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22 Nov 1999

Volume 75, Issue 21, pp. 3243-3419

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Nanometer-Au-particle-enhanced photorefractivity in a polymer composite

Feng Wang, Zhijian Chen, Bo Zhang, Qihuang Gong, Kuiwang Wu, Xuesong Wang, Baowen Zhang, and Fangqiong Tang

Appl. Phys. Lett. 75, 3243 (1999); http://dx.doi.org/10.1063/1.125360 (3 pages) | Cited 8 times

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Doped with nanometer Au particles, a low-Tg photorefractive polymer composite, poly(N-vinylcarbazole):2,4,7-trinitro-9-fluorenone:4-(dicyanovinyl-N,N-diethylaniline), exhibited an effective enhancement on its photorefractivity. Measurements on two-beam coupling (TBC) as well as four-wave mixing were carried out at 633 nm wavelength. At an applied electric field of 118 V/μm, TBC coefficient as high as 206 cm−1 was obtained in the sample doped with Au particles, while only 152 cm−1 in the sample without Au particles. The measurements on the effective electro-optic coefficient and the photorefractive phase shift for two samples with and without doping Au particles were performed, respectively. The observations of distinct difference on the photorefractive phase shift and no difference on the effective electro-optic coefficient implied that enhancement on the photorefractivity was due to the increment of the density of the effective trap center by doping Au particles. © 1999 American Institute of Physics.
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42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
78.20.Jq Electro-optical effects

Low-temperature near-field nonlinear absorption spectroscopy of InGaAs single quantum dots

Takuya Matsumoto, Motoichi Ohtsu, Kazunari Matsuda, Toshiharu Saiki, Hideaki Saito, and Kenichi Nishi

Appl. Phys. Lett. 75, 3246 (1999); http://dx.doi.org/10.1063/1.125313 (3 pages) | Cited 15 times

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Nonlinear absorption spectroscopy of InGaAs single quantum dots (QDs) was realized by means of a low-temperature near-field optical microscope. The spatial distribution of the nonlinear absorption change in single QDs was determined. The dependence of the nonlinear absorption change on the pump power density demonstrates that the nonlinearity originates from the state filling of the ground state. The nonlinear absorption spectrum showed a homogeneous broadening of the ground state of about 5 meV. Furthermore, the change in the absorption cross section of the single QD when the ground state is saturated with carriers is estimated to be 2.8±0.6 nm2, which agrees with the result predicted on the basis of theoretical consideration. © 1999 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.30.Fs III-V and II-VI semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency
07.79.Fc Near-field scanning optical microscopes

Nonlinear optical effects in chalcogenide photoresists

G. Rosenblum, B. G. Sfez, Z. Kotler, V. Lyubin, and M. Klebanov

Appl. Phys. Lett. 75, 3249 (1999); http://dx.doi.org/10.1063/1.125314 (3 pages) | Cited 11 times

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Both the “after-pulse effect” and the dynamic characteristics of photostructural transformations induced in glassy As0.5Se0.5 films by pulsed 532 nm excitation have been studied. The after-pulse effect investigation demonstrated more than a 103 times increase of the photosensitivity in case of pulsed excitation. Dynamic characteristics showed a dual time scale behavior and different intensity dependence of transient and long time scale signals. The obtained data indicate that the strong increase of photosensitivity following short intense pulsed light excitation is due to a two-photon effect that aids the process of structural rearrangement. © 1999 American Institute of Physics.
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42.65.-k Nonlinear optics
61.43.Fs Glasses
85.40.Hp Lithography, masks and pattern transfer
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
64.70.K- Solid-solid transitions
61.82.Fk Semiconductors
42.70.Gi Light-sensitive materials

Molecular organic light-emitting diodes with temperature-independent quantum efficiency and improved thermal durability

Hideyuki Murata, Charles D. Merritt, Hiroshi Inada, Yasuhiko Shirota, and Zakya H. Kafafi

Appl. Phys. Lett. 75, 3252 (1999); http://dx.doi.org/10.1063/1.125315 (3 pages) | Cited 18 times

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We demonstrate efficient and thermally stable molecular light-emitting diodes based on a multilayered structure that consists of two hole transport layers with high glass-transition temperatures, and an emitting layer doped with a highly fluorescent dye. Stable device operation was achieved up to 90° C. By using an emitting layer doped with a highly fluorescent dye, the electroluminescence quantum efficiency reaches 2.2% and does not decrease with increasing temperature in contrast to a device with an undoped emitting layer. The luminous efficiency at 100 cd/m2 increases from 4.6 lm/W at room temperature to 7.5 lm/W at 90 °C. The half-decay time of the initial luminance (∼800 cd/m2) of the devices is 3200 h (room temperature) and 200 h (80 °C) at constant dc current (10 mA/cm2). © 1999 American Institute of Physics.
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85.60.Jb Light-emitting devices

Adaptive all-order dispersion compensation of ultrafast laser pulses using dynamic spectral holography

Y. Ding, A. M. Weiner, M. R. Melloch, and D. D. Nolte

Appl. Phys. Lett. 75, 3255 (1999); http://dx.doi.org/10.1063/1.125316 (3 pages) | Cited 8 times

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The time-varying dispersion of ultrafast laser pulses can be self-adaptively stabilized using real-time dynamic spectral holography in semiconductor photorefractive quantum wells. Dispersion of all orders is compensated by forming a dynamic spectral-domain hologram of a signal pulse (that has a time-varying dispersion) referenced to a stable clock pulse. The hologram is read out using forward-scattering phase conjugation to remove phase distortion to all orders, including drift in the time of flight. We have achieved adaptive cancellation of time-of-flight excursions up to ±15 ps to an accuracy of ±15 fs with a compensation bandwidth of 1 kHz. © 1999 American Institute of Physics.
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42.40.My Applications
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
42.70.Gi Light-sensitive materials
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation

Phonon enhanced inverse population in asymmetric double quantum wells

Michael A. Stroscio, Mikhail Kisin, Gregory Belenky, and Serge Luryi

Appl. Phys. Lett. 75, 3258 (1999); http://dx.doi.org/10.1063/1.125317 (3 pages) | Cited 15 times

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Interwell optical-phonon-assisted transitions are studied in an asymmetric double-quantum-well heterostructure comprising one narrow and one wide coupled quantum wells (QWs). We show that the depopulation rate of the lower subband states in the narrow QW can be significantly enhanced thus facilitating the intersubband inverse population, if the depopulated subband is aligned with the second subband of the wider QW, while the energy separation from the first subband is tuned to the highest energy optical-phonon mode. © 1999 American Institute of Physics.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
71.38.-k Polarons and electron-phonon interactions
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials

Effects of interference in quasiphase-matched periodically segmented potassium titanyl phosphate waveguides

Zachary S. Benaich, Ranjit D. Pradhan, Shabbir M. Mian, and Noureddine Melikechi

Appl. Phys. Lett. 75, 3261 (1999); http://dx.doi.org/10.1063/1.125318 (3 pages) | Cited 5 times

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We show that optical interference of two input beams coupled into a periodically segmented KTiOPO4 waveguide can increase the efficiency of the generated second harmonic by a factor of three over coupling a single beam with the same total power. A simple model based on two interfering Gaussian beams indicates that the second harmonic output increases by enhancing the coupling of the fundamental energy into the waveguide. A Mach–Zehnder interferometer scheme is used to demonstrate this effect. The variation of the second harmonic power with the fundamental input power of the interfering beams shows excellent qualitative agreement between experimental results and the model presented. © 1999 American Institute of Physics.
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42.25.Hz Interference
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.65.Wi Nonlinear waveguides

Enhanced dynamic response of the in-plane switching liquid crystal display mode through polymer stabilization

Michael J. Escuti, Chris C. Bowley, Gregory P. Crawford, and Slobodan Žumer

Appl. Phys. Lett. 75, 3264 (1999); http://dx.doi.org/10.1063/1.125319 (3 pages) | Cited 26 times

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A significant improvement in the dynamic response time of the in-plane switching nematic liquid crystal mode, useful in flat-panel display applications, is achieved through polymer stabilization. This improvement is achieved by introducing a low-density, stabilizing polymer network that causes the nematic director to favor the zero-field orientation at the expense of transmission and slightly higher drive voltages. We present a simple model that treats the polymer network as an effective field in the general framework of elastic continuum theory. © 1999 American Institute of Physics.
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42.79.Kr Display devices, liquid-crystal devices
07.07.Hj Display and recording equipment, oscilloscopes, TV cameras, etc.

Room-temperature continuous-wave operation of a single-layered 1.3 μm quantum dot laser

Gyoungwon Park, Oleg B. Shchekin, Sebastion Csutak, Diana L. Huffaker, and Dennis G. Deppe

Appl. Phys. Lett. 75, 3267 (1999); http://dx.doi.org/10.1063/1.125320 (3 pages) | Cited 86 times

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Room-temperature continuous-wave operation of a 1.3 μm quantum dot laser is reported. The threshold current for a single layer active region with p–up mounting is only 4.1 mA with a threshold current density of 45 A/cm2. The minimum room temperature threshold current density is 25 A/cm2 for pulsed operation. Cryogenic and temperature dependent measurements are performed on broad-area lasers fabricated from the same active material. At 4 K the broad-area threshold current density for uncoated facets is 6 A/cm2. © 1999 American Institute of Physics.
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42.60.By Design of specific laser systems
42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.Pk Continuous operation

Blue polymer light-emitting diodes from poly(9,9-dihexylfluorene-alt-co-2, 5-didecyloxy-para-phenylene)

Wang-Lin Yu, Yong Cao, Jian Pei, Wei Huang, and Alan J. Heeger

Appl. Phys. Lett. 75, 3270 (1999); http://dx.doi.org/10.1063/1.125321 (3 pages) | Cited 51 times

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Deep blue photoluminescence and electroluminescence are demonstrated from a soluble conjugated polymer, poly(9,9-dihexylfluorene-alt-co-2,5-didecyloxy-para-phenylene). The PL quantum efficiency is approximately 40%. Cyclic voltammetry measurements indicate that the highest occupied molecular orbital and lowest unoccupied molecular orbital energies are 5.66 and 2.62 eV below vacuum, respectively. Single-layer and multilayer light-emitting diodes emit deep blue light (peak at ∼420 nm). © 1999 American Institute of Physics.
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78.66.Qn Polymers; organic compounds
85.60.Jb Light-emitting devices
78.60.Fi Electroluminescence
78.55.Kz Solid organic materials
42.70.Jk Polymers and organics
82.80.Fk Electrochemical methods
71.20.Rv Polymers and organic compounds

Selective excitation and thermal quenching of the yellow luminescence of GaN

J. S. Colton, P. Y. Yu, K. L. Teo, E. R. Weber, P. Perlin, I. Grzegory, and K. Uchida

Appl. Phys. Lett. 75, 3273 (1999); http://dx.doi.org/10.1063/1.125322 (3 pages) | Cited 16 times

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We report the observation of narrower structures in the yellow luminescence of bulk and thin-film n-type GaN, using the technique of selective excitation. These fine structures exhibit thermal quenching associated with an activated behavior. We attribute these fine structures to phonons and electronic excitations of a shallow donor-deep acceptor complex, and determine its activation energy for delocalization. Our results suggest that in addition to distant donor-acceptor pairs, the yellow luminescence can also involve emission complexes of shallow donors and deep acceptors. © 1999 American Institute of Physics.
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78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
71.55.Eq III-V semiconductors
63.20.K- Phonon interactions

A visible–near infrared range photonic crystal made up of Si nanopillars

Vladimir V. Poborchii, Tetsuya Tada, and Toshihiko Kanayama

Appl. Phys. Lett. 75, 3276 (1999); http://dx.doi.org/10.1063/1.125323 (3 pages) | Cited 26 times

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We studied a two-dimensional square lattice of Si nanopillars (SQLN) perspective for applications in waveguides. Reflection spectra of SQLN with the period of 270 nm were studied for different surrounding media, namely air and water. SQLN is shown to display photonic band gap (PBG) behavior in the visible–infrared spectral range. The energy positions and widths of the experimentally observed reflection bands are found to be in agreement with calculated PBG. © 1999 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
42.79.Gn Optical waveguides and couplers
78.40.Fy Semiconductors
78.30.Am Elemental semiconductors and insulators
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1540 nm light emission from Er-doped amorphous GaAsN films

A. R. Zanatta

Appl. Phys. Lett. 75, 3279 (1999); http://dx.doi.org/10.1063/1.125324 (3 pages) | Cited 6 times

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Erbium-doped amorphous gallium–arsenic–nitrogen (a-GaAsN) films have been prepared by cosputtering from a crystalline GaAs wafer partially covered with metallic Er pieces. The films were deposited at room temperature under different partial pressures of Ar and N2. After deposition, the films were characterized by optical transmission in the visible-ultraviolet energy range, photoluminescence (PL) in the infrared region, and Raman scattering spectroscopy. Compositional measurements were also performed indicating an Er content of ∼0.5 at. % and a N concentration that scales with the N2 partial pressure during deposition. According to the experimental results, to higher N contents correspond larger optical band gaps and more intense Er3+-related PL signals. This dependence is analyzed in terms of the compositional, electronic, and structural characteristics of each film. © 1999 American Institute of Physics.
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78.66.Jg Amorphous semiconductors; glasses
78.55.Cr III-V semiconductors
68.55.Nq Composition and phase identification
71.23.Cq Amorphous semiconductors, metallic glasses, glasses
61.43.Dq Amorphous semiconductors, metals, and alloys
78.40.Fy Semiconductors
78.35.+c Brillouin and Rayleigh scattering; other light scattering
78.66.Fd III-V semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
81.15.Cd Deposition by sputtering

Local structures of Ga atoms in amorphous silicon and hydrogenated amorphous silicon before and after synchrotron x-ray irradiation

Kin Man Yu, W. Walukiewicz, S. Muto, H.-C. Jin, J. R. Abelson, C. Clerc, C. J. Glover, and M. C. Ridgway

Appl. Phys. Lett. 75, 3282 (1999); http://dx.doi.org/10.1063/1.125325 (3 pages) | Cited 2 times

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The influence of intense x-ray irradiation on the local bonding structure of Ga dopants in both hydrogen-free (a-Si) and hydrogenated (a-Si:H) amorphous Si thin films has been studied. Prior to x-ray exposure, extended x-ray absorption fine structure measurements revealed that H reduced the static disorder around the Ga atoms in amorphous Si. Thereafter, x-ray irradiation modified the local structure in the a-Si and a-Si:H samples. The Ga coordination number increased from <3.5 to ∼3.80 atoms for both types of amorphous material as consistent with a greater fraction of electrically active, tetrahedrally coordinated dopant atoms. Also, greater structural disorder was observed around Ga atoms after x-ray irradiation suggesting that tetrahedrally coordinated Ga atoms were less well ordered than in threefold-coordinated sites. © 1999 American Institute of Physics.
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61.43.Dq Amorphous semiconductors, metals, and alloys
61.80.Cb X-ray effects
61.82.Fk Semiconductors
78.70.Dm X-ray absorption spectra
68.55.-a Thin film structure and morphology

Reactive-ion-etched gallium nitride: Metastable defects and yellow luminescence

S. A. Brown, R. J. Reeves, C. S. Haase, R. Cheung, C. Kirchner, and M. Kamp

Appl. Phys. Lett. 75, 3285 (1999); http://dx.doi.org/10.1063/1.125326 (3 pages) | Cited 18 times

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Gallium nitride has been reactive-ion etched with SF6 and argon plasmas. The Ar-etched samples show a striking transition from a dominant blue luminescence band to a dominant yellow luminescence band after less than 5 min of low power illumination. The observation of metastable defects which are associated with both the yellow and blue bands has important consequences for our understanding of defect-related luminescence in gallium nitride. © 1999 American Institute of Physics.
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78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
71.55.Eq III-V semiconductors
81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.05.Ea III-V semiconductors

Nucleation of single-crystal CoSi2 with oxide-mediated epitaxy

M. W. Kleinschmit, M. Yeadon, and J. M. Gibson

Appl. Phys. Lett. 75, 3288 (1999); http://dx.doi.org/10.1063/1.125327 (3 pages) | Cited 11 times

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Oxide-mediated epitaxy (OME) has shown promise as a technique for the formation of epitaxial CoSi2 on a variety of Si surfaces. With our in situ ultra-high-vacuum transmission electron microscope we have studied the phase formation sequence of the deposited Co during an anneal on both clean and oxide (OME) -covered Si (001) samples. The striking difference in OME is the absence of polycrystalline CoSi2 nucleation. We discuss the origin and consequences of this observation, and report other details of the phase evolution sequence. © 1999 American Institute of Physics.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.55.Nq Composition and phase identification
61.72.Cc Kinetics of defect formation and annealing

Polarized optical absorption and photoluminescence measurements in single-crystal thin films of 4′-dimethylamino-N-methyl-4-stilbazolium tosylate

Achintya K. Bhowmik, Jianjun Xu, and Mrinal Thakur

Appl. Phys. Lett. 75, 3291 (1999); http://dx.doi.org/10.1063/1.125328 (3 pages) | Cited 8 times

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Single-crystal thin films of the anhydrous (red) and the hydrated (orange) phases of the organic salt 4′-dimethylamino-N-methyl-4-stilbazolium tosylate were grown by a modification of the shear method. The optical absorption coefficients of the films were measured with light polarized along and normal to the dipole/molecular axis at both resonant and off-resonant wavelengths, and a strong dichroism was observed at the resonant wavelengths. The absorption measurements are important considering potential applications of these films (red phase) in high-speed single-pass thin-film electro-optic modulators [M. Thakur, J. Xu, A. Bhowmik, and L. Zhou, Appl. Phys. Lett. 74, 635 (1999)] and other photonic devices. Highly polarized photoluminescence (PL) has been observed in these films. The PL efficiencies of the red- and orange-phase single-crystal films were measured to be about 12% and 14%, respectively, which are significantly higher than the maximum PL efficiency measured in solution (3%). © 1999 American Institute of Physics.
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78.66.Qn Polymers; organic compounds
78.55.Kz Solid organic materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.20.Fm Birefringence

Influence of residual stress on thermal expansion behavior

X.-L. Wang, C. M. Hoffmann, C. H. Hsueh, G. Sarma, C. R. Hubbard, and J. R. Keiser

Appl. Phys. Lett. 75, 3294 (1999); http://dx.doi.org/10.1063/1.125329 (3 pages) | Cited 6 times

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We demonstrate that the thermal expansion behavior of a material can be substantially modified by the presence of residual stresses. In the case of a composite tube made of two layers of dissimilar steels, in situ neutron diffraction measurements revealed a significant difference in the coefficients of thermal expansion along the radial and tangential directions. It is shown that the observed difference in thermal expansion is due to the change of residual stresses with temperature. © 1999 American Institute of Physics.
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65.40.De Thermal expansion; thermomechanical effects

Experimental and theoretical studies of phonons in hexagonal InN

V. Yu. Davydov, V. V. Emtsev, I. N. Goncharuk, A. N. Smirnov, V. D. Petrikov, V. V. Mamutin, V. A. Vekshin, S. V. Ivanov, M. B. Smirnov, and T. Inushima

Appl. Phys. Lett. 75, 3297 (1999); http://dx.doi.org/10.1063/1.125330 (3 pages) | Cited 120 times

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The first- and second-order Raman scattering and IR reflection have been studied for hexagonal InN layers grown on (0001) and (1math02) sapphire substrates. All six Raman-active optical phonons were observed and assigned: E2(low) at 87 cm−1, E2(high) at 488 cm−1, A1(TO) at 447 cm−1, E1(TO) at 476 cm−1, A1(LO) at 586 cm−1, and E1(LO) at 593 cm−1. The ratio between the InN static dielectric constants for the ordinary and extraordinary directions was found to be ε⊥0/ε∥0 = 0.91. The phonon dispersion curves, phonon density-of-state function, and lattice specific heat were calculated. The Debye temperature at 0 K for hexagonal InN was estimated to be 370 K. © 1999 American Institute of Physics.
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63.20.D- Phonon states and bands, normal modes, and phonon dispersion
78.30.Fs III-V and II-VI semiconductors
78.66.Fd III-V semiconductors
65.40.-b Thermal properties of crystalline solids
65.60.+a Thermal properties of amorphous solids and glasses: heat capacity, thermal expansion, etc.
65.80.-g Thermal properties of small particles, nanocrystals, nanotubes, and other related systems
63.70.+h Statistical mechanics of lattice vibrations and displacive phase transitions

Effect of indium segregation on optical properties of V-groove InGaAs/GaAs strained quantum wires

F. Lelarge, C. Constantin, K. Leifer, A. Condo, V. Iakovlev, E. Martinet, A. Rudra, and E. Kapon

Appl. Phys. Lett. 75, 3300 (1999); http://dx.doi.org/10.1063/1.125331 (3 pages) | Cited 5 times

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Self-ordered, strained InGaAs/GaAs quantum structures are grown on V-grooved GaAs substrates. The lateral patterning of these nonplanar heterostructures allows the growth of defect-free strained structures with thickness exceeding that achieved with planar epitaxy. Indium segregation at the bottom of the groove results in the formation of a vertical InGaAs quantum-well structure with In-enriched composition. We studied in detail the influence of nominal thickness and In content on the photoluminescence peak energy of these quantum wires. Room-temperature emission at 1.16 μm with a relatively narrow linewidth (30–35 meV) is achieved as a demonstration of the potential of this approach for fabricating long-wavelength semiconductor light sources on GaAs substrates. © 1999 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
64.75.-g Phase equilibria

Characterization of the progressive growth of columns by excimer laser irradiation of silicon

F. Sánchez, J. L. Morenza, and V. Trtik

Appl. Phys. Lett. 75, 3303 (1999); http://dx.doi.org/10.1063/1.125332 (3 pages) | Cited 15 times

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The growth mechanism of columns produced by excimer laser irradiation of a silicon target is investigated. The micrometric columns are formed by a cumulative process with well-defined steps. The first steps lead to silicon hillocks, which evolve to columns through a little-understood mechanism. To investigate it, we irradiated a Si(100) single crystal in air with the necessary pulses of an excimer laser beam to obtain two samples, one with a partially and one with a fully developed column structure. Then we alternated scanning electron microscopy observations with irradiation pulses on the same target area. The progressive evolution of the laser-generated structures is presented. Columns grow at notably high rates, from around 0.5 μm/pulse during the early stages to 0.2 μm/pulse on average for 10–20 μm tall columns. The experimental results lead us to suggest a hydrodynamic growth mechanism. © 1999 American Institute of Physics.
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81.05.Cy Elemental semiconductors
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)
81.65.Cf Surface cleaning, etching, patterning

Local and external factors affecting the photodegradation of 4N,N′-dimethylamino-4′nitrostilbene polymer films

Adriana Galvan-Gonzalez, Michael Canva, and George I. Stegeman

Appl. Phys. Lett. 75, 3306 (1999); http://dx.doi.org/10.1063/1.125333 (3 pages) | Cited 8 times

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The photodegradation of the electro-optic chromophore 4N,N′-dimethylamino-4′nitrostilbene was investigated as a function of wavelength, temperature, local atmosphere, and local molecular environment, i.e., attached as a side chain to a polymer or dissolved as a guest in a host polymer. © 1999 American Institute of Physics.
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42.70.Jk Polymers and organics
78.66.Qn Polymers; organic compounds
78.20.Jq Electro-optical effects
82.50.-m Photochemistry
82.30.Qt Isomerization and rearrangement
61.41.+e Polymers, elastomers, and plastics

Beaded carbon tubes

Jyh-Ming Ting and Jones B. C. Lan

Appl. Phys. Lett. 75, 3309 (1999); http://dx.doi.org/10.1063/1.125334 (3 pages) | Cited 6 times

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Unusual tubular carbon structures were observed when preparing carbon tubes using a vapor phase process. Regular, single-diametered carbon tubes were obtained at temperatures below 1300 °C. However, at temperatures greater than 1300 °C, in addition to regular carbon tubes, beaded carbon tubes appeared. The occurrence and appearance of such unusual beaded structure is thought to be related to the growth temperature, and is explained in terms of a three-dimensional nucleation model. © 1999 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
81.20.-n Methods of materials synthesis and materials processing

Wavelength dependence of the third-order nonlinear optical properties of a polythiophene/selenophene derivative film

Edward Van Keuren, Takanori Wakebe, Reinhard Andreaus, Helmut Möhwald, Wolfgang Schrof, Vladimir Belov, Hiro Matsuda, and Raul Rangel-Rojo

Appl. Phys. Lett. 75, 3312 (1999); http://dx.doi.org/10.1063/1.125335 (3 pages) | Cited 14 times

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The third-order nonlinear optical properties of a hybrid polymer film containing substituted thiophene rings copolymerized with unsubstituted selenophene were measured using the Z-scan technique. Large, resonantly enhanced third-order nonlinearities were found at wavelengths on the low-energy side of the absorption band. In contrast to the results on a similar copolymer film incorporating only thiophene, a strong two-photon absorption appeared in the near infrared. The imaginary part of the third-order susceptibility can be adequately explained as saturation of an exciton band, while the origin of the large negative real part is unknown. © 1999 American Institute of Physics.
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42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
42.70.Jk Polymers and organics
42.65.An Optical susceptibility, hyperpolarizability
78.66.Qn Polymers; organic compounds
78.30.Jw Organic compounds, polymers

High optical quality AlInGaN by metalorganic chemical vapor deposition

M. E. Aumer, S. F. LeBoeuf, F. G. McIntosh, and S. M. Bedair

Appl. Phys. Lett. 75, 3315 (1999); http://dx.doi.org/10.1063/1.125336 (3 pages) | Cited 36 times

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We report on the metalorganic chemical vapor deposition of the quaternary alloy AlInGaN. We found it desirable to grow quaternary films at temperatures greater than 855 °C in order to suppress deep level emissions in the room-temperature photoluminescence. Details of the conditions necessary to grow In0.1Ga0.9N at 875 °C are presented. Strained and relaxed AlInGaN films were grown with good optical and structural properties for AlN compositions up to 26% and InN content up to 11%. The effects of strain were observed by a difference in the band gap between thin and thick films with the same compositions. The potential impact of the use of quaternary films is discussed regarding strain engineering for the improvement of present device designs. © 1999 American Institute of Physics.  
Show PACS
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.05.Ea III-V semiconductors
68.55.-a Thin film structure and morphology
78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
71.20.Nr Semiconductor compounds
68.60.Bs Mechanical and acoustical properties
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