X-ray determination of mosaic structure in variable thickness EuBa ₂Cu₃O_7-δ thin films

Employing the Srikant method of extrapolating the rocking curve widths of a series of diffraction peaks across a range of angles of inclination, the out-of-plane (mosaic tilt) and in-plane (mosaic twist) misorientation angles of a series of varying thickness EuBa₂Cu₃O _7-δ thin films has been deduced. The twist angle is seen to increase as the film thickness decreases below 200 nm, from 0.2° for films approaching the bulk to 0.35° for the thinnest film (50 nm) investigated. The tilt angle follows a similar trend, increasing more strongly from 0.05° to 0.4°. Furthermore, it is shown that the tilt and twist misorientations in this class of materials are independent in nature, implying that limited information regarding the in-plane behaviour can be inferred from purely out-of-plane measurements. The reduction in the degree of misorientation in thicker films can be associated with a decreasing threading dislocation density, and correlates with the decrease in the critical current density of R123 thin films with increasing film thickness.