Solute effect of Cu on interdiffusion inAl3Ti compound films

We study the interdiffusion and formation of ${\mathrm{Al}}_3$Ti, in bimetallic thin films of Al/Ti and (Al–0.25 at. % Cu)/Ti, both with and without W diffusion markers, in the temperature range 350–500 °C. The growth kinetics of ${\mathrm{Al}}_3$Ti and marker displacement were measured by Rutherford backscattering spectroscopy. Complementary structural and compositional information were obtained by glancing-incidence x-ray diffraction, transmission electron microscopy, Auger-electron spectroscopy, and secondary-ion-mass spectroscopy. The effect of Cu, revealed by marker analysis of the intrinsic diffusivities of Al and Ti in ${\mathrm{Al}}_3$Ti, is to increase the activation energy of Ti diffusion from 1.68 eV to 2.17 eV while the diffusion of Al is much less affected. By examining the crystal structure of ${\mathrm{Al}}_3$Ti, a vacancy mechanism with Cu occupying Al sites is proposed to explain the solute effect.