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15 Feb 1992

Volume 71, Issue 4, pp. 1565-2062

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Nonlinear digital filtering of scanning‐probe‐microscopy images by morphological pseudoconvolutions

Andrew D. Weisman, Edward R. Dougherty, Howard A. Mizes, and R. J. Dwayne Miller

J. Appl. Phys. 71, 1565 (1992); http://dx.doi.org/10.1063/1.351233 (14 pages) | Cited 8 times

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A recently developed class of digital filters known as morphological pseudoconvolutions is applied to scanning tunneling microscopy (STM) images. These filters use a nonlinear branch of image processing known as morphology to improve the characteristics of both moving mean and moving median filters. They filter equally in both the x and y directions, so as not to introduce artifacts, and they have an adjustable parameter that allows the user to restore the observed image completely as the parameter tends to infinity. Very few assumptions are made concerning image and noise content; only the shape of typical data is taken into account. These filters are shown to outperform, both visually and in the mean‐square‐error sense, previously introduced Wiener filtering techniques. The filters are compared on typical STM‐type images, using both modeled and actual data. The technique is general, and has been shown to perform very well on all types of STM and atomic force microscopy images.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers
07.79.Cz Scanning tunneling microscopes
61.05.-a Techniques for structure determination

Alexandrite as a high‐temperature pressure calibrant, and implications for the ruby‐fluorescence scale

A. H. Jahren, M. B. Kruger, and Raymond Jeanloz

J. Appl. Phys. 71, 1579 (1992); http://dx.doi.org/10.1063/1.351234 (4 pages) | Cited 23 times

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The wavelength shifts of the R1 and R2 fluorescence lines of alexandrite (BeAl2O4:Cr+3) have been experimentally calibrated against the ruby‐fluorescence scale as a function of both hydrostatic and nonhydrostatic pressures between 0 and 50 GPa, and simultaneously as a function of temperatures between 290 and 550 K. The results can be expressed in nm as λ(R1)=680.26(±0.01)+8.7×10−3 (±0.3) (T−273)+0.292(±0.003)P +1.3(±0.1)×10−3 P2 and λ(R2)=678.63 (±0.01)+7.8×10−3(±0.2)(T−273)+0.031 (±0.003)P+0.8(±0.1)×10−3 P2, with pressure P in GPa and temperature T in K. Notably, we find that the pressure–temperature cross derivative of the fluorescence wavelength shifts are negligible for both ruby and alexandrite.
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78.55.Hx Other solid inorganic materials
62.50.-p High-pressure effects in solids and liquids
42.72.Bj Visible and ultraviolet sources

Stability analysis, finite current effects, and experimental results in the Autoresonance Microwave Accelerator

Reuven Shpitalnik

J. Appl. Phys. 71, 1583 (1992); http://dx.doi.org/10.1063/1.351235 (5 pages) | Cited 8 times

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The details of the autoresonance acceleration scheme suggested recently are being investigated below. The eikonal perturbation analysis is presented as well as some numerical results on the finite current effects. An electron cyclotron maser as well as a peniotron‐like interactions are discussed for the acceleration with a circularly polarized TE21 mode in a round waveguide. Experimental data, resulting from an improvement of the axial magnetic field, showing acceleration to 200 keV out of the expected 250 keV, are reported.
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29.20.dg Cyclotrons
29.25.Bx Electron sources
41.75.Ht Relativistic electron and positron beams

Canonical aberration theory of multipoles: A critical reanalysis

Zhifeng Shao and Jiye Ximen

J. Appl. Phys. 71, 1588 (1992); http://dx.doi.org/10.1063/1.351236 (6 pages) | Cited 1 time

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Canonical aberration theory has been applied to analyze the aberration structure of both electrostatic and magnetic multipoles. It is shown rigorously that for 2N‐pole magnetic multipoles with N=even, there is no axially symmetric aberration of any order, while for all the other cases of electromagnetic multipoles, there is always an axially symmetric aberration of the order of 2N−3. The method used is general in nature and can be applied to obtain detailed formulas of higher‐order aberrations of multipoles and also to study their off‐axis aberrations.  
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41.85.Gy Chromatic and geometrical aberrations
07.78.+s Electron, positron, and ion microscopes; electron diffractometers
41.20.Cv Electrostatics; Poisson and Laplace equations, boundary-value problems

Second‐order polarizabilities of nitropyridine derivatives determined with electric‐field‐induced second‐harmonic generation and a solvatochromic method: A comparative study

Ch. Bosshard, G. Knöpfle, P. Prêtre, and P. Günter

J. Appl. Phys. 71, 1594 (1992); http://dx.doi.org/10.1063/1.351237 (12 pages) | Cited 53 times

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A comparison is made between the second‐order polarizabilities of nitropyridine derivatives determined with two different methods: electric‐field‐induced second‐harmonic generation (EFISH) and a solvatochromic method. Both techniques yield the same values within the experimental errors, showing that the main contribution of the microscopic nonlinearity arises from a single intramolecular charge‐transfer transition. Based on the quantum‐mechanical two‐level model, the solvatochromic method also yields important molecular parameters, such as transition and excited‐state dipole moments. The second‐order polarizabilities determined with the EFISH method are shown to follow the theoretical two‐level dispersion.
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42.65.An Optical susceptibility, hyperpolarizability
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation

XeF(C‐A) bandwidth control measurements

A. Mandl, J. A. Russell, and L. Litzenberger

J. Appl. Phys. 71, 1606 (1992); http://dx.doi.org/10.1063/1.351216 (4 pages)

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An electron‐beam pumped XeF(C‐A) laser has been operated as an injection controlled oscillator. The electron‐beam pump rate was 290 kW/cm3 and the pulse length was 600 ns. An etalon controlled dye laser was used as the injection source and reduced the free‐running laser linewidth from 16 to 0.003 nm. The intrinsic laser efficiency of the injection controlled XeF(C‐A) excimer was 1.8% with a specific output energy of 3 J/l, exceeding the free‐running performance.
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42.55.Lt Gas lasers including excimer and metal-vapor lasers

Parametric investigation of the fission‐fragment excited helium/argon laser at 1.79 μm

G. A. Hebner and G. N. Hays

J. Appl. Phys. 71, 1610 (1992); http://dx.doi.org/10.1063/1.351217 (7 pages) | Cited 7 times

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Characteristics of the fission‐fragment excited helium/argon laser operating on the 1.79‐μm (3d[1/2]0,10−4p[3/2]1,2 argon transition are presented. Laser output occurs for approximately 80% of the 0.9 to 3 ms full width at half maximum thermal neutron pump pulse. Output power efficiency optimizes for a total gas pressure of 760 Torr and argon concentration of 0.3% to 2.0%. Power efficiency was 1.4%±0.4% for instantaneous pump rates of 45 to 230 W/cm3. The small signal gain and saturation intensity for instantaneous pump rates of 30 to 90 W/cm3 are 0.55% to 1.05%/cm and 70 to 110 W/cm2, respectively. The laser threshold as a function of helium pressure and argon concentration will be presented. The advantages of fission‐fragment excitation in predominantly helium gas mixtures will be discussed.
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42.55.Lt Gas lasers including excimer and metal-vapor lasers

Thickness and sound velocity measurement in thin transparent films with laser picosecond acoustics

O. B. Wright

J. Appl. Phys. 71, 1617 (1992); http://dx.doi.org/10.1063/1.351218 (13 pages) | Cited 36 times

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A new thin‐film optical testing method is described for both thickness and sound velocity of transparent films on opaque substrates with laser picosecond acoustics using the optical pump‐probe technique. The theory of excitation and detection of ultrasonic stress pulses for this geometry is presented in detail together with experimental results for sputtered thin films of silica of thickness 200 nm–2 μm on amorphous germanium substrates. Reflectance variations, measured as a function of pump‐probe delay time, are characterized by echoes and beating oscillations superimposed on periodic steplike changes. These effects are modeled as a sum of an echo contribution from the stress‐induced modulation of the substrate reflectance, an interference contribution from the light reflected by the moving stress pulse in the transparent film, a contribution from the modulation of the light on transmission through this stress pulse, and a contribution from the stress‐induced ultrafast vibrations of the film interfaces of order 10−3 nm. The latter contribution arises from thin‐film interference effects that represent a novel detection mechanism for surface vibrations in the picosecond regime. Sound velocity and thickness are derived from the data to an accuracy of a few percent, and the photoelastic constant of the transparent film is determined.
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42.87.-d Optical testing techniques
43.35.Cg Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in solids; elastic constants
68.60.Bs Mechanical and acoustical properties

XeF (B‐X) long‐pulse‐length laser studies

A. Mandl

J. Appl. Phys. 71, 1630 (1992); http://dx.doi.org/10.1063/1.351193 (8 pages) | Cited 1 time

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A study of the operation of the XeF(B‐X) laser under low‐electron‐beam pump rate and high‐energy loading is reported. Measurements have been performed at pump rates of 36, 44, and 66 kW/cm3 with laser output pulse lengths greater than 4 μs in duration and energy loadings up to 280 J/l. Intrinsic laser efficiencies of 2.0% at 66 kW/cm3, 1.7% at 44 kW/cm 3, and 1.5% at 36 kW/cm3 were measured in optimized NF3, Xe, Ne mixtures. Under optimum conditions specific output energies as high as 5.6 J/l were measured. Gain and absorption were also measured.
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42.55.Lt Gas lasers including excimer and metal-vapor lasers
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Holograms obtained by laser‐assisted oxidation of thin tellurium films

G. A. Shafeev and M. Wautelet

J. Appl. Phys. 71, 1638 (1992); http://dx.doi.org/10.1063/1.351370 (3 pages) | Cited 2 times

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Holograms are recorded by laser‐assisted oxidation of thin tellurium films in air. The process of recording is characterized in situ by measuring the evolution of a self‐diffracted beam of a cw Ar+ laser. Stationary diffraction efficiency is shown to be independent both on the recording beam power and on the grating period. Amplitude holograms are obtained with an efficiency of 3.2% at a spatial period of 3 μm.
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42.40.Ht Hologram recording and readout methods
81.65.-b Surface treatments
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)

Ultrasonic sensing of powder densification

Yichi Lu, Haydn N. G. Wadley, and Sanjai Parthasarathi

J. Appl. Phys. 71, 1641 (1992); http://dx.doi.org/10.1063/1.351194 (8 pages) | Cited 4 times

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An independent scattering theory has been applied to the interpretation of ultrasonic velocity measurements made on porous metal samples produced either by a cold or a high‐temperature compaction process. The results suggest that the pores in both processes are not spherical, an aspect ration of 1:3 fitting best with the data for low (<4%) pore volume fractions. For the hot compacted powders, the pores are smooth due to active diffusional processes during processing. For these types of voids, the results can be extended to a pore fraction of 10%, at which point voids form an interconnected network that violates the model assumptions. The cold pressed samples are not as well predicted by the theory because of poor particle bonding.
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43.35.-c Ultrasonics, quantum acoustics, and physical effects of sound
62.30.+d Mechanical and elastic waves; vibrations
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation

Analysis of cathode fall from a planar electrode in gas discharges at low E/P low pressure

D. P. Xi

J. Appl. Phys. 71, 1649 (1992); http://dx.doi.org/10.1063/1.351195 (5 pages)

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An analytic investigation is reported of cathode fall from a planar electrode in a gas discharge at low electric field to pressure and low gas pressure. In order to avoid complex calculations, a simple function is used to fit the experimental data on Townsend’s first ionization coefficient. Analytic expressions of variation of electric field, cathode fall, and length of the cathode dark space with the ratio of current density to pressure squared are obtained using a first‐order approximation. The results show the characteristic current‐voltage relation for subnormal and abnormal discharge. The cathode fall, the length of cathode dark space, and the ratio of current density to pressure squared are also estimated for the normal discharge. It is also shown that the length of cathode dark space is a function of the cathode fall. Numerical calculations for several gases are made to demonstrate the model.
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52.80.Dy Low-field and Townsend discharges
51.50.+v Electrical properties (ionization, breakdown, electron and ion mobility, etc.)

Numerical investigation of the kinetics and chemistry of rf glow discharge plasmas sustained in He, N2, O2, He/N2/O2, He/CF4/O2, and SiH4/NH3 using a Monte Carlo‐fluid hybrid model

Timothy J. Sommerer and Mark J. Kushner

J. Appl. Phys. 71, 1654 (1992); http://dx.doi.org/10.1063/1.351196 (20 pages) | Cited 122 times

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Capacitively coupled radio‐frequency (rf) glow discharges are standard sources in plasma assisted materials processing. Theoretical analyses of rf discharges have been hampered by the computational difficulty of simultaneously resolving nonequilibrium electron transport and plasma chemistry. We have developed a hybrid Monte Carlo‐fluid simulation that can simulate nonequilibrium electron transport while executing with the speed of a fluid simulation. An electron Monte Carlo simulation (EMCS) is used to calculate the electron energy distribution (EED) as a function of position and phase in the rf cycle. Collision rates and transport coefficients are calculated from the EED and used in a self‐consistent fluid model (SCFM) of charged particle behavior and a neutral chemistry/transport model. Electric fields from the SCFM are cycled back to the EMCS, and the process is iterated until convergence. All pertinent heavy particle (charged and neutral) reactions can be included as well as collisions of electrons with ions, excited states, and reaction products. The hybrid model is applied to a variety of gas mixtures of interest to materials processing.
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52.80.Hc Glow; corona
52.65.-y Plasma simulation

Discharge‐excited free jet source of rare gas‐halide and oxide molecules

R. B. Jones, J. H. Schloss, and J. G. Eden

J. Appl. Phys. 71, 1674 (1992); http://dx.doi.org/10.1063/1.351197 (9 pages) | Cited 5 times

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Intense rare gas‐halide and rare gas‐oxide excimer emission has been observed by coupling a pulsed electric discharge to a supersonic free jet expansion. A simple modification in the placement of the discharge anode drastically reduces the number of energetic electrons in the supersonic expansion region and permits large peak excimer populations to be produced by harpoon collisions involving rare gas metastables. The expansion velocity has been determined by spatially resolved spontaneous emission and laser‐induced fluorescence measurements. Strong emission spectra from XeF, XeCl, KrF, KrCl, ArF, and the 2 3Π ion pair state of XeO have been recorded.
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52.80.-s Electric discharges
34.50.Gb Electronic excitation and ionization of molecules
33.20.Lg Ultraviolet spectra

Laser‐induced fluorescence and emission spectroscopic study of magnetic field effects in a low‐pressure etch plasma

Friedhelm Heinrich and Peter Hoffmann

J. Appl. Phys. 71, 1683 (1992); http://dx.doi.org/10.1063/1.351397 (7 pages) | Cited 1 time

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The influence of a magnetic volume field B on the chemical and physical properties of a 13.56‐MHz CF4 plasma was studied by laser‐induced fluorescence (LIF) and by optical emission spectroscopy (OES) at typical low‐pressure etching conditions. The measurements were carried out in a commercial magnetron with a modified magnetic field configuration allowing a continuous variation of B up to a maximum field strength of 80 G. As indicated by LIF the densities of the CF2 radicals in the electronic and vibrational ground state increased by about a factor of 3 when the maximum B field was applied. No concentration gradients were detected by spatially resolved LIF. A similar increase as for CF2 was observed for actinometrically normalized F emission intensities. The ratios of CF2 LIF and CF2 OES signals are compared with the emission intensity behavior of argon, admixed to a small percentage, which suggest an increase of the electron induced production rates (electron densities) significantly stronger than that of the radical concentrations. This phenomenon is explained by simple considerations concerning B dependent production and losses of ions and radicals.
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52.80.Pi High-frequency and RF discharges
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
81.65.-b Surface treatments

Room‐temperature hydrogenation effect on Si‐ and Be‐ion‐implanted GaAs

Hoon Young Cho, Eun Kyu Kim, Ho Sub Lee, and Suk‐Ki Min

J. Appl. Phys. 71, 1690 (1992); http://dx.doi.org/10.1063/1.351198 (3 pages) | Cited 2 times

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Hydrogenation effects on Si‐ and Be‐ion‐implanted GaAs exposed to the hydrogen plasma were investigated. In the sample hydrogenated for 60 min at room temperature, electron mobilities were increased about 21% at 300 K and 1400 cm2/V s at 150 K, showing a little change of the activated Si donor profile. Also, by using deep‐level transient spectroscopy and optical deep‐level transient spectroscopy, it was observed that the electron and hole traps at Ec−0.62‐ and Ev+0.68‐eV levels, which have been reported as defects due to the implanted damage, were efficiently decreased during the room‐temperature hydrogenation. This effect persists during the anneal at 400 °C during 5 min in an argon ambient.  
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71.55.Eq III-V semiconductors
72.80.Ey III-V and II-VI semiconductors
81.65.-b Surface treatments
61.72.U- Doping and impurity implantation

Control of microstructure in a‐SiC:H

Hsueh Yi Lu and Mark A. Petrich

J. Appl. Phys. 71, 1693 (1992); http://dx.doi.org/10.1063/1.351199 (6 pages) | Cited 5 times

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We demonstrate a means of controlling the microstructure and carbon content in amorphous hydrogenated silicon carbide (a‐SiC:H) thin films prepared in a plasma‐enhanced chemical vapor deposition system. The capacitively coupled, parallel‐plate deposition apparatus includes provision for adjusting the potential of the powered electrode by application of an additional, independent dc voltage. This voltage affects the deposition chemistry. Films prepared when various positive and negative dc voltages are applied are studied with infrared absorption, nuclear magnetic resonance, and electron spin resonance. Their optical band gaps, electrical conductivities, and dark conductivity activation energies are also measured. The films have carbon contents ranging from 1 to 4 at. %. We find that we can alter the microstructure of a‐SiC:H by adjusting the powered‐electrode potential during deposition, and that these microstructural changes are reflected in the film properties. A small increase in the self‐biased voltage of the powered electrode leads to a film with the least amount of infrared‐observable microstructure and the highest photoconductivity. Applying an external dc voltage leads to an increase in deposition rate regardless of voltage polarity. The films prepared with externally applied voltage all have lower hydrogen contents than the film prepared with self‐biased voltage, which may explain the observed property changes. The addition of an external dc voltage can have beneficial effects on the deposition rate, structure, and properties of a‐SiC:H films.
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61.43.Fs Glasses
61.43.-j Disordered solids
61.44.Br Quasicrystals
78.66.-w Optical properties of specific thin films
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Annealing studies of low‐temperature‐grown GaAs:Be

D. E. Bliss, W. Walukiewicz, J. W. Ager, E. E. Haller, K. T. Chan, and S. Tanigawa

J. Appl. Phys. 71, 1699 (1992); http://dx.doi.org/10.1063/1.351200 (9 pages) | Cited 79 times

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The isochronal and isothermal annealing characteristics of acceptor‐doped GaAs:Be grown at low substrate temperatures (300 °C) by molecular‐beam epitaxy (LTMBE) have been studied. The Be was introduced in a range of concentrations from 1016 to 1019 cm−3. Electrical measurements of as‐grown material up to the highest Be concentration of 1019 cm−3 show that no free holes are contributed to the valence band even though Raman spectroscopy of the Be local vibrational mode indicates that the majority of the Be impurities occupy substitutional sites. It is proposed that Be acceptors are rendered inactive by the high concentration of AsGa‐related native donor defects present in LTMBE material. The concentration of AsGa‐related defects in the neutral charge state was estimated from infrared absorption measurements to be as high as 3×1019 cm−3. A distinct annealing stage at 500 °C, similar to that found in irradiation‐damaged and plastically deformed GaAs, marks a rapid decrease in the concentration of AsGa‐related defects. A second annealing stage near 800 °C corresponds to the activation of Be acceptors. The presence of gallium vacancies VGa was investigated by slow positron annihilation. Results indicate an excess concentration of VGa in LTMBE layers over bulk‐grown crystals. Analysis of isothermal annealing kinetics for the removal of AsGa‐related defects gives an activation energy of 1.7±0.3 eV. The defect removal mechanism is modeled with VGa‐assisted diffusion of AsGa to As precipitates.
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61.72.Yx Interaction between different crystal defects; gettering effect
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
72.80.Ey III-V and II-VI semiconductors

Electrical activation of group‐IV elements implanted at MeV energies in InP

M. C. Ridgway, C. Jagadish, T. D. Thompson, and S. T. Johnson

J. Appl. Phys. 71, 1708 (1992); http://dx.doi.org/10.1063/1.351201 (5 pages) | Cited 12 times

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The electrical activation and carrier mobility of InP implanted with the group‐IV elements at MeV energies has been studied as a function of implanted atom (C, Si, Ge, and Sn) and rapid thermal annealing temperature (500–800 °C). In addition, electrical results have been correlated with photoluminescence (PL) measurements. In general, for a dose of 5×1014/cm2 and a projected range of ∼1.0 μm, the electrical activation and carrier mobility increase then saturate with increasing annealing temperature. Similarily, PL emission intensity increases with increasing annealing temperature. At a temperature of 750 °C, the electrically active fraction increases from C, Ge, Si, to Sn, respectively, while carrier mobility and PL emission intensity decreases with increasing atomic mass. Thus, Sn exhibits the highest electrical activation yet lowest carrier mobility with little optically observable, postanneal lattice recovery.
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61.72.U- Doping and impurity implantation
78.55.Cr III-V semiconductors
72.80.Ey III-V and II-VI semiconductors

Suppression mechanisms for oxidation stacking faults in silicon on insulator

N. Guillemot, D. Tsoukalas, C. Tsamis, J. Margail, A. M. Papon, and J. Stoemenos

J. Appl. Phys. 71, 1713 (1992); http://dx.doi.org/10.1063/1.351202 (8 pages) | Cited 8 times

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Oxidation of the Si overlayer in silicon separated by oxygen (SIMOX) is expected to form oxidation stacking faults (OSF) since this process generates Si interstitials into the active Si layer. In spite of this process, recent experiments reveal that the density of OSF is very low. A possible mechanism to explain the absence of OSF in SIMOX is that Si interstitials rejected from the Si‐overlayer/SiO2 interface could react with the SiO2 of the buried layer to form SiO molecules (Si+SiO2=2SiO). These species, which can diffuse four orders of magnitude faster than Si through the SiO2 buried layer, are recombined by the reverse reaction at the back interface due to the absence of Si‐interstitial supersaturation. Since the activation energy for this process is 4.4 eV, OSF can be generated if the Si overlayer is subjected to a preoxidation treatment that introduces a high density of stacking fault (SF) nucleation sites, because the activation energy for heterogeneous generation of OSF is only 2.3 eV. In this case 0.21×10−3 of Si interstitials are incorporated in OSF over the total Si atoms that are consumed during the oxidation. This value agrees with the proportion of Si interstitials incorporated in OSF when the SiO2 buried layer is replaced by a Si3N4 buried layer since this layer is a barrier for the Si‐interstitial migration to the substrate. The value 0.21×10−3 is very close to the expected theoretical value revealing that almost all the Si interstitials were captured by the OSF.
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81.65.-b Surface treatments
61.72.Nn Stacking faults and other planar or extended defects
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Shock compression of tungsten and molybdenum

R. S. Hixson and J. N. Fritz

J. Appl. Phys. 71, 1721 (1992); http://dx.doi.org/10.1063/1.351203 (8 pages) | Cited 85 times

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New high‐pressure shock‐wave data have been obtained for W and Mo. These data have been combined with previous data sets for these materials to extend the range of linear us–up fits for the Hugoniot to 480 GPa for Mo and 680 GPa for W. The shock‐wave data, supplemented by the necessary thermodynamic information, have been used to generate several isotherms (100, 200,...1000 K). Tables of pressure versus relative volume up to 380 GPa suitable for comparison with statically obtained data are given.
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62.50.-p High-pressure effects in solids and liquids

Numerical investigations of the electromigration boundary value problem

J. J. Clement and J. R. Lloyd

J. Appl. Phys. 71, 1729 (1992); http://dx.doi.org/10.1063/1.351204 (3 pages) | Cited 26 times

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The electromigration diffusion boundary value problem with the perfectly blocking diffusion barrier is numerically investigated. Three possible boundary conditions are identified as physically meaningful and the solutions compared at the blocking barrier. It is seen that the solution of M. Shatzkes and J. R. Lloyd [J. Appl. Phys. 59, 3890 (1986)] is a good approximation for the time to failure if the critical vacancy concentration for failure is not too near a steady‐state value. A dimensionless parameter is introduced which may be useful in estimating ultimate electromigration performance.  
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66.30.Qa Electromigration
73.61.-r Electrical properties of specific thin films

Experimental test of theories for the effective thermal conductivity of a dispersed composite

Vladimir Kutcherov, Björn Håkansson, Russell G. Ross, and Gunnar Bäckström

J. Appl. Phys. 71, 1732 (1992); http://dx.doi.org/10.1063/1.351205 (5 pages) | Cited 5 times

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The effective thermal conductivity of binary dispersed composites prepared from mixed and compacted powders of NaCl and low‐density polyethylene (LDPE) was measured over the entire range of volume fraction at temperatures in the range 120–320 K together with pressures up to 1.73 GPa. Measurements were made using the transient hot‐wire method. The ratio of thermal conductivities of NaCl and LDPE varied over the range 10–50 at the temperatures and pressures employed. Using our results (together with previous data for AgCl‐LDPE composites), we tested theoretical predictions from both the effective‐medium approximation and the real‐space renormalization group approximation. The two approximations exhibited a comparable overall level of agreement with experiment and neither was successful in describing our data within experimental inaccuracy over the entire range of volume fraction. For both approximations, the extent to which agreement with experiment was achieved depended significantly on the volume fraction being considered.
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66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
44.10.+i Heat conduction
81.05.Qk Reinforced polymers and polymer-based composites
62.50.-p High-pressure effects in solids and liquids

Growth and structural properties of epitaxial GaxIn1−xP on InP

A. Bensaada, A. Chennouf, R. W. Cochrane, R. Leonelli, P. Cova, and R. A. Masut

J. Appl. Phys. 71, 1737 (1992); http://dx.doi.org/10.1063/1.351206 (7 pages) | Cited 12 times

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The growth of heteroepitaxial GaxIn1−xP on InP for 0<x<0.25 has been carried out by low‐pressure metalorganic chemical vapor deposition and characterized by high‐resolution x‐ray diffraction and low‐temperature photoluminescence measurements. The x‐ray data indicate that the epilayers are under biaxial tensile strain and that, for samples with x<0.05, the lattice mismatch is accommodated almost completely by tetragonal distortions. From photoluminescence measurements, the energy band gap is found to vary monotonically with the Ga concentration; it also shifts linearly with the elastic strain in the layer. The calculated value of 0.99×104 meV per unit strain is in good agreement with that predicted from elasticity theory.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
61.05.cf X-ray scattering (including small-angle scattering)
61.05.cj X-ray absorption spectroscopy: EXAFS, NEXAFS, XANES, etc.
78.55.Cr III-V semiconductors

On the evolution of GaInAs/GaAs strained epitaxial layers

O. Brafman, D. Fekete, and R. Sarfaty

J. Appl. Phys. 71, 1744 (1992); http://dx.doi.org/10.1063/1.351207 (4 pages) | Cited 3 times

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We find that in a highly lattice‐mismatched heteroepitaxial growth, as critical thickness is reached, defects are formed within a thin layer at the surface and do not necessarily propagate to the interface. At that thin layer the strain is locally decreased resulting in a larger lattice parameter, which persists until the next step takes place. This procedure is inferred from the Raman scattering data of InxGa1−xAs/GaAs. Disorder induced Raman spectroscopy in a scattering forbidden configuration is shown to be an extremely sensitive tool for observing this stepwise release of the strain.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
78.30.Fs III-V and II-VI semiconductors
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