Research Activities > Programs > Nonequilibrium Interface and Surface Dynamics 2007

Growth and Pattern Formation for Epitaxial Surfaces

CSIC Building (#406), Seminar Room 4122.

Growth and Pattern Formation for Epitaxial Surfaces

Professor Russel Caflisch


Abstract:   Growth of an epitaxial thin film involves physics on both atomistic and continuum length scales. For example, diffusion of adatoms can be coarse-grained, but nucleation of new islands and breakup for existing islands are best described atomistically. The lattice properties of the film are determined by those of the underlying substrate. In heteroepitaxial growth, e.g., Germanium on Silicon, mismatch between the lattice spacing of the Silicon substrate and the Germanium film will introduce a strain into the film, which can significantly influence the material structure. leading for example to the formation of quantum dots. Technological applications of quantum dot arrays require a degree of geometric uniformity that has been difficult to achieve. One approach to overcoming this difficulty is to prepattern the system, for example with buried dislocation lines. This talk will describe mathematical modelling, simulation methods and computational results for epitaxial growth, strain in thin films and pattern formation. The growth simulations use an island dynamics model with a level set simulation method. Strain computations can be computationally intensive, so that effective simulation of atomistic strain effects relies on an accelerated method that incorporates algebraic multigrid and an artificial boundary condition. Simulations that combine growth and strain will be presented showing spontaneous and directed self-assembly of patterns (quantum dots and wires) on thin films.

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