Electrical transport properties of artificially layered films of [BaCuO2](2)/[(Sr,Ca)CuO2](n)

In this letter we show that SrCuO2/BaCuO2 and CaCuO2/BaCuO2 based artificial structures of very good crystallographic quality can be grown by pulsed laser deposition. We demonstrate that the most important parameters which determine the superconductive properties are the chemical composition, the oxygen growth pressure, and the CO2 contamination. A major difference is found in the behavior of resistivity between films containing Sr and Ca, respectively. Namely [BaCuO2](2)/[SrCuO2](n) films never show any trace of superconductivity, while [BaCuO2](2)/[CnCuO(2)](n) films result in having, for growth oxygen pressures P-o2> 0.2 mbar, a full transition with T-c (zero resistance) up to 46 K. Furthermore we demonstrate that even a tiny amount of CO2 in the oxygen growth atmosphere can suppress completely the superconducting properties of these artificial structures. (C) 1997 American Institute of Physics.