Tunable Broadband Photoresponse Electron‐Emission Nanostructure: Metasurface‐Extended Spectrum‐Selecting and Plasmon‐Enhanced Emitting

Abstract

Exploring novel nanotechnology schemes for tunable broadband vacuum photodetection devices is of great significance. Herein, a strategy to combine a field‐emission cold cathode with plasmonic nanostructures to form a plasmon‐enhanced field‐emission metasurface array is proposed. Mo nanostructures with excellent emission properties act as field‐emission cold cathode materials. Au nanospheres are applied to enhance the photocurrent of Mo nanopyramid emitters and to generate tunable resonance responses by plasmonic couplings. The response frequency and polarization can be selective in a broadband range from visible to near‐infrared, which originates from the periodic couplings of the Mo–Mo microcavities and the Au–Mo interfaces in the designed metasurface emitter arrays. The amplitude of photodetection signals is experimentally demonstrated to be tunable not only by the geometrical dimensions of the Mo nanopyramid and the number of decorated Au plasmons, but also by the applied external electrostatic fields. This plasmon‐enhanced photoresponse field‐emission process is attributed to plasmon‐mediated electron emission. Herein, a route to tunable broadband photoresponse electron‐emission nanostructures at room temperature (≈300 K) and low energy consumption for photocathode and vacuum device applications is provided in the results.

High‐Performance Planar Field‐Emission Photodetector of Monolayer Tungsten Disulfide with Microtips

“…In many studies, the researchers found that the photogenerated electric field can be ignored even if the irradiation power of incident light is as high as several 10 4 W cm −2 because the photoelectric field is far lower than the applied field. [55] The finite-difference time-domain (FDTD) simulation is carried out to further analyze the effect of the photogenerated electric field on the FE process of ML WS 2 with microtips, as seen in Figure S4, Supporting Information. Combined with the FDTD simulation and recent research results, the effect of the photogenerated field on the FE process of ML WS 2 with microtips can be ignored in our measurements.…”

Promoting 2D Material Photodetectors by Optical Antennas beyond Noble Metals

“…Beyond the typical precious metals, such as Au, [115][116][117] Ag, [118] Pt, [119] Ir, [120] and Pd, [121] there also exist several non-precious metals manifesting pronounced plasmonic effects, including Al, [122,123] Cu, [124][125][126] In, [127] Mo, [128] Sn, [129] Mg, [130] Sb, [131] Cu-Ni alloy, [132] Ga-In alloy, [133] etc. With the advantage of much lower cost, these materials have provided promising alternatives for the optical engineering research of next-generation optoelectronic devices.…”

A tunable photo-electric co-excited point electron source: low-intensity excitation emission and structure-modulated spectrum-selection

“…Second, electrons pumped into the vacuum may be confined to a nano or even atomic scale by the nano-cold-cathode materials employed. Third, the electron emission yield and quantum efficiency are believed to be significantly improved, with the assistance of applied electrostatic field 30,31 and plasmon-enhanced nearfield 32,33 that may exist, and simultaneously the driving power consumption for the cathode and device are greatly reduced. These advantages are particularly important for point electron sources, where the performance demand of electron beam from an individual emitter is extremely high, such as low energy spread, high brightness and low energy consumption.…”