高真空系统气体成分对GaAs光电阴极稳定性的影响

GaAs 光电阴极以其量子效率高、光谱可调等优点广泛应用于微光夜视领域，尤其以高积分灵敏度的特性区别于多碱光电阴极，而 GaAs 光电阴极负电子亲合势的特性是通过 Cs,O 激活实现的，但是激活结束后，负电子亲合势的维持受诸多因素影响，如激活源、激活方式、气体氛围等。为了探究超高真空系统中影响 GaAs 光电阴极稳定性的因素，开展了 GaAs 光电阴极的激活实验和稳定性实验，对激活光电流曲线与腔室气体成分进行了监测，实验结果表明，在真空度优于 1×10^-6 Pa 的高真空系统中，影响其稳定性的是腔室中的气体成分，其中对稳定性影响最大的是 H₂O，真空系统中 H₂O分压的增加会导致 GaAs 光电阴极的 Cs,O 激活层迅速破坏，光电发射能力急剧下降。

Influence of Chamber Gas Composition on the Stability of GaAs Photocathode

GaAs photocathodes are widely used in low-light night vision owing to their high quantum efficiency and adjustable spectra. In particular, they are distinguished from multi-alkali photocathodes based on their high integration sensitivity. The negative electron affinity of GaAs photocathodes is determined through Cs, and O activation is achieved. However, after activation, the maintenance of negative electron affinity is affected by many factors, such as the activation source, activation method, and gas atmosphere. To explore the factors that affect the stability of GaAs photocathodes in ultra-high vacuum systems, an activation and stability experiment was performed with a GaAs photocathode. The activation photocurrent curve and gas composition in a chamber were monitored. The experimental results show that in a high-vacuum system with vacuum degree less than 1×10?6 Pa, the stability of the GaAs photocathode was not directly affected by the degree of vacuum but by the gas composition in the chamber. Among these, H₂O had the greatest impact on stability. The increase in the H₂O partial pressure in the vacuum system rapidly destroyed the Cs and O activation layers of the GaAs photocathode and dramatically reduced the photoemission.