Preparation of Cu2Sn1-xGexS3 bulk single crystals by chemical vapor transport with iodine

Bulk crystals of monoclinic Cu2Sn1−xGexS3 were prepared by chemical vapor transport with iodine. The samples were investigated using electron-probe microanalysis, transmission electron microscopy, Raman spectroscopy and X-ray diffraction (XRD). All of the samples had a Cu-rich and S-poor composition. As the Ge content increased, the XRD peaks shifted to higher angle, the Raman peaks shifted to higher wavenumber, and the lattice constants decreased. Selected-area electron diffraction patterns showed that the samples were single crystal and had a monoclinic structure.