Raman light scattering study and microstructural analysis of epitaxial films of the electron-doped superconductor La_{2-x}Ce_{x}CuO_{4}

Abstract

We present a detailed temperature-dependent Raman light scattering study of optical phonons in molecular-beam-epitaxy-grown films of the electron-doped superconductor La_{2-x}Ce_{x}CuO_{4} close to optimal doping (x ~ 0.08, T_c = 29 K and x ~ 0.1, T_c = 27 K). The main focus of this work is a detailed characterization and microstructural analysis of the films. Based on micro-Raman spectroscopy in combination with x-ray diffraction, energy-dispersive x-ray analysis, and scanning electron microscopy, some of the observed phonon modes can be attributed to micron-sized inclusions of Cu_{2}O. In the slightly underdoped film (x ~ 0.08), both the Cu_{2}O modes and others that can be assigned to the La_{2-x}Ce_{x}CuO_{4} matrix show pronounced softening and narrowing upon cooling below T ~ T_c. Based on control measurements on commercial Cu_{2}O powders and on a comparison to prior Raman scattering studies of other high-temperature superconductors, we speculate that proximity effects at La_{2-x}Ce_{x}CuO_{4}/Cu_{2}O interfaces may be responsible for these anomalies. Experiments on the slightly overdoped La_{2-x}Ce_{x}CuO_{4} film (x ~ 0.1) did not reveal comparable phonon anomalies.

7 pages, 8 figures

References in corpus (14)

• Inelastic Light Scattering From Correlated Electrons
• Anomalous electronic structure and pseudogap effects in Nd_1.85Ce_0.15CuO_4
• Nonmonotonic d_{x^2-y^2} Superconducting Order Parameter in Nd_{2-x}Ce_xCuO_4
• New class of T-prime-structure cuprate superconductors
• Superconductivity phase diagrams of electron doped cuprates R(2-x)CexCuO4 (R = La, Pr, Nd, Sm, and Eu)
• Phase Decomposition and Chemical Inhomogeneity in Nd2-xCexCuO4
• Infrared Properties of Electron Doped Cuprates: Tracking Normal State Gaps and Quantum Critical Behavior in Pr(2-x)Ce(x)CuO(4)
• Evolution of Superconductivity in Electron-Doped Cuprates: Magneto-Raman Spectroscopy
• Electronic and phononic Raman scattering in detwinned YBa${}_2$Cu${}_3$O${}_{6.95}$ and Y${}_{0.85}$Ca${}_{0.15}$Ba${}_2$Cu${}_3$O${}_{6.95}$: s-wave admixture to the $d_{x^2-y^2}$-wave order parameter
• Symmetry dependence of phonon lineshapes in superconductors with anisotropic gaps
• Tunneling into the normal state of Pr(2-x)CexCuO4
• Doping of Ce in T-La2CuO4: Rigorous test for electron-hole symmetry for high-Tc superconductivity
• Phase control in La-214 epitaxial thin films
• Andreev bound states at a cuprate grain boundary junction: A lower bound for the upper critical field