Fabrication and optical properties of a self-organized ferromagnetic Ni/Si-nanocomposite

A mesoscopic composite consisting of porous silicon (PS) and two kinds of Ni precipitations is investigated by FTIR-spectroscopy and SQUID-magnetometry, respectively. The electrochemically produced PS/Ni-composite system consists of wires and non-spherical particles with a diameter around 60 nm and a one-dimensional extension of a few tens of micrometers, which imposes a significant out of plane magnetic anisotropy. Transmission in the mid-infrared is found near 10% for both, bare PS and the Ni-filled system. The transmission spectra of unprocessed Si and PS are similar, apart from the Si-Hx vibration modes due to the PS template. In the presence of Ni a broad absorbance structure at wavenumbers of 3500 cm−1 is found, caused by NiOx or Schottky barrier absorption across the Si/Ni-interface between Ni nanoparticles/wires and the silicon skeleton.