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15 Jun 1992

Volume 71, Issue 12, pp. 5747-6209

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Generation and laser diagnostic analysis of bismuth fluoride

M. J. Bohn, D. C. Berst, and E. A. Dorko

J. Appl. Phys. 71, 5747 (1992); http://dx.doi.org/10.1063/1.350467 (5 pages)

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Bismuth fluoride, BiF, a possible energy acceptor molecule in a chemically pumped donor–acceptor electronic transition laser has been produced at number densities exceeding 1013 molecules/cc in a flow tube reactor. A high voltage discharge was used to produce bismuth and fluorine atoms which combined in a three‐body collision to form ground state BiF (X1). Laser induced fluorescence studies confirmed that BiF was formed following the discharge. A vibrational temperature of 581±35 K and rotational temperatures of 340 to 370 K were measured for BiF (X1). Laser absorption measurements were performed to obtain the number density. An absorption cross section, calculated from the physical properties of BiF, was used for the determination.
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33.50.Dq Fluorescence and phosphorescence spectra
33.15.Mt Rotation, vibration, and vibration-rotation constants
42.70.Hj Laser materials

Operational theory of crossed‐field devices based on double‐box density profiles

David J. Kaup and Gary E. Thomas

J. Appl. Phys. 71, 5752 (1992); http://dx.doi.org/10.1063/1.350468 (8 pages) | Cited 2 times

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Studies of the nonlinear evolution of the electron‐density profile in crossed‐field devices indicate the classical Brillouin profile to be inadequate for the explanation of the operation of such devices. Instead, the existence of a density plateau at the edge of the electron sheath is found to be essential in the operation of such a device. Such a plateau placed at the edge of a classical Brillouin profile creates a double‐box profile. The operational theory for crossed‐field devices based on this double‐box density profile is presented. It is shown that this profile generates an operating voltage range that agrees quite well with the actual voltage operating range of such devices, except for high magnetic fields.
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52.75.-d Plasma devices
52.27.Jt Nonneutral plasmas
52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)

Performance characteristics of a high‐pressure pulsed singlet oxygen generator

M. Endo, K. Kodama, Y. Handa, and T. Uchiyama

J. Appl. Phys. 71, 5760 (1992); http://dx.doi.org/10.1063/1.350469 (8 pages) | Cited 4 times

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The characteristics of a high‐pressure pulsed singlet oxygen generator is investigated. This generator was designed for the energy source of new pulsed chemical lasers. A ceramic porous pipe is devised in it to attain the high‐pressure pulsed operation. New methods were developed to measure a water vapor pressure and a reaction efficiency in the pulsed singlet oxygen generator system. The maximum singlet oxygen pressure obtained was 35 Torr, and the estimated initial excitation efficiency was 70%–80%
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42.55.Ks Chemical lasers

Induced electrostatic confinement of the electron gas in tensile strained InGaAs/InGaAsP quantum well lasers

J. Barrau, T. Amand, M. Brousseau, R. J. Simes, and L. Goldstein

J. Appl. Phys. 71, 5768 (1992); http://dx.doi.org/10.1063/1.350470 (4 pages) | Cited 14 times

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A new mechanism, injection induced electrostatic confinement of the electron gas, is proposed to explain the origin of the laser effect in tensile strained GaInAs/GaInAsP quantum well lasers.
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42.55.Px Semiconductor lasers; laser diodes
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Experimental studies of a microsecond plasma opening switch in the positive polarity regime with inductive load/extraction ion diode

V. M. Bystritskii, I. V. Lisitsyn, V. A. Sinebryukhov, S. N. Volkov, and Ya. E. Krasik

J. Appl. Phys. 71, 5772 (1992); http://dx.doi.org/10.1063/1.350471 (11 pages) | Cited 1 time

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Systematic studies of the microsecond plasma opening switch (MPOS) operation in the positive polarity of its inner electrode with an inductive load/B‐applied ion diode of the extraction type at a level of 0.3 TW of dissipated power were performed at the DOUBLE generator (300 kA, 480 kV, 1 μs). The detailed measurements of ion flow parameters in the conductive phase of the MPOS showed the considerable enhancement of the ion current amplitude over the thermal flow limit (3–10 times) which is coupled with a significant decrease of electron conductivity in the MPOS across its self‐magnetic field. The positive polarity MPOS operation proved to be more critical to the stored current amplitudes and geometry of the electrodes in comparison with the negative polarity case. This fact resulted in limitations of satisfactory performance of the MPOS involving short high‐voltage pulse duration, low stored current amplitudes, and a narrow region of acceptable electrode diameters. The variation of the diode anode‐cathode (AC) gap provided a sensitive control of the MPOS + magnetically insulated diode (MID) system, which displayed very strong coupling, resulting in clamping of the output voltage in a wide region of diode impedances. The early long‐duration (<300 ns) high‐voltage (50–200 kV) prepulse improves plasma production at the anode of the MID prior to the application of the main pulse. The optimal performance of the MPOS+MID system was realized at the level of ZMPOS/ZMID = 2.5. The energy of the extracted high‐power ion beam made up 3.5 kJ, its power being 120 GW with 40% efficiency of energy transfer from MPOS to the MID.
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52.75.Kq Plasma switches (e.g., spark gaps)

A one‐dimensional model of dc glow discharges

Wolfgang Schmitt, Walter E. Köhler, and Hanns Ruder

J. Appl. Phys. 71, 5783 (1992); http://dx.doi.org/10.1063/1.350472 (9 pages) | Cited 9 times

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A one‐dimensional continuum model for a dc‐glow‐discharge plasma between parallel‐plate electrodes is presented, which is based on the local balance equations for particle densities and fluxes of electrons and ions, as well as on the local electron energy balance and the Poisson equation. In addition to similar treatments, the inertia term in the ion momentum balance equation leading to a singularity at the ion sound velocity, as well as the electron energy losses by excitation of atomic levels, have been taken into account. The system of nonlinear first‐order differential equations supplemented by suitably chosen boundary conditions has been solved by the numerical procedure Henyey method ordinary differential equation solver, which allows also for the occurrence of removable singular points. Calculations for an argon plasma have been performed and the influence of parameter choices on the solution has been investigated. In general, the features typical for dc discharges are reproduced and agreement with the spatial profiles obtained by other authors with different methods is found.
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52.80.Hc Glow; corona
51.50.+v Electrical properties (ionization, breakdown, electron and ion mobility, etc.)

The time evolution of the ion density and the gas temperature in pulsed radio frequency plasmas

R. J. Visser, J. A. G. Baggerman, J. P. J. Poppelaars, and E. J. H. Collart

J. Appl. Phys. 71, 5792 (1992); http://dx.doi.org/10.1063/1.350473 (7 pages) | Cited 11 times

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The kinetics of the formation and decay of pulsed nitrogen rf plasmas have been investigated with time and spatially resolved optical emission and laser induced fluorescence spectroscopy. At a gas pressure of 3 Pa the decay of the N2+ ions, after the power is switched off, is caused by dissociative recombination and ambipolar diffusion to the wall. At higher pressures (30 Pa) the formation of N4+ has to be taken into account. An accurate method to determine the ion density from the second order decay is presented. A numerical model of the time evolution of the ion concentration profile is developed, which renders good agreement with the experimental data. Kinetic measurements of the rotational (Tr) and vibrational (Tv) temperature of N2+ show that Tr and Tv of N2+ are in equilibrium with Tr and Tv of the N2 gas. The vibrational temperature is, however, much higher than the rotational temperature. This observation can be readily explained on the basis of the results of the kinetic measurements. The experimental excitation and cooling rates for the translational, rotational, and vibrational energy levels of the N2 molecules are compared to simulations.
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52.80.Pi High-frequency and RF discharges
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.25.Os Emission, absorption, and scattering of electromagnetic radiation

Reaction kinetics of CH radical during etching of polymers in argon and oxygen rf plasmas

J. A. G. Baggerman, E. J. H. Collart, and R. J. Visser

J. Appl. Phys. 71, 5799 (1992); http://dx.doi.org/10.1063/1.350474 (7 pages) | Cited 4 times

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During sputtering of polymethylmethacrylate in a low‐pressure argon rf plasma, the density and the reaction kinetics of ground‐state methylidyne (CH radical) were determined by laser induced fluorescence spectroscopy (LIF). For a plasma in a steady‐state condition at 10 Pa and 100 W, the density of CH in the bulk of the plasma was 6.8×1010 cm−3. By pulsing the rf power, the production rate of CH was determined to be 5.1×1013 cm−3 s−1. This production rate was found to be independent of CH density and time after the plasma had been switched on, indicating that CH is not formed in the gas phase, but is sputtered from the substrate. A model, taking diffusion of CH from the substrate into the plasma and chemical reactions in the gas phase into account, has been set up to calculate the CH flux from the substrate surface. The calculated rise curve of CH could be fitted to the measured data with a diffusion coefficient D=1800 cm2 s−1 and an overall reaction rate coefficient k=55 s−1. These data have been used to calculate the total CH flux from the substrate. From this CH flux and the ion current density on the powered electrode, the CH yield was determined to be 0.02 CH radicals per ion, indicating that CH is not the main sputtered species since the overall carbon yield is 4.8 per ion. In an oxygen plasma the CH density is below the detection limit of LIF due to a high overall reaction rate coefficient with O and O2.
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52.80.Pi High-frequency and RF discharges
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
81.65.-b Surface treatments

Parametric analysis of a surface electrical discharge model

A. Kadish

J. Appl. Phys. 71, 5806 (1992); http://dx.doi.org/10.1063/1.350475 (14 pages) | Cited 1 time

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A transmission line model for electric surface flashovers is analyzed. The model features an empirical scaling of resistance with current: The local resistance per unit length is taken to be inversely proportional to the magnitude of the local current. This scaling results in thresholds for discharge current onset and local abrupt termination of discharge current, as well as other observed properties of transient electrical discharges. The model predicts secondary current propagation: The current may terminate in a portion of the current channel and be restarted there at a later time. This results from the wave dynamics of voltage gradients in the channel. Conditions for current reversal and current termination are derived, and the dynamics of the free boundary between current‐carrying and current‐free regions of the current channel is studied.
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52.80.Mg Arcs; sparks; lightning; atmospheric electricity
52.80.Pi High-frequency and RF discharges

Analytic approach to glow discharge theory: The physical model

S. T. Pai

J. Appl. Phys. 71, 5820 (1992); http://dx.doi.org/10.1063/1.350476 (6 pages) | Cited 10 times

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On the basis of fluid approximation, a physical model in analytic form for dc glow discharge is presented. The model has yielded a variety of analytic expressions for the physical quantities concerned. These analytic expressions are functional, self‐consistent, and satisfy all the governing equations as well as the real boundary conditions. With the builtin feature of mode indexing, the model may be employed for a wide range of applications. Several physically significant points which have not been reported previously were revealed from the present model.
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52.80.Hc Glow; corona
51.50.+v Electrical properties (ionization, breakdown, electron and ion mobility, etc.)

Analytic approach to glow discharge theory: Result and analysis

S. T. Pai and X. M. Guo

J. Appl. Phys. 71, 5826 (1992); http://dx.doi.org/10.1063/1.350477 (8 pages) | Cited 6 times

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Using the analytic expressions given in the preceding article, S. T. Pai [J. Appl. Phys. 71, 5820 (1992)] the concerned physical quantities n, N, V, Ez, Γ−, Γ+, and Jz and many others for dc glow discharges were calculated and systematically analyzed under various conditions. Several physically significant points have been brought forward via the analysis. Comparisons between the present results and the corresponding ones obtained by previous investigators showed similarities between them in many aspects. Such similarities signify the wide range applicability of the present model. The builtin feature of mode indexing in the model has been quantitatively demonstrated. Results yielded from such a demonstration are consistent with the corresponding physical situations.
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52.80.Hc Glow; corona
51.50.+v Electrical properties (ionization, breakdown, electron and ion mobility, etc.)

Size effect of the alkali cation on the structure and the molecular mobility of solid polymeric electrolytes

G. Di Marco, A. Bartolotta, and G. Carini

J. Appl. Phys. 71, 5834 (1992); http://dx.doi.org/10.1063/1.350478 (7 pages) | Cited 10 times

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Polymeric electrolytes of the poly(ethylene) oxide (PEO) potassium thiocyanate system have been studied by analyzing the temperature dependence of the low‐frequency (0.3–30 Hz) mechanical characteristics. It is found that the local and cooperative molecular motions characterizing the host polymer are strongly influenced by the addition of the salt, as a result of strong interactions between the polymeric chains and the alkaline salt molecules, which ensure the formation of homogeneous complexes. In the low‐concentration region (molar fraction X≤0.08) a relevant enhancement of the noncrystallinity and a considerable shift of the glass‐to‐rubber transition toward higher temperatures characterize the blends. Further salt addition stiffens the material, this peculiarity being connected to the gradual formation of a crystalline complex with a fixed stoichiometry. It is believed that the observed inversion in the structural trend arises from an increase of the interchain interactions via the polarizing effects of the salt molecules. At low temperatures the single γ relaxation, observed in pure PEO and in complexes of the same kind with smaller cations, is modified by the presence of the salt; two close peaks appear, whose strength follows behavior closely correlated to that of the primary relaxation. A quantitative interpretation in terms of a parallel relaxation permits the microscopic origin to be discussed and the underlying local motions to be ascribed to the amorphous fraction of the polymer.
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61.41.+e Polymers, elastomers, and plastics
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances

Behavior of excess As in nonstoichiometric Si‐doped GaAs

K. Winer

J. Appl. Phys. 71, 5841 (1992); http://dx.doi.org/10.1063/1.350479 (6 pages)

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The Si doping efficiency (≡[e−]/[Si]) in homoepitaxial GaAs has been measured as a function of molecular beam epitaxial growth conditions (As pressure, substrate temperature, and growth rate) and post‐growth thermal annealing conditions. The doping efficiency decreases from one under optimal growth conditions to almost zero: (1) exponentially with inverse substrate temperature below 400 °C and (2) as a power law in the As4‐to‐Ga beam‐equivalent fluence ratio above unity. The doping efficiency of nonoptimally grown films increases from almost zero to near one upon post‐growth thermal annealing above 650 °C with slower than exponential kinetics. These changes are attributed to charge trapping into and release from, respectively, excess‐As‐related defects, which are incorporated during growth and removed by out‐diffusion during annealing.
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61.72.U- Doping and impurity implantation
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Selenium residual doping of (AlGa)Sb/GaSb epilayers grown by molecular beam epitaxy

M. Gauneau, R. Chaplain, Y. Toudic, A. Rupert, G. Grandpierre, and M. Salvi

J. Appl. Phys. 71, 5847 (1992); http://dx.doi.org/10.1063/1.350480 (6 pages) | Cited 1 time

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Some (AlGa)Sb layers grown by molecular beam epitaxy were found unexpectedly to be n type. Characterizing these layers by secondary ion mass spectrometry it was observed that they contained selenium (Se). Systematic analyses showed that selenium was present in all our antimonide layers, even those which were p type, at concentrations between 6×1014 and 3×1017 cm−3. The thermodynamical study of this contaminant incorporation led us to conclude that it comes from the solid antimony used for growths. That was confirmed by spark source mass spectrometry investigations. During growths, selenium behaves as other elements of group VI, sulphur for example, and this behavior is described by a simple kinetic model. It incorporates more easily at low substrate temperatures and saturates at levels depending on the antimony (Sb4) flux. At higher substrate temperatures, the incorporation is balanced by desorption according to an activation energy of 3.2 eV. As a consequence, selenium constitutes an accurate thermal probe to follow substrate temperature variations during growths. As could be expected, sulphur was also found to contaminate (AlGa)Sb films at levels of the order of a few 1015 cm−3. However, oxygen was not detected, probably being lower than 1016 cm−3 the detection limit of the analytical technique. This residual doping of antimonides by chalcogens presumably compensates their natural p‐type doping, but relationships with mobilities have not been evidenced yet.
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61.72.U- Doping and impurity implantation
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Estimation of the core cut‐off parameter for misfit dislocations at a SixGe1−x/Si interface

Krishna Rajan

J. Appl. Phys. 71, 5853 (1992); http://dx.doi.org/10.1063/1.350481 (5 pages) | Cited 4 times

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The misfit dislocation structure at a partially relaxed Si/SixGe1−x interface has been investigated using weak‐beam electron microscopy in order to probe features near the dislocation core. The dislocations were found to be dissociated, allowing for the direct measurement of the stacking fault energy at the epitaxial interface. This has been supplemented with the measurement of the width of symmetrical threefold stacking fault nodes at the same interface. These independent measurements have been combined to estimate the dislocation core cut‐off parameter using isotropic approximations of anisotropic elasticity theories. The size of the core of the misfit dislocation is consistent with both geometric and atomistic models predicting core delocalization at coherent interfaces.
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61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
07.79.Cz Scanning tunneling microscopes
61.05.-a Techniques for structure determination

Kinetics of gettering in silicon

C. S. Chen and D. K. Schroder

J. Appl. Phys. 71, 5858 (1992); http://dx.doi.org/10.1063/1.350482 (7 pages) | Cited 9 times

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Two basic functions of getters in silicon during gettering processes are investigated in detail. The sink action of getters for absorbing impurities is described by a gettering parameter g, which relates to the diffusion ratio gd, segregation coefficient S, and the activation energies Em,Si, Em,G of impurities in intrinsic Si and in the getter phase. The kickout mechanism is suggested for describing the diffusion of impurities because of the contribution of Si interstitials to kick out the impurities to be gettered. Based on the interaction of Si interstitials with impurities and the influence of the sink in absorbing impurities, a set of gettering equations is derived and used to calculate the gettering of gold in silicon with back surface getters. Theoretical results agree well with reported experimental data and five conclusions are provided to determine the optimal gettering conditions for a given gettering cycle.
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61.72.Yx Interaction between different crystal defects; gettering effect
66.30.J- Diffusion of impurities
61.72.Bb Theories and models of crystal defects

Mode‐III cracks in piezoelectric materials

Tong‐Yi Zhang and J. E. Hack

J. Appl. Phys. 71, 5865 (1992); http://dx.doi.org/10.1063/1.350483 (6 pages) | Cited 53 times

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The stress and electric fields around a mode‐III crack containing a dielectric medium are formulated. Mechanical equilibrium requires that the crack surfaces be traction free. Previous solutions have used the electrical boundary condition that the electric displacement component perpendicular to the crack surfaces should be zero. However, cracks that are filled with a dielectric medium, such as vacuum or air, require that the electric displacement be continuous across the crack faces. Using the boundary condition appropriate for an insulating crack, the stress, strain, and electric‐field strength are found to exhibit r−1/2 singularities while the electric displacement does not. The singularity in the electric‐field strength arises from piezoelectricity. The driving force for crack growth is only related to the effective level of applied stress. Under constant displacement, the applied field may increase or decrease the effective applied stress depending on its direction. As a result the electric field may promote or retard the crack propagation.
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62.20.M- Structural failure of materials
77.65.-j Piezoelectricity and electromechanical effects
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure

Characterization of electromigration‐induced mass divergences in multilayer interconnects by energy‐dispersive x‐ray spectroscopy

C.‐C. Lee, E. S. Machlin, and H. Rathore

J. Appl. Phys. 71, 5871 (1992); http://dx.doi.org/10.1063/1.350484 (6 pages)

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A nondestructive technique, based on energy‐dispersive x‐ray spectroscopy, was applied to characterize mass divergences in multilayer interconnects. The technique was used to reveal less than 0.5‐μm‐diam subsurface voids, precipitates, local changes in thickness of subsurface conducting layer, electromigration‐induced mass divergences at conjugate mass source and sink in both the Al‐Cu conducting layer and intermetallic compound overlayer, and a thin, hairline crack in the surface layer that is hardly visible in scanning electron microscopy.
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66.30.Qa Electromigration
85.40.Ls Metallization, contacts, interconnects; device isolation
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods

Roles of Ti‐intermetallic compound layers on the electromigration resistance of Al‐Cu interconnecting stripes

C.‐C. Lee, E. S. Machlin, and H. Rathore

J. Appl. Phys. 71, 5877 (1992); http://dx.doi.org/10.1063/1.350485 (11 pages) | Cited 11 times

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Various suggestions for the origin of the beneficial effect of TiAl3 layers on the electromigration resistance of Al‐Cu interconnect stripes have been evaluated experimentally. The leading candidate for this effect, the shunting of current through the intermetallic compound layer that spans opens (voids) in the Al‐Cu layer, cannot account for the correlation found in the present investigation between the median time to failure and the median rate of increase of electrical resistance in the Al‐Cu layer of different multilayer interconnect configurations. When the TiAl3 layer lies above the Al‐Cu conducting layer, the major enhancement of median lifetime to failure is an effect the TiAl3 layer has on the ‘‘electromigration resistance’’ of the Al‐Cu layer. This effect arises from the overlayer acting to decrease the rate of mass transport in the Al‐Cu layer rather than from any effect on the grain size or texture of the Al‐Cu layer. It is believed that the TiAl3 overlayer acts to produce triaxiality in the local stress fields developed at mass sinks and sources. This triaxiality of the stress field should act to increase the local yield strengths. A model analysis shows that the yield strengths required to reduce the mass flux by the observed amount are reasonable for a near triaxial state of stress. Only when the TiAl3 layer is below the Al‐Cu layer is it possible that shunting is the cause of the enhancement in the median time to failure relative to that for a single Al‐Cu interconnect layer.  
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66.30.Qa Electromigration
85.40.Ls Metallization, contacts, interconnects; device isolation
81.70.-q Methods of materials testing and analysis

Direct laser indiffusion of Ti into LiNbO3 single crystals

M. Bertolotti, M. Rossi, A. Ferrari, V. Craciun, I. N. Mihailescu, I. Ursu, G. N. Mikhailova, A. Dhaul, and R. Chander

J. Appl. Phys. 71, 5888 (1992); http://dx.doi.org/10.1063/1.350486 (4 pages) | Cited 7 times

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The successful indiffusion of Ti into single‐crystalline LiNbO3 substrates is reported as a result of high‐intensity ruby laser irradiation of LiNbO3 samples coated with films of Ti of 400 Å thickness. The experimental data are compared to the results of cw CO2 or Ar ion laser irradiations. We conclude that the Ti indiffusion process starts with the oxidation of Ti and continues in a liquid phase.
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66.30.J- Diffusion of impurities
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)

Ellipsometric measurements of the CoSi2 formation from very thin cobalt films on silicon

Sen‐Hou Ko, Shyam P. Murarka, and A. R. Sitaram

J. Appl. Phys. 71, 5892 (1992); http://dx.doi.org/10.1063/1.350487 (5 pages) | Cited 8 times

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Thin CoSi2 films (<80 nm) were formed by rapid thermal annealing of Co films sputtered on a single‐crystal Si substrate. The kinetics of the formation of CoSi2 from CoSi was followed by the use of ellipsometry. Mixed phases of CoSi and CoSi2 were created at temperatures of 600, 625, 650, and 675 °C. The ellipsometric response of these samples were simulated using a model of two layers of silicide on a silicon substrate. The refractive indices of CoSi and CoSi2 were measured separately and were found to be 3.2+i2.44 and 2.2+i1.34, respectively. The analyses of the data indicate that the phase transformation from CoSi to CoSi2 is diffusion controlled and the activation energy of the reaction in this temperature range is 1.78 eV.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
78.66.Bz Metals and metallic alloys
66.30.Ny Chemical interdiffusion; diffusion barriers

Dielectric properties of cement mortar as a function of water content

A. Berg, G. A. Niklasson, K. Brantervik, B. Hedberg, and L. O. Nilsson

J. Appl. Phys. 71, 5897 (1992); http://dx.doi.org/10.1063/1.350488 (7 pages) | Cited 19 times

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We have studied the dielectric properties of cement mortars, with water/cement ratios between 0.5 and 0.78, in the frequency range 10−3≤f≤107 Hz. The dielectric response can be modeled by an equivalent circuit incorporating electrode polarization and bulk conduction. The bulk dc conductance and the amplitude of a constant phase element describing the dispersive part of the bulk response display characteristic dependencies on the water content of the samples. The power‐law exponent of the constant phase element is independent of water content and can be related to the fractal dimension of the pore surfaces.
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66.10.Ed Ionic conduction
77.90.+k Other topics in dielectrics, piezoelectrics, and ferroelectrics and their properties (restricted to new topics in section 77)

Random successive nucleation model for simulating multiple fractal formation in a‐Ge/Au bilayer films

Dai‐mu Wang, Ya‐dun Zhao, and Zi‐qin Wu

J. Appl. Phys. 71, 5904 (1992); http://dx.doi.org/10.1063/1.350489 (4 pages) | Cited 5 times

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Multiple fractal formation in a‐Ge/Au bilayer films has been simulated by use of the random successive nucleation model in which cluster is grown by the random nucleation generation after generation and no long‐range diffusion is necessary. The random successive nucleation process is stimulated by the local temperature rise after releasing the latent heat during crystallization, if the short‐range effect from the nearby nuclei related to the interdiffusion and the strain energy release are lower than a certain level.
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68.55.-a Thin film structure and morphology
64.60.A- Specific approaches applied to studies of phase transitions
05.40.-a Fluctuation phenomena, random processes, noise, and Brownian motion

Epitaxial and interface properties of InAs/InGaSb multilayered structures

J. T. Zborowski, W. C. Fan, T. D. Golding, A. Vigliante, P. C. Chow, H. D. Shih, and J. M. Anthony

J. Appl. Phys. 71, 5908 (1992); http://dx.doi.org/10.1063/1.350490 (5 pages) | Cited 7 times

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We have used the technique of molecular beam epitaxy to grow InAs on GaSb, GaSb on InAs, and InAs/InxGa1−xSb (0≤x≤0.4) multilayered structures and have performed a detailed investigation of the layers and resultant interfaces. The structures were grown on (100) oriented GaSb or GaAs substrates. Combined reflection high energy electron diffraction, x‐ray photoelectron spectroscopy (XPS), and Auger electron spectroscopy (AES) studies indicate that Sb is persistently present on the InAs growth surface. XPS and AES analysis of InAs/GaSb heterojunctions indicates no compound formation at either the InAs/GaSb or GaSb/InAs interface. Secondary ion mass spectroscopy (SIMS) and XPS extinction profiles reveal the presence of approximately 5–10% As in the nominally pure GaSb layers. Analysis of InAs/GaSb/GaSb (100) structures by SIMS indicates that the As is incorporated during growth. The multilayer structures have been characterized by double crystal x‐ray diffraction and the data has been modeled using kinematic formulations. We find that the experimental data is fitted by assuming atomically abrupt composition changes across the interfaces.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.35.Fx Diffusion; interface formation

Elimination of misfit dislocations in Si1−xGex/Si heterostructures by limited‐area molecular‐beam epitaxial growth

A. Nishida, K. Nakagawa, E. Murakami, and M. Miyao

J. Appl. Phys. 71, 5913 (1992); http://dx.doi.org/10.1063/1.350440 (5 pages) | Cited 15 times

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Limited‐area molecular‐beam epitaxial growth of Si1−xGex films, on a Si substrate with patterned SiO2, has been studied in order to eliminate misfit dislocations in Si1−xGex/Si heterostructures. This method is found to dramatically reduce misfit dislocations in Si1−xGex films. Hence, a thicker Si1−xGex film can be grown, without introducing misfit dislocations, on a Si substrate with patterned SiO2 than on a Si substrate without patterned SiO2. This phenomenon is attributed to the blocking of misfit dislocation extension and to a partial relaxation of the residual strain in the boundary between the crystal and polycrystalline Si1−xGex film.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
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