Raman line shapes from sputtered thin films of Y(Pr)Ba{sub 2}Cu{sub 3}O{sub 6+{delta}}: Fine structures and oxygen ordering

Journal Article · Sat Feb 01 04:00:00 EST 1997 · Physical Review, B: Condensed Matter

DOI:https://doi.org/10.1103/PhysRevB.55.3974· OSTI ID:450396

Faulques, E; Ivanov, V G ^[1]

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1. Laboratoire de Physique Cristalline, Institut des Materiaux de Nantes, 2 rue de la Houssiniere, F-44072 Nantes Cedex 03 (France)

A temperature dependence study of Raman line shapes taken from superconducting and insulating Y(Pr)Ba{sub 2}Cu{sub 3}O{sub 6+{delta}} thin films with well-characterized electrophysical properties and morphologies (a-axis or c-axis orientation) has been carried out using the excitation energies at 1.83 eV and 2.41 eV. Ba and Cu bands show doublets, with 113{endash}119 cm{sup {minus}1} and 146{endash}152 cm{sup {minus}1} components and have been calculated using a Green{close_quote}s function model. The shapes of the 113 and 152 cm{sup {minus}1} lines are well described by Lorentzians whereas those of the other two components can be satisfactorily reproduced in the assumption that two phonons of bare frequencies 119 and 146 cm{sup {minus}1} interact with a {ital common} continuum of excitations. The temperature dependence of the phonon-continuum coupling parameters allows us to ascribe the scattering continuum to low-energy electronic interband transitions. The model is able to explain qualitatively the overestimated mixing between pure Ba and plane Cu A{sub g} vibrational modes found in previous first-principles calculations. We also find that for the 1.83 eV exciting line, the B{sub 1g} oxygen phonon at 335 cm{sup {minus}1} presents a strong Fano effect and anomalous temperature dependence. We link Raman features occuring at {approx}220{endash}240, 270{endash}290, and 560{endash}596 cm{sup {minus}1} to the existence of {ital local} variations in oxygen composition resulting from the conditions of deposition. These lines could originate from chain defects and be activated by a coupling between A{sub g} and B{sub 2g}-B{sub 3g} modes. The presence of microphases of oxygen-depleted domains (ortho-II phase) reproducing macroscopic oxygen disorder is proposed. {copyright} {ital 1997} {ital The American Physical Society}

• OSTI ID: 450396
• Journal Information: Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 6 Vol. 55; ISSN PRBMDO; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BARIUM OXIDES
COPPER OXIDES
CRYSTAL STRUCTURE
HIGH-TC SUPERCONDUCTORS
PHONONS
PRASEODYMIUM OXIDES
RAMAN SPECTRA
SUPERCONDUCTING FILMS
YTTRIUM OXIDES