Showing papers in "Journal of Applied Physics in 1987"
TL;DR: An improved description of copper and ironcylinder impact (Taylor) test results has been obtained through the use of dislocation-mechanics-based constitutive relations in the Lagrangian material dynamics computer program EPIC•2.
Abstract: An improved description of copper‐ and iron‐cylinder impact (Taylor) test results has been obtained through the use of dislocation‐mechanics‐based constitutive relations in the Lagrangian material dynamics computer program EPIC‐2. The effects of strain hardening, strain‐rate hardening, and thermal softening based on thermal activation analysis have been incorporated into a reasonably accurate constitutive relation for copper. The relation has a relatively simple expression and should be applicable to a wide range of fcc materials. The effect of grain size is included. A relation for iron is also presented. It also has a simple expression and is applicable to other bcc materials but is presently incomplete, since the important effect of deformation twinning in bcc materials is not included. A possible method of acounting for twinning is discussed and will be reported on more fully in future work. A main point made here is that each material structure type (fcc, bcc, hcp) will have its own constitutive beha...
1,718 citations
IBM1
TL;DR: In this paper, a modified version of the atomic force microscope is introduced that enables a precise measurement of the force between a tip and a sample over a tip-sample distance range of 30-150 A.
Abstract: A modified version of the atomic force microscope is introduced that enables a precise measurement of the force between a tip and a sample over a tip‐sample distance range of 30–150 A. As an application, the force signal is used to maintain the tip‐sample spacing constant, so that profiling can be achieved with a spatial resolution of 50 A. A second scheme allows the simultaneous measurement of force and surface profile; this scheme has been used to obtain material‐dependent information from surfaces of electronic materials.
1,405 citations
TL;DR: Plasma source ion implantation (PSII) as discussed by the authors is a new ion-implantation technique which has been optimized for surface modification of materials such as metals, plastics, and ceramics.
Abstract: Plasma source ion‐implantation (PSII) is a new ion‐implantation technique which has been optimized for surface modification of materials such as metals, plastics, and ceramics. PSII departs radically from conventional implantationtechnology by circumventing the line‐of‐sight restriction inherent in conventional ion implantation. In PSII, targets to be implanted are placed directly in a plasma source and then pulse biased to a high negative potential. A plasma sheath forms around the target and ions bombard the entire target simultaneously. Preliminary experiments have demonstrated that PSII: (1) efficiently implants ions to concentrations and depths required for surface modification, (2) produces material with improved microhardness and wear properties, and (3) dramatically improves the life of manufacturing tools in actual industrial applications. For example, the tool life of M‐2 pierce punches used to produce holes in mild steel plate has been increased by a factor of 80.
1,054 citations
TL;DR: In this paper, the light trapping properties of textured optical sheets have become of recent interest in photovoltaic energy conversion since light trapping allows a significant reduction in the thickness of active solar cell material.
Abstract: The light trapping properties of textured optical sheets have become of recent interest in photovoltaic energy conversion since light trapping allows a significant reduction in the thickness of active solar cell material. Previous analyses have concentrated on sheets with randomly textured (Lambertian) surfaces. The texturing of crystalline silicon substrates with anisotropic etches to give surfaces covered by square based pyramids defined by intersecting (111) crystallographic planes is a widely used technique for reflection control in silicon solar cells. This paper analyzes the light trapping properties of substrates with such pyramidally textured surfaces. Important differences are found from the case of Lambertian surfaces with practical consequences for the design of high efficiency silicon solar cells.
919 citations
TL;DR: In this article, the authors show that the exchange field of a thin exchange coupled ferromagnetic film reaches a limiting value no matter how large the exchange coupling is, due to domain wall formation in the antiferromagnet.
Abstract: The exchange field Hex transferred from a thick antiferromagnetic substrate to a thin exchange coupled ferromagnetic film is shown to reach a limiting value no matter how large the exchange coupling is. The limit is due to domain‐wall formation in the antiferromagnet. Numerical results based on a simple model for the interface are presented and compared to experimental results.
740 citations
TL;DR: In this article, it was shown that superlattices made of InAs−Ga1−xInxSb x∼0.4 have favorable optical properties for infrared detection.
Abstract: We show that strained type II superlattices made of InAs‐Ga1−xInxSb x∼0.4 have favorable optical properties for infrared detection. By adjusting the layer thicknesses and the alloy composition, a wide range of wavelengths can be reached. Optical absorption calculations for a case where λc∼10 μm show that near threshold the absorption is as good as for the HgCdTe alloy with the same band gap. The electron effective mass is nearly isotropic and equal to 0.04 m. This effective mass should give favorable electrical properties, such as small diode tunneling currents and good mobilities and diffusion lengths.
680 citations
TL;DR: In this paper, single-crystal TiN/VN strained-layer superlattices with layer thicknesses ranging from 0.75 to 16 nm have been grown on MgO(100 ) substrates by reactive magnetron sputtering and cross-sectional transmission electron microscopy (TEM) and x-ray diffraction examinations showed that the films were single crystals exhibiting coherent interfaces and several orders of super-lattice reflections.
Abstract: Single‐crystal TiN/VN strained‐layer superlattices (SLS’s) with layer thicknesses lTiN =lVN =λ/2 (where λ is the period of the superlattice) ranging from 0.75 to 16 nm have been grown on MgO(100 ) substrates by reactive magnetron sputtering. Cross‐sectional transmission electron microscopy (TEM) and x‐ray diffraction examinations showed that the films were single crystals exhibiting coherent interfaces and several orders of superlattice reflections. There was no evidence in either plan‐view or cross‐sectional TEM analyses of misfit interfacial dislocation arrays. The primary defects observed were dislocation loops with a diameter of 8–10 nm extending through several layers and small defects with a diameter of 1–2 nm that were confined within single layers. Microindentation hardness values H, measured as a function of λ in films with a total thickness of 2.5 μm, increased from 2035±280 kg mm−2 for Ti0.5V0.5N alloys (i.e., λ=0) to reach a maximum of 5560±1000 kg mm−2 at λ=5.2 nm and then decreased rapidly t...
677 citations
TL;DR: In this article, the buffing process orients the polymer's molecular chains in a manner similar to cold drawing of bulk polymer samples, and the formation of a liquid-crystal phase on the crystalline, oriented polymer surface is analogous to the epitaxial growth of conventional solid crystals.
Abstract: Smetic and nematic liquid‐crystal materials can be homogeneously aligned by buffed thin films of appropriate polymers. We propose that the buffing process orients the polymer’s molecular chains in a manner similar to cold drawing of bulk polymer samples. Experimental verification of this theory is obtained by measuring buffing‐induced birefringence in thin films of various polymers coated on glass. Further experiments establish that the oriented state of the polymer chains, and not scratching or grooving of the surface, is necessary to produce alignment. Alignment is found to occur when the polymer is both oriented and crystalline. A picture of alignment is presented in which the formation of a liquid‐crystal phase on the crystalline,oriented polymer surface is analogous to the epitaxial growth of conventional solid crystals.
605 citations
TL;DR: In this paper, Chen et al. report measurements of all the material constants necessary to fully characterize barium borate as a nonlinear optical material, including the crystal structure, the optical absorption, the refractive indices from the UV to the near IR, the thermo-optic coefficients, the non-linear optical or coefficients, resistance to laser damage, the elastic constants, the thermal expansion, thermal conductivity and dielectric constants, and the fracture toughness.
Abstract: We report measurements of all the material constants necessary to fully characterize barium borate as a nonlinear optical material. All data was taken on crystals supplied by Professor Chuangtien Chen, Fuzhou, People’s Republic of China. We have determined the crystal structure, the optical absorption, the refractive indices from the UV to the near IR, the thermo‐optic coefficients, the nonlinear optical or coefficients, the resistance to laser damage, the elastic constants, the thermal expansion, thermal conductivity and dielectric constants, and the fracture toughness. This data is used to evaluate barium borate for a variety of applications. We find that, in general, barium borate has a low acceptance angle, and that despite its higher optical nonlinearity, it is therefore not significantly more efficient than other commonly available materials, except in the UV below 250 nm. On the other hand, it has a high damage threshold, it is physically robust, it has good UV and IR transparency, and it has excellent average power capability. It permits deep UV generation, and has great potential for generating tunable visible and IR light as an optical parametric amplifier.
605 citations
TL;DR: In this article, the optical properties of glasses containing a small amount of thermally developed CdSexS1−x microcrystalline phase are studied with emphasis on quantum confinement effects exhibited at small crystallite size.
Abstract: The optical properties of glasses containing a small amount of thermally developed CdSexS1−x microcrystalline phase are studied with emphasis on quantum confinement effects exhibited at small crystallite size. Optical absorption, photoluminescence, x‐ray diffraction, and transmission electron microscopy are used to examine microcrystallites as a function of composition and development. Results are presented for a series of commercially available CorningR filter glasses with a selenium mole fraction in the range 0.28≤x≤0.74, as well as for several experimental glasses in which the average microcrystallite diameters range from 30 to 80 A. Optical effects observed in the experimental glasses that are due to electron and hole confinement are not present in the filter glasses considered; variations in optical properties of the filters are due to changes in stoichiometry of the CdSexS1−x mixed anion system. A brief discussion of other microcrystalline phases in glass is also presented. These microcrystallites show room‐temperature optical absorption structure analogous to bulk crystal excitons; the temperature dependence of this structure is contrasted with that resulting from quantum confinement in CdSexS1−x glasses.
564 citations
TL;DR: A scanning tunneling microscope (STM) can provide atomic-resolution images of samples in ultra high vacuum, moderate vacuum, gases including air at atmospheric pressure, and liquids including oil, water, liquid nitrogen, and even conductive solutions as mentioned in this paper.
Abstract: A scanning tunneling microscope (STM) can provide atomic‐resolution images of samples in ultra‐high vacuum, moderate vacuum, gases including air at atmospheric pressure, and liquids including oil, water, liquid nitrogen, and even conductive solutions. This review contains images of single‐crystal metals, metal films, both elemental and compound semiconductors, superconductors, layered materials, adsorbed atoms, and even DNA. A discussion of results on lithography leads into speculations on a bright future in which STMs may not only observe, but also manipulate surfaces, right down to the atomic level.
TL;DR: In this article, the acting slip mechanism for the generation of misfit dislocations in diamond-type-semiconductor heterostructures was investigated with transmission electron microscopy.
Abstract: The acting slip mechanism for the generation of misfit dislocations in diamond‐type–semiconductor heterostructures is investigated with transmission electron microscopy. It is shown that dissociation of the 60°‐mixed dislocations can lead to a difference in strain accommodation for tensile and compressive strain. A strain/thickness relation is obtained from the energy expression for nucleation of half‐loops. This relation is compared with other theoretical relations and with experimental strain data for Si/GaP(001) and In0.07Ga0.93As/GaAs(001) , measured with transmission electron microscopy and ion blocking.
TL;DR: In this paper, a phenomenological thermodynamic theory of PbTiO3 was developed using a modified Devonshire form of the elastic Gibbs free energy, which provided a way of predicting the intrinsic single domain dielectric and piezoelectric properties, which have not been completely determined from experimental measurements.
Abstract: A phenomenological thermodynamic theory of PbTiO3 was developed using a modified Devonshire form of the elastic Gibbs free energy. The spontaneous strain as a function of temperature was determined from pure sol‐gel derived PbTiO3 powder and used with selected data from the literature to determine the coefficients of the energy function. The theoretical prediction of the phase stability, spontaneous polarization and strains, and dielectric and piezoelectric properties agree well with experimental data. This theory provides a way of predicting the intrinsic single domain dielectric and piezoelectric properties of PbTiO3, which have not been completely determined from experimental measurements.
TL;DR: In this paper, a multistep potential approximation method was proposed to calculate quantum mechanical transmission probability and current across arbitrary potential barriers by using the multi-stage potential approximation, which is applicable to various potential barriers and wells, including continuous variations of potential energy and electron effective mass.
Abstract: This paper presents a simple method for accurately calculating quantum mechanical transmission probability and current across arbitrary potential barriers by using the multistep potential approximation. This method is applicable to various potential barriers and wells, including continuous variations of potential energy and electron effective mass. Various potential barrier structures and a hot‐electron transistor are analyzed to show the feasibility of this method.
TL;DR: In this article, the lattice constant, the lowest direct and indirect gap energies, and the refractive index of a quaternary lattice matched to GaSb and InAs were calculated using an interpolation scheme and the effects of compositional variations were properly taken into account in calculations.
Abstract: The methods for calculation of material parameters in compound alloys are discussed, and the results for AlxGa1−xAsySb1−y, GaxIn1−xAsySb1−y, and InPxAsySb1−x−y quaternaries lattice matched to GaSb and InAs are presented. These quaternary systems may provide the basis for optoelectronic devices operating over the 2–4‐μm wavelength range. The material parameters considered are: the lattice constant, the lowest direct‐ and indirect‐gap energies, and the refractive index. The model used is based on an interpolation scheme, and the effects of compositional variations are properly taken into account in the calculations. Key properties of the material parameters for a variety of optoelectronic device applications are also discussed in detail.
TL;DR: In this article, the intrinsic stresses of Al, Ti, Fe, Ta, Mo, W, Ge, Si, AlN, TiN, and Si3N4 films prepared by ion beam sputtering were investigated at low Td/Tm values.
Abstract: The intrinsic stresses of Al, Ti, Fe, Ta, Mo, W, Ge, Si, AlN, TiN, and Si3N4 films prepared by ion beam sputtering were investigated at low Td/Tm values. The intrinsic stress is compressive and its origin is explained in terms of the ion peening model. Knock‐on linear cascade theory of forward sputtering is applied to derive a simple scaling law with the film’s physical properties. The results show that the stress is directly proportional to the elastic energy/mole, given by the quantity Q=EM/(1−ν)D, where E is Young’s modulus, M the atomic mass, D the density, and ν Poisson’s ratio. Stress data taken from the literature for a variety of materials deposited by low‐pressure magnetron sputtering, and rf and ion beam sputtering also fit the correlation with Q. Furthermore, the model predicts a square‐root dependence on the incident ion energy, suggesting that the stress is momentum rather than energy driven.
TL;DR: In this paper, a general theory for the elastic interactions in a composite plate of layers with different relaxed planar dimensions is presented, and the experimental determination of the planar substrate strain is presented as a rigorous test of the correctness of the theory.
Abstract: A general theory is presented for the elastic interactions in a composite plate of layers with different relaxed planar dimensions. Solutions are obtained for the case of equivalent elastic properties and for the case of different elastic properties among the layers. Approximations for the case of thin films on a substrate lead to the governing equations for stresses in multilayered thin‐film systems. Finally, the experimental determination of the planar substrate strain, which is first order in the film/substrate thickness ratio, is presented as a rigorous test of the correctness of the theory.
TL;DR: Ferromagnetic resonance data indicate that the two inplane 〈110〉 directions are inequivalent and, together with magnetometry data, show that the average film magnetization decreases as the thickness decreases.
Abstract: Single‐crystal (100)Fe films 90–330 A thick have been grown on etch‐annealed (100)GaAs substrates by molecular‐beam‐epitaxy techniques. Ferromagnetic resonance data indicate that the two in‐plane 〈110〉 directions are inequivalent and, together with magnetometry data, show that the average film magnetization decreases as the thickness decreases. The inequivalence is attributed to the nature of the interface bonding at a (100) zinc‐blende surface. The decreased magnetization is attributed to the formation of Fe2As microclusters in the film due to As diffusion which is supported by Auger and electron diffraction studies. In general, the Fe films grown to date on etch‐annealed (100)GaAs substrates are significantly inferior to those grown on (110)GaAs.
TL;DR: In this paper, an improved boundary condition may be written simply in terms of the linear extrapolation length λ, whose inverse is the logarithmic gradient of the particle density at the boundary.
Abstract: Diffusion theory is often employed to calculate the effects of wall destruction on the local concentration of an active species immersed in a scattering gas. In many situations the spatial dependence of the concentration is given to a good approximation by the fundamental diffusion mode, and the local loss frequency can be calculated using the container’s fundamental mode diffusion length Λ. The additional assumption that the density of the active species may be taken to be zero at the container boundaries gives a value of Λ=Λ0 which depends only on the container dimensions, but use of Λ0 can be seriously in error if the diffusion mean free path λm is comparable to the dimensions, or if the particle reflection coefficient R becomes of significance. An improved boundary condition may be written simply in terms of the linear extrapolation length λ, whose inverse is the logarithmic gradient of the particle density at the boundary. The equation λ=2(1+R)λm/3(1−R) allows the representation of the full range of ...
TL;DR: In this paper, the magnetic forces involved in the interaction between a single-domain microtip and the sample surface magnetic domains were investigated and the influence of the experimental conditions on the performance of the atomic force microscope as a magnetic profiling device was discussed.
Abstract: We present a new way to observe the surface domain distribution of a magnetic sample at a submicrometer scale. This magnetic microscopy is based on the idea of measuring magnetic forces with the recently developed atomic force microscope (AFM). We study the magnetic forces involved in the interaction between a single‐domain microtip and the sample surface magnetic domains. The influence of the experimental conditions on the performance of the AFM as a magnetic profiling device is also discussed. Preliminary experimental results are reported.
TL;DR: In this paper, a theoretical and experimental study of the recrystallization behavior of polycrystalline silicon films amorphized by self-implantation was carried out and the crystallization behavior was found to be similar to the crystallisation behavior of films deposited in the amorphous state, however, a transient time was observed, during which negligible crystallization occurs.
Abstract: This paper presents a theoretical and experimental study of the recrystallization behavior of polycrystalline silicon films amorphized by self‐implantation. The crystallization behavior was found to be similar to the crystallization behavior of films deposited in the amorphous state, as reported in the literature; however, a transient time was observed, during which negligible crystallization occurs. The films were prepared by low‐pressure chemical vapor deposition onto thermally oxidized silicon wafers and amorphized by implantation of silicon ions. The transient time, nucleation rate, and characteristic crystallization time were determined from the crystalline fraction and density of grains in partially recrystallized samples for anneal temperatures from 580 to 640 °C. The growth velocity was calculated from the nucleation rate and crystallization time and is lower than values in the literature for films deposited in the amorphous state. The final grain size, as calculated from the crystallization param...
TL;DR: In this paper, the effective thermal conductivity of a particulate composite exhibiting a thermal contact resistance at interphase boundaries is considered, and two micromechanical models, the generalized selfconsistent scheme and the Mori-Tanaka theory [Acta Metall. 21, 571 (1973)] previously used in composite media with perfect interfaces, are generalized to allow for the phenomenon of thermal contact resistances between the constituents.
Abstract: The effective thermal conductivity of a particulate composite exhibiting a thermal contact resistance at interphase boundaries is considered. Two micromechanical models, the generalized self‐consistent scheme, and the Mori–Tanaka theory [Acta Metall. 21, 571 (1973)] previously used in composite media with perfect interfaces, are generalized to allow for the phenomenon of thermal contact resistance between the constituents. Spherical inclusions are considered and their interaction is approximately taken into account, so that the presented treatment is valid at nondilute concentrations. Both methods, distinctly different in their approach, result in the same closed‐form simple expression for the effective thermal conductivity.
TL;DR: In this paper, analytical expressions for the potential profile and sheath thickness of the transient ion-matrix sheath formed when a large negative step potential is applied to planar, cylindrical, and spherical electrodes immersed in a plasma.
Abstract: Analytic expressions have been obtained for the potential profile and sheath thickness of the transient ion‐matrix sheath which forms when a large negative step potential is applied to planar, cylindrical, and spherical electrodes immersed in a plasma.
TL;DR: In this paper, the capability of the atomic force microscope to image the surface of an electrically insulating solid with atomic resolution was demonstrated, including graphite and molybdenum disulfide.
Abstract: We have demonstrated the capability of the atomic force microscope to image the surface of an electrically insulating solid with atomic resolution. Images of highly oriented pyrolytic boron nitride taken in air show atomic corrugations with a lateral resolution better than 3 A. Low‐noise images of graphite and molybdenum disulfide are also presented.
TL;DR: A novel method of checking on the numerical accuracy with which the algorithm solves the transport equations is presented, based on the results of two‐dimensional computer simulations of streamer initiation and propagation in atmospheric pressure N2.
Abstract: We present the results of two‐dimensional computer simulations of streamer initiation and propagation in atmospheric pressure N2. The simulation algorithm makes use of flux‐corrected transport techniques and was used as a tool to study the solutions of the transport equations under conditions suitable for streamers, for which realistic analytic solutions are not known. We present and discuss conclusions about streamer transport based on the results of these studies. Finally, we present a novel method of checking on the numerical accuracy with which the algorithm solves the transport equations.
TL;DR: In this paper, a current transfer model is proposed in which weak conduction along the c axis plays a role in limiting critical-current density at grain boundaries, and the effect of intrinsic conduction anisotropy is discussed.
Abstract: Measurements of the transport critical‐current density (Jc), magnetization Jc, and magnetoresistance in a number of bulk sintered samples of Y1Ba2Cu3Ox from several different laboratories indicate that the transport Jc is limited by weak‐link regions between high Jc regions. The weak‐link Jc has a Josephson character, decreasing by two orders of magnitude as the magnetic field is increased from 0.1 to 10 mT at 77 K. An examination of the grain‐boundary region in Y1Ba2Cu3Ox shows no observable impurities or second phases to the scale of the [001] lattice planes (∼12 A). The effect of intrinsic conduction anisotropy is discussed. A current‐transfer model is proposed in which weak conduction along the c axis plays a role in limiting Jc at grain boundaries. Orienting the grains in the powder state during processing may result in enhanced transport Jc in bulk conductors.
TL;DR: In small external fields such double layers order antiparallel with their magnetization perpendicular to the external field in analogy to the spin‐flop phase of antiferromagnets, revealed by the behavior of the static magnetization of such samples as a function of external field and the spectrum of spin‐wave modes with the wave vector parallel to a small external field.
Abstract: Double layers of (100)‐oriented Fe with an individual thickness of ≊100 A, separated by interlayers of Cr or Au with variable thickness were grown epitaxially on Au (100) surfaces. The spin‐wave mode spectra of these double layers as detected by means of light scattering were used to measure the effective exchange coupling of the Fe films across the interlayer. For Au interlayers it decreases monotonically with increasing Au thickness dAu and disappears at dAu≳20 A. For Cr interlayers of proper thickness dCr, i.e., 4 A≲dCr≲9 A we obtain antiferromagnetic coupling of the Fe layers. In small external fields such double layers order antiparallel with their magnetization perpendicular to the external field in analogy to the spin‐flop phase of antiferromagnets. This is revealed by the behavior of the static magnetization of such samples as a function of external field and the spectrum of spin‐wave modes with the wave vector parallel to a small external field.
TL;DR: In this paper, the authors measured the coupling of two optical beams in strontium-barium niobate crystals and determined the photorefractive properties: the effective density, sign, and spectral response of the dominant charge carrier, the grating formation rate, dark conductivity, and carrier diffusion length.
Abstract: We have grown and optically characterized strontium‐barium niobate crystals, including both undoped and cerium‐doped crystals having two different Sr/Ba ratios (61/39 and 75/25). By measuring the coupling of two optical beams in the crystals, we have determined the following photorefractive properties: the effective density, sign, and spectral response of the dominant charge carrier, the grating formation rate, dark conductivity, and carrier diffusion length. We find that electrons are the dominant photorefractive charge carriers in all of our samples; the typical density of photorefractive charges is ∼1×1016 cm−3 in the undoped samples. The grating formation rate increases with intensity, with a slope of ∼0.3 cm2/(W s) over an intensity range of ∼1–15 W/cm2 in undoped samples. Cerium doping improves both the charge density (increased by a factor of ∼3) and the response rate per unit intensity (∼5 times faster).
TL;DR: In this paper, a new type of vector finite-element approximation function is introduced that interpolates not to point values of each component of vector potential, but rather to the tangential projection of the vector potential on each edge of tetrahedral finite elements.
Abstract: Finite‐element vector potential solutions of three‐dimensional magnetic field problems are usually obtained by approximating each component of the vector potential by a separate set of scalar finite‐element approximation functions and by imposing continuity conditions between elements on all three components This procedure is equivalent to imposing continuity of both the normal and the tangential components of the vector potential We show in this paper that this procedure is too restrictive: While continuity of the tangential component of the vector potential is required, continuity of the normal components is not essential in the variational formulation We introduce a new type of vector finite‐element approximation function that has the property that it interpolates not to point values of each component of vector potential, but rather to the tangential projection of the vector potential on each edge of tetrahedral finite elements With the new basis functions, continuity of the normal component of the vector potential is provided only approximately by means of the natural interface conditions inherent in the variational procedure This results in a more efficient procedure for the solution of three‐dimensional magnetostatic field problems than is obtained by enforcing normal component continuity exactly
TL;DR: In this paper, the decay of excess minority carriers produced in a silicon wafer of thickness d by a laser pulse is analyzed, and a comprehensive theory based on this analysis is presented for the determination of bulk lifetime Tau(b) and surface recombination velocity S.
Abstract: The decay of excess minority carriers produced in a silicon wafer of thickness d by a laser pulse is analyzed. A comprehensive theory based on this analysis is presented for the determination of bulk lifetime Tau(b) and surface recombination velocity S. It is shown that, starting with an exponential spatial profile, the carrier profile assumes a spatially symmetrical form after approximately one time constant of the fundamental mode of decay. Expressions for the spatial average of the carrier density as a function of time are derived for three temporal laser pulse shapes: impulse, square, and Gaussian. Particular attention is paid to the time constants of the fundamental and higher modes of decay. The ratios of the time constants of the higher modes to the fundamental mode, as well as the time constant of the fundamental mode, are presented over wide ranges of values of S and d. For Sd less than about 40 sq cm/s, a two-wafer method is developed to determine Tau(b) and S; it is also shown that the requirement of d/Tau(b) greater than about 20S is sufficient to adequately guarantee that the asymptotic value of the instantaneous observed lifetime differs from the bulk lifetime by no more than 10 percent.