Fabrication of p-type copper oxide thin-film transisters at different oxygen partial pressure

P-type copper-based oxide thin films are fabricated by DC reactive sputtering of copper at room temperature (RT) and studied as a function of oxygen partial pressure (O_PP). Cu₂O crystalline phase is observed at 10% O_PP and it changes to CuO when O_PP increases to 15%. The crystallinity of the deposited films decreases sharply when O_PP increases to ≥20%. The p-type conductivity of the deposited films is identified by Hall measurements. Both the as-deposited and post-annealed bottom gate TFTs using CuO as active layers show significant field effect. The post-annealed CuO TFT with 30% O_PP has the p-type characteristics with μ_FE ≈ 5 × 10^-3 cm^-2/V·s, and an on/off ratio around 10².