VICINAL FACES ON SYNTHETIC GOETHITE OBSERVED BY ATOMIC-FORCE MICROSCOPY

In this paper atomic force microscopy-studies are reported suggesting the existence of vicinal faces on the (100) plane of artificially grow n goethite. Goethite crystals are commonly regarded to have boundary p lanes of (100), (010) and (001) faces. In contradiction to these theor etical models TEM and SEM images exhibit (110) and (021) faces to be d ominating. These goethite particles consist of many crystallographic c oherent domains so that the existence of dislocations on the surfaces has to be assumed. These sites on the surfaces may serve as a nucleati on site for the formation of steps. The vicinal faces on the (100) fac e found with the AFM are (021) faces. They influence the growth veloci ty of the (100) face to such a degree, that this face vanishes and onl y (110) faces remain as stable boundary surfaces. The (021) faces are also stable, but have the highest growth rate among the faces consider ed.