2 research outputs found
Chemical Interface Damping Depends on Electrons Reaching the Surface
Metallic
nanoparticles show extraordinary strong light absorption
near their plasmon resonance, orders of magnitude larger compared
to nonmetallic nanoparticles. This âantennaâ effect
has recently been exploited to transfer electrons into empty states
of an attached material, for example to create electric currents in
photovoltaic devices or to induce chemical reactions. It is generally
assumed that plasmons decay into hot electrons, which then transfer
to the attached material. Ultrafast electronâelectron scattering
reduces the lifetime of hot electrons drastically in metals and therefore
strongly limits the efficiency of plasmon induced hot electron transfer.
However, recent work has revived the concept of plasmons decaying
directly into an interfacial charge transfer state, thus avoiding
the intermediate creation of hot electrons. This direct decay mechanism
has mostly been neglected, and has been termed chemical interface
damping (CID). CID manifests itself as an additional damping contribution
to the homogeneous plasmon line width. In this study, we investigate
the size dependence of CID by following the plasmon line width of
gold nanorods during the adsorption process of thiols on the gold
surface with single particle spectroscopy. We show that CID scales
inversely with the effective path length of electrons, i.e., the average
distance of electrons to the surface. Moreover, we compare the contribution
of CID to other competing plasmon decay channels and predict that
CID becomes the dominating plasmon energy decay mechanism for very
small gold nanorods
Momentum Distribution of Electrons Emitted from Resonantly Excited Individual Gold Nanorods
Electron emission
by femtosecond laser pulses from individual Au
nanorods is studied with a time-of-flight momentum resolving photoemission
electron microscope (ToF k-PEEM). The Au nanorods adhere to a transparent
indiumâtin oxide substrate, allowing for illumination from
the rear side at normal incidence. Localized plasmon polaritons are
resonantly excited at 800 nm with 100 fs long pulses. The momentum
distribution of emitted electrons reveals two distinct emission mechanisms:
a coherent multiphoton photoemission process from the optically heated
electron gas leads to an isotropic emission distribution. In contrast,
an additional emission process resulting from the optical field enhancement
at both ends of the nanorod leads to a strongly directional emission
parallel to the nanorodâs long axis. The relative intensity
of both contributions can be controlled by the peak intensity of the
incident light