Figure 2. RSMs around the {103}_pc lattice reflections (left) with the corresponding side view diagrams (middle) and diagrams of the unit cell orientations (right).

(a) The undosed film shows a clear orthorhombic distortion of the crystal structure that is in agreement with an in-plane oriented unit cell and a a⁻a⁺c⁻ rotation pattern. (b) A He dose of 2.5 × 10¹⁵ ions/cm² is sufficient to remove orthorhombic distortions present in undosed samples and drive a tetragonal structure with an upright unit cell and a⁰a⁰c⁻ rotation pattern. The reciprocal-lattice units are in terms of the lattice parameter of the SrTiO₃ substrate. The circles around the axis of the coordinate system on the right illustrate the out-of-phase (red) and in-phase (blue) octahedral rotations about the relevant cubic principle axis.