V. Milinović

Swift heavy ion irradiation of a-Si/Fe/c-Si trilayers

Si∕Fe∕Si trilayers, with 12nm amorphous Si and 45nm polycrystalline Fe films deposited on Si(100) wafers, were irradiated with 350MeV Au26+ ions at fluences of (0.6–11.3)×1014ions∕cm2. The ion-induced modifications of their structural and magnetic properties were characterized by means of Rutherford backscattering, glancing angle x-ray diffractometry, and the magneto-optical Kerr effect. The mixing rate at the upper a‐Si∕Fe interface was three times as high as that at the lower Fe∕c‐Si interface. A simple formula is proposed, which on the basis of (nuclear) thermal-spike mixing reproduces the observed (electronic) mixing rates. Ion irradiation at a moderate fluence (6.7×1014∕cm2) induced a magnetic anisotropy in the sample, which was magnetically isotropic after deposition. At the highest fluence, full interface mixing occurred and the magnetic anisotropy almost disappeared. The results are compared with those obtained in Fe∕Si and Ni∕Si bilayers ion irradiated in the regimes of nuclear and electronic sto...

Ion Beam Modification of Al/Ti Multilayers

Aluminum/titanium multilayers were sputter deposited on (100) Si wafers and irradiated with 200 keV Ar+ and N ions. Irradiation fluences were in the range from 5 · 1015 to 4 · 1016 ions cm−2, for argon ions, and 1 · 1017 to 2 · 1017 ions cm−2 for nitrogen. The samples were analyzed by Rutherford backscattering spectroscopy (RBS), transmission electron microscopy (TEM), and X-ray diffraction (XRD). Nano-hardness measurements were performed by Vickers method. Irradiation with argon ions induces mixing between Ti and Al layers, which is most pronounced in the vicinity of the projected range of implanted species. TEM cross-section analysis shows significant growth of grain size with the increase of Ar ion fluence. Implantation with nitrogen ions, up to these high fluences, causes a full intermixing of Al/Ti layers, resulting in multilayered structures with different content of Al, Ti, and N. In the latter case, nitrogen ion irradiation, probably, induces the formation of nitrides of titanium, aluminum, and AlTi. Nano-hardness measurements show significant increase of hardness for all applied ion fluences.

Ion Beam Mixing at Crystalline and Amorphous Fe/Si Interfaces

Ion beam irradiation of a‐Si/Fe/c‐Si trilayers with 350‐MeV Au ions and of Fe/a‐Si bilayers with 250‐keV Xe ions were carried out in order to measure the interface mixing rates and microstructure, phase formation, and magnetic polarization in the regimes of electronic and nuclear stopping. For Fe/a‐Si and nuclear stopping, an enhancement of the interface mixing rate of 1.75±0.15 was observed relative to Fe/c‐Si. For electronic stopping, the enhancement is 3.21 ±0.34. A plausible explanation of this enhancement lies in the much smaller thermal conductivity in a‐Si relative to c‐Si, which prolongates the relaxation phase of the ion‐induced thermal spikes.