The effect of silver incorporation on the properties of co-evaporated arsenic telluride thin films

Electrical resistivity and optical absorption of amorphous As2Te3:Ag co-evaporated films are investigated as a function of the Ag content up to 25 at%. The film resistivity decreased from 2.1 × 104 to 2.6 × 102ω cm and the activation energy for conduction decreased from 0.45 to 0.36 eV with increasing the film Ag content. The dependence of the optical absorption coefficient on the photon energy is ascribed by the relation (αhv) = B(hv − E0)2. The optical gap E0 of the as-prepared films decreases with increasing Ag content. The tail width of the localized states at the band gap was calculated and it increases with increasing the Ag content. The effect of the thermal annealing on the optical absorption was investigated. The changes were attributed to the thermally induced transformations in the chalcogenide films.