Dislocation activities in SnI 2 and SnI 4 single crystals

Abstract

As-grown (010) and (111) surfaces of SnI 2 and SnI 4 single crystals respectively were successively chemically etched in 0.15 M hydrochloric acid solution. It was established that the pits indicate the sites of dislocations in these crystals. This was further confirmed from a comparison of the etch patterns before and after the (010) and (111) surfaces were chemically polished. The average density of the dislocations was found to be greater in SnI 2 crystals than in SnI 4 crystals. The lateral and normal velocities of the growth of pits in these crystals were then measured at various temperatures. The time dependence of the growth of the pits was found to be linear, whereas the temperature dependence of the growth was found to be exponential, i.e. V = A exp( -E kT ) . The dissolution parameters, i.e the activation energies and the pre-exponential factors for dissolution along the surface and along the dislocation lines, were computed. It was observed that the activation energies for dissolution along the various directions were different and were greater for SnI 4 than for SnI 2 crystals. The implications are discussed.