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Nemouchi F.,CEA Grenoble | Carron V.,CEA Grenoble | Labar J.L.,MTA TTK MFA | Vandroux L.,CEA Grenoble | And 3 more authors.
Microelectronic Engineering | Year: 2013

Germanium based devices are of interest due to their performance potential. The use of germanium as source and drain requires low resistance access achieved by the formation of germanide (metal-germanium compound). The nickel mono-germanide (NiGe) is claimed to be the best candidate since it presents suitable electrical and thermo-kinetic qualities. However, since the germanium oxidizes instantaneously in air, we provide in this paper a study of reactions between a nanometric Ni film and a germanium (001) substrate in the presence of a native or controlled grown germanium oxide. The goal is to study the influence of the germanium oxide onto germanidation process. We report that whatever the germanium oxide types (native or grown) formation of nickel germanides can occur unlike to silica which inhibits metal/silicon reactions. Numerous characterizations such as XRD, TEM, EFTEM, SIMS and SEM lead us to propose a model. Whatever the oxide type as thick as 8 nm, nickel reacts with GeO 2 during its deposition and transforms into a continuous germanate layer allowing NiGe nucleation on Ge substrate. After heat treatment the entire pure Ni film has reacted while the germanate NixOyGe z were present. This means that Ni transport occurred even through germanate. Finally, this NixOyGez film shifted toward the surface as a discontinued layer. © 2013 Elsevier B.V. All rights reserved.

Kovacs N.,MTA TTK MFA | Patko D.,MTA TTK MFA | Patko D.,University of Pannonia | Orgovan N.,MTA TTK MFA | And 6 more authors.
Analytical Chemistry | Year: 2013

The surface adsorption of the protein flagellin was followed in situ using optical waveguide lightmode spectroscopy (OWLS). Flagellin did not show significant adsorption on a hydrophilic waveguide, but very rapidly formed a dense monolayer on a hydrophobic (silanized) surface. The homogeneous and isotropic optical layer model, which has hitherto been generally applied in OWLS data interpretation for adsorbed protein films, failed to characterize the flagellin layer, but it could be successfully modeled as an uniaxial thin film. This anisotropic modeling revealed a significant positive birefringence in the layer, suggesting oriented protein adsorption. The adsorbed flagellin orientation was further evidenced by monitoring the surface adsorption of truncated flagellin variants, in which the terminal protein regions or the central (D3) domain were removed. Without the terminal regions the protein adsorption was much slower and the resulting films were significantly less birefringent, implying that intact flagellin adsorbs on the hydrophobic surface via its terminal regions. © 2013 American Chemical Society.

Desfours C.,CNRS Charles Coulomb Laboratory | Calas-Etienne S.,CNRS Charles Coulomb Laboratory | Horvath R.,MTA TTK MFA | Martin M.,CNRS Charles Coulomb Laboratory | And 3 more authors.
Applied Physics A: Materials Science and Processing | Year: 2014

The aim of this work is to demonstrate the sensing ability of reverse-symmetry waveguides to investigate adsorption of casein and build-up of poly-L-lysine mediated casein multilayers. A first part of this study is dedicated to the elaboration and characterization of ultra-porous thin films with very low refractive indices by an appropriate sol-gel method. This will form the basis of our planar optical sensors. Optical waveguide light mode spectroscopy is a real-time and sensitive method to study protein adsorption kinetics and lipid bilayers. We used it to test the obtained waveguides for in-situ monitoring of biomolecule adsorption. As a result, significant changes in the incoupling peak position were observed during the layer-by-layer adsorption. Finally, refractive index and thickness of the adsorbed layers were established. © 2013 Springer-Verlag Berlin Heidelberg.

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