Structural and optical properties of SiO2-sheathed MgO nanowires

초록

It is essential to passivate of 1D nanostructures with insulating materials to avoid crosstalking between the building blocks of complex nanoscale circuits as well as to protect them from contamination and oxidation. Passivation also offers many advantages such as substantial reduction of surface densities, prevention of the surface from adsorption of unwanted species, prevention of unnecessary charge injection, and partial screening of the external fields. In particular, passivation of nanowires is required in fabrication of field effect transistors and sensor devices based on nanowires. Various techniques have been reported to be used to form passivation layers on the 1D nanowire cores. We have fabricated MgO-core/SiO2-shell one-dimensional nanostructures by coating the MgO nanowires with SiO2. MgO nanowires were synthesized by thermal evaporation of Mg3N2 powders and then coated with SiO2 by using a sputtering technique. 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 MgO-core/ SiO2-shell coaxial nanowires. TEM and XRD analyses revealed that the MgO cores and the SiO2 shells had crystalline face-centered cubic (fcc) and amorphous structures, respectively. The interplanar spacings corresponding to the {111} planes of the MgO core and the {112} planes of the SiO2 shell are 0.243 and 0.331 nm, respectively. PL measurement at room temperature shows that the photoluminescence (PL) emission intensity of MgO nanowires can be increased by coating them with an SiO2 layer with an appropriate thickness. The PL emission of MgO/SiO2 coaxial nanorods is centered at around 610 nm in the orange region whereas that of MgO nanorods is centered at around 590 nm in the yellow region. The PL properties of the MgO-core/SiO2-shell nanowires are found to strongly depend on the annealing atmosphere. The PL emission