# Enhancement of electron mobility at oxide interfaces induced by WO3 overlayers

## TL;DR

This study demonstrates that amorphous WO3 overlayers can significantly enhance electron mobility at oxide interfaces by controlling defect formation, leading to high mobility and effective mass in LaAlO3/SrTiO3 heterostructures.

## Contribution

Introduction of amorphous WO3 overlayers as a versatile method to improve electron mobility and control defects at oxide interfaces, independent of crystal symmetry constraints.

## Key findings

- Electron mobility up to 80,000 cm²/Vs achieved.
- Sharp insulator-to-metal transition observed.
- High magnetoresistance of 900% at 10 T and 1.5 K.

## Abstract

Interfaces between complex oxides constitute a unique playground for 2D electron systems (2DES), where superconductivity and magnetism can arise from combinations of bulk insulators. The 2DES at the LaAlO3/SrTiO3 interface is one of the most studied in this regard, and its origin is determined by both the presence of a polar field in LaAlO3 and the insurgence of point defects, such as oxygen vacancies and intermixed cations. These defects usually reside in the conduction channel and are responsible for a decreased electronic mobility. In this work we use an amorphous WO3 overlayer to control the defect formation and obtain an increased electron mobility and effective mass in WO3/LaAlO3/SrTiO3 heterostructures. The studied system shows a sharp insulator-to-metal transition as a function of both LaAlO3 and WO3 layer thickness. Low-temperature magnetotransport reveals a strong magnetoresistance reaching 900% at 10 T and 1.5 K, the presence of multiple conduction channels with carrier mobility up to 80 000 cm2/Vs and an unusually high effective mass of 5.6 me. The amorphous character of the WO3 overlayer makes this a versatile approach for defect control at oxide interfaces, which could be applied to other heterestrostures disregarding the constraints imposed by crystal symmetry.