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

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 σ₀ = 10^-3-10^-2 (Ωcm)^-1 or 0.1-1 (Ω cm)^-1. An electric field of 6 × 10²-3 × 10⁴ 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 σ₀ and by a factor of 2-3 for the films with higher σ₀. Subsequent TCI in air restored the previous conductivity of the high σ₀ 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 O₂, 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.