Abstract
To acquire device-quality TiOx films usually needs high-temperature growth or additional post-thermal treatment. However, both processes make it very difficult to form the p-type TiOx 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 TiOx 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 TiOx-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.
Highlights
Great progress in oxide semiconductor-based electronics have been made in this decade[1]
The thickness of the titanium oxide (TiOx) films prepared at the oxygen flow rate of 15, 17.5 and 20 sccm are estimated to be approximately 16.2, 13.5, and 12.3 nm, respectively, i.e., the growth rate slightly decreased with increase in oxygen flow rate
Upon close inspection of selected area electron diffraction (SAED) patterns, we can find that both metallic Ti and γ-titanium monoxide (TiO) phases are co-existing in the TiOx film obtained under the oxygen flow rate of 15 sccm as evidenced from the lattice spacing (Fig. 1), whereas diffraction pattern from pure γ-TiO phase were detected at the oxygen flow rate of 17.5 sccm (Fig. 2)
Summary
Great progress in oxide semiconductor-based electronics have been made in this decade[1]. The carrier conduction path (valence band) in p-type oxide semiconductors is mainly formed from oxygen p orbitals. The localized nature of p-orbitals leads to large hole effective mass, which severely limits the hole mobility in p-type metal oxides. Such reason results the main difficulty in achieving high performance p-channel oxide semiconductors-based TFTs6,8. Its unique characteristics including intrinsic defects, wide band gap, and high field-effect carrier mobility, renders TiO2 a promising oxide semiconductor as active channel for resistive random access memory[11] and n-type TFT12,13. The tunable conductivity of materials via HIPIMS can be used for other oxides consisting of ZnO, SnO2, In2O3, and so on), expanding the practicality of this growth method
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
