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

Flickr Twitter UniPHY Group iResearch App Facebook

BROWSE VOLUMES

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

15 Oct 2010

Volume 108, Issue 8, Articles (08xxxx)

Issue Cover Spotlight Figure

J. Appl. Phys. 108, 081101 (2010); http://dx.doi.org/10.1063/1.3493111 (18 pages)

Yiping Wang
Enlarge Image | Read More
Page 1 of 7 Pages Next Page | Jump to Page
back to top
RSS Feeds
Author Select

Review of long period fiber gratings written by CO2 laser

Yiping Wang

J. Appl. Phys. 108, 081101 (2010); http://dx.doi.org/10.1063/1.3493111 (18 pages) | Cited 2 times

Online Publication Date: 22 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
This paper presents a systematic review of long period fiber gratings (LPFGs) written by the CO2 laser irradiation technique. First, various fabrication techniques based on CO2 laser irradiations are demonstrated to write LPFGs in different types of optical fibers such as conventional glass fibers, solid-core photonic crystal fibers, and air-core photonic bandgap fibers. Second, possible mechanisms, e.g., residual stress relaxation, glass structure changes, and physical deformation, of refractive index modulations in the CO2-laser-induced LPFGs are analyzed. Third, asymmetrical mode coupling, resulting from single-side laser irradiation, is discussed to understand unique optical properties of the CO2-laser-induced LPFGs. Fourthly, several pretreament and post-treatment techniques are proposed to enhance the efficiency of grating fabrications. Fifthly, sensing applications of the CO2-laser-induced LPFGs are investigated to develop various LPFG-based temperature, strain, bend, torsion, pressure, and biochemical sensors. Finally, communication applications of the CO2-laser-induced LPFGs are investigated to develop various LPFG-based band-rejection filters, gain equalizers, polarizers, and couplers.
Show PACS
42.79.Dj Gratings
42.81.Wg Other fiber-optical devices
42.55.Lt Gas lasers including excimer and metal-vapor lasers
42.60.By Design of specific laser systems
42.82.Cr Fabrication techniques; lithography, pattern transfer
42.70.Qs Photonic bandgap materials
42.25.-p Wave optics
back to top
RSS Feeds
back to top Lasers, Optics, and Optoelectronics

Suppression of bimolecular recombination by UV-sensitive electron transport layers in organic solar cells

Doo-Hyun Ko, John R. Tumbleston, Myoung-Ryul Ok, Honggu Chun, Rene Lopez, and Edward Samulski

J. Appl. Phys. 108, 083101 (2010); http://dx.doi.org/10.1063/1.3488609 (6 pages) | Cited 1 time

Online Publication Date: 18 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Incorporating UV-sensitive electron transport layers (ETLs) into organic bulk heterojunction (BHJ) photovoltaic devices dramatically impacts short-circuit current (Jsc) and fill factor characteristics. Resistivity changes induced by UV illumination in the ETL of inverted BHJ devices suppress bimolecular recombination producing up to a two orders of magnitude change in Jsc. Electro-optical modeling and light intensity experiments effectively demonstrate that bimolecular recombination, in the form of diode current losses, controls the extracted photocurrent and is directly dependent on the ETL resistivity.
Show PACS
88.40.H- Solar cells (photovoltaics)
78.40.-q Absorption and reflection spectra: visible and ultraviolet
72.40.+w Photoconduction and photovoltaic effects
79.60.-i Photoemission and photoelectron spectra

Energy splitting of resonant photonic states in nonlinear nanophotonic double waveguides

Joel D. Cox and Mahi R. Singh

J. Appl. Phys. 108, 083102 (2010); http://dx.doi.org/10.1063/1.3498811 (7 pages)

Online Publication Date: 19 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We have studied the energy splitting of bound photonic states in Kerr-nonlinear double photonic waveguides. The structure is formed by embedding two Kerr-nonlinear photonic crystals in a linear photonic crystal. When an intense external laser field is applied to the system, two coupled waveguides are induced. These waveguides may also be induced by applying a stress field to the system. Due to the coupling between waveguides, bound states split into symmetric and antisymmetric pairs. Using the transfer matrix method we obtained expressions for these split bound states and their energy separation. We have shown that the energy splitting depends on the separation of the waveguides and the intensity of the applied laser. The energy splitting predicted by our expressions agrees well with the splitting of resonant states in simulated transmission spectra. Our findings agree qualitatively with existing experimental observations of coupled photonic wells fabricated from photonic crystals. We found that the bound state energy levels can be tuned using the laser and stress fields, and that the system can be switched between zero to one or more pairs of resonant states. The results described here can be used to develop all-optical switches, tunable filters and nonlinear coupled waveguides.
Show PACS
42.65.Wi Nonlinear waveguides
42.79.Gn Optical waveguides and couplers
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
42.70.Qs Photonic bandgap materials

Microwave annealing of Mg-implanted and in situ Be-doped GaN

Geetha S. Aluri, Madhu Gowda, Nadeemullah A. Mahadik, Siddarth G. Sundaresan, Mulpuri V. Rao, John A. Schreifels, J. A. Freitas, Jr., S. B. Qadri, and Y.-L. Tian

J. Appl. Phys. 108, 083103 (2010); http://dx.doi.org/10.1063/1.3493266 (7 pages)

Online Publication Date: 19 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
An ultrafast microwave annealing method, different from conventional thermal annealing, is used to activate Mg-implants in GaN layer. The x-ray diffraction measurements indicated complete disappearance of the defect sublattice peak, introduced by the implantation process for single-energy Mg-implantation, when the annealing was performed at ≥ 1400 °C for 15 s. An increase in the intensity of Mg-acceptor related luminescence peak (at 3.26 eV) in the photoluminescence spectra confirms the Mg-acceptor activation in single-energy Mg-implanted GaN. In case of multiple-energy implantation, the implant generated defects persisted even after 1500 °C/15 s annealing, resulting in no net Mg-acceptor activation of the Mg-implant. The Mg-implant is relatively thermally stable and the sample surface roughness is 6 nm after 1500 °C/15 s annealing, using a 600 nm thick AlN cap. In situ Be-doped GaN films, after 1300 °C/5 s annealing have shown Be out-diffusion into the AlN layer and also in-diffusion toward the GaN/SiC interface. The in-diffusion and out-diffusion of the Be increased with increasing annealing temperature. In fact, after 1500 °C/5 s annealing, only a small fraction of in situ doped Be remained in the GaN layer, revealing the inadequateness of using Be-implantation for forming p-type doped layers in the GaN.
Show PACS
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
61.72.uj III-V and II-VI semiconductors
78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
68.35.bg Semiconductors
66.30.J- Diffusion of impurities

Diffraction and fringing field effects in small pixel liquid crystal devices with homeotropic alignment

Pieter J. M. Vanbrabant, Jeroen Beeckman, Kristiaan Neyts, Eero Willman, and F. Anibal Fernandez

J. Appl. Phys. 108, 083104 (2010); http://dx.doi.org/10.1063/1.3499279 (6 pages) | Cited 1 time

Online Publication Date: 20 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Reducing the pixel dimensions of liquid crystal microdisplays in search of high resolution has a fundamental impact on their electro-optic behavior. The liquid crystal director orientation becomes distorted due to fringing fields and diffraction effects influence the optical characteristics of the device once the structure features approach the wavelength of the incident light. Three-dimensional finite element simulation of the liquid crystal dynamics with a variable order approach is combined with a full-vector beam propagation analysis to investigate how elasticity and diffraction limit the resolution as a function of the pixel size for transmissive and reflective architectures with vertical liquid crystal alignment. The key liquid crystal properties are considered and the importance of materials with high birefringence is confirmed for small pixel devices as these improve the contrast for a fixed pixel size.
Show PACS
42.79.Kr Display devices, liquid-crystal devices

Confinement factors and optical gain in subwavelength plasmonic resonators

A. V. Maslov and M. Miyawaki

J. Appl. Phys. 108, 083105 (2010); http://dx.doi.org/10.1063/1.3490766 (6 pages)

Online Publication Date: 21 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We define the confinement factor for a subwavelength resonator, present a simple approach to calculate it numerically, and demonstrate that by using a specific resonator based on a silver rod coated with active material. Unlike the common approach of using the profile of the resonant electromagnetic mode, our formulation relies on using the characteristic equation for the complex frequency with inclusion of damping due to Joule and radiative losses. This removes an arbitrariness related to the definition of the mode volume in subwavelength resonators. Our analysis of a coated silver rod suggests that there is an optimal value for the active region thickness. The confinement factors can be comparable to that in Fabry–Perot resonators, radiative losses are comparable or exceed Joule losses and the threshold gain is high.
Show PACS
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.66.Bz Metals and metallic alloys

Temperature dependence of middle infrared absorption lines in silver halide crystals doped with Pr3+, Dy3+, and Nd3+ ions

I. Shafir, L. Nagli, and A. Katzir

J. Appl. Phys. 108, 083106 (2010); http://dx.doi.org/10.1063/1.3483954 (6 pages)

Online Publication Date: 22 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The electron-phonon coupling was investigated for mid-infrared transitions in silver halide crystals doped with Pr, Dy, or Nd. The temperature dependence of the absorption spectral line widths and the line shifts were measured in mid-infrared absorption lines in these crystals. It was shown that in each case the temperature dependence is consistent with the two-phonon Raman process model having a single characteristic Debye temperature. This Debye temperature was found to be in the range of 142–155.5 K. It was also found that below 50 K the line widths are caused by inhomogeneous crystal strains.
Show PACS
61.72.U- Doping and impurity implantation
63.20.kd Phonon-electron interactions

Concentration quenching of electroluminescence in neat Ir(ppy)3 organic light-emitting diodes

Y. Q. Zhang, G. Y. Zhong, and X. A. Cao

J. Appl. Phys. 108, 083107 (2010); http://dx.doi.org/10.1063/1.3504599 (5 pages) | Cited 3 times

Online Publication Date: 22 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We studied concentration quenching of electroluminescence (EL) in organic light-emitting diodes with a neat fac-tris(2-phenylpyridinato-N, C2′) iridium (III) [Ir(ppy)3] emitting layer of different thicknesses sandwiched between electron and hole blocking layers. The intensity of the green emission decreased rapidly with increasing Ir(ppy)3 thickness and was reversely correlated with the tail band emission. The overall light output power reached the minimum at 4 nm, and attained a saturated value for Ir(ppy)3 thicker than 6 nm. These results are interpreted as evidence that concentration quenching in Ir(ppy)3 originates from both short and long-range energy transfer between excited and ground states of molecules. The EL quenching magnitude was found to be independent of the injection current, indicating that biexcitonic annihilation plays a minor role.
Show PACS
85.60.Jb Light-emitting devices

Optical polarization anisotropy of tensile strained InGaN/AlInN quantum wells for TM mode lasers

Po-Yuan Dang (鄧博元) and Yuh-Renn Wu (吳育任)

J. Appl. Phys. 108, 083108 (2010); http://dx.doi.org/10.1063/1.3498805 (4 pages)

Online Publication Date: 22 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
In this paper, we discuss the optical characteristics and polarization anisotropy of a tensile strained polar c-plane InGaN/AlInN quantum well. We found that if the quantum well is under the tensile strain, the |Z〉-like state will be lifted up so that the emitted light will be TM mode. In addition, with a particular aluminum composition of the AlInN alloy as the barrier for the tensile strained InGaN quantum well, it is possible to reduce quantum-confined Stark effect. The self-consistent Poisson and 6×6 k⋅p Schrödinger solver has been used for studying light emitting characteristics. Our results show that the tensile strained InGaN quantum well on AlInN barrier has much larger optical gain and lower threshold carrier density compared to the conventional InGaN/GaN system, and it has a potential to be TM light source for edge emitting laser diodes with the photonic crystal cavity made by nanorod arrays.
Show PACS
78.67.De Quantum wells
73.63.Hs Quantum wells

Spectroscopic analysis of temperature and density of Sn plasma produced by a CO2 laser

Nek M. Shaikh, Y. Tao, R. A. Burdt, S. Yuspeh, N. Amin, and M. S. Tillack

J. Appl. Phys. 108, 083109 (2010); http://dx.doi.org/10.1063/1.3475369 (5 pages) | Cited 1 time

Online Publication Date: 22 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The temporal and spatial evolution of electron temperature and electron density from Sn plasma produced by a CO2 laser has been investigated in vacuum using spectroscopic methods. The plasma parameters were inferred by the Boltzmann plot method from experimentally observed line profiles of singly ionized Sn and Stark broadened profiles. At a laser intensity of 1010 W/cm2, electron temperature and density were measured to be within 1.13 eV to 0.53 eV and 5.3×1016 cm−3 to 1.4×1016 cm−3, respectively, for delay times between 200 ns and 1100 ns, and at distances up to 5 mm along the target normal. The results show the electron temperature and density from Sn plasma produced by a CO2 laser with wavelength of 10.6 μm to be lower than previously reported results using a 1064 nm laser in a similar parameter regime. The lower temperature in the region far away from the target surface confirms the smaller interaction region for CO2 laser as compared with that of neodymium-doped yttrium aluminum garnet laser.
Show PACS
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.25.-b Plasma properties

Piezoelectric fields of localized states in trapezoidal InGaN quantum wells

Dong-Yul Lee, Jae-Hoon Lee, Sang-Heon Han, Myung Goo Cheong, Dong-Joon Kim, June-Sik Park, Sangsu Hong, and Jae-Young Leem

J. Appl. Phys. 108, 083110 (2010); http://dx.doi.org/10.1063/1.3499638 (6 pages)

Online Publication Date: 25 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The piezoelectric fields of localized states in trapezoidal InGaN quantum wells (QWs) were investigated using electric field dependent electroreflectance (ER) spectroscopy. From the energy shift in ER peak in a bias range from 0 to −24 V, the piezoelectric field of the dominant QWs was estimated to be −1.22 MV/cm. In contrast, the localized states exhibited a piezoelectric field that was about 30%–60% weaker than for the dominant QW states. The reduced piezoelectric field in the localized states can be attributed to the partial release of compressive strain in the local InGaN regions, along with a relative reduction in the effective reverse-bias. The relative decrease in the reverse-bias can be explained by the voltage drop in the localized states that is caused by an increase in the leakage current under a reverse-bias.
Show PACS
77.65.Ly Strain-induced piezoelectric fields
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
77.84.-s Dielectric, piezoelectric, ferroelectric, and antiferroelectric materials
72.20.-i Conductivity phenomena in semiconductors and insulators

All-optical injection and detection of ballistic charge currents in germanium

Eric J. Loren, Hui Zhao, and Arthur L. Smirl

J. Appl. Phys. 108, 083111 (2010); http://dx.doi.org/10.1063/1.3500547 (7 pages) | Cited 2 times

Online Publication Date: 26 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
All optical techniques are used to inject and to study the relaxation dynamics of ballistic charge currents in clean germanium at room temperature without the application of external contacts or the use of externally applied fields. Ballistic currents are injected by the quantum interference between the transition amplitudes for direct one and two photon absorption of a pair of phase-locked and harmonically related ultrafast laser pulses. The transport of carriers following ballistic injection is temporally and spatially resolved using optical differential transmission techniques that are sensitive to the relative optical phase of the two injection pulses. The electron-hole dynamics are determined by the initial ballistic injection velocity, momentum relaxation, and space charge field effects. The injection process in Ge is similar to that in direct band gap materials but the indirect nature of Ge complicates the monitoring of the carrier dynamics, allowing the holes to play a more prominent role than in direct gap materials. The latter opens the possibility of following the hole (as opposed to the electron) dynamics.
Show PACS
73.23.Ad Ballistic transport
72.20.Ht High-field and nonlinear effects
77.22.Jp Dielectric breakdown and space-charge effects
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Intersubband absorption energy shifts in 3-level system for asymmetric quantum well terahertz emitters

Yafeng Song, Yanwu Lu, Biao Zhang, Xiaoqing Xu, Jun Wang, Yan Guo, Kai Shi, Zhiwei Li, Xianglin Liu, Shaoyan Yang, Qinsheng Zhu, and Zhanguo Wang

J. Appl. Phys. 108, 083112 (2010); http://dx.doi.org/10.1063/1.3487953 (10 pages)

Online Publication Date: 29 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Intersubband absorption energy shifts in 3-level system stemming from depolarization and excitonlike effects are investigated. Analytically, the expressions we derive present good explanations to the conventional 2-level results and bare potential transition energy results; and numerical results show that they are more exact than the previous studies to describe the 3-level system depolarization and excitonlike shift (DES) character especially for higher carrier density (more than 8×1011 cm−2). One interesting detail we find is that the “large blue” DES becomes “slight redshift” in the low doping limit (less than 1.9×1011 cm−2), which may be neglected by the previous studies of intersubband transitions. Temperature character of DES in the step well structure is also numerically studied. Finally the above are applied to calculate asymmetric step quantum well structures. The two main functional aspects of terahertz (THz) emitters are discussed and several basic optimizing conditions are considered. By adjusting the well geometry parameters and material composition systematically, some optimized structures which satisfy all of the six conditions are recommended in tables. These optimizations may provide useful references to the design of 3-level-based optically pumping THz emitters.
Show PACS
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Experimental verification of metamaterial based subwavelength microwave absorbers

Kamil Boratay Alici, Filiberto Bilotti, Lucio Vegni, and Ekmel Ozbay

J. Appl. Phys. 108, 083113 (2010); http://dx.doi.org/10.1063/1.3493736 (6 pages) | Cited 1 time

Online Publication Date: 29 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We designed, implemented, and experimentally characterized electrically thin microwave absorbers by using the metamaterial concept. The absorbers consist of (i) a metal back plate and an artificial magnetic material layer; (ii) metamaterial back plate and a resistive sheet layer. We investigated absorber performance in terms of absorbance, fractional bandwidth, and electrical thickness, all of which depend on the dimensions of the metamaterial unit cell and the distance between the back plate and metamaterial layer. As a proof of concept, we demonstrated a λ/4.7 thick absorber of type I, with a 99.8% absorption peak along with a 8% fractional bandwidth. We have shown that as the electrical size of the metamaterial unit cell decreases, the absorber electrical thickness can further be reduced. We investigated this concept by using two different magnetic metamaterial inclusions: the split-ring resonator (SRR) and multiple SSR (MSRR). We have also demonstrated experimentally a λ/4.7 and a λ/4.2 thick absorbers of type II, based on SRR and MSRR magnetic metamaterial back plates, respectively. The absorption peak of the SRR layout is 97.4%, while for the MSRR one the absorption peak is 98.4%. The 10 dB bandwidths were 9.9% and 9.6% for the SRR and MSRR cases, respectively.
Show PACS
84.40.-x Radiowave and microwave (including millimeter wave) technology
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
61.72.Qq Microscopic defects (voids, inclusions, etc.)
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
back to top Plasmas and Electrical Discharges

Suppression of current fluctuations in an intense electron beam

J. R. Harris and J. W. Lewellen

J. Appl. Phys. 108, 083301 (2010); http://dx.doi.org/10.1063/1.3468176 (5 pages)

Online Publication Date: 19 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
When an intense beam encounters an aperture, the transmitted current depends on the properties of the beam and the transport channel, as well as those of the aperture itself. In some cases, an increase in the incident beam current will be exactly compensated by an increase in the incident beam area, so that the current density at the aperture remains unchanged. When this occurs, the transmitted beam current becomes independent of changes in the incident beam current, providing a passive means for suppressing current fluctuations in the beam. In this article, a key requirement for the existence of this condition is derived. This requirement is shown to be fulfilled in the case of an idealized uniform focusing channel in the small-signal limit, but to be violated when the current fluctuations are not small. Even in this case, the apertured transport system retains the ability to suppress—but not totally eliminate—fluctuations in the transmitted beam current for a wide range of incident beam currents.
Show PACS
41.85.Lc Particle beam focusing and bending magnets, wiggler magnets, and quadrupoles

Optical and electrical characterization of pulse-modulated argon atmospheric-pressure inductively coupled microplasma jets

Satomi Tajima, Masashi Matsumori, Shigeki Nakatsuka, Shouichi Tsuchiya, and Takanori Ichiki

J. Appl. Phys. 108, 083302 (2010); http://dx.doi.org/10.1063/1.3499272 (5 pages) | Cited 1 time

Online Publication Date: 21 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The critical parameters determining the generation of the pulse-modulated argon atmospheric-pressure inductively coupled plasma (AP-ICP) microjet were studied by varying the power, P, pulse-modulation frequency, f, and duty ratio, DR. The temporal changes in the net output power, Pnet, monitored between the very high frequency power supply and matching network by an rf sampler, and ArI 4s′[1/2]1O–4p′[1/2]0 emission from the antenna were measured to elucidate the behavior of this plasma. The AP-ICP microjet, which produces high-density (0.9–1.1×1015 cm−3) nonequilibrium plasma, consists of an alumina discharge tube with the inner diameter of 0.8 mm. The generation diagram of the pulse-modulated plasma was created by having f as the horizontal axis and DR as the vertical axis while varying P up to 50 W. At f ≤ 10 kHz, the plasma was generated at above the linear lines of f and DR, which indicated the existence of the critical power-off period of approximately 80 μs. At f>10 kHz, the pulse-modulated plasma was produced above constant DR and almost independent of f. The time-averaged power, math, which is the product of P and DR, had to be more than 8–10 W to sustain the pulse-modulated plasma. From the measurement of the temporal changes in the net power and ArI emission, the dynamic behavior of the pulse-modulated plasma was revealed as follows. The prebreakdown period was present for ∼ 5 μs after the power was turned on. Once the plasma was generated, the impedance was changed and the reflected power gradually decreased. A strong emission peak was observed immediately after the breakdown, followed by the gradual increase up to the steady state. Finally, the intense afterpeak was observed at 0.8 μs after the power was turned off.
Show PACS
52.75.-d Plasma devices
52.25.Kn Thermodynamics of plasmas
52.40.Fd Plasma interactions with antennas; plasma-filled waveguides
52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.70.Ds Electric and magnetic measurements
52.70.Kz Optical (ultraviolet, visible, infrared) measurements

Nanowire charging in collisionless plasma

Anaram Shahravan, Chris Lucas, and Themis Matsoukas

J. Appl. Phys. 108, 083303 (2010); http://dx.doi.org/10.1063/1.3483300 (7 pages) | Cited 1 time

Online Publication Date: 27 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We calculate the collision cross section of a charged finite cylinder (nanowire) with a beam of ions and electrons in collisionless plasma. We find that, while the shape and area of the cross section has complex dependence on the charge and orientation of the nanowire relative to the charged beam, its orientational average has a remarkably simple form: for attractive interactions, it is a linear function of the electrostatic ratio qjqpe2/4πϵ0L0kT, where qje is the charge of the ions/electrons, qpe is the charge on the cylinder, L0 is the half-length of the nanowire, T is the temperature of the charged species, and ϵ0 is the permittivity of free space. This linearity persists into the repulsive regime up until the cross sectional area is reduced to about 5% of its value for neutral collisions. We calculate the corresponding charging currents and show that the charging behavior of the nanowire in Maxwellian plasma is described by an equivalent sphere whose radius depends only on the aspect ratio of the nanowire. For small aspect ratios, the equivalent sphere has the same surface area as the nanowire.
Show PACS
52.27.Lw Dusty or complex plasmas; plasma crystals
52.20.Fs Electron collisions
52.20.Hv Atomic, molecular, ion, and heavy-particle collisions
61.46.Km Structure of nanowires and nanorods (long, free or loosely attached, quantum wires and quantum rods, but not gate-isolated embedded quantum wires)
73.63.Nm Quantum wires
52.25.-b Plasma properties
back to top Structural, Mechanical, Thermodynamic, and Optical Properties of Condensed Matter

Effect of TiO2 nanoparticles on the thermal properties of decorated multiwall carbon nanotubes: A Raman investigation

Angela M. O. de Zevallos-Márquez, Maria José S. P. Brasil, Fernando Iikawa, Alireza Abbaspourrad, Carla Verissimo, Stanislav A. Moshkalev, and Oswaldo L. Alves

J. Appl. Phys. 108, 083501 (2010); http://dx.doi.org/10.1063/1.3496671 (6 pages)

Online Publication Date: 18 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We have investigated multiwalled carbon nanotubes decorated with TiO2 nanoparticles. Scanning electron microscopy and transmission electron microscopy measurements revealed that the TiO2 incorporates on the nanotubes forming large cauliflowerlike aggregates and/or small crystalline particles attached to the nanotube wall, depending on the growth conditions. A detailed Raman study was performed in pristine and a series of decorated nanotubes, where we analyzed both the Raman signal from the nanotubes and from the TiO2 nanoparticles. We demonstrate that the attached TiO2 nanoparticles affect significantly the thermal properties of the resulting hybrid nanostructure, as revealed by differentiated reactions to laser heating. This is a crucial point for modeling and optimization of devices based on nanotubes, which properties are strongly temperature dependent.
Show PACS
78.30.Hv Other nonmetallic inorganics
78.67.Ch Nanotubes
61.46.Fg Nanotubes
65.80.-g Thermal properties of small particles, nanocrystals, nanotubes, and other related systems
66.70.Lm Other systems such as ionic crystals, molecular crystals, nanotubes, etc.

Resonant subband Landau level coupling in symmetric quantum well

L.-C. Tung, X.-G. Wu, L. N. Pfeiffer, K. W. West, and Y.-J. Wang

J. Appl. Phys. 108, 083502 (2010); http://dx.doi.org/10.1063/1.3496516 (4 pages) | Cited 1 time

Online Publication Date: 18 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Subband structure and depolarization shifts in an ultrahigh mobility GaAs/Al0.24Ga0.76As quantum well are studied using magnetoinfrared spectroscopy via resonant subband Landau level coupling. Resonant couplings between the first and up to the fourth subbands are identified by well-separated antilevel-crossing split resonance, while the hy-lying subbands were identified by the cyclotron resonance linewidth broadening in the literature. In addition, a forbidden intersubband transition (first to third) has been observed. With the precise determination of the subband structure, we find that the depolarization shift can be well described by the semiclassical slab plasma model and the possible origins for the forbidden transition are discussed.
Show PACS
81.07.St Quantum wells
73.21.Fg Quantum wells
78.67.De Quantum wells
73.63.Hs Quantum wells
78.30.Fs III-V and II-VI semiconductors
81.05.Ea III-V semiconductors

Effect of gap thickness on the viscoelasticity of magnetorheological fluids

Modesto T. López-López, Laura Rodríguez-Arco, Andrey Zubarev, Larisa Iskakova, and Juan D. G. Durán

J. Appl. Phys. 108, 083503 (2010); http://dx.doi.org/10.1063/1.3498804 (9 pages)

Online Publication Date: 18 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
In this work, the effect of confinement distance on the magnetorheological (MR) properties of a conventional MR fluid, constituted by 30 vol % of iron microparticles dispersed in a liquid carrier, is studied. With this aim a commercial magnetorheometer supplied with parallel-plate geometry was used. The distance between the upper and the lower plate (gap thickness) was tuned from 10 to 400 μm. The steady-state and the dynamic regimes of the MR fluid in the presence of applied magnetic fields were studied as a function of the gap length. The experimental results show that in the preyield regime there is a strong increase in the magnitude of the viscoelastic moduli and the shear stress as the gap thickness is increased. The physical reason for this effect might be the influence of gap thickness on the particle structures induced by the field. This hypothesis is corroborated by microscopic observations in diluted systems. These experiments show that the aspect ratio (length/diameter) of the field-induced structures increases with the gap thickness. Theoretical analysis shows that the increase in the storage modulus with gap thickness can be explained by a decrease in the demagnetizing factor of these structures and, as a consequence, by an increase in the restoring torque, acting on them. The dissipation effects in the suspension under oscillating flow are rather produced by contact friction between the particles in the dense structures.
Show PACS
83.80.Gv Electro- and magnetorheological fluids
75.50.Mm Magnetic liquids
62.10.+s Mechanical properties of liquids

1.8 μm emission of highly thulium doped fluorophosphate glasses

Ying Tian, Rongrong Xu, Liyan Zhang, Lili Hu, and Junjie Zhang

J. Appl. Phys. 108, 083504 (2010); http://dx.doi.org/10.1063/1.3499283 (7 pages) | Cited 4 times

Online Publication Date: 18 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A new type of fluorophosphate glasses with high thulium doping concentration (up to 10 mol % Tm3+) is investigated. The intensive 1.8 μm fluorescence is demonstrated with lower concentration quenching. On the basis of the measured Raman spectroscopy, it is revealed that the glass structure will be changed when adding Tm3+ ions into fluorophosphate glasses. Besides, the Judd–Ofelt parameters and radiative properties are calculated and discussed based on Judd–Ofelt theory. And the absorption and emission cross-sections of 3F4→3H6 transition are also calculated by using McCumber and Beer–Lambert theories.
Show PACS
78.55.Qr Amorphous materials; glasses and other disordered solids
78.35.+c Brillouin and Rayleigh scattering; other light scattering
61.72.up Other materials
61.43.Fs Glasses
42.70.Ce Glasses, quartz

Morphological control of GaAs quantum dots grown by droplet epitaxy using a thin AlGaAs capping layer

Masafumi Jo, Takaaki Mano, and Kazuaki Sakoda

J. Appl. Phys. 108, 083505 (2010); http://dx.doi.org/10.1063/1.3493262 (3 pages)

Online Publication Date: 18 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We demonstrate the control of GaAs quantum dots morphology by using a thin AlGaAs capping layer. The AlGaAs layer uniformly covers the GaAs quantum dots and provides protections against thermally induced deformation up to 580 °C, which allows improved dot quality. In addition, annealing of AlGaAs-capped quantum dots at 640 °C flattens the top of the dots, leading to the formation of height-controlled quantum dots and their narrow inhomogeneous width of 28 meV.
Show PACS
68.65.Hb Quantum dots (patterned in quantum wells)
68.35.bg Semiconductors
78.67.Hc Quantum dots
61.72.Cc Kinetics of defect formation and annealing

Size-dependent elastic properties of Au nanowires under bending and tension—Surfaces versus core nonlinearity

Zhi-Jia Wang, Chong Liu, Zhigang Li, and Tong-Yi Zhang

J. Appl. Phys. 108, 083506 (2010); http://dx.doi.org/10.1063/1.3493264 (8 pages)

Online Publication Date: 18 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The present work investigates contributions from surfaces and core nonlinearity to the size-dependent elastic properties of nanowires under bending and tension-compression. When a nanowire is formed by removing it from its parent bulk material, relaxation occurs inevitably because of high energy of newly created surfaces or born high surface eigenstress. Relaxation-induced initial strain could be large and nonlinear, which causes the size-dependent elastic properties of nanowires. If relaxation-induced initial strain is small and linear, the size-dependent elastic properties of nanowires are caused by surface Young’s modulus. The eigenstress model for surface stress of solids { Zhang et al. [Phys. Rev. B 81, 195427 (2010)] } is further developed here for nanowires under bending and tension-compression. The developed eigenstress model leads to general scaling laws for nanowires under bending and tension-compression. In the scaling laws, there are the surface and nonlinearity factors, which measure quantitatively the contributions of surfaces and core nonlinearity, respectively, to the nominal Young’s modulus of nanowires. Atomistic simulations on Au [001] nanowires verify the theoretical predictions.
Show PACS
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.de Elastic moduli
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
62.23.Hj Nanowires

Influence of surface topography and chemical structure on wettability of electrodeposited ZnO thin films

S. Patra, S. Sarkar, S. K. Bera, G. K. Paul, and R. Ghosh

J. Appl. Phys. 108, 083507 (2010); http://dx.doi.org/10.1063/1.3493735 (6 pages) | Cited 1 time

Online Publication Date: 19 October 2010

Full Text: Read Online (HTML) | Download PDF


See Also: RETRACTION

Show Abstract
The wettability of electrodeposited zinc oxide (ZnO) thin films has been rationally controlled by individually engineering surface topography and surface chemical structure. We have studied the wettability of hydrophobic ZnO thin films that were rendered ultrahydrophobic by coating with low surface-energy self-assembled monolayer of octadecyltrichlorosilane and also hydrophilized by annealing at elevated temperature in air ambient. The as deposited ZnO film was hydrophobic with contact angle of around 105°±3° against water, while the annealed films were distinctly hydrophilic. The silanized films were ultrahydrophobic with a contact angle of 143°±3°. The films could be successfully tailored to obtain hydrophilic, hydrophobic as well as ultrahydrophobic behavior. It is likely that similar tunable wetting behavior may be observed in other oxide materials also.
Show PACS
68.55.ag Semiconductors
68.08.Bc Wetting
81.15.Pq Electrodeposition, electroplating
82.45.Qr Electrodeposition and electrodissolution
68.55.-a Thin film structure and morphology
68.03.Cd Surface tension and related phenomena

High pressure stability of bismuth sillenite: A Raman spectroscopic and x-ray diffraction study

Rekha Rao, Alka B. Garg, and T. Sakuntala

J. Appl. Phys. 108, 083508 (2010); http://dx.doi.org/10.1063/1.3496659 (5 pages)

Online Publication Date: 20 October 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
High pressure behavior of the compound Bi12SiO20 is investigated using in situ Raman spectroscopic and synchrotron-based angle dispersive x-ray diffraction techniques. Results indicate that the compound remains stable in the ambient pressure cubic structure up to 26 GPa. From the structural studies, bulk modulus B0, and its pressure derivative B′ of Bi12SiO20 are evaluated to be 36 GPa and 16.7 GPa, respectively. Mode Grüneissen parameters of various Raman active modes of Bi12SiO20 are also reported. The stability of Bi12SiO20 at high pressure is discussed in the light of the pressure-induced amorphization reported in bismuth-orthosilicate (Bi4Si3O12) and -orthogermanate. Comparison of the observed phonon behavior with that reported for Bi4Si3O12 reveals that two of the Raman modes in Bi4Si3O12 have negative pressure dependencies clearly indicating dynamic instability while Bi12SiO20 does not show any signatures of zone-center instabilities.
Show PACS
78.30.Hv Other nonmetallic inorganics
62.50.-p High-pressure effects in solids and liquids
62.20.de Elastic moduli
81.40.Jj Elasticity and anelasticity, stress-strain relations
Page 1 of 7 Pages Next Page | Jump to Page
Close

Google Calendar

ADVERTISEMENT

Your Recent History Recent History Help

Recently Viewed

  1. Nonlinear piezoelectricity in electroelastic energy harvesters: Modeling and experimental identification
  2. Two-dimensional carbon nanostructures: Fundamental properties, synthesis, characterization, and potential applications
  3. Time-resolved x-ray diffraction study of the piezoelectric crystal response to a fast change of an applied electric field
  4. Energy transfer mechanism and Auger effect in Er3+ coupled silicon nanoparticle samples
  5. High aspect ratio silicon etch: A review
Go to AIP Home
Copyright © American Institute of Physics
close