Richard Wagner

Advisor: Ben Burton

Ceramics Division

Materials Science and Engineering Laboratory

Building 223, Room A-317

301-975-8359 (ph)

301-975-5334 (fax)


Category: Materials





Simulation of Phase Transformations During Nanoindentation of Silicon


Nanoindentation is an experimental technique for probing the mechanical properties of materials on the nanoscale (1-1000 nm).  These measurements are performed by pressing a diamond indentor into a planar sample and recording the force versus displacement response.


A material of particular interest is silicon, due to its widespread use in microelectronic and microelectromechanical devices.  Nanoindentations into crystalline silicon have detected changes in crystal structure from the initial diamond lattice (Si-I) to other crystalline (Si-II, Si-III, Si-XII) and amorphous phases.  Since these other phases exhibit different mechanical properties than the original material, it is important to understand how they form and how they respond to mechanical loads.


We are currently studying these phase transformations by atomistic simulation.  We use an empirical interatomic potential to model the forces between atoms as a sample system is subjected to varying conditions of compression and temperature.  The results are allowing us to determine when silicon will transform from its original crystalline structure and how the phase composition evolves during deformation.