Structural characterization of ZnO/ Er2O3 core/shell nanowires

Zinc oxide/erbium oxide core/shell nanowires are of great potential value to optoelectronics because of the possible demonstration of laser emission in the 1.5 μm range. In this paper we present a convenient technique to obtain structures of this composition. ZnO core nanowires were first obtained by a vapor-liquid-solid (VLS) method using gold as a catalyst. ZnO nanowires ranging from 50 to 100 nm in width were grown on the substrates. Erbium was incorporated into these nanowires by their exposure to Er(tmhd)3 at elevated temperatures. After annealing at 700 ∘C in air, the nanowires presented 1.54 μm emission when excited by any of the lines of an Ar+ laser. An investigation of nanowire structure by HRTEM indicates that indeed the cores consist of hexagonal ZnO grown in the 001 direction while the surface contains randomly oriented Er2O3 nanoparticles. EXAFS analysis reveals that the Er atoms possess a sixfold oxygen coordination environment, almost identical to that of Er2O3. Taken collectively, these data suggest that the overall architectures of these nanowires are discrete layered ZnO/ Er2O3 core/shell structures whereby erbium atoms are not incorporated into the ZnO core geometry.