Surface and interface properties of high-temperature superconductors

This paper presents photoemission and inverse photoemission results for a number of copper-oxide-based polycrystalline and single crystalline 2-1-4, 1-2-3, and 2-1-2-2 compounds. It is demonstrated that it is possible to identify those parts of the valence band and core level emission features which are intrinsic to the superconductor and those which are due to grain boundary phases. A number of overlayer/superconductor interface problems was examined, reviewing the effects of deposition of adatoms of reactive metals and semiconductors (Ti, Fe, Cu, Pd, La, Al, In, Bi, and Ge). It is shown that Bi2O3 and CaF2 can be used to form layers for passivation and encapsulation.