GROWTH AND PROPERTIES OF MOCVD YBA2CU3O7-X THIN-FILMS

Epitaxial thin layers of YBa2Cu3O7-x are synthesised by thermal decomp osition (750 - 830-degrees-C) of tetramethylheptanedionates of yttrium , barium and copper in the presence of oxygen. Argon is used as a carr ier gas and the partial pressures of the different precursors are moni tored via a careful control of the sources temperatures. The supercond ucting films with thicknesses ranging between 40 nm and 200 nm are gro wn on (100) SrTiO3, (012) LaAlO3 Or (100) MgO. The growth rate varies between 2.7 nm/min and 4 nm/min. The layers are analysed by scanning a nd transmission electron microscopy, x-ray diffraction and Rutherford backscattering spectrometry. The normal - superconductor transition is investigated via DC and AC resistance, magnetization and AC susceptib ility measurements as a function of temperature. Magnetisation hystere sis loops recordings, I-V measurements on microbridges and non linear susceptibility analysis are used to explore the irreversible propertie s of the layers. Typical parameters for MOCVD films grown on LaAlO3 ar e as follows: T(c) = 90 K, DELTAT(c) = 0.4 K and J(c) (77 K) = 2 10(6) A cm-2.