New structural model for GeO2/Ge interface: A first-principles study

TL;DR

This study uses first-principles calculations to propose a new sixfold GeO2 structure at the GeO2/Ge interface, which reduces lattice mismatch and alters electronic properties, offering insights for interface stability.

Contribution

It introduces a novel sixfold GeO2 interface structure derived from cristobalite, demonstrating improved stability and distinct electronic characteristics compared to traditional fourfold interfaces.

Findings

Sixfold GeO2 dramatically reduces lattice mismatch.

Sixfold GeO2 is more stable than fourfold at the interface.

Electronic structure shifts valence band maximum away from the interface.

Abstract

First-principles modeling of a GeO2/Ge(001) interface reveals that sixfold GeO2, which is derived from cristobalite and is different from rutile, dramatically reduces the lattice mismatch at the interface and is much more stable than the conventional fourfold interface. Since the grain boundary between fourfold and sixfold GeO2 is unstable, the sixfold GeO2 forms a large grain at the interface. On the contrary, a comparative study with SiO2 demonstrates that SiO2 maintains a fourfold structure. The sixfold GeO2/Ge interface is shown to be a consequence of the ground-state phase of GeO2. In addition, the electronic structure calculation reveals that sixfold GeO2 at the interface shifts the valence band maximum far from the interface toward the conduction band.