Structure and properties of (Sr,Ca)CuO 2–BaCuO 2 superlattices grown by pulsed laser interval deposition

Abstract

We report on the preparation of CuBa 2(Sr x Ca 1− x ) n Cu n −1O y compounds by fabrication of (Ba,Sr,Ca)CuO 2 superlattices with pulsed laser deposition (PLD). A technique called interval deposition is used to suppress multi-level or island growth resulting in high-quality superlattice structures. Both, the applicability of PLD to atomic engineering as well as the fabrication of artificial superconductors is demonstrated. The (Sr,Ca)CuO 2–BaCuO 2 superlattices are characterized by X-ray diffraction, high-resolution electron microscopy (HREM) and selected area electron diffraction. The superlattice period has been deduced from electron diffraction patterns and XRD measurements. For Sr containing films, the best growth behavior is observed and films with the highest degree of crystallinity are obtained, whereas superconductivity is only found in less crystalline, Ca containing films. Under some deposition conditions and depending on the amount of Ba containing layers in the superlattice, it was observed that the BaCuO 2 material is converted to Ba 2CuO 4− δ . Image simulations to interpret the HREM contrast are performed.