Investigation of structural and gas sensing characteristics of un-doped and Co-doped SnO2 nanostructured thin films

Gas sensing behavior of un-doped and cobalt-doped tin oxide (Co-SnO2) thin films, synthesized by conventional spray pyrolysis technique, has been investigated for carbon dioxide and oxygen gases. To find the structural and physical properties of these samples we have used X-ray diffraction (XRD) and scanning electron microscopy (SEM) images. Measurements showed that these samples have a tetragonal polycrystalline structure with (110) as the preferred direction and crystallite size of 17–27 nm, with surface grain sizes in the range of 25–60 nm. Based on the sensitivity measurements, samples with 16 wt% Co impurity as well as the lowest crystallite and surface grain size, has the highest gas sensitivity, at the optimum operation temperatures of 170 and 180 °C, for O2 and CO2 respectively.