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Improving secondary ion mass spectrometry C60(n+) sputter depth profiling of challenging polymers with nitric oxide gas dosing.

Havelund, R; Licciardello, A*; Bailey, J*; Tuccitto, N*; Sapuppo, D*; Gilmore, I S; Sharp, J S*; Lee, J L S; Mouhib, T*; Delcorte, A* (2013) Improving secondary ion mass spectrometry C60(n+) sputter depth profiling of challenging polymers with nitric oxide gas dosing. Anal. Chem., 85 (10). pp. 5064-5070.

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Abstract

Organic depth profiling using secondary ion mass spectrometry (SIMS) provides valuable information about the three dimensional distribution of organic molecules. However, for a range of materials, commonly used cluster ion beams such as C60 do not yield useful depth profiles. A promising solution to this problem is offered by the use of nitric oxide (NO) gas dosing during sputtering to reduce molecular cross-linking. In this study a C602+ ion beam is used to depth profile a polystyrene film. By systematically varying NO pressure and sample temperature, we evaluate their combined effect on organic depth profiling. Profiles are also acquired from a multi-layered polystyrene and polyvinylpyrrolidone film and from a polystyrene-polymethylmethacrylate bilayer, in the former case by using an optimised set of conditions for C602+ and, for comparison, an Ar2000+ ion beam. Our results show a dramatic improvement for depth profiling with C602+ using NO at pressures above 10 -6 mbar and sample temperatures below -75°C. For the multi-layered polymer film, the depth profile acquired using C602+ exhibits high signal stability with the exception of an initial signal loss transient and thus allows for successful chemical identification of each of the six layers. The depth resolution is observed to degrade with increasing sampling depth. The results demonstrate that NO dosing can significantly improve SIMS depth profiling analysis for certain organic materials that are difficult to analyse with C60 sputtering using conventional approaches/conditions. While the analytical capability is not as good as large gas cluster ion beams, NO dosing comprises a useful low-cost alternative for instruments equipped with C60 sputtering.

Item Type: Article
Keywords: secondary ion mass spectrometry, SIMS, depth profiling
Subjects: Nanoscience
Nanoscience > Surface and Nanoanalysis
Identification number/DOI: 10.1021/ac4003535
Last Modified: 02 Feb 2018 13:14
URI: http://eprintspublications.npl.co.uk/id/eprint/5857

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