Tunability of p- and n-channel TiO_x thin film transistors

To acquire device-quality TiO_x films usually needs high-temperature growth or additional post-thermal treatment. However, both processes make it very difficult to form the p-type TiO_x even under oxygen-poor growth condition. With the aid of high energy generated by high power impulse magnetron sputtering (HIPIMS), a highly stable p-type TiO_x film with good quality can be achieved. In this research, by varying the oxygen flow rate, p-type γ-TiO and n-type TiO₂ films were both prepared by HIPIMS. Furthermore, p- and n-type thin film transistors employing γ-TiO and TiO₂ as channel layers possess the field-effect carrier mobilities of 0.2 and 0.7 cm²/Vs, while their on/off current ratios are 1.7 × 10⁴ and 2.5 × 10⁵, respectively. The first presented p-type γ-TiO TFT is a major breakthrough for fabricating the TiO_x-based p-n combinational devices. Additionally, our work also confirms HIPIMS offers the possibility of growing both p- and n-type conductive oxides, significantly expanding the practical usage of this technique.