Understanding Iron-Doping Modulating Domain Orientation and Improving the Device Performance of Monolayer Molybdenum Disulfide.

Domain orientation modulation and controlled doping of two-dimensional (2D) transition-metal dichalcogenides (TMDCs) are two pivotal tasks for synthesizing wafer-scale single crystals and boosting device performances. However, realizing two such targets and uncovering internal physical mechanisms remain daunting challenges. We develop an accurate Fe doping strategy, which enables domain orientation control and electron mobility improvement of monolayer MoS. By tuning of the Fe dopant dosages, parallel steps with different heights are formed, which induce edge-nucleation of unidirectionally aligned monolayer MoS. In parallel, Fe doping induces the down shift of the conduction band minimum of monolayer MoS and matches well with the work function of an electrode, which reduces Schottky barrier height and delivers ultralow contact resistance (561 Ω μm) and excellent electron mobility (37.5 cm V s). The modulation mechanism is clarified by combining theory calculations and electronic structure characterizations. This work hereby provides a new paradigm for synthesizing wafer-scale 2D TMDC single crystals and constructing high-performance devices.