A generalized 3D elastic model for nanoscale, self-assembled oxide-metal thin films with pillar-in-matrix configurations

TL;DR

This paper presents a generalized 3D elastic model for nanoscale oxide-metal thin films with pillar-in-matrix structures, incorporating lattice mismatch and capillary forces, and uses finite element analysis to study their energetics and configurations.

Contribution

It introduces a comprehensive 3D elastic model that accounts for interface curvature and lattice mismatch effects in oxide-metal nanocomposites, validated through finite element simulations.

Findings

Random pillar configurations have lower total energy than ordered ones.

Interfacial energy is the dominant factor influencing system energetics.

Interfacial energy is a key design parameter for nanocomposite growth.

Abstract

In recent years, functional oxide-metal based vertically aligned nanocomposite (VAN) thin films have gained interest due to their intriguing physical properties and multifunctionalities stemming from the complex interactions between the two phases in the film and the substrate. In this work, we develop a model for studying the energetics of these thin film systems, including the effects of both lattice mismatch and capillary forces due to interface curvature. Each phase is incorporated into the model using a phase indicator function, and we introduce the capillary forces as body forces using a vector density representation of the interface. The model is implemented using the finite element method to study the deformation of the thin film which is composed of Au nanopillars embedded in a La0.7Sr0.3MnO3 (LSMO) matrix on an SrTiO3 (STO) substrate. The results suggest that the total energy is lowest for random configurations of pillars compared to ordered square and hexagonal lattice configurations, consistent with the random distribution of pillars found in experiments. Furthermore, we find that the interfacial energy dominates the total energy of each configuration, suggesting that interfacial energy in the system is an important design parameter for nanocomposite growth, along with the lattice mismatch.