Exploring Hot Electron Behavior in the Steady State*

Plasmonic nanostructures could provide new pathways for photocatalysis. Upon illumination, non-thermal carriers are generated, which later thermalize to generate “hot” carriers. These carriers relax to elevate the lattice temperature of the metal. Hot electrons are often envisioned to be used under steady state (SS) conditions which may impart distinct electronic behavior compared to under pulsed conditions which are used in hot electron ultra-fast studies.

To quantify hot electron dynamics under SS conditions, our lab has developed a continuous wave Raman spectroscopy method that probes non-equilibrium electron behavior under SS optical excitation conditions using two Fermi-Dirac distributions with distinct temperatures: the hot electron temperature and the lattice temperature.

In this talk, I will discuss our studies of interband versus intraband excitation of a gold nanostructures. Although interband (532 nm) and intraband excitation (658 nm) have different carrier excitation mechanisms, theoretically there is no expected difference in carrier populations after carriers have thermalized. Our studies, however, show clear differences in hot electron temperature and population size in the SS. We observe increases of hot electron lifetime up to 217% for intra- versus interband excitation and increases of hot electron temperature up to 145%. We discuss possible interpretations for this observation, which exemplifies the importance of probing hot electrons in the steady state.