Amorphization of Fe/Zr Multilayers by Ar-Ion-Beam-Mixing
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AMORPHIZATION OF Fe/Zr MULTILAYERS BY Ar-ION-BEAM-MIXING M. KOPCEWICZ*, J. JAGIELSKI*, T. STOBIECKI**, F. STOBIECKI# AND K. ROLL## * Institute of Electronic Materials Technology, W6lczyfiska 133, 01-919 Warszawa, Poland, ** Institute of Electronics, Academy of Mining and Metallurgy, Al. Mickiewicza 30, 30-059 Krak6w, Poland, # Institute of Molecular Physics, Smoluchowskiego 17/19, 60-179 Poznafi, Poland, 44 Gesamthochschule-Universitiat Kassel, FB Physik, 3500 Kassel, Germany. ABSTRACT The Ar-ion-beam-mixing of the FeZr multilayer system is studied by conversion electron Mdssbauer spectroscopy. The dependence of the amorphization process on the layer thickness and ion dose is studied in detail for samples with Fe to Zr ratio of 1 and 0.5 and modulation wavelength of 5 to 90 nm. INTRODUCTION The ion-beam-mixing technique, extensively used in recent years, allows to obtain unique phases which cannot be formed in another way, and greatly expands the possible application of ion beams to modify properties of materials. Typical ion-beam-mixing experiments were performed for bilayer materials consisting of a thin layer of one constituent deposited on the bulk substrate of another material, or for multilayer structures [1-3]. It was shown that the mixing efficiency depends on ion mass and energy and is directly related to the nuclear energy density deposited by the ion, and that the mixing rate is independent of the ion dose. Most of the mixing experiments were performed for Ar, Kr or Xe ions [1-3], however, ion-beam-mixing induced by light ions (protons) was also reported [4]. As a result of the mass transport induced by the interaction of the energetic ions with the target atoms the irradiated material may undergo transition from the crystalline to amorphous state. The Fe/Zr system is particularly convenient for studying the formation of the amorphous phase due to ion-beammixing because all amorphous FeZr phases are dia- or paramagnetic at room temperature [6] and reveal the quadrupole splitting doublet (QS) in the M6ssbauer spectra in clear distinction to ferromagnetic a-Fe and crystalline interfacial Fe/Zr regions which show a magnetic hyperfine structure. Amorphous Fe/Zr was formed by all the commonly used methods, such as liquid quenching [6,7], vapour deposition [6,8,9], mechanical alloying [10,11], solid state reaction [4,8,9,12-14] and ion-beam-mixing [4,5]. In the present study the amorphization and interfacial mixing induced by Ar ion-beam-mixing is reported for the Fe/Zr multilayer system. The dose dependence of the mixing effect is studied in detail for Fe/Zr with 1 and 0.5 Fe to Zr ratio and with a modulation wavelength of 5 nm to 90 nm. EXPERIMENT Multilayer Fe/Zr films were prepared by rf sputter deposition from Fe and Zr targets [15]. Samples of two dFe/dZr thickness ratios of 0.5 and 1.0 were prepared. The modulation wavelengths A-dFe+dZr varied from 5 nm to 80 nm for dFe/dZrffil and from 7.5 nm to 90 nm for dFe/dZrO0.5. The total thickness of the film stacks deposited on Si or glass was about 200 nm and
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