Abstract
This mini review is comprised of two approaches of the enhancement of gas sensor response: microwave-assisted and flame-assisted strategies. To achieve enhancement, defects and surface modifications must be addressed. When a SnO2-graphene mixture is irradiated with microwaves, SnO2 acquires oxygen vacancies because carbon takes oxygen away from its surroundings. An oxygen vacancy, a type of defect, creates free electrons, increasing the response [1]. In addition, decoration with amorphous carbon, which is a type of surface modification, establishes a heterojunction in the main substance [2]. The heterojunction leads to rectification; hence, electrons flow in one direction to balance the electron concentration. A change in the concentration of electrons affects electron mobility. The gas sensor response is affected by the mobility and concentration of electrons. Oxygen vacancies create electrons according to the Kröger-Vink equation, and heterojunctions accelerate electrons. The sensor response changes when the metal oxide semiconductor gas sensor is exposed to oxidizing and reducing gases. When a substance is oxidized, surface functional groups lose their electrons to remain in equilibrium. Oxygen, a surface functional group, loses electrons and traps them as ions on the surface, resulting in band-bending [3]. Therefore, defects and decorations increase gas sensor response.
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Acknowledgments
This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2016R1A6A1A03013422). This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (2019R1A2C1006193). This work was supported by the Technology Innovation Program (20013726) funded By the Ministry of Trade, Industry & Energy (MOTIE, Korea).
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Kang, S. et al. (2023). Microwave-Assisted Generation of Secondary Nanoparticles and Flame-Assisted Generation of an Amorphous Layer for Improving NO2 Gas Sensing Behaviors: A Mini Review. In: Suryadevara, N.K., George, B., Jayasundera, K.P., Mukhopadhyay, S.C. (eds) Sensing Technology. ICST 2022. Lecture Notes in Electrical Engineering, vol 1035. Springer, Cham. https://doi.org/10.1007/978-3-031-29871-4_7
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