The chemical compatibility at high temperature between the fuel kernel (U,Pu)C and SiC cladding, the reference materials for the GFR reactor, is studied. For that purpose, a thermodynamic database on the U-Pu-C-Si system was developed with the Calphad method to calculate the phase diagrams. Differential thermal analysis experiments were performed to measure phase transition temperatures in Si-U and C-Si-U systems. According to the calculated isopleth section between the hyperstoichiometric uranium carbide UC1.02 and SiC, the materials shall not react below 2056 K, the temperature at which a liquid phase shall form. These calculations are in good agreement with two chemical compatibility tests performed at 1873 K and 2073 K between the materials. Calculations were also performed to study the chemical interaction between the mixed carbide (U,Pu)C1.04 and SiC. The presence of plutonium in the fuel kernel lowers the liquid formation temperature of 167 K.

We have investigated the resistance switching effect in Cu nanogap junction. Nanogap structures were created by means of electromigration and their electrical properties were measured in a high vacuum chamber. The measured current-voltage characteristics exhibited a clear negative resistance and memory effect with a large on-off ratio of over 105. The estimation from I-V curves indicates that the resistance switching was caused by the gap size change, which implies that the nanogap switching (NGS) effect also occurs in Cu electrodes, a popular wiring material in an integrated circuit.

Highly Focused Ion Beams (FIB) are used to produce in one step large quantities of solid state nanopores drilled in thin dielectric films with high reproducibility and well controlled morphologies. We explore both the production of nanopores of various diameters and study their applicability to different biological molecules such as DNA, or folded and unfolded proteins, and then we compare their transport properties. We also report on the translocation of Fibronectin which an original experiment made possible is using the methodology described in this article.

The performance of dye-sensitized solar cells (DSSCs) is limited by the back-reaction of photogenerated electrons from the porous titanium oxide (TiO2) nanoparticles back into the electrolyte solution, which occurs almost exclusively through the interface. This and the fact that DSSCs have a very large interfacial area makes their performance greatly dependant on the density and activity of TiO2 surface states. Thus, effectively engineering the TiO2/dye/electrolyte interface to reduce carrier losses is critically important for improving the photovoltaic performance of the solar cell. Atomic layer deposition (ALD), which uses high purity gas precursors that can rapidly diffuse through the porous network, was used to grow a conformal and controllable aluminum oxide (Al2O3) and hafnium oxide (HfO2) ultra thin layer on the TiO2 surface. The effects of this interfacial treatment on the DSSC performance was studied with dark and illuminated current-voltage and electrochemical impedance spectroscopy (EIS) measurements.

A series of LaCo1-xRhxO3 (x=0-1) samples and La1-ySryCo1-xRhxO3 (y = 0.05, 0.15 and x = 0.1-0.3) samples were prepared to study the effect of Rh substituion for Co in the four component system and Sr substitution for La in the five component system on the crystal structure and thermoelectric performance of the LaCoO3. At Rh substitution for Co of x=0.2 greater, the crystal structure shifts from rhombohederal (LaCoO3) to orthorhombic (LaRhO3). Thermoelectric evaluation revealed that Rh doped samples (0.3 <x <1) show large positive seebeck coefficients indicating a P-type conduction in the temperature range of the tests (273 to 775K). Rh substitution for Co decreases thermal conductivity, increases Seebeck coefficient and consequently increases the theroelectric figure of merit ZT. Sr substitution for La increases thermal and electrical conductivity and consquenently negligiblely decreases the seebeck coefficient. A thermoelectric figure-of-merit (ZT) around 0.075 has been achieved for LaCo0.5Rh0.5O3 at 775 K, and is expected to be above 0.1 at 1000 K. Sr substitution improved the TE properties throughout the lower temperature range with a ZT =0.045 observed for La0.95Sr0.05Co0.9Rh0.1O3 at 425 K and ZT = 0.05 for La0.85Sr0.15Co0.5Rh0.5O3 at 775 K. These findings provide new insight into thermoelectric perovskite oxides containing rhodium and strontium.

Electrical conduction of metal nanoclusters by percolation is a very interesting area in nano-device. For more functional nano-sensors consisting of multiple nanocluster blending film, various metals, such as Cu and Ni nanocluster films were fabricated using inert-gas condensation method. The percolation threshold of the films was measured. In addition, for the operation of sensors using these nanocluster films in air, aging experiments of the percolated films in air were carried out. While the percolation threshold was in connection not with the material species but with the area coverage of nanocluster films, the conductive characteristics according to the aging temperature depended on the material species. Reversible and irreversible conduction behaviors of nanocluster films were investigated with nanoscale microstructures using electron microscopes.

Critical dimension (CD) shrink and patterning of contact features via plasma etching were studied for typical resistive random access memory (RRAM) stacks. These consist of SiO2 and Si3N4 (total thickness of 65 80 nm) with NiO or pure Ni at the bottom. First, the contact patterning of RRAM stacks was investigated for 90 nm contacts. Thus, a standard high power contact etch recipe was shown to give rise to resist strip challenges due to the incorporation of sputtered Ni in the resist film. Therefore, a low-sputter-yield contact etch recipe based on a CF4/H2/Ar gas chemistry was introduced. The ion sputter efficiency of the recipe was estimated from a blanket SiO2 sputter-yield experiment in Ar plasma for the same recipe settings: this yielded values close to the Ni sputter-yield threshold. Second, plasma-assisted CD shrink was studied in combination with the newly developed patterning scheme to get the contact CD well below the initial 90-nm litho print size. It was shown that a low contact etch power regime could also provide a larger window for contact CD shrink using a C2H4-based chemistry: e.g. the demonstrated CD shrink from 90 nm down to sub-40 nm was shown to be extremely challenging in the case of a high power regime due to polymer instability enhanced with the resulting thickness increase. Perhaps, the relaxation of the polymer film stress, which was measured to be in the range of 1200-1500 MPa, is more easily triggered at higher power settings, which leads to polymer blistering. Finally, the optimization of the plasma-assisted CD shrink step in combination with the low-sputter-yield contact etch recipe was demonstrated to be able to provide CDs as small as 27 nm. The demonstrated approach shows that plasma-assisted CD shrink can provide a robust test vehicle for research programs that require the patterning of small features in the sub-40-nm CD range.

An effect of electron irradiation on the concentrations of deep-level centers in C-rich and Si-rich 6H-SiC wafers is investigated. In the former material, the main deep-level centers with activation energies of Ec -0.50, Ec -0.64 and Ec -0.67 eV are found to be related to dicarbon interstitials and CiNC complexes located in hexagonal and quasi-cubic lattice sites, respectively. In the latter material, the dicarbon interstitials are dominant after the irradiation with 1.5-MeV electrons. At the energy of bombarding electrons equal to 0.3 and 0.7 MeV, the activation energies of the dominant deep-level centers are Ec -0.38 and Ec -0.52 eV, respectively. The first center is related to carbon vacancies and the second to silicon interstitials.

Poor conductivity is a bottleneck hindering the production of nanocrystal-based devices. In most nanocrystal syntheses, ligands with long alkyl chains are used to prepare monodisperse, crystalline particles. When these nanocrystals are incorporated into devices as films, the bulky ligands form an insulating layer that prevents charge transfer between particles. While annealing or post-deposition chemical treatments can be used to strip surface ligands, each of these approaches has disadvantages. Here we demonstrate the use of a novel family of ligands comprised of primary alkyl dithiocarbamates to stabilize PbSe/CdSe core-shell nanocrystals. Primary dithiocarbamates, which can bind to cadmium and lead, are known to decompose to the corresponding sulfides when heated under mild conditions. In our scheme, PbSe/CdSe core-shell nanocrystals are first synthesized with standard ligands. These ligands are then exchanged to short chain dithiocarbamates in solution. When a film is cast and annealed at low temperature, the dithiocarbamates are removed. Electron microscopy reveals that the particles move closer together, and, along with x-ray diffraction, shows that the nanocrystals remain quantum confined. Transport measurements show a 10,000-fold increase in conductivity after annealing.

Rapidly responding, reversible, sensitive, and selective porous silicon-based (PS) gas sensors, operating at low power, are formed with a highly efficient electrical contact to a nanopore covered microporous array. Significant changes in sensor surface sensitivity can be correlated with the strong and weak acid-base (HSAB) character of the interacting gas analyte and the acidic nature of the PS surface so as to produce a dominant physisorption and create a range of highly selective surface coatings. This selection process dictates the application of nanostructured metal oxide and/or nanoparticle catalytic coatings, and provide for notably higher sensitivities which, in concert, form a basis for selectivity. Depositions which include AuxO, SnOx (Sn+2,+4) , CuxO ( Cu+1,+2), NiO(Ni+2) , nano-alumina, and titania, provide for the detection of gases including NO, NO2, CO, NH3, PH3, and H2S in an array-based format at the sub-ppm level. The value of this conductometric sensor technology results from a combination of (1) its sensitivity and short recovery time, (2) its operation at room temperature as well as at a single, readily accessible, temperature with an insensitivity to temperature drift, (3) its potential operation in a heat-sunk configuration allowing operation to a surface temperature of 80°C even in highly elevated temperature environments (in sharp contrast to metal oxide sensors), (4) its ease of coating with diversity of clearly mapped gas-selective materials for form sensor arrays, (5) its low cost of fabrication and operation, (6) its low power consumption, (7) its ease of rejuvenation following contamination, and (8) its ability to rapidly assess false positives using FFT techniques, operating the sensor in a pulsed gas mode.

The thermoluminescence (TL) properties of beta particle irradiated Ce and Er doped LiMgF3 phosphors are presented. Pellet-shaped samples were prepared by cool-pressing 74 μm size particle powder, followed by thermal annealing at 700 °C during 5 h in air atmosphere. Some samples were irradiated with beta particles in the dose range from 8 up to 128 Gy. The sensitivity of Er doped samples was greater than the one of Ce-doped. In both cases, a 2 % mol of dopant concentration was used. The TL fading was between 19 % for Ce-doped samples, and 24 % for the Er-doped. The integrated TL increases as dose increases, with no saturation clues. The TL sensitivity of samples exhibited a loss in successive irradiation – readout cycles.

On the road to miniaturization, nanocrystal layers are promising as floating gate in nonvolatile flash memories. Although much experimental work has been devoted to the study of these new memory devices, only few theoretical models exist to help the experimentalists to understand the physical phenomena encountered and explain the behavior of the device.

We have developed a model based on the geometrical and physical properties of the elementary structure of a nanocrystal flash memory, i.e. one nanocrystal embedded in an oxide between the channel and the gate electrodes. To obtain a fine analysis of the observed phenomena, several specific hypotheses have been taken into account. Concerning the channel, the contribution of the subbands is explicitly included. In the case of an electrode with a quasi-continuum of energy levels, we replace the continuum by equivalent sets of 2D subbands in order to be able to isolate the energy range that really contributes to the charging/discharging of the nanocrystal. The properties of the materials (bulk band structure, dielectric permittivity, …) can be easily set as well as the geometrical specifications of the elementary structure (nanocrystal radius, tunnel and control oxyde thicknesses, …).

The behavior of a layer of nanocrystals is described according to a statistical approach starting from single nanocrystal results. This method allows us to take into account the fluctuations of geometrical parameters. Thus we are able to simulate various types of materials for the nanocrystals (Si, Ge, …), the oxide layer (SiO2, HfO2, …) and the electrodes, for both a single nanocrystal and layers of nanocrystals.

To successfully incorporate the highly spin-polarized material La0.7Sr0.3MnO3 (LSMO) into spin-based electronic devices it is essential to be able to control and tune the magnetic domain structure. In this work, we geometrically confine epitaxial thin films of LSMO into hexagons to examine the effect of magnetostatic and magnetic anisotropy energies on the domain formation. We find through careful choice of hexagon aspect ratio, crystalline direction, and substrate orientation, we can tune the magnetic domain formation to be single, two, six (flux closure), or other domain configurations.

Studies on microstructures in thermoelectric compounds in the pseudobinary PbTe-Sb2Te3 system are overviewed and strategies to control the microstructure of thermoelectric compounds are discussed on the basis of the phase diagram and phase transformation theories. The morophology of solidification from the melt results in dendrite or lamellar structure depending on composition. The size-scales of the microstructures obtained by solidification can be controlled from the order of micrometers to tens of micrometers by controlling cooling rates (dendrites) or solidification velocity (lamellae). Lamellar and Widmansttäten structures are obtained by eutectoid (Pb2Sb6Te11 → PbTe + Sb2Te3) and precipitation (PbTe (Sb2Te3) → PbTe + Sb2Te3) reactions, respectively. These solid-state transformations show features with nanometer size-scales. For the eutectoid reaction the size-scale depends on annealing temperature and time. For precipitation, the size-scale depends on composition as well as cooling rate or annealing temperature. Such behavior can be understood in terms of phase transformation theories.

(GexSi1-x:H) films are of much interest for many device applications because of narrow band gap and compatibility with films deposited by plasma. However, electronic properties of GexSi1-x:H films for high Ge content x > 0.5 have been studied less than those of Si films. In this work, we present a study of sub-gap photoconductivity (σpc ) in GexSi1-x:H films for x = 1 and x = 0.97 deposited by low frequency plasma enhanced chemical vapor deposition (LF PECVD) with both various H-dilution (RH) during growth (non-doped films) and boron (B) incorporation in the films. Spectra of sub-gap photoconductivity σpc (hν) were measured in the photon energy range of hν = 0.6 to 1.8 eV. σpc (hν) spectra were normalized to constant intensity. For hν < Eg two regions in σpc (hν) can be distinguished: “A”, where σpc is related to transitions between tail and extended states, and “B”, where photoconductivity is due to defect states. σpc (hν) in ”A” region showed exponential behavior that could be described by some characteristic energy EUPC similar to Urbach energy EU in spectral dependence of optical absorption. EUPC > EU was observed in all the films studied. This together with higher relative values (i.e. normalized by the maximum value at hν = Eg) for photoconductivity comparing with those for α means that mobility-lifetime product (μτ) depends on photon energy μτ = f(hν) that was determined from α(hν)and σpc (hν). μτ(hν) increases by factor of 20 to 40 depending on the sample with reducing hν from 1.1 to 0.7 eV. In some samples, this dependence was monotonous, while in others demonstrated maxima related to both interference and density of states. Effects of both RH and boron incorporation have been found and are discussed.

Dynamics of structural transformation of supported heteropoly compound was investigated by IR-spectroscopy, XRD, TPR, and TPO methods. The 15-30 wt.% H3PMo12O40 and H3PV2Mo10O40, supported on SiO2 catalysts were investigated in process under various conditions by interaction with O2 (air) in the presence of water vapor, H2, alkane in TPR regime, O2 in TPO regime (298-1273K) and H2O (298, 923K). The rank of reversible structural conversion of supported heteropoly compounds was established under influence of temperatureand medium. These new findings of reversible structural cycle explains the stability of the 12th series Mo heteropoly compounds supported on Si-containing carrier at high temperatures (873-1073K) which is close to the actual operation temperatures of the partial oxidation reactions and oxidative dehydrogenation of alkanes.

A novel system has been developed to catalyze reactions at the oil/water interface of a biphasic liquid system. Stabilization of emulsions was accomplished through the use of nanohybrids composed of hydrophilic oxide particles and hydrophobic Single-Walled Carbon Nanotubes (SWNT), generated in the CoMoCAT process. These nanohybrids are inherently amphiphilic, and tend to adsorb at the interface of a biphasic water/oil liquid system. When enough energy is added to the system, these particles stabilize emulsions by suppressing the coalescence of the droplets and increasing the viscoelastic or pseudoplastic character of the liquid film between droplets. , Depending on contact angle of the particles at the liquid-liquid interface it was possible to stabilize water-in-oil or oil-in-water emulsions. The resulting emulsions are remarkably stable against coalescence and sedimentation, and can be easily separated by filtration or centrifugation, which make them suitable for applications in interfacial catalytic processes in which the catalyst can be easily recovered after reaction. Catalytic activity was imparted by transition metal clusters supported onto the nanohybrids. These metals selectively catalyze reactions at the Oil/Water interface. The proof-of-concept of the biphasic hydrogenation and condensation catalysis was obtained with three reactions of interest in biorefining. The first example was the hydrodeoxygenation of vanillin (4-hydroxy-3-methoxybenzaldehyde). The second example was the conversion of molecules that were exclusively soluble in the aqueous or the organic phase, like glutaraldehyde (water phase) and octanal (oil phase). In the third example we explored a tandem reaction sequence in which Pd-catalyzed hydrogenation was paired with a preceding Aldol-condensation of 5- methylfurfural and acetone. It was demonstrated that with these nanohybrids it is possible to selectively accomplish hydrodeoxygenation and condensation reactions at the water/oil interface of a biphasic system, followed by migration of the products to the oil phase. This contribution provides a proof-of-concept for a promising catalytic system with many potential applications in the liquid phase, such as bio-oil upgrading, production of specialty chemicals, and pharmaceutical applications in which selective reaction and product separations, based on water solubility can be desirable.

The paper presents the results of studies related to the technology for obtaining glass-insulated bifilar microwires (BMWs) of a thermoelectric material based on Bi2Te3 with one wire exhibiting the n-type and the other p-type conduction as well as the study of their mechanical properties by the strain method and the microscopic analysis of the morphology of structural defects with a view to preparing microthermocouples on their basis.

Preliminary studies showed that BMWs are more flexible than single microwires of the same material. The rupture strength of BMWs per unit cross section of a sample (together with the glass) ranges within 18-6 kg/mm2 with respect to diameters of 90-120 μm.

Microthermocouples with a signal value on the order of 2-12 mV in a temperature range of 23-50°C have been developed. The preparation of thermoelectric microthermocouples of BMWs significantly reduces the number of process operations in the course of their production and considerably increases their resistance to impacts and vibrations. Microthermocouples based on glass-insulated BMWs have smaller sizes and weight; they can be used for measuring temperatures in chemically aggressive media.

We have proposed spin quantum cross (SQC) devices, in which organic materials are sandwiched between two edges of magnetic thin films whose edges are crossed, towards the realization of novel beyond-CMOS switching devices. In SQC devices, nanometer-size junctions can be produced since the junction area is determined by the film thickness. In this study, we have fabricated Ni SQC devices with poly-3-hexylthiophene (P3HT): 6, 6-phenyl C61-butyric acid methyl ester (PCBM) organic materials and investigated the current-voltage (I-V) characteristics experimentally and theoretically. As a result of I-V measurements, ohmic I-V characteristics have been obtained at room temperature for Ni SQC devices with P3HT:PCBM organic materials, where the junction area is as small as 16 nm × 16 nm. This experimental result shows quantitative agreement with the theoretical calculation results performed within the framework of the Anderson model under the strong coupling limit. Our calculation also shows that a high on/off ratio beyond 10000:1 can be obtained in Ni SQC devices with P3HT:PCBM organic materials under the weak coupling condition.

A new Float Foil Growth (FFG) technique has been demonstrated for growing thin Si foils from molten metal solvent, such as molten indium (In) or tin (Sn), at temperatures below 1,000°C. Si source is first dissolved to saturation (or close to saturation) in a molten metallic bath (or solvent) at a temperature T2 (T2 ≤ 1,000°C), and the molten bath is then cooled to T1, where T2 » T1. Due to lower solubility of Si at T1 than at T2, Si separates (or is driven) out of solution and, due to its much lower density than that of the molten metallic bath, it floats to the top of the melt to form a floating thin Si-foil. The thickness of the Si foil is determined primarily by T2, the dissolution temperature (i.e., Si solubility at T2), and the depth of the molten bath. This paper reports preliminary results demonstrating the utility of the FFG technique for growing Si-foils. Si foils with thickness range of 50-200μm were obtained from molten In baths. The Si foils were multicrystalline with crystalline (or grain) size of several millimeters, having a strong <111> preferred orientation. The Si-foils were very pure; with In (solvent) content as low as 14ppb. Other metallic impurities were below 0.1ppm, oxygen content was as low as 1.8ppm, and carbon content was below the detection level (50ppb). It is expected that large FFG thin Si-foils, when produced on large scale, will offer significant Si material cost and energy savings (> 80%), compared with conventional sliced Si wafers, with similar photovoltaic conversion efficiency.