Ion beam mixing of aluminium and titanium

The ion beam mixing of Al and Ti by 600 keV Xe ions was studied at room temperature and near 80 K. In view of recent observations of large differences between bilayer and multilayer mixing rates in the Fe-Ti, Ni-Ti, and Cu-Ti systems, both bilayer and buried-layer samples were investigated. Results obtained with the various sample configurations were in good mutual agreement. Comparison to literature data on marker experiments in Al suggested no significant dependence on layer thickness above ∼5 Å. At room temperature, the mixing rate is in excellent agreement with previous multilayer mixing experiments. The initial mixing rate was found to vary by less than 20% between 80 and 300 K. The results are discussed in terms of theoretical models for the mixing mechanisms together with published data on comparable systems. In spite of the low Z values involved, the mixing rate is in good agreement with an expression based on a thermal spike mechanism. At large fluences, a 1260-Å-thick surface layer of Al would suddenly start to degrade quite rapidly.