Surface/interface-dominated growth dynamics of novel transition metal dichalcogenide monolayers

The investigation of material growth and evolution mechanisms is of great importance for the controllable synthesis and property manipulation. In this talk, I will discuss our recent efforts in exploring the growth and evolution dynamics of novel transition metal dichalcogenide (TMD) monolayers using (scanning) transmission electron microscopy ((S)TEM) techniques, especially with the focus on the driven effect of surface/interface structures during these processes. We have demonstrated the synthesis of ultra-long MoS₂ nano-channels within MoSe₂ monolayers, based on intrinsic grain boundaries. A strain-driven growth mechanism is proposed that the strain fields near the grain boundaries not only lead to the preferred substitution of selenium by sulfur atoms but also drive the coherent extension and formation of MoS₂ channels [1]. In addition, we have developed a co-deposition strategy to fabricate a wafer-scale network of platinum single-metal-atom-chains within monolayer MoS₂ film. The stable four-coordinated motifs at the zigzag edges of MoS₂ are uncovered to be responsible for the migration of platinum atoms along the growth direction, and the followed connection of inversely oriented MoS₂ domains, obeying a surf-zip dynamic mechanism [2]. Besides, we also unraveled the surface-vacancy [3] guided phase evolution mechanism of PtSe₂, from crystalline structure to amorphous phase. During this process, the sequential generation of selenium vacancies give rise to the decrease of coordination number, the followed displacement of platinum atoms, and the finally complete amorphization of PtSe_x monolayers [4].