用于真空电子太赫兹器件的微型热阴极电子束源研究

太赫兹波辐射源是太赫兹(THz)波技术的关键.真空电子太赫兹器件在高频、大功率太赫兹源发展中较其他技术有明显的优势,微米尺度高电流密度微型电子束源则是研制真空电子太赫兹器件的核心之一.本文在研制低温、大电流纳米粒子氧化钪掺杂含钪扩散阴极(nanosized-scandia doped dispenser cathode)的基础上,采用发射抑制膜沉积与聚焦离子束(FIB)刻蚀技术,研制无需压缩直接提供高电流密度的微型电子束的电子源.所研究的电子束源直径400μm,在工作温度950fiC,提供空间电荷限制电流密度50 A/cm2时,已稳定工作1000 h以上,并且层流性良好.本文阐述了阴极制备工艺、电子发射特性、微米尺度电子束源的获得和特性,介绍了发射抑制膜的结构和抑制特性的评估.并探讨了镀膜和刻蚀对发射的影响机理.这一电子束源在常规毫米尺度电子源的基础上产生微米尺度的微区高电流密度的电子束,为真空电子太赫兹辐射源的研制提供了新的途径.

Study of mini-themionic electron sources for vacuum electron THz devices

THz technology has attracted great attention for decades of years. Among the wide research areas of THz technologies, vacuum electron terahertz radiation sources have obvious advantages in high power region. For the THz vacuum electro devices (VED), high current density electron beams with small dimensions are required. Nanosized scandia doped dispenser (SDD) cathodes have the capability to operate stably at pulsed current densities of over 100 A/ cm² at 950 ℃ so it becomes the most promising cathodes to meet the requirements for THz VEDs. In this paper, we report a new approach for developing miniaturized electron beam sources on normal SDD cathodes. An electron beam of 400 μm in diameter has been directly generated on an SDD cathode by deposition of a Zr/W double-layer anti-emission film and followed by a focused ion beam (FIB) milling. Results indicate that the electron beam is able to provide a space charge limited (SCL) current density of over 50 A/cm² at the operating temperature of 950 ℃ with proper laminarity and works stably for more than 1000 hours. The beam emission characteristics and the function of the anti-emission film have been discussed and related to the surface analysis results. The approach opens a new way for producing high emission mini-electron sources to satisfy the requirment of THz VEDs.
Keywords： THz source scandate cathode electron beam surface analysis