Regensburg 2007 – scientific programme

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MA: Fachverband Magnetismus

MA 27: Micro- and Nanostructured Magnetic Materials II

MA 27.4: Talk

Thursday, March 29, 2007, 16:00–16:15, H22

Ferromagnetic Nanotubes by Atomic Layer Deposition — •Mihaela Daub, Mato Knez, Julien Bachmann, Ulrich Gösele, and Kornelius Nielsch — Max Planck Institute of Microstructure Physics, Halle, Germany.

Magnetic nanotubes are a new class of anisotropic ultifunctional nanoobjects. By coating the inner or outer nanotube wall with oxides or metals, a range of physical and chemical properties can be realized within a single nanoobject. Atomic Layer Deposition (ALD) is a very versatile technology for the conformal coating of Al2O3 membranes. Due to the low reactivity of molecular hydrogen and in comparison to the ALD deposition of metal oxides (0.5-2 Å/cycle), most processes for transition metals, e.g. Ni, Co, Cu, based on the reaction of hydrogen and a metal-organic precursor, are rather slow (0.03-0.2 Å/cycle). We propose a three-step process for the ALD deposition of transition metals. When the ALD cycle starts, the sample is exposed to the metal-organic precursor. After the removal of the excess recursor molecules, the chemisorbed precursor molecules on the sample surface are exposes to an oxidizing gas specious, e.g. ozone or water. In the final step of the ALD cycle the sub-monolayer of metal oxide is transferred into a pure metallic layer by a hydrogen exposure. The arrays of cobalt nanotubes exhibit a preferential magnetisation direction along the nanowire axis, whereas the Ni nanotubes show a nearly isotropic magnetic behaviour. The authors thanks the German Ministry of Education and Research (BMBF) for financial support (FKZ: 03N8701).