MOS2 THIN-FILM SYNTHESIS BY SOFT SULFURIZATION OF A MOLYBDENUM LAYER

MoS2 layers synthesized by annealing Mo foils and evaporated Mo thin films under sulfur pressure have been investigated by scanning electron microscopy, X-ray analysis, X-ray photoelectron spectroscopy and electrical resistance measurements. After appropriate processing (T greater than or equal to 823 K) the films crystallize in the hexagonal structure. When the annealing temperature is lower than the glass melting temperature, the crystallites develop preferentially with the c axis parallel to the plane of the substrate. The mean grain size, estimated by the full-width-at-half-maximum method, is about 8 nm. When the annealing temperature is 1173 K, the crystallites develop preferentially with the c axis perpendicular to the plane of the substrate and the mean grain size is about 20 nm. It has been found that, when they are annealed under dynamic vacuum (4 h, 673 K) after the first annealing, the films are stoichiometric. The bonding energies of the S(2p) and Mo(3d) lines are in close agreement with those obtained with a reference powder. The surface morphology of the layers obtained from an evaporated Mo thin film is more homogeneous than that of the layers obtained directly from a Mo foil. The electrical resistance is governed by grain boundary scattering mechanisms.