WS 2 nanotube formation by sulphurization: Effect of precursor tungsten film thickness and stress

Transition metal dichalcogenides can exhibit as 2-dimensional layers, 1-dimensional nanotubes or 0-dimensional quantum dot structures. In general, dichalcogenide nanotubes are grown under stringent conditions, using high growth temperatures with tedious processes. Here, we report the controlled formation of tungsten disulphide (WS2) nanostructures by manipulating the precursor film thickness, followed by a direct sulphurization process. WS2 nanotubes were formed by ultra-thin tungsten precursor films, while particle-like WS2 were obtained from thicker tungsten films under identical sulphurization conditions. To elucidate the origin of WS2 nanostructure formation, micron-sized tungsten film tracks were prepared, and such patterned films were found to suppress the growth of WS2 nanotubes. We attribute the suppression of nanotube formation to the relieving of film stress in patterned precursor films.