Topographic and etching investigations on melt grown doped KMgF3 crystals

The surfaces of the melt grown doped KMgF3 crystals, grown by czochralski p ulling technique with 5% doping of NiF2, were investigated using an optical microscope The crystals exhibit striations of type-I and type-II. From the topography of matched cleavages, it is demonstrated that these crystals ex hibit perfect cleavages along (1 0 0) planes. The results of etching of (1 0 0) cleavages at different concentrations of the etchant are reported. Ten percent H2SO4 is shown to be the most suitable concentration for delineati ng dislocations intersecting (1 0 0) planes of these crystals. The shape of the etch pits is dependent on concentration of the etchant. Hundred percen t H2SO4 produces circular, whereas lower concentrations produce square etch pits. Besides isolated dislocations, low angle grain boundaries and helica l dislocations are shown to exist. Variations of lateral, vertical and area l etch rates with etchant. concentrations of the etchant are graphically an alysed. (C) 2001 Elsevier Science B.V. All rights reserved.