Space Irradiation Effects on Gas Sensing Properties of Graphene

With the surging interest in the space industry, the influence of cosmic rays on electronic devices is attracting enormous attention. Among them, research on electronic devices integrated with two-dimensional (2D) materials is particularly needed, since 2D materials possess an ultrathin structure with excellent radiation endurance. With this advantage, Graphene is also promising gas sensing material that can potentially replace commercialized metal-oxide semiconductors due to its excellent gas sensing properties at room temperature, as well as its mechanical and chemical stability. For these reasons, graphene-based gas sensors have been extensively explored for harsh environments such as nuclear reactors, outer space and high-altitude flights to effectively monitor air quality. However, the specific mechanism and the standard damage controls depending on detailed dosages have not been defined and discussed yet. The high-energy radiation from the space environment inevitably induces damage to the material's structure, morphology, and sensing performance, leading to significant degradation in the usability of these sensors in aerospace applications. Consequently, thorough investigations about the effects of space radiation on graphene gas sensors are crucial for advancing their further development and application.<br/>Herein, we report the degradation evaluation of gas sensing properties of graphene layers subjected to the space radiation including electrons, protons and heavy ions. After electron beam irradiation, the changes of gas sensor response were calculated to be less than about 3%, 1.5%, and 1.5% for 5 ppm NO₂, 50 ppm NH₃, and 50 ppm H₂S, respectively. To fabricate the sensors, we used CVD grown-graphene synthesized on a Cu foil and transferred graphene onto the SiO₂ substrate by wet transfer method. After that, the layer was patterned by photolithography and reactive oxygen ion etching to form H-shaped pattern with a channel having a width of 10 μm. X-ray photoelectron spectrum (XPS) and Raman analysis were conducted before and after irradiation to examine the influence of radiation and its impact on the surface chemical bonding. The gas sensing performance change of graphene gas sensors in a space irradiation environment was also assessed. Gas sensing characteristics of the sensor were measured at room temperature using various gases such as 50 ppm CH₃COCH₃, 50 ppm C₂H₅OH, 100 ppm C₇H₈, 100 ppm CO, 1 % CO₂, 50 ppm H₂, 50 ppm H₂S, 5 ppm NO₂, and 50 ppm NH₃. The results showed that the sensor exhibited remarkable invariance even after exposure to high level of cosmic radiation, indicating its robustness and reliability for space applications. Ultimately, our study stands to greatly advance the space industry, bolstering the development of space technologies.