The surface activation layer of GaAs negative electron affinity photocathode activated by Cs, Li, and NF3

Sun, Y.; Kirby, R. E.; Maruyama, T.; Mulhollan, G. A.; Bierman, J. C.; Pianetta, P.
October 2009
Applied Physics Letters;10/26/2009, Vol. 95 Issue 17, p174109
Academic Journal
The lifetime of GaAs photocathodes can be greatly improved by introducing Li in the Cs+NF3 activation process. The surface activation layer of such photocathodes is studied by synchrotron radiation photoemission and is compared with GaAs photocathodes activated without Li. The charge distributions of N, F, and Cs experience significant changes when Li is added in the activation. In addition, the presence of Li causes NFx molecules to take an orientation with F atoms on top. All these changes induced by Li hold the key for the lifetime improvement of GaAs photocathodes.


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