Pure and cobalt-doped SnO2(101) films grown by molecular beam epitaxy on Al2O3

M. Batzill, J. M. Burst, U. Diebold

Department of Physics, Tulane University, New Orleans, Louisiana 70118, U.S.A.
Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, 44780 Bochum, Germany

Thin Solid Films 484 (2005) 132-139

Pure and Co-doped epitaxial SnO2 films grown by oxygen plasma assisted molecular beam epitaxy on r-cut α-alumina substrates were investigated by electron diffraction, X-ray photoelectron spectroscopy (XPS), and X-ray photoelectron diffraction (XPD). On hot alumina substrates (∼ 800 °C) only a submonolayer amount of Sn adsorbs, indicating a strong adhesion of the first monolayer of tin on the alumina surface. SnO2 films grown at ∼400-600 °C substrate temperature exhibit a SnO2(101)[010]||Al2O3(-1012)[12-10] epitaxial relationship. Subtle differences in the XPD data of SnO2 films compared to measurements on SnO2(101) single crystal surfaces are consistent with the presence of a high density of stoichiometric antiphase domain boundaries in the film. These planar defects are introduced in the SnO2 film to compensate for the more than 10% lattice mismatch between the SnO2 films and the alumina substrate along the SnO2[-101] direction. CoxSn1-xO2 films with a Co-cation concentration of 5-15% were also grown. XPS indicates that Co is in a 2+ oxidation state and XPD shows that tin is replaced substitutionally by Co.

Corresponding author: U. Diebold (diebold at iap_tuwien_ac_at).

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