Digital transfer growth of patterned 2D metal chalcogenides by confined nanoparticle evaporation

Developing methods for the facile synthesis of two-dimensional (2D) metal chalcogenides and other layered materials is crucial for emerging applications in functional devices. Controlling the stoichiometry, number of the layers, crystallite size, growth location, and areal uniformity is challenging in conventional vapor-phase synthesis. Here, we demonstrate a method to control these parameters in the growth of metal chalcogenide (GaSe) and dichalcogenide (MoSe2) 2D crystals by precisely defining the mass and location of the source materials in a confined transfer growth system. A uniform and precise amount of stoichiometric nanoparticles are first synthesized and deposited onto a substrate by pulsed laser deposition (PLD) at room temperature. This source substrate is then covered with a receiver substrate to form a confined vapor transport growth (VTG) system. By simply heating the source substrate in an inert background gas, a natural temperature gradient is formed that evaporates the confined nanoparticles to grow large, crystalline 2D nanosheets on the cooler receiver substrate, the temperature of which is controlled by the background gas pressure. Large monolayer crystalline domains (∼100 μm lateral sizes) of GaSe and MoSe2 are demonstrated, as well as continuous monolayer films through the deposition of additional precursor materials. This PLD-VTG synthesis and processing method offers a unique approach for the controlled growth of large-area metal chalcogenides with a controlled number of layers in patterned growth locations for optoelectronics and energy related applications.