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Hiraoui M.,CNRS Foton Laboratory | Guendouz M.,CNRS Foton Laboratory | Lorrain N.,CNRS Foton Laboratory | Moadhen A.,Unite de Spectroscopie Raman | And 2 more authors.
Materials Chemistry and Physics | Year: 2011

In this paper we report detailed Fourier transform infra-red (FTIR) and Raman spectroscopic results obtained after the modification of a porous silica surface using different steps of functionalization and protein grafting. After the elaboration of porous silicon (PS) layers, with sufficient adjusted pore size and well defined porosity, we carried out complete thermal oxidation and we optimized the silanization step by varying the concentration of 3-aminopropyltriethoxysilane (APTES) molecules using different immersion and rinsing durations. Then we introduced a coupling agent, glutaraldehyde (GL) molecules, which has a great affinity for bovine serum albumin (BSA) molecule grafting. FTIR and Raman spectroscopic analyses present complementary spectra that allow us to get an idea about the chemical links and vibrational modes that appear during the functionalization process and after protein attachment. This proves that the biological molecules are covalently attached on the modified porous silica surface. Moreover, a modelling study of the reflectance spectra allows values of the volume fraction and refractive index variations to be estimated by assigning them with the number of APTES, glutaraldehyde and protein layers after each step. These results are well correlated to those obtained by the FTIR and Raman analyses. This work on porous silica single-layers is carried out in order to exploit it for the elaboration of functionalized optical waveguides to obtain a sensitive label-free optical biosensor. © 2011 Published by Elsevier B.V.


Hiraoui M.,French National Center for Scientific Research | Guendouz M.,French National Center for Scientific Research | Lorrain N.,French National Center for Scientific Research | Haji L.,French National Center for Scientific Research | Oueslati M.,Unite de Spectroscopie Raman
Applied Physics Letters | Year: 2012

A buried anti resonant reflecting optical waveguide for an integrated Mach Zehnder structure based on porous silicon material is achieved using a classical photolithography process. Three distinct porous silicon layers are then elaborated in a single step, by varying the porosity (thus the refractive index) and the thickness while respecting the anti-resonance conditions. Simulations and experimental results clearly show the antiresonant character of the buried waveguides. Significant variation of the reflectance and light propagation with different behavior depending on the polarization and the Mach Zehnder dimensions is obtained. Finally, we confirm the feasibility of this structure for sensing applications. © 2012 American Institute of Physics.


Hiraoui M.,French National Center for Scientific Research | Haji L.,French National Center for Scientific Research | Guendouz M.,French National Center for Scientific Research | Lorrain N.,French National Center for Scientific Research | And 2 more authors.
Biosensors and Bioelectronics | Year: 2012

Recently, we demonstrated that Anti Resonant Reflecting Optical Waveguide (ARROW) based on porous silicon (PS) material can be used as a transducer for the development of a new optical biosensor. Compared to a conventional biosensor waveguide based on evanescent waves, the ARROW structure is designed to allow a better overlap between the propagated optical field and the molecules infiltrated in the porous core layer and so to provide better molecular interactions sensitivity.The aim of this work is to investigate the operating mode of an optical biosensor using the ARROW structure. We reported here an extensive study where the antiresonance conditions were adjusted just before the grafting of the studied molecules for a given refractive index range.The interesting feature of the studied ARROW structure is that it is elaborated from the same material which is the porous silicon obtained via a single electrochemical anodization process. After oxidation and preparation of the inner surface of porous silicon by a chemical functionalization process, bovine serum albumin (BSA) molecules, were attached essentially in the upper layer. Simulation study indicates that the proposed sensor works at the refractive index values ranging from 1.3560 to 1.3655.The experimental optical detection of the biomolecules was obtained through the modification of the propagated optical field and losses. The results indicated that the optical attenuation decreases after biomolecules attachment, corresponding to a refractive index change Δn c of the core. This reduction was of about 2dB/cm and 3dB/cm for Transverse Electric (TE) and Transverse Magnetic (TM) polarizations respectively. Moreover, at the detection step, the optical field was almost located inside the core layer. This result was in good agreement with the simulated near field profiles. © 2012 Elsevier B.V.


Boukadhaba M.A.,University of Monastir | Fouzri A.,University of Monastir | Saidi C.,University of Monastir | Sakly N.,University of Monastir | And 5 more authors.
Journal of Crystal Growth | Year: 2014

Zn (1-x)CdxO solid solutions have been grown by us on Zn- and O-polar surfaces of ZnO substrate by metal organic chemical vapor deposition (MOCVD), with the same cadmium flow. We carried out photoluminescence spectroscopy (PL) and optical transmission measurements to investigate the incorporation of cadmium in the layers, as well as its influence on the optical properties. The lattice parameters and the morphology of these films were examined using high resolution X-ray diffraction (HRXRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM). In our case, the Cd incorporation is obtained at 2.5% for Zn(1-x)CdxO grown on the Zn-polar surface of ZnO substrate, which is confirmed by the greatest energy shift (237 meV) toward lower energies of the PL emission, and by the appearance of a new peak located at 270 cm-1 in the Raman spectra. HRXRD studies show that all layers exhibit a wurtzite phase with c-axis orientation. In particular, regarding the Zn0.975Cd0.025O layer grown on Zn-face, the in-plane lattice parameter remains unchanged while the c-axis parameter is elongated to 5.399 Å. © 2014 Published by Elsevier B.V.


El Helali S.,University of Monastir | Daoudi K.,Unite de Spectroscopie Raman | Fouzri A.,University of Monastir | Oumezzine M.,University of Monastir | And 2 more authors.
Applied Physics A: Materials Science and Processing | Year: 2012

We have studied the structural and electrical properties of epitaxial La 0.7Ca 0.3MnO 3 (LCMO) thin films prepared by metal organic deposition under different types and degrees of substrate-induced strain. 40-nm-thick films have been epitaxially grown on single-crystalline (LaAlO3)0.3- (SrAlTaO 6) 0.7 (negligible tensile strain), SrTiO3 (tensile strain) and LaAlO3 (compressive strain) substrates. Highresolution X-ray diffraction and reciprocal space maps demonstrate a direct correlation between the crystalline quality and the substrate-induced strain. The electrical properties were found to be strongly dependent on the substrate used. The temperature dependence of resistivity curves was fitted using various approaches in different phases (below and above the ferromagnetic transition temperature TP). In the ferromagnetic metallic phase, p(T ) follows a T a power law. The obtained values of the coefficient a (3.5-4) indicate that the electrical transport in our films is a combination of spin wave scattering processes and electron-magnon or twomagnon scattering phenomena. In the paramagnetic insulator phase, the activation energy EA and the variable range hopping characteristics (characteristic temperature T0) were found to be strongly dependent on the strain-induced lattice mismatch between the LCMO and the substrate used. © Springer-Verlag 2012.


Daoudi K.,Unite de Spectroscopie Raman | Tsuchiya T.,Japan National Institute of Advanced Industrial Science and Technology | Nakajima T.,Japan National Institute of Advanced Industrial Science and Technology | Fouzri A.,University of Monastir | Oueslati M.,Unite de Spectroscopie Raman
Journal of Alloys and Compounds | Year: 2010

La0.7Sr0.3CoO3 thin films have been epitaxially grown on SrTiO3 (0 0 1) single-crystal substrates by metal-organic deposition process. Crystallinity and morphology of the obtained films were examined in detail using X-ray diffraction and transmission electron microscopy. The evolution of the out-of-plane lattice parameter with film thickness is investigated. The critical thickness for strain relaxation is found in the 60-80 nm range. The electrical properties of the obtained films in various conditions have been investigated. By increasing the annealing temperature to 1000 °C and the film thickness to 120 nm, the electrical resistivity was decreased by several orders of magnitude. We measured a resistivity of approximately 5 × 10-4 Ω cm in a wide interval of temperature 77-320 K, making this material a promising candidate for a variety of applications. © 2010 Elsevier B.V. All rights reserved.


Daoudi K.,Unite de Spectroscopie Raman | Oueslati M.,Unite de Spectroscopie Raman | Tsuchiya T.,Japan National Institute of Advanced Industrial Science and Technology | Nakajima T.,Japan National Institute of Advanced Industrial Science and Technology | Kawaguchi K.,Japan National Institute of Advanced Industrial Science and Technology
Journal of Superconductivity and Novel Magnetism | Year: 2010

La 0.7Ba 0.3MnO 3 thin films have been epitaxially grown by metal-organic deposition on SrTiO 3 (STO) and LaAlO 3 (LAO) single-crystal substrates. Temperature dependence of magnetization M(T) and resistivity ρ(T) are used to characterize the Curie temperature (T C) of the ferromagnetic transition. T C is found to be extremely sensitive to the biaxial strain and film thickness. The T C increases gradually by increasing the film thickness on both STO and LAO substrates, but does not reach the value of the bulk material. This behavior is interpreted in terms of lattice strain in the films and correlated to the microstructural properties. © 2010 Springer Science+Business Media, LLC.


Souissi A.,Unite de Spectroscopie Raman | Haneche N.,University of Versailles | Meftah A.,Unite de Spectroscopie Raman | Sartel C.,University of Versailles | And 5 more authors.
Journal of Luminescence | Year: 2013

ZnO nanowires with different nitrogen concentrations were grown by metalorganic chemical vapour deposition (MOCVD) using DEZn, NO2 and NH3 as zinc, oxygen and nitrogen doping sources respectively. The NH3 concentration in the vapour phase varied from 0 to 13.8 μmol min-1 to favour the nitrogen incorporation. The ZnO nanowires were characterised by scanning electron microscopy, photoluminescence and micro-Raman spectroscopy. Two additional intense Raman peaks at 272 and 580 cm-1 are found to be related to the nitrogen incorporation. Micro-Raman scattering of a single nanowire probes the uniformity of the nitrogen concentration along the nanowire for highly doped samples. The photoluminescence (PL) spectra exhibit donor-acceptor pair band which confirms the incorporation of the nitrogen in the ZnO nanowires. © 2012 Elsevier B.V. All rights reserved.


Souissi A.,Unite de Spectroscopie Raman | Sartel C.,University of Versailles | Sayari A.,King Abdulaziz University | Meftah A.,Unite de Spectroscopie Raman | And 4 more authors.
Solid State Communications | Year: 2012

ZnO thin films were grown by metalorganic chemical vapor deposition on (0001) Zn- and O-polar surfaces of ZnO substrate. The surface morphology of these films was investigated by micro-Raman scattering and scanning electron microscopy. In the case of Zinc-polar face and using back scattering configuration, two new Raman bands were observed at 398 and 584.5 cm -1. They have been interpreted as quasi phonons TO (qTO) and LO (qLO) respectively. The origin of these modes was attributed to the particular morphology of ZnO films grown on Zn-polar face, which consists in c-axis nano-platelets, randomly tilted from the substrate. qTO and qLO frequencies have been calculated using the model of Loudon. SEM observation is in agreement with our Raman interpretation. © 2012 Elsevier Ltd. All rights reserved.

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