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a -SiC:H films with energy gap in the range 2.00–2.65 eV have been grown by plasma enhanced chemical vapor deposition in undiluted and H2 diluted SiH4+CH4 gas mixtures, by making use of optimized deposition conditions. A complete picture of structural, compositional, optoelectronic, and defective properties for high quality films has been drawn for the first time. We show that the addition of H2 to the gas mixture leads to a different chemical composition of the deposited films; in particular, carbon incorporation is enhanced and a carbon fraction in the solid matrix up to C/(C+Si)≈0.45 can be obtained. These films have a higher mass density, a reduced microvoid and carbon cluster concentration, a better structural connectivity, and improved optoelectronic properties. For samples with optical gap below 2.4 eV, the reduced defect concentration of H2 diluted films results in an increase of the photoconductivity gain and the steady-state (ημτ)ss values up to two orders of magnitude.

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High rate deposition of diamond like carbon films by very high frequency plasma enhanced chemical vapor deposition at 100 MHz Wide band gap amorphous hydrogenated carbon films grown by plasma enhanced chemical vapor depositionThe use of very high frequency (VHF) plasma enhanced chemical vapor deposition in a capacitive discharge is investigated to fabricate hydrogenated amorphous silicon carbon alloys, using silane and methane as silicon and carbon precursors, respectively, and hydrogen dilution of the gas mixture. The properties of samples differ significantly from that is normally observed for rf deposition. A wide band-gap material is obtained, with a carbon ratio ranging from 0.2 to 0.63. An energy gap up to 3.4 eV is measured, indicating a large sp 3 content. The most interesting properties are observed using 90% hydrogen dilution and 350°C as substrate temperature. In this case, a Siu C bond concentration up to 6 ϫ 10 22 cm −3 was measured for stoichiometric samples, associated to a highly crosslinked structure and no detectable Siu CH 3 bending signal. The role of hydrogen in determining the optical properties of the film is established and is shown to affect mainly the valence electron concentration. Based on the free energy model, hydrogen bonding is observed to lie in between a random and chemically ordered configuration. The results are obtained at a deposition rate much larger than both rf and electron cyclotron resonance deposition, and are associated to a limited gas consumption, both aspects being advantageous for practical applications. The large Siu C bond concentration, associated to a limited silicon and carbon hydrogenation, makes the VHF deposited a-SiC : H a good starting material for subsequent crystallization.