In a proof-of-concept study, the team fabricated field-effect transistors (FETs) based on nine-atom-wide armchair graphene nanoribbons (9-AGNRs), synthesized using a bottom-up, on-surface approach.
These devices were characterized before and after gamma irradiation using Raman spectroscopy and electrical transport measurements.
This indicates that high-energy gamma photons, despite their strong penetration capability, do not induce catastrophic structural damage in the ribbons.
As a result, current flow is sharply reduced, producing a clear electrical signature of radiation exposure.
Because gamma radiation can penetrate shielding and packaging, compact, chip-integrated sensors capable of detecting subtle exposure-induced changes are in high demand for spacecraft, satellites, and other radiation-intensive applications.
University of Arizona researchers have demonstrated that atomically precise graphene nanoribbons (GNRs) can function as highly sensitive gamma-radiation sensors, while maintaining their underlying structural integrity under exposure - an unusual combination that could be valuable for fusion energy systems and space electronics.
In a proof-of-concept study, the team fabricated field-effect transistors (FETs) based on nine-atom-wide armchair graphene nanoribbons (9-AGNRs), synthesized using a bottom-up, on-surface approach. The resulting structures were one atom thick and approximately 45 nanometers long on average, placing them in the quasi-one-dimensional regime where quantum transport effects dominate. These devices were characterized before and after gamma irradiation using Raman spectroscopy and electrical transport measurements.
Raman analysis showed that the primary lattice structure of the GNRs remained intact after exposure, with only subtle spectral changes consistent with mild oxidation or localized lattice perturbations. This indicates that high-energy gamma photons, despite their strong penetration capability, do not induce catastrophic structural damage in the ribbons. However, electrical measurements told a markedly different story: device performance degraded significantly after irradiation, revealing a strong sensitivity of charge transport to even minor structural or chemical modifications.
This apparent discrepancy between structural stability and electronic fragility is central to the sensing mechanism. The researchers attribute the pronounced drop in conductivity to Anderson localization, a quantum effect in which disorder enhances interference and effectively traps charge carriers. In atomically narrow, quasi-1D systems such as 9-AGNRs, even small perturbations - such as edge oxidation induced by reactive species generated during gamma exposure - can strongly disrupt coherent transport pathways. As a result, current flow is sharply reduced, producing a clear electrical signature of radiation exposure.
“The devices survive the exposure and still respond, but their electrical performance changes dramatically,” said principal investigator Zafer Mutlu. “That's exactly the behavior we want from a sensor.”
This combination of lattice resilience and transport sensitivity distinguishes GNRs from conventional materials used in radiation detection. Silicon-based sensors, for example, cannot operate directly within high-radiation regions such as the first wall of a fusion reactor, where continuous exposure leads to rapid degradation. By contrast, the observed response suggests that GNR-based devices could be positioned closer to such environments, enabling more direct and real-time monitoring.
“Real-time monitoring is our vision for this project,” Mutlu said.
The implications extend beyond fusion systems. Because gamma radiation can penetrate shielding and packaging, compact, chip-integrated sensors capable of detecting subtle exposure-induced changes are in high demand for spacecraft, satellites, and other radiation-intensive applications. The intrinsic tunability of GNRs - where width, length, and edge structure can be controlled with atomic precision - further enables tailoring of sensitivity, potentially allowing devices to be engineered for specific radiation environments or dose ranges.
The study highlights a key advantage of atomically precise graphene nanoribbons: while their structural framework remains robust under gamma irradiation, their quantum transport properties act as an extremely sensitive probe of environmental perturbations. This duality positions GNR-based devices as promising candidates for next-generation radiation sensing and monitoring technologies in extreme operational conditions.
