Enhanced tunability of two-dimensional electron gas on SrTiO3 through heterostructuring

TL;DR

This study demonstrates that adding a monolayer LaTiO3 to SrTiO3 significantly enhances the tunability of the 2DEG carrier density, allowing more precise control via UV irradiation and oxygen exposure, surpassing bare STO.

Contribution

The paper introduces a heterostructuring approach with LaTiO3 to improve 2DEG tunability on SrTiO3, providing a more reliable control mechanism than defect-driven methods.

Findings

UV irradiation increases 2DEG density in LTO/STO by ~4 times.

Oxygen exposure reduces 2DEG density in LTO/STO by a factor of 10.

Enhanced tunability is due to surface property changes of the polar LTO layer.

Abstract

Two-dimensional electron gases (2DEGs) on the SrTiO3 (STO) surface or in STO-based heterostructures have exhibited many intriguing phenomena, which are strongly dependent on the 2DEG-carrier density. We report that the tunability of the 2DEG-carrier density is significantly enhanced by adding a monolayer LaTiO3 (LTO) onto the STO. Ultraviolet (UV) irradiation induced maximum carrier density of the 2DEG in LTO/STO is increased by a factor of ~4 times, compared to that of the bare STO. By oxygen gas exposure, it becomes 10 times smaller than that of the bare STO. This enhanced tunability is attributed to the drastic surface property change of a polar LTO layer by UV irradiation and O2 exposure. This indicates that the 2DEG controllability in LTO/STO is more reliable than that on the bare STO driven by defects, such an oxygen vacancy.