Wafer-sized WS₂ monolayer deposition by sputtering

Abstract

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 Å for the ML films. The chemical composition WS_<i>x</i> (<i>x</i> = 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.