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Articles you may be interested inTime-of-flight secondary ion mass spectrometry with transmission of energetic primary cluster ions through foil targets Rev. Sci. Instrum. 85, 033107 (2014); 10.1063/1.4869036Self-assembled monolayers for polymer and protein cationization with time-of-flight secondary ion mass spectrometry J.Timeofflight static secondary ion mass spectrometry of additives on polymer surfaces J. Vac. Sci. Technol. A 9, 1307 (1991); 10.1116/1.577617 MASTIF: Mass analysis of secondaries by timeofflight technique. A new approach to secondary ion mass spectrometry Rev. Sci. Instrum. 60, 3188 (1989);A pulsed alkaliion gun for timeofflight secondary ion mass spectrometry Rev.Secondary ion formation from polystyrene standards with well-defined molecular weight distributions between 10 3 and 10 6 amu has systematically been investigated. Maximum yields of cationized fragments and oligomers are obtained from silver substrates covered by about one monolayer of polymer material. Intact o1igomers of polystyrene are detected in the mass range up to 10 000 amu. Disappearance cross sections of sputtered molecules are correlated to the size of the des orbed species and increase almost linearly with mass. Transformation probabilities of catlonized oligomers decrease by about three orders of magnitude between 1000 and 10 000 amu. Number and weight average molecular weights (M", Mw) determined from peak intensities of intact polymer molecules compare well with data from gel permeation chromatography, A correction of Mn and Mw for decreasing transformation probabilities is necessary for broad molecular weight distributions. The formation of high molecular weight fragment ions can be explained by a statistical main chain scission. For polystyrenes with Mn > 10 000 amu the emission offragment ions in the mass range between 500 and 5000 amu seems to be independent of the chain length of the original polymer.

A new charge compensation system for time-of-flight (TOF) secondary ion mass spectrometry is described. A pulsed low-energy electron source (10 eV) in combination with a pulsed extraction voltage of the TOF analyzer allows low-energy electrons to reach the target in the relatively long period of time between two excitation pulses. Low-energy electrons allow self-adjusting of the surface potential. Sample damages by these electrons are not detectable. Effects due to electron stimulated desorption are suppressed by pulsing the anode of the electron source. Compensation is possible for the accumulation of positive as well as negative spectra. With this experimental arrangement we investigated a variety of insulating materials (e.g., thick polymer films, glasses, ceramics). In all cases we found stable and reproducible spectra, even of insulators with extremely low conductivity.

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SynopsisNegative secondary ion mass spectra of poly(methylmethacry1ate) (PMMA), poly(ethy1methacrylate) (PEMA), and two copolymers of methylmethacrylate (MMA) and ethylmethacrylate (EMA) are presented. The spectra were obtained with a time of flight-static secondary ion mass spectrometer without charge compensation. The structures of typical ions in the mass range 20-220 amu are given, and the intensities of these ions were used to obtain some quantitative information about the ion formation processes. It is shown that quantification of a simple two-component system like the copolymers mentioned above is rather straightforward.