Growth of (001)La1.85Sr0.15CuO4 ultrathin films without buffer or cap layers

We report the growth of (001) La1.85Sr0.15CuO4 films with thicknesses less than 5 unit cells on LaSrAlO4 substrates without any buffer or cap layers. Results of surface analyses indicate that all samples with 0.5-unit-cells-thick films are well crystallized and have a finite density of states at the Fermi level. Films 4 unit cells thick show bulk-like transport properties and T-c(R = 0). T-c disappears in films with thicknesses less than 2 unit cells, suggesting that the minimum number of CuO2 planes necessary for superconductivity in LSCO is less than or equal to four, (C) 1996 Elsevier Science B.V.