Gate voltage control of the AlO x /SrTiO 3 interface electrical properties

Electron-beam deposition of an insulating granular aluminium or off-stoichiometric amorphous alumina layer on a SrTiO 3 surface is a simple way to get a metallic interface from insulating materials. No heating nor specific preparation of the SrTiO 3 surface is needed. In this paper, we investigate how the electrical properties of this interface can be tuned by the use of a back gate voltage (electrical field through the SrTiO 3 substrate). We demonstrate that the slow field-effect observed at room temperature can be used to tune in a controlled, reversible way the low temperature electrical properties of the interface. In particular, important parameters of a transistor such as the amplitude of the resistance response to gate voltage changes or the existence of an ‘on’ or an ‘off’ state at zero gate voltage and at low temperature can be adjusted in a single sample. This method should be applicable to any SrTiO 3 -based interface in which oxygen vacancies are involved and might provide a powerful way to study the metal or superconductor insulator transition observed in such systems.