Katsuyo Thornton

L.H. and F.E. Van Vlack Professor

kthorn@umich.edu

2022 HH Dow

T: (734) 615-1498

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NSF-EC Cooperative Activity in Computational Materials Research: Bridging Atomistic to Continuum Scales - Multiscale Investigation of Self-Assembling Magnetic Dots During Epitaxial Growth

Collaborators: Mark Asta, John Lowengrub, Peter Vorhees, Axel Voigt, Olivier Fruchart, Tapio Ala-Nissila, Miroslav Kotrla
Sponsor: NSF DMR-0502737
In the fabrication of nanostructures for optoelectronic applications, tremendous advances have been realized in the development of self-assembly methods for semiconductor materials based on heteroepitaxial vapor-phase growth techniques. In particular, so-called directed self-assembly methods have been demonstrated recently based on the use of prepatterned substrates or vertical alignment in growth of multilayers, allowing a high degree of control over size distributions and growth of complex patterned arrays. While tremendous progress has been made for semiconductor systems, self-assembly of metallic nanostructures has not been advanced to the same degree. Such developments offer the potential to revolutionize the development of future media for ultra-high-density magnetic recording. The primary goal of the project is to advance the state of the art in multiscale computational materials science through development of a suite of tools for predictive modeling of directed self-assembly. These tools will be utilized to build fundamental understanding of important microscopic and continuum-level phenomena governing nanoscale self-assembly. Although the computational tools to be developed are general and will have application beyond the systems studied, the feasibility of our approach in applications to specific systems will be demonstrated for the well-studied magnetic material systems Fe/Mo and Fe/W. We propose an integrated approach by joining forces of computational experts from the European Community and the United States, spanning the atomistic to the continuum scales. The goal of this project is to investigate the underlying physics of magnetic dots formation during heteroepitaxy. Our group will work mainly on the continuum modeling based on the phase-field model, integrated with the results from ab initio calculations and Kinetic Monde Carlo simulations. Therefore, our simulations will encompass the aspects from an entire scale of atomic to continuum scales, and can provide a comprehensive picture of the self-assembly of magnetic dots.
Highlights (Click an image for more information)
  • Simulation of Multilayer Magnetic Dot Growth

    We use the phase-field method to simulate alternating epitaxial deposition of a strained film material on a different substrate material.  Due to elasticity effects, the thin film forms nanoscale dots on the surface to minimize the free energy of the system.  In subsequent layers, energetics cause new dots to grow directly above those below, forming vertical dot arrays.  These simulations will be used to study growth of multilayer nanostructures and their resulting properties.