In Situ IR Spectroscopic Study of a-Si:H Films Growing under Photo-Chemical Vapor Deposition Condition

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Abstract
Polarization modulation infrared spectroscopy has been successfully applied for in situ observations of a-Si:H films growing under photo-chemical vapor deposition conditions. The thin films exhibited absorption bands arising from SiH3 or SiH2 species, depending upon the substrate temperature. Whereas the mass thickness of the film deposited at 293 K increased in proportion to the deposition time, the IR absorption intensity of SiH3 species decreased in rate when the film grew beyond 15 Å in thickness, showing that the concentration of the SiH3 species becomes reduced with the deposition time. Although the band ascribable to the Si-O stretching vibration could not be observed during the deposition, it grew when the film was exposed to air. This fact suggests that the origin of the oxygen incorporated in the film is mainly atmospheric oxidizing agents.