Cap‐Like Ellipsoid Deposition on the ZnO Nanowires for Large Increase of Fluorescence Induced by Localized Field Enhancement Effect

Abstract

The cap-like ZnO ellipsoids are deposited on the top of the ZnO nanowire (NW) arrays to synthesize ZnO-based ellipsoid/NW nanostructures. By controlling the deposition time, the aspect ratio of ZnO ellipsoids from 100/70 to 270/120 is improved. The effect of the ellipsoid deposition time on the fluorescence properties is systematically investigated and successfully enhanced. Photoluminescence (PL) emission for 5 min ZnO ellipsoid/NW nanostructures is enhanced by an enhancement factor of around 3.2 compared with the as-grown ZnO NW arrays. Moreover, using the finite element method simulation, the most vigorous electric field intensity appears on the top of nanostructures owing to the localized field enhancement effect of ZnO ellipsoids, which can effectively prolong the photons remaining in the ZnO ellipsoid/NW nanostructures, enable electrons to exchange energy with photons and then generate more electron-hole pairs, resulting in PL emission enhancement. In addition, the maximum area integration for electric field values higher than 3 × 10 8 V m −1 can also be obtained corresponding to the most vigorous PL emission. This shows great potential applications as fluorescence materials in photoelectric devices.