Multilayer epitaxial graphene formed by pyrolysis of polycrystalline silicon-carbide grown on c-plane sapphire substrates

TL;DR

This study demonstrates a method to produce high-quality multilayer graphene on sapphire substrates by annealing polycrystalline silicon carbide, with improvements in graphene quality through surface planarization.

Contribution

It introduces a novel process combining ultra-high vacuum CVD and surface planarization to enhance multilayer graphene growth on sapphire.

Findings

Conformal multilayer graphene is formed despite SiC surface roughness.

Polishing SiC reduces defects and improves layer order.

Polished SiC yields higher carrier mobility in graphene.

Abstract

We use ultra-high vacuum chemical vapor deposition to grow polycrystalline silicon carbide (SiC) on c-plane sapphire wafers which are then annealed between 1250 and 1450{\deg}C in vacuum to create epitaxial multilayer graphene (MLG). Despite the surface roughness and small domain size of the polycrystalline SiC, a conformal MLG film is formed. By planarizing the SiC prior to graphene growth, a reduction of the Raman defect band is observed in the final MLG. The graphene formed on polished SiC films also demonstrates significantly more ordered layer-by-layer growth and increased carrier mobility for the same carrier density as the non-polished samples.