CONSEQUENCE OF THE FRACTAL NATURE OF THE COLLISION CASCADE - END-OF-RANGE SPIKES IN BALLISTIC SYSTEMS

Based on the fractal geometry approach of the collision cascade, a new concept of spike formation at the end of the ion range is presented. This ''end-of-range spike'' occurs when the ion energy becomes smaller than the spike initiation threshold; its spatial distribution resembles the ion range distribution. For ions of sufficiently large atomic numbers, end-of-range spikes may form even in ''ballistic'' systems where spike initiation by the recoil atoms does not occur. Experimental results on ion beam mixing of nitride/metal bilayers and on noble gas precipitation at the irradiated interfaces are discussed. In both cases end-of-range spikes explain the experimental data.