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Appl. Phys. Lett., Vol. 84, No. 23, 7 June 2004
Hiramatsu et al.
F abstraction. At a substrate temperature of 500 °C, H radi-
2
cals would play an important role for producing sp bonded
2
carbons at the surface to form continuous sp network, re-
sulting in the formation of carbon nanowalls. The ratio of
CF (xϭ1–3) radicals to H radicals would be an important
x
factor to form carbon nanowalls. Measurement of H atom
density in the plasma is being carried out.16
In summary, we have presented a fabrication of verti-
cally aligned carbon nanowalls using capacitively coupled, rf
PECVD assisted by H radical injection. The aggregation of
carbon nanowalls would be useful as templates for the fab-
rication of other types of nanostructured materials, and
would certainly find applications in energy storage and elec-
trodes for fuel cell due to their large surface areas.
FIG. 3. SEM images of the carbon nanowalls grown on Si substrate using
CH /H system for 3 h; ͑a͒ top view and ͑b͒ tilted view.
4
2
the formation of linked nanowalls like a maze. With the fur-
ther increase of growth time, it became more difficult for the
reactive carbon species to reach the sidewall, resulting in the
saturation of increase in the wall thickness.
Growth experiments were carried out using CH or CF4
4
under similar conditions as those for the case using the
C F /H system. Typical SEM images of the carbon nanow-
1
C. Bower, W. Zhu, S. Jin, and O. Zhou, Appl. Phys. Lett. 77, 830 ͑2000͒.
C. Bower, O. Zhou, W. Zhu, D. J. Werder, and S. Jin, Appl. Phys. Lett. 77,
2767 ͑2000͒.
J. B. O. Caughman, L. R. Baylor, M. A. Gulliorn, V. I. Merkulov, D. H.
Lowndes, and L. F. Allard, Appl. Phys. Lett. 83, 1207 ͑2003͒.
A. G. Rinzler, J. H. Hafner, P. Nikolaev, L. Lou, S. G. Kim, D. Tomanek,
P. Nordlander, D. T. Cobert, and R. E. Smalley, Science 269, 1550 ͑1995͒.
2
6
2
2
alls grown using the CH /H system for 3 h are shown in
4
2
3
Figs. 3͑a͒ and 3͑b͒. The carbon nanowalls grown using CH4
were rather wavy and very thin, and their thickness was less
than 10 nm. The growth rate using the CH /H system was
4
4
2
lower by about 15% than that for the case using the C F /H
5
2
6
2
A. C. Dillon, K. M. Jones, T. A. Bekkedahl, C. H. Kiang, D. S. Bethune,
system. On the other hand, the morphology of the carbon
nanowalls grown using the CF /H system was similar to
and M. J. Heben, Nature ͑London͒ 386, 377 ͑1997͒.
G. Che, B. B. Lakshmi, E. R. Fisher, and C. R. Martin, Nature ͑London͒
6
4
2
393, 346 ͑1998͒.
those grown using the C F /H system shown in Fig. 1͑a͒,
7
8
9
2
6
2
W. A. de Heer, A. Chatelain, and D. Ugarrte, Science 270, 1179 ͑1995͒.
Y. Ando, X. Zhao, and M. Ohkohchi, Carbon 35, 153 ͑1997͒.
Y.-H. Wu, P.-W. Qiao, T.-C. Chong, and Z.-X. Shen, Adv. Mater. ͑Wein-
heim, Ger.͒ 14, 64 ͑2002͒.
M. Ikeda, H. Ito, M. Hiramatsu, M. Hori, and T. Goto, Jpn. J. Appl. Phys.,
Part 1 34, 2484 ͑1995͒.
M. Hiramatsu, M. Inayoshi, K. Yamada, E. Mizuno, M. Nawata, M. Ikeda,
M. Hori, and T. Goto, Rev. Sci. Instrum. 67, 2360 ͑1996͒.
R. J. Nemanich and S. A. Solin, Phys. Rev. B 20, 392 ͑1979͒.
J. Yu, Q. Zhang, J. Ahn, S. F. Yoon, Rusli, Y. J. Li, B. Gan, K. Chew, and
K. H. Tan, Diamond Relat. Mater. 10, 2157 ͑2001͒.
N. M. Mackie, N. F. Dalleska, D. G. Castner, and E. R. Fisher, Chem.
Mater. 9, 349 ͑1997͒.
except that the growth rate was decreased by about one-half
as compared with the case using the C F /H system.
2
6
2
Gas phase and surface reactions of fluorocarbon radicals
such as CF2 in the fluorocarbon–hydrogen plasmas have
10
1
4,15
11
been studied extensively by Fisher’s group.
It was re-
ported that with C F /H and CF /H plasmas, the film
2
6
2
4
2
1
1
2
3
structure would vary from fluorocarbon polymer, through
amorphous hydrogenated fluorinated carbon to diamondlike
1
1
4
5
carbon as the H flow rate ratio increased. In the case of our
2
deposition without H ICP, a fluorocarbon polymer with a
2
C. I. Butoi, N. M. Mackie, K. L. Williams, N. E. Capps, and E. R. Fisher,
J. Vac. Sci. Technol. A 18, 2685 ͑2000͒.
S. Takashima, M. Hori, T. Goto, A. Kono, M. Ito, and K. Yoneda, Appl.
Phys. Lett. 75, 3929 ͑1999͒.
cauliflower shape was deposited as shown in Fig. 1͑d͒. In-
jected H radicals would react more effectively with fluoro-
carbon radicals in the gas phase as well as at the surface by
16
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