A NEW EXPERIMENTAL-METHOD FOR DETERMINING SECONDARY ION YIELDS FROM SURFACES BOMBARDED BY COMPLEX HETEROGENEOUS IONS

We report on a new experimental method for determining the relative negative secondary ion (SI) yields for a number of different molecular and cluster primary ions. The method is based on the time-of-flight (TOF) analysis of primary ions which are desorbed from a source target by fission fragments of 252Cf. By using secondary electrons, emitted from a sample target upon primary ion impact, and an event-by-event coincidence counting technique, secondary ion TOF spectra correlated to several different primary ions may be obtained simultaneously. We have used this technique to measure the relative SI yields from organic (e.g., phenylalanine) as well as metallic (e.g., gold) surfaces using (CsI)*Cs+(n~ 0, 1, 2) and the monomer and dimer ions of coronene, C24Hi2, and phenylalanine, C6H5CH2CH(NH2)COOH, as primary ions. For both the organic and metallic surfaces, strong enhancements in the SI yields are observed when a more complex projectile is used. © 1990, American Vacuum Society. All rights reserved.