Oral Presentation 24th Australian Conference on Microscopy and Microanalysis 2016

Localized surface plasmon resonance mapping on aluminium voids with three-dimensional nanostructures (#42)

Ye Zhu 1 , Philip N.H. Nakashima 1 , Alison M. Funston 2 , Laure Bourgeois 1 3 , Joanne Etheridge 1 3
  1. Department of Materials Science and Engineering, Monash University, Clayton, VIC, Australia
  2. School of Chemistry, Monash University, Clayton, VIC, Australia
  3. Monash Centre for Electron Microscopy (MCEM), Monash University, Clayton, VIC, Australia

Today’s nanotechnology has enabled the fabrication of metallic nanoparticles with a variety of geometries, greatly advancing the research field of plasmonics. The complementary system of the inverted nanostructures such as nano-voids, however, has so far been limited to either 2D holes or spherical voids, owing to the challenge to create voids with well-defined 3D geometries. Here we present the first localized surface plasmon resonance (LSPR) study, both experimentally and theoretically, on aluminium nano-voids in the shape of truncated octahedral.

Nano-voids were created in high-purity aluminium using an annealing and quenching process.1 To characterize LSPRs of these fully buried voids, we employed electron energy-loss spectroscopy (EELS) in a scanning transmission electron microscope (STEM) – an aberration-corrected FEI Titan operating at 80 kV. The lower accelerating voltage causes less damage on aluminium, which is essential to achieve reliable EELS mapping on voids. To compare with experimental observations, electrodynamic EELS simulations were performed based on electron-driven discrete dipole approximation (e-DDA).2

Our results show that these aluminium nano-voids exhibit strongly localized field enhancements, with the LSPR energies 10.7 - 13.3 eV (116 - 93 nm), well beyond the conventional LSPR spectrum range. The LSPR tunability can be achieved by tailoring the shape of nano-voids using controlled electron irradiation. Furthermore, owing to the simplicity of the nano-void system which is free of aluminium oxidation and supporting substrates, we demonstrate that the intrinsic LSPR properties of pure Al nanoparticles can be revealed from nano-voids characterization using the sum rule for the complementary systems. Combining with the unique properties of Al, a cheap, abundant, and mass-producible metal, our results indicate that both the Al nanoparticles and nano-voids can effectively extend the available plasmonic spectrum range to the extreme UV region (≤ 124 nm), and are promising for applications such as LSPR-enhanced UV photoemission spectroscopy and photoionization.

  1. Z. Zhang, T. Liu, A. E. Smith, N. V. Medhekar, P. N. H. Nakashima and L. Bourgeois, submitted to Acta Mater. (2015).
  2. N. W. Bigelow, A. Vaschillo, V. Iberi, J. P. Camden and D. J. Masiello, ACS Nano. 6, 7497-7504 (2012).