SEM Hot Stage Investigation of Surface Bubble Formation and Rupture in Helium-Implanted Rare Earth Films

Abstract

Helium atoms introduced into metal films by radioactive decay and by ion implantation migrate under the influence of thermal or stress fields, and form expanding bubbles which ultimately deform the lattice and rupture the film surface. Though several studies have been performed to investigate internal migration of submicroscopic helium bubbles, relatively little work has been reported on the influence of gas bubbles on surface microtopography and on the dynamics of bubble rupture. We have investigated localized surface deformation in thin metal films which have been implanted with helium to high doses and then annealed in situ in a scanning electron microscope. The progress of bubble-induced surface deformation and exfoliation in selected areas was observed and recorded photographically. Sequential shots relating the chronological progression of events were made into a time-lapse movie. The influence of (implanted) helium concentration, anneal temperature and post implantation aging on the onset of surface bubble formation and rupture was observed.