Abstract
We performed Raman scattering measurements and a comprehensive study of different types of Raman modes associated with phonon vibrations on pure and Ga, Al, Fe, Co, Ni, and Zn doped (110)‐oriented PrBa2Cu3O7 (PBCO) thin films to identify the substitution of Cu (1) or Cu (2) ions in PBCO lattice. In Raman spectrum of (110)–oriented PBCO thin film, we observed four prominent Ag type Raman modes at ∼130 cm−1, ∼150 cm−1, ∼440 cm−1, and ∼520 cm−1 corresponding to Ba, Cu (2), O (2)–O (3) in‐phase, and O (4) apical oxygen vibration along c‐axis, respectively. The Raman mode of pure PBCO at ∼520 cm−1 softened on Ga, Al, Fe, and Co doped PBCO thin films while it remained unaffected on Zn and Ni doped PBCO thin films. We explain these results in the context of their correlation with Cu (1)–O (4) and Cu (2)–O (4) bond lengths. In addition, we observed a new Raman mode near 610 cm−1 in the Raman spectra of Ga, Al, Fe, and Co doped PBCO thin films, an infrared (IR) active mode that became Raman active when the symmetry was broken at the Cu‐O chain site after the partial substitution of Cu (1) ion. Moreover, the “O (2)–O (3) in‐phase Raman mode” near 440 cm−1 remained unaffected in Fe, Co, Ga, and Al doped PBCO thin films but softened in Zn and Ni doped PBCO thin films. Based on these results, we argue that Ga, Al, Fe, and Co ions replace Cu (1) ion at the Cu‐O chain site, break the crystal symmetry, and produce disorder locally, whereas Zn and Ni ions replace Cu (2) ion at the CuO2 plane of the PBCO lattice structure.
Highlights
Raman spectroscopy is an ideal analytical tool for site detection of Cu ion substitution in the family of cuprate oxide compound RBa2Cu3O7 (R Rare Earth element)
We observed four prominent Ag lines in zz polarization Raman spectra of our (110)-oriented Ga, Al, Fe, and Co doped thin films. ree of them were at ∼130 cm−1, ∼160 cm−1, and ∼440 cm−1, which belong to Raman vibrational modes of Ba, Cu (2), and O (2)–O (3) along c-axis, respectively. e fourth Raman mode related to the O (4) apical oxygen vibration mode was observed in the frequency regime (485–502 cm−1)
We did not observe this Raman mode in the Raman spectra of pure PBCO and Zn or Ni doped PBCO thin film
Summary
Raman spectroscopy is an ideal analytical tool for site detection of Cu ion substitution in the family of cuprate oxide compound RBa2Cu3O7 (R Rare Earth element). Vibrational mode of Ag symmetry are observed in the orthorhombic (D2h) point group for a parallel polarization of incident and scattered light, for example, x(z, z)x′. If O (1) atoms of the chains are removed, the unit cell of Figure 1 becomes tetragonal (D4h point group). E Raman vibration mode at 500 cm−1 in YBCO and 520 cm−1 in PBCO is due to axial vibration of the apical oxygen atom between the two copper atoms: Cu (1) and Cu (2). It is an Ag mode and has a ccpolarization, which refers to incident radiation polarized along the c-axis of the crystal and scattered radiation polarized along the c-axis. We present a comprehensive study of Raman scattering on pure and Ga, Al, Fe, Co, Ni, and Zn doped (110)-oriented PrBa2Cu3O7 (PBCO) thin films in which 20% Cu atoms in Cu (1) or Cu (2) sites are substituted by Fe, Co, Ni, Zn, Ga, and Al
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