Microstructure and Superconductivity of Ultrathin YBa₂Cu₃O_7-δ Films

Two unit cells to 200Å thick ultrathin YBa₂Cu₃O_7-δ films have been synthesized and their growth mechanism and physical properties have been studied. Atomic force microscopy showed that the films grow with both spiral and layer by layer modes and the screw dislocations appeared even in the 6 unit cells thick films. In the initial growth stages of the films, the strong dependence of T_c on the film thickness is discussed.