3 research outputs found
Optical Resonances in Short-Range Ordered Nanoholes in Ultrathin Aluminum/Aluminum Nitride Multilayers
Nanoholes with short-range ordering
were fabricated in ultrathin
aluminum/aluminum nitride multilayer films where each layer is as
thin as a few nanometers. Optical resonances of the trilayer system
with a single metallic layer and five-layer system with two metallic
layers were successfully tuned in the visible–near-infrared
(vis/NIR) range. The resonance wavelength as well as the width can
be predicted and designed by solving the dispersion relation and comparing
with the lateral dimension of the short-range ordering. To solve the
dispersion relation, we developed a general formulation for multilayer
systems. The thermal stability of the fabricated nanoholes in ultrathin
multilayers was also tested by vacuum annealing the samples up to
400 °C. While no structural change of the nanohole or the multilayer
surface has been observed, the optical property showed almost no change
in the resonance confirming no structural change but emergence of
the interband transition around the wavelength of 900 nm. It means
crystallinity improvement without grain growth by thermal annealing,
which is consistent with the previous crystallographic studies on
the same multilayer systems. The fabricated sensor revealed comparable
refractive index sensitivity to the gold based sensors even with the
top protective AlN layer. The chemical sensing test using the nanohole
sensor with a bare aluminum top surface confirmed the applicability
to the monitoring of aluminum surface reactions