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

Abstract

Highly efficient ultraviolet (UV) photodetector based on Molybdenum Disulfide (MoS 2 ) 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 MoS 2 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 MoS 2 layers. Layers of MoS 2 grown at 100 pulses were found to exhibit the characteristic Raman phonon modes i.e. E 1 2g and A 1g at 383.8 cm −1 and 405.1 cm −1 respectively and Photoluminescence (PL) spectra show B exciton peak for MoS 2 at around 625 nm suggesting the growth of high-quality MoS 2 layers. Atomic force microscopy (AFM) thickness profiling and cross sectional-high resolution transmission electron microscopy (HRTEM) analysis gives the thickness of grown MoS 2 to be 2.074 nm and 1.94 nm, respectively, confirming the growth of trilayers of MoS 2 . X-ray photoelectron spectroscopy (XPS) spectra of the grown trilayer sample show characteristic peaks corresponding to Molybdenum and Sulphur doublet (Mo 4+ 3d 5/2,3/2 and S 2p 3/2 , 1/2 ) confirming the chemical state of pure MoS 2 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 × 10 4 A/W at 24 μW optical power of the incident laser (λ = 365 nm) and very high detectivity of 1.81 × 10 14 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 MoS 2 layers. • Optimization of high-quality large area MoS2 layers utilizing the PLD technique. • Demonstration of low power operated UV photodetector on optimized MoS2 layers. • Explained the Physics of the UV photodetector using energy band diagrams. • Work justifies the development of efficient photodetectors using PLD technique.