Electron doping into the surface of SrTiO3 single crystal by using a field effect transistor structure having a polyvinyl alcohol gate insulator layer

We fabricated an n-channel accumulation-type field-effect transistor (FET) on a SrTiO3 single crystal having a polyvinyl alcohol (PVA) layer and a Na+-doped PVA layer as a gate insulator. Both devices show an n-type FET performance having a response time of 10 – 100 second order. This slow response is due to the gradual formation of an electric double layer by solvated Na+ ions moving through the water absorbed in the PVA layer towards the surface of SrTiO3 by applying a gate voltage (VG), which is manifested by the fact that Na+-doping into the PVA layer dramatically reduces the driving voltages and the response time. In these devices, metallic or semiconducting behaviors are observed if the applied VG is large enough to form a conducting channel during cooling of the devices. These results indicate that electrons are certainly doped into the surface of SrTiO3 by applying VG in both devices.