Ion beam mixing at nickel-silicon interfaces

Ion-beam mixing at Ni-Si interfaces was investigated as a function of dose, temperature, and dose rate. In the temperature range 10-443 K, the thickness of the mixed Ni-Si layer grew proportionally to the square root of dose for 250-keV Kr** plus irradiations. The apparent diffusion coefficient for mixing during irradiation comprises temperature-dependent and independent contributions. The activation enthalpy for the temperature-dependent part is approximately 0. 09 ev. Varying the dose rate by a factor of approximately 20 had little effect upon mixing at either 80 or 368 K. Analysis of these results using chemical rate theory showed that the low activation enthalpy for diffusion was not associated with point-defect motion. More likely the temperature dependence of mixing in Ni-Si is associated with the effect of temperature on compound formation.