Effect of precursor chemistry on the structural and sensing properties of hydrothermally grown nanorods

We report on the effect of precursor chemistry on ZnO nanorods (NRs) growth and their hydrogen sensing characteristics probably for the first time. We found that zinc acetate grown nanorods were dislocated at the center and showed better sensitivity towards hydrogen gas than conventional NRs without dislocation. For nanorods growth, a ZnO seed layer of thickness 80 nm was deposited by RF sputtering at room temperature over SiO₂/p-Si substrate; oxidation in silicon substrate was done by the thermal oxidation method. The crystalline phases and the surface nanostructure of the ZnO thin film (seed layer) were investigated by the X-ray diffraction and atomic force microscope. The ZnO nanorods' surface morphology and their crystalline nature were studied by SEM and X-ray diffraction. The chemical properties of the ZnO nanorods were investigated by the X-ray photoluminescence spectroscopy. Using DC sputtering and shadow mask, Ti (80 nm)/Au (100 nm) metal layers were deposited over the ZnO nanorods to fabricate a metal semiconductor metal structure for sensor fabrication. I–V characteristics of the devices were obtained by the semiconductor parameter analyzer. The hydrogen gas was exposed over the devices using mass flow controller, and it was found that device containing nanorods grown by zinc acetate shows 98% sensitivity for 24 ppm gas concentration in a nitrogen atmosphere that was the largest reported till date than with bare conventional non-dislocated NRs.