Characterization of zinc-tin-oxide films deposited by thermal co-evaporation

The structural, electrical, and optical properties of zinc-tin-oxide (ZTO) films with different compositions prepared by thermal co-evaporation using ZnO and SnO2 sources were investigated. The as-deposited films were amorphous but opaque. The lowest resistivity, similar to 8x10(-5) Omega cm, was obtained for ZTO with 33 at.% Sn. Upon post-annealing in air, a sharp increase in transparency was observed between 350 and 550 degrees C, accompanying with a marked decrease in conductivity. This was attributed to re-oxidation of partially reduced oxides, leading to a lower density of oxygen vacancies. Our study showed that conductive and transparent ZTO films with low Sn content may be prepared by co-evaporation deposition, and suitable for use in devices as transparent electrodes. (C) 2012 Elsevier B. V. All rights reserved.