title: Improving secondary ion mass spectrometry C60(n+) sputter depth profiling of challenging polymers with nitric oxide gas dosing.
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(n+) 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 C60(2+) 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 multilayered polystyrene and polyvinylpyrrolidone film and from a polystyrene/polymethylmethacrylate bilayer, in the former case by using an optimized set of conditions for C60(2+) and, for comparison, an Ar2000(+) ion beam. Our results show a dramatic improvement for depth profiling with C60(2+) using NO at pressures above 10(-6) mbar and sample temperatures below -75 °C. For the multilayered polymer film, the depth profile acquired using C60(2+) 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 results demonstrate that NO dosing can significantly improve SIMS depth profiling analysis for certain organic materials that are difficult to analyze with C60(n+) 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(n+) sputtering.
authors.affiliation: National Physical Laboratory, Teddington, Middlesex, United Kingdom. rasmus.havelund@npl.co.uk
authors.forename: R
authors.initials: R
authors.lastname: Havelund
authors.forename: A
authors.initials: A
authors.lastname: Licciardello
authors.forename: J
authors.initials: J
authors.lastname: Bailey
authors.forename: N
authors.initials: N
authors.lastname: Tuccitto
authors.forename: D
authors.initials: D
authors.lastname: Sapuppo
authors.forename: I S
authors.initials: IS
authors.lastname: Gilmore
authors.forename: J S
authors.initials: JS
authors.lastname: Sharp
authors.forename: J L S
authors.initials: JL
authors.lastname: Lee
authors.forename: T
authors.initials: T
authors.lastname: Mouhib
authors.forename: A
authors.initials: A
authors.lastname: Delcorte
mesh_terms: D001128:Argon / Q000737:chemistry*; D037741:Fullerenes / Q000737:chemistry*; D013058:Mass Spectrometry / Q000379:methods*; D008958:Models, Molecular; D008968:Molecular Conformation; D009569:Nitric Oxide / Q000737:chemistry*; D011137:Polystyrenes / Q000737:chemistry*; D011205:Povidone / Q000737:chemistry*
chemical_list: D037741:Fullerenes; D011137:Polystyrenes; D009569:Nitric Oxide; D001128:Argon; D011205:Povidone; C069837:fullerene C60