Extrinsic oxygen defects in SnO/SnO2 heterostructure for efficient NO2 gas detection

High selectivity and fast response in the detection of NO2 are key factors in protecting human health in lifethreatening environments. The p-n SnO/SnO2 heterostructure is a promising material as a metal oxide for effective chemical reactions with a target gas. It has a synergistic effect on the intrinsic semiconducting properties and the formation of an interfacial electric field in the heterojunction. The extrinsic oxygen vacancies in the SnO/SnO2 structure enhance the chemical reaction in the sensing property. In this study, we developed a defect-SnO/SnO2 heterostructure-based NO2 gas sensor. It shows excellent sensing performances with a high response of 100.86, fast response time of 5.83 s, and superior selectivity (approximately 23 times higher than those of other target gases) in the detection of 50 ppm NO2 at 150 degrees C. Raman and electron paramagnetic resonance (EPR) results supported the presence of oxygen vacancies in the defect-rich SnO/SnO2 crystal and Xray photoelectron spectroscopy (XPS) and time-of flight secondary ion mass spectrometry (ToF-SIMS) analyses described the role of SnO/SnO2 heterostructure with oxygen defects as an effective electron donor for the adsorbed oxygen molecules and NO2 target gas. We believe that the direct formation of oxygen vacancies in the SnO/SnO2 heterostructures is a significant reference for the development of high-performance NO2 gas sensors.

Automated summary

High selectivity and fast response are crucial for protecting human health in dangerous environments. The p-n SnO/SnO2 heterostructure, with its synergistic effect on semiconducting properties and interfacial electric field, shows excellent sensing performances. It has a high response rate, fast response time, and superior selectivity compared to other target gases. The presence of oxygen vacancies in the SnO/SnO2 heterostructure is supported by Raman and EPR results, and the role of these vacancies as an effective electron donor for adsorbed oxygen molecules and NO2 target gas is described by XPS and ToF-SIMS analyses. The direct formation of oxygen vacancies in SnO/SnO2 heterostructures is an important reference for the development of high-performance NO2 gas sensors.