MICROSCOPIC STRUCTURE AND STRUCTURING OF PEROVSKITE SURFACES AND INTERFACES - SRTIO3, RBA2CU3O7-DELTA

In this paper we review investigations of the microscopic structure of SrTiO3 surfaces and bicrystal interfaces and the growth of YBa2Cu3O7- delta thin films on such substrates using scanning tunneling microscop y and X-ray diffraction. Proper annealing of SrTiO3 in oxygen and/or u ltrahigh vacuum produces uniformly terminated, atomically flat and wel l-ordered surfaces. For vicinal SrTiO3(001) surfaces the particular an nealing sequence and miscut angle sensitively determines the resulting step structure and thus the microscopic surface morphology. Steps of SrTiO3(001) surfaces can be adjusted to a height of one, two, or multi ple times the unit-cell height (a(STO) = 0.3905 nm). The growth of YBa 2Cu3O7-delta films On these substrates by pulsed laser deposition was traced from the initial nucleation to a thickness of about 300 nm. The morphology, texture, and defect structure of the films is determined by the specific structure and morphology of the pristine substrate. An isotropic, planar defects, originating from substrate step edges, stro ngly modify the electronic transport properties of the film leading to critical currents up to approximate to 9 x 10(7) A/cm(2) at 4 K as we ll as pronounced transport anisotropies. Surfaces and interface energy terms are discussed, which also determine the observed structure of b icrystal boundaries.