Molybdenum disulfide thin films have been prepared by annealing, under constant argon flow at 823 K. structures composed of molybdenum, sulfur and sodium fluorine co-deposited on glass substrates. The films have been studied by X-ray diffraction, X-ray photoelectron spectroscopy, electron microprobe analysis and scanning electron microscopy. After annealing, the thin films were composed of large grains having their c-axis perpendicular to the plane of the substrate when they are deposited at a substrate temperature below 500 K. It is shown that these crystalline properties are induced by the presence of sodium in the films, which allows the formation of an intermediate solid solution during annealing. This solid solution is decomposed with textured MoS2 growth when the films are exposed to air.