Morphology-controlled three-dimensional nanoarchitectures produced by exploiting vertical and in-plane crystallographic orientations in hydrothermal ZnO crystals

Herein we describe the morphology-controlled synthesis of three-dimensional (3D) ZnO nanoarchitectures via a facile hydrothermal route. In this approach, vertical and inplane crystallographic orientations of ZnO crystals were tuned by appropriate patterning of growth masks and seed layer control, which enabled the formation of three types of ZnO nanoarchitectures. If polycrystalline ZnO layers with poor c-axis orientation were used as a seed, flower-like ZnO nanoarchitectures composed of radially oriented ZnO nanorods were achieved. In the case of c-axis oriented ZnO seeds, polygonal ZnO pillars grew vertically at the center of the growth holes. Even in the latter case, multidomain columnar - joint structures or single domain crystal structures with well-defined hexagonal facets were achieved based on the existence of six-fold in-plane symmetry of the ZnO seed layers. These morphology-controlled ZnO nanoarchitectures exhibited clear differences in light propagation characteristics, which could be ascribed to strong light guiding in the one-dimensional nanostructures.