Photoactivity enhancement of WS2 sputtered thin films by use of nickel

Photoactive thin films of WS2 have been prepared by radio frequency magnetron sputtering. Physico-chemical properties of the films are mainly investigated by Rutherford backscattering and X-ray diffraction. Optical and transport properties are also studied. Films sputtered at a high substrate temperature are made of small bidimensional grains (2H-WS2) surrounded by amorphous boundaries. The photoactivity of these films is weak because of the electron trapping at boundaries. Films sputtered at a low substrate temperature are amorphous and then annealed to produce bidimensional films. It is shown that annealed Ni-coated films give highly textured samples. A nickel-sulphur phase is assumed to act as a surfactant. The strong photoactivity enhancement of these films is attributed to an increase in the grain size. (C) 1997 Elsevier Science S.A.