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Lookup NU author(s): Professor Peter Cumpson, Dr Jose Portoles, Dr Anders Barlow, Dr Naoko Sano, Dr Mark Birch
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Argon gas cluster ion beam sources are likely to become much more widely available on XPS and SIMS instruments in the next few years. Much attention has been devoted to their ability to depth profile organic materials with minimum damage. What has not been the focus of attention (possibly because it has been very difficult to measure) is the large ratio of sputter yield for organic materials compared with inorganic materials using these sources and the special opportunities this presents for studies of organic/inorganic interfaces. Traditional depth profiling by monatomic argon ions introduces significant damage into the organic overlayer, and because sputter rates in both organic and inorganic are similar for monatomic ions the interface is often blurred' due to knock-on and other damage mechanisms. We have used a quartz crystal technique to measure the total sputter yield for argon cluster ions in a number of materials important in medical implants, biomaterials and diagnostic devices, including polymethyl methacrylate, collagen, hydroxyapatite, borosilicate glass, soda lime glass, silicon dioxide and the native oxides on titanium and stainless steel. These data fit a simple semi-empirical equation very well, so that the total sputter yield can now be estimated for any of them for the entire range of cluster ion energy typical in XPS or SIMS. On the basis of our total sputter yield measurements, we discuss three useful figures-of-merit' for choosing the optimum cluster ion energy to use in depth profiling organic/inorganic samples. For highest selectivity in removing the organic but not the inorganic material the energy-per-atom in the cluster should be below 6eV. A practical balance between selectivity and reasonably rapid depth profiling is achieved by choosing a cluster ion energy having between around 3 and 9eV energy-per-atom. Copyright (c) 2013 John Wiley & Sons, Ltd.
Author(s): Cumpson PJ; Birch M; Portoles JF; Sano N; Barlow AJ
Publication type: Article
Publication status: Published
Journal: Surface and Interface Analysis
Year: 2013
Volume: 45
Issue: 13
Pages: 1859-1868
Print publication date: 17/10/2013
ISSN (print): 0142-2421
ISSN (electronic): 1096-9918
Publisher: John Wiley & Sons Ltd
URL: http://dx.doi.org/10.1002/sia.5333
DOI: 10.1002/sia.5333
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