Radiation damage and abnormal photoluminescence enhancement of multilayer MoS2 under neutron irradiation

In this work, neutron irradiation effects on the optical property of multilayer MoS2 have been investigated in depth. Our results display that the intensity of the photoluminescence (PL) spectra of MoS2 flakes tends to slightly decrease after exposed to neutron irradiation with low fluence of 4.0 × 108 n/cm2. An unexpected improvement of PL intensity, however, is observed when the irradiation fluence accumulates to 3.2 × 109 n/cm2. Combined with the experimental results and first-principles calculations, neutron irradiation damage effects of multilayer MoS2 are analyzed deeply. Sulfur vacancy (V S) is found to be responsible for the attenuation of the PL intensity as a major defect. In addition, our results reveal that the adsorbed hydroxyl groups (OH) and oxygen atoms (O) on the surface of MoS2 flakes not only promote the transition from trion excitons to neutral excitons, but also repair the V S in MoS2, both of which contribute to the enhancement of luminescence properties. The detailed evolution process of irradiation-induced defects is discussed to reveal the microscopic mechanism of the significantly difference in luminescence intensity of MoS2 under different irradiation stages. This work has great significance for evaluating the neutron radiation hardness of multilayer MoS2, which is helpful to enrich the fundamental research on neutron irradiation effects.