GROWTH AND CHARACTERIZATION OF A-AXIS ORIENTED YBA2CU3O7-X THIN-FILMSON (100)LASRGAO4 SUBSTRATES

We grew a-axis oriented YBa2Cu3O7-delta thin films on (100) oriented t etragonal single crystalline LaSrGaO4 substrates by inverted cylindric al magnetron de sputtering. PrBa2Cu3O7-delta thin films deposited in s itu by rf sputtering were used as template layers, The growth of the f ilms was studied by X-ray diffraction, high-resolution transmission el ectron microscopy and Raman spectroscopy. Their surface morphology has been characterized by atomic force microscopy, In addition, normal st ate and superconducting transport properties were measured on patterne d films by use of a four-probe arrangement. The film composition was c ontrolled by energy-dispersive X-ray analysis and Rutherford backscatt ering spectrometry that also enabled the determination of the film thi ckness. We obtained YBa2Cu3O7-delta films with pure a-axis growth and full c-axis in-plane alignment with the orientational relationship of (010) YBCOH parallel to(010) LSGO and (001) YBCO parallel to(001) LSGO . The crystalline anisotropy is also reflected in the transport proper ties where the resistivity and j(c) anisotropies parallel and perpendi cular to the ab-plane reach 18 and 7, respectively, at 100 K, T-c amou nts to 90.5 K and j(c) parallel to the ab-plane is 1.3 X 10(5) A/cm(2) . The film surfaces showed large grains with a size of 500 X 170 nm(2) but no significant outgrowths resulting in a mean surface roughness o f R-a = 5 nm. Grain boundaries, including antiphase boundaries in the b-direction and stacking fault boundaries in the c-direction have been observed and are discussed with respect to their influence on the ani sotropic transport. (C) 1997 Elsevier Science B.V.