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5 Sep 2011

Volume 99, Issue 10, Articles (10xxxx)

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Appl. Phys. Lett. 99, 103701 (2011); http://dx.doi.org/10.1063/1.3633066 (3 pages)

Yinan Zhang, David J. S. Birch, and Yu Chen
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Tuning the wavelength drift between resonance light absorption and scattering of plasmonic nanoparticle

Jian Zhu, Jian-jun Li, and Jun-wu Zhao

Appl. Phys. Lett. 99, 101901 (2011); http://dx.doi.org/10.1063/1.3636403 (3 pages) | Cited 5 times

Online Publication Date: 6 September 2011

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Local surface plasmon resonance in a metallic nanoparticle can induce intense light absorption and scattering simultaneously. However, the light absorption does not always have the same resonance wavelength with the scattering. Both the red and blue drifts of the scattering peak from the absorption peak are observed in the dielectric coated gold nanosphere, gold nanoshell, and nanorod. The wavelength drift between the absorption and scattering has been optimized by changing the particle shape and structure. This tunable wavelength drift can be used in selecting the resonance absorption or scattering for optical applications by altering the incident wavelength.
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78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
78.68.+m Optical properties of surfaces

Compositional effects on the electronic structure of ZnSe1−xSx ternary quantum dots

Sumeet C. Pandey, T. J. Mountziaris, and Dimitrios Maroudas

Appl. Phys. Lett. 99, 101902 (2011); http://dx.doi.org/10.1063/1.3633354 (3 pages) | Cited 5 times

Online Publication Date: 6 September 2011

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We report first-principles density functional theory calculations of the electronic structure of ZnSe1−xSx ternary quantum dots (TQDs) and the impact of composition and compositional distribution on the electron density distribution, electronic density of states, and band gap. We find that the band gaps for ZnSe/ZnS core/shell TQDs are nearly independent of the number of S atoms in the shell, whereas the presence of S in the core of alloyed TQDs modifies the electronic energy levels significantly. Our results imply that distribution of S atoms can be used to achieve quantum confinement in different regions of the TQDs.
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73.21.La Quantum dots
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
71.20.Nr Semiconductor compounds

Absence of Casimir regime in two-dimensional nanoribbon phonon conduction

Zhao Wang and Natalio Mingo

Appl. Phys. Lett. 99, 101903 (2011); http://dx.doi.org/10.1063/1.3635394 (3 pages) | Cited 8 times

Online Publication Date: 7 September 2011

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In stark contrast with three-dimensional (3D) nanostructures, we show that boundary scattering in two-dimensional (2D) nanoribbons alone does not lead to a finite phonon mean free path. If combined with an intrinsic scattering mechanism, 2D boundary scattering does reduce the overall mean free path; however, the latter does not scale proportionally to the ribbon width, unlike the well known Casimir regime occurring in 3D nanowires. We show that boundary scattering can be accounted for by a simple Mathiessen-type approach for many different 3D nanowire cross sectional shapes; however, this is not possible in the 2D nanoribbon case, where a complete solution of the Boltzmann transport equation is required. These facts have strong implications for the thermal conductivity of suspended nanostructures.
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63.22.Gh Nanotubes and nanowires
81.07.Gf Nanowires

Amorphous interface layer in thin graphite films grown on the carbon face of SiC

R. Colby, M. L. Bolen, M. A. Capano, and E. A. Stach

Appl. Phys. Lett. 99, 101904 (2011); http://dx.doi.org/10.1063/1.3635786 (3 pages) | Cited 4 times

Online Publication Date: 7 September 2011

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Cross-sectional transmission electron microscopy (TEM) is used to characterize an amorphous layer observed at the interface in graphite and graphene films grown via thermal decomposition of C-face 4H-SiC. The amorphous layer does not cover the entire interface, but uniform contiguous regions span microns of cross-sectional interface. Scanning transmission electron microscopy (STEM) images and electron energy loss spectroscopy (EELS) demonstrate that the amorphous layer is a carbon-rich composition of Si/C. The amorphous layer is clearly observed in samples grown at 1600 °C for a range of growth pressures in argon, but not at 1500 °C, suggesting a temperature-dependent formation mechanism.
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68.55.ap Fullerenes
81.05.ub Fullerenes and related materials
79.20.Uv Electron energy loss spectroscopy
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
61.48.-c Structure of fullerenes and related hollow and planar molecular structures

Measurement of electric field across individual wurtzite GaN quantum dots using electron holography

Lin Zhou, David J. Smith, Martha R. McCartney, Tao Xu, and Theodore D. Moustakas

Appl. Phys. Lett. 99, 101905 (2011); http://dx.doi.org/10.1063/1.3636109 (3 pages) | Cited 2 times

Online Publication Date: 7 September 2011

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Electrostatic potential profiles across wurtzite AlN/GaN quantum dot (QD) superlattices grown by molecular beam epitaxy have been measured using off-axis electron holography. The profiles for individual GaN QDs show large phase shifts which can be understood in terms of spontaneous polarization and piezoelectric fields and the accumulation of positive and negative charge at the GaN/AlN interfaces. An electric field with magnitude of ∼7.8 ± 2 MV/cm was measured across the center of a GaN QD, in reasonable agreement with reported simulations.
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06.30.Ka Basic electromagnetic quantities
42.40.My Applications
77.65.-j Piezoelectricity and electromechanical effects
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)

Broadband slow-wave systems of subwavelength thickness excited by a metal wire

Yong Jin Zhou and Tie Jun Cui

Appl. Phys. Lett. 99, 101906 (2011); http://dx.doi.org/10.1063/1.3634024 (3 pages) | Cited 3 times

Online Publication Date: 7 September 2011

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We propose a broadband slow-wave system based on metallic graded grating structures of subwavelength thickness. A metal wire is used to excite the slow waves propagating along the gratings. The analysis and full-wave simulations show that the electromagnetic waves could be stopped at designed positions under different frequencies. Experiments are conducted in the microwave frequencies to verify the proposed system. The measured results show very good agreements to the full-wave simulations. We have further modeled a broadband slow-wave system of subwavelength thickness in the terahertz (THz) frequencies to demonstrate its validity.
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42.79.Dj Gratings
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.15.Eq Optical system design

Magnetic resonance on core-shell nanowires with notches

Lina Xu, Zhi-Jian Zhang, and Bong Jae Lee

Appl. Phys. Lett. 99, 101907 (2011); http://dx.doi.org/10.1063/1.3637042 (3 pages) | Cited 1 time

Online Publication Date: 7 September 2011

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In this paper, a two-dimensional core-shell nanowire made of a dielectric core and metallic cladding is proposed for exciting the magnetic resonance on an isolated nanostructure. The key idea is to remove a small portion of the metallic cladding on the nanowire so that the incident magnetic field can be localized in the dielectric core. It is also found that the core-shell nanowire can support the localized surface plasmon, whose resonance frequency mainly depends on the thickness of the metallic cladding. The finite-difference time-domain method is employed to calculate the scattering cross-section of the proposed structure and the near-field distribution of the magnetic field at resonance conditions. The results obtained from this study will advance our fundamental understanding of the light-matter interaction at nanometer scales and facilitate the development of multi-dimensional metamaterials for subwavelength imaging.
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81.07.Gf Nanowires
75.30.Cr Saturation moments and magnetic susceptibilities
75.50.Tt Fine-particle systems; nanocrystalline materials
77.22.Ch Permittivity (dielectric function)
02.70.Bf Finite-difference methods
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Selectively solvated triblock copolymer networks under biaxial strain

Arjun S. Krishnan, John H. van Zanten, Sönke Seifert, Byeongdu Lee, and Richard J. Spontak

Appl. Phys. Lett. 99, 101908 (2011); http://dx.doi.org/10.1063/1.3635780 (3 pages) | Cited 3 times

Online Publication Date: 9 September 2011

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Triblock copolymers swollen with a midblock-selective solvent provide a test platform by which to interrogate the properties of highly elastic physical gel networks. Here, such networks are biaxially strained and studied by synchrotron small-angle x-ray scattering. Analysis of the form factor reveals that initially spherical micellar cores deform to ellipsoids when strained. The Percus-Yevick hard-sphere model describes the structure factor of micelles exhibiting liquid-like order prior to deformation but requires an attractive potential to match the structure factor under strain. The magnitude of this potential increases with increasing strain, indicating a change in coronal overlap as the network is stretched.
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82.70.Gg Gels and sols
61.25.hk Polymer melts and blends
62.10.+s Mechanical properties of liquids
78.70.Ck X-ray scattering
81.40.Cd Solid solution hardening, precipitation hardening, and dispersion hardening; aging
82.70.Dd Colloids

Charge propagation dynamics at trapping centers that induce the luminescence of rare-earth dopants in wide-gap materials

Masashi Ishii, Susumu Harako, Xinwei Zhao, Shuji Komuro, and Bruce Hamilton

Appl. Phys. Lett. 99, 101909 (2011); http://dx.doi.org/10.1063/1.3636393 (3 pages) | Cited 3 times

Online Publication Date: 9 September 2011

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For rare-earth doped semiconductors, charge propagation from semiconductors to rare-earths is essential for excitation of optically active dopants. However, the qualitative model that has been widely accepted to describe this process is based upon indirect evidence; in this model, it is believed that trapping and subsequent recombination of the charges at some rare-earth-related defect excite the dopants. In this work, we observe the sequential process directly, and quantify the trapped charge density and relaxation frequency using a photoelectric measurement technique for samarium-doped titanium dioxide with intense visible luminescence under ultraviolet light.
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78.55.Hx Other solid inorganic materials
61.72.jn Color centers
72.40.+w Photoconduction and photovoltaic effects
72.80.Jc Other crystalline inorganic semiconductors
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