Cleavage and Twinning in CuInSe 2 Crystals

A study was made of the cleavage and twinning character in single crystals of the chalcopyrite CuInSe 2 , copper indium diselenide, grown in the laboratory by a vertical Bridgman method. In this material, with a c / a ratio of 2.006, the two main cleavage orientations were found to be {10 1 } and {11 2 } (corresponding to the descriptions {201} and {111}, respectively, in a cubic lattice). The plane identifications were made by measuring angles between adjacent cleaved surfaces and verifying the orientations by X-ray Laue and diffractometry. Cleavage was also found less frequently in a {11 0 } plane, but here microscopic examination of the surface revealed it to consist of ridges in a direction, where the microplanes on either side of the ridge edge were {11 2 } planes. Twinning in the grown crystals was found, by angle measurements and X-ray diffraction, to occur along {11 2 } planes, which is similar to the result in face-centred cubic, diamond and zinc blende lattices, where they are the corresponding {111} planes.