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29 May 2006

Volume 88, Issue 22, Articles (22xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 88, 222501 (2006); http://dx.doi.org/10.1063/1.2207827 (3 pages)

L. X. You, M. Torstensson, A. Yurgens, D. Winkler, C. T. Lin, and B. Liang
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Three-dimensional horizontal circular spiral photonic crystals with stop gaps below 1 μm

Kock Khuen Seet, Vygantas Mizeikis, Saulius Juodkazis, and Hiroaki Misawa

Appl. Phys. Lett. 88, 221101 (2006); http://dx.doi.org/10.1063/1.2207841 (3 pages) | Cited 20 times

Online Publication Date: 30 May 2006

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Three-dimensional photonic crystals with a circular spiral architecture were fabricated by direct laser writing (DLW) in a photoresist. DLW was performed with a laser beam having the direction of propagation and elongation of the ellipsoidal focal region perpendicular to the spirals’ orientation. This allowed the reduction of the turning period of the spirals while avoiding the overlap between their adjacent turns. Consequently, optical transmission and reflection spectra of the fabricated samples revealed multiple photonic stop gaps whose shortest wavelength was 0.88 μm, the lowest observed so far in spiral structures. These results were qualitatively reproduced by finite-difference time-domain simulations. This fabrication scheme can be useful for DLW of structures where photonic stop gaps along particular directions, rather than complete photonic band gaps, are required.
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42.70.Qs Photonic bandgap materials
42.62.-b Laser applications
42.86.+b Optical workshop techniques
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.30.-j Infrared and Raman spectra
78.40.Ha Other nonmetallic inorganics

Pancharatnam-Berry phase optical elements for wave front shaping in the visible domain: Switchable helical mode generation

L. Marrucci, C. Manzo, and D. Paparo

Appl. Phys. Lett. 88, 221102 (2006); http://dx.doi.org/10.1063/1.2207993 (3 pages) | Cited 38 times

Online Publication Date: 30 May 2006

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We report the realization of a Pancharatnam-Berry phase optical element [ Z. Bomzon, G. Biener, V. Kleiner, and E. Hasman, Opt. Lett. 27, 1141 (2002)] , for wave front shaping working in the visible spectral domain, based on patterned liquid crystal technology. This device generates helical modes of visible light with the possibility of electro-optically switching between opposite helicities by controlling the handedness of the input circular polarization. By cascading this approach, fast switching among multiple wave front helicities can be achieved, with potential applications to multistate optical information encoding. The approach demonstrated here can be generalized to other polarization-controlled devices for wave front shaping, such as switchable lenses, beam splitters, and holographic elements.
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42.79.Ci Filters, zone plates, and polarizers
42.65.Pc Optical bistability, multistability, and switching, including local field effects
42.79.Kr Display devices, liquid-crystal devices

Experimental demonstration of negative index of refraction

Jiangfeng Zhou, Thomas Koschny, Lei Zhang, Gary Tuttle, and Costas M. Soukoulis

Appl. Phys. Lett. 88, 221103 (2006); http://dx.doi.org/10.1063/1.2208264 (3 pages) | Cited 70 times

Online Publication Date: 30 May 2006

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We introduce an improved and simplified structure made of periodic arrays of pairs of H-shaped metallic wires that offer a potentially simpler approach in building negative-index materials. Using simulations and microwave experiments, we have investigated the negative-index n properties of these structures. We have measured experimentally both the transmittance and the reflectance properties and found unambiguously that a negative refractive index with Re(n)<0 and Im(n)<Re(n). The same is true for ε and μ. Our results show that H-shaped wire pairs can be used very effectively in producing materials with negative refractive indices.
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42.70.-a Optical materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Experimental investigations on the suppression of Q switching in monolithic 40 GHz mode-locked semiconductor lasers

B. Hüttl, R. Kaiser, Ch. Kindel, S. Fidorra, W. Rehbein, H. Stolpe, G. Sahin, U. Bandelow, M. Radziunas, A. Vladimirov, and H. Heidrich

Appl. Phys. Lett. 88, 221104 (2006); http://dx.doi.org/10.1063/1.2208277 (3 pages) | Cited 7 times

Online Publication Date: 30 May 2006

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Inherent Q switching as a source of intracavity pulse energy modulations, i.e., unwanted amplitude noise, is still a challenging task in order to fabricate monolithic mode-locked semiconductor lasers in view of different commercial applications. In this letter, the results of experimental investigations on the influence of the quantum well number on the occurrence and suppression of Q switching in 40 GHz mode-locked multiple quantum well lasers are presented. Improved mode-locked lasers emit short optical pulses ( ⩽ 1.6 ps) with very low amplitude noise (1%–2%) and timing jitter (50–100 fs).
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42.55.Px Semiconductor lasers; laser diodes
42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.Fc Modulation, tuning, and mode locking
42.60.Mi Dynamical laser instabilities; noisy laser behavior

Two-photon-induced quenching of photoluminescence in wide-gap semiconductor crystals

Makoto Torizawa and Yoshimasa Kawata

Appl. Phys. Lett. 88, 221105 (2006); http://dx.doi.org/10.1063/1.2208278 (2 pages) | Cited 3 times

Online Publication Date: 31 May 2006

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We present photoinduced quenching of photoluminescence in a wide-gap semiconductor crystal. Because the photoluminescence is excited by a two-photon process, the quenched region is spatially localized in three dimensions. We found that the photoinduced quenching had a clear threshold at 0.70 MW/cm2 of excitation intensity. Under the intensity of the threshold, photoluminescence intensity did not decrease with long exposure time. We demonstrated three-dimensional control of photoluminescence intensity distribution in a ZnSe crystal.
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78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
78.55.Et II-VI semiconductors

Chalcogenide glass Raman fiber laser

Stuart D. Jackson and Gilberto Anzueto-Sánchez

Appl. Phys. Lett. 88, 221106 (2006); http://dx.doi.org/10.1063/1.2208369 (3 pages) | Cited 20 times

Online Publication Date: 31 May 2006

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We report the operation of a chalcogenide glass Raman fiber laser. To mitigate photoinduced effects and minimize impurity absorption, a 2051 nm Tm3+-doped silica fiber laser was employed as the pump source. Vibrations between the polymerlike layers comprising the glass produced first Stokes emission at 2062 nm, an output power of 0.64 W, and a slope efficiency of ∼ 66%. Bond bending and bond stretching vibrations within the layers simultaneously produced first Stokes output at 2102 nm (0.2 W) and 2166 nm (16 mW), respectively. Second Stokes output at 2074 nm was produced when the fiber length was extended.
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42.55.Wd Fiber lasers
42.55.Ye Raman lasers
42.60.By Design of specific laser systems
42.65.Dr Stimulated Raman scattering; CARS
42.65.Es Stimulated Brillouin and Rayleigh scattering
42.70.Ce Glasses, quartz

Ground-state lasing of stacked InAs/GaAs quantum dots with GaP strain-compensation layers grown by metal organic chemical vapor deposition

J. Tatebayashi, N. Nuntawong, Y. C. Xin, P. S. Wong, S. H. Huang, C. P. Hains, L. F. Lester, and D. L. Huffaker

Appl. Phys. Lett. 88, 221107 (2006); http://dx.doi.org/10.1063/1.2208553 (3 pages) | Cited 10 times

Online Publication Date: 31 May 2006

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We report the device characteristics of stacked InAs/GaAs quantum dots (QDs) with GaP strain-compensation (SC) layers grown by metal organic chemical vapor deposition. By inserting GaP SC layers within the stacked structures, decrease in the density of QDs by stacking QDs can be suppressed due to reduction of overall compressive strain within the stacked QDs. We demonstrate ground-state lasing at 1.265 μm of six layers of InAs/GaAs QDs with GaP SC layers. The threshold current density is as low as 108 A/cm2. We also assess the internal loss and maximum modal gain of fabricated QD lasers by using a segmented contact method. The internal loss is as low as 5 cm−1, and the maximum modal gain of the ground state of the stacked QDs is approximately 10 cm−1.
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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.)

60 mW continuous-wave operation of InGaN laser diodes made by plasma-assisted molecular-beam epitaxy

C. Skierbiszewski, P. Wiśniewski, M. Siekacz, P. Perlin, A. Feduniewicz-Zmuda, G. Nowak, I. Grzegory, M. Leszczyński, and S. Porowski

Appl. Phys. Lett. 88, 221108 (2006); http://dx.doi.org/10.1063/1.2208929 (3 pages) | Cited 23 times

Online Publication Date: 31 May 2006

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We demonstrate continuous-wave operation at 411 nm of InGaN multi-quantum-well laser diodes (LDs) made by plasma-assisted molecular-beam epitaxy (PAMBE). The threshold current density and voltage for these LDs are 4.2 kA/cm2 and 5.3 V, respectively. High optical output power of 60 mW is achieved. The LDs are fabricated on low-dislocation-density bulk GaN substrates, at growth conditions which resemble liquid-phase epitaxy. We show that use of such substrates eliminates spiral growth, which is the dominant growth mechanism for PAMBE on high-dislocation-density substrates. Therefore, PAMBE opens new perspectives for next generation of InGaN LDs.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
52.77.-j Plasma applications

High-efficiency integrated polarized backlight system for liquid crystal display

Xingpeng Yang, Yingbai Yan, and Guofan Jin

Appl. Phys. Lett. 88, 221109 (2006); http://dx.doi.org/10.1063/1.2207219 (3 pages) | Cited 4 times

Online Publication Date: 1 June 2006

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We propose a multiwavelength polarized backlight system (BLS) that is based on the stress-induced birefringence and the multilayer subwavelength grating. The polarized BLS requires no prism sheets and no quarter wave plate. Moreover, because of the high extinction ratio, the rear absorbing polarizer of the liquid crystal display panel is not required anymore. The proposed backlight can fully utilize the light, and the intensity at near normal angles is 2.3 times higher than that of a conventional unpolarized light emitting backlight.
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42.79.Kr Display devices, liquid-crystal devices
85.60.Pg Display systems

Terahertz radiation emission from GaMnAs

J. B. Héroux, Y. Ino, M. Kuwata-Gonokami, Y. Hashimoto, and S. Katsumoto

Appl. Phys. Lett. 88, 221110 (2006); http://dx.doi.org/10.1063/1.2206154 (3 pages) | Cited 5 times

Online Publication Date: 1 June 2006

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Terahertz radiation is observed from ferromagnetic GaMnAs samples excited with 400 nm wavelength pump pulses and is related to the sample magnetization M. The emission can be explained by the strong influence of M on the photogenerated carrier motion, a phenomenon related to the dc anomalous Hall effect. Results illustrate the potential of ferromagnetic materials to be used as compact terahertz sources emitting in a direction normal to the surface.
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75.50.Pp Magnetic semiconductors
75.50.Dd Nonmetallic ferromagnetic materials
78.20.Ls Magneto-optical effects
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
72.20.My Galvanomagnetic and other magnetotransport effects

Direct imaging of propagation and damping of near-resonance surface plasmon polaritons using cathodoluminescence spectroscopy

J. T. van Wijngaarden, E. Verhagen, A. Polman, C. E. Ross, H. J. Lezec, and H. A. Atwater

Appl. Phys. Lett. 88, 221111 (2006); http://dx.doi.org/10.1063/1.2208556 (3 pages) | Cited 30 times

Online Publication Date: 1 June 2006

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Cathodoluminescence imaging spectroscopy is used to determine the propagation distance of surface plasmon polaritons near the surface plasmon resonance on both silver and gold films. Surface plasmon polaritons are generated by a focused (diameter of 5 nm) electron beam spot in the metal and coupled out through a grating. By gradually varying the distance between the excitation spot and the grating the damping is probed. Propagation lengths as small as several hundred nanometers are probed, and an increase in propagation length is observed if the wavelength is increased above resonance. The measured data are compared with the calculated propagation lengths taking into account both absorption in the film and leakage radiation, and it is found that other loss mechanisms appear to be significant as well.
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78.66.Bz Metals and metallic alloys
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)

Comparison of epitaxial thin layer GaN and InP passivations on InGaAs/GaAs near-surface quantum wells

A. Aierken, J. Riikonen, J. Sormunen, M. Sopanen, and H. Lipsanen

Appl. Phys. Lett. 88, 221112 (2006); http://dx.doi.org/10.1063/1.2208557 (3 pages) | Cited 4 times

Online Publication Date: 1 June 2006

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The optical properties of the in situ epitaxial GaN and InP passivated InGaAs/GaAs near-surface quantum wells, which were fabricated by metal organic vapor phase epitaxy, are investigated. Low-temperature photoluminescence (PL), time-resolved photoluminescence, and photoreflectance are used to study the passivation effect. Both GaN and InP passivations are observed to significantly enhance the PL intensity and carrier lifetime and to reduce the surface electrical fields. Comparison of the methods shows that the epitaxial InP passivation is more effective. However, epitaxial GaN and nitridation methods are comparable with InP passivation.
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81.65.Rv Passivation
78.67.De Quantum wells
73.63.Hs Quantum wells
78.55.Cr III-V semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Band gap discontinuity in Ga0.9In0.1N0.027As0.973−xSbx/GaAs single quantum wells with 0 ⩽ x<0.06 studied by contactless electroreflectance spectroscopy

R. Kudrawiec, M. Motyka, M. Gladysiewicz, J. Misiewicz, H. B. Yuen, S. R. Bank, H. Bae, M. A. Wistey, and James S. Harris

Appl. Phys. Lett. 88, 221113 (2006); http://dx.doi.org/10.1063/1.2208949 (3 pages) | Cited 15 times

Online Publication Date: 1 June 2006

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Contactless electroreflectance (CER) spectroscopy has been applied to study optical transitions in Ga0.9In0.1N0.027As0.973−xSbx/GaAs single quantum well (QW) with antimony content varying from 0% to 5.4%. CER features related to optical transitions between the ground and excited states have been clearly observed. Energies of the QW transitions have been matched with those obtained from theoretical calculations. It has been determined that the conduction band offset decreases from ∼ 55% to ∼ 45% with the increase in Sb content from 0% to 5.4%. This result demonstrates that the band gap discontinuity for Ga0.9In0.1N0.027As0.973−xSbx/GaAs system can be simply tuned by a change in antimony content.
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71.20.Nr Semiconductor compounds
73.21.Fg Quantum wells
78.67.De Quantum wells
78.20.Jq Electro-optical effects

Multiphoton excitation of quantum dots by ultrashort and ultraintense laser pulses

Y. Fu, T.-T. Han, Y. Luo, and H. Ågren

Appl. Phys. Lett. 88, 221114 (2006); http://dx.doi.org/10.1063/1.2209209 (3 pages) | Cited 6 times

Online Publication Date: 2 June 2006

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Multiphoton optical processes in semiconductor quantum dots (QDs) excited by ultrafast (femtosecond) and ultraintense (GW/cm2) lasers are considered as the ultimate tags for cellular bioimaging. By solving the time-dependent Schrödinger equation unperturbatively, experimentally observed strong multiphoton excitation is reproduced when optical transitions among all confined states and a few hundred more extended states are taken into account. Model calculations indicate a significant excitation of a CdS QD of 3.7 nm in radius by a 100 fs laser pulse with a 10 GW/cm2 peak optical power. The excitation rate is almost constant between 1300 and 560 nm, a useful region for bioimaging.
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78.67.Hc Quantum dots
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
87.17.-d Cell processes
87.80.-y Biophysical techniques (research methods)

Overannealing effects in GaInNAs(Sb) alloys and their importance to laser applications

Seth R. Bank, Homan B. Yuen, Hopil Bae, Mark A. Wistey, and James S. Harris

Appl. Phys. Lett. 88, 221115 (2006); http://dx.doi.org/10.1063/1.2208375 (3 pages) | Cited 8 times

Online Publication Date: 2 June 2006

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The photoluminescence efficiency and linewidth are well-established metrics for characterizing potential laser active regions. We demonstrate the critical importance of a new parameter for predicting the performance of dilute-nitride lasers: the “optimal” postgrowth annealing temperature, defined as the annealing temperature giving the highest photoluminescence efficiency. We validate this assertion with two 1.55 μm edge-emitting GaInNAsSb lasers containing active regions with different optimal annealing temperatures. Although both active regions showed comparable photoluminescence efficiency and linewidth under optimal annealing conditions, laser performance was significantly different. The room-temperature threshold current density for the active region with higher optimal annealing temperature was 630 A/cm2, compared with 2380 A/cm2 for the sample with lower optimal annealing temperature. We conclude that overannealing of the gain region during upper cladding growth is the responsible mechanism. The dependence of the optimal annealing temperature on composition and growth conditions is also discussed.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
61.72.Cc Kinetics of defect formation and annealing

Near-field optical micromanipulation with cavity enhanced evanescent waves

Peter J. Reece, Veneranda Garcés-Chávez, and Kishan Dholakia

Appl. Phys. Lett. 88, 221116 (2006); http://dx.doi.org/10.1063/1.2208272 (3 pages) | Cited 32 times

Online Publication Date: 2 June 2006

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We show that the forces associated with near-field optical micromanipulation can be greatly increased through the use of cavity enhanced evanescent waves. This approach utilizes a resonant dielectric waveguide structure and a prism coupler to produce Fabry-Pérot-like cavity modes at a dielectric-fluid interface. Fabricated structures show a ten times enhancement in the optical interaction and optical force for micrometer-sized colloids. In addition, stable accumulation and ordering of large scale arrays of colloids are demonstrated using two counter-propagating cavity enhanced evanescent waves.
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37.10.Vz Mechanical effects of light on atoms, molecules, and ions
42.79.Gn Optical waveguides and couplers
42.79.Bh Lenses, prisms and mirrors
82.70.Dd Colloids

Efficient diode-pumped Yb:Gd2SiO5 laser

Wenxue Li, Haifeng Pan, Liang’en Ding, Heping Zeng, Wei Lu, Guangjun Zhao, Chengfeng Yan, Liangbi Su, and Jun Xu

Appl. Phys. Lett. 88, 221117 (2006); http://dx.doi.org/10.1063/1.2206150 (3 pages) | Cited 18 times

Online Publication Date: 2 June 2006

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An efficient diode-pumped laser was demonstrated by using an ytterbium-doped laser crystal, Yb:Gd2SiO5 (Yb:GSO), wherein Yb3+ ions exhibit the largest ground-state splitting among all the ytterbium-doped crystals. The Yb:GSO laser can be operated at a low pumping threshold, and the most efficient laser occurs around 1088 nm since the corresponding emission band has the largest emission cross section and the lowest thermal population. A slope efficiency of 75% was demonstrated for a continuous-wave Yb:GSO laser at 1094 nm, and self-pulsed lasers were achieved within the tunable range of 1091–1105 nm, which are the longest laser wavelengths achieved for Yb3+ lasers.
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42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.By Design of specific laser systems
42.60.Fc Modulation, tuning, and mode locking
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
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Reduction of noise in strapped magnetron by electric priming using anode shape modification

J. I. Kim, J. H. Won, G. S. Park, H. J. Ha, and J. C. Shon

Appl. Phys. Lett. 88, 221501 (2006); http://dx.doi.org/10.1063/1.2208273 (3 pages) | Cited 3 times

Online Publication Date: 30 May 2006

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Noise reduction in a 2.45 GHz strapped magnetron oscillator is experimentally demonstrated by electric priming using anode shape modification. The sideband noise is reduced by approximately 15 dB at the nominal operating current and by 28 dB at the start-oscillation current; this is due to electron prebunching into the π mode, resulting from the modulation of the drift velocity of the electrons by an azimuthally periodic electric field. In this experiment, a 4.3 kV–330 mA half-wave rectified input power is employed.
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84.40.Fe Microwave tubes (e.g., klystrons, magnetrons, traveling-wave, backward-wave tubes, etc.)
84.30.Ng Oscillators, pulse generators, and function generators
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Realization of freestanding InP membranes on Si by low-temperature wafer bonding and stress analysis using micro-Raman spectroscopy

J. Arokiaraj, S. Tripathy, S. Vicknesh, and A. Ramam

Appl. Phys. Lett. 88, 221901 (2006); http://dx.doi.org/10.1063/1.2207834 (3 pages) | Cited 8 times

Online Publication Date: 30 May 2006

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We present a method to realize freestanding InP membranes on Si substrate by combination of low-temperature wafer bonding, layer transfer, and wet chemical release processes. The removal of InP substrate and sacrificial etching of an InGaAs layer defines the 2.0 μm InP thin layer bonded to Si. The InP membranes are subsequently released by a two-step wet etching process and the surface stress profiling in these freestanding membranes has been carried out by high spectral resolution micro-Raman measurements. Realization of such micromechanical structures on Si platform would be suitable for the integration of InP-based photonic devices on large area Si-based microelectronic systems.
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85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
81.05.Ea III-V semiconductors
81.65.Cf Surface cleaning, etching, patterning
78.30.Fs III-V and II-VI semiconductors

Analysis of second-harmonic generation of Lamb waves propagating in layered planar structures with imperfect interfaces

Mingxi Deng

Appl. Phys. Lett. 88, 221902 (2006); http://dx.doi.org/10.1063/1.2207847 (3 pages) | Cited 5 times

Online Publication Date: 30 May 2006

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Under second-order perturbation the modal analysis approach for waveguide excitation is used to investigate the generation of second harmonics of Lamb waves propagating in layered planar structures with imperfect interfaces. The imperfect interfaces of layered structures are characterized by the well-known finite interfacial stiffness technique. The analytical results clearly indicate that the efficiency of generation of second harmonics by Lamb wave propagation is strongly dependent on the interfacial stiffness constants. This letter shows a potential that the interfacial properties of layered planar structures can sensitively be evaluated by the effect of second-harmonic generation of Lamb wave propagation.
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68.35.Iv Acoustical properties

Exciton radiative lifetime in ZnO quantum dots embedded in SiOx matrix

X. H. Zhang, S. J. Chua, A. M. Yong, S. Y. Chow, H. Y. Yang, S. P. Lau, and S. F. Yu

Appl. Phys. Lett. 88, 221903 (2006); http://dx.doi.org/10.1063/1.2207848 (3 pages) | Cited 13 times

Online Publication Date: 30 May 2006

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Using a simple process of the deposition of ZnO thin films on SiOx/Si substrates and subsequent thermal annealing, we fabricated ZnO quantum dots embedded in silicon oxide matrix. The ZnO quantum dots were characterized using transmission electron microscopy, and time-integrated and time-resolved photoluminescences. We measured an exciton radiative lifetime of 65 ps at 4.3 K, which is much shorter than the exciton radiative lifetime of 322 ps in bulk ZnO. The short exciton radiative lifetime can be explained in terms of exciton superradiance.
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78.67.Hc Quantum dots
78.55.Et II-VI semiconductors
78.45.+h Stimulated emission
71.35.-y Excitons and related phenomena

First-principles study of low compressibility osmium borides

Huiyang Gou, Li Hou, Jingwu Zhang, Hui Li, Guifang Sun, and Faming Gao

Appl. Phys. Lett. 88, 221904 (2006); http://dx.doi.org/10.1063/1.2208367 (3 pages) | Cited 56 times

Online Publication Date: 30 May 2006

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Using first-principles total energy calculations we investigate the structural, elastic, and electronic properties of OsB2 and OsB, respectively. The calculated equilibrium structural parameters of OsB2 are in agreement with the available experimental results. The calculations indicate that OsB in tungsten carbide is more energetically stable under the ambient condition than the metastable cesium chloride phase of OsB. Results of bulk modulus show that they are potential low compressible materials. The hardness of OsB2 is estimated by employing a semiempirical theory. The results indicate that OsB2 is an ultraincompressible material, but not a superhard material. The method designing superhard materials is different from one creating ultraincompressible materials.
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81.40.Jj Elasticity and anelasticity, stress-strain relations
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
81.40.Lm Deformation, plasticity, and creep
62.20.D- Elasticity
62.20.Qp Friction, tribology, and hardness
62.20.F- Deformation and plasticity

Current-driven interactions between voids in metallic interconnect lines and their effects on line electrical resistance

Jaeseol Cho, M. Rauf Gungor, and Dimitrios Maroudas

Appl. Phys. Lett. 88, 221905 (2006); http://dx.doi.org/10.1063/1.2207849 (3 pages) | Cited 11 times

Online Publication Date: 31 May 2006

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We present a theoretical analysis based on self-consistent numerical simulations of current-driven interactions between voids in metallic thin-film interconnects and the resulting void migration, morphological evolution, and coalescence phenomena. The analysis reveals the complex nature of electromigration-induced void-void interactions, and their implications for the evolution of interconnect line electrical resistance. Most importantly, it is demonstrated that current-driven void-void interaction effects, such as void coalescence, can cause sudden changes in the interconnect line electrical resistance, in qualitative agreement with observations in accelerated electromigration testing experiments.
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66.30.Qa Electromigration
85.40.Ls Metallization, contacts, interconnects; device isolation

Optical characterization of Eu-doped β-Ga2O3 thin films

P. Gollakota, A. Dhawan, P. Wellenius, L. M. Lunardi, J. F. Muth, Y. N. Saripalli, H. Y. Peng, and H. O. Everitt

Appl. Phys. Lett. 88, 221906 (2006); http://dx.doi.org/10.1063/1.2208368 (3 pages) | Cited 15 times

Online Publication Date: 31 May 2006

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Europium-doped β-Ga2O3 thin films were grown on double-side polished c-axis (0001) sapphire substrates by pulsed laser deposition at 850 °C. Transmission measurements of the films revealed a sharp band edge with a band gap at 5.0 eV. The films exhibited intense red emission at 611 nm (2.03 eV) due to the transitions from math to math levels in europium, with intensities that increased with the concentration of europium. Time-resolved photoluminescence measurements revealed a temperature-insensitive lifetime of 1.4 ms, which is much longer than the lifetimes of europium luminescence observed in GaN hosts.
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78.66.Li Other semiconductors
78.55.Hx Other solid inorganic materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
78.47.-p Spectroscopy of solid state dynamics

Directed growth of single-crystal indium wires

Ishan Talukdar, Birol Ozturk, Bret N. Flanders, and Tetsuya D. Mishima

Appl. Phys. Lett. 88, 221907 (2006); http://dx.doi.org/10.1063/1.2208431 (3 pages) | Cited 8 times

Online Publication Date: 31 May 2006

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Show Abstract
Tailored electric fields were used to direct the dendritic growth of crystalline indium wires between lithographic electrodes immersed in solutions of indium acetate. Determination of the conditions that suppress sidebranching on these structures has enabled the fabrication of arbitrarily long needle-shaped wires with diameters as small as 370 nm. Electron diffraction studies indicate that these wires are crystalline indium, that the unbranched wire segments are single-crystal domains, and that the predominant growth direction is near ⟨110⟩. This work constitutes a critical step towards the use of simply prepared aqueous mixtures as a convenient means of controlling the composition of submicron, crystalline wires.
Show PACS
68.70.+w Whiskers and dendrites (growth, structure, and nonelectronic properties)
68.65.La Quantum wires (patterned in quantum wells)
81.10.Dn Growth from solutions
61.46.-w Structure of nanoscale materials
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