Synthesis of millimeter-sized Mo_xW_(1−x) S_2ySe_2(1−y)monolayer alloys with adjustable optical and electrical properties and their magnetic doping

Alloying has emerged as an effective approach for elec/optoelectronics applications by modulating the bandgap engineering of two-dimensional (2D) transition metal dichalcogenides (TMDs). Based on our earlier liquid phase edge epitaxy (LPEE) method, we have grown millimeter-sized quaternary Mo_xW_(1−x) S_2ySe_2(1−y) monolayer films and Mo_xW_(1−x) S_2ySe_2(1−y) monolayers with different morphologies by controlling the growth temperature and time. The homogeneity and good crystallinity of as-grown alloys are demonstrated by energy-dispersive spectroscopy (EDS), elemental mapping, Raman mapping, and high-resolution transmission electron microscopy (HRTEM). Atomic-resolution scanning transmission electron microscopy (STEM) strongly demonstrates the uniform distribution of Mo, W, S, and Se. Furthermore, alloy-based field-effect transistors (FETs) displaying bipolar conduction behavior with a weak p-branch and conduction behavior show component-dependent properties. In addition, this strategy has been broadened to prepare M-doped Mo_xW_(1−x) S_2ySe_2(1−y) monolayers (M: Fe, Co, and Ni) for the first time, where magnetic hysteresis (M-H) measurements indicated room temperature ferromagnetism of Mo_xW_(1−x) S_2ySe_2(1−y). Therefore, the synthesized pristine and M-doped alloys have greatly enriched the family of 2D materials and are prospective candidates for applications in future industrial device applications.