Secondary ion emission from polymethacrylate LB-layers under 0.5–11 keV atomic and molecular primary ion bombardment

Secondary ion yields Y Xiq. increase considerably when changing from atomic to molecular primary ions, whereas the parallel increase in the corresponding damage cross sections s Xiq. is much smaller. This results in a net increase of ion formation efficiencies E Xiq.sYrs . For a more detailed understanding of the complex sputtering and ion formation processes, in particular for molecular primary ion bombardment, the secondary ion emission of well-defined polymethacrylate LB mono- and multilayers on Ag was investigated. For characteristic secondary ions Xiq emitted from these overlayers Y Xiq.and s Xiq. for 11 keV Neq, Arq, Xeq, Oq2 , SF5q, C7Hq7 , C10Hq8 , C6F6qand C10F8qbombardment were determined and compared. The influence of primary ion energy was investigated in the energy range between 0.5 and 10 keV for Xeq and SF5q bombardment. For multilayers we found yield increases up to nearly a factor of 1000, when changing from Neq to SF5q bombardment. We found a more pronounced yield and efficiency enhancement for multi than for monolayer coverages, a saturation of Y, s and E enhancement for primary ions made of more than 6 heavy constituents at constant primary ion energy, no chemical effect on the secondary ion yields under static SIMS conditions SF5qr C7Hq7 e.g.., and a pronounced decrease in secondary ion yields and secondary ion formation efficiencies for SF5q primary ions with impact energies below 2 keV. q2000 Elsevier Science B.V. All rights reserved.