Influence of the ion type on the ion beam mixing of Cr/Al interfaces

The room temperature ion beam mixing (IBM) of Cr/Al interfaces by 3 keV Ar+ and He+ ions has been carried out in order to study the influence of the ion type on the IBM process. A two stages IBM kinetics has been found by application of factor analysis to X-ray photoelectron spectroscopy data. The first stage is characterized by a strong decrease of the metallic Cr species concentration associated with sputtering and formation of a nearly stoichiometric chromium aluminide, CrAl. The CrAl related species concentration reaches a maximum at the end of the first stage, slowly decreasing subsequently during the second stage because of sputtering. The differences observed between the final ion dose and maximum CrAl species concentration at the end of the first stage between Ar+ and He+ IBM have been explained as due to the different sputtering yields and energy deposited per incoming ion. Likewise, the difference observed in the stoichiometry of the CrAl compound formed has been associated with Cr preferential sputtering effects taking place during Ar+ IBM. The disagreement between experimental results and Monte Carlo TRIDYN simulations suggests that radiation-enhanced diffusion processes contribute to the low energy Ar+ and He+ IBM of Cr/Al interfaces at room temperature, especially when He+ is used.