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 Aug 2002

Volume 92, Issue 4, pp. 1727-2219

Page 1 of 4 Pages Next Page | Jump to Page
back to top
RSS Feeds

Space-charge dynamics in photorefractive polymers

Oksana Ostroverkhova and Kenneth D. Singer

J. Appl. Phys. 92, 1727 (2002); http://dx.doi.org/10.1063/1.1491279 (17 pages) | Cited 28 times

Online Publication Date: 30 July 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The model of space-charge formation in photorefractive polymers due to Schildkraut and Buettner has been modified to include thermally accessible deep traps as well as shallow traps. The dynamic equations have been solved semiempirically using independent measurements of photoconductive properties to predict photorefractive dynamics. Dependencies of the dynamics on charge generation, mobility, trap density, acceptor density, ionized acceptor density, as well as their associated rates are examined. The magnitude of the fast time constant of photorefractive development is successfully predicted. The introduction of deep traps into the model has allowed us to qualitatively predict the reduction in speed due to deep trap filling and ionized acceptor growth. Experimental studies of photoconductivity and photorefraction (PR) in several polyvinyl carbazole photorefractive composites are carried out to demonstrate the applicability of the model. By choosing chromophores with different ionization potentials and by varying the chromophore concentrations, we investigate the influence of the chromophore ionization potential on the photoelectric and PR properties and reveal the nature of deep traps in the composites and their contribution to both photoconductivity and PR dynamics. Effects of plasticizer components are also discussed. © 2002 American Institute of Physics.
Show PACS
77.22.Jp Dielectric breakdown and space-charge effects
42.70.Jk Polymers and organics
42.70.Gi Light-sensitive materials
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
71.55.Jv Disordered structures; amorphous and glassy solids
72.40.+w Photoconduction and photovoltaic effects

Fully leaky guided wave determination of the original alignment direction for the directors at the walls in a twisted nematic liquid crystal cell

F. Z. Yang, H. J. Gao, and J. R. Sambles

J. Appl. Phys. 92, 1744 (2002); http://dx.doi.org/10.1063/1.1491025 (8 pages) | Cited 3 times

Online Publication Date: 30 July 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Fully leaky guided optical modes are used to explore the director profile in a twisted nematic liquid crystal cell built using a pair of high-index glass plates. This allows access to the pseudocritical angles corresponding to the liquid-crystal indices. Optical data is recorded over a range of angles of incidence with the cell subject to ac voltages. At higher-applied fields, the director in the cell center aligns almost homeotropically. Then the two surface regions become elastically decoupled, the directors at the surfaces realigning along the original alignment axes. Beyond the pseudo-critical angle corresponding to the low index of the liquid-crystal two minima of the polarization conserving transmission signal, for transverse electric polarization, TSS (over a particular range of incidence angles) are found as the cell rotation angle is changed. These two minima give the original alignment directions of the director, the easy axes, at the two substrates, information vital to the measurement of the torsional anchoring energies at the interfaces of the cells. © 2002 American Institute of Physics.
Show PACS
61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order
42.70.Df Liquid crystals
42.65.Wi Nonlinear waveguides
77.22.Ej Polarization and depolarization

Pretilted and grating alignment of liquid crystals by oblique ultraviolet irradiation of polyimide

C. J. Newsome and M. O'Neill

J. Appl. Phys. 92, 1752 (2002); http://dx.doi.org/10.1063/1.1492863 (5 pages) | Cited 19 times

Online Publication Date: 30 July 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We discuss the formation of pretilt by oblique irradiation of photosensitive polymers that homogeneously align liquid crystals in the direction corresponding to the maximum density of unreacted polymer. We show that a tilted polymer distribution is formed by oblique illumination with one beam of unpolarized or partially polarized light. When unpolarized radiation is used, a small azimuthal anisotropy is generated and the polymer tilt angle increases with incident angle. Pretilted liquid crystal alignment is possible up to a threshold angle at which the azimuthal alignment direction changes. Irradiation with partially polarized light gives a higher azimuthal anisotropy but smaller polymer tilt angles. We obtain liquid crystal pretilt angles up to 4° by oblique irradiation of polyimide with light from an excimer laser operating below the threshold for ablation. A simple two step process is used to obtain pretilted alignment for liquid crystals using surface gratings: a grating etched into polyimide by laser ablation is subsequently irradiated at oblique incidence to give planar liquid crystal alignment with a pretilt angle of 3°. © 2002 American Institute of Physics.
Show PACS
42.70.Jk Polymers and organics
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
42.79.Kr Display devices, liquid-crystal devices
85.60.Pg Display systems
back to top
RSS Feeds

Thomson-scattering observation of non-Maxwellian electron energy distribution in inductively coupled C4F8/Ar and CF4/Ar plasmas and the effect of vibrational excitation and nonlocal electron kinetics

A. Kono and H. Funahashi

J. Appl. Phys. 92, 1757 (2002); http://dx.doi.org/10.1063/1.1493659 (7 pages) | Cited 4 times

Online Publication Date: 30 July 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Laser Thomson-scattering diagnostics of electron energy distribution function (EEDF) was carried out for inductively coupled cyclo–C4F8/Ar and CF4/Ar plasmas at 25 mTorr. Care was taken to ascertain that the observed Thomson spectra are unaffected by other laser-induced effects, in particular by Raman scattering. Admixing of C4F8 and CF4 with Ar resulted in marked deviation of EEDF from Maxwellian. The mechanism leading to non-Maxwellian EEDF was also studied by a Monte Carlo simulation. The results suggest that the major factors responsible are rapid electron energy loss due to vibrational excitation and the effect nonlocal electron kinetics associated with localized electron heating. © 2002 American Institute of Physics.
Show PACS
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.65.Pp Monte Carlo methods

Far field modeling of the plasma plume of a Hall thruster

Iain D. Boyd and Rainer A. Dressler

J. Appl. Phys. 92, 1764 (2002); http://dx.doi.org/10.1063/1.1492014 (11 pages) | Cited 24 times

Online Publication Date: 30 July 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Hall thrusters are an attractive form of electric propulsion that are being developed and implemented to replace chemical systems for many in orbit propulsion tasks on communications satellites. One concern in the use of these devices is the possible damage their plumes may cause to the host spacecraft. Computer models of Hall thruster plumes play an important role in integration of these devices onto spacecraft as the space environment is not easily reproduced in ground testing facilities. In this article, a hybrid particle-fluid model of a Hall thruster plume is applied to model the SPT-100 thrusters used on the Russian Express satellites. The emphasis of the article is on making assessment of the model through direct comparison with measurements of ion current density and ion energy distributions taken on board Express spacecraft. A model for simulating atom–ion collisions is described. The sensitivity of the plume simulation results to various aspects of the physical modeling is investigated. The plume model is able to predict many of the most important characteristics of the measured data. © 2002 American Institute of Physics.
Show PACS
52.75.Di Ion and plasma propulsion

High resolution laser-driven proton radiography

J. A. Cobble, R. P. Johnson, T. E. Cowan, N. Renard-Le Galloudec, and M. Allen

J. Appl. Phys. 92, 1775 (2002); http://dx.doi.org/10.1063/1.1494128 (5 pages) | Cited 42 times

Online Publication Date: 30 July 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Laser-accelerated beams of Mega-electron volt protons have been produced at the Los Alamos Trident laser facility and used for high-resolution point-projection proton radiography of Au grids. The effective proton source size affords an inherent resolution of 2–3 μm in the object plane. The proton beam is characterized by ion time-of-flight Faraday cup measurements and nuclear particle track detectors. Laser-driven proton radiography appears promising as a valuable research tool for probing plasmas or modest density objects. © 2002 American Institute of Physics.
Show PACS
07.77.Ka Charged-particle beam sources and detectors
29.40.Gx Tracking and position-sensitive detectors
52.70.Nc Particle measurements
41.75.Ak Positive-ion beams

Model and probe measurements of inductively coupled CF4 discharges

T. Kimura and K. Ohe

J. Appl. Phys. 92, 1780 (2002); http://dx.doi.org/10.1063/1.1491023 (8 pages) | Cited 12 times

Online Publication Date: 30 July 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A global model for electronegative plasma, in which the negative ion distribution is assumed to be a parabolic profile in the axial direction with a flat central region and a similar edge profile in the radial direction in the electronegative region, is applied to study the power and pressure dependences of plasma parameters in low-pressure CF4 discharges. The electron density increases approximately linearly with the power. The electron temperature also increases with the power due to the decrease in neutral number density with increase in power, resulting in the increase in plasma potential. The density of CF3+ is a weak function of the power, while the densities of CF2+, CF+, and F+, which are strongly correlated to the densities of the respective radicals, depend on the power. On the other hand, the decrease in electron temperature with the pressure significantly results in a decrease in the degree of dissociation. The electron density also decreases gradually with the pressure except for the case of pressure lower than 5 mTorr. The densities of CF2+, CF+, and F+ decrease gradually with the pressure at pressures higher than 5 mTorr, while the density of CF3+ increases gradually with the pressure. The electron energy probability function (EEPF) is measured with a Langmuir probe in an inductively coupled rf (13.56 MHz) CF4 discharge over a pressure range from 2 to 30 mTorr, while keeping the power injected into the plasma at about 70 W. The measured EEPFs are approximately Maxwellian at any pressure, although there is a slight deviation from a Maxwellian distribution at pressures higher than 10 mTorr. The results estimated from the measured EEPF are compared to the model and show reasonably good agreement. © 2002 American Institute of Physics.
Show PACS
52.70.Ds Electric and magnetic measurements
52.65.-y Plasma simulation
52.25.-b Plasma properties

Arc erosion characteristics of pseudospark discharge in multiaperture geometry

Ahmer Naweed, Jochen Kiefer, Constantin Gavrilescu, and Willi Neff

J. Appl. Phys. 92, 1788 (2002); http://dx.doi.org/10.1063/1.1491022 (5 pages) | Cited 1 time

Online Publication Date: 30 July 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Analysis of discharge mechanism in especially designed pseudosparks that facilitate pseudospark characteristic low-erosive conduction at very high currents is presented. The alternate formulation of criterion for transition to arc discharge phase developed here enables us to account for the emergence of arcs at each aperture after a threshold electric charge is transmitted in these devices. The use of a large number of apertures is found to have no influence on discharge condition that initiates arc formation at individual apertures. © 2002 American Institute of Physics.
Show PACS
52.80.Mg Arcs; sparks; lightning; atmospheric electricity
52.80.Hc Glow; corona
back to top
RSS Feeds

Photoreflectance spectroscopy of wurtzite CdS

Akinori Imada, Shunji Ozaki, and Sadao Adachi

J. Appl. Phys. 92, 1793 (2002); http://dx.doi.org/10.1063/1.1493655 (6 pages) | Cited 17 times

Online Publication Date: 30 July 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Photoreflectance (PR) spectra have been measured to determine the lowest direct-band edge E0α (α=A, B, and C) of wurtzite CdS single crystal in the temperature range T=13–300 K for both E⊥c and E∥c polarizations. The measured PR spectra can be interpreted by the three-dimensional (3D) excitonic plus one-electron line shapes over the entire temperature range. The temperature dependence of the excitonic and critical-point parameters (energy, amplitude, and broadening parameter) have been determined and analyzed using the Varshni [Physica (Amsterdam) 34, 149 (1967)] equation and an analytical four-parameter expression recently developed for the explanation of the band-gap shrinkage effect in semiconductors. The 3D- exciton binding energies have also been determined to be 27 (A), 31 (B), and 30 meV (C), respectively. © 2002 American Institute of Physics.
Show PACS
71.20.Nr Semiconductor compounds
78.20.-e Optical properties of bulk materials and thin films
71.35.Cc Intrinsic properties of excitons; optical absorption spectra
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Formation of cellular defect structure on GaSb ion-implanted at low temperature

Noriko Nitta, Masafumi Taniwaki, Yoshihiko Hayashi, and Toshimasa Yoshiie

J. Appl. Phys. 92, 1799 (2002); http://dx.doi.org/10.1063/1.1493662 (4 pages) | Cited 24 times

Online Publication Date: 30 July 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Formation of the anomalous cellular structure in (100) GaSb with Sn ion-implantation at a low temperature is investigated by cross-sectional scanning electron microscopy, atomic force microscopy, and transmission electron microscopy. A fine structure consisting of many cells was formed on GaSb surface implanted by 60 keV Sn. The cell diameter and the thickness of the walls partitioning the cells were about 50 and 10 nm, respectively, which are almost constant in the range of the ion dose 4.0×1014–8.9×1014 ions/cm2. The depth of the cells increased linearly with increasing ion dose, from 100 nm in the sample implanted with a dose of 4.0×1014 ions/cm2 to 220 nm in that implanted with a dose of 8.9×1014 ions/cm2. From the experimental results, it is concluded that the development of the cellular structure originates in formation of the voids. An improved defect formation mechanism based on movement of the implantation-induced point defects is discussed. © 2002 American Institute of Physics.
Show PACS
61.80.Jh Ion radiation effects
61.82.Fk Semiconductors
61.72.uj III-V and II-VI semiconductors
61.72.J- Point defects and defect clusters
81.05.Ea III-V semiconductors
61.72.Qq Microscopic defects (voids, inclusions, etc.)

In situ study of void growth kinetics in electroplated Cu lines

E. Liniger, L. Gignac, C.-K. Hu, and S. Kaldor

J. Appl. Phys. 92, 1803 (2002); http://dx.doi.org/10.1063/1.1492871 (8 pages) | Cited 29 times

Online Publication Date: 30 July 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
An in situ electromigration apparatus was used to study the kinetics of void growth in unpassivated, electropolated copper damascene lines. Voids were observed to grow by consuming grains in a stepwise fashion, either by grain thinning or by an edge displacement mechanism. Surface diffusion was found to be the primary diffusion path for void growth. In addition, grain boundaries provided a secondary path for copper diffusion in polycrystalline structures and nucleation sites for void growth in bamboo structures. Void growth rate was measured as a function of sample temperature and linewidth using a scanning electron microscope. An electromigration activation energy of 0.9±0.1 eV was determined for the copper voiding process. The effect of linewidth on void growth rate was also investigated and found to be negligible, consistent with a surface-diffusion dominated model for void growth. The in situ apparatus also made it possible to directly correlate changes in electrical resistance with physical changes taking place in the test structures. © 2002 American Institute of Physics.
Show PACS
85.40.Ls Metallization, contacts, interconnects; device isolation
66.30.Qa Electromigration
68.35.Fx Diffusion; interface formation
61.72.Qq Microscopic defects (voids, inclusions, etc.)
61.72.Mm Grain and twin boundaries
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)

Crystal growth and characterization of the cubic semiconductor Cu2SnSe4

G. Marcano, C. Rincón, G. Marín, R. Tovar, and G. Delgado

J. Appl. Phys. 92, 1811 (2002); http://dx.doi.org/10.1063/1.1492018 (5 pages) | Cited 5 times

Online Publication Date: 30 July 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
X-ray powder diffraction study of the p-type semiconductor Cu2SnSe4 shows that this material crystallizes in the cubic structure, space group Fmath3m, with unit cell parameter a=5.6846(3) Å. The temperature variation of the hole concentration between 120 and 300 K, obtained from the Hall effect and electrical resistivity measurements, is due to the thermal activation of an acceptor level with ionization energy of about 0.02 eV. The temperature variation of the hole mobility is explained by considering the scattering of charge carriers by ionized impurities and acoustic phonons. From this analysis, the density-of-states effective mass of the holes is estimated to be about 0.8 me, me being the free electron effective mass. From the optical absorption spectra, the fundamental absorption edge is found to be direct. The value of the lowest energy gap and the spin-orbit splitting were estimated to be about 0.35 and 0.20 eV, respectively. The temperature dependence of the magnetization measurements shows that Cu2SnSe4 is paramagnetic, indicating that most of the copper atoms have the divalent charge state. © 2002 American Institute of Physics.
Show PACS
81.10.Fq Growth from melts; zone melting and refining
72.20.Fr Low-field transport and mobility; piezoresistance
81.05.Hd Other semiconductors
61.66.Fn Inorganic compounds
72.80.Ga Transition-metal compounds
72.20.My Galvanomagnetic and other magnetotransport effects
71.55.Ht Other nonmetals
63.20.K- Phonon interactions
71.38.-k Polarons and electron-phonon interactions
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.20.Ck Nonmetals
71.20.Nr Semiconductor compounds

Optical response of one-dimensional (Si/SiO2)m photonic crystals

M. Patrini, M. Galli, M. Belotti, L. C. Andreani, G. Guizzetti, G. Pucker, A. Lui, P. Bellutti, and L. Pavesi

J. Appl. Phys. 92, 1816 (2002); http://dx.doi.org/10.1063/1.1492866 (5 pages) | Cited 8 times

Online Publication Date: 30 July 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
One-dimensional photonic crystals made of (Si/SiO2)m multilayers with m=2,…8 have been grown on SiO2 4-in. wafers by repeated polysilicon low-pressure chemical vapor deposition, oxidation, and wet etching steps. The poly-Si and SiO2 layers were about 220 and 660 nm thick, respectively, thus realizing λ/4 distributed Bragg reflectors. Spectroscopic ellipsometry in the 1.4–5 eV range was used to determine the dielectric function of poly-Si and the actual layer thicknesses, as well as to check the structural and compositional homogeneity of the structures. In order to measure the photonic crystal properties, specular reflectance and transmittance measurements were performed from 0.2 to 6 eV at different angles of incidence θ⩽50° and for transverse electric and transverse magnetic polarizations. The stop-bands characteristic of Bragg reflector multilayers appear up to the fifth order and become more pronounced with increasing m, reaching almost complete rejection for m=4 periods. The experimental spectra were fitted by the transfer-matrix method, both versus θ and m. Moreover, the experimental stop bands of the finite multilayers matched the calculated photonic band gaps of an infinite one-dimensional photonic crystal very well. © 2002 American Institute of Physics.
Show PACS
42.70.Qs Photonic bandgap materials
78.66.Db Elemental semiconductors and insulators
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
77.22.Ch Permittivity (dielectric function)
81.65.Cf Surface cleaning, etching, patterning
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures
81.65.Mq Oxidation

Ion-beam doping of silver in amorphous As2S3 thin films

Takenobu Suzuki and Hideo Hosono

J. Appl. Phys. 92, 1821 (2002); http://dx.doi.org/10.1063/1.1492862 (4 pages)

Online Publication Date: 30 July 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Double layers of metallic Ag/amorphous (a-)As2S3 on silica substrates were irradiated with 300 keV He+ ions to examine doping of Ag+ into a-As2S3 by dense electronic excitation. The irradiating ions passed through the double layers and came to rest in the silica substrates. Thus, energy deposition from energetic He+ ions into the double layers was completely almost due to electronic processes (99.4%). Ionized silver found to diffuse into a-As2S3 as a result of electronic excitation by ion-beam irradiation. Rutherford backscattering spectroscopy revealed that the highest concentration of silver doped into a-As2S3 was 35 at. %. When the resulting Ag-doped a-As2S3 was illuminated by band gap light, photo-surface-deposition of metallic silver particles, which was not observed for Ag photo-doped specimens, was observed. © 2002 American Institute of Physics.
Show PACS
61.72.up Other materials
61.82.Fk Semiconductors
61.80.Jh Ion radiation effects
66.30.J- Diffusion of impurities
68.49.Sf Ion scattering from surfaces (charge transfer, sputtering, SIMS)
61.72.S- Impurities in crystals
68.35.Dv Composition, segregation; defects and impurities

Characterization of photorefractive GaAlAs multiple quantum well structures by ac photoelectromotive force and modulated photocarrier grating techniques

S. Stepanov, I. Seres, S. Mansurova, and D. Nolte

J. Appl. Phys. 92, 1825 (2002); http://dx.doi.org/10.1063/1.1490155 (8 pages) | Cited 3 times

Online Publication Date: 30 July 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Simultaneous utilization of ac photoelectromotive (photo-EMF) and modulated photocarrier grating (MPG) techniques for characterization of bipolar transport in semi-insulating photorefractive GaAlAs multiple quantum well structure is reported. From the ac photo-EMF experiment the electrons were determined as the dominant photocarriers for interband optical excitation at λ=633 nm. From the self-consistent data obtained from photo-EMF and MPG experiments the diffusion length of the photoelectrons was evaluated as LD≃1.4±0.2 μm, and that of the photoholes (minority carriers)—as LDm≃0.6±0.1 μm. In the MPG configuration, the contrast of the illuminating interference pattern was controlled by electro-optic modulation of the signal beam polarization, which allowed us to measure dielectric relaxation time of the photoconductor as well. As evaluated by both techniques it proved to be about τdi≃0.05 μs for the average light intensity I0≃0.3 mW/mm2. The proposed combination of the characterization techniques seems to be especially promising for amorphous a–Si and polymer films. © 2002 American Institute of Physics.
Show PACS
73.63.Hs Quantum wells
78.67.De Quantum wells
81.07.St Quantum wells
72.40.+w Photoconduction and photovoltaic effects
81.05.Ea III-V semiconductors
73.50.Pz Photoconduction and photovoltaic effects
42.70.Gi Light-sensitive materials
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
42.79.Dj Gratings
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
77.22.Gm Dielectric loss and relaxation

Influence of growth temperature on properties of zirconium dioxide films grown by atomic layer deposition

Kaupo Kukli, Mikko Ritala, Jaan Aarik, Teet Uustare, and Markku Leskelä

J. Appl. Phys. 92, 1833 (2002); http://dx.doi.org/10.1063/1.1493657 (8 pages) | Cited 37 times

Online Publication Date: 30 July 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
ZrO2 films were grown by atomic layer deposition from ZrCl4 and H2O or a mixture of H2O and H2O2 on Si(100) substrates in the temperature range of 180–600  °C. The films were evaluated in the as-deposited state, in order to follow the effect of deposition temperature on the film quality. The rate of crystal growth increased and the content of residual impurities decreased with increasing temperature. The zirconium-to-oxygen atomic ratio, determined by ion-beam analysis, corresponded to the stoichiometric dioxide regardless of the growth temperature. The effective permittivity of ZrO2 in Al/ZrO2/Si capacitor structures increased from 13–15 in the films grown at 180  °C to 19 in the films grown at 300–600  °C, measured at 100 kHz. The permittivity was relatively high in the crystallized films, compared to the amorphous ones, but rather insensitive to the crystal structure. The permittivity was higher in the films grown using water. The leakage current density tended to be lower and the breakdown field higher in the films grown using hydrogen peroxide. © 2002 American Institute of Physics.
Show PACS
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.55.-g Dielectric thin films
77.22.Ch Permittivity (dielectric function)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.-a Thin film structure and morphology
68.55.Nq Composition and phase identification
77.22.Jp Dielectric breakdown and space-charge effects

Competitive effects of grooves and photoalignment on nematic liquid-crystal alignment using azobenzene polymer

Doo-Han Chung, Takashi Fukuda, Yoichi Takanishi, Ken Ishikawa, Hiro Matsuda, Hideo Takezoe, and Mikhail A. Osipov

J. Appl. Phys. 92, 1841 (2002); http://dx.doi.org/10.1063/1.1493658 (4 pages) | Cited 16 times

Online Publication Date: 30 July 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Effect of an anisotropic photoalignment layer and microgrooves on nematic liquid-crystal (LC) alignment was quantitatively examined using azobenzene polymer thin film with surface relief grating (SRG) of about 1 μm pitch. The SRG with various modulation depths was treated with polarized light irradiation to align molecules at 45° from the groove. Nematic LC molecules, 4′-n-pentyl-4-cyanobiphenyl, orient to the photoaligned direction on the SRG being shallower than 200 nm. The orientation rather sharply deviates from the photoaligned direction toward the groove direction with increasing grating depth into the deeper region than 200 nm and finally becomes parallel to the grooves on the SRG of 400 nm deep. This behavior is successfully simulated by the consideration of anisotropic surface interaction and an elastic energy of LCs. © 2002 American Institute of Physics.
Show PACS
61.30.Eb Experimental determinations of smectic, nematic, cholesteric, and other structures
61.30.Hn Surface phenomena: alignment, anchoring, anchoring transitions, surface-induced layering, surface-induced ordering, wetting, prewetting transitions, and wetting transitions
61.41.+e Polymers, elastomers, and plastics
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
42.70.Df Liquid crystals
68.35.B- Structure of clean surfaces (and surface reconstruction)

Substrate bias dependence of Raman spectra for TiN films deposited by filtered cathodic vacuum arc

Y. H. Cheng, B. K. Tay, S. P. Lau, H. Kupfer, and F. Richter

J. Appl. Phys. 92, 1845 (2002); http://dx.doi.org/10.1063/1.1491588 (5 pages) | Cited 21 times

Online Publication Date: 30 July 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Raman spectroscopy was used to characterize TiN films deposited by using an off-plane double bend filtered cathodic vacuum arc technique. The influence of substrate bias on the Raman spectra was systematically studied. Four peaks at 235, 320, 440, and 570 cm−1, related to transverse acoustic (TA), longitudinal acoustic (LA), second-order acoustic (2A), and transverse optical (TO) modes of TiN, respectively, were observed in the Raman spectra of TiN films. The intensity of all four peaks and the area fraction as well as the full width at half maximum (FWHM) of the TO peak increase drastically with increasing substrate bias, reaching a maximum at −100 V, and then decrease greatly. However, the area fraction of TA, LA, and 2A peaks, the FWHM of TA and 2A peaks, as well as the frequency of all four peaks decrease rapidly with increasing substrate bias to −100 V, and then increase greatly. At a bias above −200 V, only a slight change in the Raman spectra of TiN films were observed. The change in the N/Ti ratio is the main reason for the evolution in the Raman spectra of TiN films with increasing substrate bias. The internal stress and the crystal size play only a minor role in the Raman spectra of TiN films in the present study. © 2002 American Institute of Physics.
Show PACS
78.30.Hv Other nonmetallic inorganics
78.66.Nk Insulators
63.20.-e Phonons in crystal lattices
68.55.-a Thin film structure and morphology
68.60.Bs Mechanical and acoustical properties

Electrical damage of an ultrathin Si oxynitride layer induced by scanning tunneling spectroscopy

Noriyuki Miyata and Masakazu Ichikawa

J. Appl. Phys. 92, 1850 (2002); http://dx.doi.org/10.1063/1.1492865 (8 pages) | Cited 2 times

Online Publication Date: 30 July 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Ultrathin Si oxynitride layers were examined by using scanning tunneling microscopy (STM) and spectroscopy (STS). These techniques revealed that a structural change from an intrinsic defect (Si–Si bond) to a damaged structure (Si cluster) takes place under conventional STM/STS conditions. Comparison of the damaged structures formed in the oxynitride with those in the oxide indicated that nitrogen atoms suppress the expansion of the damaged regions. It was also found that nitrogen incorporation enhances both the defect density and the atomic-scale roughness at the oxynitride/Si interface. We suggested that this degradation is related to a local strain produced by the N≡Si3 structures at the oxynitride/Si interface. On the contrary, a normal oxynitride structure had a higher resistance to an electrical stress than an intrinsic defect, but, when the constant electrical stress was applied, the normal oxynitride structure was also damaged. This damage proceeds in two steps: creation of charge traps, and then formation of Si cluster. From these STM/STS results, we proposed that the electrical breakdown of the conventional gate-oxide film proceeds as a four-step process: (1) formation of Si clusters by the damage of intrinsic defects, (2) creation of traps in the normal structure, (3) formation of Si clusters in the normal structure, and (4) complete local breakdown when the Si clusters become connected. © 2002 American Institute of Physics.
Show PACS
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.35.Ct Interface structure and roughness
77.22.Jp Dielectric breakdown and space-charge effects
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Silicon–on–insulator waveguide photodetector with Ge/Si self-assembled islands

M. El kurdi, P. Boucaud, S. Sauvage, G. Fishman, O. Kermarrec, Y. Campidelli, D. Bensahel, G. Saint-Girons, I. Sagnes, and G. Patriarche

J. Appl. Phys. 92, 1858 (2002); http://dx.doi.org/10.1063/1.1493656 (4 pages) | Cited 13 times

Online Publication Date: 30 July 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We have investigated a silicon-based near-infrared photodetector using a waveguide with strong optical confinement. The high-difference index waveguide is obtained with a silicon–on–insulator substrate. The optically active region consists of self-assembled Ge/Si islands embedded in a p-i-n junction. The Ge/Si islands grown by high-pressure chemical-vapor deposition exhibit a broad photoluminescence and electroluminescence which are resonant around 1.5 μm. The photoluminescence and electroluminescence energies are correlated to the island size and to the island composition using a six-band k⋅p calculation. The spectral responsivity of the detectors is measured in a front facet coupling geometry with a broadband source and with semiconductor laser diodes. For a 0 V applied bias, responsivities of 25 and 0.25 mA/W are measured at room temperature at 1.3 and 1.55 μm, respectively. © 2002 American Institute of Physics.
Show PACS
85.60.Gz Photodetectors (including infrared and CCD detectors)
42.79.Gn Optical waveguides and couplers
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Structural characterization of Ni–Al (111) interface by surface x-ray absorption spectroscopy

L. Damoc, E. Fonda, P. Le Fevre, and A. Traverse

J. Appl. Phys. 92, 1862 (2002); http://dx.doi.org/10.1063/1.1493652 (6 pages) | Cited 4 times

Online Publication Date: 30 July 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The evolution of the Ni/Al(111) interface has been studied in situ by x-ray absorption spectroscopy at the Ni–K edge. Ni films were deposited on bulk Al(111) with thickness ranging from 2 monolayers (ML) up to 30 ML. The aim was to determine the diffusion length of Ni and the phases that have formed. Ni diffused spontaneously at room temperature to a depth that we estimated to be of the order of 11 ML. The structure of Ni/Al(111) mixed interface has been characterized by x-ray absorption spectroscopy. With respect to previous studies on Al(110) the first phase formed on Al(111) is Al3Ni2-like instead of AlNi-like. Accordingly to previous observations, an AlNi3 phase forms on top of Al3Ni2 after the deposition of the first few monolayers. We propose that the pure Ni growth observed after deposition of 11 ML is due to the presence of the AlNi3 aluminide that acts as a diffusion barrier preventing deeper Ni penetration into Al at room temperature. © 2002 American Institute of Physics.
Show PACS
78.70.Dm X-ray absorption spectra
68.35.Fx Diffusion; interface formation
68.35.Ct Interface structure and roughness
68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)

Dependence of luminescence efficiency on dopant concentration and sintering temperature in the erbium-doped Ba0.7Sr0.3TiO3 thin films

Shou-Yi Kuo, Chin-Sheng Chen, Tseung-Yuen Tseng, S.-C. Chang, and Wen-Feng Hsieh

J. Appl. Phys. 92, 1868 (2002); http://dx.doi.org/10.1063/1.1492870 (5 pages) | Cited 12 times

Online Publication Date: 30 July 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We found the dependence of luminescence efficiency on Er3+ concentration and sintering temperature in the Er-doped Ba0.7Sr0.3TiO3 (BST) thin films is governed by crystallinity and ion–ion interaction. X-ray diffraction and Raman studies of the sol-gel prepared samples show that the BST polycrystalline phase occurred when the sintering temperature reaches 700 °C, whereas, it becomes worse for temperature above 700 °C resulting from phase separation and the Er3+ concentration exceeding 3 mol % due to charge compensation mechanism. The observed green emission reaches maximum at sintering temperature 700 °C and 3 mol % Er3+ ions concentration. We also showed the Er dopant does not affect the dielectric property of BST thin films in C–V measurement and the Ba0.7Sr0.3TiO3 films doped with Er3+ ions may have potential use for electroluminescence devices. © 2002 American Institute of Physics.
Show PACS
78.55.Hx Other solid inorganic materials
78.30.Hv Other nonmetallic inorganics
78.66.Nk Insulators
77.80.-e Ferroelectricity and antiferroelectricity
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
64.75.-g Phase equilibria

Influence of overlayers on determination of the optical constants of ZnSe thin films

Daniel Franta, Ivan Ohlídal, Petr Klapetek, Alberto Montaigne-Ramil, Alberta Bonanni, David Stifter, and Helmut Sitter

J. Appl. Phys. 92, 1873 (2002); http://dx.doi.org/10.1063/1.1489068 (8 pages) | Cited 19 times

Online Publication Date: 30 July 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
In this article a multisample modification of variable angle spectroscopic ellipsometry is used to characterize ZnSe thin films prepared by molecular beam epitaxy on substrates formed by GaAs single crystals. Atomic force microscopy (AFM) is employed to characterize the morphology of the upper boundaries of these films. To interpret the ellipsometric data a relatively complicated physical model that contains a rough overlayer between the ambient and the ZnSe film and a transition layer between the GaAs substrate and the ZnSe film is employed. Several models of dispersion of the optical constants of the overlayers are examined to interpret the ellipsometric data. It is shown that the choice of overlayer dispersion model has a strong influence on determining the optical constants and dielectric function of the ZnSe films in the near-UV region. Within the visible region there are no differences between the overlayer dispersion models regarding determination of the ZnSe optical constants. The spectral dependences of the ZnSe dielectric function obtained are compared with those presented by other researchers. Further, by AFM it is shown that the upper boundaries of the ZnSe films are randomly rough and partially covered with small objects. © 2002 American Institute of Physics.
Show PACS
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.66.Hf II-VI semiconductors
81.05.Dz II-VI semiconductors
07.60.Fs Polarimeters and ellipsometers
68.37.Ps Atomic force microscopy (AFM)
68.35.B- Structure of clean surfaces (and surface reconstruction)
77.22.Ch Permittivity (dielectric function)
78.40.Fy Semiconductors

Electrical and optical properties of beryllium-implanted Mg-doped GaN

Chang-Chin Yu, C. F. Chu, J. Y. Tsai, C. F. Lin, and S. C. Wang

J. Appl. Phys. 92, 1881 (2002); http://dx.doi.org/10.1063/1.1494110 (7 pages) | Cited 11 times

Online Publication Date: 30 July 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We investigated the electrical and optical characteristics of beryllium implanted Mg-doped GaN materials. The Mg-doped GaN samples were grown by metalorganic chemical vapor deposition system and implanted with Be ions at two different energies of 50 and 150 keV and two different doses of about 1013 and 1014 cm−2. The implanted samples were subsequently rapidly thermal annealed at 900, 1000, and 1100 °C for various periods. The annealed samples showed an increase of hole concentration by three orders of magnitude from nonimplanted value of 5.5×1016 to 8.1×1019 cm−3 as obtained by Hall measurement. The high hole concentration samples also showed low specific resistance ohmic contact of about 10−3 Ω cm2 and 10−6 Ω cm2 using Ni/Au and Ni/Pd/Au metallization, respectively, without any further annealing process. It is also found from the temperature dependent photoluminescence that the activation energy of Mg dopants of the Be implanted samples has an estimated value of about 170 meV, which is nearly 30% lower than the as-grown samples of about 250 meV. The crystal quality and surface morphology of the Be implanted samples measured by x-ray diffraction and atomic force microscopy show no obvious degradation in the crystal quality and surface morphology. © 2002 American Institute of Physics.
Show PACS
73.61.Ey III-V semiconductors
78.66.Fd III-V semiconductors
81.05.Ea III-V semiconductors
68.55.-a Thin film structure and morphology
72.80.Ey III-V and II-VI semiconductors
78.55.Cr III-V semiconductors
61.72.uj III-V and II-VI semiconductors
61.80.Jh Ion radiation effects
61.82.-d Radiation effects on specific materials
61.82.Fk Semiconductors
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.72.Cc Kinetics of defect formation and annealing
72.20.My Galvanomagnetic and other magnetotransport effects
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
73.40.Ns Metal-nonmetal contacts
85.40.Ls Metallization, contacts, interconnects; device isolation
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.37.Ps Atomic force microscopy (AFM)

Thermal equilibrium governing the formation of negatively charged excitons in resonant tunneling diodes

A. Vercik, Y. Galvão Gobato, and M. J. S. P. Brasil

J. Appl. Phys. 92, 1888 (2002); http://dx.doi.org/10.1063/1.1494851 (5 pages) | Cited 2 times

Online Publication Date: 30 July 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The thermal equilibrium of the formation of negatively charged excitons is studied in this work, by measuring the current and quantum-well photoluminescence in biased resonant tunneling double barrier diodes. We observe that the intensity ratio of negatively charged and neutral excitons depends linearly on the current for fixed temperature and illumination conditions. We propose that the results can be interpreted in terms of a mass-action law governing the concentrations of neutral and charged excitons and free electrons. Measurements at different temperatures and bias yield an electron concentration and a dwell time in the well that are in good agreement with the values previously reported in the literature. We also analyze the dependence of the luminescence on excitation intensity. © 2002 American Institute of Physics.
Show PACS
85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)
71.35.-y Excitons and related phenomena
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
Page 1 of 4 Pages Next Page | Jump to Page
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close