Studies of substrate induced disorder in amorphous silicon by in-situ-Raman backscattering during film growth

In situ Raman investigations on a-Si:H films as thin as 12 nm were performed, indicating that stress originating from the a-Si:H/substrate interface is induced in the film and relieved as film growth propagates. Amorphous silicon matrix disorder is found to be extremely sensitive to the material and to the chemical composition of the substrate. The correlation with Urbach energies from photothermal deflection spectroscopy indicates complicated changes in the electron density of states, thus contradicting a simple correlation of the valence band edge with angle fluctuations. Raman measurements performed in situ during subsequent breaks of deposition give strong evidence for the presence of a highly distorted interfacial layer on ITO and some lesser distortions on glass and on ZnO, while fully, relaxed film growth is observed on metal layers. Hydrogen-related Raman modes centered at 625 cm/sup -1/ decrease during film growth with decreasing TO half-width, i.e. in parallel to propagating relaxation of the network. An additional influence of substrate morphology on film distortion could not be ruled out.<>