Adventitious carbon—the panacea for energy referencing?

Abstract

A brief historical review has been made of the values assigned to the binding energy of Cls electrons from hydrocarbon contamination on sample surfaces. The particular energy calibration technique used for each electron spectrometer on which the CIS determination was made has been identified. There are notable variations in the CIS electron binding energy for a hydrocarbon contamination layer with respect to the substrate on which it was measured. The possible source and nature of adventitious carbon have been discussed, as have factors which can affect its Cls binding energy value. Sodium phosphate salts have been used to illustrate the relative merits of using an internal energy reference line rather than the Cls electrons from the adventitious carbon layers of these salts. Alternative energy referencing techniques, which include deposition of soot from a candle flame and deliberate 'in situ' condensation of a volatile organic compound onto the sample surface, have been compared with the method under review. Another possible method is the mixing of powdered samples with reference compounds (e.g. graphite). It is concluded that, although the use of Cls electrons from adventitious carbon layers is often a convenient method of energy referencing, interpretation of binding energy data obtained should be treated with caution.

X-ray photoelectron spectroscopy study of the passive films formed on thermally sprayed and wrought Inconel 625

“…were identified in both the wrought and coated samples, details of the species identified are presented in Appendix A and Appendix B. Charge correction was performed with respect to the C1s peak at 285eV, which was common to all samples and was attributed to adventitious carbon contamination [11]. The satellite peak of the Ni2p region both for the metal and oxide form is a well known feature associated with some elements such as Ni [12], however our analysis only considers the main photoelectric peaks.…”

Spectroscopic and Theoretical Study of the Grafting Modes of Phosphonic Acids on ZnO Nanorods

“…The XPS binding energy (BE) scale was calibrated by centering C 1s peak due to hydrocarbon moieties and "adventitious" carbon at 285.0 eV. 36,37 Transmission FTIR measurements were recorded on a JASCO FTIR 430, using the KBr pellet technique, with 100 scans collected per spectrum (scan range 560−4000 cm −1 , resolution 4 cm −1 ). SEM micrographs were obtained using a LEO SUPRA 55VP equipped with a field emission gun.…”

Determination of chromium valence over the range Cr(0)–Cr(VI) by electron energy loss spectroscopy

“…In XPS. Various methods are used for referencing XPSaddition, the Cr-L 2 , 3 edges of Cr(VI) are further differmeasured binding energies that lead to differences of up to entiated in that they appear asymmetric because each is 0.5eV in reported energies [84]. The literature values in split into two not fully resolved peaks separated by -2 eV.…”