Tomographic study of the three-dimensional distribution of a high-fluence implant in a polymer

5-MeV Li-6(+) ions were implanted into PMMA at high flux up to fluences of 1 x 10(15) cm(-2) under angles of 0 degrees to 70 degrees towards the surfa ce normal. The Li depth distributions were determined by means of neutron d epth profiling, and compared with theoretical simulations. The three-dimens ional Li distribution was reconstructed from the one-dimensional depth prof iles by means of a tomographic technique. It turned out that the measured Li depth distributions can be described by a superposition of Gaussian and exponential functions. This points at consi derable Li mobility during or after the ion implantation, with trapping in unsaturable traps in the ion-irradiated region which roughly follow the ele ctronic energy transfer distribution. The Li redistribution is more pronoun ced along the track direction than transversely to it. The normalized Li distributions in various implantation directions were fed into our tomographic program to reconstruct the three-dimensional distribu tion of the deposited lithium. As expected, the lithium preferentially dist ributes along the ion tracks. This work is another hint that mobility of im planted ions in solids does not proceed isotropically, but is strongly infl uenced by the radiation-damage distributions.