Incubation dose for ion beam induced anisotropic growth of amorphous alloys: insight into amorphous state modifications

Under energetic ion bombardment, amorphous materials deform plastically in the form of anisotropic growth. At medium electronic stopping power (5 to 30 keV/nm) this phenomenon starts only after a certain incubation dose depending on values of the electronic stopping power and temperature. This delay is modeled on the basis of the assumption of a drastic irradiation induced viscosity reduction, resulting from accumulation of atomic displacements in the matrix and local material heating in the heavy ion track. A simple analytical expression is derived which is in a good agreement with experimental data for the amorphous alloy Fe85B15.