Thermodynamic Equilibrium Conditions of Graphene Films on SiC

Lydia Nemec,Patrick Rinke,Volker Blum,Matthias Scheffler

doi:10.1103/physrevlett.111.065502

Lydia Nemec, Patrick Rinke + Show 2 more

Open Access

https://doi.org/10.1103/physrevlett.111.065502

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Abstract

First-principles surface phase diagrams reveal that epitaxial monolayer graphene films on the Si side of 3C-SiC(111) can exist as thermodynamically stable phases in a narrow range of experimentally controllable conditions, defining a path to the highest quality graphene films. Our calculations are based on a van der Waals corrected density functional. The full, experimentally observed (6sqrt[3]×6sqrt[3])-R30° supercells for zero- to trilayer graphene are essential to describe the correct interface geometries and the relative stability of surface phases and possible defects.

Highlights

First-principles surface phase diagrams reveal that epitaxial monolayer graphene films on the Si side of 3C-SiC(111) can exist as thermodynamically stable phases in a narrow range of experimentally controllable conditions, defining a path to the highest quality graphene films
On the semiconductor SiC, well-ordered graphene films can be grown directly by a simple process (Si sublimation from the surface; see, e.g., Refs. [1,2,3,4,5,6,7]) and the standard tools of semiconductor technology can be used for further manipulation
Controlling the precise thickness of graphene films is important to minimize the coexistence of monolayer graphene (MLG) and bilayer graphene (BLG) [3,5,10,11]

Summary

Introduction

First-principles surface phase diagrams reveal that epitaxial monolayer graphene films on the Si side of 3C-SiC(111) can exist as thermodynamically stable phases in a narrow range of experimentally controllable conditions, defining a path to the highest quality graphene films. Reference [16] shows that the carbon-rich ‘‘zero-layer graphene’’ (ZLG) or ‘‘buffer layer’’ precursor phase [1,2,13,17] (not yet graphene) on the Si face is a reversible thermodynamic equilibrium phase at high T and controlled disilane background pressure.

Results

Conclusion