Effects of post-annealing temperature on the properties of ZnO nanorods grown on homogenous seed-layers by using the hydrothermal method

ZnO nanorods were grown on Si substrates by using the hydrothermal method; then, they were post-annealed at various temperatures ranging from 573 to 973 K. The effects of post-annealing temperature on the structural and the optical properties were investigated by using scanning electron microscopy (SEM), X-ray diffraction, and photoluminescence (PL). After the post-annealing process, small pores had been formed on the surface of the ZnO nanorods without any change in the shape of the ZnO nanorods. A tensile stress was observed in the as-grown and the post-annealed ZnO nanorods. The PL intensity ratio of the near-band-edge emission (NBE) to the deep-level emission (DLE) was enhanced, and the DLE peak shifted from yellow to orange emission with increasing post-annealing temperature. The activation energy of the post-annealed ZnO nanorods was increased by the post-annealing process.