bluuebunny/crossref_metadata_2025_split huggingface dataset:
Virtual Synthesis and Optoelectronic Properties of Prismatic Artificial Molecules of In-N and Zn-O: Comparative Studies
Authors: Pozhar Liudmila A , Brown Gail J , Mitchel William C 
Published: April 2011

ABSTRACTThe Hartree-Fock (HF), restricted open shell HF (ROHF), configuration interaction (CI), complete active space (ICASCF), and multiconfiguration self-consistent field (MCSCF) methods provide sophisticated fundamental theory-based, computational tools to study structure, composition,chemistry and electronic properties of small artificial molecules composed of semiconductor compound atoms. These tools are used to synthesize virtually several prismatic In-N and Zn-O artificial molecules whose structure is derived from that of the symmetry elements of the respective wurtzite bulk lattices. Applications of spatial constraints to the atomic coordinates allow modeling molecular synthesis in quantum confinement, to obtain pre-designed molecules with tunable electronic properties. Relaxation of these constraints, or optimization, leads to the corresponding molecules synthesized in “vacuum”. The development of computational templates of the studied artificial molecules synthesized in confinement reflects effects of quantum confinement on the electronic level structure, bonding, the direct optical transition energy, and charge and spin density distributions of the molecules. Comparison of the structure and properties of these molecules to those of their vacuum counterparts leads to a conclusion that a small changes in atomic positions in otherwise structurally similar molecules cause a significant change in their electronic properties. Thus, the electronic properties of artificial molecules can be tuned by changing their synthesis conditions that are defined by atomistic details of quantum confinement where the molecules are synthesized.
Guided Self Assembly of InAs Quantum Dots on a Cleaved Facet
Authors: Uccelli Emanuele , Schuh Dieter , Bauer Jochen , Bichler Max , Finley Jonathan J. , Grayson Matthew , Abstreiter Gerhard , Fontcuberta i Morral Anna 
Published: April 2011

ABSTRACTThe long range ordering of epitaxial semiconductor quantum dots (QDs) has been obtained by combing self assembly with the cleaved edge overgrowth technique. The introduction of nanometer thick AlAs stripes on a (110) oriented GaAs surface avoids the misfit dislocation growth mechanism of InAs on GaAs (110) and drives the formation of array of QDs. Atomic Force Microscopy (AFM) investigations highlight that InAs QDs only nucleate in chain like structure on Al-rich regions. Here, we present experimental results that demonstrate the ability to create ordered QDs lattices and discuss the conditions under which preferential growth of QDs on the AlAs stripes occurs.
First-principles Calculations of Energetic Properties of Vacancies, Mn-atomic Defects in CdTe
Authors: Merad Ghouti , Rerbal Benali , Aourag Hafid , Cibert Joël 
Published: April 2011

ABSTRACTAn atomistic modelling based on density functional theory within the framework of the local density approximation is used to show the trends in the energetic properties of single and double defects in CdTe semiconductor, without phase transformation. A systematic study of vacancies, Mn substituting Cd atoms in a supercell structure consisting of 16-atoms is presented. The changes of structural properties and lattice parameters due to the addition of Mn-atomic type defects in CdTe matrix are compared, and the number of vacancies is also determined from the total energy calculations.
Modelling Size-Selected Growth of Nanodots by Using Reaction Kinetic Approach
Authors: Nevalainen Kirsi , Rusanen Marko , Koponen Ismo T. 
Published: April 2011

ABSTRACTThe size selection of nanodots during the growth is modelled by using the reaction kinetic model with reaction rates for dot size dependent attachment and detachment processes, related to the free energy of dots. Long-lived metastable state is found near the minimum of free energy, but the kinetics of the growth causes the peak to overshoot the location of minimum of the energy. The size distribution of dots is shown to be nearly Gaussian with minor skewness originated from kinetics. However, it is argued that this skewness is inherently related to the effect of overshooting, and thus to the formation of the long lived metastable state with size selected nanodots. Based on RKM, a simple continuum model is derived to describe the size selection and narrowing of the size distribution.
Structural and Magnetic Characterization of MOCVD Grown GaMnN and GaFeN Nanostructures
Authors: Gupta Shalini , Kang Hun , Kane Matthew H. , Park Eun Hyun , Ferguson Ian T. 
Published: April 2011

ABSTRACTThe growth of Ga1-xMnxN and Ga1-xFexN nanostructures was carried out by MOCVD. Introduction of transition metals (TM) Mn and Fe in GaN nanostructures enhanced the nucleation of the nanostructures resulting in reduced lateral dimensions and increased nanostructure density. The Ga1-xMnxN nanostructures showed hysteresis behavior at 5K. Room temperature ferromagnetism was obtained in the Ga1-xFexN nanostructures unlike its bulk counterpart. This paper presents the growth and magnetization study of Ga1-xTMxN nanostructures. These structures could be used to enhance the efficiency of spintronic devices.
Spray Produced Coral-Shaped Assemblies of MnS Nanocrystal Clusters
Authors: Amirav Lilac , Lifshitz Efrat 
Published: April 2011

ABSTRACTA novel spray-based technique enables the production of high quality, free, uncoated semiconductor nanocrystals. Their collection, following spray droplet desolvation during flight, could result in unusual structures. We report on spray-produced ordered clusters (∼50nm diameter) of MnS nanocrystals with grain size range of 1-2nm, and their assembly into micron-sized coral-shaped fractal aggregates. Ballistic cluster-particle aggregation, with the introduction of physical interaction between particles, is suggested as a model for the assemblies' growth.
Photo-Induced Structural Changes in Titanium Alkoxides for Directing Molecular Assembly
Authors: Musgraves J. David , Potter B.G. , Sewell Robin M. , Boyle Timothy J. 
Published: April 2011

ABSTRACTThe effects of ultraviolet irradiation on a heteroleptic titanium alkoxide ((OPy)2Ti(4MP)2) have been investigated. The molecule has been studied in solution and in thin film form using FTIR and Raman spectroscopies. Quantum computational modeling was used to associate vibrational modes with structural moieties present in the molecule. In all cases examined, a preferential photoinduced modification in vibrational resonances linked to the 4-mercaptophenol (4MP) ligand was observed. In contrast, little or no change was exhibited in the vibrational structure of the OPy ligands.
Self Assembled Patterns of Gold Nanoclusters in Silicon (100) Produced by Metal Vapour Vacuum Arc Ion Implantation
Authors: Venkatachalam Dinesh Kumar , Sood Dinesh Kumar , Bhargava Suresh Kumar 
Published: April 2011

ABSTRACTSelf assembled gold nanoclusters are attractive building blocks for future nanoscale sensors and optical devices due to their exciting catalytic properties. Recently several methods have been employed to produce nanoclusters on solid substrates, which result in a random spatial distribution of the clusters. In this work, we have achieved ordered circular patterns of gold nanoclusters in Silicon (100) substrates by Au ion implantation followed by thermal annealing. This unique phenomenon is observed only above a critical threshold implantation dose and anneal temperature. Based on a systematic study (SEM, XTEM and XRD) of the growth and morphology of the nanoclusters, we propose a tentative model for the formation mechanism of this unusual self-assembled pattern.
Quantum-Cross Tunneling Junction for High Density Memory
Authors: Kaiju Hideo , Kondo Kenji , Ishibashi Akira 
Published: April 2011

ABSTRACTWe calculated transport properties of edge-to-edge quantum cross structure that consists of two metal nano-ribbons having edge-to-edge configuration with a tunnel barrier and showed current-voltage characteristics depending on the metal-ribbon thickness (5-30 nm), the barrier height (0.5-1.5 eV) and the barrier thickness (0.5-1.0 nm). Interesting behavior of transport properties is that the metal-ribbon thickness affects the current density due to the quantization of nano-ribbon and also the current density, being dependent on the barrier height and the barrier thickness, decreases with high and thick barrier. These calculated results indicate that we can precisely obtain the information on the material sandwiched between two electrodes, such as the barrier height and the barrier thickness, by a fit of experimental data to our derived equation, and these approaches result in a distinction between the sandwiched material and the electrode.
Memory Effects in Manganese Perovskites. Experiment and Theory
Authors: Noginova Natalia , McClure J. , Gavrilenko V. , Novikov D 
Published: April 2011

ABSTRACTElectrically induced quasi-permanent changes in low-field conductivity have been observed in single crystals of LaGa1-xMnxO3 in the broad range of Mn ion concentrations. The memory effects can last for a long time at room temperature and can be easily erased by heating up to Tc ∼300 C. The temperature dependence of the resistivity has a sharp drop around the phase transformation temperature, pointing to the role of phase transformation processes. The switching between high resistance and low resistance states is demonstrated. We explain our experimental data in terms of thermo induced local phase transition with the oxidation of Mn ions. The results of the ab initio calculations of the electron energy structure in Jahn-Teller-distorted and non-distorted cells confirm the mechanism suggested.
Nanoline Templating of metals and the underlying surface processes
Authors: Owen James Hugh Gervase , Miki Kazushi 
Published: April 2011

ABSTRACTBi nanolines, which self-assemble on Si(001), have been used as templates for the deposition of a variety of metals: noble metals, transition metals, and Gr. III metals. The different metals show a variety of behaviours on this surface, from a strong interaction in the case of In and Al, to a very weak interaction in the case of Ag. The different phenomena are discussed in terms of a balance of different competing surface mechanisms, such as diffusion and nucleation, which drives the observed behaviours.
Quasi-Ordered Nano-Sized Structure On Surface Of Oxide Crystals
Authors: Doichinovic Iavn , Dojcilovic Jablan , Popovic Dusan , Puric Jagos , Kulagin Nicolay Alex 
Published: April 2011

ABSTRACTAn article is given of research of SEM, AFM and optic data of pure and doped strontium titanate as bulk single crystals and nano-scale sized samples before and after plasma treatment. Quasi-ordered system of nano-scale sized triangle piramids was discovered on surface of separate doped samples after plasma treatment
Supramolecular Self-Assemblies as High-Density Data-Storage Media
Authors: Wintjes Nikolai , Wahl Markus , Kiebele Andreas , Stohr Meike , Schintke Silvia , Spillmann Hannes , Güntherodt Hans-Joachim , Gade Lutz , Bonifazi D , Cheng F , Diederich F , Jung Thomas 
Published: April 2011

ABSTRACTThe affordable and reproducible creation of nanoscale functional material layers is a key desire towards the progressing miniaturization of devices and the continuous increase of data storage densities. While top-down structuring costs are exploding, the self-assembly [1] of dedicated building blocks in functional molecular layers provides an alternative to produce structures in the few nanometer range. Several different approaches, exploit characteristic materials properties for this purpose: A) the dedicated assembly of two dimensional molecular layers on prepatterned surfaces provides the basis for structural transitions involving only some hundred molecules. These transitions can be reversibly triggered by an electric field. [2] B) The complex balance of inter-molecular interactions with adsorbate-adsorbent interactions provides the basis for tuning the assembly. Long range ordering is a crucial requirement to match self-assembled functional devices with top-down manufactured methods for addressing and operation. [3] C) Using larger molecular entities and conformational flexure [4], even larger periodicity functional arrays can be manufactured by extending site blocking mechanisms to nearest neighbour interactions. [5] D) By a hierarchical two step approach, i.e. the initial assembly of a specific host-layer and the second step assembly of molecular guests upon this host layer, a wealth of new molecular properties is achievable in extended supra-molecular layers. [6] All these new supra-molecular self-assembled systems offer a valid alternative toward the fabrication of reproducibly identical and addressable “molecular switches” which are impossible to achieve by using established lithographic methods.
Tailoring Microdomain Orientation in Block Copolymer Thin Films for Lithographic Application
Authors: Yoshida Hiroshi , Kitano Hirofumi , Akasaka Satoshi , Inoue Tomohiro , Taknaka Mikihito , Hasegawa Hirokazu , Nagano Hideki 
Published: April 2011

ABSTRACTBlock copolymer lithography is a promising method for fabricating periodical nano patterns less than 20nm by self-assembly and can be applicable for fabricating patterned magnetic media with recording density over 1Tbit/inch2. We found a simple technique to control the orientation of cylindrical microdomains in thin films. Only by mixing polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) diblock copolymers with the constituent homopolymer (PS or PMMA), we could align the cylindrical microdomains perpendicular to the film surface. The added homopolymer induces conformational entropic relaxation of the block chains in microdomain space and stabilizes perpendicular orientation of hexagonally packed cylindrical microdomains. Thus formed perpendicular cylinders can be readily aligned in a regular array with a grating substrate.
Measurement of Arrays of Dots Produced by Electron-beam Lithography
Authors: Hoyle Philip C. , Laidler Ian 
Published: April 2011

ABSTRACTElectron-beam mastering of templates for patterned media presents a challenge to the toolmaker to simultaneously meet throughput, resolution and placement requirements. Fundamental to tool development is the ability to measure the placement to true grid of shapes as small as 7 nm over the whole substrate. In this article we describe a technique, consisting of acquiring and analyzing scanning electron (SE) micrographs, for measuring the placement errors in lithography similar to that required for patterned media, albeit over a few square microns and without scale and orthogonality components. The method enabled the measurement of placement errors of dots in an array with accuracy down to about 2 nm. The technique was used to benchmark current X-Y tool performance and the smallest 3× standard deviation of placement error was found to be around 4.5 nm. A clearer understanding of the necessary tool improvements was obtained. The use of the technique as basis for measuring errors to true grid over the entire substrate is discussed.
Development of a Novel Metal Epitaxy Method towards Ni Based Electro-magnetic Hybrid Systems
Authors: Matsuda Akifumi , Kasahara Masayasu , Watanabe Takahiro , Hara Wakana , Otaka Sei , Koyama Kouji , Yoshimoto Mamoru 
Published: April 2011

ABSTRACTThe epitaxial Ni (111) thin film on the oxide substrate could be obtained by a novel epitaxy method, employing pulsed laser deposition (PLD) of NiO (111) epitaxial film on the sapphire (α-Al2O3single crystal) substrate and successive hydrogen reduction of NiO. The NiO (111) epitaxial film was deposited on the sapphire (0001) substrate at room-temperature by PLD, and then reduced into the Ni epitaxial film by annealing (300 °C to 500 °C) in the hydrogen-atmosphere. On the other hand, the polycrystalline Ni metal thin film was obtained by reduction of the polycrystalline NiO film, indicating necessity of epitaxial growth for the precursor oxide thin film in the metal epitaxy. The present epitaxy method suggests the possible formation of [Ni/α-Al2O3] epitaxial multilayer via selective reduction of oxide multilayer.
Hydrothermal Synthesis of Zinc-Doped Magnetite Nanoparticles
Authors: Sorescu Monica , Diamandescu Lucian , Tarabasanu-Mihaila Doina , Teodorescu Valentin 
Published: April 2011

ABSTRACTHydrothermal techniques have been used to synthesize samples of ZnxFe3−xO4 (x=0.0-1.0) starting with ZnSO4.7H2O/FeSO4.7H2O aqueous solution. The sequence of phases, structural and magnetic properties were followed by X-ray diffraction (XRD), Mössbauer spectroscopy and transmission electron microscopy (TEM). Refinement of the XRD spectra yielded the dependence of the lattice parameters of zinc–doped magnetite and zinc ferrite phase as function of the Zn molar concentration x. As well, the particle diameter was derived as a function of Zn content x. As a function of Zn concentration, the phase content of hydrothermally synthesized samples was found to consist of zinc-doped magnetite, goethite and zinc ferrite. Consistent with the XRD results, Mössbauer spectroscopy data indicate the presence of magnetite and goethite at x≤0.2, magnetite and zinc ferrite at x≤0.9 and pure zinc ferrite only at high zinc concentrations. The presence of different magnetite phases was confirmed by TEM and particles with a size of 50 nm were identified. Our results show that zinc ferrite is formed at high zinc concentration by the hydrothermal method and an acicular component of goethite-magnetite is obtained at low zinc content.
Synthesis of a Magnetic-Dielectric YIG@BaTiO3 Composite via Hydrothermal Processing
Authors: Lin Shin-Wei , Ko Wen-Song , Tung Mean-Jue 
Published: April 2011

ABSTRACTYIG@BaTiO3 composite was synthesized by a sequential process involving the formation of TiO2 by sol-gel reaction and a subsequent hydrothermal transformation from TiO2 to BaTiO3. TiO2 layer was coated on YIG particle via sol-gel reaction which comprised hydrolysis and condensation reaction of titanium n-butoxide. The pH value of the solution was precisely controlled to ensure that YIG particles could be well dispersed in the solution and the concentrations of TBOT and H2O were adjusted to obtain variant thickness of TiO2 layer. Nano-sized BaTiO3 coating on YIG was achieved by a hydrothermal conversion of the TiO2 shell layer. BaTiO3 shell layer was synthesized in an autoclave at 240°C for 12 hours and the concentration ratio of [Ba]/[Ti] was 1.6. Phases and morphology of the composite are identified by X-ray diffraction and SEM, respectively. Magnetic properties of YIG@BaTiO3 composite were investigated by vibrating sample magnetometer. Coercivity of YIG@BaTiO3 composites with different composition were not affected but the saturated magnetization dropped down with increasing of the volume ratio of BaTiO3. Permittivity of YIG was raised by coating of BaTiO3 layer and was varied from 6 to 60 and 75 by tuning up the volume ratio of BaTiO3 in the composite. The mechanism of the formation of YIG@BaTiO3 composite was also discussed in the article.
Synthesis of Silicon Based Opal by Chemical Reduction of Silica Opal
Authors: Aliev Ali E. , Royer M. A. O. , Zakhidov A. A. , Baughman R. H. 
Published: April 2011

ABSTRACTBy reduction of SiO2 opal in atmosphere of nitrogen (80%)-helium (15%)-hydrogen (5%) gas mixture at various temperatures we tuned the dielectric contrast ratio and band gap of photonic crystal (PC) up to 10 %. The SEM images dose not show any detectible change in lattice parameters, whereas the elemental analysis shows remarkable decrease of oxygen content. The shift of reflectance spectra toward the long wavelength and increase of transmission in infrared region confirm the redaction of silica and partial transformation to the silicon.
Functional Metamaterials Based on Mesoscale Gold Sponges, Particulate Aggregates, and Their Composites with Dielectric Materials
Authors: Cortie Michael , Maaroof Abbas , Smith Geoff B 
Published: April 2011

ABSTRACTThe optical properties of some nanoscale composites may deviate from that expected from a simple law of mixture of their individual components. In these cases the resulting structure can be considered to be a type of “metamaterial”. Here we explore some of the possibilities for nanoscale composite structures comprised of gold and VO2 – the latter being a functional material that undergoes a reversible insulator to metallic phase transition at 68°C. Two microstructures are examined: aggregates of gold nanoparticles surrounded by VO2 as the continuous phase, and its geometric inverse, mesoporous gold sponge with discontinuous VO2 inclusions. A composite, right-angled parallelepiped measuring 40×100×100 nm is taken as representative of the mixture, and calculations of the optical properties performed using the discrete dipole approximation code of Draine and Flatau. The VO2 matrix strongly attenuates the dipole-dipole plasmon resonance of the gold structure, and thermochromic switching of the remaining plasmon resonance occurs
Ferroelectricity from Electron Ordering
Authors: Ikeda Naoahi , Mori Shigeo , Yoshii Kenji , Matsuo Yoji 
Published: April 2011

ABSTRACTWe report ferroelectricity in triangular mixed valence material RFe2O4 (R=Y, Dy, Ho, Er, Tm, Yb, Lu). This ferroelectricity originates from the polar ordering of Fe3+ and Fe2+ or the polar ordering of electrons on Fe3+.
Capacitance Tunability of Magneto-electric Material:Cr2O3 using Ferromagnetic (La,Sr)MnO3 Electrode
Authors: Yokota Takeshi , Kuribayashi Takaaki , Shundo Takeshi , Hattori Keita , Sakakibara Yasutoshi , Gomi Manabu 
Published: April 2011

ABSTRACTWe have investigated the dielectric properties of the Cr2O3 films using ferromagnetic electrode; (La0.66, Sr0.33)MnO3. The relationships between those properties and their crystallinity also have been investigated. The well crystallized sample was exhibited low leakage current density. Although all samples show capacitance decreasing by applying voltages, the decreasing ratio was the largest on the sample with lowest leakage current density. Since the Cr2O3 film with same leakage current density as that sample using non-magnetic electrode didn't show any capacitance changes by applying voltages, it is suggested that the dielectric properties of Cr2O3 film might be affected by the ferromagnetic film.
Doping Effect on the Charge Ordering in LuFe2O4
Authors: Matsuo Yoji , Shinohara Satoshi , Mori Shigeo , Horibe Yoichi , Yoshii Kenji , Ikeda Naoshi 
Published: April 2011

ABSTRACTChange of the charge ordered (CO) structure by substituting Cu2+ for Fe2+ in LuFe2O4 was investigated by means of the transmission electron microscopy. The CO structure in LuFe2O4 is characterized by the modulated structure with the wave vector of q=1/3[1-13/2] and the average size of the CO domains can be estimated to be about 10-20nm. On the contrary, the Cu2+ substitution in LuFe2O4 destroyed the CO structure drastically and induced characteristic local lattice distortion, which gives rise to characteristic diffuse scattering in the reciprocal space. High-resolution lattice images revealed that there exist nano-scale clusters, which are characterized as the short-range ordering of the Fe3+ and Cu2+ ions on the triangular lattice. In addition, the magnetic measurement revealed that LuFeCuO4 exhibits an antiferromagnetic transition around 50K, which is lower than the Neel temperature of 250K in LuFe2O4.