Microcleavage, bonding character and surface structure in materials with tetrahedral coordination

Abstract

The investigation of mierocleavage, defined as the separation of crystals parallel to certain crystallo- graphic directions, proves useful for detecting atomic arrays held together by strong bonds (PBC vectors). Estimates of ionic and covalent bonding character can be made and surface properties can be investigated. A structural collapse of the crystal surface layers in some materials with a low coordination (Si, Ge; HgSe, HgTe; AuGa 2, AuIn~_), is indicated for certain crystal planes. For Si and Ge, these results confirm earlier data on crystal habit and corroborate a similar hypothesis proposed by Schlier & Farnsworth (1956) from low-energy electron diffraction data.