Journal de Physique IV

Issue		J. Phys. IV France Volume 04, Number C9, Novembre 1994 Proceedings of the European Symposium on Frontiers in Science and Technology with Synchrotron Radiation
Page(s)		C9-183 - C9-186
DOI		10.1051/jp4:1994931

Proceedings of the European Symposium on Frontiers in Science and Technology with Synchrotron Radiation

J. Phys. IV France 04 (1994) C9-183-C9-186
DOI: 10.1051/jp4:1994931

Oxygen 2s spectroscopy of tin oxides with synchrotron radiation-induced photoemission

J.-M. Themlin¹, J.-M. Gilles² and R.L. Johnson³

¹ Groupe de Physique des Etats Condensés, URA 783 du CNRS, Faculté des Sciences de Luminy, Case 901, 13288 Marseille cedex 9, France
² LASMOS, Facultés Universitaires Notre-Dame de la Paix, 61 rue de Bruxelles, 5000 Namur, Belgium
³ II Institute for Experimental Physics, Uni. Hamburg, 149 Luruper Chaussee, 2000 Hamburg 52, Germany

Abstract
Oxygen 2s spectroscopy can be especially useful in studies using synchrotron radiation (SR) where the deeper O 1s level frequently can not be excited. For tin oxides (SnO and SnO₂), the weak emission from the O 2s levels has been previously found degenerate with the intense photoemission peak from Sn 4d levels around a binding energy (BE) of 26 eV. By working at the Cooper minimum of the interfering tin signal, a distinct peak near BE ≈22.5 eV could be unambiguously attributed to emission from O 2s levels in tin oxides considering photoionization cross-section arguments. The O 2s intensity could now be used for the quantitative evaluation of the near-surface oxygen-species concentration. We have used the O 2s in combination with the Sn 4d areas to study the variations of the [Sn]/[O] ratio as a function of the preparation of a SnO₂ single crystal. Although the dominant formal valence state for tin determined from a Sn 4d lineshape analysis remains essentially Sn⁴⁺, we show that this [Sn]/[O] ratio can vary from simple to double. This can be explained by oxygen interstitials buried in a sub-surface region during ion bombardment, which segregate at the surface upon annealing.

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