GEOC 68 |
| The ability to control surface morphology at the nanometer scale may enhance several technological applications for alpha-Fe2O3 (0001) including catalysis, photoelectrochemistry, magnetic data storage, and spintronics. In pursuit of this goal, atomic force microscopy is employed to study the nanoscale morphology of alpha-Fe2O3 following annealing treatments in oxygen-rich atmospheres. The alpha-Fe2O3 (0001) crystals were grown via chemical vapor transport using the equilibrium reaction. [1] [2] [3] Upon annealing the crystals in oxygen rich atmospheres at 900°C for 2 hours, the originally featureless surface was transformed to one with broad (~100 microns wide) atomically flat terraces separated by narrow (~1 microns wide) regions with dense step bunching. The terraces support two-dimensional circular domains with diameters on the order of hundreds of nanometers and depths of 2.2 ± 0.2 Å. The domains extend across >90% of the surface and can locally coalesce to form layered domains that are multiple unit cell lengths deep. The formation of these circular domain structures are consistent with a theoretical model based on relatively long range repulsive dipole interactions among the domains. [4] [5] [6] The generality of this model will be discussed by comparing the case of circular domains in alpha-Fe2O3 with similar domain formation observed in other oxide systems (e.g., SrTiO3 and TiO2). [1] V.P. Kleinert, Z Anorg Allgem Chem 378 (1970) 71. [2] K.R. Poepplemeier & B.B. Ansell, J Crystal Growth 51 (1981), 587. [3] H. Schäfer, Chemical Transport Reactions, New York, Academic Press, 1964. [4] K.-O. Ng & D. Vanderbilt, 52 (1995) 2177. [5] R. Plass, J.A. Last, N.C. Bartlett, & G.L. Kellogg, Nature, 412 (2001) 875. [6] J.B. Hannon, J. Tersoff, & R.M. Tromp, Science 295 (2002) 299. |
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Research, Education and Outreach in the NSF Environmental Molecular Science Institutes
8:00 AM-12:00 PM, Tuesday, 30 August 2005 Washington DC Convention Center -- 204C, Oral
Division of Geochemistry |