Atomic scale engineering of SrTiO3 single crystal surfaces and bicrystal boundaries for epitaxial growth of oxide thin films

We introduce a new annealing procedure to prepare well defined surfaces of SrTiO3 single crystal and bicrystal substrates. Annealing SrTiO3 (001) substrates in oxygen and then in ultra high vacuum produces a uniformly TiO2-terminated, atomically hat and ordered SrTiO3 (001) surfaces, as revealed by Auger electron spectroscopy, low energy electron diffraction, and high resolution scanning tunneling microscopy. Applying this annealing procedure to slightly off-cut (similar to 1.2 degrees) SrTiO3 (001) surfaces has a strong influence on the resulting step structure. Particular annealing procedures can be used to tailor the structure and morphology of the surface and of bicrystal boundaries down to the atomic lever. For example, steps of SrTiO3 (001) surfaces can be adjusted to a height of one, two, or multiple times the unit-cell size of STO (a(STO)=0.3905 nm). Atomically flat SrTiO3 (001) substrates were used for deposition of SmBa(2)Cu(3)O(7-)delta (SBCO) thin films. The thickness (in a range from 10 nm to 200 nm) dependency of the surface morphology of SmBa2Cu3O7-delta films was investigated with UHV-STM. No spiral growth was observed. Surfaces of all films exhibit stacks of flat terraces which are frequently separated by steps, smaller than the c-axis length c(SBCO) of SBCO (c(SBCO)=1.17 nm).