Effect of impurity (Te and Zn) incorporation in the density of defect states in thin films of Se90In10 and Se75In25 glassy alloys

In this paper we report the effect of Te and Zn incorporation on the density of defect states of two binary Se–In glassy systems. For this purpose, we have chosen here two well known Se₉₀In₁₀ and Se₇₅In₂₅ binary glassy alloys. Thin films of Se₉₀In₁₀, Se₇₅In₂₅, Se₇₅In₁₀Te₁₅ and Se₇₅In₁₀Zn₁₅ glassy alloys prepared by quenching method, were deposited on glass substrate using thermal evaporation technique. Current–voltage characteristics have been measured at various fixed temperatures in the thin films under study. Ohmic behavior was observed at low electric fields while at high electric fields current becomes superohmic. An analysis of the experimental data confirms the presence of space charge limited conduction in Se₉₀In₁₀, Se₇₅In₁₀Te₁₅ and Se₇₅In₁₀Zn₁₅ glassy alloys. It was found that the absence of space charge limited conduction in Se₇₅In₂₅ may be due to joule's heating at high fields. By applying the theory of space charge limited conduction, the density of defect states near Fermi level was calculated. The peculiar role of the additives (Te and Zn) in the pure binary Se₉₀In₁₀ and Se₇₅In₂₅ glassy alloys is also discussed in terms of electro-negativity difference between the elements involved.