Effects of buffer layer thickness on growth and properties of ZnO nanorods grown by metalorganic chemical vapour deposition

We investigated the effect of the buffer layer thickness on the structural and optical properties of ZnO nanorods grown on Si substrates by metalorganic chemical vapour deposition. Increasing the thickness of the buffer layer significantly enhanced the vertical alignment and density of the nanorods. The ZnO nanorods grown on the buffer layer with a thickness exceeding 500 nm were inclined on the substrate surface, due to the formation of a rugged morphology with a pyramidal shape on the surface of the buffer layer, which was attributed to the surface undulation resulting from the increased tensile strain. This inclination also resulted in a decrease in the intensity of the (0002) ZnO diffraction peak and the ultraviolet emission peak. This paper discusses the microstructural properties and growth mechanism of the ZnO nanorods on buffer layers with various thicknesses.