The question of surface charging

Decomposition of Surface Functionality during Spectral Collection 

An important point is that surface functionality is usually sensitive to heal and may therefore be lost by decomposition caused by heat from the X-ray gun (see Section 2.3). Such decomposition is illustrated in Fig. 7, which shows how the C Is spectrum from a PAN-based carbon fiber oxidized in 0.22 M nitric acid at 2.0 V (versus SCE) changed after spectral recording for 10 and 90 min. The data were fitted using the same peak positions as those in Table 2 (discussed later) and a nonlinear background (discussed later). The amount of oxidized carbon fell from about 50% to about 40% during the period of data acquisition [11]. 

Detailed discussion of the features in the core and valence-band regions will be left until later. However, some simple observations can be made now. The 

The data in Figs. 7 and 8 were collected with achromatic x-radiation. The decomposition would have been avoided if monochromatized X-rays had been used. 

XPS Data Analysis and Interpretation of Core Chemical Shifts 

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