Substantial effect of Pd incorporation on the room temperature hydrogen sensing performance of ZnO/ITO nanowires prepared by spray pyrolysis method

Abstract

The room temperature hydrogen sensing characteristics of Pd-decorated ZnO nanowires was fabricated on ITO substrate by spray pyrolysis technique. The crystal structure revealed that the Pd dopants were well integrated into ZnO wurtzite lattice. The average crystallite size decreased with increasing Pd dopant concentration. The band gap energies of the ZnO films were affected by the Pd concentration. The blue shift in the PL emission of Pd:ZnO film signify the modulation of band gap caused by Pd addition. The morphology of ZnO films changed from nanotubes to nanowires with Pd dopant concentration. The gas sensing measurement results demonstrated that the Pd:ZnO/ITO sensor revealed good response even for low concentration of H2, with characteristics reliant on the morphology, size of the grains and the increasing incorporation of Pd concentration. A doping level of 2 at.% palladium in ZnO was found to give optimum response. The lowest detection limit of hydrogen was found to be100 ppm. We strongly believe that the Pd:ZnO sensor with ITO underlayer can be widely used for selective hydrogen gas detection. It can be summarized that this high performance H2 sensor has potential for use as a portable room temperature gas sensor.