SILICON INTERFACES WITH HIGH-TEMPERATURE SUPERCONDUCTORS

X-ray photoelectron spectroscopy was used to study vapor-deposition and growth of Si overlayers on polycrystalline YBa2Cu3O7 - x and (PbBi)2Sr2 - xCa1 + xCu2O8 - y. Interface reactions at low coverage for both superconductors were characterized by O withdrawal from the near-surface region of the superconductors and oxidation of the Si adatoms. Oxygen loss from the substrate resulted in substantial disruption and reduction of the nominal Cu oxidation state from 2 + to 1 + . Disruption and O loss were more extensive for YBa2Cu3O7 - x, demonstrating the higher surface stability of (PbBi)2Sr2 - xCa1 + xCu2O8 - y. Surface modification for Si/YBa2Cu3O7 - x resulted in the loss of Cu-O derived states near the Fermi level and a shift of the Fermi level in the resulting gap. A Si film formed on the reacted interface region as O redistribution was kinetically limited at higher coverages. © 1990.