Structural and optical properties of ZnO nanorods: The effect of concentration and pH of the growth solution

We prepared ZnO nanorods using a hydrothermal method in the c-axis orientation and perpendicular on an ITO substrate. The structural and optical properties were examined for samples prepared under various concentrations and pHs. The XRD results showed that the Bragg peak (002) is more intense than other peaks. This result reveals the tendency of the uniaxial growth of nanorods. The FE-SEM images showed that increasing the concentration increases the diameter and length of the nanorods, while the orientation remains almost constant. On the other hand, with increasing the pH, the diameter and length of nanorods decrease, so that at pH = 11, there is even no trace of nanorods formation. The photoluminescence spectra show that the intensity of near band edge emission (NBE) peaks was higher than the intensity of deep-level emission (DLE) peaks, which indicates the high crystalline quality of the samples. These results show the distinct effect of concentration and pH and provide a possibility to find an optimal condition to yield a sample with selected structural and optical properties.