Control of electronic conduction at an oxide heterointerface using surface polar adsorbates

TL;DR

This study demonstrates that polar surface adsorbates like water and alcohols can significantly modulate electronic conduction at oxide heterointerfaces, revealing a polarization-driven mechanism for interface charge control useful in sensor technology.

Contribution

It provides experimental evidence that surface polar adsorbates can remotely control buried interface conductivity through electrostatic coupling, a novel insight into oxide interface electronics.

Findings

Polar solvents induce a threefold increase in interface conductivity.

Surface adsorbates cause electron accumulation at the LaAlO3/SrTiO3 interface.

The effect is specific to polar solvents, indicating a polarization-driven mechanism.

Abstract

The transfer of electrons between a solid surface and adsorbed atomic or molecular species is fundamental in natural and synthetic processes, being at the heart of most catalytic reactions and many sensors. In special cases, metallic conduction can be induced at the surface of, for example, Si-terminated SiC1, or mixed-terminated ZnO2, in the presence of a hydrogen adlayer. Generally, only the surface atoms are significantly affected by adsorbates. However, remotely changing electronic states far from the adsorbed layer is possible if these states are electrostatically coupled to the surface. Here we show that the surface adsorption of common solvents such as acetone, ethanol, and water can induce a large change (factor of three) in the conductivity at the buried interface between SrTiO3 substrates and LaAlO3 thin films3-8. This phenomenon is observed only for polar solvents. Our result provides experimental evidence that adsorbates at the LaAlO3 surface induce accumulation of electrons at the LaAlO3/SrTiO3 interface, suggesting a general polarization-facilitated electronic transfer mechanism, which can be used for sensor applications.