The development of SnO2 thin film gas sensors

Within the scope of this thesis, undoped SnO2 thin films with different thicknesses (212 nm, 258 nm, 412 nm) were coated on Si and glass substrates using RF magnetron sputtering system. In order to determine the structural, morphological, optical and electrical characteristics of the films produced, XRD, AFM, UV-Vis and Hall effect measurement systems were used, respectively. As a result of the structural analysis, it was determined that SnO2 films were formed on Si substrates. Surface roughness values were determined by surface morphology analysis of the films. Energy-band gap values of undoped SnO2 thin films were determined via optical analysises of samples coated on glass. The resistivity and Hall effect measurements of undoped SnO2 thin films, which are coated with different thicknesses on Si substrate, were carried out under a constant magnetic field of 0.4 T in the temperature range of 25-350 K using the Van der Pauw technique. It was determined that the conduction mechanism in SnO2 thin films was metallic conduction. According to the characterization results; the parameters which is appropriate for the production of gas sensor in the undoped SnO2 thin film called as Sample C was obtained. The production of SnO2 gas sensor device was carried out by applying the lithographic processes which are heater fabrication, electrode fabrication and sensor layer fabrication, respectively. The characterizations of gas detection of the produced gas sensor were investigated under different butane gas concentrations (Air, 250 ppm, 500 ppm, 750 ppm, 1000 ppm) at certain operating temperature (25 °C, 100 °C, 200 °C). It was determined that while the sensivity of the produced sensor against butane gas was to be ~ 0.45 % for the operating temperature of 25 °C, it was to be ~ 5 % for the operating temperature of 100 °C and 200 °C.