Structure, Raman, and photoluminescence properties of SnO2/MgO core-shell nanowires

Abstract

We prepared MgO-coated SnO2 nanowires, by means of fabricating SnO2 core nanowires and subsequently evaporating an MgB2 powder onto the core nanowires. We investigated changes in the morphological, structural, Raman, and photoluminescence (PL) characteristics resulting from application of the coating process and of a thermal annealing process. The surface of the nanowires became roughened by the MgO coating. While the core nanowires corresponded to the tetragonal ruffle SnO2 structure, the shell was comprised of the cubic MgO phase. Raman spectra revealed that the core-shell nanowires exhibited a weak line for MgO-associated with surface phonon modes in a TO-LO phonon gap, in addition to the SnO2-related lines. The room-temperature PL spectrum of core SnO2 nanowires exhibited a 2.1 eV-centered broad band and the peak position was invariant not also by the shell coating but also by the subsequent thermal annealing. The PL intensity was increasd by the MgO coating, being attributed to a diffusion effect. The PL reduction by the subsequent thermal annealing is ascribed to oxygen incorporation into the SnO2 core nanowires.