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1

Electrical effect of titanium diffusion on amorphous indium gallium zinc oxide  

SciTech Connect

In this work, thermal diffusion phenomenon of Ti into amorphous indium gallium zinc oxide ({alpha}-IGZO) was carefully investigated with secondary ion mass spectroscopy, I-V, and R{sub s} measurement systems and HSC chemistry simulation tool. According to the experimental and simulated results, the diffused Ti atoms were easily oxidized due to its lowest oxidation free energy. Since oxygen atoms were decomposed from the {alpha}-IGZO during the oxidation of Ti, the number of oxygen vacancies working as electron-donating sites in {alpha}-IGZO was dramatically increased, contributing to the decrease of resistivity ({rho}) from 1.96 {Omega} cm (as-deposited {alpha}-IGZO) to 1.33 Multiplication-Sign 10{sup -3}{Omega} cm (350 Degree-Sign C annealed {alpha}-IGZO).

Choi, Seung-Ha [School of Electronic and Electrical Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Development Group of Oxide Semiconductor, Samsung Display, Yongin 446-711 (Korea, Republic of); Jung, Woo-Shik [Department of Electrical Engineering, Stanford University, Stanford, California 94305 (United States); Park, Jin-Hong [School of Electronic and Electrical Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)

2012-11-19

2

High responsivity of amorphous indium gallium zinc oxide phototransistor with Ta2O5 gate dielectric  

NASA Astrophysics Data System (ADS)

This study investigates the electrical performance of amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs) with a Ta2O5 gate dielectric under monochromatic illumination. The relationship between the phototransistor performance and oxygen partial pressure is determined. The oxygen content of the a-IGZO channel significantly affects the electrical and optical characteristics of a-IGZO TFTs. At applied gate biases of 0, 0, and 0.25 V, oxygen partial pressures of 0%, 0.1%, and 0.2% yielded measured device responsivities of 0.23, 0.44, and 4.75 A/W, respectively. Oxygen content can be used to control the mobility of TFTs, which can amplify photocurrent and enhance the responsivity of a-IGZO TFTs with a Ta2O5 gate dielectric.

Chang, T. H.; Chiu, C. J.; Weng, W. Y.; Chang, S. J.; Tsai, T. Y.; Huang, Z. D.

2012-12-01

3

Thermal Conductivity of Amorphous Indium--Gallium--Zinc Oxide Thin Films  

NASA Astrophysics Data System (ADS)

We investigated the thermal conductivity of 200-nm-thick amorphous indium--gallium--zinc-oxide (a-IGZO) films. Films with a chemical composition of In:Ga:Zn= 1:1:0.6 were prepared by dc magnetron sputtering using an IGZO ceramic target and an Ar--O2 sputtering gas. The carrier density of the films was systematically controlled from 1014 to >1019 cm-3 by varying the O2 flow ratio. Their Hall mobility was slightly higher than 10 cm2\\cdotV-1\\cdots-1. Those films were sandwiched between 100-nm-thick Mo layers; their thermal diffusivity, measured by a pulsed light heating thermoreflectance technique, was 5.4 10-7 m2\\cdots-1 and was almost independent of the carrier density. The average thermal conductivity was 1.4 W\\cdotm-1\\cdotK-1.

Yoshikawa, Toru; Yagi, Takashi; Oka, Nobuto; Jia, Junjun; Yamashita, Yuichiro; Hattori, Koichiro; Seino, Yutaka; Taketoshi, Naoyuki; Baba, Tetsuya; Shigesato, Yuzo

2013-02-01

4

Low-frequency noise in amorphous indium-gallium-zinc oxide thin-film transistors from subthreshold to saturation  

NASA Astrophysics Data System (ADS)

We investigate the low-frequency noise (LFN) behaviors of amorphous indium-gallium-zinc oxide thin-film transistors in the subthreshold, Ohmic, and saturation regimes. Measured LFNs are proportional to 1/f?, with ?=0.8-0.9 in all operation regimes. It is found that the LFN behavior follows the carrier number fluctuation model in the subthreshold regime, whereas in the Ohmic and saturation regimes, it agrees well with the bulk mobility fluctuation model. We also observe that the origin of 1/f noise in the Ohmic regime changes from the bulk mobility fluctuation to the carrier number fluctuation as the channel length decreases.

Park, Jae Chul; Kim, Sang Wook; Kim, Chang Jung; Kim, Sungchul; Kim, Dae Hwan; Cho, In-Tak; Kwon, Hyuck-In

2010-09-01

5

Electronic State of Amorphous Indium Gallium Zinc Oxide Films Deposited by DC Magnetron Sputtering with Water Vapor Introduction  

NASA Astrophysics Data System (ADS)

Amorphous indium gallium zinc oxide (a-IGZO) films were fabricated using dc magnetron sputtering with water vapor (H2O or D2O) introduction. To determine the incorporation pattern of water, films were characterized by secondary ion mass, Fourier transform infrared, Raman, and hard X-ray photoelectron spectroscopies. Chemically bound hydroxyl groups were observed, and more hydroxyl bonds existed nearer to the interface between the substrate and film than in the film. Furthermore, for a-IGZO films, subgap densities of states near valence band maxima increased with the H2O partial pressure during deposition, which can be attributed to defect-level generations due to H and O.

Oka, Nobuto; Aoi, Takafumi; Hayashi, Ryo; Kumomi, Hideya; Shigesato, Yuzo

2012-07-01

6

Low temperature characteristics in amorphous indium-gallium-zinc-oxide thin-film transistors down to 10 K  

NASA Astrophysics Data System (ADS)

We report on the characteristics of amorphous indium-gallium-zinc-oxide thin-film transistors (TFTs) in the temperature range of 10-300 K. In the range of 80-300 K, the transfer characteristics are consistent with thermally activated band conduction. Below 80 K, the drain current vs. temperature behavior follows Mott's law, exp(-B/T-1/4), with constant B, indicating variable range hopping. The subthreshold swing of the TFT remains unchanged in the band conduction region, but it increases rapidly with decreasing temperature below 80 K. With decreasing temperature, the hopping activation energy decreases and hopping distance increases, and are 16.8 meV and ~11.6 nm, respectively, at 60 K.

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

2013-10-01

7

Analysis of amorphous indium-gallium-zinc-oxide thin-film transistor contact metal using Pilling-Bedworth theory and a variable capacitance diode model  

NASA Astrophysics Data System (ADS)

It is widely reported that threshold voltage and on-state current of amorphous indium-gallium-zinc-oxide bottom-gate thin-film transistors are strongly influenced by the choice of source/drain contact metal. Electrical characterisation of thin-film transistors indicates that the electrical properties depend on the type and thickness of the metal(s) used. Electron transport mechanisms and possibilities for control of the defect state density are discussed. Pilling-Bedworth theory for metal oxidation explains the interaction between contact metal and amorphous indium-gallium-zinc-oxide, which leads to significant trap formation. Charge trapping within these states leads to variable capacitance diode-like behavior and is shown to explain the thin-film transistor operation.

Kiani, Ahmed; Hasko, David G.; Milne, William I.; Flewitt, Andrew J.

2013-04-01

8

Improved Mobility and Transmittance of Room-Temperature-Deposited Amorphous Indium Gallium Zinc Oxide (a-IGZO) Films with Low-Temperature Postfabrication Anneals  

NASA Astrophysics Data System (ADS)

Thin films of amorphous indium gallium zinc oxide with high transmittance were deposited at room temperature onto flexible polymer substrates. Postdeposition anneals were performed at low temperatures in different ambients to obtain films with one of the highest transmittance and mobility values reported in the literature. As-deposited and postanneal films were characterized for electrical and optical properties. Oxygen anneal degraded the electrical performance of the films, which was recovered by succeeding vacuum anneals. A surface scattering model is proposed to determine the relation between mobility and carrier concentrations at low values of carrier concentrations. This model takes into account electronic scattering as a result of grain structure and morphology.

Alford, T. L.; Gadre, M. J.; Vemuri, Rajitha N. P.

2013-04-01

9

Amorphous Indium Gallium Zinc Oxide Thin-Film Transistors with a Low-Temperature Polymeric Gate Dielectric on a Flexible Substrate  

NASA Astrophysics Data System (ADS)

Amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs) with a solution-processed polymeric gate dielectric of cross-linked poly(4-vinylphenol) (c-PVP) film were fabricated on a poly(ethylene terephthalate) (PET) substrate on which an a-IGZO film, as the active channel layer, was deposited by radio frequency (RF) sputtering. The entire TFT fabrication process was carried out at a temperature below 110 C. The device exhibited an on/off ratio of 1.5 106 and a high field-effect mobility of 10.2 cm2 V-1 s-1, which is, to our knowledge, the best result ever achieved among a-IGZO TFTs with polymeric gate dielectrics on a plastic substrate.

Hyung, Gun Woo; Park, Jaehoon; Wang, Jian-Xun; Lee, Ho Won; Li, Zhao-Hui; Koo, Ja-Ryong; Kwon, Sang Jik; Cho, Eou-Sik; Kim, Woo Young; Kim, Young Kwan

2013-07-01

10

Border trap characterization in amorphous indium-gallium-zinc oxide thin-film transistors with SiOX and SiNX gate dielectrics  

NASA Astrophysics Data System (ADS)

We investigate the border traps in amorphous indium-gallium-zinc oxide thin-film transistors with SiOX and SiNX interfacial gate dielectrics. Border traps have been known as trapping centers of electronic carriers in field-effect transistors, and non-negligible hysteresis is observed in the bidirectional high-frequency capacitance-voltage curve with a slow ramp rate in both dielectric devices. From the gate voltage transient method and 1/f noise analysis, the spatially and energetically uniform trap distribution is obtained, and approximately four to five times higher border trap densities are extracted from SiNX dielectric devices than from the SiOX dielectric ones.

Jeong, Chan-Yong; Lee, Daeun; Song, Sang-Hun; Cho, In-Tak; Lee, Jong-Ho; Cho, Eou-Sik; Kwon, Hyuck-In

2013-09-01

11

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

SciTech Connect

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}).

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

12

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)

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.

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

2013-07-01

13

High performance transparent thin film transistors based on indium gallium zinc oxide as the channel material  

Microsoft Academic Search

The fabrication of high performance amorphous indium gallium zinc oxide (IGZO) transparent thin film transistors (TTFT) and their bias stress stability is presented. N-channel enhancement mode devices were fabricated with an extracted field effect mobility of ~ 11-15 cm2 V-1s-1, on\\/off current ratios > 107, subthreshold gate voltage swing of 0.20-0.25 V\\/decade, low off-state currents and good saturation. Low and

A. Suresh; P. Wellenius; J. F. Muth

2007-01-01

14

Meyer-Neldel Rule and Extraction of Density of States in Amorphous Indium-Gallium-Zinc-Oxide Thin-Film Transistor by Considering Surface Band Bending  

NASA Astrophysics Data System (ADS)

In this study, we analyzed the temperature-dependent characteristics of amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs). We observed that a-IGZO TFTs obey the Meyer-Neldel rule (MN rule) at low gate-to-source voltage (VGS) and the inverse MN rule at high VGS, both of which can be explained by the statistical shift of Fermi level and electrostatic potential. Large Fermi level movement for small VGS change and the inverse MN rule, which are hardly observed for conventional amorphous TFTs, indicate that there is a very low density of state (DOS) in the sub-bandgap region for a-IGZO TFTs and the performance of TFTs is not affected by contact characteristics, respectively. By using the field-effect method and considering surface band bending, we extracted the DOS in the sub-bandgap region, the distribution of which is clearly distinguished by deep and tail states. The calculated parameters for tail and deep states were Nta = 3.5 1017 cm-3 eV-1, Eta = 0.18 eV, Nda = 1.6 1016 cm-3 eV-1, and ?da = 0.21 eV.

Jaewook Jeong,; Jae Kyeong Jeong,; Jin-Seong Park,; Yeon-Gon Mo,; Yongtaek Hong,

2010-03-01

15

Amorphous Indium Gallium Zinc Oxide Thin-Film Transistors, Non-volatile Memory and Circuits for Transparent Electronics  

Microsoft Academic Search

The ability to make electronic devices, that are transparent to visible and near infrared wavelength, is a relatively new field of research in the development of the next generation of optoelectronic devices. A new class of inorganic thin-film transistor (TFT) channel material based on amorphous oxide semiconductors, that show high carrier mobility and high visual transparency, is being researched actively.

Arun Suresh

2009-01-01

16

Fast All-Transparent Integrated Circuits Based on Indium Gallium Zinc Oxide Thin-Film Transistors  

Microsoft Academic Search

We describe the fabrication and characterization of visible transparent small-scale indium gallium zinc oxide (IGZO) integrated circuits. The IGZO channel and indium tin oxide (ITO) contacts and interconnects were pulsed laser deposited at room temperature. Low-temperature (200 ??C ) atomic-layer-deposited Al2O3 was used as the gate dielectric in bottom-gated thin-film transistors with field-effect mobility near 15 cm2\\/V??s. Logic inverters and

Arun Suresh; Patrick Wellenius; Vinay Baliga; Haojun Luo; Leda M. Lunardi; John F. Muth

2010-01-01

17

Solution-processed indium gallium zinc oxide thin-film transistors with infrared irradiation annealing  

NASA Astrophysics Data System (ADS)

In this paper, an infrared annealing method was proposed for solution-processed indium gallium zinc oxide films. The optimized IGZO thin-film transistors (TFTs) exhibited a field-effect mobility of 2.04 cm2 (Vs)-1, on-off current ratio of 1.52106 and subthreshold swing of 0.84 V/dec. Spectroscopic analysis confirmed that the infrared irradiation could enhance the removal of organic species and dehydroxylation. The results suggest that infrared annealing method is a potential process for low-temperature preparation of solution-processed oxide semiconductor layers and dielectric layers, and can be applied to the fabrication of TFT devices.

Pu, Haifeng; Zhou, Qianfei; Yue, Lan; Zhang, Qun

2013-10-01

18

In situ analyses on negative ions in the indium-gallium-zinc oxide sputtering process  

NASA Astrophysics Data System (ADS)

The origin of negative ions in the dc magnetron sputtering process using a ceramic indium-gallium-zinc oxide target has been investigated by in situ analyses. The observed negative ions are mainly O- with energies corresponding to the target voltage, which originates from the target and barely from the reactive gas (O2). Dissociation of ZnO-, GaO-, ZnO2-, and GaO2- radicals also contributes to the total negative ion flux. Furthermore, we find that some sputtering parameters, such as the type of sputtering gas (Ar or Kr), sputtering power, total gas pressure, and magnetic field strength at the target surface, can be used to control the energy distribution of the O- ion flux.

Jia, Junjun; Torigoshi, Yoshifumi; Shigesato, Yuzo

2013-07-01

19

High-Performance IndiumGalliumZinc Oxide Thin-Film Transistors Based on Anodic Aluminum Oxide  

Microsoft Academic Search

Thin-film transistors (TFTs) based on indium- gallium-zinc oxide (IGZO) active layer and anodic aluminum oxide (Al2O3) gate dielectric were investigated. The anodic Al2O3 gate dielectric possesses low leakage current and relatively high dielectric constant. The IGZO TFT based on anodic Al2O3 shows a mobility of as high as 21.6 cm 2 \\/V s, an on\\/off current ratio of as

Linfeng Lan; Junbiao Peng

2011-01-01

20

Transparent indium gallium zinc oxide transistor based floating gate memory with platinum nanoparticles in the gate dielectric  

NASA Astrophysics Data System (ADS)

A transparent memory device has been developed based on an indium gallium zinc oxide thin film transistor by incorporating platinum nanoparticles in the gate dielectric stack as the charge storage medium. The transfer characteristics of the device show a large clockwise hysteresis due to electron trapping and are attributed to the platinum nanoparticles. Effect of the gate bias stress (program voltage) magnitude, duration, and polarity on the memory window characteristics has been studied. Charge retention measurements were carried out and a loss of less than 25% of the trapped elec-trons was observed over 104 s indicating promising application as nonvolatile memory.

Suresh, Arun; Novak, Steven; Wellenius, Patrick; Misra, Veena; Muth, John F.

2009-03-01

21

High performance indium gallium zinc oxide thin film transistors fabricated on polyethylene terephthalate substrates  

SciTech Connect

High-performance amorphous ({alpha}-) InGaZnO-based thin film transistors (TFTs) were fabricated on flexible polyethylene terephthalate substrates coated with indium oxide (In{sub 2}O{sub 3}) films. The InGaZnO films were deposited by rf magnetron sputtering with the presence of O{sub 2} at room temperature. The n-type carrier concentration of InGaZnO film was {approx}2x10{sup 17} cm{sup -3}. The bottom-gate-type TFTs with SiO{sub 2} or SiN{sub x} gate dielectric operated in enhancement mode with good electrical characteristics: saturation mobility 11.5 cm{sup 2} V{sup -1} s{sup -1} for SiO{sub 2} and 12.1 cm{sup 2} V{sup -1} s{sup -1} for SiN{sub x} gate dielectrics and drain current on-to-off ratio >10{sup 5}. TFTs with SiN{sub x} gate dielectric exhibited better performance than those with SiO{sub 2}. This is attributed to the relatively high dielectric constant (i.e., high-k material) of SiN{sub x}. After more than 500 h aging time at room temperature, the saturation mobility of the TFTs with SiO{sub 2} gate dielectric was comparable to the as-fabricated value and the threshold voltage shift was 150 mV.

Lim, Wantae; Jang, Jung Hun; Kim, S.-H.; Norton, D. P.; Craciun, V; Pearton, S. J. [Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611 (United States); Ren, F. [Department of Chemical Engineering, University of Florida, Gainesville, Florida 32611 (United States); Shen, H. [Sensors and Electron Devices Directorate, Army Research Laboratory, Adelphi, Maryland 20783 (United States)

2008-08-25

22

Fabrication Process Assessment and Negative Bias Illumination Stress Study of Indium-Gallium-Zinc Oxide and Zinc-Tin Oxide Thin-Film Transistors  

NASA Astrophysics Data System (ADS)

Indium-gallium-zinc oxide (IGZO) and zinc-tin oxide (ZTO) are investigated for thin-film transistor (TFT) applications. Negative bias illumination stress (NBIS) is employed for electrical stability assessment. Unpassivated IGZO and ZTO TFTs suffer from severe NBIS instabilities. Zinc-tin-silicon oxide is found to be an effective passivation layer for IGZO and ZTO TFTs, significantly improving the NBIS stability. NBIS instabilities in unpassivated TFTs are attributed to an NBIS-induced desorption of chemisorbed oxygen from the channel layer top surface, exposing surface oxygen vacancies. A ZTSO layer protects the channel layer top surface from adsorbed gas interactions and also appears to reduce the density of oxygen vacancies. The best device architectures investigated with respect to TFT electrical performance are found to be staggered with aluminum electrodes for unpassivated TFTs and coplanar with ITO electrodes for ZTSO-passivated TFTs. Annealing in wet-O2 is not found to be effective for improving the performance of IGZO or ZTO TFTs or for reducing the post-deposition annealing temperature.

Hoshino, Ken

23

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

NASA Astrophysics Data System (ADS)

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.

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

2013-04-01

24

Endurance Characteristics of Amorphous-InGaZnO Transparent Flash Memory With Gold Nanocrystal Storage Layer  

Microsoft Academic Search

The amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistor (TFT)-based nonvolatile transparent Flash memory devices were fabricated with gold (Au) nanocrystal storage layer. The performance and the reliability of transparent memory devices have been characterized by experiment and technology computer-aided design simulation. This memory device shows a large-enough memory window ?V = 4.7 V at the program\\/erase (P\\/E) voltage VPGM\\/VERS = 35\\/ ?

Jaeman Jang; Jae Chul Park; Dongsik Kong; Dong Myong Kim; Jang-Sik Lee; Byeong-Hyeok Sohn; Il Hwan Cho; Dae Hwan Kim

2011-01-01

25

Impact of High-k HfO2 Dielectric on the Low-Frequency Noise Behaviors in Amorphous InGaZnO Thin Film Transistors  

Microsoft Academic Search

We have investigated the impact of high-k HfO2 gate dielectric on the low-frequency noise (LFN) behaviors of amorphous indium-gallium-zinc oxide thin-film transistors by comparing the LFNs of devices with SiO2 and HfO2 dielectrics. Measured LFNs are nearly 1\\/ f type for both devices, but the normalized noise for the HfO2 device is around one order of magnitude higher than that

Jae Chul Park; Sun Il Kim; Chang Jung Kim; Sungchul Kim; Dae Hwan Kim; In-Tak Cho; Hyuck-In Kwon

2010-01-01

26

Multilevel resistive switching memory with amorphous InGaZnO-based thin film  

NASA Astrophysics Data System (ADS)

Multi-level storage capability of resistive random access memory (RRAM) using amorphous indium-gallium-zinc-oxide (InGaZnO) thin film is demonstrated by the TiN/Ti/InGaZnO/Pt device structure under different operation modes. The distinct four-level resistance states can be obtained by varying either the trigger voltage pulse or the compliance current. In addition, the RRAM devices exhibit superior characteristics of programming/erasing endurance and data retention for the application of multi-level nonvolatile memory technology. Physical transport mechanisms for the multi-level resistive switching characteristics are also deduced in this study.

Hsu, Ching-Hui; Fan, Yang-Shun; Liu, Po-Tsun

2013-02-01

27

Effect of surface roughness on electrical characteristics in amorphous InGaZnO thin-film transistors with high-? Sm2O3 dielectrics  

NASA Astrophysics Data System (ADS)

We investigated the effect of surface roughness on the electrical characteristics in amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistors (TFTs) fabricating high-? Sm2O3 gate dielectrics, prepared under different annealing temperatures. The high-? Sm2O3 a-IGZO TFT device annealed at 200 C exhibited better electrical characteristics, including a large field effect mobility of 6.25 cm2/V s, small threshold voltage of 0.79 V, low subthreshold swing of 354 mV/decade, and high Ion/Ioff ratio of 3.1107. These results are attributed to the formation of smooth surface at the oxide/channel interface. Furthermore, the reliability of a Sm2O3 a-IGZO TFT device can be improved by oxygen annealing at low temperature.

Chen, Fa-Hsyang; Hung, Meng-Ning; Yang, Jui-Fu; Kuo, Shou-Yi; Her, Jim-Long; Matsuda, Yasuhiro H.; Pan, Tung-Ming

2013-04-01

28

Analysis of temperature-dependent electrical characteristics in amorphous In-Ga-Zn-O thin-film transistors using gated-four-probe measurements  

NASA Astrophysics Data System (ADS)

We analyzed the temperature-dependent electrical characteristics of amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs) using a gated-four-probe method (GFP) with temperatures ranging from 93 to 373 K. The intrinsic field-effect mobility and source/drain parasitic resistance were separately extracted using the GFP method. We found that temperature-dependent transfer characteristics originated from the temperature-dependent intrinsic field-effect mobility of the a-IGZO TFTs. The parasitic resistance was also correlated with the intrinsic-field effect mobility, which decreases as the intrinsic field-effect mobility increases, indicating that access parasitic resistance originated from bulk regions rather than metal/semiconductor junction barrier is a key factor to determine the parasitic resistance of a-IGZO TFTs.

Jeong, Jaewook; Jun Lee, Gwang; Kim, Joonwoo; Moon Jeong, Soon; Kim, Jung-Hye

2013-09-01

29

Impact of High-k HfO2 Dielectric on the Low-Frequency Noise Behaviors in Amorphous InGaZnO Thin Film Transistors  

NASA Astrophysics Data System (ADS)

We have investigated the impact of high-k HfO2 gate dielectric on the low-frequency noise (LFN) behaviors of amorphous indium-gallium-zinc oxide thin-film transistors by comparing the LFNs of devices with SiO2 and HfO2 dielectrics. Measured LFNs are nearly 1/ f type for both devices, but the normalized noise for the HfO2 device is around one order of magnitude higher than that for the SiO2 device. The bulk mobility fluctuation is considered as the dominant LFN mechanism in both devices, and the increased LFN in the HfO2 device is attributed to the enhanced mobility fluctuation by the remote phonon scattering from the HfO2.

Park, Jae Chul; Kim, Sun Il; Kim, Chang Jung; Kim, Sungchul; Kim, Dae Hwan; Cho, In-Tak; Kwon, Hyuck-In

2010-10-01

30

Enhancement in electrical performance of indium gallium zinc oxide-based thin film transistors by low temperature thermal annealing  

Microsoft Academic Search

We have studied the characteristics of transparent bottom-gate thin film transistors (TFTs) using InGaZnO (IGZO) as an active channel material. IGZO films were deposited on SiO2\\/Si substrates by DC sputtering techniques. Thereafter, the bottom-gate TFT devices were fabricated by depositing Ti\\/Au metal pads on IGZO films, where the channel length and width were defined to be 200 and 1000?m, respectively.

Sang-Jin Jeon; Jong-Woong Chang; Kwang-Soo Choi; Jyoti Prakash Kar; Tae-Il Lee; Jae-Min Myoung

31

Investigation of the Low-Frequency Noise Behavior and Its Correlation with the Subgap Density of States and Bias-Induced Instabilities in Amorphous InGaZnO Thin-Film Transistors with Various Oxygen Flow Rates  

NASA Astrophysics Data System (ADS)

The low-frequency noise (LFN) behavior and its correlation with the subgap density of states (DOSs) and bias-induced instabilities are investigated in the amorphous indium--gallium--zinc--oxide (a-IGZO) thin-film transistors (TFTs) with various oxygen flow rates. Higher LFN is measured in the higher oxygen flow rate devices in the subthreshold regime, which is attributed to the increased trapping/release processes. We also obtain higher subgap DOSs and larger threshold voltage shifts under positive bias stresses in higher oxygen flow rate devices, which represents that the LFN measured in the subthreshold regime is deeply correlated with the subgap DOSs and electrical instabilities in a-IGZO TFTs.

Jeong, Chan-Yong; Park, Ick-Joon; Cho, In-Tak; Lee, Jong-Ho; Cho, Euo-Sik; Ryu, Min Ki; Park, Sang-Hee Ko; Song, Sang-Hun; Kwon, Hyuck-In

2012-10-01

32

High mobility amorphous zinc oxynitride semiconductor material for thin film transistors  

SciTech Connect

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.

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

2009-10-01

33

Effect of hydrogen incorporation on the negative bias illumination stress instability in amorphous In-Ga-Zn-O thin-film-transistors  

NASA Astrophysics Data System (ADS)

In amorphous indium-gallium-zinc oxide (a-IGZO) thin film transistors, negative shifts of the threshold voltage commonly occur under negative bias illumination stress (NBIS), and its origin is attributed to hole traps such as O-vacancy (VO) defects. We perform density functional calculations to investigate the effect of hydrogenation on the NBIS instability. We find that hydrogen passivates the electrical activity of VO in form of HO, in which H occupies the vacancy site. The activation energy for dissociating HO into VO and an interstitial H (Hi) is about 1.27 eV, much higher than the migration barrier of about 0.51 eV for Hi diffusion. Kinetic Monte Carlo simulations show that HO defects are quite stable upon post thermal annealing up to 200 C. Thus, we propose that H incorporation into a-IGZO not only effectively reduces the density of VO defects but also mitigates the NBIS instability in devices fabricated at low temperatures.

Noh, Hyeon-Kyun; Park, Ji-Sang; Chang, K. J.

2013-02-01

34

The influence of RF power on the electrical properties of sputtered amorphous InGaZnO thin films and devices  

NASA Astrophysics Data System (ADS)

The influence of radio frequency (RF) power on the properties of magnetron sputtered amorphous indium gallium zinc oxide (a-IGZO) thin films and the related thin-film transistor (TFT) devices is investigated comprehensively. A series of a-IGZO thin films prepared with magnetron sputtering at various RF powers are examined. The results prove that the deposition rate sensitively depends on RF power. In addition, the carrier concentration increases from 0.91 1019 to 2.15 1019 cm?3 with the RF power rising from 40 to 80 W, which may account for the corresponding decrease in the resistivity of the a-IGZO thin films. No evident impacts of RF power are observed on the surface roughness, crystalline nature and stoichiometry of the a-IGZO samples. On the other hand, optical transmittance is apparently influenced by RF power where the extracted optical band-gap value increases from 3.48 to 3.56 eV with RF power varying from 40 to 80 W, as is supposed to result from the carrier-induced band-filling effect. The rise in RF power can also affect the performance of a-IGZO TFTs, in particular by increasing the field-effect mobility clearly, which is assumed to be due to the alteration of the extended states in a-IGZO thin films.

Junfei, Shi; Chengyuan, Dong; Wenjun, Dai; Jie, Wu; Yuting, Chen; Runze, Zhan

2013-08-01

35

Rare-Earth Doped Wide Bandgap Oxide Semiconductor Materials and Devices  

NASA Astrophysics Data System (ADS)

Amorphous oxide semiconductors composed of indium gallium zinc oxide are transparent to visible light and have higher electron mobilities than conventional amorphous semiconductors, such as amorphous silicon. The advantages of higher switching speed, lack of dangling bonds leading to good electronic stability and visible spectrum transparency of amorphous oxide semiconductor devices are expected to lead to numerous applications, including transparent displays and flexible electronics. In this thesis the integration of transparent thin film transistors with transparent electroluminescent pixels was investigated. Compared with display technologies employing organic semiconductors that degrade with exposure to moisture and ultraviolet light, the all-oxide structure of this device is expected to be environmentally robust. This is believed to be the first demonstration of an integrated active matrix pixel using amorphous oxide semiconductor materials as both the light emitter and addressing circuit elements. The transparent active matrix pixel was designed, fabricated and characterized, that integrated amorphous indium gallium zinc oxide (IGZO) thin film transistors (TFTs) with a europium-doped IGZO thin film electroluminescent (TFEL) device. The integrated circuits were fabricated using room temperature pulsed laser deposition (PLD) of IGZO and ITO thin films onto substrates of Corning 7059 glass, sputter coated with an ITO back contact and subsequent atomic layer deposited ATO high-k dielectric. A second ITO layer is deposited by PLD as a contact and interconnect layer. All deposition steps were carried out at room temperature. In addition to the integration task, an important part of this thesis concerns the investigation of europium as a dopant in different oxide hosts including gallium oxide, gadolinium oxide, and amorphous IGZO. Amorphous IGZO was chosen for the integration task since it could be deposited at room temperature, however it was found that the emission intensity of Eu:IGZO thin films was strongly dependent on the oxygen pressure during deposition. It was determined that Eu3+ emission only occurs when the films are insulating, the result of increased oxygen pressure during deposition. Relatively low concentrations of Eu3+ of 1 mole percent were used for this study, with the intensity of these first generation pixels at 6 cd/m 2. Both gadolinium and gallium oxide films were investigated at higher substrate temperatures with a range of europium dopant concentrations. It was found that the both cubic and monoclinic phases of gadolinium oxide could be deposited, with the phase determined by deposition oxygen pressure. The film structure was analyzed by x-ray diffraction and transmission electron microscopy and optical spectra were obtained using time resolved photoluminescence (performed by a collaborator). These results were found to be in agreement with Stark-split energy levels calculated by another collaborator. Using 2.5 mole percent europium-doped gallium oxide as a host, bright thin film electroluminescent devices with intensities of 221 cd/m2 observed for a TFEL device excited by a symmetric +/-100 V max square pulse train at 1 kHz. This compares favorably with other red TFEL devices in the literature. Comparison with cathodoluminescence and photoluminescence data suggests that these performance metrics can be improved since the optimal concentration of europium by those experimental techniques was found to be near 10 mole percent. Time resolved photoluminescence revealed that radiative relaxation of the Eu3+ dopant could be modeled by two exponential decay components. Comparison of the intensity versus frequency of the electroluminescent data with time resolved photoluminescence data suggests that the faster component dominates the emission of the TFEL device.

Wellenius, Ian Patrick

36

Toward Active-Matrix Lab-On-A-Chip: Programmable Electrofluidic control Enaled by Arrayed Oxide Thin Film Transistors  

SciTech Connect

Agile micro- and nano-fluidic control is critical to numerous life science and chemical science synthesis as well as kinetic and thermodynamic studies. To this end, we have demonstrated the use of thin film transistor arrays as an active matrix addressing method to control an electrofluidic array. Because the active matrix method minimizes the number of control lines necessary (m + n lines for the m x n element array), the active matrix addressing method integrated with an electrofluidic platform can be a significant breakthrough for complex electrofluidic arrays (increased size or resolution) with enhanced function, agility and programmability. An amorphous indium gallium zinc oxide (a-IGZO) semiconductor active layer is used because of its high mobility of 1-15 cm{sup 2} V{sup -1} s{sup -1}, low-temperature processing and transparency for potential spectroscopy and imaging. Several electrofluidic functionalities are demonstrated using a simple 2 x 5 electrode array connected to a 2 x 5 IGZO thin film transistor array with the semiconductor channel width of 50 {mu}m and mobility of 6.3 cm{sup 2} V{sup -1} s{sup -1}. Additionally, using the TFT device characteristics, active matrix addressing schemes are discussed as the geometry of the electrode array can be tailored to act as a storage capacitor element. Finally, requisite material and device parameters are discussed in context with a VGA scale active matrix addressed electrofluidic platform.

Noh, Joo Hyon [University of Tennessee, Knoxville (UTK); Noh, Jiyong [University of Tennessee, Knoxville (UTK); Kreit, Eric [University of Cincinnati; Heikenfeld, Jason [University of Cincinnati; Rack, Philip D [ORNL

2012-01-01

37

Toward active-matrix lab-on-a-chip: programmable electrofluidic control enabled by arrayed oxide thin film transistors.  

PubMed

Agile micro- and nano-fluidic control is critical to numerous life science and chemical science synthesis as well as kinetic and thermodynamic studies. To this end, we have demonstrated the use of thin film transistor arrays as an active matrix addressing method to control an electrofluidic array. Because the active matrix method minimizes the number of control lines necessary (m + n lines for the mn element array), the active matrix addressing method integrated with an electrofluidic platform can be a significant breakthrough for complex electrofluidic arrays (increased size or resolution) with enhanced function, agility and programmability. An amorphous indium gallium zinc oxide (a-IGZO) semiconductor active layer is used because of its high mobility of 1-15 cm(2) V(-1) s(-1), low-temperature processing and transparency for potential spectroscopy and imaging. Several electrofluidic functionalities are demonstrated using a simple 2 5 electrode array connected to a 2 5 IGZO thin film transistor array with the semiconductor channel width of 50 ?m and mobility of 6.3 cm(2) V(-1) s(-1). Additionally, using the TFT device characteristics, active matrix addressing schemes are discussed as the geometry of the electrode array can be tailored to act as a storage capacitor element. Finally, requisite material and device parameters are discussed in context with a VGA scale active matrix addressed electrofluidic platform. PMID:22134753

Noh, Joo Hyon; Noh, Jiyong; Kreit, Eric; Heikenfeld, Jason; Rack, Philip D

2011-12-01

38

David Adler Lectureship Award in the Field of Materials Physics Talk: Novel Nitride and Oxide Electronics  

NASA Astrophysics Data System (ADS)

Recent progress in development of GaN-based transistors for gas and bio-sensing applications and amorphous IGZO layers for use thin film transistors (TFTs)on flexible substrates, including paper,will be presented. For the detection of gases such as hydrogen, the gateless GaN transistors are typically coated with a catalyst metal such as Pd or Pt to increase the detection sensitivity at room temperature. Functionalizing the surface with oxides, polymers and nitrides is also useful in enhancing the detection sensitivity for gases and ionic solutions.The use of enzymes or adsorbed antibody layers on the semiconductor surface leads to highly specific detection of a broad range of antigens of interest in the medical and security fields. We give examples of recent work showing sensitive detection of glucose, lactic acid, prostate cancer and breast cancer markers and the integration of the sensors with wireless data transmission systems to achieve robust, portable sensors. The amorphous transparent conducting oxide InZnGaO4 (IGZO) is attracting attention because of its high electron mobility (10-50 cm2.V-1.sec-1), high transparency in the visible region of the spectrum and its ability to be deposited with a wide range of conductivities.This raises the possibility of making low-cost electronics on a very wide range of arbitrary surfaces, including paper and plastics. N-type oxides such as zinc oxide, zinc tin oxide, indium gallium oxide, and indium gallium zinc tin oxide (IGZO) exhibit surprisingly high carrier mobilities even for amorphous films deposited at 300K. This has been explained by the fact that the conduction in these materials is predominantly through non-directional s orbitals which are less affected by disorder than the directional sp3 orbitals which control electron transport in Si. Examples of progress and discussion of remaining obstacles to use of IGZO TFTs will be presented

Pearton, Stephen

2011-03-01

39

Facile encapsulation of oxide based thin film transistors by atomic layer deposition based on ozone.  

PubMed

A simplified encapsulation strategy for metal-oxide based TFTs, using ozone instead of water as an oxygen source in a low-temperature ALD process is demonstrated. Thereby, the threshold voltage remains unaltered and the hysteresis is permanently reduced. Costly energy- and time-consuming post-treatment processes can be avoided. This concept is widely applicable to various encapsulation materials (e.g., Al2 O3 , TiO2 , ZrO2 ) and metal-oxide channel semiconductors (e.g., zinc-tin-oxide (ZTO), indium-gallium-zinc-oxide (IGZO)). PMID:23592395

Fakhri, Morteza; Babin, Nikolai; Behrendt, Andreas; Jakob, Timo; Grrn, Patrick; Riedl, Thomas

2013-04-17

40

Scaling behaviour of a-IGZO TFTs with transparent a-IZO source\\/drain electrodes  

Microsoft Academic Search

We analysed the scaling behaviour of amorphous indium gallium zinc oxide thin-film transistors (a-IGZO TFTs) with amorphous indium zinc oxide (a-IZO) transparent source\\/drain (S\\/D) electrodes. Due to the sputtering damage of the back-channel region during the a-IZO deposition process, the output characteristics show early saturation behaviour and the field-effect mobility in the saturation region is severely decreased in comparison with

Jaewook Jeong; Gwang Jun Lee; Joonwoo Kim; Byeongdae Choi

2012-01-01

41

Wet etching rates of InGaZnO for the fabrication of transparent thin-film transistors on plastic substrates  

Microsoft Academic Search

The wet etch process for amorphous indium gallium zinc oxide (a-IGZO or a-InGaZnO) by using various etchants is reported. The etch rates of a-IGZO, compared to another indium-based oxides including indium gallium oxide (IGO), indium zinc oxide (IZO), and indium tin oxide (ITO), are measured by using acetic acid, citric acid, hydrochloric acid, perchloric acid, and aqua ammonia as etchants,

Chi-Yuan Lee; Chienliu Chang; Wen-Pin Shih; Ching-Liang Dai

2010-01-01

42

Verification of Interface State Properties of a-InGaZnO Thin-Film Transistors With $\\\\hbox{SiN}_{x}$ and $ \\\\hbox{SiO}_{2}$ Gate Dielectrics by Low-Frequency Noise Measurements  

Microsoft Academic Search

To verify the interface state properties of amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs) with SiNx and SiO2 gate dielectrics, the low-frequency noise (LFN) of various gate-length devices from 5 to 50 ?m was mea- sured and evaluated. Before LFN measurements, the dc charac- teristics, such as the subthreshold slope (S), were measured for comparison. The interface state density (Nit) extracted

Hyun-Sik Choi; Sanghun Jeon; Hojung Kim; Jaikwang Shin; Changjung Kim; U-In Chung

2011-01-01

43

Amorphous manganese oxide remains amorphous upon lithium intercalation and cycling  

Microsoft Academic Search

Lithium intercalation in amorphous manganese oxide, synthesized by a room temperature aqueous oxidation route, is analyzed. As reported before, the material yields a very high intercalation capacity and also shows promising rate capability as cathode for rechargeable lithium batteries. The present study investigates the structure of the material using X-ray powder diffraction conducted on composite cathode pellets at different stages

Xu Jun John; Ye Hui; Jain Gaurav; Yang Jingsi

2004-01-01

44

High-Performance a-IGZO TFT With Gate Dielectric Fabricated at Room Temperature  

Microsoft Academic Search

We have investigated the high-performance oxide thin-film transistor (TFT) with an amorphous indium gallium zinc oxide (a-IGZO) channel and ZrO2 gate dielectrics. The a-IGZO TFT is fully fabricated at room temperature without any thermal treatments. ZrO2 is one of the most promising high-k materials. The a-IGZO TFT (channel W\\/L = 240\\/30 ??m) with ZrO2 shows high performance such as high

Jae Sang Lee; Seongpil Chang; Sang-Mo Koo; Sang Yeol Lee

2010-01-01

45

Crystallization process and magnetic properties of amorphous iron oxide nanoparticles  

Microsoft Academic Search

This paper studied the crystallization process, phase transition and magnetic properties of amorphous iron oxide nanoparticles prepared by the microwave heating technique. Thermal analysis and magnetodynamics studies revealed many interesting aspects of the amorphous iron oxide nanoparticles. The as-prepared sample was amorphous. Crystallization of the maghemite gamma-Fe2O3 (with an activation energy of 0.71 eV) and the hematite alpha-Fe2O3 (with an

N. D. Phu; D. T. Ngo; L. H. Hoang; N. H. Luong; N. Chau; N. H. Hai

2011-01-01

46

Comparative Study of the Low-Frequency-Noise Behaviors in a-IGZO Thin-Film Transistors With and Gate Dielectrics  

Microsoft Academic Search

A comparative study is made of the low-frequency noise (LFN) in amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistors (TFTs) with Al2O3 and Al2O3\\/SiNx gate dielectrics. The LFN is proportional to 1\\/fgamma, with gamma ~ 1 for both devices, but the normalized noise for the Al2O3\\/SiNx device is two to three orders of magnitude lower than that for the Al2O3 device. The

In-Tak Cho; Woo-Seok Cheong; Chi-Sun Hwang; Jeong-Min Lee; Hyuck-In Kwon; Jong-Ho Lee

2009-01-01

47

Metal oxide powder synthesized with amorphous metal chelates  

Microsoft Academic Search

Chelate powder consisting of amorphous particles was synthesized through the process in which the droplet of the chelate solution is dried in the gas phase and solidified in a moment using a splay-dry technique. To investigate the advantage of the use of amorphous chelate powder in the processing of metal oxide powder, this study provides following two routes: a conventional

H. Saitoh; R. Satoh; A. Nakamura; N. Nambu; S. Ohshio

2002-01-01

48

Acidic amorphous silica prepared from iron oxide of bacterial origin.  

PubMed

Microporous and mesoporous silica derived from biogenous iron oxide is an attractive catalyst for various organic reactions. Biogenous iron oxide contains structural silicon, and amorphous silica remains after iron oxide is dissolved in concentrated hydrochloric acid. The amorphous silica containing slight amounts of iron (Si/Fe = ?150) is composed of ?6-nm-diameter granular particles. The amorphous silica has a large surface area of 540 m(2)/g with micropores (1.4 nm) and mesopores (<3 nm). By using pyridine vapor as a probe molecule to evaluate the active sites in the amorphous silica, it was found that this material has strong Brnsted and Lewis acid sites. When the catalytic performance of this material was evaluated for reactions including the ring opening of epoxides and Friedel-Crafts-type alkylations, which are known to be catalyzed by acid catalysts, this material showed yields higher than those obtained with common silica materials. PMID:23331569

Hashimoto, Hideki; Itadani, Atsushi; Kudoh, Takayuki; Kuroda, Yasushige; Seno, Masaharu; Kusano, Yoshihiro; Ikeda, Yasunori; Nakanishi, Makoto; Fujii, Tatsuo; Takada, Jun

2013-02-04

49

Amorphous copper tungsten oxide with tunable band gaps  

SciTech Connect

We report on the synthesis of amorphous copper tungsten oxide thin films with tunable band gaps. The thin films are synthesized by the magnetron cosputtering method. We find that due to the amorphous nature, the Cu-to-W ratio in the films can be varied without the limit of the solubility (or phase separation) under appropriate conditions. As a result, the band gap and conductivity type of the films can be tuned by controlling the film composition. Unfortunately, the amorphous copper tungsten oxides are not stable in aqueous solution and are not suitable for the application of photoelectrochemical splitting of water. Nonetheless, it provides an alternative approach to search for transition metal oxides with tunable band gaps.

Chen Le; Shet, Sudhakar; Tang Houwen; Wang Heli; Yan Yanfa; Turner, John; Al-Jassim, Mowafak [National renewable Energy Laboratory, Golden, Colorado 80401 (United States); Ahn, Kwang-soon [School of Display and Chemical Engineering, Yeungnam University, Dae-dong, Kyungsan 712-749 (Korea, Republic of)

2010-08-15

50

Lithium ion transport in a model of amorphous polyethylene oxide  

Microsoft Academic Search

Summary We have made a molecular dynamics study of transport of a single lithium ion in a previously reported model of amorphous polyethylene oxide. New ab initio calculations of the interaction of the lithium ion with 1,2-dimethoxyethane and with dimethyl ether are reported which are used to determine force fields for the simulation. We report preliminary calculations of solvation energies

P. T. Boinske; L. Curtiss; J. W. Halley; B. Lin; A. Sutjianto

1996-01-01

51

Unified interatomic potential and energy barrier distributions for amorphous oxides  

NASA Astrophysics Data System (ADS)

Amorphous tantala, titania, and hafnia are important oxides for biomedical implants, optics, and gate insulators. Understanding the effects of oxide doping is crucial to optimize performance in these applications. However, no molecular dynamics potentials have been created to date that combine these and other oxides that would allow computational analyses of doping-dependent structural and mechanical properties. We report a novel set of computationally efficient, two-body potentials modeling van der Waals and covalent interactions that reproduce the structural and elastic properties of both pure and doped amorphous oxides. In addition, we demonstrate that the potential accurately produces energy barrier distributions for pure and doped samples. The distributions can be directly compared to experiment and used to calculate physical quantities such as internal friction to understand how doping affects material properties. Future analyses using these potentials will be of great value to determine optimal doping concentrations and material combinations for myriad material science applications.

Trinastic, J. P.; Hamdan, R.; Wu, Y.; Zhang, L.; Cheng, Hai-Ping

2013-10-01

52

Unified interatomic potential and energy barrier distributions for amorphous oxides.  

PubMed

Amorphous tantala, titania, and hafnia are important oxides for biomedical implants, optics, and gate insulators. Understanding the effects of oxide doping is crucial to optimize performance in these applications. However, no molecular dynamics potentials have been created to date that combine these and other oxides that would allow computational analyses of doping-dependent structural and mechanical properties. We report a novel set of computationally efficient, two-body potentials modeling van der Waals and covalent interactions that reproduce the structural and elastic properties of both pure and doped amorphous oxides. In addition, we demonstrate that the potential accurately produces energy barrier distributions for pure and doped samples. The distributions can be directly compared to experiment and used to calculate physical quantities such as internal friction to understand how doping affects material properties. Future analyses using these potentials will be of great value to determine optimal doping concentrations and material combinations for myriad material science applications. PMID:24160526

Trinastic, J P; Hamdan, R; Wu, Y; Zhang, L; Cheng, Hai-Ping

2013-10-21

53

Working hypothesis to explore novel wide band gap electrically conducting amorphous oxides and examples  

Microsoft Academic Search

A working hypothesis for exploring optically transparent and electrically conducting amorphous oxides is proposed on the basis of simple considerations concerning chemical bonding. The hypothesis predicts that amorphous oxides composed of heavy metal cations with an electronic configuration of (n ? 1)d10ns0 may be converted into transparent conducting amorphous oxides when doped by Li ion implantation or heating at temperatures

Hideo Hosono; Naoto Kikuchi; Naoyuki Ueda; Hiroshi Kawazoe

1996-01-01

54

Amorphous Zinc-Oxide-Based Thin-film Transistors  

Microsoft Academic Search

Recently, RF-sputtered zinc oxide-based field effect transisters (FETs) have been demonstrated with higher mobilities and performance than amorphous silicon, the dominant material used for display backplanes [1,2]. The low temperature processing possible for zinc oxide-based FETs [3] makes these materials compatible with flexible polymer substrates, but patterning with shadow masks limits feature size and accuracy. This project aims to develop

A. Wang; I. Kymissis; P. Mardilovich; V. Bulovic; C. G. Sodini; A. I. Akinwande

2005-01-01

55

Atomistic Modeling of Mechanical Loss in Amorphous Oxides  

NASA Astrophysics Data System (ADS)

The mechanical and optical loss in amorphous solids, described by the internal friction and light scattering susceptibility are investigated using classical, atomistic molecular dynamics simulation. We implemented the trajectory bisection method and the non-local ridge method in DL-POLY molecular dynamics simulation software. These methods were used to locate the different local potential energy minima that a system visits through an MD trajectory and the transition state between any two consecutive minima. From the distributions of the barrier height and asymmetry, and the relaxation time of the different transition states we calculated the internal friction of pure amorphous silica and mixed oxides.

Hamdan, Rashid; Trinastic, Jonathan; Cheng, Hai-Ping

2013-03-01

56

Nanostructured amorphous manganese oxide cryogel as a high-rate lithium intercalation host  

Microsoft Academic Search

Amorphous manganese oxides have received increasing attention in recent years as high-capacity intercalation cathodes for rechargeable lithium batteries. Nanostructured electrodes have been shown to exhibit enhanced rate capabilities. In this paper, a nanostructured amorphous manganese oxide cryogel is reported that combines the advantages of the amorphous structure and the nano-architecture, leading to high lithium intercalation capacity and high rate capability.

Jun John Xu; Jingsi Yang

2003-01-01

57

Universal Medium-Range Order of Amorphous Metal Oxides  

NASA Astrophysics Data System (ADS)

We propose that the structure of amorphous metal oxides can be regarded as a dual-dense-random-packing structure, which is a superposition of the dense random packing of metal atoms and that of oxygen atoms. Our ab initio molecular dynamics simulations show that the medium-range order of amorphous HfO2, ZrO2, TiO2, In2O3, Ga2O3, Al2O3,, and Cu2O is characterized by the pentagonal-bipyramid arrangement of metal atoms and that of oxygen atoms, and prove the validity of our dual-random-sphere-packing model. In other words, we find that the pentagonal medium-range order is universal independent of type of metal oxide.

Nishio, Kengo; Miyazaki, Takehide; Nakamura, Hisao

2013-10-01

58

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

Microsoft Academic Search

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

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

59

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

Microsoft Academic Search

Amorphous manganese oxides have received increasing attention in recent years as intercalation cathodes for rechargeable lithium batteries. The solgel method is a versatile method for achieving nanostructured amorphous oxides. In this paper, two different solgel 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

Jingsi Yang; Jun John Xu

2003-01-01

60

Hydrogenated Amorphous Silicon Oxide Solar Cells Fabricated near the Phase Transition between Amorphous and Microcrystalline Structures  

NASA Astrophysics Data System (ADS)

We investigated the properties of hydrogenated amorphous silicon oxide (a-Si1-xOx:H) deposited near the phase transition between amorphous and microcrystalline structures. a-Si1-xOx:H films were prepared by plasma-enhanced chemical vapor deposition using a gas mixture of silane, hydrogen, and carbon dioxide. The film structure was changed from amorphous to microcrystalline phase by increasing hydrogen dilution. Optical and electrical characterizations revealed that wide-gap a-Si1-xOx:H films were deposited under phase transition conditions. We also fabricated a-Si1-xOx:H single-junction p-i-n solar cells by varying the hydrogen dilution for the i-layer. The solar cells showed a maximum open circuit voltage of 1.04 V (Jsc=7.92 mA/cm2, \\mathit{FF}=0.64, Eff=5.2%) when the i-layer was deposited under phase transition conditions.

Inthisang, Sorapong; Sriprapha, Kobsak; Miyajima, Shinsuke; Yamada, Akira; Konagai, Makoto

2009-12-01

61

Methanol oxidation on vanadium oxide catalyst prepared by in situ activation of amorphous vanadium pentoxide precursor  

SciTech Connect

Amorphous vanadium pentoxide was prepared using the sol-gel process and vanadyl triisobutoxide as precursor. The catalytic properties of this material for methanol oxidation to formaldehyde were investigated in the temperature range 300 to 520 K. At 520 K the initial activity of the amorphous V{sub 2}O{sub 5} was very low. However, during in situ activation at this temperature the activity increased steadily and reached a steady-state value which was about 30 times higher than the initial activity of the amorphous V{sub 2}O{sub 5} and also considerably higher than the activity of crystalline V{sub 2}O{sub 5}. X-ray diffraction indicated that upon exposure to methanol oxidation conditions the amorphous vanadia crystallized slowly and was partly reduced. These changes were accompanied by drastic alterations of the bulk and surface structure of the amorphous precursor as evidence by electron microscopy. The final catalysts exhibiting steady-state activity consisted of crystalline V{sub 2}O{sub 5} and V{sub 3}O{sub 7}. Partial reduction of the bulk was not observed with crystalline vanadia catalysts and appears to be characteristic for the amorphous vanadia. The results indicate that amorphous vanadia undergoes structural changes more easily than its crystalline counterpart and may thus be an interesting catalyst precursor.

Gasser, D.; Baiker, A. (Swiss Federal Institute of Technology, Zuerich (Switzerland))

1988-10-01

62

Photoassisted catalytic oxidation of alcohols and halogenated hydrocarbons with amorphous manganese oxides  

Microsoft Academic Search

This manuscript discusses the synthesis of Amorphous Manganese Oxide (AMO) materials that are used for efficient photoassisted catalytic oxidation of alcohols and halogenated hydrocarbons. Characterization studies suggest that oxygen is lost from AMO very readily under illumination, creating oxygen vacancies that may be important in photooxidation reactions. Alcohols are converted to ketones such as acetone from isopropanol with 100% selectivity

Jie Chen; Jung Chou Lin; Vandana Purohit; Michael B. Cutlip; Steven L. Suib

1997-01-01

63

Improved cycling performance of bismuth-modified amorphous manganese oxides as cathodes for rechargeable lithium batteries  

Microsoft Academic Search

Bismuth-modified amorphous manganese oxides were synthesized via a room temperature aqueous route. They were galvanostatically tested as intercalation cathodes for rechargeable lithium batteries at 1mAcm?2 between 1.5 and 4.3V. In sharp contrast to severe capacity fading of unmodified amorphous manganese oxide synthesized by the same route, a stable cycling performance of the bismuth-modified amorphous manganese oxide was observed. After an

Jingsi Yang; Terrill B Atwater; Jun John Xu

2005-01-01

64

Compositional disorder and transport peculiarities in the amorphous indium oxides  

NASA Astrophysics Data System (ADS)

We present results of the disorder-induced metal-insulator transition (MIT) in three-dimensional amorphous indium-oxide films. The amorphous version studied here differs from the one reported by Shahar and Ovadyahu [Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.46.10917 46, 10917 (1992)] in that it has a much lower carrier concentration. As a measure of the static disorder we use the dimensionless parameter kF?. Thermal annealing is employed as the experimental handle to tune the disorder. On the metallic side of the transition, the low temperature transport exhibits weak-localization and electron-electron correlation effects characteristic of disordered electronic systems. These include a fractional power-law conductivity versus temperature behavior anticipated to occur at the critical regime of the transition. The MIT occurs at a kF??0.3 for both versions of the amorphous material. However, in contrast with the results obtained on the electron-rich version of this system, no sign of superconductivity is seen down to ?0.3 K even for the most metallic sample used in the current study. This demonstrates that using kF? as a disorder parameter for the superconductor-insulator transition (SIT) is an ill defined procedure. A microstructural study of the films, employing high resolution chemical analysis, gives evidence for spatial fluctuations of the stoichiometry. This brings to light that, while the films are amorphous and show excellent uniformity in transport measurements of macroscopic samples, they contain compositional fluctuations that extend over mesoscopic scales. These, in turn, reflect prominent variations of carrier concentrations thus introducing an unusual type of disorder. It is argued that this compositional disorder may be the reason for the apparent violation of the Ioffe-Regel criterion in the two versions of the amorphous indium oxide. However, more dramatic effects due to this disorder are expected when superconductivity sets in, which are in fact consistent with the prominent transport anomalies observed in the electron-rich version of indium oxide. The relevance of compositional disorder (or other agents that are effective in spatially modulating the BCS potential) to other systems near their SIT is discussed.

Givan, U.; Ovadyahu, Z.

2012-10-01

65

Lithium ion transport in a model of amorphous polyethylene oxide.  

SciTech Connect

We have made a molecular dynamics study of transport of a single lithium ion in a previously reported model of amorphous polyethylene oxide. New ab initio calculations of the interaction of the lithium ion with 1,2-dimethoxyethane and with dimethyl ether are reported which are used to determine force fields for the simulation. We report preliminary calculations of solvation energies and hopping barriers and a calculation of the ionic conductivity which is independent of any assumptions about the mechanism of ion transport. We also report some details of a study of transport of the trapped lithium ion on intermediate time and length scales.

Boinske, P. T.; Curtiss, L.; Halley, J. W.; Lin, B.; Sutjianto, A.; Chemical Engineering; Univ. of Minnesota

1996-01-01

66

Study of amorphous tin oxide thin films for ISFET applications  

Microsoft Academic Search

In this study, an amorphous tin oxide (SnO2) obtained by thermal evaporation was used as a pH-sensitive material for pH-ISFETs. Capacitancevoltage (CV) curves of the EIS diode were used to evaluate pH response of SnO2 thin film. Subsequently, SnO2\\/SiO2 gate ISFET was fabricated and pH sensitivity was determined through a shift in the threshold voltage of an ISFET sensor. The

Hung-Kwei Liao; Jung-Chuan Chou; Wen-Yaw Chung; Tai-Ping Sun; Shen-Kan Hsiung

1998-01-01

67

Enhanced bias stress stability of a-InGaZnO thin film transistors by inserting an ultra-thin interfacial InGaZnO:N layer  

NASA Astrophysics Data System (ADS)

Amorphous indium-gallium-zinc oxide (a-IGZO) thin film transistors (TFTs) having an ultra-thin nitrogenated a-IGZO (a-IGZO:N) layer sandwiched at the channel/gate dielectric interface are fabricated. It is found that the device shows enhanced bias stress stability with significantly reduced threshold voltage drift under positive gate bias stress. Based on x-ray photoelectron spectroscopy measurement, the concentration of oxygen vacancies within the a-IGZO:N layer is suppressed due to the formation of N-Ga bonds. Meanwhile, low frequency noise analysis indicates that the average trap density near the channel/dielectric interface continuously drops as the nitrogen content within the a-IGZO:N layer increases. The improved interface quality upon nitrogen doping agrees with the enhanced bias stress stability of the a-IGZO TFTs.

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

2013-05-01

68

Investigation of oxygen plasma treatment on the device performance of solution-processed a-IGZO thin film transistors  

NASA Astrophysics Data System (ADS)

We reported the impact of oxygen plasma treatment on solution-processed amorphous indium gallium zinc oxide (a-IGZO) thin film transistors (TFTs). Plasma-treated devices showed higher mobility, larger on/off current ratio, but a monotonically increased SS with plasma treatment time as well. The phenomenon was mainly due to two components in oxygen plasma, atomic oxygen and O2+, according to the photoluminescence (PL) measurement. Atomic oxygen reacted with oxygen vacancies in channel layer resulting in an improved mobility, and O2+ tends to aggregated at the surface acting as trapping states simultaneously. Our study suggests that moderate oxygen plasma treatment can be adopted to improve the device performance, while O2+ should be eliminated to obtain good interfacial states.

Pu, Haifeng; Zhou, Qianfei; Yue, Lan; Zhang, Qun

2013-10-01

69

Influence of positive bias stress on N2O plasma improved InGaZnO thin film transistor  

NASA Astrophysics Data System (ADS)

A post-treatment using N2O-plasma is applied to enhance the electrical characteristics of amorphous indium gallium zinc oxide thin film transistors. Improvements in the field-effect mobility and the subthreshold swing demonstrate that interface states were passivated after N2O-plasma treatment, and a better stability under positive gate-bias stress was obtained in addition. The degradation of mobility, resulted from bias stress, reduces from 6.1% (untreated devices) to 2.6% (N2O-plasma treated devices). Nevertheless, a strange hump characteristic occurs in transfer curve during bias stress, inferring that a parasitic transistor had been caused by the gate-induced electrical field.

Tsai, Chih-Tsung; Chang, Ting-Chang; Chen, Shih-Ching; Lo, Ikai; Tsao, Shu-Wei; Hung, Ming-Chin; Chang, Jiun-Jye; Wu, Chen-Yi; Huang, Chun-Yao

2010-06-01

70

Increased corrosion resistance of stent materials by converting current surface film of polycrystalline oxide into amorphous oxide.  

PubMed

Current efforts of new stent technology have been aimed largely at the improvement of intravascular stent biocompatibility. Among the chemical characteristics of metallic stents, surface oxide corrosion properties are paramount. Using our unique technique, the currently marketed 316 L stainless steel and nitinol stent wires covered with polycrystalline oxide were chemically etched and then passivated to form amorphous oxide. Excellent metallic-stent corrosion resistance with an amorphous oxide surface was demonstrated in our previous in vitro study. For in vivo validation, we compared the corrosion behavior of different oxide surfaces on various forms of test wires in the abdominal aorta of mongrel dogs using open-circuit potential and cyclic anodic polarization measurements. After conduction, the retrieved test wires were observed under scanning electron microscope. No passivity breakdown was found for wires covered with amorphous oxide, while wires with polycrystalline oxide showed breakdown at potentials between +0.2 to + 0.6 V. It has been proven that severe pitting or crevice corrosion occurred on the surface of polycrystalline oxide, while the surface of amorphous oxide was free of degradations in our experiment. We have demonstrated that this amorphous oxide coating on metallic material provides better corrosion resistance, not only in vitro but also in vivo, and it is superior not only in strength safety but also in medical device biocompatibility. PMID:10951371

Shih, C C; Lin, S J; Chung, K H; Chen, Y L; Su, Y Y

2000-11-01

71

Low temperature nitridation of amorphous high-K metal-oxide in inter-gates insulator stack  

US Patent & Trademark Office Database

An OXO-type inter-poly insulator (where X is a high-K metal oxide and O is an insulative oxide) is defined by forming an amorphous metal oxide layer on a silicon-based insulator (e.g., a silicon oxide layer) and then nitridating at least upper and lower sub-layers of the amorphous metal oxide with a low temperature plasma treatment that maintains temperature below the recrystallization temperature of the amorphous material. Such a plasma treatment has been found to improve breakdown voltage characteristics of the insulator. In one embodiment, the metal oxide includes aluminum oxide and it is fluorinated with low temperature plasma prior to nitridation.

Lee; Tai-Peng (Milpitas, CA); Haselden; Barbara (Cupertino, CA)

2005-08-23

72

Tungsten oxide as a p-type window material in amorphous silicon solar cells  

Microsoft Academic Search

A p-type amorphous tungsten oxide (p-a-WO3) film was prepared using a vacuum thermal evaporator with a WO3 source. By replacing a 10 nm-thick p-type amorphous silicon carbide window layer of a pin-type amorphous silicon based solar cell with a 10 nm-thick p-a-WO3 film, the short circuit current density increased from 12.75 to 13.83 mA\\/cm2. Although the open circuit voltage was

Liang Fang; Seung Jae Baik; Jeong Won Kim; Seung Hyup Yoo; Jin-Wan Jeon; Sang Jung Kang; Yoon Hak Kim; Koeng Su Lim

2010-01-01

73

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

NASA Astrophysics Data System (ADS)

Amorphous hafnium oxide (HfOx) is deposited by sputtering while achieving a very high k~30. Structural characterization suggests that the high k is a consequence of a previously unreported cubiclike short range order in the amorphous HfOx (cubic k~30). The films also possess a high electrical resistivity of 1014 ? cm, a breakdown strength of 3 MV cm-1, and an optical gap of 6.0 eV. Deposition at room temperature and a high deposition rate (~25 nm min-1) makes these high-k amorphous HfOx films highly advantageous for plastic electronics and high throughput manufacturing.

Li, Flora M.; Bayer, Bernhard C.; Hofmann, Stephan; Dutson, James D.; Wakeham, Steve J.; Thwaites, Mike J.; Milne, William I.; Flewitt, Andrew J.

2011-06-01

74

High quality hydrogenated amorphous silicon oxide film and its application in thin film silicon solar cells  

Microsoft Academic Search

Wide gap, high quality hydrogenated intrinsic amorphous silicon oxide (i-a-SiO:H) films have been prepared by very high frequency plasma-enhanced chemical vapor deposition (60MHz VHF-PECVD) technique for using as an absorber layer for the single junction amorphous silicon solar cells. In this study, we mainly investigated the effect of plasma power density on the defect density of the films, since the

Jaran Sritharathikhun; Apichan Moollakorn; Songkiate Kittisontirak; Amornrat Limmanee; Kobsak Sriprapha

2011-01-01

75

The magnetic properties of a magnetic detector using oxidized amorphous Co 95? x Fe 5(BSi) x alloys  

Microsoft Academic Search

A comparative oxidation study of several amorphous Co75?xFe5(BSi)20+x alloys was carried out. Reentrant magnetization behavior and field-induced anisotropy which are of a critical importance for a magnetic detector were obtained after oxidation of the amorphous Co-rich ribbons. During this oxidation, the ribbons develop surface oxides which are primarily nonmagnetic borosilicate or a combination of borosilicate and magnetic oxides such CoO

S. J Ahn; C. K Kim; S. J Kim; D. K Choi; R. C O'Handley

2000-01-01

76

Nanosized metal oxide and nanobelts prepared by selective dealloying of Ti-based amorphous powders.  

PubMed

Two typical nanomaterials, nanosized metal oxides and nanobelts, are obtained in one-pot selective dealloying process by using multiple-component Ti-based amorphous powders as dealloying precursors. The microstructure and photoelectric conversion property of the as-synthesized Zr-doped nanobelts are comprehensively investigated. Particularly, a core-shell structure, for example, residual amorphous alloy as the microsized core and nanosized metal oxide composites (mainly TiO2 and CuO) as the shell, forms as a byproduct of the selective dealloying. These resultant metal oxide composites show large specific surface area, and superior adsorption efficiency and capacity for removing toxic Cr(6+) in aqueous solution. The differences in the standard electrode potentials between the multiple-component elements in amorphous powders trigger their selective dealloying in alkaline solutions. PMID:23738525

Wang, Dong Jun; Li, Zhong Hua; Rahman, Md Anisur; Shen, Jun

2013-06-05

77

Unipolar resistive switching behaviors in amorphous lutetium oxide films  

NASA Astrophysics Data System (ADS)

The resistive switching properties in the amorphous Lu2O3 films deposited by pulsed laser deposition have been investigated. Well unipolar switching behaviors of Pt/Lu2O3/Pt stacks were obtained. The memory cells exhibited a high resistance ratio over 1103, fast programming speed within 30 ns, and no obvious degradation after an endurance of 300 switching cycles and a duration of 3.2106 s. The first-principles calculation indicates that the oxygen vacancies in cubic Lu2O3 will form defective energy level below the bottom of conduction band, and reduce the band gap. The absence of grain boundaries in the amorphous Lu2O3 films helps us attribute the switching mechanism of such stacks to the possible redistribution of defects related to oxygen vacancies along the filamentary paths during the resistive switching process.

Gao, Xu; Xia, Yidong; Xu, Bo; Kong, Jizhou; Guo, Hongxuan; Li, Kui; Li, Haitao; Xu, Hanni; Chen, Kai; Yin, Jiang; Liu, Zhiguo

2010-10-01

78

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

SciTech Connect

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.

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

1986-09-01

79

Electrical and optical properties of sputtered amorphous vanadium oxide thin films  

SciTech Connect

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.

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

80

Development of High Quality P-Type Hydrogenated Amorphous Silicon Oxide Film and Its Use in Improving the Performance of Single Junction Amorphous Silicon Solar Cells  

Microsoft Academic Search

By using radio frequency plasma enhanced chemical vapour deposition (RF-PECVD) method (13.56 MHz) we have developed high quality wide band gap p-type hydrogenated amorphous silicon oxide (p-a-SiO:H) films having characteristics suitable for use as the window layer for single and multijunction amorphous silicon (a-Si) solar cells. The films have been characterized in detail. The p-a-SiO:H films having thickness >=100

Arindam Sarker; Asok K. Barua

2002-01-01

81

Enhanced capacitance of composite anodic ZrO? films comprising high permittivity oxide nanocrystals and highly resistive amorphous oxide matrix.  

PubMed

Anodic oxide films with nanocrystalline tetragonal ZrO(2) precipitated in an amorphous oxide matrix were formed on Zr-Si and Zr-Al alloys and had significantly enhanced capacitance in comparison with those formed on zirconium metal. The capacitance enhancement was associated with the formation of a high-temperature stable tetragonal ZrO(2) phase with high relative permittivity as well as increased ionic resistivity, which reduces the thickness of anodic oxide films at a certain formation voltage. However, there is a general empirical trend that single-phase materials with higher permittivity have lower ionic resistivity. This study presents a novel material design based on a nanocrystalline-amorphous composite anodic oxide film for capacitor applications. PMID:21648468

Habazaki, Hiroki; Koyama, Shun; Aoki, Yoshitaka; Sakaguchi, Norihito; Nagata, Shinji

2011-06-20

82

Electrodeposited amorphous iron(III) oxides as anodes for photoelectrolysis of water  

Microsoft Academic Search

Deposition of amorphous iron(III)-oxide films on a conducting glass substrate was achieved via a cathodic bias in a 0.1M hydrated ammonium iron(II) sulfate ((NH4)2Fe(SO4)26H2O) solution at ?1.6V versus Ag\\/AgCl. Analysis by X-ray absorption near edge structure confirmed the iron(III) feature of the amorphous films. The deposited films exhibited n-type semiconducting characteristics by showing photoresponses under an anodic bias. The MottSchottky

Pei-Shan Li; Hsisheng Teng

2007-01-01

83

Damage at hydrogenated amorphous/crystalline silicon interfaces by indium tin oxide overlayer sputtering  

NASA Astrophysics Data System (ADS)

Damage of the hydrogenated amorphous/crystalline silicon interface passivation during transparent conductive oxide sputtering is reported. This occurs in the fabrication process of silicon heterojunction solar cells. We observe that this damage is at least partially caused by luminescence of the sputter plasma. Following low-temperature annealing, the electronic interface properties are recovered. However, the silicon-hydrogen configuration of the amorphous silicon film is permanently changed, as observed from infra-red absorbance spectra. In silicon heterojunction solar cells, although the as-deposited film's microstructure cannot be restored after sputtering, no significant losses are observed in their open-circuit voltage.

Demaurex, Bndicte; De Wolf, Stefaan; Descoeudres, Antoine; Charles Holman, Zachary; Ballif, Christophe

2012-10-01

84

P-type conductive amorphous oxides of transition metals from solution processing  

NASA Astrophysics Data System (ADS)

We report a series of solution-processed p-type conductive amorphous Ln-M-O (a-Ln-M-O, where M = Ru, Ir, and Ln is a lanthanide element except Ce) having low resistivities (10-3 to 10-2 ? cm). These oxides are thermally stable to a high degree, being amorphous up to 800 C, and processable below 400 C. Their film surfaces are smooth on the atomic scale, and the process allows patterning simply by direct imprinting without distortion of the pattern after annealing. These properties have high potential for use in printed electronics. The electron configurations of these oxides are apparently different from existing p-type oxides.

Li, Jinwang; Kaneda, Toshihiko; Tokumitsu, Eisuke; Koyano, Mikio; Mitani, Tadaoki; Shimoda, Tatsuya

2012-07-01

85

Transmission electron microscopy studies of the specific structure of crystals formed by phase transition in iron oxide amorphous films  

Microsoft Academic Search

The crystal growth and the structure of crystallised areas in amorphous iron oxide films prepared by pyrolysis is studied (in particular, in situ) by means of transmission electron microscopy. The bend-contour (BC) technique reveals an unusual phenomenon of regular internal bending of the lattice planes associated with a phase transition also observed earlier in some other amorphous films. The peculiarity

V. Yu Kolosov; A. R. Thoelen

2000-01-01

86

Model for determination of mid-gap states in amorphous metal oxides from thin film transistors  

NASA Astrophysics Data System (ADS)

The electronic density of states in metal oxide semiconductors like amorphous zinc oxide (a-ZnO) and its ternary and quaternary oxide alloys with indium, gallium, tin, or aluminum are different from amorphous silicon, or disordered materials such as pentacene, or P3HT. Many ZnO based semiconductors exhibit a steep decaying density of acceptor tail states (trap DOS) and a Fermi level (EF) close to the conduction band energy (EC). Considering thin film transistor (TFT) operation in accumulation mode, the quasi Fermi level for electrons (Eq) moves even closer to EC. Classic analytic TFT simulations use the simplification EC-EF> `several'kT and cannot reproduce exponential tail states with a characteristic energy smaller than 1/2 kT. We demonstrate an analytic model for tail and deep acceptor states, valid for all amorphous metal oxides and include the effect of trap assisted hopping instead of simpler percolation or mobility edge models, to account for the observed field dependent mobility.

Bubel, S.; Chabinyc, M. L.

2013-06-01

87

Oxidation of Amorphous Cu54Zr22Ti18Ni6 Coating Between 573 and 769 K in Air  

NASA Astrophysics Data System (ADS)

Gas-atomized amorphous Cu54Zr22Ti18Ni6 powders were sprayed onto a steel substrate by the kinetic spraying method to make an amorphous Cu54Zr22Ti18Ni6 coating. The oxidation behavior of the coating was studied over the temperature range 573-769 K in air. The oxidation products were primarily Cu2O, CuO, ?-ZrO2, ZrTiO4, and Cu. Copper oxides were the major oxides. Preferential oxidation of Cu occurred around the surface of the coating.

Choi, J. H.; Lee, D. B.

88

Inelastic electron scattering in amorphous silicon nitride and aluminum oxide with multiple-scattering corrections  

Microsoft Academic Search

Electron-energy-loss measurements for an amorphous chemical-vapor-deposited silicon nitride film and evaporated sapphire in the broad energy range 1-200 eV are investigated. A method, not requiring the zero-loss peak, to remove the multiple scattering is discussed, applied, and the optical constants obtained. An Elliot-type model used with aluminum oxide gives a valence-exciton binding energy of 1.36+\\/-0.2 eV with a band gap

Peteris Livins; T. Aton; S. E. Schnatterly

1988-01-01

89

Nanoindentation of amorphous aluminum oxide films III. The influence of the substrate on the elastic properties  

Microsoft Academic Search

Using nanoindentation, the elastic moduli of composite film\\/substrate systems of amorphous Al2O3 thin films, with the thickness ranging from approximately 3 nm (native oxide) to 300 nm on aluminum and sapphire substrates, were studied. When indenting deeper into the samples, the transition from the elastic modulus of the film to that of the substrate is found to scale with the

N. G. Chechenin; J. Bottiger; J. P. Krog

1997-01-01

90

Optimization of indium tin oxide by pulsed DC power on single junction amorphous silicon solar cells  

Microsoft Academic Search

We investigated the optimal deposition conditions of a thin indium tin oxide (ITO) film on an amorphous silicon (a-Si) single-junction solar cell using pulsed DC magnetron sputtering. Thin ITO films were deposited while power, deposition time, pressure, gas flow and temperature were varied to find such conditions. The efficiency of a-Si solar cells with ITO films was 6.65% at the

Rebecca K. Carlson; Yunsic Shim; William B. Ingler

2011-01-01

91

A study of low temperature crystallization of amorphous thin film indium-tin-oxide  

NASA Astrophysics Data System (ADS)

Deposition of tin-doped-indium-oxide (ITO) on unheated substrates via low energy processes such as electron-beam deposition can result in the formation of amorphous films. The amorphous-to-crystalline transformation was studied in this system using in situ resistivity, time resolved reflectivity, glancing incidence angle x-ray diffraction, and transmission electron microscopy. The resistivity of 180 nm thick In2O3(9.9 wt. %SnO2) was monitored during isothermal anneals at 125, 135, 145, and 165 C. The dependence of the resistance on the volume fraction of crystalline phase was established using glancing incidence angle x-ray diffraction and a general two phase resistivity model for this system was developed. These studies show that, upon annealing, as-deposited amorphous ITO undergoes both a structural relaxation and crystallization. Structural relaxation of the amorphous material includes local ordering that increases the ionized vacancy concentration which, in turn, increases the carrier density in the material. Kinetic growth parameters were extracted from the data, which reveal that the relaxation of the amorphous structure occurs via a process that obeys a first order reaction rate law, while crystallization occurs via classical nucleation and growth with a growth mode parameter that is consistent with two- to three-dimensional transformation geometry. Both the relaxation and crystallization processes have an activation energy of approximately 1.3+/-0.2 eV. Time resolved reflectivity analysis of the electron beam deposited ITO reveals that there is a sharp and monotonic decrease in reflectivity during the anneal of the sample which is associated with the amorphous relaxation process.

Paine, David C.; Whitson, T.; Janiac, D.; Beresford, R.; Yang, Cleva Ow; Lewis, Brian

1999-06-01

92

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

Microsoft Academic Search

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

Sabine Goldberg; Cliff T. Johnstony

2001-01-01

93

Amorphous alumina oxidation protective coatings for Zircaloy based on a compositional gradient layer system  

NASA Astrophysics Data System (ADS)

Waterside corrosion of the Zircaloy cladding encasing the uranium oxide pellets is one of the primary factors limiting high "burn up" of nuclear fuel in pressurized water reactors (PWRs). High "burn up" can significantly impact plant safety and economics. Amorphous aluminum oxide coatings with aluminum-based compositional gradient layers (CGLs) were fabricated to develop ceramic coating corrosion protection systems for Zircaloy. Aluminum films were deposited on Zircaloy substrates by electron-beam evaporation, and two-step heat treatments were performed at near the melting temperature of aluminum. Amorphous alumina coatings by rf magnetron sputtering were overcoated on the CGL structures. Morphological and compositional studies were completed using field emission scanning electron microscopy (FE SEM), energy dispersive x-ray analysis (EDX), and auger electron spectroscopy (AES). The AES depth profiles of the annealed coatings showed that gradient compositions of Al, Zr, and O were obtained. Glancing angle x-ray diffraction (GAXRD) analysis showed that a variety of intermetallic and oxide phases (such as Al3Zr, Al2Zr3, Al2O3, ZrO2 and Zr3O) were formed in the coatings during processing. The intermetallic layers improved the adhesion property of the alumina overcoating to Zircaloy substrate, and functioned as oxidation resistant layers. In spite of the successful construction of the compositional gradient layer system with a good adhesion and thermal stability, and the report about the stability of pure alumina and amorphous ceramics in hydrothermal conditions, the amorphous alumina coatings in our study were not stable under nuclear reactor conditions of subcritical water at 350C and 20.1 MPa (3000 psi). We investigated the behavior of amorphous alumina thin films deposited on Zircaloy substrates in the near-supercritical water. When the coatings were exposed to the subcritical conditions, hydrothermally grown well-faceted crystallite formation was observed. Surface morphology and composition were characterized by FE SEM, AES and EDX. The crystallites were identified to be aluminum hydroxide, boehmite (gamma-AlOOH) by XRD spectra, peak shift in x-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) images. We hypothesized the mechanism of the boehmite formation as the dissolution of amorphous alumina and the reprecipitation of boehmite during the cooling process.

Park, Sang Tae

94

Seeded growth induced amorphous to crystalline transformation of niobium oxide nanostructures.  

PubMed

A novel high-temperature synthesis of niobium oxide nanostructures has been developed through an amorphous intermediate that crystallizes into anisotropic crystalline structures through a complex mechanism of nucleation-dissolution-selective growth induced by seeded growth. The amorphous materials formed by the thermolysis of niobium oleate transformed into crystalline platelets, wires or bundled wires after the injection of additional niobium oleate at different temperatures. The temperature of the solution during injection of the additional precursor determined the morphology of the formed crystalline structure. The time- and temperature-dependent evolution of the niobium oxide nanostructures demonstrates that amorphous materials progressively turned to crystalline materials. We tuned the size of wires and platelets by the consecutive injection of the precursor solution into the reaction mixture under isothermal conditions. With the sequential injection of the precursor solution, we demonstrate that the anisotropic growth of individual nanowires occurs exclusively along the ends, without the formation of any new nuclei. A mechanism for the transformation of well-defined platelets from wires has been proposed and is due to the exclusive loss of mass at the ends of the wires while growth of the platelets initially occurs along the (001) direction which is then replaced by the (110) face. PMID:22286141

Jana, Subhra; Rioux, Robert M

2012-01-30

95

Optical and electrochromic properties of amorphous and crystalline tungsten oxide films  

NASA Astrophysics Data System (ADS)

A detailed systematic study of the tungsten oxide thin films has been carried out using colored WO3 films after they were annealed at progressively increasing temperatures ranging from 350 to 450 degree(s)C in oxygen environments. The structural properties of the films were characterized using x-ray diffraction (XRD) and Raman spectroscopy. The amorphous WO3 films remain as an amorphous phase up to 385 degree(s)C and begin to crystallize at 390 degree(s)C and then are completely crystallized at 450 degree(s)C. Absorption peaks of the films are found to shift to a higher energy side with increasing annealing temperature up to 385 degree(s)C and then shift abruptly to a lower energy as the films begin to crystallize at 390 degree(s)C.

Ozkan, Esra; Lee, Se-Hee; Tracy, C. Ed; Tepehan, Fatma; Pitts, J. Roland; Deb, Satyen K.

2001-11-01

96

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

SciTech Connect

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.

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

1996-10-01

97

Studies of catalytic aerobic oxidation with nanostructured amorphous metals, alloys and metal oxides  

Microsoft Academic Search

The oxidation of cyclohexane with molecular oxygen in the presence of isobutyraldehyde catalyzed by nanostructured iron and cobalt oxides and iron oxide supported on titania has been studied. It was found that highly dispersed transi- tion metal oxide is more effective for oxidation than the corresponding zero-valent metal powders. Nanostructured cobalt oxide on MCM-41 is found to be efficient for

J. Indian; V. K ESAVANa; D. DHAR; Y. KOLTYPIN; N. PERKAS; A. GEDANKEN; S. CHANDRASEKARAN

98

Methane combustion over catalysts prepared by oxidation of ternary Pd 15X 10Zr 75 (X = Co, Cr, Cu, Mn and Ni) amorphous alloys  

Microsoft Academic Search

Catalysts for the combustion of methane have been prepared by controlled oxidation of various ternary amorphous alloys with the composition X10Pd15Zr75 (X = Co, Cr, Cu, Mn and Ni). As a reference material, a Pd25Zr75 amorphous alloy was used. The oxidation of the amorphous precursors led, in some cases, to highly active catalysts for the deep oxidation of methane. The

Christian A. Mller; Ren A. Koeppel; Marek Maciejewski; Josef Heveling; Alfons Baiker

1996-01-01

99

A non-thermal chemical synthesis of hydrophilic and amorphous cobalt oxide films for supercapacitor application  

NASA Astrophysics Data System (ADS)

Present work explored a room temperature, simple and low cost chemical route for the preparation of hydrophilic cobalt oxide films from alkaline cobalt chloride (CoCl 2:6H 2O) and double distilled water precursor solutions. As-deposited cobalt oxide films showed amorphous nature, which is one of the prime requirements for supercapacitor, as confirmed from X-ray diffraction studies. Changes in direct band gap energy and electrical resistivity of as-deposited cobalt oxide films were confirmed after annealing. Spherical grains of about 40-50 nm diameters were uniformly distributed over the substrate surface. Surface wettability studied in contact with liquid interface, showed hydrophilic nature as water contact angle was <90. Finally, presence of cobalt-oxygen covalent bond was observed from Raman shift experiment.

Kandalkar, Sunil G.; Lokhande, C. D.; Mane, R. S.; Han, Sung-Hwan

2007-02-01

100

Performance tuning of InGaZnO thin-film transistors with a SnInGaZnO electron barrier layer  

NASA Astrophysics Data System (ADS)

Indium gallium zinc oxide (InGaZnO) thin-film transistors (TFTs) with a co-sputtered tin indium gallium zinc oxide (SnInGaZnO) electron barrier layer (EBL) are fabricated. The effect of the SnInGaZnO layer thickness on device characteristics is investigated. With stacking a 250-nm-thick SnInGaZnO EBL in the source/drain region, it introduces an additional potential barrier of around 0.14 V to the channel carriers. Experimental results show that the turn-off voltage of TFTs increases from -0.5 V to about 0 V, the on/off current ratio increases from 1.9 105 to 1.9 106, and the subthreshold swing decreases from 0.13 V/dec to 0.073 V/dec.

Huang, Hau-Yuan; Wang, Shui-Jinn; Wu, Chien-Hung; Chiang, Chen-Kuo; Su, Je-Yi

2013-03-01

101

Ni(II) Complexation to Amorphous Hydrous Ferric Oxide: An X-ray Absorption Spectroscopy Study  

SciTech Connect

Ni(II) sorption onto iron oxides and in particular hydrous ferric oxide (HFO) is among the important processes impacting its distribution, mobility, and bioavailability in environment. To develop mechanistic models for Ni, extended X-ray absorption fine structure (EXAFS) analysis has been conducted on Ni(II) sorbed to HFO. Coprecipitation revealed the formation of the metastable {alpha}-Ni(OH){sub 2} at a Ni(II) loading of 3.5 x 10{sup -3} mol g{sup -1}. On the other hand, Ni(II) formed inner-sphere mononuclear bidentate complexes along edges of FeO{sub 6} octahedra when sorbed to HFO surfaces with Ni-O distances of 2.05-2.07 {angstrom} and Ni-Fe distances of 3.07-3.11 {angstrom}. This surface complex was observed by EXAFS study over 2.8 x 10{sup -3} to 10{sup -1} ionic strength, pH from 6 to 7, a Ni(II) loading of 8 x 10{sup -4} to 8.1 x 10{sup 03} mol g{sup -1} HFO, and reaction times from 4 hours to 8 months. The short- and long-range structure analyses suggest that the presence of Ni(II) inhibited transformation of the amorphous iron oxide into a more crystalline form. However, Ni{sup 2+} was not observed to substitute for Fe{sup 3+} in the oxide structure. This study systematically addresses Ni(II) adsorption mechanisms to amorphous iron oxide. The experimentally defined surface complexes can be used to constrain surface complexation modeling for improved prediction of metal distribution at the iron oxide/aqueous interface.

Xu,Y.; Axe, L.; Boonfueng, T.; Tyson, T.; Trivedi, P.; Pandya, K.

2007-01-01

102

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

Microsoft Academic Search

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

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

2002-01-01

103

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

Microsoft Academic Search

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

M. P. Cuypers; J. T. C. Grotenhuis; K. G. J. Nierop; E. Maneiro Franco; Jager de A; W. H. Rulkens

2002-01-01

104

Thermally induced changes in amorphous indium-tin-oxide thin films  

Microsoft Academic Search

Amorphous indium-tin-oxide (ITO) transparent conducting film (15 at% Sn; thickness, 150190 nm) was deposited on silicon wafer\\u000a at room temperature by RF magnetron sputtering for temperature programmed desorption (TPD) in vacuum. The thermal crystallization\\u000a was accompanied by evolution of water vapor (the main gas), argon and carbon dioxide. The total amount of evolved water vapor\\u000a (H2O [mol]\\/(In [mol]+Sn [mol])>0.2) was

M. H. Wang; S. Tokiwa; T. Nishide; Y. Kasahara; S. Seki; T. Uchida; M. Ohtsuka; T. Kondo; Y. Sawada

2008-01-01

105

Amorphous silicon thin-film transistor with fluorinated silicon oxide ion stopper  

Microsoft Academic Search

We propose fluorinated silicon oxide (SiOF) as the ion-stopper of bottom-gate amorphous silicon thin film transistors (a-Si:H TFTs). The low dielectric constant SiOF on both the back-channel of the TFT and the crossover regions of gate\\/data lines can contribute to reducing the RC delay of the gate pulse signal in active-matrix liquid-crystal displays. Besides, the a-Si:H TFT with a SiOF

Kyung Wook Kim; Kyu Sik Cho; Jai Il Ryu; Keon Ho Yoo; Jin Jang

2000-01-01

106

Characterization of an amorphous iridium water-oxidation catalyst electrodeposited from organometallic precursors.  

PubMed

Upon electrochemical oxidation of the precursor complexes [Cp*Ir(H(2)O)(3)]SO(4) (1) or [(Cp*Ir)(2)(OH)(3)]OH (2) (Cp* = pentamethylcyclopentadienyl), a blue layer of amorphous iridium oxide containing a carbon admixture (BL) is deposited onto the anode. The solid-state, amorphous iridium oxide material that is formed from the molecular precursors is significantly more active for water-oxidation catalysis than crystalline IrO(2) and functions as a remarkably robust catalyst, capable of catalyzing water oxidation without deactivation or significant corrosion for at least 70 h. Elemental analysis reveals that BL contains carbon that is derived from the Cp* ligand (? 3% by mass after prolonged electrolysis). Because the electrodeposition of precursors 1 or 2 gives a highly active catalyst material, and electrochemical oxidation of other iridium complexes seems not to result in immediate conversion to iridium oxide materials, we investigate here the nature of the deposited material. The steps leading to the formation of BL and its structure have been investigated by a combination of spectroscopic and theoretical methods. IR spectroscopy shows that the carbon content of BL, while containing some C-H bonds intact at short times, is composed primarily of components with C?O fragments at longer times. X-ray absorption and X-ray absorption fine structure show that, on average, the six ligands to iridium in BL are likely oxygen atoms, consistent with formation of iridium oxide under the oxidizing conditions. High-energy X-ray scattering (HEXS) and pair distribution function (PDF) analysis (obtained ex situ on powder samples) show that BL is largely free of the molecular precursors and is composed of small, <7 , iridium oxide domains. Density functional theory (DFT) modeling of the X-ray data suggests a limited set of final components in BL; ketomalonate has been chosen as a model fragment because it gives a good fit to the HEXS-PDF data and is a potential decomposition product of Cp*. PMID:23383971

Blakemore, James D; Mara, Michael W; Kushner-Lenhoff, Maxwell N; Schley, Nathan D; Konezny, Steven J; Rivalta, Ivan; Negre, Christian F A; Snoeberger, Robert C; Kokhan, Oleksandr; Huang, Jier; Stickrath, Andrew; Tran, Lan Anh; Parr, Maria L; Chen, Lin X; Tiede, David M; Batista, Victor S; Crabtree, Robert H; Brudvig, Gary W

2013-02-05

107

Transparent IGZO-Based Logic Gates  

Microsoft Academic Search

Optically transparent indiumgalliumzincoxide-based nand and nor gates and inverters were fabricated and characterized using transistors deposited at room temperature with 5-, 10-, and 20-$\\\\mu \\\\hbox{m}$ gate lengths and beta ratio between 2.5 and 40. The nand and nor gates' operation frequencies were measured up to 5 kHz. The individual transistors were measured to have saturation mobility of 14 $ \\\\hbox{cm}^{2}\\/\\\\hbox{V}

Haojun Luo; Patrick Wellenius; Leda Lunardi; John F. Muth

2012-01-01

108

Optimizing amorphous indium zinc oxide film growth for low residual stress and high electrical conductivity  

NASA Astrophysics Data System (ADS)

With recent advances in flexible electronics, there is a growing need for transparent conductors with optimum conductivity tailored to the application and nearly zero residual stress to ensure mechanical reliability. Within amorphous transparent conducting oxide (TCO) systems, a variety of sputter growth parameters have been shown to separately impact film stress and optoelectronic properties due to the complex nature of the deposition process. We apply a statistical design of experiments (DOE) approach to identify growth parametermaterial property relationships in amorphous indium zinc oxide (a-IZO) thin films and observed large, compressive residual stresses in films grown under conditions typically used for the deposition of highly conductive samples. Power, growth pressure, oxygen partial pressure, and RF power ratio (RF/(RF + DC)) were varied according to a full-factorial test matrix and each film was characterized. The resulting regression model and analysis of variance (ANOVA) revealed significant contributions to the residual stress from individual growth parameters as well as interactions of different growth parameters, but no conditions were found within the initial growth space that simultaneously produced low residual stress and high electrical conductivity. Extrapolation of the model results to lower oxygen partial pressures, combined with prior knowledge of conductivitygrowth parameter relationships in the IZO system, allowed the selection of two promising growth conditions that were both empirically verified to achieve nearly zero residual stress and electrical conductivities >1480 S/cm. This work shows that a-IZO can be simultaneously optimized for high conductivity and low residual stress.

Kumar, Mukesh; Sigdel, A. K.; Gennett, T.; Berry, J. J.; Perkins, J. D.; Ginley, D. S.; Packard, C. E.

2013-10-01

109

Transmission electron microscope-induced structural evolution in amorphous Fe, Co, and Ni oxide nanoparticles.  

PubMed

The high-energy electron beams in transmission electron microscopes (TEM) are known to cause structural changes and damage in some materials. In this paper, we describe unique and reproducible TEM-induced changes to the morphology of amorphous metal oxide (Fe, Co, and Ni) nanoparticles. The studied particles were synthesized via literature methods and fully characterized by X-ray powder diffraction and time-resolved, low-dose TEM. As a result of electron beam irradiation, we observe these particles to transform from initially solid spheres to core/void/shell structures and eventually to hollow nanoparticles. The rate of these transformations depends on the size and composition of the particles but is not unique to the Fe oxide we previously reported. These data suggest that structural analysis of nanoparticles by TEM must consider the impact of the high-energy electron beam and use low-dose imaging. PMID:19360944

Latham, Andrew H; Williams, Mary Elizabeth

2008-12-16

110

Structural and electrical characterization of amorphous lanthanum hafnium oxide thin films  

NASA Astrophysics Data System (ADS)

This paper describes the structural and electronic characterization of lanthanum hafnium oxide thin films deposited by metal organic chemical vapor deposition using a novel precursor mixture. Structural characterization is obtained using x-ray diffraction and cross-sectional transmission electron microscopy and indicates that the as-deposited films and films annealed up to 900 C remain effectively amorphous. Capacitance voltage and current voltage measurements on metal-oxide-semiconductor capacitors made using the films as a gate dielectric show the films exhibit good electrical integrity following post deposition annealing at temperatures up to 950 C. A dielectric constant, k for the films of 20+/-1.5 is determined and a density of interface states (at midgap) Dit of 3.91011 cm-2 eV-1 was measured.

Loo, Yim Fun; Taylor, Stephen; Murray, Robert T.; Jones, Anthony C.; Chalker, Paul R.

2006-05-01

111

A planar violet electroabsorption modulator and modeling of electric effects on zinc oxide excitons  

NASA Astrophysics Data System (ADS)

First principle electroabsorption calculations based on WTK spectral density theorem and Dow and Redfield theory were performed and used as the basis of a model to fit experimental electroabsorption data. The calculation results were compared to absorption measurements taken from 4.5 K to 300 K on a c-plane ZnO thin film sample to obtain the temperature broadening linewidth. The extracted broadening parameters were then expressed with two material related coefficients: the exciton-acoustic-phonon interaction strength gammaph = 79.6 +/- 3 microeV/K and exciton-LO-phonon interaction strength Gamma LO G = 242 +/- 10 meV. This expression is independent of sample qualities, or is "generalized" to accommodate the exciton band edge. A concept called "effective microfield intensity" was introduced to represent the crystalline quality. The microfield intensities of two ZnO samples with rocking curve FWHMs 0.25 and 0.42 are 1.3x105 and 2.26x105 kV/cm respectively. Buffer-assisted growth technique was applied to improve the quality of PLD grown ZnO on sapphire. ZnO thin films were deposited on ATO/ITO/glass substrate at 500 to 700 K, with higher temperature producing better films. XRD of these samples show highly c-oriented ZnO growth on the ATO substrate. ZnO electroabsorption modulators were fabricated based on ZnO/ATO/ITO/glass structure. Two types of top electrodes, Ni semi-transparent electrode (TE) and conducting indium gallium zinc oxide (IGZO) were experimented with the IGZO-coated device reducing the insertion loss by 50%. The DC percentage modulation of these devices have two peaks, over 40% near 370 nm and around 20% near 385 nm at 140 V bias. AC testing confirms purely field modulation and shows no evident of frequency cut-off up to 100 kHz. A simple device model attributes the threshold voltage of ZnO electroabsorption modulators to the charge screening effects. Applied voltage was obtained both by converting the electric field based on device model and fitting the observed electroabsorption spectra with the first principle calculation and Gaussian broadening. The field strengths obtained from the two approaches is consistent.

Zhang, Xiyao

112

High-temperature oxidation of a rapidly solidified amorphous Ta-Ir alloy  

SciTech Connect

The oxidation products formed at 500 and 700/sup 0/C on an amorphous Ta44.5 at% Ir alloy in an Ar-0.1% O/sub 2/ gas mixture were characterized using SEM, XRD, EPMA, TEM, STEM, AES, and XPS. Initially, a thin (3-4 nm) layer of Ta/sub 2/O/sub 5/ formed at the surface of the alloy. Continued growth of the Ta/sub 2/O/sub 5/, which occurred very rapidly, involved diffusion of oxygen anions from the Ta/sub 2/O/sub 5//gas interface to the alloy/Ta/sub 2/O/sub 5/ interface, where tantalum was selectively oxidized. Because the oxide grew more quickly than iridium could diffuse back into the alloy, the iridium coalesced into platelets of crystalline iridium-rich alloy that were oriented approximately parallel to the oxide/alloy interface, and which became embedded in a matrix of Ta/sub 2/O/sub 5/. The unoxidized core remained in the glassy state. The oxidation process and/or the dissolution of oxygen into the unoxidized alloy caused the alloy to become embrittled.

Cotell, C.M.; Yorek, G.J.

1986-12-01

113

High temperature mechanical and oxidation behavior of amorphous silicon carbonitride processed via chemical nanoprecursor route  

NASA Astrophysics Data System (ADS)

Polymer precursor derived ceramics have been studied since last four decades. They promise higher purity and excellent properties with lower processing temperatures in comparison to the traditional route of processing ceramics from powders. The main focus in the literature for polymer derived materials has been on the study of cross linking and pyrolysis of precursors. Relatively fewer reports are available on processing bulk components and property characterization. The polymer precursor determines the nanostructure of the resulting amorphous material and is therefore termed nanoprecursor. In the present dissertation the processing of nanoprecursor to obtain bulk ceramics is studied, with development of an innovative process to fabricate dense defect free materials. The properties of these defect free materials are characterized. Commercially available oligo-ureamethylvinylsilazane (Ceraset(TM)-SN) was used in the present dissertation. The pyrolysis at 1000C in nitrogen or argon resulted in an amorphous ceramic with chemical composition SiC 0.86N0.82. The specimens obtained by the new process are called cast specimens. Mechanical properties such as flexural strength, hardness, Young s modulus and fracture toughness were determined. The cast specimens showed much better properties as compared to nanoprecursor derived ceramics processed by methods published in the literature. Nanoprecursor derived SiCN show excellent creep resistance at 1350C at uniaxial stresses ranging from 25--100 MPa. Though a small deformation was measured (~2% in 7 hours), careful analysis showed that this deformation was not creep deformation. The deformation was sintering like, but resulted mainly from the reduction of the activation volume of the amorphous material. The oxidation behavior of the silicon carbonitrides was studied. The material showed passive oxidation, in air at temperature of 1350C and exhibited parabolic kinetics. Growth rate of the oxidation scale was about a factor of 4 higher than the lowest reported value of CVD Si3N 4 and SiC. Overall the nanoprecursor derived SiCN exhibits excellent thermo-mechanical properties and is a potential candidate for high temperature structural applications.

Shah, Sandeep Rameshchandra

114

Effect of Hydrogen Dilution on the Metastability of Hydrogenated Amorphous Silicon Oxide Solar Cells  

NASA Astrophysics Data System (ADS)

We investigated the effect of H2 dilution on the stability of hydrogenated amorphous silicon oxide (a-Si1-xOx:H) films and solar cells. a-Si1-xOx:H films were prepared by very high frequency plasma-enhanced chemical vapor deposition (VHF-PECVD) using a gas mixture of silane (SiH4), hydrogen (H2), and carbon dioxide (CO2). The degradation results after light soaking for 310 h under AM1.5, 125 mW/cm2 at 48 C clearly showed that the film and device stabilities were improved substantially with increasing H2 dilution. Our best stable result with a high open-circuit voltage (Voc) of 1.03 V for a-Si1-xOx:H single-junction solar cells showed a degradation of 16.6%. This result indicates that the stability against the light soaking of the a-Si1-xOx:H material is not inferior to that of a conventional hydrogenated amorphous silicon (a-Si:H) material. The temperature dependences of current--voltage (I--V) characteristics observed before and after light soaking showed that a-Si1-xOx:H solar cells had a similar temperature dependence to conventional a-Si:H solar cells.

Inthisang, Sorapong; Krajangsang, Taweewat; Sichanugrist, Porponth; Watahiki, Tatsuro; Miyajima, Shinsuke; Yamada, Akira; Konagai, Makoto

2011-11-01

115

Exchange bias effect in partially oxidized amorphous Fe-Ni-B based metallic glass nanostructures.  

PubMed

The magnetic properties of amorphous Fe-Ni-B based metallic glass nanostructures were investigated. The nanostructures underwent a spin-glass transition at temperatures below 100 K and revealed an irreversible temperature following the linear de Almeida-Thouless dependence. When the nanostructures were cooled below 25 K in a magnetic field, they exhibited an exchange bias effect with enhanced coercivity. The observed onset of exchange bias is associated with the coexistence of the spin-glass phase along with the appearance of another spin-glass phase formed by oxidation of the structurally disordered surface layer, displaying a distinct training effect and cooling field dependence. The latter showed a maximum in exchange bias field and coercivity, which is probably due to competing multiple equivalent spin configurations at the boundary between the two spin-glass phases. PMID:22634874

Thomas, S; Pookat, G; Nair, S S; Daniel, M; Dymerska, B; Liebig, A; Al-Harthi, S H; Ramanujan, R V; Anantharaman, M R; Fidler, J; Albrecht, M

2012-05-25

116

Reaction of Formic Acid over Amorphous Manganese Oxide Catalytic Systems: An In Situ Study  

SciTech Connect

The interaction of formic acid with amorphous manganese oxide (AMO) is investigated using in situ photoelectron and infrared spectroscopy techniques. Soft X-ray photoelectron spectroscopy (sXPS) and in situ FTIR illustrate two possible modes of formate bound species at the AMO surface. Two peaks in the IR region from 1340-1390 cm{sup -1} are indicative of formate species bound to the surface in a bidentate configuration. However, a 224 cm{sup -1} band gap between v{sub s}OCO and v{sub as}OCO suggests formate is bound in a bridging configuration. Temperature-programmed desorption studies confirm the formate bound species desorbs as carbon dioxide from the surface at multiple binding sites. At temperatures above 700 K, the presence of K{sup +} {hor_ellipsis} OC complex suggests the bound species interacts at vacant sites related to framework oxygen and cation mobility.

J Durand; S Senanayake; S Suib; D Mullins

2011-12-31

117

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

PubMed

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. PMID:20687701

Widjonarko, N Edwin; Perkins, John D; Leisch, Jennifer E; Parilla, Philip A; Curtis, Calvin J; Ginley, David S; Berry, Joseph J

2010-07-01

118

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

119

Polaron and phonon properties in proton intercalated amorphous tungsten oxide thin films  

NASA Astrophysics Data System (ADS)

We report on the evolution of the polaron and phonon mode properties in amorphous tungsten oxide thin films measured by spectroscopic ellipsometry in the infrared to ultraviolet spectral regions as a function of the intercalated proton density. A parametric physical model dielectric function is presented, which excellently describes the ellipsometry data over a large intercalated charge-density range. Upon increased amounts of intercalated charge we observe a strong increase in the polaron absorption in the visible spectral range, a decrease in the infrared W-O bond polarity, and an increase in the W=O bond polarity. Our findings support the oxygen-extraction model as the polaron formation mechanism in tungsten oxide in agreement with previous theoretical works based on first-principles pseudopotential calculations. We discuss and suggest polaron formation by oxygen-related defect generation as origin for the coloration mechanism in tungsten oxide. We further discuss possible evidence for very large effective mass of the polarons within the insulator-to-metal transition regime.

Saenger, M. F.; Hing, T.; Robertson, B. W.; Billa, R. B.; Hofmann, T.; Schubert, E.; Schubert, M.

2008-12-01

120

Identification of the native defect doping mechanism in amorphous indium zinc oxide thin films studied using ultra high pressure oxidation  

NASA Astrophysics Data System (ADS)

The mechanism of native defect doping in amorphous In-Zn-O (a-IZO) has not previously been established but is likely associated with native oxygen defect doping. We have used high pressure oxidation and defect equilibrium analysis to show a -1/6 power dependence of carrier density on oxygen fugacity in a-IZO. This dependency is predicted for oxygen vacancy-like donor defects. Extrapolation of equilibrium constants established at high pressures to atmospheric pressure reveals that the equilibrium carrier density in a-IZO at 200 C is higher (>1020/cm3) than typical as-deposited channel carrier densities (<1017/cm3). This is consistent with observed increases in channel carrier density and negative threshold voltage shift in annealed a-IZO thin film transistor devices.

Lee, Sunghwan; Paine, David C.

2013-02-01

121

Optimized amorphous silicon oxide buffer layers for silicon heterojunction solar cells with microcrystalline silicon oxide contact layers  

NASA Astrophysics Data System (ADS)

We report on the systematic optimization of the intrinsic amorphous silicon oxide buffer layer in interplay with doped microcrystalline silicon oxide contact layers for silicon heterojunction solar cells using all silicon oxide based functional layers on flat p-type float-zone wafers. While the surface passivation quality is comparably good within a wide range of low oxygen contents, the optical band gap increases and the dark conductivity decreases with increasing oxygen content, giving rise to an inevitable trade-off between optical transparency and electrical conductivity. On the cell level, fill factor FF and short circuit current density Jsc losses compete with the open circuit voltage Voc gains resulting from a thickness increase of the front buffer layers, whereas Jsc and Voc gains compete with FF losses resulting from increasing thickness of the rear buffer layers. We obtained the highest active area efficiency of ?act = 18.5% with Voc = 664 mV, Jsc = 35.7 mA/cm2, and FF = 78.0% using 4 nm front and 8 nm rear buffer layer with an oxygen content of 5%.

Ding, Kaining; Aeberhard, Urs; Finger, Friedhelm; Rau, Uwe

2013-04-01

122

Transmission electron microscopy studies of the specific structure of crystals formed by phase transition in iron oxide amorphous films  

SciTech Connect

The crystal growth and the structure of crystallized areas in amorphous iron oxide films prepared by pyrolysis is studied (in particular, in situ) by means of transmission electron microscopy. The bend-contour (BC) technique reveals an unusual phenomenon of regular internal bending of the lattice planes associated with a phase transition also observed earlier in some other amorphous films. The peculiarity of the crystals studied (transrotational crystals) is a very complex texture usually formed with a permanent rotation of [001] at the front of the growing crystals resulting in a variable change of imperfection and growth rate attributed to crystal anisotropy.

Kolosov, V.Y.; Thoelen, A.R.

2000-05-11

123

Photocatalytic characteristics of hydro-oxygenated amorphous titanium oxide films prepared using remote plasma enhanced chemical vapor deposition  

NASA Astrophysics Data System (ADS)

The photocatalytic activity and photoconductive characteristics of hydro-oxygenated amorphous titanium oxide (a-TiOx:OH) films prepared using remote plasma enhanced chemical vapor deposition (RPE-CVD) were studied. The a-TiOx:OH films have OH groups, which when exposed to UV irradiation, show high photoconductivity. The photoconductivity is drastically affected by oxygen gas. The results suggest that the recombination states present in the film are non-activated by the OH endings in the dangling bond like the hydrogen endings in hydrogenated amorphous silicon. Oxygen-sensitive photoconductivity is useful for environmental sensor applications.

Hatanaka, Y.; Naito, H.; Itou, C. S.; Kando, M.

2005-05-01

124

In situ Study of the Crystallization from Amorphous to Cubic Zirconium Oxide: Rietveld and Reverse Monte Carlo Analyses  

SciTech Connect

The amorphous-to-cubic (a-c) crystallization of nanoZrO{sub 2} in a reducing environment was studied by synchrotron X-ray diffraction. Rietveld analysis was performed to study the changes in crystallite size and lattice parameter as the cubic phase emerged. The pair distribution function (PDF) was obtained from the Fourier transformation of the normalized XRD patterns. A reverse Monte Carlo (RMC) simulation was applied to provide details of the local structure during the crystallization process as well as to calculate partial PDFs of Zr-Zr and Zr-O during the crystallization. The number of Zr's next-nearest neighbors of Zr remains 12, whereas the number of O's as nearest neighbors of Zr increases from 6.7 to 7.3 as the material evolves from an amorphous into a cubic structure, suggesting the persistence of a high concentration of oxygen vacancies. These simulated atomic structures show that the local structure of the amorphous phase bears resemblance to the short-range arrangement of cubic ZrO2, consistent with the results of X-ray absorption near edge spectroscopy (XANES) at Zr L{sub II} and L{sub III}. The amorphous-to-crystalline phase transformation is affected by the environment. Under an oxidizing condition, the amorphous phase crystallizes directly to tetragonal and subsequently to monoclinic zirconia.

Zhang,F.; Chupas, P.; Lui, S.; Hanson, J.; Caliebe, W.; Lee, P.; Chan, S.

2007-01-01

125

In situ study of the crystallization from amorphous to cubic zirconium oxide : rieetveld and reverse monte carlo analyses.  

SciTech Connect

The amorphous-to-cubic (a-c) crystallization of nanoZrO{sub 2} in a reducing environment was studied by synchrotron X-ray diffraction. Rietveld analysis was performed to study the changes in crystallite size and lattice parameter as the cubic phase emerged. The pair distribution function (PDF) was obtained from the Fourier transformation of the normalized XRD patterns. A reverse Monte Carlo (RMC) simulation was applied to provide details of the local structure during the crystallization process as well as to calculate partial PDFs of Zr-Zr and Zr-O during the crystallization. The number of Zr's next-nearest neighbors of Zr remains 12, whereas the number of O's as nearest neighbors of Zr increases from 6.7 to 7.3 as the material evolves from an amorphous into a cubic structure, suggesting the persistence of a high concentration of oxygen vacancies. These simulated atomic structures show that the local structure of the amorphous phase bears resemblance to the short-range arrangement of cubic ZrO{sub 2}, consistent with the results of X-ray absorption near edge spectroscopy (XANES) at Zr L{sub II} and L{sub III}. The amorphous-to-crystalline phase transformation is affected by the environment. Under an oxidizing condition, the amorphous phase crystallizes directly to tetragonal and subsequently to monoclinic zirconia.

Zhang, F.; Chupas, P. J.; Lui, S. L. A.; Hanson, J. C.; Caliebe, W. A.; Lee, P. L.; Chan, S.-W.; X-Ray Science Division; Columbia Univ.; State Univ. of New York at Stony Brook; BNL

2007-01-01

126

Effect of Zr-content on the oxidation and phase transformation of Zr-base amorphous alloys in air  

Microsoft Academic Search

The oxidation and phase transformation of three Zr-base amorphous alloys, Zr20Cu12Ni10Al5Ti (Zr53), Zr30Cu10Al5Ni (Zr55), and Zr15Cu10Al10Ni (Zr65), were studied over the temperature range of 300500 C in dry air. Oxidation kinetics of these alloys generally followed a parabolic rate law at T>350C, but linear kinetics was obeyed at 300350 C. It was found that Zr65 was the most oxidation-resistant alloy

H. H. Hsieh; W. Kai; R. T. Huang; M. X. Pan; T. G. Nieh

2004-01-01

127

Modeling the adsorption of mercury(II) on (hydr)oxides. 1: Amorphous iron oxide and {alpha}-quartz  

SciTech Connect

In this study, the authors provide a single model capable of describing the behavior of mercury(II) at two different solid/water interfaces. Mercury(II) sorption on amorphous ferric oxide (HFO) and {alpha}-SiO{sub 2} can be simulated using the surface complexation approach. In both cases, experiments are best reproduced when ternary surface complexes between the surface ({triple_bond}S-OH{sup 0}), Hg{sup 2+}, OH{sup {minus}} or Cl{sup {minus}} are included in the model. Sorption of ternary surface complexes predominates in the case of {alpha}-SiO{sub 2}. In addition, in the case of HFO, additional precipitation reactions of a nonideal Hg(OH){sub 2}-Fe(OH){sub 3} solid solution are needed at high sorbate to sorbent ratios. The modeling leads to a new set of surface complexation constants for the interaction between Hg{sup 2+} and these oxide surfaces which are described herein.

Tiffreau, C.; Luetzenkirchen, J.; Behra, P. [Univ. Louis Pasteur, Strasbourg (France). Inst. de Mecanique des Fluides

1995-06-01

128

EXAFS studies of MeO3-x (Me = W, Mo, Re, Ir) crystalline and amorphous oxides  

Microsoft Academic Search

The structure of the first coordination sphere of transition metals in such compounds as c-ReO3, c-IrO2, c-WO3, a-WO3, c-MoO3 and a-MoO3 has been studied by the EXAFS method in the ``ADONE'' synchrotron source. Different approximations are discussed and the sets of the most suitable parameters are presented. It has been found that different methods of preparing amorphous tungsten oxide thin

A. Balerna; E. Bernieri; E. Burattini; A. Kuzmin; A. Lusis; J. Purans; P. Cikmach

1991-01-01

129

Improving organic light-emitting devices by modifying indium tin oxide anode with an ultrathin tetrahedral amorphous carbon film  

Microsoft Academic Search

The characteristics of organic light-emitting devices based on tris-(8-hydroxyqunoline) aluminum with an ultrathin tetrahedral amorphous carbon (ta-C) film on indium tin oxide have been investigated. The device with a 1.0-nm ta-C layer has the highest current and power efficiency. The current efficiency of a device with a ta-C layer thickness of 1.0 nm is 3.7 cd?A at 20 mA?cm2, however,

B. J. Chen; X. W. Sun; Y. Divayana; B. K. Tay

2005-01-01

130

Improving organic light-emitting devices by modifying indium tin oxide anode with an ultrathin tetrahedral amorphous carbon film  

Microsoft Academic Search

The characteristics of organic light-emitting devices based on tris-(8-hydroxyqunoline) aluminum with an ultrathin tetrahedral amorphous carbon (ta-C) film on indium tin oxide have been investigated. The device with a 1.0-nm ta-C layer has the highest current and power efficiency. The current efficiency of a device with a ta-C layer thickness of 1.0 nm is 3.7 cd\\/A at 20 mA\\/cm2, however,

B. J. Chen; X. W. Sun; Y. Divayana; B. K. Tay

2005-01-01

131

Long-term research in Japan: amorphous metals, metal oxide varistors, high-power semiconductors and superconducting generators  

SciTech Connect

The review revealed that significant activity is under way in the research of amorphous metals, but that little fundamental work is being pursued on metal oxide varistors and high-power semiconductors. Also, the investigation of long-term research program plans for superconducting generators reveals that activity is at a low level, pending the recommendations of a study currently being conducted through Japan's Central Electric Power Council.

Hane, G.J.; Yorozu, M.; Sogabe, T.; Suzuki, S.

1985-04-01

132

Moisture-assisted cracking and atomistic crack path meandering in oxidized hydrogenated amorphous silicon carbide films  

NASA Astrophysics Data System (ADS)

Moisture-assisted cracking of silica-derived materials results from a stress-enhanced reaction between water molecules and moisture-sensitive Si-O-Si bonds at the crack tip. We report the moisture-assisted cracking of oxidized hydrogenated amorphous silicon carbide films (a-SiCO:H) consisting of both moisture-sensitive Si-O-Si bonds and moisture-insensitive bonds. The sensitivity of the films to moisture-assisted cracking was observed to increase with the Si-O-Si bond density, ?Si-O-Si. This sensitivity was correlated with the number of Si-O-Si bonds ruptured, NSi-O-Si, through an atomistic kinetic fracture model. By comparing these correlated NSi-O-Si values with those estimated by a planar crack model, we demonstrated that at the atomistic scale the crack path meanders three-dimensionally so as to intercept the most Si-O-Si bonds. This atomistic crack path meandering was verified by a computational method based on graph theory and molecular dynamics. Our findings could provide a basis for better understanding of moisture-assisted cracking in materials consisting of other types of moisture-sensitive and moisture-insensitive bonds.

Matsuda, Yusuke; King, Sean W.; Oliver, Mark; Dauskardt, Reinhold H.

2013-02-01

133

Solution-processed amorphous niobium oxide as a novel electron collection layer for inverted polymer solar cells  

NASA Astrophysics Data System (ADS)

Amorphous niobium oxide (NbOx) as an electron collection layer in inverted polymer solar cells was prepared by a solution process. The power conversion efficiency of inverted polymer solar cells based on a blend of poly(3-hexylthiophene) and [6,6]-phenyl C61 butyric acid methyl ester was improved to 2.22% by inserting an NbOx layer between the active layer and indium tin oxide electrode. An energy level diagram of component materials in the inverted polymer solar cell indicated that the NbOx layer works as both an electron collection layer and hole blocking layer in polymer solar cells.

Hamada, Keisuke; Murakami, Naoya; Tsubota, Toshiki; Ohno, Teruhisa

2013-10-01

134

Synthesis of Amorphous FeOOH/Reduced Graphene Oxide Composite by Infrared Irradiation and Its Superior Lithium Storage Performance.  

PubMed

A new hybrid nanostructure composed of mildly reduced graphene oxide (mRGO) nanosheets and homogeneous loading of amorphous FeOOH with ultrafine particles (?2 nm) is successfully synthesized via a facile infrared irradiation approach. Surprisingly, the as-prepared FeOOH/mRGO hybrid exhibits high reversible capacity, long-term stability, and excellent rate performance, when used as an anode material for lithium-ion batteries. A high reversible capacity of 767 mA h g(-1), with a coulombic efficiency of ?100%, can be achieved at a high current density of 1000 mA g(-1) even after 600 discharge/charge cycles. The superior electrochemical performances are attributed to the synergistic effects of the small particle size, amorphous structure, and conductive mRGO. PMID:24066738

Sun, Yongming; Hu, Xianluo; Luo, Wei; Xu, Henghui; Hu, Chenchen; Huang, Yunhui

2013-10-09

135

Magnetic properties and surface crystallization induced by selective oxidation in Fe-B-Si amorphous alloy  

Microsoft Academic Search

The relationship between the annealing atmosphere and the magnetic properties of Fe78.5B13Si8.5 amorphous alloy has been studied, showing that annealing in nitrogen, argon, hydrogen and air significantly improved the iron loss of the amorphous ribbon, giving much better results than annealing in an H2 + H2O atmosphere. A boron-depletion zone with the alloy composition O to 3 mol % B

N. Morito; T. Suzuki; C. Maeda; T. Yamashita; Y. Kitano

1990-01-01

136

Transport behavior across the field-driven superconductor-insulator transition in amorphous indium oxide films  

NASA Astrophysics Data System (ADS)

Superconductor-insulator transition (SIT) in two-dimensional (2D) thin films is a beautiful realization of a zero temperature quantum phase transition (QPT) and has been explored both theoretically and experimentally over the last two decades. In addition to the several intrinsic ways (such as thickness) of tuning the transition, external magnetic field has been used to tune from one ground state to another in various condensed matter systems. Amorphous indium oxide thin films, with their unique capability of tuning the disorder level in the system easily, have been proven to be an excellent model system to study the transport mechanisms near and across the SIT in 2D. In this thesis, magnetic field-driven SIT in 2D films of amorphous InO x is studied. The goal of this work is to understand the microscopic transport mechanisms responsible for driving the SIT when the magnetic field direction is continually varied from being perpendicular to the sample plane to parallel. Applying a perpendicular magnetic field resulting in a clear field-driven SIT and a magneto-resistance peak on the insulating side in InO x films have been previously understood in a bosonic picture put forward by M. P. A. Fisher and coworkers. However, this boson-vortex duality picture is expected to give rise to markedly different transport characteristics when the magnetic field is applied parallel to the sample plane. Features found in the parallel-field transport data however can also be explained by the bosonic picture, thereby questioning the applicability of the hitherto successful models to the physics of SIT. An isotropic magnetic field value, where the sample has the exact same resistance irrespective of the angle between the sample plane and magnetic field direction, is found. This isotropic point lies at field values above the critical field (Bc) of the SIT (in both perpendicular and parallel configurations) and above the magnetoresistance peak. The isotropic point is very weakly dependent on disorder levels and is temperature-independent. These observations suggest a possible fermionic role in the conduction near the quantum critical point of the SIT and would require newer models to be developed to completely understand the physics. Current-voltage characteristics measured in superconducting samples (below Bc) show that the true superconducting behavior (with a critical current to conduction) appears only in the B = 0 limit. Especially, application of a small magnetic field ( 0.2 T) drives the system into a flux flow regime and hence dissipative. The role of this dissipative channel in the superconducting phase in driving the SIT is not well understood. Competing roles of dissipation and bosonic mechanisms need to be treated simultaneously to decipher the underlying physics. When magnetic field is applied to a mesoscopic scale superconducting film, the film breaks into puddles of superconductors and insulators, thereby suggesting percolation-type transport behavior near the quantum critical point. Interestingly, the nonuniform nature of conduction occurs only in magnetic fields below and above Bc at very low temperature below 400 mK and the sample is completely homogeneous at B c. A complete understanding of the scale of inhomogeneous regions and their role in driving the QPT are still unclear. And the results presented suggest that more experimental and theoretical efforts are needed for understanding the physics near the QPT clearly.

Kim, Min-Soo

137

Amorphous Manganese-Calcium Oxides as a Possible Evolutionary Origin for the CaMn4 Cluster in Photosystem II  

NASA Astrophysics Data System (ADS)

In this paper a few calcium-manganese oxides and calcium-manganese minerals are studied as catalysts for water oxidation. The natural mineral marokite is also studied as a catalyst for water oxidation for the first time. Marokite is made up of edge-sharing Mn3+ in a distorted octahedral environment and eight-coordinate Ca2+ centered polyhedral layers. The structure is similar to recent models of the oxygen evolving complex in photosystem II. Thus, the oxygen evolving complex in photosystem II does not have an unusual structure and could be synthesized hydrothermally. Also in this paper, oxygen evolution is studied with marokite (CaMn2O4), pyrolusite (MnO2) and compared with hollandite (Ba0.2Ca0.15K0.3Mn6.9Al0.2Si0.3O16), hausmannite (Mn3O4), Mn2O3.H2O, CaMn3O6.H2O, CaMn4O8.H2O, CaMn2O4.H2O and synthetic marokite (CaMn2O4). I propose that the origin of the oxygen evolving complex in photosystem II resulted from absorption of calcium and manganese ions that were precipitated together in the archean oceans by protocyanobacteria because of changing pH from ~5 to ~8-10. As reported in this paper, amorphous calcium-manganese oxides with different ratios of manganese and calcium are effective catalysts for water oxidation. The bond types and lengths of the calcium and manganese ions in the calcium-manganese oxides are directly comparable to those in the OEC. This primitive structure of these amorphous calcium-manganese compounds could be changed and modified by environmental groups (amino acids) to form the oxygen evolving complex in photosystem II.

Najafpour, Mohammad Mahdi

2011-06-01

138

Structure and dielectric properties of amorphous high-? oxides: HfO2, ZrO2, and their alloys  

NASA Astrophysics Data System (ADS)

High-? metal oxides are a class of materials playing an increasingly important role in modern device physics and technology. Here we report theoretical investigations of the properties of structural and lattice dielectric constants of bulk amorphous metal oxides by a combined approach of classical molecular dynamics (MD), for structure evolution, and quantum mechanical first-principles density function theory (DFT), for electronic structure analysis. Using classical MD based on the Born-Mayer-Buckingham potential function within a melt and quench scheme, amorphous structures of high-? metal oxides Hf1-xZrxO2 with different values of the concentration x are generated. The coordination numbers and the radial distribution functions of the structures are in good agreement with the corresponding experimental data. We then calculate the lattice dielectric constants of the materials from quantum mechanical first principles, and the values averaged over an ensemble of samples agree well with the available experimental data and are very close to the dielectric constants of their cubic form.

Wang, Yin; Zahid, Ferdows; Wang, Jian; Guo, Hong

2012-06-01

139

EXAFS studies of MeO3-x (Me = W, Mo, Re, Ir) crystalline and amorphous oxides  

NASA Astrophysics Data System (ADS)

The structure of the first coordination sphere of transition metals in such compounds as c-ReO3, c-IrO2, c-WO3, a-WO3, c-MoO3 and a-MoO3 has been studied by the EXAFS method in the ``ADONE'' synchrotron source. Different approximations are discussed and the sets of the most suitable parameters are presented. It has been found that different methods of preparing amorphous tungsten oxide thin films lead to differences in their structure.

Balerna, A.; Bernieri, E.; Burattini, E.; Kuzmin, A.; Lusis, A.; Purans, J.; Cikmach, P.

1991-10-01

140

Role of Hydrophobicity in Adhesion of the Dissimilatory Fe(III)-Reducing Bacterium Shewanella alga to Amorphous Fe(III) Oxide  

PubMed Central

The mechanisms by which the dissimilatory Fe(III)-reducing bacterium Shewanella alga adheres to amorphous Fe(III) oxide were examined through comparative analysis of S. alga BrY and an adhesion-deficient strain of this species, S. alga RAD20. Approximately 100% of S. alga BrY cells typically adhered to amorphous Fe(III) oxide, while less than 50% of S. alga RAD20 cells adhered. Bulk chemical analysis, isoelectric point analysis, and cell surface analysis by time-of-flight secondary-ion mass spectrometry and electron spectroscopy for chemical analysis demonstrated that the surfaces of S. alga BrY cells were predominantly protein but that the surfaces of S. alga RAD20 cells were predominantly exopolysaccharide. Physicochemical analyses and hydrophobic interaction assays demonstrated that S. alga BrY cells were more hydrophobic than S. alga RAD20 cells. This study represents the first quantitative analysis of the adhesion of a dissimilatory Fe(III)-reducing bacterium to amorphous Fe(III) oxide, and the results collectively suggest that hydrophobic interactions are a factor in controlling the adhesion of this bacterium to amorphous Fe(III) oxide. Despite having a reduced ability to adhere, S. alga RAD20 reduced Fe(III) oxide at a rate identical to that of S. alga BrY. This result contrasts with results of previous studies by demonstrating that irreversible cell adhesion is not requisite for microbial reduction of amorphous Fe(III) oxide. These results suggest that the interaction between dissimilatory Fe(III)-reducing bacteria and amorphous Fe(III) oxide is more complex than previously believed.

Caccavo, F.; Schamberger, P. C.; Keiding, K.; Nielsen, P. H.

1997-01-01

141

Amorphous iron-(hydr) oxide networks at liquid/vapor interfaces: In situ X-ray scattering and spectroscopy studies  

SciTech Connect

Surface sensitive X-ray reflectivity (XR), fluorescence (XF), and grazing incidence X-ray diffraction (GIXD) experiments were conducted to determine the accumulation of ferric iron Fe (III) or ferrous iron Fe (II) under dihexadecyl phosphate (DHDP) or arachidic acid (AA) Langmuir monolayers at liquid/vapor interfaces. Analysis of the X-ray reflectivity and fluorescence data of monolayers on the aqueous subphases containing FeCl3 indicates remarkably high levels of surface-bound Fe (III) in number of Fe3 ions per molecule (DHDP or AA) that exceed the amount necessary to neutralize a hypothetically completely deprotonated monolayer (DHDP or AA). These results suggest that nano-scale iron (hydr) oxide complexes (oxides, hydroxides or oxyhydroxides) bind to the headgroups and effectively overcompensate the maximum possible charges at the interface. The lack of evidence of in-plane ordering in GIXD measurements and strong effects on the surface-pressure versus molecular area isotherms indicate that an amorphous network of iron (hydr) oxide complexes contiguous to the headgroups is formed. Similar experiments with FeCl2 generally resulted with the oxidation of Fe (II)Fe (III) which consequently leads to ferric Fe (III) complexes binding albeit with less iron at the interface. Controlling the oxidation of Fe (II) changes the nature and amount of binding significantly. The implications to biomineralization of iron (hydr) oxides are briefly discussed.

Wang, W.; Pleasants, J.; Bu, W.; Park, R.Y.; Kuzmenko, I.; Vaknin, D.

2012-06-23

142

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

SciTech Connect

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.

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

2006-05-01

143

Amorphous silica nanoparticles trigger nitric oxide/peroxynitrite imbalance in human endothelial cells: inflammatory and cytotoxic effects  

PubMed Central

Background The purpose of this study was to investigate the mechanism of noxious effects of amorphous silica nanoparticles on human endothelial cells. Methods Nanoparticle uptake was examined by transmission electron microscopy. Electrochemical nanosensors were used to measure the nitric oxide (NO) and peroxynitrite (ONOO?) released by a single cell upon nanoparticle stimulation. The downstream inflammatory effects were measured by an enzyme-linked immunosorbent assay, real-time quantitative polymerase chain reaction, and flow cytometry, and cytotoxicity was measured by lactate dehydrogenase assay. Results We found that the silica nanoparticles penetrated the plasma membrane and rapidly stimulated release of cytoprotective NO and, to a greater extent, production of cytotoxic ONOO?. The low [NO]/[ONOO?] ratio indicated increased nitroxidative/oxidative stress and correlated closely with endothelial inflammation and necrosis. This imbalance was associated with nuclear factor ?B activation, upregulation of key inflammatory factors, and cell death. These effects were observed in a nanoparticle size-dependent and concentration-dependent manner. Conclusion The [NO]/[ONOO?] imbalance induced by amorphous silica nanoparticles indicates a potentially deleterious effect of silica nanoparticles on vascular endothelium.

Corbalan, J Jose; Medina, Carlos; Jacoby, Adam; Malinski, Tadeusz; Radomski, Marek W

2011-01-01

144

Growth of ultrathin amorphous alumina films during the oxidation of NiAl(100)  

NASA Astrophysics Data System (ADS)

The effect of temperature on the oxidation of NiAl(100) is comparatively studied at 25 C and 300 C using X-ray Photoelectron Spectroscopy to elucidate the effect of oxidealloy interfacial reaction on the growth of ultrathin alumina thin films. The oxidation at 25 C results in self-limiting aluminum oxide film growth to a less extent of the limiting thickness regimes with non-stoichiometric oxide films exhibiting a deficiency of Al cations, whereas for the oxidation at 300 C the oxide films grow to a larger limiting thickness with relatively enriched with Al at the limiting thickness. The temperature dependent limiting thickness and composition of the oxide films are ascribed to the transport velocity of Al from deeper layers to the oxide/alloy interface during the oxide growth. For the oxidation at 25 C the oxide film growth depletes Al and forms an underlying Ni-rich interfacial layer that blocks the supply of Al atoms to the oxide/substrate interface, whereas for the oxidation at 300 C the enhanced diffusion rate maintains adequate supply of Al atoms to the oxide/alloy interface to sustain the oxide film growth to the full extent of the limiting thickness.

Cai, Na; Qin, Hailang; Tong, Xiao; Zhou, Guangwen

2013-12-01

145

Amorphous Indium-Zinc-Oxide Transparent Conductors for Thin Film PV: Preprint  

SciTech Connect

Amorphous InZnO's (a-IZO) basic PV applicability has now been demonstrated in prototype CIGS, Si Heterojunction (SiHJ) and organic photovoltaics (OPV). However, to move beyond initial demonstration devices, improved TCO properties and processibility of the a-IZO films are needed. Here, RF-superimposed DC sputtering was used to improve the reliable deposition of a-IZO with conductivity > 3000 S/cm.

Perkins, J.; Gennett, T.; Galante, M.; Gillaspie, D.; Ginley, D.

2011-07-01

146

Preparation and evaluation of amorphous metal oxide magnetic thin films and nanocomposites for spintronics  

Microsoft Academic Search

In this work, photochemical metalorganic deposition (PMOD) using thin films of metal 2-ethylhexanoates (Mo and Fe) was used to deposit patterned thin films of a-MoO3 and a-Fe 2O3 (where a stands for amorphous) in a positive tone. The mechanism of positive tone PMOD of a-Fe 2O3 was examined by using spectroscopic ellipsometry, which allowed the determination that the development preferentially

Simon Trudel

2008-01-01

147

Thermal change of amorphous indium tin oxide films sputter-deposited in water vapor atmosphere  

Microsoft Academic Search

Amorphous ITO thin films were deposited on silicon wafers at room temperature by RF+DC magnetron sputtering at water vapor partial pressures between 0 and 610?5Torr. The O\\/(In+Sn) ratio was determined by Rutherford backscattering spectroscopy. The effect of water vapor on the thermal crystallization process was monitored by high-temperature X-ray diffraction (XRD) analysis. We found a simple dependence between the crystallization

M. H. Wang; Y. Onai; Y. Hoshi; H. Lei; T. Kondo; T. Uchida; S. Singkarat; T. Kamwanna; S. Dangtip; S. Aukkaravittayapun; T. Nishide; S. Tokiwa; Y. Sawada

2008-01-01

148

Room-temperature fabrication of transparent flexible thin-film transistors using amorphous oxide semiconductors  

Microsoft Academic Search

Transparent electronic devices formed on flexible substrates are expected to meet emerging technological demands where silicon-based electronics cannot provide a solution. Examples of active flexible applications include paper displays and wearable computers. So far, mainly flexible devices based on hydrogenated amorphous silicon (a-Si:H) and organic semiconductors have been investigated. However, the performance of these devices has been insufficient for use

Kenji Nomura; Hiromichi Ohta; Akihiro Takagi; Toshio Kamiya; Masahiro Hirano; Hideo Hosono

2004-01-01

149

Temperature-Dependent Tunnelling into Amorphous Silicon.  

National Technical Information Service (NTIS)

Conductance measurements are presented for junctions of the type metal-oxide-amorphous silicon, where the oxide is sufficiently thin to permit tunnelling. The conductance exhibits a temperature dependence essentially identical to that for amorphous silico...

C. J. Mogab D. Adler J. A. Sauvage

1972-01-01

150

Control and characterization of the structural, electrical, and optical properties of amorphous zinc-indium-tin oxide thin films.  

PubMed

Zinc-indium-tin oxide (ZITO) films are grown by pulsed-laser deposition in which 30% of the indium in the In(2)O(3) structure is replaced by substitution with zinc and tin in equal molar proportions: In(2-2x)Zn(x)Sn(x)O(3), where x = 0.3. Films grown at 25 and 100 degrees C exhibit electron diffraction patterns (EDPs) typical of amorphous materials. At a deposition temperature of 200 degrees C, evidence of crystallinity begins to appear in the EDP data and becomes more evident in films deposited at 400 degrees C. The advent of crystallinity affects the electrical properties of the ZITO film, and the effect is ascribed to the boundaries between phases in the films. The electrical and optical properties of the amorphous ZITO films grown at 25 degrees C are dependent on the oxygen partial pressure (P(O(2))) during film growth, transitioning from a high-mobility (36 cm(2)/V x s) conductor (sigma approximately 1700 S/cm) at P(O(2)) = 5 mTorr to a high-mobility semiconductor at P(O(2)) approximately 20 mTorr. Field-effect transistors (FETs) prepared with as-deposited amorphous ZITO channel layers on p(+)-Si/300 nm SiO(2) substrates yield FETs with on/off ratios of 10(6), off currents of 10(-8) A, and field-effect saturation mobilities of 10 cm(2)/V x s. PMID:20355848

Buchholz, D Bruce; Liu, Jun; Marks, Tobin J; Zhang, Ming; Chang, Robert P H

2009-10-01

151

Role of oxygen diffusion in photoinduced changes of the electronic and optical properties in amorphous indium oxide  

SciTech Connect

A stable increase by much as 10{sup 8} in the conductivity of amorphous indium oxide to {sigma} >= 10{sup 3} {Omega}{sup -1}cm{sup -1} can be achieved by ultraviolet photoreduction. This treatment also increases the absorption coefficient, {alpha}(h{upsilon}), by up to a factor of 10{sup 3} for h{upsilon}<1.5 eV due to free carrier absorption and causes a 0.1 eV shift of the absorption edge to the blue. These changes are controlled by the Fermi level, E{sub F}, which is presumably determined by doping due to oxygen vacancies. A diffusion constant D>3x10{sup -12} cm{sup 2}/s for oxygen at 300 K is determined from a constant flow experiment. Oxygen diffusion is verified by secondary ion mass spectrometry with {sup 18}O. The functions {alpha}(h{upsilon}) and {sigma}(T) are simulated as E{sub F} is varied using a simple density of states model appropriate for amorphous semiconductors. These simulations qualitatively agree with the experimental data if transitions from the conduction band tail to the conductions band are assumed to be forbidden. 13 refs., 9 figs.

Claflin, B; Fritzsche, H. [Univ. of Chicago, IL (United States)

1996-11-01

152

Studies on a New Method for the Syntheses of SiO2-MxOy and MxOy (M=A1, Ti, Zr) Amorphous Oxides,  

National Technical Information Service (NTIS)

A new method for the synthesis of SiO2-MxOy and MxOy (M equals Al, Ti, Zr) amorphous oxides was investigated. Condensation polymerization of silicic acid and metal chelate compounds formed polymetalloxane compounds composed of Si-O-M and Si-O-Si linkage w...

Y. Abe Y. Nagao T. Misono

1988-01-01

153

Fully transparent nonvolatile memory employing amorphous oxides as charge trap and transistor's channel layer  

NASA Astrophysics Data System (ADS)

A fully transparent nonvolatile memory with the conventional sandwich gate insulator structure was demonstrated. Wide band gap amorphous GaInZnO (a-GIZO) thin films were employed as both the charge trap layer and the transistor channel layer. An excellent program window of 3.5 V with a stressing time of 100 ms was achieved through the well-known Fowler-Nordheim tunneling method. Due to the similar energy levels extracted from the experimental data, the asymmetrical program/erase characteristics are believed to be the result of the strong trapping of the injected negative charges in the shallow donor levels of the GIZO film.

Yin, Huaxiang; Kim, Sunil; Kim, Chang Jung; Song, Ihun; Park, Jaechul; Kim, Sangwook; Park, Youngsoo

2008-10-01

154

Thin-film transistors fabricated by low-temperature process based on Ga- and Zn-free amorphous oxide semiconductor  

NASA Astrophysics Data System (ADS)

We propose the use of indium tungsten oxide (IWO) as a channel material for thin-film transistors (TFTs). In the present study, an IWO film was deposited at room temperature by means of DC magnetron sputtering and then annealed at 100 C in N2 prior to formation of Au source and drain electrodes. Analysis using X-ray diffraction and transmission electron microscopy revealed that the film remained amorphous even after the post-deposition annealing treatment. TFTs fabricated using a Si substrate as a back-gate electrode showed good performance, with a saturation field-effect mobility of 19.3 cm2 . V-1 . s-1, an on/off current ratio of 8.9 109.

Aikawa, Shinya; Darmawan, Peter; Yanagisawa, Keiichi; Nabatame, Toshihide; Abe, Yoshiyuki; Tsukagoshi, Kazuhito

2013-03-01

155

Comparison of amorphous iridium water-oxidation electrocatalysts prepared from soluble precursors.  

PubMed

Electrodeposition of iridium oxide layers from soluble precursors provides a route to active thin-layer electrocatalysts for use on water-oxidizing anodes. Certain organometallic half-sandwich aqua complexes of iridium form stable and highly active oxide films upon electrochemical oxidation in aqueous solution. The catalyst films appear as blue layers on the anode when sufficiently thick, and most closely resemble hydrous iridium(III,IV) oxide by voltammetry. The deposition rate and cyclic voltammetric response of the electrodeposited material depend on whether the precursor complex contains a pentamethylcyclopentadieneyl (Cp*) or cyclopentadienyl ligand (Cp), and do not match, in either case, iridium oxide anodes prepared from non-organometallic precursors. Here, we survey our organometallic precursors, iridium hydroxide, and pre-formed iridium oxide nanoparticles. From electrochemical quartz crystal nanobalance (EQCN) studies, we find differences in the rate of electrodeposition of catalyst layers from the two half-sandwich precursors; however, the resulting layers operate as water-oxidizing anodes with indistinguishable overpotentials and H/D isotope effects. Furthermore, using the mass data collected by EQCN and not otherwise available, we show that the electrodeposited materials are excellent catalysts for the water-oxidation reaction, showing maximum turnover frequencies greater than 0.5 mol O(2) (mol iridium)(-1) s(-1) and quantitative conversion of current to product dioxygen. Importantly, these anodes maintain their high activity and robustness at very low iridium loadings. Our organometallic precursors contrast with pre-formed iridium oxide nanoparticles, which form an unstable electrodeposited material that is not stably adherent to the anode surface at even moderately oxidizing potentials. PMID:22725667

Blakemore, James D; Schley, Nathan D; Kushner-Lenhoff, Maxwell N; Winter, Andrew M; D'Souza, Francis; Crabtree, Robert H; Brudvig, Gary W

2012-06-22

156

Difference in high-temperature oxidation resistance of amorphous Zr Si N and W Si N films with a high Si content  

NASA Astrophysics Data System (ADS)

The high-temperature oxidation resistance of amorphous Zr-Si-N and W-Si-N films with a high Si content (?20 at.%) deposited by reactive dc magnetron sputtering at different partial pressures of nitrogen was systematically investigated by means of a symmetrical high-resolution thermogravimetry in a flowing air up to an annealing temperature of 1300 C (a temperature limit for Si(1 0 0) substrate). Additional analyses including X-ray diffraction (XRD), light optical microscopy (LOM), scanning electron microscopy (SEM), atomic force microscopy (AFM), and microhardness measurement were carried out as well. The obtained results showed (i) an excellent high-temperature oxidation resistance of the Zr-Si-N films up to 1300 C, (ii) a considerably lower oxidation resistance of the W-Si-N films. The W-Si-N films are completely oxidized at 800 C with a subsequent volatilization of unstable WO x oxides. On the other hand, the Zr-Si-N films are oxidized only very slightly on the surface, where a stable oxide barrier layer preventing further inward oxygen diffusion is formed. The thickness of the oxide layer is only about of 3% of the total film thickness. The phase composition, thermal stability of individual phases and amorphous structure were found to be key factors to achieve a high oxidation resistance.

Zeman, P.; Musil, J.

2006-09-01

157

Oxidation behavior of amorphous metallic Ni{sub 3}(SbTe{sub 3}){sub 2} compound  

SciTech Connect

Amorphous Ni{sub 3}(SbTe{sub 3}){sub 2} compound was prepared from a metathesis between Zintl phase K{sub 3}SbTe{sub 3} and NiBr{sub 2} in solution and its oxidation behavior was investigated in the temperature range of 200-700 deg. C in air. To characterize the sample, thermogravimetry (TG), X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive analysis by X-ray (EDAX) analyses were performed and electrical conductivity was measured as a function of temperature in the range of 25-800 deg. C in air. The specimen showed a metallic conducting-like behavior below 585 deg. C while a semiconducting-like behavior above 585 deg. C. At a first oxidation step of Ni{sub 3}(SbTe{sub 3}){sub 2} below 500 deg. C, TeO{sub 2} phase is formed. Above 500 deg. C, NiO phase is formed, then some NiO reacts with TeO{sub 2} to form NiTeO{sub 3} and NiSb{sub 2}O{sub 6} is simultaneously formed. Above 700 deg. C, NiTeO{sub 3} is further reacted with TeO{sub 2} to form NiTe{sub 2}O{sub 5}. Both NiTeO{sub 3} and NiTe{sub 2}O{sub 5} are decomposed above 774 deg. C.

Jun, Jong-Ho [Department of Applied Chemistry, Konkuk University, Choongju 380-701 (Korea, Republic of); Jung, Jin-Seung [Department of Chemistry, Kangnung National University, Kangnung 210-702 (Korea, Republic of)]. E-mail: jjscm@kangnung.ac.kr; Oh, Seung-Lim [Department of Chemistry, Yonsei University, Seoul 120-749 (Korea, Republic of); Kim, Yong-Rok [Department of Chemistry, Yonsei University, Seoul 120-749 (Korea, Republic of); Lee, Sung-Han [Department of Chemistry, Yonsei University, Seoul 120-749 (Korea, Republic of); O'Connor, Charles J. [Advanced Materials Research Institute, University of New Orleans, New Orleans, LA 70148 (United States)

2006-03-09

158

Advanced high-k gate dielectric amorphous LaGdO3 gated metal-oxide-semiconductor devices with sub-nanometer equivalent oxide thickness  

NASA Astrophysics Data System (ADS)

Careful selection of pulsed laser deposition conditions was executed to achieve sub-nanometer EOT (equivalent oxide thickness) in amorphous LaGdO3 based high-k/metal gate stacks. The lowest EOTs attained were ~5.4 A? and 8.4 A? with and without quantum mechanical correction, respectively. The electrical measurements yielded a high permittivity of 20.5 +/- 2.4, a thin bottom interfacial layer of thickness 4.5 +/- 1 A?, and interface (cm-2 eV-1) and fixed (cm-2) charge densities of ~1012. Analysis of temperature dependent leakage currents revealed that gate injection current was dominated by Schottky emission below 1.2 MV/cm and quantum mechanical tunneling above this field. The physical origin of substrate injection was found to be a combination of Schottky emission and trap assisted tunneling.

Pavunny, S. P.; Misra, P.; Thomas, R.; Kumar, A.; Schubert, J.; Scott, J. F.; Katiyar, R. S.

2013-05-01

159

Integration of perovskite oxide dielectrics into complementary metal-oxide-semiconductor capacitor structures using amorphous TaSiN as oxygen diffusion barrier  

NASA Astrophysics Data System (ADS)

The high permittivity perovskite oxides have been intensively investigated for their possible application as dielectric materials for stacked capacitors in dynamic random access memory circuits. For the integration of such oxide materials into the CMOS world, a conductive diffusion barrier is indispensable. An optimized stack p++-Si/Pt/Ta21Si57N21/Ir was developed and used as the bottom electrode for the oxide dielectric. The amorphous TaSiN film as oxygen diffusion barrier showed excellent conductive properties and a good thermal stability up to 700 C in oxygen ambient. The additional protective iridium layer improved the surface roughness after annealing. A 100-nm-thick (Ba,Sr)TiO3 film was deposited using pulsed laser deposition at 550 C, showing very promising properties for application; the maximum relative dielectric constant at zero field is ? ~ 470, and the leakage current density is below 10-6 A/cm2 for fields lower then +/- 200 kV/cm, corresponding to an applied voltage of +/- 2 V.

Mei?, Biljana; Schroeder, Herbert

2011-09-01

160

Characteristics of hollow microtubes consisting of amorphous iron oxide nanoparticles produced by iron oxidizing bacteria, Leptothrix ochracea  

Microsoft Academic Search

Some features of characteristic iron oxide sheaths which the iron oxidizing bacteria Leptothrix ochracea (L. oceracea) formed were studied in order to make clear their morphology microstructure, chemical composition, and crystal structure through scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDX), and X-ray diffraction (XRD). Each sheath was a hollow tube with average outer and inner diameters of 1.1

H. Hashimoto; S. Yokoyama; H. Asaoka; Y. Kusano; Y. Ikeda; M. Seno; J. Takada; T. Fujii; M. Nakanishi; R. Murakami

2007-01-01

161

Electrodeposited amorphous manganese oxide nanowire arrays for high energy and power density electrodes  

Microsoft Academic Search

Arrays of manganese oxide nanowires were electrodeposited into anodized alumina membranes. These nanowire arrays were investigated in terms of their structural and electrochemical properties as cathodes for high energy and high power density Li ion batteries. The nanowire arrays were assembled with a Li counter electrode and non-aqueous electrolyte to form secondary batteries. These cells were capable of multiple charge\\/discharge

W. C. West; N. V. Myung; J. F. Whitacre; B. V. Ratnakumar

2004-01-01

162

The role of oxide interlayers in back reflector configurations for amorphous silicon solar cells  

NASA Astrophysics Data System (ADS)

Thin oxide interlayers are commonly added to the back reflector of thin-film silicon solar cells to increase their current. To gain more insight in the enhancement mechanism, we tested different back reflector designs consisting of aluminium-doped zinc oxide (ZnO:Al) and/or hydrogenated silicon oxide (SiOx:H) interlayers with different metals (silver, aluminium, and chromium) in standard p-i-n a-Si:H solar cells. We use a unique inverse modeling approach to show that in most back reflectors the internal metal reflectance is lower than expected theoretically. However, the metal reflectance is increased by the addition of an oxide interlayer. Our experiments demonstrate that SiOx:H forms an interesting alternative interlayer because unlike the more commonly used ZnO:Al it can be deposited by plasma-enhanced chemical vapour deposition and it does not reduce the fill factor. The largest efficiency enhancement is obtained with a double interlayer of SiOx:H and ZnO:Al.

Demontis, V.; Sanna, C.; Melskens, J.; Santbergen, R.; Smets, A. H. M.; Damiano, A.; Zeman, M.

2013-02-01

163

First-principles study of oxidation kinetics in amorphous SiO_2.  

NASA Astrophysics Data System (ADS)

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 is well described phenomenologically by the Deal-Grove model, there is little consensus about the mechanisms of oxidation kinetics for ultrathin films (<100 We 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.

Ng, Kwok-On; Vanderbilt, David

1998-03-01

164

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

165

XPS study of amorphous zirconium oxide films prepared by solgel  

Microsoft Academic Search

Zirconium oxide gel films deposited by dip coating on Si substrates have been studied by XPS as a function of the annealing temperature between 150 to 400C and Ar+ ion irradiation time. The use of both ultra-thin (?4 nm) and thick (?100 nm) films allowed separation of chemical from charging shifts in the O1S and Zr3d binding energies. The preferential

R. Brenier; J Mugnier; E Mirica

1999-01-01

166

Amorphous polymorphism  

Microsoft Academic Search

Recent studies of amorphous solid materials have revealed the possibility that more than one distinct amorphous phase may be formed from the same substance. In analogy with the phenomenon of crystalline polymorphism, this behavior has been termed amorphous polymorphism. We review the experimental manifestation of amorphous polymorphism, especially in tetrahedrally coordinated materials such as H2O and SiO2. Guided by computer

Peter H. Poole; Tor Grande; F. Sciortino; H. E. Stanley; C. Austen Angell

1995-01-01

167

Effect of alloying by gadolinium on the magnetic properties of irradiation-amorphized oxides of the Y3 - x Gd x Fe5O12 system  

NASA Astrophysics Data System (ADS)

Magnetometry and X-ray diffraction have been used to study the structural state and magnetic properties of the system of oxides with an iron garnet structure, Y3 - x Gd x Fe5O12 ( x = 0, 0.75, 1.5), in the course of amorphization via irradiation by fast neutrons. It has been established that the partial replacement of diamagnetic yttrium ions by paramagnetic gadolinium dramatically changes the behavior of the magnetic moment of the garnets during their gradual amorphization. The magnetic moment of the yttrium iron garnet decreases significantly with increasing fluence, whereas the magnetic moments of gadolinium-alloyed garnets, on the contrary, increase noticeably along with the simultaneous increase in the compensation temperatures of the sublattice magnetizations. The observed differences in the radiation behavior of the garnets are explained by the different behavior of the iron and gadolinium sublattices under irradiation. It is shown that the irradiation to a fluence of 3 1020 cm-2 leads to a complete amorphization of all samples investigated. It has been established that the amorphous samples were in a spin-glass state.

Chukalki, Yu. G.

2012-04-01

168

Ce-Ti amorphous oxides for selective catalytic reduction of NO with NH3: confirmation of Ce-O-Ti active sites.  

PubMed

The amorphous Ce-Ti mixed oxides were reported to be catalysts for selective catalytic reduction of NO(x) with NH(3), in which Ce and not Ti acts as their solvent in spite of the fact that Ce is low in content. The amorphous catalysts were characterized by X-ray powder diffraction (XRD) and transmission electron microscopy (TEM) equipped with selective area electron diffraction (SAED). The Ce-Ti amorphous oxide shows higher activity than its crystalline counterpart at lower temperatures. Moreover, the presence of small CeO(2) crystallites as for the impregnated sample is deleterious to activity. The Ce-O-Ti short-range order species with the interaction between Ce and Ti in atomic scale was confirmed for the first time to be the active site using temperature programmed reduction with H(2) (H(2)-TPR), in situ FTIR spectra of NO adsorption, X-ray photoelectron spectroscopy (XPS), and X-ray absorption fine-structure (XAFS). Lastly, the Ce-O-Ti structure was directly observed by field-emission TEM (FETEM). PMID:22888951

Li, Ping; Xin, Ying; Li, Qian; Wang, Zhongpeng; Zhang, Zhaoliang; Zheng, Lirong

2012-08-21

169

Amorphous tungstate precursor route to nanostructured tungsten oxide film with electrochromic property.  

PubMed

Electrochromic tungsten oxide (WO3) films on ITO glass were fabricated by spin-coating with a tungsten peroxy acid solution, which was prepared by adding an equivolume mixture of hydrogen peroxide and glacial acetic acid to tungsten metal powder. The structural evolution of the tungstate precursor upon heat treatment was studied by X-ray diffraction (XRD) and X-ray absorption near edge structure (XANES) analyses, which indicated that the as-synthesized tungstate transformed into nanocrystalline WO3 upon heating. It is, therefore, quite clear that as-synthesized tungstate can be a good precursor for electrochromic WO3 films. A series of WO3 thin films were prepared on ITO glass by spin-coating with different concentrations of tungsten peroxy acid solution and then post-annealing at various temperatures. Depending on the concentration of the tungstate coating solution (200-500 mg mL(-1)) and the annealing temperature (100-300 degrees C), the thickness and WO3 content as well as the electrochromic properties of WO3 films can be controlled. As a result, the optimum fabrication conditions were determined to be a tungstate solution concentration of 300-400 mg mL(-1) and a post-annealing temperature of 200 degrees C. Finally, an inorganic-inorganic hybrid electrochromic device (ECD) composed of optimized WO3 and Prussian Blue (PB) with desirable coloration efficiency was successfully developed. PMID:22121748

Jeon, Ie-Rang; Kang, Joo-Hee; Paek, Seung-Min; Hwang, Seong-Ju; Choy, Jin-Ho

2011-07-01

170

Nitrogen plasma treatment of fluorine-doped tin oxide for enhancement of photo-carrier collection in amorphous Si solar cells  

NASA Astrophysics Data System (ADS)

Nitrogen plasma treatment was performed on fluorine-doped tin oxide (SnO2:F) front electrodes, and its impact on the performance of pin type amorphous Si (a-Si) solar cells was investigated. Nitrogen plasma treatment reverses the surface band bending of SnO2:F from accumulation to depletion, thus in turn reversing the band bending of the p type amorphous silicon carbide (p-a-SiC) window layer. The reversal of band bending leads to the collection of carriers generated in p-a-SiC, and quantum efficiency in the short wavelength regime is thereby enhanced. On the other hand, surface depletion of SnO2:F causes a reduction of the diode built-in voltage and increased series resistance, which could degrade the open circuit voltage (Voc) and fill factor (FF), the degradation of which is strongly affected by the deposition time of p-a-SiC.

Baik, Seung Jae; Lim, Koeng Su

2011-04-01

171

Photobias instability of high performance solution processed amorphous zinc tin oxide transistors.  

PubMed

The effects of the annealing temperature on the structural and chemical properties of soluble-processed zinc-tin-oxide (ZTO) films were examined by transmission electron microscopy, atomic force microscopy, high resolution X-ray reflectivity, and X-ray photoelectron spectroscopy. The density and purity of the resulting ZTO channel layer increased with increasing annealing temperature, whereas the oxygen vacancy defect density decreased. As a result, the device performance of soluble ZTO thin film transistors (TFTs) was improved at higher annealing temperature. Although the 300 C-annealed ZTO TFT showed a marginal field-effect mobility (?FE) and high threshold voltage (Vth) of 0.1 cm(2)/(V s) and 7.3 V, respectively, the 500 C-annealed device exhibited a reasonably high ?FE, low subthreshold gate swing (SS), Vth, and Ion/off of 6.0 cm(2)/(V s), 0.28 V/decade, 0.58 V, and 4.0 10(7), respectively. The effects of dark negative bias stress (NBS) and negative bias illumination stress (NBIS) on the degradation of transfer characteristics of ZTO TFTs were also investigated. The instability of Vth values of the ZTO TFTs under NBS and NBIS conditions was suppressed with increasing annealing temperature. To better understand the charge trapping mechanism, the dynamics of Vth shift with NBS and NBIS time for all ZTO TFTs was analyzed on the basis of the stretched exponential relaxation. The negative Vth shift for each transistor was accelerated under NBIS conditions compared to NBS, which resulted in a higher dispersion parameter and smaller relaxation time for NBIS degradation. The relaxation time for NBS and NBIS instability increased with increasing annealing temperature, which is discussed on the basis of the transition mechanism of oxygen vacancy defects. PMID:23540523

Kim, Yoon Jang; Yang, Bong Seob; Oh, Seungha; Han, Sang Jin; Lee, Hong Woo; Heo, Jaeyeong; Jeong, Jae Kyeong; Kim, Hyeong Joon

2013-04-12

172

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

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

Sivayoganathan, Mugunthan; Tan, Bo; Venkatakrishnan, Krishnan

2012-11-09

173

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)

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.

Sivayoganathan, Mugunthan; Tan, Bo; Venkatakrishnan, Krishnan

2012-11-01

174

Kinetics of the amorphous {r_arrow} {gamma} {r_arrow} {alpha} transformations in aluminum oxide: Effect of crystallographic orientation  

SciTech Connect

Time-resolved reflectivity (TRR) measurements have been used to determine the growth kinetics of both the amorphous-to-{gamma}-phase and the {gamma}-to-{alpha} phase transformations of alumina films that have been deposited on (0001), (1{bar 2}10), and (01{bar 1}2) sapphire substrates. The activation energies for the amorphous-to-{gamma}-phase and {gamma}-to-{alpha} transformations respectively are 4.5 and 5.2 eV, irrespective of the crystallographic orientation of the underlying sapphire substrate. For both transformations, the relative transformation rates seem to reflect the symmetry of the sapphire substrates, with the fastest kinetics being on the lowest symmetry orientation and slowest kinetics being on the highest symmetry orientation. These relative rates are attributed to the differences in step mobility on the different substrate orientations.

Simpson, T.W. [Univ. of Western Ontario, London, Ontario (Canada). Dept. of Physics; Wen, Q.; Clarke, D.R. [Univ. of California, Santa Barbara, CA (United States). Materials Dept.; Yu, N. [Texas Instruments, Dallas, TX (United States). Semiconductor Process and Device Center

1998-01-01

175

Study of transparent conductive oxides and back reflectors for amorphous and nano-crystalline silicon based thin film solar cells  

Microsoft Academic Search

In this dissertation, back reflectors (BR) for hydrogenated amorphous silicon (a-Si:H) and hydrogenated nanocrystalline silicon (nc-Si:H) based solar cells have been systematically studied. The main results achieved in the dissertation are as follows: (1) By using the optical scattering theory and PVOPTICS simulation program, it is found that to characterize the texture of the BR, not only the texture height,

Xiesen Yang

2007-01-01

176

Amorphous materials: Characterizing amorphous strain  

NASA Astrophysics Data System (ADS)

The engineering performance of materials is controlled to a large extent by their elastic stress/strain response. The first X-ray strain measurements in amorphous metals allow for new understanding of complex glassy materials.

Ice, Gene

2005-01-01

177

Photo-oxidation of SO2 and of SO2 trapped in amorphous water ice studied by IR spectroscopy. Implications for Jupiter's satellite Europa  

NASA Astrophysics Data System (ADS)

Fourier Transform Infrared Spectroscopy (FTIR), is used to characterize thin films of sulfur dioxide trapped in excess of amorphous water ice and to study the photo-oxidation of pure solid SO2 or of SO2 diluted in water ice. These laboratory experiments were undertaken in an attempt to find information on the formation of hydrated sulfuric acid detected on Europa's surface. Vibrational spectra at 30 K of mixed films containing SO2 with an excess of water depend on the deposition conditions. A metastable (SO2)(m)(H2O)(n) phase and a solid solution of SO2 in water ice have been evidenced. Irradiation at 266 nm of mixed films SO2/O-3/H2O produces sulfur trioxide and hydrogen peroxide without traces of sulfuric acid. Irradiation of films of pure SO2, under 200 nm, leads to sulfur trioxide and to ozone. When SO2 is diluted in amorphous water ice, new weak bands that appear after irradiation suggest the formation of sulfuric acid.

Schriver-Mazzuoli, L.; Schriver, A.; Chaabouni, H.

2003-01-01

178

Light-extraction enhancement in GaN-based light-emitting diodes using grade-refractive-index amorphous titanium oxide films with porous structures  

SciTech Connect

Amorphous titanium oxide (a-TiO{sub x}:OH) films prepared by plasma-enhanced chemical-vapor deposition at 200 and 25 deg. C are in turn deposited onto the GaN-based light-emitting diode (LED) to enhance the associated light extraction efficiency. The refractive index, porosity, and photocatalytic effect of the deposited films are correlated strongly with the deposition temperatures. The efficiency is enhanced by a factor of {approx}1.31 over that of the uncoated LEDs and exhibited an excellent photocatalytic property after an external UV light irradiation. The increase in the light extraction is related to the reduction in the Fresnel transmission loss and the enhancement of the light scattering into the escape cone by using the graded-refractive-index a-TiO{sub x}:OH film with porous structures.

Liu, D.-S.; Lin, T.-W.; Huang, B.-W.; Juang, F.-S.; Lei, P.-H. [Institute of Electro-Optical and Materials Science, National Formosa University, Huwei 63201, Taiwan (China); Hu, C.-Z. [Chilin Technology Co. Ltd., Tainan County 71758, Taiwan (China)

2009-04-06

179

Cost-Effective and Self-Textured Gallium-Doped Zinc Oxide Front Contacts for Hydrogenated Amorphous Silicon Thin-Film Solar Cells  

NASA Astrophysics Data System (ADS)

We adopt a economical and original method to fabricate self-textured gallium-doped zinc oxide (GZO) front contacts for hydrogenated amorphous silicon (a-Si:H) single-junction solar cells. This technique involves an atmospheric-pressure plasma jet (APPJ) and a dc sputtering process. The electro-optical characteristics of the textured GZO films are mainly controlled by the haze of organosilicon underlayers deposited by the APPJ. The films exhibit an average optical transmittance of about 80% and resistivity below 9.91 10-4 ? cm. Moreover, compared with flat solar cells, textured cells fabricated on moderate GZO front contacts show 7.9 and 10.9% enhancements in conversion efficiency and short-circuit current density, respectively.

Yu, Shu-Hung; Ho, Po-Ching; Lee, Chia-Ling; Bi, Chien-Chung; Yeh, Chih-Hung; Chang, Chun-Yen

2013-02-01

180

Gate bias-stress induced hump-effect in transfer characteristics of amorphous-indium-galium-zinc-oxide thin-fim transistors with various channel widths  

NASA Astrophysics Data System (ADS)

A hump in the subthreshold regime of the transfer characteristics is reported for amorphous-indium-galium-zinc-oxide thin-film transistors (TFTs) when they are exposed to large positive gate bias-stress. As stress time progresses, transfer characteristics shift in two opposite directions; the main transistor shifts in the positive, while the hump shifts in the negative gate-voltage direction. The hump occurs at the same current level in all TFTs with channel widths ranging from 10 to 200 ?m, which supports the exclusion of bulk and back surface effects. We therefore propose the accumulation of positive charge at the interface of the channel edges, along the channel width direction, as the origin of the hump effect.

Mativenga, Mallory; Seok, Manju; Jang, Jin

2011-09-01

181

Oxidation of carbon monoxide over palladium on zirconia prepared from amorphous Pd-Zr alloy. 1. Bulk structural, morphological, and catalytic properties of catalyst  

SciTech Connect

Catalysts highly active for the oxidation of carbon monoxide have been prepared by oxidation of amorphous and crystalline Pd{sub 1}Zr{sub 2} metal alloys. The oxidation was carried out in situ; i.e., the fresh metal alloys were exposed to CO-oxidation conditions at temperature of 473-553 K. Under these conditions, the initially almost inactive metal alloys underwent a series of solid state reactions and were finally transformed into stable and highly active microporous catalysts. Bulk structural characterization using X-ray diffraction and electron microscopy revealed that the final catalysts were made up of small intergrown and poorly crystalline domains of different palladium and zirconia phases. Palladium was present in three forms in the active catalysts, as a solid solution of palladium and oxygen, as metallic palladium, and a PdO. Zirconia existed in monoclinic and tetragonal forms. Comparative kinetic measurements carried out in a differential fixed bed reactor in the temperature range 300-500 K indicated that the activity of the palladium species in the catalysts derived from the metal alloys was more than an order of magnitude higher than the activity of the palladium species in a palladium on zirconia catalyst prepared by impregnation. The comparison of the activities was based on turnover frequencies calculated on the basis of accessible palladium sites determined by CO chemisorption. The higher activity of the catalysts derived from the metal alloys is attributed to their unique structural and chemical properties leading to extremely large interfacial areas and possibly to enhanced oxygen transfer via the solid-solid interphase.

Baiker, A.; Gasser, D.; Lenzner, J. (Swiss Federal Institute of Technology, Zurich (Switzerland)); Reller, A. (Univ. of Zurich (Switzerland)); Schloegl, R. (Fritz Haber Institute der Max Planck Gesellschaft, Berlin (Germany))

1990-12-01

182

X-ray absorption, photoemission spectroscopy, and Raman scattering analysis of amorphous tantalum oxide with a large extent of oxygen nonstoichiometry.  

PubMed

The electronic structure and modification of the local interatomic structure of a reactive sputtered amorphous tantalum oxide (a-TaO(x)) thin film with the variation of oxygen nonstoichiometry, x in a-TaO(x) have been investigated by X-ray absorption spectroscopy (XAS), X-ray photoemission spectroscopy (XPS), Raman scattering spectroscopy, and Rutherford back scattering spectroscopy. A parallel chemical shift of Ta4f(7/2) and O1s core levels observed with the variation of x indicates the Fermi level shift by reduction and oxidation in the framework of the rigid band model. Extended X-ray absorption fine structure (EXAFS) suggests both the increase of average coordination number of the first Ta-O shell in polyhedra and a considerable reduction of the average Ta-O bond length with the increase of x. The relative intensity of Raman shift peaks at 670 cm(-1) and 815 cm(-1), corresponding to Ta-O stretching of TaO(6) octahedra and TaO(5) probably with a pyramidal form, respectively, drastically changes between x = 2.47 to 1.86, suggesting the change in the predominant polyhedron from TaO(6) to TaO(5) with a modification in multiplicity of oxygen by the reorganization of the polyhedral network. PMID:21863188

Tsuchiya, Takashi; Imai, Hideto; Miyoshi, Shogo; Glans, Per-Anders; Guo, Jinghua; Yamaguchi, Shu

2011-08-24

183

Low-Temperature Fabrication of Polycrystalline Si Thin Film Using Al-Induced Crystallization without Native Al Oxide at Amorphous Si/Al Interface  

NASA Astrophysics Data System (ADS)

Low-temperature fabrication of polycrystalline silicon (poly-Si) thin film has been performed by Al-induced crystallization (AIC), and the structural properties have been investigated. In our experiments, to prevent native oxidation of Al film, an amorphous silicon (a-Si)/Al bilayer was formed on the SiO2/Si substrate by electron beam evaporation without breaking the vacuum. The a-Si/Al/SiO2/Si structure was then heated at a low temperature of 400C to induce AIC. It was confirmed that layer exchange of the a-Si/Al bilayer is induced even though there is no native oxidation of Al film, which was demonstrated by scanning transmission electron microscopy and energy dispersive X-ray analysis. The mechanism for layer exchange of the a-Si/Al bilayer has been discussed. Furthermore, it was verified by scanning electron microscopy and spectroscopic ellipsometry that the a-Si/Al thickness ratio of roughly 1:1 is suitable to achieve a flat surface morphology of poly-Si. In addition, it was found, by X-ray diffraction and orientation imaging microscopy, that the Si(111)-oriented grain becomes dominant with decreasing thickness of the a-Si/Al bilayer.

Sugimoto, Youhei; Takata, Naoki; Hirota, Takeshi; Ikeda, Ken-ichi; Yoshida, Fuyuki; Nakashima, Hideharu; Nakashima, Hiroshi

2005-07-01

184

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

NASA Astrophysics Data System (ADS)

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.

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

185

Amorphous Magnetic Insulators for Microwave Device Applications.  

National Technical Information Service (NTIS)

Results of our studies on thin films of amorphous magnetic oxides are summarized in this report. The main emphasis of the program was on the preparation and magnetic characterization of amorphous BiFeO3 films substituted with nonmagnetic perovskites, zinc...

G. Srinivasan

1992-01-01

186

Optical properties of hydrogenated amorphous silicon based solar cells  

Microsoft Academic Search

The optical properties of intrinsic hydrogenated amorphous silicon, p-type hydrogenated amorphous silicon-carbon, and tin oxide films are measured as a function of wavelength. Computer simulations based upon these and other measurements illustrate the optical development of hydrogenated amorphous silicon solar cells and quantify losses associated with each layer. The basic structure considered is glass\\/tin oxide\\/p-i-n\\/metal where the tin oxide film

F. B. Ellis Jr.; A. E. Delahoy

1986-01-01

187

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

NASA Astrophysics Data System (ADS)

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.

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

2013-11-01

188

The sulfidation and oxidation behavior of sputter-deposited amorphous Al-Nb alloys at high temperatures  

Microsoft Academic Search

The sulfidation and oxidation behavior of sputter-deposited Al-(2754at.%)Nb alloys has been investigated as a function of temperature (10731473 K) and alloy composition in He-S2 atmospheres with partial sulfur pressures (pS2) ranging from 5 101 to 1 104Pa and in an Ar-O2 atmosphere with partial oxygen pressure (pO2) of 2 104 Pa at a total pressure of 105

H. Mitsui; H. Habazaki; K. Asami; K. Hashimoto; S. Mrowec

1996-01-01

189

Resistance switching in amorphous and crystalline binary oxides grown by electron beam evaporation and atomic layer deposition  

Microsoft Academic Search

Resistance switching random access non-volatile memories (ReRAM) could represent the leading alternative to floating gate technology for post 32nm technology nodes. Among the currently investigated materials for ReRAM, transition metal binary oxides, such as NiO, CuxO, ZrOx, TiO2, MgO, and Nb2O5 are receiving increasing interest as they offer high potential scalability, low-energy switching, thermal stability, and easy integration in CMOS

S. Spiga; A. Lamperti; C. Wiemer; M. Perego; E. Cianci; G. Tallarida; H. L. Lu; M. Alia; F. G. Volpe; M. Fanciulli

2008-01-01

190

Effects of the amorphous oxide intergranular layer structure and bonding on the fracture toughness of a high purity silicon nitride  

SciTech Connect

The microstructural evolution and structural characteristics and transitions in the thin grain-boundary oxide films in a silicon nitride ceramic, specifically between two adjacent grains and not the triple junctions, are investigated to find their effect on the macroscopic fracture properties. It is found that by heat treating a model Si3N4-2wt percent Y2O3 ceramic for {approx}200 hr at 1400 degrees C in air, the fracture toughness can be increased by {approx}100 percent, coincident with a change in fracture mechanism from transgranular to intergranular.

Ziegler, A.; Kisielowski, C.; Hoffmann, M.J.; Ritchie, R.O.

2002-11-18

191

Amorphous Materials at High Pressure  

NASA Astrophysics Data System (ADS)

This chapter reviews the different pathways towards high-pressure amorphization, how high-pressure amorphs may be characterized and what are the potential mechanisms causing pressure-induced amorphization and amorphous-amorphous transitions.

Sanloup, Chrystele

192

Amorphous metal composites  

Microsoft Academic Search

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

Martin A. Byrne; John H. Lupinski

1984-01-01

193

Amorphous metal composites  

Microsoft Academic Search

This patent discloses 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

M. A. Byrne; J. H. Lupinski

1984-01-01

194

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

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.

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

195

Structure of amorphous Al2O3  

NASA Astrophysics Data System (ADS)

The structure of amorphous Al2O3 samples, prepared by anodic oxidation of aluminium foils, was investigated by X-ray and neutron diffraction. The partial pair correlation functions were determined from computer simulation of the structure using the Reverse Monte Carlo method with the result that amorphous Al2O3 is built up by AlO4 tetrahedra with corner sharing oxygen atoms. Pores in the material were characterized by neutron small-angle scattering.

Lamparter, P.; Kniep, R.

1997-02-01

196

A Comparative Study of Interaction of End of Range (EOR) Defect Band with Upper Buried Oxide (BOX) Interface for B and BF2 Implants in SOI and Bulk Silicon with Pre-Amorphizing Implant.  

NASA Astrophysics Data System (ADS)

Highly active, ultra-shallow and abrupt dopant profiles are required for future generations of CMOS devices. A possible way to achieve this is to use pre-amorphization implantation (PAI) and solid phase epitaxial re-growth. B and BF2 implants were studied in bulk silicon and silicon-on-insulator with Ge PAI. Results show that buried oxide (BOX) in SOI can be used a sink for silicon interstitials contributing to boron Transient Enhanced Diffusion and Boron-Interstitial Clustering. The BF2 implants show high mobility values and no deactivation.

Kah, M.; Smith, A. J.; Hamilton, J. J.; Yeong, S. H.; Columbeau, B.; Gwilliam, R.; Webb, R. P.; Kirkby, K. J.

2008-11-01

197

Effect of H and OH desorption and diffusion on electronic structure in amorphous In-Ga-Zn-O metal-oxide-semiconductor diodes with various gate insulators  

NASA Astrophysics Data System (ADS)

Metal-oxide-semiconductor (MOS) diodes with various gate insulators (G/Is) were characterized by capacitance-voltage characteristics and isothermal capacitance transient spectroscopy (ICTS) to evaluate the effect of H and OH desorption and diffusion on the electronic structures in amorphous In-Ga-Zn-O (a-IGZO) thin films. The density and the distribution of the space charge were found to be varied depending on the nature of the G/I. In the case of thermally grown SiO2 (thermal SiO2) G/Is, a high space-charge region was observed near the a-IGZO and G/I interface. After thermal annealing, the space-charge density in the deeper region of the film decreased, whereas remained unchanged near the interface region. The ICTS spectra obtained from the MOS diodes with the thermal SiO2 G/Is consisted of two broad peaks at around 5 10-4 and 3 10-2 s before annealing, while one broad peak was observed at around 1 10-4 s at the interface and at around 1 10-3 s in the bulk after annealing. Further, the trap density was considerably high near the interface. In contrast, the space-charge density was high throughout the bulk region of the MOS diode when the G/I was deposited by chemical vapor deposition (CVD). The ICTS spectra from the MOS diodes with the CVD G/Is revealed the existence of continuously distributed trap states, suggesting formations of high-density tail states below the conduction band minimum. According to secondary ion mass spectroscopy analyses, desorption and outdiffusion of H and OH were clearly observed in the CVD G/I sample. These phenomena could introduce structural fluctuations in the a-IGZO films, resulting in the formation of the conduction band tail states. Thin-film transistors (TFTs) with the same gate structure as the MOS diodes were fabricated to correlate the electronic properties with the TFT performance, and it was found that TFTs with the CVD G/I showed a reduced saturation mobility. These results indicate that the electronic structures in the a-IGZO films were strongly influenced by the nature of the G/Is as well as the process conditions. It is concluded that controlling of the natures of the G/I such as film density and hydrogen content in the films is critical to obtain high-performance electronic devices using a-IGZO.

Hino, Aya; Morita, Shinya; Yasuno, Satoshi; Kishi, Tomoya; Hayashi, Kazushi; Kugimiya, Toshihiro

2012-12-01

198

Amorphous metal foams  

Microsoft Academic Search

As recently demonstrated, amorphous metal foams are highly ductile in compression, and thus offer attractive compromises in mechanical and physical properties between crystalline metallic and ceramic foams. Challenges associated with fabrication of amorphous metal foams are critically assessed in the context of current and future processing methods, and conclusions are drawn regarding the properties and future applications of ductile amorphous

A. H. Brothers; D. C. Dunand

2006-01-01

199

Testing of flexible InGaZnO-based thin-film transistors under mechanical strain  

NASA Astrophysics Data System (ADS)

Thin-film transistors (TFTs) fabricated on flexible plastic substrates are an integral part of future flexible large-area electronic devices like displays and smart textiles. Devices for such applications require stable electrical performance under electrical stress and also during applied mechanical stress induced by bending of the flexible substrate. Mechanical stress can be tensile or compressive strain depending on whether the TFT is located outside or inside of the bending plane. Especially the impact of compressive bending on TFT performance is hard to measure, because the device is covered with the substrate in this case. We present a method which allows us to continuously measure the electrical performance parameters of amorphous Indium-Gallium-Zinc Oxide (a-IGZO) based TFTs exposed to arbitrary compressive and tensile bending radii. To measure the influence of strain on a TFT it is attached and electrically connected to a flexible carrier foil, which afterwards is fastened to two plates in our bending tester. The bending radius can be adjusted by changing the distance between these plates. Thus it is possible to apply bending radii in the range between a totally flat substrate and ?1 mm, corresponding to a strain of ?3.5%. The tested bottom-gate TFTs are especially designed for use with our bending tester and fabricated on 50 ?m thick flexible Kapton E polyimide substrates. To show the different application areas of our bending method we characterized our TFTs while they are bent to different tensile and compressive bending radii. These measurements show that the field effect mobilities and threshold voltages of the tested a-IGZO TFTs are nearly, but not absolutely, stable under applied strain, compared to the initial values the mobilities shift by ?3.5% in the tensile case and ?-1.5% in the compressive one, at a bending radius of 8 mm. We also measured the influence of repeated bending (2500 cycles over ?70 h), where a shift of the performance parameters can be observed, too. The saturation mobility of the flat device decreases by 4.5%, and the threshold voltage raises 0.1 V. These results show that it is possible to characterize the influence of different kinds of bending on flexible thin-film devices in a very reliable way with one experimental setup.

Mnzenrieder, N. S.; Cherenack, K. H.; Trster, G.

2011-08-01

200

Plasma treatment for crystallization of amorphous thin films  

Microsoft Academic Search

The crystallization of amorphous metal oxide thin films was achieved by RF plasma treatment. Although various amorphous films are crystallized after 2 min or so, the sample temperature is lower than 150 C without compulsory cooling even when the films are treated for 1 h. The oxygen gas pressure on the plasma treatment was found to be the key parameter

H. Ohsaki; Y. Shibayama; A. Nakajim; A. Kinbara; T. Watanabe

2006-01-01

201

Low Temperature Thermal Properties of Amorphous Polymer Blends  

Microsoft Academic Search

Thermal conductivity (kappa) and specific heat ({rm C}_ p) of amorphous polymer blends of polystyrene (PS) and polyphenylene oxide (PPO) with a wide range of compositions have been measured for 2K < T < 100K. The results show general features expected of amorphous solids: a peak in {rm C }_ p\\/T^ 3 below about 10K and a plateau in kappa

Ryan Evan Giedd

1986-01-01

202

Amorphous Materials at High Pressure  

Microsoft Academic Search

\\u000a This chapter reviews the different pathways towards high-pressure amorphization, how high-pressure amorphs may be characterized\\u000a and what are the potential mechanisms causing pressure-induced amorphization and amorphous-amorphous transitions.

Chrystele Sanloup

2010-01-01

203

Amorphous alloys and superconductivity  

SciTech Connect

Theoretical aspects and experimental results concerning transition temperatures, coupling constants, critical field, critical current density and pressure dependence of T /sub c/ of amorphous alloys are discussed.

Luscher, E.; Fritsch, G.

1984-09-01

204

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

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.

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

205

Role of interstitial voids in oxides on formation and stabilization of reactive radicals: interstitial HO2 radicals in F2-laser-irradiated amorphous SiO2.  

PubMed

A procedure to produce stable hydroperoxy radicals (HO*2) in bulk amorphous SiO(2) (a-SiO(2)) has been developed. Oxygen molecules incorporated in the interstitial voids in a-SiO(2) react with mobile hydrogen atoms (H(0)) generated by the photolysis of silanol (SiOH) groups with F(2)-laser light (lambda = 157 nm, hnu = 7.9 eV), resulting in the efficient creation of interstitial HO*2. The high yield of HO*2 suggests that the collisions of the reaction intermediate with the void wall play an important role in dissipating the excess energy of the intermediate instead of the triple collision observed in the gas phase reaction. The resultant HO*2 is thermally stable up to 100 degrees C. PMID:16620108

Kajihara, Koichi; Hirano, Masahiro; Skuja, Linards; Hosono, Hideo

2006-04-26

206

Syntax-Directed Amorphous Slicing  

Microsoft Academic Search

An amorphous slice of a program is constructed with respect to a set of variables. The amorphous sliceis an executable program which preserves the behaviour of the original on the variables of interest. Unlikesyntax{preserving slices, amorphous slices need not preserve a projection of the syntax of a program. Thismakes the task of amorphous slice construction harder, but it also often

Mark Harman; Lin Hu; Malcolm Munro; Xingyuan Zhang; David Binkley; Sebastian Danicic; Mohammed Daoudi; Lahcen Ouarbya

2004-01-01

207

Photoconductivity in Amorphous Semiconductors.  

National Technical Information Service (NTIS)

The September 1951 issue of RCA Review that contained Albert Rose's first major attempt to describe in detail the nature of photoconductivity processes in insulators and semiconductors, also contained articles on photoconductivity in amorphous selenium an...

R. H. Bube

1975-01-01

208

Amorphous and Metastable Materials.  

National Technical Information Service (NTIS)

This report summarizes the state of the art of amorphous and metastable materials, and includes a brief review of some of the properties of these materials, methods for producing them, possible directions for exploitation, identification of 'roadblocks' t...

R. E. Maringer

1976-01-01

209

Ferromagnetic bulk amorphous alloys  

NASA Astrophysics Data System (ADS)

This article reviews our recent results on the development of ferromagnetic bulk amorphous alloys prepared by casting processes. The multicomponent Fe-(Al,Ga)-(P,C,B,Si) alloys are amorphized in the bulk form with diameters up to 2 mm, and the temperature interval of the supercooled liquid region before crystallization is in the range of 50 to 67 K. These bulk amorphous alloys exhibit good soft magnetic properties, i.e., high B s of 1.1 to 1.2 T, low H o of 2 to 6 A/m, and high ? e of about 7000 at 1 kHz. The Nd-Fe-Al and Pr-Fe-Al bulk amorphous alloys are also produced in the diameter range of up to 12 mm by the copper mold casting process and exhibit rather good hard magnetic properties, i.e., B r of about 0.1 T, high H o of 300 to 400 kA/m, and rather high ( JH)max of 13 to 20 kJ/m3. The crystallization causes the disappearance of the hard magnetic properties. Furthermore, the melt-spun Nd-Fe-Al and Pr-Fe-Al alloy ribbons exhibit soft-type magnetic properties. Consequently, the hard magnetic properties are concluded to be obtained only for the bulk amorphous alloys. The bulk Nd- and Pr-Fe-Al amorphous alloys have an extremely high T x/Tm of about 0.90 and a small ? T m(= T m- T x) of less than 100 K and, hence, their large glass-forming ability is due to the steep increase in viscosity in the supercooled liquid state. The high T x/Tm enables the development of a fully relaxed, clustered amorphous structure including Nd-Nd and Nd-Fe atomic pairs. It is, therefore, presumed that the hard magnetic properties are due to the development of Nd-Nd and Nd-Fe atomic pairs with large random magnetic anisotropy. The Nd- and Pr-based bulk amorphous alloys can be regarded as a new type of clustered amorphous material, and the control of the clustered amorphous structure is expected to enable the appearance of novel functional properties which cannot be obtained for an ordinary amorphous structure.

Inoue, Akihisa; Takeuchi, Akira; Zhang, Tao

1998-07-01

210

Hydrogenated Amorphous Carbon Films  

Microsoft Academic Search

\\u000a Hydrogenated amorphous carbon (a-C:H) thin film is one of the most studied materials due to its unique features. The a-C:H\\u000a thin film is a remarkable material because of its novel optical, mechanical and electrical properties and its similarities\\u000a to diamond. In this chapter we reviewed the structural and optical properties of hydrogenated amorphous carbon (a-C:H) thin\\u000a films prepared in a

Suriani Abu Bakar; Azira Abdul Aziz; Putut Marwoto; Samsudi Sakrani; Mohamad Rusop

211

Amorphous metal alloy  

DOEpatents

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.

Wang, R.; Merz, M.D.

1980-04-09

212

Amorphous silicon as high index photonic material  

Microsoft Academic Search

Silicon-on-Insulator (SOI) photonics has become an attractive research topic within the area of integrated optics. This paper aims to fabricate SOI-structures for optical communication applications with lower costs compared to standard fabrication processes as well as to provide a higher flexibility with respect to waveguide and substrate material choice. Amorphous silicon is deposited on thermal oxidized silicon wafers with plasma-enhanced

T. Lipka; A. Harke; O. Horn; J. Amthor; J. Mller

2009-01-01

213

Structural Amorphous Steels  

NASA Astrophysics Data System (ADS)

Recent advancement in bulk metallic glasses, whose properties are usually superior to their crystalline counterparts, has stimulated great interest in fabricating bulk amorphous steels. While a great deal of effort has been devoted to this field, the fabrication of structural amorphous steels with large cross sections has remained an alchemists dream because of the limited glass-forming ability (GFA) of these materials. Here we report the discovery of structural amorphous steels that can be cast into glasses with large cross-section sizes using conventional drop-casting methods. These new steels showed interesting physical, magnetic, and mechanical properties, along with high thermal stability. The underlying mechanisms for the superior GFA of these materials are discussed.

Lu, Z. P.; Liu, C. T.; Thompson, J. R.; Porter, W. D.

2004-06-01

214

Irreversible Damage in Amorphous Silica  

NASA Astrophysics Data System (ADS)

Glass touches every aspect of our lives including the glass dishes which we cook with to the storage of nuclear waste. The extensive use of oxide glasses can be attributed to optical transparency, electrical and heat insulation, and large hardness. However, oxide glasses have a major drawback: brittleness. Even small flaws in the structure can lead to the ultimate failure of the material. Recent Atomic Force Microscope experiments and Molecular Dynamics simulations revealed a process zone ahead of the crack tip where damage nucleates, augments, and finally merges with the advancing crack front. Furthermore, when a-SiO2 samples are nanoindented, one finds permanent damage under the indenter in the form of densified silica. To shed light on the origin of irreversible deformation in amorphous media, we have expanded our studies to examine what happens to an oxide glass when subjected to shear. MD simulations have been performed in a-SiO2 systems which are subject to a shearing force at room temperature. The system was initially isotropic and as long the maximum shear deformation remains under 5% the system remains isotropic upon unloading. However if the system is sheared to a point greater than 5% permanent plastic deformation sets in and the system is no longer isotropic upon unloading.

Rountree, Cindy; Vandembroucq, Damien; Roux, Stephane; Bouchaud, Elisabeth

2011-03-01

215

Amorphous silicon logic integrated circuits  

Microsoft Academic Search

Amorphous silicon thin-film integrated circuits, with between 4 and 18 transistor functions per chip, have been fabricated on glass substrates. The amorphous silicon and the dielectric layers are deposited by rf glow discharge. The circuits have been designed to realize basic logic functions such as inverters, NAND and NOR gates, and addressable memory cells. For the first time, an amorphous

M. Bhm; S. Salamon; Z. Kiss

1988-01-01

216

Amorphous semiconductor solar cell  

DOEpatents

A solar cell comprising a back electrical contact, amorphous silicon semiconductor base and junction layers and a top electrical contact includes in its manufacture the step of heat treating the physical junction between the base layer and junction layer to diffuse the dopant species at the physical junction into the base layer.

Dalal, Vikram L. (Newark, DE)

1981-01-01

217

Study on Er3+ emission from the erbium-doped hydrogenated amorphous silicon suboxide film  

Microsoft Academic Search

The erbium-doped hydrogenated amorphous silicon suboxide films containing amorphous silicon clusters were prepared. The samples exhibited photoluminescence peaks at around 750 nm and 1.54 ?m, which could be assigned to the electron-hole recombination in amorphous silicon clusters and the intra-4f transition in Er3+, respectively. Correlations between the intensities of these two photoluminescence peaks and oxidation and dehydrogenation of the films

C. Y. Chen; W. D. Chen; S. F. Song; Z. J. Xu; X. B. Liao; G. H. Li; K. Ding

2003-01-01

218

Electrochemical and ellipsometric investigations of the passivation of amorphous alloys  

SciTech Connect

It is shown that by homogenization after structural relaxation it is possible to increase the corrosion resistance of characteristic amorphous alloys in the active and passive states. The greatest effect of heat treatment is obtained in providing by it of self-passivation of the alloys. According to ellipsometric data the potential of the start of oxide layer growth may be more negative for amorphous alloys than for microcrystalline and the oxide layer itself has a complex structure and is not described by a unilayer model.

Vasil'ev, V.Yu.; Chechetkin, A.Yu.; Mel'nikova, E.V.; Kudryavtseva, Z.I.; Zhuchkova, N.A.

1987-01-01

219

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)

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.

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

220

Thermoluminescence characteristics of hydrogenated amorphous zirconia  

NASA Astrophysics Data System (ADS)

This paper reports the experimental results concerning the thermoluminescent (TL) characteristics of hydrogenated amorphous zirconium oxide (a-Zr:H) powder prepared by the sol-gel method. The advantages of this method are the homogeneity and the purity of the gels associated with a relatively low sintering temperature. Hydrogenated amorphous powder was characterized by thermal analysis and X-ray diffraction. The main TL characteristics investigated were the TL response as a function of the absorbed dose, the reproducibility of the TL readings and the fading. The undoped a-Zr:H powder presents a TL glow curve with two peaks centered at 150 and 260 degrees C, respectively, after beta irradiation. The TL response a-Zr:H as a function of the absorbed dose showed a linear behavior over a wide range. The results presented open the possibility to use this material as a good TL dosimeter.

Montalvo, T. R.; Tenorio, L. O.; Nieto, J. A.; Salgado, M. B.; Estrada, A. M. S.; Furetta, C.

2005-05-01

221

Nucleation and crystallization characteristics of phosphorus-doped amorphous silicon slit nano wire  

Microsoft Academic Search

Nucleation and crystallization characteristics of phosphorus-doped amorphous silicon (a-Si) 'slit nano wire' are studied, which is fabricated by conformal filling of a 100 nm wide trench by HLD (High temperature Low pressure chemical vapor Deposition) oxide, and measures about 10 nm in width and height. Nucleation rate and crystallization rate of the amorphous silicon layer, with a phosphorus doping concentration

Yasuo Wada; Takashi Kobayashi; Tokuo Kure; Toshiyuki Yoshimura; Yoshimi Sudou; Yasushi Gotou; Seiichi Kondo

1994-01-01

222

Amorphous silicon radiation detectors  

DOEpatents

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 the signal produced by incoming high energy radiation. These enhanced radiation sensitive devices can be used as measuring and detection means for visible light, low energy photons and high energy ionizing particles such as electrons, x-rays, alpha particles, beta particles and gamma radiation. Particular utility of the device is disclosed for precision powder crystallography and biological identification. 13 figs.

Street, R.A.; Perez-Mendez, V.; Kaplan, S.N.

1992-11-17

223

Amorphous silicon radiation detectors  

DOEpatents

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 the signal produced by incoming high energy radiation. These enhanced radiation sensitive devices can be used as measuring and detection means for visible light, low energy photons and high energy ionizing particles such as electrons, x-rays, alpha particles, beta particles and gamma radiation. Particular utility of the device is disclosed for precision powder crystallography and biological identification.

Street, Robert A. (Palo Alto, CA); Perez-Mendez, Victor (Berkeley, CA); Kaplan, Selig N. (El Cerrito, CA)

1992-01-01

224

Amorphous magnetic alloy  

SciTech Connect

An amorphous magnetic alloy is described having the formula Co /SUB x/ M /SUB y/ B /SUB z/ wherein M is zirconium, hafnium and/or titanium. When M is hafnium or zirconium 70x80, 8y15 and 10z16. When M is titanium, 70x72, 16y25 and 4z10. When M is hafnium together with titanium and/or zirconium, 70x80, 8y20 and 5z16.

Kanehira, J.

1984-04-03

225

Amorphous Carbon Nanospheres  

ScienceCinema

Amorphous carbon nanosphere used as the anode material for Li-intercalation in Lithium-ion energy storage. This structure was obtained through a thermal annealing process at a temperature of 3000 degree Kelvin, simulated using the LAMMPS molecular dynamics code on the LCRC Fusion resource. Science: Kah Chun Lau, Larry Curtiss, Argonne National Laboratory Visualization: Aaron Knoll, Mark Hereld, Michael E. Papka, Argonne National Laboratory

226

Mechanisms and effects of wear on amorphous carbon thin films  

Microsoft Academic Search

Amorphous carbon thin films, which are commonly used as protective layers for magnetic hard disks, experience wear during the operation of a hard disk. During sliding between these carbon films and the read-write head's slider tribochemical reactions occur, which have been predicted to remove carbon oxides. The tribochemical reactions have been investigated in this study through the use of a

Ainissa Gweneth Ramirez

1998-01-01

227

Electrochemical and ellipsometric investigations of the passivation of amorphous alloys  

Microsoft Academic Search

It is shown that by homogenization after structural relaxation it is possible to increase the corrosion resistance of characteristic amorphous alloys in the active and passive states. The greatest effect of heat treatment is obtained in providing by it of self-passivation of the alloys. According to ellipsometric data the potential of the start of oxide layer growth may be more

V. Yu. Vasilev; A. Yu. Chechetkin; E. V. Melnikova; Z. I. Kudryavtseva; N. A. Zhuchkova

1987-01-01

228

Optical multilayers with an amorphous fluoropolymer  

SciTech Connect

Multilayered coatings were made by physical vapor deposition (PVD) of a perfluorinated amorphous polymer, Teflon AF2400, together with other optical materials. A high reflector at 1064 run was made with ZnS and AF2400. An all-organic 1064-nm reflector was made from AF2400 and polyethylene. Oxide (HfO{sub 2}, SiO{sub 2}) compatibility was also tested. Each multilayer system adhered to itself. The multilayers were influenced by coating stress and unintentional temperature rises during PVD deposition.

Chow, R.; Loomis, G.E.; Lindsey, E.F.

1994-07-01

229

Pressure-induced amorphization and reduction of T-Nb2O5  

NASA Astrophysics Data System (ADS)

Energy dispersive x-ray diffraction measurements show that the T phase of Nb2O5 becomes x-ray amorphous at a pressure of 19.2 GPa at 300 K. This pressure-induced amorphization is novel since the oxide is simultaneously reduced as it becomes amorphous. The amorphization occurs because the pressure-induced reduction T-Nb2O5-->crystalline Nb12O29 is kinetically impeded. A consideration of the ambient pressure atomic mechanism of the oxidation of NbOx compounds (x<2.5) suggests that the pressure-induced amorphous state is formed by oxygen defects in the T-Nb2O5 lattice.

Serghiou, George C.; Winters, Robert R.; Hammack, William S.

1992-06-01

230

Crystallisation of crystallizable and amorphous polymer mixtures and peculiarities of their structure: an NMR study  

Microsoft Academic Search

After isothermal crystallization of the crystallizable poly(ethylene oxide)\\/amorphous poly(propylene oxide) mixture, partially crystalline structures were formed. They present a specific heterogeneous medium with a hard frame composed of the crystal phase. The isothermal crystallization of the mixture and molecular self-diffusion processes in the amorphous phase of the crystallized mixture was studied by nuclear magnetic resonance relaxation and nuclear magnetic resonance

A. V. Filippov; V. S. Smirnov; M. M. Doroginizkij

1998-01-01

231

Shock Induced Amorphization of Materials  

Microsoft Academic Search

The pressure induced crystalline to amorphous (c arrow a) transition is a topic of considerable current interest (see Sharma and Sikka, Prog. in Mat. Sci. 40 (1996), for a review and references there in). Under static pressures about 50 substances have been amorphized. Some of these have also been vitrified using shock waves. Molecular dynamics simulations have also been done.

S. K. Sikka; Satish C. Gupta

1997-01-01

232

PHOTOLITHOGRAPHIC PROCESSES IN AMORPHOUS SEMICONDUCTORS  

Microsoft Academic Search

Various photolithographic processes in a wide class of amorphous semiconductor films have been proposed and demonstrated in the past decade. The special features of the photosensitive amorphous semiconductor materials - non graininess, inorganic chemistry, deposition from the vapor phase and durability in dry and wet etchants - make them attractive photoresists for sub-micron fabrication of integrated circuits and integrated optics

M. Janai

1981-01-01

233

PERFORMANCE OF AMORPHOUS SILICON MODULES  

Microsoft Academic Search

There is a significant spread in the performance of different amorphous silicon modules, despite similar declared efficiencies. The reasons behind the observed differences in the performance of 15 amorphous silicon modules of eight different manufacturers and different vintages are investigated. The operating efficiency of the devices varies by 40% with respect to the average of the group. There is no

D. Sauter; T. R. Betts; S. R. Williams; R. Gottschalg; D. G. Infield

2004-01-01

234

Amorphous Silicon Contact Image Sensor.  

National Technical Information Service (NTIS)

Development was made of a high-speed and high-resolution amorphous silicon contact image sensor with A4 size width, 16 elements/mm and 0.8-ms/line reading speed. It was believed to be difficult to apply amorphous silicon to a high-speed image sensor becau...

Y. Suda K. Suzuki T. Saito

1984-01-01

235

Bulk amorphous materials  

SciTech Connect

This is the final report for a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The objective of this work was to develop the competency for the synthesis of novel bulk amorphous alloys. The authors researched their synthesis methods and alloy properties, including thermal stability, mechanical, and transport properties. The project also addressed the development of vanadium-spinel alloys for structural applications in hostile environments, the measurement of elastic constants and thermal expansion in single-crystal TiAl from 300 to 750 K, the measurement of elastic constants in gallium nitride, and a study of the shock-induced martensitic transformations in NiTi alloys.

Schwarz, R.B.; Archuleta, J.I.; Sickafus, K.E. [and others

1998-12-01

236

Perspective on photovoltaic amorphous silicon  

NASA Astrophysics Data System (ADS)

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 U.S. 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 U.S. 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 States, and by Germany in the last 2-3 years more than twice that of the U.S. 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/Wp for plants with 10 MW/year capacities.

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

1992-12-01

237

Perspective on photovoltaic amorphous silicon  

SciTech Connect

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 U.S. 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 U.S. 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 States, and by Germany in the last 2--3 years more than twice that of the U.S. 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 [ital p

Luft, W.; Stafford, B.; von Roedern, B. (National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, Colorado 80401 (United States))

1992-12-01

238

Perspective on photovoltaic amorphous silicon  

SciTech Connect

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.

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

1992-05-01

239

Perspective on photovoltaic amorphous silicon  

NASA Astrophysics Data System (ADS)

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 percent to 7.2 percent stabilized amorphous silicon module efficiencies for U.S. products, and 8.1 percent 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 U.S. 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 percent greater than that in the United States, and by Germany in the last 2 to 3 years, more than twice that of the U.S. 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 to $1.50/W(sub p) for plants with 10 MW/year capacities.

Luft, W.; Stafford, B.; Vonroedern, B.

1992-05-01

240

Thermal conductivity of sputtered oxide films  

Microsoft Academic Search

The thermal conductivity of oxide thin films deposited using dc, rf, and ion-beam sputtering is measured in the temperature range 80-400 K using the 3omega method. Thermal conductivity data for amorphous thin films of SiO2 are nearly identical to bulk a-SiO2. Data for amorphous Al2O3, while having a magnitude and temperature dependence similar to bulk amorphous oxides, show a dependence

S.-M. Lee; David G. Cahill; Thomas H. Allen

1995-01-01

241

[Pharmaceutical significance of amorphous materials].  

PubMed

The solid-state characteristics play an important role during the development and manufacture of medicinal products, because they may influence the effectiveness, stability as well as the processibility of pharmaceutical systems. The amorphous state is critical in determining the solid-state physical and chemical properties of many pharmaceutical dosage forms. The main reason of the growing interest toward amorphous materials is the need to improve the bioavailability of compounds with poor aqueous solubility. However the disordered structure of higher energy state assures increased solubility and faster dissolution rate, the amorphous state is a non-equilibrium state. Materials often go through spontaneous transformations towards lower energy equilibrium states. PMID:18986089

Antal, Istvn; Zelk, Romna

2008-01-01

242

Fabrication of amorphous diamond films  

SciTech Connect

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.

Falabella, S.

1995-12-12

243

Dynamic heterogeneity in amorphous materials  

NASA Astrophysics Data System (ADS)

Amorphous solids are mechanically rigid while possessing a disordered structure similar to that of dense liquids. Recent research indicates that dynamical heterogeneity, spatio-temporal fluctuations in local dynamical behavior, might help understanding the statistical mechanics of glassy states.

Berthier, Ludovic

2011-05-01

244

Polyamorphic transition in amorphous fullerites  

Microsoft Academic Search

Samples of amorphous fullerites have been prepared by mechanoactivation (grinding in a ball mill), and their structure has been studied using neutron diffraction. It has been found that the amorphous fullerites subjected to high-temperature (600-1700C) annealing undergo a polyamorphic transition from the molecular glass to the atomic glass, which is accompanied by the disappearance of fullerene halos at small scattering

S. S. Agafonov; V. P. Glazkov; I. F. Kokin; V. A. Somenkov

2010-01-01

245

Polyamorphic transition in amorphous fullerites  

Microsoft Academic Search

Samples of amorphous fullerites have been prepared by mechanoactivation (grinding in a ball mill), and their structure has\\u000a been studied using neutron diffraction. It has been found that the amorphous fullerites subjected to high-temperature (6001700C)\\u000a annealing undergo a polyamorphic transition from the molecular glass to the atomic glass, which is accompanied by the disappearance\\u000a of fullerene halos at small scattering

S. S. Agafonov; V. P. Glazkov; I. F. Kokin; V. A. Somenkov

2010-01-01

246

Perspective on photovoltaic amorphous silicon  

Microsoft Academic Search

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%

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

1992-01-01

247

Perspective on photovoltaic amorphous silicon  

Microsoft Academic Search

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

W. Luft; B. Stafford; B. Vonroedern

1992-01-01

248

Amorphous metal alloy and composite  

DOEpatents

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.

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

1985-01-01

249

Excitations of amorphous solid helium  

NASA Astrophysics Data System (ADS)

We present neutron scattering measurements of the dynamic structure factor S(Q,?) of amorphous solid helium confined in 47- pore diameter MCM-41 at pressure 48.6 bars. At low temperature T=0.05 K, we observe S(Q,?) of the confined quantum amorphous solid plus the bulk polycrystalline solid between the MCM-41 powder grains. No liquidlike phonon-roton modes, other sharply defined modes at low energy (?< 1.0 meV), or modes unique to a quantum amorphous solid that might suggest superflow are observed. Rather, the S(Q,?) of confined amorphous and bulk polycrystalline solid appear to be very similar. At higher temperature (T> 1 K), the amorphous solid in the MCM-41 pores melts to a liquid which has a broad S(Q,?) peaked near w?0, characteristic of normal liquid 4He under pressure. Expressions for the S(Q,?) of amorphous and polycrystalline solid helium are presented and compared. In previous measurements of liquid 4He confined in MCM-41 at lower pressure, the intensity in the liquid roton mode decreases with increasing pressure until the roton vanishes at the solidification pressure (38 bars), consistent with no roton in the solid observed here.

Bossy, Jacques; Ollivier, Jacques; Schober, Helmut; Glyde, H. R.

2012-12-01

250

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

SciTech Connect

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.

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

1995-12-31

251

Inhibitory Effect of Soil Organic Matter on the Crystallization of Amorphous Ferric Hydroxide  

Microsoft Academic Search

SOILS and sediments often contain large quantities of hydrous ferric oxide which, according to X-ray analysis, cannot be accounted for by crystalline forms of iron oxide. This is surprising in view of the fact that crystallization in vitro of freshly prepared amorphous ferric hydroxide to goethite or haematite is virtually complete after a few months or years, even at room

U. Schwertmann

1966-01-01

252

Allotropic composition of amorphous carbon  

SciTech Connect

Using the concept of an inhomogeneous broadening of spectral lines of the basic oscillators responsible for forming the spectrum, the experimental dependences of the dispersion of the imaginary part of permittivity are analyzed for amorphous carbon. It turned out that four types of oscillators contribute to this dependence. The first three types represent the electron transitions from the energy-spectrum ground state for {pi} and {sigma} electrons of amorphous carbon to an excited state. The fourth type is related to the absorption of electromagnetic radiation by free charge carriers. The absolute values of squared plasma frequencies of oscillators are estimated, and, using them, the relative fraction of sp{sup 2}-bonded atoms forming the amorphous-carbon skeleton is calculated. This estimate agrees closely with the theoretical predictions for amorphous carbon of the same density as the material under study. The dependence of the relative fraction of sp{sup 2}-bonded atoms contained in amorphous hydrogenised carbon on annealing temperature is determined. The developed method is also applied to the analysis of the normalized curve for the light extinction in the interstellar medium. The contribution to the extinction of two varieties of interstellar matter is detected.

Yastrebov, S. G., E-mail: yastrebov@mail.ioffe.ru; Ivanov-Omskii, V. I. [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation)

2007-08-15

253

Effect of high-energy electron beam irradiation on the gate-bias stability of IGZO TFTs  

NASA Astrophysics Data System (ADS)

We explored the effects of high-energy electron beam irradiation (HEEBI) on the gate-bias and light stabilities of indium-gallium-zinc-oxide (IGZO)-based transparent thin film transistors (TTFTs). The developed TTFTs had a top gate structure, which used IGZO and Al2O3 films for the active layer and the gate dielectric, respectively. The developed TTFTs were treated with HEEBI in air at room temperature at an electron beam energy of 0.8 MeV and a dose of 1 1014 electrons/cm2. Without the gate bias and/or light stresses, the HEEBI-treated devices showed a positive threshold voltage ( V th ) shift (+? V th ), suggesting that acceptor defects might have been generated by HEEBI treatment near the valence band edge. The HEEBI-treated devices also exhibited a lower +? V th , a higher negative V th shift (-? V th ), and a much lower -? V th under positive gate bias, negative gate bias, and light stresses compared to those for the HEEBI-untreated devices, respectively. These V th instabilities were observed without significant change in the sub-threshold slope, indicating that charge trapping in the gate dielectric and/or at the active layer/dielectric interface was the dominant mechanism of the device instability.

Moon, Hye Ji; Jung, So Hyun; Ryu, Min Ki; Cho, Kyoung Ik; Yun, Eui-Jung; Bae, Byung Seong

2012-01-01

254

Investigation of defect generation and annihilation in IGZO TFTs during practical stress conditions: illumination and electrical bias  

NASA Astrophysics Data System (ADS)

This investigation elucidates the influence of standalone-bias stress and standalone-illumination stress, and their combinatory effect on indium-gallium-zinc oxide (IGZO) thin-film transistors (TFTs). Each phenomenon associated with illumination (wavelengths of 410, 467, 532 and 632 nm) and bias (Vg = 20 V Vd = 0, 20 V) stresses is categorized individually. Wavelengths below 532 nm are responsible for ionized vacancy creation, carrier generation and interface state creation while only gate stresses of +20 V create excessive charge trap states. Failure conditions are identified as gate stresses of -20 V with 410 nm illumination. An improvement in the Ion/Ioff ratio from 106 to 107 is due to increased charge contribution for on currents, and trapping of holes at the intermetallic dielectric near the source-channel junction in the off region. Upon stress removal TFTs exhibit incomplete recovery due to slow trapping of excited carriers from dielectric layers and inability created by the passivation layer to absorb oxygen for vacancy regeneration. The low-temperature fabrication and optimized post-fabrication anneal have created reduced defect and vacancy densities that make the IGZO TFTs more stable than the previous generation TFTs.

Vemuri, Rajitha N. P.; Mathews, Winnie P.; Marrs, Michael; Alford, T. L.

2013-01-01

255

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

NASA Astrophysics Data System (ADS)

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 1103, 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 6.2104, 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.

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

2013-08-01

256

Amorphous-diamond electron emitter  

DOEpatents

An electron emitter comprising a textured silicon wafer overcoated with a thin (200 .ANG.) layer of nitrogen-doped, amorphous-diamond (a:D-N), which lowers the field below 20 volts/micrometer have been demonstrated using this emitter compared to uncoated or diamond coated emitters wherein the emission is at fields of nearly 60 volts/micrometer. The silicon/nitrogen-doped, amorphous-diamond (Si/a:D-N) emitter may be produced by overcoating a textured silicon wafer with amorphous-diamond (a:D) in a nitrogen atmosphere using a filtered cathodic-arc system. The enhanced performance of the Si/a:D-N emitter lowers the voltages required to the point where field-emission displays are practical. Thus, this emitter can be used, for example, in flat-panel emission displays (FEDs), and cold-cathode vacuum electronics.

Falabella, Steven (Livermore, CA)

2001-01-01

257

High Density Amorphous Metal Matrix Composites for Kinetic Energy Penetrators.  

National Technical Information Service (NTIS)

The aims of the project were to acquire metallic based amorphous metal alloy powder, consolidate the powder into bulk structural amorphous metal (SAM), blend the amorphous powder with crystalline Ta or W powders and consolidate the blends into bulk amorph...

K. T. Hartwig I. Karaman

2005-01-01

258

Compaction of Amorphous Ferromagnetic Metal Powders.  

National Technical Information Service (NTIS)

The attractive magnetic properties of certain amorphous metal powders might be exploited in the electrical industry if the powders can be consolidated into relatively dense compacts. The production of integral bodies of an amorphous powder was attempted u...

R. D. Caligiuri

1982-01-01

259

Infrared Spectroscopy of Amorphous Sulfate Phases  

NASA Astrophysics Data System (ADS)

Stability experiments have indicated that amorphous sulfate phases may be important constituents of martian surface materials. IR spectral properties of X-ray amorphous Mg- and Fe-sulfate phases are described and compared with their crystalline counterparts.

Rogers, A. D.; Reeder, R. J.; Glotch, T. D.

2009-03-01

260

Metal Film Coatings on Amorphous Metallic Alloys.  

National Technical Information Service (NTIS)

Fe-metalloid amorphous metallic alloy ribbons, when properly annealed in a transverse magnetic field, exhibit extremely high magnetomechanical coupling. Other amorphous metallic alloys (or glassy metals) have desirable properties such as high strength, co...

L. Kabacoff

1989-01-01

261

Lithium insertion in tungsten oxide thin films  

NASA Astrophysics Data System (ADS)

Intercalation of lithium ions in amorphous tungsten oxide films and in monoclinic polycrystalline tungsten oxide films has been studied using electrochemical analyses and Raman spectroscopy. We present direct evidence for W5+ 5d- electron localization in amorphous tungsten oxide films upon lithium ion and electron intercalation, by comparing the Raman spectra of amorphous and crystalline tungsten oxide films. We observe that when lithium ions and electrons are inserted into the crystalline tungsten oxide films, the monoclinic structure of the material proceeds to progressively increased symmetry. On the other hand, when lithium ions and electrons are inserted into amorphous tungsten oxide films, the inserted electrons are localized in W5+ sites and polarize their surrounding lattice to form small polarons. The extra Raman peaks due to the W5+-O single bonds and W5+equalsO double bonds appear at 330 and 450 cm-1, respectively.

Lee, Se-Hee; Seong, Maeng J.; Ozcan, Esra; Tracy, C. Ed; Tepehan, Fatma Z.; Deb, Satyen K.

2001-11-01

262

Amorphous metal alloys produced by mechanical alloying  

Microsoft Academic Search

Mechanical alloying is a powder metallurgy method used in commercial production of high temperature superalloys. Under specific conditions, mechanical alloying allows the synthesis of amorphous metal alloys from mixtures of pure metal powders or from the powders of intermetallic compounds. Because the amorphizing transformation during mechanical alloying is a solid state reaction, most of the difficulties related to the amorphization

T. J. Tiainen; R. B. Schwarz

1989-01-01

263

Narrow band gap amorphous silicon semiconductors  

Microsoft Academic Search

Disclosed is a narrow band gap amorphous silicon semiconductor comprising an alloy of amorphous silicon and a band gap narrowing element selected from the group consisting of Sn, Ge, and Pb, with an electron donor dopant selected from the group consisting of P, As, Sb, Bi and N. The process for producing the narrow band gap amorphous silicon semiconductor comprises

A. Madan; A. H. Mahan

1985-01-01

264

Investigation of Local Ordering in Amorphous Materials  

Microsoft Academic Search

The intent of the research described in this dissertation, as indicated by the title, is to provide a better understanding of the structure of amorphous material. The possibility of using electron microscopy to study the amorphous structure is investigated. Chapter 1 gives a brief introduction to the understanding and modeling of the amorphous structure, electron microscopy and the image analysis

Gary Guoyou Fan

1987-01-01

265

Transition in amorphous selenium under high pressure  

Microsoft Academic Search

The phase transition in amorphous selenium under high pressure was studied. The high pressures were generated using a diamond-indentor technique. From the behavior of electrical resistance of amorphous selenium under high pressure, it was found that amorphous selenium at room temperature starts transforming to a crystalline phase when the pressure is near 97 kbar. The effect of temperature on the

Mool C. Gupta; Arthur L. Ruoff

1978-01-01

266

Amorphous rare earth magnet powders  

SciTech Connect

Gas atomization (GA) processing does not generally have a high enough cooling rate to produce the initial amorphous microstructure needed to obtain optimal magnetic properties in RE{sub 2}Fe{sub 14}B alloys. Phase separation and an underquenched microstructure result from detrimental {alpha}-Fe precipitation, and the resulting magnetic domain structure is very coarse. Additionally, there is a dramatic dependence of the magnetic properties on the cooling rate (and therefore the particle size) and the powders can be sensitive to environmental degradation. Alloy compositions designed just for GA (as opposed to melt spinning) are necessary to produce an amorphous structure that can be crystallized to result in a fine structure with magnetic properties which are independent of particle size. The addition of titanium and carbon to the melt has been found to change the solidification process sufficiently to result in an ``overquenched`` state in which most of the powder size fractions have an amorphous component. Crystallization with a brief heat treatment produces a structure which has improved magnetic properties, in part due to the ability to use compositions with higher Fe contents without {alpha}-Fe precipitation. Results from magnetometry, magnetic force microscopy, and x-ray analyses will be used to contrast the microstructure, domain structure, and magnetic properties of this new generation of amorphous powders with their multiphase predecessors.

Sellers, C.H.; Branagan, D.J.; Hyde, T.A. [Idaho National Engineering Lab., Idaho Falls, ID (United States); Lewis, L.H. [Brookhaven National Lab., Upton, NY (United States). Dept. of Applied Science; Panchanathan, V. [Magnequench International, Anderson, IN (United States)

1996-08-01

267

Thorium sorption on amorphous silica  

Microsoft Academic Search

The sorption of Th on amorphous colloidal particles of Si02 (Aerosil OX 200) has been studied in perchlorate media in order to obtain quantitative information on the sorption of The on silica. In order to quantify the pH dependence of the charge of the silica surface, potentiometric surface titrations of the silica particles have also been made. The results from

Erik sthols

1995-01-01

268

Raman spectrum of amorphous diamond.  

National Technical Information Service (NTIS)

The Raman spectrum of an amorphous, fully sp(sup 3)-bonded carbon network is presented. The reduced Raman spectrum agrees closely with the calculated density of states of diamond. The results have been obtained from nanoclusters produced deep inside a sin...

S. Prawer K. W. Nugent D. Jamieson

1997-01-01

269

Electron Tunneling into Amorphous Germanium.  

National Technical Information Service (NTIS)

A detailed study was undertaken of electron tunneling into amorphous Ge. At low temperature, T < 100 K, the high-field conductivity of the a-Ge film is similar to the tunneling conductance. For a-Ge thicknesses t < 500 A the conductance of a-Ge blends smo...

J. W. Osmun

1974-01-01

270

Atomistic Models of Amorphous Semiconductors  

Microsoft Academic Search

Crystalline silicon is probably the best studied material, widely used by the semiconductor industry. The subject of this thesis is an intriguing form of this element namely amorphous silicon. It can contain a varying amount of hydrogen and is denoted as a-Si:H. It completely lacks the neat long range order of the crystal, yet its structure is not random. Almost

K. Jarolimek

2011-01-01

271

Diamond-like amorphous carbon  

Microsoft Academic Search

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

J. Robertson

2002-01-01

272

Model for amorphous aggregation processes  

NASA Astrophysics Data System (ADS)

The amorphous aggregation of proteins is associated with many phenomena, ranging from the formation of protein wine haze to the development of cataract in the eye lens and the precipitation of recombinant proteins during their expression and purification. While much literature exists describing models for linear protein aggregation, such as amyloid fibril formation, there are few reports of models which address amorphous aggregation. Here, we propose a model to describe the amorphous aggregation of proteins which is also more widely applicable to other situations where a similar process occurs, such as in the formation of colloids and nanoclusters. As first applications of the model, we have tested it against experimental turbidimetry data of three proteins relevant to the wine industry and biochemistry, namely, thaumatin, a thaumatinlike protein, and ? -lactalbumin. The model is very robust and describes amorphous experimental data to a high degree of accuracy. Details about the aggregation process, such as shape parameters of the aggregates and rate constants, can also be extracted.

Stranks, Samuel D.; Ecroyd, Heath; van Sluyter, Steven; Waters, Elizabeth J.; Carver, John A.; von Smekal, Lorenz

2009-11-01

273

Buried oxide layer in silicon  

DOEpatents

A process for forming Silicon-On-Insulator is described incorporating the steps of ion implantation of oxygen into a silicon substrate at elevated temperature, ion implanting oxygen at a temperature below 200.degree. C. at a lower dose to form an amorphous silicon layer, and annealing steps to form a mixture of defective single crystal silicon and polycrystalline silicon or polycrystalline silicon alone and then silicon oxide from the amorphous silicon layer to form a continuous silicon oxide layer below the surface of the silicon substrate to provide an isolated superficial layer of silicon. The invention overcomes the problem of buried isolated islands of silicon oxide forming a discontinuous buried oxide layer.

Sadana, Devendra Kumar (Pleasantville, NY); Holland, Orin Wayne (Lenoir, TN)

2001-01-01

274

Hydrogen-induced defect generation in amorphous SiO2  

Microsoft Academic Search

Dielectric breakdown of thin silicon oxides (SiO2) of metal-oxide semiconductor field-effect transistors is a long-standing problem. The breakdown is generally recognized to be due to the accumulation of defects in the oxide. An amorphous SiO2 (a-SiO2) has been known to have very few defects, thanks to its strong and flexible network of Si-O bonds. Then, why are defects created in

Masayasu Miyata; Adri C. T. van Duin

2005-01-01

275

A novel deposition concept for amorphous superlattices  

NASA Astrophysics Data System (ADS)

An efficient, photochemically controlled method has been developed which facilitates the continuous deposition of various superlattices in amorphous semiconductors. In combination with two modes of excitation, at least one of which is operated in a pulsed mode, an appropriately selected pair of source gases accumulates continuously binary layers of amorphous semiconductors. As an example of the verification of this novel process, an amorphous superlattice composed of an amorphous silicon carbide barrier layer and an amorphous silicon well layer was prepared from a mixture of disilane and carbon tetrafluoride.

Kawasaki, M.; Matsuzaki, Y.; Fueki, K.; Nakajima, K.; Yoshida, Y.

1988-01-01

276

Influence of copper on the electronic properties of amorphous chalcogenides  

NASA Astrophysics Data System (ADS)

We have studied the influence of alloying copper with amorphous arsenic sulfide on the electronic properties of this material. In our computer-generated models, copper is found in twofold near-linear and fourfold square-planar configurations, which apparently correspond to Cu(I) and Cu(II) oxidation states. The number of overcoordinated atoms, both arsenic and sulfur, grows with increasing concentration of copper. Overcoordinated sulfur is found in trigonal planar [S3]+ configuration, and overcoordinated (fourfold) arsenic is in tetrahedral As4+ configuration. Addition of copper suppresses the localization of lone-pair electrons on chalcogen atoms, and localized states at the top of the valence band are due to Cu 3d orbitals. Evidently, these additional Cu states, which are positioned at the same energies as the states due to [As4]--[S3]+ pairs, found in our amorphous As2S3 models, are responsible for masking photodarkening in Cu chalcogenides.

Simdyankin, S. I.; Elstner, M.; Niehaus, T. A.; Frauenheim, Th.; Elliott, S. R.

2005-07-01

277

New amorphous thin-film lithium electrolyte and rechargeable microbattery  

SciTech Connect

Sputtering of Li{sub 3}PO{sub 4} in pure N{sub 2} results in the formation of an amorphous lithium electrolyte that is stable in contact with lithium and has electrical properties that are suitable for application in a thin-film cell. Thin-film rechargeable lithium cells have been fabricated and characterized using this electrolyte between a lithium anode and an amorphous vanadium oxide cathode. The open circuit voltage of the cell is 3.6 to 3.7 V, and it has a capacity of 130 {mu}Ah/cm{sup 2} when discharged to 1.5 V. The ac impedance of the cells measured at different stages of discharge indicate a significant decrease in internal resistance at about the midpoint of the discharge.

Bates, J.B.; Gruzalski, G.R.; Dudney, N.J.; Luck, C.F.

1992-02-01

278

Amorphous carbon layers on polymeric  

Microsoft Academic Search

Purpose: This paper is aimed to study an effect of nitrogen incorporation on the structure and tribological properties of amorphous a C:N:H layers grown on polycarbonate substrates. Design\\/methodology\\/approach: Series of the layers were deposited from CH4 + N2 gas mixture with application of Plasma Enhanced Chemical Vapour Deposition technique assisted by radio waves (RF PE CVD). An analysis of atomic-level

R. M. Nowak; S. Jonas; S. Zimowski; K. Tkacz-?miech

279

Amorphous Diamond MEMS and Sensors  

Microsoft Academic Search

This report describes a new microsystems technology for the creation of microsensors and microelectromechanical systems (MEMS) using stress-free amorphous diamond (aD) films. Stress-free aD is a new material that has mechanical properties close to that of crystalline diamond, and the material is particularly promising for the development of high sensitivity microsensors and rugged and reliable MEMS. Some of the unique

JOHN P. SULLIVAN; THOMAS A. FRIEDMANN; CAROL I. ASHBY; MAARTEN P. DE BOER; W. KENT SCHUBERT; RANDY J. SHUL; ROBERT J. HOHLFELDER; D. A. LAVAN

2002-01-01

280

Amorphous silicon spatial light modulator  

NASA Astrophysics Data System (ADS)

This patent application discloses an amorphous silicon spatial light modulator that includes a unique three electrode structure that is used to create a two-dimensional electric field distribution in liquid crystal material. This modulator allows for the use of very thin photoconductor layers and a middle electrode in the form of a grating structure to provide control of the field shape while also providing for high spatial resolution.

Ashley, P. R.

1985-12-01

281

Elastic Properties of Amorphous Thin Films  

Microsoft Academic Search

In an attempt to gain a better understanding of the universal low temperature properties of amorphous solids, a technique has been developed for measuring the elastic properties of amorphous thin films. The technique has been applied to a study of electron beam evaporated amorphous SiO_2 films with thicknesses ranging from 0.75 nm to 1000 nm. We find that the anomalous

Bruce Edward White Jr.

1996-01-01

282

Selective laser sintering of amorphous metal powder  

Microsoft Academic Search

For the first time, selective sintering of amorphous PtCuNiP powder with a pulsed Nd:YAG laser has been studied. Upon pulsed interaction, the grains melt only superficially to build necks between the grains. Depending on the laser parameters, the sintered material can be crystallized or retained amorphous. By contrast with crystalline powder, laser sintering of amorphous powder is achieved at substantially

P. Fischer; A. Blatter; V. Romano; H. P. Weber

2005-01-01

283

Regular Cu-based amorphous alloy powder  

Microsoft Academic Search

The plate-like powder of Cu60Zr30Ti10 amorphous alloy was prepared by ball milling. The amorphization and deformation mechanisms and thermodynamic properties were also investigated. The powders are milled into plate-like powders and their thicknesses decrease with increasing of milling time. After milling for 184h, the size of the powders decreases down to 250nm and an amorphous structure appears. The average deformation

An-hui Cai; Xiang Xiong; Yong Liu; Yong Zhou; Wei-ke An; Yun Luo

2010-01-01

284

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

PubMed

Iron is a ubiquitous impurity in metamict (radiation-damaged and partially amorphized) materials such as titanite (CaSiTiO(5)). Using (57)Fe Mssbauer 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 Mssbauer 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

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

2011-02-21

285

21 CFR 73.1991 - Zinc oxide.  

Code of Federal Regulations, 2013 CFR

... (a) Identity. (1) The color additive zinc oxide is a white or yellow-white amorphous powder manufactured by the French process (described as the indirect process whereby zinc metal isolated from the zinc-containing ore is vaporized and...

2013-04-01

286

Simple synthesis of MoS 2 inorganic fullerene-like nanomaterials from MoS 2 amorphous nanoparticles  

Microsoft Academic Search

The amorphous MoS2 nanoparticles have been synthesized by a simple oxidationreduction reaction in an aqueous solution. A series of products with different morphologies, such as MoS2 nanospheres, inorganic fullerene-like nanospheres, nanorods and Mo bended rods, can be obtained by annealing the amorphous MoS2 nanoparticles under N2 atmosphere under 4001200C. These products have been characterized by X-ray diffraction, field emission scanning

Lianxia Chang; Haibin Yang; Wuyou Fu; Jianzhen Zhang; Qingjiang Yu; Hongyang Zhu; Jiuju Chen; Ronghui Wei; Yongming Sui; Xiaofen Pang; Guangtian Zou

2008-01-01

287

Correlation of photoconductivity response of amorphous In-Ga-Zn-O films with transistor performance using microwave photoconductivity decay method  

Microsoft Academic Search

The film quality of amorphous In-Ga-Zn-O (a-IGZO), an amorphous oxide semiconductor (AOS), was studied by the microwave photoconductivity decay (mu-PCD) method. Also, mu-PCD mappings over a 6 in. wafer were undertaken. It was found that the peak signal of the decay curve had a strong correlation with the a-IGZO transistor performance and hence the film quality. The film annealed under

Satoshi Yasuno; Toshihiro Kugimiya; Shinya Morita; Aya Miki; Futoshi Ojima; Shingo Sumie

2011-01-01

288

Corrosion resistant amorphous metals and methods of forming corrosion resistant amorphous metals  

Microsoft Academic Search

A system for coating a surface comprises providing a source of amorphous metal, providing ceramic particles, and applying the amorphous metal and the ceramic particles to the surface by a spray. The coating comprises a composite material made of amorphous metal that contains one or more of the following elements in the specified range of composition: yttrium (.gtoreq.1 atomic %),

Joseph C. Farmer; Frank M. G. Wong; Jeffery J. Haslam; Nancy Yang; Enrique J. Lavernia; Craig A. Blue; Olivia A. Graeve; Robert Bayles; John H. Perepezko; Larry Kaufman; Julie Schoenung; Leo Ajdelsztajn

2009-01-01

289

Chromic mechanism in amorphous WO{sub 3} films  

SciTech Connect

The authors propose a new model for the chromic mechanism in amorphous tungsten oxide films (WO{sub 3{minus}y}{center_dot}nH{sub 2}O). This model not only explains a variety of seemingly conflicting experimental results reported in the literature that cannot be explained by existing models, it also has practical implications with respect to improving the coloring efficiency and durability of electrochromic devices. According to this model, a typical as-deposited tungsten oxide film has tungsten mainly in W{sup 6+} and W{sup 4+} states and can be represented as W{sub 1{minus}y}{sup 6+} W{sub y}{sup 4+}O{sub 3{minus}y}{center_dot}nH{sub 2}O. The proposed chromic mechanism is based on the small polaron transition between the charge-induced W{sup 5+} state and the original W{sup 4+} state instead of the W{sup 5+} and W{sup 6+} states as suggested in previous models. The correlation between the electrochromic and photochromic behavior in amorphous tungsten oxide films is also discussed.

Zhang, J.G.; Benson, D.K.; Tracy, C.E.; Deb, S.K.; Czanderna, A.W. [National Renewable Energy Lab., Golden, CO (United States); Bechinger, C. [Universitaet Konstanz (Germany)

1996-11-01

290

Optimization of Conductivity and Transparency in Amorphous In-Zn-O Transparent Conductors: Preprint  

SciTech Connect

Amorphous mixed metal oxide TCOs are of increasing interest due to the excellent opto-electronic properties and smoothness (RRMS < 0.5 nm) obtained for sputtered films deposited at less than 100 ..deg..C. Here, we have investigated the combined materials phase space of oxygen stoichiometry and metals composition (In:Zn ratio) and made two key discoveries.

Perkins, J.; Berry, J.; van Hest, M.; Alleman, J.; Dabney, M.; Gedvilas, L.; Ginley, D. S.; Leenheer, A.; O'Hayre, R.

2008-05-01

291

Study of local atomic order in amorphous materials in a computerized transmission electron microscope.  

PubMed

Experimental results obtained by electron diffraction (ED) and extended electron energy loss fine structure (EXELFS) techniques to study the local atomic order in amorphous materials such as carbon, silicon, and its oxides are described. Potential applications of ED and EXELFS techniques and their limitations are also discussed. PMID:2723799

Balossier, G; Garg, R K; Bonhomme, P; Thomas, X

1989-03-01

292

Ellipsometric characterization of amorphous and polycrystalline silicon films deposited using a single wafer reactor  

Microsoft Academic Search

The optical functions of amorphous and polycrystalline silicon thin films deposited on single oxidized silicon substrates by chemical vapor deposition in a wide range of deposition temperatures have been determined using spectroscopic ellipsometry. The data analysis is performed by direct inversion of the experimental spectra, therefore, obtaining results independent of any film modeling. The optical results indicate that the film

A. Borghesi; M. E. Giardini; M. Marazzi; A. Sassella; G. de Santi

1997-01-01

293

Ni-base amorphous alloys as electrocatalysts for alkaline water electrolysis  

Microsoft Academic Search

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

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

1997-01-01

294

Electrical conductivity and crystallization of amorphous bismuth ruthenate thin films deposited by spray pyrolysis.  

PubMed

Amorphous oxide thin films with tailored functionality will be crucial for the next generation of micro-electro-mechanical-systems (MEMS). Due to potentially favorable electronic and catalytic properties, amorphous bismuth ruthenate thin films might be applied in this regard. We report on the deposition of amorphous bismuth ruthenate thin films by spray pyrolysis, their crystallization behavior and electrical conductivity. At room temperature the 200 nm thin amorphous films exhibit a high electrical conductivity of 7.7 10(4) S m(-1), which was found to be slightly thermally activated (E(a) = 4.1 10(-3) eV). It follows that a long-range order of the RuO(6) octahedra is no precondition for the electrical conductivity of Bi(3)Ru(3)O(11). Upon heating to the temperature range between 490 C and 580 C the initially amorphous films crystallize rapidly. Simultaneously, a transition from a dense and continuous film to isolated Bi(3)Ru(3)O(11) particles on the substrate takes place. Solid-state agglomeration is proposed as the mechanism responsible for disintegration. The area specific resistance of Bi(3)Ru(3)O(11) particles contacted by Pt paste on gadolinia doped ceria electrolyte pellets was found to be 7 ? cm(2) at 607 C in air. Amorphous bismuth ruthenate thin films are proposed for application in electrochemical devices operating at low temperatures, where a high electrical conductivity is required. PMID:20848026

Ryll, Thomas; Brunner, Andreas; Ellenbroek, Stefan; Bieberle-Hutter, Anja; Rupp, Jennifer L M; Gauckler, Ludwig J

2010-09-17

295

Nonclassical crystallization of amorphous iron nanoparticles by radio frequency methods  

NASA Astrophysics Data System (ADS)

Amorphous iron nanoparticles were synthesized using an aqueous reduction in iron(II) sulfate with sodium borohydride and sodium citrate. Various radio frequency (rf) exposure times were investigated in order to determine trends in nonclassical crystallization. RF times from 15 to 300 s revealed an increase in crystallite size from 5 to 60 nm, as determined by powder x-ray diffraction. Also, solvent optimization revealed that ethanol produced the largest trends for increasing crystallite size without total oxidation of the samples. Magnetic characterization by room temperature vibrating sample magnetometry and high resolution transmission microscopy was performed to verify magnetic properties and particle morphology.

Carroll, K. J.; Pitts, J. A.; Zhang, Kai; Pradhan, A. K.; Carpenter, E. E.

2010-05-01

296

Fluorination of amorphous thin-film materials with xenon fluoride  

DOEpatents

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

Weil, R.B.

1987-05-01

297

Fluorination of amorphous thin-film materials with xenon fluoride  

DOEpatents

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

Weil, Raoul B. (Haifa, IL)

1988-01-01

298

Modelling amorphous computations with transcription networks  

PubMed Central

The power of electronic computation is due in part to the development of modular gate structures that can be coupled to carry out sophisticated logical operations and whose performance can be readily modelled. However, the equivalences between electronic and biochemical operations are far from obvious. In order to help cross between these disciplines, we develop an analogy between complementary metal oxide semiconductor and transcriptional logic gates. We surmise that these transcriptional logic gates might prove to be useful in amorphous computations and model the abilities of immobilized gates to form patterns. Finally, to begin to implement these computations, we design unique hairpin transcriptional gates and then characterize these gates in a binary latch similar to that already demonstrated by Kim et al. (Kim, White & Winfree 2006 Mol. Syst. Biol. 2, 68 (doi:10.1038/msb4100099)). The hairpin transcriptional gates are uniquely suited to the design of a complementary NAND gate that can serve as an underlying basis of molecular computing that can output matter rather than electronic information.

Simpson, Zack Booth; Tsai, Timothy L.; Nguyen, Nam; Chen, Xi; Ellington, Andrew D.

2009-01-01

299

Kinetics and Mechanism for the Reaction of Cysteine with Hydrogen Peroxide in Amorphous Polyvinylpyrrolidone Lyophiles  

Microsoft Academic Search

PurposePeroxide impurities play a critical role in drug oxidation. In metal-free aqueous solutions, hydrogen peroxide (H2O2) induced thiol oxidation involves a bimolecular nucleophilic reaction to form a reactive sulfenic acid intermediate (RSOH), which reacts with a second thiol to form a disulfide (RSSR). This study examines the reaction of cysteine (CSH) and H2O2 in amorphous polyvinylpyrrolidone (PVP) lyophiles to explore

Dayong Luo; Bradley D. Anderson

2006-01-01

300

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-ZrO2/InGaAs(100)-(42)  

NASA Astrophysics Data System (ADS)

The structural properties of a-Al2O3/In0.5Ga0.5As, a-HfO2/In0.5Ga0.5As, and a-ZrO2/In0.5Ga0.5As interfaces were investigated by density-functional theory (DFT) molecular dynamics (MD) simulations. Realistic amorphous a-Al2O3, a-HfO2, and a-ZrO2 samples were generated using a hybrid classical-DFT MD ``melt-and-quench'' approach and tested against the experimental properties. For each stack type, two systems with different initial oxide cuts at the interfaces were investigated. All stacks were free of midgap states, but some had band-edge states which decreased the bandgaps by 0%-40%. The band-edge states were mainly produced by deformation, intermixing, and bond-breaking, thereby creating improperly bonded semiconductor atoms. The interfaces were dominated by metal-As and O-In/Ga bonds which passivated the clean surface dangling bonds. The valence band-edge states were mainly localized at improperly bonded As atoms, while conduction band-edge states were mainly localized at improperly bonded In and Ga atoms. The DFT-MD simulations show that electronically passive interfaces can be formed between high-? oxides dielectrics and InGaAs if the processing does not induce defects because on a short time scale the interface spontaneously forms electrically passive bonds as opposed to bonds with midgap states.

Chagarov, Evgueni A.; Kummel, Andrew C.

2011-12-01

301

On the structure of amorphous red phosphorus  

Microsoft Academic Search

The structure factor of amorphous red phosphorus has been determined by neutron diffraction. Results were analysed by inverse methods, such as MCGR ('Monte Carlo determination of G of R') and reverse Monte Carlo modelling. The diffraction pattern shows notable differences when compared to the latest known results on amorphous phosphorus.

P. Jvri; L. Pusztai

2002-01-01

302

Explosive compaction of amorphous ferromagnetic metal powders  

Microsoft Academic Search

The magnetic properties of certain amorphous metals might be better exploited by the electrical industry if these metals, currently available as ribbon, could be consolidated into high density, principally amorphous, bulk shapes. This work attempted to produce such bodies using explosive compaction techniques. Toroidal specimens were successfully produced using a cylindrical explosive compaction technique. The key to this technique was

R. D. Caligiuri; D. R. Curran; P. S. DeCarli

2009-01-01

303

Method of making amorphous metal composites  

Microsoft Academic Search

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.

M. A. Byrne; J. H. Lupinski

1982-01-01

304

Electronic Structure of Amorphous Silicon Nanoclusters  

Microsoft Academic Search

The electronic structure of amorphous silicon nanoclusters is calculated within the empirical tight-binding approximation. The electronic states are classified into three groups: extended and weakly and strongly localized. The last category practically disappears in hydrogenated amorphous silicon clusters for which the blueshift is comparable to what is predicted for crystallites. The radiative recombination rates are comparable for small clusters \\\\(~1

G. Allan; C. Delerue; M. Lannoo

1997-01-01

305

Enhanced initial susceptibility in small amorphous disks  

NASA Astrophysics Data System (ADS)

A highly enhanced initial susceptibility is predicted theoretically for thin, amorphous ferromagnetic films when they are patterned as separate disks of appropriate dimensions. The relation between the required disk radius and the film thickness is given as a function of the exchange constant and the saturation magnetization of the amorphous material.

Aharoni, Amikam

2001-01-01

306

Hydrogen evolution in amorphous silicon carbide  

Microsoft Academic Search

The influence of the hydrogen content and its evolution in the annealing treatments of the structural properties of hydrogenated amorphous silicon carbide (a-SiC:H) prepared by plasma enhanced chemical vapour deposition under different deposition conditions have been studied. The results indicate how strongly hydrogen affects the presence of defects in the amorphous network of the samples.

F. Demichelis; G. Crovini; C. F. Pirri; E. Tresso; E. Giamello; G. Dellamea

1991-01-01

307

Amorphous silicon exhibits a glass transition.  

PubMed

Amorphous silicon is a semiconductor with a lower density than the metallic silicon liquid. It is widely believed that the amorphous-liquid transition is a first-order melting transition. In contrast to this, recent computer simulations and the experimental observation of pressure-induced amorphization of nanoporous silicon have revived the idea of an underlying liquid-liquid phase transition implying the existence of a low-density liquid and its glass transition to the amorphous solid. Here we demonstrate that during irradiation with high-energy heavy ions amorphous silicon deforms plastically in the same way as conventional glasses. This behaviour provides experimental evidence for the existence of the low-density liquid. The glass transition temperature for a timescale of 10 picoseconds is estimated to be about 1,000 K. Our results support the idea of liquid polymorphism as a general phenomenon in tetrahedral networks. PMID:15502833

Hedler, Andr; Klaumnzer, Siegfried Ludwig; Wesch, Werner

2004-10-24

308

Amorphization of sugar hydrates upon milling.  

PubMed

The possibility to amorphize anhydrous crystalline sugars, like lactose, trehalose and glucose, by mechanical milling was previously reported. We test here the possibility to amorphize the corresponding crystalline hydrates: lactose monohydrate, trehalose dihydrate and glucose monohydrate using fully identical milling procedures. The results show that only the first hydrate amorphizes while the other two remain structurally invariant. These different behaviours are attributed to the plasticizing effect of the structural water molecules which can decrease the glass transition temperature below the milling temperature. The results reveal clearly the fundamental role of the glass transition in the solid-state amorphization process induced by milling, and they also explain why crystalline hydrates are systematically more difficult to amorphize by milling than their anhydrous counterpart. The investigations have been performed by differential scanning calorimetry and powder X-ray diffraction. PMID:20494339

Willart, J F; Dujardin, N; Dudognon, E; Dande, F; Descamps, M

2010-04-24

309

Elastic Properties of Amorphous Thin Films  

NASA Astrophysics Data System (ADS)

In an attempt to gain a better understanding of the universal low temperature properties of amorphous solids, a technique has been developed for measuring the elastic properties of amorphous thin films. The technique has been applied to a study of electron beam evaporated amorphous SiO_2 films with thicknesses ranging from 0.75 nm to 1000 nm. We find that the anomalous elastic properties associated with tunneling states in bulk amorphous solids are still present in films with thicknesses as small as 0.75 nm. This indicates that the universal thermal and elastic properties found in amorphous solids are not due to interactions which occur between tunneling states, at least on length scales on the order of the minimum film thickness studied. Additionally, the technique has also been applied to a study of thin films of amorphous silicon and germanium produced by a variety of techniques. In this work, for the first time, we have found two amorphous solids whose low temperature lattice vibrations can be varied by over an order of magnitude depending on the method of preparation. In particular, we report on the elastic properties of a-Si prepared by electron beam evaporation and chemical vapor deposition. We find that the elastic properties of a-Si, which are similar to those found in all amorphous solids, can be significantly altered by the addition of hydrogen which passivates the dangling bonds of the a-Si structure. The presence of hydrogen reduces the density of tunneling states by approximately one order of magnitude below the lower limit observed in all other amorphous solids. The implications of these findings on our understanding of the lattice vibrations of amorphous solids will be discussed.

White, Bruce Edward, Jr.

310

Nanoscale anodization of an amorphous silicon surface with an atomic force microscope  

NASA Astrophysics Data System (ADS)

Nanoscale anodization was performed on the surface of amorphous silicon thin films by means of an atomic force microscope. The anodization mechanism was different from that previously reported on metal thin films. We found that the anodization was a function of defect density and current through the sample. The optical properties of the anodized area were measured by means of micro-photoluminescence, in which photoluminescence intensity decreases with oxidation. We concluded that both defect reaction and creation processes are important during the nanoscale anodization of amorphous material.

Umezu, Ikurou; Yoshida, Takashi; Matsumoto, Kimihisa; Sugimura, Akira; Inada, Mitsuru

2002-08-01

311

Development and characterization of high temperature stable Ta-W-Si-C amorphous metal gates  

NASA Astrophysics Data System (ADS)

Threshold voltage variability (?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 Ta40W40Si10C10 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 C, have n-type work functions, and are stable on HfO2. This alloy is a promising gate-first compatible material that has the potential to significantly reduce ?Vth.

Grubbs, Melody E.; Zhang, Xiao; Deal, Michael; Nishi, Yoshio; Clemens, Bruce M.

2010-11-01

312

Research on stable, high-efficiency amorphous silicon multijunction modules  

NASA Astrophysics Data System (ADS)

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 sq cm and a stable, reproducible conversion efficiency of at least 6.5 percent after 600 hours of light exposure (air mass 1.5) at 50 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. New results are reported 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 percent initial efficiency in a silicon/silicon multijunction submodule with an aperture area of 4620 sq cm and incorporating devices with 2nd-junction i-layer thicknesses of about 3500 A. A single-junction silicon submodule with an aperture area of 4620 sq cm, a thickness of about 3500 A, and an initial efficiency of 6.5 percent was demonstrated.

Bhat, P. K.; Brown, S.; Hollingsworth, R.; Shen, D. S.; Delcueto, J.; Iwanicko, E.; Marshall, C.; Dehart, C.; Mentor, D.; Benson, A.

1991-04-01

313

Quantification of surface amorphous content using dispersive surface energy: the concept of effective amorphous surface area.  

PubMed

We investigate the use of dispersive surface energy in quantifying surface amorphous content, and the concept of effective amorphous surface area is introduced. An equation is introduced employing the linear combination of surface area normalized square root dispersive surface energy terms. This equation is effective in generating calibration curves when crystalline and amorphous references are used. Inverse gas chromatography is used to generate dispersive surface energy values. Two systems are investigated, and in both cases surface energy data collected for physical mixture samples comprised of amorphous and crystalline references fits the predicted response with good accuracy. Surface amorphous content of processed lactose samples is quantified using the calibration curve, and interpreted within the context of effective amorphous surface area. Data for bulk amorphous content is also utilized to generate a thorough picture of how disorder is distributed throughout the particle. An approach to quantifying surface amorphous content using dispersive surface energy is presented. Quantification is achieved by equating results to an effective amorphous surface area based on reference crystalline, and amorphous materials. PMID:21725707

Brum, Jeffrey; Burnett, Daniel

2011-07-02

314

Dielectric enhancement in amorphous TaxGe1-xOy thin films  

NASA Astrophysics Data System (ADS)

We report that the dielectric constant can be increased in amorphous thin film TaxGe1-xOy over pure amorphous Ta2O5. With only 3% substitution of Ge for Ta the relative dielectric constant ?r rises to 30.5, a 40% increase over the value obtained for pure amorphous Ta2O5 films deposited under identical conditions (?r=22). No enhancement is observed in the optical dielectric constant (i.e., refractive index). This suggests that the enhancement is dominated by the effects in the ionic polarizability rather than the electronic polarizability. This system represents a valuable opportunity to explore the sensitive relationship between bonding and electronic properties in amophous oxides.

Naoi, Taro A.; Barron, Sara C.; Noginov, Maxim M.; van Dover, R. B.

2012-08-01

315

Comprehensive phase characterization of crystalline and amorphous phases of a Class F fly ash  

SciTech Connect

A comprehensive approach to qualitative and quantitative characterization of crystalline and amorphous constituent phases of a largely heterogeneous Class F fly ash is presented. Traditionally, fly ash composition is expressed as bulk elemental oxide content, generally determined by X-ray fluorescence spectroscopy. However, such analysis does not discern between relatively inert crystalline phases and highly reactive amorphous phases of similar elemental composition. X-ray diffraction was used to identify the crystalline phases present in the fly ash, and the Rietveld quantitative phase analysis method was applied to determine the relative proportion of each of these phases. A synergistic method of X-ray powder diffraction, scanning electron microscopy, energy dispersive spectroscopy, and multispectral image analysis was developed to identify and quantify the amorphous phases present in the fly ash.

Chancey, Ryan T., E-mail: rchancey@architecturalengineers.co [Nelson Architectural Engineers, Plano, TX 75093 (United States); Stutzman, Paul [National Institute for Standards and Technology, Gaithersburg, MD 20899 (United States); Juenger, Maria C.G.; Fowler, David W. [University of Texas at Austin, Austin, TX 78712 (United States)

2010-01-15

316

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

SciTech Connect

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.

Fortner, J. A.

1998-12-16

317

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

SciTech Connect

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.

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

1999-01-01

318

Research on stable, high-efficiency amorphous silicon multijunction modules  

NASA Astrophysics Data System (ADS)

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 are described. 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.

Ghosh, M.; Delcueto, J.; Xi, J.; Kampus, F.

1993-02-01

319

Electron beam cutting in amorphous alumina sheets  

SciTech Connect

We have found that nanometer diameter holes and slots can be cut in thin sheets of amorphous alumina using an intense electron beam. The holes, formed by a nonthermal process, are uniform in diameter, are surrounded by metallic aluminum, and can penetrate a 100-nm sheet in a few seconds. The amorphous alumina sheets are formed by anodization of electropolished high purity aluminum. The electron beam cutting seems very similar to the process reported in the metal ..beta..-aluminas. Since uniform, stable, and easily handled sheets of amorphous alumina can be fabricated and electron beam cut, this process is now practical for nanolithography as well as many other applications.

Mochel, M.E.; Eades, J.A.; Metzger, M.; Meyer, J.I.; Mochel, J.M.

1984-03-01

320

Pressure induced crystallization in amorphous silicon  

NASA Astrophysics Data System (ADS)

We have investigated the high pressure behavior of amorphous silicon (a-Si) using x-ray diffraction and Raman scattering techniques. Our experiments show that a-Si undergoes a polyamorphous transition from the low density amorphous to the high density amorphous phase, followed by pressure induced crystallization to the primitive hexagonal (ph) phase. On the release path, the sequence of observed phase transitions depends on whether the pressure is reduced slowly or rapidly. Using the results of our first principles calculations, pressure induced preferential crystallization to the ph phase is explained in terms of a thermodynamic model based on phenomenological random nucleation and the growth process.

Pandey, K. K.; Garg, Nandini; Shanavas, K. V.; Sharma, Surinder M.; Sikka, S. K.

2011-06-01

321

Method of producing hydrogenated amorphous silicon film  

DOEpatents

This invention relates to hydrogenated amorphous silicon produced by thermally decomposing silane (SiH.sub.4) or other gases comprising H and Si, from a tungsten or carbon foil heated to a temperature of about 1400.degree.-1600.degree. C., in a vacuum of about 10.sup.-6 to 19.sup.-4 torr, to form a gaseous mixture of atomic hydrogen and atomic silicon, and depositing said gaseos mixture onto a substrate independent of and outside said source of thermal decomposition, to form hydrogenated amorphous silicon. The presence of an ammonia atmosphere in the vacuum chamber enhances the photoconductivity of the hydrogenated amorphous silicon film.

Wiesmann, Harold J. (Wantagh, NY)

1980-01-01

322

Selective laser sintering of amorphous metal powder  

NASA Astrophysics Data System (ADS)

For the first time, selective sintering of amorphous PtCuNiP powder with a pulsed Nd:YAG laser has been studied. Upon pulsed interaction, the grains melt only superficially to build necks between the grains. Depending on the laser parameters, the sintered material can be crystallized or retained amorphous. By contrast with crystalline powder, laser sintering of amorphous powder is achieved at substantially lower pulse energies due to its low melting point. The obtained results are compared with previous results from selective laser sintering of titanium powder.

Fischer, P.; Blatter, A.; Romano, V.; Weber, H. P.

2005-02-01

323

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

SciTech Connect

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.

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

1994-07-01

324

Pressure-induced amorphous-to-amorphous configuration change in Ca-Al metallic glasses  

PubMed Central

Pressure-induced amorphous-to-amorphous configuration changes in Ca-Al metallic glasses (MGs) were studied by performing in-situ room-temperature high-pressure x-ray diffraction up to about 40?GPa. Changes in compressibility at about 18?GPa, 15.5?GPa and 7.5?GPa during compression are detected in Ca80Al20, Ca72.7Al27.3, and Ca66.4Al33.6 MGs, respectively, whereas no clear change has been detected in the Ca50Al50 MG. The transfer of s electrons into d orbitals under pressure, reported for the pressure-induced phase transformations in pure polycrystalline Ca, is suggested to explain the observation of an amorphous-to-amorphous configuration change in this Ca-Al MG system. Results presented here show that the pressure induced amorphous-to-amorphous configuration is not limited to f electron-containing MGs.

Lou, H. B.; Fang, Y. K.; Zeng, Q. S.; Lu, Y. H.; Wang, X. D.; Cao, Q. P.; Yang, K.; Yu, X. H.; Zheng, L.; Zhao, Y. D.; Chu, W. S.; Hu, T. D.; Wu, Z. Y.; Ahuja, R.; Jiang, J. Z.

2012-01-01

325

Corrosion resistant amorphous metals and methods of forming corrosion resistant amorphous metals  

DOEpatents

A system for coating a surface comprises providing a source of amorphous metal, providing ceramic particles, and applying the amorphous metal and the ceramic particles to the surface by a spray. The coating comprises a composite material made of amorphous metal that contains one or more of the following elements in the specified range of composition: yttrium (.gtoreq.1 atomic %), chromium (14 to 18 atomic %), molybdenum (.gtoreq.7 atomic %), tungsten (.gtoreq.1 atomic %), boron (.ltoreq.5 atomic %), or carbon (.gtoreq.4 atomic %).

Farmer, Joseph C. (Tracy, CA); Wong, Frank M. G. (Livermore, CA); Haslam, Jeffery J. (Livermore, CA); Yang, Nancy (Lafayette, CA); Lavernia, Enrique J. (Davis, CA); Blue, Craig A. (Knoxville, TN); Graeve, Olivia A. (Reno, NV); Bayles, Robert (Annandale, VA); Perepezko, John H. (Madison, WI); Kaufman, Larry (Brookline, MA); Schoenung, Julie (Davis, CA); Ajdelsztajn, Leo (Walnut Creek, CA)

2009-11-17

326

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

NASA Astrophysics Data System (ADS)

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 amorphous alloy ribbons of the same component. High thermal stability enables the amorphous coatings to work below 910 K without crystallization. The results of electrochemical measurement show that the coatings exhibit extremely wide passive region and relatively low passive current density in 3.5% NaCl and 1 mol/L HCl solutions, which illustrate their superior ability to resist localized corrosion. Moreover, the corrosion behavior of the amorphous coatings in 1 mol/L H2SO4 solution is similar to their performance under conditions containing chloride ions, which manifests their flexible and extensive ability to withstand aggressive environments.

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

2011-01-01

327

Plasticity in crystalline-amorphous core-shell Si nanowires controlled by native interface defects  

NASA Astrophysics Data System (ADS)

Experimentally the silicon nanowires or nanopillars are naturally recovered by a thin oxide layer as soon as they are exposed to the air or present an amorphous layer of silicon when they are milled by focused ion beam (FIB) techniques. Here we investigate the role of the silicon amorphous shell on the plasticity of Si nanowires (NWs), thanks to molecular dynamics simulations. It is shown that the yield strain for the nucleation of the first dislocation is decreased for NWs with an amorphous shell when compared to pristine nanowires. For NWs with circular cross-sections, it is shown that the shell thickness has no influence on the yield strain. Besides, through the investigation of various rhombic cross-sections we observe that when an amorphous shell is present, the yield strain is independent of the cross-section shape. All these results can be explained by the presence of native atomic defects at the crystalline/amorphous interface, as revealed by a detailed atomistic analysis. These defects act as seeds for the dislocation nucleation. As a consequence this work raises the question about the role of point defects created in micro- and nanopillars milled by FIB techniques, in particular when they are used to study the mechanical properties at the nanoscale.

Gunol, Julien; Godet, Julien; Brochard, Sandrine

2013-01-01

328

Amorphous waveguides for high index photonic circuitry  

Microsoft Academic Search

Photonic wires, channel and rib waveguides as well as tapers were fabricated with amorphous silicon showing low propagation loss. Material analysis and RTA was carried out in order to tune the refractive index post deposition.

T. Lipka; A. Harke; O. Horn; J. Amthor; J. Muller

2009-01-01

329

Electrical and Optical Properties of Amorphous Materials.  

National Technical Information Service (NTIS)

The electronic structure of Sb2Se3, both crystalline and amorphous, has been studied and the combination of four types of spectroscopy (optical reflectivity, photoemission, photoconductivity, and ESCA) has led to a reasonably complete picture of the elect...

C. Wood

1972-01-01

330

Amorphous materials: Relaxing times for silicon  

NASA Astrophysics Data System (ADS)

A glass transition in amorphous silicon has been surmised but never clearly shown experimentally. The very fast timescale of ion hammering experiments allows observation of the long-sought low-density liquid polyamorph of silicon.

McMillan, Paul F.

2004-11-01

331

Polycrystalline- and Amorphous-Silicon Photovoltaic Cells.  

National Technical Information Service (NTIS)

The physical qualities, cost tradeoffs, fabrication techniques, and needed improvements of polycrystalline and amorphous silicon are reviewed. Casting, ribbon growth, sheet growth, and rapid ribbon growth of polycrystalline silicon is discussed as well as...

1982-01-01

332

PECVD Of Amorphous Nickel--Phosphorus Films.  

National Technical Information Service (NTIS)

We have developed a plasma deposition technique capable of producing amorphous transition metal-metalloid coatings. The technique consists of decomposing gas mixtures containing transition metal carbonyls and metalloid hydrides in a radiofrequency dischar...

A. K. Hays G. C. Nelson C. H. Seager

1988-01-01

333

Elastic properties of amorphous and nanocrystalline silicon  

Microsoft Academic Search

We review the present status of the elastic properties of amorphous silicon (a-Si) and germanium (a-Ge) thin films produced by either plasma-assisted chemical-vapor-deposition (PECVD) or hot-wire (cat) CVD (HWCVD). Using an extremely sensitive c-Si mechanical oscillator, we measure the low temperature oscillator damping for a variety of amorphous and nanocrystalline Si thin films deposited on the oscillator and thus determine

Richard S Crandall; Xiao Liu

2001-01-01

334

Amorphization of metal alloys under laser radiation  

Microsoft Academic Search

The feasibility of using laser radiation to amorphize binary Cu-Zr and Ni-Nb powder alloys on Cu and Ni substrates is demonstrated. Amorphization was achieved by using pulses from an Nd:glass laser to effect melting and mixing of the initial powder components; the character of the alloys used assured an appropriate cooling rate. Microstructure data on the alloys are presented.

V. M. Kiashkin; G. S. Zhdanov; L. I. Mirkin

1979-01-01

335

Recrystallization processes in amorphous and polycrystalline silicon  

SciTech Connect

The recrystallization process in amorphous or polycrystalline silicon was investigated using non-conventional heating techniques obtained by shining the sample with high power laser and with electron pulses. The interaction between an amorphous silicon film and a metal layer when the whole structure is submitted to a heat treatment either at low temperature is studied using a conventional furnace and with a pulsed energy source. (LEW)

Ottaviani, G.

1982-01-01

336

Towards upconversion for amorphous silicon solar cells  

Microsoft Academic Search

Upconversion of subbandgap light of thin film single junction amorphous silicon solar cells may enhance their performance in the near infrared (NIR). In this paper we report on the application of the NIRvis upconverter ?-NaYF4:Yb3+(18%) Er3+(2%) at the back of an amorphous silicon solar cell in combination with a white back reflector and its response to infrared irradiation. Currentvoltage measurements

J. de Wild; A. Meijerink; J. K. Rath; W. G. J. H. M. van Sark; R. E. I. Schropp

2010-01-01

337

Amorphous and Thin-Film Silicon  

SciTech Connect

This paper outlines the key concepts set forth in the Amorphous and Thin-Film Silicon session at the National Center for Photovoltaics and Solar Program Review Meeting held March 26, 2003 in Denver, Colorado. Key elements of discussion centered around benchmarking the NREL/NCPV amorphous and thin-film silicon program, identifying holes in the scientific understanding of these materials and devices, identifying hurdles to large scale manufacturing, and what direction the program should take for future activities.

Nelson, B. P.; Atwater, H. A.; von Roedern, B.; Yang, J.; Sims, P.; Deng, X.; Dalal, V.; Carlson, D.; Wang, T.

2003-05-01

338

Wear Resistant Amorphous and Nanocomposite Steel Coatings  

SciTech Connect

In this article, amorphous and nanocomposite thermally deposited steel coatings have been formed by using both plasma and high-velocity oxy-fuel (HVOF) spraying techniques. This was accomplished by developing a specialized iron-based composition with a low critical cooling rate (?104 K/s) for metallic glass formation, processing the alloy by inert gas atomization to form micron-sized amorphous spherical powders, and then spraying the classified powder to form coatings. A primarily amorphous structure was formed in the as-sprayed coatings, independent of coating thickness. After a heat treatment above the crystallization temperature (568C), the structure of the coatings self-assembled (i.e., devitrified) into a multiphase nanocomposite microstructure with 75 to 125 nm grains containing a distribution of 20 nm second-phase grain-boundary precipitates. Vickers microhardness testing revealed that the amorphous coatings were very hard (10.2 to 10.7 GPa), with further increases in hardness after devitrification (11.4 to 12.8 GPa). The wear characteristics of the amorphous and nanocomposite coatings were determined using both two-body pin-on-disk and three-body rubber wheel wet-slurry sand tests. The results indicate that the amorphous and nanocomposite steel coatings are candidates for a wide variety of wear-resistant applications.

Branagan, Daniel James; Swank, William David; Haggard, Delon C; Fincke, James Russell; Sordelet, D.

2001-10-01

339

Amorphization of ceramics by ion beams  

SciTech Connect

The influence of the implantation parameters fluence, substrate temperature, and chemical species on the formation of amorphous phases in Al/sub 2/O/sub 3/ and ..cap alpha..-SiC was studied. At 300/sup 0/K, fluences in excess of 10/sup 17/ ions.cm/sup -2/ were generally required to amorphize Al/sub 2/O/sub 3/; however, implantation of zirconium formed the amorphous phase at a fluence of 4 x 10/sup 16/ Zr.cm/sup -2/. At 77/sup 0/K, the threshold fluence was lowered to about 2 x 10/sup 15/ Cr.cm/sup -2/. Single crystals of ..cap alpha..-SiC were amorphized at 300/sup 0/K by a fluence of 2 x 10/sup 14/ Cr.cm/sup -2/ or 1 x 10/sup 15/ N.cm/sup -2/. Implantation at 1023/sup 0/K did not produce the amorphous phase in SiC. The micro-indentation hardness of the amorphous material was about 60% of that of the crystalline counterpart.

McHargue, C.J.; Farlow, G.C.; White, C.W.; Williams, J.M.; Appleton, B.R.; Naramoto, H.

1984-01-01

340

Radiation-induced amorphization of crystalline ice  

NASA Astrophysics Data System (ADS)

We study radiation-induced amorphization of crystalline ice, analyzing the results of three decades of experiments with a variety of projectiles, irradiation energy, and ice temperature, finding a similar trend of increasing resistance of amorphization with temperature and inconsistencies in results from different laboratories. We discuss the temperature dependence of amorphization in terms of the 'thermal spike' model. We then discuss the common use of the 1.65 ?m infrared absorption band of water as a measure of degree of crystallinity, an increasingly common procedure to analyze remote sensing data of astronomical icy bodies. The discussion is based on new, high quality near-infrared reflectance absorption spectra measured between 1.4 and 2.2 ?m for amorphous and crystalline ices irradiated with 225 keV protons at 80 K. We found that, after irradiation with 10 15 protons cm -2, crystalline ice films thinner than the ion range become fully amorphous, and that the infrared absorption spectra show no significant changes upon further irradiation. The complete amorphization suggests that crystalline ice observed in the outer Solar System, including trans-neptunian objects, may results from heat from internal sources or from the impact of icy meteorites or comets.

Fam, M.; Loeffler, M. J.; Raut, U.; Baragiola, R. A.

2010-05-01

341

Radiation-Induced Amorphization of Crystalline Ice  

NASA Astrophysics Data System (ADS)

Crystalline ice has been unambiguously identified on the surface of most of the Jovian, Saturnian and Uranian satellites, and on the surface of some trans-Neptunian objects such as Quaoar, and 2003 EL61. This result is surprising, as the low surface temperatures of these objects should cause the ice condensed on them to be amorphous. Moreover, the surface of these bodies is constantly exposed to UV photons, solar wind, cosmic rays or energetic charged particles trapped by the planetary magnetic fields, which are known to amorphize crystalline ice. Here, we review 30 years of experimental studies of radiation-induced amorphization of crystalline ice analyzing the differences found between light and heavy ions, electrons and photons. We also present high quality near-infrared absorption spectra for amorphous and crystalline ice before and after we irradiated them with 225 keV protons. After irradiation at 80 K, the crystalline ice spectrum is altered so that it is indistinguishable from the spectrum of amorphous ice, indicating that irradiation can fully amorphize crystalline ice. We will compare these results with previous studies and discuss the astrophysical implication for planetary bodies.

Fama, Marcelo A.; Loeffler, M. J.; Raut, U.; Baragiola, R. A.

2008-09-01

342

Mercury mobilization by chemical and microbial iron oxide reduction in soils of French Guyana  

Microsoft Academic Search

Iron oxy(hydr)oxides (oxides) are important mercury sinks in tropical oxisols and the geochemistry of these two elements are\\u000a thus closely entwined. We hypothesized that bacterial Fe-oxide reduction in anoxic conditions could be a significant mechanism\\u000a for mobilizing associated Hg. Iron oxide and mercury solubilisation in presence of two chemical reducers (ascorbate and dithionite,\\u000a dissolving amorphous and amorphous plus well crystallized

Jennifer Harris-Hellal; Michel Grimaldi; Evelyne Garnier-Zarli; Noureddine Bousserrhine

2011-01-01

343

In Situ Laser Synthesis of Fe-Based Amorphous Matrix Composite Coating on Structural Steel  

NASA Astrophysics Data System (ADS)

Iron-based amorphous materials, owing to their very high hardness, elastic modulus, wear resistance, and corrosion resistance, can be potential materials for surface modification and engineering of many structural alloys. The current study focuses on a novel functional coating, synthesized via laser cladding of an iron-based (Fe48Cr15Mo14Y2C15B) amorphous precursor powder, on AISI 4130 steel substrate, using a continuous-wave diode-pumped ytterbium laser. The coatings were characterized by different techniques like X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). SEM and TEM studies indicated the presence of Fe-based nanocrystalline dendrites intermixed within an amorphous matrix. A three-dimensional thermal modeling approach based on COMSOL Multiphysics (COMSOL Inc., Burlington, MA) was used to approximately predict the temperature evolution and cooling rates achieved during laser processing. The mechanisms for the formation of crystalline phases and the morphological changes in the microstructure were studied based on the thermal model developed. Although the thermal model predicted substantially high cooling rates as compared to the critical cooling rate required for retaining an amorphous phase, the formation of crystalline phases is attributed to formation of yttrium oxide, reducing the glass-forming ability, and formation of different oxide phases that act as heterogeneous nucleation sites resulting in the composite microstructure.

Katakam, Shravana; Hwang, Jun Y.; Paital, Sameer; Banerjee, Rajarshi; Vora, Hitesh; Dahotre, Narendra B.

2012-12-01

344

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

SciTech Connect

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.

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

345

From amorphous to crystalline silicon nanoclusters: structural effects on exciton properties  

NASA Astrophysics Data System (ADS)

Synchrotron x-ray absorption spectroscopy (XAS) and electron spin resonance (ESR) experiments were performed to determine, in combination with Raman spectroscopy and x-ray diffraction (XRD) data from previous reports, the structure and paramagnetic defect status of Si-nanoclusters (ncls) at various intermediate formation stages in Si-rich Si oxide films having different Si concentrations (y = 0.36-0.42 in SiyO1-y), fabricated by electron cyclotron resonance plasma-enhanced chemical vapor deposition and isochronally (2 h) annealed at various temperatures (Ta = 900-1100?C) under either Ar or (Ar + 5%H2) atmospheres. The corresponding emission properties were studied by stationary and time dependent photoluminescence (PL) spectroscopy in correlation with the structural and defect properties. To explain the experimental data, we propose crystallization by nucleation within already existing amorphous Si-ncls as the mechanism for the formation of the Si nanocrystals in the oxide matrix. The cluster-size dependent partial crystallization of Si-ncls at intermediate Ta can be qualitatively understood in terms of a crystalline core-amorphous shell Si-ncl model. The amorphous shell, which is invisible in most diffraction and electron microscopy experiments, is found to have an important impact on light emission. As the crystalline core grows at the expense of a thinning amorphous shell with increasing Ta, the PL undergoes a transition from a regime dominated by disorder-induced effects to a situation where quantum confinement of excitons prevails.

Borrero-Gonzlez, L. J.; Nunes, L. A. O.; Guimares, F. E. G.; Wojcik, J.; Mascher, P.; Gennaro, A. M.; Tirado, M.; Comedi, D.

2011-12-01

346

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

NASA Astrophysics Data System (ADS)

Amorphous carbon microspheres were synthesized using a dual-furnace chemical vapour deposition method at 800-1000 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 C. At 800 C, no regular microspheres were formed but more uniform structure is observed at 900 C. Generally the microspheres size is uniform when the heating temperature was increased to 1000 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-1 for the D and G bands, respectively. These bands become more prominent as the preparation temperature increased from 800 to 1000 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.

Zobir, S. A. M.; Zainal, Z.; Sarijo, S. H.; Rusop, M.

2011-03-01

347

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

PubMed

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

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

2011-01-31

348

Characterization of amorphous silicon-barrier Josephson junctions, resonant tunneling, and circuit applications  

SciTech Connect

The author studied the effect of processing conditions on the quality of silicon-barrier junctions and obtained junctions with low leakage. Amorphous silicon-barrier Josephson junctions were chosen with two goals in mind. One goal was to study the effect on junction behavior of localized electron states in the tunnel barrier, primarily, to see the effects of resonant tunneling. Oxidized silicon has a much lower density of localized states than amorphous silicon, so the density of states are reduced in a layer of the barrier by growing a thermal oxide on silicon. Tunnel barriers of a fixed thickness were fabricated, composed mostly of amorphous silicon, but containing a thin silicon oxide layer. An expression was derived for the conductance due to resonant tunneling in these structures as a function of the location of this oxide layer, and good agreement with experimental results was found. The other goal was the use of these barriers in circuits because of their low capacitance relative to other materials that have been shown to form good-quality junctions. This leads to higher-speed operation of Josephson circuits, everything else being fixed. A new shift register design was simulated at clock rates as high as 20 GHz. A new design for a Josephson memory circuit was simulated at sub-nanosecond cycle times and a single cell was successfully tested.

Bradley, P.D.

1988-01-01

349

Origin of ferromagnetism enhancement in bi-layer chromium-doped indium zinc oxides  

SciTech Connect

This work demonstrates that by controlling the rapid thermal annealing temperature, amorphous chromium-doped indium zinc oxide films develop an amorphous-crystalline bi-layer structure and show magnetization up to {approx}30 emu/cm{sup 3}. The crystalline layer arises from significant out-diffusion of Zn from surfaces, leading to a large difference in the Zn:In ratio in amorphous and crystalline layers. Doped Cr ions in amorphous and crystalline layers form different valence configurations, creating a charge reservoir which transfers electrons through amorphous-crystalline interfaces and in turn enhances ferromagnetism.

Hsu, C. Y. [Physics Department, National Sun Yat-Sen University, Kaohsiung 804, Taiwan (China)

2012-08-06

350

Characterization of High-k Gate Dielectric with Amorphous Nanostructure  

NASA Astrophysics Data System (ADS)

In the present study, Zr x La1-x O y amorphous nanostructures were prepared by the sol-gel method such that the Zr atomic fraction (x) ranged from 0% to 70%. An analytical model is described for the dielectric constant (k) of Zr x La1-x O y nanostructures in a metal-oxide-semiconductor (MOS) device. The structure and morphology of Zr x La1-x O y film was studied using x-ray diffraction, scanning electron microscopy, atomic force microscopy, and transmission electron microscopy. Elemental qualitative analysis was performed using energy-dispersive x-ray spectra and a map that confirmed the findings. Preliminary information on the influence of thermal annealing on the morphological control of Zr x La1-x O y amorphous nanostructures is presented. The dielectric constant of the crystalline Zr0.5La0.5O y thin film is about 36. Electrical property characterization was performed using a metal-dielectric-semiconductor structure via capacitance-voltage and current density-voltage measurements.

Bahari, Ali; Gholipur, Reza

2013-10-01

351

Hydrogen transport in amorphous silicon  

SciTech Connect

The diffusive transport of hydrogen is used to investigate H trapping in hydrogen-depleted amorphous Si ({ital a}-Si) samples and to determine a rough H-diffusion density of states. The diffusion profiles show clear evidence of deep traps separated from shallow traps, and the results are well explained by a simple division of the H states into deep traps, shallow traps, and transport states. The concentration of deep traps is about (0.8--2){times}10{sup 20} cm{sup {minus}3}, of which about 30% can be identified with dangling bonds. The energy of the deep traps is at least 1.9 eV below the transport states. The diffusion is dispersive with a power-law time dependence and can be characterized by an exponential distribution of hopping barriers with a width of roughly 0.09 eV. The shallow traps are identified with clustered H pairs which determine the H chemical potential at high H concentrations. The results are compared with calculations and other recent ideas on H bonding energetics. The results are consistent with a range of possibilities. One extreme is the case in which H is predominately bonded on void surfaces and the transport energy is substantially different in {ital a}-Si than in crystalline Si ({ital c}-Si); the other extreme is the case in which H predominately resides in platelet structures and the transport energy is roughly the same as in {ital c}-Si. The actual case depends on the deposition conditions.

Jackson, W.B.; Tsai, C.C. (Xerox Palo Alto Research Center, 3333 Coyote Hill Road, Palo Alto, California 94304 (United States))

1992-03-15

352

Chemical vapour deposition of amorphous Ru(P) thin films from Ru trialkylphosphite hydride complexes.  

PubMed

The ruthenium phosphite hydride complexes H(2)Ru(P(OR)(3))(4) (R = Me (1), Et (2), (i)Pr (3)) were used as CVD precursors for the deposition of films of amorphous ruthenium-phosphorus alloys. The as-deposited films were X-ray amorphous and XPS analysis revealed that they were predominantly comprised of Ru and P in zero oxidation states. XPS analysis also showed the presence of small amounts of oxidized ruthenium and phosphorus. The composition of the films was found to depend on ligand chemistry as well as the deposition conditions. The use of H(2) as the carrier gas had the effect of increasing the relative concentrations of P and O for all films. Annealing films to 700 C under vacuum produced films of polycrystalline hcp Ru while a flowing stream of H(2) resulted in polycrystalline hcp RuP. PMID:23018487

McCarty, W Jeffrey; Yang, Xiaoping; DePue Anderson, Lauren J; Jones, Richard A

2012-11-21

353

Crystallization of oxide high iron melts  

NASA Astrophysics Data System (ADS)

The data of thermal properties in terms of amorphous oxide melt of FeOx-SiO2-MeS (Me-Cu, Zn) system are presented in the article, temperature devitrifications of solid phase crystallization and melting are determined. Initial stages of crystal structure generation in terms of isothermal heating of amorphous alloy at the temperature 1023 ? depending on annealing duration are studied, phase composition and metal stay forms are determined.

Gulyaeva, R. I.; Selivanov, E. N.; Selmenskikh, N. I.

2011-05-01

354

Combined AFM-TEM studies of amorphous-crystalline transformation and interface in thin films of Se and Fe2O3  

NASA Astrophysics Data System (ADS)

Thin amorphous films of selenium and iron oxide were crystallized by local electron beam annealing. Two types of spherulite-like crystals grown (complicated by 'transrotational' lattice ordering) were studied by transmission electron microscopy (TEM) and atomic force microscopy (AFM) techniques. The regularities of change in lattice orientations and imperfection along the crystals obtained by TEM are analyzed in parallel with AFM data for the film surface (relief) of the crystal and amorphous surrounding.

Kolosov, V. Yu; Schwamm, C. L.; Gainutdinov, R. V.; Tolstikhina, A. L.

2008-03-01

355

Mechanisms and effects of wear on amorphous carbon thin films  

NASA Astrophysics Data System (ADS)

Amorphous carbon thin films, which are commonly used as protective layers for magnetic hard disks, experience wear during the operation of a hard disk. During sliding between these carbon films and the read-write head's slider tribochemical reactions occur, which have been predicted to remove carbon oxides. The tribochemical reactions have been investigated in this study through the use of a novel mass-spectroscopy tribotester. We have observed that the dominant species produced during sliding is COsb2, in both dry nitrogen and oxygen environments, and that the generation rate is ten times higher in oxygen. With the use of this tester, we have also investigated the effect of the slider material, which consists of alumina titanium-carbide (Alsb2Osb3-TiC), on the carbon dioxide evolution. By depositing a thin barrier coating of carbon (50A) on the slider surface, we found that the production of carbon dioxide was an order of magnitude lower than with uncoated sliders. Thermogravimetric analysis (TGA) of the slider material corroborates its role in enhancing the gasification of carbon. We have also explored the effect of wear on the microstructural features of carbon. With the aid of transmission electron spectroscopy (TEM) and electron-energy loss spectroscopy (EELS), we have found that the graphitic content of the amorphous carbon layer increases in the initial stages of wear. We also explored the temperatures achieved during sliding by comparing the microstructure of the worn carbon to that of unworn thermally-annealed carbon. Using additional techniques of Raman spectroscopy and NEXAFS, we found analogous less-randomly ordered microstructures at anneal temperatures of 300-500spC. We also explored the role of the magnetic layer (cobalt-platinum-chromium alloy) in the graphitization of amorphous carbon. With in situ heating and cooling TEM observations of the carbon/magnetic layer interface, we found that the microstructure of the carbon becomes more graphitic at low temperatures when in the presence of the magnetic layer. Crystallization temperatures of amorphous carbon, determined by calorimetry, occur in the range of 500-600spC when the carbon is in contact with this layer. TEM observations suggest carbon diffuses into the magnetic layer upon heating and precipitates as graphite upon cooling. We conclude that the wear mechanism includes frictional heating combined with metal-induced graphitization.

Ramirez, Ainissa Gweneth

356

A Method for Determining the Phosphorus Sorption Capacity and Amorphous Aluminum of Aluminum-Based Drinking Water Treatment Residuals  

Microsoft Academic Search

A high amorphous aluminum or iron oxide content in drinking water treatment residuals (WTRs) can result in a high phosphorus (P) sorption capacity. Therefore, WTR may be used beneficially to adsorb P and reduce P loss to surface or ground water. The strong relationship betwveen acid ammonium oxalate-extractable aluminum (Al,,) and Langmuir phosphorus adsorption maximum (P,,) in WTR could provide

E. A. Dayton; N. T. Basta

2005-01-01

357

Selective leaches revisited, with emphasis on the amorphous Fe oxyhydroxide phase extraction  

Microsoft Academic Search

A sequential extraction scheme for application to soils, tills and surficial sediments is described that elucidates the form in which an element is held and provides information as to its provenance. The phases selected for extraction have been categorised as: adsorbed\\/exchangeable\\/carbonate (using CH3COONa as extradant); amorphous Fe oxyhydroxide (0.25 M NH2OH-HCl); crystalline Fe oxide (l M NH2OH-HCl); sulphides and organics

G. E. M. Hall; J. E. Vaive; R. Beer; M. Hoashi

1996-01-01

358

GMI effect in CuO coated Co-based amorphous ribbons  

Microsoft Academic Search

A Copper oxide (CuO) film has been grown on a surface of Co-based amorphous ribbon using chemical successive ionic layer adsorption and reaction technique, at room temperature and atmosphere pressure. The influence of coating and width of ribbon on giant magneto impedance have been investigated over a frequency range from 0.1 to 3MHz and under a static magnetic field between

Asli Ayten Taysioglu; Ahmet Peksoz; Yunus Kaya; Naim Derebasi; Gazi Irez; Gokay Kaynak

2009-01-01

359

Development of amorphous thin film meander trilayers and investigation of GMI effect  

Microsoft Academic Search

Trilayer structures of 50 and 100 nm thin amorphous CoFeB layers with a central 100 and 200 nm thin Cu layer respectively were sputtered onto a thermally oxidized Si wafer. 300 ?m long strips of 3-20 ?m width was structured using a standard mask with various strip lines and meanders which were connected in series and were then formed by

I. Giouroudi; H. Hauser; L. Musiejovsky; J. Steurer

2004-01-01

360

Wettability and protein adsorption on ultrananocrystalline diamond\\/amorphous carbon composite films  

Microsoft Academic Search

Ultrananocrystalline diamond\\/amorphous carbon (UNCD\\/a-C) composite films have been prepared by microwave plasma chemical vapour deposition (MWCVD) from 17% CH4\\/N2 mixtures and modified with O2 and CHF3 plasmas, which changed the surface termination from hydrogen to oxygen and fluorine, respectively. X-ray photoelectron spectroscopy (XPS) showed that successful oxidation and fluorination of the UNCD surface has been achieved with surface O or

C. Popov; H. Vasilchina; W. Kulisch; F. Danneil; M. Stber; S. Ulrich; A. Welle; J. P. Reithmaier

2009-01-01

361

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

SciTech Connect

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&hthinsp;Ft{sup 2} monolithically integrated modules in manufacturing at the TF1 plant. Optimization of performance and stability of these modules is ongoing. {copyright} {ital 1999 American Institute of Physics.}

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. [Solarex, a Business Unit of Amoco/Enron Solar, 826 Newtown-Yardley Road, Newtown, Pennsylvania 18940 (United States)

1999-03-01

362

Carboxylate-containing chelating agent interactions with amorphous chromium hydroxide: Adsorption and dissolution  

Microsoft Academic Search

Anthropogenic chelating agents and biological chelating agents produced by indigenous organisms may dissolve CrIII (hydr)oxides in soils and sediments. The resulting dissolved CrIII-chelating agent complexes are more readily transported through porous media, thereby spreading contamination. With this work, we examine chelating agent-assisted dissolution of amorphous chromium hydroxide (ACH) by the (amino)carboxylate chelating agents iminodiacetic acid (IDA), nitrilotriacetic acid (NTA), tricarballylic

Richard F. Carbonaro; Benjamin N. Gray; Charles F. Whitehead; Alan T. Stone

2008-01-01

363

Improvement of high resolution lithography by using amorphous carbon hard mask  

Microsoft Academic Search

The aim of this paper is to demonstrate a new approach for improving high resolution lithography by using an amorphous carbon hard mask with an oxide capping layer. A full 3D resist pattern characterization was achieved using a Vecco Dimension X3D Atomic Force Microscope to determine process windows. Finally, we succeeded in patterning sub-30nm dense line arrays. This novel technique

S. Pauliac-Vaujour; P. Brianceau; C. Comboroure; O. Faynot

2008-01-01

364

Low loss inductors built-on PECVD intrinsic amorphous silicon for RF integrated circuits  

Microsoft Academic Search

The Q of inductors on Si is limited by the series resistance of the metal at low frequency and the substrate resistivity at high frequency. Oxide is generally used to isolate the useful signal of the inductor from the lossy substrate. However, stoichiometric SiO2 is processed at high temperature which eliminates the possibility of post-CMOS integration. PECVD amorphous Si can

Stella Chang; Siva Sivoththaman

2005-01-01

365

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

Microsoft Academic Search

Nanoparticles of calcia-doped ceria were prepared by adding CeCl3CaCl2 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

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

2004-01-01

366

XPS studies on a novel amorphous NiCoWB alloy powder  

Microsoft Academic Search

A novel amorphous NiCoWB alloy powder, which showed higher catalytic activity than NiCoB for the hydrogenation of benzene, was prepared by chemical reduction and characterized by TEM and XRD. The surface composition and the interactions between the components on the surface were studied by XPS. The measurement detected the presence of some oxides and hydroxides, such as NiO, Ni(OH)2, Co(OH)2,

Wei-Lin Dai; Ming-Hua Qiao; Jing-Fa Deng

1997-01-01

367

Characterization of Amorphous High-k Thin Films by EXAFS and GIXS  

SciTech Connect

Silicon and nitrogen incorporated Hf oxide (HfSiON) is considered to be a promising alternative gate insulator for next-generation MOSFETs. EXAFS and GIXS (Grazing Incidence X-ray Scattering) have been applied to the characterization of amorphous HfSiON films at SPring-8. Novel cluster models have been suggested based on the analogy to the ordered states for the Zr-O-N ternary system.

Takemura, Momoko; Yamazaki, Hideyuki; Ohmori, Hirobumi; Yoshiki, Masahiko; Takeno, Shiro; Ino, Tsunehiro; Nishiyama, Akira [Corporate R and D Center, Toshiba Corporation 1, Komukai Toshiba-cho, Saiwai-ku, Kawasaki 212-8582 (Japan); Sato, Nobutaka [Toshiba Nanoanalysis Corporation, 1, Komukai Toshiba-cho, Saiwai-ku, Kawasaki 212-8583 (Japan); Hirosawa, Ichiro; Sato, Masugu [JASRI/SPring-8, 1-1-1, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan)

2007-01-19

368

Photocatalytic properties of Bi 2MoO 6 nanoparticles prepared by an amorphous complex precursor  

Microsoft Academic Search

Nanoparticles of Bi2MoO6 have been synthesized using an amorphous complex precursor. The evolution of the oxide was followed by TGA\\/DTA, XRD and TEM in order to investigate the formation process, crystal structure and morphology of synthesized samples. The effects of calcination temperature on the morphology, surface area and properties of Bi2MoO6 nanoparticles have been investigated in detail. The photocatalytic activity

A. Martnez-de la Cruz; S. Obregn Alfaro; E. Lpez Cullar; U. Ortiz Mndez

2007-01-01

369

Ion beam amorphization of muscovite mica  

SciTech Connect

The microstructure of a muscovite mica exposed to a rare gas ion beam has been studied by transmission electron microscopy. The investigation of damage without implantation was carried out using argon and helium ions of sufficient energy to transverse the 100{endash}150 nm mica specimens. For 340 keV Ar{sup ++} irradiation, amorphization of mica occurred at a fluence as low as 3.5{times}10{sup 14} ions{center_dot}cm{sup {minus}2} which corresponds to 0.29 dpa. Muscovite can be amorphized using 80 keV helium ions, but this requires a much higher fluence and damage production of 4.6{times}10{sup 16} ions{center_dot}cm{sup {minus}2} and 0.60 dpa, respectively. Since helium irradiation results principally in ionization energy loss, it indicates that amorphization of muscovite results mainly from nuclear interactions. Complete amorphization of muscovite mica is found to take place for all ions at approximately the same amount of nuclear energy transfer to energetic primary knock-on atoms, assuming a recoil energy greater than 500 eV. This suggests that amorphization occurs directly in dense displacement cascades. A significant amount of helium, 100 ppm, can be implanted into muscovite mica without destroying the crystal structure. {copyright} {ital 1996 Materials Research Society.}

Templier, C.; Desage, F.; Desoyer, J.C. [Laboratoire de Metallurgie Physique, 40 Av. Recteur Pineau 86022 Poitiers, Cedex (France); Hishmeh, G. [Midwest Research Technologies Inc., 14540 Greenfield Avenue, Brookfield, Wisconsin 53005 (United States); Cartz, L. [College of Engineering, Marquette University, Milwaukee, Wisconsin 53233 (United States); Donnelly, S.E.; Vishnyakov, V. [Joule Laboratory, Science Research Institute, University of Salford M5 4WT (United Kingdom); Birtcher, R.C. [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States)

1996-07-01

370

Adhesive interaction between graphene membranes and amorphous substrates  

NASA Astrophysics Data System (ADS)

To integrate graphene in functional devices, it is essential to understand interfacial adhesion between graphene and surrounding materials for mechanical support and encapsulation. In complement with recent efforts aiming to measure the adhesion energy experimentally, we present a theoretical model for adhesive interaction between a graphene monolayer and an amorphous substrate. The model is extended to analyze the morphological stability of a graphene membrane on an oxide substrate. It is found that the bending modulus, which increases drastically from monolayer to multilayered graphene, plays an important role in the transition from conformal to non-conformal morphology of the graphene membranes on a corrugated surface. Furthermore, the work of adhesion is predicted to drop considerably from monolayer to bilayer graphene, in good agreement with recent measurements. The theoretical results suggest that tunable adhesion of graphene can be achieved by controlling the surface roughness of the substrate.

Huang, Rui; Gao, Wei

2012-02-01

371

Periodic light coupler gratings in amorphous thin film solar cells  

SciTech Connect

Efficient light trapping structures for amorphous hydrogenated silicon (a-Si:H) solar cells have been realized using periodically structured aluminum doped zinc oxide (ZnO:Al) with periods between 390 and 980 nm as a transparent front contact. Atomic force microscopy, optical reflection, and diffraction efficiency measurements were applied to characterize solar cells deposited on such gratings. A simple formula for the threshold wavelength of total internal reflection is derived. Periodic light coupler gratings reduce the reflectance to a value below 10% in the wavelength range of 400{endash}800 nm which is comparable to cells with an optimized statistical texture. Diffraction efficiency measurements and theoretical considerations indicate that a combination of transmission and reflection gratings contribute to the observed reduction of the reflectance. {copyright} 2001 American Institute of Physics.

Eisele, C.; Nebel, C. E.; Stutzmann, M.

2001-06-15

372

Research on stable, high-efficiency amorphous silicon multijunction modules  

SciTech Connect

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.

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

373

Amorphous Silicon Based Neutron Detector  

SciTech Connect

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.

Xu, Liwei

2004-12-12

374

Research on amorphous silicon based thin film photovoltaic devices: Task B, Research on stable high-efficiency, large area amorphous silicon based submodules  

SciTech Connect

This report describes a project to develop amorphous silicon p-i-n/p-i-n tandem junction photovoltaic submodules with an aperture-area efficiency of at least 9%. A second objective was to demonstrate 8%-efficient tandem submodules that degrade by no more than 5% under standard light-soaking conditions. Improved deposition conditions were established for tandem cells; the resulting efficiencies were nearly as high as those for single-junction cells. An amorphous silicon tandem cell (1 ft{sup 2}) was fabricated with an aperture-area efficiency of 7.2%. Also, good outdoor stability was observed for a glass-encapsulated tandem submodule. Also produced (by magnetron sputtering) were high-quality doped zinc-oxide films (5 ohms/square). 12 refs., 30 figs., 10 tabs.

Delahoy, A.E.; Ellis, F.B. Jr.; Kampas, F.J.; Tonon, T.; Weakliem, H.A. (Chronar Corp., Princeton, NJ (USA))

1989-12-01

375

Research on amorphous silicon based thin film photovoltaic devices. Phase 2: Research on stable high-efficiency, large area amorphous silicon based submodules  

NASA Astrophysics Data System (ADS)

A project is described which developes amorphous silicon p-i-n/p-i-n tandem junction photovoltaic submodules with an aperture-area efficiency of at least 9 percent. A second objective was to demonstrate 8 percent-efficient tandem submodules that degrade by no more than 5 percent under standard light-soaking conditions. Improved deposition conditions were established for tandem cells; the resulting efficiencies were nearly as high as those for single-junction cells. An amorphous silicon tandem cell (1 ft sq) was fabricated with an aperture-area efficiency of 7.2 percent. Also, good outdoor stability was observed for a glass-encapsulated tandem submodule. Also produced (by magnetron sputtering) were high-quality doped zinc-oxide films (5 ohms/square).

Delahoy, A. E.; Ellis, F. B., Jr.; Kampas, F. J.; Tonon, T.; Weakliem, H. A.

1989-12-01

376

Amorphous solid helium in porous media  

NASA Astrophysics Data System (ADS)

We present neutron-scattering measurements of the static structure factor, S(Q) , of helium confined in the porous media MCM-41 of pore diameter 471.5 . The S(Q) shows a transition from the liquid to an amorphous solid as temperature is decreased. No Bragg peaks are observed in the solid and the S(Q) of the amorphous solid differs little from that of the liquid. On freezing, a small additional intensity in S(Q) near the main peak of the liquid S(Q) is observed. The S(Q) is compared with simulations of freezing and melting in porous media. From the measurements of freezing, an approximate phase diagram is determined. A similar amorphous S(Q) is observed in 34 gelsil.

Bossy, Jacques; Hansen, Thomas; Glyde, Henry R.

2010-05-01

377

Measuring strain distributions in amorphous materials  

NASA Astrophysics Data System (ADS)

A number of properties of amorphous materials including fatigue, fracture and component performance are governed by the magnitude of strain fields around inhomogeneities such as inclusions, voids and cracks. At present, localized strain information is only available from surface probes such as optical or electron microscopy. This is unfortunate because surface and bulk characteristics in general differ. Hence, to a large extent, the assessment of strain distributions relies on untested models. Here we present a universal diffraction method for characterizing bulk stress and strain fields in amorphous materials and demonstrate its efficacy by work on a material of current interest in materials engineering: a bulk metallic glass. The macroscopic response is shown to be less stiff than the atomic next-neighbour bonds because of structural rearrangements at the scale of 4-10 . The method is also applicable to composites comprising an amorphous matrix and crystalline inclusions.

Poulsen, Henning F.; Wert, John A.; Neuefeind, Jrg; Honkimki, Veijo; Daymond, Mark

2005-01-01

378

Topics in the theory of amorphous materials  

NASA Astrophysics Data System (ADS)

In this Colloquium, I describe some current frontiers in the physics of semiconducting amorphous materials and glasses, including a short, but self-contained discussion of techniques for creating computer models, among them the quench from the melt method, the Activation-Relaxation Technique, the decorate and relax method, and the experimentally constrained molecular relaxation scheme. A representative study of an interesting and important glass (amorphous GeSe3:Ag) is provided. This material is a fast-ion conductor and a serious candidate to replace current FLASH memory. Next, I discuss the effects of topological disorder on electronic states. By computing the decay of the density matrix in real space, and also computing well-localized Wannier functions, we close with a quantitative discussion of Kohns Principle of Nearsightedness in amorphous silicon.

Drabold, D. A.

2009-03-01

379

Amorphous metals for hard-tissue prosthesis  

NASA Astrophysics Data System (ADS)

Owing to a unique atomic structure lacking microstructural defects, glassy metals demonstrate certain universal properties that are attractive for load-bearing biomedical-implant applications. These include a superb strength, which gives rise to very high hardness and a potential for minimizing wear and associated adverse biological reactions, and a relatively low modulus, which enables high elasticity and holds a promise for mitigating stress shielding. There are, however, other non-universal properties specific to particular amorphous metal alloys that are inferior to presently used biometals and may be below acceptable limits for hard-tissue prosthesis. In this article, features of the performance of amorphous metals relevant to hard-tissue prosthesis are surveyed and contrasted to those of the current state of the art, and guidelines for development of new biocompatible amorphous metal alloys suitable for hard-tissue prosthesis are proposed.

Demetriou, Marios D.; Wiest, Aaron; Hofmann, Douglas C.; Johnson, William L.; Han, Bo; Wolfson, Nikolaj; Wang, Gongyao; Liaw, Peter K.

2010-02-01

380

Phase transitions in biogenic amorphous calcium carbonate.  

PubMed

Crystalline biominerals do not resemble faceted crystals. Current explanations for this property involve formation via amorphous phases. Using X-ray absorption near-edge structure (XANES) spectroscopy and photoelectron emission microscopy (PEEM), here we examine forming spicules in embryos of Strongylocentrotus purpuratus sea urchins, and observe a sequence of three mineral phases: hydrated amorphous calcium carbonate (ACC H(2)O) ? dehydrated amorphous calcium carbonate (ACC) ? calcite. Unexpectedly, we find ACC H(2)O-rich nanoparticles that persist after the surrounding mineral has dehydrated and crystallized. Protein matrix components occluded within the mineral must inhibit ACC H(2)O dehydration. We devised an in vitro, also using XANES-PEEM, assay to identify spicule proteins that may play a role in stabilizing various mineral phases, and found that the most abundant occluded matrix protein in the sea urchin spicules, SM50, stabilizes ACC H(2)O in vitro. PMID:22492931

Gong, Yutao U T; Killian, Christopher E; Olson, Ian C; Appathurai, Narayana P; Amasino, Audra L; Martin, Michael C; Holt, Liam J; Wilt, Fred H; Gilbert, P U P A

2012-04-04

381

Phase transitions in biogenic amorphous calcium carbonate  

PubMed Central

Crystalline biominerals do not resemble faceted crystals. Current explanations for this property involve formation via amorphous phases. Using X-ray absorption near-edge structure (XANES) spectroscopy and photoelectron emission microscopy (PEEM), here we examine forming spicules in embryos of Strongylocentrotus purpuratus sea urchins, and observe a sequence of three mineral phases: hydrated amorphous calcium carbonate (ACCH2O)?dehydrated amorphous calcium carbonate (ACC)?calcite. Unexpectedly, we find ACCH2O-rich nanoparticles that persist after the surrounding mineral has dehydrated and crystallized. Protein matrix components occluded within the mineral must inhibit ACCH2O dehydration. We devised an in vitro, also using XANES-PEEM, assay to identify spicule proteins that may play a role in stabilizing various mineral phases, and found that the most abundant occluded matrix protein in the sea urchin spicules, SM50, stabilizes ACCH2O in vitro.

Gong, Yutao U. T.; Killian, Christopher E.; Olson, Ian C.; Appathurai, Narayana P.; Amasino, Audra L.; Martin, Michael C.; Holt, Liam J.; Wilt, Fred H.; Gilbert, P. U. P. A.

2012-01-01

382

Ion-induced crystallization and amorphization at crystal/amorphous interfaces of silicon  

NASA Astrophysics Data System (ADS)

New empirical equations describing the rate of ion-induced crystallization at a Si crystal/amorphous interface have been developed. In our model, crystallization/amorphization at the interface arises from formation of hot spots and of knock-ons in the collision cascades. It is presumed that the hot spots induce amorphous-to-crystal transformation which lowers the free energy, similarly to heating to high temperatures, and that the bond rearrangement by a series of displacements by knock-ons and recombination to the original lattice point in collision cascades can lead to both crystal-to-amorphous and amorphous-to-crystal transformations. In both hot-spot and knock-on effects, the presence of di-vacancies under irradiation with ion beams is assumed to prohibit crystallization. The model can explain the experimental observation that the crystallization/amorphization rate is scaled by X = ?exp(ev/2kT), the product of the root of the flux and the inverse of root of the Boltzmann factor for the motion of the di-vacancies. Crystallization rate in the hot-spots derived assuming that an incident ion induces spontaneous crystallization within a characteristic volume along the track reveals that the radius is 10 atomic distances and the thickness of is about 0.3 monolayer for 1.5 MeV Xe ions. The calculated crystallization/amorphization rate fits to experimental results over a wide temperature range.

Wang, Z.-L.; Itoh, N.; Matsunami, N.; Zhao, Q. T.

1995-06-01

383

Solubility advantage from amorphous etoricoxib solid dispersions.  

PubMed

Abstract Objective: This study aimed to evaluate kinetic solubility advantage of amorphous etoricoxib solid dispersions prepared with three water soluble polymers and correlate it with solid state and supersaturated drug solution stabilization potential of these polymers. Methods: Amorphous solid dispersions (ASDs) of etoricoxib were prepared with polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP) and hydroxyethyl cellulose (HEC) at 70:30w/w ratio and characterized for glass transition temperature (T(g)), miscibility and intermolecular interactions. Kinetic solubility profiles of amorphous etoricoxib and its ASDs were determined in water at 37 C. Solid-state stability was assessed by enthalpy relaxation studies at a common degree of undercooling of around 19.0 C at 0% RH. Recrystallization behavior of supersaturated drug solution was evaluated in the absence and presence of pre-dissolved polymer at 37 C. Results: Amorphous etoricoxib exhibited rapid solid-to-solid transition to yield a solubility advantage of merely 1.5-fold in water. Among the ASDs, etoricoxib-PVP dispersion exhibited maximal "peak" (2-fold) and "plateau" (1.8-fold) solubility enhancement, while etoricoxib-PVA dispersion could only sustain the "peak" solubility achieved by amorphous etoricoxib. In contrast, etoricoxib-HEC dispersion displayed no solubility advantage. The rank order for solid state and supersaturated solution stabilization followed a similar trend of amorphous etoricoxib?

Dani, Prateek; Puri, Vibha; Bansal, A K

2013-01-10

384

Effect of high-energy electron beam irradiation on the device characteristics of IGZO-based transparent thin film transistors  

NASA Astrophysics Data System (ADS)

In this study, we investigated the effects of high-energy electron beam irradiation (HEEBI) on the device properties of indium-gallium-zinc-oxide (IGZO)-based transparent thin film transistors (TTFTs). The developed TTFTs had a top gate structure, which used IGZO and Al2O3 films for the active layer and the gate dielectric, respectively. The developed TTFTs were treated with HEEBI in air at RT at an electron beam energy of 0.8 MeV and a dose of 1 1014 electrons/cm2. Without the HEEBI treatment, the devices operated in depletion mode with a threshold voltage ( V th ) of -11.25 V, a field-effect mobility ( FE ) of 8.71 cm2/Vs, an on-off ratio ( I on/off ) of 1.3 108 and a sub-threshold slope ( SS) of 0.3 V/decade. A huge positive-shifted V th of -1 V, a very high FE of 420 cm2/Vs, a high I on/off of 6.1 108, and a lower SS of 0.25 V/decade were achieved for the HEEBI-treated devices, suggesting that the device characteristics of the developed TTFTs were significantly improved by the HEEBI treatment. The best device characteristics, which include I on/off of 8.1 108, SS of 0.25 V/decade, V th of +1 V, FE of 8.8 cm2/Vs, and operation in the enhancement mode without aging, were obtained for the samples that had been annealed after HEEBI treatment. On the basis of the experimental results, we believe that HEEBI treatment can be crucial to develop IGZO-based TFTs with high performance and long-term reliability.

Moon, Hye Ji; Oh, Hye Ran; Bae, Byung Seong; Ryu, Min Ki; Cho, Kyoung Ik; Yun, Eui-Jung

2012-01-01

385

Raman Scattering in Amorphous Silicon: Numerical Modeling  

NASA Astrophysics Data System (ADS)

The present work is devoted to a numerical modeling of the Raman scattering in pure amorphous silicon. Using the vacancy model, paracrystalline atomistic models with crystalline volume fraction of ~14% have been generated. Using the anharmonic Keating model as interatomic potential, vibrational eigenmodes have been computed in the harmonic approximation. The density of vibrational states, the photon-phonon coupling coefficient and the reduced Raman spectrum have been calculated for each structural model. Comparison with Raman scattering measurements has been made from which more insights into the local microstructure of amorphous silicon have been inferred.

Chehaidar, A.; Hmad, M.

2007-09-01

386

Remarks on solid state amorphizing transformations  

SciTech Connect

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.

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

1987-01-01

387

Reversible plastic events in amorphous materials  

NASA Astrophysics Data System (ADS)

For crystalline materials, the microscopic origin of plasticity is well understood in terms of the dynamics of topological defects. For amorphous materials, the underlying structural disorder prevents such a description. Therefore identifying and characterizing the microscopic plastic events in amorphous materials remains an important challenge. We show direct evidence for the coexistence of reversible and irreversible plastic events (T1 events) at the microscopic scale in both experiments and simulations of two-dimensional foam. In the simulations, we also demonstrate a link between the reversibility of T1 events and pathways in the potential energy landscape of the system.

Lundberg, Micah; Krishan, Kapilanjan; Xu, Ning; O'Hern, Corey S.; Dennin, Michael

2008-04-01

388

Reversible plastic events in amorphous materials.  

PubMed

For crystalline materials, the microscopic origin of plasticity is well understood in terms of the dynamics of topological defects. For amorphous materials, the underlying structural disorder prevents such a description. Therefore identifying and characterizing the microscopic plastic events in amorphous materials remains an important challenge. We show direct evidence for the coexistence of reversible and irreversible plastic events (T1 events) at the microscopic scale in both experiments and simulations of two-dimensional foam. In the simulations, we also demonstrate a link between the reversibility of T1 events and pathways in the potential energy landscape of the system. PMID:18517626

Lundberg, Micah; Krishan, Kapilanjan; Xu, Ning; O'Hern, Corey S; Dennin, Michael

2008-04-15

389

Structure of highly conducting amorphous carbon  

NASA Astrophysics Data System (ADS)

We report on neutron diffraction study of a new form of conducting amorphous carbon up to Q~14.5 -1. The bond distances from first two peaks in g(r) are 1.45 and 2.49 , very similar to those in sputtered truly amorphous carbon films (Li and Lannin, Phys. Rev. Lett. 65 (1990) 1905). The first coordination number is 3.1 (+/-0.1) indicating predominantly sp2 hybridisation (ideal no.=3). However, S(Q) itself shows vestiges of (0 0 2), (1 0) and (1 1) peaks, typical of glassy carbon (Mildner, J. Non-Cryst. Solids 47 (1982) 391).

Krishna, P. S. R.; Balaya, P.; Dasannacharya, B. A.; Sayeed, Ahmed; Meenakshi, V.; Subramanyam, S. V.

1998-04-01

390

Cooling of hot electrons in amorphous silicon  

SciTech Connect

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.

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

1997-07-01

391

Amorphous silicon/polycrystalline thin film solar cells.  

National Technical Information Service (NTIS)

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 gall...

H. S. Ullal

1991-01-01

392

Structural Properties of Amorphous Semiconductors by Mossbauer Spectroscopy.  

National Technical Information Service (NTIS)

The amorphous to crystalline transition in vacuum deposited tellurium films has been observed using Mossbauer spectroscopy. Although the work is still preliminary, a large difference between the amorphous and crystalline forms of tellurium has been observ...

N. Blum

1973-01-01

393

Pressure-amorphized SiO sub 2. alpha. -quartz: An anisotropic amorphous solid  

SciTech Connect

Recent experiments (Kruger and Jeanloz, Science 249, 647 (1990)) have shown that the pressure-induced amorphous form of AlPO{sub 4} reverts to its original single-crystal'' form on release of pressure. Here we present the results of a Brillouin scattering study of the sister compound {alpha}-quartz, SiO{sub 2} (which can also be pressure amorphized but retains its amorphous structure on release of pressure), which shows that the recovered material is not elastically isotropic but retains a memory'' of its original crystallographic orientation.

McNeil, L.E. (Department of Physics and Astronomy, University of Noth Carolina, Chapel Hill, North Carolina 27599-3255 (United States)); Grimsditch, M. (Materials Science Division, Building 223, Argonne National Laboratory, Argonne, Illinois 60439 (United States))

1992-01-06

394

Physicochemical stability of cimetidine amorphous forms estimated by isothermal microcalorimetry  

Microsoft Academic Search

The effect of humidity on the physicochemical properties of amorphous forms of cimetidine was investigated using differential\\u000a scanning calorimetry, isothermal microcalorimetry, and x-ray diffraction analysis. Amorphous forms were obtained by the melting\\u000a (amorphous form M [AM]) and the cotton candy (amorphous form C [AC]) methods. Thermal behaviors of AM and AC with or without\\u000a seed crystals were measured using an

Makoto Otsuka; Fumie Kato; Yoshihisa Matsuda

2002-01-01

395

X-ray Raman scattering at the Si LII,III-edge of bulk amorphous SiO  

NASA Astrophysics Data System (ADS)

X-ray Raman spectra of bulk amorphous SiO have been measured at energy losses around the Si LII,III-edges for different momentum transfers at beamline ID16 of ESRF. The spectra are compared with measurements of the LII,III-edges of Si powder and with results of first-principles calculations for Si and ?-quartz SiO2. Indications of sub-oxidic contributions to the LII,III-edges are found in the experiment and discussed with respect to the model of interface clusters mixture in bulk amorphous SiO.

Sternemann, C.; Soininen, J. A.; Volmer, M.; Hohl, A.; Vank, G.; Streit, S.; Tolan, M.

2005-12-01

396

Transport properties of oxygen vacancy filaments in metal/crystalline or amorphous HfO2/metal structures  

NASA Astrophysics Data System (ADS)

We study from first principles the transport properties of metal/monoclinic-HfO2/metal and metal/amorphous-HfO2/metal structures where paths built from oxygen vacancies in the hafnium oxide host are created. Using a Green's function formalism coupled with a density functional theory code, we compute the conductance of vacancy filaments of different thicknesses, showing that even the thinnest filaments can sustain conductive channels, which should display signs of conductance quantization, for both the monoclinic and amorphous phases of hafnia.

Cartoix, Xavier; Rurali, Riccardo; Su, Jordi

2012-10-01

397

Correlation of photoconductivity response of amorphous In-Ga-Zn-O films with transistor performance using microwave photoconductivity decay method  

NASA Astrophysics Data System (ADS)

The film quality of amorphous In-Ga-Zn-O (a-IGZO), an amorphous oxide semiconductor (AOS), was studied by the microwave photoconductivity decay (?-PCD) method. Also, ?-PCD mappings over a 6 in. wafer were undertaken. It was found that the peak signal of the decay curve had a strong correlation with the a-IGZO transistor performance and hence the film quality. The film annealed under a wet condition showed the highest mobility and had the highest peak signal. The ?-PCD method was found to be a very useful tool to evaluate the film quality and predict the performance of AOS transistors fabricated under different process conditions.

Yasuno, Satoshi; Kugimiya, Toshihiro; Morita, Shinya; Miki, Aya; Ojima, Futoshi; Sumie, Shingo

2011-03-01

398

Biologically plausible detection of amorphous objects in the wild  

Microsoft Academic Search

The problem of amorphous object detection is investigated. A dataset of amorphous objects, Panda bears, with no defined shape or distinctive edge configurations is introduced. A biologically plausible amorphous object detector, based on discriminant saliency templates, is then proposed. The detector is based on the principles of discriminant saliency, and implemented with a hierarchical architecture of two layers. The first

Sunhyoung Han; Nuno Vasconcelos

2011-01-01

399

Direct observation of crystalline to amorphous transition by ion implantation  

Microsoft Academic Search

The amorphization of aluminium implanted iron is studied by high resolution electron microscopy - in particular its dependence on the ion fluence and the implantation temperature. Examples are given of the implantation induced amorphous structure. The formation and growth kinetics of amorphous clusters formed are discussed.

B. Rauschenbach

1991-01-01

400

Pd induced lateral crystallization of amorphous Si thin films  

Microsoft Academic Search

A thin palladium layer (?40 A?) was selectively formed on top of amorphous silicon films before annealing and the effects of palladium layer on the crystallization behavior of the amorphous silicon films were investigated. It was observed that the amorphous silicon right under the Pd layer could be crystallized to grain sizes of several hundred angstroms by annealing at 500

Seok-Woon Lee; Yoo-Chan Jeon; Seung-Ki Joo

1995-01-01

401

Magnetic Phases in Amorphous Alloys.  

NASA Astrophysics Data System (ADS)

In magnetic amorphous alloy with competiting exchange interactions, there exists a multicritical point (MCP) in the temperature (T) vs. concentration (x) phase diagram (x(,c), (theta)(,c)). In the present work, the static (equilibrium) magnetic response near the MCP is thoroughly investigated using low, d.c. fields (B(,a) < 10 Oe) in two systems of alloys: (I) Fe(,x)Ni(,75-x)P(,16)B(,6)Al(,3) and (II) Fe(,x)Ni(,80-x)P(,14)B(,6). From the measurements of the reversible magnetization M(x, T, B(,a)), the following notable results are found: (1) The phase diagram exhibits a non-montonic FM-SG transition line (i.e. T(,f)'s) in both the systems. (2) There is a dramatic change in the magnetic response as x goes across x(,c). (3) The magnetization collapses as M(,P) (TURN) (x - x(,c))('0.3(+OR-)0.1) when x (--->) x(,c)('+). (4) The peak susceptibility diverges as (chi)(,P) (TURN) (x(,c) - x)('-1.5(+OR-)0.2) when x (--->) x(,c)('-). (5) The results (2), (3), and (4) are highly suggestive of a percolation transition in the magnetic network at the critical concentration for ferromagnetism (i.e. x(,c)). (6) Dramatic changes in the transition temperatures and a perceptible shift in x(,c) are observed when normal boron is replaced by enriched boron ((TURN)100% B('11)) in the series (I) samples. (7) The non-linear susceptibility ((chi)(,H)) exhibits the expected divergence at T(,g) with 'universal' exponents in concentrated spin glasses. (8) In the latter, a divergence in the linear susceptibility ((chi)(,o)) is observed for the first time. This is attributed to the close proximity of the ferromagnetic phase at x(,c). The study of the irreversible moment M(,i) (x, T, B(,a)) reveals the following: (9) Depending on the various methods of preparation, it is possible to generate states with different values of M(,i) at low T, all of which are stable (metastable) in time. This implies non -ergodic behavior. (10) For re-entrants (x > x(,c)), the amount of freezing achieved viz. M(,i) (T = 4.2 K) on cooling in a field drops as x (--->) x(,c)('+). (11) Also, for these alloys, the temperature T(,i)*(B(,a)) at which M(,i) disappears on subsequent warming-up is greater than T(,f)*(B(,a)) where M collapses. This is indicative of the coexistence of FM and SG order over a regime in temperature. (12) For x < x(,c), one requires significantly higher cooling fields (B(,c)) to generate measurables values of M(,i) (T = 4.2 K). Also, M(,i) collapses on warming up at a temperature lower than the spin-glass temperature T(,g), thereby showing the difficulty in generating and sustaining unidirectional frozen-moments in spin glasses. (Abstract shortened with permission of author.).

Mazumdar, Prosenjit

402

Optical Characterization of the Orientation of Amorphous Polymers and Amorphous Parts of Crystalline Polymers.  

National Technical Information Service (NTIS)

Techniques for characterizing the orientation of amorphous polymers include birefringence, infrared, visible and ultraviolet dichroism, and polarization of fluorescence. The infrared dichroism technique does not have the precision of birefringence measure...

R. S. Stein B. E. Read

1967-01-01

403

Radiation-Induced Amorphization of Crystalline Ice  

Microsoft Academic Search

Crystalline ice has been unambiguously identified on the surface of most of the Jovian, Saturnian and Uranian satellites, and on the surface of some trans-Neptunian objects such as Quaoar, and 2003 EL61. This result is surprising, as the low surface temperatures of these objects should cause the ice condensed on them to be amorphous. Moreover, the surface of these bodies

Marcelo A. Fama; M. J. Loeffler; U. Raut; R. A. Baragiola

2008-01-01

404

Paradigms for Structure in an Amorphous Computer  

Microsoft Academic Search

Recent developments in microfabrication and nanotechnology will enable theinexpensive manufacturing of massive numbers of tiny computing elements withsensors and actuators. New programming paradigms are required for obtainingorganized and coherent behavior from the cooperation of large numbers of unreliableprocessing elements that are interconnected in unknown, irregular, andpossibly time-varying ways. Amorphous computing is the study of developingand programming such ultrascale computing ...

Daniel Coore; Radhika Nagpal; Ron Weiss

1997-01-01

405

Low temperature properties of amorphous solids  

Microsoft Academic Search

The low temperature properties of amorphous solids are still not well understood. The two-level states (TLS) model was generally accepted as explaining the behavior of glasses below 1 K, in particular the linear contribution to the specific heat capacity, but there remain anomalies above 1 K. This behavior was examined in epoxy resin systems which were chosen not so much

J. N. Page

1987-01-01

406

Monolithic solar cell panel of amorphous silicon  

Microsoft Academic Search

A monolithic solar cell panel has been fabricated using hydrogenated amorphous silicon (a-Si:H) as the semiconductor material. This device consists of a plate glass substrate bearing a number of long, narrow, parallel cells electrically connected in series along the lengths of the cells. It features several characteristics which make it uniquely attractive for large area devices (up to several sq

J. J. Hanak

1979-01-01

407

High density amorphous ice at room temperature  

PubMed Central

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 H2O 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 dynamicsbut all reported to exist below the crystallization temperature of approximately 150170K below 45GPa. Here, we present the evidence of high density amorphous (HDA) ice formed well above the crystallization temperature at 1GPawell inside the so-called no-mans 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.

Chen, Jing-Yin; Yoo, Choong-Shik

2011-01-01

408

Mossbauer spectra analysis in amorphous system studies  

Microsoft Academic Search

In amorphous materials, the lack of long-range order as well as a relatively poor short-range order lead to a change in hyperfine interactions from nucleus to nucleus and the Mossbauer spectra have to be analysed in terms of a continuous distribution of characteristic parameters. A method is being proposed for calculation of simultaneous hyperfine magnetic fields and electric field gradient

P. Mangin; G. Marchal; M. Piecuch; C. Janot

1976-01-01

409

Flux entry fields in amorphous superconductors  

Microsoft Academic Search

We have measured the flux entry fields (lower critical fields H c1) of homogeneous and inhomogeneous extreme type II amorphous superconductors based on zirconium. Samples are prepared by melt quenching at both ambient and elevated substrate temperatures. The degree of homogeneity is classified according to the widths of both inductive and resistive transitions. The H c1 ( T) curves for

S. J. Poon; P. L. Dunn

1984-01-01

410

Amorphous materials: Finding order in disorder  

NASA Astrophysics Data System (ADS)

Describing the structure of amorphous materials such as metallic glasses has been a longstanding problem in materials science. A new technique called fluctuation microscopy allows us to see order on length scales that are difficult to study with traditional scattering techniques.

Hufnagel, Todd C.

2004-10-01

411

Novel Deformation Processing of Amorphous MEMS.  

National Technical Information Service (NTIS)

Novel Deformation processing of amorphous metals has been conducted on a variety of metallic glasses. Both large scale (e.g. 10's mm size) and small scale (e.g. sub-micrometer size) deformation processing has been conducted using some of the unique p...

J. J. Lewandowski

2005-01-01

412

Surface-enhanced crystallization of amorphous nifedipine.  

PubMed

Amorphous solids are generally more soluble and faster dissolving than their crystalline counterparts, a property useful for delivering poorly soluble drugs. Amorphous drugs must be stable against crystallization, for crystallization negates their advantages. Recent studies found that crystal growth in amorphous indomethacin is orders of magnitude faster at the free surface than through the bulk and this surface-enhanced crystallization can be inhibited by an ultrathin coating. Herein, we report a second system that exhibits the same phenomena. Crystal growth at the free surface of amorphous nifedipine (NIF) was at least 1 order of magnitude faster than that through the bulk below the glass transition temperature Tg (42 degrees C). A thin coating of gold (10 nm) reduced the surface crystal growth rate to the bulk crystal growth rate. Surface-enhanced crystal growth was more pronounced near and below Tg than substantially above Tg, which suggests that this growth mode is more important for the glassy state. Our results support the view that a thin layer of molecules near the surface have higher mobility than the bulk molecules and can enable faster crystal growth. The higher mobility of surface molecules and the resulting fast crystal growth can be suppressed by an ultrathin coating. PMID:19434917

Zhu, Lei; Wong, Letitia; Yu, Lian

413

Progress toward stable amorphous silicon photovoltaic modules  

NASA Astrophysics Data System (ADS)

Data is presented on single-junction amorphous silicon photovoltaic devices with 3000 to 5000 Angstrom thick i-layers which have stabilized efficiencies around 6%. Light-soaking studies on i-layers prepared under the conditions used in the device fabrication show no decrease in photoconductivity resulting from light soaking.

Kampas, Frank; Del Cueto, Joe; Romero, Ralph; Xi, Jianping

1992-12-01

414

Progress toward stable amorphous silicon photovoltaic modules  

SciTech Connect

Data is presented on single-junction amorphous silicon photovoltaic devices with 3000 to 5000 Angstrom thick [ital i]-layers which have stabilized efficiencies around 6%. Light-soaking studies on [ital i]-layers prepared under the conditions used in the device fabrication show no decrease in photoconductivity resulting from light soaking.

Kampas, F.; del Cueto, J.; Romero, R.; Xi, J. (Advanced Photovoltaic Systems, P.O. Box 7093, Princeton, New Jersey 08543 (United States))

1992-12-01

415

Caking phenomena in amorphous food powders  

Microsoft Academic Search

Caking of free-flowing powders during storage is a deleterious phenomenon that is ubiquitous in the feed, fertilizer and pharmaceutical industries, and of economical importance for low-moisture foods. Among other subjects related to caking of amorphous powders, the following aspects are reviewed in this article: (1) physical and morphological changes, and quantitative procedures to assess caking; (2) proposed mechanisms of caking

Jos M. Aguilera; Jos M. del Valle; Marcus Karel

1995-01-01

416

High resolution amorphous silicon radiation detectors  

DOEpatents

A radiation detector employing amorphous Si:H cells in an array with each detector cell having at least three contiguous layers (n-type, intrinsic, p-type), positioned between two electrodes to which a bias voltage is applied. An energy conversion layer atop the silicon cells intercepts incident radiation and converts radiation energy to light energy of a wavelength to which the silicon cells are responsive. A read-out device, positioned proximate to each detector element in an array allows each such element to be interrogated independently to determine whether radiation has been detected in that cell. The energy conversion material may be a layer of luminescent material having a columnar structure. In one embodiment a column of luminescent material detects the passage therethrough of radiation to be detected and directs a light beam signal to an adjacent a-Si:H film so that detection may be confined to one or more such cells in the array. One or both electrodes may have a comb structure, and the teeth of each electrode comb may be interdigitated for capacitance reduction. The amorphous Si:H film may be replaced by an amorphous Si:Ge:H film in which up to 40 percent of the amorphous material is Ge. Two dimensional arrays may be used in X-ray imaging, CT scanning, crystallography, high energy physics beam tracking, nuclear medicine cameras and autoradiography. 18 figs.

Street, R.A.; Kaplan, S.N.; Perez-Mendez, V.

1992-05-26

417

Cracking with catalytically active amorphous silica  

SciTech Connect

Catalytically active amorphous silicas are prepared by dehydrating a silica hydrogel or precipitate prepared from an acidified aqueous silicate solution containing an amine of pK /SUB a/ above 10 or a cation containing either a nitrogen or phosphorus silica is catalytically active for, among other chemical reactions, the isomerization of ortho-xylene and the cracking of hydrocarbons.

Young, D. A.; Koepke, J. W.

1984-11-06

418

Transient amorphous calcium phosphate in forming enamel.  

PubMed

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

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

2009-02-13

419

Excess Specific Heat in Evaporated Amorphous Silicon  

NASA Astrophysics Data System (ADS)

The specific heat C of e-beam evaporated amorphous silicon (a-Si) thin films prepared at various growth temperatures TS and thicknesses t was measured from 2 to 300 K, along with sound velocity v, shear modulus G, density nSi, and Raman spectra. Increasing TS results in a more ordered amorphous network with increases in nSi, v, G, and a decrease in bond angle disorder. Below 20 K, an excess C is seen in films with less than full density where it is typical of an amorphous solid, with both a linear term characteristic of two-level systems (TLS) and an additional (non-Debye) T3 contribution. The excess C is found to be independent of the elastic properties but to depend strongly on density. The density dependence suggests that low energy glassy excitations can form in a-Si but only in microvoids or low density regions and are not intrinsic to the amorphous silicon network. A correlation is found between the density of TLS n0 and the excess T3 specific heat cex suggesting that they have a common origin.

Queen, D. R.; Liu, X.; Karel, J.; Metcalf, T. H.; Hellman, F.

2013-03-01

420

Inelastic resonant tunneling in amorphous silicon microstructures  

NASA Astrophysics Data System (ADS)

We have observed strong electron-phonon interaction on deep centers in the process of resonant tunneling conduction through localized states in amorphous silicon. Our data support the theory of Glazman and Matveev pertaining to inelastic resonant tunneling in mesoscopic junctions.

Yakimov, A. I.; Stepina, N. P.; Dvurechenskii, A. V.

1994-10-01

421

Electrical conduction in amorphous titanium nitride films  

Microsoft Academic Search

Charge transport measurements in disordered semiconductors and insulators have been of considerable interest because they can provide information regarding the electronic structure of these materials [1-3]. The study of direct current conduction in thin dielectric films is of importance in thin film applications. Exhaustive work has been done on electrical conduction phenomena in a variety of amorphous and crystalline dielectrics

Bellan Babuji; C. Balasubramanian; M. Radhakrishnan

1983-01-01

422

Method of forming buried oxide layers in silicon  

DOEpatents

A process for forming Silicon-On-Insulator is described incorporating the steps of ion implantation of oxygen into a silicon substrate at elevated temperature, ion implanting oxygen at a temperature below 200.degree. C. at a lower dose to form an amorphous silicon layer, and annealing steps to form a mixture of defective single crystal silicon and polycrystalline silicon or polycrystalline silicon alone and then silicon oxide from the amorphous silicon layer to form a continuous silicon oxide layer below the surface of the silicon substrate to provide an isolated superficial layer of silicon. The invention overcomes the problem of buried isolated islands of silicon oxide forming a discontinuous buried oxide layer.

Sadana, Devendra Kumar (Pleasantville, NY); Holland, Orin Wayne (Lenoir City, TN)

2000-01-01

423

Carrier collection losses in amorphous silicon and amorphous silicon-germanium alloy solar cells  

Microsoft Academic Search

The carrier collection losses in amorphous silicon (a-Si) and amorphous silicongermanium (a-SiGe) alloy single-junction nip cells have been experimentally investigated by measuring the biased quantum efficiency and color (blue and red) fill factor values. The study has identified losses near the p\\/i junction and the bulk of the i layer. The extent of the losses have been found to be

A. Banerjee; X. Xu; J. Yang; S. Guha

1995-01-01

424

Characteristics of electron spin resonance in hydrogenated amorphous silicon-carbon\\/hydrogenated amorphous silicon heterojunctions  

Microsoft Academic Search

The characteristics of light soaking and equilibrium electron spin resonance (ESR) in p-hydrogenated amorphous silicon-carbon\\/i-hydrogenated amorphous silicon heterojunction are investigated. The influence of the carbon content in the p layer on ESR is also studied in this letter. We find that the light-induced silicon dangling bond defects mainly originate from the i layer and the increased spin density can be

Guanghua Chen; Guosheng Sun; Fangqing Zhang

1989-01-01

425

In situ ellipsometric study of amorphous silicon\\/amorphous silicon-carbon interfaces  

Microsoft Academic Search

An ellipsometric study of the growth of hydrogenated amorphous silicon\\/hydrogenated amorphous silicon-carbon interfaces and multilayer structures is presented. Kinetic ellipsometry is used at a fixed wavelength to study the growth of the materials at the interface between the a-Si:H and a-Si1?xCx:H layers as a function of the carbon content. It is observed that for samples with carbon content below 36%,

V. Chu; M. Fang; B. Drevillon

1991-01-01

426

Total oxidation of methane over Pd catalysts supported on silicon nitride  

Microsoft Academic Search

Non-oxide refractory materials such as silicon nitride showing high thermal stability and thermal conductivity can be used as catalytic supports. Silicon nitride with different specific area and crystallinity: amorphous silicon nitride (SiN-am), amorphous silicon nitride annealed at 1450C (120min) under nitrogen flow (SiN-annl) and ?-Si3N4 were chosen as supports for Pd catalysts. Commercial amorphous silicon nitride contains a small amount

I. Kurzina; F. J. Cadete Santos Aires; G. Bergeret; J. C. Bertolini

2005-01-01

427

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

Microsoft Academic Search

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

Kazushi Arata

1996-01-01

428

Defect-induced solid state amorphization of molecular crystals  

NASA Astrophysics Data System (ADS)

We investigate the process of mechanically induced amorphization in small molecule organic crystals under extensive deformation. In this work, we develop a model that describes the amorphization of molecular crystals, in which the plastic response is calculated with a phase field dislocation dynamics theory in four materials: acetaminophen, sucrose, ?-indomethacin, and aspirin. The model is able to predict the fraction of amorphous material generated in single crystals for a given applied stress. Our results show that ?-indomethacin and sucrose demonstrate large volume fractions of amorphous material after sufficient plastic deformation, while smaller amorphous volume fractions are predicted in acetaminophen and aspirin, in agreement with experimental observation.

Lei, Lei; Carvajal, Teresa; Koslowski, Marisol

2012-04-01

429

Characterization of amorphous In{sub 2}O{sub 3}: An ab initio molecular dynamics study  

SciTech Connect

In this work, we report on the structural and electronic properties of amorphous In{sub 2}O{sub 3} obtained with ab initio molecular dynamics. Our results show crystal-like short range InO{sub 6} polyhedra having average In-O distance consistent with x-ray spectroscopy data. Structural disorder yields band tailing and localized states, which are responsible of a strong reduction of the electronic gap. Most importantly, the appearance of a peculiar O-O bond imparts n-type character to the amorphous compound and provides contribution for interpreting spectroscopic measurements on indium based oxidized systems. Our findings portray characteristic features to attribute transparent semiconductive properties to amorphous In{sub 2}O{sub 3}.

Aliano, Antonio [Department of Physics, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino (Italy); Catellani, Alessandra [CNR-IMEM, Parco Area delle Scienze 37A, I-43010 Parma (Italy); Cicero, Giancarlo [Materials Science and Chemical Engineering Department, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino (Italy)

2011-11-21

430

Atomic level in situ observation of surface amorphization in anatase nanocrystals during light irradiation in water vapor.  

PubMed

An in situ atomic level investigation of the surface structure of anatase nanocrystals has been conducted under conditions relevant to gas phase photocatalytic splitting of water. The experiments were carried out in a modified environmental transmission electron microscope fitted with a high intensity broadband light source with an illumination intensity of 1430 mW/cm(2) close to 10 suns. When the titania is exposed to light and water vapor, the initially crystalline surface converts to an amorphous phase one to two monolayers thick. Spectroscopic analyses show that the amorphous layer contains titanium in a +3 oxidation state. The amorphous layer is stable and does not increase in thickness with time and is heavily hydroxylated. This disorder layer will be present on the anatase surface under reaction conditions relevant to photocatalytic splitting of water. PMID:23294377

Zhang, Liuxian; Miller, Benjamin K; Crozier, Peter A

2013-01-11

431

Understanding intrinsic ductility from Poisson's ratio for amorphous solids through force-field tuning  

NASA Astrophysics Data System (ADS)

This work is motivated by recently observed empirical relationship between the Poisson's ratio and the fracture energy for a range of metallic glasses and oxide glasses. Glassy solids with low Poisson's ratio are brittle and vice versa, with a critical Poisson's ratio of about 0.31. Here we used a force-field tuning scheme to investigate how a near-equilibrium elastic constant determines far-from-equilibrium fracture behavior. By modifying a well-studied binary Lennard-Jones system, we obtained a family of glassy systems with different Poisson's ratio ranging from 0.2 to 0.4. Interestingly, the model glasses with low Poisson's ratio exhibit brittle fracture in tension and vice versa, which agrees with experimental observations. Finally, we will discuss how ductility of amorphous solids can be comprehended in terms of the structure and bonding of the amorphous solids, both of which also dictate the Poisson's ratio.

Shi, Yunfeng; Luo, Jian

2011-03-01

432

Charge trapping properties and retention time in amorphous SiGe/SiO2 nanolayers  

NASA Astrophysics Data System (ADS)

In this paper, we report on the electrical properties of metal-oxide-semiconductor (MOS) capacitors containing a well-confined 8 nm-thick SiGe amorphous layer (a-SiGe) embedded in a SiO2 matrix grown by RF magnetron sputtering at a low temperature (350 C). Capacitance-voltage measurements show that the introduction of the SiGe layer leads to a significant enhancement of the charge trapping capabilities, with the memory effect and charge retention time larger for hole carriers. The presented results demonstrate that amorphous floating-gate SiGe layers embedded in SiO2 may constitute a suitable alternative for memory applications.

Vieira, E. M. F.; Diaz, R.; Grisolia, J.; Parisini, A.; Martn-Snchez, J.; Levichev, S.; Rolo, A. G.; Chahboun, A.; Gomes, M. J. M.

2013-03-01

433

Magnetic Anisotropy of CoFeB Amorphous Nanotubes Prepared by Electroless Plating in Magnetic Field  

NASA Astrophysics Data System (ADS)

CoFeB nanotubes were fabricated by electroless plating in magnetic field using anodized aluminum oxide template, and the structural and magnetic properties of CoFeB nanotubes were investigated. It is found that some nano-scale particles form on the wall of nanotubes. Both coercivity ratio and squareness ratio of out-of-plane to in-plane are significantly changed by the applied magnetic field during electroless plating, which indicates that directional ordering in amorphous CoFeB nanotubes are achieved during electroless plating under magnetic field. The results show that the applied field impacts the magnetic anisotropy of amorphous nanotubes. The anisotropy is stronger with the magnitude of applied field increasing.

Liu, Z.; Li, W. L.; Fei, W. D.

2013-07-01

434

Development and characterization of high temperature stable Ta-W-Si-C amorphous metal gates  

SciTech Connect

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}.

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

435

Crystallization of amorphous Si nanoclusters in SiO(x) films using femtosecond laser pulse annealings.  

PubMed

The SiO(x) films of various stoichiometries deposited on Si substrates with the use of the co-sputtering from two separate Si and SiO2 targets were annealed by femtosecond laser pulses. Femtosecond laser treatments were applied for crystallization of amorphous silicon nanoclusters in the silicon-rich oxide films. The treatments were carried out with the use of Ti-Sapphire laser with wavelength 800 nm and pulse duration about 30 fs. Regimes of crystallization of amorphous Si nanoclusters in the initial films were found. Ablation thresholds for SiO(x) films of various stoichiometries were discovered. The effect of laser assisted formation of a-Si nanoclusters in the non-stoichiometric dielectric films with relatively low concentration of additional Si atoms was also observed. This approach is applicable for the creation of dielectric films with semiconductor nanoclusters on non-refractory substrates. PMID:23421268

Korchagina, T T; Gutakovsky, A K; Fedina, L I; Neklyudova, M A; Volodin, V A

2012-11-01

436

Status of the DOE/SERI amorphous silicon research project - Recent advances and future directions  

NASA Astrophysics Data System (ADS)

Recent advances in material, cell, and module research in the US Department of Energy/Solar Energy Research Institute (DOE/SERI) Amorphous Silicon Research Project (ASRP) are reviewed. Advances in transparent conductive oxides, high-performance back reflectors, cell interconnection/patterning schemes, and encapsulants are surveyed. The program phase that began in 1990 has major research goals of reproducible, cost-effective multijunction modules with stabilized efficiencies of 10 percent for same-bandgap modules and 12 percent for different-bandgap modules. The issue of stability and reliability of amorphous silicon modules is reviewed. Multijunction cell/module structures have demonstrated improved stability in R&D cells and modules over single-junction structures.

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

437

Wear Resistant Amorphous and Nanocomposite Coatings  

SciTech Connect

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.

Racek, O

2008-03-26

438

Computer models for amorphous silicon hydrides  

NASA Astrophysics Data System (ADS)

A procedure for generating fully coordinated model structures appropriate to hydrogenated amorphous semiconductors is described. The hydrogen is incorporated into an amorphous matrix using a bond-switching process similar to that proposed by Wooten, Winer, and Weaire, which ensures that fourfold coordination is preserved. After each inclusion of hydrogen, the structure is relaxed using a finite-temperature Monte Carlo algorithm. The method is applied to a-Si:H at various hydrogen concentrations. The resulting model structures are found to be in excellent agreement with recent neutron-scattering measurements on a sample with 12 at. % H. Our prescription, which is essentially nonlocal, allows great flexibility and can easily be extended to related systems.

Mousseau, Normand; Lewis, Laurent J.

1990-02-01

439

Amorphous graphene: a realization of Zachariasen's glass.  

PubMed

Amorphous graphene is a realization of a two-dimensional Zachariasen glass as first proposed 80 years ago. Planar continuous random networks of this archetypal two-dimensional network are generated by two complementary simulation methods. In the first, a Monte Carlo bond switching algorithm is employed to systematically amorphize a crystalline graphene sheet. In the second, molecular dynamics simulations are utilized to quench from the high temperature liquid state. The two approaches lead to similar results as detailed here, through the pair distribution function and the associated diffraction pattern. Details of the structure, including ring statistics and angular distortions, are shown to be sensitive to preparation conditions, and await experimental confirmation. PMID:23090073

Kumar, Avishek; Wilson, Mark; Thorpe, M F

2012-10-23

440

Advances in amorphous silicon photovoltaic technology  

SciTech Connect

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.}

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

441

Amorphous precursors of crystallization during spinodal decomposition.  

PubMed

A general Landau's free energy functional is used to study the dynamics of crystallization during liquid-solid spinodal decomposition (SD). The strong length scale selectivity imposed during the early stage of SD induces the appearance of small precursors for crystallization with icosahedral order. These precursors grow in densely packed clusters of tetrahedra through the addition of new particles. As the average size of the amorphous nuclei becomes large enough to reduce geometric frustration, crystalline particles with a body-centered cubic symmetry heterogeneously nucleate on the growing clusters. The volume fraction of the crystalline phase is strongly dependent on the depth of quench. At deep quenches, the SD mechanism produces amorphous structures arranged in dense polytetrahedral aggregates. PMID:21405846

Gmez, Leopoldo R; Vega, Daniel A

2011-02-10

442

Semiquantitative scattering theory of amorphous materials  

NASA Astrophysics Data System (ADS)

It is argued that the topological disorder in a small region of an amorphous solid can be described by the local strain field related to the local reference crystal. A localized state spread only in one distorted region can be viewed as the consequence of superposition among some Bloch waves and its scattering waves caused by the disorder. A semiclassical approximation is used to calculate the phase shift of Bloch waves in the amorphous solid. The inverse participation ratio and the mobility edge positions in the band tails are formulated in terms of the parameters of the disorder potential. The dependence of the band tail decay rates on static and thermal disorders is derived. The model is applied to a-Si , though conceptually it can be implemented to a wide range of disordered systems. The ab initio calculations on a-Si and the experimental results on a-Si :H are compared to the predictions of our model.

Zhang, Mingliang; Pan, Yue; Inam, F.; Drabold, D. A.

2008-11-01

443

Germanium detector passivated with hydrogenated amorphous germanium  

DOEpatents

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.

Hansen, William L. (Walnut Creek, CA); Haller, Eugene E. (Berkeley, CA)

1986-01-01

444

Thermal conductivity of amorphous carbon thin films  

SciTech Connect

Thermal conductivities {Lambda} of amorphous carbon thin films are measured in the temperatures range 80--400 K using the 3{omega} method. Sample films range from soft a-C:H prepared by remote-plasma deposition ({Lambda}=0.20 Wm{sup -1} K{sup -1} at room temperature) to amorphous diamond with a large fraction of sp{sup 3} bonded carbon deposited from a filtered-arc source ({Lambda}=2.2 Wm{sup -1} K{sup -1}). Effective-medium theory provides a phenomenological description of the variation of conductivity with mass density. The thermal conductivities are in good agreement with the minimum thermal conductivity calculated from the measured atomic density and longitudinal speed of sound.

Bullen, Andrew J.; O'Hara, Keith E.; Cahill, David G.; Monteiro, Othon; von Keudell, Achim

2000-12-01

445

Annealing behavior of high permeability amorphous alloys  

SciTech Connect

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.

Rabenberg, L.

1980-06-01

446

The Local Structure of Amorphous Silicon  

NASA Astrophysics Data System (ADS)

It is widely believed that the continuous random network (CRN) model represents the structural topology of amorphous silicon. The key evidence is that the model can reproduce well experimental reduced density functions (RDFs) obtained by diffraction. By using a combination of electron diffraction and fluctuation electron microscopy (FEM) variance data as experimental constraints in a structural relaxation procedure, we show that the CRN is not unique in matching the experimental RDF. We find that inhomogeneous paracrystalline structures containing local cubic ordering at the 10 to 20 angstrom length scale are also fully consistent with the RDF data. Crucially, they also matched the FEM variance data, unlike the CRN model. The paracrystalline model has implications for understanding phase transformation processes in various materials that extend beyond amorphous silicon.

Treacy, M. M. J.; Borisenko, K. B.

2012-02-01

447

The local structure of amorphous silicon.  

PubMed

It is widely believed that the continuous random network (CRN) model represents the structural topology of amorphous silicon. The key evidence is that the model can reproduce well experimental reduced density functions (RDFs) obtained by diffraction. By using a combination of electron diffraction and fluctuation electron microscopy (FEM) variance data as experimental constraints in a structural relaxation procedure, we show that the CRN is not unique in matching the experimental RDF. We find that inhomogeneous paracrystalline structures containing local cubic ordering at the 10 to 20 angstrom length scale are also fully consistent with the RDF data. Crucially, they also matched the FEM variance data, unlike the CRN model. The paracrystalline model has implications for understanding phase transformation processes in various materials that extend beyond amorphous silicon. PMID:22363003

Treacy, M M J; Borisenko, K B

2012-02-24

448

A DFT study of amorphous silicon oxynitride  

Microsoft Academic Search

We study amorphous silicon oxynitride, a-SiNO, for the entire compositional range between SiO2 and Si3N4. Structural models are constructed using an empirical bond switch algorithm. The continuous random alternating networks (CRAN) generated have well-defined bond topology as to represent the perfect chemical order in such materials. Consequently, the models comprise SiO and SiN bonds only and constitute an extension of

Peter Kroll

2005-01-01

449

Amorphous metal powder for coating substrates  

Microsoft Academic Search

The present invention is for a flat B containing amorphous powder based in Fe, Ni, Co or a combination thereof; a coating resulting from deposition of the powder; and a method for depositing the powder. The composition of the powder and the resulting coating consists essentially of the formulation: (Fe,Ni,Co) \\/sub bal\\/ Cr⁻(Mn,Mo,W)⁻ (B,Si,C)⁻(Al,Ti)⁻ where the subscripts are in atomic

J. Dickson; L. F. Nienart; D. W. Roth

1985-01-01

450

Synthesis of new amorphous metallic spin glasses  

DOEpatents

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.

Haushalter, Robert C. (Clinton, NJ)

1986-01-01

451

Synthesis of new amorphous metallic spin glasses  

DOEpatents

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.

Haushalter, Robert C. (Clinton, NJ)

1988-01-01

452

Flux entry field in amorphous superconductors  

Microsoft Academic Search

We have measured the flux entry fields (lower critical fields H\\/sub c1\\/) of homogeneous and inhomogeneous extreme type II amorphous superconductors based on zirconium. Samples are prepared by melt quenching of both ambient and elevated substrate temperatures. The degree of homogeneity is classified according to the widths of both inductive and resistive transitions. The H\\/sub c1\\/(T) curves for ''powdered'' homogeneous

S. J. Poon; P. L. Dunn

1984-01-01

453

Flux entry fields in amorphous superconductors  

Microsoft Academic Search

We have measured the flux entry fields (lower critical fieldsHc1) of homogeneous and inhomogeneous extreme type II amorphous superconductors based on zirconium. Samples are prepared by melt quenching at both ambient and elevated substrate temperatures. The degree of homogeneity is classified according to the widths of both inductive and resistive transitions. TheHc1 (T) curves for powdered homogeneous samples with weak

S. J. Poon; P. L. Dunn

1984-01-01

454

Crystalline-amorphous transition in silicate perovskites  

Microsoft Academic Search

CaSiO3 and MgSiO3 perovskites are known to undergo solid-state crystal to amorphous transitions near ambient pressure when decompressed from their high-pressure stability fields. In order to elucidate the mechanistic aspects of this transition we have performed detailed molecular-dynamics simulations and lattice-dynamical calculations on model silicate perovskite systems using empirical rigid-ion pair potentials. In the simulations at low temperatures, the model

Mahin Hemmati; Andrew Chizmeshya; George H. Wolf; Peter H. Poole; Jun Shao; C. Austen Angell

1995-01-01

455

Superconductivity in amorphous Bi and Ga  

Microsoft Academic Search

The electron-phonon a2(?)F(?) has been measured by Chenet al. in films of amorphous Bi and Ga. This was accomplished by inversion of low-temperature quasiparticle tunneling data. From a2(?)F(?), the phonon renormalization of the electronic effective mass was calculated and was found to be considerably greater than it is in the case of the well-known strong-coupling superconductors Pb and Hg. These

P. Vashishta; J. P. Carbotte

1973-01-01

456

Energy landscape of relaxed amorphous silicon  

Microsoft Academic Search

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

Francis Valiquette; Normand Mousseau

2003-01-01

457

Synthesis of new amorphous metallic spin glasses  

DOEpatents

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.

Haushalter, R.C.

1985-02-11

458

Tetrahedrally bonded ternary amorphous semiconductor alloys  

Microsoft Academic Search

The properties of tetrahedrally bonded ternary amorphous semiconductors a-CSiSn:H and a-CSiGe:H are reviewed with particular emphasis on the temperature dependence of dark conductivity and the coordination in random networks. It is shown here that the dark conductivity as a function of the temperature strongly depends on the carbon content and, more precisely, on the proportion of sp3 and sp2 sites

F. Demichelis; G. Kaniadakis; A. Tagliaferro; E. Tresso

1989-01-01

459

Physical properties of hydrogenated amorphous gallium arsenide  

Microsoft Academic Search

SummaryThe elemental composition and the optical properties of hydrogenated amorphous GaAs prepared by r.f. reactive sputtering at\\u000a different hydrogen and argon pressure and substrate temperature have been determined. From the dependence of the absorption\\u000a coefficient on photon energy the optical gap has been deduced according to the Tauc law. The data obtained for stoichiometric\\u000a samples are compared with similar data

A. Carbone; F. Demichelis; G. Kaniadakis; F. Gozzo; R. Murri; N. Pinto; L. Schiavulli; G. Della Mea; A. Drigo; A. Paccagnella

1991-01-01

460

Thermal conductivity of crystalline and amorphous ices and its implications on amorphization and glassy water.  

PubMed

The thermal conductivities kappa of the crystalline phases and amorphous solid states of water as well as clathrate hydrates are summarized and discussed. In particular, this review concerns the unusual temperature T and pressure p behaviors of kappa for some phases and states, which include glass-like K for crystalline clathrate hydrates and crystal-like kappa for low-density amorphous ice. The latter result implies that glassy water and low-density amorphous ice are different states. The results for the various phases and states are in most cases described well by the equations: kappa = D x T(-x) and 1n kappa = E + F x p, under isobaric and isothermal conditions, respectively. All phases that exhibit negative values for F are known to amorphize upon pressurization at low temperatures. Ice XI, which is obtained by annealing ice Ih below 70 K, exhibits positive F, which indicates that this phase does not amorphize like ice Ih upon pressurization. PMID:19787966

Andersson, Ove; Inaba, Akira

2005-04-01

461

Photoinduced expansion in hydrogenated amorphous silicon  

SciTech Connect

The structural aspect of photodegradation effect in hydrogenated amorphous silicon has been investigated by the use of the simple and sensitive detection technique, the laser optical-level bending method, for a small expansion or extraction in thin films. The volume change induced by the thermal expansion due to the photothermal effect and the residual expansion was observed in hydrogenated amorphous silicon prepared by PECVD. The latter residual expansion was persistent after light soaking and was recovered by thermal annealing at 200 C. The time dependence of the volume expansion with light soaking shows the same time dependence of photoinduced defect density. The photoinduced volume changes normalized by the initial volume are the order of 10{sup {minus}6} {approximately} 10{sup {minus}5}, which values are two orders smaller than chalcogenide glasses such as a-As{sub 2}S{sub 3}. The normalized volume change of a-Si:H with the different sample preparation conditions of PECVD such as the hydrogen dilution ratio r (r = SiH{sub 4}/H{sub 2}) and substrate temperature is shown. Also it is demonstrated that the photoinduced expansion is observed in hydrogenated amorphous silicon prepared by photo CVD and hot-wire CVD methods. The spatial extent related to a photoinduced defect creation in a-Si:H is estimated.

Nonomura, S.; Gotoh, T.; Nishio, M.; Sakamoto, T.; Kondo, M.; Matusda, A.; Nitta, S.

1999-07-01

462

Formation of iron disilicide on amorphous silicon  

NASA Astrophysics Data System (ADS)

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 525C. 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 525-625C was studied by RBS and the activation energy was found to be 1.5 0.1 eV.

Erlesand, U.; stling, M.; Bodn, K.

1991-11-01

463

Ordered mesoporous thin films of rutile TiO2 nanocrystals mixed with amorphous Ta2O5.  

PubMed

Ordered mesoporous thin films of composites of rutile TiO2 nanocrystals with amorphous Ta2O5 are fabricated by evaporation-induced self-assembly followed by subsequent heat treatment beyond 780 degrees C. Incorporation of selected amounts of Ta2O5 (20 mol %) in the mesoporous TiO2 film, together with the unique mesoporous structure itself, increased the onset of crystallization temperature which is high enough to ensure the crystallization of amorphous titania to rutile. The ordered mesoporous structure benefits from a block-copolymer template, which stabilizes the mesostructure of the amorphous mixed oxides before crystallization. The surface and in-depth composition analysis by X-ray photoelectron spectroscopy suggests a homogeneous intermixing of the two oxides in the thin film. A detailed X-ray absorption fine structure measurement on the composite film containing 20 mol % Ta2O5 and heated to 800 degrees C confirms the amorphous nature of the Ta2O5 phase. Photocatalytic activity evaluation suggests that the rutile nanocrystals in the synthesized ordered mesoporous thin film possess good ability to assist the photodegradation of rhodamine B in water under illumination by UV light. PMID:18383238

Wu, Jin-Ming; Antonietti, Markus; Gross, Silvia; Bauer, Matthias; Smarsly, Bernd M

2008-04-01

464

Advances in selective wet oxidation of AlGaAs alloys  

Microsoft Academic Search

We review the chemistry, microstructure, and processing of buried oxides converted from AlGaAs layers using wet oxidation. Hydrogen is shown to have a central role in the oxidation reaction as the oxidizing agent and to reduce the intermediate predict As2O3 to As. The stable oxide is amorphous (AlxGa1-x) 2O3 which has no defects along the oxide\\/semiconductor interfaces but can exhibit

Kent D. Choquette; Kent M. Geib; Carol I. H. Ashby; Ray D. Twesten; Olga Blum; Hong Q. Hou; David M. Follstaedt; B. Eugene Hammons; Dave Mathes; Robert Hull

1997-01-01

465

Crystallization inhibition of an amorphous sucrose system using raffinose*  

PubMed Central

The shelf life of pure amorphous sucrose systems, such as cotton candy, can be very short. Previous studies have shown that amorphous sucrose systems held above the glass transition temperature will collapse and crystallize. One study, however, showed that adding a small percent of another type of sugar, such as trehalose, to sucrose can extend the shelf life of the amorphous system by slowing crystallization. This study explores the hypothesis that raffinose increases the stability of an amorphous sucrose system. Cotton candy at 5 wt% raffinose and 95 wt% sucrose was made and stored at room temperature and three different relative humidities (%RH) 11%RH, 33%RH, and 43%RH. XRD patterns, and glass transition temperatures were obtained to determine the stability as a function of %RH. The data collected showed that raffinose slows sucrose crystallization in a low moisture amorphous state above the glass transition temperature and therefore improves the stability of amorphous sucrose systems.

Leinen, K.M.; Labuza, T.P.

2006-01-01