Growth of YBa2Cu3O7 Films with [100] Tilt of CuO Planes with Respect to the Surface on MgO Crystals

Epitaxial YBa2Cu3O7 films with CuO plane tilted with respect to the surface have been grown on crystalline MgO substrates by pulsed laser deposition. Directly before growing a film, a nucleation-center-forming SrTiO3 sublayer with an effective thickness less than the unit-cell size was deposited on the substrate. The tilt angle was varied in the range from 0 degrees (at which CuO planes are oriented parallel to the surface) to 70 degrees. The film lattice rotation is implemented at this tilt due to the substrate rotation around its [100] axis, oriented parallel to the surface. Zero tilt of the CuO plane occurs when the MgO crystal surface is oriented parallel to the (100) plane. It is found that the CuO film planes remain parallel to one or several crystallographic planes {100} of the substrate at any tilt angles. In the range of angles from 0 degrees to 41 degrees the film is a single crystal. At angles larger than 41 degrees the film is transformed into a two-domain texture, and its surface roughness sharply increases.