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14 May 2012

Volume 100, Issue 20, Articles (20xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 100, 203104 (2012); http://dx.doi.org/10.1063/1.3701731 (4 pages)

Z. Y. Jiang, X. X. Jiang, S. Su, X. P. Wei, S. T. Lee, and Y. He
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Near threshold all-optical backaction amplifier

Terry G. McRae and Warwick P. Bowen

Appl. Phys. Lett. 100, 201101 (2012); http://dx.doi.org/10.1063/1.4717717 (3 pages) | Cited 1 time

Online Publication Date: 14 May 2012

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A near threshold all-optical backaction amplifier is realized. Operating near threshold in an integrated micron scale architecture allows a nearly three orders of magnitude improvement in both gain and optical power requirements over the only previous all-optical implementation, with 37 dB of gain achieved for only 12 μW of input power. Minor parameter adjustment allows narrowband optical filtering.
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42.55.Wd Fiber lasers
42.79.Ci Filters, zone plates, and polarizers
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Thermo-optic switch based on transmission-dip shifting in a double-slot photonic crystal waveguide

Kaiyu Cui, Qiang Zhao, Xue Feng, Yidong Huang, Yongzhuo Li, Da Wang, and Wei Zhang

Appl. Phys. Lett. 100, 201102 (2012); http://dx.doi.org/10.1063/1.4718353 (4 pages) | Cited 4 times

Online Publication Date: 14 May 2012

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Optical switch based on an ultra-compact double-slot photonic crystal waveguide (DS-PCWG) with a titanium/aluminum microheater is demonstrated. The operating principle relies on shifting a transmission-dip caused by the defect mode coupling in photonic band gap (PBG). Based on the unique mode coupling in PBG, low switching power of 9.2 mW and high extinction ratio of 17 dB are achieved experimentally while the length of DS-PCWG is only 16 μm.
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42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks
42.70.Qs Photonic bandgap materials
42.79.Gn Optical waveguides and couplers

Silicon fab-compatible contacts to n-InP and p-InGaAs for photonic applications

S. Jain, M. Sysak, M. Swaidan, and J. Bowers

Appl. Phys. Lett. 100, 201103 (2012); http://dx.doi.org/10.1063/1.4714725 (4 pages)

Online Publication Date: 14 May 2012

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We report on silicon fab-compatible non-gold ohmic contacts to n-InP and p-InGaAs using Ti/W and Pd/Ge/W based metallization schemes where gold is replaced by aluminum as a thick probe layer. Specific contact resistivity of <1 × 10−7 Ω cm2 and < 2 × 10−6 Ω cm2 is obtained on n-InP and p-InGaAs after 450 °C anneal using circular transmission line model (CTLM) patterns. In addition, by varying the atomic ratio of Pd/Ge we, propose a common metal contact to both group III–V epitaxial layers with a specific contact resistivity <1 × 10−5 Ω cm2.
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42.82.-m Integrated optics
73.40.Cg Contact resistance, contact potential

Control of tensile strain in germanium waveguides through silicon nitride layers

A. Ghrib, M. de Kersauson, M. El Kurdi, R. Jakomin, G. Beaudoin, S. Sauvage, G. Fishman, G. Ndong, M. Chaigneau, R. Ossikovski, I. Sagnes, and P. Boucaud

Appl. Phys. Lett. 100, 201104 (2012); http://dx.doi.org/10.1063/1.4718525 (4 pages) | Cited 2 times

Online Publication Date: 15 May 2012

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Germanium ridge waveguides can be tensilely strained using silicon nitride thin films as stressors. We show that the strain transfer in germanium depends on the width of the waveguides. Carrier population in the zone center Γ valley can also be significantly increased when the ridges are oriented along the 〈100〉 direction. We demonstrate an uniaxial strain transfer up to 1% observed on the room temperature direct band gap photoluminescence of germanium. The results are supported by 30 band k·p modeling of the electronic structure and the finite element modeling of the strain field.
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42.79.Gn Optical waveguides and couplers

Plasmons in electrostatically doped graphene

Sukosin Thongrattanasiri, Iván Silveiro, and F. Javier García de Abajo

Appl. Phys. Lett. 100, 201105 (2012); http://dx.doi.org/10.1063/1.4714688 (4 pages) | Cited 5 times

Online Publication Date: 15 May 2012

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Graphene has raised high expectations as a low-loss plasmonic material in which the plasmon properties can be controlled via electrostatic doping. Here, we analyze realistic configurations, which produce inhomogeneous doping, in contrast to what has been so far assumed in the study of plasmons in nanostructured graphene. Specifically, we investigate backgated ribbons, co-planar ribbon pairs placed at opposite potentials, and individual ribbons subject to a uniform electric field. Plasmons in backgated ribbons and ribbon pairs are similar to those of uniformly doped ribbons, provided the Fermi energy is appropriately scaled to compensate for finite-size effects such as the divergence of the carrier density at the edges. In contrast, the plasmons of a ribbon exposed to a uniform field exhibit distinct dispersion and spatial profiles that considerably differ from uniformly doped ribbons. Our results provide a road map to understand graphene plasmons under realistic electrostatic doping conditions.
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73.22.Pr Electronic structure of graphene
71.20.Tx Fullerenes and related materials; intercalation compounds
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
72.80.Vp Electronic transport in graphene

Layer-by-layer thermal conductivities of the Group III nitride films in blue/green light emitting diodes

Zonghui Su, Li Huang, Fang Liu, Justin P. Freedman, Lisa M. Porter, Robert F. Davis, and Jonathan A. Malen

Appl. Phys. Lett. 100, 201106 (2012); http://dx.doi.org/10.1063/1.4718354 (4 pages) | Cited 2 times

Online Publication Date: 16 May 2012

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Thermal conductivities (k) of the individual layers of a GaN-based light emitting diode (LED) were measured along [0001] using the 3-omega method from 100-400 K. Base layers of AlN, GaN, and InGaN, grown by organometallic vapor phase epitaxy on SiC, have effective k much lower than bulk values. The 100 nm thick AlN layer has k = 0.93 ± 0.16 W/mK at 300 K, which is suppressed >100 times relative to bulk AlN. Transmission electron microscope images revealed high dislocation densities (4 × 1010 cm−2) within AlN and a severely defective AlN-SiC interface that cause additional phonon scattering. Resultant thermal resistances degrade LED performance and lifetime making layer-by-layer k, a critical design metric for LEDs.
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66.70.Df Metals, alloys, and semiconductors
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
85.60.Jb Light-emitting devices
81.15.Kk Vapor phase epitaxy; growth from vapor phase

Color control through plasmonic metal gratings

M. A. Vincenti, M. Grande, D. de Ceglia, T. Stomeo, V. Petruzzelli, M. De Vittorio, M. Scalora, and A. D’Orazio

Appl. Phys. Lett. 100, 201107 (2012); http://dx.doi.org/10.1063/1.4718764 (4 pages) | Cited 3 times

Online Publication Date: 16 May 2012

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We experimentally demonstrate the color tuning abilities of two-dimensional periodic arrays of gold nano-patches on silicon substrate. We observe that changes in the geometrical parameters of the array can shift significantly the plasmonic resonance that occurs at the edge of the plasmonic band gap. Experimental proof of this shift is provided by the observation of an important change in the color of the diffracted field. Calculations of the diffracted spectra match the observed color changes very well and provide an efficient means for the design of sensing platforms based on color observation.
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78.66.Bz Metals and metallic alloys
73.22.Lp Collective excitations
42.79.Dj Gratings
71.20.Be Transition metals and alloys

Indium incorporation and emission properties of nonpolar and semipolar InGaN quantum wells

Yuji Zhao, Qimin Yan, Chia-Yen Huang, Shih-Chieh Huang, Po Shan Hsu, Shinichi Tanaka, Chih-Chien Pan, Yoshinobu Kawaguchi, Kenji Fujito, Chris G. Van de Walle, James S. Speck, Steven P. DenBaars, Shuji Nakamura, and Daniel Feezell

Appl. Phys. Lett. 100, 201108 (2012); http://dx.doi.org/10.1063/1.4719100 (4 pages) | Cited 3 times

Online Publication Date: 16 May 2012

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We report indium incorporation properties on various nonpolar and semipolar free-standing GaN substrates. Electroluminescence characterization and x-ray diffraction (XRD) analysis indicate that the semipolar (20mathmath) and (11math2) planes have the highest indium incorporation rate among the studied planes. We also show that both indium composition and polarization-related electric fields impact the emission wavelength of the quantum wells (QWs). The different magnitudes and directions of the polarization-related electric fields for each orientation result in different potential profiles for the various semipolar and nonpolar QWs, leading to different emission wavelengths at a given indium composition.
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78.60.Fi Electroluminescence
78.67.De Quantum wells

Taming the thermal emissivity of metals: A metamaterial approach

N. Mattiucci, G. D’Aguanno, A. Alù, C. Argyropoulos, J. V. Foreman, and M. J. Bloemer

Appl. Phys. Lett. 100, 201109 (2012); http://dx.doi.org/10.1063/1.4719582 (4 pages) | Cited 1 time

Online Publication Date: 16 May 2012

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We demonstrate the possibility of realizing temporally coherent, wide-angle, thermal radiation sources based on the metamaterial properties of metallic gratings. In contrast to other approaches, we do not rely on the excitation of surface waves such as phonon-polaritons, plasmon-polaritons, or guided mode resonances along the grating, nor on the absorption resonances of extremely shallow metallic grating. Instead, we exploit the effective bulk properties of a thick metallic grating below the first diffraction order. We analytically model this physical mechanism of temporally coherent thermal emission based on localized bulk resonances in the grating. We validate our theoretical predictions with full-wave numerical simulations.
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42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
42.79.Dj Gratings
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
63.20.D- Phonon states and bands, normal modes, and phonon dispersion
78.20.N- Thermo-optic effects

Absorption efficiency of gold nanorods determined by quantum dot fluorescence thermometry

L. M. Maestro, P. Haro-González, J. G. Coello, and D. Jaque

Appl. Phys. Lett. 100, 201110 (2012); http://dx.doi.org/10.1063/1.4718605 (4 pages) | Cited 4 times

Online Publication Date: 17 May 2012

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In this work quantum dot fluorescence thermometry, in combination with double-beam confocal microscopy, has been applied to determine the thermal loading of gold nanorods when subjected to an optical excitation at the longitudinal surface plasmon resonance. The absorbing/heating efficiency of low (≈3) aspect ratio gold nanorods has been experimentally determined to be close to 100%, in excellent agreement with theoretical simulations of the extinction, absorption, and scattering spectra based on the discrete dipole approximation.
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78.67.Qa Nanorods
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.68.+m Optical properties of surfaces
78.30.Er Solid metals and alloys
78.40.Kc Metals, semimetals, and alloys
78.55.Hx Other solid inorganic materials

Formation of strong light-trapping nano- and microscale structures on a spherical metal surface by femtosecond laser filament

Haiyan Tao, Jingquan Lin, Zuoqiang Hao, Xun Gao, Xiaowei Song, Changkai Sun, and Xin Tan

Appl. Phys. Lett. 100, 201111 (2012); http://dx.doi.org/10.1063/1.4719108 (3 pages)

Online Publication Date: 17 May 2012

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Nano- and microscale structures on a material surface formed by femtosecond laser processing have greatly changed optical characteristics, wettability, as well as other properties of the material. In this work, we report the formation of nano- and microscale structures on a spherical Al surface with femtosecond laser filament, and find that the filament-processed surface has a strong light-trapping ability from UV to IR (0.2–2.5 μm). Our result demonstrates that this method can be used to process a spherical surface without the complexity of a 4-axis sample control, and in principle, it is applicable to any non-planar sample.
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42.62.-b Laser applications
42.60.-v Laser optical systems: design and operation
42.50.Wk Mechanical effects of light on material media, microstructures and particles
42.82.-m Integrated optics

Accurate in-situ gas temperature measurements in dielectric barrier discharges at atmospheric pressure

Michael R. Wertheimer, Meenu Ahlawat, Bachir Saoudi, and Raman Kashyap

Appl. Phys. Lett. 100, 201112 (2012); http://dx.doi.org/10.1063/1.4719208 (4 pages)

Online Publication Date: 17 May 2012

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Atmospheric pressure (AP) dielectric barrier discharges are frequently of interest for treating delicate substrates such as polymers or biological materials. In spite of its capital importance, thermometry in AP plasmas is subject to much uncertainty. We report temperature measurements in noble gases, nitrogen, and air using sensitive, accurate fibre-optic instrumentation that is a priori immune towards high voltages and high-frequency electromagnetic fields generally encountered in plasma environments.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.80.-s Electric discharges
07.20.Dt Thermometers
52.25.-b Plasma properties

Experimental verification of the concept of all-dielectric nanoantennas

Dmitry S. Filonov, Alexander E. Krasnok, Alexey P. Slobozhanyuk, Polina V. Kapitanova, Elizaveta A. Nenasheva, Yuri S. Kivshar, and Pavel A. Belov

Appl. Phys. Lett. 100, 201113 (2012); http://dx.doi.org/10.1063/1.4719209 (4 pages) | Cited 6 times

Online Publication Date: 17 May 2012

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Being motivated by the recent theoretical proposal of nanoantennas based on high-permittivity dielectric spheres [A. E. Krasnok et al., JETP Lett. 94, 22113 (2011)], we suggest and verify experimentally the concept of all-dielectric antennas in the microwave frequency range. In addition to the electric resonance, each sphere exhibits a very strong magnetic resonance, resulting in a narrow radiation pattern and overall high directivity of such antennas. We find an excellent agreement between the experimental data and numerical results and verify directly high-performance characteristics of such all-dielectric antennas potentially scalable to the nanoscale and operation at the optical frequency range.
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42.79.-e Optical elements, devices, and systems
42.82.-m Integrated optics
77.84.-s Dielectric, piezoelectric, ferroelectric, and antiferroelectric materials

Efficient terahertz generation by optical rectification in Si-LiNbO3-air-metal sandwich structure with variable air gap

Sergey B. Bodrov, Igor E. Ilyakov, Boris V. Shishkin, and Andrey N. Stepanov

Appl. Phys. Lett. 100, 201114 (2012); http://dx.doi.org/10.1063/1.4719674 (3 pages) | Cited 3 times

Online Publication Date: 17 May 2012

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A record high optical-to-terahertz conversion efficiency of 0.25% was realized with femtosecond laser pulses propagated in a planar Si-LiNbO3-air-metal structure. Terahertz spectrum tuning was demonstrated by adjusting an air gap between the LiNbO3 layer and the metal plate. The influence of optical pulse chirp on the efficiency of terahertz generation was investigated.
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85.30.Tv Field effect devices
84.40.-x Radiowave and microwave (including millimeter wave) technology

In situ etched gratings embedded in AlGaAs for efficient high power 970 nm distributed feedback broad-area lasers

C. M. Schultz, P. Crump, A. Maaßdorf, O. Brox, F. Bugge, A. Mogilatenko, H. Wenzel, S. Knigge, B. Sumpf, M. Weyers, G. Erbert, and G. Tränkle

Appl. Phys. Lett. 100, 201115 (2012); http://dx.doi.org/10.1063/1.4718916 (5 pages) | Cited 1 time

Online Publication Date: 18 May 2012

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We report optical nanostructuring technology, developed for distributed feedback gratings, broadly useable for many applications. The nanostructure is pre-structured into aluminum-free layers on top of AlGaAs then etched inside the epitaxy reactor and overgrown with AlGaAs. Oxygen contamination at the grating-interface is ∼3 × 1011 cm−2. These gratings introduce no extra internal optical loss and series resistance in broad-area lasers. Distributed feedback broad-area lasers using this technology achieve optical power >12 W, peak efficiency >60%, wide spectral locking range in current and heatsink temperature (over at least ∼30 °C) and operate at 10 W for >5000 h in a preliminary reliability test.
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42.55.-f Lasers
42.79.Dj Gratings
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A pathway between Bernal and rhombohedral stacked graphene layers with scanning tunneling microscopy

P. Xu, Yurong Yang, D. Qi, S. D. Barber, M. L. Ackerman, J. K. Schoelz, T. B. Bothwell, Salvador Barraza-Lopez, L. Bellaiche, and P. M. Thibado

Appl. Phys. Lett. 100, 201601 (2012); http://dx.doi.org/10.1063/1.4716475 (4 pages) | Cited 3 times

Online Publication Date: 14 May 2012

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Horizontal shifts in the top layer of highly oriented pyrolytic graphite, induced by a scanning tunneling microscope (STM) tip, are presented. Excellent agreement is found between STM images and those simulated using density functional theory. First-principle calculations identify that the low-energy barrier direction of the top layer displacement is toward a structure where none of the carbon pz orbitals overlap, while the high-energy barrier direction is toward AA stacking. Each directional shift yields a real-space surface charge density similar to graphene; however, the low-energy barrier direction requires only one bond length to convert ABA (Bernal) to ABC (rhombohedral).
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68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
61.48.Gh Structure of graphene

Relief of surface stress at steps during displacive adsorption of As on Si(111)

C. X. Zheng, W. X. Tang, and D. E. Jesson

Appl. Phys. Lett. 100, 201602 (2012); http://dx.doi.org/10.1063/1.4718305 (4 pages)

Online Publication Date: 15 May 2012

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The displacive adsorption of As on 1 × 1 Si(111) is examined using surface electron microscopy. High temperature adsorption experiments are used to reduce the As chemical potential and identify regions of enhanced As incorporation in the vicinity of steps. This is explained by a reduction in tensile surface stress associated with 1 × 1 As:Si(111). Cycling the incident As flux on and off creates surface roughening via respective displacive adsorption and evaporation of As. This roughness facilitates increased 1 × 1 As:Si(111) coverage during As deposition due to surface stress relief at steps.
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68.35.Gy Mechanical properties; surface strains
68.43.Fg Adsorbate structure (binding sites, geometry)
68.47.Fg Semiconductor surfaces
61.72.uf Ge and Si
68.35.bg Semiconductors
68.35.Dv Composition, segregation; defects and impurities

Combined microscopies study of the C-contamination induced by extreme-ultraviolet radiation: A surface-dependent secondary-electron-based model

S. Prezioso, M. Donarelli, F. Bisti, L. Palladino, S. Santucci, S. Spadoni, L. Avaro, A. Liscio, V. Palermo, and L. Ottaviano

Appl. Phys. Lett. 100, 201603 (2012); http://dx.doi.org/10.1063/1.4714774 (4 pages) | Cited 1 time

Online Publication Date: 15 May 2012

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SiO2 and Al2O3 surfaces exposed to periodically modulated extreme ultraviolet (EUV) light (λ = 46.9 nm) have been investigated at the μm scale by optical microscopy, scanning electron microscopy, scanning Auger microscopy, atomic force microscopy, and Kelvin probe force microscopy. The formation of a carbon contamination layer preserving the same periodical modulation of the EUV dose has been observed. The mechanisms of hydrocarbon molecules deposition have been studied with the help of correlation plots between the modulated Auger signal and the corresponding EUV dose. A surface-dependent secondary-electron-based model has been proposed.
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61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Ms Insulators
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Ps Atomic force microscopy (AFM)
81.65.-b Surface treatments

Metal-like conductivity exhibited by triboelectrically deposited polyaniline (emeraldine base) particles on microtextured SiC surfaces

I. S. Bayer, V. Caramia, A. Biswas, R. Cingolani, and A. Athanassiou

Appl. Phys. Lett. 100, 201604 (2012); http://dx.doi.org/10.1063/1.4717465 (5 pages) | Cited 1 time

Online Publication Date: 15 May 2012

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We demonstrate a simple and rapid way to deposit layers of polyaniline (emeraldine base) particles on flexible microtextured silicon carbide surfaces by contact charging them using a smooth dielectric rubber. Wetting of the layers by trifluoroacetic acid creates conductive, continuous polymeric films after drying. Pre-functionalization of the textured surfaces with anionic surfactants prevents particle coagulation during contact charging and decreases sheet resistance to metal-like levels (∼60 Ω/□). Conductivity of the films can be tuned by controlling the rate of acid evaporation. Conductive films are highly stable under ambient conditions and show no hysteresis when biased with zero delay-time.
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82.35.Gh Polymers on surfaces; adhesion
68.55.jm Texture
61.41.+e Polymers, elastomers, and plastics
68.08.Bc Wetting
73.40.Cg Contact resistance, contact potential
73.61.Ph Polymers; organic compounds

Interfacial interaction of gas molecules and single-walled carbon nanotubes

Jun Zhong, Jauwern Chiou, Chungli Dong, Per-Anders Glans, Way-Faung Pong, Chinglin Chang, Ziyu Wu, and Jinghua Guo

Appl. Phys. Lett. 100, 201605 (2012); http://dx.doi.org/10.1063/1.4718421 (4 pages) | Cited 2 times

Online Publication Date: 16 May 2012

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The interfacial interaction between single-walled carbon nanotubes (SWNTs) and various gas molecules (H2, He, and N2) at different pressures has been probed by in situ x-ray absorption near-edge structure (XANES) spectroscopy. Experimental results reveal the different strength of interfacial interaction (involving external and internal collisions) between SWNTs and various gas molecules under different pressures. At gas pressures higher than 5 Torr, the unoccupied states of SWNTs show some features corresponding to the structure deformation with a reversible behavior when cycling under vacuum and gas conditions. The XANES study for different gases (H2, He, and N2) shows a strong dependence of gas molecular weight, which provides experimental evidence to the gas scattering mechanism.
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78.70.Dm X-ray absorption spectra
62.20.F- Deformation and plasticity
81.40.Lm Deformation, plasticity, and creep

Annealing dependence of diamond-metal Schottky barrier heights probed by hard x-ray photoelectron spectroscopy

M. Gaowei, E. M. Muller, A. K. Rumaiz, C. Weiland, E. Cockayne, J. Jordan-Sweet, J. Smedley, and J. C. Woicik

Appl. Phys. Lett. 100, 201606 (2012); http://dx.doi.org/10.1063/1.4718028 (4 pages) | Cited 3 times

Online Publication Date: 17 May 2012

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Hard x-ray photoelectron spectroscopy was applied to investigate the diamond-metal Schottky barrier heights for several metals and diamond surface terminations. The position of the diamond valence-band maximum was determined by theoretically calculating the diamond density of states and applying cross section corrections. The diamond-platinum Schottky barrier height was lowered by 0.2 eV after thermal annealing, indicating annealing may increase carrier injection in diamond devices leading to photoconductive gain. The platinum contacts on oxygen-terminated diamond was found to provide a higher Schottky barrier and therefore a better blocking contact than that of the silver contact in diamond-based electronic devices.
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73.40.Ns Metal-nonmetal contacts
79.60.Jv Interfaces; heterostructures; nanostructures
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
71.20.Mq Elemental semiconductors
72.40.+w Photoconduction and photovoltaic effects
73.30.+y Surface double layers, Schottky barriers, and work functions

High mobility of the strongly confined hole gas in AgTaO3/SrTiO3

S. Nazir, M. Upadhyay Kahaly, and U. Schwingenschlögl

Appl. Phys. Lett. 100, 201607 (2012); http://dx.doi.org/10.1063/1.4719106 (4 pages)

Online Publication Date: 18 May 2012

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A theoretical study of the two-dimensional hole gas at the (AgO)−/(TiO2)0 p-type interface in the AgTaO3/SrTiO3 (001) heterostructure is presented. The Ag 4d states strongly hybridize with the O 2p states and contribute to the hole gas. It is demonstrated that the holes are confined to an ultra thin layer ( ∼ 4.9Å) with a considerable carrier density of ∼ 1014cm-2. We estimate a hole mobility of 18.6 cm2 V−1 s−1, which is high enough to enable device applications.
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73.40.-c Electronic transport in interface structures
73.20.Qt Electron solids
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On the characteristic length scales associated with plastic deformation in metallic glasses

P. Murali, Y. W. Zhang, and H. J. Gao

Appl. Phys. Lett. 100, 201901 (2012); http://dx.doi.org/10.1063/1.4717744 (4 pages) | Cited 2 times

Online Publication Date: 14 May 2012

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Atomistic simulations revealed that the spatial correlations of plastic displacements in three metallic glasses, FeP, MgAl, and CuZr, follow an exponential law with a characteristic length scale ℓc that governs Poisson’s ratio ν, shear band thickness tSB, and fracture mode in these materials. Among the three glasses, FeP exhibits smallest ℓc, thinnest tSB, lowest ν, and brittle fracture; CuZr exhibits largest ℓc, thickest tSB, highest ν, and ductile fracture, while properties of MgAl lie in between those of FeP and CuZr. These findings corroborate well with existing experimental observations and suggest ℓc as a fundamental measure of the shear transformation zone size in metallic glasses.
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81.05.Kf Glasses (including metallic glasses)
81.40.Jj Elasticity and anelasticity, stress-strain relations
81.40.Lm Deformation, plasticity, and creep
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.fq Plasticity and superplasticity
81.05.Bx Metals, semimetals, and alloys

Ring-shaped NdFeB-based magnetic tweezers enables oscillatory microrheology measurements

Jun Lin and Megan T. Valentine

Appl. Phys. Lett. 100, 201902 (2012); http://dx.doi.org/10.1063/1.4717988 (4 pages) | Cited 1 time

Online Publication Date: 14 May 2012

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We present the design and characterization of a magnetic tweezers device that employs a ring-shaped neodymium iron boron (NdFeB) magnet. Because the gradient of the magnetic field generated by ring magnets changes sign along its symmetry axis, magnetic tweezers devices that employ ring magnets can both push and pull on microscale magnetic beads, opening new avenues for the micromanipulation of soft materials. We demonstrate the application of such a device to oscillatory microrheology measurements of soft networks of microtubules, an essential cellular biopolymer.
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85.70.Ay Magnetic device characterization, design, and modeling
87.17.-d Cell processes

Nonlinear size-dependent melting of the silica-encapsulated silver nanoparticles

Chengying Tang (唐成颖), Yun-Mo Sung, and Joonho Lee

Appl. Phys. Lett. 100, 201903 (2012); http://dx.doi.org/10.1063/1.4712599 (3 pages)

Online Publication Date: 14 May 2012

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In spite of the recent report of the in situ high-resolution transmission electron microscopy observation of the melting of Ag nanoparticles (NPs) in Chen et al. [Appl. Phys. Lett. 96, 253104 (2010)], no consistent experimental investigation coupled with theoretical analysis has been reported so far. We report the size-dependence of the melting temperature (Tm) of Ag NPs by both differential scanning calorimetry experiments and thermodynamic assessments. Thermodynamically calculated Tm for the Ag NPs showed a nonlinear function with respect to the inverse of the particle size and agreed well with the present and reported experimental results within an error of 1 K.
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64.70.Nd Structural transitions in nanoscale materials
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
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