CuO-loaded nano-porous SnO2 films fabricated by anodic oxidation and RIE process and their gas sensing properties

The fabrication of nano-porous SnO2 films with 1-D nano-channels by anodic oxidation has been a challenge due to a collapse of pore structure during annealing process and an existence of non-porous upper barrier layer. A new approach is developed to synthesize the nano-porous SnO2 films by employing Sn thin film instead of Sn foil and a reactive ion etching (RIE) process. The integrity of nano-porous structure was maintained by anodizing the Sn thin film deposited on SiO2/Si substrate, and 1-D nano-channels were opened up by removing the non-porous layer by RIE. As a potential application to gas sensor, CuO was impregnated to the nano-porous SnO2 films and their gas sensing properties were investigated. The nano-porous CuO–SnO2 film sensors exhibited the enhanced sensitivity and selectivity toward H2S gas, and their H2S sensing mechanism was discussed in terms of the formation/disruption of resistive p-CuO/n-SnO2 junction based on the variation of XPS binding energy and electrical resistance during gas exposure.