PLASTIC-FLOW IN FCC METALS INDUCED BY SINGLE-ION IMPACTS

Irradiation of Au and ph foils with Xe ions at temperatures between 30 and 450 K has been monitored using in situ transmission electron micr oscopy. Single ion impacts give rise to surface craters on the irradia ted surface with sizes as large as 12 nm. Approximately 2%-5% of impin ging ions produce craters on Au while only about 0.6% produce craters on Pb. Larger craters on Au frequently have expelled material associat ed with them. Temporal details of crater formation and annihilation ha s been recorded on video with a time-resolution of 33 ms. Craters anni hilate in discrete steps due to subsequent ion impacts or anneal in a continuous manner due to surface diffusion. Craters production (those persisting for one or more video-frames) as a function of temperature indicates that the surface diffusion process responsible for thermal a nnealing of craters has an activation energy of 0.76 eV in Au. Crater creation results from plastic flaw associated with near surface cascad es. Crater annihilation in discrete steps results from plastic flow in duced by subsequent ion impacts, including those that do not themselve s produce a crater. Crown Copyright (C) 1998 Published by Elsevier Sci ence S.A.