Microstructural Effects of Chemical Island Templating in Patterned Matrix-Pillar Oxide Nanocomposites

TL;DR

This study investigates how chemical island templating influences the microstructure and nucleation of epitaxial CFO pillars in BFO matrix-pillar nanocomposites, using electron microscopy and x-ray diffraction.

Contribution

It provides detailed microstructural analysis of templated CFO-BFO nanocomposites, revealing effects of seed islands on grain boundaries and lattice tilting.

Findings

Templated islands control pillar nucleation sites.

Grain boundaries are observed at the interface.

Lattice tilting occurs due to seed island microstructure.

Abstract

The ability to pattern the location of pillars in epitaxial matrix-pillar nanocomposites is a key challenge to develop future technologies using these intriguing materials. One such model system employs a ferrimagnetic CoFe$_{2}$O$_{4}$ (CFO) pillar embedded in a ferroelectric BiFeO$_{3}$ (BFO) matrix, which has been proposed as a possible memory or logic system. These composites self-assemble spontaneously with pillars forming through nucleation at a random location when grown via physical vapor deposition. Recent results have shown that if an island of the pillar material is pre-patterned on the substrate, it is possible to control the nucleation process and determine the locations where pillars form. In this work, we employ electron microscopy and x-ray diffraction to examine the chemical composition and microstructure of patterned CFO-BFO nanocomposites. Cross-sectional transmission electron microscopy is used to examine the nucleation effects at the interface between the template island and resulting pillar.Evidence of grain boundaries and lattice tilting in the templated pillars is also presented and attributed to the microstructure of the seed island.