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31 Jul 2000

Volume 77, Issue 5, pp. 609-762

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Green upconversion luminescence in Er3+:BaTiO3 films

H. X. Zhang, C. H. Kam, Y. Zhou, X. Q. Han, S. Buddhudu, Q. Xiang, Y. L. Lam, and Y. C. Chan

Appl. Phys. Lett. 77, 609 (2000); http://dx.doi.org/10.1063/1.127060 (3 pages) | Cited 35 times

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Green upconversion emissions at 548 and 528 nm have been obtained from sol-gel derived nanocrystalline Er3+:BaTiO3 films under 980 nm excitation. The green emissions are attributed to the ground-state (4I15/2) -directed transitions from 2H11/2 (528 nm) and 4S3/2 (548 nm) of Er3+ ions. Analysis of the temporal evolution of the emission at 548 nm shows that both excited state absorption of individual ion and energy transfer between the two neighboring ions contribute to the upconversion emissions in Er3+ (3 mol %):BaTiO3 film. The lifetime of the dominant emission at 548 nm is about 90 μs. © 2000 American Institute of Physics.
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78.55.Hx Other solid inorganic materials
81.07.-b Nanoscale materials and structures: fabrication and characterization
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
78.66.Nk Insulators
71.55.Ht Other nonmetals
61.46.-w Structure of nanoscale materials

Depolarization by high aperture focusing

K. Bahlmann and S. W. Hell

Appl. Phys. Lett. 77, 612 (2000); http://dx.doi.org/10.1063/1.127061 (3 pages) | Cited 22 times

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We introduce a method employing ferroelectric monomolecular layers, by which it is possible to measure the light field polarization in the focus of a lens. This method allowed us to noninvasively establish the perpendicularly oriented focal field that is anticipated at high apertures. For a numerical aperture 1.4 oil immersion lens illuminated with linearly polarized plane waves, the integral of the modulus square of the perpendicular component amounts to (1.51±0.2) % of that of the initial polarization. It is proven that depolarization decreases with decreasing aperture angle. Whereas for regular imaging conditions depolarization is largely negligible, it plays a significant role in microscopy of highest resolution, microspectroscopy, and single molecule studies. © 2000 American Institute of Physics.
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42.79.Bh Lenses, prisms and mirrors
42.25.Ja Polarization

2.79 μm erbium laser with lead–lanthanum zirconate titanate ceramics electro-optic Q-switching output coupler

Maris Ozolinsh and Hans J. Eichler

Appl. Phys. Lett. 77, 615 (2000); http://dx.doi.org/10.1063/1.127062 (3 pages) | Cited 6 times

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Highly refractive and transparent lead–lanthanum zirconate titanate (PLZT) ceramics are used for an output coupler of the erbium yttrium scandium gallium garnet laser (λ = 2.79 μm) that simultaneously serves as the laser electro-optic Q switch. The optical aperture of such a dual-function PLZT element was 6×6 mm2 and the thickness was 3 mm. For Q switching, short ≈3 μs negative voltage pulses (1500–1800 V) were applied to the positively direct current biased (≈1400 V) PLZT element. Single-pulse lasing with a pulse half width of 160–170 ns was observed at short and long delays of the Q switch with respect to the pump flash. The highest output energy of 20–22 mJ within 1.5–2.5 μs, consisting of two or three pulses with 130 ns half width was obtained at an intermediate delay of 90–110 μs. © 2000 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.By Design of specific laser systems
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
42.79.Gn Optical waveguides and couplers

Estimation of interwell terahertz gain by photon-assisted tunneling measurement in triple-barrier resonant tunneling diodes

M. Asada, Y. Oguma, and N. Sashinaka

Appl. Phys. Lett. 77, 618 (2000); http://dx.doi.org/10.1063/1.127063 (3 pages) | Cited 2 times

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Terahertz (THz) gain due to electron transition between adjacent quantum wells was estimated from a measurement of current change in triple-barrier resonant tunneling diodes under the THz irradiation. Measured current change was separated into stimulated emission and absorption components, and the gain coefficient was estimated from the difference between these components. For a sample with relatively thick barriers and peak current density of 70 A/cm2, the room-temperature peak gain coefficient was about 0.15 cm−1 at 2.24 THz. The estimated gain coefficient is in reasonable agreement with an approximate theory. High gain is expected by increasing the current density with thin barriers. © 2000 American Institute of Physics.
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78.45.+h Stimulated emission
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
42.55.Px Semiconductor lasers; laser diodes
85.30.Kk Junction diodes
85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)
78.66.-w Optical properties of specific thin films

Artifact-free near-field optical imaging by apertureless microscopy

M. Labardi, S. Patanè, and M. Allegrini

Appl. Phys. Lett. 77, 621 (2000); http://dx.doi.org/10.1063/1.127064 (3 pages) | Cited 35 times

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A method for optical near field discrimination, leading to drastic artifact reduction in superresolved imaging by scanning interference apertureless microscopy is presented. The method relies on second harmonic detection of the modulated optical signal scattered by a vibrating silicon tip. An edge resolution of 15 nm, or 7 nm Rayleigh-type resolution, with optical contrast as high as 50%, has been obtained on aluminum projection pattern samples in the constant gap width mode. Our method has been determined not to be affected by topographical artifacts by constant height mode scans. © 2000 American Institute of Physics.
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07.79.Fc Near-field scanning optical microscopes
42.30.-d Imaging and optical processing
42.25.Hz Interference
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.25.Fx Diffraction and scattering

Enhanced degradation resistance of quantum dot lasers to radiation damage

P. G. Piva, R. D. Goldberg, I. V. Mitchell, D. Labrie, R. Leon, S. Charbonneau, Z. R. Wasilewski, and S. Fafard

Appl. Phys. Lett. 77, 624 (2000); http://dx.doi.org/10.1063/1.127065 (3 pages) | Cited 28 times

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We compare the degradation of InAs/GaAs quantum well (QW) and quantum dot (QD) laser diodes following irradiation by high energy (8.56 MeV) phosphorous ions. Over a fluence range of 108–1011 ions/cm2, the degradation of the low temperature QD photoluminescence and electroluminescence emission is greatly suppressed relative to that of QW based devices (×100 and ×1000, respectively at the highest dose studied). Irradiated QD laser diodes demonstrated lasing action over the entire range of fluences, and 2 orders of magnitude beyond the maximum dose sustainable by QW devices. The improved damage response of QD based structures results from efficient collection and localization of electrons and holes by QDs in the active region, which limit carrier transfer to nonradiative centers. This work suggests the suitability of QD device architectures for use in radiation environments, and in high power applications, wherever nonradiative processes promote the degradation or failure of traditional QW devices. © 2000 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
61.80.Jh Ion radiation effects
61.82.Fk Semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
78.60.Fi Electroluminescence
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors

High-quality phase conjugation even in a highly transient regime of stimulated Brillouin scattering

B. Králiková, J. Skála, P. Straka, and H. Turčičová

Appl. Phys. Lett. 77, 627 (2000); http://dx.doi.org/10.1063/1.127066 (3 pages) | Cited 1 time

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A high-quality phase conjugation of the stimulated Brillouin scattering has been achieved even in a highly transient regime, as proved by the mask restoration in the backscattered signal. A special two-lens system of laser beam insertion into a scattering medium was used. A reliable onset of the phase conjugation has been reached using a splitted part of the oscillator Q-switched pulse as a prepulse in the Brillouin cell. Results with and without the prepulse are compared. A possibility of the creation of the phase conjugated mirrors even in high-power gaseous lasers with short pulses is thus proved. © 2000 American Institute of Physics.
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42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
42.65.Es Stimulated Brillouin and Rayleigh scattering
42.79.Bh Lenses, prisms and mirrors
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.55.Px Semiconductor lasers; laser diodes
42.55.Rz Doped-insulator lasers and other solid state lasers

Gain in 1.3 μm materials: InGaNAs and InGaPAs semiconductor quantum-well lasers

J. Hader, S. W. Koch, J. V. Moloney, and E. P. O’Reilly

Appl. Phys. Lett. 77, 630 (2000); http://dx.doi.org/10.1063/1.127067 (3 pages) | Cited 46 times

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The absorption and gain for an InGaNAs/GaAs quantum-well structure is calculated and compared to that of a more conventional InGaAs/InGaPAs structure, both lasing in the 1.3 μm range. Despite significant differences in the band structures, the gain value is comparable for high carrier densities in both structures and the transition energy at the gain maximum shows a similar blueshift with increasing carrier density. For low and intermediate carrier densities, the calculated gain in the InGaPAs system is significantly lower and the bandwidth smaller than in the InGaNAs system. © 2000 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
78.45.+h Stimulated emission
73.61.Ey III-V semiconductors
78.66.Fd III-V semiconductors

Experimental observation of the mobility edge in a waveguide with correlated disorder

U. Kuhl, F. M. Izrailev, A. A. Krokhin, and H.-J. Stöckmann

Appl. Phys. Lett. 77, 633 (2000); http://dx.doi.org/10.1063/1.127068 (3 pages) | Cited 98 times

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The tight-binding model with correlated disorder introduced by Izrailev and Krokhin [Phys. Rev. Lett. 82, 4062 (1999)] has been extended to the Kronig–Penney model. The results of the calculations have been compared with microwave transmission spectra through a single-mode waveguide with inserted correlated scatterers. All predicted bands and mobility edges have been found in the experiment, thus demonstrating that any wanted combination of transparent and nontransparent frequency intervals can be realized experimentally by introducing appropriate correlations between scatterers. © 2000 American Institute of Physics.
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42.79.Gn Optical waveguides and couplers
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Dependence of crystallographic tilt and defect distribution on mask material in epitaxial lateral overgrown GaN layers

S. Tomiya, K. Funato, T. Asatsuma, T. Hino, S. Kijima, T. Asano, and M. Ikeda

Appl. Phys. Lett. 77, 636 (2000); http://dx.doi.org/10.1063/1.127069 (3 pages) | Cited 24 times

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We have investigated the dependence of crystallographic tilt and defect distribution on mask material in metalorganic chemical vapor deposition grown GaN layers formed utilizing an epitaxial lateral overgrowth (ELO) technique using x-ray diffraction and transmission electron microscopy. Crystallographic tilt in the ELO GaN layer was suppressed by changing the mask material from electron beam (EB)-evaporated SiO2 to plasma enhanced chemical vapor deposition (PECVD) grown SiO2 and PECVD SiNx. Defect distribution also changes in accordance with mask materials. By depositing a thin PECVD SiNx layer on the PECVD SiO2 mask, the crystalline quality of the ELO layer changes from that used with the SiO2 mask to that used with the SiNx mask. These results suggest that the interface between the ELO GaN layer and the mask has a significant effect on crystallographic tilt and defect distribution. © 2000 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.-y Defects and impurities in crystals; microstructure

Quantum confinement energies in zinc-blende III–V and group IV semiconductors

G. Allan, Y. M. Niquet, and C. Delerue

Appl. Phys. Lett. 77, 639 (2000); http://dx.doi.org/10.1063/1.127070 (3 pages) | Cited 31 times

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Blueshift of the band gap due to quantum confinement is calculated in a tight-binding model for a series of nine III–V zinc-blende AB (A=Al, Ga, or In, B=As, P, or Sb) and two diamond group-IV (Si and Ge) semiconductor clusters. Analytic expressions for the highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels are given as a function of the cluster size. Comparison is made to results obtained by the pseudopotential method and to experimental results. © 2000 American Institute of Physics.
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73.22.-f Electronic structure of nanoscale materials and related systems
71.15.Ap Basis sets (LCAO, plane-wave, APW, etc.) and related methodology (scattering methods, ASA, linearized methods, etc.)
78.66.Db Elemental semiconductors and insulators
78.66.Fd III-V semiconductors

Double-hump diffusion profiles of copper and nickel in germanium wafers yielding vacancy-related information

A. Giese, N. A. Stolwijk, and H. Bracht

Appl. Phys. Lett. 77, 642 (2000); http://dx.doi.org/10.1063/1.127071 (3 pages) | Cited 18 times

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Diffusion of Cu and Ni into Ge was investigated between 700 and 900 °C with the aid of rapid isothermal lamp annealing and spreading-resistance profiling. Using low-dislocation-density single-crystal Ge wafers with a backside gold layer, we observed typical double-hump diffusion profiles of both Cu and Ni. These profiles can be described within the dissociative model by taking into account that the front surface acts as source for both vacancies (V) and Cu or Ni while the back surface combines the V-source feature with a Cu, Ni-sink property. Profile fitting yields data regarding the V-assisted Ge self-diffusion coefficient and the equilibrium concentration of vacancies as a function of temperature. © 2000 American Institute of Physics.
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61.72.uf Ge and Si
81.05.Cy Elemental semiconductors
66.30.J- Diffusion of impurities
72.20.Fr Low-field transport and mobility; piezoresistance
72.80.Cw Elemental semiconductors
66.30.H- Self-diffusion and ionic conduction in nonmetals
85.40.Ry Impurity doping, diffusion and ion implantation technology
61.72.Cc Kinetics of defect formation and annealing
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Fk Semiconductors
61.72.J- Point defects and defect clusters
61.72.Yx Interaction between different crystal defects; gettering effect

Kinetic oscillations of red photoluminescence from nanocrystalline Si/SiO2 films

Xiaochun Wu, Alexander M. Bittner, Klaus Kern, Ch. Eggs, and S. Veprek

Appl. Phys. Lett. 77, 645 (2000); http://dx.doi.org/10.1063/1.127072 (3 pages) | Cited 22 times

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Experimental investigations on the red photoluminescence (PL) from nanocrystalline Si (nc-Si) embedded in a SiO2 matrix, fabricated by plasma-enhanced chemical vapor deposition and a subsequent post-treatment, reveal under certain conditions the occurrence of kinetic oscillations. For the red PL between 1.5 and 1.75 eV, the spectral shift and the peak intensity versus annealing times show temporal oscillations. The spectral variations are explained by the growth and decay kinetics of two oxygen thermal donors (TDs) upon annealing. The oscillatory behavior is a pure kinetic one. It reflects the regrowth of oxygen TDs by an autocatalytic process during their decay. Although the source for the autocatalysis is not clear, this PL oscillation adds more evidence that the red PL observed in our system originates from oxygen TDs-related defect states. © 2000 American Institute of Physics.
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78.66.Db Elemental semiconductors and insulators
78.55.Ap Elemental semiconductors
71.55.Cn Elemental semiconductors

Ultrafast intersubband relaxation (⩽150 fs) in AlGaN/GaN multiple quantum wells

Norio Iizuka, Kei Kaneko, Nobuo Suzuki, Takashi Asano, Susumu Noda, and Osamu Wada

Appl. Phys. Lett. 77, 648 (2000); http://dx.doi.org/10.1063/1.127073 (3 pages) | Cited 94 times

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The ultrafast intersubband relaxation in GaN quantum wells has been verified. Al0.65Ga0.35N/GaN multiple quantum wells, with as many as 200 wells, were grown by optimizing the barrier thickness and introducing GaN intermediate layers. The intersubband absorption is sufficiently strong for the relaxation time to be measured. A pump–probe measurement is performed to investigate the relaxation. An ultrashort relaxation time of less than 150 fs is obtained at a wavelength of 4.5 μm. The transient time is shorter than that of InGaAs quantum wells by approximately an order of magnitude. This result is promising for realizing ultrafast optical switches. © 2000 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.47.-p Spectroscopy of solid state dynamics
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
78.30.Fs III-V and II-VI semiconductors
42.65.Pc Optical bistability, multistability, and switching, including local field effects

Semiconductor wafer bonding via liquid capillarity

Z. L. Liau

Appl. Phys. Lett. 77, 651 (2000); http://dx.doi.org/10.1063/1.127074 (3 pages) | Cited 8 times

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Liquid surface tension has been used to pull different semiconductor wafers to very close contact and strong bonding. Bonded wafers, such as GaAs/GaP, were heat treated without pressure application to achieve wafer fusion. The bonding process has been analyzed, and criteria for surface tension, wafer flatness, and elasticity have been derived. © 2000 American Institute of Physics.
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85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology
68.03.Cd Surface tension and related phenomena
81.05.Ea III-V semiconductors

Initial growth of heteroepitaxial 3C–SiC on Si using energetic species

Nobuteru Tsubouchi, Akiyoshi Chayahara, Atsushi Kinomura, and Yuji Horino

Appl. Phys. Lett. 77, 654 (2000); http://dx.doi.org/10.1063/1.127075 (3 pages) | Cited 3 times

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Structural evolution of initial growth of heteroepitaxial 3C–SiC on Si(100) using mass-separated energetic (∼60 eV) ions of C+ and CH3+ has been investigated by in situ reflection high energy electron diffraction (RHEED). RHEED patterns indicated that carbonization reaction of Si occurred at as low as 590–690 °C by irradiation of C+ and CH3+ with 60 eV. The diffraction pattern of 3C–SiC using CH3+ ions exhibited sharp streak shapes in comparison with the use of C+ ions. The features of a carbonization process using energetic species is discussed. © 2000 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.05.Hd Other semiconductors
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)
61.80.Jh Ion radiation effects
61.82.Fk Semiconductors

Self-induced light polarization rotation in azobenzene-containing polymers

L. Nikolova, L. Nedelchev, T. Todorov, Tz. Petrova, N. Tomova, V. Dragostinova, P. S. Ramanujam, and S. Hvilsted

Appl. Phys. Lett. 77, 657 (2000); http://dx.doi.org/10.1063/1.127076 (3 pages) | Cited 36 times

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We report here a light-induced phenomenon—a self-induced rotation of the azimuth of elliptically polarized light passing through photobirefringent azopolymers. The experiments are carried out with films of amorphous and liquid-crystalline polymers. It has been shown that the induced rotation angle depends on the ellipticity of the input light. A theoretical analysis of the phenomenon has been done and it has been shown that light induces chiral structure in the polymer films. © 2000 American Institute of Physics.
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78.20.Ek Optical activity
42.70.Jk Polymers and organics
42.70.Df Liquid crystals
78.66.Qn Polymers; organic compounds
78.20.Fm Birefringence
42.70.Gi Light-sensitive materials
61.30.-v Liquid crystals

Optical properties, spectral narrowing of photoluminescence and blue electroluminescence of poly(phenylene pyridine) derivatives

A. Fujii, R. Ootake, T. Fujisawa, M. Ozaki, Y. Ohmori, Tong Laga, K. Yoshino, H.-F. Lu, H. S. O. Chan, and S.-C. Ng

Appl. Phys. Lett. 77, 660 (2000); http://dx.doi.org/10.1063/1.127077 (3 pages) | Cited 7 times

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Optical properties of poly(phenylene pyridine) derivatives, poly(2,5-dialkoxy-1,4phenylenealt-2,5-pyridine) (PHOnPY25), such as optical absorption, photoluminescence (PL), and electroluminescence (EL), have been studied. The electronic energy structures of PHOnPY25 have been determined by optical and electrochemical measurements. Strong PL with high quantum efficiency has been clarified in the films, and spectral narrowing has been observed by pulse excitation of a nitrogen laser. Intense blue EL has also been demonstrated. © 2000 American Institute of Physics.
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78.66.Qn Polymers; organic compounds
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
42.79.Wc Optical coatings
42.70.Jk Polymers and organics
78.55.Kz Solid organic materials
78.60.Fi Electroluminescence
71.20.Rv Polymers and organic compounds

Structural anisotropy of magnetically aligned single wall carbon nanotube films

B. W. Smith, Z. Benes, D. E. Luzzi, J. E. Fischer, D. A. Walters, M. J. Casavant, J. Schmidt, and R. E. Smalley

Appl. Phys. Lett. 77, 663 (2000); http://dx.doi.org/10.1063/1.127078 (3 pages) | Cited 77 times

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Thick films of aligned single wall carbon nanotubes and ropes have been produced by filtration/deposition from suspension in strong magnetic fields. We measured mosaic distributions of rope orientations in the film plane, for samples of different thicknesses. For an ∼ 1 μm film the full width at half maximum (FWHM) derived from electron diffraction is 25°–28°. The FWHM of a thicker film ( ∼ 7 μm) measured by x-ray diffraction is slightly broader, 35±3°. Aligned films are denser than ordinary filter-deposited ones, and much denser than as-grown material. Optimization of the process is expected to yield smaller FWHMs and higher densities. © 2000 American Institute of Physics.
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61.48.-c Structure of fullerenes and related hollow and planar molecular structures
81.05.ub Fullerenes and related materials
68.55.-a Thin film structure and morphology
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)

Electrical and thermal transport properties of magnetically aligned single wall carbon nanotube films

J. Hone, M. C. Llaguno, N. M. Nemes, A. T. Johnson, J. E. Fischer, D. A. Walters, M. J. Casavant, J. Schmidt, and R. E. Smalley

Appl. Phys. Lett. 77, 666 (2000); http://dx.doi.org/10.1063/1.127079 (3 pages) | Cited 224 times

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Dense, thick films of aligned single wall carbon nanotubes and nanotube ropes have been produced by filtration/deposition from suspension in strong magnetic fields. Electrical resistivity exhibits moderate anisotropy with respect to the alignment axis, while the thermopower is the same when measured parallel or perpendicular to this axis. Both parameters have identical temperature dependencies in the two orientations. Thermal conductivity in the parallel direction exceeds 200 W/mK, within a decade of graphite. © 2000 American Institute of Physics.
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73.61.Wp Fullerenes and related materials
81.05.ub Fullerenes and related materials
66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
61.48.-c Structure of fullerenes and related hollow and planar molecular structures
72.80.Rj Fullerenes and related materials
72.20.My Galvanomagnetic and other magnetotransport effects
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
72.20.Pa Thermoelectric and thermomagnetic effects
73.50.Lw Thermoelectric effects
68.55.-a Thin film structure and morphology
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)

Effect of surface steps on the microstructure of lateral composition modulation

D. M. Follstaedt, J. L. Reno, E. D. Jones, S. R. Lee, A. G. Norman, H. R. Moutinho, A. Mascarenhas, and R. D. Twesten

Appl. Phys. Lett. 77, 669 (2000); http://dx.doi.org/10.1063/1.127080 (3 pages) | Cited 13 times

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Growth of InAs/AlAs short-period superlattices on appropriately miscut (001) InP substrates is shown to alter the microstructure of composition modulation from a two-dimensional organization of short compositionally enriched wires to a single dominant modulation direction with wire lengths up to ∼ 1 μm. The effects of miscut are interpreted in terms of surface step orientation and character. The material is strongly modulated and exhibits intense optical emission. The one-dimensional modulations appear potentially useful for new devices that take advantage of the preferred direction formed in the growth plane. © 2000 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.05.Ea III-V semiconductors
68.35.B- Structure of clean surfaces (and surface reconstruction)
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Ultraviolet-blue electroluminescence from Gd3Ga5O12:Ag

Xiulai Xu, Zheng Xu, Yanbing Hou, Yanmei Su, Xurong Xu, Xiaowei Wang, and Wusheng Tong

Appl. Phys. Lett. 77, 672 (2000); http://dx.doi.org/10.1063/1.127081 (3 pages) | Cited 1 time

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UV-blue light was obtained from a thin-film electroluminescence device using Gd3Ga5O12:Ag as a light-emitting layer, which was deposited by using electron-beam evaporation. The crystal composition and structure of Gd3Ga5O12:Ag were studied by x-ray powder diffraction. The Gd3Ga5O12:Ag has a photoluminescence emission which peaked at around 397 and 467 nm, which were attributed to the oxide vacancies and Ag+, respectively. The brightness of 32 cd/m2 was obtained when an alternating voltage of 130 V at 1 kHz was applied. © 2000 American Institute of Physics.
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78.60.Fi Electroluminescence
85.60.Jb Light-emitting devices
78.66.Nk Insulators
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
75.50.Gg Ferrimagnetics
78.55.Hx Other solid inorganic materials
68.55.-a Thin film structure and morphology

Photoconductive properties of polysilane copolymers with pendant siloxane groups

Kimihiro Matsukawa, Toshiyuki Tamai, and Hiroshi Inoue

Appl. Phys. Lett. 77, 675 (2000); http://dx.doi.org/10.1063/1.127082 (3 pages) | Cited 2 times

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The oxygen durability of poly(methylphenylsilane) (PMPS) in photoconduction has been improved by the use of copolysilanes with disiloxane-pendant groups. X-ray photoelectron spectroscopy analysis shows that disiloxane groups of the copolysilanes accumulate on their top-most surface at a much higher concentration than the bulk disiloxane concentration. The preferential coverage of disiloxane groups on the surface evidently leads to formation of a highly oxygen durable surface. The hole drift mobility of the charge carriers in copolysilanes with 5 mol % of disiloxane-pendant groups is over 10−4 cm2 V−1 s−1 at E>105 V cm−1, almost comparable to that of PMPS. It was noted that the practical Xerographic potential decay was stabilized by the copolysilanes, while PMPS deteriorated after oxygen exposure. © 2000 American Institute of Physics.
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72.40.+w Photoconduction and photovoltaic effects
81.65.Mq Oxidation
79.60.Fr Polymers; organic compounds
72.80.Le Polymers; organic compounds (including organic semiconductors)
68.35.Dv Composition, segregation; defects and impurities
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials

Photo- and cathodoluminescence characteristics of blue-light-emitting epitaxial Sr2CeO4 thin-film phosphors

Yong Eui Lee, David P. Norton, John D. Budai, Philip D. Rack, and Michael D. Potter

Appl. Phys. Lett. 77, 678 (2000); http://dx.doi.org/10.1063/1.127083 (3 pages) | Cited 21 times

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Orthorhombic epitaxial Sr2CeO4 thin-film phosphors were grown on (100) SrTiO3 and yttria-stabilized-zirconia (YSZ) single crystal substrates with epitaxial relationships of (100) [010]Sr2CeO4//(100)[010]SrTiO3 and (100)[010]Sr2CeO4//(100)[011]YSZ, respectively. As-deposited films exhibit a broadband photoluminescence (PL) emission, peaking at about 477–481 nm with a maximum cathodoluminescence (CL) intensity at about 465 nm. Enhanced PL intensity was observed for the films deposited on (100) YSZ and SrTiO3 substrates as compared to deposits on c-plane sapphire substrates, correlating with improved intragranular crystallinity and reducing defects via epitaxy. Postannealing in air significantly enhanced both of the PL and CL intensities. Luminous efficiency of 0.14 lm/W at 1 kV and 22 μA/cm2 was observed for a 2-μm-thick film annealed at 1000 °C in air. © 2000 American Institute of Physics.
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78.66.Nk Insulators
78.55.Hx Other solid inorganic materials
42.79.Wc Optical coatings
78.60.Hk Cathodoluminescence, ionoluminescence
81.40.Gh Other heat and thermomechanical treatments
81.40.Tv Optical and dielectric properties related to treatment conditions

Time–temperature–transformation diagram and microstructures of bulk glass forming Pd40Cu30Ni10P20

Jörg F. Löffler, Jan Schroers, and William L. Johnson

Appl. Phys. Lett. 77, 681 (2000); http://dx.doi.org/10.1063/1.127084 (3 pages) | Cited 41 times

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Isothermal crystallization studies were performed on the bulk glass forming alloy Pd40Cu30Ni10P20 in the undercooled liquid region between the glass transition and liquidus temperature, resulting in a complete time–temperature–transformation (TTT) diagram for crystallization. The TTT diagram shows a typical “C” shape with the nose at 50 s and 680 K. Assuming steady state nucleation and a diffusion-controlled growth rate, the TTT diagram was successfully fit over the entire range of the measurement. The microstructure after isothermal crystallization shows a modulation in Cu and P for all degrees of undercooling. The primary solidified phase is Cu3Pd, which forms distinct dendrites at low undercooling. From additional constant cooling experiments, the critical cooling rate to bypass crystallization was determined to be 0.33 K/s. © 2000 American Institute of Physics.
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81.30.Bx Phase diagrams of metals, alloys, and oxides
81.05.Kf Glasses (including metallic glasses)
81.05.Bx Metals, semimetals, and alloys
64.70.D- Solid-liquid transitions
61.43.Fs Glasses
64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition
64.60.Q- Nucleation
68.70.+w Whiskers and dendrites (growth, structure, and nonelectronic properties)
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