Hot-electron nanoscopy using adiabatic compression of surface plasmons

Abstract

Surface plasmon polaritons are a central concept in nanoplasmonics and have been exploited to develop ultrasensitive chemical detection platforms, as well as imaging and spectroscopic techniques at the nanoscale. Surface plasmons can decay to form highly energetic (or hot) electrons in a process that is usually thought to be parasitic for applications, because it limits the lifetime and propagation length of surface plasmons and therefore has an adverse influence on the functionality of nanoplasmonic devices. Recently, however, it has been shown that hot electrons produced by surface plasmon decay can be harnessed to produce useful work in photodetection, catalysis and solar energy conversion. Nevertheless, the surface-plasmon-to-hot-electron conversion efficiency has been below 1% in all cases. Here we show that adiabatic focusing of surface plasmons on a Schottky diode-terminated tapered tip of nanoscale dimensions allows for a plasmon-to-hot-electron conversion efficiency of ∼30%. We further demonstrate that, with such high efficiency, hot electrons can be used for a new nanoscopy technique based on an atomic force microscopy set-up. We show that this hot-electron nanoscopy preserves the chemical sensitivity of the scanned surface and has a spatial resolution below 50 nm, with margins for improvement.

The rectenna device: From theory to practice (a review)

“…The reported 94 quantum efficiency of this structure is estimated at being just 0.01%, though improvements are suggested to reach efficiencies of 2%. Recent publication suggests 30% efficiency of converting "hot electrons" in the metal to electrons in the semiconductor 164 , though full conversion efficiency has not been estimated. In this case, although the device is based on an antenna coupled to a rectifier (similar components to a rectenna), the device is not proposed for light harvesting purposes due to its low efficiency and is instead demonstrated as a photodetector.…”

Hot‐Electron‐Mediated Photochemical Reactions: Principles, Recent Advances, and Challenges

“…[43] It is well known that a tapered structure is an efficient wave guide that directs and confines SPPs to the tip, generating a strongly localized EM field (Figure 5h). Due to the near-field localization effect, the SPP to hot electron conversion efficiency in this device was above 30%, suggesting the critical role of SPP and EM field confinement in hot electron utilization.…”

Harvesting the loss: surface plasmon-based hot electron photodetection

“…Metal layers are deposited on top of the silicon pyramids so that the Schottky interface is only formed at the apex region of the pyramids, ensuring a small dark current. More importantly, nanoscale confinement of plasmons at the apex of the tip plays a role in efficiency enhancement by relaxing momentum mismatch [71,95]. Operating at 0.1 V reverse bias, a responsivity of 5 and 12 mA/W at 1550 and 1300 nm, respectively, has been demonstrated.…”

“…As such, more work is needed in the design of plasmonic nanostructures that support the generation of hot electrons with a momentum distribution that matches well with the band structure of the semiconductor. For instance, the recent investigation that uses plasmonic tips to adiabatically compress the SPPs, producing hot electrons with momentum perpendicular to the interface, demonstrated a greatly enhanced efficiency [95]. Hot electron transfer efficiencies can further be boosted by embedding the plasmonic nanostructures within the semiconductor, providing more momentum space for hot electron emission [86] (Figure 7A).…”