Phase Formation and Microstructural Development During Solid-State Reactions in Ti-Al Multilayer Films

1994 ◽  
Vol 343 ◽  
Author(s):  
Carsten Michaelsen ◽  
Stefan Wöhlert ◽  
RÜdiger Bormann
Keyword(s):  
Solid State ◽  
Phase Formation ◽  
Boundary Diffusion ◽  
Driving Forces ◽  
Multilayer Films ◽  
Solid State Reactions ◽  
Microstructural Development ◽  
Second Phase ◽  
Equilibrium Conditions ◽  
Phase Selection

ABSTRACTThe phase selection which is generally observed in the early stages of solid-state reactions was studied using Ti-Al multilayer films as a model system.Although all Ti-Al intermetallic phases have similar driving forces of about 30 kJ/g-atom, TiAl3 is the only phase which is formed as long as the reactants are not consumed. The critical thickness beyond which a second phase is formed is larger than 100 μm. We found that the formation of TiAl3 takes place by nucleation and growth, demonstrating that the driving force available for first-phase formation is considerably reduced by a preceding formation of solid solutions. Furthermore, we observed that nucleation continues at later stages, indicating that non-equilibrium conditions are maintained which are possibly influenced by grain-boundary diffusion. However, the phase selection is determined by the different growth velocities, being much higher for TiAl3 than for all other phases.

The Early Stages of Solid-State Reactions in Ti/Al Multilayer Films

1995 ◽  
Vol 398 ◽  
Author(s):  
C. Michaelsen ◽  
S. WÖHlert ◽  
R. Bormann ◽  
K. Barmak
Keyword(s):  
Solid State ◽  
Reaction Order ◽  
Multilayer Films ◽  
Nucleation And Growth ◽  
Solid State Reactions ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Phase Selection ◽  
X Ray ◽  
Early Stages

ABSTRACTWe have investigated the solid-state reaction of Ti/Al multilayer films by x-ray diffraction (XRD) and differential scanning calorimetry (DSC), with focus on the early stages of the reaction provided by samples with pair thicknesses in the range 5 - 40 nm. This reaction, which results in formation of TiAl3 with metastable Ll2 structure, can be modeled by a nucleation and growth process on the basis of the Johnson-Mehl-Avrami theory, with a reaction-order parameter n ≈1. These observations indicate the significance of nucleation barriers even at early stages of solid-state reactions, and suggests that the phenomena of phase selection and formation of metastable phases can result from the presence of nucleation barriers.

Grain Boundary Diffusion Controlled Precipitation as a Model For thin Film Reactions

1993 ◽  
Vol 311 ◽  
Author(s):  
K. Barmak ◽  
K.K. Coffey
Keyword(s):  
Thin Film ◽  
Driving Force ◽  
Boundary Diffusion ◽  
Chemical Potential ◽  
Driving Forces ◽  
Transport Model ◽  
Interface Reaction ◽  
Grain Structure ◽  
Phase Selection ◽  
Reaction Barriers

ABSTRACTIn order to arrive at a model for nucleation in the reaction of polycrystalline thin films, we have made use of a transport model that combines atom transport across interface reaction barriers with transport along grain boundaries. Through this transport model, the boundary chemical potential, μIi, and a characteristic length Li for each specie are defined. Li and the ratio of grain size to Li determine the spatial variation and the time evolution of the boundary chemical potential respectively. Nucleation of the product phase is modeled as a process whose driving force is determined by these position dependent (and time dependent) boundary chemical potentials. Thus thin film reactions become similar to precipitation from bulk homogeneous supersaturated solid solutions. Numerical calculations, however, show that boundary diffusion results in low “effective” driving forces for nucleation which can lead to heterogeneous nucleation of even the first phase. The model provides a new approach to phase selection by re-evaluation of the driving force and considers the effect of product and reactant grain structure to be fundamental to the reaction process.

On the role of diffusion in phase selection during reactions at interfaces

1992 ◽  
Vol 7 (2) ◽  
pp. 367-373 ◽  
Author(s):  
C.V. Thompson
Keyword(s):  
Solid State ◽  
Thermodynamic Analysis ◽  
Phase Formation ◽  
Phase Selection ◽  
Transient Nucleation ◽  
State Amorphization

It is argued that interdiffusion must precede nucleation of new phases during reactions at interfaces between compositionally different phases. The relative rates at which elemental components diffuse in the reacting phases control the sequence in which phases can form, and can also strongly affect the relative nucleation rates of alloy products, especially in the transient nucleation regime. While detailed predictions of the relative nucleation rates require usually unavailable knowledge of the energies of the relevant interfaces, in some cases, knowledge of the relevant diffusivities, along with a thermodynamic analysis, can lead to predictions of likely phase formation sequences. These concepts are used to explain the association of diffusional asymmetry with systems that undergo solid state amorphization, and to specify semiquantitatively the degree of asymmetry required for solid state amorphization.

Correlations Between Electrical Properties and Solid-State Reactions in Co/N-GaAs Contacts: A Bulk and Thin-Film Study

1989 ◽  
Vol 148 ◽  
Author(s):  
F.-Y. Shiau ◽  
Y. A. Chang
Keyword(s):  
Thin Film ◽  
Phase Diagram ◽  
Solid State ◽  
Electrical Properties ◽  
Phase Formation ◽  
Electrical Characterization ◽  
Solid State Reactions ◽  
Film Diffusion ◽  
Film Study ◽  
Thin Film Diffusion

ABSTRACTA fundamental and comprehensive approach has been taken to study Co//GaAs interfacial reactions, using phase diagram determination, bulk and thin-film diffusion couple studies, and electrical characterization. Phase formation sequences and interfacial morphologies are found to be similar in bulk and thin-film couples. Thermodynamic and kinetic analyses are used to rationalize the contact formations. The electrical properties of the contacts are correlated to the phase formation sequences and phase diagram information.

scholarly journals Study of the Ti/InGaAs solid-state reactions: Phase formation sequence and diffusion schemes

2020 ◽  
Vol 113 ◽  
pp. 105038
Author(s):  
S. Bensalem ◽  
E. Ghegin ◽  
F. Boyer ◽  
J.L. Lábár ◽  
M. Menyhárd ◽  
...  
Keyword(s):  
Solid State ◽  
Phase Formation ◽  
Solid State Reactions ◽  
And Diffusion

scholarly journals Phase formation sequence in the Ti/InP system during thin film solid-state reactions

2017 ◽  
Vol 121 (24) ◽  
pp. 245311 ◽  
Author(s):  
E. Ghegin ◽  
Ph. Rodriguez ◽  
J. L. Lábár ◽  
M. Menyhárd ◽  
S. Favier ◽  
...  
Keyword(s):  
Thin Film ◽  
Solid State ◽  
Phase Formation ◽  
Solid State Reactions

Texture Effects in Solid-State Reactions of Thin Films

2012 ◽  
Vol 706-709 ◽  
pp. 2857-2862 ◽  
Author(s):  
Koen De Keyser ◽  
Christophe Detavernier ◽  
Jean Jordan Sweet ◽  
Christian Lavoie
Keyword(s):  
Thin Films ◽  
Solid State ◽  
Single Crystal ◽  
Phase Formation ◽  
Metal Film ◽  
Solid State Reactions ◽  
Single Crystal Substrate ◽  
Crystal Substrate ◽  
Semiconductor Single Crystal ◽  
Deposited Film

The texture of thin films, originating from a solid state reaction between a deposited film and a single crystal substrate is investigated. The relation between the phase formation and texture is analyzed for a number of these systems, such as Co/Si, Ni/Si or Co/Ge, where a metal film is allowed to react with a semiconductor single crystal substrate during heating and a summary of these results in presented in this article. It was found that the texture of the resulting films can be very complex, consisting of a variety of simultaneously occurring texture components such as epitaxy, fiber and axiotaxy texture. The close connection between the phase formation and texture is demonstrated by the fact that even a small intervention in either one, can have a huge effect on the resulting phase and/or its texture. From this, we show that the effect of the addition of ternary elements (e.g. Pt, W, C) to the thin films can only be understood if one considers its effects on both the kinetics and the thermodynamics of the reactions, as well as on the texture of the phases. We show how this can be used to influence technologically important properties of the films, such of formation temperature or stability.

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