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2 Aug 2010

Volume 97, Issue 5, Articles (05xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 97, 051101 (2010); http://dx.doi.org/10.1063/1.3470591 (3 pages)

Pascal Böhi, Max F. Riedel, Theodor W. Hänsch, and Philipp Treutlein
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Imaging of microwave fields using ultracold atoms

Pascal Böhi, Max F. Riedel, Theodor W. Hänsch, and Philipp Treutlein

Appl. Phys. Lett. 97, 051101 (2010); http://dx.doi.org/10.1063/1.3470591 (3 pages) | Cited 3 times

Online Publication Date: 2 August 2010

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We report a technique that uses clouds of ultracold atoms as sensitive, tunable, and noninvasive probes for microwave field imaging with micrometer spatial resolution. The microwave magnetic field components drive Rabi oscillations on atomic hyperfine transitions whose frequency can be tuned with a static magnetic field. Readout is accomplished using state-selective absorption imaging. Quantitative data extraction is simple and it is possible to reconstruct the distribution of microwave magnetic field amplitudes and phases. While we demonstrate two-dimensional imaging, an extension to three-dimensional imaging is straightforward. We use the method to determine the microwave near-field distribution around a coplanar waveguide integrated on an atom chip.
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37.10.De Atom cooling methods
84.40.Lj Microwave integrated electronics
32.10.Fn Fine and hyperfine structure
84.40.Az Waveguides, transmission lines, striplines
07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment

Strong coupling between on chip notched ring resonator and nanoparticle

S. Wang, K. Broderick, H. Smith, and Y. Yi

Appl. Phys. Lett. 97, 051102 (2010); http://dx.doi.org/10.1063/1.3474623 (3 pages) | Cited 3 times

Online Publication Date: 2 August 2010

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We have demonstrated a new photonic structure to achieve strong optical coupling between nanoparticle and photonic molecule by utilizing a notched microring resonators. By creating a notch in the ring resonator and putting a nanoparticle inside the notch, large spectral shifts and splittings at nanometer scale can be achieved, compared to only picometer scale observed by fiber tip evanescently coupled to the surface of microsphere, thereby significantly lowered the quality factor requirement for single nanoparticle detection. The ability for sorting the type of nanoparticles due to very different mode shift and splitting behavior of dielectric and metallic nanoparticles is also emphasized.
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42.82.-m Integrated optics
42.79.-e Optical elements, devices, and systems

Quantum well saturable absorber mirror with electrical control of modulation depth

Xiaomin Liu, Edik U. Rafailov, Daniil Livshits, and Dmitry Turchinovich

Appl. Phys. Lett. 97, 051103 (2010); http://dx.doi.org/10.1063/1.3474799 (3 pages) | Cited 2 times

Online Publication Date: 2 August 2010

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We demonstrate a quantum well (QW) semiconductor saturable absorber mirror (SESAM) comprising low-temperature grown InGaAs/GaAs QWs incorporated into a p-i-n structure. By applying the reverse bias voltage in the range 0–2 V to the p-i-n structure, we were able to change the SESAM modulation depth in the range 2.5–0.5%, as measured by nonlinear reflectivity of 450 fs long laser pulses with 1065 nm central wavelength, in the pump fluence range 1.6–26.7 μJ/cm2. This electrical control of the modulation depth is achieved by controlling the small-signal loss of the SESAM via quantum-confined Stark effect in the QWs.
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73.21.Fg Quantum wells
78.67.De Quantum wells
42.79.Bh Lenses, prisms and mirrors

Photonic crystal nanobeam lasers

Y. Zhang, M. Khan, Y. Huang, J. Ryou, P. Deotare, R. Dupuis, and M. Lončar

Appl. Phys. Lett. 97, 051104 (2010); http://dx.doi.org/10.1063/1.3475397 (3 pages) | Cited 18 times

Online Publication Date: 2 August 2010

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Photonic crystal lasers operating at room temperature based on high Q/V nanobeam cavities have been demonstrated. We reported a large spontaneous emission factor (β ∼ 0.97) by fitting the L-L curve with the rate equations.
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42.55.Tv Photonic crystal lasers and coherent effects
42.55.Wd Fiber lasers

Two-photon subwavelength lithography with thermal light

De-Zhong Cao, Gui-Ju Ge, and Kaige Wang

Appl. Phys. Lett. 97, 051105 (2010); http://dx.doi.org/10.1063/1.3472112 (3 pages) | Cited 1 time

Online Publication Date: 3 August 2010

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We propose an incoherent interferometer which can partly modify the spatial correlation property of thermal light. Applying the interferometer to the two-photon double-slit interference with thermal light, we find that the subwavelength interference patterns appear in the intensity correlation not only between two same polarized photons at different positions but also between two orthogonally polarized photons at the same position. The latter can correspond to the two-photon double-slit interference using a two-photon entangled source. Our experimental result suggests that a thermal light source is capable of accomplishing subwavelength lithography technique to surpass the Rayleigh resolution limit.
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07.60.Ly Interferometers
42.72.-g Optical sources and standards

Light induced tuning of quantum cascade lasers

B. Basnar, E. Mujagic, A. M. Andrews, T. Roch, W. Schrenk, and G. Strasser

Appl. Phys. Lett. 97, 051106 (2010); http://dx.doi.org/10.1063/1.3473780 (3 pages)

Online Publication Date: 3 August 2010

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A method for tuning the emission of a midinfrared quantum cascade laser using ultraviolet light is presented. The method uses a quantum cascade laser where a photochromic material is deposited as the top waveguide cladding. Changing the state of the cladding causes variations in the absorbance of the cladding. Wavelength dependent changes in the waveguide losses occur, forcing the laser to emit at a wavelength correlated with an absorbance minimum of the cladding. A blueshift by about 6 cm−1 was obtained at room temperature under UV irradiation which was fully reversed by exposure to visible light or room temperature relaxation.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Fc Modulation, tuning, and mode locking

Refractive index dynamics of quantum dot based waveguide electroabsorbers

Tomasz Piwonski, Jaroslaw Pulka, Evgeny A. Viktorov, Guillaume Huyet, and John Houlihan

Appl. Phys. Lett. 97, 051107 (2010); http://dx.doi.org/10.1063/1.3476347 (3 pages) | Cited 1 time

Online Publication Date: 4 August 2010

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The refractive index dynamics of InAs/GaAs quantum dot based waveguide absorbers is studied using heterodyne pump-probe measurements. Absorption reduction due to the pump can be accompanied by either positive or negative refractive index changes depending on the wavelength used. This change in sign of the phase amplitude coupling can be understood by considering the atomlike nature of the quantum dot transitions involved.
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78.67.Hc Quantum dots
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
81.05.Ea III-V semiconductors

Low dark current long-wave infrared InAs/GaSb superlattice detectors

Jean Nguyen, Alexander Soibel, David Z.-Y. Ting, Cory J. Hill, Mike C. Lee, and Sarath D. Gunapala

Appl. Phys. Lett. 97, 051108 (2010); http://dx.doi.org/10.1063/1.3476342 (3 pages) | Cited 9 times

Online Publication Date: 5 August 2010

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Surface leakage reduction has been achieved using BCl3/Cl2/CH4/H2/Ar inductively coupled plasma dry etching for pixel isolation of high performance long-wave infrared superlattice detectors. The leakage has been minimized by effectively increasing the surface resistivity by more than 7.4 times and decreasing the surface state density by more than 3.8 times. Through altering the etch mechanism, the dark current density was reduced by more than two orders of magnitude where a dark current of 1.01×10−5 A/cm2 at 200 mV was achieved at T = 77 K for a 10.3 μm detector with a peak quantum efficiency value of 30% (without antireflection coating).
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85.60.Gz Photodetectors (including infrared and CCD detectors)

Background carrier concentration in midwave and longwave InAs/GaSb type II superlattices on GaAs substrate

A. Khoshakhlagh, F. Jaeckel, C. Hains, J. B. Rodriguez, L. R. Dawson, K. Malloy, and S. Krishna

Appl. Phys. Lett. 97, 051109 (2010); http://dx.doi.org/10.1063/1.3457908 (3 pages) | Cited 3 times

Online Publication Date: 5 August 2010

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We report on the measurement of the background carrier concentration of midwave and long-wave infrared (MWIR and LWIR) type-II InAs/GaSb superlattices (SLs) on GaAs substrates. The transport properties of SLs are characterized using temperature dependent Hall measurements. It is found that the conduction in the MWIR SLs is dominated by holes at low temperatures and by electrons at high temperatures. However, the transport in LWIR SL is dominated by electrons at all temperatures. In-plane transport characteristics of LW SLs grown at different temperatures shows that interface roughness scattering is the dominant scattering mechanism at high temperatures.
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72.80.Ey III-V and II-VI semiconductors
73.21.Cd Superlattices
73.63.Bd Nanocrystalline materials
68.35.bg Semiconductors
73.43.Lp Collective excitations
68.35.Ct Interface structure and roughness

Terahertz photonic band gap for the transverse-magnetic modes formed by using a planar waveguide structure with a photonic crystal electrode

Y. Sakasegawa, T. Ihara, and K. Hirakawa

Appl. Phys. Lett. 97, 051110 (2010); http://dx.doi.org/10.1063/1.3474614 (3 pages)

Online Publication Date: 5 August 2010

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We have investigated the terahertz (THz) emission from a semiconductor superlattice placed in a waveguide structure with a photonic crystal surface electrode of a honeycomb lattice pattern. For uniformly applying bias voltages, we inserted a semitransparent Ti film between the superlattice layer and the photonic crystal electrode. It is found that optimization of the sheet resistivity of the Ti layer is crucial to suppress the coupling between the waveguide mode and the surface leaky mode and obtain a clear photonic band gap. When the Ti layer was 40 nm, a large extinction ratio of ∼ 120 in the THz emission intensity was obtained at the midgap frequency around 1.7 THz.
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42.70.Qs Photonic bandgap materials

Impact of heavy hole-light hole coupling on optical selection rules in GaAs quantum dots

T. Belhadj, T. Amand, A. Kunold, C.-M. Simon, T. Kuroda, M. Abbarchi, T. Mano, K. Sakoda, S. Kunz, X. Marie, and B. Urbaszek

Appl. Phys. Lett. 97, 051111 (2010); http://dx.doi.org/10.1063/1.3473824 (3 pages) | Cited 4 times

Online Publication Date: 6 August 2010

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We report strong heavy hole-light hole mixing in GaAs quantum dots grown by droplet epitaxy. Using the neutral and charged exciton emission as a monitor we observe the direct consequence of quantum dot symmetry reduction in this strain free system. By fitting the polar diagram of the emission with simple analytical expressions obtained from k⋅p theory we are able to extract the mixing that arises from the heavy-light hole coupling due to the geometrical asymmetry of the quantum dot.
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73.21.La Quantum dots
68.55.ag Semiconductors
78.55.Cr III-V semiconductors
78.67.Hc Quantum dots
73.22.Lp Collective excitations
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Transient interference implications on the subpicosecond laser damage of multidielectrics

Laurent Gallais, Benoît Mangote, Mireille Commandré, Andrius Melninkaitis, Julius Mirauskas, Maksim Jeskevic, and Valdas Sirutkaitis

Appl. Phys. Lett. 97, 051112 (2010); http://dx.doi.org/10.1063/1.3477961 (3 pages) | Cited 6 times

Online Publication Date: 6 August 2010

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Laser-induced damage in optical thin films with subpicosecond pulses is investigated. A model dedicated to optical interference coatings and based on the rate equation for free electron generation is introduced. It takes into account the transient interference effects induced by changes in the dielectric function during the laser pulse and its feedback effect on the electron density distribution in the multilayer stack. Simulations are compared to experiments on HfO2 and Ta2O5 films with pulses ranging from 45 fs to 1 ps. It is shown that this approach can improve the interpretation of femtosecond and picosecond laser induced damage in thin films.
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42.60.-v Laser optical systems: design and operation
42.25.Hz Interference
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.79.-e Optical elements, devices, and systems

Improved luminescence properties of Eu-doped GaN light-emitting diodes grown by atmospheric-pressure organometallic vapor phase epitaxy

A. Nishikawa, N. Furukawa, T. Kawasaki, Y. Terai, and Y. Fujiwara

Appl. Phys. Lett. 97, 051113 (2010); http://dx.doi.org/10.1063/1.3478011 (3 pages) | Cited 5 times

Online Publication Date: 6 August 2010

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We investigated the luminescence properties of Eu-doped GaN (GaN:Eu) grown by atmospheric-pressure organometallic vapor phase epitaxy. The GaN:Eu exhibited radiant red emission due to the intra-4f shell transition of Eu3+ ions at room temperature. The intensity of the dominant peak was about 4 times higher than that in the sample grown at 10 kPa, even though the Eu concentration was only half that of the 10 kPa sample. This was mainly caused by the enhancement of the energy transfer from the GaN host to Eu ions. The enhanced energy transfer resulted in improved luminescence properties of a GaN:Eu light-emitting diode.
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85.60.Jb Light-emitting devices
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On the hysteresis at ion extraction in the single-grid ion source

D. V. Rafalskyi and S. V. Dudin

Appl. Phys. Lett. 97, 051501 (2010); http://dx.doi.org/10.1063/1.3475924 (3 pages) | Cited 3 times

Online Publication Date: 3 August 2010

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The ion extraction in the single-grid ion source with a woven extraction grid is researched. It has been found experimentally that the extraction can occur in “low current” and “high current” modes with stepwise hysteretic transitions between them. The assumption has been made that the existence of the two extraction regimes can be explained by the existence of two kinds of the space charge sheaths near the grid wires. This assumption is confirmed by the estimations of the sheath depth for the cylindrical and plane geometries.
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52.50.Dg Plasma sources
52.40.Kh Plasma sheaths
52.40.Hf Plasma-material interactions; boundary layer effects
52.30.-q Plasma dynamics and flow
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.80.-s Electric discharges

Propagation of energetic electrons in a hollow plasma fiber

C. T. Zhou, L. Y. Chew, and X. T. He

Appl. Phys. Lett. 97, 051502 (2010); http://dx.doi.org/10.1063/1.3475414 (3 pages) | Cited 5 times

Online Publication Date: 4 August 2010

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Transport of energetic electrons in a hollow plasma fiber is investigated. The high-current electron beam induces in the fiber strong radial electric fields and azimuthal magnetic fields on the inner and outer surfaces of the hollow fiber. The hot electrons are pushed out by the surface magnetic field and returned into the fiber by the sheath electric field. Imbalance of the latter fields can drive chaotic oscillations of electrons around the fiber wall. Intense thin return-current layers inside both the inner and outer wall surfaces are observed. This enhances local joule heating around both surfaces by the return current.
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52.40.Mj Particle beam interactions in plasmas
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.50.-b Plasma production and heating
52.25.Fi Transport properties

Comatic aberration-induced wavy vortex in gas

Hong-Yu Chu, Shang-Bin Lin, and Chang-Rong Ko

Appl. Phys. Lett. 97, 051503 (2010); http://dx.doi.org/10.1063/1.3477950 (3 pages)

Online Publication Date: 5 August 2010

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We investigate the evolution of laser-induced wavy vortex at 460 torr nitrogen gas environment. We show that Rayleigh–Taylor instability and Kelvin–Helmholtz instability are not the causes of the growth of the wavy vortex. Normal diffusion inducing the growth of the ripple-type perturbation is identified. The ratio of the perturbation amplitude to the wavelength of perturbation is found with 0.16. Through a quick estimation, measurements show the consistent scaling relations. We further show that the comatic aberration is suspected to be responsible for the asymmetric rarefaction wave, which triggers Kelvin–Helmholtz instability and induces the wavy vortex.
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47.20.Ma Interfacial instabilities (e.g., Rayleigh-Taylor)
47.32.-y Vortex dynamics; rotating fluids
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Modulating the electronic structures and optical absorption spectra of BeO nanotubes by uniaxial strain

Jiangang He, Kechen Wu, Rongjian Sa, Qiaohong Li, and Yongqin Wei

Appl. Phys. Lett. 97, 051901 (2010); http://dx.doi.org/10.1063/1.3473726 (3 pages) | Cited 2 times

Online Publication Date: 3 August 2010

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The electronic structures, optical absorption spectra, and the modulation of uniaxial strain along tube axis to electronic structures and optical absorption spectra of BeO nanotubes have been studied using the density functional theory. The results show that the absorption spectrum of BeO nanotubes is anisotropic with respect to light polarization and is closely related to the chirality and diameter of tube. The uniaxial strain can effectively modulate the electronic structures and absorption spectra of BeO nanotubes, indicating the armchair BeO nanotubes can be used as the anisotropic device and sensor of photoelectron.
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73.22.-f Electronic structure of nanoscale materials and related systems
71.20.Ps Other inorganic compounds
78.67.Ch Nanotubes

Direct evidence of LO phonon-plasmon coupled modes in n-GaN

Devki N. Talwar

Appl. Phys. Lett. 97, 051902 (2010); http://dx.doi.org/10.1063/1.3473826 (3 pages) | Cited 3 times

Online Publication Date: 3 August 2010

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We report theoretical results of the far-infrared transmission in oblique incidence for undoped and doped GaN epilayers. For c-GaN, our results in p-polarization find transmission minima at LO and TO frequencies while in s-polarization only one minima corresponding to TO mode is revealed. For c-GaN/GaAs/AlN (buffer) layer we noticed minima in s-polarization corresponding to TO modes of c-GaN and c-AlN while in p-polarization the features related to TO modes as well as minima linked to LO modes are found. The shift in L+ modes with increasing carrier concentration (N) provided direct evidence of estimating N in doped GaN.
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73.61.Ey III-V semiconductors
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
68.55.ag Semiconductors
78.66.Fd III-V semiconductors
78.30.Fs III-V and II-VI semiconductors

Suppression of boron–oxygen defects in p-type Czochralski silicon by germanium doping

Xuegong Yu, Peng Wang, Peng Chen, Xiaoqiang Li, and Deren Yang

Appl. Phys. Lett. 97, 051903 (2010); http://dx.doi.org/10.1063/1.3475486 (3 pages) | Cited 5 times

Online Publication Date: 3 August 2010

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We have demonstrated the impact of germanium (Ge) doping on the boron–oxygen (B–O) defects in p-type Czochralski (CZ) silicon. It is found that germanium can effectively suppress the formation of B–O defects, whereby the reduction percentage of B–O defect concentration increases with the Ge content. The efficiency of Ge-doped CZ silicon solar cell and the power output of corresponding module both exhibit a significantly lower loss. Based on the fact of a relatively lower concentration of O2i existing in GCZ silicon, it is believed that the suppression of B–O defects is a result of Ge improving the diffusion barrier of Oi.
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61.72.U- Doping and impurity implantation
88.40.H- Solar cells (photovoltaics)
66.30.-h Diffusion in solids

Indium incorporation and optical transitions in InGaN bulk materials and quantum wells with arbitrary polarity

M. V. Durnev, A. V. Omelchenko, E. V. Yakovlev, I. Yu. Evstratov, and S. Yu. Karpov

Appl. Phys. Lett. 97, 051904 (2010); http://dx.doi.org/10.1063/1.3476344 (3 pages) | Cited 8 times

Online Publication Date: 5 August 2010

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Indium incorporation into strained InGaN coherently grown on a GaN substrate with arbitrary polarity is simulated using a simplified epitaxy model. The InGaN composition is predicted as a function of C-axis inclination angle. Effect of strain originated from the lattice mismatch on optical transitions in the bulk InGaN and quantum wells is examined with account of both complex valence band structure and polarization charges induced at the InGaN/GaN interfaces. A higher indium incorporation on nonpolar and semipolar planes, as compared to the ordinary C-plane, is found to not necessarily result in a longer emission wavelength.
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81.05.Ea III-V semiconductors
81.07.St Quantum wells
78.67.De Quantum wells
73.21.Fg Quantum wells
68.65.Fg Quantum wells
77.22.Ej Polarization and depolarization

Determination of the chiralities of isolated carbon nanotubes during superplastic elongation process

Kaori Hirahara, Keita Inose, and Yoshikazu Nakayama

Appl. Phys. Lett. 97, 051905 (2010); http://dx.doi.org/10.1063/1.3473823 (3 pages) | Cited 6 times

Online Publication Date: 5 August 2010

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The structural changes in an isolated carbon nanotube during superplastic elongation are studied using a in situ transmission electron microscopy equipped with a nanomanipulation system. Nanobeam electron diffraction reveals the chiral indices of the nanotube decrease by (1, 1) when tensile stress and electroresistive heating are simultaneously applied. The change in the chiral indices corresponds to the migration of just two pairs of defects in the nanotube walls. The experiment allows the dynamics of plastic deformation to be understood at the atomistic level, which will be beneficial for constructing advanced devices with utilization of nanotubes.
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61.46.Fg Nanotubes
81.40.Jj Elasticity and anelasticity, stress-strain relations
81.40.Gh Other heat and thermomechanical treatments
62.20.fq Plasticity and superplasticity
62.20.D- Elasticity
81.40.Lm Deformation, plasticity, and creep

Switchable metamaterial reflector/absorber for different polarized electromagnetic waves

Bo Zhu, Yijun Feng, Junming Zhao, Ci Huang, and Tian Jiang

Appl. Phys. Lett. 97, 051906 (2010); http://dx.doi.org/10.1063/1.3477960 (3 pages) | Cited 19 times

Online Publication Date: 5 August 2010

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We demonstrate a controllable electromagnetic wave reflector/absorber for different polarizations with metamaterial involving electromagnetic resonant structures coupled with diodes. Through biasing at different voltages to turn ON and OFF the diodes, we are able to switch the structure between nearly total reflection and total absorption of a particularly polarized incident wave. By arranging orthogonally orientated resonant cells, the metamaterial can react to different polarized waves by selectively biasing the corresponding diodes. Both numerical simulations and microwave measurements have verified the performance.
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41.20.Jb Electromagnetic wave propagation; radiowave propagation
42.25.Ja Polarization
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.70.-a Optical materials

Silicon impurity-induced layer disordering of AlGaN/AlN superlattices

J. J. Wierer, Jr., A. A. Allerman, and Q. Li

Appl. Phys. Lett. 97, 051907 (2010); http://dx.doi.org/10.1063/1.3478002 (3 pages) | Cited 1 time

Online Publication Date: 5 August 2010

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Impurity-induced layer disordering is demonstrated in Al0.1Ga0.9N/AlN superlattices grown by metal-organic vapor phase epitaxy. During growth at temperatures as low as 885 °C and under post growth annealing at 1000 °C in N2 the heterointerfaces of Si-doped (Si concentration >8×1019 cm−3) superlattices exhibit layer disordering (intermixing) while the unintentionally doped superlattices remain stable. Shifts in the intersubband energy transitions and scanning transmission electron microscope images showing changes in the layer abruptness are used to verify layer disordering due to Si diffusion in Al0.1Ga0.9N/AlN superlattices.
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68.65.Cd Superlattices
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
66.30.J- Diffusion of impurities
61.72.sd Impurity concentration
61.72.Cc Kinetics of defect formation and annealing
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Control of interface abruptness of polar MgZnO/ZnO quantum wells grown by pulsed laser deposition

Matthias Brandt, Martin Lange, Marko Stölzel, Alexander Müller, Gabriele Benndorf, Jan Zippel, Jörg Lenzner, Michael Lorenz, and Marius Grundmann

Appl. Phys. Lett. 97, 052101 (2010); http://dx.doi.org/10.1063/1.3475402 (3 pages) | Cited 17 times

Online Publication Date: 2 August 2010

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A strong quantum confined Stark effect (QCSE) was observed in wedge shaped MgZnO/ZnO quantum wells (QWs) grown by pulsed laser deposition. A reduced laser fluence of 1.8 J/cm2 was used. Reference samples grown at higher standard fluence 2.4 J/cm2 showed only a negligible QCSE. Using off-axis deposition without substrate rotation, a constant composition of the barriers was maintained while varying the well width in a wedge shaped QW. A redshift of the QW luminescence with increasing QW thickness up to 230 meV below the ZnO emission was found, accompanied by an increase in the exciton lifetime from 0.3 ns up to 4.2 μs.
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78.20.Jq Electro-optical effects
78.67.De Quantum wells
78.55.Et II-VI semiconductors
81.05.Dz II-VI semiconductors
81.15.Fg Pulsed laser ablation deposition
71.35.-y Excitons and related phenomena

Enhanced thermoelectricity in composites by electronic structure modifications and nanostructuring

A. Popescu and L. M. Woods

Appl. Phys. Lett. 97, 052102 (2010); http://dx.doi.org/10.1063/1.3464288 (3 pages) | Cited 11 times

Online Publication Date: 4 August 2010

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The thermoelectric performance of nanocomposites with locally distorted density of states is investigated. The analytical expressions we have derived allow us to explore the effects of localized states modeled as Lorentzians on the materials transport properties in terms of their sharpness and locations relative to the Fermi level. Further optimization of the transport through nanostructuring design is also explored. We show that composites with both locally distorted density of states and nanostructure integration open the possibility for significant enhancement of the thermoelectric performance at room temperature.
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72.20.Pa Thermoelectric and thermomagnetic effects
73.63.Bd Nanocrystalline materials
73.22.-f Electronic structure of nanoscale materials and related systems
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.20.At Surface states, band structure, electron density of states
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