Fabrication of heteroepitaxial thin films of layered oxychalcogenides LnCuOCh (Ln = La–Nd; Ch = S–Te) by reactive solid-phase epitaxy

Processes and preparation conditions for growing epitaxial thin films of Cu-based, layered oxychalcogenides LnCuOCh (Ln = La, Ce, Pr or Nd; Ch = S_1-xSe_x or Se_1-yTe_y) are reported. Epitaxial thin films on MgO (001) substrates were prepared by a reactive solid-phase epitaxy method. Four-axes high-resolution x-ray diffraction measurements revealed that the crystallographic orientation is (001)[110] LnCuOCh || (001)[110] MgO and the internal stress of the crystalline lattices in the films are relaxed during thermal-annealing process of the reactive solid-phase epitaxy. Furthermore, except for CeCuOS, systematic variations in the lattice constant by chalcogen or lanthanide ion substitutions were observed. These results demonstrated that the reactive solid-phase epitaxy is an efficient technique for fabricating LnCuOCh epitaxial films.