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Lübbe, M.; Moritz, Wolfgang (2009): A LEED analysis of the clean surfaces of α-Fe2O 3(0001) and α-Cr2O3(0001) bulk single crystals. In: Journal of Physics Condensed Matter, Vol. 21, No. 13
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We analyzed the (0001) surface structures of hematite and chromia bulk single crystals by low energy electron diffraction (LEED). The hematite crystal was annealed in an O2 atmosphere, pO2≈3 × 10 -8mbar, for several hours. The chromia crystal was sputtered with Ar+ ions, E = 1keV, and afterward heated up to 900°C for 5min under ultra-high-vacuum (UHV) conditions. I(V)-curve data sets of 12 symmetrically independent diffraction spots were measured at room temperature in the energy range E = 150-500eV. Charging effects hindered measurements at lower energies. Our analysis of the hematite single crystal surface indicates that it is terminated by a single iron layer which is occupied at ≈50\%. Relaxation effects along the c-axis are quite large and involve several iron double layers. For the chromia surface the results indicate that termination with a single Cr seems not to hold. Most probably the surface is terminated by two partially occupied Cr sites or chromyl groups. Relaxations in deeper layers are small in contrast to α-Fe2O3(0001).