Abstract
Using the first-principles method based on the density functional theory (DFT),
the work function of seven different GaN (0001) (1×1) surface models is calculated. The
calculation results show that the optimal ratio of Cs to O for activation is between 3:1
and 4:1. Then, Cs/O activation and stability testing experiments on reflection-mode
negative electron affinity GaN photocathodes are performed. The surface model [GaN (Mg):
Cs] Cs-O after being activated with cesium and oxygen is used. The experiment results
illustrate that the adsorption of O contained in the residual gas increases the surface
potential barrier and the reduction of the effective dipole quantity is the basic cause
of the quantum efficiency decay.
© 2015 Chinese Laser Press
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