Sidewall depletion in nano-patterned LAO/STO heterostructures

TL;DR

This paper demonstrates a fabrication method for nano-patterned LAO/STO heterostructures that preserves their conductive properties and reveals a narrow depletion region affecting conductivity at small scales.

Contribution

It introduces an electron beam lithography and reactive ion etching process for high-quality nano-patterning of LAO/STO heterostructures without substrate conductivity loss.

Findings

Patterned structures as small as 100nm retain conductivity.

Conductivity shows minimal size dependence at various temperatures.

Depletion region width influences nanoscale transport properties.

Abstract

We report the fabrication of nanostructures from the quasi-two-dimensional electron gas (q2DEG) formed at the LaAlO$_{3}$/ SrTiO$_{3}$ (LAO/STO) interface. The process uses electron beam lithography in combination with reactive ion etching. This technique allows to pattern high-quality structures down to lateral dimensions as small as $100$nm while maintaining the conducting properties without inducing conductivity in the STO substrate. Temperature dependent transport properties of patterned Hall bars of various widths show only a small size dependence of conductivity at low temperature as well as at room temperature. The deviation can be explained by a narrow lateral depletion region. All steps of the patterning process are fully industry compatible.