We analyzed the (0001) surface structures of hematite and chromia bulk single crystals bylow energy electron diffraction (LEED). The hematite crystal was annealed in anO2 atmosphere, pO2≈3 × 10−8 mbar, for several hours. The chromia crystal was sputtered withAr+ ions,E = 1 keV, and afterwardheated up to 900 °C for 5 min under ultra-high-vacuum (UHV) conditions.I(V)-curve data sets of 12 symmetrically independent diffractionspots were measured at room temperature in the energy rangeE = 150–500 eV. Charging effects hindered measurements at lower energies. Our analysis of the hematitesingle crystal surface indicates that it is terminated by a single iron layer which is occupied at≈50%. Relaxationeffects along the c-axis are quite large and involve several iron double layers. For the chromiasurface the results indicate that termination with a single Cr seems not tohold. Most probably the surface is terminated by two partially occupied Crsites or chromyl groups. Relaxations in deeper layers are small in contrast toα-Fe2O3(0001).
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