The effect of seed layer cycles on the structural, optical, and morphological properties of ZnO nanorods

In this study, ZnO seed layers with different cycles were formed on glass substrates by the sol-gel technique, and ZnO nanorods were grown on them by the hydrothermal method. Morphology and the structural characterization of the seed films and the ZnO nanorods are carried out by field emission scanning electron microscopy (FE-SEM) and x-ray diffraction techniques. In addition, to investigate the effect of seed layer deposition cycles on the optical properties of the ZnO nanorod arrays, UV/visible spectrophotometer and photoluminescence (PL) measurements were performed. The changes in structural and optical parameters such as dislocation density, strain, crystallite size, and optical band gap values on each seed layer deposition cycle were examined. The highest optical band gap and crystallite size were obtained for ZnO nanorods with 4 cycles seed layer as 3.22 eV and 63.6 nm, respectively. Also, in the PL spectrum, the largest ratio of UV-emission region to weak-visible emission region was obtained in ZnO nanorods having 4 cycles. In addition, the glucose detection properties of ZnO nanorods having 4 cycles were investigated using the PL measurements and it was found that UV-emission peak intensity of ZnO nanorods decreased as the glucose concentration increased from 8 to 40 mM. The results show that the number of deposition cycles of the seed layer has a strong influence on the orientation, crystal quality, and optical band gap of the growing ZnO nanorods, as well as significantly affecting their morphological properties.