A Reactive Molecular Dynamics Study of Hydrogenation on Diamond Surfaces

TL;DR

This study uses reactive molecular dynamics simulations to evaluate hydrogen coverage on various diamond surfaces, revealing that complete hydrogenation is challenging but certain surfaces achieve stable, optimal hydrogenation suitable for electronic device applications.

Contribution

The paper provides a detailed atomistic analysis of hydrogenation thresholds on multiple diamond surfaces, addressing limitations of previous models with full hydrogen coverage.

Findings

Complete hydrogenation is difficult due to steric effects.

Surfaces (001), (110), and (113) achieve higher hydrogen coverage.

Optimum hydrogenation provides stable, homogeneous p-type conductivity.

Abstract

Hydrogenated diamond has been regarded as a promising material in electronic device applications, especially in field-effect transistors (FETs). However, the quality of diamond hydrogenation has not yet been established, nor has the specific orientation that would provide the optimum hydrogen coverage. In addition, most theoretical work in the literature use models with 100% hydrogenated diamond surfaces to study electronic properties, which is far from the experimentally observed hydrogen coverage. In this work, we have carried out a detailed study using fully atomistic reactive molecular dynamics (MD) simulations on low indices diamond surfaces i.e. (001), (013), (110), (113) and (111) to evaluate the quality and hydrogenation thresholds on different diamond surfaces and their possible effects on electronic properties. Our simulation results indicate that the 100% surface hydrogenation in these surfaces is hard to achieve because of the steric repulsion between the terminated hydrogen atoms. Among all the considered surfaces, the (001), (110), and (113) surfaces incorporate a larger number of hydrogen atoms and passivate the surface dangling bonds. Our results on hydrogen stability also suggest that these surfaces with optimum hydrogen coverage are robust under extreme conditions and could provide homogeneous p-type surface conductivity in the diamond surfaces, a key requirement for high-field, high-frequency device applications.