Effects of Thin-Film Thickness on Sensing Properties of SnO₂-Based Gas Sensors for the Detection of H₂S Gas at ppm Levels.

SnO₂ thin-film gas sensors were easily created using the ion sputtering technique. The as-deposited SnO₂ thin films consist of a tetragonal SnO₂ phase and densely packed nanosized grains with diameters of approximately 20-80 nm, which are separated by microcracks. The as-deposited SnO₂ thin film is well crystallized, with a dense columnar nanostructure grown directly onto the alumina material and the Pt electrodes. The grain size and thickness of SnO₂ thin films are easily controlled by varying the sputtering time of the ion coater. The responses of the SnO₂ thin-film sensors decrease as the SnO₂ film thickness is increased, indicating that a negative association exists between the sensor response and the SnO₂ film thickness due to gas diffusion from the surface. The SnO₂ thin-film sensor, which was created by ion sputtering for 10 min, shows an excellent sensor response where Ra is the electric resistance under air and is the electric resistance under the test gas) for detecting 1 ppm H₂S at 350°C.