Peak-fitting of high resolution ToF-SIMS spectra: a preliminary study

Peak-fitting has been performed on a series of peaks obtained by time-of-flight secondary ion mass spectrometry (ToF-SIMS) analysis in order to assess whether information may be obtained from this procedure on the sa m pies' characteristics. A variety of samples were examined including a range of treatments for aluminium leading to different surface roughnesses, polymer films with a range of polydispersities, molecular weight (MW) and thicknesses as well as aluminium samples with adsorbed adhesion promoters on the surface. Variation of peak-fitting was assessed by varying the peak intensity, full width at half maximum (FWHM) and peak asymmetry. Although further studies are needed it is possible to say that the peak width increases with roughness whereas peak asymmetry seems to be related to oxide thickness. Polymer characteristics do not seem to influence the width whereas the peak asymmetry increases either versus MW or polydispersity. A possible assumption is that the peak asymmetry relates to the ion formation processes. Additional work with varying polymer films thickness indicates that both FWHM and peak asymmetry may be related to sample charging and this could be used for assessment of film thicknesses. Finally, peak-fitting was used to obtain a more reliable peak area when peaks are too close in mass to use current methods. Copyright (C) 2009 John Wiley & Sons, Ltd.