Specular beam intensity and surface morphology of BSCO films grown by MBE

Bi-Sr-Cu-O (BSCO) thin films have been epitaxially grown on cleaned SrTiO₃ (001) substrates by a sequentially shutter-controlled molecular beam epitaxy system using an oxygen radical beam. A spot intensity of specular beam in in-situ reflection high-energy electron diffraction (RHEED) was monitored during the atomic layer epitaxy. Atomic force microscopy (AFM) images of the epitaxial thin films were observed in the atmosphere at some oscillation points of the specular beam intensities. The chemical composition ratios of the films (about 100 Å) were determined from intensities of X-ray photoemission spectroscopy. The crystallinity of the films was measured by X-ray diffraction.

The amount of metal deposition corresponding to a half cycle of the intensity oscillation of the specular spot was found to be appropriate to form the flat surface. Characteristic islands were found at the surfaces covered with excess bismuth or excess copper atoms in the AFM image. The intrinsic modulated structure of the BSCO crystal was observed at the surface after the first copper deposition on Sr/Bi/SrTiO₃ in the RHEED pattern.