Developing Cu pore-filling percentage in hard anodized anodic aluminum oxide templates with large diameters

Abstract

This study aims to overcome a major challenge that is reaching high pore-filling percentage (FP) in the fabrication
of high aspect ratio (HAR) nanowires (NWs) grown electrochemically in large diameter porous templates. By
ultrathinning the barrier layer of hard anodized anodic aluminum oxide (AAO) templates with large pore diameters
(Dp) of 110 and 180 nm, while also filling its branched sections with FeCoNi, the development of Cu FP was
investigated for different Cu solution concentration (MCu = 0.05–0.3 M) in the fabrication of HAR Cu NW arrays
using a pulsed electrochemical deposition technique under optimized parameters. At Dp = 180 nm, field-emission
scanning electron microscopic investigations revealed that, increasing MCu increases the corresponding FP
up to 62%, resulting in highly uniform NW arrays. Structural properties were investigated by X-ray diffraction
analysis, indicating that different phase percentages of Cu and Cu2O are formed depending on Dp of AAO and
MCu. The resulting HAR Cu NWs were also released from the hard templates to obtain free-standing NW arrays
with a length of 70 μm, which may find potential use for large-scale nanodevice applications.