Why Some Interfaces Cannot be Sharp

TL;DR

This paper investigates the fundamental differences between ionically and electronically compensated interfaces in materials, revealing how electron mobility can be used to create sharper interfaces and improve oxide device performance.

Contribution

It introduces a novel understanding of interface compensation mechanisms and proposes a strategy to design sharper interfaces by controlling electronic screening charges.

Findings

Electronically compensated interfaces are sharper than ionically compensated ones.

There is a fundamental asymmetry in interfacial sharpness and carrier density.

Controlling electronic screening can enhance oxide device performance.

Abstract

A central goal of modern materials physics and nanoscience is control of materials and their interfaces to atomic dimensions. For interfaces between polar and non-polar layers, this goal is thwarted by a polar catastrophe that forces an interfacial reconstruction. In traditional semiconductors this reconstruction is achieved by an atomic disordering and stoichiometry change at the interface, but in multivalent oxides a new option is available: if the electrons can move, the atoms don`t have to. Using atomic-scale electron energy loss spectroscopy we find that there is a fundamental asymmetry between ionically and electronically compensated interfaces, both in interfacial sharpness and carrier density. This suggests a general strategy to design sharp interfaces, remove interfacial screening charges, control the band offset, and hence dramatically improving the performance of oxide devices.