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19 Apr 2010

Volume 96, Issue 16, Articles (16xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 96, 163101 (2010); http://dx.doi.org/10.1063/1.3327831 (3 pages)

Ramesh Nath, Seungbum Hong, Jeffrey A. Klug, Alexandra Imre, Michael J. Bedzyk, Ram S. Katiyar, and Orlando Auciello
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Role of c-screw dislocations on indium segregation in InGaN and InAlN alloys

Huaping Lei, Jun Chen, and Pierre Ruterana

Appl. Phys. Lett. 96, 161901 (2010); http://dx.doi.org/10.1063/1.3394007 (3 pages) | Cited 4 times

Online Publication Date: 19 April 2010

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Indium segregation induced by c-screw dislocations in wurtzite InGaN and InAlN alloys is investigated with molecular dynamics based on Stillinger–Weber potentials [ Stillinger and Weber, Phys. Rev. B 31, 5262 (1985)] . Beginning with the analysis of atomic structures and energetic stability of c-screw dislocations in AlN, GaN, and InN compounds, their interaction with In atoms in GaN and AlN is explored. The results show that In atoms reduce the core energy of c-screw dislocation when they are located at the center of the core region. The distance dependence of the interaction energy indicates that In atoms will tend to gather around the dislocation line and form an In-rich region. These results agree with experimental observations in InGaN and should predict a similar behavior in InAlN.
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61.72.Lk Linear defects: dislocations, disclinations
61.72.Yx Interaction between different crystal defects; gettering effect
64.75.Qr Phase separation and segregation in semiconductors
02.70.Ns Molecular dynamics and particle methods

Experimental verification of a tunable left-handed material by bias magnetic fields

Yin Poo, Rui-xin Wu, Guang-hua He, Ping Chen, Jie Xu, and Ri-feng Chen

Appl. Phys. Lett. 96, 161902 (2010); http://dx.doi.org/10.1063/1.3409120 (3 pages) | Cited 2 times

Online Publication Date: 22 April 2010

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We designed a two-dimensional periodic composite made of ferrite rods and metallic wires, and theoretically proved the composite in magnetized state had a tunable left-handed material (LHM) regime by its transmission properties and the retrieved effective permittivity and permeability. Further, we fabricated a sample as designed, and experimentally demonstrated the LHM regime by the sample’s abnormal transmission in bias magnetic fields. The abnormal transmission changes with the intensity of the bias magnetic field showing the frequency tunable character of the LHM regime.
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42.70.-a Optical materials
77.22.Ch Permittivity (dielectric function)
42.25.Bs Wave propagation, transmission and absorption

Effect of thermal annealing on properties of InSbN grown by molecular beam epitaxy

K. P. Lim, H. T. Pham, S. F. Yoon, C. Y. Ngo, and S. Tripathy

Appl. Phys. Lett. 96, 161903 (2010); http://dx.doi.org/10.1063/1.3399775 (3 pages) | Cited 5 times

Online Publication Date: 22 April 2010

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We study the annealing effects on the properties of as-grown InSbN films. The annihilation of donor defects in the form of N-N interstitials is suggested by the shifting of N induced tensile strain and a decrease in free electron concentration from ∼ 1×1018 to device level of ∼ 2×1016 cm−3. These findings support the argument that N interstitials thermally dissociate into single N. Corresponding signatures for the reduced Sb antisites and N-N interstitial defects are apparent in Raman spectra. This work will benefit those working on long wavelength infrared photodetectors.
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61.72.Cc Kinetics of defect formation and annealing
61.72.jj Interstitials
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.55.ag Semiconductors
73.61.Ey III-V semiconductors
78.66.Fd III-V semiconductors

The configurational entropy of mixing of interstitials solid solutions

Jorge Garcés

Appl. Phys. Lett. 96, 161904 (2010); http://dx.doi.org/10.1063/1.3400221 (3 pages) | Cited 2 times

Online Publication Date: 22 April 2010

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A simple and general expression for the configurational entropy of mixing of multicomponent interstitials solid solutions is deduced based on a probabilistic approach to compute the configurational entropy. The good agreement obtained with previous experimental and theoretical works based on Monte Carlo and partial configurational entropy calculations in binary systems show that the expression is suitable to be used as a reference state to compute the excess thermodynamic functions in multicomponent interstitials solid solutions. The results show that the configurational entropy can be computed to a high degree of accuracy in some systems without the use of a computer.
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65.40.gd Entropy
64.75.Ef Mixing
61.72.jj Interstitials
64.60.De Statistical mechanics of model systems (Ising model, Potts model, field-theory models, Monte Carlo techniques, etc.)

Characterization of polycrystals with elongated duplex microstructure by inversion of ultrasonic backscattering data

O. I. Lobkis and S. I. Rokhlin

Appl. Phys. Lett. 96, 161905 (2010); http://dx.doi.org/10.1063/1.3416910 (3 pages) | Cited 2 times

Online Publication Date: 23 April 2010

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In this letter a simple analytical ultrasonic backscattering model is proposed for determination of characteristic microstructural scales in polycrystalline materials with elongated grains. The inversion methodology for microstructural parameters is based on backscattering coefficient ratios measured in different propagation directions. The ultrasonic backscattering measurements were performed on a Ti alloy sample with a duplex microstructure and the model was applied to experimental data inversion to size the material microtexture.
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43.35.Yb Ultrasonic instrumentation and measurement techniques
81.40.-z Treatment of materials and its effects on microstructure, nanostructure, and properties
81.05.Bx Metals, semimetals, and alloys
62.65.+k Acoustical properties of solids
43.35.Cg Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in solids; elastic constants

Ultrafast manipulation of hard x-rays by efficient Bragg switches

M. Herzog, W. Leitenberger, R. Shayduk, R. M. van der Veen, C. J. Milne, S. L. Johnson, I. Vrejoiu, M. Alexe, D. Hesse, and M. Bargheer

Appl. Phys. Lett. 96, 161906 (2010); http://dx.doi.org/10.1063/1.3402773 (3 pages) | Cited 7 times

Online Publication Date: 23 April 2010

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We experimentally demonstrate efficient switching of the hard x-ray Bragg reflectivity of a SrRuO3/SrTiO3 superlattice by optical excitation of large-amplitude coherent acoustic superlattice phonons. The rocking curve changes drastically on a 1 ps timescale. The (0 0 116) reflection is almost extinguished (ΔR/R0 = −0.91), while the (0 0 118) reflection increases by more than an order of magnitude (ΔR/R0 = 24.1). The change of the x-ray structure factor depends nonlinearly on the phonon amplitude, allowing manipulation of the x-ray response on a timescale considerably shorter than the phonon period. Numerical simulations for a superlattice with slightly changed geometry and realistic parameters predict a switching-contrast ratio ΔR/R0 of 700 with high reflectivity.
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78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
68.65.Cd Superlattices
63.20.D- Phonon states and bands, normal modes, and phonon dispersion
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