jap banner
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Flickr Twitter iResearch App Facebook

BROWSE VOLUMES

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

15 Jan 2012

Volume 111, Issue 2, Articles (02xxxx)

Issue Cover Spotlight Figure

J. Appl. Phys. 111, 023508 (2012); http://dx.doi.org/10.1063/1.3677988 (7 pages)

Li-Yong Jiang, Hong Wu, Wei Jia, and Xiang-Yin Li

Polarization-independent negative refraction effect in SiO2-GaAs annular photonic crystals.

Enlarge Image | Read More
Page 1 of 5 Pages Return to All Sections Next Page
back to top
RSS Feeds
back to top Lasers, Optics, and Optoelectronics

Influence of Dy3+ coactivator on the luminescence properties of Gd2O2S:Tb3+ phosphor

Fei Wang, Dachun Liu, Bin Yang, Jinchao Zhang, and Yongnian Dai

J. Appl. Phys. 111, 023101 (2012); http://dx.doi.org/10.1063/1.3676252 (5 pages)

Online Publication Date: 17 January 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Gd2O2S:Tb, Dy phosphor were synthesized by co-precipitation method combined with solid-state reactions. The crystal structure and luminescent properties were investigated in this paper. It was confirmed that no new phase was introduced by the analysis of X-ray diffractions (XRD) and fluorescence spectroscopy. It was also illustrated that the lattice size was decreased by doping Dy3+ ions. The results showed that the Dy3+ coactivator had a remarkable influence on the spectral properties of the Gd2O2S:Tb phosphor and can be taken as rare earth ion detector to determine the micro-structure of phosphors. Especially the cross relaxation between Tb3+ and Dy3+ may take place to form the non-radiative energy transfer. Dy3+ as the coactivator added in Gd2O2S:Tb could enhance the luminescence and not disturb its other primary properties. With Dy3+ concentration increased, the intensity of 4F9/2—H13/2 transition at 578 nm was increased further and the emission of 5D4—7FJ transition was highly improved to cause greener emission.
Show PACS
78.55.Hx Other solid inorganic materials
61.72.up Other materials
61.66.Fn Inorganic compounds

41 GHz and 10.6 GHz low threshold and low noise InAs/InP quantum dash two-section mode-locked lasers in L band

M. Dontabactouny, R. Piron, K. Klaime, N. Chevalier, K. Tavernier, S. Loualiche, A. Le Corre, D. Larsson, C. Rosenberg, E. Semenova, and K. Yvind

J. Appl. Phys. 111, 023102 (2012); http://dx.doi.org/10.1063/1.3677976 (5 pages)

Online Publication Date: 18 January 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
This paper reports recent results on InAs/InP quantum dash–based, two-section, passively mode-locked lasers pulsing at 41 GHz and 10.6 GHz and emitting at 1.59 μm at 20 °C. The 41-GHz device (1 mm long) starts lasing at 25 mA under uniform injection and the 10.6 GHz (4 mm long) at 71 mA. Their output pulses are significantly chirped. The 41-GHz laser exhibits 7 ps pulses after propagation in 60 m of a single-mode fiber. The 10.6-GHz laser generates one picosecond pulses with 545 m of a single-mode fiber. Its single side-band phase noise does not exceed –80 dBc/Hz at 100 kHz offset, leading to an average timing jitter of 800 fs.
Show PACS
42.50.Pq Cavity quantum electrodynamics; micromasers
42.55.Px Semiconductor lasers; laser diodes
42.60.Fc Modulation, tuning, and mode locking

Enhancement of the transverse non-reciprocal magneto-optical effect

V. Zayets, H. Saito, S. Yuasa, and K. Ando

J. Appl. Phys. 111, 023103 (2012); http://dx.doi.org/10.1063/1.3677942 (7 pages) | Cited 1 time

Online Publication Date: 23 January 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The methods to enhance the transverse non-reciprocal magneto-optical (nMO) effect have been studied. The transverse nMO effect occurs in the case when light propagates perpendicularly to the magnetic field. It was demonstrated that light can experience the transverse nMO effect only when it propagates in the vicinity of a boundary between two materials and the optical field at least in one material is evanescent. The magnitude of the transverse nMO effect is comparable to or greater than the magnitude of the longitudinal nMO effect. In the case of surface plasmons propagating at a boundary between the transition metal and the dielectric it is possible to magnify the transverse nMO effect and the magneto-optical figure-of-merit may increase from a few percents to above 100%.
Show PACS
78.20.Ls Magneto-optical effects
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Efficiency improvement in fullerene-layer-inserted organic bulk-heterojunction solar cells

Zhihai Liu and Eun-Cheol Lee

J. Appl. Phys. 111, 023104 (2012); http://dx.doi.org/10.1063/1.3677979 (3 pages)

Online Publication Date: 23 January 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We have improved power conversion efficiencies of organic bulk-heterojunction solar cells with the active layer composed of poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) by inserting a PCBM layer between the active layer and adjacent Al cathode. This improvement is mainly due to the increase in short-circuit current, which prevails over the changes in other parameters. The largest improvement of 11.7% is obtained at the PCBM thickness of 10 nm, while further increasing of the thickness degrades the fill factor and eventually induces S-kinks in the current-voltage characteristics. We discuss possible models explaining the efficiency variations with the PCBM thickness and the occurrence of the S-kinks.
Show PACS
88.40.jp Multijunction solar cells
85.65.+h Molecular electronic devices
88.40.hj Efficiency and performance of solar cells

Substrate independence of THz vibrational modes of polycrystalline thin films of molecular solids in waveguide THz-TDS

S. Sree Harsha, Joseph. S. Melinger, S. B. Qadri, and D. Grischkowsky

J. Appl. Phys. 111, 023105 (2012); http://dx.doi.org/10.1063/1.3678000 (7 pages) | Cited 2 times

Online Publication Date: 23 January 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The influence of the metal substrate on the measurement of high resolution THz vibrational modes of molecular solids with the waveguide THz-TDS technique is investigated. The sample film of salicylic acid is studied using waveguide THz-TDS on three different metal substrates and two-surface passivated substrates. The independence of the observed THz vibrational modes to the metal substrate is demonstrated. Independently, surface passivation is presented as a viable experimental addition to the waveguide THz-TDS technique to aid the characterization of samples with known reactivity to metal surfaces.
Show PACS
78.70.Gq Microwave and radio-frequency interactions
81.65.Rv Passivation
63.20.-e Phonons in crystal lattices
78.30.-j Infrared and Raman spectra
78.66.-w Optical properties of specific thin films

An integrated hollow-core photonic crystal fiber transverse optical trapping system for optical manipulation and detection

V. K. Shinoj and V. M. Murukeshan

J. Appl. Phys. 111, 023106 (2012); http://dx.doi.org/10.1063/1.3676248 (5 pages) | Cited 1 time

Online Publication Date: 31 January 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Optical manipulation, separation, and detection of biological cells have immense potential biomedical applications, for example, in disease detection. In this paper, we present optical manipulation and detection of micron sized fluorescent particles inside hollow-core photonic crystal fiber (HC-PCF) by transverse optical trapping. An optical trapping system is designed where a near-infrared laser light is focused using a microscope objective to create an optical trap across a liquid-filled HC-PCF. The fluorescent microsphere particles trapped in the core of HC-PCF using the laser induced optical force further undergo imaging and fluorescence spectroscopic analysis. It is illustrated that the proposed method can track the particle into a different medium using the optical trap as well. The obtained results indicate that this proposed method has tangible potential for developing HC-PCF based lab-on-a-chip bio/chemical sensors capable of detecting reagents in ultra low sample volumes.
Show PACS
42.82.-m Integrated optics
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
42.70.Qs Photonic bandgap materials
back to top Plasmas and Electrical Discharges

Steady state discharge optimization in high-power impulse magnetron sputtering through the control of the magnetic field

J. Čapek, M. Hála, O. Zabeida, J. E. Klemberg-Sapieha, and L. Martinu

J. Appl. Phys. 111, 023301 (2012); http://dx.doi.org/10.1063/1.3673871 (9 pages) | Cited 4 times

Online Publication Date: 17 January 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
High-power impulse magnetron sputtering (HiPIMS) is a pulsed DC sputtering technique utilizing high power density peaks of typically more than 100 W cm−2. The discharge operation at such elevated powers can be hindered by the magnetron configuration (size and magnetic field) and/or the target conditions (e.g., material and thickness). In addition, target erosion is an important issue significantly affecting process reproducibility. In the present work, we propose a simple approach for the stabilization of the HiPIMS discharge by controlling the target magnetic field using paramagnetic spacers with different thicknesses in between the magnetron surface and the target. We demonstrate a straightforward discharge optimization, while using various target materials, such as Nb, Ta, Cr, Al, Ti, Si, and even C (graphite). The existence of a steady state high density discharge above the graphite target and the other targets in general is discussed in terms of the magnetic field configuration and the gas rarefaction effect.
Show PACS
52.80.Vp Discharge in vacuum
81.15.Cd Deposition by sputtering
52.25.-b Plasma properties
52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)

Inducing phase locking of multiple oscillators beyond the Adler’s condition

Wei Song, Jun Sun, Hao Shao, Ren-zhen Xiao, Chang-hua Chen, and Guo-zhi Liu

J. Appl. Phys. 111, 023302 (2012); http://dx.doi.org/10.1063/1.3671537 (5 pages) | Cited 4 times

Online Publication Date: 17 January 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
To achieve phase locking of high power microwave oscillators on a relatively weak coupling strength, an inducing phase locking method is investigated. With an external signal injected from the end of relativistic backward wave oscillator, the frequency and phase of the output microwave is pulling in the starting oscillation process and remaining stable in the later stationary oscillation process. The simulation results indicate that injecting of inducing signal prior to the onset of natural oscillations is necessary, while the duration of injection, power of injection and locking bandwidth are not limited by classic Adler’s law.
Show PACS
84.40.Fe Microwave tubes (e.g., klystrons, magnetrons, traveling-wave, backward-wave tubes, etc.)

Absorption spectroscopy measurements of argon metastable and resonant atom density in atmospheric pressure Ar-He surface-wave plasmas using a low pressure lamp

J. Muñoz, J. Margot, and M. D. Calzada

J. Appl. Phys. 111, 023303 (2012); http://dx.doi.org/10.1063/1.3671408 (7 pages)

Online Publication Date: 19 January 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The densities of metastable and resonant atom were measured in atmospheric pressure Ar-He surface-wave plasmas. Measurements were performed using an absorption spectroscopy method taking into account the Voigt profiles of the plasma lines. The density values of the argon 3P2, 3P0 (metastable atoms) and 3P1 (resonant atoms) levels measured in pure argon discharges are in good agreement with those reported in the literature. A drastic decrease of metastable and resonant densities is observed when introducing helium in amounts as low as 2%. The influence of electron density and gas temperature on the population mechanisms (direct electron excitation from the ground state and dissociative recombination) of metastable and resonant atoms is discussed using a simplified theoretical model.
Show PACS
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.80.Pi High-frequency and RF discharges
52.70.Kz Optical (ultraviolet, visible, infrared) measurements

Spark discharge formation in an inhomogeneous electric field under conditions of runaway electron generation

Tao Shao (邵涛), Victor F. Tarasenko, Cheng Zhang (章程), Mikhail I. Lomaev, Dmitrii A. Sorokin, Ping Yan (严萍), Andrei V. Kozyrev, and Evgeni Kh. Baksht

J. Appl. Phys. 111, 023304 (2012); http://dx.doi.org/10.1063/1.3677951 (10 pages) | Cited 4 times

Online Publication Date: 23 January 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
In this article we report on work where the formation of a spark in nanosecond high-voltage discharges was studied in nitrogen, nitrogen-methane mixtures, and air at increased pressures under the conditions of runaway electron generation. Voltage pulses of amplitude ∼90 and ∼250 kV were applied to a point-to-plane gap with a planar anode and a cathode of small curvature radius. Cathode spots appeared early in the discharge, within ∼200 ps of a corona discharge at high rate of rise of the voltage (∼5 × 1014 V/s) across centimeter point-to-plane gap spacing. The spark leader that bridged the point-to-plane gap propagated from the planar anode with cathode spots and a voltage pulse rise time of less than 1 ns. The discharge from diffuse clouds took the form of diffuse jets with increasing pulse repetition rate, thus achieving the accumulation effect in a repetitively pulsed discharge. Characteristic emission spectra are presented for spark diffuse and corona discharges.
Show PACS
52.80.Mg Arcs; sparks; lightning; atmospheric electricity
52.80.Hc Glow; corona
52.25.Fi Transport properties
52.75.-d Plasma devices
52.25.Os Emission, absorption, and scattering of electromagnetic radiation

Negative resistance phenomenon in dual-frequency capacitively coupled plasma-enhanced chemical vapor deposition system for photovoltaic manufacturing process

H. C. Kwon, Aman‐ur‐Rehman, I. H. Won, W. T. Park, and J. K. Lee

J. Appl. Phys. 111, 023305 (2012); http://dx.doi.org/10.1063/1.3679107 (6 pages) | Cited 1 time

Online Publication Date: 26 January 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The validity of effective frequency concept is investigated for dual‐frequency (DF) capacitively coupled plasma (CCP) discharges by using particle‐in‐cell/Monte Carlo collision simulations. This concept helps in analyzing DF CCP discharges in a fashion similar to single‐frequency (SF) CCP discharges with effective parameters. Unlike the driving frequency of SF CCP discharges, the effective frequency in DF CCP is dependent on the ratio of the two driving currents (or voltages) and this characteristic makes it possible to control the ion flux and the ion bombardment energy independently. This separate control principally allows to increase the ion flux and plasma density for high deposition rates, while keeping the ion mean energy constant at low values to prevent the bombardment of highly energetic ions at the substrate surface to avoid unwanted damage in the solar cell manufacturing. The abrupt transition of the effective frequency leads to the phenomenon of negative resistance which is one of the several physical phenomena associated uniquely with DF CCP discharges. Using effective frequency concept, the plasma characteristics have been investigated in the negative resistance regime for solar cell manufacturing.
Show PACS
88.40.H- Solar cells (photovoltaics)
52.20.Hv Atomic, molecular, ion, and heavy-particle collisions
52.77.Dq Plasma-based ion implantation and deposition
52.80.Pi High-frequency and RF discharges

Model for a transformer-coupled toroidal plasma source

Shahid Rauf, Ajit Balakrishna, Zhigang Chen, and Ken Collins

J. Appl. Phys. 111, 023306 (2012); http://dx.doi.org/10.1063/1.3679565 (10 pages)

Online Publication Date: 30 January 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A two-dimensional fluid plasma model for a transformer-coupled toroidal plasma source is described. Ferrites are used in this device to improve the electromagnetic coupling between the primary coils carrying radio frequency (rf) current and a secondary plasma loop. Appropriate components of the Maxwell equations are solved to determine the electromagnetic fields and electron power deposition in the model. The effect of gas flow on species transport is also considered. The model is applied to 1 Torr Ar/NH3 plasma in this article. Rf electric field lines form a loop in the vacuum chamber and generate a plasma ring. Due to rapid dissociation of NH3, NHx+ ions are more prevalent near the gas inlet and Ar+ ions are the dominant ions farther downstream. NH3 and its by-products rapidly dissociate into small fragments as the gas flows through the plasma. With increasing source power, NH3 dissociates more readily and NHx+ ions are more tightly confined near the gas inlet. Gas flow rate significantly influences the plasma characteristics. With increasing gas flow rate, NH3 dissociation occurs farther from the gas inlet in regions with higher electron density. Consequently, more NH4+ ions are produced and dissociation by-products have higher concentrations near the outlet.
Show PACS
52.50.Dg Plasma sources
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)
52.25.Fi Transport properties
52.40.Db Electromagnetic (nonlaser) radiation interactions with plasma
back to top Structural, Mechanical, Thermodynamic, and Optical Properties of Condensed Matter

Effects of hydrogenation on non-radiative defects in GaNP and GaNAs alloys: An optically detected magnetic resonance study

D. Dagnelund, I. P. Vorona, G. Nosenko, X. J. Wang, C. W. Tu, H. Yonezu, A. Polimeni, M. Capizzi, W. M. Chen, and I. A Buyanova

J. Appl. Phys. 111, 023501 (2012); http://dx.doi.org/10.1063/1.3676576 (6 pages) | Cited 1 time

Online Publication Date: 17 January 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Photoluminescence and optically detected magnetic resonance techniques are utilized to study defect properties of GaNP and GaNAs alloys subjected to post-growth hydrogenation by low-energy sub-threshold ion beam irradiation. It is found that in GaNP H incorporation leads to activation of new defects, which has a Ga interstitial (Gai) atom at its core and may also involve a H atom as a partner. The observed activation critically depends on the presence of N in the alloy, as it does not occur in GaP with a low level of N doping. In sharp contrast, in GaNAs hydrogen is found to efficiently passivate Gai-related defects present in the as-grown material. A possible mechanism responsible for the observed difference in the H behavior in GaNP and GaNAs is discussed.
Show PACS
61.72.jj Interstitials
61.80.Jh Ion radiation effects
78.55.Cr III-V semiconductors
81.65.-b Surface treatments

Directly grown large area single-walled carbon nanotube films with very high sensitivity to normal pressure

Jonathan Genest, Keun Su Kim, Annick Sauvé, Patrick Boissy, Gervais Soucy, and Jacques Beauvais

J. Appl. Phys. 111, 023502 (2012); http://dx.doi.org/10.1063/1.3676580 (6 pages) | Cited 1 time

Online Publication Date: 17 January 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Induction thermal plasma was used to grow a large area, ∼150 mm × 450 mm, and ∼1000 μm thick multi-layered carbon nanotube film. The film is made of a loosely woven structure of single-walled carbon nanotubes uniformly distributed among metallic impurities and carbon black particles. Under cyclic compressive strain, the film acts as a viscoelastic material. A model based on tunneling conduction was used to describe its high piezoresistive sensitivity to normal pressure. The gauge factor obtained for this film was 76.3, more than 20 times higher than the values achieved with a standard buckypaper made from the same nanotube source. This fast and straightforward approach for synthesizing pressure sensitive films is done directly inside the processing system during the growth of the carbon nanotubes. It could provide the means for producing low cost large-scale sensors, such as smart materials for civil and mechanical structures.
Show PACS
81.05.U- Carbon/carbon-based materials
61.46.Fg Nanotubes
73.63.Fg Nanotubes
81.07.De Nanotubes
81.40.Jj Elasticity and anelasticity, stress-strain relations
81.40.Lm Deformation, plasticity, and creep

Phase-controlled, heterodyne laser-induced transient grating measurements of thermal transport properties in opaque material

Jeremy A. Johnson, Alexei A. Maznev, Mayank T. Bulsara, Eugene A. Fitzgerald, T. C. Harman, S. Calawa, C. J. Vineis, G. Turner, and Keith A. Nelson

J. Appl. Phys. 111, 023503 (2012); http://dx.doi.org/10.1063/1.3675467 (7 pages) | Cited 2 times

Online Publication Date: 17 January 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The methodology for a heterodyned laser-induced transient thermal grating technique for non-contact, non-destructive measurements of thermal transport in opaque material is presented. Phase-controlled heterodyne detection allows us to isolate pure phase or amplitude transient grating signal contributions by varying the relative phase between reference and probe beams. The phase grating signal includes components associated with both transient reflectivity and surface displacement whereas the amplitude grating contribution is governed by transient reflectivity alone. By analyzing the latter with the two-dimensional thermal diffusion model, we extract the in-plane thermal diffusivity of the sample. Measurements on a 5 μm thick single crystal PbTe film yielded excellent agreement with the model over a range of grating periods from 1.6 to 2.8 μm. The measured thermal diffusivity of 1.3 × 10−6 m2/s was found to be slightly lower than the bulk value.
Show PACS
42.62.Eh Metrological applications; optical frequency synthesizers for precision spectroscopy
42.79.Dj Gratings
66.70.Df Metals, alloys, and semiconductors

Acoustic metamaterial exhibiting four different sign combinations of density and modulus

Yong Mun Seo, Jong Jin Park, Seung Hwan Lee, Choon Mahn Park, Chul Koo Kim, and Sam Hyeon Lee

J. Appl. Phys. 111, 023504 (2012); http://dx.doi.org/10.1063/1.3676262 (5 pages) | Cited 4 times

Online Publication Date: 18 January 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We fabricated a double negative acoustic metamaterial which consisted of Helmholtz resonators and membranes. Experimental data on the transmission and dispersion relation are presented. The system exhibited three frequencies where the acoustic state makes sharp transitions from density negative (ρ-NG) to double negative (DNG), modulus negative (B-NG), and double positive (DPS) in sequence with the frequency. We observed a wide range of negative refractive indexes from −0.06 to −3.7 relative to air, which will allow for new acoustic transformation techniques.
Show PACS
43.38.-p Transduction; acoustical devices for the generation and reproduction of sound
81.05.Xj Metamaterials for chiral, bianisotropic and other complex media
43.25.-x Nonlinear acoustics

Observation of quantum beat oscillations and ultrafast relaxation of excitons confined in GaAs thin films by controlling probe laser pulses

Shohei Ohta, Osamu Kojima, Takashi Kita, and Toshiro Isu

J. Appl. Phys. 111, 023505 (2012); http://dx.doi.org/10.1063/1.3676429 (4 pages) | Cited 2 times

Online Publication Date: 19 January 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We study the quantum beats and relaxation dynamics of exciton center-of-mass motion confined in GaAs thin films by a reflection-type pump-probe technique. By using spectrally narrowed probe pulses with energies comparable with the exciton energy separation, oscillations caused by quantum beats between the confined excitons and ultrafast responses which are shorter than their lifetime appear. This appearance of quantum beats does not result from the so-called detection process. Our results demonstrate that the reduction of the destructive interference of the probe pulse in the sample is a key factor to observe the excitonic quantum beats.
Show PACS
71.35.-y Excitons and related phenomena
78.47.jm Quantum beats

Kinetics of small single particle combustion of zirconium alloy

Haoyan Wei and Choong-Shik Yoo

J. Appl. Phys. 111, 023506 (2012); http://dx.doi.org/10.1063/1.3677789 (8 pages) | Cited 3 times

Online Publication Date: 20 January 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We present quantitative kinetic information regarding small, 1-10 μm in diameter, single particle combustion of Zr-rich metal alloy foils subjected to either mechanical impacts or laser-ablation. The lights from combustion of metal fragments were recorded on a high-speed camera. The particle size was determined by the motion analysis of individual particle trajectory based on an aerodynamic drag law and further verified by the microstructure and chemical composition analysis of recovered post-burn particles. The measured particle sizes show a log-normal distribution centered at around 3.1 μm in diameter, and the composition of recovered particles is that of fully oxidized ZrO2. The temperature evolution of each particle along the space/time-trajectory is determined based on the thermal emission from combustion using a single-color photographic spectro-pyrometry. The result indicates that the particle has reached the maximum combustion temperature of 4000 K, well beyond the melting temperature of ZrO2, and undergone the solidification of molten ZrO2 during the cooling stage. It also shows that the maximum combustion temperature decreases linearly with increasing the particle diameter, following the correlation t = aD1.5–1.8 between the burn time (t) and the particle diameter (D). Combining the particle size, the burn time, and the particle temperature, both temperature and mass burn rates are obtained as a function of particle size. As the particle size increases, the temperature burn rate decreases, whereas the mass burn rate goes in the opposite direction.
Show PACS
81.05.Bx Metals, semimetals, and alloys
81.30.Fb Solidification
82.33.Vx Reactions in flames, combustion, and explosions
64.70.D- Solid-liquid transitions
79.20.Eb Laser ablation

Synchronous imaging for rapid visualization of complex vibration profiles in electromechanical microresonators

Yoav Linzon, Daniel J. Joe, Bojan Ilic, Juraj Topolancik, Jeevak M. Parpia, Harold G. Craighead, and Slava Krylov

J. Appl. Phys. 111, 023507 (2012); http://dx.doi.org/10.1063/1.3677791 (6 pages)

Online Publication Date: 20 January 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Synchronous imaging is used for the dynamic space-domain studies of vibration profiles in capacitively driven, thin n + doped polysilicon microbridges oscillating at rf frequencies. Fast and high-resolution actuation profile measurements of micromachined resonators are useful when significant device nonlinearities are present. For example, bridges under compressive stress near the critical Euler value often reveal complex dynamics stemming from a state close to the onset of buckling. This leads to enhanced sensitivity of the vibration modes to external conditions, such as pressure, temperatures, and chemical composition, the global behavior of which can be conveniently evaluated using synchronous imaging combined with spectral measurements. We performed an experimental study of high drive amplitude and ambient pressure effect on the resonant vibration profiles in electrically driven microbridges near critical buckling. Numerical analysis of electrostatically driven post-buckled microbridges supports the richness of complex vibration dynamics that are possible in such microelectromechanical devices.
Show PACS
07.10.Cm Micromechanical devices and systems

Polarization-independent negative refraction effect in SiO2-GaAs annular photonic crystals

Li-Yong Jiang, Hong Wu, Wei Jia, and Xiang-Yin Li

J. Appl. Phys. 111, 023508 (2012); http://dx.doi.org/10.1063/1.3677988 (7 pages) | Cited 4 times

Online Publication Date: 23 January 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We systematically investigated the negative refraction effect for both TM and TE polarization modes in SiO2-GaAs annular photonic crystals with triangular lattice. It was found that, in comparison with normal triangular-lattice air-holes photonic crystals, the annular photonic crystals have much lower and flatter band structures, which are quite beneficial to the formation of convex equifrequency surfaces for both polarizations. Further analyses on equifrequency surfaces and the electric field distribution of annular photonic crystals with different parameters have not only first demonstrated the possibility of polarization-independent negative refraction effect in annular photonic crystals, but also revealed some important laws to control the working frequency and performance of this remarkable effect.
Show PACS
42.70.Qs Photonic bandgap materials

A simple criterion to predict the glass forming ability of metallic alloys

Marcelo Falcão de Oliveira

J. Appl. Phys. 111, 023509 (2012); http://dx.doi.org/10.1063/1.3676196 (5 pages) | Cited 6 times

Online Publication Date: 24 January 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A new and simple criterion with which to quantitatively predict the glass forming ability (GFA) of metallic alloys is proposed. It was found that the critical cooling rate for glass formation (RC) correlates well with a proper combination of two factors, the minimum topological instability (λmin) and the Δh parameter, which depends on the average work function difference (Δφ) and the average electron density difference (Δnws1/3) among the constituent elements of the alloy. A correlation coefficient (R2) of 0.76 was found between Rc and the new criterion for 68 alloys in 30 different metallic systems. The new criterion and the Uhlmann’s approach were used to estimate the critical amorphous thickness (ZC) of alloys in the Cu-Zr system. The new criterion underestimated RC in the Cu-Zr system, producing predicted ZC values larger than those observed experimentally. However, when considering a scale factor, a remarkable similarity was observed between the predicted and the experimental behavior of the GFA in the binary Cu-Zr. When using the same scale factor and performing the calculation for the ternary Zr-Cu-Al, good agreement was found between the predicted and the actual best GFA region, as well as between the expected and the observed critical amorphous thickness.
Show PACS
81.05.Kf Glasses (including metallic glasses)
64.70.pe Metallic glasses
65.40.gh Work functions
61.43.Dq Amorphous semiconductors, metals, and alloys
61.43.Fs Glasses

Perturbation analysis of acoustic wave scattering at rough solid-solid interfaces

Huarui Sun and Kevin P. Pipe

J. Appl. Phys. 111, 023510 (2012); http://dx.doi.org/10.1063/1.3676250 (6 pages) | Cited 1 time

Online Publication Date: 24 January 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We apply a boundary perturbation approach to model the scattering of acoustic waves at rough solid-solid interfaces. This method incorporates mode conversion and allows straightforward separation of specular and diffuse components, the relative fractions of which play an important role in determining thermal boundary resistance and the performance of acoustic phonon devices. The effect of acoustic impedance mismatch on the distribution of scattered waves is investigated, as well as the coupling to interface modes.
Show PACS
68.35.Iv Acoustical properties
43.20.Rz Steady-state radiation from sources, impedance, radiation patterns, boundary element methods
43.25.Jh Reflection, refraction, interference, scattering, and diffraction of intense sound waves
43.38.-p Transduction; acoustical devices for the generation and reproduction of sound

Effects of substrate orientation on the optical anisotropy spectra of GaN/AlN/Si heterostructures in the energy range from 2.0 to 3.5 eV

L. F. Lastras-Martínez, R. E. Balderas-Navarro, R. Herrera-Jasso, J. Ortega-Gallegos, A. Lastras-Martínez, Y. Cordier, J.-Ch. Moreno, E. Frayssinet, and F. Semond

J. Appl. Phys. 111, 023511 (2012); http://dx.doi.org/10.1063/1.3677949 (5 pages) | Cited 1 time

Online Publication Date: 24 January 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report reflectance (R) and reflectance difference spectroscopy (RDS) spectra of wurtzite heterostructures grown on Si(111) and Si(110) substrates in the energy range from 2.0 to 3.5 eV. Due to the threefold symmetry of the Si(111) surface, the heterostructures grown on this surface will relax isotropically through the formation of misfit dislocations, preferably at the AlN/Si interface, and no in-plane anisotropies are expected. In fact, only a small in-plane anisotropy of reflectance is observed, due to the initial residual off-cut of the silicon substrate that leads to wurtzite layers with a c-axis slightly tilted with respect to the surface. In contrast, for the Si(110) substrate, strong differences in lattice parameters appear between silicon and GaN/AlN depending on the considered in-plane direction, leading to a large in-plane anisotropy. By using a multiple reflection model for R and the in-plane anisotropies described, we developed a model to describe the RDS spectra in the vicinity and below the fundamental gap of GaN.
Show PACS
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)

Energy transfer and dynamics studies of photoluminescence of polythiophene derivative in blend thin films

Zi-Han Wang, Haiwon Lee, and Hai-Ning Cui

J. Appl. Phys. 111, 023512 (2012); http://dx.doi.org/10.1063/1.3678453 (6 pages) | Cited 1 time

Online Publication Date: 25 January 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Thin films of the blend luminescent poly 3-(2-(5-chlorobenzotriazolo)ethyl) thiophene (PCBET) with poly-(p-(methyl)-phenylmethacrylate) (PMPMA), polyvinylcarzole (PVK), and poly (methyl methacrylate) (PMMA) were deposited by spin coating. Systematic studies on optical properties, the concentration effect, and energy transfer of these conjugated polymers within the blend films are discussed. Fluorescence lifetimes of excited state in the blend films were investigated by nanosecond time-resolved spectroscopy, UV-vis, photoluminescence (PL), synchronous PL spectra. These results and analysis suggest that energy transfer, from good matrix material (PMPMA and PVK) with active chromophores to PCBET, leads to the enhancement of PL emission of PCBET in a blend system.
Show PACS
78.66.Qn Polymers; organic compounds
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
68.55.am Polymers and organics
78.47.J- Ultrafast spectroscopy (<1 psec)
78.40.Me Organic compounds and polymers
78.55.Kz Solid organic materials

Optimum quantum dot size for highly efficient fluorescence bioimaging

Laura Martínez Maestro, Carlos Jacinto, Uéslen Rocha, M. Carmen Iglesias-de la Cruz, Francisco Sanz-Rodriguez, Angeles Juarranz, José García Solé, and Daniel Jaque

J. Appl. Phys. 111, 023513 (2012); http://dx.doi.org/10.1063/1.3676251 (6 pages) | Cited 2 times

Online Publication Date: 25 January 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Semiconductor quantum dots of few nanometers have demonstrated a great potential for bioimaging. The size determines the emitted color, but it is also expected to play an important role in the image brightness. In this work, the size dependence of the fluorescence quantum yield of the highly thermal sensitive CdTe quantum dots has been systematically investigated by thermal lens spectroscopy. It has been found that an optimum quantum yield is reached for 3.8-nm quantum dots. The presence of this optimum size has been corroborated in both one-photon excited fluorescence experiments and two-photon fluorescence microscopy of dot-incubated cancer cells. Combination of quantum yield and fluorescence decay time measurements supports that the existence of this optimum size emerges from the interplay between the frequency-dependent radiative emission rate and the size-dependent coupling strength between bulk excitons and surface trapping states.
Show PACS
87.17.Uv Biotechnology of cell processes
87.64.mn Multiphoton
87.80.Dj Spectroscopies
Page 1 of 5 Pages Return to All Sections Next Page
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close