The role of the adsorbed gases on the photoelectron performance of Mg-based photocathodes

The influence of the adsorbed gases on the photoelectron performance of Mg thin film-based photocathodes was investigated. Mg thin films were deposited on Silicon and Copper substrates by pulsed laser ablation technique. The samples deposited on Silicon substrate were used to deduce the morphology, the structure and the thickness by using different diagnostic techniques. On the contrary, the samples deposited on Copper substrate were tested as photocathodes in a DC photodiode cell. The quantum efficiency of the Mg photocathodes was systematically improved by laser cleaning treatments, which appears to be necessary before any use of a metallic photocathode. The role of the hydrogen and oxygen absorption process on the emission properties is presented and discussed.