Photovoltages and hot electrons in plasmonic nanogaps

Abstract

In metal nanostructures under illumination, multiple different processes can drive current flow, and in an opencircuit configuration some of these processes lead to the production of open-circuit photovoltages. Structures that have plasmonic resonances at the illumination wavelength can have enhanced photovoltage response, due to both increased interactions with the incident radiation field, and processes made possible through the dynamics of the plasmon excitations themselves. Here we review photovoltage response driven by thermoelectric effects in continuous metal nanowires and photovoltage response driven by hot electron production and tunneling. We discuss the prospects for enhancing and quantifying hot electron generation and response via the combination of local plasmonic resonances and propagating surface plasmon polaritons.

Remote Excitation of Hot Electrons via Propagating Surface Plasmons

“…These are consistent with the generation of hot electron photocurrents. , In an open-circuit configuration in steady state, a direct-current (DC) potential difference will develop between the two sides of the junction such that ordinary tunneling current will counterbalance any net hot electron current. The open-circuit configuration provides several advantages to distinguishing between the generation of hot carriers and other competing effects (e.g., thermal expansion resulting in changes in the interelectrode conductance; thermoelectric currents). , While the pulsed regime has provided insight in some experiments, in prior OCPV measurements it was not possible to distinguish between hot carriers produced by plasmonic decay processes and those produced by direct optical absorption. We note that the production of hot carriers near some tunneling gap is not sufficient to produce hot electron currents.…”