Crystal Symmetry Engineering in Epitaxial Perovskite Superlattices

Abstract

Interface plays a critical role in determining the physical properties and device performance of heterostructures. Traditionally, lattice mismatch, resulting from the different lattice constants of the heterostructure, can induce epitaxial strain. Over past decades, strain engineering has been demonstrated as a useful strategy to manipulate the functionalities of the interface. However, mismatch of crystal symmetry at the interface is relatively less studied due to the difficulty of atomically structural characterization, particularly for the epitaxy of low symmetry correlated materials on the high symmetry substrates. Overlooking those phenomena restrict the understanding of the intrinsic properties of the as‐ determined heterostructure, resulting in some long‐standing debates including the origin of magnetic and ferroelectric dead layers. Here, perovskite LaCoO3‐SrTiO3 superlattice (SL) is used as a model system to show that the crystal symmetry effect can be isolated by the existing interface strain. Combining the state‐of‐art diffraction and electron microscopy, it is found that the symmetry mismatch of LaCoO3‐SrTiO3 SL can be tuned by manipulating the SrTiO3 layer thickness to artificially control the magnetic properties. The work suggests that crystal symmetry mismatch can also be designed and engineered to act as an effective strategy to generate functional properties of perovskite oxides.

Experimental demonstration of tunable hybrid improper ferroelectricity in double-perovskite superlattice films

“…In addition, the dramatic changes within the six perovskite layers exhibit the clamping effect of the STO substrates on OOR. This limitation of octahedral structures originates from the lattice and symmetry mismatch between the films and substrates, remaining a coherent interface and lattice connectivity 43 . According to the approximately equal values of the median and average of bond angles within a single layer, OOR tends to be stable as the clamping effect disappears.…”

Lattice Mismatch at the Heterojunction of Perovskite Solar Cells

“…Lattice mismatch at the heterojunction has been identified as a significant factor, negatively affecting the perovskite films and their corresponding device performance [100] . The implications of this mismatch extend to various aspects such as defect density, carrier transport, non‐radiative recombination and photocarrier dynamics [101,102] . Particularly, the effect of lattice mismatch on carrier dynamics can be attributed to tensile strain, which influences the growth pattern of perovskite crystals, making it more regular and orderly during strain relaxation [65] .…”

“…[100] The implications of this mismatch extend to various aspects such as defect density, carrier transport, non-radiative recombination and photocarrier dynamics. [101,102] Particularly, the effect of lattice mismatch on carrier dynamics can be attributed to tensile strain, which influences the growth pattern of perovskite crystals, making it more regular and orderly during strain relaxation. [65] Zhu et al conducted an in-depth investigation into the impact of residual strain gradient on the optoelectronic properties of perovskite thin films.…”

Lattice‐Strain Engineering for Heterogenous Electrocatalytic Oxygen Evolution Reaction

“…This chapter highlights more sophisticated strain identification methods, such as atomic electron tomography (AET), 4D-STEM, and HAADF-annular bright-field (HAADF-ABF). [283][284][285][286] Moreover, operando synchrotron X-ray absorption spectroscopy (XAS) and in situ Raman patterns are indispensable for realtime insight into the structural evolution, valence state transformation, and coordination bond lengthening/contraction in the crystalline. [287][288][289][290] Based on the experimental data recorded theoretical calculations are used to deduce the fundamental mechanisms, which optimize the catalytic activity.…”