Abstract:
In this study a model for the orientation dependent surface stabilization of diamond grown from the vapour phase is presented. The model is based on a first order broken bond analysis of the diamond crystal with additional considerations about surface reconstruction by dimer formation. Due to the formation of dimers, surface stabilization is expected for orientations corresponding to Miller indices {hhk}(h<k) in the {110} zones. It is demonstrated that this model gives a good description of growth phenomena like facets, curved bands and microfaceting, observed on homoepitaxially grown diamond samples. These specimens are obtained by flame deposition on cylindrical type IIa natural diamond substrates with {111}, {110} or {001} top faces. In conformation with the model the surfaces {hhk}(h<k) between {111} and {113} appear to be stabilized in one direction, while a discrete number of orientations between {113} and {001} are subject to two-dimensional stabilization. All other surfaces are stabilized by the development of microfacets which also have orientations close to {hhk}(h<k), as was determined by laser reflectometry. In addition it is shown that differences in the orientation dependent incorporation of nitrogen as nitrogen-vacancy pairs in the diamond lattice is consistent with the described model. For this purpose a single crystalline diamond layer grown on top of a hemispherical diamond substrate by the flame technique was investigated by cathodoluminescence topography.