PROPERTIES OF WS2 THIN-FILMS OBTAINED BY SOLID-STATE REACTION, INDUCED BY ANNEALING, BETWEEN W-CONSTITUENTS AND S-CONSTITUENTS SEQUENTIALLYDEPOSITED IN THIN-FILM FORM - INFLUENCE OF THE ANNEALING TIME

WS2 thin films (100 nm thick) have been obtained by solid-state reacti on, induced by annealing, between W and S constituents sequentially de posited in thin film form. When annealed at 820 K the properties of th e thin films appears to be improved with the annealing time (2-145 h). However there is progressive saturation and the grain size remains sm all (less than or equal to 10 nm), while the texturation of the crysta llites, c axis perpendicular to the plane of the substrate, tends towa rd 100% as shown not only by X-ray diffraction but also by selected ar ea diffraction. The conductivity measurements are in accordance with t hese results: the conductivity of the sample increases with the anneal ing time. However it is always controlled by the grain boundaries. Som e improvement of the electrical properties of the layers can be obtain ed by annealing treatment in iodine atmosphere: the conductivity and t he homogeneity of the grain boundaries increase, due to the iodine pas sivation of traps at the grain boundaries.