TEXTURED BINARY COMPOUND THIN-FILMS OBTAINED BY SUBSTITUTION OF THE CHALCOGEN OF A PRE-TEXTURED CHALCOGENIDE FILM

Layers of MoSe2, MoS2, MoO3 and WS2, WO3 on glass substrates have been obtained from MoTe2 and WSe2 films respectively. First, textured MoTe 2 and WSe2 films were prepared by annealing under chalcogen pressure o f constituents in thin film form. Then they were annealed under Se, S or O pressure in order to obtain the desired new compound. The anneali ng 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 MoSe2, MoS2, MoO3 and WS2 can be obtained while the crystal lites of WO3 films were randomly oriented. A number of proposals are a dvanced to understand how textured films can be obtained in such a way : One of the elements of the compound should have a very small pressur e vapour at the working temperature. The free enthalpy of the new comp ound should be more negative than that of the initial product. The ion ic radius of the substituent should be smaller than that of the substi tuted atom. To obtain textured film, the lattice constants of the fina l compound should not be too different from those of the initial one. The first optical results obtained for MoSe2 layers are very promising .