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1

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

2

Thermoelectric properties of amorphous indium gallium zinc oxide  

NASA Astrophysics Data System (ADS)

More than 50% of the photons present in the solar spectrum generate efficiency degrading waste heat in solar cells. Development of a transparent thermoelectric material could potentially double the overall efficiency of this renewable energy source. This dissertation focuses on understanding the thermoelectric properties of alpha-InGaZnO, a material that has the potential of fulfilling the properties necessary for a transparent thermoelectric material. Characterization of the structural, thermal, and electrical properties of alpha-InGaZnO has been carried out. The samples were made by sputtering with varying deposition and post-deposition annealing conditions. The thermal conductivity of O-rich samples is found to increase with decreasing temperature. This is in contrast to other amorphous materials in which the thermal conductivity decreases with decreasing temperature. In addition, the thermal conductivity is much lower than the predicted minimum thermal conductivity. The electrical resistivity shows thermally activated transport, but does not show the characteristic T1/4 behavior of localized electrons. These results suggest that neither the charge carriers nor the lattice vibrations are localized in this material. In addition, mobilities as high as 12 cm2/Vs were found. Finally, the highest thermoelectric figure of merit, ZT, is found to be 0.17. Modifications of the stoichiometry to produce additional Rayleigh scattering of the lattice vibrations could produce higher values of ZT.

Williams, Deborah Susan

3

Reduced contact resistance in inkjet printed high-performance amorphous indium gallium zinc oxide transistors.  

PubMed

Solution processing of amorphous metal oxide materials to fabricate thin-film transistors (TFTs) has received great recent interest. We demonstrate here an optimized "ink" and printing process for inkjet patterning of amorphous indium gallium zinc oxide (a-IGZO) TFTs and investigate the effects of device structure on derived electron mobility. Bottom-gate top-contact (BGTC) TFTs are fabricated and shown to exhibit electron mobilities comparable to a-Si:H. Furthermore, a record electron mobility of 2.5 cm(2) V(-1) s(-1) is demonstrated for bottom-gate bottom-contact (BGBC) TFTs. The mechanism underlying such impressive performance is investigated using transmission line techniques, and it is shown that the semiconductor-source/drain electrode interface contact resistance is nearly an order of magnitude lower for BGBC transistors versus BGTC devices. PMID:22321212

Hennek, Jonathan W; Xia, Yu; Everaerts, Ken; Hersam, Mark C; Facchetti, Antonio; Marks, Tobin J

2012-03-01

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

Analysis of printed silver electrode on amorphous indium gallium zinc oxide  

NASA Astrophysics Data System (ADS)

Silver (Ag) electrodes printed on amorphous indium gallium zinc oxide (a-InGaZnO) were investigated to analyze their effect on thin-film transistor (TFT) characteristics. The TFT characteristics of samples annealed at 250 °C deteriorated seriously owing to an aggregation of Ag. In addition, the TFT characteristics deteriorated even for 200 °C annealing with oxygen and nitrogen atmospheres. From measurements of secondary ion mass spectrometry and Fourier transform infrared spectroscopy, we found that carbon and hydrogen contained in printed Ag electrodes seriously affect the TFT characteristics. The reduction and protection against these impurities in Ag ink is the key point in the application of printed Ag electrodes to a-InGaZnO TFTs.

Ueoka, Yoshihiro; Nishibayashi, Takahiro; Ishikawa, Yasuaki; Yamazaki, Haruka; Osada, Yukihiro; Horita, Masahiro; Uraoka, Yukiharu

2014-01-01

6

Water-soluble thin film transistors and circuits based on amorphous indium-gallium-zinc oxide.  

PubMed

This paper presents device designs, circuit demonstrations, and dissolution kinetics for amorphous indium-gallium-zinc oxide (a-IGZO) thin film transistors (TFTs) comprised completely of water-soluble materials, including SiNx, SiOx, molybdenum, and poly(vinyl alcohol) (PVA). Collections of these types of physically transient a-IGZO TFTs and 5-stage ring oscillators (ROs), constructed with them, show field effect mobilities (?10 cm(2)/Vs), on/off ratios (?2 × 10(6)), subthreshold slopes (?220 mV/dec), Ohmic contact properties, and oscillation frequency of 5.67 kHz at supply voltages of 19 V, all comparable to otherwise similar devices constructed in conventional ways with standard, nontransient materials. Studies of dissolution kinetics for a-IGZO films in deionized water, bovine serum, and phosphate buffer saline solution provide data of relevance for the potential use of these materials and this technology in temporary biomedical implants. PMID:25805699

Jin, Sung Hun; Kang, Seung-Kyun; Cho, In-Tak; Han, Sang Youn; Chung, Ha Uk; Lee, Dong Joon; Shin, Jongmin; Baek, Geun Woo; Kim, Tae-Il; Lee, Jong-Ho; Rogers, John A

2015-04-22

7

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

8

Electrical stress-induced instability of amorphous indium-gallium-zinc oxide thin-film transistors under bipolar ac stress  

SciTech Connect

Bipolar ac stress-induced instability of amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistors is comparatively investigated with that under a positive dc gate bias stress. While the positive dc gate bias stress-induced threshold voltage shift ({delta}V{sub T}) is caused by the charge trapping into the interface/gate dielectric as reported in previous works, the dominant mechanism of the ac stress-induced {delta}V{sub T} is observed to be due to the increase in the acceptorlike deep states of the density of states (DOS) in the a-IGZO active layer. Furthermore, it is found that the variation of deep states in the DOS makes a parallel shift in the I{sub DS}-V{sub GS} curve with an insignificant change in the subthreshold slope, as well as the deformation of the C{sub G}-V{sub G} curves.

Lee, Sangwon; Jeon, Kichan; Park, Jun-Hyun; Kim, Sungchul; Kong, Dongsik; Kim, Dong Myong; Kim, Dae Hwan [School of Electrical Engineering, Kookmin University, 861-1 Jeongneung-dong, Seongbuk-gu, Seoul 136-702 (Korea, Republic of); Kim, Sangwook; Kim, Sunil; Hur, Jihyun; Park, Jae Chul; Song, Ihun; Kim, Chang Jung; Park, Youngsoo; Jung, U-In [Semiconductor Laboratory, Samsung Advanced Institute of Technology, Nongseo-Dong, Giheung-Gu, Yongin-Si, Gyeonggi-Do 446-712 (Korea, Republic of)

2009-09-28

9

Effect of organic buffer layer in the electrical properties of amorphous-indium gallium zinc oxide thin film transistor.  

PubMed

In this research, we reported on the fabrication of top-contact amorphous-indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs) with an organic buffer layer between inorganic gate dielectric and active layer in order to improve the electrical properties of devices. By inserting an organic buffer layer, it was possible to make an affirmation of the improvements in the electrical characteristics of a-IGZO TFTs such as subthreshold slope (SS), on/off current ratio (I(ON/OFF)), off-state current, and saturation field-effect mobility (muFE). The a-IGZO TFTs with the cross-linked polyvinyl alcohol (c-PVA) buffer layer exhibited the pronounced improvements of the muFE (17.4 cm2/Vs), SS (0.9 V/decade), and I(ON/OFF) (8.9 x 10(6)). PMID:22966625

Wang, Jian-Xun; Hyung, Gun Woo; Li, Zhao-Hui; Son, Sung-Yong; Kwon, Sang Jik; Kim, Young Kwan; Cho, Eou Sik

2012-07-01

10

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

11

Paraffin wax passivation layer improvements in electrical characteristics of bottom gate amorphous indium–gallium–zinc oxide thin-film transistors  

Microsoft Academic Search

In this research, paraffin wax is employed as the passivation layer of the bottom gate amorphous indium–gallium–zinc oxide thin-film transistors (a-IGZO TFTs), and it is formed by sol–gel process in the atmosphere. The high yield and low cost passivation layer of sol–gel process technology has attracted much attention for current flat-panel-display manufacturing. Comparing with passivation-free a-IGZO TFTs, passivated devices exhibit

Geng-Wei Chang; Ting-Chang Chang; Yong-En Syu; Tsung-Ming Tsai; Kuan-Chang Chang; Chun-Hao Tu; Fu-Yen Jian; Ya-Chi Hung; Ya-Hsiang Tai

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

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

14

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

NASA Astrophysics Data System (ADS)

The ability to make electronic devices, that are transparent to visible and near infrared wavelength, is a relatively new field of research in the development of the next generation of optoelectronic devices. A new class of inorganic thin-film transistor (TFT) channel material based on amorphous oxide semiconductors, that show high carrier mobility and high visual transparency, is being researched actively. The purpose of this dissertation is to develop amorphous oxide semiconductors by pulsed laser deposition, show their suitability for TFT applications and demonstrate other classes of devices such as non-volatile memory elements and integrated circuits such as ring oscillators and active matrix pixel elements. Indium gallium zinc oxide (IGZO) is discussed extensively in this dissertation. The influence of several deposition parameters is explored and oxygen partial pressure during deposition is found to have a profound effect on the electrical and optical characteristics of the IGZO films. By optimizing the deposition conditions, IGZO TFTs exhibit excellent electrical properties, even without any intentional annealing. This attribute along with the amorphous nature of the material also makes IGZO TFTs compatible with flexible substrates opening up various applications. IGZO TFTs with saturation field effect mobility of 12--16 cm 2 V-1 s-1 and subthreshold voltage swing of <200 mV decade-1 have been fabricated. By varying the oxygen partial pressure during deposition the conductivity of the channel was controlled to give a low off-state current ˜10 pA and a drain current on/off ratio of >1 x 108. Additionally, the effects of the oxygen partial pressure and the thickness of the semiconductor layer, the choice of the gate dielectric material and the device channel length on the electrical characteristics of the TFTs are explored. To evaluate IGZO TFT electrical stability, constant voltage bias stress measurements were carried out. The observed logarithmic dependence of the threshold voltage shift to the stress duration was modeled using a charge trapping/tunneling mechanism at the semiconductor/dielectric interface. By incorporating platinum nanoparticles in the dielectric layer of the TFT, non-volatile memory characteristics were achieved. The devices exhibited good memory behavior and up to 10% charge retention extrapolated over 10 years. The potential application for IGZO TFTs is examined by fabricating and characterizing 5- and 7-stage ring oscillators. The 5-stage ring oscillators operate at more than 2 MHz and have a sub 50 ns propagation delay at a supply voltage of 25 V. To the best of our knowledge these are the fastest all-transparent ring oscillators reported to date. As a practical demonstration, we integrated IGZO TFTs with a novel thin film electroluminescent phosphor to form an active matrix pixel element. The output intensity of the phosphor was successfully modulated by the TFT. These results demonstrate that IGZO TFTs are viable candidates for transparent circuits and display applications.

Suresh, Arun

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

Alumina nanoparticle/polymer nanocomposite dielectric for flexible amorphous indium-gallium-zinc oxide thin film transistors on plastic substrate with superior stability  

NASA Astrophysics Data System (ADS)

In this study, the Al2O3 nanoparticles were incorporated into polymer as a nono-composite dielectric for used in a flexible amorphous Indium-Gallium-Zinc Oxide (a-IGZO) thin-film transistor (TFT) on a polyethylene naphthalate substrate by solution process. The process temperature was well below 100 °C. The a-IGZO TFT exhibit a mobility of 5.13 cm2/V s on the flexible substrate. After bending at a radius of 4 mm (strain = 1.56%) for more than 100 times, the performance of this a-IGZO TFT was nearly unchanged. In addition, the electrical characteristics are less altered after positive gate bias stress at 10 V for 1500 s. Thus, this technology is suitable for use in flexible displays.

Lai, Hsin-Cheng; Pei, Zingway; Jian, Jyun-Ruri; Tzeng, Bo-Jie

2014-07-01

18

Alumina nanoparticle/polymer nanocomposite dielectric for flexible amorphous indium-gallium-zinc oxide thin film transistors on plastic substrate with superior stability  

SciTech Connect

In this study, the Al{sub 2}O{sub 3} nanoparticles were incorporated into polymer as a nono-composite dielectric for used in a flexible amorphous Indium-Gallium-Zinc Oxide (a-IGZO) thin-film transistor (TFT) on a polyethylene naphthalate substrate by solution process. The process temperature was well below 100?°C. The a-IGZO TFT exhibit a mobility of 5.13?cm{sup 2}/V s on the flexible substrate. After bending at a radius of 4?mm (strain?=?1.56%) for more than 100 times, the performance of this a-IGZO TFT was nearly unchanged. In addition, the electrical characteristics are less altered after positive gate bias stress at 10?V for 1500?s. Thus, this technology is suitable for use in flexible displays.

Lai, Hsin-Cheng [Department of Electrical Engineering, National Chung Hsing University, Taichung 40227, Taiwan (China); Pei, Zingway, E-mail: zingway@dragon.nchu.edu.tw [Department of Electrical Engineering, National Chung Hsing University, Taichung 40227, Taiwan (China); Graduate Institute of Optoelectronic Engineering, National Chung Hsing University, Taichung 40227, Taiwan (China); Center of Nanoscience and Nanotechnology, National Chung Hsing University, Taichung 40227, Taiwan (China); Jian, Jyun-Ruri; Tzeng, Bo-Jie [Graduate Institute of Optoelectronic Engineering, National Chung Hsing University, Taichung 40227, Taiwan (China)

2014-07-21

19

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

20

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

21

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

22

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

23

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

24

Effect of Metallic Composition on Electrical Properties of Solution-Processed Indium-Gallium-Zinc-Oxide Thin-Film Transistors  

Microsoft Academic Search

We report the combinatorial study on surface morphology and electrical properties of solution-processed amorphous indium-gallium-zinc-oxide (a- IGZO) thin-film transistors (TFTs). The sol-gel-processed a-IGZO thin films typically have shown an amorphous structure and critical dependence of mobility, carrier concentration, and surface roughness on the In, Ga, and Zn molar ratio in the solution phase. Based on efficient control of the metallic

Yong-Hoon Kim; Min-Koo Han; Jeong-In Han; Sung Kyu Park

2010-01-01

25

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

26

Improvement of bias-stability in amorphous-indium-gallium-zinc-oxide thin-film transistors by using solution-processed Y{sub 2}O{sub 3} passivation  

SciTech Connect

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 (Y{sub 2}O{sub 3}) 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 Y{sub 2}O{sub 3} passivation—performed after patterning source/drain (S/D) Mo electrodes by a conventional HNO{sub 3}-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, 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)

2014-08-04

27

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

SciTech Connect

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

Liu, P.; Chen, T. P.; Li, X. D.; Wong, J. I. [School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798 (Singapore)] [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)] [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)] [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)] [GLOBALFOUNDRIES Singapore Pte. Ltd., 60 Woodlands Industrial Park D Street 2, Singapore 738406 (Singapore)

2013-11-11

28

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

29

Study of breakdown voltage of indium-gallium-zinc-oxide-based Schottky diode  

NASA Astrophysics Data System (ADS)

In contrast to the intensive studies on thin-film transistors based on indium gallium zinc oxide (IGZO), the research on IGZO-based diodes is still very limited, particularly on their behavior and stability under high bias voltages. Our experiments reveal a sensitive dependence of the breakdown voltage of IGZO Schottky diodes on the anode metal and the IGZO film thickness. Devices with an Au anode are found to breakdown easily at a reverse bias as low as -2.5 V, while the devices with a Pd anode and a 200-nm, fully depleted IGZO layer have survived up to -15 V. All diodes are fabricated by radio-frequency magnetron sputtering at room temperature without any thermal treatment, yet showing an ideality factor as low as 1.14, showing the possibility of achieving high-performance Schottky diodes on flexible plastic substrate.

Xin, Qian; Yan, Linlong; Luo, Yi; Song, Aimin

2015-03-01

30

High-Performance Indium–Gallium–Zinc Oxide Thin-Film Transistors Based on Anodic Aluminum Oxide  

Microsoft Academic Search

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

Linfeng Lan; Junbiao Peng

2011-01-01

31

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

32

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

NASA Astrophysics Data System (ADS)

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

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

2009-03-01

33

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

34

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.

35

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

SciTech Connect

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

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

2008-08-25

36

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

37

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

38

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

39

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

40

Transparent amorphous In–Ga–Zn–O thin film as function of various gas flows for TFT applications  

Microsoft Academic Search

The electrical and optical properties of amorphous indium gallium zinc oxide (a-IGZO) films, which can be used as a channel layer, deposited by radio frequency (rf) magnetron sputtering system at room temperature (RT), were investigated as function of various gas flows. The optical transmittance of films deposited under Ar, O2 \\/ Ar + O2 and O2 \\/ Ar-4% H2 +

C. H. Jung; D. J. Kim; Y. K. Kang; D. H. Yoon

2009-01-01

41

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

of the display industry as it moves from liquid crystal to organic light emitting diode technology and with requirements for larger areas and higher resolutions. A number of alternative material systems to a-Si:H have emerged, including organic semiconductors...

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

2014-01-01

42

Operating Temperature Trends in Amorphous In–Ga–Zn–O Thin-Film Transistors  

Microsoft Academic Search

The electrical performance as a function of operating temperature of amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs) is assessed by measuring drain current versus gate voltage [log(ID) - VGS] transfer curves at temperatures from -50°C to +50°C. These bottom-gate staggered a-IGZO TFTs are fabricated using thermal silicon dioxide as the gate insulator. An almost rigid log(ID) - VGS

Ken Hoshino; John F. Wager

2010-01-01

43

Oxygen-Dependent Instability and Annealing\\/Passivation Effects in Amorphous In–Ga–Zn–O Thin-Film Transistors  

Microsoft Academic Search

This letter discusses the reason for the instability of amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film tran- sistors (TFTs) under both positive and negative bias stresses. This instability is significantly influenced by the oxygen content in the bulk IGZO and the surrounding environment. The as- fabricated low-temperature devices can only endure a single po- larized bias stress. An a-IGZO TFT that is stable

Wei-Tsung Chen; Shih-Yi Lo; Shih-Chin Kao; Hsiao-Wen Zan; Chuang-Chuang Tsai; Jian-Hong Lin; Chun-Hsiang Fang; Chung-Chun Lee

2011-01-01

44

Ferroelectric switching of poly(vinylidene difluoride-trifluoroethylene) in metal-ferroelectric-semiconductor non-volatile memories with an amorphous oxide semiconductor  

NASA Astrophysics Data System (ADS)

Ferroelectric polarization switching of poly(vinylidene difluoride-trifluoroethylene) is investigated in different thin-film device structures, ranging from simple capacitors to dual-gate thin-film transistors (TFT). Indium gallium zinc oxide, a high mobility amorphous oxide material, is used as semiconductor. We find that the ferroelectric can be polarized in both directions in the metal-ferroelectric-semiconductor (MFS) structure and in the dual-gate TFT under certain biasing conditions, but not in the single-gate thin-film transistors. These results disprove the common belief that MFS structures serve as a good model system for ferroelectric polarization switching in thin-film transistors.

Gelinck, G. H.; van Breemen, A. J. J. M.; Cobb, B.

2015-03-01

45

High-stability transparent amorphous oxide TFT with a silicon-doped back-channel layer  

NASA Astrophysics Data System (ADS)

We significantly reduced various electrical instabilities of amorphous indium gallium zinc oxide thin-film transistors (TFTs) by using the co-deposition of silicon on an a-IGZO back channel. This process showed improved stability of the threshold voltage ( V th ) under high temperature and humidity and negative gate-bias illumination stress (NBIS) without any reduction of IDS. The enhanced stability was achieved with silicon, which has higher metal-oxide bonding strengths than gallium does. Additionally, SiO X distributed on the a-IGZO surface reduced the adsorption and the desorption of H2O and O2. This process is applicable to the TFT manufacturing process with a variable sputtering target.

Lee, Hyoung-Rae; Park, Jea-Gun

2014-10-01

46

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

47

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

48

Improvement in negative bias stress stability of solution-processed amorphous In-Ga-Zn-O thin-film transistors using hydrogen peroxide.  

PubMed

We have investigated the effect of hydrogen peroxide (H2O2) on negative bias stress (NBS) stability of solution-processed amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistors (TFTs). The instability of solution-processed a-IGZO TFTs under NBS is attributed to intrinsic oxygen vacancy defects (Vo) and organic chemical-induced defects, such as pores, pin holes, and organic residues. In this respect, we added H2O2 into an indium-gallium-zinc oxide solution to reduce the defects without any degradation of electrical performance. The field-effect mobility and sub-threshold slope of the a-IGZO TFTs were improved from 0.37 cm(2) V(-1) s(-1) and 0.86 V/dec to 0.97 cm(2) V(-1) s(-1) and 0.58 V/dec, respectively. Furthermore, the threshold voltage shift under NBS was dramatically decreased from -3.73 to -0.18 V. These results suggest that H2O2 effectively reduces Vo through strong oxidation and minimizes organic chemical-induced defects by eliminating the organic chemicals at lower temperatures compared to a conventional solution process. PMID:24503476

Kwon, Jeong Moo; Jung, Joohye; Rim, You Seung; Kim, Dong Lim; Kim, Hyun Jae

2014-03-12

49

Effect of contact material on amorphous InGaZnO thin-film transistor characteristics  

NASA Astrophysics Data System (ADS)

Amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs) having several metals, namely Ag, Ti, and Mo, as the source and drain electrodes were characterized. TFTs with Ti and Mo electrodes showed drain current-gate voltage characteristics without fluctuation. However, TFTs with Ag electrodes indicated a low noisy on-state current at a large channel length under a low drain-source voltage condition. The source and drain resistances [Rs/d (?)] of the TFTs with each of the three metals were calculated from the IDS-VGS characteristics. The Rs/d values of the Ag, Ti, and Mo samples reached 4 × 104, 2 × 104, and 1 × 104 ?, respectively. This implies that a spatial potential barrier exists at the a-IGZO/Ag interface and that the resistance of the potential barrier changes with the application of gate voltage.

Ueoka, Yoshihiro; Ishikawa, Yasuaki; Bermundo, Juan Paolo; Yamazaki, Haruka; Urakawa, Satoshi; Osada, Yukihiro; Horita, Masahiro; Uraoka, Yukiharu

2014-01-01

50

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

51

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

E-print Network

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

Pearton, Stephen J.

52

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

53

Effect of etching stop layer on characteristics of amorphous IGZO thin film transistor fabricated at low temperature  

NASA Astrophysics Data System (ADS)

Transparent bottom-gate amorphous Indium-Gallium-Zinc Oxide (a-IGZO) thin-film transistors (TFTs) had been successfully fabricated at relative low temperature. The influence of reaction gas ratio of N2O and SiH4 during the growth of etching stop layer (SiOx) on the characteristics of a-IGZO TFTs was investigated. The transfer characteristics of the TFTs were changed markedly because active layer of a-IGZO films was modified by plasma in the growth process of SiOx. By optimizing the deposition parameters of etching stop layer process, a-IGZO TFTs were manufactured and exhibited good performance with a field-effect mobility of 8.5 cm2V-1s-1, a threshold voltage of 1.3 V, and good stability under gate bias stress of 20 V for 10000 s.

Li, Xifeng; Xin, Enlong; Chen, Longlong; Shi, Jifeng; Zhang, Jianhua

2013-03-01

54

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

E-print Network

, Northwestern University, Evanston, Illinois 60208­3113 The homologous compounds In1-xGa1+xO3(ZnO)k (where k = 1 in the In-Ga-Zn-O system with enhanced transparent-conducting properties has been discussed. I. Introduction-ray diffractom- etry) were 0.47 Ga]) Ga])

Poeppelmeier, Kenneth R.

55

Role of Self-Assembled Monolayers on Improved Electrical Stability of Amorphous In-Ga-Zn-O Thin-Film Transistors  

E-print Network

Self-assembled monolayers (SAMs) have been used to improve both the positive and negative bias-stress stability of amorphous indium gallium zinc oxide (IGZO) bottom gate thin film transistors (TFTs). N-hexylphosphonic acid (HPA) and fluorinated hexylphosphonic acid (FPA) SAMs adsorbed on IGZO back channel surfaces were shown to significantly reduce bias stress turn-on voltage shifts compared to IGZO back channel surfaces with no SAMs. FPA was found to have a lower surface energy and lower packing density than HPA, as well as lower bias stress turn-on voltage shifts. The improved stability of IGZO TFTs with SAMs can be primarily attributed to a reduction in molecular adsorption of contaminants on the IGZO back channel surface and minimal trapping states present with phosphonic acid binding to the IGZO surface.

Du, Xiaosong; Motley, Joshua R; Stickle, William F; Bluhm, Hendrik; Herman, Gregory S

2014-01-01

56

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

57

Analysis of electronic structure of amorphous InGaZnO/SiO{sub 2} interface by angle-resolved X-ray photoelectron spectroscopy  

SciTech Connect

The electronic structures of amorphous indium gallium zinc oxide (a-IGZO) on a SiO{sub 2} layers before and after annealing were observed by constant final state X-ray photoelectron spectroscopy (CFS-XPS) and X-ray adsorption near-edge structure spectroscopy (XANES). From the results of angle-resolved CFS-XPS, the change in the electronic state was clearly observed in the a-IGZO bulk rather than in the a-IGZO/SiO{sub 2} interface. This suggests that the electronic structures of the a-IGZO bulk strongly affected the thin-film transistor characteristics. The results of XANES indicated an increase in the number of tail states upon atmospheric annealing (AT). We consider that the increase in the number of tail states decreased the channel mobility of AT samples.

Ueoka, Y.; Ishikawa, Y.; Maejima, N.; Matsui, F.; Matsui, H.; Yamazaki, H.; Urakawa, S.; Horita, M.; Daimon, H.; Uraoka, Y. [Graduate School of Materials Science, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0192 (Japan)] [Graduate School of Materials Science, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0192 (Japan)

2013-10-28

58

Analysis of electronic structure of amorphous InGaZnO/SiO2 interface by angle-resolved X-ray photoelectron spectroscopy  

NASA Astrophysics Data System (ADS)

The electronic structures of amorphous indium gallium zinc oxide (a-IGZO) on a SiO2 layers before and after annealing were observed by constant final state X-ray photoelectron spectroscopy (CFS-XPS) and X-ray adsorption near-edge structure spectroscopy (XANES). From the results of angle-resolved CFS-XPS, the change in the electronic state was clearly observed in the a-IGZO bulk rather than in the a-IGZO/SiO2 interface. This suggests that the electronic structures of the a-IGZO bulk strongly affected the thin-film transistor characteristics. The results of XANES indicated an increase in the number of tail states upon atmospheric annealing (AT). We consider that the increase in the number of tail states decreased the channel mobility of AT samples.

Ueoka, Y.; Ishikawa, Y.; Maejima, N.; Matsui, F.; Matsui, H.; Yamazaki, H.; Urakawa, S.; Horita, M.; Daimon, H.; Uraoka, Y.

2013-10-01

59

Nontraditional Amorphous Oxide Semiconductor Thin-Film Transistor Fabrication  

NASA Astrophysics Data System (ADS)

Fabrication techniques and process integration considerations for amorphous oxide semiconductor (AOS) thin-film transistors (TFTs) constitute the central theme of this dissertation. Within this theme three primary areas of focus are pursued. The first focus involves formulating a general framework for assessing passivation. Avoiding formation of an undesirable backside accumulation layer in an AOS bottom-gate TFT is accomplished by (i) choosing a passivation layer in which the charge neutrality level is aligned with (ideal case) or higher in energy than that of the semiconductor channel layer charge neutrality level, and (ii) depositing the passivation layer in such a manner that a negligible density of oxygen vacancies are present at the channel-passivation layer interface. Two AOS TFT passivation schemes are explored. Sputter-deposited zinc tin silicon oxide (ZTSO) appears promising for suppressing the effects of negative bias illumination stress (NBIS) with respect to ZTO and IGZO TFTs. Solution-deposited silicon dioxide is used as a barrier layer to subsequent PECVD silicon dioxide deposition, yielding ZTO TFT transfer curves showing that the dual-layer passivation process does not significantly alter ZTO TFT electrical characteristics. The second focus involves creating an adaptable back-end process compatible with flexible substrates. A detailed list of possible via formation techniques is presented with particular focus on non-traditional and adaptable techniques. Two of the discussed methods, “hydrophobic surface treatment”and “printed local insulator,” are demonstrated and proven effective. The third focus is printing AOS TFT channel layers in order to create an adaptable and additive front-end integrated circuit fabrication scheme. Printed zinc indium aluminum oxide (ZIAO) and indium gallium zinc oxide (IGZO) channel layers are demonstrated using a SonoPlot piezoelectric printing system. Finally, challenges associated with printing electronic materials are discussed. Organic-based solutions are easier to print due to their ability to “stick” to the substrate and form well-defined patterns, but have poor electrical characteristics due to the weakness of organic bonds. Inorganic aqueous-based solutions demonstrate good electrical performance when deposited by spin coating, but are difficult to print because precise control of a substrate's hydrophillic/hydrophobic nature is required. However, precise control is difficult to achieve, since aqueous-based solutions either spread out or ball up on the substrate surface. Thickness control of any printed solution is always problematic due to surface wetting and the elliptical thickness profile of a dispensed solution.

Sundholm, Eric Steven

60

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

61

Low-Temperature Solution Processing of Amorphous Metal Oxide Semiconductors for High-Performance Thin-Film Transistors  

NASA Astrophysics Data System (ADS)

The growing field of large-area flexible electronics presents the need for amorphous materials with electrical performances superior to amorphous hydrogenated silicon (a-Si:H). Metal oxide semiconductors show great promise in thin film transistors (TFTs) due to their high electron mobility (micro, 1--100 cm2V-1s-1), mechanical flexibility, and electrical stability. However, most oxide semiconductor fabrication still relies on expensive, inflexible and energy intensive vacuum deposition methods. To overcome these limitations, my thesis work has focused on developing low-temperature solution processing routes to functional metal oxide materials. In Chapter 2, we demonstrate an optimized "ink" and printing process for inkjet patterning of amorphous indium gallium zinc oxide (a-IGZO) and investigate the effects of device structure on derived electron mobility. Bottom-gate top-contact (BGTC) TFTs are fabricated and shown to exhibit electron mobilities comparable to a-Si:H. Furthermore, a record micro of 2.5 cm 2V-1s-1 is demonstrated for bottom-gate bottom-contact (BGBC) TFTs. The mechanism underlying such impressive performance is investigated using transmission line techniques, and it is shown that the semiconductor-source/drain electrode interface contact resistance is nearly an order of magnitude lower for BGBC transistors versus BGTC devices. In Chapter 3, we report the implementation of amorphous indium yttrium oxide (a-IYO) as a TFT semiconductor for the first time. Amorphous and polycrystalline IYO films are grown via a low-temperature solution process utilizing exothermic "combustion" precursors. Precursor transformation and the IYO films are analyzed by DTA, TGA, XRD, AFM, XPS, and optical transmission, revealing efficient conversion to the metal-oxide lattice, and smooth, transparent films. a-IYO TFTs fabricated with a hybrid nanodielectric exhibit impressive electron mobilities of 7.3 cm2V-1s-1 (Tanneal = 300 °C) and 5.0 cm2V-1s -1 (Tanneal = 250 °C) for 2 V operation. Finally, Chapter 4 examines the role of the strong oxygen binding cation, known as the "oxygen getter" in quaternary metal oxide semiconductors. We present a systematic structural and electrical study of the carrier suppression role of gallium, scandium, yttrium, and lanthanum when introduced into IZO. We conclude that metal oxide lattice energy (HL) and metal ionic radius are the best predictors of the efficacy of an oxygen getter in IXZO and only Ga acts effectively in this role.

Hennek, Jonathan W.

62

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

63

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

64

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

NASA Astrophysics Data System (ADS)

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 ID-VG and modulated peak/base pulse time ID-VD measurements are utilized to demonstrate the self-heating induced anomalous dimension-dependent threshold voltage variation and on-state current degradation.

Liu, Kuan-Hsien; Chang, Ting-Chang; Chou, Wu-Ching; Chen, Hua-Mao; Tsai, Ming-Yen; Wu, Ming-Siou; Hung, Yi-Syuan; Hung, Pei-Hua; Hsieh, Tien-Yu; Tai, Ya-Hsiang; Chu, Ann-Kuo; Yeh, Bo-Liang

2014-10-01

65

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

PubMed Central

Amorphous mixed metal oxides are emerging as high performance semiconductors for thin film transistor (TFT) applications, with indium gallium zinc oxide, InGaZnO (IGZO), being one of the most widely studied and best performing systems. Here, we investigate alkaline earth (barium or strontium) doped InBa(Sr)ZnO as alternative, semiconducting channel layers and compare their performance of the electrical stress stability with IGZO. In films fabricated by solution-processing from metal alkoxide precursors and annealed to 450 °C we achieve high field-effect electron mobility up to 26 cm2 V–1 s–1. We show that it is possible to solution-process these materials at low process temperature (225–200 °C yielding mobilities up to 4.4 cm2 V–1 s–1) and demonstrate a facile “ink-on-demand” process for these materials which utilizes the alcoholysis reaction of alkyl metal precursors to negate the need for complex synthesis and purification protocols. Electrical bias stress measurements which can serve as a figure of merit for performance stability for a TFT device reveal Sr- and Ba-doped semiconductors to exhibit enhanced electrical stability and reduced threshold voltage shift compared to IGZO irrespective of the process temperature and preparation method. This enhancement in stability can be attributed to the higher Gibbs energy of oxidation of barium and strontium compared to gallium. PMID:24511184

2013-01-01

66

Spray-combustion synthesis: Efficient solution route to high-performance oxide transistors.  

PubMed

Metal-oxide (MO) semiconductors have emerged as enabling materials for next generation thin-film electronics owing to their high carrier mobilities, even in the amorphous state, large-area uniformity, low cost, and optical transparency, which are applicable to flat-panel displays, flexible circuitry, and photovoltaic cells. Impressive progress in solution-processed MO electronics has been achieved using methodologies such as sol gel, deep-UV irradiation, preformed nanostructures, and combustion synthesis. Nevertheless, because of incomplete lattice condensation and film densification, high-quality solution-processed MO films having technologically relevant thicknesses achievable in a single step have yet to be shown. Here, we report a low-temperature, thickness-controlled coating process to create high-performance, solution-processed MO electronics: spray-combustion synthesis (SCS). We also report for the first time, to our knowledge, indium-gallium-zinc-oxide (IGZO) transistors having densification, nanoporosity, electron mobility, trap densities, bias stability, and film transport approaching those of sputtered films and compatible with conventional fabrication (FAB) operations. PMID:25733848

Yu, Xinge; Smith, Jeremy; Zhou, Nanjia; Zeng, Li; Guo, Peijun; Xia, Yu; Alvarez, Ana; Aghion, Stefano; Lin, Hui; Yu, Junsheng; Chang, Robert P H; Bedzyk, Michael J; Ferragut, Rafael; Marks, Tobin J; Facchetti, Antonio

2015-03-17

67

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

68

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

69

Novel oxide amorphous semiconductors: transparent conducting amorphous oxides  

Microsoft Academic Search

A working hypothesis to find wide gap oxide semiconductors was proposed on the basis of simple considerations. The hypothesis predicts that amorphous double oxides composed of heavy metal cations (HMCs) with an electronic configuration (n ? 1)d10s0 are promising candidates for a novel class of amorphous semiconductors. Electrical and optical properties of three amorphous double oxides composed of the HMCs,

Hideo Hosono; Masahiro Yasukawa; Hiroshi Kawazoe

1996-01-01

70

2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 3509 www.advmat.de  

E-print Network

-Hao Chen Achieving High Field-Effect Mobility in Amorphous Indium- Gallium-Zinc Oxide by Capping a Strong composition and the oxygen vacancy concentration.[1] Ferromagnetic and ferroe- lectric behaviors observed drawn lots of attention because they possess high electron mobility at low process temperature.[4

71

Metal Oxide Thin Film Transistors on Paper Substrate: Fabrication, Characterization, and Printing Process  

NASA Astrophysics Data System (ADS)

Flexible electronics is an emerging next-generation technology that offers many advantages such as light weight, durability, comfort, and flexibility. These unique features enable many new applications such as flexible display, flexible sensors, conformable electronics, and so forth. For decades, a variety of flexible substrates have been demonstrated for the application of flexible electronics. Most of them are plastic films and metal foils so far. For the fundamental device of flexible circuits, thin film transistors (TFTs) using poly silicon, amorphous silicon, metal oxide and organic semiconductor have been successfully demonstrated. Depending on application, low-cost and disposable flexible electronics will be required for convenience. Therefore it is important to study inexpensive substrates and to explore simple processes such as printing technology. In this thesis, paper is introduced as a new possible substrate for flexible electronics due to its low-cost and renewable property, and amorphous indium gallium zinc oxide (a-IGZO) TFTs are realized as the promising device on the paper substrate. The fabrication process and characterization of a-IGZO TFT on the paper substrate are discussed. a-IGZO TFTs using a polymer gate dielectric on the paper substrate demonstrate excellent performances with field effect mobility of ˜20 cm2 V-1 s-1, on/off current ratio of ˜106, and low leakage current, which show the enormous potential for flexible electronics application. In order to complement the n-channel a-IGZO TFTs and then enable complementary metal-oxide semiconductor (CMOS) circuit architectures, cuprous oxide is studied as a candidate material of p-channel oxide TFTs. In this thesis, a printing process is investigated as an alternative method for the fabrication of low-cost and disposable electronics. Among several printing methods, a modified offset roll printing that prints high resolution patterns is presented. A new method to fabricate a high resolution printing plate is investigated and the most favorable condition to transfer ink from a blanket to a cliche is studied. Consequently, a high resolution cliche is demonstrated and the printed patterns of 10mum width and 6mum line spacing are presented. In addition, the top gate a-IGZO TFTs with channel width/length of 12/6mum is successfully demonstrated by printing etch-resists. This work validates the compatibility of a-IGZO TFT on paper substrate for the disposable microelectronics application and presents the potential of low-cost and high resolution printing technology.

Choi, Nack-Bong

72

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

73

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

74

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

SciTech Connect

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

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

2014-07-28

75

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

NASA Astrophysics Data System (ADS)

This dissertation is focused on the development of thin film transistors (TFTs) using oxide materials composed of post-transitional cations with (n-1)d 10ns0 (n?4). The goal is to achieve high performance oxide-based TFTs fabricated at low processing temperature on either glass or flexible substrates for next generation display applications. In addition, etching mechanism and Ohmic contact formation for oxide heterostructure (ZnO/CuCrO 2) system is demonstrated. The deposition and characterization of oxide semiconductors (In 2O3-ZnO, and InGaZnO4) using a RF-magnetron sputtering system are studied. The main influence on the resistivity of the films is found to be the oxygen partial pressure in the sputtering ambient. The films remained amorphous and transparent (> 70%) at all process conditions. These films showed good transmittance at suitable conductivity for transistor fabrication. The electrical characteristics of both top- and bottom-gate type Indium Zinc Oxide (InZnO) and Indium Gallium Zinc Oxide (InGaZnO4)-based TFTs are reported. The InZnO films were favorable for depletion-mode TFTs due to their tendency to form oxygen vacancies, while enhancement-mode devices were realized with InGaZnO4 films. The InGaZnO4-based TFTs fabricated on either glass or plastic substrates at low temperature (<100°C) exhibit good electrical properties: the saturation mobility of 5--12 cm2.V-1.s-1 and threshold voltage of 0.5--2.5V. The devices are also examined as a function of aging time in order to verify long-term stability in air. The effect of gate dielectric materials on electrical properties of InGaZnO 4-based TFTs was investigated. The use of SiNx film as a gate dielectric reduces the trap density and the roughness at the channel/gate dielectric interface compared to SiO2 gate dielectric, resulting in an improvement of device parameters by reducing scattering of trapped charges at the interface. The quality of interface is shown to have large effect on TFT performance. Plasma etching process of ZnO was carried out using a variety of plasma chemistries: CH4/H2-, C2H6/H 2-, Cl2-, IBr-, ICl-, BI3- and BBr3/Ar. High fidelity pattern transfer can be achieved with practical etch rate and very smooth surface in methane-based chemistries, although the sidewall is not completely vertical. Threshold energy as low as 60 +/- 20 eV for all plasma chemistries was achieved, confirming that etching is driven by ion-assisted mechanism over the whole range of ion energy. Ohmic contacts to p-CuCrO2 are examined using borides (CrB2 and W2B5), nitrides (TaN and ZrN) and a high temperature metal (Ir). These materials are used as a diffusion barrier in Ni/Au based contacts, i.e., Ni/Au/X/Ti/Au metallization scheme, where X is the refractory material. A minimum specific contact resistance of ˜ 5x10 -4 O.cm2 was achieved for the Ir-containing contacts after annealing at temperature of 500--800°C for 60s in O2 ambient. The presence of Ir diffusion barrier increase the thermal stability of the contacts by ˜ 200 °C compared to conventional Ni/Au contacts. By sharp contrast, the use of other refractory materials led to the poorer thermal stability, with the contact resistance increasing sharply above 400°C.

Lim, Wantae

2009-12-01

76

Natural realgar and amorphous AsS oxidation kinetics  

Microsoft Academic Search

The oxidation rates of natural realgar and amorphous synthetic AsS by dissolved oxygen were evaluated using mixed flow reactors at pH 7.2 to 8.8 and dissolved oxygen contents of 5.9 to 16.5 ppm over a temperature range of 25 to 40°C. The ratios of As\\/S are stoichiometric for all amorphous AsS oxidation experiments except for two experiments conducted at pH

Maggy F. Lengke; Regina N. Tempel

2003-01-01

77

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

78

Comparison of electrochromic amorphous and crystalline tungsten oxide films  

Microsoft Academic Search

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

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

2003-01-01

79

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

80

Amorphous copper tungsten oxide with tunable band gaps  

SciTech Connect

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

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

2010-08-15

81

Quantitative local environment characterization in amorphous oxides  

Microsoft Academic Search

We perform density-functional-theory calculations of electronic core levels to obtain the tellurium x-ray photoelectron spectra in the amorphous solar-energy materials CdTeOx ( x=0.2 , 1, 2, and 3). We quantify the distribution of local tellurium environments that sum up to the total two-peak structure in the experimental spectrum. The general trend is that the more oxygen neighbors tellurium has the

Alexis Amézaga; Erik Holmström; Raquel Lizárraga; Eduardo Menéndez-Proupin; P. Bartolo-Pérez; Paolo Giannozzi

2010-01-01

82

Amorphous tin-cadmium oxide films and the production thereof  

SciTech Connect

A tin-cadmium oxide film having an amorphous structure and a ratio of tin atoms to cadmium atoms of between 1:1 and 3:1. The tin-cadmium oxide film may have an optical band gap of between 2.7 eV and 3.35 eV. The film may also have a charge carrier concentration of between 1.times.10.sup.20 cm.sup.-3 and 2.times.10.sup.20 cm.sup.-3. The tin cadmium oxide film may also exhibit a Hall mobility of between 40 cm.sup.2V.sup.-1 s.sup.-1 and 60 cm.sup.2V.sup.-1 s.sup.-1. Also disclosed is a method of producing an amorphous tin-cadmium oxide film as described and devices using same.

Li, Xiaonan; Gessert, Timothy A

2013-10-29

83

Multi-scale order in amorphous transparent oxide thin films  

NASA Astrophysics Data System (ADS)

Nominally "diffraction amorphous" materials represent a pervasive challenge in establishing classical structure-property relationships. This stems from the difficulty in defining the structure of nominally amorphous materials and experimentally differentiating the short-range (<10 Å) and medium-range (10 to 30 Å) order as a function of process parameters which are important due to their influence on physical, chemical, or transport properties. Herein, we report on the determination of short- and medium-range order in nominally amorphous zinc and tin co-substituted indium oxide In1.4Zn0.3Sn0.3O3 (a-ZITO) thin films grown by pulsed laser deposition. These thin films are being explored as transparent conductors that exhibit changes in transport properties depending on deposition temperature while remaining "diffraction amorphous." Reduced density function (RDF) analysis from electron diffraction accompanied by density functional theory molecular dynamics simulation of a liquid quench suggests ordering at short range. Scanning transmission fluctuation electron microscopy (STFEM) indicates the presence of ordered ZITO regions at medium range. For a-ZITO films grown at different temperatures, RDF analysis showed no significant change in the short range order. However, STFEM revealed notable structural (and symmetry) differences at medium range. The existence of this type of multi-scale local order in amorphous ZITO thin films highlights the importance of a combined approach to unravel the structures of nominally amorphous materials and to understand structure-properties correlations.

Yan, Aiming; Sun, Tao; Borisenko, Konstantin B.; Buchholz, D. Bruce; Chang, Robert P. H.; Kirkland, Angus I.; Dravid, Vinayak P.

2012-09-01

84

Absorption of ac fields in amorphous indium-oxide films  

SciTech Connect

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

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

2014-08-20

85

Universal medium-range order of amorphous metal oxides.  

PubMed

We propose that the structure of amorphous metal oxides can be regarded as a dual-dense-random-packing structure, which is a superposition of the dense random packing of metal atoms and that of oxygen atoms. Our ab initio molecular dynamics simulations show that the medium-range order of amorphous HfO2, ZrO2, TiO2, In2O3, Ga2O3, Al2O3, and Cu2O is characterized by the pentagonal-bipyramid arrangement of metal atoms and that of oxygen atoms, and prove the validity of our dual-random-sphere-packing model. In other words, we find that the pentagonal medium-range order is universal independent of type of metal oxide. PMID:24160612

Nishio, Kengo; Miyazaki, Takehide; Nakamura, Hisao

2013-10-11

86

Universal Medium-Range Order of Amorphous Metal Oxides  

NASA Astrophysics Data System (ADS)

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

Nishio, Kengo; Miyazaki, Takehide; Nakamura, Hisao

2013-10-01

87

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

88

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

89

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

E-print Network

-blocking layer to enhance the performance of an Earth-abundant metal-oxide solar-cell material. A 5 nm thickUltrathin amorphous zinc-tin-oxide buffer layer for enhancing heterojunction interface quality amorphous ternary metal-oxide buffer layer reduces interface recombination, resulting in sizable open

90

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

91

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

92

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

93

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

94

Specific contact resistances between amorphous oxide semiconductor In–Ga–Zn–O and metallic electrodes  

Microsoft Academic Search

Specific contact resistances between an amorphous oxide semiconductor, In–Ga–Zn–O, and various metallic electrodes, Ag, Au, In, Pt, Ti, polycrystalline indium tin oxide (ITO) and amorphous indium zinc oxide (a-IZO), were examined. All the contacts except for Au and Pt showed linear current–voltage characteristics, while Au and Pt did Schottky contacts. Low contact resistances <10?4 ? cm2 were obtained for the Ag,

Yasuhiro Shimura; Kenji Nomura; Hiroshi Yanagi; Toshio Kamiya; Masahiro Hirano; Hideo Hosono

2008-01-01

95

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

96

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

97

Narrow band defect luminescence from Al-doped ZnO probed by scanning tunneling cathodoluminescence  

E-print Network

.1063/1.3647622] Aluminum-doped zinc oxide (AZO) exhibits similar electronic properties to ZnO: a wide optical band gap (Eg of magnitude and the material is called a transparent conducting oxide (TCO). In order to best exploit AZO indium gallium zinc oxide films on flexible substrate by room- temperature deposition and post

Russell, Kasey

98

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

99

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

E-print Network

were made by deposition of an amorphous alloy precursor containing two or more of the metals of copper, barium and calcium. The precursor was oxidized at ambient temperatures in the atmosphere. Thallium was diffused into the oxidized precursor...- lated since the 1986 discovery of the lanthanum-barium copper-oxide (LBCO) superconductor by Bednorz and Miiller. & The discovery of this ceramic copper-oxide superconductor ushered in the age of the high-T, superconductors as the LBCO superconductor...

Williams, John Charles

1991-01-01

100

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

101

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

102

Performance regeneration of InGaZnO transistors with ultra-thin channels  

NASA Astrophysics Data System (ADS)

Thin-film transistors (TFTs) based on ultra-thin amorphous indium gallium zinc oxide (a-IGZO) semiconductors down to 4 nm were studied motivated by the increasing cost of indium. At and below 5 nm, it was found that the field-effect mobility was severely degraded, the threshold voltage increased, and the output characteristics became abnormal showing no saturated current. By encapsulating a layer of polymethyl methacrylate on the IGZO TFTs, the performance of the 5-nm-thick device was effectively recovered. The devices also showed much higher on/off ratios, improved hysteresis, and normal output characteristic curves as compared with devices not encapsulated. The stability of the encapsulated devices was also studied over a four month period.

Zhang, Binglei; Li, He; Zhang, Xijian; Luo, Yi; Wang, Qingpu; Song, Aimin

2015-03-01

103

Influence of External Forces on the Mechanical Characteristics of the a-IGZO and Graphene Based Flexible Display  

NASA Astrophysics Data System (ADS)

Thin film transistors (TFTs) based flexible displays have optically transparent and m echanically flexible properties that are attractive for next-generation display technologies. In particular, "amorphous indium-gallium-zinc-oxide" (a- IGZO) and graphene have attracted much attention due to the advantages of their excellent unif ormity and compatibility with transparent and flexible substrates. To maintain these characteristics, it is important to confirm the deformation characteristics of TFTs with applied external for ces, such as compressive or tensile stress, distortion effects, and temperature. The mechanical c haracteristics of modeled devices applied to different active layers on TFTs, such as a- IGZO and graphene, were investigated under various external conditions. The distributions of t he stress-strain curve on each active layer and the deformed shapes were assessed graphically.

Kim, H.-J.; Kim, Youn-Jea

2014-08-01

104

Impact of Ti doping in Sm2O3 dielectric on electrical characteristics of a-InGaZnO thin-film transistors  

NASA Astrophysics Data System (ADS)

We investigated the impact of Ti doping in the Sm2O3 dielectric on the electrical stress-induced instability in amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistors (TFTs). With increasing stress time in a-IGZO TFT devices, a small initial positive shift followed by a negative shift of threshold voltage is characterized in the Sm2O3 dielectric, whereas only positive shift of threshold voltage is observed for Ti-doped Sm2O3 dielectric. The positive shift of the threshold voltage can be explained by charge trapping in the Sm2O3 film and/or the Sm2O3/IGZO interfaces, while the negative shift of threshold voltage is probably due to the extra charges from the IGZO channel by self-heating effect.

Chen, Fa-Hsyang; Her, Jim-Long; Mondal, Somnath; Hung, Meng-Ning; Pan, Tung-Ming

2013-05-01

105

High mobility undoped amorphous indium zinc oxide transparent thin films  

NASA Astrophysics Data System (ADS)

We investigated the amorphous region of the In2O3-ZnO material system. The composition dependence of the amorphous region was explored and the films exhibited an n-type semiconductor behavior with low resistivities in the range of 4×10-4-6.33×10-4 ?cm. These amorphous films have a very wide transmittance window range of 300-2500 nm, and the transmittance is higher than 85% in the fiber-optics telecommunication window of 1.30-1.55 ?m. The band gap of amorphous films can be engineered from 2.66 to 3.05 eV, by varying the zinc/(zinc+indium) atomic ratio. A monotonous decrease in mobility from 71.6 to 59.4 cm2/V s was observed with an increase in zinc/(zinc+indium) atomic ratio from 0.19 to 0.43 in the amorphous region. This trend was explained on the basis of percolation theory and overlap integral calculations. The effective mass of these amorphous films was calculated using the Drude model in the free-carrier absorption region and correlated with composition as well as the carrier concentration of the films.

Kumar, Bhupendra; Gong, Hao; Akkipeddi, Ramam

2005-10-01

106

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

E-print Network

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

Shahriar, Selim

107

Selective epitaxial growth of submicron complex oxide structures by amorphous SrTiO3  

E-print Network

a significant increase in the high-frequency surface resistance as well as to cause insulating dead layersSelective epitaxial growth of submicron complex oxide structures by amorphous SrTiO3 P. Morales,a M on selective epitaxial growth. The crystallinity and hence the conductivity of the complex oxide is inhibited

Wei, John Y.T.

108

Mesoporous amorphous rare earth silicates, new catalysts of methane oxidative coupling  

Microsoft Academic Search

253 The catalytic reaction of methane oxidative coupling (MOC) is a direct route to produce ethylene from natural gas. Rare earth oxides are efficient catalysts for this reaction [1?3]. This paper is the first report on the catalytic activity of mesoporous amorphous rare earth materials based on SiO 2 in the MOC reaction; lanthanum and cerium ions or their mixture

A. G. Dedov; A. S. Loktev; N. O. Tel’pukhovskaya; K. V. Parkhomenko; I. I. Moiseev

2008-01-01

109

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

110

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

NASA Astrophysics Data System (ADS)

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.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. Electronic supplementary information (ESI) available: X-ray diffraction results and the XPS Cu 2p3/2 spectrum for Cu nanoparticles, resistivity evolution in thermally treated Cu films, the energy dose and intensity of flash lamps used in this study, SEM images of Cu films photo-sintered at 3.0 kV for 1.5 ms, resistivity evolution in photo-sintered, drop-casted Cu films, the XPS O 1s spectrum of Cu films photo-sintered at 2.5 kV for 1.5 ms, adhesion test results for photo-sintered Cu films. See DOI: 10.1039/c4nr06816e

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

2015-02-01

111

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

112

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

SciTech Connect

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

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

2010-07-13

113

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

114

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

115

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

116

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

117

Morphology and oxidation of Zr-based amorphous alloy ablated by femtosecond laser pulses  

NASA Astrophysics Data System (ADS)

Femtosecond laser ablation of an amorphous alloy in air, including single-pulse ablation, multi-pulse drilling and trenching has been investigated. Laser-induced ablation and related effects were examined by means of scanning electron microscopy, energy dispersive X-ray analysis, transmission electron microscopy and electron diffraction. Oxidation was observed in the multi-pulse ablation region surface. With selected parameters, molten trace, spatter and crystallization can be avoided in the vicinity of the machining area. The results show that femtosecond laser ablation with selected parameters is a promising method for micromachining amorphous alloys.

Wang, Xinlin; Lu, Peixiang; Dai, Nengli; Li, Yuhua; Liao, Changrui; Chang, Yanxiao; Yang, Guang; Zheng, Qiguang

2007-11-01

118

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

119

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

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

120

Water oxidation catalysis: electrocatalytic response to metal stoichiometry in amorphous metal oxide films containing iron, cobalt, and nickel.  

PubMed

Photochemical metal-organic deposition (PMOD) was used to prepare amorphous metal oxide films containing specific concentrations of iron, cobalt, and nickel to study how metal composition affects heterogeneous electrocatalytic water oxidation. Characterization of the films by energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy confirmed excellent stoichiometric control of each of the 21 complex metal oxide films investigated. In studying the electrochemical oxidation of water catalyzed by the respective films, it was found that small concentrations of iron produced a significant improvement in Tafel slopes and that cobalt or nickel were critical in lowering the voltage at which catalysis commences. The best catalytic parameters of the series were obtained for the film of composition a-Fe20Ni80. An extrapolation of the electrochemical and XPS data indicates the optimal behavior of this binary film to be a manifestation of iron stabilizing nickel in a higher oxidation level. This work represents the first mechanistic study of amorphous phases of binary and ternary metal oxides for use as water oxidation catalysts, and provides the foundation for the broad exploration of other mixed-metal oxide combinations. PMID:23883103

Smith, Rodney D L; Prévot, Mathieu S; Fagan, Randal D; Trudel, Simon; Berlinguette, Curtis P

2013-08-01

121

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

122

Amorphous Mn oxide-ordered mesoporous carbon hybrids as a high performance electrode material for supercapacitors.  

PubMed

A supercapacitor has the advantages of both the conventional capacitors and the rechargeable batteries. Mn oxide is generally recognized one of the potential materials that can be used for a supercapacitor, but its low conductivity is a limiting factor for electrode materials. In this study, a hybrid of amorphous Mn oxide (AMO) and ordered mesoporous carbon (OMC) was prepared and characterized using X-ray diffraction, transmission electron microscopy, N2/77 K sorption techniques, and electrochemical analyses. The findings indicate that the electrochemical activities of Mn oxide were facilitated when it was in the hybrid state because OMC acted as a pathway for both the electrolyte ions and the electrons due to the characteristics of the ordered mesoporous structure. The ordered mesoporous structure of OMC was well maintained even after hybridization with amorphous Mn oxide. The electrochemical-activity tests revealed that the AMO/OMC hybrid had a higher specific capacitance and conductivity than pure Mn oxide. In the case where the Mn/C weight ratio was 0.75, the composite showed a high capacitance of 153 F/g, which was much higher than that for pure Mn oxide, due to the structural effects of OMC. PMID:22966638

Nam, Inho; Kim, Nam Dong; Kim, Gil-Pyo; Park, Junsu; Yi, Jongheop

2012-07-01

123

A novel wafer reclaim method for amorphous SiC and carbon doped oxide films  

Microsoft Academic Search

Amorphous SiC (a-SiC) films are the most promising dielectric diffusion barriers to replace silicon nitride in Cu-interconnect technology. However, reclaim of wafers with a-SiC films is a challenge issue for mass production. In this paper, a novel wafer reclaim method is proposed. It is observed that a-SiC can be oxidized to SiO2 in both dry O2 and steam ambients at

Bing-Yue Tsui; Kuo-Lung Fang

2005-01-01

124

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

Microsoft Academic Search

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

Sabine Goldberg; Cliff T. Johnstony

2001-01-01

125

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

126

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

127

Effects of microwave annealing on electrical enhancement of amorphous oxide semiconductor thin film transistor  

NASA Astrophysics Data System (ADS)

By using microwave annealing technology instead of thermal furnace annealing, this work elucidates the electrical characteristics of amorphous InGaZnO thin film transistor (a-IGZO TFT) with a carrier mobility of 13.5 cm2/Vs, threshold voltage of 3.28 V, and subthreshold swing of 0.43 V/decade. This TFT performance with microwave annealing of 100 s is well competitive with its counterpart with furnace annealing at 450 °C for 1 h. A physical mechanism for the electrical improvement is also deduced. Owing to its low thermal budget and selective heating to materials of interest, microwave annealing is highly promising for amorphous oxide in semiconductor TFT manufacturing.

Teng, Li-Feng; Liu, Po-Tsun; Lo, Yuan-Jou; Lee, Yao-Jen

2012-09-01

128

Methane oxidation over palladium on zirconia prepared from amorphous Pd[sub 1]Zr[sub 3] alloy  

Microsoft Academic Search

Catalysts for methane oxidation have been prepared by oxidation of amorphous Pd[sub 2]Zr[sub 3] metal alloy under different conditions. A sequence of chemical and morphological changes occurring during the alloy oxidation process leads to highly active microporous palladium\\/zirconia catalysts suitable for the deep oxidation of methane. Depending on the activation temperature, distinct PdO species interacting with zirconia exist in these

P. E. Marti; M. Maciejewski; A. Baiker

1993-01-01

129

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

130

REVIEWS OF TOPICAL PROBLEMS: Atomic structure of the amorphous nonstoichiometric silicon oxides and nitrides  

NASA Astrophysics Data System (ADS)

In addition to amorphous SiO2 and Si3N4, the two key dielectric film materials used in modern silicon devices, the fabrication technology of nonstoichiometric SiOxNy, SiNx, and SiOx compounds is currently under development. Varying the chemical composition of these compounds allows a wide range of control over their physical — specifically, optical and electrical — properties. The development of technology for synthesizing such films requires a detailed understanding of their atomic structure. Current views on the atomic structure of nonstoichiometric silicon nitrides and oxides are reviewed and summarized.

Gritsenko, V. A.

2008-07-01

131

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

132

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

PubMed

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 as transistors in practical computers and current-driven organic light-emitting diode displays. Fabricating high-performance devices is challenging, owing to a trade-off between processing temperature and device performance. Here, we propose to solve this problem by using a novel semiconducting material--namely, a transparent amorphous oxide semiconductor from the In-Ga-Zn-O system (a-IGZO)--for the active channel in transparent thin-film transistors (TTFTs). The a-IGZO is deposited on polyethylene terephthalate at room temperature and exhibits Hall effect mobilities exceeding 10 cm2 V(-1) s(-1), which is an order of magnitude larger than for hydrogenated amorphous silicon. TTFTs fabricated on polyethylene terephthalate sheets exhibit saturation mobilities of 6-9 cm2 V(-1) s(-1), and device characteristics are stable during repetitive bending of the TTFT sheet. PMID:15565150

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

2004-11-25

133

Arsenic availability in rice from a mining area: Is amorphous iron oxide-bound arsenic a source or sink?  

PubMed

The effect of iron (Fe) redox cycling on the mobility and bioavailability of arsenic (As) in paddy soils has attracted increasing concerns, especially in Asia, where the paddy soil is characteristic of Fe with high abundance and activity. However, whether amorphous Fe oxide-bound As acts as a source or a sink of As in natural field conditions needs to be clarified further. In this study, 73 pairs of soil and rice were collected from paddy fields contaminated by As-containing acid mining drainage. The most significant correlations between the iron fractions and As fractions suggest that Fe redox cycling can directly affect As fractionation in soils, which can then indirectly affect As bioavailability. Significantly negative correlations between amorphous Fe oxide-bound As in soil and As in rice grain were found, indicating that amorphous Fe oxide-bound As acts a sink of As. PMID:25638690

Liu, Chuanping; Yu, Huan-Yun; Liu, Chengshuai; Li, Fangbai; Xu, Xianghua; Wang, Qi

2015-04-01

134

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

135

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

NASA Astrophysics Data System (ADS)

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 (H2)-plasma post-deposition treatment improves the conductivity of amorphous aluminum-doped zinc tin oxide while retaining its low optical absorption. We found that the H2-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.; Ding, L.; Dauzou, F.; Jeangros, Q.; Hessler-Wyser, A.; Nicolay, S.; Ballif, C.

2014-09-01

136

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

137

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

SciTech Connect

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

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

2014-07-28

138

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

139

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

140

Mesostructured amorphous manganese oxides: facile synthesis and highly durable elimination of low-concentration NO at room temperature in air.  

PubMed

At a high space velocity of 120?000 mL g(-1) h(-1) and a relative humidity of 50-90%, 98% removal of 10 ppm NO has been achieved for over 237 h and no sign of deactivation was observed with mesostructured amorphous manganese oxides (AMO), due to the prevention of the catalyst active sites from deactivation. PMID:25728967

Du, Yanyan; Hua, Zile; Huang, Weimin; Wu, Meiying; Wang, Min; Wang, Jin; Cui, Xiangzhi; Zhang, Lingxia; Chen, Hangrong; Shi, Jianlin

2015-04-01

141

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

Microsoft Academic Search

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

C. E. Tracy; D. K. Benson

1986-01-01

142

Improved Stability Of Amorphous Zinc Tin Oxide Thin Film Transistors Using Molecular Passivation  

SciTech Connect

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

Rajachidambaram, Meena Suhanya; Pandey, Archana; Vilayur Ganapathy, Subramanian; Nachimuthu, Ponnusamy; Thevuthasan, Suntharampillai; Herman, Gregory S.

2013-10-21

143

Contact resistance improvement using interfacial silver nanoparticles in amorphous indium-zinc-oxide thin film transistors  

SciTech Connect

We describe an approach to reduce the contact resistance at compositional conducting/semiconducting indium-zinc-oxide (IZO) homojunctions used for contacts in thin film transistors (TFTs). By introducing silver nanoparticles (Ag NPs) at the homojunction interface between the conducting IZO electrodes and the amorphous IZO channel, we reduce the specific contact resistance, obtained by transmission line model measurements, down to ?10{sup ?2?}??cm{sup 2}, ?3 orders of magnitude lower than either NP-free homojunction contacts or solid Ag metal contacts. The resulting back-gated TFTs with Ag NP contacts exhibit good field effect mobility of ?27?cm{sup 2}/V?s and an on/off ratio >10{sup 7}. We attribute the improved contact resistance to electric field concentration by the Ag NPs.

Xu, Rui; He, Jian [School of Engineering, Brown University, Providence, Rhode Island 02912 (United States); State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China (UESTC), Chengdu 610054 (China); Song, Yang [Department of Physics, Brown University, Providence, Rhode Island 02912 (United States); Li, Wei [State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China (UESTC), Chengdu 610054 (China); Zaslavsky, A. [School of Engineering, Brown University, Providence, Rhode Island 02912 (United States); Department of Physics, Brown University, Providence, Rhode Island 02912 (United States); Paine, D. C., E-mail: David-Paine@brown.edu [School of Engineering, Brown University, Providence, Rhode Island 02912 (United States)

2014-09-01

144

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

145

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

146

Unipolar resistive switching behavior of amorphous gallium oxide thin films for nonvolatile memory applications  

NASA Astrophysics Data System (ADS)

Amorphous gallium oxide thin film with heavy oxygen deficiency was deposited on Pt/Ti/SiO2/Si substrate by pulsed laser deposition in order to explore the resistive switching behavior of the Pt/Ga2O3-x/Pt sandwich structure. A well unipolar resistive switching behavior was obtained in this structure, which exhibits a high resistance ratio of OFF/ON up to 104, non-overlapping switching voltages, and excellent repeatability and retention. Both I-V relation plots of ON and OFF states and temperature dependent variation resistances indicate that the observed resistive switching behavior can be explained by the formation/rupture of conductive filaments formed out of oxygen vacancies.

Guo, D. Y.; Wu, Z. P.; An, Y. H.; Li, P. G.; Wang, P. C.; Chu, X. L.; Guo, X. C.; Zhi, Y. S.; Lei, M.; Li, L. H.; Tang, W. H.

2015-01-01

147

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

148

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

149

Sonochemical synthesis of amorphous nanoscopic iron(III) oxide from Fe(acac)3.  

PubMed

Amorphous nanoscopic iron(III) oxide with interesting magnetic properties was prepared by sonolysis of Fe(acac)(3) under Ar in tetraglyme with a small amount of added water. The organics content and the surface area of the Fe(2)O(3) nanoparticles can be controlled with an amount of water in the reaction mixture and it increases from 48 m(2)g(-1) for dry solvent up to 260 m(2)g(-1) when wet Ar is employed. For further monitoring of the particle size and morphology and for the study of the surface, magnetic and thermal properties, the sample with 2 vol.% of H(2)O was chosen. SEM showed nanoscopic composite particles of a uniform size distribution and nearly spherical shapes with an estimated diameter of 20 nm. Such composites are built from amorphous iron(III) oxide nanoparticles (3 nm) embedded in an acetate matrix as proved by TEM and IR spectroscopy. Temperature-dependent Mössbauer spectra demonstrate a very narrow magnetic transition with an unusually low transition temperature around 25K reflecting the system of magnetically non-interacting ultrasmall particles with a narrow size distribution. The in-field (5T) Mössbauer spectrum recorded at 5K shows a minimum change compared to the zero-field spectrum indicating an absence of the long-range magnetic ordering. The composite particles are thermally stable up to 150 degrees C, which is confirmed by DSC, TG, and by the constant surface area. At higher temperatures, acetate groups are removed from the particle surface, which is documented by the increased surface area and disappearance of their IR bands. PMID:17507278

Pinkas, Jiri; Reichlova, Vendula; Zboril, Radek; Moravec, Zdenek; Bezdicka, Petr; Matejkova, Jirina

2008-03-01

150

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

151

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

SciTech Connect

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

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

1995-06-01

152

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

SciTech Connect

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

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

1998-05-01

153

Rational design of amorphous indium zinc oxide/carbon nanotube hybrid film for unique performance transistors.  

PubMed

Here we report unique performance transistors based on sol-gel processed indium zinc oxide/single-walled carbon nanotube (SWNT) composite thin films. In the composite, SWNTs provide fast tracks for carrier transport to significantly improve the apparent field effect mobility. Specifically, the composite thin film transistors with SWNT weight concentrations in the range of 0-2 wt % have been investigated with the field effect mobility reaching as high as 140 cm(2)/V·s at 1 wt % SWNTs while maintaining a high on/off ratio ?10(7). Furthermore, the introduction SWNTs into the composite thin film render excellent mechanical flexibility for flexible electronics. The dynamic loading test presents evidently superior mechanical stability with only 17% variation at a bending radius as small as 700 ?m, and the repeated bending test shows only 8% normalized resistance variation after 300 cycles of folding and unfolding, demonstrating enormous improvement over the basic amorphous indium zinc oxide thin film. The results provide an important advance toward high-performance flexible electronics applications. PMID:22694726

Liu, Xingqiang; Wang, Chunlan; Cai, Bo; Xiao, Xiangheng; Guo, Shishang; Fan, Zhiyong; Li, Jinchai; Duan, Xiangfeng; Liao, Lei

2012-07-11

154

Physico-chemical studies of cuprous oxide (Cu2O) nanoparticles coated on amorphous carbon nanotubes (?-CNTs)  

NASA Astrophysics Data System (ADS)

Amorphous carbon nanotubes (?-CNTs) were synthesized by a chemical reaction between ferrocene and ammonium chloride at a temperature (?250 °C) in an air furnace. As- synthesized ?-CNTs were purified with deionized water and hydrochloric acid. A purified ?-CNTs were hybridized with cuprous oxide nanoparticles (Cu2O) through a simple chemical process. Morphology of the samples was analyzed with field emission scanning electron microscope (FESEM) and transmission electron microscopy (TEM). Fourier transform infrared (FTIR) spectra showed the attachment of acidic functional groups onto the surface of ?-CNTs and the formation of hybridized ?-CNTs-Cu2O. Raman spectra reveal the amorphous nature of the carbon. X-ray diffraction (XRD) pattern confirmed the amorphous phase of the carbon and the formation of Cu2O crystalline phase. The coating of Cu2O was confirmed by FESEM, TEM, and XRD. Optical absorption of the samples has also been investigated and the quantum confinement effect was illustrated in the absorption spectra.

Johan, Mohd Rafie; Meriam Suhaimy, Syazwan Hanani; Yusof, Yusliza

2014-01-01

155

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

156

In–Ga–Zn–O thin film transistor with HfO{sub 2} gate insulator prepared using various O{sub 2}/(Ar + O{sub 2}) gas ratios  

SciTech Connect

We have investigated the effect of the deposition of an HfO{sub 2} thin film as a gate insulator with different O{sub 2}/(Ar + O{sub 2}) gas ratios using RF magnetron sputtering. The HfO{sub 2} thin film affected the device performance of amorphous indium–gallium–zinc oxide transistors. The performance of the fabricated transistors improved monotonously with increasing O{sub 2}/(Ar + O{sub 2}) gas ratio: at a ratio of 0.35, the field effect mobility of the amorphous InGaZnO thin film transistors was improved to 7.54 cm{sup 2}/(V s). Compared to those prepared with an O{sub 2}/(Ar + O{sub 2}) gas ratio of 0.05, the field effect mobility of the amorphous InGaZnO thin film transistors was increased to 1.64 cm{sup 2}/(V s) at a ratio of 0.35. This enhancement in the field effect mobility was attributed to the reduction of the root mean square roughness of the gate insulator layer, which might result from the trap states and surface scattering of the gate insulator layer at the lower O{sub 2}/(Ar + O{sub 2}) gas ratio.

Jo, Young Je [WCU Department of Printed Electronics, Sunchon National University, Chonnam 540-742 (Korea, Republic of)] [WCU Department of Printed Electronics, Sunchon National University, Chonnam 540-742 (Korea, Republic of); Lee, In-Hwan [School of Advanced Materials Engineering, Chonbuk National University, Chonju 561-756 (Korea, Republic of)] [School of Advanced Materials Engineering, Chonbuk National University, Chonju 561-756 (Korea, Republic of); Kwak, Joon Seop, E-mail: jskwak@sunchon.ac.kr [WCU Department of Printed Electronics, Sunchon National University, Chonnam 540-742 (Korea, Republic of)

2012-10-15

157

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

NASA Astrophysics Data System (ADS)

To avoid the problem of air sensitive and wet-etched Zn and/or Ga contained amorphous oxide transistors, we propose an alternative amorphous semiconductor of indium silicon tungsten oxide as the channel material for thin film transistors. In this study, we employ the material to reveal the relation between the active thin film and the transistor performance with aid of x-ray reflectivity study. By adjusting the pre-annealing temperature, we find that the film densification and interface flatness between the film and gate insulator are crucial for achieving controllable high-performance transistors. The material and findings in the study are believed helpful for realizing controllable high-performance stable transistors.

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

2014-10-01

158

Temperature Dependence of Transistor Characteristics and Electronic Structure for Amorphous In-Ga-Zn-Oxide Thin Film Transistor  

Microsoft Academic Search

We fabricated an inverted-staggered amorphous In-Ga-Zn-oxide (a-IGZO) thin film transistor (TFT) and measured the temperature dependence of its characteristics. A threshold voltage (Vth) shift between 120 and 180 °C was as large as 4 V. In an analysis with two-dimensional (2D) numerical simulation, we reproduced the measured result by assuming two types of donor-like states as carrier generation sources. Furthermore,

Hiromichi Godo; Daisuke Kawae; Shuhei Yoshitomi; Toshinari Sasaki; Shunichi Ito; Hiroki Ohara; Hideyuki Kishida; Masahiro Takahashi; Akiharu Miyanaga; Shunpei Yamazaki

2010-01-01

159

Development of Liquid Crystal Display Panel Integrated with Drivers Using Amorphous In-Ga-Zn-Oxide Thin Film Transistors  

Microsoft Academic Search

We designed, prototyped, and evaluated a liquid crystal panel integrated with a gate driver and a source driver using amorphous In-Ga-Zn-oxide thin film transistors (TFTs). Using bottom-gate bottom-contact (BGBC) thin film transistors, superior characteristics could be obtained. We obtained TFT characteristics with little variation even when the thickness of the gate insulator (GI) film was reduced owing to etching of

Takeshi Osada; Kengo Akimoto; Takehisa Sato; Masataka Ikeda; Masashi Tsubuku; Junichiro Sakata; Jun Koyama; Tadashi Serikawa; Shunpei Yamazaki

2010-01-01

160

Potential for the alleviation of arsenic toxicity in paddy rice using amorphous iron-(hydr)oxide amendments  

Microsoft Academic Search

A pot culture experiment was conducted to investigate the effects of amorphous iron-(hydr)oxide (Am-FeOH) amendments on arsenic (As) availability and its uptake by rice (Oryza sativa L. cv. BR28) irrigated with As-contaminated water. A rhizobag system was established using 3.5 L plastic pots, each containing one central compartment for plant growth, a middle compartment and an outside compartment. Three levels of

Venecio U. Ultra Jr; Atsushi Nakayama; Sota Tanaka; Yumei Kang; Katsutoshi Sakurai; Kozo Iwasaki

2009-01-01

161

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

162

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

163

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

SciTech Connect

The composite material nSb{sub 2}O{sub 3}·mSiO{sub 2}·xH{sub 2}O was prepared by hydrolysis of SbCl{sub 3} and Na{sub 2}SiO{sub 3} in an aqueous medium. It has been shown that the composition of the material is influenced by the ratio of the initial components and the acidity of the reaction medium. The morphology of the material particles and its specific surface area have been determined. The thermal and optic properties were also investigated. - Graphical abstract: Novel composite material containing amorphous silica and crystal antimony(III) oxide has been synthesized by hydrolysis of SbCl{sub 3} and Na{sub 2}SiO{sub 3} in an aqueous medium. Highlights: ? The composite material nSb{sub 2}O{sub 3}·mSiO{sub 2}·xH{sub 2}O was prepared in an aqueous medium. ? The composition of the material is controllable by a synthesis conditions. ? The morphology of the material and its optic properties have been determined.

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

2013-05-15

164

Experimental study of the Ioffe-Regel criterion for amorphous indium oxide films  

NASA Astrophysics Data System (ADS)

The Ioffe-Regel criterion predicts the existence of a metal-insulator transition in a film series when the parameter 0953-8984/10/4/010/img7 satisfies the criterion 0953-8984/10/4/010/img8 here 0953-8984/10/4/010/img9 is the Fermi wavenumber and 0953-8984/10/4/010/img10 is the elastic mean free path of the carriers. According to this criterion, films having 0953-8984/10/4/010/img11 are metallic, while films having 0953-8984/10/4/010/img12 are insulating. We experimentally observe the metal-insulator transition in amorphous indium oxide films at 0953-8984/10/4/010/img13. The values of 0953-8984/10/4/010/img7 were calculated from room temperature resistivity and Hall voltage measurements, while the metal-insulator transition was determined from low-temperature resistivity data using the `w'-criterion of Mobius and of Zabrodskii and Zinov'eva.

Graham, Mark R.; Adkins, C. J.; Behar, Haim; Rosenbaum, Ralph

1998-02-01

165

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

166

Determination of photocatalytic activity in amorphous and crystalline titanium oxide films prepared using plasma-enhanced chemical vapor deposition  

NASA Astrophysics Data System (ADS)

Hydro-oxygenated amorphous titanium oxide (a-TiO x:OH) films were prepared by plasma-enhanced chemical vapor deposition (PECVD) using precursors of titanium tetraisopropoxide (TTIP) and oxygen. The influences of chemical states and crystal quality on the photocatalytic activity were systematically investigated in the as-deposited and post-annealed films. The degree of the photocatalytic activity was deeply correlated with the porosity related to the hydroxyl (OH) groups in the as-deposited amorphous film. The crystallized anatase structures was observed from the 200 °C-deposited a-TiO x:OH film after a post-annealing treatment at 400 °C. The photocatalytic activity related to the film with anatase structure was markedly superior to that of an amorphous film with porous structures. The larger the crystal size of the anatase structure, the higher the photocatalytic activity obtained. At elevated annealed temperatures, the inferior anatase structure due to the crystalline transformation led to a low photocatalytic activity. It was concluded that the photocatalytic activity of an amorphous TiO x film prepared using PECVD was determined by the porosity originating from the functional OH groups in the film, whereas the crystalline quality of anatase phase in the annealed poly-TiO x film was crucial to the photocatalytic activity.

Wu, Cheng-Yang; Chiang, Bo-Sheng; Chang, Springfield; Liu, Day-Shan

2011-01-01

167

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

168

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

169

Modeling the adsorption of mercury(II) on (hydr)oxides. 2: {alpha}-FeOOH (goethite) and amorphous silica  

SciTech Connect

The surface complexation model is used to describe sorption experiments of inorganic mercury(II) in the presence of an amorphous silica, Aerosil 200, or an iron (hydr)oxide, the goethite {alpha}-FeOOH (Bayferrox 910). In the simulations, one assumes the formation of a monodentate surface complex {triple_bond}S{single_bond}OHgOH and {triple_bond}S{single_bond}OHgCl, when chlorides are present in solution. Participation of the complex {triple_bond}S{single_bond}OHgCl has been especially evidenced. Comparisons with other data from the literature have been made to investigate the influence of the nature of the oxide on the mechanism of mercury(II) adsorption. X-ray photoelectron spectroscopy was used to characterize the surface of the (hydr)oxides prior to adsorption and to observe when possible the mercury surface compounds.

Bonnissel-Gissinger, P.; Alnot, M.; Ehrhardt, J.J. [CNRS-Univ. Henri Poincare, Villers-les-Nancy (France). Lab. de Chimie Physique pour l`Environnement] [CNRS-Univ. Henri Poincare, Villers-les-Nancy (France). Lab. de Chimie Physique pour l`Environnement; Lickes, J.P. [Univ. Libre de Bruxelles, Brussels (Belgium). Service de Chimie Analytique] [Univ. Libre de Bruxelles, Brussels (Belgium). Service de Chimie Analytique; Behra, P. [Univ. Louis Pasteur-CNRS, Strasbourg (France). Inst. de Mecanique des Fluides] [Univ. Louis Pasteur-CNRS, Strasbourg (France). Inst. de Mecanique des Fluides

1999-07-15

170

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

NASA Astrophysics Data System (ADS)

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

Kim, Min-Soo

171

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

172

Domain structure for an amorphous iridium-oxide water-oxidation catalyst characterized by X-ray pair distribution function analysis.  

PubMed

The domain structure of an amorphous, "blue layer" iridium-oxide water-oxidation catalyst film (BL) electrodeposited from the soluble precursor complex, [Cp*Ir(H2O)3]SO4, was characterized by X-ray pair distribution function (PDF) analysis. The results show that the experimental PDF can be fit remarkably well using a single Ir5O22 cluster extracted from the rutile lattice. The model includes distortions that indicate the presence of Ir(?-O)3Ir or distorted Ir(?-O)2Ir substructures, and hence deviations from a rutile structure. The five Ir atom cluster is suggested to represent the population-averaged distribution of metal-oxo clusters in the film. BL is found to be distinguished from other amorphous film water-oxidation catalysts because of the remarkably small domain size and homogeneity. As such, the blue layer catalyst provides a model for investigating ligand-determined metal-oxide cluster assembly and catalyst mechanism. PMID:24336574

Huang, Jier; Blakemore, James D; Fazi, Diego; Kokhan, Oleksandr; Schley, Nathan D; Crabtree, Robert H; Brudvig, Gary W; Tiede, David M

2014-02-01

173

Structure of amorphous oxide ceramics by nuclear magnetic resonance spectroscopy and molecular dynamics simulations  

NASA Astrophysics Data System (ADS)

Molecular dynamics (MD) simulations have been used to study the structure and dynamics of sodium tetrasilicate (Na2Si4O9 ) liquid as a function of pressure, ranging from I atmosphere to 100 GPa, at a temperature of 6000 K. The calculated self-diffusivity of the ions increases with increasing pressure, up to a maximum of approximately 10--15 GPa. Above this pressure, the O2- diffusivity decreases slightly with increasing pressure. The results of the simulations allow the distinction of two different mechanisms for the pressure-induced coordination change of silicon. The first, occurring at lower pressures, involves the formation of V-coordinated silicon, via reaction with non-bridging oxygens. The high pressure mechanism involves a reaction of bridging oxygens, which results in the formation of III-coordinated oxygen. MD simulations were carried out in order to investigate the structure and transport properties of boron oxide melt, as a function of pressure. The simulations show a rapid initial increase in the diffusion coefficients of boron and oxygen ions to ˜5--7 GPa, followed by a slower increase from 7--14 GPa. The increase in ion diffusivities is correlated with an increase in the proportion of BO4 to BO3 units. These results can be used to help rationalize an increase in growth rate of boron suboxide (B6O) crystals, observed from B2O3-B 6O melts in the 0--4 GPa pressure range. Structural characterization has also been carried out on a decomposed alumina ceramic precursor material, which is synthesized via thermal decomposition of an aluminum nitrate, nanohydrate [Al(NO3)3·9H 2O] salt to yield an x-ray amorphous, water-soluble precursor. Characterization of the solid precursor is presented, along with an in-depth study on the aluminum speciation in solution. Although the solid precursor contains entirely VI-coordinated aluminum, the solution phase contains IV-, V-, and VI-coordinated aluminum, whose relative abundance does not change with increasing thermal decomposition of the starting material. Furthermore, it is the change in solution concentration which alters the relative ratios of the structural units present in solution.

Diefenbacher, Jason Ross

174

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

175

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

176

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

NASA Astrophysics Data System (ADS)

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.

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

2014-04-01

177

Preparation of Bi-Sr-Ca-Cu-O whiskers from an amorphous matrix in the presence of oxide dopants  

SciTech Connect

Attempts to prepare single crystals of bismuth-containing superconductors of the Bi{sub 2}Sr{sub 2}Ca{sub n-1}Cu{sub n}O{sub 2n+4} (n=1-3) series met serious difficulties, including high growth anisotropy, the close stability ranges of the members of the series, their incongruent melting, the volatility of some components, and slow crystallization kinetics. Whisker growth puts some additional requirements on the amorphous initial state, fixed temperature gradient, and oxygen flow. The low growth rate makes it difficult to prepare long whiskers, which are necessary for solving fundamental and technological problems. This field has been studied extensively by several research teams. In this work, the authors found that whisker growth is accelerated by doping the initial melt with some oxides or their mixtures. The principles for selecting the dopants are stated. A model for whisker growth in the dopant-oxide matrix is proposed.

Os`kina, T.E.; Kozlovskii, V.F.; Tret`yakov, Y.D. [Moscow State Univ. (Russian Federation)

1995-09-01

178

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

179

Effects of defect creation on bidirectional behavior with hump characteristics of InGaZnO TFTs under bias and thermal stress  

NASA Astrophysics Data System (ADS)

We investigated the hump characteristics of amorphous indium–gallium–zinc oxide thin-film transistors. The device showed a field effect mobility of 24.3 cm2 V?1 s?1, a threshold voltage (Vth) of 4.8 V, and a subthreshold swing of 120 mV/dec. Under positive gate bias stress, Vth showed bidirectional shift with a hump. Vth was positively and negatively shifted in the above-threshold and subthreshold regions, respectively. At high temperatures, Vth was more positively shifted without bidirectional shift. Under simultaneous drain bias stress (VDS,stress), the hump was maintained. However, the bidirectional shift was not observed with an increasing VDS,stress. The hump and positive shift are related to the defect creation of the shallow donor-like and deep-level acceptor-like states, respectively. We performed a two-dimensional device simulation to further investigate this phenomenon. By varying the peak values of the Gaussian shallow donor-like and deep acceptor-like states, we qualitatively confirmed the relationship between the two states and transfer curve changes.

Im, Hwarim; Song, Hyunsoo; Jeong, Jaewook; Hong, Yewon; Hong, Yongtaek

2015-03-01

180

Highly flexible electronics from scalable vertical thin film transistors.  

PubMed

Flexible thin-film transistors (TFTs) are of central importance for diverse electronic and particularly macroelectronic applications. The current TFTs using organic or inorganic thin film semiconductors are usually limited by either poor electrical performance or insufficient mechanical flexibility. Here, we report a new design of highly flexible vertical TFTs (VTFTs) with superior electrical performance and mechanical robustness. By using the graphene as a work-function tunable contact for amorphous indium gallium zinc oxide (IGZO) thin film, the vertical current flow across the graphene-IGZO junction can be effectively modulated by an external gate potential to enable VTFTs with a highest on-off ratio exceeding 10(5). The unique vertical transistor architecture can readily enable ultrashort channel devices with very high delivering current and exceptional mechanical flexibility. With large area graphene and IGZO thin film available, our strategy is intrinsically scalable for large scale integration of VTFT arrays and logic circuits, opening up a new pathway to highly flexible macroelectronics. PMID:24502192

Liu, Yuan; Zhou, Hailong; Cheng, Rui; Yu, Woojong; Huang, Yu; Duan, Xiangfeng

2014-03-12

181

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

182

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

183

A study on the degradation mechanism of InGaZnO thin-film transistors under simultaneous gate and drain bias stresses based on the electronic trap characterization  

NASA Astrophysics Data System (ADS)

We discuss the device degradation mechanism of amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistors (TFTs) under simultaneous gate and drain bias stresses based on the electronic trap characterization results. The transfer curve exhibits an apparent negative shift as the stress time increases, and a formation of hump is observed in the transfer curve after stresses. A notable increase of the frequency dispersion is observed after stresses in both gate-to-drain capacitance-voltage (CGD-VG) and gate-to-source capacitance-voltage (CGS-VG) curves, which implies that the subgap states are generated by simultaneous gate and drain bias stresses, and the damaged location is not limited to the drain side of TFTs. The larger frequency dispersion is observed in CGD-VG curves after stresses in a wider channel device, which implies that the heat is an important factor in the generation of the subgap states under simultaneous gate and drain bias stresses in a-IGZO TFTs. Based on the electronic trap characterization results, we conclude that the impact ionization near the drain side of the device is not a dominant mechanism causing the generation of subgap states and device degradation in a-IGZO TFTs under simultaneous gate and drain bias stresses. The generation of oxygen vacancy-related donor-like traps near the conduction band edge is considered as a possible mechanism causing the device degradation under simultaneous gate and drain bias stresses in a-IGZO TFTs.

Jeong, Chan-Yong; Lee, Daeun; Song, Sang-Hun; In Kim, Jong; Lee, Jong-Ho; Kwon, Hyuck-In

2014-04-01

184

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

185

Methane oxidation over palladium on zirconia prepared from amorphous Pd[sub 1]Zr[sub 3] alloy  

SciTech Connect

Catalysts for methane oxidation have been prepared by oxidation of amorphous Pd[sub 2]Zr[sub 3] metal alloy under different conditions. A sequence of chemical and morphological changes occurring during the alloy oxidation process leads to highly active microporous palladium/zirconia catalysts suitable for the deep oxidation of methane. Depending on the activation temperature, distinct PdO species interacting with zirconia exist in these catalysts, as revealed by oxygen desorption and thermoanalytical measurements. Smaller PdO species were found to decompose at a markedly higher temperature than larger PdO species, which only interact weakly with the support. Kinetic studies were carried out in a fixed-bed microreactor at temperatures of 400-800 K and atmospheric pressure using a reactant mixture with a ratio CH[sub 4]:O[sub 2] = 1:4. Turnover frequencies, based on the exposed palladium surface atoms determined by CO chemisorption, were more than two times higher than those of palladium on zirconia catalysts prepared by impregnation or by coprecipitation. Methane oxidation measurements carried out over the conventionally prepared palladium/zirconia catalysts and a corresponding catalyst derived from Pd[sub 1]Zr[sub 3] showed CO and H[sub 2] selectivities higher than 90% under reducing conditions, i.e., with a reactant ratio CH[sub 4]:O[sub 2] = 8:1 at 870 K. 29 refs., 12 figs., 4 tabs.

Marti, P.E. (Paul Scherrer Institut, Villigen (Switzerland)); Maciejewski, M.; Baiker, A. (Swiss Federal Institute of Technology, Zuerich (Switzerland))

1993-06-01

186

Transformation of amorphous iron oxide thin films predeposited by spray pyrolysis into a single FeSe 2-phase by selenisation  

Microsoft Academic Search

The present paper investigates a simple and non-toxic method to transform amorphous iron oxide pre-deposited by spray pyrolysis of FeCl3·6H2O (0.03M)-based aqueous solution onto glass substrates heated at 350°C into FeSe2 thin films. The amorphous iron oxide films were heat treated under a selenium atmosphere (10?4Pa) at different temperatures for 6h. X-ray diffraction (XRD) was used to investigate the structure

B. Ouertani; J. Ouerfelli; M. Saadoun; B. Bessaïs; H. Ezzaouia; J. C. Bernède

2005-01-01

187

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

188

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

189

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

190

Amorphous stability of HfO 2 based ternary and binary composition spread oxide films as alternative gate dielectrics  

NASA Astrophysics Data System (ADS)

A ternary alloyed thin film library of HfO 2-Y 2O 3-Al 2O 3 was grown on a Si(1 0 0) substrate in a few hours by a new pulsed laser deposition (PLD) system installed with a masking and substrate rotating scheme. This specially designed combinatorial ternary composition spread method enabled us to fabricate continuous ternary and binary composition spread film libraries. It is noteworthy that the library made by this system is addressable; each film composition covers the full range (from 0 to 100%) and can be directly correlated with the film location in the ternary and binary phase diagram. Rapid permittivity measurement on the film libraries was carried out by a scanning microwave microscope, while the crystal structure was by a combinatorial X-ray diffractometer (XRD). The (HfO 2) 6(Y 2O 3) 1(Al 2O 3) 3 ternary composition area in an amorphous phase was found to have a dielectric constant higher than HfO 2-Y 2O 3 binary area. This ternary oxide is promising as amorphous gate dielectric material.

Hasegawa, K.; Ahmet, P.; Okazaki, N.; Hasegawa, T.; Fujimoto, K.; Watanabe, M.; Chikyow, T.; Koinuma, H.

2004-02-01

191

Creation and Control of Two-Dimensional Electron Gas Using Al-Based Amorphous Oxides/SrTiO3 Heterostructures Grown by Atomic  

E-print Network

mobility of 4-5 cm2 / V·s. A much higher electron mobility was observed at lower temperatures. More on the oxygen vacancies generated in the STO substrate. KEYWORDS: 2-D electron gas, amorphous, LaAlO3, Al2O3, SrTiO3, atomic layer deposition (ALD), oxygen vacancy Heterostructures between complex oxide layers

192

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

193

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

194

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

195

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

NASA Technical Reports Server (NTRS)

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

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

1998-01-01

196

Influence of amorphous silica matrices on the formation, structure, and chemistry of iron and iron oxide nanoparticles.  

PubMed

Fe(CO)(5) physisorbs onto Corning's code 7930 porous Vycor glass (PVG) and dried (oxidation, where the extent and most likely the rate of aggregation are functions of the correlation lengths of these amorphous matrices. With a correlation length of 22 +/- 1 nm, aggregation exceeds oxidation in PVG and limits oxidation to the outer periphery, thereby creating particles whose Fe(0)/Fe(III) ratio is unaffected by air or water released during consolidation of the silica matrix. The correlation length of the xerogel, oxidation to the outer periphery of the particle, and the primary photoproduct oxidizes, forming only Fe(2)O(3). Desorption of decomposition products derived from the xerogel precursors creates a dynamic surface that limits nanoparticle growth during annealing. Desorption also disrupts the growing silicate matrix, creating sites that facilitate the change from octahedrally to tetrahedrally coordinated Fe(III) in the xerogel. PMID:19824730

Sunil, Dehipalawage; Dong, Jinquan; Gafney, Harry D

2009-10-21

197

Amorphous vanadium oxide matrixes supporting hierarchical porous Fe3O4/graphene nanowires as a high-rate lithium storage anode.  

PubMed

Developing electrode materials with both high energy and power densities holds the key for satisfying the urgent demand of energy storage worldwide. In order to realize the fast and efficient transport of ions/electrons and the stable structure during the charge/discharge process, hierarchical porous Fe3O4/graphene nanowires supported by amorphous vanadium oxide matrixes have been rationally synthesized through a facile phase separation process. The porous structure is directly in situ constructed from the FeVO4·1.1H2O@graphene nanowires along with the crystallization of Fe3O4 and the amorphization of vanadium oxide without using any hard templates. The hierarchical porous Fe3O4/VOx/graphene nanowires exhibit a high Coulombic efficiency and outstanding reversible specific capacity (1146 mAh g(-1)). Even at the high current density of 5 A g(-1), the porous nanowires maintain a reversible capacity of ?500 mAh g(-1). Moreover, the amorphization and conversion reactions between Fe and Fe3O4 of the hierarchical porous Fe3O4/VOx/graphene nanowires were also investigated by in situ X-ray diffraction and X-ray photoelectron spectroscopy. Our work demonstrates that the amorphous vanadium oxides matrixes supporting hierarchical porous Fe3O4/graphene nanowires are one of the most attractive anodes in energy storage applications. PMID:25314630

An, Qinyou; Lv, Fan; Liu, Qiuqi; Han, Chunhua; Zhao, Kangning; Sheng, Jinzhi; Wei, Qiulong; Yan, Mengyu; Mai, Liqiang

2014-11-12

198

Development of Textured Magnesium Oxide Templates on Amorphous Polymer Surfaces Using Ion-Beam-Assisted Deposition  

NASA Astrophysics Data System (ADS)

Biaxially textured MgO templates have been successfully fabricated on several amorphous polymer films including Kapton tapes, polyimide, poly(methyl methacrylate) (PMMA), and photoresist films using ion-beam-assisted deposition (IBAD). With a Y2O3 buffer layer on polymer surfaces, roughening of the polymer surfaces due to preferential ion beam sputtering can be effectively reduced to meet the surface compatibility requirement for IBAD-MgO texturing. In-plane full-width-at-half-maximum (FWHM) of ˜10.7° and out-of-plane FWHM ˜3.5° have been obtained on homoepitaxial MgO films grown on top of the IBAD-MgO template. This method provides a practical route for fabricating epitaxial devices on polymers needed for flexible optoelectronics.

Elliot, Alan J.; Vallejo, Ronald N.; Lu, Rongtao; Wu, Judy Z.

2011-06-01

199

Structural relaxation in amorphous oxide semiconductor, a-In-Ga-Zn-O  

SciTech Connect

Amorphous In-Ga-Zn-O (a-IGZO) is expected as a backplane transistor material to drive next-generation flat-panel and flexible displays. It has been elucidated that thermal annealing even at low temperatures <200 deg. C reduces deep subgap defects and those at {>=}300 deg. C further improve device characteristics, stability, and uniformity. These temperatures are much lower than the reported crystallization temperature (T{sub X}{approx} 600 deg. C). In this work, we investigate effects of thermal annealing on the structural and optical properties of a-IGZO thin films. We performed classical molecular dynamics simulation (CMD) and optical interference analyses including spectroscopic ellipsometry (SE). CMD reproduced the x-ray diffraction pattern of a-IGZO and exhibited a glass transition. Experimentally, it was found that T{sub X} depends largely on deposition methods and conditions, probably due to different chemical compositions. Sputter-deposited a-IGZO films exhibited onset T{sub X}{approx} 600 deg. C and crystalline volume fraction X{sub C} increased linearly from 600 deg. C. 1.2% of film densification occurred even at 600 deg. C due to crystallization. High-temperature in situ SE measurements did not detect a symptom of a glass transition temperature (T{sub g}) presumably because the T{sub X} is close to T{sub g} similar to the case of amorphous metals.

Ide, Keisuke; Hiramatsu, Hidenori; Kamiya, Toshio [Materials and Structures Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan); Nomura, Kenji [Frontier Research Center, Tokyo Institute of Technology, 4259, Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan); Hosono, Hideo [Materials and Structures Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan); Frontier Research Center, Tokyo Institute of Technology, 4259, Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan)

2012-04-01

200

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

NASA Astrophysics Data System (ADS)

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

Meši?, Biljana; Schroeder, Herbert

2011-09-01

201

Dopant selection for control of charge carrier density and mobility in amorphous indium oxide thin-film transistors: Comparison between Si- and W-dopants  

NASA Astrophysics Data System (ADS)

The dependence of oxygen vacancy suppression on dopant species in amorphous indium oxide (a-InOx) thin film transistors (TFTs) is reported. In a-InOx TFTs incorporating equivalent atom densities of Si- and W-dopants, absorption of oxygen in the host a-InOx matrix was found to depend on difference of Gibbs free energy of the dopants for oxidation. For fully oxidized films, the extracted channel conductivity was higher in the a-InOx TFTs containing dopants of small ionic radius. This can be explained by a reduction in the ionic scattering cross sectional area caused by charge screening effects.

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

2015-01-01

202

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

203

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

204

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

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

205

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

206

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

207

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

PubMed

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

2014-07-15

208

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

Microsoft Academic Search

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

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

2007-01-01

209

A Study of the Liquid Crystal Alignment Mechanism of Bond-Breaking Via Ion-Beam Irradiation of an Amorphous Aluminum-Oxide Surface  

Microsoft Academic Search

In this paper, we study the Ion-beam (IB) irradiated amorphous (a)-aluminum oxide (Al O ) inorganic layer deposited by RF magnetron sputtering as an liquid crystal (LC) alignment layer. Uniformly vertical-aligned (VA)-LC on a-Al O surface resulted from IB irradiation energy above 1800 eV. We assumed that LC molecular orientation depends on the intensity of Al 2p, O 1s peaks,

Dai-Hyun Kim; Hae-Yoon Jung; Young-Gu Kang; Young-Hwan Kim; Hong-Gyu Park; Byoung-Yong Kim; Dae-Shik Seo

2011-01-01

210

Amorphous Calcium Phosphate Based Composites: Effect of Surfactants and Poly(ethylene oxide) on Filler and Composite Properties  

PubMed Central

The uncontrolled aggregation of amorphous calcium phosphate (ACP) particulate fillers and their uneven distribution within polymer matrices can have adverse effects on the properties of ACP composites. In this paper we assessed the influence of non-ionic and anionic surfactants and poly(ethylene oxide) (PEO) introduced during the preparation of ACP on the particle size distribution and compositional properties of ACP. In addition, the mechanical strength of polymeric composites utilizing such fillers with a photo-activated binary methacrylate resin was evaluated. Zirconia-hybridized ACP (Zr-ACP) filler and its corresponding composite served as controls for this study. Surfactant- and PEO-ACPs had an average water content of 16.8 % by mass. Introduction of the anionic surfactant reduced the median particle diameter about 45 % (4.1 ?m vs. 7.4 ?m for the Zr-ACP control). In the presence of PEO, however, the dm increased to 14.1 ?m. There was no improvement in the biaxial flexure strength (BFS) in any of the dry composite specimens prepared with the surfactant- and/or PEO-ACPs compared to those formulated with Zr-ACP. The BFS of wet composite specimens decreased by 50 % or more after a month-long exposure to saline solutions. Other types of surfactants and/or polymers as well as alternative surface modification protocols need to be explored for their potential to provide better dispersion of ACP into the matrix resin and better mechanical performance ACP composites. PMID:18714365

Antonucci, J.M.; Liu, D.W.; Skrtic, D.

2008-01-01

211

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

212

Hysteresis and threshold switching characteristics in thin-film-transistors with inserted Pt-Fe2O3 core–shell nanocrystals  

NASA Astrophysics Data System (ADS)

Hysteresis and threshold switching characteristics were investigated in the indium-gallium-zinc-oxide (IGZO) thin-film-transistors (TFTs) with inserted Pt-Fe2O3 core–shell nanocrystals (NCs) layer between source/drain and IGZO channel. The output curves showed the hysteresis with threshold drain voltage and the transfer curves showed the hysteresis with the shift of threshold gate voltage. These hysteresis, threshold switching, and shift of threshold voltage in both output and transfer curves are caused by charging of inserted NCs. These unique features demonstrated the memory and on/off switching operation by controlling both threshold gate and drain voltages through charging NCs.

Baek, Yoon-Jae; Noh, Young Jun; Choi, Young Jin; Kang, Chi Jung; Lee, Hyun Ho; Yoon, Tae-Sik

2014-11-01

213

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

214

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

NASA Astrophysics Data System (ADS)

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; Diddens, Diddo; Heuer, Andreas

2014-01-01

215

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

216

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

217

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

218

A 6b 10MS\\/s current-steering DAC manufactured with amorphous Gallium-Indium-Zinc-Oxide TFTs achieving SFDR > 30dB up to 300kHz  

Microsoft Academic Search

Amorphous Gallium-Indium-Zinc-Oxide (GIZO or IGZO) has been recently proposed [1] as an interesting semiconductor for manufacturing TFTs because of its mobility (??20cm2\\/Vs), superior to other common materials for large-area electronics like organic semiconductors and a-Si (??1cm2\\/Vs). The amorphous nature of GIZO grants also a good uniformity, contrary to Low Temperature Polycrystalline Silicon (LTPS), which still offers the best mobility among

Daniele Raiteri; Fabrizio Torricelli; Kris Myny; Manoj Nag; Bas Van der Putten; Edsger Smits; Soeren Steudel; Karin Tempelaars; Ashutosh Tripathi; Gerwin Gelinck; Arthur Van Roermund; Eugenio Cantatore

2012-01-01

219

High capacitance hybrid organic-inorganic gate dielectrics for solution-processable electronic technologies  

NASA Astrophysics Data System (ADS)

Solution-processable materials offer enormous opportunity in designing lightweight, flexible, and low-cost electronic technologies. Dielectric materials and the different classes of semiconductors (derived from organics, inorganics, or nanomaterials) comprise the two most important components in transistors, which are the basic building blocks of all modern electronic devices. New semiconductors such as single-walled carbon nanotubes (SWCNTs) and inorganic amorphous oxide semiconductors (AOSs), including indium gallium zinc oxide (IGZO), are envisioned for high performance applications as a possible replacement for silicon within integrated circuits, display backplane technologies, or high throughput inkjet printing technologies that can be low in cost and waste. These new semiconductors, amongst others, require corresponding advances in gate dielectric materials to support optimum device function. Herein we describe research surrounding the advancement of organic-inorganic hybrid gate dielectric materials for use in thin-film transistor (TFT) architectures. We describe the reasoning, the strategy, and the properties of a new hafnium oxide-based self-assembled nanodielectric (Hf-SAND), and examine in detail the chemical structure/formation, and electronic performance. Record setting capacitance can be achieved by using thin multilayers of Hf-SAND (1.1 ?F/cm2). Application of this new dielectric to the aforementioned SWCNT and IGZO semiconductors in an effort to demonstrate technological feasibility, yield record field-effect mobilities (20-130 cm2V-1s-1) and large ON state transconductances (up to 5 mS) at very low operating voltages (< 3 V), while retaining the ability to be processed completely from solution and in ambient atmosphere. These TFT performance metrics are examined in detail, and placed in perspective in relation to the Hf-SAND dielectric properties. Finally, we present some forward looking statements to help identify further opportunities for research and development of SAND gate dielectrics for unconventional electronics applications.

Everaerts, Ken

220

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

PubMed

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

Sivayoganathan, Mugunthan; Tan, Bo; Venkatakrishnan, Krishnan

2012-01-01

221

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

222

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

223

TFT-Based Active Pixel Sensors for Large Area Thermal Neutron Detection  

NASA Astrophysics Data System (ADS)

Due to diminishing availability of 3He, which is the critical component of neutron detecting proportional counters, large area flexible arrays are being considered as a potential replacement for neutron detection. A large area flexible array, utilizing semiconductors for both charged particle detection and pixel readout, ensures a large detection surface area in a light weight rugged form. Such a neutron detector could be suitable for deployment at ports of entry. The specific approach used in this research, uses a neutron converter layer which captures incident thermal neutrons, and then emits ionizing charged particles. These ionizing particles cause electron-hole pair generation within a single pixel's integrated sensing diode. The resulting charge is then amplified via a low-noise amplifier. This document begins by discussing the current state of the art in neutron detection and the associated challenges. Then, for the purpose of resolving some of these issues, recent design and modeling efforts towards developing an improved neutron detection system are described. Also presented is a low-noise active pixel sensor (APS) design capable of being implemented in low temperature indium gallium zinc oxide (InGaZnO) or amorphous silicon (a-Si:H) thin film transistor process compatible with plastic substrates. The low gain and limited scalability of this design are improved upon by implementing a new multi-stage self-resetting APS. For each APS design, successful radiation measurements are also presented using PiN diodes for charged particle detection. Next, detection array readout methodologies are modeled and analyzed, and use of a matched filter readout circuit is described as well. Finally, this document discusses detection diode integration with the designed TFT-based APSs.

Kunnen, George

224

Amorphous transparent conductive oxide InGaO3 (ZnO)m (m ? 4): a Zn 4s conductor  

Microsoft Academic Search

With the purpose of creating ZnO-based am orphous transparent conductors, a range of amorphous films InGaO 3(ZnO)m (where m <= 4) was prepared using a pulsed-laser deposition method. The resulting films exhibited an optical bandgap of 2.8-3.0 eV, and an n-type electric conductivity of 170-400 S cm-1 at room temperature, displaying a slight dependence on the value of m, in

M. Orita; H. Ohta; M. Hirano; S. Narushima; H. Hosono

2001-01-01

225

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

SciTech Connect

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

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

2009-04-06

226

Valence band offset in heterojunctions between crystalline silicon and amorphous silicon (sub)oxides (a-SiOx:H, 0 < x < 2)  

NASA Astrophysics Data System (ADS)

The heterojunction between amorphous silicon (sub)oxides (a-SiOx:H, 0 < x < 2) and crystalline silicon (c-Si) is investigated. We combine chemical vapor deposition with in-system photoelectron spectroscopy in order to determine the valence band offset ?EV and the interface defect density, being technologically important junction parameters. ?EV increases from ?0.3 eV for the a-Si:H/c-Si interface to >4 eV for the a-SiO2/c-Si interface, while the electronic quality of the heterointerface deteriorates. High-bandgap a-SiOx:H is therefore unsuitable for the hole contact in heterojunction solar cells, due to electronic transport hindrance resulting from the large ?EV. Our method is readily applicable to other heterojunctions.

Liebhaber, M.; Mews, M.; Schulze, T. F.; Korte, L.; Rech, B.; Lips, K.

2015-01-01

227

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

NASA Astrophysics Data System (ADS)

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

Belener, Kevin L. A.; Kohlmann, Holger

2014-12-01

228

White light emission from heterojunction diodes based on surface-oxidized porous Si nanowire arrays and amorphous In-Ga-Zn-O capping.  

PubMed

A novel heterojunction white light emitting diode (LED) structure based on an array of vertically aligned surface-passivated p-type porous Si nanowires (PSiNWs) with n-type amorphous In-Ga-Zn-O (a-IGZO) capping is introduced. PSiNWs were initially synthesized by electroless etching of p-type Si (100) wafers assisted by Ag nanoparticle catalysts and then surface-passivated by thermal oxidation. The nanowires synthesized by metal-assisted electroless etching were found to have longitudinally varying nanoporous morphologies due to differences in the duration of exposure to etching environment. These PSiNWs were optically active with orange red photoluminescence consisting of dark red to yellow emissions attributable to quantum confinement effects and to modified band structures. The LED structures emitted visible white light while exhibiting rectifying current-voltage characteristics. The white light emission was found to be the result of the combination of dark red to yellow emissions originating from the quantum confinement effect within the PSiNWs and green to blue emissions due to the oxygen-deficiency-related recombination centers introduced during the surface oxidation. PMID:24556906

Moon, Kyeong-Ju; Lee, Tae Il; Lee, Woong; Myoung, Jae-Min

2014-04-01

229

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

230

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

231

Effect of the tungsten oxidation states in the thermal coloration and bleaching of amorphous WO 3 films  

Microsoft Academic Search

The structural, optical and electronic changes caused by thermal annealing in vacuum and in oxygen atmosphere on evaporated WO3 films, were investigated by visible and infrared transmission spectroscopy (FTIR), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The luminous transmittance of the WO3 films was related to their state of oxidation at each annealing temperature, both during thermal coloration

G. Leftheriotis; S. Papaefthimiou; P. Yianoulis; A. Siokou

2001-01-01

232

An XPS Study of Amorphous Thin Films of Mixed Oxides In2O3-SnO2 System Deposited by Co-Evaporation  

NASA Astrophysics Data System (ADS)

XPS core level measurements are used to observe the surface changes in amorphous thin films of mixed oxides In2O3-SnO2 system deposited by co-evaporation. The effects of changes in composition (in mol%), film thickness, substrate temperature, post-deposition annealing, and etching with Ar+ ions on the binding energies of In(3d) and Sn(3d) doublets in mixed oxides In2O3-SnO2 system are presented. XPS core level In(3d) and Sn(3 d) spectra at various compositions exhibit the characteristic 3d5 / 2 and 3d3 / 2 doublets. The positions of the In(3d) and Sn(3d) lines are those as expected for In3+ ions in In2O3 and Sn4+ ions in SnO2. The initial decrease in binding energy with an increase in Sn content in In2O3 lattice is caused by the Sn atom substitution of In atom, giving out one extra electron. The increase in binding energy above the critical Sn content (10 mol% SnO2) is caused by the defects formed by Sn atoms, which act as carrier traps rather than electron donors. The decrease in binding energy with film thickness is caused by the increase in free-carriers density, which is generated by oxygen vacancy acting as two electrons donor. The decrease in binding energy with a substrate and annealing temperatures is due either to the severe deficiency of oxygen, which deteriorates the film properties and reduces the mobility of the carriers or to the diffusion of Sn atoms from interstitial locations into the In cation sites and the formation of indium and tin species of lower valence states so that the In3+ and the Sn4+ oxidation states may be changed to the In2+ and the Sn2+ oxidation states respectively. The new oxidation states, In2+ and Sn2+, formed due to ion etching and annealing the samples can be attributed to the internal electron transfer from oxygen 2p to the In 5s and Sn 5s levels both in In2O3 and SnO2.

Anwar, M.; Ghauri, I. M.; Siddiqi, S. A.

233

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

Microsoft Academic Search

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

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

2008-01-01

234

4.0-inch Active-Matrix Organic Light-Emitting Diode Display Integrated with Driver Circuits Using Amorphous In-Ga-Zn-Oxide Thin-Film Transistors with Suppressed Variation  

Microsoft Academic Search

We have newly developed a 4.0-in. quarter video graphics array (QVGA) active-matrix organic light-emitting diode (AMOLED) display integrated with gate and source driver circuits using amorphous In-Ga-Zn-oxide (IGZO) thin-film transistors (TFTs). Focusing on a passivation layer in an inverted staggered bottom gate structure, the threshold voltage of the TFTs can be controlled to have ``normally-off'' characteristics with suppressed variation by

Hiroki Ohara; Toshinari Sasaki; Kousei Noda; Shunichi Ito; Miyuki Sasaki; Yuta Endo; Shuhei Yoshitomi; Junichiro Sakata; Tadashi Serikawa; Shunpei Yamazaki

2010-01-01

235

Water oxidation by electrodeposited cobalt oxides--role of anions and redox-inert cations in structure and function of the amorphous catalyst.  

PubMed

For the production of nonfossil fuels, water oxidation by inexpensive cobalt-based catalysts is of high interest. Films for the electrocatalysis of water oxidation were obtained by oxidative self-assembly (electrodeposition) from aqueous solutions containing, apart from Co, either K, Li or Ca with either a phosphate, acetate or chloride anion. X-ray absorption spectroscopy (XAS) at the Co K-edge revealed clusters of edge-sharing CoO(6) octahedra in all films, but the size or structural disorder of the Co-oxido clusters differed. Whereas potassium binding is largely unspecific, CaCo(3) O(4) cubanes, which resemble the CaMn(3) O(4) cubane of the biological catalyst in oxygenic photosynthesis, may form, as suggested by XAS at the Ca K-edge. Cyclic voltammograms in a potassium phosphate buffer at pH?7 revealed that no specific combination of anions and redox-inactive cations is required for catalytic water oxidation. However, the anion type modulates not only the size (or order) of the Co-oxido clusters, but also electrodeposition rates, redox potentials, the capacity for oxidative charging, and catalytic currents. On these grounds, structure-activity relations are discussed. PMID:22323319

Risch, Marcel; Klingan, Katharina; Ringleb, Franziska; Chernev, Petko; Zaharieva, Ivelina; Fischer, Anna; Dau, Holger

2012-03-12

236

The pH-dependent long-term stability of an amorphous manganese oxide in smelter-polluted soils: Implication for chemical stabilization of metals and metalloids.  

PubMed

An amorphous manganese oxide (AMO) and a Pb smelter-polluted agricultural soil amended with the AMO and incubated for 2 and 6 months were subjected to a pH-static leaching procedure (pH 3-8) to verify the chemical stabilization effect on metals and metalloids. The AMO stability in pure water was pH-dependent with the highest Mn release at pH 3 (47% dissolved) and the lowest at pH 8 (0.14% dissolved). Secondary rhodochrosite (MnCO3) was formed at the AMO surfaces at pH>5. The AMO dissolved significantly less after 6 months of incubation. Sequential extraction analysis indicated that "labile" fraction of As, Pb and Sb in soil significantly decreased after AMO amendment. The pH-static experiments indicated that no effect on leaching was observed for Cd and Zn after AMO treatments, whereas the leaching of As, Cu, Pb and Sb decreased down to 20%, 35%, 7% and 11% of the control, respectively. The remediation efficiency was more pronounced under acidic conditions and the time of incubation generally led to increased retention of the targeted contaminants. The AMO was found to be a promising agent for the chemical stabilization of polluted soils. PMID:25600581

Ettler, Vojt?ch; Tomášová, Zde?ka; Komárek, Michael; Mihaljevi?, Martin; Šebek, Ond?ej; Michálková, Zuzana

2015-04-01

237

Edge effect enhanced electron field emission in top assembled reduced graphene oxide assisted by amorphous CNT-coated carbon cloth substrate  

NASA Astrophysics Data System (ADS)

In this work a hybrid structure assembly of amorphous carbon nanotubes (a-CNTs) -reduced graphene oxide (RGO) has been fabricated on carbon cloth/PET substrates for enhanced edge effect assisted flexible field emission device application. The carbon nanostructures prepared by chemical processes were finally deposited one over the other by a simple electrophoretic deposition (EPD) method on carbon cloth (CC) fabric. The thin films were then characterized by X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscope (HRTEM). Field assisted electron emission measurement was performed on this hybrid structure. It was observed that the hybrid carbon nanostructure showed exceptional field emission properties with outstanding low turn-on and threshold field (Eto˜ 0.26 V?m-1, Eth ˜ 0.55 V?m1). These observed results are far better compared to standalone and plasma etched edge enhanced RGO systems due to the bottom layer a-CNTs bed which assisted in significant enhancement of edge effect in RGO sheets.

Roy, Rajarshi; Jha, Arunava; Banerjee, Diptonil; Sankar Das, Nirmalya; Chattopadhyay, Kalyan Kumar

2013-01-01

238

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

SciTech Connect

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

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

2002-11-18

239

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

PubMed

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

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

2015-04-01

240

Dc Conduction Mechanisms in Amorphous Thin Films of Mixed Oxides In2O3-SnO2 System Deposited by Co-Evaporation  

NASA Astrophysics Data System (ADS)

A discussion of dc conduction mechanisms in thermally co-evaporated amorphous thin films of Al-In2O3-SnO2-Al structure is presented. Composition (in molar %), film thickness, substrate temperature, and post deposition annealing have profound effects on the electrical properties of the films. The effects of temperature on the I-V characteristics and electrical conductivity of Al-In2O3-SnO2-Al structure are also reported. The values of dielectric constants estimated by capacitance measurements suggest that high-field conduction mechanism is predominantly of Poole-Frenkel type. At low temperature and low field the electron hopping process dominates but at higher temperature the conduction takes place by transport in the extended states (free-band conduction). The transition from hopping to free band conduction is due to overlapping of localized levels and the free band. The increase in the formation of ionized donors with increase in temperature during electrical measurements indicates that electronic part of the conductivity is higher than the ionic part. The initial increase in conductivity with increase in Sn content in In2O3 lattice is caused by the Sn atom substitution of In atom, giving out one extra electron. The decrease in electrical conductivity above the critical Sn content (10 mol % SnO2) is caused by the defects formed by Sn atoms, which act as carrier traps rather than electron donors. The increase in electrical conductivity with film thickness is caused by the increase in free carriers density, which is generated by oxygen vacancy acting as two electrons donor. The increase in conductivity with substrate temperature and annealing is due either to the severe deficiency of oxygen, which deteriorates the film properties and reduces the mobility of the carriers or to the diffusion of Sn atoms from interstitial locations into the In cation sites and formation of indium species of lower valence state so that the In3+ oxidation state may be changed to the In2+ oxidation state.

Anwar, M.; Siddiqi, S. A.; Ghauri, I. M.

241

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

242

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

243

Improvement of electrical performance of InGaZnO/HfSiO TFTs with 248-nm excimer laser annealing  

NASA Astrophysics Data System (ADS)

The influence of 248-nm KrF excimer laser annealing (ELA) with energy density between 0 and 400 mJ/cm2 on the electrical behavior of indium gallium zinc oxide (InGaZnO) thin-film transistors (TFTs) is investigated. The experimental results show that the saturation mobility and subthreshold swing are improved from 12.4 cm2/Vs and 100 mV/dec without ELA to 17.8 cm2/Vs and 75 mV/dec, respectively, by applying a 300 mJ/cm2 laser pulse after the source/drain deposition, while maintaining an almost unchanged turn-off voltage. Such improvements are attributed to the increase in the oxygen vacancies and reduction in the bulk traps in the InGaZnO channel.

Huang, Hau-Yuan; Wang, Shui-Jinn; Wu, Chien-Hung; Lu, Chien-Yuan

2014-09-01

244

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

245

Subgap states in transparent amorphous oxide semiconductor, In-Ga-Zn-O, observed by bulk sensitive x-ray photoelectron spectroscopy  

Microsoft Academic Search

We investigated the electronic states in amorphous In-Ga-Zn-O films with high carrier concentrations by optical absorption and hard x-ray photoelectron spectroscopy (HX-PES). Films having different Hall mobilities were prepared and their annealing effects were examined. All HX-PES spectra showed Fermi edge structures and extra subgap densities of states (DOSs). Tail-like structures observed in the optical spectra originate from subgap DOSs

Kenji Nomura; Toshio Kamiya; Hiroshi Yanagi; Eiji Ikenaga; Ke Yang; Keisuke Kobayashi; Masahiro Hirano; Hideo Hosono

2008-01-01

246

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.

247

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

248

Theory of amorphous ices.  

PubMed

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

2014-07-01

249

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

250

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

SciTech Connect

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

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

2008-09-22

251

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

252

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

253

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

254

Ferromagnetic bulk amorphous alloys  

Microsoft Academic Search

This article reviews our recent results on the development of ferromagnetic bulk amorphous alloys prepared by casting processes.\\u000a The multicomponent Fe-(Al,Ga)-(P,C,B,Si) alloys are amorphized in the bulk form with diameters up to 2 mm, and the temperature\\u000a interval of the supercooled liquid region before crystallization is in the range of 50 to 67 K. These bulk amorphous alloys\\u000a exhibit good

Akihisa Inoue; Akira Takeuchi; Tao Zhang

1998-01-01

255

Corrosion-resistant and wear-resistant magnetic amorphous alloy and a method for preparing the same  

SciTech Connect

There are disclosed a corrosion-resistant and wear-resistant magnetic amorphous alloy characterized by having, on the surface thereof, an oxide layer including a crystalline oxide and a method for preparing the same characterized by carrying out the oxidation treatment of the magnetic amorphous alloy at a high temperature and at a high pressure in order to form an oxide layer including a crystalline oxide on the surface of the magnetic amorphous alloy. The magnetic amorphous alloy according to this invention possesses a remarkable corrosion resistance and wear resistance and had an improved magnetic permeability in the mega-Hertz zone.

Inomata, K.; Higashinakagawa, E.; Sato, K.; Tateishi, H.

1985-03-12

256

Amorphous-Carbon Films  

NASA Technical Reports Server (NTRS)

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

Pouch, John J.; Alterovitz, Samuel A.

1993-01-01

257

Fabrication of solution-processed amorphous indium zinc oxide thin-film transistors at low temperatures using deep-UV irradiation under wet conditions  

NASA Astrophysics Data System (ADS)

We fabricated solution-processed indium zinc oxide (IZO) thin film transistors (TFTs) at annealing temperatures as low as 250 °C using deep UV (DUV) irradiation in water vapor medium. The DUV light decomposed the carbon compounds in the IZO films, and the hydroxyl radicals generated when water vapor reacted with ozone effectively oxidized the films. These phenomena were confirmed by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. Finally, we fabricated DUV-treated IZO TFTs in water-vapor medium at 250 °C with a mobility of 1.2 cm2/Vs and an on/off current ratio of 2.66 × 106.

Park, Jee Ho; Chae, Soo Sang; Yoo, Young Bum; Lee, Ji Hoon; Lee, Tae Il; Baik, Hong Koo

2014-03-01

258

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

259

Applications of amorphous metals  

NASA Astrophysics Data System (ADS)

Amorphous metals, or metallic glasses, represent the extreme case of rapid solidification metals technology, since they are formed by quenching from the melt so abruptly that no crystallization can take place. Because of the remarkable scientific and technical properties of the amorphous metals, R&D efforts relating to these materials have been vigorous since their discovery twenty years ago. At the present time, Allied Corporation is bringing its continuous casting pilot plant on-line and the prospects of large volume quantities at sharply reduced prices is intensifying the development of applications of the amorphous metals. A brief overview of amorphous metals technology and of the characteristics of these materials is given, followed by a description of their application to the electric power, electronics, transduction, security and metal-joining industries.

Raskin, D.

1982-05-01

260

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

261

Amorphous Hydrogenated Carbon Nanofilm  

Microsoft Academic Search

Amorphous hydrogenated carbon (a-C:H) nanofilm is a metastable form of amorphous carbon with significant sp3 bonding. a-C:H\\u000a is a semiconductor with a high mechanical hardness, chemical inertness, and optical transparency. This chapter will describe\\u000a the deposition methods, deposition mechanisms, characterization methods, electronic structure, gap states, defects, doping,\\u000a luminescence, field emission, mechanical properties, and some applications of a-C:H. The films have

Dechun Ba; Zeng Lin

262

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

263

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

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

264

Ferromagnetism and ferroelectricity of Bi 2O 3?Fe 2O 3?PbTiO 3 amorphous oxide films prepared by gel-coating technique  

NASA Astrophysics Data System (ADS)

Previously we reported that rf-sputtered Bi 2O 3?Fe 2O 3?ABO 3 films (ABO 3: Perovskite either of BaTiO 3, PbTiO 3, or PbZrO 3) have pronounced properties exhibiting magnetic as well as dielectric hysteresis loops simultaneously above room temperature for films with a restricted Fe 2O 3-concentration of about 70 at% after subject to thermal annealing at about 700°C. In the present study, we have prepared the same oxide films by the sol-gel method, where PbTiO 3 was chosen for ABO 3. It was found that gel-coated films onto glass substrates and/or low-resistivity Si-wafers also possess the properties similar to those of rf-sputtered films. Microstructure of the films was examined by EXAFS measurement at the Fe-absorption edge. It may be concluded that a disordered oxide state having a random glass network structure is essential for realizing magnetic and dielectric ordered state, presumably caused by strong frustration in a glassy antiferromagnet.

Wada, Takaya; Tokunaga, Yuichi; Kajima, Atsushi; Inoue, Mitsuteru; Fujii, Toshitaka; Jeyadevan, Balachandran; Tohji, Kazuyuki

1997-04-01

265

Properties of Al2O3: nc-Si nanostructures formed by implantation of silicon ions into sapphire and amorphous films of aluminum oxide  

NASA Astrophysics Data System (ADS)

Photoluminescence, infrared Fourier spectroscopy, Raman scattering, transmission electron microscopy, and electron diffraction were used to study the luminescent, optical, and structural properties of aluminum oxide layers (sapphire and films of Al2O3 deposited on silicon) implanted with Si+ to produce silicon nanocrystals. It is established that, in both cases, a high-temperature annealing of heavily implanted samples brings about the formation of silicon nanocrystals. However, the luminescent properties of the nanocrystals are strongly dependent on the type of pristine matrix; namely, nanocrystals in Al2O3 films emit light in the spectral range typical of Si quantum dots (700-850 nm), whereas in sapphire this photoluminescence is not observed. This difference is interpreted as being due to the fact that local stresses arise in the nanocrystal/sapphire system and break chemical bonds at the interface between the phases, whereas in Al2O3 films stresses are relaxed.

Tetelbaum, D. I.; Mikhaylov, A. N.; Belov, A. I.; Ershov, A. V.; Pitirimova, E. A.; Plankina, S. M.; Smirnov, V. N.; Kovalev, A. I.; Turan, R.; Yerci, S.; Finstad, T. G.; Foss, S.

2009-02-01

266

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

267

Enhanced photo-Fenton degradation of rhodamine B using graphene oxide-amorphous FePO4 as effective and stable heterogeneous catalyst.  

PubMed

A series of graphene oxide (GO)-FePO4 composites with different GO weight ratios (2.5%, 5%, 10%, w/w) were prepared using a simple precipitation process and were firstly used as heterogeneous photo-Fenton catalysts. FESEM images prove the loose structure of the 5GO-FePO4 composite. UV-vis analysis demonstrates that the introduction of GO could enhance solar energy utilization of the composites. Under visible light irradiation, the degradation rate of rhodamine B (RhB) by the 5GO-FePO4 composite was 2.87 times more than that by the pure FePO4 in the presence of hydrogen peroxide. The composite was highly effective for the degradation of RhB in a wide pH range of 2.18-10.40 with negligible iron leaching. Moreover, the composite still showed high catalytic activity after six cycles, which makes it a promising heterogeneous catalyst for wastewater treatment. The introduction of GO promotes the photo-Fenton reaction of GO-FePO4 via three roles: offering more active sites, increasing adsorption capacity and accelerating the Fe(3+)/Fe(2+) cycle by improving the utilization of solar energy. Our work may provide new insights for the development of new effective heterogeneous photo-Fenton catalyst. PMID:25768888

Guo, Sheng; Zhang, Gaoke; Yu, Jimmy C

2015-06-15

268

Structural amorphous steels.  

PubMed

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. PMID:15245095

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

2004-06-18

269

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

270

Amorphous silicon photovoltaic devices  

DOEpatents

This invention is a photovoltaic device comprising an intrinsic or i-layer of amorphous silicon and where the photovoltaic device is more efficient at converting light energy to electric energy at high operating temperatures than at low operating temperatures. The photovoltaic devices of this invention are suitable for use in high temperature operating environments.

Carlson, David E.; Lin, Guang H.; Ganguly, Gautam

2004-08-31

271

Identification of Defect Processes in Amorphous Materials Dr. Blair R. Tuttle  

E-print Network

Identification of Defect Processes in Amorphous Materials Dr. Blair R. Tuttle Associate Professor-electronics, which require a variety of amorphous oxide materials including low and high K dielectric alloys. In all of these examples, point defects limit the operation of devices, and defects prevent future improvements

Bjørnstad, Ottar Nordal

272

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

273

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

274

Amorphous Carbon Nanospheres  

SciTech Connect

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

None

2012-01-01

275

Amorphous Hydrocarbon Optical Properties  

NASA Astrophysics Data System (ADS)

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

Jones, Anthony

2015-03-01

276

Amorphous magnetic order  

Microsoft Academic Search

A review is given of the collinear and random magnetic structures which may be found in magnetically-concentrated amorphous solids. General consequences of a non-crystalline lattice on the atomic moments, exchange interactions and single-ion anisotropy are presented. Magnetic structures with one and two magnetic subnetworks are then described, taking examples from the literature of each type. Some discussion is also given

J. M. D. Coey

1978-01-01

277

DOI: 10.1002/zaac.201000430 Evidence for Tetrahedral Zinc in Amorphous In22xZnxSnxO3 (a-ZITO)  

E-print Network

conducting oxides; Transparent oxide semiconductor; Zinc indium tin oxide; Absorption spectroscopy; Zinc tetrahedra in a- Introduction Amorphous transparent conducting oxides (TCOs) and trans- parent oxide,[d] and Kenneth R. Poeppelmeier*[a] In Memory of Professor Hans Georg von Schnering Keywords: Transparent

Poeppelmeier, Kenneth R.

278

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

279

Hard magnetic bulk amorphous alloys  

Microsoft Academic Search

An amorphous phase in Ln-Fe-Al (Ln=Nd and Pr) systems is formed in wide composition ranges of 0 to 90 at% Fe and 0 to 93 at% Al by melt spinning. Ferromagnetic Ln90-xFexAl10 bulk amorphous alloys with high coercive force (iHc) at room temperature are obtained by copper mold casting. The maximum diameter of the cylindrical amorphous samples is 12 mm

A. Inoue; T. Zhang; A. Takeuchi

1997-01-01

280

Thermal oxidation of single crystalline aluminum nitride  

Microsoft Academic Search

Dry thermal oxidation of low defect density aluminum nitride single crystals was investigated by high resolution transmission electron microscopy (HRTEM) and electron energy loss spectroscopy (EELS). Oxidation at 800 °C produced an amorphous oxide layer. In the AlN near the interface were many dislocations, stacking faults and domain boundaries, molecular nitrogen and oxygen. Oxidation at 1000 °C produced a crystalline, epitaxial oxide

J.. Chaudhuri; L. Nyakiti; R. G. Lee; Z. Gu; J. H. Edgar; J. G. Wen

2007-01-01

281

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

282

Improving the performance of amorphous silicon photovoltaic modules  

Microsoft Academic Search

High-performance amorphous silicon solar cells require high-quality undoped hydrogenated amorphous silicon, a conductive p-layer or n-layer window, an effective light-trapping geometry such as textured tin oxide, a reflective back contact (e.g. silver), and low-contact resistance (less than 0.5 ohm sq cm). Requirements for high module-performance require low interconnect resistance (e.g. less than 0.005 ohm sq cm for the Al-SnO2 contact),

D. E. Carlson; R. R. Arya; A. Catalano; R. V. D'Aiello; C. R. Dickson; J ODOWD; R OSWALD

1987-01-01

283

Crystallization of amorphous bismuth titanate  

Microsoft Academic Search

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

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

2001-01-01

284

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

285

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

286

Molecular dynamics in amorphous ergocalciferol  

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

287

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

288

Structural Amorphous Metals Amorphous Steels and Ultra-Strong Light Metals  

Microsoft Academic Search

Amorphous metals are multicomponent alloys and are naturally complex. In recent years, significant progress in the design of bulk amorphous metals and fundamental understanding of the amorphous state has been achieved. In this talk, we will report current interdisciplinary studies of structural amorphous metals, with a focus on the synthesis, properties, and basic knowledge. Recent results on amorphous steels and

Joseph Poon

2005-01-01

289

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

290

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

291

Raman Spectroscopy of Amorphous Carbon  

SciTech Connect

Amorphous carbon is an elemental form of carbon with low hydrogen content, which may be deposited in thin films by the impact of high energy carbon atoms or ions. It is structurally distinct from the more well-known elemental forms of carbon, diamond and graphite. It is distinct in physical and chemical properties from the material known as diamond-like carbon, a form which is also amorphous but which has a higher hydrogen content, typically near 40 atomic percent. Amorphous carbon also has distinctive Raman spectra, whose patterns depend, through resonance enhancement effects, not only on deposition conditions but also on the wavelength selected for Raman excitation. This paper provides an overview of the Raman spectroscopy of amorphous carbon and describes how Raman spectral patterns correlate to film deposition conditions, physical properties and molecular level structure.

Tallant, D.R.; Friedmann, T.A.; Missert, N.A.; Siegal, M.P.; Sullivan, J.P.

1998-01-01

292

Resonance vibration of amorphous SiO2 nanowires driven by mechanical or electrical field excitation  

E-print Network

; this value is lower than the commonly accepted value of 72 GPa for fused silicon oxide glass fibers. For some-dimensional nanosize rods, tubes, and whiskers.1­4 Such work has fo- cused on resonant excitation of naturally and different optoelectronic de- vices. Recently, amorphous silicon oxide NW's have been syn- thesized

293

Surface Science Letters Formation mechanisms of polar and non-polar amorphous  

E-print Network

is determined by the stoichiometry of the interface bonding as opposed to charged defect formation. Ã? 2008) technology requires substituting the traditional gate oxide, SiO2, with amorphous high-j dielectrics, which- ductors without a high density of defects. Whereas many previ- ously reported simulations of oxide

Kummel, Andrew C.

294

Luminescence effect in amorphous PLT  

Microsoft Academic Search

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

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

2005-01-01

295

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

296

Dissolution rates of amorphous Al- and Fe-phosphates and their relevance to phosphate mobility on Mars  

NASA Astrophysics Data System (ADS)

Phosphate is an essential element for life on Earth, and therefore if life exists or ever existed on Mars it may have required phosphate. Amorphous Al- and Fe-phosphates rapidly precipitate from acidic solutions and amorphous Al-phosphates likely control phosphate concentrations in some natural waters on Earth. Amorphous phases may be even more important on Mars than on Earth, and amorphous phosphates are therefore likely important in the phosphate cycle on Mars. Despite this importance, however, few dissolution rates exist for amorphous Al- and Fe- phosphates. In this study, dissolution rates of amorphous Al- and Fe-phosphates were measured in flow-through reactors from steady state concentrations of Al, Fe and P. A pH--dependent rate law was calculated from the dissolution rates log R = log k -- npH, where R is the dissolution rate, k is intrinsic rate constant and n is the rate dependence on pH. For amorphous Al-phosphate, log k = -6.539 +/- 1.529, and n = 2.391 +/- 0.493. For amorphous Fe-phosphate, log k = -13.031 +/- 0.558, and n = 1.376 +/- 0.221. Amorphous Al-phosphate dissolves stoichiometrically under all conditions, and amorphous Fe-phosphate dissolves non-stoichiometrically, approaching stoichiometric dissolution as pH decreases, due potentially to Fe-oxides precipitating and armoring grain surfaces. Perhaps due to these effects, amorphous Al-phosphate dissolution rates are approximately three orders of magnitude faster than amorphous Fe-phosphate dissolution rates. Amorphous Al-phosphate dissolution rates measured in this study are also faster than published variscite dissolution rates. Dissolution rates of amorphous Al- and Fe-phosphates in this study therefore imply rapid phosphate release into acidic environments, suggesting phosphate mobility under Mars-relevant conditions.

Tu, Valerie M.

297

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

298

Magnetic Behavior and Chemical Shift of Amorphous Cr2O3  

NASA Astrophysics Data System (ADS)

The chemical shift in cristalline and amorphous Cr2O3 was determined from the X-ray absorption Cr K edge spectra. The measurements of the temperature dependence of the reciprocal susceptibility between 100 and 1200 K show an antiferromagnetic behavior for the cristalline sample, with the Neel temperature at 318 K, and a linear dependence (Curie-Weiss law) with ?p<0, for the amorphous oxide.

Pop, I.; Andrecut, M.; Burda, I.; Oprea, C.; Andrecut, C.

299

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

300

ESCA studies of sputtered amorphous Co?Nb?Zr film  

NASA Astrophysics Data System (ADS)

Detailed ESCA studies of sputtered amorphous Co?Nb?Zr film, carried out after a period of one year, reveal that Zr oxidises violently and migrates to the surface. Oxidation of Nb is limited to top layers (˜ 300 Å) while Co remains metallic through out the film. The film beyond 600 Å down to the substrate interface is quite homogeneous. Such information could be of importance in some applications of these materials.

Padalia, B. D.; Mehta, P. K.; Prasad, Shiva; Kulkarni, S. K.; Krishnan, R.

1990-09-01

301

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

302

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

303

Amorphous-diamond electron emitter  

DOEpatents

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

Falabella, Steven (Livermore, CA)

2001-01-01

304

Identification of amorphous silicon residues in a low-power CMOS technology  

NASA Astrophysics Data System (ADS)

A large variety of physical analysis techniques are used in the semiconductor industry to identify defects impacting yield or reliability. Identification of a defect often requires the combined use of several techniques to give a clear understanding of the defect nature. In the present study, several microscopy techniques (SEM, TEM, Analytical-TEM, AFM and FIB) have been intensively used to identify the origin of residues observed on the edge of large active areas in a low power CMOS technology. A KLA automatic inspection system has been used for locating and quantifying the defects. It has been shown that the defects are related to amorphous silicon residues whose origin is related to the gate deposition process. In the process, the polysilicon gate is deposited in two steps. A first thin amorphous silicon layer is deposited, through which the Vt implant is done, followed by the deposition of a thick polysilicon layer. Analysis of defaults showed that the residues are related to a non-uniform thin oxide layer located between the thick polysilicon layer and the underlying thin amorphous silicon, which halts the polysilicon gate etch. Thicker native oxide on amorphous silicon due to humidity or drying spots is the presumed source of the thin non-uniform oxide. Increasing the HF dip before the polysilicon deposition eliminated almost all residues. No negative effect on the oxide quality or other electrical parameter has been observed. Eliminating altogether the amorphous-Si gate deposition process is an even more robust solution.

Acovic, Alexandre; Buffat, Philippe A.; Brander, Paul; Jacob, Peter J.; Jeandupeux, Oliver; Marsico, Vittorio; Rosenfeld, Daniel; Moser, Jacques; Kohli, Markus; Fluckiger, Roger; Belkacem, Karim; Fazan, Pierre C.

1999-08-01

305

Iron oxidation and precipitation of ferric hydroxysulfates by resting Thiobacillus ferrooxidans cells  

Microsoft Academic Search

The oxidation of ferrous ions, in acid solution, by resting suspensions of Thiobacillus ferrooxidans produced sediments consisting of crystalline jarosites, amorphous ferric hydroxysulfates, or both. These products differed conspicuously in chemical composition and infrared spectra from precipitates formed by abiotic oxidation under similar conditions. The amorphous sediments, produced by bacterial oxidation, exhibited a distinctive fibroporous microstructure when examined by scanning

N. Lazaroff; W. Sigal; A. Wasserman

1982-01-01

306

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

307

Annealing studies of amorphous alloys  

SciTech Connect

Amorphous films of the alloys Ni-Nb, Ni-Mo, Mo-Si, and W-Si were sputter deposited on single-crystal semiconductor substrates. One-hour crystallization temperatures of the films were determined to within +-25/sup 0/C by annealing and x-ray diffraction measurements. Interdiffusion between Au or Cu overlayers and the amorphous films were studied by annealing combined with Auger Electron Spectroscopy (AES) profiling, and by Rutherford Backscatter (RBS) analysis. Supplementary measurements used to study structural relaxation and crystallization included resistivity as a function of temperature; DTA and DSC; and electron microscopy.

Wiley, J.D.; Perepezko, J.H.; Nordman, J.E.

1983-04-01

308

Amorphous nanoparticles — Experiments and computer simulations  

NASA Astrophysics Data System (ADS)

The data obtained by both experiments and computer simulations concerning the amorphous nanoparticles for decades including methods of synthesis, characterization, structural properties, atomic mechanism of a glass formation in nanoparticles, crystallization of the amorphous nanoparticles, physico-chemical properties (i.e. catalytic, optical, thermodynamic, magnetic, bioactivity and other properties) and various applications in science and technology have been reviewed. Amorphous nanoparticles coated with different surfactants are also reviewed as an extension in this direction. Much attention is paid to the pressure-induced polyamorphism of the amorphous nanoparticles or amorphization of the nanocrystalline counterparts. We also introduce here nanocomposites and nanofluids containing amorphous nanoparticles. Overall, amorphous nanoparticles exhibit a disordered structure different from that of corresponding bulks or from that of the nanocrystalline counterparts. Therefore, amorphous nanoparticles can have unique physico-chemical properties differed from those of the crystalline counterparts leading to their potential applications in science and technology.

Hoang, Vo Van; Ganguli, Dibyendu

2012-09-01

309

Mechanics of amorphous polymers and polymer gels  

E-print Network

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

Chester, Shawn Alexander

2011-01-01

310

21 CFR 73.1991 - Zinc oxide.  

Code of Federal Regulations, 2010 CFR

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

2010-04-01

311

Syntax-Directed Amorphous Slicing Sebastian Danicic  

E-print Network

Syntax-Directed Amorphous Slicing Sebastian Danicic Mark Harman Malcolm Munro Dave Binkley Mohammed of the original on the variables of interest. Unlike syntax{preserving slices, amorphous slices need not preserve a projection of the syntax of a program. This makes the task of amorphous slice construction harder

Singer, Jeremy

312

Bioclimatologie Utilisation des cellules au silicium amorphe  

E-print Network

Bioclimatologie Utilisation des cellules au silicium amorphe pour la mesure du rayonnement simulation et la confrontation expérimentale ccellules au silicium amorphe par rapport à celles des capteurs existants montrent l'intérêt des cellules au silicium amorphe pour la mesure du

Paris-Sud XI, Université de

313

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

314

Intrinsic delay of permeable base transistor  

SciTech Connect

Permeable base transistors (PBTs) fabricated by vacuum deposition or solution process have the advantages of easy fabrication and low power operation and are a promising device structure for flexible electronics. Intrinsic delay of PBT, which characterizes the speed of the transistor, is investigated by solving the three-dimensional Poisson equation and drift-diffusion equation self-consistently using finite element method. Decreasing the emitter thickness lowers the intrinsic delay by improving on-current, and a thinner base is also preferred for low intrinsic delay because of fewer carriers in the base region at off-state. The intrinsic delay exponentially decreases as the emitter contact Schottky barrier height decreases, and it linearly depends on the carrier mobility. With an optimized emitter contact barrier height and device geometry, a sub-nano-second intrinsic delay can be achieved with a carrier mobility of ?10?cm{sup 2}/V/s obtainable in solution processed indium gallium zinc oxide, which indicates the potential of solution processed PBTs for GHz operations.

Chen, Wenchao; Guo, Jing [Department of Electrical and Computer Engineering, University of Florida, Gainesville, Florida 32611 (United States); So, Franky [Department of Material Science and Engineering, University of Florida, Gainesville, Florida 32611 (United States)

2014-07-28

315

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

316

Amorphous Program Slicing Mark Harman  

E-print Network

Amorphous Program Slicing Mark Harman Brunel University, Uxbridge, Middlesex, UB8 3PH, UK. David [De Lucia et al., 1996], [Harman and Danicic, 1997] #15; Maintenance [Gallagher and Lyle, 1991] #15 and Gallagher, 1996], Har- man and Hierons [Harman and Hierons, 2001] and De Lucia [De Lucia, 2001] survey

Singer, Jeremy

317

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

318

The reliability and stability of multijunction amorphous silicon PV modules  

SciTech Connect

Solarex is developing a manufacturing process for the commercial production of 8 ft{sup 2} multijunction amorphous silicon (a-Si) PV modules starting in 1996. The device structure used in these multijunction modules is: glass/textured tin oxide/p-i-n/p-i-n/ZnO/Al/EVA/Tedlar where the back junction of the tandem structure contains an amorphous silicon germanium alloy. As an interim step, 4 ft{sup 2} multijunction modules have been fabricated in a pilot production mode over the last several months. The distribution of initial conversion efficiencies for an engineering run of 67 modules (4 ft{sup 2}) is shown. Measurements recently performed at NREL indicate that the actual efficiencies are about 5% higher than those shown, and thus exhibit an average initial conversion efficiency of about 9.5%. The data indicates that the process is relatively robust since there were no modules with initial efficiencies less than 7.5%.

Carlson, D.E. [Solarex, Newtown, PA (United States)

1995-11-01

319

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

320

Amorphous metal-organic frameworks.  

PubMed

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

Bennett, Thomas D; Cheetham, Anthony K

2014-05-20

321

Impedance spectroscopic analysis on effects of partial oxidation of TiN bottom electrode and microstructure of amorphous and crystalline HfO2 thin films on their bipolar resistive switching  

NASA Astrophysics Data System (ADS)

The electrical resistance switching (RS) properties of amorphous HfO2 (a-HfO2) and crystalline HfO2 (c-HfO2) thin films grown on a TiN substrate via atomic layer deposition were examined using DC current-voltage (I-V) sweep and AC impedance spectroscopic (IS) analyses. The rapid thermal annealing of the a-HfO2 film at 500 °C under a N2 atmosphere for 5 min crystallized the HfO2 film and induced an interfacial TiON barrier layer. The a-HfO2 sample showed fluent bipolar RS performance with a high on/off ratio (~500), whereas the c-HfO2 sample showed a much lower on/off ratio (<~10), but its switching uniformity was better than that of a-HfO2. Such critical differences can be mainly attributed to the absence and presence of the TiON barrier layer in the a-HfO2 and c-HfO2 samples, respectively. The AC IS especially enabled the resistance states of the HfO2/Pt interface and the HfO2/TiN interface to be separately examined during one complete switching cycle of each sample. Although the Pt/c-HfO2 interface has a Schottky barrier in the pristine state, it disappeared once the c-HfO2 was electroformed and was not recovered even after the reset step. In contrast, the Pt/a-HfO2 interface partly recovered the Schottky barrier after the reset.

Yoon, Ji-Wook; Yoon, Jung Ho; Lee, Jong-Heun; Hwang, Cheol Seong

2014-05-01

322

Impedance spectroscopic analysis on effects of partial oxidation of TiN bottom electrode and microstructure of amorphous and crystalline HfO2 thin films on their bipolar resistive switching.  

PubMed

The electrical resistance switching (RS) properties of amorphous HfO2 (a-HfO2) and crystalline HfO2 (c-HfO2) thin films grown on a TiN substrate via atomic layer deposition were examined using DC current-voltage (I-V) sweep and AC impedance spectroscopic (IS) analyses. The rapid thermal annealing of the a-HfO2 film at 500 °C under a N2 atmosphere for 5 min crystallized the HfO2 film and induced an interfacial TiON barrier layer. The a-HfO2 sample showed fluent bipolar RS performance with a high on/off ratio (? 500), whereas the c-HfO2 sample showed a much lower on/off ratio (

Yoon, Ji-Wook; Yoon, Jung Ho; Lee, Jong-Heun; Hwang, Cheol Seong

2014-06-21

323

Amorphous Silicon Static Induction Transistor  

Microsoft Academic Search

A hydrogenated amorphous silicon (a-Si:H) Schottky-gate static induction transistor (SIT) is proposed and its characteristics are calculated for the case that the gap-state distribution in a-Si:H is constant near the Fermi level. It is found that an a-Si:H SIT with a gate spacing of about 5 mum can yield a sufficiently high ON\\/OFF current ratio of more than 108 when

Masato Ueda; Masataka Hirose; Yukio Osaka

1985-01-01

324

Density functional theory simulations of amorphous high-? oxides on a compound semiconductor alloy: a-Al2O3/InGaAs(100)-(4×2), a-HfO2/InGaAs(100)-(4×2), and a-ZrO2/InGaAs(100)-(4×2).  

PubMed

The structural properties of a-Al(2)O(3)?In(0.5)Ga(0.5)As, a-HfO(2)?In(0.5)Ga(0.5)As, and a-ZrO(2)?In(0.5)Ga(0.5)As interfaces were investigated by density-functional theory (DFT) molecular dynamics (MD) simulations. Realistic amorphous a-Al(2)O(3), a-HfO(2), and a-ZrO(2) samples were generated using a hybrid classical-DFT MD "melt-and-quench" approach and tested against the experimental properties. For each stack type, two systems with different initial oxide cuts at the interfaces were investigated. All stacks were free of midgap states, but some had band-edge states which decreased the bandgaps by 0%-40%. The band-edge states were mainly produced by deformation, intermixing, and bond-breaking, thereby creating improperly bonded semiconductor atoms. The interfaces were dominated by metal-As and O-In?Ga bonds which passivated the clean surface dangling bonds. The valence band-edge states were mainly localized at improperly bonded As atoms, while conduction band-edge states were mainly localized at improperly bonded In and Ga atoms. The DFT-MD simulations show that electronically passive interfaces can be formed between high-? oxides dielectrics and InGaAs if the processing does not induce defects because on a short time scale the interface spontaneously forms electrically passive bonds as opposed to bonds with midgap states. PMID:22225179

Chagarov, Evgueni A; Kummel, Andrew C

2011-12-28

325

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

326

Structural and dielectric properties of amorphous ZrO2 and HfO2 Davide Ceresoli* and David Vanderbilt  

E-print Network

Structural and dielectric properties of amorphous ZrO2 and HfO2 Davide Ceresoli* and David September 2006 Zirconia ZrO2 and hafnia HfO2 are leading candidates for replacing SiO2 as the gate insulator in comple- mentary metal-oxide semiconductor technology. Amorphous versions of these materials a-ZrO2 and a

Vanderbilt, David

327

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

Microsoft Academic Search

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

Dayong Luo; Bradley D. Anderson

2006-01-01

328

Multiwalled Carbon Nanotubes Catalytically Grown from Amorphous Silica Films Deposited by Combustion CVD  

Microsoft Academic Search

Homogeneous mixtures containing iron oxide and amorphous SiO2 were obtained through the co-deposition of these oxides via combustion chemical vapor deposition technique (CCVD). This technique allows the deposition of thin films with low-cost precursors and equipments. After deposition, the deposited samples were submitted to a heat treatment in an atmosphere composed of natural gas and H2 at 1000°C, in order

M. D. Lima; S. S. Stein; R. Bonadiman; M. J. De Andrade; C. P. Bergmann

2007-01-01

329

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

330

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

331

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

332

Crystallization kinetics of amorphous ferroelectric films  

Microsoft Academic Search

The kinetic parameters characterizing the crystallite growth during annealing of PZT and PGO amorphous films were determined by proposed mathematical treatment of in situ elastic light scattering data.

V. Ya. Shur; S. A. Negashev; A. L. Subbotin; E. A. Borisova

1997-01-01

333

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

334

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

335

Bias-Stress-Stable Solution-Processed Oxide Thin Film Transistors  

E-print Network

Bias-Stress-Stable Solution-Processed Oxide Thin Film Transistors Youngmin Jeong, Changdeuck Bae We generated a novel amorphous oxide semiconductor thin film transistor (AOS-TFT) that has exellent-solution-processed transparent flexible transistors with air-stable, reproducible device characteristics. KEYWORDS: amorphous

Cao, Guozhong

336

Preparation of amorphous sulfide sieves  

DOEpatents

The present invention involves methods and compositions for synthesizing catalysts/porous materials. In some embodiments, the resulting materials are amorphous sulfide sieves that can be mass-produced for a variety of uses. In some embodiments, methods of the invention concern any suitable precursor (such as thiomolybdate salt) that is exposed to a high pressure pre-compaction, if need be. For instance, in some cases the final bulk shape (but highly porous) may be same as the original bulk shape. The compacted/uncompacted precursor is then subjected to an open-flow hot isostatic pressing, which causes the precursor to decompose and convert to a highly porous material/catalyst.

Siadati, Mohammad H.; Alonso, Gabriel; Chianelli, Russell R.

2006-11-07

337

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

338

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

339

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

NASA Astrophysics Data System (ADS)

Threshold voltage variability (?Vth) due to the polycrystalline nature of current metal gates has been identified as a problem in future generations of complementary metal oxide semiconductor (CMOS) devices. Amorphous metal Ta40W40Si10C10 gates are introduced in this work as a remedy. It was found that Ta-W-Si-C films remain amorphous at temperatures as high as 1120 °C, have n-type work functions, and are stable on HfO2. This alloy is a promising gate-first compatible material that has the potential to significantly reduce ?Vth.

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

2010-11-01

340

Radiation Response of Rhombohedral Oxides  

SciTech Connect

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

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

1997-12-31

341

Spin waves in amorphous Heisenberg ferromagnets  

Microsoft Academic Search

A self-consistent random phase approximation treatment of the amorphous Heisenberg ferromagnet is presented. The calculations are performed in the limit of small amorphicity. Results concerning the low temperature behaviour are given. Stiffness constant, life-time of the spin wave excitations and magnetization at low temperatures are discussed.

W. Brauneck; D. Wagner; E. Ziemniak

1987-01-01

342

Thermochemical studies on amorphous calcium phosphate  

Microsoft Academic Search

Previous studies have indicated that synthetically-precipitated amorphous calcium phosphate, even though not a periodically regular structure, possesses a chemically definable local unit of structure. The present paper is a report of thermochemical studies performed to more clearly define this local chemical unit. Upon ignition in the absence of water, freezedried amorphous calcium phosphate preparations converted into crystalline ?-and\\/or ?-tricalcium phosphates.

E. D. EAglES

1970-01-01

343

Method of making amorphous metal composites  

DOEpatents

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

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

1982-01-01

344

Structures and phase transitions of amorphous ices  

Microsoft Academic Search

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

Ichiro Okabe; Hideki Tanaka; Koichiro Nakanishi

1996-01-01

345

Solid-state diffusion in amorphous zirconolite  

NASA Astrophysics Data System (ADS)

We discuss how structural disorder and amorphization affect solid-state diffusion, and consider zirconolite as a currently important case study. By performing extensive molecular dynamics simulations, we disentangle the effects of amorphization and density, and show that a profound increase of solid-state diffusion takes place as a result of amorphization. Importantly, this can take place at the same density as in the crystal, representing an interesting general insight regarding solid-state diffusion. We find that decreasing the density in the amorphous system increases pre-factors of diffusion constants, but does not change the activation energy in the density range considered. We also find that atomic species in zirconolite are affected differently by amorphization and density change. Our microscopic insights are relevant for understanding how solid-state diffusion changes due to disorder and for building predictive models of operation of materials to be used to encapsulate nuclear waste.

Yang, C.; Zarkadoula, E.; Dove, M. T.; Todorov, I. T.; Geisler, T.; Brazhkin, V. V.; Trachenko, K.

2014-11-01

346

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

347

Improving the performance of amorphous silicon photovoltaic modules  

NASA Astrophysics Data System (ADS)

High-performance amorphous silicon solar cells require high-quality undoped hydrogenated amorphous silicon, a conductive p-layer or n-layer window, an effective light-trapping geometry such as textured tin oxide, a reflective back contact (e.g. silver), and low-contact resistance (less than 0.5 ohm sq cm). Requirements for high module-performance require low interconnect resistance (e.g. less than 0.005 ohm sq cm for the Al-SnO2 contact), large percentage of active area, and good uniformity of material properties over large areas. New developments such as superlattice doped layers and improved tin-oxide texturing have led to efficiencies as high as 10.l9 percent in small cells (1 sq cm). Processing improvements have led to efficiencies of 8.1 percent in small cells (1 sq cm). Processing improvements have led to efficiencies of 8.1 percent in l-sq ft modules patterned entirely by laser scribing.

Carlson, D. E.; Arya, R. R.; Catalano, A.; D'Aiello, R. V.; Dickson, C. R.

1987-08-01

348

Research on stable, high-efficiency amorphous silicon multijunction modules  

SciTech Connect

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

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

1993-02-01

349

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

SciTech Connect

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

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

2010-01-15

350

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

351

Locomotion of Amorphous Surface Robots  

NASA Technical Reports Server (NTRS)

An amorphous robot includes a compartmented bladder containing fluid, a valve assembly, and an outer layer encapsulating the bladder and valve assembly. The valve assembly draws fluid from a compartment(s) and discharges the drawn fluid into a designated compartment to displace the designated compartment with respect to the surface. Another embodiment includes elements each having a variable property, an outer layer that encapsulates the elements, and a control unit. The control unit energizes a designated element to change its variable property, thereby moving the designated element. The elements may be electromagnetic spheres with a variable polarity or shape memory polymers with changing shape and/or size. Yet another embodiment includes an elongated flexible tube filled with ferrofluid, a moveable electromagnet, an actuator, and a control unit. The control unit energizes the electromagnet and moves the electromagnet via the actuator to magnetize the ferrofluid and lengthen the flexible tube.

Bradley, Arthur T. (Inventor)

2014-01-01

352

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.

353

Amorphous metal alloys produced by mechanical alloying  

SciTech Connect

Mechanical alloying is a powder metallurgy method used in commercial production of high temperature superalloys. Under specific conditions, mechanical alloying allows the synthesis of amorphous metal alloys from mixtures of pure metal powders or from the powders of intermetallic compounds. Because the amorphizing transformation during mechanical alloying is a solid state reaction, most of the difficulties related to the amorphization by rapid solidification of melts can be avoided. Mechanical alloying allows the synthesis of amorphous alloys from metals with high melting temperatures and the resulting alloys have interesting properties such as high hardness and high crystallization temperatures. We used mechanical alloying for the synthesis of amorphous alloys in the binary alloy systems Nl-Sn, Nb-Si and Al-Hf. The amorphous alloy powders were characterized by x-ray diffraction, differential scanning calorimetry, scanning and transmission electron microscopy and hardness measurements. Produced alloys were compacted by hot pressing and the obtained compacts were characterized by x-ray diffraction, density and hardness measurements and by optical and scanning electron microscopy. The results of the amorphization and compaction studies are presented and discussed together with the characteristics of the mechanical alloying process. 15 refs., 5 figs.

Tiainen, T.J.; Schwarz, R.B.

1989-01-01

354

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

355

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

356

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

357

Atomistic modeling of ion beam induced amorphization in silicon  

Microsoft Academic Search

We have developed an atomistic model to describe ion beam induced amorphization in silicon. The building block for the amorphous phase is the bond defect or IV pair, whose stability increases with the number of surrounding IV pairs. This feature explains the regrowth behaviour of different damage topologies and the kinetics of the crystalline to amorphous transition. Amorphous regions start

Lourdes Pelaz; Luis A. Marqués; Maria Aboy; Juan Barbolla

2004-01-01

358

Amorphous to Amorphous Form Transitions of Water Ice and Astrophysical Implications  

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

359

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

360

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

NASA Astrophysics Data System (ADS)

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

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

2011-03-01

361

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

362

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

363

Super adsorption capability from amorphousization of metal oxide nanoparticles for dye removal  

PubMed Central

Transitional metal oxide nanoparticles as advanced environment and energy materials require very well absorption performance to apply in practice. Although most metal oxides are based on crystalline, high activities can also be achieved with amorphous phases. Here, we reported the adsorption behavior and mechanism of methyl blue (MB) on the amorphous transitional metal oxide (Fe, Co and Ni oxides) nanoparticles, and we demonstrated that the amorphousization of transitional metal oxide (Fe, Co and Ni oxides) nanoparticles driven by a novel process involving laser irradiation in liquid can create a super adsorption capability for MB, and the maximum adsorption capacity of the fabricated NiO amorphous nanostructure reaches up to 10584.6?mgg?1, the largest value reported to date for all MB adsorbents. The proof-of-principle investigation of NiO amorphous nanophase demonstrated the broad applicability of this methodology for obtaining new super dyes adsorbents. PMID:25761448

Li, L. H.; Xiao, J.; Liu, P.; Yang, G. W.

2015-01-01

364

Super adsorption capability from amorphousization of metal oxide nanoparticles for dye removal  

NASA Astrophysics Data System (ADS)

Transitional metal oxide nanoparticles as advanced environment and energy materials require very well absorption performance to apply in practice. Although most metal oxides are based on crystalline, high activities can also be achieved with amorphous phases. Here, we reported the adsorption behavior and mechanism of methyl blue (MB) on the amorphous transitional metal oxide (Fe, Co and Ni oxides) nanoparticles, and we demonstrated that the amorphousization of transitional metal oxide (Fe, Co and Ni oxides) nanoparticles driven by a novel process involving laser irradiation in liquid can create a super adsorption capability for MB, and the maximum adsorption capacity of the fabricated NiO amorphous nanostructure reaches up to 10584.6 mgg-1, the largest value reported to date for all MB adsorbents. The proof-of-principle investigation of NiO amorphous nanophase demonstrated the broad applicability of this methodology for obtaining new super dyes adsorbents.

Li, L. H.; Xiao, J.; Liu, P.; Yang, G. W.

2015-03-01

365

Super adsorption capability from amorphousization of metal oxide nanoparticles for dye removal.  

PubMed

Transitional metal oxide nanoparticles as advanced environment and energy materials require very well absorption performance to apply in practice. Although most metal oxides are based on crystalline, high activities can also be achieved with amorphous phases. Here, we reported the adsorption behavior and mechanism of methyl blue (MB) on the amorphous transitional metal oxide (Fe, Co and Ni oxides) nanoparticles, and we demonstrated that the amorphousization of transitional metal oxide (Fe, Co and Ni oxides) nanoparticles driven by a novel process involving laser irradiation in liquid can create a super adsorption capability for MB, and the maximum adsorption capacity of the fabricated NiO amorphous nanostructure reaches up to 10584.6?mgg(-1), the largest value reported to date for all MB adsorbents. The proof-of-principle investigation of NiO amorphous nanophase demonstrated the broad applicability of this methodology for obtaining new super dyes adsorbents. PMID:25761448

Li, L H; Xiao, J; Liu, P; Yang, G W

2015-01-01

366

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

367

Tritiated amorphous silicon films and devices  

Microsoft Academic Search

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

Tome Kosteski

2001-01-01

368

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

369

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

370

Radiation-Induced Amorphization of Crystalline Ice  

NASA Technical Reports Server (NTRS)

We study radiation-induced amorphization of crystalline ice, ana lyzing the resu lts 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 micrometer 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 refl ectance absorption spectra measured between 1.4 and 2.2 micrometers for amorphous and crystalline ices irradiated with 225 keV protons at 80 K. We found that, after irradiation with 10(exp 15) protons per square centimeter, 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.

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

2009-01-01

371

Cathodoluminescence microanalysis of silica and amorphized quartz  

NASA Astrophysics Data System (ADS)

Cathodoluminescence (CL) techniques are used to investigate the defect structures of pure synthetic silicon dioxide (SiO2) polymorphs. Pure, synthetic Types I, II, III and IV amorphous SiO2 polymorphs, pure, synthetic crystal ?-SiO2 and pure, synthetic amorphized crystal ?-SiO2 have been investigated and their characteristic defects have been determined and compared. The CL emission from pure SiO2 polymorphs is generally related to local point defects in the tetrahedrally coordinated SiO2 host lattice. A range of CL emissions associated with non bridging oxygen defects, oxygen deficient defects and the radiative recombination of self trapped excitons are observed from both the pure synthetic crystal and amorphous SiO2 polymorphs. In addition CL emissions associated with residual concentrations of Aluminium impurities are also observed from ?-SiO2 (quartz) and Type I and II a-SiO2 (fused quartz). Localised amorphous micro-volumes may exist within natural ?-SiO2 due to the presence of a high concentration of pre-existing or induced defects. Amorphization of ?-SiO2 diminishes the difference between the defect structures and associated CL from ?-SiO2 and a-SiO2. Thus CL investigation of the defect structure of a-SiO2 polymorphs provides useful insight into the microstructure of amorphized ?-SiO2.

Stevens-Kalceff, Marion A.

2013-06-01

372

Amorphization of ceramics by ion beams  

SciTech Connect

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

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

1984-01-01

373

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

374

Studies on activated carbon capacitor materials loaded with different amounts of ruthenium oxide  

E-print Network

Studies on activated carbon capacitor materials loaded with different amounts of ruthenium oxide M Received 5 August 2000; accepted 29 August 2000 Abstract Ruthenium oxide±carbon composites with different reserved. Keywords: Carbon; Ruthenium oxide; Temperature treatment; Composites; Amorphous Ru oxide

375

Impact of solid-phase crystallization of amorphous silicon on the chemical structure of the buried Si\\/ZnO thin film solar cell interface  

Microsoft Academic Search

The chemical interface structure between phosphorus-doped hydrogenated amorphous silicon and aluminum-doped zinc oxide thin films is investigated with soft x-ray emission spectroscopy (XES) before and after solid-phase crystallization (SPC) at 600 °C. In addition to the expected SPC-induced phase transition from amorphous to polycrystalline silicon, our XES data indicates a pronounced chemical interaction at the buried Si\\/ZnO interface. In particular,

M. Bär; M. Wimmer; R. G. Wilks; M. Roczen; D. Gerlach; F. Ruske; K. Lips; B. Rech; L. Weinhardt; M. Blum; S. Pookpanratana; S. Krause; Y. Zhang; C. Heske; W. Yang; J. D. Denlinger

2010-01-01

376

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

NASA Technical Reports Server (NTRS)

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

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

2013-01-01

377

Characterization of High- k Gate Dielectric with Amorphous Nanostructure  

NASA Astrophysics Data System (ADS)

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

Bahari, Ali; Gholipur, Reza

2013-12-01

378

White electroluminescence from hydrogenated amorphous-SiNx thin films  

NASA Astrophysics Data System (ADS)

White electroluminescence (EL) was observed from hydrogenated amorphous-SiNx-based light-emitting device. Silicon nitride thin films were deposited on the indium-tin-oxide (ITO)-coated glass substrate by plasma enhanced chemical vapor deposition method with a mixture of Ar-diluted 5% SiH4 and pure N2 gases, in the ratio 2 to 1. Measured x value of the film is 0.56, and the corresponding photoluminescence of a-SiN0.56:H thin film exhibited a red-infrared spectrum, centered at 630 nm. The layer structure of the EL device is ITO/a-SiN0.56:H (80 nm)/Al, with light emitting from the ITO layer, recognizable by the naked eye in the dark, under the 14 V forward bias conditions. White EL spectra from ˜400 to 750 nm, with a central peak at 560 nm, were observed in the hydrogenated amorphous silicon nitride EL device. A carrier transport mechanism was suggested, and the EL was attributed to the recombination of carriers through the luminescent states.

Pei, Zingway; Chang, Y. R.; Hwang, H. L.

2002-04-01

379

Fabrication of an amorphous carbon tube from copper oxide whisker  

Microsoft Academic Search

The reduction process of tenorite whiskers grown on a copper mesh by heating in vacuum has been directly observed using a transmission electron microscope equipped with a real-time video-recording system. The coating of the carbon layer and reduction of the tenorite whisker covered with a carbon layer have also been captured in real time on video images. The growth process

Hitoshi Suzuki; Naoki Fukuzawa; Toshiaki Tanigaki; Takeshi Sato; Osamu Kido; Yuki Kimura; Chihiro Kaito

2002-01-01

380

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

381

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

382

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

383

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

384

An amorphous solid state of biogenic secondary organic aerosol particles.  

PubMed

Secondary organic aerosol (SOA) particles are formed in the atmosphere from condensable oxidation products of anthropogenic and biogenic volatile organic compounds (VOCs). On a global scale, biogenic VOCs account for about 90% of VOC emissions and of SOA formation (90?billion kilograms of carbon per year). SOA particles can scatter radiation and act as cloud condensation or ice nuclei, and thereby influence the Earth's radiation balance and climate. They consist of a myriad of different compounds with varying physicochemical properties, and little information is available on the phase state of SOA particles. Gas-particle partitioning models usually assume that SOA particles are liquid, but here we present experimental evidence that they can be solid under ambient conditions. We investigated biogenic SOA particles formed from oxidation products of VOCs in plant chamber experiments and in boreal forests within a few hours after atmospheric nucleation events. On the basis of observed particle bouncing in an aerosol impactor and of electron microscopy we conclude that biogenic SOA particles can adopt an amorphous solid-most probably glassy-state. This amorphous solid state should provoke a rethinking of SOA processes because it may influence the partitioning of semi-volatile compounds, reduce the rate of heterogeneous chemical reactions, affect the particles' ability to accommodate water and act as cloud condensation or ice nuclei, and change the atmospheric lifetime of the particles. Thus, the results of this study challenge traditional views of the kinetics and thermodynamics of SOA formation and transformation in the atmosphere and their implications for air quality and climate. PMID:20944744

Virtanen, Annele; Joutsensaari, Jorma; Koop, Thomas; Kannosto, Jonna; Yli-Pirilä, Pasi; Leskinen, Jani; Mäkelä, Jyrki M; Holopainen, Jarmo K; Pöschl, Ulrich; Kulmala, Markku; Worsnop, Douglas R; Laaksonen, Ari

2010-10-14

385

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

386

Crystallization of amorphous Zr-Be alloys  

NASA Astrophysics Data System (ADS)

The thermal stability and structure of binary amorphous Zr100 - x Be x alloys have been studied using differential scanning calorimetry and neutron diffraction over a wide concentration range (30 ? x ? 65). The amorphous alloys have been prepared by rapid quenching from melt. The studied amorphous system involves the composition range around the eutectic composition with boundary phases ?-Zr and ZrBe2. It has been found that the crystallization of alloys with low beryllium contents ("hypoeutectic" alloys with x ? 40) proceeds in two stages. Neutron diffraction has demonstrated that, at the first stage, ?-Zr crystallizes and the remaining amorphous phase is enriched to the eutectic composition; at the second stage, the alloy crystallizes in the ?-Zr and ZrBe2 phases. At higher beryllium contents ("hypereutectic" alloys), one phase transition of the amorphous phase to a mixture of the ?-Zr and ZrBe2 phases has been observed. The concentration dependences of the crystallization temperature and activation energy have been revealed.

Golovkova, E. A.; Surkov, A. V.; Syrykh, G. F.

2015-02-01

387

A photochemical method for the preparation of indium oxide and indium–cobalt oxides thin films  

Microsoft Academic Search

Indium oxide and indium–cobalt oxide thin films have been successfully prepared by direct UV irradiation of amorphous films of ?-diketonate complexes on Si(100) substrates. Deposited films were characterized by X-ray diffraction, Auger electron spectroscopy and X-ray photoelectron spectroscopy. The surface morphology of the films, examined by atomic force microscopy and scanning electron microscopy, revealed that mixed indium–cobalt oxide films are

G. E.. Buono-Core; G. Cabello; B. Torrejon; M. Tejos; R. H. Hill

2005-01-01

388

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

389

Vanadium oxide electrode synthesized by electroless deposition for electrochemical capacitors  

NASA Astrophysics Data System (ADS)

A thin film vanadium oxide electrode was synthesized by a simple electroless deposition method. Surface and structural analyses revealed that the deposited oxide is a mixture of amorphous V2O5 and VO2. Electrochemical characterizations of the synthesized vanadium oxide showed capacitive behavior with good cycle life. The electroless deposition of vanadium oxide is inexpensive, easy to process, and environmentally benign, offering a promising route for electrode development for electrochemical capacitors.

Wu, Haoran; Lian, Keryn

2014-12-01

390

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

391

Synthesis and photocurrent of amorphous boron nanowires  

NASA Astrophysics Data System (ADS)

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/I0) is 1.5 and time constants in the order of tens of seconds. I/I0 is 1.17 using a green light.

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

2014-08-01

392

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

393

Amorphous solidification and percolation in two dimensions  

NASA Astrophysics Data System (ADS)

Since the pioneering work of Stauffer and de Gennes, it has been assumed that the amorphous solidification of randomly crosslinked macromolecular systems (RCMS) can be described in terms of percolation theory. Recent detailed studies of RCMS have brought out a mixed picture in this regard: while for some aspects of the transition (e.g. the behavior of the gel fraction in 3D) there is a direct correspondence with percolation, for others (e.g. the elastic properties) this correspondence is more problematic. We show that the lower critical dimension (LCD) of amorphous solidification is two, as opposed to one in percolation. Studying amorphous solidification at the LCD is a delicate matter, owing to the random character of the quasi-ordering involved. We compute the behavior of order parameter correlations in RCMS at the LCD, and compare RCMS quasi-long-range ordering with that found in other 2D systems.

Castillo, Horacio E.; Goldbart, Paul M.; Peng, Weiqun

2000-03-01

394

Phase transitions in biogenic amorphous calcium carbonate  

PubMed Central

Crystalline biominerals do not resemble faceted crystals. Current explanations for this property involve formation via amorphous phases. Using X-ray absorption near-edge structure (XANES) spectroscopy and photoelectron emission microscopy (PEEM), here we examine forming spicules in embryos of Strongylocentrotus purpuratus sea urchins, and observe a sequence of three mineral phases: hydrated amorphous calcium carbonate (ACC·H2O) ? dehydrated amorphous calcium carbonate (ACC) ? calcite. Unexpectedly, we find ACC·H2O-rich nanoparticles that persist after the surrounding mineral has dehydrated and crystallized. Protein matrix components occluded within the mineral must inhibit ACC·H2O dehydration. We devised an in vitro, also using XANES-PEEM, assay to identify spicule proteins that may play a role in stabilizing various mineral phases, and found that the most abundant occluded matrix protein in the sea urchin spicules, SM50, stabilizes ACC·H2O in vitro. PMID:22492931

Gong, Yutao U. T.; Killian, Christopher E.; Olson, Ian C.; Appathurai, Narayana P.; Amasino, Audra L.; Martin, Michael C.; Holt, Liam J.; Wilt, Fred H.; Gilbert, P. U. P. A.

2012-01-01

395

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

396

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

SciTech Connect

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

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

2008-10-01

397

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

398

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

399

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

400

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

401

Short range order in amorphous polycondensates  

SciTech Connect

The static coherent structure factors S(Q) of the polymer glass Bisphenol-A-Polycarbonate and its chemical variation Bisphenol-A- Polyctherkctone- both in differently deuterated versions- have been measured by spin polarized neutron scattering. The method of spin polarization analysis provided an experimental separation of coherent and incoherent scattering and a reliable intensity calibration. Results are compared to structure factors calculated for model structures which were obtained by ``amorphous cell`` computer simulations. In general reasonable agreement is found between experiment and simulation; however, certain discrepancies hint at an insufficient structural relaxation in the amorphous cell method. 15 refs, 1 fig, 1 tab.

Lamers, C.; Richter, D.; Schweika, W. [Forschungszentrum Juelich GmbH (Germany). Inst. fuer Festkoerperforschung; Batoulis, J.; Sommer, K. [Bayer AG, Leverkusen (Germany); Cable, J.W. [Oak Ridge National Lab., TN (United States); Shapiro, S.M. [Brookhaven National Lab., Upton, NY (United States)

1992-12-01

402

Interstitials and vacancies in amorphous metals  

NASA Astrophysics Data System (ADS)

The structural and thermodynamic properties of vacancies and interstitials are well characterized for most crystalline metals and alloys. We explore using molecular dynamics computer simulations such properties for defects in amorphous Cu and the glass forming alloy Cu-Ti. The simulations show that the formation volume and energy for vacancies and interstitials in the amorphous state are quite different from those in their crystalline forms. Some of these changes can be explained using the Granato's interstitialcy model for the liquid and glass states [Phys. Rev. Lett. 68 (1992) 974].

Ashkenazy, Yinon; Averback, Robert S.; Granato, Andrew V.

2002-03-01

403

Amorphous Insulator Films With Controllable Properties  

NASA Technical Reports Server (NTRS)

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

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

1987-01-01

404

Inverted amorphous silicon solar cell utilizing cermet layers  

DOEpatents

An amorphous silicon solar cell incorporating a transparent high work function metal cermet incident to solar radiation and a thick film cermet contacting the amorphous silicon opposite to said incident surface.

Hanak, Joseph J. (Lawrenceville, NJ)

1979-01-01

405

Synthesis method for amorphous metallic foam Jan Schroersa)  

E-print Network

Synthesis method for amorphous metallic foam Jan Schroersa) Keck Laboratory, California Institute of Technology, Pasadena, California 91125 and Liquidmetal Technologies, Lake Forest, California 92630 Chris for the production of amorphous metallic foam is introduced. This method utilizes the thermodynamic stability

Haller, Gary L.

406

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

407

Diamond Lattice Model of Semicrystalline Polyethylene in the Amorphous Region  

E-print Network

Diamond Lattice Model of Semicrystalline Polyethylene in the Amorphous Region Zhong­Hui Duan Abstract The statistics of polyethylene chains in the amorphous region between two crystallites have been as models of the chain molecules in the amorphous region of semicrystalline polyethylene, both

Aluffi, Paolo

408

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

409

Thickness-dependent properties of sprayed iridium oxide thin films  

Microsoft Academic Search

Iridium oxide thin films with variable thickness were deposited by spray pyrolysis technique (SPT), onto the amorphous glass substrates kept at 350°C. The volume of iridium chloride solution was varied to obtain iridium oxide thin films with thickness ranging from 700 to 2250Å. The effect of film thickness on structural and electrical properties was studied. The X-ray diffraction (XRD) studies

P. S Patil; P. S Chigare; S. B Sadale; T Seth; D. P Amalnerkar; R. K Kawar

2003-01-01

410

Sols and mixtures of sols as precursors of unique oxides  

Microsoft Academic Search

There is considerable evidence that sols, or colloidal oxides, can play a critical role as precursors to the primary particles of crystalline or amorphous oxides. Sols have been demonstrated to be useful precursors to form microengineered catalysts when adsorbed onto geometric structures, such as monolith honeycombs, or onto macroporous supports capable of allowing entry of the sol structure into the

L. L. Murrell

1997-01-01

411

Preparation and characterization of spray pyrolysed cobalt oxide thin films  

Microsoft Academic Search

Cobalt oxide thin films were prepared by the spray pyrolysis method on amorphous glass substrates kept at 300 °C. The films formed were uniform, pin-hole free, and strongly adherent to the substrates. The X-ray diffraction studies revealed that the films consist of Co3O4 oxide phase. The optical and the electrical properties of the film were also studied.

P. S. Patil; L. D. Kadam; C. D. Lokhande

1996-01-01

412

Porous amorphous carbon models from periodic Gaussian chains of amorphous polymers  

E-print Network

and as catalyst supports [2­4]. NPCs are used extensively in the pressure swing adsorption process to separate amorphous [7]. Adsorption studies indicate a very narrow pore size distribution for NPCs, the mean pore size

Powles, Rebecca

413

Formation and annealing behavior of an amorphous layer induced by tin implantation into sapphire  

SciTech Connect

The formation and annealing behavior of an amorphous layer produced by tin implantation into sapphire has been studied. Tin ions with 180 keV energy were implanted into {alpha}-Al{sub 2}O{sub 3} at 300 K with fluences ranging from 10{sup 15} to 10{sup 17} ions-cm{sup {minus}2}. The thermal stability of the damaged layer was investigated with post-implantation annealing treatments at temperatures up to 1375 K in either oxidizing or reducing atmospheres. The atomic spatial distribution of the ions were determined by Rutherford backscattering spectroscopy (RBS) in random and channeling geometries. The structure of the implanted layer was determined by analytical electron microscopy (AEM). The degree of disorder was found to increase linearly with the fluence up to the threshold for amorphization, {approximately}1 {times} 10{sup 16} ions-cm{sup {minus}2}. The microstructure of the implanted layer after the thermal treatments depended on the annealing atmosphere. The well-known amorphous {yields} {gamma}-Al{sub 2}O{sub 3}{yields} {alpha}-Al{sub 2}O{sub 3} phase transition was observed during annealing in a reducing atmosphere. However, anneals in an oxidizing environment led to the formation of the compound SnO{sub 2}, which was found to stabilize the cubic {gamma}-Al{sub 2}O{sub 3} phase. 17 refs., 6 figs.

Romana, L.J. (Oak Ridge Associated Universities, Inc., TN (United States) Oak Ridge National Lab., TN (United States)); Sklad, P.S.; White, C.W.; Choudhury, A.; Horton, L.L. (Oak Ridge National Lab., TN (United States)); McCallum, J.C. (Royal Melbourne Inst. of Tech. (Australia)); Mchargue, C.J. (Tennessee Univ., Knoxville, TN (United States))

1991-01-01

414

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

415

Disorder-induced metallicity in amorphous graphene  

Microsoft Academic Search

We predict a transition to metallicity when a sufficient amount of disorder is induced in graphene. Calculations were performed by means of a first-principles stochastic quench method. The resulting amorphous graphene can be seen as nanopatches of graphene that are connected by a network of disordered small and large carbon rings. The buckling of the lattice is minimal and is

Erik Holmström; Jonas Fransson; Olle Eriksson; Raquel Lizárraga; Biplab Sanyal; Sumanta Bhandary; Mikhail I. Katsnelson

2011-01-01

416

Amorphization of sapphire during ion beam mixing  

SciTech Connect

Earlier studies indicated that implantation of zirconium into sapphire at room temperature produced an amorphous layer at a critical composition of approximately 6.5% (cation). Further insight into the amorphization of sapphire has been provided by ion beam mixing studies. Bi-layer couples of {approx}80 nm thick polycrystalline ZrO{sub 2} films deposited on the (0001) face of {alpha}-Al{sub 2}O{sub 3} single crystals were irradiated to 4 {times} 10{sup 16} ions/cm{sup 2} with Kr (475 keV, 20{degree}C), or Cr (340 keV, 20{degree}C or {approx}900{degree}C). Transmission electron microscopy showed the unirradiated couples to have sharp, planar interfaces between the films and substrates. Recoil mixing by both ion species gave Zr concentrations greater than 10% (cation) to depths of 10-20 nm. An amorphous layer containing Zr was present at the interface for samples irradiated at room temperature. The sample mixed at the elevated temperature contained a sharp interface similar to the as-deposited sample. The present results suggest that both irradiation-produced damage (defects) and certain chemical species are required to amorphize sapphire.

Joslin, D.L.; McHargue, C.J. [Univ. of Tennessee, Knoxville, TN (United States). Department of Materials Science and Engineering; White, C.W.; Evans, N.D. [Oak Ridge National Lab., TN (United States)

1994-09-01

417

Light trapping in amorphous silicon solar cells  

Microsoft Academic Search

In order to simultaneously decrease the production costs of thin film silicon solar cells and obtain higher performances, the authors have studied the possibility to increase the light trapping effect within thin film silicon solar cells deposited on flexible plastic substrates. In this context, different nano-structure shapes useable for the back contacts of amorphous silicon solar cells on plastic substrates

Vanessa Terrazzoni-Daudrix; Joelle Guillet; Xavier Niquille; Arvind Shah; R. Morf; A. Tishchenko; V. Brioude; O. Parriaux; D. Fischer

418

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.

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

1992-01-01

419

Early Photoluminescence Decay in Amorphous Hydrogenated Silicon  

Microsoft Academic Search

Photoluminescence decay in amorphous hydrogenated silicon has been measured in the time regime of 0.5 - 40 nanoseconds, and the dependence upon temperature, emission energy and excitation energy has been systematically investigated. The subnanosecond time resolution was achieved by using a single -photon counting detection system in conjunction with synchrotron radiation as the light source. The experiment was carried out

Daniel Gorman Stearns

1984-01-01

420

Excess Specific Heat in Evaporated Amorphous Silicon  

NASA Astrophysics Data System (ADS)

The specific heat C of e-beam evaporated amorphous silicon (a-Si) thin films prepared at various growth temperatures TS and thicknesses t was measured from 2 to 300 K, along with sound velocity v, shear modulus G, density nSi, and Raman spectra. Increasing TS results in a more ordered amorphous network with increases in nSi, v, G, and a decrease in bond angle disorder. Below 20 K, an excess C is seen in films with less than full density where it is typical of an amorphous solid, with both a linear term characteristic of two-level systems (TLS) and an additional (non-Debye) T3 contribution. The excess C is found to be independent of the elastic properties but to depend strongly on density. The density dependence suggests that low energy glassy excitations can form in a-Si but only in microvoids or low density regions and are not intrinsic to the amorphous silicon network. A correlation is found between the density of TLS n0 and the excess T3 specific heat cex suggesting that they have a common origin.

Queen, D. R.; Liu, X.; Karel, J.; Metcalf, T. H.; Hellman, F.

2013-03-01

421

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

422

Caking phenomena in amorphous food powders  

Microsoft Academic Search

Caking of free-flowing powders during storage is a deleterious phenomenon that is ubiquitous in the feed, fertilizer and pharmaceutical industries, and of economical importance for low-moisture foods. Among other subjects related to caking of amorphous powders, the following aspects are reviewed in this article: (1) physical and morphological changes, and quantitative procedures to assess caking; (2) proposed mechanisms of caking

José M. Aguilera; José M. del Valle; Marcus Karel

1995-01-01

423

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

424

Amorphous Siliconbased Solar Cells Xunming Deng1  

E-print Network

transistor), GaAs and the other III-V compounds (the basis for many light emitters), and CdS (often used light when excited by the current. Amorphous silicon was deposited as a thin film on substrates inserted efficient solar cells using a silane glow discharge to deposit films. In 1976, he and Christopher Wronski

Schiff, Eric A.

425

Amorphous Silicon-Carbon Nanostructure Solar Cells  

Microsoft Academic Search

Taking advantage of the ability to fabricate large area graphene and carbon nanotube networks (buckypaper), we produce Schottky junction solar cells using undoped hydrogenated amorphous silicon thin films and nanostructured carbon films. These films are useful as solar cell materials due their combination of optical transparency and conductance. In our cells, they behave both as a transparent conductor and as

Maria Schriver; Will Regan; Matthias Loster; Alex Zettl

2011-01-01

426

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

427

The Plastic Response of Magnetoelastic Amorphous Solids  

E-print Network

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

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

2012-05-04

428

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

429

Optical properties of Teflon AF amorphous  

E-print Network

Optical properties of Teflon® AF amorphous fluoropolymers Min K. Yang Roger H. French DuPont Co.k.yang@usa.dupont.com Edward W. Tokarsky DuPont Fluoropolymer Solutions Chestnut Run Plaza Wilmington, Delaware 19880 of Photo-Optical Instrumentation Engineers. DOI: 10.1117/1.2965541 Subject terms: fluoropolymer; absorbance

Rollins, Andrew M.

430

Characterization of amorphous In{sub 2}O{sub 3}: An ab initio molecular dynamics study  

SciTech Connect

In this work, we report on the structural and electronic properties of amorphous In{sub 2}O{sub 3} obtained with ab initio molecular dynamics. Our results show crystal-like short range InO{sub 6} polyhedra having average In-O distance consistent with x-ray spectroscopy data. Structural disorder yields band tailing and localized states, which are responsible of a strong reduction of the electronic gap. Most importantly, the appearance of a peculiar O-O bond imparts n-type character to the amorphous compound and provides contribution for interpreting spectroscopic measurements on indium based oxidized systems. Our findings portray characteristic features to attribute transparent semiconductive properties to amorphous In{sub 2}O{sub 3}.

Aliano, Antonio [Department of Physics, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino (Italy); Catellani, Alessandra [CNR-IMEM, Parco Area delle Scienze 37A, I-43010 Parma (Italy); Cicero, Giancarlo [Materials Science and Chemical Engineering Department, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino (Italy)

2011-11-21

431

Transparent conducting oxide semiconductors for transparent electrodes  

Microsoft Academic Search

The present status and prospects for further development of polycrystalline or amorphous transparent conducting oxide (TCO) semiconductors used for practical thin-film transparent electrode applications are presented in this paper. The important TCO semiconductors are impurity-doped ZnO, In2O3 and SnO2 as well as multicomponent oxides consisting of combinations of ZnO, In2O3 and SnO2, including some ternary compounds existing in their systems.

Tadatsugu Minami

2005-01-01

432

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

433

Attaching Molecules to Chlorinated and Brominated Amorphous Carbon Substrates via Grignard Reactions.  

PubMed

Amorphous carbon thin films are an attractive material because they provide a chemically robust surface that has been utilized in biomolecule array, biosensor, and bioelectronic applications. These thin films are particularly versatile because they are deposited at room temperature, making them readily integrated with other materials and devices. Here we present an alternative means of functionalizing carbon substrates based on Grignard chemistry. First, the amorphous carbon substrates are halogenated with a solution-based, radical-initiated halogenation reaction using PX(5) (X = Br or Cl). Next, the halogenated surfaces are modified via the formation of a carbon-carbon bond between the surface and the Grignard reagents employed. Alkyl-, perfluoroalkyl-, and poly(ethylene glycol)-Grignard reagents were chosen to show the utility of this reaction scheme in functionalizing carbon surfaces to withstand oxidation and provide a hydrophobic and/or biocompatible substrate. PMID:19209862

Lockett, Matthew R; Smith, Lloyd M

2009-03-17

434

Attaching molecules to chlorinated and brominated amorphous carbon substrates via Grignard reactions.  

PubMed

Amorphous carbon thin films are an attractive material because they provide a chemically robust surface that has been utilized in biomolecule array, biosensor, and bioelectronic applications. These thin films are particularly versatile because they are deposited at room temperature, making them readily integrated with other materials and devices. Here we present an alternative means of functionalizing carbon substrates based on Grignard chemistry. First, the amorphous carbon substrates are halogenated with a solution-based, radical-initiated halogenation reaction using PX5 (X = Br or Cl). Next, the halogenated surfaces are modified via the formation of a carbon-carbon bond between the surface and the Grignard reagents employed. Alkyl-, perfluoroalkyl-, and poly(ethylene glycol)-Grignard reagents were chosen to show the utility of this reaction scheme in functionalizing carbon surfaces to withstand oxidation and provide a hydrophobic and/or biocompatible substrate. PMID:19708232

Lockett, Matthew R; Smith, Lloyd M

2009-04-01

435

Non-crosslinked, amorphous, block copolymer electrolyte for batteries  

DOEpatents

Solid battery components are provided. A block copolymeric electrolyte is non-crosslinked and non-glassy through the entire range of typical battery service temperatures, that is, through the entire range of at least from about 0.degree. C. to about 70.degree. C. The chains of which the copolymer is made each include at least one ionically-conductive block and at least one second block immiscible with the ionically-conductive block. The chains form an amorphous association and are arranged in an ordered nanostructure including a continuous matrix of amorphous ionically-conductive domains and amorphous second domains that are immiscible with the ionically-conductive domains. A compound is provided that has a formula of LixMyNzO2. M and N are each metal atoms or a main group elements, and x, y and z are each numbers from about 0 to about 1. y and z are chosen such that a formal charge on the MyNz portion of the compound is (4-x). In certain embodiments, these compounds are used in the cathodes of rechargeable batteries. The present invention also includes methods of predicting the potential utility of metal dichalgogenide compounds for use in lithium intercalation compounds. It also provides methods for processing lithium intercalation oxides with the structure and compositional homogeneity necessary to realize the increased formation energies of said compounds. An article is made of a dimensionally-stable, interpenetrating microstructure of a first phase including a first component and a second phase, immiscible with the first phase, including a second component. The first and second phases define interphase boundaries between them, and at least one particle is positioned between a first phase and a second phase at an interphase boundary. When the first and second phases are electronically-conductive and ionically-conductive polymers, respectively, and the particles are ion host particles, the arrangement is an electrode of a battery.

Mayes, Anne M.; Ceder, Gerbrand; Chiang, Yet-Ming; Sadoway, Donald R.; Aydinol, Mehmet K.; Soo, Philip P.; Jang, Young-Il; Huang, Biying

2006-04-11

436

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

E-print Network

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

Zhou, Chongwu

437

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

Microsoft Academic Search

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

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

1972-01-01

438

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

PubMed

Synchrotron x-ray absorption spectroscopy (XAS) and electron spin resonance (ESR) experiments were performed to determine, in combination with Raman spectroscopy and x-ray diffraction (XRD) data from previous reports, the structure and paramagnetic defect status of Si-nanoclusters (ncls) at various intermediate formation stages in Si-rich Si oxide films having different Si concentrations (y = 0.36-0.42 in Si(y)O(1-y)), fabricated by electron cyclotron resonance plasma-enhanced chemical vapor deposition and isochronally (2 h) annealed at various temperatures (T(a) = 900-1100 °C) under either Ar or (Ar + 5%H(2)) atmospheres. The corresponding emission properties were studied by stationary and time dependent photoluminescence (PL) spectroscopy in correlation with the structural and defect properties. To explain the experimental data, we propose crystallization by nucleation within already existing amorphous Si-ncls as the mechanism for the formation of the Si nanocrystals in the oxide matrix. The cluster-size dependent partial crystallization of Si-ncls at intermediate T(a) can be qualitatively understood in terms of a 'crystalline core-amorphous shell' Si-ncl model. The amorphous shell, which is invisible in most diffraction and electron microscopy experiments, is found to have an important impact on light emission. As the crystalline core grows at the expense of a thinning amorphous shell with increasing T(a), the PL undergoes a transition from a regime dominated by disorder-induced effects to a situation where quantum confinement of excitons prevails. PMID:22129528

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

2011-12-21

439

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

440

Process to produce silicon carbide fibers using a controlled concentration of boron oxide vapor  

NASA Technical Reports Server (NTRS)

A process for producing polycrystalline silicon carbide includes heating an amorphous ceramic fiber that contains silicon and carbon in an environment containing boron oxide vapor. The boron oxide vapor is produced in situ by the reaction of a boron containing material such as boron carbide and an oxidizing agent such as carbon dioxide, and the amount of boron oxide vapor can be controlled by varying the amount and rate of addition of the oxidizing agent.

Barnard, Thomas Duncan (Inventor); Lipowitz, Jonathan (Inventor); Nguyen, Kimmai Thi (Inventor)

2000-01-01