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15 May 2006

Volume 88, Issue 20, Articles (20xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 88, 203101 (2006); http://dx.doi.org/10.1063/1.2203932 (3 pages)

Andrea Ponzoni, Elisabetta Comini, Giorgio Sberveglieri, Jun Zhou, Shao Zhi Deng, Ning Sheng Xu, Yong Ding, and Zhong Lin Wang
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1.54 μm Si:Er light emitting diode with memory function

B. A. Andreev, Z. F. Krasilnik, D. I. Kryzhkov, V. P. Kuznetsov, T. Gregorkiewicz, and W. Jantsch

Appl. Phys. Lett. 88, 201101 (2006); http://dx.doi.org/10.1063/1.2203935 (3 pages) | Cited 1 time

Online Publication Date: 15 May 2006

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We report a memory effect in electroluminescence of Er-doped silicon light emitting diodes: applying a voltage pulse in reverse-bias direction below breakdown we observe 1.54 μm emission only, if a forward pulse was issued before. This effect occurs for temperatures T ⩽ 120 K in sublimation molecular-beam epitaxy grown structures. This finding opens perspectives for the development of a fully complementary metal-oxide-semiconductor compatible electro-optical converter with a memory function, operating in the 1.5 μm telecommunication band. Such an element could find numerous applications in telecommunication and silicon photonics and optoelectronics circuitry.
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85.60.Jb Light-emitting devices
42.79.Sz Optical communication systems, multiplexers, and demultiplexers
42.82.Gw Other integrated-optical elements and systems

Model for mode locking in quantum dot lasers

E. A. Viktorov, Paul Mandel, Andrei G. Vladimirov, and Uwe Bandelow

Appl. Phys. Lett. 88, 201102 (2006); http://dx.doi.org/10.1063/1.2203937 (3 pages) | Cited 28 times

Online Publication Date: 15 May 2006

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We propose a model for passive mode locking in quantum dot lasers and report on specific dynamical properties of the regime which is characterized by a fast gain recovery. No Q-switching instability has been found accompanying the mode locking. Bistability can occur between the mode locking regime and the nonlasing state.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Fc Modulation, tuning, and mode locking
42.55.Rz Doped-insulator lasers and other solid state lasers
42.65.Pc Optical bistability, multistability, and switching, including local field effects

Ultraviolet lasing in high-order bands of three-dimensional ZnO photonic crystals

Michael Scharrer, Alexey Yamilov, Xiaohua Wu, Hui Cao, and Robert P. H. Chang

Appl. Phys. Lett. 88, 201103 (2006); http://dx.doi.org/10.1063/1.2203939 (3 pages) | Cited 46 times

Online Publication Date: 15 May 2006

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UV lasing in three-dimensional ZnO photonic crystals is demonstrated at room temperature. The photonic crystals are inverse opals with high refractive index contrast that simultaneously confine light and provide optical gain. Highly directional lasing with tunable wavelength is obtained by optical pumping. Comparison of the experimental results to the calculated band structure shows that lasing occurs in high-order bands with abnormally low group velocity. This demonstrates that the high-order band structure of three-dimensional photonic crystals can be used to effectively confine light and enhance emission. Our findings may also impact other applications of photonic crystal devices.
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42.70.Qs Photonic bandgap materials
78.45.+h Stimulated emission
42.55.Tv Photonic crystal lasers and coherent effects
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.55.Px Semiconductor lasers; laser diodes
42.60.Fc Modulation, tuning, and mode locking

Whispering gallery mode of modified octagonal quasiperiodic photonic crystal single-defect microcavity and its side-mode reduction

Po-Tsung Lee, Tsan-Wen Lu, Feng-Mao Tsai, Tien-Chang Lu, and Hao-Chung Kuo

Appl. Phys. Lett. 88, 201104 (2006); http://dx.doi.org/10.1063/1.2203943 (3 pages) | Cited 7 times

Online Publication Date: 15 May 2006

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Single-mode lasing action is obtained from a modified octagonal quasiperiodic photonic crystal single-defect microcavity which supports a well-confined whispering gallery mode with ultralow threshold and high-quality factor. Side-mode reduction is achieved by inserting a central air-hole in the cavity region.
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42.55.Sa Microcavity and microdisk lasers
42.55.Tv Photonic crystal lasers and coherent effects
42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.By Design of specific laser systems

Lateral photocurrent spectroscopy on self-assembled PbSe quantum dots

M. Simma, T. Fromherz, A. Raab, G. Springholz, and G. Bauer

Appl. Phys. Lett. 88, 201105 (2006); http://dx.doi.org/10.1063/1.2202127 (3 pages) | Cited 9 times

Online Publication Date: 15 May 2006

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Wavelength- and temperature-dependent lateral photocurrent measurements were performed on self-assembled PbSe/PbEuTe quantum-dot superlattices. The comparison of the measured data with absorption spectra calculated within the envelope function approach allows a clear identification of the different features in the photocurrent spectra. The photocurrent signal from the dots is observed over a wide temperature range and no quenching occurs even at 5 K. This indicates a type-II band alignment for the strained PbSe/PbEuTe quantum-dots.
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73.21.La Quantum dots
79.60.Bm Clean metal, semiconductor, and insulator surfaces

Highly dispersive photonic crystal-based coupled-cavity structures

A. Talneau, G. Aubin, A. Uddhammar, A. Berrier, M. Mulot, and S. Anand

Appl. Phys. Lett. 88, 201106 (2006); http://dx.doi.org/10.1063/1.2203955 (3 pages) | Cited 6 times

Online Publication Date: 15 May 2006

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We measured the wavelength dependence of the group velocity dispersion (GVD) for different photonic-crystal coupled-cavity structures through a phase analysis of the transmitted modulated signal. GVD values as large as 106–107 times the dispersion of a standard single mode fiber are obtained when operating close to the band edge of the miniband, in agreement with the calculated group index. The GVD is found to be smaller for the structure based on more open cavities.
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42.70.Qs Photonic bandgap materials
42.25.Bs Wave propagation, transmission and absorption

Toward nκd spectroscopy: Analytic solution of the three-phase model of polarimetry in the thin-film limit

I. K. Kim and D. E. Aspnes

Appl. Phys. Lett. 88, 201107 (2006); http://dx.doi.org/10.1063/1.2203967 (3 pages) | Cited 2 times

Online Publication Date: 15 May 2006

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We find an analytic solution of the three-phase (substrate/overlayer/ambient) model of polarimetry in the thin-film limit, which allows overlayer thicknesses d and refractive indices math = n+iκ to be determined from measured changes Δρ/ρ of the complex reflectance ratio ρ and ΔRp/Rp or ΔRs/Rs of the p- or s-polarized reflectances Rp or Rs, from a quadratic equation without the need for potentially unstable numerical methods. We also find a transformation of the data that extends the range of accuracy by up to an order of magnitude without introducing additional mathematical complications. The results are illustrated by the application to a layer of physisorbed H2O on oxidized GaAs, and show that the wavelength-by-wavelength spectroscopy of adsorbed monolayers is now within range of existing polarimetric technology.
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07.60.Fs Polarimeters and ellipsometers
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.66.Fd III-V semiconductors
68.43.-h Chemisorption/physisorption: adsorbates on surfaces

Quasiphase matching of second-harmonic generation in quantum cascade lasers by Stark shift of electronic resonances

Mikhail A. Belkin, Mariano Troccoli, Laurent Diehl, Federico Capasso, Alexey A. Belyanin, Deborah L. Sivco, and Alfred Y. Cho

Appl. Phys. Lett. 88, 201108 (2006); http://dx.doi.org/10.1063/1.2203938 (3 pages) | Cited 5 times

Online Publication Date: 16 May 2006

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We demonstrate a quasiphase matching scheme for second-harmonic generation in quantum cascade lasers with integrated resonant nonlinearity. Modulation of the nonlinear susceptibility is achieved by the periodic modulation of the bias voltage along the ridge waveguide leading to a periodic shift of electronic resonances and a change in the electron population in different energy levels. An up to tenfold enhancement of the conversion efficiency is observed. This technique is applicable to any resonant nonlinear optical process in quantum wells.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.Fc Modulation, tuning, and mode locking

Distributed-feedback GaInAs/AlAsSb quantum-cascade lasers operating at 300 K

Q. Yang, W. Bronner, C. Manz, B. Raynor, H. Menner, Ch. Mann, K. Köhler, and J. Wagner

Appl. Phys. Lett. 88, 201109 (2006); http://dx.doi.org/10.1063/1.2203957 (3 pages) | Cited 4 times

Online Publication Date: 16 May 2006

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Short-wavelength (λ ∼ 4 μm) single-mode distributed-feedback GaInAs/AlAsSb quantum-cascade lasers operating in pulsed mode up to room temperature (300 K) have been demonstrated by etching an index-coupled first-order distributed-feedback grating into the upper GaInAs separate confinement layer. The temperature-dependent wavelength shift of the distributed-feedback lasers is −0.14 cm−1/K (0.238 nm/K). For devices with a size of 18 μm×2.9 mm mounted epilayer-up with as-cleaved facets, a maximum peak power per facet of 840 mW has been achieved at 77 K and 4 mW at 300 K. The characteristic temperature T0 of the threshold current density is 105 K.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Quantum-well saturable absorber at 1.55 μm on GaAs substrate with a fast recombination rate

M. Le Dû, J.-C. Harmand, O. Mauguin, L. Largeau, L. Travers, and J.-L. Oudar

Appl. Phys. Lett. 88, 201110 (2006); http://dx.doi.org/10.1063/1.2204447 (3 pages) | Cited 14 times

Online Publication Date: 16 May 2006

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We propose and realize a structure designed for fast saturable absorber devices grown on GaAs substrate. The active region consists of a 1.55 μm absorbing GaInNAsSb quantum well (QW) surrounded by two narrow QWs of GaAsN with a N concentration up to 13%. Photoexcited carriers in the GaInNAsSb QW are expected to recombine by tunneling into the wide distribution of subband gap states created in the GaAsN QW. An absorption study shows that edge energy and excitonic peak intensity of the GaInNAsSb QW are not affected by the proximity of the GaAsN QWs. Pump-probe measurements provide information on the carrier relaxation dynamics which is dependent on spacer thickness, as expected for a tunneling process. We show that this process can be enhanced by increasing the N content in the GaAsN layers. Using this design, we have realized a monolithic GaAs-based saturable absorber microcavity with a 1/e recovery time of 12 ps.
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78.67.De Quantum wells
73.40.Gk Tunneling
42.50.Gy Effects of atomic coherence on propagation, absorption, and amplification of light; electromagnetically induced transparency and absorption
71.35.-y Excitons and related phenomena

Degradation mechanisms in InGaN laser diodes grown on bulk GaN crystals

L. Marona, P. Wisniewski, P. Prystawko, I. Grzegory, T. Suski, S. Porowski, P. Perlin, R. Czernecki, and M. Leszczyński

Appl. Phys. Lett. 88, 201111 (2006); http://dx.doi.org/10.1063/1.2204845 (3 pages) | Cited 19 times

Online Publication Date: 16 May 2006

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We have investigated the aging processes in InGaN laser diodes fabricated by metal organic vapor phase epitaxy on low-dislocation-density, high-pressure-grown bulk gallium nitride crystals. The measured threshold current turned out to be a square root function of aging time, indicating the importance of diffusion for device degradation. The differential efficiency, in contrast, was roughly constant during these experiments. From these two observations we can conclude that the main reason for degradation is the diffusion-enhanced increase of nonradiative recombination within the active layer of the laser diode. Additionally, microscopic studies of the degraded structures did not reveal any new dislocations within the active area of the aged diodes, thus identifying point defects as a source of nonradiative processes.
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42.55.Px Semiconductor lasers; laser diodes
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
81.40.Cd Solid solution hardening, precipitation hardening, and dispersion hardening; aging
66.30.Lw Diffusion of other defects
61.72.J- Point defects and defect clusters

GaBiAs: A material for optoelectronic terahertz devices

K. Bertulis, A. Krotkus, G. Aleksejenko, V. Pačebutas, R. Adomavičius, G. Molis, and S. Marcinkevičius

Appl. Phys. Lett. 88, 201112 (2006); http://dx.doi.org/10.1063/1.2205180 (3 pages) | Cited 52 times

Online Publication Date: 16 May 2006

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GaBiAs layers have been grown by molecular beam epitaxy at low (270–330 °C) temperatures and were characterized by several experimental techniques. It was shown that the spectral photosensitivity cutoff wavelength reaches ∼ 1.4 μm when the growth temperature is as low as 280 °C. Optical pump–terahertz probe measurements made on these layers have evidenced that the electron trapping time decreases with decreasing growth temperature from 20 to about 1 ps. GaBiAs layers were used for manufacturing photoconductive terahertz emitters and detectors, which, when excited with Ti:sapphire laser pulses, have demonstrated a signal bandwidth of 3 THz.
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07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
85.60.Gz Photodetectors (including infrared and CCD detectors)

External cavity quantum-cascade laser tunable from 8.2 to 10.4 μm using a gain element with a heterogeneous cascade

Richard Maulini, Arun Mohan, Marcella Giovannini, Jérôme Faist, and Emilio Gini

Appl. Phys. Lett. 88, 201113 (2006); http://dx.doi.org/10.1063/1.2205183 (3 pages) | Cited 54 times

Online Publication Date: 17 May 2006

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A heterogeneous quantum-cascade structure based on two bound-to-continuum designs emitting at 9.6 and 8.4 μm is presented. Its spontaneous emission spectrum at room temperature has a full width at half maximum of 350 cm−1 and shows a variation of intensity of less than 20% over more than 200 cm−1. External cavity lasers using a grating in Littrow configuration and antireflection coated chips with this active region could be tuned over 265 cm−1 from 8.2 to 10.4 μm, that is, over 24% of the center wavelength.
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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
42.60.Fc Modulation, tuning, and mode locking

Room-temperature, high-power, and continuous-wave operation of distributed-feedback quantum-cascade lasers at λ ∼ 9.6 μm

S. R. Darvish, S. Slivken, A. Evans, J. S. Yu, and M. Razeghi

Appl. Phys. Lett. 88, 201114 (2006); http://dx.doi.org/10.1063/1.2205730 (3 pages) | Cited 13 times

Online Publication Date: 17 May 2006

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High-power continuous-wave (cw) operation of distributed-feedback quantum-cascade lasers is reported. Continuous-wave output powers of 100 mW at 25 °C and 20 mW at 50 °C are obtained. The device exhibits a cw threshold current density of 1.34 kA/cm2, a maximum cw wall-plug efficiency of 1% at 25 °C, and a characteristic temperature of ∼ 190 K in pulsed mode. Single-mode emission near 9.6 μm with a side-mode suppression ratio of ≥ 30 dB and a tuning range of 2.89 cm−1 from 15 to 50 °C is obtained.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.Fc Modulation, tuning, and mode locking

High-power quantum cascade lasers grown by low-pressure metal organic vapor-phase epitaxy operating in continuous wave above 400 K

L. Diehl, D. Bour, S. Corzine, J. Zhu, G. Höfler, M. Lončar, M. Troccoli, and Federico Capasso

Appl. Phys. Lett. 88, 201115 (2006); http://dx.doi.org/10.1063/1.2203964 (3 pages) | Cited 56 times

Online Publication Date: 17 May 2006

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High-power quantum cascade lasers (QCLs) working in continuous wave (cw) above 400 K are presented. The material was grown by low-pressure metal organic vapor-phase epitaxy and processed into narrow buried heterostructure lasers. A cw output power of 204 mW was obtained at 300 K with an 8.38 μm wavelength, 3 mm long and 7.5 μm wide coated laser. The device operates in cw mode above 400 K, which exceeds the previous maximum cw temperature operation of QCLs by approximately 60 K. Preliminary reliability data obtained by accelerated aging tests indicate a remarkable robustness of the lasers.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase

Antireflective subwavelength structures on crystalline Si fabricated using directly formed anodic porous alumina masks

Hitoshi Sai, Homare Fujii, Koji Arafune, Yoshio Ohshita, Masafumi Yamaguchi, Yoshiaki Kanamori, and Hiroo Yugami

Appl. Phys. Lett. 88, 201116 (2006); http://dx.doi.org/10.1063/1.2205173 (3 pages) | Cited 46 times

Online Publication Date: 18 May 2006

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A simple fabrication technique for subwavelength structured (SWS) surfaces by means of anodic porous alumina masks directly formed on Si substrates was proposed and demonstrated. By this technique, SWS surfaces were fabricated on polished single-crystalline Si and chemically etched as-cut multicrystalline Si wafers. Smoothly tapered SWS surfaces with a periodicity of 100 nm and a height of 300–400 nm were obtained. A low reflectivity below 1% was observed from 300 to 1000 nm for both of the wafers, in agreement with numerical simulation. After thermal annealing at 800 °C, the reflectivity of the SWS surface increased to 3%.
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81.05.Cy Elemental semiconductors
68.47.Fg Semiconductor surfaces
81.65.Cf Surface cleaning, etching, patterning
61.72.Cc Kinetics of defect formation and annealing
42.86.+b Optical workshop techniques
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Three-dimensional simulation of super-radiant Smith-Purcell radiation

D. Li, K. Imasaki, Z. Yang, and Gun-Sik Park

Appl. Phys. Lett. 88, 201501 (2006); http://dx.doi.org/10.1063/1.2204750 (2 pages) | Cited 13 times

Online Publication Date: 15 May 2006

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A simulation of coherent and super-radiant Smith-Purcell radiation is performed in the gigahertz regime using a three-dimensional particle-in-cell code. The simulation model supposes a rectangular grating to be driven by a single electron bunch and a train of periodic bunches, respectively. The true Smith-Purcell radiation is distinguished from the evanescent wave, which has an angle independent frequency lower than the minimum allowed Smith-Purcell frequency. We also find that the super-radiant radiations excited by periodic bunches are emitted at higher harmonics of the bunching frequency and at the corresponding Smith-Purcell angles.
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52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.65.Rr Particle-in-cell method
52.40.Mj Particle beam interactions in plasmas

Microwave plasma burner and temperature measurements in its flames

Yong Cheol Hong, Soon Cheon Cho, Chan Uk Bang, Dong Hun Shin, Jong Hun Kim, Han Sup Uhm, and Won Ju Yi

Appl. Phys. Lett. 88, 201502 (2006); http://dx.doi.org/10.1063/1.2205008 (3 pages) | Cited 12 times

Online Publication Date: 16 May 2006

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An apparatus for generating flames and more particularly the microwave plasma burner for generating high-temperature large-volume plasma flame was presented. The plasma burner is operated by injecting liquid hydrocarbon fuels into a microwave plasma torch in air discharge and by mixing the resultant gaseous hydrogen and carbon compounds with air or oxygen gas. The microwave plasma torch can instantaneously vaporize and decompose the hydrogen and carbon containing fuels. It was observed that the flame volume of the burner was more than 50 times that of the torch plasma. While the temperature of the torch plasma flame was only 550 K at a measurement point, that of the plasma-burner flame with the addition of 0.025 lpm (liters per minute) kerosene and 20 lpm oxygen drastically increased to about 1850 K. A preliminary experiment was carried out, measuring the temperature profiles of flames along the radial and axial directions.
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52.75.Hn Plasma torches
52.70.Ds Electric and magnetic measurements
52.50.Dg Plasma sources
52.80.Pi High-frequency and RF discharges
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)
82.33.Vx Reactions in flames, combustion, and explosions

Low-debris, efficient laser-produced plasma extreme ultraviolet source by use of a regenerative liquid microjet target containing tin dioxide (SnO2) nanoparticles

Takeshi Higashiguchi, Naoto Dojyo, Masaya Hamada, Wataru Sasaki, and Shoichi Kubodera

Appl. Phys. Lett. 88, 201503 (2006); http://dx.doi.org/10.1063/1.2206131 (3 pages) | Cited 24 times

Online Publication Date: 18 May 2006

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We demonstrated a low-debris, efficient laser-produced plasma extreme ultraviolet (EUV) source by use of a regenerative liquid microjet target containing tin-dioxide (SnO2) nanoparticles. By using a low SnO2 concentration (6%) solution and dual laser pulses for the plasma control, we observed the EUV conversion efficiency of 1.2% with undetectable debris.
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52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
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Room temperature interactions of water vapor with HfO2 films on Si

C. Driemeier, E. P. Gusev, and I. J. R. Baumvol

Appl. Phys. Lett. 88, 201901 (2006); http://dx.doi.org/10.1063/1.2203944 (3 pages) | Cited 11 times

Online Publication Date: 15 May 2006

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HfO2/SiO2/Si(001) thin film structures were exposed at room temperature to water vapor isotopically enriched in math and math followed by quantification and profiling of these nuclides by nuclear reaction analysis. We showed (i) the formation of strongly bonded hydroxyls at the HfO2 surface; (ii) room temperature migration of oxygen and water-derived oxygenous species through the HfO2 films, indicating that HfO2 is a weak diffusion barrier for these oxidizing species; (iii) hydrogenous, water-derived species attachment to the SiO2 interlayer, resulting in detrimental hydrogenous defects therein. Consequences of these results to HfO2-based metal-oxide-semiconductor devices are discussed.
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77.55.-g Dielectric thin films
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
66.30.J- Diffusion of impurities
68.35.Fx Diffusion; interface formation

High-pressure x-ray diffraction study of Ta4AlC3

Bouchaib Manoun, S. K. Saxena, T. El-Raghy, and M. W. Barsoum

Appl. Phys. Lett. 88, 201902 (2006); http://dx.doi.org/10.1063/1.2202387 (3 pages) | Cited 44 times

Online Publication Date: 15 May 2006

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Using a synchrotron radiation source and a diamond anvil cell, we measured the pressure dependence of the lattice parameters of a recently discovered phase, Ta4AlC3. This phase adopts a hexagonal structure with the space group P63/mmc; at room conditions, the a and c parameters are 3.087(5) and 23.70(4) Å, respectively. Up to a pressure of 47 GPa, no phase transformations were observed. Like Ta2AlC, but unlike many related phases such as Ti4AlN3, Ti3SiC2, Ti3GeC2, and Zr2InC, the compressibility of Ta4AlC3 along the c and a axes are almost identical. The bulk modulus of Ta4AlC3, 261±2 GPa, is ≈ 4% greater than that of Ta2AlC. Both, however, are ≈ 37% lower than the 345±9 GPa of TaC.
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62.50.-p High-pressure effects in solids and liquids
64.70.K- Solid-solid transitions
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity

Ni-based bulk glassy alloys with superhigh strength of 3800 MPa in Ni–Fe–B–Si–Nb system

Baolong Shen, Chuntao Chang, and Akihisa Inoue

Appl. Phys. Lett. 88, 201903 (2006); http://dx.doi.org/10.1063/1.2204440 (3 pages) | Cited 11 times

Online Publication Date: 15 May 2006

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The effects of replacement of Ni by Fe on the glass-forming ability (GFA) and mechanical properties of Ni–B–Si–Nb glassy alloys were examined. The substitution of Fe for Ni caused increases of GFA and mechanical properties. Ni-based bulk glassy alloys (BGAs) with diameters up to 3 mm were formed in a [(Ni1−xFex)0.75B0.2Si0.05]96Nb4 alloy system. The BGAs exhibit a superhigh fracture strength of 3680–3840 MPa and Young’s modulus of 172–186 GPa, which are the highest values for Ni-based BGAs. The improvement of GFA and fracture strength is interpreted to result from the enhanced atomic bonding nature among the constituent elements by adding Fe.
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81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.M- Structural failure of materials
62.20.D- Elasticity
61.43.Fs Glasses

Various low group velocity effects in photonic crystal line defect waveguides and their demonstration by laser oscillation

Kazuaki Kiyota, Tomofumi Kise, Noriyuki Yokouchi, Toshihide Ide, and Toshihiko Baba

Appl. Phys. Lett. 88, 201904 (2006); http://dx.doi.org/10.1063/1.2204647 (3 pages) | Cited 17 times

Online Publication Date: 15 May 2006

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We investigated propagating modes in a two-dimensional photonic crystal slab waveguide with a line defect narrower than a single line missing hole structure from the low group velocity point of view. These modes showed low group velocities not due to the conventional distributed feedback (DFB) between a forward and a backward mode with the same lateral field distribution, but due to a DFB between modes with different lateral field distribution or property of a start point of a photonic-band-gap-guided mode. These low group velocities of over 40 were demonstrated as a Fabry-Pérot lasing oscillation due to gain enhancement.
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42.70.Qs Photonic bandgap materials
42.79.Gn Optical waveguides and couplers

Surface energy and the equilibrium shape of hexagonal structured Ge2Sb2Te5 grain

Yu Jin Park, Jeong Yong Lee, and Yong Tae Kim

Appl. Phys. Lett. 88, 201905 (2006); http://dx.doi.org/10.1063/1.2204837 (3 pages) | Cited 4 times

Online Publication Date: 15 May 2006

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Surface energy and the equilibrium shape of hexagonal structured grain in Ge2Sb2Te5 were investigated by a transmission electron microscopy (TEM) study. As a result, we have found that the equilibrium shape of hexagonal structured Ge2Sb2Te5 is a lengthened shape with (0001) plane at the major axis, which was experimentally revealed by TEM images. The hexagonal structured Ge2Sb2Te5 grain has low surface energy in {0001}, {1math03}, and {math106} planes which have no additional broken bonds from the atoms on the steps. Therefore, it is strongly facetted by the plane having low surface energy, thus, becoming an equilibrium shape.
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68.35.Md Surface thermodynamics, surface energies
61.43.Dq Amorphous semiconductors, metals, and alloys
68.55.-a Thin film structure and morphology

180° domain structure and its evolution in Ca0.28Ba0.72Nb2O6 ferroelectric single crystals of tungsten bronzes structure

C. J. Lu, C. J. Nie, X. F. Duan, J. Q. Li, H. J. Zhang, and J. Y. Wang

Appl. Phys. Lett. 88, 201906 (2006); http://dx.doi.org/10.1063/1.2203751 (3 pages) | Cited 9 times

Online Publication Date: 16 May 2006

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Ferroelectric domain structure and its evolution in uniaxial relaxor Ca0.28Ba0.72Nb2O6 single crystals were investigated using transmission electron microscopy. It was found that there exists a high density of 180° domain walls in the crystals. The domains appear predominantly spike shaped along the polar axis and have a typical diameter of 50–500 nm. Domain wall motion was occasionally induced by electron beam irradiation. Macrodomains-to-microdomains switching has been observed corresponding to the normal-to-relaxor ferroelectrics transition during an in situ heating experiments. At temperature just below ferroelectric phase transition temperature TC, zero-field-cooled needlelike nanodomains were also observed.
Show PACS
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.Dj Domain structure; hysteresis
77.80.Fm Switching phenomena
77.80.B- Phase transitions and Curie point
61.80.Fe Electron and positron radiation effects
68.37.Lp Transmission electron microscopy (TEM)
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