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Journal of Applied Physics

Issue 6 • Date Sep 1992

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Displaying Results 1 - 25 of 69
  • Issue Table of Contents

    Page(s): toc1
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    Freely Available from IEEE
  • Microcircuit imaging using an ion‐beam‐induced charge

    Page(s): 2097 - 2104
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    Ionizing radiation such as photons, keV electrons, or MeV ions can generate electron‐hole pairs in semiconducting material. The high penetrating power of MeV light ions allows them to generate electron‐hole pairs from deep within intact microelectronic devices, so images can be formed of the device active areas with very little degradation of the spatial resolution of the focused MeV ion beam. Furthermore, the ion‐beam‐induced charge (IBIC) image contrast is not strongly affected by the energy loss through the overlying device layers. This article is the first to demonstrate the capability of a nuclear microprobe to generate IBIC images of the active regions of devices through the passivation and metallization layers. The effect of the carrier generation volume on IBIC resolution is assessed. The ability of IBIC to align the major crystal axes of semiconductor samples is shown, and the effect of ion‐induced damage on IBIC image contrast is considered. View full abstract»

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  • A study of the coupling efficiency versus grating periodicity in a normal incident GaAs/AlGaAs multiquantum well infrared detector

    Page(s): 2105 - 2109
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    A detailed study of the dependence of coupling quantum efficiency on the grating periodicity of planar metal grating coupled GaAs/AlGaAs quantum well infrared photodetectors has been made in this work. Five different detector samples with grating periodicities of Λ=1.1, 3.2, 5, 7, and 10 μm have been fabricated for the present study. The results showed that the device with a 5 μm grating periodicity gave the best front‐side coupling efficiency, which was in good agreement with our theoretical prediction. A single pass quantum efficiency (η) of 11% was achieved for the front‐side illumination at λp=9.8 μm and T=77 K. View full abstract»

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  • Influence of the axially varying quasi‐Fermi‐level separation of the active region on spatial hole burning in distributed‐feedback semiconductor lasers

    Page(s): 2110 - 2118
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    The longitudinal‐mode characteristics of distributed‐feedback semiconductor lasers subjected to longitudinal spatial hole burning have been investigated using an improved numerical modeling scheme. The main new feature of the model is that it allows for the natural axial variations of the separation between the quasi‐Fermi levels (Fermi voltage) in the laser’s active region. This gives rise to a current density injected into the active region that varies along the laser axis, even for uniformly biased lasers. It is found that compared to the results obtained by assuming an uniform current density, the detrimental influence of the longitudinal spatial hole burning on important static characteristics of quarter‐wave‐shifted distributed‐feedback lasers, such as the gain margin and the lasing wavelength stability, is weakened. Therefore, the usual assumption of an uniform injected current density gives rise to an overestimated influence of the spatial hole burning, this overestimation being more important for long‐cavity lasers having a grating structure with a large coupling coefficient. View full abstract»

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  • Estimation of the reliability of 0.98 μm InGaAs/GaAs strained quantum well lasers

    Page(s): 2119 - 2124
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    A reliability study has been made on 0.98 μm InGaAs/GaAs strained quantum well ridge waveguide lasers for pumping erbium‐doped fiber optical amplifiers (EDFAs). Analysis of a constant power long‐term aging test over 104 h shows that the degradation rate is proportional to the square root of the aging time irrespective of operating output power. A simple relationship is found between degradation rate and both operation current density and optical density. The change in light‐current characteristics and emission wavelength during constant current aging are also investigated. It is found that emission wavelength exhibits a blue shift for an identical operation current accompanied by laser degradation due to an increased threshold carrier density. In constant‐power mode aging, on the other hand, the shift is found to be rather complicated because of an additional factor of an increase in junction temperature causing a red shift. The influence of the wavelength shift on amplification characteristics in EDFAs is also discussed. View full abstract»

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  • Reflectivity and transmission of amorphous thin films at the melting temperature

    Page(s): 2125 - 2130
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    A method to evaluate the evolution of the optical properties (reflectivity and transmission) of thin solid films as a function of temperature has been developed. A pulsed Ar+ laser focused on the sample surface to a 1/e‐beam radius of 4 μm is used as a local heat source while the optical properties of the irradiated surface are monitored in real time by means of another laser focused to 1.7 μm. The use of laser pulses combined with real time optical measurements provides a suitable means to determine accurately the optical properties of thin‐film materials for temperatures up to the melting point. In addition, the irradiation pulse can be sufficiently shortened to avoid crystallization prior to melting in the case of amorphous films and therefore the optical properties of amorphous films up to the melting point can be also determined. The analysis of the optical transients with a simple thermal model allows either the determination of the thermal conductivity of a transparent substrate if the film melting temperature is known or the film melting temperature if the thermal properties of the substrate are well characterized. The results obtained in Ge and Si amorphous thin films prove the accuracy of the method and the melting temperature of amorphous Ge is determined to be 987 K. View full abstract»

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  • High‐power single‐mode AlGaAs lasers with bent‐waveguide nonabsorbing etched mirrors

    Page(s): 2131 - 2135
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    A nonabsorbing etched mirror structure for AlGaAs single‐quantum‐well graded‐refractive‐index separate‐confinement heterostructure ridge lasers is analyzed with respect to mirror coupling coefficient, threshold current penalty, and far‐field pattern. Measurements of the mirror temperature showed a reduction from 50 to 20 K at 30 mW optical power depending on the degree of overlap of the optical intensity with the absorbing bent‐waveguide profile. Pulsed catastrophic optical damage power levels up to 400 mW and a thermally saturated cw power of 165 mW with single‐mode operation up to 80 mW have been achieved. Lifetime measurements at 40 mW constant optical power indicated degradation rates ≤10-5/h comparable to AlGaAs lasers with cleaved and coated mirrors. View full abstract»

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  • The formation of jets from shaped charges in the presence of asymmetry

    Page(s): 2136 - 2143
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    The jet from a nominally axisymmetric shaped charge is formed by the collapse of the typically conical liner under the high pressures resulting from detonation of the explosive around it. Where asymmetries are present the velocities imparted to the elements of the liner at a given axial distance from the cone tip will vary as a function of the azimuthal angle among other variables. In general these elements will not meet at all. Conversely a pair of liner elements that do meet will in general have started from different axial positions, and will meet away from the nominal axis of symmetry of the charge. This effect renders the formation process asymmetrical. Consequently the jet particles have an off‐axis velocity component which can substantially degrade the penetrative capability of the charge. A complete analysis of asymmetrical liner collapse and jet formation is presented for the case where the liner is axisymmetric, but there is an azimuthal variation in liner projection velocity. The classical analysis of symmetric liner collapse and jet formation is extended to include this type of asymmetry. Earlier work on linear shaped charges, particularly a model for asymmetric jet formation, is drawn upon to consider plane sections of the liner individually. A fully three‐dimensional analysis is then achieved by the combination of the results for these sections. This analysis is implemented in a computational model and example results are presented and compared in as far as is possible and meaningful with previous theoretical and experimental results. Good agreement with the previous theoretical work is obtained, and the values of the off‐axis velocity components predicted are of the orders observed in the limited experimental data as yet available. View full abstract»

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  • Faraday rotation of spontaneous magnetization in a laser‐produced plasma from solid target

    Page(s): 2144 - 2148
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    Interaction of elliptically polarized laser radiation with plasma produced from a solid target generates magnetic fields simultaneously along axial and transverse directions. The axial magnetic field induces the plane of polarization of the incident laser beam to rotate due to the Faraday effect. Numerically the Faraday rotation has been calculated for interaction of Nd glass laser (λ=1.06 μm) in the subdense plasma in which the plasma density, temperature, and self‐generated magnetic field vary in the axial direction. View full abstract»

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  • Filamentation instability of an electromagnetic wave in an expanding plasma

    Page(s): 2149 - 2151
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    A laser beam propagating at an angle to the density gradient in an expanding plasma is susceptible to filamentation instability. For a linear density profile and self consistent temperature and expansion velocity profiles, the amplitude of the perturbation grows as an Airy function with the distance of propagation. The characteristic growth length decreases with the size of perturbation and the ratio of expansion velocity to sound velocity. It increases the angle laser k vector makes with the density gradient. Moreover, the growth length does not always increase with θ0: it depends on vb(0). The spatial growth of perturbation of larger size starts occurring deeper into the plasma. View full abstract»

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  • Crystal structure and electron microprobe analyses of a lanthanum lutetium gallium garnet

    Page(s): 2152 - 2155
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    Single‐crystal electron microprobe analysis of a lanthanum lutetium gallium garnet has resulted in a composition of La2.37Nd0.07Pb0.01Lu2.54Cr0.01 Ga3.00O12. This composition gives better agreement between observed and calculated total dielectric polarizabilities than previously reported compositions (La2.26–2.32Nd0.04Lu2.57–2.63Ga3.07O12 by x‐ray fluorescence and La2.655Nd0.027Lu2.656Ga2.655O12 by inductively coupled plasma analyses), and does not imply the crystal‐chemically improbable presence of Lu3+ in the tetrahedral site. X‐ray and neutron crystal‐structure analyses have confirmed that little or no Lu resides in this site. View full abstract»

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  • Interaction of a dislocation with an elliptic hole or rigid inclusion in an anisotropic material

    Page(s): 2156 - 2163
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    Two‐dimensional problem of a dislocation interacting with an elliptic hole or rigid inclusion in an anisotropic medium is considered. Closed‐form solutions of the displacements and stresses are obtained. Explicit expressions for the interaction energy are given. For dislocations very near to the elliptic boundary, it is shown that the level curve of the interaction energy is geometrically similar to the elliptic boundary regardless of the types of the dislocations. For dislocations very far from the elliptic boundary, real‐form expressions for interaction energy are obtained. The degenerate case of a crack or a rigid line inclusion is also discussed. View full abstract»

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  • The elastic interaction between a moving screw dislocation and a crack

    Page(s): 2164 - 2166
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    We investigate the elastic interaction between a moving screw dislocation and a crack. The stress intensity factor at the crack tip decreases with the increasing velocity of the screw dislocation. This implies that the shielding effect of the moving screw dislocation on crack propagation is reduced. The image force on the moving screw dislocation arising from the crack surface decreases with the increasing velocity of the screw dislocation itself. Finally, Newton’s third law is not valid in the system. View full abstract»

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  • Defect levels in H+‐, D+‐, and He+‐bombarded silicon

    Page(s): 2167 - 2173
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    Defect levels produced by H+, D+, and He+ bombardment of silicon with different phosphorus doping and oxygen content were investigated using transient capacitance spectroscopy. After He+ implantation only pure damage defect levels occur, whereas after H+ and D+ implantation additional hydrogen‐related defects are observed. For vacancy‐related defects both the peak concentration and the halfwidth of the profiles depend only on the Fermi energy. The profiles were found to be broader than the theoretical vacancy distribution. The broadening which increases with decreasing doping level is explained by a model based on electric‐field‐enhanced diffusion. The production behavior of the defects shows a linear dependence of the sheet concentration on the ion dose for vacancy‐related defects and a quadratic dependence for the hydrogen related defect E(0.30). This defect is tentatively identified as the (H‐V) pair. View full abstract»

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  • Theoretical study of laser heating and dissociation reactions in solids using ultrafast time‐resolved x‐ray diffraction

    Page(s): 2174 - 2178
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    A theory of ultrafast time‐resolved x‐ray diffraction is presented. We show that for the case in which vibrational relaxation is fast, the x‐ray diffraction intensities in pulse laser heating are determined by the Debye–Waller factor. We also show how the scattering intensities of the diffraction spots change with the position of the dissociating atoms in a time‐resolved x‐ray diffraction experiment studying dissociation reactions in solids. Our results show that the scattering intensities change in both the fully dissociated and the partially dissociated cases, and that time‐resolved x‐ray diffraction could be a useful tool in probing dissociation reactions in solids. View full abstract»

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  • MeV B compensation implants into n‐type GaAs and InP

    Page(s): 2179 - 2184
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    High energy B implantations were performed into n‐type GaAs and InP at room temperature in the range of energies from 1 to 5 MeV and fluences from 1011 to 1016 cm-2. The material did not become amorphous for any of the fluences used. Buried layers with resistivities as high as 108 Ω cm and 106 Ω cm were obtained in GaAs and InP, respectively, after heat treatments. The breakdown voltages corresponding to the highest resistivities are 80 and 35 V, respectively, in GaAs and InP. In GaAs, the Rutherford backscattering analysis on the annealed samples showed an aligned yield close to that of a virgin sample, whereas, the yield in InP is more than that of the as‐implanted sample. View full abstract»

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  • Oxide defects originating from Czochralski silicon substrates

    Page(s): 2185 - 2191
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    Oxide defects originating from Czochralski silicon substrates are characterized. It is shown that oxide defect density is significantly large for the oxide thickness range of 20–200 nm. This noteworthy feature is valid for dry oxidation and HCl oxidation alike. It is considered that small defects in the silicon substrate surface layer are introduced into the growing oxides during thermal oxidation and that the small defects in oxides provide conductive paths across the oxides. The origin of the small defects is not known at present. A simple model is proposed in an effort to show the relation between the size and density of the small defects. The oxide thickness dependence data of oxide defect density are characterized in terms of the small‐defect behaviors. The relationship between the small‐defect size L and the density ρ in the Cz‐Si substrates is shown as ρ=ρ0 exp(-L/L0), where ρ0=107 cm-3 and L0=48 nm. In addition, oxide surface etching of thick oxides followed by oxide defect evaluation of the thinned oxides reveals that even thick oxides with seemingly low oxide density contain many small defects. The small defect density in 130 nm oxides is estimated as 120 cm-2. View full abstract»

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  • SiO2 precipitate strain relief in Czochralski Si: Self‐interstitial emission versus prismatic dislocation loop punching

    Page(s): 2192 - 2196
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    Formation of SiO2 precipitates in Czochralski Si is associated with a volume expansion of more than 100%. The needed extra volume for precipitate growth to occur is primarily supplied by emission of Si self‐interstitials (I) into the Si matrix, in balance with a compressive growth residual strain. During cooling after the anneal, an additional compressive cooling strain component also develops because of the different thermal expansion coefficients of SiO2 and Si. For precipitates grown to a sufficiently large size, the growth residual strain and/or the cooling strain can be further relieved by punching interstitial type prismatic dislocation loops into the Si matrix. Otherwise, only I emission can occur. Up to now, there have been no quantitatively determined strain values, which constitute in a given experiment a measure of the I emission efficiency on the one hand, and a basis for determining whether prismatic punching can also occur on the other. In this study, we have calculated the strain values and obtained a quantitative criterion for prismatic punching to occur. In the order of ∼10-3–10-2, the growth residual strain component values indicate that I emission has attained an efficiency of relieving the precipitate growth strain by ∼90%–99%. Available experimental data on the precipitate size dependence of prismatic dislocation loop punching have been satisfactorily fitted using the obtained strain values and the punching criterion, indicating that these calculated values are in acceptable accuracy ranges. View full abstract»

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  • Nondestructive determination of damage depth profiles in ion‐implanted semiconductors by multiple‐angle‐of‐incidence single‐wavelength ellipsometry using different optical models

    Page(s): 2197 - 2201
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    Several‐parameter fitting of multiple‐angle‐of‐incidence ellipsometry data is developed to characterize near‐surface layers on semiconductors damaged by implantation. The damage depth profiles were described by either rectangular, trapezoid‐type, or coupled half‐Gaussian (realistic) optical models. The rectangular model has three parameters: the average damage level and effective thickness of the implanted layer, plus the thickness of the native oxide. The trapezoid‐type model is enhanced with a fourth parameter, the width of the back (a/c) interface. The realistic optical model consists of a stack of layers with fixed and equal thicknesses and damage levels determined by a depth profile function (presently the coupled half‐Gaussians). Five parameters were used: the center, the height, and two standard deviations of the profile, plus the thickness of the native oxide. The complex refractive index of each layer is calculated from the actual damage level by the Bruggeman effective medium approximation. The method was tested on Ge‐implanted silicon layers (at a wavelength of 632.8 nm) and was cross checked with high depth resolution Rutherford backscattering spectrometry and channeling. View full abstract»

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  • Temperature dependence of elastic nonlinearities in single‐crystal gallium arsenide

    Page(s): 2202 - 2208
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    The six third‐order elastic moduli (TOEM) of single‐crystal gallium arsenide were determined by a combination of measurements of ultrasonic second‐harmonic generation, and pressure dependence of the second‐order elastic moduli, at room temperature. In the temperature range 77–300 K, the nonlinearity parameter for the propagation directions [100], [110], and [111] was measured. Utilizing the Keating model, these data were used in evaluating all six TOEM as a function of temperature. The TOEM C111, C144, and C456 turn out to be nearly constant in the above temperature range. The Cauchy relations seem to be obeyed somewhat better as 0 K is approached. The measured values of the TOEM have been employed in calculating a Murnaghan equation of state, which predicts a somewhat higher volume change than the measured one. The elastic Grüneisen constants deduced from the TOEM are in reasonable agreement with the thermal ones in the high‐temperature limit. View full abstract»

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  • The effect of superdislocation on fracture: Dislocation‐free zone in the front of a semi‐infinite crack tip

    Page(s): 2209 - 2214
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    The effect of superdislocation on mode II or mode III fracture has been investigated. The plastic zone between a semi‐infinite crack tip and a superdislocation with a dislocation‐free zone is simulated by a continuous dislocation distribution. The dislocation distribution functions in the crack and plastic zone are analytically derived. A close form of the number of dislocations in the plastic zone and stress field along the x axis are obtained. From the stress field, the stress intensity factor KIII at the crack tip and stress concentration at the superdislocation are available. When the distance between crack tip and superdislocation is larger than the plastic zone size, the stress intensity factor is proportional to the square root of plastic zone size KIII, but is inversely proportional to the distance between crack tip and superdislocation. On the other hand, when the distance between crack tip and superdislocation is almost the same as the plastic zone size, the stress intensity factor is inversely proportional to the square root of distance between crack tip and superdislocation. It is also found that the applied stress is determined by the superdislocation. Finally, our results can be reduced to several special cases. View full abstract»

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  • Interaction of an edge dislocation with an interfacial crack

    Page(s): 2215 - 2226
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    The stress and displacement fields of an edge dislocation near a semi‐infinite or a finite interfacial crack are formulated by using the complex potential theory of Muskhelishvili’s elasticity treatment of plane strain problems. The image forces exerted on the dislocation have an oscillatory character (with respect to the dislocation position) if the dislocation is originated elsewhere and moves to the vicinity of a finite interfacial crack. There is no such oscillation of image forces if the edge dislocation is emitted from the finite interfacial crack or if the crack is semi‐infinite. The stress intensity factors produced by the edge dislocation also have an oscillatory character for both semi‐infinite and finite interfacial cracks. They also depend on whether the dislocation is emitted from the crack or comes from elsewhere. View full abstract»

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  • Electromigration‐induced drift failure of via contacts in multilevel metallization

    Page(s): 2227 - 2231
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    Much effort has been expended to improve metal sidewall coverage of via contacts in multilevel metallization schemes because of the possibility of an enhanced rate of electromigration failure at the sidewall. Multilayered conductors, which incorporate a refractory material beneath an Al alloy layer, will be more resistant to these voiding failures. These metallizations are not ideal, however, because of the discontinuities in the flux of electromigrating atoms at the Al/refractory interfaces of the via, which render the interfaces vulnerable to voiding. This paper examines the relative importance of electromigration at the sidewall and metal interface of vias containing AlSiCu/TiN multilayer conductors. Our results demonstrate that voiding failure is not associated with poor metal step coverage, and that the interface between the metal levels is the region most vulnerable to voiding. Formation of voids between the metal levels occurs by drift of the Al layer away from the Al/TiN interface, and there is a strong dependence of failure on the direction of electron flow through the via. This directional dependence arises because the Al drift velocity is determined by the current density in the stripes attached to the via. We present an expression for the via failure time that incorporates the stripe current density. View full abstract»

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  • Marker and radioactive silicon tracer studies of PtSi formation

    Page(s): 2232 - 2241
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    Marker and radioactive 31Si experiments have been performed to investigate atomic diffusion during PtSi formation. The marker work used a thin metallic layer (Ti, Co, Ni) as a marker. Analysis of the marker displacement indicated growth dominated by silicon diffusion (∼90%). The interpretation of data from the radioactive tracer experiments is less clear cut. However, when examined in conjunction with the marker results, it would appear that either PtSi growth took place by silicon substitutional diffusion or by a mixed interstitial mechanism (i.e., a mixture of interstitial and interstitialcy diffusion). Arguments are presented to suggest that silicon vacancy diffusion during silicide growth is the most likely mechanism. This interpretation is found to be generally consistent with other recently published work on PtSi formation. View full abstract»

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  • The energy of finite systems of misfit dislocations in epitaxial strained layers

    Page(s): 2242 - 2248
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    Previous approaches to calculating the energy of a system of misfit dislocations in epitaxial strained layers have assumed that the system is infinite in the plane of the epitaxial interface and that the dislocations are uniformly spaced. Here a method is presented which is capable of dealing with finite systems of nonuniformly spaced dislocations of the type observed experimentally. The principle of the method is to explicitly account for the interactions between pairs of misfit dislocations. When the dislocations are infinite and uniformly spaced the present approach is shown to be equivalent to an earlier exact treatment. The present approach applied to finite systems of uniformly spaced dislocations shows that the energy per unit area converges to that of the infinite system very slowly; particularly when the spacing of the dislocations is less than the thickness of the epitaxial layer. Typically, systems must be larger than 30×30 dislocations for their energy per unit area to be within 10% of that of the infinite system. Similarly the infinite system will overestimate the energy of a 10×10 array by about 30%. View full abstract»

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Aims & Scope

Journal of Applied Physics is the American Institute of Physics' (AIP) archival journal for significant new results in applied physics

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Editor
P. James Viccaro
Argonne National Laboratory