Gate voltage control of the $AlO_x$/$SrTiO_3$ interface electrical properties

TL;DR

This study demonstrates that applying a back gate voltage can reversibly and precisely tune the electrical properties of a $AlO_x$/$SrTiO_3$ interface, enabling control over transistor parameters at low temperatures.

Contribution

It introduces a simple, non-thermal method to control $SrTiO_3$-based interface properties via gate voltage, applicable to systems involving oxygen vacancies.

Findings

Reversible tuning of interface resistance with gate voltage.

Control over 'on' and 'off' states at low temperature.

Potential to study metal-insulator and superconductor-insulator transitions.

Abstract

Electron-beam deposition of an insulating granular aluminium or of an 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 are 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 reversibly and in a controlled 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.