Electronic structure

R. Vasquez, D. Novikov, Arthur J Freeman

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

The core levels of (Formula presented)(Formula presented)(Formula presented) (Tl-1212) epitaxial films have been measured with x-ray photoelectron spectroscopy (XPS). The valence electronic structure has been determined using the full-potential linear muffin-tin-orbital band-structure method and measured with XPS. The calculations show that a van Hove singularity (VHS) lies above the Fermi level ((Formula presented)) for the stoichiometric compound (δ=0), while for 50% oxygen vacancies in the Tl-O layer (δ=0.5) (Formula presented) is in close proximity to the VHS. Samples annealed in nitrogen (to reduce the hole overdoping by the removal of oxygen) exhibit higher core-level binding energies and a higher (Formula presented), consistent with a shift of (Formula presented) closer to the VHS. Comparisons are made to the core levels and valence bands of (Formula presented)(Formula presented)(Formula presented)(Formula presented) (Tl-2212) and (Formula presented)(Formula presented)(Formula presented) (Hg-1212). The similarity of the Cu (Formula presented) spectra for Tl-1212 and Tl-2212 indicates that the number of Tl-O layers has little effect on the Cu-O bonding. However, the Tl-1212 and Hg-1212 Cu (Formula presented) signals exhibit differences which suggest that the replacement of (Formula presented) with (Formula presented) results in a decrease in the O 2p→Cu 3d charge-transfer energy and differences in the probabilities of planar vs apical oxygen charge transfer and/or Zhang-Rice singlet-state formation. Differences between the Tl-1212 and the Tl-2212 and Hg-1212 measured valence bands are consistent with the calculated Cu 3d and (Tl, Hg) 6s/5d partial densities of states.

Original languageEnglish
Pages (from-to)14623-14631
Number of pages9
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume55
Issue number21
DOIs
Publication statusPublished - Jan 1 1997

Fingerprint

Core levels
Electronic structure
Photoelectron spectroscopy
electronic structure
Valence bands
Charge transfer
Oxygen
X rays
Tin
Epitaxial films
Oxygen vacancies
Fermi level
Binding energy
Band structure
Nitrogen
trucks
valence
x ray spectroscopy

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

Cite this

Electronic structure. / Vasquez, R.; Novikov, D.; Freeman, Arthur J.

In: Physical Review B - Condensed Matter and Materials Physics, Vol. 55, No. 21, 01.01.1997, p. 14623-14631.

Research output: Contribution to journalArticle

Vasquez, R. ; Novikov, D. ; Freeman, Arthur J. / Electronic structure. In: Physical Review B - Condensed Matter and Materials Physics. 1997 ; Vol. 55, No. 21. pp. 14623-14631.
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AB - The core levels of (Formula presented)(Formula presented)(Formula presented) (Tl-1212) epitaxial films have been measured with x-ray photoelectron spectroscopy (XPS). The valence electronic structure has been determined using the full-potential linear muffin-tin-orbital band-structure method and measured with XPS. The calculations show that a van Hove singularity (VHS) lies above the Fermi level ((Formula presented)) for the stoichiometric compound (δ=0), while for 50% oxygen vacancies in the Tl-O layer (δ=0.5) (Formula presented) is in close proximity to the VHS. Samples annealed in nitrogen (to reduce the hole overdoping by the removal of oxygen) exhibit higher core-level binding energies and a higher (Formula presented), consistent with a shift of (Formula presented) closer to the VHS. Comparisons are made to the core levels and valence bands of (Formula presented)(Formula presented)(Formula presented)(Formula presented) (Tl-2212) and (Formula presented)(Formula presented)(Formula presented) (Hg-1212). The similarity of the Cu (Formula presented) spectra for Tl-1212 and Tl-2212 indicates that the number of Tl-O layers has little effect on the Cu-O bonding. However, the Tl-1212 and Hg-1212 Cu (Formula presented) signals exhibit differences which suggest that the replacement of (Formula presented) with (Formula presented) results in a decrease in the O 2p→Cu 3d charge-transfer energy and differences in the probabilities of planar vs apical oxygen charge transfer and/or Zhang-Rice singlet-state formation. Differences between the Tl-1212 and the Tl-2212 and Hg-1212 measured valence bands are consistent with the calculated Cu 3d and (Tl, Hg) 6s/5d partial densities of states.

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