The influence of ion irradiation on the structure of binary nanoparticles

FePt and CuAu nanoparticles with a narrow size distribution and a diameter of about 5 nm are prepared through inert gas condensation. Since as-deposited particles usually exhibit the metastable disordered A1 phase we have investigated, how ion irradiation influences the phase stability of various crystal motifs such as icosahedral or decahedral multiply twinned structures.
Ion irradiation leads to the creation of vacancies within the particles and thereby enhances the bulk diffusion of their constituents. In the present study, gas-phase prepared single crystalline and multiply twinned FePt and CuAu nanoparticles are irradiated with ions of different noble gases and different energy. It is shown that the He+ ion irradiation promotes the de-twinning of the binary nanoparticles and the formation of single crystalline A1 phase particles. A comparison of the experiments on CuAu nanoparticles with the results of molecular dynamic simulations will be presented. The effect of the energy difference between the different morphologies for both the ordered and disordered structures is discussed.