Energy distribution of electrons reaching the cathode surface. is the incident electron energy and and are the energy distributions of the - and -valley electrons reaching the surface at room temperature, respectively.
Band structure and surface barrier for a typical NEA GaAs photocathode. is the conduction band minimum, is the valence band peak level, is the width of the band gap, is the Fermi level, is the height of the surface band bending, is the width of the surface band bending, is the start height of barrier I, and are the end height of barriers I and II ( is actually the vacuum level), and and are the thicknesses of barriers I and II.
Spectral response for the GaAs photocathodes as a function of degradation time. Curve 1 is the spectral response for the original cathode. Curves 2, 3, and 4 are the spectral responses for the original cathodes degraded for 5, 9, and 12 h in the vacuum system, respectively. There was no illumination on the cathode surface during the degradation (after Ref. 31).
Angle-dependent , , and spectra for the freshly activated GaAs cathode.
Angle-dependent , , and spectra for the degraded GaAs cathode.
Surface layer structure model for the GaAs photocathodes.
Fitted performance parameters of cathodes.
Fitted surface barrier parameters of cathodes.
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