Dresden 2009 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 3: Oxides and insulators I
O 3.6: Vortrag
Montag, 23. März 2009, 12:30–12:45, SCH A01
Thin iron oxides on corundum - Raman and XRD investigations — •Alexander M. Gigler1,2, Maike Lübbe1, Robert W. Stark1,2, and Wolfgang Moritz1 — 1Sect. Crystallography, LMU-München, D-80333 München — 2Center for Nanoscience (CeNS), LMU-München, D-80799 München
Iron oxides are a material of great interest as oxidation catalyst [1], for styrene synthesis [2], for corrosion processes [3], as gas sensing material [4]. For its initial growth, a complicated behavior has been supposed including faceting [5], interface expansion [6], or formation of different iron oxide phases such as an additional metastable FeO like iron oxide phase by LEED measurements [7]. We report on the formation of magnetite (Fe3O4) and hematite (Fe2O3) on corundum (Al2O3) as observed by XRD and Raman spectroscopy. Magnetite appears independently from the substrate temperature during evaporation and cannot be removed by post-annealing in an oxygen atmosphere. The temperature range for formation of hematite was 400°C to 500°C. For 300°C, only magnetite can be observed, since growth of hematite is inhibited by the slow activation kinetics at the surface causing a lack of oxygen. For 600°C, the partial pressure of oxygen is too low for hematite growth and the phase-diagram is in favor of magnetite.
[1] G. Samsonov, The Oxide Handbook (1973). [2] M. Muhler, J. of Catalysis 138, 413 (1992). [3] S.J. Oh, Hyperfine Int. 112, 59 (1998). [4] M. Ivanovskaya, Sens. and Act. B 93, 422 (2003). [5] S.I. Yi, Surf. Sci. 443, 212 (1999). [6] T. Fujii, Surf. Sci. 366, 579 (1996). [7] S. Gota, PRB 60, 14387 (1999).