Generalized model-driven design and fabrication of ultrasensitive and ultrafast β-Ga₂O₃/SnO₂ethanol gas sensors

The intrinsically existing trade-off between gas response and response speed is a big obstacle for fabricating high-performance gas sensors with ultrahigh sensitivity, ultrafast real-time detection, and ultralow detection limits. The spill-over effect offers a promising strategy to address this trade-off, and its implementation still relies on empirical approaches, leading to uncertainties and limited optimization accuracy. In this study, a generalized theoretical model is proposed to clarify the relationship between the coverage ratio and the behavior of response and recovery for nanocomposite structures. Using Ga₂O₃-SnO₂systems as the prediction object, it is found that β-Ga₂O₃/SnO₂nanocomposites using β-Ga₂O₃as the host material possess a strong spill-over effect and fast response speed over a wide SnO₂coverage ratio range, whereas SnO₂/β-Ga₂O₃nanocomposites using SnO₂as the host material have the same behavior only within a narrow β-Ga₂O₃coverage ratio range. According to theoretical predictions, highly-sensitive and fast ethanol sensors are fabricated on β-Ga₂O₃/SnO₂nanocomposites with a SnO₂coverage ratio of 25 % ± 5 %, exhibiting an exceptionally-high gas response (5.78–434.3), short response/recovery time (8/6 s), ultralow detection limits and a wide sensing dynamic range across ethanol concentrations from 500 ppb to 5000 ppm. The corresponding sensing mechanism is systematically demonstrated through theoretical analysis and experimental measurements. This work lays the theoretical foundation for the optimized design of nanocomposites gas sensing, and paves the way for the evolution of Ga₂O₃-based nanocomposites sensors.