Effects of lattice misfit
Researchers using the XSD 11-BM-B beamline at the APS are collecting High Resolution Synchrotron Powder Diffraction Data (PXRD) to gain insight into the influence of lattice misfit on the growth mechanism of a series of Prussian Blue Analogues (PBAs) heterostructures using Nickel Hexacyanocobaltate (KNiCo) particles as the substrate.
The engineering of highly efficient electronic, magnetic and optical devices requires careful considerations of epitaxial growth processes and control of defects in thin film heterostructures. Strain and strain-relief mechanisms are known to play a key role in determining the morphology and properties of thin films, with elastic strain and dislocations both contributing to the lattice energy at the material interfaces.
A small mismatch between the substrate and overlayer generally results in the growth of a strained pseudomorphic layer. To accommodate larger misfits, the formation of dislocations becomes energetically more favorable. These concepts are well established in the context of traditional solid-state materials, but nucleation and growth of coordination polymer thin films and heterostructures remain relatively unexplored.
The heterogeneous growth of a series of Prussian Blue Analogues (PBAs) on Nickel Hexacyanocobaltate (KNiCo) seeds to achieve coordination polymer heterostructues was investigated to determine the influence of lattice misfit over the growth mode. For small lattice misfits, the observation of a core@shell-type morphology indicates the growth of a pseudomorphic layer while larger lattice misfits result in the growth of islands. A structural study suggests an efficient mechanical coupling of the substrate and overlayer materials. The difference in lattice constants between the heterostructure components induces anisotropic strain that is relieved by switching to a different growth mode.
Olivia N. Risset and Daniel R. Talham, “Effects of Lattice Misfit on the Growth of Coordination Polymer Heterostructures,” Chemistry of Materials, Just Accepted Manuscript. DOI: 10.1021/acs.chemmater.5b00205, Published May 5, 2015.