Superconductivity and surface morphology of YBCO thin films prepared by metalorganic chemical vapor deposition

Device quality superconducting thin films of YBCO have been prepared by metalorganic chemical vapor deposition (MOCVD). Superconducting films with T/sub co/ higher than 80 K have been deposited at low temperatures, 500-550/spl deg/C, essential for heteroepitaxial device structure,on MgO substrates. Superconductivity of ultrathin (less than 10 nm) films of YBCO have been investigated together with surface morphology measured by atomic force microscopy. Atomic layer-by-layer growth has also been investigated. Tco=85 K has been obtained for a 24 nm-thick YBCO deposits for 20 cycle on SrTiO3 substrates at 650/spl deg/C. A very smooth surface with roughness of less than monomolecular layer and free of precipitates has been obtained over 10 /spl mu/m/spl times/10 /spl mu/m. Critical current density of 3/spl times/10/sup 7/ A/cm/sup 2/ has been obtained at 4.2 K and 3/spl times/10/sup 6/ A/cm/sup 2/ at 77 K for a 40 nm-thick film.<>