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24 May 2004

Volume 84, Issue 21, pp. 4141-4340

Issue Cover Spotlight Figure

Appl. Phys. Lett. 84, 4316 (2004); http://dx.doi.org/10.1063/1.1756684 (3 pages)

Seok Pil Jang and Stephen U. S. Choi
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Spatial distribution of the red luminescence in pristine, γ rays and ultraviolet-irradiated multimode optical fibers

S. Girard, J.-P. Meunier, Y. Ouerdane, A. Boukenter, B. Vincent, and A. Boudrioua

Appl. Phys. Lett. 84, 4215 (2004); http://dx.doi.org/10.1063/1.1755832 (3 pages) | Cited 13 times

Online Publication Date: 7 May 2004

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In this letter, a confocal microscopy setup was used to evaluate, with a resolution of 2 μm, the nonuniform spatial distributions of the red photoluminescence (640–750 nm) in pristine, γ rays (∼1 MeV, 1.2 kGy, and 0.33 Gy/s) and ultraviolet (244 nm and 127 J/cm2) irradiated multimode optical fibers. In pristine samples, the Raman scattering is predominant and the emitting centers are only present at low concentration in the fiber cladding. However, these centers are generated by both irradiations in the whole fiber cross sections, in particular near the core–cladding interface. The spectral deconvolution of the luminescence spectra showed that the Non-Bridging Oxygen Hole Centers are mainly responsible for this red luminescence. For both irradiation types, these centers seem to be predominantly created from precursor sites: strained Si–O–Si bonds which could be induced during the fiber drawing process. © 2004 American Institute of Physics.
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42.81.Cn Fiber testing and measurement of fiber parameters
42.88.+h Environmental and radiation effects on optical elements, devices, and systems
78.55.Hx Other solid inorganic materials
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Organic small molecule solar cells with a homogeneously mixed copper phthalocyanine: C60 active layer

Soichi Uchida, Jiangeng Xue, Barry P. Rand, and Stephen R. Forrest

Appl. Phys. Lett. 84, 4218 (2004); http://dx.doi.org/10.1063/1.1755833 (3 pages) | Cited 117 times

Online Publication Date: 7 May 2004

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An efficient organic solar cell with a vacuum codeposited donor–acceptor copper phthalocyanine (CuPc):C60 mixed layer is described. A device with a structure of indium tin oxide/330 Å CuPc:C60(1:1)/100 Å C60/75 Å 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline/Ag has a series resistance of only RS = 0.25 Ω cm2, resulting in a current density of ∼1 A/cm2 at a forward bias of +1 V, and a rectification ratio of 106 at ±1 V. Under simulated solar illumination, the short circuit current density increases linearly with light intensity up to 2.4 suns. The maximum power conversion efficiency is ηP = (3.6±0.2)% at 0.3 suns (AM1.5G simulated solar spectrum) and ηP = (3.5±0.2)% at 1 sun. Although the fill factor decreases with increasing intensity, a power efficiency as high as ηP = (3.3±0.2)% is observed at 2.4 suns intensity. © 2004 American Institute of Physics.
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84.60.Jt Photoelectric conversion
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.55.A- Nucleation and growth
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All-optical polymeric interferometeric wavelength converter comprising an excited state intramolecular proton transfer dye

Jae-Wook Kang, Sehoon Kim, Soo Young Park, and Jang-Joo Kim

Appl. Phys. Lett. 84, 4221 (2004); http://dx.doi.org/10.1063/1.1755839 (3 pages) | Cited 1 time

Online Publication Date: 7 May 2004

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We designed and demonstrated an all-optical wavelength converter using a polymeric Mach–Zehnder interferometer (MZI) comprised of an excited state intramolecular proton transfer (ESIPT) dye, 2,2′-{oxybis[4-(4-methoxyphenyl)quinoline-6,2-diyl]}bis(5-methoxyphenol) (MQ). This MZI wavelength converter is composed of the MQ dye-doped polymeric waveguide and a thick light blocking metal film. A feature of this device is that one arm of the MZI can be irradiated by 355 nm pulses (signal beam), while the other arm was not, thus allowing a differential phase shift in the submicrosecond time scale. Because of the refractive index change of the ESIPT dye in one arm of interferometer upon irradiation with the signal beam, phase modulation of the continuous-wave probe light propagating in the irradiated arm of the MZI takes place, leading to the intensity modulation at the output defined by the signal beam, resulting in an all-optical wavelength converter, that is, the conversion of the signal modulation to output signal modulation of the probe light of the MZI. The characteristics of the wavelength converter are well described by a simple kinetic model. © 2004 American Institute of Physics.
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42.79.Nv Optical frequency converters
42.70.Jk Polymers and organics
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Effects of stacking on the structural and optical properties of self-organized GaN/AlN quantum dots

N. Gogneau, F. Fossard, E. Monroy, S. Monnoye, H. Mank, and B. Daudin

Appl. Phys. Lett. 84, 4224 (2004); http://dx.doi.org/10.1063/1.1755840 (3 pages) | Cited 18 times

Online Publication Date: 7 May 2004

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We report on the effect of vertical correlation on GaN/AlN quantum dots grown by plasma-assisted molecular-beam epitaxy using the modified Stranski–Krastanow growth mode. When increasing the number of GaN periods, we observe a homogenization of the island distribution and a redshift of the luminescence line. This redshift is attributed to an increase of the quantum Stark effect due to the increase of the piezoelectric contribution to the internal electric field. © 2004 American Institute of Physics.
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68.65.Hb Quantum dots (patterned in quantum wells)
78.67.Hc Quantum dots
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
52.77.Dq Plasma-based ion implantation and deposition
77.65.Bn Piezoelectric and electrostrictive constants
78.20.Jq Electro-optical effects
78.55.Hx Other solid inorganic materials
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Relationship between the Li ionic conduction and the local structures in LiyLa(1−y)/3NbO3

Masanobu Nakayama, Hiromasa Ikuta, Yoshiharu Uchimoto, and Masataka Wakihara

Appl. Phys. Lett. 84, 4227 (2004); http://dx.doi.org/10.1063/1.1755844 (3 pages) | Cited 4 times

Online Publication Date: 7 May 2004

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In order to demonstrate the importance of local structural study for the lithium ionic conductor, we investigate the local structure of the Li+ conductor with perovskite structure, LiyLa(1−y)/3NbO3 (0 ⩽ y ⩽ 0.25) using the extended x-ray absorption fine structure (EXAFS) technique. The results of EXAFS measurement imply that changes of the local structure are more crucial for the property on ionic conductivity than that of the lattice parameter obtained by x-ray diffraction technique. © 2004 American Institute of Physics.
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66.30.H- Self-diffusion and ionic conduction in nonmetals
61.05.cj X-ray absorption spectroscopy: EXAFS, NEXAFS, XANES, etc.
82.47.Aa Lithium-ion batteries
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Coercivity enhancements by high-magnetic-field annealing in sintered Nd–Fe–B magnets

Hiroaki Kato, Terunobu Miyazaki, Masato Sagawa, and Keiichi Koyama

Appl. Phys. Lett. 84, 4230 (2004); http://dx.doi.org/10.1063/1.1756193 (3 pages) | Cited 12 times

Online Publication Date: 7 May 2004

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An influence of a high-field annealing on the magnetic properties was investigated in sintered Nd–Fe–B magnets. When the sample B, containing 0.32 at. % Al, was annealed at Ta = 550 °C under a magnetic field of Ha = 140 kOe and then cooled without field, the coercivity Hc increased by 25% with respect to the control sample annealed at zero field. As for the sample C, containing both Cu 0.13 at. % and Al 0.32 at. %, higher Hc values were obtained when it was annealed at Ta = 550 °C and the field of Ha = 140 kOe was kept applied down to the room temperature. These results were discussed in terms of a field-induced change in interface matching between Nd2Fe14B and intergranular phases. © 2004 American Institute of Physics.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Bb Fe and its alloys
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Electronic structure of Zn1−xCoxO using photoemission and x-ray absorption spectroscopy

S. C. Wi, J.-S. Kang, J. H. Kim, S.-B. Cho, B. J. Kim, S. Yoon, B. J. Suh, S. W. Han, K. H. Kim, K. J. Kim, B. S. Kim, H. J. Song, H. J. Shin, J. H. Shim, and B. I. Min

Appl. Phys. Lett. 84, 4233 (2004); http://dx.doi.org/10.1063/1.1756197 (3 pages) | Cited 66 times

Online Publication Date: 7 May 2004

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Electronic structures of homogeneous bulk samples of Zn0.9Co0.1O which do not exhibit diluted ferromagnetic semiconducting (DMS) behavior have been investigated using photoemission spectroscopy and x-ray absorption spectroscopy. We have found that the Co ions in Zn1−xCoxO are in the divalent Co2+(d7) states under the tetrahedral symmetry. Our finding indicates that the DMS properties will not be produced when Co ions are properly substituted for Zn sites, implying that the DMS properties observed in Zn1−xCoxO thin films are likely to be extrinsic. © 2004 American Institute of Physics.
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71.20.-b Electron density of states and band structure of crystalline solids
79.60.-i Photoemission and photoelectron spectra
78.70.Dm X-ray absorption spectra
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Laser trapping and manipulation under focused evanescent wave illumination

Min Gu, Jean-Baptiste Haumonte, Yoan Micheau, James W. M. Chon, and Xiaosong Gan

Appl. Phys. Lett. 84, 4236 (2004); http://dx.doi.org/10.1063/1.1756200 (3 pages) | Cited 47 times

Online Publication Date: 7 May 2004

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Laser trapping is based on the radiation pressure on a small particle in the focal region of a high numerical-aperture objective. Currently, the focal spot of a trapping beam is elongated along the longitudinal direction and thus the axial size of the trapping volume is approximately three times larger than that in the transverse direction. We report on a laser trapping technique under focused evanescent wave illumination. Therefore laser trapping of micro/nano-objects can be achieved in the near-field region with an axial trapping size of approximately 60 nm, which is reduced by approximately one order of magnitude. Hence, this technique is of significant importance in nanometry including single molecule detection and manipulation. © 2004 American Institute of Physics.
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37.10.Vz Mechanical effects of light on atoms, molecules, and ions
81.16.Ta Atom manipulation
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High-energy x-ray scattering in grazing incidence from nanometer-scale oxide wires

Osami Sakata, Masaki Takata, Hiroyoshi Suematsu, Akifumi Matsuda, Shusaku Akiba, Atsushi Sasaki, and Mamoru Yoshimoto

Appl. Phys. Lett. 84, 4239 (2004); http://dx.doi.org/10.1063/1.1756207 (3 pages) | Cited 11 times

Online Publication Date: 7 May 2004

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A method has been developed for analyzing the structure of crystalline nanowires deposited on a crystal surface. It combined in-air grazing-incidence surface scattering with high-energy synchrotron x-ray scattering. The technique has allowed a direct reciprocal-lattice space mapping of the x-ray intensities scattered from ultrathin nanowires. Using this method, the sheet-shape diffraction emanating from ultrathin NiO wires was observed. The average nanowire–nanowire distance of 46 nm and a crystallographic domain size of approximately 7.5 nm across the nanowire were evaluated. © 2004 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
85.35.-p Nanoelectronic devices
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Determination of the maximum gelation temperature in gelatin gels

Susan M. Tosh and Alejandro G. Marangoni

Appl. Phys. Lett. 84, 4242 (2004); http://dx.doi.org/10.1063/1.1756210 (3 pages) | Cited 14 times

Online Publication Date: 7 May 2004

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The maximum gelation temperature, Tgel, is widely used to characterize biopolymers that form thermoreversible gels. The Tgel of gelatin was determined using rheological techniques and compared to other methods in common use. The methods developed in this study defined a Tgel for gelatin, which was independent of gelatin concentration, and which corresponded closely to the theta temperature determined by light scattering. © 2004 American Institute of Physics.
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82.70.Gg Gels and sols
83.80.Rs Polymer solutions
87.19.rh Fluid transport and rheology
87.85.J- Biomaterials
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Generalized Snell’s law and its possible relation to coherent backscattering of ultrasonic waves

Nico F. Declercq, Joris Degrieck, and Oswald Leroy

Appl. Phys. Lett. 84, 4245 (2004); http://dx.doi.org/10.1063/1.1756675 (3 pages)

Online Publication Date: 7 May 2004

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The cause of backscattering in the Rayleigh angle has first been explained by means of finite beam models in which there are inherently present backward traveling components that explain the backscattering effect. Later, the nature of backscattered sound was proved to consist mostly of incoherent sound due to material anomalies. The present work shows that besides the well known real Snell’s law: i.e., continuity of the frequency and continuity of the wave vector component along the interface, there is also the possibility of a complex solution of Snell’s condition of continuity. The latter shows that it is possible that a part of the incident sound gets reflected into nonspecular directions including the backscatter direction. Furthermore, it is shown that this sound must have a different frequency than the incident frequency. © 2004 American Institute of Physics.
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43.35.-c Ultrasonics, quantum acoustics, and physical effects of sound
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Thermal conductivity improvement of silicone elastomer with carbon nanotube loading

C. H. Liu, H. Huang, Y. Wu, and S. S. Fan

Appl. Phys. Lett. 84, 4248 (2004); http://dx.doi.org/10.1063/1.1756680 (3 pages) | Cited 65 times

Online Publication Date: 7 May 2004

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Unpurified carbon nanotubes were introduced to silicone elastomer to investigate their effect on the thermal conductivity. Microstructure studies by a scanning electron microscope showed that the carbon nanotubes (CNTs) can be well dispersed in the matrix by the grinding method. No notable agglomerates or phase separation between the carbon and silicone matrix were observed, and the CNTs were individually in random orientation. The thermal conductivities of the composites were measured with the ASTM (American Society of Testing Materials) D5470 method. The thermal conductivities κ were found to increase with the carbon amount. There was a 65% enhancement in κ with 3.8 wt % CNT loading. The enhancement by equal loading of carbon black was found to be a little lower than that by the CNT loading. The composites loaded with CNTs displayed an abrupt increase in the electrical conductivity. © 2004 American Institute of Physics.
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66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
72.15.Eb Electrical and thermal conduction in crystalline metals and alloys
61.46.-w Structure of nanoscale materials
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Origin and repartition of the oxide fixed charges generated by electrical stress in memory tunnel oxide

Sandrine Bernardini, Pascal Masson, Michel Houssa, and Frederic Lalande

Appl. Phys. Lett. 84, 4251 (2004); http://dx.doi.org/10.1063/1.1756681 (3 pages) | Cited 1 time

Online Publication Date: 7 May 2004

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A method is proposed to determine the origin and the spatial oxide fixed charge repartition in memory tunnel oxide from Fowler–Nordheim current measurements after electrical stress. The Poisson equation resolution in the dielectric layer is required to account for the nonsymmetric tunneling barrier deformation, resulting from charges generated within the dielectric layer. From current–voltage characteristics measurements and simulations, we have determined the spatial distribution of the oxide fixed charges within the dielectric layer of metal/SiO2/metal structures. In addition, the kinetics of the oxide charge generation can be explained by a dispersive hydrogen transport model. © 2004 American Institute of Physics.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
85.30.De Semiconductor-device characterization, design, and modeling
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Electric field and temperature-induced removal of moisture in nanoporous organosilicate films

N. Biswas, J. A. Lubguban, and S. Gangopadhyay

Appl. Phys. Lett. 84, 4254 (2004); http://dx.doi.org/10.1063/1.1757019 (3 pages) | Cited 1 time

Online Publication Date: 7 May 2004

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The effects of bias-temperature-stress (BTS) or simply temperature-stress (TS) on nanoporous low-k methylsilsesquioxane films are studied. Initially, the as-given and O2 ashed/etched films exhibit physical adsorption of moisture as revealed from the electrical behavior of the samples after 15 days. The temperature stressing at 170 °C volatilized the adsorbed water but is unable to remove chemisorb and hydrophillic Si–OH groups. As a result, the TS films remain susceptible to moisture. BTS at 170 °C also removes adsorbed water. More important, the surfaces under the metal-insulator structure were dehydroxylated by breaking the chemisorb Si–OH group facilitating the formation of siloxane bonds that prevents adsorption of moisture even after 60 days. © 2004 American Institute of Physics.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
81.05.Rm Porous materials; granular materials
68.43.Mn Adsorption kinetics
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Reduction of spin transfer by synthetic antiferromagnets

N. C. Emley, F. J. Albert, E. M. Ryan, I. N. Krivorotov, D. C. Ralph, R. A. Buhrman, J. M. Daughton, and A. Jander

Appl. Phys. Lett. 84, 4257 (2004); http://dx.doi.org/10.1063/1.1757638 (3 pages) | Cited 23 times

Online Publication Date: 7 May 2004

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Synthetic antiferromagnetic layers (SAF) are incorporated into spin transfer nanopillars giving a layer composition [Cobottom/Ru/Cofixed]/Cu/Cofree, where square brackets indicate the SAF. The Cobottom and Cofixed layers are aligned antiparallel (AP) by strong indirect exchange coupling through the Ru spacer. All three magnetic layers are patterned, so this AP alignment reduces undesirable dipole fields on the Cofree layer. Adding the Cobottom/Ru layers reduces the spin polarization of the electron current passing through the nanopillar, leading to a decreased spin-torque per unit current incident on the Cofree layer. This may be advantageous for device applications requiring a reduction of the effects of a spin-torque, such as nanoscale current-perpendicular-to-plane magnetoresistive read heads. © 2004 American Institute of Physics.
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75.50.Ee Antiferromagnetics
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.30.Et Exchange and superexchange interactions
75.47.De Giant magnetoresistance
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Electrochromism in switchable nematic emulsions

F. P. Nicoletta, D. Cupelli, G. De Filpo, and G. Chidichimo

Appl. Phys. Lett. 84, 4260 (2004); http://dx.doi.org/10.1063/1.1758294 (3 pages) | Cited 10 times

Online Publication Date: 7 May 2004

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Switchable nematic emulsions are composite systems formed by liquid-crystal droplets dispersed in a fluid, homogeneous, monomer matrix, which can be turned from an opaque to an optically transparent state by application of a suitable ac electric field. An electrochromic device provides a reversible and visible change in its transmittance and/or reflectance as the result of either oxidation or reduction electrochemical processes. Both devices have been proven to be useful for a variety of electro-optical applications as switchable windows, electromagnetic shutters, and displays. This letter reports preliminary results on a bifunctional device based on a switchable nematic emulsion, which hosts electrochemical reactions. The presence of a liquid-crystal dispersion ensures the switching from a scattering and opaque state to a transmissive and transparent state, while the oxidation–reduction reactions allow a contemporary and independent change in color. © 2004 American Institute of Physics.
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42.79.Kr Display devices, liquid-crystal devices
85.60.Pg Display systems
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
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Photoinduced birefringence in tellurite glasses

V. K. Tikhomirov, K. E. Asatryan, T. V. Galstian, R. Vallee, and A. B. Seddon

Appl. Phys. Lett. 84, 4263 (2004); http://dx.doi.org/10.1063/1.1758307 (2 pages) | Cited 3 times

Online Publication Date: 7 May 2004

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We report on photoinduced birefringence in TeO2-based glasses on exposure to linearly polarized subbandgap light. It is shown that the influence of glass-network modifiers, such as ZnO, Na2O, BaO, and of dopant Er2O3, on the photoinduced birefringence is not substantial indicating a dominating role of the TeO2 component. Photoinduced birefringence is optically reversible and its mechanism is proposed to be due to laser-induced alignment of intrinsic anisotropic defects of tellurite glass, such as distorted TeO4 bipyramids. © 2004 American Institute of Physics.
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78.20.Fm Birefringence
61.82.Rx Nanocrystalline materials
61.43.Fs Glasses

Frequency locking and wavelength tuning of nanosecond pulsed broad-area semiconductor lasers

Y. Liu, V. Kireev, and Y. Braiman

Appl. Phys. Lett. 84, 4265 (2004); http://dx.doi.org/10.1063/1.1758782 (3 pages) | Cited 1 time

Online Publication Date: 7 May 2004

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We discuss experimental results of frequency locking and wavelength tuning of a nanosecond pulsed broad-area semiconductor laser. Nanosecond optical pulses with peak power of 25 W and repetition rates of 4–240 kHz are generated from a broad-area laser. An external cavity with a diffractive grating is used to reduce the linewidth of the laser from over 5 nm to less than 0.1 nm. The wavelength of the pulsed laser is tunable over more than 10 nm. The dependence of the laser linewidth on pulse parameters has been investigated. © 2004 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Fc Modulation, tuning, and mode locking
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Ultrafast InGaAs/InGaAlAs multiple-quantum-well electro-absorption modulator for wavelength conversion at high bit rates

N. El Dahdah, G. Aubin, J.-C. Harmand, A. Ramdane, A. Shen, F. Devaux, A. Garreau, and B.-E. Benkelfat

Appl. Phys. Lett. 84, 4268 (2004); http://dx.doi.org/10.1063/1.1711165 (3 pages) | Cited 5 times

Online Publication Date: 7 May 2004

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We report on InGaAs/InGaAlAs electro-absorption modulators for ultrafast all-optical signal processing. The structure design is based on the use of small conduction and valence band offsets. Switching windows as short as 5 ps for a 2 V applied reverse bias have been obtained by cross-absorption modulation. © 2004 American Institute of Physics.
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42.79.Hp Optical processors, correlators, and modulators
78.20.Jq Electro-optical effects
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
73.21.Fg Quantum wells
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Tilt angle dependent three-dimensional-position detection of a trapped cylindrical particle in a focused laser beam

Holger Kress, Ernst H. K. Stelzer, and Alexander Rohrbach

Appl. Phys. Lett. 84, 4271 (2004); http://dx.doi.org/10.1063/1.1737056 (3 pages) | Cited 6 times

Online Publication Date: 7 May 2004

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We investigated theoretically the applicability of an optically trapped cylindrical particle as a local probe in photonic force microscopy. To do this we calculated the far-field scattering from a subwavelength-sized dielectric cylinder in a highly focused laser field. From this we obtained interferometric three-dimensional-position detection signals and compared these to signals calculated for a spherical particle. We have calculated the accuracy to which the position of an optically trapped cylinder can be determined, as a function of the cylinder’s orientational fluctuations. The position accuracy is better than a few nanometers for tilt angle fluctuations up to several degrees. Our study is relevant for trapping experiments, where the influence of angle fluctuations needs to be estimated. © 2004 American Institute of Physics.
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07.79.-v Scanning probe microscopes and components
37.10.Vz Mechanical effects of light on atoms, molecules, and ions
06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)
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Pseudoelasticity of shape-memory titanium–nickel films subjected to dynamic nanoindentation

X.-G. Ma and K. Komvopoulos

Appl. Phys. Lett. 84, 4274 (2004); http://dx.doi.org/10.1063/1.1737463 (3 pages) | Cited 18 times

Online Publication Date: 7 May 2004

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Surface force microscopy was used to examine the dynamic indentation response of austenitic titanium–nickel (TiNi) films sputtered on oxidized silicon substrates. Results demonstrate the significance of indentation cycles, time at maximum contact load, and loading/unloading rate on the nanoscale pseudoelastic behavior of the TiNi films. The dynamic behavior of the films is interpreted in terms of the mechanisms responsible for the energy dissipated in the absence of irreversible deformation. The significant amount of mechanical work dissipated without permanent deformation illustrates the potential of TiNi films as structural materials for dynamic microdevice applications. © 2004 American Institute of Physics.
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68.60.Bs Mechanical and acoustical properties
62.20.D- Elasticity
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
81.40.Jj Elasticity and anelasticity, stress-strain relations
64.70.K- Solid-solid transitions
81.30.Kf Martensitic transformations
68.55.-a Thin film structure and morphology
68.35.Gy Mechanical properties; surface strains
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
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Method to sense single-particle motion using a tapered-gap microcapacitor

Ruti Kapon, Ilan Sagiv, Joseph Shappir, Noa Mazorski, Guy Ziv, Dan Shahar, and Ziv Reich

Appl. Phys. Lett. 84, 4277 (2004); http://dx.doi.org/10.1063/1.1738940 (3 pages) | Cited 2 times

Online Publication Date: 7 May 2004

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We present an approach to study the real-time dynamics of single molecules using capacitance measurements. The method is based on a nonparallel-plate microcapacitor, which has a tapered-gap geometry. A particle moving within such a capacitor induces capacitance changes that depend on its position. Monitoring these changes allows motion to be traced at a resolution which is higher than the smallest fabricated feature of the device. The detection scheme also enables the distinction between particles of different dielectric constants and the exertion of dielectrophoretic forces on the particles. This approach provides a means for studying various aspects of single-particle dynamics at high resolution, in real time, and under conditions compatible with biological systems. © 2004 American Institute of Physics.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
84.32.Tt Capacitors
82.45.-h Electrochemistry and electrophoresis
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Scanning tunneling spectroscopy of suspended single-wall carbon nanotubes

B. J. LeRoy, S. G. Lemay, J. Kong, and C. Dekker

Appl. Phys. Lett. 84, 4280 (2004); http://dx.doi.org/10.1063/1.1748836 (3 pages) | Cited 17 times

Online Publication Date: 7 May 2004

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We have performed low-temperature scanning tunneling microscopy measurements on single-wall carbon nanotubes that are freely suspended over a trench. The nanotubes were grown by chemical vapor deposition on a Pt substrate with predefined trenches etched into it. Atomic resolution was obtained on the freestanding portions of the nanotubes. Spatially resolved spectroscopy on the suspended portion of both metallic and semiconducting nanotubes was also achieved, showing a Coulomb-staircase behavior superimposed on the local density of states. The spacing of the Coulomb blockade peaks changed with tip position reflecting a changing tip-tube capacitance. © 2004 American Institute of Physics.
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81.07.De Nanotubes
61.46.-w Structure of nanoscale materials
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
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Boron diffusion in amorphous silicon and the role of fluorine

R. Duffy, V. C. Venezia, A. Heringa, B. J. Pawlak, M. J. P. Hopstaken, G. C. J. Maas, Y. Tamminga, T. Dao, F. Roozeboom, and L. Pelaz

Appl. Phys. Lett. 84, 4283 (2004); http://dx.doi.org/10.1063/1.1751225 (3 pages) | Cited 22 times

Online Publication Date: 7 May 2004

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We demonstrate that boron diffuses at high concentrations during low-temperature thermal annealing in amorphous silicon pre-amorphized by germanium ion implantation. For a typical boron ultrashallow junction doping profile, concentrations as high as 2×1020 cm−3 appear to be highly mobile at 500 and 600 °C in the amorphous silicon region before recrystallization. In crystalline silicon at the same temperatures the mobile boron concentration is at least two orders of magnitude lower. We also show that boron diffusivity in the amorphous region is similar with and without fluorine. The role of fluorine is not to enhance boron diffusivity, but to dramatically slow down the recrystallization rate, allowing the boron profile to be mobile up to the concentration of 2×1020 cm−3 for a longer time. © 2004 American Institute of Physics.
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66.30.J- Diffusion of impurities
61.72.uf Ge and Si
61.72.S- Impurities in crystals
61.72.Cc Kinetics of defect formation and annealing
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
68.49.Sf Ion scattering from surfaces (charge transfer, sputtering, SIMS)

Visible cathodoluminescence from Eu-implanted single- and polycrystal c-BN annealed under high-temperature, high-pressure conditions

Ulrich Vetter, Hans Hofsäss, and Takashi Taniguchi

Appl. Phys. Lett. 84, 4286 (2004); http://dx.doi.org/10.1063/1.1753053 (3 pages) | Cited 17 times

Online Publication Date: 7 May 2004

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Red and red/blue cathodoluminescence in the temperature range 12 to 300 K was obtained from single- and polycrystal cubic boron nitride bulk samples implanted with europium and annealed under high-temperature, high-pressure conditions. All observed radiative intra-4f electron transitions of Eu3+ can be assigned to transitions starting from the 5D0 level of Eu3+. Additionally, radiative 4fN−15d→4fN electron transitions related to Eu2+ were detected in the polycrystal c-BN specimens. The higher-resolution Stark level as well as the time-resolved cathodoluminescence spectroscopy suggest that the Eu ions occupy at least two different sites in the c-BN host. © 2004 American Institute of Physics.
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78.60.Hk Cathodoluminescence, ionoluminescence
68.47.Fg Semiconductor surfaces
61.72.uj III-V and II-VI semiconductors
78.47.-p Spectroscopy of solid state dynamics
61.72.Cc Kinetics of defect formation and annealing
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