An experimental approach to the determination of the surface ionization phi(0) in electron probe microanalysis

A compilation of experimentally determined surface ionization values for Al Ka and I'd La radiation on a wide variety of substrates, ranging from bery llium to bismuth, and measured between 4 and 30 kV, is presented. The value s were extracted from our previously reported thin-film measurements on alu minum and palladium films by electron probe microanalysis. The phi (0) valu es were determined by establishing the ratios of the intensities emitted fr om the supported and unsupported films for six film thicknesses and extrapo lating towards a film thickness approaching zero. Some 180 phi (0) data eac h for Al K alpha and Pd L alpha x-radiation were collected in this way. The purpose of this work was to provide systematic data on which the numerous existing expressions for phi (0) could be tested. In the final assessment p rocedure, in which we also included 108 data from the literature, we compar ed the performances of the various expressions from the literature for phi (0) and a newly developed expression of our own. Our final conclusion is th at there is little to be chosen between the three to four of the highest ra nking expressions. Copyright (C) 2001 John Wiley & Sons, Ltd.