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22 Nov 2010

Volume 97, Issue 21, Articles (21xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 97, 211101 (2010); http://dx.doi.org/10.1063/1.3517566 (3 pages)

J. Haase, S. Shinohara, P. Mundra, G. Risse, V. G. Lyssenko, H. Fröb, M. Hentschel, A. Eychmüller, and K. Leo
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Hemispherical resonators with embedded nanocrystal quantum rod emitters

J. Haase, S. Shinohara, P. Mundra, G. Risse, V. G. Lyssenko, H. Fröb, M. Hentschel, A. Eychmüller, and K. Leo

Appl. Phys. Lett. 97, 211101 (2010); http://dx.doi.org/10.1063/1.3517566 (3 pages) | Cited 2 times

Online Publication Date: 22 November 2010

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We report a technique to prepare hemispherical resonators on a distributed Bragg reflector (DBR). This so-called hydrophobic spreading allows the creation of hemispherical structures with diameters ranging from 5 to 50 μm. By embedding semiconductor nanocrystal quantum rods (NQRs) into these structures, we achieve a coupling of their emission into whispering-gallery modes. Although the NQR-emission is confined in three dimensions, the DBR is transparent for the excitation, allowing selective excitation of different regions of the hemisphere. Employing a two-dimensional model to approximately describe relevant modes, we are able to estimate the refractive index and diameters of the hemispheres from spectral data.
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42.79.Bh Lenses, prisms and mirrors
42.82.Cr Fabrication techniques; lithography, pattern transfer

Multilayered graphene efficiently formed by mechanical exfoliation for nonlinear saturable absorbers in fiber mode-locked lasers

You Min Chang, Hyungseok Kim, Ju Han Lee, and Yong-Won Song

Appl. Phys. Lett. 97, 211102 (2010); http://dx.doi.org/10.1063/1.3521257 (3 pages) | Cited 5 times

Online Publication Date: 22 November 2010

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An efficiently prepared graphene from a bulk graphite using mechanical exfoliation is experimentally investigated for the first practical application to ultrafast photonics. Overcoming the limitations of the method in its size and atomic layer control, the multilayered graphene guarantees a nonlinear intensity modulation. After confirming its excellent crystal quality and few-layered nanostructure employing Raman analysis and atomic force microscopy the graphene layer is introduced into a fiber laser as an intracavity saturable absorber to realize the passive mode-locking that produces picosecond pulses at the repetition rate of 10.9 MHz. Extinction ratio of the resultant pulsed output is higher than 40 dB.
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42.70.-a Optical materials
81.05.ue Graphene
42.55.Wd Fiber lasers
42.60.Fc Modulation, tuning, and mode locking
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials

Ultrafast gain dynamics in InP quantum-dot optical amplifiers

Wolfgang Langbein, Valentina Cesari, Francesco Masia, Andrey B. Krysa, Paola Borri, and Peter M. Smowton

Appl. Phys. Lett. 97, 211103 (2010); http://dx.doi.org/10.1063/1.3518715 (3 pages)

Online Publication Date: 22 November 2010

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We measured the gain dynamics at the ground-state transition in an electrically pumped InP/AlGaInP quantum-dot optical amplifier at room temperature by femtosecond differential transmission. The gain shows an ultrafast recovery within 200 fs, even faster than in state-of-the-art InAs/GaAs quantum-dot amplifiers. This finding, likely to be due to the less confined and more closely spaced hole levels in InP dots, is promising for optical signal processing at high bit rates. We furthermore measured the pump-induced refractive index changes and deduced a linewidth enhancement factor similar to the one in InAs/GaAs quantum dots.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Silicon emitter for shortwave infrared (1.6–3 μm) band by light down-conversion

V. K. Malyutenko, V. V. Bogatyrenko, and A. M. Tykhonov

Appl. Phys. Lett. 97, 211104 (2010); http://dx.doi.org/10.1063/1.3521277 (3 pages)

Online Publication Date: 22 November 2010

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No silicon-based light emitting diodes exist for shortwave infrared (1.6–3.0 μm) band due to bandgap limitations imposed on luminescence wavelengths. To alleviate this problem, we propose a photonic device in which below-bandgap radiation comes as the result of the thermal emission enhanced by free charge carriers generated by the above-bandgap excitation (light downconversion). With this approach, we demonstrate high-temperature (T>300 K) large-area (20×20 mm2) Si emitter with stable high-power output ( ∼ 100 mW/cm2) and prescribed spectrum inside the 1.6–3 μm band for applications such as dynamic scene simulation devices operating at frequencies above 1 kHz.
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85.60.Jb Light-emitting devices
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation

Direct laser writing of whispering gallery microcavities by two-photon polymerization

Zhao-Pei Liu, Yan Li, Yun-Feng Xiao, Bei-Bei Li, Xue-Feng Jiang, Yi Qin, Xiao-Bo Feng, Hong Yang, and Qihuang Gong

Appl. Phys. Lett. 97, 211105 (2010); http://dx.doi.org/10.1063/1.3517493 (3 pages) | Cited 1 time

Online Publication Date: 22 November 2010

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We demonstrate that high-Q polymer whispering gallery microcavities can be directly written by the two-photon polymerization of zirconium/silicon hybrid sol-gel, benefiting from the high spatial resolution and three-dimensional nature of this direct laser writing technique. The quality factors of the fabricated whispering gallery microcavities are up to 1.48×105 limited by the material absorption. The surface roughness is less than 12 nm. This opens the way to fabricate intricate three-dimensional microcavities for the fundamental and applied physics research based on optical resonators.
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42.79.-e Optical elements, devices, and systems
42.70.Jk Polymers and organics
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)
42.82.Cr Fabrication techniques; lithography, pattern transfer

Influence of carrier dynamics on the modulation bandwidth of quantum-dot based nanocavity devices

M. Lorke, T. R. Nielsen, and J. Mørk

Appl. Phys. Lett. 97, 211106 (2010); http://dx.doi.org/10.1063/1.3520525 (3 pages) | Cited 3 times

Online Publication Date: 23 November 2010

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We theoretically investigate the modulation response of quantum-dot based nanocavity light emitting devices. For high Purcell enhancement factors, our theory predicts the possibility of decreasing the modulation bandwidth with increasing scattering rate into the lasing quantum-dot state. This counterintuitive effect is investigated using a microscopic semiconductor model. The resulting guidelines for possible optimizations of quantum-dot based nanocavity laser devices are given.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
85.35.-p Nanoelectronic devices
72.20.Fr Low-field transport and mobility; piezoresistance
85.60.Jb Light-emitting devices

Ultrathin, ultrasmooth, and low-loss silver films via wetting and annealing

W. Chen, K. P. Chen, M. D. Thoreson, A. V. Kildishev, and V. M. Shalaev

Appl. Phys. Lett. 97, 211107 (2010); http://dx.doi.org/10.1063/1.3514257 (3 pages) | Cited 2 times

Online Publication Date: 23 November 2010

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We have demonstrated that a thermal annealing treatment can reduce the optical losses in ultrathin, ultrasmooth, silver films deposited on a Ge wetting layer to values as low as the bulk material value and at the same time maintain an ultrasmooth surface. The annealing effect is sensitive to the annealing temperature and time, both of which should be carefully controlled. This annealing treatment is also effective for Ag–SiO2 multilayer composite films.
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78.66.Bz Metals and metallic alloys
68.55.at Other materials
68.55.J- Morphology of films
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
68.08.Bc Wetting
81.40.Gh Other heat and thermomechanical treatments

Photopolymerized microscopic vortex beam generators: Precise delivery of optical orbital angular momentum

Etienne Brasselet, Mangirdas Malinauskas, Albertas Žukauskas, and Saulius Juodkazis

Appl. Phys. Lett. 97, 211108 (2010); http://dx.doi.org/10.1063/1.3517519 (3 pages) | Cited 2 times

Online Publication Date: 23 November 2010

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Direct femtosecond laser photopolymerization is used to fabricate high resolution microscopic spiral phase plates. The total phase change all around their center is prepared to be a integer multiple of 2π for the operating wavelength in the visible domain. The optical performances of the spiral plates are measured and we propose a simple single beam interferometric technique to characterize the phase singularity of the generated vortex beams. The experimental results are compared to simulations and a satisfying agreement is obtained. Potential of large scale fabrication, templating, and smart spiral plate architectures are also illustrated.
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42.79.Ci Filters, zone plates, and polarizers
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
07.60.Ly Interferometers
42.62.-b Laser applications
42.86.+b Optical workshop techniques

High-fidelity operation of quantum photonic circuits

Anthony Laing, Alberto Peruzzo, Alberto Politi, Maria Rodas Verde, Matthaeus Halder, Timothy C. Ralph, Mark G. Thompson, and Jeremy L. O’Brien

Appl. Phys. Lett. 97, 211109 (2010); http://dx.doi.org/10.1063/1.3497087 (3 pages) | Cited 1 time

Online Publication Date: 23 November 2010

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We demonstrate photonic quantum circuits that operate at the stringent levels that will be required for future quantum information science and technology. These circuits are fabricated from silica-on-silicon waveguides forming directional couplers and interferometers. While our focus is on the operation of quantum circuits, to test this operation required construction of a photon source that produced near-identical pairs of photons. We show nonclassical interference with two photons and a two-photon entangling logic gate that operate with near-unit fidelity. These results are a significant step toward large-scale operation of photonic quantum circuits.
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03.67.Lx Quantum computation architectures and implementations
84.30.Sk Pulse and digital circuits
42.50.-p Quantum optics

Injection of midinfrared surface plasmon polaritons with an integrated device

J.-P. Tetienne, A. Bousseksou, D. Costantini, R. Colombelli, A. Babuty, I. Moldovan-Doyen, Y. De Wilde, C. Sirtori, G. Beaudoin, L. Largeau, O. Mauguin, and I. Sagnes

Appl. Phys. Lett. 97, 211110 (2010); http://dx.doi.org/10.1063/1.3519985 (3 pages)

Online Publication Date: 24 November 2010

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We demonstrate a compact, integrated device in which surface plasmon polaritons (SPPs) are injected into a passive metal waveguide. We directly excite a SPP mode at a metal-air interface using a room-temperature midinfrared quantum cascade laser which is integrated onto the microchip. The SPP generation relies on end-fire coupling and is demonstrated via both far-field and near-field imaging techniques in the midinfrared. On one hand, a metallic diffraction grating is used to scatter in the far-field a portion of the propagating SPPs, thus allowing their detection with a microbolometer camera. On the other hand, direct images of the generated SPPs in the near-field were collected with a scanning optical microscope.
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42.82.-m Integrated optics
42.79.Dj Gratings
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

A low-noise, single-photon avalanche diode in standard 0.13 μm complementary metal-oxide-semiconductor process

Ryan M. Field, Jenifer Lary, John Cohn, Liam Paninski, and Kenneth L. Shepard

Appl. Phys. Lett. 97, 211111 (2010); http://dx.doi.org/10.1063/1.3518473 (3 pages)

Online Publication Date: 24 November 2010

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We present the design and characterization of a single-photon avalanche diode (SPAD) fabricated with a standard 0.13 μm complementary metal-oxide-semiconductor process. We have developed a figure of merit for SPADs when these detectors are employed in high frame-rate fluorescent lifetime imaging microscopy, which allows us to specify an optimal bias point for the diode and compare our diode with other published devices. At its optimum bias point at room temperature, our SPAD achieves a photon detection probability of 29% while exhibiting a dark count rate of only 231 Hz and an impulse response of 198 ps.
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85.60.Dw Photodiodes; phototransistors; photoresistors
85.60.Gz Photodetectors (including infrared and CCD detectors)
42.79.Pw Imaging detectors and sensors

Lensfree color imaging on a nanostructured chip using compressive decoding

Bahar Khademhosseinieh, Gabriel Biener, Ikbal Sencan, and Aydogan Ozcan

Appl. Phys. Lett. 97, 211112 (2010); http://dx.doi.org/10.1063/1.3521410 (3 pages)

Online Publication Date: 24 November 2010

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We demonstrate subpixel level color imaging capability on a lensfree incoherent on-chip microscopy platform. By using a nanostructured substrate, the incoherent emission from the object plane is modulated to create a unique far-field diffraction pattern corresponding to each point at the object plane. These lensfree diffraction patterns are then sampled in the far-field using a color sensor-array, where the pixels have three different types of color filters at red, green, and blue (RGB) wavelengths. The recorded RGB diffraction patterns (for each point on the structured substrate) form a basis that can be used to rapidly reconstruct any arbitrary multicolor incoherent object distribution at subpixel resolution, using a compressive sampling algorithm. This lensfree computational imaging platform could be quite useful to create a compact fluorescent on-chip microscope that has color imaging capability.
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42.30.Va Image forming and processing
07.60.Pb Conventional optical microscopes
42.30.Wb Image reconstruction; tomography
42.79.Pw Imaging detectors and sensors
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Four-dimensional imaging of the initial stage of fast evolving plasmas

Pengfei Zhu, Zhongchao Zhang, Long Chen, Jun Zheng, Runze Li, Weimin Wang, Junjie Li, Xuan Wang, Jianming Cao, Dong Qian, Zhengming Sheng, and Jie Zhang

Appl. Phys. Lett. 97, 211501 (2010); http://dx.doi.org/10.1063/1.3521387 (3 pages) | Cited 1 time

Online Publication Date: 24 November 2010

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Using an ultrafast electron probe capable of four-dimensional diagnosis, the initial stage of fast evolving plasmas produced by a 1014 W/cm2 laser irradiation of a metal target was investigated in real time with picosecond time resolution. The associated strong transient electric field was identified to have two components, which either focus or defocus the probe electron beam. The effects of this field on the probe electron beam can be reproduced by a self-expanding charge cloud containing about 5×107 suprathermal electrons with the outermost layer expanding at an average speed of 1.2×107 m/s.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.25.Fi Transport properties
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
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Deep level related photoluminescence in ZnMgO

M. Trunk, V. Venkatachalapathy, A. Galeckas, and A. Yu. Kuznetsov

Appl. Phys. Lett. 97, 211901 (2010); http://dx.doi.org/10.1063/1.3518480 (3 pages) | Cited 5 times

Online Publication Date: 22 November 2010

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Optically active deep levels were investigated in ZnMgO layers using temperature dependent photoluminescence. The samples, grown on c-plane sapphire by metal-organic vapor phase epitaxy, exhibited Mg contents ranging from 0% to 8.5% leading to a gradual band gap broadening. The deep level luminescence was found to consist of several emission components centered at 2, 2.3, 2.5, 2.8, and 3 eV. With increasing Mg concentration, the bands at 2.8 and 3eV were found to blueshift, the bands at 2.3 and 2.5eV redshift, while the band at 2 eV holds its position. A model is suggested explaining the deep level luminescence shift trends in terms of interaction of native Zn and O sublattice defects with the introduced Mg interstitials.
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78.66.Hf II-VI semiconductors
78.55.Et II-VI semiconductors
71.55.Gs II-VI semiconductors
68.55.ag Semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Dynamical Franz–Keldysh effect in GaAs/AlGaAs multiple quantum wells induced by single-cycle terahertz pulses

K. Shinokita, H. Hirori, M. Nagai, N. Satoh, Y. Kadoya, and K. Tanaka

Appl. Phys. Lett. 97, 211902 (2010); http://dx.doi.org/10.1063/1.3518483 (3 pages) | Cited 2 times

Online Publication Date: 22 November 2010

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We studied absorption spectra near the band gap of GaAs/AlGaAs multiple quantum wells subjected to strong single-cycle terahertz pulses. With an increasing terahertz electric field, the heavy-hole 1s exciton energy near the band gap redshifts, reaches a maximum, and turns to blueshift. The blueshift increases proportionally to the ponderomotive energy, i.e., the terahertz electric field squared, which differs from the response expected from the Frantz–Keldysh effect (FKE) in a dc electric field. This fact suggests that the observed ponderomotive energy dependence of the blueshift can be ascribed to the dynamical FKE.
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81.07.St Quantum wells
81.05.Ea III-V semiconductors
73.63.Hs Quantum wells
78.67.De Quantum wells
71.20.Nr Semiconductor compounds
72.30.+q High-frequency effects; plasma effects

The electronic structure of β-Ga2O3

M. Mohamed, C. Janowitz, I. Unger, R. Manzke, Z. Galazka, R. Uecker, R. Fornari, J. R. Weber, J. B. Varley, and C. G. Van de Walle

Appl. Phys. Lett. 97, 211903 (2010); http://dx.doi.org/10.1063/1.3521255 (3 pages) | Cited 4 times

Online Publication Date: 22 November 2010

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β-Ga2O3 has the widest energy gap of the transparent conducting oxides. The interest in its electronic properties has recently increased because of its applications in various optoelectronic devices, semiconductor lasers, and ultrasensitive gas detecting systems. In contrast, information on the electronic structure of β-Ga2O3 is very scarce. Here, we present the experimental valence-band structure of β-Ga2O3 single crystals determined by high-resolution angle-resolved photoelectron spectroscopy utilizing synchrotron radiation. We find good matching of the experimental band structure with the advanced density functional theory calculations employing hybrid functionals and projector augmented wave potentials.
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71.20.Ps Other inorganic compounds
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
79.60.-i Photoemission and photoelectron spectra

Effects of applied electrical field on electronic structures in LaNiO3 conductive metallic oxide film: An optical spectroscopic study

J. J. Zhu (诸佳俊), W. W. Li (李文武), Y. W. Li (李亚巍), Y. D. Shen (沈育德), Z. G. Hu (胡志高), and J. H. Chu (褚君浩)

Appl. Phys. Lett. 97, 211904 (2010); http://dx.doi.org/10.1063/1.3518493 (3 pages)

Online Publication Date: 22 November 2010

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The reflectance spectra of LaNiO3 film on silicon have been investigated in the wavelength range of 190–2650 nm (0.47–6.5 eV) under different external direct-current voltage. The Drude–Lorentz dispersion model is used to extract the optical function. The O 2p to Ni 3d electronic transition can be uniquely assigned to the energy of about 1.96 eV and decreases with decreasing applied voltage. The discrepancy from the real part of dielectric function with the applied voltage has a strong spectral dependence. The optical conductivity variation under different external voltage indicates that the electrical field can induce the modification of the carrier transport.
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78.66.Nk Insulators
73.61.Ng Insulators
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
68.55.-a Thin film structure and morphology
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
82.70.-y Disperse systems; complex fluids

VO2 multidomain heteroepitaxial growth and terahertz transmission modulation

Changhong Chen, Yanhan Zhu, Yong Zhao, Joon Hwan Lee, Haiyan Wang, Ayrton Bernussi, Mark Holtz, and Zhaoyang Fan

Appl. Phys. Lett. 97, 211905 (2010); http://dx.doi.org/10.1063/1.3519361 (3 pages) | Cited 6 times

Online Publication Date: 23 November 2010

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We report the epitaxial relationship of VO2 thin-films on c-plane sapphire and their terahertz transmission modulation with temperature. The films exhibit a triple-domain structure caused by the lattice mismatch between monoclinic VO2 and sapphire hexagon. The epitaxial relationship is determined to be VO2[010]∥Al2O3[0001] and VO2(math02)∥Al2O3{11math0}, with the in-plane lattice mismatch of 2.66% (tensile) along [math02] and the out-of-plane lattice mismatch of −2.19% (compressive). Terahertz measurements revealed that VO2 films have over fourfold change in transmission during the metal-insulator transition, indicating a strong potential for terahertz wave switching and modulation applications.
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72.60.+g Mixed conductivity and conductivity transitions
71.30.+h Metal-insulator transitions and other electronic transitions
84.40.-x Radiowave and microwave (including millimeter wave) technology
68.55.A- Nucleation and growth
78.70.Gq Microwave and radio-frequency interactions

In situ ellipsometry study of the kinetics of hydrogen plasma interaction with a-Si:H thin films: A particular temperature-dependence

A. Hadjadj, G. Djellouli, and O. Jbara

Appl. Phys. Lett. 97, 211906 (2010); http://dx.doi.org/10.1063/1.3517495 (3 pages)

Online Publication Date: 23 November 2010

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We performed H2 plasma treatment of hydrogenated amorphous silicon (a-Si:H) thin films and followed by in situ spectroscopic ellipsometry measurements the kinetics of hydrogen-induced film modifications at temperatures varying from 100 to 250 °C. The time-dependence of the H-modified layer thickness dH(t) follows an exponential relation of the form dH0[1−exp(−t/τ)]. The temperature-dependence of dH0 and τ shows a discontinuity at T = 200 °C. While the activation energy of dH0 changes from 0.19 eV at T<200 °C to 0.05 eV at higher temperatures, the activation energy of τ suddenly changes from 0.15 eV to a negative value (−0.26 eV). Such a discontinuity should be linked to the thermal equilibrium temperature of undoped a-Si:H. Moreover, we found that the rate of formation of the H-modified layer rH = dH0/τ varies in inverse proportion to the etching rate, indicating a balance between hydrogen insertion and film etching at the steady state.
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81.65.Cf Surface cleaning, etching, patterning
81.05.Cy Elemental semiconductors
81.05.Gc Amorphous semiconductors
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)
68.55.-a Thin film structure and morphology
78.66.Db Elemental semiconductors and insulators

Thermal stability of the OH–Li complex in hydrothermally grown single crystalline ZnO

K. M. Johansen, H. Haug, E. Lund, E. V. Monakhov, and B. G. Svensson

Appl. Phys. Lett. 97, 211907 (2010); http://dx.doi.org/10.1063/1.3522886 (3 pages)

Online Publication Date: 24 November 2010

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The thermal stability of the prominent 3577 cm−1 infrared absorption band in ZnO, assigned to an O–H stretch mode adjacent to a Li atom on Zn site (LiZn), is studied. Employing slow sample cooling after annealing, the 3577 cm−1 peak remains at temperatures ≤ 1250 °C, consistent with previous reports. However, if the samples are cooled rapidly by quenching, the peak disappears after annealing for 1 h at 650 °C. A dissociation energy of less than 2.5 eV is deduced for the OH–LiZn complex and the apparent high thermal stability after slow cooling is attributed to efficient recapturing of H by LiZn. Moreover, deuterium (D) is found to replace hydrogen in OH–LiZn after 1 h at 700 °C in D2 gas.
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78.30.Fs III-V and II-VI semiconductors
61.72.Cc Kinetics of defect formation and annealing
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)

An ab initio study of the elastic behavior of single crystal group (IV) diborides at elevated temperatures

Manny Gonzales, Jack Chessa, and C. V. Ramana

Appl. Phys. Lett. 97, 211908 (2010); http://dx.doi.org/10.1063/1.3514238 (3 pages)

Online Publication Date: 24 November 2010

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We report on an ab initio molecular dynamics study of the lattice parameters, thermal expansion coefficients, and elastic constants of ZrB2, TiB2, and HfB2 ceramics at ultrahigh temperatures (up to 2200 K). Equilibrium lattice parameters of the ceramics are determined at finite temperatures. A finite strain method is used to extract the stiffness tensor of the ceramics. The results obtained for ZrB2 and TiB2 agree well with experimental results reported in the literature. Our work demonstrate that accurate properties may be obtained from a statistical averaging of the lattice parameters alone neglecting phonon interactions.
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81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.dq Other elastic constants
61.66.Fn Inorganic compounds
65.40.De Thermal expansion; thermomechanical effects
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Abnormal humidity-dependent electrical properties of amorphous carbon/silicon heterojunctions

Xili Gao, Xiaozhong Zhang, Caihua Wan, Xin Zhang, Lihua Wu, and Xinyu Tan

Appl. Phys. Lett. 97, 212101 (2010); http://dx.doi.org/10.1063/1.3520493 (3 pages) | Cited 1 time

Online Publication Date: 22 November 2010

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Amorphous carbon (a-C) film/n-Si heterojunctions have been fabricated by pulse laser deposition, and their current-voltage characteristics have been investigated. The results show that the atmosphere relative humidity (RH) has a significant effect on the reverse bias I-V characteristics of the heterojunctions. For the low bias voltages, the resistance of the a-C/Si heterojunction decreases with the increase of the RH. However, when the applied voltage is greater than a threshold, the resistance of the a-C/Si heterojunctions increases with the increase of the RH. This humidity-dependent phenomenon is attributed to the charge transfer from the absorbed H2O molecular to a-C film.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
82.30.Fi Ion-molecule, ion-ion, and charge-transfer reactions
81.15.Fg Pulsed laser ablation deposition

Thermoelectric properties of Bi2Te3 atomic quintuple thin films

Ferdows Zahid and Roger Lake

Appl. Phys. Lett. 97, 212102 (2010); http://dx.doi.org/10.1063/1.3518078 (3 pages) | Cited 4 times

Online Publication Date: 23 November 2010

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Motivated by recent experimental realizations of quintuple atomic layer films of Bi2Te3, the thermoelectric figure of merit ZT of the quintuple layer is calculated and found to increase by a factor of 10 (ZT = 7.15) compared to that of the bulk at room-temperature. The large enhancement in ZT results from the change in the distribution of the valence band density of modes brought about by the quantum confinement in the thin film. The theoretical model uses ab initio electronic structure calculations (VASP) with full quantum-mechanical structure relaxation combined with a Landauer formalism for the linear-response transport coefficients.
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73.50.Lw Thermoelectric effects
72.20.Pa Thermoelectric and thermomagnetic effects
71.15.-m Methods of electronic structure calculations
71.20.Ps Other inorganic compounds

Electrical bistability in hybrid ZnO nanorod/polymethylmethacrylate heterostructures

Zong-Liang Tseng, Po-Ching Kao, Meng-Fu Shih, Hsin-Hsuan Huang, Jing-Yuan Wang, and Sheng-Yuan Chu

Appl. Phys. Lett. 97, 212103 (2010); http://dx.doi.org/10.1063/1.3511756 (3 pages) | Cited 4 times

Online Publication Date: 23 November 2010

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A hybrid resistance switching device consisting of ZnO nanorods embedded in an insulating polymethylmethacrylate (PMMA) heterostructure sandwiched between a transparent conductive film and an Al electrode is proposed. The current-voltage characteristics of the device are discussed in terms of the formation and rupture of its conductive filaments. The hybrid device shows stable electrical bistable behaviors after more than 200 resistance-switching cycles. The hybrid ZnO nanorod/PMMA device presented in this work has potential applications in the field of bistable random access memory devices.
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84.30.Sk Pulse and digital circuits

Triple quantum dot device designed for three spin qubits

T. Takakura, M. Pioro-Ladrière, T. Obata, Y.-S. Shin, R. Brunner, K. Yoshida, T. Taniyama, and S. Tarucha

Appl. Phys. Lett. 97, 212104 (2010); http://dx.doi.org/10.1063/1.3518919 (3 pages)

Online Publication Date: 23 November 2010

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Electron spin confined in quantum dots is a promising candidate for experimental qubits. Aiming at realizing a three spin-qubit system, we designed split micromagnets suitable for the lateral triple quantum dots. From numerical simulations of the stray magnetic field distribution, field gradients ∼ 0.8 T/μm and differences of in-plane components ∼ 10 mT can be attained, which enable the electrical and addressable manipulation of three qubits. Furthermore, this technique can be applied for up to 25 qubits in realistic multiple quantum dots. For the first step of implementing such three-qubit systems, a relevant triple quantum dot device has been fabricated and characteristic charge states were observed.
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81.07.Ta Quantum dots
76.30.-v Electron paramagnetic resonance and relaxation
75.75.-c Magnetic properties of nanostructures
75.40.Mg Numerical simulation studies
03.67.Lx Quantum computation architectures and implementations
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