No abstract

By using modern XPS systems it is possible to obtain spectra with well-resolved spin orbit, multiplet and field splitting even with powder samples mounted using adhesive tape. Measurement of Cr 2 O 3 powder with the latest generation of XPS spectrometers, which are able to analyse non-conductive powders with ultimate energy resolution, revealed multiplet splitting features and satellite emission in the Cr 2p spectrum. Therefore, peak-fit analysis of Cr 2p XPS spectra of Cr(III) compounds requires a more appropriate approach and common practice has to be reconsidered. One possible way to analyse this spectrum is proposed, based on the experimental and theoretical work of other authors.

We present experimental data on the angular distribution of Irganox 1010 organic molecules sputtered by large argon gas cluster projectiles (E/n = 5 eV, 10 keV Ar2000). Ejection probability distributions as derived from deposit patterns on planar collector surfaces were recorded at various angles of incidence of the primary cluster ion beam. The sputtered material is ejected at polar angles, on average, greater than 45° from the surface normal. At normal incidence there is no azimuthal dependence in the ejecta distribution, but the ejecta are forward directed even at incidence angles as low as 15°. After this initial rapid change, the ejecta distribution shows a rather weak dependence on the incidence angle of the primary ion beam and the polar, and azimuthal angles of preferred ejection remain relatively constant. Ejecta distributions agree with previously published results from molecular dynamics simulations for organic molecules sputtered with large argon gas cluster projectiles and are consistent with the picture derived from experimental data for metal target species. The close chemical resemblance of collector and target materials as identified by secondary ion mass spectrometry, and the large total volume of deposits accounting for over 75% of the sputtered material as inferred from symmetry considerations, indicate that a large fraction of the sputtered material is intact molecules. Findings are discussed with respect to the utilization of large cluster projectiles as primary ion beams in secondary neutral mass spectrometry.

In recent years, it has been demonstrated that cluster ion beams may be used to sputter some materials, particularly organic materials, without the significant accumulation of damage. It is therefore possible to use cluster ion beam sputtering in conjunction with a surface analytical technique, such as SIMS, to obtain depth profiles and three-dimensional images of the distribution of organic species in the near-surface region. For SIMS organic depth profiling to be useful as an analytical tool, it is important that it is able to measure physically meaningful quantities, such as the local concentration of a species within a blend. In this paper, we investigate a model system of a miscible binary mixture of codeine and poly(lactide). We show that there is a strong surface enrichment of poly(lactide), which provides a reference signal and permits the direct comparison of different samples in terms of secondary ion yield behavior. We demonstrate that it is possible to relate secondary ion intensities to local concentrations for a binary system and that there is a direct correspondence between the yield enhancement of one component and the yield suppression of the other. The dependence of secondary ion yield on composition is described using a model of the kinetically limited transfer of charge between secondary ions and secondary neutrals. Application of the model to pure materials under the assumption that only highly fragmented secondary ions are initially produced and interact with unfragmented secondary neutrals leads to the prediction that high molecular mass quasi-molecular ions have intensities proportional to the square of the total secondary ion yield. This relationship has been independently observed in other work (Seah, M. P. Surf. Interface Anal. 2007, 39, 634.).