  In hydrogenated amorphous silicon oxide (a-SiO:H) films, incorporation of
oxygen enhances optical gap due to a large number of St-O-Si bond formation,
which lies deep into valence band states. An induction effect of this Si-O on
other bonds within the network also takes place. At higher oxygen content
micro-void forms and bonded hydrogen accumulates in di and/or polyhydride form.
At this stage a phase separation of Si-rich and O-rich region taking place. A
peak shift of absorption spectra within 1850 - 2250 cm-1, towards higher wave
number is continuous. A gradual increase and broadening of 850 cm-1 absorption
band on both sides of peak position indicate higher structural disorder in
network formation. It may be considered that the stretching vibration of-OH
bonded to Si gives rise to 780 cm-1 absorption band. This Si-OH formation is
beneficial which prevents deterioration in photosensitivity due to reduction in
bonded hydrogen content. Hydrogen content is found reducing as oxygen content
increases from zero to ~15 at.%. A systematic study is carried out to correlate
the optoelectronic property with local atomic arrangement.
