Local vibrational modes and the optical absorption tail of amorphous silicon

Local vibrational modes of Si-H is an important research area in recent years. Local vibrational modes of chemical bonds between Si atom and other impurity atoms such as H and O in amorphous silicon films produced by radio frequency sputtering were studied by means of Fourier transform infrared spectroscopy. The concentrations of Si-H, Si-O and Si-C in the sample were calculated. It was found that the concentration of Si-H bond varied significantly when the material was annealed at temperatures T _a>600 K and tended to zero for T_a>1000 K. The optical absorption edge was also found to depend strongly on the thermal history of the amorphous semiconductor. A strong correlation between the optical absorption coefficient and the concentration of Si-H was also observed.