Hydrogen inserted into the Si(100)-2x1-H surface: A first-principles study

TL;DR

This study uses density functional theory to analyze how hydrogen atoms interact with the Si(100)-2x1-H surface, revealing stable configurations, charge states, and correspondence with experimental STM images.

Contribution

It provides a detailed first-principles analysis of hydrogen-induced defects and their charge states on the Si(100) surface, linking theoretical predictions with experimental observations.

Findings

Hydrogen forms dihydride units in neutral and negative charge states.

Hydrogen prefers groove sites bonded with second-layer Si in negative charge states.

Simulated STM images match experimental data for certain defect states.

Abstract

An H atom inserted into hydrogen monolayer on the Si(100)-2x1 surface has been studied using the density functional theory. Hydrogen-induced defects were considered in their neutral, negative, and positive charge states. It was found that hydrogen atom forms a dihydride unit on the surface in the most stable neutral and negative charge states. Hydrogen located in the groove between dimer rows and bonded with a second-layer Si atom is also one of the most stable negative charge states. In the positive charge state, hydrogen forms a three-center bond inside a Si dimer, Si-H-Si, similar to the bulk case. A comparison of simulated scanning tunneling microscopy (STM) images with experimental data available in the literature showed that neutral and negatively charged hydrogen-induced defects were already observed in experiments. The results reveal that the adsorption position of an H atom inserted into the Si(100)-2x1-H surface is determined by the charge state of the hydrogen-induced defect.