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24 Oct 2011

Volume 99, Issue 17, Articles (17xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 99, 173101 (2011); http://dx.doi.org/10.1063/1.3634010 (3 pages)

Sajal Dhara, Shamashis Sengupta, Hari S. Solanki, Arvind Maurya, Arvind Pavan R., M. R. Gokhale, Arnab Bhattacharya, and Mandar M. Deshmukh
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Optothermal spectroscopy of whispering gallery microresonators

Jiangang Zhu, Şahin Kaya Özdemir, Lina He, and Lan Yang

Appl. Phys. Lett. 99, 171101 (2011); http://dx.doi.org/10.1063/1.3656716 (3 pages)

Online Publication Date: 24 October 2011

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We demonstrate an optothermal resonance scanning scheme to obtain stable spectra of resonant modes in whispering gallery microresonators. A wavelength stability of 0.1 pm for a temperature variation of more than 10 °C is obtained. In this scheme, a resonance mode is thermally locked to a tunable laser, and its wavelength is linearly scanned across the lasing line of a fixed wavelength laser. The scheme enables reliable and accurate readings for whispering gallery mode (WGM) sensing platforms and allows the spectroscopy of WGM resonators within wavelength bands where tunable lasers are not available.
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79.10.Ca Deep-level photothermal spectroscopy
07.10.Cm Micromechanical devices and systems
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
46.40.Ff Resonance, damping, and dynamic stability

Strong blue and red luminescence in silicon nanoparticles based light emitting capacitors

A. Morales-Sánchez, K. Monfil-Leyva, A. A. González, M. Aceves-Mijares, J. Carrillo, J. A. Luna-López, C. Domínguez, J. Barreto, and F. J. Flores-Gracia

Appl. Phys. Lett. 99, 171102 (2011); http://dx.doi.org/10.1063/1.3655997 (3 pages) | Cited 2 times

Online Publication Date: 24 October 2011

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Light emitting capacitors (LECs) were fabricated using silicon rich oxide (SRO) films as active layer. Blue and red electroluminescence (EL) was observed by changing the silicon nanoparticle (Si-np) size from 1.5 to 2.7 nm embedded in the silica matrix. EL is ascribed to the charge injection into the Si-nps embedded in the SRO films through a balanced transport network. The EL emission is observed with the naked eye and in daylight conditions on the whole area of devices. Therefore, these results prove the feasibility to obtain LECs by using simple capacitors with SRO films as the active layer.
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85.60.Jb Light-emitting devices
81.16.-c Methods of micro- and nanofabrication and processing
84.32.Tt Capacitors

Mixed state effects in waveguide electro-absorbers based on quantum dots

T. Piwonski, J. Pulka, G. Huyet, J. Houlihan, E. A. Viktorov, and T. Erneux

Appl. Phys. Lett. 99, 171103 (2011); http://dx.doi.org/10.1063/1.3653287 (3 pages)

Online Publication Date: 24 October 2011

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Multi-pulse heterodyne pump-probe measurements are used to investigate the reverse bias dynamics of InAs/GaAs quantum dots in a waveguide structure. Using a femtosecond pulse, we simultaneously populate high energy ground states and low energy excited states and measure the resulting gain and phase dynamics over the bandwidth of the pulse. We identify a ∼5 ps timescale in the phase dynamics which can be associated with low energy ground states outside the pulse bandwidth and may provide an explanation for the deterioration of monolithic mode locked laser performance at high reverse voltages.
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42.79.Gn Optical waveguides and couplers
73.61.Ey III-V semiconductors
78.20.Jq Electro-optical effects
78.66.Fd III-V semiconductors
42.60.Fc Modulation, tuning, and mode locking
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.70.-a Optical materials

N-polar III-nitride quantum well light-emitting diodes with polarization-induced doping

Jai Verma, John Simon, Vladimir Protasenko, Thomas Kosel, Huili Grace Xing, and Debdeep Jena

Appl. Phys. Lett. 99, 171104 (2011); http://dx.doi.org/10.1063/1.3656707 (3 pages) | Cited 6 times

Online Publication Date: 25 October 2011

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Nitrogen-polar III-nitride heterostructures present unexplored advantages over Ga(metal)-polar crystals for optoelectronic devices. This work reports N-polar III-nitride quantum-well ultraviolet light-emitting diodes grown by plasma-assisted molecular beam epitaxy that integrate polarization-induced p-type doping by compositional grading from GaN to AlGaN along N-face. The graded AlGaN layer simultaneously acts as an electron blocking layer while facilitating smooth injection of holes into the active region, while the built-in electric field in the barriers improves carrier injection into quantum wells. The enhanced doping, carrier injection, and light extraction indicate that N-polar structures have the potential to exceed the performance of metal-polar ultraviolet light-emitting diodes.
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85.60.Jb Light-emitting devices
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Polarization dependent study of gain anisotropy in semipolar InGaN lasers

Jens Rass, Tim Wernicke, Simon Ploch, Moritz Brendel, Andreas Kruse, Andreas Hangleiter, Wolfgang Scheibenzuber, Ulrich T. Schwarz, Markus Weyers, and Michael Kneissl

Appl. Phys. Lett. 99, 171105 (2011); http://dx.doi.org/10.1063/1.3655183 (3 pages) | Cited 2 times

Online Publication Date: 25 October 2011

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The optical gain of single quantum well laser structures on semipolar (11math2)-GaN in dependence of the optical polarization and the resonator orientation has been studied by variable stripe length method. The c′-[11math] resonator shows maximum gain in TE mode, followed by the m-[1math00]-resonator with extraordinary polarization. The anisotropic gain behaviour is explained by valence sub-band ordering and birefringence of the wurtzite crystal, resulting in a modification of the transition matrix element for stimulated emission. Measurements are accompanied by 6 × 6 k · p band structure calculations and gain analysis.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.79.-e Optical elements, devices, and systems

Hole transport improvement in InGaN/GaN light-emitting diodes by graded-composition multiple quantum barriers

C. H. Wang, S. P. Chang, P. H. Ku, J. C. Li, Y. P. Lan, C. C. Lin, H. C. Yang, H. C. Kuo, T. C. Lu, S. C. Wang, and C. Y. Chang

Appl. Phys. Lett. 99, 171106 (2011); http://dx.doi.org/10.1063/1.3655903 (3 pages) | Cited 12 times

Online Publication Date: 25 October 2011

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Graded-composition multiple quantum barriers (GQB) were designed and incorporated in c-plane InGaN/GaN light-emitting diodes (LEDs) grown on c-plane sapphire substrate to improve hole transport and efficiency droop. The simulation of GQB LED design predicts enhancement of the hole transport in the active region at both low and high current densities. The fabricated LED with GQB structure exhibits lower series resistance and substantially reduced droop behavior of only 6% in comparison with 34% for conventional LED, supporting the improvement of hole transport in our design.
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85.60.Jb Light-emitting devices

Multimodal spectral control of a quantum-dot diode laser for THz difference frequency generation

R. Leyman, D. I. Nikitichev, N. Bazieva, and E. U. Rafailov

Appl. Phys. Lett. 99, 171107 (2011); http://dx.doi.org/10.1063/1.3654154 (3 pages) | Cited 1 time

Online Publication Date: 26 October 2011

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Generation of stable dual and/or multiple longitudinal modes emitted from a single quantum dot (QD) laser diode (LD) over a broad wavelength range by using volume Bragg gratings (VBG’s) in an external cavity setup is reported. The LD operates in both the ground and excited states and the gratings give a dual-mode separation around each emission peak of 5 nm, which is suitable as a continuous wave (CW) optical pump signal for a terahertz (THz) photomixer device. The setup also generates dual modes around both 1180 m and 1260 nm simultaneously, giving four simultaneous narrow linewidth modes comprising two simultaneous difference frequency pump signals.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.79.Dj Gratings
84.40.-x Radiowave and microwave (including millimeter wave) technology

Spin-orbit coupling effect on bismuth donor lasing in stressed silicon

R. Kh. Zhukavin, K. A. Kovalevsky, V. V. Tsyplenkov, V. N. Shastin, S. G. Pavlov, H.-W. Hübers, H. Riemann, N. V. Abrosimov, and A. K. Ramdas

Appl. Phys. Lett. 99, 171108 (2011); http://dx.doi.org/10.1063/1.3656023 (3 pages) | Cited 1 time

Online Publication Date: 26 October 2011

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We report a study on terahertz lasing from optically excited Bi donors in axially compressed silicon crystal. The laser frequency and the radiated power were measured versus stress applied along the [100] crystal axis. As shown, Bi donors lase at the optical transitions from the 2p± states to the 1s (E) state or/and to the spin-orbit split 1s (T2:Γ8) and 1s (T2:Γ7) states, and by fitting the crystal strain, one can shift the laser transitions and change the output power. The experiment is explained by the dependence of spin-orbit splitting and phonon-assisted relaxation of donor states on crystal distortion.
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42.55.Px Semiconductor lasers; laser diodes

A single spectral mode wide stripe laser with very narrow linewidth

U. Reddy, N. L. Dias, A. Garg, and J. J. Coleman

Appl. Phys. Lett. 99, 171109 (2011); http://dx.doi.org/10.1063/1.3656024 (3 pages)

Online Publication Date: 26 October 2011

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We present results on a single spectral mode wide stripe semiconductor laser with an integrated surface etched distributed Bragg reflector operating at 975 nm with very narrow linewidth. Linewidths as low as 220 kHz have been obtained from a 40 μm wide stripe laser. For 980 nm devices reporting a linewidth of sub-1 MHz, the power of 0.5 W (linewidth of 350 kHz) is the highest obtained at this wavelength.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Extremely high absolute internal quantum efficiency of photoluminescence in co-doped GaN:Zn,Si

M. A. Reshchikov, A. G. Willyard, A. Behrends, A. Bakin, and A. Waag

Appl. Phys. Lett. 99, 171110 (2011); http://dx.doi.org/10.1063/1.3655678 (3 pages) | Cited 4 times

Online Publication Date: 27 October 2011

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We report on the fabrication of GaN co-doped with silicon and zinc by metalorganic vapor phase epitaxy and a detailed study of photoluminescence in this material. We observe an exceptionally high absolute internal quantum efficiency of blue photoluminescence in GaN:Zn,Si. The value of 0.93±0.04 has been obtained from several approaches based on rate equations.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
78.55.Cr III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Counter-polarized single-photon generation from the auxiliary cavity of a weakly nonlinear photonic molecule

Motoaki Bamba and Cristiano Ciuti

Appl. Phys. Lett. 99, 171111 (2011); http://dx.doi.org/10.1063/1.3656250 (3 pages) | Cited 2 times

Online Publication Date: 28 October 2011

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We propose a scheme for the resonant generation of counter-polarized single photons in double asymmetric cavities with a small Kerr optical nonlinearity (as that created by a semiconductor quantum well) compared to the mode broadening. Due to the interplay between spatial intercavity tunneling and polarization coupling, by weakly exciting with circularly polarized light one of the cavities, we predict strong antibunching of counter-polarized light emission from the non-pumped auxiliary cavity. This scheme due to quantum interference is robust against surface scattering of pumping light, which can be suppressed both by spatial and polarization filters.
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33.80.Be Level crossing and optical pumping
42.50.-p Quantum optics
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation

Fabrication of glass micro-cavities for cavity quantum electrodynamics experiments

Arpan Roy and Murray D. Barrett

Appl. Phys. Lett. 99, 171112 (2011); http://dx.doi.org/10.1063/1.3658391 (3 pages) | Cited 1 time

Online Publication Date: 28 October 2011

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We report a process for fabricating high quality, defect-free spherical mirror templates suitable for developing high finesse optical Fabry-Perot resonators. The process utilizes the controlled re-flow of borosilicate glass and differential pressure to produce mirrors with 0.3 nm surface roughness. The dimensions of the mirrors are in the 0.5–5 mm range making them suitable candidates for integration with on-chip neutral atom and ion experiments where enhanced interaction between atoms and photons is required. Cavities constructed with these mirror templates are well suited to quantum information applications such as single photon sources and atom-photon entanglement.
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42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.70.Ce Glasses, quartz
03.67.Bg Entanglement production and manipulation
03.65.Ud Entanglement and quantum nonlocality (e.g. EPR paradox, Bell's inequalities, GHZ states, etc.)
03.67.Mn Entanglement measures, witnesses, and other characterizations
42.50.Dv Quantum state engineering and measurements

High-power blue-violet AlGaN-cladding-free m-plane InGaN/GaN laser diodes

R. M. Farrell, D. A. Haeger, P. S. Hsu, M. C. Schmidt, K. Fujito, D. F. Feezell, S. P. DenBaars, J. S. Speck, and S. Nakamura

Appl. Phys. Lett. 99, 171113 (2011); http://dx.doi.org/10.1063/1.3656970 (3 pages) | Cited 5 times

Online Publication Date: 28 October 2011

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We demonstrate AlGaN-cladding-free (ACF) m-plane InGaN/GaN laser diodes (LDs) with peak output powers and estimated front facet optical power densities that are comparable to the state-of-the-art single-stripe emitter c-plane LDs. The threshold current density, slope efficiency, and peak output power were 4.66 kA/cm2, 1.29 W/A, and 1.6 W, respectively, after facet coating and under pulsed conditions. Catastrophic optical mirror damage was not observed up to an estimated optical power density of 51.2 MW/cm2 at the front mirror facet, indicating the potential for using ACF m-plane InGaN/GaN LDs in high-power LD applications.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.79.Bh Lenses, prisms and mirrors

Amplitude and phase of shaped nonlinear excitation fields in a four-wave mixing microscope

Varun Raghunathan, Alexei Nikolaenko, Chao-Yu Chung, and Eric O. Potma

Appl. Phys. Lett. 99, 171114 (2011); http://dx.doi.org/10.1063/1.3657148 (3 pages)

Online Publication Date: 28 October 2011

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We describe precise measurements of the amplitude and phase profiles of tightly focused nonlinear excitation fields in a four-wave mixing (FWM) microscope. By combining spatial light modulator based beam shaping with interferometric detection, we present the focal FWM excitation fields of various Hermite-Gaussian and Laguerre-Gaussian LG01 beam modes. We observe well-defined spatial phase patterns for the focal fields associated with these beam modes. Such precise measurements of shaped nonlinear excitation fields have implications for the development of resolution enhancement schemes and tip-enhanced imaging methods in FWM microscopy.
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42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.79.Hp Optical processors, correlators, and modulators
07.60.Ly Interferometers
07.60.Pb Conventional optical microscopes
42.30.Va Image forming and processing

Determination of internal parameters for AlGaN-cladding-free m-plane InGaN/GaN laser diodes

R. M. Farrell, D. A. Haeger, P. S. Hsu, K. Fujito, D. F. Feezell, S. P. DenBaars, J. S. Speck, and S. Nakamura

Appl. Phys. Lett. 99, 171115 (2011); http://dx.doi.org/10.1063/1.3657149 (3 pages) | Cited 8 times

Online Publication Date: 28 October 2011

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The dependence of device characteristics on cavity length is used to determine the injection efficiency, internal loss, and material gain of electrically injected AlGaN-cladding-free m-plane InGaN/GaN laser diodes. Estimates for the transparency carrier density are discussed in the context of recombination coefficients that have been reported for c-plane InGaN-based light-emitting devices.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.79.-e Optical elements, devices, and systems
85.60.Jb Light-emitting devices
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The role of a diffusion barrier in plasma display panel with the high gamma cathode layer

Tae-Ho Lee, Hee-Woon Cheong, Ohyung Kwon, Ki-Woong Whang, Sven Ole Steinmüller, and Jürgen Janek

Appl. Phys. Lett. 99, 171501 (2011); http://dx.doi.org/10.1063/1.3655329 (3 pages) | Cited 1 time

Online Publication Date: 24 October 2011

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Plasma display panel (PDP) with MgO-SrO double cathode layer and SiO2 diffusion barrier is proposed to make the SrO layer free of contaminations. Time of flight-secondary ion mass spectrometry (TOF-SIMS) analysis shows the diffusion of impurities, like Na and K, can be effectively blocked while a new SrO layer is formed on top of the MgO layer. This structure shows that high Xe gases can be used to improve the luminous efficacy 2.3 times and decrease the voltage margin more than 10 V compared to the conventional PDP using Ne-Xe 15%. The aging time was also significantly decreased to 3–4 h.
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52.75.-d Plasma devices
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
81.40.Cd Solid solution hardening, precipitation hardening, and dispersion hardening; aging
82.45.Fk Electrodes
66.30.J- Diffusion of impurities

Surface transport of energetic electrons in intense picosecond laser-foil interactions

R. J. Gray, X. H. Yuan, D. C. Carroll, C. M. Brenner, M. Coury, M. N. Quinn, O. Tresca, B. Zielbauer, B. Aurand, V. Bagnoud, J. Fils, T. Kühl, X. X. Lin, C. Li, Y. T. Li, et al.

Appl. Phys. Lett. 99, 171502 (2011); http://dx.doi.org/10.1063/1.3655909 (3 pages) | Cited 1 time

Online Publication Date: 25 October 2011

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The angular distribution of energetic electrons emitted from thin foil targets irradiated by intense, picosecond laser pulses is measured as a function of laser incidence angle, intensity, and polarization. Although the escaping fast electron population is found to be predominantly transported along the target surface for incidence angles ≥65°, in agreement with earlier work at lower intensities, rear-surface proton acceleration measurements reveal that a significant electron current is also transported longitudinally within the target, irrespective of incident angle. These findings are of interest to many applications of laser-solid interactions, including advanced schemes for inertial fusion energy.
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79.20.Ds Laser-beam impact phenomena
42.62.-b Laser applications
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Existence of a giant hypersonic elastic mirror in porous silicon superlattices

D. Moctezuma-Enriquez, Y. J. Rodriguez-Viveros, M. B. Manzanares-Martinez, P. Castro-Garay, E. Urrutia-Banuelos, and J. Manzanares-Martinez

Appl. Phys. Lett. 99, 171901 (2011); http://dx.doi.org/10.1063/1.3655677 (3 pages) | Cited 4 times

Online Publication Date: 24 October 2011

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In this work, we theoretically predict the possibility to obtain a giant hypersonic elastic mirror in porous silicon superlattices by using a phononic heterostructure. The heterostructure is composed of a tandem of multiple phononic crystal lattices with periods in the range 37–167 nm, which recently have been experimentally reported [L. C. Parsons and G. T. Andrews, Appl. Phys. Lett. 95, 241909 (2009)]. Considering the scalability of the eigenvalues of the elastic wave equation, the lattices are chosen such that each stop band can be superposed to obtain a larger overall stop band. Theoretical evidence of a giant hypersonic phononic mirror for longitudinal and transverse vibrations is found in the gigahertz range.
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81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity
63.22.Np Layered systems
62.30.+d Mechanical and elastic waves; vibrations

The power factor of Cr-doped V2O3 near the Mott transition

S. Populoh, P. Auban-Senzier, P. Wzietek, and C.R. Pasquier

Appl. Phys. Lett. 99, 171902 (2011); http://dx.doi.org/10.1063/1.3655993 (3 pages) | Cited 1 time

Online Publication Date: 24 October 2011

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We have measured the Seebeck coefficient, S, of nominally 1.1% Cr doped V2O3 as a function of both temperature and pressure. Large variations of S are found at the Mott insulator-metal transition. A combination of our data with resistivity data allows us to estimate the power factor. Contrary to thermopower and resistivity, the power factor is not strongly modified upon crossing the first order phase transition. Such a behavior is in sharp contrast with standard semiconductors.
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71.30.+h Metal-insulator transitions and other electronic transitions
72.20.Pa Thermoelectric and thermomagnetic effects
72.60.+g Mixed conductivity and conductivity transitions

Structural properties of Bi2Te3 and Bi2Se3 topological insulators grown by molecular beam epitaxy on GaAs(001) substrates

X. Liu, D. J. Smith, J. Fan, Y.-H. Zhang, H. Cao, Y. P. Chen, J. Leiner, B. J. Kirby, M. Dobrowolska, and J. K. Furdyna

Appl. Phys. Lett. 99, 171903 (2011); http://dx.doi.org/10.1063/1.3655995 (3 pages) | Cited 9 times

Online Publication Date: 24 October 2011

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Thin films of Bi2Te3 and Bi2Se3 have been grown on deoxidized GaAs(001) substrates using molecular beam epitaxy. Cross-sectional transmission electron microscopy established the highly parallel nature of the Te(Se)-Bi-Te(Se)-Bi-Te(Se) quintuple layers deposited on the slightly wavy GaAs substrate surface and the different crystal symmetries of the two materials. Raman mapping confirmed the presence of the strong characteristic peaks reported previously for these materials in bulk form. The overall quality of these films reveals the potential of combining topological insulators with ferromagnetic semiconductors for future applications.
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73.61.At Metal and metallic alloys
78.30.Er Solid metals and alloys
78.66.Bz Metals and metallic alloys
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.at Other materials
73.25.+i Surface conductivity and carrier phenomena

Size-affected shear-band speed in bulk metallic glasses

Z. Y. Liu, Y. Yang, and C. T. Liu

Appl. Phys. Lett. 99, 171904 (2011); http://dx.doi.org/10.1063/1.3656016 (3 pages) | Cited 3 times

Online Publication Date: 24 October 2011

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In this letter, we report an important experimental finding and theoretical analysis of the shear-band speed measured in a variety of bulk metallic-glasses. Unlike the prior work, in which the shear-band speed was regarded as a constant, our current study, based on carefully designed loading-holding cyclic tests, reveals that the speed of a shear band correlates with its resultant shear offset. Such a correlation arises as a “size” effect, which could be rationalized with the energy balance principle and shear-banding dynamics entailing initial shear softening and subsequent materials recovery.
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81.40.Lm Deformation, plasticity, and creep
62.20.fq Plasticity and superplasticity

Effect of Mg codoping on Eu3+ luminescence in GaN grown by ammonia molecular beam epitaxy

Yasufumi Takagi, Takanobu Suwa, Hiroto Sekiguchi, Hiroshi Okada, and Akihiro Wakahara

Appl. Phys. Lett. 99, 171905 (2011); http://dx.doi.org/10.1063/1.3656018 (3 pages) | Cited 5 times

Online Publication Date: 24 October 2011

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The effect of Mg codoping on the Eu3+ luminescence in GaN was investigated by photoluminescence measurements. Two notable emission peaks associated with the 5D0→7F2 transition in the Eu3+ ions were governed by Mg codopants, which corresponded to the change of the dominant peak wavelength from 622.3 to 620.3 nm with an increase in Mg concentration. An optimal amount of Mg also led to enhancement of approximately 20 times of the Eu3+ luminescence. These results indicated that the Mg codopants selectively activated the optical site of 620.3 nm emission due to the elimination of nonradiative deexcitation paths from the 5D0 state.
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81.05.Ea III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors

Mechanical constraints enhance electrical energy densities of soft dielectrics

Lin Zhang, Qiming Wang, and Xuanhe Zhao

Appl. Phys. Lett. 99, 171906 (2011); http://dx.doi.org/10.1063/1.3655910 (3 pages) | Cited 1 time

Online Publication Date: 25 October 2011

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Dielectrics are essential components in modern electronics and electric systems. When a sufficiently high voltage is applied on a layer of a dielectric, the dielectric will breakdown electrically. The breakdown limits the electrical energy density of the dielectric. We show that constraining the deformation of soft dielectrics can greatly enhance their breakdown electric fields and thus increase their electrical energy densities. The mechanical constraints suppress electromechanical instabilities, a major cause for electrical breakdowns in soft dielectrics.
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81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
82.70.Gg Gels and sols
77.22.Jp Dielectric breakdown and space-charge effects
77.65.-j Piezoelectricity and electromechanical effects

On the anelasticity and strain induced structural changes in a Zr-based bulk metallic glass

A. Caron, A. Kawashima, H.-J. Fecht, D. V. Louzguine-Luzguin, and A. Inoue

Appl. Phys. Lett. 99, 171907 (2011); http://dx.doi.org/10.1063/1.3655999 (3 pages) | Cited 3 times

Online Publication Date: 25 October 2011

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We report on the anelastic behavior of a cyclically loaded Zr62.5Fe5Cu22.5Al10 bulk metallic glass well below its yield strength. The dynamic mechanical behavior of the glass is discussed on the basis of its structural and thermodynamic properties before and after tests. We show how the kinetically frozen anelastic deformation accumulates at room temperature and causes a structural relaxation and densification of the glass and further leads to its partial crystallization.
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81.05.Kf Glasses (including metallic glasses)
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
81.40.Jj Elasticity and anelasticity, stress-strain relations
81.40.Lm Deformation, plasticity, and creep
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
81.05.Bx Metals, semimetals, and alloys

Effect of graded-temperature arsenic prelayer on quality of GaAs on Ge/Si substrates by metalorganic vapor phase epitaxy

H. W. Yu, E. Y. Chang, Y. Yamamoto, B. Tillack, W. C. Wang, C. I. Kuo, Y. Y. Wong, and H. Q. Nguyen

Appl. Phys. Lett. 99, 171908 (2011); http://dx.doi.org/10.1063/1.3656737 (3 pages) | Cited 1 time

Online Publication Date: 26 October 2011

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The growth of GaAs epitaxy on Ge/Si substrates with an arsenic prelayer grown with graded temperature ramped from 300 to 420 °C is investigated. It is demonstrated that the graded-temperature arsenic prelayer grown on a Ge/Si substrate annealed at 650 °C not only improves the surface morphology (roughness: 1.1 nm) but also reduces the anti-phase domains’ (APDs) density in GaAs epitaxy (dislocation density: ∼2 × 107 cm−2). Moreover, the unwanted interdiffusion between Ge and GaAs epitaxy is suppressed by using the graded-temperature arsenic prelayer due to the low energy of the Ge-As bond and the use of a low V/III ratio of 20.
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81.05.Ea III-V semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.40.Gh Other heat and thermomechanical treatments
68.55.ag Semiconductors
68.35.bg Semiconductors
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