PREPARATION, STRUCTURAL AND OPTICAL-PROPERTIES OF NOVEL HYDROGENATED AND FLUORINATED AMORPHOUS SILICON-SULFUR ALLOYS

Hydrogenated and fluorinated amorphous silicon-sulfur alloy thin films were grown by capacitively coupled radio frequency glow discharge dec omposition of SiH4, SiF4 and H2S gas mixtures. Infrared spectroscopy w as used to probe the bonding structure of the material. The infrared s pectra contains three sets of vibrational modes normally observed in a -Si:H, a-Si:F, H and a-Si,S:H. Analysis of the spectra reveals the pre sence of a strong induction effect arising from the high electronegati vity of sulfur and fluorine atoms. The optical Tauc gap was determined from the optical transmission spectra and found to increase from 1.92 eV in a-Si:F, H to 2.12 eV in sulfur rich alloys. The gas evolution s pectra reveals that hydrogen, fluorine and sulfur based species evolve at temperatures which are in direct proportion to their binding energ y with the silicon matrix.