Structure and stress of Re(112̄1); chiral terraces at a racemic surface

H A Etman,R A Bennett,S J Jenkins,G Held

doi:10.1039/c3cp53165a

Abstract

The surface structure and morphology of the clean Re(1121) surface has been investigated through combined low energy electron diffraction intensity analysis of data taken at multiple angles of incidence, scanning tunneling microscopy, and first-principles density functional calculations. The results show how this globally racemic surface terminates in two chirally distinct terraces, which show large-scale out-of-plane atomic relaxations and in-plane lateral movement of the uppermost atoms. We further identify and discuss the initial stages of step bunching upon adsorption of oxygen that leads ultimately to the large-scale faceting of the surface. Finally, we present calculations of surface stress and the response to applied surface strain, which suggest routes to the exertion of control over the expression of chirality at the surface.

Highlights

Understanding the structure of solid surfaces is a key requirement for the development of new technologies based on controlling the structure and growth of nano-materials[1] and the engineering of interfaces in device structures
The experimental LEED and STM results confirm that this surface is globally racemic: that is, terminated by two chiral terrace structures that are stereoisomers and degenerate in energy
The surface atoms in each chiral hcp terrace are found to relax in a similar pattern to the chiral fcc(531) Pt and Cu surfaces with a large 32% contraction of the first interlayer spacing, negligible changes in the second interlayer spacing, an 11% contraction of the third interlayer spacing, followed by a large expansion of the fourth by 21%

Summary

Introduction

Understanding the structure of solid surfaces is a key requirement for the development of new technologies based on controlling the structure and growth of nano-materials[1] and the engineering of interfaces in device structures. The experimental LEED and STM results confirm that this surface is globally racemic: that is, terminated by two chiral terrace structures that are stereoisomers and degenerate in energy. The surface atoms in each chiral hcp terrace are found to relax in a similar pattern to the chiral fcc(531) Pt and Cu surfaces (which are uniterminated) with a large 32% contraction of the first interlayer spacing, negligible changes in the second interlayer spacing, an 11% contraction of the third interlayer spacing, followed by a large expansion of the fourth by 21%.

Results

Conclusion