Nanostructured MoS(2) and WS(2) Photoresponses under Gas Stimuli

This study was on the optoelectronic properties of multilayered two-dimensional MoS(2) and WS(2) materials on a silicon substrate using sputtering physical vapor deposition (PVD) and chemical vapor deposition (CVD) techniques. For the first time, we report ultraviolet (UV) photoresponses under air, CO(2), and O(2) environments at different flow rates. The electrical Hall effect measurement showed the existence of MoS(2) (n-type)/Si (p-type) and WS(2) (P-type)/Si (p-type) heterojunctions with a higher sheet carrier concentration of 5.50 × 10(5) cm(−2) for WS(2) thin film. The IV electrical results revealed that WS(2) is more reactive than MoS(2) film under different gas stimuli. WS(2) film showed high stability under different bias voltages, even at zero bias voltage, due to the noticeably good carrier mobility of 29.8 × 10(2) cm(2)/V. WS(2) film indicated a fast rise/decay time of 0.23/0.21 s under air while a faster response of 0.190/0.10 s under a CO(2) environment was observed. Additionally, the external quantum efficiency of WS(2) revealed a remarkable enhancement in the CO(2) environment of 1.62 × 10(8) compared to MoS(2) film with 6.74 × 10(6). According to our findings, the presence of CO(2) on the surface of WS(2) improves such optoelectronic properties as photocurrent gain, photoresponsivity, external quantum efficiency, and detectivity. These results indicate potential applications of WS(2) as a photodetector under gas stimuli for future optoelectronic applications.