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31 May 2010

Volume 96, Issue 22, Articles (22xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 96, 223101 (2010); http://dx.doi.org/10.1063/1.3439728 (3 pages)

Seokho Yun, Jeremy A. Bossard, Theresa S. Mayer, and Douglas H. Werner
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Scatterer induced mode splitting in poly(dimethylsiloxane) coated microresonators

Lina He, Sahin Kaya Ozdemir, Jiangang Zhu, and Lan Yang

Appl. Phys. Lett. 96, 221101 (2010); http://dx.doi.org/10.1063/1.3435480 (3 pages) | Cited 5 times

Online Publication Date: 1 June 2010

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We investigate scatterer induced mode splitting in a composite microtoroidal resonator (Q ∼ 106) fabricated by coating a silica microtoroid (Q ∼ 107) with a thin poly(dimethylsiloxane) layer. We show that the two split modes in both coated and uncoated silica microtoroids respond in the same way to the changes in the environmental temperature. This provides a self-referencing scheme which is robust to temperature perturbations. Together with the versatile functionalities of polymer materials, mode splitting in polymer and polymer coated microresonators offers an attractive sensing platform that is robust to thermal noise.
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68.55.-a Thin film structure and morphology
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices

Strong coupling in a quantum dot micropillar system under electrical current injection

C. Kistner, K. Morgener, S. Reitzenstein, C. Schneider, S. Höfling, L. Worschech, A. Forchel, P. Yao, and S. Hughes

Appl. Phys. Lett. 96, 221102 (2010); http://dx.doi.org/10.1063/1.3442912 (3 pages) | Cited 1 time

Online Publication Date: 1 June 2010

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Integrating In0.3Ga0.7As quantum dots (QDs) featuring a high oscillator strength into a high quality electrically contacted micropillar cavity enabled us to realize strong coupling under electrical carrier injection. In the micropillar cavity with a quality factor of 10 000 and a diameter of 1.9 μm, a vacuum Rabi splitting of 108 μeV was observed when an electrically excited QD exciton was tuned through resonance with the fundamental cavity mode by varying the temperature.
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73.63.Kv Quantum dots
78.67.Hc Quantum dots
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
73.21.La Quantum dots

Optical performance of single-mode hybrid dielectric-loaded plasmonic waveguide-based components

Hong-Son Chu, Er-Ping Li, Ping Bai, and Ravi Hegde

Appl. Phys. Lett. 96, 221103 (2010); http://dx.doi.org/10.1063/1.3437088 (3 pages) | Cited 18 times

Online Publication Date: 2 June 2010

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The single mode hybrid dielectric-loaded plasmonic waveguide is presented at the wavelength of 1.55 μm. We show that this waveguiding structure, consisting of a low-index SiO2-stripe sandwiched between a high-index Si-nanowire and a silver film, achieves both long propagation length and strong field confinement with high power intensity. Components such as 90°-circular and S-shaped bends, based on the proposed waveguide with an intensity confinement area of 50×200 nm2, can obtain a total transmission efficiency exceeding 85% for various bend radii. Finally, we demonstrate that the efficient directional couplers can be developed using two coupled waveguides. In particular, we determine the typical coupling lengths and maximum transfer power for different structural parameters of the coupler. These investigations provide the foundations for the design of chip-scale integrated plasmonic circuitry.
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42.82.Et Waveguides, couplers, and arrays
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.79.Gn Optical waveguides and couplers

Free-standing subwavelength metallic gratings for snapshot multispectral imaging

Riad Haïdar, Grégory Vincent, Stéphane Collin, Nathalie Bardou, Nicolas Guérineau, Joël Deschamps, and Jean-Luc Pelouard

Appl. Phys. Lett. 96, 221104 (2010); http://dx.doi.org/10.1063/1.3442487 (3 pages) | Cited 7 times

Online Publication Date: 2 June 2010

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A mosaic of ten spectral filters has been fabricated in a single 20 mm2 membrane drilled by nanoslits and coated by a gold layer. The nanostructured core-shell gratings exhibit 70% average maximum transmission efficiency in 15% aperture area, which represents a fivefold enhancement compared to the geometrical transmission. This mosaic of bandpass filters regularly spaced in the 3–5 μm wavelength range is used to demonstrate real-time spectral imaging in a multichannel camera.
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42.79.Ls Scanners, image intensifiers, and image converters
42.79.Dj Gratings
42.79.Ci Filters, zone plates, and polarizers
42.86.+b Optical workshop techniques

Improvement of peak quantum efficiency and efficiency droop in III-nitride visible light-emitting diodes with an InAlN electron-blocking layer

Suk Choi, Hee Jin Kim, Seong-Soo Kim, Jianping Liu, Jeomoh Kim, Jae-Hyun Ryou, Russell D. Dupuis, Alec M. Fischer, and Fernando A. Ponce

Appl. Phys. Lett. 96, 221105 (2010); http://dx.doi.org/10.1063/1.3441373 (3 pages) | Cited 36 times

Online Publication Date: 3 June 2010

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InAlN electron-blocking layers (EBLs) are shown to improve the emission intensity and to mitigate the efficiency droop problem in III-nitride-based visible light-emitting diodes (LEDs). Using an In0.18Al0.82N EBL in blue LEDs, we have achieved a significant improvement in the electroluminescence emission intensity and a mitigated efficiency droop compared to similar LEDs without an EBL or with an Al0.2Ga0.8N EBL. This indicates that an In0.18Al0.82N EBL is more effective in electron confinement and reduces the efficiency droop possibly caused by carrier spill-over than conventional AlGaN EBLs.
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85.60.Jb Light-emitting devices
85.60.-q Optoelectronic devices
78.66.Fd III-V semiconductors
78.60.Fi Electroluminescence
85.30.De Semiconductor-device characterization, design, and modeling
81.05.Ea III-V semiconductors

Density-activated defect recombination as a possible explanation for the efficiency droop in GaN-based diodes

J. Hader, J. V. Moloney, and S. W. Koch

Appl. Phys. Lett. 96, 221106 (2010); http://dx.doi.org/10.1063/1.3446889 (3 pages) | Cited 36 times

Online Publication Date: 3 June 2010

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It is shown that a carrier loss process modeling density-activated defect recombination can reproduce the experimentally observed droop of the internal quantum efficiency in GaN-based laser diodes.
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42.55.Px Semiconductor lasers; laser diodes
81.05.Ea III-V semiconductors

Highly efficient Brillouin amplification of strong Stokes seed

Qi Guo, Zhiwei Lu, and Yulei Wang

Appl. Phys. Lett. 96, 221107 (2010); http://dx.doi.org/10.1063/1.3435385 (3 pages) | Cited 3 times

Online Publication Date: 3 June 2010

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Brillouin amplification of strong Stokes seed, which can achieve the output energy of 400 mJ and amplified efficiency of about 85% under the condition that the energy of Stokes beam and pump beam is in the ratio of 39.5/1, is reported. The relationship between output energy of strong signal Brillouin amplification and the energy of Stokes beam as well as pump beam, the interaction length, absorption coefficient is investigated. The design of strong signal Brillouin amplification system with high output energy is also provided.
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42.55.Wd Fiber lasers
78.60.-b Other luminescence and radiative recombination

Optical chirality of bacteriorhodopsin films via second harmonic Maker’s fringes measurements

M. C. Larciprete, A. Belardini, C. Sibilia, M.-b. Saab, G. Váró, and C. Gergely

Appl. Phys. Lett. 96, 221108 (2010); http://dx.doi.org/10.1063/1.3442503 (3 pages) | Cited 2 times

Online Publication Date: 3 June 2010

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We experimentally investigated second harmonic generation from an oriented multilayer film of bacteriorhodopsin protein, deposited onto a charged surface. The generated signal is obtained as a function of incidence angle, at different polarization state of both fundamental and generated beams. We show that the measurements, together with the analytical curves, allow to retrieve the nonvanishing elements of the nonlinear optical tensor, including the ones introduced by optical chirality.
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87.16.Nn Motor proteins (myosin, kinesin dynein)
42.65.An Optical susceptibility, hyperpolarizability
43.25.-x Nonlinear acoustics
33.15.Bh General molecular conformation and symmetry; stereochemistry
36.20.-r Macromolecules and polymer molecules
87.15.-v Biomolecules: structure and physical properties

Enhanced telecom wavelength single-photon detection with NbTiN superconducting nanowires on oxidized silicon

M. G. Tanner, C. M. Natarajan, V. K. Pottapenjara, J. A. O’Connor, R. J. Warburton, R. H. Hadfield, B. Baek, S. Nam, S. N. Dorenbos, E. Bermúdez Ureña, T. Zijlstra, T. M. Klapwijk, and V. Zwiller

Appl. Phys. Lett. 96, 221109 (2010); http://dx.doi.org/10.1063/1.3428960 (3 pages) | Cited 24 times

Online Publication Date: 3 June 2010

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Superconducting nanowire single-photon detectors (SNSPDs) have emerged as a highly promising infrared single-photon detector technology. Next-generation devices are being developed with enhanced detection efficiency (DE) at key technological wavelengths via the use of optical cavities. Furthermore, new materials and substrates are being explored for improved fabrication versatility, higher DE, and lower dark counts. We report on the practical performance of packaged NbTiN SNSPDs fabricated on oxidized silicon substrates in the wavelength range from 830 to 1700 nm. We exploit constructive interference from the SiO2/Si interface in order to achieve enhanced front-side fiber-coupled DE of 23.2 % at 1310 nm, at 1 kHz dark count rate, with 60 ps full width half maximum timing jitter.
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85.25.Pb Superconducting infrared, submillimeter and millimeter wave detectors
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
85.60.Gz Photodetectors (including infrared and CCD detectors)

Surface 210 nm light emission from an AlN p–n junction light-emitting diode enhanced by A-plane growth orientation

Yoshitaka Taniyasu and Makoto Kasu

Appl. Phys. Lett. 96, 221110 (2010); http://dx.doi.org/10.1063/1.3446834 (3 pages) | Cited 10 times

Online Publication Date: 4 June 2010

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(11math0) A-plane AlN p–n junction light-emitting diode (LED) with a wavelength of 210 nm is demonstrated. The electroluminescence from the A-plane LED is inherently polarized for the electric field parallel to the [0001] c-axis due to a negative crystal-field splitting energy. The polarization ratio (electric-field component ratio of parallel and perpendicular to c-axis) is as high as 0.9. The radiation pattern of the A-plane LED shows higher emission intensity along the surface normal, while that of a conventional (0001) C-plane LED shows lower emission intensity along the surface normal. The different radiation patterns can be explained by the polarization property.
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85.60.Jb Light-emitting devices
78.60.Fi Electroluminescence

Observations of temporal group delays in slow-light multiple coupled photonic crystal cavities

S. Kocaman, X. Yang, J. F. McMillan, M. B. Yu, D. L. Kwong, and C. W. Wong

Appl. Phys. Lett. 96, 221111 (2010); http://dx.doi.org/10.1063/1.3446893 (3 pages) | Cited 6 times

Online Publication Date: 4 June 2010

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We demonstrate temporal group delays in coherently coupled high-Q multicavity photonic crystals, in an all-optical analog to electromagnetically induced transparency. We report deterministic control of the group delay up to 4× the single cavity lifetime in our room-temperature chip. Supported by three-dimensional numerical simulations and theoretical analyses, our multipump beam approach enables control of the multicavity resonances and intercavity phase, in both single and double transparency peaks. The standing-wave wavelength-scale photon localization allows direct scalability for chip-scale optical pulse trapping and coupled-cavity quantum electrodynamics.
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42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.50.Gy Effects of atomic coherence on propagation, absorption, and amplification of light; electromagnetically induced transparency and absorption
42.70.Qs Photonic bandgap materials

Upper limit for the modulation bandwidth of a quantum dot laser

Levon V. Asryan and Robert A. Suris

Appl. Phys. Lett. 96, 221112 (2010); http://dx.doi.org/10.1063/1.3446968 (3 pages) | Cited 7 times

Online Publication Date: 4 June 2010

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We derive a closed-form expression for the upper limit for the modulation bandwidth of a semiconductor quantum dot (QD) laser. The highest possible bandwidth increases directly with overlap integral of the electron and hole wave functions in a QD, number of QD-layers, and surface density of QDs in a layer, and is inversely proportional to the inhomogeneous line broadening caused by the QD-size dispersion. At 10% QD-size fluctuations and 100% overlap, the upper limit for the modulation bandwidth in a single QD-layer laser can be as high as 60 GHz.
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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
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Production of highly ionized species in high-current pulsed cathodic arcs

R. Sanginés, A. M. Israel, I. S. Falconer, D. R. McKenzie, and M. M. M. Bilek

Appl. Phys. Lett. 96, 221501 (2010); http://dx.doi.org/10.1063/1.3442509 (3 pages) | Cited 1 time

Online Publication Date: 1 June 2010

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Time resolved optical diagnostic techniques were used to study the production of highly ionized species in aluminum plasma produced by a centered-triggered high-current pulsed cathodic arc. Controlling the spacing between cathode spots enabled a correlation between a reduction in the mean charge state and an increase in the spacing of cathode spots to be observed. As the cathode current was increased, the distances between spots were reduced and these charge states were produced for longer times. Strong cathode spot coupling is proposed as a mechanism for the production of high charge states.
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52.50.Dg Plasma sources
52.80.Mg Arcs; sparks; lightning; atmospheric electricity
52.25.Jm Ionization of plasmas
52.25.Fi Transport properties
52.70.Kz Optical (ultraviolet, visible, infrared) measurements

Extreme water state produced by underwater wire-array electrical explosion

A. Fedotov-Gefen, S. Efimov, L. Gilburd, S. Gleizer, G. Bazalitsky, V. Tz. Gurovich, and Ya. E. Krasik

Appl. Phys. Lett. 96, 221502 (2010); http://dx.doi.org/10.1063/1.3446832 (3 pages) | Cited 3 times

Online Publication Date: 2 June 2010

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The generation of an extreme water state (130 GPa, 5000 K, and 3.4 g/cm3) which is characterized as dense plasma at the axis of a converging shock wave is reported. A 4 kJ pulse generator was used to explode a 40 Cu-wire array, generating a cylindrical shock wave. The measured shock wave trajectory and energy deposited into the water flow were used in hydrodynamic simulations coupled with the equation of state to determine the water parameters. The temperature estimated using the emission data of water in the vicinity of the implosion axis agrees with the simulation results, indicating shock wave symmetry in such extreme conditions.
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52.50.Lp Plasma production and heating by shock waves and compression
52.25.-b Plasma properties
52.65.-y Plasma simulation
52.70.-m Plasma diagnostic techniques and instrumentation

Chirped pulse shadowgraphy for single shot time resolved plasma expansion measurements

Y. B. S. R. Prasad, S. Barnwal, P. A. Naik, J. A. Chakera, R. A. Khan, and P. D. Gupta

Appl. Phys. Lett. 96, 221503 (2010); http://dx.doi.org/10.1063/1.3442510 (3 pages) | Cited 4 times

Online Publication Date: 2 June 2010

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The dynamics of ultrashort laser plasmas demand single shot temporal measurements on fast time scales. We describe a method to record the plasma expansion on picosecond (ps) timescales continuously over hundreds of ps, in single shot. The method uses the chirp of a Ti:sapphire laser as a time-resolved optical diagnostic tool. Using this technique, the evolution of the plasma expansion had been recorded with ps time resolutions, by probing with a chirped laser pulse of 200 ps duration. A peak expansion velocity of 1.8×107 cm/s is observed and its evolution in time is obtained for ∼ 300 ps.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
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Effective band gap narrowing of anatase TiO2 by strain along a soft crystal direction

Wan-Jian Yin, Shiyou Chen, Ji-Hui Yang, Xin-Gao Gong, Yanfa Yan, and Su-Huai Wei

Appl. Phys. Lett. 96, 221901 (2010); http://dx.doi.org/10.1063/1.3430005 (3 pages) | Cited 18 times

Online Publication Date: 2 June 2010

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Due to its large band gap (3.2 eV), TiO2 cannot absorb sun light effectively. To reduce its band gap, various approaches have been attempted; most of them are using doping to modify its band structure. Using first-principles band structure calculations, we show that unlike the rutile phases, the band gap of TiO2 in the anatase phase can be effectively reduced by applying stress along a soft direction. We propose that this approach of tuning the band gap by applying stress along soft direction of a layered semiconductor is general and should be applicable to other anisotropic materials.
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71.20.-b Electron density of states and band structure of crystalline solids
73.20.At Surface states, band structure, electron density of states
71.15.Mb Density functional theory, local density approximation, gradient and other corrections

Compositionally driven ferroelectric phase transition in xBiInO3–(1−x)BaTiO3: a lead-free perovskite-based piezoelectric material

K. Datta, E. Suard, and P. A. Thomas

Appl. Phys. Lett. 96, 221902 (2010); http://dx.doi.org/10.1063/1.3442504 (3 pages) | Cited 2 times

Online Publication Date: 2 June 2010

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A comprehensive structural investigation has been carried out on xBiInO3–(1−x)BaTiO3, where x ≤ 0.25, using the high resolution neutron powder diffractometer D2B at Institut Laue-Langevin, France. The room temperature structures of eight different compositions between x = 0.03 and 0.25 of this solid solution have been determined through Rietveld refinement. A gradual structural phase transition has been observed as a function of composition, where the tetragonal (P4mm) structure (ferroelectric phase) has transformed into a cubic (Pmmathm) structure (paraelectric phase) after passing through a region of coexisting phases. Details of the crystallographic information obtained from the refinement have been presented.
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77.80.B- Phase transitions and Curie point
77.84.-s Dielectric, piezoelectric, ferroelectric, and antiferroelectric materials
64.75.Nx Phase separation and segregation in solid solutions

Synthesis and characterization of CsSnI3 thin films

Kai Shum, Zhuo Chen, Jawad Qureshi, Chonglong Yu, Jian J. Wang, William Pfenninger, Nemanja Vockic, John Midgley, and John T. Kenney

Appl. Phys. Lett. 96, 221903 (2010); http://dx.doi.org/10.1063/1.3442511 (3 pages) | Cited 6 times

Online Publication Date: 2 June 2010

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We report on the synthesis and characterization of CsSnI3 perovskite semiconductor thin films deposited on inexpensive substrates such as glass and ceramics. These films contained polycrystalline domains with typical size of 300 nm. It is confirmed experimentally that CsSnI3 compound in its black phase is a direct band-gap semiconductor, consistent with the calculated band structure from the first principles. The band gap is determined to be ∼ 1.3 eV at Γ point at room temperature.
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68.55.ag Semiconductors
73.61.Le Other inorganic semiconductors
78.66.Li Other semiconductors

Microstructure of epitaxial strained BiCrO3 thin films

A. David, Ph. Boullay, R. V. K. Mangalam, N. Barrier, and W. Prellier

Appl. Phys. Lett. 96, 221904 (2010); http://dx.doi.org/10.1063/1.3435486 (3 pages) | Cited 4 times

Online Publication Date: 2 June 2010

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The structure and microstructure of fully strained BiCrO3 thin films have been investigated by x-rays diffraction and transmission electron diffraction, at room temperature. Interestingly, three structural variants are simultaneously stabilized within the film. While two of them are consistent with the existing phases in the bulk-below and above the 420 K structural transition, a different phase is identified. The existence of various structures has been attributed to the inhomogeneous distribution of local strains and oxygens resulting from a minimization of the strain-energy at the interface. These findings will open the route to a better understanding of Bi-based perovskites and metastable phases.
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81.15.Fg Pulsed laser ablation deposition
68.55.aj Insulators
68.55.J- Morphology of films
68.55.Nq Composition and phase identification
68.60.Bs Mechanical and acoustical properties

Ferroelectric polarization and domain walls in orthorhombic (K1−xNax)NbO3 lead-free ferroelectric ceramics

Ning Lu, Rong Yu, Zhiying Cheng, Yejing Dai, Xiaowen Zhang, and Jing Zhu

Appl. Phys. Lett. 96, 221905 (2010); http://dx.doi.org/10.1063/1.3442905 (3 pages) | Cited 3 times

Online Publication Date: 2 June 2010

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Combining aberration-corrected high-resolution transmission electron microscopy with first-principles calculations, we have investigated the ferroelectric polarization and the atomic structures of 60°/120° domain walls in orthorhombic (K0.46Na0.54)NbO3 lead-free ferroelectric ceramics. The projections of cation-oxygen dipoles across the 60°/120° domain walls were determined using the recently developed negative spherical-aberration imaging technique. The measured ferroelectric distortion matched well with that obtained from first-principles calculations. The width across the wall was measured to be ∼ 1.1 nm.
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77.80.Dj Domain structure; hysteresis
75.60.Ch Domain walls and domain structure
78.20.Jq Electro-optical effects
71.15.-m Methods of electronic structure calculations

Terahertz radiation from coherent antiferromagnetic magnons excited by femtosecond laser pulses

Junichi Nishitani, Kohei Kozuki, Takeshi Nagashima, and Masanori Hangyo

Appl. Phys. Lett. 96, 221906 (2010); http://dx.doi.org/10.1063/1.3436635 (3 pages) | Cited 4 times

Online Publication Date: 3 June 2010

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We report on the observation of terahertz (THz) radiation emitted from antiferromagnetic (AFM) single-crystal nickel oxide irradiated with femtosecond laser pulses. Periodic oscillations observed in the THz waveforms are assigned to the radiation from coherent AFM magnons excited by the laser pulses. Impulsive stimulated Raman scattering process is a possible mechanism of the coherent AFM magnon excitation by the laser pulses. The excited magnons in NiO generate THz waves by magnetic dipole radiation, which is the inverse process of AFM resonance absorption of THz waves.
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78.70.Gq Microwave and radio-frequency interactions
76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
78.30.Hv Other nonmetallic inorganics
75.50.Ee Antiferromagnetics

Electron coherent diffraction tomography of a nanocrystal

Roman Dronyak, Keng S. Liang, Jin-Sheng Tsai, Yuri P. Stetsko, Ting-Kuo Lee, and Fu-Rong Chen

Appl. Phys. Lett. 96, 221907 (2010); http://dx.doi.org/10.1063/1.3436639 (3 pages)

Online Publication Date: 3 June 2010

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Coherent diffractive imaging (CDI) with electron or x-ray sources is a promising technique for investigating the structure of nanoparticles down to the atomic scale. In electron CDI, a two-dimensional reconstruction is demonstrated using highly coherent illumination from a field-emission gun as a source of electrons. In a three-dimensional (3D) electron CDI, we experimentally determine the morphology of a single MgO nanocrystal using the Bragg diffraction geometry. An iterative algorithm is applied to invert the 3D diffraction pattern about a (200) reflection of the nanoparticle measured at an angular range of 1.8°. The results reveal a 3D image of the sample at ∼ 8 nm resolution, and agree with a simulation. Our work demonstrates an alternative approach to obtain the 3D structure of nanocrystals with an electron microscope.
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61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
61.05.J- Electron diffraction and scattering

Structural evolution during the sub-Tg relaxation of hyperquenched metallic glasses

Lina Hu, Chunzhi Zhang, and Yuanzheng Yue

Appl. Phys. Lett. 96, 221908 (2010); http://dx.doi.org/10.1063/1.3447373 (3 pages) | Cited 3 times

Online Publication Date: 4 June 2010

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We report the structural characteristics during the sub-Tg relaxation in hyperquenched La55Al25Ni20 glasses. The sub-Tg relaxation is associated with the structural change in intermediate range order, as manifested by the appearance of a prepeak in the x-ray diffraction spectrum. Such structural change could be the source of the Johari–Goldstein relaxation in metallic glasses. The mechanism governing the evolution of the prepeak is different between the glasses with the fictive temperature below 604 K and those above 604 K. Cooperative motion of atoms in La-centered clusters was further discussed in terms of the atomic bond deficiency model.
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61.43.Fs Glasses
64.70.pe Metallic glasses
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Permanent optical doping of amorphous metal oxide semiconductors by deep ultraviolet irradiation at room temperature

Hyungtak Seo, Young-Je Cho, Jinwoo Kim, Santosh M.bobade, Kyoung-Youn Park, Jaegab Lee, and Duck-Kyun Choi

Appl. Phys. Lett. 96, 222101 (2010); http://dx.doi.org/10.1063/1.3429586 (3 pages) | Cited 4 times

Online Publication Date: 1 June 2010

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We report an investigation of two photon ultraviolet (UV) irradiation induced permanent n-type doping of amorphous InGaZnO (a-IGZO) at room temperature. The photoinduced excess electrons were donated to change the Fermi-level to a conduction band edge under the UV irradiation, owing to the hole scavenging process at the oxide interface. The use of optically n-doped a-IGZO channel increased the carrier density to ∼ 1018 cm−3 from the background level of 1016 cm−3, as well as the comprehensive enhancement upon UV irradiation of a-IGZO thin film transistor parameters, such as an on-off current ratio at ∼ 108 and field-effect mobility at 22.7 cm2/V s.
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61.82.Fk Semiconductors
71.23.Cq Amorphous semiconductors, metallic glasses, glasses
73.61.Jc Amorphous semiconductors; glasses
73.61.Ga II-VI semiconductors
73.50.Dn Low-field transport and mobility; piezoresistance
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)

Theory of electroluminescence intensity and insights into recombination in thin film solar cells

Gregory Brown, Vladimir Faifer, Ben Cardozo, Eugene Bykov, and Miguel Contreras

Appl. Phys. Lett. 96, 222102 (2010); http://dx.doi.org/10.1063/1.3443637 (3 pages) | Cited 4 times

Online Publication Date: 1 June 2010

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Equations describing the electroluminescence (EL) intensity as a function of material properties are derived for thin film solar cells and experimentally validated using Cu(In,Ga)Se2 solar cells. EL intensity at constant voltage is controlled by the electronic properties of the neutral bulk even when the diode current is controlled by recombination in the space charge region. Using a combination of techniques, it is found that recombination in the quasineutral bulk does not correlate with recombination in the space charge region. Differences between EL measurements on thin film cells and crystalline silicon cells are discussed including the effects of secondary barriers.
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88.40.jn Thin film Cu-based I-III-VI2 solar cells
85.30.De Semiconductor-device characterization, design, and modeling
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