- Real-time neutron irradiation analysis reveals the mechanism behind reliability degradation in next-generation 2D semiconductors for aerospace applications.

- Published in the international journal ACS Applied Materials & Interfaces, a leading publication in materials and nanoscience.

  A research team led by Professor Taewan Kim of the Intelligent Semiconductor Department at the University of Seoul, in collaboration with research teams led by Professor Sungjune Park of Sungkyunkwan University and Professor Hagyoul Bae of Jeonbuk National University, as well as Q-Beam Solution Inc. (CEO Bong-ki Jung), a spin-off company of the Korea Atomic Energy Research Institute, has successfully elucidated the reliability of next-generation semiconductors in space environments. The joint research paper, titled “Dynamic Probing of Neutron-Induced Reliability Degradation in MoS₂ and WS₂ Transistors,” was published in ACS Applied Materials & Interfaces, a world-renowned journal in the field of materials and nanoscience.

*Paper link: https://doi.org/10.1021/acsami.6c06775

  In this study, the researchers experimentally investigated the mechanisms of reliability degradation under neutron irradiation in two-dimensional transition metal dichalcogenide (2D TMD) semiconductor transistors, which are garnering attention as next-generation electronic devices for space, aviation, and extreme environments. Although 2D TMD semiconductors are expected to serve as key materials for next-generation ultra-low-power, high-density semiconductors because of their thin atomic layers and excellent electrical properties, systematic research on their neutron resistance and the causes of degradation in space radiation environments has been relatively scarce.

  The research team irradiated field-effect transistors (FETs) based on MoS₂ and WS₂—representative 2D semiconductor materials—with neutrons having an average energy of 2.2 MeV, and conducted a precise analysis of changes in their electrical characteristics before, after, and in real time during irradiation. In particular, using Q-Beam Solution’s neutron source, the team achieved neutron fluence conditions in the range of 10⁶–10⁹ n/cm², which is highly significant because it corresponds to the low-dose range relevant to radiation exposure conditions that could accumulate over an extended period in the space environment.

  The results showed that after neutron irradiation, both MoS₂ and WS₂ devices exhibited distinct electrical performance degradation, including a decrease in on-current, reduced mobility, changes in threshold voltage, and an increase in subthreshold swing. Specifically, a much higher neutron sensitivity was observed for WS₂ devices in comparison to MoS₂, as evidenced by a substantial decrease in on-current even under the lowest irradiation conditions. This result was attributed to greater energy transfer and defect generation due to interactions between the constituent elements in WS₂ and neutrons.

  The present study is different from previous research in that the researchers measured the devices’ electrical characteristics in real time during neutron irradiation in situ. The real-time measurements revealed that the MoS₂ device maintained relatively stable characteristics, whereas the WS₂ device exhibited rapid performance degradation from the onset of irradiation, which demonstrates that the difference in neutron sensitivity between the two materials is directly reflected in the operating environment of the device. These results suggest that to evaluate the reliability of 2D semiconductor devices in real space and aviation environments, real-time analyses during operation, rather than post-irradiation analysis, are necessary.

  Professor Taewan Kim of the University of Seoul said, “The significance of this study lies in its comprehensive elucidation of neutron-induced degradation phenomena in two-dimensional semiconductor devices across the channel, interfaces, oxide layer, and contacts.” He also stated, “This is important foundational research that proposes radiation-tolerant 2D semiconductor design strategies applicable to aerospace, defense, and electronic systems in extreme environments.”

  The joint research team expects these findings will serve as important design guidelines for the development of next-generation AI semiconductors, space electronic devices, and low-power, high-reliability semiconductor technologies. In particular, the difference in neutron sensitivity between MoS₂ and WS₂ was clearly demonstrated. Also, it is expected that the results will be utilized in future material selection, device structure optimization, and the development of radiation shielding and defect control processes.

  This achievement, which precisely elucidates the radiation reliability limits of single-atom-layer semiconductors, is regarded as a major milestone that will accelerate the realization of next-generation space, AI, and ultra-low-power semiconductor technologies.

  This research was conducted with support from the Deep Science Startup Promotion Project, led by the Ministry of Science and ICT and supported by the Korea Institute of Science and Technology Commercialization; the Nano and Materials Technology Development Project, supported by the National Research Foundation of Korea; and the Ministry of Education’s Semiconductor Specialized University Project.

△From left: Master’s student Seung-yong Baek and Professor Taewan Kim at the University of Seoul, and Bong-ki Jung, CEO of Q-Beam Solution Inc.