Sample records for amorphous indium-gallium-zinc oxide

  1. Room-temperature-operated sensitive hybrid gas sensor based on amorphous indium gallium zinc oxide thin-film transistors

    E-print Network

    . Sensitive vapor sensors are important for the development of noninvasive diagnostic breath analy- sis systemRoom-temperature-operated sensitive hybrid gas sensor based on amorphous indium gallium zinc oxide Institute of Physics. Related Articles Semiconductor core-shell quantum dot: A low temperature nano-sensor

  2. Room-temperature-operated sensitive hybrid gas sensor based on amorphous indium gallium zinc oxide thin-film transistors

    E-print Network

    . Sensitive vapor sensors are important for the development of noninvasive diagnostic breath analy- sis systemRoom-temperature-operated sensitive hybrid gas sensor based on amorphous indium gallium zinc oxide-film transistor TFT to form a hybrid sensor. The organic layer, served as a second gate, forms a p-n junction

  3. Amorphous indium-gallium-zinc-oxide as electron transport layer in organic photodetectors

    NASA Astrophysics Data System (ADS)

    Arora, H.; Malinowski, P. E.; Chasin, A.; Cheyns, D.; Steudel, S.; Schols, S.; Heremans, P.

    2015-04-01

    Amorphous indium-gallium-zinc-oxide (a-IGZO) is demonstrated as an electron transport layer (ETL) in a high-performance organic photodetector (OPD). Dark current in the range of 10 nA/cm2 at a bias voltage of -2 V and a high photoresponse in the visible spectrum were obtained in inverted OPDs with poly(3-hexylthiophene) and phenyl-C61-butyric acid methyl ester active layer. The best results were obtained for the optimum a-IGZO thickness of 7.5 nm with specific detectivity of 3 × 1012 Jones at the wavelength of 550 nm. The performance of the best OPD devices using a-IGZO was shown to be comparable to state-of-the-art devices based on TiOx as ETL, with higher rectification achieved in reverse bias. Yield and reproducibility were also enhanced with a-IGZO, facilitating fabrication of large area OPDs. Furthermore, easier integration with IGZO-based readout backplanes can be envisioned, where the channel material can be used as photodiode buffer layer after additional treatment.

  4. Room-temperature-operated sensitive hybrid gas sensor based on amorphous indium gallium zinc oxide thin-film transistors

    NASA Astrophysics Data System (ADS)

    Zan, Hsiao-Wen; Li, Chang-Hung; Yeh, Chun-Cheng; Dai, Ming-Zhi; Meng, Hsin-Fei; Tsai, Chuang-Chuang

    2011-06-01

    An organic sensing layer is capped onto an amorphous indium gallium zinc oxide (a-IGZO) thin-film transistor (TFT) to form a hybrid sensor. The organic layer, served as a second gate, forms a p-n junction with the a-IGZO film. Oxidizing or reducing vapor molecules act like electron acceptors or electron donors to change the potential of the organic layer and the current of a-IGZO TFT. A sensitive and reversible response to 100 ppb ammonia and 100 ppb acetone is obtained at room temperature. This letter opens a route to develop low-cost large-area bio/chemical sensor arrays based on the emerging a-IGZO TFT technology.

  5. Defect generation in amorphous-indium-gallium-zinc-oxide thin-film transistors by positive bias stress at elevated temperature

    SciTech Connect

    Um, Jae Gwang; Mativenga, Mallory; Jang, Jin, E-mail: jjang@khu.ac.kr [Advanced Display Research Center, Department of Information Display, Kyung Hee University, Dongdaemun-gu, Seoul 130-701 (Korea, Republic of); Migliorato, Piero [Advanced Display Research Center, Department of Information Display, Kyung Hee University, Dongdaemun-gu, Seoul 130-701 (Korea, Republic of); Electrical Engineering Division, Department of Engineering, Cambridge University, Cambridge CB3 0FA (United Kingdom)

    2014-04-07

    We report on the generation and characterization of a hump in the transfer characteristics of amorphous indium gallium zinc-oxide thin-film transistors by positive bias temperature stress. The hump depends strongly on the gate bias stress at 100?°C. Due to the hump, the positive shift of the transfer characteristic in deep depletion is always smaller that in accumulation. Since, the latter shift is twice the former, with very good correlation, we conclude that the effect is due to creation of a double acceptor, likely to be a cation vacancy. Our results indicate that these defects are located near the gate insulator/active layer interface, rather than in the bulk. Migration of donor defects from the interface towards the bulk may also occur under PBST at 100?°C.

  6. Surface reactivity and oxygen migration in amorphous indium-gallium-zinc oxide films annealed in humid atmosphere

    SciTech Connect

    Watanabe, Ken, E-mail: Watanabe.Ken@nims.go.jp [International Center for Young Scientists (ICYS-MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba 305-0044 (Japan)] [International Center for Young Scientists (ICYS-MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba 305-0044 (Japan); Lee, Dong-Hee [Optical and Electronic Materials Unit, NIMS, 1-1 Namiki, Tsukuba 305-0044 (Japan) [Optical and Electronic Materials Unit, NIMS, 1-1 Namiki, Tsukuba 305-0044 (Japan); Materials and Structures Laboratory (MSL), Tokyo Institute of Technology, Mailbox R3-4, 4259 Nagatsuta, Midori-ku, Yokohama 226-0026 (Japan); Sakaguchi, Isao; Haneda, Hajime [Optical and Electronic Materials Unit, NIMS, 1-1 Namiki, Tsukuba 305-0044 (Japan)] [Optical and Electronic Materials Unit, NIMS, 1-1 Namiki, Tsukuba 305-0044 (Japan); Nomura, Kenji [Frontier Research Center, Tokyo Institute of Technology, Mailbox S2-13, 4259 Nagatsuta, Midori-ku, Yokohama 226-0026 (Japan)] [Frontier Research Center, Tokyo Institute of Technology, Mailbox S2-13, 4259 Nagatsuta, Midori-ku, Yokohama 226-0026 (Japan); Kamiya, Toshio [Materials and Structures Laboratory (MSL), Tokyo Institute of Technology, Mailbox R3-4, 4259 Nagatsuta, Midori-ku, Yokohama 226-0026 (Japan) [Materials and Structures Laboratory (MSL), Tokyo Institute of Technology, Mailbox R3-4, 4259 Nagatsuta, Midori-ku, Yokohama 226-0026 (Japan); Materials Research Center for Element Strategy (MCES), Mailbox S2-13, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-0026 (Japan); Hosono, Hideo [Materials and Structures Laboratory (MSL), Tokyo Institute of Technology, Mailbox R3-4, 4259 Nagatsuta, Midori-ku, Yokohama 226-0026 (Japan) [Materials and Structures Laboratory (MSL), Tokyo Institute of Technology, Mailbox R3-4, 4259 Nagatsuta, Midori-ku, Yokohama 226-0026 (Japan); Frontier Research Center, Tokyo Institute of Technology, Mailbox S2-13, 4259 Nagatsuta, Midori-ku, Yokohama 226-0026 (Japan); Materials Research Center for Element Strategy (MCES), Mailbox S2-13, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-0026 (Japan); Ohashi, Naoki, E-mail: Ohashi.Naoki@nims.go.jp [Optical and Electronic Materials Unit, NIMS, 1-1 Namiki, Tsukuba 305-0044 (Japan) [Optical and Electronic Materials Unit, NIMS, 1-1 Namiki, Tsukuba 305-0044 (Japan); Materials Research Center for Element Strategy (MCES), Mailbox S2-13, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-0026 (Japan)

    2013-11-11

    An isotope tracer study, i.e., {sup 18}O/{sup 16}O exchange using {sup 18}O{sub 2} and H{sub 2}{sup 18}O, was performed to determine how post-deposition annealing (PDA) affected surface reactivity and oxygen diffusivity of amorphous indium–gallium–zinc oxide (a-IGZO) films. The oxygen tracer diffusivity was very high in the bulk even at low temperatures, e.g., 200?°C, regardless of PDA and exchange conditions. In contrast, the isotope exchange rate, dominated by surface reactivity, was much lower for {sup 18}O{sub 2} than for H{sub 2}{sup 18}O. PDA in a humid atmosphere at 400?°C further suppressed the reactivity of O{sub 2} at the a-IGZO film surface, which is attributable to –OH-terminated surface formation.

  7. Temperature-dependent bias-stress-induced electrical instability of amorphous indium-gallium-zinc-oxide thin-film transistors

    NASA Astrophysics Data System (ADS)

    Qian, Hui-Min; Yu, Guang; Lu, Hai; Wu, Chen-Fei; Tang, Lan-Feng; Zhou, Dong; Ren, Fang-Fang; Zhang, Rong; Zheng, You-Liao; Huang, Xiao-Ming

    2015-07-01

    The time and temperature dependence of threshold voltage shift under positive-bias stress (PBS) and the following recovery process are investigated in amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors. It is found that the time dependence of threshold voltage shift can be well described by a stretched exponential equation in which the time constant ? is found to be temperature dependent. Based on Arrhenius plots, an average effective energy barrier E?stress = 0.72 eV for the PBS process and an average effective energy barrier E?recovery = 0.58 eV for the recovery process are extracted respectively. A charge trapping/detrapping model is used to explain the threshold voltage shift in both the PBS and the recovery process. The influence of gate bias stress on transistor performance is one of the most critical issues for practical device development. Project supported by the National Basic Research Program of China (Grant Nos. 2011CB301900 and 2011CB922100) and the Priority Academic Program Development of Jiangsu Higher Education Institutions, China

  8. Semiconductor to metallic transition in bulk accumulated amorphous indium-gallium-zinc-oxide dual gate thin-film transistor

    NASA Astrophysics Data System (ADS)

    Chun, Minkyu; Chowdhury, Md Delwar Hossain; Jang, Jin

    2015-05-01

    We investigated the effects of top gate voltage (VTG) and temperature (in the range of 25 to 70 oC) on dual-gate (DG) back-channel-etched (BCE) amorphous-indium-gallium-zinc-oxide (a-IGZO) thin film transistors (TFTs) characteristics. The increment of VTG from -20V to +20V, decreases the threshold voltage (VTH) from 19.6V to 3.8V and increases the electron density to 8.8 x 1018cm-3. Temperature dependent field-effect mobility in saturation regime, extracted from bottom gate sweep, show a critical dependency on VTG. At VTG of 20V, the mobility decreases from 19.1 to 15.4 cm2/V ? s with increasing temperature, showing a metallic conduction. On the other hand, at VTG of - 20V, the mobility increases from 6.4 to 7.5cm2/V ? s with increasing temperature. Since the top gate bias controls the position of Fermi level, the temperature dependent mobility shows metallic conduction when the Fermi level is above the conduction band edge, by applying high positive bias to the top gate.

  9. Mechanism of positive bias stress-assisted recovery in amorphous-indium-gallium-zinc-oxide thin-film transistors from negative bias under illumination stress

    NASA Astrophysics Data System (ADS)

    Um, Jae Gwang; Mativenga, Mallory; Jang, Jin

    2013-07-01

    We have analyzed the effect of applying positive bias stress (PBS) to amorphous-indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs) immediately after applying negative bias under illumination stress (NBIS). By monitoring TFT current-voltage and capacitance-voltage characteristics, we found that PBS facilitates the recovery process. NBIS results in positive charge trapping at the active-layer/gate-insulator interface and the formation of shallow donors in the bulk a-IGZO when neutral oxygen vacancies are ionized by hole capture. In addition to the release of trapped positive charges from the active-layer/gate-insulator interface during the PBS-assisted recovery, ionized oxygen vacancies are neutralized by electron capture and relax back to their original deep levels—well below EF.

  10. Time-temperature dependence of positive gate bias stress and recovery in amorphous indium-gallium-zinc-oxide thin-film-transistors

    NASA Astrophysics Data System (ADS)

    Chowdhury, Md Delwar Hossain; Migliorato, Piero; Jang, Jin

    2011-04-01

    We have analyzed the time-temperature dependence of positive bias stress (PBS) and recovery in amorphous indium-gallium-zinc-oxide (a-IGZO) Thin-film-transistors (TFTs) incorporating SiO2 back channel passivation. The data are fitted to stretched exponentials, yielding the time constant ? and stretch parameter ? as fitting parameters. As-fabricated samples and samples annealed in vacuum at 250 °C 200 h are compared. The time constant for room temperature stress increases fivefold with the 200 h anneal to the value ? =1.3×106 s. The dependence of ? from stress temperature is well described by an Arrhenius plot, with activation E?=0.95 eV. Stress and recovery show very similar activation energies, supporting the defect formation in the bulk or at the gate insulator/a-IGZO interface as the mechanism responsible for PBS.

  11. Study on interface characteristics in amorphous indium-gallium-zinc oxide thin-film transistors by using low-frequency noise and temperature dependent mobility measurements

    NASA Astrophysics Data System (ADS)

    Wu, Chenfei; Huang, Xiaoming; Lu, Hai; Yu, Guang; Ren, Fangfang; Chen, Dunjun; Zhang, Rong; Zheng, Youdou

    2015-07-01

    In this work, the interface properties of amorphous indium-gallium-zinc oxide thin film transistors annealed at different temperatures ranging from 150 to 250 °C are studied by temperature dependent mobility and low-frequency noise (LFN) characterizations. The dominant scattering mechanism for carrier transport is found to be Coulomb scattering based on gate bias and temperature dependent mobility measurement. Meanwhile, as the annealing temperature increases, the dominant mechanism of LFN within the device channel varies from carrier number fluctuation to carrier mobility fluctuation. The border trap density as well as the distribution properties of charged border traps is deduced. The present results suggest that annealing at higher temperature has a more remarkable effect on removing deeper border traps than traps closer to the channel/dielectric interface.

  12. Highest transmittance and high-mobility amorphous indium gallium zinc oxide films on flexible substrate by room-temperature deposition and post-deposition anneals

    SciTech Connect

    Gadre, Mandar J. [School for Engineering of Matter, Transport and Energy, Arizona State University, Tempe, Arizona 85287 (United States); Alford, T. L. [School for Engineering of Matter, Transport and Energy, Arizona State University, Tempe, Arizona 85287 (United States); Flexible Display Center at Arizona State University, Tempe, Arizona 85284 (United States)

    2011-08-01

    Amorphous indium gallium zinc oxide (a-IGZO) thin films of the highest transmittance reported in literature were initially deposited onto flexible polymer substrates at room temperature. The films were annealed in vacuum, air, and oxygen to enhance their electrical and optical performances. Electrical and optical characterizations were done before and after anneals. A partial reversal of the degradation in electrical properties upon annealing in oxygen was achieved by subjecting the films to subsequent vacuum anneals. A model was developed based on film texture and structural defects which showed close agreement between the measured and calculated carrier mobility values at low carrier concentrations (2-6 x 10{sup 19} cm{sup -3}).

  13. A thermalization energy analysis of the threshold voltage shift in amorphous indium gallium zinc oxide thin film transistors under simultaneous negative gate bias and illumination

    NASA Astrophysics Data System (ADS)

    Flewitt, A. J.; Powell, M. J.

    2014-04-01

    It has been previously observed that thin film transistors (TFTs) utilizing an amorphous indium gallium zinc oxide (a-IGZO) semiconducting channel suffer from a threshold voltage shift when subjected to a negative gate bias and light illumination simultaneously. In this work, a thermalization energy analysis has been applied to previously published data on negative bias under illumination stress (NBIS) in a-IGZO TFTs. A barrier to defect conversion of 0.65-0.75 eV is extracted, which is consistent with reported energies of oxygen vacancy migration. The attempt-to-escape frequency is extracted to be 106-107 s-1, which suggests a weak localization of carriers in band tail states over a 20-40 nm distance. Models for the NBIS mechanism based on charge trapping are reviewed and a defect pool model is proposed in which two distinct distributions of defect states exist in the a-IGZO band gap: these are associated with states that are formed as neutrally charged and 2+ charged oxygen vacancies at the time of film formation. In this model, threshold voltage shift is not due to a defect creation process, but to a change in the energy distribution of states in the band gap upon defect migration as this allows a state formed as a neutrally charged vacancy to be converted into one formed as a 2+ charged vacancy and vice versa. Carrier localization close to the defect migration site is necessary for the conversion process to take place, and such defect migration sites are associated with conduction and valence band tail states. Under negative gate bias stressing, the conduction band tail is depleted of carriers, but the bias is insufficient to accumulate holes in the valence band tail states, and so no threshold voltage shift results. It is only under illumination that the quasi Fermi level for holes is sufficiently lowered to allow occupation of valence band tail states. The resulting charge localization then allows a negative threshold voltage shift, but only under conditions of simultaneous negative gate bias and illumination, as observed experimentally as the NBIS effect.

  14. A thermalization energy analysis of the threshold voltage shift in amorphous indium gallium zinc oxide thin film transistors under simultaneous negative gate bias and illumination

    SciTech Connect

    Flewitt, A. J., E-mail: ajf@eng.cam.ac.uk [Electrical Engineering Division, Cambridge University, J J Thomson Avenue, Cambridge CB3 0FA (United Kingdom); Powell, M. J. [252, Valley Drive, Kendal LA9 7SL (United Kingdom)

    2014-04-07

    It has been previously observed that thin film transistors (TFTs) utilizing an amorphous indium gallium zinc oxide (a-IGZO) semiconducting channel suffer from a threshold voltage shift when subjected to a negative gate bias and light illumination simultaneously. In this work, a thermalization energy analysis has been applied to previously published data on negative bias under illumination stress (NBIS) in a-IGZO TFTs. A barrier to defect conversion of 0.65–0.75?eV is extracted, which is consistent with reported energies of oxygen vacancy migration. The attempt-to-escape frequency is extracted to be 10{sup 6}?10{sup 7}?s{sup ?1}, which suggests a weak localization of carriers in band tail states over a 20–40?nm distance. Models for the NBIS mechanism based on charge trapping are reviewed and a defect pool model is proposed in which two distinct distributions of defect states exist in the a-IGZO band gap: these are associated with states that are formed as neutrally charged and 2+ charged oxygen vacancies at the time of film formation. In this model, threshold voltage shift is not due to a defect creation process, but to a change in the energy distribution of states in the band gap upon defect migration as this allows a state formed as a neutrally charged vacancy to be converted into one formed as a 2+ charged vacancy and vice versa. Carrier localization close to the defect migration site is necessary for the conversion process to take place, and such defect migration sites are associated with conduction and valence band tail states. Under negative gate bias stressing, the conduction band tail is depleted of carriers, but the bias is insufficient to accumulate holes in the valence band tail states, and so no threshold voltage shift results. It is only under illumination that the quasi Fermi level for holes is sufficiently lowered to allow occupation of valence band tail states. The resulting charge localization then allows a negative threshold voltage shift, but only under conditions of simultaneous negative gate bias and illumination, as observed experimentally as the NBIS effect.

  15. Fabrication of Indium Gallium Zinc Oxide (IGZO) TFTs Using a Solution-Based Process

    Microsoft Academic Search

    Mi Sun Park; Doo Hyoung Lee; Eun Jin Bae; Dae-Hwan Kim; Jin Gyu Kang; Dae-Ho Son; Si Ok Ryu

    2010-01-01

    Highly transparent (?90% in the visible region) indium gallium zinc oxide (IGZO) thin films were deposited using a spin coating process with a newly developed precursor solution. Acetonitrile was used as the solvent in the preparation of the metal halide precursor solution for the deposition of the IGZO thin films. Ethylene glycol was added to the solvent at four different

  16. Remarkable changes in interface O vacancy and metal-oxide bonds in amorphous indium-gallium-zinc-oxide thin-film transistors by long time annealing at 250 °C

    NASA Astrophysics Data System (ADS)

    Chowdhury, Md Delwar Hossain; Um, Jae Gwang; Jang, Jin

    2014-12-01

    We have studied the effect of long time post-fabrication annealing on negative bias illumination stress (NBIS) of amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film-transistors. Annealing for 100 h at 250 °C increased the field effect mobility from 14.7 cm2/V s to 17.9 cm2/V s and reduced the NBIS instability remarkably. Using X-ray photoelectron spectroscopy, the oxygen vacancy and OH were found to exist at the interfaces of a-IGZO with top and bottom SiO2. Long time annealing helps to decrease the vacancy concentration and increase the metal-oxygen bonds at the interfaces; this leads to increase in the free carrier concentrations in a-IGZO and field-effect mobility. X-ray reflectivity measurement indicated the increment of a-IGZO film density of 5.63 g cm-3 to 5.83 g cm-3 (3.4% increase) by 100 h annealing at 250 °C. The increase in film density reveals the decrease of O vacancy concentration and reduction of weak metal-oxygen bonds in a-IGZO, which substantially helps to improve the NBIS stability.

  17. Flexible indium-gallium-zinc-oxide Schottky diode operating beyond 2.45?GHz.

    PubMed

    Zhang, Jiawei; Li, Yunpeng; Zhang, Binglei; Wang, Hanbin; Xin, Qian; Song, Aimin

    2015-01-01

    Mechanically flexible mobile phones have been long anticipated due to the rapid development of thin-film electronics in the last couple of decades. However, to date, no such phone has been developed, largely due to a lack of flexible electronic components that are fast enough for the required wireless communications, in particular the speed-demanding front-end rectifiers. Here Schottky diodes based on amorphous indium-gallium-zinc-oxide (IGZO) are fabricated on flexible plastic substrates. Using suitable radio-frequency mesa structures, a range of IGZO thicknesses and diode sizes have been studied. The results have revealed an unexpected dependence of the diode speed on the IGZO thickness. The findings enable the best optimized flexible diodes to reach 6.3?GHz at zero bias, which is beyond the critical benchmark speed of 2.45?GHz to satisfy the principal frequency bands of smart phones such as those for cellular communication, Bluetooth, Wi-Fi and global satellite positioning. PMID:26138510

  18. Recovery from ultraviolet-induced threshold voltage shift in indium gallium zinc oxide thin film transistors by positive gate bias

    NASA Astrophysics Data System (ADS)

    Liu, P.; Chen, T. P.; Li, X. D.; Liu, Z.; Wong, J. I.; Liu, Y.; Leong, K. C.

    2013-11-01

    The effect of short-duration ultraviolet (UV) exposure on the threshold voltage (Vth) of amorphous indium gallium zinc oxide thin film transistors (TFTs) and its recovery characteristics were investigated. The Vth exhibited a significant negative shift after UV exposure. The Vth instability caused by UV illumination is attributed to the positive charge trapping in the dielectric layer and/or at the channel/dielectric interface. The illuminated devices showed a slow recovery in threshold voltage without external bias. However, an instant recovery can be achieved by the application of positive gate pulses, which is due to the elimination of the positive trapped charges as a result of the presence of a large amount of field-induced electrons in the interface region.

  19. Examination of the ambient effects on the stability of amorphous indium-gallium-zinc oxide thin film transistors using a laser-glass-sealing technology

    NASA Astrophysics Data System (ADS)

    Yamada, Kazuo; Nomura, Kenji; Abe, Katsumi; Takeda, Satoshi; Hosono, Hideo

    2014-09-01

    The effect of an ambient atmosphere with a positive bias constant current stress (CCS) and a negative bias illumination stress (NBIS) on the stability of amorphous In-Ga-Zn-O thin film transistors (TFTs) is examined by utilizing a glass-hermetic-sealant with a moisture permeability of less than 10-6 g/m2 . day. In the CCS test, the threshold voltage shift (?Vth) was remarkably suppressed in the glass-sealed TFTs. The unsealed and resin-sealed TFTs exhibited large ?Vth values. During the NBIS tests, the glass-sealed TFTs had almost the same negative ?Vth as the unsealed and resin sealed TFTs. Among the different TFTs, no significant differences were observed in the threshold voltage, the subthreshold swing and the saturation mobility as a function of the photon energy. It is concluded that ambient molecules were the primary origin of the instability of the ?Vth, induced by a CCS, but they were not related to the NBIS instability. The major role of the effective passivation layers in the NBIS test was not to simply block out the ambient effects, but to reduce the extra density of states at/near the surface of the back channel.

  20. Examination of the ambient effects on the stability of amorphous indium-gallium-zinc oxide thin film transistors using a laser-glass-sealing technology

    SciTech Connect

    Yamada, Kazuo; Takeda, Satoshi [Electronics Company, Asahi Glass Co., Ltd. 1150 Hazawa-cho Kanagawa-ku, Yokohama 221-8755 (Japan); Nomura, Kenji; Abe, Katsumi; Hosono, Hideo [Materials and Structures Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan)

    2014-09-29

    The effect of an ambient atmosphere with a positive bias constant current stress (CCS) and a negative bias illumination stress (NBIS) on the stability of amorphous In-Ga-Zn-O thin film transistors (TFTs) is examined by utilizing a glass-hermetic-sealant with a moisture permeability of less than 10{sup ?6} g/m{sup 2}?·?day. In the CCS test, the threshold voltage shift (?V{sub th}) was remarkably suppressed in the glass-sealed TFTs. The unsealed and resin-sealed TFTs exhibited large ?V{sub th} values. During the NBIS tests, the glass-sealed TFTs had almost the same negative ?V{sub th} as the unsealed and resin sealed TFTs. Among the different TFTs, no significant differences were observed in the threshold voltage, the subthreshold swing and the saturation mobility as a function of the photon energy. It is concluded that ambient molecules were the primary origin of the instability of the ?V{sub th}, induced by a CCS, but they were not related to the NBIS instability. The major role of the effective passivation layers in the NBIS test was not to simply block out the ambient effects, but to reduce the extra density of states at/near the surface of the back channel.

  1. Ohmic contact formation process on low n-type gallium arsenide (GaAs) using indium gallium zinc oxide (IGZO)

    SciTech Connect

    Yang, Seong-Uk [Samsung-SKKU Graphene Center and School of Electronics and Electrical Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Product and Test Engineering Team, System LSI Division, Samsung Electronics Co., Ltd, Yongin 446-711 (Korea, Republic of); Jung, Woo-Shik [Department of Electrical Engineering, Stanford University, Stanford, CA 94305 (United States); Lee, In-Yeal; Jung, Hyun-Wook; Kim, Gil-Ho [Samsung-SKKU Graphene Center and School of Electronics and Electrical Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Park, Jin-Hong, E-mail: jhpark9@skku.edu [Samsung-SKKU Graphene Center and School of Electronics and Electrical Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)

    2014-02-01

    Highlights: • We propose a method to fabricate non-gold Ohmic contact on low n-type GaAs with IGZO. • 0.15 A/cm{sup 2} on-current and 1.5 on/off-current ratio are achieved in the junction. • InAs and InGaAs formed by this process decrease an electron barrier height. • Traps generated by diffused O atoms also induce a trap-assisted tunneling phenomenon. - Abstract: Here, an excellent non-gold Ohmic contact on low n-type GaAs is demonstrated by using indium gallium zinc oxide and investigating through time of flight-secondary ion mass spectrometry, X-ray photoelectron spectroscopy, transmission electron microscopy, J–V measurement, and H [enthalpy], S [entropy], Cp [heat capacity] chemistry simulation. In is diffused through GaAs during annealing and reacts with As, forming InAs and InGaAs phases with lower energy bandgap. As a result, it decreases the electron barrier height, eventually increasing the reverse current. In addition, traps generated by diffused O atoms induce a trap-assisted tunneling phenomenon, increasing generation current and subsequently the reverse current. Therefore, an excellent Ohmic contact with 0.15 A/cm{sup 2} on-current density and 1.5 on/off-current ratio is achieved on n-type GaAs.

  2. A normally-off microcontroller unit with an 85% power overhead reduction based on crystalline indium gallium zinc oxide field effect transistors

    NASA Astrophysics Data System (ADS)

    Ohshima, Kazuaki; Kobayashi, Hidetomo; Nishijima, Tatsuji; Yoneda, Seiichi; Tomatsu, Hiroyuki; Maeda, Shuhei; Tsukida, Kazuki; Takahashi, Kei; Sato, Takehisa; Watanabe, Kazunori; Yamamoto, Ro; Kozuma, Munehiro; Aoki, Takeshi; Yamade, Naoto; Ieda, Yoshinori; Miyairi, Hidekazu; Atsumi, Tomoaki; Shionoiri, Yutaka; Kato, Kiyoshi; Maehashi, Yukio; Koyama, Jun; Yamazaki, Shunpei

    2014-01-01

    A low-power normally-off microcontroller unit (NMCU) having state-retention flip-flops (SRFFs) using a c-axis aligned crystalline oxide semiconductor (CAAC-OS) such as indium gallium zinc oxide (IGZO) transistors and employing a distributed backup and recovery method (distributed method) is fabricated. Compared to an NMCU employing a centralized backup and recovery method (centralized method), the NMCU employing the distributed method can be powered off approximately 75 µs earlier after main processing and can start the main processing approximately 75 µs earlier after power-on. The NMCU employing the distributed method can reduce power overhead by approximately 85% and power consumption by approximately 18% compared to the NMCU employing the centralized method. The NMCU employing the distributed method can retain data even when it is powered off, can back up data at high speed, and can start effective processing immediately after power-on. The NMCU could be applied to a low-power MCU.

  3. Temperature dependence of negative bias under illumination stress and recovery in amorphous indium gallium zinc oxide thin film transistors

    NASA Astrophysics Data System (ADS)

    Hossain Chowdhury, Md Delwar; Migliorato, Piero; Jang, Jin

    2013-04-01

    We have investigated the temperature dependence of negative bias under illumination stress and recovery. The transfer characteristics exhibits a non-rigid shift towards negative gate voltages. For both stress and recovery, the voltage shift in deep depletion is twice that in accumulation. The results support the mechanism we previously proposed, which is creation and annealing of a double donor, likely to be an oxygen vacancy. The time dependence of stress and recovery can be fitted to stretched exponentials. Both processes are thermally activated with activation energies 1.06 eV and 1.25 eV for stress and recovery, respectively. A potential energy diagram is proposed to explain the results.

  4. Low temperature annealed amorphous indium gallium zinc oxide (a-IGZO) as a pH sensitive layer for applications in field effect based sensors

    NASA Astrophysics Data System (ADS)

    Kumar, Narendra; Kumar, Jitendra; Panda, Siddhartha

    2015-06-01

    The use of a-IGZO instead of the conventional high-k dielectrics as a pH sensitive layer could lead to the simplification of fabrication steps of field effect based devices. In this work, the pH sensitivities of a-IGZO films directly deposited over a SiO2/Si surface were studied utilizing electrolyte-insulator-semiconductor (EIS) structures. Annealing of the films was found to affect the sensitivity of the devices and the device with the film annealed at 400 oC in N2 ambience showed the better sensitivity, which reduced with further increase in the annealing temperature to 500 oC. The increased pH sensitivity with the film annealed at 400 oC in N2 gas was attributed to the enhanced lattice oxygen ions (based on the XPS data) and improved C-V characteristics, while the decrease in sensitivity at an increased annealing temperature of 500 oC was attributed to defects in the films as well as the induced traps at the IGZO/SiO2 interface based on the stretched accumulation and the peak in the inversion region of C-V curves. This study could help to develop a sensor where the material (a-IGZO here) used as the active layer in a thin film transistors (TFTs) possibly could also be used as the pH sensitive layer without affecting the TFT characteristics, and thus obviating the need of high-K dielectrics for sensitivity enhancement.

  5. RF Characteristics of Room-Temperature-Deposited, Small Gate Dimension Indium Zinc Oxide TFTs

    E-print Network

    Pearton, Stephen J.

    RF Characteristics of Room-Temperature-Deposited, Small Gate Dimension Indium Zinc Oxide TFTs Yu, North Carolina 27709, USA Depletion-mode indium zinc oxide channel thin film transistors TFTs with gate semiconductors such as zinc oxide, zinc tin oxide, indium gallium oxide, and indium gallium zinc tin oxide have

  6. Large scale integration of flexible non-volatile, re-addressable memories using P(VDF-TrFE) and amorphous oxide transistors

    NASA Astrophysics Data System (ADS)

    Gelinck, Gerwin H.; Cobb, Brian; van Breemen, Albert J. J. M.; Myny, Kris

    2015-07-01

    Ferroelectric polymers and amorphous metal oxide semiconductors have emerged as important materials for re-programmable non-volatile memories and high-performance, flexible thin-film transistors, respectively. However, realizing sophisticated transistor memory arrays has proven to be a challenge, and demonstrating reliable writing to and reading from such a large scale memory has thus far not been demonstrated. Here, we report an integration of ferroelectric, P(VDF-TrFE), transistor memory arrays with thin-film circuitry that can address each individual memory element in that array. n-type indium gallium zinc oxide is used as the active channel material in both the memory and logic thin-film transistors. The maximum process temperature is 200 °C, allowing plastic films to be used as substrate material. The technology was scaled up to 150 mm wafer size, and offers good reproducibility, high device yield and low device variation. This forms the basis for successful demonstration of memory arrays, read and write circuitry, and the integration of these.

  7. Study of mechanism of stress-induced threshold voltage shift and recovery in top-gate amorphous-InGaZnO4 thin-film transistors with source- and drain-offsets

    NASA Astrophysics Data System (ADS)

    Mativenga, Mallory; Kang, Dong Han; Lee, Ung Gi; Jang, Jin

    2012-09-01

    Bias instability of top-gate amorphous-indium-gallium-zinc-oxide thin-film transistors with source- and drain-offsets is reported. Positive and negative gate bias-stress (VG_STRESS) respectively induce reversible negative threshold-voltage shift (?VTH) and reduction in on-current. Migration of positive charges towards the offsets lowers the local resistance of the offsets, resulting in the abnormal negative ?VTH under positive VG_STRESS. The reduction in on-current under negative VG_STRESS is due to increase in resistance of the offsets when positive charges migrate away from the offsets. Appropriate drain and source bias-stresses applied simultaneously with VG_STRESS either suppress or enhance the instability, verifying lateral ion migration to be the instability mechanism.

  8. Poole-Frenkel behavior in amorphous oxide thin-film transistors prepared on SiOC

    NASA Astrophysics Data System (ADS)

    Oh, Teresa

    2014-05-01

    The electron behavior in amorphous indium-gallium-zinc-oxide thin film transistors (a-IGZO TFTs) depends on the polar characteristics of SiOC, which is used as a gate dielectric. The properties of the interface between the semiconductor and SiOC were defined by using a Schottky contact with a low potential barrier and Poole-Frenkel contacts with a high potential barrier. The leakage current of SiOC, which was used as a gate insulator, decreased at the Poole-Frenkel contacts because of the high potential barrier. The ambipolar properties in the field effect transistor were observed to depend on the various characteristics of SiOC, which ranged from its behaving as an ideal insulator or as a material with a high dielectric constant. The resistance of the a-IGZO channel changed from positive to negative at SiOC, which had the lowest polarity. As to the conduction due to the diffusion current, the mobility increased with increasing carrier concentrations. However, the drift carrier conduction was related to the reduced mobility at higher carrier concentrations. The performance of the transistors was enhanced by the tunneling and the diffusion currents Rather than by the drift current caused by trapping. The Schottky contact and the Poole-Frenkel (PF) contacts at an interface between the IGZO channel and the SiOC were defined according to the heights of potential barriers caused by the depletion layer. The leakage current was very low about 10-12 A at SiOC with PF contacts because of the height of potential barrier was double that with a Schottky contact because the tunneling conductance due to the diffusion current originated from the PF contacts of non-polar SiOC.

  9. Monolithic metal oxide transistors.

    PubMed

    Choi, Yongsuk; Park, Won-Yeong; Kang, Moon Sung; Yi, Gi-Ra; Lee, Jun-Young; Kim, Yong-Hoon; Cho, Jeong Ho

    2015-04-28

    We devised a simple transparent metal oxide thin film transistor architecture composed of only two component materials, an amorphous metal oxide and ion gel gate dielectric, which could be entirely assembled using room-temperature processes on a plastic substrate. The geometry cleverly takes advantage of the unique characteristics of the two components. An oxide layer is metallized upon exposure to plasma, leading to the formation of a monolithic source-channel-drain oxide layer, and the ion gel gate dielectric is used to gate the transistor channel effectively at low voltages through a coplanar gate. We confirmed that the method is generally applicable to a variety of sol-gel-processed amorphous metal oxides, including indium oxide, indium zinc oxide, and indium gallium zinc oxide. An inverter NOT logic device was assembled using the resulting devices as a proof of concept demonstration of the applicability of the devices to logic circuits. The favorable characteristics of these devices, including (i) the simplicity of the device structure with only two components, (ii) the benign fabrication processes at room temperature, (iii) the low-voltage operation under 2 V, and (iv) the excellent and stable electrical performances, together support the application of these devices to low-cost portable gadgets, i.e., cheap electronics. PMID:25777338

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

    SciTech Connect

    Ye Yan; Lim, Rodney; White, John M. [Display and SunFab Solar Business Group, Applied Materials, Santa Clara, California 95054 (United States)

    2009-10-01

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

  11. Facile Routes To Improve Performance of Solution-Processed Amorphous Metal Oxide Thin Film Transistors by Water Vapor Annealing.

    PubMed

    Park, Won-Tae; Son, Inyoung; Park, Hyun-Woo; Chung, Kwun-Bum; Xu, Yong; Lee, Taegweon; Noh, Yong-Young

    2015-06-24

    Here, we report on a simple and high-rate oxidization method for producing solution-based compound mixtures of indium zinc oxide (IZO) and indium gallium zinc oxide (IGZO) metal-oxide semiconductors (MOS) for thin-film transistor (TFT) applications. One of the issues for solution-based MOS fabrication is how to sufficiently oxidize the precursor in order to achieve high performance. As the oxidation rate of solution processing is lower than vacuum-based deposition such as sputtering, devices using solution-processed MOS exhibit relatively poorer performance. Therefore, we propose a method to prepare the metal-oxide precursor upon exposure to saturated water vapor in a closed volume for increasing the oxidization efficiency without requiring additional oxidizing agent. We found that the hydroxide rate of the MOS film exposed to water vapor is lower than when unexposed (?18%). Hence, we successfully fabricated oxide TFTs with high electron mobility (27.9 cm(2)/V·s) and established a rapid process (annealing at 400 °C for 5 min) that is much shorter than the conventional as-deposited long-duration annealing (at 400 °C for 1 h) whose corresponding mobility is even lower (19.2 cm(2)/V·s). PMID:26043206

  12. Amorphous transition metal oxide films

    Microsoft Academic Search

    Neil Heiman; N. S. Kazama

    1979-01-01

    We have been able to prepare amorphous oxides of Fe and Cr by sputter deposition. Magnetization measurements were made between 4.2 K and 300 K. Mössbauer spectra were obtained for the iron oxide samples in the same temperature range. Amorphous CrO2 films showed no evidence of magnetic order. For the amorphous Fe oxide films, the 4.2 K Mössbauer spectrum showed

  13. Amorphous niobium oxide thin films

    Microsoft Academic Search

    G. Ramírez; S. E. Rodil; S. Muhl; D. Turcio-Ortega; J. J. Olaya; M. Rivera; E. Camps; L. Escobar-Alarcón

    2010-01-01

    Amorphous niobium oxide thin films were deposited by unbalanced reactive magnetron sputtering under different conditions of pressure (2 to 4Pa) and oxygen percentage (9, 17, and 23%). The films were characterized to obtain the relationships between the deposition parameters and the most relevant physical properties (structural, optical, mechanical, surface morphology and optical). The composition was determined by Rutherford backscattering spectroscopy

  14. 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.

  15. Light-induced hysteresis and recovery behaviors in photochemically activated solution-processed metal-oxide thin-film transistors

    SciTech Connect

    Jo, Jeong-Wan; Park, Sung Kyu, E-mail: yhkim76@skku.edu, E-mail: skpark@cau.ac.kr [School of Electrical and Electronics Engineering, Chung-Ang University, Seoul 156-756 (Korea, Republic of); Kim, Yong-Hoon, E-mail: yhkim76@skku.edu, E-mail: skpark@cau.ac.kr [School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)

    2014-07-28

    In this report, photo-induced hysteresis, threshold voltage (V{sub T}) shift, and recovery behaviors in photochemically activated solution-processed indium-gallium-zinc oxide (IGZO) thin-film transistors (TFTs) are investigated. It was observed that a white light illumination caused negative V{sub T} shift along with creation of clockwise hysteresis in electrical characteristics which can be attributed to photo-generated doubly ionized oxygen vacancies at the semiconductor/gate dielectric interface. More importantly, the photochemically activated IGZO TFTs showed much reduced overall V{sub T} shift compared to thermally annealed TFTs. Reduced number of donor-like interface states creation under light illumination and more facile neutralization of ionized oxygen vacancies by electron capture under positive gate potential are claimed to be the origin of the less V{sub T} shift in photochemically activated TFTs.

  16. Light-induced hysteresis and recovery behaviors in photochemically activated solution-processed metal-oxide thin-film transistors

    NASA Astrophysics Data System (ADS)

    Jo, Jeong-Wan; Kim, Yong-Hoon; Park, Sung Kyu

    2014-07-01

    In this report, photo-induced hysteresis, threshold voltage (VT) shift, and recovery behaviors in photochemically activated solution-processed indium-gallium-zinc oxide (IGZO) thin-film transistors (TFTs) are investigated. It was observed that a white light illumination caused negative VT shift along with creation of clockwise hysteresis in electrical characteristics which can be attributed to photo-generated doubly ionized oxygen vacancies at the semiconductor/gate dielectric interface. More importantly, the photochemically activated IGZO TFTs showed much reduced overall VT shift compared to thermally annealed TFTs. Reduced number of donor-like interface states creation under light illumination and more facile neutralization of ionized oxygen vacancies by electron capture under positive gate potential are claimed to be the origin of the less VT shift in photochemically activated TFTs.

  17. Consolidation of amorphous oxide powders using spark plasma sintering

    Microsoft Academic Search

    Daniela Marisa Fredrick

    2009-01-01

    The objective of this study is to synthesize amorphous oxide powders and sinter the systems close to or at theoretical density for optical transparency while retaining the amorphous structure using the Spark Plasma Sintering (SPS) method. In addition, the parameters that govern the formation of these systems were investigated. The main powder processing techniques are sol-gel, flame-spaying and spherodizing. The

  18. Unveiling the complex electronic structure of amorphous metal oxides

    PubMed Central

    ?rhammar, C.; Pietzsch, Annette; Bock, Nicolas; Holmström, Erik; Araujo, C. Moyses; Gråsjö, Johan; Zhao, Shuxi; Green, Sara; Peery, T.; Hennies, Franz; Amerioun, Shahrad; Föhlisch, Alexander; Schlappa, Justine; Schmitt, Thorsten; Strocov, Vladimir N.; Niklasson, Gunnar A.; Wallace, Duane C.; Rubensson, Jan-Erik; Johansson, Börje; Ahuja, Rajeev

    2011-01-01

    Amorphous materials represent a large and important emerging area of material’s science. Amorphous oxides are key technological oxides in applications such as a gate dielectric in Complementary metal-oxide semiconductor devices and in Silicon-Oxide-Nitride-Oxide-Silicon and TANOS (TaN-Al2O3-Si3N4-SiO2-Silicon) flash memories. These technologies are required for the high packing density of today’s integrated circuits. Therefore the investigation of defect states in these structures is crucial. In this work we present X-ray synchrotron measurements, with an energy resolution which is about 5–10 times higher than is attainable with standard spectrometers, of amorphous alumina. We demonstrate that our experimental results are in agreement with calculated spectra of amorphous alumina which we have generated by stochastic quenching. This first principles method, which we have recently developed, is found to be superior to molecular dynamics in simulating the rapid gas to solid transition that takes place as this material is deposited for thin film applications. We detect and analyze in detail states in the band gap that originate from oxygen pairs. Similar states were previously found in amorphous alumina by other spectroscopic methods and were assigned to oxygen vacancies claimed to act mutually as electron and hole traps. The oxygen pairs which we probe in this work act as hole traps only and will influence the information retention in electronic devices. In amorphous silica oxygen pairs have already been found, thus they may be a feature which is characteristic also of other amorphous metal oxides.

  19. Comparison of electrochromic amorphous and crystalline tungsten oxide films

    Microsoft Academic Search

    Esra Ozkan; Se-Hee Lee; C. Edwin Tracy; J. Roland Pitts; Satyen K. Deb

    2003-01-01

    A detailed systematic study of the tungsten oxide thin films has been carried out using WO3 films after they were annealed at progressively increasing temperatures ranging from 350°C to 450°C in oxygen environments. The structural properties of the films were characterized using X-ray diffraction and Raman spectroscopy. The amorphous WO3 films remain as an amorphous phase up to 385°C and

  20. Natural realgar and amorphous AsS oxidation kinetics

    NASA Astrophysics Data System (ADS)

    Lengke, Maggy F.; Tempel, Regina N.

    2003-03-01

    The oxidation rates of natural realgar and amorphous synthetic AsS by dissolved oxygen were evaluated using mixed flow reactors at pH 7.2 to 8.8 and dissolved oxygen contents of 5.9 to 16.5 ppm over a temperature range of 25 to 40°C. The ratios of As/S are stoichiometric for all amorphous AsS oxidation experiments except for two experiments conducted at pH ˜8.8. In these experiments, stoichiometric ratios of As/S were only observed in the early stages of AsS (am) oxidation whereas lower As/S ratios were observed during steady state. For realgar oxidation experiments, the As/S ratio is less than the stoichiometric ratio of realgar, ranging between 0.61 and 0.71. This nonstoichiometric release of As and S to solution indicates that realgar oxidation is more selective for S after the rates of oxidation become constant. All measured oxidation rates at 25°C can be described within experimental uncertainties as follows: Table 1

  1. Absorption of ac fields in amorphous indium-oxide films

    SciTech Connect

    Ovadyahu, Z. [Racah Institute of Physics, the Hebrew University, Jerusalem 91904 (Israel)

    2014-08-20

    Absorption data from applied ac fields in Anderson-localized amorphous indium-oxide (In{sub x}O) films are shown to be frequency and disorder dependent. The absorption shows a roll-off at a frequency which is much lower than the electron-electron scattering rate of the material when it is in the diffusive regime. This is interpreted as evidence for discreteness of the energy spectrum of the deeply localized regime. This is consistent with recent many-body localization scenarios. As the metal-insulator transition is approached, the absorption shifts to higher frequencies. Comparing with the previously obtained results on the crystalline version of indium-oxide (In{sub 2}O{sub 3?x}) implies a considerably higher inelastic electron-phonon scattering rate in the amorphous material. The range over which the absorption versus frequency decreases may indicate that a wide distribution of localization length is a common feature in these systems.

  2. Materials, Devices, and Circuits of Transparent Amorphous-Oxide Semiconductor

    Microsoft Academic Search

    Hideya Kumomi; Seiichiro Yaginuma; Hideyuki Omura; Amita Goyal; Ayumu Sato; Masaya Watanabe; Mikio Shimada; Nobuyuki Kaji; Kenji Takahashi; Masato Ofuji; Tomohiro Watanabe; Naho Itagaki; Hisae Shimizu; Katsumi Abe; Yoshinori Tateishi; Hisato Yabuta; Tatsuya Iwasaki; Ryo Hayashi; Toshiaki Aiba; Masafumi Sano

    2009-01-01

    This paper presents the following recent investigations of transparent amorphous-oxide semiconductors (TAOS) from materials to devices and circuits. 1) Composition of metals in TAOS are widely explored with the aim of seeking semiconductors suitable for the channel layers of thin-film transistors (TFTs) composing backplanes for flat-panel displays. It is found in combinatorial approaches to the materials exploration that indium-based ternary

  3. Instabilities in Amorphous Oxide Semiconductor Thin-Film Transistors

    Microsoft Academic Search

    2010-01-01

    Thin-film transistors (TFTs) fabricated using amorphous oxide semiconductors (AOS) exhibit good electron mobility (5 to >; 50 cm2\\/V · s), they are transparent, and they can be processed at low temperatures. These new materials show a great promise for high-performance large-area electronics applications such as flexible electronics, transparent electronics, and analog current drivers for organic light-emitting diode displays. Before any

  4. Niobium nitride Josephson tunnel junctions with oxidized amorphous silicon barriers

    Microsoft Academic Search

    F. Shinoki; A. Shoji; S. Kosaka; S. Takada; H. Hayakawa

    1981-01-01

    High-quality NbN\\/NbN Josephson tunnel junctions have been fabricated by rf sputtering. Tunneling barriers are formed by oxidizing amorphous silicon films produced with rf glow discharge deposition. For patterning the base and counter electrode, sputtered ZnO films are employed as a resist mask. The juncitons are found to have large gaps (2?NbN) =4.4 mV), to have low leakage current, and to

  5. Amorphization and Recrystallization of the ABO(3) Oxides

    SciTech Connect

    Meldrum, Alkiviathes (Alberta, University of) [Alberta, University of; Boatner, Lynn A.(Oak Ridge National Laboratory) [Oak Ridge National Laboratory; Weber, William J.(BATTELLE (PACIFIC NW LAB)) [BATTELLE (PACIFIC NW LAB); Ewing, Rodney C.(Michigan, Univ Of - Ann Arbor) [Michigan, Univ Of - Ann Arbor

    2002-01-31

    Single crystals of the ABO3 phases CaTiO3, SrTiO3, BaTiO3, LiNbO3, KNbO3, LiTaO3, and KTaO3 were irradiated by 800 keV Kr+, Xe+, or Ne+ ions over the temperature range from 20 to 1100 K. The critical amorphization temperature, Tc, above which radiation-induced amorphization does not occur varied from approximately 450 K for the titanate compositions to more than 850 K for the tantalates. While the absolute ranking of increasing critical amorphization temperatures could not be explained by any simple physical parameter associated with the ABO3 oxides, within each chemical group defined by the B-site cation (i.e., within the titanates, niobates, and tantalates), Tc tends to increase with increasing mass of the A-site cation. Tc was lower for the Ne+ irradiations as compared to Kr+, but it was approximately the same for the irradiations with Kr+ or Xe+. Thermal recrystallization experiments were performed on the ion-beam-amorphized thin sections in situ in the transmission electron microscope (TEM). In the high vacuum environment of the microscope, the titanates recrystallized epitaxially from the thick areas of the TEM specimens at temperatures of 800 to 850 K. The niobates and tantalates did not recrystallize epitaxially, but instead, new crystals nucleated and grew in the amorphous region in the temperature range 825 to 925 K. These new crystallites apparently retain some''memory'' of the original crystal orientation prior to ion-beam amorphization.

  6. Bismuth oxide coated amorphous manganese dioxide for electrochemical capacitors

    NASA Astrophysics Data System (ADS)

    Li, Xiaofeng; Zhang, Linsen; Dong, Huichao; Xia, Tongchi; Huang, Zhigang

    2015-05-01

    With MnSO4, NaOH and K2S2O8 as the raw materials, the amorphous and ?-type manganese dioxide (MnO2) is separately prepared by using different chemical precipitation-oxidation methods. The results of charge-discharge and electrochemical impedance spectroscopy (EIS) tests show that (i) the specific capacitance of the amorphous MnO2 reaches to 301.2 F g-1 at a current density of 200 mA g-1 and its capacitance retention rate after 2000 cycles is 97%, which is obviously higher than 250.8 F g-1 and 71% of the ?-type one, respectively; (ii) good electrochemical capacitance properties of the amorphous MnO2 should be contributed to easy insertion/extraction of ions within the material; (iii) when 5 wt% Bi2O3 is coated on the amorphous MnO2, its specific capacitance increases to 352.8 F g-1 and the capacitance retention rate is 90% after 2000 cycles.

  7. Amorphous and nanocrystalline oxide electrodes for rechargeable lithium batteries

    SciTech Connect

    Manthiram, A.; Kim, J.; Tsang, C.

    1998-07-01

    Oxo ions (MO{sub 4}){sup n-} (M = V, Cr, Mn and Mo) have been reduced in aqueous solutions with potassium borohydride to obtain the binary oxides MO{sub 2+{delta}}. While the vanadium and manganese oxides are nanocrystalline, the chromium and molybdenum oxides are amorphous. The nanocrystalline VO{sub 2} having a metastable structure and the amorphous CrO{sub 2} and MoO{sub 2.3} transform to the thermodynamically more stable phases upon heating above 300--400 C. These metastable oxides after heating in vacuum at 200--300 C to remove water show good electrode performance in lithium cells. VO{sub 2}, CrO{sub 2} and MoO{sub 2.3} show a reversible capacity of, respectively, 290 mAh/g in the range 4--1.5 V, 180 mAh/g in the range 3.3--2.3 V, and 220 mAh/g in the range 3--1 V. MnO{sub 2} obtained by this process does not show good electrode properties.

  8. Kinetics of enhanced thermal oxidation of silicon carbide using amorphization by ion implantation

    SciTech Connect

    Alok, D.; Baliga, B.J. [North Carolina State Univ., Raleigh, NC (United States). Power Semiconductor Research Center

    1997-03-01

    The kinetics of a thermal oxidation scheme with enhanced growth rate for 6H-SiC is reported in this paper. This scheme is based upon the formation of a thick amorphous layer created using high-dose ion implantation followed by thermal oxidation. The oxide thickness has been demonstrated to be larger in the amorphized region, when compared to the unimplanted (monocrystalline SiC) region, after dry oxidation. The oxide growth rate was parabolic in nature in the amorphized region, in contrast to a mixed linear-parabolic growth rate observed for the monocrystalline region.

  9. Hydrogen permeation barrier performance characterization of vapor deposited amorphous aluminum oxide films using coloration of tungsten oxide

    Microsoft Academic Search

    Y Yamada-Takamura; F Koch; H Maier; H Bolt

    2002-01-01

    Low hydrogen diffusivity and solubility of aluminum oxide make a vapor deposited aluminum oxide (Al2O3) film an anticipated hydrogen permeation barrier coating. In this paper, amorphous Al2O3 film was deposited using filtered vacuum arc method. As a substrate, vapor deposited amorphous tungsten oxide (WO3) film was used in order to characterize hydrogen permeation barrier performance of the Al2O3 film utilizing

  10. Kinetics of dissolution and bio-availability of iron in amorphous siliceous iron oxides 

    E-print Network

    Seaman, John C.

    1990-01-01

    microbial chelate deferroxamine methanesulfonate (DFOB), 3) the ability of a Pseudomonas species to acquire necessary levels of Fe for growth from these oxides. CHAPTERII MINERALOGY AND COMPOSITION OF AMORPHOUS SILICEOUS IRON OXIDES REVIEW...KINETICS OF DISSOLUTION AND BIO-AVAILABILITY OF IRON IN AMORPHOUS SILICEOUS IRON OXIDES A Thesis By John C. Seaman Submitted to the Graduate College of Texas AIIM University in partial fulfillment of the requirements for the degree of MASTER...

  11. Amorphization of oxides in ODS materials under low and high energy ion irradiations

    NASA Astrophysics Data System (ADS)

    Lescoat, M.-L.; Monnet, I.; Ribis, J.; Dubuisson, P.; de Carlan, Y.; Costantini, J.-M.; Malaplate, J.

    2011-10-01

    Oxide Dispersion Strengthened (ODS) ferritic/martensitic (F/M) steels are promising materials as structural components for fusion reactors. Their excellent creep properties are provided by the nano-dispersed oxides reinforcing the material. This oxide dispersion has to be as stable as possible under irradiation at high temperatures. In the present work, low and high energy ion irradiation experiments were used to investigate microstructural stability under irradiation of oxides. Two iron base ODS alloys were studied: the ODS DY reinforced by yttrium and titanium oxides and the ODS EM10 reinforced by magnesium oxides. TEM investigations of the crystallinity for large oxides ( d ? 50 nm) after irradiations reveal that, in both alloys, amorphization can occur due to electronic excitations or ballistic damages. Amorphization appears to depend on the nature of the oxides. Low energy ion irradiation results show that a critical temperature and a critical dose may exist, for which no amorphization is observed.

  12. Electrochemical corrosion and oxidation resistances of Zr60Ni21Al19 bulk amorphous alloys

    NASA Astrophysics Data System (ADS)

    Jing, Qin; Zhang, Bing; Zhang, Jin; Ma, Mingzhen; Liu, Riping

    2010-12-01

    Electrochemical corrosion and oxidation resistances of Zr60Ni21Al19 amorphous alloy were studied. The ternary amorphous alloy exhibits greater positive potential than its crystalline counterpart and 0Cr19Ni9Ti stainless steel. Its weight loss result measured in 2 mol/L HCl solution is in agreement with the potentiodynamic curve. But there is no obvious difference in the oxidation resistances between Zr60Ni21Al19 amorphous and its crystalline alloys. They both exhibit high oxidation resistance.

  13. Better than crystalline: amorphous vanadium oxide for sodium-ion batteries

    E-print Network

    Cao, Guozhong

    development.1,2 Among commercially available energy storage media, lithium-ion (Li-ion) batteries constituteBetter than crystalline: amorphous vanadium oxide for sodium-ion batteries E. Uchaker, Y. Z. Zheng and investigated as cathodes for sodium- ion batteries. Amorphous V2O5 demonstrated superior electro- chemical

  14. Kinetics of dissolution and bio-availability of iron in amorphous siliceous iron oxides

    E-print Network

    Seaman, John C.

    1990-01-01

    KINETICS OF DISSOLUTION AND BIO-AVAILABILITY OF IRON IN AMORPHOUS SILICEOUS IRON OXIDES A Thesis By John C. Seaman Submitted to the Graduate College of Texas AIIM University in partial fulfillment of the requirements for the degree of MASTER... OF SCIENCE December 1990 Major Subject: Soil Science KINETICS OF DISSOLUTION AND BIO-AVAILABILITY OF IRON IN AMORPHOUS SILICEOUS IRON OXIDES A Thesis By John C. Seaman Approved as to style and content by: Richard H. Loeppert (Chair of Committee...

  15. Size dependent transport of amorphous Indium Oxide films.

    NASA Astrophysics Data System (ADS)

    Soman, Swati; Shahar, Dan

    2009-03-01

    Superconductivity in presence of disorder is a topic of interest among experimentalists as well as theoreticians for past several decades. Experiments performed on disordered films of various materials, elemental as well as mixture, have demonstrated Superconductor to Insulator transition (SIT) with increase in disorder or externally applied magnetic field. Disorder is difficult to quantify. However, in an experiment it is controlled by tuning film thickness and/or composition. We present experimental evidence of SIT, in disordered, amorphous Indium Oxide (a:InOx) films, which is tuned by films' lateral dimensions. By fabricating films of same thickness and composition in Hall bar geometry and changing only the sizes of Hall bars, we observe that the sheet resistance per square, R changes with the size of the square, contrary to its definition. The systematic dependence of R on square size is observed to occur only for a critical disorder, similar to percolation model. The observations suggest an inhomogeneous nature of transport near SIT in our samples which are found to be structurally homogeneous. We postulate that such size dependent transport properties are possible to observe in disordered films of other materials that exhibit SIT.

  16. Electrically conducting ternary amorphous fully oxidized materials and their application

    NASA Technical Reports Server (NTRS)

    Giauque, Pierre (Inventor); Nicolet, Marc (Inventor); Gasser, Stefan M. (Inventor); Kolawa, Elzbieta A. (Inventor); Cherry, Hillary (Inventor)

    2004-01-01

    Electrically active devices are formed using a special conducting material of the form Tm--Ox mixed with SiO2 where the materials are immiscible. The immiscible materials are forced together by using high energy process to form an amorphous phase of the two materials. The amorphous combination of the two materials is electrically conducting but forms an effective barrier.

  17. The Electrical and Band-Gap Properties of Amorphous Zinc-Indium-Tin Oxide Thin Films

    E-print Network

    Shahriar, Selim

    MRSEC The Electrical and Band-Gap Properties of Amorphous Zinc-Indium-Tin Oxide Thin Films D Science & Engineering Center For zinc-indium-tin oxide (ZITO) films, grown by pulsed-laser deposition, ZITO-50 and ZITO-70 in which, respectively, 30%, 50% and 70% of the indium in the In2O3 structure

  18. Review of recent developments in amorphous oxide semiconductor thin-film transistor devices

    Microsoft Academic Search

    Joon Seok Park; Wan-Joo Maeng; Hyun-Suk Kim; Jin-Seong Park

    The present article is a review of the recent progress and major trends in the field of thin-film transistor (TFT) research involving the use of amorphous oxide semiconductors (AOS). First, an overview is provided on how electrical performance may be enhanced by the adoption of specific device structures and process schemes, the combination of various oxide semiconductor materials, and the

  19. Photoluminescence of amorphous niobium oxide films synthesized by solid-state reaction

    Microsoft Academic Search

    Xiaofeng Zhou; Zhengcao Li; Yuquan Wang; Xing Sheng; Zhengjun Zhang

    2008-01-01

    Niobium oxide amorphous films were deposited on silicon substrates at a temperature range of 300–400 °C by heating a pure niobium foil in a rough vacuum. The films were amorphous in structure and with morphology of vertically aligned nano-columns. This feature resulted in interesting photoluminescence (PL) property in the visible light range. The intensity of the photoluminescence spectrum of the as-deposited

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

    DOEpatents

    Perkins, John (Boulder, CO); Van Hest, Marinus Franciscus Antonius Maria (Lakewood, CO); Ginley, David (Evergreen, CO); Taylor, Matthew (Golden, CO); Neuman, George A. (Holland, MI); Luten, Henry A. (Holland, MI); Forgette, Jeffrey A. (Hudsonville, MI); Anderson, John S. (Holland, MI)

    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.

  1. Observation of the amorphous zinc oxide recrystalline process by molecular dynamics simulation

    PubMed Central

    Lin, Ken-Huang; Sun, Shih-Jye; Ju, Shin-Pon; Tsai, Jen-Yu; Chen, Hsin-Tsung; Hsieh, Jin-Yuan

    2013-01-01

    The detailed structural variations of amorphous zinc oxide (ZnO) as well as wurtzite (B4) and zinc blende (B3) crystal structures during the temperature elevation process were observed by molecular dynamics simulation. The amorphous ZnO structure was first predicted through the simulated-annealing basin-hopping algorithm with the criterion to search for the least stable structure. The density and X-ray diffraction profiles of amorphous ZnO of the structure were in agreement with previous reports. The local structural transformation among different local structures and the recrystalline process of amorphous ZnO at higher temperatures are observed and can explain the structural transformation and recrystalline mechanism in a corresponding experiment [Bruncko et al., Thin Solid Films 520, 866-870 (2011)]. PMID:23509413

  2. Preparation of amorphous electrochromic tungsten oxide and molybdenum oxide by plasma enhanced chemical vapor deposition

    SciTech Connect

    Tracy, C.E.; Benson, D.K.

    1986-09-01

    Preliminary experiments have been performed to probe the feasibility of using plasma enhanced chemical vapor deposition (PE--CVD) to prepare electrochromic thin films of tungsten oxide and molybdenum oxide by plasma reaction of WF/sub 6/, W(CO)/sub 6/, and Mo(CO)/sub 6/ with oxygen. Thin films produced in a 300 W, electrodeless, radio-frequency (rf), capacitive discharge were found to be electrochromic when tested with either liquid or solid electrolytes. Optical spectroscopy was performed on two electrochromic coatings after Li/sup +/ ion insertion from a propylene carbonate liquid electrolyte. Broad absorption peaks at --900 nm for WO/sub 3/ and 600 nm for MoO/sub 3/ were observed. Optical results for PE--CVD MoO/sub 3/ films differ from those reported for evaporated MoO/sub 3/ films which have an absorption peak at --800 nm. The shorter wavelength absorption in the PE--CVD MoO/sub 3/ films offers the potential for fabricating electrochromic devices with higher contrast ratios and less color change. Optical emission spectroscopy, Auger, and x-ray diffraction analyses indicate these thin film deposits to be predominantly amorphous tungsten and molybdenum oxides.

  3. Influence of synthesis conditions on the electrochemical properties of nanostructured amorphous manganese oxide cryogels

    NASA Astrophysics Data System (ADS)

    Yang, Jingsi; Xu, Jun John

    Amorphous manganese oxides have received increasing attention in recent years as intercalation cathodes for rechargeable lithium batteries. The sol-gel method is a versatile method for achieving nanostructured amorphous oxides. In this paper, two different sol-gel routes are investigated, where nanostructured amorphous manganese oxide cryogels are obtained via freeze drying Mn(IV) oxide hydrogels formed in situ. In one route the hydrogels are formed by reaction between a solution of sodium permanganate and a solution of disodium fumarate, and in the other route by reaction between a solution of sodium permanganate and solid fumaric acid. Highly homogeneous monolithic manganese oxide hydrogels are obtained from both synthesis routes with precursor concentrations between 0.1 and 0.2 M. The freeze drying method proves to be an efficient method for obtaining nanostructured amorphous manganese oxide cryogels out of the hydrogels. Depending on the synthesis conditions of the hydrogels, the resultant cryogels can yield very high specific capacities for lithium intercalation and excellent rate performance. The cryogel with the best performance exhibits 289 mAh/g at a C/100 rate and 174 mAh/g at a 2 C rate. Strong dependence of electrochemical properties of the cryogels on the synthesis conditions of the parent hydrogels has been observed. The different electrochemical properties are believed to be due to different surface areas and local structures of the cryogels derived from hydrogels synthesized under different conditions. This strong dependence gives rise to the possibility of achieving promising intercalation materials through tailoring the surface area and the local structure of amorphous manganese oxides by adjusting sol-gel synthesis conditions.

  4. Composition-dependent structural and transport properties of amorphous transparent conducting oxides

    NASA Astrophysics Data System (ADS)

    Khanal, Rabi; Buchholz, D. Bruce; Chang, Robert P. H.; Medvedeva, Julia E.

    2015-05-01

    Structural properties of amorphous In-based oxides, In -X -O with X =Zn , Ga, Sn, or Ge, are investigated using ab initio molecular dynamics liquid-quench simulations. The results reveal that indium retains its average coordination of 5.0 upon 20% X fractional substitution for In, whereas X cations satisfy their natural coordination with oxygen atoms. This finding suggests that the carrier generation is primarily governed by In atoms, in accord with the observed carrier concentration in amorphous In-O and In -X -O . At the same time, the presence of X affects the number of six-coordinated In atoms as well as the oxygen sharing between the InO6 polyhedra. Based on the obtained interconnectivity and spatial distribution of the InO6 and XO x polyhedra in amorphous In -X -O , composition-dependent structural models of the amorphous oxides are derived. The results help explain our Hall mobility measurements in In -X -O thin films grown by pulsed-laser deposition and highlight the importance of long-range structural correlations in the formation of amorphous oxides and their transport properties.

  5. Intrinsic stress evolution during amorphous oxide film growth on Al surfaces

    SciTech Connect

    Flötotto, D., E-mail: d.floetotto@is.mpg.de; Wang, Z. M.; Jeurgens, L. P. H. [Max Planck Institute for Intelligent Systems (former Max Planck Institute for Metals Research), Heisenbergstraße 3, D-70569 Stuttgart (Germany); Mittemeijer, E. J. [Max Planck Institute for Intelligent Systems (former Max Planck Institute for Metals Research), Heisenbergstraße 3, D-70569 Stuttgart (Germany); Institute for Materials Science, University of Stuttgart (Germany)

    2014-03-03

    The intrinsic stress evolution during formation of ultrathin amorphous oxide films on Al(111) and Al(100) surfaces by thermal oxidation at room temperature was investigated in real-time by in-situ substrate curvature measurements and detailed atomic-scale microstructural analyses. During thickening of the oxide a considerable amount of growth stresses is generated in, remarkably even amorphous, ultrathin Al{sub 2}O{sub 3} films. The surface orientation-dependent stress evolutions during O adsorption on the bare Al surfaces and during subsequent oxide-film growth can be interpreted as a result of (i) adsorption-induced surface stress changes and (ii) competing processes of free volume generation and structural relaxation, respectively.

  6. Oxidation induced amorphous stabilization of the subsurface region in Zr-Cu metallic glass

    SciTech Connect

    Lim, K. R. [Light Metal Division, Korea Institute of Materials Science, 797 Changwondaero, Seongsan-gu, Changwon, Gyeongnam 642-831 (Korea, Republic of); Park, J. M. [Materials Research Center, Samsung Advanced Institute of Technology (SAIT) San 14-1, Nongseo-dong, Giheung-gu, Yongin-si, Gyeonggi-do 446-712 (Korea, Republic of); Park, S. H.; Na, M. Y.; Kim, K. C.; Kim, D. H., E-mail: dohkim@yonsei.ac.kr [Department of Materials Science and Engineering, Center for Non-crystalline Materials, Yonsei University, 134 Shinchon-dong, Seodaemun-gu, Seoul 120-749 (Korea, Republic of); Kim, W. T. [Department of Optical Engineering, Cheongju University, 36 Naedock-dong, Cheongju 360-764 (Korea, Republic of)

    2014-01-20

    In the present study, we demonstrate that selective surface oxidation of Zr{sub 70}Cu{sub 30} metallic glass can stabilize the amorphous structure in the subsurface region of the matrix. The oxidation proceeds by selective oxidation of Zr, forming monoclinic ZrO{sub 2} layer on the surface, and the subsurface layer becomes Cu-enriched due to back diffusion of Cu atoms from the oxide layer. Interestingly, in this system, the composition change in the subsurface region leads to enhancement of glass stability, forming of a double layered surface structure consisted of inner amorphous layer and outer monoclinic ZrO{sub 2} layer even when the remaining matrix is completely crystallized.

  7. Thickness dependence of optical properties of amorphous indium oxide thin films deposited by reactive evaporation

    Microsoft Academic Search

    K. Uluta; D. Deer; Y. Skarlatos

    2006-01-01

    The electrical conductivity and absorption coefficient of amorphous indium oxide thin films, thermally evaporated on glass substrates at room temperature, were evaluated. For direct transitions the variation of the optical band gap with thickness was determined and this variation was supposed to appear due to the variation of localized gap states, whereas the variation of conductivity with thickness was supposed

  8. Electrical and optical properties of sputtered amorphous vanadium oxide thin films

    SciTech Connect

    Podraza, N. J. [Department of Physics and Astronomy, University of Toledo, Toledo, Ohio 43606 (United States); Gauntt, B. D. [Materials Characterization Department, Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); Motyka, M. A.; Horn, M. W. [Department of Engineering Science and Mechanics, Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Dickey, E. C. [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States)

    2012-04-01

    Amorphous vanadium oxide (VO{sub x}) is a component found in composite nanocrystalline VO{sub x} thin films. These types of composite films are used as thermistors in pulsed biased uncooled infrared imaging devices when containing face centered cubic vanadium monoxide phase crystallites, and substantial fractions of amorphous material in the composite are necessary to optimize device electrical properties. Similarly, optoelectronic devices exploiting the metal-to-semiconductor transition contain the room-temperature monoclinic or high-temperature (>68 deg. C) rutile vanadium dioxide phase. Thin films of VO{sub x} exhibiting the metal-to-semiconductor transition are typically polycrystalline or nanocrystalline, implying that significant amounts of disordered, amorphous material is present at grain boundaries or surrounding the crystallites and can impact the overall optical or electronic properties of the film. The performance of thin film material for either application depends on both the nature of the crystalline and amorphous components, and in this work we seek to isolate and study amorphous VO{sub x}. VO{sub x} thin films were deposited by pulsed dc reactive magnetron sputtering to produce amorphous materials with oxygen contents {>=}2, which were characterized electrically by temperature dependent current-voltage measurements and optically characterized by spectroscopic ellipsometry. Film resistivity, thermal activation energy, and complex dielectric function spectra from 0.75 to 6.0 eV were used to identify the impact of microstructural variations including composition and density.

  9. Two spin-freezing behavior in concentrated amorphous ferrite oxides

    NASA Astrophysics Data System (ADS)

    Okuno, S. N.; Hashimoto, S.; Inomata, K.; Morimoto, S.; Ito, A.

    1991-04-01

    Amorphous CoFe2O4 with metal ions coordinated in a manner similar to the spinal crystal was prepared by the ion-beam sputter deposition method. The study of magnetic properties was carried out by dc- and ac-susceptibility measurements and Mössbauer spectroscopy. The strong spin-freezing behavior was observed in 80-Hz, 1-Oe ac susceptibility at two spin-freezing temperatures: 284 K (Tf1), which is considered to be caused by a random anisotropy of Co ions coordinated in distorted octahedral sites, and 86 K (Tf2), which might be caused by the frustration of antiferromagnetic interactions due to the amorphous structure. The dc susceptibility showed irreversibility below Tf1 which decreased with increasing applied field. However, a distinct change was not observed at Tf2. The Mössbauer spectrum revealed that some of the paramagnetic Fe ions were frozen below Tf1, with relaxation phenomena, and that the residual paramagnetic ions were frozen at Tf2. The time decay of the thermoremanent magnetization observed below Tf1 showed different behavior compared to that above and below Tf2.

  10. Intrinsic nature of visible-light absorption in amorphous semiconducting oxides

    NASA Astrophysics Data System (ADS)

    Kang, Youngho; Song, Hochul; Nahm, Ho-Hyun; Jeon, Sang Ho; Cho, Youngmi; Han, Seungwu

    2014-03-01

    To enlighten microscopic origin of visible-light absorption in transparent amorphous semiconducting oxides, the intrinsic optical property of amorphous InGaZnO4 is investigated by considering dipole transitions within the quasiparticle band structure. In comparison with the crystalline InGaZnO4 with the optical gap of 3.6 eV, the amorphous InGaZnO4 has two distinct features developed in the band structure that contribute to significant visible-light absorption. First, the conduction bands are down-shifted by 0.55 eV mainly due to the undercoordinated In atoms, reducing the optical gap between extended states to 2.8 eV. Second, tail states formed by localized oxygen p orbitals are distributed over ˜0.5 eV near the valence edge, which give rise to substantial subgap absorption. The fundamental understanding on the optical property of amorphous semiconducting oxides based on underlying electronic structure will pave the way for resolving instability issues in recent display devices incorporating the semiconducting oxides.

  11. High-k (k=30) amorphous hafnium oxide films from high rate room temperature deposition

    SciTech Connect

    Li, Flora M.; Bayer, Bernhard C.; Hofmann, Stephan; Milne, William I.; Flewitt, Andrew J. [Department of Engineering, Electrical Engineering Division, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0FA (United Kingdom); Dutson, James D.; Wakeham, Steve J.; Thwaites, Mike J. [Plasma Quest Ltd., Unit 1B, Rose Estate, Osborn Way, Hook, Hampshire RG27 9UT (United Kingdom)

    2011-06-20

    Amorphous hafnium oxide (HfO{sub x}) is deposited by sputtering while achieving a very high k{approx}30. Structural characterization suggests that the high k is a consequence of a previously unreported cubiclike short range order in the amorphous HfO{sub x} (cubic k{approx}30). The films also possess a high electrical resistivity of 10{sup 14} {Omega} cm, a breakdown strength of 3 MV cm{sup -1}, and an optical gap of 6.0 eV. Deposition at room temperature and a high deposition rate ({approx}25 nm min{sup -1}) makes these high-k amorphous HfO{sub x} films highly advantageous for plastic electronics and high throughput manufacturing.

  12. Crystallization and magnetic properties of amorphous iron–chromium oxide nanoparticles synthesized by sonochemistry

    NASA Astrophysics Data System (ADS)

    Phu Nguyen, Dang; Tran, Quoc Tuan; Trinh, Xuan Sy; Cao Hoang, Thanh; Nguyen, Hoang Nam; Hai Nguyen, Hoang

    2012-03-01

    Amorphous iron–chromium oxide Fe2?xCrxO3 (x=0, 0.05, 0.10, 0.15, 0.20) nanoparticles were synthesized by sonochemical method at 80?°C. Crystallization process of the annealed samples showed a strong ferromagnetic behavior due to the existence of the maghemite phase. The effect of chromium replacing iron in the crystallization process of Fe2?xCrxO3 nanoparticles was systematically studied by adjusting initial concentration of Cr3+. The activation energy of the samples deduced from thermal analysis and increased with doping chromium showed that the existence of chromium can significantly slow down the ageing effect of the amorphous iron oxide.

  13. Microstructure and wet oxidation of low-temperature-grown amorphous (Al/Ga,As)

    SciTech Connect

    Chang, K. L.; Pickrell, G. W.; Wohlert, D. E.; Epple, J. H.; Lin, H. C.; Cheng, K. Y.; Hsieh, K. C.

    2001-01-01

    Amorphous and polycrystalline compounds of (Ga,As) and (Al,As) grown at very low temperatures by molecular-beam epitaxy are characterized. The ultimate microstructure and the amount of excess arsenic incorporated in the (Ga,As) or (Al,As) layers are found to depend on the arsenic overpressure during the low-temperature growth. With lower arsenic overpressure, a polycrystalline structure prevails and less excess arsenic is observed inside the layer. In contrast, a high incorporation of excess arsenic achieved by high-arsenic overpressures leads to the formation of amorphous films. Upon wet oxidation, the lateral oxidation rate of (Al,As) is found to depend on the crystallinity of the (Al,As) layer and the amount of excess arsenic. During the same process, recrystallization proceeds in the (Ga,As) layer.

  14. Mechanisms of Arsenic Adsorption on Amorphous Oxides Evaluated Using Macroscopic Measurements, Vibrational Spectroscopy, and Surface Complexation Modeling

    Microsoft Academic Search

    Sabine Goldberg; Cliff T. Johnstony

    2001-01-01

    Arsenic adsorption on amorphous aluminum and iron oxides was investigated as a function of solution pH, solution ionic strength, and redox state. In this study in situ Raman and Fourier transform infrared (FTIR) spectroscopic methods were combined with sorption techniques, electrophoretic mobility measurements, and surface complexation modeling to study the interaction of As(III) and As(V) with amorphous oxide surfaces. The

  15. Evaluation of Subretinal Implants Coated with Amorphous Aluminum Oxide and Diamond-like Carbon

    Microsoft Academic Search

    Robyn Sweitzer; Carmen Scholz; Sandra Montezuma; Joseph F. Rizzo

    2006-01-01

    Retinal prostheses may be used to support patients suffering from age-related macular degeneration (AMD) or retinitis pigmentosa (RP). A hermetic encapsulation of the poly(imide) (PI)-based prosthesis is important in order to prevent the leakage of water and ions into the electric circuitry embedded in the poly(imide) matrix. The deposition of amorphous aluminum oxide (by sputtering) and diamond like carbon (by

  16. Permanent optical doping of amorphous metal oxide semiconductors by deep ultraviolet irradiation at room temperature

    Microsoft Academic Search

    Hyungtak Seo; Young-Je Cho; Jinwoo Kim; Santosh M. Bobade; Kyoung-Youn Park; Jaegab Lee; Duck-Kyun Choi

    2010-01-01

    We report an investigation of two photon ultraviolet (UV) irradiation induced permanent n-type doping of amorphous InGaZnO (a-IGZO) at room temperature. The photoinduced excess electrons were donated to change the Fermi-level to a conduction band edge under the UV irradiation, owing to the hole scavenging process at the oxide interface. The use of optically n-doped a-IGZO channel increased the carrier

  17. Oxidative and tribological properties of amorphous and quasicrystalline approximant Al-Cu-Fe thin films.

    PubMed

    Rampulla, D M; Mancinelli, C M; Brunell, I F; Gellman, A J

    2005-05-10

    The origins of the tribological properties and corrosion resistance of amorphous and quasicrystalline approximant alloys have been studied by comparing their properties in thin Al-Cu-Fe alloy films with compositions lying near the quasicrystalline region of the ternary compositional phase diagram. Six sputtered thin films of an Al-Cu-Fe alloy were studied using X-ray diffraction, X-ray photoemission spectroscopy (XPS), and an in situ ultrahigh vacuum (UHV) tribometer. The films were annealed in UHV to induce the formation of orthorhombic, rhombohedral, and amorphous bulk structures. The properties of these thin films were then determined in the same UHV apparatus without exposing the films to air. The rates of surface oxidation by H2O and O2 were measured using XPS. Although the oxidation rates and oxide thicknesses were dependent on the oxidant, they were not sensitive to the structures of the films. Friction was measured between identical samples in sliding contact. The friction coefficients (micros = 0.36 +/- 0.11 to 0.56 +/- 0.08) were comparable to those observed in other experiments using quasicrystals and approximants in UHV; however, there was no strong correlation between the friction coefficients and either the film structure or the degree of surface oxidation. These results suggest that the tribological and corrosion resistance properties of these quasicrystalline approximant alloys are not directly connected to crystalline structure. PMID:16032871

  18. Development of Pinhole-Free Amorphous Aluminum Oxide Protective Layers for Biomedical Device Applications.

    PubMed

    Litvinov, Julia; Wang, Yi-Ju; George, Jinnie; Chinwangso, Pawilai; Brankovic, Stanko; Willson, Richard C; Litvinov, Dmitri

    2013-06-15

    This paper describes synthesis of ultrathin pinhole-free insulating aluminum oxide layers for electronic device protection in corrosive liquid environments, such as phosphate buffered saline (PBS) or clinical fluids, to enable emerging biomedical applications such as biomolecular sensors. A pinhole-free 25-nm thick amorphous aluminum oxide layer has been achieved using ultra-high vacuum DC magnetron reactive sputtering of aluminum in oxygen/argon plasma followed by oxygen plasma post-processing. Deposition parameters were optimized to achieve the best corrosion protection of lithographically defined device structures. Electrochemical deposition of copper through the aluminum oxide layers was used to detect the presence (or absence) of pinholes. FTIR, XPS, and spectroscopic ellipsometry were used to characterize the material properties of the protective layers. Electrical resistance of the copper device structures protected by the aluminum oxide layers and exposed to a PBS solution was used as a metric to evaluate the long-term stability of these device structures. PMID:23682201

  19. Preparation and anti-oxidation characteristics of ZrSiO4-SiBCN(O) amorphous coating

    NASA Astrophysics Data System (ADS)

    Tang, Baojun; Feng, Zelong; Hu, Shujuan; Zhang, Yue

    2015-03-01

    In this paper, a dense and seamless SiBCN(O) amorphous coating with a few ZrSiO4 particles is prepared by low-cost slurry method and sintered at 1573 K, namely ZrSiO4-SiBCN(O) amorphous coating. During its preparation process, by employing the polyborosilazane (PBSZ)-ethanol solution as the precursor, the sintering temperature of the coating is significantly reduced and its densification is greatly improved as well. The coating was heat-treated in stagnant laboratory air at 1773 K from 5 min to 8 h. It shows high oxidation protecting performance during oxidation and the oxidation mechanism includes three stages, that are active oxidation, defection healing and oxygen diffusion at 1773 K. It was also found that, by introducing the ZrSiO4 particles into the SiBCN(O) amorphous coating, the propagation of micro-cracks during its oxidation process is prominently inhibited.

  20. Amorphous microporous titania-silica mixed oxides: Preparation, characterization, and catalytic redox properties

    SciTech Connect

    Klein, S.; Thorimbert, S.; Maier, W.F. [Max-Planck-Institut fuer Kohlenforschung, Ruhr (Germany)] [Max-Planck-Institut fuer Kohlenforschung, Ruhr (Germany)

    1996-10-01

    Microporous titania-silica mixed oxides with a narrow monomodal pore size distribution at pore diameters of 0.7 nm with highly dispersed titanium in the silica matrix have been obtained by a simple acid-catalyzed sol-gel process in the absence of chelating agents or the prehydrolysis techniques. A mixture of titanium(IV)alkoxide and tetraethoxysilane (TEOS) has been hydrolysed in alcoholic solution with aqueous hydrochloric acid followed by calcination, resulting in amorphous, microporous mixed oxides. There is no limitation on the chemical composition, which covers the whole range from microporous silica to microporous titania. The glasses show not only catalytic activity for selective oxidation reactions with TBHP comparable with that of other titania containing materials, but size selective epoxidations of olefins are interpreted as shape selectivity resulting from their distinct microporosity. Competitive adsorption experiments of water and octane suggest the hydrophilicity of the amorphous oxides to be the major difference in comparison to their zeolitic analogues. 78 refs., 9 figs., 5 tabs.

  1. Photocatalytic decompositions of gaseous HCHO over thin films of anatase titanium oxide converted from amorphous in a heated air and in an aqueous solution of hydrogen peroxide

    Microsoft Academic Search

    Fumihide Shiraishi; Shotaro Ikeda; Naoya Kamikariya

    2009-01-01

    This work investigates photocatalytic decompositions of HCHO in air over thin films of titanium oxide prepared on inside surfaces of glass tubes by the following two methods: Method I (the inside surface of a glass tube was covered with an aqueous H2O2 solution containing amorphous titanium oxide, followed by calcination at 500°C to convert amorphous titanium oxide to anatase one)

  2. Electron beam deposition of amorphous manganese oxide thin film electrodes and their predominant electrochemical properties

    NASA Astrophysics Data System (ADS)

    Sarkar, Abhimanyu; Satpati, Ashis Kumar; Rao, Pritty; Kumar, Sanjiv

    2015-06-01

    Electron beam evaporated manganese oxide films display excellent electrochemical properties on post deposition oxidative annealing in air. The films annealed below 573 K are amorphous, exhibit minor deficiency in oxygen and are characterized by a specific discharge capacitance of 398 F g-1 at a discharge current of 1.1 A g-1 and 236 F g-1 at a discharge current of 5.5 A g-1. In terms of stability, these films retain 99.6% of their specific capacitance even after 400 cycles. The electrochemical properties of these films are explained in terms of their structure and composition which have been measured by X-ray diffraction and proton elastic backscattering spectrometry. In addition, the electrochemical properties are influenced by their morphology; the oxidatively annealed films contain nanometric, spherical and elongated grains which acquire extensive networking during electrochemical measurements.

  3. Amorphous indium tin oxide electrodes for piezoelectric and light-emitting device deposited by vacuum roll to roll process

    Microsoft Academic Search

    Sangyub Ie; Ji-Hwan Kim; Byeong Taek Bae; Dong-Hee Park; Ji-Won Choi; Won-Kook Choi

    2009-01-01

    The amorphous indium tin oxides (ITOs) and the transparent conducting oxides (TCOs) electrode on the flexible polymer substrate, polyvinylidene difluoride (PVDF), and their application to the suggested combinational device system were studied. The lower range ordered crystalline structure of the ITOs enable the reduction of micro-cracks or defect grains under flexible conditions. With the piezoelectric function of substrate polymer, which

  4. Dielectric properties of crystalline and amorphous transition metal oxides and silicates

    NASA Astrophysics Data System (ADS)

    Rignanese, Gian-Marco

    2004-03-01

    Until recently, silicon dioxide has been the dielectric of choice in integrated MOS devices. By 2004, the thickness of this insulating layer is expected to decrease to 1.0 nm to 1.5 nm (about five silicon atoms deep) precluding its effective use due to severe leakage problems. An alternative high-permittivity (high-k) gate dielectric is required. In this framework, transition metal oxides and silicates have attracted considerable attention as possible substitutes. Their dielectric properties constitute an issue of great practical relevance. In particular, it is highly desirable to develop a better understanding of how the permittivity is related to the underlying microstructure. This is the aim of the present work. Using first-principles calculations, we investigate the dielectric properties of group IVB transition metal (Ti, Zr, and Hf) oxides and silicates. We first study various crystalline phases for the oxides (cubic, tetragonal, and rutile) and the silicates (zircon). Then, the amorphous silicates are considered. We introduce a scheme which relates the dielectric constants to the local bonding of silicon and metal atoms. This scheme is based on the definition of parameters characteristic of the basic structural units formed by silicon and metal atoms and their nearest neighbors, and allows us to avoid heavy large-scale calculations, which are beyond current computational capabilities. Applied to amorphous Zr silicates, our scheme provides a good description of the measured dielectric constants, and highlights the role of sixfold coordinated metal atoms.

  5. Amorphous and condensed organic matter domains: the effect of persulfate oxidation on the composition of soil\\/sediment organic matter

    Microsoft Academic Search

    Chiel Cuypers; Tim Grotenhuis; Klaas G. J. Nierop; Elena Maneiro Franco; Adrie de Jager; Wim Rulkens

    2002-01-01

    The composition of amorphous and condensed soil\\/sediment organic matter (SOM) domains was investigated for one soil sample and four sediment samples. These samples were oxidized with persulfate to remove amorphous SOM, before and after which the composition of SOM was studied by thermogravimetric analysis, pyrolysis-GC\\/MS, and cross polarization magic angle spinning 13C-NMR. Comparison of the SOM composition before and after

  6. Silicon nanocrystal memories by LPCVD of amorphous silicon, followed by solid phase crystallization and thermal oxidation

    NASA Astrophysics Data System (ADS)

    Tsoi, E.; Normand, P.; Nassiopoulou, A. G.; Ioannou-Sougleridis, V.; Salonidou, A.; Giannakopoulos, K.

    2005-01-01

    Silicon nanocrystals memory cells of an n-MOSFET type were fabricated and tested, based on a silicon nanocrystal gate MOS structure fabricated by low-pressure chemical vapor deposition (LPCVD) of amorphous silicon (?-Si) on a tunneling silicon dioxide layer, followed by solid phase crystallization and high temperature thermal oxidation. A layer of silicon nanocrystals embedded in SiO2 at a tunneling distance (3.5 nm) from the silicon substrate was thus formed. The obtained memory cells showed a full-write, full-erase memory window of the order of 0.5 V under charging with pulses of 7 V and -8 V respectively at 100 ms.

  7. Thickness dependence of optical properties of amorphous indium oxide thin films deposited by reactive evaporation

    NASA Astrophysics Data System (ADS)

    Uluta, K.; Deer, D.; Skarlatos, Y.

    2006-08-01

    The electrical conductivity and absorption coefficient of amorphous indium oxide thin films, thermally evaporated on glass substrates at room temperature, were evaluated. For direct transitions the variation of the optical band gap with thickness was determined and this variation was supposed to appear due to the variation of localized gap states, whereas the variation of conductivity with thickness was supposed to be due to the variation of carrier concentration. We attribute the variation of absorption coefficient with thickness to the variation of optical band gap energy rather than optical interference.

  8. Hydrogen plasma treatment for improved conductivity in amorphous aluminum doped zinc tin oxide thin films

    SciTech Connect

    Morales-Masis, M., E-mail: monica.moralesmasis@epfl.ch; Ding, L.; Dauzou, F. [Photovoltaics and Thin-Film Electronics Laboratory (PVLab), Institute of Microengineering (IMT), Ecole Polytechnique Fédérale de Lausanne - EPFL, Rue de la Maladière 71b, CH-2002 Neuchatel (Switzerland); Jeangros, Q. [Interdisciplinary Centre for Electron Microscopy, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne (Switzerland); Hessler-Wyser, A. [Photovoltaics and Thin-Film Electronics Laboratory (PVLab), Institute of Microengineering (IMT), Ecole Polytechnique Fédérale de Lausanne - EPFL, Rue de la Maladière 71b, CH-2002 Neuchatel (Switzerland); Interdisciplinary Centre for Electron Microscopy, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne (Switzerland); Nicolay, S. [Centre Suisse d’Electronique et de Microtechnique (CSEM) SA, Rue Jaquet-Droz 1, CH-2002 Neuchatel (Switzerland); Ballif, C. [Photovoltaics and Thin-Film Electronics Laboratory (PVLab), Institute of Microengineering (IMT), Ecole Polytechnique Fédérale de Lausanne - EPFL, Rue de la Maladière 71b, CH-2002 Neuchatel (Switzerland); Centre Suisse d’Electronique et de Microtechnique (CSEM) SA, Rue Jaquet-Droz 1, CH-2002 Neuchatel (Switzerland)

    2014-09-01

    Improving the conductivity of earth-abundant transparent conductive oxides (TCOs) remains an important challenge that will facilitate the replacement of indium-based TCOs. Here, we show that a hydrogen (H{sub 2})-plasma post-deposition treatment improves the conductivity of amorphous aluminum-doped zinc tin oxide while retaining its low optical absorption. We found that the H{sub 2}-plasma treatment performed at a substrate temperature of 50?°C reduces the resistivity of the films by 57% and increases the absorptance by only 2%. Additionally, the low substrate temperature delays the known formation of tin particles with the plasma and it allows the application of the process to temperature-sensitive substrates.

  9. Significant improvement in electronic properties of transparent amorphous indium zinc oxide through yttrium doping

    NASA Astrophysics Data System (ADS)

    Sun, Jian; Yu, Zhigen; Huang, Yanhua; Xia, Yijie; Lai, Weng Soon; Gong, Hao

    2014-04-01

    One big challenge in transparent conducting oxides (TCOs) is to achieve high conductivity and mobility at a low processing temperature. Although optimized conductivity has been achieved in indium zinc oxide (IZO) without doping, it is still interesting to find whether doping can improve conductivity of IZO further. In this paper, we report a low processing temperature achievement of high conductivity and mobility of IZO through yttrium (Y) doping. We found that with different Y doping levels, room temperature fabricated amorphous IZO (a-IZO) samples can be controlled to exhibit either metallic or semiconductor characteristics. Y2O3 is demonstrated to be an effective doping source to achieve conductivity 300% higher than the non-doped IZO sample. Anomalously improved mobility of certain Y2O3-doped IZO samples compared with the non-doped IZO sample is found and analyzed. Besides, a low-temperature resistivity anomaly (semiconductor metal transition) phenomenon is observed and discussed.

  10. Crystalline to amorphous phase transition of tin oxide nanocrystals induced by SHI at low temperature

    NASA Astrophysics Data System (ADS)

    Kumar, Vijay; Pratap, Deepti; Jain, Anshul; Agarwal, D. C.; Sulania, I.; Tripathi, A.; Chaudhary, R. J.; Chauhan, R. S.

    2012-06-01

    Tin oxide (SnO2) thin films were deposited using pulsed laser deposition (PLD) technique on Si substrates. The as-deposited films were irradiated using 100 MeV Ag ions at different fluences ranging from 3×1013 to 3×1014 ions/cm2 at an incidence angle of 75° with respect to surface normal at liquid nitrogen (LN2) temperature. The as-deposited and irradiated films have been characterized using X-ray diffraction (XRD) and atomic force microscopy (AFM) techniques to study the modifications in structural and surface morphological properties. Nanocrystalline film become completely amorphous and nanograins of tin oxide disappeared from the surface as indicated by XRD spectra and AFM micrographs respectively.

  11. Stoichiometry determined exchange interactions in amorphous ternary transition metal oxides: Theory and experiment

    SciTech Connect

    Hu, Shu-jun; Yan, Shi-shen, E-mail: shishenyan@sdu.edu.cn; Zhang, Yun-peng; Zhao, Ming-wen; Kang, Shi-shou; Mei, Liang-mo [School of Physics, National Key Laboratory of Crystal Materials, Shandong University, Jinan, Shandong 250100 (China)

    2014-07-28

    Amorphous transition metal oxides exhibit exotic transport and magnetic properties, while the absence of periodic structure has long been a major obstacle for the understanding of their electronic structure and exchange interaction. In this paper, we have formulated a theoretical approach, which combines the melt-quench approach and the spin dynamic Monte-Carlo simulations, and based on it, we explored amorphous Co{sub 0.5}Zn{sub 0.5}O{sub 1?y} ternary transition metal oxides. Our theoretical results reveal that the microstructure, the magnetic properties, and the exchange interactions of Co{sub 0.5}Zn{sub 0.5}O{sub 1?y} are strongly determined by the oxygen stoichiometry. In the oxygen-deficient sample (y?>?0), we have observed the long-range ferromagnetic spin ordering which is associated with the non-stoichiometric cobalt-rich region rather than metallic clusters. On the other hand, the microstructure of stoichiometric sample takes the form of continuous random networks, and no long-range ferromagnetism has been observed in it. Magnetization characterization of experimental synthesized Co{sub 0.61}Zn{sub 0.39}O{sub 1?y} films verifies the relation between the spin ordering and the oxygen stoichiometry. Furthermore, the temperature dependence of electrical transport shows a typical feature of semiconductors, in agreement with our theoretical results.

  12. All solution-processed amorphous oxide thin-film transistors using UV/O3 treatment

    NASA Astrophysics Data System (ADS)

    Umeda, Kenichi; Miyasako, Takaaki; Sugiyama, Ayumu; Tanaka, Atsushi; Suzuki, Masayuki; Tokumitsu, Eisuke; Shimoda, Tatsuya

    2014-02-01

    In the fabrication of amorphous oxide thin-film transistors (TFTs) by all-solution process, an ultraviolet-ozone (UV/O3) treatment and solution materials were adopted. By applying the UV/O3 treatment for solution-processed In2-xGaxZnO4 channel layers, enhancement of TFT characteristics was achieved. In particular, the most appropriate metal composition for the In2-xGaxZnO4 system with UV/O3 treatment was found to be x = 1.0. In addition to the channel layers, solution-processed LaNiO3, Bi-Nb-O/La-Ta-O stacked layer, and ITO films were formed as the gate electrode, gate insulator, and source and drain electrodes, respectively, for TFT fabrication. Using UV/O3 treatment and solution materials, all-solution-processed amorphous oxide TFTs were successfully fabricated, and superior TFT properties, including an on-off current ratio of 107, a threshold voltage of 1.6 V, a subthreshold swing of 200 mV/decade, and a field-effect mobility of 0.49 cm2 V-1 s-1, were achieved.

  13. In vitro platelet aggregation and oxidative stress caused by amorphous silica nanoparticles

    PubMed Central

    Nemmar, Abderrahim; Yuvaraju, Priya; Beegam, Sumaya; Yasin, Javed; Dhaheri, Rauda Al; Fahim, Mohamed A; Ali, Badreldin H

    2015-01-01

    Amorphous silica nanoparticles (SiNP) are being investigated for their potential use in various industrial and medical fields. Therefore, the assessment of their possible pathophysiological effect on circulating cells such as platelets is essential. We recently showed that intraperitoneal administration of SiNP causes proinflammatory and prothrombotic responses in vivo. However, little is known about the interaction of amorphous SiNP with platelets in vitro. Presently, we investigated the in vitro effects of SiNP (1, 5 and 25 ?g/ml) on platelet aggregation, oxidative stress and intracellular calcium in mouse platelets. Incubation of platelets with SiNP caused a significant and dose-dependent platelet aggregation. Similarly, the activity of lactate dehydrogenase (as a marker of cell membrane integrity) was significantly increased by SiNP. Total antioxidant activity and lipid platelets vulnerability to in vitro peroxidation (measured by malondialdehyde production) were significantly increased after SiNP exposure. Additionally, SiNP exposure significantly increased the cytosolic calcium concentration. In conclusion, our in vitro data show that incubation of platelets with SiNP caused platelet aggregation, oxidative stress and increased intracellular calcium. This finding provides evidence on the toxicity of SiNP on platelet physiology.

  14. Ni-B amorphous alloy nanoparticles modified nanoporous Cu toward ethanol oxidation in alkaline medium

    NASA Astrophysics Data System (ADS)

    Zhang, Shu-Jin; Zheng, Yi-Xiong; Yuan, Lin-Shan; Zhao, Li-Hua

    2014-02-01

    Nanoporous Cu (NPC) prepared by dealloying CuZn alloy is used as an economic substrate for the fabrication of Ni-B alloy (Ni-B/NPC) by ultrasonic-assisted electroless technique. The results of scanning electron microscopy (SEM) and X-ray diffraction (XRD) demonstrate the NPC has a bicontinuous network structure and the Ni-B/NPC alloy is amorphous structure with highly dispersed nanoparticles. Electrochemical performances are measured by cyclic voltammetry (CV), chronoamperometry (CA) and linear sweep voltammetry (LSV). The results suggest that the Ni-B/NPC electrode prepared for 5 min shows the highest electrochemical activity and its redox species coverage and proton diffusion coefficient are remarkably improved compared with the bulk Ni. Ethanol oxidation at the Ni-B/NPC electrode suggests the onset oxidation potential has a negative shift of 52 mV and the oxidation peak current increases by 19.4 times, and apparent activation energy decreases 4.75-30.60 kJ mol-1 at the same potential, in comparison with the bulk Ni. Additionally, the reaction rate constant for ethanol oxidation at the Ni-B/NPC electrode is improved by about one order of magnitude relative to the reported value. Finally, the Ni-B/NPC electrode has a stable redox behavior after complete activation and superior catalytic stability for ethanol oxidation.

  15. Thermal Transport in Graphene Oxide – From Ballistic Extreme to Amorphous Limit

    PubMed Central

    Mu, Xin; Wu, Xufei; Zhang, Teng; Go, David B.; Luo, Tengfei

    2014-01-01

    Graphene oxide is being used in energy, optical, electronic and sensor devices due to its unique properties. However, unlike its counterpart – graphene – the thermal transport properties of graphene oxide remain unknown. In this work, we use large-scale molecular dynamics simulations with reactive potentials to systematically study the role of oxygen adatoms on the thermal transport in graphene oxide. For pristine graphene, highly ballistic thermal transport is observed. As the oxygen coverage increases, the thermal conductivity is significantly reduced. An oxygen coverage of 5% can reduce the graphene thermal conductivity by ~90% and a coverage of 20% lower it to ~8.8?W/mK. This value is even lower than the calculated amorphous limit (~11.6?W/mK for graphene), which is usually regarded as the minimal possible thermal conductivity of a solid. Analyses show that the large reduction in thermal conductivity is due to the significantly enhanced phonon scattering induced by the oxygen defects which introduce dramatic structural deformations. These results provide important insight to the thermal transport physics in graphene oxide and offer valuable information for the design of graphene oxide-based materials and devices. PMID:24468660

  16. X-ray absorption fine structure study of amorphous metal oxide thin films prepared by photochemical metalorganic deposition

    SciTech Connect

    Trudel, Simon; Crozier, E. Daryl; Gordon, Robert A.; Budnik, Peter S.; Hill, Ross H. (Calgary); (Simon)

    2011-09-06

    The oxidation state and local geometry of the metal centers in amorphous thin films of Fe{sub 2}O{sub 3} (Fe{sup 3+} oxidation state), CoFe{sub 2}O{sub 4} (Co{sup 2+}/Fe{sup 3+} oxidation states), and Cr{sub 2}O{sub 3} (Cr{sup 3+} oxidation state) are determined using K edge X-ray absorption near-edge structure (XANES) spectroscopy and extended X-ray absorption fine structure (EXAFS) spectroscopy. The metal oxide thin films were prepared by the solid-state photochemical decomposition of the relevant metal 2-ethylhexanoates, spin cast as thin films. No peaks are observed in the X-ray diffraction patterns, indicating the metal oxides are X-ray amorphous. The oxidation state of the metals is determined from the edge position of the K absorption edges, and in the case of iron-containing samples, an analysis of the pre-edge peaks. In all cases, the EXAFS analysis indicates the first coordination shell consists of oxygen atoms in an octahedral geometry, with a second shell consisting of metals. No higher shells are observed beyond 3.5 {angstrom} for all samples, indicating the metal oxides are truly amorphous, consistent with X-ray diffraction results.

  17. Self-aligned coplanar amorphous indium zinc oxide thin-film transistors with high performance

    NASA Astrophysics Data System (ADS)

    Park, Jae Chul; Lee, Ho-Nyeon

    2015-01-01

    Self-aligned coplanar amorphous indium zinc oxide thin-film transistors (a-IZO TFTs) were fabricated. The a-IZO TFTs had a field-effect mobility of ?FE = 24.4 cm2 V-1 s-1, a subthreshold slope of 180 mV/dec, and an on/off ratio of 109. As the channel length decreased, the threshold voltage VTH shifted to more negative voltages, and ?FE increased due to the diffused carriers from the contact regions. The intrinsic field-effect mobility was estimated to be 15.05 cm2 V-1 s-1 in the linear mode and 13.28 cm2 V-1 s-1 in saturation mode. Under positive/negative bias-temperature-illumination stress, the shift in VTH was less than ±0.7 V after 11,000 s.

  18. Stoichiometric analysis of compositionally graded combinatorial amorphous thin film oxides using laser-induced breakdown spectroscopy

    SciTech Connect

    Widjonarko, N. Edwin [Department of Physics, 390 UCB, University of Colorado, Boulder, Colorado 80309-0390 (United States); National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, Colorado 80401 (United States); Perkins, John D.; Leisch, Jennifer E.; Parilla, Philip A.; Curtis, Calvin J.; Ginley, David S.; Berry, Joseph J. [National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, Colorado 80401 (United States)

    2010-07-15

    Laser-induced breakdown spectroscopy (LIBS) is a recently developed locally destructive elemental analysis technique that can be used to analyze solid, liquid, and gaseous samples. In the system explored here, a neodymium-doped yttrium aluminum garnet laser ablates a small amount of the sample and spectral emission from the plume is analyzed using a set of synchronized spectrometers. We explore the use of LIBS to map the stoichiometry of compositionally graded amorphous indium zinc oxide thin-film libraries. After optimization of the experimental parameters (distance between lens and samples, spot size on the samples, etc.), the LIBS system was calibrated against inductively coupled plasma atomic emission spectroscopy which resulted in a very consistent LIBS-based elemental analysis. Various parameters that need to be watched closely in order to produce consistent results are discussed. We also compare LIBS and x-ray fluorescence as techniques for the compositional mapping of libraries.

  19. A novel composite material based on antimony(III) oxide and amorphous silica

    SciTech Connect

    Zemnukhova, Ludmila A. [Institute of Chemistry, Far-Eastern Branch, Russian Academy of Sciences, 690022 Vladivostok (Russian Federation); Panasenko, Alexander E., E-mail: panasenko@ich.dvo.ru [Institute of Chemistry, Far-Eastern Branch, Russian Academy of Sciences, 690022 Vladivostok (Russian Federation)

    2013-05-01

    The composite material nSb?O?·mSiO?·xH?O was prepared by hydrolysis of SbCl? and Na?SiO? in an aqueous medium. It has been shown that the composition of the material is influenced by the ratio of the initial components and the acidity of the reaction medium. The morphology of the material particles and its specific surface area have been determined. The thermal and optic properties were also investigated. - Graphical abstract: Novel composite material containing amorphous silica and crystal antimony(III) oxide has been synthesized by hydrolysis of SbCl? and Na?SiO? in an aqueous medium. Highlights: • The composite material nSb?O?·mSiO?·xH?O was prepared in an aqueous medium. • The composition of the material is controllable by a synthesis conditions. • The morphology of the material and its optic properties have been determined.

  20. Improved stability of amorphous zinc tin oxide thin film transistors using molecular passivation

    NASA Astrophysics Data System (ADS)

    Rajachidambaram, M. S.; Pandey, A.; Vilayurganapathy, S.; Nachimuthu, P.; Thevuthasan, S.; Herman, G. S.

    2013-10-01

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

  1. Crystallization of amorphous titanium oxide thin films by pulsed UV-laser irradiation

    SciTech Connect

    Ichikawa, Yo; Adachi, Hideaki; Setsune, Kentaro; Kawashima, Syunichiro; Kugimiya, Koichi [Matsushita Electric Industrial Co., Ltd., Kyoto (Japan). Central Research Labs.

    1996-12-31

    Oxide ceramic materials are applied to many electric devices using dielectric, ferroelectric, piezoelectric and elastic properties. Effects of ultraviolet (UV) laser irradiation on the local crystal structure have been investigated for amorphous Ti-O thin films sputtered on ST-cut quartz substrates. The irradiation was conducted with a pulsed KrF excimer laser of 248 nm in wavelength. There were few changes in the optical transmission spectra of the films before and after the irradiation. The crystal structure of the films was characterized by electron diffraction, XPS and EXAFS analyses. The results obtained from these analyses suggest the films gradually crystallize to a TiO{sub 2} crystal with the rutile type structure by the increasing of the laser pulses.

  2. Preparation of amorphous electrochromic tungsten oxide and molybdenum oxide by plasma enhanced chemical vapor deposition

    Microsoft Academic Search

    C. E. Tracy; D. K. Benson

    1986-01-01

    Preliminary experiments have been performed to probe the feasibility of using plasma enhanced chemical vapor deposition (PE--CVD) to prepare electrochromic thin films of tungsten oxide and molybdenum oxide by plasma reaction of WFâ, W(CO)â, and Mo(CO)â with oxygen. Thin films produced in a 300 W, electrodeless, radio-frequency (rf), capacitive discharge were found to be electrochromic when tested with either liquid

  3. Amorphous Nb/Fe-oxide ion-storage films for counter electrode applications in electrochromic devices

    SciTech Connect

    Orel, B.; Macek, M.; Lavrencic-Stangar, U. [National Inst. of Chemistry, Ljubljana (Slovenia); Pihlar, B. [Univ. of Ljubljana (Slovenia). Faculty of Chemistry

    1998-05-01

    The electrochromic properties of mixed Nb/Fe-oxide films with amorphous structure which were prepared via the sol-gel route were determined. Films with Nb/Fe molar concentration ratios 0.2:1, 0.4:1, and 1:1 exhibit ion-storage capacities up to 18 mC/cm{sup 2} depending on Nb/Fe molar ratio. Electrochromically films behave as optically passive electrodes with a coloration efficiency of nearly zero at {lambda} > 480 nm, while at shorter wavelengths a relatively strong anodic coloring was observed, yielding negative coloration efficiencies up to {minus}20 cm{sup 2}/C. Coloring/bleaching changes of films are correlated with the ex situ IR spectroscopic measurements of charged/discharged films showing distortions of the film structure with Li{sup +} ion insertion/extraction reactions. Electrochemical stability of Nb/Fe (0.4:1)-oxide films was tested up to 2,000 cycles in a sol-gel electrochromic device consisting of sol-gel-derived WO{sub 3} films and hybrid organic/inorganic ionic conductor with ionic conductivity of about 10{sup {minus}4} S/cm serving for lamination of the electrodes.

  4. Amorphous copper-palladium-zirconium ternary alloys for formaldehyde oxidation anode materials

    SciTech Connect

    Machida, K.I.; Nishimura, K.; Enyo, M.

    1986-12-01

    The electro-oxidation of HCHO and HCOO/sup -/ on a series of amorphous Cu-Pd-Zr ternary alloys after surface treatments with aq. HF has been investigated in 1.0M NaOH and 0.5M Na/sub 2/CO/sub 3/ at 303 K, together with surface area measurements and XPS observations. The acid treatment led to the formation of a Raney-type porous Cu-Pd alloy layer on the surface after the Zr was leached out. The surface analyses indicated a minor degree of enrichment in Pd or Cu, before or after the acid treatment, respectively. The alloy electrodes with the bulk composition of Cu:Pd = 1:3 showed the same activity of 1.2 X 10/sup -4/ A cm/sup -2/ (true) at 0.30 V (RHE) for the HCHO and HCOO/sup -/ electro-oxidation in 1.0M NaOH. The composition of 2:1 exhibited similar behaviour with the activity of 2.0 X 10/sup -5/ A cm/sup -2/ (true) in 0.5M Na/sub 2/CO/sub 3/.

  5. Lithium Storage in Microstructures of Amorphous Mixed-Valence Vanadium Oxide as Anode Materials.

    PubMed

    Zhao, Di; Zheng, Lirong; Xiao, Ying; Wang, Xia; Cao, Minhua

    2015-07-01

    Constructing three-dimensional (3?D) nanostructures with excellent structural stability is an important approach for realizing high-rate capability and a high capacity of the electrode materials in lithium-ion batteries (LIBs). Herein, we report the synthesis of hydrangea-like amorphous mixed-valence VOx microspheres (a-VOx MSs) through a facile solvothermal method followed by controlled calcination. The resultant hydrangea-like a-VOx MSs are composed of intercrossed nanosheets and, thus, construct a 3?D network structure. Upon evaluation as an anode material for LIBs, the a-VOx MSs show excellent lithium-storage performance in terms of high capacity, good rate capability, and long-term stability upon extended cycling. Specifically, they exhibit very stable cycling behavior with a highly reversible capacity of 1050?mA?h?g(-1) at a rate of 0.1?A?g(-1) after 140?cycles. They also show excellent rate capability, with a capacity of 390?mA?h?g(-1) at a rate as high as 10?A?g(-1) . Detailed investigations on the morphological and structural changes of the a-VOx MSs upon cycling demonstrated that the a-VOx MSs went through modification of the local V?O coordinations accompanied with the formation of a higher oxidation state of V, but still with an amorphous state throughout the whole discharge/charge process. Moreover, the a-VOx MSs can buffer huge volumetric changes during the insertion/extraction process, and at the same time they remain intact even after 200?cycles of the charge/discharge process. Thus, these microspheres may be a promising anode material for LIBs. PMID:26018759

  6. Oxygen partial pressure influence on the character of InGaZnO thin films grown by PLD

    NASA Astrophysics Data System (ADS)

    Lu, Yi; Wang, Li

    2012-11-01

    The amorphous oxide semiconductors (AOSs) are promising for emerging large-area optoelectronic applications because of capability of large-area, uniform deposition at low temperatures such as room temperature (RT). Indium-gallium-zinc oxide (InGaZnO) thin film is a promising amorphous semiconductors material in thin film transistors (TFT) for its excellent electrical properties. In our work, the InGaZnO thin films are fabricated on the SiO2 glass using pulsed laser deposition (PLD) in the oxygen partial pressure altered from 1 to 10 Pa at RT. The targets were prepared by mixing Ga2O3, In2O3, and ZnO powder at a mol ratio of 1: 7: 2 before the solid-state reactions in a tube furnace at the atmospheric pressure. The targets were irradiated by an Nd:YAG laser(355nm). Finally, we have three films of 270nm, 230nm, 190nm thick for 1Pa, 5Pa, 10Pa oxygen partial pressure. The product thin films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), Hall-effect investigation. The comparative study demonstrated the character changes of the structure and electronic transport properties, which is probably occurred as a fact of the different oxygen partial pressure used in the PLD.

  7. X-ray absorption spectroscopy elucidates the impact of structural disorder on electron mobility in amorphous zinc-tin-oxide thin films

    E-print Network

    Siah, Sin Cheng

    We investigate the correlation between the atomic structures of amorphous zinc-tin-oxide (a-ZTO) thin films grown by atomic layer deposition (ALD) and their electronic transport properties. We perform synchrotron-based ...

  8. Controllable film densification and interface flatness for high-performance amorphous indium oxide based thin film transistors

    NASA Astrophysics Data System (ADS)

    Ou-Yang, Wei; Mitoma, Nobuhiko; Kizu, Takio; Gao, Xu; Lin, Meng-Fang; Nabatame, Toshihide; Tsukagoshi, Kazuhito

    2014-10-01

    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.

  9. Development of thin film amorphous silicon oxide\\/microcrystalline silicon double-junction solar cells and their temperature dependence

    Microsoft Academic Search

    K. Sriprapha; C. Piromjit; A. Limmanee; J. Sritharathikhun

    2011-01-01

    We have developed thin film silicon double-junction solar cells by using micromorph structure. Wide bandgap hydrogenated amorphous silicon oxide (a-SiO:H) film was used as an absorber layer of top cell in order to obtain solar cells with high open circuit voltage (Voc), which are attractive for the use in high temperature environment. All p, i and n layers were deposited

  10. Bulk mixed ion electron conduction in amorphous gallium oxide causes memristive behaviour

    NASA Astrophysics Data System (ADS)

    Aoki, Yoshitaka; Wiemann, Carsten; Feyer, Vitaliy; Kim, Hong-Seok; Schneider, Claus Michael; Ill-Yoo, Han; Martin, Manfred

    2014-03-01

    In thin films of mixed ionic electronic conductors sandwiched by two ion-blocking electrodes, the homogeneous migration of ions and their polarization will modify the electronic carrier distribution across the conductor, thereby enabling homogeneous resistive switching. Here we report non-filamentary memristive switching based on the bulk oxide ion conductivity of amorphous GaOx (x~1.1) thin films. We directly observe reversible enrichment and depletion of oxygen ions at the blocking electrodes responding to the bias polarity by using photoemission and transmission electron microscopies, thus proving that oxygen ion mobility at room temperature causes memristive behaviour. The shape of the hysteresis I-V curves is tunable by the bias history, ranging from narrow counter figure-eight loops to wide hysteresis, triangle loops as found in the mathematically derived memristor model. This dynamical behaviour can be attributed to the coupled ion drift and diffusion motion and the oxygen concentration profile acting as a state function of the memristor.

  11. Bulk mixed ion electron conduction in amorphous gallium oxide causes memristive behaviour.

    PubMed

    Aoki, Yoshitaka; Wiemann, Carsten; Feyer, Vitaliy; Kim, Hong-Seok; Schneider, Claus Michael; Ill-Yoo, Han; Martin, Manfred

    2014-01-01

    In thin films of mixed ionic electronic conductors sandwiched by two ion-blocking electrodes, the homogeneous migration of ions and their polarization will modify the electronic carrier distribution across the conductor, thereby enabling homogeneous resistive switching. Here we report non-filamentary memristive switching based on the bulk oxide ion conductivity of amorphous GaOx (x~1.1) thin films. We directly observe reversible enrichment and depletion of oxygen ions at the blocking electrodes responding to the bias polarity by using photoemission and transmission electron microscopies, thus proving that oxygen ion mobility at room temperature causes memristive behaviour. The shape of the hysteresis I-V curves is tunable by the bias history, ranging from narrow counter figure-eight loops to wide hysteresis, triangle loops as found in the mathematically derived memristor model. This dynamical behaviour can be attributed to the coupled ion drift and diffusion motion and the oxygen concentration profile acting as a state function of the memristor. PMID:24632885

  12. Amorphous oxide alloys as interfacial layers with broadly tunable electronic structures for organic photovoltaic cells.

    PubMed

    Zhou, Nanjia; Kim, Myung-Gil; Loser, Stephen; Smith, Jeremy; Yoshida, Hiroyuki; Guo, Xugang; Song, Charles; Jin, Hosub; Chen, Zhihua; Yoon, Seok Min; Freeman, Arthur J; Chang, Robert P H; Facchetti, Antonio; Marks, Tobin J

    2015-06-30

    In diverse classes of organic optoelectronic devices, controlling charge injection, extraction, and blocking across organic semiconductor-inorganic electrode interfaces is crucial for enhancing quantum efficiency and output voltage. To this end, the strategy of inserting engineered interfacial layers (IFLs) between electrical contacts and organic semiconductors has significantly advanced organic light-emitting diode and organic thin film transistor performance. For organic photovoltaic (OPV) devices, an electronically flexible IFL design strategy to incrementally tune energy level matching between the inorganic electrode system and the organic photoactive components without varying the surface chemistry would permit OPV cells to adapt to ever-changing generations of photoactive materials. Here we report the implementation of chemically/environmentally robust, low-temperature solution-processed amorphous transparent semiconducting oxide alloys, In-Ga-O and Ga-Zn-Sn-O, as IFLs for inverted OPVs. Continuous variation of the IFL compositions tunes the conduction band minima over a broad range, affording optimized OPV power conversion efficiencies for multiple classes of organic active layer materials and establishing clear correlations between IFL/photoactive layer energetics and device performance. PMID:26080437

  13. Metal-insulator transitions in IZO, IGZO, and ITZO films

    SciTech Connect

    Makise, Kazumasa, E-mail: makise@nict.go.jp [National Institute of Information and Communications Technology, Kobe 651-2492 (Japan); Hidaka, Kazuya; Ezaki, Syohei; Asano, Takayuki; Shinozaki, Bunju [Department of Physics, Kyushu University, Fukuoka 810-8560 (Japan); Tomai, Shigekazu; Yano, Koki; Nakamura, Hiroaki [Central Research Laboratories, Idemitsu Kosan Co. Ltd, Chiba 299-0293 (Japan)

    2014-10-21

    In this study, we measured the low-temperature resistivity of amorphous two- and three-dimensional (2D and 3D) indium-zinc oxide, indium-gallium-zinc oxide, and indium-tin-zinc oxide films with a wide range of carrier densities. To determine their critical characteristics at the metal-insulator transition (MIT), we used the Ioffe–Regel criterion. We found that the MIT occurs in a narrow range between k{sub F}??=0.13 and k{sub F}??=0.25, where k{sub F} and ? are the Fermi wave number and electron mean free path, respectively. For films in the insulating region, we analyzed ?(T) using a procedure proposed by Zabrodskii and Zinov'eva. This analysis confirmed the occurrence of Mott and Efros–Shklovskii (ES) variable-range hopping. The materials studied show crossover behavior from exp(T{sub Mott}/T){sup 1/4} or exp(T{sub Mott}/T){sup 1/3} for Mott hopping conduction to exp(T{sub ES}/T){sup 1/2} for ES hopping conduction with decreasing temperature. For both 2D and 3D materials, we found that the relationship between T{sub Mott} and T{sub ES} satisfies T{sub ES}?T{sub Mott}{sup 2/3}.

  14. Controlled ambient and temperature treatment of InGaZnO thin film transistors for improved bias-illumination stress reliability

    SciTech Connect

    Vemuri, Rajitha N. P., E-mail: rvemuri@asu.edu [School for Engineering of Matter, Transport and Energy, Arizona State University, Tempe 85287 (United States); Hasin, Muhammad R. [School of Electrical, Computer and Energy Engineering, Arizona State University, Tempe 85287 (United States); Alford, T. L., E-mail: TA@asu.edu [School for Engineering of Matter, Transport and Energy, Arizona State University, Tempe 85287 and School of Electrical, Computer and Energy Engineering, Arizona State University, Tempe 85287 (United States)

    2014-03-15

    The failure mechanisms arising from the instability in operation of indium gallium zinc oxide based thin film transistors (TFTs) upon prolonged real application stresses (bias and illumination) have been extensively studied and reported. Positive and negative gate bias conditions, along with high photonic energy wavelengths within visible light spectrum are used as stress conditions. The increased carrier concentration due to photonic excitation of defects within bandgap and ionization of deep level vacancies is compensated by the reduction in off currents under illumination due to the trapping of carriers in the intermetal dielectric. Band lowering at the source-channel junction due to accumulation of negative carriers repelled due to negative gate bias stress further causes high carrier flow into the channel and drives the devices into failure. The defect identification during failure and degradation assisted in proposing suitable low temperature post processing in specific ambients. Reliability tests after specific anneals in oxygen, vacuum, and forming gas ambients confirm the correlation of the defect type with anneal ambient. Annealed TFTs demonstrate high stabilities under illumination stresses and do not fail when subjected to combined stresses that cause failure in as-fabricated TFTs. Oxygen and forming gas anneals are impactful on the reliability and opens an area of study on donor and vacancy behavior in amorphous mixed oxide based TFTs. The subthreshold swing, field-effect mobilities, and off currents provide knowledge on best anneal practices by understanding role of hydrogen and oxygen in vacancy annihilation and transistor switching properties.

  15. Widespread oxidized and hydrated amorphous silicates in CR chondrites matrices: Implications for alteration conditions and H2 degassing of asteroids

    NASA Astrophysics Data System (ADS)

    Le Guillou, Corentin; Changela, Hitesh G.; Brearley, Adrian J.

    2015-06-01

    The CR chondrites carry one of the most pristine records of the solar nebula materials that accreted to form planetesimals. They have experienced very variable degrees of aqueous alteration, ranging from incipient alteration in their matrices to the complete hydration of all of their components. In order to constrain their chemical alteration pathways and the conditions of alteration, we have investigated the mineralogy and Fe oxidation state of silicates in the matrices of 8 CR chondrites, from type 3 to type 1. Fe-L edge X-ray Absorption Near Edge Structure (XANES) was performed on matrix FIB sections using synchrotron-based scanning transmission X-ray microscopy (STXM). The Fe3+ / ? Fe ratio of submicron silicate particles was obtained and coordinated with TEM observations. In all the least altered CR chondrites (QUE 99177, EET 87770, EET 92042, LAP 02342, GRA 95229 and Renazzo), we find that the matrices consist of abundant submicron Fe-rich hydrated amorphous silicate grains, mixed with nanometer-sized phyllosilicates. The Fe3+ / ? Fe ratios of both amorphous and nanocrystalline regions are very high with values ranging from 68 to 78%. In the most altered samples (Al Rais and GRO 95577), fine-grained phyllosilicates also have a high Fe3+ / ? Fe ratio (around 70%), whereas the coarse, micrometer-sized phyllosilicates are less oxidized (down to 55%) and have a lower iron content. These observations suggest the following sequence: submicron Fe2+-amorphous silicate particles were the building blocks of CR matrices; after accretion they were quickly hydrated and oxidized, leading to a metastable, amorphous gel-like phase. Nucleation and growth of crystalline phyllosilicates was kinetically-limited in most type 3 and 2 CRs, but increased as alteration became more extensive in Al Rais and GRO 95577. The decreasing Fe3+ / ? Fe ratio is interpreted as a result of the transfer of Fe3+ from silicates to oxides during growth, while aqueous alteration progressed (higher temperature, longer duration, change of fluid composition). In a fully closed system, equilibrium thermodynamics suggest that the water to rock ratios, typically assumed to be low (<1) for chondrites, should primarily control the iron valency of the silicates and predict a lower Fe3+ / ? Fe ratio. Such a high Fe3+ / ? Fe value could be accounted for, however, if the system was partially open, at least with respect to H2 (and other gases as well). Rapid degassing of the fluid would have favored more oxidizing fluid conditions. Recently proposed scenarios involving some degree of water D/H increase through Rayleigh isotopic fractionation are supported by these results.

  16. Controlled Microwave Processing of IGZO Thin Films for Improved Optical and Electrical Properties

    NASA Astrophysics Data System (ADS)

    Dhar, Aritra; Alford, T. L.

    2015-06-01

    Amorphous indium gallium zinc oxides (IGZO) of 100 nm thickness were deposited onto glass substrates by sputtering at room temperature. The films were subsequently annealed in air, vacuum, forming gas and O2 environments by both conventional and microwave methods. The optical and electrical properties of the as-deposited and annealed samples were measured and compared. It was seen that microwave annealing had a dual advantage of reduced time and lower temperature compared to conventional annealing. The optical and electrical properties of the IGZO thin films were measured by UV-Visible spectrophotometry, Hall measurement and four-point probe analyses, respectively. On microwave anneals of 4 min at 200°C, the resistivity of IGZO thin films was lowered to 4.45 and 4.24 × 10-3 ?-cm in vacuum and forming gas, respectively. However in conventional annealing at 400°C, it took 24 h to reach 4.5 and 4.2 × 10-3 ?-cm in vacuum and forming gas, respectively. The average transmittance of IGZO improved from 80% to almost 86% for microwave annealing.

  17. Large-area, low-voltage, antiambipolar heterojunctions from solution-processed semiconductors.

    PubMed

    Jariwala, Deep; Sangwan, Vinod K; Seo, Jung-Woo Ted; Xu, Weichao; Smith, Jeremy; Kim, Chris H; Lauhon, Lincoln J; Marks, Tobin J; Hersam, Mark C

    2015-01-14

    The emergence of semiconducting materials with inert or dangling bond-free surfaces has created opportunities to form van der Waals heterostructures without the constraints of traditional epitaxial growth. For example, layered two-dimensional (2D) semiconductors have been incorporated into heterostructure devices with gate-tunable electronic and optical functionalities. However, 2D materials present processing challenges that have prevented these heterostructures from being produced with sufficient scalability and/or homogeneity to enable their incorporation into large-area integrated circuits. Here, we extend the concept of van der Waals heterojunctions to semiconducting p-type single-walled carbon nanotube (s-SWCNT) and n-type amorphous indium gallium zinc oxide (a-IGZO) thin films that can be solution-processed or sputtered with high spatial uniformity at the wafer scale. The resulting large-area, low-voltage p-n heterojunctions exhibit antiambipolar transfer characteristics with high on/off ratios that are well-suited for electronic, optoelectronic, and telecommunication technologies. PMID:25438195

  18. Structural and electrical characteristics of high-? Er2O3 and Er2TiO5 gate dielectrics for a-IGZO thin-film transistors

    PubMed Central

    2013-01-01

    In this letter, we investigated the structural and electrical characteristics of high-? Er2O3 and Er2TiO5 gate dielectrics on the amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistor (TFT) devices. Compared with the Er2O3 dielectric, the a-IGZO TFT device incorporating an Er2TiO5 gate dielectric exhibited a low threshold voltage of 0.39 V, a high field-effect mobility of 8.8 cm2/Vs, a small subthreshold swing of 143 mV/decade, and a high Ion/Ioff current ratio of 4.23 × 107, presumably because of the reduction in the oxygen vacancies and the formation of the smooth surface roughness as a result of the incorporation of Ti into the Er2TiO5 film. Furthermore, the reliability of voltage stress can be improved using an Er2TiO5 gate dielectric. PMID:23294730

  19. Amorphous GeOx-Coated Reduced Graphene Oxide Balls with Sandwich Structure for Long-Life Lithium-Ion Batteries.

    PubMed

    Choi, Seung Ho; Jung, Kyeong Youl; Kang, Yun Chan

    2015-07-01

    Amorphous GeOx-coated reduced graphene oxide (rGO) balls with sandwich structure are prepared via a spray-pyrolysis process using polystyrene (PS) nanobeads as sacrificial templates. This sandwich structure is formed by uniformly coating the exterior and interior of few-layer rGO with amorphous GeOx layers. X-ray photoelectron spectroscopy analysis reveals a Ge:O stoichiometry ratio of 1:1.7. The amorphous GeOx-coated rGO balls with sandwich structure have low charge-transfer resistance and fast Li(+)-ion diffusion rate. For example, at a current density of 2 A g(-1), the GeOx-coated rGO balls with sandwich and filled structures and the commercial GeO2 powders exhibit initial charge capacities of 795, 651, and 634 mA h g(-1), respectively; the corresponding 700th-cycle charge capacities are 758, 579, and 361 mA h g(-1). In addition, at a current density of 5 A g(-1), the rGO balls with sandwich structure have a 1600th-cycle reversible charge capacity of 629 mA h g(-1) and a corresponding capacity retention of 90.7%, as measured from the maximum reversible capacity at the 100th cycle. PMID:26047208

  20. Solid 7Li-NMR and in situ XRD studies of the insertion reaction of lithium with tin oxide and tin-based amorphous composite oxide

    NASA Astrophysics Data System (ADS)

    Furuya, Kazuhiko; Ogawa, Keizou; Mineo, Yasushi; Matsufuji, Akihiro; Okuda, Jun; Erata, Tomoki

    2001-04-01

    The lithium insertion reactions with tin (II) oxide (SnO) and tin-based composite oxide (abbreviated as TBCO) are studied by solid 7Li-NMR Knight shift, T1 and T1? relaxation rate, TEM and in situ XRD methods. By the insertion reaction for SnO, the lithium oxide and ?-tin are produced first at Li/Sn = 2; at Li/Sn = 3 to 6 the products are not simple and a mixture of LiSn2, LiSn, Li5Sn2 and Li7Sn2 alloys is detected during the insertion. For the TBCO, which is revealed as amorphous, mainly constituted by randomly distributed very short-range (order of 10-9 m) regions by TEM observation, it is found that electrochemically inserted lithium forms Li2O and produces metallic tin (Sn) in the first step (Li/Sn <2), then the highly ionic lithium-tin alloys, Li7Sn2 (and Li7Si2), are produced in the second step (Li/Sn >2). During the second step, the Li/Sn ratio of formed lithium-tin alloy is kept at almost 4. By the analyses of 7Li NMR Knight shifts, line shape and in situ XRD, the lithium-inserted TBCOs are characterized as almost amorphous and mixtures of highly ionic components.

  1. Amorphous Transparent Conducting Oxides (TCOs) Deposited at T 100<= ..deg.. C (Presentation)

    SciTech Connect

    Perkins, J.; van Hest, M.; Teplin, C.; Alleman, J.; Dabney, M.; Gedvilas, L.; Keyes, B.; To, B.; Ginley D.

    2006-05-01

    The summary of this report is that amorphous InZnO (a-IZO) is a very versatile TCO with: (1) low process temperatures ({approx} 100 C); (2) easy to make by sputtering; (3) excellent optical and electronic properties; (4) very smooth etchable films; and (5) remarkable thermal processing stability.

  2. Low-Temperature Synthesis of Hierarchical Amorphous Basic Nickel Carbonate Particles for Water Oxidation Catalysis.

    PubMed

    Yang, Yisu; Liang, Fengli; Li, Mengran; Rufford, Thomas E; Zhou, Wei; Zhu, Zhonghua

    2015-07-01

    Amorphous nickel carbonate particles are catalysts for the oxygen evolution reaction (OER), which plays a critical role in the electrochemical splitting of water. The amorphous nickel carbonate particles can be prepared at a temperature as low as 60?°C by an evaporation-induced precipitation (EIP) method. The products feature hierarchical pore structures. The mass-normalized activity of the catalysts, measured at an overpotential of 0.35?V, was 55.1?A?g(-1) , with a Tafel slope of only 60?mV?dec(-1) . This catalytic activity is superior to the performance of crystalline NiOx particles and ?-Ni(OH)2 particles, and compares favorably to state-of-the-art RuO2 catalysts. The activity of the amorphous nickel carbonate is remarkably stable during a 10?000?s chronoamperometry test. Further optimization of synthesis parameters reveals that the amorphous structure can be tuned by adjusting the H2 O/Ni ratio in the precursor mixture. These results suggest the potential application of easily prepared hierarchical basic nickel carbonate particles as cheap and robust OER catalysts with high activity. PMID:26097200

  3. Ferroelectric-Like Properties of Amorphous Metal Oxide Thin Films Prepared by Sol-Gel Technique

    Microsoft Academic Search

    Yuhuan Xu

    1995-01-01

    Advances in the field of both optical and electrical integrated circuit devices require new thin film materials. Ferroelectric materials have attractive properties such as hysteresis behavior, pyroelectricity, piezoelectricity and nonlinear optical properties. Many ferroelectric thin films have been successfully prepared from metal organic compounds via sol-gel processing. Thus far, research has concentrated upon polycrystalline or epitaxial ferroelectric films. For amorphous

  4. Preparation and properties of amorphous titania-coated zinc oxide nanoparticles

    SciTech Connect

    Liao Minhung [Applied Science and Technology Research Center, Department of Cosmetology and Styling, Transworld Institute of Technology, Douliu 640, Yulin, Taiwan (China)]. E-mail: liaomh@mail.tit.edu.tw; Hsu, C.-H. [Department of Chemical Engineering, National Cheng Kung University, Tainan, Taiwan 701 (China); Chen, D.-H. [Department of Chemical Engineering, National Cheng Kung University, Tainan, Taiwan 701 (China)]. E-mail: chendh@mail.ncku.edu.tw

    2006-07-15

    Amorphous TiO{sub 2}-coated ZnO nanoparticles were prepared by the solvothermal synthesis of ZnO nanoparticles in ethanol and the followed by sol-gel coating of TiO{sub 2} nanolayer. The analyses of X-ray diffraction (XRD) and transmission electron microscopy (TEM) revealed that the resultant ZnO nanoparticles were hexagonal with a wurtzite structure and a mean diameter of about 60 nm. Also, after TiO{sub 2} coating, the TEM images clearly indicated the darker ZnO nanoparticles being surrounded by the lighter amorphous TiO{sub 2} layers. The zeta potential analysis revealed the pH dependence of zeta potentials for ZnO nanoparticles shifted completely to that for TiO{sub 2} nanoparticles after TiO{sub 2} coating, confirming the formation of core-shell structure and suggesting the coating of TiO{sub 2} was achieved via the adhesion of the hydrolyzed species Ti-O{sup -} to the positively charged surface of ZnO nanoparticles. Furthermore, the analyses of Fourier transform infrared (FTIR) and Raman spectra were also conducted to confirm that amorphous TiO{sub 2} were indeed coated on the surface of ZnO nanoparticles. In addition, the analyses of ultraviolet-visible (UV-VIS) and photoluminescence (PL) spectra revealed that the absorbance of amorphous TiO{sub 2}-coated ZnO nanoparticles at 375 nm gradually decreased with an increase in the Ti/Zn molar ratio and the time for TiO{sub 2} coating, and the emission intensity of ZnO cores could be significantly enhanced by the amorphous TiO{sub 2} shell. - Graphical abstract: Amorphous titania-coated ZnO nanoparticles with a core-shell structure were prepared. It was found that the emission intensity of ZnO cores could be significantly enhanced by the amorphous TiO{sub 2} shell.

  5. MAGNETIC PROPERTIES OF AMORPHOUS IRON (ill) OXIDE THIN FILMS T. Shigematsu, Y. Bando and T. Takada

    E-print Network

    Paris-Sud XI, Université de

    the preparation of iron oxide films by reactive evaporation method /1, 2/. We obtained the films of iron oxide) oxide films were prepared by deposition of iron metal in an oxygen atmosphere of SxlO"1 * torr, the same as those in the previous works /1,2/. An iron oxide film was obtained by evaporation of iron

  6. Evolution of nanoscale amorphous, crystalline and phase-segregated PtNiP nanoparticles and their electrocatalytic effect on methanol oxidation reaction.

    PubMed

    Ma, Yanjiao; Wang, Rongfang; Wang, Hui; Linkov, Vladimir; Ji, Shan

    2014-02-28

    The design of amorphous noble metallic nanoparticle electrocatalysts is an important fundamental and applied research challenge because their surface is rich in low-coordination sites and defects which could act as the active sites in various catalytic processes. Here we describe new findings on the amorphous platinum-nickel-phosphorous nanoparticles supported on carbon black (PtNiP(a)/C) and the comparison between their catalytic activity and that of the nanoscale crystalline and phase-segregated PtNiP nanoparticles. The nanoscale amorphous, crystalline and phase-segregated catalysts were probed as a function of surface composition, particle size, and thermal treatment conditions using X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, selected area electron diffraction and electrochemical characterization. The results provide the experimental evidence in support of nanoscale amorphous, crystalline, and phase-segregated PtNiP nanoparticles evolution dependence on the catalyst synthesis temperature. More importantly, the results of the electrochemical performance investigation showed that the amorphous structure has not only better catalytic activity for methanol oxidation but also stronger tolerance to carbon monoxide poisoning compared to the crystalline and phase-segregated structure. Besides, the thermal control of the formation of nanoscale amorphous, crystalline and phase-segregated structured catalysts provided the opportunity for establishing the correlation between the nanoscale phase structures of the catalysts and their electrocatalytic activity in methanol oxidation reaction, which plays an important role in developing highly active electrocatalysts for direct methanol fuel cells. PMID:24414092

  7. Preparation and properties of amorphous titania-coated zinc oxide nanoparticles

    Microsoft Academic Search

    Min-Hung Liao; Chih-Hsiung Hsu; Dong-Hwang Chen

    2006-01-01

    Amorphous TiO2-coated ZnO nanoparticles were prepared by the solvothermal synthesis of ZnO nanoparticles in ethanol and the followed by sol–gel coating of TiO2 nanolayer. The analyses of X-ray diffraction (XRD) and transmission electron microscopy (TEM) revealed that the resultant ZnO nanoparticles were hexagonal with a wurtzite structure and a mean diameter of about 60nm. Also, after TiO2 coating, the TEM

  8. X-ray absorption spectroscopy elucidates the impact of structural disorder on electron mobility in amorphous zinc-tin-oxide thin films

    E-print Network

    ).7­15 To synthesize high-quality a- ZTO thin films, various techniques have been used, including sol-gel in amorphous zinc-tin-oxide thin films Sin Cheng Siah,1,a),b) Sang Woon Lee,2,c) Yun Seog Lee,1 Jaeyeong Heo,3-ZTO) thin films grown by atomic layer deposition (ALD) and their electronic transport properties. We perform

  9. Effects of pulse voltage on the formation of nanoporous Ti oxides by dealloying amorphous TiCu alloy

    NASA Astrophysics Data System (ADS)

    Zhu, Shengli; Pi, Lele; Xie, Guoqiang; Cui, Zhenduo; Yang, Xianjin; Inoue, Akihisa

    2013-03-01

    In present study, we prepared nanoporous Ti oxides by potentiostat and pulse dealloying TiCu amorphous alloy in HNO3 solution. The influence of applied voltage on the morphology was investigated by SEM. The mechanism of dealloying was also discussed. A multilayer nanoporous structure was fabricated using pulse dealloying. The ideal nanoporous structure with mean pore diameter of about 50-100 nm and mean pore wall thickness of about 50 nm was obtained using pulse dealloying with initial voltage of 1.0 V and pulse size of 0.4 V. The static currents for pulse dealloying are higher than those for potentiostat dealloying under the same initial potentials. The nanoporous surface is mainly composed of TiO, Ti2O3 and TiO2.

  10. High-performance amorphous gallium indium zinc oxide thin-film transistors through N2O plasma passivation

    NASA Astrophysics Data System (ADS)

    Park, Jaechul; Kim, Sangwook; Kim, Changjung; Kim, Sunil; Song, Ihun; Yin, Huaxiang; Kim, Kyoung-Kok; Lee, Sunghoon; Hong, Kiha; Lee, Jaecheol; Jung, Jaekwan; Lee, Eunha; Kwon, Kee-Won; Park, Youngsoo

    2008-08-01

    Amorphous-gallium-indium-zinc-oxide (a-GIZO) thin filmtransistors (TFTs) are fabricated without annealing, using processes and equipment for conventional a-Si :H TFTs. It has been very difficult to obtain sound TFT characteristics, because the a-GIZO active layer becomes conductive after dry etching the Mo source/drain electrode and depositing the a-SiO2 passivation layer. To prevent such damages, N2O plasma is applied to the back surface of the a-GIZO channel layer before a-SiO2 deposition. N2O plasma-treated a-GIZO TFTs exhibit excellent electrical properties: a field effect mobility of 37cm2/Vs, a threshold voltage of 0.1V, a subthreshold swing of 0.25V/decade, and an Ion/off ratio of 7.

  11. Magnesium-Aluminum-Zirconium Oxide Amorphous Ternary Composite: A Dense and Stable Optical Coating

    NASA Technical Reports Server (NTRS)

    Sahoo, N. K.; Shapiro, A. P.

    1998-01-01

    In the present work, the process parameter dependent optical and structural properties of MgO-Al(2)O(3)-ZrO(2) ternary mixed-composite material have been investigated. Optical properties were derived from spectrophotometric measurements. The surface morphology, grain size distributions, crystallographic phases and process dependent material composition of films have been investigated through the use of Atomic Force Microscopy (AFM), X-ray diffraction analysis and Energy Dispersive X- ray (EDX) analysis. EDX analysis made evident the correlation between the optical constants and the process dependent compositions in the films. It is possible to achieve environmentally stable amorphous films with high packing density under certain optimized process conditions.

  12. Highly conductive p-type amorphous oxides from low-temperature solution processing

    SciTech Connect

    Li Jinwang [Japan Science and Technology Agency (JST), ERATO, Shimoda Nano-Liquid Process Project, 2-5-3 Asahidai, Nomi, Ishikawa 923-1211 (Japan); Green Devices Research Center, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa 923-1292 (Japan); Tokumitsu, Eisuke [Japan Science and Technology Agency (JST), ERATO, Shimoda Nano-Liquid Process Project, 2-5-3 Asahidai, Nomi, Ishikawa 923-1211 (Japan); Green Devices Research Center, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa 923-1292 (Japan); School of Materials Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa 923-1292 (Japan); Precision and Intelligence Laboratory, Tokyo Institute of Technology, 4259-R2-19 Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan); Koyano, Mikio [Green Devices Research Center, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa 923-1292 (Japan); School of Materials Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa 923-1292 (Japan); Mitani, Tadaoki [Japan Science and Technology Agency (JST), ERATO, Shimoda Nano-Liquid Process Project, 2-5-3 Asahidai, Nomi, Ishikawa 923-1211 (Japan); Shimoda, Tatsuya [Japan Science and Technology Agency (JST), ERATO, Shimoda Nano-Liquid Process Project, 2-5-3 Asahidai, Nomi, Ishikawa 923-1211 (Japan); Green Devices Research Center, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa 923-1292 (Japan); School of Materials Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa 923-1292 (Japan)

    2012-09-24

    We report solution-processed, highly conductive (resistivity 1.3-3.8 m{Omega} cm), p-type amorphous A-B-O (A = Bi, Pb; B = Ru, Ir), processable at temperatures (down to 240 Degree-Sign C) that are compatible with plastic substrates. The film surfaces are smooth on the atomic scale. Bi-Ru-O was analyzed in detail. A small optical bandgap (0.2 eV) with a valence band maximum (VBM) below but very close to the Fermi level (binding energy E{sub VBM} = 0.04 eV) explains the high conductivity and suggests that they are degenerated semiconductors. The conductivity changes from three-dimensional to two-dimensional with decreasing temperature across 25 K.

  13. Defect passivation and homogenization of amorphous oxide thin-film transistor by wet O2 annealing

    NASA Astrophysics Data System (ADS)

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

    2008-11-01

    Roles of H2O addition to an annealing atmosphere were investigated for amorphous In-Ga-Zn-O thin-film transistors fabricated at room temperature. Although dry O2 annealing improved saturation mobility (?sat) and subthreshold voltage swings (S), wet O2 annealing further improved them to ?sat˜12cm2(Vs)-1 and S <0.12Vdecade-1 along with improvement of their uniformity. Desorption of OH-related species caused conductivity increase during thermal annealing at <310°C. Zn-O components started to desorb at ˜300°C for the unannealed and the dry O2 annealed films, while these were suppressed remarkably by the wet O2 annealing.

  14. High mechanical endurance RRAM based on amorphous gadolinium oxide for flexible nonvolatile memory application

    NASA Astrophysics Data System (ADS)

    Zhao, Hongbin; Tu, Hailing; Wei, Feng; Shi, Zhitian; Xiong, Yuhua; Zhang, Yan; Du, Jun

    2015-05-01

    In this paper, we use amorphous Gd2O3 as the switching layer for fabricated RRAM devices with novel high performance, excellent flexibility, and mechanical endurance properties as potential candidate memory for flexible electronics applications. The obtained Cu/Gd2O3/Pt devices on flexible polyethylene terephthalate (PET) substrates show bipolar switching characteristics, low voltage operation (<2?V) and long retention time (>106?s). No performance degradation occurs, and the stored information is not lost after the device has been bent to different angles and up to 104 times in the bending tests. Based on temperature-dependent switching characteristics, the formation of Cu conducting filaments stemming from electrochemical reactions is believed to be the reason for the resistance switching from a high resistance state to a low resistance state. The studies of the integrated experiment and mechanism lay the foundation for the development of high-performance flexible RRAM.

  15. Highly durable inverted-type organic solar cell using amorphous titanium oxide as electron collection electrode inserted between ITO and organic layer

    Microsoft Academic Search

    Takayuki Kuwabara; Taketoshi Nakayama; Konosuke Uozumi; Takahiro Yamaguchi; Kohshin Takahashi

    2008-01-01

    An indium tin oxide\\/titanium oxide\\/[6,6]-phenyl C61 butyric acid methyl ester:regioregular poly(3-hexylthiophene)\\/poly(3,4-ethylenedioxylenethiophene):poly(4-styrene sulfonic acid)\\/Au type organic solar cell (ITO\\/TiOx\\/PCBM:P3HT\\/PEDOT:PSS\\/Au) with 1cm2 active area, which is called “inverted-type solar cell”, was developed using an ITO\\/amorphous titanium oxide (TiOx) electrode prepared by a sol–gel technique instead of a low functional electrode such as Al. The power conversion efficiency (?) of 2.47% was obtained

  16. MC3T3-E1 cell response of amorphous phase/TiO2 nanocrystal composite coating prepared by microarc oxidation on titanium.

    PubMed

    Zhou, Rui; Wei, Daqing; Yang, Haoyue; Feng, Wei; Cheng, Su; Li, Baoqiang; Wang, Yaming; Jia, Dechang; Zhou, Yu

    2014-06-01

    Bioactive amorphous phase/TiO2 nanocrystal (APTN) composite coatings were fabricated by microarc oxidation (MAO) on Ti. The APTN coatings are composed of much amorphous phase with Si, Na, Ca, Ti and O elements and a few TiO2 nanocrystals. With increasing applied voltage, the micropore density of the APTN coating decreases and the micropore size of the APTN coating increases. The results indicate that less MC3T3-E1 cells attach on the APTN coatings as compared to Ti. However, the APTN coatings greatly enhance the cell proliferation ability and the activity of alkaline phosphatase. The amorphous phase and the concentrations of the released Ca and Si from the APTN coatings during cell culture have significant effects on the cell response. PMID:24863215

  17. Hybrid density functional calculations of the defect properties of ZnO:Rh and ZnO:Ir

    E-print Network

    Muñoz Ramo, David; Bristowe, Paul D.

    2014-03-31

    with high transmittance (>80%) in the visible region of the electromagnetic spectrum. n-type TCOs like indium tin oxide,[1] indium gallium zinc oxide[2] and many others have been extensively studied.[3] However, the field of p-type conductors is still... , J. Am. Ceram. Soc. 95, 269 (2012). [11] S. Lany and A. Zunger, Phys. Rev. B 81, 205209 (2010). [12] D. O. Scanlon and G. W. Watson, Phys. Chem. Chem. Phys. 13, 9667 (2011). [13] J. P. Perdew, K. Burke, and M. Ernzerhof, Phys. Rev. Lett. 77, 3865...

  18. Light induced instability mechanism in amorphous InGaZn oxide semiconductors

    SciTech Connect

    Robertson, John; Guo, Yuzheng [Department of Engineering, Cambridge University, Cambridge CB2 1PZ (United Kingdom)

    2014-04-21

    A model of the negative bias illumination stress instability in InGaZn oxide is presented, based on the photo-excitation of electrons from oxygen interstitials. The O interstitials are present to compensate hydrogen donors. The O interstitials are found to spontaneously form in O-rich conditions for Fermi energies at the conduction band edge, much more easily that in related oxides. The excited electrons give rise to a persistent photoconductivity due to an energy barrier to recombination. The formation energy of the O interstitials varies with their separation from the H donors, which leads to a voltage stress dependence on the compensation.

  19. Comparative study of transparent rectifying contacts on semiconducting oxide single crystals and amorphous thin films

    NASA Astrophysics Data System (ADS)

    Lajn, Alexander; von Wenckstern, Holger; Grundmann, Marius; Wagner, Gerald; Barquinha, Pedro; Fortunato, Elvira; Martins, Rodrigo

    2013-01-01

    We demonstrate fully transparent, highly rectifying contacts (TRC) on amorphous GaInZnO and compare them to TRC fabricated on single crystalline bulk ZnO and heteroepitaxial ZnO thin films. The contacts' transparency in the visible spectral range exceeds 70%. From numerical simulations, we conclude that thermionic emission is the dominating transport mechanism, however, for several samples with low net doping density diffusion theory must be applied. The detailed investigation of the rectification properties of the TRC using temperature-dependent current-voltage and capacitance-voltage measurements reveals that barrier inhomogeneities govern the IV-characteristics of all diodes irrespective of the sample crystallinity. Assuming a Gaussian barrier height distribution, the extracted mean barrier heights typically range between 1.1 and 1.3 V. The width of the barrier distribution correlates with the mean barrier height and ranges from 110 to 130 mV. By compiling literature data, we found that this correlation holds also true for Schottky diodes on elemental and III-V semiconductors.

  20. Strain-induced transformation of amorphous spherical precipitates into platelets: Application to oxide particles in silicon

    SciTech Connect

    Voronkov, V. V.; Falster, R.

    2001-06-01

    The spherical shape of an amorphous precipitate becomes unstable if the combination P{sup 2}R of precipitate radius R and pressure P exceeds some critical value. This critical value was found to be about 4.44 G{sigma}, where G is the matrix shear modulus and {sigma} is the specific energy of the precipitate/matrix interface. Once this instability criterion is fulfilled, the initially spherical particle will reduce the total free energy (the sum of strain energy and the surface energy) by becoming a thin oblate spheroid (effectively, a platelet). The actual pressure P in the course of oxygen precipitation in silicon is controlled by a high self-interstitial supersaturation caused by emission of self-interstitials by growing precipitates. The duration of annealing necessary to reach the stage of collapse of spheres into platelets is calculated as a function of temperature and the precipitate density. Calculated results are compatible with the experimentally observed annealing conditions for platelet formation. Another important example of sphere to platelet transformation is microdefect formation in vacancy-type silicon. In this case a large negative value of P is sufficient to induce collapse. {copyright} 2001 American Institute of Physics.

  1. Ultrathin amorphous zinc-tin-oxide buffer layer for enhancing heterojunction interface quality in

    E-print Network

    -abundant, non-toxic, and air-stable materials represent a promising class of photovoltaic (PV) devices compatible with terawatts-scale deployment.1­3 Cuprous oxide (Cu2O) is one of several candidate materials candidates for renewable energy applications due to their sustainable raw- material usage and potential

  2. Dielectric properties of crystalline and amorphous transition metal oxides and silicates as potential high-? candidates: the contribution of density-functional theory

    Microsoft Academic Search

    G-M Rignanese

    2005-01-01

    A review is given of various first-principles studies of the dielectric properties of crystalline and amorphous transition metal oxides and silicates, which have drawn considerable attention as potential high-? materials. After a brief summary of the principal equations of density-functional theory related to the dielectric properties of solids, the results obtained for group IVb M = (Hf,Zr,Ti) and IIIb M

  3. Local coordination structure and electronic structure of the large electron mobility amorphous oxide semiconductor In-Ga-Zn-O: Experiment and ab initio calculations

    Microsoft Academic Search

    Kenji Nomura; Hiromichi Ohta; Masahiro Hirano; Toshio Kamiya; Tomoya Uruga; Hideo Hosono

    2007-01-01

    Ionic amorphous oxide semiconductors (IAOSs) are new materials for flexible thin film transistors that exhibit field-effect mobilities of â10 cm² V⁻¹ s⁻¹ [K. Nomura et al., Nature 488, 432 (2004)]. The local coordination structure in an IAOS, In-Ga-Zn-O (a-IGZO), was examined using extended x-ray absorption fine structure analysis combined with ab initio calculations. The short-range ordering and coordination structures in

  4. Local coordination structure and electronic structure of the large electron mobility amorphous oxide semiconductor In-Ga-Zn-O: Experiment and ab initio calculations

    Microsoft Academic Search

    Kenji Nomura; Toshio Kamiya; Hiromichi Ohta; Tomoya Uruga; Masahiro Hirano; Hideo Hosono

    2007-01-01

    Ionic amorphous oxide semiconductors (IAOSs) are new materials for flexible thin film transistors that exhibit field-effect mobilities of ˜10cm2V-1s-1 [K. Nomura , Nature 488, 432 (2004)]. The local coordination structure in an IAOS, In-Ga-Zn-O ( a -IGZO), was examined using extended x-ray absorption fine structure analysis combined with ab initio calculations. The short-range ordering and coordination structures in a -IGZO

  5. First-principles study of oxidation kinetics in amorphous SiO_2.

    NASA Astrophysics Data System (ADS)

    Ng, Kwok-On; Vanderbilt, David

    1998-03-01

    Understanding the atomic structure of ultrathin SiO2 films grown on Si substrates is an outstanding problem of great importance for microelectronics applications. While the formation of thick oxide films (>200 Åis well described phenomenologically by the Deal-Grove model, there is little consensus about the mechanisms of oxidation kinetics for ultrathin films (<100 ÅWe have chosen to investigate one aspect of this problem, namely, the behavior of atomic oxygen in a-SiO_2. We use first-principles ultrasoft-pseudopotential methods, and consider several kinds of geometries. These include non-bonded O atoms at interstitial sites; oxygen atoms forming peroxyl bridge (...Si-O-O-Si...) configurations; and other Si-O defects. Because the defects of interest involve coordination changes, we have implemented the gradient corrections of Perdew, Burke and Ernzerhof to improve the accuracy of the defect energies within density-functional theory.

  6. Packing and the structural transformations in liquid and amorphous oxides from ambient to extreme conditions

    PubMed Central

    Zeidler, Anita; Salmon, Philip Stephen; Skinner, Lawrie Basil

    2014-01-01

    Liquid and glassy oxide materials play a vital role in multiple scientific and technological disciplines, but little is known about the part played by oxygen–oxygen interactions in the structural transformations that change their physical properties. Here we show that the coordination number of network-forming structural motifs, which play a key role in defining the topological ordering, can be rationalized in terms of the oxygen-packing fraction over an extensive pressure and temperature range. The result is a structural map for predicting the likely regimes of topological change for a range of oxide materials. This information can be used to forecast when changes may occur to the transport properties and compressibility of, e.g., fluids in planetary interiors, and is a prerequisite for the preparation of new materials following the principles of rational design. PMID:24982151

  7. Electrical and optical properties of amorphous vanadium oxide thin films deposited by DC magnetron sputtering

    Microsoft Academic Search

    Zhenfei Luo; Zhiming Wu; Mingjun Du; Xiangdong Xu; Junsheng Yu; Tao Wang; Yadong Jiang

    2010-01-01

    In this work, vanadium oxide thin films were grown on glass slides by using reactive direct current (DC) magnetron sputtering from a vanadium target in an Ar+O2 atmosphere. It was found that the surface morphology, electrical and optical properties were strongly affected by the deposition temperature. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the structure

  8. Low-temperature synthetic route based on the amorphous nature of giant species for preparation of lower valence oxides

    SciTech Connect

    Eda, Kazuo [Department of Chemistry, Faculty of Science, Kobe University, Nada-ku, Kobe-shi, Hoyogo-ken 657-8501 (Japan)]. E-mail: eda@kobe-u.ac.jp; Kunotani, Fumiko [Department of Chemistry, Faculty of Science, Kobe University, Nada-ku, Kobe-shi, Hoyogo-ken 657-8501 (Japan); Uchiyama, Noriki [Department of Chemistry, Faculty of Science, Kobe University, Nada-ku, Kobe-shi, Hoyogo-ken 657-8501 (Japan)

    2005-05-15

    We examined low-temperature synthetic route based on the amorphous nature of giant species to succeed to prepare Cs blue bronze (Cs{sub 0.3}MoO{sub 3}), which has never obtained by usual high-temperature methods, at ca. 680K. Solid solutions (K{sub 1-x}Rb{sub x}){sub 0.28}MoO{sub 3} and (Li{sub 1-x}Na{sub x}){sub 0.9}Mo{sub 6}O{sub 17} were also obtained at lower temperatures (ca. 670K). For the latter system consisting of non-isostructural end members, Li{sub 0.9}Mo{sub 6}O{sub 17}-structure type solid solution was formed even when 0.25oxides Ln{sub 2}Mo{sub 3}O{sub 9} (Ln=La, Gd) were obtained, but not as single phases.

  9. Formation of thin film Tl-based high-Tc? superconducting oxides from amorphous alloy precursors 

    E-print Network

    Williams, John Charles

    1991-01-01

    -based thin film superconductors. The most popular deposition method seems to be through the use of sputter techniques. IS SO 31 32 33 Sputter deposition methods have been used to produce nearly single-phase 2212 films with a T, near 100 K1s 3o 3~ 32 ss... highly oriented 2021 and 2212 phase films. 4S 44 Hermann et aL reports using two different techniques. 4s One technique uses either magnetron sputtering or laser ablation of Ba-Ca-Cu oxides onto various substrates. Thallium vapor diffusion...

  10. Photo-induced oxidation and amorphization of trigonal tellurium: A means to engineer hybrid nanostructures and explore glass structure under spatial confinement

    SciTech Connect

    Vasileiadis, Thomas [Foundation for Research and Technology Hellas–Institute of Chemical Engineering Sciences (FORTH/ICE-HT), P.O. Box 1414, GR-26504 Rio-Patras (Greece); Department of Materials Science, University of Patras, GR-26504 Rio-Patras (Greece); Yannopoulos, Spyros N., E-mail: sny@iceht.forth.gr [Foundation for Research and Technology Hellas–Institute of Chemical Engineering Sciences (FORTH/ICE-HT), P.O. Box 1414, GR-26504 Rio-Patras (Greece)

    2014-09-14

    Controlled photo-induced oxidation and amorphization of elemental trigonal tellurium are achieved by laser irradiation at optical wavelengths. These processes are monitored in situ by time-resolved Raman scattering and ex situ by electron microscopies. Ultrathin TeO? films form on Te surfaces, as a result of irradiation, with an interface layer of amorphous Te intervening between them. It is shown that irradiation, apart from enabling the controllable transformation of bulk Te to one-dimensional nanostructures, such as Te nanotubes and hybrid core-Te/sheath-TeO? nanowires, causes also a series of light-driven (athermal) phase transitions involving the crystallization of the amorphous TeO? layers and its transformation to a multiplicity of crystalline phases including the ?-, ?-, and ?-TeO? crystalline phases. The kinetics of the above photo-induced processes is investigated by Raman scattering at various laser fluences revealing exponential and non-exponential kinetics at low and high fluence, respectively. In addition, the formation of ultrathin (less than 10 nm) layers of amorphous TeO? offers the possibility to explore structural transitions in 2D glasses by observing changes in the short- and medium-range structural order induced by spatial confinement.

  11. The effect of B 2O 3 addition on the crystallization of amorphous TiO 2-ZrO 2 mixed oxide

    NASA Astrophysics Data System (ADS)

    Mao, Dongsen; Lu, Guanzhong

    2007-02-01

    The effect of B 2O 3 addition on the crystallization of amorphous TiO 2-ZrO 2 mixed oxide was investigated by X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG/DTA). TiO 2-ZrO 2 mixed oxide was prepared by co-precipitation method with aqueous ammonia as the precipitation reagent. Boric acid was used as a source of boria, and boria contents varied from 2 to 20 wt%. The results indicate that the addition of small amount of boria (<8 wt%) hinders the crystallization of amorphous TiO 2-ZrO 2 into a crystalline ZrTiO 4 compound, while a larger amount of boria (?8 wt%) promotes the crystallization process. FT-IR spectroscopy and 11B MAS NMR results show that tetrahedral borate species predominate at low boria loading, and trigonal borate species increase with increasing boria loading. Thus it is concluded that highly dispersed tetrahedral BO 4 units delay, while a build-up of trigonal BO 3 promote, the crystallization of amorphous TiO 2-ZrO 2 to form ZrTiO 4 crystals.

  12. X-ray absorption spectroscopy elucidates the impact of structural disorder on electron mobility in amorphous zinc-tin-oxide thin films

    SciTech Connect

    Siah, Sin Cheng, E-mail: siahsincheng@gmail.com, E-mail: buonassisi@mit.edu; Lee, Yun Seog; Buonassisi, Tonio, E-mail: siahsincheng@gmail.com, E-mail: buonassisi@mit.edu [Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Lee, Sang Woon; Gordon, Roy G. [Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138 (United States); Heo, Jaeyeong [Department of Materials Science and Engineering, Chonnam National University, Gwangju 500-757 (Korea, Republic of); Shibata, Tomohiro; Segre, Carlo U. [Physics Department and CSRRI, Illinois Institute of Technology, Chicago, Illinois 606016 (United States)

    2014-06-16

    We investigate the correlation between the atomic structures of amorphous zinc-tin-oxide (a-ZTO) thin films grown by atomic layer deposition (ALD) and their electronic transport properties. We perform synchrotron-based X-ray absorption spectroscopy at the K-edges of Zn and Sn with varying [Zn]/[Sn] compositions in a-ZTO thin films. In extended X-ray absorption fine structure (EXAFS) measurements, signal attenuation from higher-order shells confirms the amorphous structure of a-ZTO thin films. Both quantitative EXAFS modeling and X-ray absorption near edge spectroscopy (XANES) reveal that structural disorder around Zn atoms increases with increasing [Sn]. Field- and Hall-effect mobilities are observed to decrease with increasing structural disorder around Zn atoms, suggesting that the degradation in electron mobility may be correlated with structural changes.

  13. Electrical ferroelectric-like properties of amorphous thin films of ferroelectric oxides prepared by the sol-gel technique

    SciTech Connect

    Xu, Y.; Cheng, C.H.; Mackenzie, J.D. [Univ. of California, Los Angeles, CA (United States)

    1995-12-31

    Lead zirconate titanate [Pb(Zr{sub x}Ti{sub 1-x})O{sub 3}, or PZT], BaTiO{sub 3} and LiNbO{sub 3} thin films on silicon wafer and titanium foil were fabricated by the sol-gel technique. Amorphous LiNbO3 thin film was obtained at 150{degrees}C. Amorphous PZT and BaTiO{sub 3} thin films were obtained at the heat-treatment temperature of 350{degrees}C and 400{degrees}C, respectively. The microstructure of these films was determined by x-ray and electron diffractions and HRTEM technique. The electrical properties of these thin films were measured. For these amorphous thin films ferroelectric hysteresis loop and pyroelectric current were observed. The dielectric permittivity of amorphous thin films is much lower than those of corresponding polycrystalline materials.

  14. Amorphous Rover

    NASA Technical Reports Server (NTRS)

    Curtis, Steven A.

    2010-01-01

    A proposed mobile robot, denoted the amorphous rover, would vary its own size and shape in order to traverse terrain by means of rolling and/or slithering action. The amorphous rover was conceived as a robust, lightweight alternative to the wheeled rover-class robotic vehicle heretofore used in exploration of Mars. Unlike a wheeled rover, the amorphous rover would not have a predefined front, back, top, bottom, or sides. Hence, maneuvering of the amorphous rover would be more robust: the amorphous rover would not be vulnerable to overturning, could move backward or sideways as well as forward, and could even narrow itself to squeeze through small openings.

  15. Synthesis of crystalline and amorphous, particle-agglomerated 3-D nanostructures of Al and Si oxides by femtosecond laser and the prediction of these particle sizes

    PubMed Central

    2012-01-01

    We report a single step technique of synthesizing particle-agglomerated, amorphous 3-D nanostructures of Al and Si oxides on powder-fused aluminosilicate ceramic plates and a simple novel method of wafer-foil ablation to fabricate crystalline nanostructures of Al and Si oxides at ambient conditions. We also propose a particle size prediction mechanism to regulate the size of vapor-condensed agglomerated nanoparticles in these structures. Size characterization studies performed on the agglomerated nanoparticles of fabricated 3-D structures showed that the size distributions vary with the fluence-to-threshold ratio. The variation in laser parameters leads to varying plume temperature, pressure, amount of supersaturation, nucleation rate, and the growth rate of particles in the plume. The novel wafer-foil ablation technique could promote the possibilities of fabricating oxide nanostructures with varying Al/Si ratio, and the crystallinity of these structures enhances possible applications. The fabricated nanostructures of Al and Si oxides could have great potentials to be used in the fabrication of low power-consuming complementary metal-oxide-semiconductor circuits and in Mn catalysts to enhance the efficiency of oxidation on ethylbenzene to acetophenone in the super-critical carbon dioxide. PMID:23140103

  16. Synthesis of crystalline and amorphous, particle-agglomerated 3-D nanostructures of Al and Si oxides by femtosecond laser and the prediction of these particle sizes

    NASA Astrophysics Data System (ADS)

    Sivayoganathan, Mugunthan; Tan, Bo; Venkatakrishnan, Krishnan

    2012-11-01

    We report a single step technique of synthesizing particle-agglomerated, amorphous 3-D nanostructures of Al and Si oxides on powder-fused aluminosilicate ceramic plates and a simple novel method of wafer-foil ablation to fabricate crystalline nanostructures of Al and Si oxides at ambient conditions. We also propose a particle size prediction mechanism to regulate the size of vapor-condensed agglomerated nanoparticles in these structures. Size characterization studies performed on the agglomerated nanoparticles of fabricated 3-D structures showed that the size distributions vary with the fluence-to-threshold ratio. The variation in laser parameters leads to varying plume temperature, pressure, amount of supersaturation, nucleation rate, and the growth rate of particles in the plume. The novel wafer-foil ablation technique could promote the possibilities of fabricating oxide nanostructures with varying Al/Si ratio, and the crystallinity of these structures enhances possible applications. The fabricated nanostructures of Al and Si oxides could have great potentials to be used in the fabrication of low power-consuming complementary metal-oxide-semiconductor circuits and in Mn catalysts to enhance the efficiency of oxidation on ethylbenzene to acetophenone in the super-critical carbon dioxide.

  17. TOPICAL REVIEW: Dielectric properties of crystalline and amorphous transition metal oxides and silicates as potential high-? candidates: the contribution of density-functional theory

    NASA Astrophysics Data System (ADS)

    Rignanese, G.-M.

    2005-02-01

    A review is given of various first-principles studies of the dielectric properties of crystalline and amorphous transition metal oxides and silicates, which have drawn considerable attention as potential high-? materials. After a brief summary of the principal equations of density-functional theory related to the dielectric properties of solids, the results obtained for group IVb M = (Hf,Zr,Ti) and IIIb M = (Y,La,Lu) transition metals crystalline oxides and/or silicates are discussed. For the group IVb transition metals, four crystalline phases (cubic, tetragonal, monoclinic and rutile) of dioxide MO2 with M = (Hf,Zr,Ti) have been considered in the literature. The results of density-functional theory calculations of the dielectric properties of three crystalline transition metal silicates (hafnon HfSiO4, zircon ZrSiO4 and a hypothetical TiSiO4 structure) are also presented. For the group IIIb transition metals, two crystalline phases (cubic and hexagonal) of sesquioxides M2O3 with M = Lu have been investigated within density-functional theory. Finally, the first-principles results that have been obtained for the amorphous silicates are discussed. A presentation is given of a scheme recently introduced which relates the dielectric constants to the local bonding of Si and metal atoms. It is based on the definition of parameters characteristic of the basic structural units centred on Si and metals atoms and including their nearest O neighbours. Applied to amorphous Zr silicates, it provides a good description of the measured dielectric constants, both of the optical and the static ones.

  18. Morphological and Electrical Properties of Self-Textured Aluminum-Doped Zinc Oxide Films Prepared by Direct Current Magnetron Sputtering for Application to Amorphous Silicon Solar Cells

    NASA Astrophysics Data System (ADS)

    Kim, Young Baek; Choi, Bum Ho; Lee, Jong Ho; Hyeok Kim, Jin

    2011-06-01

    Self-textured Al-doped zinc oxide (AZO) transparent conducting oxide (TCO) layers were grown by DC magnetron sputtering, and their morphological and electrical properties were investigated. The self-textured AZO layers were fabricated by controlling the deposition conditions, without employing wet or dry etching for surface texturing. The polycrystalline AZO layers with a high surface roughness (42 nm) were grown on a glass substrate at various DC plasma power. The lowest sheet resistance was 3.7×10-4 ? cm and the highest carrier mobility obtained was 30 cm2 V-1 s-1, which are comparable to those of chemically textured AZO layers. The electrical and optical characteristics of the self-textured AZO films are comparable to those of wet-etched AZO films that were etched using the conventional HCl solution. Our study suggests a possible way to inexpensively fabricate amorphous silicon thin-film solar cells.

  19. Density functional theory simulations of amorphous high-oxides on a compound semiconductor alloy: a-Al2O3/InGaAs(100)-(42), a-HfO2/InGaAs(100)-(42), and a-

    E-print Network

    Kummel, Andrew C.

    Density functional theory simulations of amorphous high- oxides on a compound semiconductor alloy on atomic bonding and electronic properties at HfO2/GaAs interface: A first-principles study J. Appl. Phys (2011) Density functional theory simulations of amorphous high- oxides on a compound semiconductor alloy

  20. The silicon/zinc oxide interface in amorphous silicon-based thin-film solar cells: Understanding an empirically optimized contact

    NASA Astrophysics Data System (ADS)

    Gerlach, D.; Wilks, R. G.; Wippler, D.; Wimmer, M.; Lozac'h, M.; Félix, R.; Mück, A.; Meier, M.; Ueda, S.; Yoshikawa, H.; Gorgoi, M.; Lips, K.; Rech, B.; Sumiya, M.; Hüpkes, J.; Kobayashi, K.; Bär, M.

    2013-07-01

    The electronic structure of the interface between the boron-doped oxygenated amorphous silicon "window layer" (a-SiOx:H(B)) and aluminum-doped zinc oxide (ZnO:Al) was investigated using hard x-ray photoelectron spectroscopy and compared to that of the boron-doped microcrystalline silicon (?c-Si:H(B))/ZnO:Al interface. The corresponding valence band offsets have been determined to be (-2.87 ± 0.27) eV and (-3.37 ± 0.27) eV, respectively. A lower tunnel junction barrier height at the ?c-Si:H(B)/ZnO:Al interface compared to that at the a-SiOx:H(B)/ZnO:Al interface is found and linked to the higher device performances in cells where a ?c-Si:H(B) buffer between the a-Si:H p-i-n absorber stack and the ZnO:Al contact is employed.

  1. Crystalline mesoporous K(2-x)Mn?O?? and ?-MnO? by mild transformations of amorphous mesoporous manganese oxides and their enhanced redox properties.

    PubMed

    Poyraz, Altug S; Song, Wenqiao; Kriz, David; Kuo, Chung-Hao; Seraji, Mohammad S; Suib, Steven L

    2014-07-23

    Synthesis of crystalline mesoporous K(2-x)Mn8O16 (Meso-OMS-2), and ?-MnO2 (Meso-?-MnO2) is reported. The synthesis is based on the transformation of amorphous mesoporous manganese oxide (Meso-Mn-A) under mild conditions: aqueous acidic solutions (0.5 M H(+) and 0.5 M K(+)), at low temperatures (70 °C), and short times (2 h). Meso-OMS-2 and Meso-?-MnO2 maintain regular mesoporosity (4.8-5.6 nm) and high surface areas (as high as 277 m(2)/g). The synthesized mesoporous manganese oxides demonstrated enhanced redox (H2-TPR) and catalytic performances (CO oxidation) compared to nonporous analogues. The order of reducibility and enhanced catalytic performance of the samples is Commercial-Mn2O3 < nonporous-OMS-2 < Meso-Mn2O3 < Meso-OMS-2 < Meso-?-MnO2 < Meso-Mn-A. PMID:24971574

  2. Reaction pathways of oxide-reduction-diffusion (ORD) synthesis of SmCo5 and in situ study of its hydrogen induced amorphization (HIA)

    NASA Astrophysics Data System (ADS)

    Belener, Kevin L. A.; Kohlmann, Holger

    2014-12-01

    A modified oxide-reduction-diffusion (ORD) method for the synthesis of single-phase SmCo5 is described. Samarium oxide, cobalt and calcium (20% excess) are heated in sealed niobium tubes following an optimized temperature programme. The reaction proceeds via Ca1-xSmxO as an intermediate and yields SmCo5, and CaO, which may be washed off with dilute acetic acid. Single-phase SmCo5 prepared by this route shows an enhanced reactivity towards hydrogen and reacts already at moderate conditions of p(H2)=0.1 MPa and T<770 K. in situ difference scanning calorimetry and X-ray powder diffraction suggest the formation of ternary hydrides SmCo5Hx at temperatures around 473 and 573 K, and disproportionation into cobalt of poor crystallinity and probably an amorphous binary samarium hydride at 700 K, i.e. a hydrogen induced amorphization (HIA) of SmCo5. Neutron powder diffraction was carried out on a 154SmCo5 sample with the high-intensity neutron powder diffractometer D20 at the Institute Laue-Langevin, Grenoble, France. The CaCu5 type crystal structure was confirmed (space group P6/mmm, a=500.60 (2) pm, c=397.01 (2) pm at T=298 (1) K) and the magnetic moments along the crystallographic c axis, ?||c, were refined to be 0.15 (6), 2.02 (6) and 1.75 (5) ?B for Sm, Co1 and Co2 atoms, respectively, in ferromagnetic SmCo5. The HIA process was confirmed by in situ neutron powder diffraction at higher pressures of 8.1 MPa deuterium gas.

  3. Electronic Structure of Low-Temperature Solution-Processed Amorphous Metal Oxide Semiconductors for Thin-Film Transistor Applications

    E-print Network

    Socratous, Josephine; Banger, Kulbinder K.; Vaynzof, Yana; Sadhanala, Aditya; Brown, Adam D.; Sepe, Alessandro; Steiner, Ullrich; Sirringhaus, Henning

    2015-02-18

    FU LL P A P ER © 2015 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1873wileyonlinelibrary.com performance than amorphous silicon devices with mobilities µ>10cm 2 V ?1 s ?1 and better threshold voltage stability making them... . Funct. Mater. 2015, 25, 1873–1885 www.afm-journal.de www.MaterialsViews.com Figure 1. a) Red: drain current. Black: gate leakage current. Blue: Linear Mobility. Solid lines represent forward scan. Dotted lines represent reverse scan. Transfer curves...

  4. Investigation of the effects of deposition parameters on indium-free transparent amorphous oxide semiconductor thin-film transistors fabricated at low temperatures for flexible electronic applications

    NASA Astrophysics Data System (ADS)

    Alston, Robert; Iyer, Shanthi; Bradley, Tanina; Lewis, Jay; Cunningham, Garry; Forsythe, Eric

    2014-02-01

    Low temperature gallium tin zinc oxide (GSZO) based thin film transistors fabricated on silicon has been investigated as a potential indium free transparent amorphous oxide semiconductor thin film transistor (TAOS TFT) with potential device applications on plastic substrates. A comprehensive and detailed study on the performance of GSZO TFTs has been carried out by studying the effects of processing parameters such as deposition temperature and annealing temperature/duration, as well as the channel thickness with all temperatures held below 150 °C. Variety of characterization techniques, namely Rutherford backscattering (RBS), x-ray photoelectron spectroscopy (XPS) and x-ray reflectivity (XRR) in addition to I-V and C-V measurements were employed to determine the effects of the above parameters on the composition and quality of the channel. Optimized TFT characteristics of ID=3×10-7 A, ION/OFF =2×106, VON ~ -2 V, SS ~ 1 V/dec and ?FE = 0.14 cm2/V· s with a ?VON of 3.3 V under 3 hours electrical stress were produced.

  5. Chemical mechanical planarization of amorphous Ge2Sb2Te5 using KClO4 as oxidizer in acidic slurry

    NASA Astrophysics Data System (ADS)

    He, Aodong; Song, Zhitang; Bo, Liu; Zhong, Min; Weili, Liu; Wang, Liangyong; Yan, Weixia; Lei, Yu; Wu, Guangping

    Amorphous Ge2Sb2Te5 (a-GST) chemical mechanical planarization (CMP) using KClO4 as the oxidizer in an acidicslurry is investigated in the present work. It is shown that the removal rate (RR ) of the a-GST firstly increases and thentends to saturate when the KClO4 concentration is greater than 0.8 wt%, but the static etch rate (SER) linearly increasesfrom low to high KClO4 concentration. To understand the oxidation-reaction capability of Ge, Sb and Te, depth profilesof composition of elements and etch morphology of a-GST immersed in the slurry for some time are measured,respectively. It is found that selective corrosion occurs among Ge, Sb and Te, and an accumulation of Te and loss of Gein a-GST surface region are obvious observed, especially at high KClO4 concentrations. Temperature dependent sheetresistance measurements of all the samples pre- and post-CMP reveal a similar trend, which implies a-GST CMP is ableto keep its characteristic well.

  6. On the nature of amorphous-to-amorphous and crystal-to-amorphous transitions under high pressure

    Microsoft Academic Search

    V. V. Brazhkin; A. G. Lyapin; O. V. Stalgorova; E. L. Gromnitskaya; S. V. Popova; O. B. Tsiok

    1997-01-01

    A number of experimental methods have been applied to study the kinetics of high-pressure solid-state amorphization for some covalent crystals (Si, Ge and GaSb), molecular crystals, C60 and ionic oxides (stishovite and H2O), as well as the amorphous-to-amorphous transitions for H2O and GeO2. The low activation energy for the stishovite ? a-SiO2 transition and appreciable variation of kinetic characteristics in

  7. Enhancement on photocatalytic activity of an amorphous titanium oxide film with nano-textured surface by selective-fluorination etching process

    SciTech Connect

    Shih, Pin-Chun; Huang, Cheng-Hao [Institute of Electro-Optical and Materials Science, National Formosa University, Huwei, Yunlin 63201, Taiwan, ROC (China); Chen, Tai-Hong; Lai, Li-Wen [ITRI South, Industrial Technology Research Institute, Liujia, Tainan 73445, Taiwan, ROC (China); Lu, Yi-Shan [Institute of Electro-Optical and Materials Science, National Formosa University, Huwei, Yunlin 63201, Taiwan, ROC (China); Liu, Day-Shan, E-mail: dsliu@sunws.nfu.edu.tw [Institute of Electro-Optical and Materials Science, National Formosa University, Huwei, Yunlin 63201, Taiwan, ROC (China)

    2014-04-01

    Highlights: • The amorphous TiO{sub x} film surface was modified via selective fluorination etching process. • The resulting nano-textured surface markedly enriched the specific surface area and surface acidity. • The photocatalytic activity was comparable to an annealed TiO{sub x} film with anatase structure. - Abstract: A selective-fluorination etching process achieved by an UV light pre-irradiation and the subsequently fluorination etching was developed to enhance the photocatalytic activity of a low-temperature deposited amorphous titanium oxide (a-TiO{sub x}) film. Textured surface on the a-TiO{sub x} films formed by this process were investigated using atomic force microscope and field emission scanning electron microscope. Evidence of the fluorine ions introduced into the a-TiO{sub x} films was examined using Fourier transform infrared spectrometry and X-ray photoelectron spectroscopy. The etching thickness of the a-TiO{sub x} film was found to be deeply relevant to the film pre-irradiated by the UV light. An a-TiO{sub x} film with nano-textured surface, which was favorable to enlarge the specific surface area, thus was obtainable from the notable etching selectivity of the film pre-irradiated by UV light through a nano-sized mask. In addition, the surface acidity of the a-TiO{sub x} film was enhanced by the formation of the Ti-F chemical bonds originating from the fluorination etching process, which also was functional to facilitate the production of surface OH free radicals. Accordingly, the resulting fluorinated a-TiO{sub x} film with nano-textured surface performed a quality photocatalytic activity comparable to that of the high-temperature achieved TiO{sub x} film with anatase structures.

  8. Controlled aluminum-induced crystallization of an amorphous silicon thin film by using an oxide-layer diffusion barrier

    NASA Astrophysics Data System (ADS)

    Hwang, Ji-Hyun; Kwak, Hyunmin; Kwon, Myeung Hoi

    2014-03-01

    Aluminum-induced crystallization (AIC) of amorphous silicon with an Al2O3 diffusion barrier was investigated for controlling Si crystallization and preventing layer exchange during the annealing process. An Al2O3 layer was deposited between the a-Si and the Al films (a-Si/Al2O3/Al/Glass) and was blasted with an air spray gun with alumina beads to form diffusion channels between the Si and the Al layers. During the annealing process, small grain Si x Al seeds were formed at the channels. Then, the Al2O3 diffusion barrier was restructured to close the channels and prevent further diffusion of Al atoms into the a-Si layer. A polycrystalline Si film with (111), (220) and (311) crystallization peaks in the X-ray diffraction pattern was formed by annealing at 560 °C in a conventional furnace. That film showed a p-type semiconducting behavior with good crystallinity and a large grain size of up to 14.8 µm. No layer conversion occurred between the Si and the Al layers, which had been the fundamental obstacle to the applications in the crystallization of a-Si films by using the AIC method.

  9. Diffused transmission and texture-induced defect with transparent conducting oxide front electrode of amorphous silicon solar cell

    NASA Astrophysics Data System (ADS)

    Park, Hyeongsik; Iftiquar, S. M.; Kim, Hee Won; Lee, Jaehyeong; Le, Anh Huy Tuan; Yi, Junsin

    2013-11-01

    Highly textured transparent conducting front electrode (TFE) can enhance light trapping; however, we observed an improved performance of a solar cell by nanometer level modification of surface texture. A 40 nm thick aluminum doped zinc oxide was sputter deposited at an oblique flux on the textured fluorine doped tin oxide TFE, and a TFE double layer was used for the front electrode of solar cells. The cells fabricated on these modified TFEs exhibited an increased open circuit voltage, enhancement in short circuit current density and an increase in fill factor that reached up to 74% because of reduced series resistance of the cell. The surface texture of the TFE was modified with various angular fluxes of the zinc oxide sputter particle, which shows lower texture-induced-surface defect, higher work function. These are thought to have helped in improving the performance of the thin-film solar cells. However, at a near normal angular flux of the zinc oxide sputter particle, light trapping was observed to have reduced significantly, leading to a significant reduction in current density of the cell.

  10. Amorphous TiO? coatings stabilize Si, GaAs, and GaP photoanodes for efficient water oxidation.

    PubMed

    Hu, Shu; Shaner, Matthew R; Beardslee, Joseph A; Lichterman, Michael; Brunschwig, Bruce S; Lewis, Nathan S

    2014-05-30

    Although semiconductors such as silicon (Si), gallium arsenide (GaAs), and gallium phosphide (GaP) have band gaps that make them efficient photoanodes for solar fuel production, these materials are unstable in aqueous media. We show that TiO2 coatings (4 to 143 nanometers thick) grown by atomic layer deposition prevent corrosion, have electronic defects that promote hole conduction, and are sufficiently transparent to reach the light-limited performance of protected semiconductors. In conjunction with a thin layer or islands of Ni oxide electrocatalysts, Si photoanodes exhibited continuous oxidation of 1.0 molar aqueous KOH to O2 for more than 100 hours at photocurrent densities of >30 milliamperes per square centimeter and ~100% Faradaic efficiency. TiO2-coated GaAs and GaP photoelectrodes exhibited photovoltages of 0.81 and 0.59 V and light-limiting photocurrent densities of 14.3 and 3.4 milliamperes per square centimeter, respectively, for water oxidation. PMID:24876492

  11. Using amorphous manganese oxide for remediation of smelter-polluted soils: a pH-dependent long-term stability study

    NASA Astrophysics Data System (ADS)

    Ettler, Vojtech; Tomasova, Zdenka; Komarek, Michael; Mihaljevic, Martin; Sebek, Ondrej

    2015-04-01

    In soil systems, manganese (Mn) oxides are commonly found to be powerful sorbents of metals and metalloids and are thus potentially useful in soil remediation. A novel amorphous manganese oxide (AMO) and a Pb smelter-polluted agricultural soil amended with the AMO and incubated for 2 and 6 months were subjected to a pH-static leaching procedure (pH = 3 - 8) to verify the chemical stabilization effect on metals and metalloids. The AMO stability in pure water was pH-dependent with the highest Mn release at pH 3 (47% dissolved) and the lowest at pH 8 (0.14% dissolved). Secondary rhodochrosite (MnCO3) was formed at the AMO surfaces at pH > 5. The AMO dissolved significantly less after 6 months of incubation. Sequential extraction analysis indicated that "labile" fraction of As, Pb and Sb in soil significantly decreased after AMO amendment. The pH-static experiments indicated that no effect on leaching was observed for Cd and Zn after AMO treatments, whereas the leaching of As, Cu, Pb and Sb decreased down to 20%, 35%, 7% and 11% of the control, respectively. The remediation efficiency was more pronounced under acidic conditions and the time of incubation generally led to increased retention of the targeted contaminants. The AMO was found to be a promising agent for the chemical stabilization of polluted soils and other in situ applications need to be evaluated. This study was supported by the Czech Science Foundation (GA?R 15-07117S).

  12. Ultra-flexible, "invisible" thin-film transistors enabled by amorphous metal oxide/polymer channel layer blends.

    PubMed

    Yu, Xinge; Zeng, Li; Zhou, Nanjia; Guo, Peijun; Shi, Fengyuan; Buchholz, Donald B; Ma, Q; Yu, Junsheng; Dravid, Vinayak P; Chang, Robert P H; Bedzyk, Michael; Marks, Tobin J; Facchetti, Antonio

    2015-04-01

    Ultra-flexible and transparent metal oxide transistors are developed by doping In2 O3 films with poly(vinylphenole) (PVP). By adjusting the In2 O3 :PVP weight ratio, crystallization is frustrated, and conducting pathways for efficient charge transport are maintained. In2 O3 :5%PVP-based transistors exhibit mobilities approaching 11 cm(2) V(-1) s(-1) before, and retain up to ca. 90% performance after 100 bending/relaxing cycles at a radius of 10 mm. PMID:25712894

  13. The effect of B{sub 2}O{sub 3} addition on the crystallization of amorphous TiO{sub 2}-ZrO{sub 2} mixed oxide

    SciTech Connect

    Mao Dongsen [Research Institute of Applied Catalysis, Department of Chemical Engineering, Shanghai Institute of Technology, Number 120, Caobaolu, Shanghai 200235 (China)], E-mail: dsmao1106@yahoo.com.cn; Lu Guanzhong [Research Institute of Applied Catalysis, Department of Chemical Engineering, Shanghai Institute of Technology, Number 120, Caobaolu, Shanghai 200235 (China)

    2007-02-15

    The effect of B{sub 2}O{sub 3} addition on the crystallization of amorphous TiO{sub 2}-ZrO{sub 2} mixed oxide was investigated by X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG/DTA). TiO{sub 2}-ZrO{sub 2} mixed oxide was prepared by co-precipitation method with aqueous ammonia as the precipitation reagent. Boric acid was used as a source of boria, and boria contents varied from 2 to 20 wt%. The results indicate that the addition of small amount of boria (<8 wt%) hinders the crystallization of amorphous TiO{sub 2}-ZrO{sub 2} into a crystalline ZrTiO{sub 4} compound, while a larger amount of boria ({>=}8 wt%) promotes the crystallization process. FT-IR spectroscopy and {sup 11}B MAS NMR results show that tetrahedral borate species predominate at low boria loading, and trigonal borate species increase with increasing boria loading. Thus it is concluded that highly dispersed tetrahedral BO{sub 4} units delay, while a build-up of trigonal BO{sub 3} promote, the crystallization of amorphous TiO{sub 2}-ZrO{sub 2} to form ZrTiO{sub 4} crystals. - Graphical abstract: The addition of small amount of boria (<8 wt%) hinders the crystallization of amorphous TiO{sub 2}-ZrO{sub 2} into a crystalline ZrTiO{sub 4} compound, while the larger amount of boria ({>=}8 wt%) promotes the crystallization process.

  14. Amorphous metal composites

    DOEpatents

    Byrne, Martin A. (Troy, NY); Lupinski, John H. (Scotia, NY)

    1984-01-01

    An improved amorphous metal composite and process of making the composite. The amorphous metal composite comprises amorphous metal (e.g. iron) and a low molecular weight thermosetting polymer binder. The process comprises placing an amorphous metal in particulate form and a thermosetting polymer binder powder into a container, mixing these materials, and applying heat and pressure to convert the mixture into an amorphous metal composite.

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

    NASA Astrophysics Data System (ADS)

    Cheong, Heajeong; Ogura, Shintaro; Ushijima, Hirobumi; Yoshida, Manabu; Fukuda, Nobuko; Uemura, Sei

    2015-06-01

    We fabricated solution-processed indium-gallium-zinc oxide (IGZO) thin-film transistors (TFTs) by microwave (MW) annealing an IGZO precursor film followed by irradiating with vacuum ultraviolet (VUV) light. MW annealing allows more rapid heating of the precursor film than conventional annealing processes using a hot plate or electric oven and promotes the crystallization of IGZO. VUV irradiation was used to reduce the duration and temperature of the post-annealing step. Consequently, the IGZO TFTs fabricated through MW annealing for 5 min and VUV irradiation for 1 min exhibited an on/off current ratio of 108 and a field-effect mobility of 0.3 cm2 V-1 s-1. These results indicate that MW annealing and photoirradiation is an effective combination for annealing solution processed IGZO precursor films to prepare the semiconductor layers of TFTs.

  16. Creation of high-refractive-index amorphous titanium oxide thin films from low-fractal-dimension polymeric precursors synthesized by a sol-gel technique with a hydrazine monohydrochloride catalyst.

    PubMed

    Shimizu, Wataru; Nakamura, Satoshi; Sato, Takaaki; Murakami, Yasushi

    2012-08-21

    Amorphous titanium dioxide (TiO(2)) thin films exhibiting high refractive indices (n ? 2.1) and high transparency were fabricated by spin-coating titanium oxide liquid precursors having a weakly branched polymeric structure. The precursor solution was prepared from titanium tetra-n-butoxide (TTBO) via the catalytic sol-gel process with hydrazine monohydrochloride used as a salt catalyst, which serves as a conjugate acid-base pair catalyst. Our unique catalytic sol-gel technique accelerated the overall polycondensation reaction of partially hydrolyzed alkoxides, which facilitated the formation of liner polymer-like titanium oxide aggregates having a low fractal dimension of ca. (5)/(3), known as a characteristic of the so-called "expanded polymer chain". Such linear polymeric features are essential to the production of highly dense amorphous TiO(2) thin films; mutual interpenetration of the linear polymeric aggregates avoided the creation of void space that is often generated by the densification of high-fractal-dimension (particle-like) aggregates produced in a conventional sol-gel process. The mesh size of the titanium oxide polymers can be tuned either by water concentration or the reaction time, and the smaller mesh size in the liquid precursor led to a higher n value of the solid thin film, thanks to its higher local electron density. The reaction that required no addition of organic ligand to stabilize titanium alkoxides was advantageous to overcoming issues from organic residues such as coloration. The dense amorphous film structure suppressed light scattering loss owing to its extremely smooth surface and the absence of inhomogeneous grains or particles. Furthermore, the fabrication can be accomplished at a low heating temperature of <80 °C. Indeed, we successfully obtained a transparent film with a high refractive index of n = 2.064 (at ? = 633 nm) on a low-heat-resistance plastic, poly(methyl methacrylate), at 60 °C. The result offers an efficient route to high-refractive-index amorphous TiO(2) films as well as base materials for a wider range of applications. PMID:22817104

  17. Comparison of structural and electrical properties of Lu2O3 and Lu2TiO5 gate dielectrics for ?-InGaZnO thin-film transistors

    NASA Astrophysics Data System (ADS)

    Pan, Tung-Ming; Chen, Ching-Hung; Her, Jim-Long; Koyama, Keiichi

    2014-11-01

    We compared the structural properties and electrical characteristics of high-? Lu2O3 and Lu2TiO5 gate dielectrics for amorphous indium-gallium-zinc oxide (?-InGaZnO) thin-film transistor (TFT) applications. The Lu2O3 film has a strong Lu2O3 (400) peak in the X-ray diffraction pattern, while the Lu2TiO5 sample shows a relatively weak Lu2TiO5 (102) peak. Atomic force microscopy reveals that the Lu2O3 dielectric exhibits a rougher surface (about three times) than Lu2TiO5 one. In X-ray photoelectron spectroscopy analysis, we found that the intensity of the O 1s peak corresponding to Lu(OH)x for Lu2O3 film was higher than that of Lu2TiO5 film. Furthermore, compared with the Lu2O3 dielectric, the ?-InGaZnO TFT using the Lu2TiO5 gate dielectric exhibited a lower threshold voltage (from 0.43 to 0.25 V), a higher Ion/Ioff current ratio (from 3.5 × 106 to 1.3 × 108), a smaller subthreshold swing (from 276 to 130 mV/decade), and a larger field-effect mobility (from 14.5 to 24.4 cm2/V s). These results are probably due to the incorporation of TiOx into the Lu2O3 film to form a Lu2TiO5 structure featuring a smooth surface, a low moisture absorption, a high dielectric constant, and a low interface state density at the oxide/channel interface. Furthermore, the stability of Lu2O3 and Lu2TiO5 ?-InGaZnO TFTs was investigated under positive gate-bias stress (PGBS) and negative gate-bias stress (NGBS). The threshold voltage of the TFT performed under NGBS is more degradation than that under PGBS. This behavior may be attributed to the electron charge trapping at the dielectric-channel interface under PGBS, whereas the oxygen vacancies occurred in the InGaZnO under NGBS.

  18. Amorphous Computing

    NASA Astrophysics Data System (ADS)

    Sussman, Gerald

    2002-03-01

    Digital computers have always been constructed to behave as precise arrangements of reliable parts, and our techniques for organizing computations depend upon this precision and reliability. Two emerging technologies, however, are begnning to undercut these assumptions about constructing and programming computers. These technologies -- microfabrication and bioengineering -- will make it possible to assemble systems composed of myriad information- processing units at almost no cost, provided: 1) that not all the units need to work correctly; and 2) that there is no need to manufacture precise geometrical arrangements or interconnection patterns among them. Microelectronic mechanical components are becoming so inexpensive to manufacture that we can anticipate combining logic circuits, microsensors, actuators, and communications devices integrated on the same chip to produce particles that could be mixed with bulk materials, such as paints, gels, and concrete. Imagine coating bridges or buildings with smart paint that can sense and report on traffic and wind loads and monitor structural integrity of the bridge. A smart paint coating on a wall could sense vibrations, monitor the premises for intruders, or cancel noise. Even more striking, there has been such astounding progress in understanding the biochemical mechanisms in individual cells, that it appears we'll be able to harness these mechanisms to construct digital- logic circuits. Imagine a discipline of cellular engineering that could tailor-make biological cells that function as sensors and actuators, as programmable delivery vehicles for pharmaceuticals, as chemical factories for the assembly of nanoscale structures. Fabricating such systems seem to be within our reach, even if it is not yet within our grasp Fabrication, however, is only part of the story. We can envision producing vast quantities of individual computing elements, whether microfabricated particles, engineered cells, or macromolecular computing agents constructed by engineered cells, but we have few ideas for programming them effectively: How can one engineer prespecified, coherent behavior from the cooperation of immense numbers of unreliable parts that are interconnected in unknown, irregular, and time-varying ways? This is the challenge of Amorphous Computing.

  19. Glutamate Surface Speciation on Amorphous Titanium Dioxide and

    E-print Network

    Sverjensky, Dimitri A.

    Glutamate Surface Speciation on Amorphous Titanium Dioxide and Hydrous Ferric Oxide D I M I T R I (HFO) and titanium dioxide exhibit similar strong attachment of many adsorbates including biomolecules on amorphous titanium dioxide. The results indicate that glutamate adsorbs on HFO as a deprotonated divalent

  20. Amorphous silicon research project government\\/industry program

    Microsoft Academic Search

    Werner Luft; Byron Stafford

    1990-01-01

    This summary report covers that the second DOE\\/SERI three-year amorphous silicon initiative (1987 to 1989). Increased performance of amorphous silicon cells has resulted as a result of progress in the areas of light (photon) management and device structure. An improved utilization of the solar spectrum has resulted from developing textured transparent conducting oxide contacts and multilayer back reflectors, which have

  1. Theory of amorphous ices.

    PubMed

    Limmer, David T; Chandler, David

    2014-07-01

    We derive a phase diagram for amorphous solids and liquid supercooled water and explain why the amorphous solids of water exist in several different forms. Application of large-deviation theory allows us to prepare such phases in computer simulations. Along with nonequilibrium transitions between the ergodic liquid and two distinct amorphous solids, we establish coexistence between these two amorphous solids. The phase diagram we predict includes a nonequilibrium triple point where two amorphous phases and the liquid coexist. Whereas the amorphous solids are long-lived and slowly aging glasses, their melting can lead quickly to the formation of crystalline ice. Further, melting of the higher density amorphous solid at low pressures takes place in steps, transitioning to the lower-density glass before accessing a nonequilibrium liquid from which ice coarsens. PMID:24858957

  2. Performance enhancement of n-channel inversion type In{sub x}Ga{sub 1-x}As metal-oxide-semiconductor field effect transistor using ex situ deposited thin amorphous silicon layer

    SciTech Connect

    Sonnet, A. M.; Hinkle, C. L.; Jivani, M. N.; Chapman, R. A. [Department of Electrical Engineering, University of Texas at Dallas, Richardson, Texas 75080 (United States); Pollack, G. P.; Wallace, R. M. [Department of Materials Science and Engineering, University of Texas at Dallas, Richardson, Texas 75080 (United States); Vogel, E. M. [Department of Electrical Engineering, University of Texas at Dallas, Richardson, Texas 75080 (United States); Department of Materials Science and Engineering, University of Texas at Dallas, Richardson, Texas 75080 (United States)

    2008-09-22

    Significant enhancement in metal-oxide-semiconductor field effect transistor (MOSFET) transport characteristics is achieved with In{sub x}Ga{sub 1-x}As (x=0.53, x=0.20) channel material using ex situ plasma enhanced chemical vapor deposited amorphous Si layer. In{sub x}Ga{sub 1-x}As MOSFETs (L=2 {mu}m, V{sub gs}-V{sub t}=2.0 V) with Si interlayer show a maximum drain current of 290 mA/mm (x=0.53) and 2 {mu}A/mm (x=0.20), which are much higher compared to devices without a Si interlayer. However, charge pumping measurements show a lower average interface state density near the intrinsic Fermi level for devices without the silicon interlayer indicating that a reduction in the midgap interface state density is not responsible for the improved transport characteristics.

  3. Fabrication of amorphous metal matrix composites by severe plastic deformation

    E-print Network

    Mathaudhu, Suveen Nigel

    2006-10-30

    -ideal particle bonding conditions such as surface oxides and crystalline phase morphology and chemistry. It is demonstrated that the addition of a dispersed crystalline phase to an amorphous matrix by ECAE powder consolidation increases the plasticity...

  4. Electrochromic Properties of Li+-Intercalated Amorphous Tungsten (aWO3-x) and Titanium (aTiO2-x) Oxide Thin Films

    NASA Astrophysics Data System (ADS)

    Triana, C. A.; Granqvist, C. G.; Niklasson, G. A.

    2014-11-01

    We report on electrochromic properties of stoichiometric and oxygen-deficient amorphous films, denoted aWO3-x and aTiO2-x, under Li+-ion-electron inter/deintercalation. Optical characterization of the films in their as-deposited, fully intercalated (dark), and bleached states were performed by in-situ optical transmittance measurements. We explore electrochromism and optical absorption phenomena in the context of oxygen deficiency and nanostructure. Studies by cyclic voltammetry suggest good optical modulation and charge capacity upon Li+-ion-electron inter/deintercalation for almost stoichiometric films.

  5. Pulmonary inflammation in rats after intratracheal instillation of quartz, amorphous SiO2, carbon black, and coal dust and the influence of poly-2-vinylpyridine-N-oxide (PVNO).

    PubMed

    Ernst, Heinrich; Rittinghausen, Susanne; Bartsch, Wilfried; Creutzenberg, Otto; Dasenbrock, Clemens; Görlitz, Bernd-Detlef; Hecht, Matthias; Kairies, Ulf; Muhle, Hartwig; Müller, Meike; Heinrich, Uwe; Pott, Friedrich

    2002-08-01

    Effects of poly-2-vinylpyridine-N-oxide (PVNO) were investigated in numerous in vivo and in vitro studies published in the nineteen sixties and seventies. These studies showed that PVNO inhibited development of fibrosis from quartz dust and improved lung clearance of quartz after inhalation exposure. Ameliorating effects of PVNO were observed also for pulmonary damage from colloidal SiO2 and organic substances, and the fibrogenic inflammation caused by carrageenan. Although it is not proven that silicosis is a precondition for quartz-induced lung tumours, we investigated the hypothesis that PVNO could reduce the lung tumour risk from quartz in rats. A carcinogenicity study was therefore started in rats with the main focus on the quantitative relationships among pulmonary inflammation, fibrosis and neoplasia caused by intratracheal instillation of 3 mg quartz DQ 12 with or without additional subcutaneous PVNO treatment. Other study groups were treated with multiple dust instillations, i.e. 30 instillations of 0.5 mg amorphous SiO2 at intervals of 2 weeks, 10 instillations of 0.5 mg of ultrafine carbon black or 1 mg coal at weekly intervals. The analyses of the bronchoalveolar lavage fluid (BALF) 9 months after start of the life-time study showed that the aim of producing similar levels of increased enzyme concentrations in the four groups treated with quartz/PVNO, amorphous SiO2, carbon black and coal was achieved. A 2.5- to 7.7-fold increase for lactate dehydrogenase (LDH), total protein, alkaline phosphatase and gamma-glutamyl transferase (gamma-GT) was found in these groups as compared to the control. In contrast, quartz treatment without PVNO increased the LDH level up to 24-fold and of total protein to 13-fold. However, the cell counts in the BALF were not so much different in all five groups, i.e. quartz without PVNO (leukocytes: 480.000, PMN: 190.000), quartz with PVNO (leukocytes: 300.000, PMN: 100.000), amorphous SiO2 (leukocytes: 570.000, PMN: 315.000), carbon black (leukocytes: 390.000, PMN: 150.000) and coal (leukocytes: 200.000, PMN: 65.000). Histopathological investigations after four weeks and three months revealed that the used PVNO sample was active in the quartz and amorphous SiO2 groups and markedly reduced the incidences or severity of several pulmonary changes such as macrophage accumulation, inflammatory cell infiltration, interstitial fibrosis, bronchiolo-alveolar hyperplasia, alveolar lipoproteinosis and amorphous SiO2 -induced granulomatous alveolitis/interstitial fibrotic granulomas. Also in the lung-associated lymph nodes (LALN), PVNO treatment significantly reduced the incidence and severity of inflammation in both quartz and amorphous SiO2 groups as evidenced by the presence of well-circumscribed aggregates of intact particle-laden macrophages without signs of degeneration and accompanying granulocytic infiltration and fibrosis. Immunological investigations at the 9 months timepoint on the in vitro production of reactive nitrogen (RNI) or oxygen (ROI) intermediates and tumour necrosis factor (TNF-alpha) from BALF-derived cells indicated a diminished responsiveness to LPS in all particle treatment groups. A diminished production of ROI was also found in the quartz, carbon black, and coal dust groups, respectively, as compared to the values seen in the quartz/PVNO- and amorphous SiO2 treated groups. Treatment with quartz plus PVNO restored the capability of the cells to respond to LPS as compared to the treatment with quartz alone. TNF-alpha production was diminished in the groups treated with quartz, carbon black, and coal dust alone whereas in the quartz/PVNO- and amorphous SiO2-treated groups an elevated TNF-alpha production was seen. These results led to the conclusion that only amorphous SiO2 did not affect the "normal" ability of the cells to respond to LPS and that PVNO protected the cells from a toxic effect of the quartz particles. PMID:12211632

  6. Tritium in amorphous silicon

    SciTech Connect

    Sidhu, L.S.; Kosteski, T.; O`Leary, S.K.; Gaspari, F.; Zukotynski, S. [Univ. of Toronto, Ontario (Canada). Dept. of Electrical and Computer Engineering; Kherani, N.P.; Shmadya, W. [Ontario Hydro Technologies, Toronto, Ontario (Canada)

    1996-12-31

    Preliminary results on infrared and luminescence measurements of tritium incorporated amorphous silicon are reported. Tritium is an unstable isotope that readily substitutes hydrogen in the amorphous silicon network. Due to its greater mass, bonded tritium is found to introduce new stretching modes in the infrared spectrum. Inelastic collisions between the beta particles, produced as a result of tritium decay, and the amorphous silicon network, results in the generation of excess electron-hole pairs. Radiative recombination of these carriers is observed.

  7. Nanocrystal dispersed amorphous alloys

    NASA Technical Reports Server (NTRS)

    Perepezko, John H. (Inventor); Allen, Donald R. (Inventor); Foley, James C. (Inventor)

    2001-01-01

    Compositions and methods for obtaining nanocrystal dispersed amorphous alloys are described. A composition includes an amorphous matrix forming element (e.g., Al or Fe); at least one transition metal element; and at least one crystallizing agent that is insoluble in the resulting amorphous matrix. During devitrification, the crystallizing agent causes the formation of a high density nanocrystal dispersion. The compositions and methods provide advantages in that materials with superior properties are provided.

  8. Amorphous-Carbon Films

    NASA Technical Reports Server (NTRS)

    Pouch, John J.; Alterovitz, Samuel A.

    1993-01-01

    Report describes structure, preparation, characterization, and applications of films of amorphous-carbon. Amorphous-carbon films potentially useful as masks in x-ray lithography, layers for passivation of high-speed microelectronic circuits, hard films to protect magnetic recording media and optical components from degradation by chemical etching or wear, and radiation detectors.

  9. Amorphous silicon radiation detectors

    Microsoft Academic Search

    V. Perez-Mendez; S. N. Kaplan

    1992-01-01

    Hydrogenated amorphous silicon radiation detector devices having enhanced signal are disclosed. Specifically provided are transversely oriented electrode layers and layered detector configurations of amorphous silicon, the structure of which allow high electric fields upon application of a bias thereby beneficially resulting in a reduction in noise from contact injection and an increase in signal including avalanche multiplication and gain of

  10. PHONONS IN AMORPHOUS MATERIALS

    Microsoft Academic Search

    S. Hunklinger

    1982-01-01

    The study of the propagation of phonons is an important tool to investigate the sometimes unexpected and puzzling dynamic properties of amorphous solids. At first, as a typical- example, we shall discuss the acoustic Properties of vitreous silica. In the second part of the review emphasis will be given to the anomalous low temperature properties of amorphous materials. A. Introduction.

  11. Effect of an Al2O3/TiO2 Passivation Layer on the Performance of Amorphous Zinc-Tin Oxide Thin-Film Transistors

    NASA Astrophysics Data System (ADS)

    Han, Dong-Suk; Park, Jae-Hyung; Kang, Min-Soo; Shin, So-Ra; Jung, Yeon-Jae; Choi, Duck-Kyun; Park, Jong-Wan

    2015-02-01

    The effect of an Al2O3/TiO2 stacked passivation layer on the performance of amorphous ZnSnO ( a-ZTO) thin-film transistors (TFTs) was investigated by comparing field-effect mobility ( ? FE) and subthreshold swing after passivation layer deposition. The values observed were 4.7 cm2/Vs and 0.64 V/decade, respectively, for uncoated TFTs and 4.6 cm2/Vs and 0.62 V/decade for passivated TFTs. In addition, excellent water vapor transmission was observed for electron beam-irradiated Al2O3/TiO2-passivated poly(ether sulfone) substrates in a humidity test, because the Al2O3/TiO2 passivation layer can enhance the interface properties between Al2O3 and TiO2. To investigate the origin of this enhancement, we performed x-ray photoelectron spectroscopy of both unpassivated and Al2O3/TiO2-passivated TFTs with a-ZTO back-channel layers after Ar annealing.

  12. MIT Amorphous Computing

    NSDL National Science Digital Library

    This site covers the interesting new frontier of molecular computing, which links molecular biology with computer science. It is Massachusetts Institute of Technology's (MIT's) Amorphous Computing homepage. Amorphous computing is defined by the MIT amorphous computer engineers as "methods for instructing myriads of programmable entities to cooperate to achieve particular goals," and sometimes involves the use of organic molecules. In the News, Research, and Demos are among the pages available at the site. The demonstration of "gunk" software is particularly informative and unusual (HSLIM software required).

  13. Evidence for tribochemical wear on amorphous carbon thin films

    Microsoft Academic Search

    Bruno Marchon; Neil Heiman; Mahbub R. Khan

    1990-01-01

    The friction and wear properties between a smooth oxide-based ceramic sliding and an amorphous carbon surface are greatly influenced by the surface chemistry of the carbon layer. Like most carbon compounds, surface oxides can form if the surface is exposed to oxygen. These surface species can desorb as carbon monoxide and\\/or carbon dioxide under the rubbing action of the slider.

  14. Amorphous pharmaceutical solids.

    PubMed

    Vrani?, Edina

    2004-07-01

    Amorphous forms are, by definition, non-crystalline materials which possess no long-range order. Their structure can be thought of as being similar to that of a frozen liquid with the thermal fluctuations present in a liquid frozen out, leaving only "static" structural disorder. The amorphous solids have always been an essential part of pharmaceutical research, but the current interest has been raised by two developments: a growing attention to pharmaceutical solids in general, especially polymorphs and solvates and a revived interest in the science of glasses and the glass transition. Amorphous substances may be formed both intentionally and unintentionally during normal pharmaceutical manufacturing operations. The properties of amorphous materials can be exploited to improve the performance of pharmaceutical dosage forms, but these properties can also give rise to unwanted effects that need to be understood and managed in order for the systems to perform as required. PMID:15629010

  15. Amorphous silicon solar cells

    Microsoft Academic Search

    W. Juergens; W. Kruehler; M. Moeller; H. Pfleiderer; R. Plaettner; B. Rauscher; W. Stetter

    1983-01-01

    A technique for manufacturing amorphous silicon solar cells is described. Hydrogenated amorphous silicon (a-Si:H) with excellent photoconductivity (ratio of photo and dark conductivity = 10,000 for 0,25 mW\\/sqcm light intensity) photoluminescence, and low density of states was manufactured. Doping behavior in a-Si:H-films and dependence of geometrical cell structure on electrical properties were investigated. A-Si:H-Schottky barrier cells with Pt, Pd, Au

  16. Amorphous metal alloy

    DOEpatents

    Wang, R.; Merz, M.D.

    1980-04-09

    Amorphous metal alloys of the iron-chromium and nickel-chromium type have excellent corrosion resistance and high temperature stability and are suitable for use as a protective coating on less corrosion resistant substrates. The alloys are stabilized in the amorphous state by one or more elements of titanium, zirconium, hafnium, niobium, tantalum, molybdenum, and tungsten. The alloy is preferably prepared by sputter deposition.

  17. Entropy of amorphous ice

    Microsoft Academic Search

    Edward Whalley; D. D. Klug; Y. P. Handa

    1989-01-01

    THE configurational entropies of amorphous solids reflect certain aspects of their structures, in particular the numbers of accessible molecular configurations. The configurational entropy of vitreous silica has been estimated theoretically1 as no more than 5.8 J K-1 mol-1, which agrees reasonably with experiment. That of low-density amorphous ice has been estimated theoretically2 as ~6.3 J K-1 mol-1 more than that

  18. High efficiency multi-junction solar cells using amorphous silicon and amorphous silicon-germanium alloys

    Microsoft Academic Search

    J. Yang; R. Ross; T. Glatfelter; R. Mohr; G. Hammond; C. Bernotaitis; E. Chen; J. Burdick; M. Hopson; S. Guha

    1988-01-01

    Using a novel cell design the authors have achieved a 13.7% conversion efficiency with amorphous silicon and amorphous silicon-germanium alloys in a three-cell stacked-junction configuration. 13.0% conversion efficiency was achieved in the tandem configuration. The efficiency value was measured using a triple-source solar simulator adjusted for global AM1.5 test conditions. This device has a structure of stainless steel\\/textured silver\\/zinc oxide\\/ni1p\\/ni2p\\/ni3p\\/ITO\\/grid.

  19. Non-Arrhenius conduction due to the interface-trap-induced disorder in X-doped amorphous In-X-Zn oxides thin-film transistors

    NASA Astrophysics Data System (ADS)

    Benwadih, Mohammed; Chroboczek, J. A.; Ghibaudo, Gérard; Coppard, Romain; Vuillaume, Dominique

    2015-02-01

    Thin film transistors, with channels composed of In-X-Zn oxides, IXZO, with X dopants: Ga, Sb, Be, Mg, Ag, Ca, Al, Ni, and Cu, were fabricated and their I-V characteristics were taken at selected temperatures in the 77 K < T < 300 K range. The low field mobility, ?, and the interface defect density, NST, were extracted from the characteristics for each of the studied IXZOs. At higher T, the mobility follows the Arrhenius law with an upward distortion, increasing as T is lowered, gradually transforming into the exp [-(T0/T)1/4] variation. We showed that ?(T, NST) follows ?0 exp[-Eaeff(T,NST)/kT], with T-dependent effective activation energy Eaeff(T, NST) accounts for the data, revealing a linear correlation between Eaeff and NST at higher T. Temperature variation of Eaeff(T, NST) was evaluated using a model assuming a random distribution of conduction mobility edge Ec values in the oxides, stemming from spatial fluctuations induced by disorder in the interface traps distribution. For a Gaussian distribution of Ec, the activation energy Eaeff(T, NST) varies linearly with 1/T, which accounts satisfactorily for the data obtained on all the studied IXZOs. The model also shows that Eaeff(T, NST) is a linear function of NST at a fixed T, which explains the exponential decrease of ? with NST.

  20. Formation of amorphous materials

    DOEpatents

    Johnson, William L. (Pasadena, CA); Schwarz, Ricardo B. (Westmont, IL)

    1986-01-01

    Metastable amorphous or fine crystalline materials are formed by solid state reactions by diffusion of a metallic component into a solid compound or by diffusion of a gas into an intermetallic compound. The invention can be practiced on layers of metals deposited on an amorphous substrate or by intermixing powders with nucleating seed granules. All that is required is that the diffusion of the first component into the second component be much faster than the self-diffusion of the first component. The method is practiced at a temperature below the temperature at which the amorphous phase transforms into one or more crystalline phases and near or below the temperature at which the ratio of the rate of diffusion of the first component to the rate of self-diffusion is at least 10.sup.4. This anomalous diffusion criteria is found in many binary, tertiary and higher ordered systems of alloys and appears to be found in all alloy systems that form amorphous materials by rapid quenching. The method of the invention can totally convert much larger dimensional materials to amorphous materials in practical periods of several hours or less.

  1. Bias-stress-induced threshold voltage shift dependence of negative charge trapping in the amorphous indium tin zinc oxide thin-film transistors

    NASA Astrophysics Data System (ADS)

    Phu Thi Nguyen, Cam; Thuy Trinh, Thanh; Dao, Vinh Ai; Raja, Jayapal; Jang, Kyungsoo; Le, Tuan Anh Huy; Iftiquar, S. M.; Yi, Junsin

    2013-10-01

    Indium tin zinc oxide (ITZO)-based thin-film transistors (TFTs) were fabricated by dc magnetron sputtering in Ar + O2 reactive gas, at room temperature. We present the effect of post-deposition annealing of ITZO thin films on the oxygen vacancies and on the characteristics of TFT devices. When the annealing temperature was increased from room temperature to 350 °C, the resistivity of ITZO film increased from 2.05 × 101 to 2.60 × 103 ? cm and the interface trap density (Nt) of the TFTs reduced from 3.18 × 1013 to 4.83 × 1011 cm-2. The TFT with the ITZO film which was annealed at 350 °C showed a very small shift in turn-on voltage, even after applying positive bias stress of +12 V for 104 s. The current-voltage characteristics of 350 °C annealing temperature sample indicated that these TFTs were in an enhanced mode of transistor operation with a high on-to-off current ratio of ˜1.26 × 106, high field-effect mobility of 14.17 cm2 V-1 s-1, and low subthreshold slope of 1.23 V/dec. The trapping time reduced from 3720 to 1546 s as the annealing temperature increased from room temperature to 350 °C. These results suggest that thermal annealing played an important role in reducing defects as well as improvement in stability of the TFTs.

  2. Reaction rates of natural orpiment oxidation at 25 to 40°C and pH 6.8 to 8.2 and comparison with amorphous As 2S 3 oxidation

    NASA Astrophysics Data System (ADS)

    Lengke, Maggy F.; Tempel, Regina N.

    2002-09-01

    The oxidation rate of natural orpiment from Carlin-type deposits was measured at 25 to 40°C in a mixed flow reactor as a function of pH (6.8 to 8.2) and dissolved oxygen concentration (6.4 to 17.4 ppm) with a starting ionic strength of 0.01 M NaCl. All experiments ran for approximately 30 h, where steady-state conditions were reached after 20 h at a flow rate of 10 mL/min. The stoichiometric ratio of As/S was observed once steady state was reached. The rate law of orpiment oxidation is as follows: R=10 -11.77(±0.36)[ DO] 0.36(±0.09)[H +] -0.47(±0.05), where R signifies the rate of orpiment destruction (mol m -2 s -1), [DO] is the concentration of dissolved oxygen (M), and [H +] is the concentration of proton (M). The activation energy for the orpiment oxidation by dissolved oxygen at a temperature range of 25 to 40°C is 59.1 kJ/mol. Oxidation reactions of orpiment show incomplete oxidation of arsenic and sulfide in solution. At a pH range of 6.8 to 8.2, As(III) exists as H 3AsO 3 and As(V) is present as HAsO 42- and H 2AsO 4-. Sulfite, sulfate, and thiosulfate are present as small fractions of total sulfur. The possible major sulfur species are intermediate oxidation state species. The oxidation rate of natural orpiment oxidation is slightly lower by a factor of 0.002 to 0.560 than that of As 2S 3(am) at the considered pH 7 to 10 and DO concentrations of 1 to 10 ppm. The dependence factors on pH for natural orpiment oxidation are lower by a factor of 0.37 compared with As 2S 3(am). However, the calculated activation energy is much larger for natural orpiment than As 2S 3(am) by a factor of 3.5. As(III) and As(V) are the major products for both As 2S 3(am) and natural orpiment oxidation along with intermediate sulfur species. The rate of orpiment oxidation increases with pH and results in an increase in the release of As. In mining-impacted environments with alkaline waters, as may be found in carbonate-hosted ore deposits, the natural attenuation of As oxyanions by sorption to oxide/hydroxide mineral surfaces is minimized because of a negative surface charge at a higher pH range. Thus, As concentrations may increase in mining-impacted waters at higher pH values (>8).

  3. Torque magnetometry of an amorphous-alumina/strontium-titanate interface

    E-print Network

    Lee, S. W.

    We report torque magnetometry measurements of an oxide heterostructure consisting of an amorphous Al[subscript 2]O[subscript 3] thin film grown on a crystalline SrTiO[subscript 3] substrate (a-AO/STO) by atomic layer ...

  4. Amorphous Hydrocarbon Optical Properties

    NASA Astrophysics Data System (ADS)

    Jones, Anthony

    2015-03-01

    Hydrogenated amorphous carbon materials, a-C(:H), whose optical properties evolve in response to UV irradiation processing are promising candidate materials for cosmic carbonaceous dust. The optical properties of a:C(:H) particles have been derived as a function of size, band gap and hydrogen content over a wide wavelength range (EUV-cm) and can be used to investigate the size-dependent evolution of a-C(:H) material properties in the ISM.

  5. Amorphous Carbon Fibrilliform Nanomaterials Prepared by Chemical Vapor Deposition

    NASA Astrophysics Data System (ADS)

    Takikawa, Hirofumi; Yatsuki, Miki; Miyano, Ryuichi; Nagayama, Makoto; Sakakibara, Tateki; Itoh, Shigeo; Ando, Yoshinori

    2000-09-01

    Carbon nanomaterials were prepared by chemical vapor deposition (CVD) and hot-filament CVD (HF-CVD) methods. The substrates were silicon < 100 > and copper plates on which catalytic metal or metal-oxide thin films were coated by means of the cathodic arc deposition technique. Ethylene gas was used as a precursor. HF-CVD with a filament temperature of 1,000°C yielded a larger amount of carbon deposit at a lower furnace temperature of 600°C@. High-resolution microscopic observation revealed a variety of amorphous carbon nanomaterials, such as frost columns, coral beads, microcoils, nanocoils, and amorphous nanotubes.

  6. Crystallization of amorphous bismuth titanate

    Microsoft Academic Search

    Seiji Kojima; Anwar Hushur; Fuming Jiang; Sinichi Hamazaki; Masaaki Takashige; Min-Su Jang; Shiro Shimada

    2001-01-01

    We studied the transformation of amorphous bismuth titanate by heat treatments. After an as-quenched amorphous sample was annealed at 500 °C, the lowest Raman peak became intense like a boson peak for glass. This fact indicates the formation of intermediate range order. The medium range correlation length of 7 nm calculated from the boson peak frequency is in agreement with

  7. Molecular dynamics in amorphous ergocalciferol

    NASA Astrophysics Data System (ADS)

    Mohamed, Sahra; Thayyil, M. Shahin; Capaccioli, S.

    2014-04-01

    While developing new pharmaceutical products based on drug substances in their amorphous form, the molecular mobility of amorphous active ingredients have to be characterized in detail. The molecular mobility in the supercooled liquid and glassy states of ergocalciferol is studied using broadband dielectric spectroscopy over wide frequency and temperature ranges. Dielectric studies revealed a number of relaxation process of different molecular origin.

  8. Adsorption of selenium by amorphous iron oxyhydroxide and manganese dioxide

    USGS Publications Warehouse

    Balistrieri, L.S.; Chao, T.T.

    1990-01-01

    This work compares and models the adsorption of selenium and other anions on a neutral to alkaline surface (amorphous iron oxyhydroxide) and an acidic surface (manganese dioxide). Selenium adsorption on these oxides is examined as a function of pH, particle concentration, oxidation state, and competing anion concentration in order to assess how these factors might influence the mobility of selenium in the environment. The data indicate that 1. 1) amorphous iron oxyhydroxide has a greater affinity for selenium than manganese dioxide, 2. 2) selenite [Se(IV)] adsorption increases with decreasing pH and increasing particle concentration and is stronger than selenate [Se(VI)] adsorption on both oxides, and 3. 3) selenate does not adsorb on manganese dioxide. The relative affinity of selenate and selenite for the oxides and the lack of adsorption of selenate on a strongly acidic surface suggests that selenate forms outer-sphere complexes while selenite forms inner-sphere complexes with the surfaces. The data also indicate that the competition sequence of other anions with respect to selenite adsorption at pH 7.0 is phosphate > silicate > molybdate > fluoride > sulfate on amorphous iron oxyhydroxide and molybdate ??? phosphate > silicate > fluoride > sulfate on manganese dioxide. The adsorption of phosphate, molybdate, and silicate on these oxides as a function of pH indicates that the competition sequences reflect the relative affinities of these anions for the surfaces. The Triple Layer surface complexation model is used to provide a quantitative description of these observations and to assess the importance of surface site heterogeneity on anion adsorption. The modeling results suggest that selenite forms binuclear, innersphere complexes with amorphous iron oxyhydroxide and monodentate, inner-sphere complexes with manganese dioxide and that selenate forms outer-sphere, monodentate complexes with amorphous iron oxyhydroxide. The heterogeneity of the oxide surface sites is reflected in decreasing equilibrium constants for selenite with increasing adsorption density and both experimental observations and modeling results suggest that manganese dioxide has fewer sites of higher energy for selenite adsorption than amorphous iron oxyhydroxide. Modeling and interpreting the adsorption of phosphate, molybdate, and silicate on the oxides are made difficult by the lack of constraint in choosing surface species and the fact that equally good fits can be obtained with different surface species. Finally, predictions of anion competition using the model results from single adsorbate systems are not very successful because the model does not account for surface site heterogeneity. Selenite adsorption data from a multi-adsorbate system could be fit if the equilibrium constant for selenite is decreased with increasing anion adsorption density. ?? 1990.

  9. Transport In Amorphous Semiconductors

    Microsoft Academic Search

    P. Thomas; H. Overhof

    \\u000a Electronic quasi-equilibrium transport (at low applied field and in the absence of illumination) in hydrogenated and unhydrogenated\\u000a amorphous thin film semiconductors exhibits three different regimes:\\u000a \\u000a \\u000a \\u000a (a) \\u000a \\u000a At higher temperatures (above 420 K in a-Si:H) the atomic bond configuration and therewith the density of states distribution\\u000a (DOS) changes with temperature.\\u000a \\u000a \\u000a \\u000a \\u000a (b) \\u000a \\u000a At very low temperatures a cross-over to variable-range hopping in

  10. Plasticity of amorphous carbon

    NASA Astrophysics Data System (ADS)

    von Lautz, Julian; Moseler, Michael; Pastewka, Lars

    2014-03-01

    We use molecular dynamics simulations to probe the plastic response of representative bulk volumes of amorphous carbon at densities from 2.0 g cm-3 to 3.3 g cm-3 in simple and triaxial shear. After an initial elastic response the samples yield with only little strain hardening or softening. Individual plastic events in this network forming glass are strikingly similar to those observed for bulk metallic glasses: We find that plasticity is carried by fundamental rearrangements of regions of around 100 atoms, the shear transformation zone. In the simple shear geometry, those events coalesce to form a shear-band on longer time scales. During plastic deformation, the material changes its hybridization by transforming sp3 carbon atoms to sp2. We provide evidence that this transformation of the structural state occurs before the material yields, hence weakening the material. This work was supported by the European Commission (Marie-Curie IOF 272619).

  11. Perspective on photovoltaic amorphous silicon

    SciTech Connect

    Luft, W.; Stafford, B.; von Roedern, B.

    1992-05-01

    Amorphous silicon is a thin film option that has the potential for a cost-effective product for large-scale utility photovoltaics application. The initial efficiencies for single-junction and multijunction amorphous silicon cells and modules have increased significantly over the past 10 years. The emphasis of research and development has changed to stabilized efficiency, especially that of multijunction modules. NREL has measured 6.3%--7.2% stabilized amorphous silicon module efficiencies for US products, and 8.1% stable efficiencies have been reported by Fuji Electric. This represents a significant increase over the stabilized efficiencies of modules manufactured only a few years ago. An increasing portion of the amorphous silicon US government funding is now for manufacturing technology development to reduce cost. The funding for amorphous silicon for photovoltaics by Japan over the last 5 years has been about 50% greater than that in the United State, and by Germany in the last 2--3 years more than twice that of the US Amorphous silicon is the only thin-film technology that is selling large-area commercial modules. The cost for amorphous silicon modules is now in the $4.50 range; it is a strong function of plant production capacity and is expected to be reduced to $1.00--1.50/W{sub p} for plants with 10 MW/year capacities. 10 refs.

  12. Processing of amorphous PEEK and amorphous PEEK based composites

    SciTech Connect

    Kenny, J.; D'amore, A.; Nicolais, L.; Iannone, M.; Scatteia, B. (Napoli Universita, Naples (Italy); Aeritalia, S.p.A., Naples (Italy))

    1989-08-01

    An analysis of the crystallization behavior of amorphous PEEK, its carbon fiber composite, and its relationships with dynamic-mechanical properties of the system measured during and after processing is presented. The effect of the processing conditions, time and temperature, on the quality and on the amount of the crystallinity developed during cold crystallization has been investigated in order to evaluate the processability window of amorphous PEEK and amorphous PEEK based composite above the glass transition temperature and below the melting point. Also, the anomalous behavior of the amorphous matrix, crystallized at low temperatures, has been studied. Multiple melting peaks and changes of the glass transition during crystallization are explained in terms of crystalline morphology and molecular mobility. 20 refs.

  13. Containerless processing of amorphous ceramics

    NASA Technical Reports Server (NTRS)

    Weber, J. K. Richard; Krishnan, Shankar; Schiffman, Robert A.; Nordine, Paul C.

    1990-01-01

    The absence of gravity allows containerless processing of materials which could not otherwise be processed. High melting point, hard materials such as borides, nitrides, and refractory metals are usually brittle in their crystalline form. The absence of dislocations in amorphous materials frequently endows them with flexibility and toughness. Systematic studies of the properties of many amorphous materials have not been carried out. The requirements for their production is that they can be processed in a controlled way without container interaction. Containerless processing in microgravity could permit the control necessary to produce amorphous forms of hard materials.

  14. Processing Bi-Pb-Sr-Ca-Cu-O superconductors from amorphous state

    NASA Technical Reports Server (NTRS)

    Chiang, C. K.; Wong-Ng, W.; Cook, L. P.; Freiman, S. W.; Hwang, N. M.; Vaudin, M.; Hill, M. D.; Shull, R. D.; Shapiro, A. J.; Swartzendruber, L. J.

    1991-01-01

    The bismuth based high T sub c superconductors can be processed via an amorphous Bi-Pb-Sr-Ca-Cu oxide. The amorphous oxides were prepared by melting the constituent powders in an alumina crucible at 1200 C in air followed by pouring the liquid onto an aluminum plate, and rapidly pressing with a second plate. In the amorphous state, no crystalline phase was identified in the powder x ray diffraction pattern of the quenched materials. After heat treatment at high temperature the amorphous materials crystallized into a glass ceramic containing a large fraction of the Bi2Sr2Ca2Cu3O(x) phase T sub c = 110 K. The processing method, crystallization, and results of dc electrical resistivity and ac magnetic susceptibility measurements are discussed.

  15. Fabrication of amorphous diamond films

    DOEpatents

    Falabella, S.

    1995-12-12

    Amorphous diamond films having a significant reduction in intrinsic stress are prepared by biasing a substrate to be coated and depositing carbon ions thereon under controlled temperature conditions. 1 fig.

  16. Luminescence effect in amorphous PLT

    Microsoft Academic Search

    G. F. G. Freitas; R. S. Nasar; M. Cerqueira; D. M. A. Melo; E. Longo; P. S. Pizani; J. A. Varela

    2005-01-01

    Amorphous and crystalline powder of PLT phase was synthesized by using the Pechini method. Infrared (FTIR) analysis of the polymeric resin shows intense bands of organic materials from 250 to 1620cm?1. X-ray diffraction (XRD) and Raman spectra of calcined powder at different temperatures show amorphous phase at 450°C\\/3h, semi-crystalline phase at 550°C\\/3h and a crystalline phase at 800°C\\/3h. Luminescence effect

  17. Amorphous metal alloy and composite

    DOEpatents

    Wang, Rong (Richland, WA); Merz, Martin D. (Richland, WA)

    1985-01-01

    Amorphous metal alloys of the iron-chromium and nickel-chromium type have excellent corrosion resistance and high temperature stability and are suitable for use as a protective coating on less corrosion resistant substrates. The alloys are stabilized in the amorphous state by one or more elements of titanium, zirconium, hafnium, niobium, tantalum, molybdenum, and tungsten. The alloy is preferably prepared by sputter deposition.

  18. Multijunction amorphous silicon solar cells

    Microsoft Academic Search

    D. E. Carlson

    1991-01-01

    Thin-film multijunction solar cells have the potential to meet the performance and cost reauirements for grid-connected power generation. At present, multijunction amorphous silicon solar cells have exhibited stabilized conversion efficiencies of about 10% in the laboratory, and large-area modules of comparable performance should be available commercially by the mid-1990s. Further improvements in the properties of amorphous silicon alloys should lead

  19. Dopant effect on in situ doped metal-induced lateral crystallization of amorphous silicon films

    Microsoft Academic Search

    Jun-Dar Hwang; Jyh-Yeu Chang; Ching-Yuan Wu

    2005-01-01

    Dopant (boron or phosphorus) effect on metal-induced lateral crystallization (MILC) of amorphous silicon (a-Si) films has been systematically studied by using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The MILC was realized by depositing a-Si film onto an oxidized Si wafer and then annealing in a N2 atmosphere. The doped amorphous films have been developed by plasma-enhanced chemical vapor

  20. Microstructure and Electrochemical Behavior of Fe-Based Amorphous Metallic Coatings Fabricated by Atmospheric Plasma Spraying

    Microsoft Academic Search

    Z. Zhou; L. Wang; D. Y. He; F. C. Wang; Y. B. Liu

    2011-01-01

    A Fe48Cr15Mo14C15B6Y2 alloy with high glass forming ability (GFA) was selected to prepare amorphous metallic coatings by atmospheric plasma spraying (APS). The as-deposited coatings present a dense layered structure and low porosity. Microstructural studies show that some nanocrystals and a fraction of yttrium oxides formed during spraying, which induced the amorphous fraction of the coatings decreasing to 69% compared with

  1. Deep ultraviolet laser direct write for patterning sol-gel InGaZnO semiconducting micro/nanowires and improving field-effect mobility

    PubMed Central

    Lin, Hung-Cheng; Stehlin, Fabrice; Soppera, Olivier; Zan, Hsiao-Wen; Li, Chang-Hung; Wieder, Fernand; Ponche, Arnaud; Berling, Dominique; Yeh, Bo-Hung; Wang, Kuan-Hsun

    2015-01-01

    Deep-UV (DUV) laser was used to directly write indium-gallium-zinc-oxide (IGZO) precursor solution and form micro and nanoscale patterns. The directional DUV laser beam avoids the substrate heating and suppresses the diffraction effect. A IGZO precursor solution was also developed to fulfill the requirements for direct photopatterning and for achieving semi-conducting properties with thermal annealing at moderate temperature. The DUV-induced crosslinking of the starting material allows direct write of semi-conducting channels in thin-film transistors but also it improves the field-effect mobility and surface roughness. Material analysis has been carried out by XPS, FTIR, spectroscopic ellipsometry and AFM and the effect of DUV on the final material structure is discussed. The DUV irradiation step results in photolysis and a partial condensation of the inorganic network that freezes the sol-gel layer in a homogeneous distribution, lowering possibilities of thermally induced reorganization at the atomic scale. Laser irradiation allows high-resolution photopatterning and high-enough field-effect mobility, which enables the easy fabrication of oxide nanowires for applications in solar cell, display, flexible electronics, and biomedical sensors. PMID:26014902

  2. Effects of controlling the interface trap densities in InGaZnO thin-film transistors on their threshold voltage shifts

    NASA Astrophysics Data System (ADS)

    Jeong, S.-W.; Lee, J.-T.; Roh, Y.

    2014-12-01

    In this paper, the threshold voltage stability characteristics of indium-gallium-zinc-oxide (IGZO) thin-film transistors (TFT) are discussed. The IGZO TFTs were found to induce a parallel threshold voltage ( V th ) shift with changing field effect mobility ( ? FE ) or a sub-threshold gate voltage swing ( SS) due to various thermal annealing conditions. The IGZO TFT that was post-annealed in an O2 ambient was found to be more stable for use in oxide-based TFT devices and to have better performance characteristics, such as the on/off current ratio ( I on/off ), SS, and V th , than other TFTs did. The mechanism for improving the V th stability in the post-annealed IGZO TFT is a decrease in the number of trap sites for the electrons and the weak oxygen bonding in the IGZO thin films. The device's performance could be significantly affected by adjusting the annealing conditions. This mechanism is closely related to that of modulation annealing, where the number of localized trapped carriers and defect centers at the interface or in the channel layer are reduced.

  3. Influence of irradiation spectrum and implanted ions on the amorphization of ceramics

    SciTech Connect

    Zinkle, S.J.; Snead, L.L.

    1995-12-31

    Polycrystalline Al2O3, magnesium aluminate spinel (MgAl2O4), MgO, Si3N4, and SiC were irradiated with various ions at 200-450 K, and microstructures were examined following irradiation using cross-section TEM. Amorphization was not observed in any of the irradiated oxide ceramics, despsite damage energy densities up to {similar_to}7 keV/atom (70 displacements per atom). On the other hand, SiC readily amorphized after damage levels of {similar_to}0.4 dpa at room temperature (RT). Si3N4 exhibited intermediate behavior; irradiation with Fe{sup 2+} ions at RT produced amorphization in the implanted ion region after damage levels of {similar_to}1 dpa. However, irradiated regions outside the implanted ion region did not amorphize even after damage levels > 5 dpa. The amorphous layer in the Fe-implanted region of Si3N4 did not appear if the specimen was simultaneoulsy irradiated with 1-MeV He{sup +} ions at RT. By comparison with published results, it is concluded that the implantation of certain chemical species has a pronounced effect on the amorphization threshold dose of all five materials. Intense ionizing radiation inhibits amorphization in Si3N4, but does not appear to significantly influence the amorphization of SiC.

  4. Nanocrystalline Cr 2O 3 and amorphous CrO 3 produced by solution combustion synthesis

    Microsoft Academic Search

    M. D. Lima; R. Bonadimann; M. J. de Andrade; J. C. Toniolo; C. P. Bergmann

    2006-01-01

    The synthesis of chromium oxides by solution combustion synthesis was investigated. Ammonium dichromate, glycine, urea and ammonium nitrate dissolved in aqueous solution were used as the precursors of the oxides. The effect of different reaction parameters, such as fuel richness, stoichiometry and fuel leanness was evaluated; such parameters were modified by changing the reagents and the fuel\\/oxidant ratio. Amorphous CrO3

  5. Improved performances in low-voltage-driven InGaZnO thin film transistors using a SiO2 buffer layer insertion

    NASA Astrophysics Data System (ADS)

    Zheng, Z. W.; Chen, Y. C.

    2014-06-01

    In this paper, we report the device characteristics of indium gallium zinc oxide (IGZO) thin film transistors (TFTs) with high- ? lanthanum aluminate (LaAlO3) based gate insulators. The IGZO TFT with single LaAlO3 gate insulator has an operation voltage as low as 1.5 V but suffers a low on-off-state drive current ratio ( I on/ I off) of 1×103, a large subthreshold swing ( SS) of 0.405 V/dec and a small field effect mobility ( ? FE) of 0.84 cm2/V sec. Inserting a SiO2 buffer layer between IGZO active channel layer and LaAlO3 gate insulator results in a reduced effective dielectric constant but with significant improved characteristics including a high I on/ I off of 6.2×104, a small SS of 0.113 V/dec and a large ? FE of 5.2 cm2/V sec. Such good performances can be attributed to the lowered gate leakage and reduced interface trap issue owing to the smooth SiO2 buffer layer insertion.

  6. Mechanics of amorphous polymers and polymer gels

    E-print Network

    Chester, Shawn Alexander

    2011-01-01

    Many applications of amorphous polymers require a thermo-mechanically coupled large-deformation elasto-viscoplasticity theory which models the strain rate and temperature dependent response of amorphous polymeric materials ...

  7. AMORPHOUS AND SPIN GLASSES. Random magnetic anisotropy in amorphous alloys containing rare earth

    E-print Network

    Paris-Sud XI, Université de

    AMORPHOUS AND SPIN GLASSES. Random magnetic anisotropy in amorphous alloys containing rare earth anisotropy in amorphous alloys containing non 5-state rare earth ions is analysed in detail. Magnetisation of amorphous rare-earth-transition metal/noble metal alloys is reasonably described by dense random packing

  8. Tritiated amorphous silicon for micropower applications

    Microsoft Academic Search

    N. P. Kherani; T. Kosteski; S. Zukotynski; W. T. Shmayda

    1995-01-01

    The application of tritiated amorphous silicon as an intrinsic energy conversion semiconductor for radioluminescent structures and betavoltaic devices is presented. Theoretical analysis of the betavoltaic application shows an overall efficiency of 18% for tritiated amorphous silicon. This is equivalent to a 330 Ci intrinsic betavoltaic device producing 1 mW of power for 12 years. Photoluminescence studies of hydrogenated amorphous silicon,

  9. Physicochemical determinants in the cellular responses to nanostructured amorphous silicas.

    PubMed

    Gazzano, Elena; Ghiazza, Mara; Polimeni, Manuela; Bolis, Vera; Fenoglio, Ivana; Attanasio, Angelo; Mazzucco, Gianna; Fubini, Bice; Ghigo, Dario

    2012-07-01

    Amorphous silicas, opposite to crystalline polymorphs, have been regarded so far as nonpathogenic, but few studies have addressed the toxicity of the wide array of amorphous silica forms. With the advent of nanotoxicology, there has been a rising concern about the safety of silica nanoparticles to be used in nanomedicine. Here, we report a study on the toxicity of amorphous nanostructured silicas obtained with two different preparation procedures (pyrolysis vs. precipitation), the pyrogenic in two very different particle sizes, in order to assess the role of size and origin on surface properties and on the cell damage, oxidative stress, and inflammatory response elicited in murine alveolar macrophages. A quartz dust was employed as positive control and monodispersed silica spheres as negative control. Pyrogenic silicas were remarkably more active than the precipitated one as to cytotoxicity, reactive oxygen species production, lipid peroxidation, nitric oxide synthesis, and production of tumor necrosis factor-?, when compared both per mass and per unit surface. Between the two pyrogenic silicas, the larger one was the more active. Silanols density is the major difference in surface composition among the three silicas, being much larger than the precipitated one as indicated by joint calorimetric and infrared spectroscopy analysis. We assume here that full hydroxylation of a silica surface, with consequent stable coverage by water molecules, reduces/inhibits toxic behavior. The preparation route appears thus determinant in yielding potentially toxic materials, although the smallest size does not always correspond to an increased toxicity. PMID:22491428

  10. Energy release properties of amorphous boron and boron-based propellant primary combustion products

    NASA Astrophysics Data System (ADS)

    Liang, Daolun; Liu, Jianzhong; Xiao, Jinwu; Xi, Jianfei; Wang, Yang; Zhang, Yanwei; Zhou, Junhu

    2015-07-01

    The microstructure of amorphous boron and the primary combustion products of boron-based fuel-rich propellant (hereafter referred to as primary combustion products) was analyzed by scanning electron microscope. Composition analysis of the primary combustion products was carried out by X-ray diffraction and X-ray photoelectron spectroscopy. The energy release properties of amorphous boron and the primary combustion products were comparatively studied by laser ignition experimental system and thermogravimetry-differential scanning calorimetry. The primary combustion products contain B, C, Mg, Al, B4C, B13C2, BN, B2O3, NH4Cl, H2O, and so on. The energy release properties of primary combustion products are different from amorphous boron, significantly. The full-time spectral intensity of primary combustion products at a wavelength of 580 nm is ~2% lower than that of amorphous boron. The maximum spectral intensity of the former at full wave is ~5% higher than that of the latter. The ignition delay time of primary combustion products is ~150 ms shorter than that of amorphous boron, and the self-sustaining combustion time of the former is ~200 ms longer than that of the latter. The thermal oxidation process of amorphous boron involves water evaporation (weight loss) and boron oxidation (weight gain). The thermal oxidation process of primary combustion products involves two additional steps: NH4Cl decomposition (weight loss) and carbon oxidation (weight loss). CL-20 shows better combustion-supporting effect than KClO4 in both the laser ignition experiments and the thermal oxidation experiments.

  11. Diamond-like amorphous carbon

    Microsoft Academic Search

    J. Robertson

    2002-01-01

    Diamond-like carbon (DLC) is a metastable form of amorphous carbon with significant sp3 bonding. DLC is a semiconductor with a high mechanical hardness, chemical inertness, and optical transparency. This review will describe the deposition methods, deposition mechanisms, characterisation methods, electronic structure, gap states, defects, doping, luminescence, field emission, mechanical properties and some applications of DLCs. The films have widespread applications

  12. Optical absorption in amorphous silicon

    SciTech Connect

    O`Leary, S.K.; Zukotynski, S.; Perz, J.M.; Sidhu, L.S. [Univ. of Toronto, Ontario (Canada). Dept. of Electrical and Computer Engineering

    1996-12-31

    The role that disorder plays in shaping the form of the optical absorption spectrum of hydrogenated amorphous silicon is investigated. Disorder leads to a redistribution of states, which both reduces the Tauc gap and broadens the absorption tail. The observed relationship between the Tauc gap and the breadth of the absorption tail is thus explained.

  13. Tunneling states in amorphous solids

    Microsoft Academic Search

    W. A. Phillips

    1972-01-01

    A linear temperature dependence of the specific heat in amorphous solids at very low temperatures is shown to follow from an ionic tunneling model. Moreover, this model predicts both the observed temperature dependence and the magnitude of the thermal conductivity and also explains the anomalous results obtained for the phonon free path by means of stimulated Brillouin scattering.

  14. Innovative diodes based on amorphous-porous silicon heterojunction

    SciTech Connect

    De Rosa, R.; La Ferrara, V.; Di Francia, G.; Quercia, L.; Roca, F.; Tucci, M.

    1999-07-01

    In this paper the authors present an innovative diode based on the heterojunction between amorphous silicon and porous silicon grown on crystalline silicon. The device architecture gives several advantages. Deposition of amorphous silicon on porous material realizes high performance junction at temperature less than 250 C and it passives the porous layer against the natural oxidation due to aging in the environment. Porous technology allows to obtain a controlled textured silicon surface independently from crystalline silicon orientation just to give the opportunity to reduce surface reflectivity and the blue shift of the absorption spectra in solar cell application. Solar cells were characterized by I-V dark/light and quantum yield measurements. Under standard AM 1.5 light they obtained photovoltaic conversion efficiency greater than 10%. Change in photoluminescence in different gas environments showed for gas sensor applications give rise to encouraging results. In dark condition they found the typical diode behavior.

  15. Tetrahedral bonding in amorphous carbon

    NASA Astrophysics Data System (ADS)

    McKenzie, D. R.

    1996-12-01

    Electron configurations close to the tetrahedral 0034-4885/59/12/002/img1 hybridization are found in pure amorphous carbon at a concentration which depends on preparation conditions. Tetrahedral bonding at levels of approximately 80% is found in amorphous carbons formed from beams of carbon ions with energies in a `window' between 20 eV and approximately 500 eV. Suitable techniques for its formation include cathodic arc deposition, ion beam deposition and laser ablation. Similar material appears to be formed by pressure treatment of fullerene precursors and by displacement damage in diamond. Highly tetrahedral forms of amorphous carbon (ta-C) show electronic, optical and mechanical properties which approach those of diamond and are quite different from amorphous carbons with low 0034-4885/59/12/002/img1 content. Useful techniques for determining the 0034-4885/59/12/002/img1 content include electron energy loss spectroscopy, electron and neutron diffraction and Raman spectroscopy. Considerable progress has been made in the understanding of this material by simulating its structure in the computer with a range of techniques from empirical potentials to ab initio quantum mechanics. The structure shows departures from an idealized glassy state of diamond which would have a random tetrahedral network structure as used to describe amorphous silicon and germanium. A surprising feature of the structure simulated using ab initio methods is the presence of small rings containing three or four 0034-4885/59/12/002/img1 carbon atoms. The electronic and optical properties are strongly influenced by the residual of 0034-4885/59/12/002/img5 carbon. Applications to electronic devices are at an early stage with the demonstration of photoconductivity and some simple junction devices. Applications as a wear resistant coating are promising, since the theoretically predicted high values of elastic constants, comparable to but less than those of diamond, are achieved experimentally, together with low friction coefficients.

  16. Amorphous mineral phases in magnetotactic multicellular aggregates.

    PubMed

    Lins, U; Farina, M

    2001-11-01

    Magnetotactic multicellular aggregates consist of several bacteria that produce iron sulfide magnetosomes through a complex and poorly understood process. We observed new amorphous mineral particles within the cytoplasm of magnetotactic multicellular aggregates. Elemental mapping and electron energy loss spectroscopy detected iron and oxygen, but not sulfur, in these particles. These amorphous particles were about the same size as mature magnetosomes, around 50-70 nm in diameter. No membranes were observed surrounding the amorphous minerals. Partially crystalline inclusions composed of a crystalline core and an amorphous region around them similar in texture to the amorphous particles were also present. The shape of these amorphous regions followed the shape of the crystalline cores they enveloped. These regions also contained oxygen and iron. The crystalline phase, as previously reported, contained sulfur and iron. The presence of independent amorphous particles has not been reported before in magnetotactic multicellular aggregates. PMID:11702073

  17. Thermal Oxidation of Aluminum Nitride Powder

    SciTech Connect

    Gu, Zheng; Edgar, James H.; Wang, Chong M.; Coffey, Dorothy

    2006-07-31

    The kinetics of the thermal oxidation of AlN powder in flowing oxygen over temperatures from 800 to 1150 C and the morphology and crystallinity of the resultant oxide were determined. The oxidation of two types of AlN powder was investigated and compared. Complex difference in the oxidation behavior was observed, probably due to their different morphology, particle size, particle size distribution, and residual impurities. Amorphous alumina formed at relatively low oxidation temperatures (800-1000 C), with a linear oxidation rate governed by interfacial reaction. Crystalline alumina formed at higher temperatures (>1000 C), and the oxidation rate was parabolic which suggested an oxidant diffusion controlled process.

  18. A predictive model (ETLM) for As(III) adsorption and surface speciation on oxides consistent with spectroscopic data

    E-print Network

    Sverjensky, Dimitri A.

    been built into a recent extension of the triple-layer model (ETLM) for the formation of inner for magnetite, goethite, gibbsite, amorphous hydrous alumina, hydrous ferric oxide (HFO), ferrihydrite constants on all oxides, including both amorphous and poorly crys- talline oxides, enables prediction

  19. Amorphous metal-organic frameworks.

    PubMed

    Bennett, Thomas D; Cheetham, Anthony K

    2014-05-20

    Crystalline metal-organic frameworks (MOFs) are porous frameworks comprising an infinite array of metal nodes connected by organic linkers. The number of novel MOF structures reported per year is now in excess of 6000, despite significant increases in the complexity of both component units and molecular networks. Their regularly repeating structures give rise to chemically variable porous architectures, which have been studied extensively due to their sorption and separation potential. More recently, catalytic applications have been proposed that make use of their chemical tunability, while reports of negative linear compressibility and negative thermal expansion have further expanded interest in the field. Amorphous metal-organic frameworks (aMOFs) retain the basic building blocks and connectivity of their crystalline counterparts, though they lack any long-range periodic order. Aperiodic arrangements of atoms result in their X-ray diffraction patterns being dominated by broad "humps" caused by diffuse scattering and thus they are largely indistinguishable from one another. Amorphous MOFs offer many exciting opportunities for practical application, either as novel functional materials themselves or facilitating other processes, though the domain is largely unexplored (total aMOF reported structures amounting to under 30). Specifically, the use of crystalline MOFs to detect harmful guest species before subsequent stress-induced collapse and guest immobilization is of considerable interest, while functional luminescent and optically active glass-like materials may also be prepared in this manner. The ion transporting capacity of crystalline MOFs might be improved during partial structural collapse, while there are possibilities of preparing superstrong glasses and hybrid liquids during thermal amorphization. The tuning of release times of MOF drug delivery vehicles by partial structural collapse may be possible, and aMOFs are often more mechanically robust than crystalline materials, which is of importance for industrial applications. In this Account, we describe the preparation of aMOFs by introduction of disorder into their parent crystalline frameworks through heating, pressure (both hydrostatic and nonhydrostatic), and ball-milling. The main method of characterizing these amorphous materials (analysis of the pair distribution function) is summarized, alongside complementary techniques such as Raman spectroscopy. Detailed investigations into their properties (both chemical and mechanical) are compiled and compared with those of crystalline MOFs, while the impact of the field on the processing techniques used for crystalline MOF powders is also assessed. Crucially, the benefits amorphization may bring to existing proposed MOF applications are detailed, alongside the possibilities and research directions afforded by the combination of the unique properties of the amorphous domain with the versatility of MOF chemistry. PMID:24707980

  20. Determination of iron sites and the amount of amorphization in radiation-damaged titanite (CaSiTiO5).

    PubMed

    Salje, E K H; Safarik, D J; Taylor, R D; Pasternak, M P; Modic, K A; Groat, L A; Lashley, J C

    2011-03-16

    Iron is a ubiquitous impurity in metamict (radiation-damaged and partially amorphized) materials such as titanite (CaSiTiO(5)). Using (57)Fe Mössbauer spectroscopy we find that iron in metamict titanite is partitioned between amorphous and crystalline regions based on valence. Trivalent iron exists in the crystalline titanite matrix whereas divalent iron exists almost exclusively in radiation-amorphized regions. We find that the relative abundances of the oxidation states correlate with the volume fraction of amorphous and crystalline regions. Our data also show that oxidation of iron proceeds along with the recrystallization of the amorphized regions. Recrystallization is confirmed to occur over the range 700 °C < T < 925 °C, and no further structural changes are observed at higher temperatures. It is surprising that our Mössbauer measurements show divalent iron to be surrounded by titanite with a high degree of short-range structural order in the amorphized regions. This observation is fundamentally different from other metamict materials such as zircon (ZrSiO(4)), where amorphized regions show no short-range order. PMID:21339587

  1. Synthesis and Characterization of Zinc-Doped Amorphous Carbon Films by Plasma-Assisted Organometallic Chemical Vapor Deposition

    Microsoft Academic Search

    Hiroki Akasaka; Koji Inazu; Naoto Ohtake

    2008-01-01

    Zinc (Zn)-doped hydrogenated amorphous carbon (a-C:H) films have been fabricated from zinc acetylacetonate by organometallic chemical vapor deposition (CVD). Zn concentration was controlled by a heated flow controller. Deposited films were Zn-doped hydrogenated oxygenated amorphous carbon films because they consisted of carbon, hydrogen, zinc, and oxide. The maximum concentration ratio of zinc to carbon (Zn\\/C) was as large as 0.069.

  2. R&D issues in scale-up and manufacturing of amorphous silicon tandem modules

    NASA Astrophysics Data System (ADS)

    Arya, R. R.; Carlson, D. E.; Chen, L. F.; Ganguly, G.; He, M.; Lin, G.; Middya, R.; Wood, G.; Newton, J.; Bennett, M.; Jackson, F.; Willing, F.

    1999-03-01

    R & D on amorphous silicon based tandem junction devices has improved the throughtput, the material utilization, and the performance of devices on commercial tin oxide coated glass. The tandem junction technology has been scaled-up to produce 8.6 Ft2 monolithically integrated modules in manufacturing at the TF1 plant. Optimization of performance and stability of these modules is ongoing.

  3. Ni-base amorphous alloys as electrocatalysts for alkaline water electrolysis

    Microsoft Academic Search

    D. W. Kirk; S. J. Thorpe; H. Suzuki

    1997-01-01

    The development of efficient and cost effective electrodes for hydrogen generation from water electrolysis and for hydrogen oxidation in power generation from fuel cells is very important in developing the hydrogen economy. This paper focuses on the role of the structure and chemistry of amorphous metal alloys (AMA) on the electrocatalytic activity for the hydrogen evolution reaction (HER) in alkaline

  4. Modeling of Amorphous Calcium Carbonate

    NASA Astrophysics Data System (ADS)

    Sinha, Sourabh; Rez, Peter

    2011-10-01

    Many species (e.g. sea urchin) form amorphous calcium carbonate (ACC) precursor phases that subsequently transform into crystalline CaCO3. It is certainly possible that ACC might have up to 10 wt% Mg and ˜3 wt% of water. The structure of ACC and mechanisms by which it transforms to crystalline phase are still unknown. Our goal here is to determine an atomic structure model that is consistent with diffraction and IR measurements of ACC. For this purpose a calcite supercell with 24 formula units (120 atoms) was constructed. Various configurations with 6 Mg atoms substituting for Ca (6 wt%) and 3-5 H2O molecules (2.25- 3.75 wt%) inserted in the spaces between Ca atoms, were relaxed using VASP. Most noticeable effects were the tilts of CO3 groups and distortion of Ca sub-lattice, especially in the case of water. The distributions of nearest Ca-Ca distance and CO3 tilts were extracted from those configurations. We also performed the same analysis starting with aragonite. Sampling from above distributions we built models for amorphous calcite/aragonite of size ˜1700 nm^3. We found that the induced distortions were not enough to generate a diffraction pattern typical of an amorphous material. Next we studied diffraction pattern of several nano-crystallites as recent studies suggest that amorphous calcite might be composed of nano- crystallites. We could then generate a diffraction pattern that appeared similar to that from ACC, for a nano-crystallite of size ˜2 nm^3.

  5. Tritiated amorphous silicon betavoltaic devices

    Microsoft Academic Search

    T. Kosteski; N. P. Kherani; P. Stradins; F. Gaspari; W. T. Shmayda; L. S. Sidhu; S. Zukotynski

    2003-01-01

    The introduction of tritium into hydrogenated amorphous silicon has given rise to a novel material with interesting physical properties and potential applications. Tritium undergoes radioactive decay, transforming into 3 He + and emitting an electron with average energy 5.7 keV, at a rate equivalent to a half-life of 12.3 years. The decay of tritium results in the creation of electron-

  6. Comparison of electrochromic amorphous and crystalline electron beam deposited WO 3 thin films

    Microsoft Academic Search

    A. A. Joraid

    2009-01-01

    Tungsten oxide (WO3) thin films were prepared by an electron beam deposition technique. Films were deposited onto fluorine-doped tin oxide (FTO)-coated glass substrates maintained at 523K. The as-deposited films were found to be amorphous and crystallized after annealing at 673K. The electrochromic and optical properties, structure, and morphology are strongly dependent on the annealing conditions. Cyclic voltammetry (C-V) was carried

  7. Coating of calcia-doped ceria with amorphous silica shell by seeded polymerization technique

    SciTech Connect

    El-Toni, Ahmed Mohamed [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577 (Japan)]. E-mail: el-toni@mail.tagen.tohoku.ac.jp; Yin, Shu [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577 (Japan); Yabe, Shinryo [Research and Development division, KOSE Co., 48-18 Sakae-cho, Kita-ku, Tokyo 114-0005 (Japan); Sato, Tsugio [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577 (Japan)

    2005-07-12

    Calcia-doped ceria is of potential interest as an ultraviolet (UV) radiation blocking material in personal care products. However, its high catalytic ability for oxidation of organic materials makes it difficult to use as a sunscreen material. Therefore, calcia-doped ceria was coated with amorphous silica by means of seeded polymerization technique in order to depress its oxidation catalytic ability. The catalytic ability as well as UV-shielding ability was investigated for coated particles.

  8. Definition and Properties of Ideal Amorphous Solids

    NASA Astrophysics Data System (ADS)

    Stachurski, Zbigniew H.

    2003-04-01

    It is proposed that two ideal amorphous structures, typeI and typeII, based on maximally random jammed packing of spheres of equal size, form a distinct class of ideal amorphous solids. The ideal amorphous structures contain wide variations in local density, limited by the condition of solidity. Four distinct characteristics, based on statistical geometry and topology, are shown to define this class. Voronoi tessellations carried out on simulated cells of random packed spheres and amorphous polymers give a broad distribution of individual volumes, skewed, with a tail at the high volume end.

  9. Definition and properties of ideal amorphous solids.

    PubMed

    Stachurski, Zbigniew H

    2003-04-18

    It is proposed that two ideal amorphous structures, type I and type II, based on maximally random jammed packing of spheres of equal size, form a distinct class of ideal amorphous solids. The ideal amorphous structures contain wide variations in local density, limited by the condition of solidity. Four distinct characteristics, based on statistical geometry and topology, are shown to define this class. Voronoi tessellations carried out on simulated cells of random packed spheres and amorphous polymers give a broad distribution of individual volumes, skewed, with a tail at the high volume end. PMID:12732045

  10. Electronic properties of calcium borate glasses containing iron oxide

    Microsoft Academic Search

    M. Gawish; M. N. Saleh

    1976-01-01

    The electronic properties of calcium borate glasses containing iron oxide have been investigated. It was found that glasses with an Fe2O3 content less than 20 mole% were amorphous, while those above 20 mole% were devitrified. It was observed that increasing the iron molar content in the amorphous samples caused an increase in their dc conductivity, ac conductivity, dielectric constant, and

  11. Radiation Response of Rhombohedral Oxides

    SciTech Connect

    Devanathan, R.; Weber, W.J. [Pacific Northwest National Lab., Richland, WA (United States); Mitchell, J.N.; Sickafus, K.E.; Nastasi, M. [Los Alamos National Lab., NM (United States)

    1997-12-31

    The radiation response of three rhombohedral oxides, namely, sapphire ({alpha}-Al{sub 2}O{sub 3}), ilmenite (FeTiO{sub 3}), and geikielite (MgTiO{sub 3}), has been examined by irradiating electron transparent samples with 1 MeV Kr(+) and 1.5 MeV Xe(+)ions. The microstructural changes during irradiation were observed in situ in a high-voltage electron microscope using electron diffraction and microscopy. The irradiation conditions were designed to minimize beam heating and chemical effects due to the implanted ion. Of the three oxides studied, ilmenite is the most susceptible to radiation-induced amorphization while sapphire is the least susceptible. In all three materials, the critical temperature for amorphization was below 300 K indicating good room temperature resistance to amorphization by energetic beams.

  12. Models for Amorphous Calcium Carbonate

    NASA Astrophysics Data System (ADS)

    Sinha, Sourabh

    Many species e.g. sea urchin form amorphous calcium carbonate (ACC) precursor phases that subsequently transform into crystalline CaCO3. It is certainly possible that the biogenic ACC might have more than 10 wt% Mg and ˜3 wt% of water. The structure of ACC and the mechanisms by which it transforms to crystalline phase are still poorly understood. In this dissertation our goal is to determine an atomic structure model that is consistent with diffraction and IR measurements of ACC. For this purpose a calcite supercell with 24 formula units, containing 120 atoms, was constructed. Various configurations with substitution of Ca by 6 Mg ions (6 wt.%) and insertion of 3-5 H 2O molecules (2.25-3.75 wt.%) in the interstitial positions of the supercell, were relaxed using a robust density function code VASP. The most noticeable effects were the tilts of CO3 groups and the distortion of Ca sub-lattice, especially in the hydrated case. The distributions of Ca-Ca nearest neighbor distance and CO3 tilts were extracted from various configurations. The same methods were also applied to aragonite. Sampling from the calculated distortion distributions, we built models for amorphous calcite/aragonite of size ˜ 1700 nm3 based on a multi-scale modeling scheme. We used these models to generate diffraction patterns and profiles with our diffraction code. We found that the induced distortions were not enough to generate a diffraction profile typical of an amorphous material. We then studied the diffraction profiles from several nano-crystallites as recent studies suggest that ACC might be a random array of nano-cryatallites. It was found that the generated diffraction profile from a nano-crystallite of size ˜ 2 nm3 is similar to that from the ACC.

  13. Microstructure and Electrochemical Behavior of Fe-Based Amorphous Metallic Coatings Fabricated by Atmospheric Plasma Spraying

    Microsoft Academic Search

    Z. Zhou; L. Wang; D. Y. He; F. C. Wang; Y. B. Liu

    2011-01-01

    A Fe48Cr15Mo14C15B6Y2 alloy with high glass forming ability (GFA) was selected to prepare amorphous metallic coatings by atmospheric plasma spraying\\u000a (APS). The as-deposited coatings present a dense layered structure and low porosity. Microstructural studies show that some\\u000a nanocrystals and a fraction of yttrium oxides formed during spraying, which induced the amorphous fraction of the coatings\\u000a decreasing to 69% compared with

  14. Room temperature oxidation of ion bombarded silicon

    NASA Astrophysics Data System (ADS)

    Ponpon, J. P.

    1985-10-01

    The room temperature oxidation of silicon surfaces under air ambient after ion bombardment either during dry etching or during ion implantation has been investigated. Depending on the amount of crystalline damage produced by the ion beams the oxidation kinetics was found to change from the crystalline-like to the amorphous-like behavior.

  15. Laser surface treatment of amorphous metals

    NASA Astrophysics Data System (ADS)

    Katakam, Shravana K.

    Amorphous materials are used as soft magnetic materials and also as surface coatings to improve the surface properties. Furthermore, the nanocrystalline materials derived from their amorphous precursors show superior soft magnetic properties than amorphous counter parts for transformer core applications. In the present work, laser based processing of amorphous materials will be presented. Conventionally, the nanocrystalline materials are synthesized by furnace heat treatment of amorphous precursors. Fe-based amorphous/nanocrystalline materials due to their low cost and superior magnetic properties are the most widely used soft magnetic materials. However, achieving nanocrystalline microstructure in Fe-Si-B ternary system becomes very difficult owing its rapid growth rate at higher temperatures and sluggish diffusion at low temperature annealing. Hence, nanocrystallization in this system is achieved by using alloying additions (Cu and Nb) in the ternary Fe-Si-B system. Thus, increasing the cost and also resulting in reduction of saturation magnetization. laser processing technique is used to achieve extremely fine nanocrystalline microstructure in Fe-Si-B amorphous precursor. Microstructure-magnetic Property-laser processing co-relationship has been established for Fe-Si-B ternary system using analytical techniques. Laser processing improved the magnetic properties with significant increase in saturation magnetization and near zero coercivity values. Amorphous materials exhibit excellent corrosion resistance by virtue of their atomic structure. Fe-based amorphous materials are economical and due to their ease of processing are of potential interest to synthesize as coatings materials for wear and corrosion resistance applications. Fe-Cr-Mo-Y-C-B amorphous system was used to develop thick coatings on 4130 Steel substrate and the corrosion resistance of the amorphous coatings was improved. It is also shown that the mode of corrosion depends on the laser processing conditions. The microstructure evolution and the corrosion mechanisms operating are evaluated using post processing and post corrosion analysis.

  16. Optimization of transparent and reflecting electrodes for amorphous-silicon solar cells. Final subcontract report, 1 May 1991--30 April 1994

    SciTech Connect

    Gordon, R.G.; Hu, J.; Lacks, D.; Musher, J.; Thornton, J.; Liang, H. [Harvard Univ., Cambridge, MA (United States)

    1994-07-01

    Fluorine-doped zinc oxide was shown to have the lowest absorption loss of any of the known transparent conductors. An apparatus was constructed to deposit textured, transparent, conductive, fluorine-doped zinc oxide layers with uniform thickness over a 10 cm by 10 cm area, using inexpensive, high-productivity atmospheric pressure chemical vapor deposition. Amorphous silicon solar cells grown on these textured films show very high peak quantum efficiencies (over 90%). However, a significant contact resistance develops at the interface between the amorphous silicon and the zinc oxide. Transparent, conductive gallium-doped zinc oxide films were grown by APCVD at a low enough temperature (260{degree}C) to be deposited on amorphous silicon as a final conductive back contact to solar cells. A quantum-mechanical theory of bonding was developed and applied to some metal oxides; it forms a basis for understanding TCO structures and the stability of their interfaces with silicon.

  17. Molecular dynamics study of the mechanical loss in amorphous pure and doped silica.

    PubMed

    Hamdan, Rashid; Trinastic, Jonathan P; Cheng, H P

    2014-08-01

    Gravitational wave detectors and other precision measurement devices are limited by the thermal noise in the oxide coatings on the mirrors of such devices. We have investigated the mechanical loss in amorphous oxides by calculating the internal friction using classical, atomistic molecular dynamics simulations. We have implemented the trajectory bisection method and the non-local ridge method in the DL-POLY molecular dynamics simulation software to carry out those calculations. These methods have been used to locate the local potential energy minima that a system visits during a molecular dynamics trajectory and the transition state between any two consecutive minima. Using the numerically calculated barrier height distributions, barrier asymmetry distributions, relaxation times, and deformation potentials, we have calculated the internal friction of pure amorphous silica and silica mixed with other oxides. The results for silica compare well with experiment. Finally, we use the numerical calculations to comment on the validity of previously used theoretical assumptions. PMID:25106591

  18. Amorphous silicon research project government/industry program

    SciTech Connect

    Luft, W.; Stafford, B.

    1990-09-01

    This summary report covers that the second DOE/SERI three-year amorphous silicon initiative (1987--1989). Increased performance of amorphous silicon cells has resulted as a result of progress in the areas of light (photon) management and device structure. An improved utilization of the solar spectrum has resulted from developing textured transparent conducting oxide contacts and multilayer back reflectors, which have enhanced the light trapping in cells. For example, researchers developed a high-conductivity, textured SnO{sub 2}:F front contact deposited by atmospheric-pressure chemical vapor deposition on glass; the sheet resistance is low (8--10 {Omega}/square) and the optical transmittance is high (over 80% over the wavelength range 450--700 nm). Subsequently, researchers developed a textured ZnO front contact with an optical transmittance over a wider range than that of SnO{sub 2}:F. Reactors also developed highly reflective indium tin oxide (ITO)/aluminum and ZnO/Al or ZnO/Ag multilayer back reflectors that result in enhanced quantum efficiencies for a-SiGe:H(F) of up to 67% at 700 nm. Notable efficiencies were achieved for all-amorphous-silicon alloy, two-terminal, different-band-gap multijunction devices. Efficiencies for two-terminal, same-band-gap, multijunction 0.25-cm{sup 2} cells and 900-cm{sup 2} submodules were also improved, as were the efficiencies for four-terminal, 4-cm{sup 2} cells and 900-cm{sup 2} submodules.

  19. Amorphous soft magnetic materials and their application

    Microsoft Academic Search

    B. V. Molotilov; V. V. Sadchikov

    1992-01-01

    This paper reports on the amorphous soft magnetic alloys produced in Russia. There are about 20 sorts of alloys - Fe and Co-based, their magnetic properties are described, data on the application of amorphous alloys in various equipment are cited.

  20. Method of making amorphous metal composites

    DOEpatents

    Byrne, Martin A. (Troy, NY); Lupinski, John H. (Scotia, NY)

    1982-01-01

    The process comprises placing an amorphous metal in particulate form and a low molecular weight (e.g., 1000-5000) thermosetting polymer binder powder into a container, mixing these materials, and applying heat and pressure to convert the mixture into an amorphous metal composite.

  1. Radial distribution function of amorphous carbon

    Microsoft Academic Search

    Fang Li; Jeffrey S. Lannin

    1990-01-01

    The radial distribution function obtained by neutron diffraction on amorphous carbon films is compared to recent theoretical models. The first-neighbor peak is found to be quite broad for an amorphous semiconductor, in qualitative agreement with the predictions of molecular dynamics. However, the detailed shape of the first two peaks, including contributions in the minimum region, differs from all current models.

  2. Structures and phase transitions of amorphous ices

    Microsoft Academic Search

    Ichiro Okabe; Hideki Tanaka; Koichiro Nakanishi

    1996-01-01

    Molecular dynamics simulations have been carried out in order to clarify the structural and hydrogen bond network differences among high density amorphous ice (HDA), low density amorphous ice (LDA), and hexagonal ice (ice Ih). Ice Ih is transformed to HDA at 1.27 GPa and 77 K. A very long time (order of a nanosecond) to complete the transition is required.

  3. Ductile crystalline–amorphous nanolaminates

    PubMed Central

    Wang, Yinmin; Li, Ju; Hamza, Alex V.; Barbee, Troy W.

    2007-01-01

    It is known that the room-temperature plastic deformation of bulk metallic glasses is compromised by strain softening and shear localization, resulting in near-zero tensile ductility. The incorporation of metallic glasses into engineering materials, therefore, is often accompanied by complete brittleness or an apparent loss of useful tensile ductility. Here we report the observation of an exceptional tensile ductility in crystalline copper/copper–zirconium glass nanolaminates. These nanocrystalline–amorphous nanolaminates exhibit a high flow stress of 1.09 ± 0.02 GPa, a nearly elastic-perfectly plastic behavior without necking, and a tensile elongation to failure of 13.8 ± 1.7%, which is six to eight times higher than that typically observed in conventional crystalline–crystalline nanolaminates (<2%) and most other nanocrystalline materials. Transmission electron microscopy and atomistic simulations demonstrate that shear banding instability no longer afflicts the 5- to 10-nm-thick nanolaminate glassy layers during tensile deformation, which also act as high-capacity sinks for dislocations, enabling absorption of free volume and free energy transported by the dislocations; the amorphous–crystal interfaces exhibit unique inelastic shear (slip) transfer characteristics, fundamentally different from those of grain boundaries. Nanoscale metallic glass layers therefore may offer great benefits in engineering the plasticity of crystalline materials and opening new avenues for improving their strength and ductility. PMID:17592136

  4. Development of laminated nickel\\/manganese oxide and nickel\\/niobium oxide electrochromic devices

    Microsoft Academic Search

    Yan-Ping Ma; Phillip C. Yu; Carl M. Lampert

    1991-01-01

    This paper reports on the preparation, electrical, and optical analysis of electrodes and prototype electrochromic devices using a solid polymer ion conductor. For these devices electrodes were developed consisting of cobalt-doped nickel oxide, manganese-nickel oxide, and niobium oxide. Optical and voltammetric data was obtained for each electrode. Solid polymer electrolytes were synthesized from modified amorphous poly(ethylene oxide) [a-PEO] complexed with

  5. Research on stable, high-efficiency amorphous silicon multijunction modules

    SciTech Connect

    Ghosh, M.; DelCueto, J.: Kampas, F.; Xi, J. (Advanced Photovoltaic Systems, Princeton, NJ (United States))

    1993-02-01

    This report describes results from the first phase of a three-phase contract for the development of stable, high-efficiency, same-band-gap, amorphous silicon (a-Si) multijunction photovoltaic (PV) modules. The program involved improving the properties of individual layers of semiconductor and non-semiconductor materials and small-area single-junction and multijunction devices, as well as the multijunction modules. The semiconductor materials research was performed on a-Si p, i, and n layers, and on microcrystalline silicon n layers. These were deposited using plasma-enhanced chemical vapor deposition. The non-semiconductor materials studied were tin oxide, for use as a transparent-conducting-oxide (TCO), and zinc oxide, for use as a back reflector and as a buffer layer between the TCO and the semiconductor layers. Tin oxide was deposited using atmospheric-pressure chemical vapor deposition. Zinc oxide was deposited using magnetron sputtering. The research indicated that the major challenge in the fabrication of a-Si multijunction PV modules is the contact between the two p-i-n cells. A structure that has low optical absorption but that also facilitates the recombination of electrons from the first p-i-n structure with holes from the second p-i-n structure is required. Non-semiconductor layers and a-Si semiconductor layers were tested without achieving the desired result.

  6. Tritiated amorphous silicon for micropower applications

    SciTech Connect

    Kherani, N.P. [Ontario Hydro Technologies, Toronto, Ontario (Canada)]|[Univ. of Toronto, Ontario (Canada); Kosteski, T.; Zukotynski, S. [Univ. of Toronto, Ontario (Canada); Shmayda, W.T. [Ontario Hydro Technologies, Toronto, Ontario (Canada)

    1995-10-01

    The application of tritiated amorphous silicon as an intrinsic energy conversion semiconductor for radioluminescent structures and betavoltaic devices is presented. Theoretical analysis of the betavoltaic application shows an overall efficiency of 18% for tritiated amorphous silicon. This is equivalent to a 330 Ci intrinsic betavoltaic device producing 1 mW of power for 12 years. Photoluminescence studies of hydrogenated amorphous silicon, a-Si:H, show emission in the infra-red with a maximum quantum efficiency of 7.2% at 50 K; this value drops by 3 orders of magnitude at a temperature of 300 K. Similar studies of hydrogenated amorphous carbon show emission in the visible with an estimated quantum efficiency of 1% at 300 K. These results suggest that tritiated amorphous carbon may be the more promising candidate for room temperature radioluminescence in the visible. 18 refs., 5 figs.

  7. Structural analysis of a completely amorphous {sup 238}Pu-doped zircon by neutron diffraction.

    SciTech Connect

    Fortner, J. A.; Badyal, Y.; Price, D. C.; Hanchar, J. M.; Weber, W. J.; Materials Science Division; PNNL

    1999-01-01

    The structure of a completely amorphous zircon was determined by time-of-flight neutron diffraction at Argonne's Intense Pulsed Neutron Source (IPNS). The sample of metamict zircon (ZrSiO{sub 4}), initially doped to 8.85 weight percent {sup 238}Pu, had been completely amorphized by alpha-recoil damage since its synthesis in 1981 at the Pacific Northwest National Laboratory (PNNL). The measured diffraction structure factor, S(Q), indicated a completely amorphous sample, with no signs of residual zircon microcrystallinity. The pair distribution function obtained indicated that the structure was that of an oxide glass, retaining the Si-0, Zr-0, and O-O bond lengths of crystalline zircon.

  8. Structural analysis of a completely amorphous {sup 238}Pu-doped zircon by neutron diffraction.

    SciTech Connect

    Fortner, J. A.

    1998-12-16

    The structure of a completely amorphous zircon was determined by time-of-flight neutron diffraction at Argonne's Intense Pulsed Neutron Source (IPNS). The sample of metamict zircon (ZrSiO{sub 4}),initially doped to 8.85 weight percent {sup 238}Pi, had been completely amorphized by alpha-recoil damage since its synthesis in 1981 at the Pacific Northwest National Laboratory (PNNL). The measured diffraction structure factor, S(Q), indicated a completely amorphous sample, with no signs of residual zircon microcrystallinity. The pair distribution function obtained indicated that the structure was that of an oxide glass, retaining the Si-0, Zr-0, and O-O bond lengths of crystalline zircon.

  9. Infrared absorption in amorphous selenium

    NASA Astrophysics Data System (ADS)

    Nakamura, Kazuma; Ikawa, Atushi

    2001-12-01

    The infrared (IR) absorption spectrum of amorphous selenium (a-Se) are calculated for the atomic structure constructed by a molecular dynamics with recently proposed chain model using an semiempirical electronic structure calculation. Its microscopic mechanism is investigated with an IR formula for chains in terms of bond and induced current correlations. The stretching band in the IR spectrum has two peaks, which are related to the intermediate range order that dihedral angle sequences with the signs of (+,-,+,-) and (-,+,-,+) hardly occur due to steric hindrance. The result urges us to modify the conventional picture that a-Se consists of the polymer chains with completely random sequences of the signs of the dihedral angles.

  10. Amorphization and reduction of thermal conductivity in porous silicon by irradiation with swift heavy ions

    NASA Astrophysics Data System (ADS)

    Newby, Pascal J.; Canut, Bruno; Bluet, Jean-Marie; Gomès, Séverine; Isaiev, Mykola; Burbelo, Roman; Termentzidis, Konstantinos; Chantrenne, Patrice; Fréchette, Luc G.; Lysenko, Vladimir

    2013-07-01

    In this article, we demonstrate that the thermal conductivity of nanostructured porous silicon is reduced by amorphization and also that this amorphous phase in porous silicon can be created by swift (high-energy) heavy ion irradiation. Porous silicon samples with 41%-75% porosity are irradiated with 110 MeV uranium ions at six different fluences. Structural characterisation by micro-Raman spectroscopy and SEM imaging show that swift heavy ion irradiation causes the creation of an amorphous phase in porous Si but without suppressing its porous structure. We demonstrate that the amorphization of porous silicon is caused by electronic-regime interactions, which is the first time such an effect is obtained in crystalline silicon with single-ion species. Furthermore, the impact on the thermal conductivity of porous silicon is studied by micro-Raman spectroscopy and scanning thermal microscopy. The creation of an amorphous phase in porous silicon leads to a reduction of its thermal conductivity, up to a factor of 3 compared to the non-irradiated sample. Therefore, this technique could be used to enhance the thermal insulation properties of porous Si. Finally, we show that this treatment can be combined with pre-oxidation at 300 °C, which is known to lower the thermal conductivity of porous Si, in order to obtain an even greater reduction.

  11. Crystalline to amorphous transformation in silicon

    SciTech Connect

    Cheruvu, S.M.

    1982-09-01

    In the present investigation, an attempt was made to understand the fundamental mechanism of crystalline-to-amorphous transformation in arsenic implanted silicon using high resolution electron microscopy. A comparison of the gradual disappearance of simulated lattice fringes with increasing Frenkel pair concentration with the experimental observation of sharp interfaces between crystalline and amorphous regions was carried out leading to the conclusion that when the defect concentration reaches a critical value, the crystal does relax to an amorphous state. Optical diffraction experiments using atomic models also supported this hypothesis. Both crystalline and amorphous zones were found to co-exist with sharp interfaces at the atomic level. Growth of the amorphous fraction depends on the temperature, dose rate and the mass of the implanted ion. Preliminary results of high energy electron irradiation experiments at 1.2 MeV also suggested that clustering of point defects occurs near room temperature. An observation in a high resolution image of a small amorphous zone centered at the core of a dislocation is presented as evidence that the nucleation of an amorphous phase is heterogeneous in nature involving clustering or segregation of point defects near existing defects.

  12. Effect of cyclodextrin derivation and amorphous state of complex on accelerated degradation of ziprasidone.

    PubMed

    Hong, Jinyang; Shah, Jaymin C; Mcgonagle, Maura D

    2011-07-01

    Inclusion complexes of ziprasidone with several ?-cyclodextrins [?-CDs; sulfobutylether-?-cyclodextrins (SBE?CD), hydroxypropyl-?-cyclodextrins (HP?CD), methyl-?-cyclodextrins (M?CD), and carboxyethyl-?-cyclodextrins (CE?CD)] were prepared and solution stability was evaluated at elevated temperature. Solid-state stability was assessed by subjecting various CD complexes of ziprasidone, spray-dried dispersion (SDD), partially crystalline ziprasidone-SBE?CD salts, and the physical mixture of ziprasidone-SBE?CD to ?-irradiation. Degradant I was formed by oxidation of ziprasidone, which upon aldol condensation with ziprasidone formed degradant II in both solution and solid states. In the solution state, CD complexes with electron-donating side chains, such as SBE?CD and CE?CD, produced the highest oxidative degradation followed by HP?CD with 6, 3, and 4 degrees of substitution. In the solid state, crystalline drug substance and physical mixture of crystalline drug-SBE?CD showed very little to no degradation. In contrast, amorphous ?CD, M?CD, CE?CD, and SBE?CD complexes as well as the amorphous SDD exhibited greatest extent of oxidative degradation. Results suggest that electron-donating side chains of the derivatized CD interact with transition state of the oxidation reaction and catalyze drug degradation in solution, However, higher mobility in the amorphous state of CD-drug complexes promoted chemical instability of ziprasidone under accelerated conditions irrespective of the chemical nature of the side chain on CD. PMID:21283987

  13. Pressure-induced reversible amorphization and an amorphous-amorphous transition in Ge?Sb?Te? phase-change memory material.

    PubMed

    Sun, Zhimei; Zhou, Jian; Pan, Yuanchun; Song, Zhitang; Mao, Ho-Kwang; Ahuja, Rajeev

    2011-06-28

    Ge(2)Sb(2)Te(5) (GST) is a technologically very important phase-change material that is used in digital versatile disks-random access memory and is currently studied for the use in phase-change random access memory devices. This type of data storage is achieved by the fast reversible phase transition between amorphous and crystalline GST upon heat pulse. Here we report pressure-induced reversible crystalline-amorphous and polymorphic amorphous transitions in NaCl structured GST by ab initio molecular dynamics calculations. We have showed that the onset amorphization of GST starts at approximately 18 GPa and the system become completely random at approximately 22 GPa. This amorphous state has a cubic framework (c-amorphous) of sixfold coordinations. With further increasing pressure, the c-amorphous transforms to a high-density amorphous structure with trigonal framework (t-amorphous) and an average coordination number of eight. The pressure-induced amorphization is investigated to be due to large displacements of Te atoms for which weak Te-Te bonds exist or vacancies are nearby. Upon decompressing to ambient conditions, the original cubic crystalline structure is restored for c-amorphous, whereas t-amorphous transforms to another amorphous phase that is similar to the melt-quenched amorphous GST. PMID:21670255

  14. Electronic Structure of Transparent Conducting Oxides

    Microsoft Academic Search

    J. Robertson; B. Falabretti

    \\u000a Metallic oxides are a materials class showing one of the greatest range of properties – superconducting, ferroelectric, ferromagnetic\\u000a [1], multiferroic, magneto-resistive, dielectric, or conducting. Of particular interest are the so-called transparent conducting\\u000a oxides (TCOs) and amorphous semiconducting oxides (ASOs). The TCOs are heavily used for flat panel displays, photovoltaic\\u000a cells, low emissivity windows, electrochromic devices, sensors and transparent electronics [2–4].

  15. Surface smoothing effect of an amorphous thin film deposited by atomic layer deposition on a surface with nano-sized roughness

    SciTech Connect

    Lau, W. S., E-mail: liuweicheng@zju.edu.cn; Wan, X.; Xu, Y.; Wong, H. [Zhejiang University, Department of Information Science and Electronic Engineering, No. 38 Zheda Road, Hangzhou 310027 (China)] [Zhejiang University, Department of Information Science and Electronic Engineering, No. 38 Zheda Road, Hangzhou 310027 (China); Zhang, J. [Zhejiang University, Department of Materials Science and Engineering, No. 38 Zheda Road, Hangzhou 310027 (China)] [Zhejiang University, Department of Materials Science and Engineering, No. 38 Zheda Road, Hangzhou 310027 (China); Luo, J. K. [Zhejiang University, Department of Information Science and Electronic Engineering, No. 38 Zheda Road, Hangzhou 310027 (China) [Zhejiang University, Department of Information Science and Electronic Engineering, No. 38 Zheda Road, Hangzhou 310027 (China); Institute of Renewable Energy and Environment Technology, Bolton University, Deane Road, Bolton BL3 5 AB (United Kingdom)

    2014-02-15

    Previously, Lau (one of the authors) pointed out that the deposition of an amorphous thin film by atomic layer deposition (ALD) on a substrate with nano-sized roughness probably has a surface smoothing effect. In this letter, polycrystalline zinc oxide deposited by ALD onto a smooth substrate was used as a substrate with nano-sized roughness. Atomic force microscopy (AFM) and cross-sectional transmission electron microscopy (XTEM) were used to demonstrate that an amorphous aluminum oxide thin film deposited by ALD can reduce the surface roughness of a polycrystalline zinc oxide coated substrate.

  16. Hydrogen induced phase transitions in amorphous alloys

    Microsoft Academic Search

    V. A. Somenkov; S. S. Agafonov; V. P. Glazkov; G. F. Syrykh; V. N. Verbetsky; Yu. L. Yaropolov

    2011-01-01

    Hydrogen induced structure transformations in amorphous alloys ZrPd, ZrRh and ZrRhBe were studied by neutron and X-ray-diffraction technique under gas pressure up to 2 kbar. It was shown that the amorphous alloy Zr0.7Pd0.3 which was hydrogenated at temperature below the temperature of crystallization decomposes into metastable hyper-stoichiometric Pd-hydride with bcc lattice and amorphous hypo-stoichiometric Zr-hydride. The polyamorphous transition (transition between the

  17. Properties of Amorphous Carbon Microspheres Synthesised by Palm Oil-CVD Method

    SciTech Connect

    Zobir, S. A. M. [Faculty of Applied Sciences, (UiTM), 40450 Shah Alam, Selangor (Malaysia); Nano-SciTech Centre, (UiTM), 40450 Shah Alam, Selangor (Malaysia); Zainal, Z. [Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, 43400UPM, Serdang, Selangor (Malaysia); Sarijo, S. H. [Faculty of Applied Sciences, (UiTM), 40450 Shah Alam, Selangor (Malaysia); Institute of Science, Universiti Teknologi MARA Malaysia, (UiTM), 40450 Shah Alam, Selangor (Malaysia); Rusop, M. [Nano-SciTech Centre, (UiTM), 40450 Shah Alam, Selangor (Malaysia); Institute of Science, Universiti Teknologi MARA Malaysia, (UiTM), 40450 Shah Alam, Selangor (Malaysia)

    2011-03-30

    Amorphous carbon microspheres were synthesized using a dual-furnace chemical vapour deposition method at 800-1000 deg. C. Palm oil-based cooking oil (PO) and zinc nitrate solution was used as a carbon source and catalyst precursor, respectively with PO to zinc nitrate ratio of 30:20 (v/v) and a silicon wafer as the sample target. Regular microsphere shape of the amorphous carbons was obtained and a uniform microsphere structure improved as the carbonization temperature increased from 800 to 1000 deg. C. At 800 deg. C, no regular microspheres were formed but more uniform structure is observed at 900 deg. C. Generally the microspheres size is uniform when the heating temperature was increased to 1000 deg. C, but the presence of mixed sizes can still be observed. X-ray diffraction patterns show the presence of oxide of carbon, ZnO phase together with Zn oxalate phase. Raman spectra show two broad peaks characteristic to amorphous carbon at 1344 and 1582 cm{sup -1} for the D and G bands, respectively. These bands become more prominent as the preparation temperature increased from 800 to 1000 deg. C. This is in agreement with the formation of amorphous carbon microspheres as shown by the FESEM study and other Zn-based phases as a result of the oxidation process of the palm oil as the carbon source and the zinc nitrate as the catalyst precursor, respectively.

  18. Amorphous to Amorphous Form Transitions of Water Ice and Astrophysical Implications

    NASA Technical Reports Server (NTRS)

    Jenniskens, Peter; Blake, David F.; Chang, Sherwood (Technical Monitor)

    1994-01-01

    We have combined Selected Area Electron Diffraction (SAED) and cryogenic techniques in an instrumental configuration that allows observing the structure of vapor deposited ice as it evolves during warmup. The ice is deposited in-situ inside an Hitachi H-500 H transmission electron microscope at a base pressure of 1-5 x 10(exp -7) torr on a thin amorphous carbon substrate at 15K or 86K and warmed up at a rate of 1-2 K/min. We find a progression of amorphous forms and well defined amorphous to amorphous transitions. Apart from the well known low-density form of ice, we confirm the presence of a high-density form and find a third amorphous form that coexists with cubic ice. We will report too on the amorphous to crystalline transition and the implications of these results for radical diffusion and gas retention observed in laboratory analog studies of interstellar and cometary ices.

  19. Preparation of superacids by metal oxides for reactions of butanes and pentanes

    Microsoft Academic Search

    Kazushi Arata

    1996-01-01

    Recent works on preparation of solid superacid catalysts which are active for reactions of butanes and pentanes are reviewed. Sulfated metal oxides are obtained by adsorbing sulfate ion onto amorphous oxides of Fe, Ti, Zr, Hf, Sn, and Si followed by calcination in air; a superacid of Al2O3 is prepared from the crystallized oxide. Superacids by metal oxides are synthesized

  20. Raman spectroscopy of ion irradiated amorphous carbons

    NASA Astrophysics Data System (ADS)

    Baratta, G. A.; Arena, M. M.; Strazzulla, G.; Colangeli, L.; Mennella, V.; Bussoletti, E.

    1996-08-01

    We have studied, by "in situ" Raman spectroscopy, the modifications induced by 3 keV He + ions on thin amorphous carbon grain deposits. Previous results obtained with our experimental apparatus show that in the case of carbon-containing frozen targets (such as benzene and butane) for doses greater than about 100 eV/mol, ion irradiation induces the formation of an hydrogenated amorphous carbon. In this paper, the bombarded material is already an amorphous carbon with a relatively high order degree. In this case ion irradiation progressively decreases the order degree in the amorphous carbon. This result is in agreement with analogous ion irradiation experiments carried out on highly ordered pyrolitic graphite crystals. These studies are important to understand physical characteristics and evolution of refractory carbon grains in astrophysical environments.

  1. Solar system ice - Amorphous or crystalline?

    NASA Technical Reports Server (NTRS)

    Smoluchowski, R.

    1983-01-01

    The meteoritic bombardment of icy surfaces is discussed, focusing on the formation of amorphous ice and its thermal, mechanical, and optical properties. A numerical code has been developed for evaluating the ratio of the volume of the melted and vaporized ice target to the volume of the projectile that has impacted the surface and left a crater. However, water will only vaporize with impact speeds over 4 to 6 km/sec, and subsequent condensation into ice below 150 K will produce amorphous ice. A denser form of amorphous ice exists below 10 K, with the transition into a crystalline form occurring above 150 K. Maximum impact velocities have been defined for all major bodies in the solar system, with the finding that crystalline ice will form in the crater while amorphous ice will form on the ejecta. The amount of each is dependent on the ratio of solidified water to condensed water vapor and on the fraction of solid ejecta.

  2. Modelling morphogenesis as an amorphous computation

    E-print Network

    Bhattacharyya, Arnab

    2006-01-01

    This thesis presents a programming-language viewpoint for morphogenesis, the process of shape formation during embryological development. We model morphogenesis as a self-organizing, self-repairing amorphous computation ...

  3. Pressure amorphized ices--an atomistic perspective.

    PubMed

    Tse, John S; Klug, Dennis D

    2012-06-21

    We offer our viewpoint on the nature of amorphous ices produced by pressurization of crystalline ice Ih and the inter-relationship between them from an atomistic perspective. We argue that the transformation of high density amorphous (HDA) ice from crystalline ice is due to a mechanical process arising from the instability of the ice Ih structure. The densification of HDA upon thermal annealing under pressure is a relaxation process. The conversion of the densified amorphous ice to a lower density form (LDA) upon the release of pressure can be attributed to a similar process. It is speculated that amorphous ices are metastable frustrated structures due to the large activation barriers associated with proton reorientation in the formation of the underlying stable crystalline ice polymorphs. PMID:22584826

  4. Suppression of excess oxygen for environmentally stable amorphous In-Si-O thin-film transistors

    NASA Astrophysics Data System (ADS)

    Aikawa, Shinya; Mitoma, Nobuhiko; Kizu, Takio; Nabatame, Toshihide; Tsukagoshi, Kazuhito

    2015-05-01

    We discuss the environmental instability of amorphous indium oxide (InOx)-based thin-film transistors (TFTs) in terms of the excess oxygen in the semiconductor films. A comparison between amorphous InOx doped with low and high concentrations of oxygen binder (SiO2) showed that out-diffusion of oxygen molecules causes drastic changes in the film conductivity and TFT turn-on voltages. Incorporation of sufficient SiO2 could suppress fluctuations in excess oxygen because of the high oxygen bond-dissociation energy and low Gibbs free energy. Consequently, the TFT operation became rather stable. The results would be useful for the design of reliable oxide TFTs with stable electrical properties.

  5. Amorphous\\/crystalline interrelationships in bone mineral

    Microsoft Academic Search

    J. D. Termine; A. S. Posner

    1967-01-01

    Amorphous calcium phosphate was found to be a major mineral component of skeletal tissue by X-ray diffraction techniques. This non-crystalline bone mineral phase can be converted into crystalline apatitein vitro upon exposure to water for a prolonged period of time. The amorphous calcium phosphate content of whole rat femur, tibia-fibula and calvarium decreases as the crystalline apatite content of these

  6. A Magnetic Sensor with Amorphous Wire

    PubMed Central

    He, Dongfeng; Shiwa, Mitsuharu

    2014-01-01

    Using a FeCoSiB amorphous wire and a coil wrapped around it, we have developed a sensitive magnetic sensor. When a 5 mm long amorphous wire with the diameter of 0.1 mm was used, the magnetic field noise spectrum of the sensor was about 30 pT/?Hz above 30 Hz. To show the sensitivity and the spatial resolution, the magnetic field of a thousand Japanese yen was scanned with the magnetic sensor. PMID:24940865

  7. Amorphous thin-film solar cells

    Microsoft Academic Search

    W. Krühler

    1991-01-01

    This report gives an overview of the present status of thin-film solar cells made from hydrogenated amorphous semiconductors (a-Si:H, a-Ge:H) together with new results emphasizing the physics of amorphous materials and devices. Preparation techniques, quality and performances of a-Si:H and a-Ge:H films as well as solar cells with pin structures are reviewed. Dark and light current-voltage I(V) characteristics and spectral

  8. Radial distribution functions of amorphous silicon

    Microsoft Academic Search

    J. Fortner; J. S. Lannin

    1989-01-01

    Substantial changes in the radial distribution function of amorphous Si films have been observed in neutron-diffraction studies. The spectra indicate changes in short-range order associated with an ~11% modification in the bond-angle distribution width. The results allow the first direct comparison of structural and vibrational Raman probes of variations in local order in thin-film amorphous solids. Good agreement is obtained

  9. Synthesis and characterization of amorphous carbon nanowires

    NASA Astrophysics Data System (ADS)

    Tang, Y. H.; Wang, N.; Zhang, Y. F.; Lee, C. S.; Bello, I.; Lee, S. T.

    1999-11-01

    By heating a pressed tablet of graphite powder mixed with nickel in a quartz tube mounted inside a high-temperature tube furnace at 1200 °C, amorphous carbon nanowires were formed on the inner wall of the quartz tube near a copper cooling finger. Bright-field images of transmission electron microscopy show that the diameters of the nanowires are around 40 nm. Selected-area electron diffraction and Raman study reveal that the nanowires have an amorphous structure.

  10. Tritiated amorphous silicon films and devices

    Microsoft Academic Search

    Tome Kosteski

    2001-01-01

    The do saddle-field glow discharge deposition technique has been used to bond tritium within an amorphous silicon thin film network using silane and elemental tritium in the glow discharge. The concentration of tritium is approximately 7 at. %. Minimal outgassing of tritium from tritiated hydrogenated amorphous silicon (a-Si:H:T) at room temperature suggests that tritium is bonded stably. Tritium effusion only

  11. Amorphous and microcrystalline silicon technology -- 1998

    Microsoft Academic Search

    R. Schropp; H. M. Branz; Isamu Shimizu; S. Wagner; M. Hack

    1999-01-01

    Although this new volume from MRS is the 16th in a long-standing and successful series, the focus is no longer limited to hydrogenated amorphous silicon (a-Si:H). The distinction between short- and medium-range order, and between homogeneous and heterogeneous semiconductor materials, is indeed too difficult to maintain. Instead, the volume covers amorphous and microcrystalline silicon from materials physics to new applications.

  12. Relationship between melting and amorphization of ice

    Microsoft Academic Search

    Osamu Mishima

    1996-01-01

    THE discovery1 in 1984 that an ice crystal can be transformed by pressure to an amorphous phase has since been followed by other examples of pressure-induced amorphization2. This transition, like melting, involves loss of long-ranged order, prompting the question of whether the two transitions are related. Here I describe experiments probing this relationship for a form of crystalline ice (denoted

  13. Anorthite, andesine, wollastonite, diopside, cordierite and pyrope: thermodynamics of melting, glass transitions, and properties of the amorphous phases

    Microsoft Academic Search

    Pascal Richet; Yan Bottinga

    1984-01-01

    Drop calorimetry measurements between 900 and 1850 K are reported for amorphous anorthite, andesine, wollastonite, diopside, cordierite and pyrope. The isobaric heat capacities of the glassy and liquid phases of these materials, and the enthalpies of fusion of the minerals have been derived. The calorimetric entropies of fusion of these substances and of other oxide minerals are generally consistent with

  14. The XRD Amorphous Component in John Klein Drill Fines at Yellowknife Bay, Gale Crater, Mars

    NASA Technical Reports Server (NTRS)

    Morris, Richard V.; Ming,, Douglas W.; Blake, David; Vaniman, David; Bish, David L; Chipera, Steve; Downs, Robert; Morrison, Shaunna; Gellert, Ralf; Campbell, Iain; Treiman, Alan H.; Achilles, Cherie; Bristow, Thomas; Crisp, Joy A.; McAdam, Amy; Archer, Paul Douglas; Sutter, Brad; Rampe, Elizabeth B.

    2013-01-01

    Drill fines of mudstone (targets John Klein and Cumberland) from the Sheepbed unit at Yel-lowknife Bay were analyzed by MSL payload elements including the Chemistry and Mineralogy (CheMin), APXS (Alpha Particle X-Ray Spectrometer), and Sample Analysis at Mars (SAM) instruments. CheMin XRD results show a variety of crystalline phases including feldspar, pyroxene, olivine, oxides, oxyhydroxides, sulfates, sulfides, a tri-octahedral smectite, and XRD amorphous material. The drill fines are distinctly different from corresponding analyses of the global soil (target Rocknest) in that the mudstone samples contained detectable phyllosilicate. Here we focus on John Klein and combine CheMin and APXS data to calculate the chemical composition and concentration of the amorphous component. The chemical composition of the amorphous plus smectite component for John Klein was calculated by subtracting the abundance-weighted chemical composition of the individual XRD crystalline components from the bulk composition of John Kline as measured by APXS. The chemical composition of individual crystalline components was determined either by stoichiometry (e.g., hematite and magnetite) or from their unit cell parameters (e.g., feldspar, olivine, and pyroxene). The chemical composition of the amorphous + smectite component (approx 71 wt.% of bulk sample) and bulk chemical composition are similar. In order to calculate the chemical composition of the amorphous component, a chemical composition for the tri-octahedral smectite must be assumed. We selected two tri-octahedral smectites with very different MgO/(FeO + Fe2O3) ratios (34 and 1.3 for SapCa1 and Griffithite, respectively). Relative to bulk sample, the concentration of amorphous and smectite components are 40 and 29 wt.% for SapCa1 and 33 and 36 wt.% for Griffithite. The amount of smectite was calculated by requiring the MgO concentration to be approx 0 wt.% in the amorphous component. Griffithite is the preferred smectite because the position of its 021 diffraction peak is similar to that reported for John Klein. In both cases, the amorphous component has low SiO2 and MgO and high FeO + Fe2O3, P2O5, and SO3 concentrations relative to bulk sample. The chemical composition of the bulk drill fines and XRD crystalline, smectite, and amorphous components implies alteration of an initially basaltic material under near neutral conditions (not acid sulfate), with the sulfate incorporated later as veins of CaSO4 injected into the mudstone.

  15. In situ measurement and modification of the interface potential in hydrogenated amorphous silicon solar cells

    Microsoft Academic Search

    Ahmad Nuruddin

    1997-01-01

    We investigate the electronic properties of the top junction in hydrogenated amorphous silicon solar cells. In-situ Kelvin probe method is employed to reveal the contact potential profile of the transparent conductive oxide\\/p+ a-Si,C:H, and p+ a-Si,C:H\\/a-Si:H interfaces. The films are deposited by dc reactive magnetron sputtering of a silicon target in a plasma of (Ar + Hsb2 + CHsb4). The

  16. Chemiluminescent Detection of Horseradish Peroxidase Using an Integrated Amorphous Silicon Thin-Film Photosensor

    Microsoft Academic Search

    A. T. Pereira; A. C. Pimentel; V. Chu; D. M. F. Prazeres; J. P. Conde

    2009-01-01

    A hydrogenated amorphous silicon p-i-n photodiode fabricated on a glass substrate is used for the integrated, real-time detection of biochemiluminescent reactions. The light emission at 425 nm resulting from the oxidation of luminol catalyzed by the enzyme horseradish peroxidase (HRP) is detected. This enzyme is commonly used as a label attached to biomolecules such as proteins and nucleic acids. In

  17. The effects of rare earths on supported amorphous NiB\\/Al 2O 3 catalysts

    Microsoft Academic Search

    Rongbin Zhang; Fengyi Li; Qiujie Shi; Laitao Luo

    2001-01-01

    The technique of pulse microreaction was applied to study the effects of rare earths on the catalytic properties of supported amorphous NiB\\/Al2O3 catalyst for benzene hydrogenation. The characteristics of catalysts are investigated by using ICP, XRD, TPR, TPD, DSC and H2 chemisorption. Experimental results show that rare earth addition is helpful for the reduction of nickel oxide, makes the nickel

  18. Electrochemical properties of amorphous comb-shaped composite PEO polymer electrolyte

    Microsoft Academic Search

    J.-S Chung; H.-J Sohn

    2002-01-01

    The electrochemical behaviour of a polyethylene oxide (PEO)-based composite polymer electrolyte are studied. The crystallinity of the PEO is suppressed by using a comb-shaped polymer to improve polymer chain mobility. An amorphous comb-shaped polymer, ‘TEC-24’, with a side-chain content of 24mol%, is designed and fine silica powder is dispersed within it to enhance the mechanical properties above the melting point.

  19. Synthesis and UV-shielding properties of calcia-doped ceria nanoparticles coated with amorphous silica

    Microsoft Academic Search

    Tsugio Sato; Toshihiko Katakura; Shu Yin; Tsuyoshi Fujimoto; Shinryo Yabe

    2004-01-01

    Nanoparticles of calcia-doped ceria were prepared by adding CeCl3–CaCl2 mixed solution and NaOH solution simultaneously in distilled water followed by oxidation with hydrogen peroxide solution at 40 °C and pH 12. After that, amorphous silica was coated by dispersing them in Na2SiO3 aqueous solution at pH 10, followed by decreasing the solution pH to 5. Doping with calcia resulted in

  20. Template confined synthesis of amorphous carbon nanotubes and its confocal Raman microscopy

    NASA Astrophysics Data System (ADS)

    Maity, Supratim; Roychowdhury, Tuhin; Chattopadhyay, Kalyan Kumar

    2014-04-01

    Amorphous carbon nanotubes (aCNTs) were synthesized by AAO (anodic aluminum oxide) template at a temperature 500 °C in nitrogen atmosphere using the citric acid as a carbon source without the help of any catalyst particles. Morphological analysis of the as prepared samples was carried out by field emission scanning electron microscopy (FESEM). Confocal Raman imaging has been studied and an attempt has been made to find out the graphitic (sp2) and disordered phase of the CNTs.

  1. Self-passivated copper gates for amorphous silicon thin-film transistors

    Microsoft Academic Search

    Henning Sirringhaus; S. D. Theiss; A. Kahn; S. Wagner

    1997-01-01

    A solution to the amorphous silicon transistor gate metallization problem in active matrix liquid crystal displays (AMLCD's) is demonstrated, in the form of a self-passivated copper (Cu) process. Cu is passivated by a self-aligned chromium (Cr) oxide encapsulation formed by surface segregation of Cr in dilute Cu-10-30 at.%Cr alloys at 400°C, solving the problems of chemical reactivity during the plasma

  2. Electron-beam-assisted superplastic shaping of nanoscale amorphous silica

    PubMed Central

    Zheng, Kun; Wang, Chengcai; Cheng, Yong-Qiang; Yue, Yonghai; Han, Xiaodong; Zhang, Ze; Shan, Zhiwei; Mao, Scott X; Ye, Miaomiao; Yin, Yadong; Ma, Evan

    2010-01-01

    Glasses are usually shaped through the viscous flow of a liquid before its solidification, as practiced in glass blowing. At or near room temperature (RT), oxide glasses are known to be brittle and fracture upon any mechanical deformation for shape change. Here, we show that with moderate exposure to a low-intensity (<1.8×10?2 A cm?2) electron beam (e-beam), dramatic shape changes can be achieved for nanoscale amorphous silica, at low temperatures and strain rates >10?4 per second. We show not only large homogeneous plastic strains in compression for nanoparticles but also superplastic elongations >200% in tension for nanowires (NWs). We also report the first quantitative comparison of the load-displacement responses without and with the e-beam, revealing dramatic difference in the flow stress (up to four times). This e-beam-assisted superplastic deformability near RT is useful for processing amorphous silica and other conventionally-brittle materials for their applications in nanotechnology. PMID:20975693

  3. Transport of Li+ Ions In Amorphous Tungsten Oxide Films

    NASA Astrophysics Data System (ADS)

    Kamimori, Tadatoshi; Nagai, Junichi; Mizuhashi, Mamoru

    1983-12-01

    Coloring / bleaching processes of LixWO3 electrochrothismwere examined by means of emf, chronoamperometry, voltammetry and ac impedance measurements. Current-potential relation was found to be ohmic in the short time region and expressed by i=(Eapp-emf(x))/ R. Satisfactory fittings were obtained for chronoamperometry and voltammetry measurements on the basis of the assumption of diffusion-limited process with above i-E relation. It was elucidated from the detailed analysis of impedance that R was given by the summation of the resistances of solution, electrode, charge transfer and material transfer. It was newly found that diffusion coefficients for several WO3 films were in the range of 1.5 X 10-9 to 3 x 10-12 cm2,sec at 20°C and they were strongly dependent on water content in the electrolyte solution.

  4. Development and Characterization of an Ultrathin Barium Oxide Film on a Surface Oxidized Ni(110) Substrate

    Microsoft Academic Search

    D. Vlachos; S. D. Foulias; M. Kamaratos

    2008-01-01

    In this work we develop an ultrathin barium oxide film by Ba adsorption on a pre?oxidized Ni(110) surface, and characterize it by means of Auger electron spectroscopy, low energy electron diffraction and work function measurements. The results show that the Ba adatoms reduce the NiO surface oxide forming an amorphous and incomplete BaO layer. At higher coverages, the Ba adsorbate

  5. Porous amorphous carbon models from periodic Gaussian chains of amorphous polymers

    E-print Network

    Powles, Rebecca

    and puri- fication processes. Activated carbons, for example, are used in water purification, sugarPorous amorphous carbon models from periodic Gaussian chains of amorphous polymers Amit Kumar, Raul carbons using Monte Carlo simulations in the canonical ensemble. The simulation method used follows

  6. Constraints on abundance, composition, and nature of X-ray amorphous components of soils and rocks at Gale crater, Mars

    NASA Astrophysics Data System (ADS)

    Dehouck, Erwin; McLennan, Scott M.; Meslin, Pierre-Yves; Cousin, Agnès.

    2014-12-01

    X-ray diffraction patterns of the three samples analyzed by Curiosity's Chemistry and Mineralogy (CheMin) instrument during the first year of the Mars Science Laboratory mission—the Rocknest sand, and the John Klein and Cumberland drill fines, both extracted from the Sheepbed mudstone—show evidence for a significant amorphous component of unclear origin. We developed a mass balance calculation program that determines the range of possible chemical compositions of the crystalline and amorphous components of these samples within the uncertainties of mineral abundances derived from CheMin data. In turn, the chemistry constrains the minimum abundance of amorphous component required to have realistic compositions (all oxides ? 0 wt %): 21-22 wt % for Rocknest and 15-20 wt % for Cumberland, in good agreement with estimates derived from the diffraction patterns (~27 and ~31 wt %, respectively). Despite obvious differences between the Rocknest sand and the Sheepbed mudstone, the amorphous components of the two sites are chemically very similar, having comparable concentrations of SiO2, TiO2, Al2O3, Cr2O3, FeOT, CaO, Na2O, K2O, and P2O5. MgO tends to be lower in Rocknest, although it may also be comparable between the two samples depending on the exact composition of the smectite in Sheepbed. The only unambiguous difference is the SO3 content, which is always higher in Rocknest. The observed similarity suggests that the two amorphous components share a common origin or formation process. The individual phases possibly present within the amorphous components include: volcanic (or impact) glass, hisingerite (or silica + ferrihydrite), amorphous sulfates (or adsorbed SO42-), and nanophase ferric oxides.

  7. Research on stable, high-efficiency amorphous silicon multijunction modules

    SciTech Connect

    Bhat, P.K.; Brown, S.; Hollingsworth, R.; Shen, D.S.; del Cueto, J.; Iwanicko, E.; Marshall, C.; DeHart, C.; Mentor, D.; Benson, A.; Matovich, C.; Sandwisch, J. (Glasstech Solar, Inc., Golden, CO (USA))

    1991-04-01

    This report describes a contract to produce multijunction modules based entirely on amorphous silicon alloys, the modules having an aperture area of at least 900 cm{sup 2} and a stable, reproducible conversion efficiency of at least 6.5% after 600 hours of light exposure (air mass 1.5) at 50{degrees} C. The work focussed on (1) producing opto-electronic-grade amorphous silicon material for band gaps of about 1.7 and 1.9 eV by changing the hydrogen content in the film bonded to the silicon, (2) studying and obtaining data on the light stability of single-junction p-i-n solar cells with gaps of about 1.7 and 1.9 eV, and (3) analyzing losses in a silicon/silicon multijunction cell. We report new results on an indium tin oxide (ITO)/silver back contact and the deposition of granular tin oxide by atmospheric-pressure chemical vapor deposition. Progress toward module fabrication at the end of six months has been good, with the demonstration of 5.4% initial efficiency in a silicon/silicon multijunction submodule with an aperture area of 4620 cm{sup 2} and incorporating devices with 2nd-junction i-layer thicknesses of about 3500 {angstrom}. We also demonstrated a single-junction silicon submodule with an aperture area of 4620 cm{sup 2}, a thickness of about 3500 {angstrom}, and an initial efficiency of 6.5%. 4 refs., 39 figs., 5 tabs.

  8. Synthesis method for amorphous metallic foam

    NASA Astrophysics Data System (ADS)

    Schroers, Jan; Veazey, Chris; Demetriou, Marios D.; Johnson, William L.

    2004-12-01

    A synthesis method for the production of amorphous metallic foam is introduced. This method utilizes the thermodynamic stability and thermoplastic formability of the supercooled liquid state to produce low-density amorphous metallic foams in dimensions that are not limited to the critical casting thickness. The method consists of three stages: the prefoaming stage, in which a large number of small bubbles are created in the equilibrium liquid under pressure; the quenching stage, in which the liquid prefoam is quenched to its amorphous state; the foam expansion stage, in which the amorphous prefoam is reheated to the supercooled liquid region and is processed under pressures substantially lower than those applied in the prefoaming step. Results from a dynamic model suggest that the foam expansion process is feasible, as the kinetics of bubble expansion in the supercooled liquid region are faster than the kinetics of crystallization. Within the proposed synthesis method, bulk amorphous foam products characterized by bubble volume fractions of as high as 85% are successfully produced.

  9. Silicon carbide amorphization by electron irradiation

    SciTech Connect

    Bentley, J.

    1998-02-01

    Observations made more than ten years ago showed that SiC could be made amorphous at cryogenic temperatures by in-situ 300kV electron irradiation. However, high voltage electron microscope (HVEM) results indicate a threshold voltage of 725 kV for amorphization of SiC at 140 K. In addition, a recent review exposes the considerable uncertainty in the literature regarding displacement energies for SiC. Therefore, further experiments have been performed in a Philips CM30 (LaB{sub 6} cathode) with a Gatan double-tilt cooling holder in an attempt to determine the threshold voltage for amorphization at {approximately} 140 K. Sintered {alpha}-SiC (defected 6H polytype), beam direction B = <11{bar 2}0>, and probes containing {approximately} 75 nA in {approximately} 0.5 {micro}m, were used. Amorphization occurred in <10 min at 300 kV and after {approximately} 60 min at 180 kV; visible darkening occurred at lower voltages and doses. Similar behavior occurred for B = [0001]. The critical dose for amorphization was measured as a function of accelerating voltage. Probe current profiles were measured by post-specimen scanning (CM30 SCIM mode with 100 {micro}m diameter Gatan STEM detector) images of the focused probes positioned in a hole, and probe currents were measured from the exposure time, which had previously been calibrated with a Faraday cup.

  10. Amorphous silicon detectors in positron emission tomography

    SciTech Connect

    Conti, M. (Istituto Nazionale di Fisica Nucleare, Pisa (Italy) Lawrence Berkeley Lab., CA (USA)); Perez-Mendez, V. (Lawrence Berkeley Lab., CA (USA))

    1989-12-01

    The physics of the detection process is studied and the performances of different Positron Emission Tomography (PET) system are evaluated by theoretical calculation and/or Monte Carlo Simulation (using the EGS code) in this paper, whose table of contents can be summarized as follows: a brief introduction to amorphous silicon detectors and some useful equation is presented; a Tantalum/Amorphous Silicon PET project is studied and the efficiency of the systems is studied by Monte Carlo Simulation; two similar CsI/Amorphous Silicon PET projects are presented and their efficiency and spatial resolution are studied by Monte Carlo Simulation, light yield and time characteristics of the scintillation light are discussed for different scintillators; some experimental result on light yield measurements are presented; a Xenon/Amorphous Silicon PET is presented, the physical mechanism of scintillation in Xenon is explained, a theoretical estimation of total light yield in Xenon and the resulting efficiency is discussed altogether with some consideration of the time resolution of the system; the amorphous silicon integrated electronics is presented, total noise and time resolution are evaluated in each of our applications; the merit parameters {epsilon}{sup 2}{tau}'s are evaluated and compared with other PET systems and conclusions are drawn; and a complete reference list for Xenon scintillation light physics and its applications is presented altogether with the listing of the developed simulation programs.

  11. SURVIVAL OF AMORPHOUS WATER ICE ON CENTAURS

    SciTech Connect

    Guilbert-Lepoutre, Aurelie, E-mail: aguilbert@ucla.edu [Department of Earth and Space Sciences, UCLA, Los Angeles, CA 90095 (United States)

    2012-10-01

    Centaurs are believed to be Kuiper Belt objects in transition between Jupiter and Neptune before possibly becoming Jupiter family comets. Some indirect observational evidence is consistent with the presence of amorphous water ice in Centaurs. Some of them also display a cometary activity, probably triggered by the crystallization of the amorphous water ice, as suggested by Jewitt and this work. Indeed, we investigate the survival of amorphous water ice against crystallization, using a fully three-dimensional thermal evolution model. Simulations are performed for varying heliocentric distances and obliquities. They suggest that crystallization can be triggered as far as 16 AU, though amorphous ice can survive beyond 10 AU. The phase transition is an efficient source of outgassing up to 10-12 AU, which is broadly consistent with the observations of the active Centaurs. The most extreme case is 167P/CINEOS, which barely crystallizes in our simulations. However, amorphous ice can be preserved inside Centaurs in many heliocentric distance-obliquity combinations, below a {approx}5-10 m crystallized crust. We also find that outgassing due to crystallization cannot be sustained for a time longer than 10{sup 4}-10{sup 4} years, leading to the hypothesis that active Centaurs might have recently suffered from orbital changes. This could be supported by both observations (although limited) and dynamical studies.

  12. Remarkable Thermal Stability of Amorphous In-Zn-O Transparent Conductors

    SciTech Connect

    Taylor, M. P.; Readey, D. W.; van Hest, M. F. A. M.; Teplin, C. W.; Alleman, J. L.; Dabney, M. S.; Gedvilas, L. M.; Keyes, B. M.; To, B.; Perkins, J. D.; Ginley, D. S.

    2008-10-01

    Transparent conducting oxides (TCOs) are increasingly critical components in photovoltaic cells, low-e windows, flat panel displays, electrochromic devices, and flexible electronics. The conventional TCOs, such as Sn-doped In{sub 2}O{sub 3}, are crystalline single phase materials. Here, we report on In-Zn-O (IZO), a compositionally tunable amorphous TCO with some significantly improved properties. Compositionally graded thin film samples were deposited by co-sputtering from separate In{sub 2}O{sub 3} and ZnO targets onto glass substrates at 100 C. For the metals composition range of 55-84 cation% indium, the as-deposited IZO thin films are amorphous, smooth (R{sub RMS} < 0.4 nm), conductive ({sigma} {approx} 3000 {Omega}{sup -1} {center_dot} cm{sup -1}), and transparent in the visible (T{sub Vis} > 90%). Furthermore, the amorphous IZO thin films demonstrate remarkable functional and structural stability with respect to heating up to 600 C in either air or argon. Hence, though not completely understood at present, these amorphous materials constitute a new class of fundamentally interesting and technologically important high performance transparent conductors.

  13. The XRD Amorphous Component in John Klein Drill Fines at Yellowknife Bay, Gale Crater, Mars

    NASA Astrophysics Data System (ADS)

    Morris, R. V.; Ming, D. W.; Blake, D.; Vaniman, D.; Bish, D. L.; Chipera, S.; Downs, R.; Morrison, S.; Gellert, R.; Campbell, I.; Treiman, A. H.; Achilles, C.; Bristow, T.; Crisp, J. A.; McAdam, A.; Archer, P. D.; Sutter, B.; Rampe, E. B.; Team, M.

    2013-12-01

    Drill fines of mudstone (targets John Klein and Cumberland) from the Sheepbed unit at Yel-lowknife Bay were analyzed by MSL payload elements including the Chemistry and Mineralogy (CheMin), APXS (Alpha Particle X-Ray Spectrometer), and Sample Analysis at Mars (SAM) instruments. CheMin XRD results show a variety of crystalline phases including feldspar, pyrox-ene, olivine, oxides, oxyhydroxides, sulfates, sulfides, a tri-octahedral smectite, and XRD amorphous material. The drill fines are distinctly different from corresponding analyses of the global soil (target Rocknest) in that the mudstone samples contained detectable phyllosilicate. Here we focus on John Klein and combine CheMin and APXS data to calculate the chemical composition and concentration of the amorphous component. The chemical composition of the amorphous plus smectite component for John Klein was cal-culated by subtracting the abundance-weighted chemical composition of the individual XRD crystalline components from the bulk composition of John Kline as measured by APXS. The chemical composition of individual crystalline components was determined either by stoichiome-try (e.g., hematite and magnetite) or from their unit cell parameters (e.g., feldspar, olivine, and pyroxene). The chemical composition of the amorphous + smectite component (~71 wt.% of bulk sample) and bulk chemical compositon are similar. In order to calculate the chemical composition of the amorphous component, a chemical composition for the tri-octahedral smectite must be assumed. We selected two tri-octahedral smectites with very different MgO/(FeO + Fe2O3) ratios (34 and 1.3 for SapCa1 and Griffithite, respectively). Relative to bulk sample, the concentration of amorphous and smectite components are 40 and 29 wt.% for SapCa1 and 33 and 36 wt.% for Griffithite. The amount of smectite was calculated by requiring the MgO concentration to be~0 wt.% in the amporphous component. Griffithite is the preferred smectite because the position of its 02l diffraction peak is similar to that reported for John Klein. In both cases, the amorphous component has low SiO2 and MgO and high FeO + Fe2O3, P2O5, and SO3 concentrations relative to bulk sample. The chemical composition of the bulk drill fines and XRD crystalline, smectite, and amorphous components implies alteration of an initially basaltic material under near neutral conditions (not acid sulfate), with the sulfate incorporated later as veins of CaSO4 injected into the mudstone.

  14. Hydrogenated amorphous carbon grains in Comet Halley?

    NASA Astrophysics Data System (ADS)

    Colangeli, L.; Schwehm, G.; Bussoletti, E.; Fonti, S.; Blanco, A.; Orofino, V.

    1990-01-01

    Recent IR observations of Comets Halley, Wilson, and Bradfield have shown the existence of an emission feature falling at around 3.4 microns. In this paper, it is shown that a good fit of both the IR continuum and the band can be obtained by assuming a simple thermal emission model based upon the optical properties of hydrogenated amorphous carbon (HAC) grains, measured in laboratory. The best fits of P/Halley's spectra are obtained for HAC dust amounts which appear consistent with the constraints imposed by the observed production rates. The presence of amorphous carbon solid particles is also supported on the basis of in situ mass spectrometry measurements performed by the Vega 1/2 and Giotto spacecraft in the environment of P/Halley. At present, it appears reasonable to suggest that amorphous carbon grains are able to match the observations and can be considered among likely candidates for cometary materials.

  15. Amorphous and microcrystalline silicon technology -- 1998

    SciTech Connect

    Schropp, R. [ed.] [Utrecht Univ. (Netherlands); Branz, H.M. [ed.] [National Renewable Energy Lab., Golden, CO (United States); Shimizu, Isamu [ed.] [Tokyo Inst. of Tech. (Japan); Wagner, S. [ed.] [Princeton Univ., NJ (United States); Hack, M. [ed.

    1999-08-01

    Although this new volume from MRS is the 16th in a long-standing and successful series, the focus is no longer limited to hydrogenated amorphous silicon (a-Si:H). The distinction between short- and medium-range order, and between homogeneous and heterogeneous semiconductor materials, is indeed too difficult to maintain. Instead, the volume covers amorphous and microcrystalline silicon from materials physics to new applications. Papers from a joint session with a symposium on ``Flat-Panel Display Materials and Large-Area Processes`` are included. The volume also features special focused sessions on heterogeneous materials, color sensors and radiation imaging, and parameter extraction and device modeling. Topics include: amorphous and polycrystalline thin-film transistors; solar cells; color and X-ray sensors, novel devices, luminescence and sensitization; device modeling and parameter extraction; growth, alloys and clathrates; metastability, hydrogen, atomic and electronic structure; defects and charge transport; and heterogeneous silicon--formation, properties and devices. It includes 152 papers.

  16. Amorphous Silicon Based Neutron Detector

    SciTech Connect

    Xu, Liwei

    2004-12-12

    Various large-scale neutron sources already build or to be constructed, are important for materials research and life science research. For all these neutron sources, neutron detectors are very important aspect. However, there is a lack of a high-performance and low-cost neutron beam monitor that provides time and temporal resolution. The objective of this SBIR Phase I research, collaboratively performed by Midwest Optoelectronics, LLC (MWOE), the University of Toledo (UT) and Oak Ridge National Laboratory (ORNL), is to demonstrate the feasibility for amorphous silicon based neutron beam monitors that are pixilated, reliable, durable, fully packaged, and fabricated with high yield using low-cost method. During the Phase I effort, work as been focused in the following areas: 1) Deposition of high quality, low-defect-density, low-stress a-Si films using very high frequency plasma enhanced chemical vapor deposition (VHF PECVD) at high deposition rate and with low device shunting; 2) Fabrication of Si/SiO2/metal/p/i/n/metal/n/i/p/metal/SiO2/ device for the detection of alpha particles which are daughter particles of neutrons through appropriate nuclear reactions; and 3) Testing of various devices fabricated for alpha and neutron detection; As the main results: · High quality, low-defect-density, low-stress a-Si films have been successfully deposited using VHF PECVD on various low-cost substrates; · Various single-junction and double junction detector devices have been fabricated; · The detector devices fabricated have been systematically tested and analyzed. · Some of the fabricated devices are found to successfully detect alpha particles. Further research is required to bring this Phase I work beyond the feasibility demonstration toward the final prototype devices. The success of this project will lead to a high-performance, low-cost, X-Y pixilated neutron beam monitor that could be used in all of the neutron facilities worldwide. In addition, the technologies developed here could be used to develop X-ray and neutron monitors that could be used in the future for security checks at the airports and other critical facilities. The project would lead to devices that could significantly enhance the performance of multi-billion dollar neutron source facilities in the US and bring our nation to the forefront of neutron beam sciences and technologies which have enormous impact to materials, life science and military research and applications.

  17. Physics of supercooled water and amorphous ices

    NASA Astrophysics Data System (ADS)

    Giovambattista, Nicolas

    In this thesis, I perform molecular dynamics simulations to investigate water in two metastable states: supercooled liquid and amorphous ice. Supercooled water is liquid water at temperatures below the freezing point. Amorphous ice is glassy water, where molecules are arranged in a disordered structure similar to the one found in liquids. In Part I, I give a brief introduction to the concepts needed to understand the main results of this thesis. In Part II, I investigate the microscopic dynamics in supercooled water. I describe the dynamics using the potential energy landscape (PEL) approach, and using an alternative approach proposed by Adam and Gibbs (AG). In agreement with the AG theory, I find that dynamics in water is heterogeneous. The AG theory is based on the vague concept of "cooperatively rearranging regions" (CRR). From my simulations I give a precise definition of the CRR and study the CRR properties with temperature. I relate the presence of CRR to the dynamics of the system as described in the PEL approach. Cooling a liquid fast enough below the glass transition temperature Tg produces a glass. In Part III, I study the glass transition in water. The effect of cooling/heating rates and aging are shown to be crucial in the determination of Tg. Our simulations support the view that the glass transition in water is not experimentally accessible. The PEL properties sampled during the glass transition indicate that the common view of the glass as a "frozen" liquid is not always correct. Amorphous ice can exist in at least two different forms, low-density amorphous (LDA) and high-density amorphous (HDA). In Part IV, I show that the LDA-HDA transition can be found in computer simulations and describe it using the PEL approach. I also explore the entire phase diagram of amorphous ice not accessible to experiments. I find that the recently suggested third glass found experimentally in water, very-high density amorphous (VHDA) ice, is not a new glass but a result of aging effects. Furthermore, I find that a continuum of amorphous ices can be identified in glassy water.

  18. Properties of obliquely deposited amorphous silicon films

    SciTech Connect

    Ablova, M.S.; Andreev, A.A.; Golikova, O.A.; Guts, Z.A.; Sidorova, T.A.

    1986-04-01

    This paper attempts to clarify the effect of the columnar nature of the film on the electrical and optical properties of amorphous silicon films. The authors monitored the film structure by the method of transmission electron microscopy using an EVM-100A microscope with a resolution of 5 A. The total external reflection of x-rays was studied and the anisotropy of the electrical conductivity was examined. A comparison of the properties of amorphous silicon films deposited normally and obliquely relative to the substrate revealed the effect of the columnar microstructure, forming in the latter case, on the electrical and optical properties of the film.

  19. Amorphous Insulator Films With Controllable Properties

    NASA Technical Reports Server (NTRS)

    Alterovitz, Samuel A.; Warner, Joseph D.; Liu, David C.; Pouch, John J.

    1987-01-01

    In experiments described in report, amorphous hydrogenated carbon films grown at room temperature by low-frequency plasma deposition, using methane or butane gas. Films have unique array of useful properties; (a) adhere to wide variety of materials; (b) contain only carbon and hydrogen; (c) smooth and free of pinholes; (d) resistant to attack by moisture and chemicals; and (e) have high electric-breakdown strength and electrical resistivity. Two of optical properties and hardness of this film controlled by deposition conditions. Amorphous a-C:H and BN films used for hermetic sealing and protection of optical, electronic, magnetic, or delicate mechanical systems, and for semiconductor field dielectrics.

  20. Ion bombardment and disorder in amorphous silicon

    SciTech Connect

    Sidhu, L.S.; Gaspari, F.; Zukotynski, S.

    1997-07-01

    The effect of ion bombardment during growth on the structural and optical properties of amorphous silicon are presented. Two series of films were deposited under electrically grounded and positively biased substrate conditions. The biased samples displayed lower growth rates and increased hydrogen content relative to grounded counterparts. The film structure was examined using Raman spectroscopy. The transverse optic like phonon band position was used as a parameter to characterize network order. Biased samples displayed an increased order of the amorphous network relative to grounded samples. Furthermore, biased samples exhibited a larger optical gap. These results are correlated and attributed to reduced ion bombardment effects.

  1. Cooling of hot electrons in amorphous silicon

    SciTech Connect

    Vanderhaghen, R.; Hulin, D.; Cuzeau, S.; White, J.O.

    1997-07-01

    Measurements of the cooling rate of hot carriers in amorphous silicon are made with a two-pump, one-probe technique. The experiment is simulated with a rate-equation model describing the energy transfer between a population of hot carriers and the lattice. An energy transfer rate proportional to the temperature difference is found to be consistent with the experimental data while an energy transfer independent of the temperature difference is not. This contrasts with the situation in crystalline silicon. The measured cooling rates are sufficient to explain the difficulty in observing avalanche effects in amorphous silicon.

  2. Amorphous germanium contacts on germanium detectors

    NASA Astrophysics Data System (ADS)

    Hull, Ethan L.; Pehl, Richard H.

    2005-02-01

    The rectification properties of sputtered amorphous germanium contacts made under a variety of conditions on germanium detectors have been measured as a function of temperature and electric field. The leakage current increased as a function of voltage above depletion voltage. The rectifying amorphous-crystalline heterojunction theory derived by Döhler and Brodsky describes the behavior well. Values of barrier height were measured to be ˜0.30-0.35 eV and the density of states was found to be NF˜10 18 eV -1 cm -3.

  3. Remarks on solid state amorphizing transformations

    SciTech Connect

    Schwarz, R.B.; Johnson, W.L.

    1987-01-01

    Amorphous solids can now be produced through a variety of laboratory synthesis techniques as well as through many naturally occurring processes. In general, we can classify the methods of synthesis of amorphous solids as follows: (1) rapid solidification of melts or vapors; (2) atomic disordering of crystalline lattices; (3) solid state reactions between pure elements; (4) solid-state transformations from metastable crystalline states; and (5) deposition from electrolytes. We give a short summary of the historical development of methods (1)-(4) (method (5) is clearly outside the focus of this conference) and we discuss the basic physical principles behind the methods. 21 refs., 1 fig.

  4. An electron-yield EXAFS study of anodic-oxide and hydrated-oxide films on pure aluminium

    Microsoft Academic Search

    S. M. El-mashri; R. G. Jones; A. J. Forty

    1983-01-01

    The molecular structures of the amorphous films formed on pure aluminium by anodic oxidation in sodium tartrate and phosphoric acid electrolytes, which are known to give quite different oxide morphologies, have been investigated using the technique of electron-yield EXAFS. The Al-0 ‘bond length’ derived from the EXAFS is found to be different for these two types of film, which suggests

  5. Wet oxidation of AlxGa1 - xAs: Temporal evolution of composition and microstructure and the implications for metal-insulator-semiconductor applications

    NASA Astrophysics Data System (ADS)

    Ashby, Carol I. H.; Sullivan, John P.; Newcomer, Paula P.; Missert, Nancy A.; Hou, Hong Q.; Hammons, B. E.; Hafich, Michael J.; Baca, Albert G.

    1997-05-01

    Three important processes dominate the wet thermal oxidation of AlxGa1-xAs on GaAs: (1) oxidation of Al and Ga in the AlxGa1-xAs alloy to form an amorphous oxide, (2) formation and elimination of crystalline and amorphous elemental As and of amorphous As2O3, and (3) crystallization of the amorphous oxide film. Residual As can lead to strong Fermi-level pinning at the oxidized AlGaAs/GaAs interface, up to a 100-fold increase in leakage current, and a 30% increase in the dielectric constant of the oxide layer. Thermodynamically favored interfacial As may impose a fundamental limitation on the use of AlGaAs wet oxidation in metal-insulatorsemiconductor devices in the GaAs material system.

  6. Amorphous and nanocrystalline materials for applications as soft magnets

    E-print Network

    Laughlin, David E.

    Amorphous and nanocrystalline materials for applications as soft magnets Michael E. Mc, and applications in the ®elds of amorphous, bulk amorphous, and nanocrystalline soft magnetic materialsHenry*, Matthew A. Willard, David E. Laughlin Department of Materials Science and Engineering, Carnegie Mellon

  7. HAL-2Feb2006 Raman microspectroscopic characterization of amorphous silica

    E-print Network

    Paris-Sud XI, Université de

    HAL-2Feb2006 Raman microspectroscopic characterization of amorphous silica plastic behavior A amorphous silica plastic behavior. Using a correlation between Raman spectrum and density, a map. These results open the way to more accurate description of a constitutive law for amorphous silica. Electronic

  8. Visible photoluminescence in amorphous SiOx thin films prepared by silicon evaporation under a molecular oxygen atmosphere

    NASA Astrophysics Data System (ADS)

    Molinari, M.; Rinnert, H.; Vergnat, M.

    2003-06-01

    A simple reactive evaporation method is proposed to prepare light-emitting amorphous SiOx thin films. By evaporating pure silicon in a controlled molecular oxygen atmosphere, it is possible to obtain a very large composition range. By changing the pressure in the preparation chamber, x can be varied from 0.7 to 1.85. The composition and the structure of the films were investigated using energy dispersive x-ray, infrared absorption and x-ray photoelectron spectroscopies. The samples contain amorphous silicon clusters dispersed inside an insulating silicon oxide matrix. The room-temperature photoluminescence properties were then measured. By conveniently choosing the oxygen pressure, the as-deposited films exhibit visible photoluminescence without any annealing post-treatments. The luminescence intensity initially increases with excess silicon concentration and then disappears for a too-high silicon excess. The above effect is interpreted in terms of confinement of the amorphous silicon clusters in the insulating matrix.

  9. New Amorphous Silicon Alloy Systems

    NASA Astrophysics Data System (ADS)

    Kapur, Mridula N.

    1990-01-01

    The properties of hydrogenated amorphous silicon (a-Si:H) have been modified by alloying with Al, Ga and S respectively. The Al and Ga alloys are in effect quaternary alloys as they were fabricated in a carbon-rich discharge. The alloys were prepared by the plasma assisted chemical vapor deposition (PACVD) method. This method has several advantages, the major one being the relatively low defect densities of the resulting materials. The PACVD system used to grow the alloy films was designed and constructed in the laboratory. It was first tested with known (a-Si:H and a-Si:As:H) materials. Thus, it was established that device quality alloy films could be grown with the home-made PACVD setup. The chemical composition of the alloys was characterized by secondary ion mass spectrometry (SIMS), and electron probe microanalysis (EPMA). The homogeneous nature of hydrogen distribution in the alloys was established by SIMS depth profile analysis. A quantitative analysis of the bulk elemental content was carried out by EPMA. The analysis indicated that the alloying element was incorporated in the films more efficiently at low input gas concentrations than at the higher concentrations. A topological model was proposed to explain the observed behavior. The optical energy gap of the alloys could be varied in the 0.90 to 1.92 eV range. The Al and Ga alloys were low band gap materials, whereas alloying with S had the effect of widening the energy gap. It was observed that although the Si-Al and Si-Ga alloys contained significant amounts of C and H, the magnitude of the energy gap was determined by the metallic component. The various trends in optical properties could be related to the binding characteristics of the respective alloy systems. A quantitative explanation of the results was provided by White's tight binding model. The dark conductivity-temperature dependence of the alloys was examined. A linear dependence was observed for the Al and Ga systems. Electronic conduction in the S-alloys appeared to proceed by a two step mechanism. The thermal activation energies for the high Al content and S-alloys were close to half the band gap value. The photoresponse of the films was determined from the light to dark conductivity ratio. The best photoresponse (sigma_ {L}/sigma_{D} = 4 times 10^2) was obtained for the Si-S alloys showing that they are promising electrode materials for solar cell application. A single unit photovoltaic electrolyzer was constructed by combining a-Si:H solar cells with an electrolysis cell. Several different configurations ((PIN), (PIN)^2 , and (PIN)^3) of the solar cells were tested. Both electric power and chemical energy (H_2) could be simultaneously drawn from the electrolyzer.

  10. High-Performance Single-Crystalline Arsenic-Doped Indium Oxide Nanowires

    E-print Network

    Zhou, Chongwu

    High-Performance Single-Crystalline Arsenic-Doped Indium Oxide Nanowires for Transparent Thin 20 V).14 17 For instance, TTFTs with amorphous indium gallium oxide (a- IGO) films display device (As)-doped indium oxide (In2O3) nanowires for transparent electronics, including their implementation

  11. The role of noncrystalline films in the oxidation and corrosion of metals

    Microsoft Academic Search

    A. G. Revesz; F. P. Fehlner

    1981-01-01

    The role of oxide perfection is a major factor in controlling the rate of oxidation and corrosion of metals. Studies of the reactivity of tantalum, silicon, and amorphous metals are particularly revealing in this regard. Two states of oxide perfection are found: single crystal and vitreous. The former is seldom encountered in practice because it requires epitaxial growth of a

  12. Oral bacterial adhesion on amorphous carbon films

    Microsoft Academic Search

    A. Almaguer-Flores; R. Olivares-Navarrete; A. Lechuga-Bernal; L. A. Ximénez-Fyvie; S. E. Rodil

    2009-01-01

    It is now well established that all the different forms of amorphous carbon films are biocompatible and suitable for specific biomedical applications. On the other hand, bacterial adhesion on implant surfaces has also a strong influence on the healing and long-term outcome of biomedical devices and this has not been thoroughly studied for the carbon films. The purpose of this

  13. Transient amorphous calcium phosphate in forming enamel.

    PubMed

    Beniash, Elia; Metzler, Rebecca A; Lam, Raymond S K; Gilbert, P U P A

    2009-05-01

    Enamel, the hardest tissue in the body, begins as a three-dimensional network of nanometer size mineral particles, suspended in a protein gel. This mineral network serves as a template for mature enamel formation. To further understand the mechanisms of enamel formation we characterized the forming enamel mineral at an early secretory stage using X-ray absorption near-edge structure (XANES) spectromicroscopy, transmission electron microscopy (TEM), FTIR microspectroscopy and polarized light microscopy. We show that the newly formed enamel mineral is amorphous calcium phosphate (ACP), which eventually transforms into apatitic crystals. Interestingly, the size, shape and spatial organization of these amorphous mineral particles and older crystals are essentially the same, indicating that the mineral morphology and organization in enamel is determined prior to its crystallization. Mineralization via transient amorphous phases has been previously reported in chiton teeth, mollusk shells, echinoderm spicules and spines, and recent reports strongly suggest the presence of transient amorphous mineral in forming vertebrate bones. The present finding of transient ACP in murine tooth enamel suggests that this strategy might be universal. PMID:19217943

  14. Amorphous silicon coatings with silver nanoparticles

    NASA Astrophysics Data System (ADS)

    Tuleushev, Yu. Zh.; Volodin, V. N.; Zhakanbaev, E. A.; Zdorovets, M. V.

    2013-11-01

    We describe a plasma-ion sputtering technology for obtaining amorphous silicon coatings containing dispersed silver nanoparticles with average dimensions of 20-30 nm. Results of X-ray diffraction and electron-microscopic investigations of these coatings are presented, and a possible mechanism of silver nano-particle formation from 2- to 3-nm-sized nanoclusters is considered.

  15. The Plastic Response of Magnetoelastic Amorphous Solids

    E-print Network

    H. G. E. Hentschel; Valery Ilyin; Itamar Procaccia

    2012-05-04

    We address the cross effects between mechanical strains and magnetic fields on the plastic response of magnetoelastic amorphous solids. It is well known that plasticity in non-magnetic amorphous solids under external strain $\\gamma$ is dominated by the co-dimension 1 saddle-node bifurcation in which an eigenvalue of the Hessian matrix vanishes at $\\gamma_P$ like $\\sqrt{\\gamma_P-\\gamma}$. This square-root singularity determines much of the statistical physics of elasto-plasticity, and in particular that of the stress-strain curves under athermal-quasistatic conditions. In this Letter we discuss the much richer physics that can be expected in magnetic amorphous solids. Firstly, magnetic amorphous solids exhibit co-dimension 2 plastic instabilities, when an external strain and an external magnetic field are applied simultaneously. Secondly, the phase diagrams promise a rich array of new effects that have been barely studied; this opens up a novel and extremely rich research program for magnetoplastic materials.

  16. The Electronic Structure of Amorphous Carbon Nanodots.

    PubMed

    Margraf, Johannes T; Strauss, Volker; Guldi, Dirk M; Clark, Timothy

    2015-06-18

    We have studied hydrogen-passivated amorphous carbon nanostructures with semiempirical molecular orbital theory in order to provide an understanding of the factors that affect their electronic properties. Amorphous structures were first constructed using periodic calculations in a melt/quench protocol. Pure periodic amorphous carbon structures and their counterparts doped with nitrogen and/or oxygen feature large electronic band gaps. Surprisingly, descriptors such as the elemental composition and the number of sp(3)-atoms only influence the electronic structure weakly. Instead, the exact topology of the sp(2)-network in terms of effective conjugation defines the band gap. Amorphous carbon nanodots of different structures and sizes were cut out of the periodic structures. Our calculations predict the occurrence of localized electronic surface states, which give rise to interesting effects such as amphoteric reactivity and predicted optical band gaps in the near-UV/visible range. Optical and electronic gaps display a dependence on particle size similar to that of inorganic colloidal quantum dots. PMID:25731776

  17. Sonochemically Prepared Nanostructured Amorphous Molybdenum Sulfide

    E-print Network

    Suslick, Kenneth S.

    sulfur and molybdenum hexacarbonyl in isodurene is irradiated with high-intensity ultrasound (20 k. CLASSIFICATION form: amorphous, nanostructured fine powder function: hydrodesulfurization catalyst, lubricant the relative amount of exposed edge sites. By making MoS2 (i) nanostructured to increase surface area, and (ii

  18. TRANSIENT AMORPHOUS CALCIUM PHOSPHATE IN FORMING ENAMEL

    PubMed Central

    Beniash, Elia; Metzler, Rebecca A.; Lam, Raymond S.K.; Gilbert, P.U.P.A.

    2009-01-01

    Enamel, the hardest tissue in the body, begins as a three-dimensional network of nanometer size mineral particles, suspended in a protein gel. This mineral network serves as a template for mature enamel formation. To further understand the mechanisms of enamel formation we characterized the forming enamel mineral at an early secretory stage using x-ray absorption near-edge structure (XANES) spectromicroscopy, transmission electron microscopy (TEM), FTIR microspectroscopy and polarized light microscopy. We show that the newly formed enamel mineral is amorphous calcium phosphate (ACP), which eventually transforms into apatitic crystals. Interestingly, the size, shape and spatial organization of these amorphous mineral particles and older crystals are essentially the same, indicating that the mineral morphology and organization in enamel is determined prior to its crystallization. Mineralization via transient amorphous phases has been previously reported in chiton teeth, mollusk shells, echinoderm spicules and spines, and recent reports strongly suggest the presence transient amorphous mineral in forming vertebrate bones. The present finding of transient ACP in murine tooth enamel suggests that this strategy might be universal. PMID:19217943

  19. High density amorphous ice at room temperature.

    PubMed

    Chen, Jing-Yin; Yoo, Choong-Shik

    2011-05-10

    The phase diagram of water is both unusual and complex, exhibiting a wide range of polymorphs including proton-ordered or disordered forms. In addition, a variety of stable and metastable forms are observed. The richness of H(2)O phases attests the versatility of hydrogen-bonded network structures that include kinetically stable amorphous ices. Information of the amorphous solids, however, is rarely available especially for the stability field and transformation dynamics--but all reported to exist below the crystallization temperature of approximately 150-170 K below 4-5 GPa. Here, we present the evidence of high density amorphous (HDA) ice formed well above the crystallization temperature at 1 GPa--well inside the so-called "no-man's land." It is formed from metastable ice VII in the stability field of ice VI under rapid compression using dynamic-diamond anvil cell (d-DAC) and results from structural similarities between HDA and ice VII. The formation follows an interfacial growth mechanism unlike the melting process. Nevertheless, the occurrence of HDA along the extrapolated melt line of ice VII resembles the ice Ih-to-HDA transition, indicating that structural instabilities of parent ice VII and Ih drive the pressure-induced amorphization. PMID:21518902

  20. Photoelectron spectroscopic study of the cleaned, thermally treated and oxidized Zr??Ni?? amorphaus alloy 

    E-print Network

    Liang, Guiping

    1987-01-01

    PHOTOELECTRON SPECTROSCOPIC STUDY OF THE CLEANED, THERMALLY TREATED AND OXIDIZED ZrssNi34 AMORPHOUS ALLOY A Thesis by GUIPING LIANG Submitted to the Graduate College of Texas A & 51 University in partial fulfillment of the requirement... for the degree of MASTER OF SCIENCE May 1987 Major Subject: Physics PHOTOELECTRON SPECTROSCOPIC STUDY OF THE CLEANED, THERMALLY TREATED AND OXIDIZED ZrssNi34 AMORPHOUS ALLOY A Thesis by GUIPING LIANG Approved as to style and content by: Donald G...

  1. Investigation of the aluminium-aluminium oxide reversible transformation as observed by hot stage electron microscopy

    Microsoft Academic Search

    C. A. Grove; G. Judd; G. S. Ansell

    1972-01-01

    Thin foils of high purity aluminium and an Al-Al2O3 SAP type of alloy were oxidised in a specially designed hot stage specimen chamber in an electron microscope. Below 450\\u000a C, amorphous aluminium oxide formed on the foil surface and was first detectable at foil edges, holes, and pits. Islands of\\u000a aluminium then nucleated in this amorphous oxide. The aluminium islands

  2. Comparing hardness and wear data for tetrahedral amorphous carbon and hydrogenated amorphous carbon thin films

    Microsoft Academic Search

    P. Lemoine; J. P. Quinn; P. Maguire; J. A. McLaughlin

    2004-01-01

    We compared nanoindentation and nanoscratch testing of 10 and 50nm thick tetrahedral amorphous carbon (ta-C) and hydrogenated amorphous carbon (a-C:H). Raman spectroscopy shows the expected spectral features for the two carbon forms, however, luminescence from the ceramic substrate can alter the spectra. We find that hard ta-C films can blunt the diamond tip and hence use a tip area function

  3. Molecular dynamics simulation of amorphous indomethacin.

    PubMed

    Xiang, Tian-Xiang; Anderson, Bradley D

    2013-01-01

    Molecular dynamics (MD) simulations have been conducted using an assembly consisting of 105 indomethacin (IMC) molecules and 12 water molecules to investigate the underlying dynamic (e.g., rotational and translational diffusivities and conformation relaxation rates) and structural properties (e.g., conformation, hydrogen-bonding distributions, and interactions of water with IMC) of amorphous IMC. These properties may be important in predicting physical stability of this metastable material. The IMC model was constructed using X-ray diffraction data with the force-field parameters mostly assigned by analogy with similar groups in Amber-ff03 and atomic charges calculated with the B3LYP/ccpVTZ30, IEFPCM, and RESP models. The assemblies were initially equilibrated in their molten state and cooled through the glass transition temperature to form amorphous solids. Constant temperature dynamic runs were then carried out above and below the T(g) (i.e., at 600 K (10 ns), 400 K (350 ns), and 298 K (240 ns)). The density (1.312 ± 0.003 g/cm(3)) of the simulated amorphous solid at 298 K was close to the experimental value (1.32 g/cm(3)) while the estimated T(g) (384 K) was ~64 degrees higher than the experimental value (320 K) due to the faster cooling rate. Due to the hindered rotation of its amide bond, IMC can exist in different diastereomeric states. Different IMC conformations were sufficiently sampled in the IMC melt or vapor, but transitions occurred rarely in the glass. The hydrogen-bonding patterns in amorphous IMC are more complex in the amorphous state than in the crystalline polymorphs. Carboxylic dimers that are dominant in ?- and ?-crystals were found to occur at a much lower probability in the simulated IMC glasses while hydrogen-bonded IMC chains were more easily identified patterns in the simulated amorphous solids. To determine molecular diffusivity, a novel analytical method is proposed to deal with the non-Einsteinian behavior, in which the temporal evolution of the apparent diffusivity D(t) is described by a relaxation model such as the KWW function and extrapolated to infinite time. The diffusion coefficient found for water diffusing in amorphous indomethacin at 298 K (2.7 × 10(-9) cm(2)/s) compares favorably to results obtained in experimental IMC glasses (0.9-2.0 × 10(-9) cm(2)/s) and is mechanistically associated with ?-relaxation processes that are dominant in sub-T(g) glasses. PMID:23116319

  4. Preparation of Niobium-Doped Titanium Oxide Film by Liquid Phase Deposition

    Microsoft Academic Search

    Ming-Kwei Lee; Chung-Min Shih; Shih-Chang Fang; Hwei-Fu Tu; Chen-Lin Ho

    2007-01-01

    Niobium-doped amorphous titanium oxide film can be deposited on a Corning glass substrate using a mixture of ammonium hexafluorotitanate, boric acid, niobium oxide and ammonium hydrogen fluoride aqueous solutions. After thermal annealing, the nanocrystallite niobium-doped titanium oxide film can be obtained. The smaller crystallite size of nanocrystallite niobium-doped titanium oxide than that of undoped-titanium oxide benefits the catalytic activity for

  5. Graphene as a transparent electrode for amorphous silicon-based solar cells

    NASA Astrophysics Data System (ADS)

    Vaianella, F.; Rosolen, G.; Maes, B.

    2015-06-01

    The properties of graphene in terms of transparency and conductivity make it an ideal candidate to replace indium tin oxide (ITO) in a transparent conducting electrode. However, graphene is not always as good as ITO for some applications, due to a non-negligible absorption. For amorphous silicon photovoltaics, we have identified a useful case with a graphene-silica front electrode that improves upon ITO. For both electrode technologies, we simulate the weighted absorption in the active layer of planar amorphous silicon-based solar cells with a silver back-reflector. The graphene device shows a significantly increased absorbance compared to ITO-based cells for a large range of silicon thicknesses (34.4% versus 30.9% for a 300 nm thick silicon layer), and this result persists over a wide range of incidence angles.

  6. Direct tunneling through high-? amorphous HfO2: Effects of chemical modification

    NASA Astrophysics Data System (ADS)

    Wang, Yin; Yu, Zhizhou; Zahid, Ferdows; Liu, Lei; Zhu, Yu; Wang, Jian; Guo, Hong

    2014-07-01

    We report first principles modeling of quantum tunneling through amorphous HfO2 dielectric layer of metal-oxide-semiconductor (MOS) nanostructures in the form of n-Si/HfO2/Al. In particular, we predict that chemically modifying the amorphous HfO2 barrier by doping N and Al atoms in the middle region—far from the two interfaces of the MOS structure—can reduce the gate-to-channel tunnel leakage by more than one order of magnitude. Several other types of modification are found to enhance tunneling or induce substantial band bending in the Si, both are not desired from leakage point of view. By analyzing transmission coefficients and projected density of states, the microscopic physics of electron traversing the tunnel barrier with or without impurity atoms in the high-? dielectric is revealed.

  7. Crystalline-Amorphous Silicon Nanocomposites with Reduced Thermal Conductivity for Bulk Thermoelectrics.

    PubMed

    Miura, Asuka; Zhou, Shu; Nozaki, Tomohiro; Shiomi, Junichiro

    2015-06-24

    Responding to the need for thermoelectric materials with high efficiency in both conversion and cost, we developed a nanostructured bulk silicon thermoelectric materials by sintering silicon crystal quantum dots of several nanometers in diameters synthesized by plasma-enhanced chemical vapor deposition (PECVD). The material consists of hybrid structures of nanograins of crystalline silicon and amorphous silicon oxide. The percolated nanocrystalline region gives rise to high power factor with the high doping concentration realized by PECVD, and the binding amorphous region reduces thermal conductivity. Consequently, the nondimensional figure of merit reaches 0.39 at 600 °C, equivalent to the best reported value for silicon thermoelectrics. The thermal conductivity of the densely packed material is as low as 5 W m(-1) K(-1) in a wide temperature range from room temperature to 1000 °C, which is beneficial not only for the conversion efficiency but also for material cost by requiring less material to establish certain temperature gradient. PMID:26046688

  8. Development and characterization of high temperature stable Ta-W-Si-C amorphous metal gates

    SciTech Connect

    Grubbs, Melody E.; Clemens, Bruce M. [Department of Materials Science and Engineering, Stanford University, Stanford, California 94305 (United States); Zhang Xiao; Deal, Michael; Nishi, Yoshio [Department of Electrical Engineering, Stanford University, Stanford, California 94305 (United States)

    2010-11-29

    Threshold voltage variability ({sigma}{sub Vth}) due to the polycrystalline nature of current metal gates has been identified as a problem in future generations of complementary metal oxide semiconductor (CMOS) devices. Amorphous metal Ta{sub 40}W{sub 40}Si{sub 10}C{sub 10} gates are introduced in this work as a remedy. It was found that Ta-W-Si-C films remain amorphous at temperatures as high as 1120 deg. C, have n-type work functions, and are stable on HfO{sub 2}. This alloy is a promising gate-first compatible material that has the potential to significantly reduce {sigma}{sub Vth}.

  9. Nitroxide-Functionalized Graphene Oxide from Graphite Oxide

    PubMed Central

    Avila-Vega, Yazmin I.; Leyva-Porras, Cesar C.; Mireles, Marcela; Quevedo-López, Manuel; Macossay, Javier; Bonilla-Cruz, José

    2013-01-01

    A facile method for preparing functionalized graphene oxide single layers with nitroxide groups is reported herein. Highly oxidized graphite oxide (GO=90.6%) was obtained, slightly modifying an improved Hummer’s method. Oxoammonium salts (OS) were investigated to introduce nitroxide groups to GO, resulting in a one-step functionalization and exfoliation. The mechanisms of functionalization/exfoliation are proposed, where the oxidation of aromatic alcohols to ketone groups, and the formation of alkoxyamine species are suggested. Two kinds of functionalized graphene oxide layers (GOFT1 and GOFT2) were obtained by controlling the amount of OS added. GOFT1 and GOFT2 exhibited a high interlayer spacing (d0001 = 1.12nm), which was determined by X-ray diffraction. The presence of new chemical bonds C-N (~9.5 %) and O-O (~4.3 %) from nitroxide attached onto graphene layers were observed by X-ray photoelectron spectroscopy. Single-layers of GOFT1 were observed by HRTEM, exhibiting amorphous and crystalline zones at a 50:50 ratio; in contrast, layers of GOFT2 exhibited a fully amorphous surface. Fingerprint of GOFT1 single layers was obtained by electron diffraction at several tilts. Finally, the potential use of these materials within Nylon 6 matrices was investigated, where an unusual simultaneous increase in tensile stress, tensile strain and Young’s modulus was observed. PMID:24347671

  10. Phononic Amorphous Silicon: Theory, Material, and Devices

    SciTech Connect

    Chawda, S.; Mawyin, J.; Mahan, H.; Fortmann, C.; Halada, G.

    2006-01-01

    The field of phononic-engineered amorphous silicon is introduced. Specifically the construction of devices and waveguides for information conveyance and manipulation via phonons are considered. Typically the phononic properties of a given material are immutable and the phonons have such a limited diffusion length (nanometers) as to be unsuitable for engineering purposes. Crystalline silicon on the other hand has a reasonably large thermal conductivity and phonon diffusion length at sufficiently low temperatures. Phonon diffusion lengths can measure up to centimeters (e.g., crystalline SiO2) at temperature less than 10K but drop to sub microns at room temperature. Amorphous silicon, owing to the inherent scattering structures and owing to localization (of at least some phonon bands), has an anomalously large phonon lifetime [1]. This lifetime maybe indicative of a large phonon diffusion length and/or a fast phonon hop rate from one domain to the next and/or an indication that more than the typical three phonons (umklapp process) are involved in phonon scattering. Techniques involving small-scaled devices and phonon bands to control umklapp phonon-phonon scattering are described. The potential to exploit inherent amorphous silicon structure as well as the engineering (post film deposition) of di-hydride distributions to induce phonon forbidden bands for significantly reduced multi-phonon scattering is explored. The indirect optical band gap of small domain (and possibly amorphous) silicon [3] provides the physical basis for the transduction of phonon and optical energies. Experimental methods for the post-deposition introduction of phonon scattering structure, the transduction of phononic information to optical information, and experimental approaches including the use of micro-Raman to probe phonon spectra and transport are described. The prospects of a fully integrated phononic, photonic, electronic amorphous silicon technology have been described.

  11. Amorphous Carbon: State of the Art - Proceedings of the 1st International Specialist Meeting on Amorphous Carbon (smac '97)

    NASA Astrophysics Data System (ADS)

    Silva, S. R. P.; Robertson, J.; Milne, W. I.; Amaratunga, G. A. J.

    1998-05-01

    The Table of Contents for the full book PDF is as follows: * Preface * GROWTH AND STRUCTURE * The Structure of Tetrahedral Amorphous Carbon * Growth of DLC Films and Related Structure and Properties * Deposition Mechanism of Diamond-Like Carbon * Relaxation of sp3 Bonds in Hydrogen Free Carbon Films During Growth * MODELLING * Correlations Between Microstructure and Electronic Properties in Amorphous Carbon Based Materials * Review of Monte Carlo Simulations of Diamondlike Amorphous Carbon: Bulk, Surface, and Interface Structural Properties * DEPOSITION * Preparation of Disordered Amorphous and Partially Ordered Nano Clustered Carbon Films by Arc Deposition: A Critical Review * Plasma Deposition of Diamond-Like Carbon in an ECR-RF Discharge * Deposition of Amorphous Hydrogenated Carbon-Nitrogen Films by PECVD Using Several Hydrocarbon / Nitrogen Containing Gas Mixtures * ELECTRONIC STRUCTURE * 'Defects' and Their Detection in a-C and a-C:H * Valence Band and Gap State Spectroscopy of Amorphous Carbon by Photoelectron Emission Techniques * Photoluminescence Spectroscopy: A Probe for Inhomogeneous Structure in Polymer-Like Amorphous Carbon * Raman Characterization of Amorphous and Nanocrystalline sp3 Bonded Structures * Ultraviolet Raman Spectroscopy of Tetrahedral Amorphous Carbon Thin Films * Excitation Energy Dependent Raman and Photoluminescence Spectra of Hydrogenated Amorphous Carbon * MECHANICAL PROPERTIES * Pulsed Laser Deposited a-C: Growth, Structure and Mechanical Properties * Mechanical Properties of Laser-Assisted Deposited Amorphous Carbon Films * Mechanical and Morphology Study on Tetrahedral Amorphous Carbon Films * Time-Dependent Changes in the Mechanical Properties of Diamond-Like Carbon Films * ELECTRONIC PROPERTIES * Electronic Transport in Amorphous Carbon * Electronic Properties of Undoped/Doped Tetrahedral Amorphous Carbon * The Inclusion of Graphitic Nanoparticles in Semiconducting Amorphous Carbon to Enhance Electronic Transport Properties * FIELD EMISSION * Carbon Cathode Requirements and Emission Characterization for Low-Voltage Field Emission Displays * Electron Field Emission from Carbon Films * Electron Field Emission from Carbon Thin Films

  12. Influence of proton insertion on the conductivity, structural and optical properties of amorphous and crystalline electrochromic WO 3 films

    NASA Astrophysics Data System (ADS)

    Kamal, H.; Akl, A. A.; Abdel-Hady, K.

    2004-06-01

    Amorphous and crystalline tungsten oxide films were RF-sputtered from a metallic target in oxygen/argon atmosphere onto un-heated and heated substrates. Upon cyclic electrochemical treatment in 0.1 M H 2SO 4 aqueous solution, both types of films showed good electrochromic reversibility beyond 1000 cycles. The crystallinity changes of both types of films were studied by XRD. For c-WO 3, the results showed that hydrogen insertion enhance the degree of crystallinity with the clear appearance of tungsten bronze diffraction peaks due to the formation of H 0.1WO 3, with tetragonal crystalline structure. For a-WO 3, coloration weakens the amorphous features and increases the crystallinity properties. The DC electrical conductivity increases, in a reversible way, with four order of magnitudes namely from 10 -7 to 10 -3 (? cm) -1 for bleached and colored films, respectively. Both types of films exhibit remarkable solar transmission modulation, about 51%, which is adequate for smart windows applications. In contrast to amorphous films, crystalline tungsten oxide films show reflection modulation in the NIR reaching 25% upon charge insertion. The Drude reflectance edge arises for colored films suggesting that coloration in c-WO 3 is attributed to a scattering mechanism of Drude-like free electron, while coloration of a-WO 3 is attributed to a hopping mechanism of small polaron. The visible, infrared and solar modulations are given for both types of films. Coloration/bleaching were found to be faster for amorphous films. Self-bleaching process in different oxidative environments involves a redox cycle aided by water polarity. Crystalline WO 3 showed pronounced coloring persistence relative to amorphous films which is attributed to different binding energy related to large and small polarons.

  13. An amorphous silicon alloy triple-junction solar cell with 14.6% initial and 13.0% stable efficiencies

    SciTech Connect

    Yang, J.; Banerjee, A.; Guha, S.

    1997-07-01

    An initial conversion efficiency of 14.6% has been achieved using amorphous silicon-based alloy in a spectrum splitting triple-junction structure. After 1,000 hours of indoor one-sun light soaking at 50 C, the stabilized efficiency is 13.0%. Both efficiencies are the highest reported to date for amorphous silicon alloy solar cells and have been independently confirmed by the National Renewable Energy Laboratory. The device was deposited onto a stainless steel substrate coated with textured silver/zinc oxide back reflector. The bottom and middle cells use amorphous silicon-germanium alloys, employing high hydrogen dilution in the gas mixture and bandgap profiling in the cell design. The top cell uses amorphous silicon alloy with high hydrogen dilution. Key factors leading to the achievement include (a) improvement of the bottom cell that exhibits an AM1.5 efficiency of 10.4% and quantum efficiency of 45% at 850 nm; (b) improvement of the tunnel junctions between the component cells by incorporating a novel multilayered structure with microcrystalline p and n layers; and (c) improvement of transparent conductive oxide for enhancing the short wavelength response of the top cell.

  14. Fabrication and characterization of iron oxide nanoparticles filled polypyrrole nanocomposites

    Microsoft Academic Search

    Zhanhu Guo; Koo Shin; Amar B. Karki; David P. Young; Richard B. Kaner; H. Thomas Hahn

    2009-01-01

    The effect of iron oxide nanoparticle addition on the physicochemical properties of the polypyrrole (PPy) was investigated.\\u000a In the presence of iron oxide nanoparticles, PPy was observed in the form of discrete nanoparticles, not the usual network\\u000a structure. PPy showed crystalline structure in the nanocomposites and pure PPy formed without iron oxide nanoparticles. PPy\\u000a exhibited amorphous structure and nanoparticles were

  15. Water clustering on nanostructured iron oxide films

    NASA Astrophysics Data System (ADS)

    Merte, Lindsay R.; Bechstein, Ralf; Peng, Guowen; Rieboldt, Felix; Farberow, Carrie A.; Zeuthen, Helene; Knudsen, Jan; Lægsgaard, Erik; Wendt, Stefan; Mavrikakis, Manos; Besenbacher, Flemming

    2014-06-01

    The adhesion of water to solid surfaces is characterized by the tendency to balance competing molecule-molecule and molecule-surface interactions. Hydroxyl groups form strong hydrogen bonds to water molecules and are known to substantially influence the wetting behaviour of oxide surfaces, but it is not well-understood how these hydroxyl groups and their distribution on a surface affect the molecular-scale structure at the interface. Here we report a study of water clustering on a moiré-structured iron oxide thin film with a controlled density of hydroxyl groups. While large amorphous monolayer islands form on the bare film, the hydroxylated iron oxide film acts as a hydrophilic nanotemplate, causing the formation of a regular array of ice-like hexameric nanoclusters. The formation of this ordered phase is localized at the nanometre scale; with increasing water coverage, ordered and amorphous water are found to coexist at adjacent hydroxylated and hydroxyl-free domains of the moiré structure.

  16. New transformations between crystalline and amorphous ice

    NASA Technical Reports Server (NTRS)

    Hemley, R. J.; Chen, L. C.; Mao, H. K.

    1989-01-01

    High-pressure optical and spectroscopic techniques were used to obtain directly the ice I(h) - hda-ice transformation in a diamond-anvil cell, and the stability of the amorphous form is examined as functions of pressure and temperature. It is demonstrated that hda-ice transforms abruptly at 4 GPa and 77 K to a crystalline phase close in structure to orientationally disordered ice-VII and to a more highly ordered, ice-VIII-like structure at higher temperatures. This is the first time that an amorphous solid is observed to convert to a crystalline solid at low temperatures by compression alone. Phase transitions of this type may be relevant on icy planetary satellites, and there may also be implications for the high-pressure behavior of silica.

  17. On the stability of amorphous solid

    NASA Astrophysics Data System (ADS)

    Lin, Jie; Saade, Alaa; Lerner, Edan; Rosso, Alberto; Wyart, Matthieu

    2014-03-01

    The plasticity of amorphous material occurs via local plastic rearrangements, shear transformation zones(STZ). The elastic coupling between STZs can generate large-scale avalanches of plastic events. We study the stability condition of amorphous solid toward extensive avalanches. We argue that stability is controlled by the distribution P(x) of the local stress increase x that would lead to an instability. In particular stability requres that P(x) ~x? where ? satisfies a lower bound. To investigate this, we use a elasto-plastic model based on two ingredients: local plastic events above microscopic stress, and the non-local elastic stress release generated by these plastic events. For a class of models of lond range interaction, ? is found to lie near saturation. For quadrupole interaction, the model yields ? ~ 0 . 6 in 2D, and ? ~ 0 . 4 in 3D.

  18. Advances in amorphous silicon photovoltaic technology

    SciTech Connect

    Carlson, D.E.; Rajan, K.; Arya, R.R.; Willing, F.; Yang, L. [Solarex, a Business Unit of Amoco/Enron Solar, 826 Newtown-Yardley Road, Newtown, Pennsylvania 18940 (United States)

    1998-10-01

    With the advent of new multijunction thin film solar cells, amorphous silicon photovoltaic technology is undergoing a commercial revival with about 30 megawatts of annual capacity coming on-line in the next year. These new {ital a}{endash}Si multijunction modules should exhibit stabilized conversion efficiencies on the order of 8{percent}, and efficiencies over 10{percent} may be obtained in the next several years. The improved performance results from the development of amorphous and microcrystalline silicon alloy films with improved optoelectronic properties and from the development of more efficient device structures. Moreover, the manufacturing costs for these multijunction modules using the new large-scale plants should be on the order of {dollar_sign}1 per peak watt. These new modules may find widespread use in solar farms, photovoltaic roofing, as well as in traditional remote applications. {copyright} {ital 1998 Materials Research Society.}

  19. Bonding defects in hydrogenated amorphous silicon

    SciTech Connect

    Lucovsky, G.; Yang, H. [North Carolina State Univ., Raleigh, NC (United States)

    1996-12-31

    A mechanism for charged-carrier-trapping-induced defect metastability in hydrogenated amorphous silicon (a-Si:H) and in hydrogenated amorphous silicon alloys containing relatively high concentrations of oxygen and/or nitrogen atoms (a-Si:X:H, X = O or N) is described. The experimental results that identified this defect metastability mechanism were (i) differences in the Staebler-Wronski effect in a-Si:H and a-Si:N:H alloys prepared from N{sub 2} and NH{sub 3} source gases by remote plasma-enhanced chemical-vapor deposition, and (ii) differences in defect generation at N-atom terminated Si-SiO{sub 2} interfaces prepared from NH{sub 3} and N{sub 2}O.

  20. Wear Resistant Amorphous and Nanocomposite Coatings

    SciTech Connect

    Racek, O

    2008-03-26

    Glass forming materials (critical cooling rate <10{sup 4}K.s{sup -1}) are promising for their high corrosion and wear resistance. During rapid cooling, the materials form an amorphous structure that transforms to nanocrystalline during a process of devitrification. High hardness (HV 1690) can be achieved through a controlled crystallization. Thermal spray process has been used to apply coatings, which preserves the amorphous/nanocomposite structure due to a high cooling rate of the feedstock particles during the impact on a substrate. Wear properties have been studied with respect to process conditions and feedstock material properties. Application specific properties such as sliding wear resistance have been correlated with laboratory tests based on instrumented indentation and scratch tests.

  1. Annealing behavior of high permeability amorphous alloys

    SciTech Connect

    Rabenberg, L.

    1980-06-01

    Effects of low temperature annealing on the magnetic properties of the amorphous alloy Co/sub 71/ /sub 4/Fe/sub 4/ /sub 6/Si/sub 9/ /sub 6/B/sub 14/ /sub 4/ were investigated. Annealing this alloy below 400/sup 0/C results in magnetic hardening; annealing above 400/sup 0/C but below the crystallization temperature results in magnetic softening. Above the crystallization temperature the alloy hardens drastically and irreversibly. Conventional and high resolution transmission electron microscopy were used to show that the magnetic property changes at low temperatures occur while the alloy is truly amorphous. By imaging the magnetic microstructures, Lorentz electron microscopy has been able to detect the presence of microscopic inhomogeneities in this alloy. The low temperature annealing behavior of this alloy has been explained in terms of atomic pair ordering in the presence of the internal molecular field. Lorentz electron microscopy has been used to confirm this explanation.

  2. Germanium detector passivated with hydrogenated amorphous germanium

    DOEpatents

    Hansen, William L. (Walnut Creek, CA); Haller, Eugene E. (Berkeley, CA)

    1986-01-01

    Passivation of predominantly crystalline semiconductor devices (12) is provided for by a surface coating (21) of sputtered hydrogenated amorphous semiconductor material. Passivation of a radiation detector germanium diode, for example, is realized by sputtering a coating (21) of amorphous germanium onto the etched and quenched diode surface (11) in a low pressure atmosphere of hydrogen and argon. Unlike prior germanium diode semiconductor devices (12), which must be maintained in vacuum at cryogenic temperatures to avoid deterioration, a diode processed in the described manner may be stored in air at room temperature or otherwise exposed to a variety of environmental conditions. The coating (21) compensates for pre-existing undesirable surface states as well as protecting the semiconductor device (12) against future impregnation with impurities.

  3. Retardation of nucleation rate for grain size enhancement by deep silicon ion implantation of low-pressure chemical vapor deposited amorphous silicon films

    Microsoft Academic Search

    I.-W. Wu; A. Chiang; M. Fuse; T. Y. Huang

    1989-01-01

    The effects of silicon ion implantation on the crystallization kinetics and grain size of low-pressure chemical vapor deposited amorphous silicon on oxidized silicon substrate have been studied by x-ray diffraction and transmission electron microscopy. The most effective grain size enhancement was achieved by deep silicon ion implantation with the projected range located beyond the bottom interface to allow the maximum

  4. Laser crystallization of hydrogenated amorphous silicon

    Microsoft Academic Search

    N. H. Nickel; K. Brendel; R. Saleh

    2004-01-01

    Doped and undoped hydrogenated amorphous silicon films were crystallized employing a step-by-step laser crystallization method. The influence of laser crystallization on structural properties and hydrogen bonding in polycrystalline silicon was investigated using Raman backscattering spectrometry, electron paramagnetic resonance, and hydrogen effusion measurements. At low laser fluences, EL, a two-layer system is created. With increasing EL the spin density of undoped

  5. of neodymium-based amorphous alloy

    Microsoft Academic Search

    S. Gorsse; G. Orveillon; B. Chevalier

    The Nd49Al13Ni38 amorphous alloy has been prepared by melt-spinning in the form of ribbons. Its magnetic properties have been investigated via superconducting quantum interference device magnetometry and its magnetic phase diagram was established. Hysteresis and temperature-dependent magnetization measurements show the occurrence of a re-entrant spin glass behaviour on cooling. With increasing applied field, the spin-freezing temperature decreases and disappears at

  6. Applications of amorphous soft magnetic materials

    Microsoft Academic Search

    H. Warlimont; R. Boll

    1982-01-01

    An introduction is given to melt-quenched amorphous alloys suitable as soft magnetic materials based on their saturation magnetization, hysteresis loop, core loss, elasto-magnetic and technological properties. After a survey of potential applications, the following examples are treated in particular: power distribution transformers, 400 Hz transformers, components for switched-mode power supplies, flexible magnetic shielding, elasto-magnetic transducers, variable delay lines, and magnetic

  7. Effective temperature in elastoplasticity of amorphous solids

    NASA Astrophysics Data System (ADS)

    Boué, Laurent; Hentschel, H. G. E.; Procaccia, Itamar; Regev, Ido; Zylberg, Jacques

    2010-03-01

    An effective temperature Teff which differs from the bath temperature is believed to play an essential role in the theory of elastoplasticity of amorphous solids. Here, we introduce a natural definition of Teff appearing naturally in a Boltzmann-like distribution of measurable structural features without recourse to any questionable assumption. The value of Teff is connected, using theory and scaling concepts, to the flow stress and the mean energy that characterize the elastoplastic flow.

  8. Magnetic and magnetoelastic properties of amorphous ribbons

    SciTech Connect

    Chiriac, H.; Ciobotaru, I.; Mohorianu, S. [Inst. of Technical Physics, Iasi (Romania)] [Inst. of Technical Physics, Iasi (Romania)

    1994-03-01

    A phenomenological model for the magnetic and magnetoelastic behavior of the field-annealed magnetostrictive ribbon is proposed. The basic hypothesis is that the magnetic domain coupling energy due to the inhomogeneity inherent to amorphous state is dependent on the reduced magnetization. The model takes into account the anisotropy energy, Zeeman energy, magnetoelastic energy and magnetic domain coupling energy. The magnetization, engineering magnetostriction and Young`s modulus are derived as continuous functions of the applied magnetic field and stress.

  9. Energy landscape of relaxed amorphous silicon

    Microsoft Academic Search

    Francis Valiquette; Normand Mousseau

    2003-01-01

    We analyze the structure of the energy landscape of a well-relaxed 1000-atom model of amorphous silicon using the activation-relaxation technique (ART nouveau). Generating more than 40 000 events starting from a single minimum, we find that activated mechanisms are local in nature, that they are distributed uniformly throughout the model, and that the activation energy is limited by the cost

  10. Nonequilibrium dynamics in an amorphous solid

    E-print Network

    Sunil P. Singh; Shankar P. Das

    2008-06-05

    The non-equilibrium dynamics of an amorphous solid is studied with a soft-spin type model. We show that the aging behavior in the glassy state follows a modified Kohlrausch-Williams-Watts (KWW) form similar to that obtained in Phys. Rev. Lett. {\\bf 95}, 055702 (2005) from analysis of the dielectric loss data. The nature of the fluctuation-dissipation theorem (FDT) violation is also studied in the time as well as correlation windows.

  11. Amorphous metal alloys wound cores test procedure

    Microsoft Academic Search

    A. Boglietti; P. Ferraris; M. Lazzari; F. Profumo

    1990-01-01

    The behavior of several samples of amorphous tape-wound magnetic cores excited under sine-wave voltage conditions at 50 Hz is investigated. Measurements of the induced-voltage and the excitation-current waveforms are used to obtain the dynamic (AC) core characteristic loop consisting of the flux density versus ampere-turns and to obtain the core losses. The possibility of using wound core transformers with either

  12. Synthesis of new amorphous metallic spin glasses

    DOEpatents

    Haushalter, R.C.

    1985-02-11

    Disclosed are: amorphous metallic precipitates having the formula (M/sub 1/)/sub a/(M/sub 2/)/sub b/ wherein M/sub 1/ is at least one transition metal, M/sub 2/ is at least one main group metal and the integers ''a'' and ''b'' provide stoichiometric balance; the precipitates having a degree of local order characteristic of chemical compounds from the precipitation process and useful electrical and mechanical properties.

  13. Synthesis of new amorphous metallic spin glasses

    DOEpatents

    Haushalter, Robert C. (Clinton, NJ)

    1988-01-01

    Amorphous metallic precipitates having the formula (M.sub.1).sub.a (M.sub.2).sub.b wherein M.sub.1 is at least one transition metal, M.sub.2 is at least one main group metal and the integers "a" and "b" provide stoichiometric balance; the precipitates having a degree of local order characteristic of chemical compounds from the precipitation process and useful electrical and mechanical properties.

  14. Characteristics of $\\\\hbox{Si\\/SiO}_{2}$ Interface Properties for CMOS Fabricated on Hybrid Orientation Substrate Using Amorphization\\/Templated Recrystallization (ATR) Method

    Microsoft Academic Search

    Po Chin Huang; San Lein Wu; Shoou Jinn Chang; Yao Tsung Huang; Jone F. Chen; Chien Ting Lin; Mike Ma; Osbert Cheng

    2011-01-01

    In this paper, for the hybrid orientation technology (HOT), we propose a modified amorphization\\/templated recrystallization (ATR) process to improve the material quality. The characterization of Si\\/SiO2 interface properties for comple- mentary metal-oxide-semiconductor (CMOS) devices fabricated on HOT wafers is demonstrated through charge pumping (CP) and low-frequency (1\\/f) noise measurements simultaneously. For n-type metal-oxide-semiconductor field-effect transistors (nMOSFETs), devices with the increased

  15. Wet oxidation of Al{sub x}Ga{sub 1{minus}x}As: Temporal evolution of composition and microstructure and the implications for metal-insulator-semiconductor applications

    SciTech Connect

    Ashby, C.I.; Sullivan, J.P.; Newcomer, P.P.; Missert, N.A.; Hou, H.Q.; Hammons, B.E.; Hafich, M.J.; Baca, A.G. [Sandia National Laboratories, Albuquerque, New Mexico 87185-0603 (United States)] [Sandia National Laboratories, Albuquerque, New Mexico 87185-0603 (United States)

    1997-05-01

    Three important processes dominate the wet thermal oxidation of Al{sub x}Ga{sub 1{minus}x}As on GaAs: (1) oxidation of Al and Ga in the Al{sub x}Ga{sub 1{minus}x}As alloy to form an amorphous oxide, (2) formation and elimination of crystalline and amorphous elemental As and of amorphous As{sub 2}O{sub 3}, and (3) crystallization of the amorphous oxide film. Residual As can lead to strong Fermi-level pinning at the oxidized AlGaAs/GaAs interface, up to a 100-fold increase in leakage current, and a 30{percent} increase in the dielectric constant of the oxide layer. Thermodynamically favored interfacial As may impose a fundamental limitation on the use of AlGaAs wet oxidation in metal-insulatorsemiconductor devices in the GaAs material system. {copyright} {ital 1997 American Institute of Physics.}

  16. Formation of iron disilicide on amorphous silicon

    NASA Astrophysics Data System (ADS)

    Erlesand, U.; Östling, M.; Bodén, K.

    1991-11-01

    Thin films of iron disilicide, ?-FeSi 2 were formed on both amorphous silicon and on crystalline silicon. The ?-phase is reported to be semiconducting with a direct band-gap of about 0.85-0.89 eV. This phase is known to form via a nucleation-controlled growth process on crystalline silicon and as a consequence a rather rough silicon/silicide interface is usually formed. In order to improve the interface a bilayer structure of amorphous silicon and iron was sequentially deposited on Czochralski <111> silicon in an e-gun evaporation system. Secondary ion mass spectrometry profiling (SIMS) and scanning electron micrographs revealed an improvement of the interface sharpness. Rutherford backscattering spectrometry (RBS) and X-ray diffractiometry showed ?-FeSi 2 formation already at 525°C. It was also observed that the silicide growth was diffusion-controlled, similar to what has been reported for example in the formation of NiSi 2 for the reaction of nickel on amorphous silicon. The kinetics of the FeSi 2 formation in the temperature range 525-625°C was studied by RBS and the activation energy was found to be 1.5 ± 0.1 eV.

  17. Growth and field emission properties of nanotip arrays of amorphous carbon with embedded hexagonal diamond nanoparticles

    Microsoft Academic Search

    Liang Xu; Shuankui Li; Zhiguo Wu; Huajun Li; De Yan; Chunyu Zhang; Pengju Zhang; Pengxun Yan; Xudong Li

    2011-01-01

    Nanotip arrays of amorphous carbon with embedded hexagonal diamond nanoparticles were prepared at room temperature for use\\u000a as excellent field emitters by a unique combination of anodic aluminum oxide (AAO) template and filtered cathodic arc plasma\\u000a (FCAP) technology. In order to avoid nanopore array formation on the AAO surface, an effective multi-step treatment employing\\u000a anodization and pore-widening processes alternately was

  18. Optical properties of Ba-In-Ga-based fluoride glasses for amplification at 1.3 um

    Microsoft Academic Search

    Jean-Luc Adam; Nathalie Rigout; Emmanuel Denoue; Frederic Smektala; Jacques Lucas

    1992-01-01

    Optical properties of rare-earth ions in glasses based on barium, indium, gallium, zinc, yttrium\\/lutetium, and thorium fluorides are presented. Multiphonon relaxations are determined and are found to be significantly lower than in ZBLAN fluoride glasses. Also, spectroscopic properties of the 1.3 micrometers emission of neodymium (III) and praseodymium (III) ions in fluoride glasses are studied. Excited state absorption from the

  19. Pulsed laser deposition of Co and Fe-based amorphous magnetic films and multilayers

    Microsoft Academic Search

    S. Acquaviva; A. P. Caricato; E. D'Anna; M. Fernández; A. Luches; Z. Frait; E. Majkova; M. Ozvold; S. Luby; P. Mengucci

    2003-01-01

    Magnetic films and multilayers were prepared by pulsed laser ablation of Co- and Fe-based amorphous magnetic ribbons with compositions Co67Cr7Fe4Si8B14 and Fe73.5Nb3Cu1Si13.5B9, respectively. Targets were ablated in vacuum (?10?5 Pa) by KrF excimer laser pulses at fluences from 3 to 7 J\\/cm2. Films were deposited on oxidized silicon wafers, placed 80 mm apart from the target. From X-ray diffraction spectra

  20. Fabrication and characterization of thin-film transistors with amorphous In-Ga-Zn-O layers

    NASA Astrophysics Data System (ADS)

    Taube, A.; Kaczmarski, J.; Ekielski, M.; Pucicki, D.; Kami?ska, E.; Piotrowska, A.

    2013-07-01

    We report on the fabrication and performance of amorphous oxide thin-film transistors with In-Ga-Zn-O deposited by RF magnetron reactive sputtering for semiconductor channel layer. The influence of the electrical transport properties of the channel on the electrical parameters of thin-film transistors has been determined. By optimizing process parameters depletion-mode n-channel devices with maximum field-effect mobility (?FE) 10.1 cm2/Vs, threshold voltage Vth=-4.85V and on to off current ratio (Ion/Ioff)=2.1x102 have been demonstrated.

  1. Improved conversion efficiency of amorphous Si solar cells using a mesoporous ZnO pattern

    NASA Astrophysics Data System (ADS)

    Go, Bit-Na; Kim, Yang Doo; suk Oh, Kyoung; Kim, Chaehyun; Choi, Hak-Jong; Lee, Heon

    2014-09-01

    To provide a front transparent electrode for use in highly efficient hydrogenated amorphous silicon (a-Si:H) thin-film solar cells, porous flat layer and micro-patterns of zinc oxide (ZnO) nanoparticle (NP) layers were prepared through ultraviolet nanoimprint lithography (UV-NIL) and deposited on Al-doped ZnO (AZO) layers. Through this, it was found that a porous micro-pattern of ZnO NPs dispersed in resin can optimize the light-trapping pattern, with the efficiency of solar cells based on patterned or flat mesoporous ZnO layers increased by 27% and 12%, respectively.

  2. Improved conversion efficiency of amorphous Si solar cells using a mesoporous ZnO pattern.

    PubMed

    Go, Bit-Na; Kim, Yang Doo; Suk Oh, Kyoung; Kim, Chaehyun; Choi, Hak-Jong; Lee, Heon

    2014-01-01

    To provide a front transparent electrode for use in highly efficient hydrogenated amorphous silicon (a-Si:H) thin-film solar cells, porous flat layer and micro-patterns of zinc oxide (ZnO) nanoparticle (NP) layers were prepared through ultraviolet nanoimprint lithography (UV-NIL) and deposited on Al-doped ZnO (AZO) layers. Through this, it was found that a porous micro-pattern of ZnO NPs dispersed in resin can optimize the light-trapping pattern, with the efficiency of solar cells based on patterned or flat mesoporous ZnO layers increased by 27% and 12%, respectively. PMID:25276101

  3. Defect level distributions and atomic relaxations induced by charge trapping in amorphous silica

    SciTech Connect

    Anderson, Nathan L.; Vedula, Ravi P.; Schultz, Peter A.; Van Ginhoven, Renee M.; Strachan, Alejandro

    2012-04-26

    We compute the distribution of electronic levels of native defects in amorphous silica from total energy differences of charge-state density functional theory calculations over an ensemble of atomic structures. The predicted distributions reproduce results from trap spectroscopy by charge injection experiments, validating the calculations. Furthermore, our study characterizes the experimentally inaccessible contributions of individual defect types to the overall distribution. Computed electron and hole trapping levels provide insight into the positive charge buildup in bulk silica observed in negative-bias-temperature-instability, an important degradation mechanism of metal-oxide-semiconductor devices.

  4. Multilevel unipolar resistive memory switching in amorphous SmGdO3 thin film

    NASA Astrophysics Data System (ADS)

    Sharma, Yogesh; Misra, Pankaj; Pavunny, Shojan P.; Katiyar, Ram S.

    2014-02-01

    Multilevel resistive switching was observed in random access memory device using amorphous SmGdO3 (SGO) ternary oxide thin films. Non-volatile and stable 4-level resistance states with sufficient margin of resistance ratios were observed by varying compliance current which was attributed to compliance current dependent variation in size of conducting filaments. As fabricated Pt/SGO/Pt devices exhibited excellent switching parameters such as stable resistance ratios of reset (ON) to set (OFF) states, non-overlapping switching voltages, excellent data retention, and endurance. Temperature dependent variation of resistances of ON and OFF states of the device was studied to elucidate current conduction and resistive switching mechanisms.

  5. Production of strontium-substituted lanthanum manganite perovskite powder by the amorphous citrate process

    Microsoft Academic Search

    M. S. G. Baythoun; F. R. Sale

    1982-01-01

    The amorphous citrate process has been used to produce Mn2O3, Mn3O4, LaMnO3, SrMnO3 and strontium-substituted LaMnO3. The citrate-nitrate gels were dehydrated at 70‡ C to yield solid precursor materials. The decomposition\\/oxidation of the precursors have been studied using thermogravimetry and evolved gas analysis. The products of decomposition have been characterized by X-ray diffraction analysis, scanning electron microscopy and, in the

  6. Hexagonally ordered mesoporous ternary Li2O-TiO2-P2O5 oxides with high lithium content.

    PubMed

    Li, Donglin; Zhou, Haoshen; Honma, Itaru; Ichihara, Masaki

    2005-11-01

    Hexagonally ordered mesoporous Li2O-TiO2-P2O5 oxides with high lithium content have been synthesized using surfactant-templated self-assembly; this ternary oxide has been specifically designed to yield a variety of mesoporous frameworks including a nanocomposite, amorphous multicomponent oxide, and almost fully nanocrystalline anatase. PMID:16228030

  7. Ferroelectric properties of vinylidene fluoride-trifluoroethylene copolymer thin films fabricated on amorphous alloy electrode

    NASA Astrophysics Data System (ADS)

    Nakajima, Takashi; Yamaura, Shin-ichi; Furukawa, Takeo; Okamura, Soichiro

    2014-09-01

    We have investigated the structure and ferroelectric properties of vinylidene fluoride-trifluoroethylene (VDF-TrFE) copolymer thin films fabricated on amorphous alloy electrodes. Thin films of amorphous Pd-Cu-Si alloys with various compositions were successfully prepared by sputtering deposition. An atomically flat surface resulting from a fully amorphous structure of Pd-Cu-Si was obtained upon achieving a uniform surface of a spin-coated VDF-TrFE copolymer thin film. X-ray diffraction (XRD) measurements revealed that the crystalline structure of the VDF-TrFE copolymer thin films was of ferroelectric ?-phase, being independent of the composition and crystalline state of the Pd-Cu-Si alloy. The clearly observed D-E hysteresis loops showed a remanent polarization of 0.075 C/m2 and a coercive field of 90 MV/m at a measurement frequency of 10 Hz for a 50-nm-thick film, which is almost consistent with the results obtained with Pt electrode samples. We also observed the thinning-induced reduction of remanent polarization, which was explained by the depolarization field induced by the surface dead layer in VDF-TrFE copolymer rather than the oxidized layer in Pd-Cu-Si alloy electrode.

  8. Formation of metastable structures and amorphous phases in Pu-based systems using the sputtering technique

    NASA Astrophysics Data System (ADS)

    Rizzo, H. F.; Massalski, T. B.; Echeverria, A. W.

    1989-05-01

    The triode sputtering technique with a split-target arrangement was used to obtain metastable crystalline and amorphous phases in ten binary systems of Pu with Si, Al, V, Fe, Co, Pd, Ta, Re, Os, and Ir. In addition to metastable extensions of solid solubility occurring from the binary sides of some systems, wide ranges of metallic glass formation have been observed in several systems. Extended bcc solid solution ranges were observed in Pu-Ta and Pu-V systems. Unlike in the case of many liquid-quenched alloys, the ranges of amorphous phase formation obtained with sputtering appear to have little to do with the form of the corresponding phase diagram. However, the extent of the observed ranges on the Pu-rich side was found to obey approximately the atomic size mismatch relationship. The nearest neighbor distances (NNDs) evaluated with X-ray diffraction show many unusual deviations from an assumed Vegard’s Law, which can be interpreted in relation to the changing electronic configuration of the Pu atom when present in different environments. Exposure of several amorphous alloys to severe oxidation environments did not results in observable corrosion.

  9. Amorphous silicon/amorphous silicon carbide heterojunctions applied to memory device structures

    NASA Astrophysics Data System (ADS)

    Sakata, I.; Yamanaka, M.; Nagai, K.; Sekigawa, T.; Hayashi, Y.

    1994-04-01

    It has been proposed and experimentally confirmed that band-engineered hydrogenated amorphous silicon (a-Si:H)/hydrogenated amorphous silicon carbide (a-SiC:H) heterojunction on c-Si can be applied to electrically programmable and erasable memory devices. A test diode with the structure c-Si/graded a-SiC:H/a-Si:H/uniform a-SICK/Al exhibits a large hysteresis in the C-V characteristic with a retention time of 0.8s at room temperature.

  10. Amorphization and amorphous stability of Bi2Te3 chalcogenide films

    NASA Astrophysics Data System (ADS)

    Ju, C.; Cheng, X. M.; Miao, X. S.

    2012-04-01

    Si doping is proposed to be an effective way to improve the amorphous stability of Bi2Te3 thin film. Structural changes in doped crystalline phases are revealed by the bonding nature given by x-ray photoelectron spectroscopy results. Based on ab initio simulations, the energy, electronic and structural changes induced by Si doping are studied. The results show that both nucleation and growth of crystallite are suppressed by Si doping, so that the stability of amorphous Bi2Te3 is improved.

  11. Infrared emission from hydrogenated amorphous carbon and amorphous carbon grains in the interstellar medium

    NASA Technical Reports Server (NTRS)

    Duley, W. W.; Jones, A. P.; Taylor, S. D.; Williams, D. A.

    1993-01-01

    The correlations deduced by Boulanger et al. (1990) from IRAS maps of the Chamaeleon, Taurus and Ursa Major molecular cloud complexes are interpreted in terms of the evolutionary hydrogenated amorphous carbon model of interstellar dust. In particular, regions of relatively strong 12-micron emission may be regions where recently accreted carbon is being converted by ambient UV to small PAHs in situ. Regions of weak 12-micron emission are probably quiescent regions where carbon has been annealed to amorphous carbon. Observational consequences of these inferences are briefly described.

  12. Proximity Effect - Amorphous Sn-Fe, Amorphous Bi-Fe Films

    E-print Network

    CORT, G.; Naugle, Donald G.

    1981-01-01

    report the results of an experimental investigation of the proximity effect in sandwiches of amorphous Bi-Fe and amorphous Sn-Fe. The measurements on a-Bi films resolve a controver- sy concerning its coherence length while that derived for a... are apparent. The most obvious is that the thicknesses measured for the two experiments were in error and that their agreement was fortuitous. Silverman" has suggested that expansion of the a-Bi films on crystallization to the semimetal phase which occurs...

  13. Amorphous silicon/polycrystalline thin film solar cells

    SciTech Connect

    Ullal, H.S.

    1991-03-13

    An improved photovoltaic solar cell is described including a p-type amorphous silicon layer, intrinsic amorphous silicon, and an n-type polycrystalline semiconductor such as cadmium sulfide, cadmium zinc sulfide, zinc selenide, gallium phosphide, and gallium nitride. The polycrystalline semiconductor has an energy bandgap greater than that of the amorphous silicon. The solar cell can be provided as a single-junction device or a multijunction device.

  14. Anisotropic grain growth of mullite in high-energy ball milled powders doped with transition metal oxides

    Microsoft Academic Search

    L. B. Kong; T. S. Zhang; J. Ma; F. Boey

    2003-01-01

    Dense mullite ceramics with anisotropic grains were derived from the high-energy ball milled mixtures of Al2O3 and amorphous silica with the presence of transition metal oxides (FeO1.5, CoO and NiO). The mullitization and grain growth behavior of the unmilled mixture without the addition of the transition metal oxides and the undoped system of Al2O3 and amorphous silica with and without

  15. Chain Conformation of Amorphous Substituted Poly(paraphenylenes)

    NASA Astrophysics Data System (ADS)

    Vaia, Richard A.; Dean, Derrick R.; Krishnamoorti, Ramanan; Trimmmer, Mark

    1997-03-01

    High molecular weight, substituted poly(paraphenylenes) (SPPP) are emerging as a family of heat-resistant, high modulus resins which have many potential military and civilian applications. In addition to a high thermal-oxidative stability (500 C) and a large tensile and flexural moduli (7-10 GPa), the molecular architecture, para-linked phenyl units with various benzyol substituents randomly distributed along the backbone, leads to amorphous polymers exhibiting traditional thermoplastic behavior. Given the rigid nature of the paraphenylene backbone, these structural characteristics are surprising. Thermomechanical experiments and scattering experiments (small-angle neutron scattering and wide-angle x-ray diffraction) have been used to determine the effect of repeat-unit orientation and substituent size on the conformation of the polymer chain. Understanding the influence of molecular architecture on chain conformation in these systems will lead to new structure-property relationships that may be applicable to the design of other high-performance rigid-rod systems.

  16. Transient laser annealing of zinc oxide nanoparticle inks to fabricate zinc oxide thin film transistors

    NASA Astrophysics Data System (ADS)

    Willemann, Michael

    Display technology, which relies exclusively on amorphous silicon as the active material for driver electronics, has reached multiple impasses that limit future progress. In order to deliver higher resolutions, higher refresh rates, new display technologies, and innovative form factors, driver electronics must transition to higher performance materials like amorphous oxide semiconductors (AOSs). Transient laser annealing offers an attractive means to maximize performance while minimizing thermal budget, making it compatible with flexible back plane materials and roll-to-roll processing. This research investigates the deposition and annealing of zinc oxide nanoparticle inks to form fully densified crystalline and amorphous zinc oxide films. Processing routes for nanoparticle annealing, including ligand removal, calcining, and excimer pulse laser sintering on the nanosecond time scale, will be introduced that minimize defect formation and suppress the anomalous n-conductivity which is a major challenge to zinc oxide processing. Resistivities as high as 6 x 107 O-cm have been demonstrated. Laser processing on longer millisecond time scales can control defect formation to produce ZnO films without extrinsic doping which have low resistivity for intrinsic oxides, in the range of 10-1 - 10-2 O-cm. Finally, a viable process for the production of backgated ZnO transistors with promising characteristics is presented and the future implications for AOSs and transient thermal processing will be discussed.

  17. Triple-junction amorphous silicon alloy solar cell with 14.6{percent} initial and 13.0{percent} stable conversion efficiencies

    SciTech Connect

    Yang, J.; Banerjee, A.; Guha, S. [United Solar Systems Corporation, Troy, Michigan 48084 (United States)] [United Solar Systems Corporation, Troy, Michigan 48084 (United States)

    1997-06-01

    We have achieved 14.6{percent} initial and 13.0{percent} stable conversion efficiencies using an amorphous silicon-based alloy in a spectrum-splitting, triple-junction structure. These efficiencies have been confirmed independently by the National Renewable Energy Laboratory. Key factors leading to this major advance include improvements made in the low band-gap amorphous silicon{endash}germanium alloy cell, the pn tunnel junction between the component cells, and the top conducting oxide. {copyright} {ital 1997 American Institute of Physics.}

  18. Amorphous and crystalline aerosol particles interacting with water vapor: conceptual framework and experimental evidence for restructuring, phase transitions and kinetic limitations

    NASA Astrophysics Data System (ADS)

    Mikhailov, E.; Vlasenko, S.; Martin, S. T.; Koop, T.; Pöschl, U.

    2009-12-01

    Interactions with water are crucial for the properties, transformation and climate effects of atmospheric aerosols. Here we present a conceptual framework for the interaction of amorphous aerosol particles with water vapor, outlining characteristic features and differences in comparison to crystalline particles. We used a hygroscopicity tandem differential mobility analyzer (H-TDMA) to characterize the hydration and dehydration of crystalline ammonium sulfate, amorphous oxalic acid and amorphous levoglucosan particles (diameter ~100 nm, relative humidity 5-95% at 298 K). The experimental data and accompanying Köhler model calculations provide new insights into particle microstructure, surface adsorption, bulk absorption, phase transitions and hygroscopic growth. The results of these and related investigations lead to the following conclusions: (1) Many organic substances, including carboxylic acids, carbohydrates and proteins, tend to form amorphous rather than crystalline phases upon drying of aqueous solution droplets. Depending on viscosity and microstructure, the amorphous phases can be classified as glasses, rubbers, gels or viscous liquids. (2) Amorphous organic substances tend to absorb water vapor and undergo gradual deliquescence and hygroscopic growth at lower relative humidity than their crystalline counterparts. (3) In the course of hydration and dehydration, certain organic substances can form rubber- or gel-like structures (supramolecular networks) and undergo transitions between swollen and collapsed network structures. (4) Organic gels or (semi-)solid amorphous shells (glassy, rubbery, ultra-viscous) with low molecular diffusivity can kinetically limit the uptake and release of water and may influence the hygroscopic growth and activation of aerosol particles as cloud condensation nuclei (CCN) and ice nuclei (IN). Moreover, (semi-)solid amorphous phases may influence the uptake of gaseous photo-oxidants and the chemical transformation and aging of atmospheric aerosols. (5) The shape and porosity of amorphous and crystalline particles formed upon dehydration of aqueous solution droplets depend on chemical composition and drying conditions. The apparent volume void fractions of particles with highly porous structures can range up to ~50% or more (xerogels, aerogels). (6) For efficient description of water uptake and phase transitions of aerosol particles, we propose not to limit the terms deliquescence and efflorescence to equilibrium phase transitions of crystalline substances. Instead we propose generalized definitions according to which amorphous and crystalline components can undergo gradual or prompt, partial or full deliquescence or efflorescence. We suggest that (semi-)solid amorphous phases may be important not only in the upper atmosphere as suggested in recent studies of glass formation at low temperatures. Depending on relative humidity, (semi-)solid phases and moisture-induced glass transitions may also play a role in gas-particle interactions at ambient temperatures in the lower atmosphere.

  19. Extremal model for amorphous media plasticity.

    PubMed

    Baret, Jean-Christophe; Vandembroucq, Damien; Roux, Stéphane

    2002-11-01

    An extremal model for the plasticity of amorphous materials is studied in a simple two-dimensional antiplane geometry. The steady state is analyzed through numerical simulations. Long-range spatial and temporal correlations in local slip events are shown to develop, leading to nontrivial and highly anisotropic scaling laws. In particular, the plastic strain is shown to concentrate statistically over a region which tends to align perpendicular to the displacement gradient. By construction, the model can be seen as giving rise to a depinning transition, the threshold of which (i.e., the macroscopic yield stress) also reveals scaling properties reflecting the localization of the activity. PMID:12443126

  20. Progress in amorphous silicon based multijunction modules

    SciTech Connect

    Arya, R.R.; Oswald, R.S.; Li, Y.M. [Solarex Corp., Newtown, PA (United States). Thin-Film Div.] [and others

    1994-12-31

    Advances in amorphous silicon based alloys and device structure have led to the demonstration of 10.5% initial efficiency and 9.1% stabilized efficiency on 1 Ft{sup 2} a-Si/a-SiGe tandem junction module. Scale-up to 4 Ft{sup 2} in pilot production has resulted in the best initial efficiency of 9.75% as measured by NREL, which should result in a stabilized efficiency over 8%. Presently the 4 Ft{sup 2} modules have an average initial efficiency of 8.75% and a stabilized average efficiency of about 7.5%, as measured by Solarex.

  1. Femtosecond laser crystallization of amorphous Ge

    SciTech Connect

    Salihoglu, Omer; Aydinli, Atilla [Physics Department, Bilkent University, Ankara 06800 (Turkey); Kueruem, Ulas; Gul Yaglioglu, H.; Elmali, Ayhan [Department of Engineering Physics, Ankara University, 06100 Ankara (Turkey)

    2011-06-15

    Ultrafast crystallization of amorphous germanium (a-Ge) in ambient has been studied. Plasma enhanced chemical vapor deposition grown a-Ge was irradiated with single femtosecond laser pulses of various durations with a range of fluences from below melting to above ablation threshold. Extensive use of Raman scattering has been employed to determine post solidification features aided by scanning electron microscopy and atomic force microscopy measurements. Linewidth of the Ge optic phonon at 300 cm{sup -1} as a function of laser fluence provides a signature for the crystallization of a-Ge. Various crystallization regimes including nanostructures in the form of nanospheres have been identified.

  2. On the crystallization of amorphous germanium films

    NASA Astrophysics Data System (ADS)

    Edelman, F.; Komem, Y.; Bendayan, M.; Beserman, R.

    1993-06-01

    The incubation time for crystallization of amorphous Ge (a-Ge) films, deposited by e-gun, was studied as a function of temperature between 150 and 500°C by means of both in situ transmission electron microscopy and Raman scattering spectroscopy. The temperature dependence of t0 follows an Arrhenius curve with an activation energy of 2.0 eV for free-sustained a-Ge films. In the case where the a-Ge films were on Si 3N 4 substrate, the activation energy of the incubation process was 1.3 eV.

  3. Deuterium in crystalline and amorphous silicon

    SciTech Connect

    Borzi, R.; Ma, H.; Fedders, P.A.; Leopold, D.J.; Norberg, R.E.; Boyce, J.B.; Johnson, N.M.; Ready, S.E.; Walker, J.

    1997-07-01

    The authors report deuteron magnetic resonance (DMR) measurements on aged deuterium-implanted single crystal n-type silicon and comparisons with amorphous silicon spectra. The sample film was prepared six years ago by deuteration from a-D{sub 2} plasma and evaluated by a variety of experimental methods. Deuterium has been evolving with time and the present DMR signal shows a smaller deuteron population. A doublet from Si-D configurations along (111) has decreased more than have central molecular DMR components, which include 47 and 12 kHz FWHM gaussians. Transient DMR magnetization recoveries indicate spin lattice relaxation to para-D{sub 2} relaxation centers.

  4. Ion beam hydrogenation of amorphous silicon

    SciTech Connect

    Tsuo, Y.S.; Smith, E.B.; Deb, S.K.

    1987-11-02

    A Kaufman ion beam source was used to implant hydrogen atoms into glow-discharge-deposited amorphous silicon materials in which the hydrogen content had been driven out by heating. We found that the hydrogen atoms introduced by this low-energy (less than 700 eV) ion implantation method bonded predominantly as SiH. An air mass one, photo-to-dark-conductivity ratio as high as 5.6 x 10/sup 5/ has been obtained with hydrogen-implanted materials. No light-induced reduction of the photo- and dark conductivities has been observed in these materials after 20 h of AMl illumnination.

  5. Preferred orientations of laterally grown silicon films over amorphous substrates using the vapor-liquid-solid technique

    NASA Astrophysics Data System (ADS)

    LeBoeuf, J. L.; Brodusch, N.; Gauvin, R.; Quitoriano, N. J.

    2014-12-01

    A novel method has been optimized so that adhesion layers are no longer needed to reliably deposit patterned gold structures on amorphous substrates. Using this technique allows for the fabrication of amorphous oxide templates known as micro-crucibles, which confine a vapor-liquid-solid (VLS) catalyst of nominally pure gold to a specific geometry. Within these confined templates of amorphous materials, faceted silicon crystals have been grown laterally. The novel deposition technique, which enables the nominally pure gold catalyst, involves the undercutting of an initial chromium adhesion layer. Using electron backscatter diffraction it was found that silicon nucleated in these micro-crucibles were 30% single crystals, 45% potentially twinned crystals and 25% polycrystals for the experimental conditions used. Single, potentially twinned, and polycrystals all had an aversion to growth with the {1 0 0} surface parallel to the amorphous substrate. Closer analysis of grain boundaries of potentially twinned and polycrystalline samples revealed that the overwhelming majority of them were of the 60° ?3 coherent twin boundary type. The large amount of coherent twin boundaries present in the grown, two-dimensional silicon crystals suggest that lateral VLS growth occurs very close to thermodynamic equilibrium. It is suggested that free energy fluctuations during growth or cooling, and impurities were the causes for this twinning.

  6. Angle-dependent photoluminescence spectra of hydrogenated amorphous silicon thin films

    NASA Astrophysics Data System (ADS)

    Marra, D. C.; Aydil, E. S.; Joo, S.-J.; Yoon, E.; Srdanov, V. I.

    2000-11-01

    Multiple sharp peaks were observed in the visible photoluminescence spectra of amorphous silicon thin films, prepared by ultrahigh vacuum electron cyclotron resonance chemical vapor deposition on oxidized silicon substrates. The angular dependence of the photoluminescence, measured by a home-built fiber-optics device, revealed that the origin of these sharp features was due to Fabry-Pérot cavity interference effects. The interference is enhanced by deposition on thermally grown oxide layers with relatively smooth surfaces. We also consider how thin-film interference effects can add to the already existing confusion regarding the photoluminescence (PL) mechanism of porous and other luminescent forms of silicon and propose angle-dependent PL spectroscopy as a remedy for identifying spectral features due to interference effects.

  7. Interpretation of Raman spectra of disordered and amorphous carbon

    Microsoft Academic Search

    A. C. Ferrari; J. Robertson

    2000-01-01

    The model and theoretical understanding of the Raman spectra in disordered and amorphous carbon are given. The nature of the G and D vibration modes in graphite is analyzed in terms of the resonant excitation of pi states and the long-range polarizability of pi bonding. Visible Raman data on disordered, amorphous, and diamondlike carbon are classified in a three-stage model

  8. Pentagonal puckering in a sheet of amorphous graphene

    E-print Network

    Thorpe, Michael

    Pentagonal puckering in a sheet of amorphous graphene Y. Li 1 , F. Inam 2 , Avishek Kumar 3 , M. F 2011 Published online 13 July 2011 Keywords amorphous graphene, density functional theory, fullerenes Ordered graphene has been extensively studied. In this paper, we undertake a density functional study

  9. 13th International Conference on Liquid and Amorphous Metals

    Microsoft Academic Search

    Pjotr Popel; Boris Gelchinskii; Valeriy Sidorov; Leonid Son; Alexandre Sabirzjanov

    2007-01-01

    The state of the art in the field of liquid and amorphous metals and alloys is regularly updated through two series of complementary international conferences, the LAM (Liquid and Amorphous Metals) and the RQ (Rapidly Quenched Materials). The first series of the conferences started as LM-1 in 1966 at Brookhaven for the basic understanding of liquid metals. The subsequent LM

  10. Optical conductivity of amorphous Ta and beta-Ta films

    NASA Technical Reports Server (NTRS)

    Nestell, J. E., Jr.; Scoles, K. J.; Christy, R. W.

    1982-01-01

    Tantalum films evaporated in high vacuum onto liquid-nitrogen-cooled substrates had an amorphous structure that persisted even after warming to room temperature. The optical conductivity (as well as the dc conductivity) of the amorphous films differed significantly from that of the bcc films.

  11. Design and Preparation of New Soft Magnetic Amorphous Ferromagnets

    Microsoft Academic Search

    H. Chiriac; N. Lupu

    DC and AC magnetic properties of Fe-based bulk amorphous alloys as thick meltspun ribbons, cast rods and torroids are investigated. The influence of the preparation conditions, composition, frequency, and treatments on the electrical and magnetic characteristics is discussed. The magnetic behaviour of amorphous wires and microwires is presented. The correlation between the diameter of the wires, the magnitude of the

  12. Spin Relaxation Theory in Amorphous Silicon and Germanium

    NASA Astrophysics Data System (ADS)

    Harmon, Nicholas; Flatté, Michael E.

    2014-03-01

    Research into spintronic devices using amorphous inorganic semiconductors has seen little attention despite the surge of interest in amorphous organic spintronics. In many ways the two materials are similar - for instance hopping transport is observed in both for certain regimes. Amorphous semiconductors such as silicon and germanium offer advantages such as the ability to greatly reduce and control hyperfine field effects by the process of hydrogenation, and considerably higher mobilities. We present a theory of spin relaxation in amorphous semiconductors based on the theory of a continuous-time random walk, and obtain analytic results in several regimes. We also calculate the spin relaxation with a Monte Carlo simulation. We find that the spin-orbit coupling is the primary limit to long spin lifetimes in amorphous silicon and germanium. The theory we introduce is very general and can also be applied to amorphous organic semiconductors. We compare our results for amorphous inorganic and amorphous organic materials. This work was supported in part by C- SPIN, one of six centers of STARnet, a Semiconductor Research Corporation program, sponsored by MARCO and DARPA.

  13. Annealed high-density amorphous ice under pressure

    E-print Network

    Loss, Daniel

    ARTICLES Annealed high-density amorphous ice under pressure RICHARD J. NELMES1 *, JOHN S. LOVEDAY1 ices--LDA and HDA--as proxies for the supercooled liquids. But numerous studies over the past decade a previously uncharacterized state of high-density amorphous ice obtained if HDA is annealed at pressures near

  14. A converter-type magnetometer using amorphous ribbon or wire

    Microsoft Academic Search

    Marek Z. Kozak; Eugeniusz Misiuk; Waldemar Kwiatkowski

    1991-01-01

    The accurate and quick-response magnetometer presented here is composed of a resonant circuit with an amorphous core, an operational amplifier, and a voltage-current converter. Nonmagnetostrictive amorphous ribbons or wires are used in the straight form for sensing strength and direction of the dc magnetic field. The range having good linearity strongly depends on the converter current and the demagnetizing field

  15. Synthesis of transition metal nitride by nitridation of metastable oxide precursor

    NASA Astrophysics Data System (ADS)

    Wang, Huamin; Wu, Zijie; Kong, Jing; Wang, Zhiqiang; Zhang, Minghui

    2012-10-01

    Metastable transition metal oxides were used as precursors to synthesize transition metal nitrides at low temperature. Amorphous MoO2 was prepared by reduction of (NH4)6Mo7O24 solution with hydrazine. As-synthesized amorphous MoO2 was transformed into fcc ?-Mo2N at 400 °C and then into hexagonal ?-MoN by further increasing the temperature to 600 °C under a NH3 flow. The nitridation temperature employed here is much lower than that employed in nitridation of crystalline materials, and the amorphous materials underwent a unique nitridation process. Besides this, the bimetallic nitride Ni2Mo3N was also synthesized by nitridating amorphous bimetallic precursor. These results suggested that the nitridation of amorphous precursor possessed potential to be a general method for synthesizing many interstitial metallic compounds, such as nitrides and carbides at low temperature.

  16. The future of amorphous silicon photovoltaic technology

    SciTech Connect

    Crandall, R.; Luft, W.

    1995-06-01

    Amorphous silicon modules are commercially available. They are the first truly commercial thin-film photovoltaic (PV) devices. Well-defined production processes over very large areas (>1 m{sup 2}) have been implemented. There are few environmental issues during manufacturing, deployment in the field, or with the eventual disposal of the modules. Manufacturing safety issues are well characterized and controllable. The highest measured initial efficiency to date is 13.7% for a small triple-stacked cell and the highest stabilized module efficiency is 10%. There is a consensus among researchers, that in order to achieve a 15% stabilized efficiency, a triple-junction amorphous silicon structure is required. Fundamental improvements in alloys are needed for higher efficiencies. This is being pursued through the DOE/NREL Thin-Film Partnership Program. Cost reductions through improved manufacturing processes are being pursued under the National Renewable Energy Laboratory/US Department of Energy (NREL/DOE)-sponsored research in manufacturing technology (PVMaT). Much of the work in designing a-Si devices is a result of trying to compensate for the Staebler-Wronski effect. Some new deposition techniques hold promise because they have produced materials with lower stabilized defect densities. However, none has yet produced a high efficiency device and shown it to be more stable than those from standard glow discharge deposited material.

  17. Structural Characteristics of Synthetic Amorphous Calcium Carbonate

    SciTech Connect

    Michel, F. Marc; MacDonald, Jason; Feng, Jian; Phillips, Brian L.; Ehm, Lars; Tarabrella, Cathy; Parise, John B.; Reeder, Richard J. (SBU)

    2008-08-06

    Amorphous calcium carbonate (ACC) is an important phase involved in calcification by a wide variety of invertebrate organisms and is of technological interest in the development of functional materials. Despite widespread scientific interest in this phase a full characterization of structure is lacking. This is mainly due to its metastability and difficulties in evaluating structure using conventional structure determination methods. Here we present new findings from the application of two techniques, pair distribution function analysis and nuclear magnetic resonance spectroscopy, which provide new insight to structural aspects of synthetic ACC. Several important results have emerged from this study of ACC formed in vitro using two common preparation methods: (1) ACC exhibits no structural coherence over distances > 15 {angstrom} and is truly amorphous; (2) most of the hydrogen in ACC is present as structural H{sub 2}O, about half of which undergoes restricted motion on the millisecond time scale near room temperature; (3) the short- and intermediate-range structure of ACC shows no distinct match to any known structure in the calcium carbonate system; and (4) most of the carbonate in ACC is monodentate making it distinctly different from monohydrocalcite. Although the structure of synthetic ACC is still not fully understood, the results presented provide an important baseline for future experiments evaluating biogenic ACC and samples containing certain additives that may play a role in stabilization of ACC, crystallization kinetics, and final polymorph selection.

  18. Hydrogenated amorphous silicon-germanium alloys

    SciTech Connect

    Luft, W.

    1988-02-01

    This report describes the effects of the germanium fraction in hydrogenated amorphous silicon-germanium alloys on various parameters, especially those that are indicators of film quality, and the impact of deposition methods, feedgas mixtures, and other deposition parameters on a SiGe:H and a-SiGe:H:F film characteristics and quality. Literature data show the relationship between germanium content, hydrogen content, deposition method (various glow discharges and CVD), feedgas lmixture, and other parameters and properties, such as optical band gap, dark and photoconductivities, photosensitivity, activation energy, Urbach parameter, and spin density. Some of these are convenient quality indicators; another is the absence of microstructure. Examining RF glow discharge with both a diode and triode geometry, DC proximity glow discharge, microwave glow discharge, and photo-CVD, using gas mixtures such as hydrogen-diluted and undiluted mixtures of silane/germane, disilane/germane, silane/germaniumtetrafluoride, and others, it was observed that hydrogen dilution (or inert gas dilution) is essential in achieving high photosensitivity in silicon-germanium alloys (in contradistinction to amorphous hydrogenated silicon). Hydrogen dilution results in a higher photosensitivity than do undiluted gas mixtures. 81 refs., 42 figs., 7 tabs.

  19. Characterization of sputtered amorphous platinum dioxide films

    SciTech Connect

    Maya, L. [Chemical and Analytical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6119 (United States)] [Chemical and Analytical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6119 (United States); Riester, L. [Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)] [Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Thundat, T. [Life Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)] [Life Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Yust, C.S. [Consultant, Oak Ridge, Tennessee 37830 (United States)] [Consultant, Oak Ridge, Tennessee 37830 (United States)

    1998-12-01

    Amorphous platinum dioxide, a-PtO{sub 2}, films are formed commonly during reactive sputtering of platinum at relatively high power density levels and high oxygen partial pressures. The structure of a-PtO{sub 2} is intermediate between the crystalline alpha and beta phases of this compound and either phase may form upon annealing or by lowering the power density during sputtering. Amorphous platinum dioxide is a semiconductor, and its resistivity depends on deposition parameters. Films of a-PtO{sub 2} are dense, chemically resistant, smooth, reflective, and have a hardness similar to titanium nitride. The films may be reduced in hydrogen at room temperature or in carbon monoxide at 200thinsp{degree}C to produce metallic platinum with crystallite sizes in the range of 5{endash}10 nm. Any of these properties may be exploited to produce films that could be used in the development of sensors, optical materials, and in microelectronics. {copyright} {ital 1998 American Institute of Physics.}

  20. A Surface Precipitation Model for the Sorption of Cations on Metal Oxides

    E-print Network

    Morel, François M. M.

    A Surface Precipitation Model for the Sorption of Cations on Metal Oxides KEVIN J. FARLEY, ~ DAVID metallic oxides, as homogeneous phases or more commonly as coatings on other solid particles, are dominant to describethe equilibrium sorption of metal cations on amorphous iron hydroxide is demonstrated. The model can

  1. Low Temperature, High-Performance, Solution-Processed Indium Oxide Thin Film Transistors

    Microsoft Academic Search

    Seung-Yeol Han; Gregory S. Herman; Chih-hung Chang

    Transparent oxide semiconductors have been studied extensively as active layers in thin film transistors (TFTs) (1). Oxide-based semiconductors have various merits compared to hydrogenated amorphous silicon and organic semiconductors. However, most AOS TFTs are fabricated by vacuum deposition techniques, such as pulsed laser deposition, and rf magnetron sputtering, dc sputtering, and plasma enhanced chemical vapor deposition. Recently, a great deal

  2. Salt Fog Testing Iron-Based Amorphous Alloys

    SciTech Connect

    Rebak, Raul B. [Chemistry and Materials Science, Lawrence Livermore National Laboratory, 7000 East Ave, L- 631, Livermore, CA, 94550 (United States); Aprigliano, Louis F. [Consultant, Berlin, MD, 21811 (United States); Day, S. Daniel; Farmer, Joseph C. [LLNL, Livermore, CA, 94550 (United States)

    2007-07-01

    Iron-based amorphous alloys are hard and highly corrosion resistant, which make them desirable for salt water and other applications. These alloys can be produced as powder and can be deposited as coatings on any surface that needs to be protected from the environment. It was of interest to examine the behavior of these amorphous alloys in the standard salt-fog testing ASTM B 117. Three different amorphous coating compositions were deposited on 316L SS coupons and exposed for many cycles of the salt fog test. Other common engineering alloys such as 1018 carbon steel, 316L SS and Hastelloy C-22 were also tested together with the amorphous coatings. Results show that amorphous coatings are resistant to rusting in salt fog. Partial devitrification may be responsible for isolated rust spots in one of the coatings. (authors)

  3. Pressure-Induced Structural Transformation in Radiation-Amorphized Zircon

    SciTech Connect

    Trachenko, Kostya; Dove, Martin T.; Salje, E. K. H. [Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EQ (United Kingdom); Brazhkin, V. V.; Tsiok, O. B. [Institute for High Pressure Physics, Troitsk 142190 (Russian Federation)

    2007-03-30

    We study the response of a radiation-amorphized material to high pressure. We have used zircon ZrSiO{sub 4} amorphized by natural radiation over geologic times, and have measured its volume under high pressure, using the precise strain-gauge technique. On pressure increase, we observe apparent softening of the material, starting from 4 GPa. Using molecular dynamics simulation, we associate this softening with the amorphous-amorphous transformation accompanied by the increase of local coordination numbers. We observe permanent densification of the quenched sample and a nontrivial 'pressure window' at high temperature. These features point to a new class of amorphous materials that show a response to pressure which is distinctly different from that of crystals.

  4. Oxidation of carbynes: Signatures in infrared spectra

    SciTech Connect

    Cinquanta, E., E-mail: eugenio.cinquanta@mdm.imm.cnr.it, E-mail: p.rudolf@rug.nl [CIMAINA, University of Milan, Via Celoria 16, 20133 Milano (Italy); Department of Materials Science, University of Milan Bicocca, Via Cozzi 53, 20125 Milano (Italy); Manini, N.; Caramella, L.; Onida, G. [European Theoretical Spectroscopy Facility (ETSF), Via Celoria 16, 20133 Milano (Italy); Physics Department, University of Milan, Via Celoria 16, 20133 Milano (Italy); Ravagnan, L.; Milani, P. [CIMAINA, University of Milan, Via Celoria 16, 20133 Milano (Italy); Physics Department, University of Milan, Via Celoria 16, 20133 Milano (Italy); Rudolf, P., E-mail: eugenio.cinquanta@mdm.imm.cnr.it, E-mail: p.rudolf@rug.nl [Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747AG Groningen (Netherlands)

    2014-06-28

    We report and solidly interpret the infrared spectrum of both pristine and oxidized carbynes embedded in a pure-carbon matrix. The spectra probe separately the effects of oxidation on sp- and on sp{sup 2}-hybridized carbon, and provide information on the stability of the different structures in an oxidizing atmosphere. The final products are mostly short end-oxidized carbynes anchored with a double bond to sp{sup 2} fragments, plus an oxidized sp{sup 2} amorphous matrix. Our results have important implications for the realization of carbyne-based nano-electronics devices and highlight the active participation of carbynes in astrochemical reactions where they act as carbon source for the promotion of more complex organic species.

  5. High-Density Amorphous Ice, the Frost on Interstellar Grains

    NASA Technical Reports Server (NTRS)

    Jenniskens, P.; Blake, D. F.; Wilson, M. A.; Pohorille, A.

    1995-01-01

    Most water ice in the universe is in a form which does not occur naturally on Earth and of which only minimal amounts have been made in the laboratory. We have encountered this 'high-density amorphous ice' in electron diffraction experiments of low-temperature (T less than 30 K) vapor-deposited water and have subsequently modeled its structure using molecular dynamics simulations. The characteristic feature of high-density amorphous ice is the presence of 'interstitial' oxygen pair distances between 3 and 4 A. However, we find that the structure is best described as a collapsed lattice of the more familiar low-density amorphous form. These distortions are frozen in at temperatures below 38 K because, we propose, it requires the breaking of one hydrogen bond, on average, per molecule to relieve the strain and to restructure the lattice to that of low-density amorphous ice. Several features of astrophysical ice analogs studied in laboratory experiments are readily explained by the structural transition from high-density amorphous ice into low-density amorphous ice. Changes in the shape of the 3.07 gm water band, trapping efficiency of CO, CO loss, changes in the CO band structure, and the recombination of radicals induced by low-temperature UV photolysis all covary with structural changes that occur in the ice during this amorphous to amorphous transition. While the 3.07 micrometers ice band in various astronomical environments can be modeled with spectra of simple mixtures of amorphous and crystalline forms, the contribution of the high-density amorphous form nearly always dominates.

  6. Aqueous precursors for electrochromic tungsten oxide hydrates

    Microsoft Academic Search

    J. Livage; G. Guzman

    1996-01-01

    Tungsten oxide hydrates WO3 · nH2O are formed upon the acidification of tungstate aqueous solutions. Different amorphous or crystalline phases can be obtained depending on the experimental conditions (pH, concentration, temperature). The chemical mechanisms for the formation of these hydrates are discussed and the electrochromic properties of thin films deposited from these solutions are described. Hydrogen peroxide H2O2 reacts with

  7. Arsenate Adsorption On Ruthenium Oxides: A Spectroscopic And Kinetic Investigation

    EPA Science Inventory

    Arsenate adsorption on amorphous (RuO2?1.1H2O) and crystalline (RuO2) ruthenium oxides was evaluated using spectroscopic and kinetic methods to elucidate the adsorption mechanism. Extended X-ray absorption fine structure spectroscopy (EXAFS) was ...

  8. Instabilities in oxide semiconductor transparent thin film transistors

    Microsoft Academic Search

    J. F. Conley

    2009-01-01

    New amorphous oxide semiconductor transparent thin film transistors (TTFTs) exhibit good mobility (5 to >50 cm2\\/V-sec), are transparent, and can be processed at low temperatures. They show great promise for high performance large area electronics applications such as flexible electronics, transparent electronics, and analog current drivers for OLED displays. An overview of TFT operation, expected reliability concerns, and an up

  9. The adsorption of aquatic humic substances by iron oxides

    Microsoft Academic Search

    E. Tipping

    1981-01-01

    The interactions of humic substances from Esthwaite Water with hydrous iron oxides ( -FeOOH, -Fe 2 O 3 , amorphous Fe-gel) have been examined by measuring adsorption isotherms and by microelectrophoresis. In Na + -Cl - -HCO 3 - at I = 0.002 M (medium I) the extent of adsorption decreases with increasing pH. The results are consistent with a

  10. ADSORPTION OF TRACE METALS BY HYDROUS FERRIC OXIDE IN SEAWATER

    EPA Science Inventory

    The adsorption of trace metals by amorphous hydrous ferric oxide in seawater is studied with reference to simple model systems designed to isolate the factors which may have an effect on the isotherms. Results show that the complex system behaves in a remarkably simple way and th...

  11. Tritiated amorphous silicon films and devices

    NASA Astrophysics Data System (ADS)

    Kosteski, Tome

    The do saddle-field glow discharge deposition technique has been used to bond tritium within an amorphous silicon thin film network using silane and elemental tritium in the glow discharge. The concentration of tritium is approximately 7 at. %. Minimal outgassing of tritium from tritiated hydrogenated amorphous silicon (a-Si:H:T) at room temperature suggests that tritium is bonded stably. Tritium effusion only occurred at temperatures above the film's growth temperature. The radioactive decay of tritium results in the production of high-energy beta particles. Each beta particle can generate on average approximately 1300 electron-hole pairs in a-Si:H:T. Electrical conductivity of a-Si:H:T is shown to be due to a thermally activated process and due to the generation of excess carriers by the beta particles. p-i-n betavoltaic devices have been made with a-Si:H:T in the intrinsic (i-) region. The i-region consisted of either a-Si:H:T, or a thin section of a-Si:H:T (a Delta layer) sandwiched between undoped hydrogenated amorphous silicon (a-Si:H). The excess carriers generated in the i-region are separated by the device's built-in electric field. Short-circuit currents (Isc ), open-circuit voltages (Voc), and power have been measured and correlated to the generation of excess carriers in the i-region. Good devices were made at a substrate temperature of 250°C and relatively large flow rates of silane and tritium; this ensures that there are more monohydride bonds than dihydride bonds. Under dark conditions, Isc, and Voc have been found to decrease rapidly. This is consistent with the production of silicon neutral dangling bonds (5 x 1017cm-3 per day) from the loss of tritium due to its transmutation into helium. Dangling bonds reduce carrier lifetime and weaken the electric field in the i-region. The short-circuit current from Delta layer devices decreased more slowly and settled to higher values for narrower Delta layers. This is because the dangling bonds are isolated to the Delta layer and the lifetime of excess carriers generated in the a-Si:H remains unaffected. Annealing a-Si:H:T at 120°C for approximately one hour is shown to remove dangling bonds produced from the decay of bonded tritium.

  12. Theoretical studies of amorphous silicon and hydrogenated amorphous silicon with molecular dynamics simulations

    SciTech Connect

    Kwon, I.

    1991-12-20

    Amorphous silicon (a-Si) and hydrogenated amorphous silicon (a-Si:H) have been studied with molecular dynamics simulations. The structural, vibrational, and electronic properties of these materials have been studied with computer-generated structural models and compare well with experimental observations. The stability of a-si and a-Si:H have been studied with the aim of understanding microscopic mechanisms underlying light-induced degradation in a-Si:H (the Staebler-Wronski effect). With a view to understanding thin film growth processes, a-Si films have been generated with molecular dynamics simulations by simulating the deposition of Si-clusters on a Si(111) substrate. A new two- and three-body interatomic potential for Si-H interactions has been developed. The structural properties of a-Si:H networks are in good agreement with experimental measurements. The presence of H atoms reduces strain and disorder relative to networks without H.

  13. Development of laminated nickel/manganese oxide and nickel/niobium oxide electrochromic devices

    NASA Astrophysics Data System (ADS)

    Ma, Yan-Ping; Yu, Phillip C.; Lampert, Carl M.

    1991-12-01

    This paper reports on the preparation, electrical, and optical analysis of electrodes and prototype electrochromic devices using a solid polymer ion conductor. For these devices electrodes were developed consisting of cobalt-doped nickel oxide, manganese-nickel oxide, and niobium oxide. Optical and voltammetric data was obtained for each electrode. Solid polymer electrolytes were synthesized from modified amorphous poly(ethylene oxide) [a-PEO] complexed with a metal silicate. Electrochromic devices were made using cobalt-doped nickel oxide/niobium oxide, and cobalt-doped nickel oxide/manganese-nickel electrode laminations. Optical spectra as a function of voltage was obtained for each device. The best cobalt-doped nickel oxide/a-PEO/manganese-nickel oxide device showed photopic transmittance to be Tp(bleached) equals 0.76 and Tp(colored) equals 0.44. The corresponding integrated solar transmittance was Ts(bleached) equals 0.64, Ts(colored) equals 0.46. The best cobalt- doped nickel oxide/a-PEO/niobium oxide device had photopic transmittance of Tp(bleached) equals 0.65 and Tp(colored) equals 0.16. The corresponding integrated solar transmittance was Ts(bleached) equals 0.45 and Ts(colored) equals 0.15. Of the two devices, the nickel/niobium oxide device had the best combination of electrical and optical properties. Better device properties are expected with improvements in the solid polymer electrolyte and lamination process.

  14. Pressure-induced amorphization in orthorhombic Ta{sub 2}O{sub 5}: An intrinsic character of crystal

    SciTech Connect

    Li, Quanjun; Zhang, Huafang; Cheng, Benyuan; Liu, Ran; Liu, Bo; Zou, Bo; Cui, Tian; Liu, Bingbing, E-mail: liubb@jlu.edu.cn [State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012 (China); Liu, Jing [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Chen, Zhiqiang [GeoScience Department, Stony Brook University, Stony Brook, New York 11794 (United States)

    2014-05-21

    The phase transition of orthorhombic Ta{sub 2}O{sub 5} was investigated by in situ synchrotron X-ray diffraction and Raman spectroscopy. The orthorhombic phase transforms into an amorphous form completely at 24.7?GPa. A bulk modulus B{sub 0}?=?139 (9) GPa for the orthorhombic Ta{sub 2}O{sub 5} is derived from the P-V data. We suggest that the pressure-induced amorphization (PIA) in Ta{sub 2}O{sub 5} can be attributed to the unstability of the a axis under high pressure leads to the connections of polyhedral breaking down and even triggers disorder of the whole crystal frame. These results demonstrate that the PIA is an intrinsic character of Ta{sub 2}O{sub 5} which depends on its orthorhombic crystal structure rather than nanosize effects. This study provides a new kind of bulk material for investigating PIA in metal oxides.

  15. Enhanced photocurrent in thin-film amorphous silicon solar cells via shape controlled three-dimensional nanostructures

    NASA Astrophysics Data System (ADS)

    Hilali, Mohamed M.; Yang, Shuqiang; Miller, Mike; Xu, Frank; Banerjee, Sanjay; Sreenivasan, S. V.

    2012-10-01

    In this paper, we have explored manufacturable approaches to sub-wavelength controlled three-dimensional (3D) nano-patterns with the goal of significantly enhancing the photocurrent in amorphous silicon solar cells. Here we demonstrate efficiency enhancement of about 50% over typical flat a-Si thin-film solar cells, and report an enhancement of 20% in optical absorption over Asahi textured glass by fabricating sub-wavelength nano-patterned a-Si on glass substrates. External quantum efficiency showed superior results for the 3D nano-patterned thin-film solar cells due to enhancement of broadband optical absorption. The results further indicate that this enhanced light trapping is achieved with minimal parasitic absorption losses in the deposited transparent conductive oxide for the nano-patterned substrate thin-film amorphous silicon solar cell configuration. Optical simulations are in good agreement with experimental results, and also show a significant enhancement in optical absorption, quantum efficiency and photocurrent.

  16. Optical properties of amorphous ZnO thin film prepared from boiled Zn thin film in ultra high pure water

    NASA Astrophysics Data System (ADS)

    Subramania, S.; Devarajan, M.

    2012-06-01

    Amorphous zinc oxide (a-ZnO) thin films were synthesized from RF sputtered Zn thin films. The conversion was performed by processing Zn thin film in ultra high pure water at 95°C in various process times (120-180 min). X-ray spectra revealed the presence of amorphous ZnO in the processed films. The calculated band gap was laid in between 3.25 and 3.2 eV. Non-linear behavior in I-V characteristics was observed for all films. The structural defects of a-ZnO were confirmed with PL and Raman studies. The synthesized films at 180 min were more oxygen deficient.

  17. Polarization Stability of Amorphous Piezoelectric Polyimides

    NASA Technical Reports Server (NTRS)

    Park, C.; Ounaies, Z.; Su, J.; Smith, J. G., Jr.; Harrison, J. S.

    2000-01-01

    Amorphous polyimides containing polar functional groups have been synthesized and investigated for potential use as high temperature piezoelectric sensors. The thermal stability of the piezoelectric effect of one polyimide was evaluated as a function of various curing and poling conditions under dynamic and static thermal stimuli. First, the polymer samples were thermally cycled under strain by systematically increasing the maximum temperature from 50 C to 200 C while the piezoelectric strain coefficient was being measured. Second, the samples were isothermally aged at an elevated temperature in air, and the isothermal decay of the remanent polarization was measured at room temperature as a function of time. Both conventional and corona poling methods were evaluated. This material exhibited good thermal stability of the piezoelectric properties up to 100 C.

  18. Amorphous silicon-based microchannel plates

    NASA Astrophysics Data System (ADS)

    Franco, Andrea; Riesen, Yannick; Wyrsch, Nicolas; Dunand, Sylvain; Powolny, François; Jarron, Pierre; Ballif, Christophe

    2012-12-01

    Microchannel plates (MCP) based on hydrogenated amorphous silicon (a-Si:H) were recently introduced to overcome some of the limitations of crystalline silicon and glass MCP. The typical thickness of a-Si:H based MCPs (AMCP) ranges between 80 and 100 ?m and the micromachining of the channels is realized by deep reactive ion etching (DRIE). Advantages and issues regarding the fabrication process are presented and discussed. Electron amplification is demonstrated and analyzed using Electron Beam Induced Current (EBIC) technique. The gain increases as a function of the bias voltage, limited to -340 V on account of high leakage currents across the structure. EBIC maps on 10° tilted samples confirm that the device active area extend to the entire channel opening. AMCP characterization with the electron beam shows gain saturation and signal quenching which depends on the effectiveness of the charge replenishment in the channel walls.

  19. Effective temperature in elastoplasticity of amorphous solids

    NASA Astrophysics Data System (ADS)

    Regev, Ido; Boue, Laurent; Zylberg, Jacques; Procaccia, Itamar; Hentschel, George

    2011-03-01

    An effective temperature Teff which differs from the bath temperature is believed to play an essential role in the theory of elasto-plasticity of amorphous solids. The definition of a measurable Teff in the literature on sheared solids suffers however from being connected to a fluctuation-dissipation theorem which is correct only in equilibrium. Here we introduce a natural definition of Teff based on measurable structural features without recourse to any questionable assumption. The value of Teff is connected, using theory and scaling concepts, to the flow stress and the mean energy that characterize the elasto-plastic flow. This work was supported in part by the Israel Science Foundation and the German Israeli Foundation.

  20. Yield strain in shear banding amorphous solids

    NASA Astrophysics Data System (ADS)

    Dasgupta, Ratul; Hentschel, H. George E.; Procaccia, Itamar

    2013-02-01

    In recent research it was found that the fundamental shear-localizing instability of amorphous solids under external strain, which eventually results in a shear band and failure, consists of a highly correlated array of Eshelby quadrupoles all having the same orientation and some density ?. In this paper we calculate analytically the energy E(?,?) associated with such highly correlated structures as a function of the density ? and the external strain ?. We show that for strains smaller than a characteristic strain ?Y the total strain energy initially increases as the quadrupole density increases, but that for strains larger than ?Y the energy monotonically decreases with quadrupole density. We identify ?Y as the yield strain. Its value, derived from values of the qudrupole strength based on the atomistic model, agrees with that from the computed stress-strain curves and broadly with experimental results.

  1. Theory of hydrogen interactions with amorphous silicon

    SciTech Connect

    Walle, C.G. van de; Tuttle, B.

    1999-07-01

    The authors present an overview of recent results for hydrogen interactions with amorphous silicon (a-Si), based on first-principles calculations. They review the current understanding regarding molecular hydrogen, and show that H{sub 2} molecules are far less inert than previously assumed. They then discuss results for motion of hydrogen through the material, as relating to diffusion and defect formation. They present a microscopic mechanism for hydrogen-hydrogen exchange, and examine the metastable {triple_bond}SiH{sub 2} complex formed during the exchange process. They also discuss the enhanced stability of Si-D compared to Si-H bonds, which may provide a means of suppressing light-induced defect generation.

  2. Tunable plasticity in amorphous silicon carbide films.

    PubMed

    Matsuda, Yusuke; Kim, Namjun; King, Sean W; Bielefeld, Jeff; Stebbins, Jonathan F; Dauskardt, Reinhold H

    2013-08-28

    Plasticity plays a crucial role in the mechanical behavior of engineering materials. For instance, energy dissipation during plastic deformation is vital to the sufficient fracture resistance of engineering materials. Thus, the lack of plasticity in brittle hybrid organic-inorganic glasses (hybrid glasses) often results in a low fracture resistance and has been a significant challenge for their integration and applications. Here, we demonstrate that hydrogenated amorphous silicon carbide films, a class of hybrid glasses, can exhibit a plasticity that is even tunable by controlling their molecular structure and thereby leads to an increased and adjustable fracture resistance in the films. We decouple the plasticity contribution from the fracture resistance of the films by estimating the "work-of-fracture" using a mean-field approach, which provides some insight into a potential connection between the onset of plasticity in the films and the well-known rigidity percolation threshold. PMID:23876200

  3. Structural relaxation of vacancies in amorphous silicon

    SciTech Connect

    Kim, E.; Lee, Y.H.; Chen, C.; Pang, T.

    1997-07-01

    The authors have studied the structural relaxation of vacancies in amorphous silicon (a-Si) using a tight-binding molecular-dynamics method. The most significant difference between vacancies in a-Si and those in crystalline silicon (c-Si) is that the deep gap states do not show up in a-Si. This difference is explained through the unusual behavior of the structural relaxation near the vacancies in a-Si, which enhances the sp{sup 2} + p bonding near the band edges. They have also observed that the vacancies do not migrate below 450 K although some of them can still be annihilated, particularly at high defect density due to large structural relaxation.

  4. Amorphous and Microcrystalline Silicon Solar Cells: Preprint

    SciTech Connect

    Wagner, S. (Princeton University); Carlson, D. E. (Solarex); Branz, H. M. (National Renewable Energy Laboratory)

    1999-04-01

    We review the progress made by amorphous silicon solar cells, including the emerging technology of solar cells of microcrystalline silicon. The long-term trend in the efficiency of stabilized laboratory cells based on a-Si:H has been a rise of {approx}0.6 % per year. The recent trend in the a-Si,Ge:H cell efficiency alone, measured in the spectral window assigned to the bottom device in a triple-junction cell, has been an increase of {approx}0.16% per year. These improvements have brought within reach the target of 15% efficiency identified by EPRI and DOE for widespread application. Our review leads to an identification of areas of promising research, with emphasis on the fundamental science required to reach the 15% target, and then to move to the next-level efficiency goal.

  5. Tailored magnetic anisotropy in an amorphous trilayer

    SciTech Connect

    Fu Yu [Department of Physics, Southeast University, 211189 Nanjing (China); Fakultaet fuer Physik and Center for Nanointegration Duisburg-Essen (CeNIDE), Universitaet Duisburg-Essen, 47048 Duisburg (Germany); Barsukov, I.; Spasova, M.; Lindner, J.; Meckenstock, R.; Farle, M. [Fakultaet fuer Physik and Center for Nanointegration Duisburg-Essen (CeNIDE), Universitaet Duisburg-Essen, 47048 Duisburg (Germany); Raanaei, H. [Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120 Uppsala (Sweden); Department of Physics, Persian Gulf University, Bushehr 75168 (Iran, Islamic Republic of); Hjoervarsson, B. [Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120 Uppsala (Sweden)

    2011-06-01

    An amorphous Co{sub 68}Fe{sub 24}Zr{sub 8}(3 nm)/Al{sub 70}Zr{sub 30}(3 nm)/Co{sub 68}Fe{sub 24}Zr{sub 8}(3 nm) trilayer system has been investigated using in-plane and out-of-plane angular dependent ferromagnetic resonance at different frequencies. The in-plane magnetic anisotropy is uniaxial, retaining its value of (2.9 {+-} 0.1) x 10{sup 3} J/m{sup 3} for each magnetic layer, whereas its direction was tailored independently in an arbitrary manner by applying an external magnetic field during the film deposition. The perpendicular anisotropy constant, supposed to reflect the interface quality, is nearly identical for both layers. Furthermore, the magnetic layers act independently upon each other due to the absence of interlayer coupling.

  6. Molecular motion of amorphous silicone polymers.

    PubMed

    Shemella, Philip T; Laino, Teodoro; Fritz, Oliver; Curioni, Alessandro

    2011-03-31

    In this paper, we have studied silicone polymers based on poly(dimethylsiloxane) (PDMS) molecules, which have versatile applications in many fields because of their flexible molecular properties. These polymers are of interest because when used for high-voltage insulation, surfaces exposed to weather need to be hydrophobic because a hydrophilic surface can cause leakage currents. Indeed, after damaging electrical discharges, self-recovery of the hydrophobic surface occurs, requiring molecular diffusion and surface reconstruction for repair. We use large-scale, all-atom molecular dynamics simulations that enable an atomic-level description of molecular motion in mixed, amorphous, PDMS-based materials. The local properties that contribute to enhanced molecular motion are characterized based on their local structural and electrostatic environment. With this knowledge, molecular components with desirable diffusion properties may be designed for improved material functionality. PMID:21370843

  7. Formation of physically stable amorphous drugs by milling with Neusilin.

    PubMed

    Gupta, Manish K; Vanwert, Adam; Bogner, Robin H

    2003-03-01

    Each of four drugs (ketoprofen, indomethacin, naproxen, and progesterone) was milled with Neusilin (amorphous magnesium aluminosilicate) to effect conversion from crystalline to amorphous states, and the physical stability of the resultant drugs was investigated. Ball milling the drugs alone for 48 h resulted in no amorphization. X-ray powder diffractometry (XPD), birefringence, and differential scanning calorimetry (DSC) data indicated amorphization of all the four drugs on ball milling with Neusilin. Fourier transform infrared spectroscopy (FTIR) data showed a reduction in the absorbance of the free and the hydrogen-bonded acid carbonyl peaks accompanied by a corresponding increase in the absorbance of the carboxylate peak, indicating an acid-base reaction between the carboxylic acid-containing drugs and Neusilin on milling. On storage of milled powders (at 40 degrees C and 75% RH for 4 weeks), XPD, birefringence, and DSC data showed the absence of reversion to the crystalline state, and FTIR data revealed continued absence of the carbonyl peaks. Whereas the carboxylic acid-containing drugs convert from their crystalline acid form to amorphous salt form on milling with Neusilin, progesterone seems to interact with Neusilin via hydrogen bonding. The amorphous Neusilin-bound states of all four drugs were physically stable during storage. The water of adsorption seems to mediate the conversion of the crystalline state to an amorphous Neusilin-bound state. PMID:12587115

  8. Phyllosilicates and Amorphous Gel in the Nakhlites

    NASA Astrophysics Data System (ADS)

    Hicks, L. J.; Bridges, J. C.; Gurman, S. J.

    2013-09-01

    Previous studies of the nakhlite martian meteorites have revealed hydrothermal minerals present within the fractures of the olivine minerals and the mesostasis. The olivine fractures of the Lafayette nakhlite reveal variations with initial deposits of siderite on the fracture walls, followed by crystalline phyllosilicates (smectite), and finishing with a rapidly cooled amorphous silicate gel within the central regions of the fractures. The mesostasis fractures of Lafayette also contain a crystalline phyllosilicate (serpentine). The amorphous gel is the most abundant secondary phase within the fractures of the other nakhlites [1, 2]. By studying nine nakhlite samples, including Lafayette, Governador Valadares, Nakhla, Y-000593, Y-000749, Miller-Range 03346, NWA 817, NWA 998, and NWA 5790, our aim is to constrain the identity of the phyllosilicate secondary phase minerals found throughout the nakhlite martian meteorites. This is achieved using methods including Electron Probe Micro-analysis (EPMA); X-ray Absorption Near-Edge Structure (Fe-K XANES) spectroscopy measured using Beamline I-18 at the Diamond Light Source synchrotron; and the use of Transmission Electron Microscopy (TEM) at the University of Leicester for High-Resolution (HR) imaging and Selected Area Electron Diffraction (SAED). BF studying nine nakhlite samples, including Lafayette, Governador Valadares, Nakhla, Y-000593, Y-000749, Miller-Range 03346, NWA 817, NWA 998, and NWA 5790, our aim is to constrain the identity of the phyllosilicate secondary phase minerals found throughout the nakhlite martian meteorites. This is achieved using methods including Electron Probe Micro-analysis (EPMA); X-ray Absorption Near-Edge Structure (Fe-K XANES) spectroscopy measured using Beamline I-18 at the Diamond Light Source synchrotron; and the use of Transmission Electron Microscopy (TEM) at the University of Leicester for High-Resolution (HR) imaging and Selected Area Electron Diffraction (SAED).

  9. Health hazards due to the inhalation of amorphous silica.

    PubMed

    Merget, R; Bauer, T; Küpper, H U; Philippou, S; Bauer, H D; Breitstadt, R; Bruening, T

    2002-01-01

    Occupational exposure to crystalline silica dust is associated with an increased risk for pulmonary diseases such as silicosis, tuberculosis, chronic bronchitis, chronic obstructive pulmonary disease (COPD) and lung cancer. This review summarizes the current knowledge about the health effects of amorphous (non-crystalline) forms of silica. The major problem in the assessment of health effects of amorphous silica is its contamination with crystalline silica. This applies particularly to well-documented pneumoconiosis among diatomaceous earth workers. Intentionally manufactured synthetic amorphous silicas are without contamination of crystalline silica. These synthetic forms may be classified as (1) wet process silica, (2) pyrogenic ("thermal" or "fumed") silica, and (3) chemically or physically modified silica. According to the different physicochemical properties, the major classes of synthetic amorphous silica are used in a variety of products, e.g. as fillers in the rubber industry, in tyre compounds, as free-flow and anti-caking agents in powder materials, and as liquid carriers, particularly in the manufacture of animal feed and agrochemicals; other uses are found in toothpaste additives, paints, silicon rubber, insulation material, liquid systems in coatings, adhesives, printing inks, plastisol car undercoats, and cosmetics. Animal inhalation studies with intentionally manufactured synthetic amorphous silica showed at least partially reversible inflammation, granuloma formation and emphysema, but no progressive fibrosis of the lungs. Epidemiological studies do not support the hypothesis that amorphous silicas have any relevant potential to induce fibrosis in workers with high occupational exposure to these substances, although one study disclosed four cases with silicosis among subjects exposed to apparently non-contaminated amorphous silica. Since the data have been limited, a risk of chronic bronchitis, COPD or emphysema cannot be excluded. There is no study that allows the classification of amorphous silica with regard to its carcinogenicity in humans. Further work is necessary in order to define the effects of amorphous silica on morbidity and mortality of workers with exposure to these substances. PMID:11876495

  10. Dissolution and analysis of amorphous silica in marine sediments.

    USGS Publications Warehouse

    Eggimann, D.W.; Manheim, F. T.; Betzer, P.R.

    1980-01-01

    The analytical estimation of amorphous silica in selected Atlantic and Antarctic Ocean sediments, the U.S.G.S. standard marine mud (MAG-1), A.A.P.G. clays, and samples from cultures of a marine diatom, Hemidiscus, has been examined. Our values for amorphous silica-rich circum-Antarctic sediments are equal to or greater than literature values, whereas our values for a set of amorphous silica-poor sediments from a transect of the N. Atlantic at 11oN, after appropriate correction for silica released from clays, are significantly lower than previous estimates from the same region. -from Authors

  11. The 'depletion layer' of amorphous p-n junctions

    NASA Technical Reports Server (NTRS)

    Von Roos, O.

    1981-01-01

    It is shown that within reasonable approximations for the density of state distribution within the mobility gap of a:Si, a one-to-one correspondence exists between the electric field distribution in the transition region of an amorphous p-n junction and that in the depletion layer of a crystalline p-n junction. Thus it is inferred that the depletion layer approximation which leads to a parabolic potential distribution within the depletion layer of crystalline junctions also constitutes a fair approximation in the case of amorphous junctions. This fact greatly simplifies an analysis of solid-state electronic devices based on amorphous material (i.e., solar cells).

  12. Amorphous Silicates in Primitive Meteoritic Materials: Acfer 094 and IDPs

    NASA Technical Reports Server (NTRS)

    Keller, L. P.; Nakamura-Messenger, K.; Messenger, S.; Walker, Robert M.

    2009-01-01

    The abundance of presolar grains is one measure of the primitive nature of meteoritic materials. Presolar silicates are abundant in meteorites whose matrices are dominated by amorphous silicates such as the unique carbonaceous chondrite Acfer 094. Presolar silicates are even more abundant in chondritic-porous interplanetary dust particles (CP-IDPs). Amorphous silicates in the form of GEMS (glass with embedded metal and sulfides) grains are a major component of CP IDPs. We are studying amorphous silicates in Acfer 094 matrix in order to determine whether they are related to the GEMS grains in CPIDPs

  13. Formation of molecular hydrogen on amorphous silicate surfaces

    E-print Network

    Ling Li; Giulio Manico; Emanuele Congiu; Joe Roser; Sol Swords; Hagai B. Perets; Adina Lederhendler; Ofer Biham; John Robert Brucato; Valerio Pirronello; Gianfranco Vidali

    2007-09-16

    Experimental results on the formation of molecular hydrogen on amorphous silicate surfaces are presented and analyzed using a rate equation model. The energy barriers for the relevant diffusion and desorption processes are obtained. They turn out to be significantly higher than those obtained for polycrystalline silicates, demonstrating the importance of grain morphology. Using these barriers we evaluate the efficiency of molecular hydrogen formation on amorphous silicate grains under interstellar conditions. It is found that unlike polycrystalline silicates, amorphous silicate grains are efficient catalysts of H_2 formation in diffuse interstellar clouds.

  14. Formation of molecular hydrogen on amorphous silicate surfaces

    E-print Network

    Li, Ling; Congiu, Emanuele; Roser, Joe; Swords, Sol; Perets, Hagai B; Lederhendler, Adina; Biham, Ofer; Brucato, John Robert; Pirronello, Valerio; Vidali, Gianfranco

    2007-01-01

    Experimental results on the formation of molecular hydrogen on amorphous silicate surfaces are presented and analyzed using a rate equation model. The energy barriers for the relevant diffusion and desorption processes are obtained. They turn out to be significantly higher than those obtained for polycrystalline silicates, demonstrating the importance of grain morphology. Using these barriers we evaluate the efficiency of molecular hydrogen formation on amorphous silicate grains under interstellar conditions. It is found that unlike polycrystalline silicates, amorphous silicate grains are efficient catalysts of H_2 formation in diffuse interstellar clouds.

  15. Formation of molecular hydrogen on amorphous silicate surfaces

    NASA Astrophysics Data System (ADS)

    Li, L.; Manico, G.; Congiu, E.; Roser, J.; Swords, S.; Perets, H. B.; Lederhendler, A.; Biham, O.; Brucato, J. R.; Pirronello, V.; Vidali, G.

    2007-12-01

    Experimental results on the formation of molecular hydrogen on amorphous silicate surfaces are presented and analyzed using a rate equation model. The energy barriers for the relevant diffusion and desorption processes are obtained. They turn out to be significantly higher than those obtained for polycrystalline silicates, demonstrating the importance of grain morphology. Using these barriers we evaluate the efficiency of molecular hydrogen formation on amorphous silicate grains under interstellar conditions. It is found that unlike polycrystalline silicates, amorphous silicate grains are efficient catalysts of H2 formation in diffuse interstellar clouds.

  16. Propagation characteristics of magnetoelastic waves in amorphous wires

    SciTech Connect

    Masuda, S.; Yamada, T.; Mochida, H.; Kakuno, K. (Yokohama City Univ. (Japan))

    1988-06-01

    The authors previously reported that when magnetoelastic waves propagate in as quenched amorphous wires, the main wave (MW) propagating directly from the source is accompanied by an anomalous wave (AW) with an irregular waveform, and that this AW seems to occur as the result of scattering of the MW in the amorphous wire. In this paper they report the results of experimental studies on the mechanism of AW generation, as well as information on the internal structure of the amorphous wire obtained from the waveforms of the AW.

  17. Photoemission studies of amorphous silicon induced by P + ion implantation

    NASA Astrophysics Data System (ADS)

    Petö, G.; Kanski, J.

    1995-12-01

    An amorphous Si layer was formed on a Si (1 0 0) surface by P + implantation at 80 keV. This layer was investigated by means of photoelectron spectroscopy. The resulting spectra are different from earlier spectra on amorphous Si prepared by e-gun evaporation or cathode sputtering. The differences consist of a decreased intensity in the spectral region corresponding to p-states, and appearace of new states at higher binding energy. Qualitativity similar results have been reported for Sb implanted amorphous Ge and the modification seems to be due to the changed short range order.

  18. An infrared and luminescence study of tritiated amorphous silicon

    SciTech Connect

    Sidhu, L.S.; Kosteski, T.; Kherani, N.P.; Gaspari, F.; Zukotynski, S.; Shmayda, W.

    1997-07-01

    Tritium has been incorporated into amorphous silicon. Infrared spectroscopy shows new infrared vibration modes due to silicon-tritium (Si-T) bonds in the amorphous silicon network. Si-T vibration frequencies are related to Si-H vibration frequencies by simple mass relationships. Inelastic collisions of {beta} particles, produced as a result of tritium decay, with the amorphous silicon network results in the generation of electron-hole pairs. Radiative recombination of these carriers is observed. Dangling bonds associated with the tritium decay reduce luminescence efficiency.

  19. Robust hydrophobic Fe-based amorphous coating by thermal spraying

    NASA Astrophysics Data System (ADS)

    Zhang, C.; Wu, Y.; Liu, L.

    2012-09-01

    Metallic surface is intrinsically hydrophilic due to its high surface energy. In this work, we present a different picture that highly hydrophobic metallic coatings could be directly fabricated by thermal spraying of Fe-based amorphous powders through the surface roughness control. These hydrophobic coatings are amorphous, exhibiting super-high hardness and excellent corrosion resistance. With low surface energy modification, the coatings become superhydrophobic and exhibit clearly self-cleaning effect. The present work opens a window for the applications of the amorphous coatings.

  20. Radial distribution function of a new form of amorphous diamond shock induced from C60 fullerene

    Microsoft Academic Search

    H. Hirai; Y. Tabira; K. Kondo; T. Oikawa; N. Ishizawa

    1995-01-01

    The radial distribution function of a new form of amorphous diamond, synthesized from C60 fullerene by shock compression and rapid quenching, was obtained from an electron diffraction pattern using an imaging plate. The present amorphous diamond was essentially amorphous material based on diffractometry. Analysis of the local structure around an atom revealed that the amorphous material was distinguishable not only

  1. Electron probe and auger electron microprobe characterization of modified Cu-based amorphous alloys.

    PubMed

    Szummer, A; Janik-Czachor, M; Mack, P; Pisarek, M

    2003-08-01

    Changes in morphology and local chemical composition due to various methods of modification of surfaces of Cu-Zr, Cu-Hf, and Cu-Ti amorphous alloys (caused by aging in air/dry corrosion or hydrogen charging) were investigated. These modification/activation procedures transform the original amorphous ribbons of low surface area into efficient and stable catalysts, due to the segregation of a distinct amount of Cu and the development of a large specific surface area of Cu on a ZrO x or HfO x support. It was found that aging in air resulted in the formation of a bilayer of rough copper (containing small Cu particles indispensable for catalysis) on top of a rather smooth oxide underlayer (ZrO x, HfO x ). Careful examination of the cross sections of the modified Cu-based ribbons revealed that, even after prolonged aging in air, only the first few microns of the surface layer was modified. Cu-Ti alloy was stable in air and did not undergo the expected modification. Hydrogenation followed by air exposure resulted in a disintegration of the ribbons into small pieces. Each piece was covered with many small Cu clusters 0.1-0.5 microm in diameter formed on an oxide underlayer. High-energy resolution Auger spectroscopy allowed identification of the underlayers (ZrO2, HfO2, or TiO x ), identification of small Cu clusters, determination of the degree of surface oxidation of them, and mapping of the surface to identify the Cu-covered and "naked" heavy metal. PMID:12901771

  2. Optimization of transparent and reflecting electrodes for amorphous silicon solar cells. Annual subcontract report, April 1, 1994--March 31, 1995

    SciTech Connect

    Gordon, R.G. [Harvard Univ., Cambridge, MA (United States)

    1995-10-01

    Transparent and reflecting electrodes are important parts of the structure of amorphous silicon solar cells. We report improved methods for depositing zinc oxide, deposition of tin nitride as a potential reflection-enhancing diffusion barrier between the a-Si and back metal electrodes. Highly conductive and transparent fluorine-doped zinc oxide was successfully produced on small areas by atmospheric pressure CVD from a less hazardous zinc precursor, zinc acetylacetonate. The optical properties measured for tin nitride showed that the back-reflection would be decreased if tin nitride were used instead of zinc oxide as a barrier layer over silver on aluminum. Niobium-doped titanium dioxide was produced with high enough electrical conductivity so that normal voltages and fill factors were obtained for a-Si cells made on it.

  3. The use of amorphous and quasi-amorphous Fe-Cr-P powders for fabrication of magneto-rheological suspensions

    NASA Astrophysics Data System (ADS)

    Li ??, Marin; Nicoar?, Mircea

    1999-07-01

    Magneto-rheological suspensions (MRS) have been obtained by mean of ultrasonic dispersion of Fe-Cr-P amorphous and quasi-amorphous ferromagnetic powders in a polymeric solution. Ferromagnetic powders have more than 80% amorphous phase and the average dimension smaller than 1 ?m. The resulting suspensions present interesting magnetic and magneto-rheological properties, as well as good structural stability of powder over time and temperature. The suspension has also a good gravitational stability for periods of time longer than one week.

  4. Silicide formation in cobalt\\/amorphous silicon, amorphous Co Si and bias-induced Co Si films

    Microsoft Academic Search

    Jae Yeob Shim; Sang Wook Park; Hong Koo Baik

    1997-01-01

    The silicide formation in cobalt\\/amorphous silicon multilayer films, amorphous cobalt-silicon films, and bias-induced cobalt-silicon films has been examined by differential scanning calorimetry, X-ray diffraction, and transmission electron microscopy. For amorphous cobalt-silicon and bias-induced cobalt-silicon films, Co2Si forms as a firstsilicide phase, followed by the formation of CoSi and CoSi2. For a Co\\/a-Si multilayer film with the atomic concentration ratio of

  5. Laboratory studies of refractory metal oxide smokes

    NASA Technical Reports Server (NTRS)

    Nuth, Joseph A.; Nelson, R. N.; Donn, Bertram

    1989-01-01

    Studies of the properties of refractory metal oxide smokes condensed from a gas containing various combinations of SiH4, Fe(CO)5, Al(CH3)3, TiCl4, O2 and N2O in a hydrogen carrier stream at 500 K greater than T greater than 1500 K were performed. Ultraviolet, visible and infrared spectra of pure, amorphous SiO(x), FeO(x), AlO(x) and TiO(x) smokes are discussed, as well as the spectra of various co-condensed amorphous oxides, such as FE(x)SiO(y) or Fe(x)AlO(y). Preliminary studies of the changes induced in the infrared spectra of iron-containing oxide smokes by vacuum thermal annealing suggest that such materials become increasingly opaque in the near infrared with increased processing: hydration may have the opposite effect. More work on the processing of these materials is required to confirm such a trend: this work is currently in progress. Preliminary studies of the ultraviolet spectra of amorphous Si2O3 and MgSiO(x) smokes revealed no interesting features in the region from 200 to 300 nm. Studies of the ultraviolet spectra of both amorphous, hydrated and annealed SiO(x), TiO(x), AlO(x) and FeO(x) smokes are currently in progress. Finally, data on the oxygen isotopic composition of the smokes produced in the experiments are presented, which indicate that the oxygen becomes isotopically fractionated during grain condensation. Oxygen in the grains is as much as 3 percent per amu lighter than the oxygen in the original gas stream. The authors are currently conducting experiments to understand the mechanism by which fractionation occurs.

  6. Synthesis of iron-based bulk metallic glasses as nonferromagnetic amorphous steel alloys

    Microsoft Academic Search

    V. Ponnambalam; S. Joseph Poon; Gary J. Shiflet; Veerle M. Keppens; R. Taylor; G. Petculescu

    2003-01-01

    Iron-based amorphous metals are investigated as nonferromagnetic amorphous steel alloys with magnetic transition temperatures well below ambient temperatures. Rod-shaped amorphous samples with diameters reaching 4 mm are obtained using injection casting. Amorphous steel alloys are designed by considering atomistic factors that enhance the stability of the amorphous phase, coupled with the realization of low-lying liquidus temperatures. The present alloys are

  7. Constitutive equations and failure criteria for amorphous polymeric solids

    E-print Network

    Gearing, Brian P. (Brian Paul), 1972-

    2002-01-01

    Anand & Gurtin (2002) have recently developed a continuum theory for the elastic-viscoplastic deformation of amorphous solids. Their theory is motivated by and builds on the work of Parks, Argon, Boyce, Arruda, and their ...

  8. Side-Jump Effect in Paramagnetic Amorphous Metals 

    E-print Network

    RHIE, K.; Naugle, Donald G.; O, BH; MARKERT, JT.

    1993-01-01

    A systematic study of the resistivity (rho), the Hall coefficients (R(H)), and the magnetic susceptibilities (chi) of the Zr-based paramagnetic amorphous alloys suggests a self-consistent explanation for the frequently observed positive values of R...

  9. Simulating the amorphization of [alpha]-quartz under pressure

    SciTech Connect

    Binggeli, N. (Institut Romand de Recherche Numerique en Physique des Materiaux (IRRMA), PHB-Ecublens, 1015 Lausanne (Switzerland)); Chelikowsky, J.R. (Department of Chemical Engineering and Materials Science and Minnesota Supercomputer Institute, University of Minnesota, Minneapolis, Minnesota 55455 (United States)); Wentzcovitch, R.M. (The Royal Institution of Great Britain, 21 Albemarle Street, London W1 (United Kingdom))

    1994-04-01

    Extensive molecular-dynamics simulations have been performed within a classical force-field model for the pressure-induced amorphization of quartz. In agreement with earlier molecular-dynamics studies, we find that a phase transition occurs within the experimental pressure range of the amorphization transformation. However, at variance with previous interpretations, we find that the resulting phase is not amorphous. The correlation functions of the equilibrated structure can be shown to be consistent with those of a crystalline phase. Two transformations to ordered structures occur sequentially during the simulations. The first transformation is likely to be related to the recently discovered transition of quartz to an intermediate crystalline phase before its amorphization. The second transformation, instead, yields a compact octahedrally coordinated Si sublattice. The latter structure may be an artifact of the classical force field.

  10. Theory and simulation of amorphous organic electronic devices

    E-print Network

    Madigan, Conor (Conor Francis), 1978-

    2006-01-01

    The electronic properties of amorphous organic thin films are of great interest due to their application in devices such as light emitting devices, solar cells, photodetectors, and lasers. Compared to conventional inorganic ...

  11. Hydrogenated amorphous silicon films prepared by glow discharge of disilane

    SciTech Connect

    Wiesmann, H.J. (UHT Corp., Dobbs Ferry, NY (USA))

    1990-01-01

    This report describes the results of an investigation of the properties of hydrogenated amorphous silicon films and the efficiency of amorphous silicon solar cells deposited from disilane at rates of 1.5 nanometers/second or greater. The study was divided into two parts, investigation of basic materials properties of hydrogenated amorphous silicon thin films and the fabrication of glass-P-I-N-metal solar cells. The thin film materials properties investigated included the dark conductivity, photoconductivity, dihydride/monohydride concentration ratio, activation energy, and mobility-lifetime product. Hydrogenated amorphous silicon solar cells were fabricated with an intrinsic layer which was deposited at 1.5 nanometers/second. The absolute and reverse bias quantum yields were measured and solar cell efficiencies of 5% were achieved. Attempts to increase the efficiency by reverse bias annealing are also reported. 7 refs., 27 figs.

  12. Amorphous powders of Al-Hf prepared by mechanical alloying

    SciTech Connect

    Schwarz, R.B.; Hannigan, J.W.; Sheinberg, H.; Tiainen, T.

    1988-01-01

    We synthesized amorphous Al/sub 50/Hf/sub 50/ alloy powder by mechanically alloying an equimolar mixture of crystalline powders of Al and Hf using hexane as a dispersant. We characterized the powder as a function of mechanical-alloying time by scanning electron microscopy, x-ray diffraction, and differential scanning calorimetry. Amorphous Al/sub 50/Hf/sub 50/ powder heated at 10 K s/sup /minus/1/ crystallizes polymorphously at 1003 K into orthorhombic AlHf (CrB-type structure). During mechanical alloying, some hexane decomposes and hydrogen and carbon are incorporated into the amorphous alloy powder. The hydrogen can be removed by annealing the powder by hot pressing at a temperature approximately 30 K below the crystallization temperature. The amorphous compacts have a diamond pyramidal hardness of 1025 DPH. 24 refs., 7 figs., 1 tab.

  13. Electrochromic properties of niobium oxide thin films prepared by chemical vapor deposition

    Microsoft Academic Search

    Toshiro Maruyama; Tetsuya Kanagawa

    1994-01-01

    Electrochromic niobium oxide thin films were prepared by chemical vapor deposition. The source material was niobium(V) ethoxide. Amorphous niobium oxide thin films were obtained at a substrate temperature 350 C. Reduction and oxidation of the films in a 0.1M Na[sub 2]Co[sub 3] + 0.1M NaHCO[sub 3] buffer solution resulted in desirable changes in optical absorption. Coulometry indicated that the coloration

  14. Electrochromic properties of niobium oxide thin films prepared by chemical vapor deposition

    SciTech Connect

    Maruyama, Toshiro; Kanagawa, Tetsuya (Kyoto Univ. (Japan). Dept. of Chemical Engineering)

    1994-10-01

    Electrochromic niobium oxide thin films were prepared by chemical vapor deposition. The source material was niobium(V) ethoxide. Amorphous niobium oxide thin films were obtained at a substrate temperature 350 C. Reduction and oxidation of the films in a 0.1M Na[sub 2]Co[sub 3] + 0.1M NaHCO[sub 3] buffer solution resulted in desirable changes in optical absorption. Coulometry indicated that the coloration efficiency was 160 cm[sup 2].

  15. Formation and Processing of Amorphous Silicates in Primitive Carbonaceous Chondrites and Cometary Dust

    NASA Technical Reports Server (NTRS)

    Keller, Lindsay P.; Messenger, S.

    2012-01-01

    Chondritic-porous interplanetary dust particles (CP IDPs) exhibit strongly heterogeneous and unequilibrated mineralogy at sub-micron scales, are enriched in carbon, nitrogen and volatile trace elements, and contain abundant presolar materials [1-4]. These observations suggest that CP IDPs have largely escaped the thermal processing and water-rock interactions that have severely modified or destroyed the original mineralogy of primitive meteorites. CP IDPs are believed to represent direct samples of the building blocks of the Solar System - a complex mixture of nebular and presolar materials largely unperturbed by secondary processing. The chemical and isotopic properties of CP IDPs and their atmospheric entry velocities are also consistent with cometary origins. GEMS (glass with embedded metal and sulfides) grains are a major silicate component of CP IDPs. GEMS grains are < 0.5 microns in diameter objects that consist of numerous 10 to 50 nm-sized Fe-Ni metal and Fe-Ni sulfide grains dispersed in a Mg-Si-Al-Fe amorphous silicate matrix [2, 5]. Based on their chemistry and isotopic compositions, most GEMS appear to be non-equilibrium condensates from the early solar nebula [2]. If GEMS grains are a common nebular product, then they should also be abundant in the matrices of the most physically primitive chondritic meteorites. Although amorphous silicates are common in the most primitive meteorites [6-9], their relationship to GEMS grains and the extent to which their compositions and microstructure have been affected by parent body processing (oxidation and aqueous alteration) is poorly constrained. Here we compare and contrast the chemical, microstructural and isotopic properties of amorphous silicates in primitive carbonaceous chondrites to GEMS grains in IDPs.

  16. Low-temperature formation of amorphous InGaZnOx films with inductively coupled plasma-enhanced reactive sputter deposition

    NASA Astrophysics Data System (ADS)

    Takenaka, Kosuke; Cho, Ken; Ohchi, Yasufumi; Otani, Hirofumi; Uchida, Giichiro; Setsuhara, Yuichi

    2015-06-01

    A plasma-enhanced sputter deposition system has been developed via enhancement of target sputter discharge with inductively coupled RF plasma (ICP) driven by multiple inner-type low-inductance antennas (LIAs). The advantage of fine control of reactivity during the deposition is of great significance for the deposition of a transparent amorphous oxide semiconductor films, amorphous InGaZnOx (a-IGZO), whose electrical properties are significantly sensitive to the reactivity of the films with oxidation species during the film deposition. The characteristics of thin-film transistors (TFTs) fabricated with an a-IGZO film using the plasma-enhanced magnetron sputter deposition system have been investigated. The a-IGZO channel TFTs fabricated using the plasma-enhanced reactive sputtering system at a substrate temperature as low as or lower than 150 °C exhibited a good performance of ?FE = 18.5 cm2 V?1 s?1.

  17. Surface Roughness and Metastable Pitting of Amorphous Nickel Alloy

    Microsoft Academic Search

    Y. Zuo; S. Fu

    1998-01-01

    The effects of surface finish on nucleation and growth of metastable pits on an amorphous Ni-Cr-Fe-Si-B alloy was studied using potentiostatic and potentiodynamic polarization tests. Nucleation of metastable pits on the amorphous alloy was facilitated significantly by a rougher surface. Both growth rate constants and peak currents of metastable pits followed a log-normal distribution. A rougher surface also promoted the

  18. Surface roughness and metastable pitting of amorphous nickel alloy

    SciTech Connect

    Zuo, Y.; Fu, S. [Beijing Univ. of Chemical Technology (China). Dept. of Applied Chemistry

    1998-04-01

    The effects of surface finish on nucleation and growth of metastable pits on an amorphous Ni-Cr-Fe-Si-B alloy was studied using potentiostatic and potentiodynamic polarization tests. Nucleation of metastable pits on the amorphous alloy was facilitated significantly by a rougher surface. Both growth rate constants and peak currents of metastable pits followed a log-normal distribution. A rougher surface also promoted the growth of metastable pits and led to a wider distribution in growth rates.

  19. Physicochemical investigations and stability studies of amorphous gliclazide.

    PubMed

    Jondhale, Shital; Bhise, Satish; Pore, Yogesh

    2012-06-01

    Gliclazide (GLI), a poorly water-soluble antidiabetic, was transformed into a glassy state by melt quench technique in order to improve its physicochemical properties. Chemical stability of GLI during formation of glass was assessed by monitoring thin-layer chromatography, and an existence of amorphous form was confirmed by differential scanning calorimetry and X-ray powder diffractometry. The glass transition occurred at 67.5°C. The amorphous material thus generated was examined for its in vitro dissolution performance in phosphate buffer (pH 6.8). Surprisingly, amorphous GLI did not perform well and was unable to improve the dissolution characteristics compared to pure drug over entire period of dissolution studies. These unexpected results might be due to the formation of a cohesive supercooled liquid state and structural relaxation of amorphous form toward the supercooled liquid region which indicated functional inability of amorphous GLI from stability point of view. Hence, stabilization of amorphous GLI was attempted by elevation of T(g) via formation of solid dispersion systems involving comprehensive antiplasticizing as well as surface adsorption mechanisms. The binary and ternary amorphous dispersions prepared with polyvinylpyrrolidone K30 (as antiplasticizer for elevation of T (g)) and Aerosil 200® and/or Sylysia® 350 (as adsorbent) in the ratio of 1:1:1 (w/w) using kneading and spray-drying techniques demonstrated significant enhancement in rate and extent of dissolution of drug initially. During accelerated stability studies, ternary systems showed no significant reduction in drug dissolution performance over a period of 3 months indicating excellent stabilization of amorphous GLI. PMID:22382730

  20. Fe-based bulk amorphous soft magnetic materials

    Microsoft Academic Search

    S. Roth; M. Stoica; J. Degmová; U. Gaitzsch; J. Eckert; L. Schultz

    2006-01-01

    Fe-based bulk amorphous materials have no crystal anisotropy. This is why they are good candidates for the application as soft magnetic materials, although conventional soft magnetic alloys have a higher saturation magnetization than the amorphous alloys. An Fe65.5Cr4Mo4Ga4P12C5B5.5 alloy shows, together with excellent soft magnetic behaviour, a very high mechanical strength and a high resistance against corrosion which may be

  1. Supplementary Information for: Structure, electronic, and vibrational properties of amorphous

    E-print Network

    Supplementary Information for: Structure, electronic, and vibrational properties of amorphous AsS2 amorphous AsS2 and AgAsS2: pair distribution functions (PDF) (Fig. SF1), bond orders in AsS2 (Fig. SF2(r) r (Å) AsS2 AgAsS2 ND XRD XRD Figure 1: [Fig. SF1] Pair distribution functions (PDF) determined

  2. Effect of counterions on the properties of amorphous atorvastatin salts.

    PubMed

    Sonje, Vishal M; Kumar, Lokesh; Puri, Vibha; Kohli, Gunjan; Kaushal, Aditya M; Bansal, Arvind K

    2011-11-20

    Amorphous systems have gained importance as a tool for addressing delivery challenges of poorly water soluble drugs. A careful assessment of thermodynamic and kinetic behavior of amorphous form is necessary for successful use of amorphous form in drug delivery. The present study was undertaken to evaluate effect of monovalent sodium (Na(+); ATV Na), and bivalent calcium (Ca(2+); ATV Ca) and magnesium (Mg(2+); ATV Mg) counterions on properties of amorphous salts of atorvastatin (ATV) model drug. Amorphous form was generated from crystalline salts of ATV by spray drying, and characterized for glass transition temperature (T(g)), fragility and devitrification tendency. In addition, chemical stability of the amorphous salt forms was evaluated. Fragility was studied by calculating activation enthalpy for structural relaxation at T(g), from heating rate dependency of T(g). Density functional theory and relative pK(a)'s of counterions were evaluated to substantiate trend in glass transition temperature. T(g) of salts followed order: ATV Ca>ATV Mg>ATV Na. All salts were fragile to moderately fragile, with D value ranging between 9 and 16. Ease of devitrification followed the order: ATV Na?ATV Mg?ATV Ca, using isothermal crystallization and reduced crystallization temperature method. Chemical stability at 80°C showed higher degradation of amorphous ATV Ca (?5%), while ATV Na and ATV Mg showed degradation of 1-2%. Overall, ATV Ca was better in terms of glass forming ability, higher T(g) and physical stability. The study has importance in selection of a suitable amorphous form, during early drug development phase. PMID:21907794

  3. Superconductivity of Zr-Nb-Si amorphous alloys

    Microsoft Academic Search

    A. Inoue; N. Toyota; T. Fukase; T. Masumoto; Y. Takahashi

    1983-01-01

    Superconducting amorphous alloys with high strength and good ductility have been found in rapidly quenched alloys of the Zr-Nb-Si system. These alloys were produced in a continuous ribbon form of 1 to 2 mm width and 0.02 to 0.03 mm thickness using a modified single roller quenching apparatus. The amorphous alloys were formed over the whole composition range between zirconium

  4. Thermal Properties of Amorphous Al-Ni-Si Alloy

    SciTech Connect

    Goegebakan, Musa; Okumus, Mustafa [Department of Physics, Faculty of Art and Science, Kahramanmaras Sutcu Imam University, Kahramanmaras, 46000 (Turkey)

    2007-04-23

    Thermal properties of the amorphous phases in rapidly solidified Al70Ni13Si17 alloy has been investigated by a combination of differential scanning calorimetry DSC. During continuous heating, three exothermic crystallization peaks were observed. Activation energies for the three crystallization peaks were calculated by the Kissinger and Ozawa methods give good agreement. This study describes the thermal properties of rapidly solidified Al70Ni13Si17 amorphous alloy.

  5. Crystallization Behaviour of Amorphous Al-Ni-Nd Alloy

    SciTech Connect

    Goegebakan, Musa; Guendes, Alaaddin [Department of Physics, Faculty of Art and Science, Kahramanmaras Sutcu Imam University, Kahramanmaras, 46000 (Turkey)

    2007-04-23

    In this study, crystallization behaviour of rapidly solidified Al85Ni5Nd10 alloy has been investigated by differential scanning calorimetry (DSC). Continuous heating DSC trace of amorphous Al85Ni5Nd10 alloy consisted of three exothermic peaks. This indicated that; crystallization of amorphous Al85Ni5Nd10 alloy during continous heating takes places in three stages. Before the first exothermic peak, a glass transition temperature was observed.

  6. Atomic structure of amorphous particles produced by spark erosion

    Microsoft Academic Search

    S. Aur; T. Egami; A. E. Berkowitz; J. L. Walter

    1982-01-01

    The atomic structure of amorphous particles of composition Fe75Si15B10 produced by spark erosion was studied by the energy-dispersive x-ray diffraction technique and was compared to that of the amorphous ribbon of the same composition produced by melt spinning. It was found that the nearest-neighbor Fe-Fe correlation is almost identical for the ribbon and the particles of different sizes, whereas the

  7. Tritium-powered betavoltaic cells based on amorphous silicon

    Microsoft Academic Search

    Steffen Deus

    2000-01-01

    Betavoltaic cells based on hydrogenated amorphous silicon nip drift junctions with ultrathin (5 nm) metal contact layers were developed for tritium-powered batteries. A large variety of amorphous silicon cells has been exposed to a tritium gas atmosphere for 46 days, and their performance has been studied in several time intervals. Initially, a short circuit current density of 637 nA\\/cm2, an

  8. Stability and crystallization of amorphous clusters in crystalline Si

    Microsoft Academic Search

    Sebastian von Alfthan; Adrian P. Sutton; Antti Kuronen; Kimmo Kaski

    2005-01-01

    We have simulated using molecular dynamics the thermal stability and crystallization kinetics of nanometre-sized clusters of amorphous Si embedded in crystalline Si, which are of interest for phase-change memory devices. We have calculated the interfacial and bulk excess energies of the amorphous clusters, and studied their crystallization kinetics at 700-1500 K. At temperatures below (above) 1150 K the activation energy

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

    SciTech Connect

    Hellman, Frances

    1998-10-03

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

  10. Amorphous silicon carbide coatings for extreme ultraviolet optics

    Microsoft Academic Search

    J. B. Kortright; David L. Windt

    1988-01-01

    Amorphous silicon carbide films formed by sputtering techniques are shown to have high reflectance in the extreme ultraviolet spectral region. X-ray scattering verifies that the atomic arrangements in these films are amorphous, while Auger electron spectroscopy and Rutherford backscattering spectroscopy show that the films have composition close to stoichiometric SiC, although slightly C-rich, with low impurity levels. Reflectance vs incidence

  11. Effect of different "states" of sorbed water on amorphous celecoxib.

    PubMed

    Shete, Ganesh; Kuncham, Swathi; Puri, Vibha; Gangwal, Rahul P; Sangamwar, Abhay T; Bansal, Arvind Kumar

    2014-07-01

    Glass transition temperature (Tg) of an amorphous drug is a vital physical phenomenon that influences its visco-elastic properties, physical, and chemical stability. Water acts as a plasticizer for amorphous drugs thus increasing their recrystallization kinetics. This reduces the solubility advantage of an amorphous drug. Hence, there is an interest in understanding the relationship between water content and Tg of amorphous drug. We have studied the effect of "state" of sorbed water on Tg of amorphous celecoxib (ACLB). ACLB was allowed to sorb water at relative humidity of 33%, 53%, 75%, and 93%. ALCB showed biphasic sorption of water designated as "bound" and "solvent-like" state of water associated with ACLB. Molecular modeling studies provided deeper insights into the interaction of water with ACLB. A distinct co-relationship between the state of water and its plasticization capacity was observed. Bound state of water had a very profound effect on the fall in experimentally observed Tg (T(g-exp)) value. Solvent-like state of water had little impact on T(g-exp) value. Tg of ACLB-water mixture was predicted by Gordon-Taylor equation (T(g-pre)). The deviations in T(g-exp) and Tg-pre were correlated to volume non-additivity and non-ideal mixing. This study has implications on the development of formulations based on amorphous forms. PMID:24801826

  12. Characterization of amorphous material in shocked quartz by NMR spectroscopy

    SciTech Connect

    Assink, R.A.; Boslough, M.B.; Cygan, R.T.

    1993-08-01

    Nuclear magnetic resonance (NMR) analysis of the recovered products from a series of controlled explosive shock-loading experiments on quartz powders was performed to investigate shock-induced amorphization processes. Silicon-29 NMR spectroscopy is an excellent probe of the local bonding environment of silicon in minerals and is capable of detecting and characterizing amorphous and disordered components. NMR spectra obtained for the recovered material exhibit a narrow resonance associated with the shocked crystalline material, and a broad component consistent with an amorphous phase despite the absence of evidence for glass from optical microscopy. The NMR measurements were performed over a range of recycle times from 1 to 3 {times} 10{sup 5} S. Results demonstrate that the magnetization in both the crystalline and amorphous material following power-law behavior as a function of recycle time. The amorphous component dominates the spectra for short NMR recycle times due to its shorter relaxation time relative to the crystalline material. Fractal analysis of the power-law relations suggests a fractal dimension of 2 for the amorphous phase and 3 for the crystalline phase.

  13. Variable-amplitude oscillatory shear response of amorphous materials

    NASA Astrophysics Data System (ADS)

    Perchikov, Nathan; Bouchbinder, Eran

    2014-06-01

    Variable-amplitude oscillatory shear tests are emerging as powerful tools to investigate and quantify the nonlinear rheology of amorphous solids, complex fluids, and biological materials. Quite a few recent experimental and atomistic simulation studies demonstrated that at low shear amplitudes, an amorphous solid settles into an amplitude- and initial-conditions-dependent dissipative limit cycle, in which back-and-forth localized particle rearrangements periodically bring the system to the same state. At sufficiently large shear amplitudes, the amorphous system loses memory of the initial conditions, exhibits chaotic particle motions accompanied by diffusive behavior, and settles into a stochastic steady state. The two regimes are separated by a transition amplitude, possibly characterized by some critical-like features. Here we argue that these observations support some of the physical assumptions embodied in the nonequilibrium thermodynamic, internal-variables based, shear-transformation-zone model of amorphous viscoplasticity; most notably that "flow defects" in amorphous solids are characterized by internal states between which they can make transitions, and that structural evolution is driven by dissipation associated with plastic deformation. We present a rather extensive theoretical analysis of the thermodynamic shear-transformation-zone model for a variable-amplitude oscillatory shear protocol, highlighting its success in accounting for various experimental and simulational observations, as well as its limitations. Our results offer a continuum-level theoretical framework for interpreting the variable-amplitude oscillatory shear response of amorphous solids and may promote additional developments.

  14. Amorphous silicon-carbon alloys and amorphous carbon from direct methane and ethylene activation by ECR

    SciTech Connect

    Conde, J.P.; Chu, V.; Giorgis, F.; Pirri, C.F.; Arekat, S.

    1997-07-01

    Hydrogenated amorphous silicon-carbon alloys are prepared using electron-cyclotron resonance (ECR) plasma-enhanced chemical vapor deposition. Hydrogen is introduced into the source resonance cavity as an excitation gas. Silane is introduced in the main chamber in the vicinity of the plasma stream, whereas the carbon source gases, methane or ethylene, are introduced either with the silane or with the hydrogen as excitation gases. The effect of the type of carbon-source gas, excitation gas mixture and silane-to-carbon source gas flow ratio on the deposition rate, bandgap, subgap density of states, spin density and hydrogen evolution are studied.

  15. Synthesis of Amorphous Platinum Nanofibers Directly on an ITO Substrate and Its Heterogeneous Catalytic Hydrogenation Characterization.

    PubMed

    Balouch, Aamna; Ali Umar, Akrajas; Mawarnis, Elvy Rahmi; Md Saad, Siti Khatijah; Mat Salleh, Muhamad; Abd Rahman, Mohd Yusri; Kityk, I V; Oyama, Munetaka

    2015-04-15

    This paper reports a facile, solution-phase approach to synthesizing a one-dimensional amorphous face-centered-cubic (fcc) platinum (a-Pt) nanostructure (nanofibers) directly on an indium-tin oxide (ITO) substrate. The electron microscopy analysis result shows that the a-Pt nanofiber has a diameter and length of approximately 50 nm and 1 ?m, respectively, and is grown in high density on the entire surface of the ITO substrate. The X-ray photoelectron spectroscopy analysis result further reveals that the a-Pt nanofibers feature metallic properties with highly reactive surface chemistry, promising novel performance in electrochemistry, catalysis, and sensors. A synergetic interplay between the formic acid reducing agent and the hexamethylenetetramine surfactant in the reduction of Pt ions is assumed as the driving force for the formation of the amorphous phase in the Pt nanostructure. The catalytic properties of a-Pt were examined in the acetone hydrogenation reaction under microwave irradiation. a-Pt shows excellent heterogeneous catalytic properties for converting acetone to isopropyl alcohol with turnover number and frequency as high as 400 and 140 min(-1), respectively. The preparation and formation mechanism of the a-Pt nanofibers will be discussed in detail in this paper. PMID:25807116

  16. Influence of surface conductivity on the apparent zeta potential of amorphous silica nanoparticles.

    PubMed

    Leroy, Philippe; Devau, Nicolas; Revil, André; Bizi, Mohamed

    2013-11-15

    Zeta potential is a physicochemical parameter of particular importance in describing ion adsorption and double layer interactions between charged particles. However, for metal-oxide nanoparticles, the conversion of electrophoretic mobility measurements into zeta potentials is difficult. This is due to their very high surface electrical conductivity, which is inversely proportional to the size of the particle. When surface conductivity is similar to or higher than the electrical conductivity of bulk water, it can significantly lower the electrophoretic mobility of the particles. It follows that the magnitude of the apparent zeta potential determined from the Smoluchowski equation (disregarding surface conductivity) can be grossly underestimated. We use a basic Stern model to describe the electrochemical properties and to calculate the true zeta potential of amorphous silica nanoparticles immersed in NaCl solution. The parameters of our surface complexation model are adjusted by potentiometric titration and electrophoretic mobility measurements at high salinity (10(-1)M NaCl). Electrophoretic mobilities are calculated using Henry's electrokinetic transport model with specific surface conductivities and zeta potentials estimated by our surface complexation model. The very good agreement of calculated and measured electrophoretic mobilities confirms that the true zeta potential corresponds to the electrical potential at the outer Helmholtz plane (OHP). Consequently, the shear plane might be located close to the OHP. The assumption of the presence of a stagnant diffuse layer at the amorphous silica/water interface is therefore not required. PMID:24011560

  17. Research on high-efficiency, large area amorphous silicon based solar cells

    SciTech Connect

    Arya, R.R.; Bennett, M.; Fleselmann, B.; Morris, J.; Newton, J.; Podlesny, R.; Twesme, E.; Wiedeman, S.; Yang, L. (Solarex Corp., Newtown, PA (USA). Thin Film Div.); Rothwarf, A.; Shapiro, F. (Drexel Univ., Philadelphia, PA (USA))

    1990-09-01

    This document presents the results of studies in three areas: materials research, non-semiconductor materials research, and submodule research. In materials research, hydrogen dilution of a SiGe:H alloys improved alloys homogeneity and reduced light-induced degradation. Performance improvements were made in both microcrystalline and amorphous doped films, and a method was demonstrated that appears to overcome nucleation and film growth problems by recrystallizing the amorphous n-layer. In non-semiconductor materials research, ITO/Ag production was scaled up to successfully coat 1000-cm{sup 2} submodules. Work on atmospheric chemical vapor deposition of zinc oxide produced 2-{mu}m-thick films with 50--80 {Omega}/sq. sheet resistance. In submodule research, all processes were scaled up and single-junction submodules were prepared with 9.9% aperture-area conversion efficiencies. Triple-junction submodules were produced with 8.98% aperture-area efficiencies, and laser scribing was improved to allow only a 2% loss in area. Modeling was used to optimize module performance by predicting parasitic losses given the material constraints of a given device design. Modules were laser patterned to define an array of small-area devices, and topographic maps were produced to alloy visualization of both isolated defects and performance gradients. 27 refs., 41 figs., 7 tabs.

  18. Synthesis of Antimony Doped Amorphous Carbon Films

    NASA Astrophysics Data System (ADS)

    Okuyama, H.; Takashima, M.; Akasaka, H.; Ohtake, N.

    2013-06-01

    We report the effects of antimony (Sb) doping on the electrical and optical properties of amorphous carbon (a-C:H) films grown on silicon and copper substrates by magnetron sputtering deposition. For film deposition, the mixture targets fabricated from carbon and antimony powders was used. The atomic concentration of carbon, hydrogen, and antimony, in the film deposited from the 1.0 mol% Sb containing target were 81, 17, 2 at.%, respectively. These elements were homogeneously distributed in the film. On the structural effect, the average continuous sp2 carbon bonding networks decreased with Sb concentration increasing, and defects in the films were increased with the Sb incorporation because atomic radius of Sb atoms is twice larger size than that of carbon. The optical gap and the electrical resistivity were carried out before and after the Sb doping. The results show that optical gap dropped from 3.15 to 3.04 eV corresponding to non-doping to Sb-doping conditions, respectively. The electrical resistivity reduced from 10.5 to 1.0 M?m by the Sb doping. These results suggest the doping level was newly formed in the forbidden band.

  19. Mechanical Performance of Amorphous Metallic Cellular Structures

    NASA Astrophysics Data System (ADS)

    Schramm, Joseph P.

    Metallic glass and metallic glass matrix composites are excellent candidates for application in cellular structures because of their outstanding plastic yield strengths and their ability to deform plastically prior to fracture. The mechanical performance of metallic-glass and metallic-glass-matrix-composite honeycomb structures are discussed, and their strength and energy absorption capabilities examined in quasi-static compression tests for both in-plane and out-of-plane loading. These structures exhibit strengths and energy absorption that well exceed the performance of similar structures made from crystalline metals. The strength and energy absorption capabilities of amorphous metal foams produced by a powder metallurgy process are also examined, showing that foams produced by this method can be highly porous and are able to inherit the strength of the parent metallic glass and absorb large amounts of energy. The mechanical properties of a highly stochastic set of foams are examined at low and high strain rates. It is observed that upon a drastic increase in strain rate, the dominant mechanism of yielding for these foams undergoes a change from elastic buckling to plastic yielding. This mechanism change is thought to be the result of the rate of the mechanical test approaching or even eclipsing the speed of elastic waves in the material.

  20. An amorphous magnetic bimetallic sensor material

    NASA Astrophysics Data System (ADS)

    Kraus, L.; Hašlar, V.; Záv?ta, K.; Pokorný, J.; Duhaj, P.; Polak, C.

    1995-11-01

    An amorphous bimetal ribbon consisting of magnetostrictive (Fe40Ni40B20) and nonmagnetostrictive (Co67Fe4Cr7Si8B12) layers was prepared by planar flow casting from a double-chamber crucible. The effect of applied tensile stress on hysteresis loops and the surface domain structures of the stress-relieved bimetal was investigated at room temperature. The hysteresis loops can be well explained by superpositions of hysteresis loops of the individual layers. Only the magnetostrictive layer is responsible for the influence of applied stress on magnetic behavior. At a certain stress, the magnetic anisotropy of the magnetostrictive layer abruptly changes from a hard-ribbon-axis to an easy-ribbon-axis type. This transition is accompanied by a change of domain structure and a sharp maximum of the coercive field. A simple model taking into account an interplay of the applied tensile stress with the compressive stress produced by thermal contraction after stress relief and/or by bending of the ribbon has been developed. The observed behavior can be well explained by the model.