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7 Dec 2009

Volume 95, Issue 23, Articles (23xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 95, 161108 (2009); http://dx.doi.org/10.1063/1.3253713 (3 pages)

Nanfang Yu, Mikhail A. Kats, Christian Pflügl, Markus Geiser, Qi Jie Wang, Mikhail A. Belkin, Federico Capasso, Milan Fischer, Andreas Wittmann, Jérôme Faist, Tadataka Edamura, Shinichi Furuta, Masamichi Yamanishi, and Hirofumi Kan

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Low voltage blue-phase liquid crystal displays

Linghui Rao, Zhibing Ge, Shin-Tson Wu, and Seung Hee Lee

Appl. Phys. Lett. 95, 231101 (2009); http://dx.doi.org/10.1063/1.3271771 (3 pages) | Cited 60 times

Online Publication Date: 7 December 2009

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A protrusion electrode structure is proposed to dramatically lower the operation voltage of the emerging blue-phase liquid crystal displays (BP-LCDs). Simulation results indicate that the generated horizontal electric field is not only strong but also penetrates deeply into the bulk LC layer. As a result, a low voltage ( ∼ 10 Vrms) and reasonably high transmittance ( ∼ 70%) BP-LCD can be achieved. This approach enables the BP-LCDs to be addressed by amorphous silicon thin-film transistors (TFTs). Widespread application of TFT BP-LCDs is foreseeable.
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85.60.Pg Display systems
42.79.Kr Display devices, liquid-crystal devices

Photonic crystal based back reflectors for light management and enhanced absorption in amorphous silicon solar cells

Benjamin Curtin, Rana Biswas, and Vikram Dalal

Appl. Phys. Lett. 95, 231102 (2009); http://dx.doi.org/10.1063/1.3269593 (3 pages) | Cited 14 times

Online Publication Date: 7 December 2009

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Photonic crystal back-reflectors offer enhanced optical absorption in thin-film solar cells, without undesirable losses. We fabricated metallic photonic crystal back-reflectors using photolithography and reactive-ion etching and deposited a-Si:H solar cells. The photonic crystal has triangular lattice symmetry, a pitch of 760 nm, and was designed with rigorous simulations. Scanning electron microscopy demonstrates excellent long range periodicity and conformal a-Si:H growth. The average light absorption increases by 7%, relative to a flat reference device, with an enhancement factor approaching 6 at near-infrared wavelengths. The photonic crystal back reflector strongly diffracts light and increases optical path lengths of solar photons.
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88.40.J- Types of solar cells
42.70.Qs Photonic bandgap materials
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
81.16.Nd Micro- and nanolithography

Corrugated-sidewall interband cascade lasers with single-mode midwave-infrared emission at room temperature

C. S. Kim, M. Kim, W. W. Bewley, J. R. Lindle, C. L. Canedy, J. Abell, I. Vurgaftman, and J. R. Meyer

Appl. Phys. Lett. 95, 231103 (2009); http://dx.doi.org/10.1063/1.3272676 (3 pages) | Cited 15 times

Online Publication Date: 8 December 2009

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We report interband cascade lasers operating in a single spectral mode (λ ≈ 3.6 μm) at −5–30 °C. A corrugated pattern etched into both sidewalls of the 6- and 9-μm-wide ridges serves to suppress higher-order lateral modes by increasing their loss, and also provides a fourth-order distributed-feedback grating for longitudinal mode selection. Despite the grating’s weak coupling strength, the 9 μm ridge produced up to 12 mW per facet of single-mode cw output power at 25 °C, with a side-mode suppression ratio of >30 dB.
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42.55.Px Semiconductor lasers; laser diodes
42.79.Dj Gratings
42.60.By Design of specific laser systems

Nonradiative recombination in 1.56 μm GaInNAsSb/GaNAs quantum-well lasers

J. W. Ferguson, P. M. Smowton, P. Blood, H. Bae, T. Sarmiento, and J. S. Harris, Jr.

Appl. Phys. Lett. 95, 231104 (2009); http://dx.doi.org/10.1063/1.3271182 (3 pages) | Cited 1 time

Online Publication Date: 8 December 2009

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We have shown experimentally that in GaInNAsSb/GaAs quantum-well lasers there are significant nonradiative contributions to threshold current from the barriers and the well. By matching a simulation to the experiment we find that Auger recombination in the barriers is very weak, due to the low carrier density. Shockley–Read–Hall recombination is the dominant source of nonradiative current, with the barriers making the major contribution, possibly due to their higher defect density than the wells. This suggests that significant improvements could be made by optimizing growth conditions and layer design, with particular attention to the barrier.
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42.55.Px Semiconductor lasers; laser diodes
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
42.60.By Design of specific laser systems

Terahertz Kerr effect

Matthias C. Hoffmann, Nathaniel C. Brandt, Harold Y. Hwang, Ka-Lo Yeh, and Keith A. Nelson

Appl. Phys. Lett. 95, 231105 (2009); http://dx.doi.org/10.1063/1.3271520 (3 pages) | Cited 11 times

Online Publication Date: 8 December 2009

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We have observed optical birefringence in liquids induced by single-cycle terahertz pulses with field strengths exceeding 100 kV/cm. The induced change in polarization is proportional to the square of the terahertz electric field. The time-dependent terahertz Kerr signal is composed of a fast electronic response that follows the individual cycles of the electric field and a slow exponential response associated with molecular orientation.
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78.20.Jq Electro-optical effects
78.20.Fm Birefringence
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Electron bunch length monitors using spatially encoded electro-optical technique in an orthogonal configuration

X. Yang, T. Tsang, T. Rao, J. B. Murphy, Y. Shen, and X. J. Wang

Appl. Phys. Lett. 95, 231106 (2009); http://dx.doi.org/10.1063/1.3266919 (3 pages) | Cited 1 time

Online Publication Date: 8 December 2009

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A single-shot, nondestructive, electro-optical, electron bunch length monitor is experimentally verified by encoding the Coulomb field of the bunch profile on the spatial intensity distribution of an unchirped femtosecond laser pulse in an orthogonal geometry, hence a temporal-to-spatial transformation. This electron bunch measurement scheme can simultaneously measure large timing jitter (approximately in picoseconds) with a wide measurement time span covering picosecond to subpicosecond ranges.
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29.27.Eg Beam handling; beam transport
29.20.-c Accelerators
29.25.-t Particle sources and targets

Relaxation characteristics of quantum-dash-based semiconductor lasers

Thomas Erneux, Evgeny A. Viktorov, Paul Mandel, Sheherazade Azouigui, and Abderrahim Ramdane

Appl. Phys. Lett. 95, 231107 (2009); http://dx.doi.org/10.1063/1.3271999 (3 pages)

Online Publication Date: 8 December 2009

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We analyze the relaxation dynamics of quantum dot/dash lasers in terms of the energy exchange between the ground state and the wetting layer. We consider the case where both capture and escape times are of the same order of magnitude and determine the relaxation oscillation frequency and its damping rate. We show that the escape process may significantly affect the modulation characteristics and the tolerance to optical feedback.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.60.Fc Modulation, tuning, and mode locking

Optical phase recovery in the dispersive Fourier transform

D. R. Solli, S. Gupta, and B. Jalali

Appl. Phys. Lett. 95, 231108 (2009); http://dx.doi.org/10.1063/1.3271678 (3 pages) | Cited 1 time

Online Publication Date: 9 December 2009

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The dispersive Fourier transform permits real-time acquisition of optical spectra with analog-to-digital converters. The method utilizies the property that a signal’s temporal envelope matches its spectral profile if sufficiently dispersed. Unfortunately, the dispersion demand can be substantial and signal losses in highly dispersive elements represent a significant challenge, especially outside the telecommunications band. We address this problem by experimentally demonstrating that a time-domain equivalent of the Gerchberg–Saxton algorithm removes the fundamental dispersion requirement in the dispersive Fourier transform. The algorithm recovers the phase from time-domain intensity measurements.
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42.30.Rx Phase retrieval
42.79.Sz Optical communication systems, multiplexers, and demultiplexers
02.30.Uu Integral transforms

Excitation wavelength independent sensitized Er3+ concentration in as-deposited and low temperature annealed Si-rich SiO2 films

Oleksandr Savchyn, Ravi M. Todi, Kevin R. Coffey, Luis K. Ono, Beatriz Roldan Cuenya, and Pieter G. Kik

Appl. Phys. Lett. 95, 231109 (2009); http://dx.doi.org/10.1063/1.3272271 (3 pages) | Cited 6 times

Online Publication Date: 9 December 2009

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Erbium sensitization is observed in as-deposited Er3+ doped Si-rich SiO2, ruling out the involvement of Si nanocrystals in the Er3+ excitation in these samples. The Er3+ excitation cross section in this material is similar within a factor 3 to that of samples annealed at 600 °C under 355 and 532 nm excitation. The density of sensitized Er3+ ions is shown to be excitation wavelength independent, while the shape of the Er3+ excitation spectra is governed by a wavelength dependent Er3+ excitation cross section. These findings enable the use of a broad range of wavelengths for the efficient excitation of this gain medium.
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78.66.Nk Insulators
78.55.Hx Other solid inorganic materials
61.72.sd Impurity concentration
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization

Near infrared long-persistent phosphorescence in SrAl2O4:Eu2+,Dy3+,Er3+ phosphors based on persistent energy transfer

Naiyin Yu, Feng Liu, Xufan Li, and Zhengwei Pan

Appl. Phys. Lett. 95, 231110 (2009); http://dx.doi.org/10.1063/1.3272672 (3 pages) | Cited 10 times

Online Publication Date: 10 December 2009

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Eu2+, Dy3+, and Er3+ ions codoped SrAl2O4 phosphors with near infrared (NIR) (at 1530 nm) long-persistent phosphorescence were synthesized by a combustion method. The NIR phosphorescence emission was realized through a persistent energy transfer process from Eu2+ ions to Er3+ ions. Optimal Er3+ concentration for the maximum energy transfer efficiency was determined and NIR phosphorescence persisting for more than 10 min was achieved. A model of charge trapping and energy transfer process among Eu, Dy, and Er ions in SrAl2O4 host was proposed.
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78.60.-b Other luminescence and radiative recombination
61.72.sd Impurity concentration

Nonequilibrium many body theory for quantum transport in terahertz quantum cascade lasers

T. Schmielau and M. F. Pereira, Jr.

Appl. Phys. Lett. 95, 231111 (2009); http://dx.doi.org/10.1063/1.3272675 (3 pages) | Cited 13 times

Online Publication Date: 10 December 2009

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This paper presents a predictive Keldysh nonequilibrium many body Green’s functions theory for quantum transport including high order electron-electron, electron-phonon, electron-impurity, and interface roughness scattering processes. Our approach is fully frequency and momentum dependent including nondiagonal dephasing terms in both frequency and k-space. A detailed balance between coherent and scattering processes leads to local current conservation even if a small number of states is considered. Good agreement with experiments is obtained for a terahertz quantum cascade laser.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Terahertz pulsed spectroscopic imaging using optimized binary masks

Y. C. Shen, L. Gan, M. Stringer, A. Burnett, K. Tych, H. Shen, J. E. Cunningham, E. P. J. Parrott, J. A. Zeitler, L. F. Gladden, E. H. Linfield, and A. G. Davies

Appl. Phys. Lett. 95, 231112 (2009); http://dx.doi.org/10.1063/1.3271030 (3 pages) | Cited 4 times

Online Publication Date: 10 December 2009

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We report the development of a terahertz pulsed spectroscopic imaging system based on the concept of compressive sensing. A single-point terahertz detector, together with a set of 40 optimized two-dimensional binary masks, was used to measure the terahertz waveforms transmitted through a sample. Terahertz time- and frequency-domain images of the sample comprising 20×20 pixels were subsequently reconstructed. We demonstrate that both the spatial distribution and the spectral characteristics of a sample can be obtained by this means. Compared with conventional terahertz pulsed imaging, no raster scanning of the object is required, and ten times fewer terahertz spectra need be taken. It is therefore ideal for real-time imaging applications.
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07.57.Pt Submillimeter wave, microwave and radiowave spectrometers; magnetic resonance spectrometers, auxiliary equipment, and techniques
07.05.Pj Image processing
42.30.Wb Image reconstruction; tomography
78.70.Gq Microwave and radio-frequency interactions
84.40.-x Radiowave and microwave (including millimeter wave) technology

Room temperature photocurrent response of PbS/InP heterojunction

Zhijun Liu, Jin Ho Kim, Gustavo E. Fernandes, and Jimmy Xu

Appl. Phys. Lett. 95, 231113 (2009); http://dx.doi.org/10.1063/1.3271526 (3 pages) | Cited 1 time

Online Publication Date: 11 December 2009

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We report on the observation of photocurrent response of a PbS/InP heterojunction. The PbS/InP heterostructure is synthesized via aqueous solution-based heteroepitaxial growth, and is fabricated into a photodetector. At zero bias, two photoresponse bands between 0.75 and 3.1 μm are measured at room temperature, which correspond to interband photocarrier generations in PbS and InP, respectively. An anomalous polarity of the photocurrent is observed and its possible origins are analyzed.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
81.05.Ea III-V semiconductors
72.40.+w Photoconduction and photovoltaic effects
85.60.Gz Photodetectors (including infrared and CCD detectors)
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Random laser action in dielectric-metal-dielectric surface plasmon waveguides

Ashwani Kumar, S. F. Yu, and X. F. Li

Appl. Phys. Lett. 95, 231114 (2009); http://dx.doi.org/10.1063/1.3274042 (3 pages) | Cited 4 times

Online Publication Date: 11 December 2009

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A dielectric-metal-dielectric (DMD) surface plasmon (SP) waveguide, in which the top and bottom dielectric layers are incorporated with scatters and optical gain, respectively, was realized to support random lasing action. For the DMD waveguide under 532 nm optical excitation, sharp peaks at around 590 nm were observed from the edge of the top dielectric layer. Furthermore, the number of sharp peaks increases with the pump intensity. The dependence of lasing threshold on the excitation area also agrees with the random laser theory. Hence, it is verified that the SP waves, which supported inside the DMD waveguide, exhibit random lasing action.
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42.55.Zz Random lasers
42.55.Ah General laser theory
42.82.Et Waveguides, couplers, and arrays
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.79.Gn Optical waveguides and couplers
42.55.Rz Doped-insulator lasers and other solid state lasers
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Cavity pressure acceleration: An efficient laser-based method of production of high-velocity macroparticles

S. Borodziuk, A. Kasperczuk, T. Pisarczyk, J. Badziak, T. Chodukowski, J. Ullschmied, E. Krousky, K. Masek, M. Pfeifer, K. Rohlena, J. Skala, and P. Pisarczyk

Appl. Phys. Lett. 95, 231501 (2009); http://dx.doi.org/10.1063/1.3271693 (3 pages) | Cited 2 times

Online Publication Date: 8 December 2009

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We propose an efficient method of accelerating macroparticles to high velocities, which employs pressure of the plasma produced by a focused pulsed high-power laser beam inside a cavity-type target. That is why we have called it the cavity pressure acceleration (CPA) scheme. The method was tested during our experiments at the Prague Asterix Laser System, the results of which are reported here. They show that CPA makes it possible to accelerate both light and heavy macroparticles in arbitrary direction, with the acceleration efficiency far exceeding that achieved upto now by using the classic ablative acceleration scheme. High velocities of the macroparticles (foil fragments) produced and possibility of accelerating even rather heavy macroparticles are promising from the point of view of impact fusion studies, of the impact fast ignition, in particular.
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52.38.Kd Laser-plasma acceleration of electrons and ions
28.52.Cx Fueling, heating and ignition
52.57.Kk Fast ignition of compressed fusion fuels
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
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Defect kinetics and dopant activation in submicrosecond laser thermal processes

K. Huet, G. Fisicaro, J. Venturini, H. Besaucèle, and A. La Magna

Appl. Phys. Lett. 95, 231901 (2009); http://dx.doi.org/10.1063/1.3268472 (3 pages) | Cited 4 times

Online Publication Date: 7 December 2009

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Defect evolution in ion implanted c-Si at the submicrosecond time scales during a laser thermal annealing process is investigated by means of kinetic simulations. Nonmelting, melting, and partial melting regimes are simulated. Our modeling considers irradiation, heat diffusion, and phase transition together with defect diffusion, annihilation, and clustering. The reduction in the implantation damage and its reorganization in defect aggregates are studied as a function of the process conditions. The approach is applied to double implanted Si and compared to experimental data, indicating a relationship between damage reduction and dopant activation.
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61.72.uf Ge and Si
61.80.Jh Ion radiation effects
61.82.Fk Semiconductors
61.72.Cc Kinetics of defect formation and annealing
66.30.Lw Diffusion of other defects
66.30.Xj Thermal diffusivity

Wetting layer evolution upon quantum dots self-assembly

Y. Y. Cao, X. L. Li, and G. W. Yang

Appl. Phys. Lett. 95, 231902 (2009); http://dx.doi.org/10.1063/1.3271692 (3 pages) | Cited 1 time

Online Publication Date: 7 December 2009

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A quantitatively thermodynamic model has been established to address the problem of the wetting layer evolution upon the quantum dots (QDs) self-assembly based on the embedded islands. It was found that the mismatch induced by the embedded islands breaks the balance of the strain energies between the islands and the wetting layer, and then results in the island’s volume increasing and the wetting layer’s thickness decreasing for creating a thermodynamic equilibrium upon the QD self-assembly. The stable thickness of the wetting layer can be determined by balancing the strain energies between the islands and the wetting layer. The theoretical results are in agreement with the experiments.
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68.08.Bc Wetting
81.07.Ta Quantum dots
68.35.B- Structure of clean surfaces (and surface reconstruction)

High-throughput fabrication of nanoantennae over large areas for biosensing and nanospectroscopy

Arda Kiristopuryan, Yasin Ekinci, Reto Giannini, Pratap K. Sahoo, Ganna Gorodyska, and Jörg F. Löffler

Appl. Phys. Lett. 95, 231903 (2009); http://dx.doi.org/10.1063/1.3267078 (3 pages) | Cited 1 time

Online Publication Date: 7 December 2009

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We report on a simple and high-throughput method for the fabrication of gold and silver nanoparticle dimers with extremely small gaps and extending over large areas, using colloidal lithography and shadow thermal-evaporation techniques. The plasmon resonances of the individual dimers with various structural parameters were studied, as well as their coupling phenomena in the nearly touching regime. The method presented enables fabrication of efficient and low-cost plasmonics structures for applications such as surface-enhanced Raman scattering, plasmon-enhanced fluorescence, and biosensing.
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87.80.Dj Spectroscopies
87.15.B- Structure of biomolecules
87.15.M- Spectra of biomolecules
81.16.Nd Micro- and nanolithography

Improving microstructural quality of semipolar (11math2) GaN on m-plane sapphire by a two-step growth process

Qian Sun, Benjamin Leung, Christopher D. Yerino, Yu Zhang, and Jung Han

Appl. Phys. Lett. 95, 231904 (2009); http://dx.doi.org/10.1063/1.3269605 (3 pages) | Cited 12 times

Online Publication Date: 7 December 2009

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This letter reports a two-step growth process for improving microstructural quality of semipolar (11math2) GaN on nitridized m-plane sapphire. The two-step growth of (11math2) GaN, islanding growth under high pressure followed by islands coalescence under low pressure, went through a roughening-recovery process, which was found very effective in reducing the density of stacking faults and dislocations in (11math2) GaN. The x-ray rocking curves of both on-axis and off-axis planes were narrowed down by more than 50%. The improvement of GaN quality was confirmed by a boost in blue and green optical output of semipolar (11math2) InGaN/GaN quantum wells.
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81.05.Ea III-V semiconductors
61.72.Nn Stacking faults and other planar or extended defects
68.65.Fg Quantum wells
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.35.Ct Interface structure and roughness

Size-effects on the optical properties of zirconium oxide thin films

C. V. Ramana, R. S. Vemuri, I. Fernandez, and A. L. Campbell

Appl. Phys. Lett. 95, 231905 (2009); http://dx.doi.org/10.1063/1.3271697 (3 pages) | Cited 8 times

Online Publication Date: 8 December 2009

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Zirconium oxide (ZrO2) thin films with an average crystallite-size (L) ranging from 5 to 25 nm were grown by sputter deposition onto optical grade quartz substrates. The optical properties of grown ZrO2 films were evaluated using optical transmission and reflectance spectroscopic measurements. The size-effects were significant on the optical characteristics of ZrO2 films. The bandgap energy (Eg) was found to increase from 5.78 to 6.07 eV with decreasing L values from 20 to 7 nm. A direct, linear inverse L-Eg relationship found for ZrO2 films suggest that tuning optical properties for desired applications can be achieved by controlling the size.
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78.66.Db Elemental semiconductors and insulators
78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures
81.16.-c Methods of micro- and nanofabrication and processing
81.15.Cd Deposition by sputtering
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
73.22.-f Electronic structure of nanoscale materials and related systems

First-principles studies of the effect of oxygen vacancies on the electronic structure and linear optical response of multiferroic BiFeO3

Sheng Ju and Tian-Yi Cai

Appl. Phys. Lett. 95, 231906 (2009); http://dx.doi.org/10.1063/1.3272107 (3 pages) | Cited 5 times

Online Publication Date: 8 December 2009

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Oxygen vacancies (OVs) have a significant influence on the carrier mobility and optical conductivity in transition metal oxides. In this letter, using density-functional theory, we investigate the effect of OVs on the optical response in multiferroic BiFeO3. Within the generalized gradient approximation plus the on-site Coulomb repulsion, we show that the absorption edge shifts to lower energy with the increase of OV concentration, while the location of the main absorption peak does not change. The agreement between theoretical calculations and experimental measurements of the dielectric function is greatly improved when OVs are considered.
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77.22.Ch Permittivity (dielectric function)
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
61.72.jd Vacancies
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
71.20.Ps Other inorganic compounds

Low temperature growth of epitaxial graphene on SiC induced by carbon evaporation

A. Al-Temimy, C. Riedl, and U. Starke

Appl. Phys. Lett. 95, 231907 (2009); http://dx.doi.org/10.1063/1.3265916 (3 pages) | Cited 12 times

Online Publication Date: 8 December 2009

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Low temperature growth of epitaxial graphene on SiC is facilitated by carbon evaporation under ultrahigh vacuum (UHV) conditions. By counteracting the need for complete Si depletion as in the conventional sublimation method, monolayer graphene evolves at significantly lower temperatures by depositing additional carbon, so that a degradation of the initial SiC surface quality can be avoided. The original, well ordered terrace structure of SiC(0001) is preserved, the graphene layers grow on top and show the typical linear π-band dispersion. On SiC(000math) the graphene lattice is rotated by 30° in comparison to the conventional UHV preparation method.
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68.55.A- Nucleation and growth
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
78.40.Ri Fullerenes and related materials
61.48.Gh Structure of graphene

Jerky elasticity: Avalanches and the martensitic transition in Cu74.08Al23.13Be2.79 shape-memory alloy

Ekhard K. H. Salje, Johannes Koppensteiner, Marius Reinecker, Wilfried Schranz, and Antoni Planes

Appl. Phys. Lett. 95, 231908 (2009); http://dx.doi.org/10.1063/1.3269578 (3 pages) | Cited 11 times

Online Publication Date: 9 December 2009

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Jerky elasticity was observed by dynamical mechanical analyzer measurements in a single crystal of the shape memory alloy Cu74.08Al23.13Be2.79. Jerks appear as spikes in the dissipation of the elastic response function and relate to the formation of avalanches during the transformation between the austenite and the martensite phase. The statistics of the avalanches follows the predictions of avalanche criticality P(E)∝E−ε where P(E) is the probability of finding an avalanche with the energy E. This result reproduces, within experimental uncertainties, previous findings by acoustic emission techniques.
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81.40.Jj Elasticity and anelasticity, stress-strain relations
64.70.kd Metals and alloys
62.20.fg Shape-memory effect; yield stress; superelasticity
81.40.Lm Deformation, plasticity, and creep
81.30.Kf Martensitic transformations

The origin and evolution of V-defects in InxAl1−xN epilayers grown by metalorganic chemical vapor deposition

Z. L. Miao, T. J. Yu, F. J. Xu, J. Song, C. C. Huang, X. Q. Wang, Z. J. Yang, G. Y. Zhang, X. P. Zhang, D. P. Yu, and B. Shen

Appl. Phys. Lett. 95, 231909 (2009); http://dx.doi.org/10.1063/1.3272017 (3 pages) | Cited 11 times

Online Publication Date: 9 December 2009

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Near-lattice-matched and highly compressive-strained InxAl1−xN epilayers were grown on GaN templates by metalorganic chemical vapor deposition. The V-defects associated with screw-component threading dislocations (TDs) were found in all the InxAl1−xN layers. Their origin and evolution were investigated through near-lattice-matched In0.173Al0.827N layers with different thicknesses. Furthermore, small V-defects not associated with TDs were also found in InxAl1−xN layers with high In composition (x = 0.231). Stacking mismatch boundaries induced by lattice relaxation in InxAl1−xN epilayers under large strain is believed to be another mechanism forming V-defects.
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61.72.jn Color centers
68.55.ag Semiconductors
61.72.Lk Linear defects: dislocations, disclinations
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.72.Nn Stacking faults and other planar or extended defects

Control of current-jump induced by voltage, temperature, light in p-type GaAs: Programmable critical temperature sensor

Sungyoul Choi, Bong-Jun Kim, Yong Wook Lee, Yong Sik Lim, Jeongyong Choi, and Hyun-Tak Kim

Appl. Phys. Lett. 95, 231910 (2009); http://dx.doi.org/10.1063/1.3272683 (3 pages)

Online Publication Date: 10 December 2009

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For two-terminal devices fabricated by Be (or Mn)-doped p-type epitaxial GaAs thin films, when the Mott metal-insulator transition (MIT) as current jump occurs, we observe that the energy gap of GaAs is not shifted, its peak intensity decreases in an applied voltage, and that the MIT temperature is between 410 and 440 K, and that the current jump is controlled by temperature, voltage and light intensity. The control of the jump voltage, a characteristic of the Mott MIT, reveals that these devices can be applied for programmable critical temperature sensors or optical sensors with high sensitivity.
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85.30.-z Semiconductor devices
07.20.Dt Thermometers
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
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