Early stage formation of graphene on the C-face of 6H-SiC

TL;DR

This study explores the initial stages of graphene formation on the C-face of 6H-SiC, revealing that sublimation and layer growth are non-uniform and originate from defect sites, resulting in characteristic pyramid-shaped flakes.

Contribution

It provides detailed insights into the early formation mechanisms of graphene on SiC, highlighting the role of defects and temperature in non-homogeneous growth patterns.

Findings

Graphene nucleates at defect sites such as dislocations.

Growth results in pyramid-shaped flakes with a volcano-like structure.

Layer thickness varies across the surface, indicating non-uniform growth.

Abstract

An investigation of the early stage formation of graphene on the C-face of 6H-SiC is presented. We show that the sublimation of few atomic layers of Si out of the SiC substrate is not homogeneous. In good agreement with the results of theoretical calculations it starts from defective sites, mainly dislocations that define nearly circular flakes, which have a pyramidal, volcano-like, shape with a center chimney where the original defect was located. At higher temperatures, complete conversion occurs but, again, it is not homogeneous. Within the sample surface the intensity of the Raman G and 2D bands, evidences non-homogeneous thickness.