Synthesis of large-scale SiC–SiO
2
nanowires decorated with amorphous carbon
nanoparticles and Raman and PL properties
Ryongjin Kim
a,b
, Weiping Qin
a,
*
, Guodong Wei
a
, Guofeng Wang
a
, Lili Wang
a
, Daisheng Zhng
a
,
Kezhi Zheng
a
, Ning Liu
a
a
State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Weiping Qin, 2699 Qianjin Street, Changchun 130012, PR China
b
Semiconductor Research Laboratory, Department of Physics, Kim Il Sung University, Democratic People’s Republic of Korea
article info
Article history:
Received 19 March 2009
In final form 8 May 2009
Available online 13 May 2009

ablation in 1998 and have great potential for applications because
they have the 1D features of both nanocables and nanotubes in the
axial direction and build an ideal semiconductor-insulator hetero-
junction in the radial direction [14]. One of the promising applica-
tions of SiC–SiO
2
nanowires is related to photoluminescence (PL)
property. Up to now, numerous publications have been made
assigning to the outstanding ultraviolet-blue emission property
of SiC–SiO
2
nanowires. In previous works, the PL property of SiC–
SiO
2
nanowires has been studied as-grown [15–19] and no effort
has been paid to control it. In present work, we present a novel
SiC–SiO
2
nanostructure decorated with amorphous carbon nano-
particles and its unique PL property. The SiC–SiO
2
nanowires dec-
orated with carbon nanoparticles have been synthesized on Si
substrate under atmospheric environment. Thermal decomposi-
tion of ethanol was used to produce carbon source for synthesis
of this nanostructure. Strong enhancement of blue emission band
and appearance of a new yellow emission band were observed
from this novel nanostructure. Structure and Raman property of
this nanostructure were characterized and the origins of several
PL bands were discussed. A synthesis process of SiC–SiO

using Ar as carrier gas. The flow rate of Ar through the bubbler was
held at 10 ml/min. The synthesis of SiC–SiO
2
nanowires decorated
with carbon nanoparticles was carried out at 1100 °C for 3 h under
the atmospheric pressure. After finished synthesis, the surface of
the sample synthesized at 300 ml/min Ar gas flow rate (condi-
tion-1) was covered with wheat-colored product. For comparison,
same synthesis route was carried out under 100 ml/min Ar gas
0009-2614/$ - see front matter Ó 2009 Published by Elsevier B.V.
doi:10.1016/j.cplett.2009.05.013
* Corresponding author. Fax: +86 431 85168240 8325.
E-mail address: [email protected] (W. Qin).
Chemical Physics Letters 475 (2009) 86–90
Contents lists available at ScienceDirect
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journal homepage: www.elsevier.com/locate/cplett
flow rate. The sample synthesized at 100 ml/min flow rate (condi-
tion-2) was covered with white-colored product. The products
were characterized by scanning electron microscopy (SEM), X-ray
diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX),
transmission electron microscopy (TEM), high-resolution trans-
mission electron microscopy (HRTEM), selected area electron dif-
fraction (SAED), and Raman spectroscopy. Photoluminescence
experiment was carried out at room temperature by using the
He–Cd laser as an exciting source.
3. Results and discussion
Fig. 1 is the XRD pattern of the SiC–SiO
2
nanowires decorated

. Therefore it is
concluded that our nanowires consist of SiC–SiO
2
core–shell nano-
structure. Like the above result of SEM observation, smooth surface
was observed from TEM image of the nanowires synthesized under
the condition-2. Meanwile, a lot of hemispheric depositions were
found on the surface of the nanowires synthesized under the con-
dition-1. The mean diameter of hemispheric depositions was eval-
uated to be about 20 nm and their concentration on the surface of
SiO
2
shell was about 120
l
m
À2
. The interface between hemispheric
deposition and SiO
2
shell layer is clearly observed from HRTEM im-
age (an up-left insert of Fig. 3a). The distance between two fringes
in HRTEM image of a hemispherical deposition was estimated to be
0.346 nm, which is slightly superior to the theoretical value of d
002
interplanar distance in graphite (0.338 nm, JCPDS Card No. 00-001-
0640). The graphitic plane was found to be roughly oriented along
the axial direction of nanowires. The corresponding EDX spectra
confirm that the carbon content in the nanowires having hemi-
spherical depositions on it is higher than that in the nanowires
having smooth surface morphology. It is obvious that such high

sp
À C
2
sp
Þ bonds (E
2g
symmetry in-plane stretching
mode of single crystal graphite) [22,25]. The D-band grows in
intensity with increasing disorder or decreasing crystal size and
the ratio of its intensity to that of G-band, I
D
/I
G
, is inversely propor-
tional to the average size, L
a
, for disordered graphite in the range
2nm<L
a
< 300 nm [26,27]. The intensity ratio of two bands, I
D
/
I
G
, can be expressed as follows:
I
D
I
G
¼

482 nm remains as a shoulder and yellow band is absent. It is
known that the PL from SiC–SiO
2
core–shell nanowires is mainly
originated from their SiO
2
shells [31]. Meanwhile, there are many
reports on the blue emission from SiO
2
[32–35]. In these reports,
Fig. 1. XRD pattern of SiC-SiO
2
nanowires decorated with carbon nanoparticles.
R. Kim et al. / Chemical Physics Letters 475 (2009) 86–90
87
it is commonly accepted that blue emission from SiO
2
is mainly
originated from the oxygen deficiency. In the SiC–SiO
2
nanowires
decorated with carbon nanoparticles, it is possible that the higher
defect density is caused in SiO
2
shell by the diffusion and reactions
of carbon species in SiO
2
matrix [24]. The higher defect density will
result in the enhancement of blue emission. The yellow band can
also be regarded in connection with carbon. The SiC–SiO

,CH
4
,
C
2
H4, C
2
H
2
,H
2
O and H
2
at the temperature higher than 700 °C
[37]. As the temperature goes above 1000 °C, the hydrocarbon spe-
cies are decomposed into H
2
and C [38]. Among the several species
produced by ethanol pyrolysis, H
2
and CO are main gaseous prod-
ucts [37]. In the catalyst-assisted synthesis, SiC–SiO
2
core–shell
nanowires grow via a well known vapor–liquid–solid (VLS) mech-
anism [26]. If the flow rate of Ar dilution gas is slow, carbon is oxi-
dized by H
2
O and O
2

carbon diffusion into SiO
2
and electronic state at the interface be-
tween carbon nanoparticles and SiO
2
shell.
Acknowledgement
This research was supported by Natural Science Foundation of
China (Grant Nos. 50672030 and 10874058).
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