Approaching ideal graphene: The structure of hydrogen-intercalated graphene on 6H-SiC(0001)

TL;DR

This study combines experimental measurements and density functional calculations to analyze hydrogen-intercalated graphene on 6H-SiC(0001), revealing it closely resembles ideal graphene with minimal buckling and low adsorption energy.

Contribution

It provides detailed structural insights into hydrogen-intercalated graphene, demonstrating its near-ideal properties and low interaction energy with the substrate.

Findings

Experimental adsorption height matches calculations

Graphene exhibits very low buckling and homogeneous electron density

Lowest known adsorption energy per atom for graphene on any substrate

Abstract

We measure the adsorption height of hydrogen-intercalated quasi-free-standing monolayer graphene on the (0001) face of 6H silicon carbide by the normal incidence x-ray standing wave technique. A density functional calculation for the full ($6 \sqrt{3} \times 6 \sqrt{3}$)-R30$^\circ$ unit cell, based on a van der Waals corrected exchange correlation functional, finds a purely physisorptive adsorption height in excellent agreement with experiments, a very low buckling of the graphene layer, a very homogeneous electron density at the interface and the lowest known adsorption energy per atom for graphene on any substrate. A structural comparison to other graphenes suggests that hydrogen intercalated graphene on 6H-SiC(0001) approaches ideal graphene.