Binding Energy and Chemical Shift

It became common in the early development of X-ray photoelectron spectroscopy (XPS or ESCA) for users to classify some of the shifts detected for elemental covalent bonding energy peaks following changes in the chemistry of that element as a chemical shift. This section will describe how Eb can be affected and how measurement of Eb can be used to analyze the materials chemistry. Using current nomenclature and/or arguments, the problem of accurately measuring 

As demonstrated in the selected examples that follow, it is very difficult to achieve detailed closure on the arguments concerning the degree to which one may directly relate measured binding energy shifts to changes in the chemistry. 

1 The Initial vs Final State Binding Energy Problem 

The essential features of the dilemma rest on several points. First, as is well known, the measured core level chemical shifts for many oxides (M Oy) symbolized as (M ) relative to their respective metal elemental (M°) states are often quite small, that is. 

Nothing is seriously wrong with the size or the progression of these values unless one considers the following. 

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Only one carbonyl component appears in the NR-055X spectrum after the 300 C cure treatment. Its 3.8 eV chemical shift is consistent with imide. The F binding energy and chemical shift values were identical to those observed for the polyamic acid. The most intense C Is component peak characteristics showed little change with temperature spanning 85 -400 C. 

Gelius, U. (1974). Binding Energies and Chemical Shifts in ESCA. Phys.Scr, 9,133-147. 

Triguero L, Plashkevych O, Pettersson L, Agren H (1999) Separate state vs transition state Kohn-Sham calculations of X-ray photoelectron binding energies and chemical shifts. J Electron Spectrosc Relat Phenom 104 195-207... 

XPS Binding Energies and Chemical Shifts. The interpretation of the binding energies of the P2p and of the curve-fitted 01s spectra provides an insight into the binding of the phosphate headgroup of the ODP molecule at the surface. 

Finally one should be aware that the interpretation of electron spectroscopic results for insulating samples raises the very difficult question of the nature of the screening. Our ignorance of the exact screening mechanism in insulators should make us cautious in the analysis of binding energies and chemical shifts, particularly when metallic and insulating systems are compared (see section 6.2.1). 

Figure 6. Comparison of Si 2p binding energies from XPS and chemical shifts from NMR. No Si data is available for the S1-VPI-5A sample.

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