Controllable growth of ZnO nanorods by seed layers annealing using hydrothermal method

• ZnO nanorods with diameters ranging from 30 nm to 200 nm have been controlled by seed layer annealing using hydrothermal method.
• With increasing the seed layer annealing temperature, the morphologies of ZnO nanorods change from tapered needle- to hexagonal-like structures.
• All nanorods possess a strong diffraction peak at 34.78° corresponding to ZnO (002) plane and no impurity phase is observed.
• With increasing ZnO seeds anneal temperature, the photoluminescence intensity in visible region decreases gradually.

ZnO nanorods have been synthesized by hydrothermal method on sol–gel derived ZnO seeds/p-Si substrates. The effect of annealing temperature of seed layers on the morphological, structural and optical properties of ZnO nanorods is systematically investigated. It is found that the diameters of nanorods is controllable ranging from 30 to 200 nm via seed layers annealing and the morphologies of ZnO nanorods change from tapered needle- to hexagonal-like structures. X-ray diffraction measurement shows that all nanorods possess a strong diffraction peak at 34.78° corresponding to ZnO (002) plane and no impurity phase is observed. Photoluminescence (PL) spectrum study shows that all samples exhibit strong near band edge emissions at 392 nm and defect related broad visible emissions centered at 550 nm. With increasing ZnO seeds anneal temperature, the visible emission intensity decreases gradually, which is attributed to the decreases of oxygen vacancies at high annealing temperature.