Controllable growth of two-dimensional WSe₂ using salt as co-solvent

Various structures of two-dimensional (2D) WSe₂ were controllably grown in a chemical vapor deposition (CVD) system. Using salt as the co-solvent and surfactant, we were able to grow monolayer single-crystalline WSe₂ flakes with lateral size of up to 215 μm and monolayer polycrystalline WSe₂ with lateral size of a few millimeters on amorphous SiO₂ substrates. Optical microscopy, atomic force microscopy, Raman spectra, photoluminescence spectra and X-ray photoelectron spectra measurements disclosed high quality of as-grown 2D WSe₂. Moreover, multilayer WSe₂ flakes with spiral dislocations and uniform size were also achieved. Our study demonstrates that the salt-assisted CVD technique can be applied for the controllable synthesis of 2D transition metal dichalcogenides with various structures and morphologies, paving the way for developing novel catalysts and electronic devices.