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29 Sep 2003

Volume 83, Issue 13, pp. 2503-2719

Issue Cover Spotlight Figure

Appl. Phys. Lett. 83, 2680 (2003); http://dx.doi.org/10.1063/1.1614845 (3 pages)

F. Nakajima, Y. Miyoshi, J. Motohisa, and T. Fukui
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High-power continuous-wave operation of a 6 μm quantum-cascade laser at room temperature

J. S. Yu, S. Slivken, A. Evans, L. Doris, and M. Razeghi

Appl. Phys. Lett. 83, 2503 (2003); http://dx.doi.org/10.1063/1.1613354 (3 pages) | Cited 41 times

Online Publication Date: 23 September 2003

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We report continuous-wave (cw) operation of quantum-cascade lasers (λ = 6 μm) using a thick electroplated Au top contact layer and epilayer-up bonding on a copper heat sink up to a temperature of 308 K (35 °C). The high cw optical output powers of 132 mW at 293 K and 21 mW at 308 K are achieved with threshold current densities of 2.29 and 2.91 kA/cm2, respectively, for a high-reflectivity-coated 15 μm wide and 2 mm long laser. © 2003 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Theoretical analysis of spectral gain in a terahertz quantum-cascade laser: Prospects for gain at 1 THz

S.-C. Lee and A. Wacker

Appl. Phys. Lett. 83, 2506 (2003); http://dx.doi.org/10.1063/1.1614440 (3 pages) | Cited 14 times

Online Publication Date: 23 September 2003

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In a recent letter [B. S. Williams et al. Appl. Phys. Lett. 82, 1015 (2003)], Williams et al. reported the development of a terahertz quantum-cascade laser operating at 3.4 THz or 14.2 meV. We have calculated and analyzed the gain spectra of the quantum-cascade structure described in their work, and in addition to gain at the reported lasing energy of ≃14 meV, we have discovered substantial gain at a much lower energy of around 5 meV or just over 1 THz. This suggests an avenue for the development of a terahertz laser at this lower energy, or of a two-color terahertz laser. © 2003 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

Two-dimensional photonic crystals with Ge/Si self-assembled islands

S. David, M. El kurdi, P. Boucaud, A. Chelnokov, V. Le Thanh, D. Bouchier, and J.-M. Lourtioz

Appl. Phys. Lett. 83, 2509 (2003); http://dx.doi.org/10.1063/1.1612892 (3 pages) | Cited 36 times

Online Publication Date: 23 September 2003

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Two-dimensional photonic crystals were fabricated on silicon-on-insulator waveguides with self-assembled Ge/Si islands deposited on top of the upper silicon layer. The photonic crystals consist of triangular lattices of air holes designed to exhibit a forbidden band around 1.5 μm. Different hexagonal photonic crystals microcavities were processed whose optical properties are probed at room temperature with the Ge/Si island photoluminescence. Quality factors larger than 200 are measured for hexagonal H3 cavities. A significant enhancement of the Ge/Si island photoluminescence is achieved in the 1.3–1.55 μm spectral region using the photonic crystal microcavities. We show that the energy resonance of the defect modes can be tuned with the filling factor of the photonic crystal. © 2003 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
73.61.Cw Elemental semiconductors
78.55.Ap Elemental semiconductors

Low-threshold 1317-nm InGaAsN quantum-well lasers with GaAsN barriers

Nelson Tansu, Jeng-Ya Yeh, and Luke J. Mawst

Appl. Phys. Lett. 83, 2512 (2003); http://dx.doi.org/10.1063/1.1613998 (3 pages) | Cited 43 times

Online Publication Date: 23 September 2003

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Very low threshold-current-density InGaAsN quantum-well lasers with GaAsN barriers, grown using metalorganic chemical vapor deposition, have been realized with a room-temperature emission wavelength of 1317 nm. The GaAsN barriers are employed to extend the wavelength, to strain compensate the quantum well, and to improve the hole confinement inside the quantum well. RT threshold current densities of only 210–270 A/cm2 are measured for InGaAsN quantum-well lasers (Lcav = 1000–2000 μm) with an emission wavelength of 1317 nm. © 2003 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Highly-efficient backlight for liquid crystal display having no optical films

Takamitsu Okumura, Akihiro Tagaya, Yasuhiro Koike, Masahiro Horiguchi, and Hiromasa Suzuki

Appl. Phys. Lett. 83, 2515 (2003); http://dx.doi.org/10.1063/1.1613051 (3 pages) | Cited 29 times

Online Publication Date: 23 September 2003

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We propose a highly-efficient backlight that requires no optical films with a polymer containing spherical particles of micron size. The developed backlight is provided with microprisms at the bottom surface, which can reflect directly the incident light into the front direction. The modeling simulation program, employing a Monte Carlo method based on Mie scattering theory, has optimized both the prismatic condition and the multiple scattering characteristics. We confirm that a uniformity of brightness can be achieved without using any optical films, resulting in a high optical efficiency of 62%. © 2003 American Institute of Physics.
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42.70.Jk Polymers and organics
85.60.Pg Display systems

Ultrafast three-dimensional tunable photonic crystal

Xiaoyong Hu, Qi Zhang, Yuanhao Liu, Bingying Cheng, and Daozhong Zhang

Appl. Phys. Lett. 83, 2518 (2003); http://dx.doi.org/10.1063/1.1615309 (3 pages) | Cited 39 times

Online Publication Date: 23 September 2003

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We demonstrate a continuously tunable photonic crystal with several picoseconds response, which is fabricated through a self-assembly formation method of polystyrene spheres. The large optical nonlinearity originates from the delocalization of the conjugated π-electron along polymer chains. The pump and probe scheme is adopted to measure the transmission changes based on the optical Kerr effect. The dynamic shift of the photonic band gap is studied. It is found that the band gap shifts about 13 nm when the input peak intensity is 40.4 GW/cm2, which is in agreement with the theoretical predictions. © 2003 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation

Guided mode lasing in a double-layered square microcavity

Hee-Jong Moon, Sang-Pil Sun, Jai-Hyung Lee, and Kyungwon An

Appl. Phys. Lett. 83, 2521 (2003); http://dx.doi.org/10.1063/1.1615291 (3 pages) | Cited 3 times

Online Publication Date: 23 September 2003

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We investigated the lasing characteristics of guided modes in a double-layered square microcavity made of a fused-silica hollow square capillary, in which the modes were formed by the total internal reflections off the inner and outer boundaries. Periodically peaked spectra of guided modes were observed when a dye-doped dielectric was coated on the outer boundary for a laser gain. By reducing the distance between the outer and the inner boundaries, we could achieve even a lasing of single closed guided modes with multiple reflections at each side of the inner boundary. Our double-layered square cavity can be adapted for various applications, particularly in the photonic integrated circuits. © 2003 American Institute of Physics.
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42.55.Sa Microcavity and microdisk lasers
42.82.Gw Other integrated-optical elements and systems

Characterization of the optical loss of an integrated silicon oxynitride optical switch structure

Ailing Zhang and Kam Tai Chan

Appl. Phys. Lett. 83, 2524 (2003); http://dx.doi.org/10.1063/1.1614416 (3 pages) | Cited 5 times

Online Publication Date: 23 September 2003

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An optical switch structure based on total internal reflection effects in intersecting silicon oxynitride waveguides has been designed and successfully fabricated. The optical reflection losses of the waveguides have been analyzed and compared with experimental results. It was shown that, apart from materials and scattering losses, the major factors contributing to the reflection losses are waveguide width, reflection facet displacement, and reflection facet tilt angle, with the last factor being the most critical in deciding the overall loss of the device. © 2003 American Institute of Physics.
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42.79.Gn Optical waveguides and couplers
42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks
42.65.Pc Optical bistability, multistability, and switching, including local field effects

Nonlinear refraction in potassium gadolinium tungstate: An efficient Raman crystal and laser host

J. A. Dharmadhikari, A. K. Dharmadhikari, and G. R. Kumar

Appl. Phys. Lett. 83, 2527 (2003); http://dx.doi.org/10.1063/1.1614442 (3 pages) | Cited 2 times

Online Publication Date: 23 September 2003

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Third order nonlinear optical properties of a promising laser host and Raman shifting crystal—potassium gadolium tungstate are reported. The intensity dependent refractive index, n2, measured at 1064 and 532 nm are 8.76×10−16 and 43.1×10−16 cm2 W−1, respectively, using 35 ps pulses by the z-scan technique. The two-photon absorption (TPA) coefficient β at 532 nm is 0.29 cm GW−1. Furthermore, we examine the behavior of self-focusing and nonlinear lens inside a laser resonator and discuss its influence on laser performance. © 2003 American Institute of Physics.
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42.70.Mp Nonlinear optical crystals
42.70.Hj Laser materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Long-wavelength strain-compensated GaAsSb quantum-well heterostructures laser grown by metalorganic chemical vapor deposition

M. S. Noh, R. D. Dupuis, D. P. Bour, G. Walter, and N. Holonyak

Appl. Phys. Lett. 83, 2530 (2003); http://dx.doi.org/10.1063/1.1615312 (3 pages) | Cited 6 times

Online Publication Date: 23 September 2003

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We report data on strain-compensated GaAsSb double-quantum-well lasers having a type-I band alignment and grown by metalorganic chemical vapor deposition on GaAs substrates. In order to compensate for strain effects and to establish a type-I band alignment, tensile-strained higher-band-gap GaAsP quantum-well barriers have been employed. A lasing wavelength of λ∼1.200 μm from a 500 μm long device at 1.15Ith has been achieved at room temperature in pulsed-mode operation. The maximum output power was 20 mW for the same device. A low threshold current density of 608.0 A/cm2 was obtained for 1370 μm long and 60 μm stripe lasers. The calculated internal quantum efficiency and internal loss were 33.8% and 8.4 cm−1, respectively. We also calculated an infinite cavity length threshold current density of 265 A/cm2. From these data, a gain constant G0 ∼ 1728 cm−1 and transparency current density of 135 A/cm2 were calculated. The result showed that the strain-compensated GaAsSb quantum wells are promising active materials for 1.3 μm vertical-cavity surface-emitting lasers. © 2003 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Amplified spontaneous emission and distributed feedback lasing from a conjugated compound in various polymer matrices

Naoto Tsutsumi, Tetsuya Kawahira, and Wataru Sakai

Appl. Phys. Lett. 83, 2533 (2003); http://dx.doi.org/10.1063/1.1614834 (3 pages) | Cited 19 times

Online Publication Date: 23 September 2003

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This letter presents amplified spontaneous emission (ASE) and distributed feedback (DFB) lasing of the conjugated compound, 1,4-bis[2-[4-[N,N-di(p-tolyl)amino]phenyl] vinyl]benzene, in various polymer matrices of poly(methylmethacrylate), poly(styrene) (PS), poly(vinyl butyral), poly(N-vinyl carbazole), and poly(methyl phenylsilane). Effective and large ASE intensity, lowest threshold, and maximum optical gain were measured in the PS matrix. Sharp DFB lasing with full width at half-maximum = 0.6 nm was measured at 490 nm. The lasing wavelength of 490 nm was fitted well by the theoretically calculated value of 491 nm. © 2003 American Institute of Physics.
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42.70.Hj Laser materials
78.45.+h Stimulated emission

Spectral narrowing of the emission from rhodamine 6G infiltrated in synthetic opals enhanced by the surface plasmon resonance

Keiji Ishikawa and Tatsuya Okubo

Appl. Phys. Lett. 83, 2536 (2003); http://dx.doi.org/10.1063/1.1615306 (3 pages) | Cited 4 times

Online Publication Date: 23 September 2003

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We report on the observation of spectrally narrowed emission (SNE) from rhodamine 6G infiltrated in synthetic opals, and the enhancement of the spectral narrowing by the surface plasmon resonance effect of Ag particles anchored on the internal surface of the opals. With Ag particles, SNE is observed at a lower pump intensity, and the threshold of the spectral narrowing is one-tenth lower than that without Ag. It was clarified that enhancement is not caused by the light scattering of the Ag particles, but by the surface plasmon resonance. © 2003 American Institute of Physics.
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78.55.Hx Other solid inorganic materials
78.68.+m Optical properties of surfaces
73.22.Lp Collective excitations
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
61.46.-w Structure of nanoscale materials

Raman scattering and anti-Stokes emission from a single spherical microcavity with a CdTe quantum dot monolayer

Yu. P. Rakovich, J. F. Donegan, N. Gaponik, and A. L. Rogach

Appl. Phys. Lett. 83, 2539 (2003); http://dx.doi.org/10.1063/1.1615316 (3 pages) | Cited 15 times

Online Publication Date: 23 September 2003

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We have studied the Raman and luminescence spectra of a microcavity–quantum dot system consisting of a melamine formaldehyde latex microsphere coated by CdTe colloidal quantum dots. The cavity-induced enhancement of the Raman scattering allows the observation of Raman spectra from only a monolayer of CdTe quantum dots. Periodic structure with very narrow peaks in the luminescence spectra of a single microsphere was detected arising from the coupling between the emission from quantum dots and spherical cavity modes. Strong anti-Stokes emission from CdTe quantum dots coupled to the cavity modes was observed using low intensity below band-gap excitation and attributed to the strong field enhancement at the microcavity resonances. © 2003 American Institute of Physics.
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78.67.Hc Quantum dots
78.55.Et II-VI semiconductors
78.30.-j Infrared and Raman spectra

Seventy-fold enhancement of light extraction from a defectless photonic crystal made on silicon-on-insulator

M. Zelsmann, E. Picard, T. Charvolin, E. Hadji, M. Heitzmann, B. Dal’zotto, M. E. Nier, C. Seassal, P. Rojo-Romeo, and X. Letartre

Appl. Phys. Lett. 83, 2542 (2003); http://dx.doi.org/10.1063/1.1614832 (3 pages) | Cited 40 times

Online Publication Date: 23 September 2003

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Very high photoluminescence extraction is observed from defectless two-dimensional photonic crystals etched in the upper 200-nm-thick silicon layer of a silicon-on-insulator (SOI) substrate. Predicted very low group velocity modes near the Γ point of the band structure lying above the light line are used to extract light from the photonic crystal slab into the free space. It is found that light is extracted on a 80-nm-wide band along directions near to the perpendicular to the slab, with an extraction enhancement up to 70 compared to an unpatterned SOI. © 2003 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
78.55.-m Photoluminescence, properties and materials

Oligomer-based organic distributed feedback lasers by room-temperature nanoimprint lithography

Dario Pisignano, Luana Persano, Paolo Visconti, Roberto Cingolani, Giuseppe Gigli, Giovanna Barbarella, and Laura Favaretto

Appl. Phys. Lett. 83, 2545 (2003); http://dx.doi.org/10.1063/1.1613362 (3 pages) | Cited 36 times

Online Publication Date: 23 September 2003

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Room-temperature nanoimprint lithography in air is used in order to pattern a nonthermoplastic, low-molar-mass thiophene-based pentamer with excellent gain properties. No degradation of the luminescence efficiency of the active medium was observed after patterning. In this way, we fabricated single-mode emission distributed feedback lasers having a threshold excitation fluence of 140 μJ/cm2. The lasing line is peaked at 637 nm and exhibits a linewidth of less than 0.7 nm and a well-behaved input-output characteristic in the whole range of pump fluences. These results demonstrate room-temperature nanoimprint lithography as powerful and straightforward fabrication technique for oligomer-based nanostructured optoelectronic devices. © 2003 American Institute of Physics.
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42.55.Rz Doped-insulator lasers and other solid state lasers
81.16.Nd Micro- and nanolithography

High-contrast optical modulation by surface acoustic waves

Srinivasan Krishnamurthy and P. V. Santos

Appl. Phys. Lett. 83, 2548 (2003); http://dx.doi.org/10.1063/1.1615683 (3 pages) | Cited 3 times

Online Publication Date: 23 September 2003

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Numerical calculations are employed to study the modulation of light by surface acoustic waves (SAWs) in photonic band gap (PBG) structures. The on/off contrast ratio in a PBG switch based on an optical cavity is determined as a function of the SAW-induced dielectric modulation. We show that these structures exhibit high-contrast ratios even for moderate acousto-optic coupling. © 2003 American Institute of Physics.
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68.35.Iv Acoustical properties
42.70.Qs Photonic bandgap materials
77.22.Ch Permittivity (dielectric function)
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Anode sheath in Hall thrusters

L. Dorf, V. Semenov, and Y. Raitses

Appl. Phys. Lett. 83, 2551 (2003); http://dx.doi.org/10.1063/1.1615307 (3 pages) | Cited 22 times

Online Publication Date: 23 September 2003

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A set of hydrodynamic equations is used to describe quasineutral plasma in ionization and acceleration regions of a Hall thruster. The electron distribution function and Poisson equation are invoked for description of a near-anode region. Numerical solutions suggest that steady-state operation of a Hall thruster can be achieved at different anode sheath regimes. It is shown that the anode sheath depends on the thruster operating conditions, namely the discharge voltage and the mass flow rate. © 2003 American Institute of Physics.
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52.40.Kh Plasma sheaths
85.30.Fg Bulk semiconductor and conductivity oscillation devices (including Hall effect devices, space-charge-limited devices, and Gunn effect devices)
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Contraction of aluminum oxide thin layers in optical heterostructures

O. Durand, F. Wyckzisk, J. Olivier, M. Magis, P. Galtier, A. De Rossi, M. Calligaro, V. Ortiz, V. Berger, G. Leo, and G. Assanto

Appl. Phys. Lett. 83, 2554 (2003); http://dx.doi.org/10.1063/1.1612893 (3 pages) | Cited 7 times

Online Publication Date: 23 September 2003

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We precisely determine the contraction of AlAs in multilayer optical waveguides, associated with selective oxidation of AlAs/GaAs epitaxial heterostructures. The average thickness of each layer was determined via x-ray reflectometry before and after oxidation, yielding an induced shrinkage of 11.4%±0.7% normal to the stack. The waveguide refractive indices were evaluated via modal-index measurements in the near-infrared. The achieved accuracy is compatible with form-birefringent phase matching in AlGaAs guided-wave frequency converters. © 2003 American Institute of Physics.
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68.65.Ac Multilayers
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
42.79.Gn Optical waveguides and couplers
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.20.Fm Birefringence

Liquid/liquid dynamic phase separation induced by a focused laser

Sada-Atsu Mukai, Nobuyuki Magome, Hiroyuki Kitahata, and Kenichi Yoshikawa

Appl. Phys. Lett. 83, 2557 (2003); http://dx.doi.org/10.1063/1.1613795 (3 pages) | Cited 13 times

Online Publication Date: 23 September 2003

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We found that a focused laser can generate microscopic phase separation in an oil/water system. An oil droplet emerges and grows at the focus of the laser in a water-rich homogeneous medium. In contrast, in an oil-rich homogeneous phase, water droplets spring out in a successive manner from the focus of the laser, move away, and disappear in the surroundings, forming a flower-like pattern. The mechanism of this dynamic phase separation is discussed under the framework of the mean field theory. © 2003 American Institute of Physics.
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64.75.-g Phase equilibria
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)

First-principle study on GaN epitaxy on lattice-matched ZrB2 substrates

J.-I. Iwata, K. Shiraishi, and A. Oshiyama

Appl. Phys. Lett. 83, 2560 (2003); http://dx.doi.org/10.1063/1.1613353 (3 pages) | Cited 6 times

Online Publication Date: 23 September 2003

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We theoretically investigate GaN epitaxy on ZrB2 substrates by clarifying the atomic and electronic structures of GaN/ZrB2 interfaces by first-principle calculations. Both the GaN epitaxial layer and the ZrB2 substrate almost maintain the bulk structures when the epitaxial growth begins with the formation of N–Zr bonds. On the other hand, a remarkable zigzag structural change, which seems to deteriorate the lattice-matched nature of ZrB2 substrates, is found in the interfacial B plane when B–N bonds are formed at the interface. These results indicate that suppression of the B–N bond formation is a key point for the effective use of ZrB2 as a substrate of GaN. We also estimate the Schottky barrier heights of these interfaces. The calculated p-type Schottky barrier height of the interface which contains three N–Zr bonds is small enough to form ohmic contacts. © 2003 American Institute of Physics.
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68.55.A- Nucleation and growth
61.50.Lt Crystal binding; cohesive energy
68.35.Ct Interface structure and roughness
71.15.-m Methods of electronic structure calculations
68.43.Bc Ab initio calculations of adsorbate structure and reactions
73.40.Ns Metal-nonmetal contacts
73.30.+y Surface double layers, Schottky barriers, and work functions
73.20.At Surface states, band structure, electron density of states
81.05.Ea III-V semiconductors

Nanorheological approach for characterization of electroluminescent polymer thin films

Tomoko Gray, Cynthia Buenviaje, René M. Overney, Samson A. Jenekhe, Lixin Zheng, and Alex K. Y. Jen

Appl. Phys. Lett. 83, 2563 (2003); http://dx.doi.org/10.1063/1.1613045 (3 pages) | Cited 9 times

Online Publication Date: 23 September 2003

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Shear-modulated scanning force microscopy (SM-SFM) is introduced as a nanorheological characterization method for the determination of optoelectronic properties of semiconducting polymer thin films (<100 nm). In this letter, the photoluminescence quantum efficiency of poly(p-phenylenevinylene) (PPV) was directly correlated to the glass transition property by SM-SFM. Conformational changes and chain packing were discussed as a function of the conversion temperature of the soluble PPV precursor. Compared to the bulk, very low glass transition temperature values in the range of 65 to 85 °C were found, which imply an increased molecular mobility in thin films of conjugated polymers. © 2003 American Institute of Physics.
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78.60.Fi Electroluminescence
78.66.Qn Polymers; organic compounds
83.85.Cg Rheological measurements—rheometry
68.37.Ps Atomic force microscopy (AFM)
42.70.Jk Polymers and organics
64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition
78.55.Kz Solid organic materials

High-filling-fraction inverted ZnS opals fabricated by atomic layer deposition

J. S. King, C. W. Neff, C. J. Summers, W. Park, S. Blomquist, E. Forsythe, and D. Morton

Appl. Phys. Lett. 83, 2566 (2003); http://dx.doi.org/10.1063/1.1609240 (3 pages) | Cited 43 times

Online Publication Date: 23 September 2003

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The infiltration of three-dimensional opal structures has been investigated by atomic layer deposition. Demonstrations using ZnS:Mn show that filling fractions >95% can be achieved and that the infiltrated material is of high-quality crystalline material as assessed by photoluminescence measurements. These results demonstrate a flexible and practical pathway to attaining high-performance photonic crystal structures and optical microcavities. © 2003 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
68.55.-a Thin film structure and morphology
78.55.Et II-VI semiconductors

Stress relaxation in mismatched layers due to threading dislocation inclination

A. E. Romanov and J. S. Speck

Appl. Phys. Lett. 83, 2569 (2003); http://dx.doi.org/10.1063/1.1613360 (3 pages) | Cited 40 times

Online Publication Date: 23 September 2003

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A recently observed mechanism of elastic stress relaxation in mismatched layers is discussed. The relaxation is achieved by the inclination of pure edge threading dislocation lines with respect to the layer surface normal. The relaxation is not assisted by dislocation glide but rather is caused by the “effective climb” of edge dislocations. The effective dislocation climb may result from the film growth and it is not necessarily related to bulk diffusion processes. The contribution of the dislocation inclination to strain relaxation has been formulated and the energy release due to the dislocation inclination in mismatched stressed layers has been determined. This mechanism explains recently observed relaxation of compressive stresses in the (0001) growth of AlxGa1−xN layers. © 2003 American Institute of Physics.
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68.60.Bs Mechanical and acoustical properties
81.05.Ea III-V semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
61.72.Lk Linear defects: dislocations, disclinations
61.72.Bb Theories and models of crystal defects

Identification of Te alloys with suitable phase change characteristics

Ralf Detemple, Daniel Wamwangi, Matthias Wuttig, and Gustav Bihlmayer

Appl. Phys. Lett. 83, 2572 (2003); http://dx.doi.org/10.1063/1.1608482 (3 pages) | Cited 29 times

Online Publication Date: 23 September 2003

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At present, the discovery and development of phase change materials is mainly based upon empirical strategies and trial and error approaches. Here, we present a structural criterion that needs to be met to enable the mandatory fast recrystallization with sufficient optical contrast that characterizes suitable phase change materials. Comparing the behavior of AgInTe2 and AgSbTe2 films it is demonstrated that only the AgSbTe2 films, which show a cubic coordination, have sufficient density contrast, and hence, also optical contrast to allow phase change recording. © 2003 American Institute of Physics.
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42.79.Vb Optical storage systems, optical disks
64.70.K- Solid-solid transitions

Metallic glass ingots based on yttrium

Faqiang Guo, S. Joseph Poon, and Gary J. Shiflet

Appl. Phys. Lett. 83, 2575 (2003); http://dx.doi.org/10.1063/1.1614420 (3 pages) | Cited 95 times

Online Publication Date: 23 September 2003

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We report a family of yttrium metallic alloys that are able to form glassy ingots directly from the liquid, as well as forming bulk-sized amorphous rods with diameters over 2 cm by water cooling of the alloy melt sealed in quartz tubes. It is apparent that, in addition to the strong chemical interaction among the components, the simultaneous occurrence of well-distributed atom sizes and a strongly depressed liquidus temperature in multicomponent metallic alloys is responsible for the formation of glassy ingots. © 2003 American Institute of Physics.
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61.43.Fs Glasses
81.05.Kf Glasses (including metallic glasses)
81.05.Bx Metals, semimetals, and alloys
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