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18 Jun 2012

Volume 100, Issue 25, Articles (25xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 100, 252401 (2012); http://dx.doi.org/10.1063/1.4727909 (4 pages)

Ming Yan, Christian Andreas, Attila Kákay, Felipe García-Sánchez, and Riccardo Hertel
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Efficient single-photon extraction from quantum-dots embedded in GaAs micro-pyramids

Daniel Rülke, Daniel M. Schaadt, Heinz Kalt, and Michael Hetterich

Appl. Phys. Lett. 100, 251101 (2012); http://dx.doi.org/10.1063/1.4729482 (4 pages)

Online Publication Date: 18 June 2012

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We demonstrate an easy method to fabricate efficient single-photon sources based on In(Ga)As quantum-dots embedded in reversed GaAs micro-pyramids. It relies on a single wet-chemical etching step utilizing an AlAs sacrificial layer. Due to the pyramidal shape of the cavities, we have been able to separate a small number of quantum-dots from the self-assembled ensemble and improve the extraction efficiency for single photons. The latter is predicted by finite difference time domain and finite elements method simulations to be about 80%–90% over a broad spectral range of 40 nm. Single-photon emission has been proven experimentally by means of auto-correlation measurements.
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81.07.Ta Quantum dots
02.70.Dh Finite-element and Galerkin methods
81.16.Dn Self-assembly
81.05.Ea III-V semiconductors

Investigation of green InGaN light-emitting diodes with asymmetric AlGaN composition-graded barriers and without an electron blocking layer

Yi-An Chang, Jih-Yuan Chang, Yih-Ting Kuo, and Yen-Kuang Kuo

Appl. Phys. Lett. 100, 251102 (2012); http://dx.doi.org/10.1063/1.4729880 (4 pages) | Cited 3 times

Online Publication Date: 19 June 2012

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In this study, a green InGaN light-emitting diode with asymmetric AlGaN composition-graded barriers and without the use of an AlGaN electron blocking layer is presented to possess markedly enhanced optical and electrical performance. The simulation results show that the output power is increased by 10.0% and 33.2%, which corresponds to an increment of 7% and 29.4% in internal quantum efficiency, at 100 mA when the conventional GaN barriers are replaced by the asymmetric AlGaN composition-graded barriers and the commonly used AlGaN electron blocking layer is removed. The simulation results suggest that the improved device performance is due mainly to the markedly enhanced injection of holes into the active region.
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85.60.Jb Light-emitting devices

Single GaInP nanowire p-i-n junctions near the direct to indirect bandgap crossover point

Jesper Wallentin, Laura Barrutia Poncela, Anna M. Jansson, Kilian Mergenthaler, Martin Ek, Daniel Jacobsson, L. Reine Wallenberg, Knut Deppert, Lars Samuelson, Dan Hessman, and Magnus T. Borgström

Appl. Phys. Lett. 100, 251103 (2012); http://dx.doi.org/10.1063/1.4729929 (4 pages) | Cited 1 time

Online Publication Date: 19 June 2012

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Axially defined GaInP single nanowire (NW) p-i-n junctions are demonstrated, with photocurrent response and yellow-green electroluminescence near the indirect bandgap crossover point at 2.18 eV (569 nm). We use DEZn and H2S as p- and n-type dopants, and find that they both affect the material composition and the crystal structure. The photovoltaic efficiency is comparable to single NW devices from binary III-V materials. These results demonstrate the potential of GaInP nanowires as a high-bandgap material for multijunction solar cells and light-emitting devices in the visible regime.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
78.55.Cr III-V semiconductors
78.60.Fi Electroluminescence
81.05.Ea III-V semiconductors
81.07.Vb Quantum wires

Terahertz sources based on Čerenkov difference-frequency generation in quantum cascade lasers

Karun Vijayraghavan, Robert W. Adams, Augustinas Vizbaras, Min Jang, Christian Grasse, Gerhard Boehm, Markus C. Amann, and Mikhail A. Belkin

Appl. Phys. Lett. 100, 251104 (2012); http://dx.doi.org/10.1063/1.4729042 (4 pages) | Cited 3 times

Online Publication Date: 20 June 2012

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We report room-temperature terahertz sources based on Čerenkov difference-frequency generation in dual-wavelength mid-infrared quantum cascade lasers with giant resonant optical nonlinearities originating from intersubband transitions. A Čerenkov difference-frequency generation scheme allows for extraction of THz radiation along the whole length of the laser waveguide and provides directional terahertz emission. Experimentally, our sources demonstrate a conversion efficiency of up to 70 μW/W2 approximately an order of magnitude improvement over the previous reports.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation

Pulse fluence dependent nanograting inscription on the surface of fused silica

Feng Liang, Réal Vallée, and See Leang Chin

Appl. Phys. Lett. 100, 251105 (2012); http://dx.doi.org/10.1063/1.4729620 (4 pages)

Online Publication Date: 20 June 2012

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Pulse fluence dependent nanograting inscription on the surface of fused silica is investigated. The nanograting period is found to decrease with the increase of the incident pulse fluence. Local intensity distribution and incubation effect are responsible for the change of the nanograting period.
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81.65.-b Surface treatments
42.62.-b Laser applications
42.79.Dj Gratings

Non-linear luminescent coupling in series-connected multijunction solar cells

Myles A. Steiner and John F. Geisz

Appl. Phys. Lett. 100, 251106 (2012); http://dx.doi.org/10.1063/1.4729827 (5 pages)

Online Publication Date: 21 June 2012

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The assumption of superposition or linearity of photocurrent with solar flux is widespread for calculations and measurements of solar cells. The well-known effect of luminescent coupling in multijunction solar cells has also been assumed to be linear with excess current. Here we show significant non-linearities in luminescent coupling in III-V multijunction solar cells and propose a simple model based on competition between radiative and nonradiative processes in the luminescent junction to explain these non-linearities. We demonstrate a technique for accurately measuring the junction photocurrents under a specified reference spectrum, that accounts for and quantifies luminescent coupling effects.
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88.40.jp Multijunction solar cells
85.60.-q Optoelectronic devices
88.40.jm Thin film III-V and II-VI based solar cells

In-plane steering of nematicon waveguides across an electrically tuned interface

Armando Piccardi, Alessandro Alberucci, Raouf Barboza, Oleksandr Buchnev, Malgosia Kaczmarek, and Gaetano Assanto

Appl. Phys. Lett. 100, 251107 (2012); http://dx.doi.org/10.1063/1.4729294 (4 pages) | Cited 4 times

Online Publication Date: 21 June 2012

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We study the interaction of a spatial soliton waveguide with a voltage defined and electrically tuned interface in nematic liquid crystals, whereby the optic axis is reoriented through the use of patterned electrodes. We investigate refraction and total internal reflection of nematicon wavepackets, disclosing the role of anisotropy and obtaining a remarkable in-plane steering as large as 55°.
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42.65.Wi Nonlinear waveguides
42.70.Df Liquid crystals
61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order
42.65.Tg Optical solitons; nonlinear guided waves

Nanometer-scale thickness control of amorphous silicon using isotropic wet-etching and low loss wire waveguide fabrication with the etched material

K. Furuya, K. Nakanishi, R. Takei, E. Omoda, M. Suzuki, M. Okano, T. Kamei, M. Mori, and Y. Sakakibara

Appl. Phys. Lett. 100, 251108 (2012); http://dx.doi.org/10.1063/1.4729416 (3 pages) | Cited 2 times

Online Publication Date: 21 June 2012

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Wet-etching with an organic alkaline solution was monitored in situ in semi-real time by optical reflection spectroscopy to achieve high resolution thickness control of hydrogenated amorphous silicon (a-Si:H) film for use in wire waveguides. Isotropic etching resulting from the intrinsic isotropic structure of a-Si:H led to uniform etching with a surface roughness of <1 nm. A moderate etching rate enabled accurate endpoint detection with a resolution of ≤1 nm at room temperature. A wire waveguide made of the etched a-Si:H film had a low propagation loss of 1.2 dB/cm, which was almost equivalent to that of an unetched one.
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81.65.Cf Surface cleaning, etching, patterning
68.55.jd Thickness
42.82.Cr Fabrication techniques; lithography, pattern transfer
42.82.Et Waveguides, couplers, and arrays
78.66.Nk Insulators

Evidence of anomalous refraction of self-assembled curved gold nanowires

A. Belardini, F. Pannone, G. Leahu, M. C. Larciprete, M. Centini, C. Sibilia, C. Martella, M. Giordano, D. Chiappe, and F. Buatier de Mongeot

Appl. Phys. Lett. 100, 251109 (2012); http://dx.doi.org/10.1063/1.4729829 (5 pages) | Cited 3 times

Online Publication Date: 22 June 2012

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Resonant metallic nanostructures, located at the interface between two dielectrics, can produce abrupt phase discontinuities on propagating light that will be anomalously refracted by following the generalized Snell’s law. In this work, we show evidence of anomalous refraction arising when such an interface is nano-patterned with self-assembled bent gold nano-wires having sub-wavelength periodicity.
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78.67.Uh Nanowires
81.07.Gf Nanowires
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
81.16.Dn Self-assembly
81.16.Rf Micro- and nanoscale pattern formation
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)

A transportable spectrometer for in situ and local measurements of iodine monoxide at mixing ratios in the 10−14 range

Guillaume Méjean, Roberto Grilli, Chadi Abd Alrahman, Irène Ventrillard, Samir Kassi, and Daniele Romanini

Appl. Phys. Lett. 100, 251110 (2012); http://dx.doi.org/10.1063/1.4726190 (3 pages)

Online Publication Date: 22 June 2012

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We present a robust, compact, and transportable instrument that measures the iodine monoxide atmospheric radical at extremely low concentration, down to 40 ppqv (parts per quadrillion by volume, 1:1015). As nitrogen dioxide is strongly absorbed in the same spectral region it could be simultaneously measured down to 4 pptv (parts per trillion by volume, 1:1012). Relying on “mode locked cavity-enhanced absorption spectroscopy,” the instrument makes use of a free-running commercial femtosecond Titane Saphir laser. We demonstrate that this multiplex detection scheme provides shot noise limited spectra for acquisition times as long as 5 min. Moreover, this instrument is very versatile as it can be potentially tuned from the infrared to the ultraviolet (1080-340 nm) to reach various molecular absorptions. It has been recently deployed at the Station Biologique de Roscoff on the North West Atlantic coast of France.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
42.55.-f Lasers
42.62.Eh Metrological applications; optical frequency synthesizers for precision spectroscopy
82.80.-d Chemical analysis and related physical methods of analysis

Anti-reflection coating for nitrogen-vacancy optical measurements in diamond

T. K. Yeung, D. Le Sage, L. M. Pham, P. L. Stanwix, and R. L. Walsworth

Appl. Phys. Lett. 100, 251111 (2012); http://dx.doi.org/10.1063/1.4730401 (4 pages) | Cited 1 time

Online Publication Date: 22 June 2012

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We realize anti-reflection (AR) coatings for optical excitation and fluorescence measurements of nitrogen-vacancy (NV) color centers in bulk diamond by depositing quarter-wavelength thick silica layers on the diamond surface. These AR coatings improve NV-diamond optical measurements by reducing optical reflection at the diamond-air interface from ≈17% to ≈2%, which allows more effective NV optical excitation and more efficient detection of NV fluorescence. We also show that diamond AR coatings eliminate standing-wave interference patterns of excitation laser intensity within bulk diamond, and thereby greatly reduce spatial variations in NV fluorescence, which can degrade spatially resolved magnetic field sensing using NV centers.
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78.55.Hx Other solid inorganic materials
61.72.jn Color centers
61.72.jd Vacancies
42.79.Wc Optical coatings
78.40.Ha Other nonmetallic inorganics

Proposal of an optical nonvolatile switch utilizing surface plasmon antenna resonance controlled by giant magnetoresistance

Takeshi Ogasawara, Haruhiko Kuwatsuka, Toshifumi Hasama, and Hiroshi Ishikawa

Appl. Phys. Lett. 100, 251112 (2012); http://dx.doi.org/10.1063/1.4730406 (4 pages)

Online Publication Date: 22 June 2012

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We propose an operating principle for an optical nonvolatile switch utilizing surface plasmon antenna resonance controlled by giant magnetoresistance. The optical spectra of an array of nanoscale dipole antennas composed of Co/Cu multilayers with parallel and anti-parallel magnetization alignments were estimated by a first-principle calculation and a finite difference time domain electromagnetic field analysis. The extinction efficiency changed more than 40% in the infrared region due to the magnetization alignment, demonstrating its promise as a nonvolatile optical switch.
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42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks
84.40.Ba Antennas: theory, components and accessories

The wavelength dependent photovoltaic effects caused by two different mechanisms in carbon nanotube film/CuO nanowire array heterodimensional contacts

Jia Xu, Jia-Lin Sun, Jinquan Wei, and Jinliang Xu

Appl. Phys. Lett. 100, 251113 (2012); http://dx.doi.org/10.1063/1.4730433 (5 pages)

Online Publication Date: 22 June 2012

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Hetrodimensional contacts were fabricated by coating double-walled carbon nanotube (CNT) films on CuO nanowire arrays. Wavelength dependent photovoltaic effects by irradiating the devices with 405, 532, and 1064 nm lasers were observed. Two possible mechanisms responsible for the observed results were discussed. Photoexcitations within CuO nanowires and Schottky barriers in the heterojunctions dominate the photovoltaics in the 405 and 532 nm cases. For the 1064 nm case, the photovoltaic is the result of the excitation within the CNTs and of the heterodimensionality effect. Control experiments on CNT film/CuO granular film hetrodimensional contacts further show the relationship between these two mechanisms.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
72.40.+w Photoconduction and photovoltaic effects
73.30.+y Surface double layers, Schottky barriers, and work functions

Semiconductor ring lasers coupled by a single waveguide

W. Coomans, L. Gelens, G. Van der Sande, G. Mezosi, M. Sorel, J. Danckaert, and G. Verschaffelt

Appl. Phys. Lett. 100, 251114 (2012); http://dx.doi.org/10.1063/1.4730615 (4 pages)

Online Publication Date: 22 June 2012

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We experimentally and theoretically study the characteristics of semiconductor ring lasers bidirectionally coupled by a single bus waveguide. This configuration has, e.g., been suggested for use as an optical memory and as an optical neural network motif. The main results are that the coupling can destabilize the state in which both rings lase in the same direction, and it brings to life a state with equal powers at both outputs. These are both undesirable for optical memory operation. Although the coupling between the rings is bidirectional, the destabilization occurs due to behavior similar to an optically injected laser system.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.79.Gn Optical waveguides and couplers
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Ab initio-based study for adatom kinetics on AlN(0001) surfaces during metal-organic vapor-phase epitaxy growth

Toru Akiyama, Kohji Nakamura, and Tomonori Ito

Appl. Phys. Lett. 100, 251601 (2012); http://dx.doi.org/10.1063/1.4729479 (3 pages)

Online Publication Date: 18 June 2012

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The kinetics of Al and N adatoms on reconstructed AlN(0001) surfaces under growth conditions is investigated by performing first-principles pseudopotential calculations. Our calculations reveal that the adsorption of Al adatom strongly depends on the surface reconstruction while its diffusion is not affected by the reconstruction: the adsorption of Al adatom on the surface under N-rich conditions is much easier than that under H-rich conditions. These results indicate that the growth of AlN during metal-organic vapor-phase epitaxy is prominent under N-rich conditions rather than H-rich conditions, consistent with experimentally reported growth rate difference.
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68.43.Mn Adsorption kinetics
68.43.Bc Ab initio calculations of adsorbate structure and reactions
68.35.bg Semiconductors
66.30.-h Diffusion in solids
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.05.Ea III-V semiconductors

Zener tunneling between Landau orbits in two-dimensional electron Corbino rings

A. A. Bykov, D. V. Dmitriev, I. V. Marchishin, S. Byrnes, and S. A. Vitkalov

Appl. Phys. Lett. 100, 251602 (2012); http://dx.doi.org/10.1063/1.4729590 (3 pages) | Cited 3 times

Online Publication Date: 18 June 2012

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Current induced oscillations of differential conductivity of two-dimension electrons, placed in quantizing magnetic fields, are observed in GaAs quantum wells in Corbino geometry. The oscillations are periodic in the square of the inverse magnetic field and occur in Corbino rings with a width which is much lesser than the radius of the rings. The conductance oscillations are described by Zener tunneling between Landau orbits in the absence of the Hall electric field.
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73.40.Gk Tunneling
72.20.My Galvanomagnetic and other magnetotransport effects
73.63.Hs Quantum wells

Characterization of irradiation damage distribution near TiO2/SrTiO3 interfaces using coherent acoustic phonon interferometry

Dmitry Yarotski, Engang Fu, Li Yan, Quanxi Jia, Yongqiang Wang, Antoinette J. Taylor, and Blas P. Uberuaga

Appl. Phys. Lett. 100, 251603 (2012); http://dx.doi.org/10.1063/1.4729621 (3 pages)

Online Publication Date: 18 June 2012

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We apply ultrafast coherent acoustic phonon interferometry to characterize the distribution of the radiation damage near the TiO2/SrTiO3 interfaces. We show that the optical and mechanical properties of anatase TiO2 remain unaffected by the radiation dosages in the 0.1÷5 dpa (displacements per atom) range, while the degraded optical response indicates a significant defect accumulation in the interfacial region of SrTiO3 at 0.1 dpa and subsequent amorphization at 3 dpa. Comparison between the theoretical simulations and the experimental results reveals an almost threefold reduction of the sound velocity in the irradiated SrTiO3 layer with peak damage levels of 3 and 5 dpa.
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61.80.Jh Ion radiation effects
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
63.20.-e Phonons in crystal lattices
68.60.Bs Mechanical and acoustical properties
78.66.Li Other semiconductors

Few-layer graphene growth on 6H-SiC(0001) surface at low temperature via Ni-silicidation reactions

C. Y. Kang, L. L. Fan, S. Chen, Z. L. Liu, P. S. Xu, and C. W. Zou

Appl. Phys. Lett. 100, 251604 (2012); http://dx.doi.org/10.1063/1.4729876 (5 pages) | Cited 2 times

Online Publication Date: 19 June 2012

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Few-layer graphene (FLG) has been prepared by thermal annealing of SiC crystal via the surface Ni-silicidation reactions. Results reveal that the temperature plays an important role for the final FLG quality and the optimized annealing temperature is about 800 °C. The investigation of surface morphology and microstructure for the FLG sample indicates that after the rapid cooling, the carbon atoms will segregate to form the FLG layer and the NiSix particles will congregate on the top surface. The mechanism of the FLG formation on SiC surface assisted by the Ni ultra-thin layer is briefly discussed based on the experimental results.
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68.55.ag Semiconductors
61.48.Gh Structure of graphene
71.20.Nr Semiconductor compounds
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
81.40.Gh Other heat and thermomechanical treatments
68.35.bg Semiconductors

Surface metallic states in ultrathin Bi(001) films studied with terahertz time-domain spectroscopy

K. Yokota, J. Takeda, C. Dang, G. Han, D. N. McCarthy, T. Nagao, S. Hishita, M. Kitajima, and I. Katayama

Appl. Phys. Lett. 100, 251605 (2012); http://dx.doi.org/10.1063/1.4729149 (4 pages)

Online Publication Date: 19 June 2012

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Dynamical response of surface metallic states in single crystalline ultrathin Bi(001) films on Si(111) 7 × 7 surface was investigated at a spectral range of 0.1–12 THz by broadband terahertz time-domain spectroscopy. The observed transmittance increased with a decrease in the thickness, without showing a gap structure. The measured complex dielectric dispersion was analyzed using a Drude model, and the plasma frequency (ωp) and damping constant (γ) were found to be inversely proportional to the thickness. The results strongly indicate the existence of surface metallic states, whose carrier density and damping constant are estimated to be 3.08 × 1019 cm−3 and 4.83 × 102 THz, respectively.
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73.20.At Surface states, band structure, electron density of states
73.50.Mx High-frequency effects; plasma effects
73.61.At Metal and metallic alloys
77.22.Ch Permittivity (dielectric function)
78.70.Gq Microwave and radio-frequency interactions
68.55.jd Thickness

Domain epitaxy in TiO2/α-Al2O3 thin film heterostructures with Ti2O3 transient layer

M. R. Bayati, R. Molaei, R. J. Narayan, J. Narayan, H. Zhou, and S. J. Pennycook

Appl. Phys. Lett. 100, 251606 (2012); http://dx.doi.org/10.1063/1.4729937 (3 pages) | Cited 7 times

Online Publication Date: 21 June 2012

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Rutile TiO2 films were grown epitaxially on α-alumina (sapphire(0001)) substrates and characterized by x-ray diffraction and scanning transmission electron microscopy. It was revealed that the rutile film initially grows pseudomorphically on sapphire as Ti2O3 and, after a few monolayers, it grows tetragonally on the Ti2O3/sapphire platform. Formation of the Ti2O3 transient layer was attributed to the symmetry mismatch between tetragonal structure of TiO2 and hexagonal structure of alumina. The separation between the ½[10math](101) misfit dislocations was dictated by Ti2O3 and was determined to be 9.7 Å which is consistent with 4/3 and 3/2 alternating domains across the film/substrate interface.
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81.15.Fg Pulsed laser ablation deposition
68.55.ag Semiconductors
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
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India-stabilized-gadolinia and gadolinia-stabilized-India: Their structural and magnetic properties

S. B. Qadri, D. H. Wu, K. Bussmann, E. F. Skelton, and N. Bayya

Appl. Phys. Lett. 100, 251901 (2012); http://dx.doi.org/10.1063/1.4729821 (4 pages)

Online Publication Date: 18 June 2012

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Gd2O3-In2O3 solid solutions were synthesized starting with powders of Gd2O3 and In2O3 in the appropriate stoichiometric ratio and heating them in air to temperatures of 1425 °C. Their crystalline structures were determined using high resolution x-ray diffractometry. Cubic, monoclinic, and hexagonal phases were observed for different compositions. The present study demonstrates that large quantities of the high pressure phases of either Gd2O3 or In2O3 can be obtained in the solid solutions of Gd2−xInxO3 (0 < x < 1.6). The solid solutions show increasing paramagnetic response with increasing Gd content deriving from the Gd3+:4f7 ground sate configuration.
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75.20.Ck Nonmetals
81.40.Gh Other heat and thermomechanical treatments
62.50.-p High-pressure effects in solids and liquids
61.43.Gt Powders, porous materials
61.66.Bi Elemental solids
61.66.Dk Alloys
61.66.Fn Inorganic compounds

New insights on strain energies in hexagonal systems

Ludovic Thuinet and Rémy Besson

Appl. Phys. Lett. 100, 251902 (2012); http://dx.doi.org/10.1063/1.4729426 (4 pages) | Cited 1 time

Online Publication Date: 18 June 2012

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The preferential habit planes of coherent precipitates, strongly influencing alloy properties, can be investigated by direct-space elasticity methods, providing new insight into delicate issues such as elastic inhomogeneities or anharmonicity. Focusing on the poorly known hexagonal system, this work enlightens important trends overlooked hitherto, such as the critical role of C44, leading to the identification of distinct families of hexagonal alloys for precipitation. Moreover, it demonstrates the complex influence of inhomogeneities for real, finite-thickness morphologies. Finally, it provides the missing material required for atomic-scale studies of precipitation in low-symmetry systems with long-range interactions.
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81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.de Elastic moduli
61.66.Dk Alloys

Stability and optical limiting properties of a single wall carbon nanotubes dispersion in a binary water-glycerol solvent

Anastasiya V. Venediktova, Andrey Yu. Vlasov, Elena D. Obraztsova, Dmitry A. Videnichev, Ivan M. Kislyakov, and Ekaterina P. Sokolova

Appl. Phys. Lett. 100, 251903 (2012); http://dx.doi.org/10.1063/1.4729790 (5 pages) | Cited 2 times

Online Publication Date: 19 June 2012

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We report the temporal stability of the dispersion of single-wall carbon nanotubes in a binary solvent “water + glycerol” having eutectic composition (ca. 67% wt.) with sodium dodecylbenzene sulfonate as a dispersant. The system procures good temporal and thermal stability: its absorption spectra demonstrate no changes during one-year storage with temperature spanning −40 to +40 °C. The system provides non-linear optical power limiting of the incident laser radiation (532 nm) in a one-shot and pulse-periodic regimes of its applying.
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61.46.Fg Nanotubes
42.25.Bs Wave propagation, transmission and absorption

Room temperature electroluminescence from light-emitting diodes based on In0.5Ga0.5As/GaP self-assembled quantum dots

Yuncheng Song and Minjoo Larry Lee

Appl. Phys. Lett. 100, 251904 (2012); http://dx.doi.org/10.1063/1.4729591 (3 pages) | Cited 2 times

Online Publication Date: 19 June 2012

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Room-temperature electroluminescence from In0.5Ga0.5As/GaP(001) self-assembled quantum dot light emitting diodes is demonstrated. Output light versus input current measurements indicate that stacking multiple periods of self-assembled quantum dots can substantially increase the electroluminescence intensity. Aside from potential applications in transparent-substrate light emitting diodes, InxGa1-xAs/GaP self-assembled quantum dots could be a possible candidate for monolithic integration of optoelectronics with Si due to recent advances in the growth of high-quality GaP on Si.
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85.60.Jb Light-emitting devices
78.67.Hc Quantum dots
81.16.Dn Self-assembly

Length scale of mechanical heterogeneity in a glassy polymer determined by atomic force microscopy

Dong Wang, Yanhui Liu, Toshio Nishi, and Ken Nakajima

Appl. Phys. Lett. 100, 251905 (2012); http://dx.doi.org/10.1063/1.4729931 (4 pages)

Online Publication Date: 20 June 2012

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Using dynamic force microscopy, nanoscale mechanical heterogeneity in glassy polymer was characterized. The correlation length of heterogeneous viscoelasticity was measured to be ∼2.1 nm, consistent with the length scale of cooperatively rearranging regions at glass transition and is independent of molecular weight. Apparent energy dissipation with the variation of ∼57%, originating from non-uniform distribution of local viscoelasticity, was revealed. The results provide definite experimental evidences on the nanoscale heterogeneity in glassy polymers and bear important insights in understanding the puzzling glass transition.
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81.40.Jj Elasticity and anelasticity, stress-strain relations
64.70.pj Polymers
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
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