Influence of Exposure to CO, CO₂ and H₂O on the Stability of GaAs Photocathodes

Abstract

The influence of CO, CO2 and H2O gases on the stability of negative-electron-affinity (NEA) GaAs photocathodes during operation is investigated in the present work. We have found that exposure both to H2O and CO2 decreases the photocurrent of the photocathode. However, exposure to CO, which is known as a harmful gas to various photocathodes, has little effect on the photocathode stability. Furthermore, the effects of these gases on the restoration of the photocurrent by additional cesium deposition are investigated. These results are discussed with regard to the Cs/O activation layer which plays an important role in NEA GaAs photocathodes.

Lifetime and reliability results for a negative electron affinity photocathode in a demountable vacuum system

“…1 Recesiation works even after the cathode was exposed to a variety of gases. 7 All of these results seem to indicate that when these conditions are carefully controlled, lifetimes would be at least an order of magnitude longer, making the NEA photocathodes a viable electron source for lithography.…”

Enhanced chemical immunity for negative electron affinity GaAs photoemitters

“…Notwithstanding studies on the sensitivity of activated NEA photocathode yield to various gas species, 3 there has been relatively little work to enhance the chemical immunity of activated GaAs. They are currently restricted to operation in the very best ultrahigh vacuum environments, particularly when it is required that they exhibit stable operation over long periods.…”

Attenuation performance of reflection-mode AlGaN photocathode under different preparation methods

“…The adsorption of O contained in residual gas such as H 2 O, CO, or CO 2 in the demountable vacuum system can influence photocathode stability [16]. It is known that the coverage Cs atom on the photocathode surface is less than one monolayer.…”