Judicious Selection of Precursors with Suitable Chemical Valence State for Controlled Growth of Transition Metal Chalcogenides

Abstract Transition metal chalcogenides (TMCs) have attracted wide attentions as a class of promising material for both fundamental investigations and electronic applications due to their atomic thin thickness, dangling bond‐free surface, and excellent electronic properties. Specifically, TMCs show outstanding properties such as good thermal conductivity, robust mechanical properties, and extraordinary electronical characteristics, bestowing them utility in both fundamental research and applications. Recently, the development of post‐Moore electronics based on TMCs calls for their large‐size and single‐crystal growth. However, researchers about synthesis usually focus on controlling several growth parameters (such as growth temperature, flow rate, and time). Herein, it is reported that the chemical valence states of transition metal precursors play an important role in controlling the lateral size and crystal quality for TMCs. The study discusses the valence states‐dependent growth mechanism for WS₂ and MoS₂ from four factors: evaporation temperature, skipping of reaction steps, atomic binding energy of the precursors, and formation energy. In addition, the as‐grown WS₂ and MoS₂ nanoflakes exhibit good photoelectric response properties. For EuS, the growth results are obviously different by using EuBr₃ and EuBr₂ as precursors. The studies provide a unique perspective and also new knowledge to controllably grow large‐size and good crystal quality TMCs.