Cation ordering and physicochemical characterization of the quaternary diamond-like semiconductor Ag2CdGeS4

The quaternary diamond-like semiconductor, Ag2CdGeS4, was synthesized via high-temperature solid-state synthesis as well as structurally and physicochemically characterized. Single crystal X-ray diffraction provided a model for Ag2CdGeS4 in the orthorhombic, noncentrosymmetric space group Pna21 with a=13.7415(8) Å, b=8.0367(5) Å and c=6.5907(4) Å, in contrast to a previously published model in Pmn21 from the Rietveld analysis of laboratory X-ray powder diffraction data. The Pna21 space group is supported by the Rietveld analysis of synchrotron X-ray powder diffraction data. Differential thermal analysis suggests that Ag2CdGeS4 exists in two polymorphs. Optical diffuse reflectance UV/vis/NIR spectroscopy indicates that the orange compound is a semiconductor with a band gap of 2.32 eV. Optical microscopy, scanning electron microscopy, energy dispersive spectroscopy and inductively coupled plasma optical emission spectroscopy were used to further characterize the material.

The structure of the diamond-like semiconductor Ag2CdGeS4 has been solved and refined in the orthorhombic noncentrosymmetric space group Pna21. A view down the a-axis shows that all MS4 tetrahedra are pointing in the same direction along the c-axis. The structure can be derived from that of lonsdaleite.Figure optionsDownload as PowerPoint slideHighlights
► The structure of Ag2CdGeS4 is solved from single crystal X-ray diffraction.
► The structure is supported by the Rietveld analysis of synchrotron diffraction data.
► Ag2CdGeS4 is a semiconductor with an optical band gap of 2.32 eV.
► Additional characterization is reported.