OPTIMUM EXPERIMENTAL CONDITIONS FOR QUANTITATIVE SURFACE MICROANALYSIS BY REFLECTION ELECTRON ENERGY-LOSS SPECTROSCOPY

Experimental conditions for obtaining high quality core-shell ionization edges in reflection electron energy-loss spectroscopy (REELS) are investigated. Under the (600) specular "mirror" reflection conditions and using the relative ionization cross-section measured from a MgO thin foil in the transmission geometry for collection semi-angle beta = 1.2 mrad, the chemical composition of MgO (100) surfaces is determined to be N(O)/N(Mg) = 1.5 +/- 0.15. This value is not significantly affected by varying the resonance diffraction conditions near the [001] zone axis, under which the spectra were acquired. An incorrect apparent composition will result if channeling effects along the [011] zone axis are not considered properly. Surface microanalysis is limited by the accuracy of the core-shell effective ionization cross-section (EICS), which depends not only on the property of a single atom but also on the dynamical elastic and inelastic scattering and channeling processes of electrons. An experimental method is outlined by which to measure the relative EICS from a thin foil specimen in the transmission case under the equivalent resonance conditions as in reflection geometry.