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

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 m...

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Bibliographic Details
Published in:Heliyon 2024-06, Vol.10 (11), p.e31461-e31461, Article e31461
Main Authors: Benjamin, C., Seddon, S.D., Walker, M., Jones, L.B., Noakes, T.C.Q., Bell, G.R.
Format: Article
Language:English
Subjects:
Dark current
Kelvin probe
Photocathode
Surface oxides
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Summary: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. •UV ozone treatment increases the work function of clean Cu by up to 0.5 eV.•A simple mask of silica glass or Si protects the Cu from ozone exposure.•Prospects for dark current reduction in accelerators are discussed.•An efficient polish-etch method for surface oxide-free Cu is given.
ISSN:2405-8440
2405-8440
DOI:10.1016/j.heliyon.2024.e31461