RAMAN-STUDY OF LIGHT-INDUCED-CHANGES IN SILICON-HYDROGEN BOND STRETCHING VIBRATION IN A-SI-H

Amorphous hydrogenated silicon films prepared by a dc magnetron sputtering method was soaked by light of an argon ion laser and studied "in situ" by Raman spectroscopy in order to resolve the apparent inconsistency in the assignments of the silicon-hydrogen bond stretching vibrations. The bond-stretching frequency region between 1850 and 2250 cm-1 was decomposed in two Gaussian-shaped bands. The laser-induced changes at the power density from 20 to 500 W/cm2 show: a) the continious increase of the integrated intensity of the band at about 2100 cm-1 compared to the band at about 2000 cm-1; b) the frequency shift of both bands to the lower values; c) the linewidth decrease of the band at about 2000 cm-1, and d) linewidth increase of the band at about 2100 cm-1. Contrary to the previous proposals that in the stretching region of the Raman spectra only two bands exist, our data show the existence of four vibrational bands.