Amorphous semiconducting films prepared by plasma decomposition of H2S-N2-NH3

In an attempt to produce amorphous polymeric films of (SN) x by plasma decomposition of H 2 S-N 2 and H 2 S-NH 3 gas mixtures, we obtained amorphous semiconducting material containing S and about 20at.% Fe, Cr, N and H. Inadvertent sputtering from the stainless-steel chamber introduced the transition-metal elements. These, as well as nitrogen, were important in promoting the film deposition. The films have several unusual properties. The optical gap is only E 0 = 0.2 eV wide. The electrical conductivity curve shows two distinct activation energies, both much smaller than E 0 . Above 80 K, σ = σ 0 exp (− ΔE/kT) with σ o = 200 Ω −1 cm −1 and ΔE = 0028eV. Between 3 and 70 K one finds σ 0 = 20 Ω −1 cm −1 and ΩE = 0.007 eV. The thermopower is positive and increases from 68 μV/deg at 80 K to 88 μV/deg at 300 K.