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Multiple Scattering, Rather than Stress, Causes the Low EnergyLow Angle Constant Wavelength Bifurcation of Argon Ion
 

Summary: Multiple Scattering, Rather than Stress, Causes the Low
Energy­Low Angle Constant Wavelength Bifurcation of Argon Ion
Bombarded Silicon surfaces
Charbel S. Madia), Scott A. Norrisb), and Michael J. Aziza)
April 9, 2011
a)Harvard School of Engineering and Applied Sciences, Cambridge MA 02138 USA
b)Department of Mathematics, Southern Methodist University, Dallas TX 75205 USA
Abstract
We show that holes and perpendicular mode ripples that are generated at low argon ion beam energies and inci-
dence angles on room temperature silicon targets (C. S. Madi et al., Phys. Rev. Lett. 101, 246102 (2008) and C.
S. Madi et al, J. Phys. Condens. Matter 21, 224010 (2009)) are caused by multiple scattering events from the im-
pingement of the primary ion beam on adjacent silicon shields. We present a linear stability analysis of a model for
ion beam induced stress in a thin viscoelastic ion-stimulated surface layer and conclude that the flat surface should
be unconditionally stable to topographic perturbations, corroborating the experimental observations. We present a re-
vised topographical phase diagram of 250-1000 eV Ar+ ion bombarded silicon surfaces in the linear regime of surface
dynamics in the absence of secondary scattering effects. It is characterized only by a diverging wavelength bifurcation
from parallel mode ripples to a flat stable surface as the incidence angle falls below about 50 from normal, and a
crossover to perpendicular mode ripples as the incidence angle crosses above about 80.
1 Introduction
Pattern formation resulting from uniform ion irradiation of solid surfaces in the low energy regime (typically 102 -104

  

Source: Aziz, Michael J.- School of Engineering and Applied Sciences, Harvard University

 

Collections: Physics; Materials Science