纳米光子学结构K2CsSb光电阴极的研究

K2CsSb双碱锑化物光电阴极因其低暗电流、宽工作波段等特征被广泛应用于微光成像和电子加速器领域。然而，量子效率、寿命等性能的提升仍是其当前面临的重要问题。课题组发现亚波长纳米光子学结构的Mie散射光学共振具有优良的光电调控性能，因此提出利用衬底-有源层复合纳米光子学结构提升K2CsSb光电阴极的性能。拟采用热蒸发法将K2CsSb沉积在纳米压印或自组装纳米球法刻蚀制备的SiO2纳米阵列表面以制备所提出的光电阴极，探索并获得共振增强光电发射所需要的高品质纳米光子学结构最佳工艺条件。拟建立物理模型，结合实验研究纳米光子学结构K2CsSb有源层光电子的产生、输运及发射过程物理规律，揭示光学共振调控阴极光电性能并增强量子效率的物理机理，实现共振增强的高量子效率K2CsSb光电阴极。相关研究可为纳米光子学结构在碱金属锑化物阴极中的应用积累经验，促进光电阴极及其应用技术的发展。

K2CsSb bialkali antimonide photocathodes have proven to be highly suitable in areas of high-resolution low light level spectral imaging and electron source for large-scale electron accelerators due to their low dark current, broadband response and low intrinsic emittance characteristics. However, further improvements on photo - electron emission quantum efficiency and operation lifetime are still the key problems of these photocathodes for practical application. The research field of nanophotonics studies the behavior of light at the scale of nanometer, i.e. at a scale comparable to or smaller than the wavelength of light. Recently, the extensively concerned nanomaterials in this field are nanostructured semiconductor and dielectric materials that can show Mie-type scattering resonant interaction with light. By tailoring the optically resonance properties, controlled by the physical dimensions of the nanostructured material, one can greatly enhance light absorption and control the distribution of optical field and photoelectrons in material. In this project, a Mie-type substrate - active layer composite nanophotonic resonator is used to develop the K2CsSb photocathode with high performance. Nanostructured K2CsSb will be fabricated on nano-array structured SiO2 substrates that fabricated by nanoimprinting or self-assembly nano-sphere etching technologies and the photo - electron emission performances will be tested in an ultra-high vacuum activation chamber. The physical model of the investigated photocathode will be established by finite difference time domain and Monte Carlo method, and the influences of nanophotonic properties of the Mie resonance modes and geometrical structures on the generating, transporting and emitting processes of the photoelectrons in active layer will be studied in detail. The effects of the material structure and process parameters on the photo-electron emission performances will be studied in detail to obtain the high-performance photocathode. Through this work, the advanced nanophotonic structured alkali antimonide photocathodes and the related technical reserves will be provided to the electronic accelerator and the low-light-level detecting instruments, and to improve the research and application level of advanced light source, high-resolution night-vision imaging etc.