Epitaxial growth of Ag₂S films on MgO(001)

Epitaxial films of monoclinic Ag₂S on polished and annealed surfaces and on cleaved surfaces of MgO(001) were prepared by molecular beam epitaxy. The films were characterized by X-ray diffraction method. Ag ₂S films generally consisted of crystallites with orientations of (012), (-1,1,2) and (010) parallel to substrate surfaces, but for a thick film (180nm) on cleaved MgO, the (010) orientation was not observed. In-plane orientation of the (-1,1,2) oriented crystallites was essentially the same as that of the (012) oriented crystallites in any case. That for the (010) oriented crystallites was not determined. For a film deposited on the polished MgO substrate, in-plane orientation for (012) oriented crystallites was [100]∥[110]_MgO. For a film on the cleaved MgO substrate, the main in-plane orientation was [100]∥[100]_MgO. For the thick film on the cleaved MgO substrate, the in-plane orientation was basically [4,-2,1]∥[100]_MgO with slight modifications. There exist additional orientations due to twinning based on the monoclinic lattice of Ag₂S in each case.