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28 Jan 2008

Volume 92, Issue 4, Articles (04xxxx)

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Appl. Phys. Lett. 92, 041901 (2008); http://dx.doi.org/10.1063/1.2831926 (3 pages)

M. A. Avila, K. Suekuni, K. Umeo, H. Fukuoka, S. Yamanaka, and T. Takabatake
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Ba8Ga16Sn30 with type-I clathrate structure: Drastic suppression of heat conduction

M. A. Avila, K. Suekuni, K. Umeo, H. Fukuoka, S. Yamanaka, and T. Takabatake

Appl. Phys. Lett. 92, 041901 (2008); http://dx.doi.org/10.1063/1.2831926 (3 pages) | Cited 30 times

Online Publication Date: 28 January 2008

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For the past decade, intermetallic clathrates have been rattling their way into mainstream research in thermoelectrics. The unusual vibrations of their guest ions inside oversized cages interfere with the cage phonons while leaving the electronic flow intact, providing an exotic way to achieve a best-of-both-worlds scenario in terms of electrical and thermal transport in the same material. Here, we present the structural and thermoelectric properties of Ba8Ga16Sn30 single crystals grown in the type-I clathrate structure (β-BGS), showing one of the lowest recorded thermal conductivities κ(T) for any bulk compound, while still behaving electronically as a heavily doped n-type semiconducting crystal.
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72.20.Pa Thermoelectric and thermomagnetic effects
63.20.-e Phonons in crystal lattices
72.80.Jc Other crystalline inorganic semiconductors

Temperature effects on pinpoint photopolymerization and polymerized micronanostructures

Kenji Takada, Koshiro Kaneko, Yu-Dong Li, Satoshi Kawata, Qi-Dai Chen, and Hong-Bo Sun

Appl. Phys. Lett. 92, 041902 (2008); http://dx.doi.org/10.1063/1.2834365 (3 pages) | Cited 3 times

Online Publication Date: 28 January 2008

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The spatial resolution in pinpoint two-photon photopolymerization of radical-type resins was found to be improved by varying the liquid sample temperature from a critical value Tc. For SCR-500 and NOA-61, the currently widely used resins, Tc is around room temperature. The improvement of spatial resolution by temperature decrease was attributable to restraint radicals diffusion; while the voxel size reduction versus temperature increase was considered as arising from enhanced chain termination. Furthermore, temperature plays an important role in size tuning of polymerized structures, for example, a photonic crystal blueshifted its working wavelength for 50 and 400 nm when heated at 200 and 300 °C, respectively, indicating the possibility to precisely tailor the photonic bandgap by means of thermal processing.
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82.35.-x Polymers: properties; reactions; polymerization
42.70.Jk Polymers and organics
81.07.Bc Nanocrystalline materials

The α-particle excited scintillation response of the liquid phase epitaxy grown LuAG:Ce thin films

P. Prusa, T. Cechak, J. A. Mares, M. Nikl, A. Beitlerova, N. Solovieva, Yu. V. Zorenko, V. I. Gorbenko, J. Tous, and K. Blazek

Appl. Phys. Lett. 92, 041903 (2008); http://dx.doi.org/10.1063/1.2835458 (3 pages) | Cited 13 times

Online Publication Date: 28 January 2008

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Liquid phase epitaxy grown Lu3Al5O12:Ce (LuAG:Ce) 20 μm thick films and plate cut from the bulk Czochralski-grown LuAG:Ce crystal were prepared for comparison of photoelectron yield (PhY) and PhY dependence on shaping time (0.5–10 μs). 241Am (α particles) was used for excitation. At the 0.5 μs shaping time, the best film shows comparable PhY with the bulk sample. PhY of bulk material increases noticeably more with shaping time than that of the films. Energy resolution of films is better. Influence of Pb2+ contamination in the films (from the flux) and antisite LuAl defect in bulk material is discussed.
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78.60.-b Other luminescence and radiative recombination
61.80.Jh Ion radiation effects
61.72.U- Doping and impurity implantation
61.72.J- Point defects and defect clusters
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)

Compositional inhomogeneity of a high-efficiency InxGa1−xN based multiple quantum well ultraviolet emitter studied by three dimensional atom probe

M. J. Galtrey, R. A. Oliver, M. J. Kappers, C. McAleese, D. Zhu, C. J. Humphreys, P. H. Clifton, D. Larson, and A. Cerezo

Appl. Phys. Lett. 92, 041904 (2008); http://dx.doi.org/10.1063/1.2829592 (3 pages) | Cited 8 times

Online Publication Date: 29 January 2008

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An InxGa1−xN based multiple quantum well structure emitting in the ultraviolet, which has the highest reported efficiency (67%) at its wavelength (380 nm), was analyzed with the three-dimensional atom probe. The results reveal gross discontinuities and compositional variations within the quantum well layers on a 20–100 nm length scale. In addition, the analysis shows the presence of indium in the AlyGa1−yN barrier layers, albeit at a very low level. By comparing with analogous epilayer samples, we suggest that the quantum well discontinuities we observe may play an important role in improving the efficiency of these structures.
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85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
85.60.Jb Light-emitting devices

High tensile strength reliability in a bulk metallic glass

J. H. Yao, J. Q. Wang, L. Lu, and Y. Li

Appl. Phys. Lett. 92, 041905 (2008); http://dx.doi.org/10.1063/1.2838715 (3 pages) | Cited 9 times

Online Publication Date: 30 January 2008

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We report high strength reliability under tension of a bulk metallic glass (BMG), demonstrated by its high uniformity in strength found over a statistically significant number of specimens, despite the fact that the samples all showed no macroscopic plasticity. Weibull statistical analysis showed that the Weibull modulus of the material is 36.5, which is much higher than the values of more typical brittle materials, further confirming BMGs’ high reliability [ Appl. Mech. Rev. 5, 449 (1952) ].
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81.40.Lm Deformation, plasticity, and creep
81.40.Jj Elasticity and anelasticity, stress-strain relations
81.70.Bt Mechanical testing, impact tests, static and dynamic loads
62.20.de Elastic moduli
62.20.F- Deformation and plasticity

Experimental analysis for the effect of dynamic capillarity on stress transformation in porous silicon

Wei Qiu, Yi-Lan Kang, Qiu Li, Zhen-Kun Lei, and Qing-Hua Qin

Appl. Phys. Lett. 92, 041906 (2008); http://dx.doi.org/10.1063/1.2838716 (3 pages) | Cited 3 times

Online Publication Date: 30 January 2008

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The evolution of real-time stress in porous silicon (PS) during drying is investigated using micro-Raman spectroscopy. The results show that the PS sample underwent non-negligible stress when immersed in liquid and suffered a stress impulsion during drying. Such nonlinear transformation and nonhomogeneneous distribution of stress are regarded as the coupling effects of several physical phenomena attributable to the intricate topological structure of PS. The effect of dynamic capillarity can induce microcracks and even collapse in PS structures during manufacture and storage.
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81.05.Cy Elemental semiconductors
81.05.Rm Porous materials; granular materials
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.mt Cracks
78.30.Am Elemental semiconductors and insulators

Rheological behavior probed by vibrating microcantilevers

Naser Belmiloud, Isabelle Dufour, Annie Colin, and Liviu Nicu

Appl. Phys. Lett. 92, 041907 (2008); http://dx.doi.org/10.1063/1.2837181 (3 pages) | Cited 8 times

Online Publication Date: 30 January 2008

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The aim of this paper is to demonstrate that vibrating microcantilevers can be used to quantify fluid properties such as density and viscosity. Contrary to classical rheological measurements using microcantilevers, the development of the proposed microrheometer is based on the measurement of fluid properties over a range of vibration frequencies, without necessarily being restricted to resonant phenomena. To this end, an analytical model is implemented and, when combined with measurements, allows the determination of the viscosity as a function of frequency. The preliminary results are encouraging for the development of a useful microrheometer on a silicon chip for microfluidic applications.
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47.80.-v Instrumentation and measurement methods in fluid dynamics
47.85.Np Fluidics

Study of thermal stability and luminescence quenching properties of bismuth-doped silicate glasses for fiber laser applications

V. G. Truong, L. Bigot, A. Lerouge, M. Douay, and I. Razdobreev

Appl. Phys. Lett. 92, 041908 (2008); http://dx.doi.org/10.1063/1.2828035 (3 pages) | Cited 45 times

Online Publication Date: 30 January 2008

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In the present work, we report on the luminescence properties of bismuth-doped silicate preforms and fibers under the influence of high temperature annealing and hydrogen-loading then annealing processes. Bismuth-related luminescence is found to be very sensitive to thermal annealing processes and can even totally disappear for specific annealing processes. The observed quenching of the luminescence was attributed to the reduction of part of bismuth ions responsible for the infrared luminescence into a lower valence state of bismuth.
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42.70.Ce Glasses, quartz
78.55.Hx Other solid inorganic materials

First-principles study of structural, elastic, and electronic properties of chromium carbides

Chao Jiang

Appl. Phys. Lett. 92, 041909 (2008); http://dx.doi.org/10.1063/1.2838345 (3 pages) | Cited 23 times

Online Publication Date: 30 January 2008

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Using first-principles calculations, we systematically studied the structural, elastic, and electronic properties of the technologically important chromium carbides: Cr3C2, Cr7C3, Cr23C6, Cr3C, and CrC. Our calculations show that the ground state structure for Cr7C3 is hexagonal, not orthorhombic. We further predict WC to be the energetically most stable structure for CrC. Our results indicate that all chromium carbides considered in this study are metallic and mechanically stable under the ambient condition. Among all chromium carbides, WC-type CrC exhibits the highest bulk and shear moduli and the lowest Poisson’s ratio, and is a potential low-compressibility and hard material.
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81.40.Jj Elasticity and anelasticity, stress-strain relations
81.40.Lm Deformation, plasticity, and creep
62.20.de Elastic moduli
62.20.dj Poisson's ratio
62.20.F- Deformation and plasticity
71.20.Ps Other inorganic compounds
71.15.-m Methods of electronic structure calculations

Room temperature contactless electroreflectance of the ground and excited state transitions in Ga0.76In0.24As0.08Sb0.92/GaSb single quantum wells of various widths

R. Kudrawiec, M. Motyka, J. Misiewicz, M. Hümmer, K. Rößner, T. Lehnhardt, M. Müller, and A. Forchel

Appl. Phys. Lett. 92, 041910 (2008); http://dx.doi.org/10.1063/1.2840161 (3 pages) | Cited 9 times

Online Publication Date: 31 January 2008

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The optical transitions in Ga0.76In0.24As0.08Sb0.92/GaSb quantum wells with the width varying from 10 to 21 nm were studied by room temperature contactless electroreflectance (CER). In addition to the quantum well (QW) ground state transition (11H), the 22H and 33H transitions (where klH denotes transition between the kth heavy hole and the lth electron subbands) have been clearly observed in CER spectra. The experimental QW transition energies were compared with theoretical predictions based on an effective mass formalism model. It has been concluded that this QW is type I for both electron and holes and the conduction band offset for the unstrained Ga0.76In0.24As0.08Sb0.92/GaSb interface equals ∼ 90%.
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78.20.Jq Electro-optical effects
78.67.De Quantum wells
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
73.21.Fg Quantum wells

The influence of substrate polarity on the structural quality of InN layers grown by high-pressure chemical vapor deposition

N. Dietz, M. Alevli, R. Atalay, G. Durkaya, R. Collazo, J. Tweedie, S. Mita, and Z. Sitar

Appl. Phys. Lett. 92, 041911 (2008); http://dx.doi.org/10.1063/1.2840192 (3 pages) | Cited 6 times

Online Publication Date: 31 January 2008

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The influence of substrate polarity on the properties of InN layers grown by high-pressure chemical vapor deposition has been studied. The 2Θ-ω x-ray diffraction scans on InN layers deposited on polar GaN epilayers revealed single-phase InN(0002) with a full width at half maximum (FWHM) of around 200 arc sec. InN layers grown on N-polar GaN exhibit larger FWHMs. Rocking curve analysis confirmed single-phase InN for both growth polarities, with FWHM values for ω-RC(002) at 2080 arc sec for InN grown on Ga-polar templates. The A1(LO) Raman mode analysis shows higher free carrier concentrations in InN grown on N-polar templates, indicating that polarity affects the incorporation of impurities.
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68.55.J- Morphology of films
68.55.ag Semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.66.Fd III-V semiconductors
78.30.Fs III-V and II-VI semiconductors

Flexible all-solid-state switchable mirror on plastic sheet

Kazuki Tajima, Yasusei Yamada, Shanhu Bao, Masahisa Okada, and Kazuki Yoshimura

Appl. Phys. Lett. 92, 041912 (2008); http://dx.doi.org/10.1063/1.2839298 (3 pages) | Cited 17 times

Online Publication Date: 31 January 2008

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We developed all-solid-state switchable mirror on flexible plastic [polyethylene terephthalate (PET)] sheet in the view point of low process cost and easy handling. Its optical switching property was investigated. Though the device on PET sheet showed over 4000 cycles of switching in durability test, it was lower than that on glass. The reasons seemed to be related with heterogeneous structure, oxidation of surface layer and adhesion of the film. However, it remarkably results that the device on plastic sheet showed such a high durability nonetheless because the sheet is weak to mechanical stress.
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42.82.Gw Other integrated-optical elements and systems
42.79.Bh Lenses, prisms and mirrors
42.82.Bq Design and performance testing of integrated-optical systems
42.65.Pc Optical bistability, multistability, and switching, including local field effects
42.87.-d Optical testing techniques

Formation of two conjoint fivefold deformation twins in copper nanowires with molecular dynamics simulation

Y. G. Zheng, H. W. Zhang, Z. Chen, L. Wang, Z. Q. Zhang, and J. B. Wang

Appl. Phys. Lett. 92, 041913 (2008); http://dx.doi.org/10.1063/1.2839581 (3 pages) | Cited 9 times

Online Publication Date: 31 January 2008

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The formation of two conjoint fivefold deformation twins (DTs) in copper nanowires under bending is reported based on molecular dynamics simulations. It is found that an intermediate icosahedral phase is formed to facilitate the transformation from a low dense (010) plane in a face-centered-cubic lattice to a {111} close-packed fashion, forming trijunctions composed of three DTs. These trijunctions can easily interact with other DTs, forming two conjoint fivefold DTs. This formation process differs from the one observed by Cao and Wei [Appl. Phys. Lett. 89, 041919 (2006)] , that is, fivefold DTs could be formed without introducing initial imperfections in simulations.
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64.70.Nd Structural transitions in nanoscale 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)
61.72.Mm Grain and twin boundaries
62.23.Hj Nanowires
61.44.Br Quasicrystals

Colorizing metals with femtosecond laser pulses

A. Y. Vorobyev and Chunlei Guo

Appl. Phys. Lett. 92, 041914 (2008); http://dx.doi.org/10.1063/1.2834902 (3 pages) | Cited 66 times

Online Publication Date: 31 January 2008

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For centuries, it had been the dream of alchemists to turn inexpensive metals into gold. Certainly, it is not enough from an alchemist’s point of view to transfer only the appearance of a metal to gold. However, the possibility of rendering a certain metal to a completely different color without coating can be very interesting in its own right. In this work, we demonstrate a femtosecond laser processing technique that allows us to create a variety of colors on a metal that ultimately leads us to control its optical properties from UV to terahertz.
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81.05.Bx Metals, semimetals, and alloys
42.62.-b Laser applications
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Discrimination of quantum dots using an optically created nuclear field

H. Sasakura, R. Kaji, S. Adachi, and S. Muto

Appl. Phys. Lett. 92, 041915 (2008); http://dx.doi.org/10.1063/1.2839615 (3 pages) | Cited 2 times

Online Publication Date: 1 February 2008

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We investigated an optically created nuclear field in a single InAlAs quantum dot and demonstrated that the nuclear field can be used to discriminate whether photoluminescence lines originate from the same dot or a different dot. Since the nonlinear response of the nuclear field is sensitive to the electron g factor and correlation time of a coupled electron-nuclear spin system, the resultant Overhauser shift is their good measure for individual quantum dots. This method provides a simple and convenient alternative to the standard photon cross-correlation method.
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78.67.Hc Quantum dots
78.55.Cr III-V semiconductors
72.25.Fe Optical creation of spin polarized carriers
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