Direct growth of ZnO nanodisk networks with an exposed (0Â 0Â 0Â 1) facet on Au comb-shaped interdigitating electrodes and the enhanced gas-sensing property of polar {0Â 0Â 0Â 1} surfaces

ZnO nanodisk networks were grown directly on Au comb-shaped interdigitating electrodes on SiO2/Si substrate by thermal evaporation of a mixture of ZnCl2 and InCl3·4H2O at 450 °C in air. The nanodisk has hexagonal shape with a side length of ∼1.8 μm, a diagonal of ∼3.8 μm and thickness 64-125 nm. It grows mainly along 011¯0 directions, and is enclosed by ±(0 0 0 1) top and bottom surfaces. The as-prepared ZnO nanodisks having mostly {0 0 0 1} facets exhibit better gas-sensing performance for NH3, N(C2H5)3 and C2H5OH comparing to ZnO nanorods with 011¯0 facets. The sensor response measured at 300 °C are 1.68, 11.84 and 10.19 for NH3, N(C2H5)3 and C2H5OH with concentration 5, 10 and 10 ppm, respectively. The enhancement in the gas-sensing properties is mainly attributed to the exposed {0 0 0 1} facets which provide more active sites for oxygen adsorption and subsequent reaction with the vapor than 101¯0 facets, and therefore improved response. The observation motivates us to further explore new synthetic methods to prepare other metal oxides with a high percentage of reactive facets with potential applications in gas sensors, photocatalysts, solar cells, and optoelectronic devices.