Vacancy-Impurity Binding Energy in Aluminum—1.7 at.% Zinc Using Positron-Annihilation Lifetimes

Positron-annihilation lifetimes were measured in pure aluminum and in aluminum—1.7 at.% zinc at temperatures between 20 and 550°C. The data were analyzed using an extension of the trapping model to obtain the vacancy formation energy in aluminum ($E_F=0.62\mathrm{}\pm 0.02$ eV). Under certain restrictive assumptions the binding energy of vacancies to zinc atoms in aluminum was found to be $E_B=0.019\mathrm{}\pm 0.004$ eV. A relaxation of these assumptions yielded only an upper bound ($E_B<0.04\mathrm{}$ eV).