Effects of porosity and particle size on the gas sensing properties of SnO2 films.

Metal oxide semiconductors are widely used as gas sensing materials; thus, improving their gas sensing properties is of some interest. The microstructure of a SnO 2 film was controlled using the thermal evaporation technique at a relatively high process pressure. Scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET) analysis were used to characterize microstructures, crystallinity, particle size, and the surface area that was dramatically altered as a function of the process pressure. In all cases, SnO 2 films had interconnected network structures with open pores; continuous grain growth was observed through the neck between the SnO 2 nanoparticles. The responses of sensors fabricated at different depositional pressure were evaluated by monitoring changes in the electrical resistance of CO gas. The gas sensor deposited at 0.2 Torr showed a high response and short response time owing to its high porosity (97%) and nano-sized particles (8.4 nm). The results confirm that porosity and particle size play key roles in determining the gas response. Unlabelled Image • Various SnO 2 films were prepared by thermal evaporation at high pressure. • SnO 2 films had an interconnected network structure between nanoparticles. • SnO 2 films had open pores and porosity of over 70%. • Nanoporous SnO 2 films exhibited a high gas response and a short response time. • Porosity and particle size play a key role in determining the gas response. [ABSTRACT FROM AUTHOR]