SURFACE-STRUCTURE AND COMPOSITION OF CU2-XS CRYSTALS

A sample of Cu2-xS synthesized at 1000-degrees-C from the components Cu and S showed crystals 200-800-mu-m in size on the surface under the scanning electron microscope (SEM). The crystals were shaped like truncated octahedra with well-developed (100) and (111) faces. Previous SEM studies of the surface structure revealed the presence of various figures about 5-30-mu-m in size on the (100) and (111) faces [1]. These included pyramids and prisms, truncated pyramids, skeleton forms, and others. Especially interesting were the mushroom shaped figures on the (100) face. In the present work X-ray energy dispersive spectroscopy of the above mentioned Cu2-xS sample surface was performed. Some compositional changes were observed on the figure surfaces. This compositional analysis showed the real decrease in sulfur content. The factors influencing these analytic results are discussed. It is suggested that the changes in surface composition constitute one of the reasons for the appearance of the figures on the crystal faces described above.