氮化钛基新型光阴极研究

Photocathodes are a critical performance-limiting component of ultra-fast electron microscopes, energy recovery linacs, free-electron lasers and other 4th generation light sources. The photoemission properties of photocathode are important for performances of these systems. Focusing on new-type photocathode, this project will explore the applications of conductive TiN ceramic, which has great thermodynamic stability and surface plasmon polariton performance. Researches will be done on the synthesis, thermal emittance, quantum efficiency and stability of TiN film based photocathode. Ultra-smooth surface of TiN film will be used to reduce the thermal emittance. Surface plasmon resonance will be introduced by nano-structrues designed and fabricated on TiN film to enhance the photoemission and quantum efficiency. The physical mechanism will be studied on surface plasmon polariton enhanced multi-photon process in photoemission. Nano-structures on surface of TiN film will increase the surface roughness and then the thermal emittance. To solve the problem, structures under the ultra-thin TiN layer will be designed to generate vertical surface plasmon resonance mode, which can hold the ultra-smooth surface to reduce thermal emittance and enhance the photoemission to increase quantum efficiency simultaneously. This project must be a beneficial exploration for new-type high-performance photocathodes, especially for time-resolved scientific instruments like high-brightness pulsed electron sources.

光阴极是超快电子显微镜、直线加速器、自由电子激光及其它第四代光源研制的关键部件之一，其光电子发射特性将影响相应科学装置的性能。本项目立足新型光阴极基础研究，将探索具有高热力学稳定性和优异表面等离激元特性的氮化钛(TiN)导电陶瓷材料在光阴极中的应用。项目拟研究TiN薄膜光阴极的制备及其热发射度、量子效率和寿命；拟引入超平滑（RMS粗糙度小于0.5 nm）TiN薄膜以降低热发射度，以此为基础在薄膜表面设计加工表面等离激元共振纳米结构以提高量子效率；拟研究表面等离激元增强光电子发射的物理机制。薄膜表面微纳结构将导致粗糙度增加，进而增大热发射度。针对该问题，拟探索超平滑超薄TiN膜层内部垂直纳米结构的表面等离激元共振，一方面能提高量子效率，另一方面得以保持超平滑的光电子发射面以降低热发射度。本项目对新型高性能光阴极研究，特别是为研制高亮度脉冲电子源等时间分辨的科学仪器将是一种非常有意义的探索。

光阴极是超快电子显微镜、直线加速器、自由电子激光及其它第四代光源研制的关键部件之一，其光电子发射特性将影响相应科学装置的性能。本项目立足新型光阴极基础研究，探索具有高热力学稳定性和优异表面等离激元特性的氮化钛(TiN)导电陶瓷材料在光阴极中的应用。项目拟研究TiN薄膜光阴极的制备及其热发射度、量子效率和寿命；采用高质量薄膜以降低热发射度，以此为基础在薄膜表面设计加工表面等离激元共振纳米结构以提高量子效率。.本项目研究了氮化钛薄膜作为光阴极材料的制备工艺，制备得到多晶氮化钛薄膜光阴极结构；在制备的多晶氮化钛薄膜上设计并制备了表面等离激元结构；着重研究了氮化钛薄膜作为光阴极材料的光电子发射特性，获得了系统的光阴极发射特性，包括热发射度、量子效率和光电发射时间响应等，为材料的应用研究提供了详细的参考依据。项目所研究的薄膜氮化钛光阴极具有较低的热发射度，可达到0.3um，同时具有可与金属光阴极相比拟的时间响应，将能够作为光阴极材料的选择之一，应用于光阴极注入器，超快电子显微镜中。本项目还开展了测量仪器的搭建，所搭建的透射率反射率测量系统将能够作为测试平台开展相关的光学测试。本项目对新型高性能光阴极研究，特别是为研制高亮度脉冲电子源等时间分辨的科学仪器将是一种非常有意义的探索。.