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14 Mar 2011

Volume 98, Issue 11, Articles (11xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 98, 111101 (2011); http://dx.doi.org/10.1063/1.3561770 (3 pages)

Mike Woerdemann, Christina Alpmann, and Cornelia Denz
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Optical assembly of microparticles into highly ordered structures using Ince–Gaussian beams

Mike Woerdemann, Christina Alpmann, and Cornelia Denz

Appl. Phys. Lett. 98, 111101 (2011); http://dx.doi.org/10.1063/1.3561770 (3 pages) | Cited 7 times

Online Publication Date: 14 March 2011

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Ince–Gaussian (IG) beams are a third complete family of solutions of the paraxial Helmholtz equation. While many applications of Hermite–Gaussian and Laguerre–Gaussian beams have been demonstrated for manipulation of microparticles, the potential of the more general class of IG beams has not yet been exploited at all. We describe the unique properties of IG beams with respect to optical trapping applications, demonstrate a flexible experimental realization of arbitrary IG beams and prove the concept by creating two- and three-dimensional, highly ordered assemblies of typical microparticles. The concept is universal and can easily be integrated into existing holographic optical tweezers setups.
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42.50.Wk Mechanical effects of light on material media, microstructures and particles
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

Cloaking of a phase object in ghost imaging

Shu Gan, Su-Heng Zhang, Ting Zhao, Jun Xiong, Xiangdong Zhang, and Kaige Wang

Appl. Phys. Lett. 98, 111102 (2011); http://dx.doi.org/10.1063/1.3564895 (3 pages)

Online Publication Date: 14 March 2011

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Ghost imaging is a nonlocal imaging technique in which the image or diffraction pattern of an object can be observed through the intensity correlation measurement other than the intensity itself. Here, we report the experimental observation of invisibility cloaking in ghost imaging with thermal light. We show that when two identical phase-modulated objects are placed at equal distances from the thermal light source, they are offset completely in ghost imaging. The experimental results can be understood through the phase conjugation established by the intensity correlation of thermal light.
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42.30.Va Image forming and processing
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation

The formation of an intense filament controlled by interference of ultraviolet femtosecond pulses

Yongdong Wang, Yisan Zhang, Peng Chen, Liping Shi, Xin Lu, Jian Wu, Liang’en Ding, and Heping Zeng

Appl. Phys. Lett. 98, 111103 (2011); http://dx.doi.org/10.1063/1.3565158 (3 pages) | Cited 1 time

Online Publication Date: 14 March 2011

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We experimentally investigated the formation of a wavelength-scale photonic plasma grating induced by interference-assisted coalescence of two noncollinear ultraviolet femtosecond laser pulses. The period of the created plasma grating decreased with the crossing angle of the interacting laser pulses. For a proper small crossing angle, the noncollinear ultraviolet filaments were coalesced and an intense single ultraviolet filament was formed with a diameter of 5 μm which was below the focused limitation. This may provide a way to control ultraviolet femtosecond filamentation.
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52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.38.Hb Self-focussing, channeling, and filamentation in plasmas

Nonlinear switching in arrays of semiconductor on metal photonic wires

C. Milián and D. V. Skryabin

Appl. Phys. Lett. 98, 111104 (2011); http://dx.doi.org/10.1063/1.3565167 (3 pages) | Cited 2 times

Online Publication Date: 14 March 2011

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Using three-dimensional finite element modeling of the time independent Maxwell equations we demonstrate nonlinearity induced suppression of the power transfer in the arrays of nanoscale semiconductor on metal photonic wires. Nonlinear switching of the plasmonic modes can be achieved over few micron propagation distances using few hundred watts of the peak power.
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42.65.Pc Optical bistability, multistability, and switching, including local field effects
42.65.Wi Nonlinear waveguides
42.79.Gn Optical waveguides and couplers
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
02.70.Dh Finite-element and Galerkin methods

Third harmonic generation at 223 nm in the metallic regime of GaP

V. Roppo, J. V. Foreman, N. Akozbek, M. A. Vincenti, and M. Scalora

Appl. Phys. Lett. 98, 111105 (2011); http://dx.doi.org/10.1063/1.3565240 (3 pages) | Cited 4 times

Online Publication Date: 14 March 2011

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We demonstrate second and third harmonic generation from a GaP substrate 500 μm thick. The second harmonic field is tuned at the absorption resonance at 335 nm, and the third harmonic signal is tuned at 223 nm, in a range where the dielectric function is negative. These results show that a phase locking mechanism that triggers transparency at the harmonic wavelengths persists regardless of the dispersive properties of the medium, and that the fields propagate hundreds of microns without being absorbed even when the harmonics are tuned to portions of the spectrum that display metallic behavior.
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42.25.Bs Wave propagation, transmission and absorption

The effect of a semiconductor-metal interface on localized terahertz plasmons

C. A. Baron, M. Egilmez, C. J. E. Straatsma, K. H. Chow, J. Jung, and A. Y. Elezzabi

Appl. Phys. Lett. 98, 111106 (2011); http://dx.doi.org/10.1063/1.3565247 (3 pages) | Cited 3 times

Online Publication Date: 14 March 2011

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We demonstrate the terahertz frequency plasmonic characteristics of a metallic/semiconductor interface. The high-frequency transmission of terahertz radiation through dense ensembles of subwavelength sized Cu/CuxO microparticles via near-field coupling of localized plasmons is shown to increase when a CuxO/Au or CuxO/Pt interface is introduced. This finding introduces a previously undocumented characteristic of plasmonic interaction with material interfaces, and lays the physical groundwork for the integration of plasmonic circuits with traditional semiconductor electronics.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.70.Gq Microwave and radio-frequency interactions
72.30.+q High-frequency effects; plasma effects

Closed-form expression for the scattering coefficients at an interface between two periodic media

W. Śmigaj, P. Lalanne, J. Yang, T. Paul, C. Rockstuhl, and F. Lederer

Appl. Phys. Lett. 98, 111107 (2011); http://dx.doi.org/10.1063/1.3565970 (3 pages) | Cited 1 time

Online Publication Date: 15 March 2011

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We use the Bloch-mode orthogonality to derive simple closed-form expressions for the scattering coefficients at an interface between two periodic media, a computationally-challenging electromagnetic scattering problem that can be solved only with advanced numerical tools. The derivation relies on the assumptions that the interface is illuminated by the fundamental Bloch mode and that the two media have only slightly different geometrical parameters. Through comparison with fully-vectorial three-dimensional computations, the analytical expressions are shown to be highly predictive for various geometries, including dielectric waveguides and metallic metamaterials. They can thus be used with confidence for designing and engineering stacks of periodic structures.
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41.20.Jb Electromagnetic wave propagation; radiowave propagation
02.10.Ud Linear algebra

Measurement of hard x-ray lens wavefront aberrations using phase retrieval

Manuel Guizar-Sicairos, Suresh Narayanan, Aaron Stein, Meredith Metzler, Alec R. Sandy, James R. Fienup, and Kenneth Evans-Lutterodt

Appl. Phys. Lett. 98, 111108 (2011); http://dx.doi.org/10.1063/1.3558914 (3 pages) | Cited 4 times

Online Publication Date: 15 March 2011

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Measuring the deviation of a wavefront from a sphere provides valuable feedback on lens alignment and manufacturing errors. We demonstrate that these aberrations can be accurately measured at hard x-ray wavelengths, from far-field intensity measurements, using phase retrieval with a moveable structure in the beam path. We induce aberrations on a hard x-ray kinoform lens through deliberate misalignment and show that the reconstructed wavefronts are in good agreement with numerical simulations. Reconstructions from independent data, with the structure at different longitudinal positions and significantly separated from the beam focus, agreed with a root mean squared error of 0.006 waves.
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07.85.-m X- and γ-ray instruments
42.79.Bh Lenses, prisms and mirrors
42.30.Rx Phase retrieval

Four-level polarization discriminator based on a surface plasmon polaritonic crystal

M. I. Benetou, B. C. Thomsen, P. Bayvel, W. Dickson, and A. V. Zayats

Appl. Phys. Lett. 98, 111109 (2011); http://dx.doi.org/10.1063/1.3561748 (3 pages) | Cited 2 times

Online Publication Date: 17 March 2011

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A compact, four-level polarization discriminator based on a surface plasmon polaritonic crystal (SPPC) has been experimentally demonstrated. It is able to uniquely resolve and spatially separate four signals that have been linearly polarized at azimuth angles 0°, 45°, 90°, and 135°. It exploits the excitation of multiple surface plasmon polariton eigenmodes in nondegenerate directions when the SPPC is illuminated with monochromatic light. The device is planar and of micrometer scale, which makes it suitable for on-chip integration and miniaturization of photonic circuits.
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84.30.Qi Modulators and demodulators; discriminators, comparators, mixers, limiters, and compressors
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
42.79.Sz Optical communication systems, multiplexers, and demultiplexers

Monopole antenna arrays for optical trapping, spectroscopy, and sensing

A. E. Çetin, Ahmet Ali Yanik, Cihan Yilmaz, Sivasubramanian Somu, Ahmed Busnaina, and Hatice Altug

Appl. Phys. Lett. 98, 111110 (2011); http://dx.doi.org/10.1063/1.3559620 (3 pages) | Cited 4 times

Online Publication Date: 17 March 2011

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We introduce a nanoplasmonic platform merging multiple modalities for optical trapping, nanospectroscopy, and biosensing applications. Our platform is based on surface plasmon polariton driven monopole antenna arrays combining complementary strengths of localized and extended surface plasmons. Tailoring of spectrally narrow resonances lead to large index sensitivities (S ∼ 675 nm/RIU) with record high figure of merits (FOM ∼ 112.5). These monopole antennas supporting strong light localization with easily accessible near-field enhanced hotspots are suitable for vibrational nanospectroscopy and optical trapping. Strong optical forces (350 pN/W/μm2) are shown at these hotspots enabling directional control with incident light polarization.
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87.80.Cc Optical trapping
42.79.-e Optical elements, devices, and systems
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
84.40.Ba Antennas: theory, components and accessories

A multicolor microfluidic droplet dye laser with single mode emission

G. Aubry, Q. Kou, J. Soto-Velasco, C. Wang, S. Meance, J. J. He, and A. M. Haghiri-Gosnet

Appl. Phys. Lett. 98, 111111 (2011); http://dx.doi.org/10.1063/1.3565242 (3 pages) | Cited 5 times

Online Publication Date: 17 March 2011

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A digital microfluidic dye laser that integrates a Fabry–Perot cavity with two fiber-based mirrors is shown to exhibit a single mode emission. In addition, fast switching is achieved via the alternation of droplet streams that contain two different dyes. Single-longitudinal-mode emission is observed for each dye wavelength (at 565 and 586 nm) with a linewidth narrower than 0.12 nm. This system appears thus well suited for on-chip spectroscopy and flow cytometry.
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42.55.Mv Dye lasers
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.79.Bh Lenses, prisms and mirrors
42.55.Wd Fiber lasers

Spatially resolved lasers using a glassy cholesteric liquid crystal film with lateral pitch gradient

Simon K. H. Wei and Shaw H. Chen

Appl. Phys. Lett. 98, 111112 (2011); http://dx.doi.org/10.1063/1.3568889 (3 pages) | Cited 1 time

Online Publication Date: 17 March 2011

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To fabricate spatially resolved glassy cholesteric liquid crystal (CLC) lasers, a lateral pitch gradient was introduced by thermally activated diffusion across the interface of two films comprising nematic and cholesteric oligofluorene doped with a red-emitting oligifluorene. The formation of spatially resolved Grandjean–Cano bands was accountable by strong surface anchoring at substrates and the qualitative chiral concentration profile. Across each band there was a common stop band, and a set of bands produced multiple lasing peaks across the spectral range determined by light-emitter’s fluorescence spectrum. The resultant lasing thresholds, 6.6–7.6 mJ/cm2, and slope efficiencies, 0.2%–1.5%, are superior to those reported to date for gradient-pitch CLC lasers.
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42.79.Kr Display devices, liquid-crystal devices
42.70.Hj Laser materials
42.70.Df Liquid crystals
42.60.By Design of specific laser systems

Manipulation of optical field distribution in layered composite polymeric-inorganic waveguides

Jussi Hiltunen, Sanna Uusitalo, Pentti Karioja, Stuart Pearce, Martin Charlton, Meng Wang, Jarkko Puustinen, and Jyrki Lappalainen

Appl. Phys. Lett. 98, 111113 (2011); http://dx.doi.org/10.1063/1.3567756 (3 pages)

Online Publication Date: 18 March 2011

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We discuss the manipulation of optical field distribution in a low-refractive index polymeric waveguide by depositing a thin high refractive index Ta2O5 film on top of the waveguide. According to microstructure studies, the sputtered Ta2O5 thin films deposited on the polymer layer were very smooth with root mean square surface roughness value of 0.58 nm, had amorphous phase, and were optimal for integrated optical devices. Both computational and experimental optical studies suggest that the inorganic-polymeric composite waveguide design greatly increases the intensity distribution of the propagating mode at the surface. Consequently, the interaction of the optical field with the ambient surrounding medium is enhanced by a factor of about 1.7 in order of magnitude.
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42.79.Gn Optical waveguides and couplers
42.82.Et Waveguides, couplers, and arrays
42.70.Jk Polymers and organics

Deep-ultraviolet light-emitting diodes with gradually increased barrier thicknesses from n-layers to p-layers

Miao-Chan Tsai, Sheng-Horng Yen, and Yen-Kuang Kuo

Appl. Phys. Lett. 98, 111114 (2011); http://dx.doi.org/10.1063/1.3567786 (3 pages) | Cited 2 times

Online Publication Date: 18 March 2011

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In this work, the structure with gradually increased barrier thicknesses from the n-layers to p-layers is proposed to replace the traditional structure with equal barrier thickness in deep-ultraviolet AlGaN light-emitting diodes. Simulation approach yields to a result that, when increased barrier thicknesses are used, the distribution of electron and hole carriers inside the active region becomes quite uniform, which leads to efficient recombination of electrons and holes and thereby a significant enhancement in output power.
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85.60.Jb Light-emitting devices

Turbulence-free ghost imaging

Ronald E. Meyers, Keith S. Deacon, and Yanhua Shih

Appl. Phys. Lett. 98, 111115 (2011); http://dx.doi.org/10.1063/1.3567931 (3 pages) | Cited 12 times

Online Publication Date: 18 March 2011

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Atmospheric turbulence is a serious problem for satellite and aircraft-to-ground based classical imaging. Taking advantage of the natural, nonfactorizable, point-to-point correlation of thermal light, this experiment demonstrated turbulence-free ghost imaging, which will be extremely useful for these applications. In addition, this observation suggests that the nontrivial intensity-intensity correlation of thermal light cannot be caused by the statistical correlation of intensity fluctuations.
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42.30.-d Imaging and optical processing

Strong-field plasmonic electron acceleration with few-cycle, phase-stabilized laser pulses

P. Rácz, S. E. Irvine, M. Lenner, A. Mitrofanov, A. Baltuška, A. Y. Elezzabi, and P. Dombi

Appl. Phys. Lett. 98, 111116 (2011); http://dx.doi.org/10.1063/1.3567941 (3 pages) | Cited 7 times

Online Publication Date: 18 March 2011

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We carried out experimental investigations on surface plasmon enhanced electron acceleration with few-cycle, carrier-envelope phase (CEP) stabilized laser pulses. We determined the spectrum of electrons accelerated in the plasmonic field and found that signatures of the phase stabilized optical waveform driving the individual electron trajectories are washed out in the electron spectra. We attribute this effect to nanoscale surface roughness of the metallic samples, as supported by extensive numerical simulations. This finding explains the previously observed, low CEP sensitivity of photoemission processes from metallic films and enables the development of femtosecond electron sources for ultrafast time-resolved applications.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.47.J- Ultrafast spectroscopy (<1 psec)
68.35.B- Structure of clean surfaces (and surface reconstruction)

High-Q transverse-electric/transverse-magnetic photonic crystal nanobeam cavities

Murray W. McCutcheon, Parag B. Deotare, Yinan Zhang, and Marko Lončar

Appl. Phys. Lett. 98, 111117 (2011); http://dx.doi.org/10.1063/1.3568897 (3 pages) | Cited 4 times

Online Publication Date: 18 March 2011

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We experimentally demonstrate high quality factor dual-polarized photonic crystal nanobeam cavities. The free-standing nanobeams are fabricated in a 500 nm thick silicon layer, and are probed using both tapered optical fiber and free-space resonant scattering set-ups. We measure Q factors greater than 104 for both transverse magnetic (TM) and transverse electric modes, and observe fiber transmission drops as large as 1−T = 0.8 at the TM mode resonances.
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85.60.-q Optoelectronic devices
42.81.Wg Other fiber-optical devices
42.70.Qs Photonic bandgap materials
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The spatiotemporal oscillation characteristics of the dielectric wall sheath in stationary plasma thrusters

Fengkui Zhang, Daren Yu, Yongjie Ding, and Hong Li

Appl. Phys. Lett. 98, 111501 (2011); http://dx.doi.org/10.1063/1.3564898 (3 pages) | Cited 4 times

Online Publication Date: 14 March 2011

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A two-dimensional particle in cell model is used to simulate the sheath oscillation in stationary plasma thrusters. The embedded secondary electron emission (SEE) submodel is based on that of Morozov but improved by considering the electron elastic reflection effect. The simulation results show that when the SEE coefficient is smaller than one due to the relative low electron temperature, one-dimensional static sheath can be found; as the electron temperature increase, the SEE coefficient approaches to one and temporal oscillation sheath appears; when the electron temperature increases so high that the SEE coefficient is beyond one, the sheath oscillates not only in time but also in space.
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52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
52.40.Kh Plasma sheaths
52.75.-d Plasma devices
52.65.Rr Particle-in-cell method
52.25.Os Emission, absorption, and scattering of electromagnetic radiation

Surface reactions as carbon removal mechanism in deposition of silicon dioxide films at atmospheric pressure

R. Reuter, D. Ellerweg, A. von Keudell, and J. Benedikt

Appl. Phys. Lett. 98, 111502 (2011); http://dx.doi.org/10.1063/1.3565965 (3 pages) | Cited 5 times

Online Publication Date: 14 March 2011

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The deposition of thin SiOxCyHz or SiOxHy films by means of an atmospheric pressure microplasma jet with helium/hexamethyldisiloxane (HMDSO)/O2 mixtures and the surface reactions involving oxygen have been studied. It is shown, that the carbon content in the film can be controlled by choosing the right O2/HMDSO ratio in the gas mixture. The microplasma jet geometry and localization of the deposition at a spot of few square millimeters allows studying the role of oxygen in the deposition process. This is done by alternating application of He/HMDSO plasma and He/O2 plasma to the same deposition area, here achieved by a treatment of a rotating substrate by two jets with above mentioned gas mixtures. It is shown that carbon-free SiOxHy film can be deposited in this way and that surface reaction with oxygen is the main loss mechanism of carbon from the film.
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82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
52.77.Dq Plasma-based ion implantation and deposition
68.55.A- Nucleation and growth
81.15.Jj Ion and electron beam-assisted deposition; ion plating
81.15.Kk Vapor phase epitaxy; growth from vapor phase
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Transient surface photovoltage in n- and p-GaN as probed by x-ray photoelectron spectroscopy

Hikmet Sezen, Ekmel Ozbay, Ozgur Aktas, and Sefik Suzer

Appl. Phys. Lett. 98, 111901 (2011); http://dx.doi.org/10.1063/1.3564892 (3 pages) | Cited 6 times

Online Publication Date: 14 March 2011

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Transient surface photovoltage (SPV) of n and p-GaN was measured using x-ray photoelectron spectroscopy (XPS) with a time resolution of 0.1 s. The measured SPV transients for both n- and p-GaN are ⪡0.1 s, and for the n-GaN they are not affected by flood-gun electrons. However, for the p-GaN, the transient character of the SPV is dramatically changed in the presence of flood-gun electrons. The combination of time-resolved XPS, flood gun, and laser illumination give us a new way to study the surface electronic structure and other surface properties of semiconducting materials in a chemically specific fashion.
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79.60.Bm Clean metal, semiconductor, and insulator surfaces
71.20.Nr Semiconductor compounds
73.25.+i Surface conductivity and carrier phenomena

Quantitative effective atomic number imaging using simultaneous x-ray absorption and phase shift measurement

Taihei Mukaide, Masatoshi Watanabe, Kazuhiro Takada, Atsuo Iida, Kazunori Fukuda, and Takashi Noma

Appl. Phys. Lett. 98, 111902 (2011); http://dx.doi.org/10.1063/1.3565171 (3 pages)

Online Publication Date: 14 March 2011

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A scanning type x-ray imaging system which measures the absorption and differential phase shift in a material quantitatively and simultaneously has been developed. The absorption and differential phase are used to obtain the effective atomic number of organic material samples which closely reflects their chemical composition. An effective atomic number map of polymer fibers has been obtained. The experimentally obtained effective atomic numbers of these polymers agree well with the corresponding calculated values.
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78.70.Dm X-ray absorption spectra
07.85.-m X- and γ-ray instruments
07.68.+m Photography, photographic instruments; xerography

Raman scattering in InAs/AlGaAs quantum dot nanostructures

E. Giulotto, M. Geddo, M. S. Grandi, G. Guizzetti, G. Trevisi, L. Seravalli, P. Frigeri, and S. Franchi

Appl. Phys. Lett. 98, 111903 (2011); http://dx.doi.org/10.1063/1.3567024 (3 pages) | Cited 1 time

Online Publication Date: 15 March 2011

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We report on Raman scattering experiments on InAs/AlxGa1−xAs quantum dot heterostructures with 0 ≤ x ≤ 0.6. The samples were prepared by using molecular beam epitaxy (MBE) and atomic layer MBE for the growth of different layers. For x>0, we detected several lines originating from the AlxGa1−xAs alloy. These can be related to scattering from GaAs-like and AlAs-like phonons with q ≅ 0, and weaker scattering from disorder-activated phonons with q ≠ 0. In particular, we identified a line at ∼ 250 cm−1 as due to disorder-activated longitudinal optical phonons in the alloy. This conclusion is different than the attribution of this line to scattering from dots and, consequently, we do not recognize the possibility of deriving any information about the actual composition of the dots from an analysis of this line as proposed by other authors.
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78.67.Hc Quantum dots
78.30.Fs III-V and II-VI semiconductors
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.ag Semiconductors

Effect of annealing on the microstructure and optical properties of ZnO/V2O5 composite

C. W. Zou, X. D. Yan, R. Q. Chen, Z. Y. Wu, A. Alyamani, and W. Gao

Appl. Phys. Lett. 98, 111904 (2011); http://dx.doi.org/10.1063/1.3566997 (3 pages) | Cited 2 times

Online Publication Date: 15 March 2011

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Vanadium pentoxide (V2O5) films capped with a thin ZnO layer were prepared by magnetron sputtering at room temperature. The effect of annealing on the microstructure and optical properties of films was systematically investigated. Results indicated that the initially smooth films transformed to porous composite nanocrystals at 500 °C and then further to agglomerated nanoslices at 550 °C. This microstructure transformation is attributed to the distinct temperature-sensitive crystallization of V2O5. The annealed films exhibited enhanced visible photoluminescence, which was attributed to the coupling between V2O5 nanorods and ZnO nanoparticles as well as the improved V2O5 crystallinity.
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61.72.Cc Kinetics of defect formation and annealing
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
64.70.Nd Structural transitions in nanoscale materials
81.07.Bc Nanocrystalline materials
78.67.Sc Nanoaggregates; nanocomposites
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)

Multiple excitation of silicon nanoclusters during erbium sensitization process in silicon rich oxide host

M. Q. Huda and S. Subrina

Appl. Phys. Lett. 98, 111905 (2011); http://dx.doi.org/10.1063/1.3565964 (3 pages) | Cited 1 time

Online Publication Date: 16 March 2011

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Sensitization of erbium through silicon nanocluster (Si-nc) in silicon rich oxide host has been analyzed through a statistical approach. Our analysis shows that significant fraction of Si-ncs can experience multiple excitations during the Er lifecycle. The probability of Si-nc being excited at every alternate cycles of excitation increases from small fractions to percentage levels for incident flux levels above 1018/cm2 s. We show that, for typical values of Er and Si-nc incorporation, saturating effects in Er luminescence starts at flux levels much lower than that for Si-nc excitation. Occurrence of multiple excitation of Si-nc has been correlated with the deteriorating effects in Er sensitization at higher flux incidence.
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78.55.Hx Other solid inorganic materials
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters

Synthesis and physical properties of ZnO/CdTe core shell nanowires grown by low-cost deposition methods

V. Consonni, G. Rey, J. Bonaimé, N. Karst, B. Doisneau, H. Roussel, S. Renet, and D. Bellet

Appl. Phys. Lett. 98, 111906 (2011); http://dx.doi.org/10.1063/1.3567764 (3 pages) | Cited 9 times

Online Publication Date: 17 March 2011

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Vertically aligned ZnO/CdTe core/shell nanowire arrays have been grown by low-cost deposition techniques. ZnO nanowires have a wurtzite structure and are c-axis oriented. The CdTe shell completely covers ZnO nanowires and consists of nanograins, which are slightly oriented along the 〈111〉 direction owing to a grain growth process driven by surface energy minimization. Their nucleation follows the Volmer–Weber growth mechanism: in particular, island coalescence results in the generation of high tensile stress, which significantly reduces the CdTe optical band gap. Furthermore, both ZnO and CdTe exhibit excitonic emission bands around 3.36 eV and 1.56 eV, respectively.
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81.07.Gf Nanowires
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
68.65.La Quantum wires (patterned in quantum wells)
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)
78.67.Uh Nanowires
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