Measurements by x-ray diffraction, secondary ion mass spectrometry and atom
ic force microscopy are reported for single crystalline KTaO3 after thermal
treatment under oxidizing conditions in the temperature range of 700 to 11
00 degrees C. The formation of a series of new phases KO*(KTaO3)(n) of Rudd
lesden-Popper type is observed. Atomic force microscopy of (100) surfaces r
eveals corresponding dramatic changes in the surface morphology. Secondary
ion mass spectrometry gives evidence of a redistribution of material leadin
g to an enrichment of K with respect to Ta close to the surface and a corre
sponding depletion in deeper parts of the nearsurface region. The results a
re in strong contrast to standard point defect models. Instead, our experim
ental observations have to be interpreted in terms of an evolving chemical
inhomogeneity due to segregation processes in the near-surface region of th
e crystals and intergrowth of KO, which results in the formation of the Rud
dlesden-Popper phases. The additional effect of K2O evaporation above 900 d
egrees C is discussed and the corresponding topographical changes induced a
re documented.