Large Area Nanostructured Arrays: Optical Properties
of Metallic Nanotubes
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Abstract
In
this study, large area metallic nanotube arrays on flexible plastic
substrates are produced by templating the growth of a cosputtered
alloy using anodized aluminum oxide membranes. These nanotube arrays
are prepared over large areas (ca. squared centimeters) by reducing
the residual stress within the thin multilayered structure. The nanotubes
are approximately 20 nm in inner diameter, having walls of <10
nm in thickness, and are arranged in a close packed configuration.
Optically the nanotube arrays exhibit light trapping behavior (not
plasmonic), where the reflectivity is less than 15% across the visible
spectra compared to >40% for a flat sample using the same alloy.
When the nanotubes are exposed to high relative humidity, they spontaneously
fill, with a concomitant change in their visual appearance. The filling
of the nanotubes is confirmed using contact angle measurements, with
the nanotubes displaying a strong hydrophilic character compared to
the weak behavior of the flat sample. The ability to easily fabricate
large area nanotube arrays which display exotic behavior paves the
way for their uptake in real world applications such as sensors and
solar energy devices