Defect Healing and Defect Metrology of WSe2 by Gate-Modulated Photoluminescence

Defects in semiconductors have been at the focus of advanced materials research in the past century. Still, it is one of the most vibrant topics in materials research and particularly two-dimensional (2D) semiconductors. Spectroscopy and particularly photoluminescence is one of the main tools for inspecting 2D semiconductors, and in this work we have modulated the spectral measurements with a field effect potential in order to enhance the charge trapping and detrapping from point defects.<br/>By performing gate modulated spectroscopy we determined a lower bound for the intrinsic defect density of CVD grown ( and exfoliated WSe₂ samples. We demonstrated that a thin hBN buffer between the device and substrate eliminates hysteresis associated with injected holes.<br/>Additionally, we performed a chemical healing process which replaces the oxygen defects with sulfur via adsorption of thiol molecules in solution and trimming of the carbon chains using rapid thermal treatment. We confirmed the efficiency of process in eliminating vacancy defects by XPS, cryogenic photoluminescence and by gate-modulated photoluminescence. <br/>Lastly, we showed that the thermal detrapping process can be described as an activated reaction with an energy barrier of, which is an estimate for the defect states’ electronic binding energy.