Nanostructured gold thin films

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Nanostructured Thin Films for Fluorescence Enhancement

Nanostructured Thin Films for Fluorescence Enhancement

75005 Paris Cedex, France ABSTRACT Fluorescence is widely used as a spectroscopic tool or for biomedical imaging, in particular for DNA chips. Nanostructured metallic substrates permit to locally enhance the fluorescence signal which offer the possibility both to detect very small fluorophore concentrations and to trace precisely the bio- markers. We have developed substrates made of silver or gold nanoparticles covered with a spacer layer of alumina. Double metallic and dielectric gradients permit to directly map the fluorescence enhancement factor and to determine the best condition for maximum enhancement. One and two photons excitations are studied. Fluorescence enhancement reaches two orders of magnitudes. Lifetime measurements reveal additional information on the decay channels induced by the nanoparticle presence.
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Structural and gas-sensing properties of CuO-CuxFe3−xO4 nanostructured thin films

Structural and gas-sensing properties of CuO-CuxFe3−xO4 nanostructured thin films

The XPS spectra of CuO–Cu x Fe 3−x O 4 after H 2 testing are shown in Fig. 8 . The survey scan spectrum Fig. 8 a shows photoelectron lines for Cu2p, C1s, O1s, Fe2p, Au4f, Na1s and the Auger lines LMM. The XPS peak for Na observed in the spectrum imply that chemical reactions occur at the interface between the film and the glass sub- strate and that sodium migrates from the glass substrate into the thin film. The element C in the film is attributed to residual carbon. The XPS peaks for Au come from the gold electrode sputtered at the surface of the thin film for the formation of electrodes (the sur- face analysis is close to the distance between two gold electrodes). High-resolution scan of Cu2p includes four peaks at 934, 942, 954, and 962 eV ( Fig. 8 b).
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Gold nanoparticle-doped TiO₂ semiconductor thin films : Gas sensing properties

Gold nanoparticle-doped TiO₂ semiconductor thin films : Gas sensing properties

1. Introduction Nanostructured semiconductor metal oxides, such as SnO 2 , ZnO, TiO 2 , and NiO, are promising sensing materials for a wide range of gases and vapors. The enhanced sensing features are determined by the high chemical activity and porosity of the active materials, which are direct consequences of their nanostructure. Because of this, gas sensing capabilities depend critically on the synthesis method and parameters that allow for tailoring of selectivity and sensitivity toward the target species. These materials can be further developed into nanocomposites, which are materials where metal nanoparti- cles (NPs) are dispersed in a matrix of metal oxides. The NPs play both passive and active roles in the sensing process. The presence of NPs increases the active surface area and improves gas diffusion inside the film. Nanocomposites have physical properties that differ from those of the nanostructured single phase oxides and improve the conditions for sensing by
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Structural and gas-sensing properties of CuO–CuxFe3−xO4 nanostructured thin films

Structural and gas-sensing properties of CuO–CuxFe3−xO4 nanostructured thin films

The XPS spectra of CuO–Cu x Fe 3−x O 4 after H 2 testing are shown in Fig. 8 . The survey scan spectrum Fig. 8 a shows photoelectron lines for Cu2p, C1s, O1s, Fe2p, Au4f, Na1s and the Auger lines LMM. The XPS peak for Na observed in the spectrum imply that chemical reactions occur at the interface between the film and the glass sub- strate and that sodium migrates from the glass substrate into the thin film. The element C in the film is attributed to residual carbon. The XPS peaks for Au come from the gold electrode sputtered at the surface of the thin film for the formation of electrodes (the sur- face analysis is close to the distance between two gold electrodes). High-resolution scan of Cu2p includes four peaks at 934, 942, 954, and 962 eV ( Fig. 8 b).
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Determination of Lithium-Ion Distributions in Nanostructured Block Polymer Electrolyte Thin Films by X-ray Photoelectron Spectroscopy Depth Profiling

Determination of Lithium-Ion Distributions in Nanostructured Block Polymer Electrolyte Thin Films by X-ray Photoelectron Spectroscopy Depth Profiling

Determination of Lithium-Ion Distribution. To analyze the distribution of lithium ions within block polymer elec- trolyte films, the effective C 60 þ etch rate was decreased to allow for higher resolution in the axial distribution. Also, lithium salt was added at a [EO]:[Li] = 6:1 ratio to maximize the lithium signal. Figure 5dg shows the alternating C1s, Li1s, F1s, and O1s signals and the resulting depth profile (Figure 5a) captured the repeat- ing structure of a lamellar PSPOEM film doped with lithium salt. The domain spacing as measured by the distance between the peaks of Figure 5a (∼40 nm) also matched the spacing measured via XRR (Figure 3). Furthermore, in the O1s-rich region, there was signifi- cant Li1s and F1s signal, supporting the segregation of the lithium ion and fluorine-containing triflate
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Modeling thin curved ferromagnetic films

Modeling thin curved ferromagnetic films

The first mathematical works on ferromagnetic films concerned wide films with constant thickness, see A. De Simone [6], B. Dacorogna and I. Fonseca [4]. Then, G. Gioia and R.D. James [8] studied the behavior of a thin ferromagnetic film, with no external magnetic field, when its thickness goes to zero. Gioia and James considered a thin film of thickness h occupying the domain Ω h . The film

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Lanthanum titanium oxynitride thin films

Lanthanum titanium oxynitride thin films

L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignemen[r]

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Evaporated NiFeCu thin magnetic films

Evaporated NiFeCu thin magnetic films

L’accès à ce site Web et l’utilisation de son contenu sont assujettis aux conditions présentées dans le site LISEZ CES CONDITIONS ATTENTIVEMENT AVANT D’UTILISER CE SITE WEB. Report (Nati[r]

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Optical pumping in Silicon thin films

Optical pumping in Silicon thin films

laxation time. At the same time, classical approaches to the study of the conduction electrons’ polarization, such as luminescence, are ineffective for Silicon due to the weak spin-orbit interaction and indirect-bandgap structure. In the present work, the polariza- tion of the conduction electrons is studied by means of spin-resolved low-energy electron photoemission spectroscopy. The Silicon surface is activated to negative electron affin- ity by Cesium and Oxygen adsorption so that electron emission can be achieved with photon excitation very close to the band gap (1.12 eV at 300 K). We use a tunable laser which allows a systematic measurement of the polarization spectra from the absorption onset up to energies above the Γ − 2 band. We measured spin polarization spectra on Silicon-on-insulator films of different thicknesses. Based on the obtained data, band structure parameters such as direct band gap and the spin-orbit splitting are evalu- ated. However, contrary to expectations, when diminishing the Silicon film thickness, even below the value of the spin diffusion length, the electron polarization remains close to zero (−0.4 %), much lower than the theoretically predicted values of the initial polarization (−20 %), thus bringing into question their straightforward interpretation. A theoretical investigation was performed on the basis of an ab initio band structure model in order to calculate the full spin polarization spectra. These calculations are still on-going but predictions for strained Silicon confirm that this material should be an interesting candidate for further spin polarization studies.
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FFLO state in thin superconducting films

FFLO state in thin superconducting films

and critical current may be considered as a smoking gun of the FFLO phase formation. Note that in 25 it has been demonstrated that the superconducting fluctuational regime changes drastically near the FFLO TCP. However in the case of the first order FFLO transition the fluctuational regime could be inaccessible on experiment. Our analysis was based on the very general MGL functional approach which is valid for both s-wave and d-wave superconductors. This approach is fully justified near the tricritical point and in the case of the weakly first order phase transition. Nevertheless qualitatively the obtained results could be extrapolated to the whole region of the FFLO phase existence and may be relevant for the CeCoIn 5 thin film experiments. In conclusion we stress that the predicted anisotropy of
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Contact resistance in flat thin films

Contact resistance in flat thin films

II. S AMPLE P REPARATION A two-coupon system was used to measure the contact resistance between two films of multiple thicknesses of sputtered and electroplated Au. The system consists of a bottom silicon coupon having 1) a metal trace and 2) three spherical contacts as well as a top silicon coupon having 1) a metal trace, 2) a flexible membrane with a stiff center cylinder, and 3) three KOH etched pits. The coupons are assembled by placing the KOH etched pits of the top coupon over the spherical contacts of the bottom coupon. This type of assembly creates a pseudo kinematic coupling, allowing for repeatable positioning [7]. This system is described in detail in [5]. The assembly leaves a gap between the top and bottom metal traces. When a force is applied to the stiff cylinder in the center of the membrane, the membrane strains which brings the two metal traces into contact [5]. The traces are each 1mm wide. The diameter of the stiff cylinder in the center of the membrane is 4 mm making the overall apparent contact area 4mm 2 . The metal traces create a Kelvin structure allowing for the isolation of the contact resistance. This assembly and Kelvin structure are shown in Fig 5.
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Morphological, structural, optical, and electrical study of nanostructured thin films: Charge transport mechanism of p-type Co3O4

Morphological, structural, optical, and electrical study of nanostructured thin films: Charge transport mechanism of p-type Co3O4

3.1. Film!composition! The!"lms!composition!is!investigated!by!EPMA.!The!analysis!of!the!X-! ray!dispersive!spectra!are!done!considering!a!140-nm-thick!2-layers!"lm! architecture!consisting!of!a!thin!carbon!layer!on!the!surface!of!the!cobalt! oxide!layer.!We!found!that!the!surface!carbon!layers!thicknesses!are!of! 2.4! and! 1.2!nm,! and! that! the! cobalt! oxide! layers! are! composed! of! 42.3! 1.2!and! 43.1! 1.2!at.%!of!Co,!for! the!400!  C! and!500!  C! "lm,! respectively.! Co/O! ratios! are! close! to! the! Co 3 O 4! stoichiometry! (0.73! 0.03! and! 0.76! 0.03! for! the! 400!  C! and! 500!  C! "lm,! respec- tively).! Nevertheless,! lower! densities! of! 4.5! and! 4.6!g!cm !3! for! the! 400!  C!and!500!  C!"lm,!respectively,!should!be!used!to!accurately!"t!the! spectra!rather!than!the!bulk!density!of!Co 3 O 4! (6.11!g!cm !3 ).!The!lower! densities!are!explained!by!the!presence!of!voids!created!during!the!"lm! growth!that!are!visible!in!the!FE-SEM!images!(see! Fig.!2 )!and!con"rmed! by!SE!analysis!(see!section! 3.2 ).!The!evolution!of!x-ray!photoelectron! spectra!(not!shown!here)!as!a!function!of!the!Ar þ -etching!duration,!used! to! probe! the! composition! as! a! function! of! the! depth,! shows! that! the! carbon-contamination!is!predominantly!located!at!the!surface!which!is! in!full!agreement!with!the!EPMA!analysis.!The!carbon!content!may!be! generated!during!the!deposition!and/or!during!exposition!to!air.!We!also! observed!that!the!Ar þ -etching!considerably!reduces!the!O-content.!Then,! the! effects! of! the! Ar þ -etching! on! the! nature! (composition,! crystal! structure,!and!morphology)!of!the!oxides!prevent!any!depth!analysis!of! the!Co 3 O 4! "lms.!
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Morphological, structural, optical, and electrical study of nanostructured thin films: Charge transport mechanism of p-type Co3O4

Morphological, structural, optical, and electrical study of nanostructured thin films: Charge transport mechanism of p-type Co3O4

2.2. Composition,!morphological,!crystal!and!optical!characterizations! Films!compositions!are!investigated!by!electron!probe!microanalysis! (EPMA)!using!a!Cameca!SXFive!instrument,!and!by!X-ray!photoelectron! spectroscopy!(XPS)!using!a!ThermoScienti"c!K-alpha!apparatus.!X-ray! dispersive! spectra! are! analyzed! by! Layer! Quant! add! on! of! PeakSight! software.! Depth! analysis! of! the! composition! is! probed! by! XPS! after! sequential! 2!keV! Ar þ -etching.! Films! morphology! is! characterized! by! scanning!electron!microscopy!(SEM)!using!a!"eld!emission!FE-SEM!Jeol! JSM-6700!F!instrument!after!Pt-metallization!and!by!atomic!force!mi- croscopy! (AFM)! using! a! Bruker! multimode! 8! microscope.! Samples! deposited!on!Si!wafer!are!analyzed!by!re#ection!spectroscopic!ellips- ometry!(SE)!with!an!incidence!angle!of!70  using!a!Semilab!SE-2000! apparatus.! The! SE! data! are! analyzed! by! the! Semilab! SEA! software! using!a!multi-layer!architecture!composed!of!a!mixture!of!Co 3 O 4! and! void!using!a!Bruggeman!effective!medium!approach.!With!this!optical! model,!the!"t!regression!goodness!is!over!0.99.!SE!analysis!provides!"lm! thickness,!effective!refractive!index,!and!porosity.!The!optical!absorp- tion! spectra! of! thin! "lms! deposited! on! fused! silica! windows! are! measured!by!transmission!and!re#ection!spectroscopy,!using!an!Agilent-! Cary!5000!spectrophotometer!equipped!with!an!integrating!sphere.!The! crystal!structure!is!investigated!by!X-ray!diffraction!(XRD)!in!a!Bruker-! D8!diffractometer!equipped!with!a!Cu!K α (λ K α Cu! ¼ 0.154!nm)!anode!in! theta-theta!mode!with!a!!3  offset!(angular!step!of!0.03  ,!and!acquisi- tion!time!of!4!s).!Mid-infrared!(MIR-FTIR)!and!far-infrared!(FIR-FTIR)! Fourier!transformed!infrared!spectra!are!recorded!with!a!PerkinElmer! Frontier,! and! a! Nicolet! iS50! Thermo-Fischer! Scienti"c! spectrometer,! respectively,!with!4!and!128!accumulations,!respectively,!with!a!com- mon! resolution! of! 4!cm !1 .! The! transmission! spectra! of! thin! "lms! deposited!on!Si!wafer!are!obtained!at!normal!and!60  incidence.!The! spectra! are!subsequently!corrected!from!the!Si!substrate!contribution!
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Film Thinckness effect on Structure and Optical Properties of nanostructured ZnS thin films Deposited By spray Technique

Film Thinckness effect on Structure and Optical Properties of nanostructured ZnS thin films Deposited By spray Technique

obtained with 577 nm film thickness. ➢ From optic measurements in visible region, ZnS thin films have a transparency of 50-80%, the band gap energy of all deposit films were varied in rang 3.9 to 4.1 eV. At lower film thickness, the ZnS thin films become less disorder and fewer defects.

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Magnetic properties of nanostructured thin films of transition metal obtained by low energy cluster beam deposition

Magnetic properties of nanostructured thin films of transition metal obtained by low energy cluster beam deposition

Magnetic properties of nanostructured thin films of transition metal obtained by low energy cluster beam deposition V. Dupuis , J. P. Perez , J. Tuaillon , V. Paillard , P. Mélinon et al. Citation: J. Appl. Phys. 76, 6676 (1994); doi: 10.1063/1.358165 View online: http://dx.doi.org/10.1063/1.358165

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Porous SiO2 and TiO2 thin films with gold and NiO nanoparticles for optically based gas sensors

Porous SiO2 and TiO2 thin films with gold and NiO nanoparticles for optically based gas sensors

Access and use of this website and the material on it are subject to the Terms and Conditions set forth at Porous SiO2 and TiO2 thin films with gold and NiO nanoparticles for optically based gas sensors Post, Michael; Martucci, Allesandro; Della Gaspera, Enrico; Buso, Dario

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Thiol-functionalization of Mn5Ge3 thin films

Thiol-functionalization of Mn5Ge3 thin films

deposition of organic self-assembled monolayers (SAMs). SAMs constitute a method of choice to achieve highly dense and ordered thin films, robustly anchored to large surface areas either on clean metallic (e.g. Au, Ag), oxidized (e.g. SiO 2 , ITO) or semiconducting (e.g. Si, Ge) substrates. This method does not require either sophisticated and expensive instrumentation, or intricate sample preparations, expert manpower and allows the opportunity to vary both the length of the chains and functional groups to manipulate macroscopic properties of the surface, such as wettability,
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Thermal antenna behavior for thin films structures

Thermal antenna behavior for thin films structures

In the present paper we demonstrate that, under proper conditions, quantum size effects in absorbing thin films can give rise to an antenna behavior for both polarization states and over a relatively large spectral band. It has been recognized for some time with the semiclassical Lamb theory of laser 3-4 that absorbing media are able to support the presence of metastable waves. In bounded media such waves are quantified and can be stimulated by external propagative waves. Their interaction are described by the theory of the partially coherent light 5-6 when the film thickness is of the same order than the coherence length of light . In this paper we suggest that thin films can be used to designed thermal sources that are able to emit in narrow solid angles as a antenna would do it. To our knowledge, so far, this effect has never been analyzed.
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Transparent conductive Nd-doped ZnO thin films

Transparent conductive Nd-doped ZnO thin films

epitaxy’. In the frame of the domain matching epitaxy, two distinct possibilities may be considered: either the coinci- dence of 7 Al 2 O 3 lattice units with 6 ZnO lattice units or the coincidence of 6 and 5 lattice units, leading to a lattice mis- match of 1.38 and 1.43%, respectively. It has been found that these two epitaxial domains (7 –6 and 6–5) are both present in undoped ZnO films to accommodate the lattice mismatch [ 27 ]. By comparison with the lattice mismatch of the ‘0 ° epitaxy’, this ‘30 ° epitaxy’ looks much more favorable. Moreover, the hexagonal close-packed oxygen sub-lattices in both sapphire substrate and zinc oxide film have an identical in-plane orien- tation [ 27 , 29 ], ensuring a continuity of the oxygen network through the film-substrate interface.
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Thermal properties of methyltrimethoxysilane aerogel thin films

Thermal properties of methyltrimethoxysilane aerogel thin films

optics 4 and antireflection coatings. 5 Silica aerogels can be easily synthesized in monoliths, grains, powders and films via sol-gel, 2 , 6 using common precursors such as tetramethyl orthosilicate (TMOS) and tetraethyl orthosilicate (TEOS), following a critical point drying process. To reduce costs and synthesis complexity, aerogels have been fabricated in ambient conditions using, for instance, TEOS with a silylation process 7 – 9 or a dedicated precursor such as methyltrimethoxysilane (MTMS). 5 , 10 , 11 Both methods produce aerogels covered with methyl groups, providing hydrophobic behavior which prevents the possible collapse of the aerogel that might occur upon drying. Silylation is based on the introduction of silyl groups in the aerogel surface before drying, while MTMS precursors yield aerogels in ambient conditions without any modification, since their molecular structure 11 (Fig. S1 in the supplementary material ), including methyl groups, provides hydrophobicity 5 , 10 and mechanical flexibility 12 to the aerogel. The 3-omega method has been used extensively for measuring the thermal conductivity and diffusivity of isotropic and anisotropic thin films, bulk materials, 13 porous films 7 , 14 , 15 and multilayer stacks. 16 , 17
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