WSE2 THIN-FILM REALIZATION BY SYNTHESIS AND BY TARNISHING

Thin W films were deposited by RF sputtering onto a glass substrate and then covered with an Se layer. The WSe2 layers were obtained either by annealing the W layers in a vacuum sealed Pyrex tube or by the tarnishing reaction of Se vapour on W films. The properties of the thin WSe2 films made by synthesis and by tarnishing are described. The layers were examined by x-ray diffraction, x-ray photoelectron spectroscopy, scanning and transmission electron microscopy, electron microprobe analysis, optical transmission and resistivity measurements. The films crystallize in the hexagonal structure. It has been found that stoichiometric layers are obtained after synthesis while layers obtained by tarnishing are partly oxidized. The optical gap of the synthesized layers is in good agreement with the expected value. The electrical resistance is governed by grain boundary scattering mechanisms.