Epitaxial insulator for bottom-gate field-effect devices based on TiO₂

Field-effect devices with bottom-gate structure based on anatase TiO₂ active channels were fabricated. The key factor to achieve this was the quality of epitaxial insulator layers, viz.; the insulating property and their crystallinity, because they work not only as a well insulator for field-effect devices but also as a template for the subsequent growth of epitaxial active layers. Our devices showed typical transistor actions. On-to-off current ratio exceeded 10⁴ and the field effect mobility of 0.04 cm²/V s were obtained. Interestingly, the device characteristics were found to be sensitive to ambient and light, suggesting their potential for manipulating the fruitful TiO₂ surface functions by tuning the gate voltage.