Nanoscale Mapping of Plasmonic Charge Transport in Nano‐Resonators Based on Resistive Switching Materials

ABSTRACT Metamaterials‐based nano‐resonators have been extensively studied due to their precise controllability for tuning electromagnetic waves, while it is difficult to map the effects of resonating‐light on electrical‐transport. Here, conductivities and the effects of charge‐traps with nanoscale resolutions are mapped in Ge 2 Sb 2 Te 5 (GST)‐based nano‐resonator under resonant excitations. In this strategy, a high electric‐field out of surface‐plane is applied through a conducting nano‐probe, and the probe scans to induce a phase‐transition. Results implicate an insulating‐to‐conducting‐phase transition induced by electric‐field, due to the formation of filament‐like conducting‐paths. Utilizing contrasting electrical and optical properties of conducting‐ and insulating‐phases, nano‐resonators are fabricated on the surface of GST. Then, plasmonic‐conductivities and the effects of charge‐trap in nano‐resonators are mapped. Nano‐resonators with linear‐gratings show plasmonic photocurrent upon illumination at selective‐wavelengths depending on grating‐elements. Contrarily, square‐shaped nano‐resonators effectively produce plasmonic effects on a broad wavelength range due to the large number of available modes, as evident from plasmonic‐wave simulations. Importantly, plasmonic effects prohibit the re‐trapping of carriers, resulting in dramatically low trap densities. Moreover, simulation shows that plasmonic effects are pronounced at short‐wavelengths, providing high plasmonic‐conductivities and low charge‐trap densities. The mapping of plasmonic‐transport properties can have significant impacts on basic research and applications of phase‐change material‐based‐plasmonic devices.