CVD Formation of Graphene on SiC Surface in Argon Atmosphere

TL;DR

This study combines experimental and ab-initio calculations to explore how argon atmosphere influences graphene growth on SiC surfaces, revealing catalytic effects and surface deprotonization mechanisms.

Contribution

It provides a detailed quantum chemical analysis of the catalytic role of argon in graphene formation on SiC, highlighting the limitations of zero-temperature models.

Findings

Argon accelerates dehydrogenation at high temperatures.

Surface exhibits catalytic effects in hydrocarbon adsorption.

Zero-temperature models suggest environmental effects are temperature-dependent.

Abstract

We investigate the microscopic processes leading to graphene growth by the chemical vapor deposition of propane in the argon atmosphere at the SiC surface. Experimentally, it is known that the presence of argon fastens the dehydrogenation processes at the surface, in high temperature of about 2000K. We perform ab-initio calculations, at zero temperature, to check whether chemical reactions can explain this phenomenon. Density functional theory and supporting quantum chemistry methods qualitatively describe formation of the graphene wafers. We find that the 4H-SiC(0001) surface exibits large catalytic effect in the adsorption process of hydrocarbon molecules, this is also supported by preliminary molecular dynamics results. Existence of the ArH+ molecule, and an observation from the Raman spectra that the negative charge transfers into the SiC surface, would suggest that presence of argon atoms leads to a deprotonization on the surface, which is necessary to obtain pure carbon add-layer. But the zero-temperature description shows that the cold environment is insufficient to promote the argon-assisted surface cleaning.