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8 Oct 2012

Volume 101, Issue 15, Articles (15xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 101, 153501 (2012); http://dx.doi.org/10.1063/1.4756693 (3 pages)

Brandon G. Cook, William R. French, and Kálmán Varga
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Helical domain walls in constricted cylindrical NiFe nanowires

M. Chandra Sekhar, H. F. Liew, I. Purnama, W. S. Lew, M. Tran, and G. C. Han

Appl. Phys. Lett. 101, 152406 (2012); http://dx.doi.org/10.1063/1.4758469 (5 pages) | Cited 2 times

Online Publication Date: 11 October 2012

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Reducing the magnetic shape anisotropy of a cylindrical NiFe nanowire allows the formation of two vortices with opposite chirality at the two ends. At relatively low aspect ratio these two vortices are connected via a gradual rotation of the magnetization over a short region, which forms a three-dimensional helical domain wall. Micromagnetic simulations reveal that it is possible to control the number of helical domain walls in the cylindrical nanowire by geometrical constrictions engineering. A technique to create constricted Ni95Fe5/Ni87Fe13 multilayered nanowires is demonstrated, and magnetic force microscopy imaging was carried out to confirm the prediction of simulated helical domain walls.
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75.60.Ch Domain walls and domain structure
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.75.-c Magnetic properties of nanostructures
75.78.Cd Micromagnetic simulations
75.50.Bb Fe and its alloys
75.50.Tt Fine-particle systems; nanocrystalline materials

Observation of spin dependent photocoductivity in InSb quantum well nanowires

Juerong Li, A. M. Gilbertson, K. L. Litvinenko, L. F. Cohen, and S. K. Clowes

Appl. Phys. Lett. 101, 152407 (2012); http://dx.doi.org/10.1063/1.4760223 (4 pages)

Online Publication Date: 12 October 2012

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We report on the electrical detection of spin dependent photoconductivity in 500 nm wide InSb quantum well nanowires using the optical orientation of electron spins. By applying weak magnetic fields ( ≈ 200 mT), we observe a spin filtering effect of classical origin caused by spin dependent back scattering of electrons from the sidewalls. Spin dependent features in the longitudinal photovoltage decay with temperature and disappears at characteristic energy ( ≈ 50 K) consistent with the theoretical spin splitting and the thermal level broadening. We show that the observed signal is due to the inversion asymmetry of the quantum well, with an additional Zeeman contribution.
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72.40.+w Photoconduction and photovoltaic effects
73.63.Hs Quantum wells
78.67.De Quantum wells
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Complex transport behavior accompanying domain switching in La0.1Bi0.9FeO3 sandwiched capacitors

R. L. Gao, Y. S. Chen, J. R. Sun, Y. G. Zhao, J. B. Li, and B. G. Shen

Appl. Phys. Lett. 101, 152901 (2012); http://dx.doi.org/10.1063/1.4757987 (5 pages) | Cited 1 time

Online Publication Date: 8 October 2012

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Polarization-modulated resistive switching and fatigue behaviors of the Ag/La0.1Bi0.9FeO3/La0.7Sr0.3MnO3 capacitors have been investigated. The device resistance is found to show a V-shaped dependence on poling voltage, and the lowest resistance appears at the voltage corresponding to the coercive field of La0.1Bi0.9FeO3. Based on this relation, three distinct resistance states can be achieved by applying appropriate pulse trains, which manifests a potential application in high-density storage technology. The fatigue properties of the sample under repeated bipolar or unipolar pulses were further analyzed. Bipolar pulses enhance the rectifying characters of the current-voltage relation, whereas unipolar pulses produce a reverse effect. Based on impedance analysis, we propose the formation of leakage paths along conductive domain walls, and it is the domain reconstruction during repeated polarization flipping that results in the complex transport behavior observed.
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84.32.Tt Capacitors
62.20.me Fatigue
77.80.Dj Domain structure; hysteresis
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure

Resonances in ferroelectric phononic superlattice

Igor Ostrovskii and Lucien Cremaldi

Appl. Phys. Lett. 101, 152902 (2012); http://dx.doi.org/10.1063/1.4757989 (4 pages)

Online Publication Date: 8 October 2012

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The periodically poled ferroelectric wafer is a two-dimensional phononic superlattice. The important applications of such a solid include ultrasonic transducers at the micro/nano-scale for low intensity ultra-sonography, ferroelectric data storage, and development of very high frequency chips for next generation communication and information technologies, and others. In this work, we show theoretically and experimentally that a ferroelectric phononic superlattice has two distinctive resonances in acousto-electric transformation. They are associated with a split acoustic mode at the boundary between the first and second acoustic Brillouin zone.
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63.20.D- Phonon states and bands, normal modes, and phonon dispersion
72.50.+b Acoustoelectric effects
77.80.Dj Domain structure; hysteresis

Roles of Schottky barrier and oxygen vacancies in the electroforming of SrTiO3

Xin Guo

Appl. Phys. Lett. 101, 152903 (2012); http://dx.doi.org/10.1063/1.4759030 (4 pages) | Cited 1 time

Online Publication Date: 10 October 2012

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Single crystalline SrTiO3 was used as a model system to evaluate the roles of the Schottky barrier and oxygen vacancies in electroforming. An advantage of single crystalline SrTiO3 is that the electrochemical processes at intermediate temperatures have been thoroughly investigated. To take this advantage, the electroforming was performed at 200 °C and subsequently at 24 °C; an electrical stress of 4 × 103 V/cm, which was about two orders of magnitude lower than the electrical stress in previous works, decreased the cell resistance by orders of magnitude. After the electroforming, bipolar resistive switching was realized at 24 °C.
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73.30.+y Surface double layers, Schottky barriers, and work functions
61.72.jd Vacancies
82.45.-h Electrochemistry and electrophoresis

Significant enhancement in energy density of polymer composites induced by dopamine-modified Ba0.6Sr0.4TiO3 nanofibers

Yu Song, Yang Shen, Penghao Hu, Yuanhua Lin, Ming Li, and C. W. Nan

Appl. Phys. Lett. 101, 152904 (2012); http://dx.doi.org/10.1063/1.4760228 (3 pages)

Online Publication Date: 11 October 2012

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Ba0.6Sr0.4TiO3 (BST) nanofibers prepared via electrospinning and modified by dopamine are used as dielectric fillers in polyvinylidene fluoride (PVDF)-based composites. With 4.4 vol. % of BST nanofibers, the extractable energy density of the BST/PVDF composites is more than doubled as compared with pure PVDF matrix. Such significant enhancement is attributed to the combined effect of both surface modification by dopamine and large aspect ratio of the BST nanofibers. Paraelectric or anti-ferroelectric fillers of large aspect ratio may serve as a general strategy for enhanced electric energy density in polymer composites.
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81.16.-c Methods of micro- and nanofabrication and processing
77.84.Lf Composite materials
77.80.-e Ferroelectricity and antiferroelectricity
61.46.-w Structure of nanoscale materials

Magnetic field-dependent effective microwave properties of microwire-epoxy composites

F. X. Qin, H. X. Peng, J. Fuller, and C. Brosseau

Appl. Phys. Lett. 101, 152905 (2012); http://dx.doi.org/10.1063/1.4758483 (5 pages) | Cited 1 time

Online Publication Date: 11 October 2012

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In this work, we report on the observation of the electromagnetic parameters of glass-covered amorphous microwires/epoxy composites with various concentrations of microwires over a broad magnetic field range up to 1 kOe. The effective permittivity presents a strong tunability with respect to a dc magnetic field excitation. An inherent crossover field due to the microwires is further observed at 300 Oe suggesting that the giant magnetoimpedance effect dominates the features of dipolar absorption at low magnetic field bias (<300 Oe), while the opposite behavior is expected at larger dc magnetic field excitations. This crossover field is found to be insensitive to changes in the microwire content.
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75.47.De Giant magnetoresistance
72.20.My Galvanomagnetic and other magnetotransport effects
77.22.Ch Permittivity (dielectric function)

Crystal structure of 0.96(Na0.5Bi0.5TiO3)–0.04(BaTiO3) from combined refinement of x-ray and neutron diffraction patterns

T.-M. Usher, J. S. Forrester, C. R. dela Cruz, and J. L. Jones

Appl. Phys. Lett. 101, 152906 (2012); http://dx.doi.org/10.1063/1.4759117 (4 pages)

Online Publication Date: 12 October 2012

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High-resolution x-ray and neutron diffraction of (0.96)Na0.5Bi0.5TiO3–(0.04)BaTiO3 (NBT-4BT) reveal subtle structural distortions that evidence lower symmetry than allowed in the R3c space group. The combined refinement that best models the diffraction patterns is a two phase mixture of a monoclinic Cc phase and a minor fraction of a metrically cubic Pmmathm phase (13 wt. %). The cubic phase is utilized to account for nanometer-scale regions whose local deviations from the long-range symmetry are not observed, such as polar nano-regions or tetragonal platelets. This suggests that the low symmetry found in the NBT-rich phases extends from 0 at. % to at least 4 at. % BT.
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61.66.Fn Inorganic compounds
81.30.Bx Phase diagrams of metals, alloys, and oxides
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Antenna effect in laser assisted atom probe tomography: How the field emitter aspect ratio can enhance atomic scale imaging

L. Arnoldi, A. Vella, J. Houard, and B. Deconihout

Appl. Phys. Lett. 101, 153101 (2012); http://dx.doi.org/10.1063/1.4757884 (4 pages)

Online Publication Date: 8 October 2012

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In this Letter, we show that, in contrast to what is generally admitted in laser assisted atom probe, it is possible to probe a tip under optimal analysis conditions using a single wavelength. We show that the field emitter geometry can be adjusted to the wavelength of the femtosecond laser pulses used to trigger the evaporation by taking into account the optical and thermal properties of the material. The resulting enhanced absorption at the tip apex generates an ultrafast ion emission leading to a surprisingly high mass resolving power and signal over noise ratio on materials having a bad thermal diffusivity. This antenna effect is discussed based on theoretical considerations and a modeling of the laser-tip interaction. It is then demonstrated though experimental results obtained on different specimen geometries.
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78.47.J- Ultrafast spectroscopy (<1 psec)
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Theory of the suspended graphene varactor

M. AbdelGhany, E. Ledwosinska, and T. Szkopek

Appl. Phys. Lett. 101, 153102 (2012); http://dx.doi.org/10.1063/1.4757991 (4 pages)

Online Publication Date: 8 October 2012

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We report the theory and design equations of the suspended graphene varactor, wherein device capacitance is tuned by the voltage controlled deflection of a suspended graphene membrane. A simple model based on large membrane deflection predicts a capacitor tuning range of 76%, with a membrane pull-in voltage tuneable from 1 V to 30 V. An intrinsic electric quality factor approaching 200 is predicted based on experimentally determined Young's modulus and sheet resistance.
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84.32.Tt Capacitors
85.30.Kk Junction diodes
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices

Hydrogen segregation and lattice reorientation in palladium hydride nanowires

J. H. He, D. L. Knies, G. K. Hubler, K. S. Grabowski, R. J. Tonucci, and L. F. Dechiaro

Appl. Phys. Lett. 101, 153103 (2012); http://dx.doi.org/10.1063/1.4757999 (3 pages)

Online Publication Date: 8 October 2012

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We study palladium hydride nanowires of different sizes and hydrogen concentrations at 300 K using molecular dynamic simulations. Strong surface segregation of hydrogen with a depletion zone behind is observed in the palladium hydride nanowires. We also show that lattice reorientation is controlled by the hydrogen concentration as well as the nanowire size. The interplay of surface stresses and hydrogen induced stresses is responsible for the observations.
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68.35.Dv Composition, segregation; defects and impurities
02.60.-x Numerical approximation and analysis
61.46.Bc Structure of clusters (e.g., metcars; not fragments of crystals; free or loosely aggregated or loosely attached to a substrate)

Ultra low field electron emission of graphene exfoliated from carbon cloth

Jianlong Liu (柳建龙), Baoqing Zeng (曾葆青), Xiangru Wang (汪相如), Jinfeng Zhu (朱锦锋), and Ying Fan (范英)

Appl. Phys. Lett. 101, 153104 (2012); http://dx.doi.org/10.1063/1.4758291 (4 pages) | Cited 1 time

Online Publication Date: 8 October 2012

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Graphene emitters with high enhancement factor and ultra low emission field were exfoliated from carbon fibers in carbon cloth. This method made the graphene sheets to stay on the carbon fiber and were used, in situ, as emitters. Due to their high multistage enhancement factor and intrinsic good contact, electron emission from these graphene sheets required ultra low emission field. The threshold-field corresponding to emission current density of 1 mA/cm2 was about 0.7 V/μm. This high enhancement factor was attributed to the effects of the high aspect ratio of graphene sheets and the geometry of carbon cloth.
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79.70.+q Field emission, ionization, evaporation, and desorption

High quality ultrathin Bi2Se3 films on CaF2 and CaF2/Si by molecular beam epitaxy with a radio frequency cracker cell

Li Zhang, Robert Hammond, Merav Dolev, Min Liu, Alexander Palevski, and Aharon Kapitulnik

Appl. Phys. Lett. 101, 153105 (2012); http://dx.doi.org/10.1063/1.4758466 (4 pages) | Cited 2 times

Online Publication Date: 8 October 2012

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We report a method to fabricate high quality Bi2Se3 thin films using molecular beam epitaxy with a radio frequency cracker cell as an atomic selenium source. With Se-to-Bi ratios close to exact stoichiometry, optimal layer-by-layer growth of high quality Bi2Se3 thin films with smooth surfaces has been achieved on CaF2(111) substrates and Si(111) substrates with a thin epitaxial CaF2 buffer layer (CaF2/Si). Transport measurements show a characteristic weak-antilocalization magnetoresistance in all the films, with the emergence of a weak-localization contribution in the ultrathin film limit. Quantum oscillations, attributed to the topological surface states have been observed, including in films grown on CaF2/Si.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.aj Insulators
72.20.My Galvanomagnetic and other magnetotransport effects
73.20.At Surface states, band structure, electron density of states
73.20.Fz Weak or Anderson localization
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

Improvement of resistive switching in NiO-based nanowires by inserting Pt layers

Yen-Chun Huang, Po-Yuan Chen, Tsung-Shune Chin, Ru-Shi Liu, Chao-Yuan Huang, and Chih-Huang Lai

Appl. Phys. Lett. 101, 153106 (2012); http://dx.doi.org/10.1063/1.4758482 (4 pages)

Online Publication Date: 8 October 2012

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Nonpolar resistive switching is demonstrated in polycrystalline NiO-based nanowires. The lower switching voltages and narrower switching distributions are exhibited in multilayered NiO/Pt nanowires, compared to the monolithic NiO nanowires. The temperature dependence of resistance at low resistance state reveals the conduction is attributed to the hopping through percolation paths composed of oxygen-related defects. The inserted Pt layers behave as intermediate electrodes to reduce migration length of oxygen ions and to store the oxygen ions near the electrodes. Therefore, the localized formation/migration of oxygen ions confines the occurrence of percolation paths, leading to improvement of the switching parameters.
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73.63.Nm Quantum wires
61.46.Km Structure of nanowires and nanorods (long, free or loosely attached, quantum wires and quantum rods, but not gate-isolated embedded quantum wires)

74-fs nanotube-mode-locked fiber laser

D. Popa, Z. Sun, T. Hasan, W. B. Cho, F. Wang, F. Torrisi, and A. C. Ferrari

Appl. Phys. Lett. 101, 153107 (2012); http://dx.doi.org/10.1063/1.4757293 (4 pages) | Cited 2 times

Online Publication Date: 8 October 2012

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We report an erbium-doped, nanotube mode-locked fiber oscillator generating 74 fs pulses with 63 nm spectral width. This all-fiber-based laser is a simple, low-cost source for time-resolved optical spectroscopy, as well as for many applications where high resolution driven by short pulse durations is required.
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42.55.Wd Fiber lasers
42.60.-v Laser optical systems: design and operation
42.60.Fc Modulation, tuning, and mode locking
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.65.Yj Optical parametric oscillators and amplifiers

Assembled Fe3O4 nanoparticles on graphene for enhanced electromagnetic wave losses

P. F. Guan, X. F. Zhang, and J. J. Guo

Appl. Phys. Lett. 101, 153108 (2012); http://dx.doi.org/10.1063/1.4758931 (4 pages) | Cited 2 times

Online Publication Date: 9 October 2012

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We present an one-step procedure for the synthesis of hybrid Fe3O4 nanoparticles/graphene composite with self-assemble superlattices of Fe3O4 nanoparticles. We find that the Fe3O4/graphene nanocomposite exhibits both enhanced dielectric losses and magnetic losses at 2–18 GHz, resulting from the interfacial polarizations between the Fe3O4 nanoparticles and the graphene, as well as the coupling between the neighbouring Fe3O4 nanoparticles. Theoretical simulations uncover the origins of the electromagnetic losses of hybrid Fe3O4/graphene nanocomposite and provide additional insight into the microscopic dielectric polarization mechanism.
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81.16.Dn Self-assembly
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
77.22.Ej Polarization and depolarization
77.22.Gm Dielectric loss and relaxation
75.75.Cd Fabrication of magnetic nanostructures

Electronic structures of single-layer boron pnictides

Houlong L. Zhuang and Richard G. Hennig

Appl. Phys. Lett. 101, 153109 (2012); http://dx.doi.org/10.1063/1.4758465 (4 pages)

Online Publication Date: 9 October 2012

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Single-layer materials such as graphene and boron nitride promise alternative routes to electronic devices. Hybrid density functional calculations for single-layer boron pnictides boron nitride (BN), boron phosphide (BP), boron arsenide (BAs), and boron antimonide (BSb) show that these materials exhibit a direct bandgap of 6.1, 1.4, 1.2, and 0.6 eV, respectively, that originates from the energy difference of the pz orbitals of the species and is tunable by strain. The bandgap linearly decreases with strain for BN, while it increases non-linearly for BP, BAs, and BSb. The calculated natural band offsets between the various boron pnictides are all of type I.
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71.20.Nr Semiconductor compounds
71.20.Ps Other inorganic compounds
71.15.Mb Density functional theory, local density approximation, gradient and other corrections

Highly efficient potentiometric glucose biosensor based on functionalized InN quantum dots

N. H. Alvi, P. E. D. Soto Rodriguez, V. J. Gómez, Praveen Kumar, G. Amin, O. Nur, M. Willander, and R. Nötzel

Appl. Phys. Lett. 101, 153110 (2012); http://dx.doi.org/10.1063/1.4758701 (4 pages)

Online Publication Date: 9 October 2012

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We present a fast, highly sensitive, and efficient potentiometric glucose biosensor based on functionalized InN quantum-dots (QDs). The InN QDs are grown by molecular beam epitaxy. The InN QDs are bio-chemically functionalized through physical adsorption of glucose oxidase (GOD). GOD enzyme-coated InN QDs based biosensor exhibits excellent linear glucose concentration dependent electrochemical response against an Ag/AgCl reference electrode over a wide logarithmic glucose concentration range (1 × 10−5 M to 1 × 10−2 M) with a high sensitivity of 80 mV/decade. It exhibits a fast response time of less than 2 s with good stability and reusability and shows negligible response to common interferents such as ascorbic acid and uric acid. The fabricated biosensor has full potential to be an attractive candidate for blood sugar concentration detection in clinical diagnoses.
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87.85.Ox Biomedical instrumentation and transducers, including micro-electro-mechanical systems (MEMS)
87.14.ej Enzymes
82.47.Rs Electrochemical sensors
81.07.Ta Quantum dots
81.05.Ea III-V semiconductors
73.61.Ey III-V semiconductors

Self-consistently modeling the electronic behavior of “active” nanostructures: Scaling of ionized donor density at the nanoscale

Owen L. Williams, Paul Rees, and Steve P. Wilks

Appl. Phys. Lett. 101, 153111 (2012); http://dx.doi.org/10.1063/1.4756790 (4 pages)

Online Publication Date: 10 October 2012

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We present a powerful and versatile method for calculating the electronic properties of real nanostructures. It is applied to a spherical quantum dot, self-consistently reconciling the non-linear Poisson equation with the Kohn-Sham equations, balancing the charge in the surface states and the “bulk” (dot interior). Excellent agreement is obtained between theory and experiment, with the model predicting a spatial dependency of donor ionization for dots below 10 nm radii. This has far reaching implications for nano-device design.
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73.21.La Quantum dots
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
71.20.Nr Semiconductor compounds
71.55.Ht Other nonmetals
73.20.At Surface states, band structure, electron density of states
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Capillary filling dynamics of water in nanopores

Chirodeep Bakli and Suman Chakraborty

Appl. Phys. Lett. 101, 153112 (2012); http://dx.doi.org/10.1063/1.4758683 (5 pages) | Cited 1 time

Online Publication Date: 10 October 2012

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We portray a universal description of dynamic slip-stick behavior of water flowing through nanoscale pores. Based on fundamental molecular transport considerations, we derive a generalized constitutive model for describing resistive forces acting on the water column in a capillary that is being dynamically filled, as a combined function of the meniscus height, surface wettability, and roughness. This effectively acts like a unique signature of nanopore imbibition characteristics of water, which, when substituted in a simple one-dimensional force balance model agrees quantitatively with results from molecular dynamics simulations for a general class of problems, without necessitating the employment of any artificially tunable fitting parameters.
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68.03.Cd Surface tension and related phenomena
47.56.+r Flows through porous media
62.10.+s Mechanical properties of liquids
61.20.Ja Computer simulation of liquid structure
68.08.Bc Wetting
47.55.nb Capillary and thermocapillary flows
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Silver nanoisland enhanced Raman interaction in graphene

Alexander Urich, Andreas Pospischil, Marco M. Furchi, Daniel Dietze, Karl Unterrainer, and Thomas Mueller

Appl. Phys. Lett. 101, 153113 (2012); http://dx.doi.org/10.1063/1.4758696 (4 pages) | Cited 2 times

Online Publication Date: 10 October 2012

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Graphene shows great potential for optoelectronic applications but suffers from rather weak interaction with light due its single-atomic thickness. Here, we report the enhanced interaction of graphene and light for Raman transitions using localized surface plasmons. The plasmons are generated in silver nanoislands that we fabricate by simple means of metal deposition on top of graphene. Despite the broad size distribution of the nanoislands, we find a 100-fold enhancement of the Raman signal. We provide an analytical model for the description of the optical properties and obtain the scattering cross section as well as enhancement factors for the Raman transitions. In addition, we investigate, both optically and electrically, the doping that is introduced by the nanoislands.
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78.30.Hv Other nonmetallic inorganics
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
81.07.Bc Nanocrystalline materials

An alternative approach to efficient simulation of micro/nanoscale phonon transport

Jean-Philippe M. Péraud and Nicolas G. Hadjiconstantinou

Appl. Phys. Lett. 101, 153114 (2012); http://dx.doi.org/10.1063/1.4757607 (4 pages) | Cited 1 time

Online Publication Date: 10 October 2012

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Starting from the recently proposed energy-based deviational formulation for solving the Boltzmann equation [J.-P. Péraud and N. G. Hadjiconstantinou, Phys. Rev. B 84, 205331 (2011)], which provides significant computational speedup compared to standard Monte Carlo methods for small deviations from equilibrium, we show that additional computational benefits are possible in the limit that the governing equation can be linearized. The proposed method exploits the observation that under linearized conditions (small temperature differences) the trajectories of individual deviational particles can be decoupled and thus simulated independently; this leads to a particularly simple and efficient algorithm for simulating steady and transient problems in arbitrary three-dimensional geometries, without introducing any additional approximation.
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63.20.D- Phonon states and bands, normal modes, and phonon dispersion
05.60.-k Transport processes

Embedded TiO2 waveguides for sensing nanofluorophores in a microfluidic channel

Masayuki Furuhashi, Masazumi Fujiwara, Takahito Ohshiro, Kazuki Matsubara, Makusu Tsutsui, Masateru Taniguchi, Shigeki Takeuchi, and Tomoji Kawai

Appl. Phys. Lett. 101, 153115 (2012); http://dx.doi.org/10.1063/1.4757759 (4 pages)

Online Publication Date: 10 October 2012

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Crossed structure of a microfluidic channel and an optical channel waveguide is simple and promising to realize detection of weak fluorescence on an integrated device. Usage of TiO2 waveguides is suitable for the device because of the high numerical aperture. In this study, we developed fabrication processes for the TiO2 channel waveguides traversed by microfluidic channels of 0.5–6 μm widths and investigated the effect of the microfluidic channel to the transmittances. The results elucidated that the photointensity at the microfluidic channel was enough to excite fluorophores. Furthermore, we demonstrated detection of fluorescence from 350 quantum dots.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
42.79.Gn Optical waveguides and couplers
42.82.Et Waveguides, couplers, and arrays
47.85.Np Fluidics
78.55.Hx Other solid inorganic materials
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices

Phase-locked loop based on nanoelectromechanical resonant-body field effect transistor

S. T. Bartsch, A. Rusu, and A. M. Ionescu

Appl. Phys. Lett. 101, 153116 (2012); http://dx.doi.org/10.1063/1.4758991 (5 pages)

Online Publication Date: 11 October 2012

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We demonstrate the room-temperature operation of a silicon nanoelectromechanical resonant-body field effect transistor (RB-FET) embedded into phase-locked loop (PLL). The very-high frequency resonator uses on-chip electrostatic actuation and transistor-based displacement detection. The heterodyne frequency down-conversion based on resistive FET mixing provides a loop feedback signal with high signal-to-noise ratio. We identify key parameters for PLL operation, and analyze the performance of the RB-FET at the system level. Used as resonant mass detector, the experimental frequency stability in the ppm-range translates into sub atto-gram (10−18 g) sensitivity in high vacuum. The feedback and control system are generic and may be extended to other mechanical resonators with transistor properties, such as graphene membranes and carbon nanotubes.
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85.30.Tv Field effect devices
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
84.30.Qi Modulators and demodulators; discriminators, comparators, mixers, limiters, and compressors

Enhanced radiation tolerance in nitride multilayered nanofilms with small period-thicknesses

Mengqing Hong, Feng Ren, Hongxiu Zhang, Xiangheng Xiao, Bing Yang, Canxin Tian, Dejun Fu, Yongqiang Wang, and Changzhong Jiang

Appl. Phys. Lett. 101, 153117 (2012); http://dx.doi.org/10.1063/1.4759004 (5 pages)

Online Publication Date: 11 October 2012

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This paper demonstrates a substantial enhancement in radiation tolerance for small period-thickness of CrN/AlTiN multilayered nanofilms. CrN/AlTiN multilayered nanofilms with period-thicknesses of 3, 5, 7, and 9 nm were irradiated by 190 keV Ar+ ions to fluences ranging from 1 to 5 × 1016 ions/cm2. Nanofilm with 3 nm period-thickness begins to be amorphized under 5 × 1016 ions/cm2, while those with larger period-thicknesses are amorphized under 3 × 1016 ions/cm2. Our results show that multilayered ceramic nanofilms are potential radiation tolerant materials with good properties. The interfaces in the multilayered nanofilms act as good sinks to absorb the radiation-induced defects.
Show PACS
61.80.Jh Ion radiation effects
61.82.Ms Insulators
68.65.Ac Multilayers
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