Surface Octahedral Distortions and Atomic Design of Perovskite Interfaces
Progress in understanding and exploiting the properties of complex oxide heterostructures requires advances in state-of-the-art growth and characterization techniques for these materials, as atomic control of their synthesis is demonstrably inferior to that of their semiconductor counterparts. Here we report significant improvements in the atomic design of perovskite interfaces made possible by advances in in situ control of the surface by reflection high-energy electron diffraction (RHEED) during growth that reveal the surface termination and characteristic octahedral distortions in the surface layer as it is being deposited.
This RHEED approach applies generally to growth of polar and nonpolar perovskite unit cells when a desorption-controlled growth regime is not utilized. As an example, we demonstrate its use in the optimization of atomically-designed manganite/titante interfaces that eliminates cation intermixing and anomalous unit cell dilations that have previously been observed. Careful analysis of the crystal structure shows an unusual evolution of the octahedral distortions that include both J-T type and rotations near the interface that are not seen in bulk. These new results should be included in electronic structure calculations modeling the properties of real heterointerfaces.