Wet Chemical Approaches to Patterned Arrays of Well-Aligned ZnO Nanopillars Assisted by Monolayer Colloidal Crystals

Abstract

Hexagonally patterned arrays of well-aligned, regular ZnO nanopillars with controlled size, shape, and orientation were directly fabricated on zinc foils via a facile wet chemical approach with the assistance of monolayer colloidal crystals (MCC). Two kinds of templates that were derived from MCC, i.e., inverted MCC (IMCC) and connected MCC (CMCC), were employed as masks to define the growth sites and spaces on zinc foils for the realization of site-specific patterned growth of ZnO nanopillars. Individually patterned arrays of ZnO nanopillars (i.e., one ZnO nanopillar growing at one single growth site) were readily produced. Interestingly, the vertically aligned ZnO nanopillars were also side-oriented, indicating a quasi-epitaxial growth on the zinc substrate. The diameter of the ZnO nanopillars can be controlled in a wide range from 60 to 900 nm by varying the structural parameters of the MCC templates and the growth conditions. Moreover, by decreasing the reaction solution concentration, a bundle of ZnO nanorods rather than an individual nanopillar were selectively grown at one single growth site. The as-grown ZnO nanopillar arrays were well-crystallized and exhibited strong excitonic emission and weak defect-related emission at room temperature, which promises their potential applications in optical devices such as stimulated emitters and lasing cavities.