Secondary ion emission from arachidic acid LB-layers under Ar+, Xe+, Ga+ and SF5+ 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 multi layers, deposited on gold substrates, has been investigated. Ga+, Ar+, Xe-1 29(+) and SF5+ in the energy range 5-25 keV were used as primary ions. Yiel ds Y, damage cross-sections sigma, and ion formation efficiencies E have be en determined for selected secondary ions, characterizing the molecular ove rlayer, the overlayer substrate interface and the substrate. We found a str ong influence of layer thickness and of primary ion energy, mass and compos ition on Y, a and E. Information depth increases with increasing ion energy and decreasing mass of primary ions, being higher for SF: than for Xe+. Y, sigma and E increase with increasing primary ion mass. They are considerab ly higher for a molecular (SF5+) than for atomic ions of comparable mass (X e-129(+)). The experimental results supply information on the extension of impact cascades, generated in different substrate materials by different pr imary ion species and different energies. They demonstrate that in analytic al SIMS application information depths can be minimized and yields and ion formation efficiencies can be maximized by the use of molecular primary ion s. (C) 1999 Elsevier Science B.V. All rights reserved.