Surface heterogeneity in KTaO₃ (001)

Surface heterogeneity in Ar⁺ ion bombarded samples of (001) oriented KTaO₃ was studied using (in-situ) electron microscopy and atomic force microscopy. Ion bombardment results in surface damage as well as in off-stoichiometry of K and Ta due to the large differences in atomic radii of the two constituent elements and hence different dry etching rates. Subsequent annealing of such samples reduces the potassium content via vaporization and results in the formation of tantalum-rich secondary phases on the surface. The phase that segregates on the surface is dependent on the oxygen partial pressure, annealing temperature as well as K:Ta stoichiometry. However, samples etched with chemical means to remove lattice damage and surface disorder prior to annealing exhibit little to no surface heterogeneity.