Surface morphology and critical current density of high quality YB2Cu3O7 thin films on sapphire substrates

Pulsed laser deposition has been used to prepare YBa2Cu3O7 (YBCO) film on CeO2 buffer layers on single crystal Al2O3 (1 (1) over bar 02) substrates. High quality YBCO films have been obtained when 500-Angstrom-thick CeO2 buffer layers were deposited with fluence of 1.5 J/cm(2) and oxygen pressure of 50 mTorr. Surface morphology of the c-axis oriented YBCO films were strongly dependent on the preparation conditions of CeO2 buffer layers, resulting in significant changes of critical current densities. Critical current densities of YBCO films increased with the increase of the substrate temperature for CeO2 buffer layer deposition in the range 400 degrees C less than or equal to T-S less than or equal to 800 degrees C. Superconducting properties in YBCO/CeO2/Al2O3 exhibit T-C = 89.5 B, Delta T-C less than or equal to 0.5 K, and J(C) > 3x10(6) A/cm(2) at 77 K.