Multivariate Auger Feature Imaging (MAFI) - a new approach towards chemical state identification of novel carbons in XPS imaging

Abstract

The clear identification of allotropes and similar chemical states of carbon in XPS imaging can be made difficult because of the subtle differences observed in spectra, particularly when varying from sp2 to sp3 hybridised carbon. By shifting focus from the commonly analysed C1s region in XPS spectra to the often ignored C KVV region, we utilise the so‐called D‐Parameter to identify different forms of carbon in a surface. When this methodology is applied to XPS imaging, the result is a powerful and unambiguous tool for the chemical state identification of carbon in XPS images. Further enhancement by multivariate statistics improves XPS spectral and image quality, and we call this technique Multivariate Auger Feature Imaging. Herein, we have applied this technique to clearly identify in XPS imaging a graphite film mounted on carbon tape. Copyright © 2015 John Wiley & Sons, Ltd.

Detecting carbon in carbon: Exploiting differential charging to obtain information on the chemical identity and spatial location of carbon nanotube aggregates in composites by imaging X-ray photoelectron spectroscopy

“…Recently, XPS characterization of a CNT: poly(vinyl alcohol) (PVA) composite series was effectively demonstrated using peak fitting by taking advantage of minor differential charging to calculate the relative surface percentage of carbon species from nanofiller and matrix material 28 . Other approaches have employed XPS imaging through analysis of the carbon Auger feature to differentiate graphitic carbon (sp 2 hybridized) from an adhesive carbon (sp 3 hybridized) background (comparable with CNT and polymeric carbon, respectively) to spatially separate different carbon components 29 .…”

Imaging XPS for industrial applications

“…To further map such carbon variances, Barlow and co-workers derived the so-called Multivariate Auger Feature Imaging (MAFI) method for differentiating between sp 2 and sp 3 carbon, through imaging the x-ray induced C(KLL) auger feature [59,60], which itself is derived from the work of Lascovich et al [61], who derived the "D-parameter" to quantify the amount of sp 2 carbon present in a sample. Application of the MAFI technique, clearly provides strong and unambiguous identification of areas of varying sp 2 content in a rapid fashion.…”

Challenges in imaging and predictive modeling of rhizosphere processes

“…The former has been applied to map C forms in air-dried thin slices taken from soil micro-aggregates ) and was combined with nearedge X-ray absorption fine structure spectroscopy (NEXAFS) for mapping of total organic C content. XPS has the potential to be used for imaging (Barlow et al 2015). Matrix-assisted laser desorption/ionization mass spectroscopy (MALDI-MS) is another high resolution method, which is able to map the spatial distribution of specific substances including individual effective compounds of pesticides and their metabolites.…”