Valence bands, oxygen in planes and chains, and surface changes for single crystals of M/sub 2/CuO/sub 4/ and MBa/sub 2/Cu/sub 3/O/sub x/ (M = Pr,Nd,Eu,Gd)

Journal Article · Thu Sep 01 00:00:00 EDT 1988 · Phys. Rev. B: Condens. Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.38.4668· OSTI ID:6844732

Weaver, J H; Meyer, III, H M; Wagener, T J; Hill, D M; Gao, Y; Peterson, D; Fisk, Z; Arko, A J

X-ray photoemission results for single crystals of M/sub 2/CuO/sub 4/ (M = Pr,Eu,Gd), MBa/sub 2/Cu/sub 3/O/sub x/ (M = Nd,Gd), and CuO are sintered La/sub 1.85/Sr/sub 0.15/CuO/sub 4/ and YBa/sub 2/Cu/sub 3/O/sub 6.9/ show valence-band spectra within 10 eV of the Fermi energy that are remarkably similar in appearance, with contributions that reflect Cu-O hybrid states and the rare-earth 4f states. For Pr/sub 2/CuO/sub 4/ and NdBa/sub 2/Cu/sub 3/O/sub x/, there are two distinct 4f features due to ligand screening in the photoemission final state. The rare-earth 5p core-level emission overlaps the O 2s emission and reveals complex 5p-4f multiplet interactions. All O 1s spectra show a dominant peak at /similar to/528 eV that can be resolved into features separated by /similar to/0.7 eV. These reflect inequivalent oxygen bonding configurations in the lattice and are associated with the planes and chains for the 1:2:3 compounds and the planes and off-planes for the 2:1:4 compounds. The lower-binding-energy feature is associated with the Cu-O chains of the 1:2:3 compounds and the Cu-O planes of the 2:1:4 compounds. In addition to the O 1s main line for the Cu-O planes there is also a weak satellite. Time dependent studies of the Cu 2p and O 1s emission indicate surface modification, dependent upon the quality of the cleave. The effects of surface changes and the presence of imperfections are discussed in the context of surface studies and surface superconductivity.

• Research Organization: Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455
• OSTI ID: 6844732
• Journal Information: Phys. Rev. B: Condens. Matter; (United States), Vol. 38:7
• Country of Publication: United States
• Language: English

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