The influence of varying OH− ion concentration on the surface morphology of chemically deposited ZnO-SiO 2 nanostructures on glass substrate was investigated. The morphological features, phase structure, and infrared characteristics were examined by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR), respectively. Results revealed that silica significantly changes the hexagonal morphology of bare ZnO rod to "pointed tips" when using low initial OH − precursor concentration. Increasing OH − ion concentration resulted in a "flower-like" formation of ZnO-SiO 2 and a remarkable change from "pointed tips" to "hemispherical tips" at the top surface of the rods. The surface capping of SiO 2 to ZnO leads to the formation of these "hemispherical tips." The infrared spectroscopic analysis showed the characteristics peaks of ZnO and SiO 2 as well as the Si-O-Zn band which confirms the formation of ZnO-SiO 2 . Phase analysis manifested that the formed ZnO-SiO 2 is of wurtzite structure. Furthermore, a possible growth mechanism is proposed based on the obtained results.

Abstract. Growing ZnO on Si via low-cost CBD is difficult owing to the large lattice mismatch between ZnO and Si and the intricate control of nanoparticle aggregation. In this work, a Pt buffer layer and addition of SiO2 on the chemical solution were introduced. The effect of these parameters on the resulting morphology and composition were investigated using SEM-EDX and FTIR. Pt-coated Si showed higher density of ZnO nanostructure growth than bare Si due to the additional nucleation sites provided by Pt. Moreover, SiO2 addition resulted to a different ZnO nanostructure.

ZnO-SiO2 nanostructures were grown on both bare Si and Pt-coated Si substrates via chemical bath deposition (CBD). The grown nanostructures were characterized using Scanning Electron Microscope with Energy Dispersive X-ray Spectroscopy (SEM-EDS), Fourier Transform Infrared (FTIR) measurement and Ultraviolet-Visible (UV-Vis) absorption spectroscopy. Surface morphology results revealed that Pt-coated Si substrate have promoted the growth of ZnO-SiO2 nanostructures by providing more active sites for nucleation thus formation ZnO-SiO2 nanostructures were observed. It is believed that SiO2 will adhere to the non-polar sides of the grown ZnO nanostructures. This result is manifested in the FTIR spectra which showed a pronounced peak corresponding to ZnO-SiO2 grown on bare Si suggesting that more Si-O bonds are present. However, Pt-coating did not significantly affect the band gap of the grown ZnO-SiO2 nanostructures.

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