Laser- and Ion-Induced Defect Engineering in WS2 Monolayers

Tungsten disulfide is one of the prominent transition metal dichalcogenide materials, which shows a transition from an indirect to a direct bandgap as the layer thickness is reduced down to a monolayer. To use WS2 monolayers in devices, detailed knowledge about the luminescence properties regarding not only the excitonic but also the defect-induced contributions is needed. Herein, WS2 monolayers are irradiated with Xe30+ ions with different fluences to create different defect densities. Apart from the excitonic contributions, two additional emission bands are observed at low temperatures. These bands can be reduced or even suppressed, if the flakes are exposed to laser light with powers up to 1.5 mW. Increasing the temperature up to room temperature leads to recovery of this emission, so that the luminescence properties can be modified using laser excitation and temperature. The defect bands emerging after ion irradiation are attributed to vacancy defects together with physisorbed adsorbates at different defect sites.

Automated summary

The study found that irradiating WS2 monolayers with Xe30+ ions can create different defect densities, which exhibit different luminescent properties at various temperatures. Furthermore, using laser excitation and adjusting temperature can also modify the luminescence properties of WS2 monolayers.