Non-Monotonic Behaviour In The Mean Transverse Energy Of Electrons Emitted From A Reflection-Mode P-Gaas(Cs,O) Photocathode During Its Qe Degradation Through Oxygen Exposure

We present a study on the evolution of both transverse and longitudinal energy distributions due to oxygen-induced quantum efficiency degradation in the electrons emitted from a reflection-mode p-GaAs(Cs,O)-photocathode over an effective electron affinity range of chi*similar to -0.1 eV to chi*similar to +0.3 eV under illumination wavelengths lambda = 808, 635 and 532 nm. For lambda = 635 and 532 nm, we found that the mean transverse energy of electrons emitted as the photocathode effective electron affinity increased has a non-monotonic character. Our proposed fitting model links the measured response to changes in the relative number of thermalised and non-thermalised electrons in the total emitted photocurrent.