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Journal ArticleDOI

Catalytic chemical vapor deposition method to prepare high quality hydro‐fluorinated amorphous silicon

01 Dec 1988-Journal of Applied Physics (American Institute of Physics)-Vol. 64, Iss: 11, pp 6505-6509
TL;DR: In this paper, a new type of chemical vapor deposition method, named "Catalytic-CVD" method, is presented, in which deposition gases are decomposed by catalytic or pyrolytic reaction between deposition gases and a heated catalyzer, and films are thermally grown on a substrate at temperatures lower than 300°C without any help from glow discharge plasma.
Abstract: A new type of chemical vapor deposition method, named ‘‘Catalytic‐CVD’’ method, is presented. In the method, deposition gases are decomposed by catalytic or pyrolytic reaction between deposition gases and a heated catalyzer, and films are thermally grown on a substrate at temperatures lower than 300 °C without any help from glow discharge plasma. Hydro‐fluorinated amorphous silicon (a‐Si:F:H) films are deposited by this method using both a SiF2 and H2 gas mixture and a SiH2F2 and H2 mixture. It is found that a very high quality a‐Si:F:H film can be obtained, and for instance, that the photosensitivity for AM‐1 of 100 mW/cm2 exceeds 106 and the spin density is as low as 6×1015 cm−3.
Citations
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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: The optical, electronic and structural properties of thin films deposited by Hot-Wire chemical vapor deposition with filament temperatures, Tfil, between 1500 and 1900 C from silane and hydrogen are studied in this paper.
Abstract: The optical, electronic and structural properties of thin films deposited by Hot‐wire chemical vapor deposition with filament temperatures, Tfil, between 1500 and 1900 °C from silane and hydrogen are studied. The substrate temperature, Tsub, was kept constant at 220 °C. Amorphous silicon films (a‐Si:H) are obtained at high filament temperatures, low deposition pressures and low hydrogen‐to‐silane flow rate ratio (Tfil∼1900 °C, p<30 mTorr and FH2/FSiH4≤1). At these deposition conditions, high growth rates are observed (rd≥10 As−1) both with and without hydrogen dilution, and no silicon deposition was observed on the filaments. However, if a lower filament temperature is used (Tfil∼1500 °C) a transition from a‐Si:H to microcrystalline silicon (μc‐Si:H) occurs as the pressure is decreased from above 0.3 Torr to below 0.1 Torr. The highest dark conductivity and lowest activation energy, of ∼1 Scm−1 and <0.1 eV, respectively, were observed for μc‐Si:H deposited at p∼50 mTorr. In this Tfil regime, μc‐Si:H growt...

50 citations

Journal ArticleDOI
TL;DR: In this article, it was shown that the temperature dependence of the carbon deposition rate is similar to the sublimation rate of carbon from graphite and tungsten carbide.
Abstract: Pure glassy carbon films [no x‐ray photoelectron spectroscopy (XPS) detectable impurities above the 0.5% level] as thick as 25 000 A have been grown on nearby silicon substrates (T≳100 °C) as a result of reactions between a hot tungsten filament and cyclopentane. Above ∼2500 °C, cyclopentane‐tungsten reactions yield a liquid W/C eutectic which limits filament operation. Below ∼2500 °C, resistance changes of the filament and XPS spectra show such reactions form carbides and graphite. It is shown that the temperature dependence of the carbon deposition rate is similar to the sublimation rate of carbon from graphite and tungsten carbide. Moreover, it is also shown that C1, C2, and C3 (carbon monomers, dimers, and trimers) are evaporated from carbarized tungsten and also from graphite. These results suggest that carbon film growth is a consequence of evaporation of carbon from the carbarized tungsten filament, with steady‐state film deposition occurring as a result of a quasisteady state in the formation and ...

24 citations

Journal ArticleDOI
TL;DR: In this article, a kinetic growth model for hot-wire chemical vapor deposition in the Tfil∼1200°C regime is proposed, and the Optoelectronic properties are controlled by the substrate temperature Tsub, and show different dependences for new and old filaments.
Abstract: Hydrogenated amorphous silicon, a‐Si:H, is deposited from silane and hydrogen by hot‐wire chemical vapor deposition using a tungsten wire filament at a temperature Tfil=1200 °C. Film properties depend on whether the films were deposited using filaments with an accumulated deposition time lower than 90 min (‘‘new’’ filaments) or longer than 90 min (‘‘old’’ filaments). The deposition rate for films deposited with ‘‘new’’ filaments is 4 times higher than that for aged filaments. For ‘‘new’’ filaments, a monotonic increase of the growth rate, rd, with the pressure is observed, as well as a maximum of rd for FH2/FSiH4 close to unity. The optoelectronic properties are controlled by the substrate temperature Tsub, and show different dependences for ‘‘new’’ and ‘‘old’’ filaments. The Urbach band tail energy, Eu, is lower for films deposited with ‘‘new’’ filaments. A kinetic growth model for hot‐wire chemical vapor deposition in the Tfil∼1200 °C regime is proposed.

21 citations

References
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Journal ArticleDOI
TL;DR: In this article, a new catalytic chemical vapor deposition (CTL) method was proposed to produce high quality amorphous silicon germanium (a•SiGe:H) films.
Abstract: High‐quality amorphous silicon germanium (a‐SiGe:H) films are produced by a new ‘‘catalytic chemical vapor deposition (CTL CVD)’’ method. In the method, a SiH4, GeH4, and H2 gas mixture is decomposed without using any plasmas or photochemical excitation, but using only the thermal or the catalytic reaction with a heated tungsten catalyzer. Photoconductive properties of CTL CVD a‐SiGe:H are apparently not degraded as the Ge content increases. The photoconductivity and the photosensitivity for AM‐1 of 100 mW/cm2 are 10−5–10−4 (Ω cm)−1 and 104, respectively, even for the sample of optical band gap of 1.40–1.45 eV.

64 citations

Journal ArticleDOI
TL;DR: In this paper, the a-SiGe alloy prepared by glow discharge from gaseous mixture of GeF4SiF4-H2 showed a satisfactory photoresponse and an effective doping feasibility to control its Fermi-levels.
Abstract: Systematic investigations had been made of preparing a-SiGe alloy with high photoconductivity The a-SiGe alloy prepared by glow discharge from gaseous mixture of GeF4SiF4H2 showed a satisfactory photoresponse and an effective doping feasibility to control its Fermi-levels, resulting from a great reduction in the amount of the dangling bonds

60 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, hydrogenated amorphous silicon films are made by atmospheric pressure chemical vapor deposition from polysilanes between 430 and 480 degrees C. The films have hole diffusion lengths up to 0.4 μm, as measured by the surface photovoltage technique.
Abstract: Hydrogenated amorphous silicon films are made by atmospheric pressure chemical vapor deposition from polysilanes between 430 and 480 °C. The films have hole diffusion lengths up to 0.4 μm, as measured by the surface photovoltage technique. Oxygen impurities are shown to reduce the diffusion length. Stainless‐steel and crystalline silicon substrates give slightly different results, implying that contamination is introduced by the substrates.

12 citations