Aluminum nanostructures
support tunable surface plasmon resonances and have become an alternative
to gold nanoparticles. Whereas gold is the most-studied plasmonic
material, aluminum has the advantage of high earth abundance and hence
low cost. In addition to understanding the size and shape tunability
of the plasmon resonance, the fundamental relaxation processes in
aluminum nanostructures after photoexcitation must be understood to
take full advantage of applications such as photocatalysis and photodetection.
In this work, we investigate the relaxation following ultrafast pulsed
excitation and the launching of acoustic vibrations in individual
aluminum nanodisks, using single-particle transient extinction spectroscopy.
We find that the transient extinction signal can be assigned to a
thermal relaxation of the photoexcited electrons and phonons. The
ultrafast heating-induced launching of in-plane acoustic vibrations
reveals moderate binding to the glass substrate and is affected by
the native aluminum oxide layer. Finally, we compare the behavior
of aluminum nanodisks to that of similarly prepared and sized gold
nanodisks