Stacking Sequence Dependence of Graphene Layers on SiC(000-1) - Experimental and Theoretical Investigation

TL;DR

This study combines experimental HRTEM imaging and theoretical DFT calculations to analyze how different stacking sequences of graphene on SiC(000-1) influence their stability and electronic properties, revealing stacking-dependent band structures.

Contribution

It provides a comprehensive experimental and theoretical analysis of the stacking sequence dependence of graphene layers on SiC(000-1), identifying stable configurations and their electronic characteristics.

Findings

Three metastable stacking configurations identified: ABAB, AAAA, ABCA.

The most stable structure was determined via DFT calculations.

Electronic band structures vary significantly with stacking, affecting dispersion relations.

Abstract

Different stacking sequences of graphene are investigated using a combination of experimental and theoretical methods. The high-resolution transmission electron microscopy (HRTEM) of the stacking sequence of several layers of graphene, formed on the C-terminated 4H-SiC(0001) surface, was used to determine the stacking sequence and the interlayer distances. These data prove that the three metastable configurations exist: ABAB, AAAA, ABCA. In accordance to these, findings those three cases were considered theoretically, using Density Functional Theory calculations comparing graphene sheets, freestanding and positioned on the SiC(0001) substrate. The total energies were calculated, the most stable structure was identified and the electronic band structure was obtained. The four graphene layer electron band structure depends crucially on the stacking: for the ABAB and ABCA stacking, the bands, close to the K point, are characterized by the hyperbolic dispersion relation while the AA stacking the dispersion in this region is linear, similar to that of a single graphene layer. It was also shown that the linear dispersion relation is preserved in the presence of the SiC substrate, and also for different distances between adjacent carbon layers.