Influence of different Cs-to-O current ratios on sensitivity and stability of activating GaAs photocathodes
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摘要: 鉴于不同的铯氧电流激活GaAs光阴极时会对激活过程和结果产生不同的影响，从而影响GaAs光阴极的灵敏度和稳定性。以固定铯源电流，改变氧源电流的方式获取不同铯、氧电流比，激活同类GaAs光阴极，得到了3组实验数据。对数据进行分析，结果表明：同类光阴极在相同条件下激活时，光电流出现的时间几乎一致，并且首个光电流峰值也非常接近；激活时ICs/IO=1.07是目前获得高灵敏度、高稳定性GaAs光阴极的最佳电流比，而ICs/IO=1.10时光阴极灵敏度低但稳定性好，ICs/IO=1.03时光阴极灵敏度高但稳定性差。双偶极层模型认为Cs、O激活后GaAs表面形成了稳定均匀的GaAs-O-Cs:Cs-O-Cs双偶极层，并达到了负电子亲和势，这一点与实验数据的分析结果相一致。该方法可用于提高GaAs光阴极灵敏度和稳定性。
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关键词:
- 光阴极灵敏度 /
- 光阴极稳定性 /
- Cs-to-O电流比 /
- 光电流
Abstract: Since the different cesium and oxygen currents during the activating process may cause the undefined influence on the sensitivity and stability of GaAs photocathodes, the long-term research was implemented. For the purpose of increasing sensitivity and stability of GaAs photocathodes, three different cesium-to-oxygen current ratios (fixed cesium current and alterable oxygen current) were used to activate the similar GaAs photocathodes, and three sets of experimental results were obtained. The analysis results of experimental data show that the appearance times of photocurrent are almost identical and the peak values of the first photocurrent are very close; ICs/IO=1.07 is the optimum current ratio for high sensitivity and high stability, ICs/IO=1.10 is for low sensitivity but high stability, and ICs/IO=1.03 is for high sensitivity but low stability. Based on the double-dipole model, the stable and uniform double-dipole layers of GaAs-O-Cs:Cs-O-Cs are formed and negative electron affinity is achieved on GaAs surface activated by cesium and oxygen, which cnsists with the analysis results for theexperimental data. The effective technical method can be used to improve the sensitivity and stability of GaAs photocathodes. -
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