K. Tatemoto et al. / Journal of Physics and Chemistry of Solids 66 (2005) 526–529
529
Table 2
2
Growth constant, k , of the cobalt silicides
disilicide (MSi ) layer, while Fe, Ni and Co formed the
2
silicon-poor silicide layer (MSi , n!2), such as Fe Si. This
n
3
2
k (10
K16
2
m /s)
Temperature
K)
is because the diffusivity of metal inside the deposited layer
is different from that of silicon.
(
a-Co
7.1
40
2
Si
CoSi
CoSi
2
Barge et al. [17]
Jan et al. [18]
This work
1119
64
1000
743
2.5
2.8
67
1
1
206
273
186
85
1173
160
3.2
19
Acknowledgements
1
1
273
323
430
850
2000
3700
149
47
The authors thank Mr M. Unesaki for SEM/EDX
analysis. This work was financially supported in part by
JFE 21st Century Foundation.
1173
35.8
–
silicide, MSi (m!n), is formed as:,
n
MSi þ SiðdepositedÞ/MSi ðat surfaceÞ
(5)
m
n
2
Table 2 lists the growth constants, k , determined by the
diffusion couples in the Co–Si binary system [17,18]
References
[
1] A.V. Byalobzheskii, M.S. Tsirlin, B.I. Krasilov, High-Temperature
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Moscow, 1977.
2
2
k Z d =t
(6)
where d and t are thickness of the silicide layer and the
reaction time, respectively. When we assumed the solid
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12) (1995) 1173–1179 (in Japanese).
[
2
reaction of Eq. (5), the k values deduced from this work
4
agreed well with the reported ones. Therefore, we may
conclude that the reactions of lower silicide formation are
diffusion-limited, although the silicon deposition on the
surface, the electrochemical reactions in the salt and the
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determining steps.
[
(
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[
[
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In the case of Fe, we detected only Fe Si phase formation
3
[9] T. Oki, J. Tanikawa, Molten Salt (Yoyuen) 25 (2) (1982) 115–137 (in
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even after the long reaction time. This is consistent with the
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Fe was reported previously [10,11].
[
[
[
[
[
[
[
[
[
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(
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2
80–285.
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61 (1965) 2665.
2
6
. Conclusion
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16] J.-Y. Byun, J.-K. Yoon, G.-H. Kim, J.-S. Kim, C.-S. Choi, Scr. Mater.
The molten salt consisting of NaCl, KCl, Na SiF and Si
2
6
4
6 (7) (2002) 537–542.
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134–1145.
formed the silicide layer on the refractory elements, Cr, Fe,
Co, Ni, Nb and Mo. The silicide formation was classified as
two groups; (A) di-silicide formers and (B) lower silicide
formers. Nb, Mo and Cr mainly formed the silicon-rich
1
18] C.H. Jan, C.P. Chen, Y.A. Chang, J. Appl. Phys. 73 (3) (1993)
1168–1179.