Effects of passivation and postannealing on the photoluminescence properties of MgO/SiO 2 core‐shell nanorods

MgO nanorods were grown by the thermal evaporation of Mg 3 N 2 powders on the Si (100) substrate coated with a gold thin film. The MgO nanorods grown on the Si (100) substrate were a few tens of nanometers in diameter and up to a few hundreds of micrometers in length. MgO/SiO 2 core‐shell nanorods were also fabricated by the sputter‐deposition of SiO 2 onto the MgO nanorods. Transmission electron microscopy (TEM) and X–ray diffraction (XRD) analysis results indicated that the cores and shells of the annealed core‐shell nanorods were a face‐centered cubic‐type single crystal MgO and amorphous SiO 2 , respectively. The photoluminescence (PL) spectroscopy analysis results showed that SiO 2 coating slightly decreased the PL emission intensity of the MgO nanorods. The PL emission of the MgO/SiO 2 core‐shell nanorods was, however, found to be considerably enhanced by thermal annealing and strongly depends on the annealing atmosphere. The PL emission of the MgO/SiO 2 core‐shell nanorods was substantially enhanced in intensity by annealing in a reducing atmosphere, whereas it was slightly enhanced by annealing in an oxidative atmosphere. The origin of the PL enhancement by annealing in a reducing atmosphere is discussed with the aid of energy‐dispersive X‐ray spectroscopy analyses. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)