Photoresponsive and Gas Sensing Field-Effect Transistors based on Multilayer WS(2) Nanoflakes

The photoelectrical properties of multilayer WS(2) nanoflakes including field-effect, photosensitive and gas sensing are comprehensively and systematically studied. The transistors perform an n-type behavior with electron mobility of 12 cm(2)/Vs and exhibit high photosensitive characteristics with response time (τ) of <20 ms, photo-responsivity (R(λ)) of 5.7 A/W and external quantum efficiency (EQE) of 1118%. In addition, charge transfer can appear between the multilayer WS(2) nanoflakes and the physical-adsorbed gas molecules, greatly influencing the photoelectrical properties of our devices. The ethanol and NH(3) molecules can serve as electron donors to enhance the R(λ) and EQE significantly. Under the NH(3) atmosphere, the maximum R(λ) and EQE can even reach 884 A/W and 1.7 × 10(5)%, respectively. This work demonstrates that multilayer WS(2) nanoflakes possess important potential for applications in field-effect transistors, highly sensitive photodetectors, and gas sensors, and it will open new way to develop two-dimensional (2D) WS(2)-based optoelectronics.