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30 Sep 2002

Volume 81, Issue 14, pp. 2493-2662

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Enhanced second-order nonlinear optical response of LiNbO3 films upon Er doping

J. Gonzalo, J. A. Chaos, A. Suárez-García, C. N. Afonso, and V. Pruneri

Appl. Phys. Lett. 81, 2532 (2002); http://dx.doi.org/10.1063/1.1506949 (3 pages) | Cited 2 times

Online Publication Date: 23 September 2002

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Erbium-doped LiNbO3 films have been produced in a single-step process by alternate pulsed laser deposition. The dopant is incorporated in submonolayers whose nominal indepth separation is varied in the range 1.7–4.0 nm to lead respectively to Er concentrations in the range 3.4–0.6×1020 atoms/cm−3. All the films exhibit the characteristic Er3+ photoluminescence at 1.54 μm with lifetime values as high as 3 ms. The d33 nonlinear coefficients determined from second-harmonic generation experiments are in the range 22–28 pm/V, the films having nominal Er submonolayer indepth separation of 3–4 nm exhibiting d33 values slightly above that of the bulk material. The comparison of the d33 values obtained in the Er-doped films to those reported earlier for similar undoped films shows clearly that both the structural quality and the second-harmonic performance of the films can be enhanced by Er doping. © 2002 American Institute of Physics.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.70.Mp Nonlinear optical crystals
78.66.Nk Insulators
68.55.-a Thin film structure and morphology
81.15.Fg Pulsed laser ablation deposition

Dynamical x-ray microscopy investigation of electromigration in passivated inlaid Cu interconnect structures

G. Schneider, G. Denbeaux, E. H. Anderson, B. Bates, A. Pearson, M. A. Meyer, E. Zschech, D. Hambach, and E. A. Stach

Appl. Phys. Lett. 81, 2535 (2002); http://dx.doi.org/10.1063/1.1509465 (3 pages) | Cited 22 times

Online Publication Date: 23 September 2002

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Quantitative time-resolved x-ray microscopy mass transport studies of the early stages of electromigration in an inlaid Cu line/via structure were performed with about 40 nm lateral resolution. The image sequences show that void formation is a highly dynamic process, with voids being observed to nucleate and grow within the Cu via and migrate towards the via sidewall. Correlation of the real time x-ray microscopy images with postmortem high voltage electron micrographs of the sample indicates that the void nucleation occurs at the site of grain boundaries in Cu, and that the voids migrate along these grain boundaries during electromigration. © 2002 American Institute of Physics.
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85.40.Ls Metallization, contacts, interconnects; device isolation
85.40.Qx Microcircuit quality, noise, performance, and failure analysis
07.85.Tt X-ray microscopes
66.30.Qa Electromigration
81.65.Rv Passivation
61.72.Qq Microscopic defects (voids, inclusions, etc.)
61.72.Mm Grain and twin boundaries

Superhigh-frequency surface-acoustic-wave transducers using AlN layers grown on SiC substrates

Y. Takagaki, P. V. Santos, E. Wiebicke, O. Brandt, H.-P. Schönherr, and K. H. Ploog

Appl. Phys. Lett. 81, 2538 (2002); http://dx.doi.org/10.1063/1.1509471 (3 pages) | Cited 25 times

Online Publication Date: 23 September 2002

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We demonstrate the operation of surface-acoustic-wave (SAW) transducers fabricated on AlN/SiC structures at frequencies as high as 19 GHz. The high SAW velocity of the AlN film is enhanced by the even higher sound velocity of the SiC substrate, enabling us to achieve these frequencies with a SAW wavelength of 400 nm. © 2002 American Institute of Physics.
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43.38.Rh Surface acoustic wave transducers
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
68.35.Iv Acoustical properties

Method to measure shear moduli of nonequilibrium phases pseudomorphically stabilized in superlattices

V. Pankov, M. Evstigneev, and R. H. Prince

Appl. Phys. Lett. 81, 2541 (2002); http://dx.doi.org/10.1063/1.1510966 (3 pages)

Online Publication Date: 23 September 2002

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A method to measure shear moduli of nonequilibrium phases pseudomorphically stabilized in superlattices is proposed. The method is based on the use of a stress-free coherent superlattice as a modeling structure whereby the lattice misfit strain is distributed between the individual layers according to their shear moduli and Poisson ratios. The method is applied to estimate the shear modulus of the nonequilibrium rocksalt-type (B1) AlN phase pseudomorphically stabilized in AlN/TiN superlattices. The value of shear modulus of B1–AlN in these superlattices was found to increase from 288±50 GPa to 457±80 GPa with decreasing bilayer thickness from 1 to 0.6 nm. © 2002 American Institute of Physics.
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81.70.Bt Mechanical testing, impact tests, static and dynamic loads
68.65.Cd Superlattices
68.35.Gy Mechanical properties; surface strains

Micro-Raman studies of vertical-cavity surface-emitting lasers with AlxOy/GaAs distributed Bragg reflectors

V. A. Haisler, F. Hopfer, R. L. Sellin, A. Lochmann, K. Fleischer, N. Esser, W. Richter, N. N. Ledentsov, D. Bimberg, C. Möller, and N. Grote

Appl. Phys. Lett. 81, 2544 (2002); http://dx.doi.org/10.1063/1.1511533 (3 pages) | Cited 10 times

Online Publication Date: 23 September 2002

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Micro-Raman spectroscopy studies of the oxidation processes in high Al content AlxGa1−xAs layers used in distributed Bragg reflectors (DBRs) in vertical-cavity surface-emitting lasers (VCSELs) are presented. Precise characterization of the composition of oxidized layers, control over residual As precipitates, as well as the determination of the mechanical strain in DBR layers is demonstrated. Proper optimization of the processing steps on the basis of Micro-Raman spectroscopy allows the realization of reliable oxide-DBR VCSELs. © 2002 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
81.65.Mq Oxidation

Photoluminescence upconversion in 4H–SiC

Mt. Wagner, I. G. Ivanov, L. Storasta, J. P. Bergman, B. Magnusson, W. M. Chen, and E. Janzén

Appl. Phys. Lett. 81, 2547 (2002); http://dx.doi.org/10.1063/1.1511813 (3 pages) | Cited 1 time

Online Publication Date: 23 September 2002

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Efficient photoluminescence upconversion is observed in 4H–SiC samples containing both the UD-3 defect and the titanium impurity. In this process, the titanium photoluminescence emission with no-phonon (NP) lines at 2.848 eV (A0) and 2.789 eV (B0) can be excited by tuning the laser to the NP line of UD-3 at 1.356 eV. In samples containing either only UD-3 or only titanium, a different photoluminescence upconversion process can be observed, which occurs at photon energies higher than ∼ 1.5 eV without exhibiting sharp features. At least one of the two processes generates both free electrons and free holes and can, therefore, be a candidate for an important recombination channel. © 2002 American Institute of Physics.
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78.55.Hx Other solid inorganic materials
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
81.05.Hd Other semiconductors
71.55.Ht Other nonmetals

Multiple splitting of G-band modes from individual multiwalled carbon nanotubes

Xinluo Zhao, Yoshinori Ando, Lu-Chang Qin, Hiromichi Kataura, Yutaka Maniwa, and Riichiro Saito

Appl. Phys. Lett. 81, 2550 (2002); http://dx.doi.org/10.1063/1.1502196 (3 pages) | Cited 26 times

Online Publication Date: 23 September 2002

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Surface-enhanced Raman scattering spectra of an individual multiwalled carbon nanotube (MWNT) with the innermost diameter ∼ 1 nm, prepared by hydrogen arc discharge, show a single peak of radial breathing mode and multiple splitting of the tangential stretching G-band modes. Based on Lorentzian line shape analysis and related theoretical calculations, the G-band modes of MWNT are confirmed to be composed of both G-band modes (linewidth 4 cm−1) from the innermost tube and graphite-like mode (linewidth ∼ 20 cm−1) from the outer cylinders in MWNT. This observation indicates that MWNTs are unique and possess characteristic Raman spectra different from other sp2 carbon allotropes. © 2002 American Institute of Physics.
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78.30.Na Fullerenes and related materials
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials

Permanent grayscales in bistable twisted nematic liquid-crystal displays

Z. L. Xie, Z. G. Meng, M. Wong, and H. S. Kwok

Appl. Phys. Lett. 81, 2553 (2002); http://dx.doi.org/10.1063/1.1511807 (3 pages) | Cited 2 times

Online Publication Date: 23 September 2002

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Permanent grayscales in a π bistable twisted nematic-liquid-crystal display have been demonstrated. This display can be switched between the −22.5° and 157.5° twist states by a combination of a strong in-plane electric field and a vertical electric field for creating both planar anchoring breaking and an electrohydrodynamic backflow. The switching of the twist states during the Frederiks transition is sufficiently inhomogeneous such that domains of −22.5° and 157.5° twisted states can coexist permanently. The ratio of these domains can be controlled by the vertical electric field. © 2002 American Institute of Physics.
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42.79.Kr Display devices, liquid-crystal devices

Three-dimensional band mapping of graphite

Fumihiko Matsui, Yoshiaki Hori, Hiroaki Miyata, Nobutaka Suganuma, Hiroshi Daimon, Hidekazu Totsuka, Koji Ogawa, Tomoya Furukubo, and Hidetoshi Namba

Appl. Phys. Lett. 81, 2556 (2002); http://dx.doi.org/10.1063/1.1511818 (3 pages) | Cited 22 times

Online Publication Date: 23 September 2002

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We developed a method to visualize the curved surfaces of valence band dispersion by a display-type spherical mirror analyzer. The π and σ band “surfaces” of graphite measured and displayed three dimensionally contain fruitful information compared to the conventional band dispersion “curves” along a certain direction in k space. The slope and the curvature of local band structure correspond to the velocity and the mass of the valence electrons. By integrating band energy over the entire Brillouin zone, the electronic part of the condensation energy is obtained. Furthermore, the atomic orbitals composing each band are determined from two-dimensional photoelectron intensity distribution by using linearly polarized synchrotron radiation. © 2002 American Institute of Physics.
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71.20.Ps Other inorganic compounds
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
79.60.Bm Clean metal, semiconductor, and insulator surfaces

Sensitive detection of voids in solid materials by refraction-enhanced synchrotron radiation imaging

Keiko Imamura, Norishige Ehara, Keiji Umetani, Keiko Miyamoto, Yoshihide Kanemaki, Kentarou Uesugi, Yoichi Inada, Haruki Ogata, Yasuo Nakajima, and Mamoru Fukuda

Appl. Phys. Lett. 81, 2559 (2002); http://dx.doi.org/10.1063/1.1510585 (2 pages) | Cited 1 time

Online Publication Date: 23 September 2002

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Voids in opaque materials (minute air bubbles) were imaged with synchrotron radiation in a refraction enhancement mode. The voids are imaged by an enhanced x-ray intensity inside the bubble, surrounded by a border region with decreased x-ray intensity, thus allowing sensitive detection of air bubbles in plastic materials. As those “impurities” could not be depicted with conventional radiography, and optical inspection is not useful if the matrix is opaque, this in-situ imaging technique offers the potential to obtain information of air inclusions, voids, and cracking that appear inadvertently in opaque plastics and possibly in metals as well. © 2002 American Institute of Physics.
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81.70.Ex Nondestructive testing: electromagnetic testing, eddy-current testing
07.85.Qe Synchrotron radiation instrumentation
61.72.Qq Microscopic defects (voids, inclusions, etc.)

Evaluation of the thermal stability of a Cu60Hf25Ti15 metallic glass

Dmitri V. Louzguine and Akihisa Inoue

Appl. Phys. Lett. 81, 2561 (2002); http://dx.doi.org/10.1063/1.1509466 (2 pages) | Cited 24 times

Online Publication Date: 23 September 2002

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The present letter shows how a continuous heating transformation diagram for a Cu60Hf25Ti15 metallic glass can be obtained by applying an extension of the Kissinger analysis. According to the calculation this glass is completely stable in the Earth’s climate for its lifetime. This extension of the Kissinger analysis method can be applied to any other metallic glass. © 2002 American Institute of Physics.
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65.60.+a Thermal properties of amorphous solids and glasses: heat capacity, thermal expansion, etc.
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder
64.70.K- Solid-solid transitions
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