Density-functional study of hydrogen chemisorption on vicinal Si(001) surfaces

TL;DR

This study uses density-functional theory to analyze hydrogen chemisorption on vicinal Si(001) surfaces, revealing stable step structures and preferential hydrogen binding sites, aligning with recent experimental findings.

Contribution

It provides detailed computational insights into hydrogen adsorption energies and stable surface configurations on vicinal silicon surfaces, expanding understanding of surface chemistry.

Findings

Rebonded D_B step remains stable with hydrogen coverage.

Hydrogen prefers binding at rebonded step edges over terraces.

Results agree with recent experimental observations.

Abstract

Relaxed atomic geometries and chemisorption energies have been calculated for the dissociative adsorption of molecular hydrogen on vicinal Si(001) surfaces. We employ density-functional theory, together with a pseudopotential for Si, and apply the generalized gradient approximation by Perdew and Wang to the exchange-correlation functional. We find the double-atomic-height rebonded D_B step, which is known to be stable on the clean surface, to remain stable on partially hydrogen-covered surfaces. The H atoms preferentially bind to the Si atoms at the rebonded step edge, with a chemisorption energy difference with respect to the terrace sites of >sim 0.1 eV. A surface with rebonded single atomic height S_A and S_B steps gives very similar results. The interaction between H-Si-Si-H mono-hydride units is shown to be unimportant for the calculation of the step-edge hydrogen-occupation. Our results confirm the interpretation and results of the recent H_2 adsorption experiments on vicinal Si surfaces by Raschke and Hoefer described in the preceding paper.