Comparison of the photoemission behaviour between negative electron affinity GaAs and GaN photocathodes |
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Authors: | Zhang Yi-Jun Zou Ji-Jun Wang Xiao-Hui Chang Ben-Kang Qian Yun-Sheng Zhang Jun-Ju and Gao Pin |
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Affiliation: | Institute of Electronic Engineering and Optoelectronic Technology, Nanjing University of Science and Technology, Nanjing 210094, China |
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Abstract: | In view of the important application of GaAs and GaN photocathodes in electron sources, differences in photoemission behaviour, namely the activation process and quantum yield decay, between the two typical types of III-V compound photocathodes have been investigated using a multi-information measurement system. The activation experiment shows that a surface negative electron affinity state for the GaAs photocathode can be achieved by the necessary Cs-O two-step activation and by Cs activation alone for the GaN photocathode. In addition, a quantum yield decay experiment shows that the GaN photocathode exhibits better stability and a longer lifetime in a demountable vacuum system than the GaAs photocathode. The results mean that GaN photocathodes are more promising candidates for electron source emitter use in comparison with GaAs photocathodes. |
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Keywords: | III--V photocathode negative electron affinity Cs--O activation quantum yield decay |
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