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Journal ArticleDOI

Amorphous silicon produced by a new thermal chemical vapor deposition method using intermediate species SiF2

15 Oct 1985-Applied Physics Letters (American Institute of Physics)-Vol. 47, Iss: 8, pp 833-835
TL;DR: Amorphous silicon (a•Si) films are deposited at about 320˚C by a new thermal chemical vapor deposition method as mentioned in this paper, where the gas mixture of intermediate species SiF2 and H2, decomposed thermally by the catalytic reaction, is used as a material gas.
Abstract: Amorphous silicon (a‐Si) films are deposited at about 320 °C by a new thermal chemical vapor deposition method. In this method, the gas mixture of intermediate species SiF2 and H2, decomposed thermally by the catalytic reaction, is used as a material gas. It is found that the photosensitivity of the a‐Si film for AM1 of 100 mW/cm2 exceeds over 106 and that the spin density is as low as 1.5×1016 cm−3 for the film deposited with a rate of several A/s.
Citations
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Journal ArticleDOI
TL;DR: It is demonstrated that during irradiation with high-energy heavy ions amorphous silicon deforms plastically in the same way as conventional glasses, providing experimental evidence for the existence of a low-density liquid.
Abstract: Amorphous silicon is a semiconductor with a lower density than the metallic silicon liquid. It is widely believed that the amorphous-liquid transition is a first-order melting transition. In contrast to this, recent computer simulations and the experimental observation of pressure-induced amorphization of nanoporous silicon have revived the idea of an underlying liquid-liquid phase transition implying the existence of a low-density liquid and its glass transition to the amorphous solid. Here we demonstrate that during irradiation with high-energy heavy ions amorphous silicon deforms plastically in the same way as conventional glasses. This behaviour provides experimental evidence for the existence of the low-density liquid. The glass transition temperature for a timescale of 10 picoseconds is estimated to be about 1,000 K. Our results support the idea of liquid polymorphism as a general phenomenon in tetrahedral networks.

138 citations

Journal ArticleDOI
TL;DR: In this paper, a new type of thermal chemical vapor deposition (CVD) method is presented, where material gases are decomposed by catalytic or pyrolytic reaction with a heated catalyzer, so that films can be deposited at temperatures less than 300°C without any plasma or photochemical excitation.
Abstract: A new type of thermal chemical vapor deposition (CVD) method is presented. In the method, material gases are decomposed by catalytic or pyrolytic reaction with a heated catalyzer, so that films can be deposited at temperatures less than 300 °C without any plasma or photochemical excitation, and the method is particularly called ‘‘Catalytic‐CVD.’’ Hydrogenated amorphous silicon films are deposited by this method, and the deposition mechanism is also investigated. It is found that device‐quality amorphous silicon films can be obtained and that inactive species, which are generated at the catalyzer and transported without gas‐phase reactions, are key species to make a high‐quality film by this method.

125 citations

Journal ArticleDOI
TL;DR: In this article, an air-stable n-type carbon nanotube field effect transistors (CNTFETs) were fabricated with Si3N4 passivation films formed by catalytic chemical vapor deposition (Cat-CVD).
Abstract: Air-stable n-type carbon nanotube field-effect transistors (CNTFETs) were fabricated, with Si3N4 passivation films formed by catalytic chemical vapor deposition (Cat-CVD). Electrical measurements reveal that the p-type characteristics of CNTFETs are converted to n-type after fabricating Si3N4 passivation films at 270°C. This indicates that adsorbed oxygen on the CNT sidewalls was removed during the formation process of the Si3N4 passivation films. In addition, the source-drain current of the n-type CNTFETs does not change over time under vacuum, or in air. Consequently, the n-type CNTFETs are completely protected by the Si3N4 passivation film from further effects of ambient gases. Therefore, Cat-CVD is one of the best candidates to fabricate Si3N4 passivation films on CNTFETs.

95 citations

Journal ArticleDOI
TL;DR: In this paper, the recent progress in the catalytic chemical vapor deposition (Cat-CVD) research project, supported by the New Energy and Industrial Technology Development Organization (NEDO), is reviewed.

84 citations

Journal ArticleDOI
TL;DR: In this article, a method for crystallizing amorphous silicon (a-Si) films at low temperatures was proposed, where the hydrogen atoms were generated by catalytic cracking reaction of H2 gas on a heated tungsten catalyzer in the catalytic chemical vapor deposition apparatus.
Abstract: A method for crystallizing amorphous silicon (a-Si) films at low temperatures is proposed. In the method, a-Si films are crystallized at temperatures lower than 400 °C by annealing in the presence of atomic hydrogen. The hydrogen atoms are generated by catalytic cracking reaction of H2 gas on a heated tungsten catalyzer in the catalytic chemical vapor deposition apparatus. It is found that the crystalline fraction of such an a-Si film is increased from 0% to several tens %, and at the same time the a-Si film itself is etched with the rate of several tens nm/min by annealing in atomic hydrogen. This increment of crystalline fraction appears dependent on the quality of initial a-Si films. It is implied that there are several types of a-Si even if the difference among a-Si films cannot be detected by Raman scattering spectroscopy and other means for measurements.

70 citations

References
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Journal ArticleDOI
TL;DR: In this article, a new method of amorphous hydrogenated silicon (a•Si:H) chemical vapor deposition is presented in which SiH4 is homogeneously decomposed at high temperature and pressure to produce films on low-temperature substrates having up to 30% H and properties very similar to plasmadeposited material.
Abstract: A new method of amorphous hydrogenated silicon (a‐Si:H) chemical vapor deposition is presented in which SiH4 is homogeneously decomposed at high temperature and pressure to produce films on low‐temperature substrates having up to 30‐at. % H and properties very similar to plasma‐deposited material. Kinetic studies provide a film growth activation energy of 54 kcal/mole, confirming that SiH2 is the primary gas phase intermediate. A mechanism based on SiH2 chemistry is presented to account for the rapid surface reactions leading to a‐Si:H growth and its possible relevance to the plasma deposition process is emphasized.

97 citations

Journal ArticleDOI
TL;DR: In this paper, the authors studied the dissociation of hydrogen at a tungsten filament in the temperature range 1200 to 1800?K and at pressures between 10-2 and 10-6 mm.
Abstract: The dissociation of hydrogen at a tungsten filament has been studied in the temperature range 1200 to 1800 ?K and at pressures between 10-2 and 10-6 mm. The results obtained differ from those found in the literature and it is shown that this is because the surfaces employed by previous workers were contaminated, very probably by vapours derived from tap grease. At temperatures below 1400 ?K and at pressures exceeding 10-6 mm, the rate of atomization of hydrogen is given by the expression, va (atoms cm-2 s-1) = 18 x 1024 (PU2 mm) exp (52600/RT). The theory of absolute reaction rates is applied to the two possible mechanisms, namely W-H = W + H and H2 + W = W-H +H; under the conditions considered, equilibrium between adsorbed and gaseous hydrogen is maintained throughout the reaction. Reasons are given for rejecting the second mechanism, which was the one favoured in the past. From a consideration of both the atomization and recombination reactions, it is demonstrated that the first equation is applicable and, further, that the adsorbed atoms have full translatory freedom on the surface at the temperature of reaction. The observation that molecular and atomic hydrogen leave the filament in their equilibrium ratio, as determined by the temperature of the filament and the pressure of hydrogen, is shown to be compatible only with this description of the reaction. At temperatures in the region of 1800 ?K, the rate of reaction ceases to be proportional to VP at relatively high pressures and has become linearly dependent on P3U2 at pressures less than 10-6 mm. This behaviour is discussed quantitatively in terms similar to those employed for the low-temperature reaction, but now there no longer exists an equilibrium between adsorbed and gaseous hydrogen. A study of the atomization on surfaces exposed to oxygen indicated that the adsorbed oxygen layer is rapidly removed by exposure to hydrogen at 1200 ?K and that, thereafter, the dissociation proceeds at the same velocity as on a clean surface. The reaction on a carbided surface occurred at a rather slower rate than obtained with a clean surface, but the activation energy remained unaffected. The nature of the contamination responsible for the low activation energies of about 45 kcal/mole reported by previous workers has thus not been identified.

43 citations

Journal ArticleDOI
TL;DR: In this paper, intermediate species SiF 2, mixed with H 2, is used instead of SiF 4 as the material gas for a hydrofluorinated amorphous silicon (a-Si:F:H).
Abstract: Intermediate species SiF 2 , mixed with H 2 , is used instead of SiF 4 as the material gas for a hydro-fluorinated amorphous silicon (a-Si:F:H). The deposition rate can be easily increased up to about 20 A/sec without apparent degradation of photo-conductive property by using intermediate species, and also, Si-F or Si-H single bond configuration becomes dominant although there apparently exist Si-H 2 or Si-F 2 higher order bonds in the film produced by using SiF 4 .

15 citations

Journal ArticleDOI
TL;DR: In this article, a new chemical vapor deposition (CVD) method for the production of amorphous silicon films from SiF2 gas is described, and optical, electronic, and structural properties of the films are reported.
Abstract: A new chemical vapor deposition (CVD) method for the production of amorphous silicon films from SiF2 gas is described. About 1% (atomic) fluorine is incorporated in the film, its concentration decreasing with increasing deposition temperature. Optical, electronic, and structural properties of the films are reported.

12 citations