bluuebunny/crossref_metadata_2025_split huggingface dataset:
Flat-band Voltage Shift of MOS Capacitors with Tantalum Nitride Gate Electrodes Induced by Post Metallization Annealing
Authors: Kadoshima M. , Yamamoto K. , Fujiwara H. , Akiyama K. , Tominaga K. , Yamagishi N. , Iwamoto K. , Ohno M. , Yasuda T. , Nabatame T. , Toriumi A. 
Published: April 2011

ABSTRACTWe have investigated the flat-band voltage (VFB) shifts of tantalum nitride gate MOS capacitors prepared by two methods. One is CVD-tantalum nitride (CVD-TaN) deposited by the chemical vapor deposition technique using Ta[NC(CH3)2C2H5][N(CH3)2]3 as a precursor, and the other one is sputtered tantalum nitride (sp-TaN) electrodes deposited by reactive DC magnetron sputtering. In the case of the CVD-TaN electrodes, the effective work function estimated from the relationship between VFB and the equivalent oxide thickness (EOT) of the MOS capacitors was about 4.4eV after post metallization annealing (PMA) at 400°C, and shifted to the mid-gap after PMA at 950°C. Moreover, the VFB values of MOS capacitors with sp-TaN electrodes also showed the same behavior after PMA. This shift is mainly dependent on the PMA temperature, regardless of the deposition method used. Similar VFB shifts induced by PMA were also observed in sp-TaN/ Al2O3/ SiO2/ p-Si and sp-TaN/ TaOx/ SiO2/ p-Si capacitors. However, in the case of the sp-TaN/ TaOx/ SiO2/ p-Si capacitors, the VFB shift was also observed when the PDA temperature after the TaOx deposition was 800°C and the PMA temperature after the TaN deposition was only 400°C. These results strongly suggest that this VFB shift caused by the PMA originates from a thin interfacial oxide layer between the TaN gate electrode and the dielectrics. Therefore, the maximum processing temperature after gate electrode deposition is important in order to control the threshold voltage of tantalum nitride gate MOSFETs.
Progress in Developing Nerve Agent Sensors Using Combinatorial Techniques
Authors: DiCesare John C. , Parker Jennifer , Horne Starr N. , Kita Justin , Earni Raghu , Peeples Christopher 
Published: April 2011

ABSTRACTDevelopment of a sensor capable of selective detection of specific nerve agents is imperative in today’s atmosphere of terrorism. The sensor needs to be inexpensive, portable, reliable, absent of false positives and available to all military and first responders. By utilizing the techniques of molecular imprinting, combinatorial chemistry, silica sol-gel synthesis and lanthanide luminescence, a sensor for the detection of the hydrolysis product of the nerve agent soman is being developed. There are many parameters that require investigation in order for the sensor to become a reality. These parameters include 1) the selection of a chelate that can bind to the lanthanide and anchor the nerve agent simulant during the formation of the molecularly imprinted polymer, 2) the determination of the environment best suited for this complex formation, 3) the formation, as well as modification of the silica sol-gel for molecular imprinting to take place, and 4) the proper quantity and ratios of monomers used to create the three dimensional imprint. Key to the success of optimizing these parameters is the development of a combinatorial assay that allows for the synthesis and testing of tens of thousands of combinations of parameters. Work on the development of the combinatorial assay has lead to a method of preparing thin film polymers capable of analyzing the presence of nerve agent simulants. Current work is underway to validate the combinatorial assay and to synthesize and evaluate a library of sensor materials selective for nerve agents.
Nanorods Produced on the Surface of Thin Films of TiOx by Surface-Imprinting
Authors: Roberts M. Joseph , Johnson Scott K. 
Published: April 2011

ABSTRACTWorldwide, there is great interest in new processes for production of nanoscale features in materials surfaces. Our recent work explores imprinting of nanosized objects into thin films. In this paper, we present results from surface imprinting of TiOx sol-gel films with anodized alumina. Scanning Probe Microscopy provides evidence for the quality of the imprinting process.
Highly Efficient Formation of TiO2-XNX–Based Photocatalysts - Potential Applications For Active Sites in Microreactors, Sensors, and Photovoltaics
Authors: Gole James L. , Burda Clemens , Fedorov Andrei , Prokes S. M. 
Published: April 2011

ABSTRACTWe have produced nitrogen doped, stable, and environmentally benign TiO2-xNx photocatalysts whose optical response can be tuned across the entire visible region using a nanoscale exclusive synthesis route, performed in seconds at room temperature. This synthesis, which can be simultaneously accompanied by metal atom seeding, that can be accomplished through the direct nitration of anatase TiO2 nanostructures with alkyl ammonium salts. Tunability throughout the visible spectrum depends on the degree of TiO2 nano- particle agglomeration and the influence of metal seeding. The introduction of a small quantity of palladium, in the form of the chloride or nitrate, promotes further nitrogen uptake, appears to lead to a partial phase transformation, displays a counter ion effect with the acetate, and produces a material absorbing well into the near infrared. The nitridation process also induces the formation of oxygen hole centers. Silver introduced as the nitrate into a TiO2 or TiO2-xNx nanostructure framework, forms seeded AgxO - TiO2 or TiO2-xNx nanostructure mixtures which can be induced to self-assemble and to agglomerate into nano-needle and planar arrays using select metal probes. Surprisingly, no organics are incorporated into the final TiO2-xNx products. These visible light absorbing photocatalysts readily photodegrade methylene blue and when used to create photocatalytic sites on a surface based microreactor induce ethylene oxidation with visible light. They can be transformed from liquids to gels and placed on the surfaces of sensor and microreactor based configurations to 1) facilitate a photocatalytically induced solar pumped sensor response, and 2) provide a possible means for the catalytically induced disinfection of airborne pathogens. In contrast to a process which is facile at the nanoscale, we find little or no direct nitridation of micrometer sized anatase or rutile TiO2 powders at room temperature. Thus, we demonstrate an example of how a traversal to the nanoscale can vastly improve the efficiency for producing important submicron materials.
Influence of the Network Geometry on Electron Transport in Nanoparticle Networks
Authors: Benkstein K. D. , Kopidakis N. , van de Lagemaat J. , Frank A. J. 
Published: April 2011

ABSTRACTComputer simulations are applied to understand the influence of network geometry on the electron transport dynamics in random nanoparticle networks, and the predicted results are compared with those measured in one class of random nanoparticle networks: dye-sensitized nanocrystalline TiO2 solar cells. The model is applicable to all classes of random nanoparticle networks, such as highly disordered quantum dot arrays. The random nanoparticle networks are simulated by the step-wise condensation of a diffusion-limited aggregate. The fractal dimension of the nanoparticle films was estimated from the simulations to be 2.28, which is in quantitative agreement with gas-sorption measurements of TiO2 nanoparticle films. Electron transport on the computer-generated networks is simulated by random walk. The experimental measurements and random-walk simulations are found to be in quantitative agreement. For both a power-law dependence of the electron diffusion coefficient D on the film porosity P is found as described by the relation: D ∝ | P -Pc |μ. This power-law relation can also be derived from percolation theory, although only qualitatively. The critical porosity Pc (percolation threshold) and the conductivity exponent μ are found to be 0.76 ± 0.01 and 0.82 ± 0.05, respectively. It is estimated that during their respective transit through 50 and 75% porous 10-μm thick films as employed in the dye-cell, the average number of particles visited by electrons increases by 10-fold, from 106 to 107.
Spectroscopy Studies of InP Nanocrystals Synthesized Through a Fast Reaction
Authors: Furis Madalina , MacRae David J. , Lucey D. W. , Sahoo Yudhisthira , Cartwright Alexander N. , Prasad Paras N. 
Published: April 2011

ABSTRACTWe present spectroscopic characterization of InP nanocrystals grown through a fast reaction in a non-coordinating solvent. The photoluminescence (PL) spectra collected from these nanocrystals exhibit a sharp feature associated with the band-edge emission and a broad infrared feature associated with deep level surface trap emission. The emission efficiencies of the as-grown nanocrystals vary between 0.3% and 1% from sample to sample. After undergoing an HF etching process, the emission efficiency increases to 18% and the emission associated with surface states is eliminated from the PL spectrum. Time-resolved photoluminescence (TRPL) experiments conducted at room temperature on the as-grown and HF-etched nanocrystals show that before etching the PL intensity decay is multi-exponential, with a fast (3ns) component independent of wavelength, associated with the non-radiative recombination processes. The etching process effectively eliminates the non-radiative component and the post-etching PL decay can be fitted with a single exponential decay characterized by long (45ns) lifetimes. We tentatively associate these long lifetimes with the recombination of carriers from spin-forbidden states. This assignment is supported by the observation of a significant redshift of the feature associated with band-edge recombination in the PL spectrum with respect to the lowest energy feature in the photoluminescence excitation (PLE) spectrum.
Deposition of Functionalised Gold Nanoparticles by the Layer-by-Layer Electrostatic Technique
Authors: Paul S. , Palumbo M. , Petty M. C. , Cant N. , Evans S. D. 
Published: April 2011

ABSTRACTIntensive research is currently underway to exploit the intriguing optical and electronic behaviour of nano-sized particles. The basis of the unique properties of these particles is the smallness of their size; dimensions on the nanometre scale can result in interesting quantum mechanical phenomena, such as Coulomb blockade. There are currently a number of ways by which the nanoparticles can be deposited onto solid substrates. Here, we report on the use of the layer-by-layer electrostatic method, which has shown much promise in the context of deposition of thin films of certain organic materials. In this technique, layers of oppositely charged materials are generated by dipping an appropriate substrate into solutions of polyelectrolytes. For example, the polybases poly(ethyleneimine) (PEI), when adsorbed on a substrate, produce a positively charged surface. We have deposited carboxylic acid (-COOH) derivatised gold nanoparticles onto a PEI-coated silicon substrate and an amine funtionalised silicon substrate. The distribution of the gold nanoparticles was compared using atomic force microscopy.
Magnetic Characterization of CoFe2O4 Nanoparticles
Authors: Lawes G. , Naughton B. , Clark D. R. , Ramirez A. P. , Seshadri R. 
Published: April 2011

We have synthesized CoFe2O4 nanoparticles with length scales ranging from 3.5 nm to 14.2 nm. We have characterized the magnetic properties of these samples using both DC and AC magnetization, and find some slightly anomalous behavior in two of the samples. We tentatively attribute these features to interactions between the magnetic nanoparticles.There is a great deal of interest in understanding the physical basis for the magnetic properties of nanoparticles in order to facilitate their incorporation into a wide range of commercial applications. By studying the magnetic characteristics of CoFe2O4 nanoparticles using bulk measurement techniques, we are able to probe the properties of both the individual nanoparticles and interactions in these systems. In this report, we discuss our magnetic characterization of a series of CoFe2O4 nanoparticles grown using an aqueous co-precipitation technique. In addition to DC magnetization at fixed fields and temperatures, we also investigated the magnetic properties using AC susceptibility measurements. The long term goal of this research is to understand interparticle interactions in magnetic nanoparticles.
Turbostratic Disorder in [(Bi2Te3)x(TiTe2)y] Superlattices
Authors: Harris Fred R. , Standridge Stacey , Feik Carolyn , Johnson David C. 
Published: April 2011

ABSTRACTA family of metastable [(Bi2Te3)x(TiTe2)y] superlattices (where × and y denote the number of layers of each of the two components) was prepared by annealing modulated elemental reactant precursors at temperatures below 280°C. Structural analysis by traditional XRD shows the superlattice structures are highly aligned to the substrate with many orders of diffraction peaks from the c direction of the superlattice. Off-axis diffraction techniques presented in this paper suggest that the order between the layers in the a-b direction of these superlattice structures is turbostratic. In this type of behavior, the quasi two-dimensional crystals of Bi2Te3 and TiTe2 that comprise the superlattice structure lie like a deck of cards thrown in disarray on a surface. An analysis of the diffraction data leading to this conclusion is given.
High-Temperature PbTe Thin Films for Use in Cascade Thermoelectric Power Generation
Authors: Posthill J.B. , Caylor J.C. , Crocco P.D. , Colpitts T.S. , Venkatasubramanian R. 
Published: April 2011

ABSTRACTPbTe-based thin films were deposited by thermal evaporation at temperatures ranging from ambient temperature to 430°C on different vicinal GaAs (100) substrates and BaF2 (111). This materials system is being evaluated as a potential candidate thermoelectric material for a mid-temperature stage in a cascade power generation module. Pure PbTe, PbSe, and multilayer PbTe/PbSe films were investigated. All films deposited on different vicinal GaAs (100) substrates were found to be polycrystalline when deposited at 250°C or lower. A subtle effect of substrate orientation and multilayer periodicity appears to contribute to the more randomly oriented polycrystallinity, which also lowers the thermal conductivity. These results are compared with PbTe epitaxial results on BaF2 (111).
Synthesis and thermoelectric properties of Ce(Ru0.67Rh0.33)4Sb12.
Authors: Staneff Geoff D. , Asimow Paul D. , Caillat Thierry 
Published: April 2011

ABSTRACTExotic filled skutterudite compositions show promise for thermoelectric applications. Current work was undertaken with a nominal composition of Ce(Ru0.67Rh0.33)4Sb12 to experimentally verify its potential as an n-type thermoelectric material. Nominal electroneutrality was expected at 0.89 cerium filling and fully filled materials were expected to be strongly n-type. Filled precursors of the nominal composition were synthesized using straightforward solid state reaction techniques, but standard synthesis routes failed to produce a fully-filled homogenous phase. Instead, the filled thermoelectric Ce(Ru0.67Rh0.33)4Sb12 was synthesized using a combination of solid state reaction of elemental constituents and high pressure hot pressing. A range of pressure-temperature conditions was explored; the upper temperature limit of filled skutterudite in this system decreases with increasing pressure and disappears by 12 GPa. The optimal synthesis was performed in multi-anvil devices at 4–6 GPa pressure and dwell temperatures of 350–700 °C. rutheniumThe result of this work, a Ce(Ru0.67Rh0.33)4Sb12 fully filled skutterudite material, exhibited unexpected p-type conductivity and an electrical resistance of 1.755 mΩ-cm that increased with temperature. Thermal conductivity, Seebeck coefficient, and resistivity were measured on single phase samples. In this paper, we report the details of the synthesis routeand measured thermoelectric properties, speculate on the deviation from expected carrier charge balance, and discuss implications for other filled skutterudite systems.
Effect of High Valence Metal Doping on Thermoelectric Properties of [Ca2CoO3-δ]0.62CoO2
Authors: Fujie K. , Horii S. , Matsubara I. , Shin W. , Murayama N. , Shimoyama J. , Kishio K. 
Published: April 2011

ABSTRACTWe report the synthesis and thermoelectric properties of high valence metal-doped [Ca2Co1-xMxO3-δ]0.62CoO2 (M = Re, Mo or Nb) compounds. Approximately 10% M-doping for Co sites in block layer was found to be effective for dramatic suppression of oxygen nonstoichiometries. Seebeck coefficients were systematically enhanced with M-doping levels (x), and however, electrical resistivities also increased with x for conventionally sintered bulk samples. On the other hand, magnetic alignment and/or densification were remarkably effective for reduction of the resistivity. In the case of Mo-doped (x = 0.1) sample, a highly c-axis aligned and densified sample showed 1–3 times larger power factor at 1100K (5.3 μ WK−2cm−1) than the non-doped one. Moreover, these high valence metal doped Ca349 compounds exhibited the oxygen nonstoichiometry suppressed dramatically.
Thermoelectric Properties of Semiconducting Intermetallic Compounds: FeGa3and RuGa3
Authors: Amagai Y. , Yamamoto A. , Lee C. H. , Takazawa H. , Noguchi T. , Obara H. , Iida T. , Takanashi Y. 
Published: April 2011

ABSTRACTWe report transport properties of polycrystalline TMGa3(TM = Fe and Ru) compounds in the temperature range 313K<T<973K. These compounds exhibit semiconductorlike behavior with relatively high Seebeck coefficient, electrical resistivity, and Hall carrier concentrations at room temperature in the range of 1017- 1018cm−3. Seebeck coefficient measurements reveal that FeGa3isn-type material, while the Seebeck coefficient of RuGa3changes signs rapidly from large positive values to large negative values around 450K. The thermal conductivity of these compounds is estimated to be 3.5Wm−1K−1at room temperature and decreased to 2.5Wm−1K−1for FeGa3and 2.0Wm−1K−1for RuGa3at high temperature. The resulting thermoelectric figure of merit,ZT, at 945K for RuGa3reaches 0.18.
The effects of passivation layer and film thickness on the mechanical behavior of freestanding electroplated Cu thin films with constant microstructure
Authors: Xiang Yong , Vlassak Joost J. , Perez-Prado Maria T. , Tsui Ting Y. , McKerrow Andrew J. 
Published: April 2011

ABSTRACTThe goal of this paper is to investigate the effects of film thickness and the presence of a passivation layer on the mechanical behavior of electroplated Cu thin films. In order to study the effect of passivating layers, freestanding Cu membranes were prepared using standard silicon micromachining techniques. Some of these Cu membranes were passivated by sputter depositing thin Ti films with thicknesses ranging from 20 nm to 50 nm on both sides of the membrane. The effect of film thickness was evaluated by preparing freestanding films with varying thickness but constant microstructure. To that effect, coatings of a given thickness were first vacuum annealed at elevated temperature to stabilize the microstructure. The annealed films were subsequently thinned to various thicknesses by means of chemical mechanical planarization (CMP) and freestanding membranes were prepared both with and without Ti passivation. The stress-strain curves of the freestanding Cu films were evaluated using the bulge test technique. The residual stress and elastic modulus of the film are not affected significantly by the passivation layer. The elastic modulus does not change with film thickness if the microstructure keeps constant. The yield stress increases if the film is passivated. For passivated films, yield stress is proportional to the inverse of the film thickness, which is consistent with the formation of a boundary layer of high dislocation density near the interfaces.
The Thermal Annealing Effect On The Residual Stress And Interface Adhesion In The Compressive Stressed DLC Film.
Authors: Choi Heon Woong , Moon Myoung-Woon , Kim Tae-Young , Lee Kwang-Ryeol , Oh Kyu Hwan 
Published: April 2011

ABSTRACTWe studied on the thermal annealing effect on the residual stress and the mechanical properties in thin compressive stressed diamond-like carbon film on Si substrate. Annealing experiments were carried out with Rapid Thermal Procedure system at 200–600 °C, and the stress change with annealing temperature was investigated by in-situ stress measurement system. The apparent stress reduction occurred with minimal structure changes. In order to measure the change of chemical structure of diamond-like carbon film by annealing, we used Raman spectrometer. The adhesion deterioration in interface has been detected as annealing temperature increased. In the compressive stressed DLC film, we observed the dramatic evolution of interface delamination at certain high temperature using in-situ heating stage built in Environment SEM. The quantitative change of adhesion affected by annealing process was also measured with scratch testing. For exploring the interface structure affected by the thermal annealing process at high temperature, the cross section of annealed film has been observed with HR TEM.
Investigation of Structural and Mechanical Properties of UV and Microwave-Irradiated Al2O3 / ZrO2 Multilayers by Sol-Gel Coating
Authors: Phani A. R. , Haefke H. 
Published: April 2011

ABSTRACTThin film multilayers of Al2O3 / ZrO2 have been deposited on quartz and AISI 440C steel substrates at room temperature by sol-gel dip coating technique followed by annealing at different temperatures ranging from 200°C to 800°C for 5h. Prior to annealing the deposited films have been exposed 10 min to ultraviolet radiation (248 nm wavelength) and microwave (2.45 MHz at 800 W power) respectively. Unlike conventional annealing methods, microwave heating is generally quite faster, simpler, and very energy efficient. The lower temperature and shorter time with microwave irradiation might be ascribed to the activating and facilitating effect of microwave on solid phase diffusion. X-ray diffraction (XRD) and scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analyser techniques have been employed to characterize structural, morphological and elemental composition of the thin films. Adhesion strength failure measurements on films have shown critical loads up to 35 N. Nanohardness indentation tests of the films exposed to microwave have shown hardness of 10 GPa with elastic modulus of 85 GPa compared to the annealed films hardness of 4.5 GPa with elastic modulus 57 GPa.
Interdiffusion in Coherent Si0.90Ge0.10/Si0.95Ge0.05 Superlattices
Authors: Aubertine D. B. , McIntyre P. C. 
Published: April 2011

ABSTRACTWe present the use of x-ray scattering from Si1-XGeX/Si1-YGeY superlattices as a tool for measuring the concentration dependence of interdiffusivity in Si/SiGe epitaxial thin films. Although x-ray scattering from compositionally modulated films is an ultra-high-sensitivity technique for measuring interdiffusion in a variety of systems, the concentration dependence of Si/SiGe interdiffusion complicates its interpretation. We show that these complications can be avoided using Si1-XGeX/Si1-YGeY superlattices with a small compositional modulation. This strategy is assessed using numerical simulations of both interdiffusion and dynamical x-ray diffraction. We demonstrate its effectiveness by measuring the activation enthalpy and exponential prefactor for interdiffusion in compressively strained Si0.925Ge0.075. The results are 4.38 ± 0.05 eV and 36 ± 9 cm2/s respectively.