Non-Chalcopyrite Ordering in CuInS2 Epilayers on Si(111)

Long-range order of the CuAu type has been observed in the I-III-VI₂ epilayer CuInS₂ on Si(111) surface. Strong extra reflections in electron diffraction patterns and the doubling of lattice period along the [001] direction in high-resolution images have been observed by transmission electron microscopy. The ordering was found both in Cu- and In-rich epilayers, located in the bulk of the layers. No ordering at the interface to Si(111) was observed.