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7 Sep 2009

Volume 95, Issue 10, Articles (10xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 95, 083506 (2009); http://dx.doi.org/10.1063/1.3216851 (3 pages)

J. Z. Sun, M. C. Gaidis, E. J. O’Sullivan, E. A. Joseph, G. Hu, D. W. Abraham, J. J. Nowak, P. L. Trouilloud, Yu Lu, S. L. Brown, D. C. Worledge, and W. J. Gallagher

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Characterization of terahertz emission from a dc-biased filament in air

Yanping Chen, Tie-jun Wang, Claude Marceau, Francis Théberge, Marc Châteauneuf, Jacques Dubois, Olga Kosareva, and See Leang Chin

Appl. Phys. Lett. 95, 101101 (2009); http://dx.doi.org/10.1063/1.3224944 (3 pages) | Cited 7 times

Online Publication Date: 8 September 2009

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We demonstrate that the terahertz emission from a dc-biased filament can be regarded as a sum of an elliptically polarized terahertz source (generated by a filament without external electric field) and a linearly polarized terahertz source induced by the external electric field applied to the filament. The peak frequency and linewidth of the linearly polarized terahertz source are related to the average plasma density of the filament.
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52.25.-b Plasma properties

Active control of surface plasmon polaritons by optical isomerization of an azobenzene polymer film

D. G. Zhang, X.-C. Yuan, A. Bouhelier, G. H. Yuan, P. Wang, and H. Ming

Appl. Phys. Lett. 95, 101102 (2009); http://dx.doi.org/10.1063/1.3225156 (3 pages) | Cited 10 times

Online Publication Date: 8 September 2009

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Active control of surface plasmon polaritons (SPPs) by optical isomerization of an azobenzene polymer film is proposed and demonstrated in this letter. A tightly focused 532 nm laser beam was used to change the wave number of the SPPs and a separate unpolarized light source was employed to erase the change, forming one cycle of the control. The largest change of the SPPs wave number obtained in the experiments is about 0.0382K0 in the case of 54 nm thickness azo-polymer film. Validity of this method is confirmed by consistence between theoretical and experimental results.
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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)
42.70.Jk Polymers and organics
82.30.Qt Isomerization and rearrangement
78.66.Qn Polymers; organic compounds

Strong improvement in the photonic stop-band edge sharpness of a lithium niobate photonic crystal slab

S. Diziain, S. Harada, R. Salut, P. Muralt, and M.-P. Bernal

Appl. Phys. Lett. 95, 101103 (2009); http://dx.doi.org/10.1063/1.3223595 (3 pages) | Cited 5 times

Online Publication Date: 8 September 2009

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We report on a photonic crystal (PhC) etched into a 380 nm thick lithium niobate (LN) thin film deposited on a MgO substrate by pulsed laser deposition. The transmission properties of this device were assessed by optical near-field measurements and compared to the transmission spectra of the same PhC drilled into bulk LN and calculated by a two dimensional finite-difference time domain method. We show a strong improvement in the transmission properties of the LN PhC by etching it into a thin layer rather than into a 500 μm thick wafer. This result appears to be very promising for applications based on LN tunable PhCs.
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42.70.Qs Photonic bandgap materials
81.15.Fg Pulsed laser ablation deposition

High-speed all-optical modulation of a standard quantum cascade laser by front facet illumination

Gang Chen, Clyde G. Bethea, Rainer Martini, P. D. Grant, R. Dudek, and H. C. Liu

Appl. Phys. Lett. 95, 101104 (2009); http://dx.doi.org/10.1063/1.3223597 (3 pages) | Cited 5 times

Online Publication Date: 8 September 2009

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A simple experimental scheme to control intersubband lasing transition by optically induced nonresonant interband transition is presented, allowing for high-speed all-optical modulation of mid-infrared (MIR) quantum cascade laser (QCL). Illuminating the QCL front facet with 100 fs Ti:sapphire laser pulse, a fast modulation of a cw-MIR emission is observed with an estimated transient time of less than 81 ps, limited by instrument bandwidth, and a modulation depth of 18%. It has a great potential for high-speed modulation of high power QCL at room temperature.
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42.60.Fc Modulation, tuning, and mode locking
42.55.Px Semiconductor lasers; laser diodes
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.60.By Design of specific laser systems

Verification of p-n junctions in polymer light-emitting electrochemical cells via electrical characterization

Yueqing Lei, Feng Teng, Yanbing Hou, Zhidong Lou, and Yongsheng Wang

Appl. Phys. Lett. 95, 101105 (2009); http://dx.doi.org/10.1063/1.3224178 (3 pages) | Cited 2 times

Online Publication Date: 8 September 2009

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We report micrometer thick sandwich light-emitting electrochemical cells (LECs) based on a blend of poly[5-(2′-ethylhexyloxy)-2-methoxy-1, 4-phenylene vinylene] and poly(ethylene oxide) complexed with lithium trifluoromethanesulfonate. These LECs exhibit very similar properties as those of thin LECs including bipolar current-voltage characteristics and light emission. Mixing of aluminum nanoparticles into polymer layers improves electroluminescence because of smaller series resistance and larger light-emitting area. Taking series resistance into account, we confirm the operating mechanism of an LEC is the formation of a p-n junction by in situ electrochemical doping via fitting the steady state current-voltage characteristics to the expression for the Shockley model of a p-n diode.
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85.60.Jb Light-emitting devices
78.60.Fi Electroluminescence
64.75.Ef Mixing
82.45.Wx Polymers and organic materials in electrochemistry
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Internal quantum efficiency of c-plane InGaN and m-plane InGaN on Si and GaN

X. Ni, J. Lee, M. Wu, X. Li, R. Shimada, Ü. Özgür, A. A. Baski, H. Morkoç, T. Paskova, G. Mulholland, and K. R. Evans

Appl. Phys. Lett. 95, 101106 (2009); http://dx.doi.org/10.1063/1.3224192 (3 pages) | Cited 9 times

Online Publication Date: 8 September 2009

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We investigated internal quantum efficiency (IQE) of polar (0001) InGaN on c-sapphire, and (1math00) nonpolar m-plane InGaN on both m-plane GaN and specially patterned Si. The IQE values were extracted from the resonant photoluminescence intensity versus the excitation power. Data indicate that at comparable generated carrier concentrations the efficiency of the m-plane InGaN on patterned Si is approximately a factor of 2 higher than that of the highly optimized c-plane layer. At the highest laser excitation employed ( ∼ 1.2×1018 cm−3), the IQE of m-plane InGaN double heterostructure on Si is approximately 65%. We believe that the m-plane would remain inherently advantageous, particularly at high electrical injection levels, even with respect to highly optimized c-plane varieties. The observations could be attributed to the lack of polarization induced field and the predicted increased optical matrix elements in m-plane orientation.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
78.55.Cr III-V semiconductors
72.20.Ht High-field and nonlinear effects
72.80.Ey III-V and II-VI semiconductors

Submicron ionography of nanostructures using a femtosecond-laser-driven-cluster-based source

A. Ya. Faenov, T. A. Pikuz, Y. Fukuda, M. Kando, H. Kotaki, T. Homma, K. Kawase, T. Kameshima, A. Pirozhkov, A. Yogo, M. Tampo, M. Mori, H. Sakaki, Y. Hayashi, T. Nakamura, et al.

Appl. Phys. Lett. 95, 101107 (2009); http://dx.doi.org/10.1063/1.3210785 (3 pages) | Cited 6 times

Online Publication Date: 9 September 2009

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An intense isotropic source of multicharged carbon and oxygen ions with energy above 300 keV and particle number >108 per shot was obtained by femtosecond Ti:Sa laser irradiation of submicron clusters. The source was employed for high-contrast contact ionography images with 600 nm spatial resolution. A variation in object thickness of 100 nm was well resolved for both Zr and polymer foils.
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61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
42.55.Rz Doped-insulator lasers and other solid state lasers

Controlling the directional emission of holey organic microlasers

N. Djellali, I. Gozhyk, D. Owens, S. Lozenko, M. Lebental, J. Lautru, C. Ulysse, B. Kippelen, and J. Zyss

Appl. Phys. Lett. 95, 101108 (2009); http://dx.doi.org/10.1063/1.3205474 (3 pages) | Cited 3 times

Online Publication Date: 10 September 2009

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The far-field pattern of stadium-shaped organic microlasers is strongly modified by introducing circular air vacancies within the cavity, so as to control it in a predictive way. Experimental results are in good agreement with geometrical optics predictions whereas spectral properties of emission are investigated to improve the understanding of the lasing modes.
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42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.By Design of specific laser systems

Combined optical trapping and microphotoluminescence of single InP nanowires

Peter J. Reece, Suriati Paiman, Osama Abdul-Nabi, Qiang Gao, Michael Gal, H. Hoe Tan, and C. Jagadish

Appl. Phys. Lett. 95, 101109 (2009); http://dx.doi.org/10.1063/1.3225148 (3 pages) | Cited 5 times

Online Publication Date: 11 September 2009

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In this letter, we demonstrate that microphotoluminescence may be combined with optical trapping for effective optical characterization of single target InP semiconductor nanowires in suspension. Using this technique, we may investigate structural properties of optically trapped nanowires, such as crystalline polytypes and stacking faults. This arrangement may also be used to resolve structural variations along the axis of the trapped nanowire. These results show that photoluminescence measurements may be coupled with optical tweezers without degrading the performance of the optical trap and provide a powerful interrogation tool for preselection of components for nanowire photonic devices.
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78.67.Lt Quantum wires
78.55.Cr III-V semiconductors
68.65.La Quantum wires (patterned in quantum wells)
81.07.Vb Quantum wires
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.72.Nn Stacking faults and other planar or extended defects
82.70.Kj Emulsions and suspensions

Nanoscale band gap spectroscopy on ZnO and GaN-based compounds with a monochromated electron microscope

M. Bosman, L. J. Tang, J. D. Ye, S. T. Tan, Y. Zhang, and V. J. Keast

Appl. Phys. Lett. 95, 101110 (2009); http://dx.doi.org/10.1063/1.3222974 (3 pages) | Cited 2 times

Online Publication Date: 11 September 2009

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Monochromated low-loss EELS (electron energy-loss spectroscopy) is explored as an analytical technique for nanoscale mapping of the electronic band gap energy on arsenic-implanted ZnO, CdZnO, and InGaN compounds. Its accuracy is confirmed independently with Raman spectroscopy. From a ternary compound, the relationship between the band gap energy and the chemical composition is determined, a powerful application of low-loss EELS. The effects of electron beam delocalization are discussed using examples from In0.25Ga0.75N quantum wells.
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78.30.Fs III-V and II-VI semiconductors
78.67.De Quantum wells
73.21.Fg Quantum wells
61.72.uj III-V and II-VI semiconductors
79.20.Uv Electron energy loss spectroscopy
71.20.Nr Semiconductor compounds

Self-pulsing 1050 nm quantum dot edge emitting laser diodes

Haoling Liu, Peter Smowton, Huw Summers, Gareth Edwards, and Wolfgang Drexler

Appl. Phys. Lett. 95, 101111 (2009); http://dx.doi.org/10.1063/1.3227654 (3 pages) | Cited 1 time

Online Publication Date: 11 September 2009

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We examine self-pulsing, edge emitting, quantum dot laser diodes as continuous broad spectrum light sources emitting at ∼ 1050 nm. Devices are configured with split contacts. When operated without a saturable absorber, the laser emits a number of discrete narrow modes, which merge to form a broad continuous lasing spectrum on application of the saturable absorber. The broadened spectra are consistent with the modulated carrier density expected under Q-switched operation. This provides a simple technique for generating emission suitable for biomedical applications. The spectral width achieved is ∼ 10 nm, and the average output power is 7.5 mW.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.50.Gy Effects of atomic coherence on propagation, absorption, and amplification of light; electromagnetically induced transparency and absorption
42.55.Rz Doped-insulator lasers and other solid state lasers
42.72.-g Optical sources and standards
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Ion implantation and energy loss effect during high-voltage pulsed glow discharge in a tube

Langping Wang, Yang Lu, Xiaofeng Wang, Zhiwen Xie, Lei Huang, and Yanhong Wei

Appl. Phys. Lett. 95, 101501 (2009); http://dx.doi.org/10.1063/1.3225155 (3 pages)

Online Publication Date: 9 September 2009

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Plasma parameters of high-voltage pulsed glow discharge in a tube were studied using a static probe and optical emission spectrometry. Experiment results show that two kinds of plasma can be obtained in the tube and a virtual anode can be formed at the center of the tube. The potential of the virtual anode is about 20%–30% of the applied bias. The Auger electron spectroscopy depth profile shows that the peak depth of the implanted ions in the tube is about 70%–80% of that outside the tube, owing to the virtual anode.
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52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.25.Tx Emission, absorption, and scattering of particles
52.50.-b Plasma production and heating
52.70.Ds Electric and magnetic measurements
52.77.Dq Plasma-based ion implantation and deposition
52.80.Hc Glow; corona

Photoelectric charging of dust particles: Effect of spontaneous and light induced field emission of electrons

M. S. Sodha and A. Dixit

Appl. Phys. Lett. 95, 101502 (2009); http://dx.doi.org/10.1063/1.3223618 (3 pages) | Cited 1 time

Online Publication Date: 10 September 2009

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The authors have analyzed the charging of dust particles in a plasma, taking into account the electron/ion currents to the particles, electron/ion generation and recombination, electric field emission, photoelectric emission and photoelectric field emission of electrons under the influence of light irradiation; the irradiance has been assumed to be at a level, which lets the particles retain the negative sign of the charge. Numerical results and discussion conclude the papers.
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52.27.Lw Dusty or complex plasmas; plasma crystals
52.25.Tx Emission, absorption, and scattering of particles
52.40.Db Electromagnetic (nonlaser) radiation interactions with plasma
52.20.Fs Electron collisions
52.20.Hv Atomic, molecular, ion, and heavy-particle collisions

MeV proton beams generated by 3 mJ ultrafast laser pulses at 0.5 kHz

Bixue Hou, John Nees, James Easter, Jack Davis, George Petrov, Alexander Thomas, and Karl Krushelnick

Appl. Phys. Lett. 95, 101503 (2009); http://dx.doi.org/10.1063/1.3224180 (3 pages) | Cited 4 times

Online Publication Date: 10 September 2009

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Well-collimated proton beams are generated from bulk glass along the target normal direction by tightly focused 55 fs, 3 mJ pulses from a laser operating at 0.5 kHz repetition rate. Proton beams with energies of >265 keV have an emission angle of about 16° full width at half maximum. Spectral measurements indicate proton energies exceeding 0.5 MeV with a flux of 3.2×109 s−1 sr−1 and the flux of measured protons with energies of greater than 90 keV is 8.5×1011 s−1 sr−1 on center.
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42.65.Re Ultrafast processes; optical pulse generation and pulse compression
41.75.Ak Positive-ion beams

Properties of electron swarms in CF3I

H. Hasegawa, H. Date, M. Shimozuma, and H. Itoh

Appl. Phys. Lett. 95, 101504 (2009); http://dx.doi.org/10.1063/1.3224197 (3 pages)

Online Publication Date: 11 September 2009

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We report the electron swarm parameters, the drift velocity, and the ionization coefficients in CF3I gas for relatively wide ranges of reduced electric fields (E/N). The drift velocity is measured based on the arrival-time spectra of electrons for E/N = 200–3000 Td, and the first and second ionization coefficients are determined by the steady-state Townsend method for E/N = 400–5000 Td. The results are compared with those of CF4 to show that CF3I has a high reactivity for electron attachment in a low E/N region resulting in a much higher limiting E/N value (440 Td) than that of CF4.
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51.50.+v Electrical properties (ionization, breakdown, electron and ion mobility, etc.)
52.80.Dy Low-field and Townsend discharges
51.10.+y Kinetic and transport theory of gases
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Tunable in situ growth of porous cubic silicon carbide thin films via methyltrichlorosilane-based chemical vapor deposition

Wei-Cheng Lien, Nicola Ferralis, Albert P. Pisano, Carlo Carraro, and Roya Maboudian

Appl. Phys. Lett. 95, 101901 (2009); http://dx.doi.org/10.1063/1.3224895 (3 pages) | Cited 3 times

Online Publication Date: 8 September 2009

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The growth of cubic silicon carbide films with tunable porosity is demonstrated on Si(100) using a single precursor, methyltrichlorosilane, chemical vapor deposition process in the temperature range of 950–1200 °C. The pore size varies in the range from 250 nm to 2 μm and it is controlled by the growth temperature and the details of hydrogen introduction during substrate heating stage. It is proposed that silicon outdiffusion from substrate combined with hydrogen chloride production and adsorption on the surface at high temperature may be responsible for the porous films thus produced.
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68.55.ag Semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.43.Gt Powders, porous materials
68.35.Fx Diffusion; interface formation
68.43.-h Chemisorption/physisorption: adsorbates on surfaces
81.05.Rm Porous materials; granular materials

Crystallization kinetics in electron-beam evaporated amorphous silicon on ZnO:Al-coated glass for thin film solar cells

T. Sontheimer, C. Becker, U. Bloeck, S. Gall, and B. Rech

Appl. Phys. Lett. 95, 101902 (2009); http://dx.doi.org/10.1063/1.3222917 (3 pages) | Cited 17 times

Online Publication Date: 8 September 2009

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To systematically study the crystallization process of electron-beam evaporated amorphous silicon on ZnO:Al-coated glass for polycrystalline silicon thin film solar cells, transmission electron microscopy and optical microscopy were employed. A time and temperature dependent analysis allowed the individual investigation of the growth and nucleation processes. The growth velocities of Si-crystals on ZnO:Al and SiN-coated glass were found to be identical within the investigated temperature regime of 500–600 °C. However, with a high steady state nucleation rate and a low activation energy, the nucleation process of Si on ZnO:Al-coated glass has shown to differ significantly from nucleation on glass.
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64.70.K- Solid-solid transitions
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder
64.60.Q- Nucleation
61.80.Fe Electron and positron radiation effects

Effects of film dimension on the phase transformation behavior of NiTi thin films

Xu Huang and A. G. Ramirez

Appl. Phys. Lett. 95, 101903 (2009); http://dx.doi.org/10.1063/1.3226104 (3 pages) | Cited 2 times

Online Publication Date: 8 September 2009

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This letter demonstrates the role of film geometry on the phase transformation and shape memory behaviors of NiTi thin films. Lithographically patterned lines possess a strain profile that significantly alters their phase transformation behavior and surface morphology in comparison to continuous films, although the microstructures remain the same. The stress profile causes the film curvature to change with direction: concave parallel to the line and convex when perpendicular. Additionally, patterned lines require higher temperature excursions for complete phase transformations; their transformation temperature interval doubled that of the continuous film. Such observations illuminate how microelectromechanical system embodiments of these materials may behave.
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81.30.Kf Martensitic transformations
64.70.kd Metals and alloys
85.40.Hp Lithography, masks and pattern transfer
68.35.B- Structure of clean surfaces (and surface reconstruction)
07.10.Cm Micromechanical devices and systems
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
68.55.-a Thin film structure and morphology
81.40.Lm Deformation, plasticity, and creep
62.20.fg Shape-memory effect; yield stress; superelasticity

Local electroluminescence and time-resolved photoluminescence study of InGaN light-emitting diodes

Grigory A. Onushkin, Sang-Su Hong, Jin-Hyun Lee, June-Sik Park, Joong-Kon Son, Min-Ho Kim, and YongJo Park

Appl. Phys. Lett. 95, 101904 (2009); http://dx.doi.org/10.1063/1.3224896 (3 pages) | Cited 2 times

Online Publication Date: 9 September 2009

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Uniformity of luminescence properties in blue InGaN light-emitting diodes has been studied and analyzed by local time-resolved photoluminescence and microelectroluminescence measurements at different biasing. For studied structures, some nonuniform distribution of photoluminescence properties has been observed at reverse biasing conditions. This nonuniformity revealed inhomogeneous distribution of electric field over the active region. It is supposed that nonuniform distribution of acceptors concentration in p-GaN is a source of electric field fluctuations. Microelectroluminescence measurements showed that areas with locally lower acceptor concentration in p-GaN layer emit lower electroluminescence intensity. This was caused by limited hole injection efficiency into multiple quantum wells region at high current.
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85.60.Jb Light-emitting devices
78.60.Fi Electroluminescence
78.55.Cr III-V semiconductors
78.47.jd Time resolved luminescence
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.80.Ey III-V and II-VI semiconductors

Surfactant effect of arsenic doping on modification of ZnO (0001) growth kinetics

J. D. Ye, S. T. Tan, S. Pannirselvam, S. F. Choy, X. W. Sun, G. Q. Lo, and K. L. Teo

Appl. Phys. Lett. 95, 101905 (2009); http://dx.doi.org/10.1063/1.3226105 (3 pages) | Cited 8 times

Online Publication Date: 9 September 2009

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The effect of arsenic doping on the growth kinetics of ZnO during metalorganic vapor phase epitaxy has been investigated. Arsenic was found to segregate to the growth surface and facilitate layer-by-layer growth. Such surfactant enhances the lateral expansion of the terraces preferential along [mathmath20] direction and also reduces the screw lattice distortion. Arsenic is expected to reduce the total surface energy and diffusion barrier of oxygen adatoms, hence producing Zn-rich surface condition on the growth front, in which two-dimensional growth is thermodynamically and kinetically favored. The origin of tiny hexagonal pits formed on the wide terrace is discussed in terms of the modified step-bunching mechanism.
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81.05.Hd Other semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.55.ag Semiconductors
61.72.uj III-V and II-VI semiconductors
64.75.Qr Phase separation and segregation in semiconductors
64.75.St Phase separation and segregation in thin films

Modeling deformation behavior of Cu–Zr–Al bulk metallic glass matrix composites

S. Pauly, G. Liu, G. Wang, J. Das, K. B. Kim, U. Kühn, D. H. Kim, and J. Eckert

Appl. Phys. Lett. 95, 101906 (2009); http://dx.doi.org/10.1063/1.3222973 (3 pages) | Cited 15 times

Online Publication Date: 9 September 2009

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In the present work we prepared an in situ Cu47.5Zr47.5Al5 bulk metallic glass matrix composite derived from the shape memory alloy CuZr. We use a strength model, which considers percolation and a three-microstructural-element body approach, to understand the effect of the crystalline phase on the yield stress and the fracture strain under compressive loading, respectively. The intrinsic work-hardenability due to the martensitic transformation of the crystalline phase causes significant work hardening also of the composite material.
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62.20.F- Deformation and plasticity
81.40.Lm Deformation, plasticity, and creep
81.30.Kf Martensitic transformations
64.70.kj Glasses
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
62.20.mm Fracture
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure

Combinatorial investigation of (Ti1−xNbx)2AlC

T. H. Scabarozi, C. Gennaoui, J. Roche, T. Flemming, K. Wittenberger, P. Hann, B. Adamson, A. Rosenfeld, M. W. Barsoum, J. D. Hettinger, and S. E. Lofland

Appl. Phys. Lett. 95, 101907 (2009); http://dx.doi.org/10.1063/1.3207748 (3 pages) | Cited 4 times

Online Publication Date: 9 September 2009

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We have synthesized thin films of (Ti1−xNbx)2AlC by combinatorial method on TiC (111) seed layers grown on c-axis sapphire (Al2O3) substrates at 900 °C using magnetron sputter. X-ray diffraction showed the films to be c-axis oriented and epitaxial, and films contained a minor secondary phase of (Ti,Nb)C, irrespective of stoichiometry. Most notably, Raman spectroscopy suggest a sizable increase in the elastic modulus in the Nb-rich region as compared to either of the end members.
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78.30.Hv Other nonmetallic inorganics
78.66.Nk Insulators
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.de Elastic moduli
68.60.Bs Mechanical and acoustical properties
68.55.Nq Composition and phase identification
81.15.Cd Deposition by sputtering

Formation and incorporation of SiF4 molecules in F-implanted preamorphized Si

D. De Salvador, G. Bisognin, E. Napolitani, M. Mastromatteo, N. Baggio, A. Carnera, F. Boscherini, G. Impellizzeri, S. Mirabella, S. Boninelli, F. Priolo, and F. Cristiano

Appl. Phys. Lett. 95, 101908 (2009); http://dx.doi.org/10.1063/1.3216806 (3 pages) | Cited 5 times

Online Publication Date: 9 September 2009

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The local structure of fluorine incorporated in crystalline silicon following solid phase epitaxial regrowth was investigated by means of x-ray absorption spectroscopy at the F K-edge. We clearly demonstrate that most F is found in SiF4 molecules in the crystalline matrix. A kinetic pathway, which explains our observation and which is also able to rationalize previous results in a common and coherent framework, is proposed.
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61.72.uf Ge and Si
33.20.Rm X-ray spectra
78.70.Dm X-ray absorption spectra

Influence of crystal quality of underlying GaN buffer on the formation and optical properties of InGaN/GaN quantum dots

S. C. Davies, D. J. Mowbray, Q. Wang, F. Ranalli, and T. Wang

Appl. Phys. Lett. 95, 101909 (2009); http://dx.doi.org/10.1063/1.3224897 (3 pages) | Cited 4 times

Online Publication Date: 10 September 2009

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A study of InGaN quantum dots (QDs) grown on two different GaN templates—GaN growth using a conventional two-step approach and growth using our recently developed high temperature (HT) AlN as a buffer—is reported. The HT AlN buffer leads to a significant reduction in the dislocation density, particularly screw dislocations, in subsequently deposited GaN. This reduction is confirmed by a significant decrease in the (0002) x-ray diffraction rocking curve width. The GaN on the HT AlN buffer leads to a high density (1010/cm2) of InGaN QDs, whereas in contrast InGaN QDs on the conventional GaN layer grown using the two-step approach have a much smaller density ( ∼ 108/cm2). Furthermore, the carrier lifetimes for the QDs on the GaN/HT AlN have been found to be up to nine times longer than those for the QDs on the conventional GaN.
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78.67.Hc Quantum dots
81.07.Ta Quantum dots
68.55.ag Semiconductors
68.65.Hb Quantum dots (patterned in quantum wells)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
73.61.Ey III-V semiconductors
78.55.Cr III-V semiconductors
81.05.Ea III-V semiconductors
78.66.Fd III-V semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.63.Kv Quantum dots

Effect of inserted ultrathin barrier layer on luminescence of GaN/Al0.5Ga0.5N multiple quantum wells

Young S. Park, Tae W. Kang, Yongmin Kim, and Hyunsik Im

Appl. Phys. Lett. 95, 101910 (2009); http://dx.doi.org/10.1063/1.3226107 (3 pages) | Cited 1 time

Online Publication Date: 10 September 2009

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report that luminescence properties in GaN/Al0.5Ga0.5N multiquantum wells (multi-QWs) are tailored by inserting an ultrathin Al0.5Ga0.5N layer ( ∼ 5 Å) in the middle of QWs. The inserted layer causes a dramatic redshift in photoluminescence and cathodeluminescence because of a huge piezoelectric polarization due to the additional strain along the growth direction. Quantitative analysis on the effects of the ultrathin inserted layer on the luminescence properties is performed using self-consistent Schrödinger–Poisson band profile calculations.
Show PACS
78.67.De Quantum wells
77.22.Ej Polarization and depolarization
78.60.Fi Electroluminescence
73.21.Fg Quantum wells
78.55.Cr III-V semiconductors
68.55.ag Semiconductors
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