Textured binary compound thin films obtained by substitution of the chalcogen of a pre-textured chalcogenide film

Abstract

Layers of MoSe 2, MoS 2, MoO 3 and WS 2, WO 3 on glass substrates have been obtained from MoTe 2 and WSe 2 films respectively. First, textured MoTe 2 and WSe 2 films were prepared by annealing under chalcogen pressure of constituents in thin film form. Then they were annealed under Se, S or O pressure in order to obtain the desired new compound. The annealing conditions were optimized for each compound by checking the texture of the films with an X-ray diffractometer. It was found that textured layers of MoSe 2, MoS 2, MoO 3 and WS 2 can be obtained while the crystallites of WO 3 films were randomly oriented. A number of proposals are advanced to understand how textured films can be obtained in such a way: • — One of the elements of the compound should have a very small pressure vapour at the working temperature. • — The free enthalpy of the new compound should be more negative than that of the initial product. • — The ionic radius of the substituent should be smaller than that of the substituted atom. • — To obtain textured film, the lattice constants of the final compound should not be too different from those of the initial one. The first optical results obtained for MoSe 2 layers are very promising.