Fabrication of p-type TiO₂ and transparent p-TiO₂/n-ITO p-n junctions

This study reports a transparent p-type TiO₂ thin film by DC reactive magnetron sputtering method with 10% O₂ partial pressure. The p-type conduction of TiO₂ thin film was also confirmed by Seebeck effect. The lowest resistivity (1.458×10^-2 Ω·cm) of the studied TiO₂ thin film occurs at the annealing temperature of 500 °C in the under N₂ atmosphere ambient. We believe that the p-type conduction mechanism of the as-deposited TiO₂ thin films with 10% O₂ partial pressure could be caused by the defect reaction mechanism, i.e., the Ti²⁺-Ti⁴⁺ substitution reaction. A transparent p-n junction of p-TiO₂/n-ITO was fabricated by photolithography and lift-off processes. The I-V curve of p-TiO₂/n-ITO junction shows that p-TiO₂/n-ITO p-n junction clearly exhibits a good diode characteristic with a turn-on voltage of about 3.19 V under forward-biased voltage, which corresponds to the band gap of the TiO₂. It further proves that the current studied TiO₂ thin film prepared with 10% O₂ partial pressure is the p-type conduction.