Dale Barkey - Profile on Academia.edu (original) (raw)
Papers by Dale Barkey
Pattern Formation in Anodic Aluminum Oxide Growth by Flow Instability and Dynamic Re-Stabilization
ECS transactions, Dec 17, 2019
The viscous flow of oxide driven by the electrostriction force during growth of anodic aluminum o... more The viscous flow of oxide driven by the electrostriction force during growth of anodic aluminum oxide is treated by linear stability analysis and scale analysis. It is shown that a uniform oxide film is unstable to a periodic deformation. The re-stabilization of pore growth is examined by scale analysis of the steady pore diameter. The pattern spatial period and pore radius predicted by the analysis is compared with experimental observations reported in the literature.
Corrosion of Steel Reinforcement in Concrete Adjacent to Surface Repairs
American Concrete Institute, Journal of, 2004
Reinforced concrete may be damaged by chloride-induced corrosion of steel reinforcement, resultin... more Reinforced concrete may be damaged by chloride-induced corrosion of steel reinforcement, resulting in spalling and delamination as corrosion products accumulate. A surface repair entails removal of damaged concrete and its replacement with repair material. The resulting inhomogeneity between the repair material and remaining chloride-contaminated concrete, however, may produce active-passive corrosion macrocells that drive rapid anodic dissolution of the metal. This experimental study was conducted to characterize the geometry, current distribution, and controlling resistance of corrosion macrocells driven by differences in the electrochemical environment in repair material and contaminated concrete. Additional influences such as galvanic contact between the test reinforcement bar and remote cathode bars were also considered. The tests were based on ASTM G 109, with modifications to incorporate simulated repairs.
Influence of Additives on the Growth Velocity and Morphology of Branching Copper Electrodeposits
Journal of The Electrochemical Society, 2005
... SK Chawla, Polyhedron, 18, 1397 (1999). GB McFadden, SR Coriell, TP Moffat, D. Josell, D. Whe... more ... SK Chawla, Polyhedron, 18, 1397 (1999). GB McFadden, SR Coriell, TP Moffat, D. Josell, D. Wheeler, W. Schwarzacher, and J. Mallet, A Mechanism for Brightening, J. Electrochem. ... MAPasquale, SL Marchiano, and AJ Arvia, J. Electroanal. Chem., 532, 255 (2002). ...
Journal of The Electrochemical Society, 2005
Through-chip electrodes for three-dimensional packaging can offer short interconnection and reduc... more Through-chip electrodes for three-dimensional packaging can offer short interconnection and reduced signal delay. Formation of suitable vias by electrodeposition into cavities presents a filling problem similar to that encountered in the damascene process. Because via dimensions for through-chip filling are larger and have a higher aspect ratio relative to features in damascene, process optimization requires modification of existing superconformal plating baths and plating parameters. In this study, copper filling of high-aspect-ratio through-chip vias was investigated and optimized with respect to plating bath composition and applied current wavetrain. Void-free vias 70 m deep and 10 m wide were formed in 60 min using additives in combination with pulse-reverse current and dissolved-oxygen enrichment. The effects of reverse current and dissolved oxygen on the performance of superfilling additives is discussed in terms of their effects on formation, destruction, and distribution of a Cu͑I͒ thiolate accelerant.
Adsorption of Benzyl Viologen Dichloride and Its Displacement By 3-Mercapto-1-Propanesulfonate during Copper Electrodeposition
Meeting abstracts, 2017
PhDT, Aug 1, 1987
Studies on high-speed electroforming were undertaken to evaluate the potential for electroforming... more Studies on high-speed electroforming were undertaken to evaluate the potential for electroforming at rates comparable to those of mechanical forming. A rotating cylindrical cathode was used to provide intense turbulent convective transport. Transport in the cylindrical cell equipped with radial baffles was characterized by direct measurement of limiting currents of high rate copper deposition. Copper electroforms of thicknesses of several hundred micrometers were produced by deposition at rates of up to 7.5 A/cm 2 corresponding to 160~-tm per minute. A quantitative theory of morphological stability, accounting for transport, kinetic and ohmic effects, was formulated for copper deposition at high rates. Surfaces of deposits produced in the electroforming experiments were charaterized by surface profilometry, and digitallized profiles were analyzed by Fourier transform for comparison with predictions of the stability theory. Decrease in roughness protrusion spacing with both increasing current density and increasing fraction of limiting current is correctly predicted. Differences between expected and observed roughness characteristics are attributed to constraints on
Nucleation of Tin and Tin–Silver Alloy on Copper and Nickel in Acid Plating Baths
Journal of The Electrochemical Society, 2007
The rate of nucleation and number density of nuclei of tin and tin-silver deposits on copper and ... more The rate of nucleation and number density of nuclei of tin and tin-silver deposits on copper and nickel substrates in acid sulfate and acid methanesulfonate baths were measured by application of a nucleation model to chronoamperometric data. Based on the dependence of nucleation rate on overpotential, the critical Gibbs free energy of nucleation and the critical nucleation size were calculated. A mechanism of alloy nucleation in the presence of thiourea is proposed.
Studies on Through-Chip Via Filling for Wafer-Level 3D Packaging
ECS Meeting Abstracts, 2006
not Available.
Journal of Nanomaterials, 2020
Silver nanowires (AgNWs) have a broad range of applications including nanoelectronics, energy con... more Silver nanowires (AgNWs) have a broad range of applications including nanoelectronics, energy conversion, health care, solar cells, touch screens, sensors and biosensors, wearable electronics, and drug delivery systems. As their characteristics depend strongly on their size and morphology, it is essential to find the optimal and most cost-effective synthesis method with precise control over the size and morphology of the wires. Various methods for AgNW synthesis have been reported along with process optimization and novel techniques to increase the yield and aspect ratios of synthesized AgNWs. The most promising processes for synthesis of AgNWs are wet chemical techniques, in which the polyol process is low cost and simple and provides high yield compared to other chemical methods. Reaction mechanism is one of the most important factors in strategies to control the process. Our purpose here is to provide an overview on the main findings regarding synthesis, preparation, and characte...
Parametric Study, Sensitivity Analysis, and Optimization of Polyol Synthesis of Silver Nanowires
ECS Journal of Solid State Science and Technology, 2017
Proceedings of the Royal Society A: Mathematical, Physical and Engineering Science, 2017
The formation of pores in anodic aluminium oxide films is treated with a model equation. The mode... more The formation of pores in anodic aluminium oxide films is treated with a model equation. The model treats the oxide layer as a thin viscous liquid in two dimensions. Surface tension on the top boundary, electrostriction due to the external electric field and mass flow through the bottom boundary due to oxide formation are all included. Viscous flow is treated with the creeping flow assumption. The model equation is solved numerically using a Fourier spectral method in space and Adams-Bashforth/Adams-Moulton methods in time. Initial conditions include sinusoidal shapes as well as random shapes. The results show that pores form at the trough of the initial sinusoidal shape. Random shapes get smoothed before forming pore structures with spacing different than predicted by linear theory.
Rheological behavior of silver nanowire conductive inks during screen printing
Journal of Nanoparticle Research, 2016
The rheological behavior of silver nanowire (AgNW) suspensions adapted for screen printing inks w... more The rheological behavior of silver nanowire (AgNW) suspensions adapted for screen printing inks was investigated. Aqueous silver nanowire inks consisting of AgNW (length of 30 μm, and diameter of 40 and 90 nm), dispersant and binder were formulated. The effect of AgNW content on the rheological behavior of the ink and the build-up of ink structure after screen printing were examined as they depend on applied shear and temperature. Rheological measurements under conditions that mimic the screen printing process were done to assess viscoelastic properties induced by flow alignment of the wires and the subsequent recovery of the low shear structure. The Stretched Exponential model (SEmo) was used to model the recovery process after screen printing to obtain the characteristic time of the recovery or build-up process. The characteristic time was determined at several temperatures to obtain the activation energy of recovery. The domination of Brownian motion or non-Brownian motion behavior can be characterized by a Peclet number, which is the ratio of shear rate to the rotational diffusion coefficient. The Peclet number and the dimensionless concentration of wires were used to assess the recovery mechanism. The steady viscosity at low and high shear rates was also treated by an activation energy analysis.
Ph D Thesis California Univ Berkeley Lawrence Berkeley Lab, Aug 1, 1987
Studies on high-speed electroforming were undertaken to evaluate the potential for electroforming... more Studies on high-speed electroforming were undertaken to evaluate the potential for electroforming at rates comparable to those of mechanical forming. A rotating cylindrical cathode was used to provide intense turbulent convective transport. Transport in the cylindrical cell equipped with radial baffles was characterized by direct measurement of limiting currents of high rate copper deposition. Copper electroforms of thicknesses of several hundred micrometers were produced by deposition at rates of up to 7.5 A/cm 2 corresponding to 160~-tm per minute. A quantitative theory of morphological stability, accounting for transport, kinetic and ohmic effects, was formulated for copper deposition at high rates. Surfaces of deposits produced in the electroforming experiments were charaterized by surface profilometry, and digitallized profiles were analyzed by Fourier transform for comparison with predictions of the stability theory. Decrease in roughness protrusion spacing with both increasing current density and increasing fraction of limiting current is correctly predicted. Differences between expected and observed roughness characteristics are attributed to constraints on
Corrosion of copper in acid-sulfate plating baths with additives
Plating and Surface Finishing, 2003
Acid copper plating baths exposed to air present a corrosive environment for copper. With feature... more Acid copper plating baths exposed to air present a corrosive environment for copper. With feature sizes in some plating applications falling well below the micrometer scale, dissolution of metal at open circuit potential may become a consideration in process design. This paper presents a reaction-zone model of the corrosion process that can be used to estimate corrosion rates based on process parameters and open-circuit potential measurements. Corrosion of copper in acid-sulfate plating baths with additives chloride, benzotriazole and bis (3-sulfopropyl) disulfide is examined experimentally with the aid of the model.
Erratum to: Acceleration Effect
Nanostructure Science and Technology, 2014
Physical review letters, Jan 5, 1989
We distinguish the roles of the Laplace and diffusion fields in electrochemical deposition during... more We distinguish the roles of the Laplace and diffusion fields in electrochemical deposition during growth of the dense-branching morphology. The shape of the growth is controlled by the Laplace field; the microscopic morphology is characteristic of diffusion-field-controlled growth; and the branch size length scale is hypothesized to be the result of the interplay of the two fields. The branching rate varies with system parameters so as to select an apparently constant interfacial velocity.
Structure and Pattern Formation in Electrodeposition
Advances in Electrochemical Science and Engineering, Volume 7
Acceleration Effect
Nanostructure Science and Technology, 2013
Copper Electrodeposition for Nanofabrication of Electronics Devices
Nanostructure Science and Technology, 2014
Preface (Kazuo Kondo) PART 1 Copper electrodepositon and additive chemistry Chapter 1 - Copper el... more Preface (Kazuo Kondo) PART 1 Copper electrodepositon and additive chemistry Chapter 1 - Copper electrodeposition (Masayuki Yokoi) Chapter 2 - Suppression effect and Additive Chemistry (Masayuki Yokoi) Chapter 3- Acceleration effect (Dale P. Barkey) Chapter 4- Modeling and Simulation ( Yutaka Kaneko) PART 2 Copper on chip metallization Chapter 5- Frontiers of Cu Electrodeposition and Electroless Plating for On-Chip Interconnects (James R. Rohan) Chapter 6- Microstructure of Evolution of Copper in Nano-scale Interconnect Features (James Kelly, Christopher Parks, James Demarest, and Christopher Penny) Chapter 7- Direct Copper Plating (Aleksandar Radisic and Philippe M. Vereecken) Part 3 - Through Silicon Via and Other Methods Chapter 8- Through Silicon Via (Kazuo Kondo) Chapter 9- Build-up Printed Wiring board (Kiyoshi Takagi a and Toshkazu Okubo) Chapter 10- Copper Foil Smooth on Both Sides for Lithium Ion Battery (Akitoshi Suzuki and Jun Shinozaki) Chapter 11- Through hole plating (Wei-Ping Dow)
Physical Review E, 1998
Ramified copper deposits were formed by electrochemical deposition from well supported acid sulfa... more Ramified copper deposits were formed by electrochemical deposition from well supported acid sulfate solution under conditions of mixed kinetic and transport control. The growth velocity, morphology, and global rate of growth were measured over a range of applied driving force. Chloride was added to the solutions to modify the interfacial kinetics, and the kinetic parameters were obtained as a function of surface orientation by polarization measurements on copper single crystals. Chloride produces an anisotropic differential resistance to growth at the interface and a tendency toward high-velocity dendritic growth with formation of open lowdensity deposits. ͓S1063-651X͑98͒13406-2͔
Pattern Formation in Anodic Aluminum Oxide Growth by Flow Instability and Dynamic Re-Stabilization
ECS transactions, Dec 17, 2019
The viscous flow of oxide driven by the electrostriction force during growth of anodic aluminum o... more The viscous flow of oxide driven by the electrostriction force during growth of anodic aluminum oxide is treated by linear stability analysis and scale analysis. It is shown that a uniform oxide film is unstable to a periodic deformation. The re-stabilization of pore growth is examined by scale analysis of the steady pore diameter. The pattern spatial period and pore radius predicted by the analysis is compared with experimental observations reported in the literature.
Corrosion of Steel Reinforcement in Concrete Adjacent to Surface Repairs
American Concrete Institute, Journal of, 2004
Reinforced concrete may be damaged by chloride-induced corrosion of steel reinforcement, resultin... more Reinforced concrete may be damaged by chloride-induced corrosion of steel reinforcement, resulting in spalling and delamination as corrosion products accumulate. A surface repair entails removal of damaged concrete and its replacement with repair material. The resulting inhomogeneity between the repair material and remaining chloride-contaminated concrete, however, may produce active-passive corrosion macrocells that drive rapid anodic dissolution of the metal. This experimental study was conducted to characterize the geometry, current distribution, and controlling resistance of corrosion macrocells driven by differences in the electrochemical environment in repair material and contaminated concrete. Additional influences such as galvanic contact between the test reinforcement bar and remote cathode bars were also considered. The tests were based on ASTM G 109, with modifications to incorporate simulated repairs.
Influence of Additives on the Growth Velocity and Morphology of Branching Copper Electrodeposits
Journal of The Electrochemical Society, 2005
... SK Chawla, Polyhedron, 18, 1397 (1999). GB McFadden, SR Coriell, TP Moffat, D. Josell, D. Whe... more ... SK Chawla, Polyhedron, 18, 1397 (1999). GB McFadden, SR Coriell, TP Moffat, D. Josell, D. Wheeler, W. Schwarzacher, and J. Mallet, A Mechanism for Brightening, J. Electrochem. ... MAPasquale, SL Marchiano, and AJ Arvia, J. Electroanal. Chem., 532, 255 (2002). ...
Journal of The Electrochemical Society, 2005
Through-chip electrodes for three-dimensional packaging can offer short interconnection and reduc... more Through-chip electrodes for three-dimensional packaging can offer short interconnection and reduced signal delay. Formation of suitable vias by electrodeposition into cavities presents a filling problem similar to that encountered in the damascene process. Because via dimensions for through-chip filling are larger and have a higher aspect ratio relative to features in damascene, process optimization requires modification of existing superconformal plating baths and plating parameters. In this study, copper filling of high-aspect-ratio through-chip vias was investigated and optimized with respect to plating bath composition and applied current wavetrain. Void-free vias 70 m deep and 10 m wide were formed in 60 min using additives in combination with pulse-reverse current and dissolved-oxygen enrichment. The effects of reverse current and dissolved oxygen on the performance of superfilling additives is discussed in terms of their effects on formation, destruction, and distribution of a Cu͑I͒ thiolate accelerant.
Adsorption of Benzyl Viologen Dichloride and Its Displacement By 3-Mercapto-1-Propanesulfonate during Copper Electrodeposition
Meeting abstracts, 2017
PhDT, Aug 1, 1987
Studies on high-speed electroforming were undertaken to evaluate the potential for electroforming... more Studies on high-speed electroforming were undertaken to evaluate the potential for electroforming at rates comparable to those of mechanical forming. A rotating cylindrical cathode was used to provide intense turbulent convective transport. Transport in the cylindrical cell equipped with radial baffles was characterized by direct measurement of limiting currents of high rate copper deposition. Copper electroforms of thicknesses of several hundred micrometers were produced by deposition at rates of up to 7.5 A/cm 2 corresponding to 160~-tm per minute. A quantitative theory of morphological stability, accounting for transport, kinetic and ohmic effects, was formulated for copper deposition at high rates. Surfaces of deposits produced in the electroforming experiments were charaterized by surface profilometry, and digitallized profiles were analyzed by Fourier transform for comparison with predictions of the stability theory. Decrease in roughness protrusion spacing with both increasing current density and increasing fraction of limiting current is correctly predicted. Differences between expected and observed roughness characteristics are attributed to constraints on
Nucleation of Tin and Tin–Silver Alloy on Copper and Nickel in Acid Plating Baths
Journal of The Electrochemical Society, 2007
The rate of nucleation and number density of nuclei of tin and tin-silver deposits on copper and ... more The rate of nucleation and number density of nuclei of tin and tin-silver deposits on copper and nickel substrates in acid sulfate and acid methanesulfonate baths were measured by application of a nucleation model to chronoamperometric data. Based on the dependence of nucleation rate on overpotential, the critical Gibbs free energy of nucleation and the critical nucleation size were calculated. A mechanism of alloy nucleation in the presence of thiourea is proposed.
Studies on Through-Chip Via Filling for Wafer-Level 3D Packaging
ECS Meeting Abstracts, 2006
not Available.
Journal of Nanomaterials, 2020
Silver nanowires (AgNWs) have a broad range of applications including nanoelectronics, energy con... more Silver nanowires (AgNWs) have a broad range of applications including nanoelectronics, energy conversion, health care, solar cells, touch screens, sensors and biosensors, wearable electronics, and drug delivery systems. As their characteristics depend strongly on their size and morphology, it is essential to find the optimal and most cost-effective synthesis method with precise control over the size and morphology of the wires. Various methods for AgNW synthesis have been reported along with process optimization and novel techniques to increase the yield and aspect ratios of synthesized AgNWs. The most promising processes for synthesis of AgNWs are wet chemical techniques, in which the polyol process is low cost and simple and provides high yield compared to other chemical methods. Reaction mechanism is one of the most important factors in strategies to control the process. Our purpose here is to provide an overview on the main findings regarding synthesis, preparation, and characte...
Parametric Study, Sensitivity Analysis, and Optimization of Polyol Synthesis of Silver Nanowires
ECS Journal of Solid State Science and Technology, 2017
Proceedings of the Royal Society A: Mathematical, Physical and Engineering Science, 2017
The formation of pores in anodic aluminium oxide films is treated with a model equation. The mode... more The formation of pores in anodic aluminium oxide films is treated with a model equation. The model treats the oxide layer as a thin viscous liquid in two dimensions. Surface tension on the top boundary, electrostriction due to the external electric field and mass flow through the bottom boundary due to oxide formation are all included. Viscous flow is treated with the creeping flow assumption. The model equation is solved numerically using a Fourier spectral method in space and Adams-Bashforth/Adams-Moulton methods in time. Initial conditions include sinusoidal shapes as well as random shapes. The results show that pores form at the trough of the initial sinusoidal shape. Random shapes get smoothed before forming pore structures with spacing different than predicted by linear theory.
Rheological behavior of silver nanowire conductive inks during screen printing
Journal of Nanoparticle Research, 2016
The rheological behavior of silver nanowire (AgNW) suspensions adapted for screen printing inks w... more The rheological behavior of silver nanowire (AgNW) suspensions adapted for screen printing inks was investigated. Aqueous silver nanowire inks consisting of AgNW (length of 30 μm, and diameter of 40 and 90 nm), dispersant and binder were formulated. The effect of AgNW content on the rheological behavior of the ink and the build-up of ink structure after screen printing were examined as they depend on applied shear and temperature. Rheological measurements under conditions that mimic the screen printing process were done to assess viscoelastic properties induced by flow alignment of the wires and the subsequent recovery of the low shear structure. The Stretched Exponential model (SEmo) was used to model the recovery process after screen printing to obtain the characteristic time of the recovery or build-up process. The characteristic time was determined at several temperatures to obtain the activation energy of recovery. The domination of Brownian motion or non-Brownian motion behavior can be characterized by a Peclet number, which is the ratio of shear rate to the rotational diffusion coefficient. The Peclet number and the dimensionless concentration of wires were used to assess the recovery mechanism. The steady viscosity at low and high shear rates was also treated by an activation energy analysis.
Ph D Thesis California Univ Berkeley Lawrence Berkeley Lab, Aug 1, 1987
Studies on high-speed electroforming were undertaken to evaluate the potential for electroforming... more Studies on high-speed electroforming were undertaken to evaluate the potential for electroforming at rates comparable to those of mechanical forming. A rotating cylindrical cathode was used to provide intense turbulent convective transport. Transport in the cylindrical cell equipped with radial baffles was characterized by direct measurement of limiting currents of high rate copper deposition. Copper electroforms of thicknesses of several hundred micrometers were produced by deposition at rates of up to 7.5 A/cm 2 corresponding to 160~-tm per minute. A quantitative theory of morphological stability, accounting for transport, kinetic and ohmic effects, was formulated for copper deposition at high rates. Surfaces of deposits produced in the electroforming experiments were charaterized by surface profilometry, and digitallized profiles were analyzed by Fourier transform for comparison with predictions of the stability theory. Decrease in roughness protrusion spacing with both increasing current density and increasing fraction of limiting current is correctly predicted. Differences between expected and observed roughness characteristics are attributed to constraints on
Corrosion of copper in acid-sulfate plating baths with additives
Plating and Surface Finishing, 2003
Acid copper plating baths exposed to air present a corrosive environment for copper. With feature... more Acid copper plating baths exposed to air present a corrosive environment for copper. With feature sizes in some plating applications falling well below the micrometer scale, dissolution of metal at open circuit potential may become a consideration in process design. This paper presents a reaction-zone model of the corrosion process that can be used to estimate corrosion rates based on process parameters and open-circuit potential measurements. Corrosion of copper in acid-sulfate plating baths with additives chloride, benzotriazole and bis (3-sulfopropyl) disulfide is examined experimentally with the aid of the model.
Erratum to: Acceleration Effect
Nanostructure Science and Technology, 2014
Physical review letters, Jan 5, 1989
We distinguish the roles of the Laplace and diffusion fields in electrochemical deposition during... more We distinguish the roles of the Laplace and diffusion fields in electrochemical deposition during growth of the dense-branching morphology. The shape of the growth is controlled by the Laplace field; the microscopic morphology is characteristic of diffusion-field-controlled growth; and the branch size length scale is hypothesized to be the result of the interplay of the two fields. The branching rate varies with system parameters so as to select an apparently constant interfacial velocity.
Structure and Pattern Formation in Electrodeposition
Advances in Electrochemical Science and Engineering, Volume 7
Acceleration Effect
Nanostructure Science and Technology, 2013
Copper Electrodeposition for Nanofabrication of Electronics Devices
Nanostructure Science and Technology, 2014
Preface (Kazuo Kondo) PART 1 Copper electrodepositon and additive chemistry Chapter 1 - Copper el... more Preface (Kazuo Kondo) PART 1 Copper electrodepositon and additive chemistry Chapter 1 - Copper electrodeposition (Masayuki Yokoi) Chapter 2 - Suppression effect and Additive Chemistry (Masayuki Yokoi) Chapter 3- Acceleration effect (Dale P. Barkey) Chapter 4- Modeling and Simulation ( Yutaka Kaneko) PART 2 Copper on chip metallization Chapter 5- Frontiers of Cu Electrodeposition and Electroless Plating for On-Chip Interconnects (James R. Rohan) Chapter 6- Microstructure of Evolution of Copper in Nano-scale Interconnect Features (James Kelly, Christopher Parks, James Demarest, and Christopher Penny) Chapter 7- Direct Copper Plating (Aleksandar Radisic and Philippe M. Vereecken) Part 3 - Through Silicon Via and Other Methods Chapter 8- Through Silicon Via (Kazuo Kondo) Chapter 9- Build-up Printed Wiring board (Kiyoshi Takagi a and Toshkazu Okubo) Chapter 10- Copper Foil Smooth on Both Sides for Lithium Ion Battery (Akitoshi Suzuki and Jun Shinozaki) Chapter 11- Through hole plating (Wei-Ping Dow)
Physical Review E, 1998
Ramified copper deposits were formed by electrochemical deposition from well supported acid sulfa... more Ramified copper deposits were formed by electrochemical deposition from well supported acid sulfate solution under conditions of mixed kinetic and transport control. The growth velocity, morphology, and global rate of growth were measured over a range of applied driving force. Chloride was added to the solutions to modify the interfacial kinetics, and the kinetic parameters were obtained as a function of surface orientation by polarization measurements on copper single crystals. Chloride produces an anisotropic differential resistance to growth at the interface and a tendency toward high-velocity dendritic growth with formation of open lowdensity deposits. ͓S1063-651X͑98͒13406-2͔