(Invited) Pore Filling of Porous Silicon with Ferromagnetic Nanostructures

Metal deposition within porous silicon is under investigation for more than 2 decades whereat the incorporation of metals has been examined with respect to the influence of the light emission or to the modification of the conductivity of porous silicon but also to the growth of different metals inside macropores has been studied in detail. In the frame of this work the deposition of different metals, especially ferromagnetic ones within high aspect ratio mesopores will be elucidated with respect to the specific nucleation and growth of the deposited nanostructures under various conditions. To ensure that the nanostructure growth starts at the pore bottom pulsed electrodeposition has been used. Since mesoporous morphologies offer dendritic pore walls these structural inhomogeneities of the matrices are critical for the deposition process. From experiments one can see that the nucleation preferentially starts at the “tops” of the rough surface. The electrochemical parameters offer the opportunity, but have to be chosen exactly, to obtain desired results. A further key point of the presentation is the magnetic characterization of the various nanocomposites. Magnetic characterization of the three dimensional nanowire/nanoparticle arrays shows that not only the morphology of the deposited metal structures (size, shape, distribution) determines the magnetic properties but also the morphology of the template, e.g. side-pores of different length. In this sense magnetic coupling between the nanostructures plays a crucial role and is strongly influenced by morphological parameters. From all these findings it is possible to prepare samples with specific magnetic properties which could be of interest for on-the-chip devices.