SUPERCONDUCTIVITY OF (BA,SR,CA)CUO2 ARTIFICIAL LATTICES

Two types of (Ba,Sr,Ca)CuO2 infinite layer artificial lattices have been grown by successive deposition with laser molecular beam epitaxy. The first one is prepared by periodical stacking of BaCuO2 and CaCuO2 and the second one is formed by the insertion of extra BaOx layer into the CaCuO2 thin films. The lattice with the stacking of 3 unit cell layers of BaCuO2 and 1 unit cell layer of CaCuO2, (BaCuO2)(3)/(CaCuO2)(1), shows a zero-resistance at 30 to 38K with onset of 70 to 80K. The diamagnetic transition is also observed below 26 to 30K. X-ray diffraction analysis shows the c-axis orientation of the films with the lattice constant of c=15.38 Angstrom. The second one is BaO-inserted CaCuO2 lattice, which is unstable and easily transforms into (BaCuOx)(2)/(CaCuO2)(n) structure with vertical diffusion of the elements during the growth. On the (BaCuOx)(2)/(CaCuO2)(n) lattices, resistive anomaly is observed below 110K, where the resistance depends on the magnetic field.