Effect of annealing temperature on structural, optical and electrical properties of hydrothermal assisted zinc oxide nanorods

• ZnO nanorods were synthesized by hydrothermal method on microslide glass substrates.
• Pre-deposited ZnO seeds were used.
• Structural, optical and electrical properties of ZnO nanorods were studied.
• Crystalline structure of ZnO nanorods was improved with increase in annealing temperature.
• Resistivity decrease was observed with increase in the annealing temperature.

Zinc oxide nanorods were grown employing a low cost hydrothermal method on microslide glass substrates pre-coated with ZnO seed layer. The as grown nanorods were annealed in air at 350 °C, 450 °C and 550 °C. The effect of annealing at different temperatures on morphology, structural, optical and electrical properties was investigated using field emission scanning electron microscopic, X-ray diffraction, UV–vis spectral, photoluminescence and electrical studies. The X-ray diffraction pattern of all the samples showed wurtzite structure preferentially oriented along the c-axis (0 0 2) direction. It was found that diameter of the nanorods increased with increasing of annealing temperature. The UV–vis absorption spectra showed a red shift from which it was inferred that the optical bandgap of the material decreases from 3.33 eV to 3.28 eV with increase in annealing temperature. Photoluminescence measurements showed increase in the UV emission intensity with respect to annealing temperature and also produced additional peaks attributed to defects and impurities. Annealing the ZnO nanorod structures at various temperatures evidently showed that the sample annealed at 550 °C acquired the lowest resistivity about 1.62 × 10− 4 Ω­cm.