for advancing thin film technology. It is concluded that the growth of NLO thin films by vapor processes is a promising method for the fabrication of planar waveguides for nonlinear optical devices. Two innovative approaches are proposed including a method of controlling the input beam frequency to maximize nonlinear effects in thin films and single crystals, and the alternate approach to the molecular design of organic NLO materials by increasing the transition dipole moment between ground and excited states of the molecule.

  14. Thin film materials and devices for resistive temperature sensing applications

    NASA Astrophysics Data System (ADS)

    Basantani, Hitesh A.

    Thin films of vanadium oxide (VOx) and hydrogenated amorphous silicon (a-Si:H) are the two dominant material systems used in resistive infrared radiation detectors (microbolometers) for sensing long wave infrared (LWIR) wavelengths in the 8--14 microm range. Typical thin films of VO x (x < 2) currently used in the bolometer industry have a magnitude of temperature coefficient of resistance (TCR) between 2%/K -- 3%/K. In contrast, thin films of hydrogenated germanium (SiGe:H) have |TCR| between 3%/K to 4%/K. Devices made from either of these materials have resulted in similar device performance with NETD ≈ 25 mK. The performance of the microbolometers is limited by the electronic noise, especially 1/f noise. Therefore, regardless of the choice of bolometer sensing material and read out circuitry, manufacturers are constantly striving to reduce 1/f noise while simultaneously increasing TCR to give better signal to noise ratios in their bolometers and ultimately, better image quality with more thermal information to the end user. In this work, thin films of VOx and hydrogenated germanium (Ge:H), having TCR values > 4 %/K are investigated as potential candidates for higher sensitivity next generation of microbolometers. Thin films of VO x were deposited by Biased Target Ion Beam Deposition (BTIBD) (˜85 nm thick). Electrical characterization of lateral resistor structures showed resistivity ranging from 104 O--cm to 2.1 x 104 O--cm, TCR varying from --4%/K to --5%/K, normalized Hooge parameter (alphaH/n) of 5 x 10 -21 to 5 x 10-18 cm3. Thin films of Ge:H were deposited by plasma enhanced chemical vapor deposition (PECVD) by incorporating an increasing amount of crystal fraction in the growing thin films. Thin films of Ge:H having a mixed phase, amorphous + nanocrystalline, having a |TCR| > 6 %/K were deposited with resistivity < 2,300 O--cm and a normalized Hooge's parameter 'alphaH/n' < 2 x 10-20 cm3. Higher TCR materials are desired, however, such materials have

  15. Permanent laser conditioning of thin film optical materials

    DOEpatents

    Wolfe, C. Robert; Kozlowski, Mark R.; Campbell, John H.; Staggs, Michael; Rainer, Frank

    1995-01-01

    The invention comprises a method for producing optical thin films with a high laser damage threshold and the resulting thin films. The laser damage threshold of the thin films is permanently increased by irradiating the thin films with a fluence below an unconditioned laser damage threshold.

  16. Permanent laser conditioning of thin film optical materials

    DOEpatents

    Wolfe, C.R.; Kozlowski, M.R.; Campbell, J.H.; Staggs, M.; Rainer, F.

    1995-12-05

    The invention comprises a method for producing optical thin films with a high laser damage threshold and the resulting thin films. The laser damage threshold of the thin films is permanently increased by irradiating the thin films with a fluence below an unconditioned laser damage threshold. 9 figs.

  17. Thin film microelectronics materials production in the vacuum of space

    NASA Astrophysics Data System (ADS)

    Ignatiev, A.; Sterling, M.; Horton, C.; Freundlich, A.; Pei, S.; Hill, R.

    1997-01-01

    The international Space Station era will open up a new dimension in the use of one of the unique attributes of space, vacuum, for the production of advanced semiconductor materials and devices for microelectronics applications. Ultra-vacuum is required for the fabrication in thin film form of high quality semiconductors. This can be accomplished behind a free flying platform similar to the current Wake Shield Facility which is specifically designed to support in-space production. The platform will require apparatus for thin film growth, a robotics interface to allow for the change out of raw materials and the harvesting of finished product, and a servicing plant incorporating Space Station that will support long-term utilization of the platform.

  18. Microwave plasma assisted supersonic gas jet deposition of thin film materials

    DOEpatents

    Schmitt, III, Jerome J.; Halpern, Bret L.

    1993-01-01

    An apparatus for fabricating thin film materials utilizing high speed gas dynamics relies on supersonic free jets of carrier gas to transport depositing vapor species generated in a microwave discharge to the surface of a prepared substrate where the vapor deposits to form a thin film. The present invention generates high rates of deposition and thin films of unforeseen high quality at low temperatures.

  19. Thin films of copper antimony sulfide: A photovoltaic absorber material

    SciTech Connect

    Ornelas-Acosta, R.E.; Shaji, S.; Avellaneda, D.; Castillo, G.A.; Das Roy, T.K.; Krishnan, B.

    2015-01-15

    Highlights: • CuSbS{sub 2} thin films were prepared by heating Sb{sub 2}S{sub 3}/Cu layers. • Analyzed the structure, composition, optical, and electrical properties. • PV structures: glass/SnO{sub 2}:F/n-CdS/p-CuSbS{sub 2}/C/Ag were formed at different conditions. • The PV parameters (J{sub sc}, V{sub oc}, and FF) were evaluated from the J–V characteristics. • J{sub sc}: 0.52–3.20 mA/cm{sup 2}, V{sub oc}:187–323 mV, FF: 0.27–0.48 were obtained. - Abstract: In this work, we report preparation and characterization of CuSbS{sub 2} thin films by heating glass/Sb{sub 2}S{sub 3}/Cu layers and their use as absorber material in photovoltaic structures: glass/SnO{sub 2}:F/n-CdS/p-CuSbS{sub 2}/C/Ag. The Sb{sub 2}S{sub 3} thin films of 600 nm were prepared by chemical bath deposition on which copper thin films of 50 nm were thermally evaporated, and the glass/Sb{sub 2}S{sub 3}/Cu multilayers were heated in vacuum at different temperatures. X-ray diffraction analysis showed the formation of orthorhombic CuSbS{sub 2} after heating the precursor layers. Studies on identification and chemical state of the elements were done using X-ray photoelectron spectroscopy. The optical band gap of the CuSbS{sub 2} thin films was 1.55 eV and the thin films were photoconductive. The photovoltaic parameters of the devices using CuSbS{sub 2} as absorber and CdS as window layer were evaluated from the J–V curves, yielding J{sub sc}, V{sub oc}, and FF values in the range of 0.52–3.20 mA/cm{sup 2}, 187–323 mV, and 0.27–0.48, respectively, under illumination of AM1.5 radiation.

  20. Electronic processes in thin-film PV materials. Final report

    SciTech Connect

    Taylor, P.C.; Chen, D.; Chen, S.L.

    1998-07-01

    The electronic and optical processes in an important class of thin-film PV materials, hydrogenated amorphous silicon (a-Si:H) and related alloys, have been investigated using several experimental techniques designed for thin-film geometries. The experimental techniques include various magnetic resonance and optical spectroscopies and combinations of these two spectroscopies. Two-step optical excitation processes through the manifold of silicon dangling bond states have been identifies as important at low excitation energies. Local hydrogen motion has been studied using nuclear magnetic resonance techniques and found to be much more rapid than long range diffusion as measured by secondary ion mass spectroscopy. A new metastable effect has been found in a-Si:H films alloyed with sulfur. Spin-one optically excited states have been unambiguously identified using optically detected electron spin resonance. Local hydrogen bonding in microcrystalline silicon films has been studied using NMR.

  1. Photoacoustic characterization of the mechanical properties of thin film materials

    NASA Astrophysics Data System (ADS)

    Zhang, Feifei; Krishnaswamy, Sridhar; Fei, Dong; Rebinsky, Douglas A.

    2005-05-01

    Two high frequency photoacoustic techniques were applied to investigate the mechanical properties of two sets of thin film materials in this work. Broadband photoacoustic guided-wave method was used to measure the guided-wave phase velocity dispersion curves of nano-structured diamond-like carbon hard coatings. The experimental velocity spectra were analyzed by a nonlinear optimization approach in conjunction with a multi-layer wave-propagation model. The derived Young"s moduli using the broadband photoacoustic technique were compared with line-focus acoustic microscopy and nano-indentation tests and good quantitative agreement is found. In a second set of experiments, ultra-thin two-layer aluminum and silicon nitride thin film materials were tested using the femtosecond transient pump-probe method using high frequency bulk waves generated by the ultra-fast laser pulses. The measured moduli of silicon nitride thin layers are in the range of 270 - 340 GPa. Photoacoustic methods are shown to be suitable for in-situ and non-destructive evaluation of the mechanical properties of thin films.

  2. Deposition of thin films of multicomponent materials

    NASA Technical Reports Server (NTRS)

    Thakoor, Sarita (Inventor)

    1993-01-01

    Composite films of multicomponent materials, such as oxides and nitrides, e.g., lead zirconate titanate, are deposited by dc magnetron sputtering, employing a rotating substrate holder, which rotates relative to a plurality of targets, one target for each metal element of the multicomponent material. The sputtering is carried out in a reactive atmosphere. The substrates on which the layers are deposited are at ambient temperature. Following deposition of the composite film, the film is heated to a temperature sufficient to initiate a solid state reaction and form the final product, which is substantially single phase and substantially homogeneous.

  3. Electrodeposited polymer encapsulated nickel sulphide thin films: frequency switching material

    NASA Astrophysics Data System (ADS)

    Jana, Sumanta; Mukherjee, Nillohit; Chakraborty, Biswajit; Mitra, Bibhas Chandra; Mondal, Anup

    2014-05-01

    Polyvinylpyrrolidone (PVP) encapsulated nickel sulfide (NiS) thin films have been synthesized electrochemically from aqueous solution of hydrated nickel chloride (NiCl2, 6H2O), thioacetamide (CH3C(S) NH2) (TAA) and polyvinylpyrrolidone (PVP). Surface modification of nickel sulfide (NiS) thin films was achieved by this polymer encapsulation. X-ray diffraction (XRD), high resolution transmission electron microscope (HRTEM), field emission scanning electron microscopy (FESEM) and Energy dispersive X-radiation (EDAX) techniques were used for the characterization of thin films. Infrared spectroscopy (IR) confirmed the formation of polymer encapsulated semiconductor. Frequency switching generation study shows that the encapsulated material could be used as a frequency switching device that generates a frequency ∼ 50 Hz under 1 Sun illumination. Encapsulation with PVP causes surface modification that reduces the surface states and barrier height. As a result, the width of the depletion region decreases. So the number of electron-hole pairs increases. Consequently, the number of excitons and exciton related emission increases and this leads to reduction of recombination process and shows photo induced frequency switching phenomenon.

  4. Thin film thermocouples for thermoelectric characterization of nanostructured materials

    NASA Astrophysics Data System (ADS)

    Grayson, Matthew; Zhou, Chuanle; Varrenti, Andrew; Chyung, Seung Hye; Long, Jieyi; Memik, Seda

    2011-03-01

    The increased use of nanostructured materials as thermoelectrics requires reliable and accurate characterization of the anisotropic thermal coefficients of small structures, such as superlattices and quantum wire networks. Thin evaporated metal films can be used to create thermocouples with a very small thermal mass and low thermal conductivity, in order to measure thermal gradients on nanostructures and thereby measure the thermal conductivity and the Seebeck coefficient of the nanostructure. In this work we confirm the known result that thin metal films have lower Seebeck coefficients than bulk metals, and we also calibrate the Seebeck coefficient of a thin-film Ni/Cr thermocouple with 50 nm thickness, showing it to have about 1/4 the bulk value. We demonstrate reproducibility of this thin-filmSeebeck coefficient on multiple substrates, and we show that this coefficient does, in fact, change as a function of film thickness. We will discuss prototype measurement designs and preliminary work as to how these thin films can be used to study both Seebeck coefficients and thermal conductivities of superlattices in various geometries. The same technology can in principle be used on integrated circuits for thermal mapping, under the name ``Integrated On-Chip Thermocouple Array'' (IOTA).

  5. Waveguides in Thin Film Polymeric Materials

    NASA Technical Reports Server (NTRS)

    Sakisov, Sergey; Abdeldayem, Hossin; Venkateswarlu, Putcha; Teague, Zedric

    1996-01-01

    Results on the fabrication of integrated optical components in polymeric materials using photo printing methods will be presented. Optical waveguides were fabricated by spin coating preoxidized silicon wafers with organic dye/polymer solution followed by soft baking. The waveguide modes were studied using prism coupling technique. Propagation losses were measured by collecting light scattered from the trace of a propagation mode by either scanning photodetector or CCD camera. We observed the formation of graded index waveguides in photosensitive polyimides after exposure of UV light from a mercury arc lamp. By using a theoretical model, an index profile was reconstructed which is in agreement with the profile reconstructed by the Wentzel-Kramers-Brillouin calculation technique using a modal spectrum of the waveguides. Proposed mechanism for the formation of the graded index includes photocrosslinking followed by UV curing accompanied with optical absorption increase. We also developed the prototype of a novel single-arm double-mode interferometric sensor based on our waveguides. It demonstrates high sensitivity to the chance of ambient temperature. The device can find possible applications in aeropropulsion control systems.

  6. Molecular Sieves: Porous Organic Cage Thin Films and Molecular-Sieving Membranes (Adv. Mater. 13/2016).

    PubMed

    Song, Qilei; Jiang, Shan; Hasell, Tom; Liu, Ming; Sun, Shijing; Cheetham, Anthony K; Sivaniah, Easan; Cooper, Andrew I

    2016-04-01

    Porous organic cage molecules are a new class of molecular materials that combine microporosity and solution-processability. On page 2629, E. Sivaniah, A. I. Cooper, and co-workers demonstrate solution processing of cage molecules into thin films with tunable structures. For the first time, cage molecules are fabricated into continuous and pinhole-free microporous molecular-sieving membranes, as confirmed by selective gas transport in terms of high permeance and molecular selectivity. Image credit: Adam Kewley. PMID:27037946

  7. Designing thin film materials — Ternary borides from first principles

    PubMed Central

    Euchner, H.; Mayrhofer, P.H.

    2015-01-01

    Exploiting the mechanisms responsible for the exceptional properties of aluminum based nitride coatings, we apply ab initio calculations to develop a recipe for designing functional thin film materials based on ternary diborides. The combination of binary diborides, preferring different structure types, results in supersaturated metastable ternary systems with potential for phase transformation induced effects. For the exemplary cases of MxW1 − xB2 (with M = Al, Ti, V) we show by detailed ab initio calculations that the respective ternary solid solutions are likely to be experimentally accessible by modern depositions techniques. PMID:26082562

  8. Characterization of diamond thin films and related materials

    NASA Astrophysics Data System (ADS)

    McKindra, Travis Kyle

    Thin carbon films including sputtered deposited graphite and CO 2 laser-assisted combustion-flame deposited graphite and diamond thin films were characterized using optical and electron microscopy, X-ray diffraction and micro-Raman spectroscopy. Amorphous carbon thin films were deposited by DC magnetron sputtering using Ar/O2 gases. The film morphology changed with the oxygen content. The deposition rate decreased as the amount of oxygen increased due to oxygen reacting with the growing film. The use of oxygen in the working gas enhanced the crystalline nature of the films. Graphite was deposited on WC substrates by a CO2 laser-assisted O2/C2H2 combustion-flame method. Two distinct microstructural areas were observed; an inner core of dense material surrounded by an outer shell of lamellar-like material. The deposits were crystalline regardless of the laser power and deposition times of a few minutes. Diamond films were deposited by a CO2 laser-assisted O 2/C2H2/C2H4 combustion-flame method with the laser focused parallel to the substrate surface. The laser enhanced diamond growth was most pronounced when deposited with a 10.532 microm CO2 laser wavelength tuned to the CH2-wagging vibrational mode of the C2H4 molecule. Nucleation of diamond thin films deposited with and without using a CO 2 laser-assisted combustion-flame process was investigated. With no laser there was nucleation of a sub-layer of grains followed by irregular grain growth. An untuned laser wavelength yielded nucleation of a sub-layer then columnar grain growth. The 10.532 microm tuned laser wavelength caused growth of columnar grains.

  9. The Constitutive Modeling of Thin Films with Randon Material Wrinkles

    NASA Technical Reports Server (NTRS)

    Murphey, Thomas W.; Mikulas, Martin M.

    2001-01-01

    Material wrinkles drastically alter the structural constitutive properties of thin films. Normally linear elastic materials, when wrinkled, become highly nonlinear and initially inelastic. Stiffness' reduced by 99% and negative Poisson's ratios are typically observed. This paper presents an effective continuum constitutive model for the elastic effects of material wrinkles in thin films. The model considers general two-dimensional stress and strain states (simultaneous bi-axial and shear stress/strain) and neglects out of plane bending. The constitutive model is derived from a traditional mechanics analysis of an idealized physical model of random material wrinkles. Model parameters are the directly measurable wrinkle characteristics of amplitude and wavelength. For these reasons, the equations are mechanistic and deterministic. The model is compared with bi-axial tensile test data for wrinkled Kaptong(Registered Trademark) HN and is shown to deterministically predict strain as a function of stress with an average RMS error of 22%. On average, fitting the model to test data yields an RMS error of 1.2%

  10. Channel cracks in atomic-layer and molecular-layer deposited multilayer thin film coatings

    SciTech Connect

    Long, Rong; Dunn, Martin L.

    2014-06-21

    Metal oxide thin film coatings produced by atomic layer deposition have been shown to be an effective permeation barrier. The primary failure mode of such coatings under tensile loads is the propagation of channel cracks that penetrate vertically into the coating films. Recently, multi-layer structures that combine the metal oxide material with relatively soft polymeric layers produced by molecular layer deposition have been proposed to create composite thin films with desired properties, including potentially enhanced resistance to fracture. In this paper, we study the effects of layer geometry and material properties on the critical strain for channel crack propagation in the multi-layer composite films. Using finite element simulations and a thin-film fracture mechanics formalism, we show that if the fracture energy of the polymeric layer is lower than that of the metal oxide layer, the channel crack tends to penetrate through the entire composite film, and dividing the metal oxide and polymeric materials into thinner layers leads to a smaller critical strain. However, if the fracture energy of the polymeric material is high so that cracks only run through the metal oxide layers, more layers can result in a larger critical strain. For intermediate fracture energy of the polymer material, we developed a design map that identifies the optimal structure for given fracture energies and thicknesses of the metal oxide and polymeric layers. These results can facilitate the design of mechanically robust permeation barriers, an important component for the development of flexible electronics.

  11. Thin film resistive materials: past, present and future

    NASA Astrophysics Data System (ADS)

    Cherian Lukose, C.; Zoppi, G.; Birkett, M.

    2016-01-01

    This paper explores the key developments in thin film resistive materials for use in the fabrication of discrete precision resistors. Firstly an introduction to the preparation of thin films and their fundamental properties is given with respect to well established systems such as NiCr, TaN and CrSiO. The effect of doping these systems in both solid and gaseous forms to further refine their structural and electrical properties is then discussed before the performance of more recent materials systems such as CuAlMo and MmAgCuN are reviewed. In addition to performance of the materials themselves, the effect of varying processing parameters such as deposition pressure and temperature and subsequent annealing environment, as well as laser trimming energy and geometry are also studied. It is shown how these parameters can be systematically controlled to produce films of the required properties for varying applications such as high precision, long term stability and high power pulse performance.

  12. Failure and fracture of thin film materials for MEMS

    NASA Astrophysics Data System (ADS)

    Jonnalagadda, Krishna Nagasai

    Design and reliable operation of Microelectromechanical systems (MEMS) depend on the material parameters that influence the failure and fracture properties of brittle and metallic thin films. Failure in brittle materials is quantified by the onset of catastrophic fracture, while in metals, the onset of inelastic deformation is considered as failure as it increases the material compliance. This dissertation research developed new experimental methods to address three aspects on the failure response of these two categories of materials: (a) the role of microstructure and intrinsic stress gradients in the opening mode fracture of mathematically sharp pre-cracks in amorphous and polycrystalline brittle thin films, (b) the critical conditions for mixed mode I/II pre-cracks and their comparison with linear elastic fracture mechanics (LEFM) criteria for crack initiation in homogeneous materials, and (c) the strain rate sensitivity of textured nanocrystalline Au and Pt films with grain sizes of 38 nm and 25 nm respectively. One of the technical objectives of this research was to develop experimental methods and tools that could become standards in MEMS and thin film experimental mechanics. In this regard, a new method was introduced to conduct mode I and mixed mode I/II fracture studies with microscale thin film specimens containing sharp edge pre-cracks. The mode I experiments permitted the direct application of LEFM handbook solutions. On the other hand, the newly introduced mixed mode I/II experiments in thin films were conducted by establishing a new protocol that employs non-standard oblique edge pre-cracks and a numerical analysis based on the J-integral to calculate the stress intensity factors. Similarly, a new experimental protocol has been implemented to carry out experiments with metallic thin films at strain rates that vary by more than six orders of magnitude. The results of mode I fracture experiments concluded that grain inhomogeneity in polycrystalline

  13. Chemically Deposited Thin-Film Solar Cell Materials

    NASA Technical Reports Server (NTRS)

    Raffaelle, R.; Junek, W.; Gorse, J.; Thompson, T.; Harris, J.; Hehemann, D.; Hepp, A.; Rybicki, G.

    2005-01-01

    We have been working on the development of thin film photovoltaic solar cell materials that can be produced entirely by wet chemical methods on low-cost flexible substrates. P-type copper indium diselenide (CIS) absorber layers have been deposited via electrochemical deposition. Similar techniques have also allowed us to incorporate both Ga and S into the CIS structure, in order to increase its optical bandgap. The ability to deposit similar absorber layers with a variety of bandgaps is essential to our efforts to develop a multi-junction thin-film solar cell. Chemical bath deposition methods were used to deposit a cadmium sulfide (CdS) buffer layers on our CIS-based absorber layers. Window contacts were made to these CdS/CIS junctions by the electrodeposition of zinc oxide (ZnO). Structural and elemental determinations of the individual ZnO, CdS and CIS-based films via transmission spectroscopy, x-ray diffraction, x-ray photoelectron spectroscopy and energy dispersive spectroscopy will be presented. The electrical characterization of the resulting devices will be discussed.

  14. Novel solutions for thin film layer deposition for organic materials

    NASA Astrophysics Data System (ADS)

    Keiper, Dietmar; Long, Michael; Schwambera, Markus; Gersdorff, Markus; Kreis, Juergen; Heuken, Michael

    2011-03-01

    Innovative systems for carrier-gas enhanced vapor phase deposition of organic layers offer advanced methods for the precise deposition of complex thin-film layer stacks. The approach inherently avoids potential short-comings from solvent-based polymer deposition and offers new opportunities. The process operates at low pressure (thus avoiding complex vacuum setups), and, by employing AIXTRON's extensive experience in freely scalable solutions, can be adapted to virtually any production process and allows for R&D and production systems alike. Deposition of organic layers and stacks recommends the approach for a wide range of organic small molecule and polymer materials (including layers with gradual change of the composition), for conductive layers, for dielectric layers, for barrier systems, for OLED materials, and surface treatments such as oleophobic / hydrophobic coatings. With the combination of other vapor phase deposition solutions, hybrid systems combining organic and inorganic materials and other advanced stacks can be realized.

  15. Novel wide band gap materials for highly efficient thin film tandem solar cells. Final report

    SciTech Connect

    Brian E. Hardin; Connor, Stephen T.; Peters, Craig H.

    2012-06-11

    Tandem solar cells (TSCs), which use two or more materials to absorb sunlight, have achieved power conversion efficiencies of >25% versus 11-20% for commercialized single junction solar cell modules. The key to widespread commercialization of TSCs is to develop the wide-band, top solar cell that is both cheap to fabricate and has a high open-circuit voltage (i.e. >1V). Previous work in TSCs has generally focused on using expensive processing techniques with slow growth rates resulting in costs that are two orders of magnitude too expensive to be used in conventional solar cell modules. The objective of the PLANT PV proposal was to investigate the feasibility of using Ag(In,Ga)Se2 (AIGS) as the wide-bandgap absorber in the top cell of a thin film tandem solar cell (TSC). Despite being studied by very few in the solar community, AIGS solar cells have achieved one of the highest open-circuit voltages within the chalcogenide material family with a Voc of 949 mV when grown with an expensive processing technique (i.e. Molecular Beam Epitaxy). PLANT PV's goal in Phase I of the DOE SBIR was to (1) develop the chemistry to grow AIGS thin films via solution processing techniques to reduce costs and (2) fabricate new device architectures with high open-circuit voltage to produce full tandem solar cells in Phase II. PLANT PV attempted to translate solution processing chemistries that were successful in producing >12% efficient Cu(In,Ga)Se2 solar cells by replacing copper compounds with silver. The main thrust of the research was to determine if it was possible to make high quality AIGS thin films using solution processing and to fully characterize the materials properties. PLANT PV developed several different types of silver compounds in an attempt to fabricate high quality thin films from solution. We found that silver compounds that were similar to the copper based system did not result in high quality thin films. PLANT PV was able to deposit AIGS thin

  16. Microwave plasma assisted supersonic gas jet deposition of thin film materials

    DOEpatents

    Schmitt, J.J. III; Halpern, B.L.

    1993-10-26

    An apparatus for fabricating thin film materials utilizing high speed gas dynamics relies on supersonic free jets of carrier gas to transport depositing vapor species generated in a microwave discharge to the surface of a prepared substrate where the vapor deposits to form a thin film. The present invention generates high rates of deposition and thin films of unforeseen high quality at low temperatures. 5 figures.

  17. Nonlinear Optical Properties of Organic and Polymeric Thin Film Materials of Potential for Microgravity Processing Studies

    NASA Technical Reports Server (NTRS)

    Abdeldayem, Hossin; Frazier, Donald O.; Paley, Mark S.; Penn, Benjamin; Witherow, William K.; Bank, Curtis; Shields, Angela; Hicks, Rosline; Ashley, Paul R.

    1996-01-01

    In this paper, we will take a closer look at the state of the art of polydiacetylene, and metal-free phthalocyanine films, in view of the microgravity impact on their optical properties, their nonlinear optical properties and their potential advantages for integrated optics. These materials have many attractive features with regard to their use in integrated optical circuits and optical switching. Thin films of these materials processed in microgravity environment show enhanced optical quality and better molecular alignment than those processed in unit gravity. Our studies of these materials indicate that microgravity can play a major role in integrated optics technology. Polydiacetylene films are produced by UV irradiation of monomer solution through an optical window. This novel technique of forming polydiacetylene thin films has been modified for constructing sophisticated micro-structure integrated optical patterns using a pre-programmed UV-Laser beam. Wave guiding through these thin films by the prism coupler technique has been demonstrated. The third order nonlinear parameters of these films have been evaluated. Metal-free phthalocyanine films of good optical quality are processed in our laboratories by vapor deposition technique. Initial studies on these films indicate that they have excellent chemical, laser, and environmental stability. They have large nonlinear optical parameters and show intrinsic optical bistability. This bistability is essential for optical logic gates and optical switching applications. Waveguiding and device making investigations of these materials are underway.

  18. Epitaxial thin film deposition of magnetostrictive materials and its effect on magnetic anisotropy

    NASA Astrophysics Data System (ADS)

    McClure, Adam Marc

    Magnetostriction means that the dimensions of a material depend on its magnetization. The primary goal of this dissertation was to understand the effect of magnetostriction on the magnetic anisotropy of single crystal magnetostrictive thin films, where the epitaxial pinning of the material to a substrate could inhibit its conversion to new dimensions. In order to address this goal, several Fe-based binary alloys were deposited onto various substrates by molecular beam epitaxy. The samples were characterized by an array of techniques including electron diffraction, Rutherford backscattering, vibrating sample magnetometry, ferromagnetic resonance, and x-ray absorption spectroscopies. The attempted growths of crystalline magnetostrictive thin films resulted in successful depositions of Fe1-xGax and Fe1-x Znx. Depositions onto MgO(001) substrates result in an in-plane cubic magnetic anisotropy, as expected from the cubic symmetry of the Fe-based thin films, and a strong out-of-plane uniaxial anisotropy that forces the magnetization to lie in the plane of the films. Depositions onto ZnSe/GaAs(001) substrates feature an additional in-plane uniaxial anisotropy. The magnitudes and signs of the in-plane anisotropies depend on the Ga content. Furthermore, the cubic anisotropy constant of Fe1-xGax samples deposited onto MgO substrates switches sign at a lower Ga concentration than is seen in bulk Fe1-xGax. The effect on the magnetic anisotropy of depositing a magnetostrictive material as an epitaxial thin film is influenced by the material's magnetostrictive properties and the substrate upon which it is deposited. In particular, pinning a magnetoelastic material to a substrate will modify its cubic anisotropy, and depositions on substrates compliant to an anisotropic strain relaxation may result in a strong in-plane uniaxial anisotropy.

  19. Fundamentals of polycrystalline thin film materials and devices

    NASA Astrophysics Data System (ADS)

    Baron, Bill N.; Birkmire, Robert W.; Phillips, James E.; Shafarman, William N.; Hegedus, Steven S.; McCandless, Brian E.

    1991-01-01

    This report presents the results of a one-year research program on polycrystalline thin-film solar cells. The research was conducted to better understand the limitations and potential of solar cells using CuInSe2 and CdTe by systematically investigating the fundamental relationships linking material processing, material properties, and device behavior. By selenizing Cu and In layers, we fabricated device-quality CuInSe2 thin films and demonstrated a CuInSe2 solar cell with 7 percent efficiency. We added Ga, to increase the band gap of CuInSe2 devices to increase the open-circuit voltage to 0.55 V. We fabricated and analyzed CuInGaSe2/CuInSe2 devices to demonstrate the potential for combining the benefits of higher V(sub oc) while retaining the current-generating capacity of CuInSe2. We fabricated an innovative superstrate device design with more than 5 percent efficiency, as well as a bifacial spectral-response technique for determining the electron diffusion length and optical absorption coefficient of CuInSe2 in an operational cell. The diffusion length was found to be greater than 1 micron. We qualitatively modeled the effect of reducing heat treatments in hydrogen and oxidizing treatments in air on the I-V behavior of CuInSe2 devices. We also investigated post-deposition heat treatments and chemical processing and used them to fabricate a 9.6 percent-efficient CdTe/CdS solar cell using physical vapor deposition.

  20. Fundamentals of polycrystalline thin film materials and devices

    SciTech Connect

    Baron, B.N.; Birkmire, R.W.; Phillips, J.E.; Shafarman, W.N.; Hegedus, S.S.; McCandless, B.E. . Inst. of Energy Conversion)

    1991-01-01

    This report presents the results of a one-year research program on polycrystalline thin-film solar cells. The research was conducted to better understand the limitations and potential of solar cells using CuInSe{sub 2} and CdTe by systematically investigating the fundamental relationships linking material processing, material properties, and device behavior. By selenizing Cu and In layers, we fabricated device-quality CuInSe{sub 2} thin films and demonstrated a CuInSe{sub 2} solar cell with 7% efficiency. We added Ga, to increase the band gap of CuInSe{sub 2} devices to increase the open-circuit voltage to 0.55 V. We fabricated and analyzed Cu(InGa)Se{sub 2}/CuInSe{sub 2} devices to demonstrate the potential for combining the benefits of higher V{sub oc} while retaining the current-generating capacity of CuInSe{sub 2}. We fabricated an innovative superstrate device design with more than 5% efficiency, as well as a bifacial spectral-response technique for determining the electron diffusion length and optical absorption coefficient of CuInSe{sub 2} in an operational cell. The diffusion length was found to be greater than 1 {mu}m. We qualitatively modeled the effect of reducing heat treatments in hydrogen and oxidizing treatments in air on the I-V behavior of CuInSe{sub 2} devices. We also investigated post-deposition heat treatments and chemical processing and used them to fabricate a 9.6%-efficient CdTe/CdS solar cell using physical vapor deposition.

  1. Ordered nanocolumn-array organic semiconductor thin films with controllable molecular orientation

    NASA Astrophysics Data System (ADS)

    Yang, Bingchu; Duan, Haichao; Zhou, Conghua; Gao, Yongli; Yang, Junliang

    2013-12-01

    Ordered nanocolumn-array phthalocynine semiconductor thin films with controllable molecular orientation were fabricated by combining molecular template growth (MTG) and glancing angle deposition (GLAD) techniques. The pre-deposited planar perylene-3,4,9,10-tetracarboxylic-3,4,9,10-dianhydride (PTCDA) molecular template layer induces phthalocynine molecules arrange with a lying-down molecular orientation, in which the π-π stacking is vertical to the substrate improving the charge transport along the vertical direction; While the GLAD technique supports the formation of nanocolumn-array thin films, supplying a much larger exposed surface area than the conventional compact thin films. The ordered nanocolumn-array thin films with controllable molecular orientation fabricated by combining MTG and GLAD techniques show the potentials to fabricate ordered bulk heterojunction for improving the performance in organic photovoltaics.

  2. Molecular dynamics studies of thin film nucleation and substrate modification

    NASA Astrophysics Data System (ADS)

    Hu, Yanhong

    Deposition of energetic particles on solid surfaces has found increasing application in surface science. However, the detailed surface chemistry and relevant atomic mechanisms are not well understood. Molecular dynamics (MD) simulations are an ideal method to study these processes atomistically because they usually occur on short time scales (of the order of a few picoseconds). In this dissertation, MD simulations are performed to investigate thin film formation through organic cluster beam deposition and chemical modification of carbon nanotube/polymer composites via polyatomic ion beam deposition. The interatomic forces are calculated from the reactive empirical bond-order (REBO) potential for carbon-based systems coupled with the Lennard-Jones potentials. The reliability of this approach is examined by comparing its predictions for ethylene-cluster beam deposition with the results of a more accurate order-N nonorthogonal tight-binding method. The results show that the REBO potential captures the general characters of the relevant chemistry. The deposition processes of interest occur at room temperature; hence, appropriate temperature control methods must be employed in the simulations. A comparison study of four temperature control methods during the simulation of cluster deposition finds that the generalized Langevin equation approach is sufficient for dissipation of excess system energy if the deposition occurs on a large enough substrate at a moderate incident energy (<40 eV/cluster-atom). A new temperature control method has been developed for use at higher incident energies. In the simulations of thin film formation through organic cluster beam deposition, the dependence of the results on the intracluster bonding, incident angle and deposition direction is examined. Beams of ethylene clusters, adamantane molecules, and C20 molecules are thus deposited on a diamond surface with varying lateral momenta along two different crystallographic orientations at

  3. Molecular dynamics simulation of VN thin films under indentation

    NASA Astrophysics Data System (ADS)

    Fu, Tao; Peng, Xianghe; Huang, Cheng; Yin, Deqiang; Li, Qibin; Wang, Zhongchang

    2015-12-01

    We investigated with molecular dynamics simulation the mechanical responses of VN (0 0 1) thin films subjected to indentation with a diamond columnar indenter. We calculated the generalized stacking-fault energies as a function of the displacement in the rbond2 1 1 0lbond2 directions on the {0 0 1}, {1 1 0}, and {1 1 1} planes, and analyzed systematically the microstructures and their evolution during the indentation with the centro-symmetry parameters and the slices of the VN films. We found the slips on {1 1 0}rbond2 1 1 0lbond2 of the VN film under indentation at the initial stage. With the increase of indentation depth, slips are also activated on {1 1 1}rbond2 1 1 0lbond2 and {1 0 0}rbond2 0 1 1lbond2 systems. We further found that the slip system is determined by the stacking-fault energy rather than the layer spacing. The indentations with other different parameters were also performed, and the results further prove the validity of the conclusion.

  4. Using Organic Light-Emitting Electrochemical Thin-Film Devices to Teach Materials Science

    ERIC Educational Resources Information Center

    Sevian, Hannah; Muller, Sean; Rudmann, Hartmut; Rubner, Michael F.

    2004-01-01

    Materials science can be taught by applying organic light-emitting electrochemical thin-film devices and in this method students were allowed to make a light-emitting device by spin coating a thin film containing ruthenium (II) complex ions onto a glass slide. Through this laboratory method students are provided with the opportunity to learn about…

  5. Organic and inorganic-organic thin film structures by molecular layer deposition: A review.

    PubMed

    Sundberg, Pia; Karppinen, Maarit

    2014-01-01

    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

  6. 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

  7. FMR study of thin film FeGe skyrmionic material

    NASA Astrophysics Data System (ADS)

    Bhallamudi, Vidya P.; Page, Michael R.; Gallagher, James; Purser, Carola; Schulze, Joseph; Yang, Fengyuan; Hammel, P. Chris

    Magnetic Skyrmions have attracted intense interest due to their novel topological properties and the potential for energy efficient computing. Magnetic dynamics play an important part in enabling some of these functionalities. Understanding these dynamics can shed light on the interplay of the various magnetic interactions that exist in these materials and lead to a rich magnetic phase diagram, including the Skyrmion phase. We have grown phase-pure FeGe epitaxial films on Si (111) and studied them using ferromagnetic resonance (FMR). FeGe has one of the highest recorded skyrmion transition temperatures, close to room temperature, and thin films are known to further stabilize the Skyrmion phase in the magnetic field-temperature space. We have performed cavity-based single frequency FMR from liquid nitrogen to room temperature on 120 nm thick films in both in-plane and out-of-plane geometries. The resulting complex spectra are consistent with those reported in literature for the bulk material and can be understood in terms of a conical model for the magnetism. Variable temperature broadband spectroscopy and measurements on thinner films, to better identify the various magnetic phases and their dynamic behavior, are ongoing and their progress will be discussed. Funding for this research was provided by the Center for Emergent Materials: an NSF MRSEC under Award Number DMR-1420451.

  8. Materials genomics of thin film strain relaxation by misfit dislocations

    NASA Astrophysics Data System (ADS)

    Hull, R.; Parvaneh, H.; Andersen, D.; Bean, John C.

    2015-12-01

    We summarize the development and implementation of a "process simulator" for modeling thin film strain relaxation by injection of misfit dislocations. The process simulator, initially developed for GexSi1-x/Si(100) lattice-mismatched epitaxy, integrates elasticity and dislocation theory with experimental measurements of kinetic parameters describing dislocation nucleation, propagation, and interactions. This enables predictive simulation of the development of misfit dislocation arrays during growth and thermal annealing sequences. Further, in the spirit of the materials genome initiative, we show how once a relatively complete description is built for one materials system, extension to a related system may be implemented using a greatly reduced data set. We illustrate this concept by translation of the simulator for GexSi1-x/Si(100) epitaxy into predictive simulation for the GexSi1-x/Si(110) system (which has quite different dislocation microstructure and kinetics) using greatly reduced data sets for the latter system and incorporating data refinement methods to extract unknown kinetic parameters. This sets the platform for extension of these methods to a broader set of strained layer systems.

  9. Thin film hydrogen sensors: A materials processing approach

    NASA Astrophysics Data System (ADS)

    Jayaraman, Raviprakash

    Hydrogen (H2) is consumed and produced in large quantities by chemical, petroleum, plastic, space and glass industries. Detection and quantitative estimation of H2 in a reliable and efficient manner is of great value in these applications, not only from a safety stand point but also economically beneficial. Hence the requirement for a simple but efficient hydrogen sensor. The simplest hydrogen sensors are based on monitoring changes in electrical properties of group VIII transition metals, especially palladium (Pd). Hydrogen adsorbs on Pd surface and diffuses into its bulk altering its electrical and optical properties. This variation is used to detect/estimate hydrogen in the ambience. However, at high hydrogen concentrations palladium undergoes a phase change. This causes an expansion of the lattice---a problem for fabricating reliable sensors using this metal. This problem was overcome by alloying palladium with nickel. Currently, sensors made from palladium alloy thin films (resistors and FET's) can detect/estimate hydrogen from ppm to 100% concentrations. However, these sensors are affected by the total gas pressure and other gases like carbon monoxide (CO), sulfur dioxide (SO 2), hydrogen sulfide (H2S). This work, for most part deals with resistors (chemiresistors). Resistors estimate hydrogen by correlating the change in resistance to the hydrogen concentration. Magnetron sputtering enables the deposition of films of different compositions and morphology. In this work, Pd and Pd/Ni alloy thin films resistors were fabricated by sputtering. Morphology was seen to have a significant effect on the hydrogen sensing property of these films. In presence of CO the response of these sensors are extremely sluggish, however by employing SiO2 barrier layer the response was greatly improved. It was noted that despite the sluggish response, the signal from the chemiresistors did saturate to same level as seen in absence of CO from gas mixture; contrary to the earlier

  10. Growth Parameters for Thin Film InBi Grown by Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Keen, B.; Makin, R.; Stampe, P. A.; Kennedy, R. J.; Sallis, S.; Piper, L. J.; McCombe, B.; Durbin, S. M.

    2014-04-01

    The alloying of bismuth with III-V semiconductors, in particular GaAs and InAs thin films grown by molecular beam epitaxy (MBE), has attracted considerable interest due to the accompanying changes in band structure and lattice constant. Specifically, bismuth incorporation in these compounds results in both a reduction in band gap (through shifting of the valence band) and an increase in the lattice constant of the alloy. To fully understand the composition of these alloys, a better understanding of the binary endpoints is needed. At present, a limited amount of literature exists on the III-Bi family of materials, most of which is theoretical work based on density functional theory calculations. The only III-Bi material known to exist (in bulk crystal form) is InBi, but its electrical properties have not been sufficiently studied and, to date, the material has not been fabricated as a thin film. We have successfully deposited crystalline InBi on (100) GaAs substrates using MBE. Wetting of the substrate is poor, and regions of varying composition exist across the substrate. To obtain InBi, the growth temperature had to be below 100 °C. It was found that film crystallinity improved with reduced Bi flux, into an In-rich regime. Additionally, attempts were made to grow AlBi and GaBi.

  11. Enhanced Rates of Photoinduced Molecular Orientation in a Series of Molecular Glassy Thin Films.

    PubMed

    Snell, Kristen E; Hou, Renjie; Ishow, Eléna; Lagugné-Labarthet, François

    2015-07-01

    Photoinduced orientation in a series of molecular glasses made of small push-pull azo derivatives is dynamically investigated for the first time. Birefringence measurements at 632.8 nm are conducted with a temporal resolution of 100 ms to probe the fast rate of the azo orientation induced under polarized light and its temporal stability over several consecutive cycles. To better evaluate the influence of the azo chemical substituents and their electronic properties on the orientation of the whole molecule, a series of push-pull azo derivatives involving a triphenylaminoazo core substituted with distinct electron-withdrawing moieties is studied. All resulting thin films are probed using polarization modulation infrared spectroscopy that yields dynamical linear dichroism measurements during a cycle of orientation followed by relaxation. We show here in particular that the orientation rates of small molecule-based azo materials are systematically increased up to 7-fold compared to those of a reference polymer counterpart. For specific compounds, the percentage of remnant orientation is also higher, which makes these materials of great interest and promising alternatives to azobenzene-containing polymers for a variety of applications requiring a fast response and absolute control over the molecular weight. PMID:26072966

  12. Thin film lithium-based batteries and electrochromic devices fabricated with nanocomposite electrode materials

    DOEpatents

    Gillaspie, Dane T; Lee, Se-Hee; Tracy, C. Edwin; Pitts, John Roland

    2014-02-04

    Thin-film lithium-based batteries and electrochromic devices (10) are fabricated with positive electrodes (12) comprising a nanocomposite material composed of lithiated metal oxide nanoparticles (40) dispersed in a matrix composed of lithium tungsten oxide.

  13. ZnO Thin Films Deposited on Textile Material Substrates for Biomedical Applications

    NASA Astrophysics Data System (ADS)

    Duta, L.; Popescu, A. C.; Dorcioman, G.; Mihailescu, I. N.; Stan, G. E.; Zgura, I.; Enculescu, I.; Dumitrescu, I.

    We report on the coating with ZnO adherent thin films of cotton woven fabrics by Pulsed laser deposition technique in order to obtain innovative textile materials, presenting protective effects against UV radiations and antifungal action.

  14. Multiferroic fluoride BaCoF4 Thin Films Grown Via Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Borisov, Pavel; Johnson, Trent; García-Castro, Camilo; Kc, Amit; Schrecongost, Dustin; Cen, Cheng; Romero, Aldo; Lederman, David

    Multiferroic materials exhibit exciting physics related to the simultaneous presence of multiple long-range orders, in many cases consisting of antiferromagnetic (AF) and ferroelectric (FE) orderings. In order to provide a new, promising route for fluoride-based multiferroic material engineering, we grew multiferroic fluoride BaCoF4 in thin film form on Al2O3 (0001) substrates by molecular beam epitaxy. The films grow with the orthorhombic b-axis out-of-plane and with three in-plane structural twin domains along the polar c-axis directions. The FE ordering in thin films was verified by FE remanent hysteresis loops measurements at T = 14 K and by room temperature piezoresponse force microscopy (PFM). An AF behavior was found below Neel temperature TN ~ 80 K, which is in agreement with the bulk properties. At lower temperatures two additional magnetic phase transitions at 19 K and 41 K were found. First-principles calculations demonstrated that the growth strain applied to the bulk BaCoF4 indeed favors two canted spin orders, along the b- and a-axes, respectively, in addition to the main AF spin order along the c-axis. Supported by FAME (Contract 2013-MA-2382), WV Research Challenge Grant (HEPC.dsr.12.29), and DMREF-NSF 1434897.

  15. Thermal Contact Conductance Analysis of Nitride and Carbonitride Thin Film Coatings for Thermal Interface Material Application

    NASA Astrophysics Data System (ADS)

    Subramani, Shanmugan; Thing, Lee Yuan; Devarajan, Mutharasu

    2015-12-01

    In order to reduce and maintain the bond line thickness between substrate and LED package, solid thin film with good thermal conductivity is suggested as thermal interface material and the proposed film thickness is about less than 1 µ. The surface parameter such as roughness and hardness is a key factor which alters the contact conductance between the two matt surfaces. Consequently, filtered vacuum cathodic arc deposited nitride thin films (CrN, TiN, AlTiN, and TiCN) on copper substrate were tested for thermal interface material applications in electronic packaging. The thermal contact conductance of the prepared thin films was evaluated using surface properties such as microhardness and surface roughness. The results were verified with the theoretical model. The measured microhardness and surface roughness of CrN thin film are 17 GPa (low) and 0.768 µm (high), respectively. The measured thermal contact conductance of all thin films showed linear properties for applied pressure and very close to the values of theoretical model. High value in thermal contact conductance of about 256 W/m2 K was noticed with CrN thin film at 1100 kPa. The percentage of deviation for our measured contact conductance value from the theoretical model value was decreasing for the increased contact pressure and observed low value (7 pct) for CrN thin film at 1100 kPa. The thermal conductivity of all thin films was also calculated from the conductance model and observed high value (19.34 W/mK) with CrN thin film.

  16. Vibrational modes and changing molecular conformation of perfluororubrene in thin films and solution

    NASA Astrophysics Data System (ADS)

    Anger, F.; Scholz, R.; Gerlach, A.; Schreiber, F.

    2015-06-01

    We investigate the vibrational properties of perfluororubrene (PF-RUB) in thin films on silicon wafers with a native oxide layer as well as on silicon wafers covered with a self-assembled monolayer and in dichloromethane solution. In comparison with computed Raman and IR spectra, we can assign the molecular modes and identify two molecular conformations with twisted and planar tetracene backbones of the molecule. Moreover, we employ Raman imaging techniques to study the morphology and distribution of the molecular conformation in PF-RUB thin films.

  17. Antireflection effects at nanostructured material interfaces and the suppression of thin-film interference

    NASA Astrophysics Data System (ADS)

    Yang, Qiaoyin; Zhang, Xu A.; Bagal, Abhijeet; Guo, Wei; Chang, Chih-Hao

    2013-06-01

    Thin-film interference is a well-known effect, and it is commonly observed in the colored appearance of many natural phenomena. Caused by the interference of light reflected from the interfaces of thin material layers, such interference effects can lead to wavelength and angle-selective behavior in thin-film devices. In this work, we describe the use of interfacial nanostructures to eliminate interference effects in thin films. Using the same principle inspired by moth-eye structures, this approach creates an effective medium where the index is gradually varying between the neighboring materials. We present the fabrication process for such nanostructures at a polymer-silicon interface, and experimentally demonstrate its effectiveness in suppressing thin-film interference. The principle demonstrated in this work can lead to enhanced efficiency and reduce wavelength/angle sensitivity in multilayer optoelectronic devices.

  18. Thin Films of Molecular Metals TTF-TCNQ

    NASA Astrophysics Data System (ADS)

    Fraxedas, J.; Molas, S.; Figueras, A.; Jiménez, I.; Gago, R.; Auban-Senzier, P.; Goffman, M.

    2002-11-01

    We present recent results on the characterization of highly ordered polycrystalline thin films of the charge transfer salt TTF-TCNQ (TTF=tetrathiafulvalene, TCNQ=tetracyanoquinodimethane) prepared by thermal sublimation in high vacuum under different conditions. The increase in orientation and microcrystal size as a function of substrate and annealing temperatures is addressed. A consequence of such an increase is the reduction of the conductivity activation energy, which eventually leads to the observation of the Peierls transition by resistivity measurements. X-ray absorption near edge spectroscopy studies performed with synchrotron radiation reveal directly the influence of charge transfer on unoccupied states near the Fermi level.

  19. Anomalous scaling behavior and surface roughening in molecular thin-film deposition

    SciTech Connect

    Yim, S.; Jones, T. S.

    2006-04-15

    The thin film growth dynamics of a molecular semiconductor, free-base phthalocyanine (H{sub 2}Pc), deposited by organic molecular beam deposition, has been studied by atomic force microscopy (AFM) and height difference correlation function (HDCF) analysis. The measured dynamic scaling components ({alpha}{sub loc}=0.61{+-}0.12, {beta}=1.02{+-}0.08, and 1/z=0.72{+-}0.13) are consistent with rapid surface roughening and anomalous scaling behavior. A detailed analysis of AFM images and simple growth models suggest that this behavior arises from the pronounced upward growth of crystalline H{sub 2}Pc mounds during the initial stages of thin film growth.

  20. Modeling Ellipsometry Measurements of Molecular Thin-Film Contamination on Genesis Array Samples

    NASA Technical Reports Server (NTRS)

    Calaway, Michael J.; Stansbery, E. K.; McNamara, K. M.

    2006-01-01

    The discovery of a molecular thin-film contamination on Genesis flown array samples changed the course of preliminary assessment strategies. Analytical techniques developed to measure solar wind elemental abundances must now compensate for a thin-film contamination. Currently, this is done either by experimental cleaning before analyses or by depth-profiling techniques that bypass the surface contamination. Inside Johnson Space Center s Genesis dedicated ISO Class 4 (Class 10) cleanroom laboratory, the selection of collector array fragments allocated for solar wind analyses are based on the documentation of overall surface quality, visible surface particle contamination greater than 1 m, and the amount of thin film contamination measured by spectroscopic ellipsometry. Documenting the exact thickness, surface topography, and chemical composition of these contaminates is also critical for developing accurate cleaning methods. However, the first step in characterization of the molecular film is to develop accurate ellipsometry models that will determine an accurate thickness measurement of the contamination film.

  1. Molecular Packing Structure of Mesogenic Octa-Hexyl Substituted Phthalocyanine Thin Film by X-ray Diffraction Analysis.

    PubMed

    Ohmori, Masashi; Higashi, Takuya; Fujii, Akihiko; Ozaki, Masanori

    2016-04-01

    The molecular packing structure in a thin film of the liquid crystalline phthalocyanine, 1,4,8,11,15,18,22,25-octahexylphthalocyanine (C6PcH2), which is a promising small-molecular material for solution-processable organic thin-film solar cells, has been investigated by X-ray diffraction (XRD) measurement. The crystal structure of C6PcH2 in the spin-coated film was determined to be a centered rectangular structure (a = 36.4 Å, b = 20.3 Å). The tilt angle of the phthalocyanine core normal vector was 34-39° from the column axis, and the shortest intermolecular distance was 3.9-4.0 A. The crystal structure determined by XRD analysis was ascertained to be consistent with that calculated by Fourier analvsis. PMID:27451624

  2. Defect-Controlled Preparation of UiO-66 Metal-Organic Framework Thin Films with Molecular Sieving Capability.

    PubMed

    Zhang, Caiqin; Zhao, Yajing; Li, Yali; Zhang, Xuetong; Chi, Lifeng; Lu, Guang

    2016-01-01

    Metal-organic framework (MOF) UiO-66 thin films are solvothermally grown on conducting substrates. The as-synthesized MOF thin films are subsequently dried by a supercritical process or treated with polydimethylsiloxane (PDMS). The obtained UiO-66 thin films show excellent molecular sieving capability as confirmed by the electrochemical studies for redox-active species with different sizes. PMID:26548455

  3. Chalcogenide phase-change thin films used as grayscale photolithography materials.

    PubMed

    Wang, Rui; Wei, Jingsong; Fan, Yongtao

    2014-03-10

    Chalcogenide phase-change thin films are used in many fields, such as optical information storage and solid-state memory. In this work, we present another application of chalcogenide phase-change thin films, i.e., as grayscale photolithgraphy materials. The grayscale patterns can be directly inscribed on the chalcogenide phase-change thin films by a single process through direct laser writing method. In grayscale photolithography, the laser pulse can induce the formation of bump structure, and the bump height and size can be precisely controlled by changing laser energy. Bumps with different height and size present different optical reflection and transmission spectra, leading to the different gray levels. For example, the continuous-tone grayscale images of lifelike bird and cat are successfully inscribed onto Sb(2)Te(3) chalcogenide phase-change thin films using a home-built laser direct writer, where the expression and appearance of the lifelike bird and cat are fully presented. This work provides a way to fabricate complicated grayscale patterns using laser-induced bump structures onto chalcogenide phase-change thin films, different from current techniques such as photolithography, electron beam lithography, and focused ion beam lithography. The ability to form grayscale patterns of chalcogenide phase-change thin films reveals many potential applications in high-resolution optical images for micro/nano image storage, microartworks, and grayscale photomasks. PMID:24663836

  4. Molecular orientation dependence of hole-injection barrier in pentacene thin film on the Au surface in organic thin film transistor

    NASA Astrophysics Data System (ADS)

    Ihm, Kyuwook; Kim, Bongsoo; Kang, Tai-Hee; Kim, Ki-Jeong; Joo, Min Ho; Kim, Tae Hyeong; Yoon, Sang Soo; Chung, Sukmin

    2006-07-01

    We have investigated the effects of a buffer layer insertion on the performance of the pentacene based thin film transistor with a bottom contact structure. When the pentacene molecules have a standing up coordination on the Au surface that is modified by the benzenethiol or methanethiol, the transition region in the pentacene thin film is removed along the boundary between the Au and silicon oxide region, and the hole-injection barrier decreases by 0.4eV. Pentacene on various surfaces showed that the highly occupied molecular level is 0.2-0.4eV lower in the standing up coordination than in the lying down coordination.

  5. Dewetting dynamics of nickel thin film on alpha-quartz substrate: A molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Maekawa, Yuki; Shibuta, Yasushi

    2016-08-01

    Dewetting dynamics of the nickel thin film on the alpha-quartz substrate is closely investigated by molecular dynamics simulation. Morphology after the spontaneous dewetting of thin films changes from multi-droplets, single-droplet and cylindrical structure as the film thickness increases. In the thin cylindrical structure, a neck is induced to break into the droplet due to the Plateau-Rayleigh instability whereas the thick cylindrical structure does not break. Nucleation and subsequent solidification happen only in the large droplet after the dewetting due to the size effect, which is dominated by the kinetic factor of nucleation in the small system.

  6. Evaporation system and method for gas jet deposition of thin film materials

    DOEpatents

    Schmitt, Jerome J.; Halpern, Bret L.

    1994-01-01

    A method and apparatus for depositing thin films of materials such as metals, oxides and nitrides at low temperature relies on a supersonic free jet of inert carrier gas to transport vapor species generated from an evaporation source to the surface of a substrate. Film deposition vapors are generated from solid film precursor materials, including those in the form of wires or powders. The vapor from these sources is carried downstream in a low pressure supersonic jet of inert gas to the surface of a substrate where the vapors deposit to form a thin film. A reactant gas can be introduced into the gas jet to form a reaction product with the evaporated material. The substrate can be moved from the gas jet past a gas jet containing a reactant gas in which a discharge has been generated, the speed of movement being sufficient to form a thin film which is chemically composed of the evaporated material and reactant gases.

  7. Thin films of energetic materials by physical vapor deposition: TATB and LLM-105

    NASA Astrophysics Data System (ADS)

    Williamson, David; Gymer, Sue; O'Conner, Colum; Hazelwood, Adam; Jardine, Andrew

    2015-06-01

    Thin films of energetic materials enable a diverse range of characterization measurements: structure, surface energy and adhesion, and even reactivity. Here we present a method to grow thin films by a physical vapor deposition method (sublimation) using a dedicated instrument which can operate at ultra-high vacuum. The approach enables fabrication of thin films of energetic materials that are otherwise difficult to process by traditional methods, for example because of their low solubility. The intention is to use this instrument as a platform for studying pure materials and co-deposited materials grown either as multi-layers or as co-crystals. Examples of TATB and LLM-105 film morphologies grown using this technique are presented.

  8. Method of forming particulate materials for thin-film solar cells

    DOEpatents

    Eberspacher, Chris; Pauls, Karen Lea

    2004-11-23

    A method for preparing particulate materials useful in fabricating thin-film solar cells is disclosed. Particulate materials is prepared by the method include for example materials comprising copper and indium and/or gallium in the form of single-phase, mixed-metal oxide particulates; multi-phase, mixed-metal particulates comprising a metal oxide; and multinary metal particulates.

  9. Structural and Magnetic Phase Transitions in Manganese Arsenide Thin-Films Grown by Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Jaeckel, Felix Till

    Phase transitions play an important role in many fields of physics and engineering, and their study in bulk materials has a long tradition. Many of the experimental techniques involve measurements of thermodynamically extensive parameters. With the increasing technological importance of thin-film technology there is a pressing need to find new ways to study phase transitions at smaller length-scales, where the traditional methods are insufficient. In this regard, the phase transitions observed in thin-films of MnAs present interesting challenges. As a ferromagnetic material that can be grown epitaxially on a variety of technologically important substrates, MnAs is an interesting material for spintronics applications. In the bulk, the first order transition from the low temperature ferromagnetic alpha-phase to the beta-phase occurs at 313 K. The magnetic state of the beta-phase has remained controversial. A second order transition to the paramagnetic gamma-phase takes place at 398 K. In thin-films, the anisotropic strain imposed by the substrate leads to the interesting phenomenon of coexistence of alpha- and beta-phases in a regular array of stripes over an extended temperature range. In this dissertation these phase transitions are studied in films grown by molecular beam epitaxy on GaAs (001). The films are confirmed to be of high structural quality and almost purely in the A0 orientation. A diverse set of experimental techniques, germane to thin-film technology, is used to probe the properties of the film: Temperature-dependent X-ray diffraction and atomic-force microscopy (AFM), as well as magnetotransport give insights into the structural properties, while the anomalous Hall effect is used as a probe of magnetization during the phase transition. In addition, reflectance difference spectroscopy (RDS) is used as a sensitive probe of electronic structure. Inductively coupled plasma etching with BCl3 is demonstrated to be effective for patterning MnAs. We show

  10. Rupture mechanism of liquid crystal thin films realized by large-scale molecular simulations

    SciTech Connect

    Nguyen, Trung D; Carrillo, Jan-Michael Y; Brown, W Michael; Matheson, Michael A

    2014-01-01

    The ability of liquid crystal (LC) molecules to respond to changes in their environment makes them an interesting candidate for thin film applications, particularly in bio-sensing, bio-mimicking devices, and optics. Yet the understanding of the (in)stability of this family of thin films has been limited by the inherent challenges encountered by experiment and continuum models. Using unprecedented largescale molecular dynamics (MD) simulations, we address the rupture origin of LC thin films wetting a solid substrate at length scales similar to those in experiment. Our simulations show the key signatures of spinodal instability in isotropic and nematic films on top of thermal nucleation, and importantly, for the first time, evidence of a common rupture mechanism independent of initial thickness and LC orientational ordering. We further demonstrate that the primary driving force for rupture is closely related to the tendency of the LC mesogens to recover their local environment in the bulk state. Our study not only provides new insights into the rupture mechanism of liquid crystal films, but also sets the stage for future investigations of thin film systems using peta-scale molecular dynamics simulations.

  11. Rupture mechanism of liquid crystal thin films realized by large-scale molecular simulations.

    PubMed

    Nguyen, Trung Dac; Carrillo, Jan-Michael Y; Matheson, Michael A; Brown, W Michael

    2014-03-21

    The ability of liquid crystal (LC) molecules to respond to changes in their environment makes them an interesting candidate for thin film applications, particularly in bio-sensing, bio-mimicking devices, and optics. Yet the understanding of the (in)stability of this family of thin films has been limited by the inherent challenges encountered by experiment and continuum models. Using unprecedented large-scale molecular dynamics (MD) simulations, we address the rupture origin of LC thin films wetting a solid substrate at length scales similar to those in experiment. Our simulations show the key signatures of spinodal instability in isotropic and nematic films on top of thermal nucleation, and importantly, for the first time, evidence of a common rupture mechanism independent of initial thickness and LC orientational ordering. We further demonstrate that the primary driving force for rupture is closely related to the tendency of the LC mesogens to recover their local environment in the bulk state. Our study not only provides new insights into the rupture mechanism of liquid crystal films, but also sets the stage for future investigations of thin film systems using peta-scale molecular dynamics simulations. PMID:24264516

  12. Theoretical and material studies of thin-film electroluminescent devices

    NASA Technical Reports Server (NTRS)

    Summers, C. J.

    1989-01-01

    Thin-film electroluminescent (TFEL) devices are studied for a possible means of achieving a high resolution, light weight, compact video display panel for computer terminals or television screens. The performance of TFEL devices depends upon the probability of an electron impact exciting a luminescent center which in turn depends upon the density of centers present in the semiconductor layer, the possibility of an electron achieving the impact excitation threshold energy, and the collision cross section itself. Efficiency of such a device is presently very poor. It can best be improved by increasing the number of hot electrons capable of impact exciting a center. Hot electron distributions and a method for increasing the efficiency and brightness of TFEL devices (with the additional advantage of low voltage direct current operation) are investigated.

  13. Characterization of the deposition and materials parameters of thin-film TiNi for microactuators and smart materials

    SciTech Connect

    Jardine, A.P.; Madsen, J.S.; Mercado, P.G. . Dept. of Materials Science)

    1994-04-01

    Development of smart materials and materials for microelectromechanical systems (MEMS) are complicated by the need to grow dissimilar active or adaptive materials in close proximity. This entails discouraging unwanted chemical and physical interactions that prevent production of the appropriate phases. An important component of these systems will be thin-film shape memory effect TiNi. This article discusses the characterization of the deposition of thin film TiNi for these applications as well as the cycling speed for MEMS.

  14. Tunneling Nanoelectromechanical Switches Based on Compressible Molecular Thin Films.

    PubMed

    Niroui, Farnaz; Wang, Annie I; Sletten, Ellen M; Song, Yi; Kong, Jing; Yablonovitch, Eli; Swager, Timothy M; Lang, Jeffrey H; Bulović, Vladimir

    2015-08-25

    Abrupt switching behavior and near-zero leakage current of nanoelectromechanical (NEM) switches are advantageous properties through which NEMs can outperform conventional semiconductor electrical switches. To date, however, typical NEMs structures require high actuation voltages and can prematurely fail through permanent adhesion (defined as stiction) of device components. To overcome these challenges, in the present work we propose a NEM switch, termed a "squitch," which is designed to electromechanically modulate the tunneling current through a nanometer-scale gap defined by an organic molecular film sandwiched between two electrodes. When voltage is applied across the electrodes, the generated electrostatic force compresses the sandwiched molecular layer, thereby reducing the tunneling gap and causing an exponential increase in the current through the device. The presence of the molecular layer avoids direct contact of the electrodes during the switching process. Furthermore, as the layer is compressed, the increasing surface adhesion forces are balanced by the elastic restoring force of the deformed molecules which can promote zero net stiction and recoverable switching. Through numerical analysis, we demonstrate the potential of optimizing squitch design to enable large on-off ratios beyond 6 orders of magnitude with operation in the sub-1 V regime and with nanoseconds switching times. Our preliminary experimental results based on metal-molecule-graphene devices suggest the feasibility of the proposed tunneling switching mechanism. With optimization of device design and material engineering, squitches can give rise to a broad range of low-power electronic applications. PMID:26244821

  15. Highly-oriented molecular arrangements and enhanced magnetic interactions in thin films of CoTTDPz using PTCDA templates.

    PubMed

    Eguchi, Keitaro; Nanjo, Chihiro; Awaga, Kunio; Tseng, Hsiang-Han; Robaschik, Peter; Heutz, Sandrine

    2016-07-14

    In the present work, the templating effect of thin layers of perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) on the growth of cobalt tetrakis(thiadiazole)porphyrazine (CoTTDPz) thin films was examined. X-ray diffraction and optical absorption spectra indicate that while CoTTDPz forms amorphous thin films on the bare substrates, it forms crystalline thin films on the PTCDA templates, in which the molecular planes of CoTTDPz are considered to be parallel to the substrates. Magnetic measurements reveal a significantly enhanced antiferromagnetic interaction of CoTTDPz in the templated thin films, with values reaching over 13 K. The ability to generate crystalline films and to control their orientation using molecular templates is an important strategy in the fields of organic electronics and spintronics in order to tailor the physical properties of organic thin films to suit their intended application. PMID:27183955

  16. Molybdenum as a contact material in zinc tin oxide thin film transistors

    SciTech Connect

    Hu, W.; Peterson, R. L.

    2014-05-12

    Amorphous oxide semiconductors are of increasing interest for a variety of thin film electronics applications. Here, the contact properties of different source/drain electrode materials to solution-processed amorphous zinc tin oxide (ZTO) thin-film transistors are studied using the transmission line method. The width-normalized contact resistance between ZTO and sputtered molybdenum is measured to be 8.7 Ω-cm, which is 10, 20, and 600 times smaller than that of gold/titanium, indium tin oxide, and evaporated molybdenum electrodes, respectively. The superior contact formed using sputtered molybdenum is due to a favorable work function lineup, an insulator-free interface, bombardment of ZTO during molybdenum sputtering, and trap-assisted tunneling. The transfer length of the sputtered molybdenum/ZTO contact is 0.34 μm, opening the door to future radio-frequency sub-micron molybdenum/ZTO thin film transistors.

  17. Design of camouflage material for visible and near infrared based on thin film technology

    NASA Astrophysics Data System (ADS)

    Miao, Lei; Shi, Jia-ming; Zhao, Da-peng; Liu, Hao; Wang, Chao; Xu, Yan-liang

    2015-11-01

    Visible light and near infrared based camouflage materials achieve good stealth under traditional optical detection equipment but its spectral differences with green plants can be taken advantage of by high spectrum based detection technologies. Based on the thin structure of bandpass filter, we designed an optical film with both green and near infrared spectrum. We conducted simulations using transfer matrix methods and optimized the result by simplex methods. The spectral reflectance curve of the proposed thin film matches that of green plants, and experiments show that the proposed thin film achieve good invisibility under visible light and near infrared in a wide viewing angle.

  18. Non-Traditional Spectroscopy for Analysis of Semiconductor and Photovoltaic Thin Film Materials

    NASA Astrophysics Data System (ADS)

    Li, Fuhe; Anderson, Scott

    2009-09-01

    Characterization of semiconductor thin films has long been determined by a number of traditional surface analysis techniques; Auger, ESCA/XPS, SEM-EDS and SIMS to name only a few. Depth profiles, contamination in the thin film or quantitative stoichiometry are specific application examples that predicate the technique best suited for the analysis need. The evolution of photovoltaic (PV) thin film compositions with new chemistries and growing importance of atomic layer deposition (ALD) for semiconductor and nanoscale applications provide a sustaining need for thin film analyses along with an avenue for new analytical tools. In this paper we will discuss the applications of two non-traditional material analysis techniques for the semiconductor and PV applications, glow discharge optical emission spectroscopy (RF GD-OES) and laser ablation inductively coupled plasma mass spectrometry (LA ICP-MS). Depth profiles are available via both techniques with the ability to analyze monolayers (single nm) as well as analysis in the bulk (μm thickness). Depth resolution capabilities allow analysis without surface equilibrium issues seen with other techniques. In addition, the charging effect that can cause issues with electron and ion beam techniques is avoided with RF GD-OES and LA ICP-MS, and thus analysis of both conductive and non-conductive materials is very straight-forward. Contaminant analysis in thin films is very straight-forward and elements across the periodic table are analyzed in a simultaneous mode with both techniques. Detection limits to part-per-billion levels can be achieved and quantitation at low concentrations up to 99% achieved with LA ICP-MS. Lastly, t will be discussed that for some thin film applications, LA ICP-MS and RF GD-OES provide advantages over more traditional techniques, and these aspects as well as complementary features will be discussed.

  19. Molecular dynamics simulations of irradiation of α-Fe thin films with energetic Fe ions under channeling conditions

    NASA Astrophysics Data System (ADS)

    Aliaga, M. J.; Prokhodtseva, A.; Schaeublin, R.; Caturla, M. J.

    2014-09-01

    Using molecular dynamics simulations with recent interatomic potentials developed for Fe, we have studied the defects in thin films of pure bcc Fe induced by the displacement cascade produced by Fe atoms of 50, 100, and 150 keV impinging under a channeling incident angle of 6° to a [0 0 1] direction. The thin films have a thickness between 40 and 100 nm, to reproduce the thickness of the samples used in transmission electron microscope in situ measurements during irradiation. In the simulations we focus mostly on the effect of channeling and free surfaces on damage production. The results are compared to bulk cascades. The comparison shows that the primary damage in thin films of pure Fe is quite different from that originated in the volume of the material. The presence of near surfaces can lead to a variety of events that do not occur in bulk collisional cascades, such as the production of craters and the glide of self-interstitial defects to the surface. Additionally, in the range of energies and the incident angle used, channeling is a predominant effect that significantly reduces damage compared to bulk cascades.

  20. Graphene nanosheet: synthesis, molecular engineering, thin film, hybrids, and energy and analytical applications.

    PubMed

    Guo, Shaojun; Dong, Shaojun

    2011-05-01

    The emergence of graphene nanosheet (GN, 2010 Nobel Prize for Physics) has recently opened up an exciting new field in the science and technology of two-dimensional (2D) nanomaterials with continuously growing academic and technological impetus. GN exhibits unique electronic, optical, magnetic, thermal and mechanical properties arising from its strictly 2D structure and thus has many important technical applications. Actually, GN-based materials have enormous potential to rival or even surpass the performance of carbon nanotube-based counterparts, given that cheap, large-scale production and processing methods for high-quality GN become available. Therefore, the studies on GN in the aspects of chemistry, physical, materials, biology and interdisciplinary science have been in full flow in the past five years. In this critical review, from the viewpoint of chemistry and materials, we will cover recent significant advances in synthesis, molecular engineering, thin film, hybrids, and energy and analytical applications of the "star-material" GN together with discussion on its major challenges and opportunities for future GN research (315 references). PMID:21283849

  1. 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.

  2. Molecular-Orientation-Induced Rapid Roughening and Morphology Transition in Organic Semiconductor Thin-Film Growth

    PubMed Central

    Yang, Junliang; Yim, Sanggyu; Jones, Tim S.

    2015-01-01

    We study the roughening process and morphology transition of organic semiconductor thin film induced by molecular orientation in the model of molecular semiconductor copper hexadecafluorophthalocyanine (F16CuPc) using both experiment and simulation. The growth behaviour of F16CuPc thin film with the thickness, D, on SiO2 substrate takes on two processes divided by a critical thickness: (1) D ≤ 40 nm, F16CuPc thin films are composed of uniform caterpillar-like crystals. The kinetic roughening is confirmed during this growth, which is successfully analyzed by Kardar-Parisi-Zhang (KPZ) model with scaling exponents α = 0.71 ± 0.12, β = 0.36 ± 0.03, and 1/z = 0.39 ± 0.12; (2) D > 40 nm, nanobelt crystals are formed gradually on the caterpillar-like crystal surface and the film growth shows anomalous growth behaviour. These new growth behaviours with two processes result from the gradual change of molecular orientation and the formation of grain boundaries, which conversely induce new molecular orientation, rapid roughening process, and the formation of nanobelt crystals. PMID:25801646

  3. Molecular orientation in soft matter thin films studied by resonant soft X-ray reflectivity

    SciTech Connect

    Mezger, Markus; Jerome, Blandine; Kortright, Jeffrey B.; Valvidares, Manuel; Gullikson, Eric; Giglia, Angelo; Mahne, Nicola; Nannarone, Stefano

    2011-01-12

    We present a technique to study depth profiles of molecular orientation in soft matter thin films with nanometer resolution. The method is based on dichroism in resonant soft X-ray reflectivity using linear s- and p-polarization. It combines the chemical sensitivity of Near-Edge X-ray Absorption Fine Structure spectroscopy to specific molecular bonds and their orientation relative to the polarization of the incident beam with the precise depth profiling capability of X-ray reflectivity. We demonstrate these capabilities on side chain liquid crystalline polymer thin films with soft X-ray reflectivity data at the carbon K edge. Optical constants of the anisotropic refractive index ellipsoid were obtained from a quantitative analysis using the Berreman formalism. For films up to 50 nm thickness we find that the degree of orientation of the long axis exhibits no depth variation and isindependent of the film thickness.

  4. Molecular Aspects of Transport in Thin Films of Controlled Architecture

    SciTech Connect

    Paul W. Bohn

    2009-04-16

    coupled to analyte sampling both by LIF and mass spectrometry. Detection of electrophoresis separation products by electrospray mass spectrometry was achieved through direct interfacing to an electrospray mass spectrometer. Pb(II) interactions with the DNAzyme have been realized in an NCAM-coupled integrated microfluidic structure allowing cation separations to be coupled to molecular beacon detection motifs for the determination of Pb(II) in an electroplating sludge reference material. By changing the DNAzyme to select for other compounds of interest, it is possible to incorporate multiple sensing systems within a single device, thereby achieving great flexibility.

  5. Molecular layer-by-layer assembled thin-film composite membranes for water desalination.

    PubMed

    Gu, Joung-Eun; Lee, Seunghye; Stafford, Christopher M; Lee, Jong Suk; Choi, Wansuk; Kim, Bo-Young; Baek, Kyung-Youl; Chan, Edwin P; Chung, Jun Young; Bang, Joona; Lee, Jung-Hyun

    2013-09-14

    Molecular layer-by-layer (mLbL) assembled thin-film composite membranes fabricated by alternating deposition of reactive monomers on porous supports exhibit both improved salt rejection and enhanced water flux compared to traditional reverse osmosis membranes prepared by interfacial polymerization. Additionally, the well-controlled structures achieved by mLbL deposition further lead to improved antifouling performance. PMID:23847127

  6. NMR characterization of thin films

    DOEpatents

    Gerald II, Rex E.; Klingler, Robert J.; Rathke, Jerome W.; Diaz, Rocio; Vukovic, Lela

    2010-06-15

    A method, apparatus, and system for characterizing thin film materials. The method, apparatus, and system includes a container for receiving a starting material, applying a gravitational force, a magnetic force, and an electric force or combinations thereof to at least the starting material, forming a thin film material, sensing an NMR signal from the thin film material and analyzing the NMR signal to characterize the thin film of material.

  7. NMR characterization of thin films

    DOEpatents

    Gerald, II, Rex E.; Klingler, Robert J.; Rathke, Jerome W.; Diaz, Rocio; Vukovic, Lela

    2008-11-25

    A method, apparatus, and system for characterizing thin film materials. The method, apparatus, and system includes a container for receiving a starting material, applying a gravitational force, a magnetic force, and an electric force or combinations thereof to at least the starting material, forming a thin film material, sensing an NMR signal from the thin film material and analyzing the NMR signal to characterize the thin film of material.

  8. Synthesis, characterization, and pulsed laser ablation of molecular sieves for thin film applications

    NASA Astrophysics Data System (ADS)

    Munoz, Trinidad, Jr.

    1998-12-01

    Molecular sieves are one class of crystalline low density metal oxides which are made up of one-, two-, and three dimensional pores and/or cages. We have investigated the synthesis and characterization of metal substituted aluminophosphates and all silica molecular sieves for thin film applications. A new copper substituted aluminophosphate, CuAPO-5 has been synthesized and characterized using x-ray powder diffraction, FT-IR spectroscopy and scanning electron microscopy. Electron spin resonance and electron spin echo modulation provided supporting evidence of framework incorporation of Cu(II) ions. Thus, an exciting addition has been added to the family of metal substituted aluminophosphates where substitution of the metal has been demonstrated as framework species. Also presented here is the synthesis and characterization of an iron substituted aluminophosphate, FeAPO-5, and an all silica zeolite, UTD-1 for thin film applications. Pulsed laser ablation has been employed as the technique to generate thin films. Here an excimer laser (KrFsp*, 248 nm) was used to deposit the molecular sieves on a variety of substrates including polished silicon, titanium nitride, and porous stainless steel disks. The crystallinity of the deposited films was enhanced by a post hydrothermal treatment. A vapor phase treatment of the laser deposited FeAPO-5 films has been shown to increase the crystallinity of the film without increasing film thickness. Thin films of the FeAPO-5 molecular sieves were subsequently used as the dielectric phase in capacitive type chemical sensors. The capacitance change of the FeAPO-5 devices to the relative moisture makes them potential humidity sensors. The all silica zeolite UTD-1 thin films were deposited on polished silicon and porous supports. A brief post hydrothermal treatment of the laser deposited films deposited on polished silicon and porous metal supports resulted in oriented film growth lending these films to applications in gas separations

  9. Control method and system for use when growing thin-films on semiconductor-based materials

    DOEpatents

    McKee, Rodney A.; Walker, Frederick J.

    2001-01-01

    A process and system for use during the growth of a thin film upon the surface of a substrate by exposing the substrate surface to vaporized material in a high vacuum (HV) facility involves the directing of an electron beam generally toward the surface of the substrate as the substrate is exposed to vaporized material so that electrons are diffracted from the substrate surface by the beam and the monitoring of the pattern of electrons diffracted from the substrate surface as vaporized material settles upon the substrate surface. When the monitored pattern achieves a condition indicative of the desired condition of the thin film being grown upon the substrate, the exposure of the substrate to the vaporized materials is shut off or otherwise adjusted. To facilitate the adjustment of the crystallographic orientation of the film relative to the electron beam, the system includes a mechanism for altering the orientation of the surface of the substrate relative to the electron beam.

  10. Photoluminescence of localized excitons in ZnCdO thin films grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Wu, T. Y.; Huang, Y. S.; Hu, S. Y.; Lee, Y. C.; Tiong, K. K.; Chang, C. C.; Shen, J. L.; Chou, W. C.

    2016-07-01

    We have investigated the luminescence characteristics of Zn1-xCdxO thin films with different Cd contents grown by molecular beam epitaxy system. The temperature-dependent photoluminescence (PL) and excitation power-dependent PL spectra were measured to clarify the luminescence mechanisms of the Zn1-xCdxO thin films. The peak energy of the Zn1-xCdxO thin films with increasing the Cd concentration is observed as redshift and can be fitted by the quadratic function of alloy content. The broadened full-width at half-maximum (FWHM) estimated from the 15 K PL spectra as a function of Cd content shows a larger deviation between the experimental values and theoretical curve, which indicates that experimental FWHM values are affected not only by alloy compositional disorder but also by localized excitons occupying states in the tail of the density of states. The Urbach energy determined from an analysis of the lineshape of the low-energy side of the PL spectrum and the degree of localization effect estimated from the temperature-induced S-shaped PL peak position described an increasing mean exciton-localization effects in ZnCdO films with increasing the Cd content. In addition, the PL intensity and peak position as a function of excitation power are carried out to clarify the types of radiative recombination and the effects of localized exciton in the ZnCdO films with different Cd contents.

  11. Determination of Structural Parameters of Thin-Film Photocatalytic Materials by BDS

    NASA Astrophysics Data System (ADS)

    Korte, Dorota; Franko, Mladen

    2015-09-01

    A method for determination of structural parameters of some thin-film photocatalytic materials is presented. The analysis was based on the material's thermal parameter dependences on its surface structure or porosity and was thus performed by the use of beam deflection spectroscopy (BDS) supported by theoretical analysis made in the framework of complex geometrical optics. The results obtained by BDS were than compared with those received on the basis of AFM and SEM measurements and found to be in good agreement.

  12. Apparatus for producing ultraclean bicrystals by the molecular beam epitaxy growth and ultrahigh vacuum bonding of thin films

    SciTech Connect

    Amiri-Hezaveh, A.; Balluffi, R.W. )

    1993-10-01

    An apparatus has been designed and constructed which is capable of growing single-crystal thin films and then bonding them together face-to-face to produce bicrystals under ultrahigh vacuum (UHV) conditions. The films are grown in molecular beam epitaxy (MBE) system capable of growing well-characterized single-crystal thin films of metals, semiconductors, and high [ital T][sub [ital c

  13. Self-regulated growth of LaVO{sub 3} thin films by hybrid molecular beam epitaxy

    SciTech Connect

    Zhang, Hai-Tian; Engel-Herbert, Roman; Dedon, Liv R.; Martin, Lane W.

    2015-06-08

    LaVO{sub 3} thin films were grown on SrTiO{sub 3} (001) by hybrid molecular beam epitaxy. A volatile metalorganic precursor, vanadium oxytriisopropoxide (VTIP), and elemental La were co-supplied in the presence of a molecular oxygen flux. By keeping the La flux fixed and varying the VTIP flux, stoichiometric LaVO{sub 3} films were obtained for a range of cation flux ratios, indicating the presence of a self-regulated growth window. Films grown under stoichiometric conditions were found to have the largest lattice parameter, which decreased monotonically with increasing amounts of excess La or V. Energy dispersive X-ray spectroscopy and Rutherford backscattering measurements were carried out to confirm film compositions. Stoichiometric growth of complex vanadate thin films independent of cation flux ratios expands upon the previously reported self-regulated growth of perovskite titanates using hybrid molecular beam epitaxy, thus demonstrating the general applicability of this growth approach to other complex oxide materials, where a precise control over film stoichiometry is demanded by the application.

  14. Laser annealing of textured thin film cathode material for lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Kohler, R.; Bruns, M.; Smyrek, P.; Ulrich, S.; Przybylski, M.; Pfleging, W.

    2010-02-01

    The material development for advanced lithium ion batteries plays an important role in future mobile applications and energy storage systems. It is assumed that electrode materials made of nano-composited materials will improve battery lifetime and will lead to an enhancement of lithium diffusion and thus improve battery capacity and cyclability. Lithium cobalt oxide (LiCoO2) is commonly used as a cathode material. Thin films of this electrode material were synthesized by non-reactive r.f. magnetron sputtering of LiCoO2 targets on silicon or stainless steel substrates. For the formation of the high temperature phase of LiCoO2 (HT-LiCoO2), which exhibits good electrochemical performance with a specific capacity of 140 mAh/g and high capacity retention, a subsequent annealing treatment is necessary. For this purpose laser annealing of thin film LiCoO2 was investigated in detail and compared to conventional furnace annealing. A high power diode laser system operating at a wavelength of 940 nm with an integrated pyrometer for temperature control was used. Different temperatures (between 200°C and 700°C) for the laser structured and unstructured thin films were applied. The effects of laser treatment on the LiCoO2 thin films studied with Raman spectroscopy, X-ray photoelectron spectroscopy and X-ray diffraction to determine their stoichiometry and crystallinity. The development of HT-LiCoO2 and also the formation of a Co3O4 phase were discussed. The electrochemical properties of the manufactured films were investigated via electrochemical cycling against a lithium anode.

  15. Centrifugation-based Purification of Emerging Low-dimensional Materials and Their Thin-film Applications

    NASA Astrophysics Data System (ADS)

    Seo, Jung Woo

    Polydispersity in low-dimensional materials offers many interesting challenges and properties. In particular, the one- and two-dimensional carbon allotropes such as carbon nanotubes and graphene have demonstrated exquisite optoelectronic properties that are highly sensitive to their physical structures, where subtle variations in diameter and thickness render them with significantly different electronic band structures. Thus, the carbon nanomaterials have been the subject of extensive studies that address their polydispersity issues. Among these, solution-phase, buoyant density-based methods such as density gradient ultracentrifugation have been widely utilized to enrich subpopulations of carbon nanotubes and graphene with narrow distribution in diameter and thickness, enabling their applications in various next-generation thin-film devices. In this thesis, I present further advancement of centrifugation-based processing methods for emerging low-dimensional materials through systematic utilization of previously explored surfactant systems, development of novel surfactant types, and study of correlation between the chemical structure of surfactants and the dispersion and optoelectronic properties of the nanomaterials. First, I employ an iterative density gradient ultracentrifugation with a combination of anionic surfactants and addition of excess counter-ions to achieve isolation of novel diameter species of semiconducting single-walled carbon nanotubes. The purification of carbon nanotubes with simultaneous, ultrahigh-purity refinement in electronic type and diameter distribution leads to collaborative studies on heat distribution characteristics and diameter-dependent direct current and radio frequency performances in monodisperse carbon nanotube thin-film transistors. Next, I develop the use of non-ionic polymeric surfactants for centrifugation-based processes. Specifically, I utilize polypropylene and polyethylene oxide-based block copolymers with density

  16. Tailoring of a metastable material: alfa-FeSi2 thin film

    DOE PAGESBeta

    Cao, Guixin; Singh, David J; Zhang, Xiaoguang; Samolyuk, German D; Qiao, Liang; Parish, Chad M; Ke, Jin; Zhang, Yanwen; Guo, Hangwen; Wang, Wenbin; et al

    2015-01-01

    The epitaxially stabilized metallic -FeSi2 thin films on Si(001) were grown using pulsed laser deposition. While the bulk material of -FeSi2 is a high temperature metastable phase and nonmagnetic, the thin film is stabilized at room temperature and shows unusual electronic transport and magnetic properties due to strain modification. The transport renders two different conducting states with a strong crossover at 50 K accompanied by an onset of ferromagnetism as well as a substantial magnetocaloric effect and magnetoresistance. These experimental results are discussed in terms of the unusual electronic structure of -FeSi2 obtained within density functional calculations and Boltzmann transportmore » calculations with and without strain. Our findings provide an example of a tailored material with interesting physics properties for practical applications.« less

  17. Evaporation system and method for gas jet deposition of thin film materials

    DOEpatents

    Schmitt, J.J.; Halpern, B.L.

    1994-10-18

    A method and apparatus are disclosed for depositing thin films of materials such as metals, oxides and nitrides at low temperature relies on a supersonic free jet of inert carrier gas to transport vapor species generated from an evaporation source to the surface of a substrate. Film deposition vapors are generated from solid film precursor materials, including those in the form of wires or powders. The vapor from these sources is carried downstream in a low pressure supersonic jet of inert gas to the surface of a substrate where the vapors deposit to form a thin film. A reactant gas can be introduced into the gas jet to form a reaction product with the evaporated material. The substrate can be moved from the gas jet past a gas jet containing a reactant gas in which a discharge has been generated, the speed of movement being sufficient to form a thin film which is chemically composed of the evaporated material and reactant gases. 8 figs.

  18. Molecular beam epitaxy deposition of Gd2O3 thin films on SrTiO3 (100) substrate

    NASA Astrophysics Data System (ADS)

    Wang, Jinxing; Hao, Jinghua; Zhang, Yangyang; Wei, Hongmei; Mu, Juyi

    2016-06-01

    Gd2O3 thin films are grown on the SrTiO3 (100) substrate by molecular beam epitaxy (MBE) deposition. X-ray diffraction (XRD) analysis, conventional transmission electron microscopy (TEM) and aberration-corrected scanning transmission electron microscopy (STEM) are performed to investigate the microstructure of deposited thin films. It is found that the as-deposited thin film possesses a very uniform thickness of ∼40 nm and is composed of single cubic phase Gd2O3 grains. STEM and TEM observations reveal that Gd2O3 thin film grows epitaxially on the SrTiO3 (100) substrate with (001)Gd2O3//(100)STO and [110]Gd2O3//[001]STO orientations. Furthermore, the Gd atoms are found to diffuse into the SrTiO3 substrate for a depth of one unit cell and substitute for the Sr atoms near the interface.

  19. Atomic/Molecular Layer Deposition of Lithium Terephthalate Thin Films as High Rate Capability Li-Ion Battery Anodes.

    PubMed

    Nisula, Mikko; Karppinen, Maarit

    2016-02-10

    We demonstrate the fabrication of high-quality electrochemically active organic lithium electrode thin films by the currently strongly emerging combined atomic/molecular layer deposition (ALD/MLD) technique using lithium terephthalate, a recently found anode material for lithium-ion battery (LIB), as a proof-of-the-concept material. Our deposition process for Li-terephthalate is shown to well comply with the basic principles of ALD-type growth including the sequential self-saturated surface reactions, a necessity when aiming at micro-LIB devices with three-dimensional architectures. The as-deposited films are found crystalline across the deposition temperature range of 200-280 °C, which is a trait highly desired for an electrode material but rather unusual for hybrid inorganic-organic thin films. Excellent rate capability is ascertained for the Li-terephthalate films with no conductive additives required. The electrode performance can be further enhanced by depositing a thin protective LiPON solid-state electrolyte layer on top of Li-terephthalate; this yields highly stable structures with capacity retention of over 97% after 200 charge/discharge cycles at 3.2 C. PMID:26812433

  20. Theoretical and material studies on thin-film electroluminescent devices

    NASA Technical Reports Server (NTRS)

    Summers, C. J.; Brennan, K. F.

    1986-01-01

    Electroluminescent materials and device technology were assessed. The evaluation strongly suggests the need for a comprehensive theoretical and experimental study of both materials and device structures, particularly in the following areas: carrier generation and multiplication; radiative and nonradiative processes of luminescent centers; device modeling; new device concepts; and single crystal materials growth and characterization. Modeling of transport properties of hot electrons in ZnSe and the generation of device concepts were initiated.

  1. Magnetic Properties of FeNi-Based Thin Film Materials with Different Additives.

    PubMed

    Liang, Cai; Gooneratne, Chinthaka P; Wang, Qing Xiao; Liu, Yang; Gianchandani, Yogesh; Kosel, Jurgen

    2014-09-01

    This paper presents a study of FeNi-based thin film materials deposited with Mo, Al and B using a co-sputtering process. The existence of soft magnetic properties in combination with strong magneto-mechanical coupling makes these materials attractive for sensor applications. Our findings show that FeNi deposited with Mo or Al yields magnetically soft materials and that depositing with B further increases the softness. The out-of-plane magnetic anisotropy of FeNi thin films is reduced by depositing with Al and completely removed by depositing with B. The effect of depositing with Mo is dependent on the Mo concentration. The coercivity of FeNiMo and FeNiAl is reduced to less than a half of that of FeNi, and a value as low as 40 A/m is obtained for FeNiB. The surfaces of the obtained FeNiMo, FeNiAl and FeNiB thin films reveal very different morphologies. The surface of FeNiMo shows nano-cracks, while the FeNiAl films show large clusters and fewer nano-cracks. When FeNi is deposited with B, a very smooth morphology is obtained. The crystal structure of FeNiMo strongly depends on the depositant concentration and changes into an amorphous structure at a higher Mo level. FeNiAl thin films remain polycrystalline, even at a very high concentration of Al, and FeNiB films are amorphous, even at a very low concentration of B. PMID:25587418

  2. Single superconducting thin film devices for applications in high T/sub c/ materials circuits

    SciTech Connect

    Martens, J.S.; Beyer, J.B.; Nordman, J.E.; Ginley, D.S.; Hohenwarter, G.K.G.; McGinnis, D.P.

    1989-03-01

    The authors have investigated several different devices based on regions of weak superconductivity and multiple parallel links in thin films. Hysteretic symmetric and asymmetric IV curves have been observed. Flux flow was indicated. Device switching properties and the dependence of the flux flow signature in the IV curve on applied magnetic field were explored. Both Nb and high T/sub c/ thin films were used in circuit fabrication. Contrary to vortex flow devices based on Josephson junctions those described here do not possess a tunneling barrier and are made of only a single superconducting layer. Hence they should be applicable to electronic circuits based on high T/sub c/ superconducting materials without the need for tunnel junctions.

  3. Theoretical and material studies on thin-film electroluminescent devices

    NASA Technical Reports Server (NTRS)

    Summers, C. J.; Benz, R., II

    1987-01-01

    The effect of surface nucleation processes on the quality of ZnS layers grown on (001) GaAs substrates by molecular beam epitaxy is reported. Reflection high energy electron diffraction indicated that nucleation at high temperatures produced more planar surfaces than nucleation at low temperatures, but the crystalline quality as accessed by x ray double crystal diffractometry is relatively independent of nucleation temperature. A critical factor in layer quality was the initial roughness of the GaAs surfaces.

  4. Influence of molecular structure and microstructure on device performance of polycrystalline pentacene thin-film transistors

    NASA Astrophysics Data System (ADS)

    Cheng, Horng-Long; Mai, Yu-Shen; Chou, Wei-Yang; Chang, Li-Ren

    2007-04-01

    The authors have fabricated the pentacene thin films on polymethylmethacrylate (PMMA) and on silicon dioxide dielectric surfaces featuring similar surface energy and surface roughness. On both surfaces the pentacene films displayed high crystal quality from x-ray diffraction scans, although the film on PMMA had significantly smaller grain size. The pentacene transistors with PMMA exhibited excellent electrical characteristics, including high mobility of above 1.1cm2/Vs, on/off ratio above 106, and sharp subthreshold slope below 1V/decade. The analysis of molecular microstructure of the pentacene films provided a reasonable explanation for the high performance using resonance micro-Raman spectroscopy.

  5. Yttrium Iron Garnet Thin Films with Very Low Damping Obtained by Recrystallization of Amorphous Material

    PubMed Central

    Hauser, Christoph; Richter, Tim; Homonnay, Nico; Eisenschmidt, Christian; Qaid, Mohammad; Deniz, Hakan; Hesse, Dietrich; Sawicki, Maciej; Ebbinghaus, Stefan G.; Schmidt, Georg

    2016-01-01

    We have investigated recrystallization of amorphous Yttrium Iron Garnet (YIG) by annealing in oxygen atmosphere. Our findings show that well below the melting temperature the material transforms into a fully epitaxial layer with exceptional quality, both structural and magnetic. In ferromagnetic resonance (FMR) ultra low damping and extremely narrow linewidth can be observed. For a 56 nm thick layer a damping constant of α = (6.15 ± 1.50) · 10−5 is found and the linewidth at 9.6 GHz is as small as 1.30 ± 0.05 Oe which are the lowest values for PLD grown thin films reported so far. Even for a 20 nm thick layer a damping constant of α = (7.35 ± 1.40) · 10−5 is found which is the lowest value for ultrathin films published so far. The FMR linewidth in this case is 3.49 ± 0.10 Oe at 9.6 GHz. Our results not only present a method of depositing thin film YIG of unprecedented quality but also open up new options for the fabrication of thin film complex oxides or even other crystalline materials. PMID:26860816

  6. Full potential of radial junction Si thin film solar cells with advanced junction materials and design

    NASA Astrophysics Data System (ADS)

    Qian, Shengyi; Misra, Soumyadeep; Lu, Jiawen; Yu, Zhongwei; Yu, Linwei; Xu, Jun; Wang, Junzhuan; Xu, Ling; Shi, Yi; Chen, Kunji; Roca i Cabarrocas, Pere

    2015-07-01

    Combining advanced materials and junction design in nanowire-based thin film solar cells requires a different thinking of the optimization strategy, which is critical to fulfill the potential of nano-structured photovoltaics. Based on a comprehensive knowledge of the junction materials involved in the multilayer stack, we demonstrate here, in both experimental and theoretical manners, the potential of hydrogenated amorphous Si (a-Si:H) thin film solar cells in a radial junction (RJ) configuration. Resting upon a solid experimental basis, we also assess a more advanced tandem RJ structure with radially stacking a-Si:H/nanocrystalline Si (nc-Si:H) PIN junctions, and show that a balanced photo-current generation with a short circuit current density of Jsc = 14.2 mA/cm2 can be achieved in a tandem RJ cell, while reducing the expensive nc-Si:H absorber thickness from 1-3 μ m (in planar tandem cells) to only 120 nm. These results provide a clearly charted route towards a high performance Si thin film photovoltaics.

  7. Crystallization of amorphous silicon thin films using nanoenergetic intermolecular materials with buffer layers

    NASA Astrophysics Data System (ADS)

    Lee, Choong Hee; Jeong, Tae Hoon; Kim, Do Kyung; Jeong, Woong Hee; Kang, Myung-Koo; Hwang, Tae Hyung; Kim, Hyun Jae

    2009-02-01

    Optimization of the crystallization of amorphous silicon (a-Si) using a mixture of nanoenergetic materials of iron oxide/aluminum (Fe 2O 3/Al) was studied. To achieve high-quality polycrystalline Si (poly-Si) thin films, silicon oxide (SiO 2) and silver (Ag) layer were deposited on the a-Si as buffer layers to prevent the metal diffusion in a-Si during thermite reaction and to transport the thermal energy released from nanoenergetic materials, respectively. Raman measurement was used to define the crystallinity of poly-Si. For molar ratio of Al and Fe of 2 with 100-nm-thick-SiO 2, Raman measurement showed the 519.59 cm -1 of peak position and the 5.08 cm -1 of full width at half maximum with 353 MPa of low tensile stress indicating high quality poly-Si thin film. These results showed that optimized thermite reaction could be used successfully in crystallization of a-Si to high -quality poly-Si thin films.

  8. 7-Octenyltrichrolosilane/trimethyaluminum hybrid dielectrics fabricated by molecular-atomic layer deposition on ZnO thin film transistors

    NASA Astrophysics Data System (ADS)

    Huang, Jie; Lee, Mingun; Lucero, Antonio T.; Cheng, Lanxia; Ha, Min-Woo; Kim, Jiyoung

    2016-06-01

    We demonstrate the fabrication of 7-octenytrichlorosilane (7-OTS)/trimethylaluminum (TMA) organic–inorganic hybrid films using molecular-atomic layer deposition (MALD). The properties of 7-OTS/TMA hybrid films are extensively investigated using transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), and electrical measurements. Our results suggest that uniform and smooth amorphous hybrid thin films with excellent insulating properties are obtained using the MALD process. Films have a relatively high dielectric constant of approximately 5.0 and low leakage current density. We fabricate zinc oxide (ZnO) based thin film transistors (TFTs) using 7-OTS/TMA hybrid material as a back gate dielectric with the top ZnO channel layer deposited in-situ via MALD. The ZnO TFTs exhibit a field effect mobility of approximately 0.43 cm2 V‑1 s‑1, a threshold voltage of approximately 1 V, and an on/off ratio of approximately 103 under low voltage operation (from ‑3 to 9 V). This work demonstrates an organic–inorganic hybrid gate dielectric material potentially useful in flexible electronics application.

  9. Screening of Novel Li-Air Battery Catalyst Materials by a Thin Film Combinatorial Materials Approach.

    PubMed

    Hauck, John G; McGinn, Paul J

    2015-06-01

    A combinatorial synthesis and high-throughput screening process was developed for the investigation of potential oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalysts for use as Li-air battery cathode materials. Libraries of discrete ternary metal alloy compositions were deposited via thin-film sputtering. The samples were electrochemically tested in parallel using cyclic voltammetry in O2-saturated KOH electrolyte. Compositions were ranked by ORR and OER onset potentials with respect to an internal Pt reference. Results from the Pt-Mn-Co, Cr-Mn-Co, Pd-Mn-Co, and Pd-Mn-Ru systems are reported. Many alloy compositions showed marked improvement in catalytic activity compared to pure Pt. Among the systems considered, Pt12Mn44Co44, Pd43Co57 and Pd36Mn28Ru36 in particular exhibited lower overpotentials for oxygen reactions, which occur at the cathode in Li-air batteries. PMID:25965839

  10. Development of a Thin Film Magnetic Moment Reference Material

    PubMed Central

    Pappas, D. P.; Halloran, S. T.; Owings, R. R.; da Silva, F. C. S.

    2008-01-01

    In this paper we present the development of a magnetic moment reference material for low moment magnetic samples. We first conducted an inter-laboratory comparison to determine the most useful sample dimensions and magnetic properties for common instruments such as vibrating sample magnetometers (VSM), SQUIDs, and alternating gradient field magnetometers. The samples were fabricated and then measured using a vibrating sample magnetometer. Their magnetic moments were calibrated by tracing back to the NIST YIG sphere, SRM 2853. PMID:27096108

  11. Development of a Thin Film Magnetic Moment Reference Material.

    PubMed

    Pappas, D P; Halloran, S T; Owings, R R; da Silva, F C S

    2008-01-01

    In this paper we present the development of a magnetic moment reference material for low moment magnetic samples. We first conducted an inter-laboratory comparison to determine the most useful sample dimensions and magnetic properties for common instruments such as vibrating sample magnetometers (VSM), SQUIDs, and alternating gradient field magnetometers. The samples were fabricated and then measured using a vibrating sample magnetometer. Their magnetic moments were calibrated by tracing back to the NIST YIG sphere, SRM 2853. PMID:27096108

  12. Small molecular weight organic thin-film photodetectors and solar cells

    NASA Astrophysics Data System (ADS)

    Peumans, Peter; Yakimov, Aharon; Forrest, Stephen R.

    2003-04-01

    In this review, we discuss the physics underlying the operation of single and multiple heterojunction, vacuum-deposited organic solar cells based on small molecular weight thin films. For single heterojunction cells, we find that the need for direct contact between the deposited electrode and the active organics leads to quenching of excitons. An improved device architecture, the double heterojunction, is shown to confine excitons within the active layers, allowing substantially higher internal efficiencies to be achieved. A full optical and electrical analysis of the double heterostructure architecture leads to optimal cell design as a function of the optical properties and exciton diffusion lengths of the photoactive materials. Combining the double heterostructure with novel light trapping schemes, devices with external efficiencies approaching their internal efficiency are obtained. When applied to an organic photovoltaic cell with a power conversion efficiency of 1.0%±0.1% under 1 sun AM1.5 illumination, devices with external power conversion efficiencies of 2.4%±0.3% are reported. In addition, we show that by using materials with extended exciton diffusion lengths LD, highly efficient double heterojunction photovoltaic cells are obtained, even in the absence of a light trapping geometry. Using C60 as an acceptor material, double heterostructure external power conversion efficiencies of 3.6%±0.4% under 1 sun AM1.5 illumination are obtained. Stacking of single heterojunction devices leads to thin film multiple heterojunction photovoltaic and photodetector structures. Thin bilayer photovoltaic cells can be stacked with ultrathin (˜5 Å), discontinuous Ag layers between adjacent cells serving as efficient recombination sites for electrons and holes generated in the neighboring cells. Such stacked cells have open circuit voltages that are n times the open circuit voltage of a single cell, where n is the number of cells in the stack. In optimized structures, the

  13. Vacuum thermal switch made of phase transition materials considering thin film and substrate effects

    NASA Astrophysics Data System (ADS)

    Yang, Yue; Basu, Soumyadipta; Wang, Liping

    2015-06-01

    In the present study, we theoretically demonstrate a vacuum thermal switch based on near-field thermal radiation between phase transition materials, i.e., vanadium dioxide (VO2), whose phase changes from insulator to metal at 341 K. Strong coupling of surface phonon polaritons between two insulating VO2 plates significantly enhances the near-field heat flux, which on the other hand is greatly reduced when the VO2 emitter becomes metallic, resulting in strong thermal switching effect. Fluctuational electrodynamics incorporated with anisotropic wave propagation predicts more than 80% heat transfer reduction at sub-30-nm vacuum gaps and 50% at vacuum gap of 1 μm. Furthermore, the penetration depth inside the uniaxial VO2 insulator is studied at the vacuum gap of 50 nm, suggesting the possible impact of reduced VO2 thickness on the near-field thermal radiation with thin-film structures. By replacing the bulk VO2 receiver with a thin film of several tens of nanometers, the switching effect is further improved over a broad range of vacuum gaps from 10 nm to 1 μm. Finally, the effect of SiO2 substrate for the thin-film emitter or receiver is also considered to provide insights for future experimental demonstrations. By controlling heat flow with near-field radiative transport, the proposed vacuum thermal switch would find practical applications for energy dissipation in microelectronic devices and for the realization of thermal circuits.

  14. Polycrystalline thin film materials and devices. Final subcontract report, 16 January 1990--15 January 1993

    SciTech Connect

    Birkmire, R.W.; Phillips, J.E.; Shafarman, W.N.; Hegedus, S.S.; McCandless, B.E.; Yokimcus, T.A.

    1993-08-01

    This report describes results and conclusions of the final phase (III) of a three-year research program on polycrystalline thin-film heterojunction solar cells. The research consisted of the investigation of the relationships between processing, materials properties, and device performance. This relationship was quantified by device modeling and analysis. The analysis of thin-film polycrystalline heterojunction solar cells explains how minority-carrier recombination at the metallurgical interface and at grain boundaries can be greatly reduced by the proper doping of the window and absorber layers. Additional analysis and measurements show that the present solar cells are limited by the magnitude of the diode current, which appears to be caused by recombination in the space charge region. Developing an efficient commercial-scale process for fabricating large-area polycrystalline, thin-film solar cells from a research process requires a detailed understanding of the individual steps in making the solar cell, and their relationship to device performance and reliability. The complexities involved in characterizing a process are demonstrated with results from our research program on CuInSe{sub 2}, and CdTe processes.

  15. Polycrystalline thin film materials and devices. Annual subcontract report, 16 January 1991--15 January 1992

    SciTech Connect

    Baron, B.N.; Birkmire, R.W.; Phillips, J.E.; Shafarman, W.N.; Hegedus, S.S.; McCandless, B.E.

    1992-10-01

    Results of Phase II of a research program on polycrystalline thin film heterojunction solar cells are presented. Relations between processing, materials properties and device performance were studied. The analysis of these solar cells explains how minority carrier recombination at the interface and at grain boundaries can be reduced by doping of windows and absorber layers, such as in high efficiency CdTe and CuInSe{sub 2} based solar cells. The additional geometric dimension introduced by the polycrystallinity must be taken into consideration. The solar cells are limited by the diode current, caused by recombination in the space charge region. J-V characteristics of CuInSe{sub 2}/(CdZn)S cells were analyzed. Current-voltage and spectral response measurements were also made on high efficiency CdTe/CdS thin film solar cells prepared by vacuum evaporation. Cu-In bilayers were reacted with Se and H{sub 2}Se gas to form CuInSe{sub 2} films; the reaction pathways and the precursor were studied. Several approaches to fabrication of these thin film solar cells in a superstrate configuration were explored. A self-consistent picture of the effects of processing on the evolution of CdTe cells was developed.

  16. Biotinylated polyalkylthiophene thin films and monolayers that specifically incorporate phycobiliproteins: toward smart materials

    NASA Astrophysics Data System (ADS)

    Ayyagari, Madhu S. R.; Pande, Rajiv; Lim, Jeong O.; Kamath, Manohar; Beladakere, Nagendra; Gao, Harry H.; Marx, Kenneth A.; Tripathy, Sukant K.; Kumar, Jayant; Samuelson, Lynne A.; Akkara, Joseph A.; Kaplan, David L.

    1994-05-01

    We are investigating thin film and monolayer systems that involve conjugated conducting polymers and specific biological macromolecules. One class of conducting polymers, polyalkylthiophenes, are derivatized with biotin. These biotinylated polymers form the basis for a generic cassette system of attachment for any biological molecule through biotinylation or interaction with streptavidin. The high affinity of the biotin-streptavidin system, used in sequential steps, forms the basis of the cassette method. We have formed both monolayers and thin films (a few nanometers) of the cassette assembly in which phycobiliproteins are incorporated. We are investigating the optical signal transduction properties of specific phycobiliproteins (phycoerythrin, phycocyanin and allophycocyanain) using the cassette system on the inner surface of glass capillaries and on optical fiber surfaces. Phycobiliprotein photocurrent signals in conducting polymer matrices on microelectrodes are also being investigated. Our aim is to integrate the signal transduction mechanisms of the phycobiliproteins within monolayers or thin films of the conducting polymers to create biosensors and related smart materials for applications in biomedicine and biotechnology.

  17. Chemical-bath deposition of ZnSe thin films: Process and material characterization

    SciTech Connect

    Dona, J.M.; Herrero, J.

    1995-03-01

    Chemical-bath deposition of ZnSe thin films from NH{sub 3}/NH{sub 2}-NH{sub 2}/SeC(NH{sub 2}){sub 2}/Na{sub 2}SO{sub 3}/ZnSO{sub 4} solutions has been studied. The effect of various process parameters on the growth and the film quality is presented. A first approach to a mechanistic interpretation of the chemical process, based on the influence of the process parameters on the film growth rate, is reported. The structural, optical, chemical, and electrical properties of the ZnSe thin-films deposited by this method have been studied. The electron diffraction (EDS) analysis shows that the films are microcrystalline with mixed cubic and hexagonal structure. EDS analysis has demonstrated that the films are highly stoichiometric. Scanning electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy studies of the ZnSe thin films deposited by this method show that the films are continuous and homogeneous. Optical measurements have allowed the authors to detect the presence of the spin-orbit splitting effect in this material. Electrical conductivity measurements have shown the highly resistive nature of these films ({rho} {approximately} 10{sup 9} {Omega} cm).

  18. Phase sensitive molecular dynamics of self-assembly glycolipid thin films: A dielectric spectroscopy investigation

    NASA Astrophysics Data System (ADS)

    Velayutham, T. S.; Ng, B. K.; Gan, W. C.; Majid, W. H. Abd.; Hashim, R.; Zahid, N. I.; Chaiprapa, Jitrin

    2014-08-01

    Glycolipid, found commonly in membranes, is also a liquid crystal material which can self-assemble without the presence of a solvent. Here, the dielectric and conductivity properties of three synthetic glycolipid thin films in different thermotropic liquid crystal phases were investigated over a frequency and temperature range of (10-2-106 Hz) and (303-463 K), respectively. The observed relaxation processes distinguish between the different phases (smectic A, columnar/hexagonal, and bicontinuous cubic Q) and the glycolipid molecular structures. Large dielectric responses were observed in the columnar and bicontinuous cubic phases of the longer branched alkyl chain glycolipids. Glycolipids with the shortest branched alkyl chain experience the most restricted self-assembly dynamic process over the broad temperature range studied compared to the longer ones. A high frequency dielectric absorption (Process I) was observed in all samples. This is related to the dynamics of the hydrogen bond network from the sugar group. An additional low-frequency mechanism (Process II) with a large dielectric strength was observed due to the internal dynamics of the self-assembly organization. Phase sensitive domain heterogeneity in the bicontinuous cubic phase was related to the diffusion of charge carriers. The microscopic features of charge hopping were modelled using the random walk scheme, and two charge carrier hopping lengths were estimated for two glycolipid systems. For Process I, the hopping length is comparable to the hydrogen bond and is related to the dynamics of the hydrogen bond network. Additionally, that for Process II is comparable to the bilayer spacing, hence confirming that this low-frequency mechanism is associated with the internal dynamics within the phase.

  19. Advances in thin film photonics: materials, science, and technology

    NASA Astrophysics Data System (ADS)

    Fortmann, Charles M.; Tonucci, Ronald J.; Anderson, Wayne A.; Teplin, C. W.; Mahan, A. H.

    2003-10-01

    Control of refractive index in amorphous silicon materials is investigated. Elementary waveguide structures were prepared on two micron thick amorphous silicon by photon lithographic patterning of a silver masking layer. Hydrogen was implanted at fluence of ~5×1017 cm2 for three energies, 50, 100 and 175 KeV yielding a total does of ~1.5×1018 cm2 consistent with a 10% increase in atoms due to the hydrogen addition. The optical properties of the implanted and non-implanted regions were probed as a function of low temperature annealing. The optical band gap shift to higher energy was consistent with hydrogen addition. Some darkening, absorption increase, were noted on the implanted regions. However, low temperature annealing is known to remove dangling bond damage in amorphous silicon. Prospects of utilizing these waveguides to probe light induced optical changes in amorphous silicon is described as well as the prospects of more advanced devices.

  20. Growth of SrVO{sub 3} thin films by hybrid molecular beam epitaxy

    SciTech Connect

    Eaton, Craig; Brahlek, Matthew; Engel-Herbert, Roman; Moyer, Jarrett A.; Alipour, Hamideh M.; Grimley, Everett D.; LeBeau, James M.

    2015-11-15

    The authors report the growth of stoichiometric SrVO{sub 3} thin films on (LaAlO{sub 3}){sub 0.3}(Sr{sub 2}AlTaO{sub 6}){sub 0.7} (001) substrates using hybrid molecular beam epitaxy. This growth approach employs a conventional effusion cell to supply elemental A-site Sr and the metalorganic precursor vanadium oxytriisopropoxide (VTIP) to supply vanadium. Oxygen is supplied in its molecular form through a gas inlet. An optimal VTIP:Sr flux ratio has been identified using reflection high-energy electron-diffraction, x-ray diffraction, atomic force microscopy, and scanning transmission electron microscopy, demonstrating stoichiometric SrVO{sub 3} films with atomically flat surface morphology. Away from the optimal VTIP:Sr flux, characteristic changes in the crystalline structure and surface morphology of the films were found, enabling identification of the type of nonstoichiometry. For optimal VTIP:Sr flux ratios, high quality SrVO{sub 3} thin films were obtained with smallest deviation of the lattice parameter from the ideal value and with atomically smooth surfaces, indicative of the good cation stoichiometry achieved by this growth technique.

  1. Apparatus and method for treating a cathode material provided on a thin-film substrate

    DOEpatents

    Hanson, Eric J.; Kooyer, Richard L.

    2001-01-01

    An apparatus and method for treating a cathode material provided on a surface of a continuous thin-film substrate and a treated thin-film cathode having increased smoothness are disclosed. A web of untreated cathode material is moved between a feed mechanism and a take-up mechanism, and passed through a treatment station. The web of cathode material typically includes areas having surface defects, such as prominences extending from the surface of the cathode material. The surface of the cathode material is treated with an abrasive material to reduce the height of the prominences so as to increase an 85 degree gloss value of the cathode material surface by at least approximately 10. The web of cathode material may be subjected to a subsequent abrasive treatment at the same or other treatment station. Burnishing or lapping film is employed at a treatment station to process the cathode material. An abrasive roller may alternatively be used to process the web of cathode material. The apparatus and method of the present invention may also be employed to treat the surface of a lithium anode foil so as to cleanse and reduce the roughness of the anode foil surface.

  2. Apparatus and method for treating a cathode material provided on a thin-film substrate

    DOEpatents

    Hanson, Eric J.; Kooyer, Richard L.

    2003-01-01

    An apparatus and method for treating a cathode material provided on a surface of a continuous thin-film substrate and a treated thin-film cathode having increased smoothness are disclosed. A web of untreated cathode material is moved between a feed mechanism and a take-up mechanism, and passed through a treatment station. The web of cathode material typically includes areas having surface defects, such as prominences extending from the surface of the cathode material. The surface of the cathode material is treated with an abrasive material to reduce the height of the prominences so as to increase an 85 degree gloss value of the cathode material surface by at least approximately 10. The web of cathode material may be subjected to a subsequent abrasive treatment at the same or other treatment station. Burnishing or lapping film is employed at a treatment station to process the cathode material. An abrasive roller may alternatively be used to process the web of cathode material. The apparatus and method of the present invention may also be employed to treat the surface of a lithium anode foil so as to cleanse and reduce the roughness of the anode foil surface.

  3. Atomic/molecular layer deposition: a direct gas-phase route to crystalline metal-organic framework thin films.

    PubMed

    Ahvenniemi, E; Karppinen, M

    2016-01-21

    Atomic/molecular layer deposition offers us an elegant way of fabricating crystalline copper(ii)terephthalate metal-organic framework (MOF) thin films on various substrate surfaces. The films are grown from two gaseous precursors with a digital atomic/molecular level control for the film thickness under relatively mild conditions in a simple and fast one-step process. PMID:26612265

  4. Highly Ordered Organic Molecular Thin Films on Silicon Studied by STM and LEED

    NASA Astrophysics Data System (ADS)

    Wagner, Sean; Zhang, Pengpeng

    2014-03-01

    Achieving growth of long-range ordered organic molecular thin films on inorganic substrates continues to be a significant challenge for organic electronics applications. Here, we report the growth of highly ordered zinc phthalocyanine (ZnPc) thin films both in-plane and out-of-plane on the deactivated Si(111) surface by scanning tunneling microscopy (STM) and low energy electron diffraction (LEED). By adjusting the substrate temperature during deposition, the anisotropic step-flow growth mode can be accessed causing a reduction in the substrate symmetry which allows for the long-range in-plane ordering as well as the decrease of grain boundary density. Additionally, the ZnPc molecules are able to maintain a highly ordered configuration in multi-layers despite a gradual decrease in the molecule-substrate interaction, which is attributed to the strong interlayer π- π interaction. We appreciate the fruitful discussion with Prof. Richard Lunt. This research is funded by the DOE Office of Science Early Career Research Program (Grant number DE-SC0006400) through the Office of Basic Energy Sciences.

  5. Coherent growth of superconducting TiN thin films by plasma enhanced molecular beam epitaxy

    SciTech Connect

    Krockenberger, Yoshiharu; Karimoto, Shin-ichi; Yamamoto, Hideki; Semba, Kouich

    2012-10-15

    We have investigated the formation of titanium nitride (TiN) thin films on (001) MgO substrates by molecular beam epitaxy and radio frequency acitvated nitrogen plasma. Although cubic TiN is stabile over a wide temperature range, superconducting TiN films are exclusively obtained when the substrate temperature exceeds 710 Degree-Sign C. TiN films grown at 720 Degree-Sign C show a high residual resistivity ratio of approximately 11 and the superconducting transition temperature (T{sub c}) is well above 5 K. Superconductivity has been confirmed also by magnetiztion measurements. In addition, we determined the upper critical magnetic field ({mu}{sub 0}H{sub c2}) as well as the corresponding coherence length ({xi}{sub GL}) by transport measurements under high magnetic fields. High-resolution transmission electron microscopy data revealed full in plane coherency to the substrate as well as a low defect density in the film, in agreement with a mean-free path length Script-Small-L Almost-Equal-To 106 nm, which is estimated from the residual resistivity value. The observations of reflection high energy electron diffraction intensity oscillations during the growth, distinct Laue fringes around the main Bragg peaks, and higher order diffraction spots in the reciprocal space map suggest the full controlability of the thickness of high quality superconducting TiN thin films.

  6. Epitaxial Cd3As2 Thin Films Synthesized by Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Schumann, Timo; Goyal, Manik; Stemmer, Susanne

    Cd3As2 is a three-dimensional (3D) Dirac semimetal, i.e. it possesses Dirac cones in a 3D bulk state where the band dispersion relation is linear near the Fermi energy. Cd3As2 is has raised considerable interest due to its high electron mobilities in bulk crystals and for novel quantum phenomena, such as chiral anomalies. However, few studies have been performed using thin films of Cd3As2. In this presentation, we report on the synthesis of Cd3As2 thin films by molecular beam epitaxy (MBE). Single phase, epitaxial films were grown on undoped GaSb(111)B substrates with the (112) facet of Cd3As2 parallel to the GaSb(111) surface. We report on the structural quality and orientation variants in the films. Electrical transport properties indicate electron mobilities exceeding 6000 cm2V-1s-1. We discuss the impact of the MBE growth parameters and substrate preparation on the structural and electrical properties of the films.

  7. Thin film growth of CaFe2As2 by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Hatano, T.; Kawaguchi, T.; Fujimoto, R.; Nakamura, I.; Mori, Y.; Harada, S.; Ujihara, T.; Ikuta, H.

    2016-01-01

    Film growth of CaFe2As2 was realized by molecular beam epitaxy on six different substrates that have a wide variation in the lattice mismatch to the target compound. By carefully adjusting the Ca-to-Fe flux ratio, we obtained single-phase thin films for most of the substrates. Interestingly, an expansion of the CaFe2As2 lattice to the out-of-plane direction was observed for all films, even when an opposite strain was expected. A detailed microstructure observation of the thin film grown on MgO by transmission electron microscope revealed that it consists of cube-on-cube and 45°-rotated domains. The latter domains were compressively strained in plane, which caused a stretching along the c-axis direction. Because the domains were well connected across the boundary with no appreciable discontinuity, we think that the out-of-plane expansion in the 45°-rotated domains exerted a tensile stress on the other domains, resulting in the unexpectedly large c-axis lattice parameter, despite the apparently opposite lattice mismatch.

  8. Alternative nano-structured thin-film materials used as durable thermal nanoimprint lithography templates

    NASA Astrophysics Data System (ADS)

    Bossard, M.; Boussey, J.; Le Drogoff, B.; Chaker, M.

    2016-02-01

    Nanoimprint templates made of diamond-like carbon (DLC) and amorphous silicon carbide (SiC) thin films and fluorine-doped associated materials, i.e. F-DLC and F-SiC were investigated in the context of thermal nanoimprint lithography (NIL) with respect to their release properties. Their performances in terms of durability and stability were evaluated and compared to those of conventional silicon or silica molds coated with antisticking molecules applied as a self-assembled monolayer. Plasma-enhanced chemical vapor deposition parameters were firstly tuned to optimize mechanical and structural properties of the DLC and SiC thin films. The impact of the amount of fluorine dopant on the deposited thin films properties was then analyzed. A comparative analysis of DLC, F-DLC as well as SiC and F-SiC molds was then carried out over multiple imprints, performed into poly (methyl methacrylate) (PMMA) thermo-plastic resist. The release properties of un-patterned films were evaluated by the measurement of demolding energies and surface energies, associated with a systematic analysis of the mold surface contamination. These analyses showed that the developed materials behave as intrinsically easy-demolding and contamination-free molds over series of up to 40 imprints. To our knowledge, it is the first time that such a large number of imprints has been considered within an exhaustive comparative study of materials for NIL. Finally, the developed materials went through standard e-beam lithography and plasma etching processes to obtain nanoscale-patterned templates. The replicas of those patterned molds, imprinted into PMMA, were shown to be of high fidelity and good stability after several imprints.

  9. Alternative nano-structured thin-film materials used as durable thermal nanoimprint lithography templates.

    PubMed

    Bossard, M; Boussey, J; Le Drogoff, B; Chaker, M

    2016-02-19

    Nanoimprint templates made of diamond-like carbon (DLC) and amorphous silicon carbide (SiC) thin films and fluorine-doped associated materials, i.e. F-DLC and F-SiC were investigated in the context of thermal nanoimprint lithography (NIL) with respect to their release properties. Their performances in terms of durability and stability were evaluated and compared to those of conventional silicon or silica molds coated with antisticking molecules applied as a self-assembled monolayer. Plasma-enhanced chemical vapor deposition parameters were firstly tuned to optimize mechanical and structural properties of the DLC and SiC thin films. The impact of the amount of fluorine dopant on the deposited thin films properties was then analyzed. A comparative analysis of DLC, F-DLC as well as SiC and F-SiC molds was then carried out over multiple imprints, performed into poly (methyl methacrylate) (PMMA) thermo-plastic resist. The release properties of un-patterned films were evaluated by the measurement of demolding energies and surface energies, associated with a systematic analysis of the mold surface contamination. These analyses showed that the developed materials behave as intrinsically easy-demolding and contamination-free molds over series of up to 40 imprints. To our knowledge, it is the first time that such a large number of imprints has been considered within an exhaustive comparative study of materials for NIL. Finally, the developed materials went through standard e-beam lithography and plasma etching processes to obtain nanoscale-patterned templates. The replicas of those patterned molds, imprinted into PMMA, were shown to be of high fidelity and good stability after several imprints. PMID:26783068

  10. Laser induced deflection (LID) method for absolute absorption measurements of optical materials and thin films

    NASA Astrophysics Data System (ADS)

    Mühlig, Christian; Bublitz, Simon; Paa, Wolfgang

    2011-05-01

    We use optimized concepts to measure directly low absorption in optical materials and thin films at various laser wavelengths by the laser induced deflection (LID) technique. An independent absolute calibration, using electrical heaters, is applied to obtain absolute absorption data without the actual knowledge of the photo-thermal material properties. Verification of the absolute calibration is obtained by measuring different silicon samples at 633 nm where all laser light, apart from the measured reflection/scattering, is absorbed. Various experimental results for bulk materials and thin films are presented including measurements of fused silica and CaF2 at 193 nm, nonlinear crystals (LBO) for frequency conversion and AR coated fused silica for high power material processing at 1030 nm and Yb-doped silica raw materials for high power fiber lasers at 1550 nm. In particular for LBO the need of an independent calibration is demonstrated since thermal lens generation is dominated by stress-induced refractive index change which is in contrast to most of the common optical materials. The measured results are proven by numerical simulations and their influence on the measurement strategy and the obtained accuracy are shown.

  11. Fundamental studies of the mechanical behavior of microelectronic thin film materials

    NASA Astrophysics Data System (ADS)

    Nix, William D.

    1987-03-01

    A fundamental program of research on the mechanical properties of microelectronic thin film material has been initiated at Stanford University. The work is being supported under AFOSR Grant No. 86-0051. In this interim Scientific Report, some of the progress made during the first year of the program is reviewed. We have made very rapid progress,expecially in the development of new experimental techniques for measuring mechanical properties. The work has already led to several publications and to an equal number of invited oral presentations, both of which are listed at the end of this report. The primary motivation of this work is to understand the mechanical properties of microelectronic this film materials. Although these materials are not structural materials as such, they are, nevertheless, expected to withstand very high stresses, both during manufacturing and in service. As a consequence, the mechanical properties of these materials are almost as important as their electronic properties for successful device applicaitions. because these materials often exist only as thin films bonded to substrates, it is necessary to study their mechanical properties in that state.

  12. Molecular doping for control of gate bias stress in organic thin film transistors

    SciTech Connect

    Hein, Moritz P. Lüssem, Björn; Jankowski, Jens; Tietze, Max L.; Riede, Moritz K.; Zakhidov, Alexander A.; Leo, Karl; Fraunhofer COMEDD, Maria-Reiche-Str. 2, 01109 Dresden

    2014-01-06

    The key active devices of future organic electronic circuits are organic thin film transistors (OTFTs). Reliability of OTFTs remains one of the most challenging obstacles to be overcome for broad commercial applications. In particular, bias stress was identified as the key instability under operation for numerous OTFT devices and interfaces. Despite a multitude of experimental observations, a comprehensive mechanism describing this behavior is still missing. Furthermore, controlled methods to overcome these instabilities are so far lacking. Here, we present the approach to control and significantly alleviate the bias stress effect by using molecular doping at low concentrations. For pentacene and silicon oxide as gate oxide, we are able to reduce the time constant of degradation by three orders of magnitude. The effect of molecular doping on the bias stress behavior is explained in terms of the shift of Fermi Level and, thus, exponentially reduced proton generation at the pentacene/oxide interface.

  13. Fine-Tunable Absorption of Uniformly Aligned Polyurea Thin Films for Optical Filters Using Sequentially Self-Limited Molecular Layer Deposition.

    PubMed

    Park, Yi-Seul; Choi, Sung-Eun; Kim, Hyein; Lee, Jin Seok

    2016-05-11

    Development of methods enabling the preparation of uniformly aligned polymer thin films at the molecular level is a prerequisite for realizing their optoelectronic characteristics as innovative materials; however, these methods often involve a compromise between scalability and accuracy. In this study, we have grown uniformly aligned polyurea thin films on a SiO2 substrate using molecular layer deposition (MLD) based on sequential and self-limiting surface reactions. By integrating plane-polarized Fourier-transform infrared, Raman spectroscopic tools, and density functional theory calculations, we demonstrated the uniform alignment of polyurea MLD films. Furthermore, the selective-wavelength absorption characteristics of thickness-controlled MLD films were investigated by integrating optical measurements and finite-difference time-domain simulations of reflection spectra, resulting from their thickness-dependent fine resonance with photons, which could be used as color filters in optoelectronics. PMID:27092573

  14. Vacuum sublimed α ,ω-dihexylsexithiophene thin films: Correlating electronic structure and molecular orientation

    NASA Astrophysics Data System (ADS)

    Duhm, S.; Salzmann, I.; Koch, N.; Fukagawa, H.; Kataoka, T.; Hosoumi, S.; Nebashi, K.; Kera, S.; Ueno, N.

    2008-08-01

    In order to correlate the molecular orientation of organic thin films with charge injection barriers at organic/metal interfaces, the electronic structure and molecular orientation of vacuum sublimed thin films of α ,ω-dihexylsexithiophene (DH6T) on the substrates Ag(111), highly oriented pyrolytic graphite (HOPG), and tetratetracontane (TTC) precovered Ag(111) were investigated. Results from metastable atom electron spectroscopy, ultraviolet photoelectron spectroscopy, and x-ray diffraction were used to derive growth models (including molecular orientation and conformation) of DH6T on the different substrates. On Ag(111), DH6T exhibits a transition from lying molecules in the monolayer/bilayer range to almost standing upright molecules in multilayers. This is accompanied by a shift of the molecular energy levels to a lower binding energy by 0.65 eV with respect to the vacuum level. The unit cell of standing DH6T on lying DH6T on Ag(111) is estimated to be similar to the DH6T bulk phase. On HOPG, DH6T grows in the bulk phase with lying orientation, starting already from the monolayer coverage. DH6T on TTC precovered Ag(111) grows in an almost lying orientation and a conformation that allows a strong overlap of the hexyl chains of DH6T with the alkyl chains of TTC. In all cases, the electronic structure and, particulary, the ionization energy of DH6T is dependent on the orientation of DH6T, i.e., lying DH6T has higher ionization energy than standing DH6T.

  15. Thin-film optical initiator

    DOEpatents

    Erickson, Kenneth L.

    2001-01-01

    A thin-film optical initiator having an inert, transparent substrate, a reactive thin film, which can be either an explosive or a pyrotechnic, and a reflective thin film. The resultant thin-film optical initiator system also comprises a fiber-optic cable connected to a low-energy laser source, an output charge, and an initiator housing. The reactive thin film, which may contain very thin embedded layers or be a co-deposit of a light-absorbing material such as carbon, absorbs the incident laser light, is volumetrically heated, and explodes against the output charge, imparting about 5 to 20 times more energy than in the incident laser pulse.

  16. Solar Selective Coatings Prepared From Thin-Film Molecular Mixtures and Evaluated

    NASA Technical Reports Server (NTRS)

    Jaworske, Don A.

    2003-01-01

    Thin films composed of molecular mixtures of metal and dielectric are being considered for use as solar selective coatings for a variety of space power applications. By controlling molecular mixing during ion-beam sputter deposition, researchers can tailor the solar selective coatings to have the combined properties of high solar absorptance and low infrared emittance. On orbit, these combined properties simultaneously maximize the amount of solar energy captured by the coating and minimize the amount of thermal energy radiated. The solar selective coatings are envisioned for use on minisatellites, for applications where solar energy is used to power heat engines or to heat remote regions in the interior of the spacecraft. Such systems may be useful for various missions, particularly those to middle Earth orbit. Sunlight must be concentrated by a factor of 100 or more to achieve the desired heat inlet operating temperature. At lower concentration factors, the temperature of the heat inlet surface of the heat engine is too low for efficient operation, and at high concentration factors, cavity type heat receivers become attractive. The an artist's concept of a heat engine, with the annular heat absorbing surface near the focus of the concentrator coated with a solar selective coating is shown. In this artist's concept, the heat absorbing surface powers a small Stirling convertor. The astronaut's gloved hand is provided for scale. Several thin-film molecular mixtures have been prepared and evaluated to date, including mixtures of aluminum and aluminum oxide, nickel and aluminum oxide, titanium and aluminum oxide, and platinum and aluminum oxide. For example, a 2400- Angstrom thick mixture of titanium and aluminum oxide was found to have a solar absorptance of 0.93 and an infrared emittance of 0.06. On the basis of tests performed under flowing nitrogen at temperatures as high as 680 C, the coating appeared to be durable at elevated temperatures. Additional durability

  17. Multifunctional thin film surface

    SciTech Connect

    Brozik, Susan M.; Harper, Jason C.; Polsky, Ronen; Wheeler, David R.; Arango, Dulce C.; Dirk, Shawn M.

    2015-10-13

    A thin film with multiple binding functionality can be prepared on an electrode surface via consecutive electroreduction of two or more aryl-onium salts with different functional groups. This versatile and simple method for forming multifunctional surfaces provides an effective means for immobilization of diverse molecules at close proximities. The multifunctional thin film has applications in bioelectronics, molecular electronics, clinical diagnostics, and chemical and biological sensing.

  18. Biomimetic thin film synthesis

    SciTech Connect

    Graff, G.L.; Campbell, A.A.; Gordon, N.R.

    1995-05-01

    The purpose of this program is to develop a new process for forming thin film coatings and to demonstrate that the biomimetic thin film technology developed at PNL is useful for industrial applications. In the biomimetic process, mineral deposition from aqueous solution is controlled by organic functional groups attached to the underlying substrate surface. The coatings process is simple, benign, inexpensive, energy efficient, and particularly suited for temperature sensitive substrate materials (such as polymers). In addition, biomimetic thin films can be deposited uniformly on complex shaped and porous substrates providing a unique capability over more traditional line-of-sight methods.

  19. Magnetic anisotropy and permeability in sputtered iron aluminum nitride thin-film materials

    NASA Astrophysics Data System (ADS)

    Liu, Yi-Kuang

    Significant improvement in magnetic properties of FeXN (X = Al, Zr, Ta...) thin films deposited on the sloping surfaces, especially at 60°, was achieved by using various interlayer materials or proper sputtering conditions. The oblique incidence problems in permalloy and CoZrRe thin films were also greatly improved. Test heads fabricated using these materials showed improved permeability. Significant improvement of the thermal stability in FeXN thin films was also achieved. Sputtered at the reduced target-substrate spacing of 38 mm, 200 nm thick thermally stable FeXN thin films were obtained. They had hard axis coercivity ≈0.1--2.0 Oe, easy axis coercivity ≈1.5--3.0 Oe, Hk = 8--16 Oe and Bs = 19--20 kG. Results from transverse field annealing experiments in a uniform field of 700 Oe show no significant change of magnetic properties at 150°C for 3 hours. At 150°C for 24 hours, Hk decreased by 2--4 Oe. Their easy/hard axes did not rotate and the coercivity remained almost unchanged. This superior thermal stability of FeXN films is promising for high moment write heads. The effects of N doping on the magnetic and structural properties of a series of 100 nm FeAlN films sputtered in the presence of N partial pressures were investigated. Increasing N doping increased film resistivity but decreased MS. Extended x-ray absorption fine structure spectra of the short-range atomic order in the Fe(Al) lattices directly indicated that the N went into octahedral sites of bcc Fe and fcc Fe in alpha-Fe and gamma'-Fe 4N phases, respectively, and triggered the order-disorder phase transition observed in x-ray 0--20 diffraction spectra. Mild N doping decreased the grain size and reduced Hc. It also increased the local atomic disorder, which coincided with the maximal value of Ku and the in-plane anisotropic behaviors in the as-deposited films. The roles of N doping in FeXN film optimization processes and its effects on magnetic and structural properties, especially the uniaxial

  20. Improved Stability Of Amorphous Zinc Tin Oxide Thin Film Transistors Using Molecular Passivation

    SciTech Connect

    Rajachidambaram, Meena Suhanya; Pandey, Archana; Vilayur Ganapathy, Subramanian; Nachimuthu, Ponnusamy; Thevuthasan, Suntharampillai; Herman, Gregory S.

    2013-10-21

    The role of back channel surface chemistry on amorphous zinc tin oxide (ZTO) bottom gate thin film transistors (TFT) have been characterized by positive bias-stress measurements and x-ray photoelectron spectroscopy. Positive bias-stress turn-on voltage shifts for ZTO-TFTs were significantly reduced by passivation of back channel surfaces with self-assembled monolayers of n-hexylphosphonic acid (n-HPA) when compared to ZTO-TFTs with no passivation. These results indicate that adsorption of molecular species on exposed back channel of ZTO-TFTs strongly influence observed turn-on voltage shifts, as opposed to charge injection into the dielectric or trapping due to oxygen vacancies.

  1. Self-Limiting Growth of Metal Fluoride Thin Films by Oxidation Reactions Employing Molecular Precursors

    SciTech Connect

    Qiu, S. R.; Lai, H.-F.; Yarmoff, J. A.

    2000-08-14

    FeF{sub 2} films are grown by the reaction of XeF{sub 2} and SeF{sub 6} with iron foil. The growth initially follows the Mott-Cabrera parabolic rate law, indicating that the process is diffusion limited. At a certain film thickness, however, the growth abruptly stops, with the thickness using XeF{sub 2} being nearly double that with SeF{sub 6} . It is suggested that the shutdown is due to the inability of the molecules to dissociate when too far from the substrate and that SeF{sub 6} must approach more closely than XeF{sub 2} . This work suggests the use of molecular precursors to grow thin films via a self-limiting chemical process. (c) 2000 The American Physical Society.

  2. Development of Nb and Alternative Material Thin Films Tailored for SRF Applications

    SciTech Connect

    Valente-Feliciano, A -M; Reece, C E; Spradlin, J K; Xiao, B; Zhao, X; Gu, Diefeng; Baumgart, Helmut; Beringer, Douglas; Lukaszew, Rosa

    2011-09-01

    Over the years, Nb/Cu technology, despite its shortcomings due to the commonly used magnetron sputtering, has positioned itself as an alternative route for the future of superconducting structures used in accelerators. Recently, significant progress has been made in the development of energetic vacuum deposition techniques, showing promise for the production of thin films tailored for SRF applications. JLab is pursuing energetic condensation deposition via techniques such as Electron Cyclotron Resonance and High Power Impulse Magnetron Sputtering. As part of this project, the influence of the deposition energy on the material and RF properties of the Nb thin film is investigated with the characterization of their surface, structure, superconducting properties and RF response. It has been shown that the film RRR can be tuned from single digits to values greater than 400. This paper presents results on surface impedance measurements correlated with surface and material characterization for Nb films produced on various substrates, monocrystalline and polycrystalline as well as amorphous. A progress report on work on NbTiN and AlN based multilayer structures will also be presented.

  3. Molecular separations using nanostructured porous thin films fabricated by glancing angle deposition

    NASA Astrophysics Data System (ADS)

    Bezuidenhout, Louis Wentzel

    Biomolecular separation techniques are an enabling technology that indirectly in.uence many aspects of our lives. Advances have led to faster analyses, reduced costs, higher specificity, and new analytical techniques, impacting areas such as health care, environmental monitoring, polymer sciences, agriculture, and nutrition. Further development of separations technology is anticipated to follow the path of computing technology such that miniaturization through the development of microfluidics technology, lab-on-a-chip systems, and other integrative, multi-component systems will further extend our analysis capabilities. Creation of new and improvement of existing separation technologies is an integral part of the pathway to miniaturized systems. the work of this thesis investigates molecular separations using porous nanostructured films fabricated by the thin film process glancing angle deposition (GLAD). Structural architecture, pore size and shape, and film density can be finely controlled to produce high-surface area thin films with engineered morphology. The characteristic size scales and structural control of GLAD films are well-suited to biomolecules and separation techniques, motivating investigation into the utility and performance of GLAD films for biomolecular separations. This project consisted of three phases. First, chromatographic separation of dye molecules on silica GLAD films was demonstrated by thin layer chromatography Direct control of film nanostructure altered the separation characteristics; most strikingly, anisotropic structures provided two-dimensional analyte migration. Second, nanostructures made with GLAD were integrated in PDMS microfluidic channels using a sacrificial etching process; DNA molecules (10/48 kbp and 6/10/20 kbp mixtures) were electrophoretically separated on a microfluidic chip using a porous bed of SiO2 vertical posts. Third, mass spectrometry of proteins and drugs in the mass range of 100-1300 m/z was performed using

  4. High-gravity-assisted pulsed laser ablation system for the fabrication of functionally graded material thin film.

    PubMed

    Nishiyama, T; Morinaga, S; Nagayama, K

    2009-03-01

    This paper describes a novel method for the fabrication of a thin film deposited on an appropriate substrate having a continuous composition gradient. The composition gradient was achieved by a combination of pulsed laser ablation (PLA) of the target material with a very strong acceleration field generated on a moving disk rotating at a very high speed. The PLA process was used to produce a cloud of high-energy particles of the target material that will be deposited on a substrate placed on the rotating disk. After deposition, the particles will diffuse on the surface of the thin film under a strong acceleration field. The high energy of the particles and their diffusion on the substrate surface in a high-vacuum environment produces a macroscopic composition distribution in the thin film. We have constructed an experimental apparatus consisting of a vacuum chamber in which a circular disk made of titanium is driven by a high-frequency inductive motor. An acceleration field of up to 10,000 G can be generated by this apparatus. Functionally graded material thin films of FeSi(2) with a continuous concentration gradient were successfully fabricated by this method under a gravity field of 5400 G. A significant advantage of this method is that it allows us to fabricate graded thin films with a very smooth surface covered by few droplets. PMID:19334931

  5. Thin film mechanics

    NASA Astrophysics Data System (ADS)

    Cooper, Ryan C.

    This doctoral thesis details the methods of determining mechanical properties of two classes of novel thin films suspended two-dimensional crystals and electron beam irradiated microfilms of polydimethylsiloxane (PDMS). Thin films are used in a variety of surface coatings to alter the opto-electronic properties or increase the wear or corrosion resistance and are ideal for micro- and nanoelectromechanical system fabrication. One of the challenges in fabricating thin films is the introduction of strains which can arise due to application techniques, geometrical conformation, or other spurious conditions. Chapters 2-4 focus on two dimensional materials. This is the intrinsic limit of thin films-being constrained to one atomic or molecular unit of thickness. These materials have mechanical, electrical, and optical properties ideal for micro- and nanoelectromechanical systems with truly novel device functionality. As such, the breadth of applications that can benefit from a treatise on two dimensional film mechanics is reason enough for exploration. This study explores the anomylously high strength of two dimensional materials. Furthermore, this work also aims to bridge four main gaps in the understanding of material science: bridging the gap between ab initio calculations and finite element analysis, bridging the gap between ab initio calculations and experimental results, nanoscale to microscale, and microscale to mesoscale. A nonlinear elasticity model is used to determine the necessary elastic constants to define the strain-energy density function for finite strain. Then, ab initio calculations-density functional theory-is used to calculate the nonlinear elastic response. Chapter 2 focuses on validating this methodology with atomic force microscope nanoindentation on molybdenum disulfide. Chapter 3 explores the convergence criteria of three density functional theory solvers to further verify the numerical calculations. Chapter 4 then uses this model to investigate

  6. Thin film tritium dosimetry

    DOEpatents

    Moran, Paul R.

    1976-01-01

    The present invention provides a method for tritium dosimetry. A dosimeter comprising a thin film of a material having relatively sensitive RITAC-RITAP dosimetry properties is exposed to radiation from tritium, and after the dosimeter has been removed from the source of the radiation, the low energy electron dose deposited in the thin film is determined by radiation-induced, thermally-activated polarization dosimetry techniques.

  7. Method for measurement of the density of thin films of small organic molecules

    SciTech Connect

    Xiang Haifeng; Xu Zongxiang; Roy, V. A. L.; Che Chiming; Lai, P. T.

    2007-03-15

    An accurate and sensitive method is reported to measure the thin-film density of vacuum-deposited, small-molecular organic semiconductor materials. A spectrophotometer and surface profiler had been used to determine the mass and thickness of organic thin film, respectively. The calculated density of tris-(8-hydroxyquinolato) aluminum (Alq{sub 3}) thin film was 1.31{+-}0.01 g/cm{sup 3}. Vacuum pressures and thin-film growth rates are found to have less impact on the thin-film density of organic material. However, the thin-film density of organic material strongly depends on its chemical structure and molecular weight. Specifically, the chemical structure determines the density of organic material that affects the molecular volume and intermolecular stacking.

  8. Element-Doped Polyacrylic Acid Thin Films as SIMS Standards for Organic Materials

    NASA Astrophysics Data System (ADS)

    Davisson, M.; Phinney, D. L.; Weber, P. K.

    2009-12-01

    To constrain relative sensitive factors for SIMS elemental analysis of organic materials, calibration standards are being developed by coordinating ppm quantities of Group I, Group II, and transition metals with polyacrylic acid resin and depositing them as thin films. Each element is prepared as an aqueous acetate, oxalate, or nitrate solution to avoid unwanted elements that compromise thin film uniformity or produce interfering masses. These are subsequently mixed proportionally with reagent grade resins (Mw ~2000 and ~50,000), and dried passively on an Al bullet or spin-coated for thin layering (~100nm). Initial results using an O- primary beam on a Cameca NanoSIMS demonstrate excellent lateral homogeneity for Na, K, Fe, Co, and Cd at nanometer scale and consistent ratios to 12C (stdev <10%) over multiple 10um raster areas, whereas Mg, Ca, Sr, and Cu show variable ratios to 12C over sputter depth (stdev >10%). Depth profiling over the entire film thickness using a Cameca 3f show high reproducibility of element trends at 250um raster areas. Additional measurements will incorporate multi-element suites of biologically-relevant species (e.g. Na, K, Ca, P) to facilitate quantitative analysis of sensitivity factors with compositional changes.

  9. Growth mechanism of CuZnInSe2 thin films grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Tseng, Ya Hsin; Yang, Chu Shou; Wu, Chia Hsing; Chiu, Jai Wei; Yang, Min De; Wu, Chih-Hung

    2013-09-01

    CuZnInSe2 (CZIS) has potential application in solar cell for absorption layer, and give an advantage to change the band gap from CuInSe2 (1.02 eV) to ZnSe (2.67 eV). Using molecular beam epitaxy technology, the CZIS thin films were grown via CuInSe (CIS) and ZnSe base. In the case of CIS, thin films were grown on Mo-coated soda lime glass with various zinc flux. CIS was transformed into chalcopyrite and sphalerite coexisting CZIS easily but it is difficult to transform into the pure sphalerite CZIS. Zn/(Zn+In+Cu) ratio has limited to approximate 36 at% and the excess-Zn played a catalyst role. In the case of ZnSe base, which was grown on GaAs (001), various In and Cu flux defined as the TIn series and TCu series, respectively. There are four types of compound in the TIn series and TCu series, including ZnSe, InxSey, ZnIn2Se4 (ZIS) and CZIS. In the TIn series under the lowest In and Cu flux, selenium (Se) were randomly combined with cations to form the CZIS. When TIn is increased in this moment, the CZIS was transformed into ZIS. In the TCu series, CZIS demonstrated via In-rich ZIS (Zn(In, Cu)Se) and InxSey base ((Zn, Cu)InSe). It is chalcopyrite and sphalerite coexisting structure in the medium TCu region. In the high TCu region, it is transformed into the Zn-poor and Cu-rich CZIS.

  10. Facile synthesis of multilayer-like Si thin film as high-performance anode materials for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Wang, Mingxu; Geng, Zhongrong

    2016-05-01

    For the silicon anodes in lithium-ion batteries, it is well known that the enormous volumetric expansion/contraction is also the mainly reason for the capacity fading. In this manuscript, a new kind of Si thin films was prepared with a radio frequency magnetron sputtering method. By using a periodic modulation negative bias on the substrate, a density-modulated multilayer-like silicon thin films with different layer densities were used as anode materials of lithium-ion batteries, and which displayed a high capacity and stable cycling performances. The reason for the charming electrochemical performances may be owned to the particular density modulated microstructure of the Si thin films. It is conjectured that the lower density can as compliant layers and which provided the volume for the higher-density layer expansion in the process of the lithiation/delithiation. In contrast to the conventional silicon anodes, the density modulated microstructure in this work could exploit a new approach to silicon thin-film anode materials with outstanding electrochemical properties and mechanical stability. And these reports may be provide a new way to prepare the Si thin films for the high-energy, safe, and low-cost batteries.

  11. Scanning Seebeck Coefficient Measurement System for Homogeneity Characterization of Bulk and Thin-Film Thermoelectric Materials

    SciTech Connect

    Iwanaga, S; Snyder, GJ

    2012-04-03

    Larger-scale production of thermoelectric materials is necessary when mass-producing thermoelectric devices at industrial level. Certain fabrication techniques can create inhomogeneity in the material through composition and doping fluctuations throughout the sample, causing local variations in thermoelectric properties. Some variations are in the range of sub-millimeter scale or larger but may be difficult to detect by traditional materials characterization techniques such as x-ray diffraction or scanning electron microscopy when the chemical variation is small but the doping variation, which strongly affects thermoelectric performance, is large. In this paper, a scanning apparatus to directly detect local variations of Seebeck coefficient on both bulk and thin-film samples is used. Results have shown that this technique can be utilized for detection of defective regions, as well as phase separation in the 100-m range or larger.

  12. Nanostructured thin film-based near-infrared tunable perfect absorber using phase-change material

    NASA Astrophysics Data System (ADS)

    Kocer, Hasan

    2015-01-01

    Nanostructured thin film absorbers embedded with phase-change thermochromic material can provide a large level of absorption tunability in the near-infrared region. Vanadium dioxide was employed as the phase-change material in the designed structures. The optical absorption properties of the designed structures with respect to the geometric and material parameters were systematically investigated using finite-difference time-domain computations. Absorption level of the resonance wavelength in the near-IR region was tuned from the perfect absorption level to a low level (17%) with a high positive dynamic range of near-infrared absorption intensity tunability (83%). Due to the phase transition of vanadium dioxide, the resonance at the near-infrared region is being turned on and turned off actively and reversibly under the thermal bias, thereby rendering these nanostructures suitable for infrared camouflage, emitters, and sensors.

  13. Development of Bismuth-based Lead-free Piezoelectric Materials: Thin Film Piezoelectric Materials via PVD and CSD Routes

    NASA Astrophysics Data System (ADS)

    Jeon, Yu Hong

    Piezoelectric materials have been widely used in electromechanical actuators, sensors, and ultrasonic transducers. Among these materials, lead zirconate titanate Pb(Zr1-xTix)O3 (PZT) has been primarily investigated due to its excellent piezoelectric properties. However, environmental concerns due to the toxicity of PbO have led to investigations into alternative materials systems. Bismuth-based perovskite piezoelectric materials such as (Bi0.5,Na0.5)TiO3 - (Bi0.5K 0.5)TiO3 (BNT - BKT), (Bi0.5,Na0.5 )TiO3 - (Bi0.5K0.5)TiO3 - BaTiO3(BNT - BKT - BT), (Bi0.5K 0.5)TiO3 - Bi(Zn0.5,Ti0.5)O 3 (BKT - BZT), and (Bi0.5,Na0.5)TiO 3 - (Bi0.5K0.5)TiO3 - Bi(Mg 0.5,Ti0.5)O3 (BNT - BKT - BMgT) have been explored as potential alternatives to PZT. These materials systems have been extensively studied in bulk ceramic form, however many of the ultimate applications will be in thin film embodiments (i.e., microelectromechanical systems). For this reason, in this thesis these lead-free piezoelectrics are synthesized in thin film form to understand the structure-property-processing relationships and their impact on the ultimate device response. Fabrication of high quality of 0.95BKT - 0.05BZT thin films on platinized silicon substrates was attempted by pulsed laser deposition. Due to cation volatility, deposition parameters such as substrate temperature, deposition pressure, and target-substrate distance, as well as target overdoping were explored to achieve phase pure materials. This route led to high dielectric loss, indicative of poor ferroelectric behavior. This was likely a result of the poor thin film morphology observed in films deposited via this method. Subsequently, 0.8BNT - 0.2BKT, 85BNT - 10BKT - 5BT, and 72.5BNT - 22.5BKT - 5BMgT (near morphotropic phase boundary composition) were synthesized via chemical solution deposition. To compensate the loss of A-site cations, overdoped precursor solutions were prepared. Crystallization after each spin cast layer were required to

  14. Positron annihilation studies of vacancy related defects in ceramic and thin film Pb(Zr,Ti)O{sub 3} materials

    SciTech Connect

    Keeble, D.J.; Krishnan, A.; Umlor, M.T.; Lynn, K.G.; Warren, W.L.; Dimos, D.; Tuttle, B.A.; Ramesh, R.; Poindexter, E.H.

    1994-07-01

    Preliminary positron annihilation studies of ceramic and thin film Pb(Zr,Ti)O{sub 3} (PZT) materials have been completed. This paper examines effects of processing conditions on vacancy related defects. Positron lifetime measurements on bulk PLZT plates showed an increase in positron trapping to a defect state with increasing grain size consistent with trapping to lead vacancy related defects formed through lead oxide loss during processing. Variable energy positron beam measurements were completed on bulk PLZT plates, sol-gel PZT thin films and laser ablated PLZT thin films. Films processed in a reduced oxygen atmosphere were found to give a higher S-parameter, due to an increase in concentration of neutral or negatively charged vacancy type defects, compared with material processed in an oxidizing ambient.

  15. Materials Growth and Optoelectronic Properties of Nano-needle Structured Sn-rich SnO Thin Films

    NASA Astrophysics Data System (ADS)

    Wong, Andrew A.

    The rising global interest in photovoltaics and consumer electronics has heightened the demand for earth-abundant optoelectronic materials. Transparent conductive oxides (TCOs) in particular have been widely studied due to their unique material properties and versatility in a variety of applications. However, many of the common TCO materials suffer tradeoffs between cost, environmental stability, and fabrication requirements in addition to their optical and electronic properties. Tin monoxide (SnO) has become an intriguing TCO candidate due to its p-type conductivity, unique among oxide semiconductors. Yet prior studies show these materials require delicate preparation conditions and result in modest electrical and optical performance. In this study, we report a novel method of preparing Sn-rich SnO thin films using a comproportionation reaction of Sn and SnO2. These thin films are fabricated through magnetron co-sputtering of Sn and SnO2 and then undergo crystallization through thermal annealing at different temperatures and in varied ambient environments. Material properties are quantified through techniques such as X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, electron backscatter diffraction, spectrophotometry (with integrating sphere), 4-point probe, hot probe and Hall effect measurements. This thesis reports the rapid (15-60 seconds), low temperature (210-300°C) crystallization of these thin films to form SnO nano-needles with embedded Sn plasmonic scatterers. Sn-rich SnO thin films can be laser pre-patterned to establish nucleation centers and control nano-needle size. These nanoscale features are advantageous for light-trapping in low temperature photovoltaic technologies such as a-Si or CIGS. Furthermore, parallel experimental-theoretical studies suggest that Sn-rich SnO thin films on thin film Ge could have 2-5x absorption increase the near infrared regime. This would be ideal for thermophotovoltaic and infrared

  16. Fabrication of hybrid thin film structures from HTS and CMR materials

    NASA Astrophysics Data System (ADS)

    Sojková, M.; Štrbík, V.; Nurgaliev, T.; Chromik, Š.; Dobročka, E.; Španková, M.; Blagoev, B.; Gál, N.

    2016-03-01

    We present the preparation of bilayers from high-temperature superconductors (HTS) and half-metallic ferromagnetic (FM) manganite with a colossal magnetoresistance (CMR). We used YBa2Cu3O7-x (YBCO) and Tl2Ba2CaCu2O8 (TBCCO) thin films as a HTS material and La0.67Sr0.33MnO3 (LSMO) film as a CMR material. In the case of YBCO/LSMO, we prepared FM/HTS heterostructure for studying the spin-polarized current injection effect on the electrical properties of the YBCO strip in dc or low-frequency regimes and on the microwave characteristics of the strip. For the first time, we report the preparation of a TBCCO/LSMO bilayer. In some applications, the TBCCO offers better parameters (higher working temperature, lower surface resistance, lower 1/f noise) than YBCO.

  17. High-temperature antiferromagnetism in molecular semiconductor thin films and nanostructures.

    PubMed

    Serri, Michele; Wu, Wei; Fleet, Luke R; Harrison, Nicholas M; Hirjibehedin, Cyrus F; Kay, Christopher W M; Fisher, Andrew J; Aeppli, Gabriel; Heutz, Sandrine

    2014-01-01

    The viability of dilute magnetic semiconductors in applications is linked to the strength of the magnetic couplings, and room temperature operation is still elusive in standard inorganic systems. Molecular semiconductors are emerging as an alternative due to their long spin-relaxation times and ease of processing, but, with the notable exception of vanadium-tetracyanoethylene, magnetic transition temperatures remain well below the boiling point of liquid nitrogen. Here we show that thin films and powders of the molecular semiconductor cobalt phthalocyanine exhibit strong antiferromagnetic coupling, with an exchange energy reaching 100 K. This interaction is up to two orders of magnitude larger than in related phthalocyanines and can be obtained on flexible plastic substrates, under conditions compatible with routine organic electronic device fabrication. Ab initio calculations show that coupling is achieved via superexchange between the singly occupied a1g () orbitals. By reaching the key milestone of magnetic coupling above 77 K, these results establish quantum spin chains as a potentially useable feature of molecular films. PMID:24445992

  18. High-temperature antiferromagnetism in molecular semiconductor thin films and nanostructures

    PubMed Central

    Serri, Michele; Wu, Wei; Fleet, Luke R.; Harrison, Nicholas M.; Hirjibehedin, Cyrus F.; Kay, Christopher W.M.; Fisher, Andrew J.; Aeppli, Gabriel; Heutz, Sandrine

    2014-01-01

    The viability of dilute magnetic semiconductors in applications is linked to the strength of the magnetic couplings, and room temperature operation is still elusive in standard inorganic systems. Molecular semiconductors are emerging as an alternative due to their long spin-relaxation times and ease of processing, but, with the notable exception of vanadium-tetracyanoethylene, magnetic transition temperatures remain well below the boiling point of liquid nitrogen. Here we show that thin films and powders of the molecular semiconductor cobalt phthalocyanine exhibit strong antiferromagnetic coupling, with an exchange energy reaching 100 K. This interaction is up to two orders of magnitude larger than in related phthalocyanines and can be obtained on flexible plastic substrates, under conditions compatible with routine organic electronic device fabrication. Ab initio calculations show that coupling is achieved via superexchange between the singly occupied a1g () orbitals. By reaching the key milestone of magnetic coupling above 77 K, these results establish quantum spin chains as a potentially useable feature of molecular films. PMID:24445992

  19. C60 as an Active Smart Spacer Material on Silver Thin Film Substrates for Enhanced Surface Plasmon Coupled Emission

    PubMed Central

    Mulpur, Pradyumna; Podila, Ramakrishna; Ramamurthy, Sai Sathish; Kamisetti, Venkataramaniah; Rao, Apparao M.

    2015-01-01

    In this study, we present the use of C60 as an active spacer material on a silver (Ag) based surface plasmon coupled emission (SPCE) platform. In addition to its primary role of protecting the Ag thin film from oxidation, the incorporation of C60 facilitated the achievement of 30-fold enhancement in the emission intensity of rhodamine b (RhB) fluorophore. The high signal yield was attributed to the unique π-π interactions between C60 thin films and RhB, which enabled efficient transfer of energy of RhB emission to Ag plasmon modes. Furthermore, minor variations in the C60 film thickness yielded large changes in the enhancement and angularity properties of the SPCE signal, which can be exploited for sensing applications. Finally, the low-cost fabrication process of the Ag-C60 thin film stacks render C60 based SPCE substrates ideal, for the economic and simplistic detection of analytes. PMID:25785916

  20. Study on Buckling of Stiff Thin Films on Soft Substrates as Functional Materials

    NASA Astrophysics Data System (ADS)

    Ma, Teng

    In engineering, buckling is mechanical instability of walls or columns under compression and usually is a problem that engineers try to prevent. In everyday life buckles (wrinkles) on different substrates are ubiquitous -- from human skin to a rotten apple they are a commonly observed phenomenon. It seems that buckles with macroscopic wavelengths are not technologically useful; over the past decade or so, however, thanks to the widespread availability of soft polymers and silicone materials micro-buckles with wavelengths in submicron to micron scale have received increasing attention because it is useful for generating well-ordered periodic microstructures spontaneously without conventional lithographic techniques. This thesis investigates the buckling behavior of thin stiff films on soft polymeric substrates and explores a variety of applications, ranging from optical gratings, optical masks, energy harvest to energy storage. A laser scanning technique is proposed to detect micro-strain induced by thermomechanical loads and a periodic buckling microstructure is employed as a diffraction grating with broad wavelength tunability, which is spontaneously generated from a metallic thin film on polymer substrates. A mechanical strategy is also presented for quantitatively buckling nanoribbons of piezoelectric material on polymer substrates involving the combined use of lithographically patterning surface adhesion sites and transfer printing technique. The precisely engineered buckling configurations provide a route to energy harvesters with extremely high levels of stretchability. This stiff-thin-film/polymer hybrid structure is further employed into electrochemical field to circumvent the electrochemically-driven stress issue in silicon-anode-based lithium ion batteries. It shows that the initial flat silicon-nanoribbon-anode on a polymer substrate tends to buckle to mitigate the lithiation-induced stress so as to avoid the pulverization of silicon anode. Spontaneously

  1. Molecular dynamic simulations of surface morphology and pulsed laser deposition growth of lithium niobate thin films on silicon substrate

    NASA Astrophysics Data System (ADS)

    Liu, Yue; Zhu, Hao-Nan; Pei, Zi-Dong; Kong, Yong-Fa; Xu, Jing-Jun

    2015-05-01

    The molecular dynamic simulation of lithium niobate thin films deposited on silicon substrate is carried out by using the dissipative particle dynamics method. The simulation results show that the Si (111) surface is more suitable for the growth of smooth LiNbO3 thin films compared to the Si(100) surface, and the optimal deposition temperature is around 873 K, which is consistent with the atomic force microscope results. In addition, the calculation molecular number is increased to take the electron spins and other molecular details into account. Project supported by the National Basic Research Program of China (Grant No. 2011CB922003), the International S&T Cooperation Program of China (Grant No. 2013DFG52660), the Taishan Scholar Construction Project Special Fund, China, and the Fundamental Research Funds for the Central Universities, China (Grant Nos. 65030091 and 65010961).

  2. High-throughput characterization of stresses in thin film materials libraries using Si cantilever array wafers and digital holographic microscopy

    NASA Astrophysics Data System (ADS)

    Lai, Y. W.; Hamann, S.; Ehmann, M.; Ludwig, A.

    2011-06-01

    We report the development of an advanced high-throughput stress characterization method for thin film materials libraries sputter-deposited on micro-machined cantilever arrays consisting of around 1500 cantilevers on 4-inch silicon-on-insulator wafers. A low-cost custom-designed digital holographic microscope (DHM) is employed to simultaneously monitor the thin film thickness, the surface topography and the curvature of each of the cantilevers before and after deposition. The variation in stress state across the thin film materials library is then calculated by Stoney's equation based on the obtained radii of curvature of the cantilevers and film thicknesses. DHM with nanometer-scale out-of-plane resolution allows stress measurements in a wide range, at least from several MPa to several GPa. By using an automatic x-y translation stage, the local stresses within a 4-inch materials library are mapped with high accuracy within 10 min. The speed of measurement is greatly improved compared with the prior laser scanning approach that needs more than an hour of measuring time. A high-throughput stress measurement of an as-deposited Fe-Pd-W materials library was evaluated for demonstration. The fast characterization method is expected to accelerate the development of (functional) thin films, e.g., (magnetic) shape memory materials, whose functionality is greatly stress dependent.

  3. High-throughput characterization of stresses in thin film materials libraries using Si cantilever array wafers and digital holographic microscopy

    SciTech Connect

    Lai, Y. W.; Ludwig, A.; Hamann, S.; Ehmann, M.

    2011-06-15

    We report the development of an advanced high-throughput stress characterization method for thin film materials libraries sputter-deposited on micro-machined cantilever arrays consisting of around 1500 cantilevers on 4-inch silicon-on-insulator wafers. A low-cost custom-designed digital holographic microscope (DHM) is employed to simultaneously monitor the thin film thickness, the surface topography and the curvature of each of the cantilevers before and after deposition. The variation in stress state across the thin film materials library is then calculated by Stoney's equation based on the obtained radii of curvature of the cantilevers and film thicknesses. DHM with nanometer-scale out-of-plane resolution allows stress measurements in a wide range, at least from several MPa to several GPa. By using an automatic x-y translation stage, the local stresses within a 4-inch materials library are mapped with high accuracy within 10 min. The speed of measurement is greatly improved compared with the prior laser scanning approach that needs more than an hour of measuring time. A high-throughput stress measurement of an as-deposited Fe-Pd-W materials library was evaluated for demonstration. The fast characterization method is expected to accelerate the development of (functional) thin films, e.g., (magnetic) shape memory materials, whose functionality is greatly stress dependent.

  4. Center for thin film studies

    NASA Astrophysics Data System (ADS)

    Shannon, Robert P.; Gibson, Ursula J.

    1987-11-01

    This report covers the first year of operation of the URI Thin Film Center (TFC), and describes a diverse array of studies on thin-film materials, substrates, and their processing and analysis. Individual efforts are highlighted in sections on nucleation studies, ion-assisted deposition, Rutherford backscattering spectrometry, Brillouin scattering, a continuum theory of the evolution of structure in thin films, a study of polishing parameters relevant to the preparation of substrates, and the setup of a characterization facility for the Center.

  5. In-situ TEM - a tool for quantitative observations of deformation behavior in thin films and nano-structured materials

    SciTech Connect

    Stach, E.A.

    2001-09-04

    This paper highlights future developments in the field of in-situ transmission electron microscopy, as applied specifically to the issues of deformation in thin films and nanostructured materials. Emphasis is place on the forthcoming technical advances that will aid in extraction of improved quantitative experimental data using this technique.

  6. Epitaxial Bi2 FeCrO6 Multiferroic Thin Film as a New Visible Light Absorbing Photocathode Material.

    PubMed

    Li, Shun; AlOtaibi, Bandar; Huang, Wei; Mi, Zetian; Serpone, Nick; Nechache, Riad; Rosei, Federico

    2015-08-26

    Ferroelectric materials have been studied increasingly for solar energy conversion technologies due to the efficient charge separation driven by the polarization induced internal electric field. However, their insufficient conversion efficiency is still a major challenge. Here, a photocathode material of epitaxial double perovskite Bi(2) FeCrO(6) multiferroic thin film is reported with a suitable conduction band position and small bandgap (1.9-2.1 eV), for visible-light-driven reduction of water to hydrogen. Photoelectrochemical measurements show that the highest photocurrent density up to -1.02 mA cm(-2) at a potential of -0.97 V versus reversible hydrogen electrode is obtained in p-type Bi(2) FeCrO(6) thin film photocathode grown on SrTiO(3) substrate under AM 1.5G simulated sunlight. In addition, a twofold enhancement of photocurrent density is obtained after negatively poling the Bi(2) FeCrO(6) thin film, as a result of modulation of the band structure by suitable control of the internal electric field gradient originating from the ferroelectric polarization in the Bi(2) FeCrO(6) films. The findings validate the use of multiferroic Bi(2) FeCrO(6) thin films as photocathode materials, and also prove that the manipulation of internal fields through polarization in ferroelectric materials is a promising strategy for the design of improved photoelectrodes and smart devices for solar energy conversion. PMID:25988512

  7. Effect of native oxide layers on copper thin-film tensile properties: A reactive molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Skarlinski, Michael D.; Quesnel, David J.

    2015-12-01

    Metal-oxide layers are likely to be present on metallic nano-structures due to either environmental exposure during use, or high temperature processing techniques such as annealing. It is well known that nano-structured metals have vastly different mechanical properties from bulk metals; however, difficulties in modeling the transition between metallic and ionic bonding have prevented the computational investigation of the effects of oxide surface layers. Newly developed charge-optimized many body [Liang et al., Mater. Sci. Eng., R 74, 255 (2013)] potentials are used to perform fully reactive molecular dynamics simulations which elucidate the effects that metal-oxide layers have on the mechanical properties of a copper thin-film. Simulated tensile tests are performed on thin-films while using different strain-rates, temperatures, and oxide thicknesses to evaluate changes in yield stress, modulus, and failure mechanisms. Findings indicate that copper-thin film mechanical properties are strongly affected by native oxide layers. The formed oxide layers have an amorphous structure with lower Cu-O bond-densities than bulk CuO, and a mixture of Cu2O and CuO charge character. It is found that oxidation will cause modifications to the strain response of the elastic modulii, producing a stiffened modulii at low temperatures (<75 K) and low strain values (<5%), and a softened modulii at higher temperatures. While under strain, structural reorganization within the oxide layers facilitates brittle yielding through nucleation of defects across the oxide/metal interface. The oxide-free copper thin-film yielding mechanism is found to be a tensile-axis reorientation and grain creation. The oxide layers change the observed yielding mechanism, allowing for the inner copper thin-film to sustain an FCC-to-BCC transition during yielding. The mechanical properties are fit to a thermodynamic model based on classical nucleation theory. The fit implies that the oxidation of the films

  8. Materials-based control of ultrafast relaxation in ferromagnetic thin films

    NASA Astrophysics Data System (ADS)

    Cheng, Lili

    As data rates in magnetic information storage approach 1GHz and above, strategies to control the magnetization dynamics in films become a more pressing need. Materials-based techniques to control relaxation can offer a straightforward implementation for this purpose. Strategies to both increase and decrease the damping constant in ferromagnetic thin films are described in this thesis. By doping rare earth elements, both damping constant and precessional frequency of Ni81Fe19 (Permalloy) can be widely tuned. Sm, Tb, Dy, and Ho all contribute to damping in Ni81Fe19, among which the contribution of relaxation rate from Ho (1.9GHz/%) is the most, which is four times of that from Tb. The increased damping correlates well to the magnetic states of the rare earths. One element, Eu, does not contribute to damping, but it boosts the precessional frequency over a large range (>500 MHz) in Ni 81Fe19. Fe has the lowest damping constant of all elemental ferromagnets. We demonstrate that by doping V into pure Fe, the damping constant can be further reduced. High quality MgO(100)/Fe1-xV x epitaxial thin films are deposited by UHV deposition, with the 35 GHz FMR linewidth (42 Oe) of MgO(100)/Fe film even smaller than the narrowest linewidth of Fe ever reported. As V is doped in, Gilbert damping G decreases. The minimum G value observed is only 14% of that of undoped Fe film, and is even only 34% of the lowest G value ever reported on metallic ferromagnets. The decrease in the Gilbert damping G is closely related to the reduced magnetic anisotropy in the system. The results of this thesis will help advance the understanding of the damping mechanisms in ferromagnets and provide more freedom in engineering the GHz response of the magnetoelectronic devices.

  9. Angle-resolved photoemission spectroscopy of strontium lanthanum copper oxide thin films grown by molecular-beam epitaxy

    NASA Astrophysics Data System (ADS)

    Harter, John Wallace

    Among the multitude of known cuprate material families and associated structures, the archetype is "infinite-layer" ACuO2, where perfectly square and flat CuO2 planes are separated by layers of alkaline earth atoms. The infinite-layer structure is free of magnetic rare earth ions, oxygen chains, orthorhombic distortions, incommensurate superstructures, ordered vacancies, and other complications that abound among the other material families. Furthermore, it is the only cuprate that can be made superconducting by both electron and hole doping, making it a potential platform for decoding the complex many-body interactions responsible for high-temperature superconductivity. Research on the infinite-layer compound has been severely hindered by the inability to synthesize bulk single crystals, but recent progress has led to high-quality superconducting thin film samples. Here we report in situ angle-resolved photoemission spectroscopy measurements of epitaxially-stabilized Sr1-chiLa chiCuO2 thin films grown by molecular-beam epitaxy. At low doping, the material exhibits a dispersive lower Hubbard band typical of other cuprate parent compounds. As carriers are added to the system, a continuous evolution from Mott insulator to superconducting metal is observed as a coherent low-energy band develops on top of a concomitant remnant lower Hubbard band, gradually filling in the Mott gap. For chi = 0.10, our results reveal a strong coupling between electrons and (pi,pi) anti-ferromagnetism, inducing a Fermi surface reconstruction that pushes the nodal states below the Fermi level and realizing nodeless superconductivity. Electron diffraction measurements indicate the presence of a surface reconstruction that is consistent with the polar nature of Sr1-chiLachiCuO2. Most knowledge about the electron-doped side of the cuprate phase diagram has been deduced by generalizing from a single material family, Re2-chi CechiCuO4, where robust antiferromagnetism has been observed past chi

  10. RESEARCH ON THE ELECTRONIC AND OPTICAL PROPERTIES OF POLYMER AND OTHER ORGANIC MOLECULAR THIN FILMS

    SciTech Connect

    ALEXEI G. VITUKHNOVSKY; IGOR I. SOBELMAN - RUSSIAN ACADEMY OF SCIENCES

    1995-09-06

    Optical properties of highly ordered films of poly(p-phenylene) (PPP) on different substrates, thin films of mixtures of conjugated polymers, of fullerene and its composition with polymers, molecular J-aggregates of cyanine dyes in frozen matrices have been studied within the framework of the Agreement. Procedures of preparation of high-quality vacuum deposited PPP films on different substrates (ITO, Si, GaAs and etc.) were developed. Using time-correlated single photon counting technique and fluorescence spectroscopy the high quality of PPP films has been confirmed. Dependence of structure and optical properties on the conditions of preparation were investigated. The fluorescence lifetime and spectra of highly oriented vacuum deposited PPP films were studied as a function of the degree of polymerization. It was shown for the first time that the maximum fluorescence quantum yield is achieved for the chain length approximately equal to 35 monomer units. The selective excitation of luminescence of thin films of PPP was performed in the temperature range from 5 to 300 K. The total intensity of luminescence monotonically decreases with decreasing temperature. Conditions of preparation of highly cristallyne fullerene C{sub 60} films by the method of vacuum deposition were found. Composites of C{sub 60} with conjugated polymers PPV and polyacetylene (PA) were prepared. The results on fluorescence quenching, IR and resonant Raman spectroscopy are consistent with earlier reported ultrafast photoinduced electron transfer from PPV to C{sub 60} and show that the electron transfer is absent in the case of the PA-C{sub 60} composition. Strong quenching of PPV fluorescence was observed in the PPV-PA blends. The electron transfer from PPV to PA can be considered as one of the possible mechanisms of this quenching. The dynamics of photoexcitations in different types of J-aggregates of the carbocyanine dye was studied at different temperatures in frozen matrices. The optical

  11. Material behavior characterization of a thin film polymer used in lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Martinsen, Michael J.

    The use of lithium-ion batteries in the automotive industry has become increasingly popular. As more hybrid and electric vehicles take to the road an understanding of how these batteries will behave structurally will be of greater concern. Impact testing can give a valuable overview of the strengths and weaknesses of a battery's design, however, these tests can be time consuming, expensive, and dangerous. Finite element analysis can deliver a reliable low cost approximation of physical testing results. The accuracy of FE results depends greatly on the mathematical representation of the material properties of Li-ion battery components. In this study, the material properties of thin film polymer used as a separator between an anode and a cathode of a lithium ion battery are tested experimentally under various temperatures, strain rates, and solvent saturations. Due to the anisotropy of the material, two similar sets of experiments were conducted on the material in perpendicular directions. It was found that temperature and strain rate have a nearly linear effect on the stress experienced by the material. Additionally, saturating the separator material in a common lithium ion solvent resulted in its softening with a positive effect on its toughness. Two viscoplastic constitutive equations developed for modeling polymeric materials were employed to model the experimental data.

  12. Research on the electronic and optical properties of polymer and other organic molecular thin films

    SciTech Connect

    1997-02-01

    The main goal of the work is to find materials and methods of optimization of organic layered electroluminescent cells and to study such properties of polymers and other organic materials that can be used in various opto-electronic devices. The summary of results obtained during the first year of work is presented. They are: (1) the possibility to produce electroluminescent cells using a vacuum deposition photoresist technology for commercial photoresists has been demonstrated; (2) the idea to replace the polyaryl polymers by other polymers with weaker hole conductivity for optimization of electroluminescent cells with ITO-Al electrodes has been suggested. The goal is to obtain amorphous processable thin films of radiative recombination layers in electroluminescent devices; (3) procedures of preparation of high-quality vacuum-deposited poly (p-phenylene) (PPP) films on various substrates have been developed; (4) it was found for the first time that the fluorescence intensity of PPP films depends on the degree of polymerization; (5) the role of interfaces between organic compounds, on one side, and metals or semiconductors, on the other side, has been studied and quenching of the fluorescence caused by semiconductor layer in thin sandwiches has been observed; (6) studies of the dynamics of photoexcitations revealed the exciton self-trapping in quasi-one-dimensional aggregates; and (7) conditions for preparation of highly crystalline fullerene C{sub 60} films by vacuum deposition have been found. Composites of C{sub 60} with conjugated polymers have been prepared.

  13. Synthesis and characterization of transparent conducting indium iron oxide bulk and thin film materials

    NASA Astrophysics Data System (ADS)

    Fahed, Charbel T.

    2009-12-01

    In this dissertation, solid solutions of indium-iron oxide (In2-xFexO3) with varying compositions were prepared and a new ultra-fast microwave method was used for deposition of thin films of this material. Non-destructive characterization methods were used for studying these transparent conducting oxide (TCO) materials. In this work, the linear thermal expansion coefficients of bulk In 2-xFexO3 have been determined using high resolution x-ray diffraction measurements. The addition of Fe2O3 to In2O3 resulted in the formation of solid solutions in body centered cubic phase. The thermal expansion coefficients for solid solutions of In2-xFexO3 showed increased values in comparison to that of pure In2O3 phase. The study of thermal properties of these TCO materials is crucial for their potential applications in photovoltaic and spintronic devices operating at various temperatures. In addition, the bulk samples of In2-xFexO 3 were studied for their structural, transport, and magnetic properties, as a function of composition. The lattice parameters of the solid solutions decrease with increasing Fe-content. The four-probe electrical measurements showed reduced conductivities for higher Fe compositions. The magnetic data displayed ferromagnetism in these solid solutions, and that can be attributed to the presence of trace amounts of Fe2O3 or Fe 3O4. These results might be important for the use of TCOs in spintronic applications as well as structural materials such as ceramic coatings intended to withstand harsh environments. Thin films of Indium-iron oxide compositions were deposited by using ultra-fast microwave heating. This is a new method of deposition of TCOs that has never been done before. The advantage of microwave heating deposition over other deposition techniques is that it is extremely fast and can be used for materials of high evaporation temperature. In this work, the deposition was done in 50-120 seconds at 1950-2000°C. Characteristics of these transparent

  14. The Structure of Ice Nanoclusters and Thin-films of Water Ice: Implications for Icy Grains in Cold Molecular Clouds

    NASA Technical Reports Server (NTRS)

    Delzeit, Lance; Blake, David; Uffindell, Christine; DeVincenzi, Donald L. (Technical Monitor)

    2000-01-01

    The cubic to hexagonal phase transformation in water ice (I(sub c) yields I(sub h)) is used to measure the extent to which surface structure and impurities control bulk properties. In pure crystalline (I(sub c)) water ice nanoclusters and in thin-films of impure water ice, I(sub c) yields I(sub h) occurs at lower temperatures than in thin-films of pure water ice. The disordered surface of the 20 nm diameter nanoclusters promotes transformations or reactions which would otherwise be kinetically hindered. Likewise, impurities such as methanol introduce defects into the ice network, thereby allowing sluggish structural transitions to proceed. Such surface-related phenomena play an important role in promoting chemical reactions on interstellar ice grains within cold molecular clouds, where the first organic compounds are formed.

  15. Influence of molecular structure peculiarities of phthalocyanine derivatives on their supramolecular organization and properties in the bulk and thin films

    NASA Astrophysics Data System (ADS)

    Usol'tseva, Nadezhda V.; Kazak, Alexandr V.; Luk'yanov, Ivan Yu.; Sotsky, Valentin V.; Smirnova, Antonina I.; Yudin, Sergey G.; Shaposhnikov, Gennadiy P.; Galanin, Nikolay E.

    2014-08-01

    In order to study the influence of molecular structure peculiarities on supramolecular organization and properties in the bulk and thin films of discotic mesogens six new mix-substituted phthalocyanine derivatives with 3,6-dioctyloxyphthalonitrile and 3,4,5,6-tetrachlorophthalonitrile fragments were synthesized. Temperatures of phase transitions, types of mesophase and their dependence on molecule structure, chemical nature, position and ratio of different substituents as well as presence of holmium in the metal complexes were analyzed. The behavior of the studied molecules on the boundary between water and air was investigated and the peculiarity of supramolecular organization in floating layers as well as in thin films was determined. Quenching of luminescence in solutions of the studied compounds in the presence of fullerene C60 was determined, thus giving prospects for application of these compounds as sensors for fullerene microquantities.

  16. Two-Dimensional Van der Waals Materials for Thin Film Transistor Applications

    NASA Astrophysics Data System (ADS)

    George, Aaron Scott

    Research on two-dimensional nanomaterials has become a topic of considerable interest since the pioneering work experimentally introducing the two-dimensional carbon allotrope of graphene in 2004. The atomically thin hexagonally arranged carbon crystal structure has offered the opportunity for numerous studies in condensed matter physics and materials science, revealing new phenomenon and remarkable properties. Graphene has excellent chemical and mechanical stability, allowing researchers to probe the properties of graphene in a wide variety of applications and in contact with a wide variety of materials. Ballistic transport of graphene at room temperature suggests that graphene would be poised to enter in to a wide variety of microelectronic application; vii however, synthesis methods and surface effects have so far limited the widespread use of graphene. Additionally, the absence of electronic band gap in graphene, classifying it as a "semi-metal", limits the use of graphene to areas other than logic applications. In this work, fabrication methods for the improved synthesis graphene and selected two-dimensional transition metal dichalcogenides, molybdenum disulfide and tungsten disulfide, are presented for thin film transistor applications. First, the introduction of thin film zwitterionic polymer interlayers in graphene devices is outlined as a means to reduce the contact resistance between metal contacts and the underlying graphene layer. Second, a self-assembly nanoscale lithography process utilizing diblock copolymer templates as an etching mask directly on the surface of graphene is shown as a method to introduce a band gap in graphene due to quantum confinement effects. The third chapter applies to another class of two-dimensional materials, transition metal dichalcogenides, which, unlike graphene, can exhibit suitable electronic band structures for logic applications. When the thickness of these transition metal dichalcogenides is reduced to a single

  17. High mobility amorphous zinc oxynitride semiconductor material for thin film transistors

    SciTech Connect

    Ye Yan; Lim, Rodney; White, John M.

    2009-10-01

    Zinc oxynitride semiconductor material is produced through a reactive sputtering process in which competition between reactions responsible for the growth of hexagonal zinc oxide (ZnO) and for the growth of cubic zinc nitride (Zn{sub 3}N{sub 2}) is promoted. In contrast to processes in which the reaction for either the oxide or the nitride is dominant, the multireaction process yields a substantially amorphous or a highly disordered nanocrystalline film with higher Hall mobility, 47 cm{sup 2} V{sup -1} s{sup -1} for the as-deposited film produced at 50 deg. C and 110 cm{sup 2} V{sup -1} s{sup -1} after annealing at 400 deg. C. In addition, it has been observed that the Hall mobility of the material increases as the carrier concentration decreases in a carrier concentration range where a multicomponent metal oxide semiconductor, indium-gallium-zinc oxide, follows the opposite trend. This indicates that the carrier transports in the single-metal compound and the multimetal compound are probably dominated by different mechanisms. Film stability and thin film transistor performance of the material have also been tested, and results are presented herein.

  18. Antimony(III) Sulfide Thin Films as a Photoanode Material in Photocatalytic Water Splitting.

    PubMed

    DeAngelis, Alexander Daniel; Kemp, Kingsley Christian; Gaillard, Nicolas; Kim, Kwang S

    2016-04-01

    For the first time, we present exploratory investigations on the performance of thermally evaporated Sb2S3 thin film photoanodes for solar-assisted water-splitting applications. With a band gap of 1.72 eV, a 250 nm thick Sb2S3 photoanode showed a saturation photocurrent density of ∼600 μA cm(-2) measured at 1.0 V reversible hydrogen electrode (RHE) in 0.1 M Na2SO4 under 1-sun illumination, with an onset potential of ∼0.25 V RHE. However, subsequent photodegradation studies revealed that the material dissolves relatively quickly with the application of both illumination and bias. Nonetheless, Sb2S3 does have the advantage of having a relatively low optimal fabrication temperature of 300 °C and thus may have utility as a top cell absorber of a tandem device where the bottom cell is temperature sensitive, if protected from corrosion. Therefore, we characterized relevant aspects of the material in an attempt to explain the large difference between the theoretical maximum and measured current density. From our characterization it is believed that the photocatalytic efficiency of this material can be improved by modifying the surface to reduce optical reflection and addressing inherent issues such as high electrical resistivity and surface defects. PMID:27003726

  19. Thin Film?

    NASA Astrophysics Data System (ADS)

    Kariper, İ. Afşin

    2014-09-01

    This study focuses on the critical surface tension of lead sulfite (PbSO3) crystalline thin film produced with chemical bath deposition on substrates (commercial glass).The PbSO3 thin films were deposited at room temperature at different deposition times. The structural properties of the films were defined and examined according to X-ray diffraction (XRD) and the XRD results such as dislocation density, average grain size, and no. of crystallites per unit area. Atomic force microscopy was used to measure the film thickness and the surface properties. The critical surface tension of the PbSO3 thin films was measured with an optical tensiometer instrument and calculated using the Zisman method. The results indicated that the critical surface tension of films changed in accordance with the average grain size and film thickness. The film thickness increased with deposition time and was inversely correlated with surface tension. The average grain size increased according to deposition time and was inversely correlated with surface tension.

  20. Polysilicon thin films and interfaces

    SciTech Connect

    Kamins, T. ); Raicu, B. ); Thompson, C.V. )

    1990-01-01

    This volume contains the proceedings of a symposium on polysilicon thin films and interfaces, held as part of the 1990 Materials Research Society Spring Meeting. Topics covered include: crystal grown fo silicon and germanium wafers for photovoltaic devices, microanalysis of tungsten silicide interface, thermal processing of polysilicon thin films, and electrical and optical properties of polysilicon sheets for photovoltaic devices.

  1. Probing mechanical properties of thin film and ceramic materials in micro- and nano-scale using indentation techniques

    NASA Astrophysics Data System (ADS)

    Charitidis, Costas A.

    2010-10-01

    In this study, we report on the mechanical properties, failure and fracture modes in two cases of engineering materials; that is transparent silicon oxide thin films onto poly(ethylene terephthalate) (PET) membranes and glass-ceramic materials. The first system was studied by the quazi-static indentation technique at the nano-scale and the second by the static indentation technique at the micro-scale. Nanocomposite laminates of silicon oxide thin films onto PET were found to sustain higher scratch induced stresses and were effective as protective coating material for PET membranes. Glass-ceramic materials with separated crystallites of different morphologies sustained a mixed crack propagation pattern in brittle fracture mode.

  2. Synthesis and modification of mesoporous silica and the preparation of molecular sieve thin films via pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Coutinho, Decio Heringer

    2001-07-01

    Hexagonal mesoporous DAM-1 (Dallas Amorphous Material-1) was prepared using Vitamin E TPGS as the structure-directing agent. Depending upon the temperature and gel composition, highly ordered and hydrothermally stable DAM-1 with various morphologies could be achieved including spheres, gyroids, discoid, hexagonal plates and rods. This synthesis was modified to prepare hybrid organic-inorganic amine and thiol bifunctionalized DAM-1 by direct co-condensation under acidic conditions. Patterned DAM-1 thin films were prepared on patterned transparencies utilizing pulsed laser deposition (PLD) and line patterning techniques. DAM-1 laser ablation onto the patterned substrate followed by hydrothermal treatment resulted in a densely packed film. Removal of the patterned lines by sonication revealed patterned DAM-1 films. Thin films of zeolite type X were also prepared using the PLD technique. Laser ablation of zeolite X onto TiN-coated silicon wafers followed by a hydrothermal treatment resulted in partially oriented, crystalline membranes. Hydrothermal treatment of PLD films on stainless steel mesh produced a coated wire mesh with a 3-mum thick zeolite X film. A novel strategy for imprinting mesoporous SBA-15 that combines a triblock copolymer template and a chiral ruthenium complex is reported. A chiral PEO helix was formed by the chiral ruthenium complex interaction with the block copolymer during the synthesis of SBA-15. Upon removal of the chiral ruthenium complex, a stereospecfic cavity was created. Preliminary results indicated stereoselective absorption of Delta or Λ-Ru(phen)3 2+ isomer from a racemic mixture could be achieved depending on the chirality of the PEO chain. Practicum Two. The industrial practicum report describes the process development unit (PDU) 3-pentenenitrile (3PN) refining operation. This distillation works was operated to refine crude 3PN product, which contained 3PN, 2-methyl-3-butenenitrile (2M3BN), and other byproducts. This report also

  3. Nanostructured multilayered thin film barriers for Mg{sub 2}Si thermoelectric materials

    SciTech Connect

    Battiston, S.; Boldrini, S.; Fiameni, S.; Agresti, F.; Famengo, A.; Fabrizio, M.; Barison, S.

    2012-06-26

    The Mg{sub 2}Si-based alloys are promising candidates for thermoelectric energy conversion in the middle-high temperature range in order to replace lead compounds. The main advantages of silicide-based thermoelectrics are the nontoxicity and the abundance of their constituent elements in the earth crust. The drawback of such kind of materials is their oxygen sensitivity at high temperature that entails their use under vacuum or inert atmosphere. In order to limit the corrosion phenomena, nanostructured multilayered molybdenum silicide-based materials were deposited via RF magnetron sputtering onto stainless steel, alumina and silicon (100) to set up the deposition process and then onto Mg{sub 2}Si pellets. XRD, EDS, FE-SEM and electrical measurements at high temperature were carried out in order to obtain, respectively, the structural, compositional, morphological and electrical characterization of the deposited coatings. At the end, the mechanical behavior of the system thin film/Mg{sub 2}Si-substrate as a function of temperature and the barrier properties for oxygen protection after thermal treatment in air at high temperature were qualitatively evaluated by FE-SEM.

  4. Transition-metal-nitride-based thin films as novel energy harvesting materials

    PubMed Central

    Kerdsongpanya, Sit; Alling, Björn

    2016-01-01

    The last few years have seen a rise in the interest in early transition-metal and rare-earth nitrides, primarily based on ScN and CrN, for energy harvesting by thermoelectricity and piezoelectricity. This is because of a number of important advances, among those the discoveries of exceptionally high piezoelectric coupling coefficient in (Sc,Al)N alloys and of high thermoelectric power factors of ScN-based and CrN-based thin films. These materials also constitute well-defined model systems for investigating thermodynamics of mixing for alloying and nanostructural design for optimization of phase stability and band structure. These features have implications for and can be used for tailoring of thermoelectric and piezoelectric properties. In this highlight article, we review the ScN- and CrN-based transition-metal nitrides for thermoelectrics, and drawing parallels with piezoelectricity. We further discuss these materials as a models systems for general strategies for tailoring of thermoelectric properties by integrated theoretical–experimental approaches. PMID:27358737

  5. Differentiated growth of human renal tubule cells on thin-film and nanostructured materials.

    PubMed

    Fissell, William H; Manley, Sargum; Westover, Angela; Humes, H David; Fleischman, Aaron J; Roy, Shuvo

    2006-01-01

    Over 300,000 Americans are dependent on hemodialysis as treatment for renal failure, and kidney transplantation is limited by scarcity of donor organs. This shortage has prompted research into tissue engineering of renal replacement therapy. Existing bioartificial kidneys are large and their use labor intensive, but they have shown improved survival compared to conventional therapy in preclinical studies and an US Food and Drug Administration-approved phase 2 clinical trial. This hybrid technology will require miniaturization of hemofilters, cell culture substrates, sensors, and integration of control electronics. Using the same harvesting and isolation techniques used in preparing bioartificial kidneys for clinical use, we characterized human renal tubule cell growth on a variety of silicon and related thin-film material substrates commonly used in the construction of microelectromechanical systems (MEMS), as well as novel silicon nanopore membranes (SNMs). Human cortical tubular epithelial cells (HCTC) were seeded onto samples of single-crystal silicon, polycrystalline silicon, silicon dioxide, silicon nitride, SU-8 photoresist, SNMs, and polyester tissue culture inserts, and grown to confluence. The cells formed confluent monolayers with tight junctions and central cilia. Transepithelial resistances were similar between SNMs and polyester membranes. The differentiated growth of human tubular epithelial cells on MEMS materials strongly suggests that miniaturization of the existing bioartificial kidney will be feasible, paving the way for widespread application of this novel technology. PMID:16760708

  6. Comparison of silicon oxide and silicon carbide absorber materials in silicon thin-film solar cells

    NASA Astrophysics Data System (ADS)

    Walder, Cordula; Kellermann, Martin; Wendler, Elke; Rensberg, Jura; von Maydell, Karsten; Agert, Carsten

    2015-02-01

    Since solar energy conversion by photovoltaics is most efficient for photon energies at the bandgap of the absorbing material the idea of combining absorber layers with different bandgaps in a multijunction cell has become popular. In silicon thin-film photovoltaics a multijunction stack with more than two subcells requires a high bandgap amorphous silicon alloy top cell absorber to achieve an optimal bandgap combination. We address the question whether amorphous silicon carbide (a-SiC:H) or amorphous silicon oxide (a-SiO:H) is more suited for this type of top cell absorber. Our single cell results show a better performance of amorphous silicon carbide with respect to fill factor and especially open circuit voltage at equivalent Tauc bandgaps. The microstructure factor of single layers indicates less void structure in amorphous silicon carbide than in amorphous silicon oxide. Yet photoconductivity of silicon oxide films seems to be higher which could be explained by the material being not truly intrinsic. On the other hand better cell performance of amorphous silicon carbide absorber layers might be connected to better hole transport in the cell.

  7. Ultrafast structural dynamics of LaVO3 thin films grown by hybrid molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Brahlek, Matthew; Lapano, Jason; Stoica, Vladimir; Zhang, Lei; Zhang, Hai-Tian; Akamatsu, Hirofumi; Eaton, Craig; Gopalan, Venkatraman; Freeland, John; Wen, Haidan; Engel-Herbert, Roman

    LaVO3, with a partially full d-shell is expected to be metallic, but due to electron-electron interactions a gap emerges and the ground state is a Mott insulator. Such effects are a strong function of the bonding geometry, and particularly the V-O-V bond angle. Controlling these structural effects on the ultrafast time scale can lead to control over the underlying electronic ground state. Here we report the ultrafast structural dynamics of 25 and 50 nm thick LaVO3 thin films grown by the hybrid molecular beam epitaxy technique on SrTiO3 when excited across the bandgap by 800 nm light. Using time-resolved x-ray diffraction on the 100 ps time scale at Sector 7 of the Advanced Photon Source, we directly measured the structural changes with atomic accuracy by monitoring integer Bragg diffraction peaks and find a large out-of-plane strain of 0.18% upon optical excitation; the recovery time is ~1 ns for the 25 nm film and ~2 ns for the 50 nm film, consistent with the thermal transport from the film to the substrate. Further, we will discuss the response of the oxygen octahedral rotation patterns indicated by changes of the half-order diffraction peaks. Understanding such ultrafast structural deformation is important for optimizing optical excitations to create new metastable phases starting from a Mott insulator. This work was supported by the Department of Energy under Grant DE-SC0012375, and DE-AC02-06CH11357.

  8. O thin films with different Mg contents on r-plane sapphire substrates by plasma-assisted molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Chen, W.; Pan, X. H.; Ding, P.; Zhang, H. H.; Chen, S. S.; Dai, W.; Huang, J. Y.; Lu, B.; Ye, Z. Z.

    2014-09-01

    We report the growth and characterization of a series of non-polar Zn1- x Mg x O thin films with different Mg contents, which have been prepared on r-plane sapphire substrates by plasma-assisted molecular beam epitaxy. Structural properties are anisotropic and surfaces of films show stripes running along the c-axis direction. The films exhibit atomically smooth surface with the minimal root mean square surface roughness of 0.36 nm. Non-polar Zn1- x Mg x O thin film is much easier to obtain pure a-plane single crystal orientation when Mg content is high. The quality of the non-polar Zn1- x Mg x O thin films is evidenced by X-ray diffraction (XRD) rocking curves full-width at half-maximum of 1,350 arcsec for the () reflection and 1,760 arcsec for the () reflection, respectively. Room temperature photoluminescence peak shifts monotonously from 3.29 to 3.56 eV as Mg content increases from 0 to 0.13. Alloying with Mg is found to widen the bandgap energy of the ZnO.

  9. Phases, line tension and pattern formation in molecularly thin films at the air-water interface

    NASA Astrophysics Data System (ADS)

    Mandal, Pritam

    A Langmuir film, which is a molecularly thin insoluble film on a liquid substrate, is one practical realization of a quasi-two dimensional matter. The major advantages of this system for the study of phase separation and phase co-existence are (a) it allows accurate control of the components and molecular area of the film and (b) it can be studied by various methods that require very flat films. Phase separation in molecularly thin films plays an important role in a range of systems from biomembranes to biosensors. For example, phase-separated lipid nano-domains in biomembranes are thought to play crucial roles in membrane function. I use Brewster Angel Microscopy (BAM) coupled with Fluorescence Microscopy (FM) and static Light Scattering Microscopy (LSM) to image phases and patterns within Langmuir films. The three microscopic techniques --- BAM, FM and LSM --- are complimentary to each other, providing distinct sets of information. They allow direct comparison with literature results in lipid systems. I have quantitatively validated the use of detailed hydrodynamic simulations to determine line tension in monolayers. Line tension decreases as temperature rises. This decrease gives us information on the entropy associated with the line, and thus about line structure. I carefully consider the thermodynamics of line energy and entropy to make this connection. In the longer run, LSM will be exploited to give us further information about line structure. I have also extended the technique by testing it on domains within the curved surface of a bilayer vesicle. I also note that in the same way that the presence of surface-active agents, known as surfactants, affects surface energy, the addiction of line active agents alters the inter-phase line energy. Thus my results set to stage to systematically study the influence of line active agents ---'linactants' --- on the inter-phase line energy. Hierarchal self-assembled chiral patterns were observed as a function of

  10. Extremely high rate deposition of polymer multilayer optical thin film materials

    SciTech Connect

    Affinito, J.D.

    1993-03-01

    This paper highlights a new technique for extremely high rate deposition of optical dielectric films (vacuum deposition of polymer multilayer thin films). This is a way to produce multilayer optical filters comprised of thousands of layers of either linear or nonlinear optical materials. The technique involves the flash evaporation of an acrylic monomer onto a moving substrate; the monomer is then cured. Acrylic polymers deposited to date are very clear for wavelengths between 0.35 and 2.5 {mu}m; they have extinction coefficients of k{approx}10{sup {minus}7}. Application of electric field during cross linking can polarize (``pole``) the film to greatly enhance the nonlinear optical properties. ``Poling`` films with the polymer multilayer technique offers advantages over conventional approaches, in that the polarization should not decay over time. Battelle`s Pacific Northwest Laboratory is well suited for bringing linear and nonlinear polymer multilayer optical filter technology to manufacturing production status for batch and wide area web applications. 10 figs.

  11. Extremely high rate deposition of polymer multilayer optical thin film materials

    SciTech Connect

    Affinito, J.D.

    1993-01-01

    This paper highlights a new technique for extremely high rate deposition of optical dielectric films (vacuum deposition of polymer multilayer thin films). This is a way to produce multilayer optical filters comprised of thousands of layers of either linear or nonlinear optical materials. The technique involves the flash evaporation of an acrylic monomer onto a moving substrate; the monomer is then cured. Acrylic polymers deposited to date are very clear for wavelengths between 0.35 and 2.5 [mu]m; they have extinction coefficients of k[approx]10[sup [minus]7]. Application of electric field during cross linking can polarize (''pole'') the film to greatly enhance the nonlinear optical properties. ''Poling'' films with the polymer multilayer technique offers advantages over conventional approaches, in that the polarization should not decay over time. Battelle's Pacific Northwest Laboratory is well suited for bringing linear and nonlinear polymer multilayer optical filter technology to manufacturing production status for batch and wide area web applications. 10 figs.

  12. Effect of top electrode material on radiation-induced degradation of ferroelectric thin film structures

    NASA Astrophysics Data System (ADS)

    Brewer, Steven J.; Deng, Carmen Z.; Callaway, Connor P.; Paul, McKinley K.; Fisher, Kenzie J.; Guerrier, Jonathon E.; Rudy, Ryan Q.; Polcawich, Ronald G.; Jones, Jacob L.; Glaser, Evan R.; Cress, Cory D.; Bassiri-Gharb, Nazanin

    2016-07-01

    The effects of gamma irradiation on the dielectric and piezoelectric responses of Pb[Zr0.52Ti0.48]O3 (PZT) thin film stacks were investigated for structures with conductive oxide (IrO2) and metallic (Pt) top electrodes. The samples showed, generally, degradation of various key dielectric, ferroelectric, and electromechanical responses when exposed to 2.5 Mrad (Si) 60Co gamma radiation. However, the low-field, relative dielectric permittivity, ɛr, remained largely unaffected by irradiation in samples with both types of electrodes. Samples with Pt top electrodes showed substantial degradation of the remanent polarization and overall piezoelectric response, as well as pinching of the polarization hysteresis curves and creation of multiple peaks in the permittivity-electric field curves post irradiation. The samples with oxide electrodes, however, were largely impervious to the same radiation dose, with less than 5% change in any of the functional characteristics. The results suggest a radiation-induced change in the defect population or defect energy in PZT with metallic top electrodes, which substantially affects motion of internal interfaces such as domain walls. Additionally, the differences observed for stacks with different electrode materials implicate the ferroelectric-electrode interface as either the predominant source of radiation-induced effects (Pt electrodes) or the site of healing for radiation-induced defects (IrO2 electrodes).

  13. Localized photoelectrochemistry on a tungsten oxide-iron oxide thin film material library.

    PubMed

    Kollender, Jan Philipp; Mardare, Andrei Ionut; Hassel, Achim Walter

    2013-12-01

    A WO3-Fe2O3 thin film combinatorial library was fabricated using a vapor phase co-deposition method followed by a combined thermal annealing and oxidation process. The scanning electron microscopy (SEM) analysis of the library microstructure combined with X-ray diffraction (XRD) investigations suggested that α-Fe2O3 grains preferentially grow from boundaries of domains, containing finer grains of WO3 and Fe2WO6, forming filiform networks on the surface. The surface density of the hematite networks depends on the amount of Fe present in the library. Photocurrents measured at different applied biases using Photo Electrochemical Scanning Droplet Cell Microscopy (PE-SDCM) were analyzed and mapped along the entire compositional spread. A distinctive photocurrent peak was detected at 21.9 atom % Fe, and its appearance was correlated to the higher amount of hematite present in the library at this specific composition together with a specific WO3 crystallographic orientation ((222) orthorhombic or (400) monoclinic). This finding is confirmed by qualitative and quantitative XPS surface analysis at the photocurrent peak position in the material library. Thus the enhancement of the photocurrent cannot be exclusively attributed to certain surface modifications since only hematite was found on the library surface at the peak composition. PMID:24151796

  14. Accurate determination of quantity of material in thin films by Rutherford backscattering spectrometry.

    PubMed

    Jeynes, C; Barradas, N P; Szilágyi, E

    2012-07-17

    Ion beam analysis (IBA) is a cluster of techniques including Rutherford and non-Rutherford backscattering spectrometry and particle-induced X-ray emission (PIXE). Recently, the ability to treat multiple IBA techniques (including PIXE) self-consistently has been demonstrated. The utility of IBA for accurately depth profiling thin films is critically reviewed. As an important example of IBA, three laboratories have independently measured a silicon sample implanted with a fluence of nominally 5 × 10(15) As/cm(2) at an unprecedented absolute accuracy. Using 1.5 MeV (4)He(+) Rutherford backscattering spectrometry (RBS), each lab has demonstrated a combined standard uncertainty around 1% (coverage factor k = 1) traceable to an Sb-implanted certified reference material through the silicon electronic stopping power. The uncertainty budget shows that this accuracy is dominated by the knowledge of the electronic stopping, but that special care must also be taken to accurately determine the electronic gain of the detection system and other parameters. This RBS method is quite general and can be used routinely to accurately validate ion implanter charge collection systems, to certify SIMS standards, and for other applications. The generality of application of such methods in IBA is emphasized: if RBS and PIXE data are analysed self-consistently then the resulting depth profile inherits the accuracy and depth resolution of RBS and the sensitivity and elemental discrimination of PIXE. PMID:22681761

  15. Ferromagnetism and Nonmetallic Transport of Thin-Film α-FeSi2 : A Stabilized Metastable Material

    DOE PAGESBeta

    Cao, Guixin; Singh, D. J.; Zhang, X. -G.; Samolyuk, German; Qiao, Liang; Parish, Chad; Jin, Ke; Zhang, Yanwen; Guo, Hangwen; Tang, Siwei; et al

    2015-04-07

    Tmore » he epitaxially stabilized metallic α-FeSi2 thin films on Si(001) were grown using pulsed laser deposition. While the bulk material of α-FeSi2 is a high temperature metastable phase and nonmagnetic, the thin film is stabilized at room temperature and shows unusual electronic transport and magnetic properties due to strain modification. he transport renders two different conducting states with a strong crossover at 50 K accompanied by an onset of ferromagnetism as well as a substantial magnetocaloric effect and magnetoresistance. hese experimental results are discussed in terms of the unusual electronic structure of α-FeSi2 obtained within density functional calculations and Boltzmann transport calculations with and without strain. Our findings provide an example of a tailored material with interesting physics properties for practical applications.« less

  16. Primary research efforts on exploring the commercial possibilities of thin film growth and materials purification in space

    NASA Technical Reports Server (NTRS)

    1989-01-01

    The progress made on research programs in the 1987 to 1988 year is reported. The research is aimed at producing thin film semiconductors and superconductor materials in space. Sophisticated vacuum chambers and equipment were attained for the epitaxial thin film growth of semiconductors, metals and superconductors. In order to grow the best possible epitaxial films at the lowest possible temperatures on earth, materials are being isoelectronically doped during growth. It was found that isoelectrically doped film shows the highest mobility in comparison with films grown at optimal temperatures. Success was also attained in growing epitaxial films of InSb on sapphire which show promise for infrared sensitive devices in the III-V semiconductor system.

  17. Epitaxial thin films

    DOEpatents

    Hunt, Andrew Tye; Deshpande, Girish; Lin, Wen-Yi; Jan, Tzyy-Jiuan

    2006-04-25

    Epitatial thin films for use as buffer layers for high temperature superconductors, electrolytes in solid oxide fuel cells (SOFC), gas separation membranes or dielectric material in electronic devices, are disclosed. By using CCVD, CACVD or any other suitable deposition process, epitaxial films having pore-free, ideal grain boundaries, and dense structure can be formed. Several different types of materials are disclosed for use as buffer layers in high temperature superconductors. In addition, the use of epitaxial thin films for electrolytes and electrode formation in SOFCs results in densification for pore-free and ideal gain boundary/interface microstructure. Gas separation membranes for the production of oxygen and hydrogen are also disclosed. These semipermeable membranes are formed by high-quality, dense, gas-tight, pinhole free sub-micro scale layers of mixed-conducting oxides on porous ceramic substrates. Epitaxial thin films as dielectric material in capacitors are also taught herein. Capacitors are utilized according to their capacitance values which are dependent on their physical structure and dielectric permittivity. The epitaxial thin films of the current invention form low-loss dielectric layers with extremely high permittivity. This high permittivity allows for the formation of capacitors that can have their capacitance adjusted by applying a DC bias between their electrodes.

  18. A simple solution to the problem of effective utilisation of the target material for pulsed laser deposition of thin films

    SciTech Connect

    Kuzanyan, A S; Kuzanyan, A A; Petrosyan, V A; Pilosyan, S Kh; Grasiuk, A Z

    2013-12-31

    The factors determining the efficiency of the target material utilisation for pulsed laser deposition of films are considered. The target volume is calculated, which is evaporated in the ablation process by the focused laser radiation having a rectangular form. The new device is suggested and developed for obtaining thin films by the method of laser deposition, which is specific in the employment of a simple optical system mounted outside a deposition chamber that comprises two lenses and the diaphragm and focuses the laser beam onto a target in the form of a sector-like spot. Thin films of CuO and YBaCuO were deposited with this device. Several deposition cycles revealed that the target material is consumed uniformly from the entire surface of the target. A maximal spread of the target thickness was not greater than ±2% both prior to deposition and after it. The device designed provides a high coefficient of the target material utilisation efficiency. (laser deposition of thin films)

  19. Effect of Doping on beta-Tricalcium Phosphate Bioresorbable Bulk Material and Thin Film Coatings

    NASA Astrophysics Data System (ADS)

    Abdalla, Suhaila

    Magnesium has emerged as a revolutionary biodegradable metal for use as an orthopedic material, it has several advantages over the current metallic materials in use, including eliminating the effects of stress shielding, improving biocompatibility and inhibiting degradation rates, thus removing the requirement of a second surgery for implant removal. Due to the rapid degradation of magnesium, it is necessary to control the corrosion rates of the materials to match the rates of bone healing. This dissertation reports on the effect of doping on the properties of beta-tricalcium phosphate (beta-TCP). It also reports on its application as a thin film coating on magnesium alloys for implant applications. Adding various dopants to beta-TCP significantly influences critical properties. In this study, discs were fabricated in two compositions: (i) undoped beta-TCP, (ii) beta-TCP doped with 1.0 wt % MgO, 0.5 wt % ZnO, and 1.0 wt % TiO2. Films were fabricated from these compositions using the pulsed laser deposition (PLD) technique. These coatings were then characterized for corrosive, hardness, and cytocompatibility. The XRD patterns of the coating confirm the amorphous nature of the films. The presence of the metal oxides in beta-TCP improved ceramic densification. The application of these doped coatings was also found to increase the hardness by 88 %, the modulus of elasticity by 66 %, and improve corrosion resistance of the magnesium alloy substrate; with a 2.4 % improvement in Ecorr and 95 % decrease in icorr. Cell viability was studied using an osteoblast precursor cell line MC3T3-E1 to assure that the biocompatibility of these ceramics was not altered due to the dopants. Long-term biodegradation studies were conducted by measuring weight change and surface microstructure as a function of time in simulated body fluid. The results suggest that these coatings could be used for bioresorbable implants with improved corrosion resistance and increased hardness.

  20. Effect of native oxide layers on copper thin-film tensile properties: A reactive molecular dynamics study

    SciTech Connect

    Skarlinski, Michael D.; Quesnel, David J.

    2015-12-21

    Metal-oxide layers are likely to be present on metallic nano-structures due to either environmental exposure during use, or high temperature processing techniques such as annealing. It is well known that nano-structured metals have vastly different mechanical properties from bulk metals; however, difficulties in modeling the transition between metallic and ionic bonding have prevented the computational investigation of the effects of oxide surface layers. Newly developed charge-optimized many body [Liang et al., Mater. Sci. Eng., R 74, 255 (2013)] potentials are used to perform fully reactive molecular dynamics simulations which elucidate the effects that metal-oxide layers have on the mechanical properties of a copper thin-film. Simulated tensile tests are performed on thin-films while using different strain-rates, temperatures, and oxide thicknesses to evaluate changes in yield stress, modulus, and failure mechanisms. Findings indicate that copper-thin film mechanical properties are strongly affected by native oxide layers. The formed oxide layers have an amorphous structure with lower Cu-O bond-densities than bulk CuO, and a mixture of Cu{sub 2}O and CuO charge character. It is found that oxidation will cause modifications to the strain response of the elastic modulii, producing a stiffened modulii at low temperatures (<75 K) and low strain values (<5%), and a softened modulii at higher temperatures. While under strain, structural reorganization within the oxide layers facilitates brittle yielding through nucleation of defects across the oxide/metal interface. The oxide-free copper thin-film yielding mechanism is found to be a tensile-axis reorientation and grain creation. The oxide layers change the observed yielding mechanism, allowing for the inner copper thin-film to sustain an FCC-to-BCC transition during yielding. The mechanical properties are fit to a thermodynamic model based on classical nucleation theory. The fit implies that the oxidation of the

  1. Electronic analog of chiral metamaterial: Helicity-resolved filtering and focusing of Dirac fermions in thin films of topological materials

    NASA Astrophysics Data System (ADS)

    Zhao, Lu; Wang, Jianfeng; Liu, Junwei; Xu, Yong; Gu, Bing-Lin; Xue, Qi-Kun; Duan, Wenhui

    2015-07-01

    Control over the helicity degree of freedom of Dirac fermions is identified in thin films of topological materials which act as a tunable "chiral-metamaterial-like" platform to tame left- and right-handed Dirac fermions in two dimensions. Using topological crystalline insulator SnTe(111) thin films as an example, we perform the first-principles calculations and show that giant helicity splitting in the band structures can be induced under moderate electric field. Based on this result, helicity-resolved functionalities, including pronounced electron dichroism, helicity switching, helical negative refraction, and birefraction, are demonstrated, where the intrahelical scattering always dominates over the interhelical one. Such intriguing control strategy for helical Dirac fermions may hold great promise for the applications of helicity-based electron optics and nanoelectronics.

  2. Thin Films

    NASA Astrophysics Data System (ADS)

    Khorshidi, Zahra; Bahari, Ali; Gholipur, Reza

    2014-11-01

    Effect of annealing temperature on the characteristics of sol-gel-driven Ta ax La(1- a) x O y thin film spin-coated on Si substrate as a high- k gate dielectric was studied. Ta ax La(1- a) x O y thin films with different amounts of a were prepared (as-prepared samples). X-ray diffraction measurements of the as-prepared samples indicated that Ta0.3 x La0.7 x Oy film had an amorphous structure. Therefore, Ta0.3 x La0.7 x O y film was chosen to continue the present studies. The morphology of Ta0.3 x La0.7 x O y films was studied using scanning electron microscopy and atomic force microscopy techniques. The obtained results showed that the size of grain boundaries on Ta0.3 x La0.7 x O y film surfaces was increased with increasing annealing temperature. Electrical and optical characterizations of the as-prepared and annealed films were investigated as a function of annealing temperature using capacitance-voltage ( C- V) and current density-voltage ( J- V) measurements and the Tauc method. The obtained results demonstrated that Ta0.3 x La0.7 x O y films had high dielectric constant (≈27), wide band gap (≈4.5 eV), and low leakage current density (≈10-6 A/cm2 at 1 V).

  3. Thin Films

    NASA Astrophysics Data System (ADS)

    Naffouti, Wafa; Nasr, Tarek Ben; Mehdi, Ahmed; Kamoun-Turki, Najoua

    2014-11-01

    Titanium dioxide (TiO2) thin films were synthesized on glass substrates by spray pyrolysis. The effect of solution flow rate on the physical properties of the films was investigated by use of x-ray diffraction (XRD), scanning electron microscopy, atomic force microscopy (AFM), and spectrophotometry techniques. XRD analysis revealed the tetragonal anatase phase of TiO2 with highly preferred (101) orientation. AFM images showed that grain size on top of TiO2 thin films depended on solution flow rate. An indirect band gap energy of 3.46 eV was determined by means of transmission and reflection measurements. The envelope method, based on the optical transmission spectrum, was used to determine film thickness and optical constants, for example real and imaginary parts of the dielectric constant, refractive index, and extinction coefficient. Ultraviolet and visible photoluminescence emission peaks were observed at room temperature. These peaks were attributed to the intrinsic emission and to the surface defect states, respectively.

  4. Chemical Fabrication Used to Produce Thin-Film Materials for High Power-to- Weight-Ratio Space Photovoltaic Arrays

    NASA Technical Reports Server (NTRS)

    Hepp, Aloysius F.; Rybicki, George C.; Raffaelle, Ryne P.; Harris, Jerry D.; Hehemann, David G.; Junek, William; Gorse, Joseph; Thompson, Tracy L.; Hollingsworth, Jennifer A.; Buhro, William E.

    2000-01-01

    The key to achieving high specific power (watts per kilogram) space solar arrays is the development of a high-efficiency, thin-film solar cell that can be fabricated directly on a flexible, lightweight, space-qualified durable substrate such as Kapton (DuPont) or other polyimide or suitable polymer film. Cell efficiencies approaching 20 percent at AM0 (air mass zero) are required. Current thin-film cell fabrication approaches are limited by either (1) the ultimate efficiency that can be achieved with the device material and structure or (2) the requirement for high-temperature deposition processes that are incompatible with all presently known flexible polyimide or other polymer substrate materials. Cell fabrication processes must be developed that will produce high-efficiency cells at temperatures below 400 degrees Celsius, and preferably below 300 degress Celsius to minimize the problems associated with the difference between the coefficients of thermal expansion of the substrate and thin-film solar cell and/or the decomposition of the substrate.

  5. Intermolecular electronic coupling in organic molecular thin films measured by temperature modulation spectroscopy

    SciTech Connect

    Yadav, Abhishek; Jin, Y; Chan, P. K. L.; Shtein, Max; Pipe, Kevin P.

    2010-01-01

    Temperature modulation spectroscopy is used to obtain the temperature dependences of oscillator strength, exciton transition energy, and line width for a copper phthalocyanine thin film. With increasing temperature, the oscillator strength exhibits a pronounced decrease for charge transfer (CT) excitons, making this technique suitable for differentiating exciton types. From the measured magnitude and temperature dependence of the CT oscillator strength, we obtain estimates for the intermolecular electronic coupling and its exponential decay coefficient.

  6. Improving stability of photoluminescence of ZnSe thin films grown by molecular beam epitaxy by incorporating Cl dopant

    NASA Astrophysics Data System (ADS)

    Wang, J. S.; Chen, W. J.; Yang, C. S.; Tsai, Y. H.; Wang, H. H.; Chen, R. H.; Shen, J. L.; Tsai, C. D.

    2011-01-01

    This investigation studies the effect of chlorine (Cl) dopant in ZnSe thin films that were grown by molecular beam epitaxy on their photoluminescence (PL) and the stability thereof. Free excitonic emission was observed at room-temperature in the Cl-doped sample. Photon irradiation with a wavelength of 404 nm and a power density of 9.1 W/cm2 has a much stronger effect on PL degradation than does thermal heating to a temperature of 150 °C. Additionally, this study shows that the generation of nonradiative centers by both photon irradiation and thermal heating can be greatly inhibited by incorporating Cl dopant.

  7. Effect of molecular coverage on the electric conductance of a multi-walled carbon nanotube thin film

    NASA Astrophysics Data System (ADS)

    Kokabu, Takuya; Inoue, Shuhei; Matsumura, Yukihiko

    2016-06-01

    We investigated the influence of water adsorption on a CNT thin film. When we assumed that the magnitude of the change in electrical resistance was correlated with the surface coverage of the adsorbed molecules, this phenomenon could be explained by two-layer adsorption. The first layer was expressed by Langmuir adsorption and that on the second layer was expressed by Fowler-Guggenheim adsorption, which was derived by Bragg-Williams approximation and involved a lateral molecular interaction. The adsorption energy estimated by this assumption was on the same order as derived by DFT calculation.

  8. Chemically deposited thin films of sulfides and selenides of antimony and bismuth as solar energy materials

    NASA Astrophysics Data System (ADS)

    Nair, M. T.; Nair, Padmanabhan K.; Garcia, V. M.; Pena, Y.; Arenas, O. L.; Garcia, J. C.; Gomez-Daza, O.

    1997-10-01

    Chemical bath deposition techniques for bismuth sulfide, bismuth selenide, antimony sulfide, and antimony selenide thin films of about 0.20 - 0.25 micrometer thickness are reported. All these materials may be considered as solar absorber films: strong optical absorption edges, with absorption coefficient, (alpha) , greater than 104 cm-1, are located at 1.31 eV for Bi2Se3, 1.33 eV for Bi2S3, 1.8 eV for Sb2S3, and 1.35 eV for Sb2Se3. As deposited, all the films are nearly amorphous. However, well defined crystalline peaks matching bismuthinite (JCPDS 17- 0320), paraguanajuatite (JCPDS 33-0214), and stibnite (JCPDS 6-0474) and antimony selenide (JCPDS 15-0861) for Bi2S3, Bi2Se3, Sb2S3 and Sb2Se3 respectively, are observed when the films are annealed in nitrogen at 300 degrees Celsius. This is accompanied by a substantial modification of the electrical conductivity in the films: from 10-7 (Omega) -1 cm-1 (in as prepared films) to 10 (Omega) -1 cm-1 in the case of bismuth sulfide and selenide films, and enhancement of photosensitivity in the case of antimony sulfide films. The chemical deposition of a CuS/CuxSe film on these Vx- VIy films and subsequent annealing at 300 degrees Celsius for 1 h at 1 torr of nitrogen leads to the formation of p-type films (conductivity of 1 - 100 (Omega) -1 cm-1) of multinary composition. Among these, the formation of Cu3BiS3 (JCPDS 9-0488) and Cu3SbS4 (JCPDS 35- 0581), CuSbS2 (JCPDS 35-0413) have been clearly detected. Solar energy applications of these films are suggested.

  9. Correlation Between Material Properties of Ferroelectric Thin Films and Design Parameters for Microwave Device Applications: Modeling Examples and Experimental Verification

    NASA Technical Reports Server (NTRS)

    Miranda, Felix A.; VanKeuls, Fred W.; Subramanyam, Guru; Mueller, Carl H.; Romanofsky, Robert R.; Rosado, Gerardo

    2000-01-01

    The application of thin ferroelectric films for frequency and phase agile components is the topic of interest of many research groups worldwide. Consequently, proof-of-concepts (POC) of different tunable microwave components using either (HTS, metal)/ferroelectric thin film/dielectric heterostructures or (thick, thin) film "flip-chip" technology have been reported. Either as ferroelectric thin film characterization tools or from the point of view of circuit implementation approach, both configurations have their respective advantages and limitations. However, we believe that because of the progress made so far using the heterostructure (i.e., multilayer) approach, and due to its intrinsic features such as planar configuration and monolithic integration, a study on the correlation of circuit geometry aspects and ferroelectric material properties could accelerate the insertion of this technology into working systems. In this paper, we will discuss our study performed on circuits based on microstrip lines at frequencies above 10 GHz, where the multilayer configuration offers greater ease of insertion due to circuit's size reduction. Modeled results of relevant circuit parameters such as the characteristic impedance, effective dielectric constant, and attenuation as a function of ferroelectric film's dielectric constant, tans, and thickness, will be presented for SrTiO3 and Ba(x)Sr(1-x)TiO3 ferroelectric films. A comparison between the modeled and experimental data for some of these parameters will be presented.

  10. Fabrication and characterization of thin-film transistor materials and devices

    NASA Astrophysics Data System (ADS)

    Hong, David

    A class of inorganic thin-film transistor (TFT) semiconductor materials has emerged involving oxides composed of post-transitional cations with (n-1)d 10ns0 (n≥4) electronic configurations. This thesis is devoted to the pursuit of topics involving the development of these materials for TFT applications: Deposition of zinc oxide and zinc tin oxide semiconductor layers via reactive sputtering from a metal target, and the characterization of indium gallium zinc oxide (IGZO)-based TFTs utilizing various insulator materials as the gate dielectric. The first topic involves the deposition of oxide semiconductor layers via reactive sputtering from a metal target. Two oxide semiconductors are utilized for fabricating TFTs via reactive sputtering from a metal target: zinc oxide and zinc tin oxide. With optimized processing parameters, zinc oxide and zinc tin oxide via this deposition method exhibit similar characteristics to TFTs fabricated via sputtering from a ceramic target. Additionally the effects of gate capacitance density and gate dielectric material are explored utilizing TFTs with IGZO as the semiconductor layers. IGZO-based TFTs exhibit ideal behavior with improved TFT performance such as higher current drive at a given overvoltage, a decrease in the subthreshold swing, and a decrease in the magnitude of the turn-on voltage. Additionally it is shown that silicon dioxide is the preferred dielectric material, with silicon nitride a poor choice for oxide-based TFTs. Finally a simple method to characterize the band tail state distribution near the conduction band minimum of a semiconductor by analyzing two-terminal current-voltage characteristics of a TFT with a floating gate is presented. The characteristics trap energy (ET) as a function of post-deposition annealing temperature is shown to correlate very well with IGZO TFT performance, with a lower value of E T, corresponding to a more abrupt distribution of band tail states, correlating with improved TFT mobility

  11. Combining a molecular modelling approach with direct current and high power impulse magnetron sputtering to develop new TiO2 thin films for antifouling applications

    NASA Astrophysics Data System (ADS)

    Guillot, Jérôme; Lecoq, Elodie; Duday, David; Puhakka, Eini; Riihimäki, Markus; Keiski, Riitta; Chemin, Jean-Baptiste; Choquet, Patrick

    2015-04-01

    The accumulation of crystallization deposits at the surface of heat exchangers results in the increase of the heat transfer resistance and a drastic loss of efficiency. Coating surfaces with a thin film can limit the scale-surface adhesion force and thus the fouling process. This study compares the efficiency of TiO2 layers exhibiting various crystalline planes and microstructures to reduce the kinetic of fouling. Molecular modelling with density functional theory is first carried out to determine the energy of CaCO3 deposition on anatase (1 0 1), (0 0 4), and (2 0 0) surfaces as well as on a rutile (1 0 1) one. TiO2 thin films (thickness < 1 μm) are then synthesized by direct current and high power impulse magnetron sputtering (dcMS and HiPIMS respectively) in order to tune their crystallinity and microstructure. Lastly, the induction time to grow CaCO3 crystals at the surface of such materials is determined. Comparing the modelling and fouling results allows to draw general trends on the potential anti-scaling properties of TiO2 crystallized under various forms. Until now, such a comparison combining a theoretical approach with experimental fouling tests has never been reported in the literature.

  12. Luminescence of W(CO){sub 4}(4-Me-phen) in photosensitive thin films: A molecular probe of acrylate polymerization

    SciTech Connect

    Rawlins, K.A.; Lees, A.J.; Fuerniss, S.J.; Papathomas, K.I.

    1996-07-01

    The complex W(CO){sub 4}(4-Me-phen) (4-Me-phen = 4-methyl-1,10-phenanthroline) has been determined to be luminescent and act as a spectroscopic probe in UV-curable trimethylolpropane triacrylate/poly(methyl methacrylate) thin films. Electronic absorption and luminescence characteristics have been measured for this complex in room-temperature solutions and low-temperature (80 K) glasses and in 10 mil thin films of the unexposed and exposed acrylate resins. In each environment dual luminescence bands were observed which are attributed to triplet-centered metal-to-ligand charge-transfer ({sup 3}MLCT) excited states. For the unexposed photoresist these transitions were recorded at 520 and 750 nm and in the exposed material these are moved to 525 and 715 nm, respectively. The lowest energy emission band undergoes a substantial blue-shift and intensified greatly on polymerization; this phenomenon provides a useful molecular probe of the acrylate cross-linking process. These changes in emission characteristics are associated with a rigidochromic effect imparted on the lowest lying and solvent sensitive b{sub 2} {yields} b{sub 2}({pi}*) {sup 3}MLCT electronically excited state in this complex. The complex W(CO){sub 5}(4-CN-py) (4-CN-py = 4-cyanopyridine) was also investigated as a spectroscopic probe in the acrylate system but appears unsuitable for this purpose as it was found to degrade significantly in the resin. 20 refs., 6 figs.

  13. Far-infrared transmission in GaN, AlN, and AlGaN thin films grown by molecular beam epitaxy

    SciTech Connect

    Ibanez, J.; Hernandez, S.; Alarcon-Llado, E.; Cusco, R.; Artus, L.; Novikov, S. V.; Foxon, C. T.; Calleja, E.

    2008-08-01

    We present a far-infrared transmission study on group-III nitride thin films. Cubic GaN and AlN layers and c-oriented wurtzite GaN, AlN, and Al{sub x}Ga{sub 1-x}N (x<0.3) layers were grown by molecular beam epitaxy on GaAs and Si(111) substrates, respectively. The Berreman effect allows us to observe simultaneously the transverse optic and the longitudinal optic phonons of both the cubic and the hexagonal films as transmission minima in the infrared spectra acquired with obliquely incident radiation. We discuss our results in terms of the relevant electromagnetic theory of infrared transmission in cubic and wurtzite thin films. We compare the infrared results with visible Raman-scattering measurements. In the case of films with low scattering volumes and/or low Raman efficiencies and also when the Raman signal of the substrate material obscures the weaker peaks from the nitride films, we find that the Berreman technique is particularly useful to complement Raman spectroscopy.

  14. Electrical and mechanical properties of molecularly functionalized mesoporous silica thin films

    NASA Astrophysics Data System (ADS)

    Singh, Amit Pratap

    Mesoporous silica (MPS) thin films are attractive for achieving low relative dielectric permittivity (low-kappa) interlayer isolation in integrated circuit wiring, but are susceptible to instabilities in electrical behavior due to water uptake and copper diffusion. This work investigates the electrical, chemical, and thermal instabilities, Cu diffusion, and adhesion of these materials for evaluating and enabling their use for applications as interlayer insulators in nanodevice wiring. Upon annealing Al/MPS/Si(001)/Al capacitors between 80 to 200°C, the flat-band voltage first increases, reaches a maximum, and then decreases. Concurrently, the initially observed deep depletion behavior is replaced by strong inversion. Subsequent air-exposure restores the preanneal C-V characteristics. Kinetics analyses reveal two thermally activated processes: proton generation through fissure of silanol bonds (activation energy Ea1 = 0.42 +/- 0.04 eV) and proton-induced depassivation of dangling bond traps (Ea2 = 0.54 +/- 0.05 eV) at the MPS/Si interface. We present an empirical model correlating these processes with the C-V characteristics. Further, we show that capping MPS films with a trimethyl-terminated organosilane irreversibly suppresses moisture-induced capacitance instabilities, and decreases the relative dielectric permittivity and Cu-induced leakage currents. Analysis of capacitance-voltage and current-voltage characteristics along with infrared spectroscopy shows that the trimethyl organosilanes inhibit hydrogen bonding of water molecules by rendering the dielectric surfaces hydrophobic. Fracture behavior and mechanical properties of pristine (i.e., un-functionalized MPS) and silylated mesoporous silica (SMPS) films were studied by four-point bend tests and nanoindentation measurements. Four-point bend measurements on Si/epoxy/Ti/Cu/MPS/Si stacks show that structures with un-silylated MPS films fracture at ˜3 J/m2, while those with SMPS films show a ˜50% lower

  15. Biomimetic thin film deposition

    SciTech Connect

    Rieke, P.R.; Graff, G.E.; Campbell, A.A.; Bunker, B.C.; Baskaran, S.; Song, L.; Tarasevich, B.J.; Fryxell, G.E.

    1995-09-01

    Biological mineral deposition for the formation of bone, mollusk shell and other hard tissues provides materials scientists with illustrative materials processing strategies. This presentation will review the key features of biomineralization and how these features can be of technical importance. We have adapted existing knowledge of biomineralization to develop a unique method of depositing inorganic thin films and coating. Our approach to thin film deposition is to modify substrate surfaces to imitate the proteins found in nature that are responsible for controlling mineral deposition. These biomimetic surfaces control the nucleation and growth of the mineral from a supersaturated aqueous solution. This has many processing advantages including simple processing equipment, environmentally benign reagents, uniform coating of highly complex shapes, and enhanced adherence of coating. Many different types of metal oxide, hydroxide, sulfide and phosphate materials with useful mechanical, optical, electronic and biomedical properties can be deposited.

  16. The role of surface electronic structure in thin film molecular ordering.

    SciTech Connect

    Sakurai, T.; Tromp, R. M.; Meyer zu Heringdorf, F.; Sadowski, J.; Thayer, Gayle Echo

    2005-05-01

    We show that the orientation of pentacene molecules is controlled by the electronic structure of the surface on which they are deposited. We suggest that the near-Fermi level density of states above the surface controls the interaction of the substrate with the pentacene {pi} orbitals. A reduction of this density as compared to noble metals, realized in semimetallic Bi(001) and Si(111)(5 x 2)Au surfaces, results in pentacene standing up. Interestingly, pentacene grown on Bi(001) is highly ordered, yielding the first vertically oriented epitaxial pentacene thin films observed to date.

  17. Molecular Beam Epitaxial (MBE) Growth and Characterization of Thin Films of Semiconductor Tin

    NASA Astrophysics Data System (ADS)

    Folkes, P.; Taylor, P.; Rong, C.; Nichols, B.; Hier, H.; Burke, R.; Neupane, M.

    Recent theoretical predictions that a two-dimensional monolayer of semiconductor tin is a two-dimensional topological insulator and experimental evidence of three-dimensional topological insulator behavior in strained ultrathin films of semiconductor tin grown by MBE on InSb has generated intense research interest. This research is primarily focused on the MBE growth and topological characteristics of ultrathin films of semiconductor tin. In this talk we present results of a study on the MBE growth and the transport, structural and optical characterization of thin films of semiconductor tin on several different substrates.

  18. Materials optimization and ghz spin dynamics of metallic ferromagnetic thin film heterostructures

    NASA Astrophysics Data System (ADS)

    Cheng, Cheng

    Metallic ferromagnetic (FM) thin film heterostructures play an important role in emerging magnetoelectronic devices, which introduce the spin degree of freedom of electrons into conventional charge-based electronic devices. As the majority of magnetoelectronic devices operate in the GHz frequency range, it is critical to understand the high-frequency magnetization dynamics in these structures. In this thesis, we start with the static magnetic properties of FM thin films and their optimization via the field-sputtering process incorporating a specially designed in-situ electromagnet. We focus on the origins of anisotropy and hysteresis/coercivity in soft magnetic thin films, which are most relevant to magentic susceptibility and power dissipation in applications in the sub-GHz frequency regime, such as magnetic-core integrated inductors. Next we explore GHz magnetization dynamics in thin-film heterostructures, both in semi-infinite samples and confined geometries. All investigations are rooted in the Landau-Lifshitz-Gilbert (LLG) equation, the equation of motion for magnetization. The phenomenological Gilbert damping parameter in the LLG equation has been interpreted, since the 1970's, in terms of the electrical resistivity. We present the first interpretation of the size effect in Gilbert damping in single metallic FM films based on this electron theory of damping. The LLG equation is intrinsically nonlinear, which provides possibilities for rf signal processing. We analyze the frequency doubling effect at small-angle magnetization precession from the first-order expansion of the LLG equation, and demonstrate second harmonic generation from Ni81 Fe19 (Permalloy) thin film under ferromagnetic resonance (FMR), three orders of magnitude more efficient than in ferrites traditionally used in rf devices. Though the efficiency is less than in semiconductor devices, we provide field- and frequency-selectivity in the second harmonic generation. To address further the

  19. Physical and Material Properties of Yttrium Barium Copper Oxide High Critical Temperature Superconducting Thin Films.

    NASA Astrophysics Data System (ADS)

    Ma, Qiyuan

    1990-01-01

    A simple method of using layered structures and rapid thermal annealing to produce Y_1 Ba_2 Cu_3 O_{7-x} (YBCO) superconducting thin films is presented. Material properties of the films depend strongly on the processing conditions, the film stoichiometry, and the substrates. The films with critical temperature (T_{ rm c}) higher than liquid nitrogen temperature (77 K) have been made on various substrates including magnesium oxide, sapphire, and silicon. The best film was obtained on a MgO substrate with T_{rm c} of 84 K. Silicon diffusion and reaction with oxygen during a high temperature anneal degrade the superconductivity of the film on a Si substrate. Using a buffer layer of gold, the Si-YBCO interaction is greatly reduced. Typical resistivity of the film shows a linear temperature dependence which may be attributed to an electron -phonon interaction. Anisotropic resistance behavior has been observed due to the layered structures. Different metal contacts to the YBCO films have been used to study the chemical and electrical properties of metal-YBCO film interfaces. Gold has been found nonreactive to YBCO film, thus, it has the lowest contact resistivity. Near the T_{rm c}, the contact resistivity of a Au-YBCO contact approaches zero. This may be due to the proximity effect. Other metals such as Pt, Pd, Sn and Ti, react with the YBCO film and form thin oxide layers at the interfaces. The oxide layer acts as an insulating barrier which forbids the proximity effect and causes a large contact resistivity. The structural and electrical properties of the Si-YBCO intermixed film have been studied for different thicknesses of the silicon layers. A novel patterning technique of using Si-YBCO intermixing has been developed for fabricating the YBCO superconducting device structures. A superconductor sample has a critical current value I _{rm c}. Below the I _{rm c} the material is superconducting, and above I_{rm c} the sample has a finite resistance. Based on this effect

  20. Growth characteristics of Ti-based fumaric acid hybrid thin films by molecular layer deposition.

    PubMed

    Cao, Yan-Qiang; Zhu, Lin; Li, Xin; Cao, Zheng-Yi; Wu, Di; Li, Ai-Dong

    2015-09-01

    Ti-based fumaric acid hybrid thin films were successfully prepared using inorganic TiCl4 and organic fumaric acid as precursors by molecular layer deposition (MLD). The effect of deposition temperature from 180 °C to 350 °C on the growth rate, composition, chemical state, and topology of hybrid films has been investigated systematically by means of a series of analytical tools such as spectroscopic ellipsometry, atomic force microscopy (AFM), high resolution X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). The MLD process of the Ti-fumaric acid shows self-limiting surface reaction with a reasonable growth rate of ∼0.93 Å per cycle and small surface roughness of ∼0.59 nm in root-mean-square value at 200 °C. A temperature-dependent growth characteristic has been observed in the hybrid films. On increasing the temperature from 180 °C to 300 °C, the growth rate decreases from 1.10 to 0.49 Å per cycle and the XPS composition of the film's C : O : Ti ratio changes from 8.35 : 7.49 : 1.00 to 4.66 : 4.80 : 1.00. FTIR spectra indicate that the hybrid films show bridging bonding mode at a low deposition temperature of 200 °C and bridging/bidentate mixed bonding mode at elevated deposition temperatures of 250 and 300 °C. The higher C and O amounts deviating from the ideal composition may be ascribed to increased organic incorporation into the hybrid films at lower deposition temperature and temperature-dependent density of reactive sites (-OH). The composition of hybrid films grown at 350 °C shows a dramatic decrease in C and O elemental composition (C : O : Ti = 1.97 : 2.76 : 1.00) due to the thermal decomposition of the fumaric acid precursor. The produced by-product H2O changes the structure of the hybrid films, resulting in the formation of more Ti-O bonds at high temperatures. The stability of the hybrid films against chemical and thermal treatment, and long-term storage by

  1. Aspects of Integrating Functional Electroceramic Material in Multilayer Thin Films for Image Sensing: Modeling and Experiment

    NASA Astrophysics Data System (ADS)

    Matin, M. A.; Oishi, K.; Katsuta, A.; Akai, D.; Sawada, K.; Ishida, M.

    2015-07-01

    Using combined experimental and simulation techniques, this study addresses the critical stress for peeling off crucial layer(s) in multilayered epitaxial functional thin films on n-Si(001) substrate. The thickness of platinum (Pt) and PZT thin films was varied from 22 nm to 142 nm and 90 nm to 450 nm, respectively. Residual stresses were measured by analyzing captured fringes using Newton's rings technique. Advanced finite element computation was next conducted to predict the evolution of residual stresses. Induced stresses in Pt thin film were found to be decreased with decreasing the thickness of film from 72 nm to 40 nm. In contrast, stresses are shown to be decreased with increasing the thickness of PZT film from 240 nm to 450 nm. The design of the pyroelectric multilayered sensors was thus optimized employing finite element (FE) simulation. Computed stresses were found to correlate well with that observed in experiments. FE simulations can thus be used as a tool to a priori predict the evolution of residual stresses, which may allow a fail-safe design before the fabrication of pyroelectric image sensors.

  2. First measurements of bulk and shear mechanical loss in optical thin film materials

    NASA Astrophysics Data System (ADS)

    Abernathy, Matthew; Harry, Gregory; Newport, Jonathan; Fair, Hanna; Hickey, Sam; Grettarsson, Andri; Penn, Steve; LIGO Collaboration

    As advanced gravitational wave detectors come online, and the possibility of the first gravitational wave detection nears, plans for the next generation of gravitational wave detectors are already in the works. These new detectors, and those already planned for the future, are expected to be limited in their most sensitive frequency bands by the Brownian thermal noise generated within the optical thin films used to produce the interferometer mirrors. In order to fully predict the level of this Brownian noise, it is necessary to know the two independent mechanical moduli (Young modulus and Poisson ratio, Bulk and Shear moduli, etc.) as well as their associated mechanical loss parameters. Traditional measurements of the mechanical loss of thin films has measured only one linear combination of these two loss parameters. Here, we present measurements of the bulk and shear mechanical loss of tantalum pentoxide (tantala) thin films made by taking advantage of the differing ratios of elastic deformation in the various resonant modes of a coated silica disc. These results may have immediate implications for the ultimate sensitivity of currently operated gravitational wave detectors.

  3. Characteristic length of phonon transport within periodic nanoporous thin films and two-dimensional materials

    NASA Astrophysics Data System (ADS)

    Hao, Qing; Xiao, Yue; Zhao, Hongbo

    2016-08-01

    In the past two decades, phonon transport within nanoporous thin films has attracted enormous attention for their potential applications in thermoelectrics and thermal insulation. Various computational studies have been carried out to explain the thermal conductivity reduction within these thin films. Considering classical phonon size effects, the lattice thermal conductivity can be predicted assuming diffusive pore-edge scattering of phonons and bulk phonon mean free paths. Following this, detailed phonon transport can be simulated for a given porous structure to find the lattice thermal conductivity [Hao et al., J. Appl. Phys. 106, 114321 (2009)]. However, such simulations are intrinsically complicated and cannot be used for the data analysis of general samples. In this work, the characteristic length Λ P o r e of periodic nanoporous thin films is extracted by comparing the predictions of phonon Monte Carlo simulations and the kinetic relationship using bulk phonon mean free paths modified by Λ P o r e . Under strong ballistic phonon transport, Λ P o r e is also extracted by the Monte Carlo ray-tracing method for graphene with periodic nanopores. The presented model can be widely used to analyze the measured thermal conductivities of such nanoporous structures.

  4. Combination of porous silica monolith and gold thin films for electrode material of supercapacitor

    NASA Astrophysics Data System (ADS)

    Pastre, A.; Cristini-Robbe, O.; Boé, A.; Raulin, K.; Branzea, D.; El Hamzaoui, H.; Kinowski, C.; Rolland, N.; Bernard, R.

    2015-12-01

    An all-solid electrical double layer supercapacitor was prepared, starting from a porous silica matrix coated with a gold thin-film. The metallization of the silica xerogel was performed by an original wet chemical process, based on the controlled growth of gold nanoparticles on two opposite faces of the silica monolith as a seed layer, followed by an electroless deposition of a continuous gold thin film. The thickness of the metallic thin film was assessed to be 700 nm. The silica plays two major roles: (1) it is used as a porous matrix for the gold electrode, creating a large specific surface area, and (2) it acts as a separator (non-metallized part of the silica). The silica monolith was soaked in a polyvinyl alcohol and phosphoric acid mixture which is used as polymer electrolyte. Capacitance effect was demonstrated by cyclic voltammetry experiments. The specific capacitance was found to be equal to 0.95 mF cm- 2 (9.5 F g-1). No major degradation occurs within more than 3000 cycles.

  5. Host thin films incorporating nanoparticles

    NASA Astrophysics Data System (ADS)

    Qureshi, Uzma

    The focus of this research project was the investigation of the functional properties of thin films that incorporate a secondary nanoparticulate phase. In particular to assess if the secondary nanoparticulate material enhanced a functional property of the coating on glass. In order to achieve this, new thin film deposition methods were developed, namely use of nanopowder precursors, an aerosol assisted transport technique and an aerosol into atmospheric pressure chemical vapour deposition system. Aerosol assisted chemical vapour deposition (AACVD) was used to deposit 8 series of thin films on glass. Five different nanoparticles silver, gold, ceria, tungsten oxide and zinc oxide were tested and shown to successfully deposit thin films incorporating nanoparticles within a host matrix. Silver nanoparticles were synthesised and doped within a titania film by AACVD. This improved solar control properties. A unique aerosol assisted chemical vapour deposition (AACVD) into atmospheric pressure chemical vapour deposition (APCVD) system was used to deposit films of Au nanoparticles and thin films of gold nanoparticles incorporated within a host titania matrix. Incorporation of high refractive index contrast metal oxide particles within a host film altered the film colour. The key goal was to test the potential of nanopowder forms and transfer the suspended nanopowder via an aerosol to a substrate in order to deposit a thin film. Discrete tungsten oxide nanoparticles or ceria nanoparticles within a titanium dioxide thin film enhanced the self-cleaning and photo-induced super-hydrophilicity. The nanopowder precursor study was extended by deposition of zinc oxide thin films incorporating Au nanoparticles and also ZnO films deposited from a ZnO nanopowder precursor. Incorporation of Au nanoparticles within a VO: host matrix improved the thermochromic response, optical and colour properties. Composite VC/TiC and Au nanoparticle/V02/Ti02 thin films displayed three useful

  6. A study of structure-property correlation in vanadium pentoxide and titanium dioxide based thin films as functional materials

    NASA Astrophysics Data System (ADS)

    Thapa, Chandra

    The focus of this thesis is to study the structure-property correlation in thin films of V2O5 and TiO2 based transition metal oxides as functional materials. V2O5 is investigated as a cathode material for lithium ion battery and TiO2 as a high-k dielectric material. We studied V2O5 thin films prepared by spin coating using three different types of precursors, MOD precursor, sol-gel organic precursor and sol-gel inorganic precursor. On the basis of structural and electrochemical studies, we find that the capacity is dependent on the degree of non-stoichiometry. We have also studied the effect of addition of Ti. Although Ti doping enhances non-stoichiometry, the capacity was found to increase only in 5% Ti-doped sol-gel film. This means the optimal degree of non-stoichiometry is crucial to enhance the capacity. TiO2 is one of the possible high-k dielectric materials because of its very high dielectric constant. We studied leakage characteristics, the dielectric strength and frequency dependent behavior of dielectric constant of TiO2 thin films prepared by MOD, sputter deposition and annealed at different temperatures. We find dielectric constant increasing with the increase in annealing temperature and leakage current density improvement by almost one order of magnitude with each 100 °C increase in annealing temperature. Since TiO2 possess two distinct thermodynamic phases: anatase and rutile, which dramatically influences the values of dielectric constant and leakage current density, it is crucial to stabilize the phase of TiO2 by doping. We find that 20% Zr-doping completely stabilizes TiO2 phase in its anatase form. The dielectric constant of the films is independent of annealing temperature but the leakage current density improves by one order of magnitude with every 100 °C increase in annealing temperature.

  7. Charge Transfer-Induced Molecular Hole Doping into Thin Film of Metal-Organic Frameworks.

    PubMed

    Lee, Deok Yeon; Kim, Eun-Kyung; Shrestha, Nabeen K; Boukhvalov, Danil W; Lee, Joong Kee; Han, Sung-Hwan

    2015-08-26

    Despite the highly porous nature with significantly large surface area, metal-organic frameworks (MOFs) can be hardly used in electronic and optoelectronic devices due to their extremely poor electrical conductivity. Therefore, the study of MOF thin films that require electron transport or conductivity in combination with the everlasting porosity is highly desirable. In the present work, thin films of Co3(NDC)3DMF4 MOFs with improved electronic conductivity are synthesized using layer-by-layer and doctor blade coating techniques followed by iodine doping. The as-prepared and doped films are characterized using FE-SEM, EDX, UV/visible spectroscopy, XPS, current-voltage measurement, photoluminescence spectroscopy, cyclic voltammetry, and incident photon to current efficiency measurements. In addition, the electronic and semiconductor properties of the MOF films are characterized using Hall Effect measurement, which reveals that, in contrast to the insulator behavior of the as-prepared MOFs, the iodine doped MOFs behave as a p-type semiconductor. This is caused by charge transfer-induced hole doping into the frameworks. The observed charge transfer-induced hole doping phenomenon is also confirmed by calculating the densities of states of the as-prepared and iodine doped MOFs based on density functional theory. Photoluminescence spectroscopy demonstrates an efficient interfacial charge transfer between TiO2 and iodine doped MOFs, which can be applied to harvest solar radiations. PMID:26226050

  8. Advanced thin film thermocouples

    NASA Astrophysics Data System (ADS)

    Kreider, K. G.; Semancik, S.; Olson, C.

    1984-10-01

    The fabrication, materials characterization, and performance of thin film platinum rhodium thermocouples on gas turbine alloys was investigated. The materials chosen for the study were the turbine blade alloy systems MAR M200+Hf with NiCoCrAlY and FeCrAlY coatings, and vane alloy systems MAR M509 with FeCrAlY. Research was focussed on making improvements in the problem areas of coating substrate stability, adhesion, and insulation reliability and durability. Diffusion profiles between the substrate and coating with and without barrier coatings of Al2O3 are reported. The relationships between fabrication parameters of thermal oxidation and sputtering of the insulator and its characterization and performance are described. The best thin film thermocouples were fabricated with the NiCoCrAlY coatings which were thermally oxidized and sputter coated with Al2O3.

  9. Advanced thin film thermocouples

    NASA Technical Reports Server (NTRS)

    Kreider, K. G.; Semancik, S.; Olson, C.

    1984-01-01

    The fabrication, materials characterization, and performance of thin film platinum rhodium thermocouples on gas turbine alloys was investigated. The materials chosen for the study were the turbine blade alloy systems MAR M200+Hf with NiCoCrAlY and FeCrAlY coatings, and vane alloy systems MAR M509 with FeCrAlY. Research was focussed on making improvements in the problem areas of coating substrate stability, adhesion, and insulation reliability and durability. Diffusion profiles between the substrate and coating with and without barrier coatings of Al2O3 are reported. The relationships between fabrication parameters of thermal oxidation and sputtering of the insulator and its characterization and performance are described. The best thin film thermocouples were fabricated with the NiCoCrAlY coatings which were thermally oxidized and sputter coated with Al2O3.

  10. Polycrystalline thin film materials and devices. Annual subcontract report, 16 January 1990--15 January 1991

    SciTech Connect

    Baron, B.N.; Birkmire, R.W.; Phillips, J.E.; Shafarman, W.N.; Hegedus, S.S.; McCandless, B.E.

    1991-11-01

    Results and conclusion of Phase I of a multi-year research program on polycrystalline thin film solar cells are presented. The research comprised investigation of the relationships among processing, materials properties and device performance of both CuInSe{sub 2} and CdTe solar cells. The kinetics of the formation of CuInSe{sub 2} by selenization with hydrogen selenide was investigated and a CuInSe{sub 2}/CdS solar cell was fabricated. An alternative process involving the reaction of deposited copper-indium-selenium layers was used to obtain single phase CuInSe{sub 2} films and a cell efficiency of 7%. Detailed investigations of the open circuit voltage of CuInSe{sub 2} solar cells showed that a simple Shockley-Read-Hall recombination mechanism can not account for the limitations in open circuit voltage. Examination of the influence of CuInSe{sub 2} thickness on cell performance indicated that the back contact behavior has a significant effect when the CuInSe{sub 2} is less than 1 micron thick. CdTe/CdS solar cells with efficiencies approaching 10% can be repeatedly fabricated using physical vapor deposition and serial post deposition processing. The absence of moisture during post deposition was found to be critical. Improvements in short circuit current of CdTe solar cells to levels approaching 25 mA/cm{sup 2} are achievable by making the CdS window layer thinner. Further reductions in the CdS window layer thickness are presently limited by interdiffusion between the CdS and the CdTe. CdTe/CdS cells stored without protection from the atmosphere were found to degrade. The degradation was attributed to the metal contact. CdTe cells with ZnTe:Cu contacts to the CdTe were found to be more stable than cells with metal contacts. Analysis of current-voltage and spectral response of CdTe/CdS cells indicates the cell operates as a p-n heterojunction with the diode current dominated by SRH recombination in the junction region of the CdTe.

  11. Device and material characterization and analytic modeling of amorphous silicon thin film transistors

    NASA Astrophysics Data System (ADS)

    Slade, Holly Claudia

    Hydrogenated amorphous silicon thin film transistors (TFTs) are now well-established as switching elements for a variety of applications in the lucrative electronics market, such as active matrix liquid crystal displays, two-dimensional imagers, and position-sensitive radiation detectors. These applications necessitate the development of accurate characterization and simulation tools. The main goal of this work is the development of a semi- empirical, analytical model for the DC and AC operation of an amorphous silicon TFT for use in a manufacturing facility to improve yield and maintain process control. The model is physically-based, in order that the parameters scale with gate length and can be easily related back to the material and device properties. To accomplish this, extensive experimental data and 2D simulations are used to observe and quantify non- crystalline effects in the TFTs. In particular, due to the disorder in the amorphous network, localized energy states exist throughout the band gap and affect all regimes of TFT operation. These localized states trap most of the free charge, causing a gate-bias-dependent field effect mobility above threshold, a power-law dependence of the current on gate bias below threshold, very low leakage currents, and severe frequency dispersion of the TFT gate capacitance. Additional investigations of TFT instabilities reveal the importance of changes in the density of states and/or back channel conduction due to bias and thermal stress. In the above threshold regime, the model is similar to the crystalline MOSFET model, considering the drift component of free charge. This approach uses the field effect mobility to take into account the trap states and must utilize the correct definition of threshold voltage. In the below threshold regime, the density of deep states is taken into account. The leakage current is modeled empirically, and the parameters are temperature dependent to 150oC. The capacitance of the TFT can be

  12. Nucleation and stochiometry dependence of rutile-TiO2 thin films grown by plasma-assisted molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Constantin, Costel; Sun, Kai; Feenstra, R. M.

    2008-03-01

    Considerable interest has been shown of late in transition-metal oxides. One case is the titanium dioxide system, which can have applications as a high-k dielectric gate insulator for Si-based devicesootnotetextZ. J. Luo et al., Appl. Phys. Lett. 79, 2803. In this study, rutile-TiO2 thin films were grown on GaN(0001) substrates by oxygen plasma-assisted molecular beam epitaxy. Two sets of films were grown, one in which the initial GaN surface is prepared WITH the pseudo 1x1 Ga-rich surface reconstruction, and the other set, WITHOUT the pseudo 1x1. On top of these two type of surfaces, the rutile-TiO2 thin films were grown at Ts˜ 600 ^oC, and with a thickness ˜ 40 - 50 nm. During growth, reflection high-energy electron diffraction indicated a reversible stoichiometry transition from O-rich to Ti-rich growth. Post-growth x-ray diffraction measurements performed on the samples WITHOUT the GaN pseudo 1x1, show the presence of additional peaks at 2θ = 52.9^o, which implies the existence of additional phases. In addition, the high-resolution transmission electron microscopy performed on these samples show a high degree of disorder, as compared to the samples prepared WITH the pseudo 1x1. Work supported by ONR.

  13. Effect of twin boundary on nanoimprint process of bicrystal Al thin film studied by molecular dynamics simulation

    NASA Astrophysics Data System (ADS)

    Xie, Yue-Hong; Xu, Jian-Gang; Song, Hai-Yang; Zhang, Yun-Guang

    2015-02-01

    The effects of a twin boundary (TB) on the mechanical properties of two types of bicrystal Al thin films during the nanoimprint process are investigated by using molecular dynamics simulations. The results indicate that for the TB direction parallel to the imprinting direction, the yield stress reaches the maximum for the initial dislocation nucleation when the mould directly imprints to the TB, and the yield stress first decreases with the increase of the marker interval and then increases. However, for the TB direction perpendicular to the imprinting direction, the effect of the TB location to the imprinting forces is very small, and the yield stress is greater than that with the TB direction parallel to the imprinting direction. The results also demonstrate that the direction of the slip dislocations and the deformation of the thin film caused by spring-back are different due to various positions and directions of the TB. Project supported by the National Natural Science Foundation of China (Grant No. 10902083), the Program for New Century Excellent Talent in University of Ministry of Education of China (Grant No. NCET-12-1046), the Program for New Scientific and Technological Star of Shaanxi Province, China (Grant No. 2012KJXX-39), and the Program for Natural Science Basic Research Plan in Shaanxi Province, China (Grant No. 2014JQ1036).

  14. Maximizing the dielectric response of molecular thin films via quantum chemical design.

    PubMed

    Heitzer, Henry M; Marks, Tobin J; Ratner, Mark A

    2014-12-23

    Developing high-capacitance organic gate dielectrics is critical for advances in electronic circuitry based on unconventional semiconductors. While high-dielectric constant molecular substances are known, the mechanism of dielectric response and the fundamental chemical design principles are not well understood. Using a plane-wave density functional theory formalism, we show that it is possible to map the atomic-scale dielectric profiles of molecule-based materials while capturing important bulk characteristics. For molecular films, this approach reveals how basic materials properties such as surface coverage density, molecular tilt angle, and π-system planarity can dramatically influence dielectric response. Additionally, relatively modest molecular backbone and substituent variations can be employed to substantially enhance film dielectric response. For dense surface coverages and proper molecular alignment, conjugated hydrocarbon chains can achieve dielectric constants of >8.0, more than 3 times that of analogous saturated chains, ∼2.5. However, this conjugation-related dielectric enhancement depends on proper molecular orientation and planarization, with enhancements up to 60% for proper molecular alignment with the applied field and an additional 30% for conformations such as coplanarity in extended π-systems. Conjugation length is not the only determinant of dielectric response, and appended polarizable high-Z substituents can increase molecular film response more than 2-fold, affording estimated capacitances of >9.0 μF/cm2. However, in large π-systems, polar substituent effects are substantially attenuated. PMID:25415650

  15. High mobility n-type organic thin-film transistors deposited at room temperature by supersonic molecular beam deposition

    SciTech Connect

    Chiarella, F. Barra, M.; Ciccullo, F.; Cassinese, A.; Toccoli, T.; Aversa, L.; Tatti, R.; Verucchi, R.

    2014-04-07

    In this paper, we report on the fabrication of N,N′-1H,1H-perfluorobutil dicyanoperylenediimide (PDIF-CN{sub 2}) organic thin-film transistors by Supersonic Molecular Beam Deposition. The devices exhibit mobility up to 0.2 cm{sup 2}/V s even if the substrate is kept at room temperature during the organic film growth, exceeding by three orders of magnitude the electrical performance of those grown at the same temperature by conventional Organic Molecular Beam Deposition. The possibility to get high-mobility n-type transistors avoiding thermal treatments during or after the deposition could significantly extend the number of substrates suitable to the fabrication of flexible high-performance complementary circuits by using this compound.

  16. Characterization of the non-uniform reaction in chemically-amplified calix[4]resorcinarene molecular resist thin films

    SciTech Connect

    Prabhu, Vivek M.; Kang, Shuhui; Kline, R. Joseph; DeLongchamp, Dean M.; Fischer, Daniel A.; Wu, Wen-li; Satija, Sushil K.; Bonnesen, Peter V; Sha, Jing; Ober, Christoper K.

    2011-01-01

    The ccc stereoisomer-purified tert-butoxycarbonyloxy (t-Boc) protected calix[4]resorcinarene molecular resists blended with photoacid generator exhibit a non-uniform photoacid catalyzed reaction in thin films. The surface displays a reduced reaction extent, compared to the bulk, with average surface-layer thickness (7.0 1.8) nm determined by neutron reflectivity with deuterium-labeled t-Boc groups. Ambient impurities (amines and organic bases) are known to quench surface reactions and contribute, but grazing incidence X-ray diffraction shows an additional effect that the protected molecular resist are preferentially oriented at the surface, while the bulk of the film displayed diffuse scattering representative of amorphous packing. The surface deprotection reaction and presence of photoacid was quantified by near-edge X-ray absorption fine structure measurements.

  17. Precision Photothermal Annealing of Nanoporous Gold Thin Films for the Microfabrication of a Single-chip Material Libraries

    SciTech Connect

    Harris, C. D.; Shen, N.; Rubenchik, A.; Demos, S. G.; Matthews, M. J.

    2015-06-30

    Single-chip material libraries of thin films of nanostructured materials are a promising approach for high throughput studies of structure-property relationship in the fields of physics and biology. Nanoporous gold (np-Au), produced by an alloy corrosion process, is a nanostructured material of specific interest in both these fields. One attractive property of np-Au is its self-similar coarsening behavior by thermally induced surface diffusion. However, traditional heat application techniques for the modification of np-Au are bulk processes that cannot be used to generate a library of different pore sizes on a single chip. Laser micromachining offers an attractive solution to this problem by providing a means to apply energy with high spatial and temporal resolution. In the present study we use finite element multiphysics simulations to predict the effects of laser mode (continuous-wave vs. pulsed) and supporting substrate thermal conductivity on the local np-Au film temperatures during photothermal annealing and subsequently investigate the mechanisms by which the np-Au network is coarsening. Our simulations predict that continuous-wave mode laser irradiation on a silicon supporting substrate supports the widest range of morphologies that can be created through the photothermal annealing of thin film np-Au. Using this result we successfully fabricate a single-chip material library consisting of 81 np-Au samples of 9 different morphologies for use in increased throughput material interaction studies.

  18. Toward High Performance Integrated Semiconductor Micro and Nano Lasers Enabled by Transparent Conducting Materials: from Thick Structure to Thin Film

    NASA Astrophysics Data System (ADS)

    Ou, Fang

    Integrated semiconductor lasers working at the wavelength around 1.3 microm and 1.55 microm are of great interest for the research of photonic integrated circuit (PIC) since they are the crucial components for optical communications and many other applications. To satisfy the requirement of the next generation optical communication and computing systems, integrated semiconductor lasers are expected to have high device performance like very low lasing threshold, high output powers, high speed and possibility of being integrated with electronics. This dissertation focuses on the design and realization of InP based high performance electrically pumped integrated semiconductor lasers. In the dissertation, we first design the tall structure based electrically pumped integrated micro-lasers. Those lasers are capable of giving >10 mW output power with a moderate low threshold current density (0.5--5 kA/cm 2). Besides, a new enhanced radiation loss based coupler design is demonstrated to realize single directional output for curvilinear cavities. Second, the thin film structure based integrated semiconductor laser designs are proposed. Both structures use the side conduction geometry to enable the electrical injection into the thin film laser cavity. The performance enhancement of the thin film structure based lasers is analyzed compared to the tall structure. Third, we investigate the TCO materials. CdO deposited by PLD and In 2O3 deposited by IAD are studied from aspects of their physical, optical and electrical properties. Those materials can give a wide range of tunability in their conductivity (1--5000 S/cm) and optical transparency (loss 200--5000 cm-1), which is of great interest in realizing novel nanophotonic devices. In addition, the electrical contact properties of those materials to InP are also studied. Experiment result shows that both CdO and In2O3 can achieve good ohmic contact to n-InP with contact resistance as low as 10-6O·cm 2. At last, we investigate

  19. Development of High Band Gap Absorber and Buffer Materials for Thin Film Solar Cell Applications

    NASA Astrophysics Data System (ADS)

    Dwyer, Dan

    2011-12-01

    CuInGaSe2 (CIGS) device efficiencies are the highest of the thin film absorber materials (vs. CdTe, alpha-Si, CuInSe2). However, the band gap of the highest efficiency CIGS cells deviates from the expected ideal value predicted by models [1]. Widening the band gap to the theoretically ideal value is one way to increase cell efficiencies. Widening the band gap can be accomplished in two ways; by finding a solution to the Ga-related defects which limit the open circuit voltage at high Ga ratios, or by utilizing different elemental combinations to form an alternative high band gap photoactive Cu-chalcopyrite (which includes any combination of the cations Cu, Al, Ga, and In along with the anions S, Se, and Te). This thesis focuses on the second option, substituting aluminum for gallium in the chalcopyrite lattice to form a CuInAlSe2 (CIAS) film using a sputtering and selenization approach. Both sequential and co-sputtering of metal precursors is performed. Indium was found to be very mobile during both sputtering processes, with a tendency to diffuse to the film surface even when deposited as the base layer in a sequential sputtering process. Elemental diffusion was controlled to a degree using thicker Cu top layer in co-sputtering. The greater thermal conductivity of stainless steel foil (16 W/mK) vs. glass (0.9-1.3 W/mK) can also be used to limit indium diffusion, by keeping the substrate cooler during sputtering. In both sputtering methods aluminum is deposited oxygen-free by capping the film with a Cu capping layer in combination with controlling the indium diffusion. Selenization of metal precursor films is completed using two different techniques. The first is a thermal evaporation approach from a heated box source (method 1 -- reactive thermal evaporation (RTE-Se)). The second is batch selenization using a heated tube furnace (method 2 -- batch selenization). Some batch selenized precursors were capped with ˜ 1mum of selenium. In both selenization methods

  20. Growth of Cr2CoGa and inverse Heusler thin films using Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Jamer, Michelle; Decapua, Matthew; Player, Gabriel; Heiman, Don

    Theoretical calculations have predicted the existence of inverse Heusler compounds that exhibit zero-moment magnetization while retaining their half-metallicity. These unique compounds have been labeled spin gapless semiconductors (SGS), where the density of states (DOS) can behave as a half-metal or gapless semiconductor. There is a special interest for zero-moment SGS compounds since traditional antiferromagnets cannot be spin-polarized. Such compounds are experimentally attractive for future spintronic devices due to their large magnetic transition temperature (400-800 K). This work focuses on zero-moment inverse Heusler compounds including Cr2CoGa and Mn3Al. Thin films have been grown using MBE and their magnetic, structural, and electrical properties of these compounds have been characterized by various techniques, including XMCD and magnetometry. The atomic moments are found to be large, but significant cancellations lead to small average moments. Supported by NSF Grant ECCS-1402738.

  1. Preparation and characterization of conducting thin films of molecular organic conductors (TTF-TCNQ)

    NASA Astrophysics Data System (ADS)

    Figueras, A.; Garelik, S.; Caro, J.; Cifré, J.; Veciana, J.; Rovira, C.; Ribera, E.; Canadell, E.; Seffar, A.; Fontcuberta, J.

    1996-09-01

    Tetrathiafulvalene (TTF) and tetracyanoquinodimethane (TCNQ) form a charge-transfer complex which exhibits a high electric conductivity. In this work TTF-TCNQ thin films were prepared by CVD (chemical vapour deposition) at low pressure and using TTF and TCNQ as precursors. Substrates were common glass. These layers exhibit preferential orientation in the crystallization along the [001] direction and have a room temperature conductivity ranged between 6-24 Ω -1 cm -1. Whereas at low temperatures (smaller than a transition temperature Tp) they display a highly resistive semiconductor-like behaviour, above Tp the conductivity exhibits a small effective activation energy. Tp ≈ 50-60 K is interpreted as a signature of the Peierls transition. The evaluation of the stoichiometry was performed by UV-visible spectroscopy. The morphology and structure of the layers were also studied.

  2. Ion and electron beam processing of condensed molecular solids to form thin films

    SciTech Connect

    Ruckman, M.W.; Strongin, M.; Mowlem, J.K.; Moore, J.F.; Strongin, D.R.

    1992-12-31

    Electron and ion beams can be used to deposit thin films and etch surfaces using gas phase precursors. However, the generation of undesirable gas phase products and the diffusion of the reactive species beyond the region irradiated by the electron or ion beam can limit selectivity. In this paper, the feasibility of processing condensed precursors such as diborane, tri-methyl aluminum, ammonia and water at 78 K with low energy ( 100--1000 eV) electron and ion beams (Ar{sup +}, N{sub 2}{sup +} and H{sub 2}{sup +}) ranging in current density from 50 nA to several {mu}a per cm{sup 2} is examined. It was found that boron, boron nitride and stoichiometric aluminum oxide films could be deposited from the condensed volatile; species using charged particle beams and some of the physical and chemical aspects and limitations of this new technique are discussed.

  3. Ion and electron beam processing of condensed molecular solids to form thin films

    SciTech Connect

    Ruckman, M.W.; Strongin, M. ); Mowlem, J.K.; Moore, J.F.; Strongin, D.R. . Dept. of Chemistry)

    1992-01-01

    Electron and ion beams can be used to deposit thin films and etch surfaces using gas phase precursors. However, the generation of undesirable gas phase products and the diffusion of the reactive species beyond the region irradiated by the electron or ion beam can limit selectivity. In this paper, the feasibility of processing condensed precursors such as diborane, tri-methyl aluminum, ammonia and water at 78 K with low energy ( 100--1000 eV) electron and ion beams (Ar[sup +], N[sub 2][sup +] and H[sub 2][sup +]) ranging in current density from 50 nA to several [mu]a per cm[sup 2] is examined. It was found that boron, boron nitride and stoichiometric aluminum oxide films could be deposited from the condensed volatile; species using charged particle beams and some of the physical and chemical aspects and limitations of this new technique are discussed.

  4. Plasma-based ion implantation: a valuable technology for the elaboration of innovative materials and nanostructured thin films

    NASA Astrophysics Data System (ADS)

    Vempaire, D.; Pelletier, J.; Lacoste, A.; Béchu, S.; Sirou, J.; Miraglia, S.; Fruchart, D.

    2005-05-01

    Plasma-based ion implantation (PBII), invented in 1987, can now be considered as a mature technology for thin film modification. After a brief recapitulation of the principle and physics of PBII, its advantages and disadvantages, as compared to conventional ion beam implantation, are listed and discussed. The elaboration of thin films and the modification of their functional properties by PBII have already been achieved in many fields, such as microelectronics (plasma doping/PLAD), biomaterials (surgical implants, bio- and blood-compatible materials), plastics (grafting, surface adhesion) and metallurgy (hard coatings, tribology), to name a few. The major advantages of PBII processing lie, on the one hand, in its flexibility in terms of ion implantation energy (from 0 to 100 keV) and operating conditions (plasma density, collisional or non-collisional ion sheath), and, on the other hand, in the easy transferrability of processes from the laboratory to industry. The possibility of modifying the composition and physical nature of the films, or of drastically changing their physical properties over several orders of magnitude makes this technology very attractive for the elaboration of innovative materials, including metastable materials, and the realization of micro- or nanostructures. A review of the state of the art in these domains is presented and illustrated through a few selected examples. The perspectives opened up by PBII processing, as well as its limitations, are discussed.

  5. Molecular beam deposition of Dy sub 1 Ba sub 2 Cu sub 3 O sub 7 minus. delta. (001) high-temperature superconductor thin films

    SciTech Connect

    Bae, J.; Seshadri, P.; Choudhary, K.M. )

    1992-03-01

    Epitaxial Dy{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7{minus}{delta}}(001) high-temperature superconductor thin films on LaAlO{sub 3} substrates have been prepared by coevaporation of Dy, BaF{sub 2}, and Cu and postannealing. The vapors in desired ratio were evaporated from effusion cells in a miniature molecular beam deposition system. The films show critical transition temperature ({ital T}{sub {ital c},0}) of 89.5{plus minus}0.5 K. During process development it was found that single phase Dy{sub 1+x}Ba{sub 2{minus}x}Cu{sub 3}O{sub y}(001) thin films can be grown ({ital x}=0 to 0.3). Their electrical properties were useful in calibration of quartz crystal thin film thickness monitor (FTM) for determination of relationships between the actual vapor arrival rate (flux) and FTM reading.

  6. Epitaxial growth of SrTiO{sub 3} thin film on Si by laser molecular beam epitaxy

    SciTech Connect

    Zhou, X. Y.; Miao, J.; Dai, J. Y.; Chan, H. L. W.; Choy, C. L.; Wang, Y.; Li, Q.

    2007-01-01

    SrTiO{sub 3} thin films have been deposited on Si (001) wafers by laser molecular beam epitaxy using an ultrathin Sr layer as the template. X-ray diffraction measurements indicated that SrTiO{sub 3} was well crystallized and epitaxially aligned with Si. Cross-sectional observations in a transmission electron microscope revealed that the SrTiO{sub 3}/Si interface was sharp, smooth, and fully crystallized. The thickness of the Sr template was found to be a critical factor that influenced the quality of SrTiO{sub 3} and the interfacial structure. Electrical measurements revealed that the SrTiO{sub 3} film was highly resistive.

  7. Polycrystalline thin film photovoltaics

    NASA Astrophysics Data System (ADS)

    Zweibel, K.; Ullal, H. S.; Mitchell, R. L.

    Significant progress has recently been made towards improving the efficiencies of polycrystalline thin-film solar cells and modules using CuInSe2 and CdTe. The history of using CuInSe2 and CdTe for solar cells is reviewed. Initial outdoor stability tests of modules are encouraging. Progress in semiconductor deposition techniques has also been substantial. Both CuInSe2 and CdTe are positioned for commercialization during the 1990s. The major participants in developing these materials are described. The US DOE/SERI (Solar Energy Research Institute) program recognizes the rapid progress and important potential of polycrystalline thin films to meet ambitious cost and performance goals. US DOE/SERI is in the process of funding an initiative in this area with the goal of ensuring US leadership in the development of these technologies. The polycrystalline thin-film module development initiative, the modeling and stability of the devices, and health and safety issues are discussed.

  8. Thin film scintillators

    NASA Astrophysics Data System (ADS)

    McDonald, Warren; McKinney, George; Tzolov, Marian

    2015-03-01

    Scintillating materials convert energy flux (particles or electromagnetic waves) into light with spectral characteristic matching a subsequent light detector. Commercial scintillators such as yttrium aluminum garnet (YAG) and yttrium aluminum perovskite (YAP) are commonly used. These are inefficient at lower energies due to the conductive coating present on their top surface, which is needed to avoid charging. We hypothesize that nano-structured thin film scintillators will outperform the commercial scintillators at low electron energies. We have developed alternative thin film scintillators, zinc tungstate and zinc oxide, which show promise for higher sensitivity to lower energy electrons since they are inherently conductive. Zinc tungstate films exhibit photoluminescence quantum efficiency of 74%. Cathodoluminescence spectroscopy was applied in transmission and reflection geometries. The comparison between the thin films and the YAG and YAP commercial scintillators shows much higher light output from the zinc tungstate and zinc oxide at electron energies less than 5 keV. Our films were integrated in a backscattered electron detector. This detector delivers better images than an identical detector with commercial YAG scintillator at low electron energies. Dr. Nicholas Barbi from PulseTor LLC, Dr. Anura Goonewardene, NSF Grants: #0806660, #1058829, #0923047.

  9. Development of electron reflection suppression materials for improved thermionic energy converter performance using thin film deposition techniques

    SciTech Connect

    Islam, Mohammad; Inal, Osman T.; Luke, James R.

    2006-10-15

    Nonideal electrode surfaces cause significant degree of electron reflection from collector during thermionic converter operation. The effect of the collector surface structure on the converter performance was assessed through the development of several electron reflection suppression materials using various thin film deposition techniques. The double-diode probe method was used to compare the J-V characteristics of converters with polished and modified collector surfaces for emitter temperature and cesium vapor pressure in the ranges of 900-2000 K and 0.02-1.5 torr, respectively. The coadsorption of cesium and oxygen with respective partial vapor pressures of {approx}1.27 torr and a few microtorrs reduced the emitter work function to a minimum value of 0.99 eV. It was found that the collector surfaces with matte black appearance such as platinum black, voided nickel from radio-frequency plasma sputtering, and etched electroless Ni-P with craterlike pore morphology exhibited much better performance compared with polished collector surface. For these thin films, the increase in the maximum output voltage was up to 2.0 eV. For optimum performance with minimum work function and maximum saturation emission current density, the emitter temperature was in the range of 1100-1500 K, depending on the collector surface structure. The use of these materials in cylindrical converter design and/or in combination with hybrid mode triode configuration holds great potential in low and medium scale power generators for commercial use.

  10. Glass Transition Temperature of Polyetherimide: Relationship between Thin Films and Nanoporous Materials

    NASA Astrophysics Data System (ADS)

    Ozisik, Rahmi; Liu, Tong; Siegel, Richard W.

    2006-03-01

    The glass transition temperature (Tg) of nanoporous polyetherimide (PEI) was investigated using differential scanning calorimetry. Nanosized pores were created by spin coating a solution of PEI and polycaprolactone-diol (PCLD) in their common solvent dichloromethane. The nanoporous structure was created by fast phase separation during spin coating and subsequent removal of PCLD with acetone. Atomic force microscopy, scanning electron microscopy and statistical methods were used to characterize the pore structure. The glass transition temperatures of both the thin PEI films and nanoporous PEI samples were lower than that of bulk PEI. The Tg of nanoporous PEI was found to depend strongly on pore volume fraction. A Monte Carlo simulation was performed to investigate the relationship between thin films and nanoporous systems. The distribution of nearest neighbor distances (h) were obtained from the Monte Carlo simulation, which was biased to create the pore size distribution obtained from experiments. Various moments of h was calculated and used to compare the findings to thin film data.

  11. Molecular solution approach to synthesize electronic quality Cu2ZnSnS4 thin films.

    PubMed

    Yang, Wenbing; Duan, Hsin-Sheng; Cha, Kitty C; Hsu, Chia-Jung; Hsu, Wan-Ching; Zhou, Huanping; Bob, Brion; Yang, Yang

    2013-05-01

    Successful implementation of molecular solution processing from a homogeneous and stable precursor would provide an alternative, robust approach to process multinary compounds compared with physical vapor deposition. Targeting deposition of chemically clear, high quality crystalline films requires specific molecular structure design and solvent selection. Hydrazine (N2H4) serves as a unique and powerful medium, particularly to incorporate selected metallic elements and chalcogens into a stable solution as metal chalcogenide complexes (MCC). However, not all the elements and compounds can be easily dissolved. In this manuscript, we demonstrate a paradigm to incorporate previously insoluble transitional-metal elements into molecular solution as metal-atom hydrazine/hydrazine derivative complexes (MHHD), as exemplified by dissolving of the zinc constituent as Zn(NH2NHCOO)2(N2H4)2. Investigation into the evolution of molecular structure reveals the hidden roadmap to significantly enrich the variety of building blocks for soluble molecule design. The new category of molecular structures not only set up a prototype to incorporate other elements of interest but also points the direction for other compatible solvent selection. As demonstrated from the molecular precursor combining Sn-/Cu-MCC and Zn-MHHD, an ultrathin film of copper zinc tin sulfide (CZTS) was deposited. Characterization of a transistor based on the CZTS channel layer shows electronic properties comparable to CuInSe2, confirming the robustness of this molecular solution processing and the prospect of earth abundant CZTS for next generation photovoltaic materials. This paradigm potentially outlines a universal pathway, from individual molecular design using selected chelated ligands and combination of building blocks in a simple and stable solution to fundamentally change the way multinary compounds are processed. PMID:23581974

  12. Atmospheric-Pressure-Spray, Chemical- Vapor-Deposited Thin-Film Materials Being Developed for High Power-to- Weight-Ratio Space Photovoltaic Applications

    NASA Technical Reports Server (NTRS)

    Hepp, Aloysius F.; Harris, Jerry D.; Raffaelle, Ryne P.; Banger, Kulbinder K.; Smith, Mark A.; Cowen, Jonathan E.

    2001-01-01

    The key to achieving high specific power (watts per kilogram) space photovoltaic arrays is the development of high-efficiency thin-film solar cells that are fabricated on lightweight, space-qualified substrates such as Kapton (DuPont) or another polymer film. Cell efficiencies of 20 percent air mass zero (AM0) are required. One of the major obstacles to developing lightweight, flexible, thin-film solar cells is the unavailability of lightweight substrate or superstrate materials that are compatible with current deposition techniques. There are two solutions for working around this problem: (1) develop new substrate or superstrate materials that are compatible with current deposition techniques, or (2) develop new deposition techniques that are compatible with existing materials. The NASA Glenn Research Center has been focusing on the latter approach and has been developing a deposition technique for depositing thin-film absorbers at temperatures below 400 C.

  13. Development of molecular precursors for deposition of indium sulphide thin film electrodes for photoelectrochemical applications.

    PubMed

    Ehsan, Muhammad Ali; Peiris, T A Nirmal; Wijayantha, K G Upul; Olmstead, Marilyn M; Arifin, Zainudin; Mazhar, Muhammad; Lo, K M; McKee, Vickie

    2013-08-14

    Symmetrical and unsymmetrical dithiocarbamato pyridine solvated and non-solvated complexes of indium(III) with the general formula [In(S2CNRR')3]·n(py) [where py = pyridine; R,R' = Cy, n = 2 (1); R,R' = (i)Pr, n = 1.5 (2); NRR' = Pip, n = 0.5 (3) and R = Bz, R' = Me, n = 0 (4)] have been synthesized. The compositions, structures and properties of these complexes have been studied by means of microanalysis, IR and (1)H-NMR spectroscopy, X-ray single crystal and thermogravimetric (TG/DTG) analyses. The applicability of these complexes as single source precursors (SSPs) for the deposition of β-In2S3 thin films on fluorine-doped SnO2 (FTO) coated conducting glass substrates by aerosol-assisted chemical vapour deposition (AACVD) at temperatures of 300, 350 and 400 °C is studied. All films have been characterized by powder X-ray diffraction (PXRD) and energy dispersive X-ray analysis (EDX) for the detection of phase and stoichiometry of the deposit. Scanning electron microscopy (SEM) studies reveal that precursors (1)-(4), irrespective of different metal ligand design, generate comparable morphologies of β-In2S3 thin films at different temperatures. Direct band gap energies of 2.2 eV have been estimated from the UV-vis spectroscopy for the β-In2S3 films fabricated from precursors (1) and (4). The photoelectrochemical (PEC) properties of β-In2S3 were confirmed by recording the current-voltage plots under light and dark conditions. The plots showed anodic photocurrent densities of 1.25 and 0.65 mA cm(-2) at 0.23 V vs. Ag/AgCl for the β-In2S3 films made at 400 and 350 °C from the precursors (1) and (4), respectively. The photoelectrochemical performance indicates that the newly synthesised precursors are highly useful in fabricating β-In2S3 electrodes for solar energy harvesting and optoelectronic application. PMID:23787951

  14. On the Sn loss from thin films of the material system Cu-Zn-Sn-S in high vacuum

    SciTech Connect

    Weber, A.; Mainz, R.; Schock, H. W.

    2010-01-15

    In this paper the Sn loss from thin films of the material system Cu-Zn-Sn-S and the subsystems Cu-Sn-S and Sn-S in high vacuum is investigated. A combination of in situ x-ray diffractometry and x-ray fluorescence (XRF) at a synchrotron light source allowed identifying phases, which tend to decompose and evaporate a Sn-containing compound. On the basis of the XRF results a quantification of the Sn loss from the films during annealing experiments is presented. It can be shown that the evaporation rate from the different phases decreases according to the order SnS{yields}Cu{sub 2}SnS{sub 3}{yields}Cu{sub 4}SnS{sub 4}{yields}Cu{sub 2}ZnSnS{sub 4}. The phase SnS is assigned as the evaporating compound. The influence of an additional inert gas component on the Sn loss and on the formation of Cu{sub 2}ZnSnS{sub 4} thin films is discussed.

  15. Molecular fouling resistance of zwitterionic and amphiphilic initiated chemically vapor-deposited (iCVD) thin films

    SciTech Connect

    Yang, R; Goktekin, E; Wang, MH; Gleason, KK

    2014-08-08

    Biofouling is a universal problem in various applications ranging from water purification to implantable biomedical devices. Recent advances in surface modification have created a rich library of antifouling surface chemistries, many of which can be categorized into one of the two groups: hydrophilic surfaces or amphiphilic surfaces. We report the straightforward preparation of antifouling thin film coatings in both categories via initiated chemical vapor deposition. A molecular force spectroscopy-based method is demonstrated as a rapid and quantitative assessment tool for comparing the differences in antifouling characteristics. The fouling propensity of single molecules, as opposed to bulk protein solution or bacterial culture, is assessed. This method allows for the interrogation of molecular interaction without the complication resulted from protein conformational change or micro-organism group interactions. The molecular interaction follows the same trend as bacterial adhesion results obtained previously, demonstrating that molecular force probe is a valid method for the quantification and mechanistic examination of fouling. In addition, the molecular force spectroscopy-based method is able to distinguish differences in antifouling capability that is not resolvable by traditional static protein adsorption tests. To lend further insight into the intrinsic fouling resistance of zwitterionic and amphiphilic surface chemistries, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, advancing and receding water contact angles, and atomic force microscopy are used to elucidate the film properties that are relevant to their antifouling capabilities.

  16. Molecular fouling resistance of zwitterionic and amphiphilic initiated chemically vapor-deposited (iCVD) thin films

    SciTech Connect

    Yang, R; Goktekin, E; Wang, MH; Gleason, KK

    2014-01-01

    Biofouling is a universal problem in various applications ranging from water purification to implantable biomedical devices. Recent advances in surface modification have created a rich library of antifouling surface chemistries, many of which can be categorized into one of the two groups: hydrophilic surfaces or amphiphilic surfaces. We report the straightforward preparation of antifouling thin film coatings in both categories via initiated chemical vapor deposition. A molecular force spectroscopy-based method is demonstrated as a rapid and quantitative assessment tool for comparing the differences in antifouling characteristics. The fouling propensity of single molecules, as opposed to bulk protein solution or bacterial culture, is assessed. This method allows for the interrogation of molecular interaction without the complication resulted from protein conformational change or micro-organism group interactions. The molecular interaction follows the same trend as bacterial adhesion results obtained previously, demonstrating that molecular force probe is a valid method for the quantification and mechanistic examination of fouling. In addition, the molecular force spectroscopy-based method is able to distinguish differences in antifouling capability that is not resolvable by traditional static protein adsorption tests. To lend further insight into the intrinsic fouling resistance of zwitterionic and amphiphilic surface chemistries, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, advancing and receding water contact angles, and atomic force microscopy are used to elucidate the film properties that are relevant to their antifouling capabilities.

  17. Realization of Cu-Doped p-Type ZnO Thin Films by Molecular Beam Epitaxy.

    PubMed

    Suja, Mohammad; Bashar, Sunayna B; Morshed, Muhammad M; Liu, Jianlin

    2015-04-29

    Cu-doped p-type ZnO films are grown on c-sapphire substrates by plasma-assisted molecular beam epitaxy. Photoluminescence (PL) experiments reveal a shallow acceptor state at 0.15 eV above the valence band edge. Hall effect results indicate that a growth condition window is found for the formation of p-type ZnO thin films, and the best conductivity is achieved with a high hole concentration of 1.54 × 10(18) cm(-3), a low resistivity of 0.6 Ω cm, and a moderate mobility of 6.65 cm(2) V(-1) s(-1) at room temperature. Metal oxide semiconductor capacitor devices have been fabricated on the Cu-doped ZnO films, and the characteristics of capacitance-voltage measurements demonstrate that the Cu-doped ZnO thin films under proper growth conditions are p-type. Seebeck measurements on these Cu-doped ZnO samples lead to positive Seebeck coefficients and further confirm the p-type conductivity. Other measurements such as X-ray diffraction, X-ray photoelectron, Raman, and absorption spectroscopies are also performed to elucidate the structural and optical characteristics of the Cu-doped p-type ZnO films. The p-type conductivity is explained to originate from Cu substitution of Zn with a valency of +1 state. However, all p-type samples are converted to n-type over time, which is mostly due to the carrier compensation from extrinsic defects of ZnO. PMID:25835032

  18. High-throughput screening of thin-film semiconductor material libraries II: characterization of Fe-W-O libraries.

    PubMed

    Meyer, Robert; Sliozberg, Kirill; Khare, Chinmay; Schuhmann, Wolfgang; Ludwig, Alfred

    2015-04-13

    Metal oxides are promising materials for solar water splitting. To identify suitable materials within the ternary system FeWO, thin-film material libraries with combined thickness and compositional gradients were synthesized by combinatorial reactive magnetron sputtering. These libraries (>1000 different samples) were investigated by means of structural and functional high-throughput characterization techniques to establish correlations between composition, crystallinity, morphology, thickness, and photocurrent density in the compositional range between (Fe6 W94 )Ox and (Fe61 W39 )Ox . In addition to the well-known phase WO3 , the binary phase W5 O14 and the ternary phase Fe2 O6 W show enhanced photoelectrochemical activity. The highest photocurrent density of 65 μA cm(-2) was achieved for the composition (Fe15 W85 )Ox , which contains the W5 O14 phase and has a thickness of 1060 nm. PMID:25727483

  19. Direct bandgap materials based on the thin films of SexTe100 − x nanoparticles

    PubMed Central

    2012-01-01

    In this study, we fabricated thin films of SexTe100 − x (x = 0, 3, 6, 9, 12, and 24) nanoparticles using thermal evaporation technique. The results obtained by X-ray diffraction show that the as-synthesized nanoparticles have polycrystalline structure, but their crystallinity decreases by increasing the concentration of Se. They were found to have direct bandgap (Eg), whose value increases by increasing the Se content. These results are completely different than those obtained in the films of SexTe100 − x microstructure counterparts. Photoluminescence and Raman spectra for these films were also demonstrated. The remarkable results obtained in these nanoparticles specially their controlled direct bandgap might be useful for the development of optical disks and other semiconductor devices. PMID:22978714

  20. Scale Dependence of the Mechanical Properties and Microstructure of Crustaceans Thin Films as Biomimetic Materials

    NASA Astrophysics Data System (ADS)

    Verma, Devendra; Qu, Tao; Tomar, Vikas

    2015-04-01

    The exoskeletons of crustacean species in the form of thin films have been investigated by several researchers to better understand the role played by the exoskeletal structure in affecting the functioning of species such as shrimps, crabs, and lobsters. These species exhibit similar designs in their exoskeleton microstructure, such as a Bouligand pattern (twisted plywood structure), layers of different thickness across cross section, change in mineral content through the layers, etc. Different parts of crustaceans exhibit a significant variation in mechanical properties based on the variation in the above-mentioned parameters. This change in mechanical properties has been analyzed by using imaging techniques such as scanning electron microscopy and energy-dispersive x-ray spectroscopy, and by using mechanical characterization techniques such as nanoindentation and atomic force microscopy. In this article, the design principles of these biological composites are discussed based on two shrimp species: Rimicaris exoculata and Pandalus platyceros.

  1. Direct bandgap materials based on the thin films of Se x Te100 - x nanoparticles

    NASA Astrophysics Data System (ADS)

    Salah, Numan; Habib, Sami S.; Khan, Zishan H.

    2012-09-01

    In this study, we fabricated thin films of Se x Te100 - x ( x = 0, 3, 6, 9, 12, and 24) nanoparticles using thermal evaporation technique. The results obtained by X-ray diffraction show that the as-synthesized nanoparticles have polycrystalline structure, but their crystallinity decreases by increasing the concentration of Se. They were found to have direct bandgap ( E g), whose value increases by increasing the Se content. These results are completely different than those obtained in the films of Se x Te100 - x microstructure counterparts. Photoluminescence and Raman spectra for these films were also demonstrated. The remarkable results obtained in these nanoparticles specially their controlled direct bandgap might be useful for the development of optical disks and other semiconductor devices.

  2. Distance and molecular weight dependence of surface enhanced fluorescence in conjugated polymer thin films

    NASA Astrophysics Data System (ADS)

    Griffo, Michael S.; Carter, Sue A.

    2008-08-01

    Photoluminescence (PL) of poly[2-methoxy-5-(2'-ethylhexyloxy)-p-phenylene vinylene] (MEH-PPV) in the presence of Silver nanoparticles (NP) is studied. The purpose of this research is to understand the PL distance dependence of plasmon-polymer separation and a correlation between the surface enhanced fluorescence (SEF) and polymer molecular weight. Distinct peaks in PL are found for plasmon-polymer separations ranging from near the far field to the near field, under 100 nm. Extinction of the devices shows that changes in absorption cannot explain all enhancement in PL and suggests that a modification of the radiative lifetime is modified. The dependence of the photoluminescence of MEH-PPV on molecular weight shows variation but overall suggests chain length does not affect film quenching. This is largely attributed to the large polydispersity of the polymer materials used.

  3. Analysis of Hard Thin Film Coating

    NASA Technical Reports Server (NTRS)

    Shen, Dashen

    1998-01-01

    MSFC is interested in developing hard thin film coating for bearings. The wearing of the bearing is an important problem for space flight engine. Hard thin film coating can drastically improve the surface of the bearing and improve the wear-endurance of the bearing. However, many fundamental problems in surface physics, plasma deposition, etc, need further research. The approach is using electron cyclotron resonance chemical vapor deposition (ECRCVD) to deposit hard thin film an stainless steel bearing. The thin films in consideration include SiC, SiN and other materials. An ECRCVD deposition system is being assembled at MSFC.

  4. Analysis of Hard Thin Film Coating

    NASA Technical Reports Server (NTRS)

    Shen, Dashen

    1998-01-01

    Marshall Space Flight Center (MSFC) is interested in developing hard thin film coating for bearings. The wearing of the bearing is an important problem for space flight engine. Hard thin film coating can drastically improve the surface of the bearing and improve the wear-endurance of the bearing. However, many fundamental problems in surface physics, plasma deposition, etc, need further research. The approach is using Electron Cyclotron Resonance Chemical Vapor Deposition (ECRCVD) to deposit hard thin film on stainless steel bearing. The thin films in consideration include SiC, SiN and other materials. An ECRCVD deposition system is being assembled at MSFC.

  5. Thin film photovoltaic device

    DOEpatents

    Catalano, Anthony W.; Bhushan, Manjul

    1982-01-01

    A thin film photovoltaic solar cell which utilizes a zinc phosphide semiconductor is of the homojunction type comprising an n-type conductivity region forming an electrical junction with a p-type region, both regions consisting essentially of the same semiconductor material. The n-type region is formed by treating zinc phosphide with an extrinsic dopant such as magnesium. The semiconductor is formed on a multilayer substrate which acts as an opaque contact. Various transparent contacts may be used, including a thin metal film of the same chemical composition as the n-type dopant or conductive oxides or metal grids.

  6. Thin film photovoltaic device

    DOEpatents

    Catalano, A.W.; Bhushan, M.

    1982-08-03

    A thin film photovoltaic solar cell which utilizes a zinc phosphide semiconductor is of the homojunction type comprising an n-type conductivity region forming an electrical junction with a p-type region, both regions consisting essentially of the same semiconductor material. The n-type region is formed by treating zinc phosphide with an extrinsic dopant such as magnesium. The semiconductor is formed on a multilayer substrate which acts as an opaque contact. Various transparent contacts may be used, including a thin metal film of the same chemical composition as the n-type dopant or conductive oxides or metal grids. 5 figs.

  7. Pyrolyzed thin film carbon

    NASA Technical Reports Server (NTRS)

    Tai, Yu-Chong (Inventor); Liger, Matthieu (Inventor); Harder, Theodore (Inventor); Konishi, Satoshi (Inventor); Miserendino, Scott (Inventor)

    2010-01-01

    A method of making carbon thin films comprises depositing a catalyst on a substrate, depositing a hydrocarbon in contact with the catalyst and pyrolyzing the hydrocarbon. A method of controlling a carbon thin film density comprises etching a cavity into a substrate, depositing a hydrocarbon into the cavity, and pyrolyzing the hydrocarbon while in the cavity to form a carbon thin film. Controlling a carbon thin film density is achieved by changing the volume of the cavity. Methods of making carbon containing patterned structures are also provided. Carbon thin films and carbon containing patterned structures can be used in NEMS, MEMS, liquid chromatography, and sensor devices.

  8. Measurement of surface acoustic wave velocity using phase shift mask and application on thin film of thermoelectric material

    NASA Astrophysics Data System (ADS)

    Li, Dongyao; Zhao, Peng; Gunning, Noel; Johnson, David; Zhao, Ji-Cheng; Cahill, David

    2014-03-01

    We describe a convenient approach for measuring the velocity vSAW of surface acoustic waves (SAWs) of the near-surface layer of a material through optical pump-probe measurements and apply this method, in combination with conventional picosecond acoustics, to determine a subset of the elastic constants of thin films of semiconducting misfit layered compounds. SAWs with a wavelength of 700 nm are generated and detected using an elastomeric polydimethylsiloxane (PDMS) phase-shift mask which is fabricated using a commercially-available Si grating as a mold. The velocity of SAWs of [(SnSe)1.04]m[MoSe2]n synthesized by elemental reactants show subtle variations in their elastic constants as a function of m and n. Precise measurements of elastic constants will enable a better understanding of interfacial stiffness in nanoscale multilayers and the effects of phonon focusing on thermal conductivity.

  9. Simple DFT-LSDA modeling of the molecular-like aspects of ultra-thin film properties

    SciTech Connect

    Trickey, S.B.; Mathar, R.J.; Boettger, J.C.

    1996-09-01

    Ordered ultra-thin films (UTF`s) are atomic n-layers (n = 1,2,3,...) with translational symmetry in-plane and molecular-like inter-planar spacings. Though commonly used (especially at relatively large n-values) as models of crystalline surfaces, they are intrinsically interesting and of growing technological significance as the basic building blocks of multi-layer electronic devices. Predicting the structure and properties of even a simple diatomic 1-layer means addressing aspects of molecular binding (and boundary conditions) in the context of an extended, periodically bounded system. At the level of refinement provided by the local spin density approximation to Density Functional Theory, the baseline standard of today`s predictive, chemically specific solid-state calculations, a number of technical and fundamental issues arise. The authors focus on treatment of the isolated atoms, on basis sets, and on numerical precision, as illustrated by the Fe atom and BN 1- and 2-layer calculations. Computational requirements are illustrated by a brief summary of recently completed calculations on crystalline sapphire, {alpha}-Al{sub 2}O{sub 3}, which used the same code.

  10. Molecular dynamics study on the effect of boundary heating rate on the phase change characteristics of thin film liquid

    NASA Astrophysics Data System (ADS)

    Hasan, Mohammad Nasim; Morshed, A. K. M. Monjur; Rabbi, Kazi Fazle; Haque, Mominul

    2016-07-01

    In this study, theoretical investigation of thin film liquid phase change phenomena under different boundary heating rates has been conducted with the help of molecular dynamics simulation. To do this, the case of argon boiling over a platinum surface has been considered. The study has been conducted to get a better understanding of the nano-scale physics of evaporation/boiling for a three phase system with particular emphasis on the effect of boundary heating rate. The simulation domain consisted of liquid and vapor argon atoms placed over a platinum wall. Initially the whole system was brought to an equilibrium state at 90K with the help of equilibrium molecular dynamics and then the temperature of the bottom wall was increased to a higher temperature (250K/130K) over a finite heating period. Depending on the heating period, the boundary heating rate has been varied in the range of 1600×109 K/s to 8×109 K/s. The variations of argon region temperature, pressure, net evaporation number with respect to time under different boundary heating rates have been determined and discussed. The heat fluxes normal to platinum wall for different cases were also calculated and compared with theoretical upper limit of maximum possible heat transfer to elucidate the effect of boundary heating rate.

  11. Thermally driven smoothening of molecular thin films: Structural transitions in n-alkane layers studied in real-time

    NASA Astrophysics Data System (ADS)

    Pithan, Linus; Meister, Eduard; Jin, Chenyu; Weber, Christopher; Zykov, Anton; Sauer, Katrein; Brütting, Wolfgang; Riegler, Hans; Opitz, Andreas; Kowarik, Stefan

    2015-10-01

    We use thermal annealing to improve smoothness and to increase the lateral size of crystalline islands of n-tetratetracontane (TTC, C44H90) films. With in situ x-ray diffraction, we find an optimum temperature range leading to improved texture and crystallinity while avoiding an irreversible phase transition that reduces crystallinity again. We employ real-time optical phase contrast microscopy with sub-nm height resolution to track the diffusion of TTC across monomolecular step edges which causes the unusual smoothing of a molecular thin film during annealing. We show that the lateral island sizes increase by more than one order of magnitude from 0.5 μm to 10 μm. This desirable behavior of 2d-Ostwald ripening and smoothing is in contrast to many other organic molecular films where annealing leads to dewetting, roughening, and a pronounced 3d morphology. We rationalize the smoothing behavior with the highly anisotropic attachment energies and low surface energies for TTC. The results are technically relevant for the use of TTC as passivation layer and as gate dielectric in organic field effect transistors.

  12. Thermally driven smoothening of molecular thin films: Structural transitions in n-alkane layers studied in real-time.

    PubMed

    Pithan, Linus; Meister, Eduard; Jin, Chenyu; Weber, Christopher; Zykov, Anton; Sauer, Katrein; Brütting, Wolfgang; Riegler, Hans; Opitz, Andreas; Kowarik, Stefan

    2015-10-28

    We use thermal annealing to improve smoothness and to increase the lateral size of crystalline islands of n-tetratetracontane (TTC, C44H90) films. With in situ x-ray diffraction, we find an optimum temperature range leading to improved texture and crystallinity while avoiding an irreversible phase transition that reduces crystallinity again. We employ real-time optical phase contrast microscopy with sub-nm height resolution to track the diffusion of TTC across monomolecular step edges which causes the unusual smoothing of a molecular thin film during annealing. We show that the lateral island sizes increase by more than one order of magnitude from 0.5 μm to 10 μm. This desirable behavior of 2d-Ostwald ripening and smoothing is in contrast to many other organic molecular films where annealing leads to dewetting, roughening, and a pronounced 3d morphology. We rationalize the smoothing behavior with the highly anisotropic attachment energies and low surface energies for TTC. The results are technically relevant for the use of TTC as passivation layer and as gate dielectric in organic field effect transistors. PMID:26520543

  13. Thermally driven smoothening of molecular thin films: Structural transitions in n-alkane layers studied in real-time

    SciTech Connect

    Pithan, Linus; Weber, Christopher; Zykov, Anton; Sauer, Katrein; Opitz, Andreas; Kowarik, Stefan; Meister, Eduard; Brütting, Wolfgang; Jin, Chenyu; Riegler, Hans

    2015-10-28

    We use thermal annealing to improve smoothness and to increase the lateral size of crystalline islands of n-tetratetracontane (TTC, C{sub 44}H{sub 90}) films. With in situ x-ray diffraction, we find an optimum temperature range leading to improved texture and crystallinity while avoiding an irreversible phase transition that reduces crystallinity again. We employ real-time optical phase contrast microscopy with sub-nm height resolution to track the diffusion of TTC across monomolecular step edges which causes the unusual smoothing of a molecular thin film during annealing. We show that the lateral island sizes increase by more than one order of magnitude from 0.5 μm to 10 μm. This desirable behavior of 2d-Ostwald ripening and smoothing is in contrast to many other organic molecular films where annealing leads to dewetting, roughening, and a pronounced 3d morphology. We rationalize the smoothing behavior with the highly anisotropic attachment energies and low surface energies for TTC. The results are technically relevant for the use of TTC as passivation layer and as gate dielectric in organic field effect transistors.

  14. A-SITE-AND/OR B-SITE-MODIFIED PBZRTIO3 MATERIALS AND (PB, SR, CA, BA, MG) (ZR, TI,NB, TA)O3 FILMS HAVING UTILITY IN FERROELECTRIC RANDOM ACCESS MEMORIES AND HIGH PERFORMANCE THIN FILM MICROACTUATORS

    NASA Technical Reports Server (NTRS)

    Roeder, Jeffrey F. (Inventor); Chen, Ing-Shin (Inventor); Bilodeau, Steven (Inventor); Baum, Thomas H. (Inventor)

    2004-01-01

    A modified PbZrTiO.sub.3 perovskite crystal material thin film, wherein the PbZrTiO.sub.3 perovskite crystal material includes crystal lattice A-sites and B-sites at least one of which is modified by the presence of a substituent selected from the group consisting of (i) A-site substituents consisting of Sr, Ca, Ba and Mg, and (ii) B-site substituents selected from the group consisting of Nb and Ta. The perovskite crystal thin film material may be formed by liquid delivery MOCVD from metalorganic precursors of the metal components of the thin film, to form PZT and PSZT, and other piezoelectric and ferroelectric thin film materials. The thin films of the invention have utility in non-volatile ferroelectric memory devices (NV-FeRAMs), and in microelectromechanical systems (MEMS) as sensor and/or actuator elements, e.g., high speed digital system actuators requiring low input power levels.

  15. Nonlinear optical thin films

    NASA Technical Reports Server (NTRS)

    Leslie, Thomas M.

    1993-01-01

    A focused approach to development and evaluation of organic polymer films for use in optoelectronics is presented. The issues and challenges that are addressed include: (1) material synthesis, purification, and the tailoring of the material properties; (2) deposition of uniform thin films by a variety of methods; (3) characterization of material physical properties (thermal, electrical, optical, and electro-optical); and (4) device fabrication and testing. Photonic materials, devices, and systems were identified as critical technology areas by the Department of Commerce and the Department of Defense. This approach offers strong integration of basic material issues through engineering applications by the development of materials that can be exploited as the active unit in a variety of polymeric thin film devices. Improved materials were developed with unprecedented purity and stability. The absorptive properties can be tailored and controlled to provide significant improvement in propagation losses and nonlinear performance. Furthermore, the materials were incorporated into polymers that are highly compatible with fabrication and patterning processes for integrated optical devices and circuits. By simultaneously addressing the issues of materials development and characterization, keeping device design and fabrication in mind, many obstacles were overcome for implementation of these polymeric materials and devices into systems. We intend to considerably improve the upper use temperature, poling stability, and compatibility with silicon based devices. The principal device application that was targeted is a linear electro-optic modulation etalon. Organic polymers need to be properly designed and coupled with existing integrated circuit technology to create new photonic devices for optical communication, image processing, other laser applications such as harmonic generation, and eventually optical computing. The progression from microscopic sample to a suitable film

  16. Directed Ordering of Block Copolymer Thin Films with Flexible Interfaces for Functional Materials

    NASA Astrophysics Data System (ADS)

    Karim, Alamgir

    2012-02-01

    Orientation control of block copolymer (BCP) films is important for advanced technological applications. We present studies on directed ordering of block copolymer thin films on rigid substrates such as quartz to elastomeric PDMS and flexible Kapton substrates for tunable orientation of microphase separated poly (styrene) -- block -poly (methylmethacrylate) (PS-PMMA) cylinder and lamellae forming BCP films. Although the crosslinked PDMS has low surface energy, its surface energy can be tuned by exposing to UV-Ozone (UVO) that presents an opportunity to change BCP-PDMS interfacial energy to control BCP orientation across full range of orientation and film wettability. On the other hand, Kapton offers a near neutral surface for PS-PMMA without surface modification. Via a modified version of a dynamic thermal processing termed cold zone annealing-sharp (CZA-S), we obtain a wide range of orientations of the block copolymer films in unfilled and nanoparticle filled systems with an interest in photovoltaic systems. With CZA-S, vertical orientation of PS-PMMA can be obtained in films as thick as 1 micron with etchable PMMA domains for membrane applications. GISAXS characterization of these etched BCP membranes reveals up to 5 orders of diffraction indicating hexagonally packed vertical nanopores that extend throughout the film. Under similar thermal gradient, but static conditions, temporally stable vertical cylinders form only within a narrow zone of maximum temperature gradient. Primary CZA-S ordering mechanism thus involves propagating this narrow vertically oriented zone of BCP cylinders created at the maximum thermal gradient section, across the film. An optimal speed is needed since the process competes with preferential surface wetting dynamics that favors parallel orientation. These results are reproduced on large area flexible films on a prototype dynamic R2R assembly platform with incorporated multi-CZA gradient for thin (100 nm) BCP films currently.

  17. Spectroscopic investigation of the chemical and electronic properties of chalcogenide materials for thin-film optoelectronic devices

    NASA Astrophysics Data System (ADS)

    Horsley, Kimberly Anne

    Chalcogen-based materials are at the forefront of technologies for sustainable energy production. This progress has come only from decades of research, and further investigation is needed to continue improvement of these materials. For this dissertation, a number of chalcogenide systems were studied, which have applications in optoelectronic devices, such as LEDs and Photovoltaics. The systems studied include Cu(In,Ga)Se2 (CIGSe) and CuInSe 2 (CISe) thin-film absorbers, CdTe-based photovoltaic structures, and CdTe-ZnO nanocomposite materials. For each project, a sample set was prepared through collaboration with outside institutions, and a suite of spectroscopy techniques was employed to answer specific questions about the system. These techniques enabled the investigation of the chemical and electronic structure of the materials, both at the surface and towards the bulk. CdS/Cu(In,Ga)Se2 thin-films produced from the roll-to-roll, ambient pressure, Nanosolar industrial line were studied. While record-breaking efficiency cells are usually prepared in high-vacuum (HV) or ultra-high vacuum (UHV) environments, these samples demonstrate competitive mass-production efficiency without the high-cost deposition environment. We found relatively low levels of C contaminants, limited Na and Se oxidation, and a S-Se intermixing at the CdS/CIGSe interface. The surface band gap compared closely to previously investigated CIGSe thin-films deposited under vacuum, illustrating that roll-to-roll processing is a promising and less-expensive alternative for solar cell production. An alternative deposition process for CuInSe2 was also studied, in collaboration with the University of Luxembourg. CuInSe2 absorbers were prepared with varying Cu content and surface treatments to investigate the potential to produce an absorber with a Cu-rich bulk and Cu-poor surface. This is desired to combine the bulk characteristics of reduced defects and larger grains in Cu-rich films, while maintaining

  18. Selective inorganic thin films

    SciTech Connect

    Phillips, M.L.F.; Weisenbach, L.A.; Anderson, M.T.

    1995-05-01

    This project is developing inorganic thin films as membranes for gas separation applications, and as discriminating coatings for liquid-phase chemical sensors. Our goal is to synthesize these coatings with tailored porosity and surface chemistry on porous substrates and on acoustic and optical sensors. Molecular sieve films offer the possibility of performing separations involving hydrogen, air, and natural gas constituents at elevated temperatures with very high separation factors. We are focusing on improving permeability and molecular sieve properties of crystalline zeolitic membranes made by hydrothermally reacting layered multicomponent sol-gel films deposited on mesoporous substrates. We also used acoustic plate mode (APM) oscillator and surface plasmon resonance (SPR) sensor elements as substrates for sol-gel films, and have both used these modified sensors to determine physical properties of the films and have determined the sensitivity and selectivity of these sensors to aqueous chemical species.

  19. Engineering the Crystalline Morphology of Polymer Thin Films at a Molecular Level via Matrix Assisted Pulsed Laser Evaporation

    NASA Astrophysics Data System (ADS)

    Jeong, Hyuncheol; Arnold, Craig; Priestley, Rodney

    2015-03-01

    Controlling the crystalline morphology of polymeric thin films at a molecular level has been increasingly important due to their potential as the active layer in organic electronics. Typically, the crystalline morphology in films is achieved via thermal annealing or melt-crystallization of spin-cast polymers. This approach often leads to a spherulitic morphology where the crystalline lamellae grow in all directions. Here, we introduce an alternative approach to make crystalline polymer films via Matrix Assisted Pulsed Laser Evaporation (MAPLE). Using polyethylene oxide (PEO) as a model polymer, we show that the preferential orientation of polymer crystals can be controlled during the film growth. By laser-ablating a frozen dilute solution of the desired polymer, MAPLE provides a non-destructive means for the deposition of polymer films. Due to the liquid nature of as-deposited polymers confined in nanodroplets, this technique can exploit the substrate effect on the crystal nucleation and growth of nano-confined polymers during the film growth. Mimicking the epitaxial growth of metallic films, this novel polymer deposition technique may enable the engineering of film properties in a way not achievable in bulk.

  20. Attachment of lead wires to thin film thermocouples mounted on high temperature materials using the parallel gap welding process

    NASA Technical Reports Server (NTRS)

    Holanda, Raymond; Kim, Walter S.; Pencil, Eric; Groth, Mary; Danzey, Gerald A.

    1990-01-01

    Parallel gap resistance welding was used to attach lead wires to sputtered thin film sensors. Ranges of optimum welding parameters to produce an acceptable weld were determined. The thin film sensors were Pt13Rh/Pt thermocouples; they were mounted on substrates of MCrAlY-coated superalloys, aluminum oxide, silicon carbide and silicon nitride. The entire sensor system is designed to be used on aircraft engine parts. These sensor systems, including the thin-film-to-lead-wire connectors, were tested to 1000 C.

  1. Growth of 3C-SiC( 1 0 0 ) thin films on Si( 1 0 0 ) by the molecular ion beam deposition

    NASA Astrophysics Data System (ADS)

    Matsumoto, Takashi; Kiuchi, Masato; Sugimoto, Satoshi; Goto, Seiichi

    2001-11-01

    Silicon carbide (SiC) thin films were produced on Si(1 0 0) at low growth temperatures of 750-1000°C, using the molecular ion beam deposition (IBD) technique with a precursor of organosilicon ions. The ions extracted at 25 keV were mass selected, and decelerated to 100 eV. The precursor of methylsilicenium ions (SiCH 3+), which has a Si-C bond in the molecular structure, was generated from dimethylsilane (SiH 2(CH 3) 2). The energy distribution of SiCH 3+ ions was measured by a PPM421 plasma process monitor. It was confirmed that the energy distributions were 100±1 eV. The chemical bondings and surface structures of SiC thin films were analyzed by Raman spectroscopy and reflection high-energy electron diffraction (RHEED). In the Raman spectrum, a peak at 796 cm -1 was assigned to transverse optic phonon scattering in 3C-SiC. As a result of the analysis of RHEED patterns, 3C-SiC(1 0 0) were formed on Si(1 0 0) substrates. Using the molecular IBD technique with the precursor of methylsilicenium ions, the formation of SiC thin films is available on Si(1 0 0) at low temperature (750°C).

  2. Material properties and applications of blended organic thin films with nanoscale domains deposited by RIR-MAPLE

    NASA Astrophysics Data System (ADS)

    Stiff-Roberts, Adrienne D.; McCormick, Ryan D.; Ge, Wangyao

    2015-03-01

    Resonant-infrared, matrix-assisted pulsed laser evaporation (RIR-MAPLE) has been used to deposit blended, organic thin-films with nanoscale domain sizes of constituent polymers, small molecules, or colloidal nanoparticles. In the emulsion-based RIR-MAPLE process, the target contains a nonpolar, organic solvent phase and a polar, water phase. The emulsion properties have a direct impact on the nanoscale morphology of single-component organic thin films, while the morphology of blended, organic thin films also depends on the RIR-MAPLE deposition mode. In addition to these fundamental aspects, applications of blended organic films (organic solar cells, anti-reflection coatings, and multi-functional surfaces) deposited by emulsion-based RIR-MAPLE are presented. Importantly, domain sizes in the blended films are critical to thin-film functionality.

  3. Growth Induced Magnetic Anisotropy in Crystalline and Amorphous Thin Films

    SciTech Connect

    Hellman, Frances

    1998-10-03

    OAK B204 Growth Induced Magnetic Anisotropy in Crystalline and Amorphous Thin Films. The work in the past 6 months has involved three areas of magnetic thin films: (1) amorphous rare earth-transition metal alloys, (2) epitaxial Co-Pt and hTi-Pt alloy thin films, and (3) collaborative work on heat capacity measurements of magnetic thin films, including nanoparticles and CMR materials.

  4. MATERIAL AND PROCESS DEVELOPMENT LEADING TO ECONOMICAL HIGH-PERFORMANCE THIN-FILM SOLID OXIDE FUEL CELLS

    SciTech Connect

    Jie Guan; Nguyen Minh

    2003-12-01

    This report summarizes the results of the work conducted under the program: ''Material and Process Development Leading to Economical High-Performance Thin-Film Solid Oxide Fuel Cells'' under contract number DE-AC26-00NT40711. The program goal is to advance materials and processes that can be used to produce economical, high-performance solid oxide fuel cells (SOFC) capable of achieving extraordinary high power densities at reduced temperatures. Under this program, anode-supported thin electrolyte based on lanthanum gallate (LSMGF) has been developed using tape-calendering process. The fabrication parameters such as raw materials characteristics, tape formulations and sintering conditions have been evaluated. Dense anode supported LSGMF electrolytes with thickness range of 10-50 micron have been fabricated. High performance cathode based on Sr{sub 0.5}Sm{sub 0.5}CoO{sub 3} (SSC) has been developed. Polarization of {approx}0.23 ohm-cm{sup 2} has been achieved at 600 C with Sr{sub 0.5}Sm{sub 0.5}CoO{sub 3}cathode. The high-performance SSC cathode and thin gallate electrolyte have been integrated into single cells and cell performance has been characterized. Tested cells to date generally showed low performance because of low cell OCVs and material interactions between NiO in the anode and lanthanum gallate electrolyte.

  5. Growth induced magnetic anisotropy in crystalline and amorphous thin films

    SciTech Connect

    Hellman, F.

    1998-07-20

    The work in the past 6 months has involved three areas of magnetic thin films: (1) amorphous rare earth-transition metal alloys, (2) epitaxial Co-Pt and Ni-Pt alloy thin films, and (3) collaborative work on heat capacity measurements of magnetic thin films, including nanoparticles and CMR materials. A brief summary of work done in each area is given.

  6. Organic thin films. Rational synthesis of organic thin films with exceptional long-range structural integrity.

    PubMed

    Seiki, Noriya; Shoji, Yoshiaki; Kajitani, Takashi; Ishiwari, Fumitaka; Kosaka, Atsuko; Hikima, Takaaki; Takata, Masaki; Someya, Takao; Fukushima, Takanori

    2015-06-01

    Highly oriented, domain-boundary-free organic thin films could find use in various high-performance organic materials and devices. However, even with state-of-the-art supramolecular chemistry, it is difficult to construct organic thin films with structural integrity in a size regime beyond the micrometer length scale. We show that a space-filling design, relying on the two-dimensional (2D) nested hexagonal packing of a particular type of triptycene, enables the formation of large-area molecular films with long-range 2D structural integrity up to the centimeter length scale by vacuum evaporation, spin-coating, and cooling from the isotropic liquid of the triptycene. X-ray diffraction analysis and microscopic observations reveal that triptycene molecules form a completely oriented 2D (hexagonal triptycene array) + 1D (layer stacking) structure, which is key for the long-range propagation of structural order. PMID:26045433

  7. A facile fabrication of chemically converted graphene oxide thin films and their uses as absorber materials for solar cells

    NASA Astrophysics Data System (ADS)

    Adelifard, Mehdi; Darudi, Hosein

    2016-07-01

    There is a great interest in the use of graphene sheets in thin film solar cells with low-cost and good-optoelectronic properties. Here, the production of absorbent conductive reduced graphene oxide (RGO) thin films was investigated. RGO thin films were prepared from spray-coated graphene oxide (GO) layers at various substrate temperature followed by a simple hydrazine-reducing method. The structural, morphological, optical, and electrical characterizations of graphene oxide (GO) and RGO thin films were investigated. X-ray diffraction analysis showed a phase shift from GO to RGO due to hydrazine treatment, in agreement with the FTIR spectra of the layers. FESEM images clearly exhibited continuous films resulting from the overlap of graphene nanosheets. The produced low-cost thin films had high absorption coefficient up to 1.0 × 105 cm-1, electrical resistance as low as 0.9 kΩ/sq, and effective optical band gap of about 1.50 eV, close to the optimum value for solar conversion. The conductive absorbent properties of the reduced graphene oxide thin films would be useful to develop photovoltaic cells.

  8. Zinc oxide thin film acoustic sensor

    SciTech Connect

    Mohammed, Ali Jasim; Salih, Wafaa Mahdi; Hassan, Marwa Abdul Muhsien; Nusseif, Asmaa Deiaa; Kadhum, Haider Abdullah; Mansour, Hazim Louis

    2013-12-16

    This paper reports the implementation of (750 nm) thickness of Zinc Oxide (ZnO) thin film for the piezoelectric pressure sensors. The film was prepared and deposited employing the spray pyrolysis technique. XRD results show that the growth preferred orientation is the (002) plane. A polycrystalline thin film (close to mono crystallite like) was obtained. Depending on the Scanning Electron Microscopy photogram, the film homogeneity and thickness were shown. The resonance frequency measured (about 19 kHz) and the damping coefficient was calculated and its value was found to be about (2.5538), the thin film be haves as homogeneous for under and over damped. The thin film pressure sensing was approximately exponentially related with frequency, the thin film was observed to has a good response for mechanical stresses also it is a good material for the piezoelectric properties.

  9. Zinc oxide thin film acoustic sensor

    NASA Astrophysics Data System (ADS)

    Mohammed, Ali Jasim; Salih, Wafaa Mahdi; Hassan, Marwa Abdul Muhsien; Mansour, Hazim Louis; Nusseif, Asmaa Deiaa; Kadhum, Haider Abdullah

    2013-12-01

    This paper reports the implementation of (750 nm) thickness of Zinc Oxide (ZnO) thin film for the piezoelectric pressure sensors. The film was prepared and deposited employing the spray pyrolysis technique. XRD results show that the growth preferred orientation is the (002) plane. A polycrystalline thin film (close to mono crystallite like) was obtained. Depending on the Scanning Electron Microscopy photogram, the film homogeneity and thickness were shown. The resonance frequency measured (about 19 kHz) and the damping coefficient was calculated and its value was found to be about (2.5538), the thin film be haves as homogeneous for under and over damped. The thin film pressure sensing was approximately exponentially related with frequency, the thin film was observed to has a good response for mechanical stresses also it is a good material for the piezoelectric properties.

  10. Calorimetry of epitaxial thin films.

    PubMed

    Cooke, David W; Hellman, F; Groves, J R; Clemens, B M; Moyerman, S; Fullerton, E E

    2011-02-01

    Thin film growth allows for the manipulation of material on the nanoscale, making possible the creation of metastable phases not seen in the bulk. Heat capacity provides a direct way of measuring thermodynamic properties of these new materials, but traditional bulk calorimetric techniques are inappropriate for such a small amount of material. Microcalorimetry and nanocalorimetry techniques exist for the measurements of thin films but rely on an amorphous membrane platform, limiting the types of films which can be measured. In the current work, ion-beam-assisted deposition is used to provide a biaxially oriented MgO template on a suspended membrane microcalorimeter in order to measure the specific heat of epitaxial thin films. Synchrotron x-ray diffraction showed the biaxial order of the MgO template. X-ray diffraction was also used to prove the high quality of epitaxy of a film grown onto this MgO template. The contribution of the MgO layer to the total heat capacity was measured to be just 6.5% of the total addenda contribution. The heat capacity of a Fe(.49)Rh(.51) film grown epitaxially onto the device was measured, comparing favorably to literature data on bulk crystals. This shows the viability of the MgO∕SiN(x)-membrane-based microcalorimeter as a way of measuring the thermodynamic properties of epitaxial thin films. PMID:21361612

  11. Comparative alternative materials assessment to screen toxicity hazards in the life cycle of CIGS thin film photovoltaics.

    PubMed

    Eisenberg, Daniel A; Yu, Mengjing; Lam, Carl W; Ogunseitan, Oladele A; Schoenung, Julie M

    2013-09-15

    Copper-indium-gallium-selenium-sulfide (CIGS) thin film photovoltaics are increasingly penetrating the market supply for consumer solar panels. Although CIGS is attractive for producing less greenhouse gas emissions than fossil-fuel based energy sources, CIGS manufacturing processes and solar cell devices use hazardous materials that should be carefully considered in evaluating and comparing net environmental benefits of energy products. Through this research, we present a case study on the toxicity hazards associated with alternative materials selection for CIGS manufacturing. We applied two numeric models, The Green Screen for Safer Chemicals and the Toxic Potential Indicator. To improve the sensitivity of the model outputs, we developed a novel, life cycle thinking based hazard assessment method that facilitates the projection of hazards throughout material life cycles. Our results show that the least hazardous CIGS solar cell device and manufacturing protocol consist of a titanium substrate, molybdenum metal back electrode, CuInS₂ p-type absorber deposited by spray pyrolysis, ZnS buffer deposited by spray ion layer gas reduction, ZnO:Ga transparent conducting oxide (TCO) deposited by sputtering, and the encapsulant polydimethylsiloxane. PMID:23811631

  12. Fabrication and Performance of Organic Thin Film Solar Cells Using the Brush Painting Method

    NASA Astrophysics Data System (ADS)

    Ishihara, Hirohumi; Kojima, Kenzo; Mizutani, Teruyoshi; Ochiai, Shizuyasu

    As organic solar thin films fabricated by an active layer of organic materials are economical, lightweight, and flexible, as well as facilitating processing, organic solar cells have attracted considerable attention within the past few decades as a clean energy source. With this in mind, there have been global investigations and studies of the power conversion efficiency (PCE) within organic solar cells. In organic thin-film solar cells, the effect of the performance is not only dependent on an adopted active material but also the molecular orientation on the electrode. Using the mixed solution of Poly (3-hexylthiophene) and PCBM, both dissolved by solvent, an organic thin film is fabricated using the paint method (The conceptual diagram of the paint method is shown in Fig. 1) The form of the thin film was evaluated, an organic thin-film solar cell using the paint method for the active layer was made, and its performance was evaluated and examined. Using the mixed solution of Poly(3-hexylthiophene) and PCBM, both dissolved by solvent, an organic thin film is fabricated using the paint method (The conceptual diagram of the paint method is shown in Fig. 1) The morphology of the thin film was evaluated using an AFM image, UV/vis spectra, and so forth. Based on these data, an organic thin-film solar cell that used the paint method for the active layer was fabricated, and the performance was evaluated and examined. For the organic thin film solar cell fabricated using the brush painting method, the open-circuit voltage (Voc) is 0.41 V, the short circuit current density (Jsc) is 2.07 mA/cm2, and the fill factor is 0.34. The efficiency η of PCE becomes 0.29%.

  13. Thin-Film Power Transformers

    NASA Technical Reports Server (NTRS)

    Katti, Romney R.

    1995-01-01

    Transformer core made of thin layers of insulating material interspersed with thin layers of ferromagnetic material. Flux-linking conductors made of thinner nonferromagnetic-conductor/insulator multilayers wrapped around core. Transformers have geometric features finer than those of transformers made in customary way by machining and mechanical pressing. In addition, some thin-film materials exhibit magnetic-flux-carrying capabilities superior to those of customary bulk transformer materials. Suitable for low-cost, high-yield mass production.

  14. Laser annealing of laser assisted molecular beam deposited ZnO thin films with application to metal-semiconductor-metal photodetectors

    SciTech Connect

    Li Meiya; Anderson, Wayne; Chokshi, Nehal; De Leon, Robert L.; Tompa, Gary

    2006-09-01

    We report on the effect of postdeposition laser annealing of undoped zinc oxide (ZnO) thin films grown by laser assisted molecular beam deposition. Hall-effect measurements show that some undoped ZnO films change from n type with mobility values in the range of 200 cm{sup 2} V{sup -1} s{sup -1} to p-type material with mobility value of 73 cm{sup 2} V{sup -1} s{sup -1}, after laser annealing. The photoconductive behavior was clearly seen on the laser-annealed samples, with values of 0.28 m{omega}{sup -1}. The structural and optical properties of the films were improved with laser annealing as shown by scanning electron microscopy, x-ray photoelectron spectroscopy analysis, and photoluminescence measurement. All of the nonlaser and laser annealed samples showed near-band emission at {approx}3.3 eV. Metal-semiconductor-metal photodetectors were fabricated from the films.

  15. Magnetic and transport properties of epitaxial thin film MgFe2O4 grown on MgO (100) by molecular beam epitaxy

    PubMed Central

    Wu, Han-Chun; Mauit, Ozhet; Coileáin, Cormac Ó; Syrlybekov, Askar; Khalid, Abbas; Mouti, Anas; Abid, Mourad; Zhang, Hong-Zhou; Abid, Mohamed; Shvets, Igor V.

    2014-01-01

    Magnesium ferrite is a very important magnetic material due to its interesting magnetic and electrical properties and its chemical and thermal stability. Here we report on the magnetic and transport properties of epitaxial MgFe2O4 thin films grown on MgO (001) by molecular beam epitaxy. The structural properties and chemical composition of the MgFe2O4 films were characterized by X-Ray diffraction and X-Ray photoelectron spectroscopy, respectively. The nonsaturation of the magnetization in high magnetic fields observed for M (H) measurements and the linear negative magnetoresistance (MR) curves indicate the presence of anti-phase boundaries (APBs) in MgFe2O4. The presence of APBs was confirmed by transmission electron microscopy. Moreover, post annealing decreases the resistance and enhances the MR of the film, suggesting migration of the APBs. Our results may be valuable for the application of MgFe2O4 in spintronics. PMID:25388355

  16. A novel approach in controlling the conductivity of thin films using molecular layer deposition

    NASA Astrophysics Data System (ADS)

    Lushington, Andrew; Liu, Jian; Bannis, Mohammad N.; Xiao, Biwei; Lawes, Stephen; Li, Ruying; Sun, Xueliang

    2015-12-01

    Here we present a novel way to grow aluminum alkoxide films with tunable conductivity with molecular level accuracy with the use of molecular layer deposition (MLD). Alternating exposures of trimethylaluminum (TMA), ethylene glycol (EG), and terephthaloyl chloride (TC) are used to grow the aluminium alkoxide films. Control over film composition was accomplished by alternating cycles of EG and TC between cycles of TMA and EG. In this fashion the aluminum to carbon ratio can be accurately controlled. These films were then pyrolyzed under a reducing atmosphere to yield a conductive Al2O3/carbon composite. Raman spectroscopy determined that nanocrystalline sp2-graphitic carbon was formed following pyrolysis while sheet resistance measurements determined that conductivity of the film is directly related to aluminium-carbon ratio. To further elucidate the origin of conductivity within the film, synchrotron based XPS was performed.

  17. Coexistence of spinodal instability and thermal nucleation in thin-film rupture: insights from molecular levels.

    PubMed

    Nguyen, Trung Dac; Fuentes-Cabrera, Miguel; Fowlkes, Jason D; Rack, Philip D

    2014-03-01

    Despite extensive investigation using hydrodynamic models and experiments over the past decades, there remain open questions regarding the origin of the initial rupture of thin liquid films. One of the reasons that makes it difficult to identify the rupture origin is the coexistence of two dewetting mechanisms, namely, thermal nucleation and spinodal instability, as observed in many experimental studies. Using a coarse-grained model and large-scale molecular dynamics simulations, we are able to characterize the very early stage of dewetting in nanometer-thick liquid-metal films wetting a solid substrate. We observe the features characteristic of both spinodal instability and thermal nucleation in the spontaneously dewetting films and show that these two macroscopic mechanisms share a common origin at molecular levels. PMID:24730848

  18. Coexistence of spinodal instability and thermal nucleation in thin-film rupture: Insights from molecular levels

    NASA Astrophysics Data System (ADS)

    Nguyen, Trung Dac; Fuentes-Cabrera, Miguel; Fowlkes, Jason D.; Rack, Philip D.

    2014-03-01

    Despite extensive investigation using hydrodynamic models and experiments over the past decades, there remain open questions regarding the origin of the initial rupture of thin liquid films. One of the reasons that makes it difficult to identify the rupture origin is the coexistence of two dewetting mechanisms, namely, thermal nucleation and spinodal instability, as observed in many experimental studies. Using a coarse-grained model and large-scale molecular dynamics simulations, we are able to characterize the very early stage of dewetting in nanometer-thick liquid-metal films wetting a solid substrate. We observe the features characteristic of both spinodal instability and thermal nucleation in the spontaneously dewetting films and show that these two macroscopic mechanisms share a common origin at molecular levels.

  19. Molecular resolution friction microscopy of Cu phthalocyanine thin films on dolomite (104) in water

    NASA Astrophysics Data System (ADS)

    Nita, Paweł; Pimentel, Carlos; Luo, Feng; Milián-Medina, Begoña; Gierschner, Johannes; Pina, Carlos M.; Gnecco, Enrico

    2014-06-01

    The reliability of ultrathin organic layers as active components for molecular electronic devices depends ultimately on an accurate characterization of the layer morphology and ability to withstand mechanical stresses on the nanoscale. To this end, since the molecular layers need to be electrically decoupled using thick insulating substrates, the use of AFM becomes mandatory. Here, we show how friction force microscopy (FFM) in water allows us to identify the orientation of copper(ii)phthalocyanine (CuPc) molecules previously self-assembled on a dolomite (104) mineral surface in ultra-high vacuum. The molecular features observed in the friction images show that the CuPc molecules are stacked in parallel rows with no preferential orientation with respect to the dolomite lattice, while the stacking features resemble well the single CuPc crystal structure. This proves that the substrate induction is low and makes friction force microscopy in water a suitable alternative to more demanding dynamic AFM techniques in ultra-high vacuum.

  20. Molecular resolution friction microscopy of Cu phthalocyanine thin films on dolomite (104) in water.

    PubMed

    Nita, Paweł; Pimentel, Carlos; Luo, Feng; Milián-Medina, Begoña; Gierschner, Johannes; Pina, Carlos M; Gnecco, Enrico

    2014-07-21

    The reliability of ultrathin organic layers as active components for molecular electronic devices depends ultimately on an accurate characterization of the layer morphology and ability to withstand mechanical stresses on the nanoscale. To this end, since the molecular layers need to be electrically decoupled using thick insulating substrates, the use of AFM becomes mandatory. Here, we show how friction force microscopy (FFM) in water allows us to identify the orientation of copper(ii)phthalocyanine (CuPc) molecules previously self-assembled on a dolomite (104) mineral surface in ultra-high vacuum. The molecular features observed in the friction images show that the CuPc molecules are stacked in parallel rows with no preferential orientation with respect to the dolomite lattice, while the stacking features resemble well the single CuPc crystal structure. This proves that the substrate induction is low and makes friction force microscopy in water a suitable alternative to more demanding dynamic AFM techniques in ultra-high vacuum. PMID:24932960

  1. Evaporation characteristics of thin film liquid argon in nano-scale confinement: A molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Hasan, Mohammad Nasim; Shavik, Sheikh Mohammad; Rabbi, Kazi Fazle; Haque, Mominul

    2016-07-01

    Molecular dynamics simulation has been carried out to explore the evaporation characteristics of thin liquid argon film in nano-scale confinement. The present study has been conducted to realize the nano-scale physics of simultaneous evaporation and condensation inside a confined space for a three phase system with particular emphasis on the effect of surface wetting conditions. The simulation domain consisted of two parallel platinum plates; one at the top and another at the bottom. The fluid comprised of liquid argon film at the bottom plate and vapor argon in between liquid argon and upper plate of the domain. Considering hydrophilic and hydrophobic nature of top and bottom surfaces, two different cases have been investigated: (i) Case A: Both top and bottom surfaces are hydrophilic, (ii) Case B: both top and bottom surfaces are hydrophobic. For all cases, equilibrium molecular dynamics (EMD) was performed to reach equilibrium state at 90 K. Then the lower wall was set to four different temperatures such as 110 K, 120 K, 130 K and 140 K to perform non-equilibrium molecular dynamics (NEMD). The variation of temperature and density as well as the variation of system pressure with respect to time were closely monitored for each case. The heat fluxes normal to top and bottom walls were estimated and discussed to illuminate the effectiveness of heat transfer in both hydrophilic and hydrophobic confinement at various boundary temperatures of the bottom plate.

  2. [Study on preparation of lanthanum-doped TiO2 nanometer thin film materials and its photocatalytic activity].

    PubMed

    Zheng, Huai-li; Tang, Ming-fang; Gong, Ying-kun; Deng, Xiao-jun; Wu, Bang-hua

    2003-04-01

    In this paper, lanthanum-doped TiO2 nanometer film materials coated on glass were prepared in Ti(OBu)4 precursor solutions by sol-gel processing. Transmittance and photocatalytic activity were respectively investigated and tested for these nanometer thin films prepared with different amount of lanthanum (La), different amount of polyethylene glycol (PEG), and different coating layer times. Some reactive mechanisms were also discussed. For one layer La-addition had little effect on the film transmissivity; but the photocatalytic activity was significantly improved due to La-addition. With increasing PEG, the transmittance of the film decreased for one layer film; but its photocatalytic activity did not rise. Increasing layer number did not affect the transmissivity of multilayer film. After coating two times, increasing layer number did not significantly improve the photocatalytic activity. The highest photocatalytic activity and best transmissivity were obtained for two layer TiO2 film when the dosage of lanthanum was 0.5 g and the dosage of polyethylene was 0.2 g in the precursor solutions. These materials will probably be used in the protection of environment, waste water treatment, and air purification. PMID:12961861

  3. Coherent control of the optical nonlinear and luminescence anisotropies in molecular thin films by multiphoton excitations.

    PubMed

    Bidault, Sébastien; Brasselet, Sophie; Zyss, Joseph

    2004-06-01

    Photoinduced orientational distributions are implemented with one- and two-photon absorption interference in polymer films containing chromophores that exhibit luminescent and nonlinear properties. The odd- and even-order parameters of the final distribution are probed by simultaneous measurement of second-harmonic generation (SHG) and two-photon fluorescence (TPF). We show the possibility of engineering local SHG and TPF anisotropies by controlling the polarization states and intensities of the writing optical fields. Complex multipolar orders are modeled with an irreducible spherical tensor-based formalism jointly applied to the molecular polarizabilities and field tensors. PMID:15214309

  4. o-Carborane functionalized pentacenes: synthesis, molecular packing and ambipolar organic thin-film transistors.

    PubMed

    Guo, Jixi; Liu, Danqing; Zhang, Jiahui; Zhang, Jiji; Miao, Qian; Xie, Zuowei

    2015-08-01

    New 6,13-bis[1'-(C≡C)-2'-R-1',2'-C2B10H10]pentacenes (R = H, Me, Et, n-Bu) are synthesized and fully characterized. The results show that the alkyl substituents on the second cage carbon have a significant impact on the molecular packing, and the incorporation of the o-carboranyl moiety into a π conjugated system can lower both LUMO and HOMO energy levels, converting a typical p-type semiconductor into an ambipolar one. PMID:26121634

  5. On the dynamic and static manifestation of molecular absorption in thin films probed by a microcantilever

    SciTech Connect

    Finot, Eric; Fabre, Arnaud; Passian, Ali; Thundat, Thomas

    2014-03-01

    Mechanical resonators shaped like microcantilevers have been demonstrated as a platform for very sensitive detection of chemical and biological analytes. However, its use as an analytical tool will require fundamental understanding of the molecular absorption-induced effects in the static and dynamic sensor response. The effect of absorption-induced surface stress on the microcantilever response is here investigated using palladium hydride formation. It is shown that the resonance and deformation states of the cantilever monitored simultaneously exhibit excellent correlation with the phase of the hydride formation. However, the associated frequency shifts and quasistatic bending are observed to be independent during solid solution phase. Importantly, absorption-induced changes in the elastic parameters of the palladium film are found to play a dominant role in the static and dynamic response. The presented results help in discerning the parameters that control the cantilever response as well as the relationships between these parameters.

  6. Ultrafast carrier dynamics in BiVO4 thin film photoanode material: time-resolved THz spectroscopic study

    NASA Astrophysics Data System (ADS)

    Belleman, Wesley; Zhou, L.; Giri, B.; Dringoli, B. J.; Rao, P. M.; Titova, L. V.

    Recent demonstrations of 3% solar conversion efficiency in thin film BiVO4 make it a promising photoanode material for photoelectrochemical water oxidation. With a bandgap of 2.4 eV, it strongly absorbs UV and visible light up to 520 nm. However, its efficiency is limited by extremely poor carrier mobility, with values from 0.01 to 1 cm2 /Vs reported in the literature, and often attributed to formation of small polarons. The precise nature of conductivity in BiVO4 is, however, not well-established. We use time-resolved terahertz (THz) spectroscopy as a non-contact probe of microscopic photoconductivity of a 100 nm-thick BiVO4 film. THz spectroscopy allows probing the dynamics of photo-injected carriers over nanometer length scales, and thus provides insight about transport of carriers inside the 100-200 nm grains. We find that intra-grain mobility may be as much as several orders of magnitude higher than macroscopic mobility that is affected by the grain boundaries.

  7. Effect of the top electrode materials on the resistive switching characteristics of TiO{sub 2} thin film

    SciTech Connect

    Oh, Sang Chul; Jung, Ho Yong; Lee, Heon

    2011-06-15

    Various metals, such as Pt, stainless steel (SUS), Al, Ni, and Ti, were used as a top electrode (TE) to evaluate the dependency of the resistive switching characteristics on the TE of the metal/TiO{sub 2}/Pt structure. The variation of the chemical composition of TiO{sub 2} in the metal/TiO{sub 2}/Pt structure before and after switching was examined to identify the factors affecting the resistive switching characteristics of the samples with various TE materials. In the case of TE/TiO{sub 2}/Pt structures showing unstable resistive switching behavior, e.g., those with the Al, Ni, and Ti TEs, secondary ion mass spectrometry revealed an increase in the oxygen concentration at the interface area between the TE metal and TiO{sub 2}. This suggests that the oxidation reaction at the interface between the TE metal and TiO{sub 2} might cause the TE/TiO{sub 2}/Pt structure to exhibit unstable resistive switching characteristics. According to these results, the oxidation reaction at the interface between the metal TE and TiO{sub 2} thin film is a primary factor affecting the resistive switching characteristics of TiO{sub 2}-based Resistive Random Access Memory devices.

  8. Epitaxial thin film growth in outer space

    NASA Technical Reports Server (NTRS)

    Ignatiev, Alex; Chu, C. W.

    1988-01-01

    A new concept for materials processing in space exploits the ultravacuum component of space for thin-film epitaxial growth. The unique LEO space environment is expected to yield 10-ftorr or better pressures, semiinfinite pumping speeds, and large ultravacuum volume (about 100 cu m) without walls. These space ultravacuum properties promise major improvement in the quality, unique nature, and throughput of epitaxially grown materials, including semiconductors, magnetic materials, and thin-film high-temperature superconductors.

  9. Evaluation of structure and material properties of RF magnetron sputter-deposited yttria-stabilized zirconia thin films

    NASA Astrophysics Data System (ADS)

    Piascik, Jeffrey Robert

    Over the past several decades, research has focused on utilizing ceramic materials in new technological applications. Their uses have been primarily in applications that involve high temperatures or corrosive environments. Unfortunately, ceramic materials have been limited especially since they can be brittle, failing in a sudden and catastrophic manner. A strong emphasis on understanding mechanical properties of ceramics and ways to improving their strength and toughness, has led to many new technologies. The present work is part of a larger research initiative that is aimed at using RF magnetron sputter deposition of yttria-stabilized zirconia to improve the fracture toughness of brittle substrates (more specifically dental ceramics). Partially-stabilized zirconia (PSZ) has been studied extensively, due to its high temperature stability and stress-induced tetragonal to monoclinic (T⇒M) martensitic phase transformation. RF magnetron sputtering was chosen as the deposition method because of its versatility, especially the ability to deposit oxides at low temperatures. Initial investigations focused on the development of process-structure-properties of YSZ sputtered deposited thin films. The YSZ thin films were deposited over a range of temperatures (22--300°C), pressures (5--25 mTorr), and gas compositions (Ar:O2 ratio). Initial studies characterized a select set of properties in relation to deposition parameters including: refractive index, structure, and film stress. X-ray Diffraction (XRD) showed that the films are comprised of mainly monoclinic and tetragonal crystal phases. The film refractive index determined by prism coupling, depends strongly on deposition conditions and ranged from 1.959 to 2.223. Wafer bow measurements indicate that the sputtered YSZ films can have initial stress ranging from 86 MPa tensile to 192 MPa compressive, depending on the deposition parameters. Exposure to ambient conditions (25°C, 75% relative humidity) led to large increase

  10. Structural and kinetic studies of metal hydride hydrogen storage materials using thin film deposition and characterization techniques

    NASA Astrophysics Data System (ADS)

    Kelly, Stephen Thomas

    Hydrogen makes an attractive energy carrier for many reasons. It is an abundant chemical fuel that can be produced from a wide variety of sources and stored for very long periods of time. When used in a fuel cell, hydrogen emits only water at the point of use, making it very attractive for mobile applications such as in an automobile. Metal hydrides are promising candidates for on-board reversible hydrogen storage in mobile applications due to their very high volumetric storage capacities---in most cases exceeding even that of liquid hydrogen. The United States Department of Energy (DOE) has set fuel system targets for an automotive hydrogen storage system, but as of yet no single material meets all the requirements. In particular, slow reaction kinetics and/or inappropriate thermodynamics plague many metal hydride hydrogen storage materials. In order to engineer a practical material that meets the DOE targets, we need a detailed understanding of the kinetic and thermodynamic properties of these materials during the phase change. In this work I employed sputter deposited thin films as a platform to study materials with highly controlled chemistry, microstructure and catalyst placement using thin film characterization techniques such as in situ x-ray diffraction (XRD) and neutron reflectivity. I observed kinetic limitations in the destabilized Mg2Si system due to the slow diffusion of the host Mg and Si atoms while forming separate MgH2 and Si phases. Conversely, I observed that the presence of Al in the Mg/Al system inhibits hydrogen diffusion while the host Mg and Al atoms interdiffuse readily, allowing the material to fall into a kinetic and/or thermodynamic trap by forming intermetallic compounds such as Mg17Al 12. By using in situ XRD to analyze epitaxial Mg films grown on (001) oriented Al2O3 substrates I observed hydride growth consistent with a model of a planar hydride layer growing into an existing metal layer. Subsequent film cycling changes the hydrogen

  11. Molecular bottle brushes in thin films: An off-lattice Monte Carlo study

    NASA Astrophysics Data System (ADS)

    Saariaho, Mika; Ikkala, Olli; ten Brinke, Gerrit

    1999-01-01

    The effect of intramolecular excluded volume interactions on the conformations of isolated comb-shaped copolymers—"molecular bottle brushes"—in athermal solvents confined between two hard impenetrable parallel plates is studied by off-lattice Monte Carlo simulations. Equilibrium conformational properties of molecules consisting of a freely jointed backbone of 100 hard spheres (beads), where 50 equally flexible side chains of lengths M up to 30 beads are connected, are determined as a function of the width of the slit, including the pure two-dimensional (2D) case. Besides general properties such as the size and the shape of the chains and the orientation of the chains with respect to the confining plates, the persistence length of the bottle-brush backbone λ is considered in particular. It is demonstrated that due to the side chains, the backbone is, in fact, effectively confined between two soft plates, i.e., the side chains act like softening springs between the backbone and plates. The most striking result is that, unlike the three-dimensional (3D) situation, in the 2D case the ratio between λ and the diameter D, λ/D, of the bottle brush starts to increase as a function of the side chain length for M⩾10. For 3D, an increase of λ/D (the essential parameter for lyotropic behavior) as a function of M is predicted by theory but has so far not been observed numerically for the regime studied (i.e., M⩽30). These results suggest that due to the weaker excluded volume effect in 3D, a possible upturn of λ/D may only be observed for longer side chains than studied so far.

  12. A new, fast and accurate spectrophotometric method for the determination of the optical constants of arbitrary absorptance thin films from a single transmittance curve: application to dielectric materials

    NASA Astrophysics Data System (ADS)

    Desforges, Jean; Deschamps, Clément; Gauvin, Serge

    2015-08-01

    The determination of the complex refractive index of thin films usually requires the highest accuracy. In this paper, we report on a new and accurate method based on a spectral rectifying process of a single transmittance curve. The agreements with simulated and real experimental data show the helpfulness of the method. The case of materials having arbitrary absorption bands at midpoint in spectral range, such as pigments in guest-host polymers, is also encompassed by this method.

  13. Dye sensitized solar cell applications of CdTiO{sub 3}–TiO{sub 2} composite thin films deposited from single molecular complex

    SciTech Connect

    Ehsan, Muhammad Ali; Khaledi, Hamid; Pandikumar, Alagarsamy; Huang, Nay Ming; Arifin, Zainudin; Mazhar, Muhammad

    2015-10-15

    A heterobimetallic complex [Cd{sub 2}Ti{sub 4}(μ-O){sub 6}(TFA){sub 8}(THF){sub 6}]·1.5THF (1) (TFA=trifluoroacetato, THF=tetrahydrofuran) comprising of Cd:Ti (1:2) ratio was synthesized by a chemical reaction of cadmium (II) acetate with titanium (IV) isopropoxide and triflouroacetic acid in THF. The stoichiometry of (1) was recognized by single crystal X-ray diffraction, spectroscopic and elemental analyses. Thermal studies revealed that (1) neatly decomposes at 450 °C to furnish 1:1 ratio of cadmium titanate:titania composite oxides material. The thin films of CdTiO{sub 3}–TiO{sub 2} composite oxides were deposited at 550 °C on fluorine doped tin oxide coated conducting glass substrate in air ambient. The micro-structure, crystallinity, phase identification and chemical composition of microspherical architectured CdTiO{sub 3}–TiO{sub 2} composite thin film have been determined by scanning electron microscopy, X-ray diffraction, Raman spectroscopy and energy dispersive X-ray analysis. The scope of composite thin film having band gap of 3.1 eV was explored as photoanode for dye-sensitized solar cell application. - Graphical abstarct: Microspherical designed CdTiO{sub 3}–TiO{sub 2} composite oxides photoanode film has been fabricated from single source precursor [Cd{sub 2}Ti{sub 4}(μ-O){sub 6}(TFA){sub 8}(THF){sub 6}]·1.5THF via aerosol assisted chemical vapor deposition technique for dye sensitized solar cell application. - Highlights: • Synthesis and characterization of a heterobimetallic Cd–Ti complex. • Fabrication of CdTiO{sub 3}–TiO{sub 2} thin film photoelectrode. • Application as dye sensitized photoanode for solar application.

  14. Interaction of Nano-Sized Materials With Polymer Chains in Polymer-Nanocomposite Thin Films-An AFM Perspective

    SciTech Connect

    Verma, Gaurav; Kaushik, Anupama; Ghosh, Anup K.

    2011-12-12

    Nanocomposite thin films were prepared with polyurethane as a matrix and organically modified clay as a filler. The interfacial interaction between the exfoliated clay nanoplatelets and the polymeric chains has been investigated by using Atomic Force Microscopy (AFM). The nanoclay platelets show a preferential association with the hard domains of polyurethane matrix on the surface of the thin films. The pendant hydroxyl group on the nanoplatelets attract the isocyanate of the polyisocyanate and a urethane group is formed. This leads to the 'clouding' and 'entwining' of the nanoplatelets by the hard segmental chains. This is the first visual evidence of nanomaterial filler and polymer matrix interaction and it could open up a spectrum of novel property achievements in nanocomposite thin films. Also the understanding of this interaction can lead to more controlled architecture of nanocomposites.

  15. Dye sensitized solar cell applications of CdTiO3-TiO2 composite thin films deposited from single molecular complex

    NASA Astrophysics Data System (ADS)

    Ehsan, Muhammad Ali; Khaledi, Hamid; Pandikumar, Alagarsamy; Huang, Nay Ming; Arifin, Zainudin; Mazhar, Muhammad

    2015-10-01

    A heterobimetallic complex [Cd2Ti4(μ-O)6(TFA)8(THF)6]·1.5THF (1) (TFA=trifluoroacetato, THF=tetrahydrofuran) comprising of Cd:Ti (1:2) ratio was synthesized by a chemical reaction of cadmium (II) acetate with titanium (IV) isopropoxide and triflouroacetic acid in THF. The stoichiometry of (1) was recognized by single crystal X-ray diffraction, spectroscopic and elemental analyses. Thermal studies revealed that (1) neatly decomposes at 450 °C to furnish 1:1 ratio of cadmium titanate:titania composite oxides material. The thin films of CdTiO3-TiO2 composite oxides were deposited at 550 °C on fluorine doped tin oxide coated conducting glass substrate in air ambient. The micro-structure, crystallinity, phase identification and chemical composition of microspherical architectured CdTiO3-TiO2 composite thin film have been determined by scanning electron microscopy, X-ray diffraction, Raman spectroscopy and energy dispersive X-ray analysis. The scope of composite thin film having band gap of 3.1 eV was explored as photoanode for dye-sensitized solar cell application.

  16. Electrochemical and microstructural characterization of magnetron-sputtered ATO thin films as Li–ion storage materials

    SciTech Connect

    Ouyang, Pan; Zhang, Hong; Chen, Wenhao; Wang, Ying; Zhang, Yu; Li, Zhicheng

    2015-01-15

    Highlights: • Nano-structured ATO thin films prepared by RF magnetron sputtering at 25 °C, 100 °C and 200 °C, respectively. • ATO thin films show a high reversible capacity and high rate performance. • Electrochemical reaction mechanism of the ATO thin film was revealed by transmission electron microscopy. - Abstract: Sb-doped SnO{sub 2} (ATO) nanostructured thin films were prepared by using radio frequency magnetron sputtering at the substrate temperatures of 25 °C, 100 °C and 200 °C, respectively. All the ATO thin films have the similar redox characteristics in the cyclic voltammetry measurements. The ATO thin film sputtered at 200 °C shows the lowest charge transfer resistance and best electrochemical performance, and has a high reversible capacity of 679 mA h g{sup −1} at 100 mA g{sup −1} after 200 charge–discharge cycles and high rate performance of 483 mA h g{sup −1} at 800 mA g{sup −1}. The electrochemical mechanisms were investigated by analyzing the phase evolution of the ATO electrodes that had been electrochemically induced at various stages. The results reveal that the ATO underwent reversible lithiation/delithiation processes during the electrochemical cycles, i.e., the SnO{sub 2} reacted with Li{sup +} to produce metallic Sn and followed by the formation of the Li{sub x}Sn alloys during discharge process, and then Li{sub x}Sn alloys de-alloyed, Sn reacted with Li{sub 2}O, and even partially formed SnO{sub 2} during charge process.

  17. Thin film production method and apparatus

    DOEpatents

    Loutfy, Raouf O.; Moravsky, Alexander P.; Hassen, Charles N.

    2010-08-10

    A method for forming a thin film material which comprises depositing solid particles from a flowing suspension or aerosol onto a filter and next adhering the solid particles to a second substrate using an adhesive.

  18. Solution processable semiconductor thin films: Correlation between morphological, structural, optical and charge transport properties

    NASA Astrophysics Data System (ADS)

    Isik, Dilek

    This Ph.D. thesis is a result of multidisciplinary research bringing together fundamental concepts in thin film engineering, materials science, materials processing and characterization, electrochemistry, microfabrication, and device physics. Experiments were conducted by tackling scientific problems in the field of thin films and interfaces, with the aim to correlate the morphology, crystalline structure, electronic structure of thin films with the functional properties of the films and the performances of electronic devices based thereon. Furthermore, novel strategies based on interfacial phenomena at electrolyte/thin film interfaces were explored and exploited to control the electrical conductivity of the thin films. Three main chemical systems were the object of the studies performed during this Ph.D., two types of organic semiconductors (azomethine-based oligomers and polymers and soluble pentacene derivatives) and one metal oxide semiconductor (tungsten trioxide, WO3). To explore the morphological properties of the thin films, atomic force microscopy was employed. The morphological properties were further investigated by hyperspectral fluorescence microscopy and tentatively correlated to the charge transport properties of the films. X-ray diffraction (Grazing incidence XRD, GIXRD) was used to investigate the crystallinity of the film and the effect of the heat treatment on such crystallinity, as well as to understand the molecular arrangement of the organic molecules in the thin film. The charge transport properties of the films were evaluated in thin film transistor configuration. For electrolyte gated thin film transistors, time dependent transient measurements were conducted, in parallel to more conventional transistor characterizations, to explore the specific effects played on the gating by the anion and cation constituting the electrolyte. The capacitances of the electrical double layers at the electrolyte/WO3 interface were obtained from

  19. High-throughput screening of thin-film semiconductor material libraries I: system development and case study for Ti-W-O.

    PubMed

    Sliozberg, Kirill; Schäfer, Dominik; Erichsen, Thomas; Meyer, Robert; Khare, Chinmay; Ludwig, Alfred; Schuhmann, Wolfgang

    2015-04-13

    An automated optical scanning droplet cell (OSDC) enables high-throughput quantitative characterization of thin-film semiconductor material libraries. Photoelectrochemical data on small selected measurement areas are recorded including intensity-dependent photopotentials and -currents, potentiodynamic and potentiostatic photocurrents, as well as photocurrent (action) spectra. The OSDC contains integrated counter and double-junction reference electrodes and is fixed on a precise positioning system. A Xe lamp with a monochromator is coupled to the cell through a thin poly(methyl methacrylate) (PMMA) optical fiber. A specifically designed polytetrafluoroethylene (PTFE) capillary tip is pressed on the sample surface and defines through its diameter the homogeneously illuminated measurement area. The overall and wavelength-resolved irradiation intensities and the cell surface area are precisely determined and calibrated. System development and its performance are demonstrated by means of screening of a TiWO thin film. PMID:25727402

  20. Thin film hydrogen sensor

    DOEpatents

    Cheng, Y.T.; Poli, A.A.; Meltser, M.A.

    1999-03-23

    A thin film hydrogen sensor includes a substantially flat ceramic substrate with first and second planar sides and a first substrate end opposite a second substrate end; a thin film temperature responsive resistor on the first planar side of the substrate proximate to the first substrate end; a thin film hydrogen responsive metal resistor on the first planar side of the substrate proximate to the fist substrate end and proximate to the temperature responsive resistor; and a heater on the second planar side of the substrate proximate to the first end. 5 figs.

  1. Thin film hydrogen sensor

    DOEpatents

    Cheng, Yang-Tse; Poli, Andrea A.; Meltser, Mark Alexander

    1999-01-01

    A thin film hydrogen sensor, includes: a substantially flat ceramic substrate with first and second planar sides and a first substrate end opposite a second substrate end; a thin film temperature responsive resistor on the first planar side of the substrate proximate to the first substrate end; a thin film hydrogen responsive metal resistor on the first planar side of the substrate proximate to the fist substrate end and proximate to the temperature responsive resistor; and a heater on the second planar side of the substrate proximate to the first end.

  2. Layer-by-layer grown scalable redox-active ruthenium-based molecular multilayer thin films for electrochemical applications and beyond.

    PubMed

    Kaliginedi, Veerabhadrarao; Ozawa, Hiroaki; Kuzume, Akiyoshi; Maharajan, Sivarajakumar; Pobelov, Ilya V; Kwon, Nam Hee; Mohos, Miklos; Broekmann, Peter; Fromm, Katharina M; Haga, Masa-aki; Wandlowski, Thomas

    2015-11-14

    Here we report the first study on the electrochemical energy storage application of a surface-immobilized ruthenium complex multilayer thin film with anion storage capability. We employed a novel dinuclear ruthenium complex with tetrapodal anchoring groups to build well-ordered redox-active multilayer coatings on an indium tin oxide (ITO) surface using a layer-by-layer self-assembly process. Cyclic voltammetry (CV), UV-Visible (UV-Vis) and Raman spectroscopy showed a linear increase of peak current, absorbance and Raman intensities, respectively with the number of layers. These results indicate the formation of well-ordered multilayers of the ruthenium complex on ITO, which is further supported by the X-ray photoelectron spectroscopy analysis. The thickness of the layers can be controlled with nanometer precision. In particular, the thickest layer studied (65 molecular layers and approx. 120 nm thick) demonstrated fast electrochemical oxidation/reduction, indicating a very low attenuation of the charge transfer within the multilayer. In situ-UV-Vis and resonance Raman spectroscopy results demonstrated the reversible electrochromic/redox behavior of the ruthenium complex multilayered films on ITO with respect to the electrode potential, which is an ideal prerequisite for e.g. smart electrochemical energy storage applications. Galvanostatic charge-discharge experiments demonstrated a pseudocapacitor behavior of the multilayer film with a good specific capacitance of 92.2 F g(-1) at a current density of 10 μA cm(-2) and an excellent cycling stability. As demonstrated in our prototypical experiments, the fine control of physicochemical properties at nanometer scale, relatively good stability of layers under ambient conditions makes the multilayer coatings of this type an excellent material for e.g. electrochemical energy storage, as interlayers in inverted bulk heterojunction solar cell applications and as functional components in molecular electronics applications

  3. Photorefractive polymers: Materials science, thin-film fabrication, and experiments in volume holography

    NASA Astrophysics Data System (ADS)

    McGee, David J.; Matlin, Mark D.

    2001-10-01

    When exposed to low power laser light, photorefractive materials can function as dynamic diffraction gratings, making them attractive for applications in holography and optical image processing. Conventional crystalline photorefractive materials are useful in demonstrations of basic nonlinear optical phenomena at the advanced undergraduate level, although the fabrication of such crystals is beyond the reach of most undergraduate facilities. Within the last five years, however, polymeric photorefractive materials have been developed that can be fabricated by collaborative teams of undergraduate physics and chemistry students. We have found that the study of photorefractive polymers provides an excellent framework to emphasize connections among optics, chemistry, and materials science at a level accessible to undergraduates. We provide an overview of photorefractive polymers, describe the fabrication of a typical photorefractive polymeric system, and discuss experiments in volume holography.

  4. 3-D photo-patterning of refractive index structures in photosensitive thin film materials

    DOEpatents

    Potter, Jr., Barrett George; Potter, Kelly Simmons

    2002-01-01

    A method of making a three-dimensional refractive index structure in a photosensitive material using photo-patterning. The wavelengths at which a photosensitive material exhibits a change in refractive index upon exposure to optical radiation is first determined and then a portion of the surface of the photosensitive material is optically irradiated at a wavelength at which the photosensitive material exhibits a change in refractive index using a designed illumination system to produce a three-dimensional refractive index structure. The illumination system can be a micro-lenslet array, a macroscopic refractive lens array, or a binary optic phase mask. The method is a single-step, direct-write procedure to produce a designed refractive index structure.

  5. Production of nanodispersed materials and thin films by laser ablation techniques in liquid and in vacuum

    NASA Astrophysics Data System (ADS)

    Tveryanovich, Yu S.; Manshina, A. A.; Tverjanovich, A. S.

    2012-12-01

    The methods of laser ablation of chemical compounds in a liquid medium and in vacuum used for the production of highly dispersed materials and films, respectively, are considered. Features and advantages of these methods are noted and the potential of their application for the design of novel materials is discussed. Examples of application of these methods in scientific research are given. The bibliography includes 177 references.

  6. Characterization of Amorphous SILICON:HYDROGEN Based Materials for Thin Film Device Applications.

    NASA Astrophysics Data System (ADS)

    Chen, Ing-Shin

    This thesis presents a methodology to investigate a-Si:H material properties using a self-consistent approach. The aim is to evaluate experimental data based on a density of states (DOS) model composed of extended states and localized states. This approach incorporates results obtained from several characterization techniques and the derived DOS parameters cover a wide energy range. The self-consistency in evaluating the results from different techniques ensures that a reliable, unified set of material parameters are obtained. The optical gap and the densities of extended states are determined from analyzing the optical constants obtained by using ex situ ellipsometry as well as transmission and reflection measurements. The representation of an optical gap in a-Si:H is examined using the proposed distribution of extended states. Results of different a-Si:H based materials are presented and discussed. The mobility gap is characterized by using internal photoemission of both electrons and holes into a-Si:H. The parabolic distribution of extended states and the amorphous nature of a-Si:H are taken into account in the analysis. The photoconductivity in a-Si:H is governed by the defect states in the gap which can be resulted from structural disorder or dangling bonds present in the material. The recombination kinetics in a-Si:H and the distributions of gap states are characterized by steady state and dual -beam photoconductivity (DBP) measurements. The densities and capture cross sections of these states are extracted by using a Subgap Absorption Modeling (SAM) program that fits model predictions to the photoconductivity data and DBP spectra. Material parameters obtained from film studies are used to predict the p-i-n solar cell characteristics using a device modeling program (AMPS). The results are compared with the experimental data obtained on cells made from these materials. This approach allows a diagnostic analysis on the correlation between material properties

  7. Fabrication and Characterization of Thin Film Ion Implanted Composite Materials for Integrated Nonlinear Optical Devices

    NASA Technical Reports Server (NTRS)

    Sarkisov, S.; Curley, M.; Williams, E. K.; Wilkosz, A.; Ila, D.; Poker, D. B.; Hensley, D. K.; Smith, C.; Banks, C.; Penn, B.; Clark, R.

    1998-01-01

    Ion implantation has been shown to produce a high density of metal colloids within the layer regions of glasses and crystalline materials. The high-precipitate volume fraction and small size of metal nanoclusters formed leads to values for the third-order susceptibility much greater than those for metal doped solids. This has stimulated interest in use of ion implantation to make nonlinear optical materials. On the other side, LiNbO3 has proved to be a good material for optical waveguides produced by MeV ion implantation. Light confinement in these waveguides is produced by refractive index step difference between the implanted region and the bulk material. Implantation of LiNbO3 with MeV metal ions can therefore result into nonlinear optical waveguide structures with great potential in a variety of device applications. We describe linear and nonlinear optical properties of a waveguide structure in LiNbO3-based composite material produced by silver ion implantation in connection with mechanisms of its formation.

  8. Microprocessor controlled ultrahigh vacuum evaporations of critical thin films, multilayer structures, and coevaporated materials

    SciTech Connect

    Fischer, H.; Grob, M.; Peter, G.; Koprio, J.A.

    1988-05-01

    The use of a quadrupole mass spectrometer as a rate monitor is described for a fast and accurate deposition control down to very low evaporation rates in an ultrahigh vacuum plant. In several applications of this concept, a rate control down to 0.1 A/s in single-source and coevaporation experiments could be documented for different materials and material combinations. The feasibility of operation at oxygen gas pressures of up to 4.5 x 10/sup -5/ mbar is shown for yttrium/copper coevaporations. Multilayer structures were deposited under microprocessor control with the same rate control method used.

  9. Polar self-assembled thin films for non-linear optical materials

    SciTech Connect

    Yang, XiaoGuang; Swanson, Basil I.; Li, DeQuan

    2000-01-01

    The design and synthesis of a family of calix[4]arene-based nonlinear optical (NLO) chromophores are discussed. The calixarene chromophores are macrocyclic compounds consisting of four simple D-.pi.-A units bridged by methylene groups. These molecules were synthesized such that four D-.pi.-A units of the calix[4]arene were aligned along the same direction with the calixarene in a cone conformation. These nonlinear optical super-chromophores were subsequently fabricated into covalently bound self-assembled monolayers on the surfaces of fused silica and silicon. Spectroscopic second harmonic generation (SHG) measurements were carried out to determine the absolute value of the dominant element of the second-order nonlinear susceptibility, d.sub.33, and the average molecular alignment, .PSI.. A value of d.sub.33 =60 pm/V at a fundamental wavelength of 890 nm, and .PSI..about.36.degree. was found with respect to the surface normal.

  10. Ceramic Composite Thin Films

    NASA Technical Reports Server (NTRS)

    Ruoff, Rodney S. (Inventor); Stankovich, Sasha (Inventor); Dikin, Dmitriy A. (Inventor); Nguyen, SonBinh T. (Inventor)

    2013-01-01

    A ceramic composite thin film or layer includes individual graphene oxide and/or electrically conductive graphene sheets dispersed in a ceramic (e.g. silica) matrix. The thin film or layer can be electrically conductive film or layer depending the amount of graphene sheets present. The composite films or layers are transparent, chemically inert and compatible with both glass and hydrophilic SiOx/silicon substrates. The composite film or layer can be produced by making a suspension of graphene oxide sheet fragments, introducing a silica-precursor or silica to the suspension to form a sol, depositing the sol on a substrate as thin film or layer, at least partially reducing the graphene oxide sheets to conductive graphene sheets, and thermally consolidating the thin film or layer to form a silica matrix in which the graphene oxide and/or graphene sheets are dispersed.

  11. Thin film metrology.

    PubMed

    Nitsch, Gerald; Flinn, Gregory

    2007-10-01

    Thin film metrology is suitable for characterising and performing quality control of a variety of coatings and films used in medical applications. The capabilities of today's systems are described. PMID:18078184

  12. Bamboo (Neosinocalamus affinis)-based thin film, a novel biomass material with high performances.

    PubMed

    Song, Fei; Xu, Chen; Bao, Wen-Yi; Wang, Xiu-Li; Wang, Yu-Zhong

    2015-03-30

    Exploration of biomass based materials to replace conventional petroleum based ones has been a trend in recent decades. In this work, bamboo (Neosinocalamus affinis) with abundant resources was used for the first time to prepare films in the presence of cellulose. The effects of weight ratio of bamboo/cellulose on the appearances and properties of the films were investigated. It was confirmed there existed strong interactions between bamboo and cellulose, which were favorable to formation of homogeneous structure of blend films. Particularly, the presence of bamboo could improve the surface hydrophobicity, water resistance and thermal stability of blend films, and the films possessed an excellent oxygen barrier property, compared with generally used commercial packaging films. The bamboo biomass, therefore, is successfully used to create a new film material with a good application prospect in the fields of packaging, coating, and food industry. PMID:25563957

  13. The effect of Ta interface on the crystallization of amorphous phase change material thin films

    SciTech Connect

    Ghezzi, G. E.; Noé, P. Marra, M.; Sabbione, C.; Fillot, F.; Bernier, N.; Ferrand, J.; Maîtrejean, S.; Hippert, F.

    2014-06-02

    The crystallization of amorphous GeTe and Ge{sub 2}Sb{sub 2}Te{sub 5} phase change material films, with thickness between 10 and 100 nm, sandwiched between either Ta or SiO{sub 2} layers, was investigated by optical reflectivity. Ta cladding layers were found to increase the crystallization temperature, even for films as thick as 100 nm. X-Ray diffraction investigations of crystallized GeTe films showed a very weak texture in Ta cladded films, in contrast with the strong texture observed for SiO{sub 2} cladding layers. This study shows that crystallization mechanism of phase change materials can be highly impacted by interface effects, even for relatively thick films.

  14. Modeling of plume dynamics in laser ablation processes for thin film deposition of materials

    SciTech Connect

    Leboeuf, J.N.; Chen, K.R.; Donato, J.M.; Geohegan, D.B.; Liu, C.L.; Puretzky, A.A.; Wood, R.F.

    1995-12-31

    The transport dynamics of laser-ablated neutral/plasma plumes are of significant interest for film growth by pulsed-laser deposition of materials since the magnitude and kinetic energy of the species arriving at the deposition substrate are key processing parameters. Dynamical calculations of plume propagation in vacuum and in background gas have been performed using particle-in-cell hydrodynamics, continuum gas dynamics, and scattering models. Results from these calculations are presented and compared with experimental observations.

  15. The feasibility of Sn, In, or Al doped ZnSb thin film as candidates for phase change material

    NASA Astrophysics Data System (ADS)

    Chen, Yimin; Shen, Xiang; Wang, Guoxiang; Xu, Tiefeng; Wang, Rongping; Dai, Shixun; Nie, Qiuhua

    2016-07-01

    The potentials of Sn, In, or Al doped ZnSb thin film as candidates for phase change materials have been studied in this paper. It was found that the Zn-Sb bonds were broken by the addition of the dopants and homopolar Zn-Zn bonds and other heteropolar bonds, such as Sn-Sb, In-Sb, and Al-Sb, were subsequently formed. The existence of homopolar Sn-Sn and In-In bonds in Zn50Sb36Sn14 and Zn41Sb36In23 films, but no any Al-Al bonds in Zn35Sb30Al35 film, was confirmed. All these three amorphous films crystallize with the appearance of crystalline rhombohedral Sb phase, and Zn35Sb30Al35 film even exhibits a second crystallization process where the crystalline AlSb phase is separated out. The Zn35Sb30Al35 film exhibits a reversible phase change behavior with a larger Ea (˜4.7 eV), higher Tc (˜245 °C), better 10-yr data retention (˜182 °C), less incubation time (20 ns at 70 mW), and faster complete crystallization speed (45 ns at 70 mW). Moreover, Zn35Sb30Al35 film shows the smaller root-mean-square (1.654 nm) and less change of the thickness between amorphous and crystalline state (7.5%), which are in favor of improving the reliability of phase change memory.

  16. The influence of oxygen partial pressure on material properties of Eu3+-doped Y2O2S thin film deposited by Pulsed Laser Deposition

    NASA Astrophysics Data System (ADS)

    Ali, A. G.; Dejene, B. F.; Swart, H. C.

    2016-01-01

    Eu3+-doping has been of interest to improve the luminescent characteristics of thin-film phosphors. Y2O2S:Eu3+ films have been grown on Si (100) substrates by using a Pulsed Laser Deposition technique. The thin films grown under different oxygen deposition pressure conditions have been characterized using structural and luminescent measurements. The X-ray diffraction patterns showed mixed phases of cubic and hexagonal crystal structures. As the oxygen partial pressure increased, the crystallinity of the films improved. Further increase of the O2 pressure to 140 mtorr reduced the crystallinity of the film. Similarly, both scanning electron microscopy and Atomic Force Microscopy confirmed that an increase in O2 pressure affected the morphology of the films. The average band gap of the films calculated from diffuse reflectance spectra using the Kubelka-Munk function was about 4.75 eV. The photoluminescence measurements indicated red emission of Y2O2S:Eu3+ thin films with the most intense peak appearing at 619 nm, which is assigned to the 5D0-7F2 transition of Eu3+. This most intense peak was totally quenched at higher O2 pressures. This phosphor may be a promising material for applications in the flat panel displays.

  17. Effects of anode materials on resistive characteristics of NiO thin films

    SciTech Connect

    Jia, Ze; Wang, Linkai; Zhang, Naiwen; Ren, Tianling; Liou, Juin J.

    2013-01-28

    This letter shows that the NiO-based structure with different anodes has different resistive switching properties. A conical conductive filament (CF) model is proposed for oxygen vacancies distributed in NiO films. Modeling analysis reveals much larger dissolution velocity of CF near anodes than near cathodes during the reset process. Different interfaces shown in Auger electron spectroscopy can be bound with the model to reveal that CF is dissolved in the structure with Pt or Au as anodes, while CF remains constant if the anode material is Ti or Al, which can explain whether switching properties occur in the specific NiO-based structures.

  18. Research on polycrystalline thin film submodules based on CuInSe sub 2 materials

    SciTech Connect

    Catalano, A.; Arya, R.; Carr, L.; Fieselmann, B.; Lommasson, T.; Podlesny, R.; Russell, L.; Skibo, S.; Rothwarf, A.; Birkmire, R. )

    1992-05-01

    This report describes progress during the first year of a three-year research program to develop 12%-efficient CuInSe{sub 2} (CIS) submodules with area greater than 900 cm{sup 2}. To meet this objective, the program was divided into five tasks: (1) windows, contacts, substrates; (2) absorber material; (3) device structure; (4) submodule design and encapsulation; and (5) process optimization. In the first year of the program, work was concentrated on the first three tasks with an objective to demonstrate a 9%-efficient CIS solar cell. 7 refs.

  19. Review of CdO thin films

    NASA Astrophysics Data System (ADS)

    Chandiramouli, R.; Jeyaprakash, B. G.

    2013-02-01

    Cadmium Oxide (CdO) thin film is one of the first transparent conducting oxide semiconductors. Its excellent optical and electronic properties have made CdO a promising material for flat panel displays. In this article, we provide a comprehensive review of the state-of-the-art research activities related to the 'preparation-property-application' triangle of CdO thin films.

  20. Advances in CZTS thin films and nanostructured

    NASA Astrophysics Data System (ADS)

    Ali, N.; Ahmed, R.; Bakhtiar-Ul-Haq; Shaari, A.

    2015-06-01

    Already published data for the optical band gap (Eg) of thin films and nanostructured copper zinc tin sulphide (CZTS) have been reviewed and combined. The vacuum (physical) and non-vacuum (chemical) processes are focused in the study for band gap comparison. The results are accumulated for thin films and nanostructured in different tables. It is inferred from the re- view that the nanostructured material has plenty of worth by engineering the band gap for capturing the maximum photons from solar spectrum.

  1. Microwave resonant technique in studies of photodielectric properties of bulk, thin film and nanoparticle materials

    NASA Astrophysics Data System (ADS)

    Pavlov, V. V.; Rakhmatullin, R. M.; Cefalas, A. C.; Semashko, V. V.

    2016-06-01

    An enhanced contactless microwave technique allows us to study the photoconductivity of materials. The transient response of the complex permittivity of matter (ε ={ε1}-j{ε2} ) under optical irradiation is measured with nanosecond time resolution. The main advantage of the novel methodology is the elimination of the polarization effect in evaluating photoconductivity. The potential of the methodology was demonstrated by photoconductivity measurements in Si [1 0 0] crystal, CeO2 nanocrystalline powder and Ce-doped LiYF4 single crystal. The variations of complex permittivity (δ {ε1} and δ {ε2} ) of Si [1 0 0] crystal, CeO2 nanocrystalline powder and Ce-doped LiYF4 single crystal under optical irradiation was measured and accurate values for crystalline band gaps were extracted. Finally, quantum confinement effects were observed in nano-size crystalline powders.

  2. Effect of capping material on interfacial ferromagnetism in FeRh thin films

    NASA Astrophysics Data System (ADS)

    Baldasseroni, C.; Pálsson, G. K.; Bordel, C.; Valencia, S.; Unal, A. A.; Kronast, F.; Nemsak, S.; Fadley, C. S.; Borchers, J. A.; Maranville, B. B.; Hellman, F.

    2014-01-01

    The role of the capping material in stabilizing a thin ferromagnetic layer at the interface between a FeRh film and cap in the nominally antiferromagnetic phase at room temperature was studied by x-ray magnetic circular dichroism in photoemission electron microscopy and polarized neutron reflectivity. These techniques were used to determine the presence or absence of interfacial ferromagnetism (FM) in films capped with different oxides and metals. Chemically stable oxide caps do not generate any interfacial FM while the effect of metallic caps depends on the element, showing that interfacial FM is due to metallic interdiffusion and the formation of a ternary alloy with a modified antiferromagnetic to ferromagnetic transition temperature.

  3. Reliability and engineering sciences area. Materials research: Single junction thin film

    NASA Technical Reports Server (NTRS)

    1986-01-01

    A test bench was designed and fabricated for the purpose of improving control of hot-spot test accuracy. Electrochemical corrosion research focused on corrosion mechanisms to which both crystalline and a-Si modules may be subjected in central station applications. A variety of cells and several designs were subjected to accelerated stress tests. Humiditiy degradation rates were determined and key electrochemical failure mechanisms were identified. Software was developed for the prediction of power loss resulting from open circuits in an array field of a-Si modules. Failure analysis was continued on the four ARCO Solar Genesis modules. The interactions of water on the silicon module was examined. An autocatalytic photooxidation model was proposed. The reliability and durability of bonding materials and electrical insulation were also studied.

  4. Reliability and engineering sciences area. Materials research: Single junction thin film

    NASA Astrophysics Data System (ADS)

    A test bench was designed and fabricated for the purpose of improving control of hot-spot test accuracy. Electrochemical corrosion research focused on corrosion mechanisms to which both crystalline and a-Si modules may be subjected in central station applications. A variety of cells and several designs were subjected to accelerated stress tests. Humiditiy degradation rates were determined and key electrochemical failure mechanisms were identified. Software was developed for the prediction of power loss resulting from open circuits in an array field of a-Si modules. Failure analysis was continued on the four ARCO Solar Genesis modules. The interactions of water on the silicon module was examined. An autocatalytic photooxidation model was proposed. The reliability and durability of bonding materials and electrical insulation were also studied.

  5. Effect of capping material on interfacial ferromagnetism in FeRh thin films

    SciTech Connect

    Baldasseroni, C.; Pálsson, G. K.; Nemsak, S.; Fadley, C. S.; Bordel, C.; Valencia, S.; Unal, A. A.; Kronast, F.; Borchers, J. A.; Maranville, B. B.; Hellman, F.

    2014-01-28

    The role of the capping material in stabilizing a thin ferromagnetic layer at the interface between a FeRh film and cap in the nominally antiferromagnetic phase at room temperature was studied by x-ray magnetic circular dichroism in photoemission electron microscopy and polarized neutron reflectivity. These techniques were used to determine the presence or absence of interfacial ferromagnetism (FM) in films capped with different oxides and metals. Chemically stable oxide caps do not generate any interfacial FM while the effect of metallic caps depends on the element, showing that interfacial FM is due to metallic interdiffusion and the formation of a ternary alloy with a modified antiferromagnetic to ferromagnetic transition temperature.

  6. Measurement of the thermoelectric properties of bulk and thin film materials

    SciTech Connect

    Danielson, L.

    1996-03-01

    The figure-of-merit (Z) of a thermoelectric material is defined as Z = S{sup 2}/{rho}k, where S is the Seebeck coefficient, {rho} is the electrical resistivity, and k is the thermal conductivity. Since Z is composed of three components, it is sensitive to measurement errors in each of the components. For example, a Seebeck coefficient measurement which is only 17% high combined with electrical resistivity and thermal conductivity measurements which are 17% too low will result in a Z value which is double the correct value. It is therefore important to observe correct technique when performing measurements of S, {rho}, and k; and to recognize the limitations of the measurements. The purpose of the course is to address some of those issues in order to increase the accuracy of the thermoelectric measurements.

  7. Chiral atomically thin films

    NASA Astrophysics Data System (ADS)

    Kim, Cheol-Joo; Sánchez-Castillo, A.; Ziegler, Zack; Ogawa, Yui; Noguez, Cecilia; Park, Jiwoong

    2016-06-01

    Chiral materials possess left- and right-handed counterparts linked by mirror symmetry. These materials are useful for advanced applications in polarization optics, stereochemistry and spintronics. In particular, the realization of spatially uniform chiral films with atomic-scale control of their handedness could provide a powerful means for developing nanodevices with novel chiral properties. However, previous approaches based on natural or grown films, or arrays of fabricated building blocks, could not offer a direct means to program intrinsic chiral properties of the film on the atomic scale. Here, we report a chiral stacking approach, where two-dimensional materials are positioned layer-by-layer with precise control of the interlayer rotation (θ) and polarity, resulting in tunable chiral properties of the final stack. Using this method, we produce left- and right-handed bilayer graphene, that is, a two-atom-thick chiral film. The film displays one of the highest intrinsic ellipticity values (6.5 deg μm–1) ever reported, and a remarkably strong circular dichroism (CD) with the peak energy and sign tuned by θ and polarity. We show that these chiral properties originate from the large in-plane magnetic moment associated with the interlayer optical transition. Furthermore, we show that we can program the chiral properties of atomically thin films layer-by-layer by producing three-layer graphene films with structurally controlled CD spectra.

  8. Chiral atomically thin films.

    PubMed

    Kim, Cheol-Joo; Sánchez-Castillo, A; Ziegler, Zack; Ogawa, Yui; Noguez, Cecilia; Park, Jiwoong

    2016-06-01

    Chiral materials possess left- and right-handed counterparts linked by mirror symmetry. These materials are useful for advanced applications in polarization optics, stereochemistry and spintronics. In particular, the realization of spatially uniform chiral films with atomic-scale control of their handedness could provide a powerful means for developing nanodevices with novel chiral properties. However, previous approaches based on natural or grown films, or arrays of fabricated building blocks, could not offer a direct means to program intrinsic chiral properties of the film on the atomic scale. Here, we report a chiral stacking approach, where two-dimensional materials are positioned layer-by-layer with precise control of the interlayer rotation (θ) and polarity, resulting in tunable chiral properties of the final stack. Using this method, we produce left- and right-handed bilayer graphene, that is, a two-atom-thick chiral film. The film displays one of the highest intrinsic ellipticity values (6.5 deg μm(-1)) ever reported, and a remarkably strong circular dichroism (CD) with the peak energy and sign tuned by θ and polarity. We show that these chiral properties originate from the large in-plane magnetic moment associated with the interlayer optical transition. Furthermore, we show that we can program the chiral properties of atomically thin films layer-by-layer by producing three-layer graphene films with structurally controlled CD spectra. PMID:26900756

  9. Using an SU-8 photoresist structure and cytochrome C thin film sensing material for a microbolometer.

    PubMed

    Lai, Jian-Lun; Liao, Chien-Jen; Su, Guo-Dung John

    2012-01-01

    There are two critical parameters for microbolometers: the temperature coefficient of resistance (TCR) of the sensing material, and the thermal conductance of the insulation structure. Cytochrome c protein, having a high TCR, is a good candidate for infrared detection. We can use SU-8 photoresist for the thermal insulation structure, given its low thermal conductance. In this study, we designed a platform structure based on a SU-8 photoresist. We fabricated an infrared sensing pixel and recorded a high TCR for this new structure. The SU-8 photoresist insulation structure was fabricated using the exposure dose method. We experimentally demonstrated high values of TCR from 22%/K to 25.7%/K, and the measured noise was 1.2 × 10(-8) V2/Hz at 60 Hz. When the bias current was 2 μA, the calculated voltage responsivity was 1.16 × 10(5) V/W. This study presents a new kind of microbolometer based on cytochrome c protein on top of an SU-8 photoresist platform that does not require expensive vacuum deposition equipment. PMID:23443384

  10. Using an SU-8 Photoresist Structure and Cytochrome C Thin Film Sensing Material for a Microbolometer

    PubMed Central

    Lai, Jian-Lun; Liao, Chien-Jen; Su, Guo-Dung John

    2012-01-01

    There are two critical parameters for microbolometers: the temperature coefficient of resistance (TCR) of the sensing material, and the thermal conductance of the insulation structure. Cytochrome c protein, having a high TCR, is a good candidate for infrared detection. We can use SU-8 photoresist for the thermal insulation structure, given its low thermal conductance. In this study, we designed a platform structure based on a SU-8 photoresist. We fabricated an infrared sensing pixel and recorded a high TCR for this new structure. The SU-8 photoresist insulation structure was fabricated using the exposure dose method. We experimentally demonstrated high values of TCR from 22%/K to 25.7%/K, and the measured noise was 1.2 × 10−8 V2/Hz at 60 Hz. When the bias current was 2 μA, the calculated voltage responsivity was 1.16 × 105 V/W. This study presents a new kind of microbolometer based on cytochrome c protein on top of an SU-8 photoresist platform that does not require expensive vacuum deposition equipment. PMID:23443384

  11. Phase Coarsening in Thin Films

    NASA Astrophysics Data System (ADS)

    Wang, K. G.; Glicksman, M. E.

    2015-08-01

    Phase coarsening (Ostwald ripening) phenomena are ubiquitous in materials growth processes such as thin film formation. The classical theory explaining late-stage phase coarsening phenomena was developed by Lifshitz and Slyozov, and by Wagner in the 1960s. Their theory is valid only for a vanishing volume fraction of the second phase in three dimensions. However, phase coarsening in two-dimensional systems is qualitatively different from that in three dimensions. In this paper, the many-body concept of screening length is reviewed, from which we derive the growth law for a `screened' phase island, and develop diffusion screening theory for phase coarsening in thin films. The coarsening rate constant, maximum size of phase islands in films, and their size distribution function will be derived from diffusion screening theory. A critical comparison will be provided of prior coarsening concepts and improvements derived from screening approaches.

  12. Mechanical Properties of Silicon Carbonitride Thin Films

    NASA Astrophysics Data System (ADS)

    Peng, Xiaofeng; Hu, Xingfang; Wang, Wei; Song, Lixin

    2003-02-01

    Silicon carbonitride thin films were synthesized by reactive rf sputtering a silicon carbide target in nitrogen and argon atmosphere, or sputtering a silicon nitride target in methane and argon atmosphere, respectively. The Nanoindentation technique (Nanoindenter XP system with a continuous stiffness measurement technique) was employed to measure the hardness and elastic modulus of thin films. The effects of sputtering power on the mechanical properties are different for the two SiCN thin films. With increasing sputtering power, the hardness and the elastic modulus decrease for the former but increase for the latter. The tendency is similar to the evolution trend of Si-C bonds in SiCN materials. This reflects that Si-C bonds provide greater hardness for SiCN thin films than Si-N and C-N bonds.

  13. Detection of charge storage on molecular thin films of tris(8-hydroxyquinoline) aluminum (Alq3) by Kelvin force microscopy: a candidate system for high storage capacity memory cells.

    PubMed

    Paydavosi, Sarah; Aidala, Katherine E; Brown, Patrick R; Hashemi, Pouya; Supran, Geoffrey J; Osedach, Timothy P; Hoyt, Judy L; Bulović, Vladimir

    2012-03-14

    Retention and diffusion of charge in tris(8-hydroxyquinoline) aluminum (Alq(3)) molecular thin films are investigated by injecting electrons and holes via a biased conductive atomic force microscopy tip into the Alq(3) films. After the charge injection, Kelvin force microscopy measurements reveal minimal changes with time in the spatial extent of the trapped charge domains within Alq(3) films, even for high hole and electron densities of >10(12) cm(-2). We show that this finding is consistent with the very low mobility of charge carriers in Alq(3) thin films (<10(-7) cm(2)/(Vs)) and that it can benefit from the use of Alq(3) films as nanosegmented floating gates in flash memory cells. Memory capacitors using Alq(3) molecules as the floating gate are fabricated and measured, showing durability over more than 10(4) program/erase cycles and the hysteresis window of up to 7.8 V, corresponding to stored charge densities as high as 5.4 × 10(13) cm(-2). These results demonstrate the potential for use of molecular films in high storage capacity nonvolatile memory cells. PMID:22332966

  14. Defect chemistry and chalcogen diffusion in thin-film Cu{sub 2}ZnSnSe{sub 4} materials

    SciTech Connect

    Harvey, Steven P.; Repins, Ingrid; Teeter, Glenn

    2015-02-21

    Selenium diffusion in polycrystalline thin-film Cu{sub 2}ZnSn(S,Se){sub 4} (CZTSe) on molybdenum-coated soda-lime glass substrates was investigated by in situ monitoring of the molybdenum back-contact resistance during high-temperature selenization treatments. In these measurements, selenium diffusion through the CZTSe layer results in conversion of the molybdenum layer to MoSe{sub 2}, increasing the sheet resistance of the film stack. By monitoring the rate of MoSe{sub 2} formation as a function of annealing temperature, an activation energy of 0.5 ± 0.1 eV has been measured for selenium diffusion in CZTSe. The partial pressure dependence of chalcogen diffusion suggests that chalcogen vacancies are not the defect controlling chalcogen diffusion in thin-film CZTSe.

  15. Metal-metal chalcogenide molecular precursors to binary, ternary, and quaternary metal chalcogenide thin films for electronic devices.

    PubMed

    Zhang, Ruihong; Cho, Seonghyuk; Lim, Daw Gen; Hu, Xianyi; Stach, Eric A; Handwerker, Carol A; Agrawal, Rakesh

    2016-04-11

    Bulk metals and metal chalcogenides are found to dissolve in primary amine-dithiol solvent mixtures at ambient conditions. Thin-films of CuS, SnS, ZnS, Cu2Sn(S(x),Se(1-x))3, and Cu2ZnSn(S(x)Se(1-x))4 (0 ≤ x ≤ 1) were deposited using the as-dissolved solutions. Cu2ZnSn(S(x)Se(1-x))4 solar cells with efficiencies of 6.84% and 7.02% under AM1.5 illumination were fabricated from two example solution precursors, respectively. PMID:26981781

  16. Thin-film metal hydrides.

    PubMed

    Remhof, Arndt; Borgschulte, Andreas

    2008-12-01

    The goal of the medieval alchemist, the chemical transformation of common metals into nobel metals, will forever be a dream. However, key characteristics of metals, such as their electronic band structure and, consequently, their electric, magnetic and optical properties, can be tailored by controlled hydrogen doping. Due to their morphology and well-defined geometry with flat, coplanar surfaces/interfaces, novel phenomena may be observed in thin films. Prominent examples are the eye-catching hydrogen switchable mirror effect, the visualization of solid-state diffusion and the formation of complex surface morphologies. Thin films do not suffer as much from embrittlement and/or decrepitation as bulk materials, allowing the study of cyclic absorption and desorption. Therefore, thin-metal hydride films are used as model systems to study metal-insulator transitions, for high throughput combinatorial research or they may be used as indicator layers to study hydrogen diffusion. They can be found in technological applications as hydrogen sensors, in electrochromic and thermochromic devices. In this review, we discuss the effect of hydrogen loading of thin niobium and yttrium films as archetypical examples of a transition metal and a rare earth metal, respectively. Our focus thereby lies on the hydrogen induced changes of the electronic structure and the morphology of the thin films, their optical properties, the visualization and the control of hydrogen diffusion and on the study of surface phenomena and catalysis. PMID:18980236

  17. Research on Advanced Thin Film Batteries

    SciTech Connect

    Goldner, Ronald B.

    2003-11-24

    During the past 7 years, the Tufts group has been carrying out research on advanced thin film batteries composed of a thin film LiCo02 cathode (positive electrode), a thin film LiPON (lithium phosphorous oxynitride) solid electrolyte, and a thin film graphitic carbon anode (negative electrode), under grant DE FG02-95ER14578. Prior to 1997, the research had been using an rfsputter deposition process for LiCoOi and LiPON and an electron beam evaporation or a controlled anode arc evaporation method for depositing the carbon layer. The pre-1997 work led to the deposition of a single layer cell that was successfully cycled for more than 400 times [1,2] and the research also led to the deposition of a monolithic double-cell 7 volt battery that was cycled for more than 15 times [3]. Since 1997, the research has been concerned primarily with developing a research-worthy and, possibly, a production-worthy, thin film deposition process, termed IBAD (ion beam assisted deposition) for depositing each ofthe electrodes and the electrolyte of a completely inorganic solid thin film battery. The main focus has been on depositing three materials - graphitic carbon as the negative electrode (anode), lithium cobalt oxide (nominally LiCoCb) as the positive electrode (cathode), and lithium phosphorus oxynitride (LiPON) as the electrolyte. Since 1998, carbon, LiCoOa, and LiPON films have been deposited using the IBAD process with the following results.

  18. Carbon Nanotube Thin-Film Antennas.

    PubMed

    Puchades, Ivan; Rossi, Jamie E; Cress, Cory D; Naglich, Eric; Landi, Brian J

    2016-08-17

    Multiwalled carbon nanotube (MWCNT) and single-walled carbon nanotube (SWCNT) dipole antennas have been successfully designed, fabricated, and tested. Antennas of varying lengths were fabricated using flexible bulk MWCNT sheet material and evaluated to confirm the validity of a full-wave antenna design equation. The ∼20× improvement in electrical conductivity provided by chemically doped SWCNT thin films over MWCNT sheets presents an opportunity for the fabrication of thin-film antennas, leading to potentially simplified system integration and optical transparency. The resonance characteristics of a fabricated chlorosulfonic acid-doped SWCNT thin-film antenna demonstrate the feasibility of the technology and indicate that when the sheet resistance of the thin film is >40 ohm/sq no power is absorbed by the antenna and that a sheet resistance of <10 ohm/sq is needed to achieve a 10 dB return loss in the unbalanced antenna. The dependence of the return loss performance on the SWCNT sheet resistance is consistent with unbalanced metal, metal oxide, and other CNT-based thin-film antennas, and it provides a framework for which other thin-film antennas can be designed. PMID:27454334

  19. Laser processing for thin-film photovoltaics

    NASA Astrophysics Data System (ADS)

    Compaan, Alvin D.

    1995-04-01

    Over the past decade major advances have occurred in the field of thin- film photovoltaics (PV) with many of them a direct consequence of the application of laser processing. Improved cell efficiencies have been achieved in crystalline and polycrystalline Si, in hydrogenated amorphous silicon, and in two polycrystalline thin-film materials. The use of lasers in photovoltaics includes laser hole drilling for emitter wrap-through, laser trenching for buried bus lines, and laser texturing of crystalline and polycrystalline Si cells. In thin-film devices, laser scribing is gaining increased importance for module interconnects. Pulsed laser recrystallization of boron-doped hydrogenated amorphous silicon is used to form highly conductive p-layers in p-i-n amorphous silicon cells and in thin-film transistors. Optical beam melting appears to be an attractive method for forming metal semiconductor alloys for contact formation. Finally, pulsed lasers are used for deposition of the entire semiconductor absorber layer in two types of polycrystalline thin-film cells-those based on copper indium diselenide and those based on cadmium telluride. In our lab we have prepared and studied heavily doped polycrystalline silicon thin films and also have used laser physical vapor deposition (LPVD) to prepare 'all-LPVD' CdS/CdTe solar cells on glass with efficiencies tested at NREL at 10.5%. LPVD is highly flexible and ideally suited for prototyping PV cells using ternary or quaternary alloys and for exploring new dopant combinations.

  20. Quantitative determination of molecular structure in multilayered thin films of biaxial and lower symmetry from photon spectroscopies. I. Reflection infrared vibrational spectroscopy

    NASA Astrophysics Data System (ADS)

    Parikh, Atul N.; Allara, David L.

    1992-01-01

    A semitheoretical formalism based on classical electromagnetic wave theory has been developed for application to the quantitative treatment of reflection spectra from multilayered anisotropic films on both metallic and nonmetallic substrates. Both internal and external reflection experiments as well as transmission can be handled. The theory is valid for all wavelengths and is appropriate, therefore, for such experiments as x-ray reflectivity, uv-visible spectroscopic ellipsometry, and infrared reflection spectroscopy. Further, the theory is applicable to multilayered film structures of variable number of layers, each with any degree of anisotropy up to and including full biaxial symmetry. The reflectivities (and transmissivities) are obtained at each frequency by solving the wave propagation equations using a rigorous 4×4 transfer matrix method developed by Yeh in which the optical functions of each medium are described in the form of second rank (3×3) tensors. In order to obtain optical tensors for materials not readily available in single crystal form, a method has been developed to evaluate tensor elements from the complex scalar optical functions (n̂) obtained from the isotropic material with the limitations that the molecular excitations are well characterized and obey photon-dipole selection rules. This method is intended primarily for infrared vibrational spectroscopy and involves quantitative decomposition of the isotropic imaginary optical function (k) spectrum into a sum of contributions from fundamental modes, the assignment of a direction in molecular coordinates to the transition dipole matrix elements for each mode, the appropriate scaling of each k vector component in surface coordinates according to a selected surface orientation of the molecule to give a diagonal im(n̂) tensor, and the calculation of the real(n̂) spectrum tensor elements by the Kramers-Kronig transformation. Tensors for other surface orientations are generated by an

  1. Thin film temperature sensor

    NASA Technical Reports Server (NTRS)

    Grant, H. P.; Przybyszewski, J. S.

    1980-01-01

    Thin film surface temperature sensors were developed. The sensors were made of platinum-platinum/10 percent rhodium thermocouples with associated thin film-to-lead wire connections and sputtered on aluminum oxide coated simulated turbine blades for testing. Tests included exposure to vibration, low velocity hydrocarbon hot gas flow to 1250 K, and furnace calibrations. Thermal electromotive force was typically two percent below standard type S thermocouples. Mean time to failure was 42 hours at a hot gas flow temperature of 1250 K and an average of 15 cycles to room temperature. Failures were mainly due to separation of the platinum thin film from the aluminum oxide surface. Several techniques to improve the adhesion of the platinum are discussed.

  2. Thin film photovoltaics

    SciTech Connect

    Zweibel, K; Ullal, H S

    1989-05-01

    Thin films are considered a potentially attractive technological approach to making cost-effective electricity by photovoltaics. Over the last twenty years, many have been investigated and some (cadmium telluride, copper indium diselenide, amorphous silicon) have become leading candidates for future large-scale commercialization. This paper surveys the past development of these key thin films and gives their status and future prospects. In all cases, significant progress toward cost-effective PV electricity has been made. If this progress continues, it appears that thin film PV could provide electricity that is competitive for summer daytime peaking power requirements by the middle of the 1990s; and electricity in a range that is competitive with fossil fuel costs (i.e., 6 cents/kilowatt-hour) should be available from PV around the turn of the century. 22 refs., 9 figs.

  3. CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES: Structural and Electrical Properties of Single Crystalline Ga-Doped ZnO Thin Films Grown by Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Lu, Zhong-Lin; Zou, Wen-Qin; Xu, Ming-Xiang; Zhang, Feng-Ming; Du, You-Wei

    2009-11-01

    High-quality Ga-doped ZnO (ZnO:Ga) single crystalline films with various Ga concentrations are grown on a-plane sapphire substrates using molecular-beam epitaxy. The site configuration of doped Ga atoms is studied by means of x-ray absorption spectroscopy. It is found that nearly all Ga can substitute into ZnO lattice as electrically active donors, a generating high density of free carriers with about one electron per Ga dopant when the Ga concentration is no more than 2%. However, further increasing the Ga doping concentration leads to a decrease of the conductivity due to partial segregation of Ga atoms to the minor phase of the spinel ZnGa2O4 or other intermediate phase. It seems that the maximum solubility of Ga in the ZnO single crystalline film is about 2 at.% and the lowest resistivity can reach 1.92 × 10-4 Ω·cm at room temperature, close to the best value reported. In contrast to ZnO:Ga thin film with 1% or 2% Ga doping, the film with 4% Ga doping exhibits a metal semiconductor transition at 80 K. The scattering mechanism of conducting electrons in single crystalline ZnO:Ga thin film is discussed.

  4. Thin film ceramic thermocouples

    NASA Technical Reports Server (NTRS)

    Gregory, Otto (Inventor); Fralick, Gustave (Inventor); Wrbanek, John (Inventor); You, Tao (Inventor)

    2011-01-01

    A thin film ceramic thermocouple (10) having two ceramic thermocouple (12, 14) that are in contact with each other in at least on point to form a junction, and wherein each element was prepared in a different oxygen/nitrogen/argon plasma. Since each element is prepared under different plasma conditions, they have different electrical conductivity and different charge carrier concentration. The thin film thermocouple (10) can be transparent. A versatile ceramic sensor system having an RTD heat flux sensor can be combined with a thermocouple and a strain sensor to yield a multifunctional ceramic sensor array. The transparent ceramic temperature sensor that could ultimately be used for calibration of optical sensors.

  5. Sample-morphology effects on x-ray photoelectron peak intensities. II. Estimation of detection limits for thin-film materials

    SciTech Connect

    Powell, Cedric J.; Werner, Wolfgang S. M.; Smekal, Werner

    2014-09-01

    The authors show that the National Institute of Standards and Technology database for the simulation of electron spectra for surface analysis (SESSA) can be used to determine detection limits for thin-film materials such as a thin film on a substrate or buried at varying depths in another material for common x-ray photoelectron spectroscopy (XPS) measurement conditions. Illustrative simulations were made for a W film on or in a Ru matrix and for a Ru film on or in a W matrix. In the former case, the thickness of a W film at a given depth in the Ru matrix was varied so that the intensity of the W 4d{sub 5/2} peak was essentially the same as that for a homogeneous RuW{sub 0.001} alloy. Similarly, the thickness of a Ru film at a selected depth in the W matrix was varied so that the intensity of the Ru 3p{sub 3/2} peak matched that from a homogeneous WRu{sub 0.01} alloy. These film thicknesses correspond to the detection limits of each minor component for measurement conditions where the detection limits for a homogeneous sample varied between 0.1 at. % (for the RuW{sub 0.001} alloy) and 1 at. % (for the WRu{sub 0.01} alloy). SESSA can be similarly used to convert estimates of XPS detection limits for a minor species in a homogeneous solid to the corresponding XPS detection limits for that species as a thin film on or buried in the chosen solid.

  6. Progress in polycrystalline thin-film solar cells

    SciTech Connect

    Zweibel, K; Hermann, A; Mitchell, R

    1983-07-01

    Photovoltaic devices based on several polycrystalline thin-film materials have reached near and above 10% sunlight-to-electricity conversion efficiencies. This paper examines the various polycrystalline thin-film PV materials including CuInSe/sub 2/ and CdTe in terms of their material properties, fabrication techniques, problems, and potentials.

  7. Thin film solar cell workshop

    NASA Technical Reports Server (NTRS)

    Armstrong, Joe; Jeffrey, Frank

    1993-01-01

    A summation of responses to questions posed to the thin-film solar cell workshop and the ensuing discussion is provided. Participants in the workshop included photovoltaic manufacturers (both thin film and crystalline), cell performance investigators, and consumers.

  8. Liquid crystals for organic thin-film transistors

    NASA Astrophysics Data System (ADS)

    Iino, Hiroaki; Usui, Takayuki; Hanna, Jun-Ichi

    2015-04-01

    Crystalline thin films of organic semiconductors are a good candidate for field effect transistor (FET) materials in printed electronics. However, there are currently two main problems, which are associated with inhomogeneity and poor thermal durability of these films. Here we report that liquid crystalline materials exhibiting a highly ordered liquid crystal phase of smectic E (SmE) can solve both these problems. We design a SmE liquid crystalline material, 2-decyl-7-phenyl-[1]benzothieno[3,2-b][1]benzothiophene (Ph-BTBT-10), for FETs and synthesize it. This material provides uniform and molecularly flat polycrystalline thin films reproducibly when SmE precursor thin films are crystallized, and also exhibits high durability of films up to 200 °C. In addition, the mobility of FETs is dramatically enhanced by about one order of magnitude (over 10 cm2 V-1 s-1) after thermal annealing at 120 °C in bottom-gate-bottom-contact FETs. We anticipate the use of SmE liquid crystals in solution-processed FETs may help overcome upcoming difficulties with novel technologies for printed electronics.

  9. Scanning electron and cathodoluminescence imaging of thin film Lu{sub 2}SiO{sub 5}:Ce scintillating materials

    SciTech Connect

    Rack, P. D.; Peak, J. D.; Melcher, C. L.; Fitz-Gerald, J. M.

    2007-12-10

    Cerium doped lutetium orthosilicate thin films were sputter deposited onto rough and smooth alumina substrates to compare their extrinsic photoluminescence efficiency. To understand the photoluminescence results, scanning electron and cathodoluminescence imaging were performed. The plane view and cross-section images revealed that dark cathodoluminescence regions were correlated with topology in both films, though the mechanisms for the degraded luminescence were different. For the rough films, substrate topology causes localized shadowing of the sputtered species which creates compositional inhomogeneities. The smooth films have protrusions caused by thermally induced stress and the reduced cathodoluminescence intensity is attributed to electron-hole surface recombination.

  10. Probing differential hydration of poly(vinylpyrrolidone) thin films using tracer mobility: an insight from fluorescence correlation spectroscopy.

    PubMed

    Bhattacharya, Sukanya; Dey, Arghya; Chowdhury, Arindam

    2014-05-15

    Dynamics of small probe molecules have been routinely used to unravel the intrinsic details of charged ion transport in polymer brushes and polyelectrolyte multilayer (PEM) thin films. However, corresponding morphological properties affected with absorption of moisture have been hardly dealt with despite numerous applications of isotropic thin films in material chemistry and medical purposes. We have explored the overall structural changes associated with plasticization of PVP thin films by probing dynamics of small reporter (rhodamine 6G, Rh6G) molecules using fluorescence correlation spectroscopy (FCS). It was observed that under lesser amounts of absorbed moisture, the rigidity of the film matrix was high enough to inhibit appreciable molecular mobility. Nonetheless, with gradual increase in the moisture level within the film, molecular movement became extremely facile, so much so that it almost attained close to a solution like state. Molecular mobility was found to be dependent on both the method of preparation and the thickness of the thin films. The diffusivities mostly followed anomalous subdiffusive behaviors, reminiscent of dynamics of tracers in crowded cellular environments. The mobility was found to be independent of any electrostatic interaction between probe and polymer thin film. Hence, the tracer dynamics was attributed most likely to the viscoelasticity of the thin film matrix. PMID:24738930

  11. Defect study of molecular beam epitaxy grown undoped GaInNAsSb thin film using junction-capacitance spectroscopy

    SciTech Connect

    Monirul Islam, Muhammad; Miyashita, Naoya; Ahsan, Nazmul; Okada, Yoshitaka

    2013-02-18

    Defects in undoped GaInNAsSb thin film (i-GaInNAsSb) were investigated by junction-capacitance technique using admittance and transient photocapacitance (TPC) spectroscopy. An electron trap D2 was identified at 0.34 eV below the conduction band (E{sub C}) of i-GaInNAsSb using admittance spectroscopy. Optical transition of valance band (E{sub V}) electrons to a localized state OH1 (E{sub V} + 0.75 eV) was manifested in negative TPC signal. Combined activation energy of OH1 and D2 defect corresponds to the band-gap of i-GaInNAsSb, suggesting that OH1/D2 acts as an efficient recombination center. TPC signal at {approx}1.59 eV above E{sub V} was attributed to the nitrogen-induced localized state in GaInNAsSb.

  12. Pulsed laser deposition and characterization of cellulase thin films

    NASA Astrophysics Data System (ADS)

    Cicco, N.; Morone, A.; Verrastro, M.; Viggiano, V.

    2013-08-01

    Thin films of cellulase were obtained by pulsed laser deposition (PLD) on an appropriate substrate. Glycoside hydrolase cellulase has received our attention because it emerges among the antifouling enzymes (enzymes being able to remove and prevent the formation of micro-organism biofilms) used in industry and medicine field. Pressed cellulase pellets, used as target material, were ablated with pulses of a Nd-YAG laser working at wavelength of 532 nm. In this work, we evaluated the impact of PLD technique both on molecular structure and hydrolytic activity of cellulase. Characteristic chemical bonds and morphology of deposited layers were investigated by FTIR spectroscopy and SEM respectively. The hydrolytic activity of cellulase thin films was detected by a colorimetric assay.

  13. SBA-15 mesoporous silica free-standing thin films containing copper ions bounded via propyl phosphonate units - preparation and characterization

    NASA Astrophysics Data System (ADS)

    Laskowski, Lukasz; Laskowska, Magdalena; Jelonkiewicz, Jerzy; Dulski, Mateusz; Wojtyniak, Marcin; Fitta, Magdalena; Balanda, Maria

    2016-09-01

    The SBA-15 silica thin films containing copper ions anchored inside channels via propyl phosphonate groups are investigated. Such materials were prepared in the form of thin films, with hexagonally arranged pores, laying rectilinear to the substrate surface. However, in the case of our thin films, their free standing form allowed for additional research possibilities, that are not obtainable for typical thin films on a substrate. The structural properties of the samples were investigated by X-ray reflectometry, atomic force microscopy (AFM) and transmission electron microscopy (TEM). The molecular structure was examined by Raman spectroscopy supported by numerical simulations. Magnetic measurements (SQUID magnetometry and EPR spectroscopy) showed weak antiferromagnetic interactions between active units inside silica channels. Consequently, the pores arrangement was determined and the process of copper ions anchoring by propyl phosphonate groups was verified in unambiguous way. Moreover, the type of interactions between magnetic atoms was determined.

  14. Thin film photovoltaic cell

    DOEpatents

    Meakin, John D.; Bragagnolo, Julio

    1982-01-01

    A thin film photovoltaic cell having a transparent electrical contact and an opaque electrical contact with a pair of semiconductors therebetween includes utilizing one of the electrical contacts as a substrate and wherein the inner surface thereof is modified by microroughening while being macro-planar.

  15. Materials science and integration bases for fabrication of (BaxSr1-x)TiO3 thin film capacitors with layered Cu-based electrodes

    NASA Astrophysics Data System (ADS)

    Fan, W.; Kabius, B.; Hiller, J. M.; Saha, S.; Carlisle, J. A.; Auciello, O.; Chang, R. P. H.; Ramesh, R.

    2003-11-01

    The synthesis and fundamental material properties of layered TiAl/Cu/Ta electrodes were investigated to achieve the integration of Cu electrodes with high-dielectric constant (κ) oxide thin films for application to the fabrication of high-frequency devices. The Ta layer is an excellent diffusion barrier to inhibit deleterious Cu diffusion into the Si substrate, while the TiAl layer provides an excellent barrier against oxygen diffusion into the Cu layer to inhibit Cu oxidation during the growth of the high-κ layer in an oxygen atmosphere. Polycrystalline (BaxSr1-x)TiO3 (BST) thin films were grown on the Cu-based bottom electrode by rf magnetron sputtering at temperatures in the range 400-600 °C in oxygen, to investigate the performance of BST/Cu-based capacitors. Characterization of the Cu-based layered structure using surface analytical methods showed that two amorphous oxide layers were formed on both sides of the TiAl barrier, such that the oxide layer on the free surface of the TiAl layer correlates with TiAlOx, while the oxide layer at the TiAl/Cu interface is an Al2O3-rich layer. This double amorphous barrier layer structure effectively prevents oxygen penetration towards the underlying Cu and Ta layers. The TiAlOx interfacial layer, which has a relatively low dielectric constant compared with BST, reduced the total capacitance of the BST thin film capacitors. In addition, the layered electrode-oxide interface roughening observed during the growth of BST films at high temperature, due to copper grain growth, resulted in large dielectric loss on the fabricated BST capacitors. These problems were solved by growing the BST layer at 450 °C followed by a rapid thermal annealing at 700 °C. This process significantly reduced the thickness of the TiAlOx layer and interface roughness resulting in BST capacitors exhibiting properties suitable for the fabrication of high-performance high-frequency devices. In summary, relatively high dielectric constant (280), low

  16. Characterization of CuInS2 thin films prepared from materials grown by using the mechanochemical method and their photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Akaki, Yoji; Sugimoto, Kanta; Nakamura, Shigeyuki; Yamaguchi, Toshiyuki; Yoshino, Kenji

    2015-08-01

    Cu-In-S thin films were deposited on glass substrates using single-source thermal evaporation with ternary compounds as source materials. Polycrystalline CuInS2 powder grown using the mechanochemical method was employed as the source material. After deposition, the films were annealed in H2S gas at different temperatures from 250 to 500 °C for 60 min. X-ray diffraction patterns indicated that single-phase CuInS2 was formed when annealed above 400 °C. The grain size of the crystals in thin films was approximately 0.2 to 2.0 µm. The best Al/ZnO:Al/ZnO/CdS/CuInS2/Mo solar cell had an open-circuit voltage of 360 mV, a short-circuit current density of 18.6 mA/cm2, and a fill factor of 35.5%, resulting in 2.38% efficiency.

  17. Effect of GaN interlayer on polarity control of epitaxial ZnO thin films grown by molecular beam epitaxy

    SciTech Connect

    Wang, X. Q.; Sun, H. P.; Pan, X. Q.

    2010-10-11

    Epitaxial ZnO thin films were grown on nitrided (0001) sapphire substrates with an intervening GaN layer by rf-plasma-assisted molecular beam epitaxy. It was found that polarity of the ZnO epilayer could be controlled by modifying the GaN interlayer. ZnO grown on a distorted 3-nm-thick GaN interlayer has Zn-polarity while ZnO on a 20-nm-thick GaN interlayer with a high structural quality has O-polarity. High resolution transmission electron microscopy analysis indicates that the polarity of ZnO epilayer is controlled by the atomic structure of the interface between the ZnO buffer layer and the intervening GaN layer.

  18. Electron spin resonance of Zn{sub 1-x}Mg{sub x}O thin films grown by plasma-assisted molecular beam epitaxy

    SciTech Connect

    Wassner, T. A.; Stutzmann, M.; Brandt, M. S.; Laumer, B.; Althammer, M.; Goennenwein, S. T. B.; Eickhoff, M.

    2010-08-30

    Zn{sub 1-x}Mg{sub x}O thin films with a Mg content x between 0 and 0.42 grown by plasma-assisted molecular beam epitaxy on c-plane sapphire substrates were investigated by electron spin resonance at 5 K. Above band gap illumination induces a persistent resonance signal, which is attributed to free conduction band electrons. The g-factors of the Zn{sub 1-x}Mg{sub x}O epitaxial layers and their anisotropy were determined experimentally and an increase from g{sub ||}=1.957 for x=0 to g{sub ||}=1.970 for x=0.42 was found, accompanied by a decrease in anisotropy. A comparison with g-factors of the Al{sub x}Ga{sub 1-x}N system is also given.

  19. Topological insulator Bi{sub 2}Se{sub 3} thin films grown on double-layer graphene by molecular beam epitaxy

    SciTech Connect

    Song Canli; Jiang Yeping; Chang Cuizu; Xue Qikun; Wang Yilin; Zhang Yi; Wang Lili; He Ke; Fang Zhong; Dai Xi; Xie Xincheng; Ma Xucun; Chen Xi; Jia Jinfeng; Wang Yayu; Qi Xiaoliang; Zhang Shoucheng

    2010-10-04

    Atomically flat thin films of topological insulator Bi{sub 2}Se{sub 3} have been grown on double-layer graphene formed on 6H-SiC(0001) substrate by molecular beam epitaxy. By a combined study of reflection high energy electron diffraction and scanning tunneling microscopy, we identified the Se-rich condition and temperature criterion for layer-by-layer growth of epitaxial Bi{sub 2}Se{sub 3} films. The as-grown films without doping exhibit a low defect density of 1.0{+-}0.2x10{sup 11}/cm{sup 2}, and become a bulk insulator at a thickness of ten quintuple layers, as revealed by in situ angle resolved photoemission spectroscopy measurement.

  20. Magnetic properties of Mn{sub x}Ti{sub 1-x}N thin films grown by plasma-assisted molecular beam epitaxy

    SciTech Connect

    Wu, S. X.; Xia, Y. Q.; Yu, X. L.; Liu, Y. J.; Li, S. W.

    2007-09-15

    High-quality Mn{sub x}Ti{sub 1-x}N thin films were grown on MgO(001) substrates using plasma-assisted molecular beam epitaxy. Magnetic measurements evidence the presence of ferromagnetism with Curie temperature exceeding 380 K. X-ray photoelectron spectroscopy indicates that the Mn ions are in a divalent state and uniformly substitute on Ti cation sites, consistent with the ferromagnetism that correlates with Mn substitution on Ti sites. The origin of the ferromagnetism might be attributed to itinerant-carrier mediated Rudermann-Kittel-Kasuya-Yosida (RKKY)-type long-range coupling which allows for arbitrary itinerant-carrier spin polarization and dynamic correlations.

  1. Domain formation due to surface steps in topological insulator Bi{sub 2}Te{sub 3} thin films grown on Si (111) by molecular beam epitaxy

    SciTech Connect

    Borisova, S.; Kampmeier, J.; Mussler, G.; Grützmacher, D.; Luysberg, M.

    2013-08-19

    The atomic structure of topological insulators Bi{sub 2}Te{sub 3} thin films on Si (111) substrates grown in van der Waals mode by molecular beam epitaxy has been investigated by in situ scanning tunneling microscopy and scanning transmission electron microscopy. Besides single and multiple quintuple layer (QL) steps, which are typical for the step-flow mode of growth, a number of 0.4 QL steps is observed. We determine that these steps originate from single steps at the substrate surface causing domain boundaries in the Bi{sub 2}Te{sub 3} film. Due to the peculiar structure of these domain boundaries the domains are stable and penetrate throughout the entire film.

  2. Molecular Engineering of Potent Sensitizers for Very Efficient Light Harvesting in Thin-Film Solid-State Dye-Sensitized Solar Cells.

    PubMed

    Zhang, Xiaoyu; Xu, Yaoyao; Giordano, Fabrizio; Schreier, Marcel; Pellet, Norman; Hu, Yue; Yi, Chenyi; Robertson, Neil; Hua, Jianli; Zakeeruddin, Shaik M; Tian, He; Grätzel, Michael

    2016-08-31

    Dye-sensitized solar cells (DSSCs) have shown significant potential for indoor and building-integrated photovoltaic applications. Herein we present three new D-A-π-A organic sensitizers, XY1, XY2, and XY3, that exhibit high molar extinction coefficients and a broad absorption range. Molecular modifications of these dyes, featuring a benzothiadiazole (BTZ) auxiliary acceptor, were achieved by introducing a thiophene heterocycle as well as by shifting the position of BTZ on the conjugated bridge. The ensuing high molar absorption coefficients enabled the fabrication of highly efficient thin-film solid-state DSSCs with only 1.3 μm mesoporous TiO2 layer. XY2 with a molar extinction coefficient of 6.66 × 10(4) M(-1) cm(-1) at 578 nm led to the best photovoltaic performance of 7.51%. PMID:27488265

  3. Investigation of ZnO thin films deposited on ferromagnetic metallic buffer layer by molecular beam epitaxy toward realization of ZnO-based magnetic tunneling junctions

    SciTech Connect

    Belmoubarik, M.; Nozaki, T.; Sahashi, M.; Endo, H.

    2013-05-07

    Deposition of ZnO thin films on a ferromagnetic metallic buffer layer (Co{sub 3}Pt) by molecular beam epitaxy technique was investigated for realization of ZnO-based magnetic tunneling junctions with good quality hexagonal ZnO films as tunnel barriers. For substrate temperature of 600 Degree-Sign C, ZnO films exhibited low oxygen defects and high electrical resistivity of 130 {Omega} cm. This value exceeded that of hexagonal ZnO films grown by sputtering technique, which are used as tunnel barriers in ZnO-MTJs. Also, the effect of oxygen flow during deposition on epitaxial growth conditions and Co{sub 3}Pt surface oxidation was discussed.

  4. Layer by layer growth of BaTiO 3 thin films with extremely smooth surfaces by laser molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Wang, H. S.; Ma, K.; Cui, D. F.; Peng, Z. Q.; Zhou, Y. L.; Lu, H. B.; Chen, Z. H.; Li, L.; Yang, G. Z.

    1997-05-01

    Using pure ozone-assisted laser molecular beam epitaxy, we have grown c-axis-oriented single crystal BaTiO 3 thin films on SrTiO 3 substrates at temperatures ( Ts) of 400-750°C and under ambient gas pressures of 5 × 10 -5 to 1 × 10 -1 Pa, respectively. Stripy reflection high-energy electron diffraction (RHEED) patterns and regular RHEED intensity oscillations reveal the smooth surface and layer-by-layer epitaxial growth of the films. Scanning electron microscopy analysis shows that the films are free of pinholes, grain boundaries and outgrowths on the surface. In addition, we found a strong dependence of the film lattice constant c on Ts, which might be related to the strain in the film.

  5. Thin film ferroelectric electro-optic memory

    NASA Technical Reports Server (NTRS)

    Thakoor, Sarita (Inventor); Thakoor, Anilkumar P. (Inventor)

    1993-01-01

    An electrically programmable, optically readable data or memory cell is configured from a thin film of ferroelectric material, such as PZT, sandwiched between a transparent top electrode and a bottom electrode. The output photoresponse, which may be a photocurrent or photo-emf, is a function of the product of the remanent polarization from a previously applied polarization voltage and the incident light intensity. The cell is useful for analog and digital data storage as well as opto-electric computing. The optical read operation is non-destructive of the remanent polarization. The cell provides a method for computing the product of stored data and incident optical data by applying an electrical signal to store data by polarizing the thin film ferroelectric material, and then applying an intensity modulated optical signal incident onto the thin film material to generate a photoresponse therein related to the product of the electrical and optical signals.

  6. Studies of Yttrium BARIUM(2) COPPER(3) OXYGEN(7 - Materials and Layered Thin Films: Their Growth and Interdiffusion Behavior, Fermi Edge Density, and the Oxygen Depletion Problem

    NASA Astrophysics Data System (ADS)

    Chen, Li-Mei

    In 1987, Paul Chu and his colleagues discovered the high-T_{c} YBa_2Cu_3O _{7-x} (1-2-3) superconductor (HTSC). The most important research still needed on this system from a scientific point of view is to get insight into the superconducting mechanism of this new material. Using these materials in the foof films seems the most realistic for widespread application. Therefore, research in this thesis on these HTSC materials have been carried out in four parts: (1) the oxygen depletion problem, (2) Fermi density of state, (3) interdiffusion behavior and (4) multilayer growth. HTSC thin films were successfully made by either ion beam deposition or R-F magnetron sputtering at the EIC Laboratory in Massachusetts. C-axis oriented epitaxial HTSC thin films were deposited onto MgO, YSZ and sapphire. A variety of different buffer layers were also deposited onto the above-mentioned substrates to try to effectuate the elimination the interaction between the substrates and the HTSC thin films. For further interdiffusion behavior studies, the above mentioned buffer layers were also deposited in a superconductor-insulator-superconductor (S-I-S) geometry. This geometry is one employed in Josephson junctions which are the key elements of superconductive electronics. We have also studied the behavior of select HTSC ceramic systems during changes in atmospheric conditions. A four-point probe was used to measure the HTSC ceramic transition temperature. From these results, we found that in the presence of an ambient oxygen background equivalent to several torr at room temperature, the HTSC materials produced a metallic R vs. T behavior with T_0 (onset) of ~103 K and T _{c} of ~ 91 K. Lowering the oxygen pressure, followed by repeated temperature cycling, produced a continuous reduction in T_{c} to value ~60 K. Reintroduction of various dose O_2 or air immediately increased the T_{c}, with apparent total restoration to the optimal resistance values at ~5 torr to 12 torr. A finite Fermi

  7. Layer-by-layer grown scalable redox-active ruthenium-based molecular multilayer thin films for electrochemical applications and beyond

    NASA Astrophysics Data System (ADS)

    Kaliginedi, Veerabhadrarao; Ozawa, Hiroaki; Kuzume, Akiyoshi; Maharajan, Sivarajakumar; Pobelov, Ilya V.; Kwon, Nam Hee; Mohos, Miklos; Broekmann, Peter; Fromm, Katharina M.; Haga, Masa-Aki; Wandlowski, Thomas

    2015-10-01

    Here we report the first study on the electrochemical energy storage application of a surface-immobilized ruthenium complex multilayer thin film with anion storage capability. We employed a novel dinuclear ruthenium complex with tetrapodal anchoring groups to build well-ordered redox-active multilayer coatings on an indium tin oxide (ITO) surface using a layer-by-layer self-assembly process. Cyclic voltammetry (CV), UV-Visible (UV-Vis) and Raman spectroscopy showed a linear increase of peak current, absorbance and Raman intensities, respectively with the number of layers. These results indicate the formation of well-ordered multilayers of the ruthenium complex on ITO, which is further supported by the X-ray photoelectron spectroscopy analysis. The thickness of the layers can be controlled with nanometer precision. In particular, the thickest layer studied (65 molecular layers and approx. 120 nm thick) demonstrated fast electrochemical oxidation/reduction, indicating a very low attenuation of the charge transfer within the multilayer. In situ-UV-Vis and resonance Raman spectroscopy results demonstrated the reversible electrochromic/redox behavior of the ruthenium complex multilayered films on ITO with respect to the electrode potential, which is an ideal prerequisite for e.g. smart electrochemical energy storage applications. Galvanostatic charge-discharge experiments demonstrated a pseudocapacitor behavior of the multilayer film with a good specific capacitance of 92.2 F g-1 at a current density of 10 μA cm-2 and an excellent cycling stability. As demonstrated in our prototypical experiments, the fine control of physicochemical properties at nanometer scale, relatively good stability of layers under ambient conditions makes the multilayer coatings of this type an excellent material for e.g. electrochemical energy storage, as interlayers in inverted bulk heterojunction solar cell applications and as functional components in molecular electronics applications

  8. Femtosecond laser ablation-based mass spectrometry: An ideal tool for stoichiometric analysis of thin films

    PubMed Central

    LaHaye, Nicole L.; Kurian, Jose; Diwakar, Prasoon K.; Alff, Lambert; Harilal, Sivanandan S.

    2015-01-01

    An accurate and routinely available method for stoichiometric analysis of thin films is a desideratum of modern materials science where a material’s properties depend sensitively on elemental composition. We thoroughly investigated femtosecond laser ablation-inductively coupled plasma-mass spectrometry (fs-LA-ICP-MS) as an analytical technique for determination of the stoichiometry of thin films down to the nanometer scale. The use of femtosecond laser ablation allows for precise removal of material with high spatial and depth resolution that can be coupled to an ICP-MS to obtain elemental and isotopic information. We used molecular beam epitaxy-grown thin films of LaPd(x)Sb2 and T′-La2CuO4 to demonstrate the capacity of fs-LA-ICP-MS for stoichiometric analysis and the spatial and depth resolution of the technique. Here we demonstrate that the stoichiometric information of thin films with a thickness of ~10 nm or lower can be determined. Furthermore, our results indicate that fs-LA-ICP-MS provides precise information on the thin film-substrate interface and is able to detect the interdiffusion of cations. PMID:26285795

  9. Femtosecond laser ablation-based mass spectrometry. An ideal tool for stoichiometric analysis of thin films

    DOE PAGESBeta

    LaHaye, Nicole L.; Kurian, Jose; Diwakar, Prasoon K.; Alff, Lambert; Harilal, Sivanandan S.

    2015-08-19

    An accurate and routinely available method for stoichiometric analysis of thin films is a desideratum of modern materials science where a material’s properties depend sensitively on elemental composition. We thoroughly investigated femtosecond laser ablation-inductively coupled plasma-mass spectrometry (fs-LA-ICP-MS) as an analytical technique for determination of the stoichiometry of thin films down to the nanometer scale. The use of femtosecond laser ablation allows for precise removal of material with high spatial and depth resolution that can be coupled to an ICP-MS to obtain elemental and isotopic information. We used molecular beam epitaxy-grown thin films of LaPd(x)Sb2 and T´-La2CuO4 to demonstrate themore » capacity of fs-LA-ICP-MS for stoichiometric analysis and the spatial and depth resolution of the technique. Here we demonstrate that the stoichiometric information of thin films with a thickness of ~10 nm or lower can be determined. Furthermore, our results indicate that fs-LA-ICP-MS provides precise information on the thin film-substrate interface and is able to detect the interdiffusion of cations.« less

  10. Femtosecond laser ablation-based mass spectrometry. An ideal tool for stoichiometric analysis of thin films

    SciTech Connect

    LaHaye, Nicole L.; Kurian, Jose; Diwakar, Prasoon K.; Alff, Lambert; Harilal, Sivanandan S.

    2015-08-19

    An accurate and routinely available method for stoichiometric analysis of thin films is a desideratum of modern materials science where a material’s properties depend sensitively on elemental composition. We thoroughly investigated femtosecond laser ablation-inductively coupled plasma-mass spectrometry (fs-LA-ICP-MS) as an analytical technique for determination of the stoichiometry of thin films down to the nanometer scale. The use of femtosecond laser ablation allows for precise removal of material with high spatial and depth resolution that can be coupled to an ICP-MS to obtain elemental and isotopic information. We used molecular beam epitaxy-grown thin films of LaPd(x)Sb2 and T´-La2CuO4 to demonstrate the capacity of fs-LA-ICP-MS for stoichiometric analysis and the spatial and depth resolution of the technique. Here we demonstrate that the stoichiometric information of thin films with a thickness of ~10 nm or lower can be determined. Furthermore, our results indicate that fs-LA-ICP-MS provides precise information on the thin film-substrate interface and is able to detect the interdiffusion of cations.

  11. Ion beam-based characterization of multicomponent oxide thin films and thin film layered structures

    SciTech Connect

    Krauss, A.R.; Rangaswamy, M.; Lin, Yuping; Gruen, D.M.; Schultz, J.A.; Schmidt, H.K.; Chang, R.P.H.

    1992-11-01

    Fabrication of thin film layered structures of multi-component materials such as high temperature superconductors, ferroelectric and electro-optic materials, and alloy semiconductors, and the development of hybrid materials requires understanding of film growth and interface properties. For High Temperature Superconductors, the superconducting coherence length is extremely short (5--15 {Angstrom}), and fabrication of reliable devices will require control of film properties at extremely sharp interfaces; it will be necessary to verify the integrity of thin layers and layered structure devices over thicknesses comparable to the atomic layer spacing. Analytical techniques which probe the first 1--2 atomic layers are therefore necessary for in-situ characterization of relevant thin film growth processes. However, most surface-analytical techniques are sensitive to a region within 10--40 {Angstrom} of the surface and are physically incompatible with thin film deposition and are typically restricted to ultra high vacuum conditions. A review of ion beam-based analytical methods for the characterization of thin film and multi-layered thin film structures incorporating layers of multicomponent oxides is presented. Particular attention will be paid to the use of time-of-flight techniques based on the use of 1- 15 key ion beams which show potential for use as nondestructive, real-time, in-situ surface diagnostics for the growth of multicomponent metal and metal oxide thin films.

  12. Structural and optical properties of In doped Se-Te phase-change thin films: A material for optical data storage

    NASA Astrophysics Data System (ADS)

    Pathak, H. P.; Shukla, Nitesh; Kumar, Vipin; Dwivedi, D. K.

    2016-02-01

    Se75-xTe25Inx (x = 0, 3, 6, & 9) bulk glasses were obtained by melt quench technique. Thin films of thickness 400 nm were prepared by thermal evaporation technique at a base pressure of 10-6 Torr onto well cleaned glass substrate. a-Se75-xTe25Inx thin films were annealed at different temperatures for 2 h. As prepared and annealed films were characterized by X-ray diffraction and UV-Vis spectroscopy. The X-ray diffraction results show that the as-prepared films are of amorphous nature while it shows some poly-crystalline structure in amorphous phases after annealing. The optical absorption spectra of these films were measured in the wavelength range 400-1100 nm in order to derive the extinction and absorption coefficient of these films. It was found that the mechanism of optical absorption follows the rule of allowed non-direct transition. The optical band gap of as prepared and annealed films as a function of photon energy has been studied. The optical band gap is found to decrease with increase in annealing temperature in the present glassy system. It happens due to crystallization of amorphous films. The decrease in optical band gap due to annealing is an interesting behavior for a material to be used in optical storage. The optical band gap has been observed to decrease with the increase of In content in Se-Te glassy system.

  13. Thin film superconductor magnetic bearings

    DOEpatents

    Weinberger, Bernard R.

    1995-12-26

    A superconductor magnetic bearing includes a shaft (10) that is subject to a load (L) and rotatable around an axis of rotation, a magnet (12) mounted to the shaft, and a stator (14) in proximity to the shaft. The stator (14) has a superconductor thin film assembly (16) positioned to interact with the magnet (12) to produce a levitation force on the shaft (10) that supports the load (L). The thin film assembly (16) includes at least two superconductor thin films (18) and at least one substrate (20). Each thin film (18) is positioned on a substrate (20) and all the thin films are positioned such that an applied magnetic field from the magnet (12) passes through all the thin films. A similar bearing in which the thin film assembly (16) is mounted on the shaft (10) and the magnet (12) is part of the stator (14) also can be constructed.

  14. Thin film superconductor magnetic bearings

    SciTech Connect

    Weinberger, B.R.

    1995-12-26

    A superconductor magnetic bearing includes a shaft that is subject to a load (L) and rotatable around an axis of rotation, a magnet mounted to the shaft, and a stator in proximity to the shaft. The stator has a superconductor thin film assembly positioned to interact with the magnet to produce a levitation force on the shaft that supports the load (L). The thin film assembly includes at least two superconductor thin films and at least one substrate. Each thin film is positioned on a substrate and all the thin films are positioned such that an applied magnetic field from the magnet passes through all the thin films. A similar bearing in which the thin film assembly is mounted on the shaft and the magnet is part of the stator also can be constructed. 8 figs.

  15. Piezoelectric thin films and their applications for electronics

    NASA Astrophysics Data System (ADS)

    Yoshino, Yukio

    2009-03-01

    ZnO and AlN piezoelectric thin films have been studied for applications in bulk acoustic wave (BAW) resonator. This article introduces methods of forming ZnO and AlN piezoelectric thin films by radio frequency sputtering and applications of BAW resonators considering the relationship between the crystallinity of piezoelectric thin films and the characteristics of the BAW resonators. Using ZnO thin films, BAW resonators were fabricated for a contour mode at 3.58 MHz and thickness modes from 200 MHz to 5 GHz. The ZnO thin films were combined with various materials, substrates, and thin films to minimize the temperature coefficient of frequency (TCF). The minimum TCF of BAW resonators was approximately 2 ppm/°C in the range -20 to 80 °C. The electromechanical coupling coefficient (k2) in a 1.9 GHz BAW resonator was 6.9%. Using AlN thin films, 5-20 GHz BAW resonators with an ultrathin membrane were realized. The membrane thickness of a 20 GHz BAW resonator was about 200 nm, k2 was 6.1%, and the quality factor (Q) was about 280. Q decreased with increasing resonant frequency. The value of k2 is almost the same for 5-20 GHz resonators. This result could be obtained by improving the thickness uniformity, by controlling internal stress of thin films, and by controlling the crystallinity of AlN piezoelectric thin film.

  16. Thin-film Rechargeable Lithium Batteries

    DOE R&D Accomplishments Database

    Dudney, N. J.; Bates, J. B.; Lubben, D.

    1995-06-01

    Thin film rechargeable lithium batteries using ceramic electrolyte and cathode materials have been fabricated by physical deposition techniques. The lithium phosphorous oxynitride electrolyte has exceptional electrochemical stability and a good lithium conductivity. The lithium insertion reaction of several different intercalation materials, amorphous V{sub 2}O{sub 5}, amorphous LiMn{sub 2}O{sub 4}, and crystalline LiMn{sub 2}O{sub 4} films, have been investigated using the completed cathode/electrolyte/lithium thin film battery.

  17. Thin-film rechargeable lithium batteries

    SciTech Connect

    Dudney, N.J.; Bates, J.B.; Lubben, D.

    1995-06-01

    Thin-film rechargeable lithium batteries using ceramic electrolyte and cathode materials have been fabricated by physical deposition techniques. The lithium phosphorous oxynitride electrolyte has exceptional electrochemical stability and a good lithium conductivity. The lithium insertion reaction of several different intercalation materials, amorphous V{sub 2}O{sub 5}, amorphous LiMn{sub 2}O{sub 4}, and crystalline LiMn{sub 2}O{sub 4} films, have been investigated using the completed cathode/electrolyte/lithium thin-film battery.

  18. [The study of selecting sample detecting position and lead plate inner material in thin film method X-ray fluorescence measurement].

    PubMed

    Gan, Ting-ting; Zhang, Yu-jun; Zhao, Nan-jing; Yin, Gao-fang; Dong, Xin-xin; Wang, Ya-ping; Liu Jian-guo; Liu, Wen-qing

    2015-01-01

    (1) In this paper type 316 stainless steel metal plate as the research object, the selection of sample detecting position was studied when thin film method X-ray fluorescence measurement was conducted. The study showed that the optimal location for the sample detection was sample distance X-ray tube and detector baseline 1cm with the baseline into a 16°angle. (2) Heavy metal pollutants of Pb, Cd and Cr in industrial ambient air as the main analysis object, when thin film method X-ray fluorescence conducted with lead plate protection, X-rays will penetrate the membrane and continuely stimulate the protective lead plate. Therefore there is lead spectral line interference in the filter membrane background spectrum, which will affect the detection of lead element in real samples. Studies show that when a layer of isolating material was applied between the thin sample and the protective lead plate, the interference of lead line can effectively be avoided. (3) Several rigid insulating material of type 316 stainless steel, brass, aluminum, red copper and PTEE as lead inner material were selected and studied. The study results showed that compared with X-ray fluorescence spectra of other lead inner materials, the X-ray fluorescence spectrum of red copper contained the least element spectral lines. There were not Cr, Cd and Pb spectrum peaks in the X-ray fluorescence spectrum of red copper. And the target timber scattering spectrum intensity in the high energy part was weaker compared to other X-ray fluorescence spectrum. The above analysis shows that red copper has the minimal disturbance to the actual measurement of heavy metals Cr, Cd and Pb. At the same time, red copper as lead inner materials can effectively avoid the interference of lead spectrum line in lead plate. So red copper is the best lead plate inner materials in thin film method X-ray fluorescence spectroscopy measurement. This study provides an important theoretical basis for the assembling and setting

  19. Ferromagnetic properties of fcc Gd thin films

    SciTech Connect

    Bertelli, T. P. Passamani, E. C.; Larica, C.; Nascimento, V. P.; Takeuchi, A. Y.

    2015-05-28

    Magnetic properties of sputtered Gd thin films grown on Si (100) substrates kept at two different temperatures were investigated using X-ray diffraction, ac magnetic susceptibility, and dc magnetization measurements. The obtained Gd thin films have a mixture of hcp and fcc structures, but with their fractions depending on the substrate temperature T{sub S} and film thickness x. Gd fcc samples were obtained when T{sub S} = 763 K and x = 10 nm, while the hcp structure was stabilized for lower T{sub S} (300 K) and thicker film (20 nm). The fcc structure is formed on the Ta buffer layer, while the hcp phase grows on the fcc Gd layer as a consequence of the lattice relaxation process. Spin reorientation phenomenon, commonly found in bulk Gd species, was also observed in the hcp Gd thin film. This phenomenon is assumed to cause the magnetization anomalous increase observed below 50 K in stressed Gd films. Magnetic properties of fcc Gd thin films are: Curie temperature above 300 K, saturation magnetization value of about 175 emu/cm{sup 3}, and coercive field of about 100 Oe at 300 K; features that allow us to classify Gd thin films, with fcc structure, as a soft ferromagnetic material.

  20. Zeolite thin films: from computer chips to space stations.

    PubMed

    Lew, Christopher M; Cai, Rui; Yan, Yushan

    2010-02-16

    Zeolites are a class of crystalline oxides that have uniform and molecular-sized pores (3-12 A in diameter). Although natural zeolites were first discovered in 1756, significant commercial development did not begin until the 1950s when synthetic zeolites with high purity and controlled chemical composition became available. Since then, major commercial applications of zeolites have been limited to catalysis, adsorption, and ion exchange, all using zeolites in powder form. Although researchers have widely investigated zeolite thin films within the last 15 years, most of these studies were motivated by the potential application of these materials as separation membranes and membrane reactors. In the last decade, we have recognized and demonstrated that zeolite thin films can have new, diverse, and economically significant applications that others had not previously considered. In this Account, we highlight our work on the development of zeolite thin films as low-dielectric constant (low-k) insulators for future generation computer chips, environmentally benign corrosion-resistant coatings for aerospace alloys, and hydrophilic and microbiocidal coatings for gravity-independent water separation in space stations. Although these three applications might not seem directly related, they all rely on the ability to fine-tune important macroscopic properties of zeolites by changing their ratio of silicon to aluminum. For example, pure-silica zeolites (PSZs, Si/Al = infinity) are hydrophobic, acid stable, and have no ion exchange capacity, while low-silica zeolites (LSZs, Si/Al < 2) are hydrophilic, acid soluble, and have a high ion exchange capacity. These new thin films also take advantage of some unique properties of zeolites that have not been exploited before, such as a higher elastic modulus, hardness, and heat conductivity than those of amorphous porous silicas, and microbiocidal capabilities derived from their ion exchange capacities. Finally, we briefly discuss our

  1. Evaporated VOx Thin Films

    NASA Astrophysics Data System (ADS)

    Stapinski, Tomasz; Leja, E.

    1989-03-01

    VOx thin films on glass were obtained by thermal evaporation of V205, powder. The structural investigations were carried out with the use of X-ray diffractometer. The electrical properties of the film were examined by means of temperature measurements of resistivity for the samples heat-treated in various conditions. Optical transmission and reflection spectra of VOX films of various composition showed the influence of the heat treatment.

  2. ALD/MLD processes for Mn and Co based hybrid thin films.

    PubMed

    Ahvenniemi, E; Karppinen, M

    2016-06-28

    Here we report the growth of novel transition metal-organic thin-film materials consisting of manganese or cobalt as the metal component and terephthalate as the rigid organic backbone. The hybrid thin films are deposited by the currently strongly emerging atomic/molecular layer deposition (ALD/MLD) technique using the combination of a metal β-diketonate, i.e. Mn(thd)3, Co(acac)3 or Co(thd)2, and terephthalic acid (1,4-benzenedicarboxylic acid) as precursors. All the processes yield homogeneous and notably smooth amorphous metal-terephthalate hybrid thin films with growth rates of 1-2 Å per cycle. The films are stable towards humidity and withstand high temperatures up to 300 or 400 °C under an oxidative or a reductive atmosphere. The films are characterized with XRR, AFM, GIXRD, XPS and FTIR techniques. PMID:27277668

  3. Photonics applications of nanostructured thin films

    NASA Astrophysics Data System (ADS)

    Kennedy, Scott Ronald

    Using an advanced thin film fabrication technique known as Glancing Angle Deposition (GLAD), it is possible to fabricate unique thin film nanostructures with characteristic dimensions on the order of a wavelength of light. By tailoring the morphologies of the films, they can be designed to exhibit particular optical properties that can be customized through advanced substrate motion and highly oblique flux incidence angles. In applications to photonics, controlling the flow of light for a specified task, GLAD thin films can be fabricated to provide the ability to manipulate incident light through controlled interactions of optical frequency electromagnetic radiation with the thin film nanostructures. Tetragonal square spiral photonic band gap crystals, a new class of periodic dielectric material that is characterized by the elimination of the density of states for frequencies lying in the stop gap of the crystal, can be fabricated using GLAD in a virtual single step process. The design and fabrication of these unique devices has been performed and the resultant crystals characterized in terms of optical response with respect to forbidden propagation modes, material properties, and advanced deposition techniques used to improve the overall structure. Chiral or helical thin films deposited using GLAD were also investigated, and have been shown to exhibit optical activity and circular birefringence due to their inherent structural anisotropy. It has been shown that the addition of nematic liquid crystals (LCs) to chiral thin films enhances the overall device performance due to order induced in the LCs by the film structure. This effect was investigated for a variety of materials and film structures. Finally, by developing a modified GLAD technique whereby the deposited film porosity is controlled through the angle of flux incidence, porous broadband antireflection coatings were produced. Using an appropriate effective medium theory to describe the index of refraction

  4. Preparation of Y-Ba-Cu oxide superconductor thin films using pulsed laser evaporation from high T/sub c/ bulk material

    SciTech Connect

    Dijkkamp, D.; Venkatesan, T.; Wu, X.D.; Shaheen, S.A.; Jisrawi, N.; Min-Lee, Y.H.; McLean, W.L.; Croft, M.

    1987-08-24

    We report the first successful preparation of thin films of Y-Ba-Cu-O superconductors using pulsed excimer laser evaporation of a single bulk material target in vacuum. Rutherford backscattering spectrometry showed the composition of these films to be close to that of the bulk material. Growth rates were typically 0.1 nm per laser shot. After an annealing treatment in oxygen the films exhibited superconductivity with an onset at 95 K and zero resistance at 85 and 75 K on SrTiO/sub 3/ and Al/sub 2/O/sub 3/ substrates, respectively. This new deposition method is relatively simple, very versatile, and does not require the use of ultrahigh vacuum techniques.

  5. Capillary stress in microporous thin films

    SciTech Connect

    Samuel, J.; Hurd, A.J.; Frink, L.J.D.; Swol, F. van; Brinker, C.J. |; Raman, N.K.

    1996-06-01

    Development of capillary stress in porous xerogels, although ubiquitous, has not been systematically studied. The authors have used the beam bending technique to measure stress isotherms of microporous thin films prepared by a sol-gel route. The thin films were prepared on deformable silicon substrates which were then placed in a vacuum system. The automated measurement was carried out by monitoring the deflection of a laser reflected off the substrate while changing the overlying relative pressure of various solvents. The magnitude of the macroscopic bending stress was found to reach a value of 180 MPa at a relative pressure of methanol, P/Po = 0.001. The observed stress is determined by the pore size distribution and is an order of magnitude smaller in mesoporous thin films. Density Functional Theory (DFT) indicates that for the microporous materials, the stress at saturation is compressive and drops as the relative pressure is reduced.

  6. Mesoscale morphologies in polymer thin films.

    SciTech Connect

    Ramanathan, M.; Darling, S. B.

    2011-06-01

    In the midst of an exciting era of polymer nanoscience, where the development of materials and understanding of properties at the nanoscale remain a major R&D endeavor, there are several exciting phenomena that have been reported at the mesoscale (approximately an order of magnitude larger than the nanoscale). In this review article, we focus on mesoscale morphologies in polymer thin films from the viewpoint of origination of structure formation, structure development and the interaction forces that govern these morphologies. Mesoscale morphologies, including dendrites, holes, spherulites, fractals and honeycomb structures have been observed in thin films of homopolymer, copolymer, blends and composites. Following a largely phenomenological level of description, we review the kinetic and thermodynamic aspects of mesostructure formation outlining some of the key mechanisms at play. We also discuss various strategies to direct, limit, or inhibit the appearance of mesostructures in polymer thin films as well as an outlook toward potential areas of growth in this field of research.

  7. Method for synthesizing thin film electrodes

    DOEpatents

    Boyle, Timothy J.

    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.

  8. Carrier lifetimes in thin-film photovoltaics

    NASA Astrophysics Data System (ADS)

    Baek, Dohyun

    2015-09-01

    The carrier lifetimes in thin-film solar cells are reviewed and discussed. Shockley-Read-Hall recombination is dominant at low carrier density, Auger recombination is dominant under a high injection condition and high carrier density, and surface recombination is dominant under any conditions. Because the surface photovoltage technique is insensitive to the surface condition, it is useful for bulk lifetime measurements. The photoconductance decay technique measures the effective recombination lifetime. The time-resolved photoluminescence technique is very useful for measuring thin-film semiconductor or solar-cell materials lifetime, because the sample is thin, other techniques are not suitable for measuring the lifetime. Many papers have provided time-resolved photoluminescence (TRPL) lifetimes for copper-indium-gallium-selenide (CIGS) and CdTe thin-film solar cell. The TRPL lifetime strongly depends on open-circuit voltage and conversion efficiency; however, the TRPL life time is insensitive to the short-circuit current.

  9. thin films as absorber

    NASA Astrophysics Data System (ADS)

    González, J. O.; Shaji, S.; Avellaneda, D.; Castillo, G. A.; Das Roy, T. K.; Krishnan, B.

    2014-09-01

    Photovoltaic structures were prepared using AgSb(S x Se1- x )2 as absorber and CdS as window layer at various conditions via a hybrid technique of chemical bath deposition and thermal evaporation followed by heat treatments. Silver antimony sulfo selenide thin films [AgSb(S x Se1- x )2] were prepared by heating multilayers of sequentially deposited Sb2S3/Ag dipped in Na2SeSO3 solution, glass/Sb2S3/Ag/Se. For this, Sb2S3 thin films were deposited from a chemical bath containing SbCl3 and Na2S2O3. Then, Ag thin films were thermally evaporated on glass/Sb2S3, followed by selenization by dipping in an acidic solution of Na2SeSO3. The duration of dipping was varied as 3, 4 and 5 h. Two different heat treatments, one at 350 °C for 20 min in vacuum followed by a post-heat treatment at 325 °C for 2 h in Ar, and the other at 350 °C for 1 h in Ar, were applied to the multilayers of different configurations. X-ray diffraction results showed the formation of AgSb(S x Se1- x )2 thin films as the primary phase and AgSb(S,Se)2 and Sb2S3 as secondary phases. Morphology and elemental detection were done by scanning electron microscopy and energy dispersive X-ray analysis. X-ray photoelectron spectroscopic studies showed the depthwise composition of the films. Optical properties were determined by UV-vis-IR transmittance and reflection spectral analysis. AgSb(S x Se1- x )2 formed at different conditions was incorporated in PV structures glass/FTO/CdS/AgSb(S x Se1- x )2/C/Ag. Chemically deposited post-annealed CdS thin films of various thicknesses were used as window layer. J- V characteristics of the cells were measured under dark and AM1.5 illumination. Analysis of the J- V characteristics resulted in the best solar cell parameters of V oc = 520 mV, J sc = 9.70 mA cm-2, FF = 0.50 and η = 2.7 %.

  10. Characteristics Of Vacuum Deposited Sucrose Thin Films

    NASA Astrophysics Data System (ADS)

    Ungureanu, F.; Predoi, D.; Ghita, R. V.; Vatasescu-Balcan, R. A.; Costache, M.

    Thin films of sucrose (C12H22O11) were deposited on thin cut glass substrates by thermal evaporation technique (p ~ 10-5 torr). The surface morphology was putted into evidence by FT-IR and SEM analysis. The experimental results confirm a uniform deposition of an adherent sucrose layer. The biological tests (e.g., cell morphology and cell viability evaluated by measuring mitochondrial dehydrogenise activity with MTT assay) confirm the properties of sucrose thin films as bioactive material. The human fetal osteoblast system grown on thin sucrose film was used for the determination of cell proliferation, cell viability and cell morphology studies.

  11. Feasibility Study of Thin Film Thermocouple Piles

    NASA Technical Reports Server (NTRS)

    Sisk, R. C.

    2001-01-01

    Historically, thermopile detectors, generators, and refrigerators based on bulk materials have been used to measure temperature, generate power for spacecraft, and cool sensors for scientific investigations. New potential uses of small, low-power, thin film thermopiles are in the area of microelectromechanical systems since power requirements decrease as electrical and mechanical machines shrink in size. In this research activity, thin film thermopile devices are fabricated utilizing radio frequency sputter coating and photoresist lift-off techniques. Electrical characterizations are performed on two designs in order to investigate the feasibility of generating small amounts of power, utilizing any available waste heat as the energy source.

  12. Emittance Theory for Thin Film Selective Emitter

    NASA Technical Reports Server (NTRS)

    Chubb, Donald L.; Lowe, Roland A.; Good, Brian S.

    1994-01-01

    Thin films of high temperature garnet materials such as yttrium aluminum garnet (YAG) doped with rare earths are currently being investigated as selective emitters. This paper presents a radiative transfer analysis of the thin film emitter. From this analysis the emitter efficiency and power density are calculated. Results based on measured extinction coefficients for erbium-YAG and holmium-YAG are presented. These results indicated that emitter efficiencies of 50 percent and power densities of several watts/sq cm are attainable at moderate temperatures (less than 1750 K).

  13. Applications of Thin Film Thermocouples for Surface Temperature Measurement

    NASA Technical Reports Server (NTRS)

    Martin, Lisa C.; Holanda, Raymond

    1994-01-01

    Thin film thermocouples provide a minimally intrusive means of measuring surface temperature in hostile, high temperature environments. Unlike wire thermocouples, thin films do not necessitate any machining of the surface, therefore leaving intact its structural integrity. Thin films are many orders of magnitude thinner than wire, resulting in less disruption to the gas flow and thermal patterns that exist in the operating environment. Thin film thermocouples have been developed for surface temperature measurement on a variety of engine materials. The sensors are fabricated in the NASA Lewis Research Center's Thin Film Sensor Lab, which is a class 1000 clean room. The thermocouples are platinum-13 percent rhodium versus platinum and are fabricated by the sputtering process. Thin film-to-leadwire connections are made using the parallel-gap welding process. Thermocouples have been developed for use on superalloys, ceramics and ceramic composites, and intermetallics. Some applications of thin film thermocouples are: temperature measurement of space shuttle main engine turbine blade materials, temperature measurement in gas turbine engine testing of advanced materials, and temperature and heat flux measurements in a diesel engine. Fabrication of thin film thermocouples is described. Sensor durability, drift rate, and maximum temperature capabilities are addressed.

  14. Materials issues in molecular beam epitaxy

    SciTech Connect

    Tsao, J.Y.

    1993-12-31

    The technology of crystal growth has advanced enormously during the past two decades; among those advances, the development and refinement of molecular beam epitaxy (MBE) has been among the most important. Crystals grown by MBE are more precisely controlled than those grown by any other method, and today form the basis for many of the most advanced device structures in solid-state physics, electronics and optoelectronics. In addition to its numerous device applications, MBE is also an enormously rich and interesting area of materials science in and of itself. This paper, discusses a few examples of some of these materials issues, organized according to whether they involve bulk, thin films, or surfaces.

  15. An overview of thin film nitinol endovascular devices.

    PubMed

    Shayan, Mahdis; Chun, Youngjae

    2015-07-01

    Thin film nitinol has unique mechanical properties (e.g., superelasticity), excellent biocompatibility, and ultra-smooth surface, as well as shape memory behavior. All these features along with its low-profile physical dimension (i.e., a few micrometers thick) make this material an ideal candidate in developing low-profile medical devices (e.g., endovascular devices). Thin film nitinol-based devices can be collapsed and inserted in remarkably smaller diameter catheters for a wide range of catheter-based procedures; therefore, it can be easily delivered through highly tortuous or narrow vascular system. A high-quality thin film nitinol can be fabricated by vacuum sputter deposition technique. Micromachining techniques were used to create micro patterns on the thin film nitinol to provide fenestrations for nutrition and oxygen transport and to increase the device's flexibility for the devices used as thin film nitinol covered stent. In addition, a new surface treatment method has been developed for improving the hemocompatibility of thin film nitinol when it is used as a graft material in endovascular devices. Both in vitro and in vivo test data demonstrated a superior hemocompatibility of the thin film nitinol when compared with commercially available endovascular graft materials such as ePTFE or Dacron polyester. Promising features like these have motivated the development of thin film nitinol as a novel biomaterial for creating endovascular devices such as stent grafts, neurovascular flow diverters, and heart valves. This review focuses on thin film nitinol fabrication processes, mechanical and biological properties of the material, as well as current and potential thin film nitinol medical applications. PMID:25839120

  16. Thin-Film Solid Oxide Fuel Cells

    NASA Technical Reports Server (NTRS)

    Chen, Xin; Wu, Nai-Juan; Ignatiev, Alex

    2009-01-01

    The development of thin-film solid oxide fuel cells (TFSOFCs) and a method of fabricating them have progressed to the prototype stage. This can result in the reduction of mass, volume, and the cost of materials for a given power level.

  17. Measuring the Thickness and Elastic Properties of Electroactive Thin-Film Polymers Using Platewave Dispersion Data

    NASA Technical Reports Server (NTRS)

    Bar-Cohen, Yoseph; Lih, Shyh-Shiuh; El-Azab, A.; Mal, Ajit K.

    1996-01-01

    Electroactive thin-film polymers are candidate sensors and actuators materials. They are also finding significant potential in muscle mechanisms and microelectromechanical systems (MEMS). In these applications, polymer thin films of thickness varying between 20 and 300 micrometers are utilized. The authors are currently studying the potential use of platewave dispersion curve measurements as an effective gauging tool for electroactive thin-film polymers.

  18. Synthesis and materials chemistry of bismuth tris-(di-i-propylcarbamate): deposition of photoactive Bi2O3 thin films.

    PubMed

    Cosham, Samuel D; Hill, Michael S; Horley, Graeme A; Johnson, Andrew L; Jordan, Laura; Molloy, Kieran C; Stanton, David C

    2014-01-01

    The bismuth carbamate Bi(O2CNPr(i)2)3, a tetramer in the solid-state, has been synthesized and used to deposit mixtures of bismuth oxides by aerosol-assisted chemical vapor deposition (AACVD). The nature of the deposited oxide is a function of both temperature and run-time. Initially, δ-Bi2O3 is deposited, over which grows a thick layer of β-Bi2O3 nanowires, the latter having an increasing degree of preferred orientation at higher deposition temperatures. The photocatalytic activity of a thin film of δ-Bi2O3 for the degradation of methylene blue dye was found to be similar to that of a commercial TiO2 film on glass, while the film overcoated with β-Bi2O3 nanowires was less active. Exposure of Bi(O2CNPr(i)2)3 to controlled amounts of moist air affords the novel oxo-cluster Bi8(O)6(O2CNPr(i)2)12, whose structure has also been determined. PMID:24387747

  19. Low-energy electron induced processes in molecular thin films condensed on silicon and titanium dioxide surfaces

    NASA Astrophysics Data System (ADS)

    Lane, Christopher D.

    The focus of the presented experimental research is to examine the fundamental physics and chemistry of electron-stimulated reactions upon adsorbate covered single crystal surfaces. Specifically, condensed SiCl4 on the Si(111) surface and condensed H2O on the TiO2 (110) surface have been studied. By varying adsorbate film thicknesses, the coupling strength of the electron target molecule to the substrate and surrounding media dictates the progression of the electron induced reactions. To investigate the electron interactions with SiCl4 on the Si(111) surface, a multilayer to monolayer approach was taken. Experiments measuring the electron stimulated desorption (ESD) of fragment cations are discussed in Chapter 3. ESD of neutrals was performed on a multilayer (100 ML) coverage of SiCl4 and is discussed in Chapter 4. These experiments remove the influence of the silicon substrate on the electron induced dissociative processes that are monitored via time of flight mass spectrometry (ToF-MS). The results in Chapter 3 and Chapter 4 have been published in Surface Science 593 (2005) 173 and in the Journal of Chemical Physics 124 (2006) 164702, respectively. Results from electron induced reactions within thin films of SiCl4 are presented in Chapter 5. In the low coverage region, the cation and neutral desorption channels are monitored simultaneously, and the adsorbate coupling strength to the silicon substrate is substantially greater. This affects the desorption yields and the autodetachment probability of the transient negative ion (SiCl4-). Chapters 6--8 discuss work that focuses on the electron-stimulated reactions within the H2O/TiO2 system. A discussion of the interactions of H2O with the TiO2(110) surface is presented in Chapter 6. The transition metal oxide surface is comprised of acidic and basic water adsorption sites along with intrinsic surface defects where surface oxygen atoms are missing. These surface defect sites significantly influence the interactions of

  20. A proposal for epitaxial thin film growth in outer space

    NASA Technical Reports Server (NTRS)

    Ignatiev, Alex; Chu, C. W.

    1988-01-01

    A new concept for materials processing in space exploits the ultravacuum component of space for thin film epitaxial growth. The unique low earth orbit space environment is expected to yield 10 to the -14th torr or better pressures, semiinfinite pumping speeds, and large ultravacuum volume without walls. These space ultravacuum properties promise major improvement in the quality, unique nature, and the throughput of epitaxially grown materials. Advanced thin film materials to be epitaxially grown in space include semiconductors, magnetic materials, and thin film high temperature superconductors.

  1. Carbon thin film thermometry

    NASA Technical Reports Server (NTRS)

    Collier, R. S.; Sparks, L. L.; Strobridge, T. R.

    1973-01-01

    The work concerning carbon thin film thermometry is reported. Optimum film deposition parameters were sought on an empirical basis for maximum stability of the films. One hundred films were fabricated for use at the Marshall Space Flight Center; 10 of these films were given a precise quasi-continuous calibration of temperature vs. resistance with 22 intervals between 5 and 80 K using primary platinum and germanium thermometers. Sensitivity curves were established and the remaining 90 films were given a three point calibration and fitted to the established sensitivity curves. Hydrogen gas-liquid discrimination set points are given for each film.

  2. Polycrystalline thin-films

    NASA Astrophysics Data System (ADS)

    Zweibel, K.; Mitchell, R.

    1986-02-01

    This annual report summarizes the status, accomplishments, and projected future research directions of the Polycrystalline Thin Film Task in the Photovoltaic Program Branch of the Solar Energy Research Institute's Solar Electric Research Division. Major subcontracted work in this area has concentrated on development of CuInSe2 and CdTe technologies. During FY 1985, major progress was achieved by subcontractors in: (1) developing a new, low-cost method of fabricating CuInSe2, and (2) improving the efficiency of CuInSe2 devices by about 10% (relative). The report also lists research planned to meet the Department of Energy's goals in these technologies.

  3. Thin film hydrogen sensor

    DOEpatents

    Lauf, Robert J.; Hoffheins, Barbara S.; Fleming, Pamela H.

    1994-01-01

    A hydrogen sensor element comprises an essentially inert, electrically-insulating substrate having a thin-film metallization deposited thereon which forms at least two resistors on the substrate. The metallization comprises a layer of Pd or a Pd alloy for sensing hydrogen and an underlying intermediate metal layer for providing enhanced adhesion of the metallization to the substrate. An essentially inert, electrically insulating, hydrogen impermeable passivation layer covers at least one of the resistors, and at least one of the resistors is left uncovered. The difference in electrical resistances of the covered resistor and the uncovered resistor is related to hydrogen concentration in a gas to which the sensor element is exposed.

  4. Apparatus for forming thin-film heterojunction solar cells employing materials selected from the class of I-III-VI.sub.2 chalcopyrite compounds

    DOEpatents

    Mickelsen, Reid A.; Chen, Wen S.

    1983-01-01

    Apparatus for forming thin-film, large area solar cells having a relatively high light-to-electrical energy conversion efficiency and characterized in that the cell comprises a p-n-type heterojunction formed of: (i) a first semiconductor layer comprising a photovoltaic active material selected from the class of I-III-VI.sub.2 chalcopyrite ternary materials which is vacuum deposited in a thin "composition-graded" layer ranging from on the order of about 2.5 microns to about 5.0 microns (.congruent.2.5 .mu.m to .congruent.5.0 .mu.m) and wherein the lower region of the photovoltaic active material preferably comprises a low resistivity region of p-type semiconductor material having a superimposed region of relatively high resistivity, transient n-type semiconductor material defining a transient p-n homojunction; and (ii), a second semiconductor layer comprising a low resistivity n-type semiconductor material wherein interdiffusion (a) between the elemental constituents of the two discrete juxtaposed regions of the first semiconductor layer defining a transient p-n homojunction layer, and (b) between the transient n-type material in the first semiconductor layer and the second n-type semiconductor layer, causes the transient n-type material in the first semiconductor layer to evolve into p-type material, thereby defining a thin layer heterojunction device characterized by the absence of voids, vacancies and nodules which tend to reduce the energy conversion efficiency of the system.

  5. Thin film bioreactors in space

    NASA Technical Reports Server (NTRS)

    Hughes-Fulford, M.; Scheld, H. W.

    1989-01-01

    Studies from the Skylab, SL-3 and D-1 missions have demonstrated that biological organisms grown in microgravity have changes in basic cellular functions such as DNA, mRNA and protein synthesis, cytoskeleton synthesis, glucose utilization, and cellular differentiation. Since microgravity could affect prokaryotic and eukaryotic cells at a subcellular and molecular level, space offers an opportunity to learn more about basic biological systems with one inmportant variable removed. The thin film bioreactor will facilitate the handling of fluids in microgravity, under constant temperature and will allow multiple samples of cells to be grown with variable conditions. Studies on cell cultures grown in microgravity would make it possible to identify and quantify changes in basic biological function in microgravity which are needed to develop new applications of orbital research and future biotechnology.

  6. David Adler Lectureship Award Talk: Friction and energy dissipation mechanisms in adsorbed molecules and molecularly thin films

    NASA Astrophysics Data System (ADS)

    Krim, Jacqueline

    2015-03-01

    Studies of the fundamental origins of friction have undergone rapid progress in recent years, with the development of new experimental and computational techniques for measuring and simulating friction at atomic length and time scales. The increased interest has sparked a variety of discussions and debates concerning the nature of the atomic-scale and quantum mechanisms that dominate the dissipative process by which mechanical energy is transformed into heat. Measurements of the sliding friction of physisorbed monolayers and bilayers can provide information on the relative contributions of these various dissipative mechanisms. Adsorbed films, whether intentionally applied or present as trace levels of physisorbed contaminants, moreover are ubiquitous at virtually all surfaces. As such, they impact a wide range of applications whose progress depends on precise control and/or knowledge of surface diffusion processes. Examples include nanoscale assembly, directed transport of Brownian particles, material flow through restricted geometries such as graphene membranes and molecular sieves, passivation and edge effects in carbon-based lubricants, and the stability of granular materials associated with frictional and frictionless contacts. Work supported by NSFDMR1310456.

  7. A-site- and/or B-site-modified PbZrTiO3 materials and (Pb, Sr, Ca, Ba, Mg) (Zr, Ti, Nb, Ta)O3 films having utility in ferroelectric random access memories and high performance thin film microactuators

    NASA Technical Reports Server (NTRS)

    Roeder, Jeffrey F. (Inventor); Chen, Ing-Shin (Inventor); Bilodeau, Steven (Inventor); Baum, Thomas H. (Inventor)

    2001-01-01

    A modified PbZrTiO.sub.3 perovskite crystal material thin film, wherein the PbZrTiO.sub.3 perovskite crystal material includes crystal lattice A-sites and B-sites at least one of which is modified by the presence of a substituent selected from the group consisting of (i) A-site substituents consisting of Sr, Ca, Ba and Mg, and (ii) B-site substituents selected from the group consisting of Nb and Ta. The perovskite crystal thin film material may be formed by liquid delivery MOCVD from metalorganic precursors of the metal components of the thin film, to form PZT and PSZT, and other piezoelectric and ferroelectric thin film materials. The thin films of the invention have utility in non-volatile ferroelectric memory devices (NV-FeRAMs), and in microelectromechanical systems (MEMS) as sensor and/or actuator elements, e.g., high speed digital system actuators requiring low input power levels.

  8. Zipper model for the melting of thin films

    NASA Astrophysics Data System (ADS)

    Abdullah, Mikrajuddin; Khairunnisa, Shafira; Akbar, Fathan

    2016-01-01

    We propose an alternative model to Lindemann’s criterion for melting that explains the melting of thin films on the basis of a molecular zipper-like mechanism. Using this model, a unique criterion for melting is obtained. We compared the results of the proposed model with experimental data of melting points and heat of fusion for many materials and obtained interesting results. The interesting thing reported here is how complex physics problems can sometimes be modeled with simple objects around us that seemed to have no correlation. This kind of approach is sometimes very important in physics education and should always be taught to undergraduate or graduate students.

  9. Thin film ion conducting coating

    DOEpatents

    Goldner, Ronald B.; Haas, Terry; Wong, Kwok-Keung; Seward, George

    1989-01-01

    Durable thin film ion conducting coatings are formed on a transparent glass substrate by the controlled deposition of the mixed oxides of lithium:tantalum or lithium:niobium. The coatings provide durable ion transport sources for thin film solid state storage batteries and electrochromic energy conservation devices.

  10. Structural properties of Bi{sub 2−x}Mn{sub x}Se{sub 3} thin films grown via molecular beam epitaxy

    SciTech Connect

    Babakiray, Sercan; Johnson, Trent A.; Borisov, Pavel; Holcomb, Mikel B.; Lederman, David; Marcus, Matthew A.; Tarafder, Kartick

    2015-07-28

    The effects of Mn doping on the structural properties of the topological insulator Bi{sub 2}Se{sub 3} in thin film form were studied in samples grown via molecular beam epitaxy. Extended x-ray absorption fine structure measurements, supported by density functional theory calculations, indicate that preferential incorporation occurs substitutionally in Bi sites across the entire film volume. This finding is consistent with x-ray diffraction measurements which show that the out of plane lattice constant expands while the in plane lattice constant contracts as the Mn concentration is increased. X-ray photoelectron spectroscopy indicates that the Mn valency is 2+ and that the Mn bonding is similar to that in MnSe. The expansion along the out of plane direction is most likely due to weakening of the Van der Waals interactions between adjacent Se planes. Transport measurements are consistent with this Mn{sup 2+} substitution of Bi sites if additional structural defects induced by this substitution are taken into account.

  11. A photoluminescence comparison of CdTe thin films grown by molecular-beam epitaxy, metalorganic chemical vapor deposition, and sputtering in ultrahigh vacuum

    NASA Astrophysics Data System (ADS)

    Feng, Z. C.; Bevan, M. J.; Krishnaswamy, S. V.; Choyke, W. J.

    1988-09-01

    High perfection CdTe thin films have been grown on (001) InSb and CdTe substrates by molecular-beam epitaxy, metalorganic chemical vapor deposition (MOCVD), and sputtering in ultrahigh vacuum techniques. The quality of the as-grown CdTe films are characterized by 2-K photoluminescence. The spectra show strong and sharp exciton transitions and weak 1.40-1.50-eV defect-related bands. Radiative defect densities of lower than 0.002 are realized. High-resolution spectroscopy shows that the full width at half maximum of the principal bound exciton lines is about 0.1 meV. Such small ρ values and narrow photoluminescence lines have not been previously reported. The largest luminescence efficiency is observed for MOCVD-CdTe films grown on CdTe substrates. A variety of impurities appear to be responsible for the observed radiative transitions in these three kinds of CdTe films. We attempt to assign the observed impurity related lines by a comparison with ``known'' impurities in bulk CdTe spectra given in the literature.

  12. Characterization of high-κ LaLuO3 thin film grown on AlGaN/GaN heterostructure by molecular beam deposition

    NASA Astrophysics Data System (ADS)

    Yang, Shu; Huang, Sen; Chen, Hongwei; Schnee, Michael; Zhao, Qing-Tai; Schubert, Jürgen; Chen, Kevin J.

    2011-10-01

    We report the study of high-dielectric-constant (high-κ) dielectric LaLuO3 (LLO) thin film that is grown on AlGaN/GaN heterostructure by molecular beam deposition (MBD). The physical properties of LLO on AlGaN/GaN heterostrucure have been investigated with atomic force microscopy, x-ray photoelectron spectroscopy, and TEM. It is revealed that the MBD-grown 16 nm-thick LLO film is polycrystalline with a thin (˜2 nm) amorphous transition layer at the LLO/GaN interface. The bandgap of LLO is derived as 5.3 ± 0.04 eV from O1s energy loss spectrum. Capacitance-voltage (C-V) characteristics of a Ni-Au/LLO/III-nitride metal-insulator-semiconductor diode exhibit small frequency dispersion (<2%) and reveal a high effective dielectric constant of ˜28 for the LLO film. The LLO layer is shown to be effective in suppressing the reverse and forward leakage current in the MIS diode. In particular, the MIS diode forward current is reduced by 7 orders of magnitude at a forward bias of 1 V compared to a conventional Ni-Au/III-nitride Schottky diode.

  13. Thin-film optical shutter

    NASA Astrophysics Data System (ADS)

    Matlow, S. L.

    1981-02-01

    The ideal solution to the excessive solar gain problem is an optical shutter, a device which switches from being highly transmissive to solar radiation to being highly reflective to solar radiation when a critical temperature is reached in the enclosure. The switching occurs because one or more materials in the device undergo a phase transition at the critical temperature. A specific embodiment of macroconjugated macromolecules, the poly (p-phenylene)'s, was chosen as the one most likely to meet all of the requirements of the thin film optical shutter project (TFOS). The reason for this choice is explored. In order to be able to make meaningful calculations of the thermodynamic and optical properties of the poly (p-phenylene)'s a quantum mechanical method, the equilibrium bond length (EBL) theory, was developed. Some results of EBL theory are included.

  14. BDS thin film damage competition

    SciTech Connect

    Stolz, C J; Thomas, M D; Griffin, A J

    2008-10-24

    A laser damage competition was held at the 2008 Boulder Damage Symposium in order to determine the current status of thin film laser resistance within the private, academic, and government sectors. This damage competition allows a direct comparison of the current state-of-the-art of high laser resistance coatings since they are all tested using the same damage test setup and the same protocol. A normal incidence high reflector multilayer coating was selected at a wavelength of 1064 nm. The substrates were provided by the submitters. A double blind test assured sample and submitter anonymity so only a summary of the results are presented here. In addition to the laser resistance results, details of deposition processes, coating materials, and layer count will also be shared.

  15. Rechargeable Thin-film Lithium Batteries

    DOE R&D Accomplishments Database

    Bates, J. B.; Gruzalski, G. R.; Dudney, N. J.; Luck, C. F.; Yu, Xiaohua

    1993-08-01

    Rechargeable thin film batteries consisting of lithium metal anodes, an amorphous inorganic electrolyte, and cathodes of lithium intercalation compounds have recently been developed. The batteries, which are typically less than 6 {mu}m thick, can be fabricated to any specified size, large or small, onto a variety of substrates including ceramics, semiconductors, and plastics. The cells that have been investigated include Li TiS{sub 2}, Li V{sub 2}O{sub 5}, and Li Li{sub x}Mn{sub 2}O{sub 4}, with open circuit voltages at full charge of about 2.5, 3.6, and 4.2, respectively. The development of these batteries would not have been possible without the discovery of a new thin film lithium electrolyte, lithium phosphorus oxynitride, that is stable in contact with metallic lithium at these potentials. Deposited by rf magnetron sputtering of Li{sub 3}PO{sub 4} in N{sub 2}, this material has a typical composition of Li{sub 2.9}PO{sub 3.3}N{sub 0.46} and a conductivity at 25{degrees}C of 2 {mu}S/cm. The maximum practical current density obtained from the thin film cells is limited to about 100 {mu}A/cm{sup 2} due to a low diffusivity of Li{sup +} ions in the cathodes. In this work, the authors present a short review of their work on rechargeable thin film lithium batteries.

  16. Solution processable semiconductor thin films: Correlation between morphological, structural, optical and charge transport properties

    NASA Astrophysics Data System (ADS)

    Isik, Dilek

    This Ph.D. thesis is a result of multidisciplinary research bringing together fundamental concepts in thin film engineering, materials science, materials processing and characterization, electrochemistry, microfabrication, and device physics. Experiments were conducted by tackling scientific problems in the field of thin films and interfaces, with the aim to correlate the morphology, crystalline structure, electronic structure of thin films with the functional properties of the films and the performances of electronic devices based thereon. Furthermore, novel strategies based on interfacial phenomena at electrolyte/thin film interfaces were explored and exploited to control the electrical conductivity of the thin films. Three main chemical systems were the object of the studies performed during this Ph.D., two types of organic semiconductors (azomethine-based oligomers and polymers and soluble pentacene derivatives) and one metal oxide semiconductor (tungsten trioxide, WO3). To explore the morphological properties of the thin films, atomic force microscopy was employed. The morphological properties were further investigated by hyperspectral fluorescence microscopy and tentatively correlated to the charge transport properties of the films. X-ray diffraction (Grazing incidence XRD, GIXRD) was used to investigate the crystallinity of the film and the effect of the heat treatment on such crystallinity, as well as to understand the molecular arrangement of the organic molecules in the thin film. The charge transport properties of the films were evaluated in thin film transistor configuration. For electrolyte gated thin film transistors, time dependent transient measurements were conducted, in parallel to more conventional transistor characterizations, to explore the specific effects played on the gating by the anion and cation constituting the electrolyte. The capacitances of the electrical double layers at the electrolyte/WO3 interface were obtained from

  17. Niobium Thin Film Characterization for Thin Film Technology Used in Superconducting Radiofrequency Cavities

    NASA Astrophysics Data System (ADS)

    Dai, Yishu; Valente-Feliciano, Anne-Marie

    2015-10-01

    Superconducting RadioFrequency (SRF) penetrates about 40-100 nm of the top surface, making thin film technology possible in producing superconducting cavities. Thin film is based on the deposition of a thin Nb layer on top of a good thermal conducting material such as Al or Cu. Thin film allows for better control of the surface and has negligible response to the Earth's magnetic field, eliminating the need for magnetic shielding of the cavities. Thin film superconductivity depends heavily on coating process conditions, involving controllable parameters such as crystal plane orientation, coating temperature, and ion energy. MgO and Al2O3 substrates are used because they offer very smooth surfaces, ideal for studying film growth. Atomic Force Microscopy is used to characterize surface's morphology. It is evident that a lower nucleation energy and a long coating time increases the film quality in the r-plane sapphire crystal orientation. The quality of the film increases with thickness. Nb films coated on r-plane, grow along the (001) plane and yield a much higher RRR compared to the films grown on a- and c-planes. This information allows for further improvement on the research process for thin film technology used in superconducting cavities for the particle accelerators. National Science Foundation, Department of Energy, Jefferson Lab, Old Dominion University.

  18. Polycrystalline thin films

    NASA Astrophysics Data System (ADS)

    Zweibel, K.; Mitchell, R.; Ullal, H.

    1987-02-01

    This annual report for fiscal year 1986 summarizes the status, accomplishments, and projected future research directions of the Polycrystalline Thin Film Task in the Photovoltaic Program Branch of the Solar Energy Research Institute's Solar Electric Research Division. Subcontracted work in this area has concentrated on the development of CuInSe2 and CdTe technologies. During FY 1986, major progress was achieved by subcontractors in (1) achieving 10.5% (SERI-verified) efficiency with CdTe, (2) improving the efficiency of selenized CuInSe2 solar cells to nearly 8%, and (3) developing a transparent contact to CdTe cells for potential use in the top cells of tandem structures.

  19. Polyimide Aerogel Thin Films

    NASA Technical Reports Server (NTRS)

    Meador, Mary Ann; Guo, Haiquan

    2012-01-01

    Polyimide aerogels have been crosslinked through multifunctional amines. This invention builds on "Polyimide Aerogels With Three-Dimensional Cross-Linked Structure," and may be considered as a continuation of that invention, which results in a polyimide aerogel with a flexible, formable form. Gels formed from polyamic acid solutions, end-capped with anhydrides, and cross-linked with the multifunctional amines, are chemically imidized and dried using supercritical CO2 extraction to give aerogels having density around 0.1 to 0.3 g/cubic cm. The aerogels are 80 to 95% porous, and have high surface areas (200 to 600 sq m/g) and low thermal conductivity (as low as 14 mW/m-K at room temperature). Notably, the cross-linked polyimide aerogels have higher modulus than polymer-reinforced silica aerogels of similar density, and can be fabricated as both monoliths and thin films.

  20. Ferromagnetic thin films

    DOEpatents

    Krishnan, Kannan M.

    1994-01-01

    A ferromagnetic .delta.-Mn.sub.1-x Ga.sub.x thin film having perpendicular anisotropy is described which comprises: (a) a GaAs substrate, (b) a layer of undoped GaAs overlying said substrate and bonded thereto having a thickness ranging from about 50 to about 100 nanometers, (c) a layer of .delta.-Mn.sub.1-x Ga.sub.x overlying said layer of undoped GaAs and bonded thereto having a thickness ranging from about 20 to about 30 nanometers, and (d) a layer of GaAs overlying said layer of .delta.-Mn.sub.1-x Ga.sub.x and bonded thereto having a thickness ranging from about 2 to about 5 nanometers, wherein x is 0.4 .+-.0.05.

  1. Ferromagnetic thin films

    DOEpatents

    Krishnan, K.M.

    1994-12-20

    A ferromagnetic [delta]-Mn[sub 1[minus]x]Ga[sub x] thin film having perpendicular anisotropy is described which comprises: (a) a GaAs substrate, (b) a layer of undoped GaAs overlying said substrate and bonded thereto having a thickness ranging from about 50 to about 100 nanometers, (c) a layer of [delta]-Mn[sub 1[minus]x]Ga[sub x] overlying said layer of undoped GaAs and bonded thereto having a thickness ranging from about 20 to about 30 nanometers, and (d) a layer of GaAs overlying said layer of [delta]-Mn[sub 1[minus]x]Ga[sub x] and bonded thereto having a thickness ranging from about 2 to about 5 nanometers, wherein x is 0.4[+-]0.05. 7 figures.

  2. Preparation and Characterization of CuInSe2 Thin Films by Molecular-Beam Deposition Method

    NASA Astrophysics Data System (ADS)

    Nishitani, Mikihiko; Negami, Takayuki; Terauchi, Masaharu; Hirao, Takashi

    1992-02-01

    Polycrystalline CuInSe2 films were prepared by coevaporation of the elements under an ultrahigh vacuum by a molecular-beam deposition method. The composition of the film was controlled by changing the In molecular-beam flux intensity while the other elements remained at a constant value. It is shown, at the substrate temperature of 500°C, that there is a critical In molecular-beam flux intensity for the fabrication of stoichiometric films. At the In molecular-beam intensities higher than the critical value, single-phase CuInSe2 films with nearly constant compositions are obtained as a result of the removal effects of excess In. It is shown that the present coevaporation process is suitable for the fabrication of stoichiometric or slightly In-rich composition films. Furthermore, the structural and electrical properties of the films were investigated and discussed in relation to film composition.

  3. Molecular aspects of transport in thin films of controlled architecture. [Annual] technical summary, July 1, 1992--June 30, 1993

    SciTech Connect

    Not Available

    1993-12-01

    Work has progressed in two principal areas during the past year: diffusion in swollen polymer films with and without a barrier layer, and molecular aspects of swelling using enhanced Raman spectroscopy.

  4. Magnetism switching and band-gap narrowing in Ni-doped PbTiO{sub 3} thin films

    SciTech Connect

    Zhou, Wenliang; Yu, Lu; Yang, Pingxiong Chu, Junhao; Deng, Hongmei

    2015-05-21

    Ions doping-driven structural phase transition accompanied by magnetism switching and band-gap narrowing effects has been observed in PbTi{sub 1−x}Ni{sub x}O{sub 3−δ} (xPTNO, x = 0.00, 0.06, and 0.33) thin films. With the increase of x, the xPTNO thin films exhibit not only a phase transition from the pseudotetragonal structure to a centrosymmetric cubic structure but also a drastic decrease of grain size. Moreover, the as-grown Ni-doped PbTiO{sub 3} (PTO) thin films show obvious room-temperature ferromagnetism and an increased saturation magnetization with increasing the Ni content, in contrast to undoped PTO, which shows diamagnetism. A bound magnetic polaron model was proposed to understand the observed ferromagnetic behavior of PTO-derived perovskite thin films. Furthermore, the 0.33PTNO thin film presents a narrowed band-gap, much smaller than that of PTO, which is attributed to new states of both the highest occupied molecular orbital and the lowest unoccupied molecular orbital in an electronic structure with the presence of Ni. These findings may open up a route to explore promising perovskite oxides as candidate materials for use in multiferroics and solar-energy devices.

  5. Thin film Cu(In,Ga)Se2 materials and devices: a versatile material for flat-plate and concentrator photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Tuttle, John R.; Contreras, M. A.; Ward, J. S.; Tennant, A. L.; Ramanathan, K. R.; Keane, J.; Noufi, R. N.

    1995-08-01

    Thin-film Cu(In,Ga)Se2(CIGS) is used as the absorber in an all-thin-film solar cell for both conventional 1-sun and concentrator applications. The absorber fabrication process is represented by time-dependent profiles of elemental Cu, In, Ga, and Se fluxes. The Cu/(In+Ga) ratio determines the phase chemistry during growth whereas the Ga/(Ga+In) ratio determines the CIGS band gap profile. All film-growth processes enter the CIGS:CuxSe two-phase field where the CuxSe facilitates large grain growth. Characterization of cells under 1-sun illumination reveals world-record total-area performance of 17.1%. Improvements relative to previous cells are linked to decreased inter-diffusion of In and Ga within the absorber. Cell parameters include an open-circuit voltage (Voc) of 654 mV and short-circuit current (Jsc) of 33.9 mA/cm2. A second cell was fabricated for operation under concentration. The 1-sun, direct-spectrum measurement yielded at 15.1%- efficient cell. Under 5- and 22-sun concentration, the cell improved to 16.5% and 17.2%, respectively. This achievement is significant in that it proves a compatibility of polycrystalline thin-film and concentrator technologies. Further optimization could yield 1-sun performance in excess of 18% and concentrator performance in excess of 20%. A path to this goal is outlined.

  6. Transient terahertz photoconductivity measurements of minority-carrier lifetime in tin sulfide thin films: Advanced metrology for an early stage photovoltaic material

    NASA Astrophysics Data System (ADS)

    Jaramillo, R.; Sher, Meng-Ju; Ofori-Okai, Benjamin K.; Steinmann, V.; Yang, Chuanxi; Hartman, Katy; Nelson, Keith A.; Lindenberg, Aaron M.; Gordon, Roy G.; Buonassisi, T.

    2016-01-01

    Materials research with a focus on enhancing the minority-carrier lifetime of the light-absorbing semiconductor is key to advancing solar energy technology for both early stage and mature material platforms alike. Tin sulfide (SnS) is an absorber material with several clear advantages for manufacturing and deployment, but the record power conversion efficiency remains below 5%. We report measurements of bulk and interface minority-carrier recombination rates in SnS thin films using optical-pump, terahertz-probe transient photoconductivity (TPC) measurements. Post-growth thermal annealing in H2S gas increases the minority-carrier lifetime, and oxidation of the surface reduces the surface recombination velocity. However, the minority-carrier lifetime remains below 100 ps for all tested combinations of growth technique and post-growth processing. Significant improvement in SnS solar cell performance will hinge on finding and mitigating as-yet-unknown recombination-active defects. We describe in detail our methodology for TPC experiments, and we share our data analysis routines in the form freely available software.

  7. [Development of cloud chamber having thin-film entrance windows and proposal of practical training for beginners using X-ray equipment and unsealed radioactive material].

    PubMed

    Konishi, Yuki; Hayashi, Hiroaki; Takegami, Kazuki; Fukuda, Ikuma; Ueno, Junji

    2014-01-01

    A cloud chamber is a detector that can visualize the tracks of charged particles. Hayashi, et al. suggested a visualization experiment in which X-rays generated by diagnostic X-ray equipment were directed into a cloud chamber; however, there was a problem in that the wall of the cloud chamber scattered the incoming X-rays. In this study, we developed a new cloud chamber with entrance windows. Because these windows are made of thin film, we were able to direct the X-rays through them without contamination by scattered X-rays from the cloud chamber wall. We have newly proposed an experiment in which beta-particles emitted from radioisotopes are directed into a cloud chamber. We place shielding material in the cloud chamber and visualize the various shielding effects seen with the material positioned in different ways. During the experiment, electrons scattered in the air were measured quantitatively using GM counters. We explained the physical phenomena in the cloud chamber using Monte Carlo simulation code EGS5. Because electrons follow a tortuous path in air, the shielding material must be placed appropriately to be able to effectively block their emissions. Visualization of the tracks of charged particles in this experiment proved effective for instructing not only trainee radiological technologists but also different types of healthcare professionals. PMID:24464061

  8. Hydrogenated nanocrystalline silicon germanium thin films

    NASA Astrophysics Data System (ADS)

    Yusoff, A. R. M.; Syahrul, M. N.; Henkel, K.

    2007-08-01

    Hydrogenated nanocrystalline silicon germanium thin films (nc-SiGe:H) is an interesting alternative material to replace hydrogenated nanocrystalline silicon (nc-Si:H) as the narrow bandgap absorber in an a-Si/a-SiGe/nc-SiGe(nc-Si) triple-junction solar cell due to its higher optical absorption in the wavelength range of interest. In this paper, we present results of optical, structural investigations and electrical characterization of nc-SiGe:H thin films made by hot-wire chemical vapor deposition (HWCVD) with a coil-shaped tungsten filament and with a disilane/germane/hydrogen gas mixture. The optical band gaps of a-SiGe:H and nc-SiGe:H thin-films, which are deposited with the same disilane/germane/hydrogen gas mixture ratio of 3.4:1.7:7, are about 1.58 eV and 2.1 eV, respectively. The nc-SiGe:H thin film exhibits a larger optical absorption coefficient of about 2-4 in the 600-900 nm range when compared to nc-Si:H thin film. Therefore, a thinner nc-SiGe:H layer of sim500 nm thickness may be sufficient for the narrow bandgap absorber in an a-Si based multiple-junction solar cell. We enhanced the transport properties as measured by the photoconductivity frequency mixing technique. These improved alloys do not necessarily show an improvement in the degree of structural heterogeneity on the nanometer scale as measured by small-angle X-ray scattering. Decreasing both the filament temperature and substrate temperature produced a film with relatively low structural heterogeneity while photoluminescence showed an order of magnitude increase in defect density for a similar change in the process.

  9. Double Laser for Depth Measurement of Thin Films of Ice.

    PubMed

    Beltrán, Manuel Domingo; Molina, Ramón Luna; Aznar, Miguel Ángel Satorre; Moltó, Carmina Santonja; Verdú, Carlos Millán

    2015-01-01

    The use of thin films is extensive in both science and industry. We have created an experimental system that allows us to measure the thicknesses of thin films (with typical thicknesses of around 1 µm) in real time without the need for any prior knowledge or parameters. Using the proposed system, we can also measure the refractive index of the thin film material exactly under the same experimental conditions. We have also obtained interesting results with regard to structural changes in the solid substance with changing temperature and have observed the corresponding behavior of mixtures of substances. PMID:26426024

  10. The state of the art of thin-film photovoltaics

    SciTech Connect

    Surek, T.

    1993-10-01

    Thin-film photovoltaic technologies, based on materials such as amorphous or polycrystalline silicon, copper indium diselenide, cadmium telluride, and gallium arsenide, offer the potential for significantly reducing the cost of electricity generated by photovoltaics. The significant progress in the technologies, from the laboratory to the marketplace, is reviewed. The common concerns and questions raised about thin films are addressed. Based on the progress to date and the potential of these technologies, along with continuing investments by the private sector to commercialize the technologies, one can conclude that thin-film PV will provide a competitive alternative for large-scale power generation in the future.

  11. Double Laser for Depth Measurement of Thin Films of Ice

    PubMed Central

    Domingo Beltrán, Manuel; Luna Molina, Ramón; Satorre Aznar, Miguel Ángel; Santonja Moltó, Carmina; Millán Verdú, Carlos

    2015-01-01

    The use of thin films is extensive in both science and industry. We have created an experimental system that allows us to measure the thicknesses of thin films (with typical thicknesses of around 1 µm) in real time without the need for any prior knowledge or parameters. Using the proposed system, we can also measure the refractive index of the thin film material exactly under the same experimental conditions. We have also obtained interesting results with regard to structural changes in the solid substance with changing temperature and have observed the corresponding behavior of mixtures of substances. PMID:26426024

  12. Microstructural characterization in nanocrystalline ceramic thin films

    NASA Astrophysics Data System (ADS)

    Kim, Hakkwan

    The primary objective of this research is to investigate the effects of process variables on microstructure in several fluoride and oxide thin films prepared by vapor deposition, in order to predict the properties and behaviors of nanocrystalline thin film materials. There are three distinct stages of this research. The first stage focuses on measuring of the porosity in polycrystalline thin films of a variety of fluorides as a function of the substrate temperature during deposition, and discussing the mechanism by which the porosity varies as a function of the process variables. We have measured the porosity in thin films of lithium fluoride (LiF), magnesium fluoride (MgF2), barium fluoride (BaF 2) and calcium fluoride (CaF2) using an atomic force microscope (AFM) and a quartz crystal thickness monitor. The porosity is very sensitive to the substrate temperature and decreases as the substrate temperature increases. Consistent behavior is observed among all of the materials in this study. The second stage is to understand the film microstructure including grain growth and texture development, because these factors are known to influence the behavior and stability of polycrystalline thin films. This study focuses on grain growth and texture development in polycrystalline lithium fluoride thin films using dark field (DF) transmission electron microscopy (TEM). It is demonstrated that we can isolate the size distribution of <111> surface normal grains from the overall size distribution, based on simple and plausible assumptions about the texture. The {111} texture formation and surface morphology were also observed by x-ray diffraction (XRD) and AFM, respectively. The grain size distributions become clearly bimodal as the annealing time increases, and we deduce that the short-time size distributions are also a sum of two overlapping peaks. The smaller grain-size peak in the distribution corresponds to the {111}-oriented grains which do not grow significantly, while

  13. The Characterization of Thin Film Nickel Titanium Shape Memory Alloys

    NASA Astrophysics Data System (ADS)

    Harris Odum, Nicole Latrice

    Shape memory alloys (SMA) are able to recover their original shape through the appropriate heat or stress exposure after enduring mechanical deformation at a low temperature. Numerous alloy systems have been discovered which produce this unique feature like TiNb, AgCd, NiAl, NiTi, and CuZnAl. Since their discovery, bulk scale SMAs have undergone extensive material property investigations and are employed in real world applications. However, its thin film counterparts have been modestly investigated and applied. Researchers have introduced numerous theoretical microelectromechanical system (MEMS) devices; yet, the research community's overall unfamiliarity with the thin film properties has delayed growth in this area. In addition, it has been difficult to outline efficient thin film processing techniques. In this dissertation, NiTi thin film processing and characterization techniques will be outlined and discussed. NiTi thin films---1 mum thick---were produced using sputter deposition techniques. Substrate bound thin films were deposited to analysis the surface using Scanning Electron Microscopy; the film composition was obtained using Energy Dispersive Spectroscopy; the phases were identified using X-ray diffraction; and the transformation temperatures acquired using resistivity testing. Microfabrication processing and sputter deposition were employed to develop tensile membranes for membrane deflection experimentation to gain insight on the mechanical properties of the thin films. The incorporation of these findings will aid in the movement of SMA microactuation devices from theory to fruition and greatly benefit industries such as medicinal and aeronautical.

  14. Multiferroic oxide thin films and heterostructures

    SciTech Connect

    Lu, Chengliang E-mail: Tao.Wu@kaust.edu.sa; Hu, Weijin; Wu, Tom E-mail: Tao.Wu@kaust.edu.sa; Tian, Yufeng

    2015-06-15

    Multiferroic materials promise a tantalizing perspective of novel applications in next-generation electronic, memory, and energy harvesting technologies, and at the same time they also represent a grand scientific challenge on understanding complex solid state systems with strong correlations between multiple degrees of freedom. In this review, we highlight the opportunities and obstacles in growing multiferroic thin films with chemical and structural integrity and integrating them in functional devices. Besides the magnetoelectric effect, multiferroics exhibit excellent resistant switching and photovoltaic properties, and there are plenty opportunities for them to integrate with other ferromagnetic and superconducting materials. The challenges include, but not limited, defect-related leakage in thin films, weak magnetism, and poor control on interface coupling. Although our focuses are Bi-based perovskites and rare earth manganites, the insights are also applicable to other multiferroic materials. We will also review some examples of multiferroic applications in spintronics, memory, and photovoltaic devices.

  15. Atomic layer epitaxy Group IV materials: Surface processes, thin films, devices and their characterization. Annual report, 1 January 1992-31 December 1992

    SciTech Connect

    Davis, R.F.; Bedair, S.; El-Masry, N.; Glass, J.T.

    1992-12-01

    An integrated growth and surface characterization system containing a hot filament reactor, sample transfer station, ESD and XPS has been established to investigate the ALE of diamond films. Complementary experiments concerned with the nucleation of diamond on molten surfaces, e. g., Al and Ge have also been conducted. Formation of GeO2 or an aluminum carbide and the degradation of the diamond by the molten material inhibited nucleation on the melted area. Monocrystalline thin films of Beta-SiC have been achieved in the temperature range of 850 deg -980 deg C by atomic layer-by-layer deposition of Si and C species via sequential exposures of Si(100) substrates to Si2H6 and C2H4. A UHV analytical system containing TPD, AES and XPS is being constructed in concert with the SiC ALE studies to determine the reaction chemistry important to this process. An eximer laser ablation system for the ALE of CeO2 has been completed and employed to successfully deposit films of this material on Si(100).... Atomic layer epitaxy(ALE), Diamond, Silicon carbide, Cerium dioxide.

  16. Advanced thin-film deposition and physical properties of high-temperature and other novel superconducting materials. Annual report, 15 October 1991-31 October 1992

    SciTech Connect

    Beasley, M.R.; Geballe, T.H.; Kapitulnik, A.

    1993-06-03

    Progress under AFOSR Contract F49620-92-C-0004 for the period 15 October 1991 to 31 October 1992 is reported. Important results include studies of the grain boundaries in a-axis oriented high-Tc superconducting 123 YBCO thin films, the study of the vortex properties of high-Tc single crystals of the superconductor 2212 BSCCO and the artificially structured Mo-Ge/Ge quasi-two-dimensional superconductors. The latter provide an outstanding model system for the study of vortices in highly anisotropic superconductors, such at the high-Tc cuprates, without all the attendant difficult materials problems. Progress in the synthesis and study of the so-called infinite layer cuprate SrCuO4 and the normally conducting oxide SrRuO3 of interest as a barrier materials in high-Tc SNS devices are also reported. Finally the authors report the development of advanced approaches to rate control of the cation fluxes in the reactive coevaporation of the high-Tc superconductors.... High-Tc superconductivity, Anisotropic superconductivity, SrCuO4, SrRuO3, Mo-Ge/Ge superconducting multilayers.

  17. Research on polycrystalline thin-film submodules based on CuInSe{sub 2} materials. Final subcontract report, 11 November 1990--30 June 1995

    SciTech Connect

    Arya, R; Fogleboch, J; Kessler, J; Russell, L; Skibo, S; Wiedeman, S

    1996-01-01

    This report describes work performed in development of CIS-based photovoltaic (PV) products. The activity began with developing manufacturable deposition methods for all required thin-film layers and developing and understanding processes using those methods. It included demonstrating the potential for high conversion efficiency and followed with developing viable methods for module segment formation and interconnection. These process steps were integrated to fabricate monolithic CIS-based submodules. An important result of this program is the basis of understanding established in developing this material for PV applications, which is necessary to address issues of manufacturability and cost-which were recognized early in the program as being determined by successful solutions to issues of yield, reproducibility, and control as much as by material and energy costs, conversion efficiency, and process speed. Solarex identified at least one absorber formation process that is very robust to shunt formation from pinholes or point defects, tolerant of variation in processing temperature and elemental composition, and is capable of producing high conversion efficiency. This program also allowed development and scale-up of processes for the deposition of all other substrate, heterojunction buffer, and window layers and associated scribing/module formation operations to 1000-CM{sup 2} size. At the completion of this program, Solarex has in place most of the necessary elements to begin the transition to pilot operation of CIS manufacturing activities.

  18. Carbon nanotubes as novel spacer materials on silver thin-films for generating superior fluorescence enhancements via surface plasmon coupled emission

    NASA Astrophysics Data System (ADS)

    Mulpur, Pradyumna; Podila, Ramakrishna; Rao, Apparao M.; Kamisetti, Venkataramaniah

    2016-06-01

    In this study, we report the first time implementation of single/multi-walled carbon nanotubes, as novel spacer materials, on a silver (Ag) thin-film based surface plasmon coupled emission (SPCE) platform. The engineered Ag-CNT SPCE substrates enabled the realization of up to ∼10-fold enhancement in fluorescence signal intensity, of the rhodamine b dye. This study addresses the issue that, while many of the biochemical sensing strategies are based on fluorescence, they are all fundamentally limited by the isotropic nature of the phenomenon that results in low signal collection efficiency (<1%). Pursuant to the aim of realizing superior levels of signal sensitivity, we previously reported graphene and C60 as novel spacer materials, and similarly project CNTs in this study as ‘active’ contributors for the amplification of fluorescence signals on the SPCE platform that generates highly directional emission, with very high signal to noise ratios and >50% signal collection efficiency. Considering the easy functionalization of these carbon nano-allotropes, and their high sensitivity; the economical Ag-CNT SPCE platforms can be effectively extended towards sensing applications.

  19. Molecular weight effects in the third-harmonic generation spectroscopy of thin films of the conjugated polymer MEH-PPV.

    PubMed

    Bahtiar, Ayi; Koynov, Kaloian; Ahn, Taek; Bubeck, Christoph

    2008-03-27

    Thin spin-cast films of poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylenevinylene] (MEH-PPV) were prepared from samples whose weight-average molecular weight (Mw) was varied in the range of 10-1600 kg/mol. We have characterized the films by means of transmission and reflection ultraviolet-visible-near-infrared (UV-vis-NIR) spectroscopy to derive the linear optical constants, and third-harmonic generation spectroscopy with variable laser wavelengths to get the modulus and phase angles of the complex third-order nonlinear optical susceptibility chi(3). Increasing molecular weight yields films with significantly larger chi(3) values, absorption coefficients, and refractive indices. The chi(3) values of films from the largest and lowest Mw differ by a factor of 4, which is caused by chain orientation effects, local field effects, and changes of the effective conjugation length. PMID:18311961

  20. Coexistence of spinodal instability and thermal nucleation in thin-film rupture:Insights from molecular levels

    SciTech Connect

    Nguyen, Trung D; Fuentes-Cabrera, Miguel A; Fowlkes, Jason Davidson; Rack, Philip D

    2014-01-01

    Despite extensive investigation using hydrodynamic models and experiments over the past decades, there remain open questions regarding the origin of the initial rupture of thin liquid films. One of the reasons that makes it difficult to identify the rupture origin is the coexistence of two dewettingmechanisms, namely, thermal nucleation and spinodal instability, as observed in many experimental studies. Using a coarse-grained model and large-scale molecular dynamics simulations, we are able to characterize the very early stage of dewetting in nanometer-thick liquid-metal films wetting a solid substrate. We observe the features characteristic of both spinodal instability and thermal nucleation in the spontaneously dewetting films and show that these two macroscopic mechanisms share a common origin at molecular levels.

  1. VUV thin films, chapter 7

    NASA Technical Reports Server (NTRS)

    Zukic, Muamer; Torr, Douglas G.

    1993-01-01

    The application of thin film technology to the vacuum ultraviolet (VUV) wavelength region from 120 nm to 230 nm has not been fully exploited in the past because of absorption effects which complicate the accurate determination of the optical functions of dielectric materials. The problem therefore reduces to that of determining the real and imaginary parts of a complex optical function, namely the frequency dependent refractive index n and extinction coefficient k. We discuss techniques for the inverse retrieval of n and k for dielectric materials at VUV wavelengths from measurements of their reflectance and transmittance. Suitable substrate and film materials are identified for application in the VUV. Such applications include coatings for the fabrication of narrow and broadband filters and beamsplitters. The availability of such devices open the VUV regime to high resolution photometry, interferometry and polarimetry both for space based and laboratory applications. This chapter deals with the optics of absorbing multilayers, the determination of the optical functions for several useful materials, and the design of VUV multilayer stacks as applied to the design of narrow and broadband reflection and transmission filters and beamsplitters. Experimental techniques are discussed briefly, and several examples of the optical functions derived for selected materials are presented.

  2. Substrate independence of THz vibrational modes of polycrystalline thin films of molecular solids in waveguide THz-TDS

    NASA Astrophysics Data System (ADS)

    Harsha, S. Sree; Melinger, Joseph. S.; Qadri, S. B.; Grischkowsky, D.

    2012-01-01

    The influence of the metal substrate on the measurement of high resolution THz vibrational modes of molecular solids with the waveguide THz-TDS technique is investigated. The sample film of salicylic acid is studied using waveguide THz-TDS on three different metal substrates and two-surface passivated substrates. The independence of the observed THz vibrational modes to the metal substrate is demonstrated. Independently, surface passivation is presented as a viable experimental addition to the waveguide THz-TDS technique to aid the characterization of samples with known reactivity to metal surfaces.

  3. Piezoelectric thin films: an integrated review of transducers and energy harvesting

    NASA Astrophysics Data System (ADS)

    Khan, Asif; Abas, Zafar; Kim, Heung Soo; Oh, Il-Kwon

    2016-05-01

    Piezoelectric thin films offer a number of advantages in various applications, such as high energy density harvesters, a wide dynamic range, and high sensitivity sensors, as well as large displacement and low power consumption actuators. This review covers the available material forms and applications of piezoelectric thin films: lead zirconate titanate (PZT)-based thin films, lead-free piezoelectric thin films, piezopolymer films, cellulose-based electroactive paper (EAPap), and many other thin films used for electromechanical transduction. The electromechanical properties and performances of piezoelectric films are compared and their suitability for particular applications are reported. The key ideas of piezoelectric thin films are reviewed and discussed for sensory and actuation systems, energy harvesting, and medical and acoustic transducers. In the last section, an insight into the future outlook and possibilities for thin film-based devices and their integration into real-world applications is presented.

  4. Interference Colors in Thin Films.

    ERIC Educational Resources Information Center

    Armstrong, H. L.

    1979-01-01

    Explains interference colors in thin films as being due to the removal, or considerable reduction, of a certain color by destructive inteference that results in the complementary color being seen. (GA)

  5. Thin films, asphaltenes, and reservoir wettability

    SciTech Connect

    Kaminsky, R.; Bergeron, V.; Radke, C.J. |

    1993-04-01

    Reservoir wettability impacts the success of oil recovery by waterflooding and other methods. To understand wettability and its alteration, thin-film forces in solid-aqueous-oil systems must be elucidated. Upon rupture of thick aqueous films separating the oil and rock phases, asphaltene components in the crude oil adsorb irreversibly on the solid surface, changing it from water-wet to oil-wet. Conditions of wettability alteration can be found by performing adhesion tests, in which an oil droplet is brought into contact with a solid surface. Exceeding a critical capillary pressure destabilizes the film, causing spontaneous film rupture to a molecularly adsorbed layer and oil adhesion accompanied by pinning at the three-phase contact line. The authors conduct adhesion experiments similar to those of Buckley and Morrow and simultaneously examine the state of the underlying thin film using optical microscopy and microinterferometry. Aqueous thin films between an asphaltic Orcutt crude oil and glass surfaces are studied as a function of aqueous pH and salinity. For the first time, they prove experimentally that strongly water-wet to strongly oil-wet wettability alteration and contact-angle pinning occur when thick aqueous films thin to molecularly adsorbed films and when the oil phase contains asphaltene molecules.

  6. MISSE 5 Thin Films Space Exposure Experiment

    NASA Technical Reports Server (NTRS)

    Harvey, Gale A.; Kinard, William H.; Jones, James L.

    2007-01-01

    The Materials International Space Station Experiment (MISSE) is a set of space exposure experiments using the International Space Station (ISS) as the flight platform. MISSE 5 is a co-operative endeavor by NASA-LaRC, United Stated Naval Academy, Naval Center for Space Technology (NCST), NASA-GRC, NASA-MSFC, Boeing, AZ Technology, MURE, and Team Cooperative. The primary experiment is performance measurement and monitoring of high performance solar cells for U.S. Navy research and development. A secondary experiment is the telemetry of this data to ground stations. A third experiment is the measurement of low-Earth-orbit (LEO) low-Sun-exposure space effects on thin film materials. Thin films can provide extremely efficacious thermal control, designation, and propulsion functions in space to name a few applications. Solar ultraviolet radiation and atomic oxygen are major degradation mechanisms in LEO. This paper is an engineering report of the MISSE 5 thm films 13 months space exposure experiment.

  7. Method for making surfactant-templated thin films

    DOEpatents

    Brinker, C. Jeffrey; Lu, Yunfeng; Fan, Hong You

    2010-08-31

    An evaporation-induced self-assembly method to prepare a porous, surfactant-templated, thin film by mixing a silica sol, a solvent, a surfactant, and an interstitial compound, evaporating a portion of the solvent to form a liquid, crystalline thin film mesophase material, and then removal of the surfactant template. Coating onto a substrate produces a thin film with the interstitial compound either covalently bonded to the internal surfaces of the ordered or disordered mesostructure framework or physically entrapped within the ordered or disordered mesostructured framework. Particles can be formed by aerosol processing or spray drying rather than coating onto a substrate. The selection of the interstitial compound provides a means for developing thin films for applications including membranes, sensors, low dielectric constant films, photonic materials and optical hosts.

  8. Method for making surfactant-templated thin films

    DOEpatents

    Brinker, C. Jeffrey; Lu, Yunfeng; Fan, Hongyou

    2002-01-01

    An evaporation-induced self-assembly method to prepare a porous, surfactant-templated, thin film by mixing a silica sol, a solvent, a surfactant, and an interstitial compound, evaporating a portion of the solvent to form a liquid, crystalline thin film mesophase material, and then removal of the surfactant template. Coating onto a substrate produces a thin film with the interstitial compound either covalently bonded to the internal surfaces of the ordered or disordered mesostructure framework or physically entrapped within the ordered or disordered mesostructured framework. Particles can be formed by aerosol processing or spray drying rather than coating onto a substrate. The selection of the interstitial compound provides a means for developing thin films for applications including membranes, sensors, low dielectric constant films, photonic materials and optical hosts.

  9. Electrically tunable multiple Dirac cones in thin films of the (LaO)2(SbSe2)2 family of materials

    NASA Astrophysics Data System (ADS)

    Dong, Xiao-Yu; Wang, Jian-Feng; Zhang, Rui-Xing; Duan, Wen-Hui; Zhu, Bang-Fen; Sofo, Jorge O.; Liu, Chao-Xing

    2015-10-01

    Two-dimensional Dirac physics has aroused great interests in condensed matter physics ever since the discovery of graphene and topological insulators. The ability to control the properties of Dirac cones, such as bandgap and Fermi velocity, is essential for various new phenomena and the next-generation electronic devices. On the basis of first-principles calculations and an analytical effective model, we propose a new Dirac system with eight Dirac cones in thin films of the (LaO)2(SbSe2)2 family of materials, which has the advantage in its tunability: the existence of gapless Dirac cones, their positions, Fermi velocities and anisotropy all can be controlled by an experimentally feasible electric field. We identify layer-dependent spin texture induced by spin-orbit coupling as the underlying physical reason for electrical tunability of this system. Furthermore, the electrically tunable quantum anomalous Hall effect with a high Chern number can be realized by introducing magnetization into this system.

  10. Impact of deposition parameters on the material quality of SPC poly-Si thin films using high-rate PECVD of a-Si:H

    NASA Astrophysics Data System (ADS)

    Kumar, Avishek; Widenborg, Per Ingemar; Dalapati, Goutam Kumar; Sandhya Subramanian, Gomathy; Aberle, Armin Gerhard

    2015-05-01

    The impact of the deposition parameters such as gas flow (sccm) and RF plasma power density (W/cm2) on the deposition rate of a-Si:H films is systematically investigated. A high deposition rate of up to 146 nm/min at 13.56 MHz is achieved for the a-Si:H films deposited with high lateral uniformity on 30 × 40 cm2 large-area glass substrates. A relationship between the SiH4 gas flow and the RF power density is established. The SiH4 gas flow to RF power density ratio of about 2.4 sccm/mW cm-2 is found to give a linear increase in the deposition rate. The influence of the deposition rate on the material quality is studied using UV-VIS-NIR spectrophotometer and Raman characterisation techniques. Poly-Si thin film with crystal quality as high as 90% of single-crystalline Si wafer is obtained from the SPC of high rate deposited a-Si:H films.

  11. Optical, morphological properties and surface energy of the transparent Li4Ti5O12 (LTO) thin film as anode material for secondary type batteries

    NASA Astrophysics Data System (ADS)

    Özen, Soner; Şenay, Volkan; Pat, Suat; Korkmaz, Şadan

    2016-03-01

    LTO thin film was deposited for the first time on a glass microscope slide (MS) by RF magnetron sputtering technology. This method has been suitable for preparation of high-quality thin films. The surface properties of the produced film were determined by atomic force microscope (AFM). The surface of the produced film appeared smooth and homogeneous. LTO coated on MS had compact structure and low roughness. A UV-vis spectrophotometer was used to determine intensity of light passing through the samples. Thus, according to the results obtained the produced film was highly transparent. The refractive index of the LTO thin film was presented in a low MSE value by spectroscopic ellipsometry (SE) and it was about 1.5. The optical band gap (E g) was determined by the Tauc method. The produced LTO thin film exhibited a wide band gap semiconductor property with a band gap energy of about 2.95 eV. Finally, the surface free energy of the LTO thin film was calculated from the contact angle measurements using the Lewis acid-base, OWRK/Fowkes, Wu and Zisman methods.

  12. Polycrystalline thin film photovoltaic technology

    SciTech Connect

    Ullal, H.S.; Zweibel, K.; Mitchell, R.L.; Noufi, R.

    1991-03-01

    Low-cost, high-efficiency thin-film modules are an exciting photovoltaic technology option for generating cost-effective electricity in 1995 and beyond. In this paper we review the significant technical progress made in the following thin films: copper indium diselenide, cadmium telluride, and polycrystalline thin silicon films. Also, the recent US DOE/SERI initiative to commercialize these emerging technologies is discussed. 6 refs., 9 figs.

  13. Thin-film microextraction.

    PubMed

    Bruheim, Inge; Liu, Xiaochuan; Pawliszyn, Janusz

    2003-02-15

    The properties of a thin sheet of poly(dimethylsiloxane) (PDMS) membrane as an extraction phase were examined and compared to solid-phase microextraction (SPME) PDMS-coated fiber for application to semivolatile analytes in direct and headspace modes. This new PDMS extraction approach showed much higher extraction rates because of the larger surface area to extraction-phase volume ratio of the thin film. Unlike the coated rod formats of SPME using thick coatings, the high extraction rate of the membrane SPME technique allows larger amounts of analytes to be extracted within a short period of time. Therefore, higher extraction efficiency and sensitivity can be achieved without sacrificing analysis time. In direct membrane SPME extraction, a linear relationship was found between the initial rate of extraction and the surface area of the extraction phase. However, for headspace extraction, the rates were somewhat lower because of the resistance to analyte transport at the sample matrix/headspace barrier. It was found that the effect of this barrier could be reduced by increasing either agitation, temperature, or surface area of the sample matrix/headspace interface. A method for the determination of PAHs in spiked lake water samples was developed based on the membrane PDMS extraction coupled with GC/MS. A linearity of 0.9960 and detection limits in the low-ppt level were found. The reproducibility was found to vary from 2.8% to 10.7%. PMID:12622398

  14. Size- and temperature-dependent Young's modulus and size-dependent thermal expansion coefficient of thin films.

    PubMed

    Zhou, Xiao-Ye; Huang, Bao-Ling; Zhang, Tong-Yi

    2016-08-21

    Nanomaterials possess a high surface/volume ratio and surfaces play an essential role in size-dependent material properties. In the present study, nanometer-thick thin films were taken as an ideal system to investigate the surface-induced size- and temperature-dependent Young's modulus and size-dependent thermal expansion coefficient. The surface eigenstress model was further developed with the consideration of thermal expansion, leading to analytic formulas of size- and temperature-dependent Young's modulus, and size-dependent thermal expansion coefficient of thin films. Molecular dynamics (MD) simulations on face-centered cubic (fcc) Ag, Cu, and Ni(001) thin films were conducted at temperatures ranging from 300 K to 600 K. The MD simulation results are perfectly consistent with the theoretical predictions, thereby verifying the theoretical approach. The newly developed surface eigenstress model will be able to attack similar problems in other types of nanomaterials. PMID:27426852

  15. Selective thermal emission from thin-film metasurfaces

    NASA Astrophysics Data System (ADS)

    Streyer, W.; Law, S.; Mason, J.; Adams, D. C.; Rooney, G.; Jacobs, T.; Wasserman, D.

    2013-09-01

    The mid-infrared (mid-IR), as the spectral range where all finite temperature biological and mechanical objects emit thermal radiation, and where numerous molecular species have strong vibrational absorption resonances, is of significant importance for both security and sensing applications. The design of materials with engineered absorption resonances, which by Kirchoff's Law, should give strongly selective emission at the design resonance upon thermal excitation, allows for the control of the spectral character of the material's thermal emission. Designed as a thin film coating, these structures can be applied to grey-body emitters to shift the grey-body thermal emission into predetermined spectral bands, altering their appearance on a thermal imaging system. Here we demonstrate strongly selective mid-infrared absorption and thermal emission from three classes of subwavelength thin-film materials. First, we demonstrate selective thermal emission from patterned, commerciallyavailable steel films, via selective out-coupling of thermally-excited surface modes. Subsequently, we show nearperfect absorption (and strongly selective thermal emission) for wavelengths between 5 - 9μm with patterned metal-dielectric-metal structures. Finally, we demonstrate strong absorption from large area, unpatterned, thinfilm high-index dielectric coatings on highly-doped Si substrates, tunable across the mid-IR (5 - 12μm). Our results are compared to numerical simulations, as well as analytical models, with good agreement between experiments and models.

  16. Functionalization of Fibers Using Azlactone-Containing Polymers: Layer-by-Layer Fabrication of Reactive Thin Films on the Surfaces of Hair and Cellulose-Based Materials

    PubMed Central

    Buck, Maren E.

    2010-01-01

    We report an approach to the functionalization of fibers and fiber-based materials that is based on the deposition of reactive azlactone-functionalized polymers and the ‘reactive’ layer-by-layer assembly of azlactone-containing thin films. We demonstrate (i) that the azlactone-functionalized polymer poly(2-vinyl-4,4-dimethylazlactone) (PVDMA) can be used to modify the surfaces of a model protein-based fiber (horsehair) and cellulose-based materials (e.g., cotton and paper), and (ii) that fibers functionalized in this manner can be used to support the fabrication of covalently crosslinked and reactive polymer multilayers assembled using PVDMA and poly(ethyleneimine) (PEI). The growth, chemical reactivity, and uniformity of films deposited on these substrates were characterized using fluorescence microscopy, confocal microscopy, and scanning electron microscopy (SEM). In addition to the direct functionalization of fibers, we demonstrate that the residual azlactone functionality in PVDMA-treated or film-coated fibers can be exploited to chemically modify the surface chemistry and physicochemical properties of fiber-based materials post-fabrication using amine functionalized molecules. For example, we demonstrate that this approach permits control over the surface properties of paper (e.g., absorption of water) by simple post-fabrication treatment of film-coated paper with the hydrophobic amine n-decylamine. The azlactone functionality present in these materials provides a platform for the modification of polymer-treated and film-coated fibers with a broad range of other chemical and biological species (e.g., enzymes, peptides, catalysts, etc.). The results of this investigation thus provide a basis for the functionalization of fibers and fiber-based materials (e.g., textile fabrics or non-woven mats) of potential utility in a broad range of consumer, industrial, and biomedical contexts. PMID:20402471

  17. Molecular beam epitaxy-grown wurtzite MgS thin films for solar-blind ultra-violet detection

    SciTech Connect

    Lai, Y. H.; He, Q. L.; Cheung, W. Y.; Lok, S. K.; Wong, K. S.; Sou, I. K.; Ho, S. K.; Tam, K. W.

    2013-04-29

    Molecular beam epitaxy grown MgS on GaAs(111)B substrate was resulted in wurtzite phase, as demonstrated by detailed structural characterizations. Phenomenological arguments were used to account for why wurtzite phase is preferred over zincblende phase or its most stable rocksalt phase. Results of photoresponse and reflectance measurements performed on wurtzite MgS photodiodes suggest a direct bandgap at around 5.1 eV. Their response peaks at 245 nm with quantum efficiency of 9.9% and enjoys rejection of more than three orders at 320 nm and close to five orders at longer wavelengths, proving the photodiodes highly competitive in solar-blind ultraviolet detection.

  18. An automated spin-assisted approach for molecular layer-by-layer assembly of crosslinked polymer thin films

    SciTech Connect

    Chan, Edwin P.; Chung, Jun Young; Stafford, Christopher M.; Lee, Jung-Hyun

    2012-11-15

    We present the design of an automated spin-coater that facilitates fabrication of polymer films based on molecular layer-by-layer (mLbL) assembly. Specifically, we demonstrate the synthesis of ultrathin crosslinked fully-aromatic polyamide (PA) films that are chemically identical to polymer membranes used in water desalination applications as measured by X-ray photoelectron spectroscopy. X-ray reflectivity measurements indicate that the automated mLbL assembly creates films with a constant film growth rate and minimal roughness compared with the traditional interfacial polymerization of PA. This automated spin-coater improves the scalability and sample-to-sample consistency by reducing human involvement in the mLbL assembly.

  19. Characterization of deep acceptor level in as-grown ZnO thin film by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Asghar, M.; K., Mahmood; A. Hasan, M.; T. Ferguson, I.; Tsu, R.; Willander, M.

    2014-09-01

    We report deep level transient spectroscopy results from ZnO layers grown on silicon by molecular beam epitaxy (MBE). The hot probe measurements reveal mixed conductivity in the as-grown ZnO layers, and the current—voltage (I—V) measurements demonstrate a good quality p-type Schottky device. A new deep acceptor level is observed in the ZnO layer having activation energy of 0.49 ±0.03 eV and capture cross-section of 8.57 × 10-18 cm2. Based on the results from Raman spectroscopy, photoluminescence, and secondary ion mass spectroscopy (SIMS) of the ZnO layer, the observed acceptor trap level is tentatively attributed to a nitrogen-zinc vacancy complex in ZnO.

  20. Superconducting thin films on potassium tantalate substrates

    DOEpatents

    Feenstra, Roeland; Boatner, Lynn A.

    1992-01-01

    A superconductive system for the lossless transmission of electrical current comprising a thin film of superconducting material Y.sub.1 Ba.sub.2 Cu.sub.3 O.sub.7-x epitaxially deposited upon a KTaO.sub.3 substrate. The KTaO.sub.3 is an improved substrate over those of the prior art since the it exhibits small lattice constant mismatch and does not chemically react with the superconducting film.