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9 Aug 2010

Volume 97, Issue 6, Articles (06xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 97, 063101 (2010); http://dx.doi.org/10.1063/1.3475490 (3 pages)

Silvia Vignolini, Francesco Riboli, Francesca Intonti, Diederik Sybolt Wiersma, Laurent Balet, Lianhe H. Li, Marco Francardi, Annamaria Gerardino, Andrea Fiore, and Massimo Gurioli
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Cross-correlation frequency-resolved optical gating by molecular alignment for ultraviolet femtosecond pulse measurement

Peifen Lu, Jia Liu, Hao Li, Haifeng Pan, Jian Wu, and Heping Zeng

Appl. Phys. Lett. 97, 061101 (2010); http://dx.doi.org/10.1063/1.3478008 (3 pages) | Cited 5 times

Online Publication Date: 9 August 2010

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We experimentally demonstrate a molecular-alignment-based cross-correlation frequency-resolved optical gating technique for ultraviolet femtosecond pulse measurement, which use laser-induced impulsive alignment of gaseous molecules as the gate function instead of the phase-matched frequency mixing process in a nonlinear crystal. The spectrogram measurements and retrieving results of the intensity and phase of the second and third harmonic pulses centered at 400 and 267 nm are presented.
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42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation

Retrieving the effective parameters of metamaterials from the single interface scattering problem

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

Appl. Phys. Lett. 97, 061102 (2010); http://dx.doi.org/10.1063/1.3478241 (3 pages) | Cited 2 times

Online Publication Date: 9 August 2010

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In order to better understand when man-made structures may be considered as metamaterials with effective properties at optical frequencies, we study the scattering (reflection, transmission) of light at a single interface between a uniform half-space and a bulk metamaterial, i.e., a semi-infinite three-dimensional periodic structure. We accurately compute the scattering coefficients between plane waves and Bloch modes and test the validity of the single-Bloch-mode approximation within the metamaterial. The knowledge of the single-interface scattering coefficients allows us to propose an innovative method for deriving effective optical parameters.
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81.05.Xj Metamaterials for chiral, bianisotropic and other complex media
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
78.66.Sq Composite materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
77.22.Ch Permittivity (dielectric function)

Near room temperature continuous-wave laser operation from type-I interband transitions at wavelengths beyond 4 μm

M. Eibelhuber, T. Schwarzl, S. Pichler, W. Heiss, and G. Springholz

Appl. Phys. Lett. 97, 061103 (2010); http://dx.doi.org/10.1063/1.3478834 (3 pages) | Cited 9 times

Online Publication Date: 10 August 2010

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Nonradiative Auger recombination has limited room temperature continuous-wave (cw) operation of type-I interband lasers to wavelengths shorter than 3.36 μm. Using IV–VI semiconductor quantum well microdisk structures, near room temperature laser operation at longer wavelengths is achieved. Their active region consists of type-I single quantum wells of PbSe embedded in PbSrSe barriers. Under optical excitation, single mode cw emission at 4.3 μm is demonstrated up to 2 °C. This proves the feasibility of cw-operation of long wavelength interband lasers up to room temperature.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
42.55.Sa Microcavity and microdisk lasers
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Surface-plasmon enhancement of band gap emission from ZnCdO thin films by gold particles

W. F. Yang, R. Chen, B. Liu, G. G. Gurzadyan, L. M. Wong, S. J. Wang, and H. D. Sun

Appl. Phys. Lett. 97, 061104 (2010); http://dx.doi.org/10.1063/1.3476357 (3 pages) | Cited 6 times

Online Publication Date: 10 August 2010

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We present our study of the dependence of surface plasmon (SP) coupled band gap emission and defect emission on the sputtering time of gold particles on ZnCdO films. Eightfold enhancement of the band gap emission from ZnCdO thin films coated with Au particles is observed, while the defect emission is completely suppressed. The remarkable enhancement of the band gap emission is mainly attributed to the coupling between excitons in ZnCdO films and the SP of Au particles. While the suppression of the defect emission may be ascribed to a combined effect of the reduction in surface defects and the charge transfer from defect level to the Au Fermi level.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
71.35.-y Excitons and related phenomena
78.55.Et II-VI semiconductors
78.66.Hf II-VI semiconductors
82.30.Fi Ion-molecule, ion-ion, and charge-transfer reactions
71.55.Gs II-VI semiconductors

Systematic study of different transitions in high operating temperature quantum dots in a well photodetectors

Ajit V. Barve, Thomas Rotter, Yagya Sharma, Sang Jun Lee, Sam Kyu Noh, and Sanjay Krishna

Appl. Phys. Lett. 97, 061105 (2010); http://dx.doi.org/10.1063/1.3475022 (3 pages) | Cited 10 times

Online Publication Date: 10 August 2010

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We report a systematic study of different transitions in quantum dots-in-a-well infrared photodetectors in order to optimize the signal to noise ratio of the detector. Bound to continuum transitions offer very high extraction probability for photoexcited electrons but poor absorption coefficient, while the bound to bound transitions have higher absorption but poorer extraction probability. Bound to quasibound transitions are optimum for intermediate values of electric fields with superior signal to noise ratio. The bound to quasibound device has the detectivity of 4×1011 cm Hz1/2 W−1 (3V, f/2 system) at 77 K and 7.4×108 cm Hz1/2 W−1 at 200 K, which is highest reported detectivity at 200 K for detector with long wave cutoff wavelength.
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85.60.Gz Photodetectors (including infrared and CCD detectors)

Thulium pumped high power supercontinuum in loss-determined optimum lengths of tellurite photonic crystal fiber

Daniel Buccoliero, Henrik Steffensen, Ole Bang, Heike Ebendorff-Heidepriem, and Tanya M. Monro

Appl. Phys. Lett. 97, 061106 (2010); http://dx.doi.org/10.1063/1.3478835 (3 pages) | Cited 9 times

Online Publication Date: 11 August 2010

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We demonstrate the formation of an ultrabroad supercontinuum (SC) generated in short lengths of highly nonlinear tellurite photonic crystal fibers (PCFs) specifically designed for high power picosecond pumping at the thulium wavelength 1930 nm. The fibers exhibit high losses caused by material absorption below ∼ 500 nm and at long wavelengths >4000 nm by both material and confinement loss. The fibers are endlessly single-mode with a relative hole size of 0.4 and we tune the pitch (Λ) from 3 to 7 μm to achieve zero-dispersion wavelengths both below and above the pump. We show how the SC has a maximum width at an optimum fiber length after which the bandwidth and power decay due to losses. We thus obtain a maximum bandwidth of 4.6 μm for the PCF with the smallest Λ, i.e., 3 μm at an optimum length of only ∼ 2.8 cm.
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42.81.Dp Propagation, scattering, and losses; solitons
42.70.Qs Photonic bandgap materials
42.65.-k Nonlinear optics

Scaling of high-order harmonic efficiencies with visible wavelength drivers: A route to efficient extreme ultraviolet sources

Edilson L. Falcão-Filho, Chien-Jen Lai, Kyung-Han Hong, Vasileios-Marios Gkortsas, Shu-Wei Huang, Li-Jin Chen, and Franz X. Kärtner

Appl. Phys. Lett. 97, 061107 (2010); http://dx.doi.org/10.1063/1.3475772 (3 pages) | Cited 4 times

Online Publication Date: 11 August 2010

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Scaling of high-order harmonic generation (HHG) efficiency versus drive wavelength is experimentally studied using 800 and 400 nm pulses and theoretically modeled for visible drive wavelength. We demonstrate good agreement of experimental results with the calculations from a recently established semianalytic HHG model and discuss the feasibility of efficient-HHG-based extreme ultraviolet sources driven by visible ultrafast lasers. Our study shows that efficiencies of >10−5 can be achieved at ∼ 90 eV by selecting appropriate drive wavelengths with He under good phase matching conditions.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.72.Bj Visible and ultraviolet sources

Stochastic simulation of photon propagation in Si for extreme-ultraviolet mask-defect inspection

Ting-Hang Pei, Kuen-Yu Tsai, and Jia-Han Li

Appl. Phys. Lett. 97, 061108 (2010); http://dx.doi.org/10.1063/1.3478013 (3 pages)

Online Publication Date: 11 August 2010

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Extreme-ultraviolet (EUV) light is used to inspect the Si photomask by analyzing the reflective photons. We demonstrated the re-emitting EUV photons from the flat Si surface and a two-dimensional semicircular Si defect by using the Monte Carlo method with a Gaussian phase function, respectively. The results of a model based on the Feynman path integral matches those of the Monte Carlo method very well by multiplying a correction function. The intensity of re-emitting photons from the defect can offer enough signals at the angle intersecting the surface less than 20°.
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85.40.Hp Lithography, masks and pattern transfer
02.70.Uu Applications of Monte Carlo methods
02.50.Ey Stochastic processes

Angle-robust resonances in cross-shaped aperture arrays

L. Lin and A. Roberts

Appl. Phys. Lett. 97, 061109 (2010); http://dx.doi.org/10.1063/1.3481068 (3 pages) | Cited 2 times

Online Publication Date: 12 August 2010

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Computational and experimental investigations of angle-dependent light transmission through nanometric cross-shaped aperture arrays in thin metal films are presented. It is shown that high-transmission associated with the excitation of localized surface plasmons within the apertures can be tailored to exhibit polarization- and angle-independent performance.
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68.55.-a Thin film structure and morphology
71.10.Li Excited states and pairing interactions in model systems
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Switching of a single propagating plasmon by two quantum dots system

Nam-Chol Kim, Jian-Bo Li, Zhong-Jian Yang, Zhong-Hua Hao, and Qu-Quan Wang

Appl. Phys. Lett. 97, 061110 (2010); http://dx.doi.org/10.1063/1.3475769 (3 pages) | Cited 12 times

Online Publication Date: 12 August 2010

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We investigated the scattering property of a single plasmon interacting with two quantum dots coupled to one-dimensional surface plasmonic waveguide. We demonstrated that the transmission of a single plasmon could be switched on or off by adjusting spectral detuning and controlling spatial separation of the two quantum dots. These transport properties of the nanosystem could find the applications in plasmonic nanodevices and quantum information processing.
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42.79.Gn Optical waveguides and couplers
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
73.21.La Quantum dots

Electrically pumped ultraviolet random lasing from heterostructures formed by bilayered MgZnO films on silicon

Ye Tian, Xiangyang Ma, Dongsheng Li, and Deren Yang

Appl. Phys. Lett. 97, 061111 (2010); http://dx.doi.org/10.1063/1.3478217 (3 pages) | Cited 4 times

Online Publication Date: 12 August 2010

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We report on electrically pumped ultraviolet random lasing (RL) from heterostructures formed by bilayered MgZnO films on silicon, where Mg0.15Zn0.85O and MgxZn1−xO (x = 0.25 or above) films act as the light-emitting and barrier layers, respectively. While, with a barrier layer composed of a Mg0.20Zn0.80O film, only spontaneous electroluminescence occurs in the heterostructures. It has thus been proved that a large enough conduction-band offset (ΔEc) is necessary for the electrically pumped RL from the MgZnO film-based heterostructures. The ΔEc required herein is estimated to be ∼ 0.17 eV. The mechanism for the results as mentioned above has been tentatively elucidated.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Enhanced tunability of the multiphoton absorption cross-section in seeded CdSe/CdS nanorod heterostructures

Guichuan Xing, Sabyasachi Chakrabortty, Kok Loong Chou, Nimai Mishra, Cheng Hon Alfred Huan, Yinthai Chan, and Tze Chien Sum

Appl. Phys. Lett. 97, 061112 (2010); http://dx.doi.org/10.1063/1.3479048 (3 pages) | Cited 4 times

Online Publication Date: 13 August 2010

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We present a method to separately tune the multiphoton absorption (MPA) and multiphoton excited photoluminescence using semiconductor core/enlarged-shell quantum dots (QDs), where the enlarged shell greatly enhances the MPA cross-sections while varying the core size facilitates emission wavelength selectivity. Following two-photon absorption (2PA) primarily in the shell and ultrafast charge-carrier localization to the core, luminescence occurs. We exemplify the validity of this method with CdSe/CdS nanorod heterostructures and find that the 2PA cross-section is enlarged to ∼ 1.4×106 GM for 180 nm nanorods (with 800 nm, 150 fs laser pulse excitation) which is two to four orders larger than that of CdSe QDs.
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81.05.Dz II-VI semiconductors
78.67.Hc Quantum dots
78.55.Et II-VI semiconductors

Fast high fidelity hole spin initialization in a single InGaAs quantum dot

T. M. Godden, S. J. Boyle, A. J. Ramsay, A. M. Fox, and M. S. Skolnick

Appl. Phys. Lett. 97, 061113 (2010); http://dx.doi.org/10.1063/1.3476353 (3 pages) | Cited 7 times

Online Publication Date: 13 August 2010

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We demonstrate fast initialization of a single hole spin trapped in an InGaAs quantum dot with a fidelity F>99% and a 1/e time of ∼ 30 ps, by applying a magnetic field parallel to the growth direction. We show that the fidelity of the hole spin, prepared by ionization of a photo-generated electron-hole pair, is limited by the precession of the exciton spin due to the anisotropic exchange interaction.
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72.25.Dc Spin polarized transport in semiconductors
73.63.Kv Quantum dots
73.21.La Quantum dots
71.70.Gm Exchange interactions
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.40.Gk Tunneling

Effect of optical feedback to the ground and excited state emission of a passively mode locked quantum dot laser

Charis Mesaritakis, Christos Simos, Hercules Simos, Spiros Mikroulis, Igor Krestnikov, Eugenia Roditi, and Dimitris Syvridis

Appl. Phys. Lett. 97, 061114 (2010); http://dx.doi.org/10.1063/1.3477955 (3 pages) | Cited 2 times

Online Publication Date: 13 August 2010

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We present an experimental study on the effect of optical feedback in both ground and excited emission of a GaAs quantum dot passively mode locked laser. The experimental setup consisted of a long external cavity with variable cavity length and feedback level ranging from –50 to –20dB. The obtained experimental results show dependence of the emission properties on the cavity length regarding both the ground and excited state. In addition a strong tolerance of the laser operation to feedback at the excited state operation regime is observed.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Fc Modulation, tuning, and mode locking

Incorporating polaritonic effects in semiconductor nanowire waveguide dispersion

Lambert K. van Vugt, Brian Piccione, and Ritesh Agarwal

Appl. Phys. Lett. 97, 061115 (2010); http://dx.doi.org/10.1063/1.3479896 (3 pages) | Cited 10 times

Online Publication Date: 13 August 2010

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We present the calculated and measured energy-propagation constant (E-β) dispersion of CdS nanowire waveguides at room temperature, where we include dispersive effects via the exciton-polariton model using physical parameters instead of a phenomenological equation. The experimental data match well with our model while the phenomenological equation fails to capture effects originating due to light-matter interaction in nanoscale cavities. Due to the excitonic-polaritonic effects, the group index of the guided light peaks close to the band edge, which can have important implications for optical switching and sensor applications.
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42.79.Gn Optical waveguides and couplers
71.35.-y Excitons and related phenomena
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)

Amplifying magneto-optical photonic crystal

A. M. Grishin

Appl. Phys. Lett. 97, 061116 (2010); http://dx.doi.org/10.1063/1.3479910 (3 pages) | Cited 2 times

Online Publication Date: 13 August 2010

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We modeled transmission and Faraday rotation characteristics of Er-doped all-garnet [Bi3Fe5O12/Gd3Ga5O12]m photonic crystals in view of their application in C-band magneto-optical amplifiers. It is found that 48 layered 11.4 μm thick crystal at λ = 1532 nm provides 45° Faraday rotation and transmission as high as 85% being pumped with 100 mW/980 nm solid state laser diode.
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78.20.Ls Magneto-optical effects
42.70.Qs Photonic bandgap materials

Generation of multiple stress waves in silica glass in high fluence femtosecond laser ablation

Haofeng Hu, Xiaolei Wang, Hongchen Zhai, Nan Zhang, and Pan Wang

Appl. Phys. Lett. 97, 061117 (2010); http://dx.doi.org/10.1063/1.3479919 (3 pages) | Cited 2 times

Online Publication Date: 13 August 2010

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Shadowgraphs of dynamic processes outside and inside transparent target during the intense femtosecond laser ablation of silica glass are recorded. Two material ejections outside the target and two corresponding stress waves inside the target are observed at different energy fluences. In particular, a third stress wave can be observed at energy fluence as high as 40 J/cm2. The first wave is a thermoelastic wave, while the second and the third may be generated subsequently by the mechanical expansions. In addition, the magnitudes of the three stress waves decrease sequentially based on our analysis.
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81.65.-b Surface treatments
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity
62.30.+d Mechanical and elastic waves; vibrations
52.38.Mf Laser ablation
42.62.-b Laser applications

Interplay of cavity thickness and metal absorption in thin-film InGaN photonic crystal light-emitting diodes

Elizabeth Rangel, Elison Matioli, Hung-Tse Chen, Yong-Seok Choi, Claude Weisbuch, James S. Speck, and Evelyn L. Hu

Appl. Phys. Lett. 97, 061118 (2010); http://dx.doi.org/10.1063/1.3480421 (3 pages) | Cited 4 times

Online Publication Date: 13 August 2010

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Thin-film InGaN photonic crystal (PhC) light-emitting diodes (LEDs) with a total semiconductor thickness of either 800 nm or 3.45 μm were fabricated and characterized. Increased directional radiance relative to Lambertian emission was observed for both cases. The 800-nm-thick PhC LEDs yielded only a slight improvement in total light output over the 3.45-μm-thick PhC LEDs. Simulations indicate that, except for ultrathin devices well below 800 nm, the balance between PhC extraction and metal absorption at the backside mirror results in modal extraction efficiencies that are almost independent of device thickness, but highly dependent on mirror reflectivity.
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85.60.Jb Light-emitting devices
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Super-radiance in the sodium resonance lines from sodium iodide arc lamps

D. Karabourniotis and E. Drakakis

Appl. Phys. Lett. 97, 061501 (2010); http://dx.doi.org/10.1063/1.3479522 (3 pages) | Cited 1 time

Online Publication Date: 13 August 2010

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Super-radiance observed within the centers of the sodium resonance D lines emitted by arc lamps containing sodium iodide as additive in a high-pressure mercury plasma environment was studied by high-resolution emission spectroscopy. The spectral radiance of these self-reversed lines including super-radiance was simulated by considering a local enhancement of the source function due to the presence of an additional source of radiation near the arc wall. Causes of this hitherto unrecognized source of radiation are given.
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52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.80.Mg Arcs; sparks; lightning; atmospheric electricity
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.50.Dg Plasma sources
52.65.-y Plasma simulation
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Formation mechanisms of metallic Zn nanodots by using ZnO thin films deposited on n-Si substrates

J. M. Yuk, J. Y. Lee, Y. Kim, Y. S. No, T. W. Kim, and W. K. Choi

Appl. Phys. Lett. 97, 061901 (2010); http://dx.doi.org/10.1063/1.3475016 (3 pages) | Cited 2 times

Online Publication Date: 9 August 2010

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High-resolution transmission electron microscopy and energy dispersive x-ray spectroscopy results showed that metallic Zn nanodots (NDs) were fabricated through transformation of ZnO thin films by deposition of SiOx on ZnO/n-Si (100) heterostructures. The Zn NDs with various sizes and densities were formed due to the occurrence of the mass diffusion of atoms along the grain boundaries in the ZnO thin films. The fabrication mechanisms of metallic Zn NDs through transformation of ZnO thin films deposited on n-Si substrates are described on the basis of the experimental results.
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81.16.-c Methods of micro- and nanofabrication and processing
61.46.-w Structure of nanoscale materials
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods
68.37.Lp Transmission electron microscopy (TEM)
68.35.Fx Diffusion; interface formation

Photovoltaic characteristics of Pd doped amorphous carbon film/SiO2/Si

Ming Ma, Qingzhong Xue, Huijuan Chen, Xiaoyan Zhou, Dan Xia, Cheng Lv, and Jie Xie

Appl. Phys. Lett. 97, 061902 (2010); http://dx.doi.org/10.1063/1.3478230 (3 pages) | Cited 10 times

Online Publication Date: 9 August 2010

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The Pd doped amorphous carbon (a-C:Pd) films were deposited on n-Si substrates with or without a native SiO2 layer using magnetron sputtering. The photovoltaic characteristics of the a-C:Pd/SiO2/Si and a-C:Pd/Si junctions were studied. It is found that under light illumination of 15 mW/cm2 at room temperature, the a-C:Pd/SiO2/Si solar cell fabricated at 350 °C has a high power conversion efficiency of 4.7%, which is much better than the a-C/Si junctions reported before. The enhanced conversion efficiency is ascribed to the Pd doping and the increase in sp2-bonded carbon clusters in the carbon film caused by the high temperature deposition.
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68.55.A- Nucleation and growth
61.43.Dq Amorphous semiconductors, metals, and alloys
81.05.Gc Amorphous semiconductors
61.72.U- Doping and impurity implantation
85.40.Ry Impurity doping, diffusion and ion implantation technology
81.15.Cd Deposition by sputtering

Homogeneous linewidth of the intraband transition at 1.55 μm in GaN/AlN quantum dots

D. T. Nguyen, W. Wüster, Ph. Roussignol, C. Voisin, G. Cassabois, M. Tchernycheva, F. H. Julien, F. Guillot, and E. Monroy

Appl. Phys. Lett. 97, 061903 (2010); http://dx.doi.org/10.1063/1.3476340 (3 pages) | Cited 2 times

Online Publication Date: 10 August 2010

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We present homogeneous line width measurements of the intraband transition at 1.55 μm in GaN/AlN quantum dots by means of nonlinear spectral hole-burning experiments. The square-root dependence of the differential transmission signal with the incident pump power reveals the importance of electron-electron scattering in the population relaxation dynamics. We find on the contrary that this scattering process plays a minor role in the coherence relaxation dynamics since the homogeneous linewidth of 15 meV at 5 K does not depend on the incident pump power. This suggests the predominance of other dephasing mechanisms such as spectral diffusion, and temperature-dependent measurements support this hypothesis.
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73.21.La Quantum dots
68.35.Fx Diffusion; interface formation
71.20.Nr Semiconductor compounds
78.67.Hc Quantum dots

Optimization of the bimetallic gold and silver alloy nanoshell for biomedical applications in vivo

DaJian Wu and XiaoJun Liu

Appl. Phys. Lett. 97, 061904 (2010); http://dx.doi.org/10.1063/1.3479053 (3 pages) | Cited 9 times

Online Publication Date: 10 August 2010

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The far- and near-field properties of Au/Ag alloy nanoshell have been investigated by using Mie theory. With increasing Au content in shell, the dipole peak of alloy nanoshell shows a redshift from that of Ag nanoshell to that of Au nanoshell. It is found that the effect of the variation in shell thickness on the near-field for Au/Ag alloy nanoshells plays dominant role and the variation in the Au content leads to a significant modulation. We have further found that the near-infrared excitation at smaller wavelength can induce stronger near-field in Au/Ag alloy nanoshell with suitable geometry.
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87.85.Rs Nanotechnologies-applications
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
73.22.Lp Collective excitations
87.85.J- Biomaterials

Carrier transfer and recombination dynamics of a long-lived and visible range emission from multi-stacked GaN/AlGaN quantum dots

Je-Hyung Kim, Bong-Joon Kwon, Yong-Hoon Cho, Thomas Huault, Mathieu Leroux, and Julien Brault

Appl. Phys. Lett. 97, 061905 (2010); http://dx.doi.org/10.1063/1.3473777 (3 pages) | Cited 2 times

Online Publication Date: 10 August 2010

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We have investigated the optical properties of multi-stacked GaN/AlGaN self-assembled quantum dots (QDs) grown by molecular beam epitaxy. The QDs that emit visible light have a broad spectral range without incorporation of indium alloy because of the quantum-confined Stark effect. We found differences in the structural and optical properties between the layers of multi-stacked QDs. The carriers are more effectively transferred from the AlGaN barrier to the low energy side of the GaN QD emission than to the high energy side. We also observed long-lived carrier recombination dynamics for the visible range emission from QDs.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
78.67.Hc Quantum dots
81.16.Dn Self-assembly
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.65.Hb Quantum dots (patterned in quantum wells)
73.63.Kv Quantum dots

Kinetics of photoinduced surface patterning in chalcogenide thin films

Yu. Kaganovskii, D. L. Beke, and S. Kökényesi

Appl. Phys. Lett. 97, 061906 (2010); http://dx.doi.org/10.1063/1.3477957 (3 pages) | Cited 10 times

Online Publication Date: 10 August 2010

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The kinetics of photoinduced variations in surface profile in chalcogenide glass films under illumination is described. It is demonstrated that the competition between the stress-induced atomic flux (toward irradiated regions of the film) and the diffusion flux induced by an increase in the bulk energy due to broken bonds (and directed from irradiated to dark regions) can result in either a positive or negative net mass transfer in the irradiated region. Depending on the light intensity, one can obtain either formation of bumps or depressions in the illuminated regions.
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81.65.-b Surface treatments
66.30.J- Diffusion of impurities
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