  The mechanisms underlying the intrinsic photoresponse of few-layer (FL)
molybdenum disulphide (MoS2) field-effect transistors are investigated via
scanning photocurrent microscopy. We attribute the locally enhanced
photocurrent to band-bending assisted separation of photoexcited carriers at
the MoS2/Au interface. The wavelength-dependent photocurrents of few layer MoS2
transistors qualitatively follow the optical absorption spectra of MoS2,
providing direct evidence of interband photoexcitation. Time and spectrally
resolved photocurrent measurements at varying external electric fields and
carrier concentrations establish that drift-diffusion currents dominate
photothermoelectric currents in devices under bias.
