Surface dangling bond states and band-lineups in hydrogen-terminated Si, Ge, and Ge/Si nanowires

TL;DR

This study uses ab initio calculations to analyze surface dangling-bond states in hydrogen-terminated Si, Ge, and heterostructure nanowires, revealing a common energy reference for charge transition levels across different materials.

Contribution

It demonstrates that the charge transition levels of surface dangling bonds are nearly constant across Si, Ge, and heterostructures, linked to atomic properties.

Findings

Charge transition levels are at 4.3 +/- 0.1 eV below vacuum.

SDB charge levels are a common reference among Si, Ge, and heterostructures.

The nearly constant value relates to atomic properties across the periodic table.

Abstract

We report an ab initio study of the electronic properties of surface dangling-bond (SDB) states in hydrogen-terminated Si and Ge nanowires with diameters between 1 and 2 nm, Ge/Si nanowire heterostructures, and Si and Ge (111) surfaces. We find that the charge transition levels e(+/-) of SDB states behave as a common energy reference among Si and Ge wires and Si/Ge heterostructures, at 4.3 +/- 0.1 eV below the vacuum level. Calculations of e(+/-) for isolated atoms indicate that this nearly constant value is a periodic-table atomic property.