ION-BEAM MIXING OF NI/TI BILAYER THIN-FILMS

Amorphization by ion beam mixing of bilayered samples consisting of nickel and titanium layers, each 50 nm thick, has been studied by selected area electron diffraction, plan and cross-sectional view transmission electron microscopy and Rutherford backscattering spectroscopy. Amorphization occurred on irradiation with 1 Mev Au** plus ions at fluences ranging from 3 multiplied by 10**1**9 to 2 multiplied by 10**2**0 m** minus **2. Cross-sectional transmission electron microscopy revealed that amorphization starts close to the original Ni-Ti ; interface. It has been shown that collisional processes alone cannot account for the observed amount of mixing. A model based on thermodynamics has been found to predict an amount of mixing higher than that observed experimentally.