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Designing reliable piezoresistive pressure sensors based on percolative nanoparticle (NP) arrays remains a challenge. Here, the authors propose a percolative NP array sensor deposited on a flexible membrane with ultra-high sensitivity and resolution by modifying the thickness of the membrane.

The topological surface states usually appear in pairs in a topological insulator, with one on the top surface and the other on the bottom surface. Here, Zhang et al. utilize Co cluster to induce a Zeeman gap on one surface through antiferromagnetic exchange coupling, and observe a quasi-half-integer plateau, suggesting the parity anomaly of Dirac fermions.

Two-dimensional materials: Repairing atomic defects via solution processing Defects can heavily influence the electrical transport properties of three-dimensional materials. But their impact becomes even more pronounced in low-dimensional systems. Fengqi Song and colleagues use a combination of calculations and experiments to show that a simple drop of a chemical solution can repair the selenium vacancies in field-effect transistors made from single layer molybdenum diselenide. By reducing the number of vacancies, which localize the electronic transport, the authors increased the carrier mobilities to nearly the intrinsic value by 2–3 orders of magnitude. The defect dynamics is visualized by the high resolution electron microscopy and multislice simulations. Such an approach could provide a route for enabling practical devices to be made from these relatively fragile materials.

A Type II Weyl fermion semimetal has been predicted in MoxW1−xTe2, but it awaits experimental evidence. Here, Belopolski et al. observe a topological Fermi arc in MoxW1−xTe2, showing it originates from a Type II Weyl fermion and offering a new platform to study novel transport phenomena in Weyl semimetals.

The electronic and magnetic properties of Mn- or Fe-doped GanAsn (n=7–12) nanocages were studied using gradient-corrected density-functional theory considering doping at substitutional, endohedral, and exohedral sites. When doped with one atom, the most energetically favorable site gradually moves from surface (n=7–11) to interior (n=12) sites for the Mn atom, while the most preferred doping site of the Fe atom alternates between the surface (n=7,9,11) and interior (n=8,10,12) sites. All of the ground-state structures of Mn@GanAsn have the atomlike magnetic moment of 5μB, while the total magnetic moments of the most stable Fe@GanAsn cages for each size are about 2μB except for the 4μB magnetic moment of Fe@Ga12As12. Charge transfer and hybridization between the 4s and 3d states of Mn or Fe and the 4s and 4p states of As were found. The antiferromagnetic (AFM) state of Mn2@GanAsn is more energetically favorable than the ferromagnetic (FM) state. However, for Fe2@GanAsn the FM state is more stable than the AFM state. The local magnetic moments of Mn and Fe atoms in the GanAsn cages are about 4μB and 3μB in the FM and AFM states, respectively. For both Mn and Fe bidoping, the most energetically favorable doping sites of the transition metal atoms are located on the surface of the GanAsn cages. The computed magnetic moments of the doped Fe and Mn atoms agree excellently with the theoretical and experimental values in the Fe(Mn)/GaAs interface as well as (Ga, Mn)As dilute magnetic semiconductors. [ABSTRACT FROM AUTHOR]

The structures of free-standing magnesium nanowires are systematically studied by using genetic algorithm simulations based on molecular dynamics with a tight-binding many body potential. Several helical multishell cylindrical growth sequences are observed for magnesium nanowires. The numbers of atomic strands show the even-odd or odd-even coupling between the inner and outershell with the differences of five strands, These multishell structures are made up of coaxial tubes in the three- and four-strands helical, centered pentagonal and hexagonal, and double-chain-core parallel curved surface epitaxy. The average binding energy and coordination numbers are calculated. The angular correlation functions and vibrational properties of magnesium nanowire have also been studied. [ABSTRACT FROM AUTHOR]

The thermal evolution and dynamics properties of small clusters in melt are investigated by molecular dynamics simulation with 500 particles. The interatomic interaction is described by a well-fitted semiempirical tight binding potential. We have studied some solidlike clusters and structural properties of liquid aluminum. The atomic volume, internal energy, pair correlation function, and bonded pairs in liquid are obtained from quick cooling and slow cooling simulation. A comparison between the slow and quick cooling process reveals that the cooling rate significantly affects the evolution route of various clusters in liquid aluminum. Our results show that glass contains a lot of 1551 and 1541 five-fold symmetry clusters. On the contrary, the crystal has some 1421 and 1422 clusters corresponding to a face-centered cubic structure and hexagonal closing-packed structure. This work gives clear physical insight of the structure evolution from liquid to solid. [ABSTRACT FROM AUTHOR]

The chemically resolved electron energy-loss spectroscopy (EELS) technique is employed to study the scaling dopant states present in the semiconducting nanostructures. The room-temperature ferromagnetism exhibited by these compounds is also analyzed.

A study reports for the first time the light manipulation of high-[T.sub.c] ferromagnetism in nanostructured oxide diluted magnetic semiconductors (DMSs). Results demonstrate that the ferromagnetic order of the nanocrystal films decays with aging in air at room temperature, but it can be reactivated and enhanced by ultraviolet irradiation.

A study reports on a simple, hierarchical approach for obtaining self-assembled silver nanocluster linear arrays where Silver nanoclusters are obliquely deposited onto the poly(styrene-b-butadiene-b-styrene) (SBS) triblock copolymer templates at low coverage. Optical absorption spectra reveal that the surface plasmon resonance (SPR) of the silver nanocluster linear arrays manifests a red shift of the ~21.4 nm compared to the SPR absorption of silver nanoclusters deposited on a fused quartz substrate.

The synthesis and Raman scattering study of rutile SnO2 nanowires obtained by a simple precursor thermal decomposition process in NaCl flux with Sn(CO)2 is detailed. In addition to the fundamental Raman scattering peaks, the other two Raman scattering peaks are observed at 300 and 601 per cm.

The spin-orbit coupling strength of graphene can be enhanced by depositing iridium nanoclusters. Weak localization is intensely suppressed near zero fields after the cluster deposition, rather than changing to weak anti-localization. Fitting the magnetoresistance gives the spin relaxation time, which increases by two orders with the application of a back gate. The spin relaxation time is found to be proportional to the electronic elastic scattering time, demonstrating the Elliot–Yafet spin relaxation mechanism. A sizeable Kane–Mele-like coupling strength of over 5.5 meV is determined by extrapolating the temperature dependence to zero. [ABSTRACT FROM AUTHOR]

Multistep dissociative chemisorption reactions of water with Pd4 and Pd7 clusters were studied using density functional theory. The adsorption energies and referred adsorption sites from water molecule (H2O) to partially dissociative (H2+O and OH+H), then to fully dissociative (O+H+H) configurations are carefully determined. It is found that the adsorption energies of three dissociative reactions are 5–6 times larger than that of water molecule. Atop sites of Pd4 and Pd7 clusters are found to be the most stable sites for the adsorbed H2O molecule. For the coadsorption cases of partially and fully dissociated products, H2 and OH molecules preferably tend to bind at the low coordination (atop or bridge) sites, and O and H atoms prefer to adsorb on the high coordination (hollow) sites. It is also found that the most favorable adsorption sites for the molecular adsorbates (H2O, H2 and OH) are adjacent to the Pd atoms with the largest site-specific polarizabilities. Therefore, site-specific polarizability is a good predictor of the favorable adsorption sites for the weakly bound molecules. The different directions of charge transfer between the Pd clusters and the adsorbate(s) is observed. Furthermore, the processes of the adsorption, dissociation, and the dissociative products diffusion of H2O are analyzed. [ABSTRACT FROM AUTHOR]

Density functional theory calculations have been carried out to investigate 3d, Pd and Pt transition metal (TM) atoms exohedrally and endohedrally doped B80 fullerene. We find that the most preferred doping site of the TM atom gradually moves from the outer surface (TM = Sc), to the inner surface (TM = Ti and V) and the center (TM = Cr, Mn, Fe and Zn), then to the outer surface (TM = Co, Ni, Cu, Pd, and Pt) again with the TM atom varying from Sc to Pt. From the formation energy calculations, we find that doping TM atom can further improve the stability of B80 fullerene. The magnetic moments of doped V, Cr, Mn, Fe, Co and Ni atoms are reduced from their free-atom values and other TM atoms are completely quenched. Charge transfer and hybridization between 4s and 3d states of TM and 2s and 2p states of B were observed. The energy gaps of TM@B80 are usually smaller than that of the pure B80. Endohedrally doped B80 fullerene with two Mn and two Fe atoms were also considered, respectively. It is found that the antiferromagnetic (AFM) state is more energetically favorable than the ferromagnetic (FM) state for Mn2- and Fe2@B80. The Mn and Fe atoms carry the residual magnetic moments of ~3 μB and 2 μB in the AFM states. [ABSTRACT FROM AUTHOR]

Pb nanoclusters were deposited onto a suspended carbon nanowire (CNW), where in situ temperature variable observation was carried out by a transmission electron microscope. The heating temperature was up to 450 °C. Both the melting and evaporation of the Pb nanoparticles on the CNW were retarded when compared to the particles on the support frame. The obvious temperature difference of up to 10 K along the CNW of less than 1 μm was demonstrated. It was attributed to the irradiating dissipation-dependent on the surface area of the decorating Pb particle by calculation. [ABSTRACT FROM AUTHOR]

By using Gaussian98 package at BPW91 6-31g(d,p) level combined a genetic algorithm (GA) simulation, we have studied the lowest energy structural and electronic properties of the AlnN (n=2-13) clusters. The ground-state structures, the charge transfers from Al to N site, HOMO-LUMO gap and the covalent, ionic and metallic nature with cluster size and atomic structure are investigated. Al7N, Al9N and Al12N cluster is found particularly stable among the AlnN clusters. [ABSTRACT FROM AUTHOR]

We report a novel experimental finding of Te cluster films with fractal structure formed at annealing process and the Monte-Carlo simulation of this process. Te cluster films were prepared by using inert gas condensation method and annealed the sample in situ at 523K under TEM. The fractal patterns were formed because of evaporation when the substrate temperature increased. The simulation results indicate that the morphology of the nanofilm is not changed at first, but with increasing temperature some cavities appear due to evaporation. With further increasing temperature, those cavities are enlarged, then networks, fractal patterns and islands are formed subsequently. The turning point of temperature, at which the system has the fastest evaporating rate, is also obtained. It is predicated that the nanostructural films with special pattern and novel property can be achieved by annealing the cluster film in a controlled manner. [ABSTRACT FROM AUTHOR]

The structural and magnetic properties of Cu-coated Co clusters are investigated with empirical genetic algorithm simulation and a spin-polarized spd tight-binding model Hamiltonian. In some specific stoichiometric compositions, icosahedral Co[sub n] (n=1, 2, 4, 7, 13, 19, 55) clusters perfectly coated with A Cu monolayer or dual layer are obtained. The outer Cu layers lead to significant modification of the magnetic moment of the Co core, depending on the structure and thickness of the Cu layers. The interaction between Cu and Co atoms induces a nonzero magnetic moment for Cu atoms. [ABSTRACT FROM AUTHOR]

AlN nanowires have been successfully prepared via melting Al powder in a NH3 atmosphere with variable flow rate. The as-prepared nanowires are composed of AlN with diameters of 5 to 40 nm, and lengths of tens of microns. Raman scattering spectra and photoluminescence (PL) of as-prepared AlN nanowires are also investigated. As a result of impurity incorporation and stress, the Raman spectra are shifted to lower frequencies. A blue emission band centered at 434 nm is observed. The PL mechanism of AlN nanowires is discussed. [ABSTRACT FROM AUTHOR]

The Pb(Zr,Ti)O3/CoFe2O4/Pb(Zr,Ti)O3 heterostructural film was prepared and the variation in its magnetoelectric output with the cycling electric polarization was investigated. The giant magnetoelectric output, which was about one order enhancement in magnitude compared with the original film, was observed after the film was subjected to the cycling electric polarization with the strength of 45 MV/m and cycling number of ∼2.2×108. We consider that both oxygen vacancy migration in the heterostructure and the polarized electric charges in the CoFe2O4 layer play important roles in such significant magnetoelectric enhancement. [ABSTRACT FROM AUTHOR]

Carbon atoms are counted at near atomic-level precision using a scanning transmission electron microscope calibrated by carbon nanocluster mass standards. A linear calibration curve governs the working zone from a few carbon atoms up to 34 000 atoms. This linearity enables adequate averaging of the scattering cross sections, imparting the experiment with near atomic-level precision despite the use of a coarse mass reference. An example of this approach is provided for layer counting of stacked graphene sheets. Suspended graphene sheets with a size below 100 nm are visualized, providing quantitative measurement in a regime inaccessible to optical and scanning probe methods. [ABSTRACT FROM AUTHOR]

The giant room-temperature magnetocapacitance is reported in the Co2+ substitutionally doped SnO2 film in which the ferromagnetism coexists with the dielectric state. The maximum magnetocapacitance is observed in the Sn0.98Co0.02O2 film in which the magnetocapacitance is as large as 0.45 at frequency of 1.0 kHz and saturated magnetic field of ∼6.0 kOe. We experimentally demonstrate that such magnetocapacitance effect correlates with the Co dopant concentration and the existence of oxygen vacancy. The electric polarization response of the oxygen vacancy–Co ion complexes to the magnetic field is attributed to the origin of the magnetocapacitance. [ABSTRACT FROM AUTHOR]

The BiFeO3–Pb(Zr0.52Ti0.48)O3 composite film in which BiFeO3 nanoparticles are distributed in the Pb(Zr0.52Ti0.48)O3 matrix was prepared by electrophoretic deposition method. The microstructural characterization revealed the structural distortion of the BiFeO3 phase, induced by the unique BiFeO3–Pb(Zr0.52Ti0.48)O3 core/shell structure. The composite film exhibited evidence of ferroelectricity with enhanced ferromagnetism as well as a magnetoelectric effect. The two origins for the magnetoelectric effect are presented. This present work provides a promising roadmap to improve the magnetoelectric effect of BiFeO3-based multiferroics for actual applications. [ABSTRACT FROM AUTHOR]

Boron nitride nanogranular films on n-type silicon substrates were prepared and their field-emission performance was tested. The films started their electron emission at a mean electric field of 4.0 V/μm. The current density reached 1 mA/cm2 at 6.2 V/μm. The Fowler-Nordheim plot gave an enhancement factor β of 360. The films were boron-rich. As measured by scanning electron microscopy and atomic force microscopy, the films contained the cone-shaped islands with the diameter of 20–40 nm, which were believed to enhance the local electric field. Their performance parameters were comparable to the values of the samples with micrometer roughness. [ABSTRACT FROM AUTHOR]

Ferromagnetic film of densely packing chromium oxide nanoparticles has been fabricated by vacuum deposition of chromium oxide clusters at room temperature. The clusters were generated with a magnetron plasma gas aggregation source by introducing a mixture of argon and oxygen as buffer gas. A magnetic hysteresis loop similar to that of bulk CrO2 was observed in a wide temperature range. The rise in the ferromagnetic property of the film was attributed to the nanoscale CrO2 composition. The work demonstrates a simple way to fabricate ferromagnetic films of chromium oxide nanoparticles under high-vacuum compatible low temperature condition. [ABSTRACT FROM AUTHOR]

The thermal stability of the PbO-coated Pb nanoclusters was evaluated in different ambient pressures by the temperature-variable Raman scattering and transmission electron microscopy. The change of the inner pressure was presented by Raman scattering to demonstrate the cell’s collapse with the final formation of the liquid nanojets. The different ambient pressures were used to tune the working of the nanojet from no jet production to multiple jets. An interpretation of gas-participated cooling that improves the working stability of the nanonozzles was proposed. The ambient-sensitive working stability was suggested to be a universal effect for the few-atom-contained nanodevices. [ABSTRACT FROM AUTHOR]

Magnetoelectric CoFe2O4-PZT (lead zirconate titanate) films as thick as 1 μm have been prepared by spin coating using a PZT sol-gel solution containing polyvinylpyrrolidone and CoFe2O4 powder. X-ray diffraction result reveals that there exists no chemical reaction or phase diffusion between the CoFe2O4 and PZT phases. The scanning electron microscopy observation confirms that the composite thick film is crack-free and has a well-defined microstructure. The composite thick films exhibit good magnetic and ferroelectric properties, as well as distinct magnetoelectric coupling behavior. The magnetoelectric coupling mechanism for the present composite thick film is discussed in detail. [ABSTRACT FROM AUTHOR]

Gold (Au) nanoplates with an average thickness of ∼70 nm and several 10 μm in edge size have been mass synthesized through a solution-phase method. Structural studies demonstrate that the Au nanoplates are single crystals with (111) planes as two basal surfaces. Fragmentation of Au nanoplates is found when temperature is higher than 450 °C. Investigations on the thermal stability of Au nanoplates suggest that the melting and breaking start mainly at the (110) bounded edges, while the (111) surfaces of Au nanoplates show high stability. This work is valuable for Au nanostructures applied at elevated temperatures. [ABSTRACT FROM AUTHOR]

By means of constant pressure molecular dynamics simulation technique, a series of simulations of the Fe[sub 50]Al[sub 50] alloy have been carried out. The atoms interact via semi-empirical n-body noncentral potential. The pair correlation functions and the pair analysis technique is applied to reveal the cluster evolution in the process of quick solidification. By using the bond orientation order parameters, we have measured both local and extended orientation symmetries for computer-generated models of dense liquid and glass. A lot of polyhedra in liquid systems, e.g., icosahedra, are also obtained. In order to test the reliance of the computational results, corresponding x-ray diffraction experiments have been performed on the material. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We demonstrate the fabrication of a single electron transistor device based on a single ultra-small silicon quantum dot connected to a gold break junction with a nanometer scale separation. The gold break junction is created through a controllable electromigration process and the individual silicon quantum dot in the junction is determined to be a Si170 cluster. Differential conductance as a function of the bias and gate voltage clearly shows the Coulomb diamond which confirms that the transport is dominated by a single silicon quantum dot. It is found that the charging energy can be as large as 300 meV, which is a result of the large capacitance of a small silicon quantum dot (∼1.8 nm). This large Coulomb interaction can potentially enable a single electron transistor to work at room temperature. The level spacing of the excited state can be as large as 10 meV, which enables us to manipulate individual spin via an external magnetic field. The resulting Zeeman splitting is measured and the g factor of 2.3 is obtained, suggesting relatively weak electron-electron interaction in the silicon quantum dot which is beneficial for spin coherence time. [ABSTRACT FROM AUTHOR]

Graphene nanomeshes (GNMs), new graphene nanostructures with tunable bandgaps, are potential building blocks for future electronic or photonic devices, and energy storage and conversion materials. In previous works, GNMs have been successfully prepared on Cu foils by the H2 etching effect. In this paper, we investigated the effect of Ar on the preparation of GNMs, and how the mean density and shape of them vary with growth time. In addition, scanning electron microscopy (SEM) and high resolution transmission electron microscopy (TEM) revealed the typical hexagonal structure of GNM. Atomic force microscopy (AFM) and x-ray photoelectron spectroscopy (XPS) indicated that large copper oxide nanoparticles produced by oxidization in purified Ar can play an essential catalytic role in preparing GNMs. Then, we exhibited the key reaction details for each growth process and proposed a growth mechanism of GNMs in purified Ar. [ABSTRACT FROM AUTHOR]

A porous ZnO nanoparticle layer coating composed of columnar ZnO nanoparticle piles and a multiple-beveled substrate was used to enhance the light extraction efficiency of GaN-based flip-chip light-emitting diodes (FC-LEDs), which were grown on high-purity SiC substrates. The SiC substrate was multiple-beveled by fabricating an ‘X’ pattern on the face of it, followed by a deposition of a porous ZnO nanoparticle layer on the ‘X’-patterned surface. A porous ZnO nanoparticle layer was fabricated with gas phase cluster beam deposition in a glancing incidence. The incident angular-resolved light transmission of the ZnO nanostructure beyond the critical angle of total internal reflection (TIR) was greatly enhanced. The light output power of the LED was improved by nearly 60% compared to the original planar GaN-based LED on an SiC substrate (FC-SLED), which contained a significant enhancement supplemental to the 18% electroluminescence (EL) enhancement realized with the ‘X’-pattern beveling. We demonstrated that a dual enhancement of light extraction efficiency was achieved by using the hierarchical surface consisting of microscale textures (the multiple-beveled surfaces) and nanoscale structures (the ZnO nanoparticle layers). [ABSTRACT FROM AUTHOR]

Films with discrete diamond-like-carbon (DLC) nanoparticles were prepared by the deposition of the carbon nanoparticle beam. Their morphologies were imaged by scanning electron microscopy and atomic force microscopy (AFM). The nanoparticles were found to be distributed on the silicon (1 0 0) substrate discretely. Hemispherical shapes of the nanoparticles were demonstrated by the AFM line profile. Electron energy loss spectra were measured and an sp3 ratio as high as 86% was found. Field-induced electron emission of the as-prepared cascade (nanoDLC/ Si) was tested and a current density of 1 mA cm[?]2 was achieved at 10.2 V µm[?]1. [ABSTRACT FROM AUTHOR]

Magnetoelectric CoFe2O4-Pb(Zr,Ti)O3 nanostructured films with various phase connectivity patterns were prepared by a pulsed laser deposition method. It was found that the microstructure as well as the phase connectivity pattern of the film varied remarkably with the variation of phase content ratio. All composite nanofilms exhibit evident ferromagnetic and ferroelectric characteristics, as well as distinct magnetoelectric coupling behavior upon increasing the magnetic field. The correlation between the phase connectivity pattern and magnetoelectric coupling behavior for the composite nanofilm was revealed. This work provides an efficient avenue to modulate the magnetoelectric coupling behavior for the ferroelectric-ferromagnetic composite nanofilm. [ABSTRACT FROM AUTHOR]

Stimulated by the experimental synthesis of BN and AlN nanotubes, there has been considerable interest in nanotubes by noncarbon elements. Our density functional calculations show that the graphitic planar structure of ZnO is relatively stable and experimentally accessible. The single-walled nanotubes of ZnO have small strain energies, less than BN tubes of the same size. Hence, under certain experimental conditions, single-walled ZnO nanotubes might be fabricated. The calculated bandgaps of single-walled ZnO nanotubes are relatively uniform (?2 eV) and almost independent of structures, which are located within a range inaccessible to BN, AlN, or GaN nanotubes. [ABSTRACT FROM AUTHOR]

In this work, we report on silver nanocubes with perfect shape prepared by a simple poly(vinyl pyrrolidone)-directed polyol synthesis process. The effects of poly(vinyl pyrrolidone)/AgNO3 ratio R and reaction temperature T on the morphology and size of the products were investigated. Ag nanocubes with an average edge length of 230 nm were obtained successfully with sharp edges and corners under a precise synthesis condition of R = 1 and T = 150°C. The optical properties of Ag nanocubes show an attractive plasma resonance red-shift with size in a wide spectra region. The growth mechanism of the Ag nanocubes is proposed to be thermodynamically and kinetically controlled. [ABSTRACT FROM AUTHOR]

Introduces a series of articles concerning the 12th International Symposium on Small Particles and Inorganic Clusters, published in the July 2005 issue of the "European Physical Journal D".

The structures of free-standing platinum nanowires are systematically investigated by using genetic algorithm simulation with an EAM potential. The magnetic properties are also studied. Several helical multi-shell cylindrical and pentagonal packing structures are observed. These multi-shell structures are composed of coaxial atomic shells with the three and four strand helical, centered pentagonal, and hexagonal, and parallel double chain-core curved surface epitaxy. Under the same growth sequence, the numbers of atomic strands in inner and outer shells exhibit even–odd coupling. [Copyright &y& Elsevier]