Effect of low-energy ion-beam irradiation on the structure and electron transport of monolayer MoS2

The presence of vacancies in two-dimensional (2D) materials, such as monolayer MoS2 (1L-MoS2), significantly affects their structural and electronic properties. In this study, 1L-MoS2 was irradiated with an Ar+ ion beam to introduce vacancies in a controlled manner. A complementary study that combines multiple evaluations was performed to verify the role of vacancies in the structural and electronic properties of MoS2. Raman spectroscopy and conductivity measurements reveal that the S vacancies, introduced into the MoS2 lattice prior to Mo vacancies at the lower dose region, cause electron-doping. The E’ lattice vibration mode was more sensitive to vacancies than the A’1 mode. According to photoluminescence studies, irradiating Ar+ at a lower dose of less than 3.8 × 1013 cm−2 does not change the band gap and only introduces mid-gap states, which is consistent with the smaller and larger influences of vacancies in carrier scattering and doping, respectively, in the electrical conductivity.