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.