Synthesis of silicon nitride nanorods using carbon nanotube as a template

Article abstract of DOI:10.1063/1.120550

A method to prepare silicon nitride nanoscale rods using carbon nanotube as a template has been presented in this letter. The products of the reaction of carbon nanotubes with a mixture of Si and SiO₂ powder in nitrogen atmosphere are β-Si₃N₄, α-Si₃N₄, and Si₂N₂O nanorods. The sizes of the nanorods are 4-40 nm in diameter and up to several microns in length. The formation mechanism of the nanorods has also been discussed.

Full text of DOI:10.1063/1.120550

Synthesis of silicon nitride nanorods using carbon nanotube as a template
Weiqiang Han, Shoushan Fan, Qunqing Li, Binglin Gu, Xiaobin Zhang, and Dapeng Yu
Citation: Applied Physics Letters 71, 2271 (1997); doi: 10.1063/1.120550
View online: http://dx.doi.org/10.1063/1.120550
View Table of Contents: http://scitation.aip.org/content/aip/journal/apl/71/16?ver=pdfcov
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Synthesis of silicon nitride nanorods using carbon nanotube as a template
Weiqiang Han, Shoushan Fan,a) Qunqing Li, and Binglin Gu
Department of Physics, Tsinghua University, Beijing 100084, People’s Republic of China
Xiaobin Zhang
Department of Materials, Zhejiang University, Hangzhou 310027, People’s Republic of China,
and Beijing Electron Microscopy Laboratory, Academia Sinica,
Beijing, 100080, People’s Republic of China
Dapeng Yu
Department of Physics, Peking University, Beijing 100871, People’s Republic of China
͑
Received 23 January 1997; accepted for publication 21 August 1997͒
A method to prepare silicon nitride nanoscale rods using carbon nanotube as a template has been
presented in this letter. The products of the reaction of carbon nanotubes with a mixture of Si and
SiO powder in nitrogen atmosphere are ␤-Si N , ␣-Si N , and Si N O nanorods. The sizes of the
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nanorods are 4–40 nm in diameter and up to several microns in length. The formation mechanism
of the nanorods has also been discussed. © 1997 American Institute of Physics.
͓
S0003-6951͑97͒02842-8͔
Synthesis of nanoscale one dimensional structures still
remain a challenge. Since the discovery of carbon nanotube,1
efforts have been made on synthesis of one dimensional
nanoscale materials by using carbon nanotube as a
copy ͑TEM, Philips-CM200͒, and high resolution transmis-
sion electron microscopy ͑HREM, Hitachi-9000NAR͒.
Figure 1 is an XRD pattern of the products, which is
identified as a mixture of ␤-Si3N4, ␣-Si3N4 and Si2N2O. As
can be seen from Fig. 1, the peaks assigned to ␤-Si3N4 are
stronger than the others, indicating the products are domi-
nantly ␤-Si3N4. There is no peak associated with crystalline
SiC, graphite, or other crystalline forms connected with car-
bon in the XRD pattern. Figure 2͑a͒ is a TEM micrograph of
the products. The TEM image shows that the products are
relatively straight nanorods with diameters ranging from 4 to
2
–6
template. Recently, Dai et al. reported that carbide nano-
rods whose diameters were similar to or much smaller than
the diameters of the carbon nanotubes could be produced via
the reaction of the carbon nanotubes with volatile transition-
7
metal and main-group halide or oxide species. We also syn-
thesized SiC nanorods in a two-step process involving the
generation of SiO followed by reacting with carbon nano-
tubes and proposed a model for growth mechanism of SiC
4
0 nm, which are close to the diameters of the starting car-
8
bon nanotubes ͓Fig. 2͑b͔͒. The lengths of the nanorods are
up to several microns. The diameters of the produced nitride
nanorods are significantly smaller than the previous observa-
nanorods. It could be suggested that in the formation of
carbide nanorod the carbon nanotube might confine the reac-
tion in a local space around the nanotube. In the experiment
reported here, we found that the nanotube space confined
reaction is more general than forming carbide nanorods. We
successfully prepared nanometer Si N rods of the diameters
tions made on the Si N whiskers prepared by other
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4
methods.9 The Si N nanorods are solid other than the
,10
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4
hollow core structure of carbon nanotubes. Figures 3͑a͒ and
͑b͒ show the selected area electron diffraction patterns of a
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4
3
similar to the diameters of starting carbon nanotubes through
nitride nanorod, which are consistent with single crystalline
nature of the sample. The patterns can be indexed to the
reflection of ␤-Si N ͓001͔ and ␤-Si N ͓100͔, respectively.
a reaction of the carbon nanotubes with Si-SiO powder mix-
2
ture in nitrogen atmosphere. Although the final products do
not contain carbon element, carbon nanotube might play an
important role as a removable template during the reaction.
Carbon nanotubes used in this study were prepared by
metal catalytic decomposition of ethylene and hydrogen in a
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Figure 4 shows a HREM image of a ␤-Si N nanorod with a
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chemical vapor deposition system. The catalytic growth
procedure yielded relatively pure multishell carbon nano-
tubes with typical diameters around 15 nm. The preparation
apparatus for synthesis of nitride nanorods is a conventional
furnace with a sintered alumina tube. An alumina crucible
containing Si-SiO2 powder mixture covered with carbon
nanotubes was placed in the hot zone inside the alumina
tube. Nitrogen gas was flowing during the overall reaction
period. The reaction was carried out at 1673 K for 1 h. After
the reaction, a white woollike layer formed at the original
nanotube bed. This layer of products was identified by x-ray
diffraction ͑XRD, D/max-RB͒, transmission electron micros-
a͒Electronic mail: fss-dmp@mail.tsinghua.edu.cn
FIG. 1. An x-ray diffraction spectrum of the sample.
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Appl. Phys. Lett. 71 (16), 20 October 1997 0003-6951/97/71(16)/2271/3/$10.00 © 1997 American Institute of Physics 2271
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FIG. 4. A HREM image of a ␤-Si N4 nanorod with a diameter about 7.4
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nm. The ͑100͒ fringes with a spacing of 0.66 nm are parallel to the edge of
the nanorod and the nanorod axis is along ␤-Si N crystallographic c direc-
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tion ͓͑001͔ direction͒.
In the reaction process, the important SiO gas for forma-
tion of Si N and Si N O nanorods was first generated via
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the silicon reduction of silica,
SiO ͑s͒ϩSi͑s͒→2SiO͑g͒ .
͑1͒
2
The generated SiO gas and inlet N gas flowed toward the
2
region of carbon nanotubes from the lower and upper direc-
tions, respectively, then reacted with carbon nanotubes to-
gether. In a Si–C–N–O system, there are two reactions that
could be responsible for the formation of Si N and Si N O
FIG. 2. TEM micrographs of ͑a͒ silicon nitride nanorods and ͑b͒ carbon
nanotubes.
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2
2
nanorod, which can be expressed as9
diam about 7.4 nm. The ͑100͒ fringes with a spacing of 0.66
nm are parallel to the edge of nanorod and the axis of nano-
rod is along ␤-Si N crystallographic c direction ͓͑001͔ di-
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2
SiO͑g͒ϩ3C͑s͒ϩ2N ͑g͒→Si N ͑s͒ϩ3CO͑g͒ , ͑2͒
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4
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SiO͑g͒ϩC͑s͒ϩN ͑g͒→Si N O͑s͒ϩCO͑g͒ .
͑3͒
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2
2
rection͒. Figure 5 shows a HREM image taken from a Si
N O nanorod, which is about 13 nm in diam and the axis of
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2
We believe that the carbon nanotube might act as a re-
movable template in the reaction to confine the reaction in a
local space around carbon nanotube. Therefore, the products
almost hold the shape and the diameter size of nanotube
skeletons, even if they do not contain carbon element.
In summary, silicon nitride nanorods have been success-
fully synthesized by carbon nanotube confined reaction. Al-
the nanorod is along its crystallographic a direction ͓͑100͔
direction͒.
FIG. 5. A HREM image taken from a Si N O nanorod, which is about 13
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FIG. 3. Selected area electron diffraction patterns of a ␤-Si N nanorod: ͑a͒
nm and the nanorod axis is along its crystallographic a direction ͓͑100͔
direction͒.
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͓001͔ diffraction pattern; ͑b͒ ͓100͔ diffraction pattern.
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272 Appl. Phys. Lett., Vol. 71, No. 16, 20 October 1997 Han et al.
32.204.37.217 On: Thu, 04 Dec 2014 14:56:51
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though a deeper understanding of growth mechanism of the
silicon nitride nanorod is needed, our results suggest the car-
bon nanotube confined reaction could in principle be used to
synthesize other nitride nanorods which might be of interest
to both fundamental research and possible applications.
This work was supported by the NSF of the People’s
Republic of China through Contract No. 59642006 and
partly supported by the foundation of Beijing Electron Mi-
croscopy Laboratory and the foundation of Optics Labora-
tory, Institute of Physics, Academia Sinica. One of the au-
thors ͑X.Z.͒ thanks the Natural Science Foundation Research
of Zhejiang Province, People’s Republic of China for its sup-
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