High Quality YBa2Cu3O7-x Superconducting Thin Films Grown by MOCVD

Abstract

YBCO thin films have been grown by Metal Organic Chemical Vapour Deposition in a cold wall type reactor. The β-diketonates of yttrium, barium and copper are used as precursors. Films have been deposited on (001) MgO and (012) LaAlO 3 single crystalline substrates. The morphology is very dependant on the gas phase composition. Different oxygen partial pressures have been investigated. An increasing oxygen partial pressure - at a fixed deposition temperature - is found to increase the growth rate and to promote the growth of a-axis grains (grains with the c axis parallel to the substrate's surface). In our standard deposition conditions, Ti subs t rate holder = 875°C, P Total = 5 Torr, and P O2 = 2 Torr, high quality films are obtained, exhibiting T C ∼ 91 K (10%-90% of the resistive transition) and J C (77K) ∼ 5.10 6 A/cm 2 . A trilayer structure YBCO/Y 2 O 3 /YBCO (900A/100A/900A) has been grown on LaAlO 3 substrate, with the epitaxial relationship: (001) YBCO // or (001) Y2O3 . No misorientations have been found in the (a,b) plane. The trilayer exhibits a sharp superconducting transition (ΔT C = 0.4 K), with T C = 82.5 K, and J C (77 K) ∼ 10 6 A/cm 2 .