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25 Jun 2007

Volume 90, Issue 26, Articles (26xxxx)

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Appl. Phys. Lett. 90, 262501 (2007); http://dx.doi.org/10.1063/1.2752015 (3 pages)

Ian Appelbaum and Douwe J. Monsma
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Superior mechanical properties of FeCrMoVC

U. Kühn, N. Mattern, T. Gemming, U. Siegel, K. Werniewicz, and J. Eckert

Appl. Phys. Lett. 90, 261901 (2007); http://dx.doi.org/10.1063/1.2751577 (3 pages) | Cited 9 times

Online Publication Date: 25 June 2007

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This work presents results on the microstructure and mechanical properties of the steel composition Fe84.3Cr4.3Mo4.6V2.2C4.6 subjected to preparation conditions typically used for manufacturing of bulk metallic glasses. Thermodynamical aspects and kinetic limitations on the specific solidification process of phase formation, particularly those, which are strongly dominated by diffusion controlled mechanisms, promote the formation of nonequilibrium phases, such as martensite and complex carbide structures already in the as-cast state. This combination of high strength phases yields material with highly desirable properties, such as an engineering compression strength of more than 4000 MPa surprisingly combined with a fracture strain of about 12%.
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81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
81.40.Lm Deformation, plasticity, and creep
81.30.Fb Solidification
81.30.Bx Phase diagrams of metals, alloys, and oxides
62.20.M- Structural failure of materials
62.20.F- Deformation and plasticity

Solitary and shock waves in discrete strongly nonlinear double power-law materials

E. B. Herbold and V. F. Nesterenko

Appl. Phys. Lett. 90, 261902 (2007); http://dx.doi.org/10.1063/1.2751592 (3 pages) | Cited 6 times

Online Publication Date: 25 June 2007

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A laminar metamaterial supporting strongly nonlinear solitary and shock waves with impact energy mitigating capabilities is presented. It consists of steel plates with intermittent polymer toroidal rings acting as strongly nonlinear springs with large allowable strain. The force-displacement relationship of a compressed o-ring is described by the addition of two power-law relationships resulting in a solitary wave speed and width depending on the amplitude. This double nonlinearity allows splitting of an initial impulse into three separate strongly nonlinear solitary wave trains. Solitary and shock waves are observed experimentally and analyzed numerically in an assembly with Teflon o-rings.
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46.40.-f Vibrations and mechanical waves

Structural and optical properties of nanocrystalline Zn1−xMnxO

K. Samanta, S. Dussan, R. S. Katiyar, and P. Bhattacharya

Appl. Phys. Lett. 90, 261903 (2007); http://dx.doi.org/10.1063/1.2751593 (3 pages) | Cited 46 times

Online Publication Date: 25 June 2007

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The multi phonon Raman scattering in Mn doped (1%–10%) ZnO was observed at room temperature using 514.5 nm Ar+ laser. The additional optical modes at 327, 332, 482, 532, and 680 cm−1 in Zn1−xMnxO targets were identified as the second order Raman modes in the disordered lattice and the precipitation of the secondary phase ZnMn2O4. The crystalline grain sizes of 1%, 3%, 5%, and 10% Mn doped ZnO samples were calculated by phonon confinement model as 31.8, 18.3, 15.9, and 14.1 nm, respectively. The optical band gap was found to be increased (3.27–3.41 eV) due to the Mn doping.
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63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
63.20.D- Phonon states and bands, normal modes, and phonon dispersion
78.30.Fs III-V and II-VI semiconductors
61.46.Hk Nanocrystals
61.72.uj III-V and II-VI semiconductors

Atomic structure of In2O3–ZnO systems

Yanfa Yan, Juarez L. F. Da Silva, Su-Huai Wei, and Mowafak Al-Jassim

Appl. Phys. Lett. 90, 261904 (2007); http://dx.doi.org/10.1063/1.2751596 (3 pages) | Cited 15 times

Online Publication Date: 25 June 2007

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The authors present first-principles density-functional theory studies on the atomic structure of the In2O3–ZnO system. They find that the In2O3–ZnO system has a polytypoid structure, which consists of wurtzite (Zn/In)O slabs separated by single In–O octahedral layers that are inversion boundaries. Another type of boundary with polarity inversion formed by fivefold coordinated In and Zn atoms exists inside the (Zn/In)O slabs. The authors find that these polarity-inversion boundaries inside the (Zn/In)O slabs prefer a low-energy modulated structure.
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61.66.Fn Inorganic compounds

Effect of microstructure on hydrogen permeation through thermally stable, sputtered palladium-silver alloy membranes

L. S. McLeod, F. L. Degertekin, and A. G. Fedorov

Appl. Phys. Lett. 90, 261905 (2007); http://dx.doi.org/10.1063/1.2751597 (3 pages) | Cited 6 times

Online Publication Date: 25 June 2007

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The authors report on fabrication and hydrogen separation performance of an array of thin, freestanding Pd/Ag alloy membranes. Film deposition from an alloyed sputtering target results in robust film characteristics. Long-term stability of the membranes has been demonstrated with experimental testing at temperatures of 473–627 K. Within the testing period the membrane has withstood more than 30 thermal cycles by returning to ambient temperature between subsequent tests. Throughout the long-term testing, hydrogen permeation levels have increased by more than a factor of 2. Electron microscopy of the membranes indicates that performance enhancement is due to microstructural changes which are promoted at elevated temperatures.
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81.05.Bx Metals, semimetals, and alloys
82.45.Mp Thin layers, films, monolayers, membranes
81.15.Cd Deposition by sputtering

Pd–In–Fe shape memory alloy

H. Ishikawa, Y. Sutou, T. Omori, K. Oikawa, K. Ishida, A. Yoshikawa, R. Y. Umetsu, and R. Kainuma

Appl. Phys. Lett. 90, 261906 (2007); http://dx.doi.org/10.1063/1.2749440 (3 pages) | Cited 3 times

Online Publication Date: 26 June 2007

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Martensitic, magnetic transformations, and crystal structures in Pd–In–Fe alloys were investigated. It was confirmed that some Pd–In–Fe alloys show martensitic transformation from a Heusler-type (L21) ordered bcc phase to a 2M-type (DO22) structure and that an almost perfect superelastic effect accompany the transformation can be obtained. Furthermore, some alloys show transformation from the paramagnetic parent phase to the ferromagnetic martensite phase.
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81.30.Kf Martensitic transformations
64.70.K- Solid-solid transitions
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
61.66.Dk Alloys
81.40.Jj Elasticity and anelasticity, stress-strain relations
75.50.Bb Fe and its alloys

Mechanism for radiative recombination in ZnCdO alloys

I. A. Buyanova, J. P. Bergman, G. Pozina, W. M. Chen, S. Rawal, D. P. Norton, S. J. Pearton, A. Osinsky, and J. W. Dong

Appl. Phys. Lett. 90, 261907 (2007); http://dx.doi.org/10.1063/1.2751589 (3 pages) | Cited 12 times

Online Publication Date: 26 June 2007

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Temperature dependent cw- and time-resolved photoluminescence combined with absorption measurements are employed to evaluate the origin of radiative recombination in ZnCdO alloys grown by molecular-beam epitaxy. The near-band-edge emission is attributed to recombination of excitons localized within band tail states likely caused by nonuniformity in Cd distribution. Energy transfer between the tail states is argued to occur via tunneling of localized excitons. The transfer is shown to be facilitated by increasing Cd content due to a reduction of the exciton binding energy and, therefore, an increase of the exciton Bohr radius in the alloys with a high Cd content.
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81.05.Dz II-VI semiconductors
73.61.Ga II-VI semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.55.Et II-VI semiconductors
71.35.-y Excitons and related phenomena

Facile assembling of gold nanorods with large aspect ratio and their surface-enhanced Raman scattering properties

Go Kawamura, Yong Yang, and Masayuki Nogami

Appl. Phys. Lett. 90, 261908 (2007); http://dx.doi.org/10.1063/1.2752026 (3 pages) | Cited 21 times

Online Publication Date: 26 June 2007

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Linear- and parallel-aligned gold nanorods (GNRs) were self-assembled on glass substrates and their surface-enhanced Raman scattering effect was investigated. GNRs were prepared by seed-mediated growth method and self-assembled to form linear and parallel aggregation on the substrate. The parallel-aligned GNRs showed weak optical absorption intensities in the visible to infrared wavelength region. On the other hand, the linear-aligned GNRs exhibited strong optical absorption bands peaking at 830 and 2200 nm, which are assigned to the weakly coupled surface plasmons of the GNRs. When Rhodamine-6G molecules were adsorbed on the linear-aligned GNRs, strong surface-enhanced Raman scattering spectra were observed.
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78.30.Er Solid metals and alloys
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
81.16.Dn Self-assembly
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
68.43.Mn Adsorption kinetics
78.40.Kc Metals, semimetals, and alloys
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Epitaxial electrodeposition of freestanding large area single crystal substrates

Jae Wook Shin, Adam Standley, and Eric Chason

Appl. Phys. Lett. 90, 261909 (2007); http://dx.doi.org/10.1063/1.2752531 (3 pages)

Online Publication Date: 26 June 2007

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The authors report on a method for producing freestanding single crystal metal films over large areas using electrodeposition and selective etching. The method can be turned into an inexpensive continuous process for making long ribbons or a large area of single crystal films. Results from a 5×5 mm2 Ni single crystal film using electron backscattering pattern pole figures and x-ray diffraction demonstrate that the quality of material produced is equivalent to the initial substrate without annealing or polishing.
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81.15.Pq Electrodeposition, electroplating
68.55.A- Nucleation and growth
81.05.Bx Metals, semimetals, and alloys
82.45.Qr Electrodeposition and electrodissolution
81.65.Cf Surface cleaning, etching, patterning
68.55.-a Thin film structure and morphology

Stabilization of the liquid crystal director in the patterned vertical alignment mode through formation of pretilt angle by reactive mesogen

Sang Gyun Kim, Sung Min Kim, Youn Sik Kim, Hee Kyu Lee, Seung Hee Lee, Gi-Dong Lee, Jae-Jin Lyu, and Kyeong Hyeon Kim

Appl. Phys. Lett. 90, 261910 (2007); http://dx.doi.org/10.1063/1.2752105 (3 pages) | Cited 40 times

Online Publication Date: 27 June 2007

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In the patterned vertical alignment (PVA) cell in which multidomains are formed from the perfect vertical alignment through an oblique field only, the formation of disclinations between liquid crystal (LC) molecules is inevitable in the presence of an electric field, which lowers transmittance and the response time. In the proposed PVA device, the pretilt angle is formed in four different directions through the polymerization of an UV curable reactive mesogen monomer at the surface. In this way, the reorientation of LC responding to an electric field is well defined, and thus the device shows reduced threshold voltage and much improved response time in all gray scales.
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42.79.Kr Display devices, liquid-crystal devices

Radiation and polarization properties of free-exciton emission from AlN (0001) surface

Yoshitaka Taniyasu, Makoto Kasu, and Toshiki Makimoto

Appl. Phys. Lett. 90, 261911 (2007); http://dx.doi.org/10.1063/1.2752727 (3 pages) | Cited 25 times

Online Publication Date: 27 June 2007

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Free-exciton emission from AlN (0001) surface was characterized by angle-dependent photoluminescence (PL) measurement. As the radiation direction was inclined from the surface normal (c-axis direction), the emission intensity increased. This is because the optical transition between the conduction band and the top valence band is mainly allowed for light with the electric field parallel to the c-axis direction of AlN (E‖c) and consequently the free-exciton emission is strongly polarized for E‖c. By analyzing the angle-dependent PL intensities, the polarization ratio was estimated to be 0.995. This high polarization ratio results from the large negative crystal-field splitting energy.
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73.20.At Surface states, band structure, electron density of states
71.35.-y Excitons and related phenomena
78.55.Cr III-V semiconductors
71.70.Ch Crystal and ligand fields

Efficient green emission from (11math2) InGaN/GaN quantum wells on GaN microfacets probed by scanning near field optical microscopy

Y. Kawakami, K. Nishizuka, D. Yamada, A. Kaneta, M. Funato, Y. Narukawa, and T. Mukai

Appl. Phys. Lett. 90, 261912 (2007); http://dx.doi.org/10.1063/1.2748309 (3 pages) | Cited 9 times

Online Publication Date: 28 June 2007

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Nanoscopic optical characterization using scanning near field optical microscopy was performed on a (11math2) microfacet quantum well (QW). It was revealed that the carrier diffusion length in the (11math2) QW is less than the probing fiber aperture of 160 nm, which is shorter than that of the (0001) QWs and is attributed to much faster radiative recombination processes in the (11math2) QW due to a reduced internal electric field. Owing to this short diffusion length, the correlation between the internal quantum efficiency (IQE) and emission wavelength is elucidated. The highest IQE is ∼ 50% at 520 nm, which is about 50 nm longer than in (0001) QWs, suggesting that the (11math2) QW is a suitable green emitter.
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78.67.De Quantum wells
78.55.Cr III-V semiconductors

Photoluminescent behavior of SrBi2Nb2O9 powders explained by means of β-Bi2O3 phase

D. P. Volanti, L. S. Cavalcante, E. C. Paris, A. Z. Simões, D. Keyson, V. M. Longo, A. T. de Figueiredo, E. Longo, J. A. Varela, F. S. De Vicente, and A. C. Hernandes

Appl. Phys. Lett. 90, 261913 (2007); http://dx.doi.org/10.1063/1.2753114 (3 pages) | Cited 17 times

Online Publication Date: 28 June 2007

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Photoluminescence (PL) behavior of SrBi2Nb2O9 (SBN) powders was explained by means of β-Bi2O3 phase on the SBN lattice. Oxygen vacancies and recombination of electrons holes in the valence band lead to the formation of [NbO5∙VOx], [NbO5∙VO•] and [NbO5∙VO••] complex clusters which are the main reason for the PL at room temperature. X-ray diffraction and Fourier transform Raman spectroscopy were used as tools to investigate the structural changes in SBN lattice allowing to correlate [NbO5∙VO•]/[NbO6]′ ratio with the evolution of the visible PL emission in the SBN powders.
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78.55.Hx Other solid inorganic materials
61.43.Gt Powders, porous materials
61.72.J- Point defects and defect clusters
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
78.30.Hv Other nonmetallic inorganics

Optical emission of directly contacted copper/sapphire interface under shock compression of megabar

G. Y. Hao, F. S. Liu, D. Y. Zhang, and M. J. Zhang

Appl. Phys. Lett. 90, 261914 (2007); http://dx.doi.org/10.1063/1.2751606 (3 pages) | Cited 2 times

Online Publication Date: 29 June 2007

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The shock-induced optical emission histories from copper/sapphire interface were measured under two different contact conditions, which simulated the typical situations of pyrometry experiments. Results showed that the “peak” feature of the radiation, previously interpreted as the appearance of so-called high-temperature layer, was nearly diminished by finely polishing and uniformly prepressing technique, and that it is possible to directly measure the equilibrium temperature of bulk metal/window interface. Study also demonstrated that the saturated value of the apparent temperature in nonideal contact situation is related to the color temperature of the shock-induced “bright spot” in sapphire window under megabar pressures.
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62.50.-p High-pressure effects in solids and liquids
62.20.F- Deformation and plasticity
81.40.Lm Deformation, plasticity, and creep
78.60.Mq Sonoluminescence, triboluminescence
81.65.Ps Polishing, grinding, surface finishing
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects

Implant damage and strain relaxation of embedded epitaxial silicon germanium layer on silicon

J. P. Liu, J. Li, A. See, M. S. Zhou, and L. C. Hsia

Appl. Phys. Lett. 90, 261915 (2007); http://dx.doi.org/10.1063/1.2749868 (3 pages) | Cited 5 times

Online Publication Date: 29 June 2007

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The authors report on the implant damage and strain relaxation in embedded silicon germanium (SiGe) layer, selectively grown on recessed silicon (Si) (001) with different recess length (defined as [110] direction, along the conventional Si transistor channel) and the same width (defined as [1−10] direction). Similar to the implant damage in blanket epi-SiGe layers on Si (001) reported previously, they observed two defect bands, one close to the surface and the other at SiGe/Si interface. Unlike the biaxial strain relaxation with misfit dislocations equally distributed along both the [110] and [1−10] directions in blanket epi-SiGe layers on Si (001), there is a gradual change from biaxial to uniaxial relaxation with misfit dislocations along only at the [1−10] direction and a decreasing density of misfit dislocation, with decreasing recess length.
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81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)

Low-frequency eigenvibrations of hollow carbon microspheres

Y. Li, H. S. Lim, S. C. Ng, M. H. Kuok, F. Su, and X. S. Zhao

Appl. Phys. Lett. 90, 261916 (2007); http://dx.doi.org/10.1063/1.2753117 (3 pages) | Cited 1 time

Online Publication Date: 29 June 2007

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Monodisperse hollow carbon microspheres have been fabricated using silica spheres as templates via a three-step chemical vapor deposition method. The vibrational eigenmodes of these hollow carbon microspheres have been measured by Brillouin light scattering. The frequencies of the eigenvibrations of a free surface hollow carbon sphere are also calculated within the framework of the elasticity theory. A comparison of the theoretical and measured frequencies shows that the observed Brillouin peaks are due to the spheroidal modes of the hollow spheres.
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63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
78.35.+c Brillouin and Rayleigh scattering; other light scattering

Use of real-time Fourier transform infrared reflectivity as an in situ monitor of YBa2Cu3O7 film deposition and processing

Gertjan Koster, Jeong-Uk Huh, R. H. Hammond, and M. R. Beasley

Appl. Phys. Lett. 90, 261917 (2007); http://dx.doi.org/10.1063/1.2753118 (3 pages) | Cited 2 times

Online Publication Date: 29 June 2007

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Fourier transform infrared reflectivity (FTIR) has been utilized as an in situ, real-time diagnostic during high-rate, e-beam deposition of YBa2Cu3O7 (YBCO). The results demonstrate the great utility of FTIR as an in situ monitor of YBCO deposition and postdeposition processing. They also point to a completely different picture of the nature and associated kinetic and thermodynamic pathways of the high-rate, e-beam process, both during deposition and as a function of subsequent trajectories through temperature and oxygen pressure space.
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74.78.-w Superconducting films and low-dimensional structures
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
74.25.Gz Optical properties
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