Shocks in Ion Sputtering Sharpen Steep Surface Topographic Features Michael J. Aziz, Harvard University, DMR predicted surface height a c b d lateral position Ion sputtering from Focused Ion Beams is used for micromachining tall, steep features. A new regime of ion sputtering has been discovered for sufficiently steep slopes. High slopes propagate over large distances without dissipating the steepest features. A feature, e.g., a metal line can be fabricated at a large length scale and, through uniform ion irradiation, reduced to a smaller length scale while preserving, or even sharpening, the sharpest features. H.H. Chen, O.A. Urquidez, S. Ichim, L.H. Rodriguez, M.P. Brenner, and M.J. Aziz, Science, in press (2005).

Nonlinear Theory of Sputtering Our treatment: small curvature, treat other terms exactly Rewrite in terms of slope b=dh/dx Erosion Rate (Sigmund sputter integral) Previous treatments (Bradley-Harper, Makeev et al.) Small-slope expansions of Sigmund sputter integral: valid for small deviations from average slope and curvature. “The Advection Diffusion Eqn”

the Advection-Diffusion Equation advection curvature effect, small for our cases where traveling wave speed surface diffusion

Slope Selection predicted evolution of h(x) conditions for formation undercompressive shock: b*=3.89

Strange Matter Illustrated in Boston Museum of Science Exhibition Michael J. Aziz, Harvard University, DMR In a collaboration with the Boston Museum of Science on the traveling exhibit “Strange Matter” developed by the Materials Research Society, the P.I. and graduate students made interactive presentations to visitors of all ages. Visitors explored the unique properties of everyday materials such as honey, cornstarch and silly putty and were introduced to unheard-of materials such as metallic glass. The exhibit exposed tens of thousands of visitors to the wonderment of materials science and gave them an enhanced appreciation of the value of materials in society.