On the influence of surface reconstruction on crystal growth processes

Abstract

Application of the morphologic Periodic Bond Chain method to diamond-like crystal structures learns that {001} faces should be K or S type, i.e. they will be atomically rough. This implies that these cubic faces should have a very high growth rate and that on these surfaces no steps should appear because the step free energy is zero. However, this is in conflict with quite a lot of experimental evidence, especially for the {001} faces of Si, Ge, GaAs and diamond which generally are slowly growing stable faces crowded with growth steps. This contradiction can be explained by accepting that under the conditions where these crystals were grown the {001} surface has reconstructed into the well known (2 × 1) reconstruction where the surface atoms lower their energy by dimerization and occupy different positions with respect to the bulk phase. This leads to the creation of a step free energy larger than zero and thus to the observed F-like behaviour. It is demonstrated that the (2 × 1) reconstruction not only is present for the cases under high vacuum conditions, but also can be operative at normal growth conditions, for instance at 1 bar pressure, where adsorption might play a role. Further the lateral orientations of growth steps on the {111} and {001} faces of diamond-like semiconductor crystals are discussed in terms of reconstruction near or at step site atoms.