Effect of an Au Nanodot Nucleation Layer on CO Gas Sensing Properties of Nanostructured SnO2 Thin Films

We report the effect of the fabric of the surface microstructure on the CO gas sensing properties of SnO2 thin films deposited on self-assembled Au nanodots (SnO2/Au) that were formed on SiO2/Si substrates. We characterized structural and morphological properties, comparing them to those of SnO2 thin films deposited directly onto SiO2/Si substrates. We observed a significant enhancement of CO gas sensing properties in the SnO2/Au gas sensors, specifically exhibiting a high maximum response at 200 C-circle and quite a low detection limit of 1 ppm level in dry air. In particular, the response of the SnO2/Au gas sensor was found to reach the maximum value of 32.5 at 200 C-circle, which is roughly 27 times higher than the response (similar to 1.2) of the SnO2 gas sensor obtained at the same operating temperature of 200 C-circle. Furthermore, the SnO2/Au gas sensors displayed very fast response and recovery behaviors. The observed enhancement in the CO gas sensing properties of the SnO2/Au sensors is mainly ascribed to the formation of a nanostructured morphology in the active SnO2 layer having a high specific surface-reaction area by the insertion of a nanodot form of Au nucleation layer.