Low-temperature and scalable CVD route to WS2 monolayers on SiO2/Si substrates

Tungsten disulfide (WS2) monolayers are promising for next-generation flat electronics, but few scalable deposition methods are currently available. Here, the authors report the fabrication of tungsten disulfide monolayers through a novel two-step chemical vapor deposition process involving the deposition of an amorphous tungsten sulfide layer at a relatively mild temperature from the W(CO)(6) and 1,2-ethanedithiol precursors, followed by a short annealing at 800 degrees C under an inert atmosphere. This two-step process allows the fabrication of a crystalline WS2 deposit with a low thermal budget. Raman, x-ray photoelectron, and wavelength dispersive x-ray fluorescence spectroscopic studies performed before and after annealing confirmed the deposition of a sulfur-rich amorphous intermediate, and further confirmed its conversion upon annealing toward oriented 2D WS2 crystals in the 1-2 monolayer range, as corroborated by high-resolution transmission electron microscopy. (C) 2017 American Vacuum Society.