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29 Oct 2012

Volume 101, Issue 18, Articles (18xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 101, 183101 (2012); http://dx.doi.org/10.1063/1.4761935 (4 pages)

S. J. Kim, J. J. Lee, H. J. Kang, J. B. Choi, Y.-S. Yu, Y. Takahashi, and D. G. Hasko
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GaP based terahertz time-domain spectrometer optimized for the 5-8 THz range

I. D. Vugmeyster, J. F. Whitaker, and R. Merlin

Appl. Phys. Lett. 101, 181101 (2012); http://dx.doi.org/10.1063/1.4764545 (4 pages) | Cited 1 time

Online Publication Date: 29 October 2012

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We use GaP to generate terahertz pulses via optical rectification in a collinear phase-matched configuration relying on the dispersion of the refractive index. The GaP-based time-domain system operates up to 8 THz and is especially well suited at high frequencies, where it has high signal-to-noise ratio and power conversion efficiency ∼30 times greater than those of commercial photoconductive emitters. These characteristics are demonstrated in measurements of ZnTe in the reflection geometry. We also discuss the power output and describe theoretically the observed THz field generation by nonlinear mixing, the field's free space propagation, and its detection.
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07.57.Pt Submillimeter wave, microwave and radiowave spectrometers; magnetic resonance spectrometers, auxiliary equipment, and techniques
84.40.-x Radiowave and microwave (including millimeter wave) technology
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Three-dimensionally isotropic negative refractive index assisted by two-photon resonance via quantum coherence

Jian Qi Shen

Appl. Phys. Lett. 101, 181102 (2012); http://dx.doi.org/10.1063/1.4764553 (3 pages)

Online Publication Date: 29 October 2012

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An experimentally feasible and promising scheme for realizing simultaneously negative permittivity and permeability in a single-photon off-resonant atomic vapor is suggested by taking full advantage of the mechanism of two-photon resonance that is assisted by atomic phase coherence. The present quantum-coherent atomic vapor can exhibit three-dimensionally isotropic negative refractive index (NRI) at visible and near-infrared wavelengths, and would find potential applications in design of NRI-based quantum optical and photonic devices.
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42.50.-p Quantum optics
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.25.Kb Coherence

Molecular beam epitaxy growth of GaAsBi/GaAs/AlGaAs separate confinement heterostructures

Dongsheng Fan, Zhaoquan Zeng, Xian Hu, Vitaliy G. Dorogan, Chen Li, Mourad Benamara, Michael E. Hawkridge, Yuriy I. Mazur, Shui-Qing Yu, Shane R. Johnson, Zhiming M. Wang, and Gregory J. Salamo

Appl. Phys. Lett. 101, 181103 (2012); http://dx.doi.org/10.1063/1.4764556 (4 pages) | Cited 1 time

Online Publication Date: 29 October 2012

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GaAsBi/GaAs/AlGaAs separate confinement heterostructures are grown using an asymmetric temperature profile due to the low optimal growth temperature of GaAsBi; the bottom AlGaAs barrier is grown at 610 °C, while the GaAsBi quantum well and the top AlGaAs barrier are grown at 320 °C. Cross-sectional transmission electron microscopy and room temperature photoluminescence measurements indicate that this approach results in samples with excellent structural and optical properties. The high quality of the low temperature AlGaAs barrier is attributed to the presence of Bi on the surface as indicated by a (1 × 3) surface reconstruction persisting throughout the low temperature growth.
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78.55.Cr III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.55.A- Nucleation and growth
68.37.Lp Transmission electron microscopy (TEM)

Integrated optofluidic index sensor based on self-trapped beams in LiNbO3

M. Chauvet, L. Al Fares, B. Guichardaz, F. Devaux, and S. Ballandras

Appl. Phys. Lett. 101, 181104 (2012); http://dx.doi.org/10.1063/1.4765059 (4 pages)

Online Publication Date: 29 October 2012

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We show that self-trapped beams can form in structured monolithic lithium niobate chips. In particular, they are observed to be unaffected when crossing few hundred microns wide gaps. The technique is employed to fabricate an index sensor constituted of a buried circular optical waveguide crossing a fluidic channel in a lithium niobate substrate. Fluidic channels are realized by precision dicing while the optical waveguides are induced by photorefractive beam self-trapping controlled by the pyroelectric effect. The self-aligning property of this latter waveguides provides a simple fabrication technique of an integrated sensor that accurately measures the refractive index of transparent liquids.
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42.82.Et Waveguides, couplers, and arrays
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
42.82.-m Integrated optics

Carrier escape mechanism dependence on barrier thickness and temperature in InGaN quantum well solar cells

J. R. Lang, N. G. Young, R. M. Farrell, Y.-R. Wu, and J. S. Speck

Appl. Phys. Lett. 101, 181105 (2012); http://dx.doi.org/10.1063/1.4765068 (5 pages)

Online Publication Date: 29 October 2012

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The properties of quantum well carrier escape were studied by varying barrier thicknesses in InGaN/GaN multi-quantum well solar cell devices. The dependence of the photocurrent on applied bias and temperature exhibited properties indicative of the quantum well carrier escape mechanisms of thermionic emission and tunneling, with tunneling dominating for thin barriers and high fields. Simulations using a self-consistent drift-diffusion and Schrödinger solver with analytical formulas extracted carrier escape lifetimes. By employing sufficiently thin barriers, it was found that escape lifetimes can be made small compared to recombination lifetimes, leading to high internal quantum efficiency.
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88.40.H- Solar cells (photovoltaics)

Self-induced spin-polarized carrier source in active photonic device with artificial optical chirality

Yuqian Ye and Shu-Wei Chang

Appl. Phys. Lett. 101, 181106 (2012); http://dx.doi.org/10.1063/1.4765082 (5 pages)

Online Publication Date: 29 October 2012

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We demonstrate a scheme of active photonic devices which can spontaneously polarize the carrier spin in active regions. Rather than externally breaking the time-reversal symmetry of carrier spin states such as applying magnetic fields, only the optical chirality is required in this setup. Spin-polarized carriers are generated by interactions between carriers and self-initiated circularly polarized photons without the spin-selective optical pumping/electrical injection and breaking of the reciprocity. The device requires a cavity which supports modes with only one circular polarization and can be implemented with the vertical-cavity type of arrangements for distributed Bragg reflectors and artificial chiral photonic structures.
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85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields
42.70.Qs Photonic bandgap materials
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Simple microwave field imaging technique using hot atomic vapor cells

Pascal Böhi and Philipp Treutlein

Appl. Phys. Lett. 101, 181107 (2012); http://dx.doi.org/10.1063/1.4760267 (4 pages)

Online Publication Date: 29 October 2012

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We demonstrate a simple technique for microwave field imaging using alkali atoms in a vapor cell. The microwave field to be measured drives Rabi oscillations on atomic hyperfine transitions, which are detected in a spatially resolved way using a laser beam and a camera. Our vapor cell geometry enables single-shot recording of two-dimensional microwave field images with 350 μm spatial resolution. Using microfabricated vapor cell arrays, a resolution of a few micrometers seems feasible. All vector components of the microwave magnetic field can be imaged. Our apparatus is simple and compact and does not require cryogenics or ultra-high vacuum.
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07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
07.10.Cm Micromechanical devices and systems
42.62.-b Laser applications
31.30.Gs Hyperfine interactions and isotope effects

Polarity inversion and coupling of laser beam induced current in As-doped long-wavelength HgCdTe infrared detector pixel arrays: Experiment and simulation

W. D. Hu, X. S. Chen, Z. H. Ye, Y. G. Chen, F. Yin, B. Zhang, and W. Lu

Appl. Phys. Lett. 101, 181108 (2012); http://dx.doi.org/10.1063/1.4764903 (5 pages) | Cited 2 times

Online Publication Date: 1 November 2012

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In this paper, experimental results of polarity inversion and coupling of laser beam induced current for As-doped long-wavelength HgCdTe pixel arrays grown on CdZnTe are reported. Models for the p-n junction transformation are proposed and demonstrated using numerical simulations. Simulation results are shown to be in agreement with the experimental results. It is found that the deep traps induced by ion implantation are very sensitive to temperature, resulting in a decrease of the quasi Fermi level in the implantation region in comparison to that in the Hg interstitials diffusion and As-doped regions. The Hg interstitial diffusion, As-doping amphoteric behavior, ion implantation damage traps, and the mixed conduction, are key factors for inducing the polarity reversion, coupling, and junction broadening at different temperatures. The results provide the near room-temperature HgCdTe photovoltaic detector with a reliable reference on the junction reversion and broadening around implanted regions, as well as controlling the n-on-p junction for very long wavelength HgCdTe infrared detector pixels.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
85.30.De Semiconductor-device characterization, design, and modeling

Increasing the switching speed of liquid crystal devices with magnetic nanorods

Yu. Garbovskiy, J. R. Baptist, J. Thompson, T. Hunter, J. H. Lim, Seong Gi Min, J. B. Wiley, L. M. Malkinski, A. Glushchenko, and Z. Celinski

Appl. Phys. Lett. 101, 181109 (2012); http://dx.doi.org/10.1063/1.4763475 (5 pages)

Online Publication Date: 1 November 2012

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Liquid crystal (LC)/magnetic nanorods colloids were fabricated and tested using a magneto-optical setup. These thermotropic ferronematics do not show any signs of macroscopic aggregation, exhibit enhanced magnetic sensitivity, and faster time response in the simultaneous presence of crossed electric and magnetic fields. Magnetic nanorods increase an effective magnetic anisotropy of the colloid and decrease magnetic Freedericksz threshold. Applying a magnetic field along the direction perpendicular to the applied electric field leads to a decrease of the time OFF by a factor of 6 for pure liquid crystals, and by a factor of 9—for ferronematics.
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42.79.Kr Display devices, liquid-crystal devices
82.70.Dd Colloids
78.20.Ls Magneto-optical effects
81.16.-c Methods of micro- and nanofabrication and processing
75.30.Gw Magnetic anisotropy

Making a continuous metal film transparent via scattering cancellations

Zhengyong Song, Qiong He, Shiyi Xiao, and Lei Zhou

Appl. Phys. Lett. 101, 181110 (2012); http://dx.doi.org/10.1063/1.4764945 (4 pages) | Cited 3 times

Online Publication Date: 1 November 2012

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Based on theoretical analyses and full-wave simulations, we propose a scheme to make a continuous metal film transparent in optical regime, with light scattered from the metal film cancelled by those from two composite layers consisting of metallic and dielectric stripes. Such a transparency fully retains the conductance of the targeted metal and is robust against incidence angle as well as structural disorders. As a proof of concept, we performed microwave experiments to verify all theoretical predictions.
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81.05.Bx Metals, semimetals, and alloys
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.66.Bz Metals and metallic alloys

Extremely temperature-insensitive continuous-wave quantum cascade lasers

Kazuue Fujita, Masamichi Yamanishi, Shinichi Furuta, Atsushi Sugiyama, and Tadataka Edamura

Appl. Phys. Lett. 101, 181111 (2012); http://dx.doi.org/10.1063/1.4765073 (4 pages)

Online Publication Date: 1 November 2012

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Conspicuous temperature performances of λ ∼ 8.7 μm quantum cascade lasers with anticrossed dual-upper laser states are reported. The lasers characterized by strong super-linear current-light output curves exhibit an extremely high characteristic temperature for the threshold current density above 330 K (T0 ∼ 750 K). The slope efficiency grows with increasing temperature (a negative T1-value). In addition, for the pulsed operation of a short 1 mm length laser, the T0-value reaches a value of 1085 K above 340 K. These distinctive characteristics are attributable to optical absorption quenching in the injector as well as to suppression of carrier leakage in the active region.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

A two-dimensional nanopatterned thin metallic transparent conductor with high transparency from the ultraviolet to the infrared

Qing Guo Du, Krishnan Sathiyamoorthy, Li Ping Zhang, Hilmi Volkan Demir, Chan Hin Kam, and Xiao Wei Sun

Appl. Phys. Lett. 101, 181112 (2012); http://dx.doi.org/10.1063/1.4765341 (4 pages)

Online Publication Date: 1 November 2012

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The optical properties of a two-dimensional nanohole patterned aluminum thin film in hexagonal lattice are studied. The transmission dip can be moved out from the visible range by manipulating the lattice constant. The resulting nanopatterned thin film is demonstrated to exhibit a high transparency in a wide wavelength range. The origins of the transmission dip and the transmission drop are explained. For constant resistance, thicker films with a larger filling ratio lead to better transmittance in the visible range. Angular response of the nanopatterned metallic film is also analyzed, and transmittances using several other metals are compared.
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78.66.Bz Metals and metallic alloys
81.16.Rf Micro- and nanoscale pattern formation
68.55.-a Thin film structure and morphology
73.61.At Metal and metallic alloys

THz emission control by tuning density profiles of neutral gas targets during intense laser-gas interaction

Hai-Wei Du, Min Chen, Zheng-Ming Sheng, Jie Zhang, Hui-Chun Wu, and Wei-Min Wang

Appl. Phys. Lett. 101, 181113 (2012); http://dx.doi.org/10.1063/1.4765365 (3 pages)

Online Publication Date: 1 November 2012

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Ionization currents generated from two-color or few-cycle intense femtosecond laser pulses interaction with neutral gas targets can emit strong THz waves. Here it is found that the initial non-uniformity of the gas density can significantly affect the ionization currents and subsequent THz emission both in amplitude and in spectrum. Density profile effects on the forward and backward emissions have been studied in details by particle-in-cell simulations, in which the field ionization module is included. Increasing the gas density gradient length, the emitted forward THz spectrum shifts from high to low frequency, and the spectrum width reduces, which offers a way to obtain a tunable THz emission source by laser-gas interaction.
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52.38.Dx Laser light absorption in plasmas (collisional, parametric, etc.)
52.65.Rr Particle-in-cell method
52.25.Fi Transport properties
52.25.Jm Ionization of plasmas
52.25.Os Emission, absorption, and scattering of electromagnetic radiation

Silicon coding-decoding photonic device by electron irradiation and light down conversion

V. K. Malyutenko, A. N. Tykhonov, O. Yu. Malyutenko, I. S. Rohutskii, and B. A. Danilchenko

Appl. Phys. Lett. 101, 181114 (2012); http://dx.doi.org/10.1063/1.4766170 (3 pages) | Cited 1 time

Online Publication Date: 2 November 2012

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We propose and demonstrate a coding-decoding procedure as an important step to realize one more Si-based photonic device. Low-fluence (<1014 e/cm2) high-energy (1 MeV) electron irradiation of a bulk Si matrix is used to code an information by forming local regions with lower free carrier lifetime that are hidden under the surface and invisible to the eye. Short-wavelength (<1 μm) free carrier generation stands for multiple, remote, and nondestructive decoding process, which makes it easy to dynamically (ms range) visualize a code by capturing two-dimensional pattern of thermal emission in the longer-wavelength (3–12 μm) band (light down conversion).
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42.50.Ex Optical implementations of quantum information processing and transfer
42.65.Lm Parametric down conversion and production of entangled photons
42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks

Direct intensity sampling of a modelocked terahertz quantum cascade laser

Joshua R. Freeman, Jean Maysonnave, Nathan Jukam, Pierrick Cavalié, Kenneth Maussang, Harvey E. Beere, David A. Ritchie, Juliette Mangeney, Sukhdeep S. Dhillon, and Jérôme Tignon

Appl. Phys. Lett. 101, 181115 (2012); http://dx.doi.org/10.1063/1.4765660 (4 pages)

Online Publication Date: 2 November 2012

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Pulses from an actively modelocked terahertz quantum cascade laser are fully characterized using an optical sampling technique to detect the total instantaneous terahertz intensity. By triggering the quantum cascade laser electronics with a femtosecond laser, we are able to measure both the formation of modelocked pulses and the quasi-steady state. The dependence of the pulse width on the modulation power and drive current are investigated. At low drive currents, we measure transform-limited gaussian-shaped pulses with a FWHM of 19 ps.
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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
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
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Direct visualization of Ni-Nb bulk metallic glasses surface: From initial nucleation to full crystallization

A. I. Oreshkin, V. N. Mantsevich, S. V. Savinov, S. I. Oreshkin, V. I. Panov, N. S. Maslova, and D. V. Louzguine-Luzgin

Appl. Phys. Lett. 101, 181601 (2012); http://dx.doi.org/10.1063/1.4760272 (4 pages)

Online Publication Date: 29 October 2012

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This article is devoted to in situ investigation of the Ni-based bulk metallic glass structural evolution and crystallization behavior by scanning tunneling microscopy/spectroscopy. The possibility of different surface nanostructures formation is shown by annealing of an original bulk glassy alloy in ultra high vacuum. Atomic locations in these surface nanostructures are completely different from those formed according to Ni-Nb binary phase diagram in the bulk area of the sample. The validity of the results is also verified by transmission electron microscopy and nano-beam diffraction measurements.
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64.70.pe Metallic glasses
81.40.Gh Other heat and thermomechanical treatments
81.16.-c Methods of micro- and nanofabrication and processing
61.46.-w Structure of nanoscale materials
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
61.43.Fs Glasses

Phase constitution and interface structure of nano-sized Ag-Cu/AlN multilayers: Experiment and ab initio modeling

Giancarlo Pigozzi, Andrej Antušek, Jolanta Janczak-Rusch, Magdalena Parlinska-Wojtan, Daniele Passerone, Carlo Antonio Pignedoli, Vinzenz Bissig, Jörg Patscheider, and Lars P. H. Jeurgens

Appl. Phys. Lett. 101, 181602 (2012); http://dx.doi.org/10.1063/1.4761471 (5 pages)

Online Publication Date: 1 November 2012

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Nano-sized Ag-Cu8nm/AlN10nm multilayers were deposited by reactive DC sputtering on α-Al2O3(0001) substrates. Investigation of the phase constitution and interface structure of the multilayers evidences a phase separation of the alloy sublayers into nanosized grains of Ag and Cu. The interfaces between the Ag grains and the quasi-single-crystalline AlN sublayers are semi-coherent, whereas the corresponding Cu/AlN interfaces are incoherent. The orientation relationship between Ag and AlN is constant throughout the entire multilayer stack. These observations are consistent with atomistic models of the interfaces as obtained by ab initio calculations.
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81.07.Bc Nanocrystalline materials
64.75.Jk Phase separation and segregation in nanoscale systems
68.35.Ct Interface structure and roughness
81.15.Cd Deposition by sputtering

Exploring the p-n junction region in Cu(In,Ga)Se2 thin-film solar cells at the nanometer-scale

O. Cojocaru-Mirédin, P. Choi, R. Wuerz, and D. Raabe

Appl. Phys. Lett. 101, 181603 (2012); http://dx.doi.org/10.1063/1.4764527 (5 pages) | Cited 1 time

Online Publication Date: 2 November 2012

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In this work we study the CdS/Cu(In,Ga)Se2 p-n junction region in Cu(In,Ga)Se2 thin-film solar cells using atom probe tomography. A Cu-, Ga-depleted, and Cd-doped region of about 1 nm thickness is detected at the Cu(In,Ga)Se2 side of the CdS/Cu(In,Ga)Se2 interface. Furthermore, Cd is also found to be enriched at Cu(In,Ga)Se2 grain boundaries connected to the CdS layer. Na and O impurities decorate the CdS/CIGS interface, where Na-rich clusters are preferentially located in CdS regions abutting to Cu(In,Ga)Se2 grain boundaries. The experimental findings of this work demonstrate the capability of atom probe tomography in studying buried interfaces and yield vital information for understanding and modeling the p-n junction band structure in Cu(In,Ga)Se2 solar cells.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
88.40.jp Multijunction solar cells
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Shock-induced intermediate-range structural change of SiO2 glass in the nonlinear elastic region

K. Ichiyanagi, N. Kawai, S. Nozawa, T. Sato, A. Tomita, M. Hoshino, K. G. Nakamura, S. Adachi, and Y. C. Sasaki

Appl. Phys. Lett. 101, 181901 (2012); http://dx.doi.org/10.1063/1.4764526 (4 pages)

Online Publication Date: 29 October 2012

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We study shock compressed fused quartz in the nonlinear elastic region using single-shot time-resolved x-ray scattering measurements. The first sharp diffraction peak (FSDP) of fused quartz shifts to the high Q region under shock compression. In contrast, the short-range order structure does not change around 3.5 GPa. The nanosecond FSDP shift provides clear evidence of intermediate-range order structural changes in the nonlinear elastic region. Because the intermediate-order structure is too short to produce the final structural state in the nonlinear elastic region, the FSDP shift is lower compared with hydrostatic experiments.
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64.70.kj Glasses
61.43.Fs Glasses
78.70.Ck X-ray scattering
81.40.Jj Elasticity and anelasticity, stress-strain relations
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity

Mechanical and thermal behaviors of nitrogen-doped Zr-Cu-Al-Ag-Ta––An alternative class of thin film metallic glass

Pao-Sheng Chen, Hsien-Wei Chen, Jenq-Gong Duh, Jyh-Wei Lee, and Jason Shian-Ching Jang

Appl. Phys. Lett. 101, 181902 (2012); http://dx.doi.org/10.1063/1.4759035 (4 pages)

Online Publication Date: 29 October 2012

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Super-plasticity and nano-scale surface roughness make thin film metallic glass (TFMG) a candidate for master mold of micro/nano imprint technique. Meanwhile, better mechanical properties of TFMG undoubtedly expand the life time of master mold. In this study, nitrogen is doped into Zr-based TFMG to exhibit the hardness higher than 10 GPa. Different from elements used to be doped into metallic glass, the role of nitrogen atoms plays in metallic glass is distinct and vital owing to its strong electronegativity. From the correlation of thermal and mechanical behavior, the role and effect of nitrogen in Ta-Zr-Cu-Al-Ag TFMG is discussed and proposed.
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81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.Qp Friction, tribology, and hardness
81.40.Lm Deformation, plasticity, and creep
65.60.+a Thermal properties of amorphous solids and glasses: heat capacity, thermal expansion, etc.
68.60.Dv Thermal stability; thermal effects
68.60.Bs Mechanical and acoustical properties

Large area orientation films based on graphene oxide self-assembly and low-temperature thermal reduction

Yongan Niu, Jiupeng Zhao, Xin Zhang, Xianjie Wang, Jie Wu, Yang Li, and Yao Li

Appl. Phys. Lett. 101, 181903 (2012); http://dx.doi.org/10.1063/1.4764549 (4 pages)

Online Publication Date: 29 October 2012

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Graphene oxide (GO) and reduced graphene oxide (RGO) have many outstanding physical and mechanical properties. Uniform and thickness controllable RGO films with large area were prepared by evaporation-induced self-assembly at a liquid/air interface on glass substrates in combination with low temperature thermal reduction at 200 °C. This process has the advantage of good compatibility with flexible and non-flexible substrates. The films are of centimeter scale and their thickness can be controlled. The structural evolution was characterized. The obtained thermal RGO films exhibit excellent optical properties, a high elastic modulus of 76.18 GPa, and a hardness of 6.89 GPa.
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81.05.ub Fullerenes and related materials
78.66.Tr Fullerenes and related materials
81.40.Jj Elasticity and anelasticity, stress-strain relations
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
61.48.-c Structure of fullerenes and related hollow and planar molecular structures
68.55.ap Fullerenes

Ion implantation induced modification of optical properties in single-crystal diamond studied by coherent acoustic phonon spectroscopy

Justin Gregory, Andrew Steigerwald, Hiroaki Takahashi, Anthony Hmelo, and Norman Tolk

Appl. Phys. Lett. 101, 181904 (2012); http://dx.doi.org/10.1063/1.4765647 (4 pages)

Online Publication Date: 1 November 2012

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Single-crystal CVD diamond specimens were implanted with 1-MeV He+ ions at fluences ranging from 1014 to 1016 cm−2 and analyzed using coherent acoustic phonon spectroscopy. The coherent acoustic phonon response varies greatly with implantation fluence and provides depth-dependent information about the implantation defect-induced modification of diamond's optical characteristics. The results indicate an increase in the real and imaginary refractive index, as well as a sign reversal of the photoelastic coefficients at higher levels of implantation damage. These studies provide insight into the application of ion implantation to the fabrication of diamond-based photonic devices.
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78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
61.72.up Other materials
63.20.dd Measurements
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects

Deformation mechanism of nanoporous materials upon water freezing and melting

Maxim Erko, Dirk Wallacher, and Oskar Paris

Appl. Phys. Lett. 101, 181905 (2012); http://dx.doi.org/10.1063/1.4764536 (4 pages)

Online Publication Date: 1 November 2012

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Temperature-induced non-monotonous reversible deformation of water-filled nanoporous silica materials is investigated experimentally using in-situ small-angle x-ray scattering. The influence of freezing and melting in the nanopores on this deformation is treated quantitatively by introducing a simple model based on the Gibbs-Thomson equation and a generalized Laplace-pressure. The physical origin of the melting/freezing induced pore lattice deformation is found to be exactly the same as for capillary condensation/evaporation, namely the curved phase boundary due to the preferred wetting of the pore walls by the liquid phase. As a practical implication, elastic properties of the nanoporous framework can be determined from the temperature-deformation curves.
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81.40.Lm Deformation, plasticity, and creep
62.20.D- Elasticity
62.20.F- Deformation and plasticity
64.70.dj Melting of specific substances
78.70.Ck X-ray scattering
81.40.Jj Elasticity and anelasticity, stress-strain relations

Fluid like behavior of oxygen in cubic zirconia under extreme conditions

Amit Samanta and S. B. Zhang

Appl. Phys. Lett. 101, 181906 (2012); http://dx.doi.org/10.1063/1.4762826 (4 pages)

Online Publication Date: 1 November 2012

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Using atomistic simulations, we analyze the defect chemistry and ionic mobility in the high temperature cubic phase of zirconia to gain insights into the stability of the zirconia lattice. In the temperature range of 2600-2980 K, we find anionic defects can occupy a significant fraction of the total anionic sites. In cognizance with the fact that these defects have low diffusion barriers, we conclude that the anionic sub-lattice is highly mobile and is fluid-like at these temperatures.
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66.30.Lw Diffusion of other defects

Organic hydrogen gas sensor with palladium-coated β-phase poly(vinylidene fluoride) thin films

Yuji Imai, Yasuo Kimura, and Michio Niwano

Appl. Phys. Lett. 101, 181907 (2012); http://dx.doi.org/10.1063/1.4764064 (4 pages) | Cited 2 times

Online Publication Date: 1 November 2012

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We have proposed an organic hydrogen gas sensor in which palladium (Pd)-coated β-phase poly(vinylidene fluoride) (PVDF) films are utilized. Volume expansion of the Pd thin film caused by absorption of hydrogen gas is monitored by a piezoelectric thin film of PVDF attached to the Pd films. We have developed a simple method of synthesizing β-phase PVDF films from α-phase PVDF powder by using a wet process in which a mixture of acetone and hexamethylphosphoric triamide is used as the solvent for the PVDF powder. The sensor works by itself at room temperature without a power source.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
82.80.-d Chemical analysis and related physical methods of analysis
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