Heterostructure of Chemical Vapor Deposition (CVD) Graphene and H2 Plasma-Treated SnO2 Nanoparticle Films for Room Temperature Sensing of SO2.

In this article, we aim to develop SO2 sensors that operate at room temperature (25 °C) by using graphene synthesized through chemical vapor deposition and spin-coated SnO2 films. H2 plasma treatment was applied to the SnO2 films, and photolithography was used to pattern the graphene into interdigital electrodes. We found that the H2 plasma treatment induced oxygen vacancies, hydroxyl groups, and other types of surface states in the SnO2 films. The hydroxyl groups could be an important reason for the onset of p-type conduction in the SnO2 film. When graphene electrodes were deposited on top of the H2 plasma-treated SnO2 film, the SO2 sensor's response was enhanced by nearly 50 times (from 4% to 190%) compared to the sensor based solely on SnO2. Additionally, the response and recovery times were reduced by 34% and 91%, respectively. This performance remained stable even after the sensor had been stored in air for over 2 months. The substrate-mediated effects on the adsorption properties of the exposed graphene surface in the graphene-metal oxide heterostructure, along with the unique properties of the SnO2 film introduced by H2 plasma treatment, highlight new strategies for the future development of room-temperature-operated gas sensors.