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Silicon oxide thin films prepared by a photo-chemical vapour deposition technique

Jana, T, Ghosh, S, Ray, S
Journal of materials science 1997 v.32 no.18 pp. 4895-4900
carbon dioxide, growth models, hydrogen, oxygen, photochemistry, refractive index, silane, silica, vapors
Wide band gap a-SiOₓ:H films have been prepared by the photochemical decomposition of a SiH₄, CO₂ and H₂ gas mixture. Deposition parameters namely the CO₂ to SiH₄ gas flow ratio, H₂ dilution and chamber pressure were optimized in order to achieve highly photoconducting (1 × 10⁻⁶ S cm⁻¹) films with an optical gap of 1.99 eV. The optical gap was found to increase with an increase in the CO₂ to SiH₄ flow ratio. A decrease in the photoconductivity, refractive index, spin g-value and a simultaneous increase in the spin density are attributed to an incorporation of oxygen into the films. Upon hydrogen dilution the photoconductivity of a-SiOₓ:H films was observed to improve along with an increase of the optical gap. The spin density of a-SiOₓ:H films was of the order of 10¹⁷ cm⁻⁹. The optoelectronic properties of the films have been correlated with the bonding configurations in the film, deposition parameters and the growth kinetics.