Solution-Processed Gas Sensors Based on ZnO Nanorods Array with an Exposed (0001) Facet for Enhanced Gas-Sensing Properties

In this paper, thin film gas sensors made from 8-nm-diameter and exposed-{10-10}-facet ZnO nanorods self-aligning along the ceramic tube are fabricated by a simple dip-coating method. On the sensor surface, we successfully synthesize a ZnO nanorods array exposed with (0001) plane in situ by a facile solution-processing technique. Compared with the unprocessed sensor (i.e., dip-coated ZnO film based sensor), the main advantages of the solution-processed sensor are a high sensitivity (3-fold prefactor A(g)), fast response (less than 10 s), and low detection limit (1 ppm) to benzene and ethanol. The enhancement in the gas-sensing performance suggests that the effect of exposed facet is dominant rather than the size effect, and the order of gas-sensing properties of ZnO crystal face is (0001) > {10-10}. On the basis of these results, it is found that the surface structure at the atomic level is a key factor in improving the oxygen adsorption and, consequently, the gas-sensing performance of a ZnO nanorods array based gas sensor.