Zinc oxide nanocolumns grown on self-assembled silica nanosphere monolayer templates

Abstract

This paper presents a concept of a two-step growth process that first lays down a nano template by self-assembly to define the spatial distribution of the nanostructures, followed by a highly directional physical vapor deposition method to selectively grow material in a columnar configuration. Langmuir–Blodgett technique was used to construct self-assembled monolayers of silica nanospheres (SNSs) with five different radii, 1.9 μm, 590 nm, 425 nm, 250 nm, and 125 nm. Z-axis oriented ZnO crystalline nanostructures grown on top of the spheres by the Glancing Angle PLD formed columnar arrays that were observed to form a hcp structure. Columnar aspect ratios as well as the density per unit area were found to be dependent on underlying sphere size. In addition to the experimental demonstration of the technique, a nucleation model is presented to understand the mechanism of growth in this novel approach.