Field-effect transistor based on atomically flat rutile TiO2

The authors have fabricated a field-effect transistor (FET) based on a rutile TiO2 active channel. Top-gate transistor structure with an amorphous LaAlO3 insulator was fabricated on the ultrasmoothed rutile single crystals. Reproducible n-type FET actions were observed only by the use of ultrasmoothed TiO2 surfaces. Moreover, an anisotropy of the field-effect mobility depending on the channel direction, which reflects intrinsic nature of rutile, was definitely observed. Inserting MgO insulating buffer between TiO2 and amorphous LaAlO3 suppressed the off-state current and realized on-to-off current ratio as high as 104.