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27 Jun 2011

Volume 98, Issue 26, Articles (26xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 98, 263101 (2011); http://dx.doi.org/10.1063/1.3587576 (3 pages)

Jing Ye, Yu Zhao, Libin Tang, Li-Miao Chen, C. M. Luk, S. F. Yu, S. T. Lee, and S. P. Lau
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Omnidirectional absorption enhancement in hybrid waveguide-plasmon system

Jing Zhang, Wenli Bai, Likang Cai, Xi Chen, Guofeng Song, and Qiaoqiang Gan

Appl. Phys. Lett. 98, 261101 (2011); http://dx.doi.org/10.1063/1.3603934 (3 pages) | Cited 2 times

Online Publication Date: 27 June 2011

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We investigate the omnidirectional absorption enhancement induced by the excitation of the localized surface plasmon in the hybrid system consisting of a gold nanowire array embedded in a slab waveguide. Assisted by the waveguide layer, the hybrid system can support the localized waveguide-plasmon resonances for a wide range of incident angles. Theoretical and experimental results are both presented to demonstrate the omnidirectional absorption enhancement which could find important applications on plasmonic-assisted photovoltaic devices or photodetectors.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
61.46.-w Structure of nanoscale materials
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Vertical field switching for blue-phase liquid crystal devices

Hui-Chuan Cheng, Jin Yan, Takahiro Ishinabe, and Shin-Tson Wu

Appl. Phys. Lett. 98, 261102 (2011); http://dx.doi.org/10.1063/1.3604011 (3 pages) | Cited 2 times

Online Publication Date: 27 June 2011

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A low-voltage (< 10 V), high-transmittance (> 80%), submillisecond-response, and hysteresis-free polymer-stabilized blue-phase liquid crystal (BPLC) device with vertical field switching (VFS) and oblique incident light are demonstrated experimentally. Unlike the commonly employed in-plane switching in which the electric field is primarily in lateral direction and not uniform spatially, the VFS mode has uniform longitudinal field. As a result, the operating voltage is reduced by ∼ 3.2 × which in turn helps to eliminate hysteresis. The VFS mode is a promising candidate for the emerging BPLC display and photonic devices.
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42.79.Kr Display devices, liquid-crystal devices
85.60.Pg Display systems

Strong coupling between excitons in J-aggregates and waveguide modes in thin polymer films

Tal Ellenbogen, Paul Steinvurzel, and Kenneth B. Crozier

Appl. Phys. Lett. 98, 261103 (2011); http://dx.doi.org/10.1063/1.3604014 (3 pages) | Cited 2 times

Online Publication Date: 28 June 2011

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We observe a large room temperature Rabi splitting for the transverse electric (190 meV) and transverse magnetic (125 meV) waveguide modes of a thin polymer film doped with J-aggregating dye, indicating strong coupling between propagating light modes and localized molecular excitons. We show that the difference in the measured splitting results from the different field distribution of the cross polarized modes. Numerical simulations indicate that the exciton-waveguide modes are as strongly coupled as exciton-surface plasmon polaritons supported by the same system.
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71.35.-y Excitons and related phenomena
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.66.Qn Polymers; organic compounds
61.41.+e Polymers, elastomers, and plastics
02.60.-x Numerical approximation and analysis
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)

Stimulated emission of near-infrared radiation in silicon fin light-emitting diode

S. Saito, T. Takahama, K. Tani, M. Takahashi, T. Mine, Y. Suwa, and D. Hisamoto

Appl. Phys. Lett. 98, 261104 (2011); http://dx.doi.org/10.1063/1.3605255 (3 pages) | Cited 1 time

Online Publication Date: 28 June 2011

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We propose top-down processes to make silicon multiple quantum wells called fins for a light-emitting diode. The silicon fins are formed vertically to a substrate and embedded in a Si3N4 waveguide. By current injections into silicon fins, we have observed stimulated emission spectra peaked at the wavelengths corresponding to the periodic structures of fins. The near-field mode profiles obtained at the edge of the waveguide qualitatively agreed with theoretical calculations. It has been turned out that both transverse-electric and transverse-magnetic fields can contribute to the optical gain.
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85.60.Jb Light-emitting devices

The influence of Hausdorff dimension on plasmonic antennas with Pascal’s triangle geometry

S. Sederberg and A. Y. Elezzabi

Appl. Phys. Lett. 98, 261105 (2011); http://dx.doi.org/10.1063/1.3605570 (3 pages) | Cited 2 times

Online Publication Date: 29 June 2011

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We introduce fractal geometry to the common bowtie antenna and investigate the influence of a key fractal parameter, Hausdorff dimension, on the broadband spectral response of the antenna. Length scaling trends are presented for antennas having various Hausdorff dimensions. We show that antennas with Pascal’s triangle geometry accommodate resonances that are red-shifted when compared to a standard bowtie antenna having the same size. Furthermore, increasing the Hausdorff dimension of the antenna blue shifts its resonance. By designing nanoplasmonic antennas with Pascal’s triangle geometry, the resonance conditions may be varied while the antenna dimensions are kept constant.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
84.40.Ba Antennas: theory, components and accessories
78.68.+m Optical properties of surfaces
73.22.Lp Collective excitations

AlN photonic crystal nanocavities realized by epitaxial conformal growth on nanopatterned silicon substrate

D. Néel, S. Sergent, M. Mexis, D. Sam-Giao, T. Guillet, C. Brimont, T. Bretagnon, F. Semond, B. Gayral, S. David, X. Checoury, and P. Boucaud

Appl. Phys. Lett. 98, 261106 (2011); http://dx.doi.org/10.1063/1.3605592 (3 pages) | Cited 6 times

Online Publication Date: 29 June 2011

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An original method to fabricate III-nitride photonic crystal membranes without etching of III-N materials is reported. A photonic crystal pattern is first realized in a silicon substrate. GaN quantum dots embedded in a thin AlN layer are then grown by conformal epitaxy using ammonia-based molecular beam epitaxy on the top of the patterned silicon substrate and a free-standing membrane is achieved by selective etching of the silicon substrate through the holes of the photonic crystal. Room temperature microphotoluminescence measurements show a quality factor as high as 1800 at 425 nm on a modified L3 cavity. Possibility to achieve lasing with this system is discussed.
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81.16.Rf Micro- and nanoscale pattern formation
78.55.Cr III-V semiconductors
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Enhancement of reflective second harmonic generation using periodically arrayed silver-island films

Chia-Jung Hsu, Kuo-Pin Chiu, Juh-Tzeng Lue, and Kuang Yao Lo

Appl. Phys. Lett. 98, 261107 (2011); http://dx.doi.org/10.1063/1.3605679 (3 pages)

Online Publication Date: 30 June 2011

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The characteristics of angle-resolved optical second harmonic generation (SHG) reflectance from periodically arrayed silver-island films were investigated. The silver-island films were fabricated using micro-spherical lithography. The SHG intensity from these arrays was more than one order of magnitude greater than that of flat silver films for some angles of incidence. This enhancement arises from the excitation of surface plasmon resonance at the pumping frequency. We found this resonance by analyzing the reciprocal lattice phase-matching condition for the silver-island films. The predicted surface plasmon wave vectors are in good agreement with those obtained using three-dimensional finite-difference time-domain numerical simulations.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
02.70.Bf Finite-difference methods

Optical gain observation on silicon nanocrystals embedded in silicon nitride under femtosecond pumping

B. M. Monroy, O. Crégut, M. Gallart, B. Hönerlage, and P. Gilliot

Appl. Phys. Lett. 98, 261108 (2011); http://dx.doi.org/10.1063/1.3607276 (3 pages) | Cited 1 time

Online Publication Date: 1 July 2011

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We report the observation of positive optical gain in silicon nanocrystals (Si-nc) embedded in silicon nitride measured by the variable stripe length technique. We evidence the onset of stimulated emission and report gain coefficients up to 52 cm−1 at the highest excitation power (6.5 W/cm2). Photoluminescence dynamics presents two distinct recombination lifetimes in the nanosecond and the microsecond ranges. This was interpreted in terms of fast carrier trapping in nitrogen-induced localized states in the Si-nc surface and subsequent slow radiative recombination, suggesting that carrier trapping in radiative surface states plays a crucial role in the optical gain mechanism of Si-nc.
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78.55.Ap Elemental semiconductors
81.05.Cy Elemental semiconductors
78.47.jd Time resolved luminescence
68.47.Fg Semiconductor surfaces
73.20.At Surface states, band structure, electron density of states
78.45.+h Stimulated emission
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Observation of coherently enhanced tunable narrow-band terahertz transition radiation from a relativistic sub-picosecond electron bunch train

P. Piot, Y.-E Sun, T. J. Maxwell, J. Ruan, A. H. Lumpkin, M. M. Rihaoui, and R. Thurman-Keup

Appl. Phys. Lett. 98, 261501 (2011); http://dx.doi.org/10.1063/1.3604017 (3 pages) | Cited 2 times

Online Publication Date: 27 June 2011

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We experimentally demonstrate the production of narrow-band (δf/f ≈ 20% at f ≈ 0.5 THz) transition radiation with tunable frequency over [0.37, 0.86] THz. The radiation is produced as a train of sub-picosecond relativistic electron bunches transits at the vacuum-aluminum interface of an aluminum converter screen. The bunch train is generated via a transverse-to-longitudinal phase space exchange technique. We also show a possible application of modulated beams to extend the dynamical range of a popular bunch length diagnostic technique based on the spectral analysis of coherent radiation.
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29.27.Fh Beam characteristics
41.75.-i Charged-particle beams
41.85.-p Beam optics

The self-consistent nonlinear theory of electron cyclotron maser based on anomalous Doppler effect

Ling-Bao Kong, Zhi-Ling Hou, and Chao-Ran Xie

Appl. Phys. Lett. 98, 261502 (2011); http://dx.doi.org/10.1063/1.3604016 (3 pages) | Cited 1 time

Online Publication Date: 29 June 2011

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The self-consistent nonlinear equations, which describe electron cyclotron maser under the condition of anomalous Doppler effect, have been developed. By employing an initially rectilinear electron beam and a guiding static magnetic field, an efficient energy transfer between electrons and microwave can be achieved. The results suggest potential applications in designing a compact and efficient microwave generation/amplification device.
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42.50.Pq Cavity quantum electrodynamics; micromasers
84.40.Ik Masers; gyrotrons (cyclotron-resonance masers)
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Low-temperature spatially resolved micro-photoluminescence mapping in CdZnTe single crystals

G. Yang, A. E. Bolotnikov, Y. Cui, G. S. Camarda, A. Hossain, K. H. Kim, R. Gul, and R. B. James

Appl. Phys. Lett. 98, 261901 (2011); http://dx.doi.org/10.1063/1.3603930 (3 pages) | Cited 1 time

Online Publication Date: 27 June 2011

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We utilized a low-temperature spatially resolved micro-photoluminescence mapping technique to investigate the spatial variation of photoluminescence- and electronic-defect states in areas of CdZnTe (CZT) single crystals containing structural-imperfections. Photoluminescence mapping of the donor-bound-exciton emission reveals an unexpected blue-shift of the CZT bandgap at Te inclusions, which indicates that for optical measurements the localized strain field needs to be considered for accurate calculation of Zn composition and energy levels near micro-scale defects. We observed that the line widths of the donor-bound-exciton peak and defect-related D band are broadened in regions with a high density of dislocations; in contrast, the donor-acceptor-pair peak is narrowed.
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78.55.Et II-VI semiconductors
81.05.Dz II-VI semiconductors
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
61.72.Qq Microscopic defects (voids, inclusions, etc.)
71.20.Nr Semiconductor compounds
71.55.Gs II-VI semiconductors

In-plane light polarization in nonpolar m-plane CdxZn1−xO/ZnO quantum wells

Hiroaki Matsui and Hitoshi Tabata

Appl. Phys. Lett. 98, 261902 (2011); http://dx.doi.org/10.1063/1.3603931 (3 pages) | Cited 1 time

Online Publication Date: 27 June 2011

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We studied polarized photoluminescence (PL) as a function of both temperature and excitation power from m-plane CdxZn1−xO/ZnO single quantum wells having different Cd contents. The polarized PL properties at 300 K were enhanced as the Cd content increased. This enhancement is due to the anisotropic compressive strains induced within the well layers. These results are linked to the modifications of the valence band (VB) structure resulting from a change in the crystalline symmetry of CdxZn1−xO. Furthermore, there is an exception to the polarization selection rules due to excitonic localization because of a mixing of the upper VB states at low temperatures.
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78.55.Et II-VI semiconductors
78.67.De Quantum wells
71.20.Nr Semiconductor compounds

Interplay between temperature and composition effects on the martensitic transformation in Ni2+xMn1−xGa alloys

Chun-Mei Li, Qing-Miao Hu, Rui Yang, Börje Johansson, and Levente Vitos

Appl. Phys. Lett. 98, 261903 (2011); http://dx.doi.org/10.1063/1.3603935 (3 pages)

Online Publication Date: 27 June 2011

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Martensitic transformation in Ni2+xMn1−xGa alloys is known to be controlled by the soft tetragonal elastic constant C′ of the high-temperature austenitic phase. The temperature (T) and composition (x) dependence of C′(T, x) are calculated using the first-principles exact muffin-tin orbitals method. We show that the temperature factor of C′ is dominated by the phonon-smearing term. The competition between the negative alloying effect (∂C′/∂x < 0) and the positive temperature effect (∂C′/∂T > 0) is found to lead to nearly constant C′(TM(x), x) at the critical temperature TM(x). We demonstrate that a proper account of the temperature and composition dependence of C′(T, x) is indispensable for reasonable theoretical TM(x) values.
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81.30.Kf Martensitic transformations
62.20.dq Other elastic constants
81.40.Jj Elasticity and anelasticity, stress-strain relations
64.70.kd Metals and alloys

Structural and optical properties of single crystalline columbite tin oxide film

Lingyi Kong, Jin Ma, Caina Luan, and Zhen Zhu

Appl. Phys. Lett. 98, 261904 (2011); http://dx.doi.org/10.1063/1.3603936 (3 pages)

Online Publication Date: 27 June 2011

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Tin oxide (SnO2) films were deposited on Y-stabilized ZrO2 (YSZ) (120) substrates at 500–750 °C by metalorganic chemical vapor deposition. The film deposited at 700 °C exhibited the best crystallinity, especially with a single crystalline columbite structure (C-SnO2). The structural and optical properties of this film were investigated in detail. A schematic diagram was proposed to clarify the growth mechanism, in which an epitaxial relationship of C-SnO2(120)||YSZ(120) with C-SnO2[001]||YSZ[001] was illustrated. The C-SnO2 film showed excellent transparency and the optical band gap was about 3.74 eV.
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81.05.Hd Other semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.66.Li Other semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
71.20.Nr Semiconductor compounds
61.66.Fn Inorganic compounds

First-principles study of Ti intercalation between graphene and Au surface

T. Kaneko and H. Imamura

Appl. Phys. Lett. 98, 261905 (2011); http://dx.doi.org/10.1063/1.3604008 (3 pages)

Online Publication Date: 28 June 2011

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We investigate the effects of Ti intercalation between graphene and Au surface on binding energy and charge doping by using the first-principles calculations. We show that the largest binding energy is realized by the intercalation of single mono-layer of Ti. We also show that electronic structure is very sensitive to the arrangement of metal atoms at the interface. If the composition of the interface layer is Ti0.33Au0.67 and the Ti is located at the top site, the Fermi level lies closely at the Dirac point, i.e., the Dirac cone of the ideal free-standing graphene is recovered.
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71.15.-m Methods of electronic structure calculations
73.22.Pr Electronic structure of graphene
71.15.Nc Total energy and cohesive energy calculations
61.72.up Other materials
73.20.At Surface states, band structure, electron density of states

Dispersion corrections in the boron buckyball and nanotubes

Rosi N. Gunasinghe, Cherno B. Kah, Kregg D. Quarles, and Xiao-Qian Wang

Appl. Phys. Lett. 98, 261906 (2011); http://dx.doi.org/10.1063/1.3604018 (3 pages) | Cited 1 time

Online Publication Date: 28 June 2011

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We have investigated structural and electronic properties of the B80 buckyball and boron nanotubes by means of dispersion-corrected density-functional calculations. Our analysis reveals the vibrational stability for the icosahedral B80 with the inclusion of dispersion corrections, in contrast to the instability to a tetrahedral B80 with puckered capping atoms from preceding density-functional theory calculations. Similarly, the dispersion-corrected density-functional calculations yield non-puckered boron nanotube conformations and an associated metallic state for zigzag tubes. Our study indicates that the incorporation of long-range dispersive interactions is particularly important to the structural and electronic properties of boron fullerenes and nanotubes.
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71.20.Tx Fullerenes and related materials; intercalation compounds
61.46.Fg Nanotubes
61.48.De Structure of carbon nanotubes, boron nanotubes, and other related systems
71.15.Mb Density functional theory, local density approximation, gradient and other corrections

Analyzing the growth of InxGa1−xN/GaN superlattices in self-induced GaN nanowires by x-ray diffraction

M. Wölz, V. M. Kaganer, O. Brandt, L. Geelhaar, and H. Riechert

Appl. Phys. Lett. 98, 261907 (2011); http://dx.doi.org/10.1063/1.3604810 (3 pages) | Cited 1 time

Online Publication Date: 28 June 2011

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Self-induced GaN nanowires are grown by plasma-assisted molecular beam epitaxy, with InxGa1−xN quantum wells inserted to form an axial superlattice. From the ω−2θ scans of a laboratory x-ray diffraction experiment, we obtain the superlattice period, the thickness of the quantum wells, and the In content in this layer. The axial growth rate of the InxGa1−xN quantum wells is significantly enhanced, which we attribute to increased Ga diffusion along the nanowire sidewalls in the presence of In.
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81.16.-c Methods of micro- and nanofabrication and processing
68.65.Cd Superlattices
81.05.Ea III-V semiconductors
81.07.St Quantum wells
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.07.Gf Nanowires

Modification of vibrational damping times in thin gold films by self-assembled molecular layers

M. Hettich, A. Bruchhausen, S. Riedel, T. Geldhauser, S. Verleger, D. Issenmann, O. Ristow, R. Chauhan, J. Dual, A. Erbe, E. Scheer, P. Leiderer, and T. Dekorsy

Appl. Phys. Lett. 98, 261908 (2011); http://dx.doi.org/10.1063/1.3604790 (3 pages) | Cited 1 time

Online Publication Date: 29 June 2011

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The mechanical contact between a thin gold film and a silicon substrate is investigated by ultrafast pump-probe spectroscopy providing quantitative values on the damping time of coherent longitudinal vibrations of the gold film. A distinct increase in damping times is observed when a self-assembled molecular layer is introduced between the gold film and the substrate. We deduce the frequency dependence of the damping times by varying the thickness of the gold films. Experimental results are compared to numerical simulations based on a visco-elastic model and the acoustic mismatch model.
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81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.dq Other elastic constants
78.47.J- Ultrafast spectroscopy (<1 psec)
02.60.-x Numerical approximation and analysis
68.55.-a Thin film structure and morphology

Spectral analysis of enhanced third harmonic generation from plasmonic excitations

G. X. Li, T. Li, H. Liu, K. F. Li, S. M. Wang, S. N. Zhu, and K. W. Cheah

Appl. Phys. Lett. 98, 261909 (2011); http://dx.doi.org/10.1063/1.3604794 (3 pages)

Online Publication Date: 29 June 2011

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We experimentally achieved enhanced third harmonic generation (THG) from hole-array in gold film. The surface plasmon polarition excitations, considered as the major contribution to this THG enhancement, are elaborately studied by a spectrum-resolved femto-second laser system. The momentum matching conditions between the fundamental and harmonic waves are well established, giving results of a series of clear THG beam spots with respect to different excitation wavelengths. This efficient THG beaming from the pure metallic structure would considerably broaden the research in the field of nonlinear plasmonics.
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78.66.Bz Metals and metallic alloys
71.35.-y Excitons and related phenomena
78.47.J- Ultrafast spectroscopy (<1 psec)
78.30.Er Solid metals and alloys
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Surface oxygen vacancy origin of electron accumulation in indium oxide

Aron Walsh

Appl. Phys. Lett. 98, 261910 (2011); http://dx.doi.org/10.1063/1.3604811 (3 pages) | Cited 2 times

Online Publication Date: 29 June 2011

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Metal oxides are typically insulating materials that can be made conductive through aliovalent doping and/or non-stoichiometry. Recent studies have identified conductive states at surfaces and interfaces of pure oxide materials; high electron concentrations are present, resulting in a high-mobility two-dimensional electron gas. We demonstrate for In2O3 that the energy required to form an oxygen vacancy decreases rapidly towards the (111) surface, where the coordination environment is lowered. This is a general feature of metal oxide systems that can result in a metal–insulator transition where donors are produced at chemically reduced extended defects.
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61.72.jd Vacancies
72.20.Fr Low-field transport and mobility; piezoresistance
71.30.+h Metal-insulator transitions and other electronic transitions
61.72.Nn Stacking faults and other planar or extended defects
71.10.Ca Electron gas, Fermi gas

High thermoelectric figure of merit in the Cu3SbSe4-Cu3SbS4 solid solution

Eric J. Skoug, Jeffrey D. Cain, and Donald T. Morelli

Appl. Phys. Lett. 98, 261911 (2011); http://dx.doi.org/10.1063/1.3605246 (3 pages) | Cited 5 times

Online Publication Date: 29 June 2011

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We report thermoelectric properties of selected compounds from the Cu3SbSe4-Cu3SbS4 system. Additional phonon scattering due to the disordered arrangement of Se and S atoms reduces the lattice thermal conductivity to near its minimum possible value at high temperature. The hole concentration is optimized at approximately 2.0 × 1020 cm−3 by doping with 3% Ge on the Sb site. Compounds of the form Cu3Sb1−yGeySe4−xSx (x = 0.8 and 1.2, y = 0.02 and 0.03) all have dimensionless thermoelectric figure of merit in excess of 0.8 at 650 K, with a maximum value of 0.89 for x = 1.2, y = 0.03.
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72.20.Pa Thermoelectric and thermomagnetic effects
66.70.Df Metals, alloys, and semiconductors
63.20.-e Phonons in crystal lattices
61.72.up Other materials

Direct observation of amplified spontaneous emission of surface plasmon polaritons at metal/dielectric interfaces

Yu-Hui Chen, Jiafang Li, Ming-Liang Ren, Ben-Li Wang, Jin-Xin Fu, Si-Yun Liu, and Zhi-Yuan Li

Appl. Phys. Lett. 98, 261912 (2011); http://dx.doi.org/10.1063/1.3605599 (3 pages)

Online Publication Date: 29 June 2011

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We report on direct observation of amplified spontaneous emission (ASE) of surface plasmon polaritons (SPPs) at the interface of a silver film and a gain medium. Based on a typical Kretschmann configuration incorporated with Rhodamine 6G molecules, the growing ASE spectra of SPPs have been clearly identified by carefully conducting a pump-dependent angle-resolved spectral measurement. Spectral narrowing effects induced by the SPP amplification are also demonstrated. The observed phenomena are helpful in understanding the fundamental interactions between SPPs and gain medium, which could enable wide applications on plasmonic sources and sensors.
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78.45.+h Stimulated emission
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.68.+m Optical properties of surfaces
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)

Bandgap engineering of sol-gel synthesized amorphous Zn1−xMgxO films

M. Wei, R. C. Boutwell, J. W. Mares, A. Scheurer, and W. V. Schoenfeld

Appl. Phys. Lett. 98, 261913 (2011); http://dx.doi.org/10.1063/1.3604782 (3 pages) | Cited 1 time

Online Publication Date: 30 June 2011

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Amorphous Zn1−xMgxO (α-Zn1−xMgxO) ternary alloy thin films across the full compositional range were synthesized by a low-cost sol-gel method on quartz substrates. The amorphous property of the α-Zn1−xMgxO films was verified by x-ray diffraction, and atomic force microscopy revealed a smooth surface with sub-nanometer root-mean square roughness. The current phase segregation issue limiting application of crystalline Zn1−xMgxO with 38% < x < 75% was completely eliminated by growing amorphous films. Optical transmission measurements showed high transmissivity of more than 90% in the visible and near infrared regions, with optical bandgap tunability from 3.3 eV to more than 6.5 eV by varying the Mg content.
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71.20.Nr Semiconductor compounds
71.55.Gs II-VI semiconductors
78.66.Hf II-VI semiconductors
61.72.uj III-V and II-VI semiconductors
81.10.Dn Growth from solutions
81.10.Fq Growth from melts; zone melting and refining
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
78.66.Fd III-V semiconductors

Effect of misfit dislocations on luminescence in m-plane InGaN quantum wells

Y. Huang, K. W. Sun, A. M. Fischer, Q. Y. Wei, R. Juday, F. A. Ponce, R. Kato, and T. Yokogawa

Appl. Phys. Lett. 98, 261914 (2011); http://dx.doi.org/10.1063/1.3605253 (3 pages) | Cited 1 time

Online Publication Date: 30 June 2011

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A correlation has been established between the optical and structural properties of blue-light-emitting diode structures grown on free-standing m-plane GaN. A double-peak InGaN quantum well emission at room temperature has been observed with a strong inhomogeneous spatial distribution, which can be associated with the presence of dislocations originating at the InGaN layers. It is argued that the difference in peak energy positions is due to in-plane piezoelectric fields within the dislocated regions.
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85.60.Jb Light-emitting devices
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Enhanced Faraday rotation in magnetophotonic crystal infiltrated with graphene

Haixia Da and Gengchiau Liang

Appl. Phys. Lett. 98, 261915 (2011); http://dx.doi.org/10.1063/1.3605593 (3 pages) | Cited 1 time

Online Publication Date: 30 June 2011

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We investigate the Faraday rotation angle of a bilayer structure composed of graphene and SiC using the transfer matrix method and find that the cyclotron resonance frequency is highly sensitive to the magnetic field due to the Dirac quasiparticles characteristics of graphene. As a truly single atomic sheet, the giant Faraday rotation angle in graphene originates from its two dimensional free carriers distributions. Compared to the bilayer structure in experiments, further enhancement in the Faraday rotation can be achieved in a designed magnetophotonic crystal infiltrated with graphene because of graphene’s nonreciprocity. The sensitivity of the optical conductivity of graphene on the magnetic field indicates its possibility of realizing tunable magnetooptical effects.
Show PACS
78.20.Ls Magneto-optical effects
68.65.Pq Graphene films
85.70.Sq Magnetooptical devices
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