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5 Apr 2004

Volume 84, Issue 14, pp. 2473-2706

Issue Cover Spotlight Figure

Appl. Phys. Lett. 84, 2244 (2004); http://dx.doi.org/10.1063/1.1690471 (3 pages)

David R. Smith, David Schurig, Jack J. Mock, Pavel Kolinko, and Patrick Rye
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Microsecond time scale lateral-mode dynamics in a narrow stripe InGaN laser

Christoph Eichler, Daniel Hofstetter, Weng W. Chow, Stephan Miller, Andreas Weimar, Alfred Lell, and Volker Härle

Appl. Phys. Lett. 84, 2473 (2004); http://dx.doi.org/10.1063/1.1691497 (3 pages) | Cited 9 times

Online Publication Date: 1 April 2004

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Time-resolved measurements of the spectrum and the far field of InGaN-based laser diodes show lateral-mode changes and gradual tilting of the far field on a microsecond time scale. Numerical simulations based on a microscopic theory are in good agreement with the measurements. The observed effects are attributed to lateral carrier diffusion in combination with thermal lensing. © 2004 American Institute of Physics.
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42.60.By Design of specific laser systems
78.47.-p Spectroscopy of solid state dynamics
78.66.Fd III-V semiconductors
85.30.De Semiconductor-device characterization, design, and modeling
42.55.Ah General laser theory

Polymer electrophosphorescence devices with high power conversion efficiencies

X. H. Yang and D. Neher

Appl. Phys. Lett. 84, 2476 (2004); http://dx.doi.org/10.1063/1.1691194 (3 pages) | Cited 92 times

Online Publication Date: 1 April 2004

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We demonstrate efficient single-layer polymer phosphorescent light-emitting devices based on a green-emitting iridium complex and a polymer host co-doped with electron-transporting and hole-transporting molecules. These devices can be operated at relatively low voltages, resulting in a power conversion efficiency of up to 24 lm/W at luminous efficiencies exceeding 30 cd/A. The overall performances of these devices suggest that efficient electrophosphorescent devices with acceptable operating voltages can be achieved in very simple device structures fabricated by spin coating. © 2004 American Institute of Physics.
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85.60.Jb Light-emitting devices
78.55.Kz Solid organic materials

Thermal-flow technique for reducing surface roughness and controlling gap size in polymer microring resonators

Chung-Yen Chao and L. Jay Guo

Appl. Phys. Lett. 84, 2479 (2004); http://dx.doi.org/10.1063/1.1691492 (3 pages) | Cited 16 times

Online Publication Date: 1 April 2004

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Q factors of microring resonator waveguide devices are primarily limited by the surface-roughness-induced scattering loss. Such surface roughness loss has been observed in waveguides that are fabricated from various types of materials, including semiconductors, dielectrics, and polymers. In this letter, we show that the surface roughness of polymer waveguides can be greatly reduced by a thermal-flow technique, and the effective reduction in waveguide loss was verified experimentally. In addition to smoothing surfaces, this technique can simultaneously shrink the gap distance in the coupling region of polymer microring resonators. This, in turn, provides higher coupling, lessens the difficulty of fabricating submicron gaps, and leads to more compact devices. © 2004 American Institute of Physics.
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42.79.Gn Optical waveguides and couplers

1.31 μm InGaAs quantum dot light-emitting diodes grown directly in a GaAs matrix by metalorganic chemical-vapor deposition

M. T. Todaro, M. De Giorgi, V. Tasco, M. De Vittorio, R. Cingolani, and A. Passaseo

Appl. Phys. Lett. 84, 2482 (2004); http://dx.doi.org/10.1063/1.1687979 (3 pages) | Cited 11 times

Online Publication Date: 1 April 2004

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We investigate the optical properties of light-emitting diodes (LEDs) operating at 1.3 μm embedding, in the intrinsic region, quantum dots (QDs) directly grown by metalorganic chemical-vapor deposition in a GaAs matrix, without indium in the barrier. The device characterization shows a full width at half maximum of the ground state emission as narrow as 24 meV at room temperature and a quenching of the emission between 30 K and room temperature as low as 2.75. Despite the low dot density (1.6×109 cm−2), the external quantum efficiency of our devices is 0.03%. This indicates that the individual QD efficiency of our devices is about 30% higher than that reported in the literature for state of the art InGaAs/InGaAs QD LEDs. © 2004 American Institute of Physics.
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78.67.Hc Quantum dots
78.60.Fi Electroluminescence
78.55.Cr III-V semiconductors
85.60.Jb Light-emitting devices
68.65.Hb Quantum dots (patterned in quantum wells)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Current-injection spiral-shaped microcavity disk laser diodes with unidirectional emission

M. Kneissl, M. Teepe, N. Miyashita, N. M. Johnson, G. D. Chern, and R. K. Chang

Appl. Phys. Lett. 84, 2485 (2004); http://dx.doi.org/10.1063/1.1691494 (3 pages) | Cited 47 times

Online Publication Date: 1 April 2004

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A spiral-shaped microcavity heterojunction laser diode fabricated with InGaN multiple quantum wells is demonstrated to operate under current injection conditions and emit unidirectionally. Room-temperature laser operation was achieved for microcavity disk radii ranging from 50 to 350 μm and threshold current densities as low as 4.6 kA/cm2. Unidirectional laser emission is clearly revealed in the far-field pattern with the lateral divergence angle ranging from 60° to 75°. Output power of more than 25 mW was obtained for emission wavelengths near 400 nm. © 2004 American Institute of Physics.
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42.55.Sa Microcavity and microdisk lasers

Optically pumped ultraviolet microdisk laser on a silicon substrate

X. Liu, W. Fang, Y. Huang, X. H. Wu, S. T. Ho, H. Cao, and R. P. H. Chang

Appl. Phys. Lett. 84, 2488 (2004); http://dx.doi.org/10.1063/1.1695090 (3 pages) | Cited 31 times

Online Publication Date: 1 April 2004

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We have fabricated ultraviolet microdisk lasers on silicon substrates. A thin layer of zinc oxide is grown on top of the silica microdisks and serves as the gain medium. Under optical pumping, lasing occurs in the whispering gallery modes of the hybrid microdisks at room temperature. Above the lasing threshold, a drastic increase of emission intensity is accompanied by a decrease of spectral width of the lasing modes. © 2004 American Institute of Physics.
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42.55.Sa Microcavity and microdisk lasers
42.55.Px Semiconductor lasers; laser diodes

Phototunable photonic bandgap in a chiral liquid crystal laser device

Seiichi Furumi, Shiyoshi Yokoyama, Akira Otomo, and Shinro Mashiko

Appl. Phys. Lett. 84, 2491 (2004); http://dx.doi.org/10.1063/1.1699445 (3 pages) | Cited 57 times

Online Publication Date: 1 April 2004

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This letter describes the phototunable photonic bandgap of cholesteric liquid crystal (CLC) doped with a fluorescent dye to generate the distributed feedback effect. Photoirradiation of the dye-doped CLC cell under UV light at 254 nm resulted in continuous changes in the chiral photonic bandgap from 550 to 720 nm due to photolysis reaction of the cholesteryl iodide embedded in the CLC host. We showed that the laser oscillation wavelength could be controlled in a wide wavelength range from 610 to 700 nm by photoassisted adjustment of CLC photonic bandgaps. © 2004 American Institute of Physics.
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42.55.Tv Photonic crystal lasers and coherent effects
42.70.Qs Photonic bandgap materials
42.70.Df Liquid crystals
78.40.Dw Liquids
82.50.Hp Processes caused by visible and UV light
42.79.Kr Display devices, liquid-crystal devices

Continuous-wave operation of terahertz quantum-cascade lasers above liquid-nitrogen temperature

Sushil Kumar, Benjamin S. Williams, Stephen Kohen, Qing Hu, and John L. Reno

Appl. Phys. Lett. 84, 2494 (2004); http://dx.doi.org/10.1063/1.1695099 (3 pages) | Cited 81 times

Online Publication Date: 1 April 2004

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We report cw operation of a quantum-cascade laser at 3.2 THz (λ≈94 μm) up to a heat-sink temperature of 93 K. Resonant longitudinal-optical phonon scattering is used to depopulate the lower radiative state and a low-loss metal–metal waveguide is used to provide high modal confinement. Optical powers of ∼1.8 mW at 10 K and ∼400 μW at 78 K are observed from a single facet of a 40-μm-wide and 1.35-mm-long laser device. A threshold current density of 432 A/cm2 at 10 K and 552 A/cm2 at 78 K was obtained in cw mode. The same device lased up to 129 K in pulsed mode with a threshold current density of 419 A/cm2 at 5 K. © 2004 American Institute of Physics.
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42.60.By Design of specific laser systems
42.55.Px Semiconductor lasers; laser diodes

Anticrossing between heavy-hole states in Si0.2Ge0.8/Si-coupled quantum wells grown on Si0.5Ge0.5 pseudosubstrate

L. Diehl, A. Borak, S. Mentese, D. Grützmacher, H. Sigg, U. Gennser, I. Sagnes, Y. Campidelli, O. Kermarrec, D. Bensahel, and J. Faist

Appl. Phys. Lett. 84, 2497 (2004); http://dx.doi.org/10.1063/1.1691173 (3 pages) | Cited 1 time

Online Publication Date: 1 April 2004

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Intersubband absorption measurements were performed on a single repetition of coupled Si0.2Ge0.8/Si quantum wells grown on a Si0.5Ge0.5 pseudosubstrate. Two resonances observed at low temperature are identified with the optical transitions between the ground and the first excited heavy-hole states confined in the coupled wells through their anticrossing behavior. The measured coupling energy agrees well with calculated values. In addition, the Stark shift of a diagonal resonance between a heavy- and light-hole level was observed. © 2004 American Institute of Physics.
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73.21.Fg Quantum wells
78.67.De Quantum wells
42.50.Hz Strong-field excitation of optical transitions in quantum systems; multiphoton processes; dynamic Stark shift
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Dependence of the sputter-etching characteristics of strontium–titanate–oxide thin films on their structural properties

L. Stafford, M. Gaidi, M. Chaker, O. Langlois, J. Margot, F. Schiettekatte, and P. Wei

Appl. Phys. Lett. 84, 2500 (2004); http://dx.doi.org/10.1063/1.1702131 (3 pages) | Cited 9 times

Online Publication Date: 1 April 2004

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Sputter-etching characteristics of polycrystalline strontium–titanate–oxide (STO) thin films are investigated using a high-density argon plasma. STO thin films were grown by means of a reactive pulsed-laser deposition technique in which the buffer oxygen pressure was varied to change the structural properties of the films. The sputter-etch rate of the rf-biased films is found to linearly increase with the oxygen deposition pressure. This result is shown to be related to the corresponding decrease of the film density. This dependence of the etch rate on the structural properties of the films has very important consequences on etching studies and on the optimization of etching processes. © 2004 American Institute of Physics.
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81.65.Cf Surface cleaning, etching, patterning
81.15.Fg Pulsed laser ablation deposition
68.55.-a Thin film structure and morphology
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
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Nanoscale analysis of the In and N spatial redistributions upon annealing of GaInNAs quantum wells

J.-M. Chauveau, A. Trampert, K. H. Ploog, and E. Tournié

Appl. Phys. Lett. 84, 2503 (2004); http://dx.doi.org/10.1063/1.1690108 (3 pages) | Cited 30 times

Online Publication Date: 1 April 2004

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By using transmission electron microscopy on as-grown and annealed GaInNAs/GaAs heterostructures, we demonstrate that annealing induces a correlated behavior of both In and N species within the GaInNAs quantum well. While no intermixing occurs, the analysis of the strain situation reveals that the main driving force for the observed inward diffusion is not composition gradients at the interfaces, but local strain fields. This mechanism leads to the improvement of the photoluminescence (PL) properties and to the blueshift of the PL peak. © 2004 American Institute of Physics.
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81.07.St Quantum wells
78.55.Cr III-V semiconductors
68.65.Fg Quantum wells
78.67.De Quantum wells
61.72.Cc Kinetics of defect formation and annealing

Nanostructures and carrier localization behaviors of green-luminescence InGaN/GaN quantum-well structures of various silicon-doping conditions

Yung-Chen Cheng, En-Chiang Lin, Cheng-Ming Wu, C. C. Yang, Jer-Ren Yang, Andreas Rosenauer, Kung-Jen Ma, Shih-Chen Shi, L. C. Chen, Chang-Chi Pan, and Jen-Inn Chyi

Appl. Phys. Lett. 84, 2506 (2004); http://dx.doi.org/10.1063/1.1690872 (3 pages) | Cited 20 times

Online Publication Date: 1 April 2004

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The results of photoluminescence (PL), detection-energy-dependent photoluminescence excitation (DEDPLE), excitation-energy-dependent photoluminescence (EEDPL), and strain state analysis (SSA) of three InGaN/GaN quantum-well (QW) samples with silicon doping in the well, barrier and an undoped structure are compared. The SSA images show strongly clustering nanostructures in the barrier-doped sample and relatively weaker composition fluctuations in the undoped and well-doped samples. Differences in silicon doping between the samples give rise to the differences in DEDPLE and EEDPL spectra, as a result of the differences in carrier localization. In addition, the PL results provide us clues for speculating that the S-shaped PL peak position behavior is dominated by the quantum-confined Stark effect in an undoped InGaN/GaN QW structure. © 2004 American Institute of Physics.
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68.65.Fg Quantum wells
78.67.De Quantum wells
78.55.Cr III-V semiconductors
61.72.uj III-V and II-VI semiconductors

Order–disorder transition of anodic alumina nanochannel arrays grown under the guidance of focused-ion-beam patterning

C. Y. Liu, A. Datta, N. W. Liu, C. Y. Peng, and Y. L. Wang

Appl. Phys. Lett. 84, 2509 (2004); http://dx.doi.org/10.1063/1.1691493 (3 pages) | Cited 15 times

Online Publication Date: 1 April 2004

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By anodizing an aluminum surface that has been patterned with different guiding lattices using a focused ion beam, the resulting anodic alumina nanochannel arrays exhibit different degree of order arrangement. Long-range order is achieved only when the guiding lattice is carefully matched to that of the self-organized hcp array formed locally in an unguided area. Lattice mismatch between the guiding and locally self-organized lattice leads to an order–disorder transition via the creation and annihilation of nanochannels. The driving force of the transition is attributed to the unbalance in the stress among the nanochannels. © 2004 American Institute of Physics.
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82.45.Cc Anodic films
64.70.K- Solid-solid transitions
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder
61.46.-w Structure of nanoscale materials
81.65.Cf Surface cleaning, etching, patterning

Highly efficient sensitizing of erbium ion luminescence in size-controlled nanocrystalline Si/SiO2 superlattice structures

V. Yu. Timoshenko, M. G. Lisachenko, B. V. Kamenev, O. A. Shalygina, P. K. Kashkarov, J. Heitmann, M. Schmidt, and M. Zacharias

Appl. Phys. Lett. 84, 2512 (2004); http://dx.doi.org/10.1063/1.1690465 (3 pages) | Cited 16 times

Online Publication Date: 1 April 2004

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Comparative studies of photoluminescence (PL) of undoped and Er-doped size-controlled nanocrystalline Si/SiO2 superlattice structures show that the optical excitation of Si nanocrystals can be completely transferred to the Er3+ ions in surrounding SiO2, resulting in a strong PL line at 1.5 μm. The PL yield of the Er-doped structure increases for higher photon energy of excitation and for smaller nanocrystal sizes. This highly efficient sensitizing of the Er-related PL is explained by a strong coupling between excitons confined in Si nanocrystals and neighboring Er3+ ions in their upper excited states. © 2004 American Institute of Physics.
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78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
73.21.Cd Superlattices
73.22.Lp Collective excitations
71.15.Qe Excited states: methodology
78.55.Hx Other solid inorganic materials
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Excimer-laser-induced activation of Mg-doped GaN layers

Yow-Jon Lin, Wen-Fung Liu, and Ching-Ting Lee

Appl. Phys. Lett. 84, 2515 (2004); http://dx.doi.org/10.1063/1.1695436 (3 pages) | Cited 5 times

Online Publication Date: 1 April 2004

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In this study, we investigated the 248 nm excimer-laser-induced activation of the Mg-doped GaN layers. According to the observed photoluminescence results and the x-ray photoelectron spectroscopy measurements, we found that the dissociation of the Mg–H complexes and the formation of hydrogenated Ga vacancies (i.e., VGaH2) and/or the Ga vacancies occupied by interstitial Mg during the laser irradiation process, led to an increase in the hole concentration. © 2004 American Institute of Physics.
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81.05.Ea III-V semiconductors
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
79.60.Dp Adsorbed layers and thin films
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
61.72.J- Point defects and defect clusters
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
81.65.-b Surface treatments

Reduction of resistivity in Cu thin films by partial oxidation: Microstructural mechanisms

Walter L. Prater, Emily L. Allen, Wen-Y. Lee, Michael F. Toney, Jonathan Daniels, and Jonathan A. Hedstrom

Appl. Phys. Lett. 84, 2518 (2004); http://dx.doi.org/10.1063/1.1691500 (3 pages) | Cited 4 times

Online Publication Date: 1 April 2004

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We report on the electrical resistance and microstructure of sputter deposited copper thin films grown in an oxygen containing ion-beam sputtering atmosphere. For films thinner than 5 nm, 6%–10% oxygen causes a minimum in film resistivity, while for thicker films, there is a monotonic increase in resistivity. X-ray reflectivity measurements show significantly smoother films for these oxygen flow rates. X-ray diffraction shows that the oxygen doping causes a refinement of the copper grain size and the formation of cuprous oxide. We suggest that the formation of cuprous oxide limits copper grain growth, which causes smoother interfaces, and thus reduces resistivity by increasing specular scattering of electrons at interfaces. © 2004 American Institute of Physics.
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81.15.Jj Ion and electron beam-assisted deposition; ion plating
73.61.At Metal and metallic alloys
68.55.-a Thin film structure and morphology
81.65.Mq Oxidation

Optical and electrical properties of amorphous GdxGa0.4−xO0.6 films in GdxGa0.4−xO0.6/Ga2O3 gate dielectric stacks on GaAs

M. Passlack, N. Medendorp, S. Zollner, R. Gregory, and D. Braddock

Appl. Phys. Lett. 84, 2521 (2004); http://dx.doi.org/10.1063/1.1695445 (3 pages) | Cited 10 times

Online Publication Date: 1 April 2004

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Optical and electrical properties of amorphous GdxGa0.4−xO0.6 films have been systematically investigated as a function of Gd mole fraction x (0 ⩽ x ⩽ 0.31). The GdxGa0.4−xO0.6 films are part of GdxGa0.4−xO0.6/Ga2O3 gate dielectric stacks grown onto the GaAs(001) surface by molecular-beam deposition. When the Gd mole percent is raised from 0 to 25 at. % (0 ⩽ x ⩽ 0.25), the refractive index n and the optical band gap increase from 1.908 to 1.987 and from 4.22 to 5.08 eV, respectively. The electrical properties of GdxGa0.4−xO0.6 films improve dramatically with increasing Gd concentration: The leakage current falls from 7.8×10−1 to 9.7×10−10 A/cm2 (measured at an electric field of 1 MV/cm) when the Gd mole percent is raised from 8.8 to 31 at. %, and the dielectric breakdown field exceeds 4 MV/cm for x>0.21. © 2004 American Institute of Physics.
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78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
77.55.-g Dielectric thin films
77.22.Jp Dielectric breakdown and space-charge effects
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
61.43.-j Disordered solids
73.61.Ng Insulators

Effect of nitrogen on the optical properties of InGaAsN p-i-n structures grown on misoriented (111)B GaAs substrates

J. Miguel-Sánchez, A. Guzmán, J. M. Ulloa, A. Hierro, and E. Muñoz

Appl. Phys. Lett. 84, 2524 (2004); http://dx.doi.org/10.1063/1.1695639 (3 pages) | Cited 9 times

Online Publication Date: 1 April 2004

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In this work, we demonstrate the growth, characterization, and processing of InGaAsN single quantum well p-i-n structures by solid-source molecular-beam epitaxy on misoriented GaAs (111)B substrates. Two different misorientations were studied simultaneously, 1° toward [−211] and 2° toward [2-1-1], the latter showing the highest optical quality. The roles of the arsenic flux, substrate misorientation, and amount of active nitrogen on the optical properties and crystal quality are discussed. We demonstrate photoluminescence emission at wavelength as long as 1.42 μm at 16 K on (111)B GaAs. Postgrowth rapid thermal annealing improves crystal quality and typical blueshifts of the peak emission are observed, like the case of (100). © 2004 American Institute of Physics.
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85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
81.07.St Quantum wells
78.67.De Quantum wells
78.55.Cr III-V semiconductors
85.30.Kk Junction diodes
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.60.Fi Electroluminescence
81.40.Gh Other heat and thermomechanical treatments
68.65.Fg Quantum wells
61.72.Cc Kinetics of defect formation and annealing

Elastic modulus and resonance behavior of boron nitride nanotubes

Abhijit P. Suryavanshi, Min-Feng Yu, Jianguo Wen, Chengchun Tang, and Yoshio Bando

Appl. Phys. Lett. 84, 2527 (2004); http://dx.doi.org/10.1063/1.1691189 (3 pages) | Cited 97 times

Online Publication Date: 1 April 2004

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The effective elastic modulus (E) of boron nitride nanotubes (BNNTs) was measured using the electric-field-induced resonance method inside a transmission electron microscope. The average value of E from the measurements of 18 individually cantilevered BNNTs was 722 GPa, comparable to the theoretical estimate of ∼850 GPa. No strong variation of E with the diameter of the BNNTs, which spanned from 34 to 94 nm, was observed. Low quality factors (<680) obtained from the mechanical resonance is attributed to the layered structural nature of BNNT. © 2004 American Institute of Physics.
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81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity
61.46.-w Structure of nanoscale materials
62.25.-g Mechanical properties of nanoscale systems
68.37.Lp Transmission electron microscopy (TEM)

Atomic-scale imaging of asymmetric Lomer dislocation cores at the Ge/Si(001) heterointerface

J. N. Stirman, P. A. Crozier, David J. Smith, F. Phillipp, G. Brill, and S. Sivananthan

Appl. Phys. Lett. 84, 2530 (2004); http://dx.doi.org/10.1063/1.1697625 (3 pages) | Cited 9 times

Online Publication Date: 1 April 2004

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Lomer edge dislocations formed at Ge/Si(001) hetero-interfaces have been imaged with a 1.25-MeV atomic-resolution electron microscope. The dislocation cores were primarily asymmetrical, and they were located close to the mean position of the interface, which was not structurally abrupt due to Ge–Si interdiffusion at the growth temperature of 550 °C. Structural models of the asymmetric dislocation cores could be derived directly from the experimental micrographs and image simulations were then used to validate the image interpretation. © 2004 American Institute of Physics.
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61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
66.30.Ny Chemical interdiffusion; diffusion barriers
68.37.-d Microscopy of surfaces, interfaces, and thin films

Characterization of Si/GexSi1−x structures by micro-Raman imaging

S. Nakashima, T. Yamamoto, A. Ogura, K. Uejima, and T. Yamamoto

Appl. Phys. Lett. 84, 2533 (2004); http://dx.doi.org/10.1063/1.1695443 (3 pages) | Cited 24 times

Online Publication Date: 1 April 2004

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GexSi1−x are characterized by Raman microspectroscopy. The strain of the 17.5-nm-thick Si layer was examined through deep UV Raman measurements. The depth profile of the GexSi1−x alloy composition and crystallinity was determined by visible Raman image measurement of the sample cross section. These measurements give results consistent with transmission electron microscopy and secondary ion mass spectrometry analyses. © 2004 American Institute of Physics.
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78.30.Am Elemental semiconductors and insulators
78.40.Fy Semiconductors
68.55.A- Nucleation and growth
78.66.Db Elemental semiconductors and insulators
68.37.Lp Transmission electron microscopy (TEM)
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)

Enhanced optical properties of the GaAsN/GaAs quantum-well structure by the insertion of InAs monolayers

Q. Gao, H. H. Tan, C. Jagadish, B. Q. Sun, M. Gal, L. Ouyang, and J. Zou

Appl. Phys. Lett. 84, 2536 (2004); http://dx.doi.org/10.1063/1.1697628 (3 pages) | Cited 2 times

Online Publication Date: 1 April 2004

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Microstructural and optical properties of InAs-inserted and reference single GaAsN/GaAs quantum-well (QW) structures grown by metalorganic chemical vapor deposition were investigated using cross-sectional transmission electron microscopy and photoluminescence (PL). Significant enhancement of PL intensity and a blueshift of PL emission were observed from the InAs-inserted GaAsN/GaAs QW structure, compared with the single GaAsN/GaAs QW structure. Strain compensation and In-induced reduction of N incorporation are suggested to be two major factors affecting the optical properties. © 2004 American Institute of Physics.
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78.67.De Quantum wells
78.55.Cr III-V semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.65.Fg Quantum wells
68.37.Lp Transmission electron microscopy (TEM)
81.05.Ea III-V semiconductors

Enhanced photoluminescence at poly(3-octyl-thiophene)/TiO2 interfaces

Barbara van der Zanden, Roel van de Krol, Joop Schoonman, and Albert Goossens

Appl. Phys. Lett. 84, 2539 (2004); http://dx.doi.org/10.1063/1.1699447 (3 pages) | Cited 4 times

Online Publication Date: 1 April 2004

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The photoluminescence (PL) of poly(3-octyl-thiophene) (P3OT) thin films applied on TiO2 substrates is compared to the PL of P3OT films applied on quartz. Quenching of excitons occurs at the P3OT/TiO2 interface and not at the P3OT/quartz interface. Yet, in the former case the PL intensity is stronger than in the latter. In particular, P3OT films less than 5 nm thick lumines much more when applied on TiO2, which is in striking contrast to what one expects. For films thicker than 10 nm, the increase of the PL as function of the film thickness is the same for TiO2 and for quartz, which indicates that the PL enhancement originates at the interface. The dissociation of excitons at the P3OT/TiO2 interface yields positive polarons in P3OT, which is not the case at the P3OT/quartz interface. We postulate that interaction between positive polarons and excitons explain the observed enhancement of the PL at the P3OT/TiO2 interface. © 2004 American Institute of Physics.
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78.66.Qn Polymers; organic compounds
68.55.-a Thin film structure and morphology
78.55.Kz Solid organic materials

In situ high-resolution transmission electron microscopy observation of photodecomposition process of poly-hydrocarbons on catalytic TiO2 films

Kenta Yoshida, Jun Yamasaki, and Nobuo Tanaka

Appl. Phys. Lett. 84, 2542 (2004); http://dx.doi.org/10.1063/1.1689747 (3 pages) | Cited 7 times

Online Publication Date: 1 April 2004

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Photocatalytic TiO2 materials have been one of the strong subjects of investigation for these ten years among various kinds of advanced functional materials. For studying the catalytic reaction by physical science techniques, a kind of transmission electron microscope technique is presented and applied to the study of photocatalysis on TiO2 films by UV light. Using the technique, we visualized in situ the decomposition process of hydrocarbons deposited on the TiO2 films in atomic level and elucidated a mechanism of the decomposition process. © 2004 American Institute of Physics.
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82.50.Hp Processes caused by visible and UV light
68.37.Lp Transmission electron microscopy (TEM)
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
52.38.Mf Laser ablation
68.55.A- Nucleation and growth
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Remote hydrogen plasma doping of single crystal ZnO

Yuri M. Strzhemechny, Howard L. Mosbacker, David C. Look, Donald C. Reynolds, Cole W. Litton, Nelson Y. Garces, Nancy C. Giles, Larry E. Halliburton, Shigeru Niki, and Leonard J. Brillson

Appl. Phys. Lett. 84, 2545 (2004); http://dx.doi.org/10.1063/1.1695440 (3 pages) | Cited 64 times

Online Publication Date: 1 April 2004

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We demonstrate that remote plasma hydrogenation can increase electron concentrations in ZnO single crystals by more than an order of magnitude. We investigated the effects of this treatment on Hall concentration and mobility as well as on the bound exciton emission peak I4 for a variety of ZnO single crystals–bulk air annealed, Li doped, and epitaxially grown on sapphire. Hydrogen increases I4 intensity in conducting samples annealed at 500 and 600 °C and partially restores emission in the I4 range for Li-diffused ZnO. Hydrogenation increases carrier concentration significantly for the semi-insulating Li doped and epitaxial thin film samples. These results indicate a strong link between the incorporation of hydrogen, increased donor-bound exciton PL emission, and increased n-type conductivity. © 2004 American Institute of Physics.
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73.61.Ga II-VI semiconductors
78.66.Hf II-VI semiconductors
61.72.uj III-V and II-VI semiconductors
81.65.-b Surface treatments
52.77.-j Plasma applications
72.20.My Galvanomagnetic and other magnetotransport effects
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
81.40.Gh Other heat and thermomechanical treatments
66.30.H- Self-diffusion and ionic conduction in nonmetals
78.55.Et II-VI semiconductors
72.80.Ey III-V and II-VI semiconductors
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