The effect of post-deposition transverse current injection on amorphous indium oxide film conductivity

Abstract

Amorphous In–O thin films with a thickness of ∼0.1 μm were produced by thermal evaporation of indium oxide powder in a vacuum of 10 −5–5×10 −4 Torr onto glass substrates at room temperature. The films had conductivities of either σ 0=10 −3–10 −2 (Ω cm) −1 or 0.1–1 (Ω cm) −1. An electric field of 6×10 2–3×10 4 V/m with its consequent transverse current injection (TCI) was applied parallel to the films for 15–400 min in vacuum after deposition, and the conductivity of films was measured as a function of the time for different applied fields. The current injection increased the film conductivity by a factor of 4–6 for the films with the lower σ 0 and by a factor of 2–3 for the films with higher σ 0. Subsequent TCI in air restored the previous conductivity of the high σ 0 films, while subsequent TCI in helium or nitrogen had no effect. The as-deposited films are suspected to consist of high conductivity islets in a low conductivity matrix. The conductivity increase is explained by TCI induced outgassing of O 2, leading to an increased carrier concentration at the cathodic extremity of the high conductivity regions, which decreases the distance between high conductivity regions and ultimately connects them together.