PHOTOACTIVITY ENHANCEMENT OF WS2 SPUTTERED THIN-FILMS BY USE OF NICKEL

Photoactive thin films of WS2 have been prepared by radio frequency ma gnetron sputtering. Physico-chemical properties of the films are mainl y investigated by Rutherford backscattering and X-ray diffraction. Opt ical and transport properties are also studied. Films sputtered at a h igh substrate temperature are made of small bidimensional grains (2H-W S2) surrounded by amorphous boundaries. The photoactivity of these fil ms is weak because of the electron trapping at boundaries. Films sputt ered at a low substrate temperature are amorphous and then annealed to produce bidimensional films. It is shown that annealed Ni-coated film s give highly textured samples. A nickel-sulphur phase is assumed to a ct as a surfactant. The strong photoactivity enhancement of these film s is attributed to an increase in the grain size. (C) 1997 Elsevier Sc ience S.A.