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15 Jun 1989

Volume 65, Issue 12, pp. 4475-5251

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A numerical simulation method for the laser‐induced temperature distribution

Tapio T. Rantala and Juhani Levoska

J. Appl. Phys. 65, 4475 (1989); http://dx.doi.org/10.1063/1.343265 (5 pages) | Cited 10 times

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A numerical simulation approach for the evaluation of temperature distribution in a substrate during the laser processing is developed. The explicit finite‐difference solution of the heat (diffusion) equation is chosen as the starting point in order to simply retain general nonlinearity, physical transparency, and flexibility of the procedure. The method is tested with a simulation of silicon substrate irradiated by cw argon laser, and the results are compared with those from experiments and exact analytical results, where available. Deficiences due to the omission of the nonlinearity, i.e., the temperature dependency of the material properties, in the results of approximative analytical approaches are discussed.
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79.20.Ds Laser-beam impact phenomena
66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves

Digital image analysis of droplet patterns in polymer systems: Point pattern

Hajime Tanaka, Takafumi Hayashi, and Toshio Nishi

J. Appl. Phys. 65, 4480 (1989); http://dx.doi.org/10.1063/1.343266 (16 pages) | Cited 27 times

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New techniques of digital image analysis which are especially suitable for analyzing particle‐distribution patterns are presented. Statistical mathematical methods are applied to the quantitative analysis of a spatial distribution of points in polymer systems. The techniques are useful for studying the spatial patterns of particles or droplets which are commonly observed in nucleation‐growth‐type phase separation and late‐stage spinodal decomposition in polymer mixtures, crystallization process, microphase separation in block copolymers, incompatible polymer alloys, and composite materials, etc. We can divide point patterns into three typical point patterns: the Poisson pattern, the clustered pattern, and the regular pattern. The kind and strength of interaction or force between points can be determined from spatial point‐distribution patterns. The point‐pattern analysis has been applied to phase‐separated structures of a polymer mixture, and it has been revealed that the pattern belongs to the regular pattern. The appearance of the regular pattern is probably a result of the Brownian coalescence mechanism for the droplet growth and it might also be due to a long‐range interaction among droplets through diffusion field.
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42.30.-d Imaging and optical processing
61.41.+e Polymers, elastomers, and plastics
81.40.-z Treatment of materials and its effects on microstructure, nanostructure, and properties

Optical velocimetry correction in Fabry–Perot measurements taken through cylindrically expanding shocked fluids with no dispersion

D. R. Goosman

J. Appl. Phys. 65, 4496 (1989); http://dx.doi.org/10.1063/1.343267 (4 pages) | Cited 1 time

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A correction is needed in interpreting optical velocity measurements made by reflected frequency versus time measurements through cylindrically expanding air or fluids. The reflected frequency seen by the velocimeter will be higher than it would be in a planar geometry, even if the fluid obeys the Gladstone–Dale model for the index of refraction versus compression. This has been pointed out by Wackerle, Stacy, and Dallman [Proc. Int. Soc. Opt. Eng. 832, 72 (1987)], who develop a general Lagrangian treatment of one‐dimensional planar, cylindrical, and spherical geometries. Our work, developed independently, uses a different, very simple, and rigorous treatment for a special case of cylindrical geometry. It also provides physical insight into the processes that lead to this frequency change. The magnitude of the correction is very small for air, but for a realistic constant density versus radius model is about 5%–10% for fluids such as water, for cylindrically expanding shocks with radii of curvature near 3 cm.
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07.60.-j Optical instruments and equipment
47.80.-v Instrumentation and measurement methods in fluid dynamics

Similarity transformations for decaying wall charge fields in a spherical shell

F. L. Curzon

J. Appl. Phys. 65, 4500 (1989); http://dx.doi.org/10.1063/1.343268 (5 pages) | Cited 2 times

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It is shown that ohmic dissipation of wall charges causes the electric field inside a spherical insulating shell to decay with a characteristic time constant, t0 =2aηϵ0 , where η is the surface resistance of the shell, a is its radius, and ϵ0 is the permittivity of a vacuum. It is demonstrated that the electric potential inside the shell at time t can be constructed by means of similarity transformations which are generated by multiplying the initial charge densities by a factor f and lengths by f 2 where f=exp(−t/2t0 ). Using this method the potential near the centers of oppositely charged disks of wall charge of radius b (b≪a) is calculated in terms of analytic expressions for the case where the externally applied field is absent. It is pointed out that the latter solution can be generalized to yield the potential distribution generated by small wall charge spots which have rotationally symmetric charge distributions. It is anticipated that the results will be useful for further studies of external electrode discharges in gases in insulating containers, Examples include low‐frequency electric field sensors and gas‐filled cavities in solid insulators.
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41.20.Cv Electrostatics; Poisson and Laplace equations, boundary-value problems
41.20.Gz Magnetostatics; magnetic shielding, magnetic induction, boundary-value problems
52.80.-s Electric discharges

Kelvin functions for determination of magnetic susceptibility in nonmagnetic metals

Renato Figueiredo Jardim and Bernardo Laks

J. Appl. Phys. 65, 4505 (1989); http://dx.doi.org/10.1063/1.343269 (4 pages) | Cited 1 time

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A method to calculate the real and imaginary parts of the magnetic permeability and susceptibility of nonmagnetic metals by using Kelvin functions is presented. The exact treatment is shown for the massive cylindrical geometry. An expression for a hollow circular cylinder is discussed and expanded to the thin‐shell limit.
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41.20.Gz Magnetostatics; magnetic shielding, magnetic induction, boundary-value problems

Radiation losses in intersecting optical waveguides

Niraj Agrawal and L. McCaughan

J. Appl. Phys. 65, 4509 (1989); http://dx.doi.org/10.1063/1.343246 (8 pages) | Cited 2 times

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A systematic theory for radiation losses in intersecting optical waveguides is presented for the first time. These losses are shown to arise from a coupling between guided and radiation fields of the individual waveguides. The existence of a doubly peaked radiation loss characteristic with respect to the intersection angle is predicted for single‐Δn intersecting waveguides and verified experimentally. A method for reducing the radiation losses by a simple modification of the intersection region is also discussed.
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84.40.Az Waveguides, transmission lines, striplines

Collision broadening of optical gain in semiconductor lasers

Doyeol Ahn

J. Appl. Phys. 65, 4517 (1989); http://dx.doi.org/10.1063/1.343247 (4 pages) | Cited 2 times

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The energy‐dependent intraband relaxation with polar‐optical‐phonon scattering is incorporated in the calculation of the linear gain and the refractive index change of the GaAs injection laser with an undoped active region. Comparison with the conventional model, which assumes a constant intraband relaxation, shows that it is difficult to fit the overall gain spectra exactly by single, energy‐independent intraband‐relaxation time. Moreover, the calculated gain spectra wth phonon broadening show strong temperature dependence due to the change of the relaxation time and the Fermi functions.
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42.55.Px Semiconductor lasers; laser diodes
72.10.Di Scattering by phonons, magnons, and other nonlocalized excitations
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.45.+h Stimulated emission

Calculation and measurement of initial electron densities in x‐ray preionized avalanche discharge lasers

R. J. M. Bonnie, J. W. Gerritsen, and R. J. Zuidema

J. Appl. Phys. 65, 4521 (1989); http://dx.doi.org/10.1063/1.343248 (8 pages) | Cited 3 times

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The initial electron density in x‐ray preionized avalanche discharge lasers has been studied extensively. A computer model has been developed to calculate this initial electron density taking into account the characteristics of the x‐ray source, x‐ray physics, and geometric effects. Results of these calculations were verified for various experimental conditions using an ionization chamber. The experimental data are in excellent agreement with the calculations. Results from this work may be directly applied in the design of x‐ray preionized gas lasers.
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42.55.Lt Gas lasers including excimer and metal-vapor lasers
07.85.-m X- and γ-ray instruments

Beam focusing in semiconductor directional couplers with saturated gain

R. J. Hwu

J. Appl. Phys. 65, 4529 (1989); http://dx.doi.org/10.1063/1.343249 (3 pages)

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The beam focusing behavior in a semiconductor directional coupler with saturated gain is studied as a function of the antiguidance factor, injection current density, input power, and initial beam radius. When the antiguidance factor b=2, and the injection current density J=5×10−5 A/μm2, the upper and lower limits of input power for the beam focusing effect of an injected Gaussian beam in the directional coupler structure considered in this paper to occur are 3.5 and 20 mW, respectively. Over this range of input power levels, the optically induced focusing beam radius shows a strong dependence on the antiguidance factor, injection current density, and initial beam radius. However, the input power is found to have a negligible effect on the focusing beam radius.
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42.79.Gn Optical waveguides and couplers
42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks
42.82.-m Integrated optics

Power extraction study of an e‐beam‐pumped atmospheric pressure, Kr‐rich KrF laser amplifier

Young‐Woo Lee, Fumihiko Kannari, and Minoru Obara

J. Appl. Phys. 65, 4532 (1989); http://dx.doi.org/10.1063/1.343250 (10 pages) | Cited 8 times

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Single‐pass (50‐cm) amplification characteristics of a short‐pulse [65 ns full width half maximum (FWHM)] e‐beam‐pumped KrF laser amplifier with an atmospheric pressure Kr‐rich and Kr/F2 mixture were investigated theoretically for wide excitation rate from 0.1 to 2.0 MW/cm3. We have constructed a one‐dimensional propagation amplifier model which considers the gain depletion and the saturated absorption spatially and temporally in the amplifying medium. With this numerical model, good agreement was obtained between the calculated result and the experiment. As a result of this theoretical study, extraction efficiencies of over 40% and power efficiencies of over 10% are obtainable at the highest output powers for all atmospheric mixtures containing 10%–99% Kr gas for excitation rates ranging from 0.5 to 2.0 MW/cm3 using a 30‐ns (FWHM) input laser pulse, indicating that high efficiency power extraction from an atmospheric pressure KrF laser amplifier is achievable.
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42.55.Lt Gas lasers including excimer and metal-vapor lasers
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.By Design of specific laser systems
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

Parametric investigation of the dirt spike generation in a pulsed metal vapor laser discharge

C. E. Lin, C. Y. Yang, T. C. Wang, and C. L. Huang

J. Appl. Phys. 65, 4542 (1989); http://dx.doi.org/10.1063/1.343251 (6 pages) | Cited 1 time

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The generation of dirt spikes in the discharge of a clean pulsed metal vapor laser is measured under various operating conditions, such as a change in pulse repetition rates, laser tube temperatures, buffer gas pressures, and charging voltages. It is shown that the dirt spikes will increase in magnitude for such conditions that the pulse repetition rate decreases, the laser tube temperature decreases, and the buffer gas pressure increases. The ratio of the dirt spike to the charging voltage will also increase as the charging voltage decreases. All experimental results are well explained by theoretical analyses. These results lead to a number of useful suggestions for the operation of a pulsed metal vapor laser.
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42.55.Lt Gas lasers including excimer and metal-vapor lasers
51.50.+v Electrical properties (ionization, breakdown, electron and ion mobility, etc.)
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Ultrafast imaging of 0.532‐μm laser ablation of polymers: Time evolution of surface damage and blast wave generation

Taehyoung Zyung, Hackjin Kim, Jay C. Postlewaite, and Dana D. Dlott

J. Appl. Phys. 65, 4548 (1989); http://dx.doi.org/10.1063/1.343252 (16 pages) | Cited 35 times

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An ultrafast two‐color laser spectrometer with image acquisition capability is used to study surface ablation of a transparent polymer, PMMA (polymethyl methacrylate). Surface ablation was produced by 100‐ps, 0.532‐μm pulses and probed by 2‐ps, 0.570‐μm pulses. Computer‐digitized images were obtained over the time range 10−12 –100 s. The images were analyzed to obtain the time‐dependent behavior of the damaged solid, and the blast wave generated at the solid‐gas interface. Near the peak of the ablation pulse, self‐focusing begins and produces a small‐diameter filament lasting for 20 ps. The polymer irradiated by the filament then undergoes explosive thermal decomposition, ejecting particles from a conical volume into the atmosphere above the surface. This ablated matter produces a hemispherical, supersonic blast wave whose kinetic energy is one‐fourth of the ablation pulse energy. The evacuated pit produced in the polymer is very hot, and the surrounding solid softens and flows, resolidifying in about 1 s. A mechanism for the ablation process involving nonlinear absorption is proposed. The steeply rising envelope of the ablation pulse simultaneously increases the absorption coefficient and decreases the absorption length, resulting in a runaway heating process with a rate of ≊1013 K/s. The polymer is overheated far beyond the normal decomposition temperature. Thermal decomposition then proceeds with a large, negative free energy.
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42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.70.-a Optical materials
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
81.65.-b Surface treatments

Multifrequency surface acoustic wave investigations of metal film percolation

R. Hock and J. Wesner

J. Appl. Phys. 65, 4564 (1989); http://dx.doi.org/10.1063/1.343429 (9 pages) | Cited 1 time

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Change of the sound velocity and the amplitude signal of surface acoustic waves (SAW) on LiNbO3 substrates has been measured as a function of frequency during the growth of metal films of Pb, Bi, and Au on the originally free‐crystal surface. Simultaneously, we recorded the conductivity of the films. SAW propagation is strongly perturbed in the percolation region where the films become conducting and mechanically connected. Au films on LiNbO3 show a new and yet unreported behavior: sound velocity and attenuation stay nearly constant over a film thickness range of ≊10 nm and conductivity is finite but low. For comparison we measured the change of sound velocity and amplitude of a SAW on a nonpiezoelectric glass substrate during the growth of a Pb film. Sound velocity is found to vary nonlinearly for a film thickness d<dc, dc corresponding to the onset of conductivity, and linearly for d>dc due to mass loading with increasing film thickness. No damping of the sound wave in the percolation region was observed. A new computerized ultrasonic system is described which made it possible to measure sound velocity and amplitude quasisimultaneously at up to three different frequencies.
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43.58.+z Acoustical measurements and instrumentation
43.35.-c Ultrasonics, quantum acoustics, and physical effects of sound
68.55.-a Thin film structure and morphology
73.50.-h Electronic transport phenomena in thin films

A comprehensive analysis of surface acoustic wave reflections

H. Robinson, Y. Hahn, and J. N. Gau

J. Appl. Phys. 65, 4573 (1989); http://dx.doi.org/10.1063/1.343253 (14 pages) | Cited 11 times

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A thorough study of the perturbative and variational approaches is carried out for the surface acoustic wave reflection problem. We have shown that the perturbation treatment by Datta and Hunsinger and potentially powerful variational formulation by Chen and Haus [IEEE Trans. Sonics Ultrason. SU‐32, 395 (1985)] are mutually consistent. In their common region of validity, these two approaches yield nearly identical results for the reflection coefficients and velocity shifts due to metal finger and groove overlays. Term‐by‐term comparison of the mass‐ and stress‐loading effects, and also the electric shorting effect, is carried out to provide a coherent picture of the reflection phenomena. The on‐ and off‐resonance behavior of the reflection coefficient can be described correctly using either one of these theories, with proper inclusion of the overlay shape dependence. A new term for electric shorting is derived for groove overlays.
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68.35.Gy Mechanical properties; surface strains
43.35.Pt Surface waves in solids and liquids

Plastic yielding at crack tips

S. Burhanettin Altan and A. Cemal Eringen

J. Appl. Phys. 65, 4587 (1989); http://dx.doi.org/10.1063/1.343254 (8 pages)

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Small‐scale plastic yielding at crack tips is studied by means of nonlocal elasticity. Plastic lines along the crack line of a mode III crack modeled by an array of dislocations. It is shown that plastic yield begins after a definite value of load as a consequence of nonlocality. The length of plastic zone and the dislocation distribution are determined as functions of the applied load. The results are in good agreement with experimental observations
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81.40.Jj Elasticity and anelasticity, stress-strain relations
81.40.Lm Deformation, plasticity, and creep
83.10.Ff Continuum mechanics

Measurement of barium loss from a fluorescent lamp electrode by laser‐induced fluorescence

A. K. Bhattacharya

J. Appl. Phys. 65, 4595 (1989); http://dx.doi.org/10.1063/1.343255 (8 pages) | Cited 19 times

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A laser‐induced fluorescence method for measuring the loss rate of barium from Ba‐Sr‐Ca oxide coated electrodes of low‐pressure discharge lamps is presented. The oxide coating from the electrode surface is depleted during lamp operation. Using this technique, the Ba loss rate from an electrode, when it is acting both as a cathode and an anode during ac operation, was measured. A significantly larger amount of neutral barium is detected in the vicinity of the electrode when it acts as an anode over when it acts as a cathode. The consumption rate of Ba and hence the life of an oxide coating depends upon the phase of the lamp current, the shape, and the magnitude of the current supplied by the lamp ballast. The consumption rate for the coating increases linearly with the discharge current. A simplified theoretical analysis of the technique for a three‐level atomic system irradiated by a pulse laser beam is discussed.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.80.Mg Arcs; sparks; lightning; atmospheric electricity
32.80.-t Photoionization and excitation

Measurement of barium ion density in the vicinity of fluorescent lamp electrodes

A. K. Bhattacharya

J. Appl. Phys. 65, 4603 (1989); http://dx.doi.org/10.1063/1.343256 (5 pages) | Cited 14 times

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A laser‐induced fluorescence technique for the detection and measurement of ionized barium atoms near the vicinity of an oxide‐coated electrode in a low‐pressure discharge lamp is presented. Ionized Ba atoms are produced by the ionization of neutral Ba atoms in the electrode fall region of the discharge. Radiation at 455.4 nm obtained from a pulsed dye laser was used to excite Ba ii from the ground state, 62S1/2, to the resonance level, 62P3/2, and the fluorescence radiation at 614.2 nm for the 62P3/2→52D5/2 transition was measured. The number density of Ba ii atoms as determined from the measured intensity of the fluorescence signal (614.2 nm) is dependent on the discharge current, and the polarity of the neighboring electrode. It is found to be larger when it is acting as an anode than when it is a cathode.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.80.Mg Arcs; sparks; lightning; atmospheric electricity

Laser‐induced ablation pressure in thin gold foils

B. K. Godwal, T. S. Shirsat, and H. C. Pant

J. Appl. Phys. 65, 4608 (1989); http://dx.doi.org/10.1063/1.343257 (4 pages) | Cited 5 times

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A study of the variation of the effective ablation pressure with thickness of laser irradiated thin gold foils is presented. Gold foils (2.5 and 12.0 μm thick) were irradiated by a glass laser (1.06 μm wavelength, 5‐ns pulse duration) in 1011–1013 W/cm2 irradiance range. Ablation pressure and its scaling is found to be higher for the 12‐μm‐thick gold target. The results are consistent with other results obtained on the basis of enhanced x‐ray transmission through thin gold foils. Theoretical estimates of the x‐ray transport are carried out to support this.
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52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
62.50.-p High-pressure effects in solids and liquids

Decay instability of an upper‐hybrid wave in a plasma cylinder

S. Konar, V. K. Jain, and V. K. Tripathi

J. Appl. Phys. 65, 4612 (1989); http://dx.doi.org/10.1063/1.343258 (5 pages) | Cited 1 time

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A nonlocal theory of parametric decay of an upper‐hybrid wave into an ion‐acoustic wave and an upper‐hybrid sideband reveals that an axially symmetric pump tends to excite axially symmetric modes. The growth rate falls off with the frequency ω0 of the pump and the azimuthal model number l of the decay waves. In cases where ion and electron temperatures are nearly equal the decay process goes over to nonlinear ion Landau damping; however, the behavior of the growth rate with ω0 and l remains the same. The resonant and nonresonant decay via ion‐cyclotron modes also show similar behavior, although with a smaller growth rate.
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52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.25.-b Plasma properties

Unipolar corona space charge in wire‐plane geometry: A first principles numerical computation

J.‐R. Li and H. J. Wintle

J. Appl. Phys. 65, 4617 (1989); http://dx.doi.org/10.1063/1.343259 (8 pages) | Cited 7 times

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We have calculated the space‐charge‐perturbed ion flow for the wire‐plane geometry using coordinate inversion and a finite‐difference method to retain the boundary at infinity. The results agree in outline with earlier finite element work, but they show a smooth variation of charge density with angle close to the wire. This suggests that the earlier work [J. L. Davis and J. F. Hoburg, J. Electrostat. 18, 1 (1986)] contains an error. We also show that the commonly used Deutsch assumption that field lines preserve their shape is not particularly good. We note that all calculations, good and poor, reproduce the well‐established Warburg (cosine power law) dependence of current density and field on the ground plane, but that careful work is needed to establish the conditions near the emitting wire.
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73.20.At Surface states, band structure, electron density of states
73.25.+i Surface conductivity and carrier phenomena
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.40.Ns Metal-nonmetal contacts

Reduction of the density profile of a field‐reversed configuration plasma from detailed interferometric measurements

S. Okada, Y. Kiso, S. Goto, and T. Ishimura

J. Appl. Phys. 65, 4625 (1989); http://dx.doi.org/10.1063/1.343260 (7 pages) | Cited 12 times

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In order to obtain a detailed density profile of a field‐reversed configuration (FRC) plasma, fast‐response multichannel heterodyne quadrature interferometers are constructed. Using these interferometers and assuming a rigid‐body radial shift motion of the plasma, a spatially fine‐grained line integrated density (∫ n dl) profile at its axial midplane is measured. A radial density profile n(r) is reduced from spline fitting of ∫ n dl. The n(r) is found to be nearly an even function of u(=r2/R2−1, R is the magnetic axis radius) as expected. The n(r) is also obtained by the fitting of a line integral of a model n(r) consisting of a modified rigid rotor (RR) profile which can describe the density steepening near the separatrix of the FRC plasma. When the plasma is fat (xs =separatrix radius/coil inner radius=0.63), the density profile is very near to the RR profile itself given by sech2 (Ku), where K is a constant. When the plasma is slender (xs =0.43), the modification is somewhat pronounced. In both cases n(r) at r=R is flatter but near to the RR profile, and the scale length of the density gradient at the separatrix is about twice the ion gyroradius. Detailed error analyses of the fitting parameters are done to show the range of allowed profiles. Although the fitting is accomplished very well (root‐mean‐square excursion of the fitted ∫ n dl from the measured one is from 1.9% to 2.5%), much variation of n(r) is still possible.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.55.Ez Theta pinch

Electron distribution function and axial variation of an electron‐beam‐generated plasma

A. M. Pointu and G. Maynard

J. Appl. Phys. 65, 4632 (1989); http://dx.doi.org/10.1063/1.343261 (7 pages) | Cited 4 times

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We compute analytically the tail of the electron distribution function, including the radial and axial diffusion, in a plasma generated by an electron beam of a few keV. With this we can determine the ionization efficiency of the tail electrons in creating bulk electrons. The asymptotic behavior that results, for large axial distances, is compared with experimental data for molecular oxygen plasma.
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52.80.Hc Glow; corona
52.50.Dg Plasma sources

Optical‐emission studies on the interaction between halogenated carbon species and noble gas during fluoropolymer sputtering

Iwao Sugimoto and Shojiro Miyake

J. Appl. Phys. 65, 4639 (1989); http://dx.doi.org/10.1063/1.343262 (7 pages) | Cited 4 times

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Using optical‐emission spectroscopy, the interaction between metastable‐excited noble gas and fluorocarbon species is investigated for poly‐chloro‐tri‐fluoro‐ethylene (PCTFE) sputtering under a mixture of noble gas and CF3Cl gas flow conditions. Among a variety of noble gases, He and Ne in an excited state were quenched through energy transfer which induced the ionization and self‐decomposition of the halogenated carbon species. Such an inactivation was not observed in the Ar, Kr, and Xe cases, in accordance with the ionization energy in CF3Cl derived from photoelectron spectroscopy. Instability in a radio‐frequency (rf) plasma was observed in the pure Xe case. However, the plasma was stabilized in the case of a mixture with CF3Cl. The CF2 band which is characteristic of PCTFE sputtering was not detected in the Xe case. In addition, it was confirmed that the oxygen introduced into the rf plasma was more likely to react with CF2(3B1) than with CF2(1B1) or CF3(1B1).
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52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.40.Mj Particle beam interactions in plasmas
33.20.-t Molecular spectra
33.70.-w Intensities and shapes of molecular spectral lines and bands

Electron‐beam‐induced current and photoetching investigations of dislocations and impurity atmospheres in n‐type liquid‐encapsulated Czochralski GaAs

C. Frigeri and J. L. Weyher

J. Appl. Phys. 65, 4646 (1989); http://dx.doi.org/10.1063/1.343239 (8 pages) | Cited 13 times

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Typical defects in n‐type liquid‐encapsulated Czochralski GaAs, i.e., grown‐in dislocations and grown‐in and then stress‐induced glide (GS) dislocations have been studied by electron‐beam‐induced current (EBIC) and diluted Sirtl‐like etching with light (DSL photoetching). The study of GS dislocations was possible because both EBIC and DSL can reveal the recombinative traces left behind the moving dislocations. Grown‐in dislocations and the ending points of GS dislocations exhibit a central feature more recombinative than the external atmosphere. No such central feature has been detected at the starting points of the GS dislocations. A model for the formation of the impurity atmospheres in the GS defects has been put forward. By quantitative EBIC measurements performed right in the impurity atmospheres (∼5–20 μm in size) around dislocations, the local space‐charge region width of the EBIC Schottky diode was determined. Information on the net ionized impurity concentration in the atmospheres could thus be obtained. It has been established that silicon (dopant) autocompensation along with the gettering of other unknown impurities and point defect reactions probably involving arsenic interstitials are important features of the atmospheres.
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61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
07.79.Cz Scanning tunneling microscopes
61.05.-a Techniques for structure determination
61.72.jd Vacancies
61.72.jj Interstitials

Effect of thermal history on oxygen precipitates in Czochralski silicon annealed at 1050 °C

Chung Yuan Kung

J. Appl. Phys. 65, 4654 (1989); http://dx.doi.org/10.1063/1.343240 (12 pages) | Cited 13 times

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The precipitation of oxygen in bulk Czochralski silicon wafers subjected to single‐step isothermal, two‐step (low‐high), two‐step (high‐high), and three‐step (high‐low‐high) annealing is studied by means of infrared spectroscopy and by preferential etching. Comparisons are made with transmission electron micrographs obtained on similar wafers. With the same amount of precipitated oxygen, the IR spectra near 1230 cm−1 and the precipitate morphology are different for samples that undergo different thermal cycles. For the single‐step and three‐step annealed samples, platelet precipitates are the dominant defect type and a peak is observed at 1230‐cm−1. For the two‐step annealed samples, the majority defects are polyhedral precipitates and stacking faults, no platelet precipitates are found and the 1230‐cm−1 peak is absent. It is believed that the stacking faults generated during two‐step annealing have a strong effect in converting the oxygen precipitate morphology from platelets to polyhedra. A model is proposed to explain this phenomenon according to the coarsening concept.
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81.10.-h Methods of crystal growth; physics and chemistry of crystal growth, crystal morphology, and orientation
61.66.Bi Elemental solids
61.66.Dk Alloys
78.30.-j Infrared and Raman spectra
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