Origin of the Mosaicity in Graphene Grown on Cu(111)

TL;DR

This study investigates the growth mechanisms of graphene on Cu(111) using low-energy electron microscopy, revealing how substrate features and temperature influence mosaicity and crystallinity.

Contribution

It provides new insights into how substrate roughness and temperature affect graphene's grain boundaries and epitaxial quality on Cu(111).

Findings

Rougher substrates increase mosaicity.

Higher temperature improves alignment.

Graphene islands are single crystals on smooth Cu(111).

Abstract

We use low-energy electron microscopy to investigate how graphene grows on Cu(111). Graphene islands first nucleate at substrate defects such as step bunches and impurities. A considerable fraction of these islands can be rotationally misaligned with the substrate, generating grain boundaries upon interisland impingement. New rotational boundaries are also generated as graphene grows across substrate step bunches. Thus, rougher substrates lead to higher degrees of mosaicity than do flatter substrates. Increasing the growth temperature improves crystallographic alignment. We demonstrate that graphene growth on Cu(111) is surface diffusion limited by comparing simulations of the time evolution of island shapes with experiments. Islands are dendritic with distinct lobes, but unlike the polycrystalline, four-lobed islands observed on (100)-textured Cu foils, each island can be a single crystal. Thus, epitaxial graphene on smooth, clean Cu(111) has fewer structural defects than it does on Cu(100).