Controllable vapor phase growth of vertically aligned ZnO nanorods on TCO/Glass substrates

Solution-free and catalyst-free vertically aligned ZnO nanorods have been synthesized by thermal CVD reactor at relatively low temperature (<500 degrees C) to produce high-surface 3D photoanode on glass substrate. Different TCOs films such as Al doped ZnO films deposited by PED, RF-sputtering techniques and ITO were considered for the growth as starting seeding layer for the nanorods. The aim of the paper is mainly focused to control the thickness and length of these nanostructures by varying not only the growth parameters, such as amount of Zn evaporation, but also substrate characteristics, such as grain size of Al doped ZnO and ITO seeding films. The morphology of the different TCO substrates and also the grown ZnO nanorods have been analyzed with the help of atomic force microscopy and scanning electron microscopy. The study revealed that size and orientation of ZnO nanorods are mainly related to TCO's grain morphology and crystallinity, while their length can be controlled by varying Zn evaporation parameters.