Fig. 3: Optoelectronic response of the devices.

a IV characteristics of a WS₂ device, measured in the dark (black) and upon illumination (red) with wavelength λ = 625 nm and power P = 228 μW (spot diameter 850 μm). b Current vs. time measurements at V_sd = 1 V, acquired while turning the illumination on (at t = 2 s) and off (at t = 4 s) for λ = 625 nm and increasing values of illumination power, from 1.3 to 228 μW. The sample is kept in dark for 20 s after each measurement cycle to allow for stabilization. c Power dependence of the photocurrent, I_PC, extracted from the on-off cycles shown in panel b as the difference between the current measured immediately before and one second after illumination is turned on. The orange line is a fitting to a power law I_PC ∝ P^α, with α ≈ 0.5. d Device photoresponsivity as a function of the illumination power for λ = 625 nm and V_sd = 1 V. e Typical spectral dependence of the photoresponsivity (red line, left axis) and optical transmittance (blue, right axis) of the WS₂ devices.