A template-free sol-gel technique for controlled growth of ZnO nanorod arrays

The growth of ZnO nanorod arrays via a template-free sol-gel process was investigated. The nanorod is single-crystalline wurtzite structure with [0 0 0 1] growth direction determined by the transmission electron microscope. The aligned ZnO arrays were obtained directly on the glass substrates by adjusting the temperatures and the withdrawal speeds, without seed-layer or template assistant. A thicker oriented ZnO nanorod arrays was obtained at proper experimental conditions by adding dip-coating layers. Room temperature photoluminescence spectrum exhibits an intensive UV emission with a weak broad green emission as well as a blue double-peak emission located at 451 and 468 nm, respectively. Further investigation results show that the difference in the alignment of nanorods ascribes to the different orientations of the nanoparticles-packed film formed prior to nanorods on the substrate. Well ordered ZnO nanorods are formed from this film with good c-axis orientation. Our study is expected to pave a way for direct growth of oriented nanorods by low-cost solution approaches.

Research highlights► The oriented ZnO nanorod arrays were fabricated by template-free sol-gel technique. ► The orientation of ZnO nanorods can be controlled by adjusting the heating temperatures and withdrawal speed. ► The room temperature PL spectrum of aligned ZnO arrays exhibits a strong UV emission with a weak green emission and a blue double-peak emission. ► The different in alignment of the nanorods is ascribed to different orientation of the film between the substrate and nanorods dependent on the experimental parameters.