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15 Jun 2002

Volume 91, Issue 12, pp. 9461-10231

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Thick inductive cross shaped metal meshes

K. D. Möller, O. Sternberg, H. Grebel, and Philippe Lalanne

J. Appl. Phys. 91, 9461 (2002); http://dx.doi.org/10.1063/1.1476073 (5 pages) | Cited 7 times

Online Publication Date: 30 May 2002

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Experimental data for inductive cross shaped metal meshes with periodicity constant g=20 μm have been reproduced by the Micro-Stripes simulation program for various thicknesses. A similar calculation has been performed with the Fourier modal method for cross shaped meshes with periodicity constant g=1 μm. The transmittances of all these meshes show similar resonance peaks and the same dependence on thickness. A rudimentary coupled oscillator model describes very well the dependence on thickness of the peaks, suggesting that the transmittance of all metal meshes in the short and long wavelength region are excited surface waves coupled by waveguide modes of the openings. © 2002 American Institute of Physics.
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42.79.Gn Optical waveguides and couplers
42.25.Bs Wave propagation, transmission and absorption
84.40.Az Waveguides, transmission lines, striplines
78.30.Er Solid metals and alloys
78.40.Kc Metals, semimetals, and alloys
42.65.Wi Nonlinear waveguides

Temperature dependence of the fluorescence of Eu3+-ion doped in various silicate glasses

Jiwei Wang, Hongwei Song, Xianggui Kong, Wu Xu, and Haiping Xia

J. Appl. Phys. 91, 9466 (2002); http://dx.doi.org/10.1063/1.1476962 (5 pages) | Cited 8 times

Online Publication Date: 30 May 2002

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The temperature dependence of emission intensity of the Eu3+ ion in several silicate glasses was investigated between 77 and 670 K, under the excitation of a 488-nm laser. It was observed that in some glasses the total emission intensity of the Eu3+ ion had a maximum at a certain temperature below 670 K, while in the other glasses increased monotonically with the increasing temperature. A unified theoretical model was given considering thermal activation, phonon-assisted absorption and nonradiative energy transfer processes. Based on the model, all of the experimental data were well fitted. The temperature-quenching channels were discussed, and the temperature-quenching rates were determined. © 2002 American Institute of Physics.
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78.55.Hx Other solid inorganic materials
81.05.Kf Glasses (including metallic glasses)
63.50.-x Vibrational states in disordered systems

Nonlinear characteristics of a cylindrical Cherenkov laser at millimeter wavelengths

A. Hirata, Y. Yuse, and T. Shiozawa

J. Appl. Phys. 91, 9471 (2002); http://dx.doi.org/10.1063/1.1477283 (4 pages) | Cited 3 times

Online Publication Date: 30 May 2002

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Nonlinear characteristics of a cylindrical Cherenkov laser, which is composed of a dielectric-loaded coaxial waveguide and a hollow relativistic electron beam, are investigated with the use of particle simulation. The results obtained in this paper are compared with those for parallel plate and rectangular models. Numerical results show that, in the cylindrical Cherenkov laser, the electromagnetic (EM) wave grows exponentially in the longitudinal direction and reaches saturation, as is the case with the parallel plate and rectangular models. However, the efficiency of energy transfer from the electron beam to the EM wave in the cylindrical model is not in good agreement with that for the parallel plate model, especially for the case of a small radius of the inner conductor. Thus, we propose a modified parallel plate model whose growth characteristics are the same as those for the cylindrical model. With the use of the corresponding modified parallel plate model, one can calculate growth characteristics for the cylindrical model at a particular frequency more easily.© 2002 American Institute of Physics.
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84.40.Ik Masers; gyrotrons (cyclotron-resonance masers)
41.60.Bq Cherenkov radiation
42.60.By Design of specific laser systems
41.60.Cr Free-electron lasers
41.75.Ht Relativistic electron and positron beams

LiInSe2: A biaxial ternary chalcogenide crystal for nonlinear optical applications in the midinfrared

L. Isaenko, A. Yelisseyev, S. Lobanov, V. Petrov, F. Rotermund, G. Slekys, and J.-J. Zondy

J. Appl. Phys. 91, 9475 (2002); http://dx.doi.org/10.1063/1.1478139 (6 pages) | Cited 27 times

Online Publication Date: 30 May 2002

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Single crystals of lithium selenoindate (LiInSe2) are grown by the Bridgman–Stockbarger technique up to sizes of 10 mm in diameter and 20 mm in length. The different phases have color from yellow (as grown) to dark red (after annealing) but all have the same wurtzite type structure mm2 with slightly differing cell parameters. The band gap for the yellow phase at 300 K is at 2.86–2.87 eV. The red color is attributed to point defects and can be removed by proper illumination. Sellmeier equations are constructed for the 0.5–11 μm range and their validity is checked with second harmonic generation which provides first estimations of the nonlinear coefficients of LiInSe2. The potential of LiInSe2 is compared to that of the widely spread and technologically mature AgGaS2. © 2002 American Institute of Physics.
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42.70.Mp Nonlinear optical crystals
42.65.-k Nonlinear optics
81.10.Fq Growth from melts; zone melting and refining
71.20.Ps Other inorganic compounds
61.72.Cc Kinetics of defect formation and annealing
61.66.Fn Inorganic compounds
61.50.Lt Crystal binding; cohesive energy
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation

Electric field-induced second harmonic generation studies of chromophore orientational dynamics in photorefractive polymers

Oksana Ostroverkhova, Andrew Stickrath, and Kenneth D. Singer

J. Appl. Phys. 91, 9481 (2002); http://dx.doi.org/10.1063/1.1476974 (6 pages) | Cited 10 times

Online Publication Date: 30 May 2002

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Photorefractive (PR) polymers are promising for use in various applications that require fast response times. The main factors that determine the PR speed in polymers are photoconductivity and chromophore reorientation in an electric field. In this article, we investigate the chromophore reorientational dynamics in various PR composites using the electric field second harmonic generation (EFISHG) technique, and then relate it to the PR dynamics observed in a four-wave mixing holographic experiment. We also report on the enhancement of the EFISHG signal in the presence of HeNe light, which we attribute to a photoinduced internal electric field that formed in the PR polymer. © 2002 American Institute of Physics.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
81.05.Qk Reinforced polymers and polymer-based composites
42.70.Jk Polymers and organics
82.35.Ej Nonlinear optics with polymers
42.40.Ht Hologram recording and readout methods
42.70.Gi Light-sensitive materials
42.70.Ln Holographic recording materials; optical storage media
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation

Ion beam generation in a diode with a ferroelectric anode

K. Chirko, Ya. E. Krasik, and J. Felsteiner

J. Appl. Phys. 91, 9487 (2002); http://dx.doi.org/10.1063/1.1479465 (7 pages) | Cited 7 times

Online Publication Date: 30 May 2002

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In this article experimental results of the application of a ferroelectric anode for the generation of ion beams are presented. The ferroelectric anode was made of a solid solution of Sr, Ba, Ti, Nb, Pb, and O. Its front side was covered by a grounded Cu strip electrode. The ion beam generation was studied in a planar diode powered by a high-voltage generator with accelerating voltage ⩽300 kV and pulse duration ⩽400 ns. The source of the ion beam was found to be the plasma which was formed on the front anode surface. This plasma was formed by a driving pulse with an amplitude ⩽18 kV and pulse duration of ∼400 ns which was applied to the rear Cu disk electrode prior to the application of the accelerating pulse. The generation of ion beams with current amplitude up to 150 A was demonstrated in the plasma prefilled mode of the diode operation. It was found that the generated ion beam consists of light (H+,C+,O+) and heavy (Ti+,Cu+,Sr+) ions. In addition, it was shown that the application of a reflex triode scheme with a negative grid cathode allowed us to separate effectively the light ions from the generated ion beam. © 2002 American Institute of Physics.
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41.75.Ak Positive-ion beams
52.59.Mv High-voltage diodes
07.77.Ka Charged-particle beam sources and detectors
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Functional design of a pulsed two-frequency capacitively coupled plasma in CF4/Ar for SiO2 etching

Kazunobu Maeshige, Gentaro Washio, Takashi Yagisawa, and Toshiaki Makabe

J. Appl. Phys. 91, 9494 (2002); http://dx.doi.org/10.1063/1.1478138 (8 pages) | Cited 44 times

Online Publication Date: 30 May 2002

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A capacitively coupled plasma (CCP) with a different frequency source at each of two parallel plates is a powerful tool for SiO2 etching. A time modulation of two-frequency CCP by a pulsed-power operation will be one of the practical solutions in the next generation of etchers, and will allow charging-free plasma processes for high-aspect-ratio holes or trench etching. We numerically predict the structure and functions of a pulsed two-frequency CCP in CF4(5%)/Ar, and discuss its ability to generate charge-free plasma processes. We also investigate the functional separation between plasma production by very high frequency (100 MHz) and bias voltage application by low frequency (1 MHz). Alternate injections of high-energy positive and negative ions are predicted during the off-phase of a pulsed two-frequency CCP. © 2002 American Institute of Physics.
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52.50.Dg Plasma sources
52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning

Simulation studies of the coplanar electrode and other plasma display panel cell designs

G. Veronis and U. S. Inan

J. Appl. Phys. 91, 9502 (2002); http://dx.doi.org/10.1063/1.1478143 (11 pages) | Cited 16 times

Online Publication Date: 30 May 2002

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A two-dimensional self-consistent simulation model is used to study the effect of the geometric parameters on the operating voltages and ultraviolet (UV) efficiency of a coplanar-electrode plasma display panel cell. It is found that in the standard coplanar-electrode geometry there is a tradeoff between high UV efficiency and low operating voltages as the electrode gap, or the parameters of the upper dielectric are varied, while variation of the sustain electrode width has no significant effect on either the operating voltages or UV efficiency. It is also found that wider discharge area results in higher efficiency. In addition, the effect of the insertion of floating electrodes in the upper dielectric is investigated. When floating electrodes are used, UV light is emitted in a more confined area, thus limiting cross talk with adjacent cells, while efficiency decreases by ∼8%. Finally, a self-erase discharge sustaining waveform is studied. Use of this waveform results in ∼17% increase in the UV efficiency. © 2002 American Institute of Physics.
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85.60.Pg Display systems
52.75.-d Plasma devices

Three-dimensional fluid simulation of a plasma display panel cell

H. C. Kim, M. S. Hur, S. S. Yang, S. W. Shin, and J. K. Lee

J. Appl. Phys. 91, 9513 (2002); http://dx.doi.org/10.1063/1.1479758 (8 pages) | Cited 41 times

Online Publication Date: 30 May 2002

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In order to understand the discharge characteristics in an alternating current plasma display panel (ac PDP) and optimize it further, a three-dimensional fluid code (FL3P) has been developed. Using this simulator, various three-dimensional features of discharges are investigated in the sustain mode of PDP. First, the striations of wall charge are observed at both the anode and cathode side. Second, the local efficiency is obtained as a function of position. It is mainly divided into the anode region and the cathode region and highest near the anode center. Finally, the effects of various three-dimensional parameters are studied. As one of the examples showing the effect of electrode shaping, the discharge characteristics of a T-shaped electrode cell are compared with those of a conventional cell. The phosphor on barrier ribs contributes to over 44% of the total luminance, but barrier ribs themselves do not play an important role in the overall discharge efficiency. Address electrode width is not always proportional to the size of the discharge because of the wall loss of the particles to barrier ribs. © 2002 American Institute of Physics.
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85.60.Pg Display systems
52.65.Kj Magnetohydrodynamic and fluid equation
52.75.-d Plasma devices

Modeling of the plasma jet of a stationary plasma thruster

L. Garrigues, J. Bareilles, J. P. Boeuf, and I. D. Boyd

J. Appl. Phys. 91, 9521 (2002); http://dx.doi.org/10.1063/1.1480480 (8 pages) | Cited 2 times

Online Publication Date: 30 May 2002

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We have developed a two-dimensional hybrid fluid – particle-in-cell Monte Carlo collisions (PIC- MCC) model to study the plume of a stationary plasma thruster. The model is based on a fluid description of the electrons (the electron density follows a Boltzmann distribution) and a particle description of the ion and neutral transport. Collisions between heavy species are taken into account with a Monte Carlo method. The electric field is obtained from Poisson's equation or from the quasineutrality assumption. We first show that the results from the PIC-MCC model are close to the results of a more time-consuming direct simulation Monte Carlo approach. We then compare the model predictions of the plume density and ion energy distribution with experimental measurements. Finally, we present a brief discussion on the assumptions of the model and on its ability to give reliable predictions on important issues such as the flux of ions backscattered to the satellite. © 2002 American Institute of Physics.
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52.75.Di Ion and plasma propulsion
52.65.Pp Monte Carlo methods
52.65.Rr Particle-in-cell method
52.65.Ww Hybrid methods
52.20.Hv Atomic, molecular, ion, and heavy-particle collisions
52.65.Kj Magnetohydrodynamic and fluid equation

Probe diagnostics of high pressure microwave discharge in helium

M. R. Talukder, D. Korzec, and M. Kando

J. Appl. Phys. 91, 9529 (2002); http://dx.doi.org/10.1063/1.1478801 (10 pages) | Cited 10 times

Online Publication Date: 30 May 2002

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A method for the determination of electron temperature and plasma density in high pressure helium plasmas is established using numerical results of the continuum probe model by Cohen [Phys. Fluids 6, 1492 (1963)]. Simple algebraic functions are derived to approximate the probe characteristics of high pressure plasmas calculated by Cohen and are applied to use iterative procedures for the determination of plasma parameters. The proposed fitting technique has allowed one to obtain reasonable plasma parameters even for the probe characteristics strongly affected by large secondary electron emission currents from the probe. Fitting of the ion saturation current may possibly be used to estimate the ion temperature, provided that the electron temperature and plasma density are known. Finally high pressure helium microwave discharges have been produced by moderate microwave power of 400 W and investigated by the present method. © 2002 American Institute of Physics.
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52.25.-b Plasma properties
52.80.Pi High-frequency and RF discharges
52.70.Ds Electric and magnetic measurements

Surface dependent electron and negative ion density in SF6/argon gas mixtures

G. A. Hebner and I. C. Abraham

J. Appl. Phys. 91, 9539 (2002); http://dx.doi.org/10.1063/1.1479459 (8 pages) | Cited 7 times

Online Publication Date: 30 May 2002

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Electron and negative ion densities were measured in an inductively driven plasma containing mixtures of SF6 and Argon. The electron and negative ion density were measured as functions of the induction coil power, pressure, bias power, and SF6/argon ratio. To investigate the influence of surface material, the rf biased electrode was covered with a silicon wafer or a fused silica (SiO2) wafer. Line integrated electron density was determined using a microwave interferometer, and absolute negative ion densities in the center of plasma were inferred using laser photodetachment spectroscopy. Voltage and current at the induction coil and rf biased electrode were also measured for both surfaces as functions of induction coil power, pressure, rf bias, and SF6/argon ratio. For the range of induction powers, pressures, and bias powers investigated, the electron density had a maximum of 5×1012 cm−2 (line-integrated) or approximately 5×1011 cm−3. Over this same range the negative ion density had a maximum of 2×1011 cm−3, and was always less than the electron density. For most conditions, the negative ion density above the oxide surface was a factor of 5 to 10 larger than the density above the silicon surface. In contrast, the electron density above the oxide surface was equal to or slightly higher than the density above the silicon surface. Surface dependent changes in the induction coil and rf bias voltage and current were also observed. © 2002 American Institute of Physics.
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52.25.-b Plasma properties
52.70.Gw Radio-frequency and microwave measurements
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)

Optical emission spectroscopy of pulsed hexalfuoropropylene oxide and tetrafluoroethylene plasmas

Brett A. Cruden, Karen K. Gleason, and Herbert H. Sawin

J. Appl. Phys. 91, 9547 (2002); http://dx.doi.org/10.1063/1.1471386 (9 pages) | Cited 7 times

Online Publication Date: 30 May 2002

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The optical emission spectra of tetrafluoroethylene (TFE) and hexafluoropropylene oxide (HFPO) have been examined for chemistry and electron distribution transients as a function of plasma pulsing, under depositing conditions (1 torr). The major identifiable peaks in these plasmas are attributable to CF2 and CF. Other expected species, including CF3, atomic F and atomic C are not observed. HFPO plasmas show significant emission from CO and O. Comparison of CF2 emission transients to absolute absorption measurements show that the continuum emission surrounding CF2 is not attributable to CF2+ emission, as has been previously proposed, but is likely rovibrational overlap. Argon emission in TFE shows a relatively slow transient toward steady state (∼20 ms), implying slower chemistry transients, such as attachment, control the electron transient in pulsed TFE plasmas. In HFPO plasmas, CO and O actinometry are applied. CO emission trends suggest that CO is actually produced during the plasma off times, and is here attributed to etching reactions in the film. The rotational structure of CO is also examined and fit to estimate plasma rotational temperature, giving temperature transients on the order of ∼20 ms. © 2002 American Institute of Physics.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
82.80.Ha Analytical methods involving rotational spectroscopy
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)
52.77.Dq Plasma-based ion implantation and deposition
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Structure, microstructure, and magneto-optical properties of laser deposited Bi3Fe5O12/Gd3Ga5O12(111) films

S. Kahl, S. I. Khartsev, A. M. Grishin, K. Kawano, G. Kong, R. A. Chakalov, and J. S. Abell

J. Appl. Phys. 91, 9556 (2002); http://dx.doi.org/10.1063/1.1477605 (5 pages) | Cited 13 times

Online Publication Date: 30 May 2002

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Bi3Fe5O12 films were deposited onto single crystal Gd3Ga5O12(111) substrates by pulsed laser deposition. X-ray diffraction patterns and cross sectional transmission electron micrographs show epitaxial film growth and a flat interface between the film and substrate. However, there are small inclusions at the interface and a network of cracks is observed by optical microscope. The refractive index is 3.4 at 800 nm wavelength. The optical transmission is low below 540 nm but increases to 90% for a 1.8 μm thick film at 850 nm. The magneto-optical Faraday rotation is high, with a peak value of −24 deg/μm at 560 nm. The angle of Faraday ellipticity reaches a maximum value of 15 deg/μm at 545 nm. © 2002 American Institute of Physics.
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68.55.-a Thin film structure and morphology
78.66.Nk Insulators
75.70.Ak Magnetic properties of monolayers and thin films
78.20.Ls Magneto-optical effects
81.15.Fg Pulsed laser ablation deposition
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Transformation kinetics for the shock wave induced phase transition in cadmium sulfide crystals

M. D. Knudson and Y. M. Gupta

J. Appl. Phys. 91, 9561 (2002); http://dx.doi.org/10.1063/1.1478790 (11 pages) | Cited 11 times

Online Publication Date: 30 May 2002

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Initial stage kinetics of the cadmium sulfide (CdS) phase transition was investigated using picosecond time-resolved electronic spectroscopy in plate-impact shock wave experiments. Real-time changes in the electronic spectra were observed, with 100 ps time resolution, in CdS single crystals shocked along a and c axes to stresses ranging between 35 and 90 kbar, which is above the phase-transition threshold stress of approximately 30 kbar. Significant difference in the transformation kinetics was observed for the two crystal orientations. At sufficiently high instantaneous stress, above approximately 60 to 70 kbar for a axis and 50 kbar for c axis, transformation to a metastable state appears to reach a constant state within the 100 ps time resolution. At lower instantaneous stresses, an incubation period on the order of several nanoseconds is observed prior to the onset of electronic changes that mark the onset of the structural change. The subsequent increase in absorbance was quite rapid, with a constant state being reached within the first few nanoseconds after the onset of the structural changes. These results suggest that the nucleation process determines the transformation rate. This insight into transformation kinetics, along with the transformation mechanism obtained from the high-stress experiments, was used to develop a phenomenological model, incorporating ideas of nucleation and growth in martensitic transformations, to simulate the time-dependent extinction of light observed in our experiments. The calculational results incorporating both extinction due to light absorption by the daughter phase volumes and scattering of light by small volumes of the daughter phase were in good agreement with experimental observations. Finally, the orientational differences observed in the transformation kinetics were interpreted in terms of the differences in the elastic-plastic response for the two orientations. © 2002 American Institute of Physics.
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62.50.-p High-pressure effects in solids and liquids
64.70.K- Solid-solid transitions
64.60.Q- Nucleation
81.30.Kf Martensitic transformations
81.05.Dz II-VI semiconductors
78.47.-p Spectroscopy of solid state dynamics
71.20.Nr Semiconductor compounds

Electron irradiation induced expansion in amorphous chalcogenide films

J. S. Romero, A. G. Fitzgerald, and K. Mietzsch

J. Appl. Phys. 91, 9572 (2002); http://dx.doi.org/10.1063/1.1478135 (3 pages) | Cited 3 times

Online Publication Date: 30 May 2002

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An expansion of the film surface is observed in amorphous germanium based chalcogenide films when an electron beam is focused in pulsed or fixed mode on the film surface. For thin films of 0.1–1 μm thick the expansion extends laterally over a range of 0.5–1.5 μm and the vertical expansion extends from 0.1–0.6 μm. Increasing the current density of the probe results in an increase in the thickness and a decrease in the width of these features. This phenomenon can be explained in terms of theoretical electrostatics. © 2002 American Institute of Physics.
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61.80.Fe Electron and positron radiation effects
68.55.-a Thin film structure and morphology
61.82.Fk Semiconductors

Metastable and equilibrium phase formation in sputter-deposited Ti/Al multilayer thin films

G. Lucadamo, K. Barmak, C. Lavoie, C. Cabral, and C. Michaelsen

J. Appl. Phys. 91, 9575 (2002); http://dx.doi.org/10.1063/1.1477257 (9 pages) | Cited 9 times

Online Publication Date: 30 May 2002

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The sequence and kinetics of metastable and equilibrium phase formation in sputter deposited multilayer thin films was investigated by combining in situ synchrotron x-ray diffraction (XRD) with ex situ electron diffraction and differential scanning calorimetry (DSC). The sequence included both cubic and tetragonal modifications of the equilibrium TiAl3 crystal structure. Values for the formation activation energies of the various phases in the sequence were determined using the XRD and DSC data obtained here, as well as activation energy data reported in the literature. © 2002 American Institute of Physics.
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68.65.Ac Multilayers
81.05.Bx Metals, semimetals, and alloys
81.30.Bx Phase diagrams of metals, alloys, and oxides
68.55.-a Thin film structure and morphology
82.60.Cx Enthalpies of combustion, reaction, and formation
68.35.Fx Diffusion; interface formation
66.30.Ny Chemical interdiffusion; diffusion barriers
61.66.Dk Alloys

Effect of chemical stress on diffusion in a hollow cylinder

W. L. Wang, Sanboh Lee, and J. R. Chen

J. Appl. Phys. 91, 9584 (2002); http://dx.doi.org/10.1063/1.1477624 (7 pages) | Cited 17 times

Online Publication Date: 30 May 2002

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The effect of chemical stress on diffusion in a hollow cylinder for plane strain and zero axial force has been investigated. Two diffusion processes of constant surface stress and constant surface potential are studied. No matter what the plane strain or zero axial force is the influence of chemical stress on the diffusion process of constant surface potential is similar to that of constant surface stress. Chemical stress enhances both the diffusion coefficient and the concentration. For a given time, the level of concentration becomes lower with a greater ratio of outer radius to inner radius for constant surface potential with given FXf and for constant surface stress with given FXi. F=2Emath/[9(1−v)RT] where E, math, R, and T are the Young’s modulus, partial molal volume, gas constant, and absolute temperature, respectively; Xi and Xf are the initial and final mole fractions at boundary surfaces. The results are also compared with those in thin plates and solid cylinders reported in the literature. © 2002 American Institute of Physics.
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66.30.Dn Theory of diffusion and ionic conduction in solids
05.60.Cd Classical transport
02.70.Bf Finite-difference methods

Influence of deposition conditions on Ir/IrO2 oxygen barrier effectiveness

C. U. Pinnow, I. Kasko, N. Nagel, S. Poppa, T. Mikolajick, C. Dehm, W. Hösler, F. Bleyl, F. Jahnel, M. Seibt, U. Geyer, and K. Samwer

J. Appl. Phys. 91, 9591 (2002); http://dx.doi.org/10.1063/1.1471574 (7 pages) | Cited 24 times

Online Publication Date: 30 May 2002

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The influence of the deposition temperature during the reactive sputtering process on the microstructure of thin Ir and IrO2 films deposited on oxidized Si substrates was investigated and related to the oxygen barrier effectiveness. For this purpose differential thermal analysis combined with residual gas analysis by mass spectrometry was used for the investigation of the microstructural and chemical behavior of the as-sputtered IrO2 films upon heating. Moreover, in situ stress relaxation analyses up to 900 °C, in and ex situ x-ray diffraction measurements were done for various annealing conditions. The investigated polycrystalline IrO2 films exhibited a large compressive stress and a distorted lattice due to the sputter deposition process. It is demonstrated that a high deposition temperature involves a delayed relaxation of the IrO2 grains which is causing an extrinsic, enhanced defect controlled oxygen mobility for the annealing temperatures below the recrystallization. The well-known low intrinsic oxygen diffusivity was only found in those samples which show—in addition to the recovery process—a recrystallization at low temperatures and thus a formation and growth of a new generation of grains with a lattice spacing as in bulk IrO2. Moreover, the oxygen diffusion in Ir films was investigated and the oxygen was found to penetrate the Ir films very quickly at elevated temperatures. The microstructure of the films was investigated by cross sectional transmission electron microscopy and it is shown that the cold-sputtered columnar IrO2 films protect the underlying layers from oxidation during a 700 °C high temperature oxygen anneal with an optimized Ir/IrO2 oxygen barrier stack. © 2002 American Institute of Physics.
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68.35.Fx Diffusion; interface formation
66.30.J- Diffusion of impurities
81.15.Cd Deposition by sputtering
68.55.-a Thin film structure and morphology
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
61.72.Cc Kinetics of defect formation and annealing
68.60.Bs Mechanical and acoustical properties
68.37.Lp Transmission electron microscopy (TEM)
85.50.Gk Non-volatile ferroelectric memories

Optical properties of a laser dye in a solid-state polymeric host

Dhiraj K. Sardar and Felipe S. Salinas

J. Appl. Phys. 91, 9598 (2002); http://dx.doi.org/10.1063/1.1476967 (5 pages) | Cited 1 time

Online Publication Date: 30 May 2002

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The optical properties of C28H20N2O2B2F4H2O, an organic laser dye embedded in a solid plastic host, have been characterized for a number of laser wavelengths in the visible region. The index of refraction of the dye in a plastic host is measured by the conventional method of minimum deviation at these wavelengths. The one-dimensional two flux Kubelka–Munk method based on the diffusion approximation has been employed to determine the absorption, scattering, and scattering anisotropy coefficients of the dye in a plastic host from the measurements of total diffuse transmittance, total diffuse reflectance, and collimated transmittance using double-integrating spheres. The total attenuation coefficients obtained by this method have been compared with those determined by the collimated transmission and from the total attenuation measurement on a Cary-14 spectrophotmeter. © 2002 American Institute of Physics.
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42.55.Mv Dye lasers
78.55.Kz Solid organic materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Model for the director and electric field in liquid crystal cells having twist walls or disclination lines

G. Panasyuk and D. W. Allender

J. Appl. Phys. 91, 9603 (2002); http://dx.doi.org/10.1063/1.1477613 (10 pages) | Cited 5 times

Online Publication Date: 30 May 2002

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Two examples of the director structure and electric field in patterned electrode liquid crystal cells are studied using a recently developed calculational model. First, a display cell that exhibits a homeotropic to multidomainlike transition with twist wall structures has been considered for a liquid crystal with positive dielectric anisotropy. The model elucidates the behavior of the electric field. Calculations show good agreement between the model and direct computer solution of the Euler–Lagrange equations, but the model is at least 30 times faster. Second, the possibility that a cell has ±1/2 disclination lines instead of a wall defect is probed. A temperature dependent estimate for the size of the defect core is given, and the total free energy of the cell with disclination lines was calculated and compared with the corresponding value for the same cell with wall defect structure. © 2002 American Institute of Physics.
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61.30.Jf Defects in liquid crystals
61.30.Cz Molecular and microscopic models and theories of liquid crystal structure
64.70.M- Transitions in liquid crystals
65.20.-w Thermal properties of liquids
61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order

Experimental investigation and modeling of diffusion in the InP/(In,Ga)As heterostructures

Jiri Bursik, Dmitri V. Malakhov, Yaoji Wang, George C. Weatherly, and Gary R. Purdy

J. Appl. Phys. 91, 9613 (2002); http://dx.doi.org/10.1063/1.1477264 (9 pages) | Cited 3 times

Online Publication Date: 30 May 2002

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The interdiffusion of lattice-matched InP/(In,Ga)As superlattice structures (nominally undoped, p-doped and n-doped) has been studied by analytical electron microscopy (x-ray analysis) using a field emission gun, scanning transmission electron microscope. The point-spread function of the electron beam was used to correct the experimental data (obtained as x-ray maps, 50×50 nm in area) in order to derive diffusion profiles of the group V elements (As, P) after annealing. The results, showing a marked asymmetry in the As profiles after annealing, are interpreted using a model based on the coherent diffusion of the group III and V elements on their own sublattices, each of which is treated as a regular solution. A mathematical procedure, based on the minimization of the difference between the measured and predicted concentration profiles, is employed to compute the two lattice-specific composition-dependent velocities from the experimental diffusion profiles. A good agreement is found between the experimental measurements and the predictions of the model. The role of coherency strains in the interdiffusion process is discussed. © 2002 American Institute of Physics.
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66.30.Ny Chemical interdiffusion; diffusion barriers
68.65.Cd Superlattices
68.35.Fx Diffusion; interface formation
68.37.Lp Transmission electron microscopy (TEM)
68.35.Ct Interface structure and roughness
81.40.Gh Other heat and thermomechanical treatments
61.72.Cc Kinetics of defect formation and annealing

Study of light emission from GaN/AlGaN quantum wells under power-dependent excitation

S. P. Łepkowski, T. Suski, P. Perlin, V. Yu. Ivanov, M. Godlewski, N. Grandjean, and J. Massies

J. Appl. Phys. 91, 9622 (2002); http://dx.doi.org/10.1063/1.1476082 (7 pages) | Cited 14 times

Online Publication Date: 30 May 2002

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We have performed a study of excitation power-dependent spectra of GaN/AlGaN single quantum wells (QWs). First, the experimental “blueshift” of the emission energy, due to screening of internal piezoelectric fields, was compared with the model calculations based on self-consistent solution of Schroedinger and Poisson equations. We found that, even for the highest applied levels of excitation power (2.5 MW/cm2), only 0.5×1012 cm−2 carriers were present in the QW layers. Second, we analyzed the evolution of power-dependent spectra of two single QW having different widths. For the thinner QW (2.1 nm), the peak corresponding to a QW photoluminescence (PL) emission dominates the entire spectrum in the whole range of the used excitation power. In the case of the wider QW (4.4 nm), for sufficiently high excitation power, we observe the effect of PL quenching. Using the rate equation model we show that the observed effect of the PL quenching can be associated with the reduction of exciton binding energy due to the many body interactions in the QW. © 2002 American Institute of Physics.
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78.67.De Quantum wells
78.55.Cr III-V semiconductors
73.21.Fg Quantum wells
71.35.Lk Collective effects (Bose effects, phase space filling, and excitonic phase transitions)

Temperature effects on the 1.0 and 1.3 μm emission lines of Nd3+ in a LaSc3(BO3)4 crystal host

Dhiraj K. Sardar, Joe A. French, Francisco Castano, Anthony Sayka, and Felipe S. Salinas

J. Appl. Phys. 91, 9629 (2002); http://dx.doi.org/10.1063/1.1476963 (6 pages) | Cited 2 times

Online Publication Date: 30 May 2002

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A detailed investigation of the temperature effect on widths and shifts of the spectral lines of Nd3+ in LaSc3(BO3)4 has been performed. The spectral lines investigated correspond to the inter-Stark transitions R1→Y3 (1062 nm) and R1→Z4 (1344 nm) within the 4F3/2→4I11/2 and 4F3/2→4I13/2 intermanifold transitions, respectively. The widths of these lines and their shifts have been measured as a function of temperature. The linewidths are found to increase with increasing temperature for both transitions; the 1062 nm line shifts to the longer wavelengths, whereas the 1344 nm line shifts to the shorter wavelengths. The theory of phonon-ion interactions has been employed to explain the temperature dependencies of widths and shifts. These interactions give rise to the phonon relaxation processes that are responsible for both the broadening and shifts of the spectral lines. © 2002 American Institute of Physics.
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78.55.Hx Other solid inorganic materials
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
63.20.-e Phonons in crystal lattices
42.70.Hj Laser materials

Polymer absorbers containing magnetic particles: Effect of polymer permittivity on wave absorption in the quasi-microwave band

Morihiko Matsumoto and Yoshimori Miyata

J. Appl. Phys. 91, 9635 (2002); http://dx.doi.org/10.1063/1.1475372 (3 pages) | Cited 16 times

Online Publication Date: 30 May 2002

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The effect of polymer permittivity on wave absorption in the quasi-microwave band has been elucidated for polymer composites containing magnetic metal particles. Absorbers composed of these composites can be thin when their real permittivities are high and their imaginary parts are low. However, in general, for polymer composites the real part actually increases as the imaginary part increases in this band. This implies that in designing absorbers we must choose a polymer species on the crossing area of the real and imaginary parts of the permittivity. Furthermore, to obtain thin absorbers, we should choose a polymer species with high real permittivities and low imaginary parts. © 2002 American Institute of Physics.
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78.70.Gq Microwave and radio-frequency interactions
77.22.Ch Permittivity (dielectric function)
75.50.Tt Fine-particle systems; nanocrystalline materials
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