Facile Production and Light Induced Dynamics of Macroscopic Single Crystal Monolayers and Heterostructures of 2D van der Waals Materials

Two dimensional (2D) semiconductors and their artificial structures hold great promises for electronic, optoelectronic, and quantum devices. We developed a facile method to disassemble van der Waals (vdW) single crystals layer-by-layer into monolayers with near-unity yield, high quality, and macroscopic dimensions limited only by bulk crystal sizes. This approach takes us one step closer to mass production and commercialization of 2D materials. With these materials, we have quantified several key dynamics in the 2D semiconductors and their heterojunctions. Using time and angle resolved photoemission spectroscopy (TR-ARPES), we quantified bandgap renormalization directly in macroscopic single crystal MoS₂ monolayer in the presence of charge carriers, and determined momentum-resolved intervalley conduction band (CB) electron transfer in the WS₂/MoS₂ heterobilayer, revealing fast scattering dynamics across multiple CB valleys on fs time scale, assisted by fast phonon scattering. These findings reveal versatile optical and electronic responses of the 2D semiconductor systems that can be engineered on demand for future applications.