Synthesis of type-II textured tungsten disulfide thin films with bismuth interfacial layer as a texture promoter

Abstract

Highly textured tungsten disulfide (WS₂) thin films have been obtained by sulfurization of tungsten trioxide. The properties of WS₂ thin films prepared with bismuth interfacial layer as texture promoter has been studied. The WS₂ thin films were found to have predominant type-II orientation. The stacking of 2H-WS₂ crystallites observed with scanning electron microscopy was not reported hitherto. The films can be pictured as an assembly of WS₂ hexagonal crystallites. The energy dispersive X-ray analysis and X-ray photoelectron spectroscopy (XPS) studies confirm that the films are stoichiometric. The XPS analysis described the local environment of the tungsten atoms and the formal oxidation states of the tungsten and sulfur atoms were + 4 and - 2. Together with the high degree of crystallinity and excellent texture of the film, a relatively smooth morphology, on submicron scale, is revealed through atomic force microscopy study. The conditions for the desired textured growth with the van der Waals planes parallel to the substrate surface are reported.