Co Anomalous Growth Kinetics of the CoSi Reaction Layer in a Si/System

Solid state reactions between amorphous Si and crystalline Co have been investigated by 4W electrical resistance and TEM. Multilayered (with 10 periods of 5nm a-Si/5nm Co and 10 nma- Si/10nm Co layers) as well as tri-layered samples (20nm a-Si/3nmCoSi/6nm Co) were produced by magnetron sputtering and isothermally heat treated at different temperatures between 473 and 523K. From the time evolution of the normalized resistance the kinetics of the process were determined by fitting a power law, tk, and k was between 0.8 and 1. Possibility of the interface reaction control and/or the effect of the diffusion asymmetry (which was recently published for the non-parabolic interface shifts on the nanoscale) will be discussed.

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Silicide Formation Reactions in a-Si/Co Multilayered Samples

Defect and Diffusion Forum ◽

10.4028/www.scientific.net/ddf.277.3 ◽

2008 ◽

Vol 277 ◽

pp. 3-8

Author(s):

Z. Balogh ◽

Csaba Cserháti ◽

Z. Erdélyi ◽

A. Csik ◽

G.A. Langer ◽

...

Keyword(s):

Growth Rate ◽

Solid State ◽

Synchrotron Radiation ◽

Magnetron Sputtering ◽

Interface Reaction ◽

Solid State Reactions ◽

Silicide Formation ◽

Parabolic Kinetics ◽

Heat Treated ◽

Interface Reaction Control

Solid state reactions between amorpous Si and crystalline Co have been investigated by synchrotron radiation at Bessy (Berlin, Germany). The multilayered samples (with 10 periods of a-Si(15 nm)/Co(15 nm) layers) were produced by magnetron sputtering and isothermally heat treated at temperatures between 523 and 593 K. From the time evolution of the XRD spectra first the growth rate of the CoSi phase as well as the decay rate of the Co layer we determined (at 523 and 543 K). The kinetics were described by a power law; tk, and for the growth of CoSi k=0.65 while for the loss of the Co the k=0.77 was obtained, respectively. At higher temperatures (at 573 and 593 K) the formation and growth of the Co2Si layer, at the expense of the Co and already existing CoSi layers, was observed with exponents of about 1 for all the above kinetics. These results, together with the results of resistance kinetics measurements, in similar multilayered as well as bi-layered samples at similar temperatures, providing similar exponents will be presented. Possibility of the interface reaction control and/or the effect of the diffusion asymmetry (which was recently published for the interpretation of solid state reactions with non-parabolic kinetics on the nanoscale) will be discussed.

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Fabrication of NiAl Intermetallic from Dense Elemental Powder Blends VIA Solid State Reactions

MRS Proceedings ◽

10.1557/proc-460-561 ◽

1996 ◽

Vol 460 ◽

Cited By ~ 2

Author(s):

L. Farber ◽

I. Gotman ◽

E. Y. Gutmanas

Keyword(s):

Solid State ◽

Solid State Reactions ◽

Full Density ◽

Reaction Products ◽

Liquid Phases ◽

High Temperature Synthesis ◽

Heat Treated ◽

Micron Size ◽

Different Temperatures ◽

Two Stages

ABSTRACTDense NiAl intermetallic was synthesized from very fine elemental powders via solid state reactions. Homogeneous blends of micron size Ni and Al powders were consolidated to full density and heat treated in a 425–800°C temperature range. During heat treatment, formation of various intermediate intermetallics phases: NiAl3, Ni2A13, Ni3Al and NiAl was observed. The sequence and kinetics of these phase formations at different temperatures were studied employing X-ray diffraction analysis (XRD). A model for a description of synthesis reaction kinetics in Ni-Al blends was developed. Based on the obtained results, the synthesis of NiAl was performed in two stages : reactions in 425–550°C range with consumption of Al, followed by a reaction at up to 800°C. It allowed uncontrolled SHS (self propagating high temperature synthesis, resulting in the occurrence of liquid phases and in formation of reaction products in a very fast /explosive manner) to be avoid. The synthesis temperatures are considerably lower than those used currently in processing of NiAl.

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Non Parabolic Shift of Interfaces and Effect of Diffusion Asymmetry on Nanoscale Solid State Reactions

Journal of Nano Research ◽

10.4028/www.scientific.net/jnanor.7.43 ◽

2009 ◽

Vol 7 ◽

pp. 43-49 ◽

Cited By ~ 4

Author(s):

Dezső L. Beke ◽

Z. Erdélyi ◽

Z. Balogh ◽

Csaba Cserháti ◽

G.L. Katona

Keyword(s):

Experimental Data ◽

Solid State ◽

Interface Reaction ◽

Diffuse Interface ◽

Solid State Reactions ◽

Diffusion Couples ◽

Parent Materials ◽

Parabolic Law ◽

And Shifts ◽

Interface Reaction Control

In a set of recent papers we have shown that the diffusion asymmetry in diffusion couples (the diffusion coefficient is orders of magnitude larger in one of the parent materials) leads to interesting phenomena: i) sharp interface remains sharp and shifts with non Fickian (anomalous) kinetics [1-5], ii) originally diffuse interface sharpens even in ideal (completely miscible) systems [6,7], iii) an initially existing thin AB phase in A/AB/B diffusion couple can be dissolved [8], iv) there exists a crossover thickness (typically between few nanometers and 1m) above which the interface shift turns back to the Fickian behaviour [9], v) the growth rate of a product of solid state reaction can be linear even if there is no any extra potential barrier present (which is the classical interpretation of the “interface reaction control” for linear kinetics) [10]. These latter results will be summarized and reformulated according to the usual expression for linear-parabolic law containing the interdiffusion coefficient, D, and interface transfer coefficient, K. Relation between the activation energies of D and K will be analyzed and compared with available experimental data.

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