Density-controlled selective growth of well-aligned ZnO nanorod arrays by a hybrid approach

We present a novel and scalable process for the growth of high-quality density-controlled uniform ZnO nanorod arrays (NRAs) in which the positions of the nanorods and the shapes are precisely tailored. The patterns and the growth locations of the nanorods are defined by electron-beam lithography (EBL). The alignment and orientation of the nanorods are determined by a solution growth process (hybrid approach). Field-emission scanning electron microscopy (FESEM) analysis of the ZnO nanorods shows that the as-grown nanorods are uniform and vertically aligned on the patterned substrate. The average diameters and lengths of nanorods are found to be ∼75±15∼75±15 and ∼250±50nm, respectively. By changing the precursor concentration, a significant change in the density of aligned ZnO nanorods has been observed. The structural analysis reveals that the as-grown nanorods are single crystalline and grown along the cc-axis direction. Cathodoluminescence studies of the nanorods revealed a sharp ultraviolet emission at a wavelength of ∼381 nm and a broad deep-level visible emission at ∼580 nm. This approach opens a new route to create complex patterns of nanorod arrays that can enhance the performance of biomolecular fluorescence detectors, sensors and optoelectronic devices.