Effects of Growth Duration and Precursor Concentration on the Growth of ZnO Nanorods Synthesized by Chemical Bath Deposition

Well-aligned ZnO nanorods were successfully fabricated on polyethylene naphthalate (PEN) substrates by a simple chemical bath deposition technique at a low temperature. The effects of growth duration (2-8 h) with precursor concentrations of 0.025 and 0.050 M on the optical and structural properties of the prepared ZnO nanorods were systematically studied by the X-ray diffraction (XRD), field emission scanning electron microscopy, transmission electron microscopy, photoluminescence (PL), and UV-visible. The XRD results demonstrated that the ZnO nanorods vertically grew in the (002) direction along the z axis on the substrate. These low compressive strain values revealed that the obtained ZnO nanorods grown on seed-layer ZnO/PEN substrates had a high quality crystal structure. The field emission scanning electron microscopy images showed that the vertical ZnO nanorods were hexagonal shaped, and that the average diameter of the ZnO nanorod arrays on PEN substrate increased from 22 to 55 nm with increased growth duration from 2 to 8 h, respectively. The high-resolution transmission electron microscopy image suggested that [0 0 0 1] is the preferred growth direction for ZnO nanorods. The PL results demonstrated that ZnO nanorods grown for shorter or longer than 5 h exhibited a strong PL peak at around 420 nm (indigo emission).