CUAU-TYPE ORDERING IN EPITAXIAL CUINS2 FILMS

Ordering of Cu and In atoms in near-stoichiometric CuInS2 epitaxial fi lms grown on Si (111) by molecular beam epitaxy was studied by transmi ssion electron microscopy. Nonchalcopyrite ordering of the metal atoms in CuInS2 is observed, which is identified as CuAu-type ordering. Sha rp spots in electron diffraction patterns reveal the ordered Cu and In atom planes alternating along the [001] direction over a long range. High-resolution electron microscopy confirms this ordering. The CuAu-o rdered structure coexists with the chalcopyrite ordered structure, in agreement with theoretical prediction. (C) 1998 American Institute of Physics. [S0003-6951(98)01132-2].