Dispersed nanoelectrodes for high performance gas sensors

Integration of nanoparticles in electronic devices such as sensors, actuators, batteries, solar and fuel cells is a key technological development for advancing their performance and miniaturization. Frequently, however, the benefit of nanoscale is lost by poor electrical conductivity through such nanoparticle structures. As a result, it is challenging to achieve both attractive conductivity and maximal performance by the device. Recently it was demonstrated that flame-made nanoparticles can be directly deposited onto substrates to form porous thick films of controlled thickness for application as gas sensors. The mechanical stability of FSP-deposited layers can be greatly increased by in situ annealing showing compatibility even with fragile CMOS-based substrates. Here, a novel asymmetric electrode assembly is described that greatly reduces the resistance of a nanostructured layer and maximizes its performance: Nanoparticles with tailored conductivity (e.g. Ag, CuO, Au) serving as electrodes are stochastically deposited by a scalable technique either below or above a functional (e.g. SnO₂, TiO₂, WO₃) film decreasing the effective length of the resistive components. As the distance between electrodes is at the nanoscale, the total film resistance is drastically decreased. The feasibility of this assembly is demonstrated with solid state sensors having controlled resistance and exceptionally high sensitivity.