γ Radiation Effects on Transition Metal Dichalcogenides: A Review of Defect Mechanisms and Device Implications

Two-dimensional (2D) transition metal dichalcogenides (TMDs) are foundational materials for next-generation electronics. For their viable use in space, nuclear, and medical applications, a comprehensive understanding of their response to high-energy ionizing radiation is critical. This review synthesizes and critically analyzes 32 experimental studies published since 2016 to build a unified framework for γ-radiation effects in TMDs. We found that the primary defect mechanism is the creation of chalcogen vacancies (CVs). The subsequent material response is decisively modulated by the irradiation environment: in ambient air, CVs are passivated, leading to oxidation, whereas in a vacuum or inert gas, pure vacancy effects dominate. This dichotomy resolves apparent contradictions in the literature regarding electronic doping; for instance, WSe₂ consistently exhibits intrinsic n-type doping (from V_Se), while WS₂ and MoS₂ in air trend toward p-type doping (from charge-transfer to oxides). These competing mechanisms of doping, strain, and disorder are mapped to their complex spectroscopic signatures in Raman and photoluminescence, including nonmonotonic dose-dependence. Beyond damage, γ-rays are shown to be a potent tool for defect engineering, inducing emergent properties such as room-temperature ferromagnetism (attributed to V_1M+2S complex vacancies) and optimizing catalytic activity. Finally, this review finds that TMD-based devices possess high intrinsic radiation hardness, with most failures originating from charge trapping in the adjacent dielectrics, not the 2D channel. We conclude by identifying critical gaps in the literature, including the unexplored effects of dose rates and the need for in situ characterization.