Mechanistic Insights into Non-Adiabatic Interband Transitions on a Semiconductor Surface Induced by Hydrogen Atom Collisions

TL;DR

This study uses a mixed quantum-classical model to reveal how hydrogen atom collisions induce site-specific non-adiabatic electron transitions on a semiconductor surface, advancing understanding of energy transfer mechanisms.

Contribution

It introduces a novel non-adiabatic molecular dynamics model that explains site-specific electron excitation during hydrogen collisions on a semiconductor surface.

Findings

Non-adiabatic transitions occur mainly at the rest atom site.

Valence electrons are excited to the conduction band during collisions.

Site-specific differences are due to local band structure changes.

Abstract

To understand the recently observed mysterious non-adiabatic energy transfer for hyperthermal H atom scattering from a semiconductor surface, Ge(111)c(2*8), we present a mixed quantum-classical non-adiabatic molecular dynamics model based on time-dependent evolution of Kohn-Sham orbitals and a classical path approximation. Our results suggest that facile non-adiabatic transitions occur selectively at the rest atom site, featuring excitation of valance band electrons to the conduction band, but not at the adatom site. This drastic site specificity can be attributed to the changes of the local band structure upon energetic H collisions at different surface sites, leading to transient near-degeneracies and significant couplings between occupied and unoccupied orbitals at the rest atom, but not at the adatom. These insights shed valuable light on the collisional induced non-adiabatic dynamics at semiconductor surfaces.