Simulations of Surface X-ray Diffraction from a Monolayer 4He Film Adsorbed on Graphite

TL;DR

This study uses simulations of surface X-ray diffraction to analyze a monolayer helium film on graphite, demonstrating sensitivity to surface structure and preliminary experimental validation of the model.

Contribution

The paper introduces detailed simulations of CTR scatterings from a helium monolayer on graphite, highlighting their sensitivity to surface structure and phase variations.

Findings

CTR scattering intensities vary with monolayer height

Simulations predict intensity modulations in incommensurate solid phase

Preliminary experimental data support simulation predictions

Abstract

We carried out simulations of crystal truncation rod (CTR) scatterings, i.e., one of the surface X-ray diffraction techniques with atomic resolution, from a monolayer He film adsorbed on graphite. Our simulations reveal that the 00L rod scatterings from the He monolayer exhibit notable intensity modifications for those from a graphite surface in the ranges of approximately L = 0.6 - 1.7 and L = 2.2 - 3.5. The height of the He monolayer from the graphite surface largely affects the CTR scattering profiles, indicating that CTR scatterings have enough sensitivities to determine the surface structure of the various phases in the He layer. In particular, in the incommensurate solid phase, our preliminary experimental data show the intensity modulations that are expected from the present simulations.