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 Apr 2008

Volume 103, Issue 8, Articles (08xxxx)

Page 2 of 8 Pages Previous Page Next Page | Jump to Page
back to top
RSS Feeds

Alignment of cellulose chains of regenerated cellulose by corona poling and its piezoelectricity

Sungryul Yun, Jung Hwan Kim, Yuanxie Li, and Jaehwan Kim

J. Appl. Phys. 103, 083301 (2008); http://dx.doi.org/10.1063/1.2908883 (4 pages) | Cited 3 times

Online Publication Date: 21 April 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Cellulose based electroactive paper has been developed as smart material. In this paper, corona poled cellulose films were prepared to improve their piezoelectricity and the influence of grid voltage to the corona poling was investigated. Cellulose was regenerated by dissolving cellulose natural fibers using a solvent, and removing it. During the regeneration process, alignment of cellulose was attempted by applying corona electrical poling. These characteristics were investigated by field emission scanning electron microscopy, transmission electron microscopy, and x-ray diffraction. As increasing the grid voltage of the corona poling, the generation of cellulose nanofibers in the cellulose layered structures was observed, which influenced the increased crystallinity resulting in improved piezoelectric charge constant of cellulose films.
Show PACS
77.84.Jd Polymers; organic compounds
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
77.65.Bn Piezoelectric and electrostrictive constants
77.22.Ej Polarization and depolarization
61.41.+e Polymers, elastomers, and plastics

Real-time plasma control in a dual-frequency, confined plasma etcher

V. Milosavljević, A. R. Ellingboe, C. Gaman, and J. V. Ringwood

J. Appl. Phys. 103, 083302 (2008); http://dx.doi.org/10.1063/1.2903137 (10 pages) | Cited 2 times

Online Publication Date: 22 April 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The physics issues of developing model-based control of plasma etching are presented. A novel methodology for incorporating real-time model-based control of plasma processing systems is developed. The methodology is developed for control of two dependent variables (ion flux and chemical densities) by two independent controls (27 MHz power and O2 flow). A phenomenological physics model of the nonlinear coupling between the independent controls and the dependent variables of the plasma is presented. By using a design of experiment, the functional dependencies of the response surface are determined. In conjunction with the physical model, the dependencies are used to deconvolve the sensor signals onto the control inputs, allowing compensation of the interaction between control paths. The compensated sensor signals and compensated set–points are then used as inputs to proportional-integral-derivative controllers to adjust radio frequency power and oxygen flow to yield the desired ion flux and chemical density. To illustrate the methodology, model-based real-time control is realized in a commercial semiconductor dielectric etch chamber. The two radio frequency symmetric diode operates with typical commercial fluorocarbon feed-gas mixtures (Ar/O2/C4F8). Key parameters for dielectric etching are known to include ion flux to the surface and surface flux of oxygen containing species. Control is demonstrated using diagnostics of electrode-surface ion current, and chemical densities of O, O2, and CO measured by optical emission spectrometry and/or mass spectrometry. Using our model-based real-time control, the set-point tracking accuracy to changes in chemical species density and ion flux is enhanced.
Show PACS
52.50.Dg Plasma sources
52.70.-m Plasma diagnostic techniques and instrumentation
52.77.-j Plasma applications

Hysteresis and mode transition in terms of electron energy distribution function for an inductively coupled argon discharge

S. V. Singh

J. Appl. Phys. 103, 083303 (2008); http://dx.doi.org/10.1063/1.2905213 (6 pages) | Cited 5 times

Online Publication Date: 23 April 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The electron energy distribution function (EEDF) with respect to the hysteresis loop of an inductively coupled argon discharge has been studied experimentally. Contrary to H mode, knowledge of EEDF in E mode is still limited, and an elaborate EEDF measurement with regard to power and pressure for this mode is presented. The Langmuir probe measurements reveal two regions with distinct EEDFs in E mode, which might be a critical missing factor in explaining the unresolved hysteresis and mode transition phenomenon of inductive discharges. Furthermore, a Poynting vector representation has been used to explain the power coupling in an inductive discharge, where (azimuthal) eθ component is proposed to be dominant in the “hybrid mode” region.
Show PACS
52.70.Ds Electric and magnetic measurements
52.80.-s Electric discharges

Ion-radical synergy in HfO2 etching studied with a XeF2/Ar+ beam setup

P. M. Gevers, H. C. W. Beijerinck, M. C. M. van de Sanden, and W. M. M. Kessels

J. Appl. Phys. 103, 083304 (2008); http://dx.doi.org/10.1063/1.2903058 (8 pages) | Cited 4 times

Online Publication Date: 23 April 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
To gain more insight into fundamental aspects of the etching behavior of Hf-based high-k materials in plasma etch reactors, HfO2 films were etched in a multiple-beam setup consisting of a low energy Ar+ ion beam and a XeF2 radical beam. The etch rate and etch products were monitored by real-time ellipsometry and mass spectrometry, respectively. Although etching of HfO2 in XeF2/Ar+ chemistry is mainly a physical effect, an unambiguous proof of the ion-radical synergistic effect for the etching of HfO2 is presented. The etch yield for 400 eV Ar+ ions at a substrate temperature of 300 °C was 0.3 atoms/ion for Ar+ sputtering and increased to 2 atoms/ion when XeF2 was also supplied. The etch yield proved to follow the common square root of ion energy dependence both for pure sputtering and radical enhanced etching, with a threshold energy at room temperature of 69±17 eV for Ar+ ions and 54±14 eV for Ar+ ions with XeF2.
Show PACS
77.55.-g Dielectric thin films
52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Subnanosecond electron transport in a gas in the presence of polarized electromagnetic waves

Indranuj Dey, Jose V. Mathew, Sudeep Bhattacharjee, and Sachin Jain

J. Appl. Phys. 103, 083305 (2008); http://dx.doi.org/10.1063/1.2907966 (6 pages) | Cited 3 times

Online Publication Date: 25 April 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
An ensemble of free electrons in a classical Boltzmann gas under equilibrium condition follow a square law for the number of collisions suffered during random walk, in the elastic limit [N∝(Λ/λ)2]. This study reveals for the first time that in the same limit the dependence is considerably modified in the presence of linearly polarized electromagnetic waves. The phenomenon happens at time scales shorter ( ∼ 10−10 s) than the characteristic discharge initiation time and the wave period. Considering the actual dependence of collision cross-sections on electron energy, a new relation is obtained, which tends to the classical result for the zero field case. The random walk parameter 〈χ2〉 characterizes a true versus constrained random process. The implications of the new relation describing the phenomena are discussed in the light of applications.
Show PACS
52.40.Mj Particle beam interactions in plasmas
51.10.+y Kinetic and transport theory of gases
05.60.-k Transport processes
52.20.Fs Electron collisions

Tailoring of structure formation and phase composition in reactively sputtered zirconium oxide films using nitrogen as an additional reactive gas

D. Severin, K. Sarakinos, O. Kappertz, A. Pflug, and M. Wuttig

J. Appl. Phys. 103, 083306 (2008); http://dx.doi.org/10.1063/1.2903492 (5 pages) | Cited 3 times

Online Publication Date: 28 April 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The structure of ZrO2 films has been controlled during reactive sputtering in an argon∕oxygen atmosphere by adding an amount of nitrogen gas to the process. Depending on the deposition conditions, amorphous, cubic, or monoclinic films have been obtained without any additional substrate heating. The resulting film structure is explained in terms of the control of fast negative oxygen ions generated at the target surface and accelerated toward the growing film. Furthermore, the nitrogen addition leads to a pronounced stabilization of the plasma discharge and fewer arcing events, while the incorporation of nitrogen atoms in the growing film is very small.
Show PACS
68.55.Nq Composition and phase identification
81.15.Cd Deposition by sputtering
back to top
RSS Feeds

Three-dimensional analysis of spontaneous surface instability and pattern formation of thin soft films

Shi-Qing Huang, Bo Li, and Xi-Qiao Feng

J. Appl. Phys. 103, 083501 (2008); http://dx.doi.org/10.1063/1.2903892 (8 pages) | Cited 9 times

Online Publication Date: 16 April 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
For soft films with a thickness on the order of microns or nanometers, the long-range surface∕interface interaction can be sufficiently strong to induce their surface instability or even rupture. By using the bifurcation theory of elasticity, we here present a three-dimensional theoretical model to study the spontaneous surface instability of a soft elastic thin film supported by a rigid substrate. By accounting for the competition of van der Waals interaction energy with elastic strain energy and surface energy, we obtain the analytical solutions for the critical conditions of three-dimensional surface morphology instability. The effects of surface energy, thickness, and elastic properties of the film on the characteristic wavelength of surface wrinkling are examined. It is found that the characteristic wavelength of the deformation bifurcation mode depends on the film thickness via an exponential relation, with the power index in the range of 0.75–1.0, which mainly depends on the ratio between the surface energy and shear modulus of the film but not on the nature of the surface∕interface interaction. Furthermore, it is shown that the interface condition between the film and the substrate significantly influences the critical condition of surface bifurcation. The theoretical solution proves to be a good agreement with the corresponding experiment results.
Show PACS
68.55.jd Thickness
68.60.Bs Mechanical and acoustical properties
81.40.Jj Elasticity and anelasticity, stress-strain relations
68.35.Md Surface thermodynamics, surface energies
81.40.Lm Deformation, plasticity, and creep
62.20.de Elastic moduli

Effect of the sliding orientation on the tribological properties of polyethylene in molecular dynamics simulations

Seong Jun Heo, Inkook Jang, Peter R. Barry, Simon R. Phillpot, Scott S. Perry, W. Gregory Sawyer, and Susan B. Sinnott

J. Appl. Phys. 103, 083502 (2008); http://dx.doi.org/10.1063/1.2900884 (6 pages) | Cited 11 times

Online Publication Date: 16 April 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The role of sliding orientation on the tribological properties of polyethylene (PE) is investigated by using classical molecular dynamics simulations. Cross-linked PE surfaces slide against one another in two different directions: one that is perpendicular to and one that is parallel to the aligned direction of the polymer chains. The results indicate that sliding in the parallel direction occurs with a lower friction coefficient than sliding in the perpendicular direction. In both cases, gross level stick-slip motion is observed to be associated with the sliding of a restrained, corrugated molecular interface. In addition, the simulations demonstrate the way in which the system stores more shear strain energy during sliding in the perpendicular direction. The tribological behavior of these PE surfaces is compared to the behavior of similarly modeled polytetrafluoroethylene surfaces; the differences and similarities between the two systems are discussed.
Show PACS
81.40.Pq Friction, lubrication, and wear
62.20.Qp Friction, tribology, and hardness

Thermal conductivity of nanofluids: Effects of graded nanolayers and mutual interaction

X. F. Zhou and L. Gao

J. Appl. Phys. 103, 083503 (2008); http://dx.doi.org/10.1063/1.2904924 (6 pages) | Cited 4 times

Online Publication Date: 16 April 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
It has been demonstrated there exists an interfacial nanolayer at the nanoparticles/fluid interface, and the nanoparticles in the base fluid aggregate easily and form clusters. As a result, both the interfacial nanolayer and the mutual interaction between nanoparticles become important. To account for the interfacial nanolayers, we first generalize differential effective dipole approximation to obtain the equivalent thermal conductivity of the coated nanoparticles with graded nanolayers. Then we employ multiple image method to investigate the effect of mutual interaction between nanoparticles on the thermal conductivity of nanofluids. Analytical formulae allow us to check the effect of nanolayer thickness, particle size, and mutual interaction. Numerical results show that when nanoparticles close up and even get touched, the effective thermal conductivity is slightly enhanced in comparison with that predicted from Maxwell–Garnett theory. The nanolayer properties also play a more important role in the conductivity enhancement. In addition, theoretical results on the effective thermal conductivity of nanofluids are in good agreement with experimental data.
Show PACS
66.25.+g Thermal conduction in nonmetallic liquids

Interaction potentials for alumina and molecular dynamics simulations of amorphous and liquid alumina

Priya Vashishta, Rajiv K. Kalia, Aiichiro Nakano, and José Pedro Rino

J. Appl. Phys. 103, 083504 (2008); http://dx.doi.org/10.1063/1.2901171 (13 pages) | Cited 21 times

Online Publication Date: 16 April 2008

Full Text: Read Online (HTML) | Download PDF


See Also: Erratum

Show Abstract
Structural and dynamical properties of crystalline alumina α-Al2O3 and amorphous and molten alumina are investigated with molecular dynamics simulation based on an effective interatomic potentials consisting of two- and three-body terms. Structural correlations are examined through pair distribution functions, coordination numbers, static structure factors, bond angle distributions, and shortest-path ring analyses. The calculated results for neutron and x-ray static structure factors are in good agreement with experimental results. Dynamical correlations, such as velocity autocorrelation function, vibrational density of states, current-current correlation function, and frequency-dependent conductivity, are also discussed.
Show PACS
61.66.Fn Inorganic compounds
61.43.Er Other amorphous solids
61.20.Ja Computer simulation of liquid structure
61.25.-f Studies of specific liquid structures

Hardness and elastic properties of covalent/ionic solid solutions from first-principles theory

Qing-Miao Hu, Krisztina Kádas, Sture Hogmark, Rui Yang, Börje Johansson, and Levente Vitos

J. Appl. Phys. 103, 083505 (2008); http://dx.doi.org/10.1063/1.2904857 (9 pages) | Cited 3 times

Online Publication Date: 17 April 2008

Full Text: Read Online (HTML) | Download PDF


See Also: Erratum

Show Abstract
Most of the engineering materials are alloys (solid solutions) and inevitably contain some impurities or defects such as vacancies. However, theoretical predictions of the hardness of this kind of materials have rarely been addressed in literature. In this paper, a hardness formula for multicomponent covalent solid solution is proposed based on the work of Šimůnek and Vackář [Phys. Rev. Lett. 96, 085501 (2006)] . With this formula, the composition dependence of the hardness is investigated for titanium nitrogencarbide (TiN1−xCx), off-stoichiometric transition-metal nitrides (TiN1−x and VN1−x), and B-doped semiconductors. The predicted hardness is in good agreement with experiments. To investigate the most frequently quoted correlation between hardness and elastic modulus, the elastic moduli of the systems involved in this paper have also been calculated. The results show that the elastic moduli cannot be used for rigorous predictions of the hardness of the solid solutions.
Show PACS
62.20.Qp Friction, tribology, and hardness
62.20.D- Elasticity

Radial distribution of the fictive temperature in pure silica optical fibers by micro-Raman spectroscopy

C. Martinet, V. Martinez, C. Coussa, B. Champagnon, and M. Tomozawa

J. Appl. Phys. 103, 083506 (2008); http://dx.doi.org/10.1063/1.2905321 (4 pages) | Cited 5 times

Online Publication Date: 17 April 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Micro-Raman spectra are performed at different radial positions in order to determine the fictive temperature distribution in pure silica optical fibers. As-received and annealed optical fibers are compared and Raman results reveal a large decrease in the fictive temperature after annealing. The fictive temperature gradient between the core and the edge of the optical fiber can be eliminated after annealing and the spectroscopic decoupling between stress and the fictive temperature variation is discussed. The micro-Raman is a good probe in determining the spatial distribution of the fictive temperature in the micrometer length scale.
Show PACS
42.81.Bm Fabrication, cladding, and splicing
42.79.-e Optical elements, devices, and systems

Magnetic texturing of ferromagnetic thin films by sputtering induced ripple formation

K. Zhang, M. Uhrmacher, H. Hofsäss, and J. Krauser

J. Appl. Phys. 103, 083507 (2008); http://dx.doi.org/10.1063/1.2905324 (7 pages) | Cited 13 times

Online Publication Date: 17 April 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Ripple patterns created by sputter erosion of iron thin films induce a correlated magnetic texture of the surface near region. We investigated the magnetic anisotropy as a function of the residual film thickness and determined the thickness of the magnetically anisotropic layer as well as the magnitude of the magnetic anisotropy using by magneto-optical Kerr effect (MOKE) and Rutherford backscattering spectroscopy measurements. Ripple patterns were created by sputter erosion with 5 keV Xe ions under grazing incidence of 80° with respect to the surface normal. For ion fluences of above 1×1016 cm−2, the formation of ripples, with wavelengths between 30 and 80 nm oriented parallel to the ion beam direction, is observed. MOKE measurements reveal a pronounced uniaxial magnetic anisotropy of the surface region of the films with orientation parallel to the ripple orientation and the ion beam direction. We find a layer thickness of 12±3 nm, in accordance with the average grain size. The magnetic anisotropy within this layer varies from about 25% for thick residual films toward 100% for films with less than 30 nm thickness. The magnitude of the magnetic anisotropy is determined by the shape anisotropy of the rippled surface as well as the interface roughness. We have demonstrated that sputter erosion yields highly anisotropic magnetic thin films and can be used to fabricate nanorods and nanowires with pronounced uniaxial magnetic anisotropy.
Show PACS
75.50.Bb Fe and its alloys
75.70.Ak Magnetic properties of monolayers and thin films
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
75.30.Gw Magnetic anisotropy
78.20.Ls Magneto-optical effects
68.49.Sf Ion scattering from surfaces (charge transfer, sputtering, SIMS)
68.35.Ct Interface structure and roughness

Deformation mechanisms and damage in α-alumina under hypervelocity impact loading

Cheng Zhang, Rajiv K. Kalia, Aiichiro Nakano, Priya Vashishta, and Paulo S. Branicio

J. Appl. Phys. 103, 083508 (2008); http://dx.doi.org/10.1063/1.2891797 (15 pages) | Cited 12 times

Online Publication Date: 17 April 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Deformation mechanisms in α-alumina under hypervelocity impact are investigated using molecular dynamics simulations containing 540×106 atoms. A cylindrical projectile impacting normal to the (0001) surface at 18 km/s generates large temperature and pressure gradients around the impact face, and consequently local amorphization of the substrate in a surrounding hemispherical region is produced. Away from the impact face, a wide range of deformations emerge and disappear as a function of time under the influence of local stress fields, e.g., basal and pyramidal slips and basal and rhombohedral twins, all of which show good agreement with the experimental and theoretical results. New deformation modes are observed, such as twins along {0math11}, which propagate at a roughly constant speed of 8 km/s and nucleate a large amount of defects where subsequent fractures initiate. The relation between deformation patterns and local stress levels is investigated. During unloading, we observe that microcracks nucleate extensively at the intersections of previous deformations within an hourglass-shaped volume that connects top and bottom free surfaces. From the simulation, the fracture toughness of alumina is estimated to be 2.0±0.5 MPa√m. The substrate eventually fails along the surface of the hourglass region during spallation when clusters of substrate material are ejected from both free surfaces.
Show PACS
62.20.F- Deformation and plasticity
81.40.Lm Deformation, plasticity, and creep
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.mm Fracture
61.72.Mm Grain and twin boundaries

The use of a macroscopic formulation describing the effects of dynamic compaction and porosity on plasma sprayed copper

M. Arrigoni, M. Boustie, C. Bolis, L. Berthe, S. Barradas, and M. Jeandin

J. Appl. Phys. 103, 083509 (2008); http://dx.doi.org/10.1063/1.2906186 (9 pages)

Online Publication Date: 17 April 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Coatings processed by thermal deposition techniques involve porosity. The Laser adhesion test developed for testing bond strength of a coating on its substrate requires a good knowledge of shock wave propagation in such media. Experiments carried out on plasma sprayed copper samples, about 14% porous, with velocity interferometer system for any reflector measurements display the discrepancy of previously used models. Hence, a one-dimensional formulation of the compaction process, based on a simple P-α model, is proposed to improve the correlation between experimental and computed data signals obtained on a plasma sprayed copper under dynamic loading. Besides, this improvement allows the estimation of the bond strength of a plasma sprayed copper on aluminum substrate.
Show PACS
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
81.15.Rs Spray coating techniques
52.77.Fv High-pressure, high-current plasmas (plasma spray, arc welding, etc.)
68.35.Np Adhesion
62.50.Ef Shock wave effects in solids and liquids
61.43.Gt Powders, porous materials

Nanocrystalline coating design for extreme applications based on the concept of complex adaptive behavior

G. S. Fox-Rabinovich, S. C. Veldhuis, G. K. Dosbaeva, K. Yamamoto, A. I. Kovalev, D. L. Wainstein, I. S. Gershman, L. S. Shuster, and B. D. Beake

J. Appl. Phys. 103, 083510 (2008); http://dx.doi.org/10.1063/1.2904907 (10 pages) | Cited 4 times

Online Publication Date: 18 April 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The development of effective hard coatings for high performance dry machining, which is associated with high stress/temperatures during friction, is a major challenge. Newly developed synergistically alloyed nanocrystalline adaptive Ti0.2Al0.55Cr0.2Si0.03Y0.02N plasma vapor deposited hard coatings exhibit excellent tool life under conditions of high performance dry machining of hardened steel, especially under severe and extreme cutting conditions. The coating is capable of sustaining cutting speeds as high as 600 m/min. Comprehensive investigation of the microstructure and properties of the coating was performed. The structure of the coating before and after service has been characterized by high resolution transmission electron microscopy. Micromechanical characteristics of the coating have been investigated at elevated temperatures. Oxidation resistance of the coating has been studied by using thermogravimetry within a temperature range of 25–1100 °C in air. The coefficient of friction of the coatings was studied within a temperature range of 25–1200 °C. To determine the causes of excellent tool life and improved wear behavior of the TiAlCrSiYN coatings, its surface structure characteristics after service have been investigated by using x-ray photoelectron spectroscopy and extended energy-loss fine spectroscopy. One of the major features of this coating is the dynamic formation of the protective tribo-oxide films (dissipative structures) on the surface during friction with a sapphire and mullite crystal structure. Aluminum- and silicon-rich tribofilms with dangling bonds form on the surface as well. These tribofilms act in synergy and protect the surface so efficiently that it is able to sustain extreme operating conditions. Moreover, the Ti0.2Al0.55Cr0.2Si0.03Y0.02N coating possesses some features of a complex adaptive behavior because it has a number of improved characteristics (tribological adaptability, ultrafine nanocrystalline structure, hot hardness and plasticity, and oxidation stability) that work synergistically as a whole. Due to the complex adaptive behavior, this coating represents a higher ordered system that has an ability to achieve unattainable wear resistance under strongly intensifying and extreme tribological conditions.
Show PACS
62.20.Qp Friction, tribology, and hardness
68.35.Gy Mechanical properties; surface strains
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
81.65.Mq Oxidation
81.40.Pq Friction, lubrication, and wear

Optical properties of polyelectrolyte quantum dot multilayer films prepared using the layer by layer self-assembly method

Emmanouil Lioudakis, Elena Koupanou, Constantina Kanari, Epameinondas Leontidis, and Andreas Othonos

J. Appl. Phys. 103, 083511 (2008); http://dx.doi.org/10.1063/1.2906121 (6 pages)

Online Publication Date: 18 April 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
In this work, we have used spectroscopic ellipsometry to study the optical properties of polyelectrolyte-PbS quantum dot (QD) multilayer films prepared using the layer by layer self-assembly method. The optical results provide information about the absorption coefficients of the materials as a function of the number of layers deposited on a quartz substrate. We have found that the fundamental energy gap of the films decreases linearly upon addition of each layer due to the formation of nanoclusters at the surface. Furthermore, the influence of PbS QD concentration in colloidal dispersion on the energy gap of the materials is examined in detail, and it is found that the optical band gap in the films is in agreement with the linear absorption measurements in the PbS colloidal dispersion from which the film deposition takes place. Finally, the observed electronic transitions of the films corroborate that nanoparticles in the regime of strong quantum confinement are present in the films. This comprehensive fundamental study provides important information, necessary for photovoltaic applications, about the absorption tunability of these nanofilms.
Show PACS
78.67.Hc Quantum dots
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
82.45.Gj Electrolytes
78.66.Qn Polymers; organic compounds
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
71.20.Rv Polymers and organic compounds

Optical properties of As33S67−xSex bulk glasses studied by spectroscopic ellipsometry

J. Orava, J. Šik, T. Wágner, and M. Frumar

J. Appl. Phys. 103, 083512 (2008); http://dx.doi.org/10.1063/1.2906138 (8 pages) | Cited 6 times

Online Publication Date: 18 April 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Variable angle spectroscopic ellipsometry (VASE) was employed to study the optical properties of As33S67−xSex (x = 0, 17, 33.5, 50, and 67 at. %) bulk glasses in the UV-vis-NIR (near infrared) spectral region for photon energies from 0.54 to 4.13 eV (photon wavelengths from 2300 to 300 nm). For data analysis, we employed Tauc–Lorentz (TL) dispersion model in the entire measured near bandgap spectral region and standard Cauchy dispersion model in the spectral region below the bandgap. With increasing Se content (x) in the bulk glass, we observed a linear decrease in optical bandgap energy Egopt from 2.52±0.02 eV for As33S67 to 1.75±0.01 eV for As33Se67 and linear increase in refractive index nTL in the NIR spectral region, e.g., at 0.80 eV from 2.327 for As33S67 to 2.758 for As33Se67. The amplitude A decreased with increasing Se content. The peak transition energy E0 and broadening C had a maximum value for x = 33.5 at. % and systematically decreased for higher S or Se content in glasses. Our study showed that TL model is suitable to describe dielectric functions of studied chalcogenide bulk glasses in the broad spectral region. The bulk glasses had a higher refractive index compared to thin films of corresponding composition. The bulk glasses with high S content had higher value of optical bandgap energy than was previously reported for thin films. The optical bandgap energy of glasses with higher Se content was very similar to the thin films.
Show PACS
61.43.Fs Glasses
78.40.Pg Disordered solids
78.35.+c Brillouin and Rayleigh scattering; other light scattering
71.23.Cq Amorphous semiconductors, metallic glasses, glasses
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons

Characterization of the donor-acceptor-pair transition in Nitrogen-implanted zinc oxide

D. Stichtenoth, J. Dürr, C. Ronning, L. Wischmeier, and T. Voss

J. Appl. Phys. 103, 083513 (2008); http://dx.doi.org/10.1063/1.2906320 (5 pages) | Cited 3 times

Online Publication Date: 18 April 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Zinc oxide bulk crystals were doped with nitrogen by ion beam implantation. After postimplantation annealing, a luminescent transition appears at 3.230 eV. Power-dependent photoluminescence studies and time-resolved measurements at several spectral positions within this band can be described by a model for donor-acceptor-pair (DAP) transitions. By tracing the luminescence in a temperature-dependent study, a connection to phonon replicas could be excluded. Based on these results, this luminescence line could be clearly assigned to a DAP transition. In order to increase the doping efficiency, various approaches are considered and discussed. A slight increase could be obtained by high-temperature implantation without postimplantation annealing.
Show PACS
61.72.uj III-V and II-VI semiconductors
78.55.Et II-VI semiconductors
61.72.Cc Kinetics of defect formation and annealing
61.80.Jh Ion radiation effects
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
78.47.jd Time resolved luminescence
71.55.Gs II-VI semiconductors

Effect of initial properties on the flow strength of aluminum during quasi-isentropic compression

J. R. Asay, T. Ao, J.-P. Davis, C. Hall, T. J. Vogler, and G. T. Gray, III

J. Appl. Phys. 103, 083514 (2008); http://dx.doi.org/10.1063/1.2902855 (16 pages) | Cited 9 times

Online Publication Date: 18 April 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A magnetic loading technique was used to ramp load pure aluminum and 6061 aluminum alloy to peak stresses of approximately 29 GPa. The peak loading rate was approximately 106/s, followed by unloading from peak stress at a rate of about 105/s. The pure aluminum samples had impurity levels ranging from about 10 ppm to 0.5 wt % and average grain sizes in the range of 144–454 μm. The 6061 alloy was prepared in either the T6 condition with grain sizes of 5–50 μm, or in the T0 or T6 heat treatment condition with a grain size of about 40 μm. A wave profile technique was used to estimate the compressive strength during unloading. It was found that the compressive strength estimated during unloading increased with peak stress for all materials and that the change in strength was insensitive to initial material properties. This observation is in agreement with previous results obtained from shock loading of the same materials [ H. Huang and J. R. Asay, J. Appl. Phys. 98, 033524 (2005) ] and suggests that the deformation mechanisms, which govern strength properties at high strain rates, are similar for the two cases. It was also found that the quasielastic strain occurring during unloading saturated at about 2% in 6061-T6 alloy for peak stresses in the range of 10–50 GPa. The change in quasielastic strain was found to be similar for pure aluminum and 6061 alloys.
Show PACS
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity
81.40.Gh Other heat and thermomechanical treatments
71.55.Ak Metals, semimetals, and alloys

Determination of buried interface composition and magnetism profiles using standing-wave excited soft x-ray emission and inelastic scattering

B. C. Sell, S. B. Ritchey, S.-H. Yang, S. S. P. Parkin, M. Watanabe, B. S. Mun, L. Plucinski, N. Mannella, A. Nambu, J. Guo, M. W. West, F. Salmassi, J. B. Kortright, and C. S. Fadley

J. Appl. Phys. 103, 083515 (2008); http://dx.doi.org/10.1063/1.2906331 (8 pages) | Cited 2 times

Online Publication Date: 18 April 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We demonstrate that a standing-wave/wedge (swedge) method for probing buried solid-solid interfaces can be carried out using soft x-ray emission spectroscopy (XES) and resonant inelastic x-ray scattering (RIXS). For the particular case of an Al2O3/Fe/Cr structure of relevance to giant magnetoresistance, measurements of Fe L and Cr L total intensities and Fe L magnetic circular dichroism are used to derive for both the top and bottom Fe interfaces the depth profile of composition and the depth dependence of the atom-specific Fe contribution to magnetization. Using XES and RIXS in this method, as compared to photoelectron spectroscopy in prior work, permits studying more deeply buried interfaces, and suggests future applications to a wide variety of magnetic and nonmagnetic nanostructures.
Show PACS
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.75.-c Magnetic properties of nanostructures
75.50.Tt Fine-particle systems; nanocrystalline materials
78.70.En X-ray emission spectra and fluorescence
78.70.Ck X-ray scattering
75.47.De Giant magnetoresistance

Sensitivity of porous silicon rugate filters for chemical vapor detection

M. S. Salem, M. J. Sailor, K. Fukami, T. Sakka, and Y. H. Ogata

J. Appl. Phys. 103, 083516 (2008); http://dx.doi.org/10.1063/1.2906337 (7 pages) | Cited 15 times

Online Publication Date: 18 April 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The characteristics of chemical vapor sensors constructed from porous Si rugate filters are examined. The peak position of the resonant wavelength exhibits a redshift response upon exposure to ethanol vapors. The filter response scales with the vapor partial pressure; the concentration level is estimated based on theoretical calculations. The formation of two stacked rugate filters with similar index contrast but different periodicities is used to test the extent of liquid infiltration into each individual filter. The penetration length of the condensate is found to be comparable to the thickness of the filter; in a 11.3‐μm-thick filter, a steady-state response is achieved in 4 min.
Show PACS
78.66.Db Elemental semiconductors and insulators
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
82.80.-d Chemical analysis and related physical methods of analysis
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing

Density-functional-theory calculations for silicon vacancy migration

A. F. Wright and R. R. Wixom

J. Appl. Phys. 103, 083517 (2008); http://dx.doi.org/10.1063/1.2906342 (5 pages) | Cited 1 time

Online Publication Date: 18 April 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The saddle-point configurations and associated formation energies of a migrating silicon vacancy in the +2, +1, 0, −1, and −2 charge states were computed using density-functional theory with a plane wave basis set, norm-conserving pseudopotentials, and the generalized-gradient approximation for exchange and correlation. Spurious electrostatic and strain contributions arising from use of periodic boundary conditions were removed by performing maximum likelihood fits on results from 215-, 511-, and 999-atom supercells, and thereby obtaining formation energies corresponding to isolated vacancies. Migration enthalpies were computed by subtracting similarly obtained formation energies for vacancies in local-energy minimum configurations. The results (0.27 eV in the +2 charge state, 0.19 eV in the +1 charge state, 0.36 eV in the 0 charge state, 0.04 eV in the −1 charge state, and 0.15 eV in the −2 charge state) are in good overall agreement with experimental results obtained at low temperatures.
Show PACS
61.72.jd Vacancies
71.15.Dx Computational methodology (Brillouin zone sampling, iterative diagonalization, pseudopotential construction)
71.15.Mb Density functional theory, local density approximation, gradient and other corrections

Electromagnetic emission memory phenomena related to LiF ionic crystal deformation

C. Mavromatou, G. S. Tombras, D. Ninos, and V. Hadjicontis

J. Appl. Phys. 103, 083518 (2008); http://dx.doi.org/10.1063/1.2906346 (4 pages) | Cited 4 times

Online Publication Date: 18 April 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
During the uniaxial compression of LiF ionic monocrystals, acoustic and electromagnetic emissions (EME) are detected. We observed that when the compression is performed in successive loading, unloading cycles and these emissions are being monitored, no new emissions will occur unless the maximum stress of the previous cycle is exceeded, meaning that the material presents memory characteristics. This is observed not only for the acoustic emission (AE), which is the well known Kaiser effect, but for the EME as well. In other words, the material appears to memorize and reveal the previously maximum stress it suffered while being deformed. The importance of an electromagnetic memory feature of a material can be related to various applications in material science, especially when the detection of AE is not feasible or gives false alert. Such cases may very well be earthquakes’ predictive indications, monitoring of mines’ stability, imminent landslides, etc.
Show PACS
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
62.65.+k Acoustical properties of solids

Single-walled carbon nanotubes filled with bimetallic alloys: Structures and buckling behaviors

L. Wang, H. W. Zhang, Y. G. Zheng, J. B. Wang, and Z. Q. Zhang

J. Appl. Phys. 103, 083519 (2008); http://dx.doi.org/10.1063/1.2909446 (6 pages) | Cited 5 times

Online Publication Date: 21 April 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Structural and mechanical properties of single-walled carbon nanotubes (SWCNTs) completely filled with bimetallic alloys are investigated using classic molecular dynamics method. Progresses on both synthesis and property researches of metal-filled carbon nanotubes are also comprehensively reviewed. Different initial equilibrium structures and buckling behaviors are exhibited for tubes filled with alloys of different species and compositions. The critical buckling strain of a SWCNT filled with mixed metals can be higher than that of the tube encapsulated with any pure component metals. Strong dependencies of buckling deformations on the initial random distributions of the encapsulated alloy metals are also reported.
Show PACS
61.46.Fg Nanotubes
81.16.-c Methods of micro- and nanofabrication and processing
81.40.Lm Deformation, plasticity, and creep
Page 2 of 8 Pages Previous Page Next Page | Jump to Page
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close