Fabrication of a Bimodal Ferromagnetic Nanosystem in an Etched Silicon Structure and its Magnetic and Magneto-Optic Characterization

Abstract

Ni-nanowires are fabricated in a two-step electrochemical process. In the first step a porous silicon template with oriented pores perpendicular to the surface is produced. The electrochemical parameters for this etching procedure, like HF-concentration, current-density, etching-time and bath-temperature have to be chosen in a very small regime to obtain the favored structure in a good quality. This mesoporous silicon skeleton with highly oriented pores and homogeneous spatial distribution is filled in a further electrochemical step by a ferromagnetic metal, like Ni. This selforganized Ni-nanowire array is characterized by Auger-spectroscopy to evidence the loading of the pores over the full length. SEM and BSE are used to reveal the orientation of the pores and the homogeneous Ni-filling. By Fourier Transform image processing a predominant quadratic self-organized grouping of the (100) grown pores is identified. An additional investigation method is EDXS to show the element distribution in the sample. Furthermore magnetization measurements are used to generate a model for the Ni-loading in the channels. Not only wires but also granules in the size up to 200 nm are present. IR-spectroscopy investigations are used to compare the bare silicon wafer, the porous silicon (PS) sample and the PS with incorporated Ni at zero and finite magnetic fields.