International Topical Meeting on Nuclear Research Applications and Utilization of Accelerators

4-8 May 2009, Vienna

High Ion Irradiation Tolerance of Multilayered AlN/TiN Nanocomposites

M. Milosavljević;¹, D. Peruško¹, V. Milinović¹, B. Timotijević¹, A. Zalar², J. Kovač², and C. Jeynes³

¹VINČA Institute of Nuclear Sciences, Belgrade, Serbia
²Jožef Stefan Institute, Ljubljana, Slovenia
³University of Surrey Ion Beam Centre, Guildford, England

Corresponding Author: momirm@vinca.rs

High strength multilayered metal or composite nanostructures are interesting as radiation protective materials, because of a large number of interfaces that act as obstacles to slip and sinks for radiation induced defects. In the investigations reported to date, mainly multilayers of immiscible metals were studied, such as Cu/Nb, W/Ni, Cu/W or Mo/Cu. This study reports on the stability of nanocrystalline AlN/TiN multilayers upon argon ion irradiation. The AlN/TiN system was chosen because it exhibits high strength and temperature stability, and the constituents are immiscible. Reactive sputtering was used to deposit (AlN/TiN)x5 films on (100) Si, to a total thickness of ~270 nm. Argon ions were implanted at 200 keV, the projected ion range being around mid-depth of the deposited structures. The applied fluences were high enough to induce a marked intermixing in normally soluble or chemically reactive materials. Structural characterizations of the samples were performed by Rutherford backscattering spectrometry (RBS), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). It was found that the investigated AlN/TiN multilayers exhibit a remarkable ion irradiation stability. Ion irradiation induced a slight increase of the mean grain size in individual layers, from ~10 nm to ~20 nm, and small local density changes around the projected ion range. Apart from this, no distinct intermixing of the layers was observed. Also, the interfaces remained sharp after irradiation to all the applied fluences, which is crucial for structural stability of multilayered structures. The results were compared to other systems and analyzed in terms of the existing ion beam mixing models. The net mixing rate found was below the predictions of the ballistic model. In fact, in immiscible systems thermal spikes and chemical driving forces invoke dynamic demixing, when the knocked on particles are driven back across the interface. In conclusion, the results obtained in this study suggest that immiscible metal-nitride multilayers should attract further attention as radiation tolerant materials.

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