Ga2O3 Nanorod-based High Temperature Gas Sensors: A 3-D Nano- Architecture and Mechanism Study

With the ever-demanding call for energy efficient industries and sustainable environment in the 21st century, monitoring and control of feedstock fuel combustion process are critically important in advanced energy generation systems such as power plants, gas turbines, and automotive engines, etc. The energy efficiency is essentially achieved through the fast, precise and self-sufficient measurement, as well as effective feedback control of physical parameters such as temperature and pressure, and chemical parameters such as specie concentration. However as of now, chemical and physical sensors that are able to operate in harsh environments, such as high temperature up to 1000°C, are extremely limited due to the daunting challenges in structural stability, sensitivity, selectivity, and functional stability required in the sensor materials. In this study, we successfully synthesized large-scale three-dimensional (3-D) b-Ga2O3 nanorod arrays (NRAs) on Si substrates using a cost-effective hydrothermal deposition process followed by high temperature annealing. Based on these 3-D b-Ga2O3 NRAs, we design and investigate three material and sensor design strategies in order to improve and understand the new materials architecture and sensing mechanism at high temperature. Firstly, using trace amount of perovskite oxide nanoparticles decoration, 3-D b-Ga2O3 NRA gas sensors are not only sensitized to a degree that rivals noble metal nanoparticle sensitizing effect, but also greatly enhanced in their oxidative gas selectivity, e.g., in NO2 detection over O2. Secondly, post hydrogen treatment is utilized to tune the defects in the b-Ga2O3 to help enhance the sensor performance at high temperature. Furthermore, UV-assisted photoelectron generation in wide bandgap b-Ga2O3 significantly enhanced the sensor performance. Finally, an in-depth understanding of the 3-D architecture and sensing mechanism is being pursued using various complementary spectroscopy tools such as ex-situ and in-situ X-ray Photoelectron Spectroscopies (XPS)