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7 Nov 2011

Volume 99, Issue 19, Articles (19xxxx)

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Appl. Phys. Lett. 99, 193101 (2011); http://dx.doi.org/10.1063/1.3657777 (3 pages)

Sungwook Chung, Jonathan R. Felts, Debin Wang, William P. King, and James J. De Yoreo
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Identification of boron clusters in silicon crystal by B1s core-level X-ray photoelectron spectroscopy: A first-principles study

Jun Yamauchi, Yoshihide Yoshimoto, and Yuji Suwa

Appl. Phys. Lett. 99, 191901 (2011); http://dx.doi.org/10.1063/1.3658030 (3 pages) | Cited 1 time

Online Publication Date: 7 November 2011

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We carried out a comprehensive study on the B1s core-level X-ray photoelectron spectroscopy (XPS) binding energies for B clusters in crystalline Si using a first-principles calculation with careful evaluation of the local potential boundary condition for the model system, where convergence within 0.1 eV was confirmed for the supercell size. For ion-implanted samples, we identified experimental peaks due to B clusters and threefold B as icosahedral B12 and 〈001〉B-Si defects, respectively. For as-doped samples prepared by plasma doping, it was found that the calculated XPS binding energies for complexes of vacancies and B atoms were consistent with the experimental spectra.
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81.05.Cy Elemental semiconductors
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
61.72.jd Vacancies
61.72.uf Ge and Si
79.60.Bm Clean metal, semiconductor, and insulator surfaces

Surface rippling on bulk metallic glass under nanosecond pulse laser ablation

Y. Liu, M. Q. Jiang, G. W. Yang, Y. J. Guan, and L. H. Dai

Appl. Phys. Lett. 99, 191902 (2011); http://dx.doi.org/10.1063/1.3656700 (3 pages) | Cited 3 times

Online Publication Date: 8 November 2011

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We report an interesting surface ripple patterns in the irradiated area of a Zr-based bulk metallic glass by nanosecond pulse laser with single shot. Such surface rippling phenomenon can be ascribed to the Kelvin-Helmholtz instability at the interface between the molten layer and the expanding plasma plume. The analytical instability criterion is obtained via a perturbation analysis. Furthermore, the model demonstrates that the characteristic spacing of the ripples is dominated by the density, transverse velocity of the plasma wind, and the surface tension of the molten layer. The predicted spacing agrees well with the experimentally observed values. The results are fundamentally useful for laser-processing bulk metallic glasses (BMGs) and even for understanding the nature of flow in BMGs.
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61.43.Fs Glasses
81.15.Fg Pulsed laser ablation deposition
47.15.Fe Stability of laminar flows
68.03.Cd Surface tension and related phenomena
81.05.Kf Glasses (including metallic glasses)
47.20.-k Flow instabilities

Electronic structure and optical properties of Ag3PO4 photocatalyst calculated by hybrid density functional method

J. J. Liu, X. L. Fu, S. F. Chen, and Y. F. Zhu

Appl. Phys. Lett. 99, 191903 (2011); http://dx.doi.org/10.1063/1.3660319 (3 pages) | Cited 5 times

Online Publication Date: 8 November 2011

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The electronic structure and optical properties of Ag3PO4 were studied by hybrid density functional theory. The results indicated that the band gap is 2.43 eV, which agrees well with the experimental value of 2.45 eV. The conduction bands of Ag3PO4 are mainly attributable to Ag 5s and 5p states, while the valence bands are dominated by O 2p and Ag 4d states. The highest valence band edge potential was 2.67 V (vs. normal hydrogen electrode), which has enough driving force for photocatalytic water oxidation and pollutants degradation. The optical absorption spectrum showed that Ag3PO4 is a visible light response photocatalyst.
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71.20.Nr Semiconductor compounds
78.40.Fy Semiconductors
82.50.Hp Processes caused by visible and UV light
71.15.Mb Density functional theory, local density approximation, gradient and other corrections

Designing shape-memory Heusler alloys from first-principles

M. Siewert, M. E. Gruner, A. Dannenberg, A. Chakrabarti, H. C. Herper, M. Wuttig, S. R. Barman, S. Singh, A. Al-Zubi, T. Hickel, J. Neugebauer, M. Gillessen, R. Dronskowski, and P. Entel

Appl. Phys. Lett. 99, 191904 (2011); http://dx.doi.org/10.1063/1.3655905 (3 pages) | Cited 10 times

Online Publication Date: 8 November 2011

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The phase diagrams of magnetic shape-memory Heusler alloys, in particular, ternary Ni-Mn-Z and quarternary (Pt, Ni)-Mn-Z alloys with Z = Ga, Sn, have been addressed by density functional theory and Monte Carlo simulations. Finite temperature free energy calculations show that the phonon contribution stabilizes the high-temperature austenite structure while at low temperatures magnetism and the band Jahn-Teller effect favor the modulated monoclinic 14M or the nonmodulated tetragonal structure. The substitution of Ni by Pt leads to a series of magnetic shape-memory alloys with very similar properties to Ni-Mn-Ga but with a maximal eigenstrain of 14%.
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81.40.Lm Deformation, plasticity, and creep
62.20.fg Shape-memory effect; yield stress; superelasticity
64.60.De Statistical mechanics of model systems (Ising model, Potts model, field-theory models, Monte Carlo techniques, etc.)
64.70.kd Metals and alloys
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
81.30.Kf Martensitic transformations

Enhanced transmission in rolled-up hyperlenses utilizing Fabry-Pérot resonances

Jochen Kerbst, Stephan Schwaiger, Andreas Rottler, Aune Koitmäe, Markus Bröll, Jens Ehlermann, Andrea Stemmann, Christian Heyn, Detlef Heitmann, and Stefan Mendach

Appl. Phys. Lett. 99, 191905 (2011); http://dx.doi.org/10.1063/1.3659287 (3 pages) | Cited 4 times

Online Publication Date: 8 November 2011

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We experimentally demonstrate that the transmission through rolled-up metal/semiconductor hyperlenses can be enhanced at desired frequencies utilizing Fabry-Pérot resonances. By means of finite difference time domain simulations, we prove that hyperlensing occurs at frequencies of high transmission.
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42.79.Bh Lenses, prisms and mirrors
02.70.Bf Finite-difference methods
42.25.Bs Wave propagation, transmission and absorption

Ab initio study of acoustic velocities in molybdenum under high pressure and high temperature

Zhao-Yi Zeng, Cui-E Hu, Xun Liu, Ling-Cang Cai, and Fu-Qian Jing

Appl. Phys. Lett. 99, 191906 (2011); http://dx.doi.org/10.1063/1.3659696 (3 pages) | Cited 2 times

Online Publication Date: 8 November 2011

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Acoustic velocities of Molybdenum (Mo) under high pressure and high temperature are calculated by using the generalized gradient approximation within density functional theory. The break in acoustic velocities of bcc Mo along Hugoniot occurs around 175–275 GPa, which agrees with shock-wave experimental results in which the phase transition was found at 210 GPa, 4100 K [R. S. Hixson, Phys. Rev. Lett. 62, 637 (1989)]. By comparing the acoustic velocities, we confirmed the phase transition from bcc to fcc Mo.
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62.65.+k Acoustical properties of solids
81.40.Jj Elasticity and anelasticity, stress-strain relations
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.mm Fracture
64.70.kd Metals and alloys
61.50.Ks Crystallographic aspects of phase transformations; pressure effects

Transmission electron microscopy study of GaInNAs(Sb) thin films grown by atomic hydrogen-assisted molecular beam epitaxy

R. Oshima, J. Y. Huang, N. Miyashita, K. Matsubara, Y. Okada, and F. A. Ponce

Appl. Phys. Lett. 99, 191907 (2011); http://dx.doi.org/10.1063/1.3660232 (3 pages) | Cited 2 times

Online Publication Date: 9 November 2011

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The quaternary GaInNAs is a promising material system for use in next generation multijunction photovoltaic devices. We have investigated the effect of introducing antimony on the growth by using transmission electron microscopy and energy dispersive x-ray (EDX) spectroscopy. Two-dimensional growth was observed in GaInNAs films with striation features associated with compositional fluctuation and nanometer scale elemental segregation on the growth front. On the contrary, GaInNAsSb films exhibit uniform contrast throughout. EDX profile indicates uniform compositional distribution, as antimony atoms suppress the surface mobilites of adatoms resulting in a lower probability to generate the favored bonds, such as Ga-N and In-As.
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81.05.Ea III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods

Terahertz coherent acoustic experiments with semiconductor superlattices

A. Huynh, B. Perrin, B. Jusserand, and A. Lemaître

Appl. Phys. Lett. 99, 191908 (2011); http://dx.doi.org/10.1063/1.3658458 (3 pages) | Cited 5 times

Online Publication Date: 9 November 2011

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We demonstrate the generation, propagation, and detection of coherent acoustic waves at 1 THz. We performed picosecond ultrasonics experiments in an acoustic transmission geometry, which allows a total decoupling of the phonon generation and detection processes, occurring in two different superlattices grown on opposite sides of a substrate, respectively. We show that a 1 ns burst of monochromatic terahertz coherent acoustic waves could be generated on one side of a substrate, propagated over a large distance and detected on the opposite side. We also measured the lattice dispersion owing to the time delay between the terahertz burst and much lower frequency acoustic waves.
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62.65.+k Acoustical properties of solids
78.70.Gq Microwave and radio-frequency interactions
63.20.D- Phonon states and bands, normal modes, and phonon dispersion

An ultrabroad terahertz bandpass filter based on multiple-resonance excitation of a composite metamaterial

Yi-Ju Chiang, Chan-Shan Yang, Yu-Hang Yang, Ci-Ling Pan, and Ta-Jen Yen

Appl. Phys. Lett. 99, 191909 (2011); http://dx.doi.org/10.1063/1.3660273 (3 pages) | Cited 3 times

Online Publication Date: 9 November 2011

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We experimentally present an ultrabroad terahertz (THz) bandpass filter based on a composite metamaterial (CMM) by exciting its multiple resonances. This metamaterial-based filter, consisting of a metal-dielectric-metal sandwiched structure, possesses a notable spectral-filtering capability with a 0.5-THz-broad bandwidth and excellent band-edge transitions of 140% THz and 182% THz in the THz-gap region. Furthermore, we manifest the mechanism for each of the resonances and the coupling within the composite metamaterial. This realization enables the capacity for engineering the electromagnetic properties to develop other complex optical functionalities. An example of a high-profile dualband THz bandpass filter is also proposed theoretically in this work.
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84.30.Vn Filters
84.40.-x Radiowave and microwave (including millimeter wave) technology

A variable constraint tube model for size effects of polymer nano-structures

Shan Tang, M. Steven Greene, and Wing Kam Liu

Appl. Phys. Lett. 99, 191910 (2011); http://dx.doi.org/10.1063/1.3660585 (3 pages) | Cited 1 time

Online Publication Date: 9 November 2011

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We develop a molecular-based hyperelastic model to simulate the size dependent mechanical properties of polymer nano-structures. We assume that polymer chains are confined to a different “tube” size in a boundary layer than that in the core, which alters the free energy and produces the size effect. Simulations also explore anisotropic orientations of polymer chains and surface tension. The axial modulus of nanofibers is studied in detail, although the model is applicable to other systems like thin films and nano-biological systems.
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81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity
65.40.G- Other thermodynamical quantities

Polarized Raman microscopy of anisotropic stress relaxation in strained-Si-on-insulator stripes

Vladimir Poborchii, Tetsuya Tada, Koji Usuda, and Toshihiko Kanayama

Appl. Phys. Lett. 99, 191911 (2011); http://dx.doi.org/10.1063/1.3660709 (3 pages) | Cited 1 time

Online Publication Date: 9 November 2011

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Using a high-numerical-aperture lens, we studied strain relaxation in the [110]-oriented strained-silicon-on-insulator (SSOI) stripes. A complete set of Si optical phonon Raman bands was observed. For a 50 nm thick SSOI, the symmetrical biaxial tensile stress in a relatively wide stripe is found to transform to the uniaxial [110] stress at its edge. The same uniaxial stress is observed in the narrow stripes with widths <200 nm, the value, probably, being a critical width for a complete SSOI transverse stress relaxation.
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81.40.Jj Elasticity and anelasticity, stress-strain relations
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
78.30.Am Elemental semiconductors and insulators

Enhancing the visibility of graphene on GaAs

K. Peters, A. Tittel, N. Gayer, A. Graf, V. Paulava, U. Wurstbauer, and W. Hansen

Appl. Phys. Lett. 99, 191912 (2011); http://dx.doi.org/10.1063/1.3660584 (3 pages) | Cited 2 times

Online Publication Date: 10 November 2011

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We present a method to enhance the visibility of graphene on GaAs. Therefore the samples are spin-coated with e-beam resist of well defined thickness. For determination of the optimal thickness, the optical contrast is calculated taking into account thicknesses and refractive indices of the layers as well as the sensitivity of the human eye. The visibility studies of single-layer graphene on GaAs are accompanied by Raman spectroscopy and magnetotransport measurements. We demonstrate that it is possible to detect graphene flakes by optical microscopy and determine the number of graphene layers by measuring the Raman signal through the resist layer.
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78.67.Wj Optical properties of graphene
78.30.Na Fullerenes and related materials
72.20.My Galvanomagnetic and other magnetotransport effects
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Acoustic scattering cancellation via ultrathin pseudo-surface

Pai-Yen Chen, Mohamed Farhat, Sébastien Guenneau, Stefan Enoch, and Andrea Alù

Appl. Phys. Lett. 99, 191913 (2011); http://dx.doi.org/10.1063/1.3655141 (3 pages) | Cited 1 time

Online Publication Date: 11 November 2011

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We propose the use of an ultrathin cloak made of an acoustic surface impedance that leads to invisibility for acoustic waves. Unlike current acoustic cloaks that require volumetric metamaterials and a significant shell thickness, the mantle cloak presented here is based on a patterned acoustic metasurface that produces similar effects in a thinner geometry. We show that by covering a cylindrical obstacle by a specific acoustic surface impedance, the total scattering may be significantly reduced in the near- and the far-field, thus suppressing its overall acoustic signature. Potential applications lie in low-detectability, camouflaging, and non-invasive acoustic probing.
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43.40.-r Structural acoustics and vibration
42.70.-a Optical materials
43.25.-x Nonlinear acoustics

Effect of anisotropic strain on the charge ordering behavior in Bi0.4Ca0.6MnO3 films

Y. H. Ding, Y. Q. Wang, R. S. Cai, Y. Z. Chen, and J. R. Sun

Appl. Phys. Lett. 99, 191914 (2011); http://dx.doi.org/10.1063/1.3660722 (3 pages)

Online Publication Date: 11 November 2011

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Anisotropic strain has a significant influence on the charge ordering (CO) behavior in Bi0.4Ca0.6MnO3 (BCMO) films on (110) SrTiO3 substrates. Effect of film thickness on the CO behavior in BCMO films was investigated at 103 K using transmission electron microscopy. It was found that the film has undergone a structural transformation with the increase of film thickness, i.e., from no modulation to a localized incommensurate modulation and further to a commensurate modulation. The distinctive thickness-dependent CO transition has a close relationship with the anisotropic strain relaxation process. Structural models are proposed to explain the modulated structures in the films.
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68.55.A- Nucleation and growth
81.15.Fg Pulsed laser ablation deposition
64.70.Rh Commensurate-incommensurate transitions
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
68.60.Bs Mechanical and acoustical properties
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