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14 Jun 1999

Volume 74, Issue 24, pp. 3595-3737

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Fast optical switching by a laser-manipulated microdroplet of liquid crystal

Saulius Juodkazis, Masaya Shikata, Toshimasa Takahashi, Shigeki Matsuo, and Hiroaki Misawa

Appl. Phys. Lett. 74, 3627 (1999); http://dx.doi.org/10.1063/1.123203 (3 pages) | Cited 28 times

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We demonstrate the feasibility of an all-optical liquid-crystal (LC) switch with submillisecond switching time. This switch is realized by optical manipulation of a three-dimensionally trapped microscopic nematic LC droplet using an “optical tweezers.” Transmission of a polarizer/LC droplet/analyzer system can be modulated at frequencies as high as 103 Hz, a faster response than that of a nematic LC demonstrated so far. The response corresponds to a submillisecond switching time when the LC droplet is rotated by an angle of π/4. The alignment of the LC droplet to the plane of the incident plane-polarized beam is also demonstrated. © 1999 American Institute of Physics.
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42.65.Pc Optical bistability, multistability, and switching, including local field effects
42.79.Kr Display devices, liquid-crystal devices
42.70.Df Liquid crystals
37.10.Vz Mechanical effects of light on atoms, molecules, and ions

Field-enhanced Stokes shifts in tensilely strained carbon-based quantum wells

Y. Sugawara, S. Fukatsu, K. Brunner, and K. Eberl

Appl. Phys. Lett. 74, 3630 (1999); http://dx.doi.org/10.1063/1.123204 (3 pages) | Cited 1 time

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A large, rigid downward shift of excitonic luminescence peak energies was observed with increasing transverse electric field in tensilely strained Si1−yCy/Si(001) symmetric quantum wells, as opposed to theoretical calculations predicting a blueshift due to exciton weakening, which more than balances the redshift due to quantum-confined Stark effects. The observed anomalies are interpreted in terms of field-enhanced Stokes shifts which occur due to carrier relaxation in an inhomogeneously distributed potential of the grown-in Si1−yCy/Si interfaces. © 1999 American Institute of Physics.
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78.66.Li Other semiconductors
78.55.Hx Other solid inorganic materials
78.20.Jq Electro-optical effects
71.35.Cc Intrinsic properties of excitons; optical absorption spectra
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Syntactic coalescence of WS2 nanotubes

M. Remškar, Z. Škraba, R. Sanjinés, and F. Lévy

Appl. Phys. Lett. 74, 3633 (1999); http://dx.doi.org/10.1063/1.123205 (3 pages) | Cited 12 times

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WS2 nanoropes merged from nanotube coalescence present a new case of inorganic fiber composites with several nanotubes grown side by side up to a few millimeters in length. The extremities of external and inner spirally rolled-up molecular layer building the tubes are at the origin of the nanotube nucleation leading to the syntactic growth of nanotubes. The model of undulation of thin crystal flakes based on stacking mismatch is discussed. The nanoropes grow also by self-assembly or by coalescence of single tubes at low angles of incidence. An attractive long-range force leading to the nanotube approach is proposed. © 1999 American Institute of Physics.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
61.46.-w Structure of nanoscale materials

Strain effects and microstructure of epitaxial manganite thin films and heterostructures

B. Wiedenhorst, C. Höfener, Yafeng Lu, J. Klein, L. Alff, R. Gross, B. H. Freitag, and W. Mader

Appl. Phys. Lett. 74, 3636 (1999); http://dx.doi.org/10.1063/1.123206 (3 pages) | Cited 44 times

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We have grown epitaxial La2/3Sr1/3MnO3 (LSMO) and La2/3Ba1/3MnO3 (LBMO) thin films as well as La2/3Ba1/3MnO3/SrTiO3 heterostructures by pulsed-laser deposition. The microstructure of the films was analyzed by x-ray diffraction and transmission electron microscopy. A significant effect of strain due to lattice mismatch was found. Whereas the thick LBMO films show perfect epitaxy and grow coherently strained over the full film thickness, the LSMO films were found to be composed of two layers separated by an intrinsic interface region containing a high density of defects. The approximately 60 nm thick bottom layer grows coherently on the SrTiO3 (STO) substrate and is highly strained, whereas the top layer is almost strain free. The LBMO/STO heterostructures are coherently strained and show a very low density of defects and sharp interfaces. © 1999 American Institute of Physics.
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68.55.-a Thin film structure and morphology
61.72.-y Defects and impurities in crystals; microstructure
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.Fg Pulsed laser ablation deposition
68.35.Ct Interface structure and roughness

Improved thermal stability of nonpolymeric organic glasses by doping with fullerene C60

T. Krieg, A. Petr, G. Barkleit, and L. Dunsch

Appl. Phys. Lett. 74, 3639 (1999); http://dx.doi.org/10.1063/1.123207 (3 pages) | Cited 3 times

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The doping of nonpolymeric organic glasses with C60 is found to improve their thermal stability. Films of triphenylamine dimer (TPD) N,N′-diphenyl-N,N′-(3-methyl-phenyl)-1,1′-biphenyl-4,4′-diamine, doped with fullerene C60 and 7,7,8,8-tetracyano-quinodimethane (TCNQ) on a level between 10 and 20 mol %, were prepared using vacuum codeposition techniques. While undoped and TCNQ-doped TPD films tend to crystallize under ambient conditions, no crystallization occurs on C60-doped TPD films on minimum doping level of 15 mol %. The crystallization can be suppressed even at temperatures about 333 K, the glass transition temperature of pure TPD, if the doping level of the C60-doped TPD films reaches 20 mol %. © 1999 American Institute of Physics.
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61.43.Er Other amorphous solids
61.48.-c Structure of fullerenes and related hollow and planar molecular structures
68.60.Dv Thermal stability; thermal effects
64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition
68.55.-a Thin film structure and morphology

Dense arrays of well-aligned carbon nanotubes completely filled with single crystalline titanium carbide wires on titanium substrates

Y. Gao, J. Liu, M. Shi, S. H. Elder, and J. W. Virden

Appl. Phys. Lett. 74, 3642 (1999); http://dx.doi.org/10.1063/1.123208 (3 pages) | Cited 19 times

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We report the synthesis of dense and uniform arrays of well-aligned carbon nanotubes on titanium substrates over large areas, in which all the tubes are simultaneously and completely filled with single crystals of titanium carbide. The carbon nanotubes were synthesized by thermal chemical vapor deposition of ethylene on iron-coated substrates, while the titanium carbide was simultaneously formed inside the nanotubes through a simultaneous solid state reaction. We propose a base dissolution and precipitation mechanism for the growth of titanium carbide filled carbon nanotubes. The same method can be used to fabricate oriented nanotube arrays filled with other carbides on a variety of substrates over large scale. Such well-aligned and densely packed uniform carbon nanotubes, completely filled with nanowires on conducting substrates, will have great potential in many applications. © 1999 American Institute of Physics.
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81.05.ub Fullerenes and related materials
61.48.-c Structure of fullerenes and related hollow and planar molecular structures
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
64.75.-g Phase equilibria
81.07.-b Nanoscale materials and structures: fabrication and characterization

Polyaniline and poly(N-vinylcarbazole) blends as anode for blue light-emitting diodes

Jinkoo Chung, Beomrak Choi, and Hong H. Lee

Appl. Phys. Lett. 74, 3645 (1999); http://dx.doi.org/10.1063/1.123209 (3 pages) | Cited 15 times

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Polyaniline and poly(N-vinylcarbazole) (PANI:PVK) blends are introduced as an anode, and the advantages are demonstrated for organic light-emitting diodes (LEDs). Compared to the usual PANI network electrodes, use of the blend allows for simpler fabrication and provides a better planarized surface, especially for the device with vapor-deposited emitting layer. PANI is not usually used for blue LEDs because of its strong light absorption in the deep-blue spectral region. This problem is practically solved by the use of the blend. © 1999 American Institute of Physics.
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42.70.Jk Polymers and organics
85.60.Jb Light-emitting devices
78.40.Me Organic compounds and polymers

Oxygen diffusion in heavily antimony-, arsenic-, and boron-doped Czochralski silicon wafers

Toshiaki Ono, George A. Rozgonyi, Eiichi Asayama, Hiroshi Horie, Hideki Tsuya, and Koji Sueoka

Appl. Phys. Lett. 74, 3648 (1999); http://dx.doi.org/10.1063/1.123210 (3 pages) | Cited 9 times

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The effect of dopant-type, antimony (Sb), arsenic (As), and boron (B), on the outdiffusion of oxygen in heavily doped Czochralski (Cz) silicon wafers has been investigated using secondary ion mass spectroscopy. The results indicate that, although oxygen diffusion in Cz silicon is retarded in heavily B- and As-doped wafers during low temperature annealing (800 °C), it is not influenced by heavy Sb doping. This indicates that charge effects and atom size effects have negligible influence on the diffusion of oxygen. The B and As diffusion retardation effect is attributed to the existence of dopant-oxygen complexes. The oxygen solubility was largest in the most heavily B-doped samples annealed at low temperature. © 1999 American Institute of Physics.
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66.30.J- Diffusion of impurities
81.05.Cy Elemental semiconductors
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
61.72.Cc Kinetics of defect formation and annealing
81.40.Gh Other heat and thermomechanical treatments
64.75.-g Phase equilibria

Graphitization of nanodiamond powder annealed in argon ambient

Jian Chen, S. Z. Deng, Jun Chen, Z. X. Yu, and N. S. Xu

Appl. Phys. Lett. 74, 3651 (1999); http://dx.doi.org/10.1063/1.123211 (3 pages) | Cited 50 times

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Nanodiamond powder was annealed at each of the following temperatures: 300, 600, 800, 1000, and 1150 °C, for an hour in flowing argon ambient. The variations of x-ray diffraction patterns and Raman spectra of the powder with different annealing temperatures were studied. While being annealed at temperatures higher than 800 °C, the powder can undergo a phase-transition process from cubic diamond to graphite. In addition, the size of nanodiamond crystallites decreased from ∼50 to ∼25 Å. The physical mechanism responsible for the variation in Raman spectra is discussed using a phonon-confinement model. © 1999 American Institute of Physics.
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81.05.ub Fullerenes and related materials
61.46.-w Structure of nanoscale materials
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
78.30.Na Fullerenes and related materials
81.40.Gh Other heat and thermomechanical treatments
61.43.Gt Powders, porous materials
64.70.K- Solid-solid transitions
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials

Supersoft elastic parameters and low melting temperature of the C49 phase in TiSi2 by Brillouin scattering and molecular dynamics

Leo Miglio, M. Iannuzzi, M. Celino, R. Pastorelli, C. Bottani, A. Sabbadini, and G. Pavia

Appl. Phys. Lett. 74, 3654 (1999); http://dx.doi.org/10.1063/1.123212 (3 pages) | Cited 11 times

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In this letter, we show that the polymorphic C49 form of TiSi2 has much smaller elastic constants than those of the C54 bulk-stable structure and that its melting temperature is about 300 °C lower. These issues supply intriguing hints in explaining the kinetic advantage of the C49 over the C54 phase and in understanding the role of the elastic energy in the phase transformation from C49 to C54. © 1999 American Institute of Physics.
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62.20.D- Elasticity
64.70.D- Solid-liquid transitions
78.35.+c Brillouin and Rayleigh scattering; other light scattering
64.70.K- Solid-solid transitions
43.35.Pt Surface waves in solids and liquids
81.40.Jj Elasticity and anelasticity, stress-strain relations
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