Amorphous hydrogenated silicon-carbon-tin alloy films

A new amorphous semiconductor alloy system a-Si-C-Sn:H has been prepared by rf magnetron sputtering of Sn in an atmosphere of ${\mathrm{SiH}}_4$, ${\mathrm{CH}}_4$, and Ar. Optical properties and dark conductivity of thin films are measured as a function of ${\mathrm{CH}}_4$ flux. The dark conductivity displays a transition to a hopping-conduction mechanism as the ${\mathrm{CH}}_4$ flux increases. In ir spectra, C-Sn and Sn-Sn vibrational bands are observed at 510 and 150 ${\mathrm{cm}}^{\mathrm{-}1}$, respectively. Dangling-bond density values are deduced from ESR measurements.