Tailoring the surface plasmon resonance energy of Au nanowire arrays by defect management and thermal treatment

We present a novel route to tune and adapt the energy of surface plasmon resonances (SPR) of 3-dimensional (3D) Au nanowire arrays. Based on an annealing and defect management of anodic aluminum oxide (AAO) we demonstrate a tuning of the longitudinal resonance mode (L mode) of plasmons towards higher energies. Here we present an experimental fabrication as well as a modeling of optical absorption spectra. As a result, the combination of tunable optical properties of AAO and controllable nanowire structures has been realized. The L mode energy is found to shift with a modification of the average dielectric constant of the host porous alumina by an annealing process. We find that in a 3D Au nanowire array system, a plasmon interaction between neighboring wires exists. It proves a complex nonlinear relationship between SPR energy, wire aspect ratio and surrounding medium of the dielectric constant. In our modeling we consider the quasistatic limit of electromagnetic fields in a nanowire array and the respective angle of the incident electromagnetic field.