Chemical bonding in Tl cuprates studied by x-ray photoemission

Journal Article · Sun Aug 01 04:00:00 EDT 1999 · Physical Review, B: Condensed Matter

DOI:https://doi.org/10.1103/PhysRevB.60.4309· OSTI ID:361602

Vasquez, R P ^[1]; Siegal, M P; Overmyer, D L ^[2]; Ren, Z F; Lao, J Y; Wang, J H ^[3]

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1. Center for Space Microelectronics Technology, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109-8099 (United States)
2. Sandia National Laboratories, Albuquerque, New Mexico 87185-1421 (United States)
3. Materials Synthesis Laboratory, Department of Chemistry, State University of New York, Buffalo, New York 14260-3000 (United States)

Epitaxial thin films of the Tl cuprate superconductors Tl{sub 2}Ba{sub 2}CaCu{sub 2}O{sub 8}, Tl{sub 2}Ba{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10}, and Tl{sub 0.78}Bi{sub 0.22}Ba{sub 0.4}Sr{sub 1.6}Ca{sub 2}Cu{sub 3}O{sub 9{minus}{delta}} are studied with x-ray photoemission spectroscopy. These data, together with previous measurements in this lab of Tl{sub 2}Ba{sub 2}CuO{sub 6+{delta}} and TlBa{sub 2}CaCu{sub 2}O{sub 7{minus}{delta}}, comprise a comprehensive data set for a comparative study of Tl cuprates with a range of chemical and electronic properties. In the Cu 2p spectra, a larger energy separation between the satellite and main peaks (E{sub s}{minus}E{sub m}) and a lower intensity ratio (I{sub s}/I{sub m}) are found to correlate with higher values of T{sub c}. Analysis of these spectra within a simple configuration interaction model suggests that higher values of T{sub c} are related to low values of the O&hthinsp;2p{r_arrow}Cu&hthinsp;3d charge transfer energy. In the O&hthinsp;1s region, a smaller bond length between Ba and Cu-O planar oxygen is found to correlate with a lower binding energy for the signal associated with Cu-O bonding, most likely resulting from the increased polarization screening by Ba{sup 2+} ions. For samples near optimum doping, maximum T{sub c} is observed to occur when the Tl 4f{sub 7/2} binding energy is near 117.9 eV, which is near the middle of the range of values observed for Tl cuprates. Higher Tl&hthinsp;4f{sub 7/2} binding energies, corresponding to formal oxidation states nearer Tl{sup 1+}, are also found to correlate with longer bond lengths between Ba and Tl-O planar oxygen, and with higher binding energies of the O&hthinsp;1s signal associated with Tl-O bonding. {copyright} {ital 1999} {ital The American Physical Society}

• OSTI ID: 361602
• Journal Information: Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 6 Vol. 60; ISSN PRBMDO; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BARIUM COMPOUNDS
BARIUM OXIDES
BINDING ENERGY
BISMUTH COMPOUNDS
BISMUTH OXIDES
BOND LENGTHS
CALCIUM COMPOUNDS
CALCIUM OXIDES
CHEMICAL BONDS
COPPER OXIDES
CUPRATES
HIGH-TC SUPERCONDUCTORS
PEROVSKITES
PHOTOEMISSION
STRONTIUM COMPOUNDS
STRONTIUM OXIDES
THALLIUM COMPOUNDS
THALLIUM OXIDES
THIN FILMS
X-RAY SPECTRA