Gas sensitive ZnO structures with reduced humidity-interference

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.