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

Two-dimensional (2D) MoS is a promising material for future electronic and optoelectronic applications. 2D MoS 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 MoS crystals under high-dose gamma irradiation is still missing. In this work, absorbed doses of up to 1000 kGy are administered to 2D MoS. 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 MoS is observed and attributed to the adsorption of O onto created vacancies. Extensive oxidation of the MoS crystal is attributed to reactions involving the products of adsorbate radiolysis. Edge-selective radiolytic etching of the uppermost layer in 2D MoS is attributed to the high reactivity of active edge sites. After irradiation with 1000 kGy, the monolayer MoS 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 MoS. Consequently, it demonstrates that radiation shielding, adsorbate concentrations, and required device lifetimes must be carefully considered, if devices incorporating 2D MoS are intended for use in high-dose radiation environments.