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7 Mar 2005

Volume 86, Issue 10, Articles (10xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 86, 103102 (2005); http://dx.doi.org/10.1063/1.1875734 (3 pages)

Tadashi Kawazoe, Kiyoshi Kobayashi, and Motoichi Ohtsu
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Directive emissions from subwavelength metamaterial-based cavities

Lei Zhou, Hongqiang Li, Yaqin Qin, Zeyong Wei, and C. T. Chan

Appl. Phys. Lett. 86, 101101 (2005); http://dx.doi.org/10.1063/1.1881797 (3 pages) | Cited 33 times

Online Publication Date: 28 February 2005

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We use experiment and theory to demonstrate a mechanism for directive emissions, which involves a double-plate resonance cavity made with metamaterials. In contrast to other mechanisms employing Fabry-Pérot cavities, photonic crystals, or zero index materials, our system is significantly thinner than the working wavelength and requires a smaller lateral size. We show the physics to be governed by subwavelength resonance modes unique to such metamaterial-based cavities.
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84.40.Az Waveguides, transmission lines, striplines
41.20.Jb Electromagnetic wave propagation; radiowave propagation
02.70.Bf Finite-difference methods

Interband cascade detectors with room temperature photovoltaic operation

Jian V. Li, Rui Q. Yang, Cory J. Hill, and Shun Lien Chuang

Appl. Phys. Lett. 86, 101102 (2005); http://dx.doi.org/10.1063/1.1875758 (3 pages) | Cited 5 times

Online Publication Date: 28 February 2005

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We investigated mid-infrared interband cascade laser structures as photodetectors, which are sensitive to normal incidence and operate in photovoltaic mode at room temperature. The proposed operation principle of these interband cascade detectors is based on the unique combination of interband photoexcitation and the much faster intersubband relaxation as well as interband tunneling recombination, which allows for the efficient collection of the photoexcited carriers. Peak responsivity and detectivity of 21 mA/W and 7.1×108 cm Hz1/2/W at λ = 4.0 μm are obtained for a device with cutoff wavelength of 4.4 μm. Peak responsivity and detectivity of 46 mA/W and 1.4×109 cm Hz1/2/W at λ = 3.0 μm are obtained for another device with cutoff wavelength of 3.3 μm. These detectors exhibit low noise (4.8×10−13 A/Hz1/2) and a large product of the differential resistance and active area (19 Ω cm2) at room temperature.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
42.55.Px Semiconductor lasers; laser diodes
72.40.+w Photoconduction and photovoltaic effects
73.40.Gk Tunneling

2-ps passively mode-locked Nd:YVO4 laser using an output-coupling-type semiconductor saturable absorber mirror

Ya-Xian Fan, Jing-Liang He, Yong-Gang Wang, Sheng Liu, Hui-Tian Wang, and Xiao-Yu Ma

Appl. Phys. Lett. 86, 101103 (2005); http://dx.doi.org/10.1063/1.1879099 (3 pages) | Cited 29 times

Online Publication Date: 28 February 2005

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We have demonstrated stable self-starting passive mode-locking in a diode-end-pumped Nd:YVO4 laser using a semiconductor saturable absorber mirror (SESAM). An In0.25Ga0.75As single quantum-well SESAM, which was grown by the metalorganic chemical-vapor deposition technique at low temperature, acts as a passive mode-locking device and an output coupler at the same time. Continuous-wave mode-locked transform-limited pulses were obtained at 1064 nm with a pulse duration of 2.1 ps and an average output power of 1.28 W at a repetition rate of 96.5 MHz.
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42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
42.60.Fc Modulation, tuning, and mode locking
42.79.Bh Lenses, prisms and mirrors
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.55.Rz Doped-insulator lasers and other solid state lasers

Vortex-like surface wave and its role in the transient phenomena of meta-material focusing

Lei Zhou and C. T. Chan

Appl. Phys. Lett. 86, 101104 (2005); http://dx.doi.org/10.1063/1.1879104 (3 pages) | Cited 10 times

Online Publication Date: 28 February 2005

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We show that a slab of meta-material (with ε = μ = −1+iΔ) possesses a vortex-like surface wave with no ability to transport energy, whose nature is completely different from a localized mode or a standing wave. Through computations based on a rigorous time-dependent Green’s function approach, we demonstrate that such a mode inevitably generates characteristic image oscillations in two-dimensional focusing with even a monochromatic source, which were observed in many numerical simulations, but such oscillations are weak in three-dimensional focusing.
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41.20.Jb Electromagnetic wave propagation; radiowave propagation

Monolithic integration of vertical-cavity surface-emitting lasers with in-plane waveguides

Jeremy Witzens, Axel Scherer, Gregory Pickrell, Duane Louderback, and Peter Guilfoyle

Appl. Phys. Lett. 86, 101105 (2005); http://dx.doi.org/10.1063/1.1880440 (3 pages) | Cited 2 times

Online Publication Date: 2 March 2005

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The ability to couple light from a vertical-cavity surface-emitting laser into a planar, on-chip waveguide creates new opportunities for achieving higher levels of integration and functionality. Here we propose to use a strong grating etched into a waveguide defined into the top layer of the epitaxially grown structure, so that epitaxial regrowth is not required. By introducing a defect mode into the cavity we were able to achieve a 40% coupling efficiency even though light is coupled through a ninety degrees bend. We also show that polarization control of the vertical-cavity surface-emitting laser is enhanced by coupling to the defect mode. Calculations were performed using the finite-difference time-domain method.
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42.55.Px Semiconductor lasers; laser diodes
42.82.Et Waveguides, couplers, and arrays
85.60.Bt Optoelectronic device characterization, design, and modeling
42.82.Bq Design and performance testing of integrated-optical systems
42.79.Gn Optical waveguides and couplers
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.79.Dj Gratings

Measurements of energy fluctuations of a saturated 46.9 nm Ar laser produced in Z-pinch capillary discharges

A. Ritucci, G. Tomassetti, A. Reale, L. Reale, F. Flora, and L. Mezi

Appl. Phys. Lett. 86, 101106 (2005); http://dx.doi.org/10.1063/1.1882748 (3 pages) | Cited 1 time

Online Publication Date: 3 March 2005

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We report on the achievement of significant energy stability in a 46.9 nm soft x-ray laser pumped by fast Z-pinch capillary discharges. The energy stability, investigated over, hundreds of shots, is optimized by operating the laser in the highly saturated regime using capillary discharges with length up to 45 cm. We demonstrate standard deviation on the energy fluctuations smaller than ±5% and an energy∕pulse of 300 μJ at 0.2 Hz. These results demonstrate the reliability of this soft x-ray laser for its widespread use for the development of applications.
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42.55.Vc X- and γ-ray lasers
42.55.Lt Gas lasers including excimer and metal-vapor lasers
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
52.38.Dx Laser light absorption in plasmas (collisional, parametric, etc.)
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.58.Lq Z-pinches, plasma focus, and other pinch devices

Compact wavelength monitoring by lateral outcoupling in wedged photonic crystal multimode waveguides

E. Viasnoff-Schwoob, C. Weisbuch, H. Benisty, C. Cuisin, E. Derouin, O. Drisse, G-H. Duan, L. Legouézigou, O. Legouézigou, F. Pommereau, S. Golka, H. Heidrich, H. J. Hensel, and K. Janiak

Appl. Phys. Lett. 86, 101107 (2005); http://dx.doi.org/10.1063/1.1879105 (3 pages) | Cited 21 times

Online Publication Date: 3 March 2005

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A device concept for laterally extracting selected wavelengths from an optical signal traveling along a waveguide, for operation in metropolitan area networks, is presented. The signal on the fundamental mode of a multimode photonic crystal waveguide is coupled to a higher-order mode, at a center frequency that spatially depends on the slowly varying guide parameters. The device is compact, intrinsically fault tolerant, and can split any desired fraction of the signal for monitoring purpose. Characterizations by the internal light source technique validate the optical concept whereas an integrated device with four photodiodes qualifies its potential with respect to real-world applications.
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84.40.Ua Telecommunications: signal transmission and processing; communication satellites
42.79.Sz Optical communication systems, multiplexers, and demultiplexers
42.82.Et Waveguides, couplers, and arrays
42.79.Gn Optical waveguides and couplers

Direct observation of coherent rotational excitation, dephasing and depopulation of methanol and its isotopes using THz pulse radiation

B. L. Yu, Y. Yang, F. Zeng, X. Xin, and R. R. Alfano

Appl. Phys. Lett. 86, 101108 (2005); http://dx.doi.org/10.1063/1.1882759 (3 pages) | Cited 4 times

Online Publication Date: 4 March 2005

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Coherent transients are directly observed in the time-domain as a sequence of decreasing commensurate pulses in methanol (CH3OH) and its isotopes (CH3OD and CD3OD) gases to yield fundamental information on its dephasing and depopulation. The delay times between coherent pulses of ∼ 21, 22, and 26 ps are measured for the CH3OH, CH3OD, and CD3OD corresponding to the inverse of rotational energy spacing for ΔJ = ±1 transitions, respectively. The dephasing time T2 = 23±0.5 ps and depopulation time T1 = 48±0.5 ps were measured for CH3OH at room temperature.
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33.20.Bx Radio-frequency and microwave spectra
34.50.Ez Rotational and vibrational energy transfer
33.15.Mt Rotation, vibration, and vibration-rotation constants
42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency
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Increased atomic hydrogen flux from a cascaded arc plasma source by changing the nozzle geometry

P. Vankan, R. Engeln, and D. C. Schram

Appl. Phys. Lett. 86, 101501 (2005); http://dx.doi.org/10.1063/1.1879112 (3 pages) | Cited 10 times

Online Publication Date: 1 March 2005

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A very high flux of hydrogen atoms with energies in the eV range has been obtained by using a thermal plasma source and by optimization of the nozzle exit geometry. It proves that the flux of hydrogen atoms emerging from a cascaded arc plasma source depends strongly on the geometry of the nozzle. By decreasing the nozzle length by a factor 2, the atomic hydrogen flux is increased by a factor of 13, and a further increase of a factor of 2.5 can be obtained by increasing the nozzle diameter. The resulting atomic hydrogen flux is 1.2×1021 s−1, corresponding to a dissociation degree of over 30%. It is argued that the main loss channel for atomic hydrogen is surface recombination, and that by using nozzle geometries that reduce the surface loss, the atomic flux is increased.
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52.30.-q Plasma dynamics and flow
52.50.Dg Plasma sources
52.25.Fi Transport properties
52.25.-b Plasma properties
52.40.Hf Plasma-material interactions; boundary layer effects

Flow actuation using radio frequency in partially ionized collisional plasmas

Subrata Roy

Appl. Phys. Lett. 86, 101502 (2005); http://dx.doi.org/10.1063/1.1879097 (3 pages) | Cited 19 times

Online Publication Date: 3 March 2005

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We present a multidimensional theoretical model for a better understanding and the design of the dielectric barrier discharge-induced momentum exchange. Specifically, the formulation is used to predict surface discharge using two-dimensional asymmetric electrode configurations. Model predictions for charge densities, the electric field, and gas velocity distributions are shown to mimic trends reported in the experimental literature. We also predict the electron charge accumulation on the dielectric surface self-limiting the discharge.
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52.30.-q Plasma dynamics and flow
52.80.Pi High-frequency and RF discharges
52.25.Mq Dielectric properties
52.65.-y Plasma simulation
52.20.Fs Electron collisions
52.25.Jm Ionization of plasmas
52.25.Fi Transport properties
52.25.Ya Neutrals in plasmas
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Two-dimensional micromanipulation using liquid crystals

Yoshitaka Mieda and Katsushi Furutani

Appl. Phys. Lett. 86, 101901 (2005); http://dx.doi.org/10.1063/1.1872218 (3 pages) | Cited 7 times

Online Publication Date: 28 February 2005

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We developed a two-dimensional micromanipulation method using liquid crystals. The combination of the backflow effect in the twisted nematic cell and the electrostatic force for the naturally charged microparticles causes the net movement. By adjusting the polarity and the duty ratio of the rectangular voltage, the particles can be driven two-dimensionally and bidirectionally. The velocity of the particles depended on the duty ratio, amplitude, and frequency of the applied voltage.
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07.10.Cm Micromechanical devices and systems
61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order
87.80.Fe Micromanipulation of biological structures

Raman active phonon modes and heat capacities of Ti2AlC and Cr2AlC ceramics: first-principles and experimental investigations

Jingyang Wang, Yanchun Zhou, Zhijun Lin, Fanling Meng, and Feng Li

Appl. Phys. Lett. 86, 101902 (2005); http://dx.doi.org/10.1063/1.1873057 (3 pages) | Cited 23 times

Online Publication Date: 28 February 2005

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Raman active phonon frequencies and corresponding vibrational eigenmodes are reported for two M2AlC ceramics, Ti2AlC and Cr2AlC, by means of first-principles calculations. The theoretical modes are approved by the experimental Raman spectrum for Ti2AlC. Compared with that of the Ti3SiC2 counterpart, the number of Raman active modes is definitely determined by the chemical formula of transition-metal carbide layers; for example, TiC0.67 in Ti3SiC2 and TiC0.5 in M2AlC. All active modes originate from stretching and bending of Al–M–C covalent bond chains, whereas the vibration of M–C bond localized inside the M6C octahedra is not Raman active. The differences in vibration characteristics between Ti2AlC and Cr2AlC are discussed in terms of atomic force constants. By including the phonon and electron contributions, trends in heat capacities as a function of temperature were illustrated and compared.
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78.20.Fm Birefringence
82.45.Xy Ceramics in electrochemistry
65.60.+a Thermal properties of amorphous solids and glasses: heat capacity, thermal expansion, etc.
63.50.-x Vibrational states in disordered systems

Comparison of blue and green InGaN/GaN multiple-quantum-well light-emitting diodes grown by metalorganic vapor phase epitaxy

Y. D. Qi, H. Liang, D. Wang, Z. D. Lu, W. Tang, and K. M. Lau

Appl. Phys. Lett. 86, 101903 (2005); http://dx.doi.org/10.1063/1.1866634 (3 pages) | Cited 25 times

Online Publication Date: 1 March 2005

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InGaN/GaN multiple-quantum-well (MQW) blue and green-light-emitting diodes (LEDs) were grown on sapphire substrates using metalorganic vapor phase epitaxy. High-resolution transmission microscopy shows that a much larger density of stacking faults exist in the quantum-well region of the blue LEDs than in the green LEDs. In the green LEDs, the blueshift in the electroluminescence (EL) emission energy at larger driving currents is more prominent than in the blue LEDs, which is explained by different strength of quantum-confined Stark effect as a result of different piezoelectric field intensity by different scales of strain relaxation in the blue and green MQWs. The steady broadening of the EL emission energy linewidth on the higher energy side with the increase of the driving current was observed in both blue and green LEDs, which is attributed to the band filling effect.
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85.60.Jb Light-emitting devices
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
78.67.De Quantum wells
78.60.Fi Electroluminescence
78.20.Jq Electro-optical effects
68.65.Fg Quantum wells
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
61.72.Nn Stacking faults and other planar or extended defects
77.65.Ly Strain-induced piezoelectric fields
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.37.Lp Transmission electron microscopy (TEM)

Optically probed wetting layer in InAs/InGaAlAs/InP quantum-dash structures

W. Rudno-Rudziński, G. Sęk, K. Ryczko, R. Kudrawiec, J. Misiewicz, A. Somers, R. Schwertberger, J. P. Reithmaier, and A. Forchel

Appl. Phys. Lett. 86, 101904 (2005); http://dx.doi.org/10.1063/1.1881782 (3 pages) | Cited 18 times

Online Publication Date: 1 March 2005

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Photoluminescence and photoreflectance measurements have been performed to investigate molecular-beam-epitaxy-grown InAs/InGaAlAs/InP structures with different-size InAs quantum dashes. Optical features related to all relevant parts of the structure have been detected and recognized, including a line which has been attributed to the ground-state wetting layer quantum well transition. The spectral position of the latter is independent of the nominal InAs layer thickness in contrast to quantum-dash emission peak, which shifts sequentially to the red due to an increase of the islands’ size. The interpretation has been supported by energy level calculations showing that the wetting layer has to be approximately 2 ML thick and that only one state is confined in such a thin well for each kind of carriers, i.e., electrons, heavy, and light holes.
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81.07.St Quantum wells
81.05.Ea III-V semiconductors
78.67.De Quantum wells
68.65.Fg Quantum wells
78.55.Cr III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Mechanisms of B deactivation control by F co-implantation

N. E. B. Cowern, B. Colombeau, J. Benson, A. J. Smith, W. Lerch, S. Paul, T. Graf, F. Cristiano, X. Hebras, and D. Bolze

Appl. Phys. Lett. 86, 101905 (2005); http://dx.doi.org/10.1063/1.1870131 (3 pages) | Cited 37 times

Online Publication Date: 1 March 2005

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Thermal annealing after preamorphization and solid-phase epitaxy of ultrashallow B implants leads to deactivation and diffusion driven by interstitials released from end-of-range defects. F inhibits these processes by forming small clusters that trap interstitials. A competing B–F interaction causes deactivation when F and B profiles overlap. Both pathways suppress B transient enhanced diffusion.
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61.72.uf Ge and Si
66.30.J- Diffusion of impurities
61.72.Cc Kinetics of defect formation and annealing
61.72.J- Point defects and defect clusters
61.72.S- Impurities in crystals

High pressure study of Ti4AlN3 to 55 GPa

Bouchaib Manoun, S. K. Saxena, and M. W. Barsoum

Appl. Phys. Lett. 86, 101906 (2005); http://dx.doi.org/10.1063/1.1875750 (3 pages) | Cited 30 times

Online Publication Date: 1 March 2005

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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 polycrystalline Ti4AlN3 sample up to a pressure of 55 GPa. No phase transformations were observed. As observed in Ti3SiC2, Ti3Si0.5Ge0.5C2, and Zr2InC, the compressibility of Ti4AlN3 along the c axis was larger than along the a axis which leads to a decrease in the c/a ratio with increasing pressure. The bulk modulus is 216±2 GPa, with a pressure derivative of 3.84±0.06.
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81.05.Mh Cermets, ceramic and refractory composites
62.50.-p High-pressure effects in solids and liquids
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

Plastic flow localization in bulk tungsten with ultrafine microstructure

Q. Wei, K. T. Ramesh, E. Ma, L. J. Kesckes, R. J. Dowding, V. U. Kazykhanov, and R. Z. Valiev

Appl. Phys. Lett. 86, 101907 (2005); http://dx.doi.org/10.1063/1.1875754 (3 pages) | Cited 27 times

Online Publication Date: 3 March 2005

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Shear localization is demonstrated in bulk tungsten (W) of commercial purity under dynamic uniaxial compression. Microstructure refinement via severe plastic deformation was the strategy used to induce this unusual deformation mode for W. The ultrafine microstructure achieved in bcc materials leads to elevated strength and ductility, as well as reduced strain hardening and strain rate hardening, thus enhancing the propensity for adiabatic plastic flow localization.
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81.05.Bx Metals, semimetals, and alloys
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
81.70.Bt Mechanical testing, impact tests, static and dynamic loads

Growth and characterization of single quantum dots emitting at 1300 nm

B. Alloing, C. Zinoni, V. Zwiller, L. H. Li, C. Monat, M. Gobet, G. Buchs, A. Fiore, E. Pelucchi, and E. Kapon

Appl. Phys. Lett. 86, 101908 (2005); http://dx.doi.org/10.1063/1.1872213 (3 pages) | Cited 64 times

Online Publication Date: 3 March 2005

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We have optimized the molecular-beam epitaxy growth conditions of self-organized InAs/GaAs quantum dots (QDs) to achieve a low density of dots emitting at 1300 nm at low temperature. We used an ultralow InAs growth rate, lower than 0.002 ML/s, to reduce the density to 2 dots/μm2 and an InGaAs capping layer to achieve longer emission wavelength. Microphotoluminescence spectroscopy at low-temperature reveals emission lines characteristic of exciton-biexciton behavior. We also study the temperature dependence of the photoluminescence, showing clear single QD emission up to 90 K. With these results, InAs/GaAs QDs appear as a very promising system for future applications of single photon sources in fiber-based quantum cryptography.
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81.07.Ta Quantum dots
81.05.Ea III-V semiconductors
78.67.Hc Quantum dots
73.21.La Quantum dots
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.55.Cr III-V semiconductors

Luminescence studies of Ti-doped Al2O3 using vacuum ultraviolet synchrotron radiation

V. B. Mikhailik, H. Kraus, D. Wahl, and M. S. Mykhaylyk

Appl. Phys. Lett. 86, 101909 (2005); http://dx.doi.org/10.1063/1.1880451 (3 pages) | Cited 10 times

Online Publication Date: 3 March 2005

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In this study, we examined the luminescence response of Ti-doped Al2O3 crystals to high-energy vacuum ultraviolet (UV) excitation. In addition to the thoroughly studied emission band of Ti3+ in the near-infrared region and blue emission at 420 nm, we detected a UV emission band at 290 nm. The excitation spectra of all emission bands were measured over the 4–20 eV spectral range. Our results indicate that intrinsic anion defects are involved in the process of the excitation of the 420 nm emission assigned to the charge transfer transitions 2pO2−→3dTi4+. Analysis of the spectral and decay characteristics of the UV emission enables us to suggest that this band is associated with radiative decay of excitons localized at Ti ions.
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78.55.Hx Other solid inorganic materials
71.35.Cc Intrinsic properties of excitons; optical absorption spectra

Extremely low surface recombination velocity in GaInAsSb/AlGaAsSb heterostructures

C. A. Wang, D. A. Shiau, D. Donetsky, S. Anikeev, G. Belenky, and S. Luryi

Appl. Phys. Lett. 86, 101910 (2005); http://dx.doi.org/10.1063/1.1873042 (3 pages) | Cited 5 times

Online Publication Date: 3 March 2005

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Low surface recombination velocity is critical to the performance of minority carrier devices. Minority carrier lifetime in double heterostructures (DHs) of 0.53-eV p-GaInAsSb confined with 1.0-eV p-AlGaAsSb, and grown lattice-matched to GaSb, was measured by time-resolved photoluminescence. The structures were designed to be dominated by the heterointerface while minimizing the contribution of photon recycling to minority carrier lifetime. Surface recombination velocity as low as 30 cm/s for DHs was achieved. This value is over an order of magnitude lower than that reported in previous studies.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
78.55.Cr III-V semiconductors
73.25.+i Surface conductivity and carrier phenomena

Relaxation of packaging-induced strains in AlGaAs-based high-power diode laser arrays

Tran Quoc Tien, Axel Gerhardt, Sandy Schwirzke-Schaaf, Jens W. Tomm, Holger Müntz, Jens Biesenbach, Myriam Oudart, Julien Nagle, and Mark L. Biermann

Appl. Phys. Lett. 86, 101911 (2005); http://dx.doi.org/10.1063/1.1880438 (3 pages) | Cited 1 time

Online Publication Date: 3 March 2005

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We monitor the mechanical strain evolution with typical use in the quantum well of AlGaAs/GaAs-based high-power diode laser arrays (cm bars) by spectroscopic means. We show experimentally that pristine devices are essentially uniaxially compressed along the 110-direction with a strain maximum of −0.16% at the center of the device. At the device edges, almost no packaging-induced strain is detectable. After 500 h of continuous wave operation at a current of I = 80 A, the strain is reduced by 50%. Furthermore, we observe the growth of a localized region of compressive strain, of hydrostatic symmetry, in one emitter of a particular cm-bar. A compression of about −0.017% is observed, and is most likely caused by point defect accumulation. Our results demonstrate information about absolute strain values and, at least in part, about strain symmetry as well can be obtained by spectroscopic means even within packaged complex optoelectronic devices.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Effects of Eu interfacial mobility on the growth of epitaxial EuBa2Cu3O7−δ films

H. Wang, X. Z. Liao, H. F. Xu, X. Zhang, Y. Lin, S. R. Foltyn, P. N. Arendt, J. L. MacManus-Driscoll, Y. T. Zhu, and Q. X. Jia

Appl. Phys. Lett. 86, 101912 (2005); http://dx.doi.org/10.1063/1.1881779 (3 pages)

Online Publication Date: 4 March 2005

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By inserting a thin YBa2Cu3O7−δ (Y123) seed layer, high quality EuBa2Cu3O7−δ (Eu123) films can grow with epitaxial c-axis orientation on SrTiO3 (STO) substrate without increasing the growth temperature. The interfacial structures of Eu123/STO and Eu123/Y123/STO were investigated using scanning transmission electron microscopy. Results show that the Eu mobility on the STO substrate is very low at the regular deposition temperature. This leads to nonuniform composition distribution at the Eu123/STO interface and a mixture of c-axis and a-axis growth. A thin Y123 seed layer greatly improves the Eu mobility and therefore facilitates high quality c-axis growth.
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74.78.-w Superconducting films and low-dimensional structures
74.70.Dd Ternary, quaternary, and multinary compounds (including Chevrel phases, borocarbides, etc.)
68.55.A- Nucleation and growth
74.72.-h Cuprate superconductors
74.25.F- Transport properties
68.55.-a Thin film structure and morphology
68.35.Ct Interface structure and roughness
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.55.Nq Composition and phase identification
81.15.Kk Vapor phase epitaxy; growth from vapor phase
74.78.Fk Multilayers, superlattices, heterostructures
81.15.Fg Pulsed laser ablation deposition
68.37.Lp Transmission electron microscopy (TEM)

Enhanced boron activation in silicon by high ramp-up rate solid phase epitaxial regrowth

B. J. Pawlak, W. Vandervorst, A. J. Smith, N. E. B. Cowern, B. Colombeau, and X. Pages

Appl. Phys. Lett. 86, 101913 (2005); http://dx.doi.org/10.1063/1.1882756 (3 pages) | Cited 18 times

Online Publication Date: 4 March 2005

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We investigate the influence of thermal conditions during solid phase epitaxial regrowth (SPER) on the electrical activation level of boron in preamorphized silicon, both with respect to heating ramp rates and the use of low temperature preanneals. Enhancement of electrically active boron concentration by 36% is observed for activation with the fastest ramp rate (487 °C/s) compared to the slowest one (1 °C/s). An important clustering pathway occurs within the amorphous silicon phase (during low temperature preanneal) prior to completion of the SPER process. In these junctions boron deactivation during isochronal post-annealing is almost independent on the maximum boron activation level.
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81.05.Cy Elemental semiconductors
81.05.Gc Amorphous semiconductors
68.55.A- Nucleation and growth
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.55.-a Thin film structure and morphology
61.72.uf Ge and Si
61.72.S- Impurities in crystals
81.15.Np Solid phase epitaxy; growth from solid phases
61.72.Cc Kinetics of defect formation and annealing

Scintillators based on aromatic dye molecules doped in a sol-gel glass host

M. Nikl, N. Solovieva, K. Apperson, D. J. S. Birch, and A. Voloshinovskii

Appl. Phys. Lett. 86, 101914 (2005); http://dx.doi.org/10.1063/1.1882758 (3 pages) | Cited 4 times

Online Publication Date: 4 March 2005

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Ultraviolet and x-ray excited luminescence of fluorescein and rhodamine-6G doped sol-gel glasses were studied at room temperature with the aim of characterizing and understanding the scintillation performance of such materials. Fast energy transfer from the glass host to the dye luminescent centers was found. While the overall radioluminescence efficiency was rather low due to nonradiative losses in the glass host, our results demonstrate the potential of sol-gel technology as a versatile tool in controlling the spectral and time response of such unusual organic–inorganic scintillators.
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42.70.Ce Glasses, quartz
78.55.Qr Amorphous materials; glasses and other disordered solids

Deformation twinning during nanoindentation of nanocrystalline Ta

Y. M. Wang, A. M. Hodge, J. Biener, A. V. Hamza, D. E. Barnes, Kai Liu, and T. G. Nieh

Appl. Phys. Lett. 86, 101915 (2005); http://dx.doi.org/10.1063/1.1883335 (3 pages) | Cited 26 times

Online Publication Date: 4 March 2005

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The deformation mechanism of body-centered cubic (bcc) nanocrystalline tantalum with grain sizes of 10–30 nm is investigated by nanoindentation, scanning electron microscopy and high-resolution transmission electron microscopy. In a deviation from molecular dynamics simulations and existing experimental observations on other bcc nanocrystalline metals, the plastic deformation of nanocrystalline Ta during nanoindentation is controlled by deformation twinning. The observation of multiple twin intersections suggests that the physical mechanism of deformation twinning in bcc nanocrystalline materials is different from that in face-centered cubic (fcc) nanocrystalline metals.
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81.05.Bx Metals, semimetals, and alloys
81.07.Bc Nanocrystalline materials
62.25.-g Mechanical properties of nanoscale systems
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
62.20.M- Structural failure of materials
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
68.60.Bs Mechanical and acoustical properties
68.35.Gy Mechanical properties; surface strains
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Mm Grain and twin boundaries
61.46.-w Structure of nanoscale materials
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)
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