Enhanced H2 sensing performance presented by Mg doped ZnO films fabricated with a novel ITO seed layer

Abstract

The present study investigates the influence of Mg doping on the H2 sensing properties of ZnO films fabricated with ITO seed layer by spray pyrolysis method. XRD results revealed that both undoped and Mg doped ZnO films were polycrystalline with a hexagonal wurtzite structure with highly oriented (002) plane perpendicular to the ITO substrate. The films were highly transparent in the visible range of electromagnetic spectrum with a significant increase in transmission to 93 % after Mg addition. The optical band gap calculated from absorption spectra of the ZnO thin films increased with Mg incorporation due to size confinement. PL spectra show sharp and high intensity peak at 411 nm in the UV region. A week peak at 465 nm in blue region confirmed the less defect density in the samples. The AFM image of Mg doped ZnO film confirmed decreased crystallite size, with large surface roughness and increased surface area, favorable for sensing. The hydrogen sensing characteristics of the films were investigated at room temperature and the resistance of the sensor was measured for different concentration of H2 gas. Both the films exhibited good response even at H2 concentration as low as 100 ppm due to the ITO seed layer. The higher response of Mg doped ZnO film was attributed to the presence of rougher grains on the ITO under layer.