Towards dark current suppression in metallic photocathodes by selected-area oxidation

• DOI: 10.1016/j.heliyon.2024.e31461
• Publication Date: 2024-05-22T01:11:23Z
• Authors: C. Benjamin; S.D. Seddon; M. Walker; L.B. Jones; T.C.Q. Noakes; G.R. Bell
• Keywords: Social sciences (General); H1-99; Kelvin probe; Q1-390; Dark current; Science (General); Surface oxides; Photocathode; Research Article

Oxide-free surfaces of polycrystalline Cu are prepared using acetic acid etching after chemical-mechanical polishing. UV ozone treatment is shown to increase the work function of the cleaned Cu by up to 0.5 eV. There is also a large reduction in quantum efficiency at 265 nm. Cu sheet can be easily masked from ozone exposure by Si or glass, meaning that selected-area oxi-dation is possible. Oxygen plasma treatment has a similar effect to the UV ozone but is more difficult to mask. There is no increase in surface roughness after oxidation, meaning that the larger work function could significantly re-duce dark current in accelerator photocathodes without affecting the desired photoemission region.