Multitechnique Fusion of Imaging Data for Heterogeneous Materials

Abstract

Complete characterization of a complex multicomponent heterogeneous material requires information not only on the surface or bulk chemical components, but also on stereometric features such as size, distance, and heterogeneity in three-dimensional space. Probing vertical structures is equally important for nanocomposite materials with surface segregation, overlayers, concentration gradients or multiple layers. Such complexity of heterogeneous materials makes it difficult to uniquely distinguish between alternative morphologies using a single analytical method and routine data acquisition and analysis. The combination of sputtering capabilities and high lateral resolution in images led to the wide spread use of three-dimensional imaging studies using Time-of-flight Secondary Ion Mass Spectrometry (TOF-SIMS). (Wucher et al., 2007; Delcorte, 2008; Jones et al., 2008; Rafati et al., 2008) Main drawback of this approach is limited quantitative information. X-ray Photoelectron Spectroscopy (XPS) has benefits of being quantitative and offers very similar capabilities in combining ion sputtering and imaging, and there have been a handful number of studies using this approach. (Gao et al., 2003; Artyushkova, 2010) Disadvantage of combining sputtering and imaging is its destructive nature and possibility of induced modification that may introduce artifacts within images. XPS has the advantage of being one of the only surface analysis techniques that provides readily interpretable, surface-specific, chemical information, which is a core analytical method of choice in obtaining surface chemical composition. (Briggs & Grant, 2003) The development of commercial imaging XPS instrumentation has occurred in parallel with imaging developments in other spectroscopic techniques. Improved spatial resolution and decreased analysis time make it possible to correlate XPS analysis with a host of other imaging techniques which have comparable fields of view, but different information content from different depth levels. There is now some field of view (FOV) overlap between XPS and a variety of techniques, including Atomic Force Microscopy (AFM), imaging FTIR, confocal microscopy (CM), SIMS and Secondary Electron Microscopy (SEM). The overlapping FOVs for the techniques listed in Table 1 make correlative data analyses and a fusion of multiple analytical perspectives achievable and valuable for obtaining quantitative structural information in three dimensions. Imaging using confocal microscopy provides three-dimensional, high-resolution, non-destructive imaging of sample features. (Fellers & Davidso; Pawley, 2006) Scanning