Synthesis and Gas-Sensing Character of SnOx Cluster-Assembled Films

Nanometric SnOx cluster-assembled films prepared by a plasma-gas-condensation cluster deposition apparatus have been examined by transmission electron microscopy (TEM) and electrical resistance. TEM observation showed that those clusters were almost spherical and size-monodispersive with a mean cluster size of 10 nm. The high-resolution TEM images indicated that the films were composed of randomly oriented nanocrystallites and that their surface roughness retained the traces of the original SnOx clusters. The electrical resistance of the SnOx cluster-assembled film decreased with decreasing partial O2 gas pressure. This result suggests that the intergranular potential barriers were responsible for the resisitvity variation. The activation energy estimated from the temperature-dependent resistivity was 0.75 eV for 330 K < T < 410 K under the partial O2 gas pressure of 0.02 MPa.