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Static SIMS: A Study of Damage Using Polymers
Author(s) -
Gilmore I. S.,
Seah M. P.
Publication year - 1996
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/(sici)1096-9918(199610)24:11<746::aid-sia177>3.0.co;2-a
Subject(s) - fragmentation (computing) , ion , ion beam , chemistry , polymer , secondary ion mass spectrometry , analytical chemistry (journal) , beam (structure) , intensity (physics) , figure of merit , atomic physics , materials science , optics , physics , optoelectronics , organic chemistry , chromatography , computer science , operating system
As a result of work to establish the surface potential of insulators accurately in a quadrupole static SIMS system of high sensitivity, we have been able to study the effects of increasing dose‐related damage on the intensities of the mass spectral peaks in the two archetypal bulk polymers PET and PTFE, as well as thin hydrocarbon contamination layers, with high accuracy. It is shown that the intensities follow very well‐defined functions which give damage cross‐sections whose values reflect the fragmentation behaviour of the polymers. The effects reflect the number of bonds to be broken to liberate the fragment, the internal complexity of that fragment and the typical damage zone of the ion impact. These concepts show that a static SIMS limit of below 3×10 15 ions m ‐2 exists for changes of <10% in the intensities of the most easily damaged species but that some larger fragments may require a dose of 2×10 17 ions m ‐2 to maximize their intensity! This work has three main conclusions. Firstly, by defining a figure of merit factor, F , equal to the ratio of the absolute intensity of a peak to the fractional rate of change of that peak with the ion dose, it is possible to define the optimal beam parameters for static SIMS measurements. The higher the value of F , the more the intensity per unit of onset of damage. The highest F values occur at higher beam energies and, in general, xenon gives greater efficiency than argon. Secondly, the development of damage may be described by simple bond breaking. Thirdly, a study of the damage process gives quite detailed structural bonding information not directly available from the traditional static SIMS spectrum.