Influence of oxygen partial pressure on the properties of undoped InO films deposited at room temperature by rf-PERTE

Transparent and conductive/semiconductive undoped indium oxide (InOx) thin films were deposited at room temperature. The deposition technique used is the radio frequency (rf) plasma enhanced reactive thermal evaporation (rf-PERTE) of indium (In) in the presence of oxygen. The influence of oxygen partial pressure on the properties of these films is presented. The oxygen partial pressure varied between 3 × 10−2 and 1.3 × 10−1 Pa. Undoped InOx films, 100 nm thick, deposited at the oxygen partial pressure of 6 × 10−2 Pa show a conductive behaviour, exhibit an average visible transmittance of 81%, a band gap around 2.7 eV and an electrical conductivity of about 1100 (Ω cm)−1. For oxygen pressures greater than 6 × 10−2 Pa, semiconductive films are obtained, maintaining the visible transmittance. Films deposited at lower pressures are conductive but dark. From XPS data, films deposited at an oxygen partial pressure of 6 × 10−2 Pa show the highest amount of oxygen in the film surface and the lowest ratio between oxygen in the oxide crystalline and amorphous phases.