Determination of the Spacing Between Hydrogen-Intercalated Quasi-Free-Standing Monolayer Graphene and 6H-SiC(0001) Using Total-Reflection High-Energy Positron Diffraction

TL;DR

This study precisely measures the distance between hydrogen-intercalated monolayer graphene and SiC substrate using advanced diffraction techniques, confirming theoretical predictions and enhancing understanding of graphene's structure.

Contribution

First application of total-reflection high-energy positron diffraction to determine the interlayer spacing in hydrogen-intercalated graphene on SiC.

Findings

Measured interlayer spacing as 4.18 Å

Confirmed agreement with density-functional theory

Resolved multiple diffraction spots for detailed analysis

Abstract

We have investigated the structure of hydrogen-intercalated quasi-free-standing monolayer graphene (QFMLG) grown on 6H-SiC(0001) by employing total-reflection high-energy positron diffraction (TRHEPD). At least nine diffraction spots of the zeroth order Laue zone were resolved along <11-20> and three along <1-100>, which are assigned to graphene, SiC and higher order spots from multiple diffraction on both lattices. We further performed rocking curve analysis based on the full dynamical diffraction theory to precisely determine the spacing between QFMLG and the SiC substrate. Our study yields a spacing of d = 4.18(6)\r{A} that is in excellent agreement with the results from density-functional theory (DFT) calculations published previously.