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12 Dec 2011

Volume 99, Issue 24, Articles (24xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 99, 241103 (2011); http://dx.doi.org/10.1063/1.3659305 (3 pages)

Yujie Chen, Benoit Guilhabert, Johannes Herrnsdorf, Yanfeng Zhang, Allan R. Mackintosh, Richard A. Pethrick, Erdan Gu, Nicolas Laurand, and Martin D. Dawson
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Nonlinear optical properties of lanthanum-modified lead zirconate titanate investigated by the femtosecond Z-scan technique

Tsong-Ru Tsai and Chih-Hsiung Yu

Appl. Phys. Lett. 99, 241101 (2011); http://dx.doi.org/10.1063/1.3668099 (3 pages)

Online Publication Date: 12 December 2011

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We used a closed-aperture Z-scan technique to study the nonlinear optical refractive index of lanthanum-modified lead zirconate titanate (PLZT) (9/65/35) ceramics. Our laser light source was a mode-locked titanium-sapphire laser, the output pulse width was approximately 100 femtoseconds at a wavelength of 790 nm, and the repetition rate was 10 kHz. We found that PLZT had a large, positive nonlinear optical refractive index, n2 = +(3.1 ± 0.6) × 10−8 esu, and its third-order susceptibility was calculated to be χ(3) = (9 ± 1.8) × 10−9 esu. When an electric field (E) was applied to the PLZT, n2 increased along in direct proportion to E2. We speculate that the increase in n2 was caused by the more ordered structural arrangement of the PLZT imposed by the applied electric field. The results show that PLZT has potential applications in fast, electric-field-controlled nonlinear optical elements.
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78.47.J- Ultrafast spectroscopy (<1 psec)
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Experimental observation of optical vortex in self-frequency-doubling generation

Haohai Yu, Huaijin Zhang, Zhengping Wang, Jiyang Wang, Zhongben Pan, Shidong Zhuang, and Dingyuan Tang

Appl. Phys. Lett. 99, 241102 (2011); http://dx.doi.org/10.1063/1.3670351 (3 pages) | Cited 3 times

Online Publication Date: 12 December 2011

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We present an experimental observation of optical vortices in phase-matching self-frequency doubling (SFD) with a simple laser-diode (LD) end-pumped SFD microchip laser. From experimental and theoretical analysis, it is found that the photons contain a linear combination of the fundamental orbital angular momentum states, and that frequency doubling photons in SFD would recombine with but do not disturb each other. All the results show that the SFD should be an efficient tool for the study of quantum phenomena and has promising applications based on its structural simplicity and compactness.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.55.Sa Microcavity and microdisk lasers
42.55.Rz Doped-insulator lasers and other solid state lasers
FREE

Flexible distributed-feedback colloidal quantum dot laser

Yujie Chen, Benoit Guilhabert, Johannes Herrnsdorf, Yanfeng Zhang, Allan R. Mackintosh, Richard A. Pethrick, Erdan Gu, Nicolas Laurand, and Martin D. Dawson

Appl. Phys. Lett. 99, 241103 (2011); http://dx.doi.org/10.1063/1.3659305 (3 pages)

Online Publication Date: 12 December 2011

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By fabricating a submicron-scale grating structure on a bendable polymer substrate, we demonstrate a flexible distributed-feedback colloidal quantum dot laser. This laser uses cadmium selenide/zinc sulfide core-shell nanostructures, operating in transverse electric polarized multiple-modes, and has a typical threshold pump fluence of ∼4 mJ/cm2.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.79.Dj Gratings
42.82.Cr Fabrication techniques; lithography, pattern transfer

Total routing and absorption of photons in dual color plasmonic antennas

Charlie Koechlin, Patrick Bouchon, Fabrice Pardo, Julien Jaeck, Xavier Lafosse, Jean-Luc Pelouard, and Riad Haïdar

Appl. Phys. Lett. 99, 241104 (2011); http://dx.doi.org/10.1063/1.3670051 (3 pages) | Cited 9 times

Online Publication Date: 13 December 2011

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We present both theoretical and experimental evidence that two metal-insulator-metal plasmonic resonators can be combined into a wideband and total photon absorber in the mid-infrared. We show that, although closely arranged in a subwavelength period, these resonators behave as angularly independent antennas at their own resonant wavelength. The structures thus allow for an efficient dual color photon routing and collection.
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42.79.-e Optical elements, devices, and systems
42.70.-a Optical materials
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.66.-w Optical properties of specific thin films
78.30.-j Infrared and Raman spectra

Germanium fin light-emitting diode

S. Saito, K. Oda, T. Takahama, K. Tani, and T. Mine

Appl. Phys. Lett. 99, 241105 (2011); http://dx.doi.org/10.1063/1.3670053 (3 pages) | Cited 2 times

Online Publication Date: 13 December 2011

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We propose a germanium fin light-emitting diode for a monolithic light source on a Si photonics chip. The germanium fins were fabricated by the oxidation condensation of silicon-germanium sidewalls epitaxially grown on silicon fins. We found that a tensile stress is applied to the pure germanium fins by the difference of the thermal expansion coefficient with that of the surrounding oxide. The electroluminescence spectra were consistent with those expected from direct recombination in germanium with a tensile stress. The strong immunity of germanium fins against high current densities would be favourable to achieve population inversions by electrical pumping.
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85.60.Jb Light-emitting devices

Robust thermal performance of Sr2Si5N8:Eu2+: An efficient red emitting phosphor for light emitting diode based white lighting

Stuart E. Brinkley, Nathan Pfaff, Kristin A. Denault, Zhijun Zhang, H. T. (Bert) Hintzen, Ram Seshadri, Shuji Nakamura, and Steven P. DenBaars

Appl. Phys. Lett. 99, 241106 (2011); http://dx.doi.org/10.1063/1.3666785 (3 pages) | Cited 19 times

Online Publication Date: 13 December 2011

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An important component to the advent of solid state lighting technology is the development of inorganic crystalline phosphors for efficient conversion of photons from blue light emitting diodes (LEDs) to other visible wavelengths for greater color rendering and “warmer” white lighting. We present the results of a recently developed rare earth doped nitride-based red emitting phosphor, Sr2Si5N8:Eu2+, combined with GaN-based blue emitting LEDs and YAG:Ce phosphor for improved white lighting applications. A unique remote phosphor packaging approach was used in all testing to isolate LED performance from phosphor performance. Luminous efficacies were achieved at 94 lm/W with an improved color rendering index (CRI) of 72, mixing red phosphor with YAG:Ce. The Sr2Si5N8:Eu2+ red emitting phosphor was found to have a low temperature sensitivity (only 28% power reduction at 150 °C) and greater luminous performance at low concentrations in the encapsulant by weight relative to other typical red emitting phosphors.
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78.55.Hx Other solid inorganic materials
85.60.Jb Light-emitting devices

Resonant enhancement of magneto-optical polarization conversion in microdisk resonators

Lev Deych, Carlos Meriles, and Vinod Menon

Appl. Phys. Lett. 99, 241107 (2011); http://dx.doi.org/10.1063/1.3670354 (4 pages)

Online Publication Date: 13 December 2011

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We theoretically investigate the effect of a periodically modulated magnetic field on the polarization properties of whispering-gallery-modes (WGM) in microdisk resonators. We show that by matching the modulation frequency to the frequency offset between WGMs with two mutually perpendicular polarizations one can achieve an enhancement of the magneto-optical polarization effect by a factor of M1/3QM(av), where M is the modal order of the WGM and QM(av) is the geometric average of the quality factors of the TE and TM polarized modes.
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85.70.Sq Magnetooptical devices
42.79.-e Optical elements, devices, and systems
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
07.10.Cm Micromechanical devices and systems

Broad gain in a bound-to-continuum quantum cascade laser with heterogeneous active region

Joshua R. Freeman, Anthony Brewer, Julien Madéo, Pierrick Cavalié, Sukhdeep S. Dhillon, Jérôme Tignon, Harvey E. Beere, and David A. Ritchie

Appl. Phys. Lett. 99, 241108 (2011); http://dx.doi.org/10.1063/1.3670050 (3 pages) | Cited 3 times

Online Publication Date: 14 December 2011

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We demonstrate the operation of heterogeneous terahertz quantum cascade lasers with broadened gain by optimising the sub-stacks to align at the same field. In single plasmon waveguides, we find two-colour operation for nearly the entire dynamic range of the lasers with similar performance to homogeneous lasers. Time domain spectroscopy measurements confirm that a flat gain spectrum is present and the sub-stacks align at the same time. When incorporated into metal-metal waveguides, we find that performance is consistent with the constituent sub-stacks and there is broadband operation over 380 GHz.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Cascaded Čerenkov third-harmonic generation in random quadratic media

Mousa Ayoub, Philip Roedig, Jörg Imbrock, and Cornelia Denz

Appl. Phys. Lett. 99, 241109 (2011); http://dx.doi.org/10.1063/1.3670322 (3 pages) | Cited 6 times

Online Publication Date: 14 December 2011

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We investigate experimentally and theoretically the conical emission of Čerenkov-type third-harmonic generation in strontium barium niobate of random 2D-χ(2) distribution. The azimuthal intensity distribution is explained by the polarization properties of the fundamental and Čerenkov second-harmonic waves, depending on the cascaded origin of the generation process. Moreover, we show the role of the individual domain shape in an additional modulation on the conical emission, controlled by the electrical switching of the spontaneous polarization of the ferroelectric medium.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
41.60.Bq Cherenkov radiation
77.80.-e Ferroelectricity and antiferroelectricity
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials

Thermo-optic plasmo-photonic mode interference switches based on dielectric loaded waveguides

K. Hassan, J.-C. Weeber, L. Markey, A. Dereux, A. Pitilakis, O. Tsilipakos, and E. E. Kriezis

Appl. Phys. Lett. 99, 241110 (2011); http://dx.doi.org/10.1063/1.3670500 (3 pages) | Cited 11 times

Online Publication Date: 14 December 2011

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We demonstrate an efficient thermo-optic dielectric loaded surface plasmon polariton waveguide (DLSPPW) 2 × 2 switch using a high thermo-optic coefficient polymer and a dual mode interference configuration. Unlike previous configurations relying on single-mode waveguide circuitry, the switch we consider is based on the interference between a plasmonic and a low-damping photonic mode of the DLSPPW, thus leading to the minimization of insertion losses of the device. Switching extinction ratios of 7 dB are measured for a compact 119 μm-long device. The overall device performances are in good agreement with numerical simulations performed using the beam propagation method.
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42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks
42.79.Gn Optical waveguides and couplers
42.70.Jk Polymers and organics
42.82.-m Integrated optics

Lasing characteristics of random cylindrical microcavity lasers

H. Zhu, S. F. Yu, and W. F. Zhang

Appl. Phys. Lett. 99, 241111 (2011); http://dx.doi.org/10.1063/1.3670501 (3 pages)

Online Publication Date: 14 December 2011

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Room-temperature lasing characteristics of random cylindrical microcavity lasers, which can be realized by coating a layer of random gain medium onto the surface of an optical fiber with various diameters, was studied experimentally. It is shown that closed-loop random modes excited inside the random gain medium are strongly confined along the radial direction so that the spacing of lasing modes is controlled by the diameter of cylindrical microcavity. In addition, lasing threshold of the random gain medium can be reduced by an order of magnitude under the influence of radial optical confinement.
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42.55.Sa Microcavity and microdisk lasers
05.40.-a Fluctuation phenomena, random processes, noise, and Brownian motion
42.55.Zz Random lasers

Single-mode quantum cascade lasers employing a candy-cane shaped monolithic coupled cavity

Peter Q. Liu, Kamil Sladek, Xiaojun Wang, Jen-Yu Fan, and Claire F. Gmachl

Appl. Phys. Lett. 99, 241112 (2011); http://dx.doi.org/10.1063/1.3664117 (3 pages) | Cited 2 times

Online Publication Date: 14 December 2011

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We demonstrate single-mode quantum cascade lasers emitting at ∼4.5 μm by employing a monolithic “candy-cane” shaped coupled-cavity consisting of a straight section connecting at one end to a spiral section. The fabrication process is identical to those for simple Fabry-Perot-type ridge lasers. Continuously tunable single-mode emission across ∼8 cm−1 with side mode suppression ratio up to ∼25 dB and a single-mode operating current range of more than 70% above the threshold current is achieved when the lasers are operated in pulsed-mode from 80 K to 155 K.
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42.55.Px Semiconductor lasers; laser diodes
42.82.Cr Fabrication techniques; lithography, pattern transfer

Stable dual-wavelength microlaser controlled by the output mirror tilt angle

Florent Pallas, Emilie Herault, Jie Zhou, Jean-Francois Roux, and Guy Vitrant

Appl. Phys. Lett. 99, 241113 (2011); http://dx.doi.org/10.1063/1.3669530 (3 pages) | Cited 3 times

Online Publication Date: 14 December 2011

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A continuous-wave dual-wavelength solid-state microlaser is presented and a technique for regulating the gain competition between the two wavelengths is proposed, based on the angular tilt of the laser cavity output mirror. Laser behavior is studied and balanced dual-wavelength emission is obtained with output power levels as high as 200 mW for 2 W pump power. Sum frequency mixing is demonstrated making the source promising for Terahertz generation in the 0.5-0.7 THz range through difference frequency generation.
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42.55.Rz Doped-insulator lasers and other solid state lasers
42.55.Sa Microcavity and microdisk lasers
42.65.Lm Parametric down conversion and production of entangled photons
42.79.Bh Lenses, prisms and mirrors
07.05.Dz Control systems

Faster recovery time of a hot-electron transition-edge sensor by use of normal metal heat-sinks

Brice Calkins, Adriana E. Lita, Anna E. Fox, and Sae Woo Nam

Appl. Phys. Lett. 99, 241114 (2011); http://dx.doi.org/10.1063/1.3659686 (3 pages)

Online Publication Date: 15 December 2011

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Transition-edge sensor microcalorimeters with recovery times near 1 μs have become highly desirable in quantum science applications as near-infrared single-photon detectors with photon-number resolving capability. Previously, the recovery times of these devices could be decreased only by changing device material or modifying the superconducting-to-normal transition. We demonstrate a method for improving this speed that uses a normal-metal heat-sink. This demonstration with tungsten devices realizes a factor of 4 decrease in recovery time without significantly affecting energy resolution. Our approach may enable the creation of high-efficiency transition-edge sensors with decay times short enough to operate with 80 MHz pulsed single-photon sources.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
07.20.Fw Calorimeters
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
85.25.Pb Superconducting infrared, submillimeter and millimeter wave detectors

Demonstration of 505 nm laser diodes using wavelength-stable semipolar (20math) InGaN/GaN quantum wells

Chia-Yen Huang, Matthew T. Hardy, Kenji Fujito, Daniel F. Feezell, James S. Speck, Steven P. DenBaars, and Shuji Nakamura

Appl. Phys. Lett. 99, 241115 (2011); http://dx.doi.org/10.1063/1.3666791 (3 pages) | Cited 5 times

Online Publication Date: 16 December 2011

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We demonstrate GaN-based semipolar (20math) laser diodes (LD) in the green region of the spectrum. 505 nm lasing was observed under pulsed operation, with a threshold current density (Jth) of 27.5 kA/cm2 and a threshold voltage (Vth) of 15.5 V. The blueshift of spontaneous emission was less than 5 nm when varying the injection current level from 125 A/cm2 to threshold. Simulations show that the reduced blueshift can be attributed to the minimal dependence of the energy potential profile in the active region on the applied bias and current injection level.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
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Laser guiding plasma channel formation criterion in highly relativistic regime

Y. J. Gu, Z. Zhu, Q. Kong, Y. Y. Li, X. F. Li, C. Y. Chen, and S. Kawata

Appl. Phys. Lett. 99, 241501 (2011); http://dx.doi.org/10.1063/1.3665181 (3 pages)

Online Publication Date: 14 December 2011

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Self-formed plasma channels induced by ultra-intense and ultra-short laser pulses have been investigated with 2.5-dimensional particle-in-cell simulations. A criterion of channel formation under the highly relativistic regime is proposed and tested by simulation results. Good matches between criterion predictions and simulations are found in most cases, but small deviations occur when the plasma density is very low or near critical. The possibility of generating a channel by a femtosecond pulsed laser is also discussed.
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52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.65.Rr Particle-in-cell method
52.25.-b Plasma properties
52.27.Ny Relativistic plasmas
52.38.Hb Self-focussing, channeling, and filamentation in plasmas
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Point defect engineering strategies to suppress A-center formation in silicon

A. Chroneos, C. A. Londos, E. N. Sgourou, and P. Pochet

Appl. Phys. Lett. 99, 241901 (2011); http://dx.doi.org/10.1063/1.3666226 (3 pages) | Cited 15 times

Online Publication Date: 12 December 2011

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We investigate the impact of tin doping on the formation of vacancy-oxygen pairs (VO or A-centers) and their conversion to VO2 clusters in electron-irradiated silicon. The experimental results are consistent with previous reports that Sn doping suppresses the formation of the A-center. We introduce a model to account for the observed differences under both Sn-poor and Sn-rich doping conditions. Using density functional theory calculations, we propose point defect engineering strategies to reduce the concentration of the deleterious A-centers in silicon. We predict that doping with lead, zirconium, or hafnium will lead to the suppression of the A-centers.
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71.55.Cn Elemental semiconductors
61.72.U- Doping and impurity implantation
61.72.jn Color centers
61.72.jd Vacancies
61.80.Fe Electron and positron radiation effects

Size-dependent elastic properties of crystalline polymers via a molecular mechanics model

Junhua Zhao, Wanlin Guo, Zhiliang Zhang, and Timon Rabczuk

Appl. Phys. Lett. 99, 241902 (2011); http://dx.doi.org/10.1063/1.3668110 (4 pages) | Cited 6 times

Online Publication Date: 12 December 2011

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An analytical molecular mechanics model is developed to obtain the size-dependent elastic properties of crystalline polyethylene. An effective “stick-spiral” model is adopted in the polymer chain. Explicit equations are derived from the Lennard-Jones potential function for the van der Waals force between any two polymer chains. By using the derived formulas, the nine size-dependent elastic constants are investigated systematically. The present analytical results are in reasonable agreement with those from present united-atom molecular dynamics simulations. The established analytical model provides an efficient route for mechanical characterization of crystalline polymers and related materials toward nanoelectromechanical applications.
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81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.dq Other elastic constants
61.41.+e Polymers, elastomers, and plastics

Intrinsic evolutions of optical functions, band gap, and higher-energy electronic transitions in VO2 film near the metal-insulator transition region

W. W. Li (李文武), Q. Yu (余倩), J. R. Liang (梁继然), K. Jiang (姜凯), Z. G. Hu (胡志高), J. Liu (刘剑), H. D. Chen (陈弘达), and J. H. Chu (褚君浩)

Appl. Phys. Lett. 99, 241903 (2011); http://dx.doi.org/10.1063/1.3665626 (3 pages) | Cited 4 times

Online Publication Date: 13 December 2011

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Transmittance spectra of (011) vanadium dioxide (VO2) film have been studied in the temperature range of 45–80 °C. Owing to increasing carrier concentration, the near-infrared extinction coefficient and optical conductivity around metal-insulator transition (MIT) rapidly increase with the temperature. Moreover, three electronic transitions can be uniquely assigned and show the hysteresis behavior near the MIT region. It was found that the optical band gap decreases from 0.457 to 0.042 eV before the MIT, then reduces to zero for the metal state. This confirms the fact that the a1g and egπ bands are moved close and finally overlap with the temperature.
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78.66.Nk Insulators
71.20.Ps Other inorganic compounds
71.30.+h Metal-insulator transitions and other electronic transitions
73.61.Ng Insulators
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.30.Hv Other nonmetallic inorganics

Band-gap narrowing in α-(CrxFe1-x)2O3 solid-solution films

Hisanori Mashiko, Takayoshi Oshima, and Akira Ohtomo

Appl. Phys. Lett. 99, 241904 (2011); http://dx.doi.org/10.1063/1.3669704 (3 pages) | Cited 3 times

Online Publication Date: 13 December 2011

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We report on structural and optical properties for the (0001)-oriented α-(CrxFe1-x)2O3 (0 ≤ x ≤ 1) epitaxial films prepared on c-sapphire substrates by using pulsed-laser deposition. Pure corundum phase with atomically flat surface was obtained in the entire composition range. Optical absorption spectra for the films with 0.2 < x < 0.9 showed a nearly constant band-gap (1.7 eV), which is narrower than those of α-Fe2O3 (2.1 eV) and α-Cr2O3 (3.0 eV). The result suggests that the band-gap narrowing arises from a type-II band alignment of these oxides and the fundamental band-gap lies between the Cr t2g and O 2p occupied states and the Fe t2g* empty state.
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71.20.Ps Other inorganic compounds
68.55.-a Thin film structure and morphology
81.15.Fg Pulsed laser ablation deposition
78.40.Ha Other nonmetallic inorganics
78.30.Hv Other nonmetallic inorganics

Pyramidal defects in Mg-doped GaN in light of strain-energy minimization

Dong Nyung Lee

Appl. Phys. Lett. 99, 241905 (2011); http://dx.doi.org/10.1063/1.3670307 (2 pages)

Online Publication Date: 14 December 2011

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The planar segregation gives rise to stress and strain fields which are approximated by a uniaxial character in a displacement controlled system. In this condition, the elastic strain energy is proportional to Young’s modulus. Young’s modulus of GaN is minimized when the directions normal to a conical segregation surface make about 48° with the c-axis of hexagonal GaN, which is close to the angle 47.3° between the c-axis and the directions normal to the {11math3} planes. This implies that the formation of pyramidal defects in magnesium-doped GaN can be a compromise between minimization of the elastic strain energy due to segregation of magnesium and the planar segregation.
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61.72.U- Doping and impurity implantation
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.de Elastic moduli

Experimental observations of surface roughness in uniaxially loaded strained Si microelectromechanical systems-based structures

E. Escobedo-Cousin, S. H. Olsen, T. Pardoen, U. Bhaskar, and J.-P. Raskin

Appl. Phys. Lett. 99, 241906 (2011); http://dx.doi.org/10.1063/1.3669413 (3 pages)

Online Publication Date: 14 December 2011

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Surface roughness in uniaxially loaded strained Si has been studied experimentally using high-resolution atomic force microscopy and a microelectromechanical systems-based on-chip loading device. A reduction in rms roughness from 0.29 nm to 0.07 nm has been identified as strain increases from 0 to 2.8% (stress from 0 to 4.9 GPa). The correlation length of the roughness, also known to affect carrier mobility, increases with increasing strain up to 1.7% before reducing at larger levels of strain. These results partly explain the high-field mobility observed in strained Si, indicating that a modified correlation length should also be considered in transport modelling of strained Si.
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07.10.Cm Micromechanical devices and systems

Temperature-induced anomalous brittle-to-ductile transition of bulk metallic glasses

D. Pan, H. Guo, W. Zhang, A. Inoue, and M. W. Chen

Appl. Phys. Lett. 99, 241907 (2011); http://dx.doi.org/10.1063/1.3669508 (4 pages) | Cited 4 times

Online Publication Date: 14 December 2011

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We report an anomalous brittle-to-ductile transition (BTDT) in Au-based bulk metallic glasses (BMGs). Despite of brittle failure without noticeable plastic strain under uniaxial compression at room temperature, the Au-based BMGs exhibit remarkable plasticity at cryogenic temperatures, which is opposite to the BTDT in crystalline materials. This anomalous transition originates from the strong temperature dependence of the fundamental deformation units, viz. shear transformation zones, giving rise to both superior plasticity and high strength of BMGs for low-temperature applications.
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81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.fq Plasticity and superplasticity
62.20.mj Brittleness
81.40.Lm Deformation, plasticity, and creep

Maximum asymmetry in strain induced mechanical instability of graphene: Compression versus tension

Yu Zhang and Feng Liu

Appl. Phys. Lett. 99, 241908 (2011); http://dx.doi.org/10.1063/1.3666856 (3 pages) | Cited 2 times

Online Publication Date: 15 December 2011

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We demonstrate that graphene, as the thinnest possible solid membrane of only one atomic layer thick, exhibits the maximum asymmetry in tensile versus compressive strain induced mechanical instability. Using continuum mechanics analysis and molecular dynamics simulations, we show that for graphene nanoribbons (sheets) with a typical length (size) of ∼100 nm, the critical compressive strain for buckling instability is only ∼10−4%, while the critical tensile strain for fracture is ∼2%, a four orders of magnitude difference. Such a large asymmetry implies that practically, strain engineering of graphene devices is only viable with application of tensile strain but difficult with compressive strain.
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81.40.Lm Deformation, plasticity, and creep
62.20.mq Buckling
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.mm Fracture
62.20.F- Deformation and plasticity
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Room temperature ballistic transport in InSb quantum well nanodevices

A. M. Gilbertson, A. Kormányos, P. D. Buckle, M. Fearn, T. Ashley, C. J. Lambert, S. A. Solin, and L. F. Cohen

Appl. Phys. Lett. 99, 242101 (2011); http://dx.doi.org/10.1063/1.3668107 (3 pages) | Cited 3 times

Online Publication Date: 12 December 2011

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We report the room temperature observation of significant ballistic electron transport in shallow etched four-terminal mesoscopic devices fabricated on an InSb/AlInSb quantum well (QW) heterostructure with a crucial partitioned growth-buffer scheme. Ballistic electron transport is evidenced by a negative bend resistance signature which is quite clearly observed at 295 K and at current densities in excess of 106 A/cm2. This demonstrates unequivocally that by using effective growth and processing strategies, room temperature ballistic effects can be exploited in InSb/AlInSb QWs at practical device dimensions.
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85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
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