Electron energy loss spectroscopy determination of Ti oxidation state at the (001) LaAlO3/SrTiO3 interface as a function of LaAlO3 growth conditions

TL;DR

This study uses electron energy loss spectroscopy to analyze how the Ti oxidation state at the LaAlO3/SrTiO3 interface varies with different growth conditions, shedding light on the origin of the electron gas.

Contribution

It introduces a spectroscopic method to quantify Ti3+ ratio at the interface as a function of growth parameters, providing new insights into interface chemistry.

Findings

Ti3+ concentration varies with growth conditions.

The method accurately maps Ti oxidation states at the nanoscale.

Results contribute to understanding the electron gas origin.

Abstract

At the (001) interface between the two band-insulators LaAlO3 and SrTiO3, a high-mobility electron gas may appear, which has been the object of numerous works over the last four years. Its origin is a subject of debate between the interface polarity and unintended doping. Here we use electron energy loss 'spectrum images', recorded in cross-section in a scanning transmission electron microscope, to analyse the Ti3+ ratio, characteristic of extra electrons. We find an interface concentration of Ti3+ that depends on growth conditions.