bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of Carbon Microcoils and Nanocoils on Various Substrates
Authors: Einarsson Erik , Jiao Jun , Prado Josie , Coia George M. , Love Logan 
Published: June 2019

AbstractThis research investigates the role of the substrate in the synthesis of carbon coils. Coils were produced on tungsten, titanium, and glassy carbon substrates via chemical vapor deposition (CVD) of acetylene (C2H2) on electrochemically deposited nickel at 800°C, but the growth varied among the samples. Coils were also produced on pure nickel by the same CVD method. Using tungsten as a substrate, carbon coils intermixed with thin carbon nanotubes were produced in high-yield from nickel particle clusters. On the titanium substrate, carbon coils were synthesized in small, high-yield patches with few co-produced carbon nanotubes. Synthesis from nickel clusters on glassy carbon usually resulted in amorphous carbon, but sparse, low-yield coil growth was observed. Carbon coils were also synthesized when pure nickel wire was used without a separate substrate. These results indicate the nickel catalyst controls the production of carbon coils, but the substrate has some effect on the yield. Carbon coils synthesized were either microcoils, which have diameters of a few microns, or nanocoils, which have diameters of one or two hundred nanometers.
Growth of Zinc Oxide Nanorods in Alocohol Solution
Authors: Yang Richard D. , Li Yuntao , Sue Hung-Jue 
Published: June 2019

AbstractZinc oxide (ZnO) nanorods have been grown by hydrolyzing Zn(OAc)2•2H2O in methanol solution. Nanoparticles in sizes ranging from 2 to 4 nm were first obtained at low concentration. The growth kinetics was monitored by UV-vis absorption spectroscopy. The precursor was then concentrated by 10 folds and refluxed at 60°C for 24 hours to form ZnO nanorods with an aspect ratio of 12. Ligand adsorption growth model was proposed to explain the anisotropic growth.
Toward Elimination of Solvents in Micro/Nanofabrication: Solventless Polymerization and Its Applications
Authors: Gu Hongwei , Fu Degang , Xu Chenjie , Tang Jun , Xie Jie , Xu Bing 
Published: June 2019

AbstractHere we report a solventless polymerization process, which involves adding catalysts on the surface of a solid substrate and polymerizing volatile monomers at the gas/solid interface. It provides an alternative to other thin-film-making processes and may lead to reduce or eliminate the use of solvents in micro/nanofabrication. On silicon or silicon dioxide substrates, solventless produced thin films show improved smoothness inside microchannels, and suits reactive ion etching (RIE) process. In addition, this process offers a simple route to generate microstructures that are inaccessible in the presence of solvent, and provides a simple and fast protocol to screen catalysts in a parallel mode.
Theoretical Study on Tunnel Magnetoresistance Oscillation Due to Coulomb Blockade in Nanoscale Magnetic Tunnel Junction
Authors: Takemura Yasushi , Shirakashi Jun-ichi 
Published: June 2019

AbstractIn a small magnetic tunnel junction (MTJ) whose charging energy is larger than a thermal energy, the tunnel magnetoresistance (TMR) is enhanced by the Coulomb blockade. Transport properties in a double MTJ were theoretically studied by using the Monte Carlo method. The temperature dependence of current-voltage and TMR characteristics indicated that a small junction with 5 nm electrodes exhibited the Coulomb blockade at 300 K. It was also found that the background charge changed the threshold voltage of the Coulomb blockade. In asymmetric double tunnel junctions, the current-voltage characteristic exhibited a Coulomb staircase and the voltage dependence of the TMR ratio oscillated.
Synthesis and characterization of Pd nano-pillar arrays in the metal hydride switchable mirror
Authors: Vece M. Di , Kelly J.J. 
Published: June 2019

AbstractA method is suggested for improving the switching characteristics of the metal-hydride mirror by enhancing hydrogen transport in the active film. Nano-pillars of palladium, which has a high diffusion coefficient for hydrogen, are introduced into the active layer and should serve as a “highway” for the rapid introduction of hydrogen. A palladium nano-pillar array is made by electrodeposition in the pores of a polycarbonate membrane. The membrane is dissolved and the active layer (an yttrium-magnesium alloy) is evaporated on the palladium nanostructures. Improved kinetics has not been shown conclusively and is still the subject of research.
Chemical Sensors Based on Individual In2O3 Nanowires
Authors: Zhang Daihua , Li Chao , Liu Xiaolei , Han Song , Tang Tao , Zhou Chongwu 
Published: June 2019

AbstractSingle crystalline In2O3 nanowires were synthesized and then utilized to construct field effect transistors (FETs) consisting of individual nanowires. Chemical sensors based on these In2O3 nanowire FETs have been demonstrated. Upon exposure to gaseous molecules such as NO2 and NH3, the electrical conductance of the In2O3 nanowire FETs are found to dramatically decrease rapidly, accompanied by substantial shifts in threshold gate voltage. Our In2O3 nanowire sensors exhibit significantly improved sensitivity, as well as shortened response times compared to most existing solid-state gas sensors. In addition, ultraviolet (UV) light is found to be able to greatly enhance the surface molecular desorption kinetics and serve as a “gas cleanser” for the In2O3 nanowire chemical sensors. It has been demonstrated that the recovery time of our devices can be shortened to ∼30 s by illuminating the devices with UV light in vacuum.
Growth and Optical Properties of GaP, GaP@GaN and GaN@GaP Core-shell Nanowires
Authors: Lin Hung-Min , Yang Jian , Chen Yong-Lin , Liu Yau-Chung , Yin Kai-Min , Kai Ji-Jung , Chen Fu-Rong , Chen Li-Chyong , Chen Yang-Fang , Chen Chia-Chun 
Published: June 2019

AbstractHigh-quality GaP, GaP@GaN and GaN@GaP nanowires were grown by a convenient vapor deposition technique. The wire-like and two-layers structures of GaP@GaN and GaN@GaP core-shell nanowires were clearly resolved using X-ray powder diffraction and high-resolution transmission electron microscopy (HRTEM) and their growth directions were identified. Photoluminescence intensity of GaP@GaN nanowires increased as temperature increased. The result was interpreted by the piezoelectric effect induced from lattice mismatch between two semiconductor layers. An unexpected peak at 386 cm-1 was found in the Raman spectra of GaN@GaP and assigned to a surface phonon mode due to the interface. Detailed synthetic conditions and possible growth mechanisms of those nanowires were proposed.
Atomic Ordering in Self-assembled Epitaxial and Endotaxial Compound and Element Semiconductor Quantum Dot Structures: The First Review
Authors: Möck Peter 
Published: June 2019

AbstractAlthough the main international research thrust on self-assembled epitaxial semiconductor quantum dots is currently being directed towards random alloy quantum dots, the suggestion is made that atomically ordered quantum dots which are grown by either epitaxy or endotaxy may in addition to their larger quantum confinement potentials possess superior long term structural stability. Such atomically ordered quantum dots should, therefore, be superior to random alloy quantum dots as far as prospective device applications are concerned. The basis for this suggestion is simple thermodynamic considerations. These considerations seem to explain our transmission electron microscopical observations of epitaxially grown atomically ordered In(Sb,As), (In,Ga)Sb, (Cd,Zn)Se, (Cd,Mn,Zn)Se quantum dots and Pb(Se,Te) quantum dot predecessor islands. Atomic ordering in (In,Ga)P quantum dot structures, as recently observed by other authors, does not seem to contradict our thermodynamic considerations. Endotaxially grown atomically ordered (In,Si,As) and (Sn,Si) quantum dots in Si matrices are briefly discussed as an even more unconventional approach to nanostructures with applications in electronics, photonics, information storage, and sensing.
From helical nanowires, nanocrosses to aligned micro-carbon fibers
Authors: Zhang Hai-Feng , Wang Chong-Min , Young James S. , Coleman James E. , Wang Lai-Sheng 
Published: June 2019

AbstractWe successfully synthesized helical core-shell crystalline SiC/SiO2 nanowires, core-shell crystalline SiC/C nano-crosses and well-aligned core-shell crystalline SiC/C fibers by using a chemical vapor deposition technique. For the helical crystalline SiC/SiO2 nanowires, the SiC core typically has diameters of 10-40 nm with a helical periodicity of 40-80 nm and is covered by a uniform layer of 30-60 nm thick amorphous SiO2. Detailed structural characterizations suggested that the growth of this novel structure was induced by screw dislocations on the nanometer scale. For the core-shell nanocrosses, the crystalline SiC core typically has diameters of 10 to 40 nm and is covered by a uniform layer of 80-110 nm graphitic carbon. The wellaligned SiC/C fibers were shown to be formed by two sequential steps: catalytic SiC growth and graphitic carbon nano-sheets coating. The helical nanowires and core-shell nanocrosses may have potential applications in nano-electronics. The formation mechanism of the carbon fibers suggested that fabrication of field emission filament carbon nano-fibers may be realized by using the aligned crystalline nanowires as templates.
Growth and Characterization of ZnO Nanowires
Authors: Baxter Jason B. , Bessems Ron E.M.W. , Aydil Eray S. 
Published: June 2019

AbstractSingle crystal ZnO nanowires were grown by chemical vapor deposition using monodisperse 5 nm or 20 nm diameter gold nanoparticle catalysts to control the nanowire diameter and location. The nanowires reach several microns in length and grow only from the gold nanoparticles. The nanowires have narrowly dispersed diameters, albeit significantly larger than the diameter of the gold particles used for catalyzing the growth. The nanowires grow in the [ 0 1 10 ] or [ 1 1 10 ] directions normal to the lowest energy planes in ZnO. ZnO nanowires emit in the near ultraviolet region of the electromagnetic spectrum upon excitation with highenergy photons or electrons. Electron diffraction and absence of luminescence associated with oxygen vacancies indicate high quality crystalline ZnO nanowires. Cathodoluminescence e mission along the entire length of the wire is consistent with a lack of non-radiative recombination sites associated with defects, lending further support for the high quality of these nanowires.
Nanoscale Surface Patterning
Authors: Yu Meng , Ivanisevic Albena 
Published: June 2019

AbstractWe present a methodology based on Dip-Pen Nanolithography 1 to fabricate nanoscale surface patterns composed of polyelectrolytes. Two widely used polymers Poly(diallyldimethylammonium chloride) (PDDA) and Poly(sodium 4-styrenesulfonate) PSS were chosen as the DPN “inks”. Patterns were created and evaluated on silicon oxide surfaces using an Atomic Force Microscope (AFM). To compare the polymer packing and the height of the nanopatterns, additional fabrication was performed using microcontact printing. We were able to generate structures with better polymer packing using DPN and control the height of the polymer structures more reproducibly compared to microcontact printing.
Generating Nanoscale Arrays Using Self-Organized Porous-Alumina Ion Implantation Masks
Authors: Rehn L. E. , Birtcher R. C. , Kestel B. J. , Baldo P. M. , Hiller J. , McCormick A.W. 
Published: June 2019

AbstractStarting from two-step anodizing recipes available in the literature, we fabricated selfsupporting ordered ion-implantation masks that are several mm2 in area and 1-4 νm thick. SEM micrographs reveal self-organized structures with straight open pores, 25-150 nm in diameter, extending completely through the mask. As reported previously, the pore diameter and spacing depend critically upon the anodization parameters, e.g., type of acid and its molality, the applied voltage and the solution temperature. Ion-milling procedures were developed for opening the bottoms of the anodized pores. These masks appear quite robust during exposure to ion beams of 1-MeV He, Ne, and Kr. The steps necessary to fabricate the implantation masks, including opening the pores, are briefly described. Here we present new results obtained with a mask fabricated with pore dimensions as small as 25 nm in diameter, i.e., at the limit of what is technically feasible. Measurements are reported of the angular dependence of the transmitted ion current; these results are consistent with the physical dimensions of the opened pores. TEM images of a partial array obtained by implantation through the 25-nm pores are also shown.
The Luminescent Properties of Ion-Implantation-Fabricated SiO2:nc-Si Nanostructures Annealed at High Temperatures
Authors: Tetelbaum David I. , Gorshkov Oleg N. , Kasatkin Alexandr P. , Burdov Vladimir A. , Trushin Sergey A. , Mikhaylov Alexey N. , Gaponova Daria M. 
Published: June 2019

AbstractThe influence of the Si+ implantation dose and postimplantation annealing temperature on the photoluminescence (PL) intensity of silicon nanoinclusions in an SiO2 matrix was experimentally investigated. The way that the PL varied with dose and annealing temperature was explained on the basis of a model which takes into account the Ostwald ripening of nanocrystals and effect of the quantum dot size on the rate of radiative recombination.
Liberation of Ion Implanted Ge Nanocrystals from a Silicon Dioxide Matrix via Hydrofluoric Acid Vapor Etching
Authors: Sharp I.D. , Xua Q. , Liao C. Y. , Ager J.W. , Beeman J.W. , Yu K.M. , Zakharov D. , Liliental-Weber Z. , Haller E.E. 
Published: June 2019

AbstractA method to liberate germanium (Ge) nanocrystals from silicon dioxide (SiO2) thin films by hydrofluoric acid (HF) vapor etching is presented. Multi-energy implantation of mass separated Ge ions into 500-nm-thick wet oxide layers on silicon (Si) substrates followed by thermal annealing produces nanocrystals that are 2 to 8 nm in diameter. Raman spectra exhibit the expected asymmetric line shapes due to the phonon confinement effect, but with a higher peak frequency than predicted. To free the nanocrystals, samples are etched in HF vapor to selectively remove the SiO2 matrix and expose the nanocrystal surfaces. Raman spectra of etched samples display peak frequencies consistent with relief of compressive stress. The liberated nanocrystals show long-term stability under ambient atmospheric conditions. Ge nanocrystals can be removed from etched surfaces using an ultrasonic methanol cleaning procedure. The nanocrystal-containing solution is applied to a TEM grid and the solvent is evaporated. Subsequently obtained electron diffraction patterns confirm that the nanocrystals survive this transfer step. Thus, liberated Ge nanocrystals are expected to be accessible for a wide range of manipulation processes and direct characterization techniques.
SOS Simulation of Sputtered Nanoripples
Authors: Stepanova Maria , Dew Steven K. 
Published: June 2019

AbstractWe report a Monte-Carlo simulation of nanostructures that self-organize on surfaces under oblique ion bombardment. We have developed a quantitative solid-on-solid (SOS) model that describes the surface morphology during ion bombardment and performed the first systematic investigation for Cu bombarded by 1000 eV Ar+ ions at 0°–80° incidence. When the angle of ion incidence exceeds ∼40°, we observe 2–5 nm wide ripples aligned parallel to the ion beam plane in agreement with existing analytic theory. We also detect ripples directed perpendicularly to the ion beam plane, but the conditions under which they arise disagree with the theory. We have investigated the effect of surface relaxation on the morphologies and found two different regimes of ripple evolution depending on the efficiency of relaxation. After ∼100 nm are removed, secondary 10–50 nm wide patterns are formed provided that relaxation is sufficiently high. We compare our simulations with those from other authors and with experiments.
Fabrication of Hologram Coins using Electron Beam Lithography
Authors: Leech Patrick W. , Sexton Brett A. , Marnock Russell J. , Smith Fiona 
Published: June 2019

AbstractDiffractive grating structures formed by electron beam lithography have been replicated into the surface of silver commemorative coins. The detailed features of the gratings and the depth of relief were accurately transferred from the resist master plate to the surface of the fine silver coins using a Ni shim as a replication tool. This method has produced an optically variable device (OVD) in the surface of the coins which exhibited a strong intensity of first order diffraction over the area of the image (3 × 1.5 cm). A feature of the grating structures formed in the coins were fine-scale protrusions located along the length of the ridges. The presence of these protrusions has been attributed to an adhesive transfer and back-transfer of Ag during the cycle of impact loading of the Ni shim for sequential coins.
Light-Induced Microstructural Ordering: Study Of Lithium-Incorporated Cobalt Oxide Films On Aluminium And Glass Substrate
Authors: Das Mahua , Subbanna G. N. , Shivashankar S.A. 
Published: June 2019

AbstractPhotocrystallization is a phenomenon whereby an amorphous matrix undergoes structural changes to micro- or nano-crystals upon irradiation with photons. Topologically, a crystalline phase embedded in an amorphous matrix is expected to be advantageous over a fully crystalline phase, in applications such the as cathode material in thin film lithium-ion rechargeable batteries. As this particular microstructural feature provides a high surface area and enables smooth contacts, it may be expected to result in fast ion conduction between cathode and electrolyte, while retaining the electrochemical property associated with the specific crystal structure of the material. Amorphous films of lithium- incorporated cobalt oxide were obtained on glass and aluminium substrate using a sol gel spin-coating technique. The photocrystallization and microstructural changes in these films upon irradiation with unpolarised light were investigated using XRD, SEM, and TEM analysis.
Amorphous calcium phosphate nano-powders made from radio frequency (RF) plasma spraying
Authors: Jinling Xu , Kumar Rajendra , Khor K.A. , Cheang P. 
Published: June 2019

AbstractPredominantly amorphous nano powders of calcium phosphate were produced by radio frequency (RF) plasma and subsequently characterised by SEM, TEM and XRD. Quantitative phase analysis was carried out by the Rietveld method. The starting feedstock was comprised of hydroxyapatite (HA) powders spray dried from a suspension. The input parameters were varied to produce predominantly amorphous calcium phosphate powders. Results showed that as the plate power was increased and the flow rate of feedstock was decreased the as-sprayed powders produced were predominantly amorphous. The average particle size of the powders was about 20-40 nm, depending on process parameters, as confirmed by TEM observation. These powders are thought to have excellent bio-resorbability and are targetted for use in gene and drug delivery technologies. These nano-sized powders are also envisioned to enhance the mechanical properties of bulk products sintered by appropriate techniques.
Direct Observations of Grain Boundary Phenomena during Indentation of Al and Al-Mg Thin Films
Authors: Soer W. A. , De Hosson J. Th. M. , Minor A. M. , Stach E. A. , Morris J. W. 
Published: June 2019

ABSTRACTThe deformation behavior of Al and Al-Mg thin films has been studied with the unique experimental approach of in-situ nanoindentation in a transmission electron microscope. This paper concentrates on the role of solute Mg additions in the transfer of plasticity across grain boundaries. The investigated Al alloys were deposited onto a Si substrate as thin films with a thickness of 200–300 nm and Mg concentrations of 0, 1.1, 1.8, 2.6 and 5.0 wt% Mg. The results show that in the Al-Mg alloys, the solutes effectively pin high-angle grain boundaries, while in pure Al considerable grain boundary motion is observed at room temperature. The mobility of low-angle grain boundaries is however not affected by the presence of Mg. In addition, Mg was observed to affect dislocation dynamics in the matrix.
Effects of α and γ Radiolysis of Water on Alteration of the Spent UO2 Nuclear Fuel Matrix
Authors: Jégou C. , Broudic V. , Poulesquen A. , Bart J. M. 
Published: June 2019

ABSTRACTAn experimental approach was developed to quantify the influence of α and γ radiolysis of water on the dissolution kinetics of the spent UO2 fuel matrix. Two types of experiments were carried out: leaching experiments in deaerated media with UO2 fuel pellets doped with alpha emitters (238Pu), and leaching experiments with UO2 fuel pellets (standard or doped with alpha emitters) submitted to γ irradiation. Leaching experiments on UO2 pellets doped with alpha-emitters in deionized water and in deaerated media showed a correlation between the alpha particle flux at the reaction interface and uranium release in solution. The higher the alpha particle flux at the reaction interface, the higher the uranium release rate (mean rates over 30 days at S/V = 3 m−1: 15-year batch, r = 2.5 mg·m−2d−1; 1500-year batch, r = 0.2 mg·m−2d−1; 40 000-year batch, r = 0.04 mg·m−2d−1). These results, obtained at low flux levels that are realistic on a disposal time scale, supplement existing data describing the effect of doping on UO2 alteration at higher flux levels. Leaching experiments with the 1500-year batch under gamma irradiation allowed us to quantify the impact of a gamma irradiation field on the UO2 release. At 650 Gy·h−1 the effects of alpha irradiation appear to be fully masked since the uranium release is 450 times higher than in the presence of the alpha irradiation field alone. The Chemsimul code was also used to model water radiolysis and uranium release into solution.
Jet-based Photonic Crystals for Terahertz Technology – A Need for Higher Resolution
Authors: Li Jin , Horgan Thomas M. , Gatesman Andrew J. , Giles Robert H. , Karakashian Aram S. , Goodhue William D. 
Published: June 2019

ABSTRACTTwo-dimensional hexagonal photonic crystals of air columns in a wax substrate were fabricated by jet-based methods. By modifying the structure of the photonic crystals (PC), electromagnetic waves can be controlled, enabling the design of novel devices for waveguides, filters, and couplers. The jet-based processing is a solid freeforming method that can fabricate complex 2D or 3D photonic structures quickly and easily as compared to micro-machining and lithographic methods. The resolution of our 3D Systems ThermoJet® solider object printer is 300 × 400 × 600 dpi (XYZ) with the layer thickness of 0.042 mm. The wax used is a thermopolymer build material, similar to production investment casting wax material. The periodicity of the lattice of our 2D PC structures was designed to form bandstop filters in the 0.1–0.3 THz range. Transmission spectra of the structures were measured with a Bruker IFS 66v FT-IR interferometer. Photonic band gaps were observed at 0.17 THz and 0.23 THz along the Γ-M direction for both the TM and TE polarized incident beam for the PC structures with lattice constant of 0.787 mm and 0.586 mm, respectively. The location and width of the bandgaps agree with theoretical calculation based on a block-iterative frequency-domain method for Maxwell's equations in a planewave basis. To the best of our knowledge, this is the first time a jet-based process has been used successfully to fabricate PC structures at these high frequencies. However, the ThermoJet® printer as well as other current available solid freeforming technologies lack the resolution to PC structures operating in the terahertz regime. To extend this technology to terahertz applications, such as terahertz lasers, waveguides, and imaging system, a 10-fold increase in machine resolution is required to produce finer structures. Engineering materials with lower electromagnetic absorption and higher dielectric constants at terahertz frequencies are also critical to developing THz photonic bandgap technology.