Self‐Assembled Epitaxial Core–Shell Nanocrystals with Tunable Magnetic Anisotropy

Abstract

Epitaxial core-shell CoO-CoFe2 O4 nanocrystals are fabricated by using pulsed laser deposition with the aid of melted material (Bi2 O3 ) addition and suitable lattice mismatch provided by substrates (SrTiO3 ). Well aligned orientations among nanocrystals and reversible core-shell sequence reveal tunable magnetic anisotropy. The interfacial coupling between core and shell further engineers the nanocrystal functionality.

Predicting Epitaxial Nanocrystal Morphology Governed by Interfacial Strain—The Case for NiO on SrTiO3

“…From a numerical perspective when the NiO crystal grows in partial oxygen pressure, gas adsorption contributes to the decrease Δγ gas of the surface energy in eqs and . A few attempts have already been made, , but the practical difficulties of the measurement of gas adsorption are a significant and challenging problem. The incorporation of the effect of oxygen adsorption on the equilibrium shape analysis of epitaxial nanocrystals in the GWK framework forms a part of our future work.…”

“…This interface-controlled morphology is a ubiquitous phenomenon irrespective of the type (vapor/liquid/solid or chemical/physical) of phase deposition. , It is primarily governed by the preferred crystallographic orientation relationship and interface structure between the overlayer and the substrate . Furthermore, more complex factors such as gas absorption or chemisorption at the exposed facets or surface reconstruction during growth also play key roles. , As such, the ultimate functional performance is shown to be strongly dependent on such shape and surface termination-driven changes to the nanocrystals. , Therefore, the interpretation of why the nanocrystal adopts a certain shape and more importantly the prediction of morphology has thus evolved to be one of the most intensely studied topics in the design and development of free-standing epitaxial nanocrystals.…”

“…6,7 As such, the ultimate functional performance is shown to be strongly dependent on such shape and surface termination-driven changes to the nanocrystals. 8,9 Therefore, the interpretation of why the nanocrystal adopts a certain shape and more importantly the prediction of morphology has thus evolved to be one of the most intensely studied topics in the design and development of free-standing epitaxial nanocrystals.…”

Mesocrystal-embedded functional oxide systems

“…For example, Liao et al demonstrated a mesocrystal system consisting of core-shell oxide nanocrystals, enabling researchers to create alternative ways to design magnetic systems. [86] In the study, the self-assembled antiferromagneticferrimagnetic CoO-Co x Fe 3−x O 4 nanocrystals were used as building blocks to form one more branch of mesocrystals, a discrete core-shell mesocrystal. [86] The discrete core-shell nanocrystals were epitaxially grown on substrates, where the epitaxy sets the orientations of building nanocrystal blocks, resulting in a two-dimensional magnetic mesocrystal.…”

“…[86] In the study, the self-assembled antiferromagneticferrimagnetic CoO-Co x Fe 3−x O 4 nanocrystals were used as building blocks to form one more branch of mesocrystals, a discrete core-shell mesocrystal. [86] The discrete core-shell nanocrystals were epitaxially grown on substrates, where the epitaxy sets the orientations of building nanocrystal blocks, resulting in a two-dimensional magnetic mesocrystal. Due to the epitaxy between selected materials and substrates, the OOP orientation, core-shell ratio, and core-shell sequence become key parameters to control the interfacial coupling to deliver desirable properties.…”