Etch Pits and Dislocations in SnO2 Crystals

Abstract

Dislocation etchants have been developed for SnO₂ single crystals grown from the vapor phase. The correlation between etch pits and dislocations was established by an analysis of the pit patterns formed on matched cleavage surfaces, and on as‐grown faces after plastic deformation and annealing. The slip systems were found to be {110}/〈001〉 and {101}/〈101̄〉, and arguments for the existence of partial dislocations on the latter slip plane are given. The shapes of pits produced by boiling HI on {110} faces are analyzed for a correlation with the following dislocation characteristics: angle of incidence of the dislocation line, the presence of segregated impurities on the dislocation, and the direction of the Burgers vector. A simple technique for decorating dislocations is described. Finally, it is shown that dislocations in as‐grown crystals arise from two processes, both occurring during cooling after growth: (1) the differential thermal expansion of the growth substrate and adhering crystals, and (2) the diffusion of oxygen into the material resulting in a stoichiometry gradient.