Model-Based Simulations to Engineer Nanoporous Thin Films

Description

This was a joint project with Prof. Gary L. Gray to create a model-based simulation (MBS) capability for tailoring the fabrication processes and the properties of wide band gap semiconductors with engineered nanoscale porosity via the:

1. computational prediction of the morphology of a thin film as it derives from a given set of deposition parameters;
2. theoretical determination of the deposition conditions leading to the creation of a given target nanostructure;
3. computational prediction of mechanical properties such as the porosity distribution throughout the film, assessment of its mechanical stability along with the spatial distributions of the intrinsic stresses, interfacial fracture toughness, and (heterogeneous) elastic moduli as well as their symmetry properties;
4. computational measure of the constitutive parameters required for use in advanced bending theories of thin films. This will contribute to future developments in which in situ measurements of the spatial distribution of thin film curvature are used for the real-time estimation of the intrinsic stresses in nanoporous thin films.

We focused on developing a computational framework based on molecular dynamics simulations (MDS) to relate a given set of deposition parameters to the resulting microstructure.

Along with the MDS development we ended up delving into the fundamental questions concerning the translation of mechanical behavior from a discrete level to the continuum level. This work, which has a strong theoretical component, resulted in the creation of a new Lagrangian-based MD scheme for the determination of the stress-strain behavior of materials starting from a knowledge of their atomic interaction potentials.

Results

• Pedro C. Andia, who earned both his M.S. and his Ph.D. under the joint supervision of myself and Prof. Gray. Following his Ph.D., Pedro took a position with ADINA R & D, Inc.;


• Thomas J. Yurick, Jr., who earned both his his Ph.D. under the joint supervision of myself and Prof. Gray. After his Ph.D., Tom took a position with Quartus Engineering Inc. in San Diego, California.

Results

You can take a look at some of our results in this presentation, which I have given at the end of June 2006 at the Structural Engineering Department of the Politecnico di Milano. To view this presentation you will need a PDF viewer, such as Adobe Acrobat Reader. Also, the presentation has a couple of QuickTime movies embedded in it and you will need a QuickTime plugin for you PDF viewer to see these movies.