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16 Nov 1998

Volume 73, Issue 20, pp. 2857-3009

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Auger coefficients in type-II InAs/Ga1−xInxSb quantum wells

J. R. Meyer, C. L. Felix, W. W. Bewley, I. Vurgaftman, E. H. Aifer, L. J. Olafsen, J. R. Lindle, C. A. Hoffman, M.-J. Yang, B. R. Bennett, B. V. Shanabrook, H. Lee, C.-H. Lin, S. S. Pei, and R. H. Miles

Appl. Phys. Lett. 73, 2857 (1998); http://dx.doi.org/10.1063/1.122609 (3 pages) | Cited 51 times

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Two different approaches, a photoconductive response technique and a correlation of lasing thresholds with theoretical threshold carrier concentrations have been used to determine Auger lifetimes in InAs/GaInSb quantum wells. For energy gaps corresponding to 3.1–4.8 μm, the room-temperature Auger coefficients for seven different samples are found to be nearly an order-of-magnitude lower than typical type-I results for the same wavelength. The data imply that at this temperature, the Auger rate is relatively insensitive to details of the band structure. © 1998 American Institute of Physics.
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73.61.Ey III-V semiconductors
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
72.40.+w Photoconduction and photovoltaic effects
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Single-mode picosecond blue laser emission from a solid conjugated polymer

S. Stagira, M. Zavelani-Rossi, M. Nisoli, S. DeSilvestri, G. Lanzani, C. Zenz, P. Mataloni, and G. Leising

Appl. Phys. Lett. 73, 2860 (1998); http://dx.doi.org/10.1063/1.122610 (3 pages) | Cited 37 times

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We demonstrate single-mode laser emission at 490 nm from a stable cavity based on a methyl-substituted poly-(para-phenylene)-type ladder polymer. The laser emission is characterized by a well-defined excitation fluence threshold, a high directionality, and a drastic spectral narrowing. The laser generates picosecond pulses of excellent amplitude stability. © 1998 American Institute of Physics.
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42.70.Hj Laser materials
42.70.Jk Polymers and organics
42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

High-temperature properties of GaInAs/AlGaAs lasers with improved carrier confinement by short-period superlattice quantum well barriers

F. Schäfer, B. Mayer, J. P. Reithmaier, and A. Forchel

Appl. Phys. Lett. 73, 2863 (1998); http://dx.doi.org/10.1063/1.122611 (3 pages) | Cited 17 times

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The influence of the carrier confinement on the output characteristics of GaInAs/AlGaAs lasers was investigated. To improve the carrier confinement, AlGaAs/GaAs short-period superlattices were used as quantum well barriers. In comparison to lasers with GaAs barriers the structures with the modified barriers show improved temperature properties at low threshold current densities without deterioration of the internal quantum efficiency (>95%). High characteristic temperatures (T0) well above 300 K were measured between 20 and 75 °C and laser operation up to 238 °C could be achieved. The large improvement in T0 is mainly attributed to the reduced thermionic emission of carriers out of the quantum well due to the increased barrier height and the carrier reflection above the barrier by the short-period superlattice. © 1998 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
73.61.Ey III-V semiconductors

Bright organic electroluminescent devices having a metal-doped electron-injecting layer

Junji Kido and Toshio Matsumoto

Appl. Phys. Lett. 73, 2866 (1998); http://dx.doi.org/10.1063/1.122612 (3 pages) | Cited 293 times

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Bright organic electroluminescent devices were developed using a metal-doped organic layer as an electron-injecting layer at the interface between the cathode and the emitter layer. The typical device structure is a glass substrate/indium-tin oxide/arylamine/tris(8-quinolinolato)Al (Alq)/metal-doped Alq/Al. Dopant metals are highly reactive metals such as Li, Sr, and Sm. A device with Li-doped Alq layer showed high luminance of over 30 000 cd/m2, while a device without the metal-doped Alq layer exhibited only 3400 cd/m2. These results suggest that the Li doping to the Alq layer generates the radical anions of Alq serving as intrinsic electron carriers, which result in low barrier height for electron injection and high electron conductivity of the Li-doped Alq layer. © 1998 American Institute of Physics.
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85.60.Jb Light-emitting devices
78.60.Fi Electroluminescence
78.66.Qn Polymers; organic compounds

High-performance, reliable, 730-nm-emitting Al-free active region diode lasers

A. Al-Muhanna, J. K. Wade, T. Earles, J. Lopez, and L. J. Mawst

Appl. Phys. Lett. 73, 2869 (1998); http://dx.doi.org/10.1063/1.122613 (3 pages) | Cited 12 times

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Compressively strained InGaAsP quantum well (QW) active (λ=732 nm) diode lasers achieve 2.9 W continuous wave (cw) power from facet-coated (4%/95%) 100-μm-wide apertures, with reliable operation demonstrated at 0.5 W cw power. A broad waveguide structure is used to obtain a large transverse spot size (d/Γ = 0.433 μm), resulting in a low internal loss (αi ∼ 2 cm−1) and narrow transverse far-field beam width (θ1/2 = 38°). Record-high characteristic temperatures for the threshold current and the differential quantum efficiency (T0 = 115 K and T1 = 285 K) are obtained by growing on misoriented substrates. © 1998 American Institute of Physics.
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42.60.By Design of specific laser systems
42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Analysis of current–voltage characteristics of organic light emitting diodes having a LiF/Al cathode and an Al–hydroxyquinoline/diamine junction

Michio Matsumura and Yukitoshi Jinde

Appl. Phys. Lett. 73, 2872 (1998); http://dx.doi.org/10.1063/1.122614 (3 pages) | Cited 40 times

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The electron injection from the composite cathode consisting of a very thin LiF layer and an Al layer (LiF/Al) into Al–hydroxyquinoline (ALQ) layers showed the voltage and temperature dependence, which is characteristic to the Schottky emission mechanism. The barrier formed at the interface is lower than that formed at the interfaces between the conventional cathodes and the ALQ layer. The current–voltage characteristics of the light emitting diodes having the LiF/Al cathode and the ALQ/diamine junction were well explained on the basis of the properties of the electron injection into the ALQ layer and the hole injection into the diamine layer. © 1998 American Institute of Physics.
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85.60.Jb Light-emitting devices
73.30.+y Surface double layers, Schottky barriers, and work functions
73.61.Ph Polymers; organic compounds

Photoluminescence and upconversion optical properties of the CaS:Sm3+ nanocrystallites

X. Gong, W. J. Chen, P. F. Wu, and W. K. Chan

Appl. Phys. Lett. 73, 2875 (1998); http://dx.doi.org/10.1063/1.122615 (3 pages) | Cited 16 times

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The CaS:Sm3+  nanocrystallites are synthesized by the modified sol-gel technique. The grain size of the nanocrystallites is approximately 60 nm, which is determined by transmission electron microscopy, x-ray diffraction and UV-vis absorption spectrum. Compared to the CaS:Sm3+ macrocrystallites, the absorption and emission of the nanocrystallites have a blueshift in their spectra, and the emission spectrum of the host CaS appears in the region of 400–500 nm. It was also found that the efficiencies of both photoluminescence and upconversion in the nanocrystallites are higher than those in the macrocrystallites. © 1998 American Institute of Physics.
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78.55.Hx Other solid inorganic materials
42.70.Ln Holographic recording materials; optical storage media
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.10.Dn Growth from solutions
81.10.Fq Growth from melts; zone melting and refining
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
78.40.Fy Semiconductors

Amplified resonant Raman scattering in conducting polymer thin films

M. N. Shkunov, W. Gellermann, and Z. V. Vardeny

Appl. Phys. Lett. 73, 2878 (1998); http://dx.doi.org/10.1063/1.122616 (3 pages) | Cited 14 times

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Using picosecond pulsed laser excitation, we investigate the optical emission characteristics of poly(2,5-dioctyloxy-p-phenylenevinylene), (DOO-PPV), thin films at high excitation intensities (∼1–90 MW/cm2). We observe the presence of amplified resonance Raman scattering in the emission spectra of conducting polymer films. The effect results in sharp Raman lines (widths smaller than 3 Å) superimposed on a significantly broader, well known, spectrally narrowed emission band (width ∼10 nm) caused by the amplified spontaneous emission in the waveguided polymer film. At the highest used excitation intensities, Raman scattering dominates the DOO-PPV emission spectrum resulting in a highly monochromatic, single-line emission spectrum. © 1998 American Institute of Physics.
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78.66.Qn Polymers; organic compounds
42.70.Jk Polymers and organics
78.45.+h Stimulated emission
78.55.Kz Solid organic materials
42.50.Nn Quantum optical phenomena in absorbing, amplifying, dispersive and conducting media; cooperative phenomena in quantum optical systems
42.65.Dr Stimulated Raman scattering; CARS
42.65.Es Stimulated Brillouin and Rayleigh scattering

Electro-optic characteristics and switching principle of a nematic liquid crystal cell controlled by fringe-field switching

S. H. Lee, S. L. Lee, and H. Y. Kim

Appl. Phys. Lett. 73, 2881 (1998); http://dx.doi.org/10.1063/1.122617 (3 pages) | Cited 236 times

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We have fabricated a nematic liquid crystal cell associated with a homogeneously aligned to twisted transition of a liquid crystal director. In the absence of an electric field, the liquid crystal molecule is homogeneously aligned under the crossed polarizers, and thus the cell appears to be black. When a fringe field induced by interdigital electrodes is applied, liquid crystal molecules rotate in plane even above electrodes and thus the cell transmits light. The device exhibits a high transmittance ratio as well as a wide viewing angle, which solves a long standing problem of low transmittance existing in the conventional in-plane switching mode. We show that the distance between electrodes smaller than the width of an electrode and cell gap is required for generating fringe field with applied voltage and rotating molecules above electrodes. We also investigate the mechanism of fringe-field switching and dependence of electro-optic effect on different cell conditions and dielectric anisotropy of liquid crystal. © 1998 American Institute of Physics.
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42.79.Kr Display devices, liquid-crystal devices
85.60.Pg Display systems
78.20.Jq Electro-optical effects
61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order

Scanning second harmonic microscopy techniques with monomode and near field optical fibers

M. Adameck, R. Blum, and M. Eich

Appl. Phys. Lett. 73, 2884 (1998); http://dx.doi.org/10.1063/1.122618 (3 pages) | Cited 7 times

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Extending our scanning second harmonic microscopy (SSHM) technique for the detection of lateral orientational inhomogeneities in high field poled polymer films, we present results with considerably improved lateral resolution by using optical fiber technology. Two experimental setups for measuring the χ(2) susceptibility of thin films are introduced. The first setup uses a standard monomode infrared-fiber with 10 μm core that carries the coherent fundamental infrared wave to the surface of a poled polymer film (illumination mode). The generated doubled frequency wave behind the nonlinear optical sample is detected by a photomultiplier tube. In the second setup a lens focuses the fundamental wave into the poled film. The resulting second harmonic wave is coupled into a 2.5 μm single mode fiber. SSHM micrographs of high field poled nonlinear optical polymer films were obtained with lateral resolutions of <3.5 μm. SSHM was also realized with a scanning near field optical microscopy fiber in pick up mode. © 1998 American Institute of Physics.
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07.79.Fc Near-field scanning optical microscopes
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
42.70.Jk Polymers and organics
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
61.41.+e Polymers, elastomers, and plastics
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
07.60.Vg Fiber-optic instruments
42.81.Pa Sensors, gyros
42.65.An Optical susceptibility, hyperpolarizability

Optical determination of molecule diffusion coefficients in polymer films

R. P. Podgorsek and H. Franke

Appl. Phys. Lett. 73, 2887 (1998); http://dx.doi.org/10.1063/1.122619 (3 pages) | Cited 9 times

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We present a method using surface-plasmon leaky mode spectroscopy for the analysis of the vapor–molecule diffusion process in polymer films leading to the diffusion coefficients of the molecules. The solution of the diffusion differential equation in the case of thin films yields a molecule concentration profile. Linearity between refractive index increase and molecule concentration gives the same variation for the index increase. Thus, a theoretical expression for the measured reflectivity can be derived using the transfer-matrix formalism for layered media, and theoretical fits to measured reflectivity data finally yield the corresponding diffusion coefficients. For the polymer TeflonAF1600 diffusion coefficients for benzene and toluene are determined to 4.9×10−10 and 2.7×10−10 cm2/s, respectively. © 1998 American Institute of Physics.
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66.30.J- Diffusion of impurities
61.41.+e Polymers, elastomers, and plastics
78.66.Qn Polymers; organic compounds
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Recombination dynamics in InAsSb quantum-well diode lasers measured using photoluminescence upconversion

W. T. Cooley, R. L. Hengehold, Y. K. Yeo, G. W. Turner, and J. P. Loehr

Appl. Phys. Lett. 73, 2890 (1998); http://dx.doi.org/10.1063/1.122620 (3 pages) | Cited 6 times

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We report Shockley–Read–Hall (SRH), radiative, and Auger recombination rates in midinfrared laser structures from time-resolved photoluminescence using frequency upconversion. The devices studied were actual InAsSb/InAlAsSb multiple-quantum-well (MQW) diode lasers emitting near 3.3 μm, which have been previously characterized for laser performance. We extend the initial studies and report on the carrier recombination dynamics. The importance of carrier density motivates a careful examination of carrier density and quantum-well effects. SRH, radiative, and Auger recombination rates (ASRH, Brad, and CAuger, respectively) were measured at 77 K and found to be ASRH−1 ≈ 10 ns, Brad ≈ 2×10−10 cm3 s−1, and CAuger ⩽ 1.0×10−29 cm6 s−1, respectively. At 150 K the nonradiative recombination coefficients increased to ASRH−1 ≈ 1.7 ns, Brad ≈ 0.78×10−10 cm3 s−1 and CAuger ≈ 7.0×10−28 cm6 s−1, respectively. This study suggests InAsSb/InAlAsSb MQW diode laser performance may be limited by SRH nonradiative recombination mechanisms rather than Auger recombination. © 1998 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
73.61.Ey III-V semiconductors
78.47.-p Spectroscopy of solid state dynamics

Maskless photolithography: Embossed photoresist as its own optical element

Kateri E. Paul, Tricia L. Breen, Joanna Aizenberg, and George M. Whitesides

Appl. Phys. Lett. 73, 2893 (1998); http://dx.doi.org/10.1063/1.122621 (3 pages) | Cited 21 times

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This letter demonstrates that features embossed on the surface of a layer of photoresist can direct UV light in the photoresist layer. These topographical features act as optical elements: they focus/disperse and phase shift incident light in the optical near field, inside the resist layer. A number of different surface topographies have been examined, which give 50–250 nm features after exposure and development. This method gives patterns of complex features over large areas, in a parallel process, that can then be transferred into silicon or metal. It provides a method for controlling the intensity of light inside a thin film of photoresist. © 1998 American Institute of Physics.
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85.40.Hp Lithography, masks and pattern transfer
68.35.B- Structure of clean surfaces (and surface reconstruction)

Second-harmonic generation in BaTiO3 films doped with cerium

Lin-zhen Xuan, Shao-hua Pan, Zheng-hao Chen, Rong-ping Wang, Wen-sheng Shi, and Chun-ling Li

Appl. Phys. Lett. 73, 2896 (1998); http://dx.doi.org/10.1063/1.122622 (3 pages) | Cited 18 times

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Second-harmonic generation of 1.064 μm incident light was measured on BaTiO3 thin films, both a-axis and c-axis oriented, undoped and doped with cerium, prepared by pulsed laser deposition. The dependence of second-harmonic generation (SHG) coefficients of these films on the incidence angle and the polarization direction of the fundamental beam were investigated. The effective SHG coefficients was enhanced greatly when the films were doped with cerium. © 1998 American Institute of Physics.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.70.Mp Nonlinear optical crystals
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Time-gated x-ray tomography

M. Grätz, L. Kiernan, C.-G. Wahlström, S. Svanberg, and K. Herrlin

Appl. Phys. Lett. 73, 2899 (1998); http://dx.doi.org/10.1063/1.122623 (3 pages) | Cited 3 times

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Time-gated x-ray tomography with scatter reduction is demonstrated using a laser-produced plasma as an ultrashort-pulse x-ray source in combination with a time-resolving streak-camera detector. Backprojections of a phantom imbedded in 9 cm of water show an effective 50% increase in contrast when scattered x-ray quanta (being delayed in time) are suppressed by gating on the prompt, nonscattered photons. Implications for future volumetric tomography, in particular concerning possible dose reductions, are discussed. © 1998 American Institute of Physics.
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87.59.bd Computed radiography
07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.25.Os Emission, absorption, and scattering of electromagnetic radiation

Guiding characteristics of an acoustic standing wave in a piezoelectric tube

C. M. Fauser, E. W. Gaul, S. P. Le Blanc, and M. C. Downer

Appl. Phys. Lett. 73, 2902 (1998); http://dx.doi.org/10.1063/1.122624 (3 pages) | Cited 2 times

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Propagation of an He–Ne laser beam through a gas filled piezoelectric tube is used to characterize the guiding properties of a radially driven acoustic standing wave. Impedance matched driving at 1 MHz of the 5-cm-long piezotube yields radial density perturbations of 0.005 at 40 V driving voltage. The frequency spectrum of the cavity resonances is used to measure the damping of the standing wave due to shear viscosity in Ar. © 1998 American Institute of Physics.
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43.20.Mv Waveguides, wave propagation in tubes and ducts
52.38.-r Laser-plasma interactions
42.79.Jq Acousto-optical devices
42.79.Gn Optical waveguides and couplers
52.40.Fd Plasma interactions with antennas; plasma-filled waveguides
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
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Random domain formation in 0°–360° bistable nematic twist cells

H. Bock

Appl. Phys. Lett. 73, 2905 (1998); http://dx.doi.org/10.1063/1.122625 (3 pages) | Cited 19 times

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An analogue gray scale effect in bistable twisted nematic displays is presented. The disappearance of twist during the Frederiks transition is sufficiently inhomogeneous to allow the formation of a variable ratio of twisted and untwisted domains by applying a short variable pulse. Thermal fluctuations in the director profile lead to lateral alterations of the unwinding voltage through the cell. The effect offers high contrast, good viewing angle characteristics, and short address times. © 1998 American Institute of Physics.
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42.79.Kr Display devices, liquid-crystal devices
42.70.Df Liquid crystals
85.60.Pg Display systems
64.70.M- Transitions in liquid crystals

The conductivity dependence of the shear stress in electrorheological fluids

Yucheng Lan, Xiaoyu Xu, Shouqiang Men, and Kunquan Lu

Appl. Phys. Lett. 73, 2908 (1998); http://dx.doi.org/10.1063/1.122626 (3 pages) | Cited 10 times

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A ferroelectric KNO3/silicone oil electrorheological (ER) fluid is introduced to investigate the conductivity dependence of the ER effect under dc electric fields where the ER effect is conductivity dominated. By measuring the temperature dependence of the shear stress across the Curie temperature of particles, the dependence of the ER effect on conductivity has been quantitatively obtained in experiments. There is a critical conductivity ratio Γc (or mismatch factor βc2): when Γ<Γc, the shear stress increases with Γ; when Γ>Γc, the shear stress decreases with Γ. An agreement is obtained between theory and experiment when Γ (or β2) is lower. In the higher Γ(or β2) range, the experimental data are not in agreement with the theoretical prediction and the interfacial effect should be taken into account. The experimental data are more reliable due to the same conditions, such as the chemical nature, the surfacial property of particles, and the interfacial property between particles and suspending liquid as well as the size and shape of the particles. © 1998 American Institute of Physics.
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83.80.Gv Electro- and magnetorheological fluids
83.80.Hj Suspensions, dispersions, pastes, slurries, colloids
83.80.Iz Emulsions and foams
62.10.+s Mechanical properties of liquids
77.84.Nh Liquids, emulsions, and suspensions; liquid crystals
72.80.Tm Composite materials
72.80.Sk Insulators
82.70.Kj Emulsions and suspensions
77.80.B- Phase transitions and Curie point

Orientation of graphitic planes during the bias-enhanced nucleation of diamond on silicon: An x-ray absorption near-edge study

Ignacio Jiménez, M. Mar García, José M. Albella, and Louis J. Terminello

Appl. Phys. Lett. 73, 2911 (1998); http://dx.doi.org/10.1063/1.122627 (3 pages) | Cited 14 times

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The bias-enhanced nucleation of diamond on Si(100) is studied by angle-dependent x-ray absorption near-edge spectroscopy (XANES). During diamond nucleation, a graphitic phase is also detected. The angle dependence of the XANES signal shows that the graphitic basal planes are oriented perpendicular to the surface. Implications of this result on the mechanism of bias-enhanced nucleation are discussed.© 1998 American Institute of Physics.
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81.05.ub Fullerenes and related materials
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.-a Thin film structure and morphology
78.70.Dm X-ray absorption spectra
81.10.Aj Theory and models of crystal growth; physics and chemistry of crystal growth, crystal morphology, and orientation

Suppression of penetration of aluminum into 8-hydroxyquinoline aluminum via a thin oxide barrier

M. B. Huang, K. McDonald, J. C. Keay, Y. Q. Wang, S. J. Rosenthal, R. A. Weller, and L. C. Feldman

Appl. Phys. Lett. 73, 2914 (1998); http://dx.doi.org/10.1063/1.122628 (3 pages) | Cited 12 times

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We report a direct observation of Al penetration into an organic film of 8-hydroxyquinoline aluminum (Alq) in a Alq/Al bilayer, a common interface occurring in many organic light-emitting diode structures. The Al penetration has a strong correlation with Alq photoluminescence quenching. We also demonstrate that the penetration and luminescence quenching can be effectively suppressed by ∼ 20 Å of an intervening layer of Al2O3 at the Alq/Al interface. © 1998 American Institute of Physics.
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66.30.Ny Chemical interdiffusion; diffusion barriers
68.35.Fx Diffusion; interface formation
85.60.Jb Light-emitting devices
78.55.Kz Solid organic materials
78.66.Qn Polymers; organic compounds

Reduction of threading dislocations by InGaAs interlayer in GaAs layers grown on Si substrates

Y. Takano, M. Hisaka, N. Fujii, K. Suzuki, K. Kuwahara, and S. Fuke

Appl. Phys. Lett. 73, 2917 (1998); http://dx.doi.org/10.1063/1.122629 (3 pages) | Cited 18 times

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High-quality GaAs epilayers with dislocation densities of 1.2×106 cm−2 on (100)Si substrates have been obtained by insertion of an InGaAs strained interlayer combined with thermal cycle annealing instead of strained layer superlattices. All the layers were grown by low-pressure metalorganic vapor phase epitaxy. The threading dislocation density near the surface of 4 μm thick GaAs was measured by plan-view transmission electron microscopy. The threading dislocation density was found to be very sensitive to the In composition of the interlayer and the specifics of thermal cycle annealing. © 1998 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
81.05.Ea III-V semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.72.Cc Kinetics of defect formation and annealing

Quasi-ideal strontium titanate crystal surfaces through formation of strontium hydroxide

Gertjan Koster, Boike L. Kropman, Guus J. H. M. Rijnders, Dave H. A. Blank, and Horst Rogalla

Appl. Phys. Lett. 73, 2920 (1998); http://dx.doi.org/10.1063/1.122630 (3 pages) | Cited 218 times

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In recent years, well-defined and nearly perfect single crystal surfaces of oxide perovskites have become increasingly important. A single terminated surface is a prerequisite for reproducible thin film growth and fundamental growth studies. In this work, atomic and lateral force microscopy have been used to display different terminations of SrTiO3. We observe hydroxylation of the topmost SrO layer after immersion of SrTiO3 in water, which is used to enhance the etch-selectivity of SrO relative to TiO2 in a buffered HF solution. We reproducibly obtain perfect and single terminated surfaces, irrespective of the initial state of polished surfaces and the pH value of the HF solution. This approach to the problem might be used for a variety of multi-component oxide single crystals. True two-dimensional reflection high-energy electron diffraction intensity oscillations are observed during homo epitaxial growth using pulsed laser deposition on these surfaces. © 1998 American Institute of Physics.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
81.65.Cf Surface cleaning, etching, patterning
81.15.Fg Pulsed laser ablation deposition
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)

Epitaxial growth of (001)-oriented and (110)-oriented SrBi2Ta2O9 thin films

J. Lettieri, Y. Jia, M. Urbanik, C. I. Weber, J-P. Maria, D. G. Schlom, H. Li, R. Ramesh, R. Uecker, and P. Reiche

Appl. Phys. Lett. 73, 2923 (1998); http://dx.doi.org/10.1063/1.122631 (3 pages) | Cited 47 times

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Epitaxial SrBi2Ta2O9 thin films have been grown with (001) and (110) orientations by pulsed laser deposition on (001) LaAlO3–Sr2AlTaO6 and (100) LaSrAlO4 substrates, respectively. Four-circle x-ray diffraction and transmission electron microscopy reveal nearly phase pure epitaxial films. Minimization of surface mesh mismatch between the film and substrate (i.e., choice of appropriate substrate material and orientation) was used to stabilize the desired orientations and achieve epitaxial growth. © 1998 American Institute of Physics.
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81.15.Fg Pulsed laser ablation deposition
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
68.55.-a Thin film structure and morphology
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films

Relationship between phase shift and energy dissipation in tapping-mode scanning force microscopy

Javier Tamayo and Ricardo García

Appl. Phys. Lett. 73, 2926 (1998); http://dx.doi.org/10.1063/1.122632 (3 pages) | Cited 96 times

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Force curves taken during a load–unload cycle show the presence of a hysteresis loop. The area enclosed by the loop is used to measure the energy dissipated by the tip-sample interaction in tapping-mode scanning force microscopy. The values of the energy loss obtained from force curves are compared with the results derived from a model based on phase shift measurements. The agreement obtained between both methods demonstrates that for the same operating conditions, the higher the phase shift the larger the amount of energy dissipated by the tip-sample interaction. It also confirms the prediction that phase-contrast images can only arise if there are tip-sample inelastic interactions. © 1998 American Institute of Physics.
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07.79.Lh Atomic force microscopes
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy

Excitation of Er3+ ions in silicon dioxide films thermally grown on silicon

A. Kozanecki, M. Stepikhova, S. Lanzerstorfer, W. Jantsch, L. Palmetshofer, B. J. Sealy, and C. Jeynes

Appl. Phys. Lett. 73, 2929 (1998); http://dx.doi.org/10.1063/1.122633 (3 pages) | Cited 9 times

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We investigate photoluminescence (PL) and photoluminescence excitation spectroscopy of Er3+ ions implanted into SiO2 films thermally grown on silicon wafers. We show that at 10 K the Er3+ PL excited with the 514.5 nm line of an Ar laser is limited by the total number of Er ions, whereas at resonant excitation within the 960–1000 nm range the PL efficiency is rather concentration limited. Some samples were codoped with Yb3+ ions to study sensitization of the 4f–4f PL of Er3+ ions. At resonant excitation the presence of Yb leads to an enhancement of the Er3+ PL only at dilute Er concentrations. © 1998 American Institute of Physics.
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78.55.Hx Other solid inorganic materials
78.66.Nk Insulators
71.55.Ht Other nonmetals
61.72.up Other materials
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