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The Storing Matter technique applied to polystyrene: a study of different methods to enhance Ag-cationization

Authors


N. Becker, Department ‘Science and Analysis of Materials (SAM)’, Centre de Recherche Public – Gabriel Lippmann, 41 rue du Brill, L-4422 Belvaux, Luxembourg. E-mail: norabecker@gmail.com

Abstract

The Storing Matter technique is derived from secondary ion mass spectrometry (SIMS) and consists in decoupling the sputtering of the specimen from the analysis step. In a dedicated prototype instrument, the sample surface is bombarded by an ion beam, and the sputtered particles are deposited at sub-monolayer level onto a collector. In a second step, this deposit is analyzed by SIMS (static or dynamic). In this work, we applied the Storing Matter technique to different types of polystyrene (PS) samples: a layer of PS spin-coated on a silicon wafer, the same sample covered with a thin Ag coating and a thin PS layer on an Ag substrate. These samples were sputter-deposited onto Si and Ag collectors in the Storing Matter prototype instrument. These deposits as well as the initial PS-based samples were analyzed by time-of-flight-SIMS conditions in positive mode. We compared the intensities of Ag-cationized oligomers for the different sample/collector combinations. The abundance and the intensities of Ag-cationized PS fragments detected in a Storing Matter deposit depend more strongly on the collector material than on the sample configuration used for sputter-deposition. For the deposits on Si collectors, almost no Ag-cationized peaks were detected, although such species are present in the positive mass spectra recorded directly on the Ag-containing PS samples. In the case of Ag collectors, Ag-cationized adducts were detected up to m/z = 1500. It seems that their abundance is mainly determined by the sputtering efficiency of large fragments during the sputter-deposition step. Copyright © 2012 John Wiley & Sons, Ltd.

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