ISO 22581:2021 Surface chemical analysis — Near real-time information from the X-ray photoelectron spectroscopy survey scan — Rules for identification of, and correction for, surface contamination by carbon-containing compounds

ISO 22581:2021 Surface chemical analysis — Near real-time information from the X-ray photoelectron spectroscopy survey scan — Rules for identification of, and correction for, surface contamination by carbon-containing compounds. 5.3 Recognition of contamination The correct identification of a given Cis peaks as being derived from and indicative of the presence of a thin film of adsorbed organic compounds is important. The ubiquitous character of a contamination film has given rise to the advice that its Cis peak can be used as a reference peak (nominally 285 eV) for correction of any electrostatic charging see ISO 19318); it is important that it is not confused with an actual component of the material surface; and it is important that it is recognised as having the characteristics of a surface film since it is only in this case that the whole spectrum can be corrected for the consequential attenuation. Recognition is based on a mix of probabilities that a contamination is present; that it is not anticipated to he present in the material sample; and that it has the characteristics of a surface film. The means to assess that these attributes are associated with the Cis peak are outlined in the following paragraphs. Each single identifierof an attribute is given in Table 1 in the form of ‘If— Then’ statements which can be utilised for computer-based, near real-time correction of the XP spectrum for the effect of a contamination film. In published work[Itl.1.]ZUl3I it was shown that the identification and characterisation of a contamination layer is reached by setting a goal, defined by an object, ‘Carbon_Contamination’, having the value ‘Yes’. The achievement of this goal marks the end of a stage in the analysis and enables further interpretation of the spectrum. It should be noted that analysts who are experts in reviewing the XPS survey spectrum will recognise the Cis peak on many materials for what it is — contamination. For them, this document will give some guidance in answering the client who asks ‘how do you know’. For non-experts it will give some assurance that they may safely assume the carbon peak to be generated by contamination but for those designing machine-assisted interpretation of a survey spectrum the analysis set out here is essential. A useful discussion of the suggested methodology, and possible pitfalls have been given b Veghl’4l and an example of its actual use in near real-time surface analysis has...