Growth and characterization of highly conducting Al-doped ZnO (AZO) thin films for optoelectronic applications

NASA Astrophysics Data System (ADS)

Sardana, Sanjay K.; Singh, Anil; Srivastava, Sanjay K.; Pandya, Dinesh K.

2018-05-01

A comparative study of undoped ZnO and Al-doped ZnO (AZO) thin films deposited on glass substrate by spray pyrolysis has been carried out at various aqueous molar concentration of zinc acetate. The thin films deposited on glass shows the wurtzite phase of ZnO, confirmed by X-ray diffraction. The optical study shows the high transmittance over 80% in the visible regime. The band gap of AZO thin films shows a blue shift as compared to undoped ZnO, which has been attributed to Burstein-Moss shift. Heat treatment of these samples in vacuum showed the improved conductivity in compared to as-deposited thin films. The electric study shows the minimum resistivity of 8 x 10-3 Ω-cm and carrier concentration of 6.5 × 1019 /cm3 correspond to AZO thin films.

Tunable electrical conductivity in oriented thin films of tetrathiafulvalene-based covalent organic framework

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

Cai, SL; Zhang, YB; Pun, AB

2014-09-16

Despite the high charge-carrier mobility in covalent organic frameworks (COFs), the low intrinsic conductivity and poor solution processability still impose a great challenge for their applications in flexible electronics. We report the growth of oriented thin films of a tetrathiafulvalene-based COF (TTF-COF) and its tunable doping. The porous structure of the crystalline TTF-COF thin film allows the diffusion of dopants such as I-2 and tetracyanoquinodimethane (TCNQ) for redox reactions, while the closely packed 2D grid sheets facilitate the cross-layer delocalization of thus-formed TTF radical cations to generate more conductive mixed-valence TTF species, as is verified by UV-vis-NIR and electron paramagneticmore » resonance spectra. Conductivity as high as 0.28 S m(-1) is observed for the doped COF thin films, which is three orders of magnitude higher than that of the pristine film and is among the highest for COF materials.« less

Sol-gel derived Al-Ga co-doped transparent conducting oxide ZnO thin films

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

Serrao, Felcy Jyothi, E-mail: jyothiserrao@gmail.com; Department of Physics, Karnataka Government Research centre SCEM, Mangalore, 575007; Sandeep, K. M.

2016-05-23

Transparent conducting ZnO doped with Al, Ga and co-doped Al and Ga (1:1) (AGZO) thin films were grown on glass substrates by cost effective sol-gel spin coating method. The XRD results showed that all the films are polycrystalline in nature and highly textured along the (002) plane. Enhanced grain size was observed in the case of AGZO thin films. The transmittance of all the films was more than 83% in the visible region of light. The electrical properties such as carrier concentration and mobility values are increased in case of AGZO compared to that of Al and Ga doped ZnOmore » thin films. The minimum resistivity of 2.54 × 10{sup −3} Ω cm was observed in AGZO thin film. The co-doped AGZO thin films exhibited minimum resistivity and high optical transmittance, indicate that co-doped ZnO thin films could be used in transparent electronics mainly in display applications.« less

n-Type Conductivity of Cu2O Thin Film Prepared in Basic Aqueous Solution Under Hydrothermal Conditions

NASA Astrophysics Data System (ADS)

Ursu, Daniel; Miclau, Nicolae; Miclau, Marinela

2018-03-01

We report for the first time in situ hydrothermal synthesis of n-type Cu2O thin film using strong alkaline solution. The use of copper foil as substrate and precursor material, low synthesis temperature and short reaction time represent the arguments of a new, simple, inexpensive and high field synthesis method for the preparation of n-type Cu2O thin film. The donor concentration of n-type Cu2O thin film obtained at 2 h of reaction time has increased two orders of magnitude than previous reported values. We have demonstrated n-type conduction in Cu2O thin film prepared in strong alkaline solution, in the contradiction with the previous works. Based on experimental results, the synthesis mechanism and the origin of n-type photo-responsive behavior of Cu2O thin film were discussed. We have proposed that the unexpected n-type character could be explained by H doping of Cu2O thin film in during of the hydrothermal synthesis that caused the p-to-n conductivity-type conversion. Also, this work raises new questions about the origin of n-type conduction in Cu2O thin film, the influence of the synthesis method on the nature of the intrinsic defects and the electrical conduction behavior.

Amorphous lithium lanthanum titanate for solid-state microbatteries

DOE PAGES

Lee, Jungwoo Z.; Wang, Ziying; Xin, Huolin L.; ...

2016-12-16

Lithium lanthanum titanate (LLTO) is a promising solid state electrolyte for solid state batteries due to its demonstrated high bulk ionic conductivity. However, crystalline LLTO has a relatively low grain boundary conductivity, limiting the overall material conductivity. In this work, we investigate amorphous LLTO (a-LLTO) thin films grown by pulsed laser deposition (PLD). By controlling the background pressure and temperature we are able to optimize the ionic conductivity to 3 × 10 –4 S/cm and electronic conductivity to 5 × 10 –11 S/cm. XRD, TEM, and STEM/EELS analysis confirm that the films are amorphous and indicate that oxygen background gasmore » is necessary during the PLD process to decrease the oxygen vacancy concentration, decreasing the electrical conductivity. Amorphous LLTO is deposited onto high voltage LiNi 0.5Mn 1.5O 4 (LNMO) spinel cathode thin films and cycled up to 4.8 V vs. Li showing excellent capacity retention. Finally, these results demonstrate that a-LLTO has the potential to be integrated into high voltage thin film batteries.« less

Low Temperature Synthesis of Fluorine-Doped Tin Oxide Transparent Conducting Thin Film by Spray Pyrolysis Deposition.

PubMed

Ko, Eun-Byul; Choi, Jae-Seok; Jung, Hyunsung; Choi, Sung-Churl; Kim, Chang-Yeoul

2016-02-01

Transparent conducting oxide (TCO) is widely used for the application of flat panel display like liquid crystal displays and plasma display panel. It is also applied in the field of touch panel, solar cell electrode, low-emissivity glass, defrost window, and anti-static material. Fluorine-doped tin oxide (FTO) thin films were fabricated by spray pyrolysis of ethanol-added FTO precursor solutions. FTO thin film by spray pyrolysis is very much investigated and normally formed at high temperature, about 500 degrees C. However, these days, flexible electronics draw many attentions in the field of IT industry and the research for flexible transparent conducting thin film is also required. In the industrial field, indium-tin oxide (ITO) film on polymer substrate is widely used for touch panel and displays. In this study, we investigated the possibility of FTO thin film formation at relatively low temperature of 250 degrees C. We found out that the control of volume of input precursor and exhaust gases could make it possible to form FTO thin film with a relatively low electrical resistance, less than 100 Ohm/sq and high optical transmittance about 88%.

Voltage Scaling of Graphene Device on SrTiO3 Epitaxial Thin Film.

PubMed

Park, Jeongmin; Kang, Haeyong; Kang, Kyeong Tae; Yun, Yoojoo; Lee, Young Hee; Choi, Woo Seok; Suh, Dongseok

2016-03-09

Electrical transport in monolayer graphene on SrTiO3 (STO) thin film is examined in order to promote gate-voltage scaling using a high-k dielectric material. The atomically flat surface of thin STO layer epitaxially grown on Nb-doped STO single-crystal substrate offers good adhesion between the high-k film and graphene, resulting in nonhysteretic conductance as a function of gate voltage at all temperatures down to 2 K. The two-terminal conductance quantization under magnetic fields corresponding to quantum Hall states survives up to 200 K at a magnetic field of 14 T. In addition, the substantial shift of charge neutrality point in graphene seems to correlate with the temperature-dependent dielectric constant of the STO thin film, and its effective dielectric properties could be deduced from the universality of quantum phenomena in graphene. Our experimental data prove that the operating voltage reduction can be successfully realized due to the underlying high-k STO thin film, without any noticeable degradation of graphene device performance.

Enhancing electrical conductivity of room temperature deposited Sn-doped In2O3 thin films by hematite seed layers

NASA Astrophysics Data System (ADS)

Lohaus, Christian; Steinert, Céline; Deyu, Getnet; Brötz, Joachim; Jaegermann, Wolfram; Klein, Andreas

2018-04-01

Hematite Fe2O3 seed layers are shown to constitute a pathway to prepare highly conductive transparent tin-doped indium oxide thin films by room temperature magnetron sputtering. Conductivities of up to σ = 3300 S/cm are observed. The improved conductivity is not restricted to the interface but related to an enhanced crystallization of the films, which proceeds in the rhombohedral phase.

Hopping conduction in zirconium oxynitrides thin film deposited by reactive magnetron sputtering

NASA Astrophysics Data System (ADS)

Guo, Jie; Zhan, Guanghui; Liu, Jingquan; Yang, Bin; Xu, Bin; Feng, Jie; Chen, Xiang; Yang, Chunsheng

2015-10-01

Zirconium oxynitrides thin film thermometers were demonstrated to be useful temperature sensors. However, the basic conduction mechanism of zirconium oxynitrides films has been a long-standing issue, which hinders the prediction and optimization of their ultimate performance. In this letter, zirconium oxynitrides films were grown on sapphire substrates by magnetron sputtering and their electric transport mechanism has been systemically investigated. It was found that in high temperatures region (>150 K) the electrical conductivity was dominated by thermal activation for all samples. In the low temperatures range, while Mott variable hopping conduction (VRH) was dominated the transport for films with relatively low resistance, a crossover from Mott VRH conduction to Efros-Shklovskii (ES) VRH was observed for films with relatively high resistance. This low temperature crossover from Mott to ES VRH indicates the presence of a Coulomb gap (~7 meV). These results demonstrate the competing and tunable conduction mechanism in zirconium oxynitrides thin films, which would be helpful for optimizing the performance of zirconium oxynitrides thermometer.

Synthesis and characterization of transparent conductive zinc oxide thin films by sol-gel spin coating method

NASA Astrophysics Data System (ADS)

Winarski, David

Zinc oxide has been given much attention recently as it is promising for various semiconductor device applications. ZnO has a direct band gap of 3.3 eV, high exciton binding energy of 60 meV and can exist in various bulk powder and thin film forms for different applications. ZnO is naturally n-type with various structural defects, which sparks further investigation into the material properties. Although there are many potential applications for this ZnO, an overall lack of understand and control of intrinsic defects has proven difficult to obtain consistent, repeatable results. This work studies both synthesis and characterization of zinc oxide in an effort to produce high quality transparent conductive oxides. The sol-gel spin coating method was used to obtain highly transparent ZnO thin films with high UV absorbance. This research develops a new more consistent method for synthesis of these thin films, providing insight for maintaining quality control for each step in the procedure. A sol-gel spin coating technique is optimized, yielding highly transparent polycrystalline ZnO thin films with tunable electrical properties. Annealing treatment in hydrogen and zinc atmospheres is researched in an effort to increase electrical conductivity and better understand intrinsic properties of the material. These treatment have shown significant effects on the properties of ZnO. Characterization of doped and undoped ZnO synthesized by the sol-gel spin coating method was carried out using scanning electron microscopy, UV-Visible range absorbance, X-ray diffraction, and the Hall Effect. Treatment in hydrogen shows an overall decrease in the number of crystal phases and visible absorbance while zinc seems to have the opposite effect. The Hall Effect has shown that both annealing environments increase the n-type conductivity, yielding a ZnO thin film with a carrier concentration as high as 3.001 x 1021 cm-3.

Transparent conductive coatings

NASA Technical Reports Server (NTRS)

Ashok, S.

1983-01-01

Thin film transparent conductors are discussed. Materials with electrical conductivity and optical transparency are highly desirable in many optoelectronic applications including photovoltaics. Certain binary oxide semiconductors such as tin oxide (SnO2) and indium oxide (In2O3) offer much better performance tradeoff in optoelectronics as well as better mechanical and chemical stability than thin semitransparent films. These thin-film transparent conductors (TC) are essentially wide-bandgap degenerate semiconductors - invariably n-type - and hence are transparent to sub-bandgap (visible) radiation while affording high electrical conductivity due to the large free electron concentration. The principal performance characteristics of TC's are, of course, electrical conductivity and optical transmission. The TC's have a refractive index of around 2.0 and hence act as very efficient antireflection coatings. For using TC's in surface barrier solar cells, the photovoltaic barrier is of utmost importance and so the work function or electron affinity of the TC is also a very important material parameter. Fabrication processes are discussed.

Effect of composition and strain on the electrical properties of LaNiO3 thin films

NASA Astrophysics Data System (ADS)

Zhu, Mingwei; Komissinskiy, Philipp; Radetinac, Aldin; Vafaee, Mehran; Wang, Zhanjie; Alff, Lambert

2013-09-01

The Ni content of LaNi1-xO3 epitaxial thin films grown by pulsed laser deposition has been varied by ablation from targets with different composition. While tensile strain and Ni substoichiometry reduce the conductivity, nearly stoichiometric and unstrained films show reproducibly resistivities below 100 μΩ × cm. Since the thermodynamic instability of the Ni3+ state drives defect formation, Ni defect engineering is the key to obtain highly conducting LaNiO3 thin films.

Electrodeposited Structurally Stable V2O5 Inverse Opal Networks as High Performance Thin Film Lithium Batteries.

PubMed

Armstrong, Eileen; McNulty, David; Geaney, Hugh; O'Dwyer, Colm

2015-12-09

High performance thin film lithium batteries using structurally stable electrodeposited V2O5 inverse opal (IO) networks as cathodes provide high capacity and outstanding cycling capability and also were demonstrated on transparent conducting oxide current collectors. The superior electrochemical performance of the inverse opal structures was evaluated through galvanostatic and potentiodynamic cycling, and the IO thin film battery offers increased capacity retention compared to micron-scale bulk particles from improved mechanical stability and electrical contact to stainless steel or transparent conducting current collectors from bottom-up electrodeposition growth. Li(+) is inserted into planar and IO structures at different potentials, and correlated to a preferential exposure of insertion sites of the IO network to the electrolyte. Additionally, potentiodynamic testing quantified the portion of the capacity stored as surface bound capacitive charge. Raman scattering and XRD characterization showed how the IO allows swelling into the pore volume rather than away from the current collector. V2O5 IO coin cells offer high initial capacities, but capacity fading can occur with limited electrolyte. Finally, we demonstrate that a V2O5 IO thin film battery prepared on a transparent conducting current collector with excess electrolyte exhibits high capacities (∼200 mAh g(-1)) and outstanding capacity retention and rate capability.

Synthesis and characterization thin films of conductive polymer (PANI) for optoelectronic device application

NASA Astrophysics Data System (ADS)

Jarad, Amer N.; Ibrahim, Kamarulazizi; Ahmed, Nasser M.

2016-07-01

In this work we report preparation and investigation of structural and optical properties of polyaniline conducting polymer. By using sol-gel in spin coating technique to synthesize thin films of conducting polymer polyaniline (PANI). Conducting polymer polyaniline was synthesized by the chemical oxidative polymerization of aniline monomers. The thin films were characterized by technique: Hall effect, High Resolution X-ray diffraction (HR-XRD), Fourier transform infrared (FTIR) spectroscopy, Field emission scanning electron microscopy (FE-SEM), and UV-vis spectroscopy. Polyaniline conductive polymer exhibit amorphous nature as confirmed by HR-XRD. The presence of characteristic bonds of polyaniline was observed from FTIR spectroscopy technique. Electrical and optical properties revealed that (p-type) conductivity PANI with room temperature, the conductivity was 6.289×10-5 (Ω.cm)-1, with tow of absorption peak at 426,805 nm has been attributed due to quantized size of polyaniline conducting polymer.

Highly conductive and transparent thin ZnO films prepared in situ in a low pressure system

NASA Astrophysics Data System (ADS)

Ataev, B. M.; Bagamadova, A. M.; Mamedov, V. V.; Omaev, A. K.; Rabadanov, M. R.

1999-03-01

Sucessful preparation of ZnO : M epitaxial thin films (ETF) in situ doped with donor impurity M=Ga, Sn by chemical vapor despsition in a low-pressure system is reported. Highly conductive (up to 10 -4 Ω cm) and transparent ( T>85%) ZnO : M ETF have been successfully produced on single crystal (1012) sapphire substrates. Electrical properties of the films as well as their excition luminescence were studied.

Direct Room Temperature Welding and Chemical Protection of Silver Nanowire Thin Films for High Performance Transparent Conductors.

PubMed

Ge, Yongjie; Duan, Xidong; Zhang, Meng; Mei, Lin; Hu, Jiawen; Hu, Wei; Duan, Xiangfeng

2018-01-10

Silver nanowire (Ag-NW) thin films have emerged as a promising next-generation transparent electrode. However, the current Ag-NW thin films are often plagued by high NW-NW contact resistance and poor long-term stability, which can be largely attributed to the ill-defined polyvinylpyrrolidone (PVP) surface ligands and nonideal Ag-PVP-Ag contact at NW-NW junctions. Herein, we report a room temperature direct welding and chemical protection strategy to greatly improve the conductivity and stability of the Ag-NW thin films. Specifically, we use a sodium borohydride (NaBH 4 ) treatment process to thoroughly remove the PVP ligands and produce a clean Ag-Ag interface that allows direct welding of NW-NW junctions at room temperature, thus greatly improving the conductivity of the Ag-NW films, outperforming those obtained by thermal or plasmonic thermal treatment. We further show that, by decorating the as-formed Ag-NW thin film with a dense, hydrophobic dodecanethiol layer, the stability of the Ag-NW film can be greatly improved by 150-times compared with that of PVP-wrapped ones. Our studies demonstrate that a proper surface ligand design can effectively improve the conductivity and stability of Ag-NW thin films, marking an important step toward their applications in electronic and optoelectronic devices.

Temperature-dependent thermal and thermoelectric properties of n -type and p -type S c1 -xM gxN

NASA Astrophysics Data System (ADS)

Saha, Bivas; Perez-Taborda, Jaime Andres; Bahk, Je-Hyeong; Koh, Yee Rui; Shakouri, Ali; Martin-Gonzalez, Marisol; Sands, Timothy D.

2018-02-01

Scandium Nitride (ScN) is an emerging rocksalt semiconductor with octahedral coordination and an indirect bandgap. ScN has attracted significant attention in recent years for its potential thermoelectric applications, as a component material in epitaxial metal/semiconductor superlattices, and as a substrate for defect-free GaN growth. Sputter-deposited ScN thin films are highly degenerate n -type semiconductors and exhibit a large thermoelectric power factor of ˜3.5 ×10-3W /m -K2 at 600-800 K. Since practical thermoelectric devices require both n- and p-type materials with high thermoelectric figures-of-merit, development and demonstration of highly efficient p-type ScN is extremely important. Recently, the authors have demonstrated p-type S c1 -xM gxN thin film alloys with low M gxNy mole-fractions within the ScN matrix. In this article, we demonstrate temperature dependent thermal and thermoelectric transport properties, including large thermoelectric power factors in both n- and p-type S c1 -xM gxN thin film alloys at high temperatures (up to 850 K). Employing a combination of temperature-dependent Seebeck coefficient, electrical conductivity, and thermal conductivity measurements, as well as detailed Boltzmann transport-based modeling analyses of the transport properties, we demonstrate that p-type S c1 -xM gxN thin film alloys exhibit a maximum thermoelectric power factor of ˜0.8 ×10-3W /m -K2 at 850 K. The thermoelectric properties are tunable by adjusting the M gxNy mole-fraction inside the ScN matrix, thereby shifting the Fermi energy in the alloy films from inside the conduction band in case of undoped n -type ScN to inside the valence band in highly hole-doped p -type S c1 -xM gxN thin film alloys. The thermal conductivities of both the n- and p-type films were found to be undesirably large for thermoelectric applications. Thus, future work should address strategies to reduce the thermal conductivity of S c1 -xM gxN thin-film alloys, without affecting the power factor for improved thermoelectric performance.

Thermoelectric Figures of Merit of Zn4Sb3 and Zrnisn-based Half-heusler Compounds Influenced by Mev Ion-beam Bombardments

NASA Astrophysics Data System (ADS)

Budak, S.; Guner, S.; Muntele, C. I.; Ila, D.

Semiconducting β-Zn4Sb3 and ZrNiSn-based half-Heusler compound thin films with applications as thermoelectric (TE) materials were prepared using ion beam assisted deposition (IBAD). High-purity solid zinc (Zn) and antimony (Sb) were evaporated by electron beam to grow the β-Zn4Sb3 thin film while high-purity zirconium (Zr) powder and nickel (Ni) tin (Sn) powders were evaporated by electron beam to grow the ZrNiSn-based half-Heusler compound thin film. Rutherford backscattering spectrometry (RBS) was used to analyze the composition of the thin films. The grown thin films were subjected to 5 MeV Si ions bombardment for generation of nanostructures in the films. We measured the thermal conductivity, Seebeck coefficient, and electrical conductivity of these two systems before and after 5 MeV Si ions beam bombardment. The two material systems have been identified as promising TE materials for the application of thermal-to-electrical energy conversion, but the efficiency still limits their applications. The electronic energy deposited due to ionization in the track of MeV ion beam couldcause localized crystallization. The nanostructures produced by MeV ion beam can cause significant change in both the electrical and the thermal conductivity of thin films, thereby improving the efficiency. We used the 3ω-method (3rd harmonic) measurement system to measure the cross-plane thermal conductivity, the van der Pauw measurement system to measure the electrical conductivity, and the Seebeck-coefficient measurement system to measure the cross-plane Seebeck coefficient. The thermoelectric figures of merit of the two material systems were then derived by calculations using the measurement results. The MeV ion-beam bombardment was found to decrease the thermal conductivity of thin films and increase the efficiency of thermal-to-electrical energy conversion.

Thermal phonon transport in Si thin film with dog-leg shaped asymmetric nanostructures

NASA Astrophysics Data System (ADS)

Kage, Yuta; Hagino, Harutoshi; Yanagisawa, Ryoto; Maire, Jeremie; Miyazaki, Koji; Nomura, Masahiro

2016-08-01

Thermal phonon transport in single-crystalline Si thin films with dog-leg shaped nanostructures was investigated. Thermal conductivities for the forward and backward directions were measured and compared at 5 and 295 K by micro thermoreflectance. The Si thin film with dog-leg shaped nanostructures showed lower thermal conductivities than those of nanowires and two-dimensional phononic crystals with circular holes at the same surface-to-volume ratio. However, asymmetric thermal conductivity was not observed at small temperature gradient condition in spite of the highly asymmetric shape though the size of the pattern is within thermal phonon mean free path range. We conclude that strong temperature dependent thermal conductivity is required to observe the asymmetric thermal phonon conduction in monolithic materials with asymmetric nanostructures.

An investigation on the In doping of ZnO thin films by spray pyrolysis

NASA Astrophysics Data System (ADS)

Mahesh, Devika; Kumar, M. C. Santhosh

2018-04-01

Indium doped zinc oxide (IGZO)thin films are gaining much interest owing to its commercial application as transparent conductive oxide thin films. In the current study thin films indium doped ZnO thin films have been deposited on glass substrates by chemical spray pyrolysis technique with an indium concentration of 1, 2.5 and 4% in Zinc source. The films show a peak shift in the X-Ray Diffraction patterns with varying indium doping concentration. The (101) peak was enhanced for the 2.5 % indium doped films and variation in grain size with the different doping levels was studied. The as-deposited films are uniform and shown high transparency (>90%) in the visible region. Average thicknesses of films are found to be 800nm, calculated using the envelope method. The film with 2.5 % of indium content was found to be highly conducting than the rest, since for the lower and higher concentrations the conductivity was possibly halted by the limit in carrier concentration and indium segregation in the grain boundaries respectively. The enhancement of mobility and carrier concentration was clearly seen in the optimum films.

Conductive polymer/fullerene blend thin films with honeycomb framework for transparent photovoltaic application

DOEpatents

Cotlet, Mircea; Wang, Hsing-Lin; Tsai, Hsinhan; Xu, Zhihua

2015-04-21

Optoelectronic devices and thin-film semiconductor compositions and methods for making same are disclosed. The methods provide for the synthesis of the disclosed composition. The thin-film semiconductor compositions disclosed herein have a unique configuration that exhibits efficient photo-induced charge transfer and high transparency to visible light.

Graphene and silver-nanoprism dispersion for printing optically-transparent electrodes

NASA Astrophysics Data System (ADS)

Sinar, Dogan; Knopf, George K.; Nikumb, Suwas

2017-02-01

Optically transparent electrodes (OTEs) are used for bioelectronics, touch screens, visual displays, and photovoltaic cells. Although the conductive coating for these electrodes is often composed of indium tin oxide (ITO), indium is a very expensive material and thin ITO films are relatively brittle compared to conductive polymer or graphene thin films. An alternative highly conductive optically transparent thin film based on a graphene (G) and silver-nanoprism (AgNP) dispersion is introduced in this paper. The aqueous G ink is first synthesized using carboxymethyl cellulose (CMC) as a stabilizing agent. Silver (Ag) nanoprisms are then prepared separately by a simple thermal process which involves the reduction of silver nitrate by sodium borohydride. These Ag nanoprisms are only a few nanometers thick but have relatively large surface areas (>1000 nm2). As a consequence, the nanoprisms provide more efficient injection of free carriers to the G layer. The concentrated G-AgNP dispersions are then deposited on optically transparent glass and polyimide substrates using an inkjet printer with a HP6602A print head. After printing, these optically thin films can be thermally treated to further increase electrical conductivity. Thermal treatment decomposes CMC which frees elemental carbon from polymer chain and, simultaneously, causes the film to become hydrophobic. Preliminary experiments demonstrate that the G-AgNP films on glass substrates exhibit high conductivity at 70% transparency (550 nm). Additional tests on the Gr-AgNP thin films printed on polymide substrates show mechanical stability under bending with minimal reduction in electrical conductivity or optical transparency.

A photoelectrochemical (PEC) study on graphene oxide based hematite thin films heterojunction (R-GO/Fe2O3)

NASA Astrophysics Data System (ADS)

Sharma, Poonam; Zachariah, Michael; Ehrman, Sheryl; Shrivastava, Rohit; Dass, Sahab; Satsangi, Vibha; Michael Zachariah, Sheryl Ehrman Collaboration; Rohit Shrivastava, Sahab Dass Collaboration; Vibha R Satsangi, Poonam Sharma Team

2013-03-01

Graphene has an excellent electronic conductivity, a high theoretical surface area of 2630 m2/g and excellent mechanical properties and, thus, is a promising component for high-performance electrode materials. Following this, GO has been used to modify the PEC response of photoactive material hematite thin films in PEC cell. A reduced graphene oxide/iron oxide (R-GO/Fe2O3) thin film structure has been successfully prepared on ITO by directly growing iron oxide particles on the thermally reduced graphene oxide sheets prepared from suspension of exfoliated graphene oxide. R-GO/Fe2O3 thin films were tested in PEC cell and offered ten times higher photocurrent density than pristine Fe2O3 thin film sample. XRD, SEM, EDS, UV-Vis, Mott-Schottky and Raman studies were carried out to study spectro-electrochemical properties. Enhanced PEC performance of these photoelectrodes was attributed to its porous morphology, improved conductivity upon favorable carrier transfer across the oxides interface.

Accurate measurements of cross-plane thermal conductivity of thin films by dual-frequency time-domain thermoreflectance (TDTR)

NASA Astrophysics Data System (ADS)

Jiang, Puqing; Huang, Bin; Koh, Yee Kan

2016-07-01

Accurate measurements of the cross-plane thermal conductivity Λcross of a high-thermal-conductivity thin film on a low-thermal-conductivity (Λs) substrate (e.g., Λcross/Λs > 20) are challenging, due to the low thermal resistance of the thin film compared with that of the substrate. In principle, Λcross could be measured by time-domain thermoreflectance (TDTR), using a high modulation frequency fh and a large laser spot size. However, with one TDTR measurement at fh, the uncertainty of the TDTR measurement is usually high due to low sensitivity of TDTR signals to Λcross and high sensitivity to the thickness hAl of Al transducer deposited on the sample for TDTR measurements. We observe that in most TDTR measurements, the sensitivity to hAl only depends weakly on the modulation frequency f. Thus, we performed an additional TDTR measurement at a low modulation frequency f0, such that the sensitivity to hAl is comparable but the sensitivity to Λcross is near zero. We then analyze the ratio of the TDTR signals at fh to that at f0, and thus significantly improve the accuracy of our Λcross measurements. As a demonstration of the dual-frequency approach, we measured the cross-plane thermal conductivity of a 400-nm-thick nickel-iron alloy film and a 3-μm-thick Cu film, both with an accuracy of ˜10%. The dual-frequency TDTR approach is useful for future studies of thin films.

Local electrical characterization of laser-recorded phase-change marks on amorphous Ge2Sb2Te5 thin films.

PubMed

Chang, Chia Min; Chu, Cheng Hung; Tseng, Ming Lun; Chiang, Hai-Pang; Mansuripur, Masud; Tsai, Din Ping

2011-05-09

Amorphous thin films of Ge(2)Sb(2)Te(5), sputter-deposited on a thin-film gold electrode, are investigated for the purpose of understanding the local electrical conductivity of recorded marks under the influence of focused laser beam. Being amorphous, the as-deposited chalcogenide films have negligible electrical conductivity. With the aid of a focused laser beam, however, we have written on these films micron-sized crystalline marks, ablated holes surrounded by crystalline rings, and other multi-ring structures containing both amorphous and crystalline zones. Within these structures, nano-scale regions of superior local conductivity have been mapped and probed using our high-resolution, high-sensitivity conductive-tip atomic force microscope (C-AFM). Scanning electron microscopy and energy-dispersive spectrometry have also been used to clarify the origins of high conductivity in and around the recorded marks. When the Ge(2)Sb(2)Te(5) layer is sufficiently thin, and when laser crystallization/ablation is used to define long isolated crystalline stripes on the samples, we find the C-AFM-based method of extracting information from the recorded marks to be superior to other forms of microscopy for this particular class of materials. Given the tremendous potential of chalcogenides as the leading media candidates for high-density memories, local electrical characterization of marks recorded on as-deposited amorphous Ge(2)Sb(2)Te(5) films provides useful information for furthering research and development efforts in this important area of modern technology. © 2011 Optical Society of America

Layered conductive polymer on nylon membrane templates for high performance, thin-film supercapacitor electrodes

NASA Astrophysics Data System (ADS)

Shi, HaoTian Harvey; Naguib, Hani E.

2016-04-01

Flexible Thin-film Electrochemical Capacitors (ECs) are emerging technology that plays an important role as energy supply for various electronics system for both present era and the future. Intrinsically conductive polymers (ICPs) are promising pseudo-capacitive materials as they feature both good electrical conductivity and high specific capacitance. This study focuses on the construction and characterization of ultra-high surface area porous electrodes based on coating of nano-sized conductive polymer materials on nylon membrane templates. Herein, a novel nano-engineered electrode material based on nylon membranes was presented, which allows the creation of super-capacitor devices that is capable of delivering competitive performance, while maintaining desirable mechanical characteristics. With the formation of a highly conductive network with the polyaniline nano-layer, the electrical conductivity was also increased dramatically to facilitate the charge transfer process. Cyclic voltammetry and specific capacitance results showed promising application of this type of composite materials for future smart textile applications.

Enhanced thermoelectric performance in three-dimensional superlattice of topological insulator thin films

PubMed Central

2012-01-01

We show that certain three-dimensional (3D) superlattice nanostructure based on Bi2Te3 topological insulator thin films has better thermoelectric performance than two-dimensional (2D) thin films. The 3D superlattice shows a predicted peak value of ZT of approximately 6 for gapped surface states at room temperature and retains a high figure of merit ZT of approximately 2.5 for gapless surface states. In contrast, 2D thin films with gapless surface states show no advantage over bulk Bi2Te3. The enhancement of the thermoelectric performance originates from a combination of the reduction of lattice thermal conductivity by phonon-interface scattering, the high mobility of the topologically protected surface states, the enhancement of Seebeck coefficient, and the reduction of electron thermal conductivity by energy filtering. Our study shows that the nanostructure design of topological insulators provides a possible new way of ZT enhancement. PMID:23072433

Enhanced thermoelectric performance in three-dimensional superlattice of topological insulator thin films.

PubMed

Fan, Zheyong; Zheng, Jiansen; Wang, Hui-Qiong; Zheng, Jin-Cheng

2012-10-16

We show that certain three-dimensional (3D) superlattice nanostructure based on Bi2Te3 topological insulator thin films has better thermoelectric performance than two-dimensional (2D) thin films. The 3D superlattice shows a predicted peak value of ZT of approximately 6 for gapped surface states at room temperature and retains a high figure of merit ZT of approximately 2.5 for gapless surface states. In contrast, 2D thin films with gapless surface states show no advantage over bulk Bi2Te3. The enhancement of the thermoelectric performance originates from a combination of the reduction of lattice thermal conductivity by phonon-interface scattering, the high mobility of the topologically protected surface states, the enhancement of Seebeck coefficient, and the reduction of electron thermal conductivity by energy filtering. Our study shows that the nanostructure design of topological insulators provides a possible new way of ZT enhancement.

A general strategy for hybrid thin film fabrication and transfer onto arbitrary substrates.

PubMed

Zhang, Yong; Magan, John J; Blau, Werner J

2014-04-28

The development of thin film-based structures/devices often requires thin films to be transferred onto arbitrary substrates/surfaces. Controllable and non-destructive transfer method, although highly desired, remains quite challenging. Here we report a general method for fabrication and transfer of hybrid (ultra)thin films. The proposed solution-based in-situ transfer method shows not only its robust ability for thin film transfer onto arbitrary substrates but also its highly controlled and non-destructive characteristic. With a hole structure as the support, fully-stretched free-standing thin film is prepared. The successful transfer to a curved surface demonstrates the possibility for production of thin film-coated complex optical components. Ultrathin (35 nm) hybrid film transferred onto PET (50 μm thick) shows high transparency (>90% in visible range), conductivity (1.54 × 10(4) S/m), and flexibility (radius of curvature down to mm scale). The reported transfer method would provide a powerful route towards complex thin film-based structures/devices.

A General Strategy for Hybrid Thin Film Fabrication and Transfer onto Arbitrary Substrates

PubMed Central

Zhang, Yong; Magan, John J.; Blau, Werner J.

2014-01-01

The development of thin film-based structures/devices often requires thin films to be transferred onto arbitrary substrates/surfaces. Controllable and non-destructive transfer method, although highly desired, remains quite challenging. Here we report a general method for fabrication and transfer of hybrid (ultra)thin films. The proposed solution-based in-situ transfer method shows not only its robust ability for thin film transfer onto arbitrary substrates but also its highly controlled and non-destructive characteristic. With a hole structure as the support, fully-stretched free-standing thin film is prepared. The successful transfer to a curved surface demonstrates the possibility for production of thin film-coated complex optical components. Ultrathin (35 nm) hybrid film transferred onto PET (50 μm thick) shows high transparency (>90% in visible range), conductivity (1.54 × 104 S/m), and flexibility (radius of curvature down to mm scale). The reported transfer method would provide a powerful route towards complex thin film-based structures/devices. PMID:24769689

Electrolyte and Electrode Passivation for Thin Film Batteries

NASA Technical Reports Server (NTRS)

West, W.; Whitacre, J.; Ratnakumar, B.; Brandon, E.; Blosiu, J.; Surampudi, S.

2000-01-01

Passivation films for thin film batteries have been prepared and the conductivity and voltage stability window have been measured. Thin films of Li2CO3 have a large voltage stability window of 4.8V, which facilitates the use of this film as a passivation at both the lithium anode-electrolyte interface at high cathodic potentials.

Dielectric Studies on Thermally Evaporated CEF3 Thin Film

NASA Astrophysics Data System (ADS)

Selvasekarapandian, S.; Gowtham, M.; Bhuvaneswari, M. S.

In recent years rare earth compounds especially their fluorides have drawn particular attention as electrochemical gas sensors. Lanthanum and cerium fluoride based sensors have been investigated for sensing the fluorine, oxygen, and carbon monoxide because of their high chemical stability and high ionic conductivity. The fast response and good sensitivity of these sensors rely on the ion conduction properties of these thin films. In the present work Cerium Fluoride thin film has been prepared by vacuum thermal evaporation method. The electrical characterization is carried out using the Impedance spectroscopy method in the frequency range of 50 Hz to 5 MHz. The temperature dependence of ionic conductivity obeys the Arrhenius behavior and the activation energy Ea is found to be 0.3eV. The modulus and the dielectric spectra analysis reveal the non - Debye nature and the distribution of relaxation time due to the presence of grain and grain boundaries in the film. The relaxation energy Ed has been calculated from the dielectric spectra. The similar value of activation and relaxation energies suggests that the charge carriers that are responsible for bulk conductivity and relaxation process are the same. The optical measurement done in the wavelength range of 400-2500 nm confirms that the CeF3 thin film is highly transparent and the band gap energy is found to be 3.5 eV.

Structure Evolution and Thermoelectric Properties of Carbonized Polydopamine Thin Films.

PubMed

Li, Haoqi; Aulin, Yaroslav V; Frazer, Laszlo; Borguet, Eric; Kakodkar, Rohit; Feser, Joseph; Chen, Yan; An, Ke; Dikin, Dmitriy A; Ren, Fei

2017-03-01

Carbonization of nature-inspired polydopamine can yield thin films with high electrical conductivity. Understanding of the structure of carbonized PDA (cPDA) is therefore highly desired. In this study, neutron diffraction, Raman spectroscopy, and other techniques indicate that cPDA samples are mainly amorphous with some short-range ordering and graphite-like structure that emerges with increasing heat treatment temperature. The electrical conductivity and the Seebeck coefficient show different trends with heat treatment temperature, while the thermal conductivity remains insensitive. The largest room-temperature ZT of 2 × 10 -4 was obtained on samples heat-treated at 800 °C, which is higher than that of reduced graphene oxide.

Ultra-smooth glassy graphene thin films for flexible transparent circuits

PubMed Central

Dai, Xiao; Wu, Jiang; Qian, Zhicheng; Wang, Haiyan; Jian, Jie; Cao, Yingjie; Rummeli, Mark H.; Yi, Qinghua; Liu, Huiyun; Zou, Guifu

2016-01-01

Large-area graphene thin films are prized in flexible and transparent devices. We report on a type of glassy graphene that is in an intermediate state between glassy carbon and graphene and that has high crystallinity but curly lattice planes. A polymer-assisted approach is introduced to grow an ultra-smooth (roughness, <0.7 nm) glassy graphene thin film at the inch scale. Owing to the advantages inherited by the glassy graphene thin film from graphene and glassy carbon, the glassy graphene thin film exhibits conductivity, transparency, and flexibility comparable to those of graphene, as well as glassy carbon–like mechanical and chemical stability. Moreover, glassy graphene–based circuits are fabricated using a laser direct writing approach. The circuits are transferred to flexible substrates and are shown to perform reliably. The glassy graphene thin film should stimulate the application of flexible transparent conductive materials in integrated circuits. PMID:28138535

Control of conduction type in ferromagnetic (Zn,Sn,Mn)As2 thin films by changing Mn content and effect of annealing on thin films with n-type conduction

NASA Astrophysics Data System (ADS)

Minamizawa, Yuto; Kitazawa, Tomohiro; Hidaka, Shiro; Toyota, Hideyuki; Nakamura, Shin-ichi; Uchitomi, Naotaka

2018-04-01

The conduction type in (Zn,Sn,Mn)As2 thin films grown by molecular beam epitaxy (MBE) on InP substrates was found to be controllable from p-type to n-type as a function of Mn content. n-type (Zn,Sn,Mn)As2 thin films were obtained by Mn doping of more than approximately 11 cat.%. It is likely that Mn interstitials (MnI) incorporated by excess Mn doping are located at tetrahedral hollow spaces surrounded by Zn and Sn cation atoms and four As atoms, which are expected to act as donors in (Zn,Sn,Mn)As2, resulting in n-type conduction. The effect of annealing on the structural, electrical and magnetic properties of n-type (Zn,Sn,Mn)As2 thin films was investigated as functions of annealing temperature and time. It was revealed that even if the annealing temperature is considerably higher than the growth temperature of 320 °C, the magnetic properties of the thin films remain stable. This suggests that a MnI complex surrounded by Zn and Sn atoms is thermally stable during high-temperature annealing. The n-type (Zn,Sn,Mn)As2 thin films may be suitable for application as n-type spin-polarized injectors.

Effect of Gallium Substitution on Lithium-Ion Conductivity and Phase Evolution in Sputtered Li7-3 xGa xLa3Zr2O12 Thin Films.

PubMed

Rawlence, M; Filippin, A N; Wäckerlin, A; Lin, T-Y; Cuervo-Reyes, E; Remhof, A; Battaglia, C; Rupp, J L M; Buecheler, S

2018-04-25

Replacing the liquid electrolyte in conventional lithium-ion batteries with thin-film solid-state lithium-ion conductors is a promising approach for increasing energy density, lifetime, and safety. In particular, Li 7 La 3 Zr 2 O 12 is appealing due to its high lithium-ion conductivity and wide electrochemical stability window. Further insights into thin-film processing of this material are required for its successful integration into solid-state batteries. In this work, we investigate the phase evolution of Li 7-3 x Ga x La 3 Zr 2 O 12 in thin films with various amounts of Li and Ga for stabilizing the cubic phase. Through this work, we gain valuable insights into the crystallization processes unique to thin films and are able to form dense Li 7-3 x Ga x La 3 Zr 2 O 12 layers stabilized in the cubic phase with high in-plane lithium-ion conductivities of up to 1.6 × 10 -5 S cm -1 at 30 °C. We also note the formation of cubic Li 7 La 3 Zr 2 O 12 at the relatively low temperature of 500 °C.

An instrument for spatial conductivity measurements of high Tc superconducting (HTSC) materials

NASA Technical Reports Server (NTRS)

Vansant, T.

1991-01-01

High T(sub c) Superconducting (HTSC) thin films are suggested for use in a number of aerospace applications such as an IR bolometer and as electromagnetic shielding. As part of its flight assurance role, the Materials Branch of the Goddard Space Flight Center has initiated development of an instrument capable of measuring variations in conductivity for flat samples using an eddy current testing device and an X-Y positioning table. This instrument was used to examine bulk HTSC samples. System changes that would enable characterization of thin film materials are discussed.

Design of low surface roughness-low residual stress-high optoelectronic merit a-IZO thin films for flexible OLEDs

DOE PAGES

Kumar, Naveen; Wilkinson, Taylor M.; Packard, Corinne E.; ...

2016-06-08

The development of efficient and reliable large-area flexible optoelectronic devices demands low surface roughness-low residual stress-high optoelectronic merit transparent conducting oxide (TCO) thin films. Here, we correlate surface roughness-residual stress-optoelectronic properties of sputtered amorphous indium zinc oxide (a-IZO) thin films using a statistical design of experiment (DOE) approach and find a common growth space to achieve a smooth surface in a stress-free and high optoelectronic merit a-IZO thin film. The sputtering power, growth pressure, oxygen partial pressure, and RF/(RF+DC) are varied in a two-level system with a full factorial design, and results are used to deconvolve the complex growth space,more » identifying significant control growth parameters and their possible interactions. The surface roughness of a-IZO thin film varies over 0.19 nm to 3.97 nm, which is not in line with the general assumption of low surface roughness in a-IZO thin films. The initial regression model and analysis of variance reveal no single optimum growth sub-space to achieve low surface roughness (=0.5 nm), low residual stress (-1 to 0 GPa), and industrially acceptable electrical conductivity (>1000 S/cm) for a-IZO thin films. The extrapolation of growth parameters in light of the current results and previous knowledge leads to a new sub-space, resulting in a low residual stress of -0.52 +/- 0.04 GPa, a low surface roughness of 0.55 +/- 0.03 nm, and moderate electrical conductivity of 1962 +/- 3.84 S/cm in a-IZO thin films. Lastly, these results demonstrate the utility of the DOE approach to multi-parameter optimization, which provides an important tool for the development of flexible TCOs for the next-generation flexible organic light emitting diodes applications.« less

Design of low surface roughness-low residual stress-high optoelectronic merit a-IZO thin films for flexible OLEDs

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

Kumar, Naveen; Kumar, Mukesh, E-mail: mkumar@iitrpr.ac.in, E-mail: cpackard@mines.edu; Wilkinson, Taylor M.

2016-06-14

The development of efficient and reliable large-area flexible optoelectronic devices demands low surface roughness-low residual stress-high optoelectronic merit transparent conducting oxide (TCO) thin films. Here, we correlate surface roughness-residual stress-optoelectronic properties of sputtered amorphous indium zinc oxide (a-IZO) thin films using a statistical design of experiment (DOE) approach and find a common growth space to achieve a smooth surface in a stress-free and high optoelectronic merit a-IZO thin film. The sputtering power, growth pressure, oxygen partial pressure, and RF/(RF+DC) are varied in a two-level system with a full factorial design, and results are used to deconvolve the complex growth space,more » identifying significant control growth parameters and their possible interactions. The surface roughness of a-IZO thin film varies over 0.19 nm to 3.97 nm, which is not in line with the general assumption of low surface roughness in a-IZO thin films. The initial regression model and analysis of variance reveal no single optimum growth sub-space to achieve low surface roughness (≤0.5 nm), low residual stress (−1 to 0 GPa), and industrially acceptable electrical conductivity (>1000 S/cm) for a-IZO thin films. The extrapolation of growth parameters in light of the current results and previous knowledge leads to a new sub-space, resulting in a low residual stress of −0.52±0.04 GPa, a low surface roughness of 0.55±0.03 nm, and moderate electrical conductivity of 1962±3.84 S/cm in a-IZO thin films. These results demonstrate the utility of the DOE approach to multi-parameter optimization, which provides an important tool for the development of flexible TCOs for the next-generation flexible organic light emitting diodes applications.« less

Reduced temperature-dependent thermal conductivity of magnetite thin films by controlling film thickness

PubMed Central

2014-01-01

We report on the out-of-plane thermal conductivities of epitaxial Fe3O4 thin films with thicknesses of 100, 300, and 400 nm, prepared using pulsed laser deposition (PLD) on SiO2/Si substrates. The four-point probe three-omega (3-ω) method was used for thermal conductivity measurements of the Fe3O4 thin films in the temperature range of 20 to 300 K. By measuring the temperature-dependent thermal characteristics of the Fe3O4 thin films, we realized that their thermal conductivities significantly decreased with decreasing grain size and thickness of the films. The out-of-plane thermal conductivities of the Fe3O4 films were found to be in the range of 0.52 to 3.51 W/m · K at 300 K. For 100-nm film, we found that the thermal conductivity was as low as approximately 0.52 W/m · K, which was 1.7 to 11.5 order of magnitude lower than the thermal conductivity of bulk material at 300 K. Furthermore, we calculated the temperature dependence of the thermal conductivity of these Fe3O4 films using a simple theoretical Callaway model for comparison with the experimental data. We found that the Callaway model predictions agree reasonably with the experimental data. We then noticed that the thin film-based oxide materials could be efficient thermoelectric materials to achieve high performance in thermoelectric devices. PMID:24571956

Characterization of a high performance ultra-thin heat pipe cooling module for mobile hand held electronic devices

NASA Astrophysics Data System (ADS)

Ahamed, Mohammad Shahed; Saito, Yuji; Mashiko, Koichi; Mochizuki, Masataka

2017-11-01

In recent years, heat pipes have been widely used in various hand held mobile electronic devices such as smart phones, tablet PCs, digital cameras. With the development of technology these devices have different user friendly features and applications; which require very high clock speeds of the processor. In general, a high clock speed generates a lot of heat, which needs to be spreaded or removed to eliminate the hot spot on the processor surface. However, it is a challenging task to achieve proper cooling of such electronic devices mentioned above because of their confined spaces and concentrated heat sources. Regarding this challenge, we introduced an ultra-thin heat pipe; this heat pipe consists of a special fiber wick structure named as "Center Fiber Wick" which can provide sufficient vapor space on the both sides of the wick structure. We also developed a cooling module that uses this kind of ultra-thin heat pipe to eliminate the hot spot issue. This cooling module consists of an ultra-thin heat pipe and a metal plate. By changing the width, the flattened thickness and the effective length of the ultra-thin heat pipe, several experiments have been conducted to characterize the thermal properties of the developed cooling module. In addition, other experiments were also conducted to determine the effects of changes in the number of heat pipes in a single module. Characterization and comparison of the module have also been conducted both experimentally and theoretically.

Highly stretchable and conductive silver nanowire thin films formed by soldering nanomesh junctions.

PubMed

Chen, Shih-Pin; Liao, Ying-Chih

2014-10-07

Silver nanowires (AgNWs) have been widely used for stretchable and foldable conductors due to their percolating network nanostructure. To enhance the mechanical strength of AgNW thin films under extreme stretching conditions, in this study, we utilize a simple chemical reaction to join AgNW network connections. Upon applying a reactive ink over AgNW thin films, silver nanoparticles are preferentially generated over the nanowire junctions and solder the nanomesh structures. The soldered nanostructure reinforces the conducting network and exhibits no obvious change in electrical conductivity in the stretching or rolling process with elongation strains up to 120%. Several examples are also demonstrated to show potential applications of this material in stretchable electronic devices.

Applications of thin carbon coatings and films in injection molding

NASA Astrophysics Data System (ADS)

Cabrera, Eusebio Duarte

In this research, the technical feasibility of two novel applications of thin carbon coatings is demonstrated. The first application consists of using thin carbon coatings on molds for molding ultra-thin plastic parts (<0.5 mm thickness) with lower pressures by promoting wall slip. The second application consists of a new approach to provide electromagnetic interference (EMI) shielding for plastic parts using in mold coated nanoparticle thin films or nanopapers to create a conductive top layer. During this research, the technical feasibility of a new approach was proven which provides injection molding of ultra-thin parts at lower pressures, without the need of fast heating/fast cooling or other expensive mold modification. An in-house developed procedure by other members of our group, was employed for coating the mold surface using chemical vapor deposition (CVD) resulting in a graphene coating with carbide bonding to the mold surface. The coating resulted in a significant decrease of surface friction and consequently easiness of flow when compared to their uncoated counterparts. Thermoplastic polymers and their composites are a very attractive alternative but are hindered by the non-conductive nature of polymers. There are two general approaches used to date to achieve EMI shielding for plastic products. One is to spray a conductive metal coating onto the plastic surface forming a layer that must maintain its shielding effectiveness (SE), and its adhesion to the plastic throughout the expected life of the product. However, metal coatings add undesirable weight and tend to corrode over time. Furthermore, scratching the coating may create shielding failure; therefore, a protective topcoat may be required. The other approach is to use polymer composites filled with conductive fillers such as carbon black (CB), carbon nanofiber (CNF), and carbon nanotube (CNT). While conductive fillers may increase the electrical conductivity of polymer composites, the loading of such fillers often cannot reach a high level (<10 wt. %) due to the dispersion difficulty and exponential increase in viscosity. In this research, the technical feasibility of a new approach to EMI shielding of plastic parts was proven using in mold coated nanoparticle thin films or nanopapers to create a conductive top layer. For many years, in-mold coating (IMC) has been commercially applied to Sheet Molding Compound (SMC) compression molded parts, as an environmentally friendly approach to improve its surface quality and provide the required conductivity for electrostatic painting using carbon black (CB). Such process can also be applied to injection molding for creating a top conductive layer. Increasing the amount of CB will increase the surface conductivity of the coated part, thus improving the paint transfer efficiency. However the CB levels needed to achieve the conductivity levels required for achieving EMI shielding would make the coating viscosity too large for proper coating. Nanopaper based composites are excellent candidates for EMI shielding because of the nanopaper's high concentration of carbon nanofibers (CNFs) (~2 wt% to 10 wt% depending on nanopaper/thermoplastic thickness and 71wt.% to 79wt.% in the nanopaper itself after resin infusion) and high conductivity of the nanopaper. Instead of premixing nanoparticles with IMC coating, nanopapers enable the use of low viscosity IMC without CB coating to impregnate the CNF network in order to reach high electrical conductivity and EMI shielding values. (Abstract shortened by UMI.).

Structure evolution and thermoelectric properties of carbonized polydopamine thin films

DOE PAGES

Li, Haoqi; Aulin, Yaroslav V.; Frazer, Laszlo; ...

2017-02-13

Carbonization of nature-inspired polydopamine can yield thin films with high electrical conductivity. Understanding of the structure of carbonized PDA (cPDA) is therefore highly desired. In this study, neutron diffraction, Raman spectroscopy, and other techniques indicate that cPDA samples are mainly amorphous with some short-range ordering and graphite-like structure that emerges with increasing heat treatment temperature. The electrical conductivity and the Seebeck coefficient show different trends with heat treatment temperature, while the thermal conductivity remains insensitive. Finally, the largest room-temperature ZT of 2 × 10 –4 was obtained on samples heat-treated at 800 °C, which is higher than that of reducedmore » graphene oxide.« less

Low-Temperature Postfunctionalization of Highly Conductive Oxide Thin-Films toward Solution-Based Large-Scale Electronics.

PubMed

Ban, Seok-Gyu; Kim, Kyung-Tae; Choi, Byung Doo; Jo, Jeong-Wan; Kim, Yong-Hoon; Facchetti, Antonio; Kim, Myung-Gil; Park, Sung Kyu

2017-08-09

Although transparent conducting oxides (TCOs) have played a key role in a wide range of solid-state electronics from conventional optoelectronics to emerging electronic systems, the processing temperature and conductivity of solution-processed materials seem to be far exceeding the thermal limitations of soft materials and insufficient for high-perfomance large-area systems, respectively. Here, we report a strategy to form highly conductive and scalable solution-processed oxide materials and their successful translation into large-area electronic applications, which is enabled by photoassisted postfunctionalization at low temperature. The low-temperature fabrication of indium-tin-oxide (ITO) thin films was achieved by using photoignited combustion synthesis combined with photoassisted reduction process under hydrogen atmosphere. It was noteworthy that the photochemically activated hydrogens on ITO surface could be triggered to facilitate highly crystalline oxygen deficient structure allowing significant increase of carrier concentration and mobility through film microstructure modifications. The low-temperature postfunctionalized ITO films demonstrated conductivity of >1607 S/cm and sheet resistance of <104 Ω/□ under the process temperature of less than 300 °C, which are comparable to those of vacuum-deposited and high-temperature annealed ITO films. Based on the photoassisted postfunctionalization route, all-solution-processed transparent metal-oxide thin-film-transistors and large-area integrated circuits with the ITO bus lines were demonstrated, showing field-effect mobilities of >6.5 cm 2 V -1 s -1 with relatively good operational stability and oscillation frequency of more than 1 MHz in 7-stage ring oscillators, respectively.

Resistive switching phenomena of tungsten nitride thin films with excellent CMOS compatibility

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

Hong, Seok Man; Kim, Hee-Dong; An, Ho-Myoung

2013-12-15

Graphical abstract: - Highlights: • The resistive switching characteristics of WN{sub x} thin films. • Excellent CMOS compatibility WN{sub x} films as a resistive switching material. • Resistive switching mechanism revealed trap-controlled space charge limited conduction. • Good endurance and retention properties over 10{sup 5} cycles, and 10{sup 5} s, respectively - Abstract: We report the resistive switching (RS) characteristics of tungsten nitride (WN{sub x}) thin films with excellent complementary metal-oxide-semiconductor (CMOS) compatibility. A Ti/WN{sub x}/Pt memory cell clearly shows bipolar RS behaviors at a low voltage of approximately ±2.2 V. The dominant conduction mechanisms at low and high resistancemore » states were verified by Ohmic behavior and trap-controlled space-charge-limited conduction, respectively. A conducting filament model by a redox reaction explains the RS behavior in WN{sub x} films. We also demonstrate the memory characteristics during pulse operation, including a high endurance over >10{sup 5} cycles and a long retention time of >10{sup 5} s.« less

Structurally-driven Enhancement of Thermoelectric Properties within Poly(3,4-ethylenedioxythiophene) thin Films

PubMed Central

Petsagkourakis, Ioannis; Pavlopoulou, Eleni; Portale, Giuseppe; Kuropatwa, Bryan A.; Dilhaire, Stefan; Fleury, Guillaume; Hadziioannou, Georges

2016-01-01

Due to the rising need for clean energy, thermoelectricity has raised as a potential alternative to reduce dependence on fossil fuels. Specifically, thermoelectric devices based on polymers could offer an efficient path for near-room temperature energy harvesters. Thus, control over thermoelectric properties of conducting polymers is crucial and, herein, the structural, electrical and thermoelectric properties of poly(3,4-ethylenedioxythiophene) (PEDOT) thin films doped with p-toluenesulfonate (Tos) molecules were investigated with regards to thin film processing. PEDOT:Tos thin films were prepared by in-situ polymerization of (3,4-ethylenedioxythiophene) monomers in presence of iron(III) p-toluenesulfonate with different co-solvents in order to tune the film structure. While the Seebeck coefficient remained constant, a large improvement in the electrical conductivity was observed for thin films processed with high boiling point additives. The increase of electrical conductivity was found to be solely in-plane mobility-driven. Probing the thin film structure by Grazing Incidence Wide Angle X-ray Scattering has shown that this behavior is dictated by the structural properties of the PEDOT:Tos films; specifically by the thin film crystallinity combined to the preferential edge-on orientation of the PEDOT crystallites. Consequentially enhancement of the power factor from 25 to 78.5 μW/mK2 has been readily obtained for PEDOT:Tos thin films following this methodology. PMID:27470637

Structurally-driven Enhancement of Thermoelectric Properties within Poly(3,4-ethylenedioxythiophene) thin Films.

PubMed

Petsagkourakis, Ioannis; Pavlopoulou, Eleni; Portale, Giuseppe; Kuropatwa, Bryan A; Dilhaire, Stefan; Fleury, Guillaume; Hadziioannou, Georges

2016-07-29

Due to the rising need for clean energy, thermoelectricity has raised as a potential alternative to reduce dependence on fossil fuels. Specifically, thermoelectric devices based on polymers could offer an efficient path for near-room temperature energy harvesters. Thus, control over thermoelectric properties of conducting polymers is crucial and, herein, the structural, electrical and thermoelectric properties of poly(3,4-ethylenedioxythiophene) (PEDOT) thin films doped with p-toluenesulfonate (Tos) molecules were investigated with regards to thin film processing. Tos thin films were prepared by in-situ polymerization of (3,4-ethylenedioxythiophene) monomers in presence of iron(III) p-toluenesulfonate with different co-solvents in order to tune the film structure. While the Seebeck coefficient remained constant, a large improvement in the electrical conductivity was observed for thin films processed with high boiling point additives. The increase of electrical conductivity was found to be solely in-plane mobility-driven. Probing the thin film structure by Grazing Incidence Wide Angle X-ray Scattering has shown that this behavior is dictated by the structural properties of the Tos films; specifically by the thin film crystallinity combined to the preferential edge-on orientation of the PEDOT crystallites. Consequentially enhancement of the power factor from 25 to 78.5 μW/mK(2) has been readily obtained for Tos thin films following this methodology.

Composite Material Switches

NASA Technical Reports Server (NTRS)

Javadi, Hamid (Inventor)

2001-01-01

A device to protect electronic circuitry from high voltage transients is constructed from a relatively thin piece of conductive composite sandwiched between two conductors so that conduction is through the thickness of the composite piece. The device is based on the discovery that conduction through conductive composite materials in this configuration switches to a high resistance mode when exposed to voltages above a threshold voltage.

Composite Material Switches

NASA Technical Reports Server (NTRS)

Javadi, Hamid (Inventor)

2002-01-01

A device to protect electronic circuitry from high voltage transients is constructed from a relatively thin piece of conductive composite sandwiched between two conductors so that conduction is through the thickness of the composite piece. The device is based on the discovery that conduction through conductive composite materials in this configuration switches to a high resistance mode when exposed to voltages above a threshold voltage.

Enhanced bipolar resistive switching behavior in polar Cr-doped barium titanate thin films without electro-forming process

NASA Astrophysics Data System (ADS)

Thakre, Atul; Kumar, Ashok

2017-12-01

An enhanced, repeatable and robust resistive switching phenomenon was observed in Cr substituted BaTiO3 polar ferroelectric thin films; fabricated and deposited by the sol-gel approach and spin coating technique, respectively. An enhanced bistable bipolar resistive switching (BRS) phenomenon without electro-forming process, low switching voltage (˜ 2 V) and moderate retention characteristics of 104 s along with a high Roff/Ron resistance ratio ˜103 was achieved. The current conduction analysis showed that the space charge limited conduction (SCLC) and Schottky emission conduction dominate in the high voltage range, while thermally active charge carriers (ohmic) in the lower voltage range. The impedance spectroscopy study indicates the formation of current conducting path and rupturing of oxygen vacancies during SET and RESET process.

Stretchable transistors with buckled carbon nanotube films as conducting channels

DOEpatents

Arnold, Michael S; Xu, Feng

2015-03-24

Thin-film transistors comprising buckled films comprising carbon nanotubes as the conductive channel are provided. Also provided are methods of fabricating the transistors. The transistors, which are highly stretchable and bendable, exhibit stable performance even when operated under high tensile strains.

Flexible Polymer/Metal/Polymer and Polymer/Metal/Inorganic Trilayer Transparent Conducting Thin Film Heaters with Highly Hydrophobic Surface.

PubMed

Kang, Tae-Woon; Kim, Sung Hyun; Kim, Cheol Hwan; Lee, Sang-Mok; Kim, Han-Ki; Park, Jae Seong; Lee, Jae Heung; Yang, Yong Suk; Lee, Sang-Jin

2017-09-27

Polymer/metal/polymer and polymer/metal/inorganic trilayer-structured transparent electrodes with fluorocarbon plasma polymer thin film heaters have been proposed. The polymer/metal/polymer and polymer/metal/inorganic transparent conducting thin films fabricated on a large-area flexible polymer substrate using a continuous roll-to-roll sputtering process show excellent electrical properties and visible-light transmittance. They also exhibit water-repelling surfaces to prevent wetting and to remove contamination. In addition, the adoption of a fluorocarbon/metal/fluorocarbon film permits an outer bending radius as small as 3 mm. These films have a sheet resistance of less than 5 Ω sq -1 , sufficient to drive light-emitting diode circuits. The thin film heater with the fluorocarbon/Ag/SiN x structure exhibits excellent heating characteristics, with a temperature reaching 180 °C under the driving voltage of 13 V. Therefore, the proposed polymer/metal/polymer and polymer/metal/inorganic transparent conducting electrodes using polymer thin films can be applied in flexible and rollable displays as well as automobile window heaters and other devices.

Deposition and thermal characterization of nano-structured aluminum nitride thin film on Cu-W substrate for high power light emitting diode package.

PubMed

Cho, Hyun Min; Kim, Min-Sun

2014-08-01

In this study, we developed AlN thick film on metal substrate for hybrid type LED package such as chip on board (COB) using metal printed circuit board (PCB). Conventional metal PCB uses ceramic-polymer composite as electrical insulating layer. Thermal conductivities of such type dielectric film are typically in the range of 1~4 W/m · K depending on the ceramic filler. Also, Al or Cu alloy are mainly used for metal base for high thermal conduction to dissipate heat from thermal source mounted on metal PCB. Here we used Cu-W alloy with low thermal expansion coefficient as metal substrate to reduce thermal stress between insulating layer and base metal. AlN with polyimide (PI) powder were used as starting materials for deposition. We could obtain very high thermal conductivity of 28.3 W/m · K from deposited AlN-PI thin film by AlN-3 wt% PI powder. We made hybrid type high power LED package using AlN-PI thin film. We tested thermal performance of this film by thermal transient measurement and compared with conventional metal PCB substrate.

Method of synthesizing polymers from a solid electrolyte

DOEpatents

Skotheim, Terje A.

1985-01-01

A method of synthesizing electrically conductive polymers from a solvent-free solid polymer electrolyte wherein an assembly of a substrate having an electrode thereon, a thin coating of solid electrolyte including a solution of PEO complexed with an alkali salt, and a thin transparent noble metal electrode are disposed in an evacuated chamber into which a selected monomer vapor is introduced while an electric potential is applied across the solid electrolyte to hold the thin transparent electrode at a positive potential relative to the electrode on the substrate, whereby a highly conductive polymer film is grown on the transparent electrode between it and the solid electrolyte.

Method of synthesizing polymers from a solid electrolyte

DOEpatents

Skotheim, T.A.

1984-10-19

A method of synthesizing electrically conductive polymers from a solvent-free solid polymer electrolyte is disclosed. An assembly of a substrate having an electrode thereon, a thin coating of solid electrolyte including a solution of PEO complexed with an alkali salt, and a thin transparent noble metal electrode are disposed in an evacuated chamber into which a selected monomer vapor is introduced while an electric potential is applied across the solid electrolyte to hold the thin transparent electrode at a positive potential relative to the electrode on the substrate, whereby a highly conductive polymer film is grown on the transparent electrode between it and the solid electrolyte.

Influence of stress on the structural and dielectric properties of rf magnetron sputtered zinc oxide thin film

NASA Astrophysics Data System (ADS)

Menon, Rashmi; Sreenivas, K.; Gupta, Vinay

2008-05-01

Highly c axis oriented zinc oxide (ZnO) thin films have been prepared on 1737 Corning glass substrate by planar rf magnetron sputtering under varying pressure (10-50mTorr) and different oxygen percentage (40%-100%) in reactive gas mixtures. The as-grown ZnO thin films were found to have stress over a wide range from -6×1010to-9×107dynes/cm2. The presence of stress depends strongly on processing conditions, and films become almost stress free under a unique combination of sputtering pressure and reactive gas composition. The studies show a correlation of stress with structural and electrical properties of the ZnO thin film. The stressed films possess high electrical conductivity and exhibits strong dielectric dispersion over a wide frequency (1kHz-1MHz). The dielectric constant ɛ'(ω) of stress free ZnO film was almost frequency independent and was close to the bulk value. The measured value of dc conductivity, σdc(ω) and ac conductivity σac(ω) of stress free ZnO film was 1.3×10-9 and 6.8×10-5Ω-1cm-1, respectively. The observed variation in the structural and electrical properties of ZnO thin film with stress has been analyzed in the light of growth kinetics.

Al-/Ga-Doped ZnO Window Layers for Highly Efficient Cu₂ZnSn(S,Se)₄ Thin Film Solar Cells.

PubMed

Seo, Se Won; Seo, Jung Woo; Kim, Donghwan; Cheon, Ki-Beom; Lee, Doh-Kwon; Kim, Jin Young

2018-09-01

The successful use of Al-/Ga-doped ZnO (AGZO) thin films as a transparent conducting oxide (TCO) layer of a Cu2ZnSn(S,Se)4 (CZTSSe) thin film solar cell is demonstrated. The AGZO thin films were prepared by radio frequency (RF) sputtering. The structural, crystallographic, electrical, and optical properties of the AGZO thin films were systematically investigated. The photovoltaic properties of CZTSSe thin film solar cells incorporating the AGZO-based TCO layer were also reported. It has been found that the RF power and substrate temperature of the AGZO thin film are important factors determining the electrical, optical, and structural properties. The optimization process involving the RF power and the substrate temperature leads to good electrical and optical transmittance of the AGZO thin films. Finally, the CZTSSe solar cell with the AGZO TCO layer demonstrated a high conversion efficiency of 9.68%, which is higher than that of the conventional AZO counterpart by 12%.

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.

Thin film polymeric gel electrolytes

DOEpatents

Derzon, Dora K.; Arnold, Jr., Charles; Delnick, Frank M.

1996-01-01

Novel hybrid thin film electrolyte, based on an organonitrile solvent system, which are compositionally stable, environmentally safe, can be produced efficiently in large quantity and which, because of their high conductivities .apprxeq.10.sup.-3 .OMEGA..sup.-1 cm.sup.-1 are useful as electrolytes for rechargeable lithium batteries.

Chemical Vapor Deposition for Ultra-lightweight Thin-film Solar Arrays for Space

NASA Technical Reports Server (NTRS)

Hepp, Aloysius F.; Raffaelle, Ryne P.; Banger, Kulbinder K.; Jin, Michael H.; Lau, Janice E.; Harris, Jerry D.; Cowen, Jonathan E.; Duraj, Stan A.

2002-01-01

The development of thin-film solar cells on flexible, lightweight, space-qualified substrates provides an attractive cost solution to fabricating solar arrays with high specific power, (W/kg). The use of a polycrystalline chalcopyrite absorber layer for thin film solar cells is considered as the next generation photovoltaic devices. A key technical issues outlined in the 2001 U.S. Photovoltaic Roadmap, is the need to develop low cost, high throughput manufacturing for high-efficiency thin film solar cells. At NASA GRC we have focused on the development of new single-source-precursors (SSPs) and their utility to deposit the chalcopyrite semi-conducting layer (CIS) onto flexible substrates for solar cell fabrication. The syntheses and thermal modulation of SSPs via molecular engineering is described. Thin-film fabrication studies demonstrate the SSPs can be used in a spray CVD process, for depositing CIS at reduced temperatures, which display good electrical properties, suitable for PV devices.

Using sputter coated glass to stabilize microstrip gas chambers

DOEpatents

Gong, Wen G.

1997-01-01

By sputter coating a thin-layer of low-resistive, electronically-conductive glass on various substrates (including quartz and ceramics, thin-film Pestov glass), microstrip gas chambers (MSGC) of high gain stability, low leakage current, and a high rate capability can be fabricated. This design can make the choice of substrate less important, save the cost of ion-implantation, and use less glass material.

Interpretation of transport measurements in ZnO-thin films

NASA Astrophysics Data System (ADS)

Petukhov, Vladimir; Stoemenos, John; Rothman, Johan; Bakin, Andrey; Waag, Andreas

2011-01-01

In order to interpret results of temperature dependent Hall measurements in heteroepitaxial ZnO-thin films, we adopted a multilayer conductivity model considering carrier-transport through the interfacial layer with degenerate electron gas as well as the upper part of ZnO layers with lower conductivity. This model was applied to the temperature dependence of the carrier concentration and mobility measured by Hall effect in a ZnO-layer grown on c-sapphire with conventional high-temperature MgO and low-temperature ZnO buffer. We also compared our results with the results of maximum entropy mobility-spectrum analysis (MEMSA). The formation of the highly conductive interfacial layer was explained by analysis of transmission electron microscopy (TEM) images taken from similar layers.

Improving uniformity and nanostructure of solution-processed thin films using ultrasonic substrate vibration post treatment (SVPT).

PubMed

Wang, Qin; Eslamian, Morteza

2016-04-01

The main goal of this paper is to introduce a novel mechanical method herein terms as substrate vibration post treatment (SVPT) technique, powered by ultrasonic vibration imposed on the substrate to enhance the characteristics and functionality of spun-on thin films or thin films made by similar casting techniques, such as drop and dip coating. In this technique, the as-casted wet films are placed on a substrate vibrated by an ultrasonic transducer with controlled power and duration to improve the film characteristics, such as uniformity and nanostructure. The performance of this technique is examined on spun-on PSS thin films used in polymer and perovskite solar cells and unprecedented results are presented. We first explore the influence of the vibration duration time on the characteristics of the films made by pristine PSS solution, where it is found that the optimized vibration duration for the pristine PSS film is about 10s, resulting in significant increase in the film electrical conductivity and lowered thickness and roughness. In order to further test the generality and merit of the method, thin films made using PSS solution modified with various types of surfactants and cured by the SVPT are studied. The results show that the application of the SVPT method combined with surfactant modification leads to an impressive twelve-fold increase in the conductivity of the PSS thin films compared with that of the pristine non-vibrated PSS thin films. The sole effect of the SVPT is a four-fold increase in the conductivity of pristine PSS film compared with that of the non-vibrated film. This remarkable enhancement in conductivity is further explained by the AFM phase images of PSS films, showing that the ultrasonic energy could loosen the Coulomb forces between PEDOT and PSS chains, resulting in phase separation and localized reordering of the conducting PEDOT chains leading to an increase in the electrical conductivity of the film. Highly conductive PSS thin film is a viable candidate as electrodes in emerging solution-processed solar cells. Copyright © 2015 Elsevier B.V. All rights reserved.

A reversible bipolar WORM device based on AlOxNy thin film with Al nano phase embedded

NASA Astrophysics Data System (ADS)

Zhu, W.; Li, J.; Zhang, L.; Hu, X. C.

2017-03-01

An Al-rich AlOxNy thin film based reversible Write-Once-Read-Many-Times (WORM) memory device with MIS structure could transit from high resistance state (HRS, ∼1011 Ω) to low resistance state (LRS, ∼105 Ω) by sweeping voltage up to ∼20 V. The first switching could be recorded as writing process for WORM device which may relate to conductive path are formed through the thin film. The conductive path should be formed by both Al nano phase and oxygen vacancies. Among of them, Al nano phases are not easy to move, but oxygen vacancies could migrate under high E-field or at high temperature environment. Such conductive path is not sensitive to charging effect after it formed, but it could be broken by heating effect, which may relate to the migration of excess Al ions and oxygen vacancies at high temperature. After baking LRS (ON state) WORM device at 200 °C for 2 min, the conductivity will decrease to HRS which indicates conductive path is broken and device back to HRS (OFF state) again. This phenomenon could be recorded as recovery process. Both writing and recovery process related to migration of oxygen vacancies and could be repeated over 10 times in this study. It also indicates that there is no permanent breakdown occurred in MIS structured WORM device operation. We suggest that this conductive path only can be dissolved by a temperature sensitive electro-chemical action. This WORM device could maintain at LRS over 105 s with on-off ratio over 4 orders.

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

Thompson, J.; Nichols, John A.; Lee, Shinbuhm

Metal electrodes are a universal element of all electronic devices. Conducting SrRuO 3 (SRO) epitaxial thin films have been extensively used as electrodes in complex-oxide heterostructures due to good lattice mismatches with perovskite substrates. However, when compared to SRO single crystals, SRO thin films have shown reduced conductivity and Curie temperatures (T C), which can lead to higher Joule heating and energy loss in the devices. In this paper, we report that high-quality SRO thin films can be synthesized by controlling the plume dynamics and growth rate of pulsed laser epitaxy (PLE) with real-time optical spectroscopic monitoring. The SRO thinmore » films grown under the kinetically controlled conditions, down to ca. 16 nm in thickness, exhibit both enhanced conductivity and T C as compared to bulk values, due to their improved stoichiometry and a strain-mediated increase of the bandwidth of Ru 4d electrons. Finally, this result provides a direction for enhancing the physical properties of PLE-grown thin films and paves a way to improved device applications.« less

Influence of Thermal Annealing Treatment on Bipolar Switching Properties of Vanadium Oxide Thin-Film Resistance Random-Access Memory Devices

NASA Astrophysics Data System (ADS)

Chen, Kai-Huang; Cheng, Chien-Min; Kao, Ming-Cheng; Chang, Kuan-Chang; Chang, Ting-Chang; Tsai, Tsung-Ming; Wu, Sean; Su, Feng-Yi

2017-04-01

The bipolar switching properties and electrical conduction mechanism of vanadium oxide thin-film resistive random-access memory (RRAM) devices obtained using a rapid thermal annealing (RTA) process have been investigated in high-resistive status/low-resistive status (HRS/LRS) and are discussed herein. In addition, the resistance switching properties and quality improvement of the vanadium oxide thin-film RRAM devices were measured by x-ray diffraction (XRD) analysis, x-ray photoelectron spectrometry (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM), and current-voltage ( I- V) measurements. The activation energy of the hopping conduction mechanism in the devices was investigated based on Arrhenius plots in HRS and LRS. The hopping conduction distance and activation energy barrier were obtained as 12 nm and 45 meV, respectively. The thermal annealing process is recognized as a candidate method for fabrication of thin-film RRAM devices, being compatible with integrated circuit technology for nonvolatile memory devices.

Method of preparing thin film polymeric gel electrolytes

DOEpatents

Derzon, Dora K.; Arnold, Jr., Charles

1997-01-01

Novel hybrid thin film electrolyte, based on an organonitrile solvent system, which are compositionally stable, environmentally safe, can be produced efficiently in large quantity and which, because of their high conductivities .apprxeq.10.sup.-3 .OMEGA..sup.-1 cm.sup.-1 are useful as electrolytes for rechargeable lithium batteries.

Optoelectronic properties and Seebeck coefficient in SnSe thin films

NASA Astrophysics Data System (ADS)

Urmila, K. S.; Namitha, T. A.; Rajani, J.; Philip, R. R.; Pradeep, B.

2016-09-01

SnSe thin films of thickness 180 nm have been deposited on glass substrates by reactive evaporation at an optimized substrate temperature of 523 ± 5 K and pressure of 10-5 mbar. The as-prepared SnSe thin films are characterized for their structural, optical and electrical properties by various experimental techniques. The p-type conductivity, near-optimum direct band gap, high absorption coefficient and good photosensitivity of the SnSe thin film indicate its suitability for photovoltaic applications. The optical constants, loss factor, quality factor and optical conductivity of the films are evaluated. The results of Hall and thermoelectric power measurements are correlated to determine the density of states, Fermi energy and effective mass of carriers and are obtained as 2.8 × 1017 cm-3, 0.03 eV and 0.05m 0 respectively. The high Seebeck coefficient ≈ 7863 μV/K, reasonably good power factor ≈ 7.2 × 10-4 W/(m·K2) and thermoelectric figure of merit ≈ 1.2 observed at 42 K suggests that, on further work, the prepared SnSe thin films can also be considered as a possible candidate for cryogenic thermoelectric applications.

Novel p-Type Conductive Semiconductor Nanocrystalline Film as the Back Electrode for High-Performance Thin Film Solar Cells.

PubMed

Zhang, Ming-Jian; Lin, Qinxian; Yang, Xiaoyang; Mei, Zongwei; Liang, Jun; Lin, Yuan; Pan, Feng

2016-02-10

Thin film solar cells, due to the low cost, high efficiency, long-term stability, and consumer applications, have been widely applied for harvesting green energy. All of these thin film solar cells generally adopt various metal thin films as the back electrode, like Mo, Au, Ni, Ag, Al, graphite, and so forth. When they contact with p-type layer, it always produces a Schottky contact with a high contact potential barrier, which greatly affects the cell performance. In this work, we report for the first time to find an appropriate p-type conductive semiconductor film, digenite Cu9S5 nanocrystalline film, as the back electrode for CdTe solar cells as the model device. Its low sheet resistance (16.6 Ω/sq) could compare to that of the commercial TCO films (6-30 Ω/sq), like FTO, ITO, and AZO. Different from the traditonal metal back electrode, it produces a successive gradient-doping region by the controllable Cu diffusion, which greatly reduces the contact potential barrier. Remarkably, it achieved a comparable power conversion efficiency (PCE, 11.3%) with the traditional metal back electrode (Cu/Au thin films, 11.4%) in CdTe cells and a higher PCE (13.8%) with the help of the Au assistant film. We believe it could also act as the back electrode for other thin film solar cells (α-Si, CuInS2, CIGSe, CZTS, etc.), for their performance improvement.

Microstructure factor and mechanical and electronic properties of hydrogenated amorphous and nanocrystalline silicon thin-films for microelectromechanical systems applications

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

Mouro, J.; Gualdino, A.; Chu, V.

2013-11-14

Thin-film silicon allows the fabrication of MEMS devices at low processing temperatures, compatible with monolithic integration in advanced electronic circuits, on large-area, low-cost, and flexible substrates. The most relevant thin-film properties for applications as MEMS structural layers are the deposition rate, electrical conductivity, and mechanical stress. In this work, n{sup +}-type doped hydrogenated amorphous and nanocrystalline silicon thin-films were deposited by RF-PECVD, and the influence of the hydrogen dilution in the reactive mixture, the RF-power coupled to the plasma, the substrate temperature, and the deposition pressure on the structural, electrical, and mechanical properties of the films was studied. Three differentmore » types of silicon films were identified, corresponding to three internal structures: (i) porous amorphous silicon, deposited at high rates and presenting tensile mechanical stress and low electrical conductivity, (ii) dense amorphous silicon, deposited at intermediate rates and presenting compressive mechanical stress and higher values of electrical conductivity, and (iii) nanocrystalline silicon, deposited at very low rates and presenting the highest compressive mechanical stress and electrical conductivity. These results show the combinations of electromechanical material properties available in silicon thin-films and thus allow the optimized selection of a thin silicon film for a given MEMS application. Four representative silicon thin-films were chosen to be used as structural material of electrostatically actuated MEMS microresonators fabricated by surface micromachining. The effect of the mechanical stress of the structural layer was observed to have a great impact on the device resonance frequency, quality factor, and actuation force.« less

Quantifying resistances across nanoscale low- and high-angle interspherulite boundaries in solution-processed organic semiconductor thin films.

PubMed

Lee, Stephanie S; Mativetsky, Jeffrey M; Loth, Marsha A; Anthony, John E; Loo, Yueh-Lin

2012-11-27

The nanoscale boundaries formed when neighboring spherulites impinge in polycrystalline, solution-processed organic semiconductor thin films act as bottlenecks to charge transport, significantly reducing organic thin-film transistor mobility in devices comprising spherulitic thin films as the active layers. These interspherulite boundaries (ISBs) are structurally complex, with varying angles of molecular orientation mismatch along their lengths. We have successfully engineered exclusively low- and exclusively high-angle ISBs to elucidate how the angle of molecular orientation mismatch at ISBs affects their resistivities in triethylsilylethynyl anthradithiophene thin films. Conductive AFM and four-probe measurements reveal that current flow is unaffected by the presence of low-angle ISBs, whereas current flow is significantly disrupted across high-angle ISBs. In the latter case, we estimate the resistivity to be 22 MΩμm(2)/width of the ISB, only less than a quarter of the resistivity measured across low-angle grain boundaries in thermally evaporated sexithiophene thin films. This discrepancy in resistivities across ISBs in solution-processed organic semiconductor thin films and grain boundaries in thermally evaporated organic semiconductor thin films likely arises from inherent differences in the nature of film formation in the respective systems.

Carbon-Nanotube Conductive Layers for Thin-Film Solar Cells

NASA Technical Reports Server (NTRS)

Landis, Geoffrey A.

2005-01-01

Thin, transparent layers comprising mats of carbon nanotubes have been proposed for providing lateral (that is, inplane) electrical conductivities for collecting electric currents from the front surfaces of the emitter layers of thin-film solar photovoltaic cells. Traditionally, thin, semitransparent films of other electrically conductive materials (usually, indium tin oxide, zinc oxide, or cadmium sulfide) have been used for this purpose. As in the cases of the traditional semitransparent conductive films, the currents collected by the nanotube layers would, in turn, be further collected by front metal contact stripes. Depending on details of a specific solar-cell design, the layer of carbon nanotubes would be deposited in addition to, or instead of, a semitransparent layer of one of these traditional conductive materials (see figure). The proposal is expected to afford the following advantages: The electrical conductivity of the carbon- nanotube layer would exceed that of the corresponding semitransparent layer of traditional electrically conductive material. The greater electrical conductivity of the carbon-nanotube layer would make it possible to retain adequate lateral electrical conductivity while reducing the thickness of, or eliminating entirely, the traditional semitransparent conductive layer. As a consequence of thinning or elimination of the traditional semitransparent conductive layer, less light would be absorbed, so that more of the incident light would be available for photovoltaic conversion. The greater electrical conductivity of the carbon-nanotube layer would make it possible to increase the distance between front metal contact stripes, in addition to (or instead of) thinning or eliminating the layer of traditional semitransparent conductive material. Consequently, the fraction of solar-cell area shadowed by front metal contact stripes would be reduced again, making more of the incident light available for photovoltaic conversion. The electrical conductivities of individual carbon nanotubes can be so high that the mat of carbon nanotubes could be made sparse enough to be adequately transparent while affording adequate lateral electrical conductivity of the mat as a whole. The thickness of the nanotube layer would be chosen so that the layer would contribute significant lateral electrical conductivity, yet would be as nearly transparent as possible to incident light. A typical thickness for satisfying these competing requirements is expected to lie between 50 and 100 nm. The optimum thickness must be calculated by comparing the lateral electrical conductivity, the distance between front metal stripes, and the amount of light lost by absorption in the nanotube layer.

Thin Film Electrodes with an Integral Current Collection Grid for Use with Solid Electrolytes

NASA Technical Reports Server (NTRS)

Ryan, M. A.; Kisor, A.; Williams, R. M.; Jeffries-Nakamura, B.; O'Connor, D.

1994-01-01

Thin film, high performance electrodes which can operate in high temperature environments are necessary for many devices which use a solid electrolyte. Electrodes of rhodium-tungsten alloy have been deposited on solid electrolyte using photolytic chemical vapor deposition (PCVD). A technique for depositing electrodes and current collection grids simultaneously has been developed using the prenucleation characteristics of PCVD. This technique makes it possible to fabricate electrodes which allow vapor transport through the thin (<1 (micro)m) portions of the electrode while integral thick grid lines improve the electronic conductivity of the electrode, thus improving overall performance.

Enhanced Performance in Al-Doped ZnO Based Transparent Flexible Transparent Thin-Film Transistors Due to Oxygen Vacancy in ZnO Film with Zn-Al-O Interfaces Fabricated by Atomic Layer Deposition.

PubMed

Li, Yang; Yao, Rui; Wang, Huanhuan; Wu, Xiaoming; Wu, Jinzhu; Wu, Xiaohong; Qin, Wei

2017-04-05

Highly conductive and optical transparent Al-doped ZnO (AZO) thin film composed of ZnO with a Zn-Al-O interface was fabricated by thermal atomic layer deposition (ALD) method. The as-prepared AZO thin film exhibits excellent electrical and optical properties with high stability and compatibility with temperature-sensitive flexible photoelectronic devices; film resistivity is as low as 5.7 × 10 -4 Ω·cm, the carrier concentration is high up to 2.2 × 10 21 cm -3 . optical transparency is greater than 80% in a visible range, and the growth temperature is below 150 °C on the PEN substrate. Compared with the conventional AZO film containing by a ZnO-Al 2 O 3 interface, we propose that the underlying mechanism of the enhanced electrical conductivity for the current AZO thin film is attributed to the oxygen vacancies deficiency derived from the free competitive growth mode of Zn-O and Al-O bonds in the Zn-Al-O interface. The flexible transparent transistor based on this AZO electrode exhibits a favorable threshold voltage and I on /I off ratio, showing promising for use in high-resolution, fully transparent, and flexible display applications.

High density associative memory

NASA Technical Reports Server (NTRS)

Moopenn, Alexander W. (Inventor); Thakoor, Anilkumar P. (Inventor); Daud, Taher (Inventor); Lambe, John J. (Inventor)

1989-01-01

A multi-layered, thin-film, digital memory having associative recall. There is a first memory matrix and a second memory matrix. Each memory matrix comprises, a first layer comprising a plurality of electrically separated row conductors; a second layer comprising a plurality of electrically separated column conductors intersecting but electrically separated from the row conductors; and, a plurality of resistance elements electrically connected between the row condutors and the column conductors at respective intersections of the row conductors and the column conductors, each resistance element comprising, in series, a first resistor of sufficiently high ohmage to conduct a sensible element current therethrough with virtually no heat-generating power consumption when a low voltage as employed in thin-film applications is applied thereacross and a second resistor of sufficiently high ohmage to conduct no sensible current therethrough when a low voltage as employed in thin-film applications is applied thereacross, the second resistor having the quality of breaking down to create a short therethrough upon the application of a breakdown level voltage across the first and second resistors.

Microminiature coaxial cable and methods manufacture

DOEpatents

Bongianni, Wayne L.

1986-01-01

A coaxial cable is provided having a ribbon inner conductor surrounded by a dielectric and a circumferential conductor. The coaxial cable may be microminiature comprising a very thin ribbon strip conductor from between 5 to 15 .mu.m thick and from 150 to 200 .mu.m wide, having a surrounding foamed dielectric or parylene applied thereon by a vapor plasma process and an outer conductor of an adhering high conductivity metal vacuum deposited on the dielectric. Alternately the foam dielectric embodiment may have a contiguous parylene coating applied adjacent the inner conductor or the outer conductor or both. Also, the cable may be fabricated by forming a thin ribbon of strip conductive material into an inner conductor, applying thereabout a dielectric by spraying on a solution of polystyrene and polyethylene and then vacuum depositing and adhering high conductivity metal about the dielectric. The cable strength may be increased by adding glass microfilament fibers or glass microballoons to the solution of polystyrene and polyethylene. Further, the outer conductive layer may be applied by electroless deposition in an aqueous solution rather than by vacuum deposition. A thin coating of parylene is preferably applied to the outer conductor to prevent its oxidation and inhibit mechanical abrasion.

Microminiature coaxial cable and method of manufacture

DOEpatents

Bongianni, W.L.

1989-03-28

A coaxial cable is provided having a ribbon inner conductor surrounded by a dielectric and a circumferential conductor. The coaxial cable may be microminiature comprising a very thin ribbon strip conductor from between 5 to 15 [mu]m thick and from 150 to 200 [mu]m wide, having a surrounding foamed dielectric or parylene applied thereon by a vapor plasma process and an outer conductor of an adhering high conductivity metal vacuum deposited on the dielectric. Alternately, the foam dielectric embodiment may have a contiguous parylene coating applied adjacent the inner conductor or the outer conductor or both. Also, the cable may be fabricated by forming a thin ribbon of strip conductive material into an inner conductor, applying thereabout a dielectric by spraying on a solution of polystyrene and polyethylene and then vacuum depositing and adhering high conductivity metal about the dielectric. The cable strength may be increased by adding glass microfilament fibers or glass microspheres to the solution of polystyrene and polyethylene. Further, the outer conductive layer may be applied by electroless deposition in an aqueous solution rather than by vacuum deposition. A thin coating of parylene is preferably applied to the outer conductor to prevent its oxidation and inhibit mechanical abrasion. 2 figs.

Microminiature coaxial cable and method of manufacture

DOEpatents

Bongianni, Wayne L.

1989-01-01

A coaxial cable is provided having a ribbon inner conductor surrounded by a dielectric and a circumferential conductor. The coaxial cable may be microminiature comprising a very thin ribbon strip conductor from between 5 to 15 .mu.m thick and from 150 to 200 .mu.m wide, having a surrounding foamed dielectric or parylene applied thereon by a vapor plasma process and an outer conductor of an adhering high conductivity metal vacuum deposited on the dielectric. Alternately, the foam dielectric embodiment may have a contiguous parylene coating applied adjacent the inner conductor or the outer conductor or both. Also, the cable may be fabricated by forming a thin ribbon of strip conductive material into an inner conductor, applying thereabout a dielectric by spraying on a solution of polystyrene and polyethylene and then vacuum depositing and adhering high conductivity metal about the dielectric. The cable strength may be increased by adding glass microfilament fibers or glass microspheres to the solution of polystyrene and polyethylene. Further, the outer conductive layer may be applied by electroless deposition in an aqueous solution rather than by vacuum deposition. A thin coating of parylene is preferably applied to the outer conductor to prevent its oxidation and inhibit mechanical abrasion.

Microminiature coaxial cable and methods of manufacture

DOEpatents

Bongianni, W.L.

1983-12-29

A coaxial cable is provided having a ribbon inner conductor surrounded by a dielectric and a circumferential conductor. The coaxial cable may be microminiature comprising a very thin ribbon strip conductor from between 5 to 15 ..mu..m thick and from 150 to 200 ..mu..m wide, having a surrounding foamed dielectric or parylene applied thereon by a vapor plasma process and an outer conductor of an adhering high conductivity metal vacuum deposited on the dieleectric. Alternately the foam dielectric embodiment may have a contiguous parylene coating applied adjacent the inner conductor or the outer conductor or both. Also, the cable may be fabricated by forming a thin ribbon of strip conductive material into an inner conductor, applying thereabout a dielectric by spraying on a solution of polystyrene and polyethylene and then vacuum depositing and adhering high conductivity metal about the dielectric. The cable strength may be increased by adding glass microfilament fibers or glass microballoons to the solution of polystyrene and polyethylene. Further, the outer conductive layer may be applied by electroless deposition in an aqueous solution rather than by vacuum deposition. A thin coating of parylene is preferably applied to the outer conductor to prevent its oxidation and inhibit mechanical abrasion.

Microminiature coaxial cable and methods manufacture

DOEpatents

Bongianni, W.L.

1986-04-08

A coaxial cable is provided having a ribbon inner conductor surrounded by a dielectric and a circumferential conductor. The coaxial cable may be microminiature comprising a very thin ribbon strip conductor from between 5 to 15 [mu]m thick and from 150 to 200 [mu]m wide, having a surrounding foamed dielectric or parylene applied thereon by a vapor plasma process and an outer conductor of an adhering high conductivity metal vacuum deposited on the dielectric. Alternately the foam dielectric embodiment may have a contiguous parylene coating applied adjacent the inner conductor or the outer conductor or both. Also, the cable may be fabricated by forming a thin ribbon of strip conductive material into an inner conductor, applying thereabout a dielectric by spraying on a solution of polystyrene and polyethylene and then vacuum depositing and adhering high conductivity metal about the dielectric. The cable strength may be increased by adding glass microfilament fibers or glass microballoons to the solution of polystyrene and polyethylene. Further, the outer conductive layer may be applied by electroless deposition in an aqueous solution rather than by vacuum deposition. A thin coating of parylene is preferably applied to the outer conductor to prevent its oxidation and inhibit mechanical abrasion. 2 figs.

Effect of high energy ions on the electrical and morphological properties of Poly(3-Hexylthiophene) (P3HT) thin film

NASA Astrophysics Data System (ADS)

Sharma, Trupti; Singhal, R.; Vishnoi, R.; Sharma, G. D.; Biswas, S. K.

2018-05-01

The spin-coated thin films of Poly(3-Hexylthiophene) (P3HT) on the glass and Si (double side polished) substrates have been irradiated with 55 MeV Si+4 swift heavy ions (SHI) at fluences in the range from 1 × 1010 to 1 × 1012 ions/cm2. Structural modifications produced by energetic ions are observed by characterization of pristine and irradiated P3HT thin films. Different techniques like high-resolution X-ray diffraction (HR-XRD), micro-Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR) were used to analyze the structural changes in the material. A significant increase in crystallinity and room temperature electrical conductivity of P3HT film has been detected on exposure to the heavy ions. The observed increase in the electrical conductivity with increased fluences is explained in the light of improved ordering of polymer chains after irradiation. Mott's variable range hopping model has been used to explain the conduction mechanism in the material in the temperature range of 230-350 K. The modification in surface properties also observed using AFM analysis and contact angle measurement. It is observed that nature of the P3HT thin films remains hydrophobic after irradiation.

Structural, Optical and Electrical Properties of ITO Thin Films

NASA Astrophysics Data System (ADS)

Sofi, A. H.; Shah, M. A.; Asokan, K.

2018-02-01

Transparent and conductive thin films of indium tin oxide were fabricated on glass substrates by the thermal evaporation technique. Tin doped indium ingots with low tin content were evaporated in vacuum (1.33 × 10-7 kpa) followed by an oxidation for 15 min in the atmosphere in the temperature range of 600-700°C. The structure and phase purity, surface morphology, optical and electrical properties of thin films were studied by x-ray diffractometry and Raman spectroscopy, scanning electron microcopy and atomic force microscopy, UV-visible spectrometry and Hall measurements in the van der Pauw configuration. The x-ray diffraction study showed the formation of the cubical phase of polycrystalline thin films. The morphological analysis showed the formation of ginger like structures and the energy dispersive x-ray spectrum confirmed the presence of indium (In), tin (Sn) and oxygen (O) elements. Hall measurements confirmed n-type conductivity of films with low electrical resistivity ( ρ) ˜ 10-3 Ω cm and high carrier concentration ( n) ˜ 1020 cm-3. For prevalent scattering mechanisms in the films, experimental data was analyzed by calculating a mean free path ( L) using a highly degenerate electron gas model. Furthermore, to investigate the performance of the deposited films as a transparent conductive material, the optical figure of merit was obtained for all the samples.

Nonlinear optical parameters of nanocrystalline AZO thin film measured at different substrate temperatures

NASA Astrophysics Data System (ADS)

Jilani, Asim; Abdel-wahab, M. Sh; Al-ghamdi, Attieh A.; Dahlan, Ammar sadik; Yahia, I. S.

2016-01-01

The 2.2 wt% of aluminum (Al)-doped zinc oxide (AZO) transparent and preferential c-axis oriented thin films were prepared by using radio frequency (DC/RF) magnetron sputtering at different substrate temperature ranging from room temperature to 200 °C. For structural analysis, X-ray Diffraction (XRD) and Atomic Force Electron Microscope (AFM) was used for morphological studies. The optical parameters such as, optical energy gap, refractive index, extinction coefficient, dielectric loss, tangent loss, first and third order nonlinear optical properties of transparent films were investigated. High transmittance above 90% and highly homogeneous surface were observed in all samples. The substrate temperature plays an important role to get the best transparent conductive oxide thin films. The substrate temperature at 150 °C showed the growth of highly transparent AZO thin film. Energy gap increased with the increased in substrate temperature of Al doped thin films. Dielectric constant and loss were found to be photon energy dependent with substrate temperature. The change in substrate temperature of Al doped thin films also affect the non-liner optical properties of thin films. The value of χ(3) was found to be changed with the grain size of the thin films that directly affected by the substrate temperature of the pure and Al doped ZnO thin films.

Restoration thinning and influence of tree size and leaf area to sapwood area ratio on water relations of Pinus ponderosa.

PubMed

Simonin, K; Kolb, T E; Montes-Helu, M; Koch, G W

2006-04-01

Ponderosa pine (Pinus ponderosa Dougl. ex P. Laws) forest stand density has increased significantly over the last century (Covington et al. 1997). To understand the effect of increased intraspecific competition, tree size (height and diameter at breast height (DBH)) and leaf area to sapwood area ratio (A(L):A(S)) on water relations, we compared hydraulic conductance from soil to leaf (kl) and transpiration per unit leaf area (Q(L)) of ponderosa pine trees in an unthinned plot to trees in a thinned plot in the first and second years after thinning in a dense Arizona forest. We calculated kl and Q(L) based on whole- tree sap flux measured with heat dissipation sensors. Thinning increased tree predawn water potential within two weeks of treatment. Effects of thinning on kl and Q(L) depended on DBH, A(L):A(S) and drought severity. During severe drought in the first growing season after thinning, kl and Q(L) of trees with low A(L):A(S) (160-250 mm DBH; 9-11 m height) were lower in the thinned plot than the unthinned plot, suggesting a reduction in stomatal conductance (g(s)) or reduced sapwood specific conductivity (K(S)), or both, in response to thinning. In contrast kl and Q(L) were similar in the thinned plot and unthinned plot for trees with high A(L):A(S) (260-360 mm DBH; 13-16 m height). During non-drought periods, kl and Q(L) were greater in the thinned plot than in the unthinned plot for all but the largest trees. Contrary to previous studies of ponderosa pine, A(L):A(S) was positively correlated with tree height and DBH. Furthermore, kl and Q(L) showed a weak negative correlation with tree height and a strong negative correlation with A(S) and thus A(L):A(S) in both the thinned and unthinned plots, suggesting that trees with high A(L):A(S) had lower g(s). Our results highlight the important influence of stand competitive environment on tree-size-related variation in A(L):A(S) and the roles of A(L):A(S) and drought on whole-tree water relations in response to thinning.

High-performance a-IGZO thin-film transistor with conductive indium-tin-oxide buried layer

NASA Astrophysics Data System (ADS)

Ahn, Min-Ju; Cho, Won-Ju

2017-10-01

In this study, we fabricated top-contact top-gate (TCTG) structure of amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistors (TFTs) with a thin buried conductive indium-tin oxide (ITO) layer. The electrical performance of a-IGZO TFTs was improved by inserting an ITO buried layer under the IGZO channel. Also, the effect of the buried layer's length on the electrical characteristics of a-IGZO TFTs was investigated. The electrical performance of the transistors improved with increasing the buried layer's length: a large on/off current ratio of 1.1×107, a high field-effect mobility of 35.6 cm2/Vs, a small subthreshold slope of 116.1 mV/dec, and a low interface trap density of 4.2×1011 cm-2eV-1 were obtained. The buried layer a-IGZO TFTs exhibited enhanced transistor performance and excellent stability against the gate bias stress.

Using high thermal stability flexible thin film thermoelectric generator at moderate temperature

NASA Astrophysics Data System (ADS)

Zheng, Zhuang-Hao; Luo, Jing-Ting; Chen, Tian-Bao; Zhang, Xiang-Hua; Liang, Guang-Xing; Fan, Ping

2018-04-01

Flexible thin film thermoelectric devices are extensively used in the microscale industry for powering wearable electronics. In this study, comprehensive optimization was conducted in materials and connection design for fabricating a high thermal stability flexible thin film thermoelectric generator. First, the thin films in the generator, including the electrodes, were prepared by magnetron sputtering deposition. The "NiCu-Cu-NiCu" multilayer electrode structure was applied to ensure the thermal stability of the device used at moderate temperature in an air atmosphere. A design with metal layer bonding and series accordant connection was then employed. The maximum efficiency of a single PN thermocouple generator is >11%, and the output power loss of the generator is <10% after integration.

Thin film polymeric gel electrolytes

DOEpatents

Derzon, D.K.; Arnold, C. Jr.; Delnick, F.M.

1996-12-31

Novel hybrid thin film electrolytes, based on an organonitrile solvent system, which are compositionally stable, environmentally safe, can be produced efficiently in large quantity and which, because of their high conductivities {approx_equal}10{sup {minus}3}{Omega}{sup {minus}1} cm{sup {minus}1} are useful as electrolytes for rechargeable lithium batteries. 1 fig.

Characterization of a new transparent-conducting material of ZnO doped ITO thin films

NASA Astrophysics Data System (ADS)

Ali, H. M.

2005-11-01

Thin films of indium tin oxide (ITO) doped with zinc oxide have the remarkable properties of being conductive yet still highly transparent in the visible and near-IR spectral ranges. The Electron beam deposi- tion technique is one of the simplest and least expensive ways of preparing. High-quality ITO thin films have been deposited on glass substrates by Electron beam evaporation technique. The effect of doping and substrate deposition temperature was found to have a significant effect on the structure, electrical and optical properties of ZnO doped ITO films. The average optical transmittance has been increased with in- creasing the substrate temperature. The maximum value of transmittance is greater than 84% in the visible region and 85% in the NIR region obtained for film with Zn/ITO = 0.13 at substrate temperature 200 °C. The dielectric constant, average excitation energy for electronic transitions (E o), the dispersion energy (E d), the long wavelength refractive index (n ), average oscillator wave length ( o) and oscillator strength S _o for the thin films were determined and presented in this work.

Optimal design of high temperature metalized thin-film polymer capacitors: A combined numerical and experimental method

NASA Astrophysics Data System (ADS)

Wang, Zhuo; Li, Qi; Trinh, Wei; Lu, Qianli; Cho, Heejin; Wang, Qing; Chen, Lei

2017-07-01

The objective of this paper is to design and optimize the high temperature metalized thin-film polymer capacitor by a combined computational and experimental method. A finite-element based thermal model is developed to incorporate Joule heating and anisotropic heat conduction arising from anisotropic geometric structures of the capacitor. The anisotropic thermal conductivity and temperature dependent electrical conductivity required by the thermal model are measured from the experiments. The polymer represented by thermally crosslinking benzocyclobutene (BCB) in the presence of boron nitride nanosheets (BNNSs) is selected for high temperature capacitor design based on the results of highest internal temperature (HIT) and the time to achieve thermal equilibrium. The c-BCB/BNNS-based capacitor aiming at the operating temperature of 250 °C is geometrically optimized with respect to its shape and volume. "Safe line" plot is also presented to reveal the influence of the cooling strength on capacitor geometry design.

Nickel-Aluminum Layered Double Hydroxide Coating on the Surface of Conductive Substrates by Liquid Phase Deposition.

PubMed

Maki, Hideshi; Takigawa, Masashi; Mizuhata, Minoru

2015-08-12

The direct synthesis of the adhered Ni-Al LDH thin film onto the surface of electrically conductive substrates by the liquid phase deposition (LPD) reaction is carried out for the development of the positive electrode. The complexation and solution equilibria of the dissolved species in the LPD reaction have been clarified by a theoretical approach, and the LPD reaction conditions for the Ni-Al LDH depositions are shown to be optimized by controlling the fluoride ion concentration and the pH of the LPD reaction solutions. The yields of metal oxides and hydroxides by the LPD method are very sensitive to the supersaturation state of the hydroxide in the reaction solution. The surfaces of conductive substrates are completely covered by the minute mesh-like Ni-Al LDH thin film; furthermore, there is no gap between the surfaces of conductive substrates and the deposited Ni-Al LDH thin film. The active material layer thickness was able to be controlled within the range from 100 nm to 1 μm by the LPD reaction time. The high-crystallinity and the arbitrary-thickness thin films on the conductive substrate surface will be beneficial for the interface control of charge transfer reaction fields and the internal resistance reduction of various secondary batteries.

Thin film photovoltaic devices with a minimally conductive buffer layer

DOEpatents

Barnes, Teresa M.; Burst, James

2016-11-15

A thin film photovoltaic device (100) with a tunable, minimally conductive buffer (128) layer is provided. The photovoltaic device (100) may include a back contact (150), a transparent front contact stack (120), and an absorber (140) positioned between the front contact stack (120) and the back contact (150). The front contact stack (120) may include a low resistivity transparent conductive oxide (TCO) layer (124) and a buffer layer (128) that is proximate to the absorber layer (140). The photovoltaic device (100) may also include a window layer (130) between the buffer layer (128) and the absorber (140). In some cases, the buffer layer (128) is minimally conductive, with its resistivity being tunable, and the buffer layer (128) may be formed as an alloy from a host oxide and a high-permittivity oxide. The high-permittivity oxide may further be chosen to have a bandgap greater than the host oxide.

Enhancing Modulation of Thermal Conduction in Vanadium Dioxide Thin Film by Nanostructured Nanogaps

DOE PAGES

Choe, Hwan Sung; Suh, Joonki; Ko, Changhyun; ...

2017-08-02

Efficient thermal management at the nanoscale is important for reducing energy consumption and dissipation in electronic devices, lab-on-a-chip platforms and energy harvest/conversion systems. For many of these applications, it is much desired to have a solid-state structure that reversibly switches thermal conduction with high ON/OFF ratios and at high speed. We describe design and implementation of a novel, all-solid-state thermal switching device by nanostructured phase transformation, i.e., modulation of contact pressure an d area between two poly-silicon surfaces activated by microstructural change of a vanadium dioxide (VO 2 ) thin film. Our solid-state devices demonstrate large and reversible alteration ofmore » cross-plane thermal conductance as a function of temperature, achieving a conductance ratio of at least 2.5. This new approach using nanostructured phase transformation provides new opportunities for applications that require advanced temperature and heat regulations.« less

Enhancing Modulation of Thermal Conduction in Vanadium Dioxide Thin Film by Nanostructured Nanogaps

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

Choe, Hwan Sung; Suh, Joonki; Ko, Changhyun

Efficient thermal management at the nanoscale is important for reducing energy consumption and dissipation in electronic devices, lab-on-a-chip platforms and energy harvest/conversion systems. For many of these applications, it is much desired to have a solid-state structure that reversibly switches thermal conduction with high ON/OFF ratios and at high speed. We describe design and implementation of a novel, all-solid-state thermal switching device by nanostructured phase transformation, i.e., modulation of contact pressure an d area between two poly-silicon surfaces activated by microstructural change of a vanadium dioxide (VO 2 ) thin film. Our solid-state devices demonstrate large and reversible alteration ofmore » cross-plane thermal conductance as a function of temperature, achieving a conductance ratio of at least 2.5. This new approach using nanostructured phase transformation provides new opportunities for applications that require advanced temperature and heat regulations.« less

Nanomechanical Behavior of High Gas Barrier Multilayer Thin Films.

PubMed

Humood, Mohammad; Chowdhury, Shahla; Song, Yixuan; Tzeng, Ping; Grunlan, Jaime C; Polycarpou, Andreas A

2016-05-04

Nanoindentation and nanoscratch experiments were performed on thin multilayer films manufactured using the layer-by-layer (LbL) assembly technique. These films are known to exhibit high gas barrier, but little is known about their durability, which is an important feature for various packaging applications (e.g., food and electronics). Films were prepared from bilayer and quadlayer sequences, with varying thickness and composition. In an effort to evaluate multilayer thin film surface and mechanical properties, and their resistance to failure and wear, a comprehensive range of experiments were conducted: low and high load indentation, low and high load scratch. Some of the thin films were found to have exceptional mechanical behavior and exhibit excellent scratch resistance. Specifically, nanobrick wall structures, comprising montmorillonite (MMT) clay and polyethylenimine (PEI) bilayers, are the most durable coatings. PEI/MMT films exhibit high hardness, large elastic modulus, high elastic recovery, low friction, low scratch depth, and a smooth surface. When combined with the low oxygen permeability and high optical transmission of these thin films, these excellent mechanical properties make them good candidates for hard coating surface-sensitive substrates, where polymers are required to sustain long-term surface aesthetics and quality.

Balancing Hole and Electron Conduction in Ambipolar Split-Gate Thin-Film Transistors.

PubMed

Yoo, Hocheon; Ghittorelli, Matteo; Lee, Dong-Kyu; Smits, Edsger C P; Gelinck, Gerwin H; Ahn, Hyungju; Lee, Han-Koo; Torricelli, Fabrizio; Kim, Jae-Joon

2017-07-10

Complementary organic electronics is a key enabling technology for the development of new applications including smart ubiquitous sensors, wearable electronics, and healthcare devices. High-performance, high-functionality and reliable complementary circuits require n- and p-type thin-film transistors with balanced characteristics. Recent advancements in ambipolar organic transistors in terms of semiconductor and device engineering demonstrate the great potential of this route but, unfortunately, the actual development of ambipolar organic complementary electronics is currently hampered by the uneven electron (n-type) and hole (p-type) conduction in ambipolar organic transistors. Here we show ambipolar organic thin-film transistors with balanced n-type and p-type operation. By manipulating air exposure and vacuum annealing conditions, we show that well-balanced electron and hole transport properties can be easily obtained. The method is used to control hole and electron conductions in split-gate transistors based on a solution-processed donor-acceptor semiconducting polymer. Complementary logic inverters with balanced charging and discharging characteristics are demonstrated. These findings may open up new opportunities for the rational design of complementary electronics based on ambipolar organic transistors.

High performance diamond-like carbon layers obtained by pulsed laser deposition for conductive electrode applications

NASA Astrophysics Data System (ADS)

Stock, F.; Antoni, F.; Le Normand, F.; Muller, D.; Abdesselam, M.; Boubiche, N.; Komissarov, I.

2017-09-01

For the future, one of the biggest challenge faced to the technologies of flat panel display and various optoelectronic and photovoltaic devices is to find an alternative to the use of transparent conducting oxides like ITO. In this new approach, the objective is to grow high conductive thin-layer graphene (TLG) on the top of diamond-like carbon (DLC) layers presenting high performance. DLC prepared by pulsed laser deposition (PLD) have attracted special interest due to a unique combination of their properties, close to those of monocrystalline diamond, like its transparency, hardness and chemical inertia, very low roughness, hydrogen-free and thus high thermal stability up to 1000 K. In our future work, we plane to explore the synthesis of conductive TLG on top of insulating DLC thin films. The feasibility and obtained performances of the multi-layered structure will be explored in great details in the short future to develop an alternative to ITO with comparable performance (conductivity of transparency). To select the best DLC candidate for this purpose, we focus this work on the physicochemical properties of the DLC thin films deposited by PLD from a pure graphite target at two wavelengths (193 and 248 nm) at various laser fluences. A surface graphenization process, as well as the required efficiency of the complete structure (TLG/DLC) will clearly be related to the DLC properties, especially to the initial sp3/sp2 hybridization ratio. Thus, an exhaustive description of the physicochemical properties of the DLC layers is a fundamental step in the research of comparable performance to ITO.

Synthesis and characterization of lithium intercalation electrodes based on iron oxide thin films

NASA Astrophysics Data System (ADS)

Sarradin, J.; Guessous, A.; Ribes, M.

Sputter-deposited iron oxide thin films are investigated as a possible negative electrode for rocking-chair microbatteries. Experimental conditions related to the manufacturing of amorphous thin films suitable to a large number of available intercalation sites are described. Structural and physical properties of the thin layer films are presented. The conductivities of the amorphous thin films were found to be very high compared with those of the respective crystalline forms. Regarding the electrochemical behaviour, Fe 2O 3-based thin films electrodes are able to store and reversibly exchange lithium ions. At a C/2 charge/discharge rate with 100% depth-of-discharge (DOD), the specific capacity of these amorphous thin film electrodes remains almost constant and close to 330 Ah/kg after more than 120 charge/discharge cycles.

Nano-crystallization in ZnO-doped In2O3 thin films via excimer laser annealing for thin-film transistors

NASA Astrophysics Data System (ADS)

Fujii, Mami N.; Ishikawa, Yasuaki; Ishihara, Ryoichi; van der Cingel, Johan; Mofrad, Mohammad R. T.; Bermundo, Juan Paolo Soria; Kawashima, Emi; Tomai, Shigekazu; Yano, Koki; Uraoka, Yukiharu

2016-06-01

In a previous work, we reported the high field effect mobility of ZnO-doped In2O3 (IZO) thin film transistors (TFTs) irradiated by excimer laser annealing (ELA) [M. Fujii et al., Appl. Phys. Lett. 102, 122107 (2013)]. However, a deeper understanding of the effect of ELA on the IZO film characteristics based on crystallinity, carrier concentrations, and optical properties is needed to control localized carrier concentrations for fabricating self-aligned structures in the same oxide film and to adequately explain the physical characteristics. In the case of as-deposited IZO film used as the channel, a high carrier concentration due to a high density of oxygen vacancies was observed; such a film does not show the required TFT characteristics but can act as a conductive film. We achieved a decrease in the carrier concentration of IZO films by crystallization using ELA. This means that ELA can form localized conductive or semi-conductive areas on the IZO film. We confirmed that the reason for the carrier concentration decrease was the decrease of oxygen-deficient regions and film crystallization. The annealed IZO films showed nano-crystalline phase, and the temperature at the substrate was substantially less than the temperature limit for flexible films such as plastic, which is 50°C. This paves the way for the formation of self-aligned structures and separately formed conductive and semi-conductive regions in the same oxide film.

Development of a liquid lithium thin film for use as a heavy ion beam stripper.

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

Momozaki, Y.; Nolen, J.; Reed, C.

2009-04-01

A series of experiments was performed to investigate the feasibility of a liquid lithium thin film for a charge stripper in a high-power heavy ion linac. Various preliminary experiments using simulants were first conducted to determine the film formation scheme, to investigate the film stability, and to obtain the design parameters for a liquid lithium thin film system. Based on the results from these preliminary studies, a prototypical, high pressure liquid lithium system was constructed to demonstrate liquid lithium thin film formation. This system was capable of driving liquid lithium at {approx}< 300 C and up to 13.9 MPa (2000more » psig) through a nozzle opening as large as 1 mm (40 mil) in diameter. This drive pressure corresponds to a Li velocity of >200 m/s. A thin lithium film of 9 mm in width at velocity of {approx}58 m/s was produced. Its thickness was estimated to be roughly {approx}< 13 {micro}m. High vacuum was maintained in the area of the film. This type of liquid metal thin film may also be used in other high power beam applications such as for intense X-ray or neutron sources.« less

Finite-size versus interface-proximity effects in thin-film epitaxial SrTiO3

NASA Astrophysics Data System (ADS)

De Souza, R. A.; Gunkel, F.; Hoffmann-Eifert, S.; Dittmann, R.

2014-06-01

The equilibrium electrical conductivity of epitaxial SrTiO3 (STO) thin films was investigated as a function of temperature, 950≤ T/K ≤1100, and oxygen partial pressure, 10-23≤ pO2/bar ≤1. Compared with single-crystal STO, nanoscale thin-film STO exhibited with decreasing film thickness an increasingly enhanced electronic conductivity under highly reducing conditions, with a corresponding decrease in the activation enthalpy of conduction. This implies substantial modification of STO's point-defect thermodynamics for nanoscale film thicknesses. We argue, however, against such a finite-size effect and for an interface-proximity effect. Indeed, assuming trapping of oxygen vacancies at the STO surface and concomitant depletion of oxygen vacancies—and accumulation of electrons—in an equilibrium surface space-charge layer, we are able to predict quantitatively the conductivity as a function of temperature, oxygen partial pressure, and film thickness. Particularly complex behavior is predicted for ultrathin films that are consumed entirely by space charge.

Durable high strength cement concrete topping for asphalt roads

NASA Astrophysics Data System (ADS)

Vyrozhemskyi, Valerii; Krayushkina, Kateryna; Bidnenko, Nataliia

2017-09-01

Work on improving riding qualities of pavements by means of placing a thin cement layer with high roughness and strength properties on the existing asphalt pavement were conducted in Ukraine for the first time. Such pavement is called HPCM (High Performance Cementitious Material). This is a high-strength thin cement-layer pavement of 8-9 mm thickness reinforced with metal or polymer fiber of less than 5 mm length. Increased grip properties are caused by placement of stone material of 3-5 mm fraction on the concrete surface. As a result of the research, the preparation and placement technology of high-strength cement thin-layer pavement reinforced with fiber was developed to improve friction properties of existing asphalt pavements which ensures their roughness and durability. It must be emphasized that HPCM is a fundamentally new type of thin-layer pavement in which a rigid layer of 10 mm thickness is placed on a non-rigid base thereby improving riding qualities of asphalt pavement at any season of a year.

Resistive switching properties and physical mechanism of cobalt ferrite thin films

NASA Astrophysics Data System (ADS)

Hu, Wei; Zou, Lilan; Chen, Ruqi; Xie, Wei; Chen, Xinman; Qin, Ni; Li, Shuwei; Yang, Guowei; Bao, Dinghua

2014-04-01

We report reproducible resistive switching performance and relevant physical mechanism of sandwiched Pt/CoFe2O4/Pt structures in which the CoFe2O4 thin films were fabricated by a chemical solution deposition method. Uniform switching voltages, good endurance, and long retention have been demonstrated in the Pt/CoFe2O4/Pt memory cells. On the basis of the analysis of current-voltage characteristic and its temperature dependence, we suggest that the carriers transport through the conducting filaments in low resistance state with Ohmic conduction behavior, and the Schottky emission and Poole-Frenkel emission dominate the conduction mechanism in high resistance state. From resistance-temperature dependence of resistance states, we believe that the physical origin of the resistive switching refers to the formation and rupture of the oxygen vacancies related filaments. The nanostructured CoFe2O4 thin films can find applications in resistive random access memory.

Determination of surface resistance and magnetic penetration depth of superconducting YBa2Cu3O(7-delta) thin films by microwave power transmission measurements

NASA Technical Reports Server (NTRS)

Bhasin, K. B.; Warner, J. D.; Miranda, F. A.; Gordon, W. L.; Newman, H. S.

1991-01-01

A novel waveguide power transmission measurement technique was developed to extract the complex conductivity of superconducting thin films at microwave frequencies. The microwave conductivity was taken of two laser ablated YBa2Cu3O(7-delta) thin films on LaAlO3 with transition temperatures of approximately 86.3 and 82 K, respectively, in the temperature range 25 to 300 K. From the conductivity values, the penetration depth was found to be approximately 0.54 and 0.43 micron, and the surface resistance (R sub s) to be approximately 24 and 36 micro-Ohms at 36 GHz and 76 K for the two films under consideration. The R sub s values were compared with those obtained from the change in the Q-factor of a 36 GHz Te sub 011-mode (OFHC) copper cavity by replacing one of its end walls with the superconducting sample. This technique allows noninvasive characterization of high transition superconducting thin films at microwave frequencies.

Determination of surface resistance and magnetic penetration depth of superconducting YBa2Cu3O(7-delta) thin films by microwave power transmission measurements

NASA Technical Reports Server (NTRS)

Bhasin, K. B.; Warner, J. D.; Miranda, F. A.; Gordon, W. L.; Newman, H. S.

1990-01-01

A novel waveguide power transmission measurement technique was developed to extract the complex conductivity of superconducting thin films at microwave frequencies. The microwave conductivity was taken of two laser ablated YBa2Cu3O(7-delta) thin films on LaAlO3 with transition temperatures of approx. 86.3 and 82 K, respectively, in the temperature range 25 to 300 K. From the conductivity values, the penetration depth was found to be approx. 0.54 and 0.43 micron, and the surface resistance (R sub s) to be approx. 24 and 36 micro-Ohms at 36 GHz and 76 K for the two films under consideration. The R sub s values were compared with those obtained from the change in the Q-factor of a 36 GHz Te sub 011-mode (OFHC) copper cavity by replacing one of its end walls with the superconducting sample. This technique allows noninvasive characterization of high transition temperature superconducting thin films at microwave frequencies.

High-throughput heterodyne thermoreflectance: Application to thermal conductivity measurements of a Fe-Si-Ge thin film alloy library.

PubMed

d'Acremont, Quentin; Pernot, Gilles; Rampnoux, Jean-Michel; Furlan, Andrej; Lacroix, David; Ludwig, Alfred; Dilhaire, Stefan

2017-07-01

A High-Throughput Time-Domain ThermoReflectance (HT-TDTR) technique was developed to perform fast thermal conductivity measurements with minimum user actions required. This new setup is based on a heterodyne picosecond thermoreflectance system. The use of two different laser oscillators has been proven to reduce the acquisition time by two orders of magnitude and avoid the experimental artefacts usually induced by moving the elements present in TDTR systems. An amplitude modulation associated to a lock-in detection scheme is included to maintain a high sensitivity to thermal properties. We demonstrate the capabilities of the HT-TDTR setup to perform high-throughput thermal analysis by mapping thermal conductivity and interface resistances of a ternary thin film silicide library Fe x Si y Ge 100-x-y (20

High-throughput heterodyne thermoreflectance: Application to thermal conductivity measurements of a Fe-Si-Ge thin film alloy library

NASA Astrophysics Data System (ADS)

d'Acremont, Quentin; Pernot, Gilles; Rampnoux, Jean-Michel; Furlan, Andrej; Lacroix, David; Ludwig, Alfred; Dilhaire, Stefan

2017-07-01

A High-Throughput Time-Domain ThermoReflectance (HT-TDTR) technique was developed to perform fast thermal conductivity measurements with minimum user actions required. This new setup is based on a heterodyne picosecond thermoreflectance system. The use of two different laser oscillators has been proven to reduce the acquisition time by two orders of magnitude and avoid the experimental artefacts usually induced by moving the elements present in TDTR systems. An amplitude modulation associated to a lock-in detection scheme is included to maintain a high sensitivity to thermal properties. We demonstrate the capabilities of the HT-TDTR setup to perform high-throughput thermal analysis by mapping thermal conductivity and interface resistances of a ternary thin film silicide library FexSiyGe100-x-y (20

Poly-silicon TFT AM-OLED on thin flexible metal substrates

NASA Astrophysics Data System (ADS)

Afentakis, Themis; Hatalis, Miltiadis K.; Voutsas, Apostolos T.; Hartzell, John W.

2003-05-01

Thin metal foils present an excellent alternative to polymers for the fabrication of large area, flexible displays. Their main advantage spurs from their ability to withstand higher temperatures during processing; microelectronic fabrication at elevated temperatures offers the ability to utilize a variety of crystallization processes for the active layer of devices and thermally grown gate dielectrics. This can lead to high performance (high mobility, low threshold voltage) low cost and highly reliable thin film transistors. In some cases, the conductive substrate can also be used to provide power to the active devices, thus reducing layout complexity. This paper discusses the first successful attempt to design and fabricate a variety of active matrix organic light emitting diode displays on thin, flexible stainless steel foils. Different pixel architectures, such as two- and four-transistor implementations, and addressing modes, such as voltage- or current-driven schemese are examined. This work clearly demonstrates the advantages associated with the fabrication of OLED displays on thin metal foils, which - through roll-to-roll processing - can potentially result in revolutionizing today's display processing, leading to a new generation of low cost, high performance versatile display systems.

Porous CrN thin films by selectively etching CrCuN for symmetric supercapacitors

NASA Astrophysics Data System (ADS)

Wei, Binbin; Mei, Gui; Liang, Hanfeng; Qi, Zhengbing; Zhang, Dongfang; Shen, Hao; Wang, Zhoucheng

2018-05-01

Transition metal nitrides are regarded as a new class of excellent electrode materials for high-performance supercapacitors due to their superior chemical stability and excellent electrical conductivity. We synthesize successfully the porous CrN thin films for binder-free supercapacitor electrodes by reactive magnetron co-sputtering and selective chemical etching. The porous CrN thin film electrodes exhibit high-capacitance performance (31.3 mF cm-2 at 1.0 mA cm-2) and reasonable cycling stability (94% retention after 20000 cycles). Moreover, the specific capacitance is more than two-fold higher than that of the CrN thin film electrodes in previous work. In addition, a symmetric supercapacitor device with a maximum energy density of 14.4 mWh cm-3 and a maximum power density of 6.6 W cm-3 is achieved. These findings demonstrate that the porous CrN thin films will have potential applications in supercapacitors.

Influence of a Boron Precursor on the Growth and Optoelectronic Properties of Electrodeposited Zinc Oxide Thin Film.

PubMed

Tsin, Fabien; Thomere, Angélica; Bris, Arthur Le; Collin, Stéphane; Lincot, Daniel; Rousset, Jean

2016-05-18

Highly transparent and conductive materials are required for many industrial applications. One of the interesting features of ZnO is the possibility to dope it using different elements, hence improving its conductivity. Results concerning the zinc oxide thin films electrodeposited in a zinc perchlorate medium containing a boron precursor are presented in this study. The addition of boron to the electrolyte leads to significant effects on the morphology and crystalline structure as well as an evolution of the optical properties of the material. Varying the concentration of boric acid from 0 to 15 mM strongly improves the compactness of the deposit and increases the band gap from 3.33 to 3.45 eV. Investigations were also conducted to estimate and determine the influence of boric acid on the electrical properties of the ZnO layers. As a result, no doping effect effect by boron was demonstrated. However, the role of boric acid on the material quality has also been proven and discussed. Boric acid strongly contributes to the growth of high quality electrodeposited zinc oxide. The high doping level of the film can be attributed to the perchlorate ions introduced in the bath. Finally, a ZnO layer electrodeposited in a boron rich electrolyte was tested as front contact of a Cu(In, Ga)(S, Se)2 based solar cell. An efficiency of 12.5% was measured with a quite high fill factor (>70%) which confirms the high conductivity of the ZnO thin film.

Analysis of discontinuities across thin inhomogeneities, groundwater/surface water interactions in river networks, and circulation about slender bodies using slit elements in the Analytic Element Method

USDA-ARS?s Scientific Manuscript database

Groundwater and surface water contain interfaces across which hydrologic functions are discontinuous. Thin elements with high hydraulic conductivity in a porous media focus groundwater, which flows through such inhomogeneities and causes an abrupt change in stream function across their interfaces, a...

Method of preparing thin film polymeric gel electrolytes

DOEpatents

Derzon, D.K.; Arnold, C. Jr.

1997-11-25

Novel hybrid thin film electrolyte is described, based on an organonitrile solvent system, which are compositionally stable, environmentally safe, can be produced efficiently in large quantity and which, because of their high conductivities {approx_equal}10{sup {minus}3}{Omega}{sup {minus}1}cm{sup {minus}1} are useful as electrolytes for rechargeable lithium batteries. 1 fig.

Hybrid Co-deposition of Mixed-Valent Molybdenum-Germanium Oxides (MoxGeyOz): A Route to Tunable Optical Transmission (Postprint)

DTIC Science & Technology

2015-08-05

to increased doping levels in indirect semiconductors [84]. The slope, and magnitude of the transmission curves continue to decrease alongside UL...periodically aluminium- doped zinc oxide thin films, Thin Solid Films 519 (2011) 2280–2286. [2] T. Minami, H. Nanto, S. Takata, Highly conductive and...transparent aluminum doped zinc oxide thin films prepared by RF magnetron sputtering, Jpn. J. Appl. Phys. 23 (1984) L280. [3] T. Minami, Present status of

Foldable interpenetrated metal-organic frameworks/carbon nanotubes thin film for lithium-sulfur batteries

NASA Astrophysics Data System (ADS)

Mao, Yiyin; Li, Gaoran; Guo, Yi; Li, Zhoupeng; Liang, Chengdu; Peng, Xinsheng; Lin, Zhan

2017-03-01

Lithium-sulfur batteries are promising technologies for powering flexible devices due to their high energy density, low cost and environmental friendliness, when the insulating nature, shuttle effect and volume expansion of sulfur electrodes are well addressed. Here, we report a strategy of using foldable interpenetrated metal-organic frameworks/carbon nanotubes thin film for binder-free advanced lithium-sulfur batteries through a facile confinement conversion. The carbon nanotubes interpenetrate through the metal-organic frameworks crystal and interweave the electrode into a stratified structure to provide both conductivity and structural integrity, while the highly porous metal-organic frameworks endow the electrode with strong sulfur confinement to achieve good cyclability. These hierarchical porous interpenetrated three-dimensional conductive networks with well confined S8 lead to high sulfur loading and utilization, as well as high volumetric energy density.

Foldable interpenetrated metal-organic frameworks/carbon nanotubes thin film for lithium–sulfur batteries

PubMed Central

Mao, Yiyin; Li, Gaoran; Guo, Yi; Li, Zhoupeng; Liang, Chengdu; Peng, Xinsheng; Lin, Zhan

2017-01-01

Lithium–sulfur batteries are promising technologies for powering flexible devices due to their high energy density, low cost and environmental friendliness, when the insulating nature, shuttle effect and volume expansion of sulfur electrodes are well addressed. Here, we report a strategy of using foldable interpenetrated metal-organic frameworks/carbon nanotubes thin film for binder-free advanced lithium–sulfur batteries through a facile confinement conversion. The carbon nanotubes interpenetrate through the metal-organic frameworks crystal and interweave the electrode into a stratified structure to provide both conductivity and structural integrity, while the highly porous metal-organic frameworks endow the electrode with strong sulfur confinement to achieve good cyclability. These hierarchical porous interpenetrated three-dimensional conductive networks with well confined S8 lead to high sulfur loading and utilization, as well as high volumetric energy density. PMID:28262801

Nonlinear spin conductance of yttrium iron garnet thin films driven by large spin-orbit torque

NASA Astrophysics Data System (ADS)

Thiery, N.; Draveny, A.; Naletov, V. V.; Vila, L.; Attané, J. P.; Beigné, C.; de Loubens, G.; Viret, M.; Beaulieu, N.; Ben Youssef, J.; Demidov, V. E.; Demokritov, S. O.; Slavin, A. N.; Tiberkevich, V. S.; Anane, A.; Bortolotti, P.; Cros, V.; Klein, O.

2018-02-01

We report high power spin transfer studies in open magnetic geometries by measuring the spin conductance between two nearby Pt wires deposited on top of an epitaxial yttrium iron garnet thin film. Spin transport is provided by propagating spin waves that are generated and detected by direct and inverse spin Hall effects. We observe a crossover in spin conductance from a linear transport dominated by exchange magnons (low current regime) to a nonlinear transport dominated by magnetostatic magnons (high current regime). The latter are low-damping magnetic excitations, located near the spectral bottom of the magnon manifold, with a sensitivity to the applied magnetic field. This picture is supported by microfocus Brillouin light-scattering spectroscopy. Our findings could be used for the development of controllable spin conductors by variation of relatively weak magnetic fields.

Surface proton transport of fully protonated poly(aspartic acid) thin films on quartz substrates

NASA Astrophysics Data System (ADS)

Nagao, Yuki; Kubo, Takahiro

2014-12-01

Thin film structure and the proton transport property of fully protonated poly(aspartic acid) (P-Asp100) have been investigated. An earlier study assessed partially protonated poly(aspartic acid), highly oriented thin film structure and enhancement of the internal proton transport. In this study of P-Asp100, IR p-polarized multiple-angle incidence resolution (P-MAIR) spectra were measured to investigate the thin film structure. The obtained thin films, with thicknesses of 120-670 nm, had no oriented structure. Relative humidity dependence of the resistance, proton conductivity, and normalized resistance were examined to ascertain the proton transport property of P-Asp100 thin films. The obtained data showed that the proton transport of P-Asp100 thin films might occur on the surface, not inside of the thin film. This phenomenon might be related with the proton transport of the biological system.

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.

Enhanced phonon scattering by nanovoids in high thermoelectric power factor polysilicon thin films

NASA Astrophysics Data System (ADS)

Dunham, Marc T.; Lorenzi, Bruno; Andrews, Sean C.; Sood, Aditya; Asheghi, Mehdi; Narducci, Dario; Goodson, Kenneth E.

2016-12-01

The ability to tune the thermal conductivity of semiconductor materials is of interest for thermoelectric applications, in particular, for doped silicon, which can be readily integrated in electronic microstructures and have a high thermoelectric power factor. Here, we examine the impact of nanovoids on the thermal conductivity of highly doped, high-power factor polysilicon thin films using time-domain thermoreflectance. Voids are formed through ion implantation and annealing, evolving from many small (˜4 nm mean diameter) voids after 500 °C anneal to fewer, larger (˜29 nm mean diameter) voids with a constant total volume fraction after staged thermal annealing to 1000 °C. The thermal conductivity is reduced to 65% of the non-implanted reference film conductivity after implantation and 500 °C anneal, increasing with anneal temperature until fully restored after 800 °C anneal. The void size distributions are determined experimentally using small-angle and wide-angle X-ray scattering. While we believe multiple physical mechanisms are at play, we are able to corroborate the positive correlation between measurements of thermal conductivity and void size with Monte Carlo calculations and a scattering probability based on Matthiessen's rule. The data suggest an opportunity for thermal conductivity suppression combined with the high power factor for increased material zT and efficiency of nanostructured polysilicon as a thermoelectric material.

Battery cell thermal-conductive coating increases efficiency

NASA Technical Reports Server (NTRS)

Doyle, H. M.

1973-01-01

Thin coating of high-temperature epoxy resin provides necessary electrical insulation, as well as good thermal conductivity between battery cells. Insulation increases efficiency of nickel-cadmium battery, as it would any multicell battery assembly in which cell-to-cell thermal balance is critical.

Photosensitive space charge limited current in screen printed CdTe thin films

NASA Astrophysics Data System (ADS)

Vyas, C. U.; Pataniya, Pratik; Zankat, Chetan K.; Patel, Alkesh B.; Pathak, V. M.; Patel, K. D.; Solanki, G. K.

2018-05-01

Group II-VI Compounds have emerged out as most suitable in the class of photo sensitive material. They represent a strong position in terms of their applications in the field of detectors as well as photo voltaic devices. Cadmium telluride is the prime member of this Group, because of high acceptance of this material as active component in opto-electronic devices. In this paper we report preparation and characterization of CdTe thin films by using a most economical screen printing technique in association with sintering at 510°C temperature. Surface morphology and smoothness are prime parameters of any deposited to be used as an active region of devices. Thus, we studied of the screen printed thin film by means of atomic force microscopy (AFM) and scanning electron microscopy (SEM) for this purpose. However, growth processes induced intrinsic defects in fabricated films work as charge traps and affect the conduction process significantly. So the conduction mechanism of deposited CdTe thin film is studied under dark as well as illuminated conditions. It is found that the deposited films showed the space charge limited conduction (SCLC) mechanism and hence various parameters of space charge limited conduction (SCLC) of CdTe film were evaluated and discussed and the photo responsive resistance is also presented in this paper.

Design Guideline for New Generation of High-Temperature Guarded Hot Plate

NASA Astrophysics Data System (ADS)

Wu, J.; Hameury, J.; Failleau, G.; Blahut, A.; Vachova, T.; Strnad, R.; Krause, M.; Rafeld, E.; Hammerschmidt, U.

2018-02-01

This paper complements the existing measurement standards and literature for high-temperature guarded hot plates (HTGHPs) by addressing specific issues relating to thermal conductivity measurement of technical insulation at high temperatures. The examples given are focused on the designs of HTGHPs for measuring thin thermal insulation. The sensitivity studies have been carried out on major influencing factors that affect the thermal conductivity measurements using HTGHPs, e.g., the uncertainty of temperature measurements, plate flatness and center-guard gap design and imbalance. A new configuration of center-guard gap with triangular shape cross section has been optimized to obtain the same thermal resistance as a 2 mm wide gap with rectangular shape cross section that has been used in the HTGHPs at NPL and LNE. Recommendations have been made on the selections of heater plate materials, high-temperature high-emissivity coatings and miniature temperature sensors. For the first time, thermal stress analysis method has been applied to the field of HTGHPs, in order to estimate the effect of differential thermal expansion on the flatness of thin rigid specimens during thermal conductivity tests in a GHP.

Hierarchically structured Co₃O₄@Pt@MnO₂ nanowire arrays for high-performance supercapacitors.

PubMed

Xia, Hui; Zhu, Dongdong; Luo, Zhentao; Yu, Yue; Shi, Xiaoqin; Yuan, Guoliang; Xie, Jianping

2013-10-17

Here we proposed a novel architectural design of a ternary MnO2-based electrode - a hierarchical Co3O4@Pt@MnO2 core-shell-shell structure, where the complemental features of the three key components (a well-defined Co3O4 nanowire array on the conductive Ti substrate, an ultrathin layer of small Pt nanoparticles, and a thin layer of MnO2 nanoflakes) are strategically combined into a single entity to synergize and construct a high-performance electrode for supercapacitors. Owing to the high conductivity of the well-defined Co3O4 nanowire arrays, in which the conductivity was further enhanced by a thin metal (Pt) coating layer, in combination with the large surface area provided by the small MnO2 nanoflakes, the as-fabricated Co3O4@Pt@MnO2 nanowire arrays have exhibited high specific capacitances, good rate capability, and excellent cycling stability. The architectural design demonstrated in this study provides a new approach to fabricate high-performance MnO2-based nanowire arrays for constructing next-generation supercapacitors.

Hierarchically Structured Co3O4@Pt@MnO2 Nanowire Arrays for High-Performance Supercapacitors

NASA Astrophysics Data System (ADS)

Xia, Hui; Zhu, Dongdong; Luo, Zhentao; Yu, Yue; Shi, Xiaoqin; Yuan, Guoliang; Xie, Jianping

2013-10-01

Here we proposed a novel architectural design of a ternary MnO2-based electrode - a hierarchical Co3O4@Pt@MnO2 core-shell-shell structure, where the complemental features of the three key components (a well-defined Co3O4 nanowire array on the conductive Ti substrate, an ultrathin layer of small Pt nanoparticles, and a thin layer of MnO2 nanoflakes) are strategically combined into a single entity to synergize and construct a high-performance electrode for supercapacitors. Owing to the high conductivity of the well-defined Co3O4 nanowire arrays, in which the conductivity was further enhanced by a thin metal (Pt) coating layer, in combination with the large surface area provided by the small MnO2 nanoflakes, the as-fabricated Co3O4@Pt@MnO2 nanowire arrays have exhibited high specific capacitances, good rate capability, and excellent cycling stability. The architectural design demonstrated in this study provides a new approach to fabricate high-performance MnO2-based nanowire arrays for constructing next-generation supercapacitors.

Highly Conductive Transparent and Flexible Electrodes Including Double-Stacked Thin Metal Films for Transparent Flexible Electronics.

PubMed

Han, Jun Hee; Kim, Do-Hong; Jeong, Eun Gyo; Lee, Tae-Woo; Lee, Myung Keun; Park, Jeong Woo; Lee, Hoseung; Choi, Kyung Cheol

2017-05-17

To keep pace with the era of transparent and deformable electronics, electrode functions should be improved. In this paper, an innovative structure is suggested to overcome the trade-off between optical and electrical properties that commonly arises with transparent electrodes. The structure of double-stacked metal films showed high conductivity (<3 Ω/sq) and high transparency (∼90%) simultaneously. A proper space between two metal films led to high transmittance by an optical phenomenon. The principle of parallel connection allowed the electrode to have high conductivity. In situ fabrication was possible because the only materials composing the electrode were silver and WO 3 , which can be deposited by thermal evaporation. The electrode was flexible enough to withstand 10 000 bending cycles with a 1 mm bending radius. Furthermore, a few μm scale patterning of the electrode was easily implemented by using photolithography, which is widely employed industrially for patterning. Flexible organic light-emitting diodes and a transparent flexible thin-film transistor were successfully fabricated with the proposed electrode. Various practical applications of this electrode to new transparent flexible electronics are expected.

Preparation of thin film silver fluoride electrodes from constituent elements

NASA Technical Reports Server (NTRS)

Odonnell, P. M.

1972-01-01

The feasibility of preparing thin-film metal fluoride electrodes from the elemental constituents has been demonstrated. Silver fluoride cathodes were prepared by deposition of silver on a conducting graphite substrate followed by fluorination under controlled conditions using elemental fluorine. The resulting electrodes were of high purity, and the variables such as size, shape, and thickness were easily controlled.

Hydrothermal Barium Titanate Thin-Film Characteristics and their Suitability as Decoupling Capacitors

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

Raj, P. Markondeya; Lee, Baik-Woo; Kang, Nam-Kee

System integration and miniaturization demands are driving integrated thin film capacitor technologies towards ultrahigh capacitance densities for noise-free power supply, power conversion and efficient power management. Hydrothermal route can deposit crystalline ferroelectric films at low temperatures of less than 150 C. It is hence an attractive route for integrating high permittivity thin film capacitors on organic, silicon or flex substrates. However, hydrothermal films are not commercialized so far because of their inferior insulation characteristics. Embedded hydroxyl groups are attributed to be the cause for high leakage currents, temperature dependent properties and lower Breakdown Voltages (BDVs). This paper discusses the dielectricmore » characteristics such as capacitance density, leakage currents and Temperature Coefficient of Capacitance (TCC) of hydrothermal barium titanate films and correlates them to the embedded water and OH groups, film morphology, stoichiometry and crystallinity. With thermal treatment, majority of the OH groups can be removed leading to improved insulation characteristics. The room temperature I-V characteristics agreed with ionic conduction models for films baked at 160 C while higher baking temperatures of above 300 C resulted in Poole-Frenkel type conduction. A brief perspective is provided on the suitability of hydrothermal thin film capacitors for power supply applications.« less

Highly uniform resistive switching properties of amorphous InGaZnO thin films prepared by a low temperature photochemical solution deposition method.

PubMed

Hu, Wei; Zou, Lilan; Chen, Xinman; Qin, Ni; Li, Shuwei; Bao, Dinghua

2014-04-09

We report on highly uniform resistive switching properties of amorphous InGaZnO (a-IGZO) thin films. The thin films were fabricated by a low temperature photochemical solution deposition method, a simple process combining chemical solution deposition and ultraviolet (UV) irradiation treatment. The a-IGZO based resistive switching devices exhibit long retention, good endurance, uniform switching voltages, and stable distribution of low and high resistance states. Electrical conduction mechanisms were also discussed on the basis of the current-voltage characteristics and their temperature dependence. The excellent resistive switching properties can be attributed to the reduction of organic- and hydrogen-based elements and the formation of enhanced metal-oxide bonding and metal-hydroxide bonding networks by hydrogen bonding due to UV irradiation, based on Fourier-transform-infrared spectroscopy, X-ray photoelectron spectroscopy, and Field emission scanning electron microscopy analysis of the thin films. This study suggests that a-IGZO thin films have potential applications in resistive random access memory and the low temperature photochemical solution deposition method can find the opportunity for further achieving system on panel applications if the a-IGZO resistive switching cells were integrated with a-IGZO thin film transistors.

High quality transparent conducting oxide thin films

DOEpatents

Gessert, Timothy A.; Duenow, Joel N.; Barnes, Teresa; Coutts, Timothy J.

2012-08-28

A transparent conducting oxide (TCO) film comprising: a TCO layer, and dopants selected from the elements consisting of Vanadium, Molybdenum, Tantalum, Niobium, Antimony, Titanium, Zirconium, and Hafnium, wherein the elements are n-type dopants; and wherein the transparent conducting oxide is characterized by an improved electron mobility of about 42 cm.sup.2/V-sec while simultaneously maintaining a high carrier density of .about.4.4e.times.10.sup.20 cm.sup.-3.

Micro-patterned ZnO semiconductors for high performance thin film transistors via chemical imprinting with a PDMS stamp.

PubMed

Seong, Kieun; Kim, Kyongjun; Park, Si Yun; Kim, Youn Sang

2013-04-07

Chemical imprinting was conducted on ZnO semiconductor films via a chemical reaction at the contact regions between a micro-patterned PDMS stamp and ZnO films. In addition, we applied the chemical imprinting on Li doped ZnO thin films for high performance TFTs fabrication. The representative micro-patterned Li doped ZnO TFTs showed a field effect mobility of 4.2 cm(2) V(-1) s(-1) after sintering at 300 °C.

Comparison of the Thermal Degradation of Heavily Nb-Doped and Normal PZT Thin Films.

PubMed

Yang, Jeong-Suong; Kang, YunSung; Kang, Inyoung; Lim, SeungMo; Shin, Seung-Joo; Lee, JungWon; Hur, Kang Heon

2017-03-01

The degradation of niobium-doped lead zirconate titanate (PZT) and two types of PZT thin films were investigated. Undoped PZT, two-step PZT, and heavily Nb-doped PZT (PNZT) around the morphotropic phase boundary were in situ deposited under optimum condition by RF-magnetron sputtering. All 2- [Formula: see text]-thick films had dense perovskite columnar grain structure and self-polarized (100) dominant orientation. PZT thin films were deposited on Pt/TiO x bottom electrode on Si wafer, and PNZT thin film was on Ir/TiW electrode with the help of orientation control. Sputtered PZT films formed on microelectromechanical system (MEMS) gyroscope and the degradation rates were compared at different temperatures. PNZT showed the best resistance to the thermal degradation, followed by two-step PZT. To clarify the effect of oxygen vacancies on the degradation of the film at high temperature, photoluminescence measurement was conducted, which confirmed that oxygen vacancy rate was the lowest in heavy PNZT. Nb-doping PZT thin films suppressed the oxygen deficit and made high imprint with self-polarization. This defect distribution and high internal field allowed PNZT thin film to make the piezoelectric sensors more stable and reliable at high temperature, such as reflow process of MEMS packaging.

An investigation of flow-limited field-injection electrostatic spraying (FFESS) and its applications to thin film deposition

NASA Astrophysics Data System (ADS)

Singh, Ravindra Pratap

Electrostatic spraying is the process of controlled disruption of a liquid surface due to excess surface charge density. The technique has found applications in a wide range of fields from agricultural sprays to fuel injectors to colloidal thrusters for space vehicle propulsion. Over the past 20 years, the technique has been intensely studied in material processing for synthesis of ceramic and metal powders, nanoparticles and thin films. The importance of the technique lies in its simple setup, high deposition efficiency, and ambient atmosphere operation. In conventional electrostatic spraying (CESS), one uses a conducting nozzle to charge the liquid, mostly by induction charging. CESS is therefore restricted to the single jet mode of spraying which occurs at low spray currents. It lacks stability and reproducibility in the high current, multiple jet regime, which can generate much finer sprays. In flow-limited field-injection electrostatic spraying (FFESS), one uses a field-injection electrode to stably and controllably inject higher currents into the liquid, a la Fowler-Nordheim, using an otherwise insulating nozzle. This way, it is possible to stably electrospray in the multiple jet mode. In addition to producing much finer sprays, the multi-jet mode atomizes liquids at higher rates, and spreads the spray over a wider region and more uniformly than single jet sprays, thus paving way for large-area uniform thin film deposition. A simple yet comprehensive theory is formulated to describe the multi jet formation. The theory, which is based on the energy minimization principle, takes into account, for the first time, the interactions between charged jets which leads to saturation in the number of jets at high spray currents. The possibility of using an array of nozzles to obtain uniform large-area high-throughput thin film deposition is also investigated. A large number of FFESS nozzles with alternating positive and negative polarities arranged in a periodic 2-dimensional array are found to produce uniform thin films over large areas. Deposition of TiO2 and silver thin films using multi jet FFESS is studied, demonstrating great control on film morphology and properties. TiO2 thin films deposited on high-intensity discharge arc lamps are found to improve the quality of its light output. Silver thin films of high purity and conductivity, and with good adhesion, could be deposited at relatively high deposition rates and high deposition efficiency as compared to CVD techniques.

Structure and conductivity of epitaxial thin films of barium ferrite and its hydrated form BaFeO2.5-x+δ (OH)2x

NASA Astrophysics Data System (ADS)

Anitha Sukkurji, Parvathy; Molinari, Alan; Benes, Alexander; Loho, Christoph; Sai Kiran Chakravadhanula, Venkata; Garlapati, Suresh Kumar; Kruk, Robert; Clemens, Oliver

2017-03-01

Barium ferrite and its hydrated form (BaFeO2.5-x+δ (OH)2x , BFO) is an interesting cathode material for protonic ceramic fuel cells (PCFC) due to its potential to be both, conducting for electrons and protons. We report on the fabrication of almost epitaxially grown thin films (22 nm) of barium ferrite BaFeO~2.5 (BFO) on Nb-doped SrTiO3 substrates via pulsed laser deposition (PLD), followed by treatment under inert, and subsequently wet inert atmospheres to induce water (respectively proton) incorporation. Microstructure, chemical composition and conducting properties are investigated for the BFO films and their hydrated forms, highlighting the influence of hydration on the conductivity characteristics between ~200-290 K. We find that water incorporation gives a strong enhancement of the conductivity to ~10-9 S cm-1 compared to argon annealed films, inducing electronic and protonic charge carriers at the same time. In comparison to bulk powders, proton conductivity is found to be strongly suppressed in such thin hydrated BFO films, pointing towards the influence of strain on the conductivity, which is evaluated based on a detailed investigation by high-resolution transmission electron microscopy.

Thin-Film Phase Plates for Transmission Electron Microscopy Fabricated from Metallic Glasses.

PubMed

Dries, Manuel; Hettler, Simon; Schulze, Tina; Send, Winfried; Müller, Erich; Schneider, Reinhard; Gerthsen, Dagmar; Luo, Yuansu; Samwer, Konrad

2016-10-01

Thin-film phase plates (PPs) have become an interesting tool to enhance the contrast of weak-phase objects in transmission electron microscopy (TEM). The thin film usually consists of amorphous carbon, which suffers from quick degeneration under the intense electron-beam illumination. Recent investigations have focused on the search for alternative materials with an improved material stability. This work presents thin-film PPs fabricated from metallic glass alloys, which are characterized by a high electrical conductivity and an amorphous structure. Thin films of the zirconium-based alloy Zr65.0Al7.5Cu27.5 (ZAC) were fabricated and their phase-shifting properties were evaluated. The ZAC film was investigated by different TEM techniques, which reveal beneficial properties compared with amorphous carbon PPs. Particularly favorable is the small probability for inelastic plasmon scattering, which results from the combined effect of a moderate inelastic mean free path and a reduced film thickness due to a high mean inner potential. Small probability plasmon scattering improves contrast transfer at high spatial frequencies, which makes the ZAC alloy a promising material for PP fabrication.

Facile green synthesis of silver nanodendrite/cellulose acetate thin film electrodes for flexible supercapacitors.

PubMed

Devarayan, Kesavan; Park, Jiyoung; Kim, Hak-Yong; Kim, Byoung-Suhk

2017-05-01

In this study, we present a highly efficient and economical solution called as 'in situ hydrogenation' for preparation of highly conductive thin film electrode based on silver nanodendrites. The silver nanodendrite (AgND)/cellulose acetate (CA) thin film electrodes exhibited sheet resistance ranging from 0.32ohm/sq to 122.1ohm/sq which could be controlled by changing the concentration of both silver and polymer. In addition, these electrodes exhibited outstanding toughness during the bending test. Further, these thin film electrodes have great potential for scale-up with an average weight of 3mg/cm 2 and can be also combined with active nanomaterials such as multiwalled carbon nanotubes (MWCNTs) to fabricate AgND/CA/MWCNTs thin film for high-performance flexible supercapacitor electrode. The AgND/CA/MWCNTs electrodes exhibited a maximum specific capacitance of 237F/g at a current density of 0.3A/g. After 1000 cycles, the AgND/MWCNT/CA exhibited a decrease of 16.0% of specific capacitance. Copyright © 2017 Elsevier Ltd. All rights reserved.

Thermoelectric Properties of Nanograined Si-Ge-Au Thin Films Grown by Molecular Beam Deposition

NASA Astrophysics Data System (ADS)

Nishino, Shunsuke; Ekino, Satoshi; Inukai, Manabu; Omprakash, Muthusamy; Adachi, Masahiro; Kiyama, Makoto; Yamamoto, Yoshiyuki; Takeuchi, Tsunehiro

2018-06-01

Conditions to achieve extremely large Seebeck coefficient and extremely small thermal conductivity in Si-Ge-Au thin films formed of nanosized grains precipitated in amorphous matrix have been investigated. We employed molecular beam deposition to prepare Si1- x Ge x Au y thin films on sapphire substrate. The deposited films were annealed under nitrogen gas atmosphere at 300°C to 500°C for 15 min to 30 min. Nanocrystals dispersed in amorphous matrix were clearly observed by transmission electron microscopy. We did not observe anomalously large Seebeck coefficient, but very low thermal conductivity of nearly 1.0 W K-1 m-1 was found at around 0.2 < x < 0.6. The compositional dependence of the thermal conductivity was well accounted for by the compositional dependence of the mixing entropy. Some of these values agree exactly with the amorphous limit predicted by theoretical calculations. The smallest lattice thermal conductivity found for the present samples is lower than that of nanostructured Si-Ge bulk material for which dimensionless figure of merit of ZT ≈ 1 was reported at high temperature.

Effects of rim thickness on spur gear bending stress

NASA Technical Reports Server (NTRS)

Bibel, G. D.; Reddy, S. K.; Savage, M.; Handschuh, R. F.

1991-01-01

Thin rim gears find application in high-power, light-weight aircraft transmissions. Bending stresses in thin rim spur gear tooth fillets and root areas differ from the stresses in solid gears due to rim deformations. Rim thickness is a significant design parameter for these gears. To study this parameter, a finite element analysis was conducted on a segment of a thin rim gear. The rim thickness was varied and the location and magnitude of the maximum bending stresses reported. Design limits are discussed and compared with the results of other researchers.

Terahertz study of hole transport in pentacene thin films

NASA Astrophysics Data System (ADS)

Engelbrecht, Stefan G.; Prinz, Markus; Arend, Thomas R.; Kersting, Roland

2014-10-01

Terahertz electromodulation spectroscopy is a novel tool for studying charge carrier transport in polycrys­talline thin films. The technique selectively probes the high-frequency response of mobile carriers and is insensitive to scattering at grain boundaries as well as to trapping processes. In thin films of pentacene we find a hole mobility of 21 cm2 /Vs, which exceeds the largest previously reported values obtained in poly­ crystalline pentacene. Additionally, the data provide an upper limit of the hole conductivity effective mass of mh ≍ 0.8 me.

Thin film electronic devices with conductive and transparent gas and moisture permeation barriers

DOEpatents

Simpson, Lin Jay

2015-07-28

Thin film electronic devices (or stacks integrated with a substrate) that include a permeation barrier formed of a thin layer of metal that provides a light transmitting and electrically conductive layer, wherein the electrical conductive layer is formed on a surface of the substrate or device layer such as a transparent conducting material layer with pin holes or defects caused by manufacturing and the thin layer of metal is deposited on the conductive layer and formed from a self-healing metal that forms self-terminating oxides. A permeation plug or block is formed in or adjacent to the thin film of metal at or proximate to the pin holes to block further permeation of contaminants through the pin holes.

Facile preparation of hierarchical nanostructured CuInS2 counter electrodes for dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Dhas, C. Ravi; Christy, A. Jennifer; Venkatesh, R.; Santhoshi Monica, S. Esther; Panda, Subhendu K.; Subramanian, B.; Ravichandran, K.; Sudhagar, P.; Ezhil Raj, A. Moses

2017-12-01

CuInS2 (CIS) thin films have been synthesized onto the glass substrates for different solvent volumes (10, 30, 50 and 70 ml) by nebulizer spray technique. The effect of solvent volume on the structural, morphological, compositional, optical and electrical properties of CIS thin films has been investigated. X-ray diffraction patterns suggest that the obtained CIS films are polycrystalline with the tetragonal structure. The surface morphology of the prepared CIS films purely depends on the solvent volume. The elemental quantitative investigation and the stoichiometric ratio of the CIS thin films were verified from XPS and EDS. High absorbance with the optical band gap of 1.13 eV was obtained at the higher solvent volume. All the deposited CIS thin films exhibited p-type semiconducting behavior with the high electrical conductivity and carrier concentration. CIS thin films deposited onto the FTO substrate were used as a counter electrode (CE) in dye-sensitized solar cells. CIS CEs possessed high electrocatalytic behavior and fast electron charge transfer at the CE/electrolyte interface. The CIS CE prepared using 50 ml solvent volume generated high energy conversion efficiency of about 3.25%.

Photovoltaic cell assembly

DOEpatents

Beavis, Leonard C.; Panitz, Janda K. G.; Sharp, Donald J.

1990-01-01

A photovoltaic assembly for converting high intensity solar radiation into lectrical energy in which a solar cell is separated from a heat sink by a thin layer of a composite material which has excellent dielectric properties and good thermal conductivity. This composite material is a thin film of porous Al.sub.2 O.sub.3 in which the pores have been substantially filled with an electrophoretically-deposited layer of a styrene-acrylate resin. This composite provides electrical breakdown strengths greater than that of a layer consisting essentially of Al.sub.2 O.sub.3 and has a higher thermal conductivity than a layer of styrene-acrylate alone.

Thermal Characterization of Nanostructures and Advanced Engineered Materials

NASA Astrophysics Data System (ADS)

Goyal, Vivek Kumar

Continuous downscaling of Si complementary metal-oxide semiconductor (CMOS) technology and progress in high-power electronics demand more efficient heat removal techniques to handle the increasing power density and rising temperature of hot spots. For this reason, it is important to investigate thermal properties of materials at nanometer scale and identify materials with the extremely large or extremely low thermal conductivity for applications as heat spreaders or heat insulators in the next generation of integrated circuits. The thin films used in microelectronic and photonic devices need to have high thermal conductivity in order to transfer the dissipated power to heat sinks more effectively. On the other hand, thermoelectric devices call for materials or structures with low thermal conductivity because the performance of thermoelectric devices is determined by the figure of merit Z=S2sigma/K, where S is the Seebeck coefficient, K and sigma are the thermal and electrical conductivity, respectively. Nanostructured superlattices can have drastically reduced thermal conductivity as compared to their bulk counterparts making them promising candidates for high-efficiency thermoelectric materials. Other applications calling for thin films with low thermal conductivity value are high-temperature coatings for engines. Thus, materials with both high thermal conductivity and low thermal conductivity are technologically important. The increasing temperature of the hot spots in state-of-the-art chips stimulates the search for innovative methods for heat removal. One promising approach is to incorporate materials, which have high thermal conductivity into the chip design. Two suitable candidates for such applications are diamond and graphene. Another approach is to integrate the high-efficiency thermoelectric elements for on-spot cooling. In addition, there is strong motivation for improved thermal interface materials (TIMs) for heat transfer from the heat-generating chip to heat-sinking units. This dissertation presents results of the experimental investigation and theoretical interpretation of thermal transport in the advanced engineered materials, which include thin films for thermal management of nanoscale devices, nanostructured superlattices as promising candidates for high-efficiency thermoelectric materials, and improved TIMs with graphene and metal particles as fillers providing enhanced thermal conductivity. The advanced engineered materials studied include chemical vapor deposition (CVD) grown ultrananocrystalline diamond (UNCD) and microcrystalline diamond (MCD) films on Si substrates, directly integrated nanocrystalline diamond (NCD) films on GaN, free-standing polycrystalline graphene (PCG) films, graphene oxide (GOx) films, and "pseudo-superlattices" of the mechanically exfoliated Bi2Te3 topological insulator films, and thermal interface materials (TIMs) with graphene fillers.

Fabrication of high crystalline SnS and SnS2 thin films, and their switching device characteristics.

PubMed

Choi, Hyeongsu; Lee, Jeongsu; Shin, Seokyoon; Lee, Juhyun; Lee, Seungjin; Park, Hyunwoo; Kwon, Sejin; Lee, Namgue; Bang, Minwook; Lee, Seung-Beck; Jeon, Hyeongtag

2018-05-25

Representative tin sulfide compounds, tin monosulfide (SnS) and tin disulfide (SnS 2 ) are strong candidates for future nanoelectronic devices, based on non-toxicity, low cost, unique structures and optoelectronic properties. However, it is insufficient for synthesizing of tin sulfide thin films using vapor phase deposition method which is capable of fabricating reproducible device and securing high quality films, and their device characteristics. In this study, we obtained highly crystalline SnS thin films by atomic layer deposition and obtained highly crystalline SnS 2 thin films by phase transition of the SnS thin films. The SnS thin film was transformed into SnS 2 thin film by annealing at 450 °C for 1 h in H 2 S atmosphere. This phase transition was confirmed by x-ray diffractometer and x-ray photoelectron spectroscopy, and we studied the cause of the phase transition. We then compared the film characteristics of these two tin sulfide thin films and their switching device characteristics. SnS and SnS 2 thin films had optical bandgaps of 1.35 and 2.70 eV, and absorption coefficients of about 10 5 and 10 4 cm -1 in the visible region, respectively. In addition, SnS and SnS 2 thin films exhibited p-type and n-type semiconductor characteristics. In the images of high resolution-transmission electron microscopy, SnS and SnS 2 directly showed a highly crystalline orthorhombic and hexagonal layered structure. The field effect transistors of SnS and SnS 2 thin films exhibited on-off drain current ratios of 8.8 and 2.1 × 10 3 and mobilities of 0.21 and 0.014 cm 2 V -1 s -1 , respectively. This difference in switching device characteristics mainly depends on the carrier concentration because it contributes to off-state conductance and mobility. The major carrier concentrations of the SnS and SnS 2 thin films were 6.0 × 10 16 and 8.7 × 10 13 cm -3 , respectively, in this experiment.

Fabrication of high crystalline SnS and SnS2 thin films, and their switching device characteristics

NASA Astrophysics Data System (ADS)

Choi, Hyeongsu; Lee, Jeongsu; Shin, Seokyoon; Lee, Juhyun; Lee, Seungjin; Park, Hyunwoo; Kwon, Sejin; Lee, Namgue; Bang, Minwook; Lee, Seung-Beck; Jeon, Hyeongtag

2018-05-01

Representative tin sulfide compounds, tin monosulfide (SnS) and tin disulfide (SnS2) are strong candidates for future nanoelectronic devices, based on non-toxicity, low cost, unique structures and optoelectronic properties. However, it is insufficient for synthesizing of tin sulfide thin films using vapor phase deposition method which is capable of fabricating reproducible device and securing high quality films, and their device characteristics. In this study, we obtained highly crystalline SnS thin films by atomic layer deposition and obtained highly crystalline SnS2 thin films by phase transition of the SnS thin films. The SnS thin film was transformed into SnS2 thin film by annealing at 450 °C for 1 h in H2S atmosphere. This phase transition was confirmed by x-ray diffractometer and x-ray photoelectron spectroscopy, and we studied the cause of the phase transition. We then compared the film characteristics of these two tin sulfide thin films and their switching device characteristics. SnS and SnS2 thin films had optical bandgaps of 1.35 and 2.70 eV, and absorption coefficients of about 105 and 104 cm‑1 in the visible region, respectively. In addition, SnS and SnS2 thin films exhibited p-type and n-type semiconductor characteristics. In the images of high resolution-transmission electron microscopy, SnS and SnS2 directly showed a highly crystalline orthorhombic and hexagonal layered structure. The field effect transistors of SnS and SnS2 thin films exhibited on–off drain current ratios of 8.8 and 2.1 × 103 and mobilities of 0.21 and 0.014 cm2 V‑1 s‑1, respectively. This difference in switching device characteristics mainly depends on the carrier concentration because it contributes to off-state conductance and mobility. The major carrier concentrations of the SnS and SnS2 thin films were 6.0 × 1016 and 8.7 × 1013 cm‑3, respectively, in this experiment.

Structural, electrical and optical properties of Al-Sn codoped ZnO transparent conducting layer deposited by spray pyrolysis technique

NASA Astrophysics Data System (ADS)

Bedia, A.; Bedia, F. Z.; Aillerie, M.; Maloufi, N.

2017-11-01

Low cost Al-Sn codoped ZnO (ATZO) Transparent Conductive Oxide films were deposited by spray pyrolysis on glass substrate. The influence of Al-Sn codoping on the structural, optical and electrical properties of ZnO thin films was studied by comparing the same properties obtained in undoped ZnO, Al doped ZnO (AZO) and Sn doped ZnO (TZO) thin films. The so-obtained films crystallized in hexagonal wurtzite structure. The morphology and structural defects have been investigated by both High resolution Field Effect Scanning Electron Microscopy (FE-SEM) and Raman spectroscopy at 532 nm excitation source. In the visible region, the undoped and doped films show an average transmittance of the order of 85%, while for ATZO thin film, it is of the order of 72%, which points out a degradation of the optical properties due to the co-doping. The optical band gap of ATZO thin film achieves 3.31eV and this shift, compared to the referred samples is attributed to the Burstein-Moss (BM) and band gap narrowing (BGN) opposite effects which is due to the increase of the carrier concentration in degenerate semiconductors. Within all the samples, the ATZO thin film exhibits the lowest electrical resistivity of 4.56 × 10-3 Ωcm with a Hall mobility equal to 2.13 cm2 V-1s-1, and the highest carrier concentration of 6.41 × 1020 cm-3. The performance of ATZO transparent conductive oxide film are determined by its figure of merit (φTC), found equal to 1.69 10-4 Ω-1, which is a suitable value for potentially high-performance solar cell applications.

Water-Enabled Healing of Conducting Polymer Films.

PubMed

Zhang, Shiming; Cicoira, Fabio

2017-10-01

The conducting polymer polyethylenedioxythiophene doped with polystyrene sulfonate (PEDOT:PSS) has become one of the most successful organic conductive materials due to its high air stability, high electrical conductivity, and biocompatibility. In recent years, a great deal of attention has been paid to its fundamental physicochemical properties, but its healability has not been explored in depth. This communication reports the first observation of mechanical and electrical healability of PEDOT:PSS thin films. Upon reaching a certain thickness (about 1 µm), PEDOT:PSS thin films damaged with a sharp blade can be electrically healed by simply wetting the damaged area with water. The process is rapid, with a response time on the order of 150 ms. Significantly, after being wetted the films are transformed into autonomic self-healing materials without the need of external stimulation. This work reveals a new property of PEDOT:PSS and enables its immediate use in flexible and biocompatible electronics, such as electronic skin and bioimplanted electronics, placing conducting polymers on the front line for healing applications in electronics. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electronic Devices Based on Oxide Thin Films Fabricated by Fiber-to-Film Process.

PubMed

Meng, You; Liu, Ao; Guo, Zidong; Liu, Guoxia; Shin, Byoungchul; Noh, Yong-Young; Fortunato, Elvira; Martins, Rodrigo; Shan, Fukai

2018-05-30

Technical development for thin-film fabrication is essential for emerging metal-oxide (MO) electronics. Although impressive progress has been achieved in fabricating MO thin films, the challenges still remain. Here, we report a versatile and general thermal-induced nanomelting technique for fabricating MO thin films from the fiber networks, briefly called fiber-to-film (FTF) process. The high quality of the FTF-processed MO thin films was confirmed by various investigations. The FTF process is generally applicable to numerous technologically relevant MO thin films, including semiconducting thin films (e.g., In 2 O 3 , InZnO, and InZrZnO), conducting thin films (e.g., InSnO), and insulating thin films (e.g., AlO x ). By optimizing the fabrication process, In 2 O 3 /AlO x thin-film transistors (TFTs) were successfully integrated by fully FTF processes. High-performance TFT was achieved with an average mobility of ∼25 cm 2 /(Vs), an on/off current ratio of ∼10 7 , a threshold voltage of ∼1 V, and a device yield of 100%. As a proof of concept, one-transistor-driven pixel circuit was constructed, which exhibited high controllability over the light-emitting diodes. Logic gates based on fully FTF-processed In 2 O 3 /AlO x TFTs were further realized, which exhibited good dynamic logic responses and voltage amplification by a factor of ∼4. The FTF technique presented here offers great potential in large-area and low-cost manufacturing for flexible oxide electronics.

A display module implemented by the fast high-temperatue response of carbon nanotube thin yarns.

PubMed

Wei, Yang; Liu, Peng; Jiang, Kaili; Fan, Shoushan

2012-05-09

Suspending superaligned multiwalled carbon nanotube (MWCNT) films were processed into CNT thin yarns, about 1 μm in diameter, by laser cutting and an ethanol atomization bath treatment. The fast high-temperature response under a vacuum was revealed by monitoring the incandescent light with a photo diode. The thin yarns can be electrically heated up to 2170 K in 0.79 mS, and the succeeding cool-down time is 0.36 mS. The fast response is attributed to the ultrasmall mass of the independent single yarn, large radiation coefficient, and improved thermal conductance through the two cool ends. The millisecond response time makes it possible to use the visible hot thin yarns as light-emitting elements of an incandescent display. A fully sealed display with 16 × 16 matrix was successfully fabricated using screen-printed thick electrodes and CNT thin yarns. It can display rolling characters with a low power consumption. More applications can be further developed based on the addressable CNT thermal arrays.

Interface engineering in epitaxial growth of layered oxides via a conducting layer insertion

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

Yun, Yu; Meng, Dechao; Wang, Jianlin

2015-07-06

There is a long-standing challenge in the fabrication of layered oxide epitaxial films due to their thermodynamic phase-instability and the large stacking layer number. Recently, the demand for high-quality thin films is strongly pushed by their promising room-temperature multiferroic properties. Here, we find that by inserting a conducting and lattice matched LaNiO{sub 3} buffer layer, high quality m = 5 Bi{sub 6}FeCoTi{sub 3}O{sub 18} epitaxial films can be fabricated using the laser molecular beam epitaxy, in which the atomic-scale sharp interface between the film and the metallic buffer layer explains the enhanced quality. The magnetic and ferroelectric properties of the high qualitymore » Bi{sub 6}FeCoTi{sub 3}O{sub 18} films are studied. This study demonstrates that insertion of the conducting layer is a powerful method in achieving high quality layered oxide thin films, which opens the door to further understand the underline physics and to develop new devices.« less

Sol-gel-processed yttrium-doped NiO as hole transport layer in inverted perovskite solar cells for enhanced performance

NASA Astrophysics Data System (ADS)

Hu, Zijun; Chen, Da; Yang, Pan; Yang, Lijun; Qin, Laishun; Huang, Yuexiang; Zhao, Xiaochong

2018-05-01

In this work, high-performance inverted planar perovskite solar cells (PSCs) using sol-gel processed Y-doped NiO thin films as hole transport layer (HTL) were demonstrated. Y-doped NiO thin films containing different Y doping concentrations were successfully prepared through a simple sol-gel process. The Y doping could significantly improve the electrical conductivity of NiO thin film, and the photovoltaic performance of Y-doped NiO HTL-based PSC devices outperformed that of the pristine NiO HTL-based device. Notably, the PSC using a 5%Y-NiO HTL exhibited the champion performance with an open-circuit voltage (Voc) of 1.00 V, a short circuit current density (Jsc) of 23.82 mA cm-2, a fill factor (FF) of 68% and a power conversion efficiency (PCE) of 16.31%, resulting in a 27.62% enhancement in PCE in comparison with the NiO device. The enhanced performance of the Y-doped NiO device could be attributed to the improved hole mobility, the high quality compact active layer morphology, the more efficient charge extraction from perovskite absorber as well as the lower recombination probability of charge carriers. Thus, this work provides a simple and effective approach to improve the electrical conductivity of p-type NiO thin films for use as a promising HTL in high performance PSCs.

Thouless length and valley degeneracy factor of ZnMnO thin films with anisotropic, highly conductive surface layers

NASA Astrophysics Data System (ADS)

Vegesna, Sahitya V.; Bürger, Danilo; Patra, Rajkumar; Abendroth, Barbara; Skorupa, Ilona; Schmidt, Oliver G.; Schmidt, Heidemarie

2017-06-01

Isothermal magnetoresistance (MR) of n-type conducting Zn1-xMnxO thin films on a sapphire substrate with a Mn content of 5 at. % has been studied in in-plane and out-of-plane magnetic fields up to 6 T in the temperature range of 5 K to 300 K. During pulsed laser deposition of the ZnMnO thin films, we controlled the thickness and roughness of a highly conductive ZnMnO surface layer. The measured MR has been modeled with constant s-d exchange (0.2 eV in ZnMnO) and electron spin (S = 5/2 for Mn2+) for samples with a single two dimensional (2D) ZnMnO layer, a single three dimensional (3D) ZnMnO layer, or a 2D and 3D (2D + 3D) ZnMnO layer in parallel. The temperature dependence of modeled Thouless length LTh (LTh ˜ T-0.5) is in good agreement with the theory [Andrearczyk et al., Phys. Rev. B 72, 121309(R) (2005)]. The superimposed positive and negative MR model for ZnCoO thin films [Xu et al., Phys. Rev. B 76, 134417 (2007)] has been extended in order to account for the increase in the density of states close to the Fermi level of n-ZnMnO due to substitutional Mn2+ ions and their effect on the negative MR in ZnMnO.

Novel Processing of a Poly(phenyleneoxide) - b –Poly(vinylbenzyltrimethylammonium) Copolymer Anion Exchange Membrane; The Effect On Mechanical And Transport Properties

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

Pandey, Tara P.; Seifert, Soenke; Yang, Yating

2016-12-01

A poly(2,6 dimethyl 1,4-phenylene oxide)-b-poly(vinyl benzyl) chloride copolymer membranes was processed by solvent casting followed by melt pressing (SCMP) to provide uniformly thin films, 25 +/- 5 mu m, with improved conductivity, mechanical strength, water uptake, dimensional swelling, and chemical stability under 1 M KOH and 80 degrees C. These properties depended strongly on the length of the melt-pressing time. The solvent cast membranes melt pressing time was optimized to provided highly conductive membranes (high OH- conductivity of 75 +/- 25 mS cm(-1) for an IEC of 1.8 mmol g(-1) at room temperature in water). Membranes that were only solventmore » cast and not melt-pressed swelled excessively and had insufficient mechanical integrity for detailed study. When the copolymer powder was melt pressed (without prior solvent casting) at 240 degrees C and ca. 30 MPa for 20 minutes, membranes with high mechanical strength (tensile stress at break of 32 +/- 6 MPa at 25% RH and 29 +/- 3 MPa when 95% RH at 60 degrees C), high conductivity (Cl conductivity of 80 mS/cm at 90 degrees C and 95% RH), and lower water uptake were formed. However, melt pressing alone did not give larger then 5 cm x 5 cm area films, homogeneously thin (< 60 mu m), or mechanical defect-free membranes. The SCMP membranes were uniformly thin, and thermally crosslinked. The mass loss via dehydrochlorination indicated by TGA and elemental analysis confirmed the crosslinking via thermal melt pressing. The SCMP membranes thickness could be reduced by more than 50% (25 +/- 5 mu m) compared to melt pressing alone, and the Cl conductivity increased by 44% at 90 degrees C and 95% RH. The tensile stress at break of the SCMP membranes, however, was reduced by 50% at 25% RH.« less

Engineering the Charge Transport of Ag Nanocrystals for Highly Accurate, Wearable Temperature Sensors through All-Solution Processes.

PubMed

Joh, Hyungmok; Lee, Seung-Wook; Seong, Mingi; Lee, Woo Seok; Oh, Soong Ju

2017-06-01

All-nanocrystal (NC)-based and all-solution-processed wearable resistance temperature detectors (RTDs) are introduced. The charge transport mechanisms of Ag NC thin films are engineered through various ligand treatments to design high performance RTDs. Highly conductive Ag NC thin films exhibiting metallic transport behavior with high positive temperature coefficients of resistance (TCRs) are achieved through tetrabutylammonium bromide treatment. Ag NC thin films showing hopping transport with high negative TCRs are created through organic ligand treatment. All-solution-based, one-step photolithography techniques that integrate two distinct opposite-sign TCR Ag NC thin films into an ultrathin single device are developed to decouple the mechanical effects such as human motion. The unconventional materials design and strategy enables highly accurate, sensitive, wearable and motion-free RTDs, demonstrated by experiments on moving or curved objects such as human skin, and simulation results based on charge transport analysis. This strategy provides a low cost and simple method to design wearable multifunctional sensors with high sensitivity which could be utilized in various fields such as biointegrated sensors or electronic skin. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Direct charge carrier injection into Ga2O3 thin films using an In2O3 cathode buffer layer: their optical, electrical and surface state properties

NASA Astrophysics Data System (ADS)

Cui, W.; Zhao, X. L.; An, Y. H.; Guo, D. Y.; Qing, X. Y.; Wu, Z. P.; Li, P. G.; Li, L. H.; Cui, C.; Tang, W. H.

2017-04-01

Conductive Ga2O3 thin films with an In2O3 buffer layer have been prepared on c-plane sapphire substrates using a laser molecular beam epitaxy technique. The effects of the In2O3 buffer layer on the structure and optical, electrical and surface state properties of the Ga2O3 films have been studied. The change in conductivity of the thin films is attributed to different thicknesses of the In2O3 buffer layer, which determine the concentration of charge carriers injected into the upper Ga2O3 layer from the interface of the bilayer thin films. In addition, the increase in flat band voltage shift and capacitance values as the In2O3 buffer layer thickens are attributed to the increase in surface state density, which also contributes to the rapid shrinkage of the optical band gap of the Ga2O3. With transparency to visible light, high n-type conduction and the ability to tune the optical band gap and surface state density, we propose that Ga2O3/In2O3 bilayer thin film is an ideal n-type semiconductor for fabrication of transparent power devices, solar cell electrodes and gas sensors.

Electrical properties of aluminum contacts deposited by DC sputtering method for photovoltaic applications

NASA Astrophysics Data System (ADS)

Krawczak, Ewelina; Gułkowski, Sławomir

2017-10-01

The use of aluminum contacts is common in the process of silicon solar cells production because of low contact resistivity. It has also a great importance in thin film technology for photovoltaics, especially in copper-indium-gallium-diselenide (CIGS) devices. The final stage of CIGS cell production is the top contact deposition of high conductivity layer for lateral current collection. Such material has to be highly optically transparent as well. In order to make a contact, metal is deposited onto TCO layer with minimum shadowing to allow as much light as possible into device. The metal grid contact is being made by deposition of few microns of aluminum. The resistivity of the deposited material as well as resistance between the metal grid and TCO layer plays a great role in high quality solar cell production. This paper presents the results of four point probe conductivity analysis of Al thin films deposited by direct current (DC) magnetron sputtering method. Influence of technological parameters of the Al deposition process on sheet resistance of deposited layers has been showed. In order to obtain the lowest resistivity of the thin contact layer, optimal set of sputtering parameters, i.e. power applied, deposition time and deposition pressure was found. The resistivity of the contact between two adjacent Al metal fingers deposited onto transparent conductive Al-doped zinc oxide film has been also examined.

YSZ thin films with minimized grain boundary resistivity

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

Mills, Edmund M.; Kleine-Boymann, Matthias; Janek, Juergen

2016-03-31

In recent years, interface engineering of solid electrolytes has been explored to increase their ionic conductivity and improve the performance of solid oxide fuel cells and other electrochemical power sources. It has been observed that the ionic conductivity of epitaxially grown thin films of some electrolytes is dramatically enhanced, which is often attributed to effects (e. g. strain-induced mobility changes) at the heterophase boundary with the substrate. Still largely unexplored is the possibility of manipulation of grain boundary resistivity in polycrystalline solid electrolyte films, clearly a limiting factor in their ionic conductivity. Here we report that the ionic conductivity ofmore » yttria stabilized zirconia thin films with nano-­ columnar grains grown on a MgO substrate nearly reaches that of the corresponding single crystal when the thickness of the films becomes less than roughly 8 nm (smaller by a factor of three at 500°C). Using impedance spectroscopy, the grain boundary resistivity was probed as a function of film thickness. The resistivity of the grain boundaries near the film- substrate interface and film surface (within 4 nm of each) was almost entirely eliminated. This minimization of grain boundary resistivity is attributed to Mg2+ diffusion from the MgO substrate into the YSZ grain boundaries, which is supported by time of flight secondary ion mass spectroscopy measurements. We suggest grain boundary “design” as an attractive method to obtain highly conductive solid electrolyte thin films.« less

YSZ thin films with minimized grain boundary resistivity

DOE PAGES

Mills, Edmund M.; Kleine-Boymann, Matthias; Janek, Juergen; ...

2016-03-31

In recent years, interface engineering of solid electrolytes has been explored to increase their ionic conductivity and improve the performance of solid oxide fuel cells and other electrochemical power sources. It has been observed that the ionic conductivity of epitaxially grown thin films of some electrolytes is dramatically enhanced, which is often attributed to effects (e.g. strain-induced mobility changes) at the heterophase boundary with the substrate. Still largely unexplored is the possibility of manipulation of grain boundary resistivity in polycrystalline solid electrolyte films, clearly a limiting factor in their ionic conductivity. Here in this paper, we report that the ionicmore » conductivity of yttria stabilized zirconia thin films with nano-columnar grains grown on a MgO substrate nearly reaches that of the corresponding single crystal when the thickness of the films becomes less than roughly 8 nm (smaller by a factor of three at 500 °C). Using impedance spectroscopy, the grain boundary resistivity was probed as a function of film thickness. The resistivity of the grain boundaries near the film–substrate interface and film surface (within 4 nm of each) was almost entirely eliminated. This minimization of grain boundary resistivity is attributed to Mg 2+ diffusion from the MgO substrate into the YSZ grain boundaries, which is supported by time of flight secondary ion mass spectroscopy measurements. We suggest grain boundary “design” as an attractive method to obtain highly conductive solid electrolyte thin films.« less

Synthesis and Characterization of Molybdenum Doped ZnO Thin Films by SILAR Deposition Method

NASA Astrophysics Data System (ADS)

Radha, R.; Sakthivelu, A.; Pradhabhan, D.

2016-08-01

Molybdenum (Mo) doped zinc oxide (ZnO) thin films were deposited on the glass substrate by Successive Ionic Layer Adsorption and Reaction (SILAR) deposition method. The effect of Mo dopant concentration of 5, 6.6 and 10 mol% on the structural, morphological, optical and electrical properties of n-type Mo doped ZnO films was studied. The X-ray diffraction (XRD) results confirmed that the Mo doped ZnO thin films were polycrystalline with wurtzite structure. The field emission scanning electron microscopy (FESEM) studies shows that the surface morphology of the films changes with Mo doping. A blue shift of the optical band gap was observed in the optical studies. Effect of Mo dopant concentration on electrical conductivity was studied and it shows comparatively high electrical conductivity at 10 mol% of Mo doping concentration.

Conduction mechanism change with transport oxide layer thickness in oxide hetero-interface diode

NASA Astrophysics Data System (ADS)

Nam, Bu-il; Park, Jong Seo; Lim, Keon-Hee; Ahn, Yong-keon; Lee, Jinwon; Park, Jun-woo; Cho, Nam-Kwang; Lee, Donggun; Lee, Han-Bo-Ram; Kim, Youn Sang

2017-07-01

An effective and facile strategy is proposed to demonstrate an engineered oxide hetero-interface of a thin film diode with a high current density and low operating voltage. The electrical characteristics of an oxide hetero-interface thin film diode are governed by two theoretical models: the space charge-limited current model and the Fowler-Nordheim (F-N) tunneling model. Interestingly, the dominant mechanism strongly depends on the insulator thickness, and the mechanism change occurs at a critical thickness. This paper shows that conduction mechanisms of oxide hetero-interface thin film diodes depend on thicknesses of transport oxide layers and that current densities of these can be exponentially increased through quantum tunneling in the diodes with the thicknesses less than 10 nm. These oxide hetero-interface diodes have great potential for low-powered transparent nanoscale applications.

Thermal conductivity of bulk and thin film β-Ga2O3 measured by the 3ω technique

NASA Astrophysics Data System (ADS)

Blumenschein, N.; Slomski, M.; Paskov, P. P.; Kaess, F.; Breckenridge, M. H.; Muth, J. F.; Paskova, T.

2018-02-01

Thermal conductivity of undoped and Sn-doped β-Ga2O3 bulk and single-crystalline thin films have been measured by the 3ω technique. The bulk samples were grown by edge-defined film-field growth (EFG) method, while the thin films were grown on c-plane sapphire by pulsed-laser deposition (PLD). All samples were with (-201) surface orientation. Thermal conductivity of bulk samples was calculated along the in-plane and cross-plane crystallographic directions, yielding a maximum value of 29 W/m-K in the [010] direction at room temperature. A slight thermal conductivity decrease was observed in the Sn-doped bulk samples, which was attributed to enhanced phonon-impurity scattering. The differential 3ω method was used for β-Ga2O3 thin film samples due to the small film thickness. Results show that both undoped and Sndoped films have a much lower thermal conductivity than that of the bulk samples, which is consistent with previous reports in the literature showing a linear relationship between thermal conductivity and film thickness. Similarly to bulk samples, Sn-doped thin films have exhibited a thermal conductivity decrease. However, this decrease was found to be much greater in thin film samples, and increased with Sn doping concentration. A correlation between thermal conductivity and defect/dislocation density was made for the undoped thin films.

Reduced graphene oxide coated thin aluminum film as an optoacoustic transmitter for high pressure and high frequency ultrasound generation

NASA Astrophysics Data System (ADS)

Hwan Lee, Seok; Park, Mi-ae; Yoh, Jack J.; Song, Hyelynn; Yun Jang, Eui; Hyup Kim, Yong; Kang, Sungchan; Seop Yoon, Yong

2012-12-01

We demonstrate that reduced graphene oxide (rGO) coated thin aluminum film is an effective optoacoustic transmitter for generating high pressure and high frequency ultrasound previously unattainable by other techniques. The rGO layer of different thickness is deposited between a 100 nm-thick aluminum film and a glass substrate. Under a pulsed laser excitation, the transmitter generates enhanced optoacoustic pressure of 64 times the aluminum-alone transmitter. A promising optoacoustic wave generation is possible by optimizing thermoelasticity of metal film and thermal conductivity of rGO in the proposed transmitter for laser-induced ultrasound applications.

Thin film method of conducting lithium-ions

DOEpatents

Zhang, J.G.; Benson, D.K.; Tracy, C.E.

1998-11-10

The present invention relates to the composition of a solid lithium-ion electrolyte based on the Li{sub 2}O-CeO{sub 2}-SiO{sub 2} system having good transparent characteristics and high ion conductivity suitable for uses in lithium batteries, electrochromic devices and other electrochemical applications. 12 figs.

Thin film method of conducting lithium-ions

DOEpatents

Zhang, Ji-Guang; Benson, David K.; Tracy, C. Edwin

1998-11-10

The present invention relates to the composition of a solid lithium-ion electrolyte based on the Li.sub.2 O--CeO.sub.2 --SiO.sub.2 system having good transparent characteristics and high ion conductivity suitable for uses in lithium batteries, electrochromic devices and other electrochemical applications.

Novel Thin Film Sensor Technology for Turbine Engine Hot Section Components

NASA Technical Reports Server (NTRS)

Wrbanek, John D.; Fralick, Gustave C.

2007-01-01

Degradation and damage that develops over time in hot section components can lead to catastrophic failure of the turbine section of aircraft engines. A range of thin film sensor technology has been demonstrated enabling on-component measurement of multiple parameters either individually or in sensor arrays including temperature, strain, heat flux, and flow. Conductive ceramics are beginning to be investigated as new materials for use as thin film sensors in the hot section, leveraging expertise in thin films and high temperature materials. The current challenges are to develop new sensor and insulation materials capable of withstanding the extreme hot section environment, and to develop techniques for applying sensors onto complex high temperature structures for aging studies of hot propulsion materials. The technology research and development ongoing at NASA Glenn Research Center for applications to future aircraft, launch vehicles, space vehicles, and ground systems is outlined.

Zirconium doped TiO{sub 2} thin films: A promising dielectric layer

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

Kumar, Arvind; Mondal, Sandip, E-mail: sandipmondal@physics.iisc.ernet.in; Rao, K. S. R. Koteswara

2016-05-06

In the present work, we have fabricated the zirconium doped TiO{sub 2} thin (ZTO) films from a facile spin – coating method. The addition of Zirconium in TiO{sub 2} offers conduction band offset to Si and consequently decreased the leakage current density by approximately two orders as compared to pure TiO{sub 2} thin (TO) films. The ZTO thin film shows a high dielectric constant 27 with a very low leakage current density ∼10{sup −8} A/cm{sup 2}. The oxide capacitate, flat band voltage and change in flat band voltage are 172 pF, -1.19 V and 54 mV. The AFM analysis confirmed the compactmore » and pore free flat surface. The RMS surface roughness is found to be 1.5 Å. The ellipsometry analysis also verified the fact with a high refractive index 2.21.« less

Electrically Conductive Polyimide Films Containing Gold Surface

NASA Technical Reports Server (NTRS)

Caplan, Maggie L.; Stoakley, Diane M.; St. Clair, Anne K.

1994-01-01

Polyimide films exhibiting high thermo-oxidative stability and including electrically conductive surface layers containing gold made by casting process. Many variations of basic process conditions, ingredients, and sequence of operations possible, and not all resulting versions of process yield electrically conductive films. Gold-containing layer formed on film surface during cure. These metallic gold-containing polyimides used in film and coating applications requiring electrical conductivity, high reflectivity, exceptional thermal stability, and/or mechanical integrity. They also find commercial potential in areas ranging from thin films for satellite antennas to decorative coatings and packaging.

High quality thin films of thermoelectric misfit cobalt oxides prepared by a chemical solution method

PubMed Central

Rivas-Murias, Beatriz; Manuel Vila-Fungueiriño, José; Rivadulla, Francisco

2015-01-01

Misfit cobaltates ([Bi/Ba/Sr/Ca/CoO]nRS[CoO2]q) constitute the most promising family of thermoelectric oxides for high temperature energy harvesting. However, their complex structure and chemical composition makes extremely challenging their deposition by high-vacuum physical techniques. Therefore, many of them have not been prepared as thin films until now. Here we report the synthesis of high-quality epitaxial thin films of the most representative members of this family of compounds by a water-based chemical solution deposition method. The films show an exceptional crystalline quality, with an electrical conductivity and thermopower comparable to single crystals. These properties are linked to the epitaxial matching of the rock-salt layers of the structure to the substrate, producing clean interfaces free of amorphous phases. This is an important step forward for the integration of these materials with complementary n-type thermoelectric oxides in multilayer nanostructures. PMID:26153533

Highly electrically conductive layered carbon derived from polydopamine and its functions in SnO2-based lithium ion battery anodes.

PubMed

Kong, Junhua; Yee, Wu Aik; Yang, Liping; Wei, Yuefan; Phua, Si Lei; Ong, Hock Guan; Ang, Jia Ming; Li, Xu; Lu, Xuehong

2012-10-25

Thin carbonized polydopamine (C-PDA) coatings are found to have similar structures and electrical conductivities to those of multilayered graphene doped with heteroatoms. Greatly enhanced electrochemical properties are achieved with C-PDA-coated SnO(2) nanoparticles where the coating functions as a mechanical buffer layer and conducting bridge.

Studies on the high electronic energy deposition in polyaniline thin films

NASA Astrophysics Data System (ADS)

Deshpande, N. G.; Gudage, Y. G.; Vyas, J. C.; Singh, F.; Sharma, Ramphal

2008-05-01

We report here the physico-chemical changes brought about by high electronic energy deposition of gold ions in HCl doped polyaniline (PANI) thin films. PANI thin films were synthesized by in situ polymerization technique. The as-synthesized PANI thin films of thickness 160 nm were irradiated using Au7+ ion of 100 MeV energy at different fluences, namely, 5 × 1011 ions/cm2 and 5 × 1012 ions/cm2, respectively. A significant change was seen after irradiation in electrical and photo conductivity, which may be related to increased carrier concentration, and structural modifications in the polymer film. In addition, the high electronic energy deposition showed other effects like cross-linking of polymer chains, bond breaking and creation of defect sites. AFM observations revealed mountainous type features in all (before and after irradiation) PANI samples. The average size (diameter) and density of such mountainous clusters were found to be related with the ion fluence. The AFM profiles also showed change in the surface roughness of the films with respect to irradiation, which is one of the peculiarity of the high electronic energy deposition technique.

Growth and interface engineering in thin-film Ba0.6Sr0.4TiO3 /SrMoO3 heterostructures

NASA Astrophysics Data System (ADS)

Radetinac, Aldin; Ziegler, Jürgen; Vafaee, Mehran; Alff, Lambert; Komissinskiy, Philipp

2017-04-01

Epitaxial heterostructures of ferroelectric Ba0.6Sr0.4TiO3 and highly conducting SrMoO3 were grown by pulsed laser deposition on SrTiO3 (0 0 1) substrates. Surface oxidation of the SrMoO3 film is suppressed using a thin cap interlayer of Ba0.6Sr0.4TiO3-δ grown in reduced atmosphere. As shown by X-ray photoelectron spectroscopy, the Mo4+ valence state of the SrMoO3 films is stable upon annealing of the sample in oxygen up to 600 °C. The described oxygen interface engineering enables utilization of the highly conducting material SrMoO3 in multilayer oxide ferroelectric varactors.

High temperature thermoelectric properties of strontium titanate thin films with oxygen vacancy and niobium doping.

PubMed

Kumar, S R Sarath; Barasheed, Abeer Z; Alshareef, H N

2013-08-14

We report the evolution of high temperature thermoelectric properties of SrTiO3 thin films doped with Nb and oxygen vacancies. Structure-property relations in this important thermoelectric oxide are elucidated and the variation of transport properties with dopant concentrations is discussed. Oxygen vacancies are incorporated during growth or annealing in Ar/H2 above 800 K. An increase in lattice constant due to the inclusion of Nb and oxygen vacancies is found to result in an increase in carrier density and electrical conductivity with simultaneous decrease in carrier effective mass and Seebeck coefficient. The lattice thermal conductivity at 300 K is found to be 2.22 W m(-1) K(-1), and the estimated figure of merit is 0.29 at 1000 K.

Programmable permanent data storage characteristics of nanoscale thin films of a thermally stable aromatic polyimide.

PubMed

Kim, Dong Min; Park, Samdae; Lee, Taek Joon; Hahm, Suk Gyu; Kim, Kyungtae; Kim, Jin Chul; Kwon, Wonsang; Ree, Moonhor

2009-10-06

We have synthesized a new thermally and dimensionally stable polyimide, poly(4,4'-amino(4-hydroxyphenyl)diphenylene hexafluoroisopropylidenediphthalimide) (6F-HTPA PI). 6F-HTPA PI is soluble in organic solvents and is thus easily processed with conventional solution coating techniques to produce good quality nanoscale thin films. Devices fabricated with nanoscale thin PI films with thicknesses less than 77 nm exhibit excellent unipolar write-once-read-many-times (WORM) memory behavior with a high ON/OFF current ratio of up to 10(6), a long retention time and low power consumption, less than +/-3.0 V. Furthermore, these WORM characteristics were found to persist even at high temperatures up to 150 degrees C. The WORM memory behavior was found to be governed by trap-limited space-charge limited conduction and local filament formation. The conduction processes are dominated by hole injection. Thus the hydroxytriphenylamine moieties of the PI polymer might play a key role as hole trapping sites in the observed WORM memory behavior. The properties of 6F-HTPA PI make it a promising material for high-density and very stable programmable permanent data storage devices with low power consumption.

Ultra-high aspect ratio copper nanowires as transparent conductive electrodes for dye sensitized solar cells

NASA Astrophysics Data System (ADS)

Zhu, Zhaozhao; Mankowski, Trent; Shikoh, Ali Sehpar; Touati, Farid; Benammar, Mohieddine A.; Mansuripur, Masud; Falco, Charles M.

2016-09-01

We report the synthesis of ultra-high aspect ratio copper nanowires (CuNW) and fabrication of CuNW-based transparent conductive electrodes (TCE) with high optical transmittance (>80%) and excellent sheet resistance (Rs <30 Ω/sq). These CuNW TCEs are subsequently hybridized with aluminum-doped zinc oxide (AZO) thin-film coatings, or platinum thin film coatings, or nickel thin-film coatings. Our hybrid transparent electrodes can replace indium tin oxide (ITO) films in dye-sensitized solar cells (DSSCs) as either anodes or cathodes. We highlight the challenges of integrating bare CuNWs into DSSCs, and demonstrate that hybridization renders the solar cell integrations feasible. The CuNW/AZO-based DSSCs have reasonably good open-circuit voltage (Voc = 720 mV) and short-circuit current-density (Jsc = 0.96 mA/cm2), which are comparable to what is obtained with an ITO-based DSSC fabricated with a similar process. Our CuNW-Ni based DSSCs exhibit a good open-circuit voltage (Voc = 782 mV) and a decent short-circuit current (Jsc = 3.96 mA/cm2), with roughly 1.5% optical-to-electrical conversion efficiency.

High Temperature Protonic Conductors

NASA Technical Reports Server (NTRS)

Dynys, Fred; Berger, Marie-Helen; Sayir, Ali

2007-01-01

High Temperature Protonic Conductors (HTPC) with the perovskite structure are envisioned for electrochemical membrane applications such as H2 separation, H2 sensors and fuel cells. Successive membrane commercialization is dependent upon addressing issues with H2 permeation rate and environmental stability with CO2 and H2O. HTPC membranes are conventionally fabricated by solid-state sintering. Grain boundaries and the presence of intergranular second phases reduce the proton mobility by orders of magnitude than the bulk crystalline grain. To enhanced protonic mobility, alternative processing routes were evaluated. A laser melt modulation (LMM) process was utilized to fabricate bulk samples, while pulsed laser deposition (PLD) was utilized to fabricate thin film membranes . Sr3Ca(1+x)Nb(2-x)O9 and SrCe(1-x)Y(x)O3 bulk samples were fabricated by LMM. Thin film BaCe(0.85)Y(0.15)O3 membranes were fabricated by PLD on porous substrates. Electron microscopy with chemical mapping was done to characterize the resultant microstructures. High temperature protonic conduction was measured by impedance spectroscopy in wet air or H2 environments. The results demonstrate the advantage of thin film membranes to thick membranes but also reveal the negative impact of defects or nanoscale domains on protonic conductivity.

Techniques for Connecting Superconducting Thin Films

NASA Technical Reports Server (NTRS)

Mester, John; Gwo, Dz-Hung

2006-01-01

Several improved techniques for connecting superconducting thin films on substrates have been developed. The techniques afford some versatility for tailoring the electronic and mechanical characteristics of junctions between superconductors in experimental electronic devices. The techniques are particularly useful for making superconducting or alternatively normally conductive junctions (e.g., Josephson junctions) between patterned superconducting thin films in order to exploit electron quantum-tunneling effects. The techniques are applicable to both low-Tc and high-Tc superconductors (where Tc represents the superconducting- transition temperature of a given material), offering different advantages for each. Most low-Tc superconductors are metallic, and heretofore, connections among them have been made by spot welding. Most high-Tc superconductors are nonmetallic and cannot be spot welded. These techniques offer alternatives to spot welding of most low-Tc superconductors and additional solutions to problems of connecting most high-Tc superconductors.

Electromechanical Behavior of Chemically Reduced Graphene Oxide and Multi-walled Carbon Nanotube Hybrid Material

NASA Astrophysics Data System (ADS)

Benchirouf, Abderrahmane; Müller, Christian; Kanoun, Olfa

2016-01-01

In this paper, we propose strain-sensitive thin films based on chemically reduced graphene oxide (GO) and multi-walled carbon nanotubes (MWCNTs) without adding any further surfactants. In spite of the insulating properties of the thin-film-based GO due to the presence functional groups such as hydroxyl, epoxy, and carbonyl groups in its atomic structure, a significant enhancement of the film conductivity was reached by chemical reduction with hydro-iodic acid. By optimizing the MWCNT content, a significant improvement of electrical and mechanical thin film sensitivity is realized. The optical properties and the morphology of the prepared thin films were studied using ultraviolet-visible spectroscopy (UV-Vis) and scanning electron microscope (SEM). The UV-Vis spectra showed the ability to tune the band gap of the GO by changing the MWCNT content, whereas the SEM indicated that the MWCNTs were well dissolved and coated by the GO. Investigations of the piezoresistive properties of the hybrid nanocomposite material under mechanical load show a linear trend between the electrical resistance and the applied strain. A relatively high gauge factor of 8.5 is reached compared to the commercial metallic strain gauges. The self-assembled hybrid films exhibit outstanding properties in electric conductivity, mechanical strength, and strain sensitivity, which provide a high potential for use in strain-sensing applications.

Electromechanical Behavior of Chemically Reduced Graphene Oxide and Multi-walled Carbon Nanotube Hybrid Material.

PubMed

Benchirouf, Abderrahmane; Müller, Christian; Kanoun, Olfa

2016-12-01

In this paper, we propose strain-sensitive thin films based on chemically reduced graphene oxide (GO) and multi-walled carbon nanotubes (MWCNTs) without adding any further surfactants. In spite of the insulating properties of the thin-film-based GO due to the presence functional groups such as hydroxyl, epoxy, and carbonyl groups in its atomic structure, a significant enhancement of the film conductivity was reached by chemical reduction with hydro-iodic acid. By optimizing the MWCNT content, a significant improvement of electrical and mechanical thin film sensitivity is realized. The optical properties and the morphology of the prepared thin films were studied using ultraviolet-visible spectroscopy (UV-Vis) and scanning electron microscope (SEM). The UV-Vis spectra showed the ability to tune the band gap of the GO by changing the MWCNT content, whereas the SEM indicated that the MWCNTs were well dissolved and coated by the GO. Investigations of the piezoresistive properties of the hybrid nanocomposite material under mechanical load show a linear trend between the electrical resistance and the applied strain. A relatively high gauge factor of 8.5 is reached compared to the commercial metallic strain gauges. The self-assembled hybrid films exhibit outstanding properties in electric conductivity, mechanical strength, and strain sensitivity, which provide a high potential for use in strain-sensing applications.

Instabilities of convection patterns in a shear-thinning fluid between plates of finite conductivity

NASA Astrophysics Data System (ADS)

Varé, Thomas; Nouar, Chérif; Métivier, Christel

2017-10-01

Rayleigh-Bénard convection in a horizontal layer of a non-Newtonian fluid between slabs of arbitrary thickness and finite thermal conductivity is considered. The first part of the paper deals with the primary bifurcation and the relative stability of convective patterns at threshold. Weakly nonlinear analysis combined with Stuart-Landau equation is used. The competition between squares and rolls, as a function of the shear-thinning degree of the fluid, the slabs' thickness, and the ratio of the thermal conductivity of the slabs to that of the fluid is investigated. Computations of heat transfer coefficients are in agreement with the maximum heat transfer principle. The second part of the paper concerns the stability of the convective patterns toward spatial perturbations and the determination of the band width of the stable wave number in the neighborhood of the critical Rayleigh number. The approach used is based on the Ginzburg-Landau equations. The study of rolls stability shows that: (i) for low shear-thinning effects, the band of stable wave numbers is bounded by zigzag instability and cross-roll instability. Furthermore, the marginal cross-roll stability boundary enlarges with increasing shear-thinning properties; (ii) for high shear-thinning effects, Eckhaus instability becomes more dangerous than cross-roll instability. For square patterns, the wave number selection is always restricted by zigzag instability and by "rectangular Eckhaus" instability. In addition, the width of the stable wave number decreases with increasing shear-thinning effects. Numerical simulations of the planform evolution are also presented to illustrate the different instabilities considered in the paper.

Water and light improvement after thinning at a xeric site: Which weights the most? A dual isotope approach

NASA Astrophysics Data System (ADS)

Giuggiola, Arnaud; Ogée, Jérôme; Gessler, Arthur; Rigling, Andreas; Bugmann, Harald; Treydte, Kerstin

2015-04-01

Reductions in stand density foster individual tree growth due to increases of resources such as water, light and nutrients. Detailed knowledge of the short- to long-term physiological response underlying the growth response to thinning is crucial for the management of forests already suffering from recurrent drought-induced dieback. We applied a dual isotope approach together with mechanistic isotope models such as MuSICA to study the physiological processes underlying growth enhancement in a long-term thinning experiment in a xeric Pinus sylvestris forest in Switzerland. This approach allowed for identifying and disentangling changes in stomatal conductance and assimilation rate. Our results indicate that an increase in stomatal conductance outweighs an increase in assimilation, meaning that the observed growth releases in heavy thinned trees at our xeric site are primarily driven by enhanced water availability rather than by the increase in light availability. We conclude that in areas with isohydric species (drought avoiders) that tend to grow close to their physiological limits, thinning is highly recommended to maintain a less negative water balance and thus foster tree growth, and ultimately the survival rate of individual trees and forests.

Structural and electrical transport properties of La2Mo2O9 thin films prepared by pulsed laser deposition

NASA Astrophysics Data System (ADS)

Paul, T.; Ghosh, A.

2017-04-01

We have studied the structure and electrical properties of La2Mo2O9 thin films of different thicknesses prepared by the laser deposition technique at different substrate temperatures. The structural properties of the thin films have been investigated using XRD, XPS, AFM, TEM, SEM, and Raman spectroscopy. The electrical transport properties of the thin films have been investigated in wide temperature and frequency ranges. The cubic nature of the thin films has been confirmed from structural analysis. An enhancement of the oxygen ion conductivity of the films up to five orders of magnitude is obtained compared to that of the bulk La2Mo2O9, suggesting usefulness of the thin films as electrolytes in micro-solid oxide fuel cells. The enhanced dc ionic conductivity of the thin films has been interpreted using the rule of the mixture model, while a power law model has been used to investigate the frequency and temperature dependences of the conductivity. The analysis of the results predicts the three-dimensional oxygen ion conduction in the thin films.

Hierarchically Structured Co3O4@Pt@MnO2 Nanowire Arrays for High-Performance Supercapacitors

PubMed Central

Xia, Hui; Zhu, Dongdong; Luo, Zhentao; Yu, Yue; Shi, Xiaoqin; Yuan, Guoliang; Xie, Jianping

2013-01-01

Here we proposed a novel architectural design of a ternary MnO2-based electrode – a hierarchical Co3O4@Pt@MnO2 core-shell-shell structure, where the complemental features of the three key components (a well-defined Co3O4 nanowire array on the conductive Ti substrate, an ultrathin layer of small Pt nanoparticles, and a thin layer of MnO2 nanoflakes) are strategically combined into a single entity to synergize and construct a high-performance electrode for supercapacitors. Owing to the high conductivity of the well-defined Co3O4 nanowire arrays, in which the conductivity was further enhanced by a thin metal (Pt) coating layer, in combination with the large surface area provided by the small MnO2 nanoflakes, the as-fabricated Co3O4@Pt@MnO2 nanowire arrays have exhibited high specific capacitances, good rate capability, and excellent cycling stability. The architectural design demonstrated in this study provides a new approach to fabricate high-performance MnO2–based nanowire arrays for constructing next-generation supercapacitors. PMID:24132040

High-conductance low-voltage organic thin film transistor with locally rearranged poly(3-hexylthiophene) domain by current annealing on plastic substrate

NASA Astrophysics Data System (ADS)

Pei, Zingway; Tsai, Hsing-Wang; Lai, Hsin-Cheng

2016-02-01

The organic material based thin film transistors (TFTs) are attractive for flexible optoelectronics applications due to the ability of lager area fabrication by solution and low temperature process on plastic substrate. Recently, the research of organic TFT focus on low operation voltage and high output current to achieve a low power organic logic circuit for optoelectronic device,such as e-paper or OLED displayer. To obtain low voltage and high output current, high gate capacitance and high channel mobility are key factors. The well-arranged polymer chain by a high temperature postannealing, leading enhancement conductivity of polymer film was a general method. However, the thermal annealing applying heat for all device on the substrate and may not applicable to plastic substrate. Therefore, in this work, the low operation voltage and high output current of polymer TFTs was demonstrated by locally electrical bias annealing. The poly(styrene-comethyl methacrylate) (PS-r-PMMA) with ultra-thin thickness is used as gate dielectric that the thickness is controlled by thermal treatment after spin coated on organic electrode. In electrical bias-annealing process, the PS-r- PMMA is acted a heating layer. After electrical bias-annealing, the polymer TFTs obtain high channel mobility at low voltage that lead high output current by a locally annealing of P3HT film. In the future, the locally electrical biasannealing method could be applied on plastic substrate for flexible optoelectronic application.

Anisotropic thermal conductivity of thin polycrystalline oxide samples

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

Tiwari, A., E-mail: abhishektiwariiitr@gmail.com; Department of Mechanical and Aerospace Engineering, Monash University, Melbourne, VIC 3800; Boussois, K.

2013-11-15

This paper reports about the development of a modified laser-flash technique and relation to measure the in-plane thermal diffusivity of thin polycrystalline oxide samples. Thermal conductivity is then calculated with the product of diffusivity, specific heat and density. Design and operating features for evaluating in-plane thermal conductivities are described. The technique is advantageous as thin samples are not glued together to measure in-plane thermal conductivities like earlier methods reported in literature. The approach was employed to study anisotropic thermal conductivity in alumina sheet, textured kaolin ceramics and montmorillonite. Since it is rare to find in-plane thermal conductivity values for suchmore » anisotropic thin samples in literature, this technique offers a useful variant to existing techniques.« less

Purely hopping conduction in c-axis oriented LiNbO3 thin films

NASA Astrophysics Data System (ADS)

Shandilya, Swati; Tomar, Monika; Sreenivas, K.; Gupta, Vinay

2009-05-01

Dielectric constant and ac conductivity of highly c-axis oriented LiNbO3 thin film grown by pulsed laser deposition were studied in a metal-insulator-metal configuration over a wide temperature (200 to 450 K) and frequency (100 Hz to 1 MHz) range. The preferred oriented Al (1%) doped ZnO film with electrical conductivity 1.1×103 Ω-1 cm-1 was deposited for dual purpose: (1) to serve as nucleating center for LiNbO3 crystallites along preferred c-axis growth direction, and (2) to act as a suitable bottom electrode for electrical studies. The room temperature dc conductivity (σdc) of LiNbO3 film was about 5.34×10-10 Ω-1 cm-1 with activation energy ˜0.3 eV, indicating extrinsic conduction. The ac conductivity σac was found to be much higher in comparison to σdc in the low temperature region (<300 K) and exhibits a power law behavior due to the hopping of charge carriers. In higher temperature region (>300 K), σac shows a weak frequency dependence, whereas dielectric constant exhibits a strong frequency dispersion. The dielectric dispersion data has been discussed in the light of theoretical models based on Debye type mixed conduction and purely hopping conduction. The dominant conduction in c-axis oriented LiNbO3 thin film is attributed to the purely hopping where both σdc and σac arise due to same mechanism.

Electrical compensation by Ga vacancies in Ga2O3 thin films

NASA Astrophysics Data System (ADS)

Korhonen, E.; Tuomisto, F.; Gogova, D.; Wagner, G.; Baldini, M.; Galazka, Z.; Schewski, R.; Albrecht, M.

2015-06-01

The authors have applied positron annihilation spectroscopy to study the vacancy defects in undoped and Si-doped Ga2O3 thin films. The results show that Ga vacancies are formed efficiently during metal-organic vapor phase epitaxy growth of Ga2O3 thin films. Their concentrations are high enough to fully account for the electrical compensation of Si doping. This is in clear contrast to another n-type transparent semiconducting oxide In2O3, where recent results show that n-type conductivity is not limited by cation vacancies but by other intrinsic defects such as Oi.

Transparent Conductive Nanofiber Paper for Foldable Solar Cells

PubMed Central

Nogi, Masaya; Karakawa, Makoto; Komoda, Natsuki; Yagyu, Hitomi; Nge, Thi Thi

2015-01-01

Optically transparent nanofiber paper containing silver nanowires showed high electrical conductivity and maintained the high transparency, and low weight of the original transparent nanofiber paper. We demonstrated some procedures of optically transparent and electrically conductive cellulose nanofiber paper for lightweight and portable electronic devices. The nanofiber paper enhanced high conductivity without any post treatments such as heating or mechanical pressing, when cellulose nanofiber dispersions were dropped on a silver nanowire thin layer. The transparent conductive nanofiber paper showed high electrical durability in repeated folding tests, due to dual advantages of the hydrophilic affinity between cellulose and silver nanowires, and the entanglement between cellulose nanofibers and silver nanowires. Their optical transparency and electrical conductivity were as high as those of ITO glass. Therefore, using this conductive transparent paper, organic solar cells were produced that achieved a power conversion of 3.2%, which was as high as that of ITO-based solar cells. PMID:26607742

Thin and Flexible Carbon Nanotube-Based Pressure Sensors with Ultra-wide Sensing Range.

PubMed

Doshi, Sagar M; Thostenson, Erik T

2018-06-26

A scalable electrophoretic deposition (EPD) approach is used to create novel thin, flexible and lightweight carbon nanotube-based textile pressure sensors. The pressure sensors can be produced using an extensive variety of natural and synthetic fibers. These piezoresistive sensors are sensitive to pressures ranging from the tactile range (< 10 kPa), in the body weight range (~ 500 kPa), and very high pressures (~40 MPa). The EPD technique enables the creation of a uniform carbon nanotube-based nanocomposite coating, in the range of 250-750 nm thick, of polyethyleneimine (PEI) functionalized carbon nanotubes on non-conductive fibers. In this work, non-woven aramid fibers are coated by EPD onto a backing electrode followed by film formation onto the fibers creating a conductive network. The electrically conductive nanocomposite coating is firmly bonded to the fiber surface and shows piezoresistive electrical/mechanical coupling. The pressure sensor displays a large in-plane change in electrical conductivity with applied out-of-plane pressure. In-plane conductivity change results from fiber/fiber contact as well as the formation of a sponge-like piezoresistive nanocomposite "interphase" between the fibers. The resilience of the nanocomposite interphase enables sensing of high pressures without permanent changes to the sensor response, showing high repeatability.

Thin film silicon by a microwave plasma deposition technique: Growth and devices, and, interface effects in amorphous silicon/crystalline silicon solar cells

NASA Astrophysics Data System (ADS)

Jagannathan, Basanth

Thin film silicon (Si) was deposited by a microwave plasma CVD technique, employing double dilution of silane, for the growth of low hydrogen content Si films with a controllable microstructure on amorphous substrates at low temperatures (<400sp°C). The double dilution was achieved by using a Ar (He) carrier for silane and its subsequent dilution by Hsb2. Structural and electrical properties of the films have been investigated over a wide growth space (temperature, power, pressure and dilution). Amorphous Si films deposited by silane diluted in He showed a compact nature and a hydrogen content of ˜8 at.% with a photo/dark conductivity ratio of 10sp4. Thin film transistors (W/L = 500/25) fabricated on these films, showed an on/off ratio of ˜10sp6 and a low threshold voltage of 2.92 volts. Microcrystalline Si films with a high crystalline content (˜80%) were also prepared by this technique. Such films showed a dark conductivity ˜10sp{-6} S/cm, with a conduction activation energy of 0.49 eV. Film growth and properties have been compared for deposition in Ar and He carrier systems and growth models have been proposed. Low temperature junction formation by undoped thin film silicon was examined through a thin film silicon/p-type crystalline silicon heterojunctions. The thin film silicon layers were deposited by rf glow discharge, dc magnetron sputtering and microwave plasma CVD. The hetero-interface was identified by current transport analysis and high frequency capacitance methods as the key parameter controlling the photovoltaic (PV) response. The effect of the interface on the device properties (PV, junction, and carrier transport) was examined with respect to modifications created by chemical treatment, type of plasma species, their energy and film microstructure interacting with the substrate. Thermally stimulated capacitance was used to determine the interfacial trap parameters. Plasma deposition of thin film silicon on chemically clean c-Si created electron trapping sites while hole traps were seen when a thin oxide was present at the interface. Under optimized conditions, a 10.6% efficient cell (11.5% with SiOsb2 A/R) with an open circuit voltage of 0.55 volts and a short circuit current density of 30 mA/cmsp2 was fabricated.

Piezoelectric actuated micro-resonators based on the growth of diamond on aluminum nitride thin films.

PubMed

Hees, J; Heidrich, N; Pletschen, W; Sah, R E; Wolfer, M; Williams, O A; Lebedev, V; Nebel, C E; Ambacher, O

2013-01-18

Unimorph heterostructures based on piezoelectric aluminum nitride (AlN) and diamond thin films are highly desirable for applications in micro- and nanoelectromechanical systems. In this paper, we present a new approach to combine thin conductive boron-doped as well as insulating nanocrystalline diamond (NCD) with sputtered AlN films without the need for any buffer layers between AlN and NCD or polishing steps. The zeta potentials of differently treated nanodiamond (ND) particles in aqueous colloids are adjusted to the zeta potential of AlN in water. Thereby, the nucleation density for the initial growth of diamond on AlN can be varied from very low (10(8) cm(-2)), in the case of hydrogen-treated ND seeding particles, to very high values of 10(11) cm(-2) for oxidized ND particles. Our approach yielding high nucleation densities allows the growth of very thin NCD films on AlN with thicknesses as low as 40 nm for applications such as microelectromechanical beam resonators. Fabricated piezo-actuated micro-resonators exhibit enhanced mechanical properties due to the incorporation of boron-doped NCD films. Highly boron-doped NCD thin films which replace the metal top electrode offer Young's moduli of more than 1000 GPa.

Aerosol jet printed p- and n-type electrolyte-gated transistors with a variety of electrode materials: exploring practical routes to printed electronics.

PubMed

Hong, Kihyon; Kim, Se Hyun; Mahajan, Ankit; Frisbie, C Daniel

2014-11-12

Printing electrically functional liquid inks is a promising approach for achieving low-cost, large-area, additive manufacturing of flexible electronic circuits. To print thin-film transistors, a basic building block of thin-film electronics, it is important to have several options for printable electrode materials that exhibit high conductivity, high stability, and low-cost. Here we report completely aerosol jet printed (AJP) p- and n-type electrolyte-gated transistors (EGTs) using a variety of different electrode materials including highly conductive metal nanoparticles (Ag), conducting polymers (polystyrenesulfonate doped poly(3,4-ethylendedioxythiophene, PEDOT:PSS), transparent conducting oxides (indium tin oxide), and carbon-based materials (reduced graphene oxide). Using these source-drain electrode materials and a PEDOT:PSS/ion gel gate stack, we demonstrated all-printed p- and n-type EGTs in combination with poly(3-hexythiophene) and ZnO semiconductors. All transistor components (including electrodes, semiconductors, and gate insulators) were printed by AJP. Both kinds of devices showed typical p- and n-type transistor characteristics, and exhibited both low-threshold voltages (<2 V) and high hole and electron mobilities. Our assessment suggests Ag electrodes may be the best option in terms of overall performance for both types of EGTs.

On fabrication procedures of Li-ion conducting garnets

NASA Astrophysics Data System (ADS)

Hanc, Emil; Zając, Wojciech; Lu, Li; Yan, Binggong; Kotobuki, Masashi; Ziąbka, Magdalena; Molenda, Janina

2017-04-01

Ceramic oxides exhibiting high lithium-ion mobility at room temperature receive broad attention as candidate electrolytes for lithium batteries. Lithium-stuffed garnets from the Li7La3Zr2O12 group seem to be especially promising because of their high ionic conductivity at room temperature and their electrochemical stability. In this work, we discuss factors that affect formation of the garnet in its bulk form or in the form of thick and thin films. We demonstrate that zinc oxide can be applied as a sintering aid that facilitate the formation of the highly conducting cubic Li7La3Zr2O12 garnet phase in a single-step sintering procedure. Based on our experience with the single-step sintering experiments, we successfully fabricated a thick-film membrane consisting of a garnet solid electrolyte using the tape casting technique. In order to reduce the thickness of the electrolyte even further we investigated the fabrication of a thin-film Li7La3Zr2O12 electrolyte by means of the pulsed laser deposition technique.

Thermally Diffused Al:ZnO Thin Films for Broadband Transparent Conductor.

PubMed

Tong, Chong; Yun, Juhyung; Chen, Yen-Jen; Ji, Dengxin; Gan, Qiaoqiang; Anderson, Wayne A

2016-02-17

Here, we report an approach to realize highly transparent low resistance Al-doped ZnO (AZO) films for broadband transparent conductors. Thin Al films are deposited on ZnO surfaces, followed by thermal diffusion processes, introducing the Al doping into ZnO thin films. By utilizing the interdiffusion of Al, Zn, and O, the chemical state of Al on the surfaces can be converted to a fully oxidized state, resulting in a low sheet resistance of 6.2 Ω/sq and an excellent transparency (i.e., 96.5% at 550 nm and higher than 85% up to 2500 nm), which is superior compared with some previously reported values for indium tin oxide, solution processed AZO, and many transparent conducting materials using novel nanostructures. Such AZO films are also applied as transparent conducting layers for AZO/Si heterojunction solar cells, demonstrating their applications in optoelectronic devices.

Role of vacancy defects in Al doped ZnO thin films for optoelectronic devices

NASA Astrophysics Data System (ADS)

Rotella, H.; Mazel, Y.; Brochen, S.; Valla, A.; Pautrat, A.; Licitra, C.; Rochat, N.; Sabbione, C.; Rodriguez, G.; Nolot, E.

2017-12-01

We report on the electrical, optical and photoluminescence properties of industry-ready Al doped ZnO thin films grown by physical vapor deposition, and their evolution after annealing under vacuum. Doping ZnO with Al atoms increases the carrier density but also favors the formation of Zn vacancies, thereby inducing a saturation of the conductivity mechanism at high aluminum content. The electrical and optical properties of these thin layered materials are both improved by annealing process which creates oxygen vacancies that releases charge carriers thus improving the conductivity. This study underlines the effect of the formation of extrinsic and intrinsic defects in Al doped ZnO compound during the fabrication process. The quality and the optoelectronic response of the produced films are increased (up to 1.52 mΩ \\cdotcm and 3.73 eV) and consistent with the industrial device requirements.

Facile fabrication of high-performance InGaZnO thin film transistor using hydrogen ion irradiation at room temperature

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

Ahn, Byung Du; Park, Jin-Seong; Chung, K. B., E-mail: kbchung@dongguk.edu

Device performance of InGaZnO (IGZO) thin film transistors (TFTs) are investigated as a function of hydrogen ion irradiation dose at room temperature. Field effect mobility is enhanced, and subthreshold gate swing is improved with the increase of hydrogen ion irradiation dose, and there is no thermal annealing. The electrical device performance is correlated with the electronic structure of IGZO films, such as chemical bonding states, features of the conduction band, and band edge states below the conduction band. The decrease of oxygen deficient bonding and the changes in electronic structure of the conduction band leads to the improvement of devicemore » performance in IGZO TFT with an increase of the hydrogen ion irradiation dose.« less

Silicon-based microfabricated tin oxide gas sensor incorporating use of Hall effect measurement

NASA Astrophysics Data System (ADS)

Hammond, Joseph Wilson

2000-10-01

Characterization of a microfabricated sol-gel derived nano-particle tin oxide thin film on a silicon substrate, through simultaneous measurement of conductivity, Hall mobility and electron density, had not been accomplished before this study. Conductivity is a function of carrier density and Hall mobility. Therefore, a full understanding of the sensing mechanism of tin oxide requires knowledge of the sensor conductivity, electron density and Hall mobility. A tin oxide thin film (1100A thick), derived by the sol-gel method, was deposited on a Si/SiO2 substrate by means of spin coating method. The sol-gel method produces films of porous interconnected nano-sized particles and is relatively inexpensive and easy to produce compared to existing methods of tin oxide thin film deposition. A goal of this study was to determine the compatibility of sol-gel derived tin oxide thin films with silicon based microfabrication procedures. It was determined that conductivity sensitivity is strongly dependant on electron density level and shows very weak dependence on Hall mobility. Lack of Hall mobility sensitivity to H2 concentration suggests that conduction is grain control limited. In this regime, in which the grain size (D) is less than twice the characteristic Debye length (LD), a change in reducing gas concentration results in a nearly simultaneous change in carrier density throughout the entire grain, while the Hall mobility remains unchanged. The sensor calcined at 500°C and operated at 250°C showed maximum conductivity sensitivity to H2 in air. The sensor exhibited a high conductivity sensitivity of 10.6 to 100ppm H2 in air with response time of (˜1) minute and recovery time of (˜4) minutes. Images of the thin film surface, obtained by SEM, were used to study the effects of calcination temperature and operating conditions on the tin oxide structure. Sensitivity decreased as average grain size increased from 7.7nm to 14.7nm, with increasing calcination temperature from 500°C to 800°C. The sensors displayed slight drift in long term baseline stability and good long term sensitivity stability (14 days). Long term operation (30 days) at elevated temperatures had no noticeable effect on the thin film structure.

Growth and Characteristic of Amorphous Nano-Granular TeO2-V2O5-NiO Thin Films

NASA Astrophysics Data System (ADS)

Hosseinzadeh, Sh.; Rahmati, A.; Bidadi, H.

2016-12-01

TeO2-V2O5-NiO thin films were deposited using thermal evaporation from 40TeO2-(60-y)V2O5-yNiO (y=0-30mol%) target. Structural analysis of the films was identified by X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The amorphous TeO2-V2O5-NiO films have nanosized clear grain structure and sharp grain boundaries. DC conductivity and current-voltage (I-V) characteristic of TeO2-V2O5-NiO thin films were measured in the temperature range of 300-423K. As nickel oxide (NiO) content increases, the DC conductivity decreases up to two orders in value (10-9-10-11Sṡcm-1). Temperature dependence of conductivity is described using the small polaron hopping (SPH) model as well. Poole-Frenkel effect is observed at high external electric field. The optical absorption spectra of the TeO2-V2O5-NiO thin films were recorded in the wavelength range of 380-1100nm. The absorption coefficient revealed bandgap shrinkage (3.01-2.3eV) and band tail widening, due to an increase in NiO content. Energy dispersive X-ray spectroscopy (EDX) was used to determine elemental composition. In TeO2-V2O5-NiO thin films, the NiO content is around fifth of the initial target.

Electronic transport in highly conducting Si-doped ZnO thin films prepared by pulsed laser deposition

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

Kuznetsov, Vladimir L.; Vai, Alex T.; Edwards, Peter P., E-mail: peter.edwards@chem.ox.ac.uk

2015-12-07

Highly conducting (ρ = 3.9 × 10{sup −4} Ωcm) and transparent (83%) polycrystalline Si-doped ZnO (SiZO) thin films have been deposited onto borosilicate glass substrates by pulsed laser deposition from (ZnO){sub 1−x}(SiO{sub 2}){sub x} (0 ≤ x ≤ 0.05) ceramic targets prepared using a sol-gel technique. Along with their structural, chemical, and optical properties, the electronic transport within these SiZO samples has been investigated as a function of silicon doping level and temperature. Measurements made between 80 and 350 K reveal an almost temperature-independent carrier concentration consistent with degenerate metallic conduction in all of these samples. The temperature-dependent Hall mobility has been modeled by considering the varying contribution of grainmore » boundary and electron-phonon scattering in samples with different nominal silicon concentrations.« less

Role of Al2O3 thin layer on improving the resistive switching properties of Ta5Si3-based conductive bridge random accesses memory device

NASA Astrophysics Data System (ADS)

Kumar, Dayanand; Aluguri, Rakesh; Chand, Umesh; Tseng, Tseung-Yuen

2018-04-01

Ta5Si3-based conductive bridge random access memory (CBRAM) devices have been investigated to improve their resistive switching characteristics for their application in future nonvolatile memory technology. Changes in the switching characteristics by the addition of a thin Al2O3 layer of different thicknesses at the bottom electrode interface of a Ta5Si3-based CBRAM devices have been studied. The double-layer device with a 1 nm Al2O3 layer has shown improved resistive switching characteristics over the single layer one with a high on/off resistance ratio of 102, high endurance of more than 104 cycles, and good retention for more than 105 s at the temperature of 130 °C. The higher thermal conductivity of Al2O3 over Ta5Si3 has been attributed to the enhanced switching properties of the double-layer devices.

Nitrogen grain-boundary passivation of In-doped ZnO transparent conducting oxide

NASA Astrophysics Data System (ADS)

Ali, D.; Butt, M. Z.; Coughlan, C.; Caffrey, D.; Shvets, I. V.; Fleischer, K.

2018-04-01

We have investigated the properties and conduction limitations of spray pyrolysis grown, low-cost transparent conducting oxide ZnO thin films doped with indium. We analyze the optical, electrical, and crystallographic properties as functions of In content with a specific focus on postgrowth heat treatment of these thin films at 320 ∘C in an inert, nitrogen atmosphere, which improves the films electrical properties considerably. The effect was found to be dominated by nitrogen-induced grain-boundary passivation, identified by a combined study using i n situ resistance measurement upon annealing, x-ray photoelectron spectroscopy, photoluminescence, and x-ray diffraction studies. We also highlight the chemical mechanism of morphologic and crystallographic changes found in films with high indium content. By optimizing growth conditions according to these findings, ZnO:In with a resistivity as low as 2 ×10 -3Ω cm , high optical quality (T ≈90 % ), and sheet resistance of 32 Ω /□ has been obtained without any need for postgrowth treatments.

Compositional ratio effect on the surface characteristics of CuZn thin films

NASA Astrophysics Data System (ADS)

Choi, Ahrom; Park, Juyun; Kang, Yujin; Lee, Seokhee; Kang, Yong-Cheol

2018-05-01

CuZn thin films were fabricated by RF co-sputtering method on p-type Si(100) wafer with various RF powers applied on metallic Cu and Zn targets. This paper aimed to determine the morphological, chemical, and electrical properties of the deposited CuZn thin films by utilizing a surface profiler, atomic force microscopy (AFM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), UV photoelectron spectroscopy (UPS), and a 4-point probe. The thickness of the thin films was fixed at 200 ± 8 nm and the roughness of the thin films containing Cu was smaller than pure Zn thin films. XRD studies confirmed that the preferred phase changed, and this tendency is dependent on the ratio of Cu to Zn. AES spectra indicate that the obtained thin films consisted of Cu and Zn. The high resolution XPS spectra indicate that as the content of Cu increased, the intensities of Zn2+ decreased. The work function of CuZn thin films increased from 4.87 to 5.36 eV. The conductivity of CuZn alloy thin films was higher than pure metallic thin films.

Enhancement of optical transmittance and electrical resistivity of post-annealed ITO thin films RF sputtered on Si

NASA Astrophysics Data System (ADS)

Ali, Ahmad Hadi; Hassan, Zainuriah; Shuhaimi, Ahmad

2018-06-01

This paper reports on the enhancement of optical transmittance and electrical resistivity of indium tin oxide (ITO) transparent conductive oxides (TCO) deposited by radio frequency (RF) sputtering on Si substrate. Post-annealing was conducted on the samples at temperature ranges of 500-700 °C. From X-ray diffraction analysis (XRD), ITO (2 2 2) peak was observed after post-annealing indicating crystallization phase of the films. From UV-vis measurements, the ITO thin film shows highest transmittance of more than 90% at post-annealing temperature of 700 °C as compared to the as-deposited thin films. From atomic force microscope (AFM), the surface roughness becomes smoother after post-annealing as compared to the as-deposited. The lowest electrical resistivity for ITO sample is 6.68 × 10-4 Ω cm after post-annealed at 700 °C that are contributed by high carrier concentration and mobility. The improved structural and surface morphological characteristics helps in increasing the optical transmittance and reducing the electrical resistivity of the ITO thin films.

Influence of pH on optoelectronic properties of zinc sulphide thin films prepared using hydrothermal and spin coating method

NASA Astrophysics Data System (ADS)

Choudapur, V. H.; Bennal, A. S.; Raju, A. B.

2018-04-01

The ZnS nanomaterial is synthesized by hydrothermal method under optimized conditions using Zinc acetate and sodium sulphide as precursors. The Zinc Sulphide thin films are obtained by simple spin coating method with high optical transmittance. The prepared thin films are adhesive and uniform. The x-ray diffraction analysis showed that the films are polycrystalline in cubic phase with the preferred orientation along (111) direction. Current-voltage curves were recorded at room temperature using Keithley 617 programmable electrometer and conductivity is calculated for the film coated on ITO by two probe method. The pH of the solution is varied by using ammonia and hydrochloric acid. The comparative studies of effect of pH on the morphology, crystallanity and optoelectronic properties of the films are studied. It is observed that the pH of the solution has large influence on optoelectronic properties. The thin film prepared with neutral pH has higher crystallanity, bandgap and conductivity as compared to the samples prepared in acidic or basic solutions.

Depositing bulk or micro-scale electrodes

DOEpatents

Shah, Kedar G.; Pannu, Satinderpall S.; Tolosa, Vanessa; Tooker, Angela C.; Sheth, Heeral J.; Felix, Sarah H.; Delima, Terri L.

2016-11-01

Thicker electrodes are provided on microelectronic device using thermo-compression bonding. A thin-film electrical conducting layer forms electrical conduits and bulk depositing provides an electrode layer on the thin-film electrical conducting layer. An insulating polymer layer encapsulates the electrically thin-film electrical conducting layer and the electrode layer. Some of the insulating layer is removed to expose the electrode layer.

Thermal conductivity model for nanoporous thin films

NASA Astrophysics Data System (ADS)

Huang, Congliang; Zhao, Xinpeng; Regner, Keith; Yang, Ronggui

2018-03-01

Nanoporous thin films have attracted great interest because of their extremely low thermal conductivity and potential applications in thin thermal insulators and thermoelectrics. Although there are some numerical and experimental studies about the thermal conductivity of nanoporous thin films, a simplified model is still needed to provide a straightforward prediction. In this paper, by including the phonon scattering lifetimes due to film thickness boundary scattering, nanopore scattering and the frequency-dependent intrinsic phonon-phonon scattering, a fitting-parameter-free model based on the kinetic theory of phonon transport is developed to predict both the in-plane and the cross-plane thermal conductivities of nanoporous thin films. With input parameters such as the lattice constants, thermal conductivity, and the group velocity of acoustic phonons of bulk silicon, our model shows a good agreement with available experimental and numerical results of nanoporous silicon thin films. It illustrates that the size effect of film thickness boundary scattering not only depends on the film thickness but also on the size of nanopores, and a larger nanopore leads to a stronger size effect of the film thickness. Our model also reveals that there are different optimal structures for getting the lowest in-plane and cross-plane thermal conductivities.

Effect of thermal annealing on the structural and optical properties of Cu2FeSnS4 thin films grown by vacuum evaporation method

NASA Astrophysics Data System (ADS)

Oueslati, H.; Rabeh, M. Ben; Kanzari, M.

2018-02-01

In this work, the effect of different types of thermal annealing on the properties of Cu2FeSnS4 (CFTS) thin films deposited by thermal evaporation at room temperature on glass substrate were investigated. CFTS powder was synthesized by direct melting of the constituent elements taken in stoichiometry compositions. The X-ray diffraction experimental data indicating that the Cu2FeSnS4 powder illustrating a stannite structure in space group I\\bar {4}2m. From the XRD analysis we have found that the polycrystalline CFTS thin film was only obtained by thermal annealed in sulfur atmosphere under a high vacuum of 400 °C temperature during 2 h. Optical study reveals that the thin films have relatively high absorption coefficients (≈ 105cm-1) and the values of optical band gap energy ranged between 1.38 and 1.48 eV. Other optical parameters were evaluated according to the models of Wemple Di-Domenico and Spitzer-Fan. Finally, hot probe measurements of CFTS thin films reveal p-type conductivity.

Dominant-tree thinning in New England northern hardwoods—a second look

Treesearch

William B. Leak

2015-01-01

A dominant-tree thinning was conducted in 2003 in a 69-year-old even-aged northern hardwood stand, clearcut in about 1935, where a precommercial thinning study had been conducted in 1959. The 2003 commercial thinning concentrated on the removal of the early maturing, short-lived paper birch and aspen, the largest-diameter trees in the stand (hence the term "...

An improved thin film approximation to accurately determine the optical conductivity of graphene from infrared transmittance

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

Weber, J. W.; Bol, A. A.; Sanden, M. C. M. van de

2014-07-07

This work presents an improved thin film approximation to extract the optical conductivity from infrared transmittance in a simple yet accurate way. This approximation takes into account the incoherent reflections from the backside of the substrate. These reflections are shown to have a significant effect on the extracted optical conductivity and hence on derived parameters as carrier mobility and density. By excluding the backside reflections, the error for these parameters for typical chemical vapor deposited (CVD) graphene on a silicon substrate can be as high as 17% and 45% for the carrier mobility and density, respectively. For the mid- andmore » near-infrared, the approximation can be simplified such that the real part of the optical conductivity is extracted without the need for a parameterization of the optical conductivity. This direct extraction is shown for Fourier transform infrared (FTIR) transmittance measurements of CVD graphene on silicon in the photon energy range of 370–7000 cm{sup −1}. From the real part of the optical conductivity, the carrier density, mobility, and number of graphene layers are determined but also residue, originating from the graphene transfer, is detected. FTIR transmittance analyzed with the improved thin film approximation is shown to be a non-invasive, easy, and accurate measurement and analysis method for assessing the quality of graphene and can be used for other 2-D materials.« less

Highly conductive homoepitaxial Si-doped Ga2O3 films on (010) β-Ga2O3 by pulsed laser deposition

NASA Astrophysics Data System (ADS)

Leedy, Kevin D.; Chabak, Kelson D.; Vasilyev, Vladimir; Look, David C.; Boeckl, John J.; Brown, Jeff L.; Tetlak, Stephen E.; Green, Andrew J.; Moser, Neil A.; Crespo, Antonio; Thomson, Darren B.; Fitch, Robert C.; McCandless, Jonathan P.; Jessen, Gregg H.

2017-07-01

Si-doped Ga2O3 thin films were fabricated by pulsed laser deposition on semi-insulating (010) β-Ga2O3 and (0001) Al2O3 substrates. Films deposited on β-Ga2O3 showed single crystal, homoepitaxial growth as determined by high resolution transmission electron microscopy and x-ray diffraction. Corresponding films deposited on Al2O3 were mostly single phase, polycrystalline β-Ga2O3 with a preferred (20 1 ¯ ) orientation. An average conductivity of 732 S cm-1 with a mobility of 26.5 cm2 V-1 s-1 and a carrier concentration of 1.74 × 1020 cm-3 was achieved for films deposited at 550 °C on β-Ga2O3 substrates as determined by Hall-Effect measurements. Two orders of magnitude improvement in conductivity were measured using native substrates versus Al2O3. A high activation efficiency was obtained in the as-deposited condition. The high carrier concentration Ga2O3 thin films achieved by pulsed laser deposition enable application as a low resistance ohmic contact layer in β-Ga2O3 devices.

Microgap x-ray detector

DOEpatents

Wuest, Craig R.; Bionta, Richard M.; Ables, Elden

1994-01-01

An x-ray detector which provides for the conversion of x-ray photons into photoelectrons and subsequent amplification of these photoelectrons through the generation of electron avalanches in a thin gas-filled region subject to a high electric potential. The detector comprises a cathode (photocathode) and an anode separated by the thin, gas-filled region. The cathode may comprise a substrate, such a beryllium, coated with a layer of high atomic number material, such as gold, while the anode can be a single conducting plane of material, such as gold, or a plane of resistive material, such as chromium/silicon monoxide, or multiple areas of conductive or resistive material, mounted on a substrate composed of glass, plastic or ceramic. The charge collected from each electron avalanche by the anode is passed through processing electronics to a point of use, such as an oscilloscope.

Microgap x-ray detector

DOEpatents

Wuest, C.R.; Bionta, R.M.; Ables, E.

1994-05-03

An x-ray detector is disclosed which provides for the conversion of x-ray photons into photoelectrons and subsequent amplification of these photoelectrons through the generation of electron avalanches in a thin gas-filled region subject to a high electric potential. The detector comprises a cathode (photocathode) and an anode separated by the thin, gas-filled region. The cathode may comprise a substrate, such a beryllium, coated with a layer of high atomic number material, such as gold, while the anode can be a single conducting plane of material, such as gold, or a plane of resistive material, such as chromium/silicon monoxide, or multiple areas of conductive or resistive material, mounted on a substrate composed of glass, plastic or ceramic. The charge collected from each electron avalanche by the anode is passed through processing electronics to a point of use, such as an oscilloscope. 3 figures.

Ion-/proton-conducting apparatus and method

DOEpatents

Yates, Matthew [Penfield, NY; Liu, Dongxia [Rochester, NY

2011-05-17

A c-axis-oriented HAP thin film synthesized by seeded growth on a palladium hydrogen membrane substrate. An exemplary synthetic process includes electrochemical seeding on the substrate, and secondary and tertiary hydrothermal treatments under conditions that favor growth along c-axes and a-axes in sequence. By adjusting corresponding synthetic conditions, an HAP this film can be grown to a controllable thickness with a dense coverage on the underlying substrate. The thin films have relatively high proton conductivity under hydrogen atmosphere and high temperature conditions. The c-axis oriented films may be integrated into fuel cells for application in the intermediate temperature range of 200-600.degree. C. The electrochemical-hydrothermal deposition technique may be applied to create other oriented crystal materials having optimized properties, useful for separations and catalysis as well as electronic and electrochemical applications, electrochemical membrane reactors, and in chemical sensors.

High conductivity and transparent aluminum-based multi-layer source/drain electrodes for thin film transistors

NASA Astrophysics Data System (ADS)

Yao, Rihui; Zhang, Hongke; Fang, Zhiqiang; Ning, Honglong; Zheng, Zeke; Li, Xiaoqing; Zhang, Xiaochen; Cai, Wei; Lu, Xubing; Peng, Junbiao

2018-02-01

In this study, high conductivity and transparent multi-layer (AZO/Al/AZO-/Al/AZO) source/drain (S/D) electrodes for thin film transistors were fabricated via conventional physical vapor deposition approaches, without toxic elements or further thermal annealing process. The 68 nm-thick multi-layer films with excellent optical properties (transparency: 82.64%), good electrical properties (resistivity: 6.64  ×  10-5 Ω m, work function: 3.95 eV), and superior surface roughness (R q   =  0.757 nm with scanning area of 5  ×  5 µm2) were fabricated as the S/D electrodes. Significantly, comprehensive performances of AZO films are enhanced by the insertion of ultra-thin Al layers. The optimal transparent TFT with this multi-layer S/D electrodes exhibited a decent electrical performance with a saturation mobility (µ sat) of 3.2 cm2 V-1 s-1, an I on/I off ratio of 1.59  ×  106, a subthreshold swing of 1.05 V/decade. The contact resistance of AZO/Al/AZO/Al/AZO multi-layer electrodes is as low as 0.29 MΩ. Moreover, the average visible light transmittance of the unpatterned multi-layers constituting a whole transparent TFT could reach 72.5%. The high conductivity and transparent multi-layer S/D electrodes for transparent TFTs possessed great potential for the applications of the green and transparent displays industry.

Optical response of nanostructured metal/dielectric composites and multilayers

NASA Astrophysics Data System (ADS)

Smith, Geoffrey B.; Maaroof, Abbas I.; Allan, Rodney S.; Schelm, Stefan; Anstis, Geoffrey R.; Cortie, Michael B.

2004-08-01

The homogeneous optical response in conducting nanostructured layers, and in insulating layers containing dense arrays of self assembled conducting nanoparticles separated by organic linkers, is examined experimentally through their effective complex indices (n*, k*). Classical effective medium models, modified to account for the 3-phase nanostructure, are shown to explain (n*, k*) in dense particulate systems but not inhomogeneous layers with macroscopic conductance for which a different approach to homogenisation is discussed. (n*, k*) data on thin granular metal films, thin mesoporous gold, and on thin metal layers containing ordered arrays of voids, is linked to properties of the surface plasmon states which span the nanostructured film. Coupling between evanescent waves at either surface counterbalanced by electron scattering losses must be considered. Virtual bound states for resonant photons result, with the associated transit delay leading to a large rise in n* in many nanostructures. Overcoating n-Ag with alumina is shown to alter (n*, k*) through its impact on the SP coupling. In contrast to classical optical homogenisation, effective indices depend on film thickness. Supporting high resolution SEM images are presented.

Pathways to Mesoporous Resin/Carbon Thin Films with Alternating Gyroid Morphology

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

Zhang, Qi; Matsuoka, Fumiaki; Suh, Hyo Seon

Three-dimensional (3D) mesoporous thin films with sub-100 nm periodic lattices are of increasing interest as templates for a number of nanotechnology applications, yet are hard to achieve with conventional top-down fabrication methods. Block copolymer self-assembly derived mesoscale structures provide a toolbox for such 3D template formation. In this work, single (alternating) gyroidal and double gyroidal mesoporous thin-film structures are achieved via solvent vapor annealing assisted co-assembly of poly(isoprene-block-styrene-block-ethylene oxide) (PI-b-PS-b-PEO, ISO) and resorcinol/phenol formaldehyde resols. In particular, the alternating gyroid thin-film morphology is highly desirable for potential template backfilling processes as a result of the large pore volume fraction. Inmore » situ grazing-incidence small-angle X-ray scattering during solvent annealing is employed as a tool to elucidate and navigate the pathway complexity of the structure formation processes. The resulting network structures are resistant to high temperatures provided an inert atmosphere. The thin films have tunable hydrophilicity from pyrolysis at different temperatures, while pore sizes can be tailored by varying ISO molar mass. A transfer technique between substrates is demonstrated for alternating gyroidal mesoporous thin films, circumventing the need to re-optimize film formation protocols for different substrates. Increased conductivity after pyrolysis at high temperatures demonstrates that these gyroidal mesoporous resin/carbon thin films have potential as functional 3D templates for a number of nanomaterials applications.« less

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.

Reduction of Defects on Microstructure Aluminium Nitride Using High Temperature Annealing Heat Treatment

NASA Astrophysics Data System (ADS)

Tanasta, Z.; Muhamad, P.; Kuwano, N.; Norfazrina, H. M. Y.; Unuh, M. H.

2018-03-01

Aluminium Nitride (AlN) is a ceramic 111-nitride material that is used widely as components in functional devices. Besides good thermal conductivity, it also has a high band gap in emitting light which is 6 eV. AlN thin film is grown on the sapphire substrate (0001). However, lattice mismatch between both materials has caused defects to exist along the microstructure of AlN thin films. The defects have affected the properties of Aluminium Nitride. Annealing heat treatment has been proved by the previous researcher to be the best method to improve the microstructure of Aluminium Nitride thin films. Hence, this method is applied at four different temperatures for two hour. The changes of Aluminium Nitride microstructures before and after annealing is observed using Transmission Electron Microscope. It is observed that inversion domains start to occur at temperature of 1500 °C. Convergent Beam Electron Diffraction pattern simulation has confirmed the defects as inversion domain. Therefore, this paper is about to extract the matters occurred during the process of producing high quality Aluminium Nitride thin films and the ways to overcome this problem.

Enhanced thermal conductance of polymer composites through embedding aligned carbon nanofibers

DOE PAGES

Nicholas, Roberts; Hensley, Dale K.; Wood, David

2016-07-08

The focus of this work is to find a more efficient method of enhancing the thermal conductance of polymer thin films. This work compares polymer thin films embedded with randomly oriented carbon nanotubes to those with vertically aligned carbon nanofibers. Thin films embedded with carbon nanofibers demonstrated a similar thermal conductance between 40–60 μm and a higher thermal conductance between 25–40 μm than films embedded with carbon nanotubes with similar volume fractions even though carbon nanotubes have a higher thermal conductivity than carbon nanofibers

Enhanced thermal conductance of polymer composites through embedding aligned carbon nanofibers

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

Nicholas, Roberts; Hensley, Dale K.; Wood, David

The focus of this work is to find a more efficient method of enhancing the thermal conductance of polymer thin films. This work compares polymer thin films embedded with randomly oriented carbon nanotubes to those with vertically aligned carbon nanofibers. Thin films embedded with carbon nanofibers demonstrated a similar thermal conductance between 40–60 μm and a higher thermal conductance between 25–40 μm than films embedded with carbon nanotubes with similar volume fractions even though carbon nanotubes have a higher thermal conductivity than carbon nanofibers

Photocurrent Suppression of Transparent Organic Thin Film Transistors

NASA Astrophysics Data System (ADS)

Chuang, Chiao-Shun; Tsai, Shu-Ting; Lin, Yung-Sheng; Chen, Fang-Chung; Shieh, Hang-Ping D.

2007-12-01

Organic thin-film transistors (OTFTs) with high transmittance and low photosensitivity have been demonstrated. By using titanium dioxide nanoparticles as the additives in the polymer gate insulators, the level of device photoresponse has been reduced. The device shows simultaneously a high transparence and a minimal threshold voltage shift under white light illumination. It is inferred that the localized energy levels deep in the energy gap of pentacene behave as the recombination centers, enhancing substantially the recombination process in the conducting channel of the OTFTs. Therefore, the electron trapping is relieved and the shift of threshold voltage is reduced upon illumination.

Thin Film Ceramic Strain Sensor Development for High Temperature Environments

NASA Technical Reports Server (NTRS)

Wrbanek, John D.; Fralick, Gustave C.; Gonzalez, Jose M.; Laster, Kimala L.

2008-01-01

The need for sensors to operate in harsh environments is illustrated by the need for measurements in the turbine engine hot section. The degradation and damage that develops over time in hot section components can lead to catastrophic failure. At present, the degradation processes that occur in the harsh hot section environment are poorly characterized, which hinders development of more durable components, and since it is so difficult to model turbine blade temperatures, strains, etc, actual measurements are needed. The need to consider ceramic sensing elements is brought about by the temperature limits of metal thin film sensors in harsh environments. The effort at the NASA Glenn Research Center (GRC) to develop high temperature thin film ceramic static strain gauges for application in turbine engines is described, first in the fan and compressor modules, and then in the hot section. The near-term goal of this research effort was to identify candidate thin film ceramic sensor materials and provide a list of possible thin film ceramic sensor materials and corresponding properties to test for viability. A thorough literature search was conducted for ceramics that have the potential for application as high temperature thin film strain gauges chemically and physically compatible with the NASA GRCs microfabrication procedures and substrate materials. Test results are given for tantalum, titanium and zirconium-based nitride and oxynitride ceramic films.

Parameters controlling microstructures and resistance switching of electrodeposited cuprous oxide thin films

NASA Astrophysics Data System (ADS)

Yazdanparast, Sanaz

2016-12-01

Cuprous oxide (Cu2O) thin films were electrodeposited cathodically from a highly alkaline bath using tartrate as complexing agent. Different microstructures for Cu2O thin films were achieved by varying the applied potential from -0.285 to -0.395 V versus a reference electrode of Ag/AgCl at 50 °C in potentiostatic mode, and separately by changing the bath temperature from 25 to 50 °C in galvanostatic mode. Characterization experiments showed that both grain size and orientation of Cu2O can be controlled by changing the applied potential. Applying a high negative potential of -0.395 V resulted in smaller grain size of Cu2O thin films with a preferred orientation in [111] direction. An increase in the bath temperature in galvanostatic electrodeposition increased the grain size of Cu2O thin films. All the films in Au/Cu2O/Au-Pd cell showed unipolar resistance switching behavior after an initial FORMING process. Increasing the grain size of Cu2O thin films and decreasing the top electrode area increased the FORMING voltage and decreased the current level of high resistance state (HRS). The current in low resistance state (LRS) was independent of the top electrode area and the grain size of deposited films, suggesting a filamentary conduction mechanism in unipolar resistance switching of Cu2O.

Nitridation-driven conductive Li4Ti5O12 for lithium ion batteries.

PubMed

Park, Kyu-Sung; Benayad, Anass; Kang, Dae-Joon; Doo, Seok-Gwang

2008-11-12

To modify oxide structure and introduce a thin conductive film on Li4Ti5O12, thermal nitridation was adopted for the first time. NH3 decomposes surface Li4Ti5O12 to conductive TiN at high temperature, and surprisingly, it also modifies the surface structure in a way to accommodate the single phase Li insertion and extraction. The electrochemically induced Li4+deltaTi5O12 with a TiN coating layer shows great electrochemical properties at high current densities.

Extending the 3ω method: thermal conductivity characterization of thin films.

PubMed

Bodenschatz, Nico; Liemert, André; Schnurr, Sebastian; Wiedwald, Ulf; Ziemann, Paul

2013-08-01

A lock-in technique for measurement of thermal conductivity and volumetric heat capacity of thin films is presented. The technique is based on the 3ω approach using electrical generation and detection of oscillatory heat along a thin metal strip. Thin films are deposited onto the backside of commercial silicon nitride membranes, forming a bilayer geometry with distinct thermal parameters. Stepwise comparison to an adapted heat diffusion model delivers these parameters for both layers. Highest sensitivity is found for metallic thin films.

Correlation Function Analysis of Fiber Networks: Implications for Thermal Conductivity

NASA Technical Reports Server (NTRS)

Martinez-Garcia, Jorge; Braginsky, Leonid; Shklover, Valery; Lawson, John W.

2011-01-01

The heat transport in highly porous fiber structures is investigated. The fibers are supposed to be thin, but long, so that the number of the inter-fiber connections along each fiber is large. We show that the effective conductivity of such structures can be found from the correlation length of the two-point correlation function of the local conductivities. Estimation of the parameters, determining the conductivity, from the 2D images of the structures is analyzed.

Transparent conducting oxides and production thereof

DOEpatents

Gessert, Timothy A; Yoshida, Yuki; Coutts, Timothy J

2014-05-27

Transparent conducting oxides and production thereof are disclosed. An exemplary method of producing a transparent conducting oxide (TCO) material may comprise: providing a TCO target (110) doped with either a high-permittivity oxide or a low-permittivity oxide in a process chamber (100). The method may also comprise depositing a metal oxide on the target (110) to form a thin film having enhanced optical properties without substantially decreasing electrical quality.

Transparent conducting oxides and production thereof

DOEpatents

Gessert, Timothy A.; Yoshida, Yuki; Coutts, Timothy J.

2014-06-10

Transparent conducting oxides and production thereof are disclosed. An exemplary method of producing a transparent conducting oxide (TCO) material may comprise: providing a TCO target doped with either a high-permittivity oxide or a low-permittivity oxide in a process chamber. The method may also comprise depositing a metal oxide on the target in the process chamber to form a thin film having enhanced optical properties without substantially decreasing electrical quality.

Transparent conducting oxide nanotubes

NASA Astrophysics Data System (ADS)

Alivov, Yahya; Singh, Vivek; Ding, Yuchen; Nagpal, Prashant

2014-09-01

Thin film or porous membranes made of hollow, transparent, conducting oxide (TCO) nanotubes, with high chemical stability, functionalized surfaces and large surface areas, can provide an excellent platform for a wide variety of nanostructured photovoltaic, photodetector, photoelectrochemical and photocatalytic devices. While large-bandgap oxide semiconductors offer transparency for incident light (below their nominal bandgap), their low carrier concentration and poor conductivity makes them unsuitable for charge conduction. Moreover, materials with high conductivity have nominally low bandgaps and hence poor light transmittance. Here, we demonstrate thin films and membranes made from TiO2 nanotubes heavily-doped with shallow Niobium (Nb) donors (up to 10%, without phase segregation), using a modified electrochemical anodization process, to fabricate transparent conducting hollow nanotubes. Temperature dependent current-voltage characteristics revealed that TiO2 TCO nanotubes, doped with 10% Nb, show metal-like behavior with resistivity decreasing from 6.5 × 10-4 Ωcm at T = 300 K (compared to 6.5 × 10-1 Ωcm for nominally undoped nanotubes) to 2.2 × 10-4 Ωcm at T = 20 K. Optical properties, studied by reflectance measurements, showed light transmittance up to 90%, within wavelength range 400 nm-1000 nm. Nb doping also improves the field emission properties of TCO nanotubes demonstrating an order of magnitude increase in field-emitter current, compared to undoped samples.

Use of space ultra-vacuum for high quality semiconductor thin film growth

NASA Technical Reports Server (NTRS)

Ignatiev, A.; Sterling, M.; Sega, R. M.

1992-01-01

The utilization of space for materials processing is being expanded through a unique concept of epitaxial thin film growth in the ultra-vacuum of low earth orbit (LEO). This condition can be created in the wake of an orbiting space vehicle; and assuming that the vehicle itself does not pertub the environment, vacuum levels of better than 10 exp -14 torr can be attained. This vacuum environment has the capacity of greatly enhancing epitaxial thin film growth and will be the focus of experiments conducted aboard the Wake Shield Facility (WSF) currently being developed by the Space Vacuum Epitaxy Center (SVEC), Industry, and NASA.

Thermoelectric studies of nanoporous thin films with adjusted pore-edge charges

NASA Astrophysics Data System (ADS)

Hao, Qing; Zhao, Hongbo; Xu, Dongchao

2017-03-01

In recent years, nanoporous thin films have been widely studied for thermoelectric applications. High thermoelectric performance is reported for nanoporous Si films, which is attributed to the dramatically reduced lattice thermal conductivity and bulk-like electrical properties. Porous materials can also be used in gas sensing applications by engineering the surface-trapped charges on pore edges. In this work, an analytical model is developed to explore the relationship between the thermoelectric properties and pore-edge charges in a periodic two-dimensional nanoporous material. The presented model can be widely used to analyze the measured electrical properties of general nanoporous thin films and two-dimensional materials.

TiN-buffered substrates for photoelectrochemical measurements of oxynitride thin films

NASA Astrophysics Data System (ADS)

Pichler, Markus; Pergolesi, Daniele; Landsmann, Steve; Chawla, Vipin; Michler, Johann; Döbeli, Max; Wokaun, Alexander; Lippert, Thomas

2016-04-01

Developing novel materials for the conversion of solar to chemical energy is becoming an increasingly important endeavour. Perovskite compounds based on bandgap tunable oxynitrides represent an exciting class of novel photoactive materials. To date, literature mostly focuses on the characterization of oxynitride powder samples which have undeniable technological interest but do not allow the investigation of fundamental properties such as the role of the crystalline quality and/or the surface crystallographic orientation toward photo-catalytic activity. The challenge of growing high quality oxynitride thin films arises from the availability of a suitable substrate, owing to strict material and processing requirements: effective lattice matching, sufficiently high conductivities, stability under high temperatures and in strongly reducing environments. Here, we have established the foundations of a model system incorporating a TiN-buffer layer which enables fundamental investigations into crystallographic surface orientation and crystalline quality of the photocatalyst against photo(electro)chemical performance to be effectively performed. Furthermore, we find that TiN as current collector enables control over the nitrogen content of oxynitride thin films produced by a modified pulsed laser deposition method and allows the growth of highly ordered LaTiO3-xNx thin films.

Photoconductivity study of acid on Zinc phthalocyanine pyridine thin films

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

Singh, Sukhwinder, E-mail: ss7667@gmail.com; Saini, G. S. S.; Tripathi, S. K.

2016-05-06

The Metal Phthalocyanine (MPc) have attracted much interest because of chemical and high thermal stability. Molecules forming a crystal of MPc are held together by weak attractive Vander Waals forces. Organic semiconductors have π conjugate bonds which allow electrons to move via π-electron cloud overlaps. Conduction mechanisms for organic semiconductor are mainly through tunneling; hopping between localized states, mobility gaps, and phonon assisted hopping. The photo conductivity of thin films of these complexes changes when exposed to oxidizing and reducing gases. Arrhenius plot is used to find the thermal activation energy in the intrinsic region and impurity scattering region. Arrheniusmore » plotsare used to find the thermal activation energy.« less

Evidence for the bias-driven migration of oxygen vacancies in amorphous non-stoichiometric gallium oxide

NASA Astrophysics Data System (ADS)

Guo, D. Y.; Qian, Y. P.; Su, Y. L.; Shi, H. Z.; Li, P. G.; Wu, J. T.; Wang, S. L.; Cui, C.; Tang, W. H.

2017-06-01

The conductivity of gallium oxide thin films is strongly dependent on the growth temperature when they deposited by pulsed laser deposition under vacuum environment, exhibiting an insulative-to-metallic transition with the decrease of the temperature. The high conductive gallium oxide films deposited at low temperature are amorphous, non-stoichiometric, and rich in oxygen vacancy. Large changes in electrical resistance are observed in these non-stoichiometric thin films. The wide variety of hysteretic shapes in the I-V curves depend on the voltage-sweep rate, evidencing that the time-dependent redistribution of oxygen vacancy driven by bias is the controlling parameter for the resistance of gallium oxide.

Impedance spectroscopy of the electrode-tissue interface of living heart with isoösmotic conductivity perturbation

NASA Astrophysics Data System (ADS)

Ovadia, Marc; Zavitz, Daniel H.

2004-06-01

Impedance spectroscopy was used to solve the Pt electrode interface with metabolically active perfused living heart. Three impedance spectra were observed: the Warburg impedance ( ZW∞), a single high angle constant-phase-element, and a thin-film impedance ( ZD). When characterized again after cyclic change of ionic strength (and hence conductivity κ) each interface had one of only two spectra, with exclusion of ZW∞. The in vivo interfacial impedance spectrum is thus neither single-valued nor stable in time. Because metal|living tissue interfaces are obligatory circuit elements in biosensors and electrodes in heart and brain, the multiple-valued and thin-film character of its impedance are significant.

Prototype thin-film thermocouple/heat-flux sensor for a ceramic-insulated diesel engine

NASA Technical Reports Server (NTRS)

Kim, Walter S.; Barrows, Richard F.

1988-01-01

A platinum versus platinum-13 percent rhodium thin-film thermocouple/heat-flux sensor was devised and tested in the harsh, high-temperature environment of a ceramic-insulated, low-heat-rejection diesel engine. The sensor probe assembly was developed to provide experimental validation of heat transfer and thermal analysis methodologies applicable to the insulated diesel engine concept. The thin-film thermocouple configuration was chosen to approximate an uninterrupted chamber surface and provide a 1-D heat-flux path through the probe body. The engine test was conducted by Purdue University for Integral Technologies, Inc., under a DOE-funded contract managed by NASA Lewis Research Center. The thin-film sensor performed reliably during 6 to 10 hr of repeated engine runs at indicated mean surface temperatures up to 950 K. However, the sensor suffered partial loss of adhesion in the thin-film thermocouple junction area following maximum cyclic temperature excursions to greater than 1150 K.

Optical Properties and Electrochemical Performance of LiFePO4 Thin Films Deposited on Transparent Current Collectors.

PubMed

Lee, HyunSeok; Yim, Haena; Kim, Kwang-Bum; Choi, Ji-Won

2015-11-01

LiFePO4 thin film cathodes are deposited on various transparent conducting oxide thin films on glass, which are used as cathode current collectors. The XRD patterns show that the thin films have the phase of LiFePO4 with an ordered olivine structure indexed to the orthorhombic Pmna space group. LiFePO4 thin film deposited on various TCO glass substrates exhibits transmittance of about 53%. The initial specific discharge capacities of LiFePO4 thin films are 25.0 μAh/cm2 x μm on FTO, 33.0 μAh/cm2 x μm on ITO, and 13.0 μAh/cm2 x μm on AZO coated glass substrates. Interestingly, the retention capacities of LiFePO4 thin films are 76.0% on FTO, 31.2% on ITO, and 37.7% on AZO coated glass substrates at 20th cycle. The initial specific discharge capacity of the LiFePO4/FTO electrode is slightly lower, but the discharge capacities of the LiFePO4/FTO electrode relatively decrease less than those of the others such as LiFePO4/ITO and LiFePO4/AZO with cycling. The results reported here provide the high transparency of LiFePO4 thin films cathode materials and the good candidate as FTO current collector of the LiFePO4 thin film cathode of transparent thin film rechargeable batteries due to its high transparency and cyclic retention.

An ultra-thin, un-doped NiO hole transporting layer of highly efficient (16.4%) organic-inorganic hybrid perovskite solar cells.

PubMed

Seo, Seongrok; Park, Ik Jae; Kim, Myungjun; Lee, Seonhee; Bae, Changdeuck; Jung, Hyun Suk; Park, Nam-Gyu; Kim, Jin Young; Shin, Hyunjung

2016-06-02

NiO is a wide band gap p-type oxide semiconductor and has potential for applications in solar energy conversion as a hole-transporting layer (HTL). It also has good optical transparency and high chemical stability, and the capability of aligning the band edges to the perovskite (CH3NH3PbI3) layers. Ultra-thin and un-doped NiO films with much less absorption loss were prepared by atomic layer deposition (ALD) with highly precise control over thickness without any pinholes. Thin enough (5-7.5 nm in thickness) NiO films with the thickness of few time the Debye length (LD = 1-2 nm for NiO) show enough conductivities achieved by overlapping space charge regions. The inverted planar perovskite solar cells with NiO films as HTLs exhibited the highest energy conversion efficiency of 16.40% with high open circuit voltage (1.04 V) and fill factor (0.72) with negligible current-voltage hysteresis.

Growth of highly textured PbTiO3 films on conductive substrate under hydrothermal conditions

NASA Astrophysics Data System (ADS)

Tang, Haixiong; Zhou, Zhi; Bowland, Christopher C.; Sodano, Henry A.

2015-08-01

Perovskite structure (ABO3) thin films have wide applications in electronic devices due to their unique properties, including high dielectric permittivity, ferroelectricity and piezoelectric coupling. Here, we report an approach to grow highly textured thick lead titanate (PbTiO3) films on conductive substrates by a two-step hydrothermal reaction. Initially, vertically aligned TiO2 nanowire arrays are grown on fluorine-doped tin oxide (FTO) coated glass, which act as template crystals for conversion to the perovskite structure. The PbTiO3 films are then converted from TiO2 NW arrays by diffusing Pb2+ ions into the template through a second hydrothermal reaction. The dielectric permittivity and piezoelectric coupling coefficient (d33) of the PbTiO3 films are as high as 795 at 1 kHz and 52 pm V-1, respectively. The reported process can also potentially be expanded for the assembly of other complex perovskite ATiO3 (A = Ba, Ca, Cd, etc) films by using the highly aligned TiO2 NW arrays as templates. Therefore, the approach introduced here opens up a new door to synthesize ferroelectric thin films on conductive substrates for application in sensors, actuators, and ultrasonic transducers that are important in various industrial and scientific areas.

Process for producing molybdenum foil and collapsible tubing

NASA Technical Reports Server (NTRS)

Bretts, G. R.; Gavert, R. B.; Groschke, G. F.

1971-01-01

Manufacturing process produces molybdenum foil 0.002 cm thick and 305 m long, and forms foil into high-strength, thin-walled tubing which can be flattened for storage on a spool. Desirable metal properties include high thermal conductivity stiffness, yield and tensile stress, and low thermal expansion coeffecient.

Single Source Precursors for Thin Film Solar Cells

NASA Technical Reports Server (NTRS)

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

2002-01-01

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

Stretchable, Twisted Conductive Microtubules for Wearable Computing, Robotics, Electronics, and Healthcare.

PubMed

Do, Thanh Nho; Visell, Yon

2017-05-11

Stretchable and flexible multifunctional electronic components, including sensors and actuators, have received increasing attention in robotics, electronics, wearable, and healthcare applications. Despite advances, it has remained challenging to design analogs of many electronic components to be highly stretchable, to be efficient to fabricate, and to provide control over electronic performance. Here, we describe highly elastic sensors and interconnects formed from thin, twisted conductive microtubules. These devices consist of twisted assemblies of thin, highly stretchable (>400%) elastomer tubules filled with liquid conductor (eutectic gallium indium, EGaIn), and fabricated using a simple roller coating process. As we demonstrate, these devices can operate as multimodal sensors for strain, rotation, contact force, or contact location. We also show that, through twisting, it is possible to control their mechanical performance and electronic sensitivity. In extensive experiments, we have evaluated the capabilities of these devices, and have prototyped an array of applications in several domains of stretchable and wearable electronics. These devices provide a novel, low cost solution for high performance stretchable electronics with broad applications in industry, healthcare, and consumer electronics, to emerging product categories of high potential economic and societal significance.

Conjunction of Conducting Polymer Nanostructures with Macroporous Structured Graphene Thin Films for High-Performance Flexible Supercapacitors.

PubMed

Memon, Mushtaque A; Bai, Wei; Sun, Jinhua; Imran, Muhammad; Phulpoto, Shah Nawaz; Yan, Shouke; Huang, Yong; Geng, Jianxin

2016-05-11

Fabrication of hybridized structures is an effective strategy to promote the performances of graphene-based composites for energy storage/conversion applications. In this work, macroporous structured graphene thin films (MGTFs) are fabricated on various substrates including flexible graphene papers (GPs) through an ice-crystal-induced phase separation process. The MGTFs prepared on GPs (MGTF@GPs) are recognized with remarkable features such as interconnected macroporous configuration, sufficient exfoliation of the conductive RGO sheets, and good mechanical flexibility. As such, the flexible MGTF@GPs are demonstrated as a versatile conductive platform for depositing conducting polymers (CPs), e.g., polyaniline (PAn), polypyrrole, and polythiophene, through in situ electropolymerization. The contents of the CPs in the composite films are readily controlled by varying the electropolymerization time. Notably, electrodeposition of PAn leads to the formation of nanostructures of PAn nanofibers on the walls of the macroporous structured RGO framework (PAn@MGTF@GPs): thereafter, the PAn@MGTF@GPs display a unique structural feature that combine the nanostructures of PAn nanofibers and the macroporous structures of RGO sheets. Being used as binder-free electrodes for flexible supercapacitors, the PAn@MGTF@GPs exhibit excellent electrochemical performance, in particular a high areal specific capacity (538 mF cm(-2)), high cycling stability, and remarkable capacitive stability to deformation, due to the unique electrode structures.

Structural and thermoelectric properties of epitaxially grown Bi2Te3 thin films and superlattices

NASA Astrophysics Data System (ADS)

Peranio, N.; Eibl, O.; Nurnus, J.

2006-12-01

Multi-quantum-well structures of Bi2Te3 are predicted to have a high thermoelectric figure of merit ZT. Bi2Te3 thin films and Bi2Te3/Bi2(Te0.88Se0.12)3 superlattices (SLs) were grown epitaxially by molecular beam epitaxy on BaF2 substrates with periods of 12 and 6nm, respectively. Reflection high-energy electron diffraction confirmed a layer-by-layer growth, x-ray diffraction yielded the lattice parameters and SL periods and proved epitaxial growth. The in-plane transport coefficients were measured and the thin films and SL had power factors between 28 and 35μW /cmK2. The lattice thermal conductivity varied between 1.60W/mK for Bi2Te3 thin films and 1.01W/mK for a 10nm SL. The best figures of merit ZT were achieved for the SL; however, the values are slightly smaller than those in bulk materials. Thin films and superlattices were investigated in plan view and cross section by transmission electron microscopy. In the Bi2Te3 thin film and SL the dislocation density was found to be 2×1010cm-2. Bending of the SL with amplitudes of 30nm (12nm SL) and 15nm (6nm SL) and a wavelength of 400nm was determined. Threading dislocations were found with a density greater than 2×109cm-2. The superlattice interfaces are strongly bent in the region of the threading dislocations, undisturbed regions have a maximum lateral sie of 500nm. Thin films and SL showed a structural modulation [natural nanostructure (nns)] with a wavelength of 10nm and a wave vector parallel to (1,0,10). This nns was also observed in Bi2Te3 bulk materials and turned out to be of general character for Bi2Te3. The effect of the microstructure on the thermoelectric properties is discussed. The microstructure is governed by the superlattice, the nns, and the dislocations that are present in the films. Our results indicate that the microstructure directly affects the lattice thermal conductivity. Thermopower and electrical conductivity were found to be negatively correlated and no clear dependence of the two quantities on the microstructure could be found.

Low intrinsic c-axis thermal conductivity in PVD grown epitaxial Sb2Te3 films

NASA Astrophysics Data System (ADS)

Rieger, F.; Kaiser, K.; Bendt, G.; Roddatis, V.; Thiessen, P.; Schulz, S.; Jooss, C.

2018-05-01

Accurate determination and comprehensive understanding of the intrinsic c-axis thermal conductivity κc of thermoelectric layered Sb2Te3 is of high importance for the development of strategies to optimize the figure of merit in thin film devices via heterostructures and defect engineering. We present here high precision measurements of κc of epitaxial Sb2Te3 thin films on Al2O3 substrates grown by physical vapor deposition in the temperature range of 100 K to 300 K. The Kapitza resistances of the involved interfaces have been determined and subtracted from the film data, allowing access to the intrinsic thermal conductivity of single crystalline Sb2Te3. At room temperature, we obtain κc = 1.9 W/m K, being much smaller than the in-plane thermal conductivity of κa b = 5 W/m K and even lower than the thermal conductivity of nano crystalline films of κnc ≈ 2.0-2.6 W/m K published by Park et al. [Nanoscale Res. Lett. 9, 96 (2014)]. High crystallinity and very low defect concentration of the films were confirmed by x-ray diffraction and high resolution transmission electron microscopy. Our data reveal that the phonon mean free path lm f p(" separators="|T ) is not limited by defect scattering and is of intrinsic nature, i.e., due to phonon-phonon scattering similar to other soft van der Waals type bonded layered systems.

Photovoltaic devices comprising cadmium stannate transparent conducting films and method for making

DOEpatents

Wu, Xuanzhi; Coutts, Timothy J.; Sheldon, Peter; Rose, Douglas H.

1999-01-01

A photovoltaic device having a substrate, a layer of Cd.sub.2 SnO.sub.4 disposed on said substrate as a front contact, a thin film comprising two or more layers of semiconductor materials disposed on said layer of Cd.sub.2 SnO.sub.4, and an electrically conductive film disposed on said thin film of semiconductor materials to form a rear electrical contact to said thin film. The device is formed by RF sputter coating a Cd.sub.2 SnO.sub.4 layer onto a substrate, depositing a thin film of semiconductor materials onto the layer of Cd.sub.2 SnO.sub.4, and depositing an electrically conductive film onto the thin film of semiconductor materials.

Electrical and structural properties of TiO2-δ thin film with oxygen vacancies prepared by RF magnetron sputtering using oxygen radical

NASA Astrophysics Data System (ADS)

Kawamura, Kinya; Suzuki, Naoya; Tsuchiya, Takashi; Shimazu, Yuichi; Minohara, Makoto; Kobayashi, Masaki; Horiba, Koji; Kumigashira, Hiroshi; Higuchi, Tohru

2016-06-01

Anatase TiO2-δ thin film was prepared by RF magnetron sputtering using oxygen radical and Ti-metal target. Degrees of the TiO2-δ crystal orientation in the thin film depends of the oxygen gas pressure (P\\text{O2}) in the radical gun. The (004)- and (112)-oriented TiO2-δ thin films crystallized without postannealing have the mixed valence Ti4+/Ti3+ state. The electrical conductivities, which corresponds to n-type oxide semiconductor, is higher in the case of (004)-oriented TiO2-δ thin film containing with high concentration of oxygen vacancy. The donor band of TiO2-δ thin film is observed at ˜1.0 eV from the Fermi level (E F). The density-of-state at E F is higher in (004)-oriented TiO2-δ thin film. The above results indicate that the oxygen vacancies can control by changing the P\\text{O2} of the oxygen radical.

A convenient method for large-scale STM mapping of freestanding atomically thin conductive membranes

NASA Astrophysics Data System (ADS)

Uder, B.; Hartmann, U.

2017-06-01

Two-dimensional atomically flat sheets with a high flexibility are very attractive as ultrathin membranes but are also inherently challenging for microscopic investigations. We report on a method using Scanning Tunneling Microscopy (STM) under ultra-high vacuum conditions for large-scale mapping of several-micrometer-sized freestanding single and multilayer graphene membranes. This is achieved by operating the STM at unusual parameters. We found that large-scale scanning on atomically thin membranes delivers valuable results using very high tip-scan speeds combined with high feedback-loop gain and low tunneling currents. The method ultimately relies on the particular behavior of the freestanding membrane in the STM which is much different from that of a solid substrate.

Codoping of zinc and tungsten for practical high-performance amorphous indium-based oxide thin film transistors

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

Kizu, Takio, E-mail: KIZU.Takio@nims.go.jp, E-mail: TSUKAGOSHI.Kazuhito@nims.go.jp; Mitoma, Nobuhiko; Tsukagoshi, Kazuhito, E-mail: KIZU.Takio@nims.go.jp, E-mail: TSUKAGOSHI.Kazuhito@nims.go.jp

2015-09-28

Using practical high-density sputtering targets, we investigated the effect of Zn and W codoping on the thermal stability of the amorphous film and the electrical characteristics in thin film transistors. zinc oxide is a potentially conductive component while W oxide is an oxygen vacancy suppressor in oxide films. The oxygen vacancy from In-O and Zn-O was suppressed by the W additive because of the high oxygen bond dissociation energy. With controlled codoping of W and Zn, we demonstrated a high mobility with a maximum mobility of 40 cm{sup 2}/V s with good stability under a negative bias stress in InWZnO thinmore » film transistors.« less

High absorption coefficients of the CuSb(Se,Te)2 and CuBi(S,Se)2 alloys enable high-efficient 100 nm thin-film photovoltaics

NASA Astrophysics Data System (ADS)

Chen, Rongzhen; Persson, Clas

2017-06-01

We demonstrate that the band-gap energies Eg of CuSb(Se,Te)2 and CuBi(S,Se)2 can be optimized for high energy conversion in very thin photovoltaic devices, and that the alloys then exhibit excellent optical properties, especially for tellurium rich CuSb(Se1-xTex)2. This is explained by multi-valley band structure with flat energy dispersions, mainly due to the localized character of the Sb/Bi p-like conduction band states. Still the effective electron mass is reasonable small: mc ≈ 0.25m0 for CuSbTe2. The absorption coefficient α(ω) for CuSb(Se1-xTex)2 is at ħω = Eg + 1 eV as much as 5-7 times larger than α(ω) for traditional thin-film absorber materials. Auger recombination does limit the efficiency if the carrier concentration becomes too high, and this effect needs to be suppressed. However with high absorptivity, the alloys can be utilized for extremely thin inorganic solar cells with the maximum efficiency ηmax ≈ 25% even for film thicknesses d ≈ 50 - 150 nm, and the efficiency increases to ˜30% if the Auger effect is diminished.

Fabrication and stability investigation of ultra-thin transparent and flexible Cu-Ag-Au tri-layer film on PET

NASA Astrophysics Data System (ADS)

Prakasarao, Ch Surya; D'souza, Slavia Deeksha; Hazarika, Pratim; Karthiselva N., S.; Ramesh Babu, R.; Kovendhan, M.; Kumar, R. Arockia; Joseph, D. Paul

2018-04-01

The need for transparent conducting electrodes with high transmittance, low sheet resistance and flexibility to replace Indium Tin Oxide is ever growing. We have deposited and studied the performance of ultra-thin Cu-Ag-Au tri-layer films over a flexible poly-ethylene terephthalate substrate. Scotch tape test showed good adhesion of the metallic film. Transmittance of the tri-layer was around 40 % in visible region. Optical profiler measurements were done to study the surface features. The XRD pattern revealed that film was amorphous. Sheet resistance measured by four probe technique was around 7.7 Ohm/Δ and was stable up to 423 K. The transport parameters by Hall effect showed high conductivity and carrier concentration with a mobility of 5.58 cm2/Vs. Tests performed in an indigenously designed bending unit indicated the films to be stable both mechanically and electrically even after 50,000 bending cycles.

Ion-conducting ceramic apparatus, method, fabrication, and applications

DOEpatents

Yates, Matthew [Penfield, NY; Liu, Dongxia [Rochester, NY

2012-03-06

A c-axis-oriented HAP thin film synthesized by seeded growth on a palladium hydrogen membrane substrate. An exemplary synthetic process includes electrochemical seeding on the substrate, and secondary and tertiary hydrothermal treatments under conditions that favor growth along c-axes and a-axes in sequence. By adjusting corresponding synthetic conditions, an HAP this film can be grown to a controllable thickness with a dense coverage on the underlying substrate. The thin films have relatively high proton conductivity under hydrogen atmosphere and high temperature conditions. The c-axis oriented films may be integrated into fuel cells for application in the intermediate temperature range of 200-600.degree. C. The electrochemical-hydrothermal deposition technique may be applied to create other oriented crystal materials having optimized properties, useful for separations and catalysis as well as electronic and electrochemical applications, electrochemical membrane reactors, and in chemical sensors.

Anatase phase stability and doping concentration dependent refractivity in codoped transparent conducting TiO2 films

NASA Astrophysics Data System (ADS)

Chen, T. L.; Furubayashi, Y.; Hirose, Y.; Hitosugi, T.; Shimada, T.; Hasegawa, T.

2007-10-01

Nb0.06SnxTi0.94-xO2 (x <= 0.3) thin films were grown by a pulsed-laser deposition method with varying Sn concentration. Through a combinatorial technique, we find that Sn concentration can reach a maximum of about x = 0.3 while maintaining the stable anatase phase and epitaxy. A doping concentration dependence of the refractivity is revealed, in which refractivity reduction at a wavelength of λ = 500 nm is estimated to be 12.4% for Nb0.06Sn0.3 Ti0.64O2 thin film. Sn doping induced band-gap blue shift can be contributed to the mixing of extended Sn 5s orbitals with the conduction band of TiO2. Low resistivity on the order of 10-4 Ω cm at room temperature and high internal transmittance of more than 95% in the visible light region are exhibited for Nb0.06Snx Ti0.94-xO2 thin films (x <= 0.2). Optical and transport analyses demonstrate that doping Sn into Nb0.06 Ti0.94O2 can reduce the refractivity while maintaining low resistivity and high transparency.

Room-Temperature Multiferroics and Thermal Conductivity of 0.85BiFe1-2xTixMgxO3-0.15CaTiO3 Epitaxial Thin Films (x = 0.1 and 0.2).

PubMed

Zhang, Ji; Sun, Wei; Zhao, Jiangtao; Sun, Lei; Li, Lei; Yan, Xue-Jun; Wang, Ke; Gu, Zheng-Bin; Luo, Zhen-Lin; Chen, Yanbin; Yuan, Guo-Liang; Lu, Ming-Hui; Zhang, Shan-Tao

2017-08-02

Thin films of 0.85BiFe 1-2x Ti x Mg x O 3 -0.15CaTiO 3 (x = 0.1 and 0.2, abbreviated to C-1 and C-2, respectively) have been fabricated on (001) SrTiO 3 substrate with and without a conductive La 0.7 Sr 0.3 MnO 3 buffer layer. The X-ray θ-2θ and ϕ scans, atomic force microscopy, and cross-sectional transmission electron microscopy confirm the (001) epitaxial nature of the thin films with very high growth quality. Both the C-1 and C-2 thin films show well-shaped magnetization-magnetic field hysteresis at room temperature, with enhanced switchable magnetization values of 145.3 and 42.5 emu/cm 3 , respectively. The polarization-electric loops and piezoresponse force microscopy measurements confirm the room-temperature ferroelectric nature of both films. However, the C-1 films illustrate a relatively weak ferroelectric behavior and the poled states are easy to relax, whereas the C-2 films show a relatively better ferroelectric behavior with stable poled states. More interestingly, the room-temperature thermal conductivity of C-1 and C-2 films are measured to be 1.10 and 0.77 W/(m·K), respectively. These self-consistent multiferroic properties and thermal conductivities are discussed by considering the composition-dependent content and migration of Fe-induced electrons and/or charged point defects. This study not only provides multifunctional materials with excellent room-temperature magnetic, ferroelectric, and thermal conductivity properties but may also stimulate further work to develop BiFeO 3 -based materials with unusual multifunctional properties.

Electronic transport in mixed-phase hydrogenated amorphous/nanocrystalline silicon thin films

NASA Astrophysics Data System (ADS)

Wienkes, Lee Raymond

Interest in mixed-phase silicon thin film materials, composed of an amorphous semiconductor matrix in which nanocrystalline inclusions are embedded, stems in part from potential technological applications, including photovoltaic and thin film transistor technologies. Conventional mixed-phase silicon films are produced in a single plasma reactor, where the conditions of the plasma must be precisely tuned, limiting the ability to adjust the film and nanoparticle parameters independently. The films presented in this thesis are deposited using a novel dual-plasma co-deposition approach in which the nanoparticles are produced separately in an upstream reactor and then injected into a secondary reactor where an amorphous silicon film is being grown. The degree of crystallinity and grain sizes of the films are evaluated using Raman spectroscopy and X-ray diffraction respectively. I describe detailed electronic measurements which reveal three distinct conduction mechanisms in n-type doped mixed-phase amorphous/nanocrystalline silicon thin films over a range of nanocrystallite concentrations and temperatures, covering the transition from fully amorphous to ~30% nanocrystalline. As the temperature is varied from 470 to 10 K, we observe activated conduction, multiphonon hopping (MPH) and Mott variable range hopping (VRH) as the nanocrystal content is increased. The transition from MPH to Mott-VRH hopping around 100K is ascribed to the freeze out of the phonon modes. A conduction model involving the parallel contributions of these three distinct conduction mechanisms is shown to describe both the conductivity and the reduced activation energy data to a high accuracy. Additional support is provided by measurements of thermal equilibration effects and noise spectroscopy, both done above room temperature (>300 K). This thesis provides a clear link between measurement and theory in these complex materials.

Tunable transport property of oxygen ion in metal oxide thin film: Impact of electrolyte orientation on conductivity.

PubMed

Arunkumar, P; Ramaseshan, R; Dash, S; Babu, K Suresh

2017-06-14

Quest for efficient ion conducting electrolyte thin film operating at intermediate temperature (~600 °C) holds promise for the real-world utilization of solid oxide fuel cells. Here, we report the correlation between mixed as well as preferentially oriented samarium doped cerium oxide electrolyte films fabricated by varying the substrate temperatures (100, 300 and 500 °C) over anode/ quartz by electron beam physical vapor deposition. Pole figure analysis of films deposited at 300 °C demonstrated a preferential (111) orientation in out-off plane direction, while a mixed orientation was observed at 100 and 500 °C. As per extended structural zone model, the growth mechanism of film differs with surface mobility of adatom. Preferential orientation resulted in higher ionic conductivity than the films with mixed orientation, demonstrating the role of growth on electrochemical properties. The superior ionic conductivity upon preferential orientation arises from the effective reduction of anisotropic nature and grain boundary density in highly oriented thin films in out-of-plane direction, which facilitates the hopping of oxygen ion at a lower activation energy. This unique feature of growing an oriented electrolyte over the anode material opens a new approach to solving the grain boundary limitation and makes it as a promising solution for efficient power generation.

Raman studied of undoped amorphous carbon thin film deposited by bias assisted-CVD

NASA Astrophysics Data System (ADS)

Ishak, A.; Fadzilah, A. N.; Dayana, K.; Saurdi, I.; Malek, M. F.; Nurbaya, Z.; Shafura, A. K.; Rusop, M.

2018-05-01

The undoped amorphous carbon thin film carbon was deposited at 200°C-350°C by bias assisted-CVD using palm oil as a precursor material. The effect of different substrate deposition temperatures on structural and electrical properties of undoped doped amorphous carbon film was discussed. The structural of undoped amorphous carbon films were correlated with Raman analysis through the evolution of D and G bands, Fourier spectra, and conductivity measurement. The spectral evolution observed showed the increase of upward shift of D and G peaks as substrate deposition temperatures increased. The spectral evolution observed at different substrate deposition temperatures show progressive formation of crystallites. It was predicted that small number of hydrogen is terminated with carbon at surface of thin film as shown by FTIR spectra since palm oil has high number of hydrogen (C67H127O8). These structural changes were further correlated with conductivity and the results obtained are discussed and compared. The conductivity is found in the range of 10-8 Scm-1. The increase of conductivity is correlated by the change of structural properties as correlated with characteristic parameters of Raman spectra including the position of G peak, full width at half maximum of G peak, and ID/IG and FTIR result.

Influence of precursor concentration on physical properties of CdO thin films prepared by spray pyrolysis technique using nebulizer

NASA Astrophysics Data System (ADS)

Anitha, M.; Amalraj, L.; Anitha, N.

2017-12-01

Cadmium oxide (CdO) thin films were prepared with different concentrations of precursor solution (0.05, 0.1, 0.15, 0.2 and 0.25 M, respectively) at the optimized temperature (200 °C) using the nebulized spray pyrolysis technique to obtain better crystallinity in polycrystalline thin films on amorphous glass substrates. The XRD characterization of those samples revealed a preferential orientation along the (111) plane having a cubic structure. The scanning electron microscopy (SEM) analysis displayed that all the as-deposited thin films have spherical shaped grains. The transmittance of the as-deposited CdO thin films had decreased from 88 to 71% for longer wavelength regions (600-900 nm) as the precursor concentration had increased and then increased for higher precursor concentration. The optical band gap was found to lie between 2.45 and 2.40 eV belonging to direct transition for those thin films. The presence of Cd-O bond (540 cm-1) was confirmed by FTIR spectrum. The emission properties of CdO thin films were studied by luminescence spectrum recorded at room temperature. A maximum carrier concentration and minimum resistivity values of 4.743 × 1019 cm- 3 and 1.06 × 10-3 Ω-cm, respectively, were obtained for 0.2 M precursor concentration. These CdO thin films have high optical transmittance and high room temperature conductivity, which can be used as the TCO and Solar cell (window layer) material.

Thin film photovoltaic device with multilayer substrate

DOEpatents

Catalano, Anthony W.; Bhushan, Manjul

1984-01-01

A thin film photovoltaic device which utilizes at least one compound semiconductor layer chosen from Groups IIB and VA of the Periodic Table is formed on a multilayer substrate The substrate includes a lowermost support layer on which all of the other layers of the device are formed. Additionally, an uppermost carbide or silicon layer is adjacent to the semiconductor layer. Below the carbide or silicon layer is a metal layer of high conductivity and expansion coefficient equal to or slightly greater than that of the semiconductor layer.

Surface charge transport in Silicon (111) nanomembranes

NASA Astrophysics Data System (ADS)

Hu, Weiwei; Scott, Shelley; Jacobson, Rb; Savage, Donald; Lagally, Max; The Lagally Group Team

Using thin sheets (``nanomembranes'') of atomically flat crystalline semiconductors, we are able to investigate surface electronic properties, using back-gated van der Pauw measurement in UHV. The thinness of the sheet diminishes the bulk contribution, and the back gate tunes the conductivity until the surface dominates, enabling experimental determination of surface conductance. We have previously shown that Si(001) surface states interact with the body of the membrane altering the conductivity of the system. Here, we extended our prior measurements to Si(111) in order to probe the electronic transport properties of the Si(111) 7 ×7 reconstruction. Sharp (7 ×7) LEED images attest to the cleanliness of the Si(111) surface. Preliminary results reveal a highly conductive Si(111) 7 ×7 surface with a sheet conductance Rs of order of μS/ □, for 110nm thick membrane, and Rs is a very slowly varying function of the back gate voltage. This is in strong contrast to Si(001) nanomembranes which have a minimum conductance several orders of magnitude lower, and hints to the metallic nature of the Si(111) surface. Research supported by DOE.

Graphene-Decorated Nanocomposites for Printable Electrodes in Thin Wafer Devices

NASA Astrophysics Data System (ADS)

Bakhshizadeh, N.; Sivoththaman, S.

2017-12-01

Printable electrodes that induce less stress and require lower curing temperatures compared to traditional screen-printed metal pastes are needed in thin wafer devices such as future solar cells, and in flexible electronics. The synthesis of nanocomposites by incorporating graphene nanopowders as well as silver nanowires into epoxy-based electrically conductive adhesives (ECA) is examined to improve electrical conductivity and to develop alternate printable electrode materials that induce less stress on the wafer. For the synthesized graphene and Ag nanowire-decorated ECA nanocomposites, the curing kinetics were studied by dynamic and isothermal differential scanning calorimetry measurements. Thermogravimetric analysis on ECA, ECA-AG and ECA/graphene nanopowder nanocomposites showed that the temperatures for onset of decomposition are higher than their corresponding glass transition temperature ( T g) indicating an excellent thermal resistance. Printed ECA/Ag nanowire nanocomposites showed 90% higher electrical conductivity than ECA films, whereas the ECA/graphene nanocomposites increased the conductivity by over two orders of magnitude. Scanning electron microscopy results also revealed the effect of fillers morphology on the conductivity improvement and current transfer mechanisms in nanocomposites. Residual stress analysis performed on Si wafers showed that the ECA and nanocomposite printed wafers are subjected to much lower stress compared to those printed with metallic pastes. The observed parameters of low curing temperature, good thermal resistance, reasonably high conductivity, and low residual stress in the ECA/graphene nanocomposite makes this material a promising alternative in screen-printed electrode formation in thin substrates.

Characterization of Polyethylene-Graft-Sulfonated Polyarylsulfone Proton Exchange Membranes for Direct Methanol Fuel Cell Applications.

PubMed

Kim, Hyung Kyu; Zhang, Gang; Nam, Changwoo; Chung, T C Mike

2015-12-04

This paper examines polymer film morphology and several important properties of polyethylene-graft-sulfonated polyarylene ether sulfone (PE-g-s-PAES) proton exchange membranes (PEMs) for direct methanol fuel cell applications. Due to the extreme surface energy differences between a semi-crystalline and hydrophobic PE backbone and several amorphous and hydrophilic s-PAES side chains, the PE-g-s-PAES membrane self-assembles into a unique morphology, with many proton conductive s-PAES channels embedded in the stable and tough PE matrix and a thin hydrophobic PE layer spontaneously formed on the membrane surfaces. In the bulk, these membranes show good mechanical properties (tensile strength >30 MPa, Young's modulus >1400 MPa) and low water swelling (λ < 15) even with high IEC >3 mmol/g in the s-PAES domains. On the surface, the thin hydrophobic and semi-crystalline PE layer shows some unusual barrier (protective) properties. In addition to exhibiting higher through-plane conductivity (up to 160 mS/cm) than in-plane conductivity, the PE surface layer minimizes methanol cross-over from anode to cathode with reduced fuel loss, and stops the HO• and HO₂• radicals, originally formed at the anode, entering into PEM matrix. Evidently, the thin PE surface layer provides a highly desirable protecting layer for PEMs to reduce fuel loss and increase chemical stability. Overall, the newly developed PE-g-s-PAES membranes offer a desirable set of PEM properties, including conductivity, selectivity, mechanical strength, stability, and cost-effectiveness for direct methanol fuel cell applications.

Characterization of Polyethylene-Graft-Sulfonated Polyarylsulfone Proton Exchange Membranes for Direct Methanol Fuel Cell Applications

PubMed Central

Kim, Hyung Kyu; Zhang, Gang; Nam, Changwoo; Chung, T.C. Mike

2015-01-01

This paper examines polymer film morphology and several important properties of polyethylene-graft-sulfonated polyarylene ether sulfone (PE-g-s-PAES) proton exchange membranes (PEMs) for direct methanol fuel cell applications. Due to the extreme surface energy differences between a semi-crystalline and hydrophobic PE backbone and several amorphous and hydrophilic s-PAES side chains, the PE-g-s-PAES membrane self-assembles into a unique morphology, with many proton conductive s-PAES channels embedded in the stable and tough PE matrix and a thin hydrophobic PE layer spontaneously formed on the membrane surfaces. In the bulk, these membranes show good mechanical properties (tensile strength >30 MPa, Young’s modulus >1400 MPa) and low water swelling (λ < 15) even with high IEC >3 mmol/g in the s-PAES domains. On the surface, the thin hydrophobic and semi-crystalline PE layer shows some unusual barrier (protective) properties. In addition to exhibiting higher through-plane conductivity (up to 160 mS/cm) than in-plane conductivity, the PE surface layer minimizes methanol cross-over from anode to cathode with reduced fuel loss, and stops the HO• and HO2• radicals, originally formed at the anode, entering into PEM matrix. Evidently, the thin PE surface layer provides a highly desirable protecting layer for PEMs to reduce fuel loss and increase chemical stability. Overall, the newly developed PE-g-s-PAES membranes offer a desirable set of PEM properties, including conductivity, selectivity, mechanical strength, stability, and cost-effectiveness for direct methanol fuel cell applications. PMID:26690232

Enhanced Remedial Amendment Delivery to Subsurface Using Shear Thinning Fluid and Aqueous Foam

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

Zhong, Lirong; Szecsody, James E.; Oostrom, Martinus

2011-04-23

A major issue with in situ subsurface remediation is the ability to achieve an even spatial distribution of remedial amendments to the contamination zones in an aquifer or vadose zone. Delivery of amendment to the aquifer using shear thinning fluid and to the vadose zone using aqueous foam has the potential to enhance the amendment distribution into desired locations and improve the remediation. 2-D saturated flow cell experiments were conducted to evaluate the enhanced sweeping, contaminant removal, and amendment persistence achieved by shear thinning fluid delivery. Bio-polymer xanthan gum solution was used as the shear thinning fluid. Unsaturated 1-D columnmore » and 2-D flow cell experiments were conducted to evaluate the mitigation of contaminant mobilization, amendment uniform distribution enhancement, and lateral delivery improvement by foam delivery. Surfactant sodium lauryl ether sulfate was used as the foaming agent. It was demonstrated that the shear thinning fluid injection enhanced the fluid sweeping over a heterogeneous system and increased the delivery of remedial amendment into low-permeability zones. The persistence of the amendment distributed into the low-perm zones by the shear thinning fluid was prolonged compared to that of amendment distributed by water injection. Foam delivery of amendment was shown to mitigate the mobilization of highly mobile contaminant from sediments under vadose zone conditions. Foam delivery also achieved more uniform amendment distribution in a heterogeneous unsaturated system, and demonstrated remarkable increasing in lateral distribution of the injected liquid compared to direct liquid injection.« less

Enhanced conductivity at orthorhombic–rhombohedral phase boundaries in BiFeO 3 thin films

DOE PAGES

Heo, Yooun; Lee, Jin Hong; Xie, Lin; ...

2016-08-26

Enhanced properties in modern functional materials can often be found at structural transition regions, such as morphotropic phase boundaries (MPB), owing to the coexistence of multiple phases with nearly equivalent energies. Strain-engineered MPBs have emerged in epitaxially grown BiFeO 3 (BFO) thin films by precisely tailoring a compressive misfit strain, leading to numerous intriguing phenomena, such as a massive piezoelectric response, magnetoelectric coupling, interfacial magnetism and electronic conduction. Recently, an orthorhombic–rhombohedral (O–R) phase boundary has also been found in tensile-strained BFO. In this study, we characterise the crystal structure and electronic properties of the two competing O and R phasesmore » using X-ray diffraction, scanning probe microscope and scanning transmission electron microscopy (STEM). We observe the temperature evolution of R and O domains and find that the domain boundaries are highly conductive. Temperature-dependent measurements reveal that the conductivity is thermally activated for R–O boundaries. STEM observations point to structurally wide boundaries, significantly wider than in other systems. Furthermore, we reveal a strong correlation between the highly conductive domain boundaries and structural material properties. These findings provide a pathway to use phase boundaries in this system for novel nanoelectronic applications.« less

The n-type conduction of indium-doped Cu{sub 2}O thin films fabricated by direct current magnetron co-sputtering

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

Cai, Xing-Min; Su, Xiao-Qiang; Ye, Fan, E-mail: yefan@szu.edu.cn

2015-08-24

Indium-doped Cu{sub 2}O thin films were fabricated on K9 glass substrates by direct current magnetron co-sputtering in an atmosphere of Ar and O{sub 2}. Metallic copper and indium disks were used as the targets. X-ray diffraction showed that the diffraction peaks could only be indexed to simple cubic Cu{sub 2}O, with no other phases detected. Indium atoms exist as In{sup 3+} in Cu{sub 2}O. Ultraviolet-visible spectroscopy showed that the transmittance of the samples was relatively high and that indium doping increased the optical band gaps. The Hall effect measurement showed that the samples were n-type semiconductors at room temperature. Themore » Seebeck effect test showed that the films were n-type semiconductors near or over room temperature (<400 K), changing to p-type at relatively high temperatures. The conduction by the samples in the temperature range of the n-type was due to thermal band conduction and the donor energy level was estimated to be 620.2–713.8 meV below the conduction band. The theoretical calculation showed that indium doping can raise the Fermi energy level of Cu{sub 2}O and, therefore, lead to n-type conduction.« less

Optical and structural properties of Al-doped ZnO thin films by sol gel process.

PubMed

Jun, Min-Chul; Koh, Jung-Hyuk

2013-05-01

Transparent conducting oxide (TCO) materials with high transmittance and good electrical conductivity have been attracted much attention due to the development of electronic display and devices such as organic light emitting diodes (OLEDs), and dye-sensitized solar cells (DSSCs). Aluminum doped zinc oxide thin films (AZO) have been well known for their use as TCO materials due to its stability, cost-effectiveness, good optical transmittance and electrical properties. Especially, AZO thin film, which have low resistivity of 2-4 x 10(-4) omega x cm which is similar to that of ITO films with wide band gap semiconductors. The AZO thin films were deposited on glass substrates by sol-gel spin-coating process. As a starting material, zinc acetate dihydrate (Zn(CH3COO)2 x 2H2O) and aluminum chloride hexahydrate (AlCl3 6H2O) were used. 2-methoxyethanol and monoethanolamine (MEA) were used as solvent and stabilizer, respectively. After deposited, the films were preheated at 300 degrees C on a hotplate and post-heated at 650 degrees C for 1.5 hrs in the furnace. We have studied the structural and optical properties as a function of Al concentration (0-2.5 mol.%).

Multi-Material Front Contact for 19% Thin Film Solar Cells.

PubMed

van Deelen, Joop; Tezsevin, Yasemin; Barink, Marco

2016-02-06

The trade-off between transmittance and conductivity of the front contact material poses a bottleneck for thin film solar panels. Normally, the front contact material is a metal oxide and the optimal cell configuration and panel efficiency were determined for various band gap materials, representing Cu(In,Ga)Se₂ (CIGS), CdTe and high band gap perovskites. Supplementing the metal oxide with a metallic copper grid improves the performance of the front contact and aims to increase the efficiency. Various front contact designs with and without a metallic finger grid were calculated with a variation of the transparent conductive oxide (TCO) sheet resistance, scribing area, cell length, and finger dimensions. In addition, the contact resistance and illumination power were also assessed and the optimal thin film solar panel design was determined. Adding a metallic finger grid on a TCO gives a higher solar cell efficiency and this also enables longer cell lengths. However, contact resistance between the metal and the TCO material can reduce the efficiency benefit somewhat.

A three-layer PMMA electrophoresis microchip with Pt microelectrodes insulated by a thin film for contactless conductivity detection.

PubMed

Liu, Junshan; Wang, Junyao; Chen, Zuanguang; Yu, Yong; Yang, Xiujuan; Zhang, Xianbin; Xu, Zheng; Liu, Chong

2011-03-07

A three-layer poly (methyl methacrylate) (PMMA) electrophoresis microchip integrated with Pt microelectrodes for contactless conductivity detection is presented. A 50 μm-thick PMMA film is used as the insulating layer and placed between the channel plate (containing the microchannel) and the electrode plate (containing the microelectrode). The three-layer structure facilitates the achievement of a thin insulating layer, obviates the difficulty of integrating microelectrodes on a thin film, and does not compromise the integration of microchips. To overcome the thermal and chemical incompatibilities of polymers and photolithographic techniques, a modified lift-off process was developed to integrate Pt microelectrodes onto the PMMA substrate. A novel two-step bonding method was created to assemble the complete PMMA microchip. A low limit of detection of 1.25 μg ml(-1) for Na(+) and high separation efficiency of 77,000 and 48,000 plates/m for Na(+) and K(+) were obtained when operating the detector at a low excitation frequency of 60 kHz.

Copper Phthalocyanine Functionalized Single-Walled Carbon Nanotubes: Thin Films for Optical Detection.

PubMed

Banimuslem, Hikmat; Hassan, Aseel; Basova, Tamara; Durmuş, Mahmut; Tuncel, Sinem; Esenpinar, Aliye Asli; Gürek, Ayşe Gül; Ahsen, Vefa

2015-03-01

Thin films of non-covalently hybridized single-walled carbon nanotubes (SWCNT) and tetra-substituted copper phthalocyanine (CuPcR4) molecules have been produced from their solutions in dimethylformamide (DMF). FTIR spectra revealed the 7π-7π interaction between SWCNTs and CuPcR4 molecules. DC conductivity of films of acid-treated SWCNT/CuPcR4 hybrid has increased by more than three orders of.magnitude in comparison with conductivity of CuPcR4 films. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) measurements have shown that films obtained from the acid-treated SWCNTs/CuPcR4 hybrids demonstrated more homogenous surface which is ascribed to the highly improved solubility of the hybrid powder in DMF Using total internal reflection ellipsometry spectroscopy (TIRE), thin films of the new hybrid have been examined as an optical sensing membrane for the detection of benzo[a]pyrene in water to demonstrate the sensing properties of the hybrid.

Bulk contribution to magnetotransport properties of low-defect-density Bi2Te3 topological insulator thin films

NASA Astrophysics Data System (ADS)

Ngabonziza, P.; Wang, Y.; Brinkman, A.

2018-04-01

An important challenge in the field of topological materials is to carefully disentangle the electronic transport contribution of the topological surface states from that of the bulk. For Bi2Te3 topological insulator samples, bulk single crystals and thin films exposed to air during fabrication processes are known to be bulk conducting, with the chemical potential in the bulk conduction band. For Bi2Te3 thin films grown by molecular beam epitaxy, we combine structural characterization (transmission electron microscopy), chemical surface analysis as function of time (x-ray photoelectron spectroscopy) and magnetotransport analysis to understand the low defect density and record high bulk electron mobility once charge is doped into the bulk by surface degradation. Carrier densities and electronic mobilities extracted from the Hall effect and the quantum oscillations are consistent and reveal a large bulk carrier mobility. Because of the cylindrical shape of the bulk Fermi surface, the angle dependence of the bulk magnetoresistance oscillations is two dimensional in nature.

Photovoltaic devices comprising cadmium stannate transparent conducting films and method for making

DOEpatents

Wu, X.; Coutts, T.J.; Sheldon, P.; Rose, D.H.

1999-07-13

A photovoltaic device is disclosed having a substrate, a layer of Cd[sub 2]SnO[sub 4] disposed on said substrate as a front contact, a thin film comprising two or more layers of semiconductor materials disposed on said layer of Cd[sub 2]SnO[sub 4], and an electrically conductive film disposed on said thin film of semiconductor materials to form a rear electrical contact to said thin film. The device is formed by RF sputter coating a Cd[sub 2]SnO[sub 4] layer onto a substrate, depositing a thin film of semiconductor materials onto the layer of Cd[sub 2]SnO[sub 4], and depositing an electrically conductive film onto the thin film of semiconductor materials. 10 figs.

Improved photocurrent of a poly (3,4-ethylenedioxythiophene)-ClO₄⁻/TiO₂ thin film-modified counter electrode for dye-sensitized solar cells.

PubMed

Sakurai, Sho; Kawamata, Yuka; Takahashi, Masashi; Kobayashi, Koichi

2011-01-01

We prepared a poly(3,4-ethylenedioxythiophene) (PEDOT)-ClO₄⁻-supported TiO₂ thin-film electrode as a counter electrode on a transparent conductive oxide glass electrode for a dye-sensitized solar cell (DSSC) using a combination of sol-gel and electropolymerization methods. The photocurrent-voltage characteristics indicate that DSSCs with PEDOT-ClO₄⁻/TiO₂ thin-film counter electrodes had a high photovoltaic conversion efficiency similar to that of PEDOT-ClO₄⁻/TiO₂ particle composite-film electrodes. Furthermore, it was found that the photocurrent was increased by attaching a reflector to the opposite side of the transparent counter electrode.

Influence of sputtering power on the optical properties of ITO thin films

NASA Astrophysics Data System (ADS)

K, Aijo John; Kumar, Vineetha V.; M, Deepak; T, Manju

2014-10-01

Tin doped indium oxide films are widely used in transparent conducting coatings such as flat panel displays, crystal displays and in optical devices such as solar cells and organic light emitting diodes due to the high electrical resistivity and optical transparency in the visible region of solar spectrum. The deposition parameters have a commendable influence on the optical and electrical properties of the thin films. In this study, ITO thin films were prepared by RF magnetron sputtering. The properties of the films prepared under varying sputtering power were compared using UV- visible spectrophotometry. Effect of sputtering power on the energy band gap, absorption coefficient and refractive index are investigated.

Highly Conductive One-Dimensional Manganese Oxide Wires by Coating with Graphene Oxides

NASA Astrophysics Data System (ADS)

Tojo, Tomohiro; Shinohara, Masaki; Fujisawa, Kazunori; Muramatsu, Hiroyuki; Hayashi, Takuya; Ahm Kim, Yoong; Endo, Morinobu

2012-10-01

Through coating with graphene oxides, we have developed a chemical route to the bulk production of long, thin manganese oxide (MnO2) nanowires that have high electrical conductivity. The average diameter of these hybrid nanowires is about 25 nm, and their average length is about 800 nm. The high electrical conductivity of these nanowires (ca. 189.51+/-4.51 µS) is ascribed to the homogeneous coating with conductive graphene oxides as well as the presence of non-bonding manganese atoms. The growth mechanism of the nanowires is theoretically supported by the initiation of morphological conversion from graphene oxide to wrapped structures through the formation of covalent bonds between manganese and oxygen atoms at the graphene oxide edge.

Mobility Enhancement in Amorphous In-Ga-Zn-O Thin-Film Transistor by Induced Metallic in Nanoparticles and Cu Electrodes.

PubMed

Hu, Shiben; Ning, Honglong; Lu, Kuankuan; Fang, Zhiqiang; Li, Yuzhi; Yao, Rihui; Xu, Miao; Wang, Lei; Peng, Junbiao; Lu, Xubing

2018-03-27

In this work, we fabricated a high-mobility amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistor (TFT) based on alumina oxide (Al 2 O 3 ) passivation layer (PVL) and copper (Cu) source/drain electrodes (S/D). The mechanism of the high mobility for a-IGZO TFT was proposed and experimentally demonstrated. The conductivity of the channel layer was significantly improved due to the formation of metallic In nanoparticles on the back channel during Al 2 O 3 PVL sputtering. In addition, Ar atmosphere annealing induced the Schottky contact formation between the Cu S/D and the channel layer caused by Cu diffusion. In conjunction with high conductivity channel and Schottky contact, the a-IGZO TFT based on Cu S/D and Al 2 O 3 PVL exhibited remarkable mobility of 33.5-220.1 cm 2 /Vs when channel length varies from 60 to 560 μ m. This work presents a feasible way to implement high mobility and Cu electrodes in a-IGZO TFT, simultaneously.

Mobility Enhancement in Amorphous In-Ga-Zn-O Thin-Film Transistor by Induced Metallic in Nanoparticles and Cu Electrodes

PubMed Central

Lu, Kuankuan; Li, Yuzhi; Xu, Miao; Wang, Lei; Peng, Junbiao; Lu, Xubing

2018-01-01

In this work, we fabricated a high-mobility amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistor (TFT) based on alumina oxide (Al2O3) passivation layer (PVL) and copper (Cu) source/drain electrodes (S/D). The mechanism of the high mobility for a-IGZO TFT was proposed and experimentally demonstrated. The conductivity of the channel layer was significantly improved due to the formation of metallic In nanoparticles on the back channel during Al2O3 PVL sputtering. In addition, Ar atmosphere annealing induced the Schottky contact formation between the Cu S/D and the channel layer caused by Cu diffusion. In conjunction with high conductivity channel and Schottky contact, the a-IGZO TFT based on Cu S/D and Al2O3 PVL exhibited remarkable mobility of 33.5–220.1 cm2/Vs when channel length varies from 60 to 560 μm. This work presents a feasible way to implement high mobility and Cu electrodes in a-IGZO TFT, simultaneously. PMID:29584710

Effect of annealing on structural, optical and electrical properties of SILAR synthesized CuO thin film

NASA Astrophysics Data System (ADS)

Das, M. R.; Mukherjee, A.; Mitra, P.

2017-05-01

Nano crystalline CuO thin films were synthesize on glass substrate using SILAR technique. The structural, optical and electrical properties of the films were carried out for as deposited as well as for films post annealed in the temperature range 300 - 500° C. The X-ray diffraction pattern shows all the films are polycrystalline in nature with monoclinic phase. The crystallite size increase and lattice strain decreases with increase of annealing temperature indicating high quality of the films for annealed films. The value of band gap decreases with increases of annealing temperature of the film. The effect of annealing temperature on ionic conductivity and activation energy to electrical conduction process are discussed.

A compact Nd:YAG DPSSL using diamond-cooled technology

NASA Astrophysics Data System (ADS)

Chou, Hsian P.; Wang, Yu-Lin; Hasson, Victor H.; Trainor, Daniel W.

2005-03-01

In our diamond-cooled approach, thin disks of laser gain material, e.g., Nd:YAG, are alternated between thin disks of single crystal synthetic diamond whose heat conductivity is over 2000 W/m-°K. The gain medium is face-pumped (along the optical axis) by the output of laser diode arrays. This optical configuration produces heat transfer from Nd:YAG to the diamond, in the direction of the optical axis, and then heat is rapidly conducted radially outward through the diamond to the cooling fluid circulating at the circumference of the diamond/YAG assembly. This geometry effectively removes the heat from the gain material in a manner that permits the attainment of high power output with excellent beam quality.

Temporary formation of highly conducting domain walls for non-destructive read-out of ferroelectric domain-wall resistance switching memories

NASA Astrophysics Data System (ADS)

Jiang, Jun; Bai, Zi Long; Chen, Zhi Hui; He, Long; Zhang, David Wei; Zhang, Qing Hua; Shi, Jin An; Park, Min Hyuk; Scott, James F.; Hwang, Cheol Seong; Jiang, An Quan

2018-01-01

Erasable conductive domain walls in insulating ferroelectric thin films can be used for non-destructive electrical read-out of the polarization states in ferroelectric memories. Still, the domain-wall currents extracted by these devices have not yet reached the intensity and stability required to drive read-out circuits operating at high speeds. This study demonstrated non-destructive read-out of digital data stored using specific domain-wall configurations in epitaxial BiFeO3 thin films formed in mesa-geometry structures. Partially switched domains, which enable the formation of conductive walls during the read operation, spontaneously retract when the read voltage is removed, reducing the accumulation of mobile defects at the domain walls and potentially improving the device stability. Three-terminal memory devices produced 14 nA read currents at an operating voltage of 5 V, and operated up to T = 85 °C. The gap length can also be smaller than the film thickness, allowing the realization of ferroelectric memories with device dimensions far below 100 nm.

A 2D Conductive Organic-Inorganic Hybrid with Extraordinary Volumetric Capacitance at Minimal Swelling.

PubMed

Xiao, Kefeng; Jiang, Donglin; Amal, Rose; Wang, Da-Wei

2018-05-16

Rational design and synthesis of 2D organic-inorganic hybrid materials is important for transformative technological advances for energy storage. Here, a 2D conductive hybrid lamella and its intercalation properties for thin-film supercapacitors are reported. The 2D organic-inorganic hybrid lamella comprises periodically stacked 2D nanosheets with 11.81 Å basal spacing, and is electronically conductive (605 S m -1 ). In contrast to the pre-existing organic-based 2D materials, this material has extremely low gas-permeable porosity (16.5 m 2 g -1 ) in contrast to the high ionic accessibility. All these structural features collectively contribute to the high capacitances up to 732 F cm -3 , combined with small structural swelling at as low as 4.8% and good stability. At a discharge time of 6 s, the thin-film intercalation electrode delivers an energy density of 24 mWh cm -3 , which universally outperforms the surface-dominant capacitive processes in porous carbons. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Highly Conductive Flexible Multi-Walled Carbon Nanotube Sheet Films for Transparent Touch Screen

NASA Astrophysics Data System (ADS)

Jung, Daewoong; Lee, Kyung Hwan; Kim, Donghyun; Burk, Dorothea; Overzet, Lawrence J.; Lee, Gil Sik

2013-03-01

Highly conductive and transparent thin films were prepared using highly purified multi-walled carbon nanotube (MWCNT) sheets. The electrical properties of the MWCNT sheet were remarkably improved by an acid treatment, resulting in densely packed MWCNTs. The morphology of the sheets reveals that continuous electrical pathways were formed by the acid treatment, greatly improving the sheet resistance all the while maintaining an excellent optical transmittance. These results encourage the use of these MWCNT sheets with low sheet resistance (450 Ω/sq) and high optical transmittance (90%) as a potential candidate for flexible display applications.

Novel organic semiconductors and a high capacitance gate dielectric for organic thin film transistors

NASA Astrophysics Data System (ADS)

Cai, Xiuyu

2007-12-01

Organic semiconductors are attracting more and more interest as a promising set of materials in the field of electronics research. This thesis focused on several new organic semiconductors and a novel high-kappa dielectric thin film (SrTiO3), which are two essential parts in Organic Thin Film Transistors (OTFTs). Structure and morphology of thin films of tricyanovinyl capped oligothiophenes were studied using atomic force microscopy and x-ray diffraction. Thin film transistors of one compound exhibited a reasonable electron mobility of 0.02 cm2/Vs. Temperature dependent measurements on the thin film transistor based on this compound revealed shallow trap states that were interpreted in terms of a multiple trap and release model. Moreover, inversion of the majority charge carrier type from electrons to holes was observed when the number of oligothiophene rings increased to six and ambipolar transport behavior was observed for tricyanovinyl sexithiophene. Another interesting organic semiconductor compound is the fluoalkylquarterthiophene, which showed ambipolar transport and large hysteresis in the transfer curve. Due to the bistable state at floating gate, the thin film transistor was exploited to study non-volatile floating gate memory effects. The temperature dependence of the retention time for this memory device revealed that the electron trapping was an activated process. Following the earlier work on hybrid acene-thiophene organic semiconductors, new compounds with similar structure were studied to reveal the mechanism of the air-stability exhibited by some compounds. They all formed highly crystalline thin films and showed reasonable device performances which are well correlated with the molecular structures, thin film microstructures, and solid state packing. The most air-stable compound had no observable degradation with exposure to air for 15 months. SrTiO3 was developed to be employed in OTFTs. Optimization of thin film growth was performed using reactive sputtering growth. Excellent SrTiO3 epitaixal thin film growth was revealed on conductive SrTiO 3:Nb substrates. A maximum charge carrier density of 1014 cm-2 was obtained based on pentacene and perylene diimide thin film transistors. Some new physical phenomena, such as step-like transfer characteristic curve and negative transconductance, were observed at such high field effect induced charge carrier density.

Amorphous indium gallium zinc oxide thin film grown by pulse laser deposition technique

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

Mistry, Bhaumik V., E-mail: bhaumik-phy@yahoo.co.in; Joshi, U. S.

Highly electrically conducting and transparent in visible light IGZO thin film were grown on glass substrate at substrate temperature of 400 C by a pulse laser deposition techniques. Structural, surface, electrical, and optical properties of IGZO thin films were investigated at room temperature. Smooth surface morphology and amorphous nature of the film has been confirmed from the AFM and GIXRD analysis. A resistivity down to 7.7×10{sup −3} V cm was reproducibly obtained while maintaining optical transmission exceeding 70% at wavelengths from 340 to 780 nm. The carrier densities of the film was obtain to the value 1.9×10{sup 18} cm{sup 3},more » while the Hall mobility of the IGZO thin film was 16 cm{sup 2} V{sup −1}S{sup −1}.« less

Optimizing electrical conductivity and optical transparency of IZO thin film deposited by radio frequency (RF) magnetron sputtering

NASA Astrophysics Data System (ADS)

Zhang, Lei

Transparent conducting oxide (TCO) thin films of In2O3, SnO2, ZnO, and their mixtures have been extensively used in optoelectronic applications such as transparent electrodes in solar photovoltaic devices. In this project I deposited amorphous indium-zinc oxide (IZO) thin films by radio frequency (RF) magnetron sputtering from a In2O3-10 wt.% ZnO sintered ceramic target to optimize the RF power, argon gas flowing rate, and the thickness of film to reach the maximum conductivity and transparency in visible spectrum. The results indicated optimized conductivity and transparency of IZO thin film is closer to ITO's conductivity and transparency, and is even better when the film was deposited with one specific tilted angle. National Science Foundation (NSF) MRSEC program at University of Nebraska Lincoln, and was hosted by Professor Jeff Shields lab.

Nano-structured variable capacitor based on P(VDF-TrFE) copolymer and carbon nanotubes

NASA Astrophysics Data System (ADS)

Lakbita, I.; El-Hami, K.

2018-02-01

A newly organic capacitor was conceived with a variable capacitance using the inverse piezoelectric effect. The device consists of two parallel plates of carbon nanotubes (CNTs), known for their large surface area, high sensitivity and high electric conductivity, separated by a thin film of a dielectric layer of Polyinylidene fluoride and trifluoroehtylene (P(VDF-TrFE)) promising material for piezoelectric and ferroelectric properties. The obtained architecture is the CNT/PVDF-TrFE/CNT capacitor device. In this study, an ultra-thin film of P(VDF-TrFE) (54/46) with thickness of 20 nm was elaborated on highly oriented pyrolytic graphite (HOPG) by spin-coating. The morphology of the ultra-thin film and the mechanical behavior of CNT/P(VDF-TrFE)/CNT system were studied using the atomic force microscopy (AFM) combined with a lock-in amplifier in contact mode. All changes in applied voltage induce a change in thin film thickness according to the inverse piezoelectric effect that affect, consequently the capacitance. The results showed that the ratio of capacitance change ΔC to initial capacitance C0 is ΔC/C0=5%. This value is sufficient to use P(VDF-TrFE) as variable organic capacitor.

Ultimately short ballistic vertical graphene Josephson junctions

PubMed Central

Lee, Gil-Ho; Kim, Sol; Jhi, Seung-Hoon; Lee, Hu-Jong

2015-01-01

Much efforts have been made for the realization of hybrid Josephson junctions incorporating various materials for the fundamental studies of exotic physical phenomena as well as the applications to superconducting quantum devices. Nonetheless, the efforts have been hindered by the diffusive nature of the conducting channels and interfaces. To overcome the obstacles, we vertically sandwiched a cleaved graphene monoatomic layer as the normal-conducting spacer between superconducting electrodes. The atomically thin single-crystalline graphene layer serves as an ultimately short conducting channel, with highly transparent interfaces with superconductors. In particular, we show the strong Josephson coupling reaching the theoretical limit, the convex-shaped temperature dependence of the Josephson critical current and the exceptionally skewed phase dependence of the Josephson current; all demonstrate the bona fide short and ballistic Josephson nature. This vertical stacking scheme for extremely thin transparent spacers would open a new pathway for exploring the exotic coherence phenomena occurring on an atomic scale. PMID:25635386

Conducting glasses recovered from thin film transistor liquid crystal display wastes for dye-sensitized solar cell cathodes.

PubMed

Chen, C-C; Chang, F-C; Peng, C Y; Wang, H Paul

2015-01-01

Transparent conductive glasses such as thin film transistor (TFT) array and colour filter glasses were recovered from the TFT-liquid crystal display panel wastes by dismantling and sonic cleaning. Noble metals (i.e. platinum (Pt)) and indium tin oxide (ITO) are generally used in the cathode of a dye-sensitized solar cell (DSSC). To reduce the DSSC cost, Pt was replaced with nano nickel-encapsulated carbon-shell (Ni@C) nanoparticles, which were prepared by carbonization of Ni²⁺-β-cyclodextrin at 673 K for 2 h. The recovered conductive glasses were used in the DSSC electrodes in the substitution of relatively expensive ITO. Interestingly, the efficiency of the DSSC having the Ni@C-coated cathode is as high as 2.54%. Moreover, the cost of the DSSC using the recovered materials can be reduced by at least 24%.

Ionic liquid gating reveals trap-filled limit mobility in low temperature amorphous zinc oxide

NASA Astrophysics Data System (ADS)

Bubel, S.; Meyer, S.; Kunze, F.; Chabinyc, M. L.

2013-10-01

In low-temperature solution processed amorphous zinc oxide (a-ZnO) thin films, we show the thin film transistor (TFT) characteristics for the trap-filled limit (TFL), when the quasi Fermi energy exceeds the conduction band edge and all tail-states are filled. In order to apply gate fields that are high enough to reach the TFL, we use an ionic liquid tape gate. Performing capacitance voltage measurements to determine the accumulated charge during TFT operation, we find the TFL at biases higher than predicted by the electronic structure of crystalline ZnO. We conclude that the density of states in the conduction band of a-ZnO is higher than in its crystalline state. Furthermore, we find no indication of percolative transport in the conduction band but trap assisted transport in the tail-states of the band.

Streamer discharges as advancing imperfect conductors: inhomogeneities in long ionized channels

NASA Astrophysics Data System (ADS)

Luque, A.; González, M.; Gordillo-Vázquez, F. J.

2017-12-01

A major obstacle for the understanding of long electrical discharges is the complex dynamics of streamer coronas, formed by many thin conducting filaments. Building macroscopic models for these filaments is one approach to attain a deeper knowledge of the discharge corona. Here, we present a one-dimensional, macroscopic model of a propagating streamer channel with a finite and evolving internal conductivity. We represent the streamer as an advancing finite-conductivity channel with a surface charge density at its boundary. This charge evolves self-consistently due to the electric current that flows through the streamer body and within a thin layer at its surface. We couple this electrodynamic evolution with a field-dependent set of chemical reactions that determine the internal channel conductivity. With this one-dimensional model, we investigate the formation of persisting structures in the wake of a streamer head. In accordance with experimental observations, our model shows that a within a streamer channel some regions are driven towards high fields that can be maintaned for tens of nanoseconds.

Depositing High-T(sub c) Superconductors On Normal-Conductor Wires

NASA Technical Reports Server (NTRS)

Kirlin, Peter S.

1994-01-01

Experiments have demonstrated feasibility of depositing thin layers of high-T(sub c) superconductor on normally electrically conductive wires. Superconductivity evident at and below critical temperature (T{sub c}) of 71 K. OMCVD, organometallic vapor deposition, apparatus coats Ag wire with layer high-T(sub c) superconductor. Superconductive phase of this material formed subsequently by annealing under controlled conditions.

Rectenna that converts infrared radiation to electrical energy

DOEpatents

Davids, Paul; Peters, David W.

2016-09-06

Technologies pertaining to converting infrared (IR) radiation to DC energy are described herein. In a general embodiment, a rectenna comprises a conductive layer. A thin insulator layer is formed on the conductive layer, and a nanoantenna is formed on the thin insulator layer. The thin insulator layer acts as a tunnel junction of a tunnel diode.

Highly-flexible, ultra-thin, and transparent single-layer graphene/silver composite electrodes for organic light emitting diodes

NASA Astrophysics Data System (ADS)

Li, Kun; Wang, Hu; Li, Huiying; Li, Ye; Jin, Guangyong; Gao, Lanlan; Marco, Mazzeo; Duan, Yu

2017-08-01

Transparent conductive electrode (TCE) platforms are required in many optoelectronic devices, including organic light emitting diodes (OLEDs). To date, indium tin oxide based electrodes are widely used in TCEs but they still have few limitations in term of achieving flexible OLEDs and display techniques. In this paper, highly-flexible and ultra-thin TCEs were fabricated for use in OLEDs by combining single-layer graphene (SLG) with thin silver layers of only several nanometers in thickness. The as-prepared SLG + Ag (8 nm) composite electrodes showed low sheet resistances of 8.5 Ω/□, high stability over 500 bending cycles, and 74% transmittance at 550 nm wavelength. Furthermore, SLG + Ag composite electrodes employed as anodes in OLEDs delivered turn-on voltages of 2.4 V, with luminance exceeding 1300 cd m-2 at only 5 V, and maximum luminance reaching up 40 000 cd m-2 at 9 V. Also, the devices could work normally under less than the 1 cm bending radius.

Carbonyl Compounds Produced by Vaporizing Cannabis Oil Thinning Agents.

PubMed

Troutt, William D; DiDonato, Matthew D

2017-11-01

Cannabis use has increased in the United States, particularly the use of vaporized cannabis oil, which is often mixed with thinning agents for use in vaporizing devices. E-cigarette research shows that heated thinning agents produce potentially harmful carbonyls; however, similar studies have not been conducted (1) with agents that are commonly used in the cannabis industry and (2) at temperatures that are appropriate for cannabis oil vaporization. The goal of this study was to determine whether thinning agents used in the cannabis industry produce potentially harmful carbonyls when heated to a temperature that is appropriate for cannabis oil vaporization. Four thinning agents (propylene glycol [PG], vegetable glycerin [VG], polyethylene glycol 400 [PEG 400], and medium chain triglycerides [MCT]) were heated to 230°C and the resulting vapors were tested for acetaldehyde, acrolein, and formaldehyde. Each agent was tested three times. Testing was conducted in a smoking laboratory. Carbonyl levels were measured in micrograms per puff block. Analyses showed that PEG 400 produced significantly higher levels of acetaldehyde and formaldehyde than PG, MCT, and VG. Formaldehyde production was also significantly greater in PG compared with MCT and VG. Acrolein production did not differ significantly across the agents. PG and PEG 400 produced high levels of acetaldehyde and formaldehyde when heated to 230°C. Formaldehyde production from PEG 400 isolate was particularly high, with one inhalation accounting for 1.12% of the daily exposure limit, nearly the same exposure as smoking one cigarette. Because PG and PEG 400 are often mixed with cannabis oil, individuals who vaporize cannabis oil products may risk exposure to harmful formaldehyde levels. Although more research is needed, consumers and policy makers should consider these potential health effects before use and when drafting cannabis-related legislation.

Interfacial band alignment and structural properties of nanoscale TiO2 thin films for integration with epitaxial crystallographic oriented germanium

NASA Astrophysics Data System (ADS)

Jain, N.; Zhu, Y.; Maurya, D.; Varghese, R.; Priya, S.; Hudait, M. K.

2014-01-01

We have investigated the structural and band alignment properties of nanoscale titanium dioxide (TiO2) thin films deposited on epitaxial crystallographic oriented Ge layers grown on (100), (110), and (111)A GaAs substrates by molecular beam epitaxy. The TiO2 thin films deposited at low temperature by physical vapor deposition were found to be amorphous in nature, and high-resolution transmission electron microscopy confirmed a sharp heterointerface between the TiO2 thin film and the epitaxially grown Ge with no traceable interfacial layer. A comprehensive assessment on the effect of substrate orientation on the band alignment at the TiO2/Ge heterointerface is presented by utilizing x-ray photoelectron spectroscopy and spectroscopic ellipsometry. A band-gap of 3.33 ± 0.02 eV was determined for the amorphous TiO2 thin film from the Tauc plot. Irrespective of the crystallographic orientation of the epitaxial Ge layer, a sufficient valence band-offset of greater than 2 eV was obtained at the TiO2/Ge heterointerface while the corresponding conduction band-offsets for the aforementioned TiO2/Ge system were found to be smaller than 1 eV. A comparative assessment on the effect of Ge substrate orientation revealed a valence band-offset relation of ΔEV(100) > ΔEV(111) > ΔEV(110) and a conduction band-offset relation of ΔEC(110) > ΔEC(111) > ΔEC(100). These band-offset parameters are of critical importance and will provide key insight for the design and performance analysis of TiO2 for potential high-κ dielectric integration and for future metal-insulator-semiconductor contact applications with next generation of Ge based metal-oxide field-effect transistors.

Cross-plane electronic and thermal transport properties of p-type La0.67Sr0.33MnO3/LaMnO3 perovskite oxide metal/semiconductor superlattices

NASA Astrophysics Data System (ADS)

Jha, Pankaj; Sands, Timothy D.; Cassels, Laura; Jackson, Philip; Favaloro, Tela; Kirk, Benjamin; Zide, Joshua; Xu, Xianfan; Shakouri, Ali

2012-09-01

Lanthanum strontium manganate (La0.67Sr0.33MnO3, i.e., LSMO)/lanthanum manganate (LaMnO3, i.e., LMO) perovskite oxide metal/semiconductor superlattices were investigated as a potential p-type thermoelectric material. Growth was performed using pulsed laser deposition to achieve epitaxial LSMO (metal)/LMO (p-type semiconductor) superlattices on (100)-strontium titanate (STO) substrates. The magnitude of the in-plane Seebeck coefficient of LSMO thin films (<20 μV/K) is consistent with metallic behavior, while LMO thin films were p-type with a room temperature Seebeck coefficient of 140 μV/K. Thermal conductivity measurements via the photo-acoustic (PA) technique showed that LSMO/LMO superlattices exhibit a room temperature cross-plane thermal conductivity (0.89 W/m.K) that is significantly lower than the thermal conductivity of individual thin films of either LSMO (1.60 W/m.K) or LMO (1.29 W/m.K). The lower thermal conductivity of LSMO/LMO superlattices may help overcome one of the major limitations of oxides as thermoelectrics. In addition to a low cross-plane thermal conductivity, a high ZT requires a high power factor (S2σ). Cross-plane electrical transport measurements were carried out on cylindrical pillars etched in LSMO/LMO superlattices via inductively coupled plasma reactive ion etching. Cross-plane electrical resistivity data for LSMO/LMO superlattices showed a magnetic phase transition temperature (TP) or metal-semiconductor transition at ˜330 K, which is ˜80 K higher than the TP observed for in-plane resistivity of LSMO, LMO, or LSMO/LMO thin films. The room temperature cross-plane resistivity (ρc) was found to be greater than the in-plane resistivity by about three orders of magnitude. The magnitude and temperature dependence of the cross-plane conductivity of LSMO/LMO superlattices suggests the presence of a barrier with the effective barrier height of ˜300 meV. Although the magnitude of the cross-plane power factor is too low for thermoelectric applications by a factor of approximately 10-4—in part because the growth conditions chosen for this study yielded relatively high resistivity films—the temperature dependence of the resistivity and the potential for tuning the power factor by engineering strain, oxygen stoichiometry, and electronic band structure suggest that these epitaxial metal/semiconductor superlattices are deserving of further investigation.

A graphene oxide-carbon nanotube grid for high-resolution transmission electron microscopy of nanomaterials.

PubMed

Zhang, Lina; Zhang, Haoxu; Zhou, Ruifeng; Chen, Zhuo; Li, Qunqing; Fan, Shoushan; Ge, Guanglu; Liu, Renxiao; Jiang, Kaili

2011-09-23

A novel grid for use in transmission electron microscopy is developed. The supporting film of the grid is composed of thin graphene oxide films overlying a super-aligned carbon nanotube network. The composite film combines the advantages of graphene oxide and carbon nanotube networks and has the following properties: it is ultra-thin, it has a large flat and smooth effective supporting area with a homogeneous amorphous appearance, high stability, and good conductivity. The graphene oxide-carbon nanotube grid has a distinct advantage when characterizing the fine structure of a mass of nanomaterials over conventional amorphous carbon grids. Clear high-resolution transmission electron microscopy images of various nanomaterials are obtained easily using the new grids.

Structural, morphological and optical studies of F doped SnO2 thin films

NASA Astrophysics Data System (ADS)

Chandel, Tarun; Thakur, Vikas; Dwivedi, Shailendra Kumar; Zaman, M. Burhanuz; Rajaram, Poolla

2018-05-01

Highly conducting and transparent FTO (flourine doped tin Oxide) thin films were grown on the glass substrates using a low cost spray pyrolysis technique. The films were characterized for their structural, morphological and optical studies using XRD, SEM and UV-Vis spectroscopy. XRD studies show that the FTO films crystallize in Tetragonal cassiterite structure. Morphological analysis using SEM show that the films are uniformly covered with spherical grains albeit high in surface roughness. The average optical transmission greater than 80% in the visible region along with the appearance of interference fringes in the transmission curves confirms the high quality of the films. Electrical studies show that the films exhibit sheet resistance below 10 Ω ϒ-1.

Computational Study of In-Plane Phonon Transport in Si Thin Films

PubMed Central

Wang, Xinjiang; Huang, Baoling

2014-01-01

We have systematically investigated the in-plane thermal transport in Si thin films using an approach based on the first-principles calculations and lattice dynamics. The effects of phonon mode depletion induced by the phonon confinement and the corresponding variation in interphonon scattering, which may be important for the thermal conductivities of ultra-thin films but are often neglected in precedent studies, are considered in this study. The in-plane thermal conductivities of Si thin films with different thicknesses have been predicted over a temperature range from 80 K to 800 K and excellent agreements with experimental results are found. The validities of adopting the bulk phonon properties and gray approximation of surface specularity in thin film studies have been clarified. It is found that in ultra-thin films, while the phonon depletion will reduce the thermal conductivity of Si thin films, its effect is largely offset by the reduction in the interphonon scattering rate. The contributions of different phonon modes to the thermal transport and isotope effects in Si films with different thicknesses under various temperatures are also analyzed. PMID:25228061

Ceramic Composite Thin Films

NASA Technical Reports Server (NTRS)

Dikin, Dmitriy A. (Inventor); Nguyen, SonBinh T. (Inventor); Ruoff, Rodney S. (Inventor); Stankovich, Sasha (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.

Current status of solid-state lithium batteries employing solid redox polymerization cathodes

NASA Astrophysics Data System (ADS)

Visco, S. J.; Doeff, M. M.; Dejonghe, L. C.

1991-03-01

The rapidly growing demand for secondary batteries having high specific energy and power has naturally led to increased efforts in lithium battery technology. Still, the increased safety risks associated with high energy density systems has tempered the enthusiasm of proponents of such systems for use in the consumer marketplace. The inherent advantages of all-solid-state batteries in regards to safety and reliability are strong factors in advocating their introduction to the marketplace. However, the low ionic conductivity of solid electrolytes relative to nonaqueous liquid electrolytes implies low power densities for solid state systems operating at ambient temperatures. Recent advances in polymer electrolytes have led to the introduction of solid electrolytes having conductivities in the range of 10(exp -4)/ohm cm at room temperature; this is still two orders of magnitude lower than liquid electrolytes. Although these improved ambient conductivities put solid state batteries in the realm of practical devices, it is clear that solid state batteries using such polymeric separators will be thin film devices. Fortunately, thin film fabrication techniques are well established in the plastics and paper industry, and present the possibility of continuous web-form manufacturing. This style of battery manufacture should make solid polymer batteries very cost-competitive with conventional secondary cells. In addition, the greater geometric flexibility of thin film solid state cells should provide benefits in terms of the end-use form factor in device design. This work discusses the status of solid redox polymerization cathodes.

Conduction mechanism of leakage current due to the traps in ZrO2 thin film

NASA Astrophysics Data System (ADS)

Seo, Yohan; Lee, Sangyouk; An, Ilsin; Song, Chulgi; Jeong, Heejun

2009-11-01

In this work, a metal-oxide-semiconductor capacitor with zirconium oxide (ZrO2) gate dielectric was fabricated by an atomic layer deposition (ALD) technique and the leakage current characteristics under negative bias were studied. From the result of current-voltage curves there are two possible conduction mechanisms to explain the leakage current in the ZrO2 thin film. The dominant mechanism is the space charge limited conduction in the high-electric field region (1.5-5.0 MV cm-1) while the trap-assisted tunneling due to the existence of traps is prevailed in the low-electric field region (0.8-1.5 MV cm-1). Conduction caused by the trap-assisted tunneling is found from the experimental results of a weak temperature dependence of current, and the trap barrier height is obtained. The space charge limited conduction is evidenced, for different temperatures, by Child's law dependence of current density versus voltage. Child's law dependence can be explained by considering a single discrete trapping level and we can obtain the activation energy of 0.22 eV.

Electrical and optical properties of sol-gel derived La modified PbTiO 3 thin films

NASA Astrophysics Data System (ADS)

Chopra, Sonalee; Sharma, Seema; Goel, T. C.; Mendiratta, R. G.

2004-09-01

Lanthanum modified lead titanate (Pb 1- xLa xTi 1- x/4 O 3) PLT x ( x=0.08 i.e. PLT8) sol-gel derived thin films have been prepared on indium tin oxide (ITO) coated glass and quartz substrates using lead acetate trihydrate, lanthanum acetate hydrate and titanium isopropoxide as precursors along with 2-methoxyethanol as solvent and acetic acid as catalyst by spin coating method. The microstructure and surface morphology of the films annealed at 650 °C have been studied by X-ray diffraction technique and atomic force microscope (AFM). XRD has shown a single phase with tetragonal structure and AFM images have confirmed a smooth and crack-free surface with low surface roughness. The dependence of leakage current on applied voltage show ohmic behavior at low field region with a space charge conduction mechanism at high fields. The wavelength dispersion curve of thin films obtained from the transmission spectrum of thin films show that the films have high optical transparency in the visible region.

High electric field conduction in low-alkali boroaluminosilicate glass

NASA Astrophysics Data System (ADS)

Dash, Priyanka; Yuan, Mengxue; Gao, Jun; Furman, Eugene; Lanagan, Michael T.

2018-02-01

Electrical conduction in silica-based glasses under a low electric field is dominated by high mobility ions such as sodium, and there is a transition from ionic transport to electronic transport as the electric field exceeds 108 V/m at low temperatures. Electrical conduction under a high electric field was investigated in thin low-alkali boroaluminosilicate glass samples, showing nonlinear conduction with the current density scaling approximately with E1/2, where E is the electric field. In addition, thermally stimulated depolarization current (TSDC) characterization was carried out on room-temperature electrically poled glass samples, and an anomalous discharging current flowing in the same direction as the charging current was observed. High electric field conduction and TSDC results led to the conclusion that Poole-Frenkel based electronic transport occurs in the mobile-cation-depleted region adjacent to the anode, and accounts for the observed anomalous current.

A nonconjugated radical polymer glass with high electrical conductivity

NASA Astrophysics Data System (ADS)

Joo, Yongho; Agarkar, Varad; Sung, Seung Hyun; Savoie, Brett M.; Boudouris, Bryan W.

2018-03-01

Solid-state conducting polymers usually have highly conjugated macromolecular backbones and require intentional doping in order to achieve high electrical conductivities. Conversely, single-component, charge-neutral macromolecules could be synthetically simpler and have improved processibility and ambient stability. We show that poly(4-glycidyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl), a nonconjugated radical polymer with a subambient glass transition temperature, underwent rapid solid-state charge transfer reactions and had an electrical conductivity of up to 28 siemens per meter over channel lengths up to 0.6 micrometers. The charge transport through the radical polymer film was enabled with thermal annealing at 80°C, which allowed for the formation of a percolating network of open-shell sites in electronic communication with one another. The electrical conductivity was not enhanced by intentional doping, and thin films of this material showed high optical transparency.

Epitaxial Growth of Oriented Metalloporphyrin Network Thin Film for Improved Selectivity of Volatile Organic Compounds.

PubMed

Li, De-Jing; Gu, Zhi-Gang; Vohra, Ismail; Kang, Yao; Zhu, Yong-Sheng; Zhang, Jian

2017-05-01

This study reports an oriented and homogenous cobalt-metalloporphyrin network (PIZA-1) thin film prepared by liquid phase epitaxial (LPE) method. The thickness of the obtained thin films can be well controlled, and their photocurrent properties can also be tuned by LPE cycles or the introduction of conductive guest molecules (tetracyanoquinodimethane and C 60 ) into the PIZA-1 pores. The study of quartz crystal microbalance adsorption confirms that the PIZA-1 thin film with [110]-orientation presents much higher selectivity of benzene over toluene and p-xylene than that of the PIZA-1 powder with mixed orientations. These results reveal that the selective adsorption of volatile organic compounds highly depends on the growth orientations of porphyrin-based metal-organic framework thin films. Furthermore, the work will provide a new perspective for developing important semiconductive sensing materials with improved selectivity of guest compounds. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Anaerobic digestion of thin stillage for energy recovery and water reuse in corn-ethanol plants.

PubMed

Alkan-Ozkaynak, A; Karthikeyan, K G

2011-11-01

Recycling of anaerobically-digested thin stillage within a corn-ethanol plant may result in the accumulation of nutrients of environmental concern in animal feed coproducts and inhibitory organic materials in the fermentation tank. Our focus is on anaerobic digestion of treated (centrifugation and lime addition) thin stillage. Suitability of digestate from anaerobic treatment for reuse as process water was also investigated. Experiments conducted at various inoculum-to-substrate ratios (ISRs) revealed that alkalinity is a critical parameter limiting digestibility of thin stillage. An ISR level of 2 appeared optimal based on high biogas production level (763 mL biogas/g volatile solids added) and organic matter removal (80.6% COD removal). The digester supernatant at this ISR level was found to contain both organic and inorganic constituents at levels that would cause no inhibition to ethanol fermentation. Anaerobic digestion of treated-thin stillage can be expected to improve the water and energy efficiencies of dry grind corn-ethanol plants. Copyright © 2011 Elsevier Ltd. All rights reserved.

Highly Thermal Conductive Nanocomposites

NASA Technical Reports Server (NTRS)

Sun, Ya-Ping (Inventor); Connell, John W. (Inventor); Veca, Lucia Monica (Inventor)

2015-01-01

Disclosed are methods for forming carbon-based fillers as may be utilized in forming highly thermal conductive nanocomposite materials. Formation methods include treatment of an expanded graphite with an alcohol/water mixture followed by further exfoliation of the graphite to form extremely thin carbon nanosheets that are on the order of between about 2 and about 10 nanometers in thickness. Disclosed carbon nanosheets can be functionalized and/or can be incorporated in nanocomposites with extremely high thermal conductivities. Disclosed methods and materials can prove highly valuable in many technological applications including, for instance, in formation of heat management materials for protective clothing and as may be useful in space exploration or in others that require efficient yet light-weight and flexible thermal management solutions.

Highly Thermal Conductive Nanocomposites

NASA Technical Reports Server (NTRS)

Sun, Ya-Ping (Inventor); Connell, John W. (Inventor); Veca, Lucia Monica (Inventor)

2017-01-01

Disclosed are methods for forming carbon-based fillers as may be utilized in forming highly thermal conductive nanocomposite materials. Formation methods include treatment of an expanded graphite with an alcohol/water mixture followed by further exfoliation of the graphite to form extremely thin carbon nanosheets that are on the order of between about 2 and about 10 nanometers in thickness. Disclosed carbon nanosheets can be functionalized and/or can be incorporated in nanocomposites with extremely high thermal conductivities. Disclosed methods and materials can prove highly valuable in many technological applications including, for instance, in formation of heat management materials for protective clothing and as may be useful in space exploration or in others that require efficient yet light-weight and flexible thermal management solutions.

Hybrid absorbers composed of Fe3O4 thin film and magnetic composite sheet and enhancement of conduction noise absorption on a microstrip line

NASA Astrophysics Data System (ADS)

Kim, Sung-Soo

2015-05-01

In response to develop wide-band noise absorbers with an improved low-frequency performance, this study investigates hybrid absorbers that are composed of conductive Fe3O4 thin film and magnetic composite sheets. The Fe3O4 films prepared via reactive sputtering exhibit a typical value of electrical resistivity of ≃10-4 Ωm. Rubber composites with flaky Fe-Si-Al particles of a high permeability and high permittivity are used as the magnetic sheet functioning as an electromagnetic shield barrier. Microstrip lines with a characteristic impedance of 50 Ω are used to measure the noise absorbing properties. For the Fe3O4 film with a low surface resistance and covered by the magnetic sheet, approximately 80% power absorption can be obtained at 1 GHz, which is significantly higher than that of the original magnetic sheet or Fe3O4 film. The high power absorption of the hybrid absorber is attributed to the enhanced ohmic loss of the Fe3O4 film through increased electric field strength bounded by the upper magnetic composite sheet. The noise absorption is further enhanced through increasing the electrical conductivity of the film containing more conductive phase (Fe3O4 + Fe), which can be prepared in a reduced oxygen partial pressure during reactive sputtering.

Uncooled thin film pyroelectric IR detector with aerogel thermal isolation

DOEpatents

Ruffner, Judith A.; Bullington, Jeff A.; Clem, Paul G.; Warren, William L.; Brinker, C. Jeffrey; Tuttle, Bruce A.; Schwartz, Robert W.

1999-01-01

A monolithic infrared detector structure which allows integration of pyroelectric thin films atop low thermal conductivity aerogel thin films. The structure comprises, from bottom to top, a substrate, an aerogel insulating layer, a lower electrode, a pyroelectric layer, and an upper electrode layer capped by a blacking layer. The aerogel can offer thermal conductivity less than that of air, while providing a much stronger monolithic alternative to cantilevered or suspended air-gap structures for pyroelectric thin film pixel arrays. Pb(Zr.sub.0.4 Ti.sub.0.6)O.sub.3 thin films deposited on these structures displayed viable pyroelectric properties, while processed at 550.degree. C.

Spot-Welding Gun With Pivoting Twin-Collet Assembly

NASA Technical Reports Server (NTRS)

Nguyen, Francis; Simpson, Gareth; Hoult, William S.

1996-01-01

Modified spot-welding gun includes pivoting twin-collet assembly that holds two spot-welding electrodes. Designed to weld highly conductive (30 percent gold) brazing-alloy foils to thin nickel alloy workpieces; also suitable for other spot-welding applications compatible with two-electrode configuration.

Solid-State Thin-Film Supercapacitors with Ultrafast Charge/Discharge Based on N-Doped-Carbon-Tubes/Au-Nanoparticles-Doped-MnO2 Nanocomposites.

PubMed

Lv, Qiying; Wang, Shang; Sun, Hongyu; Luo, Jun; Xiao, Jian; Xiao, JunWu; Xiao, Fei; Wang, Shuai

2016-01-13

Although carbonaceous materials possess long cycle stability and high power density, their low-energy density greatly limits their applications. On the contrary, metal oxides are promising pseudocapacitive electrode materials for supercapacitors due to their high-energy density. Nevertheless, poor electrical conductivity of metal oxides constitutes a primary challenge that significantly limits their energy storage capacity. Here, an advanced integrated electrode for high-performance pseudocapacitors has been designed by growing N-doped-carbon-tubes/Au-nanoparticles-doped-MnO2 (NCTs/ANPDM) nanocomposite on carbon fabric. The excellent electrical conductivity and well-ordered tunnels of NCTs together with Au nanoparticles of the electrode cause low internal resistance, good ionic contact, and thus enhance redox reactions for high specific capacitance of pure MnO2 in aqueous electrolyte, even at high scan rates. A prototype solid-state thin-film symmetric supercapacitor (SSC) device based on NCTs/ANPDM exhibits large energy density (51 Wh/kg) and superior cycling performance (93% after 5000 cycles). In addition, the asymmetric supercapacitor (ASC) device assembled from NCTs/ANPDM and Fe2O3 nanorods demonstrates ultrafast charge/discharge (10 V/s), which is among the best reported for solid-state thin-film supercapacitors with both electrodes made of metal oxide electroactive materials. Moreover, its superior charge/discharge behavior is comparable to electrical double layer type supercapacitors. The ASC device also shows superior cycling performance (97% after 5000 cycles). The NCTs/ANPDM nanomaterial demonstrates great potential as a power source for energy storage devices.

Simultaneous measurement of thermal conductivity and heat capacity of bulk and thin film materials using frequency-dependent transient thermoreflectance method.

PubMed

Liu, Jun; Zhu, Jie; Tian, Miao; Gu, Xiaokun; Schmidt, Aaron; Yang, Ronggui

2013-03-01

The increasing interest in the extraordinary thermal properties of nanostructures has led to the development of various measurement techniques. Transient thermoreflectance method has emerged as a reliable measurement technique for thermal conductivity of thin films. In this method, the determination of thermal conductivity usually relies much on the accuracy of heat capacity input. For new nanoscale materials with unknown or less-understood thermal properties, it is either questionable to assume bulk heat capacity for nanostructures or difficult to obtain the bulk form of those materials for a conventional heat capacity measurement. In this paper, we describe a technique for simultaneous measurement of thermal conductivity κ and volumetric heat capacity C of both bulk and thin film materials using frequency-dependent time-domain thermoreflectance (TDTR) signals. The heat transfer model is analyzed first to find how different combinations of κ and C determine the frequency-dependent TDTR signals. Simultaneous measurement of thermal conductivity and volumetric heat capacity is then demonstrated with bulk Si and thin film SiO2 samples using frequency-dependent TDTR measurement. This method is further testified by measuring both thermal conductivity and volumetric heat capacity of novel hybrid organic-inorganic thin films fabricated using the atomic∕molecular layer deposition. Simultaneous measurement of thermal conductivity and heat capacity can significantly shorten the development∕discovery cycle of novel materials.

Robust, Thin Optical Films for Extreme Environments

NASA Technical Reports Server (NTRS)

2006-01-01

The environment of space presents scientists and engineers with the challenges of a harsh, unforgiving laboratory in which to conduct their scientific research. Solar astronomy and X-ray astronomy are two of the more challenging areas into which NASA scientists delve, as the optics for this high-tech work must be extremely sensitive and accurate, yet also be able to withstand the battering dished out by radiation, extreme temperature swings, and flying debris. Recent NASA work on this rugged equipment has led to the development of a strong, thin film for both space and laboratory use.

A Water-Based Silver-Nanowire Screen-Print Ink for the Fabrication of Stretchable Conductors and Wearable Thin-Film Transistors.

PubMed

Liang, Jiajie; Tong, Kwing; Pei, Qibing

2016-07-01

A water-based silver-nanowire (AgNW) ink is formulated for screen printing. Screen-printed AgNW patterns have uniform sharp edges, ≈50 μm resolution, and electrical conductivity as high as 4.67 × 10(4) S cm(-1) . The screen-printed AgNW patterns are used to fabricate a stretchable composite conductor, and a fully printed and intrinsically stretchable thin-film transistor array is also realized. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Optical and low-temperature thermoelectric properties of phase-pure p-type InSe thin films

NASA Astrophysics Data System (ADS)

Urmila, K. S.; Namitha, T. A.; Philip, R. R.; Pradeep, B.

2015-08-01

Polycrystalline phase-pure p-type InSe thin films were deposited on glass substrates by reactive evaporation at an optimized substrate temperature of 473 ± 5 K and pressure of 10-5 mbar. The as-prepared InSe thin films were analyzed by X-ray diffractometry, energy-dispersive X-ray spectroscopy, atomic force microscopy, UV-Vis-NIR spectroscopy, electrical conductivity and Hall measurements. The lattice parameters, particle size, dislocation density, number of crystallites per unit area and the lattice strain of the prepared InSe thin films were calculated and found as a = 4.00 ± 0.002 Å and c = 16.68 ± 0.002 Å, 48 ± 2 nm, 4.34 × 1010 lines cm-2, 15.37 × 1010 cm-2 and 1.8 × 10-3, respectively. The as-deposited InSe thin films showed a direct allowed transition with an optical band gap of 1.35 ± 0.02 eV and high absorption coefficient of about 105 cm-1. The oscillator energy ( E o) and dispersion energy ( E d) were calculated using the single-oscillator Wemple and DiDomenico model. The p-type conductivity and photosensitivity of the as-prepared InSe thin films confirmed their potential application in photovoltaic devices. The mean free path, relaxation time, density of states, Fermi energy and effective mass of holes in the film were determined by correlating the results of thermopower and Hall measurements. The sudden and sharp increase in thermopower from 80 to 37 K was explained as due to the effect of phonon drag on charge carriers.

Triboelectric generator

DOEpatents

Wang, Zhong L; Fan, Fengru; Lin, Long; Zhu, Guang; Pan, Caofeng; Zhou, Yusheng

2015-11-03

A generator includes a thin first contact charging layer and a thin second contact charging layer. The thin first contact charging layer includes a first material that has a first rating on a triboelectric series. The thin first contact charging layer has a first side with a first conductive electrode applied thereto and an opposite second side. The thin second contact charging layer includes a second material that has a second rating on a triboelectric series that is more negative than the first rating. The thin first contact charging layer has a first side with a first conductive electrode applied thereto and an opposite second side. The thin second contact charging layer is disposed adjacent to the first contact charging layer so that the second side of the second contact charging layer is in contact with the second side of the first contact charging layer.

Resistive switching characteristics of manganese oxide thin film and nanoparticle assembly hybrid devices

NASA Astrophysics Data System (ADS)

Abbas, Haider; Park, Mi Ra; Abbas, Yawar; Hu, Quanli; Kang, Tae Su; Yoon, Tae-Sik; Kang, Chi Jung

2018-06-01

Improved resistive switching characteristics are demonstrated in a hybrid device with Pt/Ti/MnO (thin film)/MnO (nanoparticle)/Pt structure. The hybrid devices of MnO thin film and nanoparticle assembly were fabricated. MnO nanoparticles with an average diameter of ∼30 nm were chemically synthesized and assembled as a monolayer on a Pt bottom electrode. A MnO thin film of ∼40 nm thickness was deposited on the nanoparticle assembly to form the hybrid structure. Resistive switching could be induced by the formation and rupture of conducting filaments in the hybrid oxide layers. The hybrid device exhibited very stable unipolar switching with good endurance and retention characteristics. It showed a larger and stable memory window with a uniform distribution of SET and RESET voltages. Moreover, the conduction mechanisms of ohmic conduction, space-charge-limited conduction, Schottky emission, and Poole–Frenkel emission have been investigated as possible conduction mechanisms for the switching of the devices. Using MnO nanoparticles in the thin film and nanoparticle heterostructures enabled the appropriate control of resistive random access memory (RRAM) devices and markedly improved their memory characteristics.

Multi-functional properties of CaCu3Ti4O12 thin films

NASA Astrophysics Data System (ADS)

Felix, A. A.; Rupp, J. L. M.; Varela, J. A.; Orlandi, M. O.

2012-09-01

In this work, electric transport properties of CaCu3Ti4O12 (CCTO) thin films were investigated for resistive switching, rectifying and gas sensor applications. Single phase CCTO thin films were produced by polymeric precursor method (PPM) on different substrates and their electrical properties were studied. Films produced on LNO/Si substrates have symmetrical non-ohmic current-voltage characteristics, while films deposited on Pt/Si substrates have a highly asymmetrical non-ohmic behavior which is related to a metal-semiconductor junction formed at the CCTO/Pt interface. In addition, results confirm that CCTO has a resistive switching response which is enhanced by Schottky contacts. Sensor response tests revealed that CCTO films are sensitive to oxygen gas and exhibit n-type conductivity. These results demonstrate the versatility of CCTO thin film prepared by the PPM method for gas atmosphere or bias dependent resistance applications.

Physical properties of high performance fluoride ion conductor BaSnF4 thin films by pulsed laser deposition

NASA Astrophysics Data System (ADS)

Patro, L. N.; Ravi Chandra Raju, N.; Meher, S. R.; Kamala Bharathi, K.

2013-09-01

This article presents the results on the growth and characterization of BaSnF4 thin films on glass substrates prepared by pulsed laser deposition technique. The structural results of BaSnF4 thin film carried out by glancing angle X-ray diffraction technique indicates the formation of the film with similar structure (tetragonal, P4/nmm) to the bulk target material. The absorption coefficient and band gap of the film is determined by suitable analysis of the transmittance spectra. The transport properties of the thin films are studied using impedance spectroscopy in the temperature range of 323-573 K. The frequency-dependent imaginary part of impedance plot shows that the conductivity relaxation is non-Debye in nature. The scaling behavior of the imaginary part of impedance at various frequencies indicates temperature-independent relaxation behavior.

Thermoelectric effects of amorphous Ga-Sn-O thin film

NASA Astrophysics Data System (ADS)

Matsuda, Tokiyoshi; Uenuma, Mutsunori; Kimura, Mutsumi

2017-07-01

The thermoelectric effects of an amorphous Ga-Sn-O (a-GTO) thin film have been evaluated as a physical parameter of a novel oxide semiconductor. Currently, a-GTO thin films are greatly desired not only because they do not contain rare metals and are therefore free from problems on the exhaustion of resources and the increase in cost but also because their initial characteristics and performance stabilities are excellent when they are used in thin-film transistors. In this study, an a-GTO thin film was deposited on a quartz substrate by RF magnetron sputtering and postannealing was performed in air at 350 °C for 1 h using an annealing furnace. The Seebeck coefficient and electrical conductivity of the a-GTO thin film were -137 µV/K and 31.8 S/cm at room temperature, and -183 µV/K and 43.8 S/cm at 397 K, respectively, and as a result, the power factor was 1.47 µW/(cm·K2) at 397 K; these values were roughly as high as those of amorphous In-Ga-Zn-O (a-IGZO) thin films. Therefore, a-GTO thin films will be a candidate material for thermoelectric devices fabricated in a large area at a low cost by controlling the carrier mobility, carrier density, device structures, and so forth.

Origins of enhanced thermoelectric power factor in topologically insulating Bi{sub 0.64}Sb{sub 1.36}Te{sub 3} thin films

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

Liu, Wei; State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070; Chi, Hang

2016-01-25

In this research, we report the enhanced thermoelectric power factor in topologically insulating thin films of Bi{sub 0.64}Sb{sub 1.36}Te{sub 3} with a thickness of 6–200 nm. Measurements of scanning tunneling spectroscopy and electronic transport show that the Fermi level lies close to the valence band edge, and that the topological surface state (TSS) is electron dominated. We find that the Seebeck coefficient of the 6 nm and 15 nm thick films is dominated by the valence band, while the TSS chiefly contributes to the electrical conductivity. In contrast, the electronic transport of the reference 200 nm thick film behaves similar to bulk thermoelectric materialsmore » with low carrier concentration, implying the effect of the TSS on the electronic transport is merely prominent in the thin region. The conductivity of the 6 nm and 15 nm thick film is obviously higher than that in the 200 nm thick film owing to the highly mobile TSS conduction channel. As a consequence of the enhanced electrical conductivity and the suppressed bipolar effect in transport properties for the 6 nm thick film, an impressive power factor of about 2.0 mW m{sup −1} K{sup −2} is achieved at room temperature for this film. Further investigations of the electronic transport properties of TSS and interactions between TSS and the bulk band might result in a further improved thermoelectric power factor in topologically insulating Bi{sub 0.64}Sb{sub 1.36}Te{sub 3} thin films.« less

Preparation of highly conductive, transparent, and flexible graphene/silver nanowires substrates using non-thermal laser photoreduction

NASA Astrophysics Data System (ADS)

Anis, Badawi; Mostafa, A. M.; El Sayed, Z. A.; Khalil, A. S. G.; Abouelsayed, A.

2018-07-01

We present the preparation of highly conducting, transparent, and flexible reduced graphene oxide/silver nanowires (rGO/SNWs) substrates using non-thermal laser photoreduction method. High quality monolayers graphene oxide (GO) solution has been prepared by the chemical oxidation of thermally expanded large area natural graphite. Silver nanowires was prepared by using the typical polyol method. Uniform hybrid GO/silver nanowires (GO/SNWs) was prepared by growing the nanowires from silver nuclei in the presence of GO. Uniform and high-quality rGO/SNWs thin films were prepared using a dip-coating technique and were reduced to highly electrically conductive graphene and transparent conductive films using non-thermal laser scribe method. The laser scribed rGO/SNWs hybrid film exhibited 80% transparency with 70 Ω □-1 after 20 min of dipping in GO/SNWs solution.

Structural and electrical characterization of ultra-thin SrTiO3 tunnel barriers grown over YBa2Cu3O7 electrodes for the development of high Tc Josephson junctions.

PubMed

Félix, L Avilés; Sirena, M; Guzmán, L A Agüero; Sutter, J González; Vargas, S Pons; Steren, L B; Bernard, R; Trastoy, J; Villegas, J E; Briático, J; Bergeal, N; Lesueur, J; Faini, G

2012-12-14

The transport properties of ultra-thin SrTiO(3) (STO) layers grown over YBa(2)Cu(3)O(7) electrodes were studied by conductive atomic force microscopy at the nano-scale. A very good control of the barrier thickness was achieved during the deposition process. A phenomenological approach was used to obtain critical parameters regarding the structural and electrical properties of the system. The STO layers present an energy barrier of 0.9 eV and an attenuation length of 0.23 nm, indicating very good insulating properties for the development of high-quality Josephson junctions.

Charge transport and activation energy of amorphous silicon carbide thin film on quartz at elevated temperature

NASA Astrophysics Data System (ADS)

Dinh, Toan; Viet Dao, Dzung; Phan, Hoang-Phuong; Wang, Li; Qamar, Afzaal; Nguyen, Nam-Trung; Tanner, Philip; Rybachuk, Maksym

2015-06-01

We report on the temperature dependence of the charge transport and activation energy of amorphous silicon carbide (a-SiC) thin films grown on quartz by low-pressure chemical vapor deposition. The electrical conductivity as characterized by the Arrhenius rule was found to vary distinctly under two activation energy thresholds of 150 and 205 meV, corresponding to temperature ranges of 300 to 450 K and 450 to 580 K, respectively. The a-SiC/quartz system displayed a high temperature coefficient of resistance ranging from -4,000 to -16,000 ppm/K, demonstrating a strong feasibility of using this material for highly sensitive thermal sensing applications.

Characterization of conductive Al-doped ZnO thin films for plasmonic applications

NASA Astrophysics Data System (ADS)

Masouleh, F. F.; Sinno, I.; Buckley, R. G.; Gouws, G.; Moore, C. P.

2018-02-01

Highly conductive and transparent Al-doped zinc oxide films were produced by RF magnetron sputtering for plasmonic applications in the infrared region of the spectrum. These films were characterized using Fourier transform infrared spectroscopy, the Hall effect, Rutherford backscattering spectroscopy and spectral data analysis. Analysis of the results shows a carrier concentration of up to 2.6 × 1020 cm-3, as well as transmission over 80% near the plasma frequency where plasmonic properties are expected. The plasma frequency was calculated from the spectroscopy measurements and subsequent data analysis, and was in agreement with the results from the Hall effect measurements and the free electron gas (Drude) model. Based on these results, the Al-doped zinc oxide thin films are well-suited for plasmonic applications in the infrared region.

Thermal conductivity of SrVO3-SrTiO3 thin films: Evidence of intrinsic thermal resistance at the interface between oxide layers

NASA Astrophysics Data System (ADS)

Katsufuji, T.; Saiki, T.; Okubo, S.; Katayama, Y.; Ueno, K.

2018-05-01

By using a technique of thermoreflectance that can precisely measure the thermal conductivity of thin films, we found that the thermal conductivity of SrVO3-SrTiO3 multilayer thin films normal to the surface was substantially reduced by decreasing the thickness of each layer. This indicates that a large intrinsic thermal resistance exists at the interface between SrVO3 and SrTiO3 in spite of the similar phononic properties for these two compounds.

Ultra-Thin Solid-State Nanopores: Fabrication and Applications

NASA Astrophysics Data System (ADS)

Kuan, Aaron Tzeyang

Solid-state nanopores are a nanofluidic platform with unique advantages for single-molecule analysis and filtration applications. However, significant improvements in device performance and scalable fabrication methods are needed to make nanopore devices competitive with existing technologies. This dissertation investigates the potential advantages of ultra-thin nanopores in which the thickness of the membrane is significantly smaller than the nanopore diameter. Novel, scalable fabrication methods were first developed and then utilized to examine device performance for water filtration and single molecule sensing applications. Fabrication of nanometer-thin pores in silicon nitride membranes was achieved using a feedback-controlled ion beam method in which ion sputtering is arrested upon detection of the first few ions that drill through the membrane. Performing fabrication at liquid nitrogen temperatures prevents surface atom rearrangements that have previously complicated similar processes. A novel cross-sectional imaging method was also developed to allow careful examination of the full nanopore geometry. Atomically-thin graphene nanopores were fabricated via an electrical pulse method in which sub-microsecond electrical pulses applied across a graphene membrane in electrolyte solution are used to create a defect in the membrane and controllably enlarge it into a nanopore. This method dramatically increases the accuracy and reliability of graphene nanopore production, allowing consistent production of single nanopores down to subnanometer sizes. In filtration applications in which nanopores are used to selectively restrict the passage of dissolved contaminants, ultra-thin nanopores minimize the flow resistance, increasing throughput and energy-efficiency. The ability of graphene nanopores to separate different ions was characterized via ionic conductance and reversal potential measurements. Graphene nanopores were observed to conduct cations preferentially over anions with selectivity ratios of 100 or higher for pores as large as 20 nm in diameter, suggesting that porous graphene membranes can be used to create highly effective cation exchange membranes for electrodialysis filtration. These surprisingly high selectivities cannot be explained by current models of ionic conduction in graphene nanopores, motivating the development of a new model in which elevated concentrations of mobile cations near the graphene surface generate additional ion selectivity.

Correlation Function Approach for Estimating Thermal Conductivity in Highly Porous Fibrous Materials

NASA Technical Reports Server (NTRS)

Martinez-Garcia, Jorge; Braginsky, Leonid; Shklover, Valery; Lawson, John W.

2011-01-01

Heat transport in highly porous fiber networks is analyzed via two-point correlation functions. Fibers are assumed to be long and thin to allow a large number of crossing points per fiber. The network is characterized by three parameters: the fiber aspect ratio, the porosity and the anisotropy of the structure. We show that the effective thermal conductivity of the system can be estimated from knowledge of the porosity and the correlation lengths of the correlation functions obtained from a fiber structure image. As an application, the effects of the fiber aspect ratio and the network anisotropy on the thermal conductivity is studied.

Studies on surface morphology and electrical conductivity of PEDOT:PSS thin films in presence of gold nanoparticles

NASA Astrophysics Data System (ADS)

Bhowal, Ashim Chandra; Kundu, Sarathi

2018-04-01

PEDOT:PSS is a water soluble conducting polymer consists of positively charged PEDOT and negatively charged PSS. However, this polymer suffers low conductivity problem which restrict its use. In this paper, electrical conductivity of PEDOT:PSS thin films is improved by using charged gold nanoparticles. The nanoparticles used are synthesized using lysozyme protein. The nanoparticles coated with lysozyme protein possess positive zeta potential. In the presence of gold nanoparticles due to electrostatic interaction between positively charged nanoparticles and negatively charged PSS chains, modification takes place in the surface morphology and electrical behaviors of PEDOT:PSS thin films. The changes in the polymer matrix conformations in the presence of nanoparticles are studied by Fourier transformed Infra-red (FTIR) spectroscopy, whereas the surface morphology of prepared thin films before and after interaction with nanoparticles is investigated through atomic force microscopy (AFM). Four probe method is used to measure the variation of electrical conductivity from I-V characteristics curves.

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

Hanc, Emil; Zając, Wojciech, E-mail: wojciech.zajac@agh.edu.pl; Lu, Li

Ceramic oxides exhibiting high lithium-ion mobility at room temperature receive broad attention as candidate electrolytes for lithium batteries. Lithium-stuffed garnets from the Li{sub 7}La{sub 3}Zr{sub 2}O{sub 12} group seem to be especially promising because of their high ionic conductivity at room temperature and their electrochemical stability. In this work, we discuss factors that affect formation of the garnet in its bulk form or in the form of thick and thin films. We demonstrate that zinc oxide can be applied as a sintering aid that facilitate the formation of the highly conducting cubic Li{sub 7}La{sub 3}Zr{sub 2}O{sub 12} garnet phase inmore » a single-step sintering procedure. Based on our experience with the single-step sintering experiments, we successfully fabricated a thick-film membrane consisting of a garnet solid electrolyte using the tape casting technique. In order to reduce the thickness of the electrolyte even further we investigated the fabrication of a thin-film Li{sub 7}La{sub 3}Zr{sub 2}O{sub 12} electrolyte by means of the pulsed laser deposition technique.« less

Thermal conductivity and thermal boundary resistance of atomic layer deposited high-k dielectric aluminum oxide, hafnium oxide, and titanium oxide thin films on silicon

NASA Astrophysics Data System (ADS)

Scott, Ethan A.; Gaskins, John T.; King, Sean W.; Hopkins, Patrick E.

2018-05-01

The need for increased control of layer thickness and uniformity as device dimensions shrink has spurred increased use of atomic layer deposition (ALD) for thin film growth. The ability to deposit high dielectric constant (high-k) films via ALD has allowed for their widespread use in a swath of optical, optoelectronic, and electronic devices, including integration into CMOS compatible platforms. As the thickness of these dielectric layers is reduced, the interfacial thermal resistance can dictate the overall thermal resistance of the material stack compared to the resistance due to the finite dielectric layer thickness. Time domain thermoreflectance is used to interrogate both the thermal conductivity and the thermal boundary resistance of aluminum oxide, hafnium oxide, and titanium oxide films on silicon. We calculate a representative design map of effective thermal resistances, including those of the dielectric layers and boundary resistances, as a function of dielectric layer thickness, which will be of great importance in predicting the thermal resistances of current and future devices.

Graphene Nanopore Support System for Simultaneous High-Resolution AFM Imaging and Conductance Measurements

PubMed Central

2015-01-01

Accurately defining the nanoporous structure and sensing the ionic flow across nanoscale pores in thin films and membranes has a wide range of applications, including characterization of biological ion channels and receptors, DNA sequencing, molecule separation by nanoparticle films, sensing by block co-polymers films, and catalysis through metal–organic frameworks. Ionic conductance through nanopores is often regulated by their 3D structures, a relationship that can be accurately determined only by their simultaneous measurements. However, defining their structure–function relationships directly by any existing techniques is still not possible. Atomic force microscopy (AFM) can image the structures of these pores at high resolution in an aqueous environment, and electrophysiological techniques can measure ion flow through individual nanoscale pores. Combining these techniques is limited by the lack of nanoscale interfaces. We have designed a graphene-based single-nanopore support (∼5 nm thick with ∼20 nm pore diameter) and have integrated AFM imaging and ionic conductance recording using our newly designed double-chamber recording system to study an overlaid thin film. The functionality of this integrated system is demonstrated by electrical recording (<10 pS conductance) of suspended lipid bilayers spanning a nanopore and simultaneous AFM imaging of the bilayer. PMID:24581087

Metal-insulator transition in tin doped indium oxide (ITO) thin films: Quantum correction to the electrical conductivity

NASA Astrophysics Data System (ADS)

Kaushik, Deepak Kumar; Kumar, K. Uday; Subrahmanyam, A.

2017-01-01

Tin doped indium oxide (ITO) thin films are being used extensively as transparent conductors in several applications. In the present communication, we report the electrical transport in DC magnetron sputtered ITO thin films (prepared at 300 K and subsequently annealed at 673 K in vacuum for 60 minutes) in low temperatures (25-300 K). The low temperature Hall effect and resistivity measurements reveal that the ITO thin films are moderately dis-ordered (kFl˜1; kF is the Fermi wave vector and l is the electron mean free path) and degenerate semiconductors. The transport of charge carriers (electrons) in these disordered ITO thin films takes place via the de-localized states. The disorder effects lead to the well-known `metal-insulator transition' (MIT) which is observed at 110 K in these ITO thin films. The MIT in ITO thin films is explained by the quantum correction to the conductivity (QCC); this approach is based on the inclusion of quantum-mechanical interference effects in Boltzmann's expression of the conductivity of the disordered systems. The insulating behaviour observed in ITO thin films below the MIT temperature is attributed to the combined effect of the weak localization and the electron-electron interactions.

Evaluation of thin discontinuities in planar conducting materials using the diffraction of electromagnetic field

NASA Astrophysics Data System (ADS)

Savin, A.; Novy, F.; Fintova, S.; Steigmann, R.

2017-08-01

The current stage of nondestructive evaluation techniques imposes the development of new electromagnetic (EM) methods that are based on high spatial resolution and increased sensitivity. In order to achieve high performance, the work frequencies must be either radifrequencies or microwaves. At these frequencies, at the dielectric/conductor interface, plasmon polaritons can appear, propagating between conductive regions as evanescent waves. In order to use the evanescent wave that can appear even if the slits width is much smaller that the wavwelength of incident EM wave, a sensor with metamaterial (MM) is used. The study of the EM field diffraction against the edge of long thin discontinuity placed under the inspected surface of a conductive plate has been performed using the geometrical optics principles. This type of sensor having the reception coils shielded by a conductive screen with a circular aperture placed in the front of reception coil of emission reception sensor has been developed and “transported” information for obtaining of magnified image of the conductive structures inspected. This work presents a sensor, using MM conical Swiss roll type that allows the propagation of evanescent waves and the electromagnetic images are magnified. The test method can be successfully applied in a variety of applications of maxim importance such as defect/damage detection in materials used in automotive and aviation technologies. Applying this testing method, spatial resolution can be improved.

Microstructure of epitaxial ferroelectric/metal oxide electrode thin film heterostructures on LaAlO{sub 3} and silicon

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

Ghonge, S.G.; Goo, E.; Ramesh, R.

1994-12-31

TEM and X-ray diffraction studies of PZT, PLZT, lead titanate and bismuth titanate ferroelectric thin films and YBa{sub 2}Cu{sub 3}O{sub 7{minus}x}(YBCO), Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8}(BSCCO) and La{sub 0.5}Sr{sub 0.5}CoO{sub 3}(LSCO) electrically conductive oxide thin films, that are sequentially deposited by pulsed laser ablation, show that these films may be deposited epitaxially onto LaAlO{sub 3}(LAO) or Si substrates. The conductive oxides are promising candidates for use is electrodes in place of metal electrodes in integrated ferroelectric device applications. The oxide electrodes are more chemically compatible with the ferroelectric films. High resolution electron microscopy his been used to investigate the interfacemore » between the ferroelectric and metal oxide thin films and no reaction was detected. Epitaxial growth is possible due to the similar crystal structures and the small lattice mismatch. The lattice mismatch that is present causes the domains in the ferroelectric films to be preferentially oriented and in the case of lead titanate, the film is single domain. These films may also have potential applications in integrated optical devices.« less

Reaching the Ionic Current Detection Limit in Silicon-Based Nanopores

NASA Astrophysics Data System (ADS)

Puster, Matthew; Rodriguez-Manzo, Julio Alejandro; Nicolai, Adrien; Meunier, Vincent; Drndic, Marija

2015-03-01

Solid-state nanopores act as single-molecule sensors whereby passage of an individual molecule in aqueous electrolyte through a nanopore is registered as a change in ionic conductance (ΔG). Future nanopore applications such as DNA sequencing at high bandwidth require high ΔG for optimal signal-to-noise ratio. Reducing the nanopore diameter and thickness increase ΔG. Molecule size limits the diameter, thus efforts concentrate on minimizing the thickness by thinning oxide/nitride films or using 2D materials. Weighted by electrolyte conductivity the highest ΔG reported to date for DNA translocations were obtained with nanopores made in oxide/nitride films. We present a controlled electron irradiation technique to thin such films to the limit of their stability, producing nanopores tailored to molecule size in amorphous Si with thicknesses less than 2 nm. We compare ΔG values with results found in the literature for DNA translocation through these nanopores, where access resistance becomes comparable to the resistance through the nanopore itself.

Origin of high photoconductive gain in fully transparent heterojunction nanocrystalline oxide image sensors and interconnects.

PubMed

Jeon, Sanghun; Song, Ihun; Lee, Sungsik; Ryu, Byungki; Ahn, Seung-Eon; Lee, Eunha; Kim, Young; Nathan, Arokia; Robertson, John; Chung, U-In

2014-11-05

A technique for invisible image capture using a photosensor array based on transparent conducting oxide semiconductor thin-film transistors and transparent interconnection technologies is presented. A transparent conducting layer is employed for the sensor electrodes as well as interconnection in the array, providing about 80% transmittance at visible-light wavelengths. The phototransistor is a Hf-In-Zn-O/In-Zn-O heterostructure yielding a high quantum-efficiency in the visible range. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Maxwell's theory of eddy currents in thin conducting sheets, and applications to electromagnetic shielding and MAGLEV

NASA Astrophysics Data System (ADS)

Saslow, W. M.

1992-08-01

Using the example of a monopole that is spontaneously generated above a thin conducting sheet, the simplicity and power of Maxwell's 1872 theory of eddy currents in thin conducting sheets is illustrated. This theory employs a receding image construction, with a characteristic recession velocity v0=2/(μ0σd), where the sheet has conductivity σ and thickness d. A modern derivation of the theory, employing the magnetic scalar potential, is also presented, with explicit use of the uniqueness theorem. Also discussed are limitations on the theory of which Maxwell, living in a time before the discovery of the electron, could not have been aware. Previous derivations either have not appealed explicitly to the uniqueness theorem, or have employed the now unfamiliar current function, and are therefore either incomplete or inaccessible to the modern reader. After the derivation, two important examples considered by Maxwell are presented-a monopole moving above a thin conducting sheet, and a monopole above a rotating thin conducting sheet (Arago's disk)-and it is argued that the lift force thus obtained makes Maxwell the grandfather, if not the father, of eddy current MAGLEV transportation systems. An energy conservation argument is given to derive Davis's result that, for a magnet of arbitrary size and shape moving parallel to a thin conducting sheet at a characteristic height h, with velocity v, the ratio of drag force to lift force is equal to v0/v, provided that d≪δc, where δc =√2h/(μ0σv). If d≫δc, the eddy currents are confined to a thickness δc, leading to an increase in the dissipation and the drag by a factor of d/δc, so that the ratio of drag to lift force becomes proportional to √v'0/v, where v'0 = 2/(μ0σh). The case of a monopole fixed in position, but oscillating in strength (such as can be simulated by one end of a long, narrow, ac solenoid), is also treated. This is employed to obtain the results for an oscillating magnetic dipole whose moment is normal to the sheet. A general discussion of electromagnetic induction and electrical conductors, both thick and thin, is given, emphasizing the difference between the high-frequency limit, where flux expulsion occurs and the self-inductance dominates, and the low-frequency limit, where the flux penetrates and the electrical resistance dominates. A discussion of Lenz's law, as a statement about motion, is given. It is argued that the most general form of such a statement of Lenz's law is that induced currents tend to accelerate a conductor in the direction that most effectively decreases the rate of Joule heating. A calculation, in the low-frequency limit, of the drag force on a magnetic dipole falling down a long conducting tube, is also given. This last case can be given a striking demonstration with the newly available neodymium-iron-boron magnets.

Flexible Thin Metal Film Thermal Sensing System

NASA Technical Reports Server (NTRS)

Thomsen, Donald Laurence (Inventor)

2012-01-01

A flexible thin metal film thermal sensing system is provided. A thermally-conductive film made from a thermally-insulating material is doped with thermally-conductive material. At least one layer of electrically-conductive metal is deposited directly onto a surface of the thermally-conductive film. One or more devices are coupled to the layer(s) to measure an electrical characteristic associated therewith as an indication of temperature.

An Automated, High-Throughput System for GISAXS and GIWAXS Measurements of Thin Films

NASA Astrophysics Data System (ADS)

Schaible, Eric; Jimenez, Jessica; Church, Matthew; Lim, Eunhee; Stewart, Polite; Hexemer, Alexander

Grazing incidence small-angle X-ray scattering (GISAXS) and grazing incidence wide-angle X-ray scattering (GIWAXS) are important techniques for characterizing thin films. In order to meet rapidly increasing demand, the SAXSWAXS beamline at the Advanced Light Source (beamline 7.3.3) has implemented a fully automated, high-throughput system to conduct SAXS, GISAXS and GIWAXS measurements. An automated robot arm transfers samples from a holding tray to a measurement stage. Intelligent software aligns each sample in turn, and measures each according to user-defined specifications. Users mail in trays of samples on individually barcoded pucks, and can download and view their data remotely. Data will be pipelined to the NERSC supercomputing facility, and will be available to users via a web portal that facilitates highly parallelized analysis.

Nature of Dielectric Properties, Electric Modulus and AC Electrical Conductivity of Nanocrystalline ZnIn2Se4 Thin Films

NASA Astrophysics Data System (ADS)

El-Nahass, M. M.; Attia, A. A.; Ali, H. A. M.; Salem, G. F.; Ismail, M. I.

2018-02-01

The structural characteristics of thermally deposited ZnIn2Se4 thin films were indexed utilizing x-ray diffraction as well as scanning electron microscopy techniques. Dielectric properties, electric modulus and AC electrical conductivity of ZnIn2Se4 thin films were examined in the frequency range from 42 Hz to 106 Hz. The capacitance, conductance and impedance were measured at different temperatures. The dielectric constant and dielectric loss decrease with an increase in frequency. The maximum barrier height was determined from the analysis of the dielectric loss depending on the Giuntini model. The real part of the electric modulus revealed a constant maximum value at higher frequencies and the imaginary part of the electric modulus was characterized by the appearance of dielectric relaxation peaks. The AC electrical conductivity obeyed the Jonscher universal power law. Correlated barrier hopping model was the appropriate mechanism for AC conduction in ZnIn2Se4 thin films. Estimation of the density of states at the Fermi level and activation energy, for AC conduction, was carried out based on the temperature dependence of AC electrical conductivity.

Thermally induced chain orientation for improved thermal conductivity of P(VDF-TrFE) thin films

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

Zhao, Junnan; Tan, Aaron C.; Green, Peter F.

2017-01-01

A large increase in thermal conductivityκwas observed in a P(VDF-TrFE) thin film annealed above melting temperature due to extensive ordering of polymer backbone chains perpendicular to the substrate after recrystallization from the melt. This finding may lay out a straightforward method to improve the thin filmκof semicrystalline polymers whose chain orientation is sensitive to thermal annealing.

Self-assembly of a thin highly reduced graphene oxide film and its high electrocatalytic activity

NASA Astrophysics Data System (ADS)

Bai, Yan-Feng; Zhang, Yong-Fang; Zhou, An-Wei; Li, Hai-Wai; Zhang, Yu; Luong, John H. T.; Cui, Hui-Fang

2014-10-01

A thin highly reduced graphene oxide (rGO) film was self-assembled at the dimethyl formamide (DMF)-air interface through evaporation-induced water-assisted thin film formation at the pentane-DMF interface, followed by complete evaporation of pentane. The thin film was transferred onto various solid substrates for film characterization and electrochemical sensing. UV-visible spectrometry, scanning electron microscopy (SEM), atomic force microscopy (AFM) and electrochemistry techniques were used to characterize the film. An rGO film showing 82.8% of the transmittance at 550 nm corresponds to a few layers of rGO nanosheets. The rGO nanosheets cross-stack with each other, lying approximately in the plane of the film. An rGO film collected on a glassy carbon (GC) electrode exhibited improved electrical conductivity compared to GC, with the electrode charge-transfer resistance (Rct) reduced from 31 Ω to 22 Ω. The as-formed rGO/GC electrode was mechanically very stable, exhibiting significantly enhanced electrocatalytic activity to H2O2 and dopamine. Multiple layers of the rGO films on the GC electrode showed even stronger electrocatalytic activity to dopamine than that of the single rGO film layer. The controllable formation of a stable rGO film on various solid substrates has potential applications for nanoelectronics and sensors/biosensors.

Active superconducting devices formed of thin films

DOEpatents

Martens, Jon S.; Beyer, James B.; Nordman, James E.; Hohenwarter, Gert K. G.

1991-05-28

Active superconducting devices are formed of thin films of superconductor which include a main conduction channel which has an active weak link region. The weak link region is composed of an array of links of thin film superconductor spaced from one another by voids and selected in size and thickness such that magnetic flux can propagate across the weak link region when it is superconducting. Magnetic flux applied to the weak link region will propagate across the array of links causing localized loss of superconductivity in the links and changing the effective resistance across the links. The magnetic flux can be applied from a control line formed of a superconducting film deposited coplanar with the main conduction channel and weak link region on a substrate. The devices can be formed of any type to superconductor but are particularly well suited to the high temperature superconductors since the devices can be entirely formed from coplanar films with no overlying regions. The devices can be utilized for a variety of electrical components, including switching circuits, amplifiers, oscillators and modulators, and are well suited to microwave frequency applications.

MHD Flow and Heat Transfer Characteristics in a Casson Liquid Film Towards an Unsteady Stretching Sheet with Temperature-Dependent Thermal Conductivity

NASA Astrophysics Data System (ADS)

Mahmoud, Mostafa A. A.; Megahed, Ahmed M.

2017-10-01

Theoretical and numerical outcomes of the non-Newtonian Casson liquid thin film fluid flow owing to an unsteady stretching sheet which exposed to a magnetic field, Ohmic heating and slip velocity phenomena is reported here. The non-Newtonian thermal conductivity is imposed and treated as it vary with temperature. The nonlinear partial differential equations governing the non-Newtonian Casson thin film fluid are simplified into a group of highly nonlinear ordinary differential equations by using an adequate dimensionless transformations. With this in mind, the numerical solutions for the ordinary conservation equations are found using an accurate shooting iteration technique together with the Runge-Kutta algorithm. The lineaments of the thin film flow and the heat transfer characteristics for the pertinent parameters are discussed through graphs. The results obtained here detect many concern for the local Nusselt number and the local skin-friction coefficient in which they may be beneficial for the material processing industries. Furthermore, in some special conditions, the present problem has an excellent agreement with previously published work.

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

Zhou, Guangmin; Sun, Jie; Jin, Yang

A 3D graphene cage with a thin layer of electrodeposited nickel phosphosulfide for Li 2S impregnation, using ternary nickel phosphosulphide as a highly conductive coating layer for stabilized polysulfide chemistry, is accomplished by the combination of theoretical and experimental studies. As a result, the 3D interconnected graphene cage structure leads to high capacity, good rate capability and excellent cycling stability in a Li 2S cathode.

Self-healable electrically conducting wires for wearable microelectronics.

PubMed

Sun, Hao; You, Xiao; Jiang, Yishu; Guan, Guozhen; Fang, Xin; Deng, Jue; Chen, Peining; Luo, Yongfeng; Peng, Huisheng

2014-09-01

Electrically conducting wires play a critical role in the advancement of modern electronics and in particular are an important key to the development of next-generation wearable microelectronics. However, the thin conducting wires can easily break during use, and the whole device fails to function as a result. Herein, a new family of high-performance conducting wires that can self-heal after breaking has been developed by wrapping sheets of aligned carbon nanotubes around polymer fibers. The aligned carbon nanotubes offer an effective strategy for the self-healing of the electric conductivity, whereas the polymer fiber recovers its mechanical strength. A self-healable wire-shaped supercapacitor fabricated from a wire electrode of this type maintained a high capacitance after breaking and self-healing. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

High Transparent and Conductive TiO2/Ag/TiO2 Multilayer Electrode Films Deposited on Sapphire Substrate

NASA Astrophysics Data System (ADS)

Loka, Chadrasekhar; Moon, Sung Whan; Choi, YiSik; Lee, Kee-Sun

2018-03-01

Transparent conducting oxides attract intense interests due to its diverse industrial applications. In this study, we report sapphire substrate-based TiO2/Ag/TiO2 (TAT) multilayer structure of indium-free transparent conductive multilayer coatings. The TAT thin films were deposited at room temperature on sapphire substrates and a rigorous analysis has been presented on the electrical and optical properties of the films as a function of Ag thickness. The optical and electrical properties were mainly controlled by the Ag mid-layer thickness of the TAT tri-layer. The TAT films showed high luminous transmittance 84% at 550 nm along with noteworthy low electrical resistance 3.65 × 10-5 Ω-cm and sheet resistance of 3.77 Ω/square, which is better are than those of amorphous ITO films and any sapphire-based dielectric/metal/dielectric multilayer stack. The carrier concentration of the films was increased with respect to Ag thickness. We obtained highest Hackke's figure of merit 43.97 × 10-3 Ω-1 from the TAT multilayer thin film with a 16 nm thick Ag mid-layer.

Facile Synthesis of Ultralong and Thin Copper Nanowires and Its Application to High-Performance Flexible Transparent Conductive Electrodes

NASA Astrophysics Data System (ADS)

Wang, Yaxiong; Liu, Ping; Zeng, Baoqing; Liu, Liming; Yang, Jianjun

2018-03-01

A hydrothermal method for synthesizing ultralong and thin copper nanowires (CuNWs) with average diameter of 35 nm and average length of 100 μm is demonstrated in this paper. The concerning raw materials include copric (II) chloride dihydrate (CuCl2·2H2O), octadecylamine (ODA), and ascorbic acid, which are all very cheap and nontoxic. The effect of different reaction time and different molar ratios to the reaction products were researched. The CuNWs prepared by the hydrothermal method were applied to fabricate CuNW transparent conductive electrode (TCE), which exhibited excellent conductivity-transmittance performance with low sheet resistance of 26.23 Ω /\\square and high transparency at 550 nm of 89.06% (excluding Polyethylene terephthalate (PET) substrate). The electrode fabrication process was carried out at room temperature, and there was no need for post-treatment. In order to decrease roughness and protect CuNW TCEs against being oxidized, we fabricated CuNW/poly(methyl methacrylate) (PMMA) hybrid TCEs (HTCEs) using PMMA solution. The CuNW/PMMA HTCEs exhibited low surface roughness and chemical stability as compared with CuNW TCEs.

Stable aqueous based Cu nanoparticle ink for printing well-defined highly conductive features on a plastic substrate.

PubMed

Jeong, Sunho; Song, Hae Chun; Lee, Won Woo; Lee, Sun Sook; Choi, Youngmin; Son, Wonil; Kim, Eui Duk; Paik, Choon Hoon; Oh, Seok Heon; Ryu, Beyong-Hwan

2011-03-15

With the aim of inkjet printing highly conductive and well-defined Cu features on plastic substrates, aqueous based Cu ink is prepared for the first time using water-soluble Cu nanoparticles with a very thin surface oxide layer. Owing to the specific properties, high surface tension and low boiling point, of water, the aqueous based Cu ink endows a variety of advantages over conventional Cu inks based on organic solvents in printing narrow conductive patterns without irregular morphologies. It is demonstrated how the design of aqueous based ink affects the basic properties of printed conductive features such as surface morphology, microstructure, conductivity, and line width. The long-term stability of aqueous based Cu ink against oxidation is analyzed through an X-ray photoelectron spectroscopy (XPS) based investigation on the evolution of the surface oxide layer in the aqueous based ink.

In situ conductance measurements of copper phthalocyanine thin film growth on sapphire [0001].

PubMed

Murdey, Richard; Sato, Naoki

2011-06-21

The current flowing through a thin film of copper phthalocyanine vacuum deposited on a single crystal sapphire [0001] surface was measured during film growth from 0 to 93 nm. The results, expressed as conductance vs. nominal film thickness, indicate three distinct film growth regions. Conductive material forms below about 5 nm and again above 35 nm, but in the intermediate thicknesses the film conductance was observed to decrease with increasing film thickness. With the aid of ac-AFM topology images taken ex situ, the conductance results are explained based on the Stranski-Krastanov (2D + 3D) film growth mechanism, in which the formation of a thin wetting layer is followed by the growth of discrete islands that eventually coalesce into an interpenetrating, conductive network. © 2011 American Institute of Physics

Preparation of graphene thin films for radioactive samples.

PubMed

Roteta, Miguel; Fernández-Martínez, Rodolfo; Mejuto, Marcos; Rucandio, Isabel

2016-03-01

A new method for the preparation of conductive thin films is presented. The metallization of VYNS films guarantees the electrical conductivity but it results in the breaking of a high proportion of them. Graphene, a two-dimensional nanostructure of monolayer or few layers graphite has attracted a great deal of attention because of its excellent properties such as a good chemical stability, mechanical resistance and extraordinary electronic transport properties. In this work, the possibilities of graphene have been explored as a way to produce electrical conductive thin films without an extra metallization process. The procedure starts with preparing homogenous suspensions of reduced graphene oxide (rGO) in conventional VYNS solutions. Ultra-sonication is used to ensure a good dispersibility of rGO. Graphene oxide (GO) is prepared via oxidation of graphite and subsequent exfoliation by sonication. Different chemically rGO were obtained by reaction with hydrazine sulfate, sodium borohydride, ascorbic acid and hydroiodic acid as reducing agents. The preparation of the thin graphene films is done in a similar way as the conventional VYNS foil preparation procedure. Drops of the solution are deposited onto water. The graphene films have been used to prepare sources containing some electron capture radionuclides ((109)Cd, (55)Fe, (139)Ce) with an activity in the order of 3kBq. The samples have been measured to test the attainable low energy electron efficiency and the energy resolution of Auger and conversion electrons by 4π (electron capture)-γ coincidence measurements. The 4π (electron capture)-γ coincidence setup includes a pressurized proportional counter and a NaI(Tl) detector. Tests with different pressures up to 1000kPa were carried out. All these tests show similar values in both parameters (efficiency and resolution) as those obtained by using the conventional metallized films without the drawback of the high percentage of broken films. Copyright © 2015 Elsevier Ltd. All rights reserved.

Formation of Semimetallic Cobalt Telluride Nanotube Film via Anion Exchange Tellurization Strategy in Aqueous Solution for Electrocatalytic Applications.

PubMed

Patil, Supriya A; Kim, Eun-Kyung; Shrestha, Nabeen K; Chang, Jinho; Lee, Joong Kee; Han, Sung-Hwan

2015-11-25

Metal telluride nanostructures have demonstrated several potential applications particularly in harvesting and storing green energy. Metal tellurides are synthesized by tellurization process performed basically at high temperature in reducing gas atmosphere, which makes the process expensive and complicated. The development of a facile and economical process for desirable metal telluride nanostructures without complicated manipulation is still a challenge. In an effort to develop an alternative strategy of tellurization, herein we report a thin film formation of self-standing cobalt telluride nanotubes on various conducting and nonconducting substrates using a simple binder-free synthetic strategy based on anion exchange transformation from a thin film of cobalt hydroxycarbonate nanostructures in aqueous solution at room temperature. The nanostructured films before and after ion exchange transformation reaction are characterized using field emission scanning electron microscope, energy dispersive X-ray analyzer, X-ray photoelectron spectroscopy, thin film X-ray diffraction technique, high resolution transmission electron microscope, and selected area electron diffraction analysis technique. After the ion exchange transformation of nanostructures, the film shows conversion from insulator to highly electrical conductive semimetallic characteristic. When used as a counter electrode in I3(-)/I(-) redox electrolyte based dye-sensitized solar cells, the telluride film exhibits an electrocatalytic reduction activity for I3(-) with a demonstration of solar-light to electrical power conversion efficiency of 8.10%, which is highly competitive to the efficiency of 8.20% exhibited by a benchmarked Pt-film counter electrode. On the other hand, the telluride film electrode also demonstrates electrocatalytic activity for oxygen evolution reaction from oxidation of water.

Silver nanowire-based transparent, flexible, and conductive thin film

PubMed Central

2011-01-01

The fabrication of transparent, conductive, and uniform silver nanowire films using the scalable rod-coating technique is described in this study. Properties of the transparent conductive thin films are investigated, as well as the approaches to improve the performance of transparent silver nanowire electrodes. It is found that silver nanowires are oxidized during the coating process. Incubation in hydrogen chloride (HCl) vapor can eliminate oxidized surface, and consequently, reduce largely the resistivity of silver nanowire thin films. After HCl treatment, 175 Ω/sq and approximately 75% transmittance are achieved. The sheet resistivity drops remarkably with the rise of the film thickness or with the decrease of transparency. The thin film electrodes also demonstrated excellent flexible stability, showing < 2% resistance change after over 100 bending cycles. PMID:21711602

Preparation and Conductivity Measurements of Thin Film (PEO)nZnCl2 Electrolyte System

NASA Astrophysics Data System (ADS)

Salehuddin, N.; Mohamad, A. A.; Alias, Y.

2010-03-01

We report zinc ion conducting thin film polymer based on non-volatile room temperature ionic liquid, with a zinc chloride dissolved in a water and blend with poly(ethylene) oxide in different ratio of salt. The resultant films are free standing, translucent, flexible and elastic. The conductivity measurement of the films was carried out at room temperature to find the highest conductivity films.

Synthesis and characterization of Au-MWCNT/PEDOT: PSS composite film for optoelectronic applications

NASA Astrophysics Data System (ADS)

Jasna, M.; Anjana, R.; Jayaraj, M. K.

2017-08-01

Recently, flexible organic optoelectronics have got great attention because of their light weight, mechanical flexibility and cost effective fabrication process. Conjugated polymers like PEDOT: PSS are widely used for the transparent electrode applications due to its chemical stability, high conductivity, flexibility and optical transparency in the visible region. Conductivity of the PEDOT: PSS polymer can be enhanced by adding organic solvents or conducting nano fillers like CNT, graphene, etc. Carbon nanotubes are good nano fillers to enhance the conductivity and mechanical strength of PEDOT: PSS composite film. Inthe present work, the effect of gold nano particles in PEDOT: PSS/CNT composite is studied. The conductivity enhancement in PEDOT: PSS/CNT thin films can be attributed to the formation of CNT network in the polymer matrix and conformational change of the PEDOT from benzoid to quinoid structure. Even though the conductivity was enhanced, the transparency of the composite thin films decreased with increase in CNT concentration. To overcome this problem, gold nano particles were attached to CNT walls via chemical route. AuMWCNT/PEDOT: PSS composite films were prepared by spin coating method. TEM images confirmed the decoration of gold nano particles on CNT walls. Electrical and optical properties of the composite films were studied. This simple solution processed conducting films are suitable for optoelectronic applications

Low substrate temperature fabrication of high-performance metal oxide thin-film by magnetron sputtering with target self-heating

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

Yang, W. F.; Institute of Materials Research and Engineering, Agency for Science, Technology and Research; Liu, Z. G.

2013-03-18

Al-doped ZnO (AZO) films with high transmittance and low resistivity were achieved on low temperature substrates by radio frequency magnetron sputtering using a high temperature target. By investigating the effect of target temperature (T{sub G}) on electrical and optical properties, the origin of electrical conduction is verified as the effect of the high T{sub G}, which enhances crystal quality that provides higher mobility of electrons as well as more effective activation for the Al dopants. The optical bandgap increases from 3.30 eV for insulating ZnO to 3.77 eV for conducting AZO grown at high T{sub G}, and is associated withmore » conduction-band filling up to 1.13 eV due to the Burstein-Moss effect.« less

Synthesis and microstructural TEM investigation of CaCu{sub 3}Ru{sub 4}O{sub 12} ceramic and thin film

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

Brize, Virginie; STMicroelectronics, 16 rue P and M Curie, 37001 Tours; Autret-Lambert, Cecile, E-mail: cecile.autret-lambert@univ-tours.fr

2011-10-15

CaCu{sub 3}Ru{sub 4}O{sub 12} (CCRO) is a conductive oxide having the same structure as CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) and close lattice parameters. The later compound is strongly considered for high density parallel plates capacitors application due to its so-called colossal dielectric constant. The need for an electrode inducing CCTO epitaxial growth with a clean and sharp interface is therefore necessary, and CCRO is a good potential candidate. In this paper, the synthesis of monophasic CCRO ceramic is reported, as well as pulsed laser deposition of CCRO thin film onto (001) NdCaAlO{sub 4} substrate. Structural and physical properties of bulkmore » CCRO were studied by transmission electron microscopy and electron spin resonance. CCRO films and ceramic exhibited a metallic behavior down to low temperature. CCRO films were (001) oriented and promoted a CCTO film growth with the same orientation. - Graphical Abstract: Structure of CaCu{sub 3}Ru{sub 4}O{sub 12} showing the RuO{sub 6} octahedra and the square planar environment for Cu{sup 2+}. Highlights: > In this study, we investigate the structural properties and microstructure of ceramics CaCu{sub 3}Ru{sub 4}O{sub 12}. > We study the conduction properties of polycrystalline material. > Then we synthesize the conductive thin film which is deposited on a high K material with the same structure (CaCu{sub 3}Ti{sub 4}O{sub 12}).« less

Evaluations of Thin Cirrus Contamination and Screening in Ground Aerosol Observations Using Collocated Lidar Systems

NASA Technical Reports Server (NTRS)

Huang, Jingfeng; Hsu, N. Christina; Tsay, Si-Chee; Holben, Brent N.; Welton, Ellsworth J.; Smirnov, Alexander; Jeong, Myeong-Jae; Hansell, Richard A.; Berkoff, Timothy A.

2012-01-01

Cirrus clouds, particularly sub visual high thin cirrus with low optical thickness, are difficult to be screened in operational aerosol retrieval algorithms. Collocated aerosol and cirrus observations from ground measurements, such as the Aerosol Robotic Network (AERONET) and the Micro-Pulse Lidar Network (MPLNET), provide us with an unprecedented opportunity to examine the susceptibility of operational aerosol products to thin cirrus contamination. Quality assured aerosol optical thickness (AOT) measurements were also tested against the CALIPSO vertical feature mask (VFM) and the MODIS-derived thin cirrus screening parameters for the purpose of evaluating thin cirrus contamination. Key results of this study include: (1) Quantitative evaluations of data uncertainties in AERONET AOT retrievals are conducted. Although AERONET cirrus screening schemes are successful in removing most cirrus contamination, strong residuals displaying strong spatial and seasonal variability still exist, particularly over thin cirrus prevalent regions during cirrus peak seasons, (2) Challenges in matching up different data for analysis are highlighted and corresponding solutions proposed, and (3) Estimation of the relative contributions from cirrus contamination to aerosol retrievals are discussed. The results are valuable for better understanding and further improving ground aerosol measurements that are critical for aerosol-related climate research.

Processing effects on the microstructure and dielectric properties of hydrothermal barium titanate and (barium,strontium)titanate thin films

NASA Astrophysics Data System (ADS)

McCormick, Mark Alan

The goal of this work was to produce BaTiO3 and BaxSr (1-x)TiO3 (BST) thin films with high dielectric constants, using a low-temperature (<100°C) hydrothermal synthesis route. To accomplish this, titanium metal-organic precursor films were spin-cast onto metal-coated glass substrates and converted to polycrystalline BaTiO3 or BST upon reacting in aqueous solutions of Ba(OH)2 or Ba(OH)2 and Sr(OH)2. The influences of solution molarity, processing temperature, and reaction time on thin film reaction kinetics, microstructure, and dielectric properties were examined for BaTiO3 films. Post-deposition annealing at temperatures as low as 200°C substantially affected the lattice parameter, dielectric constant, and dielectric loss. This behavior is explained in terms of hydroxyl defect incorporation during film formation. Current-voltage (I-V) measurements were performed to determine the dominant conduction mechanism(s) during application of a do field, and to extract the metal/ceramic barrier height. In particular, Schottky barrier-limited conduction and Poole-Frenkel conduction were investigated as potential leakage mechanisms. For BST thin films, film stoichiometry deviated from the initial solution composition, with a preferred incorporation of Sr2+ into the perovskite lattice. The dielectric constant of the BST films was measured as a function of composition (Ba:Sr ratio) and temperature over the range 25--150°C. Finally, capacitance-voltage (C-V) measurements were made for BST films to determine the influence of film composition on dielectric tunability.

Synthesis and characterization of Zn(O,OH)S and AgInS2 layers to be used in thin film solar cells

NASA Astrophysics Data System (ADS)

Vallejo, W.; Arredondo, C. A.; Gordillo, G.

2010-11-01

In this paper AgInS2 and Zn(O,OH)S thin films were synthesized and characterized. AgInS2 layers were grown by co-evaporation from metal precursors in a two-step process, and, Zn(O,OH)S thin films were deposited from chemical bath containing thiourea, zinc acetate, sodium citrate and ammonia. X-ray diffraction measurements indicated that AgInS2 thin films grown with chalcopyrite structure, and the as-grown Zn(O,OH)S thin films were polycrystalline. It was also found that the AgInS2 films presented p-type conductivity, a high absorption coefficient (greater than 104 cm-1) and energy band-gap Eg of about 1.95 eV, Zn(O,OH),S thin films presented Eg of about 3.89 eV. Morphological analysis showed that under this synthesis conditions Zn(O,OH),S thin films coated uniformly the absorber layer. Additionally, the Zn(O,OH)S kinetic growth on AgInS2 layer was studied also. Finally, the results suggest that these layers possibly could be used in one-junction solar cells and/or as top cell in a tandem solar cell.

Terahertz conductivity of MnSi thin films

NASA Astrophysics Data System (ADS)

Dodge, J.; Mohtashemi, Laleh; Farahani, Amir; Karhu, Eric; Monchesky, Theodore

2013-03-01

We present measurements of the low-frequency optical conductivity of MnSi thin films, using time-domain terahertz spectroscopy. At low temperatures and low frequencies, we extract the DC resistivity, scattering life time and plasma frequency from a Drude fit. We obtain a value of ωp ~= 1 . 0 eV, which can be used to estimate the renormalization coefficient through comparison with band theory. At higher temperatures, deviations from Drude behavior are observed, suggesting a loss of quasi-particle coherence. In the region of low temperatures and high frequencies, we see evidence for a crossover to the anomalous power law dependence observed by Mena et al. As the temperature increases, the anomalous frequency dependence becomes more pronounced, and the plasma frequency inferred from a Drude fit decreases dramatically. Above T ~ 50 K, σ2 (ω) develops a negative slope that is inconsistent with both a Drude model and the anomalous power law observed earlier, indicating a sharp pseudogap in the conductivity spectrum.

Photoconduction in amorphous thin films of Se90Sb10-xAgx glassy alloys

NASA Astrophysics Data System (ADS)

Sharma, Suresh Kumar; Shukla, R. K.; Dwivedi, Prabhat K.; Kumar, A.

2017-10-01

The present paper reports the steady state photoconductivity and photosensitivity response of thermally evaporated amorphous thin films of Se90Sb10-xAgx(x = 2, 4, 6, 8, 10). Temperature dependence of dark conductivity is studied and activation energy is calculated for different samples. Temperature dependence of photoconductivity is also studied at different intensities. From temperature dependence of photoconductivity activation energy is computed at different intensities which are found to vary from 0.26 to 0.47 eV. Intensity dependence of photoconductivity has also been studied at different temperatures. These curves are plotted on logarithmic scale and found to be straight lines which show that photoconductivity follows a power law with intensity. Composition dependence of dark conductivity, activation energy of DC conduction and photosensitivity show that these parameters are highly. composition dependent and show a discontinuity at a particular composition when Ag concentration becomes 6 at. %. This is explained in terms of transition from floppy state to mechanically stabilized state at this composition.

Transparent conducting thin films for spacecraft applications

NASA Technical Reports Server (NTRS)

Perez-Davis, Marla E.; Malave-Sanabria, Tania; Hambourger, Paul; Rutledge, Sharon K.; Roig, David; Degroh, Kim K.; Hung, Ching-Cheh

1994-01-01

Transparent conductive thin films are required for a variety of optoelectronic applications: automotive and aircraft windows, and solar cells for space applications. Transparent conductive coatings of indium-tin-oxide (ITO)-magnesium fluoride (MgF2) and aluminum doped zinc oxide (AZO) at several dopant levels are investigated for electrical resistivity (sheet resistance), carrier concentration, optical properties, and atomic oxygen durability. The sheet resistance values of ITO-MgF2 range from 10(exp 2) to 10(exp 11) ohms/square, with transmittance of 75 to 86 percent. The AZO films sheet resistances range from 10(exp 7) to 10(exp 11) ohms/square with transmittances from 84 to 91 percent. It was found that in general, with respect to the optical properties, the zinc oxide (ZnO), AZO, and the high MgF2 content ITO-MgF2 samples, were all durable to atomic oxygen plasma, while the low MgF2 content of ITO-MgF2 samples were not durable to atomic oxygen plasma exposure.

Transparent conducting thin films for spacecraft applications

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

Perez-Davis, M.E.; Malave-Sanabria, T.; Hambourger, P.

1994-01-01

Transparent conductive thin films are required for a variety of optoelectronic applications: automotive and aircraft windows, and solar cells for space applications. Transparent conductive coatings of indium-tin-oxide (ITO)-magnesium fluoride (MgF2) and aluminum doped zinc oxide (AZO) at several dopant levels are investigated for electrical resistivity (sheet resistance), carrier concentration, optical properties, and atomic oxygen durability. The sheet resistance values of ITO-MgF2 range from 10[sup 2] to 10[sup 11] ohms/square, with transmittance of 75 to 86 percent. The AZO films sheet resistances range from 10[sup 7] to 10[sup 11] ohms/square with transmittances from 84 to 91 percent. It was found thatmore » in general, with respect to the optical properties, the zinc oxide (ZnO), AZO, and the high MgF2 content ITO-MgF2 samples, were all durable to atomic oxygen plasma, while the low MgF2 content of ITO-MgF2 samples were not durable to atomic oxygen plasma exposure.« less

Annealing temperature effect on electrical properties of MEH-PPV thin film via spin coating method

NASA Astrophysics Data System (ADS)

Azhar, N. E. A.; Shariffudin, S. S.; Alrokayan, Salman A. H.; Khan, Haseeb A.; Rusop, M.

2018-05-01

Organic semiconductor has been discovered in different application devices such as organic light emitting diodes (OLEDs). Poly [2-methoxy-5(2' -ethylhexyloxy)-1, 4-phenylenevinylene), MEH-PPV widely used in this device because its ability to produce a good optical quality films. The MEH-PPV was prepared on glass substrate by spin coating method. The thin film was investigated at different annealing temperatures. The scanning electron micrographs (SEM) revealed that sample annealed at 50°C showed uniformity and less aggregation on morphology polymer thin film. Optical properties showed the intensities of visible emission increased as temperatures increased. The current-voltage (I-V) measurement revealed that the temperature of 50°C showed high conductive and it is suitable for optoelectronic device.

Structural and optical studies on antimony and zinc doped CuInS2 thin films

NASA Astrophysics Data System (ADS)

Ben Rabeh, M.; Chaglabou, N.; Kanzari, M.; Rezig, B.

2009-11-01

The influence of Zn and Sb impurities on the structural, optical and electrical properties of CuInS2 thin films on corning 7059 glass substrates was studied. Undoped and Zn or Sb doped CuInS2 thin films were deposited by thermal evaporation method and annealed in vacuum at temperature of 450 ∘C Undoped thin films were grown from CuInS2 powder using resistively heated tungsten boats. Zn species was evaporated from a thermal evaporator all together to the CuInS2 powder and Sb species was mixed in the starting powders. The amount of the Zn or Sb source was determined to be in the range 0-4 wt% molecular weight compared with the CuInS2 alloy source. The films were studied by means of X-ray diffraction (XRD), Optical reflection and transmission and resistance measurements. The films thicknesses were in the range 450-750 nm. All the Zn: CuInS2 and Sb: CuInS2 thin films have relatively high absorption coefficient between 104 cm-1 and 105 cm-1 in the visible and the near-IR spectral range. The bandgap energies are in the range of 1.472-1.589 eV for Zn: CuInS2 samples and 1.396-1.510 eV for the Sb: CuInS2 ones. The type of conductivity of these films was determined by the hot probe method. Furthermore, we found that Zn and Sb-doped CuInS2 thin films exhibit P type conductivity and we predict these species can be considered as suitable candidates for use as acceptor dopants to fabricate CuInS2-based solar cells.

Influence of the morphology of the copper(II) phthalocyanine thin film on the performance of organic field-effect transistors

NASA Astrophysics Data System (ADS)

Xu, Jing; Liu, Xueqiang; Wang, Hailong; Hou, Wenlong; Zhao, Lele; Zhang, Haiquan

2017-01-01

Organic thin-film transistors (OTFTs) with high crystallization copper phthalocyanine (CuPc) active layers were fabricated. The performance of CuPc OTFTs was studied without and with treatment by Solvent Vapor Annealing on CuPc film. The values of the threshold voltage without and with solvent-vapor annealing are -17 V and -10.5 V respectively. The field-effect mobility values in saturation region of CuPc thin-film transistors without and with Solvent Vapor Annealing are 0.00027 cm2/V s and 0.0025 cm2/V s respectively. Meanwhile, the high crystallization of the CuPc film with a larger grain size and less grain boundaries can be observed by investigating the morphology of the CuPc active layer through scanning electron microscopy and X-ray diffraction. The experimental results showed the decreased of the resistance of the conducting channel, that led to a performance improvement of the OTFTs.

Mechanism of bonding and debonding using surface activated bonding method with Si intermediate layer

NASA Astrophysics Data System (ADS)

Takeuchi, Kai; Fujino, Masahisa; Matsumoto, Yoshiie; Suga, Tadatomo

2018-04-01

Techniques of handling thin and fragile substrates in a high-temperature process are highly required for the fabrication of semiconductor devices including thin film transistors (TFTs). In our previous study, we proposed applying the surface activated bonding (SAB) method using Si intermediate layers to the bonding and debonding of glass substrates. The SAB method has successfully bonded glass substrates at room temperature, and the substrates have been debonded after heating at 450 °C, in which TFTs are fabricated on thin glass substrates for LC display devices. In this study, we conducted the bonding and debonding of Si and glass in order to understand the mechanism in the proposed process. Si substrates are also successfully bonded to glass substrates at room temperature and debonded after heating at 450 °C using the proposed bonding process. By the composition analysis of bonding interfaces, it is clarified that the absorbed water on the glass forms interfacial voids and cause the decrease in bond strength.

Structural and optoelectronic properties of ZnGaO thin film by pulsed laser deposition

NASA Astrophysics Data System (ADS)

Han, Xiaowei; Wang, Li; Li, Shufeng; Gao, Dongwen; Pan, Yong

2018-01-01

ZnO has attracted much attention because of its high-energy gap and exciton binding energy at room temperature. Compared to ZnO thin films, ZnGaO thin films are more resistive to oxidation and have smaller deformation of lattice. In this study, the high purity ZnSe and Ga2O3 powders were weighted at a molar ratio of 18:1. Se was oxidized to Se2O3 and separated from the mixture powders by using conventional solid state reaction method in air, and the ZnGaO ceramic target was prepared. We fabricated the ZnGaO films on silica glass by pulsed laser deposition (PLD) method under different oxygen pressure at room temperature. The as-grown films were tested by X-ray diffraction and atomic force microscope (AFM) to diagnose the crystal structure and surface morphology. Moreover, we obtained the optical transmittance of ZnGaO film and found that the electrical conductivity capacity varied with the increase of oxygen pressure.

Nanoporous Ni(OH)2 thin film on 3D Ultrathin-graphite foam for asymmetric supercapacitor.

PubMed

Ji, Junyi; Zhang, Li Li; Ji, Hengxing; Li, Yang; Zhao, Xin; Bai, Xin; Fan, Xiaobin; Zhang, Fengbao; Ruoff, Rodney S

2013-07-23

Nanoporous nickel hydroxide (Ni(OH)2) thin film was grown on the surface of ultrathin-graphite foam (UGF) via a hydrothermal reaction. The resulting free-standing Ni(OH)2/UGF composite was used as the electrode in a supercapacitor without the need for addition of either binder or metal-based current collector. The highly conductive 3D UGF network facilitates electron transport and the porous Ni(OH)2 thin film structure shortens ion diffusion paths and facilitates the rapid migration of electrolyte ions. An asymmetric supercapacitor was also made and studied with Ni(OH)2/UGF as the positive electrode and activated microwave exfoliated graphite oxide ('a-MEGO') as the negative electrode. The highest power density of the fully packaged asymmetric cell (44.0 kW/kg) was much higher (2-27 times higher), while the energy density was comparable to or higher, than high-end commercially available supercapacitors. This asymmetric supercapacitor had a capacitance retention of 63.2% after 10,000 cycles.

Carbon nanotubes/fluorinated polymers nanocomposite thin films for electrical contacts lubrication

NASA Astrophysics Data System (ADS)

Benedetto, A.; Viel, P.; Noël, S.; Izard, N.; Chenevier, P.; Palacin, S.

2007-09-01

The need to operate in extreme environmental conditions (ultra high vacuum, high temperatures, aerospatial environment, …) and the miniaturization toward micro electromechanical systems is demanding new materials in the field of low-level electrical contacts lubrication. Dry and chemically immobilized lubrication is expected to be an alternative to the traditional wet lubricants oils. With the goal to conciliate electrical conductivity and lubricant properties we designed nanocomposite thin films composed of a 2D carbon nanotubes network embedded in an organic matrix. The nanotubes networks were deposited on gold surfaces modified by electrochemical cathodic grafting of poly(acrylonitrile). The same substrate served for covalently bonding the low-friction organic matrix. Three different matrixes were tested: a perfluorinated oligomer chemically grafted and two different polyfluorinated acrylates electrochemically grafted. The nanocomposite thin films have been characterized by ATR FT-IR, XPS and Raman spectroscopy. We measured the effects of the different matrixes and the nanotubes addition on the tribological properties and on the contact resistances of the films.

Thin-Film Nanowire Networks for Transparent Conductor Applications: Simulations of Sheet Resistance and Percolation Thresholds

NASA Astrophysics Data System (ADS)

Winey, Karen I.; Mutiso, Rose M.; Sherrott, Michelle C.; Rathmell, Aaron R.; Wiley, Benjamin J.

2013-03-01

Thin-film metal nanowire networks are being pursued as a viable alternative to the expensive and brittle indium tin oxide (ITO) for transparent conductors. For high performance applications, nanowire networks must exhibit high transmittance at low sheet resistance. Previously, we have used complimentary experimental, simulation and theoretical techniques to explore the effects of filler aspect ratio (L/D), orientation, and size-dispersity on the electrical conductivity of three-dimensional rod-networks in bulk polymer nanocomposites. We adapted our 3D simulation approach and analytical percolation model to study the electrical properties of thin-film rod-networks. By fitting our simulation results to experimental results, we determined the average effective contact resistance between silver nanowires. This contact resistance was then used to quantify how the sheet resistance depends on the aspect ratio of the rods and to show that networks made of nanowires with L/D greater than 100 yield sheet resistances lower than the required 100 Ohm/sq. We also report the critical area fraction of rods required to form a percolated network in thin-film networks and provide an analytical expression for the critical area fraction as a function of L/D.

Role of temperature and oxygen content on structural and electrical properties of LaBaCo2O5+δ thin films

NASA Astrophysics Data System (ADS)

Mace, Brennan; Harrell, Zach; Chen, Chonglin; Enriquez, Erik; Chen, Aiping; Jia, Quanxi

2018-02-01

The role of temperature and the oxygen content in the structural transformation and electrical conductivity of epitaxial double perovskite LaBaCo2O5+δ (0≤ δ ≤ 1) thin films was systematically investigated. Reciprocal space mapping and ω-2θ x-ray diffraction performed at different temperatures in vacuum indicate that oxygen vacancies in the films become ordered at high temperature in a reducing environment. The changes of the oxygen content and the degree of oxygen vacancy ordering in the films result in a strong in-plane anisotropic lattice deformation and a large thermal expansion coefficient along the c-axis direction. The electrical conductivity measurements reveal that these behaviors are related to the degree of oxygen vacancy formation and lattice deformation in the films.

Role of temperature and oxygen content on structural and electrical properties of LaBaCo2O5+δ thin films.

PubMed

Mace, Brennan; Harrell, Zach; Chen, Chonglin; Enriquez, Erik; Chen, Aiping; Jia, Quanxi

2018-02-12

The role of temperature and the oxygen content in the structural transformation and electrical conductivity of epitaxial double perovskite LaBaCo 2 O 5+δ (0≤ δ ≤ 1) thin films was systematically investigated. Reciprocal space mapping and ω-2θ x-ray diffraction performed at different temperatures in vacuum indicate that oxygen vacancies in the films become ordered at high temperature in a reducing environment. The changes of the oxygen content and the degree of oxygen vacancy ordering in the films result in a strong in-plane anisotropic lattice deformation and a large thermal expansion coefficient along the c-axis direction. The electrical conductivity measurements reveal that these behaviors are related to the degree of oxygen vacancy formation and lattice deformation in the films.

Synthesis of Stretchable Gold Films with Nanocracks: Stretched up to 120% Strain while Maintaining Conductivity

NASA Astrophysics Data System (ADS)

Yu, Mei; Wang, Chong; Yang, Cancan; Yu, Zhe

2017-11-01

With the great deformability of stretch, compression, bend and twisting, while preserving electrical property, metal films on elastomeric substrates have many applications for serving as bioelectrical interfaces. However, at present, most polymer-supported thin metal films reported rupture at small elongations (<10%). In this work, highly stretchable thin gold films were fabricated on PDMS substrates by a novel micro-processing technology. The as deposited films can be stretched by a maximum 120% strain while maintaining their electrical conductivity. Electrical characteristics of the gold films under single-cycle and multi-cycle stretch deformations are investigated in this work. SEM images imply that the gold films are under the structure of nanocracks. The mechanisms of the stretchability of the gold films can be explained by the nanocraks, which uniformly distribute with random orientation in the films.

High-performance flexible resistive memory devices based on Al2O3:GeOx composite

NASA Astrophysics Data System (ADS)

Behera, Bhagaban; Maity, Sarmistha; Katiyar, Ajit K.; Das, Samaresh

2018-05-01

In this study a resistive switching random access memory device using Al2O3:GeOx composite thin films on flexible substrate is presented. A bipolar switching characteristic was observed for the co-sputter deposited Al2O3:GeOx composite thin films. Al/Al2O3:GeOx/ITO/PET memory device shows excellent ON/OFF ratio (∼104) and endurance (>500 cycles). GeOx nanocrystals embedded in the Al2O3 matrix have been found to play a significant role in enhancing the switching characteristics by facilitating oxygen vacancy formation. Mechanical endurance was retained even after several bending. The conduction mechanism of the device was qualitatively discussed by considering Ohmic and SCLC conduction. This flexible device is a potential candidate for next-generation electronics device.

Epitaxial thin films of pyrochlore iridate Bi 2+xIr 2-yO 7-δ: structure, defects and transport properties

DOE PAGES

Yang, W. C.; Xie, Y. T.; Zhu, W. K.; ...

2017-08-10

While pyrochlore iridate thin films are theoretically predicted to possess a variety of emergent topological properties, experimental verification of these predictions can be obstructed by the challenge in thin film growth. We report on the pulsed laser deposition and characterization of thin films of a representative pyrochlore compound Bi 2Ir 2O 7. Moreover, the films were epitaxially grown on yttria-stabilized zirconia substrates and have lattice constants that are a few percent larger than that of the bulk single crystals. The film composition shows a strong dependence on the oxygen partial pressure. Density-functional-theory calculations indicate the existence of BiIr antisite defects,more » qualitatively consistent with the high Bi: Ir ratio found in the films. Both Ir and Bi have oxidation states that are lower than their nominal values, suggesting the existence of oxygen deficiency. The iridate thin films show a variety of intriguing transport characteristics, including multiple charge carriers, logarithmic dependence of resistance on temperature, antilocalization corrections to conductance due to spin-orbit interactions, and linear positive magnetoresistance.« less

Epitaxial thin films of pyrochlore iridate Bi 2+xIr 2-yO 7-δ: structure, defects and transport properties

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

Yang, W. C.; Xie, Y. T.; Zhu, W. K.

While pyrochlore iridate thin films are theoretically predicted to possess a variety of emergent topological properties, experimental verification of these predictions can be obstructed by the challenge in thin film growth. We report on the pulsed laser deposition and characterization of thin films of a representative pyrochlore compound Bi 2Ir 2O 7. Moreover, the films were epitaxially grown on yttria-stabilized zirconia substrates and have lattice constants that are a few percent larger than that of the bulk single crystals. The film composition shows a strong dependence on the oxygen partial pressure. Density-functional-theory calculations indicate the existence of BiIr antisite defects,more » qualitatively consistent with the high Bi: Ir ratio found in the films. Both Ir and Bi have oxidation states that are lower than their nominal values, suggesting the existence of oxygen deficiency. The iridate thin films show a variety of intriguing transport characteristics, including multiple charge carriers, logarithmic dependence of resistance on temperature, antilocalization corrections to conductance due to spin-orbit interactions, and linear positive magnetoresistance.« less

Magnetic, ferroelectric and leakage current properties of gadolinium doped bismuth ferrite thin films by sol-gel method

NASA Astrophysics Data System (ADS)

Chen, Hone-Zern; Kao, Ming-Cheng; Young, San-Lin; Hwang, Jun-Dar; Chiang, Jung-Lung; Chen, Po-Yen

2015-05-01

Bi0.9Gd0.1FeO3 (BGFO) thin films were fabricated on Pt(111)/Ti/SiO2/Si(100) substrates by using the sol-gel technology. The effects of annealing temperature (400-700 °C) on microstructure and multiferroic properties of thin films were investigated. The X-ray diffraction analysis showed that the BGFO thin films had an orthorhombic structure. The thin films showed ferroelectric and ferromagnetic properties with remanent polarization (2Pr) of 10 μC/cm2, remnant magnetization (2Mr) of 2.4 emu/g and saturation magnetization (Ms) of 5.3 emu/g. A small leakage current density (J) was 4.64×10-8 A/cm2 under applied field 100 kV/cm. It was found that more than one conduction mechanism is involved in the electric field range used in these experiments. The leakage current mechanisms were controlled by Poole-Frenkel emission in the low electric field region and by Schottky emission from the Pt electrode in the high field region.

Nanostructured Gd3+-TiO2 surfaces for self-cleaning application

NASA Astrophysics Data System (ADS)

Saif, M.; El-Molla, S. A.; Aboul-Fotouh, S. M. K.; Ibrahim, M. M.; Ismail, L. F. M.; Dahn, Douglas C.

2014-06-01

Preparation of self-cleaning surfaces based on lanthanide modified titanium dioxide nanoparticles has rarely been reported. In the present work, gadolinium doped titanium dioxide thin films (x mol Gd3+-TiO2 where x = 0.000, 0.005, 0.008, 0.010, 0.020 and 0.030 mol) were synthesized by sol-gel method and deposited using doctor-blade method. These films were characterized by studying their structural, optical and electrical properties. Doping with gadolinium decreases the band gap energy and increase conductivity of thin films. The photo self-cleaning activity in term of quantitative determination of the active oxidative species (rad OH) produced on the thin film surfaces was evaluated using fluorescent probe method. The results show that, the highly active thin film is the 0.020 Gd3+-TiO2. The structural, morphology, optical, electrical and photoactivity properties of Gd3+-TiO2 thin films make it promising surfaces for self-cleaning application. Mineralization of commercial textile dye (Remazol Red RB-133, RR) and durability using 0.020Gd3+-TiO2 film surface was studied.

Specific considerations for obtaining appropriate La1-xSrxGa1-yMgyO3-δ thin films using pulsed-laser deposition and its influence on the performance of solid-oxide fuel cells

NASA Astrophysics Data System (ADS)

Hwang, Jaeyeon; Lee, Heon; Lee, Jong-Ho; Yoon, Kyung Joong; Kim, Hyoungchul; Hong, Jongsup; Son, Ji-Won

2015-01-01

To obtain La1-xSrxGa1-yMgyO3-δ (LSGM) thin films with the appropriate properties, pulsed-laser deposition (PLD) is employed, and specific considerations regarding control of the deposition parameters is investigated. It is demonstrated that with a target of stoichiometric composition, appropriate LSGM thin films cannot be produced because of the deviation of the composition from the target to the thin film. Only after adjusting the target composition an LSGM thin film with an appropriate composition and phase can be obtained. The optimized LSGM thin film possesses an electrical conductivity close to that of the bulk LSGM. In contrast, non-optimized thin films do not yield any measurable electrical conductivity. The impact of the optimization of the LSGM thin-film electrolyte on the cell performance is quite significant, in that a solid-oxide fuel cell (SOFC) with an optimized LSGM thin-film electrolyte produces a maximum power density of 1.1 W cm-2 at 600 °C, whereas an SOFC with a non-optimal LSGM thin-film electrolyte is not operable.

Chemical and Physical Approaches to the Modulation of the Electronic Structure, Conductivities and Optical Properties of SWNT Thin Films

NASA Astrophysics Data System (ADS)

Moser, Matthew Lee

Since their discovery two decades ago, single walled carbon nanotubes (SWNT) have created an expansion of scientific interest that continues to grow to this day. This is due to a good balance between presence of bandgap, chemical reactivity and electrical conductivity. By interconnection of the individual nanotubes or modulation of the SWNT's electronic states, electronic devices made with thin films can become candidates for next generation electronics in areas such as memory devices, spintronics, energy storage devices and optoelectronics. My thesis focuses on the modulation of the electronic structure, optical properties and transport characteristics of single walled carbon nanotube films and their application in electronic and optoelectronic devices. Individual SWNTs have exceptional electronic properties but are difficult to manipulate for use in electronic devices. Alternatively, devices utilize SWNTs in thin films. SWNT thin films, however, may lose some of the properties due to Schottky barriers and electron hoping between metal-nanotube junctions and individual nanotubes within the film, respectively. Until recently, there has been no known route to preserve both conjugation and electrical properties. Prior attempts using covalent chemical functionalization led to re-hybridization of sp2 carbon centers to sp3, which introduces defects into the material and results in a decrease of electron mobility. As was discovered in Haddon Research group, depositing Group VI transition metals via atomic vapor deposition into SWNT films results in formation of bis-hexahapto covalent bonds. This (eta6-SWNT) Metal (eta6-SWNT) type of bonding was found to interconnect the delocalized systems without inducing structural re-hybridization and results in a decrease of the thin films electrical resistance. Recently, with the assistance of electron beam deposition, we deposited atomic metal vapor of various lanthanide metals on the SWNT thin films with the idea that they would also form covalent interconnects between nanotube sidewalls. In the case of highly electropositive lanthanides, the possibility of hexahapto bonding combined with ionic character can be evaluated and theorized. We have reported the first use of lanthanides to enhance the conductivities of SWNT thin films and showed that these metals can not only form bis-hexahapto interconnects at the SWNT junctions but can also inject electrons into the conduction bands of the SWNTs, forming a new type of mixed covalent-ionic bonding in the SWNT network. By monitoring electrical resistance and taking spectroscopic measurements of the Near-Infrared region we are able to show the correlation between enhanced conductivity and suppression of the S 11 interband transition of semiconducting SWNTs. Potential applications of SWNT thin films as electrochromic windows require reversible modulation of the electronic structure. In order to fabricate SWNTs devices which allow for this behavior it is necessary to modulate the electronic structure by physical means such as the application of an electrical potential. We found that ionic solutions can assist with maintaining complete suppression of two Van Hove singularities in the Density of States of semiconducting SWNTs which results in optically transparent windows in the Near-Infrared region, similar to the effect seen with the incorporation of atomic lanthanide metals in thin films. We demonstrate this behavior to provide a route to nanotube based optoelectronic devices in which we use electric fields to reversibly dope the SWNT films and thereby achieve controllable modulation of optical properties of SWNT thin film.

Silicon-sheet and thin-film cell and module technology potential: Issue study

NASA Technical Reports Server (NTRS)

Shimada, K.; Costogue, E. N.; Ferber, R. R.

1984-01-01

The development of high-efficiency low-cost crystalline silicon ribbon and thih-film solar cells for the energy national photovoltaics program was examined. The findings of an issue study conducted are presented. The collected data identified the status of the technology, future research needs, and problems experienced. The potentials of present research activities to meet the Federal/industry long-term technical goal of achieving 15 cents per kilowatt-hour levelized PV energy cost are assessed. Recommendations for future research needs related to crystalline silicon ribbon and thin-film technologies for flat-plate collectors are also included.

Effect of low-stiffness closeout overwrap on rocket thrust-chamber life

NASA Technical Reports Server (NTRS)

Kasper, H. J.; Nota-Donato, J. J.

1979-01-01

Three rocket thrust chambers with copper liners and a thrust level of 20.9 kN were cyclically test fired to failure. Two of the liners were made from oxygen free, high conductivity (OFHC) copper and from annealed Amzirc. The milled coolant channels were closed out with a thin copper closeout over which a fiberglass composite was wrapped to provide hoop strength only. Experimental data are presented, along with the results of a preliminary analysis that was performed before fabrication to evaluate the life extending potential of a thin copper closeout with a fiberglass overwrap.

Direct observation of back energy transfer in blue phosphorescent materials for organic light emitting diodes by time-resolved optical waveguide spectroscopy.

PubMed

Hirayama, H; Sugawara, Y; Miyashita, Y; Mitsuishi, M; Miyashita, T

2013-02-25

We demonstrate a high-sensitive transient absorption technique for detection of excited states in an organic thin film by time-resolved optical waveguide spectroscopy. By using a laser beam as a probe light, we detect small change in the transient absorbance which is equivalent to 10 -7 absorbance unit in a conventional method. This technique was applied to organic thin films of blue phosphorescent materials for organic light emitting diodes. We directly observed the back energy transfer from emitting guest molecules to conductive host molecules.

Effect of high temperature creep and oxidation on residual room temperature properties for several thin sheet superalloys

NASA Technical Reports Server (NTRS)

Royster, D. M.; Lisagor, W. B.

1972-01-01

Superalloys are being considered for the primary heat shields and supports in the thermal protection system of both hypersonic transport and space shuttle vehicles. Since conservative design philosophy dictates designs based on residual material properties at the end of the service life, material characterization after exposure to the environmental conditions imposed by the flight requirements of these two classes of vehicles is needed on the candidate alloys. An investigation was conducted to provide some of the necessary data, with emphasis placed on oxidation, creep, and residual properties of thin-gage sheet material.

Rechargeable thin-film electrochemical generator

DOEpatents

Rouillard, Roger; Domroese, Michael K.; Hoffman, Joseph A.; Lindeman, David D.; Noel, Joseph-Robert-Gaetan; Radewald, Vern E.; Ranger, Michel; Sudano, Anthony; Trice, Jennifer L.; Turgeon, Thomas A.

2000-09-15

An improved electrochemical generator is disclosed. The electrochemical generator includes a thin-film electrochemical cell which is maintained in a state of compression through use of an internal or an external pressure apparatus. A thermal conductor, which is connected to at least one of the positive or negative contacts of the cell, conducts current into and out of the cell and also conducts thermal energy between the cell and thermally conductive, electrically resistive material disposed on a vessel wall adjacent the conductor. The thermally conductive, electrically resistive material may include an anodized coating or a thin sheet of a plastic, mineral-based material or conductive polymer material. The thermal conductor is fabricated to include a resilient portion which expands and contracts to maintain mechanical contact between the cell and the thermally conductive material in the presence of relative movement between the cell and the wall structure. The electrochemical generator may be disposed in a hermetically sealed housing.

Variations in thermoelectric power of thin monocrystalline films with conductivity

NASA Astrophysics Data System (ADS)

Tellier, C. R.; Tosser, A. J.; Hafid, L.

1980-12-01

Starting from the bi-dimensional model for grain boundaries in monocrystalline thin films, the difference in thermoelectric power is expressed in terms of conductivity and energy dependence of the bulk electronic mean free path U. A new procedure is suggested for measuring U.

Pressurized-Flat-Interface Heat Exchanger

NASA Technical Reports Server (NTRS)

Voss, F. E.; Howell, H. R.; Winkler, R. V.

1990-01-01

High thermal conductance obtained without leakage between loops. Heat-exchanger interface enables efficient transfer of heat between two working fluids without allowing fluids to intermingle. Interface thin, flat, and easy to integrate into thermal system. Possible application in chemical or pharmaceutical manufacturing when even trace contamination of process stream with water or other coolant ruins product. Reduces costs when highly corrosive fluids must be cooled or heated.

High and low thermal conductivity of amorphous macromolecules

NASA Astrophysics Data System (ADS)

Xie, Xu; Yang, Kexin; Li, Dongyao; Tsai, Tsung-Han; Shin, Jungwoo; Braun, Paul V.; Cahill, David G.

2017-01-01

We measure the thermal conductivity, heat capacity and sound velocity of thin films of five polymers, nine polymer salts, and four caged molecules to advance the fundamental understanding of the lower and upper limits to heat conduction in amorphous macromolecules. The thermal conductivities vary by more than one order of magnitude, from 0.06 W m-1K-1 for [6,6]-phenyl-C71-butyric acid methyl ester to 0.67 W m-1K-1 for poly(vinylphosphonic acid calcium salt). Minimum thermal conductivity calculated from the measured sound velocity and effective atomic density is in good agreement with the thermal conductivity of macromolecules with various molecular structures and intermolecular bonding strength.

Synthesis of highly conductive thin-walled Al-doped ZnO single-crystal microtubes by a solid state method

NASA Astrophysics Data System (ADS)

Hu, Shuopeng; Wang, Yue; Wang, Qiang; Xing, Cheng; Yan, Yinzhou; Jiang, Yijian

2018-06-01

ZnO has attracted considerable attention in fundamental studies and practical applications for the past decade due to its outstanding performance in gas sensing, photocatalytic degradation, light harvesting, UV-light emitting/lasing, etc. The large-sized thin-walled ZnO (TW-ZnO) microtube with stable and rich VZn-related acceptors grown by optical vapor supersaturated precipitation (OVSP) is a novel multifunctional optoelectronic material. Unfortunately, the OVSP cannot achieve doping due to the vapor growth process. To obtain doped TW-ZnO microtubes, a solid state method is introduced in this work to achieve thin-walled Al-doping ZnO (TW-ZnO:Al) microtubes with high electrical conductivity. The morphology and microstructures of ZnO:Al microtubes are similar to undoped ones. The Al3+ ions are confirmed to substitute Zn2+ sites and Zn(0/-1) vacancies in the lattice of ZnO by EDS, XRD, Raman and temperature-dependent photoluminescence analyses. The Al dopant acting as a donor level offers massive free electrons to increase the carrier concentrations. The resistivity of the ZnO:Al microtube is reduced down to ∼10-3 Ω·cm, which is one order of magnitude lower than that of the undoped microtube. The present work provides a simple way to achieve doped ZnO tubular components for potential device applications in optoelectronics.

AC calorimetry of H2O at pressures up to 9 GPa in diamond anvil cells

NASA Astrophysics Data System (ADS)

Geballe, Zachary M.; Struzhkin, Viktor V.

2017-06-01

If successfully developed, calorimetry at tens of GPa of pressure could help characterize phase transitions in materials such as high-pressure minerals, metals, and molecular solids. Here, we extend alternating-current calorimetry to 9 GPa and 300 K in a diamond anvil cell and use it to study phase transitions in H2O. In particular, water is loaded into the sample chambers of diamond-cells, along with thin metal heaters (1 μm-thick platinum or 20 nm-thick gold on a glass substrate) that drive high-frequency temperature oscillations (20 Hz to 600 kHz; 1 to 10 K). The heaters also act as thermometers via the third-harmonic technique, yielding calorimetric data on (1) heat conduction to the diamonds and (2) heat transport into substrate and sample. Using this method during temperature cycles from 300 to 200 K, we document melting, freezing, and proton ordering and disordering transitions of H2O at 0 to 9 GPa, and characterize changes in thermal conductivity and heat capacity across these transitions. The technique and analysis pave the way for calorimetry experiments on any non-metal at pressures up to ˜100 GPa, provided a thin layer (several μm-thick) of thermal insulation supports a metallic thin-film (tens of nm thick) Joule-heater attached to low contact resistance leads inside the sample chamber of a diamond-cell.

Direct evidence on Ta-Metal Phases Igniting Resistive Switching in TaOx Thin Film

PubMed Central

Kyu Yang, Min; Ju, Hyunsu; Hwan Kim, Gun; Lee, Jeon-Kook; Ryu, Han-Cheol

2015-01-01

A Ta/TaOx/Pt stacked capacitor-like device for resistive switching was fabricated and examined. The tested device demonstrated stable resistive switching characteristics including uniform distribution of resistive switching operational parameters, highly promising endurance, and retention properties. To reveal the resistive switching mechanism of the device, micro structure analysis using high-resolution transmission electron microscope (HR-TEM) was performed. From the observation results, two different phases of Ta-metal clusters of cubic α-Ta and tetragonal β-Ta were founded in the amorphous TaOx mother-matrix after the device was switched from high resistance state (HRS) to low resistance state (LRS) by externally applied voltage bias. The observed Ta metal clusters unveiled the origin of the electric conduction paths in the TaOx thin film at the LRS. PMID:26365532

Direct evidence on Ta-Metal Phases Igniting Resistive Switching in TaOx Thin Film

NASA Astrophysics Data System (ADS)

Kyu Yang, Min; Ju, Hyunsu; Hwan Kim, Gun; Lee, Jeon-Kook; Ryu, Han-Cheol

2015-09-01

A Ta/TaOx/Pt stacked capacitor-like device for resistive switching was fabricated and examined. The tested device demonstrated stable resistive switching characteristics including uniform distribution of resistive switching operational parameters, highly promising endurance, and retention properties. To reveal the resistive switching mechanism of the device, micro structure analysis using high-resolution transmission electron microscope (HR-TEM) was performed. From the observation results, two different phases of Ta-metal clusters of cubic α-Ta and tetragonal β-Ta were founded in the amorphous TaOx mother-matrix after the device was switched from high resistance state (HRS) to low resistance state (LRS) by externally applied voltage bias. The observed Ta metal clusters unveiled the origin of the electric conduction paths in the TaOx thin film at the LRS.

Conductive layer for biaxially oriented semiconductor film growth

DOEpatents

Findikoglu, Alp T.; Matias, Vladimir

2007-10-30

A conductive layer for biaxially oriented semiconductor film growth and a thin film semiconductor structure such as, for example, a photodetector, a photovoltaic cell, or a light emitting diode (LED) that includes a crystallographically oriented semiconducting film disposed on the conductive layer. The thin film semiconductor structure includes: a substrate; a first electrode deposited on the substrate; and a semiconducting layer epitaxially deposited on the first electrode. The first electrode includes a template layer deposited on the substrate and a buffer layer epitaxially deposited on the template layer. The template layer includes a first metal nitride that is electrically conductive and has a rock salt crystal structure, and the buffer layer includes a second metal nitride that is electrically conductive. The semiconducting layer is epitaxially deposited on the buffer layer. A method of making such a thin film semiconductor structure is also described.

Processing/structure/property Relationships of Barium Strontium Titanate Thin Films for Dynamic Random Access Memory Application.

NASA Astrophysics Data System (ADS)

Peng, Cheng-Jien

The purpose of this study is to see the application feasibility of barium strontium titanate (BST) thin films on ultra large scale integration (ULSI) dynamic random access memory (DRAM) capacitors through the understanding of the relationships among processing, structure and electrical properties. Thin films of BST were deposited by multi-ion -beam reactive sputtering (MIBERS) technique and metallo -organic decomposition (MOD) method. The processing parameters such as Ba/Sr ratio, substrate temperature, annealing temperature and time, film thickness and doping concentration were correlated with the structure and electric properties of the films. Some effects of secondary low-energy oxygen ion bombardment were also examined. Microstructures of BST thin films could be classified into two types: (a) Type I structures, with multi-grains through the film thickness, for amorphous as-grown films after high temperature annealing, and (b) columnar structure (Type II) which remained even after high temperature annealing, for well-crystallized films deposited at high substrate temperatures. Type I films showed Curie-von Schweidler response, while Type II films showed Debted type behavior. Type I behavior may be attributed to the presence of a high density of disordered grain boundaries. Two types of current -voltage characteristics could be seen in non-bombarded films depending on the chemistry of the films (doped or undoped) and substrate temperature during deposition. Only the MIBERS films doped with high donor concentration and deposited at high substrate temperature showed space-charge -limited conduction (SCLC) with discrete shallow traps embedded in trap-distributed background at high electric field. All other non-bombarded films, including MOD films, showed trap-distributed SCLC behavior with a slope of {~}7.5-10 due to the presence of grain boundaries through film thickness or traps induced by unavoidable acceptor impurities in the films. Donor-doping could significantly improve the time -dependent dielectric breakdown (TDDB) behavior of BST thin films, mostly likely due to the lower oxygen vacancy concentration resulted from donor-doping.

Radiation and scattering by thin-wire structures in the complex frequency domain. [electromagnetic theory for thin-wire antennas

NASA Technical Reports Server (NTRS)

Richmond, J. H.

1974-01-01

Piecewise-sinusoidal expansion functions and Galerkin's method are employed to formulate a solution for an arbitrary thin-wire configuration in a homogeneous conducting medium. The analysis is performed in the real or complex frequency domain. In antenna problems, the solution determines the current distribution, impedance, radiation efficiency, gain and far-field patterns. In scattering problems, the solution determines the absorption cross section, scattering cross section and the polarization scattering matrix. The electromagnetic theory is presented for thin wires and the forward-scattering theorem is developed for an arbitrary target in a homogeneous conducting medium.

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).

Growth of Highly c-axis Oriented and/or Epitaxial Single-Domain b-axis Oriented La5Ca9Cu24O41 Thin Films by Pulsed Laser Deposition

DTIC Science & Technology

2016-04-01

project attempted to grow La5Ca9Cu24O41 (LCCO) films on important substrates with the high- thermal -conductivity direction parallel or perpendicular...to the surface of the substrate, counting success as demonstration of b-axis or c-axis oriented LCCO films along with measurement of bulk thermal ...deposition, LCCO, La5Ca9Cu24O41, thermal conductivity, epitaxy 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT SAR 18. NUMBER OF PAGES 24

Fabrication, testing and simulation of all solid state three dimensional Li-ion batteries

DOE PAGES

Talin, Albert Alec; Ruzmetov, Dmitry; Kolmakov, Andrei; ...

2016-11-10

Realization of safe, long cycle life and simple to package solid-state rechargeable batteries with high energy and power density has been a long-standing goal of the energy storage community. [1,2] Much of the research activity has been focused on developing new solid electrolytes with high Li ionic conductivity. In addition, LiPON, the only solid electrolyte currently used in commercial thin film solid state Li-ion batteris (SSLIBs), has a conductivity of ~10 -6 S/cm, compared to ~0.01 S/cm typically observed for liquid organic electrolytes [3].

Highly Conductive Thin Uniform Gold-Coated DNA Nanowires.

PubMed

Stern, Avigail; Eidelshtein, Gennady; Zhuravel, Roman; Livshits, Gideon I; Rotem, Dvir; Kotlyar, Alexander; Porath, Danny

2018-06-01

Over the past decades, DNA, the carrier of genetic information, has been used by researchers as a structural template material. Watson-Crick base pairing enables the formation of complex 2D and 3D structures from DNA through self-assembly. Various methods have been developed to functionalize these structures for numerous utilities. Metallization of DNA has attracted much attention as a means of forming conductive nanostructures. Nevertheless, most of the metallized DNA wires reported so far suffer from irregularity and lack of end-to-end electrical connectivity. An effective technique for formation of thin gold-coated DNA wires that overcomes these drawbacks is developed and presented here. A conductive atomic force microscopy setup, which is suitable for measuring tens to thousands of nanometer long molecules and wires, is used to characterize these DNA-based nanowires. The wires reported here are the narrowest gold-coated DNA wires that display long-range conductivity. The measurements presented show that the conductivity is limited by defects, and that thicker gold coating reduces the number of defects and increases the conductive length. This preparation method enables the formation of molecular wires with dimensions and uniformity that are much more suitable for DNA-based molecular electronics. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

High-performance Bi-stage process in reduction of graphene oxide for transparent conductive electrodes

NASA Astrophysics Data System (ADS)

Alahbakhshi, Masoud; Fallahi, Afsoon; Mohajerani, Ezeddin; Fathollahi, Mohammad-Reza; Taromi, Faramarz Afshar; Shahinpoor, Mohsen

2017-02-01

A novel and innovative approach to develop reduction of graphene oxide (GO) solution for fabrication of highly and truly transparent conductive electrode (TCE) has been presented. Thanks to outstanding mechanical and electronic properties of graphene which offer practical applications in synthesizing composites as well as fabricating various optoelectronic devices, in this study, conductive reduced graphene oxide (r-GO) thin films were prepared through sequential chemical and thermal reduction process of homogeneously dispersed GO solutions. The conductivity and transparency of r-GO thin film is regulated using hydroiodic acid (HI) as reducing agent following by vacuum thermal annealing. The prepared r-GO is characterized by XRD, AFM, UV-vis and Raman spectroscopy. the AFM topographic images reveal surface roughness almost ∼11 nm which became less than 2 nm for the 4 mg/mL solution. Moreover, XRD analysis and Raman spectra substantiate the interlayer spacing between rGO layers has been reduced dramatically and also electronic conjugation has been ameliorated after using HI chemical agent and 700 °C thermal annealing sequentially. Subsequently providing r-GO transparent electrode with decent and satisfactory transparency, acceptable conductivity and suitable work function, it has been exploited as the anode in organic light emitting diode (OLED). The maximum luminance efficiency and maximum power efficiency reached 4.2 cd/A and 0.83 lm/W, respectively. We believe that by optimizing the hole density, sheet resistance, transparency and surface morphology of the r-GO anodes, the device efficiencies can be remarkably increased further.

High-Performance Flexible Single-Crystalline Silicon Nanomembrane Thin-Film Transistors with High- k Nb2O5-Bi2O3-MgO Ceramics as Gate Dielectric on a Plastic Substrate.

PubMed

Qin, Guoxuan; Zhang, Yibo; Lan, Kuibo; Li, Lingxia; Ma, Jianguo; Yu, Shihui

2018-04-18

A novel method of fabricating flexible thin-film transistor based on single-crystalline Si nanomembrane (SiNM) with high- k Nb 2 O 5 -Bi 2 O 3 -MgO (BMN) ceramic gate dielectric on a plastic substrate is demonstrated in this paper. SiNMs are successfully transferred to a flexible polyethylene terephthalate substrate, which has been plated with indium-tin-oxide (ITO) conductive layer and high- k BMN ceramic gate dielectric layer by room-temperature magnetron sputtering. The BMN ceramic gate dielectric layer demonstrates as high as ∼109 dielectric constant, with only dozens of pA current leakage. The Si-BMN-ITO heterostructure has only ∼nA leakage current at the applied voltage of 3 V. The transistor is shown to work at a high current on/off ratio of above 10 4 , and the threshold voltage is ∼1.3 V, with over 200 cm 2 /(V s) effective channel electron mobility. Bending tests have been conducted and show that the flexible transistors have good tolerance on mechanical bending strains. These characteristics indicate that the flexible single-crystalline SiNM transistors with BMN ceramics as gate dielectric have great potential for applications in high-performance integrated flexible circuit.

Drying temperature effects on electrical and optical properties of poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) thin film

NASA Astrophysics Data System (ADS)

Azhar, N. E. A.; Affendi, I. H. H.; Shafura, A. K.; Shariffudin, S. S.; Alrokayan, Salman A. H.; Khan, Haseeb A.; Rusop, M.

2016-07-01

Temperature effects on electrical and optical properties of a representative semiconducting polymer, poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV), has recently attracted much attention. The MEH-PPV thin films were deposited at different drying temperature (anneal temperature) using spin-coating technique. The spin coating technique was used to produce uniform film onto large area. The MEH-PPV was dissolved in toluene solution to exhibits different optical and electrical properties. The absorption coefficient and bandgap was measured using UV-Visible-NIR (UV-VIS-NIR). The bandgap of MEH-PPV was effect by the thickness of thin films. For electrical properties, two-point probe was used to characterize the current-voltage measurement. The current-voltage measurement shows that the MEH-PPV thin films become more conductive at high temperature. This study will provide better performance and suitable for optoelectronic device especially OLEDs applications.

Drying temperature effects on electrical and optical properties of poly[2-methoxy-5-(2’-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) thin film

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

Azhar, N. E. A., E-mail: najwaezira@yahoo.com; Affendi, I. H. H., E-mail: irmahidayanti.halim@gmail.com; Shafura, A. K., E-mail: shafura@ymail.com

Temperature effects on electrical and optical properties of a representative semiconducting polymer, poly[2-methoxy-5-(2’-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV), has recently attracted much attention. The MEH-PPV thin films were deposited at different drying temperature (anneal temperature) using spin-coating technique. The spin coating technique was used to produce uniform film onto large area. The MEH-PPV was dissolved in toluene solution to exhibits different optical and electrical properties. The absorption coefficient and bandgap was measured using UV-Visible-NIR (UV-VIS-NIR). The bandgap of MEH-PPV was effect by the thickness of thin films. For electrical properties, two-point probe was used to characterize the current-voltage measurement. The current-voltage measurement showsmore » that the MEH-PPV thin films become more conductive at high temperature. This study will provide better performance and suitable for optoelectronic device especially OLEDs applications.« less

Ferroelectric, piezoelectric, and leakage current properties of (K0.48Na0.48Li0.04)(Nb0.775Ta0.225)O3 thin films grown by pulsed laser deposition

NASA Astrophysics Data System (ADS)

Wang, D. Y.; Lin, D. M.; Kwok, K. W.; Chan, N. Y.; Dai, J. Y.; Li, S.; Chan, H. L. W.

2011-01-01

Lead-free (K0.48Na0.48Li0.04)(Nb0.775Ta0.225)O3 (KNLNT) thin films were deposited on Pt(111)/Ti/SiO2/Si(001) substrates using pulsed laser deposition. The film exhibited a well-defined ferroelectric hysteresis loop with a remnant polarization 2Pr of 22.6 μC/cm2 and a coercive field Ec of 10.3 kV/mm. The effective piezoelectric coefficient d33,f of the KNLNT thin films was found to be about 49 pm/V by piezoelectric force microscope. The dominant conduction mechanisms of Au/KNLNT/Pt thin film capacitor were determined to be bulk-limited space-charge-limited-current and Poole-Frenkle emission at low and high electric field strengths, respectively, within a measured temperature range of 130-370 K.

Structural tuning of residual conductivity in highly mismatched III-V layers

DOEpatents

Han, Jung; Figiel, Jeffrey J.

2002-01-01

A new process to control the electrical conductivity of gallium nitride layers grown on a sapphire substrate has been developed. This process is based on initially coating the sapphire substrate with a thin layer of aluminum nitride, then depositing the gallium nitride thereon. This process allows one to controllably produce gallium nitride layers with resistivity varying over as much as 10 orders of magnitude, without requiring the introduction and activation of suitable dopants.

Influence of Strain on Thermal Conductivity of Silicon Nitride Thin Films

DTIC Science & Technology

2012-03-02

free path of amorphous materials is of the same order as the structural disorder [46], rendering thermal conductivity size independent. Here, the phases...16] Manninen A J, Leivo M M and Pekola J P 1997 Refrigeration of a dielectric membrane by superconductor /insulator/ normal-metal/insulator... superconductor tunneling Appl. Phys. Lett. 70 1885–7 [17] Olson E A et al 2003 The design and operation of a MEMS differential scanning nanocalorimeter for high

Nonpolar resistive memory switching with all four possible resistive switching modes in amorphous LaHoO{sub 3} thin films

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

Sharma, Yogesh; Pavunny, Shojan P.; Katiyar, Ram S., E-mail: rkatiyar@hpcf.upr.edu

2015-09-07

We studied the resistive memory switching in pulsed laser deposited amorphous LaHoO{sub 3} (a-LHO) thin films for non-volatile resistive random access memory applications. Nonpolar resistive switching (RS) was achieved in Pt/a-LHO/Pt memory cells with all four possible RS modes (i.e., positive unipolar, positive bipolar, negative unipolar, and negative bipolar) having high R{sub ON}/R{sub OFF} ratios (in the range of ∼10{sup 4}–10{sup 5}) and non-overlapping switching voltages (set voltage, V{sub ON} ∼ ±3.6–4.2 V and reset voltage, V{sub OFF} ∼ ±1.3–1.6 V) with a small variation of about ±5–8%. Temperature dependent current-voltage (I–V) characteristics indicated the metallic conduction in low resistance states (LRS). We believe that themore » formation (set) and rupture (reset) of mixed conducting filaments formed out of oxygen vacancies and metallic Ho atoms could be responsible for the change in the resistance states of the memory cell. Detailed analysis of I–V characteristics further corroborated the formation of conductive nanofilaments based on metal-like (Ohmic) conduction in LRS. Simmons-Schottky emission was found to be the dominant charge transport mechanism in the high resistance state.« less

Microbolometer SU-8 photoresist microstructure with cytochrome c protein as a sensing pixel for microbolometer

NASA Astrophysics Data System (ADS)

Lai, Jian-Lun; Su, Guo-Dung J.

2012-08-01

There are two important parts in Microbolometer: the high TCR sensing material and low thermal conductance. The high TCR material cytochrome c protein is a good candidate for infrared detection. Our group already demonstrated cytochrome c thin film has high TCR on the top of SU8 surface that has been published in Proc. of SPIE (2011). Because the very low thermal conductivity of SU-8, we proposed a new concept of SU-8 photoresist thermal insulation desk structure, and used the exposure dose method to establish it. Although exposure dose method is very sensitive to exposure time and PEB time, we successfully investigated the right recipe to create new desk insulation structure which with different height. We also explored the relationship between mask II exposure time and desktop thickness, and how the post-exposure baking (PEB) time influenced our structure. Our SU-8 photoresist insulation structure fabrication process is much easier and cheaper than present SiNx fabrication process. The desk shape structure can have low thermal conductance of 6.681*10-6 W/K. The easy-made SU-8 microstructures and cytochrome c thin films that and can reduce the cost of IR microbolometer. We believe that it is possible to fabricate a new generation of microbolometer based on cytochrome c protein and SU-8 photoresist microstructures.

Solar Cells for Lunar Application

NASA Technical Reports Server (NTRS)

Freundlich, Alex; Ignatiev, Alex

1997-01-01

In this work a preliminary study of the vacuum evaporation of silicon extracted from the lunar regolith has been undertaken. An electron gun vacuum evaporation system has been adapted for this purpose. Following the calibration of the system using ultra high purity silicon deposited on Al coated glass substrates, thin films of lunar Si were evaporated on a variety of crystalline substrates as well as on glass and lightweight 1 mil (25 microns) Al foil. Extremely smooth and featureless films with essentially semiconducting properties were obtained. Optical absorption analysis sets the bandgap (about 1.1 eV) and the refractive index (n=3.5) of the deposited thin films close to that of crystalline silicon. Secondary ion mass spectroscopy and energy dispersive spectroscopy analysis indicated that these films are essentially comparable to high purity silicon and that the evaporation process resulted in a substantial reduction of impurity levels. All layers exhibited a p-type conductivity suggesting the presence of a p-type dopant in the fabricated layers. While the purity of the 'lunar waste material' is below that of the 'microelectronic-grade silicon', the vacuum evaporated material properties seems to be adequate for the fabrication of average performance Si-based devices such as thin film solar cells. Taking into account solar cell thickness requirements (greater than 10 microns) and the small quantities of lunar material available for this study, solar cell fabrication was not possible. However, the high quality of the optical and electronic properties of evaporated thin films was found to be similar to those obtained using ultra-high purity silicon suggest that thin film solar cell production on the lunar surface with in situ resource utilization may be a viable approach for electric power generation on the moon.

Origin of the Strain Sensitivity for an Organic Heptazole Thin-Film and Its Strain Gauge Application

NASA Astrophysics Data System (ADS)

Bae, Heesun; Jeon, Pyo Jin; Park, Ji Hoon; Lee, Kimoon

2018-04-01

The authors report on the origin of the strain sensitivity for an organic C26H16N2 (heptazole) thinfilm and its application for the detection of tensile strain. From the electrical characterization on the thin-film transistor adopting a heptazole channel, heptazole film exhibits p-channel conduction with a relatively low value of field-effect mobility (0.05 cm2/Vs), suggesting a hopping conduction behavior via hole carriers. By analyzing the strain and temperature dependences of the electrical conductivity, we reveal that the electrical conduction for a heptazole thin-film is dominated by the variable range hopping process with quite a large energy separation (224.9 meV) between the localized states under a relatively long attenuation length (10.46 Å). This indicates that a change in the inter-grain spacing that is much larger than the attenuation length is responsible for the reversible modification of electrical conductivity depending on strain for the heptazole film. By utilizing our heptazole thin-film both as a strain sensitive passive resistor and an active semiconducting channel layer, we can achieve a strain gauge device exhibiting reversible endurance for tensile strains up to 2.12%. Consequently, this study advances the understanding of the fundamental strain sensing mechanism in a heptazole thin-film toward finding a promise material with a strain gauge for applications as potential flexible devices and/or wearable electronics.

In Situ Polymerization and Characterization of Highly Conducting Polypyrrole Fish Scales for High-Frequency Applications

NASA Astrophysics Data System (ADS)

Velhal, Ninad B.; Patil, Narayan D.; Puri, Vijaya R.

2015-12-01

Polypyrrole (Ppy) thin films on alumina were synthesized by an in situ chemical oxidative polymerization method at 300 K with equal monomer-to-oxidant ratio. Fourier transform infrared spectroscopy (FTIR) and FT-Raman spectroscopy confirmed the formation of Ppy. A thickness-dependent change from cauliflower to fish-scale morphology was observed. Microwave properties such as transmission, reflection, shielding effectiveness, permittivity, and microwave conductivity are reported in the frequency range from 8 GHz to 12 GHz. The direct-current (DC) conductivity varied from 9.45 × 10-3 S/cm to 17.29 × 10-3 S/cm, whereas the microwave conductivity varied from 63.07 S/cm to 349.08 S/cm. The shielding effectiveness varied between 6.18 dB and 10.39 dB.

High-performance thermoelectricity in edge-over-edge zinc-porphyrin molecular wires.

PubMed

Noori, Mohammed; Sadeghi, Hatef; Lambert, Colin J

2017-04-20

If high efficiency organic thermoelectric materials could be identified, then these would open the way to a range of energy harvesting technologies and Peltier coolers using flexible and transparent thin-film materials. We have compared the thermoelectric properties of three zinc porphyrin (ZnP) dimers and a ZnP monomer and found that the "edge-over-edge" dimer formed from stacked ZnP rings possesses a high electrical conductance, negligible phonon thermal conductance and a high Seebeck coefficient of the order of 300 μV K -1 . These combine to yield a predicted room-temperature figure of merit of ZT ≈ 4, which is the highest room-temperature ZT ever reported for a single organic molecule. This high value of ZT is a consequence of the low phonon thermal conductance arising from the stacked nature of the porphyrin rings, which hinders phonon transport through the edge-over-edge molecule and enhances the Seebeck coefficient.

Ground Based Experiments in Support of Microgravity Research Results-Vapor Growth of Organic Nonlinear Optical Thin Film

NASA Technical Reports Server (NTRS)

Zugrav, M. Ittu; Carswell, William E.; Haulenbeek, Glen B.; Wessling, Francis C.

2001-01-01

This work is specifically focused on explaining previous results obtained for the crystal growth of an organic material in a reduced gravity environment. On STS-59, in April 1994, two experiments were conducted with N,N-dimethyl-p-(2,2-dicyanovinyl) aniline (DCVA), a promising nonlinear optical (NLO) material. The space experiments were set to reproduce laboratory experiments that yielded small, bulk crystals of DCVA. The results of the flight experiment, however, were surprising. Rather than producing a bulk single crystal, the result was the production of two high quality, single crystalline thin films. This result was even more intriguing when it is considered that thin films are more desirable for NLO applications than are bulk single crystals. Repeated attempts on the ground to reproduce these results were fruitless. A second set of flight experiments was conducted on STS-69 in September 1995. This time eight DCVA experiments were flown, with each of seven experiments containing a slight change from the first reference experiment. The reference experiment was programmed with growth conditions identical to those of the STS-59 mission. The slight variations in each of the other seven were an attempt to understand what particular parameter was responsible for the preference of thin film growth over bulk crystal growth in microgravity. Once again the results were surprising. In all eight cases thin films were grown again, albeit with varying quality. So now we were faced with a phenomenon that not only takes place in microgravity, but also is very robust, resisting all attempts to force the growth of bulk single crystals.

Intrinsic high electrical conductivity of stoichiometric SrNb O3 epitaxial thin films

NASA Astrophysics Data System (ADS)

Oka, Daichi; Hirose, Yasushi; Nakao, Shoichiro; Fukumura, Tomoteru; Hasegawa, Tetsuya

2015-11-01

SrV O3 and SrNb O3 are perovskite-type transition-metal oxides with the same d1 electronic configuration. Although SrNb O3 (4 d1 ) has a larger d orbital than SrV O3 (3 d1 ), the reported electrical resistivity of SrNb O3 is much higher than that of SrV O3 , probably owing to nonstoichiometry. In this paper, we grew epitaxial, high-conductivity stoichiometric SrNb O3 using pulsed laser deposition. The growth temperature strongly affected the Sr/Nb ratio and the oxygen content of the films, and we obtained stoichiometric SrNb O3 at a very narrow temperature window around 630 °C. The stoichiometric SrNb O3 epitaxial thin films grew coherently on KTa O3 (001) substrates with high crystallinity. The room-temperature resistivity of the stoichiometric film was 2.82 ×10-5Ω cm , one order of magnitude lower than the lowest reported value of SrNb O3 and comparable with that of SrV O3 . We observed a T -square dependence of resistivity below T*=180 K and non-Drude behavior in near-infrared absorption spectroscopy, attributable to the Fermi-liquid nature caused by electron correlation. Analysis of the T -square coefficient A of resistivity experimentally revealed that the 4 d orbital of Nb that is larger than the 3 d ones certainly contributes to the high electrical conduction of SrNb O3 .

Mask-free, vacuum-free fabrication of high-conductivity metallic nanowire by spatially shaped ultrafast laser (Conference Presentation)

NASA Astrophysics Data System (ADS)

Wang, Andong; Li, Xiaowei; Qu, Lianti; Lu, Yongfeng; Jiang, Lan

2017-03-01

Metal nanowire fabrication has drawn tremendous attention in recent years due to its wide application in electronics, optoelectronics, and plasmonics. However, conventional laser fabrication technologies are limited by diffraction limit thus the fabrication resolution cannot meet the increasingly high demand of modern devices. Herein we report on a novel method for high-resolution high-quality metal nanowire fabrication by using Hermite-Gaussian beam to ablate metal thin film. The nanowire is formed due to the intensity valley in the center of the laser beam while the surrounding film is ablated. Arbitrary nanowire can be generated on the substrate by dynamically adjusting the orientation of the intensity valley. This method shows obvious advantages compared to conventional methods. First, the minimum nanowire has a width of 60 nm (≍1/13 of the laser wavelength), which is much smaller than the diffraction limit. The high resolution is achieved by combining the ultrashort nature of the femtosecond laser and the low thermal conductivity of the thin film. In addition, the fabricated nanowires have good inside qualities. No inner nanopores and particle intervals are generated inside the nanowire, thus endowing the nanowire with good electronic characteristics: the conductivity of the nanowires is as high as 1.2×107 S/m (≍1/4 of buck material), and the maximum current density is up to 1.66×108 A/m2. Last, the nanowire has a good adhesion to the substrates, which can withstand ultrasonic bath for a long time. These advantages make our method a good approach for high-resolution high-quality nanowire fabrication as a complementary method to conventional lithography methods.

A Water-Based Silver-Nanowire Screen-Print Ink for the Fabrication of Stretchable Conductors and Wearable Thin-Film Transistors

DOE PAGES

Liang, Jiajie; Tong, Kwing; Pei, Qibing

2016-05-09

Silver nanowire is a very promising material for fabricating compliant conductors which are essential for stretchable/wearable electronic devices. Screen printing is a cost-effective and scalable technology to fabricate large-area thin film coatings with modest pattern resolution. The biggest challenge to prepare a screen printable silver nanowire ink stems from the low viscosity of silver nanowire dispersions and that the addition of a thickening agent could dramatically increase the inter-nanowire contact resistance in the resulting coating. Herein, we report the synthesis of a water-based silver nanowire ink, which was formulated with low solid contents, high viscosity at 0.1 s -1 shearmore » rate, and appropriate rheological behavior suitable for screen printing. Silver nanowire coating patterns were screen printed with uniform sharp edges, ~50 μm resolution, and electrical conductivity as high as 4.67 × 10 4 S cm -1. The screen printed silver nanowires were then used to fabricate a composite conductor that retained a conductivity greater than 10,000 S cm -1 under 70% tensile strain. Fully printed and stretchable/wearable thin-film transistor arrays were also fabricated by employing the screen printed composite conductor as the source, drain, and gate, drop cast semiconducting carbon nanotubes as the channel, and a dielectric elastomer. The 10 × 6 thin-film transistor arrays had a fabrication yield of 91.7%, average mobility of 33.8 ± 3.7 cm 2V -1s -1, ON/OFF ratio ~1000, and remained stable during 1,000 cycles of wearing on and peeling off a glass tube with 5 mm diameter.« less

A Water-Based Silver-Nanowire Screen-Print Ink for the Fabrication of Stretchable Conductors and Wearable Thin-Film Transistors

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

Liang, Jiajie; Tong, Kwing; Pei, Qibing

Silver nanowire is a very promising material for fabricating compliant conductors which are essential for stretchable/wearable electronic devices. Screen printing is a cost-effective and scalable technology to fabricate large-area thin film coatings with modest pattern resolution. The biggest challenge to prepare a screen printable silver nanowire ink stems from the low viscosity of silver nanowire dispersions and that the addition of a thickening agent could dramatically increase the inter-nanowire contact resistance in the resulting coating. Herein, we report the synthesis of a water-based silver nanowire ink, which was formulated with low solid contents, high viscosity at 0.1 s -1 shearmore » rate, and appropriate rheological behavior suitable for screen printing. Silver nanowire coating patterns were screen printed with uniform sharp edges, ~50 μm resolution, and electrical conductivity as high as 4.67 × 10 4 S cm -1. The screen printed silver nanowires were then used to fabricate a composite conductor that retained a conductivity greater than 10,000 S cm -1 under 70% tensile strain. Fully printed and stretchable/wearable thin-film transistor arrays were also fabricated by employing the screen printed composite conductor as the source, drain, and gate, drop cast semiconducting carbon nanotubes as the channel, and a dielectric elastomer. The 10 × 6 thin-film transistor arrays had a fabrication yield of 91.7%, average mobility of 33.8 ± 3.7 cm 2V -1s -1, ON/OFF ratio ~1000, and remained stable during 1,000 cycles of wearing on and peeling off a glass tube with 5 mm diameter.« less

Thinning and burning result in low-level invasion by nonnative plants but neutral effects on natives.

PubMed

Nelson, Cara R; Halpern, Charles B; Agee, James K

2008-04-01

Many historically fire-adapted forests are now highly susceptible to damage from insects, pathogens, and stand-replacing fires. As a result, managers are employing treatments to reduce fuel loadings and to restore the structure, species, and processes that characterized these forests prior to widespread fire suppression, logging, and grazing. However, the consequences of these activities for understory plant communities are not well understood. We examined the effects of thinning and prescribed fire on plant composition and diversity in Pinus ponderosa forests of eastern Washington (USA). Data on abundance and richness of native and nonnative plants were collected in 70 stands in the Colville, Okanogan, and Wenatchee National Forests. Stands represented one of four treatments: thinning, burning, thinning followed by burning, or control; treatments had been conducted 3-19 years before sampling. Multi-response permutation procedures revealed no significant effect of thinning or burning on understory plant composition. Similarly, there were no significant differences among treatments in cover or richness of native plants. In contrast, nonnative plants showed small, but highly significant, increases in cover and richness in response to both thinning and burning. In the combined treatment, cover of nonnative plants averaged 2% (5% of total plant cover) but did not exceed 7% (16% of total cover) at any site. Cover and richness of nonnative herbs showed small increases with intensity of disturbance and time since treatment. Nonnative plants were significantly less abundant in treated stands than on adjacent roadsides or skid trails, and cover within these potential source areas explained little of the variation in abundance within treated stands. Although thinning and burning may promote invasion of nonnative plants in these forests, our data suggest that their abundance is limited and relatively stable on most sites.

Enhancement of conduction noise absorption by hybrid absorbers composed of indium-tin-oxide thin film and magnetic composite sheet on a microstrip line

NASA Astrophysics Data System (ADS)

Kim, Sun-Hong; Kim, Sung-Soo

2014-05-01

In order to develop wide-band noise absorbers with a focused design for low frequency performance, this study investigates hybrid absorbers that are composed of conductive indium-tin-oxide (ITO) thin film and magnetic composite sheets. The ITO films prepared via reactive sputtering exhibit a typical value of electrical resistivity of ≃10-4 Ω m. Rubber composites with flaky Fe-Si-Al particles are used as the magnetic sheet with a high permeability and high permittivity. For the ITO film with a low surface resistance and covered by the magnetic sheet, approximately 90% power absorption can be obtained at 1 GHz, which is significantly higher than that of the original magnetic sheet or ITO film. The high power absorption of the hybrid absorber is attributed to the enhanced ohmic loss of the ITO film through increased electric field strength bounded by the upper magnetic composite sheet. However, for the reverse layering sequence of the ITO film, the electric field experienced by ITO film is very weak due to the electromagnetic shielding by the under layer of magnetic sheet, which does not result in enhanced power absorption.

Differences observed in the surface morphology and microstructure of Ni-Fe-Cu ternary thin films electrochemically deposited at low and high applied current densities

NASA Astrophysics Data System (ADS)

Sarac, U.; Kaya, M.; Baykul, M. C.

2016-10-01

In this research, nanocrystalline Ni-Fe-Cu ternary thin films using electrochemical deposition technique were produced at low and high applied current densities onto Indium Tin Oxide (ITO) coated conducting glass substrates. Change of surface morphology and microstructural properties of the films were investigated. Energy dispersive X-ray spectroscopy (EDX) measurements showed that the Ni-Fe-Cu ternary thin films exhibit anomalous codeposition behaviour during the electrochemical deposition process. From the X-ray diffraction (XRD) analyses, it was revealed that there are two segregated phases such as Cu- rich and Ni-rich within the films. The crystallographic structure of the films was face-centered cubic (FCC). It was also observed that the film has lower lattice micro-strain and higher texture degree at high applied current density. Scanning electron microscopy (SEM) studies revealed that the films have rounded shape particles on the base part and cauliflower-like structures on the upper part. The film electrodeposited at high current density had considerably smaller rounded shape particles and cauliflower-like structures. From the atomic force microscopy (AFM) analyses, it was shown that the film deposited at high current density has smaller particle size and surface roughness than the film grown at low current density.

Solvent-Assisted Surface Engineering for High-Performance All-Inorganic Perovskite Nanocrystal Light-Emitting Diodes.

PubMed

Wang, Lin; Liu, Baiquan; Zhao, Xin; Demir, Hilmi Volkan; Gu, Haoshuang; Sun, Handong

2018-06-13

All-inorganic cesium halide perovskite nanocrystals have attracted much interest in optoelectronic applications for the sake of the readily adjustable band gaps, high photoluminescence quantum yield, pure color emission, and affordable cost. However, because of the ineluctable utilization of organic surfactants during the synthesis, the structural and optical properties of CsPbBr 3 nanocrystals degrade upon transforming from colloidal solutions to solid thin films, which plagues the device operation. Here, we develop a novel solvent-assisted surface engineering strategy, producing high-quality CsPbBr 3 thin films for device applications. A good solvent is first introduced as an assembly trigger to conduct assembly in a one-dimensional direction, which is then interrupted by adding a nonsolvent. The nonsolvent drives the adjacent nanoparticles connecting in a two-dimensional direction. Assembled CsPbBr 3 nanocrystal thin films are densely packed and very smooth with a surface roughness of ∼4.8 nm, which is highly desirable for carrier transport in a light-emitting diode (LED) device. Meanwhile, the film stability is apparently improved. Benefiting from this facile and reliable strategy, we have achieved remarkably improved performance of CsPbBr 3 nanocrystal-based LEDs. Our results not only enrich the methods of nanocrystal surface engineering but also shed light on developing high-performance LEDs.

Mechanisms involved in the hydrothermal growth of ultra-thin and high aspect ratio ZnO nanowires

NASA Astrophysics Data System (ADS)

Demes, Thomas; Ternon, Céline; Morisot, Fanny; Riassetto, David; Legallais, Maxime; Roussel, Hervé; Langlet, Michel

2017-07-01

Hydrothermal synthesis of ZnO nanowires (NWs) with tailored dimensions, notably high aspect ratios (AR) and small diameters, is a major concern for a wide range of applications and still represents a challenging and recurring issue. In this work, an additive-free and reproducible hydrothermal procedure has been developed to grow ultra-thin and high AR ZnO NWs on sol-gel deposited ZnO seed layers. Controlling the substrate temperature and using a low reagent concentration (1 mM) has been found to be essential for obtaining such NWs. We show that the NW diameter remains constant at about 20-25 nm with growth time contrary to the NW length that can be selectively increased leading to NWs with ARs up to 400. On the basis of investigated experimental conditions along with thermodynamic and kinetic considerations, a ZnO NW growth mechanism has been developed which involves the formation and growth of nuclei followed by NW growth when the nuclei reach a critical size of about 20-25 nm. The low reagent concentration inhibits NW lateral growth leading to ultra-thin and high AR NWs. These NWs have been assembled into electrically conductive ZnO nanowire networks, which opens attractive perspectives toward the development of highly sensitive low-cost gas- or bio-sensors.

Hybrid Surface Acoustic Wave- Electrohydrodynamic Atomization (SAW-EHDA) For the Development of Functional Thin Films

PubMed Central

Choi, Kyung Hyun; Kim, Hyun Bum; Ali, Kamran; Sajid, Memoon; Uddin Siddiqui, Ghayas; Chang, Dong Eui; Kim, Hyung Chan; Ko, Jeong Beom; Dang, Hyun Woo; Doh, Yang Hoi

2015-01-01

Conventional surface acoustic wave - electrostatic deposition (SAW-ED) technology is struggling to compete with other thin film fabrication technologies because of its limitation in atomizing high density solutions or solutions with strong inter-particle bonding that requires very high frequency (100 MHz) and power. In this study, a hybrid surface acoustic wave - electrohydrodynamic atomization (SAW-EHDA) system has been introduced to overcome this problem by integrating EHDA with SAW to achieve the deposition of different types of conductive inks at lower frequency (19.8 MHZ) and power. Three materials, Poly [2-methoxy-5-(2-ethylhexyloxy)-1, 4-phenylenevinylene] (MEH-PPV), Zinc Oxide (ZnO), and Poly(3, 4-ethylenedioxythiophene):Polystyrene Sulfonate (PEDOT:PSS) have been successfully deposited as thin films through the hybrid SAW-EHDA. The films showed good morphological, chemical, electrical, and optical characteristics. To further evaluate the characteristics of deposited films, a humidity sensor was fabricated with active layer of PEDOT:PSS deposited using the SAW-EHDA system. The response of sensor was outstanding and much better when compared to similar sensors fabricated using other manufacturing techniques. The results of the device and the films’ characteristics suggest that the hybrid SAW-EHDA technology has high potential to efficiently produce wide variety of thin films and thus predict its promising future in certain areas of printed electronics. PMID:26478189

Hybrid Surface Acoustic Wave- Electrohydrodynamic Atomization (SAW-EHDA) For the Development of Functional Thin Films

NASA Astrophysics Data System (ADS)

Choi, Kyung Hyun; Kim, Hyun Bum; Ali, Kamran; Sajid, Memoon; Uddin Siddiqui, Ghayas; Chang, Dong Eui; Kim, Hyung Chan; Ko, Jeong Beom; Dang, Hyun Woo; Doh, Yang Hoi

2015-10-01

Conventional surface acoustic wave - electrostatic deposition (SAW-ED) technology is struggling to compete with other thin film fabrication technologies because of its limitation in atomizing high density solutions or solutions with strong inter-particle bonding that requires very high frequency (100 MHz) and power. In this study, a hybrid surface acoustic wave - electrohydrodynamic atomization (SAW-EHDA) system has been introduced to overcome this problem by integrating EHDA with SAW to achieve the deposition of different types of conductive inks at lower frequency (19.8 MHZ) and power. Three materials, Poly [2-methoxy-5-(2-ethylhexyloxy)-1, 4-phenylenevinylene] (MEH-PPV), Zinc Oxide (ZnO), and Poly(3, 4-ethylenedioxythiophene):Polystyrene Sulfonate (PEDOT:PSS) have been successfully deposited as thin films through the hybrid SAW-EHDA. The films showed good morphological, chemical, electrical, and optical characteristics. To further evaluate the characteristics of deposited films, a humidity sensor was fabricated with active layer of PEDOT:PSS deposited using the SAW-EHDA system. The response of sensor was outstanding and much better when compared to similar sensors fabricated using other manufacturing techniques. The results of the device and the films’ characteristics suggest that the hybrid SAW-EHDA technology has high potential to efficiently produce wide variety of thin films and thus predict its promising future in certain areas of printed electronics.

Hybrid Surface Acoustic Wave-Electrohydrodynamic Atomization (SAW-EHDA) For the Development of Functional Thin Films.

PubMed

Choi, Kyung Hyun; Kim, Hyun Bum; Ali, Kamran; Sajid, Memoon; Uddin Siddiqui, Ghayas; Chang, Dong Eui; Kim, Hyung Chan; Ko, Jeong Beom; Dang, Hyun Woo; Doh, Yang Hoi

2015-10-19

Conventional surface acoustic wave - electrostatic deposition (SAW-ED) technology is struggling to compete with other thin film fabrication technologies because of its limitation in atomizing high density solutions or solutions with strong inter-particle bonding that requires very high frequency (100 MHz) and power. In this study, a hybrid surface acoustic wave - electrohydrodynamic atomization (SAW-EHDA) system has been introduced to overcome this problem by integrating EHDA with SAW to achieve the deposition of different types of conductive inks at lower frequency (19.8 MHZ) and power. Three materials, Poly [2-methoxy-5-(2-ethylhexyloxy)-1, 4-phenylenevinylene] (MEH-PPV), Zinc Oxide (ZnO), and Poly(3, 4-ethylenedioxythiophene):Polystyrene Sulfonate ( PSS) have been successfully deposited as thin films through the hybrid SAW-EHDA. The films showed good morphological, chemical, electrical, and optical characteristics. To further evaluate the characteristics of deposited films, a humidity sensor was fabricated with active layer of PSS deposited using the SAW-EHDA system. The response of sensor was outstanding and much better when compared to similar sensors fabricated using other manufacturing techniques. The results of the device and the films' characteristics suggest that the hybrid SAW-EHDA technology has high potential to efficiently produce wide variety of thin films and thus predict its promising future in certain areas of printed electronics.

The Electrochemical Properties of Sr(Ti,Fe)O 3-δ for Anodes in Solid Oxide Fuel Cells

DOE PAGES

Nenning, Andreas; Volgger, Lukas; Miller, Elizabeth; ...

2017-02-18

Reduction-stable mixed ionic and electronic conductors such as Sr(Ti,Fe)O 3-δ (STF) are promising materials for application in anodes of solid oxide fuel cells. The defect chemistry of STF and its properties as solid oxide fuel cell (SOFC) cathode have been studied thoroughly, while mechanistic investigations of its electrochemical properties as SOFC anode material are still scarce. In this study, thin film model electrodes of STF with 30% and 70% Fe content were investigated in H 2+H 2O atmosphere by electrochemical impedance spectroscopy. Lithographically patterned thin film Pt current collectors were applied on top or beneath the STF thin films tomore » compensate for the low electronic conductivity under reducing conditions. Oxygen exchange resistances, electronic and ionic conductivities and chemical capacitances were quantified and discussed in a defect chemical model. Increasing Fe content increases the electro-catalytic activity of the STF surface as well as the electronic and ionic conductivity. Current collectors on top also increase the electrochemical activity due to a highly active Pt-atmosphere-STF triple phase boundary. Furthermore, the electrochemical activity depends decisively on the H 2:H 2O mixing ratio and the polarization. Lastly, Fe 0 nanoparticles may evolve on the surface in hydrogen rich atmospheres and increase the hydrogen adsorption rate.« less

Coating of plasma polymerized film

NASA Technical Reports Server (NTRS)

Morita, S.; Ishibashi, S.

1980-01-01

Plasma polymerized thin film coating and the use of other coatings is suggested for passivation film, thin film used for conducting light, and solid body lubrication film of dielectrics of ultra insulators for electrical conduction, electron accessories, etc. The special features of flow discharge development and the polymerized film growth mechanism are discussed.

Structural and morphological properties of ITO thin films grown by magnetron sputtering

NASA Astrophysics Data System (ADS)

Ghorannevis, Z.; Akbarnejad, E.; Ghoranneviss, M.

2015-10-01

Physical properties of transparent and conducting indium tin oxide (ITO) thin films grown by radiofrequency (RF) magnetron sputtering are studied systematically by changing deposition time. The X-ray diffraction (XRD) data indicate polycrystalline thin films with grain orientations predominantly along the (2 2 2) and (4 0 0) directions. From atomic force microscopy (AFM) it is found that by increasing the deposition time, the roughness of the film increases. Scanning electron microscopy (SEM) images show a network of a high-porosity interconnected nanoparticles, which approximately have a pore size ranging between 20 and 30 nm. Optical measurements suggest an average transmission of 80 % for the ITO films. Sheet resistances are investigated using four-point probes, which imply that by increasing the film thickness the resistivities of the films decrease to 2.43 × 10-5 Ω cm.

Sol processing of conjugated carbon nitride powders for thin-film fabrication.

PubMed

Zhang, Jinshui; Zhang, Mingwen; Lin, Lihua; Wang, Xinchen

2015-05-18

The chemical protonation of graphitic carbon nitride (CN) solids with strong oxidizing acids, for example HNO3, is demonstrated as an efficient pathway for the sol processing of a stable CN colloidal suspension, which can be translated into thin films by dip/disperse-coating techniques. The unique features of CN colloids, such as the polymeric matrix and the reversible hydrogen bonding, result in the thin-film electrodes derived from the sol solution exhibiting a high mechanical stability with improved conductivity for charge transport, and thus show a remarkably enhanced photo-electrochemical performance. The polymer system can in principle be broadly tuned by hybridization with desired functionalities, thus paving the way for the application of CN for specific tasks, as exemplified here by coupling with carbon nanotubes. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Structural and optical properties of nano-structured CdS thin films prepared by chemical bath deposition

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

Bai, Rekha, E-mail: rekha.mittal07@gmail.com; Kumar, Dinesh; Chaudhary, Sujeet

2016-05-06

Cadmium sulfide (CdS) thin films have been deposited on conducting glass substrates by chemical bath deposition (CBD) technique. The effect of precursor concentration on the structural, morphological, compositional, and optical properties of the CdS films has been studied. Crystal structure of these CdS films is characterized by X-ray diffraction (XRD) and it reveals polycrystalline structure with mixture of cubic and wurtzite phases with grain size decreasing as precursor concentration is increased. Optical studies reveal that the CdS thin films have high transmittance in visible spectral region reaching 90% and the films possess direct optical band gap that decreases from 2.46more » to 2.39 eV with decreasing bath concentration. Our study suggests that growth is nucleation controlled.« less

Improving the optoelectronic properties of titanium-doped indium tin oxide thin films

NASA Astrophysics Data System (ADS)

Taha, Hatem; Jiang, Zhong-Tao; Henry, David J.; Amri, Amun; Yin, Chun-Yang; Mahbubur Rahman, M.

2017-06-01

The focus of this study is on a sol-gel method combined with spin-coating to prepare high-quality transparent conducting oxide (TCO) films. The structural, morphological, optical and electrical properties of sol-gel-derived pure and Ti-doped indium tin oxide (ITO) thin films were studied as a function of the concentration of the Ti (i.e. 0 at%, 2 at% and 4 at%) and annealing temperatures (150 °C-600 °C). FESEM measurements indicate that all the films are ˜350 nm thick. XRD analysis confirmed the cubic bixbyite structure of the polycrystalline indium oxide phase for all of the thin films. Increasing the Ti ratio, as well as the annealing temperature, improved the crystallinity of the films. Highly crystalline structures were obtained at 500 °C, with average grain sizes of about 50, 65 and 80 nm for Ti doping of 0 at%, 2 at% and 4 at%, respectively. The electrical and optical properties improved as the annealing temperature increased, with an enlarged electronic energy band gap and an optical absorption edge below 280 nm. In particular, the optical transmittance and electrical resistivity of the samples with a 4 at% Ti content improved from 87% and 7.10 × 10-4 Ω.cm to 92% and 1.6 × 10-4 Ω.cm, respectively. The conductivity, especially for the annealing temperature at 150 °C, is acceptable for many applications such as flexible electronics. These results demonstrate that unlike the more expensive and complex vacuum sputtering process, high-quality Ti-doped ITO films can be achieved by fast processing, simple wet-chemistry, and easy doping level control with the possibility of producing films with high scalability.

Micromachined Active Magnetic Regenerator for Low-Temperature Magnetic Coolers

NASA Technical Reports Server (NTRS)

Chen, Weibo; Jaeger, Michael D.

2013-01-01

A design of an Active Magnetic Regenerative Refrigeration (AMRR) system has been developed for space applications. It uses an innovative 3He cryogenic circulator to provide continuous remote/distributed cooling at temperatures in the range of 2 K with a heat sink at about 15 K. A critical component technology for this cooling system is a highly efficient active magnetic regenerator, which is a regenerative heat exchanger with its matrix material made of magnetic refrigerant gadolinium gallium garnet (GGG). Creare Inc. is developing a microchannel GGG regenerator with an anisotropic structured bed for high system thermal efficiency. The regenerator core consists of a stack of thin, single-crystal GGG disks alternating with thin polymer insulating layers. The insulating layers help minimize the axial conduction heat leak, since GGG has a very high thermal conductivity in the regenerator s operating temperature range. The GGG disks contain micro channels with width near 100 micrometers, which enhance the heat transfer between the circulating flow and the refrigerant bed. The unique flow configuration of the GGG plates ensures a uniform flow distribution across the plates. The main fabrication challenges for the regenerator are the machining of high-aspect-ratio microchannels in fragile, single-crystal GGG disks and fabrication and assembly of the GGG insulation layers. Feasibility demonstrations to date include use of an ultrashort- pulse laser to machine microchannels without producing unacceptable microcracking or deposition of recast material, as shown in the figure, and attachment of a thin insulation layer to a GGG disk without obstructing the flow paths. At the time of this reporting, efforts were focused on improving the laser machining process to increase machining speed and further reduce microcracking.

Electrical conduction of organic ultrathin films evaluated by an independently driven double-tip scanning tunneling microscope.

PubMed

Takami, K; Tsuruta, S; Miyake, Y; Akai-Kasaya, M; Saito, A; Aono, M; Kuwahara, Y

2011-11-02

The electrical transport properties of organic thin films within the micrometer scale have been evaluated by a laboratory-built independently driven double-tip scanning tunneling microscope, operating under ambient conditions. The two tips were used as point contact electrodes, and current in the range from 0.1 pA to 100 nA flowing between the two tips through the material can be detected. We demonstrated two-dimensional contour mapping of the electrical resistance on a poly(3-octylthiophene) thin films as shown below. The obtained contour map clearly provided an image of two-dimensional electrical conductance between two point electrodes on the poly(3-octylthiophene) thin film. The conductivity of the thin film was estimated to be (1-8) × 10(-6) S cm(-1). Future prospects and the desired development of multiprobe STMs are also discussed.

Initial response of understory vegetation to three alternative thinning treatments

Treesearch

Liane R. Davis; Klaus J. Puettmann

2009-01-01

This study compares initial understory vegetation response among three thinning treatments and a control in 30 - to 50-year-old even-aged Pseudotsuga menziesii (Mirbel) Franco (Douglas-fir) stands. It was conducted on four sites on the western slope of the central Oregon Cascades. Treatments included a control (no thinning), a light thinning, and...

Flexible shrink-induced high surface area electrodes for electrochemiluminescent sensing.

PubMed

Pegan, Jonathan D; Ho, Adrienne Y; Bachman, Mark; Khine, Michelle

2013-11-07

Photolithographically defined metallic thin film on commodity shrink-wrap is leveraged to create robust electrodes. By thermally shrinking the film, electrodes are reduced by 20× in footprint for improved resolution and conductivity with >600% enhancements in electrochemically active surface area; as electrochemiluminescent sensors, they demonstrate improved limits of detection.

Modulating Thin Film Transistor Characteristics by Texturing the Gate Metal.

PubMed

Nair, Aswathi; Bhattacharya, Prasenjit; Sambandan, Sanjiv

2017-12-20

The development of reliable, high performance integrated circuits based on thin film transistors (TFTs) is of interest for the development of flexible electronic circuits. In this work we illustrate the modulation of TFT transconductance via the texturing of the gate metal created by the addition of a conductive pattern on top of a planar gate. Texturing results in the semiconductor-insulator interface acquiring a non-planar geometry with local variations in the radius of curvature. This influences various TFT parameters such as the subthreshold slope, gate voltage at the onset of conduction, contact resistance and gate capacitance. Specific studies are performed on textures based on periodic striations oriented along different directions. Textured TFTs showed upto ±40% variation in transconductance depending on the texture orientation as compared to conventional planar gate TFTs. Analytical models are developed and compared with experiments. Gain boosting in common source amplifiers based on textured TFTs as compared to conventional TFTs is demonstrated.

Wide-range measurement of thermal effusivity using molybdenum thin film with low thermal conductivity for thermal microscopes

NASA Astrophysics Data System (ADS)

Miyake, Shugo; Matsui, Genzou; Ohta, Hiromichi; Hatori, Kimihito; Taguchi, Kohei; Yamamoto, Suguru

2017-07-01

Thermal microscopes are a useful technology to investigate the spatial distribution of the thermal transport properties of various materials. However, for high thermal effusivity materials, the estimated values of thermophysical parameters based on the conventional 1D heat flow model are known to be higher than the values of materials in the literature. Here, we present a new procedure to solve the problem which calculates the theoretical temperature response with the 3D heat flow and measures reference materials which involve known values of thermal effusivity and heat capacity. In general, a complicated numerical iterative method and many thermophysical parameters are required for the calculation in the 3D heat flow model. Here, we devised a simple procedure by using a molybdenum (Mo) thin film with low thermal conductivity on the sample surface, enabling us to measure over a wide thermal effusivity range for various materials.

Microstructural Characteristics of GeSbTe Thin Films Grown by RF Sputtering

NASA Astrophysics Data System (ADS)

Nelson, M. J.; Inglefield, C. E.; Olson, J. K.; Li, H.; Taylor, P. C.

2004-10-01

Thin films of GeSbTe are of interest due to their potential use in rewritable optical data storage media and reconfigurable electronics. The amorphous and crystalline phases of GeSbTe exhibit very different reflectivity and electrical conductivity. Films of nominally amorphous Ge_2Sb_2Te5 were grown to various thicknesses using RF sputtering on quartz substrates. The surfaces of the films were analyzed using Atomic Force Microscopy (AFM) and surface roughness measurements were taken. The thicker films had a truly isotropic surface while the thinnest films displayed crystalline features, such as angular steps. Conductivity measurements of the films in both coplanar and sandwich geometries correlate with the AFM data and indicate a high degree of crystallinity during the initial stages of growth. This work was supported by the Air Force Research Laboratory under grant number F29601-03-01-0229 and by Weber State University through the Phyllis Crosby Gardner fellowship.

Post-deposition thermal treatment of sprayed ZnO:Al thin films for enhancing the conductivity

NASA Astrophysics Data System (ADS)

Devasia, Sebin; Athma, P. V.; Shaji, Manu; Kumar, M. C. Santhosh; Anila, E. I.

2018-03-01

Here, we report the enhanced conductivity of Aluminium doped (2at.%) zinc oxide thin films prepared by simple spray pyrolysis technique. The structural, optical, electrical, morphological and compositional investigations confirm the better quality of films that can be a potential candidate for application in transparent electronics. Most importantly, the film demonstrates an average transmittance of 90 percent with a low resistivity value which was dropped from 1.39 × 10-2 to 5.10 × 10-3 Ω .cm, after annealing, and a very high carrier concentration in the order of 10 × 20cm-3. Further, we have used the Swanepoel envelop method to calculate thickness, refractive index and extinction coefficient from the interference patterns observed in the transmission spectra. The calculated figure of merit of the as-deposited sample was 1.4 × 10-3Ω-1 which was improved to 2.5 × 10-3Ω-1 after annealing.

Effect of pH of spray solution on the electrical properties of cadmium oxide thin films

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

Hodlur, R. M.; Gunnagol, Raghu M.; Rabinal, M. K., E-mail: mkrabinal@yahoo.com

2015-06-24

Highly conducting transparent cadmium oxide thin films were prepared by conventional spray pyrolysis technique on glass at 375 °C substrate temperature. The pH of the spray solution was varied by adding ammonia/hydrochloric acid in the spray solution. The XRD pattern showed cubic phase. A lowest resistivity of 9.9 × 10{sup −4} Ω cm (with carrier concentration (n) = 5.1 × 10{sup 20} cm{sup −3}, mobility (µ)=12.4 cm{sup 2}/Vs) is observed for pH ∼12. The resistivity is tuned almost by three orders of magnitude by controlling the bath pH with optical transmittance more than 70 %. Thus, without any doping, the electricalmore » conductivity of CdO films could be easily tuned by simply varying the pH of spray solution without compromising the transparency and keeping the other deposition parameters fixed.« less

CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY: Effect of Annealing Conditions on Properties of Sol-Gel Derived Al-Doped ZnO Thin Films

NASA Astrophysics Data System (ADS)

Gao, Mei-Zhen; Zhang, Feng; Liu, Jing; Sun, Hui-Na

2009-08-01

Transparent conductive Al-doped ZnO (AZO) thin films are prepared on normal glass substrates by the sol-gel spin coating method. The effects of drying conditions, annealing temperature and cooling rate on the structural, electrical and optical properties of AZO films are investigated by x-ray diffraction, scanning electron microscopy, the four-point probe method and UV-VIS spectrophotometry, respectively. The deposited films show a hexagonal wurtzite structure and high preferential c-axis orientation. As the drying temperature increases from 100°C to 300°C the resistivity of AZO films decreases dramatically. In contrast to the annealed films cooled in a furnace and in air, the resistivity of the annealed film which is cooled at -15°C is greatly reduced. Increasing the cooling rate dramatically increases the electrical conductivity of AZO films.

A three dimensional dynamic study of electrostatic charging in materials

NASA Technical Reports Server (NTRS)

Katz, I.; Parks, D. E.; Mandell, M. J.; Harvey, J. M.; Brownell, D. H., Jr.; Wang, S. S.; Rotenberg, M.

1977-01-01

A description is given of the physical models employed in the NASCAP (NASA Charging Analyzer Program) code, and several test cases are presented. NASCAP dynamically simulates the charging of an object made of conducting segments which may be entirely or partially covered with thin dielectric films. The object may be subject to either ground test or space user-specified environments. The simulation alternately treats (1) the tendency of materials to accumulate and emit charge when subject to plasma environment, and (2) the consequent response of the charged particle environment to an object's electrostatic field. Parameterized formulations of the emission properties of materials subject to bombardment by electrons, protons, and sunlight are presented. Values of the parameters are suggested for clean aluminum, Al2O3, clean magnesium, MgO, SiO2 kapton, and teflon. A discussion of conductivity in thin dielectrics subject to radiation and high fields is given, together with a sample calculation.

Suppression of persistent photo-conductance in solution-processed amorphous oxide thin-film transistors

NASA Astrophysics Data System (ADS)

Lee, Minkyung; Kim, Minho; Jo, Jeong-Wan; Park, Sung Kyu; Kim, Yong-Hoon

2018-01-01

This study offers a combinatorial approach for suppressing the persistent photo-conductance (PPC) characteristic in solution-processed amorphous oxide semiconductor (AOS) thin-film transistors (TFTs) in order to achieve rapid photo-recovery. Various analyses were used to examine the photo-instability of indium-gallium-zinc-oxide (IGZO) TFTs including negative-bias-illumination-stress (NBIS) and transient photo-response behaviors. It was found that the indium ratio in metallic components had a significant impact on their PPC and photo-recovery characteristics. In particular, when the indium ratio was low (51.5%), the PPC characteristic was significantly suppressed and achieving rapid photo-recovery was possible without significantly affecting the electrical performance of AOSs. These results imply that the optimization of the indium composition ratio may allow achieving highly photo-stable and near PPC-free characteristics while maintaining high electrical performance of AOSs. It is considered that the negligible PPC behavior and rapid photo-recovery observed in IGZO TFTs with a lower indium composition are attributed to the less activation energy required for the neutralization of ionized oxygen vacancies.

Flexible strain sensors with high performance based on metallic glass thin film

NASA Astrophysics Data System (ADS)

Xian, H. J.; Cao, C. R.; Shi, J. A.; Zhu, X. S.; Hu, Y. C.; Huang, Y. F.; Meng, S.; Gu, L.; Liu, Y. H.; Bai, H. Y.; Wang, W. H.

2017-09-01

Searching strain sensitive materials for electronic skin is of crucial significance because of the restrictions of current materials such as poor electrical conductivity, large energy consumption, complex manufacturing process, and high cost. Here, we report a flexible strain sensor based on the Zr55Cu30Ni5Al10 metallic glass thin film which we name metallic glass skin. The metallic glass skin, synthesized by ion beam deposition, exhibits piezoresistance effects with a gauge factor of around 2.86, a large detectable strain range (˜1% or 180° bending angle), and good conductivity. Compared to other e-skin materials, the temperature coefficient of resistance of the metallic glass skin is extremely low (9.04 × 10-6 K-1), which is essential for the reduction in thermal drift. In addition, the metallic glass skin exhibits distinct antibacterial behavior desired for medical applications, also excellent reproducibility and repeatability (over 1000 times), nearly perfect linearity, low manufacturing cost, and negligible energy consumption, all of which are required for electronic skin for practical applications.

Electrochemical Analysis of Conducting Polymer Thin Films

PubMed Central

Vyas, Ritesh N.; Wang, Bin

2010-01-01

Polyelectrolyte multilayers built via the layer-by-layer (LbL) method has been one of the most promising systems in the field of materials science. Layered structures can be constructed by the adsorption of various polyelectrolyte species onto the surface of a solid or liquid material by means of electrostatic interaction. The thickness of the adsorbed layers can be tuned precisely in the nanometer range. Stable, semiconducting thin films are interesting research subjects. We use a conducting polymer, poly(p-phenylene vinylene) (PPV), in the preparation of a stable thin film via the LbL method. Cyclic voltammetry and electrochemical impedance spectroscopy have been used to characterize the ionic conductivity of the PPV multilayer films. The ionic conductivity of the films has been found to be dependent on the polymerization temperature. The film conductivity can be fitted to a modified Randle’s circuit. The circuit equivalent calculations are performed to provide the diffusion coefficient values. PMID:20480052

Membrane reference electrode

DOEpatents

Redey, L.; Bloom, I.D.

1988-01-21

A reference electrode utilizes a small thin, flat membrane of a highly conductive glass placed on a small diameter insulator tube having a reference material inside in contact with an internal voltage lead. When the sensor is placed in a non-aqueous ionic electrolytic solution, the concentration difference across the glass membrane generates a low voltage signal in precise relationship to the concentration of the species to be measured, with high spatial resolution. 2 figs.

Layered CU-based electrode for high-dielectric constant oxide thin film-based devices

DOEpatents

Auciello, Orlando

2010-05-11

A layered device including a substrate; an adhering layer thereon. An electrical conducting layer such as copper is deposited on the adhering layer and then a barrier layer of an amorphous oxide of TiAl followed by a high dielectric layer are deposited to form one or more of an electrical device such as a capacitor or a transistor or MEMS and/or a magnetic device.

Nanoscale Solid State Batteries Enabled by Thermal Atomic Layer Deposition of a Lithium Polyphosphazene Solid State Electrolyte

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

Pearse, Alexander J.; Schmitt, Thomas E.; Fuller, Elliot J.

Several active areas of research in novel energy storage technologies, including three-dimensional solid state batteries and passivation coatings for reactive battery electrode components, require conformal solid state electrolytes. We describe an atomic layer deposition (ALD) process for a member of the lithium phosphorus oxynitride (LiPON) family, which is employed as a thin film lithium-conducting solid electrolyte. The reaction between lithium tert-butoxide (LiO tBu) and diethyl phosphoramidate (DEPA) produces conformal, ionically conductive thin films with a stoichiometry close to Li 2PO 2N between 250 and 300°C. The P/N ratio of the films is always 1, indicative of a particular polymorph ofmore » LiPON which closely resembles a polyphosphazene. Films grown at 300°C have an ionic conductivity of (6.51 ± 0.36)×10 -7 S/cm at 35°C, and are functionally electrochemically stable in the window from 0 to 5.3V vs. Li/Li +. We demonstrate the viability of the ALD-grown electrolyte by integrating it into full solid state batteries, including thin film devices using LiCoO 2 as the cathode and Si as the anode operating at up to 1 mA/cm 2. The high quality of the ALD growth process allows pinhole-free deposition even on rough crystalline surfaces, and we demonstrate the fabrication and operation of thin film batteries with the thinnest (<40nm) solid state electrolytes yet reported. Finally, we show an additional application of the moderate-temperature ALD process by demonstrating a flexible solid state battery fabricated on a polymer substrate.« less

Nanoscale Solid State Batteries Enabled by Thermal Atomic Layer Deposition of a Lithium Polyphosphazene Solid State Electrolyte

DOE PAGES

Pearse, Alexander J.; Schmitt, Thomas E.; Fuller, Elliot J.; ...

2017-04-10

Several active areas of research in novel energy storage technologies, including three-dimensional solid state batteries and passivation coatings for reactive battery electrode components, require conformal solid state electrolytes. We describe an atomic layer deposition (ALD) process for a member of the lithium phosphorus oxynitride (LiPON) family, which is employed as a thin film lithium-conducting solid electrolyte. The reaction between lithium tert-butoxide (LiO tBu) and diethyl phosphoramidate (DEPA) produces conformal, ionically conductive thin films with a stoichiometry close to Li 2PO 2N between 250 and 300°C. The P/N ratio of the films is always 1, indicative of a particular polymorph ofmore » LiPON which closely resembles a polyphosphazene. Films grown at 300°C have an ionic conductivity of (6.51 ± 0.36)×10 -7 S/cm at 35°C, and are functionally electrochemically stable in the window from 0 to 5.3V vs. Li/Li +. We demonstrate the viability of the ALD-grown electrolyte by integrating it into full solid state batteries, including thin film devices using LiCoO 2 as the cathode and Si as the anode operating at up to 1 mA/cm 2. The high quality of the ALD growth process allows pinhole-free deposition even on rough crystalline surfaces, and we demonstrate the fabrication and operation of thin film batteries with the thinnest (<40nm) solid state electrolytes yet reported. Finally, we show an additional application of the moderate-temperature ALD process by demonstrating a flexible solid state battery fabricated on a polymer substrate.« less

Lifetime prediction of InGaZnO thin film transistor for the application of display device and BEOL-transistors

NASA Astrophysics Data System (ADS)

Kim, Sang Min; Cho, Won Ju; Yu, Chong Gun; Park, Jong Tae

2018-04-01

In this work, the lifetime prediction models of amorphous InGaZnO thin film transistors (a-IGZO TFTs) were suggested for the application of display device and BEOL (Back End Of line) transistors with embedded a-IGZO TFTs. Four different types of test devices according to the active layer thickness, source/drain electrode materials and thermal treatments have been used to verify the suggested model. The device lifetimes under high gate bias stress and hot carrier stress were extracted through fittings of the stretched-exponential equation for threshold voltage shifts and the current estimation method for drain current degradations. Our suggested lifetime prediction models could be used in any kinds of structures of a-IGZO TFTs for the application of display device and BEOL transistors. The a-IGZO TFTs with embedded ITO local conducting layer under source/drain is better for BEOL transistor application and a-IGZO TFTs with InGaZnO thin film as source/drain electrodes may be better for the application of display devices. From 1983 to 1985, he was a Researcher at Gold-Star Semiconductor, Inc., Korea, where he worked on the development of SRAM. He joined the Department of Electronics Engineering, University of Incheon, Incheon, Korea, in 1987, where he is a Professor. As a visiting scientist at Massachusetts Institute of Technology, Cambridge, in 1991, he conducted research in hot carrier reliability of CMOS. As a visiting scholar at University of California, Davis, in 2001, he conducted research on the device structure of Nano-scale SOI CMOS. His recent interests are device structure and reliability of Nano-scale CMOS devices, flash memory, and thin film transistors.

CdO as the archetypical transparent conducting oxide. Systematics of dopant ionic radius and electronic structure effects on charge transport and band structure.

PubMed

Yang, Yu; Jin, Shu; Medvedeva, Julia E; Ireland, John R; Metz, Andrew W; Ni, Jun; Hersam, Mark C; Freeman, Arthur J; Marks, Tobin J

2005-06-22

A series of yttrium-doped CdO (CYO) thin films have been grown on both amorphous glass and single-crystal MgO(100) substrates at 410 degrees C by metal-organic chemical vapor deposition (MOCVD), and their phase structure, microstructure, electrical, and optical properties have been investigated. XRD data reveal that all as-deposited CYO thin films are phase-pure and polycrystalline, with features assignable to a cubic CdO-type crystal structure. Epitaxial films grown on single-crystal MgO(100) exhibit biaxial, highly textured microstructures. These as-deposited CYO thin films exhibit excellent optical transparency, with an average transmittance of >80% in the visible range. Y doping widens the optical band gap from 2.86 to 3.27 eV via a Burstein-Moss shift. Room temperature thin film conductivities of 8,540 and 17,800 S/cm on glass and MgO(100), respectively, are obtained at an optimum Y doping level of 1.2-1.3%. Finally, electronic band structure calculations are carried out to systematically compare the structural, electronic, and optical properties of the In-, Sc-, and Y-doped CdO systems. Both experimental and theoretical results reveal that dopant ionic radius and electronic structure have a significant influence on the CdO-based TCO crystal and band structure: (1) lattice parameters contract as a function of dopant ionic radii in the order Y (1.09 A) < In (0.94 A) < Sc (0.89 A); (2) the carrier mobilities and doping efficiencies decrease in the order In > Y > Sc; (3) the dopant d state has substantial influence on the position and width of the s-based conduction band, which ultimately determines the intrinsic charge transport characteristics.

Electromagnetic shielding effectiveness of a thin silver layer deposited onto PET film via atmospheric pressure plasma reduction

NASA Astrophysics Data System (ADS)

Oh, Hyo-Jun; Dao, Van-Duong; Choi, Ho-Suk

2018-03-01

This study presents the first use of a plasma reduction reaction under atmospheric pressure to fabricate a thin silver layer on polyethylene terephthalate (PET) film without the use of toxic chemicals, high voltages, or an expensive vacuum apparatus. The developed film is applied to electromagnetic interference (EMI) shielding. After repeatedly depositing a silver layer through a plasma reduction reaction on PET, we can successfully fabricate a uniformly deposited thin silver layer. It was found that both the particle size and film thickness of thin silver layers fabricated at different AgNO3 concentrations increase with an increase in the concentration of AgNO3. However, the roughness of the thin silver layer decreases when increasing the concentration of AgNO3 from 100 to 500 mM, and the roughness increases with a further increase in the concentration of AgNO3. The EMI shielding effectiveness (SE) of the film is measured in the frequency range of 0.045 to 1 GHz. As a result of optimizing the electrical conductivity by measuring sheet resistance of the thin silver layer, the film fabricated from 500 mM AgNO3 exhibits the highest EMI SE among all fabricated films. The maximum values of the EMI SE are 60.490 dB at 0.1 GHz and 54.721 dB at 1.0 GHz with minimum sheet resistance of 0.244 Ω/□. Given that the proposed strategy is simple and effective, it is promising for fabricating various low-cost metal films with high EMI SE.

Plasma-enhanced atomic layer deposition zinc oxide for multifunctional thin film electronics

NASA Astrophysics Data System (ADS)

Mourey, Devin A.

A novel, weak oxidant, plasma-enhanced atomic layer deposition (PEALD) process has been used to fabricate stable, high mobility ZnO thin film transistors (TFTs) and fast circuits on glass and polyimide substrates at 200°C. Weak oxidant PEALD provides a simple, fast deposition process which results in uniform, conformal coatings and highly crystalline, dense ZnO thin films. These films and resulting devices have been compared with those prepared by spatial atomic layer deposition (SALD) throughout the work. Both PEALD and SALD ZnO TFTs have high field-effect mobility (>20 cm 2/V·s) and devices with ALD Al2O3 passivation can have excellent bias stress stability. Temperature dependent measurements of PEALD ZnO TFTs revealed a mobility activation energy < 5 meV and can be described using a simple percolation model with a Gaussian distribution of near-conduction band barriers. Interestingly, both PEALD and SALD devices operate with mobility > 1 cm2/V·s even at temperatures < 10 K. The effects of high energy irradiation have also been investigated. Devices exposed to 1 MGy of gamma irradiation showed small threshold voltage shifts (<2 V) which were fully recoverable with short (1 min) low-temperature (200°C) anneals. ZnO TFTs exhibit a range of non-ideal behavior which has direct implications on how important parameters such as mobility and threshold voltage are quantified. For example, the accumulation-dependent mobility and contact effects can lead to significant overestimations in mobility. It is also found that self-heating plays and important role in the non-ideal behavior of oxide TFTs on low thermal conductivity substrates. In particular, the output conductance and a high current device runaway breakdown effect can be directly ascribed to self-heating. Additionally, a variety of simple ZnO circuits on glass and flexible substrates were demonstrated. A backside exposure process was used to form gate-self-aligned structures with reduced parasitic capacitance and circuits with propagation delay < 10 ns/stage. Finally, to combat some of the self-heating and design challenges associated with unipolar circuits, a simple 4-mask organic-inorganic hybrid CMOS process was demonstrated.

Sequential pH-dependent adsorption of ionic amphiphilic diblock copolymer micelles and choline oxidase onto conductive substrates: toward the design of biosensors.

PubMed

Sigolaeva, Larisa V; Günther, Ulrike; Pergushov, Dmitry V; Gladyr, Snezhana Yu; Kurochkin, Ilya N; Schacher, Felix H

2014-07-01

This work examines the fabrication regime and the properties of polymer-enzyme thin-films adsorbed onto conductive substrates (graphite or gold). The films are formed via two-steps, sequential adsorption of poly(n-butylmethacrylate)-block-poly(N,N-dimethylaminoethyl methacrylate) (PnBMA-b-PDMAEMA) diblock copolymer micelles (1st step of adsorption), followed by the enzyme choline oxidase (ChO) (2nd step of adsorption). The solution properties of both adsorbed components are studied and the pH-dependent step-by-step fabrication of polymer-enzyme biosensor coatings reveals rather drastic differences in their enzymatic activities in dependence on the pH of both adsorption steps. The resulting hybrid thin-films represent highly active biosensors for choline with a low detection limit of 30 nM and a good linearity in a range between 30 nM and 100 μM. The sensitivity is found to be 175 μA mM(-1) cm(-2) and the operational stability of the polymer-enzyme thin-films can be additionally improved via enzyme-to-enzyme crosslinking with glutaraldehyde. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of spin-orbit coupling on excitonic levels in layered chalcogenide-fluorides

NASA Astrophysics Data System (ADS)

Zakutayev, Andriy; Kykyneshi, Robert; Kinney, Joseph; McIntyre, David H.; Schneider, Guenter; Tate, Janet

2008-03-01

BaCuChF (Ch=S,Se,Te) comprise a family of wide-bandgap p-type semiconductors. Due to their high transparency and conductivity, they have potential applications as components of transparent thin-film transistors, solar cells and light-emitting devices. Thin films of BaCuChF have been deposited on MgO by pulsed laser deposition (PLD). Solid solutions BaCuS1-xSexTeF and BaCuSe1-xTex have been prepared by PLD of alternating thin BaCuChF layers. All films were deposited at elevated substrate temperatures. They are preferentially c-axis oriented, conductive and transparent in the visible part of the spectrum. Double excitonic peaks have been observed in the absorption spectrum of these films in the temperature range from 80 to 300K. The separation between the peaks in the doublet increases with the increase of atomic mass of the chalcogen. It also increases with the increase of the heavy chalcogen component x in the solid solutions. This separation most likely is caused by the effect of spin-orbit coupling in the chalcogen atoms on excitonic levels in BaCuChF.

Transient thermal stress wave and vibrational analyses of a thin diamond crystal for X-ray free-electron lasers under high-repetition-rate operation

DOE PAGES

Yang, Bo; Wang, Songwei; Wu, Juhao

2018-01-01

High-brightness X-ray free-electron lasers (FELs) are perceived as fourth-generation light sources providing unprecedented capabilities for frontier scientific researches in many fields. Thin crystals are important to generate coherent seeds in the self-seeding configuration, provide precise spectral measurements, and split X-ray FEL pulses, etc. In all of these applications a high-intensity X-ray FEL pulse impinges on the thin crystal and deposits a certain amount of heat load, potentially impairing the performance. In the present paper, transient thermal stress wave and vibrational analyses as well as transient thermal analysis are carried out to address the thermomechanical issues for thin diamond crystals, especiallymore » under high-repetition-rate operation of an X-ray FEL. The material properties at elevated temperatures are considered. It is shown that, for a typical FEL pulse depositing tens of microjoules energy over a spot of tens of micrometers in radius, the stress wave emission is completed on the tens of nanoseconds scale. The amount of kinetic energy converted from a FEL pulse can reach up to ~10 nJ depending on the layer thickness. Natural frequencies of a diamond plate are also computed. The potential vibrational amplitude is estimated as a function of frequency. Here, due to the decreasing heat conductivity with increasing temperature, a runaway temperature rise is predicted for high repetition rates where the temperature rises abruptly after ratcheting up to a point of trivial heat damping rate relative to heat deposition rate.« less

Transient thermal stress wave and vibrational analyses of a thin diamond crystal for X-ray free-electron lasers under high-repetition-rate operation

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

Yang, Bo; Wang, Songwei; Wu, Juhao

High-brightness X-ray free-electron lasers (FELs) are perceived as fourth-generation light sources providing unprecedented capabilities for frontier scientific researches in many fields. Thin crystals are important to generate coherent seeds in the self-seeding configuration, provide precise spectral measurements, and split X-ray FEL pulses, etc. In all of these applications a high-intensity X-ray FEL pulse impinges on the thin crystal and deposits a certain amount of heat load, potentially impairing the performance. In the present paper, transient thermal stress wave and vibrational analyses as well as transient thermal analysis are carried out to address the thermomechanical issues for thin diamond crystals, especiallymore » under high-repetition-rate operation of an X-ray FEL. The material properties at elevated temperatures are considered. It is shown that, for a typical FEL pulse depositing tens of microjoules energy over a spot of tens of micrometers in radius, the stress wave emission is completed on the tens of nanoseconds scale. The amount of kinetic energy converted from a FEL pulse can reach up to ~10 nJ depending on the layer thickness. Natural frequencies of a diamond plate are also computed. The potential vibrational amplitude is estimated as a function of frequency. Here, due to the decreasing heat conductivity with increasing temperature, a runaway temperature rise is predicted for high repetition rates where the temperature rises abruptly after ratcheting up to a point of trivial heat damping rate relative to heat deposition rate.« less

Transient thermal stress wave and vibrational analyses of a thin diamond crystal for X-ray free-electron lasers under high-repetition-rate operation.

PubMed

Yang, Bo; Wang, Songwei; Wu, Juhao

2018-01-01

High-brightness X-ray free-electron lasers (FELs) are perceived as fourth-generation light sources providing unprecedented capabilities for frontier scientific researches in many fields. Thin crystals are important to generate coherent seeds in the self-seeding configuration, provide precise spectral measurements, and split X-ray FEL pulses, etc. In all of these applications a high-intensity X-ray FEL pulse impinges on the thin crystal and deposits a certain amount of heat load, potentially impairing the performance. In the present paper, transient thermal stress wave and vibrational analyses as well as transient thermal analysis are carried out to address the thermomechanical issues for thin diamond crystals, especially under high-repetition-rate operation of an X-ray FEL. The material properties at elevated temperatures are considered. It is shown that, for a typical FEL pulse depositing tens of microjoules energy over a spot of tens of micrometers in radius, the stress wave emission is completed on the tens of nanoseconds scale. The amount of kinetic energy converted from a FEL pulse can reach up to ∼10 nJ depending on the layer thickness. Natural frequencies of a diamond plate are also computed. The potential vibrational amplitude is estimated as a function of frequency. Due to the decreasing heat conductivity with increasing temperature, a runaway temperature rise is predicted for high repetition rates where the temperature rises abruptly after ratcheting up to a point of trivial heat damping rate relative to heat deposition rate.

Growth and physical investigations of sprayed ZnMoO4 thin films along with wettability tests

NASA Astrophysics Data System (ADS)

Askri, Besma; Mhamdi, Ammar; Mahdhi, Noureddine; Amlouk, Mosbah

2018-06-01

Ternary oxides based on zinc and molybdenum elements have known as semiconductor oxides with large band gap energies. With the focus mainly on their synthesis by cost-effective process as thin films, the aspect of their stability and reactivity as transparent layers against both UV radiation and oxidation under wet medium due to their oxygen deficiency has so far not been investigated. This work covers the synthesis as well as the structural, electrical and the wettability properties of ZnMoO4 thin films which have been prepared by the spray pyrolysis method on glass substrates at 460 °C. First, X-ray diffraction analysis shows that this oxide crystallizes in triclinic structure with the space group P-1. The thickness value of ZnMoO4 thin film of about 1.5 μm was estimated by spectroscopic ellipsometry (SE). Moreover, a special emphasis has been focused on the photoluminescence properties of such films to reach possible presence of defaults and oxygen vacancy. Second, the electrical conductivity, conduction mechanism, relaxation model of these films were indeed studied using impedance spectroscopy technique in the frequency range 10-1-106 Hz at various temperatures (25-300 °C). At high temperature, σAC conductivity obeys to the power law established by Jonscher. Besides, the variation of σDC with the inverse of the temperature follows Arrhenius law. This evolution suggests that the conduction process is thermally activated and the activation energy of this process is equal to 0.97 eV. Finally, the wettability tests reveal that zinc molybdates loses its hydrophobic character during aging under UV radiation to become completely hydrophilic. All these physical investigations demonstrated that such ternary oxide contains oxygen deficiency which may be of interest for photocatalytic purposes and pave the way for various sensitivity applications like gas and bio-sensors.

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

Wu, Ruikang; Hu, Run, E-mail: hurun@hust.edu.cn, E-mail: luoxb@hust.edu.cn; Luo, Xiaobing, E-mail: hurun@hust.edu.cn, E-mail: luoxb@hust.edu.cn

In this study, we developed a first-principle-based full-dispersion Monte Carlo simulation method to study the anisotropic phonon transport in wurtzite GaN thin film. The input data of thermal properties in MC simulations were calculated based on the first-principle method. The anisotropy of thermal conductivity in bulk wurtzite GaN is found to be strengthened by isotopic scatterings and reduced temperature, and the anisotropy reaches 40.08% for natural bulk GaN at 100 K. With the GaN thin film thickness decreasing, the anisotropy of the out-of-plane thermal conductivity is heavily reduced due to both the ballistic transport and the less importance of the low-frequencymore » phonons with anisotropic group velocities. On the contrary, it is observed that the in-plane thermal conductivity anisotropy of the GaN thin film is strengthened by reducing the film thickness. And the anisotropy reaches 35.63% when the natural GaN thin film thickness reduces to 50 nm at 300 K with the degree of specularity being zero. The anisotropy is also improved by increasing the surface roughness of the GaN thin film.« less

Investigation of defects in In–Ga–Zn oxide thin film using electron spin resonance signals

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

Nonaka, Yusuke; Kurosawa, Yoichi; Komatsu, Yoshihiro

In–Ga–Zn oxide (IGZO) is a next-generation semiconductor material seen as an alternative to silicon. Despite the importance of the controllability of characteristics and the reliability of devices, defects in IGZO have not been fully understood. We investigated defects in IGZO thin films using electron spin resonance (ESR) spectroscopy. In as-sputtered IGZO thin films, we observed an ESR signal which had a g-value of g = 2.010, and the signal was found to disappear under thermal treatment. Annealing in a reductive atmosphere, such as N{sub 2} atmosphere, generated an ESR signal with g = 1.932 in IGZO thin films. The temperature dependence of the lattermore » signal suggests that the signal is induced by delocalized unpaired electrons (i.e., conduction electrons). In fact, a comparison between the conductivity and ESR signal intensity revealed that the signal's intensity is related to the number of conduction electrons in the IGZO thin film. The signal's intensity did not increase with oxygen vacancy alone but also with increases in both oxygen vacancy and hydrogen concentration. In addition, first-principle calculation suggests that the conduction electrons in IGZO may be generated by defects that occur when hydrogen atoms are inserted into oxygen vacancies.« less

Thermal, Structural, AC Conductivity, and Dielectric Properties of Ethyl-2-amino-6-ethyl-5-oxo-4-(3-phenoxyphenyl)-5,6-dihydro-4H-pyrano[3,2-c]quinoline-3-carboxylate Thin Films

NASA Astrophysics Data System (ADS)

El-Shabaan, M. M.

2018-05-01

Thermal, structural, alternating-current (AC) conductivity (σ AC), and dielectric properties of ethyl-2-amino-6-ethyl-5-oxo-4-(3-phenoxyphenyl)-5,6-dihydro-4H-pyrano[3,2-c]quinoline-3-carboxylate (HPQC) thin films have been studied. Thermogravimetry analysis and differential scanning calorimetry confirmed the thermal stability of HPQC over a wide temperature range. Fourier-transform infrared spectroscopy and x-ray diffraction analysis were carried out on HPQC in powder form and as-deposited thin film. The crystal system and space group type were determined for HPQC in powder form. The AC conductivity and dielectric properties were determined in the frequency range from 0.5 kHz to 5 MHz and temperature range from 296 K to 443 K. The AC electrical conduction of HPQC thin film was found to be governed by the small-polaron tunneling mechanism. The polaron hopping energy (W H), tunneling distance (R), and density of states (N) near the Fermi level were determined as functions of temperature and frequency. The dielectric properties of HPQC thin film were studied by analysis of Nyquist diagrams, the dissipation factor (tan δ), and real (ɛ') and imaginary (ɛ″) parts of the dielectric constant.

Vacuum die attach for integrated circuits

DOEpatents

Schmitt, E.H.; Tuckerman, D.B.

1991-09-10

A thin film eutectic bond for attaching an integrated circuit die to a circuit substrate is formed by coating at least one bonding surface on the die and substrate with an alloying metal, assembling the die and substrate under compression loading, and heating the assembly to an alloying temperature in a vacuum. A very thin bond, 10 microns or less, which is substantially void free, is produced. These bonds have high reliability, good heat and electrical conduction, and high temperature tolerance. The bonds are formed in a vacuum chamber, using a positioning and loading fixture to compression load the die, and an IR lamp or other heat source. For bonding a silicon die to a silicon substrate, a gold silicon alloy bond is used. Multiple dies can be bonded simultaneously. No scrubbing is required. 1 figure.

Vacuum die attach for integrated circuits

DOEpatents

Schmitt, Edward H.; Tuckerman, David B.

1991-01-01

A thin film eutectic bond for attaching an integrated circuit die to a circuit substrate is formed by coating at least one bonding surface on the die and substrate with an alloying metal, assembling the die and substrate under compression loading, and heating the assembly to an alloying temperature in a vacuum. A very thin bond, 10 microns or less, which is substantially void free, is produced. These bonds have high reliability, good heat and electrical conduction, and high temperature tolerance. The bonds are formed in a vacuum chamber, using a positioning and loading fixture to compression load the die, and an IR lamp or other heat source. For bonding a silicon die to a silicon substrate, a gold silicon alloy bond is used. Multiple dies can be bonded simultaneously. No scrubbing is required.

Fabrication of ultrafast laser written low-loss waveguides in flexible As₂S₃ chalcogenide glass tape.

PubMed

Lapointe, Jerome; Ledemi, Yannick; Loranger, Sébastien; Iezzi, Victor Lambin; Soares de Lima Filho, Elton; Parent, Francois; Morency, Steeve; Messaddeq, Younes; Kashyap, Raman

2016-01-15

As2S3 glass has a unique combination of optical properties, such as wide transparency in the infrared region and a high nonlinear coefficient. Recently, intense research has been conducted to improve photonic devices using thin materials. In this Letter, highly uniform rectangular single-index and 2 dB/m loss step-index optical tapes have been drawn by the crucible technique. Low-loss (<0.15  dB/cm) single-mode waveguides in chalcogenide glass tapes have been fabricated using femtosecond laser writing. Optical backscatter reflectometry has been used to study the origin of the optical losses. A detailed study of the laser writing process in thin glass is also presented to facilitate a repeatable waveguide inscription recipe.

High temperature electrical resistivity and Seebeck coefficient of Ge2Sb2Te5 thin films

NASA Astrophysics Data System (ADS)

Adnane, L.; Dirisaglik, F.; Cywar, A.; Cil, K.; Zhu, Y.; Lam, C.; Anwar, A. F. M.; Gokirmak, A.; Silva, H.

2017-09-01

High-temperature characterization of the thermoelectric properties of chalcogenide Ge2Sb2Te5 (GST) is critical for phase change memory devices, which utilize self-heating to quickly switch between amorphous and crystalline states and experience significant thermoelectric effects. In this work, the electrical resistivity and Seebeck coefficient are measured simultaneously as a function of temperature, from room temperature to 600 °C, on 50 nm and 200 nm GST thin films deposited on silicon dioxide. Multiple heating and cooling cycles with increasingly maximum temperature allow temperature-dependent characterization of the material at each crystalline state; this is in contrast to continuous measurements which return the combined effects of the temperature dependence and changes in the material. The results show p-type conduction (S > 0), linear S(T), and a positive Thomson coefficient (dS/dT) up to melting temperature. The results also reveal an interesting linearity between dS/dT and the conduction activation energy for mixed amorphous-fcc GST, which can be used to estimate one parameter from the other. A percolation model, together with effective medium theory, is adopted to correlate the conductivity of the material with average grain sizes obtained from XRD measurements. XRD diffraction measurements show plane-dependent thermal expansion for the cubic and hexagonal phases.

Lateral assembly of oxidized graphene flakes into large-scale transparent conductive thin films with a three-dimensional surfactant 4-sulfocalix[4]arene

PubMed Central

Sundramoorthy, Ashok K.; Wang, Yilei; Wang, Jing; Che, Jianfei; Thong, Ya Xuan; Lu, Albert Chee W.; Chan-Park, Mary B.

2015-01-01

Graphene is a promising candidate material for transparent conductive films because of its excellent conductivity and one-carbon-atom thickness. Graphene oxide flakes prepared by Hummers method are typically several microns in size and must be pieced together in order to create macroscopic films. We report a macro-scale thin film fabrication method which employs a three-dimensional (3-D) surfactant, 4-sulfocalix[4]arene (SCX), as a lateral aggregating agent. After electrochemical exfoliation, the partially oxidized graphene (oGr) flakes are dispersed with SCX. The SCX forms micelles, which adsorb on the oGr flakes to enhance their dispersion, also promote aggregation into large-scale thin films under vacuum filtration. A thin oGr/SCX film can be shaved off from the aggregated oGr/SCX cake by immersing the cake in water. The oGr/SCX thin-film floating on the water can be subsequently lifted from the water surface with a substrate. The reduced oGr (red-oGr) films can be as thin as 10−20 nm with a transparency of >90% and sheet resistance of 890 ± 47 kΩ/sq. This method of electrochemical exfoliation followed by SCX-assisted suspension and hydrazine reduction, avoids using large amounts of strong acid (unlike Hummers method), is relatively simple and can easily form a large scale conductive and transparent film from oGr/SCX suspension. PMID:26040436

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

Sabah, Fayroz A., E-mail: fayroz-arif@yahoo.com; Department of Electrical Engineering, College of Engineering, Al-Mustansiriya University, Baghdad; Ahmed, Naser M., E-mail: naser@usm.my

The copper sulphide (CuS) thin films were grown with good adhesion by spray pyrolysis deposition (SPD) on Ti, ITO and glass substrates at 200 °C. The distance between nozzle and substrate is 30 cm. The composition was prepared by mixing copper chloride CuCl{sub 2}.2H{sub 2}O as a source of Cu{sup 2+} and sodium thiosulfate Na{sub 2}S{sub 2}O{sub 3}.5H{sub 2}O as a source of and S{sup 2−}. Two concentrations (0.2 and 0.4 M) were used for each CuCl{sub 2} and Na{sub 2}S{sub 2}O{sub 3} to be prepared and then sprayed (20 ml). The process was started by spraying the solution formore » 3 seconds and after 10 seconds the cycle was repeated until the solution was sprayed completely on the hot substrates. The structural characteristics were studied using X-ray diffraction; they showed covellite CuS hexagonal crystal structure for 0.2 M concentration, and covellite CuS hexagonal crystal structure with two small peaks of chalcocite Cu{sub 2}S hexagonal crystal structure for 0.4 M concentration. Also the surface and electrical characteristics were investigated using Field Emission Scanning Electron Microscopy (FESEM) and current source device, respectively. The surface study for the CuS thin films showed nanorods to be established for 0.2 M concentration and mix of nanorods and nanoplates for 0.4 M concentration. The electrical study showed ohmic behavior and low resistivity for these films. Hall Effect was measured for these thin films, it showed that all samples of CuS are p- type thin films and ensured that the resistivity for thin films of 0.2 M concentration was lower than that of 0.4 M concentration; and for the two concentrations CuS thin film deposited on ITO had the lowest resistivity. This leads to the result that the conductivity was high for CuS thin film deposited on ITO substrate, and the conductivity of the three thin films of 0.2 M concentration was higher than that of 0.4 M concentration.« less

Combustion synthesized indium-tin-oxide (ITO) thin film for source/drain electrodes in all solution-processed oxide thin-film transistors

NASA Astrophysics Data System (ADS)

Tue, Phan Trong; Inoue, Satoshi; Takamura, Yuzuru; Shimoda, Tatsuya

2016-06-01

We report combustion solution synthesized (SCS) indium-tin-oxide (ITO) thin film, which is a well-known transparent conductive oxide, for source/drain (S/D) electrodes in solution-processed amorphous zirconium-indium-zinc-oxide TFT. A redox-based combustion synthetic approach is applied to ITO thin film using acetylacetone as a fuel and metal nitrate as oxidizer. The structural and electrical properties of SCS-ITO precursor solution and thin films were systematically investigated with changes in tin concentration, indium metal precursors, and annealing conditions such as temperature, time, and ambient. It was found that at optimal conditions the SCS-ITO thin film exhibited high crystalline quality, atomically smooth surface (RMS ~ 4.1 Å), and low electrical resistivity (4.2 × 10-4 Ω cm). The TFT using SCS-ITO film as the S/D electrodes showed excellent electrical properties with negligible hysteresis. The obtained "on/off" current ratio, subthreshold swing factor, subthreshold voltage, and field-effect mobility were 5 × 107, 0.43 V/decade, 0.7 V, and 2.1 cm2/V s, respectively. The performance and stability of the SCS-ITO TFT are comparable to those of the sputtered-ITO TFT, emphasizing that the SCS-ITO film is a promising candidate for totally solution-processed oxide TFTs.

Scanning Probe Microscopy on heterogeneous CaCu3Ti4O12 thin films

PubMed Central

2011-01-01

The conductive atomic force microscopy provided a local characterization of the dielectric heterogeneities in CaCu3Ti4O12 (CCTO) thin films deposited by MOCVD on IrO2 bottom electrode. In particular, both techniques have been employed to clarify the role of the inter- and sub-granular features in terms of conductive and insulating regions. The microstructure and the dielectric properties of CCTO thin films have been studied and the evidence of internal barriers in CCTO thin films has been provided. The role of internal barriers and the possible explanation for the extrinsic origin of the giant dielectric response in CCTO has been evaluated. PMID:21711646

Scanning Probe Microscopy on heterogeneous CaCu3Ti4O12 thin films

NASA Astrophysics Data System (ADS)

Fiorenza, Patrick; Lo Nigro, Raffaella; Raineri, Vito

2011-12-01

The conductive atomic force microscopy provided a local characterization of the dielectric heterogeneities in CaCu3Ti4O12 (CCTO) thin films deposited by MOCVD on IrO2 bottom electrode. In particular, both techniques have been employed to clarify the role of the inter- and sub-granular features in terms of conductive and insulating regions. The microstructure and the dielectric properties of CCTO thin films have been studied and the evidence of internal barriers in CCTO thin films has been provided. The role of internal barriers and the possible explanation for the extrinsic origin of the giant dielectric response in CCTO has been evaluated.

Scanning Probe Microscopy on heterogeneous CaCu3Ti4O12 thin films.

PubMed

Fiorenza, Patrick; Lo Nigro, Raffaella; Raineri, Vito

2011-02-04

The conductive atomic force microscopy provided a local characterization of the dielectric heterogeneities in CaCu3Ti4O12 (CCTO) thin films deposited by MOCVD on IrO2 bottom electrode. In particular, both techniques have been employed to clarify the role of the inter- and sub-granular features in terms of conductive and insulating regions. The microstructure and the dielectric properties of CCTO thin films have been studied and the evidence of internal barriers in CCTO thin films has been provided. The role of internal barriers and the possible explanation for the extrinsic origin of the giant dielectric response in CCTO has been evaluated.

Strong and electrically conductive nanopaper from cellulose nanofibers and polypyrrole.

PubMed

Lay, Makara; Méndez, J Alberto; Delgado-Aguilar, Marc; Bun, Kim Ngun; Vilaseca, Fabiola

2016-11-05

In this work, we prepare cellulose nanopapers of high mechanical performance and with the electrical conductivity of a semiconductor. Cellulose nanofibers (CNF) from bleached softwood pulp were coated with polypyrrole (PPy) via in situ chemical polymerization, in presence of iron chloride (III) as oxidant agent. The structure and morphology of nanopapers were studied, as well as their thermal, mechanical and conductive properties. Nanopaper from pure CNF exhibited a very high tensile response (224MPa tensile strength and 14.5GPa elastic modulus). The addition of up to maximum 20% of polypyrrole gave CNF/PPy nanopapers of high flexibility and still good mechanical properties (94MPa strength and 8.8GPa modulus). The electrical conductivity of the resulting CNF/PPy nanopaper was of 5.2 10(-2)Scm(-1), with a specific capacitance of 7.4Fg(-1). The final materials are strong and conductive nanopapers that can find application as biodegradable flexible thin-film transistor (TFT) or as flexible biosensor. Copyright © 2016 Elsevier Ltd. All rights reserved.

Highly stretchable and conductive fibers enabled by liquid metal dip-coating

NASA Astrophysics Data System (ADS)

Zhang, Qiang; Roach, Devin J.; Geng, Luchao; Chen, Haosen; Qi, H. Jerry; Fang, Daining

2018-03-01

Highly stretchable and conductive fibers have been fabricated by dip-coating of a layer of liquid metal (eutectic gallium indium, EGaIn) on printed silicone elastomer filaments. This fabrication method exploits a nanolayer of oxide skin that rapidly forms on the surface of EGaIn when exposed to air. Through dip-coating, the sticky nature of the oxide skin leads to the formation of a thin EGaIn coating (˜5 μm thick) on the originally nonconductive filaments and renders these fibers excellent conductivity. Electrical characterization shows that the fiber resistance increases moderately as the fiber elongates but always maintains conductivity even when stretched by 800%. Besides this, these fibers possess good cyclic electrical stability with little degradation after hundreds of stretching cycles, which makes them an excellent candidate for stretchable conductors. We then demonstrate a highly stretchable LED circuit as well as a conductive stretchable net that extends the 1D fibers into a 2D configuration. These examples demonstrate potential applications for topologically complex stretchable electronics.

High Resolution Quantitative Microbeam Analysis of Ir-coated Geological Specimens Using Conventionally Coated Standards

NASA Astrophysics Data System (ADS)

Armstrong, J. T.; Crispin, K. L.

2012-12-01

Traditionally, quantitative electron microbeam analyses of insulating specimens are performed after coating the materials with thin conducting layers of carbon. For x-ray lines greater than 1 keV in energy and beam voltages in excess of 10 keV, the results are insensitive to the exact thickness of the carbon coat. High resolution imaging, low voltage analysis, and analysis of specimens containing low levels of carbon require the use of substitute conductive coats. Typical substitutes for carbon coats (e.g., Au, Au-Pd, Cr, Al) require either using similarly coated standards or substantial corrections to be applied. Even when using modern multi-layer correction algorithms or Monte Carlo calculations, significant errors can result (e.g., Armstrong 2009, Armstrong and Crispin, 2012). We propose the use of ultra-thin layers of Ir as a substitute for C in the analysis of insulating geological specimens. Ir has been found to be an excellent coating material for high resolution imaging (e.g., Echlin, 2009). Sputtered layers as thin as 0.5 nm are found to be conductive, and layers of just a few nm provide good protection against beam damage with sub-nm grain size (Sebring et al., 1999). We have analyzed a series of geological materials with Ir coats between 1 - 8 nm and found similar levels of effects on emitted x-ray intensities as produced with typical carbon coat thicknesses (10-25 nm). E.g., for Ir thicknesses less than 5 nm, the reduction of intensity for x-ray lines between 1 and 7 keV are between 1-3% for a beam energy of 15 keV. The reduction in intensity for higher-energy lines such as Fe-K is actually less than produced by typical C-coats. We will present the results of these experiments and propose simple algorithmic equations which fit these data.

Method for transferring thermal energy and electrical current in thin-film electrochemical cells

DOEpatents

Rouillard, Roger [Beloeil, CA; Domroese, Michael K [South St. Paul, MN; Hoffman, Joseph A [Minneapolis, MN; Lindeman, David D [Hudson, WI; Noel, Joseph-Robert-Gaetan [St-Hubert, CA; Radewald, Vern E [Austin, TX; Ranger, Michel [Lachine, CA; Sudano, Anthony [Laval, CA; Trice, Jennifer L [Eagan, MN; Turgeon, Thomas A [Fridley, MN

2003-05-27

An improved electrochemical generator is disclosed. The electrochemical generator includes a thin-film electrochemical cell which is maintained in a state of compression through use of an internal or an external pressure apparatus. A thermal conductor, which is connected to at least one of the positive or negative contacts of the cell, conducts current into and out of the cell and also conducts thermal energy between the cell and thermally conductive, electrically resistive material disposed on a vessel wall adjacent the conductor. The thermally conductive, electrically resistive material may include an anodized coating or a thin sheet of a plastic, mineral-based material or conductive polymer material. The thermal conductor is fabricated to include a resilient portion which expands and contracts to maintain mechanical contact between the cell and the thermally conductive material in the presence of relative movement between the cell and the wall structure. The electrochemical generator may be disposed in a hermetically sealed housing.

Effective mobility enhancement of amorphous In-Ga-Zn-O thin-film transistors by holographically generated periodic conductor

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

Jeong, Jaewook; Kim, Joonwoo; Jeong, Soon Moon

In this study, we demonstrate a mobility enhancement structure for fully transparent amorphous indium-gallium-zinc-oxide thin-film transistors (a-IGZO TFTs) by embedding a holographically generated periodic nano-conductor in the back-channel regions. The intrinsic field-effect mobility was enhanced up to 2 times compared to that of a reference sample. The enhancement originated from a decrease in the effective channel length due to the highly conductive nano-conductor region. By combining conventional and holographic lithography, the performance of the a-IGZO TFT can be effectively improved without varying the composition of the channel layer.