YBA2CU3O7-X FILMS ON YTTRIA-STABILIZED ZRO2 SUBSTRATES - INFLUENCE OFTHE SUBSTRATE MORPHOLOGY

c-axis-oriented YBa2Cu3O7-x (YBCO) thin films were laser deposited on (001) yttria-stabilized ZrO2 (YSZ) substrates with different surface m orphologies. The in-plane orientation of the films on smooth substrate s was sensitive to the deposition conditions, often resulting in mixed orientations. However, a strongly dominating [110]YBCO//[110]YSZ orie ntation was obtained at a deposition temperature of 770-degrees-C. Fil ms on substrates with surface steps, induced by depositing a homoepita xial buffer layer or by thermally annealing the substrate, had a [110] YBCO//[100]YSZ orientation when deposited at the same temperature. It was concluded that the [110]YBCO//[100]YSZ orientation was promoted by a graphoepitaxial mechanism. Films prepared under identical condition s on smooth and stepped substrates grew with extended c axes on the fo rmer. It is proposed that the extension can be induced by disorder, in voked by a low oxygen pressure and a low density of adsorption sites. The disorder may be eliminated by either an increase of the oxygen pre ssure or an increase of the density of adsorption sites in the form of steps. The film microstructure influenced the microwave surface resis tance, which was similar for films with one exclusive in-plane orienta tion and higher for films with mixed orientations. The films on the st epped surfaces had superior superconducting properties; inductive meas urements gave a T(c)onset of 88 K, a DELTAT(c)((90% - 10%)) of 0.2 K, and the transport j(c) was 1.5 x 10(6) A/CM2 at 83 K, for films on sub strates with homoepitaxial buffer layers.