Viscoelastic Model for the Plastic Flow of Amorphous Solids under Energetic Ion Bombardment

Abstract

Under energetic ion bombardment, amorphous solids show substantial plastic flow in the form of anisotropic growth. This is attributed to the relaxation of shear stresses coupled to the thermal expansion in cylindrical thermal spikes induced by intense electronic excitations and to the subsequent freezing-in of the associated strain increment upon cooling down. An asymptotic growth rate at high electronic stopping power and low irradiation temperature is derived which correlates the growth rate with a few simple material parameters without introducing any adjustable free parameter. Good agreement with measurements justifies the basic assumptions of the model.