Approaching the diamond surface: first principles modelling the physics and chemistry of approaching radicals

Abstract

The diamond surface plays a central role in much of the diamond research, and as such much of its properties are described and studied in great detail. There is a clear picture of the atomic scale structure of the different facets and their reconstructions. Also terminations with H, O, N and other atomic species as well as the incorporation of these elements has been modelled [1,2]. The electronic structure and the negative electron affinity mechanism is elucidated and so on. In contrast, however, the atomic scale models of diamond growth are much less developed, though progress is being made [3]. In these models the reaction barriers between stable and meta-stable intermediates are being calculated, providing insights into the kinetics of the surface. However, quantum mechanical models can provide much more insights than this. In this work, we simulated the approach of radical atoms and molecules towards the H-terminated diamond 001 surface. By allowing the model to equilibrate at every step, the physics and chemistry of the approach can be followed in minute detail. It allows us to indicate at which distance the surface and radical start interacting, and what that interaction entails. The charge evolution of the radical and the surface is followed by means of Hirshfeld-I charges, providing insights into charge transfer mechanisms. [4] Throughout the approach, the interaction can be followed through different physical and chemical concepts. Different types of bonding are identified as well as H-abstraction events and covalent bonding. In this work, our focus goes to C and P based radicals, showing them to behave very differently near the surface, providing insights into the requirements for improved P incorporation.