Directional Mass Transport by Momentum Transfer from Ion Beam to Solid

Abstract

Irradiation of InP with MeV Se ions directed a few degrees off the surface normal leads to a lateral displacement of the implanted material. Adjacent surface regions that are not irradiated remain unaffected. The dependence of the displacement on ion energy and its directionality strongly suggest that the effect is caused by momentum transfer from the ion to the solid. The amount of displaced material as a function of ion beam energy or angle of incidence can be described with a simple model incorporating a shear stress, applied to the target as the ion slows down, and radiation enhanced viscosity.