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2 Feb 2009

Volume 94, Issue 5, Articles (05xxxx)

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Appl. Phys. Lett. 94, 059901 (2009); http://dx.doi.org/10.1063/1.3086725 (3 pages)

Yuta Tsukada, Tsuyoshi Honma, and Takayuki Komatsu
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Atomistic simulation of a NiZr model metallic glass under hydrostatic pressure

Yu-zheng Guo and Mo Li

Appl. Phys. Lett. 94, 051901 (2009); http://dx.doi.org/10.1063/1.3077862 (3 pages) | Cited 4 times

Online Publication Date: 2 February 2009

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Compressive behavior of a model NiZr metallic glass under hydrostatic pressure is simulated using molecular dynamics. The equation of state obtained exhibits two distinct regimes, one at low and the other at high pressure, along with an intermediate region in between. The densification is associated with topological rearrangement of atoms at low pressure and hard-sphere-like compaction dictated by the strong interatomic repulsion at high pressure. Different from many isotropic materials, the atomic rearrangement in the metallic glass during compression is accompanied by strong local topological structure change and chemical short-range (re)ordering. The possibility of a pressure-induced phase transition is briefly discussed.
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61.43.Fs Glasses
64.30.Jk Equations of state of nonmetals
64.70.kj Glasses
62.50.-p High-pressure effects in solids and liquids

High external emission efficiency in intentionally ordered GaInP/GaAs structures

J. S. Song, S. H. Seo, Y. C. Choi, H. S. Song, Y. H. Chang, M. H. Oh, D. C. Oh, T. Yao, J. H. Chang, C. S. Han, and K. W. Koo

Appl. Phys. Lett. 94, 051902 (2009); http://dx.doi.org/10.1063/1.3077013 (3 pages)

Online Publication Date: 4 February 2009

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The authors report on an additional effect of the intentionally ordered GaInP layers obtained by using the double tilt GaAs substrates, i.e., the misoriented (001) GaAs substrates toward the two directions of [110] and [−110]. In photoluminescence (PL) spectra at 7 K, it is found that the emission intensity is enhanced with the increase in the substrate misorientation angle toward [−110] direction, along with the redshift of the bandedge. However, the redshift of the bandedge means that the GaInP layers suffer from the ordering of group III atoms. The authors note that the surface morphology in the ordered GaInP layers becomes rapidly rough by the substrate misorientation, even though the linewidths of their PL spectra and x-ray rocking curves are almost similar, irrespective of the misorientation angle. As a result, the light extraction mechanism in the roughened surface structure and the surface roughening mechanism in the intentionally ordered GaInP layers are suggested.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors

Enhanced blue-violet emission by inverse energy transfer to the Ge-related oxygen deficiency centers via Er3+ ions in metal-oxide semiconductor structures

A. Kanjilal, L. Rebohle, M. Voelskow, W. Skorupa, and M. Helm

Appl. Phys. Lett. 94, 051903 (2009); http://dx.doi.org/10.1063/1.3077169 (3 pages) | Cited 11 times

Online Publication Date: 4 February 2009

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It is generally believed that the 1.5 μm Er luminescence is enhanced by transferring energy from Si nanocrystals to the nearest Er3+ ions in Er-doped Si-rich SiO2 layers during optical pumping. Here, the influence of Ge nanocrystals instead of excess Si in the same environment is studied using electroluminescence technique on metal-oxide-semiconductor structures. An increase of the 400 nm electroluminescence intensity with a concomitant reduction of the Er-related emission is observed. This is explained in the light of an inverse energy transfer process from Er3+ to the Ge-related oxygen-deficiency centers.
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78.60.Fi Electroluminescence
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters

Crystallinity and microstructure in Si films grown by plasma-enhanced chemical vapor deposition: A simple atomic-scale model validated by experiments

P. L. Novikov, A. Le Donne, S. Cereda, Leo Miglio, S. Pizzini, S. Binetti, M. Rondanini, C. Cavallotti, D. Chrastina, T. Moiseev, H. von Känel, G. Isella, and F. Montalenti

Appl. Phys. Lett. 94, 051904 (2009); http://dx.doi.org/10.1063/1.3077187 (3 pages) | Cited 7 times

Online Publication Date: 4 February 2009

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A joint theoretical and experimental analysis of the crystalline fraction in nanocrystalline films grown by low-energy plasma enhanced chemical vapor deposition is presented. The effect of key growth parameters such as temperature, silane flux, and hydrogen dilution ratio is analyzed and modeled at the atomic scale, introducing an environment-dependent crystallization probability. A very good agreement between experiments and theory is found, despite the use of a single fitting parameter.
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68.55.ag Semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
52.77.Dq Plasma-based ion implantation and deposition

Size effect of dissipative surface stress on quality factor of microbeams

C. Q. Ru

Appl. Phys. Lett. 94, 051905 (2009); http://dx.doi.org/10.1063/1.3078816 (3 pages) | Cited 10 times

Online Publication Date: 4 February 2009

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A dissipative surface stress model is suggested to study the surface dissipation of vibrating elastic microbeams. The model is an extension of the well-known Zener model from bulk materials to the surface in the presence of an initial surface tension. Explicit formulas are derived for the frequency-dependent quality factor and the maximum surface dissipation. This model predicts a size-dependent surface dissipation when the size of the cross section downs to nanometers. In particular, the model offers plausible explanation for a few experimental phenomena reported in the most recent literature.
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46.40.-f Vibrations and mechanical waves

High-Q micromechanical resonators in a two-dimensional phononic crystal slab

Saeed Mohammadi, Ali Asghar Eftekhar, William D. Hunt, and Ali Adibi

Appl. Phys. Lett. 94, 051906 (2009); http://dx.doi.org/10.1063/1.3078284 (3 pages) | Cited 51 times

Online Publication Date: 5 February 2009

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By creating line defects in the structure of a phononic crystal (PC) made by etching a hexagonal array of holes in a 15 μm thick slab of silicon, high-Q PC resonators are fabricated using a complimentary-metal-oxide-semiconductor-compatible process. The complete phononic band gap of the PC structure supports resonant modes with quality factors of more than 6000 at frequencies as high as 126 MHz. The confinement of acoustic energy is achieved by using only a few PC layers confining the cavity region. The calculated frequencies of resonance of the structure using finite element method are in a very good agreement with the experimental data. The performance of these PC resonator structures makes them excellent candidates for wireless communication and sensing applications.
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85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
02.70.Dh Finite-element and Galerkin methods

Ab initio tensile experiment on a model of an intergranular glassy film in β-Si3N4 with prismatic surfaces

W. Y. Ching, Paul Rulis, Lizhi Ouyang, and A. Misra

Appl. Phys. Lett. 94, 051907 (2009); http://dx.doi.org/10.1063/1.3079800 (3 pages) | Cited 9 times

Online Publication Date: 5 February 2009

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We report the results of a large-scale ab initio simulation of an intergranular glassy film (IGF) model in β-Si3N4. It is shown that the stress-strain behavior under uniaxial load in the model with prismatic surfaces and few defective bonds is very different from an earlier IGF model with basal planes. The results are explained by the fundamental electronic structure of the model.
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81.40.Jj Elasticity and anelasticity, stress-strain relations
71.23.Cq Amorphous semiconductors, metallic glasses, glasses
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.F- Deformation and plasticity
62.20.mm Fracture

Quantitative strain-field measurement of 1:1 B-site cation ordered domains and antiphase boundaries in Pb(Sc1/2Ta1/2)O3 ceramics by high-resolution transmission electron microscopy

Cheuk W. Tai (戴卓偉) and Y. Lereah

Appl. Phys. Lett. 94, 051908 (2009); http://dx.doi.org/10.1063/1.3079412 (3 pages) | Cited 1 time

Online Publication Date: 6 February 2009

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Quantitative strain measurements of the 1:1 B-site cation ordered domains, antiphase boundaries, and dislocations in a highly ordered Pb(Sc1/2Ta1/2)O3 ceramic have been carried out by high-resolution transmission electron microscopy and geometric phase analysis. A phase shift of π between two adjacent ordered domains across an antiphase boundary is determined unambiguously. The maximum in-plane strain and lattice rotation induced by a dislocation are 9.5% and 5.4°, respectively. In a defect-free antiphase boundary, the maximum in-plane strain and lattice rotation are 1.8% and 0.9°, respectively. The strain mainly concentrates inside the antiphase boundary.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.Dj Domain structure; hysteresis
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)

Magnetic field effect on premartensitic transition in Ni–Mn–Ga alloys

J. M. Barandiaran, V. A. Chernenko, P. Lazpita, J. Gutiérrez, I. Orue, J. Feuchtwanger, and S. Besseghini

Appl. Phys. Lett. 94, 051909 (2009); http://dx.doi.org/10.1063/1.3079677 (3 pages) | Cited 9 times

Online Publication Date: 6 February 2009

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Extensive measurements of the temperature dependencies of resistivity under constant magnetic fields made it possible to clarify the premartensitic transition sensitivity to applied magnetic field up to 14 T in polycrystalline and monocrystalline Ni–Mn–Ga alloys with compositions close to the stoichiometric one. A low-field minimum on the transition temperature versus magnetic field curves is found in both alloys. This minimum is attributed to the magnetic anisotropy contribution to the Clausius–Clapeyron relationship, which describes the premartensitic transition. This contribution is confirmed by magnetization loops measurements.
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81.30.Kf Martensitic transformations
75.50.Cc Other ferromagnetic metals and alloys
75.30.Gw Magnetic anisotropy
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
72.15.Eb Electrical and thermal conduction in crystalline metals and alloys
61.66.Bi Elemental solids
61.66.Dk Alloys
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