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

## TL;DR

This paper reviews how gamma radiation affects 2D transition metal dichalcogenides, revealing how defects form and impact electronic properties, especially in space and medical applications.

## Contribution

The paper provides a unified framework for γ-radiation effects in TMDs, resolving contradictions in doping behavior and linking defects to device performance.

## Key findings

- Chalcogen vacancies are the primary defect mechanism under γ-radiation in TMDs.
- Irradiation environment modulates material response, with oxidation in air and pure vacancy effects in vacuum.
- Gamma rays can induce room-temperature ferromagnetism and enhance catalytic activity via defect engineering.

## Abstract

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 VSe), 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
V1M+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.