Secondary ion emission from arachidic acid LB-layers under Arq, Xeq, Gaq and SFq primary ion bombardment

The influence of primary ion energy, mass and composition on sputtering and secondary ion emission of arachidic acid Langmuir–Blodgett mono- and multilayers, deposited on gold substrates, has been investigated. Gaq, Arq, 129Xeq and SFq 5 in the energy range 5–25 keV were used as primary ions. Yields Y, damage cross-sections s , and ion formation efficiencies E have been determined for selected secondary ions, characterizing the molecular overlayer, the overlayer substrate interface and the substrate. We found a strong influence of layer thickness and of primary ion energy, mass and composition on Y, s and E. Information depth increases with increasing ion energy and decreasing mass of primary ions, being higher for SFq 5 than for Xeq. Y, s and E increase with increasing primary ion mass. They are considerably higher for a molecular SF5q. than for atomic ions of comparable mass 129Xeq.. The experimental results supply information on the extension of impact cascades, generated in different substrate materials by different primary ion species and different energies. They demonstrate that in analytical SIMS application information depths can be minimized and yields and ion formation efficiencies can be maximized by the use of molecular primary ions. q1999 Elsevier Science B.V. All rights reserved