CEMS Faculty

Our graduate student research group currently emphasizes mechanical behavior of small volumes such as nanospheres and failure at bi-material interfaces. This ranges from strained-layer epitaxy of microelectronic materials to polystyrene/silicon interfaces. Materials of interest have included nanospheres of silicon, SiC and Ti; Si, NiAl and Fe-3wt%Si single crystals; and InGaAs/GaAs, Co/Si, PS/PMMA, DLC/MgO, and Cu/Si thin films. Micromechanical modeling and single crystal studies are primarily aimed at understanding the underlying mechanisms for fatigue, fracture, toughness, and strength. The principal goal is life prediction for all types of microstructurally influenced interface structures. We have recently started four initiatives with which to better understand the integrity of materials. One is real-time imaging of nanomechanical and micromechanical processes with AFM, TEM, and FEG-SEM (field emission gun scanning electron microscopy). An example of this is in situ fracture of silicon nanospheres. Such a nanoindentation instrument is currently being installed in our newest TEM (Tecnai). A second example is nanoindentation induced dislocation emission in ceramic and metallic single crystals, thin films, and nanospheres. Surfaces undergoing nanoindentation can be imaged by atomic force microscopy directly before and after revealing nanometer scale cavities. A third is the removal of copper thin films processed by microlithography to represent test structures for adhesion analysis by nanoindentation.

With the failure of any of these microelectronic or structural interfaces, analysis ranges from the nanoscopic to the macroscopic. All of these studies use powerful experimental tools--such as selected area channeling and thin-film electron microscopy, nanoindentation and atomic force microscopy--in conjunction with analysis techniques provided by continuum and atomistic theory.