Synthesizing SnO2 thin films and characterizing sensing performances

SnO2 thin films were grown on silica glass substrates using the pulsed laser deposition (PLD) method, and their structures, electric properties, and sensor performances were examined to investigate the sensing mechanism of thin-film gas sensors. Single-phase SnO2 films with rutile-type structures were obtained at 650 °C. All the SnO2 films had many columnar grains, and the grain size increased with film thickness. Measurements of the Hall coefficient at room temperature revealed that the Hall mobility of the films was independent of the film thickness. In contrast, the sensing performances of the films for NO2 and H2 gases respectively in an air atmosphere drastically improved for film thicknesses under 100 nm. These results for the film properties and sensing performances of SnO2 thin films are discussed in terms of a space-charge layer formed on the columnar grains.