Gas microsensors based on zinc oxide structures with rod- and needle-like morphology, both integrated via a non-catalyzed vapor-solid mechanism enabled using aerosol-assisted chemical vapor deposition, are developed. Analyses of the films via SEM, TEM, XPS, and water contact angle indicate a higher concentration of oxygen vacancies, higher aspect ratio and higher roughness factor for the needles than for the rods. Gas sensing tests towards hydrogen and carbon monoxide demonstrate reduced humidity-interference, and higher responses to the analytes for the needle-based systems compared to the rods. These results are attributed to the morphology of the sensitive materials, which not only affects the surface-area-to-volume-ratio of the films but also their surface chemistry. These findings indicate that a thorough optimization of morphology, structure and surface properties of gas sensitive metal oxides could allow for more reliable sensor operation in humid conditions.
Vallejos, S., Gràcia, I., Pizúrová, N., Figueras, E., Čechal, J., Hubálek, J., & Cané, C. (2019). Gas sensitive ZnO structures with reduced humidity-interference. Sensors and Actuators, B: Chemical, 301. https://doi.org/10.1016/j.snb.2019.127054