Photoemission investigations of the high-Tc superconductor BiSrCaCuO

doi:10.1016/0921-4534(88)90810-6

Physica C: Superconductivity

Volume 156, Issue 2, 1 September 1988, Pages 213-220

https://doi.org/10.1016/0921-4534(88)90810-6 Get rights and content

Abstract

XPS and UPS photoemission experiments on several multiphased samples of the high-T_c superconductor BiSrCaCuO with a composition around Bi₂Sr₂CaCu₂O_8+x and zero resistivity below 77 K showed the following results:

1.
(1) The samples are easily cleaned from carbonate contaminations by in situ scraping or UHV annealing at about 500°C without loss of the superconducting properties.
2.
(2) The valence band spectra show a well defined Fermi edge with an intensity of about 0.01 as compared to the valence band maximum. The spectroscopic valence band features correlate only qualitatively to recent band structure calculations.
3.
(3) The XPS core level spectra of the Bi-4f, Sr-3d and Ca-2p levels show a single very well resolved spectrum. The $Cu -2 p_{32}$ spectrum has satellites, typical for Cu²⁺ species as e.g. in CuO and a small shoulder at lower binding energies probably of unreacted Cu₂O. The O-1s spectrum shows a well resolved line at 528.7 eV binding energy, with no significant contributions of a satellite at higher binding energies.

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The influence of Pb doping on the electronic structure of Bi₂Sr₂CaCu₂O_8+δ superconductor was investigated by X-ray photoelectron spectroscopy. A surface preparation procedure consisting of an annealing in UHV at 450°C was used to obtain surfaces representative of the superconductor intrinsic bulk properties. A careful comparison of the XPS characteristics between Pb-doped and undoped 2212 materials has shown that the core-level spectra of O1s, Cu2p, Sr3d, Ca2p, Bi4f and Pb4f are insensitive to the presence of Pb. The ratio of the two occupation sites of Sr and Ca in the crystal lattice is strictly unchanged by doping. The most remarkable influence of Pb is the slight shift of 0.1 eV towards low binding energy of the valence band spectra and the enhancement of the thermal stability of the superconductor. This stability enhancement is attributed to the existence of a chemical bonding between the Pb-substituted BiO planes.
Doping dependence of the chemical potential in cuprate high-T<inf>c</inf> superconductors II. (Bi, Pb)<inf>2</inf>Sr<inf>2</inf>Ca<inf>2</inf>Cu<inf>3</inf>O<inf>10+ δ</inf>
1995, Physica C: Superconductivity and its applications
Using X-ray photoelectron spectroscopy, a systematic study is performed of the doping dependence of the chemical potential μ in (Bi, Pb)₂Sr₂Ca₂Cu₃O_10+δ. The doping is varied by changing the oxygen content of the sample. The measured shift of the chemical potential is compared with present models for the doping behavior of μ in high-T_c materials. Our results show best agreement with the model in which the chemical potential is assumed to shift upon doping the parent insulating material.
Alkaline earth core level photoemission spectroscopy of high temperature superconductors
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Photoemission measurements of the alkaline earth core levels of high temperature superconductors and related materials are reviewed. Models which seek to explain the large negative chemical shifts observed relative to the corresponding alkaline earth metals are discussed and critically examined. The effect of lattice site disorder on the core level spectra and the presence or absence of intrinsic surface peaks are also reviewed.
Intrinsic photoemission signals, surface preparation, and surface stability of high temperature superconductors
1994, Journal of Electron Spectroscopy and Related Phenomena
Photoemission signals which are characteristic of high quality surfaces of high temperature superconductors are briefly reviewed. Criteria for assessing surface quality are determined, and these criteria are then used to evaluate the various surface preparation procedures reported in the literature. It will be shown that some widely used procedures effectively clean surfaces of some materials, but damage other materials. For example, surfaces of YBa₂Cu₃O_7−δ and Nd_1.85Ce_0.15CuO_4−δ scraped in vacuum show clear signs of damage, such as loss of intensity at the Fermi edge, and in the case of YBa₂Cu₃O_7−δ the spectral features are consistent with loss of oxygen resulting from the “cleaning” procedure. Finally, the stability of clean high temperature superconductor surfaces is discussed.
Study of O 1s XPS binding energy in YBa<inf>2</inf>Cu<inf>3</inf>O<inf>7-x</inf>
1993, Solid State Communications
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X-ray photoelectron study of Ca, Sr and Ba ion chemical states in high-T<inf>c</inf> superconductors
1993, Physica C: Superconductivity and its applications
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Photoemission investigations of the high-Tc superconductor BiSrCaCuO

Abstract

Physica C

Phys. Rev. B

Z. Phys. B

Phys. Rev. Lett.

Jpn. J. Appl. Phys.

Appl. Phys. A

Phys. Rev. Lett.

Angew. Chem.

Nature

Nature

Science

Nature

Photoemission investigations of the high-T_c superconductor BiSrCaCuO