SnO2/TiO2 coaxial nanowires: synthesis and characterization and optical properties

초록

In recent years, extensive research into coaxial 1D nanostructures consisting of different materials in the radial direction has been carried out due to their potential applications in electronic and optoelectronic device applications owing to a couple of important reasons. One reason is that the coaxial 1D nanostructures can realize various tailor-made functions by fabricating heterojunction nanodevices or depositing multilayers with different chemical compositions in the radial direction. Another is that we can protect them from oxidation or contamination and passivation of interface states abundant at the surface of 1D nanostructures. In this study, SnO2-core/TiO2-shell 1D nanostructures have been synthesized by using a two step process: thermal evaporation of SnO2 powders and metal organic chemical vapor deposition of TiO2. We performed scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDXS), and photoluminescence (PL) spectroscopy to characterize the of SnO2-core/ TiO2-shell coaxial nanowires. The influence of the TiO2 layer thickness on the photoluminescence (PL) properties of the nanostructure was investigated by using a room temperature PL spectroscopy analysis. The intensity of the PL peak at about 595 nm characteristic of the SnO2 core decreases significantly and shifts to the lower wavelength region to form a broad emission peak ranging from 535 to 595 nm as the TiO2layer thickness increases. Our results show that the wavelength of the emitted light can be controlled by coating the SnO2 nanowires with TiO2 and optimizing the TiO2-shell layer thickness. Also, the PL emission of the TiO2-sheathed SnO2 nanowires is found to be considerably enhanced by thermal annealing and is found to strongly depend on the annealing atmosphere. In particular, the PL emission intensity of the SnO2/TiO2 coaxial nanowires has been significantly increased by annealing in a reducing atmosp