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The surface characterization of a-axis EuBa/sub 2/Cu/sub 3/O/sub 7-y/ (EBCO) films sputtered onto SrTiO/sub 3/

X-ray photoemission results for interfaces prepared by cluster assembly with nanometer-size clusters deposited on high-{ital T}{sub {ital c}} superconductors (HTS's) show a reduction in reactivity because atom interactions with the surface are replaced by cluster interactions. Results for conventional atom deposition show the formation of overlayer oxides that are related to oxygen depletion and disruption of the near-surface region of the HTS's. For cluster assembly of Cr and Cu, there is a very thin reacted region on single-crystal Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8}. Reduced reactivity is observed for Cr cluster deposition on single-crystal YBa{sub 2}Cu{sub 3}O{sub 7}-based interfaces. There is no evidence of chemical modification of the surface for Ge and Au cluster assembly on Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8}(100). The overlayer grown by Au cluster assembly on Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} covers the surface at low temperature but roughening occurs upon warming to 300 K. Scanning-tunneling-microscopy results for the Au(cluster)/Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} system warmed to 300 K shows individual clusters that have coalesced into large clusters. These results offer insight into the role of surface energies and cluster interactions in determining the overlayer morphology. Transmission-electron-microscopy results for Cu cluster assembly on silica show isolated irregularly shapedmore » clusters that do not interact at low coverage. Sintering and labyrinth formation is observed at intermediate coverage and, ultimately, a continuous film is achieved at high coverage. Silica surface wetting by Cu clusters demonstrates that dispersive force are important for these small clusters.« less

Photoemission results demonstrate that atom deposition of Ti, Cr, and Cu at 20 K on the high‐temperature superconductors (HTSs) dramatically reduces interfacial reaction relative to 300 K growth but does not completely eliminate it. Thin Ti‐O or Cr‐O layers are formed during atom deposition of ∼2 A of Ti or Cr on YBa2Cu3O7 or Bi2Sr2Ca1Cu2O8 because oxygen is withdrawn from the Bi‐O and/or Cu‐O layers. Interfacial reactions are diffusion limited at 20 K, and metal overlayers nucleate on the reacted layers. These metal layers are more uniform than those grown at 300 K because clustering is suppressed. There is no additional disruption for Cr/HTS interfaces when warmed to 300 K, but increased disruption is evident for Ti/HTS interfaces. The differences reflect the stabilities of Cr and Ti in contact with their own interfacial oxide. Cu atom deposition on Bi2Sr2Ca1Cu208(100) at 20 K also leads to much less disruption than observed for deposition at 300 K.