Annealing effects of ZnO seed layers on structural and optical properties of ZnO nanorods grown on R-plane sapphire substrates by hydrothermal Method

Abstract

ZnO nanorods were hydrothermally grown on R-plane sapphire substrates coated with an as-grown ZnO seed layer and with ZnO seed layers annealed at different temperatures. The effects of the seed-layer annealing temperature on the structural and optical properties of the ZnO nanorods were investigated using scanning electron microscopy, X-ray diffraction, and photoluminescence. ZnO nanorods and nanosheets grew on the as-prepared seed layer. Only ZnO nanorods grew on the ZnO seed layer annealed above 700 °C. The structural and optical properties of the ZnO nanorods were significantly enhanced when the seed layers were annealed at 700 °C. A cubic equation was used to establish the non-linear exciton radiative lifetime of the free exciton emission peak. Varshni's empirical equation fitting parameters were α = 4 × 10-3 eV/K, β = 1 × 104 K, and Eg(0) = 3.335 eV; the activation energy was ∼94.6 meV. Copyright © The Korean Institute of Metals and Materials