Interface chemical and electronic properties of LaAlO3/SrVO3 heterostructures

TL;DR

This study investigates the chemical and electronic properties of LaAlO3/SrVO3 heterostructures, revealing how interface chemistry influences electronic behavior and proposing methods to mitigate dead layer effects in ultrathin films.

Contribution

It provides new insights into the interface chemistry and electronic properties of LaAlO3/SrVO3 heterostructures, especially regarding chemical reconstruction and its impact on conductivity.

Findings

Ultrathin SrVO3 films are insulating across all temperatures.

LAO/SVO heterostructures show a resistivity minimum at 250 K.

Chemical reconstruction is weaker in heterostructures than in single films.

Abstract

We have studied the chemical and electronic properties of LaAlO3/SrVO3 ultrathin films by combining hard x-ray photoemission spectroscopy and transport measurements. We compare single SrVO3 (SVO) ultrathin films and SrVO3 buried below a polar LaAlO3 (LAO) thin layer, both epitaxially grown on SrTiO3. While ultrathin films (4 unit cells) of SVO do show insulating behavior over the entire temperature range, the LAO/SVO interface has a resistivity minimum at 250 K. When increasing the SVO layer thickness, the minimum is observed to shift to higher temperatures, but the resistivity stays always smaller than that of comparable SVO single films. Hard x-ray photoemission spectroscopy reveals a surface or interface related V5+ component in the V 2p spectra for SVO films and LAO/SVO heterostructures, respectively, attributed to a strongly oxidized component. This chemical reconstruction is weaker in LAO/SVO heterostructures compared to single SVO films. We show that this dead layer in SVO ultrathin films has to be considered when the film thickness reaches the few unit-cells limit and propose solutions on how to prevent this detrimental effect.