Wafer-sized WS2 monolayer deposition by sputtering

We demonstrate that tungsten disulphide (WS2) with thicknesses ranging from monolayer (ML) to several monolayers can be grown on SiO2/Si, Si, and Al2O3 by pulsed direct current-sputtering. The presence of high quality monolayer and multilayered WS2 on the substrates is confirmed by Raman spectroscopy since the peak separations between the A(1g)-E-2g and A(1g)-2LA vibration modes exhibit a gradual increase depending on the number of layers. X-ray diffraction confirms a textured (001) growth of WS2 films. The surface roughness measured with atomic force microscopy is between 1.5 and 3 angstrom for the ML films. The chemical composition WSx (x = 2.03 +/- 0.05) was determined from X-ray Photoelectron Spectroscopy. Transmission electron microscopy was performed on a multilayer film to show the 2D layered structure. A unique method for growing 2D layers directly by sputtering opens up the way for designing 2D materials and batch production of high-uniformity and high-quality (stochiometric, large grain sizes, flatness) WS2 films, which will advance their practical applications in various fields.