Theoretical description of helium and argon bubble growth in an amorphous alloy

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Abstract
A model for bubble growth during noble gas implantation in an amorphous alloy is presented, in which the excess pressure in the bubble is considered constant. Special attention is given to swelling and coalescence effects which turn out to be very important. Good agreement with experiment is obtained for the dose dependence of the radius and concentration of helium bubbles in 5keV implantation experiments on amorphous Fe40 Ni38Mo4B18. Also the maximum bubble radius which can be observed following 5keV Ar+ bombardment of the same alloy is reproduced. According to the calculation the bubble radius strongly increases immediately after the implantation of an incubation dose. For larger doses the radius increases nearly linearly with increasing dose. Analytical approximations are derived to describe the bubble growth as a function of dose. In an alternative model, it is assumed that the bubbles grow as a consequence of the combined effect of a continuous noble gas input and the existence of radiation damage. We also performed some new experiments which suggest that this alternative mechanism is probably not the most important. However, it can become important under specific experimental conditions.