On the rotational alignment of graphene domains grown on Ge(110) and Ge(111)

TL;DR

This study compares graphene growth on Ge(110) and Ge(111), revealing that Ge(110) promotes better rotational alignment due to differences in surface corrugation and reconstruction interactions.

Contribution

It provides experimental and theoretical insights into how substrate surface reconstructions influence graphene's rotational alignment during growth.

Findings

Graphene on Ge(110) exhibits superior rotational alignment.

Graphene on Ge(111) remains poorly aligned due to surface corrugation.

Density functional theory shows flat graphene on Ge(111) and corrugated on Ge(110).

Abstract

We have used low-energy electron diffraction and microscopy to compare the growth of graphene on hydrogen-free Ge(111) and Ge(110) from an atomic carbon flux. Growth on Ge(110) leads to significantly better rotational alignment of graphene domains with the substrate. To explain the poor rotational alignment on Ge(111), we have investigated experimentally and theoretically how the adatom reconstructions on Ge interact with graphene. We find that the ordering transition of the adatom reconstruction of Ge(111) is not significantly perturbed by graphene. Density functional theory calculations show that graphene on reconstructed Ge(110) has large-amplitude corrugations, whereas it is remarkably flat on reconstructed Ge(111). We argue that the absence of corrugations prevents graphene islands from locking into a preferred orientation.