Mechanism of the performance improvement of TiO_2-x-based field-effect transistor using SiO₂ as gate insulator

RF magnetron sputtered titanium oxide (TiO_2-x) thin films were used as active channel layer to fabricate field-effect transistors (FETs). In the as-prepared FETs, poor FET performance was found, with a low on-to-off current ratio of ∼500 and a high sub-threshold slope. It is attributed the existence of Si-O-Ti cross-linking bonding at TiO_2-x/SiO₂ interface, which was probed by X-ray Photoelectron Spectroscopy (XPS) measurement. A remark improvement of sub-threshold slope and on-to-off current ratio was observed due to post annealing in vacuum at 300 °C for 30min. By using the electron energy loss spectroscope (EELS) analysis, oxidization of TiO_2-x layer closing to SiO₂ layer region was found, suggesting that Si-O-Ti cross-linking bonding at TiO_2-x/SiO ₂ interface breaks due to post annealing treatment.