Etienne Ferain

Giant Magnetoresistance in Magnetic Multilayered Nanowires

Giant magnetoresistance (GMR) is observed in a new type of nanostructured material consisting of magnetic multilayered nanowires formed by electrodeposition into nanometer-sized pores of a template polymer membrane. The composition of these nanowires is modulated over nanometer length scales with distinct magnetic and nonmagnetic metallic layers. Magnetoresistance measurements with the current perpendicular to the layers were performed on the array of parallel nanowires. GMR of about 15% was observed at room temperature on Co/Cu multilayered nanowires

Track-etch templates designed for micro- and nanofabrication

This paper reports on the advances made in the laboratory in the development of porous media by track-etching process, and on their use by research partners as templates for the micro- or nanofabrication of polymeric and metallic wires or tubules with interesting properties. It mainly relates to the development of nanoporous polycarbonate-based templates, and more precisely to pore-shape control in polycarbonate films, to the development of supported track-etch templates and to the feasibility of template patterning; recent results on the development of templates from polyimide support are also reported. Finally, some nanontaterial synthesis processes and properties are listed, with references to published papers

Electrochemically synthesized polypyrrole nanotubules: Effects of different experimental conditions

Nanotubules of polypyrrole (PPy) were electrochemically synthesized using the pores of nanoporous polycarbonate (PC) particle track-etched membranes (PTM) as templates. The influence of some conditions of electrosynthesis (electrochemical method, monomer concentration, electrolyte concentration and nature) on the kinetics of pyrrole electropolymerization and on the morphology of the obtained nanomaterials has been investigated. In particular, the empirical kinetics of the electrochemical generation of polypyrrole-perchlorate (PPy-ClO4) from aqueous solution, at 0.8 V (vs SCE) was followed by electrical charges measurement. The orders with respect to pyrrole and LiClO4 are 0.34 and 0.70 respectively. The electrogeneration of polypyrrole-polystyrenesulfonate (PPy-PSS) was also followed and shows that an increase of the electrolyte concentration increases the polymerization rate at constant potential. Finally, the morphology of PPy nanotubules doped with LiClO4 and NaPSS has been studied by high resolution emission SEM and by TEM

Track-etched Membrane - Dynamics of Pore Formation

The dynamics of pore formation during etching of heavy ion (Ar9+ -4.5 MeV/amu) irradiated bisphenol-A polycarbonate (PC) and polyethylene terephthalate (PET) films is determined by a conductivity cell. This work presents the theoretical basis of this method and describes the experimental procedure. The obtained results allow the determination of the track (V(t)) and bulk (V(g)) etch rates, and an estimate of the damage zone diameter in PC before etching.

Pore shape control in nanoporous particle track etched membrane

This paper shows the possibility of preparing nanoporous particle track etched membranes (nanoPTM) with perfectly smooth and cylindrical pores from polycarbonate film. Interest in the template use of these nanoPTM for the production of polymeric or metallic nanoscale materials is also emphasized

Fabrication of a new generation of track-etched templates and their use for the synthesis of metallic and organic nanostructures

This paper reports on the realisation of nanoporous supported templates by the track-etching method. Spin-coated polycarbonate films have been irradiated by energetic heavy ions (Ar9+, 220 MeV), UV irradiated and chemically etched in aqueous NaOH (2 N, 70 degreesC). The thickness of the supported templates has been varied between 200 nm and a few microns and the pore size between 15 and 100 nm. Dynamics of pore formation in these supported templates has been compared to dynamics of pore: formation in classical self-supported track-etched membranes. This new generation of templates has been successfully used to electrochemically synthesise polypyrrole nanotubes and copper (Cu) nanowires. The pore size and the nanostructure morphology, providing information on the pore shape, have been studied by high resolution electron microscopy

Magnetic photonic band-gap material at microwave frequencies based on ferromagnetic nanowires

We present an experimental investigation of a class of microwave photonic band-gap (PBG) materials, in which the magnetic permeability μ varies periodically within the material. This material is fabricated using a periodic arrangement of arrays of magnetic nanowires. As for dielectric or metallic PBG, the band-gap behavior varies with the geometrical parameters fixing the spatial periodicity of the magnetic structure. The magnetic photonic band gap is induced by the presence of a ferromagnetic resonance effect in the vicinity of the band gap.

Characterisation of nanoporous particle track etched membrane

Nanoporous particle track etched membranes with pore size ranging from 15 to 100 nm are prepared from 10 mu m thick polycarbonate film. Mean pore size and pore size distribution are determined using electrical conductivity and small angle X-ray scattering techniques, and high resolution scanning electron microscope. NanoPTM are also used as templates for the preparation of electrodeposited nanowires giving interesting information about the pore shape. Results of these characterisation methods are compared.

Chemical modifications induced in bisphenol A polycarbonate by swift heavy ions

The chemical modifications in bisphenol A polycarbonate induced by swift heavy ion irradiation are analyzed in situ by means of Fourier transform infrared (FTIR) spectroscopy. Four beams (C-13, Ne-20, Ca-48, Xe-129) with energy of a few MeV/amu have been used. Irradiations were performed under vacuum with electronic stopping power in the range from 1.6 to 86 MeV mg(-1) cm(2). Deposited doses are less than or equal to 1 MGy. The FTIR spectra obtained after the irradiation exhibit an overall reduction of the intensities of the virgin PC typical vibration bands and the appearance of new bands. The analysis of the destruction and the new vibration bands points out that the energy deposition mechanisms are quite different depending on electronic stopping power

Anisotropic transport and magnetic properties of arrays of sub-micron wires

We report a comparative study of anisotropic magnetoresistance and magnetic properties in arrays of sub-micron Ni; and Co wires electro-deposited in the cylindrical pores of track-etched polymer membranes. The variation of coercivity and squareness as a function of wire diameter for arrays of almost isolated sub-micron wires is reported in the range 30-500 nm. The Wi and Go-based systems demonstrate different magnetic and magnetoresistive behaviors except for the smallest diameter. It is believed that the observed difference originates from the presence of competing crystal anisotropy in the Co-based system.