Magnetically interacting low dimensional Ni-nanostructures within porous silicon.

Electrodeposition of ferromagnetic metals, a common method to fabricate magnetic nanostructures, is used for the incorporation of Ni structures into the pores of porous silicon templates. The porous silicon is fabricated in various morphologies with average pore-diameters between 40 and 95 nm and concomitant pore-distances between 60 and 40 nm. The metal nanostructures are deposited with different geometries as spheres, ellipsoids or wires influenced by the deposition process parameters. Furthermore small Ni-particles with diameters between 3 and 6 nm can be deposited on the walls of the porous silicon template forming a metal tube. Analysis of this tube-like arrangement by transmission electron microscopy (TEM) shows that the distribution of the Ni-particles is quite narrow, which means that the distance between the particles is smaller than 10 nm. Such a close arrangement of the Ni-particles assures magnetic interactions between them. Due to their size these small Ni-particles are superparamagnetic but dipolar coupling between them results in a ferromagnetic behavior of the whole system. Thus a semiconducting/ferromagnetic hybrid material with a broad range of magnetic properties can be fabricated. Furthermore this composite is an interesting candidate for silicon based applications and the compatibility with today's process technology.