Local Surface Potential Modification of Few-Layer MoS₂ Via Optical Soldering Induced n-Doping Process

Local surface potential modification by defect structures in 2D transition metal dichalcogenide (2D-TMDC) is of particular interest for engineering of their optoelectronic and surface chemical properties. Optical irradiation on 2D-TMDC provides facile methodology for the defect structure patterning, however, its effect in surface potential modification has remained largely unexplored. Here, we investigate the changes in surface potential of optical soldering induced defect structures in few-layer MoS₂ by using a Kelvin probe force microscope (KPFM). Measured contact potential difference (CPD) of the defect structures shows Fermi level shift toward conduction band indicating n-doping effect. By correlating CPD with optical soldering laser power and photoluminescence (PL) emission efficiency, we identified two distinct mechanisms governing PL enhancement in two optical soldering laser power regimes. With lower optical soldering powers (<3 mW), defect formation from pristine MoS₂ introduces new edge sites leading to significant PL enhancement with increased CPD. Further increases in optical soldering power show a monotonic rise in CPD accompanied by PL quenching as a result of increased n-doping level. Our results suggest a methodology for optical doping of 2D-TMDC which is relevant to the development of Defect Engineering, Kelvin probe force microscope, optical doping, optical soldering, transition metal dichalcogenidepractical applications such as ultrasensitive chemicals and biosensors.