High performance UV photodetector based on MoS2 layers grown by pulsed laser deposition technique

Abstract Highly efficient ultraviolet (UV) photodetector based on Molybdenum Disulfide (MoS2) layers has been fabricated using pulsed laser deposition (PLD) technique. Systematic layer dependent photoresponse studies have been performed from single layer to 10 layers of MoS2 by varying the laser pulses to see the effect of the number of layers on the photoelectrical measurements. Raman and Photoluminescence studies have been carried out to ensure the growth of high-quality MoS2 layers. Layers of MoS2 grown at 100 pulses were found to exhibit the characteristic Raman phonon modes i.e. E12g and A1g at 383.8 cm−1 and 405.1 cm−1 respectively and Photoluminescence (PL) spectra show B exciton peak for MoS2 at around 625 nm suggesting the growth of high-quality MoS2 layers. Atomic force microscopy (AFM) thickness profiling and cross sectional-high resolution transmission electron microscopy (HRTEM) analysis gives the thickness of grown MoS2 to be 2.074 nm and 1.94 nm, respectively, confirming the growth of trilayers of MoS2. X-ray photoelectron spectroscopy (XPS) spectra of the grown trilayer sample show characteristic peaks corresponding to Molybdenum and Sulphur doublet (Mo4+ 3d5/2,3/2 and S 2p3/2,1/2) confirming the chemical state of pure MoS2 phase without the presence of any Molybdenum oxide state. Dynamic photoelectrical studies with Indium Tin Oxide (ITO) as contact electrode upon UV laser illumination show superior responsivity of 3 × 104 A/W at 24 μW optical power of the incident laser (λ = 365 nm) and very high detectivity of 1.81 × 1014 Jones at a low applied bias of 2 V. The obtained results are highly encouraging for the realization of low power consumption and highly efficient UV photodetectors based on MoS2 layers.