High power impulse magnetron sputtered p-type γ-titanium monoxide films: Effects of substrate bias and post-annealing on microstructure characteristics and optoelectrical properties

In view of wide potential use as p-type oxide semiconductor of titanium monoxide (TiO), it is deposited in this work by using high power impulse magnetron sputtering (HIPIMS), which is known to provide less hysteresis effect in reactive sputtering and better control in stoichiometry. A strong correlation among the preparation parameters on the microstructure and optoelectrical characteristics of the obtained Ti-O films are investigated. Experimental results show that the crystallinic cubic gamma-TiO can be directly grown on unheated glass substrate. In regard to the effects of substrate bias and post-annealing, the as-grown gamma-TiO transfers into rutile (R-TiO2) at a critical substrate bias voltage of -125 V or post-annealing temperature of 500 degrees C. For the purpose of p-type channel layer in transistor, the optimum gamma-TiO film exhibiting a high hole mobility of 8.2 cm(2)/V s is grown at the substrate bias voltage of -25 V and followed by the post-annealing at 400 degrees C.