bluuebunny/crossref_metadata_2025 huggingface dataset:
Formation of antimony 1D-nanostructures on Si (5 5 12) surface
Authors: Shivaprasad S. M. , Kumar Mahesh , Joshi Amish G. , Paliwal Vinod Kumar
Published: June 2019

Of late, high index Si surfaces like, (5 5 12) are being explored for the formation of 1D nanostructures in the form of nanowires or chains. The surface topography of Si (5 5 12) presents an unique template for the growth of 1D nanostructures. In this paper we report the adsorption-desorption studies of Sb onto (2×1) reconstructed surface of Si (5 5 12). Motivated by our earlier studies of adsorption/desorption of Sb on low index surfaces (001) and (111), studying the interaction on high index surface like (5 5 12) is found to be interesting. The experiments have been performed in UHV with in-situ growth and probed by using AES, LEED and EELS techniques. The uptake curve shows initially a simultaneous multilayer growth of Sb up to 4 ML and then at 20 ML the entire Si surface is covered by Sb. The LEED patterns show a disorder during growth at RT above 1 ML. EELS studies at 250 eV, primary beam energy show that as the adsorption proceeds the features of bulk Sb start appearing above 4ML coverage. However, the bulk Sb features are not complete until a high enough coverage of Sb (˜20ML) which suggests the existence of the primary rows up to a higher coverage. Annealing studies have also been performed on the RT adsorbed system, to study the residual thermal desorption characteristics. Annealing the system to about 7900C results in Si (337) facets at a low coverage of 0.2 ML. The anisotropy in the LEED spots suggests an ordered Sb adsorption along (1 10) and a local disorder in the (665 ) direction. Thus we provide evidence for the formation of a zig-zag 1D-nanowire of Sb grown on the (5 5 12). The new phase is also accompanied by forming a dangling bond state at 3 eV in EELS.
Spectral Sensitivity and Color Selectivity in Multilayer Stacked Devices
Authors: Louro P. , Vieira M. , Fantoni A. , Fernandes M. , Lavareda G. , Carvalho C. Nunes de
Published: June 2019

In this work, an attempt of full color discrimination is presented using as sensitive devices multilayer stacked structures (p(SiC:H)/i(SiC:H)/n(SiC:H)/p(SiC:H)/i(Si:H)/n(Si:H)) sandwiched between two transparent conductive contacts. The thickness and the absorption coefficient of the front p-i-n cell is optimized for blue collection and red transmittance and the thickness of the back one adjusted to achieve full absorption in the green and high collection in the red spectral ranges. The current-voltage characteristics and the spectral sensitivity under different electric and optical bias conditions and light fluxes are analyzed. Results show that color selectivity is achieved by tuning the spectral sensitivity at different applied voltages. A physical model supports the results.
Effect of the hydrogen content in the optical properties and etching of silicon nitride films deposited by PECVD for uncooled microbolometers
Authors: Ambrosio R. , Torres A. , Kosarev A. , Landa M. , Heredia A.
Published: June 2019

We have studied silicon nitride films a-SiN:H deposited at a substrate temperature of 350°C by means of the Low frequency (LF) PECVD from silane and nitrogen as stock gases. Film properties as hydrogen bonding and content, nitrogen content, refractive index and etch rate are reported and analyzed. Our deposited films show physical properties similar to those that are obtained deposition temperatures of 700°C by the low pressure chemical vapor deposition (LPCVD) technique. An investigation of bonding structures for the deposited films was performed, and quantitative results for hydrogen bonding based on Fourier Transform Infrared (FTIR) analysis are presented. It was observed that low hydrogen content in the films is in good correlation with low etch rate in 10% buffered HF solution, therefore these films present a material with good etch selectivity in respect to others materials (as phosphosilicate glass PSG, Al etc). Selectivity which makes these films very promising in surface micromachining for fabrication of sensors and device structures, e.g. microbolometers. Additionally, the Si-N bond at 830-840cm-1was analyzed because of its big absorption produced at 12μm; therefore these films can be used as absorber layers in uncooled microbolometres.
Photoluminescence and electroluminescence properties of FeSi2-Si structures formed by MEVVA implantation
Authors: Chow C.F. , Gao Y. , Wong S.P. , Ke N. , Li Q. , Cheung W.Y. , Shao G. , Lourenco M.A. , Homewood K.P.
Published: June 2019

We have prepared FeSi2 precipitates of nanometer size in Si by ion implantation using a metal vapor vacuum arc (MEVVA) ion source and studied their photoluminescence properties. Broad photoluminescence (PL) spectra at around 1550 nm were observed for all samples attributed to emission from the FeSi2 precipitates. It was found that all the PL spectra can be decomposed into two peaks, a main peak at near 1530 nm and a satellite peak at 1607 nm. Samples with a furnace annealing (FA) step at a lower temperature of 850°C are found to have a main peak position at a longer wavelength close to 1540 nm. For samples with a FA step at higher temperatures, the main peak position shifts to shorter wavelengths of near 1525 nm. In addition, we have also prepared MOS structures with implanted FeSi2 precipitates incorporated in the structures and measured their EL properties. The EL properties from these FeSi2-Si MOS structures after various thermal treatments were measured as a function of temperature from 80 to 300 K. Our preliminary results show that clear EL signals are obtained even at room temperature under appropriate processing conditions.
Effect of Electromigration on Mechanical Behavior of Solder Joints
Authors: Ren Fei , Nah Jae-Woong , Gan Hua , Suh Jong-Ook , Tu King-Ning , Xiong Bingshou , Xu Luhua , Pang John
Published: June 2019

Electromigration in solder joints causes a void formation between intermetallic compounds (IMC) and solder at the cathode. The effect of electromigration in mechanical test of Cu wires joined by solder was performed. The current density of electromigration was 1∼5×103 A/cm2. The working temperature was 100∼150°C. Tensile stress and shear stress were applied either before or after electromigration. The tensile strain rate was 3 μm/min. We observed that, without electromigration, tensile stress caused a ductile break at the middle of solders because the solder was softer. On the other hand, if combined with electromigration, a brittle failure always occurred at the cathodes interface during tensile test. The ultimate tensile strength decreased with longer electromigration time or higher current density. In shear test, the daisy chain of solders failed alternatively at the cathodes after electromigration.
Poly(ethynyl-p-xylylene), An Advanced Molecular Caulk CVD Polymer
Authors: Carrow Brad P. , Murray Rex E. , Woods Benjamin W. , Senkevich Jay J.
Published: June 2019

Poly(p-xylylene) (also known as parylene N) has previously been used to pore seal ultralow k (≤ 2.2) (ULK) dielectrics. The parylene polymers may facilitate the integration of ULK dielectrics by: substantially improving their fracture toughness, hermetically sealing the pores, being able to use standard wet chemical cleans, and minimally impacting the observed dielectric constant, while minimally disrupting current process flow integrations. This paper introduces a new cross-linkable polymer that is deposited using thermal chemical vapor deposition (CVD) on the same tool that is used for parylene N deposition. The polymer, poly(ethynyl-p-xylylene) (parylene X), was deposited at room temperature. A series of 30 min post-deposition anneals in helium shows that the deposited material cross-linked between 200°C and 300°C with full conversion at 380°C for a ~300 A film. After the low molecular weight species out-gassed during anneals at 200°C, there was less than a percent weight loss to 450°C with no change in the optical constants and no optical loss. Previous work with poly(ethyl-p-xylylene) suggests that the dielectric constant of parylene X will be significantly lower than parylene N.
Barrier Integrity Effect on Leakage Mechanism and Dielectric Reliability of Copper/OSG Interconnects
Authors: Li Yunlong , Tökei Zsolt , Mandrekar Tushar , Mebarki Bencherki , Groeseneken Guido , Maex Karen
Published: June 2019

In this paper, we investigate the effect of copper diffusion barrier integrity on the leakage behavior and dielectric reliability of copper/micro porous organo-silica-glass (OSG) interconnects. Significant differences in the field dependence of TDDB median-time-to-failure are observed when comparing sub-critical and sealing barriers. Also for the temperature acceleration of TDDB, a significant difference is found which is reflected in the thermal activation energies. With fast voltage ramp measurements, I-V curves of samples with subcritical and sealing barriers are compared before and after constant current stresses. Above 1.4 MV/cm, the dominant leakage mechanism is found to be Frenkel-Poole emission regardless of barrier treatments and stress times. Below 1.4 MV/cm, however, the I-V characteristic is modulated by the barrier integrity, which can be attributed to copper diffusion into the intermetal dielectric.
TEM-Based Analysis of Defects Induced by AC Thermomechanical versus Microtensile Deformation in Aluminum Thin Films
Authors: Geiss R.H. , Keller R.R. , Read D.T. , Cheng Y.W.
Published: June 2019

Thin films of sputtered aluminum were deformed by two different experimental techniques. One experiment comprised passing high electrical AC current density through patterned Al interconnect lines deposited on SiO2/Si substrates. The other consisted of uniaxial mechanical tensile deformation of a 1 μm thick by 5 μm wide free standing Al line. In the electrical tests approximately 2 x 107 W/cm2 was dissipated at 200 Hz resulting in cyclic Joule heating, which developed a total thermomechanical strain of about 0.3 % per cycle. The tension test showed a gauge length fracture strain of only 0.5 % but did display ductile chisel point fracture. In both experiments, certain grains exhibited large, > 30°, rotation away from an initial <111> normal orientation toward <001>, based on electron backscatter diffraction (EBSD) measurements in the scanning electron microscope (SEM). Transmission electron microscopy (TEM) analysis of specimens from both experiments showed an unusually high density of prismatic dislocation loops. In the mechanically-tested samples, a high density of loops was seen in the chisel point fracture zone. In cross sections of highly deformed regions of the electrical test specimens, very high densities, > 1015/cm3, of small, > 10 nm diameter, prismatic loops were observed. In both cases the presence of a high density of prismatic loops shows that a very high density of vacancies was created in the deformation. On the other hand, in both cases the density of dislocations in the deformed areas was relatively low. These results suggest very high incidence of intersecting dislocations creating jogs and subsequently vacancies before exiting the sample.
Stress-induced Void Formation in Passivated Cu Films
Authors: Gan Dongwen , Li Bin , Ho Paul S.
Published: June 2019

In this paper, we investigated void formation in passivated Cu films focusing on the kinetics of void formation under isothermal annealing as a function of temperature. Interestingly, we found that the kinetics of void formation in Cu films is consistent with that observed in Cu lines, which is driven by the combined effect of thermal stress and mass transport resulting in a peak growth rate at about 250°C. To analyze the observed results, we have calculated the stress state at the <111>/<200> Cu grain boundary to demonstrate the existence of a localized triaxial stress state as a result of elastic anisotropy. To account for void density, x-ray analysis was performed to measure the grain texture using inverse pole figure plot and the result can account for the void density observed. A kinetic model was used to analyze void growth under isothermal annealing. A threshold stress of about 40MPa was deduced for void growth in passivated Cu films with an activation energy of 0.75 eV.
Determination of Elastic Modulus and Yield Stress of Ultra-thin Cu and low-k Films Using Spherical Nanoindentation Measurement
Authors: Shimizu Satoshi , Kojima Nobuo , Ye Jiping
Published: June 2019

A spherical nanoindentation method was developed to evaluate elastic and plastic deformation parameters. The experimental reliability was confirmed by examining fused silica in the elastic deformation range. Yield stress as a quantitative plastic parameter was estimated using the Hertz contact theory and Tresca yield criterion. A copper thin film and two types of low-k thin film were examined. Reduced modulus was almost the same as the value obtained for the Cu (100) plane and yield stress was found to be between single crystals Cu (111) and Cu (100). These mechanical properties were thought to be dependent on the crystal orientation of the copper thin film. The two types of MSQ low-k film exhibited a difference in yield stress, although hardness was estimated to be similar by using the conventional nanoindentation method. These results have never been seen on a micro-mater scale.
Advanced Al Damascene Process for Fine Trench Under 70nm Design Rule
Authors: Han Sung Ho , Choi Kyung-In , Yun Sera , Park Jeong Heon , Lee Won Sok , Lee Sang Woo , Choi Gil Heyun , Hong Change Kee , Kim Sung Tae , Chung Uin , Moon Joo Tae , Ryu Byung-Il
Published: June 2019

Due to a rapid shrinkage in memory devices, backned of the line process experiences great difficulties, especially Al metallization. Furthermore, there is a continuous demands in low line resistance in order to promote device performances. In this article, Al damascene process is proposed as compared to Al patterning process, which suffers from inherent pattering issue at a fine pitch under 70nm. The most difficulties in the development of Al damascene process were to form a stable and void free Al in fine trench and to obtain scratch and corrosions free Al surface. In this study, 50nm beyond fill was successfully achieved by “bottom up growth” of CVD Al. For the process, CVD Al by using Methylpyrroridine Alane (MPA) precursor was deposited on a stacked film of CVD TiN and PVD TiN as a wetting layer, which was followed by PVD Al and reflow, then the Al surface was polished with colloidal silica based slurry.

In addition, electrical property of Al scheme and W scheme was compared with damascene pattern, along with which we demonstrated that around 36% decrease in parasitic capacitance is achievable by decrease of metal line height from 3500A to 1000A on simulation test implying that device performance could be enhanced.
A Spin-on Dielectric Material for High Aspect Ratio Gap Fill
Authors: Chen Wei , Wang Sheng , Ashraf Ather , Somerville Edward , Nowaczyk Gerard , Hwang BK , Lee JK , Moyer Eric S.
Published: June 2019

This communication describes the results of a potential spin-on glass (SOG) solution for narrow and high aspect ratio trench fill in both shallow trench isolation (STI) and premetal dielectric (PMD) applications. We have focused our development work on a hydrogen silsesquioxane (HSQ, (HSiO3/2)n) material, which offers the advantage of a carbon free gap fill solution. The main challenge for carbon-free SOG materials is to achieve material densification in the nano-scale gaps during thermal processing that of the gap filled material during the wet cleaning steps. This paper reports some approaches and findings on material densification in the nano-scale gaps and the results of subsequent wet etch tests.
Synchrotron X-ray Micro-diffraction Analysis on Microstructure Evolution in Sn under Electromigration
Authors: Wu Albert T. , Tamura N. , Lloyd J. R. , Kao C. R. , Tu K. N.
Published: June 2019

White Sn (β-Sn) thin film stripe shows a voltage drop about 10% when subjected to electromigration testing. Since β-Sn has anisotropic crystal structure, it possesses different resistivity along a-, b- and c axis. The direction of the axes determines the resistance in each grain. Under electromigration, low resistance grain tends to grow in the expense of the neighboring high resistance grains. The changes of grain orientation in the Sn stripe before and after electromigration was studied by synchrotron x-ray microdiffraction (∼1νm diameter) to achieve grain-by-grain analysis. Grain growth involves grain boundary migration and rotation of neighboring high resistance grains. A model different from normal grain growth is proposed to describe the condition and mechanism of microstructural evolution under electromigration.
Multi-Via Electromigration Test Structures for Identification and Characterization of Different Failure Mechanisms
Authors: Choi Z.S. , Chang C. W. , Lee J. H. , Gan C. L. , Thompson C. V. , Pey K. L. , Choi W. K.
Published: June 2019

Experiments on three-terminal ‘dotted-I’ test structures (copper metal lines with vias at both ends and an additional via at the center) show that the mortality of a single segment not only depends on the values of its current density and length, but also on the stress conditions in the linked segment. The current density in one 25μm long segment was fixed at 0.5MA/cm2, with electron flow toward the central via. In the othersegment, the current magnitude and sign were varied for different test populations, with the current varied from 2.5MA/cm2 to -2.5MA/cm2 with intermediate values including zero. For all cases, some test structures survived for the full 780 hours of testing and some did not. The percent of the lines that failed increased monotonically with an effective jL product defined as the maximum of the sum of the jL products from all paths through the structure. However, some lines with smaller than expected effective jL products failed, and some lines with relatively large effective jL products did not. Simulations of electromigration and electromigration-induced failures for all test conditions have been carried out. We find that test conditions leading to extreme values of the effective jL product probe different failure mechanisms than those associated with intermediate effective jL products. It is also shown that the definition of the effective jL product must be modified to account for zero current (inactive) segments that act as reservoirs or sinks. Multi-via test structures in general, and dotted-I test structures specifically, are shown to be versatile tools for identification and characterization of different failure mechanisms and length effects through the use of different test conditions with a single fixed structure.
Microstructure Evolution During Electric Current Induced Thermomechanical Fatigue of Interconnects
Authors: Keller Robert R. , Geiss Roy H. , Cheng Yi-wen , Read David T.
Published: June 2019

We demonstrate the evolution of microstructure and deformation associated with the use of electrical methods for evaluating mechanical reliability of patterned interconnects on rigid substrates. Thermomechanical fatigue in aluminum and copper interconnects was induced by means of low frequency (100 Hz), high density (> 10 MA/cm2) alternating currents, which caused cyclic Joule heating and associated thermal expansion strains between the metal lines and oxidized silicon substrate. The failure mechanism involved formation of localized plasticity, which caused topography changes on the free surfaces of the metal, leading to open circuit eventually taking place by melting at a region of severely reduced cross-sectional area. Both aluminum and copper responded to power cycling by deforming in a manner highly dependent upon variations in grain size and orientation. Isolated patches of damage appeared early within individual grains or clusters of grains, as determined by a quasi in situ scanning electron microscopy and automated electron backscatter diffraction measurement. With increased cycling, the extent of damage became more severe and widespread. We document some examples of the types of damage that mechanically confined interconnects exhibited when subjected to thousands of thermal cycles, including growth and re-orientation of grains in a systematic manner. We observed in the case of Al-1Si certain grains increasing by nearly an order of magnitude in size, and reorienting by greater than 30°. The suitability of electrical methods for accelerated testing of mechanical reliability is also discussed.
Thin-Film Color Sensor Arrays
Authors: Knipp D. , Street R.A. , Stiebig H. , Krause M. , Lu J.-P , Ready S. , Ho J.
Published: June 2019

Color information is commonly captured by silicon sensor arrays covered by a mosaic of color filters. However, the detection of the colors red, green and blue at different spatial positions of the sensor arrays leads to color aliasing or color moiré effects. This effect inherently limits conventional sensor arrays. In order to overcome this limitation we have realized color sensors based on vertically integrated thin-film structures. The complete color information can be detected at the same position of a sensor array without using optical filters. The sensors consist of a multilayer thin-film system based on amorphous silicon and its alloys. The spectral sensitivity of the sensors can be controlled by the optical and optoelectronic properties of the employed materials and the applied bias voltages. The working principle of the thin-film sensors and the sensor arrays will be presented. For the first time a large area three color sensor array was realized without using optical filters.
Integration of Zinc Oxide Thin Films with Polyimide-based Structures
Authors: Matsumura Masashi , Bandic Zvonimir , Camata Renato P.
Published: June 2019

Zinc oxide (ZnO) films were deposited on polyimide-based substrates by pulsed laser deposition. The ZnO films and the underlying polymer layers were studied using Fourier Transform Infrared (FTIR) and Photoluminescence (PL) spectroscopies. FTIR measurements in structurally well-characterized samples exhibiting all X-ray reflections of crystalline hexagonal ZnO show absorbance bands around 405 cm-1(Zn-O stretching vibration) and 1110 cm-1 (in-plane C-H vibrations on aromatic rings of polyimide). Observed shifts in both absorption features as a function of deposition temperatures can probably be attributed to thermal stress in the layers. PL measurements showed broad spectra centered around 3.35 eV from ZnO excitonic emission and a broader PL band from 2.7 to 3.1 eV defect complex emissions. The appearance of these peaks was consistent for depositions of ZnO on non-organic substrates, which indicates that the integration of ZnO thin films on polymer based substrate preserved the characteristic optical properties of ZnO.
Study of sputtered Hafnium oxide Films for Sensor Applications
Authors: Grüger H. , Kunath C. , Kurth E. , Sorge S. , Pufe W.
Published: June 2019

In this paper results of the deposition and annealing of hafnium oxide thin films are reported. Due to the sensor application in mind, thicknesses between 30 and 150 nm have been deposited by r.f. sputtering of a high purity oxide target. Annealing has an important influence on the layer structure, stress and application correlated properties. A detailed understanding of the layer preparation is necessary to adjust deposition and annealing. After deposition the layers are predominately amorphous, annealing leads to textured layers with monocline or orthorhombic phases.

Besides gas sensor applications optimized layers may serve as protective coating or combined with a second material to multi layer stacks as high reflective dielectric mirror.
Perovskite Particles from Phytoplankton
Authors: Weatherspoon Michael R. , Allan Shawn M. , Gaddis Christopher S. , Cai Ye , Haluska Michael S. , Snyder Robert L. , Sandhage Kenneth H.
Published: June 2019

Controlled-shape BaTiO3-based microparticles were synthesized with the use of diatom microshells (frustules) as templates. The SiO2-based frustules of Aulacoseira diatoms were first converted into MgO-based replicas via a gas/solid displacement reaction at 900°C. A BaTiO3 coating was then applied to the MgO-bearing frustules by a sol-gel process. After firing at 700°C for 1.5 h, a conformal nanocrystalline coating of BaTiO3was generated on the surfaces of the MgO-bearing frustules. The underlying MgO scaffolds were then selectively dissolved away to yield freestanding 3-D BaTiO3-based replicas of the original Aulacoseira diatom frustules. This work demonstrates that microparticles with well-controlled 3-D morphologies and non-natural multicomponent ceramic compositions can be produced by merging the self-assembly ability of biomineralizing micro-organisms with synthetic chemical tailoring.
Laser Light Scattering Observations of Liquid–Liquid Phase Separation in a Polymer-Induced Liquid-Precursor (PILP) Mineralization Process
Authors: DiMasi Elaine , Liu Tianbo , Olszta Matthew J. , Gower Laurie B.
Published: June 2019

A Polymer-Induced Liquid-Precursor (PILP) process for mineralization of calcium carbonate has been studied in-situ by laser light scattering. Static and dynamic light scattering data were obtained from CaCl2 solutions containing poly(aspartic acid). Under these conditions calcium carbonate mineralizes through a liquid droplet precursor phase when the solution is exposed to the decomposition products of ammonium carbonate. Our measurements probe the integrated scatterer mass and the apparent hydrodynamic radius Rh,app of the droplets as they nucleate and coalesce. The data reveal three stages in the formation of the PILP phase: an early stage of droplet growth to Rh,app ≈ 250 nm; a mid-time stage of fluctuations and polydispersity in particle size; and a final growth period where Rh,app increases from 350 nm to the micron scale. Aggregation of precursor droplets, rather than atom-by-atom growth, is the dominant mechanism of mineral formation under these conditions. With respect to biomineralization, this first observation of 100-nm-scale droplets is significant, implying a possibility to mineralize from the liquid phase within the nanoscale compartments in which many biominerals form.
Cell Biology, Biochemistry and Genomics of Coccolithophore Biomineralization.
Authors: González Elma L. , Read Betsy A.
Published: June 2019

The coccoliths that form the outer cell covering of the unicellular coccolithophores are assembled in a coccolith vesicle. The coccolith vesicle maintains the conditions and protein carriers sufficient to import the raw materials (Ca2+ and CO32-) for calcite formation and, furthermore, to initiate and sustain mineralization. We have isolated the coccolith vesicle membrane on which a proton-pumping, vacuolar ATPase has been localized. The V-ATPase has been characterized and its membrane-spanning subunit c has been cloned and sequenced. We used the highly conserved sequence for designing and constructing probes and primers that allowed us to analyze expression patterns to show a direct relationship between expression of the gene and calcification. Our collaborative work has now turned to a genomics approach that will lead us to additional calcification-specific genes.
Bio-inspired Design of Modular Multi-domain Polymers for Advanced Biomaterials
Authors: Roland Jason T. , Guzman Dora , Bai Jane , Guan Zhibin
Published: June 2019

Native load-bearing proteins, such as the muscle protein titin, exhibit a remarkable degree of combined toughness, strength, and elasticity which have yet to be matched by synthetic materials.Single molecule nanomechanical studies on titin and other modular proteins suggest that these exceptional properties arise from a modular elongation mechanism. The sequential unfolding allows modular biopolymers to sustain a large force over the whole extension of the chain, which makes the polymer strong, along with a large area under the force-extension curve, making it tough as well. In addition, when the external force is removed, the unfolded domains of modular proteins will refold automatically, making them elastic. Inspired by nature, one research effort in my group is aimed at designing synthetic macromolecules that form high order structures by programming non-covalent interactions into polymer chain. The goal is to achieve synthetic biomaterials with combined strength, toughness and elasticity. Three classes of well-defined modular polymers have been synthesized in our laboratory: (1) using quadruple hydrogen-bonding motif 2-ureidon-4-pyrimidone (Upy) to direct the formation loops along a polymer chain (J. Am. Chem. Soc.2004, 126, 2058); (2) using a peptidomimetic beta-sheet based double-closed loop (DCL) as module (J. Am. Chem. Soc.2004, 126, 14328); and (3) an engineered protein G domain III as module. Single molecule force-extension experiments revealed the sequential unfolding of the loops or domains as these modular polymers are stretched, resulting in sawtooth-patterned curves similar to those seen in titin and other biopolymers. In this paper, we will discuss our designs, syntheses and single-molecule studies of polymers having modular domain structures.
Immobilization of Proteins on the Surface of Silanized Hydroxyapatite
Authors: Monkawa Akira , Ikoma Toshiyuki , Kumagai Yuri , Yunoki Syunji , Tanaka Junzo
Published: June 2019

Hydroxyapatite (HAp) is widely used as bioceramics for bone and dental tissue reconstructions due to its excellent biocompatibility with hard tissues and high osteoconductivity. Although it is well known that HAp has the high adsorbed ability, its ability is decreased in high ionic solution. To immobilize protein on the HAp surface, this study demonstrates that Collagen (Col) and fibronectin (Fnt) were immobilized on the surface of hydroxyapatite (HAp) sintered body with and without the silane coupling agent of aminopropyltriethoxysilane (APS). The proteins immobilized on the HAp and APS/HAp surfaces were investigated by atomic force microprobe (AFM, Simadzu; SPM 9500) analyses and Ζ potential measurements. The stability of protein/APS/HAp and protein/HAp composites was evaluated after immersion in phosphate buffer and NaCl solutions with various concentrations. AFM analyses and Ζ potential measurements revealed that proteins immobilized on the APS/HAp are more stable than those immobilized on the HAp in high ionic solutions.
Preparation and Characterization of Porous Material from Self-Organized Hydroxyapatite/Collagen Nanocomposite
Authors: Yunoki Shunji , Ikoma Toshiyuk , Monkawa Akira , Kikuchi Masanori , Tanaka Junzo
Published: June 2019

Self-organized hydroxyapatite /collagen (HAp/Col) nanocomposite was synthesized by a co-precipitated method. The porous HAp/Col nanocomposites with unidirectional and interconnected pores with approximately 20μm in size were prepared by a facile method. The ice crystals were grown up at a cooling brass bottom in the paste which kneaded the HAp/Col nanocomposite with a sodium phosphate buffer. The freeze-drying technique produced the replica of ice structures, and the porous composites showed the anisotropic compressive strengths. The nanostructure and micropore structure are of great importance for developing the novel artificial bone filling materials; attachment and migration of cells and blood vessels, and early regeneration of bone tissues.
Magnetic Rings: Influence of Asymmetry on Switching Mechanism
Authors: Mani Anand Subra , Geerpuram Dwarakanath , Baskaran Vidhya Shankar , Rodriguez Guadalupe , Metlushko Vitali
Published: June 2019

We found that the introduction of well-controlled asymmetry provides precise control of the switching mechanism and leads to improved switching characteristics in magnetic nano-rings.
Langmuir Layers of Magnetic Nanoparticles
Authors: Majetich Sara A. , Sachan Madhur , Kan Shihai , Cheng Yuhang , Gardener Julie
Published: June 2019

Methods to form magnetic nanoparticle monolayers using non-aqueous Langmuir layers are reported. Following a discussion of the driving forces in various self-assembly techniques, we describe how aqueous Langmuir layers can be modified for use in conjunction with oxidationsensitive nanoparticles. Monolayers are formed using Fe and–Co nanoparticles, and transferred to carbon-coated transmission electron microscopy grids using the Langmuir-Schaefer method.
Magnetic Nanoparticle Aggregation States in Ag100-xFex Cosputtered Granular Films Investigated by Magnetic and Magnetotransport Measurements
Authors: Allia Paolo , Celegato Federica , Coisson Marco , Tiberto Paola , Vinai Franco , Spizzo Federico
Published: June 2019

Magnetoresistance and.magnetization measurements have been performed on nanogranular, cosputtered Ag100-xFex films (x= 10 to 30) in the 4 K – 300 K temperature interval. The analysis reveals that the films with x ≤ 14 are interacting superparamagnets, characterized by a magnetic correlation length of the order of the electronic mean free path λ. Films with x ≥ 26 behave as concentrated magnets with strong competing interactions among magnetic moments (frustrated ferromagnets) and magnetic correlation length much larger than λ.
Self-Assembling Magnetic Nanostructures: Wires, Helices, Nanotubes Of Ni Nanoparticles
Authors: Kislov V.V. , Gulyaev Yu.V. , Taranov I.V. , Kashin V.V. , Kozhevin V.M. , Yavsin D.A. , Zabelin M.A. , Tret'yakov P.A. , Gurevich S.A.
Published: June 2019

The formation of organized structures of magnetic nanoparticles have been studied by scanning probe microscopy when depositing Ni nanoclusters on conducting (gold on HOPG) substrates. In this case magnetic Ni nanoparticles formed by laser electrodispersion technique based on laser ablation (size of particles ∼ 2.5 nm) form highly ordered superstructures, including helical (double helix with outer diameter ∼ 10 nm, distance between sequences ∼ 5 nm, length of such helix is typically hundreds of nm), linear (chains of clusters), etc. The structures discovered were investigated also by STS methods, with clear demonstration of Coulomb blockade effect over single nanoclusters. The results of calculations for dipole-dipole and exchange interaction of magnetic nanoparticles support such formation of helix-like structures.
Structural and Magnetic Properties of Granular Co-ZrO2 Films
Authors: Konstantinović Z , Muro M García del , Hattink B J , Varela M , Batlle X , Labarta A
Published: June 2019

We present here the growth of Co-ZrO2 granular films by pulsed laser deposition (PLD). Co-ZrO2 prepared with PLD is an ideal system for investigating the properties of magnetic nanoparticle since the Co-ZrO2 interfaces are of high quality with no evidence of intermixing. The average composition of the samples is determined by x-ray photoemission spectroscopy and microprobe exsperiments. High resolution scanning electron microscopy shows existence of a regular distribution of Co nanoparticles embedded in the amorphous ZrO2 matrix. Ferromagnetic correlations among the Co nanoparticules are evident in the field-cooled state. The mean particle size and width of the distribution are determined by fitting the low-field magnetic susceptibility and isothermal magnetization in the paramagnetic regime to a distribution of Langevin functions. Magnetoresistance confirms its origin from the particle magnetization and also validates information about the particle distribution.
Fabrication of Core-shell Type FeCo-Au (Ag) High Moment Magnetic Nanoparticles
Authors: Bai Jianmin , Xu Yunhao , Wang Jian-Ping
Published: June 2019

We developed a physical vacuum deposition technique combining an on-line sputtering/evaporation process with an integrated nanocluster deposition process to prepare core-shell type nanoparticles. High magnetic moment (Fe60Co40)coreAushell and (Fe60Co40)coreAgshell superparamagnetic nanoparticles with controllable particle size of 10 – 20 nm and Au/Ag shell thickness of 1 – 3 nm were prepared successfully by using method. Au shell is not only functional for the potential biocompatibility but also the key to prevent oxidation of FeCo nanoparticles. Saturation magnetization of (Fe60Co40)coreAushell nanoparticles was found three times higher than that of iron oxide nanoparticles. This novel technique enables us to control independently the dimensions of core and shell and select individually materials for core and shell for other core-shell type nanoparticles.
Synthesis of Magnetic Self-Assembled Nickel-Rich Oxide Nanowires Using a Novel Electrochemical Process
Authors: Bhargava Yash V. , Thorne Shawn A. , Mintz Todd S. , Hyams Tzipi Cohen , Radmilovic Velimir , Suzuki Yuri , Devine Thomas M.
Published: June 2019

We present a novel self-assembly nanowire synthesis technique capable of producing nickelrich oxide nanowires of lengths up to 20μm and diameters as small as 5nm. The method was discovered while examining the oxidation of Alloy 600 (nickel- 15.5a/o Cr, 8a/o Fe) in a pressurized water reactor environment. The nanowires have been grown on substrates of Alloy 600 and other nickel-chromium substrates exposed to oxidizing conditions in 1500psi pressurized water with 2ppm lithium and 1200ppm boron at temperatures ranging from 238°C to 288°C. Oxidizing conditions can be controlled in one of two ways: by controlling the aqueous solution's dissolved oxygen concentration, or by use of a potentiostat. Compositional studies performed via energy dispersive spectroscopy (EDS) using a transmission electron microscope (TEM) indicate the content of the nanowires grown on Alloy 600 to be 49a/o oxygen, 47a/o Ni, and 4a/o Fe. Preliminary TEM analysis has revealed the nanowires to be single crystalline with an aspect ratio up to 1000:1. The nickel-rich oxide nanowires are particularly exciting because of their functional properties. The oxide composition of the nanowires gives them an inherent resistance to electrochemically aggressive environments, such as ones found in the body or many other aqueous solutions, in contrast to simple metal nanowires, which are susceptible to corrosion in such environments. Most importantly, analysis with a superconducting quantum interference device (SQUID) magnetometer indicates that the nickel-rich oxide nanowires are ferromagnetic with a coercivity of approximately 850e and a remnant field of 0.032emu/g at 300K.
Attenuation of Protein Adsorption on Static and Vibrating Magnetic Nanowires
Authors: Ainslie Kristy M. , Sharma Gaurav , Dyer Maureen A. , Grimes Craig A. , Pishko Michael V.
Published: June 2019

The research described here investigates the hypothesis that nanoarchitecture contained in a nanowire array is capable of attenuating the adverse host response, biofouling, generated when medical devices, such as sensors, are implanted in the body. This adverse host response generates an avascular fibrous mass transfer barrier between the device and the analyte of interest, disabling the sensor. Numerous studies have indicated that surface chemistry and architecture modulated the host response. These findings lead us to hypothesize that nanostructured surfaces will significantly inhibit the formation of an avascular fibrous capsule. We are investigating whether vibrating magnetostrictive nanowires, formed in nanowire arrays, can prevent protein and cell adhesion. Magnetostrictive nanowires are fabricated by electroplating a ferromagnetic metal alloy into the pores of a nanoporous alumina template. The ferromagnetic nanowires are made to vibrate by altering the magnetic field surrounding the wires. Enzyme-linked immunosorbent assay (ELISA) and other protein assays were used to study protein adhesion on the nanowire arrays. These results display a reduced protein adhesion per surface area of static nanowires. The vibrating nanowires show a further reduction in protein adhesion, compared to static wires. Studies were also preformed to investigate the effects of nanoarchitecture have on cell adhesion. These studies were performed with both static and vibrating nanowires. Preliminary protein adhesion studies have shown that a nanowire arrays modulate protein adhesion in vitro.
Room-Temperature Growth of Carbon Nanofibers
Authors: Vohs Jason K. , Raymond Jeffery E. , Brege Jonathan J. , Rozeveld Steven , Williams Geoffrey L. , Fahlman Bradley D.
Published: June 2019

We describe the growth of amorphous carbon nanofibers (CNFs) from iron-encapsulated dendrimer catalysts at ambient temperature and pressure conditions. Both fourth-generation poly (propyleneimine) (PPI) and poly(amidoamine) (PAMAM) dendrimers were suitable macromolecular hosts for the catalytic species. Average nanofiber diameters range from 10 - 15 nm, with lengths in excess of 20 microns.
Dynamics of Silicon Nanoparticle Synthesis by Pulsed Laser Ablation
Authors: Murray P.T. , Grazulis L.
Published: June 2019

Si nanoparticles have been synthesized by ablating a Si target in Ar with 355 nm laser radiation. The nanoparticle size distribution has been determined in real time by laser-induced time of flight mass spectrometry. Under these conditions, nanoparticles that are formed in 1.0 and 2.0 Torr of background Ar gas exhibit log-normal size distributions with most probable diameters of 2.6 and 3.0 nm, respectively. The speed distribution of the nanoparticles has been determined by varying the time delay between the ablation and photoionization lasers. The results indicate that the most probable speed of the nanoparticles, after formation and a 25 mm drift in background Ar, is 100 m/s. Finally, there is a deviation of the size distribution from the log-normal distribution at small nanoparticle sizes. This is attributed to multiple ionization of the nanoparticles. Confirming evidence for multiple ionization is provided by the atomic and mass spectra which show peak broadening due to Coulomb explosion.
Preparation of Free-Standing PZT and Gold Nanoparticles
Authors: Das R. N.
Published: June 2019

Free-standing PZT (Lead Zirconate Titanate ) and Gold nanoparticles (ceramic and metal) have been prepared by complex process. In case of PZT, the process involves the preparation of metal ion complex (ligand) solution followed by evaporation. Complete evaporation results in fluffy dried mass. Calcination of dried mass at low temperature produces free-standing PZT nanoparticles. The concept of the process involves choice of correct metal ion complex, stoiochiometry and drying conditions to produce free-standing individual nanoparticles. Similar process has been used to prepare free-standing gold nanoparticles where individual gold form complex with the ligands (complexing agents) to produce free-standing nanoparticles.
Synthesis, Characterization, and Growth Mechanism of Silicon Oxide Nanowires
Authors: Dong Lifeng , Coulter Michael , Ford  , Jiao Jun
Published: June 2019

Two fabrication methods have been investigated to synthesize silicon oxide nanowires. One was catalytic thermal evaporation method in which silicon monoxide was used as the precursor and Au particles served as the catalysts. Using nanosphere lithography, patterned nanowires were obtained and their growth positions were controlled by the locations of Au catalysts. For the second method, without silicon monoxide as the precursor and without the aid of Au catalyst, silicon oxide nanowires directly formed along the <110> direction of the silicon substrate only with the introduction of hydrogen gas. A series of experiments were carried out to study effects of reaction time, temperature, and hydrogen on the growth of the nanowires. Also, various electron microscopy techniques were utilized to characterize their morphologies and internal structures and to analyze their compositional distributions. In this paper, the characterization of different silicon oxide nanowires and their formation mechanisms in relation to both preparation methods are discussed.
Synthesis and Aggregation of BiBi2S3Nanocapsules
Authors: Vega-González Marina , Bokhimi Xim , Aguilar-Franco Manuel , Morales Antonio , García-Ruiz Amado F.
Published: June 2019

Nanocapsules of Bi2S3 with diameters between 5 and 10 nm and shells with an amorphous atomic distribution were synthesized at room temperature, with bismuth nitrate and thiourea as precursors. Aging the solution for several days a black powder precipitated made of a mixture of one amorphous phase and crystalline Bi2S3. When two capsules interacted between each other, the capsule regions in contact crystallized into bismuth sulfide, which explains the origin of the crystalline phase observed in the X-ray diffraction pattern. At this temperature, aggregation of the small nanocapsules also gave rise to necklaces of capsules, which eventually gave rise to nanotubes; these necklaces ordered forming bundles parallel to their largest dimension. When the solution was annealed at temperatures lower than 100 °C, aggregation gave rise to capsules as large as 1 μm in diameter, and tubes with similar diameters; in this case aggregation occurred between small and large nanocapsules. Because of the monomers aggregating had an external spherical symmetry and the low annealing temperatures, which were not high enough to produce sintering, all capsules and tubes formed during aggregation had porous walls, making these materials interesting for many applications.
Formation of ZnO Doped with Mn Thin Film by Electrodeposition and Magnetic Behaviour.
Authors: Abid M. , Terrier C. , Ansermet J-P , Hjort K.
Published: June 2019

Following the theory, ferromagnetism is predicted in Mn- doped ZnO, Indeed, ferromagnetism above room temperature was recently reported in thin films as well as in bulk samples made of this material. Here, we have prepared Mn doped ZnO by electrodeposition. The samples have been characterized by X-ray diffraction and spectroscopic methods to ensure that the dopants are substitutional. Some samples exhibit weak ferromagnetic properties at room temperature, however to be useful for spintronics this material need additional carriers provided by others means.
Preparation of Copper Nanowire/Polymer Nanocomposites by Melt Mixing
Authors: Krantz Matthew J. , Gelves Genaro A. , Sundararaj Uttandaraman , Haber Joel A.
Published: June 2019

A scaleable synthesis of metal nanowires has been developed using ac electrodeposition into the pores of porous aluminum oxide (PAO) templates, through the resistive barrier layer. Gram quantities of high aspect-ratio Cu nanowires (25 nm in diameter by ∼20,000 nm in length) were liberated by dissolving the PAO film with sodium hydroxide solution. The agglomerated nanowires were dispersed in methanol by ultrasonication and collected by centrifugation or filtration. The nanowires were blended into amorphous polyamide by melt processing. The dispersion and percolation of the nanowires in the polymer was investigated by electron microscopy and conductivity measurements as a function of nanowire loading and processing route. Mechanical properties were evaluated by tensile testing of miniature dog bone specimens.
Synthesis of Silicon Nanowires and their Heterostructures by Thermal Chemical Vapor Deposition
Authors: Jang Woo-Sung , Bae Seung Yong , Park Jeunghee
Published: June 2019

The Si nanowires were synthesized using a novel catalytic thermal reaction under Ar flow. The average diameter is in the range of 50 ∼ 100 nm. They consist of defect-free single-crystalline cubic structure with the [111] growth direction. The thickness of amorphous oxide outer layers was controllable by growth conditions or surface treatment. In order to protect the oxidation, the Si nanowires were coated with boron nitride layer by the reaction of boron oxide mixture with NH3.