Reactive laser ablation of copper in hydrocarbon atmosphere: synthesis of nanocomposite surface layers for secondary electron yield reduction

The functionality of surfaces is dependent on two characteristic properties: surface topography and chemical composition. For instance, the secondary electron yield (SEY) of metal surfaces can be adjusted by surface nanostructures or by altering the surface composition. In this study, the two concepts are combined in a one-step process. Reactive Laser ablation based nanostructuring of copper surfaces in a carbon-containing atmosphere was performed, which results in the formation of a metal-particle carbon composite layer. Copper was irradiated with IR ps laser radiation (λ = 1030 nm, Δt p = 10 ps, f rep = 100 kHz, Φ acc = 2300 J/cm 2 ) in an acetylene atmosphere. The process results in the production of a nanostructured surface with a significant carbon content. The resultant maximum SEY (δ max ) depends on the treatment parameters and on the storage time of the copper surface in air after the laser treatment process. The δ max of the laser treated copper surface was 1.2 after two weeks storage and increased to 1.4 after one year storage, while an electron conditioning (electron energy: 250 eV, electron dose: 3⋅10 -2 C/mm 2 ) after the one year allows δ max reduction down to 0.61. The results show that besides the topography the chemical composition plays an important role for the resulting SEY. In particular, the modification induced by electron conditioning results in a chemical reduction of the carbon-oxide bonds.