O2 and CO2 gas sensing by pure SnO2 polycrystaline thin films

In this research we have studied three samples of pure SnO2 thin films which are deposited by spray pyrolysis method on glass substrate. Oxygen and carbondioxide gas sensor were employed. The transmittance spectra of the samples showed that the thickness of the layers were within the nanometer scales (200-150 nm)، and XRD spectra showed that as the samples become thiner the preference orientation varies from (200) to (110). The this variation of orientations was due to the variation of their thicknesses. Also crystallites sizes were decreased from 31 to 22. 5 nm. The sensitivity of the samples to 2000 ppm of these gases showed that the optimum operational temperature in these samples was about 170°C and 180°C for oxygen and carbondioxide respectively. In addition we found that the sample with lowest thickness (150 nm) and crystallite sizes (~22. 5 nm) with preferential orientation of (110) had more sensitivity to O2 compare to CO2 gas.