Charge writing at the LaAlO3/SrTiO3 surface

TL;DR

This paper demonstrates that biased AFM can write and erase nanoscale conductive lines on LaAlO3/SrTiO3 surfaces by depositing stable surface charges, revealing polarity asymmetry linked to built-in potential.

Contribution

It uncovers the mechanism of conductivity switching as surface charge writing and provides experimental evidence for a built-in potential in ultrathin LaAlO3 layers.

Findings

Surface charges are stably deposited across various LaAlO3 thicknesses.

Polarity asymmetry observed in 1 and 2 unit cell LaAlO3, confirming theoretical predictions.

Conductivity switching is driven by surface charge writing, not other mechanisms.

Abstract

Biased conducting-tip atomic force microscopy (AFM) has been shown to write and erase nanoscale metallic lines at the LaAlO3/SrTiO3 interface. Using various AFM modes, we show the mechanism of conductivity switching is the writing of surface charge. These charges are stably deposited on a wide range of LaAlO3 thicknesses, including bulk crystals. A strong asymmetry with writing polarity was found for 1 and 2 unit cells of LaAlO3, providing experimental evidence for a theoretically predicted built-in potential.