Journal Article Photoelectron Holographic Atomic Arrangement Imaging of Cleaved Bimetal-intercalated Graphite Superconductor Surface

Matsui, Fumihiko  ,  Eguchi, Ritsuko  ,  Nishiyama, Saki  ,  Izumi, Masanari  ,  Uesugi, Eri  ,  Goto, Hidenori  ,  Matsushita, Tomohiro  ,  Sugita, Kenji  ,  Daimon, Hiroshi  ,  Hamamoto, Yuji  ,  Hamada, Ikutaro  ,  Morikawa, Yoshitada  ,  Kubozono, Yoshihiro

2016-11-04 , Macmillan Publishers
From the C 1s and K 2p photoelectron holograms, we directly reconstructed atomic images of the cleaved surface of a bimetal-intercalated graphite superconductor, (Ca, K)C8, which differed substantially from the expected bulk crystal structure based on x-ray diffraction (XRD) measurements. Graphene atomic images were collected in the in-plane cross sections of the layers 3.3 Å and 5.7 Å above the photoelectron emitter C atom and the stacking structures were determined as AB- and AA-type, respectively. The intercalant metal atom layer was found between two AA-stacked graphenes. The K atomic image revealing 2 × 2 periodicity, occupying every second centre site of C hexagonal columns, was reconstructed, and the Ca 2p peak intensity in the photoelectron spectra of (Ca, K)C8 from the cleaved surface was less than a few hundredths of the K 2p peak intensity. These observations indicated that cleavage preferentially occurs at the KC8 layers containing no Ca atoms.

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