多碱光电阴极的Cs-O激活技术研究

Study on Cs-O Activation Technology of Multi-alkali Photocathode

采用蒸镀法,分别通过单次蒸Na和多次蒸Na两种工艺制备了一系列未经激活的Na_2KSb基底层,并通过3种不同的Cs-O激活方式对其进行表面激活,然后分别与未激活、仅Cs激活以及传统Cs-Sb激活的样品进行对比。积分灵敏度和光谱响应曲线测试结果表明,与未激活的Na_2KSb光电阴极相比,所有经过Cs-O激活的光电阴极的灵敏度和长波阈值都得到了一定程度的提高和拓展,而且采用单次蒸Na工艺制作样品的积分灵敏度明显高于多次蒸Na工艺。对于单次蒸Na工艺制备的光电阴极,采用Cs-O+Cs-Sb激活能够获得较高的灵敏度和较宽的光谱响应范围。在该条件下,Cs-O激活次数存在一个最佳值,当单次蒸O量为50%时,Cs-O激活最佳次数为2次,此时样品的积分灵敏度与未激活的Na_2KSb光电阴极相比提高了45.9倍,长波阈值向长波方向拓展了231 nm,逸出功降低了0.46 e V,而且工作寿命和EBI(Equivalent background illumination)测试结果表明该样品具有比传统Cs-Sb更好的稳定性和更低的背景噪声。逸出功计算结果表明,表面激活以后样品长波阈值的拓展可以归因于阴极材料逸出功的降低。

Two kinds of Na2KSb basal layers were successfully fabricated by the vapor deposition method with single and multiple Na loops,and three kinds of activation processes were used to activate the as-prepared Na2KSb basal layers.The integral sensitivity and spectral response of the multi-alkali cathodes were measured and compared with the samples without activation,Cs activation only,and Cs-Sb activation.It is found that,when compared with the Na2KSb without activation,the integral sensitivity of the Na2KSb cathode after surface activation increased,and the long-wavelength cutoff wavelength also extended.The integral sensitivity of the activated samples prepared by a single Na loop were higher than that prepared by the multiple Na loop method.Furthermore,for the Na2KSb prepared by the single Na loop method,a higher sensitivity and wider range of responses can be achieved by Cs-O+Cs-Sb activation,and the best process is to activate Cs-O twice when the evaporation of O is 50%each time.Under these conditions,the sensitivity of the as-prepared samples was 45.9 times that of Na2KSb,the long-wavelength cutoff wavelength was shifted 231 nm toward the long wavelength,and the work function of the cathode reduced to 0.46 eV.The results of the working life and the EBI values of these samples show that the stability and background noise are better than the samples prepared by Cs-Sb activation.The results of the work function show that the expansion of the long-wavelength cutoff wavelength can be attributed to the decrease of the cathode work function after surface activation.