APL Nameplate
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Flickr Twitter iResearch App Facebook

BROWSE VOLUMES

Year Range: 
Search Issue | RSS Feeds RSS
Previous Issue Next Issue

21 May 2007

Volume 90, Issue 21, Articles (21xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 90, 213501 (2007); http://dx.doi.org/10.1063/1.2742294 (3 pages)

Jong-Hyun Ahn, Hoon-Sik Kim, Etienne Menard, Keon Jae Lee, Zhengtao Zhu, Dae-Hyeong Kim, Ralph G. Nuzzo, John A. Rogers, Islamshah Amlani, Vadim Kushner, Shawn G. Thomas, and Terrisa Duenas
Enlarge Image | Read More
Page 1 of 4 Pages Next Page | Jump to Page
back to top
RSS Feeds

Passive photonic elements based on dielectric-loaded surface plasmon polariton waveguides

A. V. Krasavin and A. V. Zayats

Appl. Phys. Lett. 90, 211101 (2007); http://dx.doi.org/10.1063/1.2740485 (3 pages) | Cited 65 times

Online Publication Date: 21 May 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The authors present full three-dimensional numerical modeling of passive photonic elements based on dielectric-loaded surface plasmon polariton waveguides (DLSPPWs). They demonstrate that at telecom wavelengths a highly confined SPP mode can be guided in a single mode DLSPPW of subwavelength cross section and estimate the achievable density of photonic integration. The size of bending and splitting photonic elements based on DLSPPW can be as small as a few micrometers with pure bend loss less than 10% (0.4 dB) and the transmission efficiency exceeding 70% (total loss of about 1.3 dB). Such DLSPPW elements are important for implementation of photonic integrated circuits, guiding optical and electric signals in the same circuitry, and lab-on-a-chip applications.
Show PACS
42.82.Et Waveguides, couplers, and arrays
42.79.Gn Optical waveguides and couplers
85.60.-q Optoelectronic devices

Experimental demonstration of the polarization-dependent photon-mediated carrier redistribution in tunneling injection InP quantum-dot lasers with external-grating feedback

J. Kim, P. K. Kondratko, S. L. Chuang, G. Walter, N. Holonyak, Jr., R. D. Heller, X. B. Zhang, and R. D. Dupuis

Appl. Phys. Lett. 90, 211102 (2007); http://dx.doi.org/10.1063/1.2741118 (3 pages) | Cited 4 times

Online Publication Date: 21 May 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Measured modal gain spectra of the tunneling injection InP quantum-dot (QD) laser with and without an external feedback are presented to experimentally demonstrate the polarization-dependent photon-mediated carrier redistribution in the tunneling injection QD laser. The peak gain wavelength in the transverse-electric gain narrowing spectra near threshold follows the external feedback wavelength. This indicates that the carrier redistribution in the QD-coupled-quantum well structure is determined by the spectral distribution of the stimulated emission, which can be controlled by external grating.
Show PACS
42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.79.Dj Gratings

Low threshold quantum-cascade lasers of room temperature continuous-wave operation grown by metal-organic chemical-vapor deposition

X. J. Wang, J. Y. Fan, T. Tanbun-Ek, and F.-S. Choa

Appl. Phys. Lett. 90, 211103 (2007); http://dx.doi.org/10.1063/1.2741409 (3 pages) | Cited 12 times

Online Publication Date: 21 May 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Very low threshold current densities are reported from buried heterojunction quantum-cascade laser (QCL) grown by metal-organic chemical-vapor deposition at an emission wavelength of 5.07 μm. Continuous-wave operation threshold current densities as low as 0.75 and 0.83 kA/cm2, efficiencies of 1079 and 879 mW/A, and total output powers of 116 and 74 mW have been achieved for temperatures of 288 and 298 K. These cw threshold current densities are lower than all previously reported values for Fabry-Pérot QCLs. Internal loss as low as 1.84 cm−1 has been extracted; also the lowest value thus far reported in the literature.
Show PACS
42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Higher nonlinear indices, Raman gain coefficients, and bandwidths in the TeO2–ZnO–Nb2O5–MoO3 quaternary glass system

Rajan Jose and Yasutake Ohishi

Appl. Phys. Lett. 90, 211104 (2007); http://dx.doi.org/10.1063/1.2741412 (3 pages) | Cited 13 times

Online Publication Date: 21 May 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A quaternary glass system, TeO2–ZnO–Nb2O5–MoO3, with higher linear and nonlinear indices, third order optical susceptibility (χ3), and Raman gain coefficient and gain bandwidth is reported. The χ3 of these glasses are ∼ 80 times higher than the silica glass and 1.6 times higher than pure TeO2 glass; Raman gain coefficient is 40 times higher than the silica glass. Amplification bandwidth of one of the glasses is 1.7 times larger than the silica glass. The present glass has a glass transition temperature 80 °C lower than the previously reported tellurite showing large Raman amplification bandwidth. These features make the TeO2–ZnO–Nb2O5–MoO3 glass a potential material for photonics devices such as fiber Raman amplifiers and/or nonlinear optical signal processing devices.
Show PACS
42.70.Ce Glasses, quartz
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.65.An Optical susceptibility, hyperpolarizability
42.65.Dr Stimulated Raman scattering; CARS
42.65.Es Stimulated Brillouin and Rayleigh scattering

Time dependent density of free carriers generated by two photon absorption in silicon waveguides

Y. Liu and H. K. Tsang

Appl. Phys. Lett. 90, 211105 (2007); http://dx.doi.org/10.1063/1.2741611 (3 pages) | Cited 17 times

Online Publication Date: 21 May 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Carrier diffusion and recombination are considered in calculating the time dependent density of free carriers generated by two photon absorption in silicon waveguides. The calculations are compared to experimental results from optical pump-probe measurements of the induced loss from free carrier absorption. A generalized definition of nonlinear effective length is proposed to describe the effects of nonlinear loss. The authors experimentally demonstrate that helium-ion implantation can reduce the effective carrier lifetime and report on the observation of enhanced self-phase modulation in the helium implanted silicon waveguide.
Show PACS
42.79.Gn Optical waveguides and couplers
42.65.Wi Nonlinear waveguides
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation

Highly circularly polarized electroluminescence from organic light-emitting diodes with wide-band reflective polymeric cholesteric liquid crystal films

Soon Moon Jeong, Youko Ohtsuka, Na Young Ha, Yoichi Takanishi, Ken Ishikawa, Hideo Takezoe, Suzushi Nishimura, and Goroh Suzaki

Appl. Phys. Lett. 90, 211106 (2007); http://dx.doi.org/10.1063/1.2741603 (3 pages) | Cited 11 times

Online Publication Date: 21 May 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The authors have observed highly circularly polarized electroluminescence from organic light-emitting diodes (OLEDs) using wide-band reflector consisting of three-layered left-handed polymeric cholesteric liquid crystal (PCLC) films. By simply attaching the wide-band reflective PCLC reflector to a conventional OLED, the authors obtained a high degree of circular polarization, i.e., the ratio of brightness between right- and left-handed circularly polarized electroluminescences is over 10 over the whole emission band.
Show PACS
85.60.Jb Light-emitting devices
42.79.Kr Display devices, liquid-crystal devices

On-chip surface-enhanced Raman scattering detection using integrated liquid-core waveguides

Philip Measor, Leo Seballos, Dongliang Yin, Jin Z. Zhang, Evan J. Lunt, Aaron R. Hawkins, and Holger Schmidt

Appl. Phys. Lett. 90, 211107 (2007); http://dx.doi.org/10.1063/1.2742287 (3 pages) | Cited 29 times

Online Publication Date: 21 May 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The authors demonstrate surface-enhanced Raman scattering (SERS) detection on an optofluidic chip. Interconnected solid- and liquid-core antiresonant reflecting optical waveguides (ARROWs) form a planar beam geometry that allows for high mode intensities along microfluidic channels containing molecules optimized for SERS. The excitation power and concentration dependence of SERS from rhodamine 6G (R6G) molecules adsorbed to silver nanoparticles were systematically studied. The data can be described by a model that takes into account the microphotonic structure. Detection sensitivity to a minimum concentration of 30 nM is found, demonstrating the suitability of ARROW-based optofluidic chips for high sensitivity detection with molecular specificity.
Show PACS
42.65.Wi Nonlinear waveguides
42.79.Gn Optical waveguides and couplers
42.82.-m Integrated optics
42.65.Dr Stimulated Raman scattering; CARS
42.65.Es Stimulated Brillouin and Rayleigh scattering
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices

Investigations of the light-induced scattering varied with HfO2 codoping in LiNbO3:Fe crystals

Wenbo Yan, Hongjian Chen, Lihong Shi, Shiguo Liu, and Yongfa Kong

Appl. Phys. Lett. 90, 211108 (2007); http://dx.doi.org/10.1063/1.2742290 (3 pages) | Cited 9 times

Online Publication Date: 22 May 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Light-induced scattering in LiNbO3:Fe crystals codoped with different concentrations of HfO2 has been investigated. Unusual behaviors with varied HfO2 codoping are observed and explained. Li vacancies are suggested to be the main contributor to the dark conductivity of the crystal and subsequently to induce the threshold effect of the pump light intensity for the light-induced scattering. High photovoltaic field produced in the crystals is thought to be the cause of the serious light-induced scattering at high pump intensity. As a result, LiNbO3:Fe, Hf crystals exhibit an enhanced ability to suppress the light-induced scattering at moderate pump intensity.
Show PACS
42.70.Gi Light-sensitive materials
61.72.S- Impurities in crystals
61.72.J- Point defects and defect clusters
72.40.+w Photoconduction and photovoltaic effects

Saturated and efficient blue phosphorescent organic light emitting devices with Lambertian angular emission

C. L. Mulder, K. Celebi, K. M. Milaninia, and M. A. Baldo

Appl. Phys. Lett. 90, 211109 (2007); http://dx.doi.org/10.1063/1.2742577 (3 pages) | Cited 18 times

Online Publication Date: 22 May 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The authors employ a microcavity to optimize the color of a phosphorescent organic light emitting device (OLED) based on the-sky blue phosphor FIrpic. The output of the OLED is filtered by scattering media to correct the angular emission intensity profile and eliminate the angular dependence of the color. With a holographic diffuser as the scattering medium, the microcavity OLED achieves an external quantum efficiency of (5.5±0.6)%, as compared to (3.8±0.4)% for a conventional structure. The color coordinates of the microcavity OLED with holographic diffuser are (x,y) = (0.116±0.004,0.136±0.010) with minimal angular color shift and a nearly ideal Lambertian angular emission profile.
Show PACS
85.60.Jb Light-emitting devices

Proposal and analysis of a silica fiber with large and thermodynamically stable second order nonlinearity

Yong Xu, Anbo Wang, James R. Heflin, and Zhiwen Liu

Appl. Phys. Lett. 90, 211110 (2007); http://dx.doi.org/10.1063/1.2740472 (3 pages) | Cited 4 times

Online Publication Date: 23 May 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The authors propose a general approach that can produce a silica fiber with large and thermodynamically stable second order nonlinearity. They estimate that it is possible to achieve second harmonic generation efficiency of more than 10% in such a nonlinear fiber with a length of a few hundred microns. By maintaining a high degree of spatial symmetry, the proposed nonlinear fiber can naturally generate polarization entangled photon pairs, a physical object of enormous significance for quantum information technology.
Show PACS
42.81.-i Fiber optics
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
03.67.Mn Entanglement measures, witnesses, and other characterizations

Effect of insulating-nanoparticles addition on ion current and voltage-holding ratio in nematic liquid crystal cells

Pei-Shiang Chen, Chiu-Chung Huang, Yung-Wei Liu, and Chih-Yu Chao

Appl. Phys. Lett. 90, 211111 (2007); http://dx.doi.org/10.1063/1.2740581 (3 pages) | Cited 9 times

Online Publication Date: 23 May 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The transient currents induced by an applied direct voltage (dc) electric field have been measured liquid-crystal cells in nematic phase. The experimental results show that the addition of insulating nanoparticles, such as diamond powders, leads to a reduction of the ion concentration in cells so as to drastically reduce the transient currents and threshold voltage. Simultaneously, a high voltage-holding ratio (VHR) in doped cells is observed. Such a high VHR, in comparison with nematic liquid crystals doped by carbon nanotubes, is a superior feature for future liquid crystal display applications.
Show PACS
61.30.-v Liquid crystals

Polarization of edge emission from III-nitride light emitting diodes of emission wavelength from 395 to 455 nm

Chuanyu Jia, Tongjun Yu, Sen Mu, Yaobo Pan, Zhijian Yang, Zhizhong Chen, Zhixin Qin, and Guoyi Zhang

Appl. Phys. Lett. 90, 211112 (2007); http://dx.doi.org/10.1063/1.2741607 (3 pages) | Cited 13 times

Online Publication Date: 24 May 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Polarization-resolved edge-emitting electroluminescence of InGaN/GaN multiple quantum well (MQW) light emitting diodes (LEDs) from 395 to 455 nm was measured. Polarization ratio decreased from 3.2 of near-ultraviolet LEDs (395 nm) to 1.9 of blue LEDs (455 nm). Based on TE mode dominant emissions in InGaN/GaN MQWs, compressive strain in well region favors TE mode, indium induced quantum-dot-like behavior leads to an increased TM component. As wavelength increased, indium enhanced quantum-dot-like behavior became obvious and E‖C electroluminescence signal increased thus lower polarization ratio. Electroluminescence spectrum shifts confirmed that quantum dotlike behaviors rather than strain might be dominant in modifying luminescence mode of InGaN/GaN MQWs from near ultraviolet to blue.
Show PACS
85.60.Jb Light-emitting devices
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Fractal independently tunable multichannel filters

Shao-Wei Wang, Xiaoshuang Chen, Wei Lu, Ming Li, and Haiqian Wang

Appl. Phys. Lett. 90, 211113 (2007); http://dx.doi.org/10.1063/1.2743380 (3 pages) | Cited 13 times

Online Publication Date: 24 May 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A simple fractal rule has been presented in this letter for the construction of one-dimensional photonic crystals with orthogonal defect states, which can be used as independently tunable multichannel filters. Each channel of the filters can be tuned independently. It overcomes the difficulty and provides an easy way for the design of multichannel filter with specific channels. In order to prove the validity of such a fractal rule, a series of two-channel filters have been fabricated by using a low frequency magnetron sputtering system. The experimental results agree with theoretical ones very well.
Show PACS
42.79.Ci Filters, zone plates, and polarizers
42.70.Qs Photonic bandgap materials
05.45.Df Fractals

Temperature stability of single-photon emission from InGaAs quantum dots in photonic crystal nanocavities

W.-Y. Chen, H.-S. Chang, T. M. Hsu, T.-P. Hsieh, and J.-I. Chyi

Appl. Phys. Lett. 90, 211114 (2007); http://dx.doi.org/10.1063/1.2743398 (3 pages) | Cited 4 times

Online Publication Date: 24 May 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
This study demonstrates the feasibility to 60 K operation of photonic crystal (PC) nanocavities for self-assembled InGaAs quantum dots (QDs) in single-photon applications. With the proper quality factor and small mode volume, this PC nanocavity exhibits excellent spontaneous emission enhancement and high thermal stability. Measuring the second-order correlation function of single QD emission yields clear photon antibunching with a small timing jitter of ∼ 1 ns, which is maintained from T = 7 to 60 K. These results demonstrate that PC nanocavities with an appropriate quality factor and mode volume are well suitable for developing thermal-stable single-photon sources.
Show PACS
78.67.Hc Quantum dots
78.66.Fd III-V semiconductors
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
42.70.Qs Photonic bandgap materials
81.16.Dn Self-assembly
42.50.Dv Quantum state engineering and measurements

Room temperature midinfrared electroluminescence from GaInAsSbP light emitting diodes

A. Krier, V. M. Smirnov, P. J. Batty, V. I. Vasil’ev, G. S. Gagis, and V. I. Kuchinskii

Appl. Phys. Lett. 90, 211115 (2007); http://dx.doi.org/10.1063/1.2741147 (3 pages) | Cited 8 times

Online Publication Date: 24 May 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Room temperature electroluminescence in the midinfrared near 4 μm is reported from GaInAsSbP light emitting diodes grown on GaSb by liquid phase epitaxy. Comparison of the electro- and photoluminescence revealed that light is generated on the p side of the diode. The energy shift (24 meV) is consistent with band gap narrowing and recombination via band tail states due to the Zn doping (1×1018 cm−3) in the p layer of the structure. The temperature dependent behavior of the luminescence and the improved emission intensity was attributed to recombination from localized states arising from electrostatic potential fluctuations due to compositional inhomogeneities in these alloys.
Show PACS
85.60.Jb Light-emitting devices
back to top
RSS Feeds

Phase-contrast x-ray imaging with intense Ar Kα radiation from femtosecond-laser-driven gas target

L. M. Chen, M. Kando, J. Ma, H. Kotaki, Y. Fukuda, Y. Hayashi, I. Daito, T. Homma, K. Ogura, M. Mori, A. S. Pirozhkov, J. Koga, H. Daido, S. V. Bulanov, T. Kimura, et al.

Appl. Phys. Lett. 90, 211501 (2007); http://dx.doi.org/10.1063/1.2742802 (3 pages) | Cited 15 times

Online Publication Date: 22 May 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Intense Ar Kα x ray with very little continuum background has been generated using a dense Ar gas irradiated with an intense femtosecond laser, with the measured flux of 1.2×103 photons/mrad2/pulse. This compact quasimonochromatic x-ray source, with a source size of only 12 μm, has been applied to x-ray radiographic imaging of a biological specimen, resulting in high-resolution, high quality phase-contrast images. Correlation between this intense Kα emission with the laser channeling in the Ar gas is discussed.
Show PACS
07.85.-m X- and γ-ray instruments
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Microwave steam torch

Han S. Uhm, Jong H. Kim, and Yong C. Hong

Appl. Phys. Lett. 90, 211502 (2007); http://dx.doi.org/10.1063/1.2742782 (3 pages) | Cited 9 times

Online Publication Date: 24 May 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Injecting steam into a discharge tube as a swirl gas at a temperature higher than 150 °C, a pure steam torch powered by 2.45 GHz microwaves is generated for various applications such as hydrogen production for fuel cells in the future vehicles. The steam torch is very stable and operates continuously. The temperature measurement of the torch exhibits two distinctive regions: a bright, whitish region of a high-temperature plasma zone and a reddish, dimmer region of a relatively low-temperature zone of hydrogen burning in oxygen, indicating efficient disintegration of water molecules, confirmed by analytical estimates and experimentally measured data.
Show PACS
84.40.-x Radiowave and microwave (including millimeter wave) technology
84.47.+w Vacuum tubes
back to top
RSS Feeds

Thermal and elastic properties of Cu–Zr–Be bulk metallic glass forming alloys

Gang Duan, Mary Laura Lind, Katrien De Blauwe, Aaron Wiest, and William L. Johnson

Appl. Phys. Lett. 90, 211901 (2007); http://dx.doi.org/10.1063/1.2741050 (3 pages) | Cited 16 times

Online Publication Date: 21 May 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The compositional dependence of thermal and elastic properties of Cu–Zr–Be ternary bulk metallic glass forming alloys was systematically studied. There exists a linear relationship between the glass transition temperature Tg and the total Zr concentration. G decreases linearly with increasing Zr concentration as well. The results also show that Tg, shear modulus G, and Poisson’s ratio ν are very sensitive to changes in compositions. Low Tg, low G, and relatively high ν can be achieved with high Zr and Ti concentration.
Show PACS
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity
64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition

Mechanism for persistent hexagonal island formation in AlN buffer layer during growth on Si (111) by plasma-assisted molecular beam epitaxy

Kuang-Yuan Hsu, Hung-Chin Chung, Chuan-Pu Liu, and Li-Wei Tu

Appl. Phys. Lett. 90, 211902 (2007); http://dx.doi.org/10.1063/1.2741054 (3 pages)

Online Publication Date: 21 May 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The characteristics of structure and morphology of AlN grown by a growth interruption method on Si (111) with plasma-assisted molecular beam epitaxy are investigated. It is found that the growth interruption method would improve the surface flatness of the AlN layer without the formation of Al droplets. However, AlN hexagonal islands were present and persistent throughout the entire growth owing to effective strain relaxation and Eherlich-Schowebel barrier effect of preexistent surface islands grown on higher terraces of the Si substrate. The density of threading dislocations underneath the hexagonal islands is much less than elsewhere in the film, which is presumably due to dislocation annihilation during the island growth process.
Show PACS
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances

Magnetocaloric effect of Ho-, Dy-, and Er-based bulk metallic glasses in helium and hydrogen liquefaction temperature range

Q. Luo, D. Q. Zhao, M. X. Pan, and W. H. Wang

Appl. Phys. Lett. 90, 211903 (2007); http://dx.doi.org/10.1063/1.2741120 (3 pages) | Cited 33 times

Online Publication Date: 21 May 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The authors study the magnetocaloric effect and refrigerant capacity of Ho30Y26Al24Co20, Dy50Gd7Al23Co20, and Er50Al24Co20Y6 bulk metallic glasses. Their magnetic entropy changes associated with spin glass to paramagnetic transition are larger than those of Gd, Gd5Si2Ge1.9Fe0.1, and many other intermetallic compounds reported in the same temperature range. The good refrigerant efficiency combined with their high electrical resistivity, high thermal stability, outstanding mechanical properties, and tunable nature makes these glassy materials be attractive candidates for magnetic refrigerants in helium and hydrogen liquefaction temperature range of 2–50 K.
Show PACS
75.30.Sg Magnetocaloric effect, magnetic cooling
61.43.Fs Glasses
75.50.Kj Amorphous and quasicrystalline magnetic materials
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.50.Lk Spin glasses and other random magnets
75.20.En Metals and alloys

Structural correlations of the enhancement of dielectric permittivity in the (Ta2O5)0.92(TiO2)0.08 system

X. Q. Liu, X. D. Han, Z. Zhang, L. F. Ji, and Y. J. Jiang

Appl. Phys. Lett. 90, 211904 (2007); http://dx.doi.org/10.1063/1.2740172 (3 pages) | Cited 2 times

Online Publication Date: 21 May 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A Ti-ion ordering which correlates to the significant enhancement of the dielectric constant was determined in the (Ta2O5)0.92(TiO2)0.08 system by high resolution electron microscopy and the corresponding simulations. The alien Ti ions were determined to selectively sit on the octahedral locations in the Ta2O5 base structure in an average of 9-time period along the ⟨110⟩ direction. The authors suggest this Ti-ion ordering induces the directional enhancement of the dielectric permittivity of the (Ta2O5)0.92(TiO2)0.08 system. The atomic mechanism of this modulated structure contributing to the enhancement of the dielectric constant was qualitatively interpreted using a one-dimensional chain model. The structural correlations of the dielectric enhancement revealed in this study suggest a way to search or design high-k materials.
Show PACS
77.22.Ch Permittivity (dielectric function)

Time-resolved dynamics of coherent acoustic phonons in CdMnTe diluted-magnetic single crystals

D. Wang, A. Cross, G. Guarino, S. Wu, Roman Sobolewski, and A. Mycielski

Appl. Phys. Lett. 90, 211905 (2007); http://dx.doi.org/10.1063/1.2738368 (3 pages) | Cited 4 times

Online Publication Date: 21 May 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The authors report on observation of pronounced coherent acoustic phonon (CAP) oscillations in diluted-magnetic Cd1−xMnxTe (x = 0.09) single crystals by means of femtosecond, optical single-color, and two-color pump-probe spectroscopy. The observed properties of CAP oscillations are consistent with the propagating-strain-pulse model, with electronic stress as the main CAP generation mechanism. The experimental dispersion relation between the CAP oscillation frequency and the probe-beam wave vector allowed them to extract the Cd0.91Mn0.09Te refractive index dependence on wavelength, while the dependence of oscillation amplitudes on the photon energy near the Cd0.91Mn0.09Te band gap edge indicated that the material energy gap is 1.63 eV. Two-color pump-probe studies showed that the speed of sound in our material is 3590 m/s and that the absorption depth of probe light, rather than the decay time of CAPs, is the dominant source of the experimentally observed oscillation dephasing time. The intrinsic lifetime of CAPs in CdMnTe crystals has been found to be at least in the nanosecond range.
Show PACS
63.20.-e Phonons in crystal lattices
78.47.-p Spectroscopy of solid state dynamics
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Rate-dependent inhomogeneous-to-homogeneous transition of plastic flows during nanoindentation of bulk metallic glasses: Fact or artifact?

Jae-il Jang, Byung-Gil Yoo, and Ju-Young Kim

Appl. Phys. Lett. 90, 211906 (2007); http://dx.doi.org/10.1063/1.2742286 (3 pages) | Cited 11 times

Online Publication Date: 21 May 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
There has been considerable controversy over the “apparent” rate-dependent transition from inhomogeneous-to-homogeneous flow during nanoindentation of bulk metallic glasses (BMGs) at room temperature: whether it arises from the existence of homogeneous-flow regime in BMG deformation map or is an artifact due to the instrumental blurring at high rates. To provide a clue to address this dispute, the authors performed nanoindentation experiments on a Zr-based BMG with two geometrically self-similar indenters. The results are discussed in terms of the discrete plasticity ratio, which is a useful parameter in analyzing the contribution of inhomogeneous plasticity to the total plastic deformation.
Show PACS
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
81.40.Lm Deformation, plasticity, and creep
62.20.M- Structural failure of materials
62.20.F- Deformation and plasticity

Diffraction of plane compressional wave by a nanosized spherical cavity with surface effects

G. F. Wang

Appl. Phys. Lett. 90, 211907 (2007); http://dx.doi.org/10.1063/1.2741604 (3 pages) | Cited 8 times

Online Publication Date: 22 May 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
For nanostructured materials and devices, the effects of surface energy become prominent due to the increasing ratio of surface area to volume. In the present letter, based on the surface elasticity theory, the authors analyzed the diffraction of plane harmonic compressional wave (P wave) by a spherical cavity. The results show that once the radius of cavity reduces to nanometers, surface energy significantly affects the diffraction of elastic waves. For incident waves with different frequencies, the surface effects on dynamic stress concentrations around the spherical cavity are discussed in detail.
Show PACS
68.35.Gy Mechanical properties; surface strains
68.35.Md Surface thermodynamics, surface energies
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity

Nearest-neighbor coordination and chemical ordering in multicomponent bulk metallic glasses

D. Ma, A. D. Stoica, L. Yang, X.-L. Wang, Z. P. Lu, J. Neuefeind, M. J. Kramer, J. W. Richardson, and Th. Proffen

Appl. Phys. Lett. 90, 211908 (2007); http://dx.doi.org/10.1063/1.2742315 (3 pages) | Cited 13 times

Online Publication Date: 22 May 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The authors report complementary use of high-energy x-ray and neutron diffraction to probe the local atomic structure in a Zr-based bulk metallic glass. By analyzing the partial coordination numbers, the authors demonstrate the presence of multiple types of solute-centered clusters in the multicomponent glass and efficient packing of the amorphous structure at atomic scale. The authors’ findings provide a basis for understanding how local structures change during phase transformation and mechanical deformation of multicomponent amorphous alloys.
Show PACS
61.43.Fs Glasses
64.70.K- Solid-solid transitions
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
Page 1 of 4 Pages Next Page | Jump to Page
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close