WSe2 thin films prepared by soft selenization

Thin films of WSe2 were prepared by soft selenization of r.f.-sputtered tungsten films in a closed tube system. Two types of orientations could be obtained depending on the selenium partial pressure. The basal plane of the crystallites was oriented either predominantly parallel or predominantly perpendicular to the substrate surface. With X-ray energy spectrometry and X-ray diffraction the stoichiometry and single phase of the WSe2 films were demonstrated. From the X-ray diffraction spectra the average grain size was calculated to be between 10 and 35 nm. The indirect band gap was found to lie between 1.20 and 1.30 eV and the direct gap was found between 1.40 and 1.50 eV.