Antisite defects were selectively incorporated in monolayer WS2 during its growth by regulating W diffusion in Au substrates, as predicted by first principles calculations. This synthesis strategy to deliberately control defect structures in emerging 2D materials may enable the development of novel quantum materials for next-generation photonics and spintronics.
The non-equilibrium CVD approach was employed to selectively form SW and S2W antisite defects during the growth of WS2 monolayers. A dilute W-Au alloy (W less than 0.1am%) was used as the substrate to maintain W-poor (S-rich) growth conditions that were predicted to significantly reduce the formation energy of antisite defects by first-principles calculations. The high density SW and S2W (~5.0%) antisite defects were observed in the obtained WS2 MLs and confirmed by scanning transmission electron microscope (STEM) and electron energy loss spectroscopy (EELS) characterizations. Scanning tunneling microscopy/spectroscopy (STM/S) combined with theoretical calculations revealed the clove- and trefoil-like structures of the antisite defects and corresponding localized defect states in the bandgap of monolayer WS2. Tuning the chemical potential of reactants during growth as a nonequilibrium synthesis strategy to form specific defects is generally applicable to tailor the electronic and optical properties of a wide variety of atomically-thin 2D materials for designed functionalities, such as local magnetism, long-lifetime quantum emission and novel electronics.
