| AVS 61st International Symposium & Exhibition | |
| Applied Surface Science | Monday Sessions |
| Session AS+MC-MoM |
| Session: | Quantitative Surface Analysis |
| Presenter: | Alberto Herrera-Gomez, CINVESTAV-Queretaro, Mexico |
| Authors: | A. Herrera-Gomez, CINVESTAV-Queretaro, Mexico M.O. Vazquez-Lepe, Universidad de Guadalajara, Mexico P.G. Mani-Gonzalez, Universidad Autónoma de Ciudad Juárez, Mexico O. Ceballos-Sanchez, CINVESTAV-Queretaro, Mexico |
| Correspondent: | Click to Email |
Because of the technological relevance of the Si [001] surface, the Si 2p is one of the most studied core levels with laboratory X-Ray Photoelectron Spectroscopy (XPS). An important application is the quantification of the thickness of oxide layer, which is done by comparing the intensity of the substrate and Si4+ components. Peak-fitting is usually done by employing one doublet for the substrate and another for the Si4+ shifted around 3.5 or 4 eV to higher binding energy (from the substrate). In detailed studies, the quantification of the suboxides is usually done employing components, originally proposed by Himpsel et al.,1 with the following shifts: 2.5 eV for Si3+, 1.75 eV for Si2+, and 0.95 eV for Si1+. A proper fit, besides those five components, actually requires a six component shifted by approximately 0.3 eV. This peak has been clearly identified in various synchrotron studies such as that by Landemark et al.,2 where it is referred as S’. In that study, and in others, it is assigned to one monolayer (the second) of the substrate. Although clearly present in Si 2p spectra obtained with laboratory XPS equipped with monochromatized Al Kα radiation, this component is largely unspoken in the literature. In one of the few studies that mention its existence it is assigned to an asymmetry of the bulk peak.3 In this presentation it is going to be shown that this interpretation is inconsistent with the angular dependence observed by S’. The physical origin of S’, which is going to be discussed in detail, goes in a direction compatible with that proposed by Landemark et al.: although it represents one monolayer for the clean Si [001] surface, for oxide-covered surfaces it corresponds to a few monolayers of the substrate.
[1] F. J. Himpsel, F. R. McFeely, A. Taleb-Ibrahimi, and J. A. Yarmoff, Phys. Rev. B 38, 6084 (1998).
[2] E. Landemark, C. J. Karlsson, Y.-C. Chao, and R. I. G. Uhrberg, Phys. Rev. Lett. 60, 1588 (1992).
[3] D. F. Mitchell, K. B. Clark, J. A. Bardwell, W. N. Lennard, G. R. Massoumi and I. V. Mitchell. Surf. Inter. Anal. 21. 44-50 (1994).