Abstract
Abstract The evolution of non-equilibrium carriers excited in the process of decay of surface plasmon polaritons (SPPs) in metal is described for each step – from the generation of carriers to their extraction from the metal. The relative importance of various carrier-generating mechanisms is discussed. It is shown that both the generation of carriers and their decay are inherently quantum processes as, for realistic illumination conditions, no more than a single SPP per nanoparticle exists at a given time. As a result, the distribution of non-equilibrium carriers cannot be described by a single temperature. It is also shown that the originally excited carriers that have not undergone a single electron-electron scattering event are practically the only ones that contribute to the injection. The role of momentum conservation in carrier extraction is discussed, and it is shown that, if all the momentum conservation rules are relaxed, it is the density of states in the semiconductor/dielectric that determines the ultimate injection efficiency. A set of recommendations aimed at improving the efficiency of plasmonic-assisted photodetection and (to a lesser degree) photocatalysis is made in the end.
Highlights
The last two decades have seen a vigorous growth of exploration in plasmonics [1,2,3] and, in a broader sense, in the interaction between light and free carriers in metal or other media
The evolution of non-equilibrium carriers excited in the process of decay of surface plasmon polaritons (SPPs) in metal is described for each step – from the generation of carriers to their extraction from the metal
A set of recommendations aimed at improving the efficiency of plasmonic-assisted photodetection and photocatalysis is made in the end
Summary
The last two decades have seen a vigorous growth of exploration in plasmonics [1,2,3] and, in a broader sense, in the interaction between light and free carriers in metal or other media (such as doped semiconductors). Capturing energy at the first stage, when it has just been transferred from the plasmon polaritons to the electron-hole pairs and before it has moved down the line to the lattice phonons, is obviously significantly more difficult because it has to be done on the sub-picosecond scale, but is potentially far more rewarding as the kinetic energies (relative to the Fermi energy) of these so-called “hot carriers” are commensurate with the photon energy, i.e. they correspond to tens of thousands of degrees of Kelvin, rather beyond the melting point of the metals For this reason, the hot carriers have sufficient energy to do what for the carriers in equilibrium with the lattice is impossible, even if the lattice is heated almost to the point of melting.
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