| AVS 62nd International Symposium & Exhibition | |
| Applied Surface Science | Thursday Sessions |
| Session AS+SS-ThA |
| Session: | Advances in 2D Chemical Mapping and Data Analysis |
| Presenter: | Adam Roberts, Kratos Analytical Limited, UK |
| Authors: | A.J. Roberts, Kratos Analytical Limited, UK N. Fairley, Casa Softaware Ltd, UK J.R. Mora, University of Durham, UK |
| Correspondent: | Click to Email |
X-ray photoelectron spectroscopy is widely used in determining surface chemistry of materials. Improvements in instrument sensitivity mean that spectra are routinely acquired from areas with diameters in the tens of microns, although most routine analysis is performed at much larger areas. The assumption is that the material and spectra are homogeneous over the area probed is often made although it may not be true. Information of the lateral distribution of elemental and chemical states on a surface can be probed using XPS imaging either at a single binding (kinetic) energy or over a narrow energy range corresponding to a core-level photoemission peak.
Multispectral XPS imaging, also referred to as spectromicroscopy, where a series of images incremented in energy such that each pixel contains a spectrum, is relatively new and under exploited for surface characterisation. An advantage of spectromicroscopy is that spectral information can be reconstructed from defined areas which are smaller than those possible with focused x-ray or virtual probe selected area XPS. This means that the reconstructed spectra are no longer averaged over the total area from which the image is acquired such that both sample and instrument dependent differences can be studied.
The 256 x 256 pixel multi-spectral image contains >65,500 spectra which is ideally suited to multivariate analysis. Development of data processing to support spectromicroscopy data reduction has been necessary and a number of approaches have been successfully applied in the characterisation of model and real-world samples[1-3]. Multivariate analysis can be used to classify regions of interest across the field of view and data can be partitioned such that chemical state, changes in peak position and background shape can be investigated. Here we detail the use of spectromicroscopy for the characterisation of complex materials including functionalised multiwall carbon nanotubes (MWCNT). This approach has allowed the considerable challenges of surface analysis of such materials to be addressed and has allowed the influence of signal from the substrate material to be removed from the MWCNT of interest.
References[1] E.F. Smith, D. Briggs and N. Fairley Surf. Interface Anal. 2005, 38, 69-75
[2] J. Walton, N. Fairley Surf. Interface Anal. 2008, 40, 478 - 481
[3] A.J. Barlow, O. Scott, N. Sano and P.J. Cumpson Surf. Interface Anal. 2015, 47, 173-175