COHESIVE ENERGY EFFECTS ON ANISOTROPIC TRANSPORT IN ION MIXING

Experimental investigations of the effect of target species cohesive energy on anisotropic transport in ion mixing of metallic systems are reported. Bilayer samples with nearly zero heats of mixing, but different cohesive energy and geometry, such as W on top of Pd (W/Pd), Pd on top of W (Pd/W), Nb/Cu, Cu/Nb, Ag/V, and V/Ag, were irradiated with 300 keV Kr2+ at doses of 1 x 10(16) Kr2+/cm2 and 2 x 10(16) Kr2+/cm2 at 77 K. The samples were investigated using embedded markers and Rutherford backscattering spectrometry. The experimental results indicate a preferential transport of higher cohesive energy material into lower cohesive energy material - in some cases contrary to ballistic arguments. This phenomenon is explained in terms of thermally activated diffusion within thermal spikes.