1. High Pressure Phase Transformations (HPPT) of Silicon, Germanium, and Silicon Nitride, John Patten, Ron Scattergood, George Pharr, and Robert Nemanich WMU, NCSU, UT-K; DMR-0403650, a FRG During this past year we concluded research on silicon, germanium, silicon nitride and pursued additional research on silicon carbide. Three important contributions during this past year include: 1.Infrared laser heating of the metallic HPPT (see image). 2.Determination of geometrical effects of indenter shape, and development of a model. 3. Established a minimum damage depth of 2-3 nm for machining semiconductors and ceramics Thermal Infrared camera image of HPPT of Silicon being preferentially heated by diode laser; IR laser beam passes through the diamond tip and into the silicon. Est. temperature 600 C (red) Silicon Surface Diamond

2. High Pressure Phase Transformations (HPPT) of Silicon, Germanium, and Silicon Nitride, John Patten, Ron Scattergood, George Pharr, and Robert Nemanich WMU, NCSU, UT-K; DMR-0403650, a FRG HPPT Workshop, 2006 Each year our Focused Research Group (FRG) sponsors a workshop for researchers interested in high pressure phase transformations of semiconductors and ceramics. In 2006 we held our 4 th HPPT workshop in Kalamazoo Mi at Western Michigan University. Participants included 6 universities and 4 industrial partners and over 20 individuals contributed talks and posters. Workshop Participants Participants not pictured: Dave Stephenson, Tatiana Mitchell, Andre Webb, Deepak Ravindra, and Hanna Wells

3. Illustration of the model FRG: High Pressure Phase Transformations of Silicon, Germanium, and Silicon Nitride John Patten Western Michigan University, George Pharr University of Tennessee, Ron Scattergood and Robert Nemanich North Carolina State University, DMR-0403650 The pop-out behavior in silicon during indentation is believed to be caused by a volume increasing phase transformation from the high pressure phase formed under the indenter to a lower pressure crystalline form. Our experimental observations and those of others have indicated that pop-out is promoted by large indentation loads, slow unloading rates, and intermediate indenter angles. We have developed a mechanistically-based model to describe the process based on the assumption that pop- out corresponds to homogeneous nucleation of the low pressure crystalline form from the high pressure phase. The model qualitatively predicts the experimental observations and gives a quantitative estimate of how the pop-out load should vary with major experimental variables. The non-popped indentations transform to the amorphous form, due to insufficient driving force for nucleation to occur during the unloading time (a structural frustration argument). Predicted Pop-out behavior of Si single crystal Si III-XII nucleus h P max transformed zone Si II (or a-Si) volume V r* driving force:  G v < 0 Si II Si-III/XII retarding force:  Attaching atoms