Abstract
Hydrothermal growth has emerged as a popular method for growing ZnO nanorods. Solution concentration can have a significant impact upon the microstructure of the resulting nanorods, and this has been investigated in a high concentration regime by growth at low temperature (90 degrees C) on seeded substrates. X-ray diffraction and scanning electron microscopy (SEM) analyses were used to characterize the structural properties of the ZnO nanorods. Optical and electrical properties of the nanorods are also discussed. SEM image analysis revealed that the ZnO the diameter of nanorods increased linearly with concentration up to a maximum of 104 nm at 0.075 M after which the diameter remained unchanged with further increase in concentration. Axial growth rate was also found to increase with concentration allowing nanorods to achieve lengths of nearly 600 nm for solution concentration of 0.1 M. The number density of nanorods showed inverse behavior as compared to the behavior of the diameter. The resistivity of the nanorods was found to decrease with concentration upto 0.075 M showing a minimum value of 5.85 x 10(-1) Omega-m. The growth process has been quantitatively modelled in terms of the dependence of nucleation rate on concentration using the Avrami equation. The nucleation rate was found to be nearly independent of solution concentration showing that the nucleation process is reaction limited. The growth model may therefore be applied to the solution growth of other materials where steric hindrance is significant.