Graphoepitaxial Y:ZrO₂ films on vicinal (110) NdGaO₃ substrates by pulsed laser deposition

Thin films of Y:ZrO2 (YSZ) have been grown on vicinal NdGaO₃ substrates (tilted by 0º–3º around [001] NdGaO₃ from (110) plane toward (010) plane) by pulsed laser deposition. The surface of the films is smooth, the signs of step-flow growth mode can be detected for small tilt angles < 0.2º. The orientation of the films followed graphoepitaxial matching with the substrates for all studied tilt angles down to 0.06º. In case of arbitrary in-plane orientation of the tilt axis, the graphoepitaxial growth mode was observed in both substrate in-plane directions. The thin YSZ films showed narrow rocking curves and contracted c lattice constant normal to the (110) plane. An increase of film thickness results in relaxation of c to 5.142 Å, in a good agreement with the bulk value for the target composition of 9 mol% Y₂O₃:ZrO₂. The width of the rocking curve increases with thickness to a relatively high level ~ 3º. Both thickness dependences show exponential saturation with characteristic thicknesses 13–19 nm. The reason for such a behavior is probably the gradual relaxation of the substrate-induced strain with thickness by generation of dislocations.