Controlled growth of transition metal dichalcogenide via thermogravimetric prediction of precursors vapor concentration

Transition metal dichalcogenide (TMD) alloys and heterostructures are attracting increasing attention thanks to their unique electronic, optical, and interfacial properties. However, the growth fundamental of TMD alloys and heterostructures during one-step growth is still beyond understanding. Here, thermogravimetric (TG/DTG) technology is introduced to predict the evolution of the precursor (MoO₃ and WO₃) concentration in the vapor during growth. We establish the correlation between precursor concentration and the corresponding growth behavior. TG/DTG predication suggests that tuning precursor temperature and powder ratio can alter their concentration in the vapor, well explaining the formation of Mo_xW_1-xSe₂ alloy or MoSe₂-WSe₂ heterostructure at different growth conditions. Based on the TG/DTG analysis, we further design and grow a complex MoSe₂-Mo_xW_1-xSe₂-WSe₂ heterostructure and Mo_xW_1-xS₂ monolayer alloys, confirming the validity of TG/DTG prediction in TMD crystal synthesis. Thus, employing TG/DTG to predict the synthesis of two-dimensional materials is of importance to understand the TMD growth behavior and provide guidance to the desired TMD heterostructure formation for future photoelectric devices.