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Search Results: 1 - 10 of 191343 matches for " D. Deresmes "
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Characterization of ion/electron beam induced deposition of electrical contacts at the sub-μm scale
D. Brunel,D. Troadec,D. Hourlier,D. Deresmes,M Zdrojek,T. Mélin
Physics , 2011, DOI: 10.1016/j.mee.2011.03.011
Abstract: We investigate the fabrication of electrical contacts using ion- and electron-beam induced deposition of platinum at the sub-\mu m scale. Halos associated with the metal surface decoration are characterized electrically in the 0.05-2 \mu m range using transport measurements, conducting atomic force microscopy and Kelvin probe microscopy. In contrast with IBID, EBID electrodes exhibit weakly conductive halos at the sub-\mu m scale, and can thus be used to achieve resist-free electrical contacts for transport measurements at the sub-\mu m scale. Four-point transport measurements using \mu m-spaced EBID contacts are provided in the case of a multiwalled carbon nanotube.
Asymmetry of Polarization Reversal and Current-Voltage Characteristics of Pt/PZT-Film/Pt:Ti/SiO2/Si-Substrate Structures
S. L. Bravina,N. V. Morozovsky,J. Costecalde,C. Soyer,D. Remiens,D. Deresmes
Smart Materials Research , 2011, DOI: 10.1155/2011/374915
Abstract: The characterization of the asymmetries of bipolar charge-voltage and current-voltage loops of polarization reversal and unipolar current-voltage curves for Pt/PZT-film/Pt:Ti/SiO2/Si-substrate systems was performed in the dynamic mode. The asymmetry of local deformation-voltage loops was observed by piezoresponse force microscopy. The comparison of the dependences of introduced asymmetry factors for the bipolar charge-voltage and current-voltage loops and unipolar current-voltage curves on drive voltage indicates the interconnection of ferroelectric and electrical space charge transfer asymmetries. 1. Introduction At present, lead zirconate titanate (PZT) film on silicon structures are considered among the best ones for creating elements of Si-integrated converters of various types. However, the practically important electrical characteristics of “metal-PZT film-metal-Si-substrate” systems manifest the well-known set of natural and technological asymmetries. Earlier [1–3], we reported the results of investigations of polar and poling asymmetries of the set of pyroelectric and related characteristics of Pt/PZT-film/Pt:Ti/SiO2/Si-substrate sandwich type structures. In this paper, we concentrate our attention on the characterization of the complex of the asymmetries of dynamic bipolar charge-voltage (Q-V-) and current-voltage (I-V-) loops and unipolar current-voltage (J-V-) curves as well as bipolar deformation-voltage (X-V-) loop asymmetry. We present the results of investigation of interrelated polarization reversal and current-voltage dynamic asymmetries of Pt/PZT-film/Pt:Ti/SiO2/Si-substrate systems. 2. Experiment 2.1. Samples The samples under investigation were PZT films prepared by the radiofrequency magnetron sputtering method. The bottom Pt electrode of 150?nm of thickness with Ti adhesive layer of 10?nm of thickness was deposited on the 350?nm SiO2 layer on a 350?μm (100) n-type Si wafer. Pb(ZrxTi1?x )O3 film with x = 0.54 of 1-2?μm of thickness was deposited on the Pt/TiOx/SiO2/Si-substrate structure just after its stabilization by annealing treatment at 650–700°C. The perovskite ferroelectric phase of PZT was obtained by annealing at 625°C for 30?min. Then, a top Pt (150?nm) electrode of ≈1?mm2 of area was deposited by sputtering. The sputtering conditions and the results of X-ray and microstructure characterization were described in details in [4]. 2.2. Measurements For the investigations of polarization reversal (PR) and current-voltage characteristics, the measuring set for complete ferroelectric characterization [2] was used. The
Conductivity of DNA probed by conducting-atomic force microscopy: effects of contact electrode, DNA structure, surface interactions
Thomas Heim,Dominique Deresmes,Dominique Vuillaume
Physics , 2004, DOI: 10.1063/1.1769606
Abstract: We studied the electrical conductivity of DNA molecules with conducting atomic force microscopy as a function of the chemical nature of the substrate surfaces, the nature of the electrical contact, and the number of DNA molecules (from a few molecules, to ropes and large fibers containing up to ~ 106 molecules). Independent of the chemical nature of the surface (hydrophobic or hydrophilic, electrically neutral or charged), we find that DNA is highly resistive. From a large number of current-voltage curves measured at several distance along the DNA, we estimate a conductivity of about 10-6-10-5 S.cm-1 per DNA molecule. For single DNA molecules, this highly resistive behavior is correlated with its flattened conformation on the surface (reduced thickness, \~0.5-1.5 nm, compared to its nominal value, ~2.4 nm). We find that intercalating an organic semiconductor buffer film between the DNA and the metal electrode improves the reliability of the contact, while direct metal evaporation usually destroys the DNA and prevents any current measurements. After long exposure under vacuum or dry nitrogen, the conductivity strongly decreases, leading to the conclusion that water molecules and ions in the hydration shell of the DNA play a major role.
Determination of the electrostatic lever arm of carbon nanotube field effect transistors using Kelvin Force Microscopy
David Brunel,Dominique Deresmes,Thierry Melin
Physics , 2009, DOI: 10.1063/1.3148364
Abstract: We use Kelvin Force Microscopy (KFM) to study the electrostatic properties of single-walled Carbon Nanotube Field Effect Transistor devices (CNTFETs) with backgate geometry at room temperature. We show that KFM maps recorded as a function of the device backgate polarization enable a complete phenomenological determination of the averaging effects associated with the KFM probe side capacitances, and thus, to obtain KFM measurements with quantitative character. The value of the electrostatic lever arm of the CNTFET is determined from KFM measurements, and found in agreement with transport measurements based on Coulomb blockade.
Localization and delocalization of charges injected in DNA
Thomas Heim,Thierry Melin,Dominique Deresmes,Dominique Vuillaume
Physics , 2004, DOI: 10.1063/1.1794852
Abstract: The electrical properties of DNA molecules are investigated by charge injection and electric force microscopy experiments. Prior to injection, DNA molecules exhibit a weak positively charged state. We probe the electrical behaviour of DNA by measuring the localized or delocalized character of the DNA charge states upon injection of excess charges. We show that injected charges do not delocalize for overstretched DNA prepared by a receding meniscus technique, while the adjunction of spermidine during the deposition leads to relaxed DNA molecules exhibiting a charge delocalization over microns. The interplay between charge localization/delocalization and deposition techniques may explain that transport behaviors ranging from insulating to conductive have been reported for DNA deposited on surfaces.
High on-off conductance switching ratio in optically-driven self-assembled conjugated molecular systems
Kacem Smaali,Stephane Lenfant,Sandrine Karpe,Maitena Ocafrain,Philippe Blanchard,Dominique Deresmes,Sylvie Godey,Alain Rochefort,Jean Roncali,Dominique Vuillaume
Physics , 2010, DOI: 10.1021/nn100295x
Abstract: A new azobenzene-thiophene molecular switch is designed, synthesized and used to form self-assembled monolayers (SAM) on gold. An "on/off" conductance ratio up to 7x1E3 (with an average value of 1.5x1E3) is reported. The "on" conductance state is clearly identified to the cis isomer of the azobenzene moiety. The high "on/off" ratio is explained in terms of photo-induced, configuration-related, changes in the electrode-molecule interface energetics (changes in the energy position of the molecular orbitals with respect to the Fermi energy of electrodes) in addition to changes in the tunnel barrier length (length of the molecules). First principles DFT calculations demonstrate a better delocalization of the frontier orbitals, as well as a stronger electronic coupling between the azobenzene moiety and the electrode for the cis configuration over the trans one. Measured photoionization cross-sections for the molecules in the SAM are close to the known values for azobenzene derivatives in solution.
Electrical Conductivity of Collapsed Multilayer Graphene Tubes  [PDF]
D. Mendoza
World Journal of Nano Science and Engineering (WJNSE) , 2012, DOI: 10.4236/wjnse.2012.22009
Abstract: Synthesis of multilayer graphene on copper wires by a chemical vapor deposition method is reported. After copper etching, the multilayer tube collapses forming stripes of graphitic films, their electrical conductance as a function of temperature indicate a semiconductor-like behavior. Using the multilayer graphene stripes, a cross junction is built and owing to its electrical behavior we propose that a tunneling process exists in the device.
Porous Carbon Grown by Chemical Vapor Deposition on Copper Substrates  [PDF]
D. Mendoza
Journal of Materials Science and Chemical Engineering (MSCE) , 2015, DOI: 10.4236/msce.2015.38003
Abstract: Amorphous porous carbon was synthesized by chemical vapor deposition on copper substrates. The average size of the pores is around 1.2 microns with some small pores decorating the big ones. Lamellar samples of this carbonaceous material can be separated from the copper support and may be useful as electrode due to its low electrical resistivity of the order of 0.4 Ωcm.
Application of Enzyme Extracted from Aloe vera Plant in Chemical Pretreatment of Cotton Knitted Textile to Reduce Pollution Load  [PDF]
D. Jothi
World Journal of Engineering and Technology (WJET) , 2015, DOI: 10.4236/wjet.2015.33B007

Nowadays, highly alkaline chemicals like caustic soda, soda ash, silicate, acetic acid and soaping agents are used for scouring to remove the non-cellulosic impurities from the cotton. Using 30 - 40 gm/Kg on weight of the fabric results in destruction of cotton structure. Intensive rinsing and more acid is needed for reutilization of cotton, which enlarges the volume of effluent. Furthermore, these hazards chemicals result in increase in COD, BOD and TDS in waste water. These chemicals also attack the cellulose leading to heavy strength loss and weight loss in the fabric. The net result is low quality control and polluted environment with high usage of energy, time, chemical and water. Aloe vera presents the finest commercial opportunity in various industrial sectors among the various plants. Also, most of the countries are gifted with the unique geographical features that are essential for cultivation of Aloe vera. Yet, none of the country has realized and reaped the full potential of such plants in various industrial applications. The reason is simple: lack of the requisite expertise in extraction of various enzymes present in aloe plant. Fortunately, the technology is now accessible to make use of enzyme in textile application. In this research an attempt has been made to make use of lipase enzyme extracted from aloe plant in textile chemical pre- treatment process. In the present research work, an attempt was made to develop bio scouring of 100% cotton knitted fabric with lipase enzyme extracted from Aloe deberena plant at various concentration (1%, 2% and 3%) at various temperature (40?C, 60?C and 70?C) for a period of 30 minutes, 60 minutes and 90 minutes. The properties of bio scoured fabrics are compared with these of conventional scoured one. Encouraging results in terms of dye uptake, dye levelness, wash fastness, light fastness and rubbing fastness are obtained in case of bio scouring fabric dyed with dark reactive colors. Further, it reduces volume of effluent as well as COD, TDS and pH. It saves a substantial thermal energy 50% and electrical energy 40%. Bio scouring waste water has 40% - 50% less COD and 60% less TDS as compared to conventional scouring waste water.

Hyporheic Zone Hydrochemistry of the Mine-Polluted River  [PDF]
D. Ciszewski
Journal of Geoscience and Environment Protection (GEP) , 2015, DOI: 10.4236/gep.2015.310008

Intensity of stream waters mixing with groundwaters and lateral extent of these processes in the hyporheic zone were investigated in a near-bank sandbar and an adjacent floodplain through the comparison of groundwaters and stream water chemistry of the Bia?a Przemsza River in southern Poland. The stream waters were polluted by the discharge of mine waters from “Boles?aw” lead and zinc mine. The investigated waters were several times more mineralized than the natural spring waters of the river valley. The concentration of: potassium, sodium, and the pH, as well as cadmium, lead, and zinc decreased in the hyporheic zone towards the stream bank, whereas conductance, calcium, magnesium, sulphates, as well as silica contents were the highest on the floodplain, diminishing towards the stream. The changes observed in the chemical composition of groundwaters were apparent in mixing stream waters below the depth of 2 m with shallow groundwaters draining the valley slope. Hyporheic mixing also takes place in the 10-meter-wide, marginal zone of the sandbar, whereas in the 5-meter-wide stream-side zone of the sandbar groundwaters represent weakly transformed stream water.

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