Gamma Radiation-Induced Oxidation, Doping, and Etching of Two-Dimensional MoS₂ Crystals

Two-dimensional (2D) MoS₂ is a promising material for future electronic and optoelectronic applications. 2D MoS₂ devices have been shown to perform reliably under irradiation conditions relevant for a low Earth orbit. However, a systematic investigation of the stability of 2D MoS₂ crystals under high-dose gamma irradiation is still missing. In this work, absorbed doses of up to 1000 kGy are administered to 2D MoS₂. Radiation damage is monitored via optical microscopy and Raman, photoluminescence, and X-ray photoelectron spectroscopy techniques. After irradiation with 500 kGy dose, p-doping of the monolayer MoS₂ is observed and attributed to the adsorption of O₂ onto created vacancies. Extensive oxidation of the MoS₂ crystal is attributed to reactions involving the products of adsorbate radiolysis. Edge-selective radiolytic etching of the uppermost layer in 2D MoS₂ is attributed to the high reactivity of active edge sites. After irradiation with 1000 kGy, the monolayer MoS₂ crystals appear to be completely etched. This holistic study reveals the previously unreported effects of high-dose gamma irradiation on the physical and chemical properties of 2D MoS₂. Consequently, it demonstrates that radiation shielding, adsorbate concentrations, and required device lifetimes must be carefully considered, if devices incorporating 2D MoS₂ are intended for use in high-dose radiation environments.