Katsuyo Thornton

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

kthorn@umich.edu

2022 HH Dow

T: (734) 615-1498

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Phase-Field Simulations of Thin-Film Evolution During Heteroepitaxy

Collaborators: Peter Voorhees, John Lowengrub, Steven Wise, Dan Gogswell, Nirand Pisutha-Arnond
In collaboration with Northwestern University and University of California, Irvine, we examine the evolution of thin films during heteroepitaxy. In semiconductor thin films, such as Ge on Si, spontaneous formation of nano-scale structures occur due to the stress caused by the difference in the lattice parameters of the substrate and film materials. Such natural tendency can be applied to develop a method for self-assembly of quantum dot array. The phase-field model utilizes advanced numerical methods such as the multigrid method and variable mesh.
Highlights (Click an image for more information)
  • Quantum Dots/Islands Array on Substrate

    Regularly arranged islands grow from a thin film patterned with small periodic perturbation. Four tiny spatially arranged pits are seeded on an originally flat surface. The system evolves to reduce its total energy by deforming of the surface. The phase-field simulation result shows the island growth can be guided by surface patterning. A regular array of quantum dots will provide a route to novel electronic devices such as charge-storage memory. The color indicates the height (red: the highest).

  • Simulation of Quantum Dots/Islands Formation on Substrate

    The animation shows a phase-field simulation of an instability developing on a strained thin-film surface that has a small random perturbation. The roughening of the surface increases the surface area and the surface energy, but reduces the elastic energy such that the total energy decreases. The phase-field model allows us to calculate the surface evolution driven by the reduction of the total energy. The color indicates the height (red: the highest).

  • Quantum Ring

    A ring shape structure forms from a pre-seeded mound on a strained flat film. The strain energy favors roughing of the surface, while the interfacial energy favors flat surface. This phase-field simulation shows that a small perturbation of the surface is enough to fix the location of the dot formation and that the secondary ring naturally forms as a consequence of dot formation. The color indicates the height (red: the highest).