Material semi-coherent interfaces impact properties, both desirable and undesirable

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Semi-coherent oxide interfaces form when two oxides with different lattice constants are joined. Because of the mismatch between the materials, they cannot align one-to-one and defects (or misfit dislocations) form at the interface to accommodate that mismatch.

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In the quest for enhanced functionality in materials, nanostructured materials are becoming more common. This is particularly true of oxide/oxide heterostructures in which interfaces (where two different materials meet) are frequent.

These interfaces can have positive effects, such as enhancing ionic conductivity, improving radiation resistance, and engineering strain across multiphase nanocomposites. In short, interfaces provide nanomaterials with desired properties. In fact, interfaces are being introduced into complex material systems to develop new properties.

However, some interfaces are responsible for degradation, which is undesirable. Despite the importance and pervasiveness of interfaces in materials, there is still much that is unknown, particularly in oxide materials, about how these interfaces influence material properties.

Learning about interfaces in complex oxide materials

In research selected as an “Editor’s Pick” in APL Materials, Los Alamos materials scientists and their collaborator present a perspective on the importance of a specific type of interface, called a semi-coherent interface, in oxides.

In this invited work, the researchers investigate the misfit dislocations that define semi-coherent interfaces. These interfaces are complex because of the inherent material strain, which is common to all materials, including metals, as well as disrupted chemical bonding, which is unique to these types of systems where chemical and ionic bonds drive structure. They state that the exciting prospect of these interfaces is in driving performance. “In such cases,” the researchers explain, “any ability to modify the misfit dislocation network density or structure would provide another knob for tuning functionality.”

The application of these materials is quite broad; therefore, harnessing and controlling performance and functionality is advantageous, particularly at the atomic scale. There is still much to explore with semi-coherent interfaces, as they offer properties that coherent interfaces cannot.

Funding and missions

Funding for the Los Alamos portion of the work was provided by the DOE Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division and the Center for Integrated Nanotechnologies, an Office of Science User Facility operated by Los Alamos and Sandia national laboratories.

Reference: Blas Uberuaga (MST-8), Pratik Dholabhai (Rochester Institute of Technology), Ghanshyam Pilania (MST-8), and Aiping Chen (MPA-CINT). “Semi-coherent oxide heterointerfaces: Structure, properties, and implications.” APL Materials, 7 100904 (2019). DOI: https://doi.org/10.1063/1.5121027.

Technical contact: Blas Uberuaga

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While only limited theoretical work has been done to examine the structure and properties of these interfaces, that work highlighted that misfit dislocation structures change fundamental properties at the interface, including the segregation of defects and dopants and mass transport at the interface.