SRTIO3(001) SURFACES AND GROWTH OF ULTRA-THIN GDBA2CU3O7-X FILMS STUDIED BY LEED/AES AND UHV-STM

The annealing of (001) surfaces of pure and 0.05% Nb doped SrTiO3 single crystal in UHV, HV and in O-2 in the 800-1200 degrees C temperature range has been systematically investigated. With LEED, 1x1, 2x1, and 2x2 reconstructions have been observed; they have also been imaged with STM. Our results demonstrate that an atomically hat SrTiO3 surface can be obtained by annealing the surface in HV (10(-5) mbar) at 880 degrees C or above. The surface morphology of laser ablated 1 and 2 unit-cell thick GdBCO films on such prepared substrates has been investigated by LEED/AES, and STM. LEED results indicate that the surfaces are flat and ordered. STM images suggest that the step edges of the substrate serve as the preferred nucleation sites. Possible stacking sequences near the interface and surface reconstructions of ultra-thin GdBCO films are discussed.