Abstract :
Photoconductive WS2 thin films were obtained by post annealing treatments of WrSrW. . . SrWrS thin layers
sequentially deposited on a mica substrate coated with a thin Ni layer. After deposition by sputtering of W layers and
evaporation of S layers, the samples were post annealed at 1073 K for half an hour under an argon flow. The films obtained
were crystallized in the hexagonal structure expected. However there is a tungsten excess and, at the surface of the films,
this tungsten is oxidized. This surface oxide is reduced by annealing of the samples under sulphur atmosphere. In order to
sublimate the sulphur condensed at the surface of the films during the cooling of the samples, at the end of the process, the
films were post annealed under vacuum. The films obtained are stochiometric, their surface oxidation has nearly disappeared
and they are textured with the c axis perpendicular to the plane of the substrate. These films are highly photoconductive. The
room temperature conductivity is about 0.5 V cm.y1 which is of the same order of magnitude than the WS2 single
crystals. q1997 Elsevier Science B.V.
