bluuebunny/crossref_metadata_2025 huggingface dataset:
Challenges of Ultra Low-k Dielectric Measurement and Plasma Damage Assessment
Authors: Abell Thomas , Lee Jeffrey , Moinpour Mansour
Published: April 2011

The implementation of porous low-k and ultra-low k dielectrics to reduce RC delay in integrated circuit interconnect wiring has been fraught with numerous challenges. The obvious challenges of materials design and preservation of the desired electrical and mechanical properties upon subsequent processing have been significant. The vulnerability of these films to damage from fast ion and radiation damage will be discussed in the context of post-deposition processing (including low-k cure and plasma processing damage). This paper attempts to review the challenges associated with destructive and non-destructive measurement of low k dielectric films with respect to underlying physical principles of the metrology. Metrology techniques, assumed to be non-destructive based on experience with dense silicon dioxide, will be discussed with regards to newer and more fragile low-k dielectric films.
Fracture Properties of Porous MSSQ Films: Impact of Porogen Loading and Burnout
Authors: Ong Markus D , Jousseaume Vincent , Maitrejean Sylvain , Dauskardt Reinhold H.
Published: April 2011

This work investigates the effect of porogen loading on the fracture properties of methylsilsesquioxane (MSSQ) both before and after the porogen burnout process. The fracture behavior of the hybrid porogen/matrix materials differed significantly from that of the post-burnout materials. The most notable differences were alternative fracture paths and a trend of increasing fracture energy with increasing porogen loading. Characterization of the fracture surfaces indicate increasing amounts of carbon at the fracture interface corresponding to the increases in fracture energy and suggest bridging porogen molecules may be responsible for the increase in adhesion for the hybrid materials.
Comparison of the Fracture Behavior of Brittle ILD Films used in the BEOL in Dry and Wet Environment using Nanoindentation
Authors: Simonyi Eva , Lane Michael , Liniger Erik , Grill Alfred
Published: April 2011

During the manufacturing process of the BEOL the low-k brittle ILD dielectrics are exposed to wet environments. These environments could and do affect the films fracture toughness, the so called critical film thickness, above which spontaneous cracking occurs. Nanoindentation combined with AFM imaging methods allow to study these phenomena.
Thin and Smooth Cu Seed Layer Deposition using the Reduction of Low Temperature Deposited Cu2O
Authors: Kim Hoon , Kojima Yasuhiko , Sato Hiroshi , Yoshii Naoki , Hosaka Shigetoshi , Shimogaki Yukihiro
Published: April 2011

Thin and continuous CVD Cu seed layer was successfully deposited on Ru under-layer by Cu oxide deposition and reduction method at 100°C with novel chemistry. Cu oxide was formed with Cu(hface)TMVS and H2O2 at 100°C, and this film was reduced with formic acid at 100°C. Deposited Cu oxide films were Cu2O that was confirmed by XRD and XPS. The morphology of oxide films showed smooth and continuous on Ru and Ta substrate. The reduced Cu film on Ru maintained good surface morphology, and no impurity was detected not only in the Cu film but also the interface between Cu and Ru. However, that on Ta had poor morphology by agglomeration of Cu film during reduction due to poor Cu wettability on oxidized Ta that was oxidized during oxide deposition. The readiness of reduction is very important merit of using Ru under-layer for this oxide deposition and reduction process. The oxide deposition and reduction method on Ru under-layer can be a promising candidate for thin and continuous seed layer deposition method.
Thermal and Electromigration-Induced Strains in Copper Conductor Lines: X-ray Microbeam Measurements and Analysis
Authors: Wang G. , Zhang H. , Cargill III G. S. , Hu C. -K. , Ge Y. , Maniatty A.
Published: April 2011

We have carried out measurements of electromigration-induced strains in copper conductor lines using microbeam energy dispersive x-ray diffraction. Strains developed in random texture damascene Cu 2μm-wide, 0.16 μm-thick conductor lines with TaN liners in low-k dielectric during electromigration at 350°C are much smaller than electromigration-induced strains in (111) fiber texture Al-on-Si, 10μm-wide, SiO2 passivated conductor lines. The reasons for these differences in electromigration behavior may involve the different roles of grain boundary and interface diffusion paths and the different passivation structures and materials for the two types of samples.
Effects of BEOL Stack on Thermal Mechanical Stress of Cu Lines
Authors: Rhee Seung-Hyun , Murray Conal E. , Besser Paul R.
Published: April 2011

The measurement and control of the stress state in BEOL interconnects are important to ensure structural integrity and long term reliability of integrated circuits. Thermal stress in interconnects is determined by the thermal-mechanical properties of Cu lines, substrate, and dielectric materials. The effect of BEOL stacks on thermal stress characteristics of Cu lines were investigated using X-ray diffraction stress measurements. The stress characteristics of M1 and M4 level interconnects in full low-k and low-k/oxide hybrid dielectric stacks were evaluated, and the results indicated reduced substrate confinement and an increased impact of the dielectric material on in-plane stresses in higher level interconnects. The effects of dielectric stack and material properties were examined and the implication in the stresses of multilevel interconnects are discussed.
Computer Simulations on the Grain Boundary Grooving and Cathode Edge Displacement in Bamboo-like Metalic Interconnects
Authors: Ogurtani Tarik Omer , Akyildiz Oncu
Published: April 2011

The process of grain boundary (GB) grooving and cathode edge displacement in sandwich type thin film bamboo lines are simulated by introducing a new mathematical model. In the absence of the electric field, the computer studies on the triple junction kinetics show that it obeys the first order reaction kinetics at early transient stage, which is followed by the familiar time law as t^1/4, at the steady state regime. The applied electric field (EF) in constant current experiments modifies this time law drastically above the well-defined electron wind intensity (EWI) threshold, and puts an upper limit for the groove depth, which decreases monotonically with EWI. Below the threshold level, the capillary regime predominates, and EF has little effect on the general kinetics of GB grooving, other then the linear increase in total elapsed time with EWI.
CMP-induced Peeling in Multi-level Ultra Low-k / Cu Interconnects
Authors: Leduc Patrick , Farjot Thierry , Savoye Mylène , Demas Anne-Cécile , Maitrejean Sylvain , Passemard Gerard
Published: April 2011

This work shows that the addition of dielectric levels in interconnect stacks increases significantly the CMP-induced peeling. The fracture energies, measured by 4-point bending technique, are less sensitive to the level number increase, even if they are slightly degraded. This leads to the conclusion that delamination during polishing depends highly on the stack elastic properties and there is no simple correlation between stack adhesion and peeling during CMP. In this work, mechanical damages generated during CMP in the dielectric stack before peeling were also investigated. It was shown that, if no peeling appears, CMP have no effect on stack reliability. This indicates that negligible “fatigue” effect takes place during CMP.
Gas Sensing with Gold Nanoparticle-Decorated GaN Nanowire Mats
Authors: Dobrokhotov Vladimir , McIlroy David , Berven Chris
Published: April 2011

The electrical properties of chemical sensors constructed from mats of bare GaN nanowires and GaN nanowires decorated with gold nanoparticles are presented. The sensors were tested in vacuum and at atmospheric pressures of Ar, N2 and methane. The current-voltage (I-V) curves of the sensor constructed with bare GaN nanowires were Ohmic and the device was insensitive to all gases tested. The I-V curves of the sensor constructed from GaN decorated with Au nanoparticles were non-linear and exhibited a drop in conductivity of five orders of magnitude relative to bare GaN nanowire sensors. The Au nanoparticle decorated nanowires also exhibited electrical responses that were chemically selective. The sensor exhibited a nominal response to Ar and a slightly greater response to N2 relative to vacuum. A suppression of the conductivity of the Au-GaN device of 50% was observed upon exposure to methane. Both the drop in conductivity of the Au-GaN nanowire-based sensor, relative to bare GaN nanowires, and the response to methane are explained in terms of the formation of a depletion layer and an increase in the depletion layer width due to physisorption induced surface potentials.
Towards Label-free Detection of Charged Macromolecules Using Field-effect-based Structures: Scaling Down from Capacitive EIS Sensor over ISFET to Nano-scale Devices
Authors: Schoening Michael J. , Abouzar Maryam H. , Ingebrandt Sven , Platen Johannes , Offenhaeusser Andreas , Poghossian Arshak
Published: April 2011

The possibility of a label-free electrical detection of charged macromolecules using semiconductor field-effect sensors offers a new approach for the development of DNA chips with fast and direct electrical readout. A deep understanding of the adsorption and interaction of charged biomolecules onto charged surfaces is of great interest also for the fundamental understanding of many key physiological processes. In the present work, two types of field-effect sensors, namely a capacitive EIS (electrolyte-insulator-semiconductor) structure and an ISFET (ion-sensitive field-effect transistor) have been utilised for monitoring layer-by-layer adsorption of polyelectrolytes as well as for the DNA immobilisation and hybridisation detection.
Metal/Porous Silicon Schottky Diode Structures as Sensors
Authors: Dzhafarov Tayyar , Lus Cigdem Oruc , AYDIN Sureyya , Cingi Emel
Published: April 2011

In this work we present data on investigation of the current-voltage and capacitance characteristics of Au/PS Schottky type structures in the presence of different hydrogen-containing solutions (glucose, ethanol, methanol, boric acid, sodium tetraborate pentahydrate, sodium borohydride, benzine, KOH). Generation of the open-circuit voltage and short-circuit current density and capacitance up to 0.55 V, 25 mA/cm2 and 1μF respectively on placing of Au/PS structures in these solutions was discovered. This effect is mainly caused by hydrogen component of solutions. The possible mechanism generation of voltage and capacitance in metal/PS sensors hydrogen-containing solutions is suggested. The advantage of metal/PS Schottky type sensors consists in working without applying external electricity.
Nano Monitors for Identification of Vulnerable Cardio-Vascular Plaque
Authors: Kondama Reddy Ravikiran , Prasad Shalini
Published: April 2011

As our nation's population ages, there will be a substantial demand for surgical services. The best predictor of postoperative outcome is the presence of perioperative ischemia, which is caused by vulnerable coronary plaque rupture. It is not know what makes plaques rupture, but inflammation has been proposed as a unifying etiology. The physiologic perioperative state is one of intense, acute inflammation and thrombosis. This is characterised by the presence of protien- Human Serum C-Reactive Protein( hsCRP) and Myeloperoxidase(MPO). There is a gap in detection capability between gold standard in proteomics detection –Enzyme Linked Immunosorbent Assay (ELISA) assay methods and electrical biosensors.

ELISA based protein biomarker detection in too slow to be applicable in early patient bedside treatment. Electrical biosensors on the other hand may overcome this limitation with their improved sensitivity, specificity and rapid detection. In this application we demonstrate the development of nanomembrane based electrical protein “nano monitor”. This technique overcomes the limitations current “state-of- the- art” methods such as:

• Specificity in detection of multiple markers that characterizes the disease pathogenesis from a single marker to multiple markers.

• Speed of detection from a turnaround time of 12/24 hours to a few minutes.

• Sensitivity of detection from milligram/ml to nanogram/ml.
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

Chromium-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

WO3 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

Several 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

We 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∙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

We 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

In 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˚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

Zr/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

The 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

In 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

One 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

We 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

The 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

The 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

Conventional 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

It 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

We 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

The 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

We 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

We 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

A 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

Carbon 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

Oligomeric 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

This 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.
Atomistic Modeling of Elasticity and Fracture of a (10,10) Single Wall Carbon Nanotube
Authors: King Ryan , Buehler Markus J
Published: April 2011

We use the ReaxFF reactive force field to model extreme tensile deformation of a (10,10) armchair carbon nanotube. The ReaxFF force field has been developed based on DFT quantum mechanical calculations without any empirical parameters (Duin et al., 2001). We report an analysis of the stress-strain relationship for the elastic and plastic regime, including a description of the microscopic fracture mechanisms. We find Young's modulus to be around 1 TPa, close to experimental values. Our modeling yields a fracture tensile strain of approximately 30%, with a maximum tensile stress of approximately 300 GPa. Fracture of the CNT originates from formation of 5-7 Stone-Wales-like defects, leading to formation of micro-cracks.
Air Bridge and Vertical Carbon Nanotube Switches for High Performance Switching Applications
Authors: Kaul Anupama B , Wong Eric W , Epp Larry , Bronikowski Michael J. , Hunt Brian D
Published: April 2011

Carbon nanotubes are attractive for switching applications since electrostatically-actuated CNT switches have low actuation voltages and power requirements, while allowing GHz switching speeds that stem from the inherently high elastic modulus and low mass of the CNT. Our first NEM structure, the air-bridge switch, consists of suspended single-walled nanotubes (SWNTs) that lie above a sputtered Nb electrode. Electrical measurements of these air-bridge devices show well-defined ON and OFF states as a dc bias of a few volts is applied. The switches were measured to have switching times down to a few nanoseconds. Our second NEM structure, the vertical CNT switch, consists of nanotubes grown perpendicular to the substrate. Vertical multi-walled nanotubes (MWNTs) are grown directly on a heavily doped Si substrate, from 200 − 300 nm wide, ∼ 1 μm deep nano-pockets, with Nb metal electrodes to result in the formation of a vertical single-pole-double-throw CNT switch architecture.
Elastodynamic Characterization of Imprinted Nanolines
Authors: Johnson Ward L. , Flannery Colm M. , Kim Sudook A. , Geiss Roy , Heyliger Paul R. , Soles Chris L. , Hu Walter , Pang Stella W.
Published: April 2011

The advancement of imprint lithography as a method for fabricating nanostructures is impeded by a lack of effective tools for characterizing mechanical properties and geometry at the nanoscale. In this report, we describe the development of methods for determining elastic moduli and cross sectional dimensions of imprinted nanolines from Brillouin light scattering (BLS) measurements using finite-element (FE) and Farnell-Adler models for the vibrational modes. An array of parallel nanoimprinted lines of polymethyl methacrylate (PMMA) with widths of ∼65 nm and heights of ∼140 nm served as a model specimen. Several acoustic modes were observed with BLS in the low-gigahertz frequency range, and the forms of the vibrational displacements were identified through correlation with calculations using measured bulk-PMMA moduli and density as input. The acoustic modes include several flexural, Rayleigh-like, and Sezawa-like modes. Fitting of Farnell-Adler calculations to the measured dispersion curves was explored as a means of extracting elastic moduli and nanoline dimensions from the data. Some values obtained from this inversion analysis were unrealistic, which suggests that geometric approximations in the model introduce significant systematic errors. In forward calculations, the frequencies determined with the FE method are found to more closely match measured frequencies. This suggests that the FE approach may be more accurate for inversion analysis. Initial estimates of uncertainties in the FE calculations support this conclusion.
Calcium Phosphate Bioceramics with Tailored Crystallographic Texture for Controlling Cell Adhesion
Authors: Kim Hyunbin , Camata Renato P. , Lee Sukbin , Rohrer Gregory S. , Rollett Anthony D. , Hennessy Kristin M. , Bellis Susan L. , Vohra Yogesh K.
Published: April 2011

The orientation distribution of crystalline grains in calcium phosphate coatings produced by pulsed laser deposition was investigated using an X-ray pole-figure diffractometer. Increased laser energy density of a KrF excimer laser in the 4–7 J/cm2 range leads to the formation of hydroxyapatite grains with the c-axis preferentially aligned perpendicularly to the substrates. This preferred orientation is most pronounced when the plume direction of incidence is normal to the substrate. This crystallographic texture of hydroxyapatite grains in the coatings is associated with the highly directional and energetic nature of the ablation plume. Anisotropic stresses, transport of hydroxyl groups, and dehydroxylation effects during deposition all seem to play important roles in texture development. Studies of cell adsorption using human Mesenchymal stem cells reveal that hydroxyapatite coatings with strong texture and random orientation show different cell adsorption behavior, which is consistent with the notion that protein attach differently on different faces of hydroxyapatite crystals. Cells seeded on textured coatings exhibit better spreading and adhesion compared to those placed on randomly oriented coatings.
Biphasic Polymeric Shell-Core 3D Fiber Deposited Scaffolds Enhance Chondrocyte Differentiation
Authors: Moroni Lorenzo , Hendriks Jeanine A.A. , Schotel Roka , de Wijn Joost R. , van Blitterswijk Clemens A.
Published: April 2011

3D fibrous scaffolds with shell-core fiber architecture offer the possibility to create multifunctional structures. In this study, a construct that combines mechanical stability with the core polymer and optimal surface properties for cell-material interactions with the shell polymer is discussed. Scaffolds were fabricated by a rapid prototyped technique known as 3D Fiber Deposition (3DF) and used for cartilage tissue engineering. Cells maintained the typical rounded morphology of cartilage in the shell-core scaffolds, while they spread into a spindle-like shape in scaffolds fabricated with the core polymer only. Extracellular matrix production and an increase in the dynamic stiffness of the engineered construct revealed a progressive maturation of the formed tissue, suggesting that shell-core 3D scaffolds could be optimal for cartilage tissue engineering.
Sequential Bone Response to Immediately Loaded Mini-Implants, in vivo Study
Authors: Guimarães Glaucio Serra , de Morais Liliane Siqueira , Elias Carlos Nelson , Meyers Marc Andre
Published: April 2011

The use of osseointegrated titanium implants has been related like an excellent alternative to traditional orthodontic anchorage methodologies, and they are a necessity when dental elements lack quantity or quality, when extraoral devices are impractical, or when noncompliance during treatment is likely. In orthodontics, the implants can be use to anchor different movements. However, conventional dental implants can only be placed in limited areas such as the retromolar or the edentulous areas. Another limitation has been the direction of the force application and conventional dental implants are troublesome for patients because of the severity of the surgery, the discomfort of the initial healing, and the difficulty of oral hygiene. Due to these factors, mini-implants became widely used. They have little limitations related to the local of implantation, the surgical procedure of insertion is relatively simple and the control of direction and quantify of the force is simple to be done. These improvements were obtained due to decrease of the size, but these changes could result on significant changes to the bone-implant interface. Since, the orthodontic treatment has to be done as fast as possible. The purpose of this work is to analyze the bone healing reactions to immediately loaded mini-implant of titanium alloy grade 4 by histological, fluorescent and SEM observation, by histomorphometric analysis and by removal torque test. Material and method: Seventy two mini-implants were inserted in eighteen New Zealand rabbits. Four mini-implants were put in the right tibiae of each rabbit and two of then were loaded immediately with 100 gf. Subcutaneous injections of fluorescent labels were administrated in defined periods. The animals were euthanized after 1, 4 and 12 weeks, performing three time analysis and the tibias were dissected and prepared to microcopy analysis and to removal torque test. Results: The results indicated that all the mini-implants remained stable during experimental time. The SEM findings indicated no differences between load and unload group in one and four weeks period, although, the 12 weeks loaded group demonstrated more mature bone formation than the unload group in the same time. These findings suggest that the force can be applied after insertion of the mini-implant without compromises their stability.
Nano Monitors for Identification of Vulnerable Cardio-vascular Plaque
Authors: Prasad Shalini , Barrett Thomas , Carruthers John
Published: April 2011

We describe highly sensitive, non–invasive, label-free, electrical detection of protein biomarkers using nanoporous alumina membrane based electrochemical conductance based devices. The principle of operation of these sensors are based on electrochemical conductance varitions associated with the binding of antibody-antigen complexes to a metallic substrate.In these devices distinct pore clusters are selectively surface functionalized with specific antibodies, that are in turn are incorporated into micro scale arrays. Protein markers were routinely detected at nanomolar concentrations. This opens the potential for developing highly sensitive and selective biomarker detection assays in clinically relevant samples for diagnosis of complex disease state like vulnerable coronary plaque rupture that results in poor post surgical outcomes and other complex diseases.
A polymer-based Chronic Nerve Interface Microelectrode Array
Authors: Farrell Brian , Jauniskis Linas , Phely-Bobin Thomas , Streeter Richard , Edell David , Dean Robert
Published: April 2011

This paper will present ongoing work in the development of a thin, flexible, photolithographically-defined polymer-based electrode array based on Liquid Crystal Polymer (LCP) films and substrates. The goal of the effort is to develop and qualify a new platform technology that would allow accurate positioning of large numbers of electrode contacts in neural tissue for chronic applications. LCP films are a far greater match to the density of neural tissue than the competing wire and silicon arrays and thus will match the bending and flexing as the neural tissues change dimension. This flexibility would cause less neural damage and will maintain a more constant relationship with local neurons. Technology development activities include thin film metallization, interconnect insulation and device microfabrication.
Cold Neutron Prompt Gamma-Ray Activation Analysis for Characterization of Hydrogen Storage and Related Materials
Authors: Paul Rick
Published: April 2011

Prompt gamma-ray activation analysis (PGAA) is an important technique for analyzing materials that may impact the hydrogen economy. An instrument for cold neutron PGAA, located at the NIST Center for Neutron Research (NCNR), has proven useful for the measurement of hydrogen and other elements in a variety of such materials. The detection limit for hydrogen is less than 10 mg/kg for most materials. PGAA has been used to characterize materials with potential for hydrogen storage (e.g. single wall carbon nanohorns, lithium magnesium imides, and zirconium beryllium hydrides), to measure hydrogen uptake by solid proton conductors, and to characterize stoichiometries of Nafion films used as membranes in fuel cells. Future upgrades to the instrument will improve detection limits, applicability, and user interface.