Temperature dependence of electrical transport properties of La₄BaCu_{5− x}Co_xO_13+δ conducting oxide thin films

Abstract

We fabricated Co-doped La4BaCu5O13+δ (La4BaCu5− x Co x O13+δ) epitaxial thin films with various amount of Co-substitution on SrTiO3 single-crystal substrates by a pulsed laser deposition method, and measured the resistivity from 10 to 1000 K. The resistivity below 700 K became large with increasing amount of Co-substitution, and that above 700 K was independent of Co-substitution. These measurement results suggested that the dominant component of carrier scattering changed from the impurity scattering of Co to phonon scattering at 700 K. As a result, the temperature dependence of the resistivity became weak systematically with increasing amount of Co-substitution. The resistivity measurement in N2-based 1% H2 clarified that the Co-substitution has no effect on the oxygen retention in the reduction atmosphere.

High Temperature Electrical Properties of Co-Substituted La4BaCu5O13+δ Thin Films Fabricated by Sputtering Method

“…As shown in Figure 3b, the LBCO films on the SrTiO 3 single crystal substrate were in single phase and of better crystallinity, and the peaks to specific crystal planes became distinct. For the lattice mismatching, without crystal rotation, the lattice misfit between the a-axis of LBCO (≈8.65 Å) and the length of a two-unit cell of SrTiO 3 (7.82 Å) would be 10.6%, but with 26.6 • rotation, lattice misfit became −1.1%, as discussed in a previous report [14]. However, there is no clear evidence of grain orientation, despite the lattice parameters of (121) for LBCO and (101) for SrTiO 3 being identical, which suggests that the grains of the deposited film were rather randomly oriented.…”

“…As it is well known, high-T c superconductivity is realized in layered cuprates with two-dimensional CuO 2 planes. The superconductivity was also achieved in quasi-one dimensional cuprates with a Cu 2 O 3 ladder such as (Sr,Ca) 14 Cu 24 O 41 [1]. Michel et al have investigated a La 4 BaCu 5 O 13+δ system and found that these perovskite-related copper oxides are highly metallic in conduction with a resistivity of 1.5 mΩcm at 673 K [2], and Murayama et al have substituted Sr for Ba to demonstrate metallic conduction but no superconductivity [3].…”

“…Further study on the electrical anisotropy of this oxide material has been reported by the fabrication of thin films on a SrTiO 3 (100) single crystal substrate by pulsed laser deposition (PLD), and has shown that the temperature dependence of the resistivity along the ab-plane is smaller than that along the c-axis in the thin-film study [13]. The epitaxial thin films of Co-doped LBCO on a SrTiO 3 substrate have been also fabricated by PLD by Tsuruta et al, who measured the resistivity and Seebeck coefficients for a wide temperature range from 10 to 1000 K, and suggested a change of carrier scattering with temperature from the impurity scattering of Co to phonon scattering at 700 K [14]. However, other dependences of the electric properties on the Co substitution, the film thickness, or quality, such as the lack of homogeneous film; different substrates, including glass; and oxygen deficiency, especially at temperatures higher than room temperature RT, have not been investigated in detail.…”