Defect-Driven MoS₂ Nanosheets toward Enhanced Sensing Sensitivity

In this study, S-deficient MoS₂ was prepared using proton irradiation and then applied as sensing materials for the detection of NO₂ gas. First, bulk MoS₂ was treated by ultrasonics to produce 2D nanosheets of MoS₂, which were subsequently bombarded by a flux of high-energy protons, resulting in the appearance of structural defects throughout MoS₂. The proton fluxes were adjusted to different densities of 1 × 10¹¹, 1 × 10¹², 1 × 10¹³, and 1 × 10¹⁴ ions/cm². The effects of proton irradiation on the defects, also referred to as atomic vacancies, were systematically investigated using Raman measurements to locate the E¹ _2g and A_1g modes and X-ray photoelectron spectroscopy to determine the binding energy of Mo 3d and S 2p orbitals. It was revealed that the density of proton irradiation greatly affects the degree of S atom vacancies in irradiated MoS₂, while also enhancing the n-type semiconducting behaviors of MoS₂. The vacancy-rich MoS₂ was then demonstrated to exhibit a higher response to NO₂ gas compared to that of nonirradiated MoS₂, showing a 4-fold increase in response within a concentration range from 1 to 20 ppm. These results could pave the way for new approaches to fabricating sensing materials.