Structural characterization of as-grown and quasi-free standing graphene layers on SiC

TL;DR

This study compares the structural properties of two types of high-quality epitaxial graphene layers on SiC, revealing differences in morphology, layer distribution, and chemical environment using various surface characterization techniques.

Contribution

It provides a detailed comparative analysis of as-grown and hydrogen-intercalated quasi-free-standing graphene layers on SiC, highlighting structural and morphological differences.

Findings

Large islands observed with different size distributions

Monolayer graphene dominates most surface areas

Bilayer and trilayer regions are localized at steps and islands

Abstract

We report on a comparative structural characterization of two types of high quality epitaxial graphene layers grown by CVD on 4H-SiC(0001). The layers under study are a single layer graphene on top of a buffer layer and a quasi-free-standing graphene obtained by intercalation of hydrogen underneath the buffer layer. We determine the morphology and structure of both layers by different complementary in-situ and ex-situ surface techniques. We found the existence of large islands in both samples but with different size distribution. Photoemission electron microscopy (PEEM) measurements were performed to get information about the chemical environment of the different regions. The study reveals that monolayer graphene prevails in most of the surface terraces, while a bilayer and trilayer graphene presence is observed at the steps, stripes along steps and islands.