bluuebunny/crossref_metadata_2025_split huggingface dataset:
Controlled direct growth of vertical and highly-ordered ’carbon nanotube - silicon’ heterojunction array
Authors: Kuo Teng-Fang , Xu Jimmy 
Published: April 2011

AbstractCarbon nanotubes (CNT) have been studied intensively for its unique electrical and mechanic properties and numerous applications. However, electronical integration of carbon nanotubes with silicon to form an electronically functional entity or device, though highly desirable, has remained a great challenge. Whereas vertical aligned bundles of nanotubes have been grown directly on silicon, the integration is mechanical, rather than electronical, in nature. In the present work, we report on Controlled growth of vertical and highly-ordered array of ’carbon nanotube silicon’ (CNS) heterojunction diodes of uniform diameter, length, and alignment. The as grown CNS heterojunction structure is not only electronically functional but also strongly rectifying with an on off ratio as high as five orders of magnitude in current voltage characteristics measured at room temperature. The controlled direct growth of the CNS hetero junction array of such high uniformity is enabled by the formation of a highly ordered nanopore array alumina matrix directly on the silicon, following a precisely controlled anodization of an aluminum thin film evaporated on silicon. Iterations of development and optimization of the anodization process conditions and real time monitoring and control of the anodization process were required for the formation and adhesion of the alumina growth matrix directly on silicon. Under carefully controlled and optimized conditions developed in this work, we are able to obtain an abrupt heterointerface between a terminal end of the carbon nanotube and the silicon substrate, without an intermediate barrier layer, as required for an electronically functional CNS hetero junction. The growth process is applicable to silicon doped in either type, enabling access to another critical parameter of the electronic function.
Protein Adsorption on the Surface Functionalized Planar Si
Authors: Tay Li-Lin , Rowell Nelson , Boukherroub Rabah , Lockwood David 
Published: April 2011

AbstractThe peak energy of photoluminescence (PL) from an undecylenic acid functionalized porous Si demonstrated a large PL red-shift (∼ 75 nm) during 2.5 hours of protein incubation in our previous work. [1] Here we present a similar in-situ PL study of surface functionalized planar Si (Si:COOH). The PL of Si:COOH exhibited a 5 nm red-shift in its peak frequency and an approximately 10% drop in its intensity after incubation in a protein solution. Vibrational spectroscopic characterization was carried out upon the Si:COOH sample for which we observed the PL red-shift. The infrared absorption spectra showed clear evidence of protein adsorption on Si:COOH. This correlation study between the PL peak energy and the vibrational spectrum provided strong evidence that the observed red-shift was due to the formation of semiconductor-protein (Si:COOH:BSA) complexes.
Laser-assisted chemical vapor deposition of carbon coated cobalt nanoparticles
Authors: Alm Oscar , Carlsson J.-O. , Boman M. 
Published: April 2011

AbstractCarbon coated nanoparticles were synthesized by laser-assisted (ArF excimer laser, λ = 193 nm) chemical vapor deposition (LCVD). The particles were formed in the gas-phase by photolytic dissociation of cobaltocene in argon and the particles were deposited onto a silicon substrate. The particles were deposited at two different laser fluencies, 70 and 300 mJ/cm2.Single crystalline spherical cobalt particles with a well-defined carbon shell were observed by transmission electron microscopy (TEM) for the highest fluence, 300 mJ/cm2. The metallic nucleus phase were identified as either β-Co or Co3O4. Polycrystalline particles were deposited at 70 mJ/cm2, these particles contained α-Co, β-Co, CoO and Co3O4. The particles deposited at 300 mJ/cm2were log-normally distributed and the total diameter had a mean geometric size of 25 nm while the nuclei had a mean diameter of 10 nm. X-ray photoelectron spectroscopy (XPS) measurements showed that the particles had a carbon content roughly ten times the amount of cobalt. Sputtering showed that both cobalt oxide and metallic cobalt was present. HRTEM micrographs of the particles revealed that only one phase was present in the whole nucleus, proving the nuclei were either oxide or metallic. Raman spectroscopy showed that that the carbon shell contained mostly amorphous carbon. Small domains of carbon of more graphitic character was embedded in the amorphous carbon shell in the 300 mJ/cm2sample.
Self-Assembly of Magnetic and Semiconductiong Nanoparticles on Modified Diblock Copolymer Templates
Authors: Yufa Nataliya A , Cisse Amadou L , Darling Seth B , Bader Sam D , Guyot-Sionnest Philippe , Sibener Steven J 
Published: April 2011

AbstractCombining inorganic and organic components to create functional materials has been an active area of research in recent years. Inorganic components possess useful electric, photonic, or magnetic properties while organic components can self-assemble into a variety of morphologies on the nanoscale. We describe a novel approach for arraying nanoparticles using a modified diblock copolymer scaffold. Thin (30 nm) films of poly(styrene-block-methylmethacrylate) (PS-b-PMMA) copolymer were used as a substrate. Upon annealing, PS-b-PMMA forms lying-down cylinders of PMMA in a matrix of PS. These thin films were modified by exposure to ultraviolet light in vacuum which photochemically thinned the PMMA, creating a more highly corrugated surface. We find that colloidal superparamagnetic FePt nanodots and semiconducting CdSe nanodots deposited on this surface show a strong preference for the photochemically modified phase. This hierarchical self-assembly method may prove useful for many nanomaterials-based applications.
STM observation of formation process of carbon nanotube from 6H-SiC (000-1)
Authors: Maruyama Takahiro , Kawamura Yasuyuki , Bang Hyungjin , Fujita Naomi , Shiraiwa Tomoyuki , Tanioku Kenji , Hozumi Yoko , Naritsuka Shigeya , Kusunoki Michiko 
Published: April 2011

AbstractFormation process of nanosized cap structures on a thermally treated 6H-SiC(000-1) substrate was investigated using atomic-resolution ultrahigh-vacuum scanning tunneling microscopy (UHV-STM). After formation of clusters of carobon particles 1-2 nanometer in diameter at 1150°C, these nanoparticles merged, forming nanosized cap structures. Hexagonal carbon networks, partly composed of pentagons, were clearly observed on the surface of the cap structures for a sample annealed above 1200°C. A model for the formation of carbon nanocaps on 6H-SiC(000-1) was proposed.
Ignition in Al-Fe2O3 Nanocomposites
Authors: Menon Latika , Bhargava Ram K. , Patibandla S. , Richter C. , Sacco A. 
Published: April 2011

AbstractWe demonstrated a novel approach to fabricate a self-assembled array of energetic nanocomposites which undergo an exothermic reaction at high temperature. The nanocomposites are a mixture of fuel and oxidizer materials where one of the components (fuel or oxidizer) is in the form of an array of nanowires embedded in the other component (oxidizer or fuel) which is in the form of a thin film. Our fabrication approach allows for a very high packing density of the nanocomposites, precise control of oxidizer-fuel sizes at the nanoscale level and intimate mechanical contact between oxidizer and fuel. Such nanocomposites will have important applications in novel energetic devices, for example MEMS-based fuzes, nanoexplosives and in applications requiring light-weight, single-use energy sources.
Sb surfactant-mediated epitaxy of Ge on Si(113) studied by AFM, SEM and GIXRD
Authors: Clausen Torben , Flege Jan-Ingo , Schmidt Thomas , Falta Jens 
Published: April 2011

AbstractWe have investigated the Sb surfactant-mediated growth of Ge on Si(113) over the temperature range from 500°C to 700°C. The surface morphology, film thickness, interface roughness and strain state of the films have been determined by the use of scanning electron microscopy, atomic force microscopy and grazing incidence x-ray diffraction. After growth at temperatures between 500°C and 600°C smooth Ge films have been observed, which show a partial strain relaxation. However, increasing the temperature to 700°C, a rough surface with a high density of three-dimensional islands has been found.
Nanoscale Assembly of Nanowires Templated by Microtubules
Authors: Zhou Jing , Luo Tzy-Jiun Mark , Gao Yan , Xue Mei , Lau Joseph , Hamasaki Toshikazu , Hu Evelyn , Wang Kang , Dunn Bruce 
Published: April 2011

AbstractConventional top-down lithographic processes approach their practical and theoretical limits at dimensional scales less than 100 nm. Alternative bottom-up methods are being investigated to build nanoscale architectures, including the use of biomolecules whose functional groups bind inorganic particles. In this study, the fabrication and alignment of microtubule-based nanowires are investigated. Microtubules (MT) are fibrous proteins found in nearly all eukaryotes. Our work was carried out using polymerized alpha- and beta-tubulins, which were cross-linked with glutaraldehyde to stabilize the protein structure. Ni coated microtubules were fabricated by reducing Ni2+ to Ni0 on Pd activated microtubule surface. Focus Ion Beam was used to write metal contacts on these Ni microtubule nanowires and DC conductivity values were measured. Au deposition on MT was performed by both electroless deposition and electrodeposition, by reducing HAuCl4 onto MT prebound with 2 nm Au colloids. Although most MTs exhibited discontinuous Au binding, a fraction of MTs were covered completely by Au. Preliminary electrical measurements for these materials are reported. Alignment of microtubules was also achieved by injecting MTs into microfluidic devices over amine-coated substrate surfaces. These biotemplating approaches are the first steps towards constructing more complicated 2D and 3D architectures.
Infrared Spectroscopic Characterization of Functional Monolayers on Silicon
Authors: Rowell Nelson , Tay Li-Lin , Baribeau Jean-Marc , Boukherroub Rabah , Lockwood David 
Published: April 2011

AbstractInfrared vibrational spectroscopy in an attenuated total reflection geometry has been employed to investigate the presence of organic and inorganic thin layers on Si-wafer surfaces. Three different processes were compared for surface contaminant removal; microwave plasma, UV-ozone, and a piranha solution cleaning. The CH vibrations at 2928 and 2856 cm-1 characteristic of organic contaminants were monitored before and after each cleaning procedure to determine how well it removed surface contaminants. We found that native oxide removal from the Si surface should only be carried out after a cleaning essay. We observed that surface oxide removal exposed a hydrophobic bare Si surface, attracting organic molecules present in solution or the ambient. A large increase of the CH vibrational signature was observed for a Si wafer after an HF dip. A combination of plasma cleaning followed by UV-Ozone treatment was found the most effective one for Si wafer cleaning. We were able to evaluate the effectiveness of the cleaning methods, hydrogen surface passivation and oxide removal/regrowth.
Directed self assembly of nanocrystals within macroscopic to nanoscopic features
Authors: Stanley Scott K. , Coffee Shawn S. , Ekerdt John G. 
Published: April 2011

AbstractThis paper discusses a kinetically-driven patterning scheme to marry top-down and bottom-up assembly of nanoparticle arrays. We explain how Ge atoms interact with different dielectric surfaces to either etch the surface or to accumulate and self assemble into nanocrystals during chemical vapor deposition. By exploiting the different reactivity of these dielectrics, the accumulation of adatoms is controlled and thus subsequent self assembly of nanocrystals is controlled. Scanning electron microscopy and atomic force microscopy are used to determine particle densities. We have achieved dense (>1011 cm-2) arrays of self-assembled Ge nanocrystals within ∼100 µm sized features (defined by optical lithography) with no Ge deposition on the adjacent SiO2 sacrificial mask region. Electron beam lithography was used to pattern smaller (100 µm to 500 nm) features in which to direct the self assembly. As features shrink below 10 µm, nanoparticle nucleation within the feature is sharply affected. Finally, diblock copolymers are used to pattern 20 nm features to template self assembly of nanoparticles at a scale useful for device applications.
HRTEM and EELS Studies of GdSi2 Nanostructures Grown by Self-Assembly
Authors: Zhang Jiaming , Ye Gangfeng , Loloee R. , Crimp Martin A. , Nogami Jun 
Published: April 2011

AbstractThere has been considerable interest in the properties of rare earth metal nanostructures grown epitaxially on Si(001) surfaces. The questions arises as to what extent the nanometer scale lateral dimensions (width and thickness) affect the material properties. We compare thin film Gd silicide samples with Gd nanostructures grown on Si(001) using high resolution transmission electron microscopy (HRTEM). The nanostructures have the same orthorhombic crystal structure as the thicker silicide films. Electron energy loss spectroscopy measurements from metallic Gd and the thin film silicides are also shown as references for similar measurements on the nanostructures.
Structural and morphological variations of encapsulated metal oxides in single walled carbon nanotubes
Authors: Costa Pedro MFJ , Thamavaranukup Narun , Rutherford Thomas , Friedrichs Steffi , Sloan Jeremy , Green Malcolm 
Published: April 2011

AbstractSingle walled carbon nanotubes have been filled with a variety of metal oxides and the structural and morphological characteristics of the metal_oxide@SWNT composites studied. Advanced techniques of software aberrations correction for transmission electron microscopy were used for characterisation. This research shows that, despite their higher reactivity compared to salts such as halides, oxides can be encapsulated within SWNTs with some compounds attaining remarkable filling yields.
Assembly of Nanomaterials using Polymers and Biomaterials: Sensing and Electronic Applications
Authors: Lee Jaebeom , Kotov Nicholas A , Govorov Alexander O 
Published: April 2011

AbstractThe hybrid assembly of inorganic nanomaterials upon chemical and biological bonding has occupied attentions to yield manifold optical and electromagnetic properties. Nanomaterials that can be virtually conjugated with any other nanomaterials by ligand-receptor / antigen-antibody reactions, polymer tethering, and DNA hybridization are of importance for fundamental comprehension of electronic process in nano-scale regime as well as for development of advanced sensing and imaging devices. Semiconducting nanoparticles(NPs)/ nanowires(NWs) like CdTe that have compatibly narrow range of strong photoluminescence (PL) with broad range of absorbance band stand in the spotlight of imaging and sensing materials. Optical effects in noble metallic NPs such as Au and Ag have been worth noticing due to localized surface plasmons. These optical modes lead to highly localized electromagnetic fields outside the particles that take advantage of the development of novel system such as surface enhanced Raman spectroscopy (SERS) and highly compacted optoelectronic devices and sensors. In particular, it is known that metallic NPs has stronger plasmon field than the surface of bulky metals, leading to potent interactions to adjacent materials in secured conjugated superstructures that induce non-linear optical properties. In this report, we review on a novel biological / polymeric inspired hybrid superstructures between semiconducting CdTe nanowires and Au or Ag nanoparticles. This superstructure demonstrates remarkable optical effects i.e., PL en-hancement of NWs, sensing application for temperature and solvents stemming from SERS-like collective interactions of NPs and NWs., and light harvest from Förster resonance energy tra-nsfer (FRET).
Integration of Top-Down and Bottom-Up Nanofabrication Schemes
Authors: Maury Pascale , Crespo-Biel Olga , Peter Maria , Reinhoudt David N. , Huskens Jurriaan 
Published: April 2011

AbstractThe fabrication of 3D nanostructures, which have tunable, sub-100 nm dimensions in all three directions, is a key issue of nanotechnology. Here we describe the integration of top-down nanoimprint lithography (NIL) and bottom-up layer-by-layer (LBL) assembly for the preparation of 3D hybrid nanostructures. NIL provided down to sub-100 nm poly(methylmethacrylate) (PMMA) structures. These were employed to fabricate patterned self-assembled monolayers of cyclodextrin (CD) host molecules on silicon oxide . The consecutive LBL assembly with adamantyl guest-functionalized dendrimers and CD-modified gold nanoparticles resulted in patterned multilayer structures with thicknesses of 3-30 nm. The x,y control by NIL and the z control by LBL assembly ultimately allowed the fabrication of circular structures with a radius of 25 nm and a thickness of 20 nm. The integration of the two methods has thus yielded a versatile 3D nanofabrication methodology comprising of 10-40 process steps.
LaB6 nanowires and their field emission properties
Authors: Zhang Han , Tang Jie , Zhang Qi , Zhao Gongpu , Yang Guang , Zhang Jian , Zhou Otto , Qin Luchang 
Published: April 2011

AbstractFor field-induced electron emission, the two factors that enable a high emission current density at low applied voltages are (a) low work function of the emitter and (b) sharpness of the emitter tip. We have developed and applied a chemical vapor deposition method to synthesize single-crystalline LaB6 nanowires for applications as point electron emitters. The crystallographic orientation of the grown nanowires can be controlled by the catalysts used in synthesis and their typical diameter is ranged from below 20 nm to over 100 nm. The nanowires’ tip is either hemispherical or flat top with rectangular cross-section depending on the catalyst being utilized. The field emission properties have also been measured from the single nanowire emitters and the results are discussed for applications as point electron sources used in high performance electron optical instruments such as the transmission and scanning electron microscopes.
Hierarchical Design of Metal Oxide Multi-Dimensional Arrays from Solutions
Authors: Vayssieres Lionel 
Published: April 2011

AbstractThe hierarchical design of well-defined and highly oriented two- and three-dimensional arrays of conventional semiconductor nanomaterials and their large scale manufacturing at low cost remain a crucial challenge to unfold the very promising future of nanodevices. In addition to economical manufacturing of nanostructured semiconductors, better fundamental knowledge of their electronic structure, physical, interfacial and structural properties and stability, is required to fully exploit their fascinating potentials. To combine such essential requirements, the predictive creation of structurally well-defined and well-ordered functional and multi-functional materials is essential. As an attempt to achieve such ambitious goals, a novel strategy to thin film metal oxide semiconductor nanotechnology processing has been developed and investigated. A thermodynamic growth control concept based on the chemical and electrostatic minimization of the surface energy as well as a thin film growth technique have been developed. Such original approach allows the generation of nanomaterials with novel and functional morphologies. Advanced metal oxide nanostructures consisting of oriented multi-dimensional arrays featuring building blocks of controlled morphologies, sizes, aspect ratios and orientations at nano-, meso-, and microscale are genuinely fabricated directly onto various substrates of large physical areas without template, surfactant, undercoating or applied field from the hydrolysis-condensation of aqueous metal salts solutions at mild temperatures (below 100°C). A survey of the innovative advances in the fabrication of highly oriented and functional nanostructure arrays of transition and post-transition metal oxides are presented as well as one-dimensional confinement effects in purpose-built bundled iron oxide quantum rods.
Micro- and Nanostructure Evolution with Exploding Wires
Authors: NLN Vandana , Sen P. 
Published: April 2011

AbstractWe present an experimental evidence of concentric ring pattern formation in a metal. They form during a single electro-explosion event in a needle-plate configuration. By measuring the dynamic progression of current during the explosion, we discuss evolution of these ring structures. Atomic force microscopy provides details of nanostructures that constitute these rings. From fluctuations in the plasma current recorded during the process, micro and nanostructure evolution is seen to be a self-organization process.
Submicron/nano Grained Stainless Steel with Superior Mechanical Properties
Authors: Rajasekhara Shreyas , Somani M. C. , Koljonen M. , Karjalainen L. P. , Kyröläinen A. , Ferreira P. J. 
Published: April 2011

AbstractMetastable austenitic stainless steels may transform to martensite when subjected to cold rolling. Upon subsequent annealing the martensite reverts back to ultra-fine grained austenite. Based on this concept, nano/submicron austenitic grains have been produced in a 63% cold rolled commercial AISI 301LN subjected to annealing treatments at 600°C, 800°C and 1000°C for 1, 10 and 100 seconds.Transmission Electron Microscopy (TEM) observations show the formation of equiaxed austenitic grains as small as ∼ 200nm in samples annealed at 800°C, and a dramatic increase in grain size as the annealing temperature and duration is increased. Additional tensile tests indicate that samples annealed at 800°C for 1 second exhibit a yield strength of ∼ 740 MPa and an total elongation of ∼ 45%. This combination of strength and ductility is excellent exceeding those of conventionally annealed steels (σy=350 MPa; Ductility ∼ 40%) or cold-rolled steels (σy=650 MPa; Ductility ∼ 30%).Finally, a correlation between the observed grain sizes and mechanical properties, in particular the yield strength, is obtained. Preliminary analysis indicates that the Hall-Petch equation can satisfactorily relate the observed yield strength with corresponding grain sizes.
Molecular Dynamics Study of the Effect of Dopant Atoms on Grain Boundary Sliding
Authors: Millett Paul Christopher , Selvam R. Panneer , Saxena Ashok 
Published: April 2011

AbstractMolecular dynamics simulations are used to study grain boundary sliding in pure and doped Cu bicrystals using both Lennard-Jones and Embedded-Atom Method potentials. Two tilt [100] grain boundaries are considered: the coincident site lattice Σ5 interface and a random high angle interface. Shear stress between 0.69 GPa and 1.61 GPa was applied to the bicrystals for a duration of 10 ps at ambient temperature (300K) and high temperature (800K). For the pure bicrystals, the sliding of the Σ5 interface with respect to the random interface was lower at 800K and higher at 300K. For the doped bicrystals, interstitial dopant atoms and substitutional dopant atoms with larger atomic radius were effective in retarding grain boundary sliding. These simulations will aid further work to determine how segregated dopant atoms alter the tensile properties of nanocrystalline metals.