| AVS 59th Annual International Symposium and Exhibition | |
| Applied Surface Science | Monday Sessions |
| Session AS-MoA |
| Session: | Quantitative Surface Chemical Analysis, Technique Development, and Data Interpretation - Part 2 |
| Presenter: | P.J. Cumpson, NEXUS XPS Facility, Newcastle University, UK |
| Authors: | P.J. Cumpson, NEXUS XPS Facility, Newcastle University, UK N. Sano, NEXUS XPS Facility, Newcastle University, UK |
| Correspondent: | Click to Email |
There has been excellent progress in the SIMS community in recent years[1,2] to identify the optimum conditions and primary ions for SIMS depth-profiling of polymers. A key step forward was the identification of Type I and Type II behaviour[3], in which polymer damage is dominated by cross-linking and polymer backbone bond-scission respectively. In many cases it is difficult, especially for a non-expert, to judge which of these two types a given polymer matrix is likely to be. For example, PAA, PMAA, PMA and PMMA are of types I, II, I and II respectively, even though their structures are very similar.
We examine this system in detail, largely in the context of XPS where polyatomic and cluster ion sources are set to become much more popular. We develop equations based on a 3D Ising ``resistor removal'' model. Some of the difficult parameters in this model can be estimated from literature values for rates of cross-linking and bond scission of polymers seen in radiation treatment at much higher energies. This model leads to some reasonably simple equations allowing analysts to make objective estimates of (a) which primary ion source is most appropriate for a particular polymer matrix, and (b) an estimate of the sputter-rate, for any arbitrary polymer matrix whose repeat unit is known.
The reliability of the model is tested using measured sputter rates for samples of 20 polymers using polyatomic (coronene) and GCIB (argon cluster) sources. White-light interferomentry combined with a novel kinematic mount for semi-automatic measurement of sputter crater volume have accelerated and improved the accuracy of these measurements.
Finally, based on the new model, we tabulate and plot estimated values for 103 polymers of technological significance.
[1] N. Winograd, Anal Chem 77 (2005) 143A
[2] J. S. Fletcher, X. A. Conlan, E. A. Jones, G. Biddulph, N. P. Lockyer, J. C. Vickerman, Anal Chem 78 (2006) 1827
[3] C. M. Mahoney, Mass Spectrometry Reviews, 29 (2010) 247