WU Haoyu, GUO Xin, GAN Linyu, CHEN Peng, XU Zhifeng, LIU Hui, JIAO Gangcheng, ZHU Yufeng, REN Yutian. Influence of Chamber Gas Composition on the Stability of GaAs Photocathode[J]. Infrared Technology , 2022, 44(8): 824-827.
Citation:
WU Haoyu, GUO Xin, GAN Linyu, CHEN Peng, XU Zhifeng, LIU Hui, JIAO Gangcheng, ZHU Yufeng, REN Yutian. Influence of Chamber Gas Composition on the Stability of GaAs Photocathode[J]. Infrared Technology , 2022, 44(8): 824-827.
WU Haoyu, GUO Xin, GAN Linyu, CHEN Peng, XU Zhifeng, LIU Hui, JIAO Gangcheng, ZHU Yufeng, REN Yutian. Influence of Chamber Gas Composition on the Stability of GaAs Photocathode[J]. Infrared Technology , 2022, 44(8): 824-827.
Citation:
WU Haoyu, GUO Xin, GAN Linyu, CHEN Peng, XU Zhifeng, LIU Hui, JIAO Gangcheng, ZHU Yufeng, REN Yutian. Influence of Chamber Gas Composition on the Stability of GaAs Photocathode[J]. Infrared Technology , 2022, 44(8): 824-827.
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.
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Figure 1. Transmission type GaAs photocathode activation and gas composition monitoring device
Figure 2. Transmission type GaAs photocathode Cs, O activation mechanism diagram
Figure 3. GaAs photocathode Cs, O activated photocurrent curve
Figure 4. Quadrupole mass spectrometer monitoring curve and photocathode photocurrent change curves: (a) The monitoring curve of quadrupole mass spectrometer after H2 partial pressure is increased; (b) The monitoring curve of the quadrupole mass spectrometer after the partial pressure of H2 and N2 is increased; (c) The monitoring curve of the quadrupole mass spectrometer after the partial pressure of H2, N2, and H2O is increased; (d) Change curve of photocathode photocurrent after H2 partial pressure is increased; (e) Change curve of photocathode photocurrent after H2 and N2 partial pressure is increased; (f) The change curve of photocathode photocurrent after the partial pressure of H2, N2, and H2O is increased
Figure 5. Comparison of the stability of the photocurrent curves