"Computational Modeling of Oxide-metal Multiphase Thin Film Growth with Pillar-in-matrix Configuration" 

Ahmad Ahmad, MSE PhD Candidate 

Advisor: Professor Anter El-Azab

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ABSTRACT

The physical and chemical properties of multiphase self-assembled oxide-metal thin films with pillar-in-matrix configurations, known as vertically aligned nanocomposite (VAN), have received a great deal of attention in the past few decades. The growth and morphology evolution processes of such films are so complicated, which limits our understanding of how these systems form under, say, pulsed-laser deposition. Current research has suggested that the ordering and evolution of the embedded phase configuration in the matrix can be described in terms of the lattice-mismatch elastic strain and the interfacial energy. From a self-assembly point of view, adatom diffusion on the surface, binding energies, as well as the effect of interfaces and elastic stain on the migration and binding energy landscapes all impact the clustering, nucleation, and growth of VAN systems. The Kinetic Monte Carlo (KMC) method efficiently parameterized by density functional theory (DFT) captures these events at the atomic and mesoscopic sales. In the case of multiphase film growth, elastic strains arise due to the heterogeneity in material properties. Therefore, the kMC model must be parameterized by DFT such that it can incorporate elastic forces. A new methodology that couples the elastic effects to kMC simulations has been developed, with the elastic strain computed using Fast Fourier Transform (FFT). The coupling of the elastic effects with the kMC simulations has also been informed by DFT by computing the strain effects on the migration and binding energies of various diffusing species on various surfaces. Coupling of the elastic effects with kMC growth simulations revealed that not only does the morphology of the minor metal phase change, but also the self-organization of the metal pillars are impacted mainly by elastic strains in the system.