Layer-modulated, wafer scale and continuous ultra-thin WS2 films grown by RF sputtering via post-deposition annealing

Tungsten disulfide (WS2) is a layered semiconducting material with a tunable bandgap that is promising in next generation nanoelectronics as well as energy harvesting devices. In this study, we presented a continuous and wafer-scale uniform WS2 layer preparation technique through sulfurization of a RF-sputtered WO3 film. Various characterization techniques were employed in order to investigate the structural and physical properties of the WS2 films. It was observed that the thickness of WS2 films could be controlled by tuning the sputtering time. The fabricated WS2 transistors exhibited high mobility values of ∼17 and 37–38 cm2 V−1 s−1 and on/off ratios in the range of ∼104 and 104–105 for 80–100 s-sputter time and 120–140 sputter time, respectively, which is in the maximum range for CVD-grown WS2 FETs with an SiO2 gate oxide. Photoresponse was also studied for a few layers of WS2 on a transparent quartz substrate and it was observed that the photosensitivity was linearly dependent on bias voltage. The proposed growth technique is attractive for next-generation transparent and nanoelectronic devices, as well as for other potential applications.