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21 Jan 2008

Volume 92, Issue 3, Articles (03xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 92, 033101 (2008); http://dx.doi.org/10.1063/1.2830979 (3 pages)

Koichiro Zaitsu, Yosuke Kitamura, Keiji Ono, and Seigo Tarucha
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Green laser emission from monolithic II-VI-based pillar microcavities near room temperature

Carsten Kruse, Henning Lohmeyer, Kathrin Sebald, Jürgen Gutowski, Detlef Hommel, Jan Wiersig, and Frank Jahnke

Appl. Phys. Lett. 92, 031101 (2008); http://dx.doi.org/10.1063/1.2832644 (3 pages) | Cited 10 times

Online Publication Date: 22 January 2008

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We report on single-mode stimulated emission at a wavelength of 510 nm in monolithic high-Q ZnSe-based vertical-cavity surface-emitting laser (VCSEL) micropillars under optical excitation at 280 K. Calculations reveal the influence of polariton coupling and the dynamic detuning of the gain maximum to the cavity modes on the spectral characteristics of the VCSEL emission. In accordance with theory, we find a systematic decrease in threshold excitation energy for decreasing pillar diameter to a minimum value of 0.09 pJ for a pillar diameter of 1.2 μm as a combined effect of reduced active area and reduced mode volume in the microcavity lasers.
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42.55.Sa Microcavity and microdisk lasers
42.55.Px Semiconductor lasers; laser diodes
42.60.Fc Modulation, tuning, and mode locking
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

Color-converting combinations of nanocrystal emitters for warm-white light generation with high color rendering index

Sedat Nizamoglu, Gulis Zengin, and Hilmi Volkan Demir

Appl. Phys. Lett. 92, 031102 (2008); http://dx.doi.org/10.1063/1.2833693 (3 pages) | Cited 50 times

Online Publication Date: 22 January 2008

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Warm-white light emitting diodes with high color rendering indices are required for the widespread use of solid state lighting especially indoors. To meet these requirements, we propose and demonstrate warm-white hybrid light sources that incorporate the right color-converting combinations of CdSe/ZnS core-shell nanocrystals hybridized on InGaN/GaN LEDs for high color rendering index. Three sets of proof-of-concept devices are developed to generate high-quality warm-white light with (1) tristimulus coordinates (x,y) = (0.37,0.30), luminous efficacy (LE) = 307 lm/W, color rending index (CR) = 82.4, and correlated color temperature (CCT) = 3228 K; (2) (x,y) = (0.38,0.31), LE = 323 lm/W, CRI = 81.0, and CCT = 3190 K; and (3) (x,y) = (0.37,0.30), LE = 303 lm/W, CRI = 79.6, and CCT = 1982 K.
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42.72.-g Optical sources and standards
07.60.Dq Photometers, radiometers, and colorimeters
85.60.Jb Light-emitting devices

Overlap integral factor enhancement using buried electrode structure in polymer Mach-Zehnder modulator

Reem Song and William H. Steier

Appl. Phys. Lett. 92, 031103 (2008); http://dx.doi.org/10.1063/1.2827196 (3 pages) | Cited 6 times

Online Publication Date: 23 January 2008

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A buried coplanar waveguide (CPW) electrode for a polymer modulator is introduced in this letter. In this configuration, the electric and the optical fields are aligned and the overlap factor is enhanced. Thus, the poling efficiency can increase and Vπ decreases. Using two electro-optic polymers, Mach-Zehnder (MZ) modulators based on the buried electrode are demonstrated and compared to the in-plane CPW based MZ modulators. The measured Vπ’s of the buried CPW MZ’s are 6.7 and 4.3 V for CLD1 and AJL8 devices, respectively, which give the overlap×r33 products of 19 and 30 pm/V. This shows 20% improvement in the overlap×poling efficiency by using the buried electrode.
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07.60.Ly Interferometers
84.40.Az Waveguides, transmission lines, striplines
42.79.Hp Optical processors, correlators, and modulators
82.45.Fk Electrodes

Flexible metal grating based optical fiber probe for photonic integrated circuits

Stijn Scheerlinck, Dirk Taillaert, Dries Van Thourhout, and Roel Baets

Appl. Phys. Lett. 92, 031104 (2008); http://dx.doi.org/10.1063/1.2827589 (3 pages) | Cited 6 times

Online Publication Date: 23 January 2008

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An optical probe for photonic integrated circuits is proposed and demonstrated. The device is based on a single-mode fiber containing a subwavelength period metal grating on the facet. When approaching an integrated waveguide, light can be efficiently coupled between probe and waveguide without the need for integrated coupling structures, paving the way for wafer-scale circuit testing. A nanoimprint-and-transfer process were developed for fabricating this probe in a single step. We report 15% coupling efficiency between a gold grating fiber probe and a 220 nm×3 μm silicon-on-insulator waveguide and demonstrate testing of an integrated microring resonator using two probes.
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42.81.Pa Sensors, gyros
42.79.Dj Gratings
42.82.Et Waveguides, couplers, and arrays
42.82.Bq Design and performance testing of integrated-optical systems
42.82.Cr Fabrication techniques; lithography, pattern transfer
42.87.-d Optical testing techniques

A miniature tunable coupled-cavity laser constructed by micromachining technology

H. Cai, A. Q. Liu, X. M. Zhang, J. Tamil, D. Y. Tang, Q. X. Zhang, and C. Lu

Appl. Phys. Lett. 92, 031105 (2008); http://dx.doi.org/10.1063/1.2831912 (3 pages) | Cited 2 times

Online Publication Date: 23 January 2008

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This letter presents a miniature tunable coupled-cavity laser by integrating a Fabry-Pérot chip, a gain chip and a deep-etched parabolic mirror using micromachining technology. The mirror is to actively adjust the gap between chips, enabling the optimal mode selection. Single-mode operation with a tuning range of 16.55 nm and a side-mode-suppression ratio of >25.1 dB is demonstrated. The device overcomes phase mismatching and instability problems encountered in conventional fixed-gap coupled-cavity lasers.
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42.60.Fc Modulation, tuning, and mode locking
42.82.Cr Fabrication techniques; lithography, pattern transfer
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
42.82.-m Integrated optics

Wide-ridge metal-metal terahertz quantum cascade lasers with high-order lateral mode suppression

Jonathan A. Fan, Mikhail A. Belkin, Federico Capasso, Suraj P. Khanna, Mohamed Lachab, A. Giles Davies, and Edmund H. Linfield

Appl. Phys. Lett. 92, 031106 (2008); http://dx.doi.org/10.1063/1.2835202 (3 pages) | Cited 12 times

Online Publication Date: 23 January 2008

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Terahertz quantum cascade lasers with wide-ridge metal-metal waveguides are prone to lasing in high-order lateral modes, which reduce the maximum light output power from these devices. We have demonstrated, theoretically and experimentally, that the output power can be improved severalfold by introducing “side absorbers” into the waveguide structure, which enforce lasing in the TM00 mode with minor temperature performance deterioration. Lasers without side absorbers operate up to 168 K, a current record for devices processed using indium/gold wafer bonding.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Multiple exciton generation and electrical extraction from a PbSe quantum dot photoconductor

Sung Jin Kim, Won Jin Kim, Yudhisthira Sahoo, Alexander N. Cartwright, and Paras N. Prasad

Appl. Phys. Lett. 92, 031107 (2008); http://dx.doi.org/10.1063/1.2835920 (3 pages) | Cited 26 times

Online Publication Date: 23 January 2008

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Multiple exciton generation and subsequent electrical extraction from a thin film photoconductive device constructed from PbSe nanocrystal quantum dots are demonstrated. The hydrazine treatment of the PbSe film drastically improves the conductivity of the film while maintaining excellent optical and structural film quality. The effects of multiple exciton generation and electrical extraction (electrons collected per photon absorbed) were quantified as a function of incident photon energy from 1.55 to 3.1 eV. The multiple carrier extraction (>100%) was observed at photon energies greater than 2.8 times of the quantum dot bandgap with ∼ 210% measured at 4.4 times the bandgap.
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85.60.Bt Optoelectronic device characterization, design, and modeling

Rabi splitting and ac-Stark shift of a charged exciton

M. Kroner, C. Lux, S. Seidl, A. W. Holleitner, K. Karrai, A. Badolato, P. M. Petroff, and R. J. Warburton

Appl. Phys. Lett. 92, 031108 (2008); http://dx.doi.org/10.1063/1.2837193 (3 pages) | Cited 16 times

Online Publication Date: 23 January 2008

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The Rabi splitting of the negatively charged exciton in a single InGaAs quantum dot is observed in resonance transmission spectroscopy. We use a pump laser excitation to drive strongly the unpolarized trion transition in a quantum dot and detect its modified absorption spectrum with a second weak probe laser. By tuning the pump laser near resonance, we observe an ac-Stark effect dispersion, with a power dependent Rabi splitting on resonance, both signatures of a strongly coupled two level system. Although the pump and probe laser fields are resonant with the same transition, we do not observe all features in the Mollow spectrum. We combine the results of pump probe with saturation spectroscopy data to deduce the individual contributions to the low power linewidth.
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71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
71.35.Pq Charged excitons (trions)
78.67.Hc Quantum dots
78.20.Jq Electro-optical effects

A visual indication of environmental humidity using a color changing hologram recorded in a self-developing photopolymer

Izabela Naydenova, Raghavendra Jallapuram, Vincent Toal, and Suzanne Martin

Appl. Phys. Lett. 92, 031109 (2008); http://dx.doi.org/10.1063/1.2837454 (3 pages) | Cited 15 times

Online Publication Date: 23 January 2008

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A reflection hologram for visual indication of environmental humidity has been studied. The hologram is recorded in a self-developing photopolymer and changes color when exposed to a change in humidity and is fully reversible. The range of color change, reversibility, and the response time of the hologram have been studied in a controlled humidity environment. Fully reversible holograms with response times from few seconds to tens of minutes have been designed. Extremely sensitive bright visual humidity indicators, capable of dramatic color change within a few seconds of breathing on them are demonstrated.
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42.70.Jk Polymers and organics
42.70.Ln Holographic recording materials; optical storage media
42.40.My Applications

1000 nm tunable acousto-optic filter based on photonic crystal fiber

K. S. Hong, H. C. Park, B. Y. Kim, I. K. Hwang, W. Jin, J. Ju, and D. I. Yeom

Appl. Phys. Lett. 92, 031110 (2008); http://dx.doi.org/10.1063/1.2806198 (3 pages) | Cited 9 times

Online Publication Date: 25 January 2008

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We report an all-fiber acousto-optic tunable filter based on a two-mode photonic crystal fiber. The properties of photonic crystal fiber allow us to demonstrate a notch filter tunable from below 700 to 1700 nm with a single acoustic transducer. The extreme dynamic range coupled with small insertion loss and fast response time ( ∼ 100 μs) makes this device promising for ultrawideband optical systems.
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42.81.Wg Other fiber-optical devices
42.79.Ci Filters, zone plates, and polarizers
42.79.Jq Acousto-optical devices
43.38.Zp Acoustooptic and photoacoustic transducers
42.70.Qs Photonic bandgap materials
42.81.Dp Propagation, scattering, and losses; solitons

Limitation of the electromagnetic cloak with dispersive material

Peijun Yao, Zixian Liang, and Xunya Jiang

Appl. Phys. Lett. 92, 031111 (2008); http://dx.doi.org/10.1063/1.2814039 (3 pages) | Cited 23 times

Online Publication Date: 25 January 2008

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Based on causality, the limitation of the electromagnetic cloak with dispersive material is investigated in this letter. The results show that perfect invisibility cannot be achieved because of the dilemma that either the group velocity Vg diverges or a strong absorption is imposed on the cloaking material. It is an intrinsic conflict which originates from the demand of causality. However, the total cross section can really be reduced through the approach of coordinate transformation. A simulation of finite-difference time-domain method is performed to validate our analysis.
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41.20.Jb Electromagnetic wave propagation; radiowave propagation
02.70.Bf Finite-difference methods

The use of a deformable photonic crystal for millimeter-wave beam steering

Shawn-Yu Lin, Zu-Po Yang, Mingfeng Chen, James A. Bur, A. Levitan, and Lester H. Kosowsky

Appl. Phys. Lett. 92, 031112 (2008); http://dx.doi.org/10.1063/1.2837620 (3 pages) | Cited 2 times

Online Publication Date: 25 January 2008

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A deformable photonic band gap (PBG) material is theoretically proposed as a transmissive element for beam steering at 77 GHz. The deformation may be achieved by integrating microsprings (as spacers) into a one-dimensional PBG structure. This PBG material can produce a specific phase shift dependent on its spacer thickness. By varying the spacer thickness, we generate a continuous phase gradient across the element. Such a PBG device is experimentally realized, capable of beam deflection of up to ±15° and suitable for beam scanning for smart automobile radar application.
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42.70.Qs Photonic bandgap materials
42.60.-v Laser optical systems: design and operation

Design and fabrication of a line-defect bend sandwiched with air trenches in a photonic crystal platform

S. H. Tao, M. B. Yu, J. F. Song, Q. Fang, R. Yang, G. Q. Lo, and D. L. Kwong

Appl. Phys. Lett. 92, 031113 (2008); http://dx.doi.org/10.1063/1.2838337 (3 pages) | Cited 2 times

Online Publication Date: 25 January 2008

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A hybrid bend is designed and fabricated on the silicon-on-insulator system. The hybrid bend comprises a line-defect 120° bend sandwiched by double air trenches in a photonic crystal platform. The simulation and experimental results show that the hybrid bend has low insertion loss and large high-transmission bandwidth.
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42.79.Gn Optical waveguides and couplers
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Self-similar neutral-plasma isothermal expansion into a vacuum

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

Appl. Phys. Lett. 92, 031501 (2008); http://dx.doi.org/10.1063/1.2837455 (3 pages) | Cited 7 times

Online Publication Date: 23 January 2008

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The self-similar solutions are obtained for isothermal expansions of neutral plasmas into a vacuum. The classic solution given by Mora [Phys. Fluids 22, 12 (1979)] corresponds to a special case of our solution. Some special solutions have been pointed out by Gurevich et al. [Phys. Rev. Lett. 42, 769 (1979)] and observed by a lot of experiments. The formulation of ion velocity with respect to the acceleration time is proposed for the general solution, and the numerical result can be obtained easily. The electric field and ion velocity at the ion front have been achieved.
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52.25.Ya Neutrals in plasmas

Kinetics of reactive ion etching upon single-walled carbon nanotubes

Toshiaki Kato and Rikizo Hatakeyama

Appl. Phys. Lett. 92, 031502 (2008); http://dx.doi.org/10.1063/1.2837463 (3 pages) | Cited 8 times

Online Publication Date: 25 January 2008

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The remarkable etching reaction of single-walled carbon nanotubes (SWNTs) has been observed in their growth of the parameter-controlled plasma chemical vapor deposition (CVD). The time evolution study of the SWNTs growth leads to establishing a growth equation which can completely express the growth kinetics of SWNTs in the plasma CVD. The growth equation is found to reveal that there are several key parameters which directly affect the etching reaction of SWNTs. Furthermore, such kinetics of the SWNT etching in plasmas can perfectly be explained with a reactive ion etching model.
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81.07.De Nanotubes
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
52.77.Dq Plasma-based ion implantation and deposition
81.65.Cf Surface cleaning, etching, patterning

Effect of surface charge trapping on dielectric barrier discharge

Ming Li, Chengrong Li, Huamao Zhan, Jinbao Xu, and Xinxin Wang

Appl. Phys. Lett. 92, 031503 (2008); http://dx.doi.org/10.1063/1.2838340 (3 pages) | Cited 18 times

Online Publication Date: 25 January 2008

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The experiment of dielectric barrier discharge in a 2 mm air gap shows that the pressure range of a uniform discharge using polytetrafluoroethylene as barrier is much wider than that using quartz or alumina. The parameters of the charge trapped on the surface of these three dielectric barriers were obtained by surface charge measurement and thermally stimulated current measurement. It was found that surface charge trapping has much influence on the uniform discharge, i.e., the seed electrons necessary for uniform discharge may be produced by the desorption of the absorbed electrons in the shallow trap with energy level lower than 1 eV.
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52.80.-s Electric discharges
73.40.-c Electronic transport in interface structures
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Write and erase mechanisms for bulk metallic glass

Golden Kumar and Jan Schroers

Appl. Phys. Lett. 92, 031901 (2008); http://dx.doi.org/10.1063/1.2834712 (3 pages) | Cited 17 times

Online Publication Date: 22 January 2008

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Microfeatures are imprinted on Pt57.5Cu14.7Ni5.3P22.5 bulk metallic glass (BMG) using thermoplastic forming. Subsequent erasing is carried out by annealing in the supercooled liquid region. The driving force for the erasing process is the capillary force controlled by the curvature and surface tension of the liquid-vacuum surface. Sluggish crystallization kinetics in this alloy permit experimental observation at temperatures where the viscosity is sufficiently low to completely erase small surface features on a time scale smaller than the crystallization time. The kinetics of the writing and erasing processes suggest that BMGs may offer a viable alternative rewritable high-density data storage technology.
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81.40.Gh Other heat and thermomechanical treatments
81.40.Cd Solid solution hardening, precipitation hardening, and dispersion hardening; aging

Electron tomography of embedded semiconductor quantum dot

Tomoya Inoue, Takashi Kita, Osamu Wada, Mitsuru Konno, Toshie Yaguchi, and Takeo Kamino

Appl. Phys. Lett. 92, 031902 (2008); http://dx.doi.org/10.1063/1.2837453 (3 pages) | Cited 14 times

Online Publication Date: 23 January 2008

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We performed an electron tomography for a single InAs quantum dot (QD) embedded in GaAs. A comprehensive three-dimensional image of indium distribution has been reconstructed by using a high-angle annular dark-field scanning transmission electron microscope. This was achieved by using a special nanopillar specimen prepared by a focused ion beam technique. The real structure of the embedded single QD has been found to have a complicated anisotropic structure reflecting the QD structure before being capped.
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68.65.Hb Quantum dots (patterned in quantum wells)
61.46.-w Structure of nanoscale materials

The influence of metallic particle size on the mechanical properties of polytetraflouroethylene-Al–W powder composites

J. Cai, V. F. Nesterenko, K. S. Vecchio, F. Jiang, E. B. Herbold, D. J. Benson, J. W. Addiss, S. M. Walley, and W. G. Proud

Appl. Phys. Lett. 92, 031903 (2008); http://dx.doi.org/10.1063/1.2832672 (3 pages) | Cited 4 times

Online Publication Date: 24 January 2008

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The dynamic mechanical properties of high density mixtures of polytetraflouroethylene, aluminum (Al), and tungsten (W) powders are tailored by changing the morphology of the particles and porosity. Powder composites with fine metallic particles exhibited higher ultimate compressive strength, despite higher porosity, than less porous composites containing coarse W particles with equivalent mass fractions. The mesoscale force chains between the fine metallic particles are responsible for this unusual phenomenon. Macrocracks forming in the sample below the critical failure strain in the matrix and a competition between densification and fracture were observed in dynamic tests.
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81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.M- Structural failure of materials
61.43.Gt Powders, porous materials

Self-assembled Ge nanocrystals on BaTiO3/SrTiO3/Si(001)

L. Largeau, G. Patriarche, G. Saint-Girons, G. Delhaye, and G. Hollinger

Appl. Phys. Lett. 92, 031904 (2008); http://dx.doi.org/10.1063/1.2837629 (3 pages) | Cited 7 times

Online Publication Date: 24 January 2008

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The structure of Ge nanocrystals (NC) grown on BaTiO3 (BTO)/SrTiO3/Si(001) is studied by high resolution transmission electron microscopy. The Ge NC are fully relaxed with {111}, {112}, {110}, and {113} planes parallel to the interface. These orientations allow to align one Ge⟨110⟩ in-plane direction with one BTO⟨100⟩ in-plane direction leading to a minimization of the mismatch in the BTO⟨100⟩ direction. Surprisingly, no NC with {100} planes parallel to the interface, leading to a minimization of the mismatch along the two BTO⟨100⟩ in-plane directions, are observed. This is interpreted in terms of surface energy minimization.
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81.16.Dn Self-assembly
68.65.Ac Multilayers
61.46.Hk Nanocrystals
81.07.Bc Nanocrystalline materials
68.35.Md Surface thermodynamics, surface energies

Shape transition between symmetric and asymmetric structures in epitaxial three-dimensional strained islands

Y. C. Chu and C. J. Tsai

Appl. Phys. Lett. 92, 031905 (2008); http://dx.doi.org/10.1063/1.2837535 (3 pages)

Online Publication Date: 25 January 2008

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The total energies for the shape transition processes between symmetric and asymmetric structures in epitaxial three-dimensional strained islands are discussed here. For structures that allow height to increase simultaneously with width and length during growth, the shapes formed should be symmetric or transform from asymmetric to symmetric; for truncated-hut structures with fixed heights smaller than a critical value, the shapes formed should be asymmetric or transform from symmetric to asymmetric. The relation between the shape transition processes and the systematic conditions obtained here can be used to anticipate whether the elongated epitaxial structures are driven energetically or kinetically.
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68.55.J- Morphology of films
64.70.K- Solid-solid transitions

Generation and detection of tunable phonon polaritons using a single transmission grating

Kenji Katayama, Hayato Inoue, Hisashi Sugiya, Qing Shen, Taro Toyoda, and Keith A. Nelson

Appl. Phys. Lett. 92, 031906 (2008); http://dx.doi.org/10.1063/1.2837617 (3 pages) | Cited 3 times

Online Publication Date: 25 January 2008

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Frequency tunable phonon polariton waves were generated and detected using an original optical configuration of the transient grating method. In this technique, the excitation beam was shone onto a transmission grating after being transmitted through a lens, and a lithium niobate wafer located at a defocus position of the lens was irradiated by an expanded or reduced image of the transmission grating, causing excitation of phonon polaritons. Because the magnification of the light intensity pattern can be controlled by the sample-grating distance, the wavelength of the phonon polaritons, which is equal to the optical fringe spacing, can be continuously varied.
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71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
63.20.D- Phonon states and bands, normal modes, and phonon dispersion
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
42.79.Dj Gratings
42.79.Bh Lenses, prisms and mirrors

Photoluminescence of near-lattice-matched GaN/AlInN quantum wells grown on free-standing GaN and on sapphire substrates

L. T. Tan, R. W. Martin, K. P. O’Donnell, I. M. Watson, Z. H. Wu, and F. A. Ponce

Appl. Phys. Lett. 92, 031907 (2008); http://dx.doi.org/10.1063/1.2837630 (3 pages) | Cited 3 times

Online Publication Date: 25 January 2008

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Near-lattice-matched GaN/Al1−xInxN single quantum wells, grown using both free-standing GaN and conventional GaN-on-sapphire substrates, are studied by photoluminescence (PL) and PL excitation spectroscopies. PL spectra distinguish luminescence originating in the wells, barriers, and underlying GaN buffer layers. The spectra also reveal significant differences between structures grown simultaneously on the different substrates. The quantum well transition energy decreases as the well width increases due to the intense in-built electric fields, estimated to be 3.0±0.5 MeV/cm, that persist in strain free GaN/Al1−xInxN. Screening of these fields is studied using the excitation power dependence of the PL.
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78.67.De Quantum wells
78.55.Cr III-V semiconductors
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Frequency dispersion in capacitance-voltage characteristics of AlGaN/GaN heterostructures

James R. Shealy and Richard J. Brown

Appl. Phys. Lett. 92, 032101 (2008); http://dx.doi.org/10.1063/1.2835708 (3 pages) | Cited 4 times

Online Publication Date: 22 January 2008

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Capacitance-voltage (CV) characterization of AlGaN/GaN heterostructures is a widely used method for determining the depletion characteristics of the two-dimensional electron gas at the heterointerface. In combination with the Hg probe, these measurements are considered nondestructive. The technique can provide accurate determination of the sheet electron density, the concentration profile, the AlGaN barrier thickness, and the pinch off voltage. If the measurement conditions are not chosen properly, significant errors result from the effects of the series resistance, the backside Hg contact, and the electron generation lifetime. The best conditions (bias and frequency) for CV data acquisition are identified.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Observation of delayed fluorescence in CdSxSe1−x nanobelts by femtosecond time-resolved fluorescence spectroscopy

Xiao-Feng Han, Yu-Xiang Weng, Anlian Pan, Bingsuo Zou, and Jing-Yuan Zhang

Appl. Phys. Lett. 92, 032102 (2008); http://dx.doi.org/10.1063/1.2836080 (3 pages) | Cited 5 times

Online Publication Date: 22 January 2008

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The time-resolved fluorescence spectra as well as the decay kinetics for CdSxSe1−x single crystal nanobelts without and with the presence of structural disorders have been investigated by femtosecond time-resolved fluorescence spectrometer based on optical parametric fluorescence amplifier technique. The structural disorders in the crystal give rise to an inhomogeneous broadening of the steady-state fluorescence spectra and also to a distinct time-dependent redshift in the transient photoluminescence spectra, due to the carrier relaxation from the conduction band to the trapped states. The delayed fluorescence was observed and it can be attributed to several mechanisms including the electron-phonon interaction and the Auger effect.
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78.55.Hx Other solid inorganic materials
71.38.-k Polarons and electron-phonon interactions
79.20.Fv Electron impact: Auger emission
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