Cation sublattice stacking faults in Cu-rich chalcopyrite CuInSe₂

Using transmission electron microscopy, we have found stacking faults on the cation sublattice in the chalcopyrite structure of CuInSe₂. These films are grown by molecular beam epitaxy under Cu-rich conditions. These stacking faults are found to extend large distances in the plane of the film, and are not found to be present in samples not grown in Cu-rich conditions. We suggest that this defect is triggered by a Cu-induced transformation of the surface structure of the growing film.