Electric excitation of plasmonic guided modes in integrated circuits is important for the development of compact optical signal processing components as well integrated bio- and chemical sensing applications. Surface plasmons in purely metallic nanostructures are typically excited by external illumination or high-energy (keV) electron beams. Low-energy inelastic electron tunnelling is an alternative way to excite surface plasmons in ambient environment with the advantages of high compactness and background free operation, and has been widely investigated using metal-insulator-metal structures and in scanning tunnelling microscopy. Recently, it has been demonstrated that optical antennas or molecules can be used to strongly enhance the electron-photon conversion efficiency and/or control the related light emission on chip scale, opening up opportunities for the practical application of tunnelling-electron-driven plasmonic devices and components. At the same time, the tunnelling behavior is extremely sensitive to the immediate property change of a medium placed in the tunnel path, which holds great opportunities for the development of tunnelling-based devices for the dynamical control of plasmons or the detections of environmental changes with high sensitivity. Here we will discuss hot-electron excitation in electrically-driven plasmonic nanorod metamaterials and their applications for light emission and gas sensing, including hydrogen and oxygen gases. Electrically-driven plasmonic nanorod metamaterials comprise a fertile platform merging photonics, electronics and chemistry, opening up opportunities for developing electron tunnelling-based nanoscale devices for light generation and modulators and chemical sensing.
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