| Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2014) | |
| Thin Films | Wednesday Sessions |
| Session TF-WeP |
| Session: | Thin Films Poster Session |
| Presenter: | Gustavo Gomez-Sosa, CINVESTAV-Unidad Queretaro, Mexico |
| Authors: | G. Gomez-Sosa, CINVESTAV-Unidad Queretaro, Mexico J.A. Torres-Ochoa, CINVESTAV-Unidad Queretaro, Mexico M. Bravo-Sanchez, CINVESTAV-Unidad Queretaro, Mexico J.H. Mata-Salazar, CINVESTAV-Unidad Queretaro, Mexico D. Cabrera- German, CINVESTAV-Unidad Queretaro, Mexico J. Ibarra-Nuno, CINVESTAV-Unidad Queretaro, Mexico A. Herrera-Gomez, CINVESTAV-Unidad Queretaro, Mexico |
| Correspondent: | Click to Email |
The current methods for quantitative analysis of X-ray photoelectron spectroscopy (XPS) data are clearly insufficient for closely reproducing the high asymmetry and strong background signal of the core level peaks of transition metals and their oxides. Using the double-Lorentzian asymmetric line-shape [1] and the active background approach [2], it is possible to obtain close fits to these core levels. The samples were prepared by metal sublimation on Si (100) wafers. The asymmetry factor found from the analysis was 1.83 for Ni 2p, 2.84 for Cr 2p and 2.9 for Co 2p. Previously unreported shake-up satellites were identified at 0.45, 1.1 and 1.9 eV away from the main peak in the metallic films of the Cr 2p, Co 2p and Ni 2p core levels, respectively. The evolution of the oxidation of metals was also studied by exposing metallic films to UHP oxygen in a range from 4 L to 400 GL. Further oxidation was obtained using a tubular oven with UHP oxygen with positive pressure. The final thickness of oxide films ranged from 2 to 3 nm. The composition was calculated employing the MultiLayer Model. The close agreement with the expected values (1:1 for nickel oxide, NiO; 2:3 for chromium oxide, Cr2O3; and 1:1 for cobalt oxide, CoO) validates the peak areas obtained with the double-Lorentzian line-shape.
Acknowledgements: This work was supported in part by CONACyT Projects INFR-2011-01 #163219 and CB-2012-01 #179304. The authors would like to acknowledge Alfredo Muñoz for his technical support.
References
[1] A. Herrera-Gomez. A double Lorentzian shape for asymmetric photoelectron peaks. Internal Report. Cinvestav-Querétaro (2011). http://www.qro.cinvestav.mx/~aherrera/reportesInternos/doubleLorentzian.pdf
[2] A. Herrera-Gomez, M. Bravo-Sanchez, O. Ceballos-Sanchez, and M.O. Vazquez-Lepe. Practical methods for background subtraction in photoemission spectra. Journal of Electron Spectroscopy and Related Phenomena (in press) DOI/ 10.1002/sia.5453.