Metal-insulator transition in SrTiO3 induced by field effect

We have induced a metal-insulator transition in nondoped SrTiO3 by an electric field. The sheet carrier concentration of a SrTiO3 single-crystal surface was increased by electrostatic doping to 3.4×1012cm−2. A crossover from an insulating phase to a metallic state was clearly observed. The conduction mechanism in the insulating phase was explained in terms of thermal carrier excitation. By applying a gate field, the activation energy of the thermally excited carriers was reduced, eventually reaching zero at a critical gate field and thus converting the transistor channel to a metallic state. The sheet resistance was found to scale with temperature in both insulating and metallic states.