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.