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4 Apr 2011

Volume 98, Issue 14, Articles (14xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 98, 141903 (2011); http://dx.doi.org/10.1063/1.3548546 (3 pages)

H. Hattab, A. T. N’Diaye, D. Wall, G. Jnawali, J. Coraux, C. Busse, R. van Gastel, B. Poelsema, T. Michely, F.-J. Meyer zu Heringdorf, and M. Horn-von Hoegen
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Two-dimensional broadband distributed-feedback quantum cascade laser arrays

Elvis Mujagić, Clemens Schwarzer, Yu Yao, Jianxin Chen, Claire Gmachl, and Gottfried Strasser

Appl. Phys. Lett. 98, 141101 (2011); http://dx.doi.org/10.1063/1.3574555 (3 pages) | Cited 6 times

Online Publication Date: 4 April 2011

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We present two-dimensional broadband quantum cascade laser arrays based on distributed-feedback (DFB) ring cavity surface emitting lasers. The 16-element arrays exhibit a linear tuning range of 180 cm−1 centered at a wavelength of 8.2 μm when operated in pulsed mode at room temperature. The devices show single-mode emission with a side mode suppression ratio of 30 dB. Given by the facetless nature of the single emitters, the spectral dependent threshold current densities and optical power reflect the gain profile of the incorporated material and are not impaired by the diversity of underlying DFB designs.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.Fc Modulation, tuning, and mode locking

Band-edge and random lasing in paintable liquid crystal emulsions

P. J. W. Hands, D. J. Gardiner, S. M. Morris, C. Mowatt, T. D. Wilkinson, and H. J. Coles

Appl. Phys. Lett. 98, 141102 (2011); http://dx.doi.org/10.1063/1.3574915 (3 pages) | Cited 8 times

Online Publication Date: 4 April 2011

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Lasing mechanisms within paintable dye-doped chiral liquid crystal emulsions are investigated. Evidence shows that by variation in liquid crystal droplet size, by simple control of mechanical mixing speeds, a change in the lasing mechanism from band-edge lasing (large droplets) to diffuse nonresonant random lasing (small droplets) can be facilitated. This approach represents a facile technique for the variation in lasing mechanism, within a self-organizing, flexible, and conformable system, and offers the opportunity of developing controllable linewidth laser sources.
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42.55.Mv Dye lasers
42.55.Zz Random lasers
42.60.By Design of specific laser systems
42.70.Hj Laser materials
42.70.Df Liquid crystals

Electrochemically tunable ultrafast optical response of graphene oxide

Ulaş Kürüm, Okan Öner Ekiz, H. Gul Yaglioglu, Ayhan Elmali, Mustafa Ürel, Hasan Güner, Alpay Koray Mızrak, Bülend Ortaç, and Aykutlu Dâna

Appl. Phys. Lett. 98, 141103 (2011); http://dx.doi.org/10.1063/1.3573797 (3 pages) | Cited 4 times

Online Publication Date: 5 April 2011

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We demonstrate reversible and irreversible changes in the ultrafast optical response of multilayer graphene oxide thin films upon electrical and optical stimulus. The reversible effects are due to electrochemical modification of graphene oxide, which allows tuning of the optical response by externally applied bias. Increasing the degree of reduction in graphene oxide causes excited state absorption to gradually switch to saturable absorption for shorter probe wavelengths. Spectral and temporal properties as well as the sign of the ultrafast response can be tuned either by changing the applied bias or exposing to high intensity femtosecond pulses.
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78.47.J- Ultrafast spectroscopy (<1 psec)
78.67.Wj Optical properties of graphene
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
78.40.Ri Fullerenes and related materials
82.45.-h Electrochemistry and electrophoresis

Extreme ultraviolet detection using AlGaN-on-Si inverted Schottky photodiodes

Pawel E. Malinowski, Jean-Yves Duboz, Piet De Moor, Kyriaki Minoglou, Joachim John, Sara Martin Horcajo, Fabrice Semond, Eric Frayssinet, Peter Verhoeve, Marco Esposito, Boris Giordanengo, Ali BenMoussa, Robert Mertens, and Chris Van Hoof

Appl. Phys. Lett. 98, 141104 (2011); http://dx.doi.org/10.1063/1.3576914 (3 pages) | Cited 4 times

Online Publication Date: 5 April 2011

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We report on the fabrication of aluminum gallium nitride (AlGaN) Schottky diodes for extreme ultraviolet (EUV) detection. AlGaN layers were grown on silicon wafers by molecular beam epitaxy with the conventional and inverted Schottky structure, where the undoped, active layer was grown before or after the n-doped layer, respectively. Different current mechanisms were observed in the two structures. The inverted Schottky diode was designed for the optimized backside sensitivity in the hybrid imagers. A cut-off wavelength of 280 nm was observed with three orders of magnitude intrinsic rejection ratio of the visible radiation. Furthermore, the inverted structure was characterized using a EUV source based on helium discharge and an open electrode design was used to improve the sensitivity. The characteristic He I and He II emission lines were observed at the wavelengths of 58.4 nm and 30.4 nm, respectively, proving the feasibility of using the inverted layer stack for EUV detection.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
85.30.Kk Junction diodes
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Influence of defects and interface on radiative transition of Ge

S.-R. Jan, C.-Y. Chen, C.-H. Lee, S.-T. Chan, K.-L. Peng, C. W. Liu, Y. Yamamoto, and B. Tillack

Appl. Phys. Lett. 98, 141105 (2011); http://dx.doi.org/10.1063/1.3571439 (3 pages) | Cited 4 times

Online Publication Date: 5 April 2011

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The influences of defects and surface roughness on the indirect bandgap radiative transition of Ge were studied. Bulk Ge has 15 times the integrated intensity of photoluminescence of Ge-on-Si. However, for Ge-on-Si sample, the direct transition related photoluminescence intensity is higher than the indirect transition related one. We affirm that the defects in the Ge-on-Si are responsible for the weak indirect transition and relatively strong direct transition. The scattering of electrons by roughness at Ge/oxide interface can provide extra momentum of the indirect band transition of Ge, and thus enhance the indirect radiative transition.
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68.35.bg Semiconductors
71.20.Mq Elemental semiconductors
78.55.Ap Elemental semiconductors
68.35.Ct Interface structure and roughness
68.47.Fg Semiconductor surfaces

Observation and characterization of mode splitting in microsphere resonators in aquatic environment

Woosung Kim, Şahin Kaya Özdemir, Jiangang Zhu, and Lan Yang

Appl. Phys. Lett. 98, 141106 (2011); http://dx.doi.org/10.1063/1.3571555 (3 pages) | Cited 6 times

Online Publication Date: 5 April 2011

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Whispering gallery mode (WGM) optical resonators utilizing resonance shift (RS) and mode splitting (MS) techniques have emerged as highly sensitive platforms for label-free detection of nanoscale objects. RS method has been demonstrated in various resonators in air and liquid. MS in microsphere resonators has not been achieved in aqueous environment up to date, despite its demonstration in microtoroid resonators. Here, we demonstrate scatterer-induced MS of WGMs in microsphere resonators in water. We determine the size range of particles that induces MS in a microsphere in water as a function of resonator mode volume and quality factor. The results are confirmed by the experimental observations.
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42.79.-e Optical elements, devices, and systems

Real time achromatic measurement of space-variant polarizations

Moti Fridman, Eran Grinvald, Amit Godel, Micha Nixon, Asher A. Friesem, and Nir Davidson

Appl. Phys. Lett. 98, 141107 (2011); http://dx.doi.org/10.1063/1.3575567 (3 pages)

Online Publication Date: 7 April 2011

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A compact configuration for real-time achromatic measurements of space-variant light polarization is presented. The experimental results reveal that the full state of polarization at each location within a light beam or at each wavelength can be obtained with accuracy of over π/18.
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42.25.Ja Polarization
07.60.-j Optical instruments and equipment

Microspectroscopy of ultrafast laser inscribed channel waveguides in Yb:tungstate crystals

F. M. Bain, W. F. Silva, A. A. Lagatsky, R. R. Thomson, N. D. Psaila, A. K. Kar, W. Sibbett, D. Jaque, and C. T. A. Brown

Appl. Phys. Lett. 98, 141108 (2011); http://dx.doi.org/10.1063/1.3573999 (3 pages) | Cited 1 time

Online Publication Date: 7 April 2011

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We report microspectroscopy measurements of crystalline channel waveguides fabricated in Yb:KGd(WO4)2 and Yb:KY(WO4)2 using the ultrafast laser inscription technique. From these measurements we find that densification of the WO2W bridge in the double tungstate crystal lattice is responsible for the refractive index increase, which creates the waveguide confinement. We identified that shifts toward lower energies in the ∼ 760 cm−1 Raman mode indicate regions, which guide light polarized along the crystallographic b axis, while higher energy shifts in the 682 and 898 cm−1 Raman lines correspond to guiding regions for light polarized along the crystallographic a axis.
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42.79.Gn Optical waveguides and couplers
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.62.-b Laser applications
78.30.Hv Other nonmetallic inorganics

Laser-excited acoustical phonons probed by ultrashort pulses from a laser-driven x-ray diode

K. S. Schulze, T. Kämpfer, I. Uschmann, S. Höfer, R. Loetzsch, and E. Förster

Appl. Phys. Lett. 98, 141109 (2011); http://dx.doi.org/10.1063/1.3577605 (3 pages) | Cited 1 time

Online Publication Date: 7 April 2011

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We demonstrate that an ultrashort-pulse laser-driven x-ray diode can be used for time-resolved experiments on a picosecond timescale. Hence, acoustical phonons in germanium are observed after ultrashort laser-excitation and the results are compared with calculations according to a microphysical model. We also show the advantages of this kind of picosecond x-ray source compared to other sources on the basis of its properties.
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63.20.-e Phonons in crystal lattices
42.62.-b Laser applications

Plasma structures for quasiphase matched high harmonic generation

A. H. Sheinfux, Z. Henis, M. Levin, and A. Zigler

Appl. Phys. Lett. 98, 141110 (2011); http://dx.doi.org/10.1063/1.3578407 (3 pages) | Cited 2 times

Online Publication Date: 7 April 2011

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A scheme for creation of periodic plasma structures by ablating a lithographic pattern is demonstrated. A proof of principle experiment was conducted, and plasma parameters were measured as a function of time with spatial resolution <10 and 100 μm periodicity. Several possible applications, in particular, quasiphase matching for high harmonic generation in plasma are considered.
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52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.38.Mf Laser ablation
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.75.-d Plasma devices

Controlling fluorescence from N2 inside femtosecond laser filaments in air by two-color laser pulses

H. L. Xu, A. Azarm, and S. L. Chin

Appl. Phys. Lett. 98, 141111 (2011); http://dx.doi.org/10.1063/1.3579246 (3 pages) | Cited 2 times

Online Publication Date: 8 April 2011

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We experimentally demonstrate the feasibility of controlling the fluorescence emission of nitrogen molecules in air induced by femtosecond laser filamentation by using a pump-probe method. An obvious enhancement or reduction in the filament-induced fluorescence signals of nitrogen molecules can be realized when a blue (400 nm) or an infrared (1338 nm) laser pulse is used as the probe. The completely opposite effect is ascribed to the excitation enhancement of ionization and population trapping of some highly excited states including Rydberg states of nitrogen molecules.
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33.50.Dq Fluorescence and phosphorescence spectra
33.80.Be Level crossing and optical pumping
37.10.Vz Mechanical effects of light on atoms, molecules, and ions

Directed self-assembly of InAs quantum dots on nano-oxide templates

N. L. Dias, A. Garg, U. Reddy, J. D. Young, V. B. Verma, R. P. Mirin, and J. J. Coleman

Appl. Phys. Lett. 98, 141112 (2011); http://dx.doi.org/10.1063/1.3579253 (3 pages) | Cited 2 times

Online Publication Date: 8 April 2011

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We describe the growth and characterization of InAs quantum dots on SiO2 patterned GaAs by metal organic chemical vapor deposition. Arrays of quantum dots with densities as high as 1.8×1010 cm−2 fabricated by electron beam lithography are demonstrated. A process consisting of dry and wet etching to minimize etch damage is developed. As the mask diameter increases, the nucleation transitions from single dots to multidot clusters. We achieve more uniform size and shape distributions of dots on patterned regions relative to unpatterned dots as revealed by structural characterization and room temperature photoluminescence emission spectra.
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81.07.Ta Quantum dots
81.16.Dn Self-assembly
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
68.65.Hb Quantum dots (patterned in quantum wells)
78.55.Cr III-V semiconductors
81.05.Ea III-V semiconductors
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Simulation of streamers propagating along helium jets in ambient air: Polarity-induced effects

G. V. Naidis

Appl. Phys. Lett. 98, 141501 (2011); http://dx.doi.org/10.1063/1.3576940 (3 pages) | Cited 9 times

Online Publication Date: 4 April 2011

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Results of modeling of streamer propagation along helium jets for both positive and negative polarities of applied voltage are presented. Obtained patterns of streamer dynamics and structure in these two cases are similar to those observed in experiments with plasma jets.
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52.80.-s Electric discharges
52.75.-d Plasma devices
52.65.-y Plasma simulation

Time-resolved gas temperature evolution in pulsed Ar–N2 microwave discharge

Nikolay Britun, Thomas Godfroid, Stephanos Konstantinidis, and Rony Snyders

Appl. Phys. Lett. 98, 141502 (2011); http://dx.doi.org/10.1063/1.3576928 (3 pages)

Online Publication Date: 6 April 2011

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Temporal evolution of the gas temperature (Tg) in a pulsed microwave surfaguide discharge is studied by measuring the N2 rotational temperature. We found that at high power applied per pulse, gas temperature grows linearly, and saturates after about 150 μs. This effect is absent at low power values, or at short pulse durations. Observed Tg behavior correlates with time-resolved measurements of the N2 vibrational temperature, as well as with N emission lines. Consequently, Tg time behavior was related to N atoms production in plasma. Using obtained Tg growth rates, the effective power used for plasma heating is determined.
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52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.80.Pi High-frequency and RF discharges
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.50.Sw Plasma heating by microwaves; ECR, LH, collisional heating

Direct thrust measurement of a permanent magnet helicon double layer thruster

K. Takahashi, T. Lafleur, C. Charles, P. Alexander, R. W. Boswell, M. Perren, R. Laine, S. Pottinger, V. Lappas, T. Harle, and D. Lamprou

Appl. Phys. Lett. 98, 141503 (2011); http://dx.doi.org/10.1063/1.3577608 (3 pages) | Cited 8 times

Online Publication Date: 7 April 2011

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Direct thrust measurements of a permanent magnet helicon double layer thruster have been made using a pendulum thrust balance and a high sensitivity laser displacement sensor. At the low pressures used (0.08 Pa) an ion beam is detected downstream of the thruster exit, and a maximum thrust force of about 3 mN is measured for argon with an rf input power of about 700 W. The measured thrust is proportional to the upstream plasma density and is in good agreement with the theoretical thrust based on the maximum upstream electron pressure.
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52.75.Di Ion and plasma propulsion
52.25.-b Plasma properties
52.40.Kh Plasma sheaths
52.70.Gw Radio-frequency and microwave measurements
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Universal stress-defect correlation at (100)semiconductor/oxide interfaces

M. Houssa, M. Scarrozza, G. Pourtois, V. V. Afanas’ev, and A. Stesmans

Appl. Phys. Lett. 98, 141901 (2011); http://dx.doi.org/10.1063/1.3575559 (3 pages) | Cited 2 times

Online Publication Date: 4 April 2011

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Interface models between various group IV and III-V (100)semiconductors and their oxides are generated from first-principles molecular dynamics simulations. The tensile strain at the interface (from the semiconductor side) is estimated, by comparing bond lengths at/near the interface and in the bulk semiconductor phase. A linear relationship between the calculated interface stress and the density of interface defects observed at such interfaces is revealed. These results suggest that the interface stress due to the volume mismatch between the semiconductor and its oxide likely plays an important role in the creation of interface defects. These findings can explain recent results pertaining to the passivation of various high-mobility channels for their integration in high-performance metal-oxide-semiconductor field-effect transistors.
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68.35.Ct Interface structure and roughness
68.35.Gy Mechanical properties; surface strains

Temperature dependence of single twin boundary motion in Ni–Mn–Ga martensite

L. Straka, H. Hänninen, and O. Heczko

Appl. Phys. Lett. 98, 141902 (2011); http://dx.doi.org/10.1063/1.3573860 (3 pages) | Cited 10 times

Online Publication Date: 4 April 2011

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Magnetic-field-induced reorientation in Ni–Mn–Ga five-layered martensite (10 M) mediated by the motion of single twin boundary was evaluated from magnetization measurements between 20 and 300 K. At 300 K, the single twin boundary moved in an exceptionally small field of 25 kA/m. Twinning stress, as a measure of the twin boundary mobility, was determined from the magnetization curves using a magnetic-energy-based model; it increased from ≈0.1 MPa at 300 K to ≈0.8 MPa at 20 K. The dependence is discussed in terms of thermal activation and the effect of intermartensitic transformation is considered.
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61.72.Mm Grain and twin boundaries
64.70.kd Metals and alloys
81.30.Kf Martensitic transformations
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Cc Other ferromagnetic metals and alloys

Growth temperature dependent graphene alignment on Ir(111)

H. Hattab, A. T. N’Diaye, D. Wall, G. Jnawali, J. Coraux, C. Busse, R. van Gastel, B. Poelsema, T. Michely, F.-J. Meyer zu Heringdorf, and M. Horn-von Hoegen

Appl. Phys. Lett. 98, 141903 (2011); http://dx.doi.org/10.1063/1.3548546 (3 pages) | Cited 5 times

Online Publication Date: 4 April 2011

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The morphology of graphene monolayers on Ir(111) prepared by thermal decomposition of ethylene between 1000 and 1530 K was studied with high resolution low energy electron diffraction. In addition to a well-oriented epitaxial phase, randomly oriented domains are observed for growth temperatures between 1255 and 1460 K. For rotational angles of ±3° around 30° these domains lock-in in a 30° oriented epitaxial phase. Below 1200 K the graphene layer exhibits high disorder and structural disintegrity. Above 1500 K the clear moiré spots reflect graphene in a single orientation epitaxial incommensurate phase.
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68.55.-a Thin film structure and morphology
81.05.ue Graphene

Doping-type dependence of phonon dephasing dynamics in Si

Keiko Kato, Katsuya Oguri, Atsushi Ishizawa, Kouta Tateno, Takehiko Tawara, Hideki Gotoh, Masahiro Kitajima, Hidetoshi Nakano, and Tetsuomi Sogawa

Appl. Phys. Lett. 98, 141904 (2011); http://dx.doi.org/10.1063/1.3574533 (3 pages) | Cited 1 time

Online Publication Date: 5 April 2011

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We studied the dephasing dynamics of coherent phonons in n-type, p-type, and intrinsic Si using time-resolved reflectivity measurements with sub-10 fs laser pulses. The dephasing time of the coherent phonons increases (decreases) for n-type (p-type) doping compared with that of intrinsic Si, while the frequencies of the coherent phonons exhibit a redshift for both types of doping. These doping-induced changes in the coherent phonon dynamics are observed when the carrier concentration exceeds 1019 cm−3. The doping-type dependent changes in the dephasing time are attributed to the interconduction and intervalence band transitions in n-type and p-type Si, respectively.
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61.72.U- Doping and impurity implantation
78.47.D- Time resolved spectroscopy (>1 psec)
78.47.jg Time resolved reflection spectroscopy
71.20.Mq Elemental semiconductors
78.47.db Conduction electrons

Spontaneous formation of highly regular superlattice structure in InGaN epilayers grown by molecular beam epitaxy

Z. H. Wu, Y. Kawai, Y.-Y. Fang, C. Q. Chen, H. Kondo, M. Hori, Y. Honda, M. Yamaguchi, and H. Amano

Appl. Phys. Lett. 98, 141905 (2011); http://dx.doi.org/10.1063/1.3574607 (3 pages) | Cited 1 time

Online Publication Date: 5 April 2011

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In this letter, we have investigated the structural properties of thick InGaN layers grown on GaN by plasma-assisted molecular beam epitaxy, using two growth rates of 1.0 and 3.6 Å/s. A highly regular superlattice (SL) structure is found to be spontaneously formed in the film grown at 3.6 Å/s but not in the film grown at 1.0 Å/s. The faster grown film also exhibits superior structural quality, which could be due to the surface roughness suppression caused by kinetic limitation, and the inhibition of the Frank–Read dislocation generation mechanism within the spontaneously formed SL structure.
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81.05.Ea III-V semiconductors
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
68.65.Cd Superlattices
68.55.ag Semiconductors
68.35.bg Semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Type II detwinning in NiTi

Tawhid Ezaz and Huseyin Sehitoglu

Appl. Phys. Lett. 98, 141906 (2011); http://dx.doi.org/10.1063/1.3574775 (3 pages) | Cited 8 times

Online Publication Date: 5 April 2011

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Shape memory effect in nickel-titanium (NiTi) alloys depends on phase transformation between two phases and growth of twin variants in martensite called detwinning. An outstanding issue regarding detwinning in NiTi has been the lack of fundamental understanding of its mechanism at the atomistic level. The present article resolves this issue via first-principles energetics calculations of twin nucleation and growth. Our results based on ion relaxation and valence charge distribution point to a distinct energy barrier during detwinning process and the mechanism is mediated by a complex conjunction of shear and shuffle.
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61.72.Mm Grain and twin boundaries
64.70.kd Metals and alloys
62.20.fg Shape-memory effect; yield stress; superelasticity
81.30.Kf Martensitic transformations

Influence of Mn dopants on InAs/GaAs quantum dot electronic states

V. D. Dasika, A. V. Semichaevsky, J. P. Petropoulos, J. C. Dibbern, A. M. Dangelewicz, M. Holub, P. K. Bhattacharya, J. M. O. Zide, H. T. Johnson, and R. S. Goldman

Appl. Phys. Lett. 98, 141907 (2011); http://dx.doi.org/10.1063/1.3567510 (3 pages) | Cited 2 times

Online Publication Date: 6 April 2011

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We have investigated the influence of Mn dopants on the electronic states in the vicinity of InAs/GaAs quantum dots (QDs) and the surrounding GaAs matrix. A comparison of cross-sectional scanning tunneling microscopy, scanning tunneling spectroscopy, and tight binding calculations of the local density of states reveals that the Mn dopants primarily influence the electronic states at the QD edges and the surrounding GaAs matrix. These results suggest that the Mn dopants reside at the QD edge, consistent with the predictions of a thermodynamic model for the nanoscale-size dependence of dopant incorporation in nanostructures.
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81.05.Ea III-V semiconductors
81.07.Ta Quantum dots
73.21.La Quantum dots
71.15.Ap Basis sets (LCAO, plane-wave, APW, etc.) and related methodology (scattering methods, ASA, linearized methods, etc.)

High resolution cathodoluminescence hyperspectral imaging of surface features in InGaN/GaN multiple quantum well structures

Jochen Bruckbauer, Paul R. Edwards, Tao Wang, and Robert W. Martin

Appl. Phys. Lett. 98, 141908 (2011); http://dx.doi.org/10.1063/1.3575573 (3 pages) | Cited 8 times

Online Publication Date: 6 April 2011

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InGaN/GaN multiple quantum wells (MQWs) have been studied by using cathodoluminescence hyperspectral imaging with high spatial resolution. Variations in peak emission energies and intensities across trenchlike features and V-pits on the surface of the MQWs are investigated. The MQW emission from the region inside trenchlike features is redshifted by approximately 45 meV and more intense than the surrounding planar regions of the sample, whereas emission from the V-pits is blueshifted by about 20 meV and relatively weaker. By employing this technique to the studied nanostructures it is possible to investigate energy and intensity shifts on a 10 nm length scale.
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78.60.Hk Cathodoluminescence, ionoluminescence
78.67.De Quantum wells
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Depth progression of dissociation reaction of the 1.014-eV photoluminescence copper center in copper-diffused silicon crystal measured by deep-level transient spectroscopy

Minoru Nakamura and Susumu Murakami

Appl. Phys. Lett. 98, 141909 (2011); http://dx.doi.org/10.1063/1.3575574 (3 pages) | Cited 3 times

Online Publication Date: 6 April 2011

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Changes in the concentration depth profiles of the 1.014-eV photoluminescence (PL) copper center and its dissociation product by annealing were measured by deep-level transient spectroscopy (DLTS). The transformation reaction between these centers by annealing was not homogeneous throughout; it started at the sample surface and extended deeper with increasing annealing time. From this finding, the precipitation of interstitial copper in the surface region and its out-diffusion in the bulk are analyzed as the underlying processes to dissociate the center. The origin of the difference in the dissociation energies of the center obtained by DLTS and PL measurements is discussed.
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71.55.Cn Elemental semiconductors
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
78.55.Ap Elemental semiconductors
81.05.Cy Elemental semiconductors
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
68.35.Fx Diffusion; interface formation
61.72.jj Interstitials
81.10.Dn Growth from solutions
81.10.Fq Growth from melts; zone melting and refining
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)

Role of microstructure in initiation of Ni–Al reactive multilayers

Joshua C. Crone, Jaroslaw Knap, Peter W. Chung, and Betsy M. Rice

Appl. Phys. Lett. 98, 141910 (2011); http://dx.doi.org/10.1063/1.3575576 (3 pages) | Cited 4 times

Online Publication Date: 6 April 2011

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Through molecular dynamics simulations, the effects of microstructure on reaction initiation are studied in nickel-aluminum (Ni–Al) reactive multilayers. Ni–Al multilayer systems of varying misfit strain and layer thickness are created and the ignition temperature is estimated by heating and thermalizing over small temperature increments until a reaction is observed. Results show that ignition temperatures drop significantly with increasing misfit strain. Our results indicate that the sensitivity of reactive multilayers can be controlled, in part, by microstructure, with changes of the order of 350 K.
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68.65.Ac Multilayers
81.40.Gh Other heat and thermomechanical treatments
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