WS₂ atomically thin nanodot array via self-organized templates

Tungsten Disulphide (WS₂) atomic layer nanodot arrays were fabricated with self- organized porous alumina templates as evaporation masks. First tungsten oxide (WO₃) was deposited on sapphire substrates through the alumina template to create WO₃ nanodot arrays, then WS₂ nanodots were formed by the reaction of sulfur with WO₃ using chemical vapor deposition (CVD) technique. The sizes of the observed two-dimensional WS₂ nanodots varies from 45nm to 70nm. These nanodots exhibit a layer thickness ranging from monolayers to a few atomic layers. This is confirmed by atomic force microscopy (AFM) measurements. Monolayer dots dominated region produces characteristic Raman peaks and high intensity photoluminescence (PL) due to direct band gap transition. Also it has more edge sites which can increase the PL of WS₂ dots. A region dominated by multilayer dots produces WS₂ Raman peaks but negligible photoluminescence due to indirect transition in multilayers. These novel atomically thin nanodots are attractive for both fundamental studies and future device applications, for e.g. ultrasensitive and ultrafast sensors.
Scanning Electron Microscopy and Atomic Force Microscopy of WS2 nanodots is shown in figure