Defect Activated Photoluminescence in WSe2 Monolayer

Defects in transition metal dichalcogenides (TMDs) play an important role in tailoring electrical and optical properties. Here we employ Ar+ plasma to controllably generate active defects in WSe2 monolayers to tune their optical properties. Two defect-activated PL emission peaks are emerging in the low temperature PL spectra of WSe2 monolayer treated with Ar+ plasma. These emissions are attributed to the recombination of excitons bound to different types of structural defects. The shallow level emission originates from the recombination of excitons at chalcogen vacancies, while the deep level emission might arise from other types of defects, such as transition metal vacancies, cluster of vacancies, rotational defects, or antisite defects. Our results demonstrate that Ar+ plasma treatment is an effective approach to induce desirable defects in TMDs monolayers and PL spectroscopy is an efficient method to investigate these defects.