Ultrafast Electron Dynamics in Single Aluminum Nanostructures

Abstract

Aluminum nanostructures are a promising alternative material to noble metal nanostructures for several photonic and catalytic applications, but their ultrafast electron dynamics remain elusive. Here, we combine singleparticle transient extinction spectroscopy and parameter-free first-principles calculations to investigate the non-equilibrium carrier dynamics in aluminum nanostructures. Unlike gold nanostructures, we find the sub-picosecond optical response of lithographically fabricated aluminum nanodisks to be more sensitive to the lattice temperature than the electron temperature. We assign the rise in the transient transmission to electron−phonon coupling with a pump-power-independent lifetime of 500 ± 100 fs and theoretically confirm this strong electron−phonon coupling behavior. We also measure electron−phonon lifetimes in chemically synthesized aluminum nanocrystals and find them to be even longer (1.0 ± 0.1 ps) than for the nanodisks. We also observe a rise and decay in the transient transmissions with amplitudes that scale with the surface-to-volume ratio of the aluminum nanodisks, implying a possible hot carrier trapping and detrapping at the native oxide shell−metal core interface.

Fast Surface Restructuring within the Gap of Au Nanocube Dimer for the Enhancement of Catalytic Efficiency

“…It has been reported that hot electrons are prone to self-thermalization after being generated, followed by a further relaxation via electron-phonon scattering. 5,6,31,[45][46][47] In this process, the hot electrons can transfer the energy to the atoms on the metal surface, causing the boosted lattice vibrations. 45,48 Moreover, since the induced lattice vibrations are believed to depend on the density of hot carriers, [49][50][51][52] it is reasonable to ascribe the faster spontaneous surface restructuring to the lattice vibrations enhanced by hot Page 15 of 29 CCS Chemistry carriers within the nanogap.…”

Emergent Opportunities with Metallic Alloys: From Material Design to Optical Devices

“…[ 90 ] It has also been shown that sample geometry and the material's band structure affect the relaxation time of the hot electrons. [ 91 ] These results suggest that the complex interplay between the atoms and the electrons in alloyed metals presents an additional route for tuning of hot carrier dynamics. As an example, we recently showed that the addition of 2% Ag into Au can increase carrier lifetime by ≈35%.…”

Sub‐3 nm Aluminum Nanocrystals Exhibiting Cluster‐Like Optical Properties

“…Previous studies raised an interesting question that whether further shrinking the size of aluminum nanocrystals will lead to properties seen in noble metals nanoclusters. [ 10 ] Since ultrasmall aluminum nanoclusters (AlNCs) in this size range (e.g., <3 nm) have been rarely studied experimentally so far, two issues need to be addressed: preparation and stability. First, metal nanoclusters are usually prepared with solution based synthetic approaches, which was hardly ever explored for AlNCs.…”

“…We accounted it to the radiative recombination from the surface states. [ 21 ] The fact that τ at shorter wavelength had nearly no contribution to the overall measured lifetime suggested much faster electron dynamics at the core, which could be a reflection of ultrafast processes seen in aluminum nanostructures in general [ 10 ] (Figure 3).…”