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

MoS2 layers synthesized by annealing Mo foils and evaporated Mo thin f ilms under sulfur pressure have been investigated by scanning electron microscopy, X-ray analysis, X-ray photoelectron spectroscopy and elec trical resistance measurements. After appropriate processing (T greate r than or equal to 823 K) the films crystallize in the hexagonal struc ture. When the annealing temperature is lower than the glass melting t emperature, the crystallites develop preferentially with the c axis pa rallel to the plane of the substrate. The mean grain size, estimated b y the full-width-at-half-maximum method, is about 8 nm. When the annea ling temperature is 1173 K, the crystallites develop preferentially wi th 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 anne aled 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 pow der. The surface morphology of the layers obtained from an evaporated Mo thin film is more homogeneous than that of the layers obtained dire ctly from a Mo foil. The electrical resistance is governed by grain bo undary scattering mechanisms.