Large-Scale Molecular Dynamics Simulation of Plastic Deformation Induced by FIB

Focused ion beam (FIB) is a novel approach for fabricating nanostructures and devices with nanometer-scale accuracy. During FIB processes, it is often reported that energetic ion bombardment induce plastic deformations. For example, the fabricated nanostructures such as cantilever beams or nanowires tend to deflect toward the direction of incoming ions. Such large-scale deformation can be manipulated to form 3D nanostructures for various applications ranging from biology to optoelectronic devices. Nevertheless, the underlying mechanisms governing the large-scale plastic deformation of nanostructures induced by ion beam bombardment still remains elusive. In this work, we carried out a series of large-scale molecular dynamics (MD) simulations to investigate the plastic deflection of Al cantilever beam induced by energetic Ga+ ion bombardment. With the aid of GPU computation, we are able to simulate the deflection process of Al cantilever beam (60x20x10 nm^3 in size) with Ga+ energy ranging from 20 keV to 7.5 keV. Our MD simulation results indicate that the deflection of Al cantilever beam originates from imbalance of Al mass transport toward the upper/lower surface upon ion beam bombardment, and the direction of Al beam deflection can be manipulated by changing impinging Ga+ energy.