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Sample records for oxide liti2o4 thin

  1. Lithium outdiffusion in LiTi2O4 thin films grown by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Mesoraca, S.; Kleibeuker, J. E.; Prasad, B.; MacManus-Driscoll, J. L.; Blamire, M. G.

    2016-11-01

    We report surface chemical cation composition analysis of high quality superconducting LiTi2O4 thin films, grown epitaxially on MgAl2O4 (111) substrates by pulsed laser deposition. The superconducting transition temperature of the films was 13.8 K. Surface chemical composition is crucial for the formation of a good metal/insulator interface for integrating LiTi2O4 into full-oxide spin-filtering devices in order to minimize the formation of structural defects and increase the spin polarisation efficiency. In consideration of this, we report a detailed angle resolved x-ray photoelectron spectroscopy analysis. Results show Li segregation at the surface of LiTi2O4 films. We attribute this process due to outdiffusion of Li toward the outermost LiTi2O4 layers.

  2. Time domain THz studies of thin film spinel superconductor LiTi2O4

    NASA Astrophysics Data System (ADS)

    Jasper, Evan; Warren, M. T.; Mai, T. T.; Brangham, J.; Valdés Aguilar, R.; Shin, J. M.; Takeuchi, I.; Greene, R. L.

    Recent advances in growth of high-quality crystalline thin films of the only known spinel superconductor (SC) LiTi2O4 have allowed the discovery of an anomalous anisotropic magnetoresistance in its normal state. We have used time domain terahertz spectroscopy, a contactless transport measurement, to determine the ac conductivity of LiTi2O4 and to examine the BCS nature of the superconducting state. We obtained the temperature dependence of the SC gap as well as the London penetration depth, and also found a hint of a second gap. We will discuss and compare these results in terms of the known dc transport properties. Work at OSU supported by start-up funds to RVA. Work at UMD supported by UMDAFOSR FA95501410332, and NSF DMR 1410665.

  3. Anomalous magnetoresistance in the spinel superconductor LiTi2O4

    NASA Astrophysics Data System (ADS)

    Jin, K.; He, G.; Zhang, X.; Maruyama, S.; Yasui, S.; Suchoski, R.; Shin, J.; Jiang, Y.; Yu, H. S.; Yuan, J.; Shan, L.; Kusmartsev, F. V.; Greene, R. L.; Takeuchi, I.

    2015-05-01

    LiTi2O4 is a unique compound in that it is the only known spinel oxide superconductor. The lack of high quality single crystals has thus far prevented systematic investigations of its transport properties. Here we report a careful study of transport and tunnelling spectroscopy in epitaxial LiTi2O4 thin films. An unusual magnetoresistance is observed which changes from nearly isotropic negative to prominently anisotropic positive as the temperature is decreased. We present evidence that shows that the negative magnetoresistance likely stems from the suppression of local spin fluctuations or spin-orbit scattering centres. The positive magnetoresistance suggests the presence of an orbital-related state, also supported by the fact that the superconducting energy gap decreases as a quadratic function of magnetic field. These observations indicate that the spin-orbital fluctuations play an important role in LiTi2O4 in a manner similar to high-temperature superconductors.

  4. Anomalous magnetoresistance in the spinel superconductor LiTi2O4.

    PubMed

    Jin, K; He, G; Zhang, X; Maruyama, S; Yasui, S; Suchoski, R; Shin, J; Jiang, Y; Yu, H S; Yuan, J; Shan, L; Kusmartsev, F V; Greene, R L; Takeuchi, I

    2015-05-20

    LiTi2O4 is a unique compound in that it is the only known spinel oxide superconductor. The lack of high quality single crystals has thus far prevented systematic investigations of its transport properties. Here we report a careful study of transport and tunnelling spectroscopy in epitaxial LiTi2O4 thin films. An unusual magnetoresistance is observed which changes from nearly isotropic negative to prominently anisotropic positive as the temperature is decreased. We present evidence that shows that the negative magnetoresistance likely stems from the suppression of local spin fluctuations or spin-orbit scattering centres. The positive magnetoresistance suggests the presence of an orbital-related state, also supported by the fact that the superconducting energy gap decreases as a quadratic function of magnetic field. These observations indicate that the spin-orbital fluctuations play an important role in LiTi2O4 in a manner similar to high-temperature superconductors.

  5. Growth and characterization of superconducting spinel oxide LiTi2O4 thin films

    SciTech Connect

    Chopdekar, R.V.; Wong, F.; Takamura, Y.; Arenholz, E.; Suzuki, Y.

    2009-03-10

    Epitaxial films of LiTi{sub 2}O{sub 4} on single crystalline substrates of MgAl{sub 2}O{sub 4}, MgO, and SrTiO{sub 3} provide model systems to systematically explore the effects of lattice strain and microstructural disorder on the superconducting state. Lattice strain that affects bandwidth gives rise to variations in the superconducting and normal state properties. Microstructural disorder, such as antiphase boundaries that give rise to Ti network disorder, reduces the critical temperature, and Ti network disorder combined with Mg interdiffusion lead to a much more dramatic effect on the superconducting state. Surface sensitive X-ray absorption spectroscopy has identified Ti to retain site symmetry and average valence of the bulk material regardless of film thickness.

  6. Reversible superconductor-insulator transition in LiTi2O4 induced by Li-ion electrochemical reaction.

    PubMed

    Yoshimatsu, K; Niwa, M; Mashiko, H; Oshima, T; Ohtomo, A

    2015-11-06

    Transition metal oxides display various electronic and magnetic phases such as high-temperature superconductivity. Controlling such exotic properties by applying an external field is one of the biggest continuous challenges in condensed matter physics. Here, we demonstrate clear superconductor-insulator transition of LiTi2O4 films induced by Li-ion electrochemical reaction. A compact electrochemical cell of pseudo-Li-ion battery structure is formed with a superconducting LiTi2O4 film as an anode. Li content in the film is controlled by applying a constant redox voltage. An insulating state is achieved by Li-ion intercalation to the superconducting film by applying reduction potential. In contrast, the superconducting state is reproduced by applying oxidation potential to the Li-ion intercalated film. Moreover, superconducting transition temperature is also recovered after a number of cycles of Li-ion electrochemical reactions. This complete reversible transition originates in difference in potentials required for deintercalation of initially contained and electrochemically intercalated Li(+) ions.

  7. Li-ion diffusion in Li4Ti5O12 and LiTi2O4 battery materials detected by muon spin spectroscopy

    NASA Astrophysics Data System (ADS)

    Sugiyama, Jun; Nozaki, Hiroshi; Umegaki, Izumi; Mukai, Kazuhiko; Miwa, Kazutoshi; Shiraki, Susumu; Hitosugi, Taro; Suter, Andreas; Prokscha, Thomas; Salman, Zaher; Lord, James S.; Mânsson, Martin

    2015-07-01

    Lithium diffusion in spinel Li4Ti5O12 and LiTi2O4 compounds for future battery applications has been studied with muon spin relaxation (μ+SR ) . Measurements were performed on both thin-film and powder samples in the temperature range between 25 and 500 K. For Li4Ti5O12 and above about ˜200 K , the field distribution width (Δ ) is found to decrease gradually, while the field fluctuation rate (ν ) increases exponentially with temperature. For LiTi2O4 , on the contrary, the Δ (T ) curve shows a steplike decrease at ˜350 K , around which the ν (T ) curve exhibits a local maximum. These behaviors suggest that Li+ starts to diffuse above around 200 K for both spinels. Assuming a jump diffusion of Li+ at the tetrahedral 8 a site to the vacant octahedral 16 c site, diffusion coefficients of Li+ at 300 K in the film samples are estimated as (3.2 ±0.8 ) ×10-11 cm2/s for Li4Ti5O12 and (3.6 ±1.1 ) ×10-11 cm2/s for LiTi2O4 . Further, some small differences are found in both thermal activation energies and Li-ion diffusion coefficients between the powder and thin-film samples.

  8. Materials Data on LiTi2O4 (SG:10) by Materials Project

    DOE Data Explorer

    Kristin Persson

    2016-02-10

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  9. Thin film hydrous metal oxide catalysts

    DOEpatents

    Dosch, Robert G.; Stephens, Howard P.

    1995-01-01

    Thin film (<100 nm) hydrous metal oxide catalysts are prepared by 1) synthesis of a hydrous metal oxide, 2) deposition of the hydrous metal oxide upon an inert support surface, 3) ion exchange with catalytically active metals, and 4) activating the hydrous metal oxide catalysts.

  10. Thin-Film Solid Oxide Fuel Cells

    NASA Technical Reports Server (NTRS)

    Chen, Xin; Wu, Nai-Juan; Ignatiev, Alex

    2009-01-01

    The development of thin-film solid oxide fuel cells (TFSOFCs) and a method of fabricating them have progressed to the prototype stage. This can result in the reduction of mass, volume, and the cost of materials for a given power level.

  11. Sprayed lanthanum doped zinc oxide thin films

    NASA Astrophysics Data System (ADS)

    Bouznit, Y.; Beggah, Y.; Ynineb, F.

    2012-01-01

    Lanthanum doped zinc oxide thin films were deposited on soda-lime glass substrates using a pneumatic spray pyrolysis technique. The films were prepared using different lanthanum concentrations at optimum deposition parameters. We studied the variations in structural, morphological and optical properties of the samples due to the change of doping concentration in precursor solutions. X-ray diffraction (XRD) patterns show that pure and La-doped ZnO thin films are highly textured along c-axis perpendicular to the surface of the substrate. Scanning electron micrographs show that surface morphology of ZnO films undergoes a significant change according to lanthanum doping. All films exhibit a transmittance higher than 80% in the visible region.

  12. Electrochromism: from oxide thin films to devices

    NASA Astrophysics Data System (ADS)

    Rougier, A.; Danine, A.; Faure, C.; Buffière, S.

    2014-03-01

    In respect of their adaptability and performance, electrochromic devices, ECDs, which are able to change their optical properties under an applied voltage, have received significant attention. Target applications are multifold both in the visible region (automotive sunroofs, smart windows, ophthalmic lenses, and domestic appliances (oven, fridge…)) and in the infrared region (Satellites Thermal Control, IR furtivity). In our group, focusing on oxide thin films grown preferentially at room temperature, optimization of ECDs performances have been achieved by tuning the microstructure, the stoichiometry and the cationic composition of the various layers. Herein, our approach for optimized ECDs is illustrated through the example of WO3 electrochromic layer in the visible and in the IR domain as well as ZnO based transparent conducting oxide layer. Targeting the field of printed electronics, simplification of the device architecture for low power ECDs is also reported.

  13. rf plasma oxidation of Ni thin films sputter deposited to generate thin nickel oxide layers

    SciTech Connect

    Hoey, Megan L.; Carlson, J. B.; Osgood, R. M. III; Kimball, B.; Buchwald, W.

    2010-10-11

    Nickel oxide (NiO) layers were formed on silicon (Si) substrates by plasma oxidation of nickel (Ni) film lines. This ultrathin NiO layer acted as a barrier layer to conduction, and was an integral part of a metal-insulator-metal (MIM) diode, completed by depositing gold (Au) on top of the oxide. The electrical and structural properties of the NiO thin film were examined using resistivity calculations, current-voltage (I-V) measurements and cross-sectional transmission electron microscopy (XTEM) imaging. The flow rate of the oxygen gas, chamber pressure, power, and exposure time and their influence on the characteristics of the NiO thin film were studied.

  14. Review of Zinc Oxide Thin Films

    DTIC Science & Technology

    2014-12-23

    Laboratory Air Force Materiel Command   a. REPORT U   b. ABSTRACT U   c. THIS PAGE U REPORT DOCUMENTATION PAGE Form ApprovedOMB No. 0704-0188 The public...PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ORGANIZATION. 1.  REPORT DATE (DD-MM-YYYY)      18-12-2014 2.  REPORT TYPE      Final Performance 3.  DATES...Standard Form 298 (Rev. 8/98) Prescribed by ANSI Std. Z39.18 1    Review of Zinc Oxide Thin Films   Abstract  The present review paper reports on the

  15. Thin films for micro solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Beckel, D.; Bieberle-Hütter, A.; Harvey, A.; Infortuna, A.; Muecke, U. P.; Prestat, M.; Rupp, J. L. M.; Gauckler, L. J.

    Thin film deposition as applied to micro solid oxide fuel cell (μSOFC) fabrication is an emerging and highly active field of research that is attracting greater attention. This paper reviews thin film (thickness ≤1 μm) deposition techniques and components relevant to SOFCs including current research on nanocrystalline thin film electrolyte and thin-film-based model electrodes. Calculations showing the geometric limits of μSOFCs and first results towards fabrication of μSOFCs are also discussed.

  16. Method of producing solution-derived metal oxide thin films

    DOEpatents

    Boyle, Timothy J.; Ingersoll, David

    2000-01-01

    A method of preparing metal oxide thin films by a solution method. A .beta.-metal .beta.-diketonate or carboxylate compound, where the metal is selected from groups 8, 9, 10, 11, and 12 of the Periodic Table, is solubilized in a strong Lewis base to form a homogeneous solution. This precursor solution forms within minutes and can be deposited on a substrate in a single layer or a multiple layers to form a metal oxide thin film. The substrate with the deposited thin film is heated to change the film from an amorphous phase to a ceramic metal oxide and cooled.

  17. Method of producing solution-derived metal oxide thin films

    SciTech Connect

    Boyle, T.J.; Ingersoll, D.

    2000-07-11

    A method is described for preparing metal oxide thin films by a solution method. A {beta}-metal {beta}-diketonate or carboxylate compound, where the metal is selected from groups 8, 9, 10, 11, and 12 of the Periodic Table, is solubilized in a strong Lewis base to form a homogeneous solution. This precursor solution forms within minutes and can be deposited on a substrate in a single layer or a multiple layers to form a metal oxide thin film. The substrate with the deposited thin film is heated to change the film from an amorphous phase to a ceramic metal oxide and cooled.

  18. Active Oxygen Generator by Silent Discharge and Oxidation Power in Formation of Oxide Thin Films

    NASA Astrophysics Data System (ADS)

    Tanaka, Masaaki; Kawagoe, Yasuyuki; Tsukazaki, Hisashi; Yamanishi, Kenichiro

    We have studied the low pressure silent discharge type active oxygen generator in terms of the application to the formation of oxide thin films. In this paper the oxidation power of active oxygen in the oxide thin film formation is compared with that of oxygen and ozone by forming silicon oxide thin films. It was confirmed that the oxidation power is in turn of active oxygen > ozone > oxygen from the experimental result of the number of x in SiOx thin film. Furthermore we applied active oxygen to the formation of the thin film high temperature super conductor and active oxygen was found to be effective to the formation of the thin film with high performance.

  19. Unidirectional oxide hetero-interface thin-film diode

    SciTech Connect

    Park, Youngmin; Lee, Eungkyu; Lee, Jinwon; Lim, Keon-Hee; Kim, Youn Sang

    2015-10-05

    The unidirectional thin-film diode based on oxide hetero-interface, which is well compatible with conventional thin-film fabrication process, is presented. With the metal anode/electron-transporting oxide (ETO)/electron-injecting oxide (EIO)/metal cathode structure, it exhibits that electrical currents ohmically flow at the ETO/EIO hetero-interfaces for only positive voltages showing current density (J)-rectifying ratio of ∼10{sup 5} at 5 V. The electrical properties (ex, current levels, and working device yields) of the thin-film diode (TFD) are systematically controlled by changing oxide layer thickness. Moreover, we show that the oxide hetero-interface TFD clearly rectifies an AC input within frequency (f) range of 10{sup 2} Hz < f < 10{sup 6} Hz, providing a high feasibility for practical applications.

  20. Structural characterization of impurified zinc oxide thin films

    SciTech Connect

    Trinca, L. M.; Galca, A. C. Stancu, V. Chirila, C. Pintilie, L.

    2014-11-05

    Europium doped zinc oxide (Eu:ZnO) thin films have been obtained by pulsed laser deposition (PLD). 002 textured thin films were achieved on glass and silicon substrates, while hetero-epilayers and homo-epilayers have been attained on single crystal SrTiO{sub 3} and ZnO, respectively. X-ray Diffraction (XRD) was employed to characterize the Eu:ZnO thin films. Extended XRD studies confirmed the different thin film structural properties as function of chosen substrates.

  1. Determination of oxygen diffusion kinetics during thin film ruthenium oxidation

    NASA Astrophysics Data System (ADS)

    Coloma Ribera, R.; van de Kruijs, R. W. E.; Yakshin, A. E.; Bijkerk, F.

    2015-08-01

    In situ X-ray reflectivity was used to reveal oxygen diffusion kinetics for thermal oxidation of polycrystalline ruthenium thin films and accurate determination of activation energies for this process. Diffusion rates in nanometer thin RuO2 films were found to show Arrhenius behaviour. However, a gradual decrease in diffusion rates was observed with oxide growth, with the activation energy increasing from about 2.1 to 2.4 eV. Further exploration of the Arrhenius pre-exponential factor for diffusion process revealed that oxidation of polycrystalline ruthenium joins the class of materials that obey the Meyer-Neldel rule.

  2. Determination of oxygen diffusion kinetics during thin film ruthenium oxidation

    SciTech Connect

    Coloma Ribera, R. Kruijs, R. W. E. van de; Yakshin, A. E.; Bijkerk, F.

    2015-08-07

    In situ X-ray reflectivity was used to reveal oxygen diffusion kinetics for thermal oxidation of polycrystalline ruthenium thin films and accurate determination of activation energies for this process. Diffusion rates in nanometer thin RuO{sub 2} films were found to show Arrhenius behaviour. However, a gradual decrease in diffusion rates was observed with oxide growth, with the activation energy increasing from about 2.1 to 2.4 eV. Further exploration of the Arrhenius pre-exponential factor for diffusion process revealed that oxidation of polycrystalline ruthenium joins the class of materials that obey the Meyer-Neldel rule.

  3. High temperature coefficient of resistance molybdenum oxide and nickel oxide thin films for microbolometer applications

    NASA Astrophysics Data System (ADS)

    Jin, Yao O.; John, David Saint; Podraza, Nikolas J.; Jackson, Thomas N.; Horn, Mark W.

    2015-03-01

    Molybdenum oxide (MoOx) and nickel oxide (NiOx) thin films were deposited by reactive biased target ion beam deposition. MoOx thin film resistivity varied from 3 to 2000 Ω.cm with a temperature coefficient of resistance (TCR) from -1.7% to -3.2%/K, and NiOx thin film resistivity varied from 1 to 300 Ω.cm with a TCR from -2.2% to -3.3%/K, both easily controlled by varying the oxygen partial pressure. Biased target ion beam deposited high TCR MoOx and NiOx thin films are polycrystalline semiconductors and have good stability in air. Compared with commonly used vanadium oxide thin films, MoOx or NiOx thin films offer improved process control for resistive temperature sensors.

  4. Lateral solid-phase epitaxy of oxide thin films on glass substrate seeded with oxide nanosheets.

    PubMed

    Taira, Kenji; Hirose, Yasushi; Nakao, Shoichiro; Yamada, Naoomi; Kogure, Toshihiro; Shibata, Tatsuo; Sasaki, Takayoshi; Hasegawa, Tetsuya

    2014-06-24

    We developed a technique to fabricate oxide thin films with uniaxially controlled crystallographic orientation and lateral size of more than micrometers on amorphous substrates. This technique is lateral solid-phase epitaxy, where epitaxial crystallization of amorphous precursor is seeded with ultrathin oxide nanosheets sparsely (≈10% coverage) deposited on the substrate. Transparent conducting Nb-doped anatase TiO2 thin films were fabricated on glass substrates by this technique. Perfect (001) orientation and large grains with lateral sizes up to 10 μm were confirmed by X-ray diffraction, atomic force microscopy, and electron beam backscattering diffraction measurements. As a consequence of these features, the obtained film exhibited excellent electrical transport properties comparable to those of epitaxial thin films on single-crystalline substrates. This technique is a versatile method for fabricating high-quality oxide thin films other than anatase TiO2 and would increase the possible applications of oxide-based thin film devices.

  5. Characterization of reliability of printed indium tin oxide thin films.

    PubMed

    Hong, Sung-Jei; Kim, Jong-Woong; Jung, Seung-Boo

    2013-11-01

    Recently, decreasing the amount of indium (In) element in the indium tin oxide (ITO) used for transparent conductive oxide (TCO) thin film has become necessary for cost reduction. One possible approach to this problem is using printed ITO thin film instead of sputtered. Previous studies showed potential for printed ITO thin films as the TCO layer. However, nothing has been reported on the reliability of printed ITO thin films. Therefore, in this study, the reliability of printed ITO thin films was characterized. ITO nanoparticle ink was fabricated and printed onto a glass substrate followed by heating at 400 degrees C. After measurement of the initial values of sheet resistance and optical transmittance of the printed ITO thin films, their reliabilities were characterized with an isothermal-isohumidity test for 500 hours at 85 degrees C and 85% RH, a thermal shock test for 1,000 cycles between 125 degrees C and -40 degrees C, and a high temperature storage test for 500 hours at 125 degrees C. The same properties were investigated after the tests. Printed ITO thin films showed stable properties despite extremely thermal and humid conditions. Sheet resistances of the printed ITO thin films changed slightly from 435 omega/square to 735 omega/square 507 omega/square and 442 omega/square after the tests, respectively. Optical transmittances of the printed ITO thin films were slightly changed from 84.74% to 81.86%, 88.03% and 88.26% after the tests, respectively. These test results suggest the stability of printed ITO thin film despite extreme environments.

  6. Review of solution-processed oxide thin-film transistors

    NASA Astrophysics Data System (ADS)

    Kim, Si Joon; Yoon, Seokhyun; Kim, Hyun Jae

    2014-02-01

    In this review, we summarize solution-processed oxide thin-film transistors (TFTs) researches based on our fulfillments. We describe the fundamental studies of precursor composition effects at the beginning in order to figure out the role of each component in oxide semiconductors, and then present low temperature process for the adoption of flexible devices. Moreover, channel engineering for high performance and reliability of solution-processed oxide TFTs and various coating methods: spin-coating, inkjet printing, and gravure printing are also presented. The last topic of this review is an overview of multi-functional solution-processed oxide TFTs for various applications such as photodetector, biosensor, and memory.

  7. Multiferroic oxide thin films and heterostructures

    NASA Astrophysics Data System (ADS)

    Lu, Chengliang; Hu, Weijin; Tian, Yufeng; Wu, Tom

    2015-06-01

    Multiferroic materials promise a tantalizing perspective of novel applications in next-generation electronic, memory, and energy harvesting technologies, and at the same time they also represent a grand scientific challenge on understanding complex solid state systems with strong correlations between multiple degrees of freedom. In this review, we highlight the opportunities and obstacles in growing multiferroic thin films with chemical and structural integrity and integrating them in functional devices. Besides the magnetoelectric effect, multiferroics exhibit excellent resistant switching and photovoltaic properties, and there are plenty opportunities for them to integrate with other ferromagnetic and superconducting materials. The challenges include, but not limited, defect-related leakage in thin films, weak magnetism, and poor control on interface coupling. Although our focuses are Bi-based perovskites and rare earth manganites, the insights are also applicable to other multiferroic materials. We will also review some examples of multiferroic applications in spintronics, memory, and photovoltaic devices.

  8. Multiferroic oxide thin films and heterostructures

    SciTech Connect

    Lu, Chengliang E-mail: Tao.Wu@kaust.edu.sa; Hu, Weijin; Wu, Tom E-mail: Tao.Wu@kaust.edu.sa; Tian, Yufeng

    2015-06-15

    Multiferroic materials promise a tantalizing perspective of novel applications in next-generation electronic, memory, and energy harvesting technologies, and at the same time they also represent a grand scientific challenge on understanding complex solid state systems with strong correlations between multiple degrees of freedom. In this review, we highlight the opportunities and obstacles in growing multiferroic thin films with chemical and structural integrity and integrating them in functional devices. Besides the magnetoelectric effect, multiferroics exhibit excellent resistant switching and photovoltaic properties, and there are plenty opportunities for them to integrate with other ferromagnetic and superconducting materials. The challenges include, but not limited, defect-related leakage in thin films, weak magnetism, and poor control on interface coupling. Although our focuses are Bi-based perovskites and rare earth manganites, the insights are also applicable to other multiferroic materials. We will also review some examples of multiferroic applications in spintronics, memory, and photovoltaic devices.

  9. 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.

  10. Zinc Oxide Thin-Film Transistors

    NASA Astrophysics Data System (ADS)

    Fortunato, E.; Barquinha, P.; Pimentel, A.; Gonçalves, A.; Marques, A.; Pereira, L.; Martins, R.

    ZnO thin film transistors (ZnO-TFT) have been fabricated by rf magnetron sputtering at room temperature with a bottom-gate configuration. The ZnO-TFT operates in the enhancement mode with a threshold voltage of 21 V, a field effect mobility of 20 cm2/Vs, a gate voltage swing of 1.24 V/decade and an on/off ratio of 2×105. The ZnO-TFT present an average optical transmission (including the glass substrate) of 80 % in the visible part of the spectrum. The combination of transparency, high channel mobility and room temperature processing makes the ZnO-TFT a very promising low cost optoelectronic device for the next generation of invisible and flexible electronics. Moreover, the processing technology used to fabricate this device is relatively simple and it is compatible with inexpensive plastic/flexible substrate technology.

  11. Ln polyoxocations: yttrium oxide solution speciation & solution deposited thin films.

    PubMed

    Marsh, David A; Goberna-Ferrón, Sara; Baumeister, Mary K; Zakharov, Lev N; Nyman, May; Johnson, Darren W

    2017-01-17

    Rare earth oxide materials, including thin film coatings, are critically important in magnetic, luminescent and microelectric devices, and few substitutes have been discovered with comparable performance. Thin film coatings from solution are almost unknown for rare earth oxides, likely due to their high activity towards hydrolysis which yields poor quality thin films. The hexamer [Ln6(O)(OH)8(H2O)12(NO3)6](2+) is a rare example of a metal-oxo cluster isolated and stabilized without additional supporting organic ligands. Herein we report a new method for both the preparation and stabilization in non-aqueous media, which makes these clusters valuable precursors for solution-processed thin films. Solution characterization (NMR, small-angle X-ray scattering and Raman spectroscopy) in wet organic solvents indicated that the clusters evolve via a fragmentation and reaggregation process. This is especially true for hexamers of the smaller Ln(3+)-ions: the higher charge density yields higher hydration rates. This process produced an entirely new hexadecameric cluster formulated Y16O3(OH)24(NO3)18(OSMe2)16(OCMe2)2(H2O)4. The new structure represents an intermediate hydrolysis product on the pathway from hexanuclear clusters to metal oxyhydroxide bulk solid. DMSO solvent ligands displace aqua ligands on the cluster and likely explain the additional stability observed for these clusters in organic solvents. The enhanced cluster stability in DMF and DMSO also enables solution-processing methods to create high quality thin films.

  12. Altering properties of cerium oxide thin films by Rh doping

    SciTech Connect

    Ševčíková, Klára; Nehasil, Václav; Vorokhta, Mykhailo; Haviar, Stanislav; Matolín, Vladimír; and others

    2015-07-15

    Highlights: • Thin films of ceria doped by rhodium deposited by RF magnetron sputtering. • Concentration of rhodium has great impact on properties of Rh–CeO{sub x} thin films. • Intensive oxygen migration in films with low concentration of rhodium. • Oxygen migration suppressed in films with high amount of Rh dopants. - Abstract: Ceria containing highly dispersed ions of rhodium is a promising material for catalytic applications. The Rh–CeO{sub x} thin films with different concentrations of rhodium were deposited by RF magnetron sputtering and were studied by soft and hard X-ray photoelectron spectroscopies, Temperature programmed reaction and X-ray powder diffraction techniques. The sputtered films consist of rhodium–cerium mixed oxide where cerium exhibits a mixed valency of Ce{sup 4+} and Ce{sup 3+} and rhodium occurs in two oxidation states, Rh{sup 3+} and Rh{sup n+}. We show that the concentration of rhodium has a great influence on the chemical composition, structure and reducibility of the Rh–CeO{sub x} thin films. The films with low concentrations of rhodium are polycrystalline, while the films with higher amount of Rh dopants are amorphous. The morphology of the films strongly influences the mobility of oxygen in the material. Therefore, varying the concentration of rhodium in Rh–CeO{sub x} thin films leads to preparing materials with different properties.

  13. Thin film zinc oxide deposited by CVD and PVD

    NASA Astrophysics Data System (ADS)

    Hamelmann, Frank U.

    2016-10-01

    Zinc oxide is known as a mineral since 1810, but it came to scientific interest after its optoelectronic properties found to be tuneable by p-type doping. Since the late 1980’s the number of publications increased exponentially. All thin film deposition technologies, including sol-gel and spray pyrolysis, are able to produce ZnO films. However, for outstanding properties and specific doping, only chemical vapor deposition and physical vapor deposition have shown so far satisfying results in terms of high conductivity and high transparency. In this paper the different possibilities for doping will be discussed, some important applications of doped ZnO thin films will be presented. The deposition technologies used for industrial applications are shown in this paper. Especially sputtering of aluminium doped Zinc Oxide (ZnO:Al or AZO) and LPCVD of boron doped Zinc Oxide (ZnO:B or BZO) are used for the commercial production of transparent conductive oxide films on glass used for thin film photovoltaic cells. For this special application the typical process development for large area deposition is presented, with the important trade-off between optical properties (transparency and ability for light scattering) and electrical properties (conductivity). Also, the long term stability of doped ZnO films is important for applications, humidity in the ambient is often the reason for degradation of the films. The differences between the mentioned materials are presented.

  14. Reactive pulsed magnetron-sputtered tantalum oxide thin films

    NASA Astrophysics Data System (ADS)

    Nielsen, Matthew Christian

    Current high speed, advanced packaging applications require the use of integrated capacitors. Tantalum oxide is one material currently being considered for use in the capacitors; however, the deposition technique used to make the thin film dielectric can alter its performance. Pulsed magnetron reactive sputtering was investigated in this thesis as it offers a robust, clean, and low temperature deposition alternative. This is a new deposition technique created to control the negative effects of target poisoning; however, to understand the relationships between the deposition variables and the resultant film properties a thorough investigation is needed. The instantaneous voltage at the target was captured using a high speed digital oscilloscope. Three target oxidation states were imaged and identified to be that of the metallic and oxidized states with an abrupt transition region separating the two. Using high resolution X-ray photoelectron spectroscopy the bonding present in the deposited films was correlated to the oxidation state of the target. While operating the target in the metallic mode, a mix of oxidized, sub-oxide and metallic states were discovered. Alternatively, the bonding present in the films deposited when the target was in the oxidized state were that of fully oxidized tantalum pentoxide. The films deposited above the critical partial pressure demonstrated excellent leakage current densities. The exact magnitude of the leakage current density inversely scaled to the relative amount of oxygen included into the sputtering atmosphere. Detailed plot analysis showed that there were two different conduction mechanisms controlling the current flow in the capacitors. High frequency test vehicles were measured up to 10 GHz in order to determine the frequency response of the dielectric material. A circuit equivalent model describing the testing system and samples was created and utilized to fit the collected data. Overall, the technique of pulsed magnetron

  15. Nitrogen doped zinc oxide thin film

    SciTech Connect

    Li, Sonny Xiao-zhe

    2003-01-01

    To summarize, polycrystalline ZnO thin films were grown by reactive sputtering. Nitrogen was introduced into the films by reactive sputtering in an NO2 plasma or by N+ implantation. All ZnO films grown show n-type conductivity. In unintentionally doped ZnO films, the n-type conductivities are attributed to Zni, a native shallow donor. In NO2-grown ZnO films, the n-type conductivity is attributed to (N2)O, a shallow double donor. In NO2-grown ZnO films, 0.3 atomic % nitrogen was found to exist in the form of N2O and N2. Upon annealing, N2O decomposes into N2 and O2. In furnace-annealed samples N2 redistributes diffusively and forms gaseous N2 bubbles in the films. Unintentionally doped ZnO films were grown at different oxygen partial pressures. Zni was found to form even at oxygen-rich condition and led to n-type conductivity. N+ implantation into unintentionally doped ZnO film deteriorates the crystallinity and optical properties and leads to higher electron concentration. The free electrons in the implanted films are attributed to the defects introduced by implantation and formation of (N2)O and Zni. Although today there is still no reliable means to produce good quality, stable p-type ZnO material, ZnO remains an attractive material with potential for high performance short wavelength optoelectronic devices. One may argue that gallium nitride was in a similar situation a decade ago. Although we did not obtain any p-type conductivity, we hope our research will provide a valuable reference to the literature.

  16. Dysprosium oxide and dysprosium-oxide-doped titanium oxide thin films grown by atomic layer deposition

    SciTech Connect

    Tamm, Aile Kozlova, Jekaterina; Aarik, Lauri; Aarik, Jaan; Kukli, Kaupo; Link, Joosep; Stern, Raivo

    2015-01-15

    Dysprosium oxide and dysprosium-oxide-doped titanium oxide thin films were grown by atomic layer deposition on silicon substrates. For depositing dysprosium and titanium oxides Dy(thd){sub 3}-O{sub 3} and TiCl{sub 4}-O{sub 3} were used as precursors combinations. Appropriate parameters for Dy(thd){sub 3}-O{sub 3} growth process were obtained by using a quartz crystal microbalance system. The Dy{sub 2}O{sub 3} films were deposited on planar substrates and on three-dimensional substrates with aspect ratio 1:20. The Dy/Ti ratio of Dy{sub 2}O{sub 3}-doped TiO{sub 2} films deposited on a planar silicon substrate ranged from 0.04 to 0.06. Magnetometry studies revealed that saturation of magnetization could not be observed in planar Dy{sub 2}O{sub 3} films, but it was observable in Dy{sub 2}O{sub 3} films on 3D substrates and in doped TiO{sub 2} films with a Dy/Ti atomic ratio of 0.06. The latter films exhibited saturation magnetization 10{sup −6} A cm{sup 2} and coercivity 11 kA/m at room temperature.

  17. Anisotropic thermal conductivity of thin polycrystalline oxide samples

    SciTech Connect

    Tiwari, A.; Boussois, K.; Nait-Ali, B.; Smith, D. S.; Blanchart, P.

    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 such anisotropic thin samples in literature, this technique offers a useful variant to existing techniques.

  18. Review paper: Transparent amorphous oxide semiconductor thin film transistor

    NASA Astrophysics Data System (ADS)

    Kwon, Jang-Yeon; Lee, Do-Joong; Kim, Ki-Bum

    2011-03-01

    Thin film transistors (TFTs) with oxide semiconductors have drawn great attention in the last few years, especially for large area electronic applications, such as high resolution active matrix liquid crystal displays (AMLCDs) and active matrix organic light-emitting diodes (AMOLEDs), because of their high electron mobility and spatial uniform property. This paper reviews and summarizes recent emerging reports that include potential applications, oxide semiconductor materials, and the impact of the fabrication process on electrical performance. We also address the stability behavior of such devices under bias/illumination stress and critical factors related to reliability, such as the gate insulator, the ambient and the device structure.

  19. Growth control of the oxidation state in vanadium oxide thin films

    SciTech Connect

    Lee, Shinbuhm; Meyer, Tricia L.; Lee, Ho Nyung; Park, Sungkyun; Egami, Takeshi

    2014-12-01

    Precise control of the chemical valence or oxidation state of vanadium in vanadium oxide thin films is highly desirable for not only fundamental research but also technological applications that utilize the subtle change in the physical properties originating from the metal-insulator transition (MIT) near room temperature. However, due to the multivalent nature of vanadium and the lack of a good understanding on growth control of the oxidation state, stabilization of phase pure vanadium oxides with a single oxidation state is extremely challenging. Here, we systematically varied the growth conditions to clearly map out the growth window for preparing phase pure epitaxial vanadium oxides by pulsed laser deposition for providing a guideline to grow high quality thin films with well-defined oxidation states of V{sub 2}{sup +3}O{sub 3}, V{sup +4}O{sub 2}, and V{sub 2}{sup +5}O{sub 5}. A well pronounced MIT was only observed in VO{sub 2} films grown in a very narrow range of oxygen partial pressure P(O{sub 2}). The films grown either in lower (<10 mTorr) or higher P(O{sub 2}) (>25 mTorr) result in V{sub 2}O{sub 3} and V{sub 2}O{sub 5} phases, respectively, thereby suppressing the MIT for both cases. We have also found that the resistivity ratio before and after the MIT of VO{sub 2} thin films can be further enhanced by one order of magnitude when the films are further oxidized by post-annealing at a well-controlled oxidizing ambient. This result indicates that stabilizing vanadium into a single valence state has to compromise with insufficient oxidation of an as grown thin film and, thereby, a subsequent oxidation is required for an improved MIT behavior.

  20. Growth control of the oxidation state in vanadium oxide thin films

    SciTech Connect

    Lee, Shinbuhm; Meyer, Tricia L.; Park, Sungkyun; Lee, Ho Nyung

    2014-12-05

    Precise control of the chemical valence or oxidation state of vanadium in vanadium oxide thin films is highly desirable for not only fundamental research, but also technological applications that utilize the subtle change in the physical properties originating from the metalinsulator transition (MIT) near room temperature. However, due to the multivalent nature of vanadium and the lack of a good understanding on growth control of the oxidation state, stabilization of phase pure vanadium oxides with a single oxidation state is extremely challenging. Here, we systematically varied the growth conditions to clearly map out the growth window for preparing phase pure epitaxial vanadium oxides by pulsed laser deposition for providing a guideline to grow high quality thin films with well-defined oxidation states of V₂⁺²O₃, V⁺⁴O₂, and V₂⁺⁵O₅. A well pronounced MIT was only observed in VO₂ films grown in a very narrow range of oxygen partial pressure P(O₂). The films grown either in lower (< 10 mTorr) or higher P(O₂) (> 25 mTorr) result in V₂O₃ and V₂O₅ phases, respectively, thereby suppressing the MIT for both cases. We have also found that the resistivity ratio before and after the MIT of VO₂ thin films can be further enhanced by one order of magnitude when the films are further oxidized by post-annealing at a well-controlled oxidizing ambient. This result indicates that stabilizing vanadium into a single valence state has to compromise with insufficient oxidation of an as grown thin film and, thereby, a subsequent oxidation is required for an 3 improved MIT behavior.

  1. Growth control of the oxidation state in vanadium oxide thin films

    NASA Astrophysics Data System (ADS)

    Lee, Shinbuhm; Meyer, Tricia L.; Park, Sungkyun; Egami, Takeshi; Lee, Ho Nyung

    2014-12-01

    Precise control of the chemical valence or oxidation state of vanadium in vanadium oxide thin films is highly desirable for not only fundamental research but also technological applications that utilize the subtle change in the physical properties originating from the metal-insulator transition (MIT) near room temperature. However, due to the multivalent nature of vanadium and the lack of a good understanding on growth control of the oxidation state, stabilization of phase pure vanadium oxides with a single oxidation state is extremely challenging. Here, we systematically varied the growth conditions to clearly map out the growth window for preparing phase pure epitaxial vanadium oxides by pulsed laser deposition for providing a guideline to grow high quality thin films with well-defined oxidation states of V2 + 3 O 3 , V + 4 O 2 , and V2 + 5 O 5 . A well pronounced MIT was only observed in VO2 films grown in a very narrow range of oxygen partial pressure P(O2). The films grown either in lower (<10 mTorr) or higher P(O2) (>25 mTorr) result in V2O3 and V2O5 phases, respectively, thereby suppressing the MIT for both cases. We have also found that the resistivity ratio before and after the MIT of VO2 thin films can be further enhanced by one order of magnitude when the films are further oxidized by post-annealing at a well-controlled oxidizing ambient. This result indicates that stabilizing vanadium into a single valence state has to compromise with insufficient oxidation of an as grown thin film and, thereby, a subsequent oxidation is required for an improved MIT behavior.

  2. Growth control of the oxidation state in vanadium oxide thin films

    DOE PAGES

    Lee, Shinbuhm; Meyer, Tricia L.; Park, Sungkyun; ...

    2014-12-05

    Precise control of the chemical valence or oxidation state of vanadium in vanadium oxide thin films is highly desirable for not only fundamental research, but also technological applications that utilize the subtle change in the physical properties originating from the metalinsulator transition (MIT) near room temperature. However, due to the multivalent nature of vanadium and the lack of a good understanding on growth control of the oxidation state, stabilization of phase pure vanadium oxides with a single oxidation state is extremely challenging. Here, we systematically varied the growth conditions to clearly map out the growth window for preparing phase puremore » epitaxial vanadium oxides by pulsed laser deposition for providing a guideline to grow high quality thin films with well-defined oxidation states of V₂⁺²O₃, V⁺⁴O₂, and V₂⁺⁵O₅. A well pronounced MIT was only observed in VO₂ films grown in a very narrow range of oxygen partial pressure P(O₂). The films grown either in lower (< 10 mTorr) or higher P(O₂) (> 25 mTorr) result in V₂O₃ and V₂O₅ phases, respectively, thereby suppressing the MIT for both cases. We have also found that the resistivity ratio before and after the MIT of VO₂ thin films can be further enhanced by one order of magnitude when the films are further oxidized by post-annealing at a well-controlled oxidizing ambient. This result indicates that stabilizing vanadium into a single valence state has to compromise with insufficient oxidation of an as grown thin film and, thereby, a subsequent oxidation is required for an 3 improved MIT behavior.« less

  3. Oxidation of Light Alkanes Using Photocatalytic Thin Films

    DTIC Science & Technology

    2006-01-01

    Transformation of the TiO2 from anatase to the rutile crystalline phase was also delayed in the mixed oxides leading to a photocatalyst with higher...at room temperature using a WO3 / TiO2 binary system compared to plain TiO2 . Improvements in the photocatalytic activity were attributed to more... TiO2 thin film photocatalyst . It was observed that efficient reactor design requires optimization of catalyst packing to minimize bypass of the

  4. Electrical properties of vanadium tungsten oxide thin films

    SciTech Connect

    Nam, Sung-Pill; Noh, Hyun-Ji; Lee, Sung-Gap; Lee, Young-Hie

    2010-03-15

    The vanadium tungsten oxide thin films deposited on Pt/Ti/SiO{sub 2}/Si substrates by RF sputtering exhibited good TCR and dielectric properties. The dependence of crystallization and electrical properties are related to the grain size of V{sub 1.85}W{sub 0.15}O{sub 5} thin films with different annealing temperatures. It was found that the dielectric properties and TCR properties of V{sub 1.85}W{sub 0.15}O{sub 5} thin films were strongly dependent upon the annealing temperature. The dielectric constants of the V{sub 1.85}W{sub 0.15}O{sub 5} thin films annealed at 400 {sup o}C were 44, with a dielectric loss of 0.83%. The TCR values of the V{sub 1.85}W{sub 0.15}O{sub 5} thin films annealed at 400 {sup o}C were about -3.45%/K.

  5. Nanostructured thin solid oxide fuel cells with high power density.

    PubMed

    Ignatiev, Alex; Chen, Xin; Wu, Naijuan; Lu, Zigui; Smith, Laverne

    2008-10-28

    Nanostructured thin film solid oxide fuel cells (SOFC) have been developed for reduced temperature operation, with high power density, and to be self reforming. A thin film electrolyte (1-2 microm thickness), e.g., yttria-stabilized zirconia (YSZ), is deposited on a nickel foil substrate. The electrolyte thin film is polycrystalline when deposited on a polycrystalline nickel foil substrate, and is (100) textured when deposited on an atomically textured nickel foil substrate. The Ni foil substrate is then converted into a porous SOFC anode by photolithographic patterning and etching to develop porosity. A composite La(0.5)Sr(0.5)CoO(3) cathode is then deposited on the thin film electrolyte. The resultant thin film hetero structure fuel cells have operated at a significantly reduced temperature: as low as 470 degrees C, with a maximum power density of 140 mW cm(-2) at 575 degrees C, and an efficiency of >50%. This drastic reduction in operating temperature for an SOFC now also allows for the use of hydrocarbon fuels without the need for a separate reformer as the nickel anode effectively dissociates hydrocarbons within this temperature range. These nanostructured fuel cells show excellent potential for high power density, small volume, high efficiency fuel cells for power generation applications.

  6. Oxidation Temperature Effects on ZnO Thin Films Prepared from Zn Thin Films on Quartz Substrates.

    PubMed

    Park, Seonhee; Kim, Younggyu; Leem, Jae-Young

    2015-11-01

    We investigated the structural and optical properties of the ZnO thin films formed by oxidation of Zn thin films. Zn thin films were deposited by thermal evaporation and were then annealed from 300 to 800 degrees C to prepare ZnO thin films. We found that ZnO thin films were formed by thermal oxidation of Zn thin films at oxidation temperatures over 400 degrees C. The grain size of ZnO thin films increased with the oxidation temperature and the highest ZnO (002) intensity was obtained at 600 degrees C. In the PL spectra, the intensity of the near-band-edge peak increased with the oxidation temperatures until 400 degrees C. However, these values gradually decreased with a further increase in the oxidation temperatures over 400 degrees C. The transmittance of the ZnO thin films was more than 90% for the visible wavelength region, and the optical band gap was red-shifted with increase in the oxidation temperature.

  7. The synthesis and characterization of multifunctional oxide thin films

    NASA Astrophysics Data System (ADS)

    Kharel, Parashu Ram

    2008-10-01

    Multifunctional materials offer a number of very interesting properties for developing new generation novel devices. Motivated by this fact, we concentrated our research efforts on investigating two different class of multifunctional materials namely: Diluted Magnetic Semiconducting Oxides (DMSO) and Multiferroic Oxides. The primary goal of this study was to determine how to resolve the controversy concerning the origin of room temperature ferromagnetic order in DMSO and to demonstrate the theoretically predicted coupling between ferroelectric and magnetic order parameters in multiferroic oxides. We chose several materials of current interest such as TiO2, ZnOand In2O3 (DMSO) and Ni3V2O8 and BiFeO 3 (multiferroic oxides) as the experimental specimens. We synthesized thin film samples of these materials using metal organic decomposition by spin coating and RF magnetron sputtering techniques. We succeeded in growing single phase polycrystalline thin films using both of the techniques with the sputter deposited samples showing highly preferred orientations. We did not observe any secondary phases and accidental impurities leading to robust ferromagnetic order in our samples within the detection limit of XRD, Raman spectroscopy and TEM. We have demonstrated that the lattice defects such as oxygen vacancies and cation vacancies play crucial role in the development of ferromagnetic order in DMSO materials. Based on the investigation carried out on TiO 2, ZnO and In2O3, we conclude that ferromagnetism can be developed in oxygen deficient DMSO thin films without the subbstitution of any external magnetic impurities but the incorporation of magnetic impurities may help in stabilizing the observed ferromagnetic order. Most importantly, we demonstrated with the direct measurement of spin polarization in In 2O3 and Cr doped In2O3 thin films that the charge carriers responsible for the ferromagnetic order are spin polarized. We have successfully demonstrated that the low

  8. Thin-film transistors with a graphene oxide nanocomposite channel.

    PubMed

    Jilani, S Mahaboob; Gamot, Tanesh D; Banerji, P

    2012-12-04

    Graphene oxide (GO) and graphene oxide-zinc oxide nanocomposites (GO-ZnO) were used as channel materials on SiO(2)/Si to fabricate thin-film transistors (TFT) with an aluminum source and drain. Pure GO-based TFT showed poor field-effect characteristics. However, GO-ZnO-nanocomposite-based TFT showed better field-effect performance because of the anchoring of ZnO nanostructures in the GO matrix, which causes a partial reduction in GO as is found from X-ray photoelectron spectroscopic data. The field-effect mobility of charge carriers at a drain voltage of 1 V was found to be 1.94 cm(2)/(V s). The transport of charge carriers in GO-ZnO was explained by a fluctuation-induced tunneling mechanism.

  9. High angular sensitivity thin film tin oxide sensor

    NASA Astrophysics Data System (ADS)

    Kaur, Davinder; Madaan, Divya; Sharma, V. K.; Kapoor, A.

    2016-05-01

    We present theoretical anlaysis of a thin film SnO2 (Tin Oxide) sensor for the measurement of variation in the refractive index of the bulk media. It is based on lossy mode resonance between the absorbing thin film lossy modes and the evanescent wave. Also the addition of low index dielectric matching layer between the prism and the lossy waveguiding layer future increase the angular sensitivity and produce an efficient refractive index sensor. The angular interrogation is done and obtained sensitivity is 110 degree/RIU. Theoretical analysis of the proposed sensor based on Fresnel reflection coefficients is presented. This enhanced sensitivity will further improve the monitoring of biomolecular interactions and the higher sensitivity of the proposed configurations makes it to be a much better option to be employed for biosensing applications.

  10. Work function recovery of air exposed molybdenum oxide thin films

    NASA Astrophysics Data System (ADS)

    Irfan, Irfan; James Turinske, Alexander; Bao, Zhenan; Gao, Yongli

    2012-08-01

    We report substantial work function (WF) recovery of air exposed molybdenum oxide thin films with vacuum annealing. We observed a sharp reduction in the MoOx WF (from 6.8 eV to 5.6 eV) as well as a very thin layer of oxygen rich adsorbate on the MoOx film after an hour of air exposure. The WF of the exposed MoOx film started to gradually recover with increasing annealing temperature in vacuum, and the saturation in the WF recovery was observed at 450 °C with WF ˜6.4 eV. We further studied the interface formation between the annealed MoOx and copper phthalocyanine (CuPc). The highest occupied molecular orbital (HOMO) level of CuPc was observed to be almost pinned to the Fermi level, strongly suggesting the possibility of efficient hole injection with the vacuum annealed MoOx film.

  11. Luminescent sulfides and solution-deposited oxide thin films

    NASA Astrophysics Data System (ADS)

    Anderson, Jeremy T.

    Solid state luminescent sulfides are prepared as powders in order to elucidate the relationship between structure and light emission. While the sulfides studied in this dissertation are known phosphors, materials are investigated in a variety of new ways. Elementary properties and structures of MgS are reviewed, and preparation of MgS is described with sufficient detail that it may be reproduced in laboratories worldwide. Luminescence of MgS:Eu is evaluated, primarily by interpretation of published work. Solid pellets of MgS:Eu are created for the purpose of depositing thin-film layers by physical vapor deposition, and incorporating the phosphor layer within ACTFEL structures. Fabricated devices are found to exhibit bright ACTFEL luminescence--the brightest known for MgS. Similarly, MgS films are doped with a variety of lanthanide atoms to investigate the hot-electron distribution in MgS layers during device operation. The system BaGa2S4--SrGa 2S4 is evaluated for mutual solid phase solubility. Addition of Eu2+ causes each of these phases to photoluminescence. The emission energies (and therefore colors) are adjusted according to composition. Thin-film oxides are deposited from solution sources. Solution-deposited ZnO serves as the semiconductor layer in transparent thin-film transistor devices. A new class of dielectric material is also developed by solution methods. HafSOx and ZircSOx films, and derivative compositions, are evaluated in simple capacitor structures and demonstrated in functioning transistor devices. High-resolution nanolaminate structures are also constructed from this class of materials. From the knowledge and experience of developing oxide thin-films, more general chemical strategies are expressed.

  12. Nanocolumnar Crystalline Vanadium Oxide-Molybdenum Oxide Antireflective Smart Thin Films with Superior Nanomechanical Properties

    NASA Astrophysics Data System (ADS)

    Dey, Arjun; Nayak, Manish Kumar; Esther, A. Carmel Mary; Pradeepkumar, Maurya Sandeep; Porwal, Deeksha; Gupta, A. K.; Bera, Parthasarathi; Barshilia, Harish C.; Mukhopadhyay, Anoop Kumar; Pandey, Ajoy Kumar; Khan, Kallol; Bhattacharya, Manjima; Kumar, D. Raghavendra; Sridhara, N.; Sharma, Anand Kumar

    2016-11-01

    Vanadium oxide-molybdenum oxide (VO-MO) thin (21–475 nm) films were grown on quartz and silicon substrates by pulsed RF magnetron sputtering technique by altering the RF power from 100 to 600 W. Crystalline VO-MO thin films showed the mixed phases of vanadium oxides e.g., V2O5, V2O3 and VO2 along with MoO3. Reversible or smart transition was found to occur just above the room temperature i.e., at ~45–50 °C. The VO-MO films deposited on quartz showed a gradual decrease in transmittance with increase in film thickness. But, the VO-MO films on silicon exhibited reflectance that was significantly lower than that of the substrate. Further, the effect of low temperature (i.e., 100 °C) vacuum (10‑5 mbar) annealing on optical properties e.g., solar absorptance, transmittance and reflectance as well as the optical constants e.g., optical band gap, refractive index and extinction coefficient were studied. Sheet resistance, oxidation state and nanomechanical properties e.g., nanohardness and elastic modulus of the VO-MO thin films were also investigated in as-deposited condition as well as after the vacuum annealing treatment. Finally, the combination of the nanoindentation technique and the finite element modeling (FEM) was employed to investigate yield stress and von Mises stress distribution of the VO-MO thin films.

  13. Nanocolumnar Crystalline Vanadium Oxide-Molybdenum Oxide Antireflective Smart Thin Films with Superior Nanomechanical Properties.

    PubMed

    Dey, Arjun; Nayak, Manish Kumar; Esther, A Carmel Mary; Pradeepkumar, Maurya Sandeep; Porwal, Deeksha; Gupta, A K; Bera, Parthasarathi; Barshilia, Harish C; Mukhopadhyay, Anoop Kumar; Pandey, Ajoy Kumar; Khan, Kallol; Bhattacharya, Manjima; Kumar, D Raghavendra; Sridhara, N; Sharma, Anand Kumar

    2016-11-17

    Vanadium oxide-molybdenum oxide (VO-MO) thin (21-475 nm) films were grown on quartz and silicon substrates by pulsed RF magnetron sputtering technique by altering the RF power from 100 to 600 W. Crystalline VO-MO thin films showed the mixed phases of vanadium oxides e.g., V2O5, V2O3 and VO2 along with MoO3. Reversible or smart transition was found to occur just above the room temperature i.e., at ~45-50 °C. The VO-MO films deposited on quartz showed a gradual decrease in transmittance with increase in film thickness. But, the VO-MO films on silicon exhibited reflectance that was significantly lower than that of the substrate. Further, the effect of low temperature (i.e., 100 °C) vacuum (10(-5) mbar) annealing on optical properties e.g., solar absorptance, transmittance and reflectance as well as the optical constants e.g., optical band gap, refractive index and extinction coefficient were studied. Sheet resistance, oxidation state and nanomechanical properties e.g., nanohardness and elastic modulus of the VO-MO thin films were also investigated in as-deposited condition as well as after the vacuum annealing treatment. Finally, the combination of the nanoindentation technique and the finite element modeling (FEM) was employed to investigate yield stress and von Mises stress distribution of the VO-MO thin films.

  14. Isothermal thermogravimetric analysis of soybean oil oxidation correlated to thin film micro-oxidation test methods

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A method of correlation between the Thin Film Micro-Oxidation (TFMO) test with isothermal thermogravimetric analysis is reported utilizing a soybean oil system. Utilizing a kinetic model, pseudo-rate constants and “activation energy” can be calculated from weight loss data. This model accounts for o...

  15. Nanocolumnar Crystalline Vanadium Oxide-Molybdenum Oxide Antireflective Smart Thin Films with Superior Nanomechanical Properties

    PubMed Central

    Dey, Arjun; Nayak, Manish Kumar; Esther, A. Carmel Mary; Pradeepkumar, Maurya Sandeep; Porwal, Deeksha; Gupta, A. K.; Bera, Parthasarathi; Barshilia, Harish C.; Mukhopadhyay, Anoop Kumar; Pandey, Ajoy Kumar; Khan, Kallol; Bhattacharya, Manjima; Kumar, D. Raghavendra; Sridhara, N.; Sharma, Anand Kumar

    2016-01-01

    Vanadium oxide-molybdenum oxide (VO-MO) thin (21–475 nm) films were grown on quartz and silicon substrates by pulsed RF magnetron sputtering technique by altering the RF power from 100 to 600 W. Crystalline VO-MO thin films showed the mixed phases of vanadium oxides e.g., V2O5, V2O3 and VO2 along with MoO3. Reversible or smart transition was found to occur just above the room temperature i.e., at ~45–50 °C. The VO-MO films deposited on quartz showed a gradual decrease in transmittance with increase in film thickness. But, the VO-MO films on silicon exhibited reflectance that was significantly lower than that of the substrate. Further, the effect of low temperature (i.e., 100 °C) vacuum (10−5 mbar) annealing on optical properties e.g., solar absorptance, transmittance and reflectance as well as the optical constants e.g., optical band gap, refractive index and extinction coefficient were studied. Sheet resistance, oxidation state and nanomechanical properties e.g., nanohardness and elastic modulus of the VO-MO thin films were also investigated in as-deposited condition as well as after the vacuum annealing treatment. Finally, the combination of the nanoindentation technique and the finite element modeling (FEM) was employed to investigate yield stress and von Mises stress distribution of the VO-MO thin films. PMID:27853234

  16. Cobalt vanadium oxide thin nanoplates: primary electrochemical capacitor application

    PubMed Central

    Zhang, Youjuan; Liu, Yuanying; Chen, Jing; Guo, Qifei; Wang, Ting; Pang, Huan

    2014-01-01

    Co3V2O8 thin nanoplates are firstly described as a kind of electrode material for supercapacitors. More importantly, from electrochemical measurements, the obtained Co3V2O8 nanoplate electrode shows a good specific capacitance (0.5 A g−1, 739 F g−1) and cycling stability (704 F g−1 retained after 2000 cycles). This study essentially offers a new kind of metal vanadium oxides as electrochemical active material for the development of supercapacitors. PMID:25023373

  17. Improved Charge Transfer by Thin Metal Oxide Films

    NASA Astrophysics Data System (ADS)

    Irfan

    The field of electronics has an immense impact on our day to day life. Efficient charge transfer at the semiconductor and electrode interface is one of the most crucial issues for the performance of any electronic device. A lot of effort has been spent to address this issue. A counter intuitive phenomenon of insertion of a thin metal oxide film at the semiconductor and electrode interface has gained momentum recently. In the current thesis, based on results of several experiments, I will propose a prominent mechanism of performance improvement with such insertions. I will also demonstrate the applicability of such metal oxide thin films in many other systems. First, I will introduce the scope of the thesis in detail. I will also introduce the background to understand the electronic structure of organic semiconductors, along with the interface formation at the semiconductor/metal interface. Then, I will discuss the measurement techniques. I will start the discussion on results with the insertion of a thin layer of MoOx (a transition metal oxide) between indium tin oxide (ITO) and two well studied organic semiconductors. I will also demonstrate that the optimum insertion layer thickness is just a few nanometers. I will illustrate the importance of high vacuum during the deposition of such insertion layers. I will also discuss the method to recover work function of air exposed MoOx films. I will further demonstrate that a thin layer of MoOx can be utilized to dope C60 strongly p-type. Then, I will discuss the application of MoO x insertion layer in CdTe based solar cells. I will further show the application of MoOx and organic double-inter-layer in organic devices. At the end, I will discuss an intense oxygen plasma treatment on ITO films and demonstrate a method to achieve high work function ITO films. The mechanism of high work function and application in devices will also be explained in detail. Finally, I will summarize the thesis.

  18. Trap States of the Oxide Thin Film Transistor

    NASA Astrophysics Data System (ADS)

    Yu, Kyeong Min; Yuh, Jin Tae; Park, Sang Hee Ko; Ryu, Min Ki; Yun, Eui Jung; Bae, Byung Seong

    2013-10-01

    We investigated the temperature dependent recovery of the threshold voltage shift observed in both ZnO and indium gallium zinc oxide (IGZO) thin film transistors (TFTs) after application of gate bias and light illumination. Two types of recovery were observed for both the ZnO and IGZO TFTs; low temperature recovery (below 110 °C) which is attributed to the trapped charge and high temperature recovery (over 110 °C) which is related to the annihilation of trap states generated during stresses. From a comparison study of the recovery rate with the analysis of hydrogen diffusion isochronal annealing, a similar behavior was observed for both TFT recovery and hydrogen diffusion. This result suggests that hydrogen plays an important role in the generation and annihilation of trap states in oxide TFTs under gate bias or light illumination stresses.

  19. Thin water film formation on metal oxide crystal surfaces.

    PubMed

    Gilbert, Benjamin; Katz, Jordan E; Rude, Bruce; Glover, T E; Hertlein, Marcus P; Kurz, Charles; Zhang, Xiaoyi

    2012-10-09

    Reactions taking place at hydrated metal oxide surfaces are of considerable environmental and technological importance. Surface-sensitive X-ray methods can provide structural and chemical information on stable interfacial species, but it is challenging to perform in situ studies of reaction kinetics in the presence of water. We have implemented a new approach to creating a micrometer-scale water film on a metal oxide surface by combining liquid and gas jets on a spinning crystal. The water films are stable indefinitely and sufficiently thin to allow grazing incidence X-ray reflectivity and spectroscopy measurements. The approach will enable studies of a wide range of surface reactions and is compatible with interfacial optical-pump/X-ray-probe studies.

  20. Enhanced electrochromism in cerium doped molybdenum oxide thin films

    SciTech Connect

    Dhanasankar, M.; Purushothaman, K.K.; Muralidharan, G.

    2010-12-15

    Cerium (5-15% by weight) doped molybdenum oxide thin films have been prepared on FTO coated glass substrate at 250 {sup o}C using sol-gel dip coating method. The structural and morphological changes were observed with the help of XRD, SEM and EDS analysis. The amorphous structure of the Ce doped samples, favours easy intercalation and deintercalation processes. Mo oxide films with 10 wt.% of Ce exhibit maximum anodic diffusion coefficient of 24.99 x 10{sup -11} cm{sup 2}/s and the change in optical transmittance of ({Delta}T at 550 nm) of 79.28% between coloured and bleached state with the optical density of ({Delta}OD) 1.15.

  1. Amorphous hafnium-indium-zinc oxide semiconductor thin film transistors

    NASA Astrophysics Data System (ADS)

    Kim, Chang-Jung; Kim, Sangwook; Lee, Je-Hun; Park, Jin-Seong; Kim, Sunil; Park, Jaechul; Lee, Eunha; Lee, Jaechul; Park, Youngsoo; Kim, Joo Han; Shin, Sung Tae; Chung, U.-In

    2009-12-01

    We developed amorphous hafnium-indium-zinc oxide (HIZO) thin films as oxide semiconductors and investigated the films electrically and physically. Adding of hafnium (Hf) element can suppress growing the columnar structure and drastically decrease the carrier concentration and hall mobility in HIZO films. The thin film transistors (TFTs) with amorphous HIZO active channel exhibit good electrical properties with field effect mobility of around 10 cm2/Vs, S of 0.23 V/decade, and high Ion/off ratio of over 108, enough to operate the next electronic devices. In particular, under bias-temperature stress test, the HIZO TFTs with 0.3 mol % (Hf content) showed only 0.46 V shift in threshold voltage, compared with 3.25 V shift in HIZO TFT (0.1 mol %). The Hf ions may play a key role to improve the instability of TFTs due to high oxygen bonding ability. Therefore, the amorphous HIZO semiconductor will be a prominent candidate as an operation device for large area electronic applications.

  2. Synthesis and Oxidation Resistance of h-BN Thin Films

    NASA Astrophysics Data System (ADS)

    Stewart, David; Meulenberg, Robert; Lad, Robert

    Hexagonal boron nitride (h-BN) is an exciting 2D material for use in sensors and other electronic devices that operate in harsh, high temperature environments. Not only is h-BN a wide band gap material with excellent wear resistance and high temperature stability, but recent reports indicate that h-BN can prevent metallic substrates from oxidizing above 600°C in low O2 pressures. However, the PVD of highly crystalline h-BN films required for this oxidation protection has proven challenging. In this work, we have explored the growth of h-BN thin films by reactive RF magnetron sputtering from an elemental B target in an Ar/N2 atmosphere. The film growth rate is extremely slow and the resulting films are atomically smooth and homogeneous. Using DC biasing during deposition and high temperature annealing treatments, the degree of film crystallinity can be controlled. The oxidation resistance of h-BN films deposited on inert sapphire and reactive metal substrates such as Zr and ZrB2 has been examined by techniques such as XPS, XRD, and SEM after oxidation between 600 and 1200°C under varying oxygen pressures. The success of h-BN as a passivation layer for metallic substrates in harsh environments is shown to depend greatly on its crystalline quality and defects. Supported by the NSF SusChEM program.

  3. Physical investigation of electrophoretically deposited graphene oxide and reduced graphene oxide thin films

    NASA Astrophysics Data System (ADS)

    Politano, Grazia Giuseppina; Versace, Carlo; Vena, Carlo; Castriota, Marco; Ciuchi, Federica; Fasanella, Angela; Desiderio, Giovanni; Cazzanelli, Enzo

    2016-11-01

    Graphene oxide and reduced graphene oxide thin films are very promising materials because they can be used in optoelectronic devices and in a growing range of applications such as touch screens and flexible displays. In this work, graphene oxide (GO) and thermally reduced graphene oxide (rGO) thin films, deposited on Ti/glass substrates, have been obtained by electrophoretic deposition. The morphological and the structural properties of the samples have been investigated by micro-Raman technique, X-ray reflectometry, and SEM analysis. In order to study the optical and electrical properties, variable angle spectroscopic ellipsometry and impedance analysis have been performed. The thermal annealing changes strongly the structural, electrical, and optical properties, because during the thermal processes some amount of sp3 bonds originally present in GO were removed. In particular, the annealing enhances the Ohmic behavior of the rGO film increasing its conductivity and the estimated optical density. Moreover, using electrophoretic deposition, we have found a higher value of optical density for GO thin films, not observed in GO films obtained with other deposition methods.

  4. Amorphous semiconducting and conducting transparent metal oxide thin films and production thereof

    DOEpatents

    Perkins, John; Van Hest, Marinus Franciscus Antonius Maria; Ginley, David; Taylor, Matthew; Neuman, George A.; Luten, Henry A.; Forgette, Jeffrey A.; Anderson, John S.

    2010-07-13

    Metal oxide thin films and production thereof are disclosed. An exemplary method of producing a metal oxide thin film may comprise introducing at least two metallic elements and oxygen into a process chamber to form a metal oxide. The method may also comprise depositing the metal oxide on a substrate in the process chamber. The method may also comprise simultaneously controlling a ratio of the at least two metallic elements and a stoichiometry of the oxygen during deposition. Exemplary amorphous metal oxide thin films produced according to the methods herein may exhibit highly transparent properties, highly conductive properties, and/or other opto-electronic properties.

  5. The structure of nickel and indium oxide thin films from EXAFS data

    NASA Astrophysics Data System (ADS)

    Bets, V.; Zamozdiks, T.; Lusis, A.; Purans, J.; Bausk, N.; Sheromov, M.

    1987-11-01

    The structure of nickel oxide and indium oxide doped by tin films prepared by reactive magnetron sputtering has been studied by the EXAFS method. It has been found that the nickel oxide thin film has a microcrystalline structure with significant disorder proved by the increase of the Debye-Waller factor and the sharp decrease of peak amplitudes. The indium oxide thin film has a noticeable structural disorder due to 8% tin dopping.

  6. Flexible Electronics Powered by Mixed Metal Oxide Thin Film Transistors

    NASA Astrophysics Data System (ADS)

    Marrs, Michael

    A low temperature amorphous oxide thin film transistor (TFT) and amorphous silicon PIN diode backplane technology for large area flexible digital x-ray detectors has been developed to create 7.9-in. diagonal backplanes. The critical steps in the evolution of the backplane process include the qualification and optimization of the low temperature (200 °C) metal oxide TFT and a-Si PIN photodiode process, the stability of the devices under forward and reverse bias stress, the transfer of the process to flexible plastic substrates, and the fabrication and assembly of the flexible detectors. Mixed oxide semiconductor TFTs on flexible plastic substrates suffer from performance and stability issues related to the maximum processing temperature limitation of the polymer. A novel device architecture based upon a dual active layer improves both the performance and stability. Devices are directly fabricated below 200 ºC on a polyethylene naphthalate (PEN) substrate using mixed metal oxides of either zinc indium oxide (ZIO) or indium gallium zinc oxide (IGZO) as the active semiconductor. The dual active layer architecture allows for adjustment to the saturation mobility and threshold voltage stability without the requirement of high temperature annealing, which is not compatible with flexible plastic substrates like PEN. The device performance and stability is strongly dependent upon the composition of the mixed metal oxide; this dependency provides a simple route to improving the threshold voltage stability and drive performance. By switching from a single to a dual active layer, the saturation mobility increases from 1.2 cm2/V-s to 18.0 cm2/V-s, while the rate of the threshold voltage shift decreases by an order of magnitude. This approach could assist in enabling the production of devices on flexible substrates using amorphous oxide semiconductors. Low temperature (200°C) processed amorphous silicon photodiodes were developed successfully by balancing the tradeoffs

  7. Self-formed copper oxide contact interlayer for high-performance oxide thin film transistors

    SciTech Connect

    Gao, Xu E-mail: TSUKAGOSHI.Kazuhito@nims.go.jp; Aikawa, Shinya; Mitoma, Nobuhiko; Lin, Meng-Fang; Kizu, Takio; Tsukagoshi, Kazuhito E-mail: TSUKAGOSHI.Kazuhito@nims.go.jp; Nabatame, Toshihide

    2014-07-14

    Oxide thin film transistor employing copper source/drain electrodes shows a small turn on voltage and reduced hysteresis. Cross-sectional high-resolution transmission electron microscopy image confirmed the formation of ∼4 nm CuO{sub x} related interlayer. The lower bond-dissociation energy of Cu-O compared to Si-O and In-O suggests that the interlayer was formed by adsorbing oxygen molecules from surrounding environment instead of getting oxygen atoms from the semiconductor film. The formation of CuO{sub x} interlayer acting as an acceptor could suppress the carrier concentration in the transistor channel, which would be utilized to control the turn on voltage shifts in oxide thin film transistors.

  8. Properties of mixed molybdenum oxide iridium oxide thin films synthesized by spray pyrolysis

    NASA Astrophysics Data System (ADS)

    Patil, P. S.; Kawar, R. K.; Sadale, S. B.; Inamdar, A. I.; Deshmukh, H. P.

    2006-09-01

    Molybdenum-doped iridium oxide thin films have been deposited onto corning glass- and fluorine-doped tin oxide coated corning glass substrates at 350 °C by using a pneumatic spray pyrolysis technique. An aqueous solution of 0.01 M ammonium molybdate was mixed with 0.01 M iridium trichloride solution in different volume proportions and the resultant solution was used as a precursor solution for spraying. The as-deposited samples were annealed at 600 °C in air medium for 1 h. The structural, electrical and optical properties of as-deposited and annealed Mo-doped iridium oxide were studied and values of room temperature electrical resistivity, and thermoelectric power were estimated. The as-deposited samples with 2% Mo doping exhibit more pronounced electrochromism than other samples, including pristine Ir oxide.

  9. Visible light-induced photocatalytic reduction of graphene oxide by tungsten oxide thin films

    NASA Astrophysics Data System (ADS)

    Choobtashani, M.; Akhavan, O.

    2013-07-01

    Tungsten oxide thin films (deposited by thermal evaporation or sol gel method) were used for photocatalytic reduction of graphene oxide (GO) platelets (synthesized through a chemical exfoliation method) on surface of the films under UV or visible light of the environment, in the absence of any aqueous ambient at room temperature. Atomic force microscopy (AFM) technique was employed to characterize surface morphology of the GO sheets and the tungsten oxide films. Moreover, using X-ray photoelectron spectroscopy (XPS), chemical state of the tungsten oxide films and the photocatalytic reduction of the GO platelets were quantitatively investigated. The better performance of the sol-gel tungsten oxide films in photocatalytic reduction of GO platelets as compared to the evaporated tungsten oxide films was assigned to lower W5+/W6+ ratio (i.e., a better stoichiometry) and higher surface water content of the sol-gel film. The GO reduction level achieved after 24 h UV-assisted photocatalytic reduction on surface of the sol-gel tungsten oxide film was comparable with the reduction level usually obtainable by hydrazine. The sol-gel tungsten oxide film even showed an efficient photocatalytic reduction of the GO platelets after exposure to the visible light of the environment for 2 days.

  10. Metal oxide semiconductor thin-film transistors for flexible electronics

    NASA Astrophysics Data System (ADS)

    Petti, Luisa; Münzenrieder, Niko; Vogt, Christian; Faber, Hendrik; Büthe, Lars; Cantarella, Giuseppe; Bottacchi, Francesca; Anthopoulos, Thomas D.; Tröster, Gerhard

    2016-06-01

    The field of flexible electronics has rapidly expanded over the last decades, pioneering novel applications, such as wearable and textile integrated devices, seamless and embedded patch-like systems, soft electronic skins, as well as imperceptible and transient implants. The possibility to revolutionize our daily life with such disruptive appliances has fueled the quest for electronic devices which yield good electrical and mechanical performance and are at the same time light-weight, transparent, conformable, stretchable, and even biodegradable. Flexible metal oxide semiconductor thin-film transistors (TFTs) can fulfill all these requirements and are therefore considered the most promising technology for tomorrow's electronics. This review reflects the establishment of flexible metal oxide semiconductor TFTs, from the development of single devices, large-area circuits, up to entirely integrated systems. First, an introduction on metal oxide semiconductor TFTs is given, where the history of the field is revisited, the TFT configurations and operating principles are presented, and the main issues and technological challenges faced in the area are analyzed. Then, the recent advances achieved for flexible n-type metal oxide semiconductor TFTs manufactured by physical vapor deposition methods and solution-processing techniques are summarized. In particular, the ability of flexible metal oxide semiconductor TFTs to combine low temperature fabrication, high carrier mobility, large frequency operation, extreme mechanical bendability, together with transparency, conformability, stretchability, and water dissolubility is shown. Afterward, a detailed analysis of the most promising metal oxide semiconducting materials developed to realize the state-of-the-art flexible p-type TFTs is given. Next, the recent progresses obtained for flexible metal oxide semiconductor-based electronic circuits, realized with both unipolar and complementary technology, are reported. In particular

  11. Melting of thin films of alkanes on magnesium oxide

    NASA Astrophysics Data System (ADS)

    Arnold, T.; Barbour, A.; Chanaa, S.; Cook, R. E.; Fernandez-Canato, D.; Landry, P.; Seydel, T.; Yaron, P.; Larese, J. Z.

    2009-02-01

    Recent incoherent neutron scattering investigations of the dynamics of thin alkane films adsorbed on the Magnesium Oxide (100) surface are reported. There are marked differences in the behaviour of these films, as a function of temperature and coverage, compared to similar measurements on graphite. In particular, it has previously been shown that adsorbed multilayer films on graphite exhibit an interfacial solid monolayer that coexists with bulk-like liquid, well above the bulk melting point. In contrast, these studies show that the alkane films on MgO exhibit no such stabilization of the solid layer closest to the substrate as a function of the film thickness, even though the monolayer crystal structures are remarkably similar. These studies are supported by extensive thermodynamic data, a growing body of structural data from neutron diffraction and state of the art computer modelling

  12. Studies on nickel-tungsten oxide thin films

    SciTech Connect

    Usha, K. S.; Sivakumar, R.; Sanjeeviraja, C.

    2014-10-15

    Nickel-Tungsten oxide (95:5) thin films were prepared by rf sputtering at 200W rf power with various substrate temperatures. X-ray diffraction study reveals the amorphous nature of films. The substrate temperature induced decrease in energy band gap with a maximum transmittance of 71%1 was observed. The Micro-Raman study shows broad peaks at 560 cm{sup −1} and 1100 cm{sup −1} correspond to Ni-O vibration and the peak at 860 cm{sup −1} can be assigned to the vibration of W-O-W bond. Photoluminescence spectra show two peaks centered on 420 nm and 485 nm corresponding to the band edge emission and vacancies created due to the addition of tungsten, respectively.

  13. Solution processed metal oxide thin film hole transport layers for high performance organic solar cells

    DOEpatents

    Steirer, K. Xerxes; Berry, Joseph J.; Chesin, Jordan P.; Lloyd, Matthew T.; Widjonarko, Nicodemus Edwin; Miedaner, Alexander; Curtis, Calvin J.; Ginley, David S.; Olson, Dana C.

    2017-01-10

    A method for the application of solution processed metal oxide hole transport layers in organic photovoltaic devices and related organic electronics devices is disclosed. The metal oxide may be derived from a metal-organic precursor enabling solution processing of an amorphous, p-type metal oxide. An organic photovoltaic device having solution processed, metal oxide, thin-film hole transport layer.

  14. Chemical Strain Engineering of Magnetism in Oxide Thin Films.

    PubMed

    Copie, Olivier; Varignon, Julien; Rotella, Hélène; Steciuk, Gwladys; Boullay, Philippe; Pautrat, Alain; David, Adrian; Mercey, Bernard; Ghosez, Philippe; Prellier, Wilfrid

    2017-04-03

    Transition metal oxides having a perovskite structure form a wide and technologically important class of compounds. In these systems, ferroelectric, ferromagnetic, ferroelastic, or even orbital and charge orderings can develop and eventually coexist. These orderings can be tuned by external electric, magnetic, or stress field, and the cross-couplings between them enable important multifunctional properties, such as piezoelectricity, magneto-electricity, or magneto-elasticity. Recently, it has been proposed that additional to typical fields, the chemical potential that controls the concentration of ion vacancies in these systems may reveal an efficient alternative parameter to further tune their properties and achieve new functionalities. In this study, concretizing this proposal, the authors show that the control of the content of oxygen vacancies in perovskite thin films can indeed be used to tune their magnetic properties. Growing PrVO3 thin films epitaxially on an SrTiO3 substrate, the authors reveal a concrete pathway to achieve this effect. The authors demonstrate that monitoring the concentration of oxygen vacancies through the oxygen partial pressure or the growth temperature can produce a substantial macroscopic tensile strain of a few percent. In turn, this strain affects the exchange interactions, producing a nontrivial evolution of Néel temperature in a range of 30 K.

  15. Highly conductive grain boundaries in copper oxide thin films

    NASA Astrophysics Data System (ADS)

    Deuermeier, Jonas; Wardenga, Hans F.; Morasch, Jan; Siol, Sebastian; Nandy, Suman; Calmeiro, Tomás; Martins, Rodrigo; Klein, Andreas; Fortunato, Elvira

    2016-06-01

    High conductivity in the off-state and low field-effect mobility compared to bulk properties is widely observed in the p-type thin-film transistors of Cu2O, especially when processed at moderate temperature. This work presents results from in situ conductance measurements at thicknesses from sub-nm to around 250 nm with parallel X-ray photoelectron spectroscopy. An enhanced conductivity at low thickness is explained by the occurrence of Cu(II), which is segregated in the grain boundary and locally causes a conductivity similar to CuO, although the surface of the thick film has Cu2O stoichiometry. Since grains grow with an increasing film thickness, the effect of an apparent oxygen excess is most pronounced in vicinity to the substrate interface. Electrical properties of Cu2O grains are at least partially short-circuited by this effect. The study focuses on properties inherent to copper oxide, although interface effects cannot be ruled out. This non-destructive, bottom-up analysis reveals phenomena which are commonly not observable after device fabrication, but clearly dominate electrical properties of polycrystalline thin films.

  16. F2-Laser-Induced Modification of Aluminum Thin Films into Transparent Aluminum Oxide

    NASA Astrophysics Data System (ADS)

    Okoshi, Masayuki; Iwai, Kazufumi; Nojiri, Hidetoshi; Inoue, Narumi

    2012-12-01

    A vacuum-UV F2 laser of 157 nm wavelength induced strong oxidation of 10-nm-thick Al thin films, forming transparent Al2O3 on silica glass. The laser-induced modification occurred at the surface of Al thin films; consequently, the thickness of the formed Al2O3 thin films increased linearly with increasing number of F2 laser photons. The formation of equivalent-phase Al2O3 thin films was confirmed by X-ray photoelectron spectroscopy. The oxidation reaction in the laser-induced modification of 10-nm-thick Al thin films was slower than that for 20- and 60-nm-thick Al thin films. Morphological changes leading to the crystallization of the Al2O3 thin films were also observed when the thickness of Al thin films increased from 10 to 20 and 60 nm.

  17. Amperometric detection and electrochemical oxidation of aliphatic amines and ammonia on silver-lead oxide thin-film electrodes

    SciTech Connect

    Ge, Jisheng

    1996-01-08

    This thesis comprises three parts: Electrocatalysis of anodic oxygen-transfer reactions: aliphatic amines at mixed Ag-Pb oxide thin-film electrodes; oxidation of ammonia at anodized Ag-Pb eutectic alloy electrodes; and temperature effects on oxidation of ethylamine, alanine, and aquated ammonia.

  18. Laser patterning of very thin indium tin oxide thin films on PET substrates

    NASA Astrophysics Data System (ADS)

    McDonnell, C.; Milne, D.; Prieto, C.; Chan, H.; Rostohar, D.; O'Connor, G. M.

    2015-12-01

    This work investigates the film removal properties of 30 nm thick Indium Tin Oxide (ITO) thin films, on flexible polyethylene terephthalate (PET) substrates, using 355, 532 and 1064 nm nanosecond pulses (ns), and 343 and 1064 nm femtosecond pulses. The ablation threshold was found to be dependent on the applied wavelength and pulse duration. The surface topography of the laser induced features were examined using atomic force microscopy across the range of wavelengths and pulse durations. The peak temperature, strain and stress tensors were examined in the film and substrate during laser heating, using finite element computational methods. Selective removal of the thin ITO film from the polymer substrate is possible at all wavelengths except at 266 nm, were damage to substrate is observed. The damage to the substrate results in periodic surface structures (LIPPS) on the exposed PET, with a period of twice the incident wavelength. Fragmented crater edges are observed at all nanosecond pulse durations. Film removal using 1030 nm femtosecond pulses results in clean crater edges, however, minor 5 nm damage to the substrate is also observed. The key results show that film removal for ITO on PET, is through film de-lamination across all wavelengths and pulse durations. Film de-lamination occurs due to thermo-elastic stress at the film substrate interface region, as the polymer substrate expands under heating from direct laser absorption and heat conduction across the film substrate interface.

  19. Zinc-oxide charge trapping memory cell with ultra-thin chromium-oxide trapping layer

    SciTech Connect

    El-Atab, Nazek; Rizk, Ayman; Nayfeh, Ammar; Okyay, Ali K.

    2013-11-15

    A functional zinc-oxide based SONOS memory cell with ultra-thin chromium oxide trapping layer was fabricated. A 5 nm CrO{sub 2} layer is deposited between Atomic Layer Deposition (ALD) steps. A threshold voltage (V{sub t}) shift of 2.6V was achieved with a 10V programming voltage. Also for a 2V V{sub t} shift, the memory with CrO{sub 2} layer has a low programming voltage of 7.2V. Moreover, the deep trapping levels in CrO{sub 2} layer allows for additional scaling of the tunnel oxide due to an increase in the retention time. In addition, the structure was simulated using Physics Based TCAD. The results of the simulation fit very well with the experimental results providing an understanding of the charge trapping and tunneling physics.

  20. Oxide nucleation on thin films of copper during in situ oxidation in an electron microscope

    NASA Technical Reports Server (NTRS)

    Heinemann, K.; Rao, D. B.; Douglass, D. L.

    1975-01-01

    Single-crystal copper thin films were oxidized at an isothermal temperature of 425 C and at an oxygen partial pressure of 0.005 torr. Specimens were prepared by epitaxial vapor deposition onto polished faces of rocksalt and were mounted in a hot stage inside the ultrahigh-vacuum chamber of a high-resolution electron microscope. An induction period of roughly 30 min was established which was independent of the film thickness but depended strongly on the oxygen partial pressure and to exposure to oxygen prior to oxidation. Neither stacking faults nor dislocations were found to be associated with the Cu2O nucleation sites. The experimental data, including results from oxygen dissolution experiments and from repetitive oxidation-reduction-oxidation sequences, fit well into the framework of an oxidation process involving the formation of a surface charge layer, oxygen saturation of the metal with formation of a supersaturated zone near the surface, and nucleation followed by surface diffusion of oxygen and bulk diffusion of copper for lateral and vertical oxide growth, respectively.

  1. Structure and Optical Properties of Nanocrystalline Hafnium Oxide Thin Films (PostPrint)

    DTIC Science & Technology

    2014-09-01

    AFRL-RX-WP-JA-2014-0214 STRUCTURE AND OPTICAL PROPERTIES OF NANOCRYSTALLINE HAFNIUM OXIDE THIN FILMS (POSTPRINT) Neil R. Murphy AFRL...OPTICAL PROPERTIES OF NANOCRYSTALLINE HAFNIUM OXIDE THIN FILMS (POSTPRINT) 5a. CONTRACT NUMBER In-House 5b. GRANT NUMBER 5c. PROGRAM ELEMENT...microstructure and optical constants is established. 15. SUBJECT TERMS hafnium oxide , sputter-deposition, structure, XRR, optical properties

  2. Electrical and structural characterization of IZO (indium oxide-zinc oxide) thin films for device applications

    NASA Astrophysics Data System (ADS)

    Yaglioglu, Burag

    Materials for oxide-based transparent electronics have been recently reported in the literature. These materials include various amorphous and crystalline compounds based on multi-component oxides and many of them offer useful combinations of transparency, controllable carrier concentrations, and reasonable n-carrier mobility. In this thesis, the properties of amorphous and crystalline In2O3-10wt%ZnO, IZO, thin films were investigated for their potential use in oxide electronics. The room temperature deposition of this material using DC magnetron sputtering results in the formation of amorphous films. Annealing amorphous IZO films at 500°C in air produces a previously unknown crystalline compound. Using electron diffraction experiments, it is reported that the crystal structure of this compound is based on the high-pressure rhombohedral phase of In2O3. Electrical properties of different phases of IZO were explored and it was concluded that amorphous films offer most promising characteristics for device applications. Therefore, thin film transistors (TFT) were fabricated based on amorphous IZO films where both the channel and metallization layers were deposited from the same target. The carrier densities in the channel and source-drain layers were adjusted by changing the oxygen content in the sputter chamber during deposition. The resulting transistors operate as depletion mode n-channel field effect devices with high saturation mobilities.

  3. Nickel oxide and molybdenum oxide thin films for infrared imaging prepared by biased target ion-beam deposition

    NASA Astrophysics Data System (ADS)

    Jin, Yao; Saint John, David; Jackson, Tom N.; Horn, Mark W.

    2014-06-01

    Vanadium oxide (VOx) thin films have been intensively used as sensing materials for microbolometers. VOx thin films have good bolometric properties such as low resistivity, high negative temperature coefficient of resistivity (TCR) and low 1/f noise. However, the processing controllability of VOx fabrication is difficult due to the multiple valence states of vanadium. In this study, metal oxides such as nickel oxide (NiOx) and molybdenum oxide (MoOx) thin films have been investigated as possible new microbolometer sensing materials with improved process controllability. Nickel oxide and molybdenum oxide thin films were prepared by reactive sputtering of nickel and molybdenum metal targets in a biased target ion beam deposition tool. In this deposition system, the Ar+ ion energy (typically lower than 25 eV) and the target bias voltage can be independently controlled since ions are remotely generated. A residual gas analyzer (RGA) is used to precisely control the oxygen partial pressure. A real-time spectroscopic ellipsometry is used to monitor the evolution of microstructure and properties of deposited oxides during growth and post-deposition. The properties of deposited oxide thin films depend on processing parameters. The resistivity of the NiOx thin films is in the range of 0.5 to approximately 100 ohm-cm with a TCR from -2%/K to -3.3%/K, where the resistivity of MoOx is between 3 and 2000 ohm-cm with TCR from -2.1%/K to -3.2%/K. We also report on the thermal stability of these deposited oxide thin films.

  4. Growth and Oxidation of Thin Film Al(2)Cu

    SciTech Connect

    SON,KYUNG-AH; MISSERT,NANCY A.; BARBOUR,J. CHARLES; HREN,J.J.; COPELAND,ROBERT GUILD; MINOR,KENNETH G.

    2000-01-18

    Al{sub 2}Cu thin films ({approx} 382 nm) are fabricated by melting and resolidifying Al/Cu bilayers in the presence of a {micro} 3 nm Al{sub 2}O{sub 3} passivating layer. X-ray Photoelectron Spectroscopy (XPS) measures a 1.0 eV shift of the Cu2p{sub 3/2} peak and a 1.6 eV shift of the valence band relative to metallic Cu upon Al{sub 2}Cu formation. Scanning Electron microscopy (SEM) and Electron Back-Scattered Diffraction (EBSD) show that the Al{sub 2}Cu film is composed of 30-70 {micro}m wide and 10-25 mm long cellular grains with (110) orientation. The atomic composition of the film as estimated by Energy Dispersive Spectroscopy (EDS) is 67 {+-} 2% Al and 33 {+-} 2% Cu. XPS scans of Al{sub 2}O{sub 3}/Al{sub 2}Cu taken before and after air exposure indicate that the upper Al{sub 2}Cu layers undergo further oxidation to Al{sub 2}O{sub 3} even in the presence of {approx} 5 nm Al{sub 2}O{sub 3}. The majority of Cu produced from oxidation is believed to migrate below the Al{sub 2}O{sub 3} layers, based upon the lack of evidence for metallic Cu in the XPS scans. In contrast to Al/Cu passivated with Al{sub 2}O{sub 3}, melting/resolidifying the Al/Cu bilayer without Al{sub 2}O{sub 3} results in phase-segregated dendritic film growth.

  5. P-channel thin film transistors using reduced graphene oxide

    NASA Astrophysics Data System (ADS)

    Chakraborty, S.; Resmi, A. N.; Renuka Devi, P.; Jinesh, K. B.

    2017-04-01

    Chemically reduced graphene oxide (rGO) samples with various degrees of reduction were prepared using hydrazine hydrate as the reducing agent. Scanning tunnelling microscope imaging shows that rGO contains rows of randomly distributed patches of epoxy groups. The local density of states of the rGO samples were mapped with scanning tunnelling spectroscopy, which shows that the bandgap in rGO originates from the epoxide regions itself. The Fermi level of the epoxide regions is shifted towards the valence band, making rGO locally p-type and a range of bandgaps from 0–2.2 eV was observed in these regions. Thin film transistors were fabricated using rGO as the channel layer. The devices show excellent output characteristics with clear saturation and gate dependence. The transfer characteristics show that rGO behaves as a p-type semiconductor; the devices exhibit an on/off ratio of 104, with a low-bias hole mobility of 3.9 cm2 V‑1 s‑1.

  6. P-channel thin film transistors using reduced graphene oxide.

    PubMed

    Chakraborty, S; Resmi, A N; Devi, P Renuka; Jinesh, K B

    2017-04-18

    Chemically reduced graphene oxide (rGO) samples with various degrees of reduction were prepared using hydrazine hydrate as the reducing agent. Scanning tunnelling microscope imaging shows that rGO contains rows of randomly distributed patches of epoxy groups. The local density of states of the rGO samples were mapped with scanning tunnelling spectroscopy, which shows that the bandgap in rGO originates from the epoxide regions itself. The Fermi level of the epoxide regions is shifted towards the valence band, making rGO locally p-type and a range of bandgaps from 0-2.2 eV was observed in these regions. Thin film transistors were fabricated using rGO as the channel layer. The devices show excellent output characteristics with clear saturation and gate dependence. The transfer characteristics show that rGO behaves as a p-type semiconductor; the devices exhibit an on/off ratio of 10(4), with a low-bias hole mobility of 3.9 cm(2) V(-1) s(-1).

  7. Thin film bismuth iron oxides useful for piezoelectric devices

    DOEpatents

    Zeches, Robert J.; Martin, Lane W.; Ramesh, Ramamoorthy

    2016-05-31

    The present invention provides for a composition comprising a thin film of BiFeO.sub.3 having a thickness ranging from 20 nm to 300 nm, a first electrode in contact with the BiFeO.sub.3 thin film, and a second electrode in contact with the BiFeO.sub.3 thin film; wherein the first and second electrodes are in electrical communication. The composition is free or essentially free of lead (Pb). The BFO thin film is has the piezoelectric property of changing its volume and/or shape when an electric field is applied to the BFO thin film.

  8. Thin copper oxide films prepared by ion beam sputtering with subsequent thermal oxidation: Application in chemiresistors

    NASA Astrophysics Data System (ADS)

    Horak, P.; Bejsovec, V.; Vacik, J.; Lavrentiev, V.; Vrnata, M.; Kormunda, M.; Danis, S.

    2016-12-01

    Copper oxide films were prepared by thermal oxidation of thin Cu films deposited on substrates by ion beam sputtering. The subsequent oxidation was achieved in the temperature range of 200 °C-600 °C with time of treatment from 1 to 7 h (with a 1-h step) in a furnace open to air. At temperatures 250 °C-600 °C, the dominant phase formed was CuO, while at 200 °C mainly the Cu2O phase was identified. However, the oxidation at 200 °C led to a more complicated composition - in the depth Cu2O phase was observed, though in the near-surface layer the CuO dominant phase was found with a significant presence of Cu(OH)2. A limited amount of Cu2O was also found in samples annealed at 600 °C. The sheet resistance RS of the as-deposited Cu sample was 2.22 Ω/□, after gradual annealing RS was measured in the range 2.64 MΩ/□-2.45 GΩ/□. The highest RS values were obtained after annealing at 300 °C and 350 °C, respectively. Oxygen depth distribution was studied using the 16O(α,α) nuclear reaction with the resonance at energy 3032 keV. It was confirmed that the higher oxidation degree of copper is located in the near-surface region. Preliminary tests of the copper oxide films as an active layer of a chemiresistor were also performed. Hydrogen and methanol vapours, with a concentration of 1000 ppm, were detected by the sensor at an operating temperature of 300 °C and 350 °C, respectively. The response of the sensors, pointed at the p-type conductivity, was improved by the addition of thin Pd or Au catalytic films to the oxidic film surface. Pd-covered films showed an increased response to hydrogen at 300 °C, while Au-covered films were more sensitive to methanol vapours at 350 °C.

  9. Perovskite Oxide Thin Film Growth, Characterization, and Stability

    NASA Astrophysics Data System (ADS)

    Izumi, Andrew

    Studies into a class of materials known as complex oxides have evoked a great deal of interest due to their unique magnetic, ferroelectric, and superconducting properties. In particular, materials with the ABO3 perovskite structure have highly tunable properties because of the high stability of the structure, which allows for large scale doping and strain. This also allows for a large selection of A and B cations and valences, which can further modify the material's electronic structure. Additionally, deposition of these materials as thin films and superlattices through techniques such as pulsed laser deposition (PLD) results in novel properties due to the reduced dimensionality of the material. The novel properties of perovskite oxide heterostructures can be traced to a several sources, including chemical intermixing, strain and defect formation, and electronic reconstruction. The correlations between microstructure and physical properties must be investigated by examining the physical and electronic structure of perovskites in order to understand this class of materials. Some perovskites can undergo phase changes due to temperature, electrical fields, and magnetic fields. In this work we investigated Nd0.5Sr 0.5MnO3 (NSMO), which undergoes a first order magnetic and electronic transition at T=158K in bulk form. Above this temperature NSMO is a ferromagnetic metal, but transitions into an antiferromagnetic insulator as the temperature is decreased. This rapid transition has interesting potential in memory devices. However, when NSMO is deposited on (001)-oriented SrTiO 3 (STO) or (001)-oriented (LaAlO3)0.3-(Sr 2AlTaO6)0.7 (LSAT) substrates, this transition is lost. It has been reported in the literature that depositing NSMO on (110)-oriented STO allows for the transition to reemerge due to the partial epitaxial growth, where the NSMO film is strained along the [001] surface axis and partially relaxed along the [11¯0] surface axis. This allows the NSMO film enough

  10. p-Channel oxide thin film transistors using solution-processed copper oxide.

    PubMed

    Kim, Sang Yun; Ahn, Cheol Hyoun; Lee, Ju Ho; Kwon, Yong Hun; Hwang, Sooyeon; Lee, Jeong Yong; Cho, Hyung Koun

    2013-04-10

    Cu2O thin films were synthesized on Si (100) substrate with thermally grown 200-nm SiO2 by sol-gel spin coating method and postannealing under different oxygen partial pressure (0.04, 0.2, and 0.9 Torr). The morphology of Cu2O thin films was improved through N2 postannealing before O2 annealing. Under relatively high oxygen partial pressure of 0.9 Torr, the roughness of synthesized films was increased with the formation of CuO phase. Bottom-gated copper oxide (CuxO) thin film transistors (TFTs) were fabricated via conventional photolithography, and the electrical properties of the fabricated TFTs were measured. The resulting Cu2O TFTs exhibited p-channel operation, and field effect mobility of 0.16 cm2/(V s) and on-to-off drain current ratio of ∼1×10(2) were observed in the TFT device annealed at PO2 of 0.04 Torr. This study presented the potential of the solution-based process of the Cu2O TFT with p-channel characteristics for the first time.

  11. Surface and sub-surface thermal oxidation of thin ruthenium films

    NASA Astrophysics Data System (ADS)

    Coloma Ribera, R.; van de Kruijs, R. W. E.; Kokke, S.; Zoethout, E.; Yakshin, A. E.; Bijkerk, F.

    2014-09-01

    A mixed 2D (film) and 3D (nano-column) growth of ruthenium oxide has been experimentally observed for thermally oxidized polycrystalline ruthenium thin films. Furthermore, in situ x-ray reflectivity upon annealing allowed the detection of 2D film growth as two separate layers consisting of low density and high density oxides. Nano-columns grow at the surface of the low density oxide layer, with the growth rate being limited by diffusion of ruthenium through the formed oxide film. Simultaneously, with the growth of the columns, sub-surface high density oxide continues to grow limited by diffusion of oxygen or ruthenium through the oxide film.

  12. Surface and sub-surface thermal oxidation of thin ruthenium films

    SciTech Connect

    Coloma Ribera, R.; Kruijs, R. W. E. van de; Yakshin, A. E.; Bijkerk, F.; Kokke, S.; Zoethout, E.

    2014-09-29

    A mixed 2D (film) and 3D (nano-column) growth of ruthenium oxide has been experimentally observed for thermally oxidized polycrystalline ruthenium thin films. Furthermore, in situ x-ray reflectivity upon annealing allowed the detection of 2D film growth as two separate layers consisting of low density and high density oxides. Nano-columns grow at the surface of the low density oxide layer, with the growth rate being limited by diffusion of ruthenium through the formed oxide film. Simultaneously, with the growth of the columns, sub-surface high density oxide continues to grow limited by diffusion of oxygen or ruthenium through the oxide film.

  13. 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.

  14. Atomic Layer-Deposited Titanium-Doped Vanadium Oxide Thin Films and Their Thermistor Applications

    NASA Astrophysics Data System (ADS)

    Wang, Shuyu; Yu, Shifeng; Lu, Ming; Liu, Mingzhao; Zuo, Lei

    2017-04-01

    Here we report the enhancement in the temperature coefficient of resistance (TCR) of atomic layer-deposited vanadium oxide thin films through the doping of titanium oxide. The Hall effect measurement provides a potential explanation for the phenomenon. The composition and morphology of the thin films are investigated by x-ray diffraction and scanning electron microscopy techniques. The high TCR, good uniformity, and low processing temperature of the material make it a good candidate for thermistor application.

  15. Interface properties of thin oxide layers grown on strained SiGe layers at low temperatures

    NASA Astrophysics Data System (ADS)

    Mukhopadhyay, M.; Ray, S. K.; Ghosh, T. B.; Sreemany, M.; Maiti, C. K.

    1996-03-01

    The chemical state and the electrical properties of the interfaces of thin oxide films grown on strained 0268-1242/11/3/014/img8 layers using plasma and thermal oxidation have been studied in detail. X-ray photoelectron spectroscopy studies show no Ge pile-up at the oxide/substrate interface. In the case of plasma oxidation, Ge at the oxide surface is found to be in a fully oxidized state, while the formation of an intermediate oxidized state is observed in the case of low-temperature thermal oxidation. High-frequency (1 MHz) capacitance - voltage (C - V) and conductance - voltage (G - V) measurements have indicated the growth of good quality gate oxides. The fixed oxide charge and interface state densities are comparable to those of low-temperature-grown metal - oxide - semiconductor capacitors on Si with aluminium gates.

  16. Nano-oxide thin films deposited via atomic layer deposition on microchannel plates.

    PubMed

    Yan, Baojun; Liu, Shulin; Heng, Yuekun

    2015-01-01

    Microchannel plate (MCP) as a key part is a kind of electron multiplied device applied in many scientific fields. Oxide thin films such as zinc oxide doped with aluminum oxide (ZnO:Al2O3) as conductive layer and pure aluminum oxide (Al2O3) as secondary electron emission (SEE) layer were prepared in the pores of MCP via atomic layer deposition (ALD) which is a method that can precisely control thin film thickness on a substrate with a high aspect ratio structure. In this paper, nano-oxide thin films ZnO:Al2O3 and Al2O3 were prepared onto varied kinds of substrates by ALD technique, and the morphology, element distribution, structure, and surface chemical states of samples were systematically investigated by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and X-ray photoemission spectroscopy (XPS), respectively. Finally, electrical properties of an MCP device as a function of nano-oxide thin film thickness were firstly studied, and the electrical measurement results showed that the average gain of MCP was greater than 2,000 at DC 800 V with nano-oxide thin film thickness approximately 122 nm. During electrical measurement, current jitter was observed, and possible reasons were preliminarily proposed to explain the observed experimental phenomenon.

  17. Physical properties in thin films of iron oxides.

    SciTech Connect

    Uribe, J. D.; Osorio, J.; Barrero, C. A.; Girata, D.; Morales, A. L.; Hoffmann, A.; Materials Science Division; Univ. de Antioquia

    2008-01-01

    We have grown hematite ({alpha}-Fe{sub 2}O{sub 3}) thin films on stainless steel substrates and magnetite (Fe{sub 3}O{sub 4}) thin films on (0 0 1)-Si single crystal substrates by a RF magnetron sputtering process. {alpha}-Fe{sub 2}O{sub 3} thin films were grown in an Ar atmosphere at substrate temperatures around 400 C, and Fe{sub 3}O{sub 4} thin films in an Ar/O{sub 2} reactive atmosphere at substrate temperatures around 500 C. Conversion electron Moessbauer (CEM) spectra of {alpha}-Fe{sub 2}O{sub 3} thin films exhibit values for hyperfine parameter characteristic of the hematite stoichiometric phase in the weak ferromagnetic state [R.E. Vandenberghe, in: Moessbauer Spectroscopy and Applications in Geology, University Gent, Belgium, 1990. [1

  18. Nickel oxide thin film from electrodeposited nickel sulfide thin film: peroxide sensing and photo-decomposition of phenol.

    PubMed

    Jana, Sumanta; Samai, Subhasis; Mitra, Bibhas C; Bera, Pulakesh; Mondal, Anup

    2014-09-14

    A novel non-enzymatic peroxide sensor has been constructed by using nickel oxide (NiO) thin films as sensing material, which were prepared by a two-step process: (i) electrodeposition of nickel sulfide (NiS) and (ii) thermal air oxidation of as-deposited NiS to NiO. The resultant material is highly porous and comprises interconnected nanofibers. UV-Vis spectroscopy, FTIR spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM) were used for a complete characterization of nanostructured NiO thin films. Cyclic voltammetry study shows that NiO/ITO electrode facilitates the oxidation of hydrogen peroxide and exhibits excellent catalytic activity towards its sensing. The amperometric study of NiO/ITO was carried out to determine the sensitivity, linear range, detection limit of the proposed sensor. The sensor exhibits prominent electrocatalytic activity toward the oxidation of H2O2 with a wide linear range and a low detection limit. The possible use of the synthesized NiO thin films as an effective photocatalyst for the decomposition of phenol is also discussed.

  19. Assessing the antimicrobial activity of zinc oxide thin films using disk diffusion and biofilm reactor

    NASA Astrophysics Data System (ADS)

    Gittard, Shaun D.; Perfect, John R.; Monteiro-Riviere, Nancy A.; Wei, Wei; Jin, Chunming; Narayan, Roger J.

    2009-03-01

    The electronic and chemical properties of semiconductor materials may be useful in preventing growth of microorganisms. In this article, in vitro methods for assessing microbial growth on semiconductor materials will be presented. The structural and biological properties of silicon wafers coated with zinc oxide thin films were evaluated using atomic force microscopy, X-ray photoelectron spectroscopy, and MTT viability assay. The antimicrobial properties of zinc oxide thin films were established using disk diffusion and CDC Biofilm Reactor studies. Our results suggest that zinc oxide and other semiconductor materials may play a leading role in providing antimicrobial functionality to the next-generation medical devices.

  20. Effect of substrate temperature on structural and electrical properties of RF sputtered hafnium oxide thin films

    SciTech Connect

    Das, K. C.; Ghosh, S. P.; Tripathy, N.; Kar, J. P.; Bose, G.; Lee, T.; Myoung, J. M.

    2015-06-24

    In this work hafnium oxide thin films were deposited on p-type silicon substrate by Radio frequency magnetron sputtering at different substrate temperature ranging from room temperature to 300 °C. The structural and electrical properties of the sputtered films were investigated by x-ray diffraction, capacitance-voltage and current-voltage measurements. The XRD results show the formation monoclinic structure of the hafnium oxide thin films. The shifting of C-V curves towards negative voltage side depicts the increase in positive oxide charges with the rise of substrate temperature. Leakage current was found increased, when temperature enhanced from room temperature to 300 °C.

  1. Novel Low Temperature Processing for Enhanced Properties of Ion Implanted Thin Films and Amorphous Mixed Oxide Thin Film Transistors

    NASA Astrophysics Data System (ADS)

    Vemuri, Rajitha

    This research emphasizes the use of low energy and low temperature post processing to improve the performance and lifetime of thin films and thin film transistors, by applying the fundamentals of interaction of materials with conductive heating and electromagnetic radiation. Single frequency microwave anneal is used to rapidly recrystallize the damage induced during ion implantation in Si substrates. Volumetric heating of the sample in the presence of the microwave field facilitates quick absorption of radiation to promote recrystallization at the amorphous-crystalline interface, apart from electrical activation of the dopants due to relocation to the substitutional sites. Structural and electrical characterization confirm recrystallization of heavily implanted Si within 40 seconds anneal time with minimum dopant diffusion compared to rapid thermal annealed samples. The use of microwave anneal to improve performance of multilayer thin film devices, e.g. thin film transistors (TFTs) requires extensive study of interaction of individual layers with electromagnetic radiation. This issue has been addressed by developing detail understanding of thin films and interfaces in TFTs by studying reliability and failure mechanisms upon extensive stress test. Electrical and ambient stresses such as illumination, thermal, and mechanical stresses are inflicted on the mixed oxide based thin film transistors, which are explored due to high mobilities of the mixed oxide (indium zinc oxide, indium gallium zinc oxide) channel layer material. Semiconductor parameter analyzer is employed to extract transfer characteristics, useful to derive mobility, subthreshold, and threshold voltage parameters of the transistors. Low temperature post processing anneals compatible with polymer substrates are performed in several ambients (oxygen, forming gas and vacuum) at 150 °C as a preliminary step. The analysis of the results pre and post low temperature anneals using device physics fundamentals

  2. Fully transparent thin film transistors based on zinc oxide channel layer and molybdenum doped indium oxide electrodes

    NASA Astrophysics Data System (ADS)

    MÄ dzik, Mateusz; Elamurugu, Elangovan; Viegas, Jaime

    2016-03-01

    In this work we report the fabrication of thin film transistors (TFT) with zinc oxide channel and molybdenum doped indium oxide (IMO) electrodes, achieved by room temperature sputtering. A set of devices was fabricated, with varying channel width and length from 5μm to 300μm. Output and transfer characteristics were then extracted to study the performance of thin film transistors, namely threshold voltage and saturation current, enabling to determine optimal fabrication process parameters. Optical transmission in the UV-VIS-IR are also reported.

  3. Measurement of faradaic current during AFM local oxidation of magnetic metal thin films

    NASA Astrophysics Data System (ADS)

    Takemura, Yasushi; Shimada, Yasuyuki; Watanabe, Genta; Yamada, Tsutomu; Shirakashi, Jun-ichi

    2007-04-01

    Faradaic current during a local oxidation using an atomic force microscope was studied. The intensity of the measured faradaic current was increased with increasing bias voltage applied to a cantilever, resulting in fabrication of larger size of nano-oxide structures on Si substrates. On the other hand, an excess current (over current) that was considered not to contribute the oxidation reaction was observed noticeably in the local oxidation of NiFe thin films. It was found that the excess current could be suppressed by depositing insulating oxide layers on the surfaces. The surface oxide layers were also advantageous for stable existence of meniscus promoting the local oxidation because of their hydrophilic properties. This method of capped oxide layers is significant for stable performance of the local oxidation technique fabricating nanostructures and nano-devices.

  4. Electrocatalytic Oxidation of Alcohols on Cu2O/Cu Thin Film Electrodeposited on Titanium Substrate

    NASA Astrophysics Data System (ADS)

    Bezghiche-Imloul, T.; Hammache-Makhloufi, H.; Ait Ahmed, N.

    2016-05-01

    A novel class of nanomaterials consisting of a composite thin film of cooper metal nanoparticles and cuprous oxide (Cu2O/Cu) for the catalytic electrooxidation of methanol, ethanol and ethylene glycol is considered here. The material was prepared by electrochemical deposition under a potentiostatic condition of -250mV vs saturated calomel electrode (SCE) from acetate bath at titanium substrate. The effect of electrodeposition time on the structure, composition and morphology of the deposit was investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicated the formation of pure cuprous oxide Cu2O thin film at low electrodeposition time (5 min) and Cu2O oxide thin film decorated with Cu nanoparticles (Cu2O/Cu) at high electrodeposition time. The obtained Cu2O and Cu2O/Cu thin films were explored for the electrochemical oxidation of alcohols in 1 M NaOH alkaline medium using cyclic voltammetry (CV) method. The Cu2O/Cu thin film grown at electrodeposition time of 15 min shows the best electrocatalytic performance toward ethanol oxidation. The effect of concentration of alcohols on the oxidation reaction was studied by CV and chronoamperometry. It was found that the reaction is governed by an irreversible diffusion process. The promising electrocatalytic activity of the Cu2O/Cu electrode provides a new platform for the fabrication of high-performance thin films for alcohols oxidation in alkaline medium. Therefore, the Cu2O/Cu electrode is a suitable as a less expensive electrocatalyst for alcohols oxidation.

  5. Evaluation of Characterization Techniques for Iron Pipe Corrosion Products and Iron Oxide Thin Films

    SciTech Connect

    Borch, Thomas; Camper, Anne K.; Biederman, Joel A.; Butterfield, Phillip; Gerlach, Robin; Amonette, James E.

    2008-10-01

    A common problem faced by drinking water studies is that of properly characterizing the corrosion products (CP) in iron pipescor synthetic Fe (hydr)oxides used to simulate the iron pipe used in municipal drinking-water systems. The present work compares the relative applicability of a suite of imaging and analytical techniques for the characterization of CPs and synthetic Fe oxide thin films and provide an overview of the type of data that each instrument can provide as well as their limitations to help researchers and consultants choose the best technique for a given task. Crushed CP from a water distribution system and synthetic Fe oxide thin films formed on glass surfaces were chosen as test samples for this evaluation. The CP and synthetic Fe oxide thin films were analyzed by atomic force microscopy (AFM), scanning electron microscopy (SEM), energy-dispersive spectroscopy, time-of-flight secondary ion mass spectrometry (ToF-SIMS), X-ray powder diffractometry (XRD), grazing incident diffractometry (GID), transmission electron microscopy (TEM), selected area electron diffraction, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared, Mössbauer spectroscopy, Brunauer-Emmett-Teller N2 adsorption and Fe concentration was determined by the ferrozine method. XRD and GID were found to be the most suitable techniques for identification of the mineralogical composition of CP and synthetic Fe oxide thin films, respectively. AFM and a combined ToF-SIMS-AFM approach proved excellent for roughness and depth profiling analysis of synthetic Fe oxide thin films, respectively. Corrosion products were difficult to study by AFM due to their surface roughness, while synthetic Fe oxide thin films resisted most spectroscopic methods due to their limited thickness (118 nm). XPS analysis is not recommended for mixtures of Fe (hydr)oxides due to their spectral similarities. SEM and TEM provided great detail on mineralogical morphology.

  6. Parallel writing on zirconium nitride thin films by local oxidation nanolithography

    NASA Astrophysics Data System (ADS)

    Farkas, N.; Comer, J. R.; Zhang, G.; Evans, E. A.; Ramsier, R. D.; Wight, S.; Dagata, J. A.

    2004-12-01

    Parallel pattern transfer of submicrometer-scale oxide features onto zirconium nitride thin films is reported. The oxidation reaction was verified by Auger microprobe analysis and secondary ion mass spectrometry. Oxide features of ˜70nm in height can be formed and selectively etched in a dilute aqueous hydrogen fluoride solution. This provides an interesting route to potential new applications for high-melting point, biocompatible surfaces that possess small feature sizes with controlled geometries.

  7. Ultra-thin resistive switching oxide layers self-assembled by field-induced oxygen migration (FIOM) technique

    PubMed Central

    Lee, Sangik; Hwang, Inrok; Oh, Sungtaek; Hong, Sahwan; Kim, Yeonsoo; Nam, Yoonseung; Lee, Keundong; Yoon, Chansoo; Kim, Wondong; Park, Bae Ho

    2014-01-01

    High-performance ultra-thin oxide layers are required for various next-generation electronic and optical devices. In particular, ultra-thin resistive switching (RS) oxide layers are expected to become fundamental building blocks of three-dimensional high-density non-volatile memory devices. Until now, special deposition techniques have been introduced for realization of high-quality ultra-thin oxide layers. Here, we report that ultra-thin oxide layers with reliable RS behavior can be self-assembled by field-induced oxygen migration (FIOM) at the interface of an oxide-conductor/oxide-insulator or oxide-conductor/metal. The formation via FIOM of an ultra-thin oxide layer with a thickness of approximately 2–5 nm and 2.5% excess oxygen content is demonstrated using cross-sectional transmission electron microscopy and secondary ion mass spectroscopy depth profile. The observed RS behavior, such as the polarity dependent forming process, can be attributed to the formation of an ultra-thin oxide layer. In general, as oxygen ions are mobile in many oxide-conductors, FIOM can be used for the formation of ultra-thin oxide layers with desired properties at the interfaces or surfaces of oxide-conductors in high-performance oxide-based devices. PMID:25362933

  8. Preparation and Optical Properties of Zirconium-Titanium-Oxide Thin Films by Reactive Sputtering

    NASA Astrophysics Data System (ADS)

    Matsumoto, Hironaga; Sekine, Masato; Miura, Noboru; Nakano, Ryotaro; Matsumoto, Setsuko

    2005-02-01

    Zirconium-titanium-oxide thin films were prepared by multi-target rf reactive sputtering using metallic targets of zirconium and titanium. The compositional ratio of zirconium to titanium in the thin films was precisely controlled through rf power. Zirconium and titanium in the thin films were found to exist as mixtures of chemically bonded ZrO2 and TiO2 from XPS spectra. The zirconium-titanium-oxide thin films with compositional ratio x<0.42 were identified to have a tetragonal crystal structure, whereas those with x≥q 0.42 were identified to be in the amorphous state. The refractive index of the zirconium-titanium-oxide thin film at a wavelength of 550 nm changed from 2.25 to 2.55 according to compositional ratio x, and the dispersion of the refractive index was analyzed using the Lorentz oscillator model with four oscillators. It was clarified that the estimated oscillator energies E1 (10.5 eV) and E2 (6.5 eV) correspond to zirconium oxide, and that E3 (5.5 eV) and E4 (4.3 eV) correspond to titanium oxide from fundamental absorption spectra and photoconductivity.

  9. Thermochemical hydrogen generation of indium oxide thin films

    NASA Astrophysics Data System (ADS)

    Lim, Taekyung; Ju, Sanghyun

    2017-03-01

    Development of alternative energy resources is an urgent requirement to alleviate current energy constraints. As such, hydrogen gas is gaining attention as a future alternative energy source to address existing issues related to limited energy resources and air pollution. In this study, hydrogen generation by a thermochemical water-splitting process using two types of In2O3 thin films was investigated. The two In2O3 thin films prepared by chemical vapor deposition (CVD) and sputtering deposition systems contained different numbers of oxygen vacancies, which were directly related to hydrogen generation. The as-grown In2O3 thin film prepared by CVD generated a large amount of hydrogen because of its abundant oxygen vacancies, while that prepared by sputtering had few oxygen vacancies, resulting in low hydrogen generation. Increasing the temperature of the In2O3 thin film in the reaction chamber caused an increase in hydrogen generation. The oxygen-vacancy-rich In2O3 thin film is expected to provide a highly effective production of hydrogen as a sustainable and efficient energy source.

  10. Preparation of Thin Melanin-Type Films by Surface-Controlled Oxidation.

    PubMed

    Salomäki, Mikko; Tupala, Matti; Parviainen, Timo; Leiro, Jarkko; Karonen, Maarit; Lukkari, Jukka

    2016-04-26

    The preparation of thin melanin films suitable for applications is challenging. In this work, we present a new alternative approach to thin melanin-type films using oxidative multilayers prepared by the sequential layer-by-layer deposition of cerium(IV) and inorganic polyphosphate. The interfacial reaction between cerium(IV) in the multilayer and 5,6-dihydroxyindole (DHI) in the adjacent aqueous solution leads to the formation of a thin uniform film. The oxidation of DHI by cerium(IV) proceeds via known melanin intermediates. We have characterized the formed DHI-melanin films using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), UV-vis spectroscopy, and spectroelectrochemistry. When a five-bilayer oxidative multilayer is used, the film is uniform with a thickness of ca. 10 nm. Its chemical composition, as determined using XPS, is typical for melanin. It is also redox active, and its oxidation occurs in two steps, which can be assigned to semiquinone and quinone formation within the indole structural motif. Oxidative multilayers can also oxidize dopamine, but the reaction stops at the dopamine quinone stage because of the limited amount of the multilayer-based oxidizing agent. However, dopamine oxidation by Ce(IV) was studied also in solution by UV-vis spectroscopy and mass spectrometry in order to verify the reaction mechanism and the final product. In solution, the oxidation of dopamine by cerium shows that the indole ring formation takes place already at low pH and that the mass spectrum of the final product is practically identical with that of commercial melanin. Therefore, layer-by-layer formed oxidative multilayers can be used to deposit functional melanin-type thin films on arbitrary substrates by a surface-controlled reaction.

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

    SciTech Connect

    Hu, W.; Peterson, R. L.

    2014-05-12

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

  12. Chemical Vapor Deposition of Aluminum Oxide Thin Films

    ERIC Educational Resources Information Center

    Vohs, Jason K.; Bentz, Amy; Eleamos, Krystal; Poole, John; Fahlman, Bradley D.

    2010-01-01

    Chemical vapor deposition (CVD) is a process routinely used to produce thin films of materials via decomposition of volatile precursor molecules. Unfortunately, the equipment required for a conventional CVD experiment is not practical or affordable for many undergraduate chemistry laboratories, especially at smaller institutions. In an effort to…

  13. Surface measurement of indium tin oxide thin film by wavelength-tuning Fizeau interferometry.

    PubMed

    Kim, Yangjin; Hibino, Kenichi; Sugita, Naohiko; Mitsuishi, Mamoru

    2015-08-10

    Indium-tin oxide (ITO) thin films have been widely used in displays such as liquid crystal displays and touch panels because of their favorable electrical conductivity and optical transparency. The surface shape and thickness of ITO thin films must be precisely measured to improve their reliability and performance. Conventional measurement techniques take single point measurements and require expensive systems. In this paper, we measure the surface shape of an ITO thin film on top of a transparent plate using wavelength-tuning Fizeau interferometry. The surface shape was determined by compensating for the phase error introduced by optical interference from the thin film, which was calculated using the phase and amplitude distributions measured by wavelength-tuning. The proposed measurement method achieved noncontact, large-aperture, and precise measurements of transparent thin films. The surface shape of the sample was experimentally measured to an accuracy of 5.13 nm.

  14. Room-temperature fabrication of light-emitting thin films based on amorphous oxide semiconductor

    SciTech Connect

    Kim, Junghwan Miyokawa, Norihiko; Ide, Keisuke; Toda, Yoshitake; Hiramatsu, Hidenori; Hosono, Hideo; Kamiya, Toshio

    2016-01-15

    We propose a light-emitting thin film using an amorphous oxide semiconductor (AOS) because AOS has low defect density even fabricated at room temperature. Eu-doped amorphous In-Ga-Zn-O thin films fabricated at room temperature emitted intense red emission at 614 nm. It is achieved by precise control of oxygen pressure so as to suppress oxygen-deficiency/excess-related defects and free carriers. An electronic structure model is proposed, suggesting that non-radiative process is enhanced mainly by defects near the excited states. AOS would be a promising host for a thin film phosphor applicable to flexible displays as well as to light-emitting transistors.

  15. Plasmonic nanodot array optimization on organic thin film solar cells using anodic aluminum oxide templates

    NASA Astrophysics Data System (ADS)

    Bae, Kyuyoung; Kim, Kyoungsik

    2013-09-01

    The fabrication method of plasmonic nanodots on ITO or nc-ZnO substrate has been developed to improve the efficiency of organic thin film solar cells. Nanoscale metallic nanodots arrays are fabricated by anodic aluminum oxide (AAO) template mask which can have different structural parameters by varying anodization conditions. In this paper, the structural parameters of metallic nanodots, which can be controlled by the diverse structures of AAO template mask, are investigated to enhance the optical properties of organic thin film solar cells. It is found that optical properties of the organic thin film solar cells are improved by finding optimization values of the structural parameters of the metallic nanodot array.

  16. Conductor Formation Through Phase Transformation in Ti-Oxide Thin Films

    NASA Astrophysics Data System (ADS)

    Liu, Y. S.; Lin, Y. H.; Wei, Y. S.; Liu, C. Y.

    2012-01-01

    The resistance and transmittance of Ti-oxide thin films sputtered on quartz substrates were studied. The electrical and optical properties can be changed by varying the percentage of O2 introduced during the sputtering. The lowest resistivity for the sputtered Ti-oxide thin film was 2.30 × 10-2 Ω cm for 12.5% O2, which was obtained after annealing at 400°C in ambient oxygen. The results of x-ray photoelectron spectroscopy (XPS) curve-fitting indicate that the Ti-oxide thin film contained both Ti2O3 and TiO2 phases during deposition. The Ti2O3 phase was transformed into the stable TiO2 phase during annealing. The Ti2O3-TiO2 phase transformation initiated the substitution reaction. The substitution of Ti4+ ions in the TiO2 phase for the Ti3+ ions in the Ti2O3 phase created the free electrons. This Ti2O3-TiO2 phase transformation demonstrates the potential mechanism for conduction in the annealed Ti-oxide thin films. The transmittance of the annealed Ti-oxide thin films can be as high as approximately 90% at the 400 nm wavelength with the introduction of 16.5% O2. This result indicates that the annealed Ti-oxide thin films are excellent candidates for use as transparent conducting layers for ultraviolet (UV) or near-UV light-emitting diode (LED) devices.

  17. Electrodeposition and electrochemical reduction of epitaxial metal oxide thin films and superlattices

    NASA Astrophysics Data System (ADS)

    He, Zhen

    The focus of this dissertation is the electrodeposition and electrochemical reduction of epitaxial metal oxide thin films and superlattices. The electrochemical reduction of metal oxides to metals has been studied for decades as an alternative to pyrometallurgical processes for the metallurgy industry. However, the previous work was conducted on bulk polycrystalline metal oxides. Paper I in this dissertation shows that epitaxial face-centered cubic magnetite (Fe3O4 ) thin films can be electrochemically reduced to epitaxial body-centered cubic iron (Fe) thin films in aqueous solution on single-crystalline Au substrates at room temperature. This technique opens new possibilities to produce special epitaxial metal/metal oxide heterojunctions and a wide range of epitaxial metallic alloy films from the corresponding mixed metal oxides. Electrodeposition, like biomineralization, is a soft solution processing method which can produce functional materials with special properties onto conducting or semiconducting solid surfaces. Paper II in this dissertation presents the electrodeposition of cobalt-substituted magnetite (CoxFe3-xO4, 0 of cobalt-substituted magnetite (CoxFe3-xO4, 0thin films and superlattices on Au single-crystalline substrates, which can be potentially used in spintronics and memory devices. Paper III in this dissertation reports the electrodeposition of crystalline cobalt oxide (Co3O4) thin films on stainless steel and Au single-crystalline substrates. The crystalline Co3O4 thin films exhibit high catalytic activity towards the oxygen evolution reaction in an alkaline solution. A possible application of the electrodeposited Co 3O4 is the fabrication of highly active and low-cost photoanodes for photoelectrochemical water-splitting cells.

  18. Effect of oxygen deficiency on electronic properties and local structure of amorphous tantalum oxide thin films

    SciTech Connect

    Denny, Yus Rama; Firmansyah, Teguh; Oh, Suhk Kun; Kang, Hee Jae; Yang, Dong-Seok; Heo, Sung; Chung, JaeGwan; Lee, Jae Cheol

    2016-10-15

    Highlights: • The effect of oxygen flow rate on electronic properties and local structure of tantalum oxide thin films was studied. • The oxygen deficiency induced the nonstoichiometric state a-TaOx. • A small peak at 1.97 eV above the valence band side appeared on nonstoichiometric Ta{sub 2}O{sub 5} thin films. • The oxygen flow rate can change the local electronic structure of tantalum oxide thin films. - Abstract: The dependence of electronic properties and local structure of tantalum oxide thin film on oxygen deficiency have been investigated by means of X-ray photoelectron spectroscopy (XPS), Reflection Electron Energy Loss Spectroscopy (REELS), and X-ray absorption spectroscopy (XAS). The XPS results showed that the oxygen flow rate change results in the appearance of features in the Ta 4f at the binding energies of 23.2 eV, 24.4 eV, 25.8, and 27.3 eV whose peaks are attributed to Ta{sup 1+}, Ta{sup 2+}, Ta{sup 3+}/Ta{sup 4+}, and Ta{sup 5+}, respectively. The presence of nonstoichiometric state from tantalum oxide (TaOx) thin films could be generated by the oxygen vacancies. In addition, XAS spectra manifested both the increase of coordination number of the first Ta-O shell and a considerable reduction of the Ta-O bond distance with the decrease of oxygen deficiency.

  19. Strong oxidation resistance of atomically thin boron nitride nanosheets.

    PubMed

    Li, Lu Hua; Cervenka, Jiri; Watanabe, Kenji; Taniguchi, Takashi; Chen, Ying

    2014-02-25

    Investigation of oxidation resistance of two-dimensional (2D) materials is critical for many of their applications because 2D materials could have higher oxidation kinetics than their bulk counterparts due to predominant surface atoms and structural distortions. In this study, the oxidation behavior of high-quality boron nitride (BN) nanosheets of 1-4 layers thick has been examined by heating in air. Atomic force microscopy and Raman spectroscopy analyses reveal that monolayer BN nanosheets can sustain up to 850 °C, and the starting temperature of oxygen doping/oxidation of BN nanosheets only slightly increases with the increase of nanosheet layer and depends on heating conditions. Elongated etch lines are found on the oxidized monolayer BN nanosheets, suggesting that the BN nanosheets are first cut along the chemisorbed oxygen chains and then the oxidative etching grows perpendicularly to these cut lines. The stronger oxidation resistance of BN nanosheets makes them more preferable for high-temperature applications than graphene.

  20. Erbium oxide thin films on Si(100) obtained by laser ablation and electron beam evaporation

    NASA Astrophysics Data System (ADS)

    Queralt, X.; Ferrater, C.; Sánchez, F.; Aguiar, R.; Palau, J.; Varela, M.

    1995-02-01

    Erbium oxide thin films have been obtained by laser ablation and electron beam evaporation techniques on Si(100) substrates. The samples were grown under different conditions of oxygen atmosphere and substrate temperature without any oxidation process after deposition. The crystal structure has been studied by X-ray diffraction. Films obtained by laser ablation are highly textured in the [ hhh] direction, although this depends on the conditions of oxygen pressure and substrate temperature. In order to study the depth composition profile of the thin films and the interdiffusion of erbium metal and oxygen towards the silicon substrates, X-ray photoelectron spectroscopy analyses have been carried out.

  1. Identification of the oxidation state of americium by thin-layer chromatography using domestic plates

    SciTech Connect

    Molochnikova, N.P.; Myasoedov, B.F.

    1994-10-01

    Methods of precipitation, solvent extraction, ion exchange, and extraction chromatography were suggested to identify trace amounts of americium in different oxidation states. Thin-layer chromatography (TLC) has not been used previously for these purposes. At the same time, this method is widely used in the separation of small quantities of elements in different valence states. Previously, the chromatographic mobility of actinide ions on thin layers of silica gel and cellulose on Silufol plates (CSFR) and plates from Merck (Germany) was investigated. The behavior of americium in different oxidation states on domestic TLC plates in nitric acid solutions was determined to be of interest.

  2. Investigation of optical properties of nickel oxide thin films deposited on different substrates

    NASA Astrophysics Data System (ADS)

    Nama Manjunatha, Krishna; Paul, Shashi

    2015-10-01

    Nickel oxide has been investigated for several potential applications, namely, ultraviolet detectors, electro chromic devices, displays, diodes for light emitting, transparent conductive electrode, and optoelectronic devices. These applications require an in depth analysis of nickel oxide prior to its exploration in aforementioned devices. Optical properties of materials were investigated by depositing thin film of nickel oxide on different substrates in order to understand if the choice of substrate can have effect on deducing various optical parameters and can lead to wrong conclusions. In view of this, we have investigated optical properties of nickel oxide deposited on different substrates (glass, transparent plastic, sapphire, potassium bromide, and calcium fluoride).

  3. Effects of working pressure on physical properties of tungsten-oxide thin films sputtered from oxide target

    SciTech Connect

    Riech, I.; Acosta, M.; Pena, J. L.; Bartolo-Perez, P.

    2010-03-15

    Tungsten-oxide films were deposited on glass substrates from a metal-oxide target by nonreactive radio-frequency sputtering. The authors have studied the effect that changing Ar gas pressure has on the electrical, optical, and chemical composition in the thin films. Resistivity of WO{sub 3} changed ten orders of magnitude with working gas pressure values from 20 to 80 mTorr. Thin films deposited at 20 mTorr of Ar sputtering pressure showed lower resistivity and optical transmittance. X-ray photoelectron spectroscopy (XPS) measurements revealed similar chemical composition for all samples irrespective of Ar pressure used. However, XPS analyses of the evolution of W 4f and O 1s peaks indicated a mixture of oxides dependent on the Ar pressure used during deposition.

  4. Investigation of physicochemical and tribological properties of transparent oxide semiconducting thin films based on Ti-V oxides

    NASA Astrophysics Data System (ADS)

    Mazur, M.; Sieradzka, K.; Kaczmarek, D.; Domaradzki, J.; Wojcieszak, D.; Domanowski, P.

    2013-08-01

    In this paper investigations of structural and optical properties of nanocrystalline Ti-V oxide thin films are described. The films were deposited onto Corning 7059 glass using a modified reactive magnetron sputtering method. Structural investigations of prepared Ti-V oxides with vanadium addition of 19 at. % revealed amorphous structure, while incorporation of 21 and 23 at. % of vanadium resulted in V2O5 formation with crystallites sizes of 12.7 and 32.4 nm, respectively. All prepared thin films belong to transparent oxide semiconductors due to their high transmission level of ca. 60-75 % in the visible light range, and resistivity in the range of 3.3·102-1.4·105 Ωcm. Additionally, wettability and hardness tests were performed in order to evaluate the usefulness of the films for functional coatings.

  5. Fabrication and characterization of oxide-based thin film transistors, and process development for oxide heterostructures

    NASA Astrophysics Data System (ADS)

    Lim, Wantae

    2009-12-01

    This dissertation is focused on the development of thin film transistors (TFTs) using oxide materials composed of post-transitional cations with (n-1)d 10ns0 (n≥4). The goal is to achieve high performance oxide-based TFTs fabricated at low processing temperature on either glass or flexible substrates for next generation display applications. In addition, etching mechanism and Ohmic contact formation for oxide heterostructure (ZnO/CuCrO 2) system is demonstrated. The deposition and characterization of oxide semiconductors (In 2O3-ZnO, and InGaZnO4) using a RF-magnetron sputtering system are studied. The main influence on the resistivity of the films is found to be the oxygen partial pressure in the sputtering ambient. The films remained amorphous and transparent (> 70%) at all process conditions. These films showed good transmittance at suitable conductivity for transistor fabrication. The electrical characteristics of both top- and bottom-gate type Indium Zinc Oxide (InZnO) and Indium Gallium Zinc Oxide (InGaZnO4)-based TFTs are reported. The InZnO films were favorable for depletion-mode TFTs due to their tendency to form oxygen vacancies, while enhancement-mode devices were realized with InGaZnO4 films. The InGaZnO4-based TFTs fabricated on either glass or plastic substrates at low temperature (<100°C) exhibit good electrical properties: the saturation mobility of 5--12 cm2.V-1.s-1 and threshold voltage of 0.5--2.5V. The devices are also examined as a function of aging time in order to verify long-term stability in air. The effect of gate dielectric materials on electrical properties of InGaZnO 4-based TFTs was investigated. The use of SiNx film as a gate dielectric reduces the trap density and the roughness at the channel/gate dielectric interface compared to SiO2 gate dielectric, resulting in an improvement of device parameters by reducing scattering of trapped charges at the interface. The quality of interface is shown to have large effect on TFT performance

  6. Fluorine compounds for doping conductive oxide thin films

    DOEpatents

    Gessert, Tim; Li, Xiaonan; Barnes, Teresa M; Torres, Jr., Robert; Wyse, Carrie L

    2013-04-23

    Methods of forming a conductive fluorine-doped metal oxide layer on a substrate by chemical vapor deposition are described. The methods may include heating the substrate in a processing chamber, and introducing a metal-containing precursor and a fluorine-containing precursor to the processing chamber. The methods may also include adding an oxygen-containing precursor to the processing chamber. The precursors are reacted to deposit the fluorine-doped metal oxide layer on the substrate. Methods may also include forming the conductive fluorine-doped metal oxide layer by plasma-assisted chemical vapor deposition. These methods may include providing the substrate in a processing chamber, and introducing a metal-containing precursor, and a fluorine-containing precursor to the processing chamber. A plasma may be formed that includes species from the metal-containing precursor and the fluorine-containing precursor. The species may react to deposit the fluorine-doped metal oxide layer on the substrate.

  7. MOCVD of zirconium oxide thin films: Synthesis and characterization

    NASA Astrophysics Data System (ADS)

    Torres-Huerta, A. M.; Domínguez-Crespo, M. A.; Ramírez-Meneses, E.; Vargas-García, J. R.

    2009-02-01

    The synthesis of thin films of zirconia often produces tetragonal or cubic phases, which are stable at high temperatures, but that can be transformed into the monoclinic form by cooling. In the present study, we report the deposition of thin zirconium dioxide films by metalorganic chemical vapor deposition using zirconium (IV)-acetylacetonate as precursor. Colorless, porous, homogeneous and well adherent ZrO 2 thin films in the cubic phase were obtained within the temperature range going from 873 to 973 K. The deposits presented a preferential orientation towards the (1 1 1) and (2 2 0) planes as the substrate temperature was increased, and a crystal size ranging between 20 and 25 nm. The kinetics is believed to result from film growth involving the deposition and aggregation of nanosized primary particles produced during the CVD process. A mismatch between the experimental results obtained here and the thermodynamic prediction was found, which can be associated with the intrinsic nature of the nanostructured materials, which present a high density of interfaces.

  8. Study on the Preparation and Properties of Colored Iron Oxide Thin Films

    NASA Astrophysics Data System (ADS)

    Zhao, Xianhui; Li, Changhong; Liu, Qiuping; Duan, Yandong; He, Junjing; Liu, Su; Wang, Hai; Liang, Song

    2013-03-01

    Colored iron oxide thin films were prepared using Sol-gel technique. The raw materials were tetraethyl orthosilicate (TEOS), etoh ehanol (EtOH), iron nitrate, and de-ionized water. Various properties were measured and analysed, including the colour of thin films, surface topography, UV-Visible spectra, corrosion resistance and hydrophobicity. To understand how these properties influenced the structural and optical properties of Fe2O3 thin films, Scanning Electron Microscope (SEM), UV Spectrophotometer and other facilities were employed. Many parameters influence the performance of thin films, such as film layers, added H2O content, and the amount of polydimethylsiloxane (PDMS). When the volume ratio of TEOS, EtOH and H2O was 15: 13: 1, the quality of Fe(NO3)3·9H2O was 6g, and pH value was 3, reddish and uniform Fe2O3 thin films with excellent properties were produced. Obtained thin films possessed corrosion resistance in hydrochloric acid with pH=l and the absorption edge wavelength was ~350.2nm. Different H2O contents could result in different morphologies of Fe2O3 nanoparticles. When 1.5 ml PDMS was added into the Sol, thin films possessed hydrophobiliry without dropping. Coating with different layers, thin films appeared different morphologies. Meanwhile, with the increment of film layers, the absorbance increased gradually.

  9. Theoretical Investigation of Supported Utra-Thin Cobalt/Nickel/Iron/Manganese Oxides

    NASA Astrophysics Data System (ADS)

    Bajdich, Michal; García Melchor, Max; Vojvodic, Alexandra

    In the last decade, a number of experiments have shown that ultra-thin layers of transition metal oxides (TMOs) can be stabilized when interfaced with precious metal supports such as Au(111) and Pt(111) or Ir(100). Moreover, gold supported Co/Ni/Mn-based catalysts have been experimentally proven to exhibit higher oxygen evolution reaction (OER) activities than other metal supported oxide catalysts. However, the synergistic effect of contact with gold support is yet to be fully understood. In this talk, I will report on our recent investigation of thermodynamic stability and and high water reactivity of ultra-thin cobalt oxide nanoislands supported on Au(111). Furthermore, the stability trends, scaling of the metal-support interaction and charge transfer of several Mn/Fe/Co/Ni supported oxides on all FCC(111) metals will be analyzed. The type and role of different edge sites for the OER activity of these nanoislands will be discussed.

  10. Self-activated ultrahigh chemosensitivity of oxide thin film nanostructures for transparent sensors

    PubMed Central

    Moon, Hi Gyu; Shim, Young-Soek; Kim, Do Hong; Jeong, Hu Young; Jeong, Myoungho; Jung, Joo Young; Han, Seung Min; Kim, Jong Kyu; Kim, Jin-Sang; Park, Hyung-Ho; Lee, Jong-Heun; Tuller, Harry L.; Yoon, Seok-Jin; Jang, Ho Won

    2012-01-01

    One of the top design priorities for semiconductor chemical sensors is developing simple, low-cost, sensitive and reliable sensors to be built in handheld devices. However, the need to implement heating elements in sensor devices, and the resulting high power consumption, remains a major obstacle for the realization of miniaturized and integrated chemoresistive thin film sensors based on metal oxides. Here we demonstrate structurally simple but extremely efficient all oxide chemoresistive sensors with ~90% transmittance at visible wavelengths. Highly effective self-activation in anisotropically self-assembled nanocolumnar tungsten oxide thin films on glass substrate with indium-tin oxide electrodes enables ultrahigh response to nitrogen dioxide and volatile organic compounds with detection limits down to parts per trillion levels and power consumption less than 0.2 microwatts. Beyond the sensing performance, high transparency at visible wavelengths creates opportunities for their use in transparent electronic circuitry and optoelectronic devices with avenues for further functional convergence. PMID:22905319

  11. High resolution Fowler-Nordheim field emission maps of thin silicon oxide layers

    NASA Astrophysics Data System (ADS)

    Ruskell, Todd G.; Workman, Richard K.; Chen, Dong; Sarid, Dror; Dahl, Sarah; Gilbert, Stephen

    1996-01-01

    An improved method for characterizing thin oxide films using Fowler-Nordheim field emission is reported. The method uses a conducting-tip atomic force microscope with dual feedback systems, one for the topography and a second for the field emission bias voltage. Images of the voltage required to maintain a 10 pA emission current through a 3 nm oxide film thermally grown on p-type Si(100) demonstrate a spatial resolution of 8 nm.

  12. Fabrication of Thin Electrolytes for Second-Generation Solid Oxide Fuel Cells

    DTIC Science & Technology

    1999-05-05

    methods for oxides, especially for stabilized zirconia and compares them with regard to SOFC applications. These methods will be classified into chemical...Keywords: SOFC ; Thin films; Zirconia; PVD; CVD; Liquid precursor methods 1. Introduction components [1-6]. One problem associated with lowering the...electrolyte material for Solid Oxide Fuel lowering the electrolyte resistance either by decreas- Cells ( SOFCs ) because of its unique combination of ing the

  13. Synthesis of Cobalt Oxides Thin Films Fractal Structures by Laser Chemical Vapor Deposition

    PubMed Central

    Haniam, P.; Kunsombat, C.; Chiangga, S.; Songsasen, A.

    2014-01-01

    Thin films of cobalt oxides (CoO and Co3O4) fractal structures have been synthesized by using laser chemical vapor deposition at room temperature and atmospheric pressure. Various factors which affect the density and crystallization of cobalt oxides fractal shapes have been examined. We show that the fractal structures can be described by diffusion-limited aggregation model and discuss a new possibility to control the fractal structures. PMID:24672354

  14. Induction of superconductivity of a La2CuO4 thin film chemically oxidized by NaClO

    NASA Astrophysics Data System (ADS)

    Wang, C. C.; Cui, M. L.; Zheng, X.; Zhu, J.

    High-quality, c-axis-oriented La2CuO4 thin films have been fabricated by the pulsed laser ablation technique. Superconductivity has been successfully induced in the films after chemical oxidation using sodium hypochlorite solution as oxidizing agent. The structural properties, surface morphology, and electrical resistivity before and after oxidation are compared. In addition, the oxidation mechanism is discussed.

  15. Properties of anodic oxides grown on a hafnium–tantalum–titanium thin film library

    PubMed Central

    Mardare, Andrei Ionut; Ludwig, Alfred; Savan, Alan; Hassel, Achim Walter

    2014-01-01

    A ternary thin film combinatorial materials library of the valve metal system Hf–Ta–Ti obtained by co-sputtering was studied. The microstructural and crystallographic analysis of the obtained compositions revealed a crystalline and textured surface, with the exception of compositions with Ta concentration above 48 at.% which are amorphous and show a flat surface. Electrochemical anodization of the composition spread thin films was used for analysing the growth of the mixed surface oxides. Oxide formation factors, obtained from the potentiodynamic anodization curves, as well as the dielectric constants and electrical resistances, obtained from electrochemical impedance spectroscopy, were mapped along two dimensions of the library using a scanning droplet cell microscope. The semiconducting properties of the anodic oxides were mapped using Mott–Schottky analysis. The degree of oxide mixing was analysed qualitatively using x-ray photoelectron spectroscopy depth profiling. A quantitative analysis of the surface oxides was performed and correlated to the as-deposited metal thin film compositions. In the concurrent transport of the three metal cations during oxide growth a clear speed order of Ti > Hf > Ta was proven. PMID:27877648

  16. Characterization and properties of multicomponent oxide thin films with gasochromic effect

    NASA Astrophysics Data System (ADS)

    Domaradzki, Jaroslaw; Baniewicz, Kosma; Mazur, Michał; Wojcieszak, Damian; Kaczmarek, Danuta

    2013-07-01

    In this work structural, optical and surface properties of gasochromic thin films based on mixtures of selected transition metal oxides have been outlined. Two sets of thin films were prepared by reactive magnetron sputtering from four-component metallic mosaic targets containing Ti, V ,Ta as a base and W or Nb as a fourth material. Neither Pd nor Pt metals were used as a catalyst. X-ray diffraction investigations revealed, that all prepared thin films were amorphous while application of x-ray photoelectron spectroscopy studies show presence of TiO2, V2O5, Ta2O5, and WO3 or Nb2O5 oxides at the surface depending on the thin films composition. Gasochromic properties were investigated through observations of the change in optical transmission response of the films exposed to reducing or oxidizing gas. Dynamic optical responses of samples were collected at room temperature. Depending on composition of the sample being investigated the change in optical transmission at room temperature ranged up to about 28 %. Based on optical transmission refraction and extinction indexes were calculated using reverse synthesis method. The obtained results are very promising for utilization of prepared thin films in optical gas sensing devices.

  17. Magnetoelectric hexaferrite thin film growth on oxide conductive layer for applications at low voltages

    NASA Astrophysics Data System (ADS)

    Zare, Saba; Izadkhah, Hessam; Vittoria, Carmine

    2016-08-01

    Magnetoelectric (ME) M-type hexaferrite thin films were deposited on conductive oxide layer of Indium-Tin Oxide (ITO) in order to lower applied voltages to observe ME effects at room temperature. The thin film of ME hexaferrites, SrCo2Ti2Fe8O19/ITO buffer layer, were deposited on sapphire substrate using Pulsed Laser Deposition (PLD) technique. The film exhibited ME effects as confirmed by vibrating sample magnetometer (VSM) in voltages as low as 0.5 V. Without the oxide conductive layer the required voltages to observe ME effects were typically 500 V and higher. The thin films were characterized by X-ray diffractometer, scanning electron microscope, energy-dispersive spectroscopy, vibrating sample magnetometer, and ferromagnetic resonance. We measured saturation magnetization of 1064 G, and coercive field of 20 Oe for these thin films. The change rate in remanence magnetization was measured with the application of DC voltage at room temperature and it gave rise to changes in remanence in the order of 15% with the application of only 0.5 V (DC voltage). We deduced a ME coupling, α, of 5×10-10 s m-1 in SrCo2Ti2Fe8O19 thin films.

  18. Enhanced Luminescence in Epitaxial Oxide Thin-Film Phosphors

    SciTech Connect

    Lee, Y.E.; Norton, D.P.; Budai, J.D.; Park, C.; Kim, M.; Pennycook, S.J.; Rack, P.D.; Potter, M.D.

    1999-11-08

    Undoped and Mn-doped ZnGa{sub 2}O{sub 4} thin-film phosphors were grown using pulsed laser ablation on (100) MgO single crystal and glass substrates. X-ray results showed the films on (100) MgO are well aligned both out-of plane and in-plane. Epitaxial films show superior photoluminescent intensity as compared to randomly oriented polycrystalline films, indicating that intragranular crystallinity strongIy influences luminescent properties. Li-doped ZnGa{sub 2}O{sub 4} exhibited significantly enhanced photoluminescence intensity.

  19. Characterization of Monolayer Formation on Aluminum-Doped Zinc Oxide Thin Films

    SciTech Connect

    Rhodes,C.; Lappi, S.; Fischer, D.; Sambasivan, S.; Genzer, J.; Franzen, S.

    2008-01-01

    The optical and electronic properties of aluminum-doped zinc oxide (AZO) thin films on a glass substrate are investigated experimentally and theoretically. Optical studies with coupling in the Kretschmann configuration reveal an angle-dependent plasma frequency in the mid-IR for p-polarized radiation, suggestive of the detection of a Drude plasma frequency. These studies are complemented by oxygen depletion density functional theory studies for the calculation of the charge carrier concentration and plasma frequency for bulk AZO. In addition, we report on the optical and physical properties of thin film adlayers of n-hexadecanethiol (HDT) and n-octadecanethiol (ODT) self-assembled monolayers (SAMs) on AZO surfaces using reflectance FTIR spectroscopy, X-ray photoelectron spectroscopy (XPS), contact angle, and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. Our characterization of the SAM deposition onto the AZO thin film reveals a range of possible applications for this conducting metal oxide.

  20. PEALD YSZ-based bilayer electrolyte for thin film-solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Yu, Wonjong; Cho, Gu Young; Hong, Soonwook; Lee, Yeageun; Kim, Young Beom; An, Jihwan; Cha, Suk Won

    2016-10-01

    Yttria-stabilized zirconia (YSZ) thin film electrolyte deposited by plasma enhanced atomic layer deposition (PEALD) was investigated. PEALD YSZ-based bi-layered thin film electrolyte was employed for thin film solid oxide fuel cells on nanoporous anodic aluminum oxide substrates, whose electrochemical performance was compared to the cell with sputtered YSZ-based electrolyte. The cell with PEALD YSZ electrolyte showed higher open circuit voltage (OCV) of 1.0 V and peak power density of 182 mW cm-2 at 450 °C compared to the one with sputtered YSZ electrolyte(0.88 V(OCV), 70 mW cm-2(peak power density)). High OCV and high power density of the cell with PEALD YSZ-based electrolyte is due to the reduction in ohmic and activation losses as well as the gas and electrical current tightness.

  1. Extremely thin bilayer electrolyte for solid oxide fuel cells (SOFCs) fabricated by chemical solution deposition (CSD).

    PubMed

    Oh, Eun-Ok; Whang, Chin-Myung; Lee, Yu-Ri; Park, Sun-Young; Prasad, Dasari Hari; Yoon, Kyung Joong; Son, Ji-Won; Lee, Jong-Ho; Lee, Hae-Weon

    2012-07-03

    An extremely thin bilayer electrolyte consisting of yttria-stabilized zirconia (YSZ) and gadolinia-doped ceria (GDC) is successfully fabricated on a sintered NiO-YSZ substrate. Major processing flaws are effectively eliminated by applying local constraints to YSZ nanoparticles, and excellent open circuit voltage and cell performance are demonstrated in a solid oxide fuel cell (SOFC) at intermediate operating temperatures.

  2. Memory switches based on metal oxide thin films

    NASA Technical Reports Server (NTRS)

    Ramesham, Rajeshuni (Inventor); Thakoor, Anilkumar P. (Inventor); Lambe, John J. (Inventor)

    1990-01-01

    MnO.sub.2-x thin films (12) exhibit irreversible memory switching (28) with an OFF/ON resistance ratio of at least about 10.sup.3 and the tailorability of ON state (20) resistance. Such films are potentially extremely useful as a connection element in a variety of microelectronic circuits and arrays (24). Such films provide a pre-tailored, finite, non-volatile resistive element at a desired place in an electric circuit, which can be electrically turned OFF (22) or disconnected as desired, by application of an electrical pulse. Microswitch structures (10) constitute the thin film element, contacted by a pair of separate electrodes (16a, 16b) and have a finite, pre-selected ON resistance which is ideally suited, for example, as a programmable binary synaptic connection for electronic implementation of neural network architectures. The MnO.sub.2-x microswitch is non-volatile, patternable, insensitive to ultraviolet light, and adherent to a variety of insulating substrates (14), such as glass and silicon dioxide-coated silicon substrates.

  3. Pseudo capacitive performance of copper oxide thin films grown by RF sputtering

    SciTech Connect

    Reddy, B. Purusottam; Ganesh, K. Sivajee; Hussain, O. M.

    2015-06-24

    Thin films of Copper Oxide were prepared by radio frequency magnetron sputtering on steel substrates maintained at 250°C under different RF powers ranging from 150W to 250W by keeping the sputtering pressure at 5.7×10{sup −3} mbar and O{sub 2}:Ar ratio of 1:7. The influence of RF power on the pseudo capacitive performance of thin films was studied. The X-ray diffraction studies and Raman studies indicates that all the thin films exhibits CuO phase. The electrochemical studies was done by using three electrode configuration with platinum as reference electrode. From the cyclic voltammetry studies a high rate pseudocapacitance of 227 mFcm{sup −2} at 0.5 mVs{sup −1} and 77% of capacity retention after 1000 cycles was obtained for the CuO thin films prepared at an RF power of 220W.

  4. Nanostructured tungsten trioxide thin films synthesized for photoelectrocatalytic water oxidation: a review.

    PubMed

    Zhu, Tao; Chong, Meng Nan; Chan, Eng Seng

    2014-11-01

    The recent developments of nanostructured WO3 thin films synthesized through the electrochemical route of electrochemical anodization and cathodic electrodeposition for the application in photoelectrochemical (PEC) water splitting are reviewed. The key fundamental reaction mechanisms of electrochemical anodization and cathodic electrodeposition methods for synthesizing nanostructured WO3 thin films are explained. In addition, the effects of metal oxide precursors, electrode substrates, applied potentials and current densities, and annealing temperatures on size, composition, and thickness of the electrochemically synthesized nanostructured WO3 thin films are elucidated in detail. Finally, a summary is given for the general evaluation practices used to calculate the energy conversion efficiency of nanostructured WO3 thin films and a recommendation is provided to standardize the presentation of research results in the field to allow for easy comparison of reported PEC efficiencies in the near future.

  5. Zinc Oxide Thin Films Fabricated with Direct Current Magnetron Sputtering Deposition Technique

    SciTech Connect

    Hoon, Jian-Wei; Chan, Kah-Yoong; Krishnasamy, Jegenathan; Tou, Teck-Yong

    2011-03-30

    Zinc oxide (ZnO) is a very promising material for emerging large area electronic applications including thin-film sensors, transistors and solar cells. We fabricated ZnO thin films by employing direct current (DC) magnetron sputtering deposition technique. ZnO films with different thicknesses ranging from 100 nm to 1020 nm were deposited on silicon (Si) substrate. The deposition pressure was varied from 12 mTorr to 25 mTorr. The influences of the film thickness and the deposition pressure on structural properties of the ZnO films were investigated using Mahr surface profilometer and atomic force microscopy (AFM). The experimental results reveal that the film thickness and the deposition pressure play significant role in the structural formation of the deposited ZnO thin films. ZnO films deposited on Si substrates are promising for variety of thin-film sensor applications.

  6. Research Update: New possibilities for the nanoscale engineering of complex oxide thin films

    NASA Astrophysics Data System (ADS)

    McMitchell, S. R. C.

    2015-06-01

    Complex oxides are becoming engrained into modern technology. Understanding the growth and properties of these materials is extremely important for development of novel devices and optimization of existing technologies. Control of the growth of thin film oxides is essential to facilitate the fine-tuning of properties needed for device optimization. In this article, some recent advances in nanoscale engineering of functional oxides are summarized. Control of film structure through manipulation of growth kinetics and substrate considerations is discussed. The construction of composites and artificial materials is also considered. Furthermore, a future outlook is investigated including a route to industrial scale application.

  7. Thermochromic vanadium oxide thin films: Electronic and optical properties

    NASA Astrophysics Data System (ADS)

    Niklasson, G. A.; Li, S.-Y.; Granqvist, C. G.

    2014-11-01

    Vanadium dioxide, VO2, is a widely studied thermochromic material with potential applications in energy efficient window technology. It undergoes a first-order metal-to- insulator transition, accompanied by a crystal structure transformation from monoclinic to tetragonal rutile, at a critical temperature of 68 °C. Below this temperature, VO2 is semiconducting and infrared transmitting whereas it is metallic and infrared reflecting above the transition temperature. However, in order to achieve significant thermochromic switching, the luminous transmittance of thin films will typically be less than 50%. Here we report on recent research to improve the luminous transmittance as well as the transmittance change at the transition temperature. We systematically evaluate the effect of antireflection coatings, doping with Mg and the performance of coatings comprising thermochromic nanoparticles in a transparent matrix. The last option is shown to give the best performance and holds great promise for practical applications.

  8. Ordered fragmentation of oxide thin films at submicron scale

    PubMed Central

    Guo, L.; Ren, Y.; Kong, L. Y.; Chim, W. K.; Chiam, S. Y.

    2016-01-01

    Crack formation is typically undesirable as it represents mechanical failure that compromises strength and integrity. Recently, there have also been numerous attempts to control crack formation in materials with the aim to prevent or isolate crack propagation. In this work, we utilize fragmentation, at submicron and nanometre scales, to create ordered metal oxide film coatings. We introduce a simple method to create modified films using electroplating on a prepatterned substrate. The modified films undergo preferential fragmentation at locations defined by the initial structures on the substrate, yielding ordered structures. In thicker films, some randomness in the characteristic sizes of the fragments is introduced due to competition between crack propagation and crack creation. The method presented allows patterning of metal oxide films over relatively large areas by controlling the fragmentation process. We demonstrate use of the method to fabricate high-performance electrochromic structures, yielding good coloration contrast and high coloration efficiency. PMID:27748456

  9. Cadmium-Tin Oxide Transparent Conductive Thin Films

    NASA Astrophysics Data System (ADS)

    Stapinski, T.; Leja, E.; Marszalek, K.

    1986-09-01

    Cadmium-tin oxide (CTO) films have been prepared by d.c. reactive sputtering of Cd-Sn alloy targets in Ar-02 gas mixture. The electrical, optical and structural properties as well as the chemical composition of transparent conducting CTO films were found to depend on sputtering conditions. The value of optical band gap, optical constants, effective mass and relaxation time of electrons have been determined.

  10. Photo-Activated Synthesis of Functional Oxide Thin Films

    DTIC Science & Technology

    2010-03-01

    o (d200 = 2.53 Å), corresponding to lattice constant ~ 5.07 Å. In cubic fluorite structure, lattice parameter (d) can be calculated from ionic...noted that aliovalently introduced oxygen vacancies have an effect on anion ionic radius, therefore lattice constant in doped fluorite structure cannot...denotes the dopant content.[26] This relation indicates that oxygen deficiency decreases the lattice constant of fluorite -structured oxides. It is

  11. Thin-film solid-oxide fuel cells

    SciTech Connect

    Jankowski, A.F.

    1997-05-01

    Fuel cells are energy conversion devices that would save billions of dollars in fuel costs alone each year in the United States if they could be implemented today for stationary and transportation applications (1-5). There are a wide variety of fuel cells available, e.g. molten carbonate, phosphoric acid, proton exchange membrane and solid-oxide. However, solid-oxide fuel cells (SOFCS) are potentially more efficient and less expensive per kilowatt of power in comparison to other fuel cells. For transportation applications, the energy efficiency of a conventional internal combustion engine would be increased two-fold as replaced with a zero-emission SOFC. The basic unit of a SOFC consists of an anode and cathode separated by an oxygen-ion conducting, electrolyte layer. Manifolded stacks of fuel cells, with electrical interconnects, enable the transport and combination of a fuel and oxidant at elevated temperature to generate electrical current. Fuel cell development has proceeded along different paths based on the configuration of the anode-electrolyte-cathode. Various configurations include the tubular, monolithic and planar geometries. A planar geometry for the anode-electrolyte-cathode accompanied by a reduction in layer thickness offers the potential for high power density. Maximum power densities will require yet additional innovations in the assembly of fuel cell stacks with all of the manifolding stipulations for gas flow and electrical interconnects.

  12. Formation of surface oxides and Ag2O thin films with atomic oxygen on Ag(111)

    NASA Astrophysics Data System (ADS)

    Derouin, Jonathan; Farber, Rachael G.; Heslop, Stacy L.; Killelea, Daniel R.

    2015-11-01

    The nature of the oxygen species adsorbed to silver surfaces is a key component of the heterogeneously catalyzed epoxidation of ethylene and partial oxidation of methanol over silver catalysts. We report the formation of two different silver-oxygen species depending on the flux and energy of incident gas-phase oxygen atoms on an Ag(111) surface. A combination of surface science techniques was used to characterize the oxidized surfaces. Atomic oxygen was generated with an Ir filament; lower temperatures created surface oxides previously reported. When O was deposited with a higher filament temperature, the surface became highly corrugated, little subsurface oxygen was observed, and thin layers of Ag2O were likely formed. These results show that the energy and flux of oxygen are important parameters in the chemical identity and abundance of oxygen on silver surfaces and suggest that formation of the Ag2O thin film hinders formation of subsurface oxygen.

  13. Enhanced electrical properties of oxide semiconductor thin-film transistors with high conductivity thin layer insertion for the channel region

    NASA Astrophysics Data System (ADS)

    Nguyen, Cam Phu Thi; Raja, Jayapal; Kim, Sunbo; Jang, Kyungsoo; Le, Anh Huy Tuan; Lee, Youn-Jung; Yi, Junsin

    2017-02-01

    This study examined the performance and the stability of indium tin zinc oxide (ITZO) thin film transistors (TFTs) by inserting an ultra-thin indium tin oxide (ITO) layer at the active/insulator interface. The electrical properties of the double channel device (ITO thickness of 5 nm) were improved in comparison with the single channel ITZO or ITO devices. The TFT characteristics of the device with an ITO thickness of less than 5 nm were degraded due to the formation of an island-like morphology and the carriers scattering at the active/insulator interface. The 5 nm-thick ITO inserted ITZO TFTs (optimal condition) exhibited a superior field effect mobility (∼95 cm2/V·s) compared with the ITZO-only TFTs (∼34 cm2/V·s). The best characteristics of the TFT devices with double channel layer are due to the lowest surface roughness (0.14 nm) and contact angle (50.1°) that result in the highest hydrophicility, and the most effective adhesion at the surface. Furthermore, the threshold voltage shifts for the ITO/ITZO double layer device decreased to 0.80 and -2.39 V compared with 6.10 and -6.79 V (for the ITZO only device) under positive and negative bias stress, respectively. The falling rates of EA were 0.38 eV/V and 0.54 eV/V for the ITZO and ITO/ITZO bi-layer devices, respectively. The faster falling rate of the double channel devices suggests that the trap density, including interface trap and semiconductor bulk trap, can be decreased by the ion insertion of a very thin ITO film into the ITZO/SiO2 reference device. These results demonstrate that the double active layer TFT can potentially be applied to the flat panel display.

  14. Methods to protect and recover work function of air exposed transition metal oxide thin films

    NASA Astrophysics Data System (ADS)

    Irfan, Irfan; Wang, Chenggong; Turinske, Alexander J.; Gao, Yongli

    2012-09-01

    Insertion of high work function (WF) transition metal oxide (TMO) layers between the anode and the hole transport layer is established to substantially enhance the performance of organic light emitting diodes (OLED). The high WF of transition metal oxide layer has been demonstrated to be the most crucial for the enhancement. The WF of a TMO layer decreases substantially with air exposure, and noticeably by the ambient even inside a low vacuum system. In the present work we discuss various methods to protect and recover the high WF after a TMO thin film has been exposed to air. We report covering a thin organic layer on top of MoOx to protect the high work function. We found that a thin layer of 1-2 nm organic layer was sufficient to protect the work function of MoOx thin film underneath. We further report methods to recover already decreased TMO WF due to air exposure. We performed oxygen plasma cleaning of air exposed MoOx film and found out that oxygen plasma could substantially recover the WF of as deposited MoOx film. We also performed annealing of air exposed MoOx film inside an ultra high vacuum system and observed a thin layer of oxygenrich adsorbate layer, which desorbed upon annealing that in turn substantially recovered the MoOx WF. We discuss the vacuum annealing and the effect of resulting surface on the interface energy level alignment.

  15. Optimization of Dimensionless Figure of Merit in Oxide Thin Film Thermoelectrics

    NASA Astrophysics Data System (ADS)

    Osborne, Daniel; Huxtable, Scott; Tiwari, Ashutosh; Abiade, Jeremiah

    2010-03-01

    The ability of uniquely functional thermoelectric materials to convert waste heat directly into electricity is critical considering the global energy economy. Profitable, energy-efficient thermoelectrics possess thermoelectric figures of merit ZT >= 1. We examined the effect of metal nanoparticle -- oxide film interfaces on the thermal conductivity κ and Seebeck coefficient S in bilayer and multilayer thin film oxide thermoelectrics in an effort to improve the dimensionless figure of merit ZT. Since a thermoelectric's figure of merit ZT is directly proportional to S/κ, reducing κ and increasing S are key strategies to optimize ZT. We reduced κ by phonon scattering due to the inclusion of metal nanoparticles in the bulk of the thermoelectric thin film, and increased S due to energy-dependent electron scattering at the metal - oxide interfaces. Doped strontium titanate (STO) thin film/Au nanoparticle composites were synthesized by alternate ablation of Au and Nb-doped STO targets during pulsed laser deposition. Characterization of the thermoelectric films involve XRD, XPS, and TEM analyses, Seebeck coefficient measurements, and also measurements of the thermal conductivity via time-domain thermoreflectance. The measured thermal conductivities and Seebeck coefficients of the thin films shows a strong dependence on the nanoscale interfaces of the films.

  16. A novel thin film solid oxide fuel cell for microscale energy conversion

    SciTech Connect

    Jankowiski, A F; Morse, J D

    1999-05-01

    A novel approach for the fabrication and assembly of a solid oxide fuel cell system is described which enables effective scaling of the fuel delivery, mainfold, and fuel cell stack components for applications in miniature and microscale energy conversion. Electrode materials for solid oxide fuel cells are developed using sputter deposition techniques. A thin film anode is formed by codeposition of nickel and yttria-stabilized zirconia (YSZ). This approach provides a mixed conducting interfacial layer between the nickel electrode and electrolyte layer. Similarly, a thin film cathode is formed by co-deposition of silver and yttria-stabilized zirconia. Additionally, sputter deposition of yttria-stabilized zirconia thin film electrolyte enables high quality, continuous films to be formed having thickness on the order of 1-2 {micro}m. This will effectively lower the temperature of operation for the fuel cell stack significantly below the traditional ranges at which solid oxide electrolyte systems are operated (600--1000 C), thereby rendering this fuel cell system suitable for miniaturization. Scaling towards miniaturization is accomplished by utilizing novel micromaching approaches which allow manifold channels and fuel delivery system to be formed within the substrate which the thin film fuel cell stack is fabricated on, thereby circumventing the need for bulky manifold components which are not directly scalable.

  17. Fabrication of Fe-Al nanoparticles by selective oxidation of Fe-Al thin films

    NASA Astrophysics Data System (ADS)

    Jang, Pyungwoo; Shin, Seungchan; Jung, Chip-Sup; Kim, Kwang-Ho; Seomoon, Kyu

    2013-04-01

    The possibility of a new technique for fabricating nanoparticles from thin films using selective oxidation in an atmosphere mixture of water vapor and hydrogen was investigated. Fe-5wt.%Al films were RF-sputtered and annealed in the atmosphere mixture at 900°C for up to 200 min, in order to oxidize aluminum selectively. Thermodynamics simulation showed that temperatures exceeding 800°C are necessary to prevent iron from being oxidized, as confirmed by the depth profile of XPS. As the annealing time increased, the morphology of the 200-nm Fe-Al films changed from the continuous to the discontinuous type; thus, particulate Fe-Al films formed after 100 min. The particulate 10- to 100-nm Fe-Al films showed super-paramagnetic behavior after the oxidation. Thus, a new technique for fabricating nanoparticles was successfully introduced using selective oxidation.

  18. Investigations on bactericidal properties of molybdenum-tungsten oxides combinatorial thin film material libraries.

    PubMed

    Mardare, Cezarina Cela; Hassel, Achim Walter

    2014-11-10

    A combinatorial thin film material library from the molybdenum-tungsten refractory metals oxides system was prepared by thermal coevaporation, and its structural and morphological properties were investigated after a multiple step heat treatment. A mixture of crystalline and amorphous oxides and suboxides was obtained, as well as surface structuring caused by the enrichment of molybdenum oxides in large grains. It was found that the oxide phases and the surface morphology change as a function of the compositional gradient. Tests of the library antimicrobial activity against E. coli were performed and the antimicrobial activity was proven in some defined compositional ranges. A mechanism for explaining the observed activity is proposed, involving a collective contribution from (i) increased local acidity due to the enrichment in large grains of molybdenum oxides with different stoichiometry and (ii) the release of free radicals from the W18O49 phase under visible light.

  19. Functional Multilayered Transparent Conducting Oxide Thin Films for Photovoltaic Devices

    SciTech Connect

    Noh, J. H.; Lee, S.; Kim, J. Y.; Lee, J. K.; Han, H. S.; Cho, C. M.; Cho, I. S.; Jung, H. S.; Hong, K. S.

    2009-01-01

    In this study, we present a thermally stable multilayered transparent conducting oxide (TCO) functionalized for dye-sensitized solar cells (DSSCs). Nb-doped TiO{sub 2} (NTO) layers deposited on conventional Sn-doped In{sub 2}O{sub 3} (ITO) substrates using pulsed laser deposition (PLD) enhanced the optical-to-electrical conversion efficiency of the DSSCs by as much as 17% compared to that of bare ITO-based DSSCs. The electrical properties and J-V characteristics of the multilayered NTO/ITO films showed that the improved cell performance was due to the facilitated charge injection from TiO{sub 2} to ITO that resulted from the formation of an ohmic contact with ITO, as well as the conserved high conductivity of ITO after the oxidizing annealing process. Moreover, the NTO/ITO-based DSSC exhibited higher efficiency than a F-doped SnO{sub 2}(FTO)-based one, which demonstrates that optimization of multilayered NTO-based TCOs is a realistic approach for achieving highly efficient photoenergy conversion devices.

  20. CSA doped polypyrrole-zinc oxide thin film sensor

    NASA Astrophysics Data System (ADS)

    Chougule, M. A.; Jundale, D. M.; Raut, B. T.; Sen, Shashwati; Patil, V. B.

    2013-02-01

    The polypyrrole-zinc oxide (PPy-ZnO) hybrid sensor doped with different weight ratios of camphor sulphonic acid (CSA) were prepared by spin coating technique. These CSA doped PPy-ZnO hybrids were characterized by field emission scanning electron microscope (FESEM) and fourier transform infrared (FTIR) which proved the formation of polypyrrole, PPy-ZnO and the interaction between polypyrrole - ZnO (PPy-ZnO) hybrid with CSA doping. The gas sensing properties of the PPy-ZnO hybrid films doped with CSA have been studied for oxidizing (NO2) as well as reducing (H2S, NH3, CH4OH and CH3OH) gases at room temperature. We demonstrate that CSA doped PPy-ZnO hybrid films are highly selective to NO2 along with high-sensitivity at low concentration (80% to 100 ppm) and better stability, which suggested that the CSA doped PPy-ZnO hybrid films are potential candidate for NO2 detection at room temperature.

  1. Study on mixed vanadium oxide thin film deposited by RF magnetron sputtering and its application

    NASA Astrophysics Data System (ADS)

    Ling, Zhang; Jianhui, Tu; Hao, Feng; Jingzhong, Cui

    Vanadium oxide (VOx) thin films were deposited on fused quartz using a pure metal vanadium target by RF reactive magnetron sputtering technique. Film microstructure, valence state, optical transmittance properties were studied. The mixed valence VOx thin films deposited with different thickness were found to be amorphous. And the optical transmittance curves are flatness in certain wavelength region. These films can be used to control the relative light intensity of the rubidium light beam between the rubidium lamp and the vapor cell, in order to optimize the working parameters of the rubidium frequency standard (RAFS).

  2. Insights into electrical characteristics of silicon doped hafnium oxide ferroelectric thin films

    NASA Astrophysics Data System (ADS)

    Zhou, Dayu; Müller, J.; Xu, Jin; Knebel, S.; Bräuhaus, D.; Schröder, U.

    2012-02-01

    Silicon doped hafnium oxide thin films were recently discovered to exhibit ferroelectricity. In the present study, metal-ferroelectric-metal capacitors with Si:HfO2 thin films as ferroelectric material and TiN as electrodes have been characterized with respect to capacitance and current density as functions of temperature and applied voltage. Polarity asymmetry of the frequency dependent coercive field was explained by interfacial effects. No ferroelectric-paraelectric phase transition was observed at temperatures up to 478 K. Clear distinctions between current evolutions with or without polarization switching were correlated to the time competition between the measurement and the response of relaxation mechanisms.

  3. Damp-Heat Induced Degradation of Transparent Conducting Oxides for Thin Film Solar Cells (Presentation)

    SciTech Connect

    Pern, J.; Noufi, R.; Li, X.; DeHart, C.; To, B.

    2008-05-01

    The objectives are: (1) To achieve a high long-term performance reliability for the thin-film CIGS PV modules with more stable materials, device structure designs, and moisture-resistant encapsulation materials and schemes; (2) to evaluate the DH stability of various transparent conducting oxides (TCOs); (3) to identify the degradation mechanisms and quantify degradation rates; (4) to seek chemical and/or physical mitigation methods, and explore new materials. It's important to note that direct exposure to DH represents an extreme condition that a well-encapsulated thin film PV module may never experience.

  4. Rayleigh instability in polymer thin films coated in the nanopores of anodic aluminum oxide templates.

    PubMed

    Tsai, Chia-Chan; Chen, Jiun-Tai

    2014-01-14

    We study the Rayleigh instability of polystyrene (PS) thin films coated in the nanopores of anodic aluminum oxide (AAO) templates. After thermal annealing, the surface of the PS thin films undulates and the nanostructures transform from nanotubes to Rayleigh-instability-induced nanostructures (short nanorods with encapsulated air bubbles). With longer annealing times, the nanostructures further transform to nanorods with longer lengths. PS samples with two different molecular weights (24 and 100 kg/mol) are used, and their instability transformation processes are compared. The morphology diagrams of the nanostructures at different stages are also constructed to elucidate the mechanism of the morphology transformation.

  5. Improved Transparent Conducting Oxides Boost Performance of Thin-Film Solar Cells (Fact Sheet)

    SciTech Connect

    Not Available

    2011-02-01

    Today?s thin-film solar cells could not function without transparent conducting oxides (TCOs). TCOs act as a window, both protecting the cell and allowing light to pass through to the cell?s active layers. Until recently, TCOs were seen as a necessary, but static, layer of a thin-film photovoltaic (PV) cell. But a group of researchers at the National Renewable Energy Laboratory (NREL) has identified a pathway to producing improved TCO films that demonstrate higher infrared transparency. To do so, they have modified the TCOs in ways that did not seem possible a few years ago.

  6. The microstructures and electrical properties of Y-doped amorphous vanadium oxide thin films

    NASA Astrophysics Data System (ADS)

    Gu, Deen; Zhou, Xin; Guo, Rui; Wang, Zhihui; Jiang, Yadong

    2017-03-01

    One of promising approaches for further improving the sensitivity of microbolometer arrays with greatly-reduced pixel size is using the thermal-sensitive materials with higher performance. In this paper, Y-doped vanadium oxide (VOx) thin films prepared by a reactively sputtering process exhibit enhanced performance for the microbolometer application compared with frequently-applied VOx thin films. Both undoped and Y-doped VOx thin films are amorphous due to the relatively low deposition temperature. Y-doped VOx thin films exhibit smoother surface morphology than VOx due to the restrained expansion of particles during depositions. Y-doping increases the temperature coefficient of resistivity by over 20% for the doping level of 1.30 at%. The change rate of resistivity, after aging for 72 h, of thin films was reduced from about 15% for undoped VOx to 2% due to the introduction of Y. Moreover, Y-doped VOx thin films have a low 1/f noise level as VOx ones. Y-doping provides an attractive approach for preparing VOx thermal-sensitive materials with enhanced performance for microbolometers.

  7. Phase transitions via selective elemental vacancy engineering in complex oxide thin films

    NASA Astrophysics Data System (ADS)

    Lee, Sang A.; Jeong, Hoidong; Woo, Sungmin; Hwang, Jae-Yeol; Choi, Si-Young; Kim, Sung-Dae; Choi, Minseok; Roh, Seulki; Yu, Hosung; Hwang, Jungseek; Kim, Sung Wng; Choi, Woo Seok

    2016-04-01

    Defect engineering has brought about a unique level of control for Si-based semiconductors, leading to the optimization of various opto-electronic properties and devices. With regard to perovskite transition metal oxides, O vacancies have been a key ingredient in defect engineering, as they play a central role in determining the crystal field and consequent electronic structure, leading to important electronic and magnetic phase transitions. Therefore, experimental approaches toward understanding the role of defects in complex oxides have been largely limited to controlling O vacancies. In this study, we report on the selective formation of different types of elemental vacancies and their individual roles in determining the atomic and electronic structures of perovskite SrTiO3 (STO) homoepitaxial thin films fabricated by pulsed laser epitaxy. Structural and electronic transitions have been achieved via selective control of the Sr and O vacancy concentrations, respectively, indicating a decoupling between the two phase transitions. In particular, O vacancies were responsible for metal-insulator transitions, but did not influence the Sr vacancy induced cubic-to-tetragonal structural transition in epitaxial STO thin film. The independent control of multiple phase transitions in complex oxides by exploiting selective vacancy engineering opens up an unprecedented opportunity toward understanding and customizing complex oxide thin films.

  8. Phase transitions via selective elemental vacancy engineering in complex oxide thin films

    PubMed Central

    Lee, Sang A.; Jeong, Hoidong; Woo, Sungmin; Hwang, Jae-Yeol; Choi, Si-Young; Kim, Sung-Dae; Choi, Minseok; Roh, Seulki; Yu, Hosung; Hwang, Jungseek; Kim, Sung Wng; Choi, Woo Seok

    2016-01-01

    Defect engineering has brought about a unique level of control for Si-based semiconductors, leading to the optimization of various opto-electronic properties and devices. With regard to perovskite transition metal oxides, O vacancies have been a key ingredient in defect engineering, as they play a central role in determining the crystal field and consequent electronic structure, leading to important electronic and magnetic phase transitions. Therefore, experimental approaches toward understanding the role of defects in complex oxides have been largely limited to controlling O vacancies. In this study, we report on the selective formation of different types of elemental vacancies and their individual roles in determining the atomic and electronic structures of perovskite SrTiO3 (STO) homoepitaxial thin films fabricated by pulsed laser epitaxy. Structural and electronic transitions have been achieved via selective control of the Sr and O vacancy concentrations, respectively, indicating a decoupling between the two phase transitions. In particular, O vacancies were responsible for metal-insulator transitions, but did not influence the Sr vacancy induced cubic-to-tetragonal structural transition in epitaxial STO thin film. The independent control of multiple phase transitions in complex oxides by exploiting selective vacancy engineering opens up an unprecedented opportunity toward understanding and customizing complex oxide thin films. PMID:27033718

  9. Synthesis and characterization of low work function alkali oxide thin films for unconventional thermionic energy converters

    NASA Astrophysics Data System (ADS)

    Giorgis, V.; Morini, F.; Zhu, T.; Robillard, J.-F.; Wallart, X.; Codron, J.-L.; Dubois, E.

    2016-11-01

    In this work, we present the synthesis and the characterization of low work function thin films for Micro Thermionic Converters (MTC). The objective is producing a device operating at relatively low temperature (<1000 K). We aim at improving the MTC efficiency by reducing the work function of the electrodes and increasing the emitted current density by alkali metal oxides electrodes coating. In particular, in this work, we analyse and compare the performances of two alkali metal oxides: potassium and caesium oxides. Our choice to exploit those materials relies on their low work function and their abundance. For both materials, we present the results on the synthesis of the oxides under high vacuum and controlled temperature. The oxide thin films were characterized by X-ray photoelectron spectroscopy, photoemission, and thermionic emission measurements. By exploiting the latter technique, a quantitative evaluation of the current density, emitted by the heated oxides, is obtained as a function of temperature. Our results demonstrate that it is possible to decrease the silicon work function by almost 3 eV, enabling significant thermionic currents despite relatively low temperatures (below 850 K).

  10. Glucose-assisted reduction achieved transparent p-type cuprous oxide thin film by a solution method

    NASA Astrophysics Data System (ADS)

    Nie, Sha; Sun, Jian; Gong, Hao; Chen, Zequn; Huang, Yifei; Xu, Jianmei; Zhao, Ling; Zhou, Wei; Wang, Qing

    2016-08-01

    The fabrication of p-type cuprous oxide thin film via a cheap and simple chemical method has been known as challenging. We first find that glucose can assist reduce Cu to a lower valence state in the preparation of cuprous oxide films by the sol-gel method. By first adding glucose in the sol as reducing agent, oxidation from the oxygen in the environment is limited and transparent p-type cuprous oxide films are eventually achieved under optimized experimental conditions. We have developed a p-type cuprous oxide thin film with an optimal Hall mobility of ∼8 cm2/Vs and an optical transmittance of 78%.

  11. Interface engineered multifunctional oxide thin films with optimized properties

    NASA Astrophysics Data System (ADS)

    Collins, Gregory Roy

    2010-06-01

    In our world today, energy has become one of the most valuable resources, in particular, renewable and clean energy sources. The research presented here represents an investigation into three separate areas of this topic. In thin film applications, the ordered structures as well as the inherent thinness of the films precludes the normal physics found in bulk materials. Characterizations of films of this type can provide information on molecular level charge transfer processes of the film layer materials since diffusive properties are minimal. With the control given by pulsed laser deposition methods, film and interface structure can be altered allowing for an examination of these effects on the materials properties. For the electrolyte and cathode materials, this equates to finding thermal and PO2 dependencies for electronic and ionic transport. For barium titanate, aside from the effects of oxygen vacancies, the interface quality between the electrodes and the ferroelectric material determines the effectiveness of energy transfer between these boundaries. That is, poor bonding characteristics or the formation of intermediate layers will introduce inconsistencies and (possibly) unwanted piezoelectric response properties of the material which could introduce parasitic dampening (resistance) of the mechanical vibrations of a piezoelectric transducer, altering its resonant characteristics. The clean reaction products and potential for high power outputs provide a strong impetus into investigations of fuel cell structures to improve their functionality. With conventional applications being dominated by high temperature (>700 °C) cells utilizing YSZ as an electrolyte medium, much gain can be made in efficiency through the lowering of cell operation temperature. The first part of my research focuses on the growth and characterization of a novel multilayered electrolyte structure consisting of alternating layers of GCO and YSZ for use in a medium temperature (400--600

  12. Enhanced optical constants of nanocrystalline yttrium oxide thin films

    SciTech Connect

    Ramana, C. V.; Mudavakkat, V. H.; Bharathi, K. Kamala; Atuchin, V. V.; Pokrovsky, L. D.; Kruchinin, V. N.

    2011-01-17

    Yttrium oxide (Y{sub 2}O{sub 3}) films with an average crystallite-size (L) ranging from 5 to 40 nm were grown by sputter-deposition onto Si(100) substrates. The optical properties of grown Y{sub 2}O{sub 3} films were evaluated using spectroscopic ellipsometry measurements. The size-effects were significant on the optical constants and their dispersion profiles of Y{sub 2}O{sub 3} films. A significant enhancement in the index of refraction (n) is observed in well-defined Y{sub 2}O{sub 3} nanocrystalline films compared to that of amorphous Y{sub 2}O{sub 3}. A direct, linear L-n relationship found for Y{sub 2}O{sub 3} films suggests that tuning optical properties for desired applications can be achieved by controlling the size at the nanoscale dimensions.

  13. Continuously controlled optical band gap in oxide semiconductor thin films

    SciTech Connect

    Herklotz, Andreas; Rus, Stefania Florina; Ward, Thomas Zac

    2016-02-02

    The optical band gap of the prototypical semiconducting oxide SnO2 is shown to be continuously controlled through single axis lattice expansion of nanometric films induced by low-energy helium implantation. While traditional epitaxy-induced strain results in Poisson driven multidirectional lattice changes shown to only allow discrete increases in bandgap, we find that a downward shift in the band gap can be linearly dictated as a function of out-of-plane lattice expansion. Our experimental observations closely match density functional theory that demonstrates that uniaxial strain provides a fundamentally different effect on the band structure than traditional epitaxy-induced multiaxes strain effects. In conclusion, charge density calculations further support these findings and provide evidence that uniaxial strain can be used to drive orbital hybridization inaccessible with traditional strain engineering techniques.

  14. Continuously controlled optical band gap in oxide semiconductor thin films

    DOE PAGES

    Herklotz, Andreas; Rus, Stefania Florina; Ward, Thomas Zac

    2016-02-02

    The optical band gap of the prototypical semiconducting oxide SnO2 is shown to be continuously controlled through single axis lattice expansion of nanometric films induced by low-energy helium implantation. While traditional epitaxy-induced strain results in Poisson driven multidirectional lattice changes shown to only allow discrete increases in bandgap, we find that a downward shift in the band gap can be linearly dictated as a function of out-of-plane lattice expansion. Our experimental observations closely match density functional theory that demonstrates that uniaxial strain provides a fundamentally different effect on the band structure than traditional epitaxy-induced multiaxes strain effects. In conclusion, chargemore » density calculations further support these findings and provide evidence that uniaxial strain can be used to drive orbital hybridization inaccessible with traditional strain engineering techniques.« less

  15. Consequence of oxidant to monomer ratio on optical and structural properties of Polypyrrole thin film deposited by oxidation polymerization technique

    NASA Astrophysics Data System (ADS)

    Jatratkar, Aviraj A.; Yadav, Jyotiprakash B.; Kamat, Sandip V.; Patil, Vaishali S.; Mahadik, D. B.; Barshilia, Harish C.; Puri, Vijaya; Puri, R. K.

    2015-05-01

    This paper reports the effect of oxidant to monomer (O/M) ratio on optical and structural properties of Polypyrrole (PPy) thin film deposited by chemical oxidation polymerization technique. Noticeable changes have observed in the properties of PPy thin films with O/M ratio. Cauliflower structure have been observed in FE-SEM images, wherein grain size is observed to decrease with increase in O/M ratio. AFM results are in good agreement with FE-SEM results. From FTIR spectra it is found that, PPy is in highly oxidized form at low O/M ratio but oxidation decreased with increase in O/M ratio. Also C-C stretching vibrations of PPy ring is decreased whereas C=C stretching is increased with ratio. Absorption peak around 450 nm corresponds to π-π* transition and around 800 nm for polarons and bipolarons. The intensity of such peaks confirms the conductivity of PPy, which is observed maximum at low O/M ratio and found to decrease with increase in ratio. Optical band gap (BG) is found to increase from 2.07 eV to 2.11 eV with increase in the O/M ratio.

  16. Electrical properties of zinc-oxide-based thin-film transistors using strontium-oxide-doped semiconductors

    NASA Astrophysics Data System (ADS)

    Wu, Shao-Hang; Zhang, Nan; Hu, Yong-Sheng; Chen, Hong; Jiang, Da-Peng; Liu, Xing-Yuan

    2015-10-01

    Strontium-zinc-oxide (SrZnO) films forming the semiconductor layers of thin-film transistors (TFTs) are deposited by using ion-assisted electron beam evaporation. Using strontium-oxide-doped semiconductors, the off-state current can be dramatically reduced by three orders of magnitude. This dramatic improvement is attributed to the incorporation of strontium, which suppresses carrier generation, thereby improving the TFT. Additionally, the presence of strontium inhibits the formation of zinc oxide (ZnO) with the hexagonal wurtzite phase and permits the formation of an unusual phase of ZnO, thus significantly changing the surface morphology of ZnO and effectively reducing the trap density of the channel. Project supported by the National Natural Science Foundation of China (Grant No. 6140031454) and the Innovation Program of Chinese Academy of Sciences and State Key Laboratory of Luminescence and Applications.

  17. Cholesterol biosensor based on rf sputtered zinc oxide nanoporous thin film

    SciTech Connect

    Singh, S. P.; Arya, Sunil K.; Pandey, Pratibha; Malhotra, B. D.; Saha, Shibu; Sreenivas, K.; Gupta, Vinay

    2007-08-06

    Cholesterol oxidase (ChOx) has been immobilized onto zinc oxide (ZnO) nanoporous thin films grown on gold surface. A preferred c-axis oriented ZnO thin film with porous surface morphology has been fabricated by rf sputtering under high pressure. Optical studies and cyclic voltammetric measurements show that the ChOx/ZnO/Au bioelectrode is sensitive to the detection of cholesterol in 25-400 mg/dl range. A relatively low value of enzyme's kinetic parameter (Michaelis-Menten constant) {approx}2.1 mM indicates enhanced enzyme affinity of ChOx to cholesterol. The observed results show promising application of nanoporous ZnO thin film for biosensing application without any functionalization.

  18. Microstructure, optical property, and electronic band structure of cuprous oxide thin films

    SciTech Connect

    Park, Jun-Woo; Jang, Hyungkeun; Kim, Sung; Choi, Suk-Ho; Lee, Hosun; Kang, Joongoo; Wei, Su-Huai

    2011-11-15

    Cuprous oxide (Cu{sub 2}O) thin films were grown via radio frequency sputtering deposition at various temperatures. The dielectric functions and luminescence properties of the Cu{sub 2}O thin films were measured using spectroscopic ellipsometry and photoluminescence, respectively. High-energy peaks were observed in the photoluminescence spectra. Several critical points (CPs) were found using second derivative spectra of the dielectric functions and the standard critical point model. The electronic band structure and the dielectric functions were calculated using density functional theory, and the CP energies were estimated to compare with the experimental data. We identified the high-energy photoluminescence peaks to quasi-direct transitions which arose from the granular structures of the Cu{sub 2}O thin films.

  19. Post-annealing-free, room temperature processed nanocrystalline indium tin oxide thin films for plastic electronics

    NASA Astrophysics Data System (ADS)

    Nyoung Jang, Jin; Jong Lee, You; Jang, YunSung; Yun, JangWon; Yi, Seungjun; Hong, MunPyo

    2016-06-01

    In this study, we confirm that bombardment by high energy negative oxygen ions (NOIs) is the key origin of electro-optical property degradations in indium tin oxide (ITO) thin films formed by conventional plasma sputtering processes. To minimize the bombardment effect of NOIs, which are generated on the surface of the ITO targets and accelerated by the cathode sheath potential on the magnetron sputter gun (MSG), we introduce a magnetic field shielded sputtering (MFSS) system composed of a permanent magnetic array between the MSG and the substrate holder to block the arrival of energetic NOIs. The MFSS processed ITO thin films reveal a novel nanocrystal imbedded polymorphous structure, and present not only superior electro-optical characteristics but also higher gas diffusion barrier properties. To the best of our knowledge, no gas diffusion barrier composed of a single inorganic thin film formed by conventional plasma sputtering processes achieves such a low moisture permeability.

  20. Microscopically crumpled indium-tin-oxide thin films as compliant electrodes with tunable transmittance

    SciTech Connect

    Ong, Hui-Yng; Shrestha, Milan; Lau, Gih-Keong

    2015-09-28

    Indium-tin-oxide (ITO) thin films are perceived to be stiff and brittle. This letter reports that crumpled ITO thin films on adhesive poly-acrylate dielectric elastomer can make compliant electrodes, sustaining compression of up to 25% × 25% equi-biaxial strain and unfolding. Its optical transmittance reduces with crumpling, but restored with unfolding. A dielectric elastomer actuator (DEA) using the 14.2% × 14.2% initially crumpled ITO thin-film electrodes is electrically activated to produce a 37% areal strain. Such electric unfolding turns the translucent DEA to be transparent, with transmittance increased from 39.14% to 52.08%. This transmittance tunability promises to make a low-cost smart privacy window.

  1. Microscopically crumpled indium-tin-oxide thin films as compliant electrodes with tunable transmittance

    NASA Astrophysics Data System (ADS)

    Ong, Hui-Yng; Shrestha, Milan; Lau, Gih-Keong

    2015-09-01

    Indium-tin-oxide (ITO) thin films are perceived to be stiff and brittle. This letter reports that crumpled ITO thin films on adhesive poly-acrylate dielectric elastomer can make compliant electrodes, sustaining compression of up to 25% × 25% equi-biaxial strain and unfolding. Its optical transmittance reduces with crumpling, but restored with unfolding. A dielectric elastomer actuator (DEA) using the 14.2% × 14.2% initially crumpled ITO thin-film electrodes is electrically activated to produce a 37% areal strain. Such electric unfolding turns the translucent DEA to be transparent, with transmittance increased from 39.14% to 52.08%. This transmittance tunability promises to make a low-cost smart privacy window.

  2. Hybrid composite thin films composed of tin oxide nanoparticles and cellulose

    NASA Astrophysics Data System (ADS)

    Mahadeva, Suresha K.; Nayak, Jyoti; Kim, Jaehwan

    2013-07-01

    This paper reports the preparation and characterization of hybrid thin films consisting of tin oxide (SnO2) nanoparticles and cellulose. SnO2 nanoparticle loaded cellulose hybrid thin films were fabricated by a solution blending technique, using sodium dodecyl sulfate as a dispersion agent. Scanning and transmission electron microscopy studies revealed uniform dispersion of the SnO2 nanoparticles in the cellulose matrix. Reduction in the crystalline melting transition temperature and tensile properties of cellulose was observed due to the SnO2 nanoparticle loading. Potential application of these hybrid thin films as low cost, flexible and biodegradable humidity sensors is examined in terms of the change in electrical resistivity of the material exposed to a wide range of humidity as well as its response-recovery behavior.

  3. Formation of thin walled ceramic solid oxide fuel cells

    DOEpatents

    Claar, Terry D.; Busch, Donald E.; Picciolo, John J.

    1989-01-01

    To reduce thermal stress and improve bonding in a high temperature monolithic solid oxide fuel cell (SOFC), intermediate layers are provided between the SOFC's electrodes and electrolyte which are of different compositions. The intermediate layers are comprised of a blend of some of the materials used in the electrode and electrolyte compositions. Particle size is controlled to reduce problems involving differential shrinkage rates of the various layers when the entire structure is fired at a single temperature, while pore formers are provided in the electrolyte layers to be removed during firing for the formation of desired pores in the electrode layers. Each layer includes a binder in the form of a thermosetting acrylic which during initial processing is cured to provide a self-supporting structure with the ceramic components in the green state. A self-supporting corrugated structure is thus formed prior to firing, which the organic components of the binder and plasticizer removed during firing to provide a high strength, high temperature resistant ceramic structure of low weight and density.

  4. Sputter deposition and characterization of lithium cobalt oxide thin films and their applications in thin-film rechargeable lithium batteries

    SciTech Connect

    Wang, B.; Bates, J.B.; Luck, C.F.; Sales, B.C.; Zuhr, R.A.; Robertson, J.D.

    1996-01-01

    Li Co oxide thin films were deposited by rf magnetron sputtering of a LiCoO{sub 2} target in a 3:1 Ar/O{sub 2} mixture gas. From proton-induced gamma-ray emission analysis and Rutherford backscattering spectrometry, the average composition of these films was determined to be Li{sub 1.15}CoO{sub 2.16}. X-ray powder diffraction patterns of films annealed in air at 500-700 C were consistent with regular rhombohedral structure of crystalline LiCoO{sub 2}. Discharge curves of thin film lithium cells with amoprohous LiCoO{sub 2} showed no obvious structural transition between 4.2 and 1.5 V. Shape of discharge curves of cells with polycrystalline cathodes were consistent with a two-phase voltage plateau at {similar_to}3.9 V with a relatively large capacity and two additional smaller plateaus at higher voltages. Cells with the 700 C annealed cathodes showed a capacity loss of {similar_to} after 1000 cycles between 4.2 and 3.0 V.

  5. A novel thin film solid oxide fuel cell for microscale energy conversion

    SciTech Connect

    Jankowiski, A; Morse, J

    1999-07-21

    A novel approach for the fabrication and assembly of a solid oxide fuel cell system is described which enables effective scaling of the fuel delivery, manifold, and fuel cell stack components for applications in miniature and microscale energy conversion. Electrode materials for solid oxide fuel cells are developed using sputter deposition techniques. A thin film anode is formed by co-deposition of nickel and yttria-stabilized zirconia (YSZ). This approach provides a mixed conducting inter-facial layer between the nickel electrode and electrolyte layer. Similarly, a thin film cathode is formed by co-deposition of silver and yttria-stabilized zirconia. Additionally, sputter deposition of yttria-stabilized zirconia thin film electrolyte enables high quality, continuous films to be formed having thicknesses on the order of 1-2 {micro}m. This will effectively lower the temperature of operation for the fuel cell stack significantly below the traditional ranges at which solid oxide electrolyte systems are operated (600-1000 C), thereby rendering this fuel cell system suitable for miniaturization, Scaling towards miniaturization is accomplished by utilizing novel micromachining approaches which allow manifold channels and fuel delivery system to be formed within the substrate which the thin film fuel cell stack is fabricated on, thereby circumventing the need for bulky manifold components which are not directly scalable. Methods to synthesize anodes for thin film solid-oxide fuel cells (TFSOFCs) from the electrolyte and a conductive material are developed using photolithographic patterning and physical vapor deposition. The anode layer must enable combination of the reactive gases, be conductive to pass the electric current, and provide mechanical support to the electrolyte and cathode layers. The microstructure and morphology desired for the anode layer should facilitate generation of maximum current density from the fuel cell. For these purposes, the parameters of the

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

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

    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.

  7. Carbon-Incorporated Amorphous Indium Zinc Oxide Thin-Film Transistors

    NASA Astrophysics Data System (ADS)

    Parthiban, S.; Park, K.; Kim, H.-J.; Yang, S.; Kwon, J.-Y.

    2014-11-01

    We propose the use of amorphous-carbon indium zinc oxide (a-CIZO) as a channel material for thin-film transistor (TFT) fabrication. This study chose a carbon dopant as a carrier suppressor and strong oxygen binder in amorphous-indium zinc oxide (a-IZO) channel material. a-CIZO thin films were deposited using radiofrequency (RF) sputtering and postannealed at 150°C. X-ray diffraction and transmission electron microscopy analysis revealed that the film remained amorphous even after postannealing. The a-CIZO TFT postannealed at 150°C exhibited saturation field-effect mobility of 16.5 cm2 V-1 s-1 and on-off current ratio of ˜4.3 × 107.

  8. Silver Nanoparticle-Embedded Thin Silica-Coated Graphene Oxide as an SERS Substrate

    PubMed Central

    Pham, Xuan-Hung; Hahm, Eunil; Kim, Hyung-Mo; Shim, Seongbo; Kim, Tae Han; Jeong, Dae Hong; Lee, Yoon-Sik; Jun, Bong-Hyun

    2016-01-01

    A hybrid of Ag nanoparticle (NP)-embedded thin silica-coated graphene oxide (GO@SiO2@Ag NPs) was prepared as a surface-enhanced Raman scattering (SERS) substrate. A 6 nm layer of silica was successfully coated on the surface of GO by the physical adsorption of sodium silicate, followed by the hydrolysis of 3-mercaptopropyl trimethoxysilane. Ag NPs were introduced onto the thin silica-coated graphene oxide by the reduction of Ag+ to prepare GO@SiO2@Ag NPs. The GO@SiO2@Ag NPs exhibited a 1.8-fold enhanced Raman signal compared to GO without a silica coating. The GO@SiO2@Ag NPs showed a detection limit of 4-mercaptobenzoic acid (4-MBA) at 0.74 μM. PMID:28335304

  9. 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

  10. Growth of textured thin Au coatings on iron oxide nanoparticles with near infrared absorbance

    PubMed Central

    Ma, L L; Borwankar, A U; Willsey, B W; Yoon, K Y; Tam, J O; Sokolov, K V; Feldman, M D; Milner, T E; Johnston, K P

    2013-01-01

    A homologous series of Au-coated iron oxide nanoparticles, with hydrodynamic diameters smaller than 60 nm was synthesized with very low Auto-iron mass ratios as low as 0.15. The hydrodynamic diameter was determined by dynamic light scattering and the composition by atomic absorption spectroscopy and energy dispersive x-ray spectroscopy (EDS). Unusually low Au precursor supersaturation levels were utilized to nucleate and grow Au coatings on iron oxide relative to formation of pure Au nanoparticles. This approach produced unusually thin coatings, by lowering autocatalytic growth of Au on Au, as shown by transmission electron microscopy (TEM). Nearly all of the nanoparticles were attracted by a magnet indicating a minimal amount of pure Au particles The coatings were sufficiently thin to shift the surface plasmon resonance (SPR) to the near infrared (NIR), with large extinction coefficients., despite the small particle hydrodynamic diameters, observed from dynamic light scattering to be less than 60 nm. PMID:23238021

  11. Graphene oxide thin films: influence of chemical structure and deposition methodology.

    PubMed

    Hidalgo, R S; López-Díaz, D; Velázquez, M Mercedes

    2015-03-10

    We synthesized graphene oxide sheets of different functionalization by oxidation of two different starting materials, graphite and GANF nanofibers, followed by purification based on alkaline washing. The chemical structure of graphene oxide materials was determined by X-ray photoelectron spectroscopy (XPS), and the nanoplatelets were characterized by ζ potential and dynamic light scattering (DLS) measurements. The XPS results indicated that the chemical structure depends on the starting material. Two different deposition methodologies, Langmuir-Blodgett (LB) and Langmuir-Schaefer (LS), were employed to build the graphene oxide thin films. The film morphology was analyzed by scanning electron microscopy (SEM). The SEM images allow us to conclude that the LB methodology provides the highest coverage. This coverage is almost independent of the chemical composition of sheets. Conversely, the coverage obtained by the LS methodology increases with the percentage of C-O groups attached to sheets. Surface-pressure isotherms of these materials were interpreted according to the Volmer model.

  12. Thin coatings for protecting titanium aluminides in high-temperature oxidizing environments

    NASA Technical Reports Server (NTRS)

    Wiedemann, K. E.; Taylor, P. J.; Clark, R. K.; Wallace, T. A.

    1991-01-01

    Titanium aluminides have high specific strengths at high temperatures but are susceptible to environmental attack. Their use in many aerospace applications would require that they be protected with coatings that, for structural efficiency, must be thin. It is conceivable that acceptable coatings might be found in several oxide systems, and consequently, oxide coatings of many compositions were prepared from sol-gels for study. Response-surface methodology was used to refine coating compositions and factorial experiments were used to develop coating strategies. Oxygen permeability diagrams of two-layer coatings for several oxide systems, an analysis of multiple-layer coatings on rough and polished surfaces, and modeling of the oxidation weight gain are presented.

  13. Formation of thin tungsten oxide layers: characterization and exposure to deuterium

    NASA Astrophysics Data System (ADS)

    Addab, Y.; Martin, C.; Pardanaud, C.; Khayadjian, J.; Achkasov, K.; Kogut, D.; Cartry, G.; Giacometti, G.; Cabié, M.; Gardarein, J. L.; Roubin, P.

    2016-02-01

    Thin tungsten oxide layers with thicknesses up to 250 nm have been formed on W surfaces by thermal oxidation following a parabolic growth rate. The reflectance of the layers in the IR range 2.5-16 μm has been measured showing a decrease with the layer thickness especially at low wavelengths. Raman microscopy and x-ray diffraction show a nanocrystalline WO3 monoclinic structure. Low energy deuterium plasma exposure (11 eV/D+) has been performed inducing a phase transition, a change in the sample colour and the formation of tungsten bronze (D x WO3). Implantation modifies the whole layer suggesting a deep diffusion of deuterium inside the oxide. After exposure, a deuterium release due to the oxidation of D x WO3 under ambient conditions has been evidenced showing a reversible deuterium retention.

  14. Boron-doped cobalt oxide thin films and its electrochemical properties

    NASA Astrophysics Data System (ADS)

    Kerli, S.

    2016-09-01

    The cobalt oxide and boron-doped cobalt oxide thin films were produced by spray deposition method. All films were obtained onto glass and fluorine-doped tin oxide (FTO) substrates at 400∘C and annealed at 550∘C. We present detailed analysis of the morphological and optical properties of films. XRD results show that boron doping disrupts the structure of the films. Morphologies of the films were investigated by using a scanning electron microscopy (SEM). Optical measurements indicate that the band gap energies of the films change with boron concentrations. The electrochemical supercapacitor performance test has been studied in aqueous 6 M KOH electrolyte and with scan rate of 5 mV/s. Measurements show that the largest capacitance is obtained for 3% boron-doped cobalt oxide film.

  15. Solution-processed high-k magnesium oxide dielectrics for low-voltage oxide thin-film transistors

    NASA Astrophysics Data System (ADS)

    Jiang, Guixia; Liu, Ao; Liu, Guoxia; Zhu, Chundan; Meng, You; Shin, Byoungchul; Fortunato, Elvira; Martins, Rodrigo; Shan, Fukai

    2016-10-01

    Solution-processed metal-oxide thin films with high dielectric constants (k) have been extensively studied for low-cost and high-performance thin-film transistors (TFTs). In this report, MgO dielectric films were fabricated using the spin-coating method. The MgO dielectric films annealed at various temperatures (300, 400, 500, and 600 °C) were characterized by using thermogravimetric analysis, optical spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and atomic-force microscopy. The electrical measurements indicate that the insulating properties of MgO thin films are improved with an increase in annealing temperature. In order to clarify the potential application of MgO thin films as gate dielectrics in TFTs, solution-derived In2O3 channel layers were separately fabricated on various MgO dielectric layers. The optimized In2O3/MgO TFT exhibited an electron mobility of 5.48 cm2/V s, an on/off current ratio of 107, and a subthreshold swing of 0.33 V/dec at a low operation voltage of 6 V. This work represents a great step toward the development of portable and low-power consumption electronics.

  16. High-K Lanthanum Zirconium Oxide Thin Film Dielectrics from Aqueous Solution Precursors.

    PubMed

    Woods, Keenan Navarre; Chiang, Tsung-Han; Plassmeyer, Paul N; Kast, Matthew G; Lygo, Alexander C; Grealish, Aidan K; Boettcher, Shannon W; Page, Catherine J

    2017-03-06

    Metal oxide thin films are critical in modern electronic applications. In particular, high-κ dielectrics are of interest for reducing power consumption in metal-insulator-semiconductor (MIS) field-effect transistors. Although thin-film materials are typically produced via vacuum-based methods, solution deposition offers a scalable and cost-efficient alternative. We report an all-inorganic aqueous solution route to amorphous lanthanum zirconium oxide (La2Zr2O7, "LZO") dielectric thin films. LZO films were spin-cast from aqueous solutions of metal nitrates and annealed at temperatures between 300 and 600 °C to produce dense, defect-free, and smooth films with sub-nm roughness. Dielectric constants of 12.2 to 16.4 and loss tangents < 0.6% were obtained for MIS devices utilizing LZO as the dielectric layer (1 kHz). Leakage currents < 10-7 A cm-2 at 4 MV cm-1 were measured for samples annealed at 600 °C. The excellent surface morphology, high dielectric constants, and low leakage current densities makes these LZO dielectrics promising candidates for thin-film transistor devices.

  17. Gas Barrier and Separation Behavior of Graphene Oxide Nanobrick Wall Thin Films

    NASA Astrophysics Data System (ADS)

    Grunlan, Jaime

    2015-03-01

    In many cases, electronics packaging requires electrical conductivity and barrier to oxygen, even under humid conditions. These two properties have simultaneously been realized through the use of surfactant-free aqueous layer-by-layer (LbL) processing, in the form of a polymer composite nanocoating. By layering graphene oxide (GO) with polyethyleneimine (PEI), a ``nano brick wall'' structure has been created, imparting gas barrier properties to the film. Reducing the graphene oxide with a thermal treatment further produces high oxygen barrier in humid conditions and imparts high electrical conductivity (σ ~ 1750 S/m). These thin films (<400 nm) are flexible relative traditional conductive thin films (e.g. ITO), and processing occurs under ambient conditions with water as the only solvent. Additionally, these PEI/GO thin films exhibit H2/CO2 selectivity (>300), making them interesting for gas purification membranes. The flexible nature of the aforementioned thin films, along with their excellent combination of transport properties, make them ideal candidates for use in a broad range of electronics and other packaging applications.

  18. Characterization of Zinc Oxide and Pentacene Thin Film Transistors for CMOS Inverters

    NASA Astrophysics Data System (ADS)

    Iechi, Hiroyuki; Watanabe, Yasuyuki; Yamauchi, Hiroshi; Kudo, Kazuhiro

    We fabricated both thin film transistors (TFTs) and diodes using zinc oxide (ZnO) and pentacene, and investigated their basic characteristics. We found that field-effect mobility is influenced by the interface state between the semiconductor and dielectric layers. Furthermore, the complementary metal oxide semiconductor (CMOS) inverter using a p-channel pentacene field-effect transistor (FET) and an n-channel ZnO FET showed a relatively high voltage gain (8 - 12) by optimizing the device structure. The hybrid complementary inverters described here are expected for application in flexible displays, radio frequency identification cards (RFID) tags, and others.

  19. Thin-film transistor fabricated in single-crystalline transparent oxide semiconductor.

    PubMed

    Nomura, Kenji; Ohta, Hiromichi; Ueda, Kazushige; Kamiya, Toshio; Hirano, Masahiro; Hosono, Hideo

    2003-05-23

    We report the fabrication of transparent field-effect transistors using a single-crystalline thin-film transparent oxide semiconductor, InGaO3(ZnO)5, as an electron channel and amorphous hafnium oxide as a gate insulator. The device exhibits an on-to-off current ratio of approximately 106 and a field-effect mobility of approximately 80 square centimeters per volt per second at room temperature, with operation insensitive to visible light irradiation. The result provides a step toward the realization of transparent electronics for next-generation optoelectronics.

  20. Thin-Film Transistor Fabricated in Single-Crystalline Transparent Oxide Semiconductor

    NASA Astrophysics Data System (ADS)

    Nomura, Kenji; Ohta, Hiromichi; Ueda, Kazushige; Kamiya, Toshio; Hirano, Masahiro; Hosono, Hideo

    2003-05-01

    We report the fabrication of transparent field-effect transistors using a single-crystalline thin-film transparent oxide semiconductor, InGaO3(ZnO)5, as an electron channel and amorphous hafnium oxide as a gate insulator. The device exhibits an on-to-off current ratio of ~106 and a field-effect mobility of ~80 square centimeters per volt per second at room temperature, with operation insensitive to visible light irradiation. The result provides a step toward the realization of transparent electronics for next-generation optoelectronics.

  1. Oxide Thin-Film Transistors Fabricated Using Biodegradable Gate Dielectric Layer of Chicken Albumen

    NASA Astrophysics Data System (ADS)

    Jeon, Da-Bin; Bak, Jun-Yong; Yoon, Sung-Min

    2013-12-01

    An oxide thin-film transistor (TFT) using chicken albumen as gate dielectric on paper substrate was demonstrated. Chicken albumen, which was directly extracted from chicken egg white, was deposited as gate dielectric layer. An In-Ga-Zn-O was chosen as an active channel. The TFT feasibilities were successfully confirmed, in which channel mobility and subthreshold slope of the TFT were 6.48 cm2 V-1 s-1 and 1.28 V/s, respectively. This is the first report on the device configuration combining the biodegradable gate insulator and oxide semiconducting channel.

  2. Amorphous thin film ruthenium oxide as an electrode material for electrochemical capacitors

    SciTech Connect

    Jow, T.R.; Zheng, J.P.

    1995-12-31

    Ruthenium oxide thin films of an amorphous phase were successfully prepared on a titanium (Ti) substrate at temperatures below 160 C. The sol-gel process using metal alkoxide precursor in nonaqueous solvents was used to prepare these films. The preliminary results showed that a specific capacitance of 430 F/g can be achieved for amorphous ruthenium oxide electrode in sulfuric acid. Films prepared by this method are compared with the films prepared by the thermal decomposition of the aqueous ruthenium chloride solution at temperatures above 300 C. The specific capacitance, the crystalline structure, and the surface morphology of these films as a function of the preparation temperature were also discussed.

  3. Non-equilibrium origin of high electrical conductivity in gallium zinc oxide thin films

    SciTech Connect

    Zakutayev, Andriy Ginley, David S.; Lany, Stephan; Perry, Nicola H.; Mason, Thomas O.

    2013-12-02

    Non-equilibrium state defines physical properties of materials in many technologies, including architectural, metallic, and semiconducting amorphous glasses. In contrast, crystalline electronic and energy materials, such as transparent conductive oxides (TCO), are conventionally thought to be in equilibrium. Here, we demonstrate that high electrical conductivity of crystalline Ga-doped ZnO TCO thin films occurs by virtue of metastable state of their defects. These results imply that such defect metastability may be important in other functional oxides. This finding emphasizes the need to understand and control non-equilibrium states of materials, in particular, their metastable defects, for the design of novel functional materials.

  4. Different properties of aluminum doped zinc oxide nanostructured thin films prepared by radio frequency magnetron sputtering

    SciTech Connect

    Bidmeshkipour, Samina Shahtahmasebi, Nasser

    2013-06-15

    Aluminium doped zinc oxide (AZO) nanostructured thin films are prepared by radio frequency magnetron sputtering on glass substrate using specifically designed ZnO target containing different amount of Al{sub 2}O{sub 3} powder as the Al doping source. The optical properties of the aluminium doped zinc oxide films are investigated. The topography of the deposited films were investigated by Atomic Force Microscopy. Variation of the refractive index by annealing temperature are considered and it is seen that the refractive index increases by increasing the annealing temperature.

  5. Thin Oxides as a Cu Diffusion Barrier for NIF Be Ablator Capsules

    SciTech Connect

    Youngblood, Kelly P.; Huang, H.; Xu, H. W.; Hayes, J.; Moreno, K. A.; Wu, J. J.; Nikroo, A.; Alford, C. A.; Hamza, A. V.; Kucheyev, S. O.; Wang, Y. M.; Wu, K. J.

    2013-03-01

    The NIF point design uses a five-layer capsule to modify the X-ray absorption in order to achieve optimized shock timing. A stepped copper dopant design defines the layer structure. The production of the capsule involves pyrolysis to remove the inner plastic mandrel. Copper atoms diffuse radially and azimuthally throughout the capsule during pyrolysis. This diffusion significantly diminishes the capsule performance during implosion. Thermal and coated oxide barrier layers employed between layers mitigate the diffusion of copper during the mandrel removal process. The copper atoms do not diffuse through this barrier during pyrolysis. A capsule fabrication method that produces a capsule with a thin oxide layer will be discussed.

  6. Difference in charge transport properties of Ni-Nb thin films with native and artificial oxide

    SciTech Connect

    Trifonov, A. S.; Lubenchenko, A. V.; Polkin, V. I.; Pavolotsky, A. B.; Ketov, S. V.; Louzguine-Luzgin, D. V.

    2015-03-28

    Here, we report on the properties of native and artificial oxide amorphous thin film on a surface of an amorphous Ni-Nb sample. Careful measurements of local current-voltage characteristics of the system Ni-Nb / NiNb oxide/Pt, were carried out in contact mode of an atomic force microscope. Native oxide showed n-type conductivity, while in the artificial one exhibited p-type one. The shape of current-voltage characteristic curves is unique in both cases and no analogical behavior is found in the literature. X-ray photoelectron spectroscopy (XPS) measurements were used to detect chemical composition of the oxide films and the oxidation state of the alloy components. Detailed analysis of the XPS data revealed that the structure of natural Ni-Nb oxide film consists of Ni-NbO{sub x} top layer and nickel enriched bottom layer which provides n-type conductivity. In contrast, in the artificial oxide film Nb is oxidized completely to Nb{sub 2}O{sub 5}, Ni atoms migrate into bulk Ni-Nb matrix. Electron depletion layer is formed at the Ni-Nb/Nb{sub 2}O{sub 5} interface providing p-type conductivity.

  7. Preparation of metal oxide thin films using coating photolysis process with ArF excimer laser

    NASA Astrophysics Data System (ADS)

    Tsuchiya, Tetsuo; Watanabe, Akio; Imai, Yoji; Niino, Hiroyuki; Yabe, Akira; Yamaguchi, Iwao; Manabe, Takaaki; Kumagai, Toshiya; Mizuta, Susumu

    2000-11-01

    The preparation of metal oxide thin films have been developed using the metalorganic (MO) compounds coating photolysis process with ArF excimer laser irradiation at room temperature. The effect of the starting materials and irradiation method on the product films was investigated by FT-IR, UV, XRD and SEM. It was found that metal acetylacetonates or metal 2-ethylhexanoate was effective as the starting materials. When using metal acetylacetonates as the starting materials, crystallized TiO2, In2O3 and ZrO2 were obtained with ArF laser irradiation at 50 mJ/cm2 at a repetition rate of 5 Hz for 5 min. When using An-acac, Fe, Sn, or In 2-ethylhexanoate as the starting material, a two-step process consisting of both preliminary weak (10mJ/cm2) and sufficiently strong irradiation (50mJ/cm2) was found to be effective for obtaining crystallized ZnO, Fe2O3, SnO2 and In2O3 films. In addition, crystallized complex oxide thin films such as ITO, PbTo3 and PbZrO3 were successfully obtained from the metal acetylacetonates or metal 2-ethylhexanoate using MO coating photolysis process. Patterned metal oxide thin films were also obtained by the ArF laser irradiation through the photomask, followed by leaching with solvents. The crystallization mechanism was discussed from the point of view of the photochemical reaction and photothermal reaction.

  8. Silver nanoparticles on Zinc Oxide thin film: An insight in fabrication and characterization

    NASA Astrophysics Data System (ADS)

    Hossain, M. K.; Drmosh, Q. A.; Yamani, Z. H.; Tabet, N.

    2014-08-01

    In this work, a simple two-steps process has been explained to fabricate silver (Ag) nanoparticles on Zinc Oxide (ZnO) thin film followed by their characterizations. The underneath layer ZnO thin film, as an example, was also investigated how the properties change during the course of nanoparticles fabrication. ZnO thin film was sputtered on standard glass substrate followed by further sputtering of an ultrathin Ag layer. Subsequently the specimen was treated at high temperature in inert environment. A periodic observation at specific temperature intervals confirmed the formation of Ag nanoparticles on ZnO thin film. Field-emission scanning electron microscopic (FESEM) observations revealed the size distribution of as-fabricated Ag nanoparticles in the range of 50-250 nm. Elemental analysis was also confirmed by SEM-aided energy dispersion spectroscopy. The underneath layer ZnO thin film was found to go through recrystallization, stress relaxation, and grain growth during the annealing process. Further treatment to ZnO only film showed a variation in surface topology with reference to those with Ag nanoparticles on ZnO. Such a system was also analysed with finite different time domain (FDTD) analysis. A typical model was considered and FDTD simulation was carried out to understand the trend of absorption depth profile within the absorbing layer involved in plasmonics solar cell.

  9. Synthesis and Characterization of Potentiostatically Electrodeposited Tungsten Oxide Thin Films for Smart Window Application

    NASA Astrophysics Data System (ADS)

    More, A. J.; Patil, R. S.; Dalavi, D. S.; Suryawanshi, M. P.; Burungale, V. V.; Kim, J. H.; Patil, P. S.

    2017-02-01

    Tungsten oxide (WO3) thin films have been synthesized using electrodeposition in potentiostatic mode and the effect of different deposition potentials on their structural, morphological, optical, and electrochromic (EC) properties investigated. The deposition potential versus saturated calomel electrode (SCE) was varied from -0.35 V to -0.50 V in steps of -0.05 V for 20 min each. The electrodeposited WO3 thin films were characterized using x-ray diffraction analysis, micro-Raman spectroscopy, field-emission scanning electron microscopy, and ultraviolet-visible (UV-Vis) spectrophotometry, revealing amorphous nature with nanograins having average size from 40 nm to 60 nm. The EC performance of the WO3 thin films exhibited response times of 1.35 s for bleaching ( t b) and 3.1 s for coloration ( t c) with excellent reversibility of 64.36%. The highest coloration efficiency of the electrodeposited WO3 thin films was found to be 87.95 cm2/C. The electrochemical reversibility and stability of the WO3 thin films obtained in this study make them promising for use in smart window applications.

  10. Structural and optical properties of DC reactive magnetron sputtered zinc aluminum oxide thin films

    SciTech Connect

    Kumar, B. Rajesh; Rao, T. Subba

    2014-10-15

    Highly transparent conductive Zinc Aluminum Oxide (ZAO) thin films have been deposited on glass substrates using DC reactive magnetron sputtering method. The thin films were deposited at 200 °C and post-deposition annealing from 15 to 90 min. XRD patterns of ZAO films exhibit only (0 0 2) diffraction peak, indicating that they have c-axis preferred orientation perpendicular to the substrate. Scanning electron microscopy (SEM) is used to study the surface morphology of the films. The grain size obtained from SEM images of ZAO thin films are found to be in the range of 20 - 26 nm. The minimum resistivity of 1.74 × 10{sup −4} Ω cm and an average transmittance of 92% are obtained for the thin film post annealed for 30 min. The optical band gap of ZAO thin films increased from 3.49 to 3.60 eV with the increase of annealing time due to Burstein-Moss effect. The optical constants refractive index (n) and extinction coefficient (k) were also determined from the optical transmission spectra.

  11. An (ultra) high-vacuum compatible sputter source for oxide thin film growth

    SciTech Connect

    Mayr, Lukas; Köpfle, Norbert; Auer, Andrea; Klötzer, Bernhard; Penner, Simon

    2013-09-15

    A miniaturised CF-38 mountable sputter source for oxide and metal thin film preparation with enhanced high-vacuum and ultra-high-vacuum compatibility is described. The all home-built sputtering deposition device allows a high flexibility also in oxidic sputter materials, suitable deposition rates for preparation of films in the nm- and the sub-monolayer regime and excellent reliability and enhanced cleanliness for usage in UHV chambers. For a number of technologically important – yet hardly volatile – materials, the described source represents a significant improvement over thermal deposition techniques like electron-beam- or thermal evaporation, as especially the latter are no adequate tool to prepare atomically clean layers of refractory oxide materials. Furthermore, it is superior to commercially available magnetron sputter devices, especially for applications, where highly reproducible sub-monolayer thin film preparation under very clean UHV conditions is required (e.g., for studying phase boundary effects in catalysis). The device in turn offers the usage of a wide selection of evaporation materials and special target preparation procedures also allow the usage of pressed oxide powder targets. To prove the performance of the sputter-source, test preparations with technologically relevant oxide components, comprising ZrO{sub 2} and yttrium-stabilized ZrO{sub 2}, have been carried out. A wide range of characterization methods (electron microscopy, X-ray photoelectron spectroscopy, low-energy ion scattering, atomic force microscopy, and catalytic testing) were applied to demonstrate the properties of the sputter-deposited thin film systems.

  12. Scanning tunneling microscopy/spectroscopy on perovskite oxide thin films deposited in situ.

    PubMed

    Hitosugi, Taro; Shimizu, Ryota; Ohsawa, Takeo; Iwaya, Katsuya

    2014-10-01

    Complex oxide surfaces and interfaces, consisting of two or more cations and oxygen anions, have attracted a great deal of attention because their properties are crucial factors in the performance of catalysts, fuel cells, and Li-ion batteries. However, atomic-scale investigations of these oxide surfaces have been hindered because of the difficulties in surface preparation. Here, we demonstrate atomic-scale surface studies of complex perovskite oxides and the initial growth processes in oxide epitaxial films deposited on (✓13 × ✓13)-R33.7° reconstructed SrTiO3 (001) substrates using a scanning tunneling microscope integrated with a pulsed laser deposition system. The atomically ordered, reconstructed SrTiO3 (001) surface is stable under the typical conditions necessary for the growth of oxide thin films, and hence is considered suitable for the study of the initial growth processes in oxide films. The atomic-scale microscopic/spectroscopic characterizations performed here shed light on the microscopic origin of electronic properties observed in complex oxides and their heterostructures.

  13. One-step synthesis of nanocrystalline transition metal oxides on thin sheets of disordered graphitic carbon by oxidation of MXenes.

    PubMed

    Naguib, Michael; Mashtalir, Olha; Lukatskaya, Maria R; Dyatkin, Boris; Zhang, Chuanfang; Presser, Volker; Gogotsi, Yury; Barsoum, Michel W

    2014-07-18

    Herein we show that heating 2D Ti3C2 in air results in TiO2 nanocrystals enmeshed in thin sheets of disordered graphitic carbon structures that can handle extremely high cycling rates when tested as anodes in lithium ion batteries. Oxidation of 2D Ti3C2 in either CO2 or pressurized water also resulted in TiO2-C hybrid structures. Similarly, other hybrids can be produced, as we show here for Nb2O5/C from 2D Nb2C.

  14. Sulfur-vanadium oxide gel composites as thin film cathodes for rechargeable lithium batteries

    SciTech Connect

    Mukherjee, S.P.; Gavrilov, A.B.; Skotheim, T.A.

    1998-07-01

    A class of novel electroactive cathode materials based on composites produced from elemental sulfur and vanadium oxide xerogels or aerogels has been developed as models for lithium battery applications. The use of elemental sulfur in rechargeable lithium batteries has been hindered due to certain limitations such as, very low electronic conductivity and the out-diffusion of polysulfides during the cycling process which reduces the cycling efficiency. Vanadium oxide xerogels and aerogels have certain desirable characteristic physico-chemical properties, such as, high surface areas with nono-scale interconnecting porosity, high electronic conductivity, non- or nanocrystallinity, and oxidation reduction catalytic activity. Since these properties may improve the performance of sulfur based rechargeable batteries, a family of composite cathodes containing elemental sulfur and vanadium oxide gels were produced. The performance of the composites cathodes, in thin film form, were evaluated in coin cells and AA cells with metallic lithium anodes and liquid electrolytes. The multifunctional role of vanadium oxide gels on the cell performance of the cells having composite cathodes has been qualitatively explored. Results indicate that the cathodes having xerogel composites based on vanadium oxide sol from vanadium oxide isopropoxide can be made with high sulfur content (80 wt %) and with low carbon content (5 wt %) and without any polymer binder. This shows the contribution of adhesive properties and electronic conductivity of vanadium oxide xerogels. A significant suppression of polysulfide out-diffusion is observed with appropriate processing of the composite cathodes. It is anticipated that the nanoscale interconnecting porosity of gels plays an important role in this behavior. An excellent rate capability is observed with the vanadium-oxide sulfur composite cathodes indicating the contribution of intrinsic electrochemical properties of the vanadium oxide.

  15. Development and Research on the Mechanism of Novel Mist Etching Method for Oxide Thin Films

    NASA Astrophysics Data System (ADS)

    Kawaharamura, Toshiyuki; Hirao, Takashi

    2012-03-01

    A novel etching process with etchant mist was developed and applied to oxide thin films such as zinc oxide (ZnO), zinc magnesium oxide (ZnMgO), and indium tin oxide (ITO). By using this process, it was shown that precise control of the etching characteristics is possible with a reasonable etching rate, for example, in the range of 10-100 nm/min, and a fine pattern of high accuracy can also be realized, even though this is usually very difficult by conventional wet etching processes, for ZnO and ZnMgO. The mist etching process was found to be similarly and successfully applied to ITO. The mechanism of mist etching has been studied by examining the etching temperature dependence of pattern accuracy, and it was shown that the mechanism was different from that of conventional liquid-phase spray etching. It was ascertained that fine pattern etching was attained using mist droplets completely (or partly) gasified by the heat applied to the substrate. This technique was applied to the fabrication of a ZnO thin-film transistor (TFT) with a ZnO active channel length of 4 µm. The electrical properties of the TFT were found to be excellent with fine uniformity over the entire 4-in. wafer.

  16. Electrochemical DNA biosensors based on thin gold films sputtered on capacitive nanoporous niobium oxide.

    PubMed

    Rho, Sangchul; Jahng, Deokjin; Lim, Jae Hoon; Choi, Jinsub; Chang, Jeong Ho; Lee, Sang Cheon; Kim, Kyung Ja

    2008-01-18

    Electrochemical DNA biosensors based on a thin gold film sputtered on anodic porous niobium oxide (Au@Nb(2)O(5)) are studied in detail here. We found that the novel DNA biosensor based on Au@Nb(2)O(5) is superior to those based on the bulk gold electrode or niobium oxide electrode. For example, the novel method does not require any time-consuming cleaning step in order to obtain reproducible results. The adhesion of gold films on the substrate is very stable during electrochemical biosensing, when the thin gold films are deposited on anodically prepared nanoporous niobium oxide. In particular, the novel biosensor shows enhanced biosensing performance with a 2.4 times higher resolution and a three times higher sensitivity. The signal enhancement is in part attributed to capacitive interface between gold films and nanoporous niobium oxide, where charges are accumulated during the anodic and cathodic scanning, and is in part ascribed to the structural stability of DNA immobilized at the sputtered gold films. The method allows for the detection of single-base mismatch DNA as well as for the discrimination of mismatch positions.

  17. Metastable tantalum oxide formation during the devitrification of amorphous tantalum thin films

    DOE PAGES

    Donaldson, Olivia K.; Hattar, Khalid; Trelewicz, Jason R.

    2016-07-04

    Microstructural evolution during the devitrification of amorphous tantalum thin films synthesized via pulsed laser deposition was investigated using in situ transmission electron microscopy (TEM) combined with ex situ isothermal annealing, bright-field imaging, and electron-diffraction analysis. The phases formed during crystallization and their stability were characterized as a function of the chamber pressure during deposition, devitrification temperature, and annealing time. A range of metastable nanocrystalline tantalum oxides were identified following devitrification including multiple orthorhombic oxide phases, which often were present with, or evolved to, the tetragonal TaO2 phase. While the appearance of these phases indicated the films were evolving to themore » stable form of tantalum oxide—monoclinic tantalum pentoxide—it was likely not achieved for the conditions considered due to an insufficient amount of oxygen present in the films following deposition. Nevertheless, the collective in situ and ex situ TEM analysis applied to thin film samples enabled the isolation of a number of metastable tantalum oxides. As a result, new insights were gained into the transformation sequence and stability of these nanocrystalline phases, which presents opportunities for the development of advanced tantalum oxide-based dielectric materials for novel memristor designs.« less

  18. Metastable tantalum oxide formation during the devitrification of amorphous tantalum thin films

    SciTech Connect

    Donaldson, Olivia K.; Hattar, Khalid; Trelewicz, Jason R.

    2016-07-04

    Microstructural evolution during the devitrification of amorphous tantalum thin films synthesized via pulsed laser deposition was investigated using in situ transmission electron microscopy (TEM) combined with ex situ isothermal annealing, bright-field imaging, and electron-diffraction analysis. The phases formed during crystallization and their stability were characterized as a function of the chamber pressure during deposition, devitrification temperature, and annealing time. A range of metastable nanocrystalline tantalum oxides were identified following devitrification including multiple orthorhombic oxide phases, which often were present with, or evolved to, the tetragonal TaO2 phase. While the appearance of these phases indicated the films were evolving to the stable form of tantalum oxide—monoclinic tantalum pentoxide—it was likely not achieved for the conditions considered due to an insufficient amount of oxygen present in the films following deposition. Nevertheless, the collective in situ and ex situ TEM analysis applied to thin film samples enabled the isolation of a number of metastable tantalum oxides. As a result, new insights were gained into the transformation sequence and stability of these nanocrystalline phases, which presents opportunities for the development of advanced tantalum oxide-based dielectric materials for novel memristor designs.

  19. Growth and surface characterization of sputter-deposited molybdenum oxide thin films

    SciTech Connect

    Ramana, Chintalapalle V.; Atuchin, Victor V.; Kesler, V. G.; Kochubey, V. A.; Pokrovsky, L. D.; Shutthanandan, V.; Becker, U.; Ewing, Rodney C.

    2007-04-15

    Molybdenum oxide thin films were produced by magnetron sputtering using a molybdenum (Mo) target. The sputtering was performed in a reactive atmosphere of argon-oxygen gas mixture under varying conditions of substrate temperature (Ts) and oxygen partial pressure (pO2). The effect of Ts and pO2 on the growth and microstructure of molybdenum oxide films was examined in detail using reflection high-energy electron diffraction (RHEED), Rutherford backscattering spectrometry (RBS), energy dispersive X-ray spectrometry (EDS), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) measurements. The analyses indicate that the effect of Ts and pO2 on the microstructure and phase of the grown molybdenum oxide thin films is remarkable. RHEED and RBS results indicate that the films grown at 445 *C under 62.3% O2 pressure were stoichiometric and polycrystalline MoO3. Films grown at lower pO2 were nonstoichiometric MoOx films with the presence of secondary phase. The microstructure of the grown Mo oxide films is discussed and conditions were optimized to produce phase pure, stoichiometric, and highly textured polycrystalline MoO3 films.

  20. Phosphorus Doping Effect in a Zinc Oxide Channel Layer to Improve the Performance of Oxide Thin-Film Transistors

    NASA Astrophysics Data System (ADS)

    Han, Dong-Suk; Moon, Yeon-Keon; Lee, Sih; Kim, Kyung-Taek; Moon, Dae-Yong; Lee, Sang-Ho; Kim, Woong-Sun; Park, Jong-Wan

    2012-09-01

    In this study, we fabricated phosphorus-doped zinc oxide-based thin-film transistors (TFTs) using direct current (DC) magnetron sputtering at a relatively low temperature of 100°C. To improve the TFT device performance, including field-effect mobility and bias stress stability, phosphorus dopants were employed to suppress the generation of intrinsic defects in the ZnO-based semiconductor. The positive and negative bias stress stabilities were dramatically improved by introducing the phosphorus dopants, which could prevent turn-on voltage ( V ON) shift in the TFTs caused by charge trapping within the active channel layer. The study showed that phosphorus doping in ZnO was an effective method to control the electrical properties of the active channel layers and improve the bias stress stability of oxide-based TFTs.

  1. Hybrid deposition of thin film solid oxide fuel cells and electrolyzers

    DOEpatents

    Jankowski, Alan F.; Makowiecki, Daniel M.; Rambach, Glenn D.; Randich, Erik

    1999-01-01

    The use of vapor deposition techniques enables synthesis of the basic components of a solid oxide fuel cell (SOFC); namely, the electrolyte layer, the two electrodes, and the electrolyte-electrode interfaces. Such vapor deposition techniques provide solutions to each of the three critical steps of material synthesis to produce a thin film solid oxide fuel cell (TFSOFC). The electrolyte is formed by reactive deposition of essentially any ion conducting oxide, such as defect free, yttria stabilized zirconia (YSZ) by planar magnetron sputtering. The electrodes are formed from ceramic powders sputter coated with an appropriate metal and sintered to a porous compact. The electrolyte-electrode interface is formed by chemical vapor deposition of zirconia compounds onto the porous electrodes to provide a dense, smooth surface on which to continue the growth of the defect-free electrolyte, whereby a single fuel cell or multiple cells may be fabricated.

  2. Hybrid deposition of thin film solid oxide fuel cells and electrolyzers

    DOEpatents

    Jankowski, A.F.; Makowiecki, D.M.; Rambach, G.D.; Randich, E.

    1998-05-19

    The use of vapor deposition techniques enables synthesis of the basic components of a solid oxide fuel cell (SOFC); namely, the electrolyte layer, the two electrodes, and the electrolyte-electrode interfaces. Such vapor deposition techniques provide solutions to each of the three critical steps of material synthesis to produce a thin film solid oxide fuel cell (TFSOFC). The electrolyte is formed by reactive deposition of essentially any ion conducting oxide, such as defect free, yttria stabilized zirconia (YSZ) by planar magnetron sputtering. The electrodes are formed from ceramic powders sputter coated with an appropriate metal and sintered to a porous compact. The electrolyte-electrode interface is formed by chemical vapor deposition of zirconia compounds onto the porous electrodes to provide a dense, smooth surface on which to continue the growth of the defect-free electrolyte, whereby a single fuel cell or multiple cells may be fabricated. 8 figs.

  3. Hybrid deposition of thin film solid oxide fuel cells and electrolyzers

    DOEpatents

    Jankowski, Alan F.; Makowiecki, Daniel M.; Rambach, Glenn D.; Randich, Erik

    1998-01-01

    The use of vapor deposition techniques enables synthesis of the basic components of a solid oxide fuel cell (SOFC); namely, the electrolyte layer, the two electrodes, and the electrolyte-electrode interfaces. Such vapor deposition techniques provide solutions to each of the three critical steps of material synthesis to produce a thin film solid oxide fuel cell (TFSOFC). The electrolyte is formed by reactive deposition of essentially any ion conducting oxide, such as defect free, yttria stabilized zirconia (YSZ) by planar magnetron sputtering. The electrodes are formed from ceramic powders sputter coated with an appropriate metal and sintered to a porous compact. The electrolyte-electrode interface is formed by chemical vapor deposition of zirconia compounds onto the porous electrodes to provide a dense, smooth surface on which to continue the growth of the defect-free electrolyte, whereby a single fuel cell or multiple cells may be fabricated.

  4. Thermal treatment of solution-processed nano-sized thin films of molybdenum oxide

    NASA Astrophysics Data System (ADS)

    Ganchev, M.; Sendova-Vassileva, M.; Popkirov, G.; Vitanov, P.

    2016-10-01

    A solution based deposition method to form nano-sized thin films of molybdenum oxide suitable for photovoltaic device applications is presented. The samples were deposited by spin-coating from molybdenum metal organic precursor solution on soda lime glass substrates. The influence of the process parameters such as spinning regime and concentration of the precursor solutions on the thickness and morphology of the films were investigated. The thermal decomposition of the molybdenum precursor and oxide formation were investigated by differential scanning calorimetry and characteristic patterns showed transitions up to 300oC followed by a zone of stability. Optical spectroscopy measurements in the wavelength range from 300 to 1800 nm presented an increase in transparency when temperature of annealing was raised up to 400oC. Raman scattering analysis revealed the presence of mixed molybdenum oxides. Measurements of the electrical conductivity were performed by the 4-point method.

  5. Characterization of zinc oxide thin film for pH detector

    NASA Astrophysics Data System (ADS)

    Hashim, Uda; Fathil, M. F. M.; Arshad, M. K. Md; Gopinath, Subash C. B.; Uda, M. N. A.

    2017-03-01

    This paper presents the fabrication process of the zinc oxide thin films for using to act as pH detection by using different PH solution. Sol-gel solution technique is used for preparing zinc oxide seed solution, followed by metal oxide deposition process by using spin coater on the silicon dioxide. Silicon dioxide layer is grown on the silicon wafer, then, ZnO seed solution is deposited on the silicon layer, baked, and annealing process carried on to undergo the characterization of its surface morphology, structural and crystalline phase. Electrical characterization is showed by using PH 4, 7, and 10 is dropped on the surface of the die, in addition, APTES solution is used as linker and also as a references of the electrical characterization.

  6. Effects of process parameters on sheet resistance uniformity of fluorine-doped tin oxide thin films.

    PubMed

    Hudaya, Chairul; Park, Ji Hun; Lee, Joong Kee

    2012-01-05

    An alternative indium-free material for transparent conducting oxides of fluorine-doped tin oxide [FTO] thin films deposited on polyethylene terephthalate [PET] was prepared by electron cyclotron resonance - metal organic chemical vapor deposition [ECR-MOCVD]. One of the essential issues regarding metal oxide film deposition is the sheet resistance uniformity of the film. Variations in process parameters, in this case, working and bubbler pressures of ECR-MOCVD, can lead to a change in resistance uniformity. Both the optical transmittance and electrical resistance uniformity of FTO film-coated PET were investigated. The result shows that sheet resistance uniformity and the transmittance of the film are affected significantly by the changes in bubbler pressure but are less influenced by the working pressure of the ECR-MOCVD system.

  7. Growth, interfacial alloying, and oxidation of ultra-thin Al films on Ru(0001)

    NASA Astrophysics Data System (ADS)

    Wu, Yutong; Tao, Hui-Shu; Garfunkel, Eric; Madey, Theodore E.; Shinn, Neal D.

    1995-08-01

    The growth and oxidation of ultra-thin aluminum films on Ru(0001) have been studied by low energy ion scattering (LEIS) and X-ray photoelectron spectroscopy (XPS) using both Mg K α and synchrotron soft X-ray radiation. For Al films of average thickness ˜ 15 Å deposited at 300 K, LEIS demonstrates that the Ru substrate is completely covered. Upon annealing to ˜ 1000 K LEIS shows the reappearance of Ru at the surface. At the same time, the metallic Al 2p peak shifts to lower binding energy and a low binding energy shoulder appears on the Ru 3d peak, suggesting {Al}/{Ru} interfacial alloying. Annealing Al films to ˜ 1000 K in 1 × 10 -4 Torr oxygen produces an oxidized surface layer that completely covers the Ru substrate; the resultant aluminum oxide films are stoichiometric.

  8. Environmentally induced chemical and morphological heterogeneity of zinc oxide thin films

    NASA Astrophysics Data System (ADS)

    Jiang, Hua; Chou, Kang Wei; Petrash, Stanislas; Williams, Garth; Thieme, Juergen; Nykypanchuk, Dmytro; Li, Li; Muto, Atsushi; Chen-Wiegart, Yu-chen Karen

    2016-08-01

    Zinc oxide (ZnO) thin films have been reported to suffer from degradation in electrical properties, when exposed to elevated heat and humidity, often leading to failures of electronic devices containing ZnO films. This degradation appears to be linked to water and oxygen penetration into the ZnO film. However, a direct observation in the ZnO film morphological evolution detailing structural and chemical changes has been lacking. Here, we systematically investigated the chemical and morphological heterogeneities of ZnO thin films caused by elevated heat and humidity, simulating an environmental aging. X-ray fluorescence microscopy, X-ray absorption spectroscopy, grazing incidence small angle and wide angle X-ray scattering, scanning electron microscopy (SEM), ultra-high-resolution SEM, and optical microscopy were carried out to examine ZnO and Al-doped ZnO thin films on two different substrates—silicon wafers and flexible polyethylene terephthalate (PET) films. In the un-doped ZnO thin film, the simulated environmental aging is resulting in pin-holes. In the Al-doped ZnO thin films, significant morphological changes occurred after the treatment, with an appearance of platelet-shaped structures that are 100-200 nm wide by 1 μm long. Synchrotron x-ray characterization further confirmed the heterogeneity in the aged Al-doped ZnO, showing the formation of anisotropic structures and disordering. X-ray diffraction and X-ray absorption spectroscopy indicated the formation of a zinc hydroxide in the aged Al-doped films. Utilizing advanced characterization methods, our studies provided information with an unprecedented level of details and revealed the chemical and morphologically heterogeneous nature of the degradation in ZnO thin films.

  9. Environmentally induced chemical and morphological heterogeneity of zinc oxide thin films

    DOE PAGES

    Jiang, Hua; Chou, Kang Wei; Petrash, Stanislas; ...

    2016-09-02

    Zinc oxide (ZnO) thin films have been reported to suffer from degradation in electrical properties, when exposed to elevated heat and humidity, often leading to failures of electronic devices containing ZnO films. This degradation appears to be linked to water and oxygen penetration into the ZnO film. However, a direct observation in the ZnO film morphological evolution detailing structural and chemical changes has been lacking. Here, we systematically investigated the chemical and morphological heterogeneities of ZnO thin films caused by elevated heat and humidity, simulating an environmental aging. X-ray fluorescence microscopy, X-ray absorption spectroscopy, grazing incidence small angle and widemore » angle X-ray scattering, scanning electron microscopy (SEM), ultra-high-resolution SEM, and optical microscopy were carried out to examine ZnO and Al-doped ZnO thin films on two different substrates—silicon wafers and flexible polyethylene terephthalate (PET) films. In the un-doped ZnO thin film, the simulated environmental aging is resulting in pin-holes. In the Al-doped ZnO thin films, significant morphological changes occurred after the treatment, with an appearance of platelet-shaped structures that are 100–200 nm wide by 1μm long. Synchrotron x-ray characterization further confirmed the heterogeneity in the aged Al-doped ZnO, showing the formation of anisotropic structures and disordering. X-ray diffraction and X-ray absorption spectroscopy indicated the formation of a zinc hydroxide in the aged Al-doped films. In conclusion, utilizing advanced characterization methods, our studies provided information with an unprecedented level of details and revealed the chemical and morphologically heterogeneous nature of the degradation in ZnO thin films.« less

  10. Environmentally induced chemical and morphological heterogeneity of zinc oxide thin films

    SciTech Connect

    Jiang, Hua; Chou, Kang Wei; Petrash, Stanislas; Williams, Garth; Thieme, Juergen; Nykypanchuk, Dmytro; Li, Li; Muto, Atsushi; Chen-Wiegart, Yu-chen Karen

    2016-09-02

    Zinc oxide (ZnO) thin films have been reported to suffer from degradation in electrical properties, when exposed to elevated heat and humidity, often leading to failures of electronic devices containing ZnO films. This degradation appears to be linked to water and oxygen penetration into the ZnO film. However, a direct observation in the ZnO film morphological evolution detailing structural and chemical changes has been lacking. Here, we systematically investigated the chemical and morphological heterogeneities of ZnO thin films caused by elevated heat and humidity, simulating an environmental aging. X-ray fluorescence microscopy, X-ray absorption spectroscopy, grazing incidence small angle and wide angle X-ray scattering, scanning electron microscopy (SEM), ultra-high-resolution SEM, and optical microscopy were carried out to examine ZnO and Al-doped ZnO thin films on two different substrates—silicon wafers and flexible polyethylene terephthalate (PET) films. In the un-doped ZnO thin film, the simulated environmental aging is resulting in pin-holes. In the Al-doped ZnO thin films, significant morphological changes occurred after the treatment, with an appearance of platelet-shaped structures that are 100–200 nm wide by 1μm long. Synchrotron x-ray characterization further confirmed the heterogeneity in the aged Al-doped ZnO, showing the formation of anisotropic structures and disordering. X-ray diffraction and X-ray absorption spectroscopy indicated the formation of a zinc hydroxide in the aged Al-doped films. In conclusion, utilizing advanced characterization methods, our studies provided information with an unprecedented level of details and revealed the chemical and morphologically heterogeneous nature of the degradation in ZnO thin films.

  11. Solution-cast metal oxide thin film electrocatalysts for oxygen evolution.

    PubMed

    Trotochaud, Lena; Ranney, James K; Williams, Kerisha N; Boettcher, Shannon W

    2012-10-17

    Water oxidation is a critical step in water splitting to make hydrogen fuel. We report the solution synthesis, structural/compositional characterization, and oxygen evolution reaction (OER) electrocatalytic properties of ~2-3 nm thick films of NiO(x), CoO(x), Ni(y)Co(1-y)O(x), Ni(0.9)Fe(0.1)O(x), IrO(x), MnO(x), and FeO(x). The thin-film geometry enables the use of quartz crystal microgravimetry, voltammetry, and steady-state Tafel measurements to study the electrocatalytic activity and electrochemical properties of the oxides. Ni(0.9)Fe(0.1)O(x) was found to be the most active water oxidation catalyst in basic media, passing 10 mA cm(-2) at an overpotential of 336 mV with a Tafel slope of 30 mV dec(-1) with oxygen evolution reaction (OER) activity roughly an order of magnitude higher than IrO(x) control films and similar to the best known OER catalysts in basic media. The high activity is attributed to the in situ formation of layered Ni(0.9)Fe(0.1)OOH oxyhydroxide species with nearly every Ni atom electrochemically active. In contrast to previous reports that showed synergy between Co and Ni oxides for OER catalysis, Ni(y)Co(1-y)O(x) thin films showed decreasing activity relative to the pure NiO(x) films with increasing Co content. This finding is explained by the suppressed in situ formation of the active layered oxyhydroxide with increasing Co. The high OER activity and simple synthesis make these Ni-based catalyst thin films useful for incorporating with semiconductor photoelectrodes for direct solar-driven water splitting or in high-surface-area electrodes for water electrolysis.

  12. Structure and properties of uranium oxide thin films deposited by pulsed dc magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Lin, Jianliang; Dahan, Isaac; Valderrama, Billy; Manuel, Michele V.

    2014-05-01

    Crystalline uranium oxide thin films were deposited in an unbalanced magnetron sputtering system by sputtering from a depleted uranium target in an Ar + O2 mixture using middle frequency pulsed dc magnetron sputtering. The substrate temperature was constantly maintained at 500 °C. Different uranium oxide phases (including UO2-x, UO2, U3O7 and U3O8) were obtained by controlling the percentage of the O2 flow rate to the total gas flow rate (f) in the chamber. The crystal structure of the films was characterized using X-ray diffraction and the microstructure of the films was studied using transmission electron microscopy and atom probe tomography. When the f was below 10%, the film contains a mixture of metallic uranium and UO2-x phases. As the f was controlled in the range of 10-13%, UO2 films with a (2 2 0) preferential orientation were obtained. The oxide phase rapidly changed to a mixture of U3O7 and U3O8 as the f was increased to the range of 15-18%. Further increasing the f to 20% and above, polycrystalline U3O8 thin films with a (0 0 1) preferential orientation were formed. The hardness and Young's modulus of the uranium oxide films were evaluated using nanoindentation. The film containing a single UO2 phase exhibited the maximum hardness of 14.3 GPa and a Young's modulus of 195 GPa. The UO2 thin film also exhibited good thermal stability in that no phase change was observed after annealing at 600 °C in vacuum for 104 h.

  13. All-amorphous-oxide transparent, flexible thin-film transistors. Efficacy of bilayer gate dielectrics.

    PubMed

    Liu, Jun; Buchholz, D Bruce; Hennek, Jonathan W; Chang, Robert P H; Facchetti, Antonio; Marks, Tobin J

    2010-09-01

    Optically transparent and mechanically flexible thin-film transistors (TF-TFTs) composed exclusively of amorphous metal oxide films are fabricated on plastic substrates by combining an amorphous Ta(2)O(5)/SiO(x) bilayer transparent oxide insulator (TOI) gate dielectric with an amorphous zinc-indium-tin oxide (a-ZITO) transparent oxide semiconductor (TOS) channel and a-ZITO transparent oxide conductor (TOC) electrodes. The bilayer gate dielectric is fabricated by the post-cross-linking of vapor-deposited hexachlorodisiloxane-derived films to form thin SiO(x) layers (v-SiO(x)) on amorphous Ta(2)O(5) (a-Ta(2)O(5)) films grown by ion-assisted deposition at room temperature. The a-Ta(2)O(5)/v-SiO(x) bilayer TOI dielectric integrates the large capacitance of the high dielectric constant a-Ta(2)O(5) layer with the excellent dielectric/semiconductor interfacial compatibility of the v-SiO(x) layer in a-ZITO TOS-based TF-TFTs. These all-amorphous-oxide TF-TFTs, having a channel length and width of 100 and 2000 microm, respectively, perform far better than a-Ta(2)O(5)-only devices and exhibit saturation-regime field-effect mobilities of approximately 20 cm(2)/V x s, on-currents >10(-4) A, and current on-off ratios >10(5). These TFTs operate at low voltages (approximately 4.0 V) and exhibit good visible-region optical transparency and excellent mechanical flexibility.

  14. Effect of silver incorporation in phase formation and band gap tuning of tungsten oxide thin films

    SciTech Connect

    Jolly Bose, R.; Kumar, R. Vinod; Sudheer, S. K.; Mahadevan Pillai, V. P.; Reddy, V. R.; Ganesan, V.

    2012-12-01

    Silver incorporated tungsten oxide thin films are prepared by RF magnetron sputtering technique. The effect of silver incorporation in micro structure evolution, phase enhancement, band gap tuning and other optical properties are investigated using techniques such as x-ray diffraction, micro-Raman spectroscopy, atomic force microscopy, scanning electron microscopy, energy dispersive x-ray spectroscopy, and UV-Visible spectroscopy. Effect of silver addition in phase formation and band gap tuning of tungsten oxide thin films are investigated. It is found that the texturing and phase formation improves with enhancement in silver content. It is also found that as the silver incorporation enhances the thickness of the films increases at the same time the strain in the film decreases. Even without annealing the desired phase can be achieved by doping with silver. A broad band centered at the wavelength 437 nm is observed in the absorption spectra of tungsten oxide films of higher silver incorporation and this can be attributed to surface plasmon resonance of silver atoms present in the tungsten oxide matrix. The transmittance of the films is decreased with increase in silver content which can be due to increase in film thickness, enhancement of scattering, and absorption of light caused by the increase of grain size, surface roughness and porosity of films and enhanced absorption due to surface plasmon resonance of silver. It is found that silver can act as the seed for the growth of tungsten oxide grains and found that the grain size increases with silver content which in turn decreases the band gap of tungsten oxide from 3.14 eV to 2.70 eV.

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

    NASA Astrophysics Data System (ADS)

    Skarlinski, Michael D.; Quesnel, David J.

    2015-12-01

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

  16. Characterization of sputtered iridium oxide thin films on planar and laser micro-structured platinum thin film surfaces for neural stimulation applications

    NASA Astrophysics Data System (ADS)

    Thanawala, Sachin

    Electrical stimulation of neurons provides promising results for treatment of a number of diseases and for restoration of lost function. Clinical examples include retinal stimulation for treatment of blindness and cochlear implants for deafness and deep brain stimulation for treatment of Parkinsons disease. A wide variety of materials have been tested for fabrication of electrodes for neural stimulation applications, some of which are platinum and its alloys, titanium nitride, and iridium oxide. In this study iridium oxide thin films were sputtered onto laser micro-structured platinum thin films by pulsed-DC reactive sputtering of iridium metal in oxygen-containing atmosphere, to obtain high charge capacity coatings for neural stimulation applications. The micro-structuring of platinum films was achieved by a pulsed-laser-based technique (KrF excimer laser emitting at lambda=248nm). The surface morphology of the micro-structured films was studied using different surface characterization techniques. In-vitro biocompatibility of these laser micro-structured films coated with iridium oxide thin films was evaluated using cortical neurons isolated from rat embryo brain. Characterization of these laser micro-structured films coated with iridium oxide, by cyclic voltammetry and impedance spectroscopy has revealed a considerable decrease in impedance and increase in charge capacity. A comparison between amorphous and crystalline iridium oxide thin films as electrode materials indicated that amorphous iridium oxide has significantly higher charge capacity and lower impedance making it preferable material for neural stimulation application. Our biocompatibility studies show that neural cells can grow and differentiate successfully on our laser micro-structured films coated with iridium oxide. This indicates that reactively sputtered iridium oxide (SIROF) is biocompatible.

  17. Thermal stimulated current response in cupric oxide single crystal thin films over a wide temperature range

    NASA Astrophysics Data System (ADS)

    Yang, Kungan; Wu, Shuxiang; Yu, Fengmei; Zhou, Wenqi; Wang, Yunjia; Meng, Meng; Wang, Gaili; Zhang, Yueli; Li, Shuwei

    2017-01-01

    Cupric oxide single crystal thin films (~26 nm) were grown by plasma-assisted molecular beam epitaxy. X-ray diffraction, Raman spectra and in situ reflection high-energy electron diffraction show that the thin films are 2  ×  2 reconstructed with an in-plane compression and out-of-plane stretching. A thermal stimulated current measurement indicates that the electric polarization response is shown in the special 2D cupric oxide single crystal thin film over a wide temperature range from 130 K to near-room temperature. We infer that the abnormal electric response involves the changing of phase transition temperature induced by structure distortion, the spin frustration and the magnetic fluctuation effect of a short-range magnetic order, or the combined action of both of the two factors mentioned above. This work suggests a promising clue for finding new room temperature single phase multiferroics or tuning phase transition temperatures.

  18. Interaction of Zr with oxidized and partially reduced ceria thin films

    NASA Astrophysics Data System (ADS)

    Wang, Weijia; Hu, Shanwei; Han, Yong; Pan, Xiao; Xu, Qian; Zhu, Junfa

    2016-11-01

    The growth and electronic properties of Zr on the ceria thin films were studied by X-ray photoelectron spectroscopy, low energy electron diffraction (LEED), scanning tunneling microscopy (STM) and work function measurements. Metallic zirconium was vapor-deposited on the well-ordered fully oxidized CeO2(111) and partially reduced CeO2-x(111) (0 < x < 0.5) thin films, which were epitaxially grown on a Ru(0001) substrate, under ultrahigh vacuum (UHV) conditions. The results show that the deposition of Zr on both ceria surfaces leads to electron transfer from Zr to ceria, accompanied by partial reduction of Ce from Ce4 + to Ce3 + states and oxidation of metallic Zr to Zr4 +. Moreover, with increasing the Zr coverage, the reduction degree of ceria films increases and eventually only Ce3 + is observed at a high coverage of Zr. The STM results suggest that Zr grows two-dimensionally (2D) on the CeO2(111) thin film at low coverages due to the strong interaction between Zr and CeO2(111).

  19. Ionic and electrochemical phenomena induced by structural and chemical defects in oxide thin films

    NASA Astrophysics Data System (ADS)

    Aruta, Carmela

    Interactions at the surfaces/interfaces between complex oxides and gaseous environment are fundamental for the efficiency of many environmental friendly systems and applications. Such interactions can be modified by the intricate interrelationship between microstructure and chemical substitution defects, being their role on functional properties, such as ionic conductivity and surface reaction rates, as particularly relevant as difficult to discriminate. New possibilities in thin film fabrication allow growth of oxide thin films with a more precise control of the structure and chemical stoichiometry, thus unveiling new perspectives in the study of electrochemical effects for physical functionalities, through nanoscale characterizations by complementary state-of-art techniques. As an example of interfacial structural defect effects, we will discuss the case of yttrium doped barium zirconate thin films, where the cation substitutions represent a viable mechanism, alternative to the formation of dislocations near the interface, to relieve the strain building up in the film growing on a highly mismatched substrate, thus providing fast transport pathways together with enhanced interface electrochemical reactivity. The effect of the chemical defects will be further presented in the case of samarium-doped ceria films with different doping concentration. We will explain the role of the trivalent doping on the conduction mechanism, i.e. proton or oxygen ion, which in turns may greatly influence the surface reactivity.

  20. The growth and evolution of thin oxide films on delta-plutonium surfaces

    SciTech Connect

    Garcia Flores, Harry G; Pugmire, David L

    2009-01-01

    The common oxides of plutonium are the dioxide (PuO{sub 2}) and the sesquioxide (Pu{sub 2}O{sub 3}). The structure of an oxide on plutonium metal under air at room temperature is typically described as a thick PuO{sub 2} film at the gas-oxide interface with a thinner PuO{sub 2} film near the oxide-metal substrate interface. In a reducing environment, such as ultra high vacuum, the dioxide (Pu{sup 4+}; O/Pu = 2.0) readily converts to the sesquioxide (Pu{sup 3+}; O/Pu = 1.5) with time. In this work, the growth and evolution of thin plutonium oxide films is studied with x-ray photoelectron spectroscopy (XPS) under varying conditions. The results indicate that, like the dioxide, the sesquioxide is not stable on a very clean metal substrate under reducing conditions, resulting in substoichiometric films (Pu{sub 2}O{sub 3-y}). The Pu{sub 2}O{sub 3-y} films prepared exhibit a variety of stoichiometries (y = 0.2-1) as a function of preparation conditions, highlighting the fact that caution must be exercised when studying plutonium oxide surfaces under these conditions and interpreting resulting data.

  1. Synthesis of Au microwires by selective oxidation of Au-W thin-film composition spreads.

    PubMed

    Hamann, Sven; Brunken, Hayo; Salomon, Steffen; Meyer, Robert; Savan, Alan; Ludwig, Alfred

    2013-02-01

    We report on the stress-induced growth of Au microwires out of a surrounding Au-W matrix by selective oxidation, in view of a possible application as 'micro-Velcro'. The Au wires are extruded due to the high compressive stress in the tungsten oxide formed by oxidation of elemental W. The samples were fabricated as a thin-film materials library using combinatorial sputter deposition followed by thermal oxidation. Sizes and shapes of the Au microwires were investigated as a function of the W to Au ratio. The coherence length and stress state of the Au microwires were related to their shape and plastic deformation. Depending on the composition of the Au-W precursor, the oxidized samples showed regions with differently shaped Au microwires. The Au48W52 composition yielded wires with the maximum length to diameter ratio due to the high compressive stress in the tungsten oxide matrix. The values of wire length (35 μm) and diameter (2 μm) achieved at the Au48W52 composition are suitable for micro-Velcro applications.

  2. High stability mechanisms of quinary indium gallium zinc aluminum oxide multicomponent oxide films and thin film transistors

    SciTech Connect

    Lee, Ching-Ting Lin, Yung-Hao; Lin, Jhong-Ham

    2015-01-28

    Quinary indium gallium zinc aluminum oxide (IGZAO) multicomponent oxide films were deposited using indium gallium zinc oxide (IGZO) target and Al target by radio frequency magnetron cosputtering system. An extra carrier transport pathway could be provided by the 3 s orbitals of Al cations to improve the electrical properties of the IGZO films, and the oxygen instability could be stabilized by the strong Al-O bonds in the IGZAO films. The electron concentration change and the electron mobility change of the IGZAO films for aging time of 10 days under an air environment at 40 °C and 75% humidity were 20.1% and 2.4%, respectively. The experimental results verified the performance stability of the IGZAO films. Compared with the thin film transistors (TFTs) using conventional IGZO channel layer, in conducting the stability of TFTs with IGZAO channel layer, the transconductance g{sub m} change, threshold voltage V{sub T} change, and the subthreshold swing S value change under the same aging condition were improved to 7.9%, 10.5%, and 14.8%, respectively. Furthermore, the stable performances of the IGZAO TFTs were also verified by the positive gate bias stress. In this research, the quinary IGZAO multicomponent oxide films and that applied in TFTs were the first studied in the literature.

  3. High-Quality Solution-Processed Silicon Oxide Gate Dielectric Applied on Indium Oxide Based Thin-Film Transistors.

    PubMed

    Jaehnike, Felix; Pham, Duy Vu; Anselmann, Ralf; Bock, Claudia; Kunze, Ulrich

    2015-07-01

    A silicon oxide gate dielectric was synthesized by a facile sol-gel reaction and applied to solution-processed indium oxide based thin-film transistors (TFTs). The SiOx sol-gel was spin-coated on highly doped silicon substrates and converted to a dense dielectric film with a smooth surface at a maximum processing temperature of T = 350 °C. The synthesis was systematically improved, so that the solution-processed silicon oxide finally achieved comparable break downfield strength (7 MV/cm) and leakage current densities (<10 nA/cm(2) at 1 MV/cm) to thermally grown silicon dioxide (SiO2). The good quality of the dielectric layer was successfully proven in bottom-gate, bottom-contact metal oxide TFTs and compared to reference TFTs with thermally grown SiO2. Both transistor types have field-effect mobility values as high as 28 cm(2)/(Vs) with an on/off current ratio of 10(8), subthreshold swings of 0.30 and 0.37 V/dec, respectively, and a threshold voltage close to zero. The good device performance could be attributed to the smooth dielectric/semiconductor interface and low interface trap density. Thus, the sol-gel-derived SiO2 is a promising candidate for a high-quality dielectric layer on many substrates and high-performance large-area applications.

  4. Polymer-assisted deposition of co-doped zinc oxide thin films for the detection of aromatic organic compounds.

    PubMed

    Li, Wei; Kim, Dojin

    2011-12-01

    Co-doped Zinc oxide thin films are deposited onto SiO2/Si substrate by polymer-assisted deposition method. The surface morphology, structures and chemical states of the thin films are examined by scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The gas-sensing properties of the thin films upon exposure to aromatic organic compound vapors are also investigated. Co-doping is shown to be very effective in enhancing the response of ZnO thin film to aromatic organic compound.

  5. Investigations on MGy ionizing dose effects in thin oxides of micro-electronic devices

    SciTech Connect

    Gaillardin, M.; Paillet, P.; Raine, M.; Martinez, M.; Marcandella, C.; Duhamel, O.; Richard, N.; Leray, J.L.; Goiffon, V.; Corbiere, F.; Rolando, S.; Molina, R.; Magnan, P.; Girard, S.; Ouerdane, Y.; Boukenter, A.

    2015-07-01

    Total ionizing dose (TID) effects have been studied for a long time in micro-electronic components designed to operate in natural and artificial environments. In most cases, TID induces both charge trapping in the bulk of irradiated oxides and the buildup of interface traps located at semiconductor/dielectric interfaces. Such effects result from basic mechanisms driven by both the shape of the electric field which stands into the oxide and by fabrication process parameters inducing pre-existing traps in the oxide's bulk. From the pioneering studies based on 'thick' oxide technologies to the most recent ones dedicated to innovative technologies, most studies concluded that the impact of total ionizing dose effects reduces with the oxide thinning. This is specifically the case for the gate-oxide of Metal-Oxide-Semiconductor Field Effect Transistors (MOSFET) for which it is generally considered that TID is not a major issue anymore at kGy dose ranges. TID effects are now mainly due to charge trapping in the field oxides such as Shallow Trench Isolation. This creates either parasitic conduction paths or Radiation-Induced Narrow Channel Effects (RINCE). Static current-voltage (I-V) electrical characteristics are then modified through a significant increase of the off-current of NMOS transistors or by shifting the whole I-V curves (of both NMOS and PMOS transistors). Based on these assumptions, no significant shift of I-V curves should be observed in modern bulk CMOS technologies. However, such phenomenon may not be directly extrapolated to higher TID ranges, typically of several MGy for which only few data are available in the literature. This paper presents evidences of large threshold voltage shifts measured at MGy dose levels despite the fact that transistors are designed in a submicron bulk technology which features a 7-nm thin gate-oxide on GO2 transistors dedicated to mixed analog/digital integrated circuits. Such electrical shifts are encountered on PMOS

  6. State-of-the-art Thin Film Electrolytes For Solid Oxide Fuel Cells

    SciTech Connect

    Thevuthasan, Suntharampillai; Nandasiri, Manjula I.

    2015-02-19

    State-of-the-Art solid oxide fuel cells (SOFC) are amongst the main candidates for clean energy technology due to their high efficiency, fuel flexibility, low air pollution, and minimal greenhouse gas emission. However, high operational temperature of SOFC is a greater challenge in commercialization these devices for low cost and portable applications. High temperature operation of SOFC degrades its performance with aging, limits the selection of materials for fuel cell components, and increases the fabrication cost. Thus, there have been enormous efforts to improve the properties of existing materials and develop new materials for SOFC components in order to lower the operating temperature of SOFC. Recent advances in thin film technology have also been utilized to develop new materials with improved properties for SOFC. One of the key components in SOFC is the electrolyte and several research groups are working on developing new electrolyte materials. In this chapter, we will discuss the recent advances in thin film SOFC electrolytes. This extensive discussion includes the evolution of doped ceria, doped zirconia, and multilayer hetero-structured thin film electrolytes. The newly developed nanoscale thin films and multi-layer hetero-structures with improved oxygen ionic conductivity will have significant impact on SOFC devices.

  7. Synthesis of Tantalum-Doped Tin Oxide Thin Films by Magnetron Sputtering for Photovoltaic Applications

    NASA Astrophysics Data System (ADS)

    Nguyen, Ngoc Minh; Luu, Manh Quynh; Nguyen, Minh Hieu; Nguyen, Duy Thien; Bui, Van Diep; Truong, Thanh Tu; Pham, Van Thanh; Nguyen-Tran, Thuat

    2017-01-01

    Tantalum-doped tin oxide transparent conductive thin films were deposited on glass substrates by radio frequency and direct current reactive magnetron co-sputtering methods in an argon and oxygen environment. Optimization of the thin films for photovoltaic applications was performed using a dimensionless figure of merit by combining electrical and transparency properties. The optimized thin film showed a weight-averaged transmittance of 83%, a band gap value of 3.2 eV, resistivity of 5.2 × 10-3 Ω cm, and bulk carrier concentration of 1.2 × 1020 cm-3. The lowest resistivity among all films was 2.1 × 10-3 Ω cm, corresponding to a weight-averaged transmittance of 62%. The optimized deposition condition was carried out by co-sputtering on heated substrates at 270°C. Thin films deposited under this optimized condition were applied for our perovskite solar cells, and demonstrated promising power conversion efficiency.

  8. Remarkably high mobility ultra-thin-film metal-oxide transistor with strongly overlapped orbitals

    NASA Astrophysics Data System (ADS)

    Wei Shih, Chen; Chin, Albert; Fu Lu, Chun; Fang Su, Wei

    2016-01-01

    High mobility channel thin-film-transistor (TFT) is crucial for both display and future generation integrated circuit. We report a new metal-oxide TFT that has an ultra-thin 4.5 nm SnO2 thickness for both active channel and source-drain regions, very high 147 cm2/Vs field-effect mobility, high ION/IOFF of 2.3 × 107, small 110 mV/dec sub-threshold slope, and a low VD of 2.5 V for low power operation. This mobility is already better than chemical-vapor-deposition grown multi-layers MoS2 TFT. From first principle quantum-mechanical calculation, the high mobility TFT is due to strongly overlapped orbitals.

  9. Morphological impact of zinc oxide layers on the device performance in thin-film transistors.

    PubMed

    Faber, Hendrik; Klaumünzer, Martin; Voigt, Michael; Galli, Diana; Vieweg, Benito F; Peukert, Wolfgang; Spiecker, Erdmann; Halik, Marcus

    2011-03-01

    Zinc oxide thin-films are prepared either by spin coating of an ethanolic dispersion of nanoparticles (NP, diameter 5 nm) or by spray pyrolysis of a zinc acetate dihydrate precursor. High-resolution electron microscopy studies reveal a monolayer of particles for the low temperature spin coating approach and larger crystalline domains of more than 30 nm for the spray pyrolysis technique. Thin-film transistor devices (TFTs) based on spray pyrolysis films exhibit higher electron mobilities of up to 24 cm2 V(-1) s(-1) compared to 0.6 cm2 V(-1) s(-1) for NP based TFTs. These observations were dedicated to a reduced number of grain boundaries within the transistor channel.

  10. Characterization and simulation on antireflective coating of amorphous silicon oxide thin films with gradient refractive index

    NASA Astrophysics Data System (ADS)

    Huang, Lu; Jin, Qi; Qu, Xingling; Jin, Jing; Jiang, Chaochao; Yang, Weiguang; Wang, Linjun; Shi, Weimin

    2016-08-01

    The optical reflective properties of silicon oxide (SixOy) thin films with gradient refractive index are studied both theoretically and experimentally. The thin films are widely used in photovoltaic as antireflective coatings (ARCs). An effective finite difference time domain (FDTD) model is built to find the optimized reflection spectra corresponding to structure of SixOy ARCs with gradient refractive index. Based on the simulation analysis, it shows the variation of reflection spectra with gradient refractive index distribution. The gradient refractive index of SixOy ARCs can be obtained in adjustment of SiH4 to N2O ratio by plasma-enhanced chemical vapor deposition (PECVD) system. The optimized reflection spectra measured by UV-visible spectroscopy confirms to agree well with that simulated by FDTD method.

  11. The solution growth route and characterization of electrochromic tungsten oxide thin films

    SciTech Connect

    Todorovski, Toni; Najdoski, Metodija

    2007-12-04

    Electrochromic tungsten oxide thin films were prepared by using an aqueous solution of Na{sub 2}WO{sub 4}.2H{sub 2}O and dimethyl sulfate. Various techniques were used for the characterization of the films such as X-ray diffraction, cyclic voltammetry, SEM analysis and VIS-spectroscopy. The thin film durability was tested in an aqueous solution of LiClO{sub 4} (0.1 mol/dm{sup 3}) for about 7000 cycles followed by cyclic voltammetry. No significant changes in the cyclic voltammograms were found, thus proving the high durability of the films. The optical transmittance spectra of coloured and bleached states showed significant change in the transmittance, which makes these films favorable for electrochromic devices.

  12. Remarkably high mobility ultra-thin-film metal-oxide transistor with strongly overlapped orbitals

    PubMed Central

    Wei Shih, Chen; Chin, Albert; Fu Lu, Chun; Fang Su, Wei

    2016-01-01

    High mobility channel thin-film-transistor (TFT) is crucial for both display and future generation integrated circuit. We report a new metal-oxide TFT that has an ultra-thin 4.5 nm SnO2 thickness for both active channel and source-drain regions, very high 147 cm2/Vs field-effect mobility, high ION/IOFF of 2.3 × 107, small 110 mV/dec sub-threshold slope, and a low VD of 2.5 V for low power operation. This mobility is already better than chemical-vapor-deposition grown multi-layers MoS2 TFT. From first principle quantum-mechanical calculation, the high mobility TFT is due to strongly overlapped orbitals. PMID:26744240

  13. Extracting the effective mass of electrons in transparent conductive oxide thin films using Seebeck coefficient

    SciTech Connect

    Wang, Yaqin; Zhu, Junhao; Tang, Wu

    2014-05-26

    A method is proposed that combines Seebeck coefficient and carrier concentration to determine the electron effective mass of transparent conductive oxide (TCO) thin films. Experiments were conducted to test the validity of this approach on the transparent conductive Ga-doped ZnO thin films deposited by magnetron sputtering. An evident agreement of the calculated electron effective mass of the films is observed between the proposed approach and the previous studies. Besides, the optical carrier concentration and mobility derived from the calculated electron effective mass and spectroscopic ellipsometry using a complex dielectric function are consistent with those from direct Hall-effect measurement. The agreements suggest that Seebeck coefficient can serve as an alternative tool for extracting the effective mass of electrons in TCO films.

  14. Significant electrical control of amorphous oxide thin film transistors by an ultrathin Ti surface polarity modifier

    SciTech Connect

    Cho, Byungsu; Choi, Yonghyuk; Shin, Seokyoon; Jeon, Heeyoung; Seo, Hyungtak; Jeon, Hyeongtag

    2014-01-27

    We demonstrate an enhanced electrical stability through a Ti oxide (TiO{sub x}) layer on the amorphous InGaZnO (a-IGZO) back-channel; this layer acts as a surface polarity modifier. Ultrathin Ti deposited on the a-IGZO existed as a TiO{sub x} thin film, resulting in oxygen cross-binding with a-IGZO surface. The electrical properties of a-IGZO thin film transistors (TFTs) with TiO{sub x} depend on the surface polarity change and electronic band structure evolution. This result indicates that TiO{sub x} on the back-channel serves as not only a passivation layer protecting the channel from ambient molecules or process variables but also a control layer of TFT device parameters.

  15. Preparation of vanadium oxide thin films modified with Ag using a hybrid deposition configuration

    NASA Astrophysics Data System (ADS)

    Gonzalez-Zavala, F.; Escobar-Alarcón, L.; Solís-Casados, D. A.; Rivera-Rodríguez, C.; Basurto, R.; Haro-Poniatowski, E.

    2016-04-01

    The application of a hybrid deposition configuration, formed by the interaction of a laser ablation plasma with a flux of atomic vapor, to deposit vanadium oxide thin films modified with different amounts of silver, is reported. The effect of the amount of Ag incorporated in the films on their structural, morphological, compositional and optical properties was studied. The obtained results reveal that films with variable Ag content from 11.7 to 24.6 at.% were obtained. Depending on the silver content, the samples show very different surface morphologies. Optical characterization indicates the presence of nanostructures of Ag. Thin films containing silver exhibit better photocatalytic performances than unmodified V2O5 films. Raman spectra reveal that as the silver content is increased, the signals associated with V2O5 disappear and new modes attributed mainly to silver vanadates appear suggesting the formation of ternary compounds.

  16. Colored and transparent oxide thin films prepared by magnetron sputtering: the glass blower approach.

    PubMed

    Gil-Rostra, Jorge; Chaboy, Jesús; Yubero, Francisco; Vilajoana, Antoni; González-Elipe, Agustín R

    2013-03-01

    This work describes the reactive magnetron sputtering processing at room temperature of several mixed oxide MxSiyOz thin films (M: Fe, Ni, Co, Mo, W, Cu) intended for optical, coloring, and aesthetic applications. Specific colors can be selected by adjusting the plasma gas composition and the Si-M ratio in the magnetron target. The microstructure and chemistry of the films are characterized by a large variety of techniques including X-ray photoemission spectroscopy, X-ray absorption spectroscopy (XAS), and infrared spectroscopy, while their optical properties are characterized by UV-vis transmission and reflection analysis. Particularly, XAS analysis of the M cations in the amorphous thin films has provided valuable information about their chemical state and local structure. It is concluded that the M cations are randomly distributed within the SiO2 matrix and that both the M concentration and its chemical state are the key parameters to control the final color of the films.

  17. Phase transitions from semiconductive amorphous to conductive polycrystalline in indium silicon oxide thin films

    NASA Astrophysics Data System (ADS)

    Mitoma, Nobuhiko; Da, Bo; Yoshikawa, Hideki; Nabatame, Toshihide; Takahashi, Makoto; Ito, Kazuhiro; Kizu, Takio; Fujiwara, Akihiko; Tsukagoshi, Kazuhito

    2016-11-01

    The enhancement in electrical conductivity and optical transparency induced by a phase transition from amorphous to polycrystalline in lightly silicon-doped indium oxide (InSiO) thin films is studied. The phase transition caused by simple thermal annealing transforms the InSiO thin films from semiconductors to conductors. Silicon atoms form SiO4 tetrahedra in InSiO, which enhances the overlap of In 5s orbitals as a result of the distortion of InO6 octahedral networks. Desorption of weakly bonded oxygen releases electrons from deep subgap states and enhances the electrical conductivity and optical transparency of the films. Optical absorption and X-ray photoelectron spectroscopy measurements reveal that the phase transition causes a Fermi energy shift of ˜0.2 eV.

  18. Modeling the transport properties of epitaxially grown thermoelectric oxide thin films using spectroscopic ellipsometry

    NASA Astrophysics Data System (ADS)

    Sarath Kumar, S. R.; Abutaha, Anas I.; Hedhili, M. N.; Alshareef, H. N.

    2012-01-01

    The influence of oxygen vacancies on the transport properties of epitaxial thermoelectric (Sr,La)TiO3 thin films is determined using electrical and spectroscopic ellipsometry (SE) measurements. Oxygen vacancy concentration was varied by ex-situ annealing in Ar and Ar/H2. All films exhibited degenerate semiconducting behavior, and electrical conductivity decreased (258-133 S cm-1) with increasing oxygen content. Similar decrease in the Seebeck coefficient is observed and attributed to a decrease in effective mass (7.8-3.2 me), as determined by SE. Excellent agreement between transport properties deduced from SE and direct electrical measurements suggests that SE is an effective tool for studying oxide thin film thermoelectrics.

  19. Hall mobility of cuprous oxide thin films deposited by reactive direct-current magnetron sputtering

    SciTech Connect

    Lee, Yun Seog; Winkler, Mark T.; Siah, Sin Cheng; Brandt, Riley; Buonassisi, Tonio

    2011-05-09

    Cuprous oxide (Cu{sub 2}O) is a promising earth-abundant semiconductor for photovoltaic applications. We report Hall mobilities of polycrystalline Cu{sub 2}O thin films deposited by reactive dc magnetron sputtering. High substrate growth temperature enhances film grain structure and Hall mobility. Temperature-dependent Hall mobilities measured on these films are comparable to monocrystalline Cu{sub 2}O at temperatures above 250 K, reaching 62 cm{sup 2}/V s at room temperature. At lower temperatures, the Hall mobility appears limited by carrier scattering from ionized centers. These observations indicate that sputtered Cu{sub 2}O films at high substrate growth temperature may be suitable for thin-film photovoltaic applications.

  20. Crack density and electrical resistance in indium-tin-oxide/polymer thin films under cyclic loading

    NASA Astrophysics Data System (ADS)

    Mora, Angel; Khan, Kamran A.; El Sayed, Tamer

    2014-11-01

    Here, we propose a damage model that describes the degradation of the material properties of indium-tin-oxide (ITO) thin films deposited on polymer substrates under cyclic loading. We base this model on our earlier tensile test model and show that the new model is suitable for cyclic loading. After calibration with experimental data, we are able to capture the stress-strain behavior and changes in electrical resistance of ITO thin films. We are also able to predict the crack density using calibrations from our previous model. Finally, we demonstrate the capabilities of our model based on simulations using material properties reported in the literature. Our model is implemented in the commercially available finite element software ABAQUS using a user subroutine UMAT. [Figure not available: see fulltext.

  1. Polymer waveguide sensor with tin oxide thin film integrated onto optical-electrical printed circuit board

    NASA Astrophysics Data System (ADS)

    Lim, Jung Woon; Kim, Seon Hoon; Kim, Jong-Sup; Kim, Jeong Ho; Kim, Yune Hyoun; Lim, Ju Young; Im, Young-Eun; Park, Jong Bok; Hann, Swook

    2014-05-01

    In this study, we proposed and fabricated optical sensor module integrated onto optical-electrical printed circuit board (PCB) for gas detection based on polymer waveguide with tin oxide thin film. Their potential application as gas sensors are confirmed through computational simulation using the two dimensional finite-difference time-domain method (2DFDTD). Optical-electrical PCB was integrated into vertical cavity surface emitting laser (VCSEL), photodiode and polymeric sensing device was fabricated by the nano-imprint lithography technique. SnO2 thin film of 100nm thickness was placed on the surface of core layer exposed by removing the specific area of the upper cladding layer of 300 μm length and 50 μm width. The performance of the device was measured experimentally. Initial study on the sensor performance for carbon monoxide gas detection indicated good sensitivity.

  2. Chemical vapor deposition and atomic layer deposition of metal oxide and nitride thin films

    NASA Astrophysics Data System (ADS)

    Barton, Jeffrey Thomas

    Processes for depositing thin films with various electronic, optical, mechanical, and chemical properties are indispensable in many industries today. Of the many deposition methods available, chemical vapor deposition (CVD) has proved over time to be one of the most flexible, efficient, and cost-effective. Atomic layer deposition (ALD) is a newer process that is gaining favor as a method for depositing films with excellent properties and unparalleled precision. This work describes the development of novel CVD and ALD processes to deposit a variety of materials. Hafnium oxide and zirconium oxide show promise as replacements for SiO 2 as gate dielectrics in future-generation transistors. These high-k materials would provide sufficient capacitance with layers thick enough to avoid leakage from tunneling. An ALD method is presented here for depositing conformal hafnium oxide from tetrakis-(diethylamido)hafnium and oxygen gas. A CVD method for depositing zirconium oxide from tetrakis-(dialkylamido)zirconium and either oxygen gas or water vapor is also described. The use of copper for interconnects in integrated circuits requires improved diffusion barrier materials, given its high diffusivity compared to the previously-used aluminum and tungsten. Tungsten nitride has a low resistivity among barrier materials, and can be deposited in amorphous films that are effective diffusion barriers in layers as thin as a few nanometers. Here we demonstrate CVD and plasma-enhanced CVD methods to deposit tungsten nitride films from bis-(dialkylamido)bis-( tert-butylimido)tungsten precursors and ammonia gas. Recent findings had shown uniform copper growth on tantalum silicate films, without the dewetting that usually occurs on oxide surfaces. Tantalum and tungsten silicates were deposited by a CVD reaction from the reaction of either tris-(diethylamido)ethylimido tantalum or bis-(ethylmethylamido)-bis-( tert-butylimido)tungsten with tris-(tert-butoxy)silanol. The ability of evaporated

  3. Effect of Polyaniline additions on structural and gas sensing behaviour of metal oxides thin films

    NASA Astrophysics Data System (ADS)

    Hj. Jumali, Mohammad H.; Izzuddin, Izura; Ramli, Norhashimah; Mat Salleh, Muhamad; Yahaya, Muhammad

    2009-07-01

    The structural and gas sensing behaviour of metal oxides namely TiO2 and ZnO thin films were investigated. In this paper, commercial Polyaniline (PANi) powder were added into two different metal oxides sol gel solutions with PANi : metal oxides weight ratios of 1wt.%, 2wt.% and 3wt.%. The thin films were fabricated using spin coating technique. Structural investigation using XRD presented that all films exhibited amorphous structure. Typical films surface morphology consists of agglomerated round shaped particles with the particles size varies between 57nm to 200nm. Addition of PANi formed network chains between the particles. Ethanol vapor detection test conducted at room temperature showed that both TiO2 and ZnO based films were capable to sense the vapor. The optimum ratio in sensing ethanol vapour for both PANi-TiO2 and PANi-ZnO films was 3:1. However, other issues such as reliability, selectability and repeatability remain as the major problems.

  4. Perpendicular magnetic anisotropy in thin ferromagnetic films adjacent to high-k oxides

    NASA Astrophysics Data System (ADS)

    Xu, Meng; Bi, Chong; Rosales, Marcus; Newhouse-Illige, Ty; Almasi, Hamid; Wang, Weigang

    2015-03-01

    Perpendicular magnetic anisotropy (PMA) in thin ferromagnetic films has attracted a great deal of attention due to interesting physics and promising application in spintronic devices. The strength of PMA is often found to be strongly influenced by the adjacent heavy metal layer and oxide layer. A strong interest has emerged recently to control the PMA of these ultra-thin films by electric fields. Here we report the fabrication and characterization of perpendicularly magnetized 3d transitional metal films next to high-k oxides such as HfO2 and ZrO2. We have investigated structural, magnetic and transport properties of these films. The PMA strongly depends on the thickness of the ferromagnetic layers and the interfacial oxidation level of the bilayers. We will also discuss electric field controlled magnetic properties in these systems. This work was supported in part by NSF (ECCS-1310338) and by C-SPIN, one of six centers of STARnet, a Semiconductor Research Corporation program, sponsored by MARCO and DARPA.

  5. Optical, structural and electrochromic properties of sputter- deposited W-Mo oxide thin films

    NASA Astrophysics Data System (ADS)

    Gesheva, K.; Arvizu, M. A.; Bodurov, G.; Ivanova, T.; Niklasson, G. A.; Iliev, M.; Vlakhov, T.; Terzijska, P.; Popkirov, G.; Abrashev, M.; Boyadjiev, S.; Jágerszki, G.; Szilágyi, I. M.; Marinov, Y.

    2016-10-01

    Thin metal oxide films were investigated by a series of characterization techniques including impedance spectroscopy, spectroscopic ellipsometry, Raman spectroscopy, and Atomic Force Microscopy. Thin film deposition by reactive DC magnetron sputtering was performed at the Ångström Laboratory. W and Mo targets (5 cm diameter) and various oxygen gas flows were employed to prepare samples with different properties, whereas the gas pressure was kept constant at about 30 mTorr. The substrates were 5×5 cm2 plates of unheated glass pre-coated with ITO having a resistance of 40 ohm/sq. Film thicknesses were around 300 nm as determined by surface profilometry. Newly acquired equipment was used to study optical spectra, optoelectronic properties, and film structure. Films of WO3 and of mixed W- Mo oxide with three compositions showed coloring and bleaching under the application of a small voltage. Cyclic voltammograms were recorded with a scan rate of 5 mV s-1. Ellipsometric data for the optical constants show dependence on the amount of MoOx in the chemical composition. Single MoOx film, and the mixed one with only 8% MoOx have the highest value of refractive index, and similar dispersion in the visible spectral range. Raman spectra displayed strong lines at wavenumbers between 780 cm-1 and 950 cm-1 related to stretching vibrations of WO3, and MoO3. AFM gave evidence for domains of different composition in mixed W-Mo oxide films.

  6. On the thermal stability of physical vapor deposited oxide-hardened nanocrystalline gold thin films

    DOE PAGES

    Argibay, Nicolas; Mogonye, J. E.; Michael, Joseph R.; ...

    2015-04-08

    We describe a correlation between electrical resistivity and grain size for PVD synthesized polycrystalline oxide-hardened metal-matrix thin films in oxide-dilute (<5 vol. % oxide phase) compositions. The correlation is based on the Mayadas-Shatzkes (M-S) electron scattering model, predictive of grain size evolution as a function of composition in the oxide-dilute regime for 2 μm thick Au-ZnO films. We describe a technique to investigate grain boundary (GB) mobility and the thermal stability of GBs based on in situelectrical resistivity measurements during annealing experiments, interpreted using a combination of the M-S model and the Michels et al. model describing solute drag stabilizedmore » grain growth kinetics. Using this technique, activation energy and pre-exponential Arrhenius parameter values of Ea = 21.6 kJ/mol and Ao = 2.3 × 10-17 m2/s for Au-1 vol. % ZnO and Ea =12.7 kJ/mol and Ao = 3.1 × 10-18 m2/s for Au-2 vol.% ZnO were determined. In the oxide-dilute regime, the grain size reduction of the Au matrix yielded a maximum hardness of 2.6 GPa for 5 vol. % ZnO. A combined model including percolation behavior and grain refinement is presented that accurately describes the composition dependent change in electrical resistivity throughout the entire composition range for Au-ZnO thin films. As a result, the proposed correlations are supported by microstructural characterization using transmission electron microscopy and electron diffraction mapping for grain size determination.« less

  7. On the thermal stability of physical vapor deposited oxide-hardened nanocrystalline gold thin films

    NASA Astrophysics Data System (ADS)

    Argibay, N.; Mogonye, J. E.; Michael, J. R.; Goeke, R. S.; Kotula, P. G.; Scharf, T. W.; Dugger, M. T.; Prasad, S. V.

    2015-04-01

    We describe a correlation between electrical resistivity and grain size for PVD synthesized polycrystalline oxide-hardened metal-matrix thin films in oxide-dilute (<5 vol. % oxide phase) compositions. The correlation is based on the Mayadas-Shatzkes (M-S) electron scattering model, predictive of grain size evolution as a function of composition in the oxide-dilute regime for 2 μm thick Au-ZnO films. We describe a technique to investigate grain boundary (GB) mobility and the thermal stability of GBs based on in situ electrical resistivity measurements during annealing experiments, interpreted using a combination of the M-S model and the Michels et al. model describing solute drag stabilized grain growth kinetics. Using this technique, activation energy and pre-exponential Arrhenius parameter values of Ea = 21.6 kJ/mol and Ao = 2.3 × 10-17 m2/s for Au-1 vol. % ZnO and Ea = 12.7 kJ/mol and Ao = 3.1 × 10-18 m2/s for Au-2 vol. % ZnO were determined. In the oxide-dilute regime, the grain size reduction of the Au matrix yielded a maximum hardness of 2.6 GPa for 5 vol. % ZnO. A combined model including percolation behavior and grain refinement is presented that accurately describes the composition dependent change in electrical resistivity throughout the entire composition range for Au-ZnO thin films. The proposed correlations are supported by microstructural characterization using transmission electron microscopy and electron diffraction mapping for grain size determination.

  8. On the thermal stability of physical vapor deposited oxide-hardened nanocrystalline gold thin films

    SciTech Connect

    Argibay, N. Mogonye, J. E.; Michael, J. R.; Goeke, R. S.; Kotula, P. G.; Scharf, T. W.; Dugger, M. T.; Prasad, S. V.

    2015-04-14

    We describe a correlation between electrical resistivity and grain size for PVD synthesized polycrystalline oxide-hardened metal-matrix thin films in oxide-dilute (<5 vol. % oxide phase) compositions. The correlation is based on the Mayadas-Shatzkes (M-S) electron scattering model, predictive of grain size evolution as a function of composition in the oxide-dilute regime for 2 μm thick Au-ZnO films. We describe a technique to investigate grain boundary (GB) mobility and the thermal stability of GBs based on in situ electrical resistivity measurements during annealing experiments, interpreted using a combination of the M-S model and the Michels et al. model describing solute drag stabilized grain growth kinetics. Using this technique, activation energy and pre-exponential Arrhenius parameter values of E{sub a} = 21.6 kJ/mol and A{sub o} = 2.3 × 10{sup −17} m{sup 2}/s for Au-1 vol. % ZnO and E{sub a} = 12.7 kJ/mol and A{sub o} = 3.1 × 10{sup −18} m{sup 2}/s for Au-2 vol. % ZnO were determined. In the oxide-dilute regime, the grain size reduction of the Au matrix yielded a maximum hardness of 2.6 GPa for 5 vol. % ZnO. A combined model including percolation behavior and grain refinement is presented that accurately describes the composition dependent change in electrical resistivity throughout the entire composition range for Au-ZnO thin films. The proposed correlations are supported by microstructural characterization using transmission electron microscopy and electron diffraction mapping for grain size determination.

  9. On the thermal stability of physical vapor deposited oxide-hardened nanocrystalline gold thin films

    SciTech Connect

    Argibay, Nicolas; Mogonye, J. E.; Michael, Joseph R.; Goeke, Ronald S.; Kotula, Paul G.; Scharf, T. W.; Dugger, Michael Thomas; Prasad, Somuri V.

    2015-04-08

    We describe a correlation between electrical resistivity and grain size for PVD synthesized polycrystalline oxide-hardened metal-matrix thin films in oxide-dilute (<5 vol. % oxide phase) compositions. The correlation is based on the Mayadas-Shatzkes (M-S) electron scattering model, predictive of grain size evolution as a function of composition in the oxide-dilute regime for 2 μm thick Au-ZnO films. We describe a technique to investigate grain boundary (GB) mobility and the thermal stability of GBs based on in situelectrical resistivity measurements during annealing experiments, interpreted using a combination of the M-S model and the Michels et al. model describing solute drag stabilized grain growth kinetics. Using this technique, activation energy and pre-exponential Arrhenius parameter values of Ea = 21.6 kJ/mol and Ao = 2.3 × 10-17 m2/s for Au-1 vol. % ZnO and Ea =12.7 kJ/mol and Ao = 3.1 × 10-18 m2/s for Au-2 vol.% ZnO were determined. In the oxide-dilute regime, the grain size reduction of the Au matrix yielded a maximum hardness of 2.6 GPa for 5 vol. % ZnO. A combined model including percolation behavior and grain refinement is presented that accurately describes the composition dependent change in electrical resistivity throughout the entire composition range for Au-ZnO thin films. As a result, the proposed correlations are supported by microstructural characterization using transmission electron microscopy and electron diffraction mapping for grain size determination.

  10. Indium oxide thin film as potential photoanodes for corrosion protection of stainless steel under visible light

    SciTech Connect

    Zhang, Yan; Yu, Jianqiang; Sun, Kai; Zhu, Yukun; Bu, Yuyu; Chen, Zhuoyuan

    2014-05-01

    Graphical abstract: If the conduction band potential of In{sub 2}O{sub 3} is more negative than the corrosion potential of stainless steel, photo-induced electrons will be transferred from In{sub 2}O{sub 3} to the steel, thus shifting the potential of the steel into a corrosion immunity region and preventing the steel from the corrosion. - Highlights: • Indium oxide performed novel application under visible light. • Indium oxide by sol–gel method behaved better photoelectrochemical properties. • Electrons were transferred to stainless steel from indium oxide once light on. - Abstract: This paper reports the photoelectrochemical cathodic protection of 304 stainless steel by In{sub 2}O{sub 3} thin-film under visible-light. The films were fabricated with In{sub 2}O{sub 3} powders, synthesized by both sol–gel (In{sub 2}O{sub 3}-sg) and solid-state (In{sub 2}O{sub 3}-ss) processes. The photo-induced open circuit potential and the photo-to-current efficiency measurements suggested that In{sub 2}O{sub 3} could be a promising candidate material for photoelectrochemical cathodic protection of metallic alloys under visible light. Moreover, the polarization curve experimental results indicated that In{sub 2}O{sub 3}-sg thin-film can mitigate the corrosion potential of 304 stainless steel to much more negative values with a higher photocurrent density than the In{sub 2}O{sub 3}-ss film under visible-light illumination. All the results demonstrated that the In{sub 2}O{sub 3}-sg thin-film provides a better photoelectrochemical cathodic protection for 304 stainless steel than In{sub 2}O{sub 3}-ss thin-film under visible-light illumination. The higher photoelectrochemical efficiency is possibly due to the uniform thin films produced with the smaller particle size of In{sub 2}O{sub 3}-sg, which facilitates the transfer of the photo-induced electrons from bulk to the surface and suppresses the charge recombination of the electrons and holes.

  11. Pulsed laser deposited metal oxide thin films mediated controlled adsorption of proteins

    NASA Astrophysics Data System (ADS)

    Kim, Se Jin

    Several metal oxide thin films were grown on Si substrate by pulsed laser deposition for controlling adsorption of proteins. No intentional heating of substrate and introduction of oxygen gas during growth were employed. Additionally, fibrinogen, bovine serum albumin (BSA), and lysozyme were used as model protein in this study. The film properties such as cyratllinity, surface roughness, surface electrical charge and chemistry were investigated by many techniques in order to obtain the relationship with protein adsorption. Firstly, as grown Ta2O5 and ZnO thin film were used to study the effects of surface charge on the behaviors of BSA and lysozyme adsorption. The protein thickness results by ellipsometry showed that negatively charged Ta2O5 had a stronger affinity to positively charged lysozyme, while positively charged ZnO had a stronger affinity to negatively charged BSA. The results confirmed electrostatic interaction due to surface charge is one of main factors for determining adsorption of proteins. Furthermore, annealing studies were performed by heat treatment of as grown Ta2O5 and ZnO at 800°C in air ambience. Annealed Ta2O5 thin film had almost wetting property (from 10.02° to less than 1˜2°) and the change of cystallinity (from amorphous to cyrsalline) while annealed ZnO thin film had a reduced contact angle (from 75.65° to 39.41°) and remained to crystalline structure. The fibrinogen thickness on annealed Ta2O5 film was increased compared with as grown sample, while heat treated ZnO film showed much reduction of fibrinogen adsorption. Binary Ta-Zn oxide thin films (TZ) were grown by preparing PLD target composed of 50 wt% Ta2O5 and 50 wt% ZnO. This binary film had IEP pH 7.1 indicating nearly neutral charge in pH 7.4 PBS solution, and hydrophilic property. Ellipsometrical results showed that TZ film had the lowest fibrinogen, BSA and lysozyme thickness after 120 min adsorption compared with Ta2O5 and ZnO. Other samples, bilayer oxide films in

  12. Oxidative degradation of acid orange 7 using Ag-doped zinc oxide thin films.

    PubMed

    Shinde, S S; Bhosale, C H; Rajpure, K Y

    2012-12-05

    Ag-doped ZnO thin films with preferred c-axis orientation along (002) have been prepared by spray pyrolysis technique in aqueous medium on to the corning glass substrates. The effect of Ag-doping on to the photoelectrochemical, structural, morphological, optical, luminescence, electrical and thermal properties has been investigated. XRD and Raman study indicates that the films have hexagonal (wurtzite) crystal structure. The effect of Ag loading on the photocatalytic activity of Ag-doped ZnO in the degradation of azo dye is studied and results are compared with pure ZnO. The results show that the rate of degradation of azo dye over Ag-doped ZnO is much higher as compared to pure ZnO. Ag doping in ZnO is highly effective and can significantly enhance the photocatalytic degradation and mineralization of azo dye. The enhancement of photocatalytic activity of Ag-doped ZnO thin films is mainly due to their smaller crystallite size and capability for reducing the electron-hole pair recombination. Kinetic parameters have been investigated in terms of a first order rate equation. The rate constant (-k) for this heterogeneous photocatalysis is evaluated as a function of the initial concentration of original species. Substantial reduction in azo dye is achieved as analyzed from COD and TOC studies.

  13. A review on the recent developments of solution processes for oxide thin film transistors

    NASA Astrophysics Data System (ADS)

    Du Ahn, Byung; Jeon, Hye-Ji; Sheng, Jiazhen; Park, Jozeph; Park, Jin-Seong

    2015-06-01

    This review article introduces the recent advances in the development of oxide semiconductor materials based on solution processes and their potential applications. In the early stage, thin film transistors based on oxide semiconductors fabricated by solution processes used to face critical problems such as high annealing temperatures (>400 °C) required to obtain reasonable film quality, and the relatively low field effect mobility (<5 cm2 V-1 s-1) compared to devices fabricated by conventional vacuum-based techniques. In order to overcome such hurdles, the proper selection of high mobility amorphous oxide semiconductor materials is addressed first. The latter involves the combination of high mobility compounds and multilayered active stacks. Ensuing overviews are provided on the selection of optimum precursors and alternative annealing methods that enable the growth of high quality films at relatively low process temperatures (<200 °C). Reasonably high field effect mobility values (~10 cm2 V-1 s-1) could thus be obtained by optimizing the above process parameters. Finally, potential applications of solution processed oxide semiconductor devices are summarized, involving, for instance, flexible displays, biosensors, and non-volatile memory devices. As such, further innovations in the solution process methods of oxide semiconductor devices are anticipated to allow the realization of cost effective, large area electronics in the near future.

  14. Periodic oxidation for fabricating titanium oxynitride thin films via atomic layer deposition

    SciTech Connect

    Iwashita, Shinya Aoyama, Shintaro; Nasu, Masayuki; Shimomura, Kouji; Noro, Naotaka; Hasegawa, Toshio; Akasaka, Yasushi; Miyashita, Kohei

    2016-01-15

    This paper demonstrates thermal atomic layer deposition (ALD) combined with periodic oxidation for synthesizing titanium oxynitride (TiON) thin films. The process used a typical ALD reactor for the synthesis of titanium nitride (TiN) films wherein oxygen was supplied periodically between the ALD-TiN cycles. The great advantage of the process proposed here was that it allowed the TiN films to be oxidized efficiently. Also, a uniform depth profile of the oxygen concentration in the films could be obtained by tuning the oxidation conditions, allowing the process to produce a wide variety of TiON films. The resistivity measurement is a convenient method to confirm the reproducibility of metal film fabrication but may not be applicable for TiON films depending upon the oxidation condition because the films can easily turn into insulators when subjected to periodic oxidation. Therefore, an alternative reproducibility confirmation method was required. In this study, spectroscopic ellipsometry was applied to monitor the variation of TiON films and was able to detect changes in film structures such as conductor–insulator transitions in the TiON films.

  15. Thermally evaporated mechanically hard tin oxide thin films for opto-electronic apllications

    NASA Astrophysics Data System (ADS)

    Tripathy, Sumanta K.; Rajeswari, V. P.

    2014-01-01

    Tungsten doped tin oxide (WTO) and Molybdenum doped tin oxide (MoTO) thin film were deposited on corn glass by thermal evaporation method. The films were annealed at 350°C for one hour. Structural analysis using Xray diffraction data shows both the films are polycrystalline in nature with monoclinic structure of tin oxide, Sn3O4, corresponding to JCPDS card number 01-078-6064. SEM photograph showed that both the films have spherical grains with size in the range of 20-30 nm. Compositional analysis was carried out using EDS which reveals the presence of Sn, O and the dopant Mo/W only thereby indicating the absence of any secondary phase in the films. The films are found to contain nearly 6 wt% of Mo, 8 wt% of W as dopants respectively. The transmission pattern for both the films in the spectral range 200 - 2000 nm shows that W doping gives a transparency of nearly 80% from 380 nm onwards while Mo doping has less transparency of 39% at 380nm. Film hardness measurement using Triboscope shows a film hardness of about 9-10 GPa for both the films. It indicates that W or M doping in tin oxide provides the films the added advantage of withstanding the mechanical wear and tear due to environmental fluctuations By optimizing the optical and electrical properties, W/Mo doped tin oxide films may be explored as window layers in opto-electronic applications such as solar cells.

  16. Solution-Processed Rare-Earth Oxide Thin Films for Alternative Gate Dielectric Application.

    PubMed

    Zhuang, Jiaqing; Sun, Qi-Jun; Zhou, Ye; Han, Su-Ting; Zhou, Li; Yan, Yan; Peng, Haiyan; Venkatesh, Shishir; Wu, Wei; Li, Robert K Y; Roy, V A L

    2016-11-16

    Previous investigations on rare-earth oxides (REOs) reveal their high possibility as dielectric films in electronic devices, while complicated physical methods impede their developments and applications. Herein, we report a facile route to fabricate 16 REOs thin insulating films through a general solution process and their applications in low-voltage thin-film transistors as dielectrics. The formation and properties of REOs thin films are analyzed by atomic force microscopy (AFM), X-ray diffraction (XRD), spectroscopic ellipsometry, water contact angle measurement, X-ray photoemission spectroscopy (XPS), and electrical characterizations, respectively. Ultrasmooth, amorphous, and hydrophilic REO films with thickness around 10 nm have been obtained through a combined spin-coating and postannealing method. The compositional analysis results reveal the formation of RE hydrocarbonates on the surface and silicates at the interface of REOs films annealed on Si substrate. The dielectric properties of REO films are investigated by characterizing capacitors with a Si/Ln2O3/Au (Ln = La, Gd, and Er) structure. The observed low leakage current densities and large areal capacitances indicate these REO films can be employed as alternative gate dielectrics in transistors. Thus, we have successfully fabricated a series of low-voltage organic thin-film transistors based on such sol-gel derived REO films to demonstrate their application in electronics. The optimization of REOs dielectrics in transistors through further surface modification has also been studied. The current study provides a simple solution process approach to fabricate varieties of REOs insulating films, and the results reveal their promising applications as alternative gate dielectrics in thin-film transistors.

  17. Light irradiation tuning of surface wettability, optical, and electric properties of graphene oxide thin films

    NASA Astrophysics Data System (ADS)

    Furio, A.; Landi, G.; Altavilla, C.; Sofia, D.; Iannace, S.; Sorrentino, A.; Neitzert, H. C.

    2017-02-01

    In this work the preparation of flexible polymeric films with controlled electrical conductivity, light transmission and surface wettability is reported. A drop casted graphene oxide thin film is photo-reduced at different levels by UV light or laser irradiation. Optical microscopy, IR spectroscopy, electrical characterization, Raman spectroscopy and static water contact angle measurements are used in order to characterize the effects of the various reduction methods. Correlations between the optical, electrical and structural properties are reported and compared to previous literature results. These correlations provide a useful tool for independently tuning the properties of these films for specific applications.

  18. Amorphous indium zinc oxide thin film transistors with poly-4-vinylphenol gate dielectric layers

    NASA Astrophysics Data System (ADS)

    Pu, Haifeng; Li, Guifeng; Feng, Jiahan; Liu, Baoying; Zhang, Qun

    2011-09-01

    Thin film transistors (TFTs) with amorphous indium zinc oxide (a-IZO) as channel layers and poly-4-vinylphenol as dielectric layers were fabricated. Transmission curves show that the double-layer structure of the a-IZO layer and the poly-4-vinylphenol layer exhibits the antireflection effect. It was found that post heat-treatment at relatively low temperature will improve the electrical performance of the transistors. TFT devices with saturation mobility of 25.4 cm2 V-1 s-1, threshold voltage of 4.0 V, subthreshold swing value of 0.88 V/decade and current on/off ratio of 106 were obtained.

  19. Charge pumping method for photosensor application by using amorphous indium-zinc oxide thin film transistors

    NASA Astrophysics Data System (ADS)

    Liu, Po-Tsun; Chou, Yi-Teh; Teng, Li-Feng

    2009-06-01

    The study investigated the photoreaction behavior of amorphous indium-zinc oxide thin film transistor (a-IZO TFT), which was thought to be insensitive to visible light. The obvious threshold voltage shift was observed after light illumination, and it exhibited slow recovery while returning to initial status. The photoreaction mechanism is well explained by the dynamic equilibrium of charge exchange reaction between O2(g) and O2- in a-IZO layer. A charge pumping technique is used to confirm the mechanism and accelerate recoverability. Using knowledge of photoreaction behavior, an operation scheme of photosensing elements consist of a-IZO TFT is also demonstrated in this work.

  20. Zinc oxide integrated area efficient high output low power wavy channel thin film transistor

    SciTech Connect

    Hanna, A. N.; Ghoneim, M. T.; Bahabry, R. R.; Hussain, A. M.; Hussain, M. M.

    2013-11-25

    We report an atomic layer deposition based zinc oxide channel material integrated thin film transistor using wavy channel architecture allowing expansion of the transistor width in the vertical direction using the fin type features. The experimental devices show area efficiency, higher normalized output current, and relatively lower power consumption compared to the planar architecture. This performance gain is attributed to the increased device width and an enhanced applied electric field due to the architecture when compared to a back gated planar device with the same process conditions.

  1. Graphene-based thin film supercapacitor with graphene oxide as dielectric spacer

    NASA Astrophysics Data System (ADS)

    Liu, Jinzhang; Galpaya, Dilini; Notarianni, Marco; Yan, Cheng; Motta, Nunzio

    2013-08-01

    Thin film supercapacitors are produced by using electrochemically exfoliated graphene (G) and wet-chemically produced graphene oxide (GO). Either G/GO/G stacked film or sole GO film are sandwiched by two Au films to make devices, where GO is the dielectric spacer. The addition of graphene film can increase the capacitance about two times, compared to the simple Au electrode. It is found that the GO film has very high dielectric constant, accounting for the high capacitance. AC measurement reveals that the relative permittivity of GO is in the order of 104 within the frequency range of 0.1-70 Hz.

  2. Electric field modulation of thermopower for transparent amorphous oxide thin film transistors

    NASA Astrophysics Data System (ADS)

    Koide, Hirotaka; Nagao, Yuki; Koumoto, Kunihito; Takasaki, Yuka; Umemura, Tomonari; Kato, Takeharu; Ikuhara, Yuichi; Ohta, Hiromichi

    2010-11-01

    To clarify the electronic density of states (DOS) around the conduction band bottom for state of the art transparent amorphous oxide semiconductors (TAOSs), InGaZnO4 and In2MgO4, we fabricated TAOS-based transparent thin film transistors (TTFTs) and measured their gate voltage dependence of thermopower (S). TAOS-based TTFTs exhibit an unusual S behavior. The |S|-value abruptly increases but then gradually decreases as Vg increases, clearly suggesting the antiparabolic shaped DOS is hybridized with the original parabolic shaped DOS around the conduction band bottom.

  3. Aligned carbon nanotube, graphene and graphite oxide thin films via substrate-directed rapid interfacial deposition.

    PubMed

    D'Arcy, Julio M; Tran, Henry D; Stieg, Adam Z; Gimzewski, James K; Kaner, Richard B

    2012-05-21

    A procedure for depositing thin films of carbon nanostructures is described that overcomes the limitations typically associated with solution based methods. Transparent and conductively continuous carbon coatings can be grown on virtually any type of substrate within seconds. Interfacial surface tension gradients result in directional fluid flow and film spreading at the water/oil interface. Transparent films of carbon nanostructures are produced including aligned ropes of single-walled carbon nanotubes and assemblies of single sheets of chemically converted graphene and graphite oxide. Process scale-up, layer-by-layer deposition, and a simple method for coating non-activated hydrophobic surfaces are demonstrated.

  4. Chemical etching of zinc oxide for thin-film silicon solar cells.

    PubMed

    Hüpkes, Jürgen; Owen, Jorj I; Pust, Sascha E; Bunte, Eerke

    2012-01-16

    Chemical etching is widely applied to texture the surface of sputter-deposited zinc oxide for light scattering in thin-film silicon solar cells. Based on experimental findings from the literature and our own results we propose a model that explains the etching behavior of ZnO depending on the structural material properties and etching agent. All grain boundaries are prone to be etched to a certain threshold, that is defined by the deposition conditions and etching solution. Additionally, several approaches to modify the etching behavior through special preparation and etching steps are provided.

  5. Hydrogen gas sensors based on electrostatically spray deposited nickel oxide thin film structures

    NASA Astrophysics Data System (ADS)

    Jamal, Raied K.; Aadim, Kadhim A.; Al-Zaidi, Qahtan G.; Taaban, Iman N.

    2015-09-01

    A simple, low-cost, and home-built electrostatic spray deposition (ESD) system with the stable cone-jet mode was used to deposit nickel oxide (NiO) thin films on glass substrates kept at temperature of 400 °C as the primary precursor solution of 0.1 M concentration hydrated nickel chloride was dissolved in isopropyl alcohol. Electrical measurements showed that these films were of n-type conductivity while their resistance response to hydrogen flow in air ambient was varied by 2.81% with the rise and recovery time of 48 s and 40 s, respectively.

  6. Chemical and optical properties of thermally evaporated manganese oxide thin films

    SciTech Connect

    Al-Kuhaili, M. F.

    2006-09-15

    Manganese oxide thin films were deposited using thermal evaporation from a tungsten boat. Films were deposited under an oxygen atmosphere, and the effects of thickness, substrate temperature, and deposition rate on their properties were investigated. The chemical properties of the films were studied using x-ray photoelectron spectroscopy and x-ray fluorescence. The optical properties were determined from normal-incidence transmittance and reflectance. Based on the chemical and optical characterizations, the optimum conditions for the deposition of the films were investigated. Subsequently, the optical properties (refractive index, extinction coefficient, and band gap) of these films were determined.

  7. Aqueous process to limit hydration of thin-film inorganic oxides

    NASA Astrophysics Data System (ADS)

    Perkins, Cory K.; Mansergh, Ryan H.; Park, Deok-Hie; Nanayakkara, Charith E.; Ramos, Juan C.; Decker, Shawn R.; Huang, Yu; Chabal, Yves J.; Keszler, Douglas A.

    2016-11-01

    Aqueous-processed aluminum oxide phosphate (AlPO) dielectric films were studied to determine how water desorbs and absorbs on heating and cooling, respectively. In-situ Fourier transform infrared spectroscopy showed a distinct, reversible mono- to bidentate phosphate structural change associated with water loss and uptake. Temperature programmed desorption measurements on a 1-μm thick AlPO film revealed water sorption was inhibited by an aqueous-processed HfO2 capping film only 11-nm thick. The HfO2 capping film prevents water resorption, thereby preserving the exceptional performance of AlPO as a thin-film dielectric.

  8. Development of Novel Magnetic Metal Oxide Thin Films and Carbon Nanotube Materials for Potential Device Applications

    DTIC Science & Technology

    2016-05-09

    spin spring materials .”To study this possibility, we extended our investigation to the synthesis of CoFe2O4/CoFe2/CoFe2O4 trilayers under different...09-05-2016 18-May-2011 17-May-2014 Final Report: Development of Novel Magnetic Metal Oxide Thin Films and Carbon Nanotube Materials for Potential...U.S. Army Research Office P.O. Box 12211 Research Triangle Park, NC 27709-2211 Nanomagnetics, carbon nanotubes, multilayer materials , spin

  9. Study of Ferromagnetic and Field Effect Properties of Zinc Oxide Thin Films

    NASA Astrophysics Data System (ADS)

    Xia, Daxue

    Spintronics (spin transport electronics), in which both spm and charge of carriers are utilized for information processing, is perceived to be a candidate to extend and possibly to become the next-generation electronics. Its advantages include nonvolatility (data retention without electrical power), lower energy consumption, faster processing speed, and higher integration densities in comparison with the current semiconductor devices relying solely on electron charge. To realize a spin-field effect transistor, two respects are prerequisite. On the one hand, the mechanism of ferromagnetism should be addressed before one could prepare magnetic semiconductor films in a controllable way. On the other hand, excellent field effect properties should be sought through a convenient and low-cost strategy for manufacturing future nano-scale spintronic devices. This thesis is comprised of two parts. Firstly, it deals with the synthesis, characterization, and magnetism of transition-metal-doped or un-doped zinc oxide (ZnO) thin films. Secondly, it focuses on the field effect properties of solution processable ZnO thin films, which are not only of great interest for current charge-carrier based thin film transistors, but also of fundamental importance in future spin-based transistors. A facile spin-coating technique has been developed to fabricate ZnO thin films. Even without magnetic element doping, the film is found to show room temperature ferromagnetism. A broad series of advanced microscopic and spectroscopic techniques are utilized to characterize the thin films properties. Oxygen vacancy defects are tentatively attributed to the observed ferromagnetism. Following the similar method, Ga doped or Ga, Co co-doped ZnO thin films are prepared. The ferromagnetism is enhanced with Ga doping, providing more carriers. It is discovered that room temperature ferromagnetism can exist in both highly conductive regime and the less conductive or near insulating regime. Transition metal

  10. Morphology, structural and optical properties of iron oxide thin film photoanodes in photoelectrochemical cell: Effect of electrochemical oxidation

    NASA Astrophysics Data System (ADS)

    Maabong, Kelebogile; Machatine, Augusto G.; Hu, Yelin; Braun, Artur; Nambala, Fred J.; Diale, Mmantsae

    2016-01-01

    Hematite (α-Fe2O3) is a promising semiconductor as photoanode in solar hydrogen production from photoelectrolysis of water due to its appropriate band gap, low cost and high electrochemical stability in aqueous caustic electrolytes. Operation of such photoanode in a biased photoelectrochemical cell constitutes an anodization with consequent redox reactions at the electrode surface. α-Fe2O3 thin film photoanodes were prepared by simple and inexpensive dip coating method on fluorine doped tin oxide (FTO) glass substrate, annealed in air at 500 °C for 2 h, then electrochemically oxidized (anodized) in 1 M KOH at 500 mV for 1 min in dark and light conditions. Changes in structural properties and morphology of α-Fe2O3 nanoparticles films were investigated by XRD, Raman spectroscopy and a high resolution FE-SEM. The average grain size was observed to increase from 57 nm for pristine samples to 73 and 77 nm for anodized samples in dark and light respectively. Broadening and red shift in Raman spectra in anodized samples may be attributed to lattice expansion upon oxidation. The UV-visible measurements revealed enhanced absorption in the photoanodes after the treatment. The findings suggest that the anodization of the photoelectrode in a biased cell causes not only changes of the molecular structure at the surface, but also changes in the crystallographic structure which can be detected with x-ray diffractometry.

  11. Tailoring the refractive index of aluminum doped zinc oxide thin films by co-doping with titanium

    NASA Astrophysics Data System (ADS)

    Wei, Tiefeng; Lan, Pinjun; Yang, Ye; Zhang, Xianpeng; Tan, Ruiqin; Li, Yong; Song, Weijie

    2012-12-01

    The refractive index of transparent conductive oxides has a direct effect on the transmission of lights into thin film solar cells. Here we report the study of improving the refractive index of aluminum doped zinc oxide through titanium co-doping. The Al-Ti co-doped zinc oxide (ATZO) thin films with different Ti doping concentration were deposited on glass substrates by radio frequency magnetron sputtering with ATZO targets in an argon atmosphere. The structural, optical and electrical properties of the thin films were investigated using X-ray diffraction, ultraviolet-visible-near-infrared spectroscopy and hall measurements, respectively. The results showed that the as-deposited thin films were all textured along c-axis and perpendicular to the surface of substrate. The average transmittance in the visible region were more than 80% for all the ATZO thin films. The minimum resistivity of the obtained ATZO (1 wt% TiO2 doping) thin films were 2.6 × 10-3 Ω cm and 1.4 × 10-3 Ω cm before and after annealing in vacuum, respectively. The refractive index of the thin films (at λ0 = 550 nm) increased from 1.91 to 2.05 as the TiO2 content increased from 0 wt% to 3 wt%.

  12. Flexible electrochromics: magnetron sputtered tungsten oxide (WO3-x) thin films on Lexan (optically transparent polycarbonate) substrates

    NASA Astrophysics Data System (ADS)

    Uday Kumar, K.; Murali, Dhanya S.; Subrahmanyam, A.

    2015-06-01

    Tungsten oxide (WO3-x) based electrochromics on flexible substrates is a topic of recent interest. The present communication reports the electrochromic properties of WO3-x thin films grown on lexan, an optically transparent polycarbonate thermoplastic substrate. The WO3-x films are prepared at room temperature (300 K) by the reactive DC magnetron sputtering technique. The physical properties of metal oxide thin films are known to be controlled by the oxygen stoichiometry of the film. In the present work, the WO3-x thin films are prepared by varying the oxygen flow rates. All the WO3-x thin films are amorphous in nature. The electrochromic performance of the WO3-x thin films is evaluated by cyclic voltammetry measurements on tin doped indium oxide (ITO) coated lexan and glass substrates. The optical band gap of WO3-x thin films grown on lexan substrates (at any given oxygen flow rate) is significantly higher than those grown on glass substrates. The coloration efficiency of WO3-x thin films (at an oxygen flow rate of 10 sccm) on lexan substrates is: 143.9 cm2 C-1 which is higher compared to that grown on glass: 90.4 cm2 C-1.

  13. 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.

  14. 1/f noise in thin oxide p-channel metal-nitride-oxide-silicon transistors

    NASA Astrophysics Data System (ADS)

    Maes, Herman E.; Usmani, Sabir H.

    1983-04-01

    The 1/f noise behavior of p-channel metal-nitride-oxide-silicon transistors is presented. Devices with different oxide thicknesses, geometries and different technological treatments were used for this study. It is shown that the noise behavior can be well explained quantitatively with the number fluctuation model developed for MOS transistors. The close correlation between the increase of the noise and of the interface state density after different levels of degradation indeed indicates that the exchange of carriers between the channel and the interface traps lies at the origin of the 1/f noise. The observed degradation in MNOS devices is consistent with a diffusion controlled model for the creation of surface traps but is found to be a saturating effect. The predictions of the mobility fluctuation model are not confirmed in our experiments.

  15. Thermal oxidation of amorphous germanium thin films on SiO2 substrates

    NASA Astrophysics Data System (ADS)

    de los Santos Valladares, L.; Bustamante Dominguez, A.; Ionescu, A.; Brown, A.; Sepe, A.; Steiner, U.; Avalos Quispe, O.; Holmes, S.; Majima, Y.; Langford, R.; Barnes, C. H. W.

    2016-12-01

    In this work we report the thermal oxidation of amorphous germanium (a-Ge) thin films (140 nm thickness) in air. Following fabrication by conventional thermal evaporation on SiO2 substrates, the samples were annealed in air at different temperatures ranging from 300 to 1000 °C. By means of x-ray diffraction, x-ray reflectivity, synchrotron grazing-incidence wide-angle x-ray scattering and cross-sectional transmission electron microscopy analysis it is found that the a-Ge films abruptly crystallize at 475 °C, while simultaneously increasing the thickness of the oxide (GeO2) in a layer by layer fashion. X-ray photoemission spectroscopy reveals that the oxidation state of the Ge atoms in the GeO2 layer is 4+. However, a reaction at the GeO2/Ge interface occurs between 500 and 550 °C reducing the oxide layer to GeO x (x < 2) and containing Ge2+ and Ge+. The thickness of the oxide layer grows with the annealing temperature following an Arrhenius behavior with an activation energy of 0.82 ± 0.09 eV up to 500 °C. Remarkably, we observed simultaneous enhancement of the oxidation and crystallization of the a-Ge in the temperature interval 450 °C-500 °C, in which the oxidation rate reaches a maximum of around 0.8 nm °C-1 at around 500 °C.

  16. Reduction of channel resistance in amorphous oxide thin-film transistors with buried layer

    NASA Astrophysics Data System (ADS)

    Chong, Eugene; Kim, Bosul; Lee, Sang Yeol

    2012-04-01

    A silicon-indium-zinc-oxide (SIZO) thin film transistor (TFT) with low channel-resistance (RCH) indium-zinc-oxide (In2O3:ZnO = 9:1) buried layer annealed at low temperature of 200°C exhibited high field-effect mobility (μFE) over 55.8 cm2/V·s which is 5 times higher than that of the conventional TFTs due to small threshold voltage (Vth) change of 1.8 V under bias-temperature stress (BTS) condition for 420 minutes. The low-RCH buried-layer allows more strong current-path formed in channel layer well within relatively high-RCH channel-layer since it is less affected by the channel bulk and/or back interface trap with high carrier concentration.

  17. Amorphous silicon-indium-zinc oxide semiconductor thin film transistors processed below 150 °C

    NASA Astrophysics Data System (ADS)

    Chong, Eugene; Chun, Yoon Soo; Lee, Sang Yeol

    2010-09-01

    Amorphous silicon-indium-zinc-oxide (a-SIZO) thin film transistor (TFT) was investigated with the process temperature below 150 °C. The a-SIZO TFT exhibited a field effect mobility of 21.6 cm2/V s and an on/off ratio of 107. The stabilities of a-SIZO TFT and indium-zinc-oxide (IZO) TFT were compared, and a-SIZO TFT showed 3.7 V shift for threshold voltage (Vth) compared to 10.8 V shift in IZO TFT after bias temperature stress. Si incorporation into IZO-system as a stabilizer, which was confirmed by x-ray photoelectron spectroscopy, resulted in small shift in Vth in a-SIZO TFT without deteriorating mobility of higher than 21.6 cm2/V s.

  18. Thin Oxides as a Cu Diffusion Barrier for NIF Be Ablator Capsules

    DOE PAGES

    Youngblood, Kelly P.; Huang, H.; Xu, H. W.; ...

    2013-03-01

    The NIF point design uses a five-layer capsule to modify the X-ray absorption in order to achieve optimized shock timing. A stepped copper dopant design defines the layer structure. The production of the capsule involves pyrolysis to remove the inner plastic mandrel. Copper atoms diffuse radially and azimuthally throughout the capsule during pyrolysis. This diffusion significantly diminishes the capsule performance during implosion. Thermal and coated oxide barrier layers employed between layers mitigate the diffusion of copper during the mandrel removal process. The copper atoms do not diffuse through this barrier during pyrolysis. A capsule fabrication method that produces a capsulemore » with a thin oxide layer will be discussed.« less

  19. Influence of oxygen partial pressure on the metastable copper oxide thin films

    NASA Astrophysics Data System (ADS)

    Geçici, Birol; Korkmaz, Şadan; Özen, Soner; Şenay, Volkan; Pat, Suat

    2016-12-01

    Paramelaconite (Cu4O3) is a metastable copper oxide. Metastable copper oxide thin films were deposited on glass substrates by reactive RF magnetron sputtering in argon (Ar) and oxygen (O2) gas mixture atmospheres. Ar/O2 gas ratios in the sputtering ambient were chosen as 1/1 and 1/9. The surface and optical properties were determined by X-ray diffractometer (XRD), atomic force microscope (AFM) and UV-Vis spectrophotometer. The XRD patterns of the samples exhibited single strong diffraction peaks at 35.39∘ and 35.49∘, corresponding to the (202) peak of Cu4O3. The mean thickness values were measured as 100 nm and 80 nm for the films deposited at 1/1 and 1/9 Ar/O2 gas ratios, respectively. The samples showed low transmittance and high absorbance in the high frequency region.

  20. Origin of fieldlike spin-orbit torques in heavy metal/ferromagnet/oxide thin film heterostructures

    NASA Astrophysics Data System (ADS)

    Ou, Yongxi; Pai, Chi-Feng; Shi, Shengjie; Ralph, D. C.; Buhrman, R. A.

    2016-10-01

    We report measurements of the thickness and temperature (T ) dependencies of current-induced spin-orbit torques, especially the fieldlike (FL) component, in various heavy metal (HM)/normal metal (NM) spacer/ferromagnet (FM)/oxide (MgO and Hf Ox/MgO ) heterostructures. The FL torque in these samples originates from spin current generated by the spin Hall effect in the HM. For a FM layer sufficiently thin that a substantial portion of this spin current can reach the FM/oxide interface, T-dependent spin scattering there can yield a strong FL torque that is, in some cases, opposite in sign to that exerted at the NM/FM interface.

  1. Influence of gaseous annealing environment on the properties of indium-tin-oxide thin films

    NASA Astrophysics Data System (ADS)

    Wang, R. X.; Beling, C. D.; Fung, S.; Djurišić, A. B.; Ling, C. C.; Li, S.

    2005-02-01

    The influence of postannealing in different gaseous environments on the optical properties of indiu-tin-oxide (ITO) thin films deposited on glass substrates using e-beam evaporation has been systematically investigated. It is found that the annealing conditions affect the optical and electrical properties of the films. Atomic force microscopy, x-ray diffraction, and x-ray photoemission spectroscopy (XPS) were employed to obtain information on the chemical state and crystallization of the films. These data suggest that the chemical states and surface morphology of the ITO film are strongly influenced by the gaseous environment during the annealing process. The XPS data indicate that the observed variations in the optical transmittance can be explained by oxygen incorporation into the film, decomposition of the indium oxide phases, as well as the removal of metallic In.

  2. Bismuth Oxide Thin Films Deposited on Silicon Through Pulsed Laser Ablation, for Infrared Detectors

    NASA Astrophysics Data System (ADS)

    Condurache-Bota, Simona; Constantinescu, Catalin; Tigau, Nicolae; Praisler, Mirela

    2016-12-01

    Infrared detectors are used in many human activities, from industry to military, telecommunications, environmental studies and even medicine. Bismuth oxide thin films have proved their potential for optoelectronic applications, but their uses as infrared sensors have not been thoroughly studied so far. In this paper, pulsed laser ablation of pure bismuth targets within a controlled oxygen atmosphere is proposed for the deposition of bismuth oxide films on Si (100) substrates. Crystalline films were obtained, whose uniformity depends on the deposition conditions (number of laser pulses and the use of a radio-frequency (RF) discharge of the oxygen inside the deposition chamber). The optical analysis proved that the refractive index of the films is higher than 3 and that their optical bandgap is around 1eV, recommending them for infrared applications.

  3. Low-temperature atomic layer deposition of copper(II) oxide thin films

    SciTech Connect

    Iivonen, Tomi Hämäläinen, Jani; Mattinen, Miika; Popov, Georgi; Leskelä, Markku; Marchand, Benoît; Mizohata, Kenichiro; Kim, Jiyeon; Fischer, Roland A.

    2016-01-15

    Copper(II) oxide thin films were grown by atomic layer deposition (ALD) using bis-(dimethylamino-2-propoxide)copper [Cu(dmap){sub 2}] and ozone in a temperature window of 80–140 °C. A thorough characterization of the films was performed using x-ray diffraction, x-ray reflectivity, UV‐Vis spectrophotometry, atomic force microscopy, field emission scanning electron microscopy, x-ray photoelectron spectroscopy, and time-of-flight elastic recoil detection analysis techniques. The process was found to produce polycrystalline copper(II) oxide films with a growth rate of 0.2–0.3 Å per cycle. Impurity content in the films was relatively small for a low temperature ALD process.

  4. Annealing effect on physical properties of evaporated molybdenum oxide thin films for ethanol sensing

    NASA Astrophysics Data System (ADS)

    Touihri, S.; Arfaoui, A.; Tarchouna, Y.; Labidi, A.; Amlouk, M.; Bernede, J. C.

    2017-02-01

    This paper deals with some physical investigations on molybdenum oxide thin films growing on glass substrates by the thermal evaporation method. These films have been subjected to an annealing process under vacuum, air and oxygen at various temperatures 673, 723 and 773 K. First, the physical properties of these layers were analyzed by means of X-ray diffraction, Raman spectroscopy, scanning electron microscopy (SEM) and optical measurements. These techniques have been used to investigate the oxygen index in MoOx properties during the heat treatment. Second, from the reflectance and transmittance optical measurements, it was found that the direct band gap energy value increased from 3.16 to 3.90 eV. Finally, the heat treatments reveal that the oxygen index varies in such molybdenum oxides showing noticeably sensitivity toward ethanol gas.

  5. Interfacial control of oxygen vacancy doping and electrical conduction in thin film oxide heterostructures.

    PubMed

    Veal, Boyd W; Kim, Seong Keun; Zapol, Peter; Iddir, Hakim; Baldo, Peter M; Eastman, Jeffrey A

    2016-06-10

    Oxygen vacancies in proximity to surfaces and heterointerfaces in oxide thin film heterostructures have major effects on properties, resulting, for example, in emergent conduction behaviour, large changes in metal-insulator transition temperatures or enhanced catalytic activity. Here we report the discovery of a means of reversibly controlling the oxygen vacancy concentration and distribution in oxide heterostructures consisting of electronically conducting In2O3 films grown on ionically conducting Y2O3-stabilized ZrO2 substrates. Oxygen ion redistribution across the heterointerface is induced using an applied electric field oriented in the plane of the interface, resulting in controlled oxygen vacancy (and hence electron) doping of the film and possible orders-of-magnitude enhancement of the film's electrical conduction. The reversible modified behaviour is dependent on interface properties and is attained without cation doping or changes in the gas environment.

  6. Interfacial control of oxygen vacancy doping and electrical conduction in thin film oxide heterostructures

    PubMed Central

    Veal, Boyd W.; Kim, Seong Keun; Zapol, Peter; Iddir, Hakim; Baldo, Peter M.; Eastman, Jeffrey A.

    2016-01-01

    Oxygen vacancies in proximity to surfaces and heterointerfaces in oxide thin film heterostructures have major effects on properties, resulting, for example, in emergent conduction behaviour, large changes in metal-insulator transition temperatures or enhanced catalytic activity. Here we report the discovery of a means of reversibly controlling the oxygen vacancy concentration and distribution in oxide heterostructures consisting of electronically conducting In2O3 films grown on ionically conducting Y2O3-stabilized ZrO2 substrates. Oxygen ion redistribution across the heterointerface is induced using an applied electric field oriented in the plane of the interface, resulting in controlled oxygen vacancy (and hence electron) doping of the film and possible orders-of-magnitude enhancement of the film's electrical conduction. The reversible modified behaviour is dependent on interface properties and is attained without cation doping or changes in the gas environment. PMID:27283250

  7. Thin film passivation of laser generated 3D micro patterns in lithium manganese oxide cathodes

    NASA Astrophysics Data System (ADS)

    Pröll, J.; Kohler, R.; Bruns, M.; Oberst, V.; Weidler, P. G.; Heißler, S.; Kübel, C.; Scherer, T.; Prang, R.; Seifert, H. J.; Pfleging, W.

    2013-03-01

    The increasing need for long-life lithium-ion batteries requires the further development of electrode materials. Especially on the cathode side new materials or material composites are needed to increase the cycle lifetime. On the one hand, spinel-type lithium manganese oxide is a promising candidate to be used as cathode material due to its non-toxicity, low cost and good thermal stability. On the other hand, the spinel structure suffers from change in the oxidation state of manganese during cycling which is also accompanied by loss of active material into the liquid electrolyte. The general trend is to enhance the active surface area of the cathode in order to increase lithium-ion mobility through the electrode/electrolyte interface, while an enhanced surface area will also promote chemical degradation. In this work, laser microstructuring of lithium manganese oxide thin films was applied in a first step to increase the active surface area. This was done by using 248 nm excimer laser radiation and chromium/quartz mask imaging techniques. In a second step, high power diode laser-annealing operating at a wavelength of 940 nm was used for forming a cubic spinel-like battery phase. This was verified by means of Raman spectroscopy and cyclic voltammetric measurements. In a last step, the laser patterned thin films were coated with indium tin oxide (ITO) layers with a thickness of 10 nm to 50 nm. The influence of the 3D surface topography as well as the ITO thickness on the electrochemical performance was studied by cyclic voltammetry. Post-mortem studies were carried out by using scanning electron microscopy and focused ion beam analysis.

  8. Gold supported on thin oxide films: from single atoms to nanoparticles.

    PubMed

    Risse, Thomas; Shaikhutdinov, Shamil; Nilius, Niklas; Sterrer, Martin; Freund, Hans-Joachim

    2008-08-01

    [Figure: see text]. Historically, people have prized gold for its beauty and the durability that resulted from its chemical inertness. However, even the ancient Romans had noted that finely dispersed gold can give rise to particular optical phenomena. A decade ago, researchers found that highly dispersed gold supported on oxides exhibits high chemical activity in a number of reactions. These chemical and optical properties have recently prompted considerable interest in applications of nanodispersed gold. Despite their broad use, a microscopic understanding of these gold-metal oxide systems lags behind their application. Numerous studies are currently underway to understand why supported nanometer-sized gold particles show catalytic activity and to explore possible applications of their optical properties in photonics and biology. This Account focuses on a microscopic understanding of the gold-substrate interaction and its impact on the properties of the adsorbed gold. Our strategy uses model systems in which gold atoms and clusters are supported on well-ordered thin oxide films grown on metal single crystals. As a result, we can investigate the systems with the rigor of modern surface science techniques while incorporating some of the complexity found in technological applications. We use a variety of different experimental methods, namely, scanning probe techniques (scanning tunneling microscopy and spectroscopy, STM and STS), as well as infrared (IR), temperature-programmed desorption (TPD), and electron paramagnetic resonance (EPR) spectroscopy, to evaluate these interactions and combine these results with theoretical calculations. We examined the properties of supported gold with increasing complexity starting from single gold atoms to one- and two-dimensional clusters and three-dimensional particles. These investigations show that the binding of gold on oxide surfaces depends on the properties of the oxide, which leads to different electronic properties of

  9. Fully transparent flexible tin-doped zinc oxide thin film transistors fabricated on plastic substrate

    PubMed Central

    Han, Dedong; Zhang, Yi; Cong, Yingying; Yu, Wen; Zhang, Xing; Wang, Yi

    2016-01-01

    In this work, we have successfully fabricated bottom gate fully transparent tin-doped zinc oxide thin film transistors (TZO TFTs) fabricated on flexible plastic substrate at low temperature by RF magnetron sputtering. The effect of O2/Ar gas flow ratio during channel deposition on the electrical properties of TZO TFTs was investigated, and we found that the O2/Ar gas flow ratio have a great influence on the electrical properties. TZO TFTs on flexible substrate has very nice electrical characteristics with a low off-state current (Ioff) of 3 pA, a high on/off current ratio of 2 × 107, a high saturation mobility (μsat) of 66.7 cm2/V•s, a steep subthreshold slope (SS) of 333 mV/decade and a threshold voltage (Vth) of 1.2 V. Root-Mean-Square (RMS) roughness of TZO thin film is about 0.52 nm. The transmittance of TZO thin film is about 98%. These results highlight that the excellent device performance can be realized in TZO film and TZO TFT can be a promising candidate for flexible displays. PMID:27941915

  10. Analysis of indium zinc oxide thin films by laser-induced breakdown spectroscopy

    SciTech Connect

    Popescu, A. C.; Beldjilali, S.; Socol, G.; Mihailescu, I. N.; Craciun, V.; Hermann, J.

    2011-10-15

    We have performed spectroscopic analysis of the plasma generated by Nd:YAG ({lambda} = 266 nm) laser irradiation of thin indium zinc oxide films with variable In content deposited by combinatorial pulsed laser deposition on glass substrates. The samples were irradiated in 5 x 10{sup 4} Pa argon using laser pulses of 5 ns duration and 10 mJ energy. The plasma emission spectra were recorded with an Echelle spectrometer coupled to a gated detector with different delays with respect to the laser pulse. The relative concentrations of indium and zinc were evaluated by comparing the measured spectra to the spectral radiance computed for a plasma in local thermal equilibrium. Plasma temperature and electron density were deduced from the relative intensities and Stark broadening of spectral lines of atomic zinc. Analyses at different locations on the deposited thin films revealed that the In/(In + Zn) concentration ratio significantly varies over the sample surface, from 0.4 at the borders to about 0.5 in the center of the film. The results demonstrate that laser-induced breakdown spectroscopy allows for precise and fast characterization of thin films with variable composition.

  11. Self-assembly of a thin highly reduced graphene oxide film and its high electrocatalytic activity.

    PubMed

    Bai, Yan-Feng; Zhang, Yong-Fang; Zhou, An-Wei; Li, Hai-Wai; Zhang, Yu; Luong, John H T; Cui, Hui-Fang

    2014-10-10

    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 H(2)O(2) 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.

  12. 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.

  13. Paramagnetic dysprosium-doped zinc oxide thin films grown by pulsed-laser deposition

    SciTech Connect

    Lo, Fang-Yuh Ting, Yi-Chieh; Chou, Kai-Chieh; Hsieh, Tsung-Chun; Ye, Cin-Wei; Hsu, Yung-Yuan; Liu, Hsiang-Lin; Chern, Ming-Yau

    2015-06-07

    Dysprosium(Dy)-doped zinc oxide (Dy:ZnO) thin films were fabricated on c-oriented sapphire substrate by pulsed-laser deposition with doping concentration ranging from 1 to 10 at. %. X-ray diffraction (XRD), Raman-scattering, optical transmission spectroscopy, and spectroscopic ellipsometry revealed incorporation of Dy into ZnO host matrix without secondary phase. Solubility limit of Dy in ZnO under our deposition condition was between 5 and 10 at. % according to XRD and Raman-scattering characteristics. Optical transmission spectroscopy and spectroscopic ellipsometry also showed increase in both transmittance in ultraviolet regime and band gap of Dy:ZnO with increasing Dy density. Zinc vacancies and zinc interstitials were identified by photoluminescence spectroscopy as the defects accompanied with Dy incorporation. Magnetic investigations with a superconducting quantum interference device showed paramagnetism without long-range order for all Dy:ZnO thin films, and a hint of antiferromagnetic alignment of Dy impurities was observed at highest doping concentration—indicating the overall contribution of zinc vacancies and zinc interstitials to magnetic interaction was either neutral or toward antiferromagnetic. From our investigations, Dy:ZnO thin films could be useful for spin alignment and magneto-optical applications.

  14. Paramagnetic dysprosium-doped zinc oxide thin films grown by pulsed-laser deposition

    NASA Astrophysics Data System (ADS)

    Lo, Fang-Yuh; Ting, Yi-Chieh; Chou, Kai-Chieh; Hsieh, Tsung-Chun; Ye, Cin-Wei; Hsu, Yung-Yuan; Chern, Ming-Yau; Liu, Hsiang-Lin

    2015-06-01

    Dysprosium(Dy)-doped zinc oxide (Dy:ZnO) thin films were fabricated on c-oriented sapphire substrate by pulsed-laser deposition with doping concentration ranging from 1 to 10 at. %. X-ray diffraction (XRD), Raman-scattering, optical transmission spectroscopy, and spectroscopic ellipsometry revealed incorporation of Dy into ZnO host matrix without secondary phase. Solubility limit of Dy in ZnO under our deposition condition was between 5 and 10 at. % according to XRD and Raman-scattering characteristics. Optical transmission spectroscopy and spectroscopic ellipsometry also showed increase in both transmittance in ultraviolet regime and band gap of Dy:ZnO with increasing Dy density. Zinc vacancies and zinc interstitials were identified by photoluminescence spectroscopy as the defects accompanied with Dy incorporation. Magnetic investigations with a superconducting quantum interference device showed paramagnetism without long-range order for all Dy:ZnO thin films, and a hint of antiferromagnetic alignment of Dy impurities was observed at highest doping concentration—indicating the overall contribution of zinc vacancies and zinc interstitials to magnetic interaction was either neutral or toward antiferromagnetic. From our investigations, Dy:ZnO thin films could be useful for spin alignment and magneto-optical applications.

  15. Sensitivity and Response of Polyvinyl Alcohol/Tin Oxide Nanocomposite Multilayer Thin Film Sensors.

    PubMed

    Sriram, G; Dhineshbabu, N R; Nithyavathy, N; Saminathan, K; Kaler, K V I S; Rajendran, V

    2016-01-01

    Nanocrystalline Tin Oxide (SnO₂) is Non-Stoichiometric in Nature with Functional Properties Suitable for gas sensing. In this study, SnO₂nanoparticles were prepared by the sol-gel technique, which were then characterised using X-ray diffraction. The nanoparticles showed tetragonal structure with an average crystallite size of 18 nm. The stretching and vibration modes of SnO₂were confirmed using Fourier transform infrared spectroscopy. The size of SnO₂ nanoparticles was determined using particle size analyser, which was found be 60 ± 10 nm on average. The surface morphology of the nanoparticles was investigated using scanning electron microscope, which showed irregular-sized agglomerated SnO₂nanostructures. In addition, primary particle size was evaluated using high-resolution transmission electron microscopy, which was found to be 50 nm on average. The polyvinyl alcohol/SnO₂ composite thin film was prepared on a glass substrate using spin-coating method. The values of band gap energy and electrical conductance of 13-layer thin film were found to be 2.96 eV and 0.0505 mho, respectively. Sulfur dioxide (SO₂) was suitably tailored to verify the sensor response over a concentration range of 10-70 ppm at room temperature. The performance, response, and recovery time of sensors were increased by increasing the layers of the thin film.

  16. Laser scribing of indium tin oxide (ITO) thin films deposited on various substrates for touch panels

    NASA Astrophysics Data System (ADS)

    Tseng, Shih-Feng; Hsiao, Wen-Tse; Huang, Kuo-Cheng; Chiang, Donyau; Chen, Ming-Fei; Chou, Chang-Pin

    2010-12-01

    In this study, a Nd:YAG laser with wavelength of 1064 nm is used to scribe the indium tin oxide (ITO) thin films coated on three types of substrate materials, i.e. soda-lime glass, polycarbonate (PC), and cyclic-olefin-copolymer (COC) materials with thickness of 20 nm, 30 nm, and 20 nm, respectively. The effect of exposure time adjusted from 10 μs to 100 μs on the ablated mark width, depth, and electrical properties of the scribed film was investigated. The maximum laser power of 2.2 W was used to scribe these thin films. In addition, the surface morphology, surface reaction, surface roughness, optical properties, and electrical conductivity properties were measured by a scanning electron microscope, a three-dimensional confocal laser scanning microscope, an atomic force microscope, and a four-point probe. The measured results of surface morphology show that the residual ITO layer was produced on the scribed path with the laser exposure time at 10 μs and 20 μs. The better edge qualities of the scribed lines can be obtained when the exposure time extends from 30 μs to 60 μs. When the laser exposure time is longer than 60 μs, the partially burned areas of the scribed thin films on PC and COC substrates are observed. Moreover, the isolated line width and resistivity values increase when the laser exposure time increases.

  17. Fully transparent flexible tin-doped zinc oxide thin film transistors fabricated on plastic substrate

    NASA Astrophysics Data System (ADS)

    Han, Dedong; Zhang, Yi; Cong, Yingying; Yu, Wen; Zhang, Xing; Wang, Yi

    2016-12-01

    In this work, we have successfully fabricated bottom gate fully transparent tin-doped zinc oxide thin film transistors (TZO TFTs) fabricated on flexible plastic substrate at low temperature by RF magnetron sputtering. The effect of O2/Ar gas flow ratio during channel deposition on the electrical properties of TZO TFTs was investigated, and we found that the O2/Ar gas flow ratio have a great influence on the electrical properties. TZO TFTs on flexible substrate has very nice electrical characteristics with a low off-state current (Ioff) of 3 pA, a high on/off current ratio of 2 × 107, a high saturation mobility (μsat) of 66.7 cm2/V•s, a steep subthreshold slope (SS) of 333 mV/decade and a threshold voltage (Vth) of 1.2 V. Root-Mean-Square (RMS) roughness of TZO thin film is about 0.52 nm. The transmittance of TZO thin film is about 98%. These results highlight that the excellent device performance can be realized in TZO film and TZO TFT can be a promising candidate for flexible displays.

  18. Work function recovery of air exposed molybdenum oxide thin films with vacuum annealing

    NASA Astrophysics Data System (ADS)

    Irfan, Irfan; Turniske, Alexander; Bao, Zhenan; Gao, Yongli

    2012-02-01

    We report substantial work function (WF) recovery of air exposed molybdenum oxide thin films with vacuum annealing. The high WF (˜6.8 eV) of thermally evaporated MoOx thin film was observed to decrease sharply to ˜5.6 eV with an air exposure of one hour. The drop in the WF was accompanied with a very thin layer of oxygen rich adsorbate on the MoOx film. The WF of the exposed MoOx film started to gradually recover with increasing annealing temperature in a vacuum chamber having base pressure of 8 x 10-11 torr. The saturation in the WF recovery was observed around 460 ^oC, with WF ˜6.4 eV. The adsorb layer was found to be removed after the vacuum annealing. We further studied the interface formation between the annealed MoOx and copper pthalocynine (CuPc). The highest occupied molecular orbital (HOMO) level of CuPc was observed to be almost pinned to the Fermi level, strongly suggesting an efficient hole injection through the vacuum annealed MoOx film.

  19. Graphene oxide/carbon nanoparticle thin film based IR detector: Surface properties and device characterization

    SciTech Connect

    Chowdhury, Farzana Aktar; Hossain, Mohammad Abul; Uchida, Koji; Tamura, Takahiro; Sugawa, Kosuke; Mochida, Tomoaki; Otsuki, Joe; Mohiuddin, Tariq; Boby, Monny Akter; Alam, Mohammad Sahabul

    2015-10-15

    This work deals with the synthesis, characterization, and application of carbon nanoparticles (CNP) adorned graphene oxide (GO) nanocomposite materials. Here we mainly focus on an emerging topic in modern research field presenting GO-CNP nanocomposite as a infrared (IR) radiation detector device. GO-CNP thin film devices were fabricated from liquid phase at ambient condition where no modifying treatments were necessary. It works with no cooling treatment and also for stationary objects. A sharp response of human body IR radiation was detected with time constants of 3 and 36 sec and radiation responsivity was 3 mAW{sup −1}. The current also rises for quite a long time before saturation. This work discusses state-of-the-art material developing technique based on near-infrared photon absorption and their use in field deployable instrument for real-world applications. GO-CNP-based thin solid composite films also offer its potentiality to be utilized as p-type absorber material in thin film solar cell, as well.

  20. Identification of the native defect doping mechanism in amorphous indium zinc oxide thin films studied using ultra high pressure oxidation

    NASA Astrophysics Data System (ADS)

    Lee, Sunghwan; Paine, David C.

    2013-02-01

    The mechanism of native defect doping in amorphous In-Zn-O (a-IZO) has not previously been established but is likely associated with native oxygen defect doping. We have used high pressure oxidation and defect equilibrium analysis to show a -1/6 power dependence of carrier density on oxygen fugacity in a-IZO. This dependency is predicted for oxygen vacancy-like donor defects. Extrapolation of equilibrium constants established at high pressures to atmospheric pressure reveals that the equilibrium carrier density in a-IZO at 200 °C is higher (>1020/cm3) than typical as-deposited channel carrier densities (<1017/cm3). This is consistent with observed increases in channel carrier density and negative threshold voltage shift in annealed a-IZO thin film transistor devices.

  1. Thermo-electrical properties of composite semiconductor thin films composed of nanocrystalline graphene-vanadium oxides.

    PubMed

    Jung, Hye-Mi; Um, Sukkee

    2014-12-01

    This paper presents an experimental comparative study involving the characterization of the thermo-electrical and structural properties of graphene-based vanadium oxide (graphene-VOx) composite thin films on insulating and conducting surfaces (i.e., fused quartz and acrylic resin-impregnated graphite) produced by a sol-gel process via dipping-pyrolysis. A combination of FE-SEM and XPS analyses revealed that the graphene-VOx composite thin films (coated onto fused quartz) exhibiting the microstructure of 2-graded nanowire arrays with a diameter of 40-80 nm were composed of graphene, a few residual oxygen-containing functional groups (i.e., C-O and C=O), and the VO2 Magnéli phase. The temperature-dependent electrical resistance measured on the as-deposited thin films clearly demonstrated that the graphene-VOx composite nanowire arrays thermally grown on fused quartz act as a semiconductor switch, with a transition temperature of 64.7 degrees C in the temperature range of -20 degrees C to 140 degrees C, resulting from the contributions of graphene and graphene oxides. In contrast, the graphene-VOx composite thin films deposited onto acrylic resin-impregnated graphite exhibit a superlinear semiconducting property of extremely low electrical resistance with negative temperature coefficients (i.e., approximately four orders of magnitude lower than that of the fused quartz), despite the similar microstructural and morphological characteristics. This difference is attributed to the synergistic effects of the paramagnetic metal feature of the tightly stacked nanowire arrays consisting of hexagonal V2O3 on the intrinsic electrical properties of the acrylic resin-impregnated graphite substrate, as revealed by FE-SEM, EDX, AFM, and XRD measurements. Although the thermo-sensitive electrical properties of the graphene-VOx composite thin films are very substrate specific, the applicability of graphene sheets can be considerably effective in the formation of highly planar arrays

  2. Sol-gel deposited aluminum-doped and gallium-doped zinc oxide thin-film transparent conductive electrodes with a protective coating of reduced graphene oxide

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

    Using a traditional sol-gel deposition technique, we successfully fabricated aluminum-doped zinc oxide (AZO) and gallium-doped zinc oxide (GZO) thin films on glass substrates. Employing a plasma treatment method as the postannealing process, we produced thin-film transparent conductive electrodes exhibiting excellent optical and electrical properties, with transmittance greater than 90% across the entire visible spectrum and the near-infrared range, as well as good sheet resistance under 200 Ω/sq. More importantly, to improve the resilience of our fabricated thin-film samples at elevated temperatures and in humid environments, we deposited a layer of reduced graphene oxide (rGO) as protective overcoating. The stability of our composite AZO/rGO and GZO/rGO samples improved substantially compared to that of their counterparts with no rGO coating.

  3. Modulation of physical properties of oxide thin films by multiple fields

    NASA Astrophysics Data System (ADS)

    Hua-Li, Yang; Bao-Min, Wang; Xiao-Jian, Zhu; Jie, Shang; Bin, Chen; Run-Wei, Li

    2016-06-01

    Recent studies of the modulation of physical properties in oxide thin films by multiple fields are reviewed. Some of the key issues and prospects of this area of study are also addressed. Oxide thin films exhibit versatile physical properties such as magnetism, ferroelectricity, piezoelectricity, metal-insulator transition (MIT), multiferroicity, colossal magnetoresistivity, switchable resistivity. More importantly, the exhibited multifunctionality can be tuned by various external fields, which has enabled demonstration of novel electronic devices. Project supported by the State Key Project of Fundamental Research of China (Grant No. 2012CB933004), the National Natural Science Foundation of China (Grant Nos. 11474295, 51571208, 51525103, and 11274322), Overseas, Hong Kong & Macao Scholars Collaborated Researching Fund (Grant No. 51428201), the Instrument Developing Project of the Chinese Academy of Sciences (Grant No. YZ201327), Ningbo Major Project for Science and Technology (Grant No. 2014B11011), Ningbo International Cooperation Projects (Grant Nos. 2012D10018 and 2014D10005), the Fund for Ningbo Science and Technology Innovation Team (Grant No. 2015B11001), the Youth Innovation Promotion Association of the Chinese Academy of Sciences, and the Key Research Program of the Chinese Academy of Sciences (Grant No. KJZD-EW-M05).

  4. Growth of different phases of yttrium manganese oxide thin films by pulsed laser deposition

    SciTech Connect

    Kumar, Manish; Choudhary, R. J.; Phase, D. M.

    2012-06-05

    Various phases of yttrium manganese oxide (YMO) thin films have been synthesized on different substrates from a single target of h-YMnO{sub 3}. It is observed that the phase stability and crystallinity of YMO thin films depend on the substrate used and oxygen partial pressure (OPP). (110) oriented and polycrystalline growth of h-YMnO{sub 3} are observed on the Al{sub 2}O{sub 3} (0001) and NGO (110) substrates respectively, when grown in OPP {approx_equal} 10{sup -6} Torr. While for similar OPP value, growth of mixed phases (h-YMnO{sub 3} and o-YMn{sub 2}O{sub 5}) is observed on Si (001) substrate. Oriented growth of O-YMn{sub 2}O{sub 5} phase film on Si (001) substrate is observed first time, when deposited at OPP value of 225 and 350 mTorr. +3 and mixed oxidation states (+3 and +4) of Mn were confirmed by x-ray photoelectron spectroscopy in pure YMnO{sub 3} phase and YMn{sub 2}O{sub 5} phase respectively.

  5. Model for determination of mid-gap states in amorphous metal oxides from thin film transistors

    NASA Astrophysics Data System (ADS)

    Bubel, S.; Chabinyc, M. L.

    2013-06-01

    The electronic density of states in metal oxide semiconductors like amorphous zinc oxide (a-ZnO) and its ternary and quaternary oxide alloys with indium, gallium, tin, or aluminum are different from amorphous silicon, or disordered materials such as pentacene, or P3HT. Many ZnO based semiconductors exhibit a steep decaying density of acceptor tail states (trap DOS) and a Fermi level (EF) close to the conduction band energy (EC). Considering thin film transistor (TFT) operation in accumulation mode, the quasi Fermi level for electrons (Eq) moves even closer to EC. Classic analytic TFT simulations use the simplification EC-EF> `several'kT and cannot reproduce exponential tail states with a characteristic energy smaller than 1/2 kT. We demonstrate an analytic model for tail and deep acceptor states, valid for all amorphous metal oxides and include the effect of trap assisted hopping instead of simpler percolation or mobility edge models, to account for the observed field dependent mobility.

  6. Purely electronic mechanism of electrolyte gating of indium tin oxide thin films

    DOE PAGES

    Leng, X.; Bozovic, I.; Bollinger, A. T.

    2016-08-10

    Epitaxial indium tin oxide films have been grown on both LaAlO3 and yttria-stabilized zirconia substrates using RF magnetron sputtering. Electrolyte gating causes a large change in the film resistance that occurs immediately after the gate voltage is applied, and shows no hysteresis during the charging/discharging processes. When two devices are patterned next to one another and the first one gated through an electrolyte, the second one shows no changes in conductance, in contrast to what happens in materials (like tungsten oxide) susceptible to ionic electromigration and intercalation. These findings indicate that electrolyte gating in indium tin oxide triggers a puremore » electronic process (electron depletion or accumulation, depending on the polarity of the gate voltage), with no electrochemical reactions involved. Electron accumulation occurs in a very thin layer near the film surface, which becomes highly conductive. These results contribute to our understanding of the electrolyte gating mechanism in complex oxides and may be relevant for applications of electric double layer transistor devices.« less

  7. Purely electronic mechanism of electrolyte gating of indium tin oxide thin films.

    PubMed

    Leng, X; Bollinger, A T; Božović, I

    2016-08-10

    Epitaxial indium tin oxide films have been grown on both LaAlO3 and yttria-stabilized zirconia substrates using RF magnetron sputtering. Electrolyte gating causes a large change in the film resistance that occurs immediately after the gate voltage is applied, and shows no hysteresis during the charging/discharging processes. When two devices are patterned next to one another and the first one gated through an electrolyte, the second one shows no changes in conductance, in contrast to what happens in materials (like tungsten oxide) susceptible to ionic electromigration and intercalation. These findings indicate that electrolyte gating in indium tin oxide triggers a pure electronic process (electron depletion or accumulation, depending on the polarity of the gate voltage), with no electrochemical reactions involved. Electron accumulation occurs in a very thin layer near the film surface, which becomes highly conductive. These results contribute to our understanding of the electrolyte gating mechanism in complex oxides and may be relevant for applications of electric double layer transistor devices.

  8. Compact chromium oxide thin film resistors for use in nanoscale quantum circuits

    SciTech Connect

    Nash, C. R.; Fenton, J. C.; Constantino, N. G. N.; Warburton, P. A.

    2014-12-14

    We report on the electrical characterisation of a series of thin amorphous chromium oxide (CrO{sub x}) films, grown by dc sputtering, to evaluate their suitability for use as on-chip resistors in nanoelectronics. By increasing the level of oxygen doping, the room-temperature sheet resistance of the CrO{sub x} films was varied from 28 Ω/◻ to 32.6 kΩ/◻. The variation in resistance with cooling to 4.2 K in liquid helium was investigated; the sheet resistance at 4.2 K varied with composition from 65 Ω/◻ to above 20 GΩ/◻. All of the films measured displayed linear current–voltage characteristics at all measured temperatures. For on-chip devices for quantum phase-slip measurements using niobium–silicon nanowires, interfaces between niobium–silicon and chromium oxide are required. We also characterised the contact resistance for one CrO{sub x} composition at an interface with niobium–silicon. We found that a gold intermediate layer is favourable: the specific contact resistivity of chromium-oxide-to-gold interfaces was 0.14 mΩcm{sup 2}, much lower than the value for direct CrO{sub x} to niobium–silicon contact. We conclude that these chromium oxide films are suitable for use in nanoscale circuits as high-value resistors, with resistivity tunable by oxygen content.

  9. Purely electronic mechanism of electrolyte gating of indium tin oxide thin films

    SciTech Connect

    Leng, X.; Bozovic, I.; Bollinger, A. T.

    2016-08-10

    Epitaxial indium tin oxide films have been grown on both LaAlO3 and yttria-stabilized zirconia substrates using RF magnetron sputtering. Electrolyte gating causes a large change in the film resistance that occurs immediately after the gate voltage is applied, and shows no hysteresis during the charging/discharging processes. When two devices are patterned next to one another and the first one gated through an electrolyte, the second one shows no changes in conductance, in contrast to what happens in materials (like tungsten oxide) susceptible to ionic electromigration and intercalation. These findings indicate that electrolyte gating in indium tin oxide triggers a pure electronic process (electron depletion or accumulation, depending on the polarity of the gate voltage), with no electrochemical reactions involved. Electron accumulation occurs in a very thin layer near the film surface, which becomes highly conductive. These results contribute to our understanding of the electrolyte gating mechanism in complex oxides and may be relevant for applications of electric double layer transistor devices.

  10. Electrical characterization of reduced graphene oxide (rGO) on organic thin film transistor (OTFT)

    NASA Astrophysics Data System (ADS)

    Musa, Nurhazwani; Halim, Nurul Farhanah Ab.; Ahmad, Mohd Noor; Zakaria, Zulkhairi; Hashim, Uda

    2017-03-01

    A green method and eco-friendly solution were used to chemically reduce graphene oxide (GO) to graphene using green reductant. In this study, graphene oxide (GO) were prepared by using Tours method. Then, reduced graphene oxides (rGO) were prepared by using three typical reduction agents: L-ascorbic acid (L-AA), formamidinesulfinic acid (FAS) and sodium sulfite (Na2SO3). The reduced materials were characterized by Fourier transform infrared spectroscopy (FTIR), Thermo gravimetric analysis (TGA) and X-ray diffraction (XRD). Graphene based organic thin film transistor (G-OTFT) was prepared by a spin coating and thermal evaporation technique. The electrical characterization of G-OTFT was analyzed by using semiconductor parameter analyzer (SPA). The G-OTFT devices show p-type semiconducting behaviour. This article focuses on the synthesis and reduction of graphene oxide using three different reductants in order to maximise its electrical conductivity. The rGO product demonstrated a good electrical conductivity performance with highly sensitivity sensor.

  11. Purely electronic mechanism of electrolyte gating of indium tin oxide thin films

    PubMed Central

    Leng, X.; Bollinger, A. T.; Božović, I.

    2016-01-01

    Epitaxial indium tin oxide films have been grown on both LaAlO3 and yttria-stabilized zirconia substrates using RF magnetron sputtering. Electrolyte gating causes a large change in the film resistance that occurs immediately after the gate voltage is applied, and shows no hysteresis during the charging/discharging processes. When two devices are patterned next to one another and the first one gated through an electrolyte, the second one shows no changes in conductance, in contrast to what happens in materials (like tungsten oxide) susceptible to ionic electromigration and intercalation. These findings indicate that electrolyte gating in indium tin oxide triggers a pure electronic process (electron depletion or accumulation, depending on the polarity of the gate voltage), with no electrochemical reactions involved. Electron accumulation occurs in a very thin layer near the film surface, which becomes highly conductive. These results contribute to our understanding of the electrolyte gating mechanism in complex oxides and may be relevant for applications of electric double layer transistor devices. PMID:27506371

  12. Super-high density Si quantum dot thin film utilizing a gradient Si-rich oxide multilayer structure.

    PubMed

    Kuo, Kuang-Yang; Huang, Pin-Ruei; Lee, Po-Tsung

    2013-05-17

    A gradient Si-rich oxide multilayer (GSRO-ML) deposition structure is proposed to achieve super-high density Si quantum dot (QD) thin film formation while preserving QD size controllability for better photovoltaic properties. Our results indicate that the Si QD thin film using a GSRO-ML structure can efficiently increase the QD density and control the QD size. Its optical properties clearly promise the capability of effective bandgap engineering even though these QDs are closely formed. The Si QD thin film using a GSRO-ML structure obviously reveals better electro-optical properties than those using a [silicon dioxide/silicon-rich oxide] multilayer ([SiO2/SRO]-ML) structure owing to the better optical absorption and carrier transport properties. Therefore, we successfully demonstrate that our proposed GSRO-ML structure has great potential for application in solar cells integrating Si QD thin films.

  13. Resistive Switching Characteristics of Tantalum Oxide Thin Film and Titanium Oxide Nanoparticles Hybrid Structure.

    PubMed

    Park, Mi Ra; Abbas, Yawar; Hu, Quanli; Yoon, Tae-Sik; Choi, Young Jin; Kang, Chi Jung

    2015-11-01

    The fabrication of hybrid structure with TiO2 nanoparticle assembly and Ta2O5 thin film layer was demonstrated. The close-packed nanoparticles could influence the resistive switching behaviors due to the huge numbers of interface states and vacancies in the nanoparticle assembly. The device with hybrid structure presented the typical bipolar resistive switching characteristics in the structure of Ti/TiO2/Ta2O5/Au on SiO2/Si substrate. The set voltage was observed at -0.7 V, and the reset voltage occurred at (-)-0.7 V, which was smaller than that of Ta2O5 layer only. The electrical conduction mechanisms were the ohmic conduction at low resistance state (LRS) and the space charge limited conduction at high resistance state (HRS), respectively. The devices showed stable current ratio of LRS to HRS. The temperature dependent properties of the devices were also investigated. The device with nanoparticle assembly showed better electrical characteristics with low HRS current level and stable LRS current level with respect to the temperature.

  14. Solution-processed gadolinium doped indium-oxide thin-film transistors with oxide passivation

    NASA Astrophysics Data System (ADS)

    Lee, Seung-Hun; Kim, Taehun; Lee, Jihun; Avis, Christophe; Jang, Jin

    2017-03-01

    We studied the effect of Gd doping on the structural properties of solution processed, crystalline In2O3 for thin-film transistor (TFT) application. With increasing Gd in In2O3 up to 20%, the material structure changes into amorphous phase, and the oxygen vacancy concentration decreases from 15.4 to 8.4%, and M-OH bonds from 33.5 to 23.7%. The field-effect mobility for the Gd doped In2O3 TFTs decreases and threshold voltage shifts to the positive voltage with increasing Gd concentration. In addition, the stability of the solution processed TFTs can also be improved by increasing Gd concentration. As a result, the optimum Gd concentration is found to be ˜5% in In2O3 and the 5% Gd doped In2O3 TFTs with the Y2O3 passivation layer exhibit the linear mobility of 9.74 cm2/V s, the threshold voltage of -0.27 V, the subthreshold swing of 79 mV/dec., and excellent bias stability.

  15. Polyelectrolyte-mediated assembly of copper-phthalocyanine tetrasulfonate multilayers and the subsequent production of nanoparticulate copper oxide thin films.

    PubMed

    Chickneyan, Zarui Sara; Briseno, Alejandro L; Shi, Xiangyang; Han, Shubo; Huang, Jiaxing; Zhou, Feimeng

    2004-07-01

    An approach to producing films of nanometer-sized copper oxide particulates, based on polyelectrolyte-mediated assembly of the precursor, copper(II)phthalocyanine tetrasulfonate (CPTS), is described. Multilayered CPTS and polydiallyldimethylammonium chloride (PDADMAC) were alternately assembled on different planar substrates via the layer-by-layer (LbL) procedure. The growth of CPTS multilayers was monitored by UV-visible spectrometry and quartz crystal microbalance (QCM) measurements. Both the UV-visible spectra and the QCM data showed that a fixed amount of CPTS could be attached to the substrate surface for a given adsorption cycle. Cyclic voltammograms at the CPTS/PDADMAC-covered gold electrode exhibited a decrease in peak currents with the layer number, indicating that the permeability of CPTS multilayers on the electrodes had diminished. When these CPTS multilayered films were calcined at elevated temperatures, uniform thin films composed of nanoparticulate copper oxide could be produced. Ellipsometry showed that the thickness of copper oxide nanoparticulate films could be precisely tailored by varying the thickness of CPTS multilayer films. The morphology and roughness of CPTS multilayer and copper oxide thin films were characterized by atomic force microscopy. X-ray diffraction (XRD) measurements indicated that these thin films contained both CuO and Cu2O nanoparticles. The preparation of such copper oxide thin films with the use of metal complex precursors represents a new route for the synthesis of inorganic oxide films with a controlled thickness.

  16. Low Temperature Annealed Zinc Oxide Nanostructured Thin Film-Based Transducers: Characterization for Sensing Applications

    PubMed Central

    Haarindraprasad, R.; Hashim, U.; Gopinath, Subash C. B.; Kashif, Mohd; Veeradasan, P.; Balakrishnan, S. R.; Foo, K. L.; Poopalan, P.

    2015-01-01

    The performance of sensing surfaces highly relies on nanostructures to enhance their sensitivity and specificity. Herein, nanostructured zinc oxide (ZnO) thin films of various thicknesses were coated on glass and p-type silicon substrates using a sol-gel spin-coating technique. The deposited films were characterized for morphological, structural, and optoelectronic properties by high-resolution measurements. X-ray diffraction analyses revealed that the deposited films have a c-axis orientation and display peaks that refer to ZnO, which exhibits a hexagonal structure with a preferable plane orientation (002). The thicknesses of ZnO thin films prepared using 1, 3, 5, and 7 cycles were measured to be 40, 60, 100, and 200 nm, respectively. The increment in grain size of the thin film from 21 to 52 nm was noticed, when its thickness was increased from 40 to 200 nm, whereas the band gap value decreased from 3.282 to 3.268 eV. Band gap value of ZnO thin film with thickness of 200 nm at pH ranging from 2 to 10 reduces from 3.263eV to 3.200 eV. Furthermore, to evaluate the transducing capacity of the ZnO nanostructure, the refractive index, optoelectric constant, and bulk modulus were analyzed and correlated. The highest thickness (200 nm) of ZnO film, embedded with an interdigitated electrode that behaves as a pH-sensing electrode, could sense pH variations in the range of 2-10. It showed a highly sensitive response of 444 μAmM-1cm-2 with a linear regression of R2 =0.9304. The measured sensitivity of the developed device for pH per unit is 3.72μA/pH. PMID:26167853

  17. Differential Adhesive and Bioactive Properties of the Polymeric Surface Coated with Graphene Oxide Thin Film.

    PubMed

    Thampi, Sudhin; Nandkumar, A Maya; Muthuvijayan, Vignesh; Parameswaran, Ramesh

    2017-02-08

    Surface engineering of implantable devices involving polymeric biomaterials has become an essential aspect for medical implants. A surface enhancement technique can provide an array of unique surface properties that improve its biocompatibility and functionality as an implant. Polyurethane-based implants that have found extensively acclaimed usage as an implant in biomedical applications, especially in the area of cardiovascular devices, still lack any mechanism to ward off bacterial or platelet adhesion. To bring out such a defense mechanism we are proposing a surface modification technique. Graphene oxide (GO) in very thin film form was wrapped onto the electrospun fibroporous polycarbonate urethane (PCU) membrane (GOPCU) by a simple method of electrospraying. In the present study, we have developed a simple single-step method for coating a polymeric substrate with a thin GO film and evaluated the novel antiadhesive activity of these films. SEM micrographs after coating showed the presence of very thin GO films over the PCU membrane. On the GOPCU surface, the contact angle was shifted by ∼30°, making the hydrophobic PCU surface slightly hydrophilic, while Raman spectral characterization and mapping showed the presence and distribution of GO over 75% of the membrane. A reduced platelet adhesion on the GOPCU surface was observed; meanwhile, bacterial adhesion also got reduced by 85% for Staphylococcus aureus (Gram positive, cocci) and 64% for Pseudomonas aeruginosa (Gram negative, bacilli). A cell adhesion study conducted using mammalian fibroblast cells projected its proliferation percentage in a MTT assay, with 82% cell survival on PCU and 86% on GOPCU after 24 h culture, while a study for an extended period of 72 h showed 87% of survival on PCU and 88% on GOPCU. This plethora of functionalities by a simple modification technique makes thin GO films a self-sufficient surface engineering material for future biomedical applications.

  18. Oxidatively Electrodeposited Thin-Film Transition Metal (Oxy)hydroxides as Oxygen Evolution Catalysts.

    PubMed

    Morales-Guio, Carlos G; Liardet, Laurent; Hu, Xile

    2016-07-20

    The electrolysis of water to produce hydrogen and oxygen is a simple and attractive approach to store renewable energies in the form of chemical fuels. The oxygen evolution reaction (OER) is a complex four-electron process that constitutes the most energy-inefficient step in water electrolysis. Here we describe a novel electrochemical method for the deposition of a family of thin-film transition metal (oxy)hydroxides as OER catalysts. The thin films have nanodomains of crystallinity with lattice spacing similar to those of double-layered hydroxides. The loadings of these thin-film catalysts were accurately determined with a resolution of below 1 μg cm(-2) using an electrochemical quartz microcrystal balance. The loading-activity relations for various catalysts were established using voltammetry and impedance spectroscopy. The thin-film catalysts have up to four types of loading-activity dependence due to film nucleation and growth as well as the resistance of the films. A zone of intrinsic activity has been identified for all of the catalysts where the mass-averaged activity remains constant while the loading is increased. According to their intrinsic activities, the metal oxides can be classified into three categories: NiOx, MnOx, and FeOx belong to category I, which is the least active; CoOx and CoNiOx belong to category II, which has medium activity; and FeNiOx, CoFeOx, and CoFeNiOx belong to category III, which is the most active. The high turnover frequencies of CoFeOx and CoFeNiOx at low overpotentials and the simple deposition method allow the fabrication of high-performance anode electrodes coated with these catalysts. In 1 M KOH and with the most active electrode, overpotentials as low as 240 and 270 mV are required to reach 10 and 100 mA cm(-2), respectively.

  19. Role of order and disorder on the electronic performances of oxide semiconductor thin film transistors

    NASA Astrophysics Data System (ADS)

    Martins, R.; Barquinha, P.; Ferreira, I.; Pereira, L.; Gonçalves, G.; Fortunato, E.

    2007-02-01

    The role of order and disorder on the electronic performances of n-type ionic oxides such as zinc oxide, gallium zinc oxide, and indium zinc oxide used as active (channel) or passive (drain/source) layers in thin film transistors (TFTs) processed at room temperature are discussed, taking as reference the known behavior observed in conventional covalent semiconductors such as silicon. The work performed shows that while in the oxide semiconductors the Fermi level can be pinned up within the conduction band, independent of the state of order, the same does not happen with silicon. Besides, in the oxide semiconductors the carrier mobility is not bandtail limited and so disorder does not affect so strongly the mobility as it happens in covalent semiconductors. The electrical properties of the oxide films (resistivity, carrier concentration, and mobility) are highly dependent on the oxygen vacancies (source of free carriers), which can be controlled by changing the oxygen partial pressure during the deposition process and/or by adding other metal ions to the matrix. In this case, we make the oxide matrix less sensitive to the presence of oxygen, widening the range of oxygen partial pressures that can be used and thus improving the process control of the film resistivity. The results obtained in fully transparent TFT using polycrystalline ZnO or amorphous indium zinc oxide (IZO) as channel layers and highly conductive poly/nanocrystalline ZGO films or amorphous IZO as drain/source layers show that both devices work in the enhancement mode, but the TFT with the highest electronic saturation mobility and on/off ratio 49.9cm2/Vs and 4.3×108, respectively, are the ones in which the active and passive layers are amorphous. The ZnO TFT whose channel is based on polycrystalline ZnO, the mobility and on/off ratio are, respectively, 26cm2/Vs and 3×106. This behavior is attributed to the fact that the electronic transport is governed by the s-like metal cation conduction bands

  20. Oxide semiconductor thin-film transistors: a review of recent advances.

    PubMed

    Fortunato, E; Barquinha, P; Martins, R

    2012-06-12

    Transparent electronics is today one of the most advanced topics for a wide range of device applications. The key components are wide bandgap semiconductors, where oxides of different origins play an important role, not only as passive component but also as active component, similar to what is observed in conventional semiconductors like silicon. Transparent electronics has gained special attention during the last few years and is today established as one of the most promising technologies for leading the next generation of flat panel display due to its excellent electronic performance. In this paper the recent progress in n- and p-type oxide based thin-film transistors (TFT) is reviewed, with special emphasis on solution-processed and p-type, and the major milestones already achieved with this emerging and very promising technology are summarizeed. After a short introduction where the main advantages of these semiconductors are presented, as well as the industry expectations, the beautiful history of TFTs is revisited, including the main landmarks in the last 80 years, finishing by referring to some papers that have played an important role in shaping transparent electronics. Then, an overview is presented of state of the art n-type TFTs processed by physical vapour deposition methods, and finally one of the most exciting, promising, and low cost but powerful technologies is discussed: solution-processed oxide TFTs. Moreover, a more detailed focus analysis will be given concerning p-type oxide TFTs, mainly centred on two of the most promising semiconductor candidates: copper oxide and tin oxide. The most recent data related to the production of complementary metal oxide semiconductor (CMOS) devices based on n- and p-type oxide TFT is also be presented. The last topic of this review is devoted to some emerging applications, finalizing with the main conclusions. Related work that originated at CENIMAT|I3N during the last six years is included in more detail, which

  1. Competing weak localization and weak antilocalization in amorphous indium-gallium-zinc-oxide thin-film transistors

    NASA Astrophysics Data System (ADS)

    Wang, Wei-Hsiang; Lyu, Syue-Ru; Heredia, Elica; Liu, Shu-Hao; Jiang, Pei-hsun; Liao, Po-Yung; Chang, Ting-Chang; Chen, Hua-Mao

    2017-01-01

    We have investigated the gate-voltage dependence and the temperature dependence of the magnetoconductivity of amorphous indium-gallium-zinc-oxide thin-film transistors. A weak-localization feature is observed at small magnetic fields on top of an overall negative magnetoconductivity at higher fields. An intriguing controllable competition between weak localization and weak antilocalization is observed by tuning the gate voltage or by varying the temperature. Our findings reflect controllable quantum interference competition in the electron systems in amorphous indium-gallium-zinc-oxide thin-film transistors.

  2. On the effect of non-degenerate doping of polysilicon gate in thin oxide MOS-devices—Analytical modeling

    NASA Astrophysics Data System (ADS)

    Habaš, Predrag; Selberherr, Siegfried

    1990-12-01

    A one-dimensional model of the polysilicon-gate-oxide-bulk structure is presented in order to analyze the implanted gate MOS-devices. The influence of the ionized impurity concentration in the polysilicon-gate near the oxide and the charge at the polysilicon-oxide interface on the flat-band voltage, threshold voltage, inversion layer charge and the quasi-static C- V characteristic is quantitatively studied. The calculations show a considerable degradation of the inversion layer charge due to the voltage drop in the gate, especially in thin oxide devices. The calculated quasi-static C- V curves agree with the recently published data of implanted gate devices.

  3. Thermally evaporated mechanically hard tin oxide thin films for opto-electronic apllications

    SciTech Connect

    Tripathy, Sumanta K.; Rajeswari, V. P.

    2014-01-28

    Tungsten doped tin oxide (WTO) and Molybdenum doped tin oxide (MoTO) thin film were deposited on corn glass by thermal evaporation method. The films were annealed at 350°C for one hour. Structural analysis using Xray diffraction data shows both the films are polycrystalline in nature with monoclinic structure of tin oxide, Sn{sub 3}O{sub 4}, corresponding to JCPDS card number 01-078-6064. SEM photograph showed that both the films have spherical grains with size in the range of 20–30 nm. Compositional analysis was carried out using EDS which reveals the presence of Sn, O and the dopant Mo/W only thereby indicating the absence of any secondary phase in the films. The films are found to contain nearly 6 wt% of Mo, 8 wt% of W as dopants respectively. The transmission pattern for both the films in the spectral range 200 – 2000 nm shows that W doping gives a transparency of nearly 80% from 380 nm onwards while Mo doping has less transparency of 39% at 380nm. Film hardness measurement using Triboscope shows a film hardness of about 9–10 GPa for both the films. It indicates that W or M doping in tin oxide provides the films the added advantage of withstanding the mechanical wear and tear due to environmental fluctuations By optimizing the optical and electrical properties, W/Mo doped tin oxide films may be explored as window layers in opto-electronic applications such as solar cells.

  4. Properties of nanostructured undoped ZrO{sub 2} thin film electrolytes by plasma enhanced atomic layer deposition for thin film solid oxide fuel cells

    SciTech Connect

    Cho, Gu Young; Noh, Seungtak; Lee, Yoon Ho; Cha, Suk Won E-mail: swcha@snu.ac.kr; Ji, Sanghoon; Hong, Soon Wook; Koo, Bongjun; Kim, Young-Beom E-mail: swcha@snu.ac.kr; An, Jihwan

    2016-01-15

    Nanostructured ZrO{sub 2} thin films were prepared by thermal atomic layer deposition (ALD) and by plasma-enhanced atomic layer deposition (PEALD). The effects of the deposition conditions of temperature, reactant, plasma power, and duration upon the physical and chemical properties of ZrO{sub 2} films were investigated. The ZrO{sub 2} films by PEALD were polycrystalline and had low contamination, rough surfaces, and relatively large grains. Increasing the plasma power and duration led to a clear polycrystalline structure with relatively large grains due to the additional energy imparted by the plasma. After characterization, the films were incorporated as electrolytes in thin film solid oxide fuel cells, and the performance was measured at 500 °C. Despite similar structure and cathode morphology of the cells studied, the thin film solid oxide fuel cell with the ZrO{sub 2} thin film electrolyte by the thermal ALD at 250 °C exhibited the highest power density (38 mW/cm{sup 2}) because of the lowest average grain size at cathode/electrolyte interface.

  5. Electro deposition of cuprous oxide for thin film solar cell applications

    NASA Astrophysics Data System (ADS)

    Shahrestani, Seyed Mohammad

    p and n type copper oxide semiconductor layers were fabricated by electrochemistry using new approaches for photovoltaic applications. Thin films were electroplated by cathodic polarization on a copper foil or indium tin oxide (ITO) substrates. The optimum deposition conditions (composition, pH and temperature of the electrolyte and applied potential) of the layers as thin films have been identified; in particular the conditions that allow getting the n-type layers have been well identified for the first time. The configuration of a photo - electrochemical cell was used to characterize the spectral response of the layers. It was shown that the p type layers exhibit a photocurrent in the cathode potential region and n layers exhibit photo current in the anode potential region. Measurements of electrical resistivity of electro chemically deposited layers of p and n type Cu2O, showed that the resistivity of p-type Cu2O varies from 3.2 x 105 to 2.0 x 108 Ocm. These values depend the electrodepositing conditions such as the pH of the solution, the deposition potential and temperature. The influence of several plating parameters of the p type layers of Cu2O, such as applied potential, pH and temperature of the bath on the chemical composition, degree of crystallinity, grain size and orientation parameters of the sample was systematically studied using X-ray diffraction and scanning electron microscopy. Depending of the electro-deposition potential, two different surface morphologies with various preferential crystal orientations were obtained for the temperatures of the electro-deposition of 30 °C and pH 9. For the same temperature, the layers of p type Cu2O of highly crystalline p type are obtained at pH 12, indicating that the crystallinity depends on the pH of the bath. Also, it has been shown that the morphology of Cu2O layers was changed by varying the potential and the duration of deposition, as well as the temperature of the solution. The conditions for the

  6. Understanding and Enhancing the Photostability of Nanoporous Metal Oxide Thin Films for Solar Hydrogen Generation

    NASA Astrophysics Data System (ADS)

    Chitrada, Kalyan Chakravarthi

    under dark conditions. The binary bismuth (III) oxide, in spite being a good photocatalytic material, did not receive as much attention as other bismuth based ternary oxides for photoelectrochemical water splitting application. In this present study, large surface area nanoporous bismuth oxide thin films were synthesized by the electrochemical anodization. These anodic oxides exhibited a dual layered structure having a planar inner oxide and nanoporous outer oxide. Effect of the nanoscale dimensions of the oxides on the photoelectrochemical behavior was studied to understand the charge transport, charge recombination behavior, and long term stability of the material. A maximum photo current density of 0.97 mA/cm2 was observed for the sample anodized at 10 V at 1.53 VRHE. The nanoporous anodic oxides showed a charge carrier density in the range of 1.2 x 1017 -- 4.8 x 1018 cm-3 without illumination and about 60% increase in the charge carrier density upon illumination. However a decay in photo current was observed for the bismuth oxide samples was due to accumulation of holes on the electrode surface. This hole-accumulation was mitigated by the addition of hole scavengers. Addition of hydrogen peroxide as hole scavenger increased the photo current density by about 4 times in 0.5 M Na2SO 4 (pH: 5.8) electrolyte. Addition of H2O2 in 1 M KOH (pH: 13.7) showed an increase-decrease behavior and high photo current density of ~10 mA/cm2 at a bias potential of 0.65 VRHE . The high photo activity observed in this electrolyte was attributed to the in-situ formation of Bi2O4-x phase by the photo-conversion of the beta-Bi2O3 at the surface. The photo-converted Bi2O4-x has a smaller band gap (1.4 eV) and therefore harvested more light in the visible region. This in-situ formation of low band gap phases in the presence of H2O2 during solar water splitting is an interesting observation which has been reported for the first time and this will help design material with very high photo-activity.

  7. Stability of Indium Gallium Zinc Aluminum Oxide Thin-Film Transistors with Treatment Processes

    NASA Astrophysics Data System (ADS)

    Lin, Yung-Hao; Lee, Ching-Ting

    2017-02-01

    The indium-gallium-zinc-aluminum-oxide (IGZAO) channel layer of the bottom-gate-type thin-film transistors (TFTs) was deposited on indium tin oxide-coated glass substrates using a magnetron radio frequency co-sputtering system with dual targets of indium gallium zinc oxide and Al. The 3 s orbital of Al cations provided an extra transport pathway and widened the bottom of the conduction band, thus increasing the electron mobility in the IGZAO films. The Al-O bonds could sustain the stability of oxygen of the IGZAO films. The IGZAO TFTs were processed by O2 plasma and post-annealing treatments. Hysteresis analysis was carried out in order to study the stability of the resulting IGZAO TFTs, the positive bias temperature stress (PBTS) performance, and the hot carrier effect were also measured. For the IGZAO TFTs, the threshold voltage shift of the PBTS performance and the hot carrier effect were 0.1 V and 0.06 V, respectively. Overall, the IGZAO TFTs exhibited good stability in this study.

  8. In situ work function study of oxidation and thin film growth on clean surfaces

    NASA Astrophysics Data System (ADS)

    Baikie, I. D.; Petermann, U.; Lägel, B.

    1999-08-01

    Using a novel ultra high vacuum compatible Kelvin probe we have studied the work function ( φ) changes on semiconductors and metals occurring during basic surface processing, for example, surface cleaning, sputtering, oxidation and thin film growth. We show that damage of the 7×7 reconstruction due to Ar ion bombardment has a profound influence on the work function changes (Δ φ) during oxidation on the Si(111) surface, tending to decrease or even reverse the surface dipole. We have also followed the variable temperature oxidation kinetics of Si(111) in the range of 100-600 K and show that magnitude of the Δ φpeak during the initial adsorption curve decreases in a linear fashion with increasing substrate temperature. We interpret this as being due to the rapid onset of oxygen permeation through the surface layer at higher temperatures producing a reverse or zero net dipole. Combining work function data with a localized technique such as scanning tunnelling microscopy permits monitoring of surface processes at both microscopic and macroscopic levels. In conjunction with Professor Behm's group at Ulm University, Germany, we have monitored work function changes during evaporation of Al on Ru(0001) and show correlation between changes in φ with topographic features such as island growth mechanism, monolayer formation, etc.

  9. Resistance repeatability study of ion-beam deposited vanadium oxide thin films

    NASA Astrophysics Data System (ADS)

    Alvarez, P.; Pearson, D. I. C.; Pochon, S.; Thomas, O.; Cooke, M.; Gunn, R.

    2016-09-01

    Ion Beam Sputter Deposition (IBSD) is a versatile technique particularly suited to applications requiring high quality, high performance layer materials as it allows independent and accurate control of the process parameters. Vanadium oxides, used for example in the fabrication of microbolometers, optical switches or optical storage, exhibit interesting properties such as a high Temperature Coefficient of Resistance (TCR), relatively low 1/f noise and a semiconductormetal phase transition close to room temperature. However, it is very challenging to control the stoichiometry of the deposited film as there are at least 25 different oxidation states of vanadium, few of which display the required electrical characteristics. In the present study, vanadium oxide thin layers were deposited by IBSD using an Oxford Ionfab300+ and analyzed with regard to their electrical properties. The impact of the system parameters on the resistance repeatability, wafer-to-wafer and batch-to-batch, was thoroughly investigated to provide the end user with a clear understanding of the factors affecting film resistivity while ensuring at the same time a steep variation of resistance with temperature, as notably required for uncooled bolometers. These parameters were balanced to also achieve a good deposition rate, throughput and uniformity over large device areas, compatible with the requirements of industrial applications.

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

    PubMed Central

    2013-01-01

    Amorphous mixed metal oxides are emerging as high performance semiconductors for thin film transistor (TFT) applications, with indium gallium zinc oxide, InGaZnO (IGZO), being one of the most widely studied and best performing systems. Here, we investigate alkaline earth (barium or strontium) doped InBa(Sr)ZnO as alternative, semiconducting channel layers and compare their performance of the electrical stress stability with IGZO. In films fabricated by solution-processing from metal alkoxide precursors and annealed to 450 °C we achieve high field-effect electron mobility up to 26 cm2 V–1 s–1. We show that it is possible to solution-process these materials at low process temperature (225–200 °C yielding mobilities up to 4.4 cm2 V–1 s–1) and demonstrate a facile “ink-on-demand” process for these materials which utilizes the alcoholysis reaction of alkyl metal precursors to negate the need for complex synthesis and purification protocols. Electrical bias stress measurements which can serve as a figure of merit for performance stability for a TFT device reveal Sr- and Ba-doped semiconductors to exhibit enhanced electrical stability and reduced threshold voltage shift compared to IGZO irrespective of the process temperature and preparation method. This enhancement in stability can be attributed to the higher Gibbs energy of oxidation of barium and strontium compared to gallium. PMID:24511184

  11. The complex interface chemistry of thin-film silicon/zinc oxide solar cell structures.

    PubMed

    Gerlach, D; Wimmer, M; Wilks, R G; Félix, R; Kronast, F; Ruske, F; Bär, M

    2014-12-21

    The interface between solid-phase crystallized phosphorous-doped polycrystalline silicon (poly-Si(n(+))) and aluminum-doped zinc oxide (ZnO:Al) was investigated using spatially resolved photoelectron emission microscopy. We find the accumulation of aluminum in the proximity of the interface. Based on a detailed photoemission line analysis, we also suggest the formation of an interface species. Silicon suboxide and/or dehydrated hemimorphite have been identified as likely candidates. For each scenario a detailed chemical reaction pathway is suggested. The chemical instability of the poly-Si(n(+))/ZnO:Al interface is explained by the fact that SiO2 is more stable than ZnO and/or that H2 is released from the initially deposited a-Si:H during the crystallization process. As a result, Zn (a deep acceptor in silicon) is "liberated" close to the silicon/zinc oxide interface presenting the inherent risk of forming deep defects in the silicon absorber. These could act as recombination centers and thus limit the performance of silicon/zinc oxide based solar cells. Based on this insight some recommendations with respect to solar cell design, material selection, and process parameters are given for further knowledge-based thin-film silicon device optimization.

  12. In situ oxidation studies on /001/ copper-nickel alloy thin films

    NASA Technical Reports Server (NTRS)

    Heinemann, K.; Rao, D. B.; Douglass, D. L.

    1977-01-01

    High-resolution transmission electron microscopy studies are reported of (001)-oriented single crystalline thin films of Cu-3%Ni, Cu-4.6%Ni, and Cu-50%Ni alloy which were prepared by vapor deposition onto (001) NaCl substrates and subsequently annealed at around 1100 K and oxidized at 725 K at low oxygen partial pressure. At all alloy concentrations, Cu2O and NiO nucleated and grew independently without the formation of mixed oxides. The shape and growth rates of Cu2O nuclei were similar to rates found earlier. For low-nickel alloy concentrations, the NiO nuclei were larger and the number density of NiO was less than that of Cu-50%Ni films for which the shape and growth rates of NiO were identical to those for pure nickel films. Phenomena involving a reduced induction period, surface precipitation, and through-thickness growth are also described. The results are consistent with previously established oxidation mechanisms for pure copper and pure nickel films.

  13. Adsorption and Reaction of Methanethiol on Thin-Film Cerium Oxide

    SciTech Connect

    Mullins, David R; McDonald, Tom S

    2008-01-01

    The adsorption and reaction of methanethiol, CH{sub 3}SH, have been studied on cerium oxide thin films that were vapor deposited on Ru(0 0 0 1). The behavior of the CH{sub 3}SH was examined as a function of the Ce oxidation state. CH{sub 3}SH weakly interacts with fully oxidized CeO{sub 2}(1 1 1) forming both chemisorbed CH{sub 3}SH and CH{sub 3}S + OH. OH forms through the reaction of the sulfhydrol H with the surface O. These species recombine and desorb near 180 K leaving the surface virtually clean. When the ceria is ca. 50% reduced, the chemisorbed CH{sub 3}SH desorbs near 150 K while the CH{sub 3}S + OH are stable to 400 K. These species react above 450 K to produce predominantly CH{sub 4} and CH{sub 3}SH. A small amount of CH{sub 2}O and water are also formed through reaction with the O in the ceria. Atomic S is left on the surface. S 2p, C 1s and O 1s soft X-ray photoelectron spectroscopy were used to identify the nature of the chemisorbed species and the adsorption site of the CH{sub 3}S or S.

  14. Chromatic annuli formation and sample oxidation on copper thin films by femtosecond laser

    NASA Astrophysics Data System (ADS)

    He, Shutong; Amoruso, Salvatore; Pang, Dongqing; Wang, Chingyue; Hu, Minglie

    2016-04-01

    We report an experimental investigation on the irradiation of copper thin films with high repetition rate femtosecond laser pulses (1040 nm, 50 MHz), in ambient air and liquid water. We observe a novel, striking phenomenon of chromatic copper oxides (CuO and Cu2O) annuli generation. The characteristic features of the chromatic copper oxide annuli are studied by exploiting micro-Raman spectroscopy, optical and scanning electron microscopies. In the case of irradiation in water, the seldom investigated effects of the immersion time, tw, after irradiation with a fixed number of pulses are analyzed, and an intriguing dependence of the color of the chromatic annuli on tw is observed. This remarkable behavior is explained by proposing an interpretation scenario addressing the various processes involved in the process. Our experimental findings show that Cu2O nanoparticles (size of ≈20 nm) and Cu2O nanocubes (nanocube edges of ≈30, ≈60 nm) can be effectively generated by exploiting high repetition rate laser-assisted oxidation.

  15. Adsorption and reaction of methanethiol on thin-film cerium oxide

    NASA Astrophysics Data System (ADS)

    Mullins, D. R.; McDonald, T. S.

    2008-03-01

    The adsorption and reaction of methanethiol, CH 3SH, have been studied on cerium oxide thin films that were vapor deposited on Ru(0 0 0 1). The behavior of the CH 3SH was examined as a function of the Ce oxidation state. CH 3SH weakly interacts with fully oxidized CeO 2(1 1 1) forming both chemisorbed CH 3SH and CH 3S + OH. OH forms through the reaction of the sulfhydrol H with the surface O. These species recombine and desorb near 180 K leaving the surface virtually clean. When the ceria is ca. 50% reduced, the chemisorbed CH 3SH desorbs near 150 K while the CH 3S + OH are stable to 400 K. These species react above 450 K to produce predominantly CH 4 and CH 3SH. A small amount of CH 2O and water are also formed through reaction with the O in the ceria. Atomic S is left on the surface. S 2p, C 1s and O 1s soft X-ray photoelectron spectroscopy were used to identify the nature of the chemisorbed species and the adsorption site of the CH 3S or S.

  16. Fatigue failure in thin-film polysilicon is due to subcriticalcracking within the oxide layer

    SciTech Connect

    Alsem, D.H.; Muhlstein, C.L.; Stach, E.A.; Ritchie, R.O.

    2005-01-11

    It has been established that microelectromechanical systems (MEMS) created from polycrystalline silicon thin-films are subject to cyclic fatigue. Prior work by the authors has suggested that although bulk silicon is not susceptible to fatigue failure in ambient air, fatigue in micron-scale silicon is a result of a ''reaction-layer'' process, whereby high stresses induce a thickening of the post-release oxide at stress concentrations such as notches, which subsequently undergoes moisture-assisted cracking. However, there exists some controversy regarding the post-release oxide thickness of the samples used in the prior study. In this Letter, we present data from devices from a more recent fabrication run that confirm our prior observations. Additionally, new data from tests in high vacuum show that these devices do not fatigue when oxidation and moisture are suppressed. Each of these observations lends credence to the '''reaction-layer'' mechanism. Recent advances in the design of microelectromechanical systems (MEMS) have increased the demand for more reliable microscale structures. Although silicon is an effective and widely used structural material at the microscale, it is very brittle. Consequently, reliability is a limiting factor for commercial and defense applications. Since the surface to volume ratio of these structural films is very large, classical models for failure modes in bulk materials cannot always be applied. For example, whereas bulk silicon is immune to cyclic fatigue failure thin micron-scale structural films of silicon appear to be highly susceptible. It is clear that at these size scales, surface effects may become dominant in controlling mechanical properties. The main reliability issues for MEMS are stiction, fatigue and wear. Fatigue is important in cases where devices are subjected to a large number of loading cycles with amplitudes below their (single-cycle) fracture stress, which may arise due to vibrations intentionally induced in the

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

    SciTech Connect

    Skarlinski, Michael D.; Quesnel, David J.

    2015-12-21

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

  18. Chemical vapour deposition of tungsten oxide thin films from single-source precursors

    NASA Astrophysics Data System (ADS)

    Cross, Warren Bradley

    This thesis describes the chemical vapour deposition (CVD) of tungsten oxide thin films on glass from a wide range of single-source precursors. Chapter 1 describes previous work that has motivated this research. Chapter 2 discusses the synthesis of conventional style candidates for single-source precursors. Reactions of WOCl4 with 3-methyl salicylic acid (MesaliH2) and 3,5-di-iso-propyl salicylic acid (di-i-PrsaliH2) yielded the ditungsten complexes [WO(Mesali)(MesaliH)2(mu-O)], 1, and [WO(di-i-Prsali)(di-i-PrsaliH)2(mu-O)], 2, and the monotungsten complex [WO(di-i-Pr sali)(di-i-PrsaliH)Cl], 3. Tungsten(VI) dioxo complexes were prepared by ligand exchange reactions of [WO2(acac)2], 4, yielding [WO2(catH)2], 5, and [WO2(malt)2], 6, (catH2 = 3,5-di-tert-butyl-catechol; maltH = maltol). Chapter 3 describes thermal analyses of the complexes 1 - 6 and tungsten hexaphenoxide, and consequently their suitability for CVD. The use of [W(OPh)6] and 2 - 6 in aerosol assisted CVD is reported in Chapter 4. Brown tungsten oxide was deposited from 2 and 3 at 600 °C; blue partially-reduced WO3-x thin films were deposited from [W(OPh)6] from 300 to 500 °C, from 4 at 600 °C and 6 at 620 °C. Sintering all of the coatings in air at 550 °C afforded yellow films of stoichiometric WO3. Raman spectroscopy and glancing angle XRD showed that coatings deposited from [W(OPh)6] at 300 °C were amorphous, whereas all the other films were the monoclinic phase gamma-tungsten oxide. Taking full advantage of the aerosol vaporisation technique led to the CVD of tungsten oxide films from polyoxometalate single-source precursors, as described in Chapter 5. The isopolyanion [nBu4N]2[W6O19], 7, afforded WO3 at 410 °C; the heteropolyanions [nBu4N]4H3[PW11O39], 8, and [nBu4N]4[PNbW11O40], 9, were used to deposit doped WO3 thin films in a highly-controlled manner at 480 °C. Thus, the unprecedented use of large, charged clusters for CVD was demonstrated. Chapter 6 describes investigations of the

  19. Ultra-Flexible, Invisible Thin-Film Transistors Enabled by Amorphous Metal Oxide/Polymer Channel Layer Blends

    DTIC Science & Technology

    2015-02-25

    Transistors Enabled by Amorphous Metal Oxide/Polymer Channel Layer Blends Xinge Yu , Li Zeng , Nanjia Zhou , Peijun Guo , Fengyuan Shi , Donald B...chemical vapor deposition processes. Thus, a key issue for inexpensive large-scale roll-to-roll production is to enable MO TFT manu- facturing with...4. TITLE AND SUBTITLE Ultra-Flexible, ’Invisible’ Thin-Film Transistors Enabled by Amorphous Metal Oxide/Polymer Channel Layer Blends 5a. CONTRACT

  20. F2-laser patterning of indium tin oxide (ITO) thin film on glass substrate

    NASA Astrophysics Data System (ADS)

    Xu, M. Y.; Li, J.; Lilge, L. D.; Herman, P. R.

    2006-10-01

    This paper reports the controlled micromachining of 100 nm thick indium tin oxide (ITO) thin films on glass substrates with a vacuum-ultraviolet 157 nm F2 laser. Partial to complete film removal was observed over a wide fluence window from 0.49 J/cm2 to an optimized single pulse fluence of 4.5 J/cm2 for complete film removal. Optical microscopy, atomic force microscopy, and energy dispersive X-ray analysis show little substrate or collateral damage by the laser pulse which conserved the stoichiometry, optical transparency and electrical conductivity of ITO coating adjacent to the trenches. At higher fluence, a parallel micron sized channel can be etched in the glass substrate. The high photon energy and top-hat beam homogenized optical system of the F2 laser opens new means for direct structuring of electrodes and microchannels in biological microfluidic systems or in optoelectronics.

  1. Thin Solid Films Topical Special Issue on ZnO related transparent conductive oxides

    SciTech Connect

    Chu, Jinn P.; Endo, Tamio; Ellmer, Klaus; Gessert, Tim; Ginley, David

    2016-04-01

    World-wide research activities on ZnO and related transparent conductive oxides (TCO) in thin film, nanostructured, and multilayered forms are driven by the vast potential of these materials for optoelectronic, microelectronic, and photovoltaic applications. Renewed interest in ZnO applications is partly stimulated by cost reduction in material processing and device development. One of the most important issues is doping and alloying with Al, Ga, In, Sn, etc. in order to tune properties. When highly doped, these materials are used as transparent-conducting contacts on solar cells, as well as in catalytic, spintronic, and surface acoustic wave devices. Film growth conditions, including substrate type and orientation, growth temperature, deposition rate, and ambient atmosphere, all play important roles in determining structural, electrical, magnetic, and optical properties.

  2. Influence of Heat Treatment Conditions on the Properties of Vanadium Oxide Thin Films for Thermochromic Applications.

    PubMed

    Kim, Donguk; Kwon, Samyoung; Park, Young; Boo, Jin-Hyo; Nam, Sang-Hun; Joo, Yang Tae; Kim, Minha; Lee, Jaehyeong

    2016-05-01

    In present work, the effects of the heat treatment on the structural, optical, and thermochromic properties of vanadium oxide films were investigated. Vanadium dioxide (VO2) thin films were deposited on glass substrate by reactive pulsed DC magnetron sputtering from a vanadium metal target in mixture atmosphere of argon and oxygen gas. Various heat treatment conditions were applied in order to evaluate their influence on the crystal phases formed, surface morphology, and optical properties. The films were characterized by an X-ray diffraction (XRD) in order to investigate the crystal structure and identify the phase change as post-annealing temperature of 500-600 degrees C for 5 minutes. Surface conditions of the obtained VO2(M) films were analyzed by field emission scanning electron microscopy (FE-SEM) and the semiconductor-metal transition (SMT) characteristics of the VO2 films were evaluate by optical spectrophotometry in the UV-VIS-NIR, controlling temperature of the films.

  3. Self-aligned top-gate amorphous gallium indium zinc oxide thin film transistors

    NASA Astrophysics Data System (ADS)

    Park, Jaechul; Song, Ihun; Kim, Sunil; Kim, Sangwook; Kim, Changjung; Lee, Jaecheol; Lee, Hyungik; Lee, Eunha; Yin, Huaxiang; Kim, Kyoung-Kok; Kwon, Kee-Won; Park, Youngsoo

    2008-08-01

    We have demonstrated a self-aligned top-gate amorphous gallium indium zinc oxide thin film transistor (a-GIZO TFT). It had a field effect mobility of 5 cm2/V s, a threshold voltage of 0.2 V, and a subthreshold swing of 0.2 V/decade. Ar plasma was treated on the source/drain region of the a-GIZO active layer to reduce the series resistance. After Ar plasma treatment, the surface of the source/drain region was divided into In-rich and In-deficient regions. The a-GIZO TFT also had a constant sheet resistance of 1 kΩ/◻ for a film thickness of over 40 nm. The interface between the source/drain Mo metal and the Ar plasma-treated a-GIZO indicated a good Ohmic contact and a contact resistivity of 50 μΩ cm2.

  4. Amorphous Indium Gallium Zinc Oxide Thin-Film Transistors Fabricated by Direct Transfer Printing

    NASA Astrophysics Data System (ADS)

    Adachi, Susumu; Okamura, Shoichi

    2010-10-01

    This letter describes the fabrication of amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs) by direct transfer printing. An a-IGZO layer and a silicon dioxide (SiO2) layer were sequentially sputtered on a poly(dimethylsiloxane) (PDMS) stamp; the stamp was then pressed onto a glass substrate on which a gate metal had been previously deposited. Then, a-IGZO/SiO2 layers were successfully transferred by simply releasing the stamp from the substrate; a bottom-gate TFT was finally constructed. The measured current-voltage characteristics exhibited good field-effect mobility exceeding 10 cm2 V-1 s-1. The on/off current ratio and subthreshold slope were 4×105 and 0.86 V/decade, respectively.

  5. Structural properties of indium tin oxide thin films prepared for application in solar cells

    SciTech Connect

    Gheidari, A. Mohammadi; Mohajerzadeh, S.; Shams-Kolahi, W.

    2005-08-11

    Indium tin oxide (ITO) thin films prepared by rf sputtering were annealed in several temperatures. The electrical, optical and structural properties of these films are systematically investigated. The post annealing of the samples lead to considerably higher electrical conductivity, better optical transparency and larger grain size for the films. In an optimum annealing temperature of 400 deg. C, we have found that a maximized conductivity of films is achieved without a remarkable loss in their transparency. The sheet resistance of 2.3 {omega}/{open_square} and average grain size of 30 nm, are the results of the optimized post processing of films. The investigation for microstructure of films investigated by X-ray diffraction measurement (XRD) shows that a preferential crystal growth toward the (2 2 2) orientation takes place when the annealing temperature increases to 400 deg. C.

  6. Structure of a zinc oxide ultra-thin film on Rh(100)

    SciTech Connect

    Yuhara, J.; Kato, D.; Matsui, T.; Mizuno, S.

    2015-11-07

    The structural parameters of ultra-thin zinc oxide films on Rh(100) are investigated using low-energy electron diffraction intensity (LEED I–V) curves, scanning tunneling microscopy (STM), and first-principles density functional theory (DFT) calculations. From the analysis of LEED I–V curves and DFT calculations, two optimized models A and B are determined. Their structures are basically similar to the planer h-BN ZnO(0001) structure, although some oxygen atoms protrude from the surface, associated with an in-plane shift of Zn atoms. From a comparison of experimental STM images and simulated STM images, majority and minority structures observed in the STM images represent the two optimized models A and B, respectively.

  7. Patterned oxide semiconductor by electrohydrodynamic jet printing for transparent thin film transistors

    NASA Astrophysics Data System (ADS)

    Lee, Sangkyu; Kim, Jeonghyun; Choi, Junghyun; Park, Hyunjung; Ha, Jaehwan; Kim, Yongkwan; Rogers, John A.; Paik, Ungyu

    2012-03-01

    This paper explores transport in transparent thin film transistors formed using a liquid precursor to indium zinc oxide, delivered to target substrates by electrohydrodynamic jet (e-jet) printing. Under optimized conditions, we observe field effect mobilities as high as 32 cm2V-1s-1, with on/off current ratios of 103 and threshold voltages of 2 V. These results provide evidence that material manipulated in fine-jet, electric field induced liquid flows can yield semiconductor devices without any adverse effects of residual charge or unintentional doping. E-jet printing methods provide levels of resolution (˜1.5 μm) that provide a path to printed transistors with small critical dimensions.

  8. Wake-up effects in Si-doped hafnium oxide ferroelectric thin films

    NASA Astrophysics Data System (ADS)

    Zhou, Dayu; Xu, Jin; Li, Qing; Guan, Yan; Cao, Fei; Dong, Xianlin; Müller, Johannes; Schenk, Tony; Schröder, Uwe

    2013-11-01

    Hafnium oxide based ferroelectric thin films have shown potential as a promising alternative material for non-volatile memory applications. This work reports the switching stability of a Si-doped HfO2 film under bipolar pulsed-field operation. High field cycling causes a "wake-up" in virgin "pinched" polarization hysteresis loops, demonstrated by an enhancement in remanent polarization and a shift of negative coercive voltage. The rate of wake-up is accelerated by either reducing the frequency or increasing the amplitude of the cycling field. We suggest de-pinning of domains due to reduction of the defect concentration at bottom electrode interface as origin of the wake-up.

  9. Influence of Metallic Indium Concentration on the Properties of Indium Oxide Thin Films

    NASA Astrophysics Data System (ADS)

    Kalkan, N.

    2016-10-01

    Current-voltage characteristics of indium-embedded indium oxide thin films (600-850 Å), with Ag electrodes approximately 1000 Å thick, prepared by reactive evaporation of pure metallic indium in partial air pressure have been studied for substrate temperatures between 50 and 125°C. The optical properties of these films have also been investigated as a function of metallic indium concentration and substrate temperature. I-V characteristics of all the samples are non-ohmic, independent of metallic indium concentration. The conductivity of the films increases but the optical transmission decreases with increasing metallic indium concentration. Metallic indium concentration was found to be an important parameter affecting the film properties. Furthermore, two possible conduction mechanisms are proposed.

  10. Electromechanical Breakdown of Barrier-Type Anodized Aluminum Oxide Thin Films Under High Electric Field Conditions

    NASA Astrophysics Data System (ADS)

    Chen, Jianwen; Yao, Manwen; Yao, Xi

    2016-02-01

    Barrier-type anodized aluminum oxide (AAO) thin films were formed on a polished aluminum substrate via electrochemical anodization in 0.1 mol/L aqueous solution of ammonium pentaborate. Electromechanical breakdown occurred under high electric field conditions as a result of the accumulation of mechanical stress in the film-substrate system by subjecting it to rapid thermal treatment. Before the breakdown event, the electricity of the films was transported in a highly nonlinear way. Immediately after the breakdown event, dramatic cracking of the films occurred, and the cracks expanded quickly to form a mesh-like dendrite network. The breakdown strength was significantly reduced because of the electromechanical coupling effect, and was only 34% of the self-healing breakdown strength of the AAO film.

  11. Water-soluble thin film transistors and circuits based on amorphous indium-gallium-zinc oxide.

    PubMed

    Jin, Sung Hun; Kang, Seung-Kyun; Cho, In-Tak; Han, Sang Youn; Chung, Ha Uk; Lee, Dong Joon; Shin, Jongmin; Baek, Geun Woo; Kim, Tae-il; Lee, Jong-Ho; Rogers, John A

    2015-04-22

    This paper presents device designs, circuit demonstrations, and dissolution kinetics for amorphous indium-gallium-zinc oxide (a-IGZO) thin film transistors (TFTs) comprised completely of water-soluble materials, including SiNx, SiOx, molybdenum, and poly(vinyl alcohol) (PVA). Collections of these types of physically transient a-IGZO TFTs and 5-stage ring oscillators (ROs), constructed with them, show field effect mobilities (∼10 cm2/Vs), on/off ratios (∼2×10(6)), subthreshold slopes (∼220 mV/dec), Ohmic contact properties, and oscillation frequency of 5.67 kHz at supply voltages of 19 V, all comparable to otherwise similar devices constructed in conventional ways with standard, nontransient materials. Studies of dissolution kinetics for a-IGZO films in deionized water, bovine serum, and phosphate buffer saline solution provide data of relevance for the potential use of these materials and this technology in temporary biomedical implants.

  12. Studies of aluminum oxide thin films deposited by laser ablation technique

    NASA Astrophysics Data System (ADS)

    Płóciennik, P.; Guichaoua, D.; Korcala, A.; Zawadzka, A.

    2016-06-01

    This paper presents the structural and optical investigations of the aluminum oxide nanocrystalline thin films. Investigated films were fabricated by laser ablation technique in high vacuum onto quartz substrates. The films were deposited at two different temperatures of the substrates equal to room temperature and 900 K. X-ray Diffraction spectra proved nanocrystalline character and the corundum phase of the film regardless on the substrate temperature during the deposition process. Values of the refractive indices, extinction and absorption coefficients were calculated by using Transmission and Reflection Spectroscopy in the UV-VIS-NIR range of the wavelength. Coupling Prism Method was used for films thickness estimations. Experimental measurements and theoretical calculations of the Third Harmonic Generation were also reported. Obtained results show that the lattice strain may affect obtained values of the third order nonlinear optical susceptibility.

  13. Research Update: Stoichiometry controlled oxide thin film growth by pulsed laser deposition

    SciTech Connect

    Groenen, Rik; Smit, Jasper; Orsel, Kasper; Vailionis, Arturas; Bastiaens, Bert; Huijben, Mark; Boller, Klaus; Rijnders, Guus; Koster, Gertjan

    2015-07-01

    The oxidation of species in the plasma plume during pulsed laser deposition controls both the stoichiometry as well as the growth kinetics of the deposited SrTiO{sub 3} thin films, instead of the commonly assumed mass distribution in the plasma plume and the kinetic energy of the arriving species. It was observed by X-ray diffraction that SrTiO{sub 3} stoichiometry depends on the composition of the background gas during deposition, where in a relative small pressure range between 10{sup −2} mbars and 10{sup −1} mbars oxygen partial pressure, the resulting film becomes fully stoichiometric. Furthermore, upon increasing the oxygen (partial) pressure, the growth mode changes from 3D island growth to a 2D layer-by-layer growth mode as observed by reflection high energy electron diffraction.

  14. Reclaim System Design of Indium Tin Oxide Thin-Film Removal from Color Filters of Displays

    NASA Astrophysics Data System (ADS)

    Pa, Pai-Shan

    2008-09-01

    A newly design precision reclaim system using electrochemical machining as an etching process for indium tin oxide (ITO) thin-film removal from the color filter surface of a displays is presented. Through the ultra precise etching of the nanostructure, the semiconductor industry can effectively recycle defective products, thereby reducing production costs. A large gyration diameter of a cathode combined with a small gap width between the cathode and a workpiece takes less time for the same amount of ITO removed. An adequate feed rate of color filters combined with a sufficient electric power produces fast machining. Pulsed direct current and higher rotational speed of the cathode can improve the effects of dregs discharge and are advantageous to be combined with a high feed rate of workpieces. Electrochemical machining only requires a short time to easily and cleanly remove ITO films.

  15. Contact resistance improvement using interfacial silver nanoparticles in amorphous indium-zinc-oxide thin film transistors

    SciTech Connect

    Xu, Rui; He, Jian; Song, Yang; Li, Wei; Zaslavsky, A.; Paine, D. C.

    2014-09-01

    We describe an approach to reduce the contact resistance at compositional conducting/semiconducting indium-zinc-oxide (IZO) homojunctions used for contacts in thin film transistors (TFTs). By introducing silver nanoparticles (Ag NPs) at the homojunction interface between the conducting IZO electrodes and the amorphous IZO channel, we reduce the specific contact resistance, obtained by transmission line model measurements, down to ∼10{sup −2 }Ω cm{sup 2}, ∼3 orders of magnitude lower than either NP-free homojunction contacts or solid Ag metal contacts. The resulting back-gated TFTs with Ag NP contacts exhibit good field effect mobility of ∼27 cm{sup 2}/V s and an on/off ratio >10{sup 7}. We attribute the improved contact resistance to electric field concentration by the Ag NPs.

  16. New strain states and radical property tuning of metal oxides using a nanocomposite thin film approach

    NASA Astrophysics Data System (ADS)

    MacManus-Driscoll, Judith; Suwardi, Ady; Kursumovic, Ahmed; Bi, Zhenxing; Tsai, Chen-Fong; Wang, Haiyan; Jia, Quanxi; Lee, Oon Jew

    2015-06-01

    Auxetic-like strain states were generated in self-assembled nanocomposite thin films of (Ba0.6Sr0.4TiO3)1-x - (Sm2O3)x(BSTO - SmO). A switch from auxetic-like to elastic-like strain behavior was observed for x > 0.50, when the SmO switched from being nanopillars in the BSTO matrix to being the matrix with BSTO nanopillars embedded in it. A simple model was adopted to explain how in-plane strain varies with x. At high x (0.75), strongly enhanced ferroelectric properties were obtained compared to pure BSTO films. The nanocomposite method represents a powerful new way to tune the properties of a wide range of strongly correlated metal oxides whose properties are very sensitive to strain.

  17. Numerical simulation of offset-drain amorphous oxide-based thin-film transistors

    NASA Astrophysics Data System (ADS)

    Jeong, Jaewook

    2016-11-01

    In this study, we analyzed the electrical characteristics of amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs) with an offset-drain structure by technology computer aided design (TCAD) simulation. When operating in a linear region, an enhancement-type TFT shows poor field-effect mobility because most conduction electrons are trapped in acceptor-like defects in an offset region when the offset length (L off) exceeds 0.5 µm, whereas a depletion-type TFT shows superior field-effect mobility owing to the high free electron density in the offset region compared with the trapped electron density. When operating in the saturation region, both types of TFTs show good field-effect mobility comparable to that of a reference TFT with a large gate overlap. The underlying physics of the depletion and enhancement types of offset-drain TFTs are systematically analyzed.

  18. Pyroelectric response in crystalline hafnium zirconium oxide (Hf1-xZrxO2) thin films

    NASA Astrophysics Data System (ADS)

    Smith, S. W.; Kitahara, A. R.; Rodriguez, M. A.; Henry, M. D.; Brumbach, M. T.; Ihlefeld, J. F.

    2017-02-01

    Pyroelectric coefficients were measured for 20 nm thick crystalline hafnium zirconium oxide (Hf1-xZrxO2) thin films across a composition range of 0 ≤ x ≤ 1. Pyroelectric currents were collected near room temperature under zero applied bias and a sinusoidal oscillating temperature profile to separate the influence of non-pyroelectric currents. The pyroelectric coefficient was observed to correlate with zirconium content, increased orthorhombic/tetragonal phase content, and maximum polarization response. The largest measured absolute value was 48 μCm-2 K-1 for a composition with x = 0.64, while no pyroelectric response was measured for compositions which displayed no remanent polarization (x = 0, 0.91, and 1).

  19. Silicon induced stability and mobility of indium zinc oxide based bilayer thin film transistors

    NASA Astrophysics Data System (ADS)

    Chauhan, Ram Narayan; Tiwari, Nidhi; Liu, Po-Tsun; Shieh, Han-Ping D.; Kumar, Jitendra

    2016-11-01

    Indium zinc oxide (IZO), silicon containing IZO, and IZO/IZO:Si bilayer thin films have been prepared by dual radio frequency magnetron sputtering on glass and SiO2/Si substrates for studying their chemical compositions and electrical characteristics in order to ascertain reliability for thin film transistor (TFT) applications. An attempt is therefore made here to fabricate single IZO and IZO/IZO:Si bilayer TFTs to study the effect of film thickness, silicon incorporation, and bilayer active channel on device performance and negative bias illumination stress (NBIS) stability. TFTs with increasing single active IZO layer thickness exhibit decrease in carrier mobility but steady improvement in NBIS; the best values being μFE ˜ 27.0, 22.0 cm2/Vs and ΔVth ˜ -13.00, -6.75 V for a channel thickness of 7 and 27 nm, respectively. While silicon incorporation is shown to reduce the mobility somewhat, it raises the stability markedly (ΔVth ˜ -1.20 V). Further, IZO (7 nm)/IZO:Si (27 nm) bilayer based TFTs display useful characteristics (field effect mobility, μFE = 15.3 cm2/Vs and NBIS value, ΔVth =-0.75 V) for their application in transparent electronics.

  20. Defects evolution and their impacts on conductivity of indium tin oxide thin films upon thermal treatment

    SciTech Connect

    Li, Qichao; Mao, Wenfeng; Zhou, Yawei; Yang, Chunhong; Liu, Yong; He, Chunqing

    2015-07-14

    Indium tin oxide (ITO) thin films were deposited on silicon substrates by radio-frequency magnetron sputtering. The influence of annealing temperature on the crystallite, surface morphology, defects evolution, and electrical property of the thin films was studied. The conductivity of the ITO films was significantly enhanced by two orders of magnitude by increasing the annealing temperature up to 600 °C, which was interpreted in point view of defects evolution in ITO films as revealed by positron annihilation. It was interesting to find that positron diffusion length was amazingly comparable to crystallite size in ITO films annealed below 300 °C, indicating positrons were preferentially localized and annihilated in defects around crystallite boundaries. By further increasing the temperature, positron diffusion length was far beyond the grain size with little increment. This demonstrated that defects were effectively removed around grain boundaries. The results indicated defect structure around crystallite/grain boundaries played an important role on carrier transportation in nanocrystal ITO films.

  1. Thin transparent W-doped indium-zinc oxide (WIZO) layer on glass.

    PubMed

    Lee, Young-Jun; Lim, Byung-Wook; Kim, Joo-Hyung; Kim, Tae-Won; Oh, Byeong-Yun; Heo, Gi-Seok; Kim, Kwang-Young

    2012-07-01

    Annealing effect on structural and electrical properties of W-doped IZO (WIZO) films for thin film transistors (TFT) was studied under different process conditions. Thin WIZO films were deposited on glass substrates by RF magnetron co-sputtering technique using indium zinc oxide (10 wt.% ZnO-doped In2O3) and WO3 targets in room temperature. The post annealing temperature was executed from 200 degrees C to 500 degrees C under various O2/Ar ratios. We could not find any big difference from the surface observation of as grown films while it was found that the carrier density and sheet resistance of WIZO films were controlled by O2/Ar ratio and post annealing temperature. Furthermore, the crystallinity of WIZO film was changed as annealing temperature increased, resulting in amorphous structure at the annealing temperature of 200 degrees C, while clear In2O3 peak was observed for the annealed over 300 degrees C. The transmittance of as-grown films over 89% in visible range was obtained. As an active channel layer for TFT, it was found that the variation of resistivity, carrier density and mobility concentration of WIZO film decreased by annealing process.

  2. Crystal structure and electronic properties of bulk and thin film brownmillerite oxides.

    SciTech Connect

    Young, Joshua; Rondinelli, James M.

    2015-11-17

    The equilibrium structure and functional properties exhibited by brownmillerite oxides, a family of perovskitederived structures with alternating layers of BO6 octahedra and BO4 tetrahedra, viz., ordered arrangements of oxygen vacancies, is dependent on a variety of competing crystal-chemistry factors. We use electronic structure calculations to disentangle the complex interactions in two ferrates, Sr2Fe2O5 and Ca2Fe2O5, relating the stability of the equilibrium (strain-free) and thin film structures to both previously identified and herein newly proposed descriptors.We show that cation size and intralayer separation of the tetrahedral chains provide key contributions to the preferred ground state. We show the bulk ground-state structure is retained in the ferrates over a range of strain values; however, a change in the orientation of the tetrahedral chains, i.e., a perpendicular orientation of the vacancies relative to the substrate, is stabilized in the compressive region. The structure stability under strain is largely governed by maximizing the intraplane separation of the dipoles generated from rotations of the FeO4 tetrahedra. Lastly, we find that the electronic band gap is strongly influenced by strain, manifesting as an unanticipated asymmetric-vacancy alignment dependent response. This atomistic understanding establishes a practical route for the design of functional electronic materials in thin film geometries.

  3. Copper Oxide Thin Films through Solution Based Methods for Electrical Energy Conversion and Storage

    NASA Astrophysics Data System (ADS)

    Zhu, Changqiong

    Copper oxides (Cu2O and CuO), composed of non-toxic and earth abundant elements, are promising materials for electrical energy generation and storage devices. Solution based techniques for creating thin films of these materials, such as electrodeposition, are important to understand and develop because of their potential for realizing substantial energy savings compared to traditional fabrication methods. Cuprous oxide (Cu2O), with its direct band gap, is a p-type semiconductor that is well suited for creating solution-processed photovoltaic devices (solar cells); several key advancements made toward this application are the primary focus of this thesis. Electrodeposition of single-phase, crystalline Cu2O thin films is demonstrated using previously unexplored, acidic lactate/Cu2+ solutions, which has provided additional understanding of the impacts of growth solution chemistry on film formation. The influence of pH on the resulting Cu2O thin film properties is revealed by using the same ligand (sodium lactate) at various solution pH values. Cu2O films grown from acidic lactate solutions can exhibit a distinctive flowerlike, dendritic morphology, in contrast to the faceted, dense films obtained using alkaline lactate solutions. Relative speciation distributions of the various metal complex ions present under different growth conditions are calculated using reported equilibrium association constants and experimentally supported by UV-Visible absorption spectroscopy. Dependence of thin film morphology on the lactate/Cu2+ molar ratio and applied potential is described. Cu2O/eutectic gallium-indium Schottky junction devices are formed and devices are tested under monochromatic green LED illumination. Further surface examination of the Cu2O films using X-ray photoelectron spectroscopy (XPS) reveals the fact that films grown from acidic lactate solution with a small lactate/Cu2+ molar ratio, which exhibit improved photovoltaic performance compared to films grown from

  4. Facile synthesis of cobalt-doped zinc oxide thin films for highly efficient visible light photocatalysts

    NASA Astrophysics Data System (ADS)

    Altintas Yildirim, Ozlem; Arslan, Hanife; Sönmezoǧlu, Savaş

    2016-12-01

    Cobalt-doped zinc oxide (Co:ZnO) thin films with dopant contents ranging from 0 to 5 at.% were prepared using the sol-gel method, and their structural, morphological, optical, and photocatalytic properties were characterized. The effect of the dopant content on the photocatalytic properties of the films was investigated by examining the degradation behavior of methylene blue (MB) under visible light irradiation, and a detailed investigation of their photocatalytic activities was performed by determining the apparent quantum yields (AQYs). Co2+ ions were observed to be substitutionally incorporated into Zn2+ sites in the ZnO crystal, leading to lattice parameter constriction and band gap narrowing due to the photoinduced carriers produced under the visible light irradiation. Thus, the light absorption range of the Co:ZnO films was improved compared with that of the undoped ZnO film, and the Co:ZnO films exhibited highly efficient photocatalytic activity (∼92% decomposition of MB after 60-min visible light irradiation for the 3 at.% Co:ZnO film). The AQYs of the Co:ZnO films were greatly enhanced under visible light irradiation compared with that of the undoped ZnO thin film, demonstrating the effect of the Co doping level on the photocatalytic activity of the films.

  5. High-mobility thin film transistors with neodymium-substituted indium oxide active layer

    SciTech Connect

    Lin, Zhenguo; Lan, Linfeng Xiao, Peng; Sun, Sheng; Li, Yuzhi; Song, Wei; Gao, Peixiong; Wang, Lei; Ning, Honglong; Peng, Junbiao

    2015-09-14

    Thin-film transistors (TFTs) with neodymium-substituted indium oxide (InNdO) channel layer were demonstrated. The structural properties of the InNdO films as a function of annealing temperature have been analyzed using X-ray diffraction and transmission electron microscopy. The InNdO thin films showed polycrystalline nature when annealed at 450 °C with a lattice parameter (cubic cell) of 10.255 Å, which is larger than the cubic In{sub 2}O{sub 3} film (10.117 Å). The high-resolution transmission electron microscopy and energy dispersive X-ray spectroscopy showed that no Nd{sub 2}O{sub 3} clusters were found in the InNdO film, implying that Nd was incorporated into the In{sub 2}O{sub 3} lattice. The InNdO TFTs annealed at 450 °C exhibited more excellent electrical properties with a high mobility of 20.4 cm{sup 2} V{sup −1} s{sup −1} and better electric bias stability compared to those annealed at 300 °C, which was attributed to the reduction of the scattering centers and/or charge traps due to the decrease of the |Nd3d{sub 5/2}{sup 5}4f{sup 4}O2p{sup −1}〉 electron configuration.

  6. ZnO transparent conductive oxide for thin film silicon solar cells

    NASA Astrophysics Data System (ADS)

    Söderström, T.; Dominé, D.; Feltrin, A.; Despeisse, M.; Meillaud, F.; Bugnon, G.; Boccard, M.; Cuony, P.; Haug, F.-J.; Faÿ, S.; Nicolay, S.; Ballif, C.

    2010-03-01

    There is general agreement that the future production of electric energy has to be renewable and sustainable in the long term. Photovoltaic (PV) is booming with more than 7GW produced in 2008 and will therefore play an important role in the future electricity supply mix. Currently, crystalline silicon (c-Si) dominates the market with a share of about 90%. Reducing the cost per watt peak and energy pay back time of PV was the major concern of the last decade and remains the main challenge today. For that, thin film silicon solar cells has a strong potential because it allies the strength of c-Si (i.e. durability, abundancy, non toxicity) together with reduced material usage, lower temperature processes and monolithic interconnection. One of the technological key points is the transparent conductive oxide (TCO) used for front contact, barrier layer or intermediate reflector. In this paper, we report on the versatility of ZnO grown by low pressure chemical vapor deposition (ZnO LP-CVD) and its application in thin film silicon solar cells. In particular, we focus on the transparency, the morphology of the textured surface and its effects on the light in-coupling for micromorph tandem cells in both the substrate (n-i-p) and superstrate (p-i-n) configurations. The stabilized efficiencies achieved in Neuchâtel are 11.2% and 9.8% for p-i-n (without ARC) and n-i-p (plastic substrate), respectively.

  7. Hydrogen storage in Ti, V and their oxides-based thin films

    NASA Astrophysics Data System (ADS)

    Tarnawski, Z.; Zakrzewska, K.; Kim-Ngan, N.-T. H.; Krupska, M.; Sowa, S.; Drogowska, K.; Havela, L.; Balogh, A. G.

    2015-03-01

    We have investigated the hydrogen storage ability and the effect of hydrogenation on structure and physical properties of Ti/V and their oxides-based thin films. A series of Ti-TiO2 and VOx-TiO2 thin films with different layer structures, geometries and thicknesses have been prepared by the sputtering technique on different (Si(111), SiO2, C) substrates. For the Ti-TiO2-Ti films up to 50 at.% of hydrogen can be stored in the Ti layers, while the hydrogen can penetrate without accumulation through the TiO2 layer. A large hydrogen storage was also found in some V2O5-TiO2 films. Hydrogen could also remove the preferential orientation in the Ti films and induce a transition of V2O5 to VO2 in the films. Invited talk at the 7th International Workshop on Advanced Materials Science and Nanotechnology IWAMSN2014, 2-6 November, 2014, Ha Long, Vietnam.

  8. Influence of annealing temperature and environment on the properties of indium tin oxide thin films

    NASA Astrophysics Data System (ADS)

    Wang, R. X.; Beling, C. D.; Fung, S.; Djurisic, A. B.; Ling, C. C.; Kwong, C.; Li, S.

    2005-06-01

    Indium tin oxide (ITO) thin films were deposited on glass substrates using the e-beam evaporating technique. The influence of deposition rate and post-deposition annealing on the optical properties of the films was investigated in detail. It is found that the deposition rate and annealing conditions strongly affect the optical properties of the films. The transmittance of films greatly increases with increasing annealing temperature below 300°C but drastically drops at 400°C when they are annealed in forming gas (mixed N2 and H2 gas). An interesting phenomenon observed is that the transmittance of the darkened film can recover under further 400°C annealing in air. Atomic force microscopy, x-ray diffraction and x-ray photoemission spectroscopy were employed to obtain information on the chemical state and crystallization of the films. Analysis of these data suggests that the loss and re-incorporating of oxygen are responsible for the reversible behaviour of the ITO thin films.

  9. Fluorine-doped zinc oxide thin films: influence of precursor flow rate on violet luminescence

    NASA Astrophysics Data System (ADS)

    Muthukumar, Anusha; Dakshnamoorthy, Arivuoli

    2015-06-01

    Fluorine-doped zinc oxide (FZO) thin films were deposited by the aerosol-assisted chemical vapor deposition method with variable precursor flow rates (0.5-2.5 ml/min). X-ray diffraction patterns revealed the polycrystalline hexagonal wurtzite structure of the derived FZO nanocrystalline thin films. Extensive crystallinity analysis of the film deposited at 1 ml/min was done by grazing incidence X-ray diffraction. Field emission scanning electron microscope images apparent the gradual evolution from spherical grains and hexagonal platelet like surface morphology with increased flow rate. Optical transparency and photoluminescence (PL) are strongly influenced by flow rate. PL intensity and transparency increase with decreased flow rate. The optical bandgap was tuned significantly by increase in flow rate and especially tuned the PL emission from violet to UV. High intense violet PL observed at flow rate of 1 ml/min and radiative transition of electrons from zinc vacancies level to the conduction band were found. Crystallinity, growth rate and roughness increase with increased flow rate.

  10. Tailoring of absorption edge by thermal annealing in tin oxide thin films

    SciTech Connect

    Thakur, Anup; Gautam, Sanjeev; Kumar, Virender; Chae, K. H.; Lee, Ik-Jae; Shin, Hyun Joon

    2015-05-15

    Tin oxide (SnO{sub 2}) thin films were deposited by radio-frequency (RF) magnetron sputtering on silicon and glass substrates in different oxygen-to-argon gas-flow ratio (O{sub 2}-to-Ar = 0%, 10%, 50%). All films were deposited at room temperature and fixed working pressures, 10 mTorr. The X-ray diffraction (XRD) measurement suggests that all films were crystalline in nature except film deposited in argon environment. Thin films were annealed in air at 200 °C, 400 °C and 600 °C for two hours. All films were highly transparent except the film deposited only in the argon environment. It was also observed that transparency was improved with annealing due to decrease in oxygen vacancies. Atomic force microscopy (AFM), results showed that the surface of all the films were highly flat and smooth. Blue shift was observed in the absorption edge with annealing temperature. It was also observed that there was not big change in the absorption edge with annealing for films deposited in 10% and 50% oxygen-to-argon gas-flow ratio.

  11. Surface chemistry of coated lithium manganese nickel oxide thin film cathodes studied by XPS

    SciTech Connect

    Baggetto, Loic; Dudney, Nancy J; Veith, Gabriel M

    2013-01-01

    The effect of coating high voltage LiMn1.5Ni0.5O4 spinel cathode thin films with three metal oxide thin layers is discussed. The changes in surface chemistry of the electrodes are measured by X-ray photoelectron spectroscopy. ZnO is found to decompose during the first charge whereas Al2O3 and ZrO2 are stable for more than 100 cycles. ZrO2, however, importantly limits the available Li storage capacity of the electrochemical reaction due to poorer kinetics. Al2O3 offers the best results in term of capacity retention. Upon cycling, the evidence of a signal at 75.4 eV in the Al2p binding energy spectrum indicates the partial conversion of Al2O3 into Al2O2F2. Moreover, the continuous formation of PEO , esters and LixPOyFz compounds on the surface of the electrodes is found for all coating materials.

  12. Electronic passivation of silicon surfaces by thin films of atomic layer deposited gallium oxide

    SciTech Connect

    Allen, T. G. Cuevas, A.

    2014-07-21

    This paper proposes the application of gallium oxide (Ga{sub 2}O{sub 3}) thin films to crystalline silicon solar cells. Effective passivation of n- and p-type crystalline silicon surfaces has been achieved by the application of very thin Ga{sub 2}O{sub 3} films prepared by atomic layer deposition using trimethylgallium (TMGa) and ozone (O{sub 3}) as the reactants. Surface recombination velocities as low as 6.1 cm/s have been recorded with films less than 4.5 nm thick. A range of deposition parameters has been explored, with growth rates of approximately 0.2 Å/cycle providing optimum passivation. The thermal activation energy for passivation of the Si-Ga{sub 2}O{sub 3} interface has been found to be approximately 0.5 eV. Depassivation of the interface was observed for prolonged annealing at increased temperatures. The activation energy for depassivation was measured to be 1.9 eV.

  13. Crystalline Molybdenum Oxide Thin-Films for Application as Interfacial Layers in Optoelectronic Devices.

    PubMed

    F Cauduro, André L; Dos Reis, Roberto; Chen, Gong; Schmid, Andreas K; Méthivier, Christophe; Rubahn, Horst-Günter; Bossard-Giannesini, Léo; Cruguel, Hervé; Witkowski, Nadine; Madsen, Morten

    2017-03-01

    The ability to control the interfacial properties in metal-oxide thin films through surface defect engineering is vital to fine-tune their optoelectronic properties and thus their integration in novel optoelectronic devices. This is exemplified in photovoltaic devices based on organic, inorganic or hybrid technologies, where precise control of the charge transport properties through the interfacial layer is highly important for improving device performance. In this work, we study the effects of in situ annealing in nearly stoichiometric MoOx (x ∼ 3.0) thin-films deposited by reactive sputtering. We report on a work function increase of almost 2 eV after inducing in situ crystallization of the films at 500 °C, resulting in the formation of a single crystalline α-MoO3 overlaid by substoichiometric and highly disordered nanoaggregates. The surface nanoaggregates possess various electronic properties, such as a work function ranging from 5.5 eV up to 6.2 eV, as determined from low-energy electron microscopy studies. The crystalline underlayer possesses a work function greater than 6.3 eV, up to 6.9 eV, characteristic of a very clean and nearly defect-free MoO3. By combining electronic spectroscopies together with structural characterizations, this work addresses a novel method for tuning, and correlating, the optoelectronic properties and microstructure of device-relevant MoOx layers.

  14. Effect of solvent ratio on the optoelectronic properties of fluorine doped tin oxide thin films

    SciTech Connect

    Karthick, P.; Divya, V.; Sridharan, M.; Jeyadheepan, K.

    2015-06-24

    Fluorine doped tin oxide (FTO) thin films were deposited on to the well cleaned microscopic glass substrates using nebulized-spray pyrolysis (n-SP) technique by varying the water to ethanol solvent proportion. The deposited thin films were characterized by X-ray diffraction (XRD), UV-Vis-NIR spectroscopy, field emission scanning electron microscopy and Hall measurements to study the structural, optical, surface morphological and electrical properties of the films, respectively. Results of the analyzes show that the films are polycrystalline, having tetragonal structure with the preferred orientation along (110) plane. The grain size varies between 7 to 20 nm. The optimized films exhibit the optical transparency of 85 % at the wavelength of 580 nm. The optical bandgap lies in the range of 3.94 to 4 eV. The optimized films, deposited with 40 % of ethanol proportion are having the mean resistivity 4.72×10{sup −3} Ω-cm, carrier concentration 1.79×10{sup 20} cm{sup 3} and the mobility 7 cm{sup 2}/Vs.

  15. Flexible thin-film battery based on graphene-oxide embedded in solid polymer electrolyte

    NASA Astrophysics Data System (ADS)

    Kammoun, M.; Berg, S.; Ardebili, H.

    2015-10-01

    Enhanced safety of flexible batteries is an imperative objective due to the intimate interaction of such devices with human organs such as flexible batteries that are integrated with touch-screens or embedded in clothing or space suits. In this study, the fabrication and testing of a high performance thin-film Li-ion battery (LIB) is reported that is both flexible and relatively safer compared to the conventional electrolyte based batteries. The concept is facilitated by the use of solid polymer nanocomposite electrolyte, specifically, composed of polyethylene oxide (PEO) matrix and 1 wt% graphene oxide (GO) nanosheets. The flexible LIB exhibits a high maximum operating voltage of 4.9 V, high capacity of 0.13 mA h cm-2 and an energy density of 4.8 mW h cm-3. The battery is encapsulated using a simple lamination method that is economical and scalable. The laminated battery shows robust mechanical flexibility over 6000 bending cycles and excellent electrochemical performance in both flat and bent configurations. Finite element analysis (FEA) of the LIB provides critical insights into the evolution of mechanical stresses during lamination and bending.Enhanced safety of flexible batteries is an imperative objective due to the intimate interaction of such devices with human organs such as flexible batteries that are integrated with touch-screens or embedded in clothing or space suits. In this study, the fabrication and testing of a high performance thin-film Li-ion battery (LIB) is reported that is both flexible and relatively safer compared to the conventional electrolyte based batteries. The concept is facilitated by the use of solid polymer nanocomposite electrolyte, specifically, composed of polyethylene oxide (PEO) matrix and 1 wt% graphene oxide (GO) nanosheets. The flexible LIB exhibits a high maximum operating voltage of 4.9 V, high capacity of 0.13 mA h cm-2 and an energy density of 4.8 mW h cm-3. The battery is encapsulated using a simple lamination method

  16. Effect of oxidative stress on the expression of thin filament-associated proteins in gastric smooth muscle cells.

    PubMed

    Al-Shboul, Othman Abdullah; Mustafa, Ayman; Mohammad, Mukhallad; Al-Shehabat, Mustafa; Yousef, Asmaa; Al-Hashimi, Farah

    2014-09-01

    Thin filament-associated proteins such as calponin, caldesmon, and smoothelin are believed to regulate acto-myosin interaction and thus, muscle contraction. Oxidative stress has been found to affect the normal contractile behavior of smooth muscle and is involved in the pathogenesis of a number of human diseases such as diabetes mellitus, hypertension, and atherosclerosis. However, very little is known about the effect of oxidative stress on the expression of smooth muscle contractile proteins. The aim of the current study is to investigate the effect of oxidative stress on the expression of thin filament-associated proteins in rat gastric smooth muscle. Single smooth muscle cells of the stomach obtained from Sprague-Dawley rats were used. Muscle cells were treated with hydrogen peroxide (H2O2) (500 μM) for 30 min or the peroxynitrite donor 3-morpholinosydnonimine (SIN-1) (1 mM) for 90 min to induce oxidative stress. Calponin, caldesmon, and smoothelin expressions were measured via specifically designed enzyme-linked immunosorbent assay. We found that exposure to exogenous H2O2 or incubation of dispersed gastric muscle cells with SIN-1 significantly increased the expression of calponin, caldesmon, and smoothelin proteins. In conclusion: oxidative stress increases the expression of thin filament-associated proteins in gastric smooth muscle, suggesting an important role in gastrointestinal motility disorders associated with oxidative stress.

  17. Hole mobility modulation of solution-processed nickel oxide thin-film transistor based on high-k dielectric

    NASA Astrophysics Data System (ADS)

    Liu, Ao; Liu, Guoxia; Zhu, Huihui; Shin, Byoungchul; Fortunato, Elvira; Martins, Rodrigo; Shan, Fukai

    2016-06-01

    Solution-processed p-type oxide semiconductors have recently attracted increasing interests for the applications in low-cost optoelectronic devices and low-power consumption complementary metal-oxide-semiconductor circuits. In this work, p-type nickel oxide (NiOx) thin films were prepared using low-temperature solution process and integrated as the channel layer in thin-film transistors (TFTs). The electrical properties of NiOx TFTs, together with the characteristics of NiOx thin films, were systematically investigated as a function of annealing temperature. By introducing aqueous high-k aluminum oxide (Al2O3) gate dielectric, the electrical performance of NiOx TFT was improved significantly compared with those based on SiO2 dielectric. Particularly, the hole mobility was found to be 60 times enhancement, quantitatively from 0.07 to 4.4 cm2/V s, which is mainly beneficial from the high areal capacitance of the Al2O3 dielectric and high-quality NiOx/Al2O3 interface. This simple solution-based method for producing p-type oxide TFTs is promising for next-generation oxide-based electronic applications.

  18. Optimization of synthesis protocols to control the nanostructure and the morphology of metal oxide thin films for memristive applications

    SciTech Connect

    Baldi, G. Bosi, M.; Attolini, G.; Berzina, T.; Mosca, R.; Ponraj, J. S.; Iannotta, S.

    2015-03-10

    We propose a multi-technique approach based on in-vacuum synthesis of metal oxides to optimize the memristive properties of devices that use a metal oxide thin film as insulating layer. Pulsed Microplasma Cluster Source (PMCS) is based on supersonic beams seeded by clusters of the metal oxide. Nanocrystalline TiO{sub 2} thin films can be grown at room temperature, controlling the oxide stoichiometry from titanium metal up to a significant oxygen excess. Pulsed Electron beam Deposition (PED) is suitable to grow crystalline thin films on large areas, a step towards producing device arrays with controlled morphology and stoichiometry. Atomic Layer Deposition (ALD) is a powerful technique to grow materials layer-by-layer, finely controlling the chemical and structural properties of the film up to thickness of 50-80 nm. We will present a few examples of metal-insulator-metal structures showing a pinched hysteresis loop in their current-voltage characteristic. The structure, stoichiometry and morphology of the metal oxide layer, either aluminum oxide or titanium dioxide, is investigated by means of scanning electron microscopy (SEM) and by Raman scattering.

  19. 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%.

  20. Titanium oxide thin films obtained with physical and chemical vapour deposition methods for optical biosensing purposes.

    PubMed

    Dominik, M; Leśniewski, A; Janczuk, M; Niedziółka-Jönsson, J; Hołdyński, M; Wachnicki, Ł; Godlewski, M; Bock, W J; Śmietana, M

    2017-07-15

    This work discusses an application of titanium oxide (TiOx) thin films deposited using physical (reactive magnetron sputtering, RMS) and chemical (atomic layer deposition, ALD) vapour deposition methods as a functional coating for label-free optical biosensors. The films were applied as a coating for two types of sensors based on the localised surface plasmon resonance (LSPR) of gold nanoparticles deposited on a glass plate and on a long-period grating (LPG) induced in an optical fibre. Optical and structural properties of the TiOx thin films were investigated and discussed. It has been found that deposition method has a significant influence on optical properties and composition of the films, but negligible impact on TiOx surface silanization effectiveness. A higher content of oxygen with lower Ti content in the ALD films leads to the formation of layers with higher refractive index and slightly higher extinction coefficient than for the RMS TiOx. Moreover, application of the TiOx film independently on deposition method enables not only for tuning of the spectral response of the investigated biosensors, but also in case of LSPR for enhancing the ability for biofunctionalization, i.e., TiOx film mechanically protects the nanoparticles and induces change in the biofunctionalization procedure to the one typical for oxides. TiOx coated LSPR and LPG sensors with refractive index sensitivity of close to 30 and 3400nm/RIU, respectively, were investigated. The ability for molecular recognition was evaluated with the well-known complex formation between avidin and biotin as a model system. The shift in resonance wavelength reached 3 and 13.2nm in case of LSPR and LPG sensors, respectively. Any modification in TiOx properties resulting from the biofunctionalization process can be also clearly detected.

  1. Synthesis and Characterization of Thionated Reduced Graphene Oxides and Their Thin Films

    NASA Astrophysics Data System (ADS)

    Jeon, Kiwan

    Thiol functionalization is one potentially useful way to tailor physical and chemical properties of graphene oxides (GOs) and reduced graphene oxides (RGOs). Despite the ubiquitous presence of thiol functional groups in diverse chemical systems, efficient thiol functionalization has been challenging for GOs and RGOs, or for carbonaceous materials in general. In this work, thionation of GOs has been achieved in high yield through two new methods that also allow concomitant chemical reduction/thermal reduction of GOs; a solid-gas metathetical reaction method with boron sulfides (BxSy) gases and a solvothermal reaction method employing phosphorus decasulfide (P4S10). The thionation products, called "mercapto reduced graphene oxides (m-RGOs)", were characterized by employing X-ray photoelectron spectroscopy, powder X-ray diffraction, UV-Vis spectroscopy, FT-IR spectroscopy, Raman spectroscopy, electron probe analysis, scanning electron microscopy, (scanning) transmission electron microscopy, nano secondary ion mass spectrometry, Ellman assay and atomic force microscopy. The excellent dispersibility of m-RGOs in various solvents including alcohols has allowed fabrication of thin films of m-RGOs. Deposition of m-RGOs on gold substrates was achieved through solution deposition and the m-RGOs were homogeneously distributed on gold surface shown by atomic force microscopy. Langmuir-Blodgett (LB) films of m-RGOs were obtained by transferring their Langmuir films, formed by simple drop casting of m-RGOs dispersion on water surface, onto various substrates including gold, glass and indium tin oxide. The m-RGO LB films showed low sheet resistances down to about 500 kΩ/sq at 92% optical transparency. The successful results make m-RGOs promising for applications in transparent conductive coatings, biosensing, etc.

  2. Tensile strain effect in ferroelectric perovskite oxide thin films on spinel magnesium aluminum oxide substrate

    NASA Astrophysics Data System (ADS)

    Zhou, Xiaolan

    Ferroelectrics are used in FeRAM (Ferroelectric random-access memory). Currently (Pb,Zr)TiO3 is the most common ferroelectric material. To get lead-free and high performance ferroelectric material, we investigated perovskite ferroelectric oxides (Ba,Sr)TiO3 and BiFeO3 films with strain. Compressive strain has been investigated intensively, but the effects of tensile strain on the perovskite films have yet to be explored. We have deposited (Ba,Sr)TiO3, BiFeO3 and related films by pulsed laser deposition (PLD) and analyzed the films by X-ray diffractometry (XRD), atomic force microscopy (AFM), etc. To obtain inherently fully strained films, the selection of the appropriate substrates is crucial. MgAl2O4 matches best with good quality and size, yet the spinel structure has an intrinsic incompatibility to that of perovskite. We introduced a rock-salt structure material (Ni 1-xAlxO1+delta) as a buffer layer to mediate the structural mismatch for (Ba,Sr)TiO3 films. With buffer layer Ni1-xAlxO1+delta, we show that the BST films have high quality crystallization and are coherently epitaxial. AFM images show that the films have smoother surfaces when including the buffer layer, indicating an inherent compatibility between BST-NAO and NAO-MAO. In-plane Ferroelectricity measurement shows double hysteresis loops, indicating an antiferroelectric-like behavior: pinned ferroelectric domains with antiparallel alignments of polarization. The Curie temperatures of the coherent fully strained BST films are also measured. It is higher than 900°C, at least 800°C higher than that of bulk. The improved Curie temperature makes the use of BST as FeRAM feasible. We found that the special behaviors of ferroelectricity including hysteresis loop and Curie temperature are due to inherent fully tensile strain. This might be a clue of physics inside ferroelectric stain engineering. An out-of-plane ferroelectricity measurement would provide a full whole story of the tensile strain. However, a

  3. Challenges and opportunities for multi-functional oxide thin films for voltage tunable radio frequency/microwave components

    SciTech Connect

    Subramanyam, Guru; Cole, M. W.; Sun, Nian X.; Kalkur, Thottam S.; Sbrockey, Nick M.; Tompa, Gary S.; Guo, Xiaomei; Chen, Chonglin; Alpay, S. P.; Rossetti, G. A.; Dayal, Kaushik; Chen, Long-Qing; Schlom, Darrell G.

    2013-11-21

    There has been significant progress on the fundamental science and technological applications of complex oxides and multiferroics. Among complex oxide thin films, barium strontium titanate (BST) has become the material of choice for room-temperature-based voltage-tunable dielectric thin films, due to its large dielectric tunability and low microwave loss at room temperature. BST thin film varactor technology based reconfigurable radio frequency (RF)/microwave components have been demonstrated with the potential to lower the size, weight, and power needs of a future generation of communication and radar systems. Low-power multiferroic devices have also been recently demonstrated. Strong magneto-electric coupling has also been demonstrated in different multiferroic heterostructures, which show giant voltage control of the ferromagnetic resonance frequency of more than two octaves. This manuscript reviews recent advances in the processing, and application development for the complex oxides and multiferroics, with the focus on voltage tunable RF/microwave components. The over-arching goal of this review is to provide a synopsis of the current state-of the-art of complex oxide and multiferroic thin film materials and devices, identify technical issues and technical challenges that need to be overcome for successful insertion of the technology for both military and commercial applications, and provide mitigation strategies to address these technical challenges.

  4. Challenges and opportunities for multi-functional oxide thin films for voltage tunable radio frequency/microwave components

    NASA Astrophysics Data System (ADS)

    Subramanyam, Guru; Cole, M. W.; Sun, Nian X.; Kalkur, Thottam S.; Sbrockey, Nick M.; Tompa, Gary S.; Guo, Xiaomei; Chen, Chonglin; Alpay, S. P.; Rossetti, G. A.; Dayal, Kaushik; Chen, Long-Qing; Schlom, Darrell G.

    2013-11-01

    There has been significant progress on the fundamental science and technological applications of complex oxides and multiferroics. Among complex oxide thin films, barium strontium titanate (BST) has become the material of choice for room-temperature-based voltage-tunable dielectric thin films, due to its large dielectric tunability and low microwave loss at room temperature. BST thin film varactor technology based reconfigurable radio frequency (RF)/microwave components have been demonstrated with the potential to lower the size, weight, and power needs of a future generation of communication and radar systems. Low-power multiferroic devices have also been recently demonstrated. Strong magneto-electric coupling has also been demonstrated in different multiferroic heterostructures, which show giant voltage control of the ferromagnetic resonance frequency of more than two octaves. This manuscript reviews recent advances in the processing, and application development for the complex oxides and multiferroics, with the focus on voltage tunable RF/microwave components. The over-arching goal of this review is to provide a synopsis of the current state-of the-art of complex oxide and multiferroic thin film materials and devices, identify technical issues and technical challenges that need to be overcome for successful insertion of the technology for both military and commercial applications, and provide mitigation strategies to address these technical challenges.

  5. Tantalum oxide thin films for high-k dielectric applications: Crystallization, anisotropy and three dimensional imaging

    NASA Astrophysics Data System (ADS)

    Min, Kyunghoon

    2004-12-01

    High dielectric constant (high-k) materials have been drawing much attention for applications such as gate oxides for transistors and dynamic random access memory (DRAM) capacitors. Tantalum pentoxide (Ta2O5) is a possible replacement because of its relatively high dielectric constant and process compatibility. The microstructure of Ta2O5 thin films, deposited on Si substrates by atomic layer deposition, was investigated primarily using transmission electron microscopy (TEM). The kinetics of the crystallization and evolution of a complicated subgrain structure were studied by in-situ TEM heating experiments carried out at nominal temperatures of 790°C, 820°C and 850°C. It was found that the crystallization behavior could be modeled by a standard kinetic approach, using the Avrami equation, and differences from conventional bulk behavior are discussed. The growth and overall crystallization activation energies extracted from the in-situ TEM results were 4.2 eV and 6.3 eV, respectively. The tantalum oxide films used in this study were found to have two predominant crystallographic orientations. In order to evaluate the possible anisotropic properties of the two types of grains, micro-capacitors were fabricated on each type using a combination of a focused ion beam machine (FIB) and the TEM. Plan-view TEM samples were prepared to identify and locate grain orientations followed by electron beam assisted chemical vapor deposition of a Pt top electrode using the local deposition capability of the FIB. Electrical measurement of the micro-capacitors was carried out using a micromanipulator inside the FIB. The dielectric properties of the two types of grains were directly compared from the measurements. A further application of FIB combined with TEM allows novel specimen preparation for electron tomography. Accordingly, we can address the three dimensional imaging of Ta2O5 thin films deposited on hemi-spherical grain silicon (HSG) structures. The post-shaped sample

  6. In-Situ Preparation of Ytterbium-Barium - Superconducting Thin Films Using Pure Ozone Vapor Oxidation

    NASA Astrophysics Data System (ADS)

    Berkley, Dale Dane

    A new process for preparing thin films of the YBa_2Cu_3O _{rm 7-x} high transition temperature superconducting oxide completely in-situ, without the need for a post-evaporation anneal has been developed. This work is a significant advancement in the effort to achieve a fully mature, high quality thin film-making process for scientific and technical applications. A pure ozone vapor, derived from the distilled liquid, is used to oxidize the co-evaporated metallic constituents during deposition to nucleate the superconducting phase in the vacuum chamber. Films exhibiting zero resistance transition temperatures at 85 K have been grown on strontium titanate substrates using a substrate temperature of 700 ^circC. Background evaporation pressures of 2 x 10^{-7}Torr are employed during film growth. Films prepared using this process contain primarily mixed a- and c-axis oriented grains which, as evidenced by Transmission Electron Microscopy, exhibit a high degree of epitaxial order with the substrate. Processing at lower substrate temperatures results in a depression of T _{rm c} consistent with the behavior observed for other in-situ techniques. It is unclear at this time whether this depression can be attributed to an oxygen deficiency or an expanded c-axis lattice parameter which is always associated with lower temperature processing. Measurements of the critical current of a prototype YBa_2Cu_3O _{rm 7-x}/Au/Pb proximity tunneling junction prepared in-situ using the ozone process do not exhibit the expected magnetic field and temperature dependence. This observation may be the result of a poorly defined tunneling geometry subject to the vagaries of edge effects or filamentary electrical shorts through the normal metal layer. Important implications for the investigation of an isotope effect in the high T_{rm c} superconductors is made possible by the development of the ozone technique. By distilling the ^{18}O gas into a "heavy ozone," thin films can be efficiently

  7. Novel nanostructure zinc zirconate, zinc oxide or zirconium oxide pastes coated on fluorine doped tin oxide thin film as photoelectrochemical working electrodes for dye-sensitized solar cell.

    PubMed

    Hossein Habibi, Mohammad; Askari, Elham; Habibi, Mehdi; Zendehdel, Mahmoud

    2013-03-01

    Zinc zirconate (ZnZrO(3)) (ZZ), zinc oxide (ZnO) (ZO) and zirconium oxide (ZrO(2)) (ZRO) nano-particles were synthesized by simple sol-gel method. ZZ, ZO and ZRO nano-particles were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and UV-Vis diffuse reflectance spectrum (DRS). Nanoporous ZZ, ZO and ZRO thin films were prepared doctor blade technique on the fluorine-doped tin oxide (FTO) and used as working electrodes in dye sensitized solar cells (DSSC). Their photovoltaic behavior were compared with standard using D35 dye and an electrolyte containing [Co(bpy)(3)](PF(6))(2), [Co(pby)(3)](PF(6))(3), LiClO(4), and 4-tert-butylpyridine (TBP). The properties of DSSC have been studied by measuring their short-circuit photocurrent density (Jsc), open-circuit voltage (VOC) and fill factor (ff). The application of ZnZrO(3) as working electrode produces a significant improvement in the fill factor (ff) of the dye-sensitized solar cells (ff=56%) compared to ZnO working electrode (ff=40%) under the same condition.

  8. Performance improvement of tin-doped zinc oxide thin-film transistor by novel channel modulation layer of indium tin oxide/tin zinc oxide

    NASA Astrophysics Data System (ADS)

    Chen, Zhuofa; Han, Dedong; Zhao, Nannan; Wu, Jing; Cong, Yingying; Dong, Junchen; Zhao, Feilong; Zhang, Shengdong; Zhang, Xing; Wang, Yi; Liu, Lifeng

    2015-04-01

    By applying a novel active modulation layer of indium tin oxide/tin zinc oxide (ITO/TZO), we have successfully fabricated high-performance bottom-gate-type dual-active-layer thin-film transistors (TFTs) on a glass substrate at a low temperature by a simple process. The as-fabricated dual-active-layer ITO/TZO TFTs exhibited excellent electrical properties compared with single-active-layer TZO TFTs. We found that the dual-layer ITO/TZO TFT with an optimized stack structure of ITO (5 nm)/TZO (45 nm) as the channel layer exhibits excellent properties, namely, a high saturation mobility of 204 cm2 V-1 s-1, a steep subthreshold slope of 219 mV/dec, a low threshold voltage of 0.8 V, and a high on-off current ratio of 4.3 × 107. A physical mechanism for the electrical improvement is also deduced. Owing to its advantages, namely, a low processing temperature, a high electrical performance, a simple process, and a low cost, this novel active modulation layer is highly promising for the manufacture of oxide semiconductor TFT and transparent displays.

  9. Poole-Frenkel-effect as dominating current mechanism in thin oxide films—An illusion?!

    SciTech Connect

    Schroeder, Herbert

    2015-06-07

    In many of the publications, over 50 per year for the last five years, the Poole-Frenkel-effect (PFE) is identified or suggested as dominating current mechanism to explain measured current–electric field dependencies in metal-insulator-metal (MIM) thin film stacks. Very often, the insulating thin film is a metal oxide as this class of materials has many important applications, especially in information technology. In the overwhelming majority of the papers, the identification of the PFE as dominating current mechanism is made by the slope of the current–electric field curve in the so-called Poole-Frenkel plot, i.e., logarithm of current density, j, divided by the applied electric field, F, versus the square root of that field. This plot is suggested by the simplest current equation for the PFE, which comprises this proportionality (ln(j/F) vs. F{sup 1/2}) leading to a straight line in this plot. Only one other parameter (except natural constants) may influence this slope: the optical dielectric constant of the insulating film. In order to identify the importance of the PFE simulation studies of the current through MIM stacks with thin insulating films were performed and the current–electric field curves without and with implementation of the PFE were compared. For the simulation, an advanced current model has been used combining electronic carrier injection/ejection currents at the interfaces, described by thermionic emission, with the carrier transport in the dielectric, described by drift and diffusion of electrons and holes in a wide band gap semiconductor. Besides the applied electric field (or voltage), many other important parameters have been varied: the density of the traps (with donor- and acceptor-like behavior); the zero-field energy level of the traps within the energy gap, this energy level is changed by the PFE (also called internal Schottky effect); the thickness of the dielectric film; the permittivity of the dielectric film simulating

  10. Poole-Frenkel-effect as dominating current mechanism in thin oxide films—An illusion?!

    NASA Astrophysics Data System (ADS)

    Schroeder, Herbert

    2015-06-01

    In many of the publications, over 50 per year for the last five years, the Poole-Frenkel-effect (PFE) is identified or suggested as dominating current mechanism to explain measured current-electric field dependencies in metal-insulator-metal (MIM) thin film stacks. Very often, the insulating thin film is a metal oxide as this class of materials has many important applications, especially in information technology. In the overwhelming majority of the papers, the identification of the PFE as dominating current mechanism is made by the slope of the current-electric field curve in the so-called Poole-Frenkel plot, i.e., logarithm of current density, j, divided by the applied electric field, F, versus the square root of that field. This plot is suggested by the simplest current equation for the PFE, which comprises this proportionality (ln(j/F) vs. F1/2) leading to a straight line in this plot. Only one other parameter (except natural constants) may influence this slope: the optical dielectric constant of the insulating film. In order to identify the importance of the PFE simulation studies of the current through MIM stacks with thin insulating films were performed and the current-electric field curves without and with implementation of the PFE were compared. For the simulation, an advanced current model has been used combining electronic carrier injection/ejection currents at the interfaces, described by thermionic emission, with the carrier transport in the dielectric, described by drift and diffusion of electrons and holes in a wide band gap semiconductor. Besides the applied electric field (or voltage), many other important parameters have been varied: the density of the traps (with donor- and acceptor-like behavior); the zero-field energy level of the traps within the energy gap, this energy level is changed by the PFE (also called internal Schottky effect); the thickness of the dielectric film; the permittivity of the dielectric film simulating different oxide

  11. 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.

  12. Impact of Nanosize on Supercapacitance: Study of 1D Nanorods and 2D Thin-Films of Nickel Oxide.

    PubMed

    Patil, Ranjit A; Chang, Cheng-Ping; Devan, Rupesh S; Liou, Yung; Ma, Yuan-Ron

    2016-04-20

    We synthesized unique one-dimensional (1D) nanorods and two-dimensional (2D) thin-films of NiO on indium-tin-oxide thin-films using a hot-filament metal-oxide vapor deposition technique. The 1D nanorods have an average width and length of ∼100 and ∼500 nm, respectively, and the densely packed 2D thin-films have an average thickness of ∼500 nm. The 1D nanorods perform as parallel units for charge storing. However, the 2D thin-films act as one single unit for charge storing. The 2D thin-films possess a high specific capacitance of ∼746 F/g compared to 1D nanorods (∼230 F/g) using galvanostatic charge-discharge measurements at a current density of 3 A/g. Because the 1D NiO nanorods provide more plentiful surface areas than those of the 2D thin-films, they are fully active at the first few cycles. However, the capacitance retention of the 1D nanorods decays faster than that of the 2D thin-films. Also, the 1D NiO nanorods suffer from instability due to the fast electrochemical dissolution and high nanocontact resistance. Electrochemical impedance spectroscopy verifies that the low dimensionality of the 1D NiO nanorods induces the unavoidable effects that lead them to have poor supercapacitive performances. On the other hand, the slow electrochemical dissolution and small contact resistance in the 2D NiO thin-films favor to achieve high specific capacitance and great stability.

  13. Thin-Film Transistors Fabricated Using Sputter Deposition of Zinc Oxide

    NASA Astrophysics Data System (ADS)

    Xiao, Nan

    2013-01-01

    Development of thin film transistors (TFTs) with conventional channel layer materials, such as amorphous silicon (a-Si) and polysilicon (poly-Si), has been extensively investigated. A-Si TFT currently serves the large flat panel industry; however advanced display products are demanding better TFT performance because of the associated low electron mobility of a-Si. This has motivated interest in semiconducting metal oxides, such as Zinc Oxide (ZnO), for TFT backplanes. This work involves the fabrication and characterization of TFTs using ZnO deposited by sputtering. An overview of the process details and results from recently fabricated TFTs following a full-factorial designed experiment will be presented. Material characterization and analysis of electrical results will be described. The investigated process variables were the gate dielectric and ZnO sputtering process parameters including power density and oxygen partial pressure. Electrical results showed clear differences in treatment combinations, with certain I-V characteristics demonstrating superior performance to preliminary work. A study of device stability will also be discussed.

  14. Reduced Graphene Oxide Thin Film on Conductive Substrates by Bipolar Electrochemistry

    PubMed Central

    Anis, Allagui; Mohammad, Ali Abdelkareem; Hussain, Alawadhi; Ahmed, S. Elwakil

    2016-01-01

    Recent years have shown an increased interest in developing manufacturing processes for graphene and its derivatives that consider the environmental impact and large scale cost-effectiveness. However, today’s most commonly used synthesis routes still suffer from their excessive use of harsh chemicals and/or the complexity and financial cost of the process. Furthermore, the subsequent transfer of the material onto a substrate makes the overall process even more intricate and time-consuming. Here we describe a single-step, single-cell preparation procedure of metal-supported reduced graphene oxide (rGO) using the principle of bipolar electrochemistry of graphite in deionized water. Under the effect of an electric field between two stainless steel feeder electrodes, grapheme layers at the anodic pole of the wireless graphite were oxidized into colloidal dispersion of GO, which migrated electrophoretically towards the anodic side of the cell, and deposited in the form of rGO (d(002) = 0.395 nm) by van der Waals forces. For substrates chemically more susceptible to the high anodic voltage, we show that the electrochemical setup can be adapted by placing the latter between the wireless graphite and the stainless steel feeder anode. This method is straightforward, inexpensive, environmentally-friendly, and could be easily scaled up for high yield and large area production of rGO thin films. PMID:26883173

  15. Oxidation-Based Continuous Laser Writing in Vertical Nano-Crystalline Graphite Thin Films

    PubMed Central

    Loisel, Loïc; Florea, Ileana; Cojocaru, Costel-Sorin; Tay, Beng Kang; Lebental, Bérengère

    2016-01-01

    Nano and femtosecond laser writing are becoming very popular techniques for patterning carbon-based materials, as they are single-step processes enabling the drawing of complex shapes without photoresist. However, pulsed laser writing requires costly laser sources and is known to cause damages to the surrounding material. By comparison, continuous-wave lasers are cheap, stable and provide energy at a more moderate rate. Here, we show that a continuous-wave laser may be used to pattern vertical nano-crystalline graphite thin films with very few macroscale defects. Moreover, a spatially resolved study of the impact of the annealing to the crystalline structure and to the oxygen ingress in the film is provided: amorphization, matter removal and high oxygen content at the center of the beam; sp2 clustering and low oxygen content at its periphery. These data strongly suggest that amorphization and matter removal are controlled by carbon oxidation. The simultaneous occurrence of oxidation and amorphization results in a unique evolution of the Raman spectra as a function of annealing time, with a decrease of the I(D)/I(G) values but an upshift of the G peak frequency. PMID:27194181

  16. Performance of Indium Gallium Zinc Oxide Thin-Film Transistors in Saline Solution

    NASA Astrophysics Data System (ADS)

    Gupta, S.; Lacour, S. P.

    2016-06-01

    Transistors are often envisioned as alternative transducing devices to microelectrodes to communicate with the nervous system. Independently of the selected technology, the transistors should have reliable performance when exposed to physiological conditions (37°C, 5% CO2). Here, we report on the reliable performance of parylene encapsulated indium gallium zinc oxide (IGZO) based thin-film transistors (TFTs) after prolonged exposure to phosphate buffer saline solution in an incubator. The encapsulated IGZO TFTs (W/L = 500 μm/20 μm) have an ON/OFF current ratio of 107 and field effect mobility of 8.05 ± 0.78 cm2/Vs. The transistors operate within 4 V; their threshold voltages and subthreshold slope are ~1.9 V and 200 mV/decade, respectively. After weeks immersed in saline solution and at 37°C, we did not observe any significant deterioration in the transistors' performance. The long-term stability of IGZO transistors at physiological conditions is a promising result in the direction of metal oxide bioelectronics.

  17. Reduced graphene oxide/molecular imprinted polymer-organic thin film transistor for amino acid detection

    NASA Astrophysics Data System (ADS)

    Halim, Nurul Farhanah AB.; Musa, Nur Hazwani; Zakaria, Zulkhairi; Von Schleusingen, Mubaraq; Ahmad, Mohd Noor; Derman, Nazree; Shakaff, Ali Yeon Md.

    2017-03-01

    This works reports the electrical performance of reduced graphene oxide (RGO)/Molecular imprinted polymer (MIP)- organic thin film transistor (OTFT) for amino-acid detection, serine. These biomimetic sensors consider MIP as man-tailored biomimetic recognition sites that play an important role in signal transduction. MIP provides recognition sites compatible with serine molecules was developed by dispersing serine with methylacrylate acid (MAA) as functional monomer and Ethylene glycol dimethylacrylate (EGDMA) as cross-linker. The imprinted polymeric were mixed with reduced graphene oxide to produced sensing layer for the sensor. RGO-MIP layer was introduced between source and drain of OTFT via spin coating as a detecting layer for serine molecules. RGO was introduced into MIP, to allow a highly conductive sensing material thus enhanced selectivity and sensitivity of the sensor. By analyzing the electrical performance of the sensors, the performances of OTFT sensor enhanced with RGO/MIP interlayer and OTFT sensor with MIP interlayer when exposed to serine analyte were obtained. The results showed that there were remarkable shifts of drain current (ID) obtained from OTFT sensor with RGO/MIP interlayer after exposed to serine analyte. Moreover, the sensitivity of OTFT sensor with RGO/MIP interlayer was nearly higher than the OTFT sensor with MIP interlayer. Hence, it proved that RGO successfully enhanced the sensing performance of OTFT sensor.

  18. Investigation on vanadium oxide thin films deposited by spray pyrolysis technique

    NASA Astrophysics Data System (ADS)

    Margoni, Mudaliar Mahesh; Mathuri, S.; Ramamurthi, K.; Babu, R. Ramesh; Sethuraman, K.

    2016-05-01

    Vanadium oxide thin films were deposited at 400 °C by spray pyrolysis technique using 0.1 M aqueous precursor solution of ammonium meta vanadate (AMV) with two different pH values. X-ray diffraction results showed that the film prepared using aqueous precursor AMV solution (solution A; pH 7) is amorphous in nature and the film prepared by adding HNO3 in the AMV aqua solution A (solution B; pH 3) is polycrystalline in nature. Vanadium oxide film prepared from the precursor solution B is in the mixed phases of V2O5 and V4O7. Crystallinity is improved for the film prepared using solution B when compared to film prepared from solution A. Crystallite size, strain and dislocation density calculated for the film prepared from solution B is respectively 72.1 nm, 0.4554 × 10-3 lin.-2m-4 and 1.7263 × 1014 lin.m-2. Morphology study revealed that the size of the flakes formed on the surface of the films is influenced by the pH of the precursor solution. Average Visible Transmittance and maximum transmittance of the deposited films exceed 70% and the direct optical band gap value calculated for the films deposited from A and B solution is 1.91 eV and 2.08 eV respectively.

  19. Oxidation-Based Continuous Laser Writing in Vertical Nano-Crystalline Graphite Thin Films

    NASA Astrophysics Data System (ADS)

    Loisel, Loïc; Florea, Ileana; Cojocaru, Costel-Sorin; Tay, Beng Kang; Lebental, Bérengère

    2016-05-01

    Nano and femtosecond laser writing are becoming very popular techniques for patterning carbon-based materials, as they are single-step processes enabling the drawing of complex shapes without photoresist. However, pulsed laser writing requires costly laser sources and is known to cause damages to the surrounding material. By comparison, continuous-wave lasers are cheap, stable and provide energy at a more moderate rate. Here, we show that a continuous-wave laser may be used to pattern vertical nano-crystalline graphite thin films with very few macroscale defects. Moreover, a spatially resolved study of the impact of the annealing to the crystalline structure and to the oxygen ingress in the film is provided: amorphization, matter removal and high oxygen content at the center of the beam; sp2 clustering and low oxygen content at its periphery. These data strongly suggest that amorphization and matter removal are controlled by carbon oxidation. The simultaneous occurrence of oxidation and amorphization results in a unique evolution of the Raman spectra as a function of annealing time, with a decrease of the I(D)/I(G) values but an upshift of the G peak frequency.

  20. Characterization of ZnO Thin Films Prepared by Thermal Oxidation of Zn

    NASA Astrophysics Data System (ADS)

    Bouanane, I.; Kabir, A.; Boulainine, D.; Zerkout, S.; Schmerber, G.; Boudjema, B.

    2016-07-01

    Zinc oxide thin films were prepared by thermal oxidation of zinc films at a temperature of 500°C for 2 h. The Zn films were deposited onto glass substrates by magnetron RF sputtering. The sputtering time varied from 2.5 min to 15 min. The physico-chemical characterization of the ZnO films was carried out depending on the Zn sputtering time. According to x-ray diffraction, ZnO films were polycrystalline and the Zn-ZnO phase transformation was direct. The mean transmittance of the ZnO films was around 80% and the band gap increased from 3.15 eV to 3.35 eV. Photoluminescence spectra show ultraviolet, visible, and infrared emission bands. The increase of the UV emission band was correlated with the improvement of the crystalline quality of the ZnO films. The concentration of native defects was found to decrease with increasing Zn sputtering time. The decrease of the electrical resistivity as a function of Zn sputtering time was linked to extrinsic hydrogen-related defects.

  1. TAPE CALENDERING MANUFACTURING PROCESS FOR MULTILAYER THIN-FILM SOLID OXIDE FUEL CELLS

    SciTech Connect

    Nguyen Minh; Kurt Montgomery

    2004-10-01

    This report summarizes the work performed by Hybrid Power Generation Systems, LLC during the Phases I and II under Contract DE-AC26-00NT40705 for the U. S. Department of Energy, National Energy Technology Laboratory (DOE/NETL) entitled ''Tape Calendering Manufacturing Process For Multilayer Thin-Film Solid Oxide Fuel Cells''. The main objective of this project was to develop the manufacturing process based on tape calendering for multilayer solid oxide fuel cells (SOFC's) using the unitized cell design concept and to demonstrate cell performance under specified operating conditions. Summarized in this report is the development and improvements to multilayer SOFC cells and the unitized cell design. Improvements to the multilayer SOFC cell were made in electrochemical performance, in both the anode and cathode, with cells demonstrating power densities of nearly 0.9 W/cm{sup 2} for 650 C operation and other cell configurations showing greater than 1.0 W/cm{sup 2} at 75% fuel utilization and 800 C. The unitized cell design was matured through design, analysis and development testing to a point that cell operation at greater than 70% fuel utilization was demonstrated at 800 C. The manufacturing process for both the multilayer cell and unitized cell design were assessed and refined, process maps were developed, forming approaches explored, and nondestructive evaluation (NDE) techniques examined.

  2. Swift heavy ion induced dewetting of metal oxide thin films on silicon

    NASA Astrophysics Data System (ADS)

    Bolse, T.; Paulus, H.; Bolse, W.

    2006-04-01

    We have observed that thin oxide coatings (NiO, Fe2O3) tend to dewet their Si substrate when being bombarded with swift heavy ions (350-600 MeV Au ions) even though the irradiation was carried out about 80 K and hence, the films never reached their melting point. Scanning electron and atomic force microscopy reveal a surprising similarity of the dewetting morphologies with those observed for molten polymer films on Si, which have recently been reported by others [S. Herminghaus, K. Jakobs, K. Mecke, J. Bischof, A. Fery, M. Ibn-Elhaj, S. Schlagowsky, Science 282 (1998) 916; R. Seemann, S. Herminghaus, K. Jacobs, J. Phys.: Condens. Matter 13 (2001) 4925]. Like in that cases also here heterogeneous and homogeneous hole nucleation could be identified. Heterogeneous nucleation is less pronounced in Fe2O3/Si than in NiO/Si. The occurrence of spinodal-like dewetting cannot be detected unambiguously. The dewetting kinetics were determined by means of Rutherford backscattering spectroscopy and found to slightly differ for the two compounds. The dewetting kinetics as well as the final dewetting pattern strongly depend on the initial film thicknesses. No dewetting occurs for film thicknesses above about 150 nm, while for very small thicknesses below about 40 nm the film decays into nm-sized spherical droplets. At intermediate film thicknesses percolated networks of small oxide bridges are formed.

  3. Process-structure-property correlations in pulsed dc reactive magnetron sputtered vanadium oxide thin films

    SciTech Connect

    Venkatasubramanian, Chandrasekaran; Cabarcos, Orlando M.; Drawl, William R.; Allara, David L.; Ashok, S.; Horn, Mark W.; Bharadwaja, S. S. N.

    2011-11-15

    Cathode hysteresis in the reactive pulsed dc sputtering of a vanadium metal target was investigated to correlate the structural and electrical properties of the resultant vanadium oxide thin films within the framework of Berg's model [Berg et al., J. Vac. Sci. Technol. A 5, 202 (1987)]. The process hysteresis during reactive pulsed dc sputtering of a vanadium metal target was monitored by measuring the cathode (target) current under different total gas flow rates and oxygen-to-argon ratios for a power density of {approx}6.6.W/cm{sup 2}. Approximately 20%-25% hysteretic change in the cathode current was noticed between the metallic and oxidized states of the V-metal target. The extent of the hysteresis varied with changes in the mass flow of oxygen as predicted by Berg's model. The corresponding microstructure of the films changed from columnar to equiaxed grain structure with increased oxygen flow rates. Micro-Raman spectroscopy indicates subtle changes in the film structure as a function of processing conditions. The resistivity, temperature coefficient of resistance, and charge transport mechanism, obeying the Meyer-Neldel relation [Meyer and Neldel, Z. Tech. Phys. (Leipzig) 12, 588 (1937)], were correlated with the cathode current hysteric behavior.

  4. Flexible thin-film battery based on graphene-oxide embedded in solid polymer electrolyte.

    PubMed

    Kammoun, M; Berg, S; Ardebili, H

    2015-11-07

    Enhanced safety of flexible batteries is an imperative objective due to the intimate interaction of such devices with human organs such as flexible batteries that are integrated with touch-screens or embedded in clothing or space suits. In this study, the fabrication and testing of a high performance thin-film Li-ion battery (LIB) is reported that is both flexible and relatively safer compared to the conventional electrolyte based batteries. The concept is facilitated by the use of solid polymer nanocomposite electrolyte, specifically, composed of polyethylene oxide (PEO) matrix and 1 wt% graphene oxide (GO) nanosheets. The flexible LIB exhibits a high maximum operating voltage of 4.9 V, high capacity of 0.13 mA h cm(-2) and an energy density of 4.8 mW h cm(-3). The battery is encapsulated using a simple lamination method that is economical and scalable. The laminated battery shows robust mechanical flexibility over 6000 bending cycles and excellent electrochemical performance in both flat and bent configurations. Finite element analysis (FEA) of the LIB provides critical insights into the evolution of mechanical stresses during lamination and bending.

  5. Effect of ultraviolet light exposure to boron doped hydrogenated amorphous silicon oxide thin film

    NASA Astrophysics Data System (ADS)

    Baek, Seungsin; Iftiquar, S. M.; Jang, Juyeon; Lee, Sunhwa; Kim, Minbum; Jung, Junhee; Park, Hyeongsik; Park, Jinjoo; Kim, Youngkuk; Shin, Chonghoon; Lee, Youn-Jung; Yi, Junsin

    2012-11-01

    We have investigated the effect of ultraviolet (UV) light exposure to boron doped (p-type) hydrogenated amorphous silicon oxide (p-a-SiO:H) thin semiconductor films by measuring changes in its structural, electrical and optical properties. After a 50 h of UV light soaking (LS) of the films, that have 1.2, 6.9, 15.2, 25.3 at.% oxygen content (C(O)) and optical gap (E04) of 1.897, 2.080, 2.146 and 2.033 eV, show a relative increase in the C(O) by 28.0%, 9.8%, 2.0%, 3.1%, a relative increase in the Urbach energy (Eu) by 42%, 24%, 8%, 0%, decrease in the E04 by 66, 2, 12, 19 meV and the gap state defect density (Nd) show an increase by 6.5%, 3.4%, 0.7%, 0.1%. At higher oxygen content the observed UV light induced degradation (LID) is relatively less than that for films with lower oxygen content, indicating that higher oxides face less changes under the UV light.

  6. MOCVD-growth of thin zinc oxide films from zinc acetylacetonate and air

    NASA Astrophysics Data System (ADS)

    Pflitsch, Christian; Nebatti, Abdelkader; Brors, Georg; Atakan, Burak

    2012-06-01

    The metalorganic chemical vapour deposition (MOCVD) of thin zinc oxide films on borosilicate glass and silicon substrates in a hot-wall CVD-reactor (HWR) was studied. Zinc acetylacetonate (Zn(acac)2) and air were used as precursors. The aim of this work was to optimize the deposition parameters, such as pressure and deposition temperature, with respect to the film quality, structure, and homogeneity. Most experiments were performed at atmospheric pressure; this approach avoids the usage of an expensive vacuum system. It turned out that polycrystalline zinc oxide is grown at deposition temperatures above 613 K. Above 823 K, they additionally are c-axis orientated. At atmospheric pressure and lower temperature (<773 K) the film deposition is homogeneously over the whole tube furnace while at higher temperature inhomogeneous film growth and particle formation are observed, indicating a shift of the growth mechanism to the diffusion controlled regime. Although the homogeneity is improved by using higher flow velocities at atmospheric pressure, particle growth cannot be suppressed. Only at reduced pressure, which was 200 mbar in the present case, the deposition at 823 K is kinetically controlled and without particle formation, resulting in the homogeneous growth of well adhering ZnO films with c-axis orientation.

  7. CdS/CdTe thin-film devices using a Cd2SnO4 transparent conducting oxide

    NASA Astrophysics Data System (ADS)

    Wu, X.; Sheldon, P.; Coutts, T. J.; Rose, D. H.; Mulligan, W. P.; Moutinho, H. R.

    1997-02-01

    Transparent conducting oxide films of cadmium stannate (Cd2SnO4) have several significant advantages over conventional transparent conducting oxides. They are more conductive, more transparent, have lower surface roughness, are patternable, and are exceptionally stable. Cd2SnO4-based CdS/CdTe polycrystalline thin-film solar cells with efficiencies of 13.7% have been fabricated for the first time. Preliminary cell results have demonstrated that device performance can be enhanced by replacing the SnO2 layer with a Cd2SnO4 transparent conductive oxide.

  8. The nano-composite nature of vanadium oxide thin films for use in infrared microbolometers

    NASA Astrophysics Data System (ADS)

    Gauntt, Bryan Douglas

    2011-12-01

    The current generation of portable, un-cooled infrared imaging devices utilizes thin-film materials with large thermal coefficients of resistivity. Incoming photons are absorbed by the material, converted into heat, and result in a decrease in the resistivity of the thermal sensing layer. Vanadium oxide thin films are used in the majority of these devices as they typically have very large thermal coefficients of resistivity with low noise characteristics. In the work reported here, reactive pulsed DC sputtering was used to grow a systematic series of vanadium oxide thin films with resistivity ranging from 1 x 10-3 to 6.8 x 104 Ohm cm and TCR varying from 0 to 4% K-1. Throughout the parameter space studied, a transition from amorphous to nano-crystalline growth was observed. Films in the range of interest for a microbolometer, i.e. 1 x 10-3 to 10 Ohm cm, contain the face-centered cubic (FCC) VO x (0.8 < x < 1.3) phase. Films with larger resistivity were found to be amorphous. Stoichiometry measurements via Rutherford backscattering spectroscopy place many of the nano-crystalline films outside of the FCC VO x phase field according to the bulk phase diagram. Electron diffraction in the transmission electron microscope confirmed the presence of a secondary oxygen-rich amorphous vanadium oxide phase. The oxygen-rich amorphous phase explains the discrepancy between the observed oxygen content, which is outside of the FCC VOx phase field, and the presence of FCC VOx, which is limited to a maximum oxygen content of x = 1.3. The resulting microstructure can be described as a nano-composite material composed of a low resistivity crystalline phase embedded in a high resistivity amorphous matrix. A mechanism has been proposed wherein the nano-composite structure of the films results from film growth in alternating oxygen deficient and oxygen rich regions in the chamber. While in the oxygen deficient region the nano-crystalline phase grows preferentially, and while in the

  9. Atomic Layer Deposited Thin Films for Dielectrics, Semiconductor Passivation, and Solid Oxide Fuel Cells

    NASA Astrophysics Data System (ADS)

    Xu, Runshen

    , ultra-thin layer of encapsulating ZnS is coated on the surface of GaSb and GaSb/InAs substrates. The 2 nm-thick ZnS film is found to provide a long-term protection against reoxidation for one order and a half longer times than prior reported passivation likely due to its amorphous structure without pinholes. Finally, a combination of binary ALD processes is developed and demonstrated for the growth of yttria-stabilized zirconia films using alkylamido-cyclopentadiengyls zirconium and tris(isopropyl-cyclopentadienyl)yttrium, as zirconium and yttrium precursors, respectively, with ozone being the oxidant. The desired cubic structure of YSZ films is apparently achieved after post-deposition annealing. Further, platinum is atomic layer deposited as electrode on YSZ (8 mol% of Yttria) within the same system. In order to control the morphology of as-deposited Pt thin structure, the nucleation behavior of Pt on amorphous and cubic YSZ is investigated. Three different morphologies of Pt are observed, including nanoparticle, porous and dense films, which are found to depend on the ALD cycle number and the structure and morphology of they underlying ALD YSZ films.

  10. High-throughput characterization of Pt supported on thin film oxide material libraries applied in the oxygen reduction reaction.

    PubMed

    Schäfer, Dominik; Mardare, Cezarina; Savan, Alan; Sanchez, Miguel D; Mei, Bastian; Xia, Wei; Muhler, Martin; Ludwig, Alfred; Schuhmann, Wolfgang

    2011-03-15

    Thin film metal oxide material libraries were prepared by sputter deposition of nanoscale Ti/Nb precursor multilayers followed by ex situ oxidation. The metal composition was varied from 6 at.% Nb to 27 at.% Nb. Additionally, thin wedge-type layers of Pt with a nominal thickness gradient from 0 to 5 nm were sputter-deposited on top of the oxides. The materials libraries were characterized with respect to metallic film composition, oxide thickness, phases, electrical conductivity, Pt thickness, and electrochemical activity for the oxygen reduction reaction (ORR). Electrochemical investigations were carried out by cyclic voltammetry using an automated scanning droplet cell. For a nominal Pt thickness >1 nm, no significant dependence of the ORR activity on the Pt thickness or the substrate composition was observed. However, below that critical thickness, a strong decrease of the surface-normalized activity in terms of reduction currents and potentials was observed. For such thin Pt layers, the conductivity of the substrate seems to have a substantial impact on the catalytic activity. Results from X-ray photoelectron spectroscopy (XPS) measurements suggest that the critical Pt thickness coincides with the transition from a continuous Pt film into isolated particles at decreasing nominal Pt thickness. In the case of isolated Pt particles, the activity of Pt decisively depends on its ability to exchange electrons with the oxide layer, and hence, a dependence on the substrate conductivity is rationalized.

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

    SciTech Connect

    Kizu, Takio E-mail: TSUKAGOSHI.Kazuhito@nims.go.jp; Mitoma, Nobuhiko; Tsukagoshi, Kazuhito E-mail: TSUKAGOSHI.Kazuhito@nims.go.jp; Miyanaga, Miki; Awata, Hideaki; Nabatame, Toshihide

    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 thin film transistors.

  12. Maria Goeppert-Mayer Award Talk: Novel Magnetism and Transport in Complex Oxide Thin Films, Multilayers and Nanostructures

    NASA Astrophysics Data System (ADS)

    Suzuki, Yuri

    2005-03-01

    In epitaxial complex oxide systems, epitaxial strain, cation substitution and nanofabrication are just some ways in which their magnetic, electronic and optical properties may be tuned. In addition, their surfaces and interfaces provide a rich playground for the exploration of novel magnetic properties not found in the bulk constituents and the development of functional interfaces to be incorporated into technological applications. We have probed magnetism in complex oxide materials through studies of epitaxial oxide thin films, nanostructures and junction devices. With our ability to control oxide film growth as well as our expertise in nanofabrication, we have been able to study the effects of surfaces and interfaces on magnetism in ultra-thin magnetic oxide films and magnetic oxide nanostructures. For example, we have found that the nature of local magnetic structure in submicron islands of colossal magnetoresistance (CMR) material reveals the importance of shape anisotropy as well as magnetostriction in determining the micromagnetics in such small CMR structures. We have also studied epitaxial oxide trilayer junctions composed of magnetite (Fe3O4) and doped manganite (La0.7Sr0.3MnO3) in which we have confirmed the theoretically predicted negative spin polarization of Fe3O4. Transport through the barrier can be understood in terms of hopping transport through localized states that preserves electron spin information.

  13. Excimer laser assisted re-oxidation of BaTiO{sub 3} thin films on Ni metal foils

    SciTech Connect

    Bharadwaja, S. S. N. Ko, S. W.; Qu, W.; Clark, T.; Rajashekhar, A.; Motyka, M.; Podraza, N.; Randall, C. A.; Trolier-McKinstry, S.

    2016-01-14

    Excimer laser assisted re-oxidation for reduced, crystallized BaTiO{sub 3} thin films on Ni-foils was investigated. It was found that the BaTiO{sub 3} can be re-oxidized at an oxygen partial pressure of ∼50 mTorr and substrate temperature of 350 °C without forming a NiO{sub x} interface layer between the film and base metal foil. The dielectric permittivity of re-oxidized films was >1000 with loss tangent values <2% at 100 Hz, 30 mV{sub rms} excitation signal. Electron Energy Loss Spectroscopy indicated that BaTiO{sub 3} thin films can be re-oxidized to an oxygen stoichiometry close to ∼3 (e.g., stoichiometric). High resolution cross sectional transmission electron microscopy showed no evidence of NiO{sub x} formation between the BaTiO{sub 3} and the Ni foil upon excimer laser re-oxidation. Spectroscopic ellipsometry studies on laser re-oxidized [001]{sub C} and [111]{sub C} BaTiO{sub 3} single crystals indicate that the re-oxidation of BaTiO{sub 3} single crystals is augmented by photo-excitation of the ozone, as well as laser pulse induced temperature and local stress gradients.

  14. Interfacial effects in oxide-polymer laminar composite thin film dielectrics for capacitor applications

    NASA Astrophysics Data System (ADS)

    Tewari, Pratyush

    Continuous increase in the density of active components on microelectronic chip/circuit board requires development of new capacitors with smaller size, weight and cost. Miniaturization in the size of capacitors demands development of high energy density dielectric materials, which are the core of parallel plate capacitors. Nano composite dielectrics comprising high polarizibility oxide fillers randomly dispersed in high breakdown strength polymer matrix are considered as a potential high energy density materials for capacitor applications. Large interfacial volume, generated due to introduction of nano fillers in polymer matrix, might have significant positive contribution towards energy storage in nano composites. However, percolation issues associated with nano fillers and generation of large interfacial volume in nano composites, where complex electric field distribution overlaps with interfacialy modified polymer lead to unclear understanding of polymer-filler interfacial interactions in nano composites. Hence, in the current work laminar composite double layered dielectric structures, which provide relatively simple local field distribution at the interface and ideal series connectivity between oxide and polymer, are used as a model system to understand polymer-oxide interfacial interactions. Interfacial effects are reported for both low permittivity (SiO2-Parylene C) and medium permittivity (ZrO2-P(VDF-TrFE)) laminar composite dielectrics. Pyrolytic vapor decomposition polymerization process was used to grow Parylene C thin films on gold and thermally grown SiO2 surfaces. Enhancement in crystallite dimension with post deposition annealing treatments of Parylene C thin films was found to reduce dielectric loss tangent and hence enhance its dielectric properties. Electric field and temperature dependant leakage current analysis suggested hopping as dominant conduction mechanism in Parylene C thin films. Parylene C thin films in laminar composites showed

  15. Metal Oxide Thin Film Transistors on Paper Substrate: Fabrication, Characterization, and Printing Process

    NASA Astrophysics Data System (ADS)

    Choi, Nack-Bong

    Flexible electronics is an emerging next-generation technology that offers many advantages such as light weight, durability, comfort, and flexibility. These unique features enable many new applications such as flexible display, flexible sensors, conformable electronics, and so forth. For decades, a variety of flexible substrates have been demonstrated for the application of flexible electronics. Most of them are plastic films and metal foils so far. For the fundamental device of flexible circuits, thin film transistors (TFTs) using poly silicon, amorphous silicon, metal oxide and organic semiconductor have been successfully demonstrated. Depending on application, low-cost and disposable flexible electronics will be required for convenience. Therefore it is important to study inexpensive substrates and to explore simple processes such as printing technology. In this thesis, paper is introduced as a new possible substrate for flexible electronics due to its low-cost and renewable property, and amorphous indium gallium zinc oxide (a-IGZO) TFTs are realized as the promising device on the paper substrate. The fabrication process and characterization of a-IGZO TFT on the paper substrate are discussed. a-IGZO TFTs using a polymer gate dielectric on the paper substrate demonstrate excellent performances with field effect mobility of ˜20 cm2 V-1 s-1, on/off current ratio of ˜106, and low leakage current, which show the enormous potential for flexible electronics application. In order to complement the n-channel a-IGZO TFTs and then enable complementary metal-oxide semiconductor (CMOS) circuit architectures, cuprous oxide is studied as a candidate material of p-channel oxide TFTs. In this thesis, a printing process is investigated as an alternative method for the fabrication of low-cost and disposable electronics. Among several printing methods, a modified offset roll printing that prints high resolution patterns is presented. A new method to fabricate a high resolution

  16. Preparation of transparent and conductive multicomponent Zn-In-Sn oxide thin films by vacuum arc plasma evaporation

    NASA Astrophysics Data System (ADS)

    Minami, Tadatsugu; Tsukada, Satoshi; Minamino, Youhei; Miyata, Toshihiro

    2005-07-01

    This article describes the preparation of transparent conducting oxide (TCO) thin films by a vacuum arc plasma evaporation (VAPE) method using multicomponent oxide materials composed of any combination of two of the following binary compounds: ZnO, In2O3, and SnO2. The resulting TCO thin films were prepared with high deposition rates with the desired chemical composition in the ZnO-In2O3, In2O3-SnO2, and SnO2-ZnO systems by altering the composition of the sintered oxide fragments used as the source materials. Minimum resistivities were obtained in amorphous In2O3-ZnO, SnO2-In2O3, and ZnO-SnO2 thin films that were prepared with a Zn content of about 8.5 at. %, an In content of about 46 at. %, and a Sn content of about 78 at. %, respectively. It was found that the electrical, optical and chemical properties in ZnO-SnO2 thin films prepared using the VAPE method could be controlled by altering the Sn content.

  17. Electronic structure investigation of atomic layer deposition ruthenium(oxide) thin films using photoemission spectroscopy

    SciTech Connect

    Schaefer, Michael E-mail: schlaf@mail.usf.edu; Schlaf, Rudy E-mail: schlaf@mail.usf.edu

    2015-08-14

    Analyzing and manipulating the electronic band line-up of interfaces in novel micro- and nanoelectronic devices is important to achieve further advancement in this field. Such band alignment modifications can be achieved by introducing thin conformal interfacial dipole layers. Atomic layer deposition (ALD), enabling angstrom-precise control over thin film thickness, is an ideal technique for this challenge. Ruthenium (Ru{sup 0}) and its oxide (RuO{sub 2}) have gained interest in the past decade as interfacial dipole layers because of their favorable properties like metal-equivalent work functions, conductivity, etc. In this study, initial results of the electronic structure investigation of ALD Ru{sup 0} and RuO{sub 2} films via photoemission spectroscopy are presented. These experiments give insight into the band alignment, growth behavior, surface structure termination, and dipole formation. The experiments were performed in an integrated vacuum system attached to a home-built, stop-flow type ALD reactor without exposing the samples to the ambient in between deposition and analysis. Bis(ethylcyclopentadienyl)ruthenium(II) was used as precursor and oxygen as reactant. The analysis chamber was outfitted with X-ray photoemission spectroscopy (LIXPS, XPS). The determined growth modes are consistent with a strong growth inhibition situation with a maximum average growth rate of 0.21 Å/cycle for RuO{sub 2} and 0.04 Å/cycle for Ru.{sup 0} An interface dipole of up to −0.93 eV was observed, supporting the assumption of a strongly physisorbed interface. A separate experiment where the surface of a RuO film was sputtered suggests that the surface is terminated by an intermediate, stable, non-stoichiometric RuO{sub 2}/OH compound whose surface is saturated with hydroxyl groups.

  18. Chemical bonding and optoelectrical properties of ruthenium doped yttrium oxide thin films

    SciTech Connect

    Yang, Lei; Han, Jiecai; Zhu, Jiaqi; Zhu, Yuankun; Schlaberg, H.Inaki

    2013-11-15

    Graphical abstract: IR transmittance of various transparent conductive materials (RYO films grown under RT, 400 °C and 600 °C, ITO films [2], Carbon Nano tube films [11], metal/dielectric multilayers [12]). - Highlights: • Y{sub 2}O{sub 3}:Ru (RYO) films were prepared on ZnS substrates by reactive magnetron sputtering. • Ru doping significantly decreases the resistivity and extends the transparent range. • Optical and electrical properties of RYO films can be tuned by substrate temperatures. • The RYO films exhibit excellent far-IR transmittance and electrical property. - Abstract: Highly infrared transparent conductive ruthenium doped yttrium oxide (RYO) films were deposited on zinc sulfide and glass substrates by reactive magnetron sputtering. The structural, optical, and electrical properties of the films as a function of growth temperature were studied. It is shown that the sputtered RYO thin films are amorphous and smooth surface is obtained. The infrared transmittance of the films increases with increasing the growth temperature. RYO films maintain greater than ∼65% transmittance over a wide wavelength range from 2.5 μm to 12 μm and the highest transmittance value reaches 73.3% at ∼10 μm. With increasing growth temperature, the resistivity changed in a wide range and lowest resistivity of about 3.36 × 10{sup −3} Ω cm is obtained at room temperature. The RYO thin films with high conductivity and transparency in IR spectral range would be suitable for infrared optical and electromagnetic shielding devices.

  19. Optimisation of amorphous zinc tin oxide thin film transistors by remote-plasma reactive sputtering

    NASA Astrophysics Data System (ADS)

    Niang, K. M.; Cho, J.; Heffernan, S.; Milne, W. I.; Flewitt, A. J.

    2016-08-01

    The influence of the stoichiometry of amorphous zinc tin oxide (a-ZTO) thin films used as the semiconducting channel in thin film transistors (TFTs) is investigated. A-ZTO has been deposited using remote-plasma reactive sputtering from zinc:tin metal alloy targets with 10%, 33%, and 50% Sn at. %. Optimisations of thin films are performed by varying the oxygen flow, which is used as the reactive gas. The structural, optical, and electrical properties are investigated for the optimised films, which, after a post-deposition annealing at 500 °C in air, are also incorporated as the channel layer in TFTs. The optical band gap of a-ZTO films slightly increases from 3.5 to 3.8 eV with increasing tin content, with an average transmission ˜90% in the visible range. The surface roughness and crystallographic properties of the films are very similar before and after annealing. An a-ZTO TFT produced from the 10% Sn target shows a threshold voltage of 8 V, a switching ratio of 108, a sub-threshold slope of 0.55 V dec-1, and a field effect mobility of 15 cm2 V-1 s-1, which is a sharp increase from 0.8 cm2 V-1 s-1 obtained in a reference ZnO TFT. For TFTs produced from the 33% Sn target, the mobility is further increased to 21 cm2 V-1 s-1, but the sub-threshold slope is slightly deteriorated to 0.65 V dec-1. For TFTs produced from the 50% Sn target, the devices can no longer be switched off (i.e., there is no channel depletion). The effect of tin content on the TFT electrical performance is explained in the light of preferential sputtering encountered in reactive sputtering, which resulted in films sputtered from 10% and 33% Sn to be stoichiometrically close to the common Zn2SnO4 and ZnSnO3 phases.

  20. Chemical vapor deposition and characterization of zinc oxide thin films and nanostructures

    NASA Astrophysics Data System (ADS)

    Liu, Xiang

    2003-07-01

    Zinc oxide (ZnO) is a wide band gap semiconductor material. It is a promising candidate for short wavelength optoelectronic devices. Single crystalline and nanocrystalline ZnO thin films have been grown by organo-metallic chemical vapor depositions in a pulsed organo-metallic beam epitaxy (POMBE) system. The structural and morphological properties of ZnO films strongly depend on growth conditions. For epitaxially grown ZnO films on sapphire under optimal conditions, excellent crystallinity have been confirmed by X-ray diffraction (XRD) and high resolution transmission electron microscopy (TEM) studies. Nanocrystalline films with columnar-shaped grains are grown with different grain sizes. With decreasing growth temperature, the morphology of POMBE grown ZnO goes through an transition from continuous thin film to nanorods. Well-aligned ZnO nanorods have been grown using two-step chemical vapor deposition methods. The growth mechanism is based on studies of ZnO nucleation. By controlling substrate temperature and oxygen concentration during the nucleation and growth steps, ZnO nanorods growth is achieved without any catalysts. High-resolution TEM studies show that ZnO nanorods are single crystals. Alignment of these nanorods depends on lattice match between ZnO and substrate. ZnO nanorods with different areal densities can be obtained by varying nucleation time. The photoluminescence (PL) spectra of nonorods have shown band edge emission at 380 nm with full width at half maximum (FWHM) of 106 meV which is comparable to films grown by molecular beam epitaxy (MBE). Green emissions are found to originate from oxygen vacancies and zinc interstitials; while orange-red emissions are attributed to oxygen interstitials. Optical properties of ZnO thin films and nanostructures are studied. Clear excitonic features observed in different optical measurements have proven good optical qualities of single crystal ZnO films. By alloying with magnesium, band gap of ZnO can be widened

  1. High Temperature - Thin Film Strain Gages Based on Alloys of Indium Tin Oxide

    NASA Technical Reports Server (NTRS)

    Gregory, Otto J.; Cooke, James D.; Bienkiewicz, Joseph M.

    1998-01-01

    A stable, high temperature strain gage based on reactively sputtered indium tin oxide (ITO) was demonstrated at temperatures up to 1050 C. These strain sensors exhibited relatively large, negative gage factors at room temperature and their piezoresistive response was both linear and reproducible when strained up to 700 micro-in/in. When cycled between compression and tension, these sensors also showed very little hysteresis, indicating excellent mechanical stability. Thin film strain gages based on selected ITO alloys withstood more than 50,000 strain cycles of +/- 500 micro-in/in during 180 hours of testing in air at 1000 C, with minimal drift at temperature. Drift rates as low as 0.0009%/hr at 1000 C were observed for ITO films that were annealed in nitrogen at 700 C prior to strain testing. These results compare favorably with state of the art 10 micro-m thick PdCr films deposited by NASA, where drift rates of 0.047%/hr at 1050 C were observed. Nitrogen annealing not only produced the lowest drift rates to date, but also produce the largest dynamic gage factors (G = 23.5). These wide bandgap, semiconductor strain sensors also exhibited moderately low temperature coefficients of resistance (TCR) at temperatures up to 1100 C, when tested in a nitrogen ambient. A TCR of +230 ppm/C over the temperature range 200 C < T < 500 C and a TCR of -469 ppm/C over the temperature range 600 C < T < 1100 C was observed for the films tested in nitrogen. However, the resistivity behavior changed considerably when the same films were tested in oxygen ambients. A TCR of -1560 ppm/C was obtained over the temperature range of 200 C < T < 1100 C. When similar films were protected with an overcoat or when ITO films were prepared with higher oxygen contents in the plasma, two distinct TCR's were observed. At T < 800 C, a linear TCR of -210 ppm/C was observed and at T > 800 C, a linear TCR of -2170 DDm/C was observed. The combination of a moderately low TCR and a relatively large gage

  2. Development of Liquid Crystal Display Panel Integrated with Drivers Using Amorphous In-Ga-Zn-Oxide Thin Film Transistors

    NASA Astrophysics Data System (ADS)

    Takeshi Osada,; Kengo Akimoto,; Takehisa Sato,; Masataka Ikeda,; Masashi Tsubuku,; Junichiro Sakata,; Jun Koyama,; Tadashi Serikawa,; Shunpei Yamazaki,

    2010-03-01

    We designed, prototyped, and evaluated a liquid crystal panel integrated with a gate driver and a source driver using amorphous In-Ga-Zn-oxide thin film transistors (TFTs). Using bottom-gate bottom-contact (BGBC) thin film transistors, superior characteristics could be obtained. We obtained TFT characteristics with little variation even when the thickness of the gate insulator (GI) film was reduced owing to etching of source/drain (S/D) wiring, which is a typical process for the BGBC TFT. Moreover, a favorable ON-state current was obtained even when an In-Ga-Zn-oxide layer was formed over the S/D electrode. Since the upper portion of the In-Ga-Zn-oxide layer is not etched, the BGBC structure is predicted to be effective in thinning the In-Ga-Zn-oxide layer in the future. Upon evaluation, we found that the prototyped liquid crystal panel integrated with the gate and source drivers using the TFTs with improved characteristics had stable drive.

  3. Oxidation Temperature Dependence of the Structural, Optical and Electrical Properties of SnO2 Thin Films

    NASA Astrophysics Data System (ADS)

    Boulainine, D.; Kabir, A.; Bouanane, I.; Boudjema, B.; Schmerber, G.

    2016-08-01

    In this work, SnO2 thin films were prepared by thermal oxidation of Sn in an oxygen-rich atmosphere. The Sn thin films were deposited onto Si (100) substrates by vacuum evaporation, and the properties of the oxide films were investigated as a function of the oxidation temperature. The x-ray diffraction patterns showed that the obtained films have a polycrystalline structure with a preferential orientation along the (101) plane. The film oxidized at 500°C was not completely oxidized. The grain growth of the films was controlled by the pore mobility process. The UV-Vis reflectance spectra revealed an increase in both the refractive index and density of the films, reflecting the densification of the investigated films. The band gap energy decreased from 3.78 eV to 3.62 eV, caused by an increase in charge carrier density due to increased grain size. The increase in film thickness can be explained by the upward diffusion of tin atoms into the oxide film surface and the downward diffusion of oxygen atoms into the metal. The increase in the O/Sn ratio, determined from Rutherford backscattering spectroscopy, indicated enhanced material stoichiometry. Electrical resistivity decreased from 9.7 × 10-3 Ω cm to 1.7 × 10-4 Ω cm, which was attributed to the increased grain size.

  4. Observation of in situ oxidation dynamics of vanadium thin film with ambient pressure X-ray photoemission spectroscopy

    NASA Astrophysics Data System (ADS)

    Kim, Geonhwa; Yoon, Joonseok; Yang, Hyukjun; Lim, Hojoon; Lee, Hyungcheol; Jeong, Changkil; Yun, Hyungjoong; Jeong, Beomgyun; Crumlin, Ethan; Lee, Jouhahn; Lee, Jaeyoung; Ju, Honglyoul; Mun, Bongjin Simon

    2016-11-01

    The evolution of oxidation/reduction states of vanadium oxide thin film was monitored in situ as a function of oxygen pressure and temperature via ambient pressure X-ray photoemission spectroscopy. Spectra analysis showed that VO2 can be grown at a relatively low temperature, T ˜ 523 K, and that V2O5 oxide develops rapidly at elevated oxygen pressure. Raman spectroscopy was applied to confirm the formation of VO2 oxide inside of the film. In addition, the temperature-dependent resistivity measurement on the grown thin film, e.g., 20 nm exhibited a desirable metal-insulator transition of VO2 with a resistivity change of ˜1.5 × 103 times at 349.3 K, displaying typical characteristics of thick VO2 film, e.g., 100 nm thick. Our results not only provide important spectroscopic information for the fabrication of vanadium oxides, but also show that high quality VO2 films can be formed at relatively low temperature, which is highly critical for engineering oxide film for heat-sensitive electronic devices.

  5. A novel synthesis of tin oxide thin films by the sol-gel process for optoelectronic applications

    SciTech Connect

    Marikkannan, M.; Vishnukanthan, V.; Vijayshankar, A.; Mayandi, J.; Pearce, J. M.

    2015-02-15

    A novel and simple chemical method based on sol-gel processing was proposed to deposit metastable orthorhombic tin oxide (SnOx) thin films on glass substrates at room temperature. The resultant samples are labeled according to the solvents used: ethanol (SnO-EtOH), isopropanol (SnO-IPA) and methanol (SnO-MeOH). The variations in the structural, morphological and optical properties of the thin films deposited using different solvents were characterized by X-ray diffraction, atomic force microscopy, Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, UV-vis spectroscopy and photoluminescence (PL) analysis. The XRD patterns confirm that all the films, irrespective of the solvents used for preparation, were polycrystalline in nature and contained a mixed phases of tin (II) oxide and tin (IV) oxide in a metastable orthorhombic crystal structure. FTIR spectra confirmed the presence of Sn=O and Sn-O in all of the samples. PL spectra showed a violet emission band centered at 380 nm (3.25 eV) for all of the solvents. The UV-vis spectra indicated a maximum absorption band shown at 332 nm and the highest average transmittance around 97% was observed for the SnO-IPA and SnO-MeOH thin film samples. The AFM results show variations in the grain size with solvent. The structural and optical properties of the SnO thin films indicate that this method of fabricating tin oxide is promising and that future work is warranted to analyze the electrical properties of the films in order to determine the viability of these films for various transparent conducting oxide applications.

  6. Growth and oxidation of thin film Al{sub 2}Cu

    SciTech Connect

    Son, K.A.; Missert, N.A.; Barbour, J.C.; Hren, J.J.; Copeland, R.G.; Minor, K.G.

    1999-11-09

    Al{sub 2}Cu thin films ({approximately}382 nm) are fabricated by melting and resolidifying Al/Cu bilayers in the presence of a {approximately}3 nm Al{sub 2}O{sub 3} passivating layer. X-ray Photoelectron Spectroscopy (XPS) measures a 1.0 eV shift of the Cu2p{sub 3/2} peak and a 1.6 eV shift of the valence band relative to metallic Cu upon Al{sub 2}Cu formation. Scanning Electron Microscopy (SEM) and Electron Back-Scattered Diffraction (EBSD) show that the Al{sub 2}Cu film is composed of 30--70 {mu}m wide and 10--25 mm long cellular grains with (110) orientation. The atomic composition of the film as estimated by Energy Dispersive Spectroscopy (EDS) is 67{+-}2% Al and 33{+-}2% Cu. XPS scans of Al{sub 2}O{sub 3}/Al{sub 2}Cu taken before and after air exposure indicate that the upper Al{sub 2}Cu layers undergo further oxidation to Al{sub 2}O{sub 3} even in the presence of {approximately}5 nm Al{sub 2}O{sub 3}. The majority of Cu produced from oxidation is believed to migrate below the Al{sub 2}O{sub 3} layers, based upon the lack of evidence for metallic Cu in the XPS scans. In contrast to Al/Cu passivated with Al{sub 2}O{sub 3}, melting/resolidifying the Al/Cu bilayer without Al{sub 2}O{sub 3} results in phase-segregated dendritic film growth.

  7. The effect of annealing temperature on the stability of gallium tin zinc oxide thin film transistors

    NASA Astrophysics Data System (ADS)

    Nguyen, Ngoc; McCall, Briana; Alston, Robert; Collis, Ward; Iyer, Shanthi

    2015-10-01

    With the growing need for large area display technology and the push for a faster and cheaper alternative to the current amorphous indium gallium zinc oxide (a-IGZO) as the active channel layer for pixel-driven thin film transistors (TFTs) display applications, gallium tin zinc oxide (GSZO) has shown to be a promising candidate due to the similar electronic configuration of Sn4+ and In3+. In this work TFTs of GSZO sputtered films with only a few atomic % of Ga and Sn have been fabricated. A systematic and detailed comparison has been made of the properties of the GSZO films annealed at two temperatures: 140 °C and 450 °C. The electrical and optical stabilities of the respective devices have been studied to gain more insight into the degradation mechanism and are correlated with the initial TFT performance prior to the application of stress. Post deposition annealing at 450 °C of the films in air was found to lead to a higher atomic concentration of Sn4+ in these films and a superior quality of the film, as attested by the higher film density and less surface and interface roughness in comparison to the lower annealed temperature device. These result in significantly reduced shallow and deep interface traps with improved performance of the device exhibiting VON of -3.5 V, ION/IOFF of 108, field-effect mobility (μFE) of 4.46 cm2 V-1s-1, and sub-threshold swing of 0.38 V dec-1. The device is stable under both electrical and optical bias for wavelengths of 550 nm and above. Thus, this work demonstrates GSZO-based TFTs as a promising viable option to the IGZO TFTs by further tailoring the film composition and relevant processing temperatures.

  8. Hierarchically oriented macroporous anode-supported solid oxide fuel cell with thin ceria electrolyte film.

    PubMed

    Chen, Yu; Zhang, Yanxiang; Baker, Jeffrey; Majumdar, Prasun; Yang, Zhibin; Han, Minfang; Chen, Fanglin

    2014-04-09

    Application of anode-supported solid oxide fuel cell (SOFC) with ceria based electrolyte has often been limited by high cost of electrolyte film fabrication and high electrode polarization. In this study, dense Gd0.1Ce0.9O2 (GDC) thin film electrolytes have been fabricated on hierarchically oriented macroporous NiO-GDC anodes by a combination of freeze-drying tape-casting of the NiO-GDC anode, drop-coating GDC slurry on NiO-GDC anode, and co-firing the electrolyte/anode bilayers. Using 3D X-ray microscopy and subsequent analysis, it has been determined that the NiO-GDC anode substrates have a porosity of around 42% and channel size from around 10 μm at the electrolyte side to around 20 μm at the other side of the NiO-GDC (away from the electrolyte), indicating a hierarchically oriented macroporous NiO-GDC microstructure. Such NiO-GDC microstructure shows a tortuosity factor of ∼1.3 along the thickness direction, expecting to facilitate gas diffusion in the anode during fuel cell operation. SOFCs with such Ni-GDC anode, GDC film (30 μm) electrolyte, and La0.6Sr0.4Co0.2Fe0.8O3-GDC (LSCF-GDC) cathode show significantly enhanced cell power output of 1.021 W cm(-2) at 600 °C using H2 as fuel and ambient air as oxidant. Electrochemical Impedance Spectroscopy (EIS) analysis indicates a decrease in both activation and concentration polarizations. This study has demonstrated that freeze-drying tape-casting is a very promising approach to fabricate hierarchically oriented porous substrate for SOFC and other applications.

  9. Novel enhancement of thin-form-factor galvanic cells: Probing halogenated organic oxidizers and metal anodes

    NASA Astrophysics Data System (ADS)

    Cardenas-Valencia, Andres M.; Adornato, Lori; Short, R. Timothy; Langebrake, Larry

    The work reported herein demonstrates a novel method to improve the overall performance of thin-form-factor galvanic cells, fabricated via micro-electromechanical systems (MEMS) processes. Use of solid, low cost, cyclic-halogenated, organic catholyte materials permits water activation of cells consisting of metal anode and catalytic platinum positive electrodes. Similar cells, employing aluminum and zinc anodes, have been activated using sodium hypochlorite (NaClO) solutions, i.e. bleach, in the past. The oxidizers chosen for this study (bromo-, chloro- and iodo-succinimides, and sodium dichloroisocyanuric acid) supply the cathode's oxy-halogenated ions when in contact with water. Zinc, magnesium and aluminum anodes are utilized to fabricate galvanic cells. A comparison between these anodes, coupled with various oxidizers, is included herein. Results using aluminum anode cells show that, even though the utilization efficiency of the catholyte reagents is low (faradic efficiencies between 16 and 19%), the performance of the new water-activated cells (6 cm × 6 cm × 0.25 cm) is superior when compared to those activated with bleach. For instance, operational lives of 6 h (activation with 10% NaClO solution) increase to more than 30 h using the new approach, with a 100-ohm-load. It is also shown that specific energies of 90-110 Wh kg -1 (calculated to include both reagent and packaging mass) could be obtained using the described approach with current draws between 10 and 20 mA. The specific energies obtained suggest that novel MEMS-type cells could have much broader application than low-current, bleach-activated cells.

  10. Anisotropy, band-to-band transitions, phonon modes, and oxidation properties of cobalt-oxide core-shell slanted columnar thin films

    SciTech Connect

    Mock, Alyssa Korlacki, Rafał; Briley, Chad; Sekora, Derek; Schubert, Eva; Schubert, Mathias; Hofmann, Tino; Wilson, Peter; Sinitskii, Alexander

    2016-02-01

    Highly ordered and spatially coherent cobalt slanted columnar thin films (SCTFs) were deposited by glancing angle deposition onto silicon substrates, and subsequently oxidized by annealing at 475 °C. Scanning electron microscopy, Raman scattering, generalized ellipsometry, and density functional theory investigations reveal shape-invariant transformation of the slanted nanocolumns from metallic to transparent metal-oxide core-shell structures with properties characteristic of spinel cobalt oxide. We find passivation of Co-SCTFs yielding Co-Al{sub 2}O{sub 3} core-shell structures produced by conformal deposition of a few nanometers of alumina using atomic layer deposition fully prevents cobalt oxidation in ambient and from annealing up to 475 °C.

  11. Optical properties and oxidation of α-phase Ag–Al thin films

    NASA Astrophysics Data System (ADS)

    De Silva, Kaludewa S. B.; Keast, Vicki J.; Gentle, Angus; Cortie, Michael B.

    2017-03-01

    We investigate a series of Ag–Al thin films containing up to 12 at% Al with the purpose of discovering whether these alloys would be a better choice for nanophotonic applications than pure Ag. Variable angle spectroscopic ellipsometry, AFM, x-ray diffraction and density functional theory are applied to explore and characterize the materials. Electromagnetic simulations of optical properties are used to place the results into a theoretical framework. We find that the increase in electron-to-atom ratio associated with the Al additions changes the optical properties: additions of the order of 1–2 at% Al are beneficial as they are associated with favorable changes in the dielectric function, but for greater additions of Al there is a flattening of the absorption edge and an increase in optical loss. In addition, contents of more than about 2 at% Al are associated with the onset of time-dependent intergranular oxidation, which causes a pronounced dip in the reflectance spectrum at about 2.3–2.4 eV (∼500–540 nm).

  12. Nitrogen-doped amorphous oxide semiconductor thin film transistors with double-stacked channel layers

    NASA Astrophysics Data System (ADS)

    Xie, Haiting; Wu, Qi; Xu, Ling; Zhang, Lei; Liu, Guochao; Dong, Chengyuan

    2016-11-01

    The amorphous oxide semiconductor (AOS) thin film transistors (TFTs) with the double-stacked channel layers (DSCL) combing the amorphous InZnO (a-IZO) films and the nitrogen-doped amorphous InGaZnO (a-IGZO:N) films were proposed and fabricated, which showed the excellent performance with the field-effect mobility of 49.6 cm2 V-1 s-1 and the subthreshold swing of 0.5 V/dec. More interestingly, very stable properties were observed in the bias stress and light illumination tests for these a-IZO/a-IGZO:N TFTs, as seemed to be the evident improvements over the prior arts. The improved performance and stability might be mainly due to the hetero-junctions in the channel layers and less interface/bulk trap density from the in situ nitrogen doping process in the a-IGZO layers. In addition, the passivation effect of the a-IGZO:N films also made some contributions to the stable properties exhibited in these novel DSCL TFTs.

  13. Mechanical Flexibility of Zinc Oxide Thin-Film Transistors Prepared by Transfer Printing Method

    NASA Astrophysics Data System (ADS)

    Eun, K. T.; Hwang, W. J.; Sharma, B. K.; Ahn, J. H.; Lee, Y. K.; Choa, S. H.

    In the present study, we demonstrate the performance of Zinc oxide thin film transistors (ZnO TFTs) array subjected to the strain under high bending test and the reliability of TFTs was confirmed for the bending fatigue test of 2000 cycles. Initially, ZnO TFTs were fabricated on Si substrate and subsequently transferred on flexible PET substrate using transfer printing process. It was observed that when the bending radius reached ≥ 11 mm then cracks start to initiate first at SiO2 bridges, acting as interconnecting layers among individual TFT. Whatever the strain is applied to the devices, it is almost equivalently adopted by the SiO2 bridges, as they are relatively weak compared to rest of the part. The initial cracking of destructed SiO2 bridge leads to the secondary cracks to the ITO electrodes upon further increment of bending radius. Numerical simulation suggested that the strain of SiO2 layer reached to fracture level of 0.55% which was concentrated at the edge of SiO2 bridge layer. It also suggests that the round shape of SiO2 bridge can be more fruitful to compensate the stress concentration and to prevent failure of device.

  14. Electrical properties of magnesium incorporated zinc tin oxide thin film transistors by solution process.

    PubMed

    Jeon, In Young; Lee, Ji Yoon; Yoon, Dae Ho

    2013-03-01

    Zinc tin oxide (ZTO) films were fabricated on SiO2/Si substrate as a function of Mg concentration (the ratio of 3 to 10 atomic%) using a spin-coating process. For the characterization of thin film transistors (TFTs), Zn0.3Sn0.70 channel TFT exhibited a higher on/off ratio compared to Zn0.5 Sn.0.5O channel TFT because the higher Sn concentration can induce more charge carriers. 3 atomic% Mg incorporated Zn0.3Sn0.7O channel TFTs showed stable electrical performances such as I(on/off) - 1 x 10(7), micro(sat) = 1.40 cm2 V(-1) s(-1), and S = 0.39 V/decade. However, 10 atomic% Mg incorporated Zn0.3Sn0.7O channel TFTs deteriorated their electrical performances due to Mg segregation. The Mg incorporated Zn0.3Sn0.7O channel TFTs effectively suppress off-current and threshold voltage change during positive gate bias stress due to their strong bonding with oxygen.

  15. Facile design of ultra-thin anodic aluminum oxide membranes for the fabrication of plasmonic nanoarrays

    NASA Astrophysics Data System (ADS)

    Hao, Qi; Huang, Hao; Fan, Xingce; Hou, Xiangyu; Yin, Yin; Li, Wan; Si, Lifang; Nan, Haiyan; Wang, Huaiyu; Mei, Yongfeng; Qiu, Teng; Chu, Paul K.

    2017-03-01

    Ultra-thin anodic aluminum oxide (AAO) membranes are efficient templates for the fabrication of patterned nanostructures. Herein, a three-step etching method to control the morphology of AAO is described. The morphological evolution of the AAO during phosphoric acid etching is systematically investigated and a nonlinear growth mechanism during unsteady-state anodization is revealed. The thickness of the AAO can be quantitatively controlled from ∼100 nm to several micrometers while maintaining the tunablity of the pore diameter. The AAO membranes are robust and readily transferable to different types of substrates to prepare patterned plasmonic nanoarrays such as nanoislands, nanoclusters, ultra-small nanodots, and core–satellite superstructures. The localized surface plasmon resonance from these nanostructures can be easily tuned by adjusting the morphology of the AAO template. The custom AAO template provides a platform for the fabrication of low-cost and large-scale functional nanoarrays suitable for fundamental studies as well as applications including biochemical sensing, imaging, photocatalysis, and photovoltaics.

  16. Optical properties and oxidation of α-phase Ag-Al thin films.

    PubMed

    De Silva, Kaludewa S B; Keast, Vicki J; Gentle, Angus; Cortie, Michael B

    2017-03-03

    We investigate a series of Ag-Al thin films containing up to 12 at% Al with the purpose of discovering whether these alloys would be a better choice for nanophotonic applications than pure Ag. Variable angle spectroscopic ellipsometry, AFM, x-ray diffraction and density functional theory are applied to explore and characterize the materials. Electromagnetic simulations of optical properties are used to place the results into a theoretical framework. We find that the increase in electron-to-atom ratio associated with the Al additions changes the optical properties: additions of the order of 1-2 at% Al are beneficial as they are associated with favorable changes in the dielectric function, but for greater additions of Al there is a flattening of the absorption edge and an increase in optical loss. In addition, contents of more than about 2 at% Al are associated with the onset of time-dependent intergranular oxidation, which causes a pronounced dip in the reflectance spectrum at about 2.3-2.4 eV (∼500-540 nm).

  17. Facile design of ultra-thin anodic aluminum oxide membranes for the fabrication of plasmonic nanoarrays.

    PubMed

    Hao, Qi; Huang, Hao; Fan, Xingce; Hou, Xiangyu; Yin, Yin; Li, Wan; Si, Lifang; Nan, Haiyan; Wang, Huaiyu; Mei, Yongfeng; Qiu, Teng; Chu, Paul K

    2017-03-10

    Ultra-thin anodic aluminum oxide (AAO) membranes are efficient templates for the fabrication of patterned nanostructures. Herein, a three-step etching method to control the morphology of AAO is described. The morphological evolution of the AAO during phosphoric acid etching is systematically investigated and a nonlinear growth mechanism during unsteady-state anodization is revealed. The thickness of the AAO can be quantitatively controlled from ∼100 nm to several micrometers while maintaining the tunablity of the pore diameter. The AAO membranes are robust and readily transferable to different types of substrates to prepare patterned plasmonic nanoarrays such as nanoislands, nanoclusters, ultra-small nanodots, and core-satellite superstructures. The localized surface plasmon resonance from these nanostructures can be easily tuned by adjusting the morphology of the AAO template. The custom AAO template provides a platform for the fabrication of low-cost and large-scale functional nanoarrays suitable for fundamental studies as well as applications including biochemical sensing, imaging, photocatalysis, and photovoltaics.

  18. Vanadium oxide thin films for bolometric applications deposited by reactive pulsed dc sputtering

    SciTech Connect

    Fieldhouse, N.; Pursel, S. M.; Carey, R.; Horn, M. W.; Bharadwaja, S. S. N.

    2009-07-15

    Vanadium oxide (VO{sub x}) thin films were deposited by reactive pulse dc magnetron sputtering process using a pure vanadium metal target. The structural, microstructure, and electrical properties were correlated as a function of processing parameters such as substrate temperature, Ar:O partial pressures ratios, and pulsed dc power to fabricate these films. The VO{sub x} films deposited at various substrate temperatures between 30 and 300 degree sign C using a range of oxygen to argon partial pressure ratios exhibited huge variation in their microstructure even though most of them are amorphous to x-ray diffraction technique. In addition, the electrical properties such as temperature coefficient of resistance (TCR), resistivity, and noise levels were influenced by film microstructure. The TCRs of the VO{sub x} films were in the range of -1.1% to -2.4% K{sup -1} having resistivity values of 0.1-100 {Omega} cm. In particular, films grown at lower substrate temperatures with higher oxygen partial pressures have shown finer columnar grain structure and exhibited larger TCR and resistivity.

  19. Formation and stability of lanthanum oxide thin films deposited from β-diketonate precursor

    NASA Astrophysics Data System (ADS)

    Nieminen, Minna; Putkonen, Matti; Niinistö, Lauri

    2001-04-01

    Lanthanum oxide thin film deposition by atomic layer epitaxy (ALE) was studied at 180-425°C on soda-lime glass and Si(1 0 0) substrates using a β-diketonate type precursor La(thd) 3 and ozone. The chemical constituents of the films were analyzed by TOF-ERDA, RBS and FTIR while XRD and AFM were used to determine the crystallinity and surface morphology. Films grown below 275°C were amorphous La 2O 2CO 3, while at deposition temperatures above 300°C XRD patterns indicated that cubic La 2O 3 phase was formed. All the films were transparent and uniform with only small thickness variations. Carbonate type impurity was found in all films, but the carbon content of the films decreased with growth temperature being 3 at.% in films grown above 400°C. Hexagonal La 2O 3 was obtained when the films grown on silicon substrates were annealed at 800°C or above in a nitrogen flow. The as-deposited cubic and annealed hexagonal La 2O 3 films were found to be chemically unstable in ambient air since a transformation to monoclinic LaO(OH) and hexagonal La(OH) 3 was detected, respectively.

  20. Electrical instability of amorphous indium-gallium-zinc oxide thin film transistors under monochromatic light illumination

    NASA Astrophysics Data System (ADS)

    Huang, Xiaoming; Wu, Chenfei; Lu, Hai; Ren, Fangfang; Xu, Qingyu; Ou, Huiling; Zhang, Rong; Zheng, Youdou

    2012-06-01

    The electrical instability behaviors of a positive-gate-bias-stressed amorphous indium-gallium-zinc oxide (a-IGZO) thin film transistor (TFT) are studied under monochromatic light illumination. It is found that as the wavelength of incident light reduces from 750 nm to 450 nm, the threshold voltage of the illuminated TFT shows a continuous negative shift, which is caused by photo-excitation of trapped electrons at the channel/dielectric interface. Meanwhile, an increase of the sub-threshold swing (SS) is observed when the illumination wavelength is below 625 nm (˜2.0 eV). The SS degradation is accompanied by a simultaneous increase of the field effect mobility (μFE) of the TFT, which then decreases at even shorter wavelength beyond 540 nm (˜2.3 eV). The variation of SS and μFE is explained by a physical model based on generation of singly ionized oxygen vacancies (Vo+) and double ionized oxygen vacancies (Vo2+) within the a-IGZO active layer by high energy photons, which would form trap states near the mid-gap and the conduction band edge, respectively.

  1. Significant Enhancement in the Conductivity of Al-Doped Zinc Oxide thin Films for TCO Application

    NASA Astrophysics Data System (ADS)

    Mohite, R. M.; Ansari, J. N.; Roy, A. S.; Kothawale, R. R.

    2016-03-01

    Nanostructured Al-doped Zinc oxide (ZnO) thin films were deposited on glass substrate by chemical bath deposition (CBD) using aqueous zinc nitrate solution and subjected for different characterizations. Effect of Al3+ substitution on the properties of ZnO annealed at 400∘C was studied by XRD and UV-Vis for structural studies, SEM and TEM for surface morphology and DC four probe resistivity measurements for electrical properties. Al3+ substitution does not influence the morphology and well-known peaks related to wurtzite structure of ZnO. Electron microscopy (SEM and TEM) confirms rod shaped Al-doped ZnO nanocrystals with average width of 50nm. The optical band gap determined by UV-Visible spectroscopy was found to be in the range 3.37eV to 3.44eV. An EPR spectrum of AZO reveals peak at g=1.96 is due to shallow donors Zn interstitial. The DC electrical resistivity measurements of Al-doped ZnO show a minimum resistivity of 3.77×10-2Ω-cm. Therefore, these samples have potential use in n-type window layer in optoelectronic devices, organic solar cells, photonic crystals, photo-detectors, light emitting diodes (LEDs), gas sensors and chemical sensors.

  2. Biofouling Mitigation in Forward Osmosis Using Graphene Oxide Functionalized Thin-Film Composite Membranes.

    PubMed

    Perreault, François; Jaramillo, Humberto; Xie, Ming; Ude, Mercy; Nghiem, Long D; Elimelech, Menachem

    2016-06-07

    Forward osmosis (FO) is an emerging membrane process with potential applications in the treatment of highly fouling feedwaters. However, biofouling, the adhesion of microorganisms to the membrane and the subsequent formation of biofilms, remains a major limitation since antifouling membrane modifications offer limited protection against biofouling. In this study, we evaluated the use of graphene oxide (GO) for biofouling mitigation in FO. GO functionalization of thin-film composite membranes (GO-TFC) increased the surface hydrophilicity and imparted antimicrobial activity to the membrane without altering its transport properties. After 1 h of contact time, deposition and viability of Pseudomonas aeruginosa cells on GO-TFC were reduced by 36% and 30%, respectively, compared to pristine membranes. When GO-TFC membranes were tested for treatment of an artificial secondary wastewater supplemented with P. aeruginosa, membrane biofouling was reduced by 50% after 24 h of operation. This biofouling resistance is attributed to the reduced accumulation of microbial biomass on GO-TFC compared to pristine membranes. In addition, confocal microscopy demonstrated that cells deposited on the membrane surface are inactivated, resulting in a layer of dead cells on GO-TFC that limit biofilm formation. These findings highlight the potential of GO to be used for biofouling mitigation in FO.

  3. Fatigue mechanism of yttrium-doped hafnium oxide ferroelectric thin films fabricated by pulsed laser deposition.

    PubMed

    Huang, Fei; Chen, Xing; Liang, Xiao; Qin, Jun; Zhang, Yan; Huang, Taixing; Wang, Zhuo; Peng, Bo; Zhou, Peiheng; Lu, Haipeng; Zhang, Li; Deng, Longjiang; Liu, Ming; Liu, Qi; Tian, He; Bi, Lei

    2017-02-01

    Owing to their prominent stability and CMOS compatibility, HfO2-based ferroelectric films have attracted great attention as promising candidates for ferroelectric random-access memory applications. A major reliability issue for HfO2 based ferroelectric devices is fatigue. So far, there have been a few studies on the fatigue mechanism of this material. Here, we report a systematic study of the fatigue mechanism of yttrium-doped hafnium oxide (HYO) ferroelectric thin films deposited by pulsed laser deposition. The influence of pulse width, pulse amplitude and temperature on the fatigue behavior of HYO during field cycling is studied. The temperature dependent conduction mechanism is characterized after different fatigue cycles. Domain wall pinning caused by carrier injection at shallow defect centers is found to be the major fatigue mechanism of this material. The fatigued device can fully recover to the fatigue-free state after being heated at 90 °C for 30 min, confirming the shallow trap characteristic of the domain wall pinning defects.

  4. A physics-based model of threshold voltage for amorphous oxide semiconductor thin-film transistors

    NASA Astrophysics Data System (ADS)

    Chen, Chi-Le; Chen, Wei-Feng; Zhou, Lei; Wu, Wei-Jing; Xu, Miao; Wang, Lei; Peng, Jun-Biao

    2016-03-01

    In the application of the Lambert W function, the surface potential for amorphous oxide semiconductor thin-film transistors (AOS TFTs) under the subthreshold region is approximated by an asymptotic equation only considering the tail states. While the surface potential under the above-threshold region is approximated by another asymptotic equation only considering the free carriers. The intersection point between these two asymptotic equations represents the transition from the weak accumulation to the strong accumulation. Therefore, the gate voltage corresponding to the intersection point is defined as threshold voltage of AOS TFTs. As a result, an analytical expression for the threshold voltage is derived from this novel definition. It is shown that the threshold voltage achieved by the proposed physics-based model is agreeable with that extracted by the conventional linear extrapolation method. Furthermore, we find that the free charge per unit area in the channel starts increasing sharply from the threshold voltage point, where the concentration of the free carriers is a little larger than that of the localized carriers. The proposed model for the threshold voltage of AOS TFTs is not only physically meaningful but also mathematically convenient, so it is expected to be useful for characterizing and modeling AOS TFTs.

  5. A comparative study of fibrinogen adsorption onto metal oxide thin films

    NASA Astrophysics Data System (ADS)

    Silva-Bermudez, P.; Muhl, S.; Rodil, S. E.

    2013-10-01

    One of the first events occurring upon foreign material-biological medium contact is the adsorption of proteins, which evolution greatly determines the cells response to the material. Protein-surface interactions are a complex phenomenon driven by the physicochemical properties of the surface, protein(s) and liquid medium involve in the interaction. In this article the adsorption of fibrinogen (Fbg) onto Ta2O5, Nb2O5, TiO2 and ZrO2 thin films is reported. The adsorption kinetics and characteristics of the adsorbed fibrinogen layer were studied in situ using dynamic and spectroscopic ellipsometry. The films wettability, surface energy (γLW/AB) and roughness were characterized aiming to elucidate their correlations with Fbg adsorption. The adsorption rate changed accordingly to the film; the fastest adsorption rate and highest Fbg surface mass concentration (Γ) was observed on ZrO2. The hydrophobic/hydrophilic character of the oxide highly influenced Fbg adsorption. On Ta2O5, Nb2O5 and TiO2, which were either hydrophilic or in the breaking-point between hydrophilicity and hydrophobicity, Γ was correlated to the polar component of γLW/AB and roughness of the surface. On ZrO2, clearly hydrophobic, Γ increased significantly off the correlation observed for the other films. The results indicated different adsorption dynamics and orientations of the Fbg molecules dependent on the surface hydrophobic/hydrophilic character.

  6. Influence of pH of spray solution on optoelectronic properties of cadmium oxide thin films

    NASA Astrophysics Data System (ADS)

    Hodlur, R. M.; Rabinal, M. K.

    2015-03-01

    Highly conducting transparent cadmium oxide thin films were prepared by the conventional spray pyrolysis technique. The pH of the spray solution is varied by adding ammonia/hydrochloric acid. The effect of pH on the morphology, crystallinity and optoelectronic properties of these films is studied. The structural analysis showed all the films in the cubic phase. For the films with pH < 7 (acidic condition), the preferred orientation is along the (111) direction and for those with pH >7 (alkaline condition), the preferred orientation is along the (200) direction. A lowest resistivity of 9.9 × 10-4 Ω·cm (with carrier concentration = 5.1 × 1020 cm-3, mobility = 12.4 cm2/(V·s)) 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, the electrical conductivity of CdO films could be easily tuned by simply varying the pH of the spray solution without compromising the optical transparency.

  7. Phase control of iridium and iridium oxide thin films in atomic layer deposition

    SciTech Connect

    Kim, Sung-Wook; Kwon, Se-Hun; Kwak, Dong-Kee; Kang, Sang-Won

    2008-01-15

    The atomic layer deposition of iridium (Ir) and iridium oxide (IrO{sub 2}) films was investigated using an alternating supply of (ethylcyclopentadienyl)(1,5-cyclooctadiene) iridium and oxygen gas at temperatures between 230 and 290 deg. C. The phase transition between Ir and IrO{sub 2} occurred at the critical oxygen partial pressure during the oxygen injection pulse. The oxygen partial pressure was controlled by the O{sub 2}/(Ar+O{sub 2}) ratio or deposition pressures. The resistivity of the deposited Ir and IrO{sub 2} films was about 9 and 120 {mu}{omega} cm, respectively. In addition, the critical oxygen partial pressure for the phase transition between Ir and IrO{sub 2} was increased with increasing the deposition temperature. Thus, the phase of the deposited film, either Ir or IrO{sub 2}, was controlled by the oxygen partial pressure and the deposition temperature. However, the formation of a thin Ir layer was detected between the IrO{sub 2} and SiO{sub 2} substrate. To remove this interfacial layer, the oxygen partial pressure is increased to a severe condition. And the impurity contents were below the detection limit of Auger electron spectroscopy in both Ir and IrO{sub 2} films.

  8. Influence of post-annealing on electrical, structural and optical properties of vanadium oxide thin films

    NASA Astrophysics Data System (ADS)

    Mustafa Öksüzoğlu, Ramis; Bilgiç, Pınar; Yıldırım, Mustafa; Deniz, Okan

    2013-06-01

    Vanadium oxide thin films were grown onto quartz substrates using the pulsed DC reactive magnetron sputtering technique at room temperature and afterwards post annealed under vacuum conditions in the temperature range from 75 to 230 °C. The electrical resistance, temperature coefficient of resistance (TCR), optical energy gap and structural properties were investigated. The films are amorphous, nanoscale grained V2O5 phase and the mean grain size increases with increasing temperature. Additionally, the post-annealing at 230 °C induces formation of both V2O5 and V4O9 phases and pinholes on the film surface. The temperature dependent variation of the electrical resistance indicates two activation energy areas corresponding to two TCR values for the films post annealed up to 180 °C, but only one activation area was found after annealing at 230 °C. Analyses of the absorption coefficient versus photon energy revealed a direct forbidden transition. The mean grain size and TCR values increase with increasing post-annealing temperature, whereas the optical energy gap and electrical resistance do not follow this tendency. The evolution of the structure and its correlation to the optical energy gap, electrical resistance, activation energy and TCR were discussed by means of the results obtained in the present study.

  9. Characterization and Electrochromic Properties of Vanadium Oxide Thin Films Prepared via Spray Pyrolysis

    NASA Astrophysics Data System (ADS)

    Mousavi, M.; Kompany, A.; Shahtahmasebi, N.; Bagheri-Mohagheghi, M.-M.

    2013-08-01

    Vanadium oxide thin films were grown on glass substrates using spray pyrolysis technique. The effects of substrate temperature, vanadium concentration in the initial solution and the solution spray rate on the nanostructural and the electrochromic properties of deposited films are investigated. Characterization and the electrochromic measurements were carried out using X-ray diffraction, scanning electron microscopy and cyclic voltammogram. XRD patterns showed that the prepared films have polycrystalline structure and are mostly mixed phases of orthorhombic α-V2O5 along with minor β-V2O5 and V4O9 tetragonal structures. The preferred orientation of the deposited films was found to be along [101] plane. The cyclic voltammogram results obtained for different samples showed that only the films with 0.2 M solution concentration, 5 ml/min solution spray rate and 450°C substrate temperature exhibit two-step electrochromic properties. The results show a correlation between cycle voltammogram, morphology and resistance of the films.

  10. Controlling preferred orientation and electrical conductivity of zinc oxide thin films by post growth annealing treatment

    NASA Astrophysics Data System (ADS)

    Kennedy, J.; Murmu, P. P.; Leveneur, J.; Markwitz, A.; Futter, J.

    2016-03-01

    We report the microstructural evolution of the preferred orientation and electrical conductivity of zinc oxide (ZnO) thin films prepared by ion beam sputtering. Elastic recoil detection analysis results showed 0.6 at% H in as-deposited film which decreased to 0.35 at% in air annealed film due to H diffusion. XRD results showed that the preferred orientation can be tuned by selecting annealing conditions. Vacuum annealed films exhibited (1 0 0) orientation, whereas air annealed film showed (0 0 2) orientation. The annealing conditions caused a dramatic increase in the resistivity of air annealed films (∼106 Ω cm), whereas vacuum annealed films showed lower resistivity (∼10-2 Ω cm). High resistivity in air annealed film is attributed to the lack of hydrogen interstitials and hydrogen-oxygen vacancy complexes. Raman results supported the XRD results which demonstrated that annealing assisted in recovery of the crystalline disorder in as-deposited films. Air annealed film exhibited the highest optical transmission (89.7%) in the UV-vis region compared to as-deposited and vacuum annealed films (∼85%). Optical bandgap was found to vary between 3.11 eV and 3.18 eV in as-deposited and annealed films, respectively. The bandgap narrowing is associated with the intrinsic defects which introduced defect states resulting in band tail in ZnO films.

  11. Mesoporous tin-doped indium oxide thin films: effect of mesostructure on electrical conductivity

    NASA Astrophysics Data System (ADS)

    von Graberg, Till; Hartmann, Pascal; Rein, Alexander; Gross, Silvia; Seelandt, Britta; Röger, Cornelia; Zieba, Roman; Traut, Alexander; Wark, Michael; Janek, Jürgen; Smarsly, Bernd M.

    2011-03-01

    We present a versatile method for the preparation of mesoporous tin-doped indium oxide (ITO) thin films via dip-coating. Two poly(isobutylene)-b-poly(ethyleneoxide) (PIB-PEO) copolymers of significantly different molecular weight (denoted as PIB-PEO 3000 and PIB-PEO 20000) are used as templates and are compared with non-templated films to clarify the effect of the template size on the crystallization and, thus, on the electrochemical properties of mesoporous ITO films. Transparent, mesoporous, conductive coatings are obtained after annealing at 500 °C these coatings have a specific resistance of 0.5 Ω cm at a thickness of about 100 nm. Electrical conductivity is improved by one order of magnitude by annealing under a reducing atmosphere. The two types of PIB-PEO block copolymers create mesopores with in-plane diameters of 20-25 and 35-45 nm, the latter also possessing correspondingly thicker pore walls. Impedance measurements reveal that the conductivity is significantly higher for films prepared with the template generating larger mesopores. Because of the same size of the primary nanoparticles, the enhanced conductivity is attributed to a higher conduction path cross section. Prussian blue was deposited electrochemically within the films, thus confirming the accessibility of their pores and their functionality as electrode material.

  12. Solution-processed zinc oxide nanoparticles/single-walled carbon nanotubes hybrid thin-film transistors

    NASA Astrophysics Data System (ADS)

    Liu, Fangmei; Sun, Jia; Qian, Chuan; Hu, Xiaotao; Wu, Han; Huang, Yulan; Yang, Junliang

    2016-09-01

    Solution-processed thin-film transistors (TFTs) are the essential building blocks for manufacturing the low-cost and large-area consumptive electronics. Herein, solution-processed TFTs based on the composites of zinc oxide (ZnO) nanoparticles and single-walled carbon nanotubes (SWCNTs) were fabricated by the methods of spin-coating and doctor-blading. Through controlling the weight of SWCNTs, the ZnO/SWCNTs TFTs fabricated by spin-coating demonstrated a field-effect mobility of 4.7 cm2/Vs and a low threshold voltage of 0.8 V, while the TFTs devices fabricated by doctor-blading technique showed reasonable electrical performance with a mobility of 0.22 cm2/Vs. Furthermore, the ion-gel was used as an efficient electrochemical gate dielectric because of its large electric double-layer capacitance. The operating voltage of all the TFTs devices is as low as 4.0 V. The research suggests that ZnO/SWCNTs TFTs have the potential applications in low-cost, large-area and flexible consumptive electronics, such as chemical-biological sensors and smart label.

  13. Density profile in thin films of polybutadiene on silicon oxide substrates: a TOF-NR study.

    PubMed

    Hoppe, E Tilo; Sepe, Alessandro; Haese-Seiller, Martin; Moulin, Jean-François; Papadakis, Christine M

    2013-08-27

    We have investigated thin films from fully deuterated polybutadiene (PB-d6) on silicon substrates with the aim of detecting and characterizing a possible interphase in the polymer film near the substrate using time-of-flight neutron reflectometry (TOF-NR). As substrates, thermally oxidized silicon wafers were either used as such or they were coated with triethylethoxysilyl modified 1,2-PB prior to deposition of the PB-d6 film. TOF-NR reveals that, for both substrates, the scattering length density (SLD) of the PB films decreases near the solid interface. The reduction of SLD is converted to an excess fraction of free volume. To further verify the existence of the interphase in PB-d6, we attempt to model the TOF-NR curves with density profiles which do not feature an interphase. These density profiles do not describe the TOF-NR curves adequately. We conclude that, near the solid interface, an interphase having an SLD lower than the bulk of the film is present.

  14. Electrical and optical properties of thin films consisting of tin-doped indium oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Ederth, J.; Johnsson, P.; Niklasson, G. A.; Hoel, A.; Hultåker, A.; Heszler, P.; Granqvist, C. G.; van Doorn, A. R.; Jongerius, M. J.; Burgard, D.

    2003-10-01

    Electrical transport and optical properties were investigated in porous thin films consisting of In2O3:Sn (indium tin oxide, ITO) nanoparticles with an initial crystallite size of ˜16 nm and a narrow size distribution. Temperature dependent resistivity was measured in the 77130 K and negative at t<130 K. Effects of annealing on the ITO nanoparticles were investigated by analyzing the spectral optical reflectance and transmittance using effective medium theory and accounting for ionized impurity scattering. Annealing was found to increase both charge carrier concentration and mobility. The ITO nanoparticles were found to have a resistivity as low as 2×10-4 Ω cm, which is comparable to the resistivity of dense high quality In2O3:Sn films. Particulate samples with a luminous transmittance exceeding 90% and a resistivity of ˜10-2 Ω cm were obtained.

  15. Investigation into the optoelectrical properties of tungsten oxide thin films annealed in an oxygen air

    SciTech Connect

    Arfaoui, A.; Ouni, B. Touihri, S.; Mannoubi, T.

    2014-12-15

    Tungsten oxide (WO{sub x}) thin film have been deposited onto glass substrates using the thermal vacuum evaporation technique, monitored by an annealing process in a variable oxygen atmosphere. Analysis by X-ray diffraction and Raman spectroscopy showed the structural changes from orthorhombic to monoclinic which depend on the annealing temperature and the oxygen content. AFM study shows that the increase of oxygen content leads to a decrease of the root-mean-square from 94.64 nm to 2 nm. Ellipsometric measurements have been used to evaluate the optical constants. Further, it is found that when the oxygen content increases, the band gap of the annealed layer varies from 3.01 eV to 3.52 eV by against, the Urbach energy decreases. The AC conductivity plot showed a universal power law according to the Jonscher model. Moreover, at high frequency semiconductor-to-metallic behavior has been observed. Finally, the effect of annealing in oxygen atmosphere on their structural modifications, morphological, optical properties and electrical conductivity are reported.

  16. Optical properties of tungsten oxide thin films with protons intercalated during sputtering

    SciTech Connect

    Yamada, Y.; Tajima, K.; Bao, S.; Okada, M.; Yoshimura, K.; Roos, A.

    2008-03-15

    Tungsten oxide thin films with protons intercalated during deposition (H{sub x}WO{sub 3}) were prepared using reactive direct-current-magnetron sputtering in a gas mixture of argon, oxygen, and hydrogen. The as-deposited films fabricated under suitable conditions were colored due to the formation of tungsten bronze. The concentration of intercalated protons, given by the x values in H{sub x}WO{sub 3}, was evaluated by ejecting protons electrochemically from the films. The x value of the films prepared at a constant working pressure was found to be proportional to the hydrogen flow ratio during deposition. On the other hand, the x value of the films prepared at a constant hydrogen flow ratio decreased sharply with increasing working pressure during deposition. The dispersion of the extinction coefficient ({kappa}) of the films was estimated by analyzing the experimental spectra of {psi} and {delta} measured with spectroscopic ellipsometry using the model composed of a homogeneous tungsten bronze layer with an additional surface roughness layer. As a result of this analysis, the {kappa} value was found to increase sharply with the number of intercalated protons. There was a linear dependence between the {kappa} value and the x value for x<0.2, while for x>0.3, the absorption saturated. This indicates that it is possible to evaluate the x value of H{sub x}WO{sub 3} films using spectroscopic ellipsometry.

  17. Chromium and Ruthenium-Doped Zinc Oxide Thin Films for Propane Sensing Applications

    PubMed Central

    Gómez-Pozos, Heberto; González-Vidal, José Luis; Torres, Gonzalo Alberto; Rodríguez-Baez, Jorge; Maldonado, Arturo; de la Luz Olvera, María; Acosta, Dwight Roberto; Avendaño-Alejo, Maximino; Castañeda, Luis

    2013-01-01

    Chromium and ruthenium-doped zinc oxide (ZnO:Cr) and (ZnO:Ru) thin solid films were deposited on soda-lime glass substrates by the sol-gel dip-coating method. A 0.6 M solution of zinc acetate dihydrate dissolved in 2-methoxyethanol and monoethanolamine was used as basic solution. Chromium (III) acetylacetonate and Ruthenium (III) trichloride were used as doping sources. The Ru incorporation and its distribution profile into the films were proved by the SIMS technique. The morphology and structure of the films were studied by SEM microscopy and X-ray diffraction measurements, respectively. The SEM images show porous surfaces covered by small grains with different grain size, depending on the doping element, and the immersions number into the doping solutions. The sensing properties of ZnO:Cr and ZnO:Ru films in a propane (C3H8) atmosphere, as a function of the immersions number in the doping solution, have been studied in the present work. The highest sensitivity values were obtained for films doped from five immersions, 5.8 and 900, for ZnO:Cr and ZnO:Ru films, respectively. In order to evidence the catalytic effect of the chromium (Cr) and ruthenium (Ru), the sensing characteristics of undoped ZnO films are reported as well. PMID:23482091

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

    SciTech Connect

    Jie Guan; Nguyen Minh

    2003-10-01

    This document summarizes the technical progress from April to September 2003 for the program, Material and Process Development Leading to Economical High-Performance Thin-Film Solid Oxide Fuel Cells, contract number DE-AC26-00NT40711. Characteristics of doped lanthanum gallate (LSGMF) powder suitable for thin electrolyte fabrication have been defined. Bilayers with thin LSGMF electrolyte supported on an anode were fabricated and the fabrication process was improved. Preliminary performance was characterized. High performance cathode material Sr{sub 0.5}Sm{sub 0.5}CoO{sub 3} has been down-selected and is being optimized by modifying materials characteristics and processing parameters. The selected cathode exhibited excellent performance with cathode polarization of {approx}0.23 ohm-cm{sup 2} at 600 C.

  19. Transparent conducting oxide contacts and textured metal back reflectors for thin film silicon solar cells

    NASA Astrophysics Data System (ADS)

    Franken, R. H.-J.

    2006-09-01

    With the growing population and the increasing environmental problems of the 'common' fossil and nuclear energy production, the need for clean and sustainable energy sources is evident. Solar energy conversion, such as in photovoltaic (PV) systems, can play a major role in the urgently needed energy transition in electricity production. At the present time PV module production is dominated by the crystalline wafer technology. Thin film silicon technology is an alternative solar energy technology that operates at lower efficiencies, however, it has several significant advantages, such as the possibility of deposition on cheap (flexible) substrates and the much smaller silicon material consumption. Because of the small thickness of the solar cells, light trapping schemes are needed in order to obtain enough light absorption and current generation. This thesis describes the research on thin film silicon solar cells with the focus on the optimization of the transparent conducting oxide (TCO) layers and textured metal Ag substrate layers for the use as enhanced light scattering back reflectors in n-i-p type of solar cells. First we analyzed ZnO:Al (TCO) layers deposited in an radio frequent (rf) magnetron deposition system equipped with a 7 inch target. We have focused on the improvement of the electrical properties without sacrificing the optical properties by increasing the mobility and decreasing the grain boundary density. Furthermore, we described some of the effects on light trapping of ZnO:Al enhanced back reflectors. The described effects are able to explain the observed experimental data. Furthermore, we present a relation between the surface morphology of the Ag back contact and the current enhancement in microcrystalline (muc-Si:H) solar cells. We show the importance of the lateral feature sizes of the Ag surface on the light scattering and introduce a method to characterize the quality of the back reflector by combining the vertical and lateral feature sizes

  20. 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.

  1. Easy and General Synthesis of Large-Sized Mesoporous Rare-Earth Oxide Thin Films by 'Micelle Assembly'.

    PubMed

    Li, Yunqi; Bastakoti, Bishnu Prasad; Imura, Masataka; Dai, Pengcheng; Yamauchi, Yusuke

    2015-12-01

    Large-sized (ca. 40 nm) mesoporous Er2O3 thin films are synthesized by using a triblock copolymer poly(styrene-b-2-vinyl pyridine-b-ethylene oxide) (PS-b-P2VP-b-PEO) as a pore directing agent. Each block makes different contributions and the molar ratio of PVP/Er(3+) is crucial to guide the resultant mesoporous structure. An easy and general method is proposed and used to prepare a series of mesoporous rare-earth oxide (Sm2O3, Dy2O3, Tb2O3, Ho2O3, Yb2O3, and Lu2O3) thin films with potential uses in electronics and optical devices.

  2. Controllable film densification and interface flatness for high-performance amorphous indium oxide based thin film transistors

    SciTech Connect

    Ou-Yang, Wei E-mail: TSUKAGOSHI.Kazuhito@nims.go.jp; Mitoma, Nobuhiko; Kizu, Takio; Gao, Xu; Lin, Meng-Fang; Tsukagoshi, Kazuhito E-mail: TSUKAGOSHI.Kazuhito@nims.go.jp; Nabatame, Toshihide

    2014-10-20

    To avoid the problem of air sensitive and wet-etched Zn and/or Ga contained amorphous oxide transistors, we propose an alternative amorphous semiconductor of indium silicon tungsten oxide as the channel material for thin film transistors. In this study, we employ the material to reveal the relation between the active thin film and the transistor performance with aid of x-ray reflectivity study. By adjusting the pre-annealing temperature, we find that the film densification and interface flatness between the film and gate insulator are crucial for achieving controllable high-performance transistors. The material and findings in the study are believed helpful for realizing controllable high-performance stable transistors.

  3. Physical/chemical properties of tin oxide thin film transistors prepared using plasma-enhanced atomic layer deposition

    SciTech Connect

    Lee, Byung Kook; Jung, Eunae; Kim, Seok Hwan; Moon, Dae Chul; Lee, Sun Sook; Park, Bo Keun; Hwang, Jin Ha; Chung, Taek-Mo; Kim, Chang Gyoun; An, Ki-Seok

    2012-10-15

    Thin film transistors (TFTs) with tin oxide films as the channel layer were fabricated by means of plasma enhanced atomic layer deposition (PE-ALD). The as-deposited tin oxide films show n-type conductivity and a nano-crystalline structure of SnO{sub 2}. Notwithstanding the relatively low deposition temperatures of 70, 100, and 130 °C, the bottom gate tin oxide TFTs show an on/off drain current ratio of 10{sup 6} while the device mobility values were increased from 2.31 cm{sup 2}/V s to 6.24 cm{sup 2}/V s upon increasing the deposition temperature of the tin oxide films.

  4. Crystallization kinetics of amorphous tin-doped indium oxide thin films

    NASA Astrophysics Data System (ADS)

    Ow-Yang, Cleva Wan

    The crystallization kinetics of amorphous tin-doped indium oxide thin films grown by dc magnetron sputtering and electron beam evaporation was investigated using time-resolved laser reflectivity in conjunction with TEM analyses. The as-grown films were established to be amorphous using glancing angle x-ray and selected area electron diffraction. The samples were then annealed at temperatures ranging from (˜111-167sp°C) some in a range of environments (oxidizing (Nsb2), strongly oxidizing (air), and reducing (wet/dry forming gas). Gross-sectional TEM analysis reveals a columnar as-sputtered microstructure that is retained after annealing to complete transformation. In contrast a-ITO films grown by evaporation show a uniformly dense microstructure. Annealing evaporated films in air produced films containing a wide distribution in grain sizes, while annealing in the more reducing environments yielded polycrystalline films with a narrow grain size distribution centered at 15 nm. Time-resolved laser reflectivity was an advantageous tool for monitoring the progress of the crystallization transformation because the technique generates quantifiable data while allowing real-time, non-contact observation. Plotting the transformation rate as a function of annealing temperature demonstrated the amorphous-to-crystalline transformation to be a thermally activated process. The energy required to crystallize sputtered a-ITO films in flowing Nsb2 is much lower than that for evaporated alpha-ITO films also in flowing Nsb2. XRD spectra of the as-sputtered a-ITO reveals the presence of an indium metal phase, which is not observed in the as-evaporated a-ITO films. The activation energy is most likely dependent on the presence of In metal, which serves as a catalyst for lowering the energy barrier. This is confirmed by the reduction in energy needed to transform evaporated a-ITO film in a reducing environment. In this study, the pre- and post-anneal microstructures were examined to

  5. Fabrication of Metal Oxide Thin Films Using the Langmuir-Blodgett Deposition Technique.

    NASA Astrophysics Data System (ADS)

    Johnson, David John

    studied in some detail, using two processes: thermal decomposition and decomposition via ultraviolet/ozone exposure. The second technique was found to reduce LB arachidate multilayers to a metal carbonate (at a rate of less than 1 minute per layer), which could be further decomposed into an oxide via a thermal treatment. The ultraviolet/ozone process allowed uniform films of CdO to be produced in addition to the thin films of Y_2O_3 , Er_2O_3 and La_2O_3 fabricated via either thermal or ultraviolet/ozone processing. Applications of the LB produced metal oxides were investigated. Electrical characterization of Y _2O_3 dielectric layers gave a permittivity of varepsilon~ 11.5 +/- 0.9 and good quality metal -oxide-semiconductor structures of <10 nm in thickness. Y_2O_3 coatings on 304 stainless steel were found to significantly reduce thermal oxidation of the steel at 800^ circC. Finally, La_2O _3 interface layers in PZT/Pt structures were found to have a significant effect on the nucleation and growth of the ferroelectric.

  6. Aqueous combustion synthesis of aluminum oxide thin films and application as gate dielectric in GZTO solution-based TFTs.

    PubMed

    Branquinho, Rita; Salgueiro, Daniela; Santos, Lídia; Barquinha, Pedro; Pereira, Luís; Martins, Rodrigo; Fortunato, Elvira

    2014-11-26

    Solution processing has been recently considered as an option when trying to reduce the costs associated with deposition under vacuum. In this context, most of the research efforts have been centered in the development of the semiconductors processes nevertheless the development of the most suitable dielectrics for oxide based transistors is as relevant as the semiconductor layer itself. In this work we explore the solution combustion synthesis and report on a completely new and green route for the preparation of amorphous aluminum oxide thin films; introducing water as solvent. Optimized dielectric layers were obtained for a water based precursor solution with 0.1 M concentration and demonstrated high capacitance, 625 nF cm(-2) at 10 kHz, and a permittivity of 7.1. These thin films were successfully applied as gate dielectric in solution processed gallium-zinc-tin oxide (GZTO) thin film transistors (TFTs) yielding good electrical performance such as subthreshold slope of about 0.3 V dec(-1) and mobility above 1.3 cm2 V(-1) s(-1).

  7. Copper Benzenetricarboxylate Metal-Organic Framework Nucleation Mechanisms on Metal Oxide Powders and Thin Films formed by Atomic Layer Deposition.

    PubMed

    Lemaire, Paul C; Zhao, Junjie; Williams, Philip S; Walls, Howard J; Shepherd, Sarah D; Losego, Mark D; Peterson, Gregory W; Parsons, Gregory N

    2016-04-13

    Chemically functional microporous metal-organic framework (MOF) crystals are attractive for filtration and gas storage applications, and recent results show that they can be immobilized on high surface area substrates, such as fiber mats. However, fundamental knowledge is still lacking regarding initial key reaction steps in thin film MOF nucleation and growth. We find that thin inorganic nucleation layers formed by atomic layer deposition (ALD) can promote solvothermal growth of copper benzenetricarboxylate MOF (Cu-BTC) on various substrate surfaces. The nature of the ALD material affects the MOF nucleation time, crystal size and morphology, and the resulting MOF surface area per unit mass. To understand MOF nucleation mechanisms, we investigate detailed Cu-BTC MOF nucleation behavior on metal oxide powders and Al2O3, ZnO, and TiO2 layers formed by ALD on polypropylene substrates. Studying both combined and sequential MOF reactant exposure conditions, we find that during solvothermal synthesis ALD metal oxides can react with the MOF metal precursor to form double hydroxy salts that can further convert to Cu-BTC MOF. The acidic organic linker can also etch or react with the surface to form MOF from an oxide metal source, which can also function as a nucleation agent for Cu-BTC in the mixed solvothermal solution. We discuss the implications of these results for better controlled thin film MOF nucleation and growth.

  8. Pulsed—Laser Deposition Of Oxide Thin Films And Laser—Induced Breakdown Spectroscopy Of Multi—Element Materials

    NASA Astrophysics Data System (ADS)

    Pedarnig, Johannes D.

    2010-10-01

    New results of the Linz group on pulsed—laser deposition (PLD) of oxide thin films and on laser—induced breakdown spectroscopy (LIBS) of multi-element materials are reported. High-Tc superconducting (HTS) films with enhanced critical current density Jc are produced by laser ablation of novel nano-composite ceramic targets. The targets contain insulating nano-particles that are embedded into the YBa2Cu3O7 matrix. Epitaxial double-layers of lithium-doped and aluminum-doped ZnO are deposited on r-cut sapphire substrates. Acoustic over-modes in the GHz range are excited by piezoelectric actuation of layers. Smooth films of rare-earth doped glass are produced by F2—laser ablation. The transport properties of HTS thin films are modified by light—ion irradiation. Thin film nano—patterning is achieved by masked ion beam irradiation. LIBS is employed to analyze trace elements in industrial iron oxide powder and reference polymer materials. Various trace elements of ppm concentration are measured in the UV/VIS and vacuum-UV spectral range. Quantitative LIBS analysis of major components in oxide materials is performed by calibration-free methods.

  9. The impact of thickness and thermal annealing on refractive index for aluminum oxide thin films deposited by atomic layer deposition.

    PubMed

    Wang, Zi-Yi; Zhang, Rong-Jun; Lu, Hong-Liang; Chen, Xin; Sun, Yan; Zhang, Yun; Wei, Yan-Feng; Xu, Ji-Ping; Wang, Song-You; Zheng, Yu-Xiang; Chen, Liang-Yao

    2015-01-01

    The aluminum oxide (Al2O3) thin films with various thicknesses under 50 nm were deposited by atomic layer deposition (ALD) on silicon substrate. The surface topography investigated by atomic force microscopy (AFM) revealed that the samples were smooth and crack-free. The ellipsometric spectra of Al2O3 thin films were measured and analyzed before and after annealing in nitrogen condition in the wavelength range from 250 to 1,000 nm, respectively. The refractive index of Al2O3 thin films was described by Cauchy model and the ellipsometric spectra data were fitted to a five-medium model consisting of Si substrate/SiO2 layer/Al2O3 layer/surface roughness/air ambient structure. It is found that the refractive index of Al2O3 thin films decrease with increasing film thickness and the changing trend revised after annealing. The phenomenon is believed to arise from the mechanical stress in ALD-Al2O3 thin films. A thickness transition is also found by transmission electron microscopy (TEM) and SE after 900°C annealing.

  10. Ultrafast carrier dynamics and third order nonlinear optical properties of aluminum doped zinc oxide (AZO) thin films

    NASA Astrophysics Data System (ADS)

    Htwe, Zin Maung; Zhang, Yun-Dong; Yao, Cheng-Bao; Li, Hui; Yuan, Ping

    2017-04-01

    Aluminum doped zinc oxide (AZO) thin films were fabricated by simultaneous RF/DC magnetron sputtering technique on sapphire (Al2O3) substrate with different DC sputtering power 2, 6, 8 and 10 W respectively. The sputtered thin films were annealed at 350 °C in order to improve the crystal quality. AZO thin films are systematically analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-VIS spectrometer for structural and optical properties. XRD patterns show that all sputtered thin films are well crystallized with hexagonal wurtzite structure. SEM images reveal the average crystallite sizes are increased after doping Al in ZnO which agreed with the calculated values from XRD. All thin films possess high optical transmittance in visible region and optical band gap values are relatively increased with Al concentration. The ultrafast transient absorption (TA) of AZO was analyzed by femtosecond pump-probe spectroscopy. The kinetic TA curves were fitted by tri-exponential decay function and obtained decay time constants are found to be in few picosecond and nanosecond range for ultrafast and slow processes respectively. Third order nonlinear optical absorption and refraction coefficients were investigated by using Z-scan technique. The observed nonlinear coefficients are enhanced with Al concentration in ZnO.

  11. Synthesis of ALD zinc oxide and thin film materials optimization for UV photodetector applications

    NASA Astrophysics Data System (ADS)

    Tapily, Kandabara Nouhoum

    Zinc oxide (ZnO) is a direct, wide bandgap semiconductor material. It is thermodynamically stable in the wurtzite structure at ambient temperature conditions. ZnO has very interesting optical and electrical properties and is a suitable candidate for numerous optoelectronic applications such as solar cells, LEDs and UV-photodetectors. ZnO is a naturally n-type semiconductor. Due to the lack of reproducible p-type ZnO, achieving good homojunction ZnO-based photodiodes such as UV-photodetectors remains a challenge. Meanwhile, heterojunction structures of ZnO with p-type substrates such as SiC, GaN, NiO, AlGaN, Si etc. are used; however, those heterojunction diodes suffer from low efficiencies. ZnO is an n-type material with numerous intrinsic defect levels responsible for the electrical and optical behaviors. Presently, there is no clear consensus about the origin of those defects. In this work, ZnO was synthesized by atomic layer deposition (ALD). ALD is a novel deposition technique suitable for nanotechnology engineering that provides unique features such as precise control of ZnO thin film with atomic resolution, high uniformity, good conformity and high aspect ratio. Using this novel deposition technique, the ALD ZnO deposition process was developed and optimized using diethyl zinc as the precursor for zinc and water vapor as the oxygen source. In order to optimize the film quality for use in electronic applications, the physical, mechanical and electrical properties were investigated. The structural and mechanical properties of the ALD ZnO thin films were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy (AFM), scanning electron microscopy (SEM), spectroscopic Ellipsometry, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, UV-VIS absorption and nanoindentation. The electrical characterizations were performed using C-V, I-V, DLTS, Hall Effect, and four-point probe. The intrinsic defects responsible

  12. Crystalline nanoporous metal oxide thin films by post-synthetic hydrothermal transformation: SnO2 and TiO2.

    PubMed

    Shao, Shaofeng; Dimitrov, Momtchil; Guan, Naijia; Köhn, Ralf

    2010-10-01

    Nanostructured and nanoporous metal oxide thin films are rarely accessible by standard synthetic approaches but highly desired for many applications, e.g. as electrodes, transparent conducting coatings, sensors or surface catalysts. Template based sol–gel chemistry combined with post-synthetic hydrothermal treatment allows now the synthesis of nanocrystalline mesostructured porous thin films of metal oxides, e.g. tin oxide and titania. Even in cases where the crystallization cannot be induced highly stable thin films can be achieved, e.g. niobium oxide thin films. We demonstrate how the size of the nanocrystallites influences and stabilizes the mesostructure at temperatures as low as 100 C and thereby in the case of titania or tin dioxide even prevents it from deterioration at higher temperatures up to 400–600 C.

  13. Facile and environmentally friendly solution-processed aluminum oxide dielectric for low-temperature, high-performance oxide thin-film transistors.

    PubMed

    Xu, Wangying; Wang, Han; Xie, Fangyan; Chen, Jian; Cao, Hongtao; Xu, Jian-Bin

    2015-03-18

    We developed a facile and environmentally friendly solution-processed method for aluminum oxide (AlOx) dielectrics. The formation and properties of AlOx thin films under various annealing temperatures were intensively investigated by thermogravimetric analysis-differential scanning calorimetry (TGA-DSC), X-ray diffraction (XRD), spectroscopic ellipsometry, atomic force microscopy (AFM), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), impedance spectroscopy, and leakage current measurements. The sol-gel-derived AlOx thin film undergoes the decomposition of organic residuals and nitrate groups, as well as conversion of aluminum hydroxides to form aluminum oxide, as the annealing temperature increases. Finally, the AlOx film is used as gate dielectric for a variety of low-temperature solution-processed oxide TFTs. Above all, the In2O3 and InZnO TFTs exhibited high average mobilities of 57.2 cm(2) V(-1) s(-1) and 10.1 cm(2) V(-1) s(-1), as well as an on/off current ratio of ∼10(5) and low operating voltages of 4 V at a maximum processing temperature of 300 °C. Therefore, the solution-processable AlOx could be a promising candidate dielectric for low-cost, low-temperature, and high-performance oxide electronics.

  14. Evaluation of the nanomechanical properties of vanadium and native oxide vanadium thin films prepared by RF magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Mamun, M. A.; Zhang, K.; Baumgart, H.; Elmustafa, A. A.

    2015-12-01

    Polycrystalline vanadium thin films of 50, 75, and 100 nm thickness were deposited by magnetron sputtering of a vanadium metal target of 2 inch diameter with 99.9% purity on native oxide covered Si substrates. One set of the fabricated samples were kept in moisture free environment and the other set was exposed to ambient air at room temperature for a long period of time that resulted in formation of native oxide prior to testing. The crystal structure and phase purity of the vanadium and the oxidized vanadium thin films were characterized by X-ray diffraction (XRD). The XRD results yield a preferential (1 1 0), and (2 0 0) orientation of the polycrystalline V films and (0 0 4) vanadium oxide (V3O7). The vanadium films thickness were verified using field emission scanning electron microscopy and the films surface morphologies were inspected using atomic force microscopy (AFM). AFM images reveal surface roughness was observed to increase with increasing film thickness and also subsequent to oxidation at room temperature. The nanomechanical properties were measured by nanoindentation to evaluate the modulus and hardness of the vanadium and the oxidized vanadium thin films. The elastic modulus of the vanadium and the oxidized vanadium films was estimated as 150 GPa at 30% film thickness and the elastic modulus of the bulk vanadium target is estimated as 135 GPa. The measured hardness of the vanadium films at 30% film thickness varies between 9 and 14 GPa for the 100 and 50 nm films, respectively, exhibiting size effects, where the hardness increases as the film thickness decreases. The hardness of the oxidized films depicted less variation and is reported as ∼10 GPa at 30% film thickness for the three oxides. The scanning electron microscopy (SEM) imaging depicted a gradual progression of pile up as the film thickness increased from 75 to 100 nm. It is noticed that as the film thickness increases the films experience softening effect due to grain coarsening and the

  15. Annealing effects on electrical properties of pure and tin-doped indium oxide thin films.

    PubMed

    Kato, Kazuhiro; Omoto, Hideo; Yonekura, Masaaki

    2012-12-01

    The annealing effects on the properties of ITO and pure In2O3 thin films have been investigated. The thin films were deposited with various O2 flow ratios to total gas flow by pulsed dc magnetron sputtering. The post-deposition annealing of the thin films was carried out for 30 minutes at various temperatures ranging up to 500 degrees C in air. It was found through the comparison of the carrier density of ITO and In2O3 thin films that the carrier electrons of the ITO thin films came from both of the dopant Sn and oxygen vacancies under the annealing less than 400 degrees C. Therefore, the ITO thin films deposited with lower O2 flow ratio exhibited higher carrier density due to many oxygen vacancies; in consequence, they exhibited lower resistivity at the annealing up to 400 degrees C. On the other hand, the carrier density of ITO thin films was almost identical regardless of O2 flow ratio when they were annealed at 500 degrees C. This fact indicates that most carrier electrons of the ITO thin films were brought by the dopant Sn at the annealing temperature of 500 degrees C. However, the ITO thin films deposited with lower O2 flow ratio exhibited higher Hall mobility; as a result, they showed lower resistivity at the annealing of 500 degrees C. Atomic force microscope, X-ray diffraction and X-ray reflectivity measurements revealed that the ITO thin films deposited with lowe O2 flow ratio exhibited dense structure even after they were annealed at 500 degrees C. Hence, the carrier electrons of the dense ITO thin films deposited with low O2 flow ratio can conduct better, as a result, the ITO thin films exhibited high Hall mobility and low resistivity.

  16. Chemical bonding, optical constants, and electrical resistivity of sputter-deposited gallium oxide thin films

    SciTech Connect

    Ramana, C. V. Rubio, E. J.; Barraza, C. D.; Miranda Gallardo, A.; McPeak, Samantha; Kotru, Sushma; Grant, J. T.

    2014-01-28

    Gallium oxide (Ga{sub 2}O{sub 3}) thin films were made by sputter deposition employing a Ga{sub 2}O{sub 3} ceramic target for sputtering. The depositions were made over a wide range of substrate temperatures (T{sub s}), from 25 to 600 °C. The effect of T{sub s} on the chemical bonding, surface morphological characteristics, optical constants, and electrical properties of the grown films was evaluated using X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), spectroscopic ellipsometry (SE), and four-point probe measurements. XPS analyses indicate the binding energies (BE) of the Ga 2p doublet, i.e., the Ga 2p{sub 3/2} and Ga 2p{sub 1/2} peaks, are located at 1118.0 and 1145.0 eV, respectively, characterizing gallium in its highest chemical oxidation state (Ga{sup 3+}) in the grown films. The core level XPS spectra of O 1s indicate that the peak is centered at a BE ∼ 531 eV, which is also characteristic of Ga-O bonds in the Ga{sub 2}O{sub 3} phase. The granular morphology of the nanocrystalline Ga{sub 2}O{sub 3} films was evident from AFM measurements, which also indicate that the surface roughness of the films increases from 0.5 nm to 3.0 nm with increasing T{sub s}. The SE analyses indicate that the index of refraction (n) of Ga{sub 2}O{sub 3} films increases with increasing T{sub s} due to improved structural quality and packing density of the films. The n(λ) of all the Ga{sub 2}O{sub 3} films follows the Cauchy's dispersion relation. The room temperature electrical resistivity was high (∼200 Ω-cm) for amorphous Ga{sub 2}O{sub 3} films grown at T{sub s} = RT-300 °C and decreased to ∼1 Ω-cm for nanocrystalline Ga{sub 2}O{sub 3} films grown at T{sub s} ≥ 500–600 °C. A correlation between growth conditions, microstructure, optical constants, and electrical properties of Ga{sub 2}O{sub 3} films is derived.

  17. Plasmonic-Based High Temperature Chemical Sensing Using Gold Nanoparticles Embedded in Metal Oxide Thin Films

    NASA Astrophysics Data System (ADS)

    Joy, Nicholas

    Thin metal oxide films embedded with Au nanoparticles (AuNPs) have been investigated as high temperature localized surface plasmon resonance (LSPR) based sensing materials to monitor H2, CO, and NO2 at a temperature of 500°C. Applications for this technology include turbine engines as well as other combustion environments where it is important to monitor emission gases for both regulatory purposes as well as combustion control. These high temperature applications, which may be oxidizing or reducing in nature, present challenges to sensor reliability and selectivity, and have therefore necessitated the development of novel sensing devices. While there has been work on developing semiconductor-based electrical sensing methods, this work examines the optical response of AuNPs in yttria-stabilized zirconia (YSZ), TiO2, and CeO2. The main challenge with this technique is to achieve a selective response to the target gases. As a means of addressing this issue, both materials and data analysis techniques have been investigated. From the materials aspect, a sensor array was developed for a direct comparison of Au-YSZ, Au-TiO2, and Au-CeO2. In order to analyze the data, the multivariate method of principle component analysis was applied. The result of this analysis showed that a unique response was seen for each of the three target gases during separate exposures, which is an initial step towards selective detection in a gas mixture. Additional material control has also been achieved with the use of electron beam lithography to pattern Au nanoparticles for size and shape control. A particular emphasis has been placed on the nanorod geometry due to its tunable longitudinal LSPR peak; however, thermal stability of this geometry has been a challenge. Encapsulating the Au nanorods with YSZ was shown to help stabilize the nanorods for sensing tests performed at 500°C. Apart from material control, a kinetics analysis has also been performed for H2 reactions with Au-YSZ in an

  18. Enhanced violet photoemission of nanocrystalline fluorine doped zinc oxide (FZO) thin films

    NASA Astrophysics Data System (ADS)

    Anusha, Muthukumar; Arivuoli, D.; Manikandan, E.; Jayachandran, M.

    2015-09-01

    Highly stable fluorine doped nanocrystalline zinc oxide thin films were prepared on corning glass substrates by aerosol assisted chemical vapor deposition (AACVD) at variable deposition temperature of 360 °C, 380 °C and 420 °C. Especially, the optimum deposition temperature was investigated for high intense violet emission. The film crystallinity improved with the increasing deposition temperature and highly textured film was obtained at 420 °C. The films exhibited surface morphology variation from spherical to platelets due to deposition temperature effect, analyzed by field emission scanning electron microscope (FE-SEM). Higher growth rate observed at 420 °C which leads larger grains and lowest resistivity of ∼5.77 Ω cm among the deposited films which may be due to reduction in zinc vacancies and grain boundary area. Zinc vacancies are acts as electron killer centres. UV-visible spectra indicated higher transmittance (83-90%) in the visible region. Red shift of optical absorption edges associated with the increase in particle size consistent well with the XRD results. Reduced E2(high) intensity was observed in Raman spectra, for the film deposited at 380 °C which indicates decreased oxygen incorporation confirmed by PL spectra. Especially, enhanced violet emission observed at 3.06 eV for the films deposited at 380 °C due to electronic transition from the defect level of zinc vacancies to the conduction band, probably attributed to enhanced incorporation of 'F' into 'O' sites associated with increased Zn vacancies and also decreased oxygen incorporation consistent with the electrical and Raman analyses.

  19. Vanadium oxide thin films produced by magnetron sputtering from a V2O5 target at room temperature

    NASA Astrophysics Data System (ADS)

    de Castro, Marcelo S. B.; Ferreira, Carlos L.; de Avillez, Roberto R.

    2013-09-01

    Vanadium oxide thin films were grown by RF magnetron sputtering from a V2O5 target at room temperature, an alternative route of production of vanadium oxide thin films for infrared detector applications. The films were deposited on glass substrates, in an argon-oxygen atmosphere with an oxygen partial pressure from nominal 0% to 20% of the total pressure. X-ray diffraction (XRD) and X-ray photon spectroscopy (XPS) analyses showed that the films were a mixture of several vanadium oxides (V2O5, VO2, V5O9 and V2O3), which resulted in different colors, from yellow to black, depending on composition. The electrical resistivity varied from 1 mΩ cm to more than 500 Ω cm and the thermal coefficient of resistance (TCR), varied from -0.02 to -2.51% K-1. Computational thermodynamics was used to simulate the phase diagram of the vanadium-oxygen system. Even if plasma processes are far from equilibrium, this diagram provides the range of oxygen pressures that lead to the growth of different vanadium oxide phases. These conditions were used in the present work.

  20. Synthesis and characterization of ZnO nanowires by thermal oxidation of Zn thin films at various temperatures.

    PubMed

    Khanlary, Mohammad Reza; Vahedi, Vahid; Reyhani, Ali

    2012-05-02

    In this research high-quality zinc oxide (ZnO) nanowires have been synthesized by thermal oxidation of metallic Zn thin films. Metallic Zn films with thicknesses of 250 nm have been deposited on a glass substrate by the PVD technique. The deposited zinc thin films were oxidized in air at various temperatures ranging between 450 °C to 650 °C. Surface morphology, structural and optical properties of the ZnO nanowires were examined by scanning electron microscope (SEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX) and photoluminescence (PL) measurements. XRD analysis demonstrated that the ZnO nanowires has a wurtzite structure with orientation of (002), and the nanowires prepared at 600 °C has a better crystalline quality than samples prepared at other temperatures. SEM results indicate that by increasing the oxidation temperature, the dimensions of the ZnO nanowires increase. The optimum temperature for synthesizing high density, ZnO nanowires was determined to be 600 °C. EDX results revealed that only Zn and O are present in the samples, indicating a pure ZnO composition. The PL spectra of as-synthesized nanowires exhibited a strong UV emission and a relatively weak green emission.