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19 Dec 2011

Volume 99, Issue 25, Articles (25xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 99, 253701 (2011); http://dx.doi.org/10.1063/1.3666819 (3 pages)

Jun Huang, Hui Li, Wei Chen, Guo-Hua Lv, Xing-Quan Wang, Guo-Ping Zhang, Kostya Ostrikov, Peng-Ye Wang, and Si-Ze Yang
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Thermal rectification in multi-walled carbon nanotubes: A molecular dynamics study

Kiarash Gordiz, S. M. Vaez Allaei, and Farshad Kowsary

Appl. Phys. Lett. 99, 251901 (2011); http://dx.doi.org/10.1063/1.3670327 (4 pages) | Cited 2 times

Online Publication Date: 19 December 2011

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Using nonequilibrium molecular dynamics simulations, we show if a multi-walled carbon nanotube (MWNT) is heated asymmetrically, an evident thermal rectification can be detected. We attribute the observed rectification to the asymmetric radial thermal transport between constructing layers in MWNT. The underlying physics is explained by calculating temperature distribution of MWNT layers and phonon power spectrum. Thermal rectification in this carbon nanotube based thermal rectifier does not diminish by increasing the system size, and exists in a wide range of temperatures. These results open a door in the applicability of MWNTs in nanoscale engineering of thermal transport devices.
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66.70.Lm Other systems such as ionic crystals, molecular crystals, nanotubes, etc.
61.46.Fg Nanotubes
63.22.Gh Nanotubes and nanowires

Morphology-dependent low-frequency Raman scattering in ultrathin spherical, cubic, and cuboid SnO2 nanocrystals

L. Z. Liu, X. L. Wu, T. H. Li, S. J. Xiong, H. T. Chen, and Paul K. Chu

Appl. Phys. Lett. 99, 251902 (2011); http://dx.doi.org/10.1063/1.3670337 (4 pages)

Online Publication Date: 19 December 2011

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Nanoscale spherical, cubic, and cuboid SnO2 nanocrystals (NCs) are used to investigate morphology-dependent low-frequency Raman scattering. A double-peak structure in which the linewidths and energy separation between two subpeaks decrease with increasing sizes of cuboid NCs is observed and attributed to the surface acoustic phonon modes confined in three dimensional directions and determined by the surface/interface compositions. The decrease in energy separation is due to weaker coupling between the acoustic modes in different vibration directions. Our experimental and theoretical studies clearly disclose the morphology-dependent surface vibrational behavior in self-assembled NCs.
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81.16.Dn Self-assembly
63.22.Kn Clusters and nanocrystals
78.30.Hv Other nonmetallic inorganics
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters

Size dependent biexciton binding energies in GaN quantum dots

S. Amloy, K. H. Yu, K. F. Karlsson, R. Farivar, T. G. Andersson, and P. O. Holtz

Appl. Phys. Lett. 99, 251903 (2011); http://dx.doi.org/10.1063/1.3670040 (3 pages) | Cited 3 times

Online Publication Date: 20 December 2011

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Single GaN/Al(Ga)N quantum dots (QDs) have been investigated by means of microphotoluminescence. Emission spectra related to excitons and biexcitons have been identified by excitation power dependence and polarization resolved spectroscopy. All investigated dots exhibit a strong degree of linear polarization (∼90%). The biexciton binding energy scales with the dot size. However, both positive and negative binding energies are found for the studied QDs. These results imply that careful size control of III-Nitride QDs would enable the emission of correlated photons with identical frequencies from the cascade recombination of the biexciton, with potential applications in the area of quantum information processing.
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71.20.Nr Semiconductor compounds
78.55.Cr III-V semiconductors
71.35.-y Excitons and related phenomena
73.21.La Quantum dots
71.15.Nc Total energy and cohesive energy calculations
78.67.Hc Quantum dots

Observation of longitudinal-optic-phonon-plasmon-coupled mode in n-type AlGaN alloy films

Jung Gon Kim, Atsuhito Kimura, Yasuhito Kamei, Noriyuki Hasuike, Hiroshi Harima, Kenji Kisoda, Yuki Shimahara, Hideto Miyake, and Kazumasa Hiramatsu

Appl. Phys. Lett. 99, 251904 (2011); http://dx.doi.org/10.1063/1.3670338 (4 pages) | Cited 2 times

Online Publication Date: 20 December 2011

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An longitudinal-optic-phonon-plasmon coupled mode (LOPC) has been clearly observed by Raman scattering in n-type AlxGa1−xN films with x ∼ 0.67 and different carrier densities n = 1 × 1017-9 × 1017 cm−3. The A1-LO-phonon mode showed a systematic frequency shift and broadening with increasing n. This is a characteristic behavior of LOPC as previously observed in n-type binary semiconductors. A theoretical line-shape fitting analysis was conducted for the LOPC profile using n and plasmon-damping rate as adjustable parameter. Assuming m*/m0 = 0.28 for the longitudinal effective mass of electron, the analysis well reproduced carrier density and mobility deduced by Hall measurement.
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63.20.kk Phonon interactions with other quasiparticles
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
78.30.Fs III-V and II-VI semiconductors
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
73.61.Ey III-V semiconductors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

Near zero temperature coefficient of resistivity in antiperovskite Mn3Ni1−xCuxN

Lei Ding, Cong Wang, Lihua Chu, Jun Yan, Yuanyuan Na, Qingzhen Huang, and Xiaolong Chen

Appl. Phys. Lett. 99, 251905 (2011); http://dx.doi.org/10.1063/1.3671183 (4 pages) | Cited 4 times

Online Publication Date: 21 December 2011

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The near zero temperature coefficient of resistivity (NZ-TCR) in Mn-based antiperovskite Mn3Ni1−xCuxN is reported. The temperature range of NZ-TCR is controllable by changing Cu content. Further, the TCR value of 0.09 ppm K−1 was obtained in Mn3Ni0.5Cu0.5N over a broad temperature range around room temperature. The anomalous resistivity change of Mn3Ni1−xCuxN from metal-like to NZ-TCR behavioris apparently due to a magnetic transition. The possible reason for the formation of NZ-TCR is interpreted on the basis of spin-disorder scattering.
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72.20.Fr Low-field transport and mobility; piezoresistance
72.80.Sk Insulators
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)

Contactless electroreflectance study of E0 and E0 + ΔSO transitions in In0.53Ga0.47BixAs1−x alloys

R. Kudrawiec, J. Kopaczek, J. Misiewicz, J. P. Petropoulos, Y. Zhong, and J. M. O. Zide

Appl. Phys. Lett. 99, 251906 (2011); http://dx.doi.org/10.1063/1.3669703 (3 pages) | Cited 4 times

Online Publication Date: 21 December 2011

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Energies of E0 and E0 + ΔSO transitions in In0.53Ga0.47BixAs1−x alloys with 0 < x ≤ 0.036 have been studied by contactless electroreflectance spectroscopy at room temperature. It has been clearly observed that the E0 transition shifts to longer wavelengths (∼50 meV/% of Bi), while the E0 + ΔSO transition is approximately unchanged with changes in Bi concentration. These changes in the energies of optical transitions are discussed in the context of the valence band anticrossing model as well as the common anion rule applied to III-V semiconductors.
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78.20.Jq Electro-optical effects
71.20.Nr Semiconductor compounds

Off-resonant coupling between a single quantum dot and a nanobeam photonic crystal cavity

Armand Rundquist, Arka Majumdar, and Jelena Vučković

Appl. Phys. Lett. 99, 251907 (2011); http://dx.doi.org/10.1063/1.3671458 (3 pages) | Cited 1 time

Online Publication Date: 21 December 2011

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We demonstrate off-resonant coupling between a single quantum dot and a nanobeam photonic crystal cavity, under resonant excitation of the quantum dot or the cavity. These results are consistent with previous descriptions of off-resonant coupling as an incoherent phonon-mediated process. The extension of this phenomenon to a nanobeam photonic crystal cavity presents interesting possibilities for coherent control of this interaction by tailoring the phonon density of states.
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42.70.Qs Photonic bandgap materials
42.79.-e Optical elements, devices, and systems
42.79.Gn Optical waveguides and couplers
42.50.-p Quantum optics
42.55.Tv Photonic crystal lasers and coherent effects

Strain enhanced electron cooling in a degenerately doped semiconductor

M. J. Prest, J. T. Muhonen, M. Prunnila, D. Gunnarsson, V. A. Shah, J. S. Richardson-Bullock, A. Dobbie, M. Myronov, R. J. H. Morris, T. E. Whall, E. H. C. Parker, and D. R. Leadley

Appl. Phys. Lett. 99, 251908 (2011); http://dx.doi.org/10.1063/1.3670330 (4 pages)

Online Publication Date: 22 December 2011

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Enhanced electron cooling is demonstrated in a strained-silicon/superconductor tunnel junction refrigerator of volume 40 μm3. The electron temperature is reduced from 300 mK to 174 mK, with the enhancement over an unstrained silicon control (300 mK–258 mK) being attributed to the smaller electron-phonon coupling in the strained case. Modeling and the resulting predictions of silicon-based cooler performance are presented. Further reductions in the minimum temperature are expected if the junction sub-gap leakage and tunnel resistance can be reduced. However, if only tunnel resistance is reduced, Joule heating is predicted to dominate.
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85.25.Cp Josephson devices

Observation of non-basal slip in semipolar InxGa1-xN/GaN heterostructures

Feng Wu, E. C. Young, I. Koslow, M. T. Hardy, P. S. Hsu, A. E. Romanov, S. Nakamura, S. P. DenBaars, and J. S. Speck

Appl. Phys. Lett. 99, 251909 (2011); http://dx.doi.org/10.1063/1.3671113 (4 pages) | Cited 10 times

Online Publication Date: 22 December 2011

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In this paper, we report on observations of the operation of secondary slip systems to relieve lattice mismatch stress in semipolar InGaN/GaN heterostructures. Two-dimensional arrays of misfit dislocations were observed. Consistent with previous reports, primary relaxation occurred along the projected c direction via primary slip on the (0001) basal plane. In addition, evidence for secondary relaxation was detected in cathodoluminescence spectroscopy, high resolution x-ray diffraction, and transmission electron microscopy (TEM) studies. The secondary misfit dislocations were determined by TEM to have a-type Burgers vectors a/3 〈math110〉 and line directions along 〈4mathmathmath〉, consistent with prismatic slip on one of the m-type planes inclined with respect to the (11math2) growth surface. Evidence of an additional slip system with approximate misfit line direction of type 〈20mathmath〉 is also given.
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61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
78.60.Hk Cathodoluminescence, ionoluminescence

Catalyst-free growth of high-optical quality GaN nanowires by metal-organic vapor phase epitaxy

X. J. Chen, B. Gayral, D. Sam-Giao, C. Bougerol, C. Durand, and J. Eymery

Appl. Phys. Lett. 99, 251910 (2011); http://dx.doi.org/10.1063/1.3671365 (3 pages) | Cited 7 times

Online Publication Date: 22 December 2011

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Catalyst-free GaN wires with 100–200 nm diameters are grown on bare c-sapphire substrates by a metal-organic vapor phase epitaxy approach using both low V/III ratio and V-III precursor flows that favor a reaction-limited growth regime. The polarity control of the initial seeds allows obtaining pencil-shape wires with very sharp pyramids at their top (∼5 nm diameter). These defect-free nanowires evidence excellent structural and optical properties as shown by a sharp photoluminescence linewidth (1–3 meV at 5 K).
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.07.Gf Nanowires
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Optoelectronic behaviors and carrier dynamics of individual localized luminescent centers in InGaN quantum-well light emitting diodes

Suman De, Dibyendu Kumar Das, Arunasish Layek, Archana Raja, Manoj Kumar Singh, Arnab Bhattacharya, Subhabrata Dhar, and Arindam Chowdhury

Appl. Phys. Lett. 99, 251911 (2011); http://dx.doi.org/10.1063/1.3671092 (4 pages) | Cited 2 times

Online Publication Date: 23 December 2011

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Spatially, spectrally, and temporally resolved photoluminescence (PL) microscopy was performed on InGaN quantum-well light emitting diodes to probe individual localized luminescent centers arising from disorder induced potential fluctuations. Two energetically distinct localization centers were identified where the photoemission quantum-efficiency (QE) are correlated to the transition energies. PL lifetime measurements on emission centers suggest that activation barrier for non-radiative recombination (NR) processes determines their QE. The disparity in carrier dynamics not only substantiate two diverse mechanisms for localization processes, but also indicate the presence of multiple NR channels even within the trap centers implying their lateral dimensions to span several nanometers.
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85.60.Jb Light-emitting devices
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Interferometric scanning microscopy for the study of disordered materials

D. Kumar and M. M. J. Treacy

Appl. Phys. Lett. 99, 251912 (2011); http://dx.doi.org/10.1063/1.3671146 (4 pages)

Online Publication Date: 23 December 2011

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We demonstrate an interferometric optical technique that probes pair-pair correlations in disordered materials. Fraunhofer diffraction patterns, using coherent double-probe illumination, exhibit Young’s interference fringes whose strength is influenced by structural correlations between the two probed regions. Fourier transforms of diffraction patterns exhibit holographic sidebands, and the strength of correlations is proportional to the sideband intensity. Autoregression analysis of the correlation strength provides a direct measure of the characteristic ordering length scales. This technique is extendable in principle to x-ray and electron probes for studying materials at atomic length scales.
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61.41.+e Polymers, elastomers, and plastics

Nucleation and propagation of voids in microbumps for 3 dimensional integrated circuits

Hsueh-Hsien Hsu, Shin-Yi Huang, Tao-Chih Chang, and Albert T. Wu

Appl. Phys. Lett. 99, 251913 (2011); http://dx.doi.org/10.1063/1.3671391 (3 pages) | Cited 1 time

Online Publication Date: 23 December 2011

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The shrinking solder dimensions greatly impact the reliability of devices and increase entire failure modes. Limited solder volumes can be consumed completely and transformed into intermetallic compound (IMC) microbumps. Microvoids surface when microbumps are formed and may be attributed to a mismatch of the thermal expansion coefficient between the constituents. After thermal aging at 150 °C, the stress induced by the growth of IMCs relaxes and enhances propagation of the cracks along the middle of the bumps. The brittle nature of the IMC showed minimal resistance to cracks and incurred a failure mode.
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85.40.Ls Metallization, contacts, interconnects; device isolation
62.20.mj Brittleness
62.20.mt Cracks
61.72.Qq Microscopic defects (voids, inclusions, etc.)
81.40.Cd Solid solution hardening, precipitation hardening, and dispersion hardening; aging
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure

Controlling split-ring resonators with light

Polina V. Kapitanova, Stanislav I. Maslovski, Ilya V. Shadrivov, Pavel M. Voroshilov, Dmitry S. Filonov, Pavel A. Belov, and Yuri S. Kivshar

Appl. Phys. Lett. 99, 251914 (2011); http://dx.doi.org/10.1063/1.3671617 (3 pages) | Cited 5 times

Online Publication Date: 23 December 2011

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We propose an original approach for creating tunable electromagnetic metamaterials. We demonstrate experimentally that magnetic resonance of a split-ring resonator (“meta-atom” of a composite material) with a photodiode operated in photovoltaic mode can be tuned by changing the intensity of an external light source. Moreover, for two coupled resonators, we show that we can achieve light-induced switching between dark- and bright-mode responses.
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42.79.-e Optical elements, devices, and systems
85.60.Dw Photodiodes; phototransistors; photoresistors
42.70.-a Optical materials
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