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27 Feb 2012

Volume 100, Issue 9, Articles (09xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 100, 093101 (2012); http://dx.doi.org/10.1063/1.3687190 (4 pages)

Jinhai Mao, Li Huang, Yi Pan, Min Gao, Junfeng He, Haitao Zhou, Haiming Guo, Yuan Tian, Qiang Zou, Lizhi Zhang, Haigang Zhang, Yeliang Wang, Shixuan Du, Xingjiang Zhou, A. H. Castro Neto, et al.
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Emissive properties of SiO2 thin films through photonic windows

D. Hernández, M. Garín, T. Trifonov, A. Rodríguez, and R. Alcubilla

Appl. Phys. Lett. 100, 091901 (2012); http://dx.doi.org/10.1063/1.3688031 (3 pages)

Online Publication Date: 27 February 2012

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In this work, we study the selective emission properties of silicon-based three-dimensional photonic crystals coated with thin films of silicon dioxide presenting temperature emission measurements at 600 K of oxidized macroporous silicon structures. The photonic band gap of the structure is centered at 9 μm with 2.5 μm bandwidth. Through this photonic window defined by the gap, a narrow emission peak arises from the oxide layer. We propose the given structure as a selective thermal source for infrared spectroscopy applications in the fingerprint spectral region (6–12 μm wavelength).
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78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
78.30.Am Elemental semiconductors and insulators
78.66.Db Elemental semiconductors and insulators
61.43.Gt Powders, porous materials
42.70.Qs Photonic bandgap materials

Soft-phonon mode observation in Li2Ge4O9 phase above room temperature

Yoshihiro Takahashi, Jun Kunitomo, Kensaku Nakamura, Minoru Osada, and Takumi Fujiwara

Appl. Phys. Lett. 100, 091902 (2012); http://dx.doi.org/10.1063/1.3688603 (3 pages)

Online Publication Date: 27 February 2012

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Li2Ge4O9 is known to be a ferroelectric phase with Curie temperature at Tc ∼ −93 °C. In this study, we found both the lowest-frequency phonon and heat-capacity anomalies around 100 °C in the Li2Ge4O9 phase, demonstrating their presence in the structural phase-transition. The phase transition is probably triggered by regularization of distorted GeO6 octahedra in the paraelectric phase, resulting in another phase consisting of the regular octahedral GeO6 unit, which was supported by in situ measurement of emission of 2E → 4A2 transition in the Mn4+-doped phase. It is deduced that the phase transition is more dynamic than ferroelectric phase-transition originating in ordering of the Li ions.
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77.80.B- Phase transitions and Curie point
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
75.40.Cx Static properties (order parameter, static susceptibility, heat capacities, critical exponents, etc.)
64.70.K- Solid-solid transitions
68.35.Ja Surface and interface dynamics and vibrations

Thermal transport in crystalline Si/Ge nano-composites: Atomistic simulations and microscopic models

Feng Hao, Daining Fang, and Zhiping Xu

Appl. Phys. Lett. 100, 091903 (2012); http://dx.doi.org/10.1063/1.3688943 (4 pages) | Cited 5 times

Online Publication Date: 27 February 2012

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Thermal transport in Si/Ge nano-composites, consisting of crystalline silicon as matrix and aligned germanium nanowires as inclusions, is investigated here through non-equilibrium and equilibrium molecular dynamics (MD) simulations. Our results show increasing of temperature gradient at the interface between silicon and germanium, which is limited in an interfacial phase of few lattices. A thermal boundary phase is included explicitly in our three-phase model, in companion with the modified effective medium theory, to be compared with MD simulation results with various nanowire concentrations. The results suggest that the presence of nanowires leads to a dramatic decrease of κ for heat transfer across nanowires arising from interfacial phase, while along the interfaces, the reduction of phonon mean free path due to interfacial scattering lowers κ of silicon matrix and germanium nanowires.
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73.63.Bd Nanocrystalline materials
61.46.Km Structure of nanowires and nanorods (long, free or loosely attached, quantum wires and quantum rods, but not gate-isolated embedded quantum wires)
63.22.Gh Nanotubes and nanowires
66.70.Df Metals, alloys, and semiconductors
61.72.Qq Microscopic defects (voids, inclusions, etc.)
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Extraordinary acoustic reflection enhancement by acoustically transparent thin plates

Zhaojian He, Shasha Peng, Rui Hao, Chunyin Qiu, Manzhu Ke, Jun Mei, and Zhengyou Liu

Appl. Phys. Lett. 100, 091904 (2012); http://dx.doi.org/10.1063/1.3691182 (4 pages) | Cited 1 time

Online Publication Date: 28 February 2012

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We report an observation of the extraordinary high reflection of acoustic waves in water by thin epoxy plates partitioned by subwavelength cuts, whereas such plates without structure are acoustically transparent as the acoustic properties of epoxy are close to water. It is demonstrated that this exotic phenomenon results from the resonant excitation of the local modes within the individual pieces derived by the cuts. The experiment agrees well with the theory. Potential applications of such simple structures can be anticipated, e.g., in blocking sound.
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43.40.-r Structural acoustics and vibration
62.65.+k Acoustical properties of solids

Organic salts as super-high rate capability materials for lithium-ion batteries

Y. Y. Zhang, Y. Y. Sun, S. X. Du, H.-J. Gao, and S. B. Zhang

Appl. Phys. Lett. 100, 091905 (2012); http://dx.doi.org/10.1063/1.3689764 (4 pages) | Cited 2 times

Online Publication Date: 28 February 2012

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First-principles calculation reveals that organic salts could be super-high rate capability electrode materials for Li-ion batteries. We show that di-lithium terephthalate, an anode material demonstrated recently by experiment, has low Li diffusion barrier (EA). A resonant bonding model for the low EA is developed, which leads to the prediction that di-potassium terephthalate (K2TPA) has even lower EA (150 meV), with diffusion rate orders of magnitude higher than that in Li-intercalated graphite. The calculated anode voltage (0.62 V), specific energy density (209 mA·h/g), and volume change upon lithiation (5%) make K2TPA a promising anode material for power-intensive applications such as electric-vehicles.
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82.47.Aa Lithium-ion batteries
66.30.Ny Chemical interdiffusion; diffusion barriers
68.35.Fx Diffusion; interface formation
71.15.-m Methods of electronic structure calculations
82.45.Fk Electrodes

Electrochromic switchable mirror glass with controllable reflectance

Kazuki Tajima, Hiromi Hotta, Yasusei Yamada, Masahisa Okada, and Kazuki Yoshimura

Appl. Phys. Lett. 100, 091906 (2012); http://dx.doi.org/10.1063/1.3691256 (3 pages) | Cited 1 time

Online Publication Date: 29 February 2012

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An electrochromic switchable mirror glass with controllable reflectance was developed. The conditions for fabricating InGaZnO4 (IGZO) thin film, which serves as a transparent conductor, were investigated. The mirror glass with IGZO thin film exhibited multiple colors arising from interference between multilayers. The mirror glass with IGZO thin film fabricated at a working pressure of 0.4 Pa showed high transmittance (63%) in the transparent state and low reflectance (16%) in the reflective state at a wavelength of 670 nm. Moreover, the developed mirror glass had low glare in the reflective state because the reflection of direct, bright light was reduced.
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42.79.Bh Lenses, prisms and mirrors
42.79.Wc Optical coatings
42.70.Ce Glasses, quartz

Defect evolution and interplay in n-type InN

Christian Rauch, Filip Tuomisto, Arantxa Vilalta-Clemente, Bertrand Lacroix, Pierre Ruterana, Simon Kraeusel, Ben Hourahine, and William J. Schaff

Appl. Phys. Lett. 100, 091907 (2012); http://dx.doi.org/10.1063/1.3688038 (3 pages) | Cited 2 times

Online Publication Date: 1 March 2012

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The nature and interplay of intrinsic point and extended defects in n-type Si-doped InN epilayers with free carrier concentrations up to 6.6×1020 cm−3 are studied using positron annihilation spectroscopy and transmission electron microscopy and compared to results from undoped irradiated films. In as-grown Si-doped samples, mixed In-N vacancy complexes (VIn-VN) are the dominant III-sublattice related vacancy defects. An increase in the number of VN in these complexes toward the interface suggests high concentrations of additional isolated VN and VN-clusters near the GaN buffer layer and coincides with elevated dislocation densities in that area.
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71.55.Eq III-V semiconductors
78.70.Bj Positron annihilation
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)

A 3-dimensional time-resolved photothermal deflection “Mirage” method

N. G. C. Astrath, L. C. Malacarne, G. V. B. Lukasievicz, H. S. Bernabe, J. H. Rohling, M. L. Baesso, J. Shen, and S. E. Bialkowski

Appl. Phys. Lett. 100, 091908 (2012); http://dx.doi.org/10.1063/1.3691253 (4 pages) | Cited 1 time

Online Publication Date: 2 March 2012

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A three-dimensional time-resolved theory and experiment for photothermal deflection spectroscopy is developed. The heat conduction equations for two semi-infinite media consisting of an opaque sample and a fluid are solved considering temperature and energy flux balance conditions for a Gaussian heat source. The time dependent perpendicular deflection signal is calculated and compared to experimental measurements on glassy carbon and copper samples. Excellent agreement with literature values for thermal diffusivity of the samples is found. The transient behavior is analyzed for different coupling fluids.
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66.25.+g Thermal conduction in nonmetallic liquids
66.70.Lm Other systems such as ionic crystals, molecular crystals, nanotubes, etc.
78.47.D- Time resolved spectroscopy (>1 psec)
78.20.nb Photothermal effects
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