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1

Electrical effect of titanium diffusion on amorphous indium gallium zinc oxide  

NASA Astrophysics Data System (ADS)

In this work, thermal diffusion phenomenon of Ti into amorphous indium gallium zinc oxide (?-IGZO) was carefully investigated with secondary ion mass spectroscopy, I-V, and Rs 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 ?-IGZO during the oxidation of Ti, the number of oxygen vacancies working as electron-donating sites in ?-IGZO was dramatically increased, contributing to the decrease of resistivity (?) from 1.96 ? cm (as-deposited ?-IGZO) to 1.33 × 10-3 ? cm (350 °C annealed ?-IGZO).

Choi, Seung-Ha; Jung, Woo-Shik; Park, Jin-Hong

2012-11-01

2

Origin of deep subgap states in amorphous indium gallium zinc oxide: Chemically disordered coordination of oxygen  

NASA Astrophysics Data System (ADS)

The origin of the deep subgap states in amorphous indium gallium zinc oxide (a-IGZO), whether intrinsic to the amorphous structure or not, has serious implications for the development of p-type transparent amorphous oxide semiconductors. We report that the deep subgap feature in a-IGZO originates from local variations in the oxygen coordination and not from oxygen vacancies. This is shown by the positive correlation between oxygen composition and subgap intensity as observed with X-ray photoelectron spectroscopy. We also demonstrate that the subgap feature is not intrinsic to the amorphous phase because the deep subgap feature can be removed by low-temperature annealing in a reducing environment. Atomistic calculations of a-IGZO reveal that the subgap state originates from certain oxygen environments associated with the disorder. Specifically, the subgap states originate from oxygen environments with a lower coordination number and/or a larger metal-oxygen separation.

Sallis, S.; Butler, K. T.; Quackenbush, N. F.; Williams, D. S.; Junda, M.; Fischer, D. A.; Woicik, J. C.; Podraza, N. J.; White, B. E.; Walsh, A.; Piper, L. F. J.

2014-06-01

3

Origin of deep subgap states in amorphous indium gallium zinc oxide: Chemically disordered coordination of oxygen  

SciTech Connect

The origin of the deep subgap states in amorphous indium gallium zinc oxide (a-IGZO), whether intrinsic to the amorphous structure or not, has serious implications for the development of p-type transparent amorphous oxide semiconductors. We report that the deep subgap feature in a-IGZO originates from local variations in the oxygen coordination and not from oxygen vacancies. This is shown by the positive correlation between oxygen composition and subgap intensity as observed with X-ray photoelectron spectroscopy. We also demonstrate that the subgap feature is not intrinsic to the amorphous phase because the deep subgap feature can be removed by low-temperature annealing in a reducing environment. Atomistic calculations of a-IGZO reveal that the subgap state originates from certain oxygen environments associated with the disorder. Specifically, the subgap states originate from oxygen environments with a lower coordination number and/or a larger metal-oxygen separation.

Sallis, S.; Williams, D. S. [Materials Science and Engineering, Binghamton University, Binghamton, New York 13902 (United States); Butler, K. T.; Walsh, A. [Center for Sustainable Technologies and Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY (United Kingdom); Quackenbush, N. F. [Department of Physics, Applied Physics, and Astronomy, Binghamton University, Binghamton, New York 13902 (United States); Junda, M.; Podraza, N. J. [Department of Physics and Astronomy, University of Toledo, Toledo, Ohio 43606 (United States); Fischer, D. A.; Woicik, J. C. [Materials Science and Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); White, B. E.; Piper, L. F. J., E-mail: lpiper@binghamton.edu [Department of Physics, Applied Physics, and Astronomy, Binghamton University, Binghamton, New York 13902 (United States); Materials Science and Engineering, Binghamton University, Binghamton, New York 13902 (United States)

2014-06-09

4

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

5

Amorphous Indium Gallium Zinc Oxide Thin-Film Transistors Fabricated by Direct Transfer Printing  

NASA Astrophysics Data System (ADS)

This letter describes the fabrication of amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs) by direct transfer printing. An a-IGZO layer and a silicon dioxide (SiO2) layer were sequentially sputtered on a poly(dimethylsiloxane) (PDMS) stamp; the stamp was then pressed onto a glass substrate on which a gate metal had been previously deposited. Then, a-IGZO/SiO2 layers were successfully transferred by simply releasing the stamp from the substrate; a bottom-gate TFT was finally constructed. The measured current-voltage characteristics exhibited good field-effect mobility exceeding 10 cm2 V-1 s-1. The on/off current ratio and subthreshold slope were 4×105 and 0.86 V/decade, respectively.

Adachi, Susumu; Okamura, Shoichi

2010-10-01

6

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·V-1·s-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·s-1 and was almost independent of the carrier density. The average thermal conductivity was 1.4 W·m-1·K-1.

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

2013-02-01

7

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

E-print Network

It has been previously observed that thin film transistors (TFTs) utilizing an amorphous indium gallium zinc oxide (a-IGZO) semiconducting channel suffer from a threshold voltage shift when subjected to a negative gate bias and light illumination...

Flewitt, Andrew J.; Powell, M.J.

2014-01-01

8

Electrical instability of amorphous indium-gallium-zinc oxide thin film transistors under monochromatic light illumination  

NASA Astrophysics Data System (ADS)

The electrical instability behaviors of a positive-gate-bias-stressed amorphous indium-gallium-zinc oxide (a-IGZO) thin film transistor (TFT) are studied under monochromatic light illumination. It is found that as the wavelength of incident light reduces from 750 nm to 450 nm, the threshold voltage of the illuminated TFT shows a continuous negative shift, which is caused by photo-excitation of trapped electrons at the channel/dielectric interface. Meanwhile, an increase of the sub-threshold swing (SS) is observed when the illumination wavelength is below 625 nm (˜2.0 eV). The SS degradation is accompanied by a simultaneous increase of the field effect mobility (?FE) of the TFT, which then decreases at even shorter wavelength beyond 540 nm (˜2.3 eV). The variation of SS and ?FE is explained by a physical model based on generation of singly ionized oxygen vacancies (Vo+) and double ionized oxygen vacancies (Vo2+) within the a-IGZO active layer by high energy photons, which would form trap states near the mid-gap and the conduction band edge, respectively.

Huang, Xiaoming; Wu, Chenfei; Lu, Hai; Ren, Fangfang; Xu, Qingyu; Ou, Huiling; Zhang, Rong; Zheng, Youdou

2012-06-01

9

Improvement in gate bias stress instability of amorphous indium-gallium-zinc oxide thin-film transistors using microwave irradiation  

NASA Astrophysics Data System (ADS)

In this study, we evaluated the effects of microwave irradiation (MWI) post-deposition-annealing (PDA) treatment on the gate bias stress instability of amorphous indium-gallium-zinc oxide thin-film transistors (a-IGZO TFTs) and compared the results with a conventional thermal annealing PDA treatment. The MWI-PDA-treated a-IGZO TFTs exhibited enhanced electrical performance as well as improved long-term stability with increasing microwave power. The positive turn-on voltage shift (?VON) as a function of stress time with positive bias and varying temperature was precisely modeled on a stretched-exponential equation, suggesting that charge trapping is a dominant mechanism in the instability of MWI-PDA-treated a-IGZO TFTs. The characteristic trapping time and average effective barrier height for electron transport indicate that the MWI-PDA treatment effectively reduces the defects in a-IGZO TFTs, resulting in a superior resistance against gate bias stress.

Jo, Kwang-Won; Cho, Won-Ju

2014-11-01

10

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

SciTech Connect

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

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

2014-04-07

11

Stabilities of amorphous indium gallium zinc oxide thin films under light illumination with various wavelengths and intensities  

NASA Astrophysics Data System (ADS)

We investigated the photo responses of an amorphous indium gallium zinc oxide (a-IGZO) thin film under light illumination with various wavelengths and intensities. By using the measured photo-conductivities of a-IGZO thin films, we extracted the photo excitation activation energy and dark relaxation activation energy through extended stretched exponential analysis. The stretched exponential analysis was found to describe well both the photoexcitation and the dark-relaxation characteristics. These analyses indicated that recombination takes place more slowly and through activation processes that are more deeply bound with the broader distribution of activation energies (Eac) than those corresponding to the photo-generation process. The longer wavelength of the incident light, the slower the dark-relaxation occurs because of the formation of higher Eac for the ionized oxygen vacancy (Vo2+) states. For the dark-relaxation process, we also observed that the stretching exponent increases and the distribution of energy levels became narrower for longer wavelengths. This suggests that the neutralization of Vo2+ to Vo is slower for longer wavelengths due to the higher energy barrier height (Eac) for the neutralization of Vo2+.

Kim, Ju-Yeon; Jeong, So Hyeon; Yu, Kyeong Min; Yun, Eui-Jung; Bae, Byung Seong

2014-08-01

12

Coplanar amorphous-indium-gallium-zinc-oxide thin film transistor with He plasma treated heavily doped layer  

SciTech Connect

We report thermally stable coplanar amorphous-indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs) with heavily doped n{sup +} a-IGZO source/drain regions. Doping is through He plasma treatment in which the resistivity of the a-IGZO decreases from 2.98 ??cm to 2.79?×?10{sup ?3} ??cm after treatment, and then it increases to 7.92?×?10{sup ?2} ??cm after annealing at 300?°C. From the analysis of X-ray photoelectron spectroscopy, the concentration of oxygen vacancies in He plasma treated n{sup +}a-IGZO does not change much after thermal annealing at 300?°C, indicating thermally stable n{sup +} a-IGZO, even for TFTs with channel length L?=?4??m. Field-effect mobility of the coplanar a-IGZO TFTs with He plasma treatment changes from 10.7 to 9.2?cm{sup 2}/V?s after annealing at 300?°C, but the performance of the a-IGZO TFT with Ar or H{sub 2} plasma treatment degrades significantly after 300?°C annealing.

Jeong, Ho-young [Advanced Display Research Center, Department of Information Display, Kyung Hee University, Dongdaemun-gu, Seoul 130-701 (Korea, Republic of); LG Display R and D Center, 245 Lg-ro, Wollong-myeon, Paju-si, Gyeonggi-do 413-811 (Korea, Republic of); Lee, Bok-young; Lee, Young-jang; Lee, Jung-il; Yang, Myoung-su; Kang, In-byeong [LG Display R and D Center, 245 Lg-ro, Wollong-myeon, Paju-si, Gyeonggi-do 413-811 (Korea, Republic of); Mativenga, Mallory; Jang, Jin, E-mail: jjang@khu.ac.kr [Advanced Display Research Center, Department of Information Display, Kyung Hee University, Dongdaemun-gu, Seoul 130-701 (Korea, Republic of)

2014-01-13

13

Microscopic structure and electrical transport property of sputter-deposited amorphous indium-gallium-zinc oxide semiconductor films  

NASA Astrophysics Data System (ADS)

We report on microscopic structures and electrical and optical properties of sputter-deposited amorphous indium-gallium-zinc oxide (a-IGZO) films. From electron microscopy observations and an x-ray small angle scattering analysis, it has been confirmed that the sputtered a-IGZO films consist of a columnar structure. However, krypton gas adsorption measurement revealed that boundaries of the columnar grains are not open-pores. The conductivity of the sputter-deposited a-IGZO films shows a change as large as seven orders of magnitude depending on post-annealing atmosphere; it is increased by N2-annealing and decreased by O2-annealing reversibly, at a temperature as low as 300°C. This large variation in conductivity is attributed to thermionic emission of carrier electrons through potential barriers at the grain boundaries, because temperature dependences of the carrier density and the Hall mobility exhibit thermal activation behaviours. The optical band-gap energy of the a-IGZO films changes between before and after annealing, but is independent of the annealing atmosphere, in contrast to the noticeable dependence of conductivity described above. For exploring other possibilities of a-IGZO, we formed multilayer films with an artificial periodic lattice structure consisting of amorphous InO, GaO, and ZnO layers, as an imitation of the layer-structured InGaZnO4 homologous phase. The hall mobility of the multilayer films was almost constant for thicknesses of the constituent layer between 1 and 6 Å, suggesting rather small contribution of lateral two-dimensional conduction It increased with increasing the thickness in the range from 6 to 15 Å, perhaps owing to an enhancement of two-dimensional conduction in InO layers.

Yabuta, H.; Kaji, N.; Shimada, M.; Aiba, T.; Takada, K.; Omura, H.; Mukaide, T.; Hirosawa, I.; Koganezawa, T.; Kumomi, H.

2014-06-01

14

Electrical features of an amorphous indium-gallium-zinc-oxide film transistor using a double active matrix with different oxygen contents  

NASA Astrophysics Data System (ADS)

The electrical characteristics of amorphous indium-gallium-zinc-oxide (a-IGZO) thin film transistors (TFTs) are systematically studied using a double a-IGZO active layer that is composed of a-IGZO x (oxygen-ion-poor region) and a-IGZO y (oxygen-ion-rich-region). An active layer is designed to have a serially-stacked bi-layer matrix with different oxygen contents, providing the formation of different electron conduction channels. Two different oxygen contents in the active layer are obtained by varying the O2 partial pressure during sputtering. The a-IGZO TFT based on a double active layer exhibits a high mobility of 9.1 cm2/Vsec, a threshold voltage (V T ) of 16.5 V, and ?V T shifts of less than 1.5 V under gate voltage stress. A possible electrical sketch for the double active layer channel is also discussed.

Koo, Ja Hyun; Kang, Tae Sung; Hong, Jin Pyo

2012-05-01

15

Effects of low-temperature (120 °C) annealing on the carrier concentration and trap density in amorphous indium gallium zinc oxide thin film transistors  

NASA Astrophysics Data System (ADS)

We report an investigation of the effects of low-temperature annealing on the electrical properties of amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs). X-ray photoelectron spectroscopy was used to characterize the charge carrier concentration, which is related to the density of oxygen vacancies. The field-effect mobility was found to decrease as a function of the charge carrier concentration, owing to the presence of band-tail states. By employing the transmission line method, we show that the contact resistance did not significantly contribute to the changes in device performance after annealing. In addition, using low-frequency noise analyses, we found that the trap density decreased by a factor of 10 following annealing at 120 °C. The switching operation and on/off ratio of the a-IGZO TFTs improved considerably after low-temperature annealing.

Kim, Jae-sung; Oh, Byung Su; Piao, Mingxing; Joo, Min-Kyu; Jang, Ho-Kyun; Ahn, Seung-Eon; Kim, Gyu-Tae

2014-12-01

16

Back-channel-etch amorphous indium–gallium–zinc oxide thin-film transistors: The impact of source/drain metal etch and final passivation  

NASA Astrophysics Data System (ADS)

We report on the impact of source/drain (S/D) metal (molybdenum) etch and the final passivation (SiO2) layer on the bias-stress stability of back-channel-etch (BCE) configuration based amorphous indium–gallium–zinc oxide (a-IGZO) thin-film transistors (TFTs). It is observed that the BCE configurations TFTs suffer poor bias-stability in comparison to etch-stop-layer (ESL) TFTs. By analysis with transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS), as well as by a comparative analysis of contacts formed by other metals, we infer that this poor bias-stability for BCE transistors having Mo S/D contacts is associated with contamination of the back channel interface, which occurs by Mo-containing deposits on the back channel during the final plasma process of the physical vapor deposited SiO2 passivation.

Nag, Manoj; Bhoolokam, Ajay; Steudel, Soeren; Chasin, Adrian; Myny, Kris; Maas, Joris; Groeseneken, Guido; Heremans, Paul

2014-11-01

17

Improvement of bias-stability in amorphous-indium-gallium-zinc-oxide thin-film transistors by using solution-processed Y2O3 passivation  

NASA Astrophysics Data System (ADS)

We demonstrate back channel improvement of back-channel-etch amorphous-indium-gallium-zinc-oxide (a-IGZO) thin-film transistors by using solution-processed yttrium oxide (Y2O3) passivation. Two different solvents, which are acetonitrile (35%) + ethylene glycol (65%), solvent A and deionized water, solvent B are investigated for the spin-on process of the Y2O3 passivation—performed after patterning source/drain (S/D) Mo electrodes by a conventional HNO3-based wet-etch process. Both solvents yield devices with good performance but those passivated by using solvent B exhibit better light and bias stability. Presence of yttrium at the a-IGZO back interface, where it occupies metal vacancy sites, is confirmed by X-ray photoelectron spectroscopy. The passivation effect of yttrium is more significant when solvent A is used because of the existence of more metal vacancies, given that the alcohol (65% ethylene glycol) in solvent A may dissolve the metal oxide (a-IGZO) through the formation of alkoxides and water.

An, Sungjin; Mativenga, Mallory; Kim, Youngoo; Jang, Jin

2014-08-01

18

Reduction of defect formation in amorphous indium-gallium-zinc-oxide thin film transistors by N{sub 2}O plasma treatment  

SciTech Connect

An abnormal sub-threshold leakage current is observed at high temperature in amorphous indium-gallium-zinc-oxide thin film transistors (a-IGZO TFTs). This phenomenon occurs due to a reduced number of defects in the device's a-IGZO active layer after the device has undergone N{sub 2}O plasma treatment. Experimental verification shows that the N{sub 2}O plasma treatment enhances the thin film bonding strength, thereby suppressing the formation of temperature-dependent holes, which are generated above 400?K by oxygen atoms leaving their original sites. The N{sub 2}O plasma treatment devices have better stability performance than as-fabricated devices. The results suggest that the density of defects for a-IGZO TFTs with N{sub 2}O plasma treatment is much lower than that in as-fabricated devices. The N{sub 2}O plasma treatment repairs the defects and suppresses temperature-dependent sub-threshold leakage current.

Jhu, Jhe-Ciou; Chang, Ting-Chang, E-mail: tcchang@mail.phys.nsysu.edu.tw [Department of Physics and Institute of Electro-Optical Engineering, Center for Nanoscience and Nanotechnology, National Sun Yat-Sen University, Kaohsiung 804, Taiwan (China); Chang, Geng-Wei; Tai, Ya-Hsiang [Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University, Hsin-Chu 300, Taiwan (China); Tsai, Wu-Wei; Chiang, Wen-Jen; Yan, Jing-Yi [Industrial Technology Research Institute, 195, Sec. 4, Chung Hsing Rd., Hsinchu 31040, Taiwan (China)

2013-11-28

19

Influence of Source and Drain Contacts on the Properties of Indium-Gallium-Zinc-Oxide Thin-Film Transistors based on Amorphous Carbon Nanofilm as Barrier Layer.  

PubMed

Amorphous indium-gallium-zinc-oxide thin film transistors (?-IGZO TFTs) with damage-free back channel wet-etch (BCE) process were achieved by introducing a carbon nanofilm as a barrier layer. We investigate the effects of different source-and-drain (S/D) materials on TFT performance. We find the TFT with Ti/C S/D electrodes exhibits a superior performance with higher output current, lower threshold voltage, and higher effective electron mobility compared to that of Mo/C S/D electrodes. Transmittance electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) are employed to analysis the interfacial interaction between S/D metal/C/?-IGZO layers. The results indicate that the better performance of TFTs with Ti/C electrodes should be attributed to the formations of Ti-C and Ti-O at the Ti/C-contact regions, which lead to a lower contact resistance, whereas Mo film is relatively stable and does not react easily with C nanofilm, resulting in a nonohmic contact behavior between Mo/C and ?-IGZO layer. However, both kinds of ?-IGZO TFTs show good stability under thermal bias stress, indicating that the inserted C nanofilms could avoid the impact on the ?-IGZO channel regions during S/D electrodes formation. Finally, we successfully fabricated a high-definition active-matrix organic lighting emitting diode prototype driven by ?-IGZO TFTs with Ti/C electrodes in a pilot line. PMID:25619280

Luo, Dongxiang; Xu, Hua; Zhao, Mingjie; Li, Min; Xu, Miao; Zou, Jianhua; Tao, Hong; Wang, Lei; Peng, Junbiao

2015-02-18

20

Dual operation characteristics of resistance random access memory in indium-gallium-zinc-oxide thin film transistors  

SciTech Connect

In this study, indium-gallium-zinc-oxide thin film transistors can be operated either as transistors or resistance random access memory devices. Before the forming process, current-voltage curve transfer characteristics are observed, and resistance switching characteristics are measured after a forming process. These resistance switching characteristics exhibit two behaviors, and are dominated by different mechanisms. The mode 1 resistance switching behavior is due to oxygen vacancies, while mode 2 is dominated by the formation of an oxygen-rich layer. Furthermore, an easy approach is proposed to reduce power consumption when using these resistance random access memory devices with the amorphous indium-gallium-zinc-oxide thin film transistor.

Yang, Jyun-Bao; Chen, Yu-Ting; Chu, Ann-Kuo [Department of Photonics, National Sun Yat-Sen University, Kaohsiung, Taiwan (China); Chang, Ting-Chang, E-mail: tcchang@mail.phys.nsysu.edu.tw [Department of Photonics, National Sun Yat-Sen University, Kaohsiung, Taiwan (China); Department of Physics, National Sun Yat-Sen University, Kaohsiung, Taiwan (China); Advanced Optoelectronics Technology Center, National Cheng Kung University, Taiwan (China); Huang, Jheng-Jie; Chen, Yu-Chun; Tseng, Hsueh-Chih [Department of Physics, National Sun Yat-Sen University, Kaohsiung, Taiwan (China); Sze, Simon M. [Department of Physics, National Sun Yat-Sen University, Kaohsiung, Taiwan (China); Department of Electronics Engineering, National Chiao Tung University, Hsinchu, Taiwan (China)

2014-04-14

21

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

SciTech Connect

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

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

2014-04-07

22

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

23

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

24

Low-voltage indium gallium zinc oxide thin film transistors on paper substrates  

NASA Astrophysics Data System (ADS)

We have fabricated bottom-gate amorphous (?-) indium-gallium-zinc-oxide (InGaZnO4) thin film transistors (TFTs) on both paper and glass substrates at low processing temperature (?100 °C). As a water and solvent barrier layer, cyclotene (BCB 3022-35 from Dow Chemical) was spin-coated on the entire paper substrate. TFTs on the paper substrates exhibited saturation mobility (?sat) of 1.2 cm2 V-1 s-1, threshold voltage (VTH) of 1.9 V, subthreshold gate-voltage swing (S ) of 0.65 V decade-1, and drain current on-to-off ratio (ION/IOFF) of ˜104. These values were only slightly inferior to those obtained from devices on glass substrates (?sat˜2.1 cm2 V-1 s-1, VTH˜0 V, S ˜0.74 V decade-1, and ION/IOFF=105-106). The uneven surface of the paper sheet led to relatively poor contact resistance between source-drain electrodes and channel layer. The ability to achieve InGaZnO TFTs on cyclotene-coated paper substrates demonstrates the enormous potential for applications such as low-cost and large area electronics.

Lim, Wantae; Douglas, E. A.; Norton, D. P.; Pearton, S. J.; Ren, F.; Heo, Young-Woo; Son, S. Y.; Yuh, J. H.

2010-02-01

25

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

26

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

SciTech Connect

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{sup -} with energies corresponding to the target voltage, which originates from the target and barely from the reactive gas (O{sub 2}). Dissociation of ZnO{sup -}, GaO{sup -}, ZnO{sub 2}{sup -}, and GaO{sub 2}{sup -} 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{sup -} ion flux.

Jia, Junjun; Torigoshi, Yoshifumi; Shigesato, Yuzo [Graduate School of Science and Engineering, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo, Sagamihara, Kanagawa 252-5258 (Japan)

2013-07-01

27

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

28

Effects of electron trapping and interface state generation on bias stress induced in indium-gallium-zinc oxide thin-film transistors  

NASA Astrophysics Data System (ADS)

The electrical characteristics of bias temperature stress (BTS) induced in amorphous indium-gallium-zinc oxide thin-film transistors (a-IGZO TFTs) were studied. We analyzed the threshold voltage (VTH) shift on the basis of the effects of positive bias temperature stress (PBTS) and negative bias temperature stress (NBTS), and applied it to the stretched-exponential model. Both stress temperature and bias are considered as important factors in the electrical instabilities of a-IGZO TFTs, and the stretched-exponential equation is well fitted to the stress condition. VTH for the drain current-gate voltage (IDS-VGS) curve and flat-band voltage (VFB) for the capacitance-voltage (C-V) curve move in the positive direction when PBTS is induced. However, in the case of NBTS, they move slightly in the negative direction. To clarify the VTH shift phenomenon by electron and hole injection, the average effective energy barrier (E?) is extracted, and the extracted values of E? under PBTS and NBTS are about 1.33 and 2.25 eV, respectively. The oxide trap charges (Not) of PBTS and NBTS calculated by C-V measurement are 4.4 × 1011 and 1.49 × 1011 cm-2, respectively. On the other hand, the border trap charges of PBTS and NBTS are 6.7 × 108 and 1.7 × 109 cm-2, respectively. This indicates that the increased interface trap charge, after PBTS is induced, captures electrons during detrap processing from the border trap to the conduction band, valence band, and interface trap.

Han, Chang-Hoon; Kim, Sang-Sub; Kim, Kwang-Ryul; Baek, Do-Hyun; Kim, Sang-Soo; Choi, Byoung-Deog

2014-08-01

29

Defect Analysis of the Indium-Gallium-Zinc-Oxygen System for Transparent Oxide Semiconductor Applications  

NASA Astrophysics Data System (ADS)

The defect chemistry of compounds in the InGaO3(ZnO) k (IGZO) system (k=1, 2, and 3) was investigated via analysis of the dependence of conductivity and thermopower on oxygen partial pressure (pO2) at high temperature (750°C), i.e., Brouwer analysis. Defect mechanisms were deduced based on the resulting Brouwer slopes for all the k-phases, the prevailing point defect species were proposed to be the Ga antisite defect (Ga·Zn ionically compensated by indium vacancies (mathrm{V('''}_{In}) ) donors.The validity of the proposed defect mechanism was supported by density functional theory predictions, which calculated intrinsic defect formation energies in crystalline IGZO and also calculated a theory-based Brouwer slope that was in agreement with experiment. The defect chemistry of IGZO was compared to that of the related In2O3(ZnO)k system in order to infer the role of cation composition in governing electrical properties in crystalline IGZO. There is a change from electronic compensation of antisite defects (in crystalline k=3 In2O3(ZnO) k) to ionic compensation for nearly all compositions in the crystalline IGZO phases. The electrical properties of amorphous IGZO (a-IGZO) were investigated in situ as a function of pO2 at moderate temperature (200°C). A sluggish decay in conductivity was observed and attributed to relaxation within the amorphous structure. Upon abrupt change of pO2, two transients were observed in the electrical property response. The initial response was attributed to a rapid change of surface states. The latter transient, with a time constant approximately an order of magnitude larger than the first, was attributed to bulk diffusion of oxygen. Bulk diffusion was confirmed by 18O tracer diffusion measurements by Isotope Exchange Depth Profiling via Secondary Ion Mass Spectrometry. Through the isolation of the bulk component of the overall conductivity change, it was possible to propose an oxygen vacancy defect mechanism for a-IGZO. To the author's knowledge, this is the first instance where in situ conductivity measurements (Brouwer analysis) has been successfully employed study the point defect chemistry in amorphous oxide (semi)conductor films, providing a complementary technique to ab initio calculations.

Adler, Alexander U.

30

Fourier spectrum based extraction of an equivalent trap state density in indium gallium zinc oxide transistors  

SciTech Connect

Segregating the dynamics of gate bias induced threshold voltage shift, and in particular, charge trapping in thin film transistors (TFTs) based on time constants provides insight into the different mechanisms underlying TFTs instability. In this Letter we develop a representation of the time constants and model the magnitude of charge trapped in the form of an equivalent density of created trap states. This representation is extracted from the Fourier spectrum of the dynamics of charge trapping. Using amorphous In-Ga-Zn-O TFTs as an example, the charge trapping was modeled within an energy range of ?E{sub t}? 0.3?eV and with a density of state distribution as D{sub t}(E{sub t?j})=D{sub t0}exp(??E{sub t}/kT)with D{sub t0}?=?5.02 × 10{sup 11} cm{sup ?2}?eV{sup ?1}. Such a model is useful for developing simulation tools for circuit design.

Thakur, Bikash; Sambandan, Sanjiv, E-mail: sanjiv@iap.iisc.ernet.in [Department of Instrumentation and Applied Physics, Indian Institute of Science, Bangalore 560075 (India); Lee, Sungsik; Nathan, Arokia, E-mail: an299@cam.ac.uk [Electrical Engineering Division, Department of Engineering, University of Cambridge, Cambridge CB3 0FA (United Kingdom); Ahnood, Arman [School of Physics, University of Melbourne, Parkville 3010 VIC (Australia); Jeon, Sanghun, E-mail: jeonsh@korea.ac.kr [Department of Applied Physics, Korea University, 2511 Sejong-ro, Sejong-si 339-700 (Korea, Republic of)

2014-05-19

31

Realization of write-once-read-many-times memory device with O2 plasma-treated indium gallium zinc oxide thin film  

NASA Astrophysics Data System (ADS)

A write-once-read-many-times (WORM) memory devices based on O2 plasma-treated indium gallium zinc oxide (IGZO) thin films has been demonstrated. The device has a simple Al/IGZO/Al structure. The device has a normally OFF state with a very high resistance (e.g., the resistance at 2 V is ˜109 ? for a device with the radius of 50 ?m) as a result of the O2 plasma treatment on the IGZO thin films. The device could be switched to an ON state with a low resistance (e.g., the resistance at 2 V is ˜103 ? for the radius of 50 ?m) by applying a voltage pulse (e.g., 10 V/1 ?s). The WORM device has good data-retention and reading-endurance capabilities.

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

2014-01-01

32

Realization of write-once-read-many-times memory device with O{sub 2} plasma-treated indium gallium zinc oxide thin film  

SciTech Connect

A write-once-read-many-times (WORM) memory devices based on O{sub 2} plasma-treated indium gallium zinc oxide (IGZO) thin films has been demonstrated. The device has a simple Al/IGZO/Al structure. The device has a normally OFF state with a very high resistance (e.g., the resistance at 2?V is ?10{sup 9} ? for a device with the radius of 50??m) as a result of the O{sub 2} plasma treatment on the IGZO thin films. The device could be switched to an ON state with a low resistance (e.g., the resistance at 2?V is ?10{sup 3} ? for the radius of 50??m) by applying a voltage pulse (e.g., 10?V/1??s). The WORM device has good data-retention and reading-endurance capabilities.

Liu, P., E-mail: liup0013@ntu.edu.sg; Chen, T. P., E-mail: echentp@ntu.edu.sg; Li, X. D.; Wong, J. I. [School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798 (Singapore); Liu, Z. [School of Materials and Energy, Guangdong University of Technology, Guangzhou 510006 (China); Liu, Y. [State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, Sichuan 610054 (China); Leong, K. C. [GLOBALFOUNDRIES Singapore Pte Ltd, 60 Woodlands Industrial Park D Street 2, Singapore 738406 (Singapore)

2014-01-20

33

Study of Novel Floating-Gate Oxide Semiconductor Memory Using Indium-Gallium-Zinc Oxide for Low-Power System-on-Panel Applications  

NASA Astrophysics Data System (ADS)

A novel floating-gate oxide semiconductor (FLOTOS) memory using a wide-band-gap indium-gallium-zinc oxide (IGZO) is presented for low-power system-on-panel applications. An IGZO thin-film-transistor (TFT) is used as a memory transistor for controlling read current as well as a switching transistor for storing charges in a storage capacitor (Cs). The FLOTOS memory is fabricated using a standard IGZO TFT process without any additional process or mask steps. The proposed precharge-assisted threshold voltage compensation technique makes it possible to realize an infinite number of write cycles and a low-power write operation with a bit-line voltage of 5 V. Furthermore, excellent data retention longer than 10 h is obtained at 60 °C even under the worst bias-stress condition of read operation with the ultra low off-state leakage (2.8×10-20 A/µm) of the IGZO TFTs, which is estimated to be smaller by more than 7 orders of magnitude than that of polycrystalline silicon TFTs.

Yamauchi, Yoshimitsu; Kamakura, Yoshinari; Isagi, Yousuke; Matsuoka, Toshimasa; Malotaux, Satoshi

2013-09-01

34

Electrical characteristics and short-channel effect of c-axis aligned crystal indium gallium zinc oxide transistor with short channel length  

NASA Astrophysics Data System (ADS)

A channel length of a c-axis aligned crystal indium gallium zinc oxide (CAAC-IGZO) transistor having low off-state current at a yA/µm level was decreased to 100 nm, and the electrical characteristics and short-channel effect of the CAAC-IGZO transistor were researched. As a result, we found that, in the CAAC-IGZO transistor with L = 100 nm, even with a gate insulator film having an equivalent oxide thickness (EOT) = 11 nm, an extremely small off-state current of 380 yA/µm at 85 °C is maintained, in addition channel length dependence of the electrical characteristics is hardly seen. Favorable values of characteristics of the CAAC-IGZO transistor can be obtained, such as subthreshold slope (SS) = 77 mV/dec, drain induced barrier lowering (DIBL) = 73 mV/V, threshold voltage (Vth) = 0.65 V, and on-state current (Ion) = 65 µA/µm. These results suggest the possibility that the CAAC-IGZO transistor can be applied to an LSI in a deep submicron region.

Kobayashi, Yoshiyuki; Matsuda, Shinpei; Matsubayashi, Daisuke; Suzawa, Hideomi; Sakakura, Masayuki; Hanaoka, Kazuya; Okazaki, Yutaka; Yamamoto, Tsutomu; Hondo, Suguru; Hamada, Takashi; Sasagawa, Shinya; Nagai, Masaharu; Hata, Yuki; Maruyama, Tetsunori; Yamamoto, Yoshitaka; Yamazaki, Shunpei

2014-01-01

35

Electrical and Optical Properties of Transparent Conducting Homologous Compounds in the IndiumGalliumZinc Oxide System  

E-print Network

has the cubic bixbyite crystal structure (space group Ia3). Kimizuka et al.9 proposed that these com, smart windows, and solar cells. Tin-doped indium oxide (ITO) is the commercial TCO of choice. ITO thin-laser-deposited tin-doped films, Phillips et al.5 reported conductivities as high as 2500 S/cm for films with a [Zn

Poeppelmeier, Kenneth R.

36

Visible-light-induced instability in amorphous metal-oxide based TFTs for transparent electronics  

SciTech Connect

We investigate the origin of visible-light-induced instability in amorphous metal-oxide based thin film transistors (oxide-TFTs) for transparent electronics by exploring the shift in threshold voltage (V{sub th}). A large hysteresis window in amorphous indium-gallium-zinc-oxide (a-IGZO) TFTs possessing large optical band-gap (?3 eV) was observed in a visible-light illuminated condition whereas no hysteresis window was shown in a dark measuring condition. We also report the instability caused by photo irradiation and prolonged gate bias stress in oxide-TFTs. Larger V{sub th} shift was observed after photo-induced stress combined with a negative gate bias than the sum of that after only illumination stress and only negative gate bias stress. Such results can be explained by trapped charges at the interface of semiconductor/dielectric and/or in the gate dielectric which play a role in a screen effect on the electric field applied by gate voltage, for which we propose that the localized-states-assisted transitions by visible-light absorption can be responsible.

Ha, Tae-Jun [Department of Electronic Materials Engineering, Kwangwoon University, Seoul 139-701 (Korea, Republic of)

2014-10-15

37

Visible-light-induced instability in amorphous metal-oxide based TFTs for transparent electronics  

NASA Astrophysics Data System (ADS)

We investigate the origin of visible-light-induced instability in amorphous metal-oxide based thin film transistors (oxide-TFTs) for transparent electronics by exploring the shift in threshold voltage (Vth). A large hysteresis window in amorphous indium-gallium-zinc-oxide (a-IGZO) TFTs possessing large optical band-gap (?3 eV) was observed in a visible-light illuminated condition whereas no hysteresis window was shown in a dark measuring condition. We also report the instability caused by photo irradiation and prolonged gate bias stress in oxide-TFTs. Larger Vth shift was observed after photo-induced stress combined with a negative gate bias than the sum of that after only illumination stress and only negative gate bias stress. Such results can be explained by trapped charges at the interface of semiconductor/dielectric and/or in the gate dielectric which play a role in a screen effect on the electric field applied by gate voltage, for which we propose that the localized-states-assisted transitions by visible-light absorption can be responsible.

Ha, Tae-Jun

2014-10-01

38

Amorphous indium-tin-zinc oxide films deposited by magnetron sputtering with various reactive gases: Spatial distribution of thin film transistor performance  

NASA Astrophysics Data System (ADS)

This work presents the spatial distribution of electrical characteristics of amorphous indium-tin-zinc oxide film (a-ITZO), and how they depend on the magnetron sputtering conditions using O2, H2O, and N2O as the reactive gases. Experimental results show that the electrical properties of the N2O incorporated a-ITZO film has a weak dependence on the deposition location, which cannot be explained by the bombardment effect of high energy particles, and may be attributed to the difference in the spatial distribution of both the amount and the activity of the reactive gas reaching the substrate surface. The measurement for the performance of a-ITZO thin film transistor (TFT) also suggests that the electrical performance and device uniformity of a-ITZO TFTs can be improved significantly by the N2O introduction into the deposition process, where the field mobility reach to 30.8 cm2 V-1 s-1, which is approximately two times higher than that of the amorphous indium-gallium-zinc oxide TFT.

Jia, Junjun; Torigoshi, Yoshifumi; Kawashima, Emi; Utsuno, Futoshi; Yano, Koki; Shigesato, Yuzo

2015-01-01

39

Field-induced carrier generation in amorphous-InGaZnO4 thin-film transistors  

NASA Astrophysics Data System (ADS)

The positive threshold voltage (VTH) shift induced by positive gate bias stress (PBS) in amorphous-indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs) is commonly attributed to carrier trapping mechanism. Here we show that in addition to these trapping mechanisms, the concentration of donors also increases during PBS when the applied gate bias stress voltage VGS_Stress?30 V. In the early stages of the PBS, this increase in donor concentration may manifest itself as a negative VTH shift. In the case of VGS_Stress?40 V, however, the increase is not detectable because electron trapping at the semiconductor/gate-insulator interface is dominant - even in the early stages of the PBS.

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

2014-09-01

40

Amorphous InGaZnO ultraviolet phototransistors with double-stack Ga2O3/SiO2 dielectric  

NASA Astrophysics Data System (ADS)

This study investigates the electrical performance of amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors with Ga2O3 gate dielectric and applied on deep-ultraviolet phototransistors. To reduce the leakage current, we introduce the SiO2 interlayer dielectric, which effectively reduces the off-current. Under the illumination of 250 nm, the measured responsivity of the device was 3.2 A/W at an applied gate bias of 0 V. The photo-generated carriers were injected into the channel by the applied electric field and Fowler-Nordheim tunneling. A large photocurrent and responsivity can be obtained which is attributed to the high mobility of the a-IGZO channel.

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

2013-06-01

41

Electrical stability enhancement of the amorphous In-Ga-Zn-O thin film transistor by formation of Au nanoparticles on the back-channel surface  

NASA Astrophysics Data System (ADS)

We demonstrate a significant improvement in various electrical instabilities of amorphous indium gallium zinc oxide (a-IGZO) thin film transistor (TFT) by implanting Au nanoparticles (NPs) on the a-IGZO back-channel. This TFT showed the enhanced stability of threshold voltage (Vth) under ambient humidity, illumination stress, and a-IGZO thickness variation tests. Application of back-channel Au NPs to a-IGZO TFT is regarded to control the surface potential, to lead reversible carrier trap/injection, and to increase incident UV light absorption by local surface plasmon. Au NPs are formed by e-beam evaporation, and therefore, this technique can be applicable to the TFT manufacturing process.

Cho, Byungsu; Lee, Jaesang; Seo, Hyungtak; Jeon, Hyeongtag

2013-03-01

42

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

43

Investigation on the negative bias illumination stress-induced instability of amorphous indium-tin-zinc-oxide thin film transistors  

NASA Astrophysics Data System (ADS)

The quantitative analysis of mechanism on negative bias illumination stress (NBIS)-induced instability of amorphous indium-tin-zinc-oxide thin-film transistor (TFT) was suggested along with the effect of equivalent oxide thickness (EOT) of gate insulator. The analysis was implemented through combining the experimentally extracted density of subgap states and the device simulation. During NBIS, it was observed that the thicker EOT causes increase in both the shift of threshold voltage and the variation of subthreshold swing as well as the hump-like feature in a transfer curve. We found that the EOT-dependence of NBIS instability can be clearly explicated with the donor creation model, in which a larger amount of valence band tail states is transformed into either the ionized oxygen vacancy VO2+ or peroxide O22- with the increase of EOT. It was also found that the VO2+-related extrinsic factor accounts for 80%-92% of the total donor creation taking place in the valence band tail states while the rest is taken by the O22- related intrinsic factor. The ratio of extrinsic factor compared to the total donor creation also increased with the increase of EOT, which could be explained by more prominent oxygen deficiency. The key founding of our work certainly represents that the established model should be considered very effective for analyzing the instability of the post-indium-gallium-zinc-oxide (IGZO) ZnO-based compound semiconductor TFTs with the mobility, which is much higher than those of a-IGZO TFTs.

Jang, Jaeman; Kim, Dae Geun; Kim, Dong Myong; Choi, Sung-Jin; Lim, Jun-Hyung; Lee, Je-Hun; Kim, Yong-Sung; Ahn, Byung Du; Kim, Dae Hwan

2014-10-01

44

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

45

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

NASA Astrophysics Data System (ADS)

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

Vemuri, Rajitha

46

Deep-level transient spectroscopy on an amorphous InGaZnO{sub 4} Schottky diode  

SciTech Connect

The first direct measurement is reported of the bulk density of deep states in amorphous IGZO (indium-gallium-zinc oxide) semiconductor by means of deep-level transient spectroscopy (DLTS). The device under test is a Schottky diode of amorphous IGZO semiconductor on a palladium (Pd) Schottky-barrier electrode and with a molybdenum (Mo) Ohmic contact at the top. The DLTS technique allows to independently measure the energy and spatial distribution of subgap states in the IGZO thin film. The subgap trap concentration has a double exponential distribution as a function energy, with a value of ?10{sup 19}?cm{sup ?3}?eV{sup ?1} at the conduction band edge and a value of ?10{sup 17}?cm{sup ?3}?eV{sup ?1} at an energy of 0.55?eV below the conduction band. Such spectral distribution, however, is not uniform through the semiconductor film. The spatial distribution of subgap states correlates well with the background doping density distribution in the semiconductor, which increases towards the Ohmic Mo contact, suggesting that these two properties share the same physical origin.

Chasin, Adrian, E-mail: adrian.chasin@imec.be; Bhoolokam, Ajay; Nag, Manoj; Genoe, Jan; Heremans, Paul [imec, Kapeldreef 75, 3001 Leuven (Belgium); ESAT, KU Leuven, Kasteelpark Arenberg 10, 3001 Leuven (Belgium); Simoen, Eddy [imec, Kapeldreef 75, 3001 Leuven (Belgium); Department of Solid State Sciences, Ghent University, Krijgslaan 281-S1, 9000 Gent (Belgium); Gielen, Georges [ESAT, KU Leuven, Kasteelpark Arenberg 10, 3001 Leuven (Belgium)

2014-02-24

47

Influence of an anomalous dimension effect on thermal instability in amorphous-InGaZnO thin-film transistors  

SciTech Connect

This paper investigates abnormal dimension-dependent thermal instability in amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors. Device dimension should theoretically have no effects on threshold voltage, except for in short channel devices. Unlike short channel drain-induced source barrier lowering effect, threshold voltage increases with increasing drain voltage. Furthermore, for devices with either a relatively large channel width or a short channel length, the output drain current decreases instead of saturating with an increase in drain voltage. Moreover, the wider the channel and the shorter the channel length, the larger the threshold voltage and output on-state current degradation that is observed. Because of the surrounding oxide and other thermal insulating material and the low thermal conductivity of the IGZO layer, the self-heating effect will be pronounced in wider/shorter channel length devices and those with a larger operating drain bias. To further clarify the physical mechanism, fast I{sub D}-V{sub G} and modulated peak/base pulse time I{sub D}-V{sub D} measurements are utilized to demonstrate the self-heating induced anomalous dimension-dependent threshold voltage variation and on-state current degradation.

Liu, Kuan-Hsien; Chou, Wu-Ching, E-mail: tcchang3708@gmail.com, E-mail: wuchingchou@mail.nctu.edu.tw [Department of Electrophysics, National Chiao Tung University, Hsin-chu 300, Taiwan (China); Chang, Ting-Chang, E-mail: tcchang3708@gmail.com, E-mail: wuchingchou@mail.nctu.edu.tw [Department of Physics, National Sun Yat-Sen University, Kaohsiung 804, Taiwan (China); Advanced Optoelectronics Technology Center, National Cheng Kung University, Taiwan (China); Chen, Hua-Mao; Tai, Ya-Hsiang [Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University, Hsin-chu 300, Taiwan (China); Tsai, Ming-Yen; Hung, Pei-Hua; Chu, Ann-Kuo [Department of Photonics, National Sun Yat-Sen University, Kaohsiung 804, Taiwan (China); Wu, Ming-Siou; Hung, Yi-Syuan [Department of Electronics Engineering, National Chiao Tung University, Hsin-Chu 300, Taiwan (China); Hsieh, Tien-Yu [Department of Physics, National Sun Yat-Sen University, Kaohsiung 804, Taiwan (China); Yeh, Bo-Liang [Advanced Display Technology Research Center, AU Optronics, No.1, Li-Hsin Rd. 2, Hsinchu Science Park, Hsin-Chu 30078, Taiwan (China)

2014-10-21

48

Highly Effective Field-Effect Mobility Amorphous InGaZnO TFT Mediated by Directional Silver Nanowire Arrays.  

PubMed

In this work, we demonstrate sputtered amorphous indium-gallium-zinc oxide thin-film transistors (a-IGZO TFTs) with a record high effective field-effect mobility of 174 cm(2)/V s by incorporating silver nanowire (AgNW) arrays to channel electron transport. Compared to the reference counterpart without nanowires, the over 5-fold enhancement in the effective field-effect mobility exhibits clear dependence on the orientation as well as the surface coverage ratio of silver nanowires. Detailed material and device analyses reveal that during the room-temperature IGZO sputtering indium and oxygen diffuse into the nanowire matrix while the nanowire morphology and good contact between IGZO and nanowires are maintained. The unchanged morphology and good interfacial contact lead to high mobility and air-ambient-stable characteristics up to 3 months. Neither hysteresis nor degraded bias stress reliability is observed. The proposed AgNW-mediated a-IGZO TFTs are promising for development of large-scale, flexible, transparent electronics. PMID:25485556

Liu, Hung-Chuan; Lai, Yi-Chun; Lai, Chih-Chung; Wu, Bing-Shu; Zan, Hsiao-Wen; Yu, Peichen; Chueh, Yu-Lun; Tsai, Chuang-Chuang

2015-01-14

49

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

50

High Performance, Low Temperature Solution-Processed Barium and Strontium Doped Oxide Thin Film Transistors.  

PubMed

Amorphous mixed metal oxides are emerging as high performance semiconductors for thin film transistor (TFT) applications, with indium gallium zinc oxide, InGaZnO (IGZO), being one of the most widely studied and best performing systems. Here, we investigate alkaline earth (barium or strontium) doped InBa(Sr)ZnO as alternative, semiconducting channel layers and compare their performance of the electrical stress stability with IGZO. In films fabricated by solution-processing from metal alkoxide precursors and annealed to 450 °C we achieve high field-effect electron mobility up to 26 cm(2) V(-1) s(-1). We show that it is possible to solution-process these materials at low process temperature (225-200 °C yielding mobilities up to 4.4 cm(2) V(-1) s(-1)) and demonstrate a facile "ink-on-demand" process for these materials which utilizes the alcoholysis reaction of alkyl metal precursors to negate the need for complex synthesis and purification protocols. Electrical bias stress measurements which can serve as a figure of merit for performance stability for a TFT device reveal Sr- and Ba-doped semiconductors to exhibit enhanced electrical stability and reduced threshold voltage shift compared to IGZO irrespective of the process temperature and preparation method. This enhancement in stability can be attributed to the higher Gibbs energy of oxidation of barium and strontium compared to gallium. PMID:24511184

Banger, Kulbinder K; Peterson, Rebecca L; Mori, Kiyotaka; Yamashita, Yoshihisa; Leedham, Timothy; Sirringhaus, Henning

2014-01-28

51

Control of threshold voltage in ZnO-based oxide thin film transistors  

NASA Astrophysics Data System (ADS)

We investigated the feasibility of controlling the threshold voltage (Vth) by adjusting the thickness of the active layer (tactive) rather than by conventional chemical doping in indium-gallium-zinc oxide (IGZO) transistors with an inverted staggered structure. The value of Vth of the IGZO transistor was linearly modulated from -15.3±1.6to-0.1±0.21V by reducing tactive without any significant change in the field-effect mobility (?FE), subthreshold gate swing, or Ion/off ratio. The free electron density extracted from the relationship between tactive and Vth was 1.9×1017cm-3, which was consistent with the value of 1.5×1017cm-3 obtained from the C-V measurement for the 30-nm-thick IGZO films. The slight increase in the ?FE with increasing tactive, which was in contradiction with the behavior of the corresponding amorphous Si transistor, was explained by the anomalous behavior of the source/drain contact resistance.

Park, Jin-Seong; Jeong, Jae Kyeong; Mo, Yeon-Gon; Kim, Hye Dong; Kim, Chang-Jung

2008-07-01

52

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

53

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

54

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; Görrn, Patrick; Riedl, Thomas

2013-05-28

55

Effect of Deposition Temperature of SiOx Passivation Layer on the Electrical Performance of a-IGZO TFTs  

Microsoft Academic Search

We investigated the effect of the deposition temperature on the electrical performance of SiOx passivation layers for amorphous indium-gallium-zinc-oxide thin-film transistors (a-IGZO TFTs). Compared to the time-of-flight secondary ion mass spectroscopy depth profile of the IGZO film with a SiOx passivation layer deposited at low temperature (150 $^{\\\\circ}\\\\hbox{C}$), that with the SiOx film formed at 300 $^{\\\\circ}\\\\hbox{C}$ exhibited the significant

Sung-Hwan Choi; Min-Koo Han

2012-01-01

56

The effect of nitrous oxide plasma treatment on the bias temperature stress of metal oxide thin film transistors with high mobility  

NASA Astrophysics Data System (ADS)

In this work, the effects of nitrous oxide plasma treatment on the negative bias temperature stress of indium tin zinc oxide (ITZO) and indium gallium zinc oxide (IGZO) thin film transistors (TFTs) were reported. ITZO TFTs were more suitable for the back channel etched-type device structure because they could withstand both Al- and Cu-acid damage. The initial threshold voltage range could be controlled to within 1 V. The root cause of poor negative bias temperature stress for ITZO was likely due to a higher mobility (?3.3 times) and more carbon related contamination bonds (?5.9 times) relative to IGZO. Finally, 65? active-matrix organic light-emitting diode televisions using the ITZO and IGZO TFTs were fabricated.

Tseng, Wei-Hao; Fang, Shao-Wei; Lu, Chia-Yang; Chuang, Hung-Yang; Chang, Fan-Wei; Lin, Guan-Yu; Chen, Tsu-Wei; Ma, Kang-Hung; Chen, Hong-Syu; Chen, Teng-Ke; Chen, Yu-Hung; Lee, Jen-Yu; Shih, Tsung-Hsiang; Ting, Hung-Che; Chen, Chia-Yu; Lin, Yu-Hsin; Hong, Hong-Jye

2015-01-01

57

Origin of major donor states in In-Ga-Zn oxide  

NASA Astrophysics Data System (ADS)

To clarify the origin of the major donor states in indium gallium zinc oxide (IGZO), we report measurement results and an analysis of several physical properties of IGZO thin films. Specifically, the concentration of H atoms and O vacancies (VO), carrier concentration, and conductivity are investigated by hard X-ray photoelectron spectroscopy, secondary ion mass spectroscopy, thermal desorption spectroscopy, and Hall effect measurements. The results of these experiments suggest that the origin of major donor states is H occupancy of VO sites. Furthermore, we use first-principles calculations to investigate the influence of the coexistence of VO and H in crystalline InGaO3(ZnO)m (m = 1). The results indicate that when H is trapped in VO, a stable complex is created that serves as a shallow-level donor.

Nakashima, Motoki; Oota, Masashi; Ishihara, Noritaka; Nonaka, Yusuke; Hirohashi, Takuya; Takahashi, Masahiro; Yamazaki, Shunpei; Obonai, Toshimitsu; Hosaka, Yasuharu; Koezuka, Junichi

2014-12-01

58

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

59

Characterization of Amorphous Zinc Tin Oxide Semiconductors  

SciTech Connect

Amorphous zinc tin oxide (ZTO) was investigated to determine the effect of deposition and post annealing conditions on film structure, composition, surface contamination, and thin film transistor (TFT) device performance. X-ray diffraction results indicated that the ZTO films remain amorphous even after annealing to 600 °C. We found that the bulk Zn:Sn ratio of the sputter deposited films were slightly tin rich compared to the composition of the ceramic sputter target, and there was a significant depletion of zinc at the surface. X-ray photoelectron spectroscopy also indicated that residual surface contamination depended strongly on the sample post-annealing conditions where water, carbonate and hydroxyl species were absorbed to the surface. Electrical characterization of ZTO films, using TFT test structures, indicated that mobilities as high as 17 cm2/Vs could be obtained for depletion mode devices.

Rajachidambaram, Jaana Saranya; Sanghavi, Shail P.; Nachimuthu, Ponnusamy; Shutthanandan, V.; Varga, Tamas; Flynn, Brendan T.; Thevuthasan, Suntharampillai; Herman, Gregory S.

2012-06-12

60

Reduced graphene oxide/InGaZn mixed oxide nanocomposite photocatalysts for hydrogen production.  

PubMed

A series of reduced graphene oxide and indium-gallium-zinc mixed oxide (RGO/IGZ) nanocomposites were successfully synthesised by a simple one-step hydrothermal method. The as-synthesised nanocomposites were characterised by crystallographic, microscopic, and spectroscopic methods to explore the robust photocatalytic activity of the prepared materials. XRD patterns confirmed the formation of highly pure, single-phase, hexagonal In2 Ga2 ZnO7 with no impurity-related peaks. All the photocatalysts absorbed visible light as observed from the diffuse reflectance UV/Vis spectra. The electron-hole recombination is effectively minimised by the formation of an RGO/metal oxide nanocomposite, which was successfully derived from a photoluminescence (PL) study and photoelectrochemical measurements. The decoration of IGZ nanocrystals onto reduced graphene sheets leads to significant quenching of its luminescent intensity, dramatically improved photocurrent generation (33 times more than neat IGZ) and significantly enhanced photostability. The high photocatalytic activity for H2 production is explained by the strong interaction between the IGZ nanocrystals with RGO sheets, low PL intensity, high photocurrent and large surface area. PMID:24127386

Martha, Satyabadi; Padhi, Deepak Ku; Parida, Kulamani

2014-02-01

61

Oxidation of antimony (III) by amorphous iron and manganese oxyhydroxides  

Microsoft Academic Search

Amorphous forms of natural and synthetic Fe oxyhydroxides and synthetic Mn oxyhydroxides were used to study the oxidation of antimonite, Sb(III), at different pH values. Sb species were measured by differential pulse adsorptive stripping voltametry (DPACSV). The oxidation of Sb(III) to Sb(V) was always rapid and completed after a few days following pseudo-first order rate laws. A slightly slower oxidation

Nelson Belzile; Yu-Wei Chen; Zijian Wang

2001-01-01

62

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

63

Ambient atmosphere-processable, printable Cu electrodes for flexible device applications: structural welding on a millisecond timescale of surface oxide-free Cu nanoparticles.  

PubMed

Recently, various functional devices based on printing technologies have been of paramount interest, owing to their characteristic processing advantages along with excellent device performance. In particular, printable metallic electrodes have drawn attention in a variety of optoelectronic applications; however, research into printable metallic nanoparticles has been limited mainly to the case of an environmentally stable Ag phase. Despite its earth-abundance and highly conductive nature, the Cu phase, to date, has not been exploited as an ambient atmosphere-processable, printable material due to its critical oxidation problem in air. In this study, we demonstrate a facile route for generating highly conductive, flexible Cu electrodes in air by introducing the well-optimized photonic sintering at a time frame of 10(-3) s, at which the photon energy, rather than conventional thermal energy, is instantly provided. It is elucidated here how the surface oxide-free, printed Cu particulate films undergo chemical structural/microstructural evolution depending on the instantly irradiated photon energy, and a successful demonstration is provided of large-area, flexible, printed Cu conductors on various substrates, including polyimide (PI), polyethersulfone (PES), polyethylene terephthalate (PET), and paper. The applicability of the resulting printed Cu electrodes is evaluated via implementation into both flexible capacitor devices and indium-gallium-zinc oxide (IGZO) flexible thin-film transistors. PMID:25626472

Oh, Sang-Jin; Jo, Yejin; Lee, Eun Jung; Lee, Sun Sook; Kang, Young Hun; Jeon, Hye-Ji; Cho, Song Yun; Park, Jin-Seong; Seo, Yeong-Hui; Ryu, Beyong-Hwan; Choi, Youngmin; Jeong, Sunho

2015-02-19

64

Synthesis and frictional properties of array film of amorphous carbon nanofibers on anodic aluminum oxide  

Microsoft Academic Search

Amorphous carbon nanofiber arrays were synthesized in porous anodic aluminum oxide templates by pyrolysis of acetylene with cobalt nanoparticles as catalyst at 640°C. The carbon nanofibers have amorphous structures under high-resolution transmission electron microscopy and Raman spectroscopy examination. The aligned amorphous carbon nanofibers grown within the pores of the aluminum oxide membranes are uniform with lengths of about 2 ?m

J. P. Tu; L. P. Zhu; K. Hou; S. Y. Guo

2003-01-01

65

Crystallization process and magnetic properties of amorphous iron oxide nanoparticles  

NASA Astrophysics Data System (ADS)

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 ?-Fe2O3 (with an activation energy of 0.71 eV) and the hematite ?-Fe2O3 (with an activation energy of 0.97 eV) phase occurred at around 300 °C and 350 °C, respectively. A transition from the maghemite to the hematite occurred at 500 °C with an activation energy of 1.32 eV. A study of the temperature dependence of magnetization supported the crystallization and the phase transformation. Raman shift at 660 cm-1 and absorption band in the infrared spectra at 690 cm-1 showed the presence of disorder in the hematite phase on the nanoscale which is supposed to be the origin of the ferromagnetic behaviour of that antiferromagnetic phase.

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

2011-08-01

66

Transparent amorphous zinc oxide thin films for NLO applications  

NASA Astrophysics Data System (ADS)

This review focuses on the growth and optical properties of amorphous zinc oxide (ZnO) thin films. A high quality ZnO films fabricated by dip-coating (sol-gel) method were grown on quartz and glass substrates at temperature equal to 350 K. The amorphous nature of the films was verified by X-ray diffraction. Atomic Force Microscopy was used to evaluate the surface morphology of the films. The optical characteristics of amorphous thin films have been investigated in the spectral range 190-1100 nm. Measurement of the polarized optical properties was shows a high transmissivity (80-99%) and low absorptivity (<5%) in the visible and near infrared regions at different angles of incidence. Linear optical properties were investigated by classic and Time-Resolved Photoluminescence (TRPL) measurements. Photoluminescence spectrum exhibits a strong ultraviolet emission while the visible emission is very weak. An innovative TRPL technique has enabled the measurement of the photoluminescence decay time as a function of temperature. TRPL measurements reveal a multiexponential decay behavior typical for amorphous thin films. Second and third harmonic generation measurements were performed by means of the rotational Maker fringe technique using Nd:YAG laser at 1064 nm in picosecond regime for investigations of the nonlinear optical properties. The obtained values of second and third order nonlinear susceptibilities were found to be high enough for the potential applications in the optical switching devices based on refractive index changes. Presented spectra confirm high structural and optical quality of the investigated zinc oxide thin films.

Zawadzka, A.; P?óciennik, P.; Strzelecki, J.; Sahraoui, B.

2014-11-01

67

Transparent conducting oxides (TCO's) for amorphous silicon solar cells  

NASA Astrophysics Data System (ADS)

The stability of various textured tin oxide and zinc oxide transparent conductors was evaluated against annealing in air, in vacuum or exposed to hydrogen plasma. Only fluorine-doped zinc oxide deposited by atmospheric pressure chemical vapor deposition (APCVD) had stable electrical and optical properties under all conditions. Thin layers of ZnO or TiO2 greatly improved the plasma resistance of SnO2. A new TCO material, niobium-doped titanium dioxide (TiO2:Nb) was able to withstand hydrogen plasmas with only slight increases in its optical absorption and conductivity. Composite TCO's consisting of glass/SnO2:F/TiO2:Nb were shown to provide good electrical contact to amorphous silicon solar cells.

Hegedus, Steven; Liang, Haifan; Gordon, Roy G.

1996-01-01

68

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

E-print Network

Better than crystalline: amorphous vanadium oxide for sodium-ion batteries E. Uchaker, Y. Z. Zheng, S. Li, S. L. Candelaria, S. Hu and G. Z. Cao* Amorphous and nanocrystalline vanadium pentoxide (V2O5 properties upon sodiation as compared to its crystalline counterpart. More specifically, amorphous vanadium

Cao, Guozhong

69

Indium tin oxide and the amorphous-crystalline silicon heterojunction  

NASA Astrophysics Data System (ADS)

Amorphous silicon-crystalline silicon heterojunctions were prepared using the DC saddle-field plasma enhanced chemical vapour deposition (DCSF-PECVD) technique followed by RF magnetron sputtering of an indium tin oxide (ITO) layer on the nano-thin amorphous film. Depth dependent time of flight secondary ion mass spectrometry (ToF-SIMS) analysis was carried out in order to examine the compositional influence of the sputtered ITO on the underlying amorphous silicon layers. Three samples were analyzed: one, as deposited, a-Si:H/c-Si heterojunction; two, ITO covered a-Si:H/c-Si heterojunction; and three, similar to sample two but now dipped in 10% HCl in order to etch the ITO prior to SIMS analysis. The pre-treatment of the third sample was done to de-couple potential SIMS sputtering-induced implantation of indium, tin, and oxygen in the underlying silicon layers. SIMS analysis shows indium, tin, and oxygen below the surface of the silicon in both the etched and as-deposited samples. AFM analysis of all the samples was also done, indicating that the ITO surface has a high degree of roughness, which could make uniform etching more difficult and could potentially lead to small residual ITO spots on the surface, creating or enhancing the appearance of mixing in the SIMS results for the etched sample.

Halliop, Basia; Gougam, Adel; Kherani, Nazir P.; Zukotynski, Stefan

2010-06-01

70

Unification of catalytic water oxidation and oxygen reduction reactions: amorphous beat crystalline cobalt iron oxides.  

PubMed

Catalytic water splitting to hydrogen and oxygen is considered as one of the convenient routes for the sustainable energy conversion. Bifunctional catalysts for the electrocatalytic oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) are pivotal for the energy conversion and storage, and alternatively, the photochemical water oxidation in biomimetic fashion is also considered as the most useful way to convert solar energy into chemical energy. Here we present a facile solvothermal route to control the synthesis of amorphous and crystalline cobalt iron oxides by controlling the crystallinity of the materials with changing solvent and reaction time and further utilize these materials as multifunctional catalysts for the unification of photochemical and electrochemical water oxidation as well as for the oxygen reduction reaction. Notably, the amorphous cobalt iron oxide produces superior catalytic activity over the crystalline one under photochemical and electrochemical water oxidation and oxygen reduction conditions. PMID:25469760

Indra, Arindam; Menezes, Prashanth W; Sahraie, Nastaran Ranjbar; Bergmann, Arno; Das, Chittaranjan; Tallarida, Massimo; Schmeißer, Dieter; Strasser, Peter; Driess, Matthias

2014-12-17

71

Comparison Between Crystalline and Amorphous Surfaces of Transition Metal Oxide Water Oxidation Catalysts: a Theoretical Perspective  

NASA Astrophysics Data System (ADS)

Amorphous films of transition-metal oxide water oxidation catalysts (WOCs) often show an enhanced catalytic activity compared to their crystalline counterparts [1-4]. In particular, in the case of cobalt-oxide based WOCs the observed similarity in their electrochemical properties and catalytic activity, under oxidative conditions, has been correlated with the formation of similar amorphous surface morphologies, suggesting the presence of a common, catalytically active amorphous structural motif [3,4]. We present ab initio calculations of cobalt oxide based material surfaces and we compare the electronic properties of crystalline and amorphous surfaces, with the aim of identifying differences related to their different catalytic activity.[4pt] [1] Blakemore, J. D., Schley, N. D., Kushner-Lenhoff, M. N., Winter, A. M., D'Souza, F., Crabtree, R. H., and Brudvig, G. W. Inorg. Chem. 51, 7749 (2012); [2] Tsuji, E., Imanishi, A., Fukui, K.-I. and Nakato, Y. Electrochimica Acta 56, 2009 (2011); [3] Jia, H., Stark, J., Zhou, L. Q., Ling, C., Takeshi, S., and Markin, Z. RSC Advances 2, 10874 (2012); [4] Lee, S. W., Carlton, C., Risch, M., Surendranath, Y., Chen, S., Furutsuki, S., Yamada, A., Nocera, D. G., and Shao-Horn, Y. J. Am. Chem. Soc. 134, 16959 (2012).

Skone, Jonathan H.; Galli, Giulia

2013-03-01

72

Ultrathin amorphous zinc-tin-oxide buffer layer for enhancing heterojunction interface quality in metal-oxide solar cells  

E-print Network

We demonstrate a tunable electron-blocking layer to enhance the performance of an Earth-abundant metal-oxide solar-cell material. A 5 nm thick amorphous ternary metal-oxide buffer layer reduces interface recombination, ...

Heo, Jaeyeong

73

Carrier-Induced Lattice Instability in Amorphous Oxide Semiconductors  

NASA Astrophysics Data System (ADS)

Amorphous oxide semiconductors (AOS's) have high electron mobility even in amorphous phase. The AOS-based thin film transistors (TFTs) are nowadays intensively pursued to be adopted into high-resolution flat-panel displays. However, a facing bottleneck of the AOS-based TFT display applications is the instability problem under bias and illumination stress conditions. Especially, by negative bias and illumination stress (NBIS) or only by illumination stress (IS), the threshold voltage of the AOS TFTs is largely negative-shifted. In this work, we study the instability mechanism of the AOS's based on first-principles calculations. The valence band tail states of the AOS's are found to be characterized by the O-O pp?* anti-bonding state. The excited localized-holes thus give lattice instability and form O-O bonds through the pp?-hybridized interaction. The pp?* level is heightened up into the conduction bands along with the O-O bond formation, and two electrons left from the created O-vacancy (VO) occupy the delocalized conduction band states. The O-O and VO complex (a peroxide defect) is found to be a meta-stable donor defect and suggested as an origin of the NBIS and IS instabilities in AOS TFTs. Based on the suggested mechanism, we propose a direction to improve the stability of AOS thin films with optimizing the cation compositions.

Kim, Yong-Sung; Nahm, Ho-Hyun; Kim, Dae-Hwan

2013-03-01

74

Low operating voltage InGaZnO thin-film transistors based on Al2O3 high- k dielectrics fabricated using pulsed laser deposition  

NASA Astrophysics Data System (ADS)

Low-voltage-driven amorphous indium-gallium-zinc-oxide (IGZO) thin-film transistors (TFTs) with an Al2O3 dielectric were fabricated on a Si substrate by using pulsed laser deposition. Both Al2O3 and IGZO thin films are amorphous, and the thin films have very smooth surfaces. The Al2O3 gate dielectric exhibits a very low leakage current density of 1.3 × 10-8 A/cm2 at 5 V and a high capacitance density of 60.9 nF/cm2. The IGZO TFT with a structure of Ni/IGZO/Al2O3/Si exhibits high performance with a low threshold voltage of 1.18 V, a high field effect mobility of 20.25 cm2V-1s-1, an ultra small subthreshold swing of 87 mV/decade, and a high on/off current ratio of 3 × 107.

Geng, G. Z.; Liu, G. X.; Zhang, Q.; Shan, F. K.; Lee, W. J.; Shin, B. C.; Cho, C. R.

2014-05-01

75

Graphitic carbon growth on crystalline and amorphous oxide substrates using molecular beam epitaxy  

PubMed Central

We report graphitic carbon growth on crystalline and amorphous oxide substrates by using carbon molecular beam epitaxy. The films are characterized by Raman spectroscopy and X-ray photoelectron spectroscopy. The formations of nanocrystalline graphite are observed on silicon dioxide and glass, while mainly sp2 amorphous carbons are formed on strontium titanate and yttria-stabilized zirconia. Interestingly, flat carbon layers with high degree of graphitization are formed even on amorphous oxides. Our results provide a progress toward direct graphene growth on oxide materials. PACS: 81.05.uf; 81.15.Hi; 78.30.Ly. PMID:22029707

2011-01-01

76

Investigation of channel width-dependent threshold voltage variation in a-InGaZnO thin-film transistors  

SciTech Connect

This Letter investigates abnormal channel width-dependent threshold voltage variation in amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors. Unlike drain-induced source barrier lowering effect, threshold voltage increases with increasing drain voltage. Furthermore, the wider the channel, the larger the threshold voltage observed. Because of the surrounding oxide and other thermal insulating material and the low thermal conductivity of the IGZO layer, the self-heating effect will be pronounced in wider channel devices and those with a larger operating drain bias. To further clarify the physical mechanism, fast IV measurement is utilized to demonstrate the self-heating induced anomalous channel width-dependent threshold voltage variation.

Liu, Kuan-Hsien; Chou, Wu-Ching [Department of Electrophysics, National Chiao Tung University, Hsinchu, Taiwan (China); Chang, Ting-Chang, E-mail: tcchang@mail.phys.nsysu.edu.tw [Department of Physics, National Sun Yat-Sen University, Kaohsiung 804, Taiwan (China); Advanced Optoelectronics Technology Center, National Cheng Kung University, Taiwan (China); Wu, Ming-Siou; Hung, Yi-Syuan; Sze, Simon M. [Department of Electronics Engineering, National Chiao Tung University, Hsinchu, Taiwan (China); Hung, Pei-Hua; Chu, Ann-Kuo [Department of Photonics, National Sun Yat-Sen University, Kaohsiung 804, Taiwan (China); Hsieh, Tien-Yu [Department of Physics, National Sun Yat-Sen University, Kaohsiung 804, Taiwan (China); Yeh, Bo-Liang [Advanced Display Technology Research Center, AU Optronics, No. 1, Li-Hsin Rd. 2, Hsinchu Science Park, Hsinchu 30078, Taiwan (China)

2014-03-31

77

Fabrication of amorphous silicon nanoribbons by atomic force microscope tip induced local oxidation for thin film device applications  

E-print Network

1 Fabrication of amorphous silicon nanoribbons by atomic force microscope tip induced local We demonstrate the feasibility of induced local oxidation of amorphous silicon by atomic force. A thin amorphous silicon layer deposited on a glass substrate is locally oxidized following narrow

Paris-Sud XI, Université de

78

Phosphate and Organic Acids as Competing Sorbates on Amorphous Aluminum Oxide. (3791)  

E-print Network

Phosphate and Organic Acids as Competing Sorbates on Amorphous Aluminum Oxide. (3791) Authors: K that organics (i.e. oxalic acid), readily present in PL, play in P retention under varying pH conditions

Sparks, Donald L.

79

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

E-print Network

FORMATION OF THIN FILM Tl-BASED HIGH-Tc SUPERCONDUCTING OXIDES FROM AMORPHOUS ALLOY PRECURSORS A Thesis JOHN CHARLES WILLIAMS Submitted to the Once of Graduate Studies of Texas A&M University in partial fulfillment of the requirements... for the degree of MASTER OF SCIENCE December 1991 Major Subject: Physics FORMATION OF THIN FILM Tl BASED HIGH Tc SUPERCONDUCTING OXIDES FROM AMORPHOUS ALLOY PRECURSORS A Thesis JOHN CHARLES WILLIAMS Approved as to style and content by: Donald G. Naugle...

Williams, John Charles

2012-06-07

80

Probing of 2 dimensional confinement-induced structural transitions in amorphous oxide thin film  

PubMed Central

Whereas the atomic structure of surface of crystals is known to be distinct from that of bulk, experimental evidence for thickness-induced structural transitions in amorphous oxides is lacking. We report the NMR result for amorphous alumina with varying thickness from bulk up to 5?nm, revealing the nature of structural transitions near amorphous oxide surfaces/interfaces. The coordination environments in the confined amorphous alumina thin film are distinct from those of bulk, highlighted by a decrease in the fractions of high-energy clusters (and thus the degree of disorder) with thickness. The result implies that a wide range of variations in amorphous structures may be identified by controlling its dimensionality. PMID:24569515

Lee, Sung Keun; Ahn, Chi Won

2014-01-01

81

Electrically conducting ternary amorphous fully oxidized materials and their application  

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

82

The effects of buffer layers on the performance and stability of flexible InGaZnO thin film transistors on polyimide substrates  

SciTech Connect

We demonstrated the fabrication of flexible amorphous indium gallium zinc oxide thin-film transistors (TFTs) on high-temperature polyimide (PI) substrates, which were debonded from the carrier glass after TFT fabrication. The application of appropriate buffer layers on the PI substrates affected the TFT performance and stability. The adoption of the SiN{sub x}/AlO{sub x} buffer layers as water and hydrogen diffusion barriers significantly improved the device performance and stability against the thermal annealing and negative bias stress, compared to single SiN{sub x} or SiO{sub x} buffer layers. The substrates could be bent down to a radius of curvature of 15?mm and the devices remained normally functional.

Ok, Kyung-Chul; Park, Jin-Seong, E-mail: hkim-2@naver.com, E-mail: jsparklime@hanyang.ac.kr [Division of Materials Science and Engineering, Hanyang University, 222, Wangsimni-ro, Seongdong-gu, Seoul 133-791 (Korea, Republic of); Ko Park, Sang-Hee; Kim, H., E-mail: hkim-2@naver.com, E-mail: jsparklime@hanyang.ac.kr [Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Hwang, Chi-Sun [Transparent Electronics Team, ETRI, Daejeon 305-350 (Korea, Republic of); Soo Shin, Hyun; Bae, Jonguk [LG Display R and D Center, LG Display Co., Ltd., Paju 413-811 (Korea, Republic of)

2014-02-10

83

Plasma treatment effect on charge carrier concentrations and surface traps in a-InGaZnO thin-film transistors  

SciTech Connect

Various plasma treatment effects such as oxygen (O{sub 2}), nitrogen (N{sub 2}), and argon (Ar) on amorphous indium gallium zinc oxide thin-film transistors (a-IGZO TFTs) are investigated. To study oxygen stoichiometry in a-IGZO TFTs with respect to various plasma environments, X-ray photoelectron spectroscopy was employed. The results showed that oxygen vacancies were reduced by O{sub 2} and N{sub 2} plasmas while they were increased after Ar plasma treatment. Additionally, the effects of plasma treatment on trap distribution in bulk and surface channels were explored by means of low-frequency noise analysis. Details of the mechanisms used for generating and restoring traps on the surface and bulk channel are presented.

Kim, Jae-Sung; Xing Piao, Ming; Jang, Ho-Kyun; Kim, Gyu-Tae, E-mail: gtkim@korea.ac.kr [School of Electrical Engineering, Korea University, Seoul 136-701 (Korea, Republic of); Joo, Min-Kyu [School of Electrical Engineering, Korea University, Seoul 136-701 (Korea, Republic of); IMEP-LAHC, Grenoble INP, Minatec, CS 50257, 38016 Grenoble (France); Ahn, Seung-Eon [School of Electrical Engineering, Korea University, Seoul 136-701 (Korea, Republic of); Samsung Advanced Institute of Technology, Samsung Electronics Corporations, Yongin, Gyeonggi-Do 446-712 (Korea, Republic of); Choi, Yong-Hee [School of Electrical Engineering, Korea University, Seoul 136-701 (Korea, Republic of); Semiconductor R and D Center, Samsung Electronics, Hwasung, Gyeonggi-do 445-701 (Korea, Republic of)

2014-03-21

84

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

NASA Astrophysics Data System (ADS)

In the present study, we demonstrate that selective surface oxidation of Zr70Cu30 metallic glass can stabilize the amorphous structure in the subsurface region of the matrix. The oxidation proceeds by selective oxidation of Zr, forming monoclinic ZrO2 layer on the surface, and the subsurface layer becomes Cu-enriched due to back diffusion of Cu atoms from the oxide layer. Interestingly, in this system, the composition change in the subsurface region leads to enhancement of glass stability, forming of a double layered surface structure consisted of inner amorphous layer and outer monoclinic ZrO2 layer even when the remaining matrix is completely crystallized.

Lim, K. R.; Park, J. M.; Park, S. H.; Na, M. Y.; Kim, K. C.; Kim, W. T.; Kim, D. H.

2014-01-01

85

Fast interfacial oxidation of amorphous Si1 - xGex:H by SnO2  

Microsoft Academic Search

Fast oxidation of amorphous (a) Si1?xGex:H by interfacial reaction with SnO2 was observed at the temperature range of 400–500 °C. The rate of interfacial oxidation was very significant, while a test in a dry O2 ambient at the same temperatures showed no oxidation of Si1?xGex:H beyond the native oxide. The interfacial reaction of the SiGe:H\\/SnO2\\/glass system resulted in a layered

F. Edelman; R. Brener; C. Cytermann; M. Eizenberg; R. Weil; W. Beyer

1995-01-01

86

Bacterial nanometric amorphous Fe-based oxide: a potential lithium-ion battery anode material.  

PubMed

Amorphous Fe(3+)-based oxide nanoparticles produced by Leptothrix ochracea, aquatic bacteria living worldwide, show a potential as an Fe(3+)/Fe(0) conversion anode material for lithium-ion batteries. The presence of minor components, Si and P, in the original nanoparticles leads to a specific electrode architecture with Fe-based electrochemical centers embedded in a Si, P-based amorphous matrix. PMID:24689687

Hashimoto, Hideki; Kobayashi, Genki; Sakuma, Ryo; Fujii, Tatsuo; Hayashi, Naoaki; Suzuki, Tomoko; Kanno, Ryoji; Takano, Mikio; Takada, Jun

2014-04-23

87

Direct /TEM/ observation of the catalytic oxidation of amorphous carbon by Pd particles  

NASA Technical Reports Server (NTRS)

The catalytic oxidation of amorphous carbon substrates by Pd particles is observed by in situ transmission electron microscopy. Various modes of selective attack of the carbon substrate in the immediate neighborhood of Pd particles are observed, which can be correlated with different degrees of particle mobility. Using amorphous substrates we have been able to demonstrate that the particle-substrate interaction is influenced by the structure of the particle. This has not previously been noted.

Moorhead, R. D.; Poppa, H.; Heinemann, K.

1980-01-01

88

Tin-based amorphous oxide: A high-capacity lithium-ion-storage material  

Microsoft Academic Search

A high-capacity lithium-storage material in metal-oxide form has been synthesized that can replace the carbon-based lithium intercalation materials currently in extensive use as the negative electrode (anode) of lithium-ion rechargeable batteries. This tin-based amorphous composite oxide (TCO) contains Sn(II)-O as the active center for lithium insertion and other glass-forming elements, which make up an oxide network. The TCO anode yields

Yoshio Idota; Tadahiko Kubota; Akihiro Matsufuji

1997-01-01

89

Structural stability and oxidation resistance of amorphous Zr-Al alloys  

NASA Astrophysics Data System (ADS)

We investigated the structural stability and oxidation resistance of Zr-Al films upon annealing in air. The concentration of Zr was varied from 0 to 100 at.%, with a step of 10 at.%. The films were fabricated using ultra-high vacuum based magnetron sputtering. The as-deposited films with Zr content from 17.3 at.% to 70.7 at.% were found to be X-ray amorphous at room temperature. When exposed to air a thin oxide layer, typically less than 6 nm, is formed. The thickness of the oxide layers increases when the samples are annealed in air and most of these are found to be fully oxidized at 700 °C with the formation of crystalline and amorphous oxides on the top of crystalline and amorphous metal films, respectively. The amorphous oxide layers are found to be dense, with well defined thicknesses. An experimental non-equilibrium phase diagram is provided, covering the whole concentration range of the Zr-Al system.

Soroka, I. L.; Vegelius, J.; Korelis, P. T.; Fallberg, A.; Butorin, S. M.; Hjörvarsson, B.

2010-06-01

90

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

PubMed Central

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

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

2013-01-01

91

Carbon-Incorporated Amorphous Indium Zinc Oxide Thin-Film Transistors  

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

92

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

2011-07-01

93

Intrinsic stress evolution during amorphous oxide film growth on Al surfaces  

SciTech Connect

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

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

2014-03-03

94

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

SciTech Connect

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

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

2014-01-20

95

Intrinsic stress evolution during amorphous oxide film growth on Al surfaces  

NASA Astrophysics Data System (ADS)

The intrinsic stress evolution during formation of ultrathin amorphous oxide films on Al(111) and Al(100) surfaces by thermal oxidation at room temperature was investigated in real-time by in-situ substrate curvature measurements and detailed atomic-scale microstructural analyses. During thickening of the oxide a considerable amount of growth stresses is generated in, remarkably even amorphous, ultrathin Al2O3 films. The surface orientation-dependent stress evolutions during O adsorption on the bare Al surfaces and during subsequent oxide-film growth can be interpreted as a result of (i) adsorption-induced surface stress changes and (ii) competing processes of free volume generation and structural relaxation, respectively.

Flötotto, D.; Wang, Z. M.; Jeurgens, L. P. H.; Mittemeijer, E. J.

2014-03-01

96

Influence of DC magnetron sputtering parameters on the properties of amorphous indium zinc oxide thin film  

Microsoft Academic Search

Amorphous or crystalline indium zinc oxide (IZO) thin films, which are highly transparent and conducting, were deposited by DC magnetron sputtering. X-Ray diffraction technique was used for analyzing microstructures of the films, and also differential thermal analysis was performed for observing their crystallization behavior. The IZO thin films prepared were crystallized at much higher temperature than ITO films were. The

Yeon Sik Jung; Ji Yoon Seo; Dong Wook Lee; Duk Young Jeon

2003-01-01

97

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

98

Magnetic nanocables—Silicon carbide sheathed with iron-oxide-doped amorphous silica  

NASA Astrophysics Data System (ADS)

High-purity nanocables of iron-containing amorphous-silica-sheathed silicon carbide were synthesized by a thermal reaction method using silicon wafer as the silicon source and growth substrate, and ferrocene as the carbon and iron catalyst precursor. The nanocables were tens of ?m in length and 40-60nm in diameter. Iron oxide nanoparticles with a mean diameter of 5nm were dispersed evenly in the amorphous silica layer. The nanocables were found to be ferromagnetic at both 10K and room temperature, which indicates that they may have important potential applications in electromagnetic nanodevices.

Liu, C.; Li, R. W.; Belik, A.; Golberg, D.; Bando, Y.; Cheng, H. M.

2006-01-01

99

Intrinsic nature of visible-light absorption in amorphous semiconducting oxides  

SciTech Connect

To enlighten microscopic origin of visible-light absorption in transparent amorphous semiconducting oxides, the intrinsic optical property of amorphous InGaZnO{sub 4} is investigated by considering dipole transitions within the quasiparticle band structure. In comparison with the crystalline InGaZnO{sub 4} with the optical gap of 3.6 eV, the amorphous InGaZnO{sub 4} has two distinct features developed in the band structure that contribute to significant visible-light absorption. First, the conduction bands are down-shifted by 0.55 eV mainly due to the undercoordinated In atoms, reducing the optical gap between extended states to 2.8 eV. Second, tail states formed by localized oxygen p orbitals are distributed over ?0.5 eV near the valence edge, which give rise to substantial subgap absorption. The fundamental understanding on the optical property of amorphous semiconducting oxides based on underlying electronic structure will pave the way for resolving instability issues in recent display devices incorporating the semiconducting oxides.

Kang, Youngho; Song, Hochul; Han, Seungwu, E-mail: hansw@snu.ac.kr [Department of Materials Science and Engineering, Seoul National University, Seoul 151-755 (Korea, Republic of); Nahm, Ho-Hyun [Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul 151-747 (Korea, Republic of); Department of Physics and Astronomy, Seoul National University, Seoul 151-747 (Korea, Republic of); Jeon, Sang Ho; Cho, Youngmi [CAE Team, Samsung Display Co., Ltd, 95 Samsung 2-ro, Giheung-gu, Youngin-City, Gyeonggi-Do 446-711 (Korea, Republic of)

2014-03-01

100

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

SciTech Connect

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

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

2011-06-20

101

Exploratory combustion synthesis: amorphous indium yttrium oxide for thin-film transistors.  

PubMed

We report the implementation of amorphous indium yttrium oxide (a-IYO) as a thin-film transistor (TFT) semiconductor. Amorphous and polycrystalline IYO films were grown via a low-temperature solution process utilizing exothermic "combustion" precursors. Precursor transformation and the IYO films were analyzed by differential thermal analysis, thermogravimetric analysis, X-ray diffraction, atomic force microscopy, X-ray photoelectron spectroscopy, and optical transmission, which reveal efficient conversion to the metal oxide lattice and smooth, transparent films. a-IYO TFTs fabricated with a hybrid nanodielectric exhibit electron mobilities of 7.3 cm(2) V(-1) s(-1) (T(anneal) = 300 °C) and 5.0 cm(2) V(-1) s(-1) (T(anneal) = 250 °C) for 2 V operation. PMID:22625409

Hennek, Jonathan W; Kim, Myung-Gil; Kanatzidis, Mercouri G; Facchetti, Antonio; Marks, Tobin J

2012-06-13

102

Suppression of subcutaneous oxidation during the deposition of amorphous lanthanum aluminate on silicon  

NASA Astrophysics Data System (ADS)

Amorphous LaAlO3 thin films have been deposited by molecular beam deposition directly on silicon without detectable oxidation of the underlying substrate. We have studied these abrupt interfaces by Auger electron spectroscopy, high-resolution transmission electron microscopy, medium-energy ion scattering, transmission infrared absorption spectroscopy, and x-ray photoelectron spectroscopy. Together these techniques indicate that the films are fully oxidized and have less than 0.2 Å of SiO2 at the interface between the amorphous LaAlO3 and silicon. These heterostructures are being investigated for alternative gate dielectric applications and provide an opportunity to control the interface between the silicon and the gate dielectric.

Edge, L. F.; Schlom, D. G.; Brewer, R. T.; Chabal, Y. J.; Williams, J. R.; Chambers, S. A.; Hinkle, C.; Lucovsky, G.; Yang, Y.; Stemmer, S.; Copel, M.; Holländer, B.; Schubert, J.

2004-06-01

103

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

Microsoft Academic Search

Thin film transistors (TFTs) with amorphous indium zinc oxide (a-IZO) as channel layers and poly-4-vinylphenol as dielectric layers were fabricated. Transmission curves show that the double-layer structure of the a-IZO layer and the poly-4-vinylphenol layer exhibits the antireflection effect. It was found that post heat-treatment at relatively low temperature will improve the electrical performance of the transistors. TFT devices with

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

2011-01-01

104

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

105

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 350°C 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

106

Wrapping and inclusion of organic molecules with ultrathin, amorphous metal oxide films.  

PubMed

In this review, we overview metal oxide nanostructures in which organic molecules play important roles as templates, as structural units, and, in some cases, as hosts. Their structural precision and diversity are discussed from the viewpoint of the topology of a metal-oxygen network. Supramolecular capsules of metal oxides are prepared by the self-assembly of polyoxometalates. Zeolites and mesoporous materials are synthesized by using organic molecules with their assemblies acting as templates. The topological networking of silsesquioxanes makes it possible to produce novel nanocomposites and microporous materials. In the final section, we demonstrate our recent studies into molecular imprinting, the encapsulation of a fluorescent dye, and the wrapping of individual polymer chains. Ultrathin, amorphous metal oxide films can retain the shape of organic molecules and can be used to create molecular composites by precisely wrapping individual molecules. These films are also effective in insulating molecular functions from external environments. The advantages of amorphous metal oxides are discussed in relation to the properties of the corresponding crystalline metal oxides and their potential prospects in nanotechnology. PMID:12369057

Ichinose, Izumi; Kunitake, Toyoki

2002-01-01

107

Band gap structure modification of amorphous anodic Al oxide film by Ti-alloying  

SciTech Connect

The band structure of pure and Ti-alloyed anodic aluminum oxide has been examined as a function of Ti concentration varying from 2 to 20 at.?%. The band gap energy of Ti-alloyed anodic Al oxide decreases with increasing Ti concentration. X-ray absorption spectroscopy reveals that Ti atoms are not located in a TiO{sub 2} unit in the oxide layer, but rather in a mixed Ti-Al oxide layer. The optical band gap energy of the anodic oxide layers was determined by vacuum ultraviolet spectroscopy in the energy range from 4.1 to 9.2?eV (300–135?nm). The results indicate that amorphous anodic Al{sub 2}O{sub 3} has a direct band gap of 7.3?eV, which is about ?1.4?eV lower than its crystalline counterpart (single-crystal Al{sub 2}O{sub 3}). Upon Ti-alloying, extra bands appear within the band gap of amorphous Al{sub 2}O{sub 3}, mainly caused by Ti 3d orbitals localized at the Ti site.

Canulescu, S., E-mail: stec@fotonik.dtu.dk; Schou, J. [Department of Photonics Engineering, Technical University of Denmark, 4000 Roskilde (Denmark); Rechendorff, K.; Pleth Nielsen, L. [Danish Technological Institute, Kongsvang Alle 29, 8000 Aarhus (Denmark); Borca, C. N. [Paul Scherrer Institute, 5232 Villigen (Switzerland); Jones, N. C.; Hoffmann, S. V. [ISA, Department of Physics and Astronomy, Aarhus University, 8000 Aarhus (Denmark); Bordo, K.; Ambat, R. [Department of Mechanical Engineering, Technical University of Denmark, 2800 Kongens Lyngby (Denmark)

2014-03-24

108

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

PubMed Central

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

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

2013-01-01

109

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

PubMed

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

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

2013-06-15

110

Improved fill factors in amorphous silicon solar cells on zinc oxide by insertion of a germanium layer to block impurity incorporation  

E-print Network

Improved fill factors in amorphous silicon solar cells on zinc oxide by insertion of a germanium 80401 (Received 22 September 2003; accepted 25 May 2004) Amorphous silicon based solar cells deposited Institute of Physics. [DOI: 10.1063/1.1773372] The performance of hydrogenated amorphous silicon a

111

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

112

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

NASA Astrophysics Data System (ADS)

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

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

2011-09-01

113

High stability of amorphous hafnium-indium-zinc-oxide thin film transistor  

NASA Astrophysics Data System (ADS)

Time dependence of the threshold voltage (Vth) shift in amorphous hafnium-indium-zinc oxide (a-HIZO) thin film transistor has been reported under on-current bias temperature stress measured at 60 °C. X-ray photoelectron spectroscopy results show the decrease in oxygen vacancies by Hf metal cations in a-HIZO systems after annealing process. High stability of a-HIZO systems has been observed due to low charge injection from the channel layer. Hf metal cations have been effectively incorporated into the IZO thin films as a suppressor against both the oxygen deficiencies and the carrier generation.

Chong, Eugene; Jo, Kyoung Chul; Lee, Sang Yeol

2010-04-01

114

The atomic structure of ternary amorphous TixSi1-xO2 hybrid oxides.  

PubMed

Atomic length-scale order characteristics of binary and ternary amorphous oxides are presented within the framework of ab initio theory. A combined numerically efficient density functional based tight-binding molecular dynamics and density functional theory approach is applied to model the amorphous (a) phases of SiO2 and TiO2 as well as the amorphous phase of atomically mixed TixSi1-xO2 hybrid-oxide alloys over the entire composition range. Short and mid-range order in the disordered material phases are characterized by bond length and bond-angle statistics, pair distribution function analysis, coordination number and coordination polyhedra statistics, as well as ring statistics. The present study provides fundamental insights into the order characteristics of the amorphous hybrid-oxide frameworks formed by versatile types of TiOn and SiOm coordination polyhedra. In a-SiO2 the fourfold crystal coordination of Si ions is almost completely preserved and the atomic structure is widely dominated by ring-like mid-range order characteristics. In contrast, the structural disorder of a-TiO2 arises from short-range disorder in the local coordination environment of the Ti ion. The coordination number analysis indicates a large amount of over and under-coordinated Ti ions (coordination defects) in a-TiO2. Aside from the ubiquitous distortions of the crystal-like coordinated polyhedra, even the basic coordination-polyhedra geometry type changes for a significant fraction of TiO6 units (geometry defects). The combined effects of topological and chemical disorder in a-TixSi1-xO2 alloys lead to a continuos increase in both the Si as well as the Ti coordination number with the chemical composition x. The important roles of intermediate fivefold coordination states of Ti and Si cations are highlighted for ternary a-TixSi1-xO2 as well as for binary a-TiO2. The continuous decrease in ring size with increasing Ti content reflects the progressive loss of mid-range order structure characteristics and the competing roles of network forming and network modifying SiOm and TiOn units in the mixed hybrid oxides. PMID:24848713

Landmann, M; Köhler, T; Rauls, E; Frauenheim, T; Schmidt, W G

2014-06-25

115

Chronological change of electrical resistance in GeCu2Te3 amorphous film induced by surface oxidation  

NASA Astrophysics Data System (ADS)

Unusual chronological electrical resistance change behavior was investigated for amorphous GeCu2Te3 phase change material. More than a 1 order decrease of electrical resistance was observed in the air even at room temperature. The resistance of the amorphous film gradually increased with increasing temperature and then showed a drop upon crystallization. Such unusual behavior was attributed to the oxidation of the amorphous GeCu2Te3 film. From the compositional depth profile measurement, the GeCu2Te3 film without any capping layer was oxidized in air at room temperature and the formed oxide was mainly composed of germanium oxide. Consequently, a highly-conductive Cu-rich layer was formed in the vicinity of the surface of the film, which reduced the total resistance of the film. The present results could provide insight into the chronological change of electrical resistance in amorphous chalcogenide materials, indicating that not only relaxation of the amorphous, but also a large atomic diffusion contributes to the chronological resistance change.

Saito, Yuta; Shindo, Satoshi; Sutou, Yuji; Koike, Junichi

2014-11-01

116

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

SciTech Connect

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

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

2014-09-01

117

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

SciTech Connect

Tin oxide (SnO{sub 2}) thin films were deposited using pulsed laser deposition (PLD) technique on Si substrates. The as-deposited films were irradiated using 100 MeV Ag ions at different fluences ranging from 3x10{sup 13} to 3x10{sup 14} ions/cm{sup 2} at an incidence angle of 75 deg. with respect to surface normal at liquid nitrogen (LN2) temperature. The as-deposited and irradiated films have been characterized using X-ray diffraction (XRD) and atomic force microscopy (AFM) techniques to study the modifications in structural and surface morphological properties. Nanocrystalline film become completely amorphous and nanograins of tin oxide disappeared from the surface as indicated by XRD spectra and AFM micrographs respectively.

Kumar, Vijay; Pratap, Deepti; Jain, Anshul; Agarwal, D. C.; Sulania, I.; Tripathi, A.; Chaudhary, R. J.; Chauhan, R. S. [Department of Physics, R.B.S. College, Agra, U.P.,-282 002 (India); Inter-University Accelerator Centre, New Delhi, -110 067 (India); UGC-DAE CSR, Khandwa Road, Indore, M.P., -452 017 (India); Department of Physics, R.B.S. College, Agra, U.P., -282 002 (India)

2012-06-05

118

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

NASA Astrophysics Data System (ADS)

Amorphous transition metal oxides exhibit exotic transport and magnetic properties, while the absence of periodic structure has long been a major obstacle for the understanding of their electronic structure and exchange interaction. In this paper, we have formulated a theoretical approach, which combines the melt-quench approach and the spin dynamic Monte-Carlo simulations, and based on it, we explored amorphous Co0.5Zn0.5O1-y ternary transition metal oxides. Our theoretical results reveal that the microstructure, the magnetic properties, and the exchange interactions of Co0.5Zn0.5O1-y are strongly determined by the oxygen stoichiometry. In the oxygen-deficient sample (y > 0), we have observed the long-range ferromagnetic spin ordering which is associated with the non-stoichiometric cobalt-rich region rather than metallic clusters. On the other hand, the microstructure of stoichiometric sample takes the form of continuous random networks, and no long-range ferromagnetism has been observed in it. Magnetization characterization of experimental synthesized Co0.61Zn0.39O1-y films verifies the relation between the spin ordering and the oxygen stoichiometry. Furthermore, the temperature dependence of electrical transport shows a typical feature of semiconductors, in agreement with our theoretical results.

Hu, Shu-jun; Yan, Shi-shen; Zhang, Yun-peng; Zhao, Ming-wen; Kang, Shi-shou; Mei, Liang-mo

2014-07-01

119

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

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

120

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

NASA Technical Reports Server (NTRS)

The oxidation products formed at 500 and 700 C on an amorphous Ta-44.5 at. pct Ir alloy in an Ar-0.1 percent O2 gas mixture were characterized using SEM, XRD, EPMA, TEM, STEM, AES, and XPS. Initially, a thin (3-4 nm) layer of Ta2O5 formed at the surface of the alloy. Continued growth of the Ta2O5, which occurred very rapidly, involved diffusion of oxygen anions from the Ta2O5/gas interface to the alloy/Ta2O5 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 Ta2O5. 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, Catherine M.; Yurek, Gregory J.

1986-01-01

121

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

PubMed Central

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

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

2014-01-01

122

Analysis of conducting-system frequency response data for an interfacial amorphous phase of copper-core oxide-shell nanocomposites  

E-print Network

treated to produce an amorphous phase of copper-core­copper-oxide-shell nanocomposites TG . The metallic-core oxide-shell nanocomposites J. R. Macdonalda Department of Physics and Astronomy, University of North

Macdonald, James Ross

123

Crystallization kinetics of amorphous tin-doped indium oxide thin films  

NASA Astrophysics Data System (ADS)

The crystallization kinetics of amorphous tin-doped indium oxide thin films grown by dc magnetron sputtering and electron beam evaporation was investigated using time-resolved laser reflectivity in conjunction with TEM analyses. The as-grown films were established to be amorphous using glancing angle x-ray and selected area electron diffraction. The samples were then annealed at temperatures ranging from (˜111-167sp°C) some in a range of environments (oxidizing (Nsb2), strongly oxidizing (air), and reducing (wet/dry forming gas). Gross-sectional TEM analysis reveals a columnar as-sputtered microstructure that is retained after annealing to complete transformation. In contrast a-ITO films grown by evaporation show a uniformly dense microstructure. Annealing evaporated films in air produced films containing a wide distribution in grain sizes, while annealing in the more reducing environments yielded polycrystalline films with a narrow grain size distribution centered at 15 nm. Time-resolved laser reflectivity was an advantageous tool for monitoring the progress of the crystallization transformation because the technique generates quantifiable data while allowing real-time, non-contact observation. Plotting the transformation rate as a function of annealing temperature demonstrated the amorphous-to-crystalline transformation to be a thermally activated process. The energy required to crystallize sputtered a-ITO films in flowing Nsb2 is much lower than that for evaporated alpha-ITO films also in flowing Nsb2. XRD spectra of the as-sputtered a-ITO reveals the presence of an indium metal phase, which is not observed in the as-evaporated a-ITO films. The activation energy is most likely dependent on the presence of In metal, which serves as a catalyst for lowering the energy barrier. This is confirmed by the reduction in energy needed to transform evaporated a-ITO film in a reducing environment. In this study, the pre- and post-anneal microstructures were examined to deduce possible processes by which transformation occurred. Models of the crystallization mechanisms are proposed and simulated on a computer. The calculated results are compared with the experimentally obtained data to gain further insight into the transformation routes.

Ow-Yang, Cleva Wan

124

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 1000°C 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 1350°C 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 1350°C 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

125

Functionalization of FeCo alloy nanoparticles with highly dielectric amorphous oxide coatings  

NASA Astrophysics Data System (ADS)

FeCo alloy nanoparticles have been prepared by using a two step modified polyol process using Fe(II) chloride and Co acetate tetrahydrate as Fe and Co metal precursors. Tetraethyl silicate, aluminum isopropoxide, and zirconium(IV) acetyl acetonate were used to make amorphous SiO2, Al2O3, and ZrO2 coatings, respectively. X-ray diffraction studies showed that there are no crystalline peaks corresponding to SiO2, Al2O3, and ZrO2 because the oxide coatings of the FeCo core are amorphous in nature. The scanning electron micrograph analysis depicted the cubic nature of the particles with mean particle size of about 45nm. The maximum saturation magnetization of 205emu /g was achieved at 300 and 4K. FeCo nanocomposites were screen printed as films and aligned by using an external magnetic field of 10kOe. The microwave properties measured by in-plane ferromagnetic resonance at various frequencies indicate a minimum linewidth of ?3700Oe.

Nguyen, Q.; Chinnasamy, C. N.; Yoon, S. D.; Sivasubramanian, S.; Sakai, T.; Baraskar, A.; Mukerjee, S.; Vittoria, C.; Harris, V. G.

2008-04-01

126

Localized tail state distribution in amorphous oxide transistors deduced from low temperature measurements  

NASA Astrophysics Data System (ADS)

In this paper, we extract density of localized tail states from measurements of low temperature conductance in amorphous oxide transistors. At low temperatures, trap-limited conduction prevails, allowing extraction of the trapped carrier distribution with energy. Using a test device with a-InGaZnO channel layer, the extracted tail state energy and density at the conduction band minima are 20 meV and 2 × 1019 cm-3 eV-1, respectively, which are consistent with values reported in the literature. Also, the field-effect mobility as a function of temperature from 77 K to 300 K is retrieved for different gate voltages, yielding the activation energy and the percolation threshold.

Lee, Sungsik; Nathan, Arokia

2012-09-01

127

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

SciTech Connect

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

Cho, Byungsu [Division of Materials Science and Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Samsung Display Co. Ltd., Tangjeong, Chungcheongnam-Do 336-741 (Korea, Republic of); Choi, Yonghyuk; Shin, Seokyoon [Division of Materials Science and Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Jeon, Heeyoung [Department of Nano-scale Semiconductor Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Seo, Hyungtak, E-mail: hseo@ajou.ac.kr [Department of Materials Science and Engineering and Energy Systems Research, Ajou University, Suwon 443-739 (Korea, Republic of); Jeon, Hyeongtag, E-mail: hjeon@hanyang.ac.kr [Division of Materials Science and Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Department of Nano-scale Semiconductor Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of)

2014-01-27

128

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

NASA Astrophysics Data System (ADS)

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

Park, Jae Chul; Lee, Ho-Nyeon

2015-01-01

129

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

SciTech Connect

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.

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

2010-07-15

130

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

SciTech Connect

We report an investigation of two photon ultraviolet (UV) irradiation induced permanent n-type doping of amorphous InGaZnO (a-IGZO) at room temperature. The photoinduced excess electrons were donated to change the Fermi-level to a conduction band edge under the UV irradiation, owing to the hole scavenging process at the oxide interface. The use of optically n-doped a-IGZO channel increased the carrier density to approx10{sup 18} cm{sup -3} from the background level of 10{sup 16} cm{sup -3}, as well as the comprehensive enhancement upon UV irradiation of a-IGZO thin film transistor parameters, such as an on-off current ratio at approx10{sup 8} and field-effect mobility at 22.7 cm{sup 2}/V s.

Seo, Hyungtak [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Cho, Young-Je; Bobade, Santosh M.; Park, Kyoung-Youn; Choi, Duck-Kyun [Division of Materials Science and Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Kim, Jinwoo [Department of Materials Sciences and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States); Lee, Jaegab [School of Advanced Materials Engineering, Kookmin University, Seoul 136-702 (Korea, Republic of)

2010-05-31

131

Enhanced photoelectrochemical water oxidation on bismuth vanadate by electrodeposition of amorphous titanium dioxide.  

PubMed

n-BiVO4 is a promising semiconductor material for photoelectrochemical water oxidation. Although most thin-film syntheses yield discontinuous BiVO4 layers, back reduction of photo-oxidized products on the conductive substrate has never been considered as a possible energy loss mechanism in the material. We report that a 15 s electrodeposition of amorphous TiO2 (a-TiO2) on W:BiVO4/F:SnO2 blocks this undesired back reduction and dramatically improves the photoelectrochemical performance of the electrode. Water oxidation photocurrent increases by up to 5.5 times, and its onset potential shifts negatively by ?500 mV. In addition to blocking solution-mediated recombination at the substrate, the a-TiO2 film-which is found to lack any photocatalytic activity in itself-is hypothesized to react with surface defects and deactivate them toward surface recombination. The proposed treatment is simple and effective, and it may easily be extended to a wide variety of thin-film photoelectrodes. PMID:25243345

Eisenberg, David; Ahn, Hyun S; Bard, Allen J

2014-10-01

132

Surface plasmon resonance of Ag nanoparticles embedded in partially oxidized amorphous Si matrix.  

PubMed

Nanocomposite films containing Ag nanoparticles embedded in partially oxidized amorphous Si matrix were deposited on silica glass substrates by co-sputtering of Ag and Si with 1.5 keV neutral Ar atoms. The Ag content and thickness of the nanocomposite films was determined by Rutherford backscattering spectrometry. Optical absorption studies revealed the presence of surface plasmon resonance (SPR) indicating the formation of Ag nanoparticles in the as-deposited films. The position, width and strength of SPR have been found to be strongly dependent on the Ag content of the films. For annealing in oxidizing atmosphere, a significant red shift in the SPR along with a drastic reduction in the resonant absorption has been observed. The amount of red shift has been found to be dependent on the Ag content of the films. Transmission electron microscopy was used to study the size distribution, shape and crystal structure of Ag nanoparticles in the nanocomposite films. TEM analysis of annealed sample revealed the formation of silver oxide nanoshells surrounding Ag nanoparticles. PMID:19049219

Mohapatra, S; Mishra, Y K; Ghatak, J; Kabiraj, D; Avasthi, D K

2008-08-01

133

Electron-beam-induced topographical, chemical, and structural patterning of amorphous titanium oxide films.  

PubMed

Electrolytically deposited amorphous TiO2 films on steel are remarkably sensitive to electron beam (e-beam) irradiation at moderate energies at 20 keV, resulting in controlled local oxide reduction and crystallization, opening the possibility for local topographical, chemical, and structural modifications within a biocompatible, amorphous, and semiconducting matrix. The sensitivity is shown to vary significantly with the annealing temperature of as-deposited films. Well-defined irradiation conditions in terms of probe current IP (5 microA) and beam size were achieved with an electron probe microanalyzer. As shown by atomic force and optical microscopy, micro-Raman spectroscopy, wavelength-dispersive X-ray (WDX), and Auger analyses, e-beam exposure below 1 Acm-2 immediately leads to electron-stimulated oxygen desorption, resulting in a well-defined volume loss primarily limited to the irradiated zone under the electron probe and in a blue color shift in this zone because of the presence of Ti2O3. Irradiation at 5 Acm(-2) (IP = 5 microA) results in local crystallization into anatase phase within 1 s of exposure and in reduction to TiO after an extended exposure of 60 s. Further reduction to the metallic state could be observed after 60 s of exposure at approximately 160 Acm(-2). The local reduction could be qualitatively sensed with WDX analysis and Auger line scans. An estimation of the film temperature in the beam center indicates that crystallization occurs at less than 150 degrees C, well below the atmospheric crystallization temperature of the present films. The high e-beam sensitivity in combination with the well-defined volume loss from oxygen desorption allows for precise electron lithographic topographical patterning of the present oxides. Irradiation effects leading to the observed reduction and crystallization phenomena under moderate electron energies are discussed. PMID:17125324

Kern, P; Müller, Y; Patscheider, J; Michler, J

2006-11-30

134

Stability of phosphonic acid self-assembled monolayers on amorphous and single-crystalline aluminum oxide surfaces in aqueous solution.  

PubMed

The formation of octadecylphosphonic acid (ODPA) self-assembled monolayers (SAMs) and their stability in water has been studied on four distinctly different aluminum oxide surfaces. The aim was to improve the understanding of the state of binding between the phosphonic acid to the oxide surface and how this interaction depends on the structure and termination of the oxide surface. Single crystalline Al(2)O(3)(0001) and Al(2)O(3)(1102) surfaces were compared to amorphous oxide passive films on aluminum and physical vapor deposited (PVD) amorphous aluminum oxide films on gold. The monolayers were adsorbed from ethanol solution, characterized by means of high-resolution in situ atomic force microscopy (AFM), contact angle measurements, polarization modulated infrared reflection absorption spectroscopy (PM-IRRAS), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and proved to be self-assembled. On Al(2)O(3)(1102) surfaces and amorphous Al(2)O(3) surfaces, the ODPA self-assembled monolayers showed high stability in aqueous environments. However, the adsorbed ODPA monolayers were substituted by the adsorption of interfacial water on the Al(2)O(3)(0001) surface via the intermediate formation of micelles. The different stability of the monolayers in aqueous environments is explained by the variation of interfacial binding states ranging from ionic interactions between phosphonate groups and the positively charged hydrolytated oxide surface to directed coordination bonds between the phosphonate group and Al ions. PMID:20000361

Thissen, Peter; Valtiner, Markus; Grundmeier, Guido

2010-01-01

135

The Structure and Properties of Amorphous Indium Oxide D. Bruce Buchholz,  

E-print Network

on amorphous silica substrates using pulsed laser deposition by varying the film growth temperature: A series of In2O3 thin films, ranging from X-ray diffraction amorphous to highly crystalline, were grown

Medvedeva, Julia E.

136

Influence of deposition temperature and amorphous carbon on microstructure and oxidation resistance of magnetron sputtered nanocomposite Crsbnd C films  

NASA Astrophysics Data System (ADS)

It is known that mechanical and tribological properties of transition metal carbide films can be tailored by adding an amorphous carbon (a-C) phase, thus making them nanocomposites. This paper addresses deposition, microstructure, and for the first time oxidation resistance of magnetron sputtered nanocomposite Crsbnd C/a-C films with emphasis on studies of both phases. By varying the deposition temperature between 20 and 700 °C and alternating the film composition, it was possible to deposit amorphous, nanocomposite, and crystalline Crsbnd C films containing about 70% C and 30% Cr, or 40% C and 60% Cr. The films deposited at temperatures below 300 °C were X-ray amorphous and 500 °C was required to grow crystalline phases. Chronoamperometric polarization at +0.6 V vs. Ag/AgCl (sat. KCl) in hot 1 mM H2SO4 resulted in oxidation of Crsbnd C, yielding Cr2O3 and C, as well as oxidation of C. The oxidation resistance is shown to depend on the deposition temperature and the presence of the a-C phase. Physical characterization of film surfaces show that very thin C/Cr2O3/Crsbnd C layers develop on the present material, which can be used to improve the oxidation resistance of, e.g. stainless steel electrodes.

Nygren, Kristian; Andersson, Matilda; Högström, Jonas; Fredriksson, Wendy; Edström, Kristina; Nyholm, Leif; Jansson, Ulf

2014-06-01

137

Effect of ultraviolet light exposure to boron doped hydrogenated amorphous silicon oxide thin film  

NASA Astrophysics Data System (ADS)

We have investigated the effect of ultraviolet (UV) light exposure to boron doped (p-type) hydrogenated amorphous silicon oxide (p-a-SiO:H) thin semiconductor films by measuring changes in its structural, electrical and optical properties. After a 50 h of UV light soaking (LS) of the films, that have 1.2, 6.9, 15.2, 25.3 at.% oxygen content (C(O)) and optical gap (E04) of 1.897, 2.080, 2.146 and 2.033 eV, show a relative increase in the C(O) by 28.0%, 9.8%, 2.0%, 3.1%, a relative increase in the Urbach energy (Eu) by 42%, 24%, 8%, 0%, decrease in the E04 by 66, 2, 12, 19 meV and the gap state defect density (Nd) show an increase by 6.5%, 3.4%, 0.7%, 0.1%. At higher oxygen content the observed UV light induced degradation (LID) is relatively less than that for films with lower oxygen content, indicating that higher oxides face less changes under the UV light.

Baek, Seungsin; Iftiquar, S. M.; Jang, Juyeon; Lee, Sunhwa; Kim, Minbum; Jung, Junhee; Park, Hyeongsik; Park, Jinjoo; Kim, Youngkuk; Shin, Chonghoon; Lee, Youn-Jung; Yi, Junsin

2012-11-01

138

Amorphous cobalt potassium phosphate microclusters as efficient photoelectrochemical water oxidation catalyst  

NASA Astrophysics Data System (ADS)

A novel amorphous cobalt potassium phosphate hydrate compound (KCoPO4·H2O) is identified to be active photocatalyst for oxygen evolution reaction (OER) to facilitate hydrogen generation from water photolysis. It has been synthesized through a facile and cost-effective solution-based precipitation method using earth-abundant materials. Its highly porous structure and large surface areas are found to be responsible for the excellent electrochemical performance featuring a low OER onset at ˜550 mVSCE and high current density in alkaline condition. Unlike traditional cobalt-based spinel oxides (Co3O4, NiCo2O4) and phosphate (Co-Pi, Co(PO3)2) electrocatalysts, with proper energy band alignment for light-assisted water oxidation, cobalt potassium phosphate hydrate also exhibits robust visible-light response, generating a photocurrent density of ˜200 ?A cm-2 at 0.7 VSCE. This catalyst could thus be considered as a promising candidate to perform photoelectrochemical water splitting.

Zhang, Ye; Zhao, Chunsong; Dai, Xuezeng; Lin, Hong; Cui, Bai; Li, Jianbao

2013-12-01

139

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

140

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

141

Comparative electrochemical analysis of crystalline and amorphous anodized iron oxide nanotube layers as negative electrode for LIB.  

PubMed

This work is a comparative study of the electrochemical performance of crystalline and amorphous anodic iron oxide nanotube layers. These nanotube layers were grown directly on top of an iron current collector with a vertical orientation via a simple one-step synthesis. The crystalline structures were obtained by heat treating the as-prepared (amorphous) iron oxide nanotube layers in ambient air environment. A detailed morphological and compositional characterization of the resultant materials was performed via transmission electron microscopy (TEM), field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and Raman spectroscopy. The XRD patterns were further analyzed using Rietveld refinements to gain in-depth information on their quantitative phase and crystal structures after heat treatment. The results demonstrated that the crystalline iron oxide nanotube layers exhibit better electrochemical properties than the amorphous iron oxide nanotube layers when evaluated in terms of the areal capacity, rate capability, and cycling performance. Such an improved electrochemical response was attributed to the morphology and three-dimensional framework of the crystalline nanotube layers offering short, multidirectional transport lengths, which favor rapid Li(+) ions diffusivity and electron transport. PMID:24964233

Pervez, Syed Atif; Kim, Doohun; Farooq, Umer; Yaqub, Adnan; Choi, Jung-Hee; Lee, You-Jin; Doh, Chil-Hoon

2014-07-23

142

A reliable aerosol-spray-assisted approach to produce and optimize amorphous metal oxide catalysts for electrochemical water splitting.  

PubMed

An aerosol-spray-assisted approach (ASAA) is proposed and confirmed as a precisely controllable and continuous method to fabricate amorphous mixed metal oxides for electrochemical water splitting. The proportion of metal elements can be accurately controlled to within (5±5)?%. The products can be sustainably obtained, which is highly suitable for industrial applications. ASAA was used to show that Fe6Ni10O(x) is the best catalyst among the investigated Fe-Ni-O(x) series with an overpotential of as low as 0.286?V (10?mA?cm(-2)) and a Tafel slope of 48?mV/decade for the electrochemical oxygen evolution reaction. Therefore, this work contributes a versatile, continuous, and reliable way to produce and optimize amorphous metal oxide catalysts. PMID:24899118

Kuai, Long; Geng, Jing; Chen, Changyu; Kan, Erjie; Liu, Yadong; Wang, Qing; Geng, Baoyou

2014-07-14

143

Excimer laser crystallization of amorphous indium–tin oxide thin films and application to fabrication of Bragg gratings  

Microsoft Academic Search

Amorphous (a-) indium–tin oxide (ITO) thin films were crystallized at ambient temperature by irradiation with KrF (248 nm) or ArF (193 nm) excimer laser pulses of ?40 mJ\\/cm2 per pulse. Electrical resistivity of the specimen at ?300 K decreased from 5.9×10?4 ? cm to 2.7×10?4 ? cm upon laser crystallization. This decrease was due to the increase in the carrier

Hideo Hosono; Masaaki Kurita; Hiroshi Kawazoe

1999-01-01

144

Change in the optical properties of amorphous films of transition metal oxides upon formation of the nanocrystalline phase  

Microsoft Academic Search

Weakly absorbing films of tantalum oxide Ta2O5 with the crystallization kinetics typical of amorphous films have been investigated. The films have been prepared by reactive\\u000a magnetron sputtering on substrates of different natures (titanium and optical silica glass). The crystallization heat treatment\\u000a of the films has been performed at temperatures ranging from 500 to 700 °C. Changes in the optical properties

V. I. Shapovalov; L. P. Efimenko; A. E. Komlev; K. E. Pugachev; V. G. Baryshnikov; I. G. Polyakova

2009-01-01

145

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

PubMed

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

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

2014-01-01

146

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

147

Hydrogen evolution from a copper(I) oxide photocathode coated with an amorphous molybdenum sulphide catalyst  

NASA Astrophysics Data System (ADS)

Concerns over climate change resulting from accumulation of anthropogenic carbon dioxide in the atmosphere and the uncertainty in the amount of recoverable fossil fuel reserves are driving forces for the development of renewable, carbon-neutral energy technologies. A promising clean solution is photoelectrochemical water splitting to produce hydrogen using abundant solar energy. Here we present a simple and scalable technique for the deposition of amorphous molybdenum sulphide films as hydrogen evolution catalyst onto protected copper(I) oxide films. The efficient extraction of excited electrons by the conformal catalyst film leads to photocurrents of up to -5.7mAcm-2 at 0V versus the reversible hydrogen electrode (pH 1.0) under simulated AM 1.5 solar illumination. Furthermore, the photocathode exhibits enhanced stability under acidic environments, whereas photocathodes with platinum nanoparticles as catalyst deactivate more rapidly under identical conditions. The work demonstrates the potential of earth-abundant light-harvesting material and catalysts for solar hydrogen production.

Morales-Guio, Carlos G.; Tilley, S. David; Vrubel, Heron; Grätzel, Michael; Hu, Xile

2014-01-01

148

Hydrogen evolution from a copper(I) oxide photocathode coated with an amorphous molybdenum sulphide catalyst.  

PubMed

Concerns over climate change resulting from accumulation of anthropogenic carbon dioxide in the atmosphere and the uncertainty in the amount of recoverable fossil fuel reserves are driving forces for the development of renewable, carbon-neutral energy technologies. A promising clean solution is photoelectrochemical water splitting to produce hydrogen using abundant solar energy. Here we present a simple and scalable technique for the deposition of amorphous molybdenum sulphide films as hydrogen evolution catalyst onto protected copper(I) oxide films. The efficient extraction of excited electrons by the conformal catalyst film leads to photocurrents of up to -5.7?mA?cm(-2) at 0?V versus the reversible hydrogen electrode (pH 1.0) under simulated AM 1.5 solar illumination. Furthermore, the photocathode exhibits enhanced stability under acidic environments, whereas photocathodes with platinum nanoparticles as catalyst deactivate more rapidly under identical conditions. The work demonstrates the potential of earth-abundant light-harvesting material and catalysts for solar hydrogen production. PMID:24402352

Morales-Guio, Carlos G; Tilley, S David; Vrubel, Heron; Grätzel, Michael; Hu, Xile

2014-01-01

149

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

NASA Astrophysics Data System (ADS)

In this study, we measured the low-temperature resistivity of amorphous two- and three-dimensional (2D and 3D) indium-zinc oxide, indium-gallium-zinc oxide, and indium-tin-zinc oxide films with a wide range of carrier densities. To determine their critical characteristics at the metal-insulator transition (MIT), we used the Ioffe-Regel criterion. We found that the MIT occurs in a narrow range between k F ? = 0.13 and k F ? = 0.25, where k F and ? are the Fermi wave number and electron mean free path, respectively. For films in the insulating region, we analyzed ? ( T ) using a procedure proposed by Zabrodskii and Zinov'eva. This analysis confirmed the occurrence of Mott and Efros-Shklovskii (ES) variable-range hopping. The materials studied show crossover behavior from exp(TMott/T)1/4 or exp(TMott/T)1/3 for Mott hopping conduction to exp(TES/T)1/2 for ES hopping conduction with decreasing temperature. For both 2D and 3D materials, we found that the relationship between TMott and TES satisfies TES ? TMott2/3.

Makise, Kazumasa; Hidaka, Kazuya; Ezaki, Syohei; Asano, Takayuki; Shinozaki, Bunju; Tomai, Shigekazu; Yano, Koki; Nakamura, Hiroaki

2014-10-01

150

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

SciTech Connect

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

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

2014-10-21

151

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

SciTech Connect

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

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

2014-03-15

152

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

PubMed

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

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

2015-01-14

153

Simple method to enhance positive bias stress stability of in-ga-zn-o thin-film transistors using a vertically graded oxygen-vacancy active layer.  

PubMed

We proposed a simple method to deposit a vertically graded oxygen-vacancy active layer (VGA) to enhance the positive bias stress (PBS) stability of amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs). We deposited a-IGZO films by sputtering (target composition; In2O3:Ga2O3:ZnO = 1:1:1 mol %), and the oxygen partial pressure was varied during deposition so that the front channel of the TFTs was fabricated with low oxygen partial pressure and the back channel with high oxygen partial pressure. Using this method, we were able to control the oxygen vacancy concentration of the active layer so that it varied with depth. As a result, the turn-on voltage shift following a 10?000 s PBS of optimized VGA TFT was drastically improved from 12.0 to 5.6 V compared with a conventional a-IGZO TFT, without a significant decrease in the field effect mobility. These results came from the self-passivation effect and decrease in oxygen-vacancy-related trap sites of the VGA TFTs. PMID:25402628

Park, Ji Hoon; Kim, Yeong-Gyu; Yoon, Seokhyun; Hong, Seonghwan; Kim, Hyun Jae

2014-12-10

154

Improved performance of solution-processed a-InGaZnO thin-film transistors due to Ar/O2 mixed-plasma treatment  

NASA Astrophysics Data System (ADS)

We investigated the effects of Ar and O2 treatment and of Ar/O2 mixedplasma treatment on the electrical characteristics of solution-processed amorphous indium-gallium-zinc-oxide ( a-IGZO) thin-film transistors (TFTs). The electrical performance and the instability of a-IGZO TFTs were significantly improved by the plasma treatments. The plasma treatments reduced the carbon-based residual contamination that acted as possible trap sites. In particular, the O2-plasma treatment produced a significant improvement in the reliability of a-IGZO TFTs when compared with the Ar-plasma-treated device, owing to the elimination of residual carbon in the active channel of the solution-processed a-IGZO. However, the optimized improvement of the solution-processed a-IGZO TFT under a gate bias stress was obtained for the device treated with an Ar/O2 mixed-gas plasma. The plasma treatment in the Ar/O2-mixed ambience remarkably enhanced not only the reliability but also the electrical performance of the a-IGZO TFT; the on/off-current ratio, the field-effect mobility, and the subthreshold slope were 6.78 × 107, 1.24 cm2/V·s, and 513 mV/dec, respectively.

Kim, Kwan-Soo; Hwang, Yeong-Hyeon; Hwang, Inchan; Cho, Won-Ju

2014-08-01

155

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 Fe3þ 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

156

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. PMID:16535706

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

1997-01-01

157

Fabrication and characterization of ferroelectric-gate thin-film transistors with an amorphous oxide semiconductor, amorphous In–Ga–Zn–O  

NASA Astrophysics Data System (ADS)

We fabricated and characterized ferroelectric-gate thin-film transistors (FeTFTs) with an amorphous In–Ga–Zn–O (a-IGZO) channel and an oxide ferroelectric (Bi,La)4Ti3O12 (BLT) gate insulator, and examined the fabrication conditions beforehand for realizing ferroelectric hysteresis in their drain current versus gate voltage (ID–VG) characteristics. First, the optimal annealing conditions for BLT-thin-film formation by the sol–gel method were considered in terms of chemical phenomena and crystallization mechanism. As a result, the leakage current density of the film was decreased by more than two orders of magnitude. Second, sputtering deposition conditions and postdeposition annealing temperatures of a-IGZO thin films were investigated to prepare the a-IGZO channel with good electrical properties. A small charge-injection-type hysteresis width of 0.2 V was obsereved in ID–VG characteristics of a-IGZO/SiO2 TFTs. Finally, a-IGZO/BLT FeTFTs were fabricated using the above results, and the ferroelectric hysteresis with a width of 0.4 V was observed.

Haga, Ken-ichi; Tokumitsu, Eisuke

2014-11-01

158

Effects of dopants in InOx-based amorphous oxide semiconductors for thin-film transistor applications  

NASA Astrophysics Data System (ADS)

Amorphous metal oxide thin-film transistors (TFTs) are fabricated using InOx-based semiconductors doped with TiO2, WO3, or SiO2. Even at low-dopant densities, the electrical properties of the film strongly depend on the dopant used. We found that this dependence could be reasonably explained by differences in the bond-dissociation energy of the dopants. By incorporating a dopant with a higher bond-dissociation energy, the film became less sensitive to the partial pressure of oxygen used during sputtering and remained electrically stable upon thermal annealing. Thus, choosing a dopant with an appropriate bond-dissociation energy is important when fabricating stable metal-oxide TFTs for flat-panel displays.

Aikawa, Shinya; Nabatame, Toshihide; Tsukagoshi, Kazuhito

2013-10-01

159

High Mobility and Stability of Thin-Film Transistors Using Silicon-Doped Amorphous Indium Tin Oxide Semiconductors  

NASA Astrophysics Data System (ADS)

We report the fabrication of high-performance thin-film transistors (TFTs) with an amorphous silicon indium tin oxide ( a-SITO) channel, which was deposited by cosputtering a silicon dioxide and an indium tin oxide target. The effect of the silicon doping on the device performance and stability of the a-SITO TFTs was investigated. The field-effect mobility and stability under positive bias stress of the a-SITO TFTs with optimized Si content (0.22 at.% Si) dramatically improved to 28.7 cm2/Vs and 1.5 V shift of threshold voltage, respectively, compared with the values (0.72 cm2/Vs and 8.9 V shift) for a-SITO TFTs with 4.22 at.% Si. The role of silicon in a-SITO TFTs is discussed based on various physical and chemical analyses, including x-ray absorption spectroscopy, x-ray photoelectron spectroscopy, and spectroscopic ellipsometry measurements.

Seo, T. W.; Kim, Hyun-Suk; Lee, Kwang-Ho; Chung, Kwun-Bum; Park, Jin-Seong

2014-09-01

160

Photoresist-Free Fully Self-Patterned Transparent Amorphous Oxide Thin-Film Transistors Obtained by Sol-Gel Process  

PubMed Central

We demonstrated self-patterned solution-processed amorphous oxide semiconductor thin-film transistors (TFTs) using photosensitive sol-gels. The photosensitive sol-gels were synthesized by adding ?-diketone compounds, i.e., benzoylacetone and acetylacetone, to sol-gels. The chemically modified photosensitive sol-gels showed a high optical absorption at specific wavelengths due to the formation of metal chelate bonds. Photoreactions of the modified solutions enabled a photoresist-free process. Moreover, Zn–Sn–O with a high Sn ratio, which is hard to wet-etch using conventional photolithography due to its chemical durability, was easily patterned via the self-patterning process. Finally, we fabricated a solution-processed oxide TFT that included fully self-patterned electrodes and an active layer. PMID:24686314

Lim, Hyun Soo; Rim, You Seung; Kim, Hyun Jae

2014-01-01

161

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

162

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 oxide-alloy 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

163

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

PubMed

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

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

2014-02-28

164

Amorphous Silicon Thin-Film Transistors Employing Photoprocessed Tantalum Oxide Films as Gate Insulators  

Microsoft Academic Search

Amorphous silicon thin-film transistors (a-Si:H TFT's) with photoprocessed TaOx\\/photo-CVD SiNx double layer gate insulator have been fabricated. The usefulness of photoprocessed TaOx film as a gate insulator and the reason for improvement in TFT characteristics thereby are discussed. There is a correlation among TFT characteristics, a-Si:H\\/SiNx interface properties and stress in the gate insulator. Better TFT characteristics are obtained for

Masahiro Matsui; Hiroshi Nagayoshi; Goro Muto; Satoshi Tanimoto; Koichi Kuroiwa; Yasuo Tarui

1990-01-01

165

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

166

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

167

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

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 {sigma} >; 3000 S/cm.

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

2011-01-01

168

Femtosecond laser-induced nanoperiodic structures and simultaneous crystallization in amorphous indium-tin-oxide thin films  

NASA Astrophysics Data System (ADS)

Fabrication of crystalline indium-tin-oxide (c-ITO) nanogratings and smooth line patterns on amorphous ITO (a-ITO) thin films by femtosecond laser-induced structuring and simultaneous crystallization followed by chemical etching is demonstrated. Three types of c-ITO structures are obtained merely by controlling the laser pulse energy of a high-repetition rate femtosecond laser at wavelength 532 nm: nanogratings perpendicular to laser polarization direction with period of 130 ± 11 nm, smooth c-ITO line patterns as well as nanogratings parallel to laser polarization direction with period of 390 ± 10 nm. Large area c-ITO patterns and nanograting structures are fabricated, which are expected to be used in optoelectronic and micro-electronic devices.

Cheng, C. W.; Lee, I. M.; Chen, J. S.

2014-10-01

169

Amorphous polymeric anode materials from poly(acrylic acid) and tin(II) oxide for lithium ion batteries  

NASA Astrophysics Data System (ADS)

The reaction of poly(acrylic acid) (PAA) and tin oxide (II) (SnO) provides an amorphous product (PSnA), which was found to be a promising precursor of an anode material for lithium ion batteries. The anode electrode composed of PSnA as the active material and polyimide as the binder showed a better cycling performance than the anode electrode using SnO as the active material. It is considered that the organic polymer chain present in PSnA might act as a buffer to the volume change in the active material during the charge-discharge cycles. The X-ray diffraction (XRD) results of the electrode after delithiation revealed that nano-sized cubic tin (?-Sn) and tetragonal tin (?-Sn) particles are formed in the active material. Therefore, it is concluded that these nano-sized tin particles in the polymer matrix were effective for the storage and release of Li ions.

Yamaguchi, Hiroyuki; Nakanishi, Shinji; Iba, Hideki; Itoh, Takahito

2015-02-01

170

Hexagonal Ag nanoarrays induced enhancement of blue light emission from amorphous oxidized silicon nitride via localized surface plasmon coupling.  

PubMed

A significant enhancement of blue light emission from amorphous oxidized silicon nitride (a-SiNx:O) films is achieved by introduction of ordered and size-controllable arrays of Ag nanoparticles between the silicon substrate and a-SiNx:O films. Using hexagonal arrays of Ag nanoparticles fabricated by nanosphere lithography, the localized surface plasmons (LSPs) resonance can effectively increase the internal quantum efficiency from 3.9% to 13.3%. Theoretical calculation confirms that the electromagnetic field-intensity enhancement is through the dipole surface plasma coupling with the excitons of a-SiNx:O films, which demonstrates a-SiNx:O films with enhanced blue emission are promising for silicon-based light-emitting applications by patterned Ag arrays. PMID:25402058

Ma, Zhongyuan; Ni, Xiaodong; Zhang, Wenping; Jiang, Xiaofan; Yang, Huafeng; Yu, Jie; Wang, Wen; Xu, Ling; Xu, Jun; Chen, Kunji; Feng, Duan

2014-11-17

171

Characterization of anodic aluminum oxide film and its application to amorphous silicon thin film transistors  

Microsoft Academic Search

Al2O3\\/SiNx double-layered dielectric films suitable for large-size amorphous silicon thin film transistor liquid crystal displays (a-Si:H TFT LCD) have been prepared by anodization and plasma enhanced chemical vapor deposition (PECVD). Al2O3 films were formed at various pH values and volume ratio of water (H2O%) in the electrolyte. The optimal quality of Al2O3 film was achieved at pH = 6 and

C. W. Liang; T. C. Luo; M. S. Feng; H. C. Cheng; David Su

1996-01-01

172

Amorphous Silicon Thin-Film Transistors Employing Photoprocessed Tantalum Oxide Films as Gate Insulators  

NASA Astrophysics Data System (ADS)

Amorphous silicon thin-film transistors (a-Si:H TFT’s) with photoprocessed TaOx/photo-CVD SiNx double layer gate insulator have been fabricated. The usefulness of photoprocessed TaOx film as a gate insulator and the reason for improvement in TFT characteristics thereby are discussed. There is a correlation among TFT characteristics, a-Si:H/SiNx interface properties and stress in the gate insulator. Better TFT characteristics are obtained for higher compressive stress in the gate insulator due to better interface properties. The photoprocessed TaOx film plays a role in changing the stress and consequently improves TFT characteristics. Annealing of TaOx film in the presence of both UV irradiation and an oxygen ambient after photo-CVD deposition also improves the stability of TFT characteristics.

Matsui, Masahiro; Nagayoshi, Hiroshi; Muto, Goro; Tanimoto, Satoshi; Kuroiwa, Koichi; Tarui, Yasuo

1990-01-01

173

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

SciTech Connect

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

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

2012-09-24

174

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 Å and 8.4 Å 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 Å, 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

175

Generalized molybdenum oxide surface chemical state XPS determination via informed amorphous sample model  

NASA Astrophysics Data System (ADS)

Accurate elemental oxidation state determination for the outer surface of a complex material is of crucial importance in many science and engineering disciplines, including chemistry, fundamental and applied surface science, catalysis, semiconductors and many others. X-ray photoelectron spectroscopy (XPS) is the primary tool used for this purpose. The spectral data obtained, however, is often very complex and can be subject to incorrect interpretation. Unlike traditional XPS spectra fitting procedures using purely synthetic spectral components, here we develop and present an XPS data processing method based on vector analysis that allows creating XPS spectral components by incorporating key information, obtained experimentally. XPS spectral data, obtained from series of molybdenum oxide samples with varying oxidation states and degree of crystallinity, were processed using this method and the corresponding oxidation states present, as well as their relative distribution was elucidated. It was shown that monitoring the evolution of the chemistry and crystal structure of a molybdenum oxide sample due to an invasive X-ray probe could be used to infer solutions to complex spectral envelopes.

Baltrusaitis, Jonas; Mendoza-Sanchez, Beatriz; Fernandez, Vincent; Veenstra, Rick; Dukstiene, Nijole; Roberts, Adam; Fairley, Neal

2015-01-01

176

Light induced instability mechanism in amorphous InGaZn oxide semiconductors  

SciTech Connect

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

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

2014-04-21

177

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

E-print Network

of this study were: to evaluate Fe oxides precipitated at various initial Si/Fe molar ratios in terms of: 1) kinetics of acid dissolution as influenced by proton and anion concentration, 2) dissolution kinetics as influenced by the commercially available... LU CO P 600 X D 0 ~ 400 0. 254 nm 0. 10 0. 05 200 0. 01 0. 00 12 22 32 42 52 '2 0 Fig. 1. X-ray patterns for synthetic oxides with 0. 00 to O. t0 Si/Fe molar ratios. 1000 800 HIGH Sl/Fe 0. 254 O LU 600 M tO I- 400 D 0 0 200 1...

Seaman, John C.

2012-06-07

178

Structure, Morphology, and Optical Properties of Amorphous and Nanocrystalline Gallium Oxide Thin Films  

SciTech Connect

Ga2O3 thin films were produced by sputter deposition by varying the substrate temperature (Ts) in a wide range (Ts=25-800 oC). The structural characteristics and optical properties of Ga2O3 films were evaluated using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDS), Rutherford backscattering spectrometry (RBS) and spectrophotometric measurements. The effect of growth temperature is significant on the chemistry, crystal structure and morphology of Ga2O3 films. XRD and SEM analyses indicate that the Ga2O3 films grown at lower temperatures were amorphous while those grown at Ts?500 oC were nanocrystalline. RBS measurements indicate the well-maintained stoichiometry of Ga2O3 films at Ts=300-700 oC. The spectral transmission of the films increased with increasing temperature. The band gap of the films varied from 4.96 eV to 5.17 eV for a variation in Ts in the range 25-800 oC. A relationship between microstructure and optical property is discussed.

Kumar, S. Sampath; Rubio, E. J.; Noor-A-Alam, M.; Martinez, G.; Manandhar, Sandeep; Shutthanandan, V.; Thevuthasan, Suntharampillai; Ramana, C.V.

2013-02-15

179

On the structural development during ultrathin amorphous Al2O3 film growth on Al(111) and Al(100) surfaces by thermal oxidation  

NASA Astrophysics Data System (ADS)

The structural developments during growth of ultrathin amorphous Al2O3 film on bare Al(100) and Al(111) surfaces, by dry thermal oxidation in the oxygen partial pressure range of 1 × 10- 5-1.0 Pa at 300 K, were investigated as function of the oxide-film thickness by (local) chemical state analysis using angle-resolved X-ray photoelectron spectroscopy in combination with low electron energy diffraction and cross-sectional high resolution transmission electron microscopy. The effect of the dielectric discontinuity, at the interfaces of the surficial Al2O3 film has been determined quantitatively and has been subtracted from the observed chemical shifts of the core level photoelectron binding energies as well as from the observed Auger transition kinetic energies. It is revealed that ultrathin amorphous Al2O3 films on the Al(111) and Al(100) surfaces experience remarkably different structural developments upon growth.

Flötotto, D.; Wang, Z. M.; Mittemeijer, E. J.

2015-03-01

180

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 200°C exhibited high field-effect mobility (?FE) over 55.8 cm2/V·s which is 5 times higher than that of the conventional TFTs due to small threshold voltage (Vth) change of 1.8 V under bias-temperature stress (BTS) condition for 420 minutes. The low-RCH buried-layer allows more strong current-path formed in channel layer well within relatively high-RCH channel-layer since it is less affected by the channel bulk and/or back interface trap with high carrier concentration.

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

2012-04-01

181

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

PubMed Central

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

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

2014-01-01

182

In situ X-Ray Absorption Spectro-Electrochemical Study of Amorphous Tin-Based Composite Oxide Material  

SciTech Connect

We have measured the XAFS spectra of a sample of tin-based composite oxide (TCO) material with a nominal composition of Sn{sub 1.0}B{sub 0.56}P{sub 0.40}Al{sub 0.42}O{sub 3.47} during the discharge and charge cycles in an ''in situ'' configuration. Our results confirm the amorphous nature of TCO and show that Sn in TCO is coordinated with 3 oxygen atoms at a distance of 2.12 {angstrom}. Upon discharging, initially, Li interacts with the electrochemically active Sn-O center forming metallic Sn in the form of clusters containing just a few atoms. Upon further discharge, Li alloys with Sn forming initially highly dispersed forms of Li{sub 2}Sn{sub 5} and/or LiSn and then Li{sub 7}Sn{sub 3}, Li{sub 5}Sn{sub 2}, Li{sub 13}Sn{sub 5}, or Li{sub 7}Sn{sub 2}. The true nature of the formed alloys could be significantly different from that of the corresponding crystalline phases. Upon charging, metallic Sn is produced with a Sn-Sn distance intermediate to those of gray and white Sn.

Mansour, A. N.; Mukerjee, S.; Yang, X. Q.; McBreen, J.

1998-11-01

183

Reduction of tail state on boron doped hydrogenated amorphous silicon oxide films prepared at high hydrogen dilution.  

PubMed

In this report, we have investigated on the defect state of diborane (B2H6) doped wide bandgap hydrogenated amorphous silicon oxide (p-type a-SiO:H) films prepared using silane (SiH4), hydrogen (H2) and nitrous oxide (N2O) in a radio frequency (RF) plasma enhanced chemical vapor deposition (PECVD) system with different hydrogen dilutions. The films prepared with higher hydrogen dilution show lower Urbach energy (Eu), lower microstructure (R*), lower short and medium range disorder (omegaTO, Gamma(TO), I(TA)/I(TO), I(LA)/I(TO)), higher dark conductivity (sigma d) and higher refractive index (n) with high optical gap (Eg). Eu decreases from 248 meV to 153 meV, and R* decreases from 0.46 to 0.26, Raman peak omegaTO-TO mode position shifts from 480.24 to 483.28, GammaTO-full width half maximum of omegaTO decreases from 78.16 to 63.87, I(TA)/I(TO)-the ratio of integrated area of TA and TO mode decreases from 0.624 to 0.474, I(LA)/I(TO)-the ratio of integrated area of LA and TO mode deceases from 0.272 to 0.151, sigma d increases from 4.6 x 10(-7) S/cm to 1.1 x 10(-6) S/cm, n increases from 3.70 to 3.86. Reduced Nd, Eu and R* at wide Eg indicates that the films are more useful for solar cell window layer. Applying this layer to a single junction solar cell shows open circuit voltage (Voc) = 0.80 V, short circuit current density (Jsc) = 16.3 mA/cm2, fill factor (FF) = 72%, efficiency (eta) = 9.4%. PMID:24266147

Park, Jinjoo; Iftiquar, S M; Lee, Sunwha; Park, Hyeongsik; Shin, Chonghoon; Jung, Junhee; Lee, Youn-Jung; Balaji, Nagarajan; Yi, Junsin

2013-12-01

184

Monochromatic light-assisted erasing effects of In-Ga-Zn-O thin film transistor memory with Al{sub 2}O{sub 3}/Zn-doped Al{sub 2}O{sub 3}/Al{sub 2}O{sub 3} stacks  

SciTech Connect

We studied how electrical erasing of indium gallium zinc oxide-thin-film-transistor memory was improved by adding concurrent irradiation with monochromatic light (ML). At fixed gate bias, irradiating at wavelengths of ?500?nm increased the erasing window (?V{sub th-e}) significantly: At a gate bias of ?20?V and an erasing time of 5?min, ML irradiation at 400?nm increased ?V{sub th-e} from 0.29 to 3.21?V. ?V{sub th-e} increased incrementally with gate bias, erasing time, and ML power density, particularly at short ML wavelengths. Analyzing our experimental results, we discuss the underlying erasure mechanisms.

Chen, Sun; Zhang, Wen-Peng; Cui, Xing-Mei; Ding, Shi-Jin, E-mail: sjding@fudan.edu.cn; Sun, Qing-Qing; Zhang, Wei [State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai 200433 (China)] [State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai 200433 (China)

2014-03-10

185

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

NASA Astrophysics Data System (ADS)

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 and 1.4 ?m, respectively. Their length ranged from 10 to 200 ?m and the aspect ratio was 10-200. Each sheath was constructed by very small particles with a diameter of less than 100 nm. The hollow sheaths were mainly composed of Fe and O with small amounts of Si and P. The chemical composition analyzed by EDX was roughly Fe:Si:P=80:15:5 with the exception of O. XRD measurement revealed that crystal structures of the sheath were similar to that of 2-line ferrihydrite. The sheath showed spin-glass-like magnetic properties.

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

2007-03-01

186

Tuning electrical properties in amorphous zinc tin oxide thin films for solution processed electronics.  

PubMed

Solution processed zinc tin oxide (ZTO) thin film transistors (TFTs) were fabricated by varying the Zn/Sn composition. The addition of Sn to the zinc oxide (ZnO) films resulted in improved electrical characteristics, with devices of Zn0.7Sn0.3O composition showing the highest mobility of 7.7 cm(2)/(V s). An improvement in subthreshold swings was also observed, indicative of a reduction of the interfacial trap densities. Mobility studies at low temperature have been carried out, which indicated that the activation energy was reduced with Sn incorporation. Kelvin probe force microscopy was performed on the films to evaluate work function and correlated to the metal-semiconductor barrier indicating Zn0.7Sn0.3O films had the smallest barrier for charge injection. Organic-inorganic hybrid complementary inverters with a maximum gain of 10 were fabricated by integrating ZTO TFTs with poly-3-hexylthiophene (P3HT) transistors. PMID:24380364

Chandra, R Devi; Rao, Manohar; Zhang, Keke; Prabhakar, Rajiv Ramanujam; Shi, Chen; Zhang, Jie; Mhaisalkar, Subodh G; Mathews, Nripan

2014-01-22

187

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

NASA Astrophysics Data System (ADS)

Controlled photo-induced oxidation and amorphization of elemental trigonal tellurium are achieved by laser irradiation at optical wavelengths. These processes are monitored in situ by time-resolved Raman scattering and ex situ by electron microscopies. Ultrathin TeO2 films form on Te surfaces, as a result of irradiation, with an interface layer of amorphous Te intervening between them. It is shown that irradiation, apart from enabling the controllable transformation of bulk Te to one-dimensional nanostructures, such as Te nanotubes and hybrid core-Te/sheath-TeO2 nanowires, causes also a series of light-driven (athermal) phase transitions involving the crystallization of the amorphous TeO2 layers and its transformation to a multiplicity of crystalline phases including the ?-, ?-, and ?-TeO2 crystalline phases. The kinetics of the above photo-induced processes is investigated by Raman scattering at various laser fluences revealing exponential and non-exponential kinetics at low and high fluence, respectively. In addition, the formation of ultrathin (less than 10 nm) layers of amorphous TeO2 offers the possibility to explore structural transitions in 2D glasses by observing changes in the short- and medium-range structural order induced by spatial confinement.

Vasileiadis, Thomas; Yannopoulos, Spyros N.

2014-09-01

188

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

SciTech Connect

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

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

2014-09-14

189

Engineering of porosity in amorphous materials. Plasma oxidation of hydrocarbon templates in polysilsesquioxanes  

SciTech Connect

Arylene- and alkylene-bridged polysilsesquioxanes were prepared by sol-gel processing of bis(triethoxysilyl)-arylene monomers 1--4, and alkylene monomers 5--9. The arylene polysilsesquioxanes were porous materials with surface areas as high as 830 m{sup 2}/g (BET). Treatment with an inductively coupled oxygen plasma resulted in the near quantitative removal of the arylene bridging groups and a coarsening of the pore structure. Solid state {sup 29}Si NMR was used to confirm the conversion of the sesquioxane silicons (T) to silica (Q). The alkylene-bridged polysilsesquioxanes were non-porous. Oxygen plasma treatment afforded silica gels with mesoporosity. The porosity in the silica gels appears to arise entirely from the oxidation of the alkylene spacers.

Loy, D.A.; Buss, R.J.; Assink, R.A. [Sandia National Labs., Albuquerque, NM (United States); Shea, K.J.; Oviatt, H. [Univ. of California, Irvine, CA (United States)

1994-12-31

190

Effects of ionic liquids on cation dynamics in amorphous polyethylene oxide electrolytes  

SciTech Connect

We perform extensive molecular dynamics simulations of a poly(ethylene oxide)-based polymer electrolyte material containing lithium bis(trifluoromethanesulfonyl)imide salt for a wide temperature regime above and below the experimental crystallization temperature with and without N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide ionic liquid (IL). The impact of the IL-concentration on the cation dynamics is studied. The increase of the cation mobility upon addition of IL is significant but temperature-independent. This can be related to distinct variations of the underlying transport properties as expressed within the previously introduced transport model of polymer electrolytes. Even for the largest IL concentration the transport model perfectly predicts the non-trivial time-dependence of the cationic mean square displacement for all temperatures. Finally, we compare our numerical and theoretical findings with the results of recent nuclear magnetic resonance experiments. In this way we can exclusively relate the strong experimentally observed dependence of the low-temperature Li-diffusivity on the IL concentration to the impact of IL on crystallization.

Chattoraj, Joyjit, E-mail: jchat-01@uni-muenster.de; Diddens, Diddo; Heuer, Andreas [Institut für Physikalische Chemie, Westfälische Wilhelms-Universität Münster, Corrensstrasse 28/30, D-48149 Münster (Germany)] [Institut für Physikalische Chemie, Westfälische Wilhelms-Universität Münster, Corrensstrasse 28/30, D-48149 Münster (Germany)

2014-01-14

191

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

SciTech Connect

Nitrogen plasma treatment was performed on fluorine-doped tin oxide (SnO{sub 2}: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 SnO{sub 2}: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 SnO{sub 2}: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 [Department of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 305-701 (Korea, Republic of)

2011-04-15

192

Electric charging/discharging characteristics of super capacitor, using de-alloying and anodic oxidized Ti-Ni-Si amorphous alloy ribbons  

NASA Astrophysics Data System (ADS)

Charging/discharging behaviors of de-alloyed and anodic oxidized Ti-Ni-Si amorphous alloy ribbons were measured as a function of current between 10 pA and 100 mA, using galvanostatic charge/discharging method. In sharp contrast to conventional electric double layer capacitor (EDLC), discharging behaviors for voltage under constant currents of 1, 10 and 100 mA after 1.8 ks charging at 100 mA show parabolic decrease, demonstrating direct electric storage without solvents. The supercapacitors, devices that store electric charge on their amorphous TiO2-x surfaces that contain many 70-nm sized cavities, show the Ragone plot which locates at lower energy density region near the 2nd cells, and RC constant of 800 s (at 1 mHz), which is 157,000 times larger than that (5 ms) in EDLC.

Fukuhara, Mikio; Sugawara, Kazuyuki

2014-05-01

193

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

SciTech Connect

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

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

2014-06-16

194

Electric charging/discharging characteristics of super capacitor, using de-alloying and anodic oxidized Ti-Ni-Si amorphous alloy ribbons.  

PubMed

Charging/discharging behaviors of de-alloyed and anodic oxidized Ti-Ni-Si amorphous alloy ribbons were measured as a function of current between 10 pA and 100 mA, using galvanostatic charge/discharging method. In sharp contrast to conventional electric double layer capacitor (EDLC), discharging behaviors for voltage under constant currents of 1, 10 and 100 mA after 1.8 ks charging at 100 mA show parabolic decrease, demonstrating direct electric storage without solvents. The supercapacitors, devices that store electric charge on their amorphous TiO2-x surfaces that contain many 70-nm sized cavities, show the Ragone plot which locates at lower energy density region near the 2nd cells, and RC constant of 800 s (at 1 mHz), which is 157,000 times larger than that (5 ms) in EDLC. PMID:24959106

Fukuhara, Mikio; Sugawara, Kazuyuki

2014-01-01

195

Electron tunnelling into amorphous germanium and silicon.  

NASA Technical Reports Server (NTRS)

Measurements of tunnel conductance versus bias, capacitance versus bias, and internal photoemission were made in the systems aluminum-oxide-amorphous germanium and aluminium-oxide-amorphous silicon. A function was extracted which expresses the deviation of these systems from the aluminium-oxide-aluminium system.

Smith, C. W.; Clark, A. H.

1972-01-01

196

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

PubMed Central

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

2012-01-01

197

Large-scale complementary macroelectronics using hybrid integration of carbon nanotubes and IGZO thin-film transistors.  

PubMed

Carbon nanotubes and metal oxide semiconductors have emerged as important materials for p-type and n-type thin-film transistors, respectively; however, realizing sophisticated macroelectronics operating in complementary mode has been challenging due to the difficulty in making n-type carbon nanotube transistors and p-type metal oxide transistors. Here we report a hybrid integration of p-type carbon nanotube and n-type indium-gallium-zinc-oxide thin-film transistors to achieve large-scale (>1,000 transistors for 501-stage ring oscillators) complementary macroelectronic circuits on both rigid and flexible substrates. This approach of hybrid integration allows us to combine the strength of p-type carbon nanotube and n-type indium-gallium-zinc-oxide thin-film transistors, and offers high device yield and low device variation. Based on this approach, we report the successful demonstration of various logic gates (inverter, NAND and NOR gates), ring oscillators (from 51 stages to 501 stages) and dynamic logic circuits (dynamic inverter, NAND and NOR gates). PMID:24923382

Chen, Haitian; Cao, Yu; Zhang, Jialu; Zhou, Chongwu

2014-01-01

198

New amorphous oxides as high capacity negative electrodes for lithium batteries: the Li xMVO 4 (M = Ni, Co, Cd, Zn; 1 < x ? 8) series  

NASA Astrophysics Data System (ADS)

The crystallized precursors LiMVO 4 (M = Co, Ni, Cd, Zn) are irreversibly transformed to lithiated amorphous oxides Li xMVO 4 ( x close to 8) during the first Li insertion in a lithium battery. Under low rate, these amorphous oxides cycle large amounts of Li per formula unit in the 0.02-3 V range (versus Li), with an average voltage in the order of 0.6 V for Li insertion and 1.4 V for Li extraction. In the case of Li xNiVO 4 at first Li extraction, for example, ? x = 6.6 and Q = 980 Ah/kg (active material alone) or 900 Ah/kg (calculated with respect to the total mass: material + carbon black) or 4230 Ah/l (active material alone), more than 5.5 times the volumic capacity of graphite. The cycling behavior at fast rate ( C/6) was very good with a peculiar increase in capacity with cycle number after an initial decrease. Characterization of lithiated Li xNiVO 4 samples, performed with the use of local techniques such as X-ray absorption spectra (XAS) and electron energy loss spectroscopy (EELS), led to an evaluation of the average oxidation states of V and Ni and of the electronic transfer from Li to V and Ni. Results are compatible with the crystal chemistry of Ni and V oxides. The Li 'incorporation/extraction' process in the series Li xMVO 4 is not a destruction/reconstruction mechanism involving Li 2O and M and V metals. However, it seems to be different from a classical topotactic intercalation reaction.

Guyomard, D.; Sigala, C.; de Gal La Salle, A.; Piffard, Y.

199

Amorphous Computing  

E-print Network

The goal of amorphous computing is to identify organizationalprinciples and create programming technologies for obtainingintentional, pre-specified behavior from the cooperation of myriadunreliable parts that are arranged ...

Abelson, Hal

2007-01-01

200

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

201

Stability of amorphous hydrous manganese oxide in contrasting soils and implications for its use in chemical stabilization of metals/metalloids in contaminated soil environments  

NASA Astrophysics Data System (ADS)

Amorphous manganese oxides are known to be efficient sorbents in soils and thus useful in remediation technologies. A novel amorphous hydrous manganese oxide (HMO) was prepared by a modified procedure generally used for birnessite synthesis. Its long-term stability in view of possible applications for chemical stabilization of metals/metalloids in polluted soils was evaluated. HMO was sealed in experimental bags prepared from polyamide fabric (pore size 1 um) and placed in the pots containing 200 g of soil. Three contrasting soils were used (two cambisols with pH values of 4.2 and 5.4, respectively, and a chernozem with a pH of 7.3). Each pot was equipped with a rhizon pore water sampler and the water content was maintained at 80% WHC throughout the experiment. HMO and pore waters were sampled after 1, 7, 15, 30, 45, 60, 75 and 90 days of incubation. Up to 113 mg Mn/L was released into pore water at the beginning of the experiment in more acidic soils indicating a slight dissolution of HMO surfaces. Manganese release into the pore water stabilized after 15 days in agreement with mass loss measurements. Mass loss decreased again after 60 days of the incubation for the neutral soil due to the formation of secondary rhodochrosite (MnCO3) detected on the HMO surfaces by X-ray diffraction analysis (XRD) and transmission electron microscopy (TEM). The efficiency of HMO for trace metal retention in soils (e.g., Zn) slightly decreased after 60 days, probably due to the mineralogical transformation of the sorbent leading to decrease of binding surfaces. Nevertheless, only approximately 10% of HMO dissolved after 90 days of experiment showing that this sorbent can be relatively stable in the studied soils. Its binding capacity for metals/metalloids should be further tested in soils with elevated contaminant concentrations.

Ettler, V.; Knytl, V.; Komarek, M.; Della Puppa, L.; Mihaljevic, M.; Sebek, O.

2012-04-01

202

Observation of memory effect in germanium nanocrystals embedded in an amorphous silicon oxide matrix of a metalinsulator  

E-print Network

of the memory array. However, such a thick tunnel oxide means that the write and erase pulse durations during-type silicon substrate in dry oxygen ambient using rapid thermal oxidation at 1000 °C. A Ge SiO2 layer

203

Resonant structures based on amorphous silicon sub-oxide doped with Er3+ with silicon nanoclusters for an efficient emission at 1550 nm  

E-print Network

We present a resonant approach to enhance 1550nm emission efficiency of amorphous silicon sub-oxide doped with Er3+ (a-SiOx) layers with silicon nanoclusters (Si-NC). Two distinct techniques were combined to provide a structure that allowed increasing approximately 12x the 1550nm emission. First, layers of SiO2 were obtained by conventional wet oxidation and a-SiOx matrix was deposited by reactive RF co-sputtering. Secondly, an extra pump channel (4I15/2 to 4I9/2) of Er3+ was created due to Si-NC formation on the same a-SiOx matrix via a hard annealing at 1150 C. The SiO2 and the a-SiOx thicknesses were designed to support resonances near the pumping wavelength (~500nm), near the Si-NC emission (~800nm) and near the a-SiOx emission (~1550nm) enhancing the optical pumping process.

Figueira, D S L; Tessler, L R; Frateschi, N C

2009-01-01

204

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

PubMed

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

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

2014-05-30

205

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

SciTech Connect

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

Gerlach, D.; Wilks, R. G.; Wimmer, M.; Felix, R.; Gorgoi, M.; Lips, K.; Rech, B. [Helmholtz-Zentrum Berlin fuer Materialien und Energie GmbH, Hahn-Meitner-Platz 1, D-14109 Berlin (Germany); Wippler, D.; Mueck, A.; Meier, M.; Huepkes, J. [Institut fuer Energie- und Klimaforschung, Forschungszentrum Juelich GmbH, Wilhelm-Johnen-Strasse, D-52428 Juelich (Germany); Lozac'h, M.; Ueda, S.; Sumiya, M. [National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Yoshikawa, H. [Synchrotron X-ray Station at SPring-8, NIMS, Kouto 1-1-1, Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan); Kobayashi, K. [Quantum Beam Science Directorate, Japan Atomic Energy Agency, Kouto 1-1-1, SPring-8, Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan); Baer, M. [Helmholtz-Zentrum Berlin fuer Materialien und Energie GmbH, Hahn-Meitner-Platz 1, D-14109 Berlin (Germany); Institut fuer Physik und Chemie, Brandenburgische Technische Universitaet Cottbus, Konrad-Wachsmann-Allee 1, D-03046 Cottbus (Germany)

2013-07-08

206

Damage-free back channel wet-etch process in amorphous indium-zinc-oxide thin-film transistors using a carbon-nanofilm barrier layer.  

PubMed

Amorphous indium-zinc-oxide thin film transistors (IZO-TFTs) with damage-free back channel wet-etch (BCE) process were investigated. A carbon (C) nanofilm was inserted into the interface between IZO layer and source/drain (S/D) electrodes as a barrier layer. Transmittance electron microscope images revealed that the 3 nm-thick C nanofilm exhibited a good corrosion resistance to a commonly used H3PO4-based etchant and could be easily eliminated. The TFT device with a 3 nm-thick C barrier layer showed a saturated field effect mobility of 14.4 cm(2) V(-1) s(-1), a subthreshold swing of 0.21 V/decade, an on-to-off current ratio of 8.3 × 10(10), and a threshold voltage of 2.0 V. The favorable electrical performance of this kind of IZO-TFTs was due to the protection of the inserted C to IZO layer in the back-channel-etch process. Moreover, the low contact resistance of the devices was proved to be due to the graphitization of the C nanofilms after annealing. In addition, the hysteresis and thermal stress testing confirmed that the usage of C barrier nanofilms is an effective method to fabricate the damage-free BCE-type devices with high reliability. PMID:24969359

Luo, Dongxiang; Zhao, Mingjie; Xu, Miao; Li, Min; Chen, Zikai; Wang, Lang; Zou, Jianhua; Tao, Hong; Wang, Lei; Peng, Junbiao

2014-07-23

207

Low-temperature photo-activated inorganic electron transport layers for flexible inverted polymer solar cells  

NASA Astrophysics Data System (ADS)

A simple and versatile route of forming sol-gel-derived metal oxide n-type electron transport layers (ETLs) for flexible inverted polymer solar cells (PSCs) is proposed using low-temperature photochemical activation process. The photochemical activation, which is induced by deep ultraviolet irradiation on sol-gel films, allows formation of metal oxide n-type ETLs such as zinc oxide (ZnO) and indium gallium zinc oxide films at a low temperature. Compared to poly(3-hexylthiophene)/phenyl-C61-butyric acid methyl ester inverted PSCs with thermally annealed ZnO ETLs (optimized efficiency of 3.26 ± 0.03 %), the inverted PSCs with photo-activated ZnO ETLs showed an improved efficiency of 3.60 ± 0.02 %. The enhanced photovoltaic property is attributed to efficient charge collection from low overall series resistance and high surface area-to-geometric area ratio by the photo-activated ZnO ETLs.

Lee, Jung-Wook; Lee, Soo-Hyoung; Kim, Yong-Hoon; Park, Sung Kyu

2014-09-01

208

Fully transparent and rollable electronics.  

PubMed

Major obstacles toward the manufacture of transparent and flexible display screens include the difficulty of finding transparent and flexible semiconductors and electrodes, temperature restrictions of flexible plastic substrates, and bulging or warping of the flexible electronics during processing. Here we report the fabrication and performance of fully transparent and rollable thin-film transistor (TFT) circuits for display applications. The TFTs employ an amorphous indium-gallium-zinc oxide semiconductor (with optical band gap of 3.1 eV) and amorphous indium-zinc oxide transparent conductive electrodes, and are built on 15-?m-thick solution-processed colorless polyimide (CPI), resulting in optical transmittance >70% in the visible range. As the CPI supports processing temperatures >300 °C, TFT performance on plastic is similar to that on glass, with typical field-effect mobility, turn-on voltage, and subthreshold voltage swing of 12.7 ± 0.5 cm(2)/V·s, -1.7 ± 0.2 V, and 160 ± 29 mV/dec, respectively. There is no significant degradation after rolling the TFTs 100 times on a cylinder with a radius of 4 mm or when shift registers, each consisting of 40 TFTs, are operated while bent to a radius of 2 mm. For handling purposes, carrier glass is used during fabrication, together with a very thin (?1 nm) solution-processed carbon nanotube (CNT)/graphene oxide (GO) backbone that is first spin-coated on the glass to decrease adhesion of the CPI to the glass; peel strength of the CPI from glass decreases from 0.43 to 0.10 N/cm, which eases the process of detachment performed after device fabrication. Given that the CNT/GO remains embedded under the CPI after detachment, it minimizes wrinkling and decreases the substrate's tensile elongation from 8.0% to 4.6%. Device performance is also stable under electrostatic discharge exposures up to 10 kV, as electrostatic charge can be released via the conducting CNTs. PMID:25526282

Mativenga, Mallory; Geng, Di; Kim, Byungsoon; Jang, Jin

2015-01-28

209

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.

Münzenrieder, N. S.; Cherenack, K. H.; Tröster, G.

2011-08-01

210

Glutamate Surface Speciation on Amorphous Titanium Dioxide and  

E-print Network

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

Sverjensky, Dimitri A.

211

Theory of amorphous ices  

PubMed Central

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

Limmer, David T.; Chandler, David

2014-01-01

212

Uranium incorporation into amorphous silica.  

PubMed

High concentrations of uranium are commonly observed in naturally occurring amorphous silica (including opal) deposits, suggesting that incorporation of U into amorphous silica may represent a natural attenuation mechanism and promising strategy for U remediation. However, the stability of uranium in opaline silicates, determined in part by the binding mechanism for U, is an important factor in its long-term fate. U may bind directly to the opaline silicate matrix, or to materials such as iron (hydr)oxides that are subsequently occluded within the opal. Here, we examine the coordination environment of U within opaline silica to elucidate incorporation mechanisms. Precipitates (with and without ferrihydrite inclusions) were synthesized from U-bearing sodium metasilicate solutions, buffered at pH ? 5.6. Natural and synthetic solids were analyzed with X-ray absorption spectroscopy and a suite of other techniques. In synthetic amorphous silica, U was coordinated by silicate in a double corner-sharing coordination geometry (Si at ? 3.8-3.9 Å) and a small amount of uranyl and silicate in a bidentate, mononuclear (edge-sharing) coordination (Si at ? 3.1-3.2 Å, U at ? 3.8-3.9 Å). In iron-bearing synthetic solids, U was adsorbed to iron (hydr)oxide, but the coordination environment also contained silicate in both edge-sharing and corner-sharing coordination. Uranium local coordination in synthetic solids is similar to that of natural U-bearing opals that retain U for millions of years. The stability and extent of U incorporation into opaline and amorphous silica represents a long-term repository for U that may provide an alternative strategy for remediation of U contamination. PMID:24984107

Massey, Michael S; Lezama-Pacheco, Juan S; Nelson, Joey M; Fendorf, Scott; Maher, Kate

2014-08-01

213

Nanocrystal dispersed amorphous alloys  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

214

Tritium in amorphous silicon  

SciTech Connect

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

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

1996-12-31

215

Containerless Solidification of Amorphous Metals  

NASA Technical Reports Server (NTRS)

Method produces large amorphous alloys. Spheres of amorphous metal alloys formed and collected after molten samples coated and cooled in drop tube. Coated spheres cooled acoustically and cryogenically. Amorphous specimens 5mm in diameter or larger possible.

Lee, M. C.; Johnson, W. L.

1984-01-01

216

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

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

217

Small-Dose-Sensitive X-Ray Image Pixel with HgI2 Photoconductor and Amorphous Oxide Thin-Film Transistor.  

PubMed

A new X-ray image sensor is demonstrated with an oxide thin-film transistor backplane and HgI2 sensing material. It displays outstanding image quality under a low X-ray exposure and a low electric field. It is promising as a state-of-the-art device to realize highly resolved images at a low X-ray dose for a variety of medical X-ray imaging applications. PMID:24753443

Park, Jae Chul; Jeon, Pyo Jin; Kim, Jin Sung; Im, Seongil

2015-01-01

218

Amorphous Medium Language  

E-print Network

Programming reliable behavior on a large mesh network composed of unreliable parts is difficult. Amorphous Medium Language addresses this problem by abstracting robustness and networking issues away from the programmer via ...

Beal, Jacob

219

Amorphous diamond films  

DOEpatents

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.

1998-06-09

220

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

221

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

Microsoft Academic Search

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

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

1988-01-01

222

Viscous Flow and Structural Relaxation in Amorphous Silicon and Amorphous Selenium  

E-print Network

Viscous Flow and Structural Relaxation in Amorphous Silicon and Amorphous Selenium Thin Films.2 Amorphous Silicon . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.3 Amorphous Selenium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix 1 Introduction 1 1.1 Amorphous Thin Films . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1

223

Formation of amorphous materials  

DOEpatents

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

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

1986-01-01

224

Pulsed direct flame deposition and thermal annealing of transparent amorphous indium zinc oxide films as active layers in field effect transistors.  

PubMed

Indium-zinc oxide (IZO) films were deposited via flame spray pyrolysis (FSP) by pulsewise shooting a Si/SiO2 substrate directly into the combustion area of the flame. Based on UV-vis measurements of thin-films deposited on glass substrates, the optimal deposition parameters with respect to low haze values and film thicknesses of around 100 nm were determined. Thermal annealing of the deposited films at temperatures between 300 and 700 °C was carried out and staggered bottom gate thin-film transistors (TFT) were fabricated. The thin films were investigated by scanning electron microscopy, atomic force microscopy, X-ray diffraction, Fourier transformed infrared spectroscopy, and room-temperature photoluminescence measurements. The outcome of these investigations lead to two major requirements in order to implement a working TFT: (i) organic residues from the deposition process need to be removed and (ii) the net free charge carrier concentration has to be minimized by controlling the trap states in the semiconductor. The optimal annealing temperature was 300 °C as both requirements are fulfilled best in this case. This leads to field effect transistors with a low hysteresis, a saturation mobility of ?Sat = 0.1 cm(2)/(V s), a threshold voltage of Vth = -18.9 V, and an Ion/Ioff ratio on the order of 10(7). Depending on thermal treatment, the defect density changes significantly strongly influencing the transfer characteristics of the device. PMID:25029269

Kilian, Daniel; Polster, Sebastian; Vogeler, Isabell; Jank, Michael P M; Frey, Lothar; Peukert, Wolfgang

2014-08-13

225

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 alchemist’s 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

226

Microstructural evolution of amorphous cobalt-rich magnetic alloys during magnetic field annealing  

Microsoft Academic Search

We have studied surface crystallization phenomenon in Co-rich amorphous alloys based on Co95?xFe5(BSi)x. Our results indicate that amorphous alloys can undergo surface crystallization in response to oxidation at temperatures well below the bulk crystallization temperature. We also add new details to this process, and in particular show that it involves a sequence of three steps: (1) formation of an amorphous

C. K. Kim

1996-01-01

227

Search-Based Amorphous Slicing  

Microsoft Academic Search

Amorphous slicing is an automated source code extrac- tion technique with applications in many areas of software engineering, including comprehension, reuse, testing and reverse engineering. Algorithms for syntax-preserving slic- ing are well established, but amorphous slicing is harder because it requires arbitrary transformation; finding good general purpose amorphous slicing algorithms therefore re- mains as hard as general program transformation. In

Deji Fatiregun; Robert M. Hierons

2005-01-01

228

Hydrogenated Amorphous Silicon  

Microsoft Academic Search

Divided roughly into two parts, the book describes the physical properties and device applications of hydrogenated amorphous silicon. The first section is concerned with the atomic and electronic structure, and covers growth defects and doping and defect reactions. The emphasis is on the optical and electronic properties that result from the disordered structure. The second part of the book describes

1991-01-01

229

Adsorption of Ethylene Glycol Vapor on r-Al2O3 (0001) and Amorphous  

E-print Network

Adsorption of Ethylene Glycol Vapor on r-Al2O3 (0001) and Amorphous SiO2 Surfaces: Observation glycol (EG) vapor onto single crystal R-Al2O3 (0001) and fused SiO2 (amorphous) surfaces was studied different oxide surfaces. EG molecules weakly physisorb onto the R-Al2O3 (0001) surface by forming

230

High-efficiency visible photoluminescence from amorphous silicon nanoparticles embedded in silicon nitride  

E-print Network

High-efficiency visible photoluminescence from amorphous silicon nanoparticles embedded in silicon succeeded in preparing high- density amorphous silicon nanoparticles in a SiOx matrix by chemical vapor 29 August 2003 Confinement of silicon nanoparticles in silicon nitride instead of an oxide matrix

Zexian, Cao

231

Generation of Realistic Amorphous Al2O3 And ZrO2 Samples By Hybrid Classical and First-Principle Molecular Dynamics Simulations  

E-print Network

Generation of Realistic Amorphous Al2O3 And ZrO2 Samples By Hybrid Classical and First, University of California, San Diego, La Jolla, California 92093 Realistic amorphous samples of a-Al2O3 and a the same capacitance with much lower leakage current. Amorphous aluminum and zirconium oxides (a-Al2O3

Kummel, Andrew C.

232

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

233

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

234

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

E-print Network

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

Lee, S. W.

235

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

236

Atomic and electronic structure of amorphous Al-Zr alloy films.  

PubMed

Amorphous Al(73)Zr(27) alloy film, grown and then subjected to heat treatments at 400 and 700 °C, was studied using a combination of x-ray diffraction and soft x-ray spectroscopic techniques. The Al L(2,3) and Al K x-ray absorption spectroscopy (XAS) and Al L(2,3) x-ray emission spectroscopy (XES) used allowed probing the unoccupied and occupied Al 3s, d states and unoccupied Al 3p states in the sample studied. An irreversible transition from amorphous alloy to a mixture of polycrystalline alloy and amorphous alloy, and then to an amorphous oxide phase was observed. After the annealing at 400 °C the Al L(2,3) spectra obtained by XAS could be explained as sums of spectra from amorphous Al(73)Zr(27) alloy and (poly)crystalline Al. This indicates that the sample consists of a mixture of Al-rich crystalline and Zr-enhanced amorphous alloys, as compared to the stoichiometry of the as-deposited Al(73)Zr(27) sample, and that the electronic wavefunctions in the crystalline and amorphous regions can be considered to be confined within the respective regions. The relative amounts of Al atoms were found to be around 1:3 in the crystalline and amorphous phases, respectively, as deduced from the analysis of changes in the electronic structure using Al L(2,3) XAS data. The interpretation was confirmed by the Al K XAS and Al L(2,3) XES. Upon further annealing at 700 °C the polycrystalline phase transformed into amorphous oxide, while the amorphous alloy phase underwent gradual oxidation. The important finding was that the greater part of the sample remained in the amorphous state throughout the temperature regimes described. PMID:21666296

Vegelius, J; Soroka, I L; Korelis, P T; Hjörvarsson, B; Butorin, S M

2011-07-01

237

Atomic and electronic structure of amorphous Al-Zr alloy films  

NASA Astrophysics Data System (ADS)

Amorphous Al73Zr27 alloy film, grown and then subjected to heat treatments at 400 and 700 °C, was studied using a combination of x-ray diffraction and soft x-ray spectroscopic techniques. The Al L2, 3 and Al K x-ray absorption spectroscopy (XAS) and Al L2, 3 x-ray emission spectroscopy (XES) used allowed probing the unoccupied and occupied Al 3s, d states and unoccupied Al 3p states in the sample studied. An irreversible transition from amorphous alloy to a mixture of polycrystalline alloy and amorphous alloy, and then to an amorphous oxide phase was observed. After the annealing at 400 °C the Al L2, 3 spectra obtained by XAS could be explained as sums of spectra from amorphous Al73Zr27 alloy and (poly)crystalline Al. This indicates that the sample consists of a mixture of Al-rich crystalline and Zr-enhanced amorphous alloys, as compared to the stoichiometry of the as-deposited Al73Zr27 sample, and that the electronic wavefunctions in the crystalline and amorphous regions can be considered to be confined within the respective regions. The relative amounts of Al atoms were found to be around 1:3 in the crystalline and amorphous phases, respectively, as deduced from the analysis of changes in the electronic structure using Al L2, 3 XAS data. The interpretation was confirmed by the Al K XAS and Al L2, 3 XES. Upon further annealing at 700 °C the polycrystalline phase transformed into amorphous oxide, while the amorphous alloy phase underwent gradual oxidation. The important finding was that the greater part of the sample remained in the amorphous state throughout the temperature regimes described.

Vegelius, J.; Soroka, I. L.; Korelis, P. T.; Hjörvarsson, B.; Butorin, S. M.

2011-07-01

238

Amorphous silicon carbide TFTs  

NASA Astrophysics Data System (ADS)

In this paper we present and characterize a-Si 1- xC x:H thin film transistors, TFTs, fabricated by PECVD deposition. Precise modeling and parameter extraction for these devices was done using a unified procedure previously developed by us for amorphous, polycrystalline, nanocrystalline and organic TFTs. The behavior with temperature and stress of the extracted parameters is analyzed to determine similarities and differences with respect to a-Si:H TFTs. Electrical simulation allowed to estimate the localized traps energy distribution.

Estrada, M.; Cerdeira, A.; Resendiz, L.; García, R.; Iñiguez, B.; Marsal, L. F.; Pallares, J.

2006-03-01

239

Optical multilayer films based on an amorphous fluoropolymer  

SciTech Connect

Multilayered coatings were made by physical vapor deposition (PVD) of a perfluorinated amorphous polymer, Teflon AF2400, and with other optical materials. A high reflector for 1064 nm light was made with ZnS and AF2400. An all-organic 1064 nm reflector was made from AF2400 and polyethylene. Oxide (HfO{sub 2} and SiO{sub 2}) compatibility with AF2400 was also tested. The multilayer morphologies were influenced by coating stress and unintentional temperature rises from the PVD process. Analysis by liquid nuclear magnetic resonance of the thin films showed slight compositional variations between the coating and starting materials of perfluorinated amorphous polymers.

Chow, R.; Loomis, G.E.; Ward, R.L. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States)] [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States)

1996-01-01

240

Potential of amorphous and microcrystalline silicon solar cells  

Microsoft Academic Search

Low pressure chemical vapour deposition (LP-CVD) ZnO as front transparent conductive oxide (TCO), developed at IMT, has excellent light-trapping properties for a-Si:H p-i-n single-junction and ‘micromorph’ (amorphous\\/microcrystalline silicon) tandem solar cells. A stabilized record efficiency of 9.47% has independently been confirmed by NREL for an amorphous silicon single-junction p-i-n cell (?1 cm2) deposited on LP-CVD ZnO coated glass. Micromorph tandem

J. Meier; J. Spitznagel; U. Kroll; C. Bucher; S. Faÿ; T. Moriarty; A. Shah

2004-01-01

241

Amorphous photonic membranes for broadband chemical sensing applications  

NASA Astrophysics Data System (ADS)

While there has been extensive development on integrated sensors in the near-IR region due to the maturation of Si, SOI, and III-V materials, these technologies are not easily translated into the visible and near-UV regions which are critical for the detection of many chemicals of environmental and security interest. This work focuses on the use of wide bandgap, amorphous materials, specifically, amorphous zinc oxide (a-ZnO), amorphous hafnium oxide (a-HfO2) and amorphous beryllium zinc oxide (a-BeZnO), in the development of broadband chemical sensors operating at critical absorption lines spanning the near-UV (200 nm) to the near-IR (1.55 ?m). The architecture employed for this research is a nanoscale membrane (typically 40 - 100 nm thick) that supports a guided low optical overlap mode (LOOM) - an optical mode in which approximately 1% of the electric field is confined to the lossy core region. The resulting extended mode has a greatly enhanced analyte overlap, yielding a device sensitivity (~70%) that is over an order of magnitude higher than current high-performance, dielectric evanescent wave sensors (~2%) as modeled by analytical and finite element methods. Due to the extended nature of the LOOM, sensing across the entire spectral range can be achieved with a single waveguide design - critical for multi-point chemical sensing architectures.

Abbey, Sonja P.; Whaley, Ralph D., Jr.

2012-01-01

242

Amorphous silicon ionizing particle detectors  

DOEpatents

Amorphous silicon ionizing particle detectors having a hydrogenated amorphous silicon (a--Si:H) thin film deposited via plasma assisted chemical vapor deposition techniques are utilized to detect the presence, position and counting of high energy ionizing particles, such as electrons, x-rays, alpha particles, beta particles and gamma radiation.

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

1988-01-01

243

Amorphous silicon ionizing particle detectors  

DOEpatents

Amorphous silicon ionizing particle detectors having a hydrogenated amorphous silicon (a--Si:H) thin film deposited via plasma assisted chemical vapor deposition techniques are utilized to detect the presence, position and counting of high energy ionizing particles, such as electrons, x-rays, alpha particles, beta particles and gamma radiation. 15 figs.

Street, R.A.; Mendez, V.P.; Kaplan, S.N.

1988-11-15

244

Compensated amorphous silicon solar cell  

DOEpatents

An amorphous silicon solar cell incorporates a region of intrinsic hydrogenated amorphous silicon fabricated by a glow discharge wherein said intrinsic region is compensated by P-type dopants in an amount sufficient to reduce the space charge density of said region under illumination to about zero.

Carlson, David E. (Yardley, PA)

1980-01-01

245

Compensated amorphous silicon solar cell  

DOEpatents

An amorphous silicon solar cell including an electrically conductive substrate, a layer of glow discharge deposited hydrogenated amorphous silicon over said substrate and having regions of differing conductivity with at least one region of intrinsic hydrogenated amorphous silicon. The layer of hydrogenated amorphous silicon has opposed first and second major surfaces where the first major surface contacts the electrically conductive substrate and an electrode for electrically contacting the second major surface. The intrinsic hydrogenated amorphous silicon region is deposited in a glow discharge with an atmosphere which includes not less than about 0.02 atom percent mono-atomic boron. An improved N.I.P. solar cell is disclosed using a BF.sub.3 doped intrinsic layer.

Devaud, Genevieve (629 S. Humphrey Ave., Oak Park, IL 60304)

1983-01-01

246

Optimization of transparent and reflecting electrodes for amorphous-silicon solar cells  

NASA Astrophysics Data System (ADS)

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 percent). 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 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.

1994-07-01

247

Adsorption of selenium by amorphous iron oxyhydroxide and manganese dioxide  

USGS Publications Warehouse

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

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

1990-01-01

248

Beyond amorphous organic semiconductors  

NASA Astrophysics Data System (ADS)

Recently it has been discovered that some types of liquid crystals, which believed to be governed by ionic conduction, exhibit a very fast electronic conduction. Their charge carrier transport is characterized by high mobility over 10-2 cm2/Vs independent of electric field and temperature. Now, the liquid crystals are being recognized as a new class of organic semiconductors. In this article, a new aspect of liquid crystals as a self-organizing molecular semiconductor are reviewed, focused on their basic charge carrier transport properties and discussed in comparison with those of molecular crystals and amorphous materials. And it is concluded that the liquid crystal is promising as a quality organic semiconductor for the devices that require a high mobility.

Hanna, Jun-ichi

2003-07-01

249

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

250

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

251

Vibrations in elemental amorphous semiconductors  

E-print Network

In this thesis calculations of the vibrational spectra appropriate to structural models of the elemental amorphous semiconductors a-Ge, a-As and a-Se are presented. Simple dynamical models, involving restoring forces for bond length and angle...

Meek, Peter Ernest

1977-06-17

252

Fabrication of amorphous diamond films  

DOEpatents

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

253

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

Microsoft Academic Search

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

Ahmed Mohamed. El-Toni; Shu Yin; Shinryo Yabe; Tsugio Sato

2005-01-01

254

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

255

Transparent conducting amorphous Zn-In-Sn-O anode for flexible organic light-emitting diodes  

NASA Astrophysics Data System (ADS)

Amorphous Zn-In-Sn-O (ZITO) films are grown by an rf magnetron cosputtering system from ceramic oxide targets of ZnO and ITO onto a flexible polyether sulfone (PES) substrate. The films exhibit resistivity as low as 1.22×10-3? cm and optical transparency comparable to greater than that of Sn-doped indium oxide (ITO) films. The amorphous ZITO films have good mechanical durability compared to ITO films against the external dynamic stress measured by the bending tester. The deposited ZITO film has been used as a transparent anode in fabrication of the flexible organic light-emitting diode (OLED) by the cluster organic evaporator system. The amorphous ZITO anode-based flexible OLED shows comparable or superior current density and luminance characteristics compared to that of the amorphous ITO-based OLED.

Heo, Gi-Seok; Matsumoto, Yuji; Gim, In-Gi; Lee, Hyun-Kee; Park, Jong-Woon; Kim, Tae-Won

2010-01-01

256

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

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

257

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

NASA Astrophysics Data System (ADS)

We report torque magnetometry measurements of an oxide heterostructure consisting of an amorphous Al2O3 thin film grown on a crystalline SrTiO3 substrate (a -AO/STO) by atomic layer deposition. We find a torque response that resembles previous studies of crystalline LaAlO3/SrTiO3 (LAO/STO) heterointerfaces, consistent with strongly anisotropic magnetic ordering in the plane of the interface. Unlike crystalline LAO, amorphous Al2O3 is nonpolar, indicating that planar magnetism at an oxide interface is possible without the strong internal electric fields generated within the polarization catastrophe model. We discuss our results in the context of current theoretical efforts to explain magnetism in crystalline LAO/STO.

Tomarken, S. L.; Young, A. F.; Lee, S. W.; Gordon, R. G.; Ashoori, R. C.

2014-11-01

258

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

259

Bimodal Dynamics of PEO in Amorphous Blends with PMMA  

Microsoft Academic Search

Quasielastic neutron scattering measurements have been carried out on miscible blends of hydrogenated poly(ethyelene oxide) [PEO] and deuterated polymethyl methacrylate [PMMA]. The blends contain 10, 20 and 30% PEO by weight and are completely amorphous. The deuteration scheme highlights the motion of PEO which was followed using a time-of-flight spectrometer. Two distinct mobilities of PEO are observed in the blend,

Victoria Garcia Sakai; Janna K. Maranas; Inmaculada Peral

2004-01-01

260

Hydrogenated amorphous silicon photonics  

NASA Astrophysics Data System (ADS)

Silicon Photonics is quickly proving to be a suitable interconnect technology for meeting the future goals of on-chip bandwidth and low power requirements. However, it is not clear how silicon photonics will be integrated into CMOS chips, particularly microprocessors. The issue of integrating photonic circuits into electronic IC fabrication processes to achieve maximum flexibility and minimum complexity and cost is an important one. In order to minimize usage of chip real estate, it will be advantageous to integrate in three-dimensions. Hydrogenated amorphous silicon (a-Si:H) is emerging as a promising material for the 3-D integration of silicon photonics for on-chip optical interconnects. In addition, a-Si:H film can be deposited using CMOS compatible low temperature plasma-enhanced chemical vapor deposition (PECVD) process at any point in the fabrication process allowing maximum flexibility and minimal complexity. In this thesis, we demonstrate a-Si:H as a high performance alternate platform to crystalline silicon, enabling backend integration of optical interconnects in a hybrid photonic-electronic network-on-chip architecture. High quality passive devices are fabricated on a low-loss a-Si:H platform enabling wavelength division multiplexing schemes. We demonstrate a broadband all-optical modulation scheme based on free-carrier absorption effect, which can enable compact electro-optic modulators in a-Si:H. Furthermore, we comprehensively characterize the optical nonlinearities in a-Si:H and observe that a-Si:H exhibits enhanced nonlinearities as compared to crystalline silicon. Based on the enhanced nonlinearities, we demonstrate low-power four-wave mixing in a-Si:H waveguides enabling high speed all-optical devices in an a-Si:H platform. Finally, we demonstrate a novel data encoding scheme using thermal and all-optical tuning of silicon waveguides, increasing the spectral efficiency in an interconnect link.

Narayanan, Karthik

2011-12-01

261

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

262

Microstructure and surface chemistry of amorphous alloys important to their friction and wear behavior  

NASA Technical Reports Server (NTRS)

An investigation was conducted to examine the microstructure and surface chemistry of amorphous alloys, and their effects on tribological behavior. The results indicate that the surface oxide layers present on amorphous alloys are effective in providing low friction and a protective film against wear in air. Clustering and crystallization in amorphous alloys can be enhanced as a result of plastic flow during the sliding process at a low sliding velocity, at room temperature. Clusters or crystallines with sizes to 150 nm and a diffused honeycomb-shaped structure are produced on the wear surface. Temperature effects lead to drastic changes in surface chemistry and friction behavior of the alloys at temperatures to 750 C. Contaminants can come from the bulk of the alloys to the surface upon heating and impart to the surface oxides at 350 C and boron nitride above 500 C. The oxides increase friction while the boron nitride reduces friction drastically in vacuum.

Miyoshi, K.; Buckley, D. H.

1983-01-01

263

Effect of annealing temperature on structural and electrical properties of high-? YbTixOy gate dielectrics for InGaZnO thin film transistors  

NASA Astrophysics Data System (ADS)

This paper describes the effect of annealing temperature on the structural properties and electrical characteristics of high–? YbTixOy gate dielectrics for indium–gallium–zinc–oxide (IGZO) thin-film transistors (TFTs). X-ray diffraction, x-ray photoelectron spectroscopy and atomic force microscopy were used to study the structural, chemical and morphological features, respectively, of these dielectric films annealed at 200, 300 and 400 °C. The YbTixOy IGZO TFT that had been annealed at 400 °C exhibited better electrical characteristics, such as a small threshold voltage of 0.53 V, a large field-effect mobility of 19.1 cm2 V?1 s?1, a high Ion/Ioff ratio of 2.8 × 107, and a low subthreshold swing of 176 mV dec.?1, relative to those of the systems that had been subjected to other annealing conditions. This result suggests that YbTixOy dielectric possesses a higher dielectric constant as well as lower oxygen vacancies (or defects) in the film. In addition, the instability of YbTixOy IGZO TFT was studied under positive gate-bias stress and negative gate-bias stress conditions.

Pan, Tung-Ming; Chen, Fa-Hsyang; Hung, Meng-Ning

2015-01-01

264

Thermal degradation of amorphous glibenclamide.  

PubMed

A glibenclamide polymorph published by Panagopoulou-Kaplani and Malamataris (2000) [1], obtained by sublimation of amorphous glibenclamide, was analysed. A new interpretation of the data is presented and experimentally confirmed by X-ray powder diffractometry, Fourier transformation infrared spectroscopy, differential scanning calorimetry, and mass spectrometry. The crystals formed during sublimation of amorphous glibenclamide do not represent a glibenclamide polymorph, but a thermal degradation product, namely 1,3-dicyclohexylurea. The reaction mechanism is suggested to be an elimination of cyclohexylisocyanate from glibenclamide. Cyclohexylisocyanate may decompose to carbon monoxide and cyclohexylamine, which may react in an addition reaction with another cyclohexylisocyanate molecule forming 1,3-dicyclohexylurea. PMID:21907802

Rehder, Sönke; Sakmann, Albrecht; Rades, Thomas; Leopold, Claudia S

2012-01-01

265

Amorphous-silicon cell reliability testing  

NASA Technical Reports Server (NTRS)

The work on reliability testing of solar cells is discussed. Results are given on initial temperature and humidity tests of amorphous silicon devices. Calibration and measurement procedures for amorphous and crystalline cells are given. Temperature stress levels are diagrammed.

Lathrop, J. W.

1985-01-01

266

Tandem junction amorphous silicon solar cells  

DOEpatents

An amorphous silicon solar cell has an active body with two or a series of layers of hydrogenated amorphous silicon arranged in a tandem stacked configuration with one optical path and electrically interconnected by a tunnel junction. The layers of hydrogenated amorphous silicon arranged in tandem configuration can have the same bandgap or differing bandgaps.

Hanak, Joseph J. (Lawrenceville, NJ)

1981-01-01

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 Östhols

1995-01-01

268

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

269

Optical absorption in amorphous silicon  

SciTech Connect

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

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

1996-12-31

270

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

271

Water clusters in amorphous pharmaceuticals.  

PubMed

Amorphous materials, although lacking the long-range translational and rotational order of crystalline and liquid crystalline materials, possess certain local (short-range) structure. This paper reviews the distribution of one particular component present in all amorphous pharmaceuticals, that is, water. Based on the current understanding of the structure of water, water molecules can exist in either unclustered form or as aggregates (clusters) of different sizes and geometries. Water clusters are reported in a range of amorphous systems including carbohydrates and their aqueous solutions, synthetic polymers, and proteins. Evidence of water clustering is obtained by various methods that include neutron and X-ray scattering, molecular dynamics simulation, water sorption isotherm, concentration dependence of the calorimetric Tg , dielectric relaxation, and nuclear magnetic resonance. A review of the published data suggests that clustering depends on water concentration, with unclustered water molecules existing at low water contents, whereas clusters form at intermediate water contents. The transition from water clusters to unclustered water molecules can be expected to change water dependence of pharmaceutical properties, such as rates of degradation. We conclude that a mechanistic understanding of the impact of water on the stability of amorphous pharmaceuticals would require systematic studies of water distribution and clustering, while such investigations are lacking. PMID:24824578

Authelin, Jean-Rene; MacKenzie, Alan P; Rasmussen, Don H; Shalaev, Evgenyi Y

2014-09-01

272

Superspin glass state and exchange bias in amorphous Fe/Fe-O core/shell nanoparticles  

NASA Astrophysics Data System (ADS)

Nanoparticles of iron and iron oxide are widely explored in several biomedical and technological applications. We report on the magnetic properties of amorphous Fe/Fe-O core/shell nanoparticles compared to those of a reference system with crystalline Fe-O nanoparticles. These nanoparticles are prepared by thermal decomposition of iron precursor, where the amorphous and crystalline nature of core and shell is determined by the choice and concentration of the ligand. The crystalline system exhibits a blocking temperature higher than 300 K and negligible exchange bias effect. In contrast, the amorphous systems display large exchange bias, and collective magnetic behavior at low temperatures, with features of magnetic frustration and disorder reminiscent of those observed in spin glass and superspin glass systems. We discuss the origin of the dynamical magnetic behavior of the amorphous particles and study the dependence of the exchange bias field on the cooling field.

Kumar, P. Anil; Singh, Gurvinder; Glomm, Wilhelm R.; Peddis, Davide; Wahlström, Erik; Mathieu, R.

2014-09-01

273

Amorphous molybdenum sulfides as hydrogen evolution catalysts.  

PubMed

Providing energy for a population projected to reach 9 billion people within the middle of this century is one of the most pressing societal issues. Burning fossil fuels at a rate and scale that satisfy our near-term demand will irreversibly damage the living environment. Among the various sources of alternative and CO2-emission-free energies, the sun is the only source that is capable of providing enough energy for the whole world. Sunlight energy, however, is intermittent and requires an efficient storage mechanism. Sunlight-driven water splitting to make hydrogen is widely considered as one of the most attractive methods for solar energy storage. Water splitting needs a hydrogen evolution catalyst to accelerate the rate of hydrogen production and to lower the energy loss in this process. Precious metals such as Pt are superior catalysts, but they are too expensive and scarce for large-scale applications. In this Account, we summarize our recent research on the preparation, characterization, and application of amorphous molybdenum sulfide catalysts for the hydrogen evolution reaction. The catalysts can be synthesized by electrochemical deposition under ambient conditions from readily available and inexpensive precursors. The catalytic activity is among the highest for nonprecious catalysts. For example, at a loading of 0.2 mg/cm(2), the optimal catalyst delivers a current density of 10 mA/cm(2) at an overpotential of 160 mV. The growth mechanism of the electrochemically deposited film catalysts was revealed by an electrochemical quartz microcrystal balance study. While different electrochemical deposition methods produce films with different initial compositions, the active catalysts are the same and are identified as a "MoS(2+x)" species. The activity of the film catalysts can be further promoted by divalent Fe, Co, and Ni ions, and the origins of the promotional effects have been probed. Highly active amorphous molybdenum sulfide particles can also be prepared from simple wet-chemical routes. Electron transport is sometimes slow in the particle catalysts, and an impedance model has been established to identify this slow electron transport. Finally, the amorphous molybdenum sulfide film catalyst has been integrated onto a copper(I) oxide photocathode for photoelectrochemical hydrogen evolution. The conformal catalyst efficiently extracts the excited electrons to give an impressive photocurrent density of -5.7 mA/cm(2) at 0 V vs RHE. The catalyst also confers good stability. PMID:25065612

Morales-Guio, Carlos G; Hu, Xile

2014-08-19

274

Optical dispersion relations for amorphous semiconductors and amorphous dielectrics  

Microsoft Academic Search

An expression for the imaginary part, k, of the complex index of refraction, N=n-ik, for amorphous materials is derived as a function of photon energy E: k(E)=A(E-Eg)2\\/(E2-BE+C) where A, B, and C are positive nonzero constants characteristic of the medium such that 4C-B2>0. Eg represents the optical energy band gap. The real part, n, of the complex index of refraction

A. R. Forouhi; I. Bloomer

1986-01-01

275

Modeling of Amorphous Calcium Carbonate  

NASA Astrophysics Data System (ADS)

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

Sinha, Sourabh; Rez, Peter

2011-10-01

276

Sonochemical synthesis of amorphous iron  

Microsoft Academic Search

AMORPHOUS metallic alloys ('metallic glasses') lack long-range crystalline order and have unique electronic, magnetic and corrosion-resistant properties1-3. Their applications include use in power-transformer cores, magnetic storage media, cryothermometry and corrosion-resistant coatings. The production of metallic glasses is made difficult, however, by the extremely rapid cooling from the melt that is necessary to prevent crystallization. Cooling rates of about 105 to

Kenneth S. Suslick; Seok-Burm Choe; Andrzej A. Cichowlas; Mark W. Grinstaff

1991-01-01

277

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

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

2011-03-16

278

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

279

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

280

Narrow band gap amorphous silicon semiconductors  

DOEpatents

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 the steps of forming an alloy comprising amorphous silicon and at least one of the aforesaid band gap narrowing elements in amount sufficient to narrow the band gap of the silicon semiconductor alloy below that of amorphous silicon, and also utilizing sufficient amounts of the aforesaid electron donor dopant to maintain the amorphous silicon alloy as an n-type semiconductor.

Madan, A.; Mahan, A.H.

1985-01-10

281

Improvement of amorphous silicon solar cells by electrochemical treatments  

SciTech Connect

In the manufacturing process of amorphous silicon (a-Si:H) solar cells, leakage currents through the pinholes in the a-Si:H film often spoils its performance. We have demonstrated that two electrochemical treatments are effective for stopping the leakage through pinholes. One method is an electrochemical dissolution of the transparent conductive oxide exposed to the pinholes, and another is an electrochemical deposition of insulating materials in the pinholes. These effects have been confirmed by use of intentionally fissured a-Si:H electrodes as well as solar cells showing large leakage currents.

Matsumura, M.; Sakai, Y.; Yae, S.; Nakato, Y.; Tsubomura, H.

1987-02-15

282

Plasmonic multilayer structure for ultrathin amorphous silicon film photovoltaic cell  

NASA Astrophysics Data System (ADS)

A plasmonic multilayer structure (PMS) is proposed for photovoltaic cells with an ultrathin active layer that is 30 nm amorphous Si ( ?-Si). The optical properties of the PMS are analyzed by rigorous coupled-wave analysis (RCWA) and finite-difference time-domain (FDTD) method. Using the PMS, the incident light can be trapped into localized surface plasmon (LSP) and then the localized surface plasmon induces the surface plasmon (SP) that propagates transversely within the ?-Si layer. Compared with the indium tin oxide (ITO)/ ?-Si/Ag structure, the photon number absorbed by PMS increase 28.7% while a normal incident transverse magnetic (TM) polarization wave is applied.

Chao, Chien-Chang; Wang, Chih-Ming; Chang, Yia-Chung; Chang, Jenq-Yang

2009-05-01

283

XRD Technique: A way to disseminate structural changes in iron-based amorphous materials  

SciTech Connect

Prevention of corrosion is a vital goal for the Department of Defense when billions of dollars are spent every year. Corrosion resistant materials have applications in all sort of military vehicles, and more importantly in naval vessels and submarines which come in contact with the seawater. It is known that corrosion resistance property can be improved by the used of structurally designed materials in the amorphous state where the atoms are arranged in a non-periodic fashion and specific atoms, tailored to the required properties can be interjected into the matrix for specific application. The XRD techniques reported here is to demonstrate the optimal conditions for characterization of these materials. The samples, which normally contain different compositions of Fe, Cr, B, Mo, Y, Mn, Si and W, are in the form of powders, ribbons and coatings. These results will be compared for the different forms of the sample which appears to correlate to the cooling rate during sample processing. In most cases, the materials are amorphous or amorphous with very small amount of crystallinity. In the ribbon samples for different compositions we observed that the materials are essentially amorphous. In most cases, starting from an amorphous powder sample, the coatings are also observed to be amorphous with a small amount of iron oxide on the surface, probably due to exposure to air.

Saw, C K; Lian, T; Day, D; Farmer, J

2007-05-24

284

Laterally inherently thin amorphous-crystalline silicon heterojunction photovoltaic cell  

NASA Astrophysics Data System (ADS)

This article reports on an amorphous-crystalline silicon heterojunction photovoltaic cell concept wherein the heterojunction regions are laterally narrow and distributed amidst a backdrop of well-passivated crystalline silicon surface. The localized amorphous-crystalline silicon heterojunctions consisting of the laterally thin emitter and back-surface field regions are precisely aligned under the metal grid-lines and bus-bars while the remaining crystalline silicon surface is passivated using the recently proposed facile grown native oxide-plasma enhanced chemical vapour deposited silicon nitride passivation scheme. The proposed cell concept mitigates parasitic optical absorption losses by relegating amorphous silicon to beneath the shadowed metallized regions and by using optically transparent passivation layer. A photovoltaic conversion efficiency of 13.6% is obtained for an untextured proof-of-concept cell illuminated under AM 1.5 global spectrum; the specific cell performance parameters are VOC of 666 mV, JSC of 29.5 mA-cm-2, and fill-factor of 69.3%. Reduced parasitic absorption, predominantly in the shorter wavelength range, is confirmed with external quantum efficiency measurement.

Chowdhury, Zahidur R.; Kherani, Nazir P.

2014-12-01

285

RESEARCH PAPER Amorphous dysprosium carbonate: characterization,  

E-print Network

RESEARCH PAPER Amorphous dysprosium carbonate: characterization, stability, and crystallization earths Á Dysprosium Á Carbonate Á Crystallization Introduction The crystallization of many simple ionic

Benning, Liane G.

286

Phase diagram of amorphous solid water: Low-density, high-density, and very-high-density amorphous ices  

E-print Network

Phase diagram of amorphous solid water: Low-density, high-density, and very-high-density amorphous low-density amorphous LDA , high-density amorphous HDA , and very-high density amorphous VHDA ices. The density of these glasses at different pressure P and temperature T agree well with experimental values. We

Sciortino, Francesco

287

Deng & Schiff, Amorphous Silicon Based Solar Cells rev. 7/30/2002, Page 1 Amorphous Silicon Based Solar Cells  

E-print Network

Deng & Schiff, Amorphous Silicon Based Solar Cells rev. 7/30/2002, Page 1 Amorphous Silicon Based Solar Cells Xunming Deng and Eric A. Schiff Table of Contents 1 Overview 3 1.1 Amorphous Silicon: The First Bipolar Amorphous Semiconductor 3 1.2 Designs for Amorphous Silicon Solar Cells: A Guided Tour 6

Deng, Xunming

288

Integration of amorphous and polycrystalline silicon thin-film transistors through selective crystallization of amorphous silicon  

E-print Network

Integration of amorphous and polycrystalline silicon thin-film transistors through selective crystallization of amorphous silicon K. Pangal,a) J. C. Sturm, and S. Wagner Department of Electrical Engineering 1999 Selective exposure of a hydrogenated amorphous silicon a-Si:H film to a room-temperature hydrogen

289

Optimization of transparent and reflecting electrodes for amorphous silicon solar cells  

NASA Astrophysics Data System (ADS)

The specific objectives of this research are to: (1) deposit and characterize textured zinc oxide with improved conductivities (less than 8 ohms/square sheet resistance) and optical transmission (greater than 85 percent for 450 to 700 nm), for use as front and back contacts in hydrogenated amorphous silicon p-i-n devices; (2) study the surface morphology of zinc oxide films deposited by chemical vapor deposition at atmospheric pressure (APCVD), their crystallite sizes, shapes and orientations, and their nucleation (early growth) as a function of chemical precursors and reaction conditions; (3) optimize the growth process to produce structures that provide good light trapping in an amorphous silicon film deposited on the zinc oxide film; (4) study the deposition rate of zinc oxide films as a function of temperature, and concentration and types of reactants; (5) maximize the growth rate, subject to the conditions of maintaining satisfactory film properties, including high transparency (85 percent), high conductivity (8 ohm/square sheet resistance), and good light trapping; (6) develop techniques for deposition of fluorinated zinc oxide films by APCVD on amorphous silicon films in the temperature range of 250 to 280 C for use as back contacts; (7) deposit titanium nitride films at a temperature of about 250 C by APCVD on amorphous silicon as diffusion barrier, and then deposit highly reflective metals such as aluminum or silver; (8) anneal samples and test for metal diffusion through the TiN into the silicon; (9) optimize the TiN film for minimum diffusion consistent with maintaining desirable TiN film properties; and (10) incorporate the front and back contacts including the TiN barrier layer developed under this research into amorphous silicon p-i-n devices and determine the film parameters that provide the greatest improvement in the device solar energy conversion efficiency.

Gordon, R. G.; Hu, Jianhua; Musher, J.; Giunta, C.

1991-02-01

290

Models for Amorphous Calcium Carbonate  

NASA Astrophysics Data System (ADS)

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

Sinha, Sourabh

291

Formation of Nanocrystalline Germanium via Oxidation of Si?.??Ge?.?? for Memory Device Applications  

E-print Network

In this work, we studied the possibility of synthesizing nanocrystalline germanium (Ge) via dry and wet oxidation of both amorphous and polycrystalline Si?.??Ge?.?? films. In dry oxidation, Ge was rejected from the growing ...

Kan, Eric Win Hong

292

Grain growth from amorphous phase  

NASA Astrophysics Data System (ADS)

Time dependence of the grain growth in phosphorus doped silicon thin films deposited in situ at 530 °C was investigated. The samples were annealed at 950 °C in different time intervals. The theories, which give the tn time dependent increase of grain size, cannot fit the observed data. We derived a differential equation which describes the grain growth from amorphous phase. Our experimental results and the solution of the differential equation show the effect of grain growth stagnation and even grain growth stop. The solution also comprises all the features of the result of the Monte Carlo simulation of the grain growth of pure materials.

O?ko, Miroslav; Žonja, Sanja; Ivanda, Mile

2014-03-01

293

Plasma Deposition of Amorphous Silicon  

NASA Technical Reports Server (NTRS)

Strongly adhering films of silicon are deposited directly on such materials as Pyrex and Vycor (or equivalent materials) and aluminum by a non-equilibrium plasma jet. Amorphous silicon films are formed by decomposition of silicon tetrachloride or trichlorosilane in the plasma. Plasma-jet technique can also be used to deposit an adherent silicon film on aluminum from silane and to dope such films with phosphorus. Ability to deposit silicon films on such readily available, inexpensive substrates could eventually lead to lower cost photovoltaic cells.

Calcote, H. F.

1982-01-01

294

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

295

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

296

Graphene oxide: A substrate for optimizing preparations of frozen-hydrated samples  

Microsoft Academic Search

Graphene oxide is a hydrophilic derivative of graphene to which biological macromolecules readily attach, with properties superior to those of amorphous carbon films commonly used in electron microscopy. The single-layered crystalline lattice of carbon is highly electron transparent, and exhibits conductivity higher than amorphous carbon. Hence, graphene oxide is a particularly promising substrate for the examination of biological materials by

Radosav S. Pantelic; Jannik C. Meyer; Ute Kaiser; Wolfgang Baumeister; Jürgen M. Plitzko

2010-01-01

297

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

298

Structural relaxation of amorphous PET matrix nanocomposites  

NASA Astrophysics Data System (ADS)

The aim of the present paper is the evaluation of the degree of dispersion and intercalation of monodimensional nanofillers in an amorphous thermoplastic matrix. Organically modified montmorillonites (omMMT) were used as monodimensional nanofillers, whereas amorphous PET copolymer (PETg) was used as matrix.

Greco, A.; Esposito Corcione, C.; Cavallo, A.; Maffezzoli, A.

2010-06-01

299

Electron beam recrystallization of amorphous semiconductor materials  

NASA Technical Reports Server (NTRS)

Nucleation and growth of crystalline films of silicon, germanium, and cadmium sulfide on substrates of plastic and glass were investigated. Amorphous films of germanium, silicon, and cadmium sulfide on amorphous substrates of glass and plastic were converted to the crystalline condition by electron bombardment.

Evans, J. C., Jr.

1968-01-01

300

Polarized electroabsorption spectra of amorphous semiconductors  

Microsoft Academic Search

Transverse electroabsorption spectra of amorphous Se and hydrogenated amorphous Si (a-Si: H) are presented. These spectra are anisotropic, with fields F parallel to the polarization E of light, causing much larger signals than F perpendicular to E. At temperatures below 350 K the signal depends little on temperature. At higher temperatures the field-induced change ?? in the absorption increases in

G. Weiser; U. Dersch; P. Thomas

1988-01-01

301

Compensated amorphous-silicon solar cell  

DOEpatents

An amorphous silicon solar cell including an electrically conductive substrate, a layer of glow discharge deposited hydrogenated amorphous silicon having regions of differing conductivity with at least one region of intrinsic hydrogenated amorphous silicon. The layer of hydrogenated amorphous silicon has opposed first and second major surfaces where the first major surface contacts the elecrically conductive substrate and an electrode for electrically contacting the second major surface. The intrinsic hydrogenated amorphous silicon region is deposited in a glow discharge with an atmosphere which includes not less than about 0.02 atom percent mono-atomic boron. An improved N.I.P. solar cell is disclosed using a BF/sub 3/ doped intrinsic layer.

Devaud, G.

1982-06-21

302

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

303

Growth of crystalline/amorphous biphase Sm Fe Ta N magnetic nanodroplets  

NASA Astrophysics Data System (ADS)

Thin films of biphase (amorphous/crystalline) magnetic Sm-Fe-Ta-N nanodroplets were fabricated at room temperature with 157 nm pulse laser deposition in nitrogen from a Sm 13.8Fe 82.2Ta 4.0 target. The 50-100 nm biphase spherical nanodroplets consist of a 5-10 nm internal crystal portion surrounded by the external amorphous phase. Nitrogen fixation in the nanodroplets occurred in the plume. The films exhibit a ferromagnetic response of 2.5 kOe coercivity at room temperature. With further annealing and thermal treatment in nitrogen, the coercivity was increased to 5.0 kOe. The surrounding amorphous layer prevents post-ablation oxidization of the crystalline magnetic nucleus of the nanodroplet.

Kobe, S.; Sarantopoulou, E.; Draži?, G.; Kova?, J.; Janeva, M.; Kollia, Z.; Cefalas, A. C.

2007-12-01

304

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

305

Crystalline to amorphous transformation in silicon  

SciTech Connect

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

Cheruvu, S.M.

1982-09-01

306

Amorphous metallic films in silicon metallization systems  

NASA Technical Reports Server (NTRS)

The general objective was to determine the potential of amorphous metallic thin films as a means of improving the stability of metallic contacts to a silicon substrate. The specific objective pursued was to determine the role of nitrogen in the formation and the resulting properties of amorphous thin-film diffusion barriers. Amorphous metallic films are attractive as diffusion barriers because of the low atomic diffusivity in these materials. Previous investigations revealed that in meeting this condition alone, good diffusion barriers are not necessarily obtained, because amorphous films can react with an adjacent medium (e.g., Si, Al) before they recrystallize. In the case of a silicon single-crystalline substrate, correlation exists between the temperature at which an amorphous metallic binary thin film reacts and the temperatures at which the films made of the same two metallic elements react individually. Amorphous binary films made of Zr and W were investigated. Both react with Si individually only at elevated temperatures. It was confirmed that such films react with Si only above 700 C when annealed in vacuum for 30 min. Amorphous W-N films were also investigated. They are more stable as barriers between Al and Si than polycrystalline W. Nitrogen effectively prevents the W-Al reaction that sets in at 500 C with polycrystalline W.

Nicolet, M. A.; Kattelus, H.; So, F.

1984-01-01

307

LASER TRANSFERRED HYDROUS RUTHENIUM OXIDE ELECTRODES FOR MICRO-ULTRACAPACITORS  

E-print Network

LASER TRANSFERRED HYDROUS RUTHENIUM OXIDE ELECTRODES FOR MICRO-ULTRACAPACITORS Craig B Hydrous ruthenium oxide (RuO2 ·0.5 H2O) electrodes have been deposited un- der ambient conditions using). Amorphous hydrous ruthenium oxide (RuO2 · x H2O) is an ideal electrode material for a micro

Arnold, Craig B.

308

Mechanical properties of graphene oxides Lizhao Liu,ab  

E-print Network

Mechanical properties of graphene oxides Lizhao Liu,ab Junfeng Zhang,ab Jijun Zhao*ab and Feng Liuc, including the Young's modulus and intrinsic strength, of graphene oxides are investigated by first-principles computations. Structural models of both ordered and amorphous graphene oxides are considered and compared

Liu, Feng

309

Sorption Properties of ?-Aluminum Oxide Modified with Decationized Silica Sol  

Microsoft Academic Search

The method of sorption of tetrachloromethane vapor at the solid\\/gas interface was applied to study the sorption and structural properties of a mesoporous aluminum oxide material obtained by deposition of amorphous hydrated silicon(IV) oxide onto a-aluminum oxide particles submerged in decationized silica sol.

T. F. Kuznetsova; A. I. Rat'ko; S. I. Eremenko

2003-01-01

310

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

311

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

SciTech Connect

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

Newby, Pascal J. [Institut des Nanotechnologies de Lyon, Universite de Lyon, INL-UMR5270, CNRS, INSA de Lyon, Villeurbanne 69621 (France); Institut Interdisciplinaire d'Innovation Technologique (3IT), Universite de Sherbrooke, CNRS UMI-LN2, Sherbrooke, Quebec J1K0A5 (Canada); Canut, Bruno; Bluet, Jean-Marie; Lysenko, Vladimir [Institut des Nanotechnologies de Lyon, Universite de Lyon, INL-UMR5270, CNRS, INSA de Lyon, Villeurbanne 69621 (France); Gomes, Severine [Centre de Thermique de Lyon, Universite de Lyon, CETHIL-UMR5008, CNRS, INSA de Lyon, Villeurbanne 69621 (France); Isaiev, Mykola; Burbelo, Roman [Faculty of Physics, Taras Shevchenko National University of Kyiv, 64/13, Volodymyrs'ka St., Kyiv 01601 (Ukraine); Termentzidis, Konstantinos [Laboratoire LEMTA, Universite de Lorraine-CNRS UMR 7563, 54506 Vandoeuvre-les-Nancy cedex (France); Chantrenne, Patrice [Universite de Lyon, INSA de Lyon, MATEIS-UMR CNRS 5510, Villeurbanne 69621 (France); Frechette, Luc G. [Institut Interdisciplinaire d'Innovation Technologique (3IT), Universite de Sherbrooke, CNRS UMI-LN2, Sherbrooke, Quebec J1K0A5 (Canada)

2013-07-07

312

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

313

Latent ion tracks in amorphous silicon  

NASA Astrophysics Data System (ADS)

We present experimental evidence for the formation of ion tracks in amorphous Si induced by swift heavy-ion irradiation. An underlying core-shell structure consistent with remnants of a high-density liquid structure was revealed by small-angle x-ray scattering and molecular dynamics simulations. Ion track dimensions differ for as-implanted and relaxed Si as attributed to different microstructures and melting temperatures. The identification and characterization of ion tracks in amorphous Si yields new insight into mechanisms of damage formation due to swift heavy-ion irradiation in amorphous semiconductors.

Bierschenk, T.; Giulian, R.; Afra, B.; Rodriguez, M. D.; Schauries, D.; Mudie, S.; Pakarinen, O. H.; Djurabekova, F.; Nordlund, K.; Osmani, O.; Medvedev, N.; Rethfeld, B.; Ridgway, M. C.; Kluth, P.

2013-11-01

314

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

315

Latent ion tracks in amorphous silicon  

SciTech Connect

We present experimental evidence for the formation of ion tracks in amorphous Si induced by swift heavy ion irradiation. An underlying core-shell structure consistent with remnants of a high density liquid structure was revealed by small-angle x-ray scattering and molecular dynamics simulations. Ion track dimensions dier for as-implanted and relaxed Si as attributed to dierent microstructures and melting temperatures. The identication and characterisation of ion tracks in amorphous Si yields new insight into mechanisms of damage formation due to swift heavy ion irradiation in amorphous semiconductors.

Bierschenk, Thomas [Australian National University, Canberra, Australia] [Australian National University, Canberra, Australia; Giulian, Raquel [Australian National University, Canberra, Australia] [Australian National University, Canberra, Australia; Afra, Boshra [Australian National University, Canberra, Australia] [Australian National University, Canberra, Australia; Rodriguez, Matias D [Australian National University, Canberra, Australia] [Australian National University, Canberra, Australia; Schauries, D [Australian National University, Canberra, Australia] [Australian National University, Canberra, Australia; Mudie, Stephen [Australian Synchrotron] [Australian Synchrotron; Pakarinen, Olli H [ORNL] [ORNL; Djurabekova, Flyura [University of Helsinki] [University of Helsinki; Nordlund, Kai [University of Helsinki] [University of Helsinki; Osmani, Orkhan [University of Duisburg-Essen, Germany] [University of Duisburg-Essen, Germany; Medvedev, Nikita [University of Kaiserslautern, Germany] [University of Kaiserslautern, Germany; Rethfield, Baerbel [University of Kaiserslautern, Germany] [University of Kaiserslautern, Germany; Ridgway, Mark C [Australian National University, Canberra, Australia] [Australian National University, Canberra, Australia; Kluth, Patrick [Australian National University, Canberra, Australia] [Australian National University, Canberra, Australia

2013-01-01

316

Ion beam deposition of amorphous hydrogenated carbon films on amorphous silicon interlayer: Experiment and simulation  

Microsoft Academic Search

A thick layer of amorphous silicon (a-Si) was deposited on industrial grade crystalline n-Si <111>substrate by means of electron beam evaporation. On top of a-Si layer, amorphous hydrogenated carbon (a-C:H) film was grown by direct ion beam deposition from acetylene precursor gas. In order to study on atomic level the a-C:H film growth on amorphous silicon, a theoretical model was

A. Ibenskas; A. Galdikas; Š. Meškinis; M. Andrulevi?ius; S. Tamulevi?ius

2011-01-01

317

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

2014-07-15

318

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

319

Ab initio simulation of first-order amorphous-to-amorphous phase transition of silicon Murat Durandurdu  

E-print Network

Ab initio simulation of first-order amorphous-to-amorphous phase transition of silicon Murat received 28 March 2001; published 1 June 2001 The pressure-induced phase transition in amorphous silicon a context of the classic amor- phous semiconductor amorphous silicon a-Si , we use cur- rent first

Drabold, David

320

Stability of Amorphous Structures with Voids  

E-print Network

We incorporate the role of free volume in the density function of the amorphous structure and study its effects on the stability of such structures. The Density Functional Theory is used to explore this ``Free Volume Model'' of the supercooled structures. The Free energy minimization is carried out using the void concentration as a variational parameter. A critical value of this concentration exists corresponding to the Free energy minima of the amorphous structure. An increase in the stability is observed due to the inclusion of voids in the density structure. This study is conducted for both the weakly and highly localized amorphous structures. The free volume concentration shows a power law decrease with density for the weakly localized states and a linear decrease for the highly localized amorphous structures.

Charanbir kaur; Shankar P. Das

2001-03-21

321

Modelling morphogenesis as an amorphous computation  

E-print Network

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

Bhattacharyya, Arnab

2006-01-01

322

Pressure-induced amorphization of methane hydrate  

NASA Astrophysics Data System (ADS)

Pressure-induced amorphization of methane hydrate has been investigated by molecular dynamics simulation. In accord with experimental results of Tulk , a crystalline ? amorphous transition was confirmed at 3.3 GPa where the water lattice collapsed around the encaged methane. Thermal annealing at 5.5 GPa allows the water to adopt a lower energy conformation with a denser structure. In both structures, methane molecules are immobilized and maintain long-range correlation as in the crystal. Consequently, both phases are predicted to revert back to the crystalline form upon decompression. Pressure-induced amorphization is a nonequilibrium process due to a mechanical instability; the interconversion between kinetically stable amorphous phases is a relaxation effect.

English, Niall J.; Tse, John S.

2012-09-01

323

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

SciTech Connect

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

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

2014-02-15

324

Amorphous Phases on the Surface of Mars  

NASA Technical Reports Server (NTRS)

Both primary (volcanic/impact glasses) and secondary (opal/silica, allophane, hisingerite, npOx, S-bearing) amorphous phases appear to be major components of martian surface materials based on orbital and in-situ measurements. A key observation is that whereas regional/global scale amorphous components include altered glass and npOx, local scale amorphous phases include hydrated silica/opal. This suggests widespread alteration at low water-to-rock ratios, perhaps due to snow/ice melt with variable pH, and localized alteration at high water-to-rock ratios. Orbital and in-situ measurements of the regional/global amorphous component on Mars suggests that it is made up of at least three phases: npOx, amorphous silicate (likely altered glass), and an amorphous S-bearing phase. Fundamental questions regarding the composition and the formation of the regional/global amorphous component(s) still remain: Do the phases form locally or have they been homogenized through aeolian activity and derived from the global dust? Is the parent glass volcanic, impact, or both? Are the phases separate or intimately mixed (e.g., as in palagonite)? When did the amorphous phases form? To address the question of source (local and/or global), we need to look for variations in the different phases within the amorphous component through continued modeling of the chemical composition of the amorphous phases in samples from Gale using CheMin and APXS data. If we find variations (e.g., a lack of or enrichment in amorphous silicate in some samples), this may imply a local source for some phases. Furthermore, the chemical composition of the weathering products may give insight into the formation mechanisms of the parent glass (e.g., impact glasses contain higher Al and lower Si [30], so we might expect allophane as a weathering product of impact glass). To address the question of whether these phases are separate or intimately mixed, we need to do laboratory studies of naturally altered samples made up of mixed phases (e.g., palagonite) and synthetic single phases to determine their short-range order structures and calculate their XRD patterns to use in models of CheMin data. Finally, to address the timing of the alteration, we need to study rocks on the martian surface of different ages that may contain glass (volcanic or impact) with MSL and future rovers to better understand how glass alters on the martian surface, if that alteration mechanism is universal, and if alteration spans across long periods of time or if there is a time past which unaltered glass remains.

Rampe, E. B.; Morris, R. V.; Ruff, S. W.; Horgan, B.; Dehouck, E.; Achilles, C. N.; Ming, D. W.; Bish, D. L.; Chipera, S. J.

2014-01-01

325

A Magnetic Sensor with Amorphous Wire  

PubMed Central

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

He, Dongfeng; Shiwa, Mitsuharu

2014-01-01

326

Tests Of Amorphous-Silicon Photovoltaic Modules  

NASA Technical Reports Server (NTRS)

Progress in identification of strengths and weaknesses of amorphous-silicon technology detailed. Report describes achievements in testing reliability of solar-power modules made of amorphous-silicon photovoltaic cells. Based on investigation of modules made by U.S. manufacturers. Modules subjected to field tests, to accelerated-aging tests in laboratory, and to standard sequence of qualification tests developed for modules of crystalline-silicon cells.

Ross, Ronald G., Jr.

1988-01-01

327

Amorphous silica nanoparticles impair vascular homeostasis and induce systemic inflammation  

PubMed Central

Amorphous silica nanoparticles (SiNPs) are being used in biomedical, pharmaceutical, and many other industrial applications entailing human exposure. However, their potential vascular and systemic pathophysiologic effects are not fully understood. Here, we investigated the acute (24 hours) systemic toxicity of intraperitoneally administered 50 nm and 500 nm SiNPs in mice (0.5 mg/kg). Both sizes of SiNPs induced a platelet proaggregatory effect in pial venules and increased plasma concentration of plasminogen activator inhibitor-1. Elevated plasma levels of von Willebrand factor and fibrinogen and a decrease in the number of circulating platelets were only seen following the administration of 50 nm SiNPs. The direct addition of SiNPs to untreated mouse blood significantly induced in vitro platelet aggregation in a dose-dependent fashion, and these effects were more pronounced with 50 nm SiNPs. Both sizes of SiNPs increased lactate dehydrogenase activity and interleukin 1? concentration. However, tumor necrosis factor ? concentration was only increased after the administration of 50 nm SiNPs. Nevertheless, plasma markers of oxidative stress, including 8-isoprostane, thiobarbituric acid reactive substances, catalase, and glutathione S-transferase, were not affected by SiNPs. The in vitro exposure of human umbilical vein endothelial cells to SiNPs showed a reduced cellular viability, and more potency was seen with 50 nm SiNPs. Both sizes of SiNPs caused a decrease in endothelium-dependent relaxation of isolated small mesenteric arteries. We conclude that amorphous SiNPs cause systemic inflammation and coagulation events, and alter vascular reactivity. Overall, the effects observed with 50 nm SiNPs were more pronounced than those with 500 nm SiNPs. These findings provide new insight into the deleterious effect of amorphous SiNPs on vascular homeostasis. PMID:24936130

Nemmar, Abderrahim; Albarwani, Sulayma; Beegam, Sumaya; Yuvaraju, Priya; Yasin, Javed; Attoub, Samir; Ali, Badreldin H

2014-01-01

328

Quantum confinement of nanocrystals within amorphous matrices  

NASA Astrophysics Data System (ADS)

Nanocrystals encapsulated within an amorphous matrix are computationally analyzed to quantify the degree to which the matrix modifies the nature of their quantum-confinement power—i.e., the relationship between nanocrystal size and the gap between valence- and conduction-band edges. A special geometry allows exactly the same amorphous matrix to be applied to nanocrystals of increasing size to precisely quantify changes in confinement without the noise typically associated with encapsulating structures that are different for each nanocrystal. The results both explain and quantify the degree to which amorphous matrices redshift the character of quantum confinement. The character of this confinement depends on both the type of encapsulating material and the separation distance between the nanocrystals within it. Surprisingly, the analysis also identifies a critical nanocrystal threshold below which quantum confinement is not possible—a feature unique to amorphous encapsulation. Although applied to silicon nanocrystals within an amorphous silicon matrix, the methodology can be used to accurately analyze the confinement softening of other amorphous systems as well.

Lusk, Mark T.; Collins, Reuben T.; Nourbakhsh, Zahra; Akbarzadeh, Hadi

2014-02-01

329

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

330

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.

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

2010-05-01

331

Can amorphization take place in nanoscale interconnects?  

PubMed

The trend of miniaturization has highlighted the problems of heat dissipation and electromigration in nanoelectronic device interconnects, but not amorphization. While amorphization is known to be a high pressure and/or temperature phenomenon, we argue that defect density is the key factor, while temperature and pressure are only the means. For nanoscale interconnects carrying modest current density, large vacancy concentrations may be generated without the necessity of high temperature or pressure due to the large fraction of grain boundaries and triple points. To investigate this hypothesis, we performed in situ transmission electron microscope (TEM) experiments on 200 nm thick (80 nm average grain size) aluminum specimens. Electron diffraction patterns indicate partial amorphization at modest current density of about 10(5) A cm(-2), which is too low to trigger electromigration. Since amorphization results in drastic decrease in mechanical ductility as well as electrical and thermal conductivity, further increase in current density to about 7 × 10(5) A cm(-2) resulted in brittle fracture failure. Our molecular dynamics (MD) simulations predict the formation of amorphous regions in response to large mechanical stresses (due to nanoscale grain size) and excess vacancies at the cathode side of the thin films. The findings of this study suggest that amorphization can precede electromigration and thereby play a vital role in the reliability of micro/nanoelectronic devices. PMID:22322399

Kumar, S; Joshi, K L; van Duin, A C T; Haque, M A

2012-03-01

332

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

333

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

334

Interaction potential for aluminum nitride: A molecular dynamics study of mechanical and thermal properties of crystalline and amorphous  

E-print Network

properties of crystalline and amorphous aluminum nitride Priya Vashishta,1,a Rajiv K. Kalia,1 Aiichiro Nakano ceramic materials, only AlN and beryllium oxide have high thermal conductivity. Aluminum nitrideInteraction potential for aluminum nitride: A molecular dynamics study of mechanical and thermal

Southern California, University of

335

Synthesis of enhanced hydrophilic and hydrophobic graphene oxide nanosheets by a solvothermal method  

Microsoft Academic Search

We report that the hydrophilic affinity of graphene oxide nanosheets can be significantly increased by reacting with allylamine. High resolution transmission electron microscopy and electron diffraction analysis confirmed that the graphene oxide nanosheets were amorphous in structure. Hydrophobic graphene oxide nanosheets were also prepared via functionalising with phenylisocynate (C6H5NCO) through a solvothermal synthesis process. Hydrophobic graphene oxide nanosheets can be

Guoxiu Wang; Bei Wang; Jinsoo Park; Juan Yang; Xiaoping Shen; Jane Yao

2009-01-01

336

Electron-beam-assisted superplastic shaping of nanoscale amorphous silica  

PubMed Central

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

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

2010-01-01

337

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

SciTech Connect

Amorphous carbon nanotubes (aCNTs) were synthesized by AAO (anodic aluminum oxide) template at a temperature 500 °C in nitrogen atmosphere using the citric acid as a carbon source without the help of any catalyst particles. Morphological analysis of the as prepared samples was carried out by field emission scanning electron microscopy (FESEM). Confocal Raman imaging has been studied and an attempt has been made to find out the graphitic (sp{sup 2}) and disordered phase of the CNTs.

Maity, Supratim [Thin Film and Nanoscience Laboratory, Department of Physics, Jadavpur University, Kolkata -700 032 (India); Roychowdhury, Tuhin [School of Materials Science and Nanotechnology, Jadavpur University, Kolkata -700 032 (India); Chattopadhyay, Kalyan Kumar, E-mail: kalyan-chattopadhyay@yahoo.com [Thin Film and Nanoscience Laboratory, Department of Physics, Jadavpur University, Kolkata -700 032, India and School of Materials Science and Nanotechnology, Jadavpur University, Kolkata -700 032 (India)

2014-04-24

338

Fabrication and characterization of amorphous lithium electrolyte thin films and rechargeable thin-film batteries  

Microsoft Academic Search

Amorphous oxide and oxynitride lithium electrolyte thin films were synthesized by r.f. magnetron sputtering of lithium silicates and lithium phosphates in Ar, Ar + O2, Ar + N2, or N2. The composition, structure, and electrical properties of the films were characterized using ion and electron beam, X ray, optical, photoelectron, and a.c. impedance techniques. For the lithium phosphosilicate films, lithium

J. B. Bates; N. J. Dudney; G. R. Gruzalski; R. A. Zuhr; A. Choudhury; C. F. Luck; J. D. Robertson

1993-01-01

339

Microstructure and surface chemistry of amorphous alloys important to their friction and wear behavior  

NASA Technical Reports Server (NTRS)

An investigation was conducted to examine the microstructure and surface chemistry of amorphous alloys, and their effects on tribological behavior. The results indicate that the surface oxide layers present on amorphous alloys are effective in providing low friction and a protective film against wear in air. Clustering and crystallization in amorphous alloys can be enhanced as a result of plastic flow during the sliding process at a low sliding velocity, at room temperature. Clusters or crystallines with sizes to 150 nm and a diffused honeycomb-shaped structure are produced on sizes to 150 nm and a diffused honeycomb-shaped structure are produced on the wear surface. Temperature effects lead to drastic changes in surface chemistry and friction behavior of the alloys at temperatures to 750 C. Contaminants can come from the bulk of the alloys to the surface upon heating and impart to the surface oxides at 350 C and boron nitride above 500 C. The oxides increase friction while the boron nitride reduces friction drastically in vacuum.

Miyoshi, K.; Buckley, D. H.

1986-01-01

340

Mechanical-contact-induced transformation from the amorphous to the partially crystalline state in metallic glass  

NASA Technical Reports Server (NTRS)

Friction and wear tests were conducted with 3.2- and 6.4-millimeter-diameter aluminum oxide spheres sliding, in reciprocating motion, on a Fe67Co18B14Si1 metallic foil. Crystallites with a size range of 10 to 150 nanometers were produced on the wear surface of the amorphous alloy. A strong interaction between transition metals and metalloids such as silicon and boron results in strong segregation during repeated sliding, provides preferential transition metal-metalloid clustering in the amorphous alloy, and subsequently produces the diffused honeycomb structure formed by dark grey bands and primary crystals, that is, alpha-Fe in the matrix. Large plastic flow occurs on an amorphous alloy surface with sliding and the flow film of the alloy transfers to the aluminum oxide pin surface. Multiple slip bands due to shear deformation are observed on the side of the wear track. Two distinct types of wear debris were observed as a result of sliding: an alloy wear debris, and/or powdery-whiskery oxide debris.

Miyoshi, K.; Buckley, D. H.

1984-01-01

341

Mechanical contact induced transformation from the amorphous to the crystalline state in metallic glass  

NASA Technical Reports Server (NTRS)

Friction and wear tests were conducted with 3.2- and 6.4-millimeter-diameter aluminum oxide spheres sliding, in reciprocating motion, on a Fe67Co18B14Si1 metallic foil. Crystallites with a size range of 10 to 150 nanometers were produced on the wear surface of the amorphous alloy. A strong interaction between transition metals and metalloids such as silicon and boron results in strong segregation during repeated sliding, provides preferential transition metal-metalloid clustering in the amorphous alloy, and subsequently produces the diffused honeycomb structure formed by dark grey bands and primary crystals, that is, alpha-Fe in the matrix. Large plastic flow occurs on an amorphous alloy surface with sliding and the flow film of the alloy transfers to the aluminum oxide pin surface. Multiple slip bands due to shear deformation are observed on the side of the wear track. Two distinct types of wear debris were observed as a result of sliding: an alloy wear debris, and/or powdery-whiskery oxide debris.

Miyoshi, K.; Buckley, D. H.

1984-01-01

342

Bimodal Dynamics of PEO in Amorphous Blends with PMMA  

NASA Astrophysics Data System (ADS)

Quasielastic neutron scattering measurements have been carried out on miscible blends of hydrogenated poly(ethyelene oxide) [PEO] and deuterated polymethyl methacrylate [PMMA]. The blends contain 10, 20 and 30% PEO by weight and are completely amorphous. The deuteration scheme highlights the motion of PEO which was followed using a time-of-flight spectrometer. Two distinct mobilities of PEO are observed in the blend, a fast and a slower process, with a cross-over time of 1ps. The fast process shows an Arrhenius temperature dependence and is independent of blend composition. This process resembles the faster process observed in pure PEO, which incidentally is more stretched than the typical beta=1 behavior observed in a number of pure polymers. The slower process is very stretched and shows a stronger dependence with temperature. Relaxation times agree with measurements using NMR. This process is believed to be the structural relaxation of PEO which has slowed down due to the presence of PMMA.

Garcia Sakai, Victoria; Maranas, Janna K.; Peral, Inmaculada

2004-03-01

343

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

344

Amorphous carbon enhancement of hydrogen penetration into UO2  

NASA Astrophysics Data System (ADS)

The interaction of D2 and H2O (humidity) with amorphous carbon covered UO2 vs. clean UO2 was studied using Secondary Ion Mass Spectrometry (SIMS) and X-ray Photoelectron Spectroscopy (XPS). It was found that SIMS depth profiles of the carbon covered side vs. the bare oxide, show significant higher intensities of H- and D- for the first, through the carbon layer and beneath it. The presence of a thin carbon layer on a UO2 surface caused a significant buildup of hydroxyl, probably adsorbed on the carbon, but maybe also beneath the layer, in the presence of atmospheric humidity. Exposure of the carbon covered oxide to D2 on a UHV annealed surface also caused a growth of the hydroxyl. It is concluded that the carbon surface strongly enhances the dissociation of water vapor as well as that of hydrogen and the penetration of the dissociation products to the oxide, as compared to the bare UO2 surface. The contribution of the latter, beneath the carbon, should be verified or ruled out by further experiments.

Zalkind, S.; Shamir, N.; Gouder, T.; Akhvlediani, R.; Hoffman, A.

2014-06-01

345

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

346

Amorphous silicon detectors in positron emission tomography  

SciTech Connect

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

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

1989-12-01

347

Novel Internal Friction of Amorphous Solids  

NASA Astrophysics Data System (ADS)

Owing to the great sensitivity of the double-paddle oscillators, we have recently measured the low-temperature internal friction of amorphous silicon films (X. Liu, B. E. White, Jr., R. O. Pohl, E. Iwanizcko, K. M. Jones, A. H. Mahan, B. N. Nelson, R. S. Crandall, S. Veprek, Phys. Rev. Lett. 78), 4418 (1997). While e-beam evaporation, sputtering, or Si^+ ion implantation produce a-Si films with similar tunneling states as in all amorphous solids, hydrogenated a-Si films with 1 at.% H prepared by hot-wire chemical vapor deposition show no sign of any significant low energy excitations. This observation offers an exciting opportunity to study the structural origin of the low energy excitations common to amorphous solids. A possible explanation is that in the hydrogenated films the amorphous structure is closer to the fourfold coordinated continuous random network expected in amorphous Si, and thus the lattice is more constrained, resulting in the absence of tunneling states.

Liu, Xiao

1998-03-01

348

Amorphous cobalt hydroxide with superior pseudocapacitive performance.  

PubMed

Cobalt hydroxide (Co(OH)2) has received extensive attention for its exceptional splendid electrical properties as a promising supercapacitor electrode material. Co(OH)2 study so far prefers to crystal instead of amorphous, in spite of amorphous impressive electrochemical properties including the ability to improve the electrochemical efficiency based on the disorder structure. The amorphous Co(OH)2 nanostructures with excellent electrochemical behaviors were successfully synthesized by a simple and green electrochemistry. Our as-prepared Co(OH)2 electrode exhibited ultrahigh capacitance of 1094 F g(-1) and super long cycle life of 95% retention over 8000 cycle numbers at a nominal 100 mV s(-1) scan rate. The united pseudo-capacitive performances of the amorphous Co(OH)2 nanostructures in electrochemical capacitors are totally comparable to those of the crystalline Co(OH)2 nanomaterials. These findings actually open a door to applications of amorphous nanomaterials in the field of energy storage as superior electrochemical pseudocapacitors materials. PMID:24386890

Li, H B; Yu, M H; Lu, X H; Liu, P; Liang, Y; Xiao, J; Tong, Y X; Yang, G W

2014-01-22

349

SURVIVAL OF AMORPHOUS WATER ICE ON CENTAURS  

SciTech Connect

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

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

2012-10-01

350

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

351

Nanocrystalline silicon/amorphous silicon dioxide superlattices  

SciTech Connect

Thin layers made of densely packed silicon nanocrystals sandwiched between amorphous silicon dioxide layers have been manufactured and characterized. An amorphous silicon/amorphous silicon dioxide superlattice is first grown by CVD or RF sputtering. The a-Si layers are recrystallized in a two-step procedure (nucleation + growth) for form layers of nearly identical nanocrystals whose diameter is given by the initial a-Si layer thickness. The recrystallization is monitored using a variety of techniques, including TEM, X-Ray, Raman, and luminescence spectroscopies. When the a-Si layer thickness decreases (from 25 nm to 2.5 nm) or the a-SiO{sub 2} layer thickness increases (from 1.5 nm to 6 nm), the recrystallization temperature increases dramatically compared to that of a single a-Si film. The removal of the a-Si tissue present between the nanocrystals, the passivation of the nanocrystals, and their doping are discussed.

Fauchet, P.M.; Tsybeskov, L. [Univ. of Rochester, NY (United States). Dept. of Electrical Engineering; Zacharias, M. [Univ. of Rochester, NY (United States). Dept. of Electrical Engineering; [Otto-von-Guericke Univ., Magdeburg (Germany). Inst. of Experimental Physics; Hirschman, K. [Univ. of Rochester, NY (United States). Dept. of Electrical Engineering; [Rochester Inst. of Tech., NY (United States). Dept. of Microelectronic Engineering

1998-12-31

352

Modeling amorphous thin films: Kinetically limited minimization  

NASA Astrophysics Data System (ADS)

Atomic-scale models of amorphous structures are typically generated using a simulated annealing (SA) quench from a melt simulation protocol. This approach resembles the preparation of bulk glasses, but it may not be suitable for modeling amorphous materials produced using low-energy and low-temperature physical vapor deposition, where a deposited atom induces only local relaxations and no equilibrated melt is formed. To account for such growth conditions, we developed the kinetically limited minimization (KLM) technique, in which an amorphous structure is constructed from a randomly initialized structure in a number of local perturbation-relaxation steps. We compare formation energies as well as short- and medium-range order of KLM- and SA-generated structures of a-In2O3, a-ZnO, and a-Si.

Zawadzki, Pawe? P.; Perkins, John; Lany, Stephan

2014-09-01

353

Amorphous and microcrystalline silicon technology -- 1998  

SciTech Connect

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

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

1999-08-01

354

Synthesis and photocurrent of amorphous boron nanowires.  

PubMed

Although theoretically feasible, synthesis of boron nanostructures is challenging due to the highly reactive nature, high melting and boiling points of boron. We have developed a thermal vapor transfer approach to synthesizing amorphous boron nanowire using a solid boron source. The amorphous nature and chemical composition of boron nanowires were characterized by high resolution transmission electron microscopy, selected area electron diffraction, and electron energy loss spectroscopy. Optical properties and photoconduction of boron nanowires have not yet been reported. In our investigation, the amorphous boron nanowire showed much better optical and electrical properties than previously reported photo-response of crystalline boron nanobelts. When excited by a blue LED, the photo/dark current ratio (I/I?) is 1.5 and time constants in the order of tens of seconds. I/I? is 1.17 using a green light. PMID:25061013

Ge, Liehui; Lei, Sidong; Hart, Amelia H C; Gao, Guanhui; Jafry, Huma; Vajtai, Robert; Ajayan, Pulickel M

2014-08-22

355

Amorphous metallic films in silicon metallization systems  

NASA Technical Reports Server (NTRS)

Diffusion barrier research was focussed on lowering the chemical reactivity of amorphous thin films on silicon. An additional area of concern is the reaction with metal overlays such as aluminum, silver, and gold. Gold was included to allow for technology transfer to gallium arsenide PV cells. Amorphous tungsten nitride films have shown much promise. Stability to annealing temperatures of 700, 800, and 550 C were achieved for overlays of silver, gold, and aluminum, respectively. The lower results for aluminum were not surprising because there is an eutectic that can form at a lower temperature. It seems that titanium and zirconium will remove the nitrogen from a tungsten nitride amorphous film and render it unstable. Other variables of research interest were substrate bias and base pressure during sputtering.

So, F.; Kolawa, E.; Nicolet, M. A.

1985-01-01

356

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

357

Novel core–shell SDC\\/amorphous Na 2CO 3 nanocomposite electrolyte for low-temperature SOFCs  

Microsoft Academic Search

Novel core–shell SDC (Ce0.8Sm0.2O1.9)\\/amorphous Na2CO3 nanocomposite was prepared for the first time. The core–shell nanocomposite particles are smaller than 100nm with amorphous Na2CO3 shell of 4–6nm in thickness. The nanocomposite electrolyte shows superionic conductivity above 300°C, where the conductivity reaches over 0.1Scm?1. Such high conductive nanocomposite has been applied in low-temperature solid oxide fuel cells (LTSOFCs) with an excellent performance

Xiaodi Wang; Ying Ma; Rizwan Raza; Mamoun Muhammed; Bin Zhu

2008-01-01

358

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

359

Dielectric and vibrational properties of crystalline and amorphous high-k lanthanum aluminate  

NASA Astrophysics Data System (ADS)

High-k oxides are the focus of intense research for their applications in MOS and FLASH devices. A material currently in focus is LaAlO3, with a dielectric constant of 23-24 in the crystal phase, and similar values of around 20-22 in the amorphous phase (although values as low as 15 have also been reported). We have studied LaAlO3 in both phases [1] to identify possible reasons for this apparent conservation of the dielectric properties upon amorphization. Amorphous samples were generated by melt-and-quench using a combination of pair potentials and ab initio dynamics. The linear response density-functional perturbation-theory approach was used to study dynamical response and phonons. We indeed find a large dielectric constant ( 24) in the amorphous: the rationale is that the expected reduction of the anomalous effective charges is compensated by the appearance of new low-frequency (weakly) IR-active modes, whose character is a mixture of La translations (IR in the crystal) and Al-O octahedra rotations (Raman in the crystal). A similar behavior is expected in any rare earth aluminate exhibiting a similar perovskite-related structure (e.g. scandates). 1) P. Delugas, V. Fiorentini, and A. Filippetti, Phys. Rev. B 71, 134302 (2005), and to be published.

Delugas, Pietro; Fiorentini, Vincenzo; Filippetti, Alessio

2006-03-01

360

Microstructure and properties of hydrophobic films derived from Fe-W amorphous alloy  

NASA Astrophysics Data System (ADS)

Amorphous metals are totally different from crystalline metals in regard to atom arrangement. Amorphous metals do not have grain boundaries and weak spots that crystalline materials contain, making them more resistant to wear and corrosion. In this study, amorphous Fe-W alloy films were first prepared by an electroplating method and were then made hydrophobic by modification with a water repellent (heptadecafluoro-1,1,2,2-tetradecyl) trimethoxysilane. Hierarchical micro-nano structures can be obtained by slightly oxidizing the as-deposited alloy, accompanied by phase transformation from amorphous to crystalline during heat treatment. The micro-nano structures can trap air to form an extremely thin cushion of air between the water and the film, which is critical to producing hydrophobicity in the film. Results show that the average values of capacitance, roughness factor, and impedance for specific surface areas of a 600°C heat-treated sample are greater than those of a sample treated at 500°C. Importantly, the coating can be fabricated on various metal substrates to act as a corrosion retardant.

Wang, Song; Ling, Yun-han; Zhang, Jun; Wang, Jian-jun; Xu, Gui-ying

2014-04-01

361

Radiation-induced amorphization of intermetallic compounds  

NASA Astrophysics Data System (ADS)

In the present paper, important results of our recent computer simulation of radiation-induced amorphization in the ordered compounds CuTi and Cu4Ti3 are summarized. The energetic, structural, thermodynamic and mechanical responses of these intermetallics during chemical disordering, point-defect production and heating were simulated, using molecular dynamics and embedded-atom potentials. From the atomistic details obtained, the critical role of radiation-induced structural disorder in driving the crystalline-to-amorphous phase transformation is discussed.

Lam, N. Q.; Sabochick, M. J.; Okamoto, P. R.

1994-06-01

362

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

363

Ion bombardment and disorder in amorphous silicon  

SciTech Connect

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

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

1997-07-01

364

Thermal conductivity of sputtered amorphous Ge films  

SciTech Connect

We measured the thermal conductivity of amorphous Ge films prepared by magnetron sputtering. The thermal conductivity was significantly higher than the value predicted by the minimum thermal conductivity model and increased with deposition temperature. We found that variations in sound velocity and Ge film density were not the main factors in the high thermal conductivity. Fast Fourier transform patterns of transmission electron micrographs revealed that short-range order in the Ge films was responsible for their high thermal conductivity. The results provide experimental evidences to understand the underlying nature of the variation of phonon mean free path in amorphous solids.

Zhan, Tianzhuo; Xu, Yibin; Goto, Masahiro; Tanaka, Yoshihisa; Kato, Ryozo; Sasaki, Michiko; Kagawa, Yutaka [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan)] [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan)

2014-02-15

365

Optimization of transparent and reflecting electrodes for amorphous silicon solar cells. Annual technical report, April 1, 1995--March 31, 1996  

SciTech Connect

The general objective is to develop methods to deposit materials which can be used to make more efficient solar cells. The work is organized into three general tasks: Task 1. Develop improved methods for depositing and using transparent conductors of fluorine-doped zinc oxide in amorphous silicon solar cells Task 2. Deposit and evaluate titanium oxide as a reflection-enhancing diffusion barrier between amorphous silicon and an aluminum or silver back-reflector. Task 3. Deposit and evaluate electrically conductive titanium oxide as a transparent conducting layer on which more efficient and more stable superstrate cells can be deposited. About one-third of the current project resources are allocated to each of these three objectives.

Gordon, R.G.; Sato, H.; Liang, H.; Liu, X.; Thornton, J. [Harvard Univ., Cambridge, MA (United States)

1996-08-01

366

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 (µ 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 µ 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, µ 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

367

Amorphous silicon waveguides for microphotonics M. J. A. de Dooda)  

E-print Network

Amorphous silicon waveguides for microphotonics M. J. A. de Dooda) and A. Polman FOM Institute were made by anisotropic etching of a 1.5 m silicon-on-insulator structure that was partly amorphized. Transmission measurements of these waveguides as function of the amorphous silicon length show that the a

Polman, Albert

368

Hydrogen plasma enhanced crystallization of hydrogenated amorphous silicon films  

E-print Network

Hydrogen plasma enhanced crystallization of hydrogenated amorphous silicon films K. Pangal,a) J. C thermal crystallization of amorphous silicon time by a factor of five. Exposure to hydrogen plasma reduces . Polysilicon formed by the crystallization of amorphous silicon (a-Si) has far superior material and electronic

369

The structure of electronic states in amorphous silicon  

E-print Network

The structure of electronic states in amorphous silicon David A. Drabold,* Uwe Stephan, Jianjun in real space, and that span the occupied electronic subspace for the amorphous silicon mod- els the structure and dynamics of electron states in amorphous Si. The nature of the states near the gap at zero

Drabold, David

370

Atomistic processes during nanoindentation of amorphous silicon carbide Izabela Szlufarskaa)  

E-print Network

Atomistic processes during nanoindentation of amorphous silicon carbide Izabela Szlufarskaa- mations of amorphous silicon carbide a-SiC by means of MD. The maximum indentation pressure of 30 GPa shown8 that nucleation and coalescence of dislocations under an indenter lead to amorphization

Southern California, University of

371

AMORPHOUS SILICON ON p-TYPE CRYSTALLINE SILICON HETEROJUNCTION  

E-print Network

641 AMORPHOUS SILICON ON p-TYPE CRYSTALLINE SILICON HETEROJUNCTION A. K. ABOUL-SEOUD and O. MOKHTAR, DÃ?CEMBRE 1978, 1 1. Introduction. - In recent years, sudden interest grew in building amorphous silicon]. There is still much to leam about the properties of amorphous silicon. The problem of dangling bonds [4] as well

Paris-Sud XI, Université de

372

Crystallization of phosphorus-doped amorphous silicon films  

E-print Network

657 Crystallization of phosphorus-doped amorphous silicon films prepared by glow discharge of phosphorus-doped amorphous silicon films prepared by glow discharge of silane is observed by using 6 août 1981, accepté le 9 septembre 1981) Résumé. 2014 La cristallisation dans le silicium amorphe

Paris-Sud XI, Université de

373

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

374

STABILITY OF AMORPHOUS SILICON THIN FILM TRANSISTORS AND CIRCUITS  

E-print Network

STABILITY OF AMORPHOUS SILICON THIN FILM TRANSISTORS AND CIRCUITS Ting Liu A DISSERTATION PRESENTED by Ting Liu. All rights reserved #12;Abstract i Hydrogenated amorphous silicon thin-film transistors (a to the breaking of weak bonds in the amorphous silicon. It can be modeled with a "unified stretched exponential

375

New Amorphous Silicon Alloy Systems  

NASA Astrophysics Data System (ADS)

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

Kapur, Mridula N.

1990-01-01

376

Amorphous Siliconbased Solar Cells Xunming Deng1  

E-print Network

light when excited by the current. Amorphous silicon was deposited as a thin film on substrates inserted was xerography [1, 2], which exploited the photoconductivity of noncrystalline selenium. As do all semicon efficient solar cells using a silane glow discharge to deposit films. In 1976, he and Christopher Wronski

Schiff, Eric A.

377

Athermal nonlinear elastic constants of amorphous solids.  

PubMed

We derive expressions for the lowest nonlinear elastic constants of amorphous solids in athermal conditions (up to third order), in terms of the interaction potential between the constituent particles. The effect of these constants cannot be disregarded when amorphous solids undergo instabilities such as plastic flow or fracture in the athermal limit; in such situations the elastic response increases enormously, bringing the system much beyond the linear regime. We demonstrate that the existing theory of thermal nonlinear elastic constants converges to our expressions in the limit of zero temperature. We motivate the calculation by discussing two examples in which these nonlinear elastic constants play a crucial role in the context of elastoplasticity of amorphous solids. The first example is the plasticity-induced memory that is typical to amorphous solids (giving rise to the Bauschinger effect). The second example is how to predict the next plastic event from knowledge of the nonlinear elastic constants. Using the results of our calculations we derive a simple differential equation for the lowest eigenvalue of the Hessian matrix in the external strain near mechanical instabilities; this equation predicts how the eigenvalue vanishes at the mechanical instability and the value of the strain where the mechanical instability takes place. PMID:20866874

Karmakar, Smarajit; Lerner, Edan; Procaccia, Itamar

2010-08-01

378

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

2009-05-01

379

Poole-Frenkel conduction in amorphous solids  

Microsoft Academic Search

The nature of the electrical conduction process in amorphous solids, using as a basis the ionization of local defects by an applied field, is investigated. It is shown that the Poole-Frenkel effect is a limiting case of a more general analysis that can be extended to cover the experimentally available range of field stress and temperature. At low temperature conduction

Robert M. Hill

1971-01-01

380

Explosive depassivation of amorphous alloys during corrosion  

SciTech Connect

It has been shown that, during active and passive corrosion, Fe{sub 80-x}Cr{sub x}P{sub 13}C{sub 7} amorphous alloys can be transformed into a crystalline modification. Crystallization of alloys is a result of selective dissolution and can lead to explosive depassivation upon long-term exposure of alloys in HCl solutions.

Vasil`ev, V.Yu.; Mikaelyan, A.S.; Isirikyan, A.A. [Moscow Institute of Steel and Alloys, Moscow (Russian Federation)

1994-09-01

381

TRANSIENT AMORPHOUS CALCIUM PHOSPHATE IN FORMING ENAMEL  

PubMed Central

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

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

2009-01-01

382

Amorphous silicon coatings with silver nanoparticles  

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

383

Plasma deposition of amorphous metal alloys  

DOEpatents

Amorphous metal alloy coatings are plasma-deposited by dissociation of vapors of organometallic compounds and metalloid hydrides in the presence of a reducing gas, using a glow discharge. Tetracarbonylnickel, phosphine, and hydrogen constitute a typical reaction mixture of the invention, yielding a NiPC alloy.

Hays, Auda K. (Albuquerque, NM)

1986-01-01

384

Excess Noise in Amorphous Selenium Avalanche Photodiodes  

Microsoft Academic Search

Excess noise in amorphous Selenium avalanche photodiodes (a-Se APD) has been measured in a frequency range from 3 kHz to 30 kHz. The deduced excess noise factors, including dependences on photocurrent, frequency, applied electric field and the a-Se layer's thickness, agreed with McIntyre's theoretical values.

Tetsuya Ohshima; Kazutaka Tsuji; Kenji Sameshima; Tadaaki Hirai; Keiichi Shidara; Kazuhisa Taketoshi

1991-01-01

385

Excess Noise in Amorphous Selenium Avalanche Photodiodes  

NASA Astrophysics Data System (ADS)

Excess noise in amorphous Selenium avalanche photodiodes (a-Se APD) has been measured in a frequency range from 3 kHz to 30 kHz. The deduced excess noise factors, including dependences on photocurrent, frequency, applied electric field and the a-Se layer’s thickness, agreed with McIntyre’s theoretical values.

Ohshima, Tetsuya; Tsuji, Kazutaka; Sameshima, Kenji; Hirai, Tadaaki; Shidara, Keiichi; Taketoshi, Kazuhisa

1991-06-01

386

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

387

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

388

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 dynamics—but all reported to exist below the crystallization temperature of approximately 150–170 K below 4–5 GPa. Here, we present the evidence of high density amorphous (HDA) ice formed well above the crystallization temperature at 1 GPa—well inside the so-called “no-man’s land.” It is formed from metastable ice VII in the stability field of ice VI under rapid compression using dynamic-diamond anvil cell (d-DAC) and results from structural similarities between HDA and ice VII. The formation follows an interfacial growth mechanism unlike the melting process. Nevertheless, the occurrence of HDA along the extrapolated melt line of ice VII resembles the ice Ih-to-HDA transition, indicating that structural instabilities of parent ice VII and Ih drive the pressure-induced amorphization. PMID:21518902

Chen, Jing-Yin; Yoo, Choong-Shik

2011-01-01

389

Optical properties of Teflon AF amorphous  

E-print Network

Optical properties of Teflon® AF amorphous fluoropolymers Min K. Yang Roger H. French DuPont Co-0713 Abstract. The optical properties of three grades of Teflon® AF-- AF1300, AF1601, and AF2400--were. The absorbances of Teflon® AF films were determined by measuring the transmission intensity of Teflon® AF films

Rollins, Andrew M.

390

Metal electrode for amorphous silicon solar cells  

DOEpatents

An amorphous silicon solar cell having an N-type region wherein the contact to the N-type region is composed of a material having a work function of about 3.7 electron volts or less. Suitable materials include strontium, barium and magnesium and rare earth metals such as gadolinium and yttrium.

Williams, Richard (Princeton, NJ)

1983-01-01

391

REGULAR ARTICLE Hydrogenated amorphous silicon nanostructures  

E-print Network

REGULAR ARTICLE Hydrogenated amorphous silicon nanostructures: novel structure and internal rotations on the reactivity of hydrogenated silicon nanostructures toward cyclization and ring for hydrides con- taining up to eight silicon atoms have been calculated using G3//B3LYP. The overall reactions

Barton, Paul I.

392

Enthalpy of formation of carbon-rich polymer-derived amorphous SiCN ceramics.  

SciTech Connect

Carbon-rich silicon carbonitride (SiCN) ceramics derived from polysilylcarbodiimides represent a novel class of materials where the incorporation of a high amount of carbon was demonstrated to be beneficial for ultrahigh-temperature resistance against crystallization. Calorimetric measurements of heat of oxidative dissolution in a molten oxide solvent show that these amorphous SiCN ceramics produced at 1000 or 1100 C possess a small positive or near zero enthalpy of formation relative to their crystalline constituents, namely silicon nitride, silicon carbide, and graphite. The enthalpy of formation does not change strongly with increasing SiC mole fraction. Because the enthalpies of formation from crystalline constituents are at most slightly positive, and the entropies of formation are expected to be significantly positive because of disorder in the amorphous phase, it is likely that the free energies of formation from silicon carbide, silicon nitride, and graphite are negative and the high-temperature persistence of amorphous SiCN ceramics may originate from thermodynamic stabilization. However, this stabilization is less pronounced than that for SiCO polymer-derived ceramics studied earlier.

Morcos, R. M.; Mera, G.; Navrotsky, A.; Varga, T.; Riedel, R.; Poli, F.; Muller, K.; Materials Science Division; Univ. of California at Davis; Technische Univ. Darmstadt; Univ. of Stuttgart

2008-10-01

393

Fabricating amorphous silicon solar cells by varying the temperature _of the substrate during deposition of the amorphous silicon layer  

DOEpatents

An improved process for fabricating amorphous silicon solar cells in which the temperature of the substrate is varied during the deposition of the amorphous silicon layer is described. Solar cells manufactured in accordance with this process are shown to have increased efficiencies and fill factors when compared to solar cells manufactured with a constant substrate temperature during deposition of the amorphous silicon layer.

Carlson, David E. (Yardley, PA)

1982-01-01

394

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

395

Amorphous TiO2 nanotube arrays for low-temperature oxygen sensors  

NASA Astrophysics Data System (ADS)

Titania nanotube arrays (TNTA) were synthesized on a titanium substrate using anodic oxidation in an electrolyte containing ammonium fluoride and evaluated for low-temperature oxygen sensing. Their sensing properties were tested at different temperatures (50, 100, 150, 200, 250 and 300 °C) when exposed to various oxygen concentrations. The as-prepared TNTA are amorphous and exhibit much higher carrier concentration than that of annealed TNTA. Such amorphous TNTA show much higher sensitivity than that of annealed TNTA, SrTiO3 and Ga2O3 sensors. This sample demonstrates the lowest detectable oxygen concentration of 200 ppm, excellent recovery and good linear correlation at 100 °C. These results indicate that TNTA are indeed very attractive oxygen-sensing materials.

Lu, Hao Feng; Li, Feng; Liu, Gang; Chen, Zhi-Gang; Wang, Da-Wei; Fang, Hai-Tao; Qing Lu, Gao; Jiang, Zhou Hua; Cheng, Hui-Ming

2008-10-01

396

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

397

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

398

Amorphous Carbon: State of the Art - Proceedings of the 1st International Specialist Meeting on Amorphous Carbon (smac '97)  

NASA Astrophysics Data System (ADS)

The Table of Contents for the full book PDF is as follows: * Preface * GROWTH AND STRUCTURE * The Structure of Tetrahedral Amorphous Carbon * Growth of DLC Films and Related Structure and Properties * Deposition Mechanism of Diamond-Like Carbon * Relaxation of sp3 Bonds in Hydrogen Free Carbon Films During Growth * MODELLING * Correlations Between Microstructure and Electronic Properties in Amorphous Carbon Based Materials * Review of Monte Carlo Simulations of Diamondlike Amorphous Carbon: Bulk, Surface, and Interface Structural Properties * DEPOSITION * Preparation of Disordered Amorphous and Partially Ordered Nano Clustered Carbon Films by Arc Deposition: A Critical Review * Plasma Deposition of Diamond-Like Carbon in an ECR-RF Discharge * Deposition of Amorphous Hydrogenated Carbon-Nitrogen Films by PECVD Using Several Hydrocarbon / Nitrogen Containing Gas Mixtures * ELECTRONIC STRUCTURE * 'Defects' and Their Detection in a-C and a-C:H * Valence Band and Gap State Spectroscopy of Amorphous Carbon by Photoelectron Emission Techniques * Photoluminescence Spectroscopy: A Probe for Inhomogeneous Structure in Polymer-Like Amorphous Carbon * Raman Characterization of Amorphous and Nanocrystalline sp3 Bonded Structures * Ultraviolet Raman Spectroscopy of Tetrahedral Amorphous Carbon Thin Films * Excitation Energy Dependent Raman and Photoluminescence Spectra of Hydrogenated Amorphous Carbon * MECHANICAL PROPERTIES * Pulsed Laser Deposited a-C: Growth, Structure and Mechanical Properties * Mechanical Properties of Laser-Assisted Deposited Amorphous Carbon Films * Mechanical and Morphology Study on Tetrahedral Amorphous Carbon Films * Time-Dependent Changes in the Mechanical Properties of Diamond-Like Carbon Films * ELECTRONIC PROPERTIES * Electronic Transport in Amorphous Carbon * Electronic Properties of Undoped/Doped Tetrahedral Amorphous Carbon * The Inclusion of Graphitic Nanoparticles in Semiconducting Amorphous Carbon to Enhance Electronic Transport Properties * FIELD EMISSION * Carbon Cathode Requirements and Emission Characterization for Low-Voltage Field Emission Displays * Electron Field Emission from Carbon Films * Electron Field Emission from Carbon Thin Films

Silva, S. R. P.; Robertson, J.; Milne, W. I.; Amaratunga, G. A. J.

1998-05-01

399

Influence of proton insertion on the conductivity, structural and optical properties of amorphous and crystalline electrochromic WO 3 films  

NASA Astrophysics Data System (ADS)

Amorphous and crystalline tungsten oxide films were RF-sputtered from a metallic target in oxygen/argon atmosphere onto un-heated and heated substrates. Upon cyclic electrochemical treatment in 0.1 M H 2SO 4 aqueous solution, both types of films showed good electrochromic reversibility beyond 1000 cycles. The crystallinity changes of both types of films were studied by XRD. For c-WO 3, the results showed that hydrogen insertion enhance the degree of crystallinity with the clear appearance of tungsten bronze diffraction peaks due to the formation of H 0.1WO 3, with tetragonal crystalline structure. For a-WO 3, coloration weakens the amorphous features and increases the crystallinity properties. The DC electrical conductivity increases, in a reversible way, with four order of magnitudes namely from 10 -7 to 10 -3 (? cm) -1 for bleached and colored films, respectively. Both types of films exhibit remarkable solar transmission modulation, about 51%, which is adequate for smart windows applications. In contrast to amorphous films, crystalline tungsten oxide films show reflection modulation in the NIR reaching 25% upon charge insertion. The Drude reflectance edge arises for colored films suggesting that coloration in c-WO 3 is attributed to a scattering mechanism of Drude-like free electron, while coloration of a-WO 3 is attributed to a hopping mechanism of small polaron. The visible, infrared and solar modulations are given for both types of films. Coloration/bleaching were found to be faster for amorphous films. Self-bleaching process in different oxidative environments involves a redox cycle aided by water polarity. Crystalline WO 3 showed pronounced coloring persistence relative to amorphous films which is attributed to different binding energy related to large and small polarons.

Kamal, H.; Akl, A. A.; Abdel-Hady, K.

2004-06-01

400

Nitroxide-Functionalized Graphene Oxide from Graphite Oxide  

PubMed Central

A facile method for preparing functionalized graphene oxide single layers with nitroxide groups is reported herein. Highly oxidized graphite oxide (GO=90.6%) was obtained, slightly modifying an improved Hummer’s method. Oxoammonium salts (OS) were investigated to introduce nitroxide groups to GO, resulting in a one-step functionalization and exfoliation. The mechanisms of functionalization/exfoliation are proposed, where the oxidation of aromatic alcohols to ketone groups, and the formation of alkoxyamine species are suggested. Two kinds of functionalized graphene oxide layers (GOFT1 and GOFT2) were obtained by controlling the amount of OS added. GOFT1 and GOFT2 exhibited a high interlayer spacing (d0001 = 1.12nm), which was determined by X-ray diffraction. The presence of new chemical bonds C-N (~9.5 %) and O-O (~4.3 %) from nitroxide attached onto graphene layers were observed by X-ray photoelectron spectroscopy. Single-layers of GOFT1 were observed by HRTEM, exhibiting amorphous and crystalline zones at a 50:50 ratio; in contrast, layers of GOFT2 exhibited a fully amorphous surface. Fingerprint of GOFT1 single layers was obtained by electron diffraction at several tilts. Finally, the potential use of these materials within Nylon 6 matrices was investigated, where an unusual simultaneous increase in tensile stress, tensile strain and Young’s modulus was observed. PMID:24347671

Avila-Vega, Yazmin I.; Leyva-Porras, Cesar C.; Mireles, Marcela; Quevedo-López, Manuel; Macossay, Javier; Bonilla-Cruz, José

2013-01-01

401

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

402

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

403

Bonding defects in hydrogenated amorphous silicon  

SciTech Connect

A mechanism for charged-carrier-trapping-induced defect metastability in hydrogenated amorphous silicon (a-Si:H) and in hydrogenated amorphous silicon alloys containing relatively high concentrations of oxygen and/or nitrogen atoms (a-Si:X:H, X = O or N) is described. The experimental results that identified this defect metastability mechanism were (i) differences in the Staebler-Wronski effect in a-Si:H and a-Si:N:H alloys prepared from N{sub 2} and NH{sub 3} source gases by remote plasma-enhanced chemical-vapor deposition, and (ii) differences in defect generation at N-atom terminated Si-SiO{sub 2} interfaces prepared from NH{sub 3} and N{sub 2}O.

Lucovsky, G.; Yang, H. [North Carolina State Univ., Raleigh, NC (United States)

1996-12-31

404

Surface modified amorphous ribbon based magnetoimpedance biosensor.  

PubMed

Magnetoimpedance (MI) changes due to surface modification of the sensitive element caused by human urine, were studied with the aim of creating a robust biosensor working on a principle of electrochemical magnetoimpedance spectroscopy. A biosensor prototype with an as-quenched amorphous ribbon sensitive element was designed and calibrated for a frequency range of 0.5-10 MHz at a current intensity of 60 mA. Measurements as a function of the exposure time were made both in a regime where chemical surface modification and MI measurements were separated as well as in a regime where they were done simultaneously. The MI variation was explained by the change of the surface magnetic anisotropy. It was shown that the magnetoimpedance effect can be successfully employed as a new option to probe the electric features of the Fe(5)Co(70)Si(15)B(10) amorphous ribbon magnetic electrode surface modified by human urine. PMID:16914305

Kurlyandskaya, Galina V; Fal Miyar, Vanessa

2007-04-15

405

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

406

Domain collapse in amorphous magnetostrictive wires  

Microsoft Academic Search

In magnetostrictive amorphous wires of composition (Fe77.5 Si7.5B15) the process of domain collapse is an important ingredient of reentrant reversal. During collapse, a narrow and high voltage pulse is generated due to the formation of an unstable domain. Experimental results showing the influence of an external magnetic field and an applied longitudinal tensile stress on the voltage pulse shape agree

L. V. Panina; H. Katoh; M. Mizutani; K. Mohri; F. B. Humphrey

1992-01-01

407

Phase Modulation Device Using Amorphous Short Wire  

Microsoft Academic Search

A new phase-modulation device with simple structure and high reliability was constructed using a short amorphous wire. A high-frequency ac current (carrier) and a signal current are simultaneously passed through the wire, which undergoes the large Barkhausen effect when the circumferential flux changes. Highly linear modulation characteristics were obtained up to 0.67¿ using a triangular-wave ac current, passed through tension-annealed

K. Mohri; K. Bushida

1994-01-01

408

Amorphous silicon photovoltaics: order from disorder  

Microsoft Academic Search

Amorphous silicon (a-Si) solar cell technology has matured to a stage where there is currently a production of 30 MW peak\\/year. The progress is due to the continuous advances made in new materials, cell designs, and large area deposition techniques for mass production. The absence of long-range order, which is present in crystalline materials, has profound consequences on the properties

Christopher R. Wronski

2000-01-01

409

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

410

Design Requirements for Amorphous Piezoelectric Polymers  

NASA Technical Reports Server (NTRS)

An overview of the piezoelectric activity in amorphous piezoelectric polymers is presented. The criteria required to render a polymer piezoelectric are discussed. Although piezoelectricity is a coupling between mechanical and electrical properties, most research has concentrated on the electrical properties of potentially piezoelectric polymers. In this work, we present comparative mechanical data as a function of temperature and offer a summary of polarization and electromechanical properties for each of the polymers considered.

Ounaies, Z.; Young, J. A.; Harrison, J. S.

1999-01-01

411

Crystallization Kinetics of Amorphous Solid Water  

Microsoft Academic Search

Amorphous solid water (ASW) is ubiquitous in space and has been identified as a major component in many astrophysical ices, including cometary nuclei, planetary rings, on the surfaces satellites and planets and frozen out on the surface of interstellar dust grains. The H2O content within these ices typically ranges between 60-70%, hence H2O plays a significant role in interstellar chemistry.

R. A. Baragiola; D. J. Burke; M. A. Fama

2009-01-01

412

Metal-induced crystallization of amorphous silicon  

Microsoft Academic Search

We studied the Ni-silicide mediated crystallization of hydrogenated amorphous silicon (a-Si:H) in the presence of an electric field. The NiSi2 precipitates were formed at temperatures less than 400°C and act as nuclei sites in the initial stage of thermal annealing. Needlelike Si crystallites are grown as a result of the migration of NiSi2 precipitates in the a-Si:H network. The crystallization

Soo Young Yoon; Seong Jin Park; Kyung Ho Kim; Jin Jang

2001-01-01

413

Crystalline-amorphous transition in silicate perovskites  

SciTech Connect

CaSiO{sub 3} and MgSiO{sub 3} 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 perovskite systems transform under tension to a low-density glass composed of corner shared chains of tetrahedral silicon. The amorphization is initiated by a thermally activated step involving a soft polar optic mode in the perovskite phase at the Brillouin zone center. Progression of the system along this reaction coordinate triggers, in succession, multiple barrierless modes of instability ultimately producing a catastrophic decohesion of the lattice. An important intermediary along the reaction path is a crystalline phase where silicon is in a five-coordinate site and the alkaline-earth metal atom is in eightfold coordination. At the onset pressure, this transitory phase is itself dynamically unstable to a number of additional vibrational modes, the most relevant being those which result in transformation to a variety of tetrahedral chain silicate motifs. These results support the conjecture that stress-induced amorphization arises from the near simultaneous accessibility of multiple modes of instability in the highly metastable parent crystalline phase.

Hemmati, M. [Department of Chemistry, Arizona State University, Tempe, Arizona 85287-1604 (United States)] [Department of Chemistry, Arizona State University, Tempe, Arizona 85287-1604 (United States); Chizmeshya, A. [Department of Chemistry, Arizona State University, Tempe, Arizona 85287-1604 (United States)] [Department of Chemistry, Arizona State University, Tempe, Arizona 85287-1604 (United States); [Idaho National Engineering Laboratory, EG& G Idaho, P.O. Box 1625, Idaho Falls, Idaho 83415-2208 (United States); Wolf, G.H.; Poole, P.H.; Shao, J.; Angell, C.A. [Department of Chemistry, Arizona State University, Tempe, Arizona 85287-1604 (United States)] [Department of Chemistry, Arizona State University, Tempe, Arizona 85287-1604 (United States)

1995-06-01

414

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 525°C. It was also observed that the silicide growth was diffusion-controlled, similar to what has been reported for example in the formation of NiSi 2 for the reaction of nickel on amorphous silicon. The kinetics of the FeSi 2 formation in the temperature range 525-625°C was studied by RBS and the activation energy was found to be 1.5 ± 0.1 eV.

Erlesand, U.; Östling, M.; Bodén, K.

1991-11-01

415

Phase transitions in biogenic amorphous calcium carbonate  

NASA Astrophysics Data System (ADS)

Geological calcium carbonate exists in both crystalline phases and amorphous phases. Compared with crystalline calcium carbonate, such as calcite, aragonite and vaterite, the amorphous calcium carbonate (ACC) is unstable. Unlike geological calcium carbonate crystals, crystalline sea urchin spicules (99.9 wt % calcium carbonate and 0.1 wt % proteins) do not present facets. To explain this property, crystal formation via amorphous precursors was proposed in theory. And previous research reported experimental evidence of ACC on the surface of forming sea urchin spicules. By using X-ray absorption near-edge structure (XANES) spectroscopy and photoelectron emission microscopy (PEEM), we studied cross-sections of fresh sea urchin spicules at different stages (36h, 48h and 72h after fertilization) and observed the transition sequence of three mineral phases: hydrated ACC ? dehydrated ACC ? biogenic calcite. In addition, we unexpectedly found hydrated ACC nanoparticles that are surrounded by biogenic calcite. This observation indicates the dehydration from hydrated ACC to dehydrated ACC is inhibited, resulting in stabilization of hydrated ACC nanoparticles. We thought that the dehydration was inhibited by protein matrix components occluded within the biomineral, and we designed an in vitro assay to test the hypothesis. By utilizing XANES-PEEM, we found that SM50, the most abundant occluded matrix protein in sea urchin spicules, has the function to stabilize hydrated ACC in vitro.

Gong, Yutao

416

Oxidation-assisted ductility of aluminium nanowires.  

PubMed

Oxidation can drastically change mechanical properties of nanostructures that typically have large surface-to-volume ratios. However, the underlying mechanisms describing the effect oxidation has on the mechanical properties of nanostructures have yet to be characterized. Here we use reactive molecular dynamics and show that the oxidation enhances the aluminium nanowire ductility, and the oxide shell exhibits superplastic behaviour. The oxide shell decreases the aluminium dislocation nucleation stress by increasing the activation volume and the number of nucleation sites. Superplasticity of the amorphous oxide shell is due to viscous flow as a result of healing of the broken aluminium-oxygen bonds by oxygen diffusion, below a critical strain rate. The interplay between the strain rate and oxidation rate is not only essential for designing nanodevices in ambient environments, but also controls interface properties in large-scale deformation processes. PMID:24887649

Sen, Fatih G; Alpas, Ahmet T; van Duin, Adri C T; Qi, Yue

2014-01-01

417

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

PubMed

We developed a technique to fabricate oxide thin films with uniaxially controlled crystallographic orientation and lateral size of more than micrometers on amorphous substrates. This technique is lateral solid-phase epitaxy, where epitaxial crystallization of amorphous precursor is seeded with ultrathin oxide nanosheets sparsely (?10% coverage) deposited on the substrate. Transparent conducting Nb-doped anatase TiO2 thin films were fabricated on glass substrates by this technique. Perfect (001) orientation and large grains with lateral sizes up to 10 ?m were confirmed by X-ray diffraction, atomic force microscopy, and electron beam backscattering diffraction measurements. As a consequence of these features, the obtained film exhibited excellent electrical transport properties comparable to those of epitaxial thin films on single-crystalline substrates. This technique is a versatile method for fabricating high-quality oxide thin films other than anatase TiO2 and would increase the possible applications of oxide-based thin film devices. PMID:24867286

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

2014-06-24

418

180nm gate length amorphous InGaZnO thin film transistor for high density image sensor applications  

Microsoft Academic Search

In this article, we propose a novel hybrid complementary metal oxide semiconductor (CMOS) image sensor architecture utilizing nanometer scale amorphous In-Ga-Zn-O (a-IGZO) thin film transistors (TFT) combined with a conventional Si photo diode. This approach will overcome the loss of quantum efficiency and image quality due to the downscaling of the photodiode. The 180nm gate length a-IGZO TFT exhibits remarkable

Sanghun Jeon; Sungho Park; Ihun Song; Ji-Hyun Hur; Sunil Kim; Sangwook Kim; Huaxiang Yin; Eunha Lee; Seungeon Ahn; Hojung Kim; Changjung Kim; U-In Chung

2010-01-01

419

Formation of amorphous silicon by light ion damage  

SciTech Connect

Amorphization by implantation of boron ions (which is the lightest element generally used in I.C. fabrication processes) has been systematically studied for various temperatures, various voltages and various dose rates. Based on theoretical considerations and experimental results, a new amorphization model for light and intermediate mass ion damage is proposed consisting of two stages. The role of interstitial type point defects or clusters in amorphization is emphasized. Due to the higher mobility of interstitials out-diffusion to the surface particularly during amorphization with low energy can be significant. From a review of the idealized amorphous structure, diinterstitial-divacancy pairs are suggested to be the embryos of amorphous zones formed during room temperature implantation. The stacking fault loops found in specimens implanted with boron at room temperature are considered to be the origin of secondary defects formed during annealing.

Shih, Y.C.

1985-12-01

420

Thermal properties of amorphous/crystalline silicon superlattices.  

PubMed

Thermal transport properties of crystalline/amorphous silicon superlattices using molecular dynamics are investigated. We show that the cross-plane conductivity of the superlattices is very low and close to the conductivity of bulk amorphous silicon even for amorphous layers as thin as ? 6 ?. The cross-plane thermal conductivity weakly increases with temperature which is associated with a decrease of the Kapitza resistance with temperature at the crystalline/amorphous interface. This property is further investigated considering the spatial analysis of the phonon density of states in domains close to the interface. Interestingly, the crystalline/amorphous superlattices are shown to display large thermal anisotropy, according to the characteristic sizes of elaborated structures. These last results suggest that the thermal conductivity of crystalline/amorphous superlattices can be phonon engineered, providing new directions for nanostructured thermoelectrics and anisotropic materials in thermal transport. PMID:25105883

France-Lanord, Arthur; Merabia, Samy; Albaret, Tristan; Lacroix, David; Termentzidis, Konstantinos

2014-09-01

421

Amorphous-silicon module hot-spot testing  

NASA Technical Reports Server (NTRS)

Hot spot heating occurs when cell short-circuit current is lower than string operating current. Amorphous cell hot spot are tested to develop the techniques required for performing reverse bias testing of amorphous cells. Also, to quantify the response of amorphous cells to reverse biasing. Guidelines are developed from testing for reducing hot spot susceptibility of amorphous modules and to develop a qualification test for hot spot testing of amorphous modules. It is concluded that amorphous cells undergo hot spot heating similarly to crystalline cells. Comparison of results obtained with submodules versus actual modules indicate heating levels lower in actual modules. Module design must address hot spot testing and hot spot qualification test conducted on modules showed no instabilities and minor cell erosion.

Gonzalez, C. C.

1985-01-01

422

Photoelectrochemical and photovoltaic characteristics of amorphous-silicon-based tandem cells as photocathodes for water splitting.  

PubMed

In this study amorphous silicon tandem solar cells are successfully utilized as photoelectrodes in a photoelectrochemical cell for water electrolysis. The tandem cells are modified with various amounts of platinum and are combined with a ruthenium oxide counter electrode. In a two-electrode arrangement this system is capable of splitting water without external bias with a short-circuit current of 4.50 mA?cm(-2) . On the assumption that no faradaic losses occur, a solar-to-hydrogen efficiency of 5.54?% is achieved. In order to identify the relevant loss processes, additional three-electrode measurements were performed for each involved half-cell. PMID:25335095

Ziegler, Jürgen; Kaiser, Bernhard; Jaegermann, Wolfram; Urbain, Félix; Becker, Jan-Philipp; Smirnov, Vladimir; Finger, Friedhelm

2014-12-15

423

Production of strontium-substituted lanthanum manganite perovskite powder by the amorphous citrate process  

Microsoft Academic Search

The amorphous citrate process has been used to produce Mn2O3, Mn3O4, LaMnO3, SrMnO3 and strontium-substituted LaMnO3. The citrate-nitrate gels were dehydrated at 70‡ C to yield solid precursor materials. The decomposition\\/oxidation of the precursors have been studied using thermogravimetry and evolved gas analysis. The products of decomposition have been characterized by X-ray diffraction analysis, scanning electron microscopy and, in the

M. S. G. Baythoun; F. R. Sale

1982-01-01

424

Improved conversion efficiency of amorphous Si solar cells using a mesoporous ZnO pattern  

NASA Astrophysics Data System (ADS)

To provide a front transparent electrode for use in highly efficient hydrogenated amorphous silicon (a-Si:H) thin-film solar cells, porous flat layer and micro-patterns of zinc oxide (ZnO) nanoparticle (NP) layers were prepared through ultraviolet nanoimprint lithography (UV-NIL) and deposited on Al-doped ZnO (AZO) layers. Through this, it was found that a porous micro-pattern of ZnO NPs dispersed in resin can optimize the light-trapping pattern, with the efficiency of solar cells based on patterned or flat mesoporous ZnO layers increased by 27% and 12%, respectively.

Go, Bit-Na; Kim, Yang Doo; suk Oh, Kyoung; Kim, Chaehyun; Choi, Hak-Jong; Lee, Heon

2014-09-01

425

Improved conversion efficiency of amorphous Si solar cells using a mesoporous ZnO pattern.  

PubMed

To provide a front transparent electrode for use in highly efficient hydrogenated amorphous silicon (a-Si:H) thin-film solar cells, porous flat layer and micro-patterns of zinc oxide (ZnO) nanoparticle (NP) layers were prepared through ultraviolet nanoimprint lithography (UV-NIL) and deposited on Al-doped ZnO (AZO) layers. Through this, it was found that a porous micro-pattern of ZnO NPs dispersed in resin can optimize the light-trapping pattern, with the efficiency of solar cells based on patterned or flat mesoporous ZnO layers increased by 27% and 12%, respectively. PMID:25276101

Go, Bit-Na; Kim, Yang Doo; Suk Oh, Kyoung; Kim, Chaehyun; Choi, Hak-Jong; Lee, Heon

2014-01-01

426

Preparation and Surface Analysis of a Fluorinated Amorphous Silicon for Photo-voltaic Device Application  

NASA Technical Reports Server (NTRS)

Amorphous silicon films (a-Si:H) have been routinely deposited on a variety of substrates. Surface and interfacial studies were carried out with a PHI 5600 X-ray photo electron spectrometer. Co-deposition with fluorine yielded films having oxygen present as bulk oxide. The higher the fluorine content, the greater the amount of bulk oxygen observed. The presence of oxygen may be a contributing factor to inconsistent film properties of fluorine doped silicon materials, reported else where. A definite chemical interface between a layer containing fluorine and a layer made from pure silane has been delineated.

McWhinney, Hylton G.; Burton, Dawn; Fogarty, Thomas N.

1998-01-01

427

Mössbauer study of an amorphous magnetic solid containing Cr  

Microsoft Academic Search

A Cr-containing transition metal based amorphous magnetic solid (Fe32Ni36Cr14P12B6) has been studied by 57Fe Mössbauer spectroscopy in both its amorphous and crystalline states. The magnetic ordering temperatures of TC=249, 254, and 238 K have been determined for samples from three batches. In the amorphous state at T>TC, well-defined quadrupole spectra are observed. At 4.2 K, the hyperfine-field distribution P(H) is

C. L. Chien

1979-01-01

428

Amorphous Silicon as Semiconductor Material for High Resolution LAPS  

E-print Network

Amorphous Silicon as Semiconductor Material for High Resolution LAPS Werner Moritz1 , Tatsuo-insulator- semiconductor (MIS) structures based on amorphous silicon (a-Si) prepared as a thin layer on transparent glass-substrate Amorphous silicon -4 -2 0 2 4 0,2 0,4 0,6 0,8 1,0 photocurrenta.u. gate voltage/V 600µm x 600µm area scan

Moritz, Werner

429

Long-term oxidization and phase transition of InN nanotextures  

PubMed Central

The long-term (6 months) oxidization of hcp-InN (wurtzite, InN-w) nanostructures (crystalline/amorphous) synthesized on Si [100] substrates is analyzed. The densely packed layers of InN-w nanostructures (5-40 nm) are shown to be oxidized by atmospheric oxygen via the formation of an intermediate amorphous In-Ox-Ny (indium oxynitride) phase to a final bi-phase hcp-InN/bcc-In2O3 nanotexture. High-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, electron energy loss spectroscopy and selected area electron diffraction are used to identify amorphous In-Ox-Ny oxynitride phase. When the oxidized area exceeds the critical size of 5 nm, the amorphous In-Ox-Ny phase eventually undergoes phase transition via a slow chemical reaction of atomic oxygen with the indium atoms, forming a single bcc In2O3 phase. PMID:21711908

2011-01-01

430

Formation of metastable structures and amorphous phases in Pu-based systems using the sputtering technique  

NASA Astrophysics Data System (ADS)

The triode sputtering technique with a split-target arrangement was used to obtain metastable crystalline and amorphous phases in ten binary systems of Pu with Si, Al, V, Fe, Co, Pd, Ta, Re, Os, and Ir. In addition to metastable extensions of solid solubility occurring from the binary sides of some systems, wide ranges of metallic glass formation have been observed in several systems. Extended bcc solid solution ranges were observed in Pu-Ta and Pu-V systems. Unlike in the case of many liquid-quenched alloys, the ranges of amorphous phase formation obtained with sputtering appear to have little to do with the form of the corresponding phase diagram. However, the extent of the observed ranges on the Pu-rich side was found to obey approximately the atomic size mismatch relationship. The nearest neighbor distances (NNDs) evaluated with X-ray diffraction show many unusual deviations from an assumed Vegard’s Law, which can be interpreted in relation to the changing electronic configuration of the Pu atom when present in different environments. Exposure of several amorphous alloys to severe oxidation environments did not results in observable corrosion.

Rizzo, H. F.; Massalski, T. B.; Echeverria, A. W.

1989-05-01

431

Investigating the medium range order in amorphous Ta2O5 coatings  

NASA Astrophysics Data System (ADS)

Ion-beam sputtered amorphous heavy metal oxides, such as Ta2O5, are widely used as the high refractive index layer of highly reflective dielectric coatings. Such coatings are used in the ground based Laser Interferometer Gravitational-wave Observatory (LIGO), in which mechanical loss, directly related to Brownian thermal noise, from the coatings forms an important limit to the sensitivity of the LIGO detector. It has previously been shown that heat-treatment and TiO2 doping of amorphous Ta2O5 coatings causes significant changes to the levels of mechanical loss measured and is thought to result from changes in the atomic structure. This work aims to find ways to reduce the levels of mechanical loss in the coatings by understanding the atomic structure properties that are responsible for it, and thus helping to increase the LIGO detector sensitivity. Using a combination of Reduced Density Functions (RDFs) from electron diffraction and Fluctuation Electron Microscopy (FEM), we probe the medium range order (in the 2-3 nm range) of these amorphous coatings.

Bassiri, Riccardo; Hart, Martin; Byer, Robert L.; Borisenko, Konstantin B.; Evans, Keith; Fejer, Martin M.; Lin, Angie C.; MacLaren, Ian; Markosyan, Ashot S.; Martin, Iain W.; Route, Roger K.; Rowan, Sheila

2014-06-01

432

Ferroelectric properties of vinylidene fluoride-trifluoroethylene copolymer thin films fabricated on amorphous alloy electrode  

NASA Astrophysics Data System (ADS)

We have investigated the structure and ferroelectric properties of vinylidene fluoride-trifluoroethylene (VDF-TrFE) copolymer thin films fabricated on amorphous alloy electrodes. Thin films of amorphous Pd-Cu-Si alloys with various compositions were successfully prepared by sputtering deposition. An atomically flat surface resulting from a fully amorphous structure of Pd-Cu-Si was obtained upon achieving a uniform surface of a spin-coated VDF-TrFE copolymer thin film. X-ray diffraction (XRD) measurements revealed that the crystalline structure of the VDF-TrFE copolymer thin films was of ferroelectric ?-phase, being independent of the composition and crystalline state of the Pd-Cu-Si alloy. The clearly observed D-E hysteresis loops showed a remanent polarization of 0.075 C/m2 and a coercive field of 90 MV/m at a measurement frequency of 10 Hz for a 50-nm-thick film, which is almost consistent with the results obtained with Pt electrode samples. We also observed the thinning-induced reduction of remanent polarization, which was explained by the depolarization field induced by the surface dead layer in VDF-TrFE copolymer rather than the oxidized layer in Pd-Cu-Si alloy electrode.

Nakajima, Takashi; Yamaura, Shin-ichi; Furukawa, Takeo; Okamura, Soichiro

2014-09-01

433

Effect of oxide formation mechanisms on lead adsorption by biogenic manganese (hydr)oxides, iron (hydr)oxides, and their mixtures.  

PubMed

The effects of iron and manganese (hydr)oxide formation processes on the trace metal adsorption properties of these metal (hydr)oxides and their mixtures was investigated by measuring lead adsorption by iron and manganese (hydr)oxides prepared by a variety of methods. Amorphous iron (hydr)oxide formed by fast precipitation at pH 7.5 exhibited greater Pb adsorption (gamma(max) = 50 mmol of Pb/mol of Fe at pH 6.0) than iron (hydr)oxide formed by slow, diffusion-controlled oxidation of Fe(II) at pH 4.5-7.0 or goethite. Biogenic manganese(III/IV) (hydr)oxide prepared by enzymatic oxidation of Mn(II) by the bacterium Leptothrix discophora SS-1 adsorbed five times more Pb (per mole of Mn) than an abiotic manganese (hydr)oxide prepared by oxidation of Mn(II) with permanganate, and 500-5000 times more Pb than pyrolusite oxides (betaMnO2). X-ray crystallography indicated that biogenic manganese (hydr)oxide and iron (hydr)oxide were predominantly amorphous or poorly crystalline and their X-ray diffraction patterns were not significantly affected by the presence of the other (hydr)oxide during formation. When iron and manganese (hydr)oxides were mixed after formation, or for Mn biologically oxidized with iron(III) (hydr)oxide present, observed Pb adsorption was similar to that expected for the mixture based on Langmuir parameters for the individual (hydr)oxides. These results indicate that interactions in iron/manganese (hydr)oxide mixtures related to the formation process and sequence of formation such as site masking, alterations in specific surface area, or changes in crystalline structure either did not occur or had a negligible effect on Pb adsorption by the mixtures. PMID:11871557

Nelson, Yarrow M; Lion, Leonard W; Shuler, Michael L; Ghiorse, William C

2002-02-01

434

Oxidation induced softening in Al nanowires  

NASA Astrophysics Data System (ADS)

The mechanical properties of metallic nanowires depend dramatically on the atmospheric conditions. Molecular-dynamics simulations with ReaxFF were conducted to study tensile elastic deformation of oxidized Al nanowires. The thin amorphous oxide shell formed around Al nanowires had a very low Young's modulus of 26 GPa, due to its low density and low Al-O coordination. Consequently, for diameters less than 100 nm, the composite Young's modulus of oxide-covered Al nanowires showed a size dependence implying that in this case "smaller is softer." The model developed also explained the discrepancies in the reported modulus values of nanometer-scale Al thin films.

Sen, Fatih G.; Qi, Yue; van Duin, Adri C. T.; Alpas, Ahmet T.

2013-02-01

435

Amorphous silicon TFT based non-volatile memory Memory devices based on amorphous Silicon (a-Si) thin film transistors (TFTs) have the  

E-print Network

Chapter 5 86 Amorphous silicon TFT based non-volatile memory Memory devices based on amorphous information. This information is accessed, by "reading" the state, with the #12;Chapter 5: Amorphous silicon: Amorphous silicon TFT based nonvolatile memory 88 the threshold voltage of the transistor, which

436

On the crystallization of amorphous germanium films  

NASA Astrophysics Data System (ADS)

The incubation time for crystallization of amorphous Ge (a-Ge) films, deposited by e-gun, was studied as a function of temperature between 150 and 500°C by means of both in situ transmission electron microscopy and Raman scattering spectroscopy. The temperature dependence of t0 follows an Arrhenius curve with an activation energy of 2.0 eV for free-sustained a-Ge films. In the case where the a-Ge films were on Si 3N 4 substrate, the activation energy of the incubation process was 1.3 eV.

Edelman, F.; Komem, Y.; Bendayan, M.; Beserman, R.

1993-06-01

437

Optical Properties of Amorphous Germanium Films  

Microsoft Academic Search

The optical constants of amorphous Ge films formed under well-defined conditions have been determined in the 0.1-25.0-eV spectral range. In the 0.1-1.8-eV range they were determined by analysis of precise reflectance and transmittance data (RT), and in the 0.1-25.0-eV range by a Kramers-Kronig analysis of normal-incidence reflectance data. Both analyses gave the same results in the region of overlap. The

T. M. Donovan; W. E. Spicer; J. M. Bennett; E. J. Ashley

1970-01-01

438

Magnetron-Sputtered Amorphous Metallic Coatings  

NASA Technical Reports Server (NTRS)

Amorphous coatings of refractory metal/metalloid-based alloys deposited by magnetron sputtering provide extraordinary hardness and wear resistance. Sputtering target fabricated by thoroughly mixing powders of tungsten, rhenium, and boron in stated proportions and pressing at 1,200 degrees C and 3,000 lb/in. to second power (21 MPa). Substrate lightly etched by sputtering before deposition, then maintained at bias of - 500 V during initial stages of film growth while target material sputtered onto it. Argon gas at pressure used as carrier gas for sputter deposition. Coatings dense, pinhole-free, extremely smooth, and significantly resistant to chemical corrosion in acidic and neutral aqueous environments.

Thakoor, A. P.; Mehra, M.; Khanna, S. K.

1985-01-01

439

Rapid Annealing Of Amorphous Hydrogenated Carbon  

NASA Technical Reports Server (NTRS)

Report describes experiments to determine effects of rapid annealing on films of amorphous hydrogenated carbon. Study represents first efforts to provide information for applications of a-C:H films where rapid thermal processing required. Major finding, annealing causes abrupt increase in absorption and concomitant decrease in optical band gap. Most of change occurs during first 20 s, continues during longer annealing times. Extend of change increases with annealing temperature. Researchers hypothesize abrupt initial change caused by loss of hydrogen, while gradual subsequent change due to polymerization of remaining carbon into crystallites or sheets of graphite. Optical band gaps of unannealed specimens on silicon substrates lower than those of specimens on quartz substrates.

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

1989-01-01

440

Radiation resistance studies of amorphous silicon films  

NASA Technical Reports Server (NTRS)

Hydrogenated amorphous silicon thin films were irradiated with 2.00 MeV helium ions using fluences ranging from 1E11 to 1E15 cm(-2). The films were characterized using photothermal deflection spectroscopy and photoconductivity measurements. The investigations show that the radiation introduces sub-band-gap states 1.35 eV below the conduction band and the states increase supralinearly with fluence. Photoconductivity measurements suggest the density of states above the Fermi energy is not changing drastically with fluence.

Woodyard, James R.; Payson, J. Scott

1989-01-01

441

Deuterium in crystalline and amorphous silicon  

SciTech Connect

The authors report deuteron magnetic resonance (DMR) measurements on aged deuterium-implanted single crystal n-type silicon and comparisons with amorphous silicon spectra. The sample film was prepared six years ago by deuteration from a-D{sub 2} plasma and evaluated by a variety of experimental methods. Deuterium has been evolving with time and the present DMR signal shows a smaller deuteron population. A doublet from Si-D configurations along (111) has decreased more than have central molecular DMR components, which include 47 and 12 kHz FWHM gaussians. Transient DMR magnetization recoveries indicate spin lattice relaxation to para-D{sub 2} relaxation centers.

Borzi, R.; Ma, H.; Fedders, P.A.; Leopold, D.J.; Norberg, R.E.; Boyce, J.B.; Johnson, N.M.; Ready, S.E.; Walker, J.

1997-07-01

442

Structure and physical properties of paracrystalline atomistic models of amorphous silicon  

E-print Network

Structure and physical properties of paracrystalline atomistic models of amorphous silicon P. M of amorphous silicon. Simulations from these models show qualitative agreement with the results of recent mesoscale fluctuation electron microscopy experiments on amorphous silicon and germanium. Such agreement

Drabold, David

443

Complex permeability and electromagnetic wave absorption properties of amorphous alloy–epoxy composites  

Microsoft Academic Search

Electromagnetic wave absorption properties of amorphous alloy–epoxy composites have been investigated with various amorphous alloy particle sizes and fractions in the 45MHz to 10GHz frequency range. The fraction of amorphous alloy in amorphous alloy–epoxy composites varied from 30 to 60vol.% at a fixed amorphous alloy particle size and the size of amorphous alloy particles was varied from several ?m to

K. M. Lim; K. A. Lee; M. C. Kim; C. G. Park

2005-01-01

444

Amorphous and crystalline aerosol particles interacting with water vapor: conceptual framework and experimental evidence for restructuring, phase transitions and kinetic limitations  

NASA Astrophysics Data System (ADS)

Interactions with water are crucial for the properties, transformation and climate effects of atmospheric aerosols. Here we present a conceptual framework for the interaction of amorphous aerosol particles with water vapor, outlining characteristic features and differences in comparison to crystalline particles. We used a hygroscopicity tandem differential mobility analyzer (H-TDMA) to characterize the hydration and dehydration of crystalline ammonium sulfate, amorphous oxalic acid and amorphous levoglucosan particles (diameter ~100 nm, relative humidity 5-95% at 298 K). The experimental data and accompanying Köhler model calculations provide new insights into particle microstructure, surface adsorption, bulk absorption, phase transitions and hygroscopic growth. The results of these and related investigations lead to the following conclusions: (1) Many organic substances, including carboxylic acids, carbohydrates and proteins, tend to form amorphous rather than crystalline phases upon drying of aqueous solution droplets. Depending on viscosity and microstructure, the amorphous phases can be classified as glasses, rubbers, gels or viscous liquids. (2) Amorphous organic substances tend to absorb water vapor and undergo gradual deliquescence and hygroscopic growth at lower relative humidity than their crystalline counterparts. (3) In the course of hydration and dehydration, certain organic substances can form rubber- or gel-like structures (supramolecular networks) and undergo transitions between swollen and collapsed network structures. (4) Organic gels or (semi-)solid amorphous shells (glassy, rubbery, ultra-viscous) with low molecular diffusivity can kinetically limit the uptake and release of water and may influence the hygroscopic growth and activation of aerosol particles as cloud condensation nuclei (CCN) and ice nuclei (IN). Moreover, (semi-)solid amorphous phases may influence the uptake of gaseous photo-oxidants and the chemical transformation and aging of atmospheric aerosols. (5) The shape and porosity of amorphous and crystalline particles formed upon dehydration of aqueous solution droplets depend on chemical composition and drying conditions. The apparent volume void fractions of particles with highly porous structures can range up to ~50% or more (xerogels, aerogels). (6) For efficient description of water uptake and phase transitions of aerosol particles, we propose not to limit the terms deliquescence and efflorescence to equilibrium phase transitions of crystalline substances. Instead we propose generalized definitions according to which amorphous and crystalline components can undergo gradual or prompt, partial or full deliquescence or efflorescence. We suggest that (semi-)solid amorphous phases may be important not only in the upper atmosphere as suggested in recent studies of glass formation at low temperatures. Depending on relative humidity, (semi-)solid phases and moisture-induced glass transitions may also play a role in gas-particle interactions at ambient temperatures in the lower atmosphere.

Mikhailov, E.; Vlasenko, S.; Martin, S. T.; Koop, T.; Pöschl, U.

2009-12-01

445

X-ray photoelectron spectroscopy studies of Ag-doped thin amorphous Ge xSb 40- xS 60 films  

NASA Astrophysics Data System (ADS)

X-ray photoelectron spectroscopy has been used to determine the binding energies of the core electrons in Ag-doped amorphous thin Ge xSb 40- xS 60 films ( x=15, 20, 25 and 27). Chemical shifts of the constituent elements have revealed that electrons are transferred from chalcogenide to metal and compounds such as Ag 2S and Ag 2O are likely to form due to photo-induced chemical modification and oxidation, respectively. Charge defects are induced in the amorphous system.

Debnath, R. K.; Fitzgerald, A. G.; Christova, K.

2002-12-01

446

Preferred orientations of laterally grown silicon films over amorphous substrates using the vapor-liquid-solid technique  

NASA Astrophysics Data System (ADS)

A novel method has been optimized so that adhesion layers are no longer needed to reliably deposit patterned gold structures on amorphous substrates. Using this technique allows for the fabrication of amorphous oxide templates known as micro-crucibles, which confine a vapor-liquid-solid (VLS) catalyst of nominally pure gold to a specific geometry. Within these confined templates of amorphous materials, faceted silicon crystals have been grown laterally. The novel deposition technique, which enables the nominally pure gold catalyst, involves the undercutting of an initial chromium adhesion layer. Using electron backscatter diffraction it was found that silicon nucleated in these micro-crucibles were 30% single crystals, 45% potentially twinned crystals and 25% polycrystals for the experimental conditions used. Single, potentially twinned, and polycrystals all had an aversion to growth with the {1 0 0} surface parallel to the amorphous substrate. Closer analysis of grain boundaries of potentially twinned and polycrystalline samples revealed that the overwhelming majority of them were of the 60° ?3 coherent twin boundary type. The large amount of coherent twin boundaries present in the grown, two-dimensional silicon crystals suggest that lateral VLS growth occurs very close to thermodynamic equilibrium. It is suggested that free energy fluctuations during growth or cooling, and impurities were the causes for this twinning.

LeBoeuf, J. L.; Brodusch, N.; Gauvin, R.; Quitoriano, N. J.

2014-12-01

447

Structural Characteristics of Synthetic Amorphous Calcium Carbonate  

SciTech Connect

Amorphous calcium carbonate (ACC) is an important phase involved in calcification by a wide variety of invertebrate organisms and is of technological interest in the development of functional materials. Despite widespread scientific interest in this phase a full characterization of structure is lacking. This is mainly due to its metastability and difficulties in evaluating structure using conventional structure determination methods. Here we present new findings from the application of two techniques, pair distribution function analysis and nuclear magnetic resonance spectroscopy, which provide new insight to structural aspects of synthetic ACC. Several important results have emerged from this study of ACC formed in vitro using two common preparation methods: (1) ACC exhibits no structural coherence over distances > 15 {angstrom} and is truly amorphous; (2) most of the hydrogen in ACC is present as structural H{sub 2}O, about half of which undergoes restricted motion on the millisecond time scale near room temperature; (3) the short- and intermediate-range structure of ACC shows no distinct match to any known structure in the calcium carbonate system; and (4) most of the carbonate in ACC is monodentate making it distinctly different from monohydrocalcite. Although the structure of synthetic ACC is still not fully understood, the results presented provide an important baseline for future experiments evaluating biogenic ACC and samples containing certain additives that may play a role in stabilization of ACC, crystallization kinetics, and final polymorph selection.

Michel, F. Marc; MacDonald, Jason; Feng, Jian; Phillips, Brian L.; Ehm, Lars; Tarabrella, Cathy; Parise, John B.; Reeder, Richard J. (SBU)