SURFACE CRYSTALLOGRAPHY OF HAEMATITE

Abstract

The surface crystallography of haematite (α- Fe 2 O 3) has been investigated for [Formula: see text], [Formula: see text], {0006} and [Formula: see text] facets using atomic resolution surface profile imaging and computer-simulated image-matching. A remarkable variety of surface depolarizing mechanisms was observed, which included monolayer relaxation and reconstruction, as well as oriented overgrowth with monolayer compound formation and essentially electronic transitions without significant atomic displacements. These mechanisms were found to apply with different emphasis for different facets. The structural results are discussed in terms of surface depolarization including doublelayer and electronic mechanisms, coherency strains for monolayer compound formation of spinel-type structure onto haematite, electron-induced and chemical oxygen desorption mechanisms. Comparisons of haematite and sapphire surface crystallographies have been included in the discussion.