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7 Apr 2008

Volume 92, Issue 14, Articles (14xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 92, 142501 (2008); http://dx.doi.org/10.1063/1.2905816 (3 pages)

M. C. Wu, A. Aziz, D. Morecroft, M. G. Blamire, M. C. Hickey, M. Ali, G. Burnell, and B. J. Hickey
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Low residual doping level in homoepitaxially grown ZnO layers

I. C. Robin, A. Ribeaud, S. Brochen, G. Feuillet, P. Ferret, H. Mariette, D. Ehrentraut, and T. Fukuda

Appl. Phys. Lett. 92, 141101 (2008); http://dx.doi.org/10.1063/1.2907562 (3 pages) | Cited 5 times

Online Publication Date: 7 April 2008

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ZnO homoepitaxial growth is shown to change the luminescent properties of ZnO in a substantial way. Temperature dependent (4–300 K) photoluminescence properties of the films grown by metal organic vapor phase epitaxy or by liquid phase epitaxy are compared to those of the hydrothermal ZnO substrate used for the growth. The intensity ratio between the free exciton and the donor bound exciton strongly increases, following homoepitaxial growth. The activation energy of the band edge emission intensity also increases from 13 meV, which corresponds to the donor bound exciton localization energy, up to a value of 60 meV, which corresponds to the free exciton binding energy. This indicates that homoepitaxial growth favors free exciton emission instead of donor bound exciton emission.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
78.55.Et II-VI semiconductors
71.35.-y Excitons and related phenomena

CW lasing of current injection blue GaN-based vertical cavity surface emitting laser

Tien-Chang Lu, Chih-Chiang Kao, Hao-Chung Kuo, Gen-Sheng Huang, and Shing-Chung Wang

Appl. Phys. Lett. 92, 141102 (2008); http://dx.doi.org/10.1063/1.2908034 (3 pages) | Cited 45 times

Online Publication Date: 7 April 2008

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Here, we report the cw laser operation of electrically pumped GaN-based vertical cavity surface emitting laser (VCSEL). The GaN-based VCSEL has a ten-pair InGaN/GaN multiple quantum well active layer embedded in a GaN hybrid microcavity of 5λ optical thickness with two high reflectivity mirrors provided by an epitaxially grown AlN/GaN distributed Bragg reflector (DBR) and a Ta2O5/SiO2 dielectric DBR. cw laser action was achieved at a threshold injection current of 1.4 mA at 77 K. The laser emitted a blue wavelength at 462 nm with a narrow linewidth of about 0.15 nm. The laser beam has a divergence angle of about 11.7° with a polarization ratio of 80%. A very strong spontaneous coupling efficiency of 7.5×10−2 was measured.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.82.-m Integrated optics

Experimental demonstration of multiwatt continuous-wave supercontinuum tailoring in photonic crystal fibers

A. Kudlinski, G. Bouwmans, Y. Quiquempois, and A. Mussot

Appl. Phys. Lett. 92, 141103 (2008); http://dx.doi.org/10.1063/1.2908041 (3 pages) | Cited 6 times

Online Publication Date: 8 April 2008

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We experimentally demonstrate that the spectral broadening of continuous-wave supercontinuum can be controlled by using photonic crystal fibers with two zero-dispersion wavelengths pumped by a fiber laser at 1064 nm. The spectrum is bounded by two dispersive waves whose spectral location depends on the two zero-dispersion wavelengths of the fiber. The bandwidth of the generated spectrum and the spectral power density may thus be tailored for particular applications, such as high-resolution optical coherence tomography or optical spectroscopy.
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42.81.Dp Propagation, scattering, and losses; solitons
42.65.-k Nonlinear optics
42.70.Qs Photonic bandgap materials

Improvement of light extraction from GaN-based thin-film light-emitting diodes by patterning undoped GaN using modified laser lift-off

Kui Bao, Xiang Ning Kang, Bei Zhang, Tao Dai, Yong Jian Sun, Qiang Fu, Gui Jun Lian, Guang Cheng Xiong, Guo Yi Zhang, and Yong Chen

Appl. Phys. Lett. 92, 141104 (2008); http://dx.doi.org/10.1063/1.2906632 (3 pages) | Cited 13 times

Online Publication Date: 8 April 2008

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To improve light extraction from GaN-based light-emitting diodes (LEDs), we demonstrated an approach of modified laser lift-off (M-LLO) technique for patterning undoped GaN (u-GaN). The M-LLO consists in sequentially forming a two-dimensional triangular lattice pattern with a 4 μm period on a polymer layer over a sapphire substrate backplane by UV imprint and delivering the pattern onto u-GaN accompanied with the removal of the sapphire substrate. The enhancement of light extraction from GaN-based M-LLO LED with a reflective Ag film on the 120 nm deep u-GaN pattern was about 31% and 100% compared to that of a LLO-LED with a reflective film and a conventional LED with a sapphire substrate, respectively.
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85.60.Jb Light-emitting devices
42.62.-b Laser applications

Line-narrowed, compact, and coherent source of widely tunable terahertz radiation

D. J. M. Stothard, T. J. Edwards, D. Walsh, C. L. Thomson, C. F. Rae, M. H. Dunn, and P. G. Browne

Appl. Phys. Lett. 92, 141105 (2008); http://dx.doi.org/10.1063/1.2907489 (3 pages) | Cited 12 times

Online Publication Date: 8 April 2008

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We report a technique for line-narrowing terahertz radiation produced through parametric generation. By incorporating an etalon within the idler-wave cavity of the parametric oscillator, radiation is generated with a linewidth of 1 GHz (freerunning linewidth 50–100 GHz) and with a center frequency continuously tunable over a band >50 GHz, settable anywhere within the coarse tuning range of the device (1–3 THz). When implemented within an intracavity cavity geometry, pulses of terahertz radiation of duration ∼ 10 ns and energy ∼ 30 nJ are generated at repetition rates up to 400 Hz (implying mean powers of >10 μW and peak powers of ∼ 3 W) in a compact device.
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07.57.Hm Infrared, submillimeter wave, microwave, and radiowave sources
84.30.Ng Oscillators, pulse generators, and function generators

Wavelength tuning limitations in optically pumped type-II antimonide lasers

A. P. Ongstad, R. Kaspi, G. C. Dente, M. L. Tilton, R. Barresi, and J. R. Chavez

Appl. Phys. Lett. 92, 141106 (2008); http://dx.doi.org/10.1063/1.2904702 (3 pages) | Cited 2 times

Online Publication Date: 8 April 2008

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In this paper, we examine the wavelength tuning limitations of type-II antimonide lasers containing InAs/InGaSb/InAs quantum wells. Wavelength tuning is accomplished by varying the thickness of the InAs electron wells while keeping all else fixed. In principle, these wells can be tuned from λ ≈ 2.5 μm out to far IR wavelengths by increasing the thickness of the InAs layers. However, a practical upper limit of λ ≈ 9.5 μm is set due to the high waveguide losses awg and the diminishing modal overlap with the gain at longer wavelengths. The waveguide losses grow as awg∝λ3.44 and are attributable to free carrier absorbance. In order for the long-IR laser devices to achieve threshold, they must continually band fill, spectrally tuning to shorter wavelengths, until the laser gain exceeds the losses, which occurs near 9.5 μm.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
42.60.Fc Modulation, tuning, and mode locking

Optical biosensor based on whispering gallery mode excitations in clusters of microparticles

Alexandre Francois and Michael Himmelhaus

Appl. Phys. Lett. 92, 141107 (2008); http://dx.doi.org/10.1063/1.2907491 (3 pages) | Cited 20 times

Online Publication Date: 8 April 2008

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A new concept for an optical biosensor based on whispering gallery mode (WGM) excitations in clusters of spherical microresonators is presented. Clusters of microresonators offer the advantage to exhibit specific WGM spectra that can be considered as their fingerprint. Therefore, individual clusters can be traced throughout an experiment even without knowledge of their precise positions. Polyelectrolyte adsorption onto clusters of 10 μm polystyrene spheres is monitored in situ. It is shown that the WGMs shift to the same amount as those of a single microresonator and thus sensitivity does not depend on the number of microresonators present in the cluster.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
07.10.Cm Micromechanical devices and systems
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
87.80.-y Biophysical techniques (research methods)

Steady state photoinduced absorption of PbS quantum dots film

Jian Zhang and Xiaomei Jiang

Appl. Phys. Lett. 92, 141108 (2008); http://dx.doi.org/10.1063/1.2907492 (3 pages) | Cited 6 times

Online Publication Date: 8 April 2008

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We have measured steady state photoinduced absorption (PIA) of PbS quantum dot (QD) film in an energy range of interband electronic transitions at low temperature. PIA spectra show both positive and negative PIAs corresponding to five consecutive interband transitions. The close resemblance between PIA spectrum and the second derivative of the linear optical absorption strongly suggests that these steady state PIAs may be caused by photoinduced local electric field, i.e., the linear Stark effect. We postulate this local electric field be generated by the trapped charges under laser excitations.
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78.66.Li Other semiconductors
68.65.Hb Quantum dots (patterned in quantum wells)
78.67.Hc Quantum dots
78.30.Hv Other nonmetallic inorganics
78.40.Fy Semiconductors
78.20.Jq Electro-optical effects

Bioinspired broadband antireflection coatings on GaSb

Wei-Lun Min, Amaury P. Betancourt, Peng Jiang, and Bin Jiang

Appl. Phys. Lett. 92, 141109 (2008); http://dx.doi.org/10.1063/1.2908221 (3 pages) | Cited 25 times

Online Publication Date: 9 April 2008

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We report an inexpensive yet scalable templating technique for fabricating moth-eye antireflection gratings on gallium antimonide substrates. Non-close-packed colloidal monolayers are utilized as etching masks to pattern subwavelength-structured nipple arrays on GaSb. The resulting gratings exhibit superior broadband antireflection properties and thermal stability than conventional multilayer dielectric coatings. The specular reflection of the templated nipple arrays match with the theoretical predictions using a rigorous coupled-wave analysis model. The effect of the nipple shape and size on the antireflection properties has also been investigated by the same model. These biomimetic coatings are of great technological importance in developing efficient thermophotovoltaic cells.
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42.79.Wc Optical coatings
42.79.Dj Gratings

Reduction of spacer layer thickness of InAs quantum dots using GaNAs strain compensation layer

Ryoichiro Suzuki, Tomoyuki Miyamoto, Tomoyuki Sengoku, and Fumio Koyama

Appl. Phys. Lett. 92, 141110 (2008); http://dx.doi.org/10.1063/1.2904705 (3 pages) | Cited 2 times

Online Publication Date: 9 April 2008

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Emission and shape characteristics of the InGaAs covered InAs quantum dots with GaNAs strain compensation layers (SCLs) are investigated, focusing on the reduction of the spacer thickness for device applications. Using the GaNAs SCL, the suppression of inhomogeneous emission broadening induced by the compressive strain from lower dot layers was confirmed with the suppression of increase in the dot size of upper dot layers. This result is effective for the suppression of the spacer thickness.
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68.65.Hb Quantum dots (patterned in quantum wells)
78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors

Wide wavelength tuning of GaAs/AlxGa1−xAs bound-to-continuum quantum cascade lasers by aluminum content control

J. Heinrich, R. Langhans, M. S. Vitiello, G. Scamarcio, D. Indjin, C. A. Evans, Z. Ikonić, P. Harrison, S. Höfling, and A. Forchel

Appl. Phys. Lett. 92, 141111 (2008); http://dx.doi.org/10.1063/1.2907503 (3 pages) | Cited 2 times

Online Publication Date: 9 April 2008

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Tuning of the emission wavelength in GaAs/AlxGa1−xAs bound-to-continuum quantum cascade lasers with different Al mole fractions (x) is reported. By varying x in the range of 0.37–0.52, a shift of the emission wavelengths of over 4 μm has been observed. Using this method, laser action in the range of 11.2–15.3 μm at temperatures T ≥ 260 K has been demonstrated with a record value of ∼ 340 K for GaAs based QCLs operating at 13.5 μm.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Fc Modulation, tuning, and mode locking

Infrared quantum cutting in Tb3+,Yb3+ codoped transparent glass ceramics containing CaF2 nanocrystals

Song Ye, Bin Zhu, Jingxin Chen, Jin Luo, and Jian Rong Qiu

Appl. Phys. Lett. 92, 141112 (2008); http://dx.doi.org/10.1063/1.2907496 (3 pages) | Cited 95 times

Online Publication Date: 10 April 2008

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Tb3+–Yb3+ codoped transparent oxyfluoride glass ceramics containing CaF2 nanocrystals were synthesized. The formation of CaF2 nanocrystals in the glass ceramics was confirmed by x-ray diffraction and high resolution transmission electron microscopy. The incorporation of Tb3+ and Yb3+ into CaF2 nanocrystal lattice was confirmed by energy dispersive spectroscopy. Infrared quantum cutting involving Yb3+ 950–1100 nm (2F5/2→2F7/2) emission was achieved upon the excitation of 5D4 energy level of Tb3+ at 484 nm. The photoluminescence properties have been studied for these glass ceramics. Yb3+ concentration dependent quantum efficiency was calculated, and the maximum efficiency approaches 155% before reaching concentration quenching threshold.
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81.05.Pj Glass-based composites, vitroceramics
61.72.up Other materials
61.46.-w Structure of nanoscale materials
78.55.Qr Amorphous materials; glasses and other disordered solids

Highly efficient surface enhanced Raman scattering using microstructured optical fibers with enhanced plasmonic interactions

Anna C. Peacock, Adrian Amezcua-Correa, Jixin Yang, Pier J. A. Sazio, and Steven M. Howdle

Appl. Phys. Lett. 92, 141113 (2008); http://dx.doi.org/10.1063/1.2907506 (3 pages) | Cited 10 times

Online Publication Date: 10 April 2008

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Microstructured optical fibers (MOFs) represent a promising platform technology for fully integrated photonic-plasmonic devices. In this paper, we experimentally investigate the properties of two MOF templates impregnated with silver nanoparticles via a high pressure chemical deposition technique. By comparing fiber templates with different air filling fractions, we have quantified the importance of an increased field-particle overlap for improved surface enhanced Raman scattering sensitivity for the next generation of optical fiber sensors.
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78.35.+c Brillouin and Rayleigh scattering; other light scattering
42.81.Cn Fiber testing and measurement of fiber parameters

Thermal emission of two-color polarized infrared waves from integrated plasmon cavities

H. T. Miyazaki, K. Ikeda, T. Kasaya, K. Yamamoto, Y. Inoue, K. Fujimura, T. Kanakugi, M. Okada, K. Hatade, and S. Kitagawa

Appl. Phys. Lett. 92, 141114 (2008); http://dx.doi.org/10.1063/1.2906375 (3 pages) | Cited 12 times

Online Publication Date: 11 April 2008

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We have demonstrated that orthogonally polarized two-color infrared waves thermally emitted from gratings integrated onto a single Au chip open a way for simple and efficient chemical analysis. Each component grating is made of high-aspect cavities with a width on the order of 100 nm and a depth close to 1 μm, and generates linearly polarized and narrow-band midinfrared light by the organ pipe resonance of surface plasmons. Effectiveness of the integrated grating emitters for nondispersive infrared analysis has been shown on the basis of a model experiment for determining the concentration of a specific chemical compound in liquids.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
82.80.-d Chemical analysis and related physical methods of analysis
78.30.C- Liquids

Hybridized surface plasmon polaritons at an interface between a metal and a uniaxial crystal

Rui Li, Chen Cheng, Fang-Fang Ren, Jing Chen, Ya-Xian Fan, Jianping Ding, and Hui-Tian Wang

Appl. Phys. Lett. 92, 141115 (2008); http://dx.doi.org/10.1063/1.2908920 (3 pages) | Cited 13 times

Online Publication Date: 11 April 2008

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The surface plasmon polariton (SPP) at an interface between a metal and a uniaxial crystal is studied. A new class of hybridized SPP found in this work is quite different from the traditional SPP at the interface between a metal and an isotropic dielectric. In contrast to the two evanescent fields for the traditional SPP, the hybridized SPP involves four evanescent fields: transverse-electric-like and transverse-magnetic-like waves in the metal, and ordinary-light-like and extraordinary-light-like waves in the uniaxial crystal. The necessary conditions and the regimes for the existence of the hybridized SPP are presented. Some potential applications are also discussed.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
68.35.Ct Interface structure and roughness
78.20.Bh Theory, models, and numerical simulation
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Properties of ceramic honeycomb cathodes

M. Friedman, M. C. Myers, Y. Chan, and J. D. Sethian

Appl. Phys. Lett. 92, 141501 (2008); http://dx.doi.org/10.1063/1.2904637 (3 pages) | Cited 4 times

Online Publication Date: 10 April 2008

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A high current electron beam was emitted from slabs of ceramic honeycomb that were placed 2 mm in front of the primary electron emitters. Inside the ceramic honeycomb pores, the primary electrons are multiplied many folds by a secondary emission process creating plasma from which the electron beam was emitted. Measurements show that there was no anode-cathode gap closure during the pulse duration and a uniform current density distribution was observed on the anode. Contrary to the measurements of “conventional” large area field emission cathodes, no transit time instability was observed.
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79.20.Hx Electron impact: secondary emission
79.70.+q Field emission, ionization, evaporation, and desorption

Angular distribution of isothermal expansions of non-quasi-neutral plasmas into a vacuum

Huang Yongsheng, Duan Xiaojiao, Shi Yijin, Lan Xiaofei, Tan Zhixin, Wang Naiyan, Tang Xiuzhang, and He Yexi

Appl. Phys. Lett. 92, 141502 (2008); http://dx.doi.org/10.1063/1.2904639 (3 pages) | Cited 1 time

Online Publication Date: 10 April 2008

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A two dimensional planar model is developed for self-similar isothermal expansions of non-quasi-neutral plasmas into a vacuum of solid targets heated by ultraintense laser pulses. The angular ion distribution and the dependence of the maximum ion velocity on laser parameters and target thicknesses are predicted. Considering the self-generated magnetic field of plasma beams as a perturbation, the ion energy on edge at the ion opening angle has an increase of 2% relative to that on the front center. Therefore, the self-generated magnetic field of plasma beams is not large enough to interpret for the ring structures.
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52.38.Fz Laser-induced magnetic fields in plasmas
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.25.Fi Transport properties
52.27.Jt Nonneutral plasmas

Velocity distribution of neutral species during magnetron sputtering by Fabry–Perot interferometry

N. Britun, J. G. Han, and S.-G. Oh

Appl. Phys. Lett. 92, 141503 (2008); http://dx.doi.org/10.1063/1.2907505 (3 pages) | Cited 9 times

Online Publication Date: 10 April 2008

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The velocity distribution of a metallic neutral species sputtered in a dc magnetron discharge was measured using a planar Fabry–Perot interferometer and a hollow cathode lamp as a reference source. The measurement was performed under different angles of view relative to the target surface. The velocity distribution function in the direction perpendicular to the target becomes asymmetrical as the Ar pressure decreases, whereas it remains nearly symmetrical when the line of sight is parallel to the target surface. The average velocity of the sputtered Ti atoms was measured to be about 2 km/s.
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07.60.Ly Interferometers
06.30.Gv Velocity, acceleration, and rotation

Energetic ion acceleration with a non-Maxwellian hot-electron tail

Yongsheng Huang, Yuanjie Bi, Xiaojiao Duan, Xiaofei Lan, Naiyan Wang, Xiuzhang Tang, and Yexi He

Appl. Phys. Lett. 92, 141504 (2008); http://dx.doi.org/10.1063/1.2908971 (3 pages) | Cited 5 times

Online Publication Date: 11 April 2008

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A half-self-similar solution on the bases of the equations of the continuity and motion of ions and Poisson’s equation is proposed for isothermal expansions of nonquasineutral plasmas with an enhanced electron tail into a vacuum from solid targets heated by ultraintense laser pulses. The ion expansion is assumed to be self-similar, while the electron expansion is non-self-similar. The expression of the self-similar variable and maximum ion velocity at the ion front is given out. It is shown that the ion acceleration with an enhanced hot-electron tail is more efficient than that with Maxwellian electrons.
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52.38.Kd Laser-plasma acceleration of electrons and ions
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.40.Kh Plasma sheaths
41.75.Jv Laser-driven acceleration
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Recovery of elastic constant of ultrathin Cu films by low temperature annealing

N. Nakamura, H. Ogi, T. Shagawa, and M. Hirao

Appl. Phys. Lett. 92, 141901 (2008); http://dx.doi.org/10.1063/1.2908039 (3 pages) | Cited 5 times

Online Publication Date: 7 April 2008

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Annealing effect on the elastic constant of Cu thin films was investigated by acoustic-phonon resonance spectroscopy. Annealing treatment was performed after the deposition in vacuum condition for 30 min at various temperatures up to 200 °C. It did not cause obvious changes in the x-ray diffraction spectra, but it significantly increased the elastic constant. The elastic constant of the as-deposited Cu film was smaller than that of bulk Cu by 20%, and it recovered to the bulk value by the postannealing at 200 °C.
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68.60.Bs Mechanical and acoustical properties
81.40.Jj Elasticity and anelasticity, stress-strain relations
81.40.Gh Other heat and thermomechanical treatments
68.55.-a Thin film structure and morphology
62.20.dq Other elastic constants
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Effect of SnO addition on optical absorption of bismuth borate glass and photocatalytic property of the crystallized glass

Hirokazu Masai, Takumi Fujiwara, and Hiroshi Mori

Appl. Phys. Lett. 92, 141902 (2008); http://dx.doi.org/10.1063/1.2903151 (3 pages) | Cited 6 times

Online Publication Date: 7 April 2008

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We have found that an addition of SnO in a bismuth-borate glass, CaO–B2O3–Bi2O3–Al2O3–TiO2, decreases the optical absorption coefficient in the visible region, in which selective crystallization of TiO2 was observed after heat treatment. Since selective crystallization of TiO2 was also attained in the SnO-containing glass, the transparency of TiO2 crystallized glass can be improved independently of selective crystallization of TiO2. We have also demonstrated that the rutile-nanocrystallized glass with SnO addition shows a higher photocatalytic activity than the glass without SnO, indicating that this crystallized glass has a large potential for application as transparent photocatalytic materials.
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61.43.Fs Glasses
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
82.50.-m Photochemistry
64.70.ph Nonmetallic glasses (silicates, oxides, selenides, etc.)
81.40.Gh Other heat and thermomechanical treatments
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

An integrated method to determine melting temperatures in high-pressure laser-heating experiments

Laura Robin Benedetti, Daniele Antonangeli, Daniel L. Farber, and Mohamed Mezouar

Appl. Phys. Lett. 92, 141903 (2008); http://dx.doi.org/10.1063/1.2906893 (3 pages) | Cited 3 times

Online Publication Date: 7 April 2008

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We present an integrated approach for the determination of melting in the laser-heated diamond-anvil cell by simultaneously monitoring several criteria. We combine x-ray diffraction based observations with detection of discontinuities in optical properties by spectroradiometric measurements. This approach increases the confidence of melt identification, especially with low-Z samples. We demonstrate the efficacy of the method with observations of melt in oxygen at 47 GPa (1500 K) and at 55 GPa (1850 K).
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64.70.dj Melting of specific substances
61.05.cp X-ray diffraction

Are there stable long-range ordered Fe1−xCrx compounds?

Paul Erhart, Babak Sadigh, and Alfredo Caro

Appl. Phys. Lett. 92, 141904 (2008); http://dx.doi.org/10.1063/1.2907337 (3 pages) | Cited 16 times

Online Publication Date: 7 April 2008

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The heat of formation of Fe–Cr alloys undergoes an anomalous change of sign at small Cr concentrations. This observation raises the question as to whether there are intermetallic phases present in this composition range. Here, we report the discovery of several long-range ordered structures that represent ground state phases at 0 K. In particular, we have identified a structure at 3.7% Cr with an embedding energy which is 49 meV/Cr atom below the solid solution. This implies that there is an effective long-range attractive interaction between Cr atoms. We propose that the structures found in this study complete the low temperature–low Cr region of the phase diagram.
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82.60.Cx Enthalpies of combustion, reaction, and formation
61.66.Dk Alloys
81.30.Bx Phase diagrams of metals, alloys, and oxides

Effects of AlAs interfacial layer on material and optical properties of GaAs/Ge(100) epitaxy

C. K. Chia, J. R. Dong, D. Z. Chi, A. Sridhara, A. S. W. Wong, M. Suryana, G. K. Dalapati, S. J. Chua, and S. J. Lee

Appl. Phys. Lett. 92, 141905 (2008); http://dx.doi.org/10.1063/1.2908042 (3 pages) | Cited 10 times

Online Publication Date: 8 April 2008

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GaAs/AlAs/Ge(100) samples grown at 650 °C with AlAs interfacial layer thickness of 0, 10, 20, and 30 nm were characterized using transmission electron microscopy, secondary ion mass spectrometry (SIMS), and photoluminescence (PL) techniques. SIMS results indicate that the presence of an ultrathin AlAs interfacial layer at the GaAs/Ge interface has dramatically blocked the cross diffusion of Ge, Ga, and As atoms, attributed to the higher Al–As bonding energy. The optical quality of the GaAs epitaxy with a thin AlAs interfacial layer is found to be improved with complete elimination of PL originated from Ge-based complexes, in corroboration with SIMS results.
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78.66.Fd III-V semiconductors
68.55.ag Semiconductors
78.55.Cr III-V semiconductors
66.30.Lw Diffusion of other defects
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Thulium-based bulk metallic glass

H. B. Yu, P. Yu, W. H. Wang, and H. Y. Bai

Appl. Phys. Lett. 92, 141906 (2008); http://dx.doi.org/10.1063/1.2908047 (3 pages) | Cited 12 times

Online Publication Date: 8 April 2008

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We report the formation and properties of a thulium-based bulk metallic glass (BMG). Compared with other known rare-earth (RE) based BMGs, Tm-based BMGs show features of excellent glass formation ability, considerable higher elastic modulus, smaller Poisson’s ratio, high mechanical strength, and intrinsic brittleness. The reasons for the different properties between the Tm-based and other RE-based BMGs are discussed. It is expected that the Tm-based glasses with the unique properties are appropriate candidates for studying some important issues in BMGs.
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81.05.Kf Glasses (including metallic glasses)
64.70.pe Metallic glasses
81.40.Jj Elasticity and anelasticity, stress-strain relations
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.dj Poisson's ratio
62.20.mj Brittleness
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