Understanding\nIron-Doping Modulating Domain Orientation\nand Improving the Device Performance of Monolayer Molybdenum Disulfide

Domain orientation modulation and controlled doping of\ntwo-dimensional\n(2D) transition-metal dichalcogenides (TMDCs) are two pivotal tasks\nfor synthesizing wafer-scale single crystals and boosting device performances.\nHowever, realizing two such targets and uncovering internal physical\nmechanisms remain daunting challenges. We develop an accurate Fe doping\nstrategy, which enables domain orientation control and electron mobility\nimprovement of monolayer MoS<sub>2</sub>. By tuning of the Fe dopant\ndosages, parallel steps with different heights are formed, which induce\nedge-nucleation of unidirectionally aligned monolayer MoS<sub>2</sub>. In parallel, Fe doping induces the down shift of the conduction\nband minimum of monolayer MoS<sub>2</sub> and matches well with the\nwork function of an electrode, which reduces Schottky barrier height\nand delivers ultralow contact resistance (561 Ω μm) and\nexcellent electron mobility (37.5 cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup>). The modulation mechanism is clarified by\ncombining theory calculations and electronic structure characterizations.\nThis work hereby provides a new paradigm for synthesizing wafer-scale\n2D TMDC single crystals and constructing high-performance devices.