Velocity and Orientation Dependence of Solute Trapping

1985 ◽  
Vol 57 ◽  
Author(s):  
M. J. Aziz ◽  
J. Y. Tsao ◽  
M. O. Thompson ◽  
P. S. Peercy ◽  
C. W. White
Keyword(s):  
Pulsed Laser ◽  
Orientation Dependence ◽  
Sufficient Accuracy ◽  
Segregation Coefficient ◽  
Solute Trapping ◽  
Impurity Atoms ◽  
Segregation Behavior ◽  
Functional Forms ◽  
Solid Liquid Interface ◽  
Solid Liquid

AbstractThe fraction of impurity atoms in the liquid at the solid-liquid interface that join the crystal, known as the segregation coefficient k, during rapid crystal growth is known to deviate away from the equilibrium value towards unity as the interface speed v increases. Several plausible models have been proposed that account qualitatively for this behavior with different functional forms of k(v). We report measurements of the segregation behavior during rapid solidification following pulsed laser melting of Bi-implanted Si. The velocity dependence and the orientation dependence of the segregation coefficient of Bi in Si has been determined to sufficient accuracy to allow us to distinguish between models. Implications for the mechanism of solute trapping are discussed.

Solute Trapping at a Rapidly Moving Solid/Liquid Interface for a Lennard-Jones Alloy

1989 ◽  
Vol 157 ◽  
Author(s):  
Stephen J. Cook ◽  
Paulette Clancy
Keyword(s):  
Dynamics Simulation ◽  
Segregation Coefficient ◽  
Equilibrium Conditions ◽  
Impurity Atoms ◽  
Lennard Jones ◽  
Interfacial Segregation ◽  
Non Equilibrium Molecular Dynamics ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
Substrate Temperatures

ABSTRACTNon-equilibrium Molecular Dynamics simulation methods have been used to study the trapping of “impurities” in an Ag5B15 Lennard-Jones alloy where the B atoms are 10% bigger in diameter than A. The observation of surface melting in this system is used to calculate an equilibrium interfacial segregation coefficient. Simulations of rapid melting and resolidification were performed for the (100) and (111) orientations at two different substrate temperatures (0.65 Tm and 0.95 Tm) for each orientation. Solute impurity atoms are shown to have been trapped at greater concentrations in the solid than under equilibrium conditions. Partitionless solidification is observed when the regrowth velocity greatly exceeds the diffusive velocity.

Transient Conductance Measurements During Pulsed Laser Annealing

1981 ◽  
Vol 4 ◽  
Author(s):  
M. O. Thompson ◽  
G. J. Galvin ◽  
J. W. Mayer ◽  
R. B. Hammond ◽  
N. Paulter ◽  
...  
Keyword(s):  
Single Crystal ◽  
Laser Annealing ◽  
Pulsed Laser ◽  
Interface Velocity ◽  
Laser Pulses ◽  
Molten Layer ◽  
Pulsed Laser Annealing ◽  
Complete Melting ◽  
Solid Liquid Interface ◽  
Solid Liquid

ABSTRACTMeasurements were made of the conductance of single crystal Au-doped Si and silicon-on-sapphire (SOS) during irradiation with 30 nsec ruby laser pulses. After the decay of the photoconductive response, the sample conductance is determined primarily by the thickness and conductivity of the molten layer. For the single crystal Au-doped Si, the solid-liquid interface velocity during recrystallization was determined from the current transient to be 2.5 m/sec for energy densities between 1.9 and 2.6 J/cm2, in close agreement with numerical simulations based on a thermal model of heat flow. SOS samples showed a strongly reduced photoconductive response, allowing the melt front to be observed also. For complete melting of a 0.4 μm Si layer, the regrowth velocity was 2.4 m/sec.

THE EFFECT OF GROWTH CONDITIONS UPON THE SOLIDIFICATION OF A BINARY ALLOY

1956 ◽  
Vol 34 (1) ◽  
pp. 96-121 ◽  
Author(s):  
W. A. Tiller ◽  
J. W. Rutter
Keyword(s):  
Binary Alloy ◽  
Impurity Content ◽  
Growth Conditions ◽  
Orientation Dependence ◽  
Liquid Interface ◽  
Critical Ratio ◽  
Liquid Lead ◽  
Careful Study ◽  
Solid Liquid Interface ◽  
Solid Liquid

This investigation provides both a theoretical and an experimental analysis of the factors which affect the mode of solidification of a binary alloy. These factors are: (i) the concentration of solute in the melt (C0); (ii) the rate of solidification (R); (iii) the temperature gradient in the melt at the solid–liquid interface (G). Extremely high purity lead was produced by zone refining and, from this material, crystals containing known concentrations of tin, silver, and gold were grown under a range of well-controlled growth conditions. The mode of solidification was investigated by a careful study of the change in appearance of the solid–liquid interface with a change in growth conditions. For a crystal containing a specific C0 of solute it was observed that (a) the transition from a smooth interface to a cellular interface occurred at a critical ratio of G to R; (b) the width of the cells varied inversely as G and inversely as R; (c) the transition from a cellular interface to a dendritic interface exhibited a large orientation dependence, and for a constant orientation breakdown occurred at a critical ratio of G to [Formula: see text]. The experimental observations confirm both the existence of a solute-rich layer of liquid adjacent to the solid-liquid interface and its quantitative features. From this agreement with theory the diffusion coefficients of tin, silver, and gold in liquid lead at 327 °C. are determined. This work serves to illustrate the effect of extremely small amounts of particular solutes upon the development of substructures during solidification. A technique is proposed for obtaining a measure of the purity of low impurity content alloys.

A Test of Two Solute-Trapping Models

1984 ◽  
Vol 35 ◽  
Author(s):  
M. J. Aziz ◽  
J. Y. Tsao ◽  
M. O. Thompson ◽  
P. S. Peercy ◽  
C. W. White ◽  
...  
Keyword(s):  
Phase Diagram ◽  
High Resolution ◽  
Pulsed Laser ◽  
Dilute Solutions ◽  
Laser Melting ◽  
Solute Trapping ◽  
Segregation Behavior

ABSTRACTTwo solute trapping models are compared. They are shown to predict identical behavior at any given end of a phase diagram but different behavior as the phase diagram is traversed. The segregation behavior of dilute solutions of Ge in Si (ke < 1) and of Si in Ge (ke > 1) during regrowth from pulsed-laser melting is being studied using transient conductance, high resolution RBS, and SIMS. Our results to date suggest a significant amount" of solute trapping (k —> 1) of Ge in Si and of Si in Ge. Such a result would be inconsistent with the predictions of one of the models.

Molecular Dynamics Simulation of Heat Transfer and Phase Change During Laser Material Interaction

2001 ◽  
Vol 124 (2) ◽  
pp. 265-274 ◽  
Author(s):  
Xinwei Wang ◽  
Xianfan Xu
Keyword(s):  
Heat Transfer ◽  
Molecular Dynamics ◽  
Phase Change ◽  
Pulsed Laser ◽  
Liquid Structure ◽  
Dynamics Simulation ◽  
Dynamics Simulations ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
Material Interaction

In this work, heat transfer and phase change of an argon crystal irradiated by a picosecond pulsed laser are investigated using molecular dynamics simulations. The result reveals no clear interface when phase change occurs, but a transition region where the crystal structure and the liquid structure co-exist. Superheating is observed during the melting and vaporizing processes. The solid-liquid interface is found to move with a velocity of hundreds of meters per second, and the vapor is ejected from the surface with a vapor front velocity of hundreds of meters per second.

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