Infrared and raman spectroscopy of a-Si, Se: H alloys prepared by r.f. glow discharge

Hydrogenated amorphous silicon-selenium alloy thin films were grown by capacitively coupled radio frequency glow discharge decomposition of (SiH 4 + He) and (H 2 Se + He) gas mixtures. Infrared and Raman measurements were performed to probe the structure of the material. In addition to the Si-H induced bands normally appearing in the i.r. spectra of unalloyed a-Si: H, new bands at 730, 350 and 380 cm −1 are observed. The nature and possible origin of these bands is discussed. Data measured for samples of various composition suggest that the 380 cm −1 band arises from the vibrational modes of the Si-Se bonds. Analysis of the Si-H stretching region shows that a mixing of vibrational modes induced by Se atoms prevails in the alloys. A correlation between the optical Tauc gap, Urbach energy, defect density and the selenium content is established.