Shocks in Ion Sputtering Sharpen Steep Surface Features
H. Henry Chen,1*
Omar A. Urquidez,2
Stefan Ichim,2
L. Humberto Rodriquez,2
Michael P. Brenner,2
Michael J. Aziz2
We report a regime of ion beam sputtering that occurs for sufficiently
steep slopes. High slopes propagate over large distances without
dissipating the steepest features. Both the propagation velocity
and the dynamically selected slope are universal, independent
of the details of the initial shape of the surface. The resulting
behavior can be understood as the propagation of a shock front
that self-selects a stable slope, as has been previously observed
in thin-film fluid flows. Experiments confirm predictions of
the theory. An important implication of the propagative behavior
at high surface slopes is that a pattern 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.
2 Division of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA.
* Present address: Lawrence Livermore National Laboratory, Livermore, CA 94550, USA.
To whom correspondence should be addressed. E-mail: maziz{at}harvard.edu
