Probing the electrical switching of a memristive optical antenna by STEM EELS

Abstract

The scaling of active photonic devices to deep-submicron length scales has been hampered by the fundamental diffraction limit and the absence of materials with sufficiently strong electro-optic effects. Plasmonics is providing new opportunities to circumvent this challenge. Here we provide evidence for a solid-state electro-optical switching mechanism that can operate in the visible spectral range with an active volume of less than (5 nm)3 or ∼10−6 λ3, comparable to the size of the smallest electronic components. The switching mechanism relies on electrochemically displacing metal atoms inside the nanometre-scale gap to electrically connect two crossed metallic wires forming a cross-point junction. These junctions afford extreme light concentration and display singular optical behaviour upon formation of a conductive channel. The active tuning of plasmonic antennas attached to such junctions is analysed using a combination of electrical and optical measurements as well as electron energy loss spectroscopy in a scanning transmission electron microscope.

Optical memristive switches

“…The atomic scale plasmonic switch presented in [7] explores the ultimate limits of atomic scale resistance switching since the quantum conductance of a single silver filament is used to switch light on or off. A similar resistance switching has also been found in memristive plasmonic antennas where resonances are shifted by single atoms [74][75][76][77].…”

Millivolt Modulation of Plasmonic Metasurface Optical Response via Ionic Conductance

“…Silver filament formation in thin amorphous silicon layer or gold filament formation in thin silica layer has been used to modulate transmittance of light through plasmonic waveguides upon application of a bias voltage. Active tuning of optical response of a plasmonic antenna attached to Ag/Al 2 O 3 /Au memristive junction has also been experimentally demonstrated . Active optical response of the antenna was attributed via indirect evidence to silver filament formation in a thin Al 2 O 3 layer.…”

“…Similarly, our results suggest that the ITO electrode is essential for observation of optical modulation under millivolt bias. By contrast, an applied bias voltage on the order of volts was required to enable optical modulation in Ag/Al 2 O 3 /Au crossbar antenna devices—which do not contain ITO—even though the Al 2 O 3 layer was only 5 nm thick. For Pt/TiO 2 /Pt structures, it is known that resistive switching occurs due to movement of oxygen vacancies.…”

On‐Demand Reconfiguration of Nanomaterials: When Electronics Meets Ionics

“…Additionally, a blue‐shift of the plasmonic resonance was observed in the LRS (Figure e) as a result of the reduction of the local field due to the presence of the filament, further confirming that the distinct plasmonic resonance states are a result of the atomic reconfiguration that accompanies electrical switching effects. Additionally, electro‐optical switching in the visible spectra range with a very small active volume of (5 nm) 3 , comparable to the sizes of modern electronic devices and much smaller than common optical devices, was demonstrated based on atomic reconfiguration in an Au/Al 2 O 3 /Ag device, as shown in Figure f,g, confirming the potential of nanoscale‐integrated photonic circuits through material reconfiguration based on ionic effects …”

“…Noticeable changes in the resonant scattering responses are observed in both unpolarized and transverse magnetic (TM)‐polarized spectra. Reproduced with permission . Copyright 2016, Nature Publishing Group.…”