Abstract
We employ laser interference lithography as a reliable and low-cost
fabrication method to create nanowire and nanosquare arrays in
photopolymers for manufacturing plasmonic perfect absorber sensors over
homogeneous areas as large as 5.7 cm(2). Subsequently, we transfer the
fabricated patterns into a palladium layer by using argon ion beam
etching. Geometry and periodicity of our large-area metallic
nanostructures are precisely controlled by adjusting the interference
conditions during single- and double-exposure processes, resulting in
active nanostructures over large areas with spectrally selective perfect
absorption of light from the visible to the near-infrared wavelength
range. In addition, we demonstrate the method's applicability for
hydrogen detection schemes by measuring the hydrogen sensing performance
of our polarization independent palladium-based perfect absorbers. Since
palladium changes its optical and structural properties reversibly upon
hydrogenation, exposure of the sample to hydrogen causes distinct and
reversible changes within seconds in the absorption of light, which are
easily measured by standard microscopic tools. The fabricated large-area
perfect absorber sensors provide nearly perfect absorption of light at
730 and 950 nm, respectively, and absolute reflectance changes from
below 1\% to above 4\% in the presence of hydrogen. This translates to a
relative signal change of almost 400\%. The large-area and fast
manufacturing process makes our approach highly attractive for simple
and low-cost sensor fabrication, and therefore, suitable for industrial
production of plasmonic devices in the near future.
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