ABSTRACTAmorphous hydrogenated silicon-tin films (α — Six Snx:H) have been prepared by co-electron beam and Knudsen cell deposition. It is shown that the dependence of Eg on x, over the entire range of 0 < x < 0.51 studied, cannot be described by a single linear relationship. The d.c. conductivity measurements indicate two distinct conduction regions as a function of x. The addition of Sn up to x = 0.10 creates a high density of dangling bonds and moves the band edges so a significant conductivity increase is observed. The bonding between Si and H is preferred to Sn and H. Sn-H bonds were observed only for x > 0.40. Photoluminescence measurements show that band edge luminescence dominates at 1.3–1.4 eV.