A statistical model of low temperature blister formation in helium-implanted metals

A model of the growth of large bubbles in solids during ion implantation is presented. In this model, the random formation of ″vacancies″ or defect clusters in a lattice is simulated by Monte Carlo methods. Lattice defects within a certain cutoff distance of one another are assumed to coalesce and rearrange themselves in as near to spherical geometry as possible. This iterative process of coalescence and rearrangement continues until all defects are farther apart than the cutoff distance. Then a new random defect is introduced and the process continues. In this way, isolated defects agglomerate into the larger bubbles. This process, rather than the radiation displacement of atoms directly on the bubble surface, dominates the growth. It is found that the growth rate of the largest bubble is slow until a critical concentration is reached, after which the bubble grows at an accelerated rate.