Performance improvement of MOCVD grown ZnGa₂O₄ based NO gas sensors using plasma surface treatment

Gas sensors are essential devices in various industrial and environmental monitoring applications. Nitric oxide (NO) is a harmful gas that is produced in various combustion processes and is associated with air pollution and respiratory diseases. Zinc gallate (ZnGa₂O₄) has shown promising results as a material for NO gas sensing applications. Previously, the performance of NO gas sensors based on ZnGa₂O₄ epilayers was not substantial. However, there is potential for further improvement by optimizing their surface properties. Plasma surface treatment has been widely utilized to modify the surface characteristics of materials, including semiconductors, for various applications. We have investigated the impact of plasma surface treatment on the performance of metal–organic chemical vapor deposition grown ZnGa₂O₄ based NO gas sensors in this work. An inductive coupled plasma reactive ion etching was used to apply Ar plasma to successfully optimize the sensing response of the ZnGa₂O₄ based gas sensor for NO gas. The sensor response for ZnGa₂O₄-based NO gas sensors is 159.5%, which is enhanced by 8 times and reached 1276.1% under 5 ppm NO gas concentration after 10 min Ar plasma treatment. The limit of detection is found to be 2.4 ppb. These results demonstrate that Ar plasma treatment significantly improved the ZnGa₂O₄-based NO gas sensor's response. The cross-selectivity of this sensor is tested among NO, CO₂, CO, and SO₂ gases, which indicated that ZnGa₂O₄ gas sensor possess highly selectivity towards NO gas. This study provides valuable insights into the surface modification techniques for enhancing the performance of gas sensors, which can have a significant impact on the development of advanced sensing technologies for environmental and industrial applications.