Homogeneous core/shell ZnO/ZnMgO quantum well heterostructures on vertical ZnOnanowires

Abstract

Low-area density ZnO nanowire arrays, growing perpendicularly to the substrate, aresynthesized with high-pressure pulsed laser deposition. The introduction of a ZnO bufferlayer enables us to fabricate individual nanowires several micrometres apart (areadensity<0.1 nanowire µm−2), suppressing any shadowing effect by neighbouring nanowiresduring subsequent growth. These low density ZnO nanowires, whosec-axis is perpendicular to the substrate surface, are then used as templates to growZnO/ZnMgO core–shell nanowire heterostructures with conventional low-pressure pulsedlaser deposition. Cathodoluminescence spectroscopy as well as transmission electronmicroscopy show that a sharp interface forms between the ZnO core and the ZnMgO shell.Based on these findings, we have grown a series of radial ZnO/ZnMgO quantum wells withdifferent thicknesses that exhibit quantum confinement effects, with thicker quantum wellsemitting at lower energies. Spatially resolved cathodoluminescence confirms thehomogeneity of the quantum well structure along the full nanowire length of about3 µm.