Emerging material zinc magnesium oxide based nanorods: Growth process optimization and sensor application towards humidity detection

In this paper, we provide a detailed investigation on the optical and physical properties of self-assembled Zinc magnesium oxide (Zn0.85Mg0.15O) based nanostructures which is an emerging material for optoelectronic devices. An enhancement was observed in the optical and material properties of vertically aligned highly crystalline Zn0.85Mgx0.15O nanorods grown using site nucleated hydrothermal treatment. Various parameters such as, the molar ratio of zinc nitrate hexahydrate, hexamethylenetetramine and growth time were optimized to achieve high-density of the nanorods. Photoluminescence (PL) measurement at 18 K revealed a peak at 3.61 eV corresponding to excitonic near-band-edge (NBE) emission from 'As annealed' sample and a peak with low intensity at 3.37 eV confirming the presence of another phase (ZnO) in grown nanorods. X-Ray diffraction (XRD) spectra of Zn0.85Mg0.15O samples showed highly c-axis-oriented growth with dominant 〈002〉 peak making them ideal for gas/humidity sensing applications. Room temperature PL spectrum exhibited reduction in defect states peak with increasing relative humidity levels. DC Current-Voltage characteristics showed increase in current intensity after exposing the sample to controlled relative humidity (RH). The proposed Zn1-xMgxO based sensor exhibited high sensitivity 1.503%/RH for change in RH and response time ∼ 7-8 min.