Synthesis, structure and physical properties of layered semiconductors MCuFCh (M=Sr, Eu, Ch=S, Se)

Effects of open shell cations on magnetic, optical and carrier transport properties were examined for layered wide bandgap semiconductors MCuFCh (M=Sr, Eu, Ch=S, Se). Single-phase MCuFCh   powder and ceramic samples were synthesized by solid-state reactions. The crystal structures refined by the Rietveld analyzes revealed that all the materials have the space group P4/nmmP4/nmm, indicating that the samples have the same crystal structure as that of layered oxychalcogenides LaCuOCh, and cation vacancies of several percent were present for Cu+ and Eu2+ sites in EuCuFCh. Thermopower measurements revealed that both SrCuFCh and EuCuFCh were p-type semiconductors. Degenerate conduction was observed for EuCuFCh with conductivities >1 S cm−1, whereas SrCuFCh exhibited thermally activated behavior. The optical band gaps of SrCuFS and SrCuFSe estimated were approximately 3.0 and 2.7 eV, respectively, and those of EuCuFCh were ∼2 eV. Temperature dependence of magnetic susceptibilities of EuCuFCh followed the Curie–Weiss law down to 5 K and the samples did not show any transition to a magnetic ordering phase.

Layered compounds MCuFCh(M=Sr, Eu, Ch=S, Se) were synthesized and their structural, optical, electrical and magnetic properties were measured. The Eu-derivatives exhibit metallic conduction and paramagnetic down to 5 K, while the Sr-derivatives have semiconducting properties with an energy gap of ∼3 eV.Figure optionsDownload as PowerPoint slide