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Title: Characterization of Hydrogenated Amorphous Silicon Thin Films by Infrared and EPR Spectroscopy
Authors: Arora, Manju
Gupta, S K
Issue Date: Jun-2005
Publisher: NISCAIR-CSIR, India
Abstract: Hydrogenated amorphous silicon thin films grown by glow - discharge process were characterized by high resolution, non - destructive infrared (IR) and electron paramagnetic resonance (EPR) spectroscopic techniques to investigate different local arrangements formed in the film network like SiH , SiH2 and (SiH2)n bonding groups, defects and microcrystalline silicon during growth. These groups and defects effect the conductivity and recombination process which plays important role in device fabrication. In this work, the vibrational bands pertaining to silicon and hydrogen bonded groups were tentatively assigned to reveal structural details of local bonding arrangements in amorphous and microcrstalline state. Infrared absorptance spectra were measured in the region 4000 - 400 cm-1 at ambient and different low temperatures. In these spectra, absorption bands of SiH, SiH2, (SiH2)2, (SiH2)n groups of amorphous hydrogenated silicon coexisted with microcrystalline silicon (mc -Si:H) stretching, bending, breathing, wagging and silicon transverse optic phonon vibrations. The appearance of microcrystalline silicon bands in these film spectra confirms its formation which starts growing due to the reaction of hydrogen radicals with unstable SiH2 group present at the grain boundery. This chemical etching reaction is exothermic which breaks weak Si-Si and Si-H bonds and form strong Si-Si microcrystalline bonds and silicon particles through reorientational ordering of silicon hydrogen bonded groups in amorphous film network. Recently microcrystalline silicon find wide usage in optoelectronic devices and these investigations are very important in this context also. Electron paramagnetic resonance studies showed an isotropic single line spectrum due to formation of dangling bonds in amorphous hydrogenated silicon film.
Page(s): 86-90
ISSN: 0975-2412 (Online); 0771-7706 (Print)
Appears in Collections:BVAAP Vol.13(1) [June 2005]

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