Scalable Deposition of MoS<sub>2</sub> Thin Films\nwith Controlled Doping for Photodetectors

Molybdenum\ndisulfide (MoS<sub>2</sub>), the most widely explored\ntransition metal dichalcogenide, is a promising candidate for developing\nhigh-performance photodetectors due to having a wide range of electric\nand optoelectronic properties. However, the controlled synthesis of\na highly crystalline large-area MoS<sub>2</sub> thin film and the\neffect of noble metal (Au, Ag) nanoparticles and TM (Co) ion doping\non its photoelectrical properties are still challenging. Herein, we\nreport the direct growth of wafer-scale MoS<sub>2</sub> thin films\nutilizing a facile polymer-free approach by a solution-phase coating\nprocess, followed by thermal annealing. A systematic study on the\nphotoelectrical properties of the Au-, Ag-, and Co-doped (all variants\nare in 10 at. wt %) MoS<sub>2</sub> photodetectors reveals that the\nCo-MoS<sub>2</sub> device exhibits excellent photoresponse properties,\nwhich are also evidenced theoretically. Moreover, the Co-dopant amount\nis varied (5, 20 at. wt %) to decipher the impact of Co-doping on\nthe photoresponse properties and determine the optimum doping percentage.\nThe highest (20 at. wt %) Co-doped MoS<sub>2</sub> photodetector exhibits\ngood photoresponse characteristics at low voltage with minimal noise\nand high stability (retaining 86% of its photoresponsivity after the\n30th day), attributed to the long-lived trap states, the photogating\neffect, more n-type doping, and generation of more charge carriers.\nInterestingly, the variations in Co-dopant concentrations lead to\ntunable photoresponse in different (blue, green, and red) laser illuminations,\nattributed to the band gap tunability with variable doping. This simple\nTM doping approach proposed in this study for improving the performance\nof MoS<sub>2</sub> photodetectors can open up an avenue for research\nfor other 2D materials, finding potential applications in photodetection\nand low-voltage-based operating devices.