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16 Nov 1998

Volume 73, Issue 20, pp. 2857-3009

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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

Role of buffer surface morphology and alloying effects on the properties of InAs nanostructures grown on InP(001)

J. Brault, M. Gendry, G. Grenet, G. Hollinger, Y. Desières, and T. Benyattou

Appl. Phys. Lett. 73, 2932 (1998); http://dx.doi.org/10.1063/1.122634 (3 pages) | Cited 68 times

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We show the role played by the buffer surface morphology and by alloying effects on the size, shape and lateral distribution of InAs nanostructures grown on InP(001) substrates by molecular beam epitaxy. Three buffers, viz., In0.53Ga0.47As, In0.52Al0.48As, and InP lattice matched on InP have been studied. Differences in nanostructure morphology and in carrier confinement have been evaluated by atomic force microscopy and by low-temperature photoluminescence measurements, respectively. Alongside the classical relaxation mode through two-dimensional/three-dimensional surface morphology change, a chemical relaxation mode has to be introduced as a competitive mode of relaxation of strained layers. This chemical relaxation mode, due to alloying between the InAs deposit and the buffer, is thought to be responsible for most of the observed differences in the InAs nanostructure properties. © 1998 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
68.35.B- Structure of clean surfaces (and surface reconstruction)
73.61.Ey III-V semiconductors
68.35.Fx Diffusion; interface formation
78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors

Argon ion damage in self-assembled quantum dots structures

W. V. Schoenfeld, C.-H. Chen, P. M. Petroff, and E. L. Hu

Appl. Phys. Lett. 73, 2935 (1998); http://dx.doi.org/10.1063/1.122635 (3 pages) | Cited 20 times

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The effects of radiation damage exposure on InGaAs quantum wells and InAs quantum dots are compared using luminescence spectroscopy techniques. A large increase in the radiation resistance of the InAs quantum dots is observed and attributed to exciton localization in the quantum dots and a point defect strain gettering effect. © 1998 American Institute of Physics.
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61.82.Fk Semiconductors
61.80.Jh Ion radiation effects
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
78.66.Fd III-V semiconductors
71.35.Cc Intrinsic properties of excitons; optical absorption spectra
78.55.Cr III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Mapping the influence of stress on the surface elasticity with an atomic force microscope

Eric Finot, Eric Lesniewska, Jean-Pierre Goudonnet, and Jean-Claude Mutin

Appl. Phys. Lett. 73, 2938 (1998); http://dx.doi.org/10.1063/1.122636 (3 pages) | Cited 1 time

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This letter reports an original experimental observation of the lateral stress effects on pure surface. The surface elasticity has been separated from topographical informations at the microscopic and atomic levels. The stress applied to the sample leads to modify the stiffness of the surface and affect the force modulation images. Measurements also revealed that the spring constant and the quality factor of cantilevers play an important role in the contrast mechanism of the elasticity images. © 1998 American Institute of Physics.
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68.35.Gy Mechanical properties; surface strains
62.20.D- Elasticity
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

Charge stability of pulsed-laser deposited polytetrafluoroethylene film electrets

Reinhard Schwödiauer, Simona Bauer-Gogonea, Siegfried Bauer, Johannes Heitz, Enno Arenholz, and Dieter Bäuerle

Appl. Phys. Lett. 73, 2941 (1998); http://dx.doi.org/10.1063/1.122637 (3 pages) | Cited 20 times

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Pulsed-laser deposited (PLD) polytetrafluoroethylene (Teflon-PTFE) films from press-sintered powder targets are found to be highly crystalline, with spherulite sizes adjustable over more than one order of magnitude by suitable thermal annealing. Films with large spherulites show an excellent charge stability, comparable and even superior to commercially available Teflon-PTFE foils. PLD-PTFE enlarges the family of Teflon materials and may thus become interesting for potential miniaturized electret devices. © 1998 American Institute of Physics.
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81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
81.15.Fg Pulsed laser ablation deposition
73.61.Ph Polymers; organic compounds
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