M. Audier

Ecole de Physique, Electronique et Matériaux (INP de Grenoble - PHELMA), Grenoble, Rhône-Alpes, France

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Publications (145)211.89 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Fabrications of ordered three-dimensional structures with submicron lattice constants were performed on organic–inorganic hybrids using a holographic lithography technique recently reported in the literature. The possibility of such a patterning has previously been demonstrated from single nanosecond laser pulse irradiation of thin films of epoxy photoresist and mixtures of methacrylate-alkoxy-silane with Zr or Ti alkoxides. In the present work, UV irradiation of similar hybrid resins were carried out through repeated laser pulses of low energy with a twofold objective: (i) to study the interference stability for future chemical gas phase decomposition experiments and (ii) to obtain patterning through large film thickness (e.g. 1 mm). The influence of several parameters on the structuration was examined from observations by scanning electron microscopy and optical diffraction. Many interdependent parameters were considered in different steps of the process, namely (i) hybrid resin preparations with required properties of stability, transparency and viscosity, (ii) film coating on different substrates, (iii) UV irradiation (energy and number of laser pulses), (iv) ultrasonic dissolution of monomer, and (v) sample drying. As results, different structuration resolutions were observed as a function of these parameters. But if the influence of a few parameters was easily understood and controlled, it has also appeared that it was not the case of all of them.
    Applied Surface Science 06/2013; · 2.54 Impact Factor
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    ABSTRACT: A method of three-dimensional (3D) holography is used for the growth of photonic crystals of sub-micron cell parameters by gas decomposition in a 3D interference field of UV laser light. Either amorphous or crystalline chromium oxides are obtained by photolysis of chromyl chloride CrO2Cl2 for different experimental conditions. The most interesting product is obtained for a photolysis of CrO2Cl2 at low pressure, on a cooled TiO2 single-crystal substrate and for a higher beam energy. The growth begins with the formation of epitaxial CrO2 metastable phase which is partly transformed into Cr2O3 under UV irradiation. Due to crystallographic orientational relationships between CrO2 and Cr2O3, the growth of a well organized 3D photonic crystal of Cr2O3 phase goes on according to the 3D periodic modulations of electromagnetic energy of the interference field. In the present case, the Cr2O3 phase exhibits four sets of equivalent crystallographic orientations with respect to the single-crystal substrate. From such a result, one can expect to produce in a further work photonic crystals constituted of single-crystalline Cr2O3 phase in epitaxy onto a Cr2O3 or sapphire Al2O3 substrate.
    Journal of Crystal Growth 06/2013; 311(8):2590-2596. · 1.55 Impact Factor
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    ABSTRACT: The crystallization behavior of Ge2Sb2Te5 nanometric clusters was studied using X-ray diffraction with in situ annealing. Clusters were made using a sputtering gas-phase condensation source, which allowed for the growth of well-defined, contaminant-free, and isolated clusters. The average size for the clusters is 5.7 ± 1 nm. As-deposited amorphous clusters crystallize in the fcc cubic phase at 180 °C, while for thin films, the phase change temperature is 155 °C. This observation illustrates the scalability of the Ge2Sb2Te5 phase change from the amorphous to the cubic state in three-dimensionally confined systems in this size range.
    Applied Physics Letters 12/2012; 101(23). · 3.52 Impact Factor
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    ABSTRACT: Among all the new memories concepts, Phase Change Memories (PCM) is one of the most promising. However, various challenges remain. This paper reviews the materials and processes required to face these challenges. As an example, attention will be made on the effect of Phase change material composition on stability of the amorphous phase i.e. on the retention of the information. Additionally, it is showed how specific processes such as CVD or ALD can be developed in order to minimize the current required to amorphize the phase change material i.e. to reset the device. Finally, with the perspectives of the advanced integration nodes, experimental results on the effect of scaling on phase transformation are presented and discussed.
    IEEE International Interconnect Technology Conference (IITC), San Jose'; 06/2012
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    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    ChemInform 01/2010; 30(13).
  • Pure and Applied Chemistry 01/2009; 81(8):1523-1534. · 3.39 Impact Factor
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    ABSTRACT: In 2000, Campbell et al. (Nature 404:53, 2000) have shown that three-dimensional periodic nanostructures can be obtained from UV laser interference irradiation of photoresist for 6 nanosecond single pulse. We have developed a similar experiment for photolytic gas phase decomposition and for photopatternable organic–inorganic hybrid resins. Different steps in results, presently reported, were first to determine the characteristics of both the 3D interference pattern and interferometer to be associated to a CVD reactor and second to verify the mechanical stability of the set up confirmed with the structuration of a siloxane based methacrylic resins by UV polymerization and finally to grow periodic nanostructures by photolytic gas phase decomposition of chromyl chloride. The experimental results obtained so far indicate that, depending on the electromagnetic energy density, a vapor phase decomposition of chromyl chloride leads to periodic arrays of either Cr–O amorphous or Cr2O3 particles on glass and (001)TiO2 substrates at room temperature.
    Applied Physics A 09/2008; 93(1):105-110. · 1.69 Impact Factor
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    ABSTRACT: A fabrication process is proposed for obtaining thin and dense nano-crystalline membranes on porous substrates. The key issue of this process implies the formation of a layer of composite structure in between membrane and substrate in order to reach a high mechanical stability of the membrane through heating and cooling cycling treatments. The membrane is obtained by metal-organic chemical vapour deposition in an amorphous state. The intermediate composite layer is formed by creep of the amorphous membrane through the substrate porosity, followed by a thermal treatment for crystallisation. This process was applied with success to a fabrication of La0.7Sr0.3Fe0.8Co0.2O3−δ and La0.4Sr0.6Fe0.25Co0.75O3−δ nano-crystalline membranes of less than 1μm thickness on porous yttria-stabilised zirconia substrates. Catalytic measurements performed on these thin membranes show that ionic conductivities measured at 500°C are comparable with values reported in the literature obtained on thick membranes of similar composition.
    Journal of Materials Processing Technology 08/2008; 204(1):248-254. · 2.04 Impact Factor
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    ABSTRACT: We present high-resolution electron microscopy and x-ray diffraction studies of the Al63Cu17.5Co17.5Si2 alloy at room temperature. The sample is found periodic in one direction c and presents tenfold symmetry in the l = 0 diffraction plane perpendicular to this direction. The two complementary techniques show that the sample is not in a 2D quasi-crystalline state but in a microcrystalline state, which restores the overall tenfold symmetry in diffraction pattern. On the basis of our present results, we discuss some relationships that could exist between microcrystalline and quasi-crystalline phases.
    EPL (Europhysics Letters) 07/2007; 13(7):629. · 2.26 Impact Factor
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    ABSTRACT: Quasi-crystals of the Al-Cu-Fe system, when given enough time for reaching equilibrium cannot be maintained as a single phase down to room temperature. For the first time, reversible transitions have been observed from rhombohedral microcrystals to a modulated icosahedral structure around (650 ÷ 700) °C, which transforms further into a perfect icosahedral quasi-crystal between (750 ÷ 820) °C and finally turns into a mixture of cubic and monoclinic crystals above 865 °C before total melting.
    EPL (Europhysics Letters) 07/2007; 14(4):355. · 2.26 Impact Factor
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    ABSTRACT: A comparison is made between the theoretical determination of the interference contrast function with fabricated two-dimensional hexagonal structures of submicron lattice constant. Experiments were performed using a siloxane based hybrid organic–inorganic material and a holographic lithography method.Thin hybrid structured layers were fabricated and characterized for different conditions of beam polarizations between 0° and 90°. As a result, the photo patterning appears to be strongly dependent on beam polarization in accordance with theoretical predictions.
    Applied Surface Science 01/2007; 254:850. · 2.54 Impact Factor
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    ABSTRACT: A method to obtain three-dimensional sub-micrometric periodic structures is presented. The experimental set-up consists in a pulsed UV laser beam source (λ=355nm) coming into an interferometer in order to generate four beams converging inside a chamber. According to the directions, to the relative intensities and to the polarizations of these four beams, a 3D interference pattern can be obtained inside the overlapping volume of these four beams; the characteristics of the four laser beams have been optimized in order to obtain a maximal contrast of intensity. In order to visualize the interference pattern, its contrast and its stability at each laser pulse, a video camera coupled to an oil immersion microscope objective has been installed above the interferometer. By suppressing the central beam, it is also possible to generate a bidimensional interference pattern which defines an hexagonal structure in the (111) plane with a period of 377nm.This optical set-up has been used to obtain 3D sub-micrometric periodic structures in negative photoresists. Experiments consist in a one- or multi-pulse irradiation of the photoresist followed by a development procedure which leads to a sub-micrometric face-centred cubic structure cut in a (111) plane with a cell parameter of 650nm. The optimization of the experimental conditions is presented for two kinds of photoresists; the role of the substrate according to its reflectivity at the laser wavelength and its influence on the interference pattern is also discussed.
    Applied Surface Science 01/2007; 253:7947. · 2.54 Impact Factor
  • V. Faucheux, M. Audier, S. Pignard
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    ABSTRACT: Epitaxial thin films of layered nickelates La2NiO4+δ were grown on single crystal substrates by metalorganic chemical vapour deposition with the (1 1 0) plane of the nickelate parallel to the surface of substrate. High resolution transmission electron microscopy (HRTEM) confirms the epitaxial relationship between film and substrate and reveals planar structural faults.Magnetization and resistivity of the films have been measured as a function of temperature. A surprising ferromagnetic behaviour is observed until 400 K which is the highest temperature to be reached; this ferromagnetic component does not come from the nickelate film but most probably from an iron oxide impurity which has been evidenced by X-ray energy dispersive spectroscopy. The temperature dependence of the resistivity, measured from room temperature down to 30 K, corresponds to a semiconductor. In order to examine the electrical conduction mechanism, data have been analysed according to different conduction models; the best description is obtained in the case of a variable range hopping mechanism; this form of conductivity is discussed in relation with the disorder of the structure observed by HRTEM.
    Applied Surface Science 05/2006; 252(15):5504–5507. · 2.54 Impact Factor
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    ABSTRACT: SrTiO3 thin films (STO), were deposited on Si(100) covered by 2nm of SiO2, at different temperatures from 450°C to 850°C using liquid injection MOCVD, the bimetallic precursor being Sr2Ti2(OiPr)8(tmhd)4. The STO films were analysed by XRD, FTIR, SIMS and TEM. An amorphous layer was observed between STO and SiO2/Si. The nature and thickness of the interlayer were determined, as well as the most favourable conditions for a good quality crystalline STO film, and a reduced interlayer.
    Microelectronics Reliability 05/2005; 45:941-944. · 1.14 Impact Factor
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    ABSTRACT: HfO2 and SrTiO3 films were grown on silicon by liquid injection metal organic chemical vapour deposition. The microstructure and structure of the films were characterised by X-ray and electron diffraction, X-ray reflectometry, infrared spectroscopy, and microscopy techniques. In both cases, we emphasised the role of precursors in the resulting composition and microstructure of the films. Dense films of HfO2, either amorphous or crystalline depending on the deposition temperature, were synthesised using Hf(OtBu)2(mmp)2 precursor. Permittivity values of 14–19 were obtained, consistent with the monoclinic structure determined from X-ray diffraction. Optimised films exhibit breakdown field of 6 MV cm−1 and leakage current densities as low as 10−8 A cm−2 at 1 V.Polycrystalline SrTiO3 films were grown using either a mixture of precursors or a heterometallic precursor. The heterometallic precursor provides some advantages such as a lowering of the crystallisation temperature of the perovskite-type phase and a reduction of carbonate impurities at low temperatures. It also allows to keep the films composition constant over a wide temperature range (550–750 °C). The films are highly textured with [0 0 1]SrTiO3 parallel to [0 0 1]Si. The permittivity depends strongly on the films thickness (ɛr ∼ 30 for 10 nm and ɛr ∼ 100 for 100 nm). An equivalent oxide thickness of 1.36 nm (for physical thickness of 15.0 nm) was obtained for optimised SrTiO3 film, with a leakage current density of 10−2 A cm−2 at 1 V.
    Materials Science and Engineering B 04/2005; · 1.85 Impact Factor
  • V. Faucheux, S. Pignard, M. Audier
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    ABSTRACT: We report on the synthesis of thin films of layered nickelates La2NiO4 by metalorganic chemical vapor deposition (CVD). Films have been prepared in a low pressure CVD reactor on three different substrates: MgO (100), LaAlO3 (012) and SrTiO3 (100). The influence of the substrate on the crystallinity of the films has been studied using X-ray diffraction in the Bragg–Brentano geometry and using a texture diffractometer.Films present an epitaxial growth on the three kinds of substrates with the (110) plane of the tetragonal cell of La2NiO4 parallel to the surface of the substrates; two other minority orientations with a- and c- axis perpendicular to the surface are also evidenced. Concerning the in-plane orientation of the epitaxial crystallites, films synthesized on LaAlO3 (012) present a single orientation; in the case of MgO (100) and SrTiO3 (100), another in-plane orientation with crystallites tilted from 45° in the plane of the substrate are also present.
    Journal of Crystal Growth 02/2005; 275(1). · 1.55 Impact Factor
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    ABSTRACT: HfO2 films were deposited at low temperature (∼400°C) by UV assisted injection metal-organic chemical vapor deposition (UVI-MOCVD). A three-step process was used for this study, consisting of (A) Pre-deposition anneal for nitridation; (B) Deposition step; (C) Post-deposition annealing in oxygen. Special attention was paid to the effect of UV exposure during these steps. Films were characterized by physical, optical and electrical techniques. Thickness was determined by different methods (X-ray Reflectrometry (XRR), spectroscopic ellipsometry and transmission electron microscopy) and a good agreement was found for all samples. The HfO2 permittivity, equivalent oxide thickness (EOT), flat-band voltage (Vfb) and total charge (Qt) were extracted from the CV response at high frequency taking into account the HfO2 and SiO2 thicknesses obtained by XRR. The calculated permittivity values were in the range 7–13, i.e. lower than theoretical values for the monoclinic phase. Explanations are suggested in the context of the other characterizations. JEeff characteristics were constructed taking into account the EOT values (Eeff=V/EOT). Effective breakdown fields range between 8.7 and 16.9MV/cm. No dependence of Eeff with UV exposure was found.
    Microelectronics Reliability 01/2005; 45:929-932. · 1.14 Impact Factor
  • Microelectronics Reliability. 01/2005; 45:929-932.
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    ABSTRACT: In this study we report results on a series of Si/SiO2 multilayers periods deposited by standard CMOS processes on thermally oxidised Si substrates. Each period was formed by alternating a low-pressure chemical vapour deposition (LPCVD) nanocrystalline silicon thin film and a SiO2 thin film obtained by atmospheric pressure chemical vapour deposition (APCVD). High-resolution TEM (HRTEM) and Raman spectroscopy have been used for the physical characterisation of the nc-Si/SiO2 multilayers. The HRTEM analysis revealed a columnar structure, with an average grain size of 15nm for the silicon layers. The Si–SiO2 interfaces were smooth with a surface roughness for silicon layers less than 1nm, as estimated from HRTEM analysis. Raman measurements demonstrate that the nanocrystalline silicon (nc-Si) layers are free-of-stress. Room temperature photoluminescence (PL) spectra, obtained by using a 325nm continuous wave (CW) laser excitation, showed a broad blue peak centred on 440nm. The intensity of the blue PL band increased with the number of periods in the nc-Si/SiO2 multilayers. The origin of this intense room temperature blue PL band is discussed.
    Optical Materials 01/2005; 27(5):1020-1025. · 2.08 Impact Factor
  • Microelectronics Reliability. 01/2005; 45:941-944.

Publication Stats

929 Citations
211.89 Total Impact Points

Institutions

  • 2012
    • Ecole de Physique, Electronique et Matériaux (INP de Grenoble - PHELMA)
      Grenoble, Rhône-Alpes, France
  • 2004
    • Moscow State Textile University
      Moskva, Moscow, Russia
  • 1999–2004
    • French National Centre for Scientific Research
      • Institut Néel
      Lutetia Parisorum, Île-de-France, France
  • 1986–2004
    • Grenoble Institute of Technology
      Grenoble, Rhône-Alpes, France
  • 2001
    • Université de Cergy-Pontoise
      • Laboratoire de physique théorique et modélisation
      95001 CEDEX, Ile-de-France, France
  • 1998
    • Institut Laue-Langevin
      Grenoble, Rhône-Alpes, France
    • State University of New York
      New York City, New York, United States