bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reliability of 4-Mbit Toggle MRAM
Authors: Åkerman Johan , Brown Philip , Butcher Brian , Dave Renu , DeHerrera Mark , Durlam Mark , Engel Brad , Fuchs Earl , Griswold Mark , Grynkewich Greg , Janesky Jason , Martin John , Nahas Joseph , Pietambaram Srinivas , Rizzo Nick , Slaughter Jon , Smith Ken , Sun Ji-Jun , Tehrani Saied 
Published: April 2011

ABSTRACTA 4Mb magnetoresistive random access memory (MRAM) with a novel magnetic free layer and toggle switching mode is presented. The new free layer uses a balanced synthetic-antiferromagnet trilayer structure and a novel write pulse sequence to provide robust switching performance with immunity from ½-select disturbs. This new mode greatly improves the switching performance of the MRAM as compared to conventional MRAM. The intrinsic reliability of the magnetoresistive tunnel junction (MTJ) and the metal interconnect system of MRAM are two other areas of great interest due to the new materials involved. Time dependent dielectric breakdown (TDDB) and resistance drift were the two main failure mechanisms identified for intrinsic memory bit reliability. Results indicated that a lifetime over 10 years is achievable under the operating conditions. Finally data retention is demonstrated over times that are orders of magnitude longer than 10 years.
Stress Hysteresis and Thermal-Mechanical Behavior of PECVD Silicon Nitride and Ebeam Aluminum Films for Microbolometer Applications
Authors: Huang Shusen , Zhang Xin 
Published: April 2011

ABSTRACTUncooled cantilever-based microbolometer arrays received more attention recently due to high sensitivity and low cost. The central idea is built on the deflection of a bilayer SiNx/Al material upon the temperature change. The thermal-mechanical behavior of the bilayer is significant for the performance of the microbolometers. In this paper, we perform thermal cyclings to aluminum and SiNx films. The CTEs and the stress evolutions were measured using a curvature measurement system. The curvature profile of a SiNx/Al/Si component was predicted using an extension of Stoney's formula, well agreeing with the experimental results. This work demonstrates fundamental mechanics issues in bilayer SiNx/Al components, which have a great potential for the use in uncooled microbolometer applications.
Structural Evolution and Alignment of Cylinder-Forming PS-b-PEP Thin Films in Confinement Studied by Time-Lapse Atomic Force Microscopy
Authors: Zheng Qin , Lee Dong-Chan , Yu Luping , Sibener S. J. 
Published: April 2011

ABSTRACTWe have utilized time-resolved high-temperature atomic force microscopy (AFM) to investigate the mechanism by which topographic templates induce alignment of cylinder-forming diblock copolymer thin films. By tracking the same sample spot during thermal annealing, we observed that the structural evolution and alignment of thin films in confinement involve an intermediate state with disordered morphology and the evolution and annihilation of disclination quadrupoles guided by the channel edges, which ultimately lead to the essentially perfect alignment of cylindrical microdomains.
Nano-scale Stress and Compositional Analysis of Epitaxial Si1-xGex/Si (100) Undulated Films
Authors: Wu Chi-Chin , Hull Robert 
Published: April 2011

ABSTRACTSpontaneous surface roughening, stress relaxation and composition re-distribution are coupled fundamental processes during the growth of strained epitaxial Si1-xGex / Si (100) alloy layers. In this work, we will present both modeling and experimental approaches to investigate the inter-relationships among these mechanisms. Stress distributions in undulated layers were calculated via the Finite Element Method by assuming a sinusoidal surface geometry. They were investigated as functions of undulation wavelength and amplitude between the trough and peak regions. For example, with a 50 nm layer of × = 0.3 having undulations of 250 nm wavelength and 40 nm amplitude, the compressive stress is twice as high in the trough regions than in the peak regions even without compositional redistribution. To explore compositional redistribution in response to these laterally varying strain fields, an experimental approach has been developed to determine local germanium concentrations for such undulated alloy layers. An etchant consisting of HNO3 (70 wt %): H2O: HF (0.5 wt %), 25: 35: 5, at 28 °C etches Si1-xGex / Si (100) alloy layers at a rate of several nanometers per minute. The etching rate increases linearly with increasing Ge concentration in the alloy layer. Such etching experiments can thus be applied to etch alloy layers with compositionally varying undulations on the free surface and utilized to quantify the local germanium concentrations. For an alloy layer with × = 0.3, the Ge concentration from this analysis is estimated to be about 20 % enhanced / depleted in the peak / trough regions, respectively.
Real-Time Coarsening Dynamics of Ge/Si(100) Nanostructures Using Elevated Temperature Scanning Tunneling Microscopy.
Authors: Mckay Michael R. , Drucker Jeff , Shumway John 
Published: April 2011

ABSTRACTCoarsening dynamics of Ge/Si(100) nanostructures were monitored using real-time, elevated temperature scanning tunneling microscopy. Gas-source molecular beam epitaxy from digermane at 0.2 ML / min onto Si(100) at temperatures near 500 °C produced mixed hut and pyramid cluster ensembles. The width of the most elongated rectangular-based hut clusters is always less than the side length of square-based pyramid clusters for island ensembles grown using these conditions. This suggests that pyramid elongation to form hut clusters occurred at early growth stages for some smaller clusters. Growth temperature annealing revealed that pyramid clusters are more stable than narrow hut clusters with larger volumes. These larger volume huts decay by reducing their length at constant width, finally becoming small pyramids. These pyramids, which are smaller than those which never elongated to form huts, are less stable and consequently dissolve. Atomistic elastic modeling confirms that hut clusters less efficiently store elastic energy than pyramid clusters which explains our observations. Large (> 1μm diameter), low chemical potential clusters deplete the surface of Ge adatoms as evidenced by the existence of denuded zones devoid of smaller clusters. These large clusters are responsible for the decrease in total island volume in the STM field of view during the anneal.
Stability Study of Highly Dispersed Au Clusters Produced on Defected TiO2 (110); Evidence from SEM and Olefin TPD
Authors: Yang Y. , McFarland E. 
Published: April 2011

ABSTRACTThe stability of Au nanoclusters created at defect sites on TiO2(110) surfaces is under investigation. Using Ar ion sputtering, 0 - 10% of the surface area of ideal surfaces are modified with defects at a controlled defect density. Defected surfaces are also produced using controlled vacuum heating to 1300 K for 25 minutes. Identical exposures (< 1Å) of Au were evaporated on each surface and results of propylene temperature programmed desorption (TPD) heating cycles to < 700 K are compared with ideal control surfaces. Results support the model that Au deposited on a sputtered surface is immobilized at defect sites and the clusters so formed are stable with respect to sintering. As previously observed, with increased sputtering time there is a decrease in the cluster size and increased defect density. The desorption peak of propylene from the Au-TiO2 surface is used as an in situ probe of cluster size stability. By cyclically performing TPD to 700 K for longer times and additional cycles (or higher temperature), the sintering stability can be assessed. On the sputtered TiO2 (110) surface, evaporated gold clusters sinter with only ∼25% maintaining their initial size. On the unsputtered 1300 K annealed TiO2, Au is stable with respect to sintering for many cycles of 800 K heating. This phenomenon is attributed to both the surface stability and Au affinity for the thermal defects created on the surface. This work extends our previous investigations of Au cluster formation on defected TiO2 to their stability with respect to sintering.
The Geometry of Amorphous Silicon Effect on Metal Induced Lateral Crystallization Rate
Authors: Kim Y.-S. , Kim M.-S. , Joo S.-K. 
Published: April 2011

ABSTRACTIn this study, we observed that the MILC behavior changed when the amorphous silicon active pattern width was changed abruptly and explain that phenomena with novel MILC mechanism model. The 10nm thick Ni layers were deposited on glass substrate that has various amorphous silicon patterns on it. Then we annealed the sample at 550 °C with RTA (rapid thermal annealing) machine and measured the crystallized length with optical microscope. The MILC rate was reduced dramatically and stopped for several hours (incubation time). After the incubation time, the MILC started again and the incubation time increased as the amorphous silicon pattern width difference getting larger. We can explain these phenomena with the tensile stress that was caused by volume shrinkage due to the phase transform from amorphous silicon to crystalline silicon.
Growth, crystal structure and stability of Ag-Ni/Cu films
Authors: Bdikin I. K. , Strukova G. K. , Strukov G.V. , Kedrov V.V. , Matveev D.V. , Zver'kov S. A. , Kholkin A. L. 
Published: April 2011

ABSTRACTAgxNi1−x (x=0.0–1.0) films were grown on Cu substrates by electrodeposition method. The films were found to be a nanocrystalline mixture of pure silver and nickel. The grain sizes were determined by X-ray diffraction and electron microscopy techniques. The minimal value was 3.3 nm for the alloy with 70 wt% Ni concentration. The stability of the grown films upon heating in air and in vacuum was examined. An increase in the grain size was found to begin at 150 °C.
Sub-critical telephone cord delamination propagation and adhesion measurements
Authors: Volinsky Alex A. , Waters Patrick , Kiely James D. , Johns Earl C. 
Published: April 2011

ABSTRACTThin film delamination can occur when the stored elastic energy per unit area in the film due to the residual stress exceeds the interfacial toughness. Telephone cord morphology is commonly observed in delaminating thin films under compressive stresses. Here, the biaxial film stress is partially relieved by film buckling in the direction perpendicular to the telephone cord propagation, and by “secondary” blister buckling in the direction of telephone cord propagation, which results in the sinusoidal fracture patterns.A superlayer indentation test, in which additional stress is supplied to the crack tip using a nanoindenter, can be used to measure the interfacial toughness. Estimates of the energy release rate for diamond-like carbon (DLC) films on magnetic media were obtained using the superlayer indentation test, as well as the delaminated buckling profiles. The results obtained by these two independent methods are in good agreement with each other. We find the average adhesion energy to be 6 J/m2 for DLC films on magnetic media.Normally telephone cord blisters “run out of steam” and stop once the interfacial toughness exceeds the strain energy release rate. It is possible to make blisters propagate further by either putting mechanical energy into the system, or by introducing liquids at the crack tip, thus reducing the film interfacial toughness. Environmental species can assist cracking and contribute to thin film delamination, which is readily observed in vintage mirrors. Crack propagation rates on the order of microns per minute were measured for DLC films in different fluid environments. We identify how telephone cord buckling delamination can be used as a test vehicle for studying crack propagation rates and environmentally assisted cracking in thin films.
Superelastic Thin Film NiTi-Polymer Composites and Sputtered Thin-walled Tubes
Authors: Rumpf Holger , Zamponi Christiane , Bourauel Christoph , Drescher Dieter , Quandt Eckhard 
Published: April 2011

ABSTRACTSuperelastic shape memory materials are of special interest in medical applications due to the large obtainable strains, the constant stress level and their biocompatibility. Superelastic NiTi-polymer-composites have the potential to be used for novel applications in orthodontics and medical instrumentation as well as in certain areas of mechanical engineering. Especially, using NiTi thin films these composites have the potential to substantially reduce those forces compared to conventional NiTi wires and tubes. In orthodontic applications lowering the forces during archwire treatment is of special importance due to tooth root resorption, which can be caused by the application of oversized forces. Furthermore, the use of superelastic materials or composites enables the application of constant forces independent of diminutive tooth movements during the therapy due to the superelastic plateau. Superelastic NiTi thin films have been fabricated by magnetron sputtering using extremely pure cast melted targets. Special heat treatments were performed for the adjustment of the superelastic properties and the transformation temperatures. A superelastic strain exceeding 4% at 36°C was obtained. In this paper the fabrication of superelastic NiTi thin walled tubes by magnetron sputtering is presented and their mechanical properties are compared to conventional wires and tubes in view of orthodontic applications.
Applying NiTi Shape-Memory Thin Films to Thermomechanical Data Storage Technology
Authors: Crone Wendy C. , Shaw Gordon A. 
Published: April 2011

ABSTRACTAs the data storage density in cutting edge microelectronic devices continues to increase, the superparamagnetic effect poses a problem for magnetic data storage media. One strategy for overcoming this obstacle is the use of thermomechanical data storage technology. In this approach, data is written by a nanoscale mechanical probe as an indentation on a surface, read by a transducer built into the probe, and then erased by the application of heat. An example of such a device is the IBM millipede, which uses a polymer thin film as the data storage medium. It is also possible, however, to use other kinds of media for thermomechanical data storage, and in the following work, we explore the possibility of using thin film Ni-Ti shape memory alloy (SMA). Previous work has shown that nanometer-scale indentations made in martensite phase Ni-Ti SMA thin films recover substantially upon heating. Issues such as repeated thermomechanical cycling of indentations, indent proximity, and film thickness impact the practicability of this technique. While there are still problems to be solved, the experimental evidence and theoretical predictions show SMA thin films are an appropriate medium for thermomechanical data storage.
Raman Imaging and Thermal Expansion of Highly Textured Pb(Mg1/3Nb2/3)O3-PbTiO3 Piezoelectric Ceramics
Authors: Colomban Philippe , Pham-Thi Mai 
Published: April 2011

ABSTRACTPMN(PZN)-PT single crystals exhibit unique electromechanical properties when oriented and poled along the <001> direction. While expensive crystal growth techniques are advancing slowly, it is of great practical importance to develop an alternative low-cost production method based on strongly oriented or textured ceramics. We present here the thermal expansion, dielectric properties and Raman spectroscopy study of Pb(Mg1/3Nb2/3)O3-PbTiO3 solid solution ((1-x)PMN-xPT, 0.2<x <0.4, here after called PMN xPT) single crystals, random ceramics and ceramics prepared by homo-templated grain growth (HTGG) using cubic PMN-PT single crystal seeds as templates and nanoparticles as ceramic matrix. Representative medium to highly textured ceramics were sintered at 1150°C and 1200°C, respectively, and studied by Raman imaging. Raman peak centre of gravity is used to image the x-composition whereas peak intensity is correlated to the unit-cell distortion and related short-range structure. Smart Raman imaging shows that the final composition is very close to that of the matrix. We compare their thermal expansion (-150 to 300°C) and dielectric properties (R.T. to 300°C) with those of corresponding poled or non-poled single crystals and random ceramics homologues. Short-range ordering and phase diagram are discussed.
A Shape Memory Polymer with Improved Shape Recovery
Authors: Liu Changdeng , Mather Patrick T. 
Published: April 2011

ABSTRACTThermally actuated shape memory polymers (SMPs) interest, both academically and industrially, due to their ability to memorize a permanent shape that is set during processing and a temporary shape that is later programmed by manipulation above a critical temperature, either Tg or Tm. However, the thermal triggering process for SMPs is usually retarded compared to that of shape memory alloys, because the thermal conductivity of polymers is much lower (<0.30 W/m.K). In the present study, we incorporated a highly thermal conducting filler into a shape memory matrix to increase its thermal conductivity and therefore, shorten the heat transfer progress. A mathematical was worked out that quantitatively relates the material's thermal conductivity with the heat transfer time, τ, also defined as a shape memory induction time. The model fit nicely with our experimental data. In addition, mechanical reinforcement was observed with the addition of this rigid thermal conducting filler.
Controllable growth of single walled CNTs using nanotemplates from diblock copolymers
Authors: Lu Jennifer , Bai Jia , Moll Nick , Roitman Daniel , Yang Dorothy , Fu Qiang , Liu Jie , Rider David , Manners Ian , Winnik Mitch 
Published: April 2011

AbstractWe use diblock copolymers as nanotemplates to produce various catalyst nanoclusters or catalyst-containing inorganic nanostructures with controlled size and spacing for carbon nanotube growth. We are able to generate periodically ordered catalytic nanostructures by spin coating polymer-based catalyst systems. As a result, uniformly distributed, low defect density single walled nanotubes(CNTs) have been obtained. CNTs with diameters of 1nm or less have been produced from iron-containing inorganic nanostructures using conventional chemical vapor deposition. The superior film forming ability of polymer-based catalyst systems enables selective growth of carbon nanotubes on lithographically predefined catalyst islands over a large surface area. The ability to control the density and location of CNTs offers great potential for practical applications. The initial MALDI-MS (Matrix Assisted Laser Desorption Ionization-Mass Spectrometry) results indicate that we can positively identify bovine serum albumin (BSA) at 500 attomoles using CNT surfaces produced by this method.
SWNT NETWORK for BIOMOLECULE DETECTION
Authors: Atashbar Massood Z. , Bejcek Bruce , Singamaneni Srikanth 
Published: April 2011

ABSTRACTIn this paper we describe a single wall carbon nanotube (SWNT) based biological sensor for the detection of biomolecules using streptavidin and IgG. Two types of sensing mechanisms have been used to demonstrate the ability of carbon nanotubes to form nanoscale biosensors. The first sensing mechanism involves a CNT based conduction sensor in which the decrease in the current was observed when the specific biomolecule was bound. In the second mechanism Quartz Crystal Microbalance (QCM) was used to quantify the mass of the biomolecule bound on the sidewalls of the carbon nanotube. Both sensing mechanisms proved to be efficient and consistent. Immobilization of the biomolecules on the carbon nanotube surface was confirmed by Atomic Force Microscopy.
Low Temperature Growth of Carbon Nanotubes and Nanofibres
Authors: Robertson J , Hofmann S , Kleinsorge B , Golokov V , Ducati C , Geng J , Cantoro M , Boskovic B , Huck W , Johnson B F G 
Published: April 2011

AbstractThis paper reviews work on low temperature growth of carbon nanotubes, on Si, on plastic, on carbon cloth, using sputtered and colloidal catalysts, and with nano-imprinted patterning.
Bulk Synthesis of Helical Coiled Carbon Nanostructures
Authors: Wang Wei , Rao A. M. 
Published: April 2011

ABSTRACTThree dimensional helical coiled carbon nanostructures including coiled nanowires and nanotubes were synthesized at ambient pressure using a thermal chemical vaporization deposition (CVD) process in which xylene and acetylene were used as the primary carbon source. A bi-metal catalyst formed from a mixture of ferrocene and indium isopropoxide served as the seed to initiate the growth of these helical coiled nanostructures. The as-synthesized coiled nanowires and nanotubes are pure without the presence of amorphous carbon nanoparticles. By precisely controlling the atomic ratio of In / (Fe+In), coiled nanowires or nanotubes can be synthesized exclusively. The diameters of the as-grown coiled nanowires vary from several tens to several hundreds nanometers, whereas the diameters of the coiled nanotubes are around 20 nm. The structure of coiled nanowires and nanotubes were determined using scanning electron microscopy and transmission electron microscopy. The key novel aspects of this research are: (i) to synthesize helical coiled nanotubes or nanowires exclusively by controlling the bi-catalyst concentration of Fe and In, and (ii) no preformed substrates are required which implies that our process is amenable for scaled-up synthesis of these nanostructures.
Thermal Conductivity of Single-Walled Carbon Nanotube/PMMA Nanocomposites
Authors: Guthy Csaba , Du Fangming , Brand Stijn , Fischer John E. , Winey Karen I. 
Published: April 2011

ABSTRACTDue to their exceptional thermal properties, single-wall carbon nanotubes (SWNT) are considered as very promising filler materials for improving the thermal conductivity of conventional polymers. We carefully investigated the thermal conductivity of SWNT/PMMA nanocomposites with SWNT loading in the range up to10 wt% using the comparative technique. The samples were prepared by coagulation method. We demonstrated moderate improvement in the composites’ thermal conductivity of about 250% at 10wt%. The experimental results were analyzed using the versatile Nielsen model, which takes into account many important factors, like the fillers aspect ratio and maximum packing fraction. The aspect ratio of SWNT material used to prepare our composites was determined by AFM and careful image analysis in order to use it as an input parameter in the Nielsen model. We obtained good agreement between our experimental results and the predictions of the Nielsen model. Based on our analysis we concluded that higher aspect ratio of filler material was needed to achieve better improvement in the composites thermal conductivities. One should also take steps in order to improve the thermal contact between the SWNT network and the matrix material.
Chemically Engineered Carbon Nanotube-Polymer Composite Coatings for use as Remote Strain-Sensors
Authors: Halary Jérôme , Stanford John L. , Lovell Peter A. , Young Robert J. 
Published: April 2011

ABSTRACTCarbon nanotubes nanocomposites with unique opto-mechanical properties have been developed as smart coatings. Remote polarized Raman spectroscopy has been used to monitor optical strain sensitivity of deformed coatings and determine local strains on the micron scale directly from stress/strain induced Raman band shifts.Chemically engineered carbon nanotubes and polymer matrices have been developed in order to overcome the limitations highlighted in previous reports. They have proved to be of significance importance in the optimization of the stress transfer between the nanotubes and the polyurethane matrix.