bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of Nano-size Indium Cluster in InGaN/GaN Multiple QuantumWells with High Indium Composition
Authors: Cho Hyung Koun , Lee Jeong Yong 
Published: June 2019

AbstractWe report the effect of strain-induced indium clustering on the emission properties of InGaN/GaN multiple quantum wells grown with high indium composition by MOCVD. Nanosize indium clustering confirmed by high-resolution transmission electron microscopy results in the redshift of the emission peak and the increase of the integrated photoluminescence (PL) intensity. We found that strong carrier localization in indium clustering induces the increases of the activation energy of PL integrated intensity and the temperature independence of PL decay profiles. All these observations suggest structurally and optically that the improved emission properties in the InGaN/GaN multiple quantum well with high indium composition are associated with the localized states in the nano-size indium cluster.
Nanopatterned Si(001) Substrates as Templates for Quantum Dot Growth
Authors: Ney A. , Pampuch C. , Schulz J. J. , Perepelittchenko L. , Koch R. 
Published: June 2019

AbstractIt has been shown recently, that the formation of GeSi quantum dots on Si(001) is strongly affected by the surface properties of the substrate. With an increasing number of missing dimer vacancies the growth mode can even change from a Stranski-Krastanow to a kinetic 3D island growth mode. Here we report on atomically resolved scanning tunneling microscopy images of Si(001) after different preparation procedures, namely the conventional high temperature procedure employed for commercial wafers, and Shiraki-type samples which require only low temperature treatment. The latter method yields an atomically flat Si(001) (2 × 1) surface, however, with a defect (ad- and missing dimers) concentration depending on the respective preparation conditions. Furthermore, repeated flashing occasionally yields a (2 × n) reconstructed surface consisting of well-ordered self-assembled trenches of missing dimers, similar to the ones discussed controversially in the previous literature. From our results we can clearly exclude contaminants to be involved.
Atomistic Simulation Study of Controlled Nanostructure Patterning
Authors: Lee Byeongchan , Cho Kyeongjae 
Published: June 2019

AbstractWe investigate the surface kinetics of Pt using the extended embedded-atom method, an extension of the embedded-atom method with additional degrees of freedom to include the nonbulk data from lower-coordinated systems as well as the bulk properties. The surface energies of the clean Pt (111) and Pt (100) surfaces are found to be 0.13 eV and 0.147 eV respectively, in excellent agreement with experiment. The Pt on Pt (111) adatom diffusion barrier is found to be 0.38 eV and predicted to be strongly strain-dependent, indicating that, in the compressive domain, adatoms are unstable and the diffusion barrier is lower; the nucleation occurs in the tensile domain. In addition, the dissociation barrier from the dimer configuration is found to be 0.82 eV. Therefore, we expect that atoms, once coalesced, are unlikely to dissociate into single adatoms. This essentially tells that by changing the applied strain, we can control the patterning of nanostructures on the metal surface.
Nanostructure of Surface Formed by Vacancy Clustering in FeAl
Authors: Yoshimi Kyosuke , Haraguchi Tomohide , Ogawa Tomohisa , Kobayashi Takayuki , Sung Min-Seok , Hanada Shuji 
Published: June 2019

AbstractIn B2-type FeAl, supersaturated vacancies retained upon rapidly quenching are absorbed near surface during an aging treatment, being agglomerated into nano- to meso-clusters through the absorption process. Eventually, surface morphology is self-patterned in nano-order by the vacancy clustering. If FeAl was not quenched from high temperature or plastic strain remained near surface, the surface self-patterning never occurs, indicating that the change in surface morphology is caused by the clustering of supersaturated vacancies. The clusters have specific shape with cluster surfaces faceted toward {100} planes. Thus, the shape of the clusters formed near surface is controllable by changing surface orientation. Vacancy cluster size and its distribution density can be also controlled by varying the concentration of supersaturated vacancies and/or the clustering condition. These indicate that the vacancy clustering is a unique process to efficiently pattern the surfaces of metals, alloys and intermetallics in nano-scale.
1.3 νm InAs/GaAs Quantum Dots Directly CappedWith GaAs Grown By Metal Organic Chemical Vapor Deposition
Authors: Huang K.F. , Hsieh T.P. , Yeh N.T. , Ho W.J. , Chyi J.I. , Wu M.C. 
Published: June 2019

AbstractSystematic studies of the growth temperature and growth rate effect of the formation of InAs/GaAs quantum dots (QDs) have been demonstrated. These QDs are formed with large InAs coverage (3.0 MLs) and periodic growth interruption via Strnski-Krastonov (S-K) epitaxial growth mode by using metalorganic chemical vapor deposition (MOCVD). The room temperature photoluminescence (PL) spectra show red-shift of peak wavelength by decreasing the InAs growth temperature from 540°C to 500°C. As growth rate increases from 0.05 ML/s to 0.2 ML/s at growth temperature of 500°C, PL linewidth could be narrowed and emission intensity could be increased. These results could be correlated to the In clusters and uniformity of InAs/GaAs QDs observed by scanning electron microscopy (SEM) image. Finally, the room temperature photoluminescence spectra of InAs/GaAs QDs directly capped with GaAs shows peak wavelength of 1.35 μm with narrow linewidth of 30.8 meV is obtained.
Formation of Luminescent Si Nanocrystals by High-Temperature Annealing of Ion-Beam-Sputtered Si/SiO2 Multilayers
Authors: Choi Suk-Ho , Bae Jun Sung , Kim Kyung Jung , Moon Dae Won 
Published: June 2019

AbstractSi/SiO2 multilayers (MLs) have been prepared under different deposition temperatures (TS) by ion beam sputtering. The annealing at 1200°C leads to the formation of Si nanocrystals in the Si layer of MLs. The high resolution transmission electron microscopy images clearly demonstrate the existence of Si nanocrystals, which exhibit photoluminescence (PL) in the visible range when TS is ≥ 300°C. This is attributed to well-separation of nanocrystals in the higher-TS samples, which is thought to be a major cause for reducing non-radiative recombination in the interface between Si nanocrystal and surface oxide. The visible PL spectra are enhanced in its intensity and are shifted to higher energy by increasing TS. These PL behaviours are consistent with the quantum confinement effect of Si nanocrystals.
Red shifted-Photoluminescence of Ensembles of GaN Nano-Crystallites
Authors: Bergman Leah , Chen Xiang-Bai , Feldmeier Joel , Purdy Andrew P. 
Published: June 2019

AbstractWe present optical analysis concerning the redshift of the photoluminescence (PL) of ensembles of GaN nano-crystals. We found that the extent of the redshift depends on the laser power as well as on the ensemble size. For ensemble of size ∼ 30 μm, the laser power in our experimental specification impacted the PL energy and caused a redshift of up to 120 meV. This phenomena was not observed for a small ensemble of ∼ 1 νm or less. For the small ensemble the PL redshift was negligible and depended weakly on the laser power; similar behavior was found in GaN thin film. The above findings were observed in the PL of GaN nano-crystalline of Wurtzite as well as cubic structure. Our results point to a laser heating event occurring in the large ensemble; the emitted and scattered light is confined among the nano-crystallites thus causing the heating. For a small ensemble the light has a higher probability of diffusing outside the enclosure, and thus no laser heating occurs.
Optical Properties and Local Structure of Cu(II) Dopant in ZnSe Nanoparticles
Authors: Norman Thaddeus J. , Magana Donny , Bridges Frank , Zhang Jin Z. 
Published: June 2019

AbstractCu(II) doped ZnSe nanoparticles were synthesized using molecular cluster precursors. The Cu(II) dopant had the effect of quenching the ZnSe band edge emission, yet only weak emission from Cu(II) centers was observed. An X-ray Absorption Fine Structure (XAFS) experiment was performed on the Cu(II) doped ZnSe nanoparticles. It was determined that the Cu(II) occupies a tetrahedral site in the lattice in an environment similar to that of Cu in bulk Cu2Se, and is likely to have substituted for Zn(II) in the lattice.
Formation, Patterning, and Polymerization of Surface Adlayers Using Self-Assembled Monolayers as Templates
Authors: Mosley David W. , Sellmyer Mark A. , Jacobson Joseph 
Published: June 2019

AbstractOrdered surface adlayers of diacetylene-containing molecules were formed using amide hydrogen-bonding interactions with a pre-formed self-assembled monolayer on gold. Photopolymerization of the diacetylene molecules in the adlayer results in enhanced solvent and processing stability of the adlayer. Patterning of the base monolayer using soft lithography techniques allows patterning of the adlayer as well, and may lead to methods for templating soluble two-dimensional monolayer sheets.
Electric Field Induced Carbon Nanostructures for Electronics and High Surface Areaapplications
Authors: Lin Chao Hsun , Lee Shu Hsing , Hsu Chih Ming , Tsai Ming Her , Kuo Cheng Tzu 
Published: June 2019

AbstractStrong influence of the applied or self-induced (i.e. self-biasing) electric field on the alignment, orientation and structures was found in the carbon nano-structure deposition process. This study applied microwave-plasma electron-cyclotron-resonance CVD (ECR-CVD) technique for carbon nano-structure deposition. The deposited structures and properties were characterized with SEM and field emission I–V measurements. The result shows that a negative dc bias applied on the substrate is a necessary condition. In this condition, all carbon nanostructures were well aligned and perpendicular to the substrate surfaces and independent to the plasma/gas flowing directions. Interestingly, when applied an additional electric field near the substrate surface by a guiding metal plate, the CNT growth direction could be manipulated from perpendicular to nearly parallel to the substrate surface. Moreover, a rattan-like CNT would form when prolonging the deposition time or increasing the plasma carbon concentration. These novel nanostructures are expected to have high potential in energy storage, field emission display, nanoelectronics and gas sensing applications accordingly.
Field Emission of Zinc Oxide Nanostructure
Authors: Lee Sang Hyun , Yu SeGi , Jeong Taewon , Heo Jungna , Kim Wonseok , Lee Chang Soo , Lee Jeonghee , Kim J. M. , Kim Tae Yun , Nahm Kee Suk 
Published: June 2019

AbstractField emission characteristics were investigated for zinc oxide nanostructures which were grown on NiO catalyzed silicon (100) substrate by chemical vapor deposition method. The asgrown zinc oxide showed needle-shaped nanostructures with tip diameters of 20∼40 nm and length of 3∼5 νm. The turn-on field was found to be about 6 V/νm at a current density of 1 νA/cm2. After several field emission measurements, the turn-on field was increased up to 8.5 V/νm and the magnitude of field enhancement factor was decreased from 1190 to 940. According to SEM, the tip diameter increase of the zinc oxide to 60 nm was observed after several emission measurements. Therefore, degradation of the field emission characteristic after measurements is attributed to this deformation of the tip shape.
Design and Characterization of Nanoarchitectures from Multifunctional Polyparaphenylenes
Authors: Ravindranath Renu , Valiyaveettil Suresh , Baskar Chinnapan , Putra Ananda , Fitrilawati Fitri , Knoll Wolfgang 
Published: June 2019

AbstractConducting polymers are interesting materials due to their wide range of applications in electronics, sensing, photonics and display applications. The present paper delineates the synthesis and characterization of the three functionalized poly (p-phenylene)s (PPP) (A-C) and solution properties of the polymers. The self-assembly of the polymers were investigated on various substrates and the optical/morphological properties of thin films of these polymers were also studied. The spontaneous self assembly of the modified PPP's lead to the formation of thin films on both hydrophilic and modified surfaces.
Synthesis of carbon-encapsulated magnetic nanoparticles by a grain-boundary-reaction
Authors: Wang Qixiang , Ning Guoqing , Wei Fei , Luo Guohua 
Published: June 2019

AbstractCarbon-encapsulated ferric magnetic nanoparticles were prepared by the grain-boundary-reaction of ultrafine goethite particles. The mechanism of the grain-boundary-reaction was studied with high-resolution transmission electronic microscope, X-ray diffraction and thermo gravimetric analysis. The magnetic properties are measured with a vibrating sample magnetometer. The diameter of carbon-encapsulated ferric magnetic nanoparticles is 30~60 nm, and the coercive force and saturate magnetization are 315 Oe and 30 emu /(g powder), respectively. These composite particles are very stable in air.
Chalcogen Nanowires: Synthesis and Properties
Authors: Mayers Brian T. , Xia Younan 
Published: June 2019

AbstractWe have demonstrated a variety of solution-phase approaches for the synthesis of 1- dimensional nanostructures from chalcogens such as Se and Te. These nanostructures include uniform, single crystalline nanowires and nanorods (lateral dimensions from 10 to 1000 nm, and lengths ranging from 2 to >100 νm). These nanostructures grew via a solid-solution-solid transformation mechanism, in which Se and Te atoms were transported from the less stable source (amorphous colloids) into the more stable product (trigonal phase nanocrystallites). The nanocrystallites (or seeds) were formed either through temperature driven homogeneous nucleation or by sonochemical cavitation. As directed by the highly anisotropic crystal structure, the growth could be confined to one particular direction. These nanowires could be prepared both as dispersions in various solvents or as networked arrays on solid supports.
Dielectrophoretic Assembly of Switchable Two-Dimensional Photonic Crystals with Specific Orientation
Authors: Lumsdon Simon O. , Kaler Eric W. , Velev Orlin D. 
Published: June 2019

AbstractOne and two-dimensional colloidal crystals are assembled from aqueous suspensions of latex and silica microspheres in an alternating electric field. These crystals of size up to 25 mm2 are formed in the gap between two planar gold electrodes. They have specific axis orientation parallel to the direction of the applied field without the need for expensive micropatterned templates. The field gradient causes the particles to accumulate on the surface between the two electrodes, align into rows along the field direction, and then crystallize into hexagonal arrays. The lattice spacing can be controlled via electrostatic repulsion. The system can find application in switchable photonic devices.
Fabrication of Polymer Photonic Crystals by Two-Photon Nanolithography
Authors: Lee Tae-Woo , Mitrofanov Oleg , White Christopher A. , Hsu Julia W. P. 
Published: June 2019

AbstractWe use a two-photon laser-scanning microscope to fabricate two-dimensional (2D) photonic crystal structures in commercially available SU-8 polymer films, and successfully demonstrate making nanostructures beyond the diffraction limit with high aspect ratios. By varying the laser beam power, scanning speed, focal depth, line spacing and scanning angles, we obtain 2D photonic crystals with circular, elliptical, rectangular, or diamond-shape unit cells in a hexagonal or square lattice. An aspect ratio as high as 6.9 with 250 nm line width was achieved. In addition, we can controllably place defects of specific patterns, e.g. lines, dots, and Y-splitters, in the otherwise perfect photonic crystal. We also combine two-photon nanolithography with conventional UV photolithography to make 2D photonic crystals between waveguides. The combination of these two lithography methods was done on a single polymer film, suggesting potential for easy fabrication of complex photonic devices.
Fabrication and Characterization of Iron-Cobalt Alloy Magnetic NanoclusterWires by Thermal DecompositionMethod inMagnetic Fields
Authors: Moon Heesung , Nam Changhun , Kim Changwook , Kim Bongsoo , Lee Gangho 
Published: June 2019

AbstractWe present one-step synthetic method of magnetic alloy nanocluster wires. This process is simple, less expensive, and saves time. The gas is vaporized in a vacuum chamber from a solution of dicobalt octacarbonyl (Co2(CO)8) and iron pentacarbonyl (Fe(CO)5) mixture, and thermally decomposed by using a nichrome wire. The silicon substrate is placed in a homogeneous magnetic field which is produced by two permanent magnets (4000 gauss), so that the nanowires easily grow in the direction of the magnetic flux. From X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM), we confirmed that these have a body-centered-cubic (BCC) structure with the magnetization easy axis of [110] direction, and a diameter in the range of 4 to 6 nm with a few micrometers in length. Also, we investigated that the squareness of the hysteresis loop is 61% for magnetic fields parallel to the wires and the coercivity along the easy axis is 670 oersteds by using vibrating scanning magnetometer (VSM).
Proton Beam Nano-Machining: End Station Design and Testing
Authors: Kan J.A. van , Bettiol A.A. , Watt F. 
Published: June 2019

AbstractA new nuclear nanoprobe facility has been developed at the Centre for Ion Beam Applications (CIBA) in the Physics Department of the National University of Singapore. This facility is the first of its type dedicated to proton beam micromachining on a micron as well as a nano scale. The design and performance of the facility, which is optimized for 3D lithography with MeV protons, is discussed here. The system has been designed to be compatible with Si wafers up to 6”.The production of good quality high aspect ratio microstructures requires a lithographic technique capable of producing microstructures with smooth vertical sidewalls. In proton beam micromachining, a high energy (e.g. 2 MeV) proton beam is focused to a sub-100 nm spot size and scanned over a resist material (e.g. SU-8 and polymethylmethacrylate (PMMA)). When a proton beam interacts with matter it follows an almost straight path, the depth of which is dependent on the proton beam energy. These features enable the production of nanometer sized polymer structures. Experiments have shown that post-bake and curing steps are not required in this SU-8 process, reducing the effects of cracking and internal stress in the resist. Since proton beam micromachining is a fast direct write lithographic technique it has high potential for the production of high-aspect-ratio nano-structures.
Thermal stability of Pt nanowires manufactured by Ga+ focused ion beam (FIB)
Authors: Inkson B.J. , Dehm G. 
Published: June 2019

AbstractPt nanowires have been produced by FIB deposition of Pt thin films in a commercial Ga+ focused ion beam (FIB) system, followed by cross-sectional sputtering to form electron transparent Pt nanowires. The thermal stability of amorphous FIB manufactured Pt wires has been investigated by in-situ thermal cycling in a TEM. The Pt wires are stable up to 580-650°C where partial crystallization is observed in vacuum. Facetted nanoparticles grow on the wire surface, growing into free space by surface diffusion and minimising contact area with the underlying wire. The particles are fcc Pt with some dissolved Ga. Continued heating results in particle spheroidization, coalescence and growth, retaining the fcc structure.
Magnetic Nanostructures Produced By Electron Beam Direct Writing
Authors: Wang J.P. , Zhao Y. , Zhou T.J. , Thong J.T.L. , Chong T.C. 
Published: June 2019

AbstractWe present a method of direct magnetic patterning of nonmagnetic CoC and CoTaC films by electron irradiation-induced nano-scale phase transition. CoxC1-x (0.4<X<0.8) films were prepared by co-sputtering. The as-deposited films with Co concentration less than 60% are amorphous and non-ferromagnetic. All films become ferromagnetic after annealing. Doping Ta into the CoC films can enhance the segregation of Co and C and therefore reduce the phase transition temperature. It is found that the magnetic properties of annealed (Co60C40)97Ta3 films are much better than that of annealed Co60C40 films at the same annealing condition. Magnetic nano-patterning (dot/line array) of the as-deposited CoC and Co(TaC) films was realized by subjecting them to electron irradiation using a focused 30keV electron beam with a current of 7.1 nA and dwell time per dot of 0.75 to 15.2 seconds. A 250nm magnetic dot/line array was produced by this method. It was also found that the time required to magnetically pattern non-magnetic (Co60C40)97Ta3 thin films (0.75 seconds) is much shorter than that required for Co60C40 films (3.8 seconds). The present method of magnetically patterning a nonmagnetic film has the potential application for nanoscale solid magnetic devices.
Electron beam induced effects in Cu/GeSe2amorphous films
Authors: Romero J.S. , Fitzgerald A.G. 
Published: June 2019

AbstractCopper migration is observed in the SEM in amorphous GeSe2/Cu thin films when an electron beam is focused in pulsed or continuous operation on the surface of these thin films. The phenomenon can be explained using a simple model in which the population of D- centers is considered to increase upon electron irradiation. The increase in the D- center population is envisaged as due to the breaking of bonds by the electron radiation and by the constant presence of negative charge in irradiated regions. Changes in copper concentration of 20%-30% have been obtained. Additionally we have observed the local crystallization of amorphous GeSe2/Cu thin films in the TEM when the samples were subjected to intense electron bombardment. The crystalline product has been identified as Berzelianite (Cu2Se).
Magnetization dynamics of irradiation-fabricated perpendicularly magnetized dots inside a softer magnetic matrix
Authors: Devolder T. , Belmeguenai M. , Chappert C. , Bernas H. , Suzuki Y. 
Published: June 2019

AbstractGlobal Helium ion irradiation can tune the magnetic properties of thin films, notably their magneto-crystalline anisotropy. Helium ion irradiation through nanofabricated masks can been used to produce sub-micron planar magnetic nanostructures of various types. Among these, perpendicularly magnetized dots in a matrix of weaker magnetic anisotropy are of special interest because their quasi-static magnetization reversal is nucleation-free and proceeds by a very specific domain wall injection from the magnetically “soft” matrix, which acts as a domain wall reservoir for the “hard” dot. This guarantees a remarkably weak coercivity dispersion. This new type of irradiation-fabricated magnetic device can also be designed to achieve high magnetic switching speeds, typically below 100 ps at a moderate applied field cost. The speed is obtained through the use of a very high effective magnetic field, and high resulting precession frequencies. During magnetization reversal, the effective field incorporates a significant exchange field, storing energy in the form of a domain wall surrounding a high magnetic anisotropy nanostructure's region of interest. The exchange field accelerates the reversal and lowers the cost in reversal field. Promising applications to magnetic storage are anticipated.