An ion beam mixing model for compound formation: the case of Pd/Si

Abstract

The squared thickness of the mixed layer in the case of ion-beam-irradiated Pd/Si displays a quadratic dependence on the fluence below a critical value Φ c and a linear dependence above Φ c. A qualitative interpretation of such a behavior has been provided in terms of a formation-controlled process below Φ c and a diffusion-controlled process above Φ c. In this paper, we give a short presentation of a model associating Fick's law and a chemical driving force in order to simulate the chemical reaction at the irradiated boundary leading to the formation of Pd 2Si. The mixing rate above Φ c is enhanced as compared to the one due to collisional processes only. In the particular case of Pd/Si, we have used this model to account for the experimental mixing rates measured above Φ c at 300 K on a wide range of the density of energy deposited in nuclear collisions from 0.01 to 6 keV/nm.