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Nanoscale deformation and instability

The objective of this work is to understand the role of femtosecond dynamics of atomic collisions and subsequent nanoscale deformation on morphological instability in solids, subjected to impact by a projectile atom. From continuum perspective, it is tempting to leave out the atomistic mechanisms that occur at the femto-level time scales in explaining hour-scale experimental observation of ripple pattern in solids. Nevertheless, using a multiscale framework, it is found that the mechanics of morphological instability in solids under energetic impact is coupled strongly to the geometric features, characterizing momentum transport, of the deformed nanocale domain. For example, the asymmetry of the craters, which represents deformation on the nanoscale and is formed at the femtosecond level time scales, creates asymmetry in momentum transfer, leading to the formation of orientations and their transitions on solid surfaces. In addition to providing fundamental mechanics insights, this study has important implications in understanding fabrication of nano-electronic devices.

                                                                  
        Fig. Effect of angle of incidence on formation of crater shapes. The black arrows indicate projectile's direction.

Further reading
   
M. Z. Hossain, K. Das, J. B. Freund, and H. T. Johnson
Ion impact crater asymmetry determines surface ripple orientation
Applied Physics Letters 99, 151913 (2011)