Molecular beam epitaxy of electron-doped infinite-layer Ca1-xRxCuO2 thin films

Thin films of the electron-doped infinite-layer Ca1-xRxCuO2, with R = La3+, Nd3+, and Ce4+, have been synthesized using molecular beam epitaxy. The solubility limits of R in Ca1-xRxCuO2 are 0.060 +/- 0.002, 0.080 +/- 0.010, and <0.01 for R = Nd3+, La3+, and Ce4+, respectively. Using high-resolution reciprocal space mapping we show that the in-plane lattice constants of Ca1-xRxCuO2 follow the same trend as is observed for other cuprates with square-planar coordinated copper, i.e., elongation of the Cu-O bond length upon electron doping. We measured the temperature dependencies of the resistivity and the Hall coefficient to trace the influence of the doped charge carriers on the electronic response. We show that the Hall coefficient is negative below 300 K and that the R substitution level is insufficient to achieve a positive Hall coefficient, a necessary prerequisite for superconductivity.