Self-catalysed vapor-liquid-solid growth mechanism of ZnO nanowires grown on silicon substrate pre-coated with ZnO buffer layer

Abstract

The present article reports the growth mechanism of zinc oxide (ZnO) nanowires grown on silicon substrate pre-coated with ZnO buffer layer by thermal evaporation method. ZnO nanowires are grown for different growth time of 0, 30, 90 and 120 mins with controlled supply of Ar and O2 gas at 650oC. The structural, morphological and crystallinity properties of ZnO nanowires are analyzed by field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) spectroscopy, high resolution transmission electron microscopy (HRTEM), and X-ray diffraction (XRD). FESEM images infers that, the nanowires growth is driven by self-catalysed vapor-liquid-solid mechanism, where the buffer layer serve as nucleation site. EDX spectra show the uniform composition and purity of ZnO nanowires. A strong (002) peak is detected in XRD spectra which indicates that the preferred growth orientation of the nanowires is toward the c-axis with a hexagonal wurtzite structure. The HRTEM microscopic graphs confirm the growth of nanowire along the preferred [0001] axis. Based on the analysis of grown ZnO nanowires, the probable growth mechanism is schematically presented.