| AVS 64th International Symposium & Exhibition | |
| Applied Surface Science Division | Tuesday Sessions |
| Session AS+MI+SS-TuM |
| Session: | Quantitative Surface Analysis: Effective Quantitation Strategies |
| Presenter: | Dagoberto Cabrera-German, Universidad de Sonora, Mexico |
| Authors: | D. Cabrera-German, Universidad de Sonora, Mexico G. Molar-Velazquez, CINVESTAV-Unidad Queretaro, Mexico G. Gómez-Sosa, CINVESTAV-Unidad Queretaro, Mexico W. De la Cruz, Universidad Nacional Autónoma de México A. Herrera-Gomez, CINVESTAV-Unidad Queretaro, Mexico |
| Correspondent: | Click to Email |
The quantitative analysis of the X-ray photoelectron spectra of Zn and ZnO is a challenging task due to plasmon-loss features and small binding energy shifts that lead to inaccurate results on the assessment of the chemical state of mixed systems of metallic zinc and zinc oxide.[1] Additionally, the Zn 2p spectra hold a complex background that traditional background modeling methods are unable to reproduce accurately.
We have analyzed the Zn 2p and O 1s spectra of a metallic Zn film that has been subject to pressure and time controlled oxidations at high vacuum. Through the state-of-the-art peak-fitting methods[2–4] we have overcome the difficulties, as mentioned earlier, of performing a quantitative analysis of a metal and oxide system and we have also noted several interesting features of the Zn 2p spectrum.
We found that the assessed chemical composition for several oxygen exposures is ZnO1.00±0.10, this suggests that the set of peak parameters employed to resolve the metallic and oxide photoemission signals, are accurate and can be applied in quantitative studies.
The main characteristic of the peak-fitting procedure is that close experimental data reproduction requires an individual assignment of Shirley backgrounds for each peak comprising the spectra. Therefore an accurate quantitative analysis can only be done employing the Shirley-Vegh-Salvi-Castle (SVSC) background under the active approach.[2–4]
Another feature is that the intensity of plasmon-peaks and their background are not accurately described by any existing energy loss (intrinsic and extrinsic) formalism. In fact, the modeling of their background trend requires the addition of an intense Shirley contribution, up to 10 times larger than the Shirley contribution of the main photoemission line. These are outstanding results that suggest that these plasmon-peaks are produced by a loss process that remains unaccounted.
[1] M.C. Biesinger, L.W.M. Lau, A.R. Gerson, R.S.C. Smart, Resolving surface chemical states in XPS analysis of first row transition metals, oxides and hydroxides: Sc, Ti, V, Cu and Zn, Appl. Surf. Sci. 257 (2010) 887–898.
[2] J. Végh, The analytical form of the Shirley-type background, J. Electron Spectros . Relat. Phenomena. 46 (1988) 411–417.
[3] A.M. Salvi, J.E. Castle, The intrinsic asymmetry of photoelectron peaks: dependence on chemical state and role in curve fitting., J. Electron Spectros . Relat. Phenomena. 95 (1998) 45–56.
[4] A. Herrera-Gomez, M. Bravo-Sanchez, O. Ceballos-Sanchez, M.O. Vazquez-Lepe, Practical methods for background subtraction in photoemission spectra, Surf. Interface Anal. 46 (2014) 897–905.