Single crystal SrTiO3 field-effect transistor with an atomically flat amorphous CaHfO3 gate insulator

We have observed prominent transistor action in a transition-metal oxide which is not traditionally viewed as a semiconductor. We have fabricated a field-effect transistor composed of SrTiO3(100) single crystal as a channel and an amorphous CaHfO3 layer as a gate insulator. The amorphous CaHfO3 gate insulator layer was atomically flat and had a breakdown field of over 5MV∕cm. All electrode and channel patterning was done with simple contact masks. The whole fabrication process took place at room temperature. The device showed a field-effect mobility of 0.4–0.5cm2∕Vs and an on-to-off channel current ratio of ∼105 at room temperature.