bluuebunny/crossref_metadata_2025_split huggingface dataset:
WAXS and PDF-Based Analyses of Chromium Doping in Nanocrystalline Titania (Anatase and Brookite)
Authors: Zhang Hengzhong , Gilbert Benjamin , Chen Bin , Banfield Jillian F. 
Published: April 2011

AbstractChromium-doped (0.5-10 % Cr:Ti molar ratio) nanocrystalline titania (5–6 nm) prepared via sol-gel method was examined by synchrotron-based wide angle x-ray scattering (WAXS) for crystal structure determination. Atomic pair-distribution functions (PDF) for both raw and heat-treated samples were obtained by Fourier transforms of the WAXS data. The PDF data were fitted using structural models of nanocrystalline titania that considered phase compositions, lattice parameters, atomic positions and thermal factors. The unit cell of Cr-doped nanocrystalline titania expanded 1-2 % with respect to bulk titania as a consequence of the substitution of Ti by Cr and the generation of oxygen vacancies. We observed a lattice contraction after heat-treatment that may be caused by the redistribution of Cr atoms to nanoparticle surfaces during phase transformation and particle coarsening.
High Temperature Phases of Nanostructured Tungsten Oxide for Gas Sensing Applications
Authors: Ponzoni Andrea , Comini Elisabetta , Ferroni Matteo , Faglia Guido , Sberveglieri Giorgio 
Published: April 2011

AbstractWO3 layers have been synthesized by thermal evaporation at high temperature in order to induce the crystallization of stable films. Phase stability has been proved by annealing treatments carried out at different temperatures. Annealing effects on gas sensing performances have been explained in terms of crystallinity degree and grain coarsening phenomena.
Sulfide Phosphors for LED White Light Sources
Authors: Jia Dongdong , Goonewardene Anura , Jia Weiyi , Guo Xiaomei , Zou Yingyin K. , Li Kewen 
Published: April 2011

AbstractSeveral sulfide phosphors, such as CaS:Ce3+,Na+, CaS:Eu2+,Ce3+, ZnS:Te,Mn, ZnS:Se,Te,Mn and ZnS:Ce,Li were prepared and their excitation and luminescent spectra were investigated. The possible applications in LED-Phosphors white light devices are discussed.
Growth of cubic GaN on Si (100) Substrates
Authors: Nishimura Suzuka , Naritsuka Shigeya , Terashima Kazutaka 
Published: April 2011

AbstractWe have focused to grow cubic GaN (c-GaN) on Si(100) substrates using boronmonophosphide(BP) buffer crystals. We have successfully grown BP crystals by MOVPE technique with electrically n-type and thickness deviation is within several % along 2inch wafer under undoped conditions. The electrical conductivity is less than 0.5mohm&#8729;cm. We have preliminary grown GaN by RF-MBE technique, before we carry out mass-producing MOVPE on larger diameter Si substrates. It has been found the cubic type GaN has been successfully grown on the substrates by measuring X-ray diffraction. The crystal quality and defect generation were observed by TEM. It has been found that there are much more dislocations than 109cm-2 generated at GaN/BP interface.
280 nm Emission Deep UV LEDs with Integrated Fresnel Microlenses
Authors: Gaevski Mikhail E , Shatalov Maxim , Wu Shuai , Khan Asif M 
Published: April 2011

AbstractWe report on the integration of flowable oxide based Fresnel microlenses with AlGaN based 280 nm light emitting diodes (LED). The lenses were fabricated on the back side of the LED sapphire substrates using direct electron beam writing. Ten concentric rings with different width and variable thickness were designed for 360 degree phase correction. Within each ring the thickness was varied in five steps to approximate a linear profile. The width of each thickness step varied from 100 nm to several microns. Outer diameter of the lens was 65μm. A focal distance of 68 μm was measured for the fabricated microlenses. At the focal plane a FWHM of intensity profile as small as 14 μm was measured for lenses integrated with 30 μm diameter UV LEDs . The maximum intensity at focal plane exceeded the background radiation by a factor of 50. Comparison of the LED performance before and after the lens fabrication did not reveal any degradation of integral efficiency of devices. These results demonstrate the feasibility of using flowable oxide Fresnel microlenses in optical systems based on micro-pixel deep UV AlGaN LEDs.
A Systematic Approach of Understanding and Retaining Pmos Compatible Work Function of Metal Electrodes On HfO2 Gate Dielectrics
Authors: Jha Rashmi , Chung Jiyoung , Chen Bei , Nemanich Robert , Misra Veena 
Published: April 2011

AbstractIn this work we have performed Ultraviolet Photoelectron Spectroscopy (UPS) and X-Ray Photoelectron Spectroscopy (XPS) on: (i) 40Å of Ru deposited on 20Å of ALD-HfO2 (Ru-HfO2), (ii) 40Å of Re deposited on 20Å of ALD-HfO2 (Re-HfO2), and (iii) 40Å of W deposited on 20Å of ALD-HfO2 (W-HfO2) in as deposited as well as after 600&#730;C in-situ anneal exposure. The samples with Ru and Re indicated significant reduction in the oxygen content and shift in the Hf peaks towards higher binding energy after anneal as compared to the as deposited state. The loss of oxygen after anneal was associated with the reduction in the surface work function of Ru and Re measured by UPS. However, the sample with W showed a redistribution of oxygen after anneal leading to the formation of multiple oxides of W having a net higher surface work function. The spectroscopic measurements were correlated with the electrical measurements made on MOS capacitors with Ru metal gates on HfO2 gate dielectric. The results indicated that the oxygen content at metal/high-k interface plays an important role in governing the effective work function of Ru on HfO2 gate dielectric.
Chemical Vapor Deposition of ZrxTi1-xO and HfxTi1-xO Thin Films Using the Composite Anhydrous Nitrate Precursors
Authors: Shao Qi-Yue , Li Ai-Dong , Zhang Wen-Qi , Wu Di , Liu Zhi-Guo , Ming Nai-Ben 
Published: April 2011

AbstractZr/Ti an Hf/Ti composite nitrate were developed as single-source precursors for deposition of multi-component metal oxide films. X-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS) analyses confirmed that ZrxTi1-xO2 and HfxTi1-xO2 films were successfully prepared by the CVD technique from these composite precursors. The Zr/Ti nitrate can be taken as a solid solution of the individual Zr and Ti nitrate, and the Zr/Ti molar ratio in as-deposited ZrxTi1-xO2 films is nicely consistent with that of the precursor. The Hf/Ti nitrate appears to be a mixture of the Zr and Ti nitrates and the composition of the as-deposited HfxTi1-xO2 films depends remarkably on the heating time of precursor. Both ZrxTi1-xO2 and HfxTi1-xO2 films exhibit trading-off properties between band gap and dielectric constant, which suggesting that ZrxTi1-xO2 and HfxTi1-xO2 can be the promising candidates for gate dielectric application to improve the scalability and reduce the leakage current of the next generation complementary metal-oxide-semiconductor transistor (CMOS) devices.
Influence of Intrinsic Defects and Strain on Electronic Reliability of Gate Oxide films
Authors: Suzuki Ken , Ito Yuta , Miura Hideo 
Published: April 2011

AbstractThe effect of strain and intrinsic defects on both electronic and structural characteristics of HfO2-x used for sub-100-nm semiconductor devices was analyzed by a quantum chemical molecular dynamics analysis. The magnitude of the band gap of HfO2 decreases by about 10% under the applied strain. The stable crystallographic structure of the monoclinic HfO2 changes to a cubic-like structure under the strain. The magnitude of the band gap of the HfO2-x decreases drastically from 5.7 eV to about 1.0 eV due to the formation of an electronic state within the band gap when an oxygen vacancy is introduced to the perfect HfO2. In the HfO2-x film, oxygen atoms near the oxygen vacancy can move drastically at temperatures higher than 800 K. Therefore, it is very important to control the chemical composition of the hafnium oxide film and to optimize the annealing condition to maintain both the high reliability and performance of the gate oxide film.
Metal Electrodes Work Function Measurement at Deca-Nanometer Scale using Kelvin Probe Force Microscope: a Step Forward to the Comprehension of Deposition Techniques Impact on Devices Electrical Properties
Authors: Gaillard Nicolas , Mariolle Denis , Bertin Francois , Gros-Jean Mickael , Bsiesy Ahmad 
Published: April 2011

AbstractIn this letter, we report on Work Function (WF) measurements performed at deca-nanometer scale on various metals using Kelvin probe Force Microscope (KFM). We first demonstrated the relationship between the WF value and the grain crystallographic orientation by combining KFM and Electron Back Scattered Diffraction (EBSD) performed over the same Cu area. Once this relationship was established, KFM was used to provide, in addition to WF value, crystallographic properties of TiN PVD films grown on various substrates. Finally we characterized the effect of N2/H2 plasma treatment on the WF of TiN grown by CVD. In the latter case, the modification of the bulk chemical potential by post-treatment was proposed.
Simulating Liquid GeTe
Authors: Chelikowsky James R. 
Published: April 2011

AbstractOne of the most difficult problems in condensed matter physics is to describe the microscopic liquid state. Owing to the dynamical nature of the liquid state, it is not possible to discuss specific microscopic structures, only ensemble averages can be specified. Such averages can be performed via molecular dynamics simulations. A problematic issue in performing such simulations is computing accurate interatomic forces. Although classical many-body potentials can be use for simulations of covalent materials, one must effectively map quantum phenomena such as hybridization onto such potentials. This mapping is complex and lacking a well-defined prescription. This step can be avoided by employing quantum forces from the pseudopotential-density functional method. Using molecular dynamics with quantum forces, we examine the local atomic order as well as some dynamic and electronic properties of the semiconducting liquid GeTe. Near the melting temperature, the Peierls distortion responsible for the lower temperature crystal phase of GeTe is shown to manifest itself within the liquid structure. At higher temperatures in the liquid, increasing disorder leads to an eventual semiconductor-metal transition. The calculated kinematic viscosity of the liquid is found to agree with the experimental value and is shown to arise from the small diffusion coefficient of the Te atoms. Using an ensemble average, we predict the dc conductivity of the melt to be consistent with recent measurements.
A Computational Study of Oxygen Contamination in Sb2Te3
Authors: Boyd John Earl , Edwards Arthur , Pineda Andrew C. 
Published: April 2011

AbstractWe present first principles electronic structure calculations of oxygen substitutional defects in the Sb2Te3 layered crystalline system and a model of amorphous Sb2Te3 using density functional theory (DFT). Our calculated formation energies for oxygen substitutional defects at Sb sites are above 2 eV, so most of our results are on the Sb2Te3-xOx [x = .0074 - .20] system, where one of two inequivalent Te sites are instead occupied by a single oxygen atom with formation energies between -1.2 eV and .2 eV. Defect formation energies for the system show a preference for oxygen atoms on the Te1 site at low concentrations that switches to the Te2 site at high concentrations at approximately 6 atomic percent. In agreement with experiment, we find that oxygen does widen the band gap, even at relatively low concentrations.
Kinetics of optically-induced crystallization and structure of Agx(As0.48S0.26Se0.26)100-x chalcogenide films.
Authors: Krbal Milos , Wagner Tomas , Frumar Miloslav , Vlcek Milan , Bezdicka Petr 
Published: April 2011

AbstractThe high density optical and/or thermal, electrical memories based on recording into chalcogenide thin films are currently used in industrial dimension but search for new materials continues due to request of higher recording density and shorter lasers wavelength available. The thin films of amorphous chalcogenides e.g. of Ag-As-S(Se) systems making or ternary use different techniques i.e. optically-induced silver dissolution in the binary As-S or As-S-Se chalcogenides prepared by thermal evaporation or by spin coating techniques were prepared and studied. Ternary Ag-As-S and quarternary Ag-As-S(Se) chalcogenide films were also deposited by direct-pulsed laser deposition. Films with euthectic or stoichiometric compositions were prepared. Optically-induced phase-changes in films, process kinetics and analysis of the structural changes and their potential application are described.
Characteristics of Si-Sb-Te Films for Phase Change Memory
Authors: Feng Jie , ZHANG Yin , Qiao Baowei , Cai Yanfei , Lin Yinyin , Tang Tingao , Cai Bingchu , Chen Bomy 
Published: April 2011

AbstractThe novel phase change materials Si-Sb-Te films were prepared. The crystallization temperature of films increases with the increasing of Si concentration. Phase separation was observed in the Si-Sb-Te films, the dominant phase is Sb2Te3. The melting temperature of Si-Sb-Te decreased to ~550°C lower than 640°C of Ge2Sb2Te5. The decrease of film thickness of Si-Sb-Te films is less than 2% after annealing at 400°C, which is less than ~7% of the film thickness change of Ge2Sb2Te5 film. The crystalline resistivity of Si-Sb-Te films increased and the ratio of amorphous/crystalline resistivity of Si-Sb-Te films increased also comparing with Ge2Sb2Te5 film, which is benefit to reduce the writing current and keep higher on/off ratio of phase change memory. Reversible switch was performed in the devices with Si-Sb-Te films. The device with Si14.3Sb28.6Te57.2 film can be programmed with a 100 ns SET pulse and a 20 ns RESET pulse. The Reset current is only 1.37mA for a 10μm-sized device.
Optical Silver Superlens Imaging Below the Diffraction Limit
Authors: Lee Hyesog , Xiong Yi , Fang Nicholas , Srituravanich Werayut , Durant Stephane , Ambati Muralidhar , Sun Cheng , Zhang Xiang 
Published: April 2011

AbstractConventional optical imaging systems cannot resolve the features smaller than approximately half the size of the working wavelength, called the diffraction limit. The superlens theory predicts that a flat lens made of an ideal material with negative permittivity and/or permeability is able to resolve features much smaller than working wavelength through the restoration of evanescent waves. We experimentally demonstrated the superlens concept for the first time using a thin silver slab in a quasi-static regime; a 60nm half-pitch object was imaged with 365nm illumination wavelength, λ/6 resolution, and the imaging of 50nm half-pitch object under the same light source, λ/7, was also reported. Here, we present mainly experimental studies of near-field optical superlens imaging.
Molecular Scale Imaging with a Multilayer Superlens
Authors: Chaturvedi Pratik , Fang Nicholas X. 
Published: April 2011

AbstractIt has been experimentally demonstrated that a single layer of silver functions as a “superlens” [Fang et al, Science 308, 534 (2005)], providing image resolution much better than the diffraction limit. Resolution as high as 60 nanometer (λ/6) half-pitch was achieved. In this paper, we explore the possibility of further refining the image resolution using a “multilayer superlens” design. With optimized design of silver-alumina multilayer superlens, our numerical simulations show a feasibility of resolving 15nm features, about 1/26th of the illumination wavelength. We present preliminary experimental results targeted towards achieving the molecular scale imaging resolution. The development of potential low-loss and high resolution superlens opens the door to exciting applications in nanoscale optical metrology and nanomanufacturing.
Drawing of Hollow Multilayered All-Polymer Fibers
Authors: Pone Elio , Dubois Charles , Guo Ning , Gao Yan , Dupuis Alexandre , Lacroix Suzanne , Skorobogatiy Maksim 
Published: April 2011

AbstractWe present a fluid dynamics model for the drawing of hollow multilayer polymer optical fiber. A newtonian model is considered assuming slender geometries. Hollow core collapse during drawing and layer thickness non-uniformity are investigated as a function of draw temperature, draw ratio, feeding speed, core pressurization and mismatch of material properties in a multilayer.
Fabrication of Ag Nanoparticles/poly(3,4-ethylenedioxythiophene) Nanocomposite Electrodes by Ink-jet Printing
Authors: Seoul Chang , Kim Jin heon , Kim Tea-Heon , Seoul Chang 
Published: April 2011

AbstractThe conductive polymer poly (3,4-Ethylenedioxythiophene) (PEDOT) is a low band-gap polymer with high charge mobility and good thermal and chemical stability. Nanosized Ag particles have found many potential applications in technical fields because of their reduced sizes, high surface-to-volume ratio, and relatively high chemical stability in air. In this report, 3,4-Ethylenedioxythiophene (EDOT) was used as the reductant for the first time in the preparation of silver nanoparticles by the reduction of AgNO3 in water. And Ag/PEDOT nanoparticles composites conducting films deposited by inkjet printing technique on plastic substrates.
Stereocomplex PMMA Fibers
Authors: Crne Matija , Park Jung O , Kang Shin-Woong , Kumar Satyendra , Srinivasarao Mohan 
Published: April 2011

AbstractWe have utilized the fact that syndiotactic and isotactic Poly(methyl methacrylate) {PMMA} form a stereocomplex to spin semi-crystalline PMMA fibers. Our goal is to produce oriented semi-crystalline fibers with a high enough melting point to withstand atactic-PMMA processing conditions. We successfully developed stereocomplex PMMA fibers by wet spinning and gel spinning, and characterized their properties by means of differential scanning calorimetry, optical/electron microscopy, mechanical testing and X-ray crystallography. Stereocomplex fibers from gel spinning have highest melting points and polymer chain orientation, hence are the best reinforcing agents. We are currently working on producing self-reinforced composites using these fibers.
Piezoresistive Sensors on Textiles by Inkjet Printing and Electroless Plating
Authors: Sawhney Amit , Agrawal Animesh , Patra Prabir , Calvert Paul 
Published: April 2011

AbstractWe have printed arrays of strain sensors on textiles by inkjet printing of conducting lines and piezoresistive polymer (PEDOT) in order to provide detailed information about the response of a fabric in use. Conducting polymer has been printed onto polyamide and cellulose woven fabrics to form sensors using a modified HP inkjet print-head and X-Y linear positioning table. Good penetration and attachment is found on mercerized cotton but not on polyamide. Silver nitrate lines have been printed onto polyamide and converted to silver connectors by electroless plating. We observed that resistance of silver lines ranged from 0.7-1.5Ω/cm whereas for the conducting polymer it was 1-3 kΩ/mm by a four point probe method. The conducting polymer formed a surface coat on the fabric and also penetrated the weave. On stretching, the surface layer tended to crack but the embedded polymer acts as a strain gauge with a gauge factor of about 5. On the other hand the silver showed minimal change in resistance with stretching, as is required for connectors. Sensitivity towards temperature and humidity and the effect of orientation to stress and weave directions will be reported. Preliminary experiments show that these sensors attached to a sleeve could be effective for monitoring human joint motion.
Fabrication of Inorganic Tubular Structures Using a Lipid Nanotube as a Template in Aqueous Solutions
Authors: Ji Qingmin , Iwaura Rika , Kogiso Masaki , Shimizu Toshimi 
Published: April 2011

AbstractA secondary ammonium hydrochloride of the peptidic lipid, in which an L-prolyl-L-prolyl-L-proline fragment is coupled with an L-glutamate derivative carrying two long alkyl chains, self-assembles in water to form nanotube structures consisting of a single bilayer wall. Using this lipid nanotube as a template, we carried out the sol—gel transcription to metal oxide nanotubes from aqueous lipid nanotubes without solution catalysts. TEM analysis of the aqueous gel phase, coupled with electron energy-loss spectroscopy (EELS) revealed the presence of a high population of hybrid nanotube architectures with a well-defined lipid/silica interface and thus proved the success of structural transcription from the lipid nanotube template. Besides silica, when changing the lipid nanotube in aqueous solutions to an iced lipid nanotube as a template, we also succeeded in the transcription to transition metal oxide nanotubes (titanium oxide, tantalum oxide, vanadium oxide) was also succeeded. The weakly acidic and mildly catalytic headgroup of the lipid is responsible for the formation of the metal oxide on the surface of the lipid nanotube template.
Electrical Transport in Carbon Nanotube Y-junctions- a Paradigm for Novel Functionality at the Nanoscale
Authors: Park Jeongwon , Daraio Chiara , Rao Apparao , Bandaru Prabhakar 
Published: April 2011

AbstractCarbon Nanotube (CNT) morphologies with a self-contained gate, such as Y-junctions, offer a new way of exploiting features unique to the nanoscale, such as quantum ballistic transport. The advantages of low power and high frequency operation can then be applied to the fabrication of novel devices. Several other novel functionalities in Y- CNTs, including rectification, switching, high-frequency performance, and logic gates have been experimentally verified1. Y-CNT geometry dependent current blocking behavior, as a function of annealing temperature has also been observed. In view of the above observations, we propose that Y-CNTs can be used as prototypical nanoelectronic components.
Proton-Sweeping Role of Oligomeric Electrolyte Chains Grown on Silica Nanospheres
Authors: Zhang Xinhui , Hong Liang , Liu Zhaolin 
Published: April 2011

ABSTRACTOligomeric ionmer-grafted silica nanoparticles were synthesized via atom transfer radical polymerization (ATRP) and applied to dope Nafion to investigate proton-sweeping effect of these hybrid nanoparticles. Two types of vinyl monomers, sulfopropyl acrylate, potassium (SPA) and N,N’-methyl-(6-hexylcarbamatoethylmethacrylate) imidazolonium bromide (EMACI), were employed to construct the grafted ionmer chains. The ionmer-grafted silica particles present a thick polymer layer surrounding the SiO2 core according to TEM investigation. The DSC analysis shows that the grafted ionmer oligomers (DP < 10) exhibit a stronger ionic attractive interaction than the corresponding long chain counterparts. The other structural characterizations of the ionmer-grafted SiO2 nanoparticles also include FT-IR and EDX. The most interesting feature of the grafted ionmer shrub lies in its proton-conduction enhancing effect when combined with Nafion® polymer. A series of such composite membranes were prepared through dispersing the ionmer-grafted SiO2 nanoparticles in Nafion solution and followed by casting. The grafted copolymer (SPA-co-EMACI) demonstrated a greater promoting effect on proton conduction than its homopolymer counterparts of either (SPA) or (EMACI) in the matrix of Nafion. This outcome could be attributed to the adjacent proton-sweeping effect of the pendant imidazolonium group.
Wrinkling of Ultrathin Polymer Films
Authors: Huang Rui , Stafford Christopher M. , Vogt Bryan D. 
Published: April 2011

ABSTRACTThis paper presents a bilayer model to account for surface effects on the wrinkling of ultrathin polymer films. Assuming a surface layer of finite thickness, effects of surface properties on the critical strain, the equilibrium wavelength, and the wrinkle amplitude are discussed in comparison with conventional analysis. Experimental measurements of wrinkling in polymer films with thickness ranging from 200 nm to 5 nm are conducted. The bilayer model provides a consistent understanding of the experiments that deviate from conventional analysis for thickness less than 30 nm. A set of empirical surface properties is deduced from the experimental data.