MOLECULAR-BEAM EPITAXIAL-GROWTH OF SUPERCONDUCTING PB2SR2DY1-XCAXCU3O8-FILMS - DISORDERED SURFACE-LAYER DURING PB DEPOSITION(DELTA THIN)

Superconducting Pb2Sr2RE1-xCaxCu3O8+delta (RE = Dy, Eu) films have bee n grown by sequential deposition using the molecular beam epitaxy (MBE ) technique. The growth mechanism of these films has been studied by i n situ reflection high-energy electron diffraction (RHEED). Over the g rowth period, the intensity of the streak pattern decreases during Pb deposition and then recovers during the deposition of other elements. At an early stage of Pb deposition during initial growth, a RHEED patt ern with no sign of surface diffraction rods appears, suggesting that a liquid-like layer of Pb oxide wets the growing surface. After the li quid-like layer was re-evaporated during an intermission, the surface lattice order or flatness of the perovskite structure seemed to be imp roved. The origin of RHEED intensity oscillations is discussed and a c omparison with the case of Bi2Sr2CaCu2O8+delta is made.