Substrate-active layer composite nano photonics structure alkali metal compound photocathode

Abstract

The invention discloses a substrate-active layer composite nano photonics structure alkali metal compound photocathode. The photoelectric cathode sequentially comprises a substrate, a nano array and an alkali metal compound active layer from bottom to top, the optical resonance effect generated by the action of the nano array and incident light is utilized, the light reflectivity can be reduced, and the photoelectron generation and transportation efficiency is improved, so that the performance of the photoelectric cathode is effectively improved. According to the composite nano photonics structure alkali metal compound photocathode, the active layer is directly deposited and prepared on the upper surface of a nano array so as to avoid etching of a photoelectric emission surface; the nano array is prepared by directly etching the substrate by adopting mature processes such as nano imprinting or self-assembly nanospheres, the preparation process is simple, the stability is good, and thenano array can be applied to the fields of weak signal detection and imaging, biomedical treatment, accelerator electron sources, advanced light sources and the like.

Description

technical field [0001] The invention relates to the technical field of vacuum photoelectric emission and application, in particular to a substrate-active layer composite nanophotonic structure alkali metal compound photocathode. Background technique [0002] The working wavelength of the positron affinity (Positive Electron Affinity, PEA) alkali metal compound photocathode covers the ultraviolet to near-infrared light region, the quantum efficiency (Quantum efficiency, QE) is high, and the working life is long when the continuous output of strong beam current, The response speed can reach the picosecond level, and it has important application value in the technical fields of electron accelerators, advanced light sources, space detection technology, high-resolution night vision imaging, low-energy field emission electron microscopy, and electron beam lithography. Recently, with the development of science and technology, the requirements for the quality of the cathode are cons...

AI Technical Summary

Problems solved by technology

[0003] Although widely concerned, the performance of the alkali metal compound PEA photocathode still cannot meet the current application requirements, especially high-sensitivity low-light detection and high-brightness output, high QE and long-term operation that are urgently needed for advanced light sources that operate stably for a long time. Lifespan, improving QE can not only obtain high-current electron beams, but also reduce the light intensity required for a specific current intensity, thereby avoiding laser damage, reducing laser costs and reducing the adverse effects of photo-thermal conversion on lifespan

According to Spicer's three-step emission model, the valence band electrons of the PEA photocathode absorb photons and are excited to the conduction band high-energy state, and then diffuse and transport to the surface and escape from the material. The conduction band electrons must have an energy greater than the surface effective electron affinity. To achieve escape, that is, electrons need to be maintained in a high-energy state during the diffusion process, but the high-energy state electrons can easily return to the bottom of the conduction band through thermal relaxation, which leads to the effective transport distance of photoelectrons in the active region of the PEA cathode is much smaller than that of negative electrophiles. Negative Electron Affinity (NEA) cathode, so the effective thickness of the low active layer and high light reflectivity severely limit light absorption, which becomes the main factor affecting the QE of PEA cathode

However, there is no report on the application of the MSR effect of the nanophotonics structure in the photocathode of the alkali metal compound PEA.

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