Đây là một bài báo khoa học về dây nano silic trong lĩnh vực nghiên cứu công nghệ nano dành cho những người nghiên cứu sâu về vật lý và khoa học vật liệu.Tài liệu có thể dùng tham khảo cho sinh viên các nghành vật lý và công nghệ có đam mê về khoa học
Trang 1Physica E 23 (2004) 131–134
www.elsevier.com/locate/physe
Silicon nanowires fabricatedby thermal evaporation of
silicon monoxide
Junjie Niua, Jian Shaa;b, Deren Yanga;∗
a State Key Lab of Silicon Materials, Zhejiang University, Hangzhou 310027, People’s Republic of China
b Department of Physics, Zhejiang University, Hangzhou 310027, People’s Republic of China
Received9 January 2004; accepted30 January 2004 Abstract
A large-scale crystalline silicon nanowires (SiNWs) with a diameter of ∼30 nm andlength of tens of micrometers on
Al2O3templates andsilicon wafers were synthesizedby the thermal evaporation of silicon monoxide (SiO) The SiNWs were measuredby transmission electron microscopy, scanning electron microscopy, X-ray di4raction andRaman spectroscopy, respectively It was pointedout that the SiNWs possessedthe well crystalline structure Therefore, it is consideredthat SiO couldbe usedas Si sources to produce larger-scale SiNWs andcrystalline SiNWs may grow from amorphous nuclei
? 2004 Elsevier B.V All rights reserved
PACS: 71.55.Cn; 81.05.Ys
Keywords: Nanowires; Silicon; Thermal evaporation
1 Introduction
Recently one-dimensional materials such as silicon
nanowires (SiNWs) have stimulatedmuch interest
be-cause of their di4erent electronic and optical
charac-teristics comparedwith bulk materials [1 4] Many
favorable specialities of SiNWs have been reported
extensively, including p–n junction [5], chemical
sen-sors [6], electrical transport properties [7], andnoise
characteristics [8], etc Therefore, both the
fabrica-tion of large-scale uniform SiNWs andthe
under-standing of the growth mechanism of SiNWs are very
important for their application In fact, several
dif-ferent methods have been used for producing SiNWs
∗Corresponding author Tel.: +86-571-87951667;
fax: +86-571-87952322.
E-mail address: mseyang@dial.zju.edu.cn (D Yang).
such as laser ablation [9], chemical-vapor-deposition
1200◦C [13,14], andelectrochemistry [15] The dif-ferent growth models including vapor–liquid–solid (VLS) [10], oxygen-assisted[13,16,17], andsolid– liquid–solid (SLS) [18] have been reported
In this paper, we successfully synthesizedlarge
templates andsilicon wafers by thermal evaporation
The results of the scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray di4raction (XRD) experiments indicate that the SiNWs crystallizedwell
2 Experimental The samples were preparedin a CVD system as
we reportedpreviously [10] An Al2O3 template and
1386-9477/$ - see front matter ? 2004 Elsevier B.V All rights reserved.
doi:10.1016/j.physe.2004.01.013
Trang 2132 J Niu et al / Physica E 23 (2004) 131–134
a p-type (1 1 1) silicon wafer with a resistivity of
about 0:001 G cm as substrates were placedin a
hor-izontal quartz tube furnace, respectively AndSiO
particles (purity: 99.99%) were placedin an alumina
boat which was placedin the center of the furnace
The furnace was evacuatedfor several hours to reach
a low vacuum of 20 Pa The temperature of the
fur-nace was then raisedto 1100◦C at a heating rate of
20◦C=s andheldat a constant pressure of 1500 Pa
for 6 h When the temperature reachedto 750◦C, the
steady mixture gas of 200 sccm argon and 70 sccm
hydrogen were sent through the chamber, which
actedas the protective gas The thermal evaporation
conditions for SiNWs synthesis were similar to the
previously reportedwork [16,19] After the
reac-tion, the as-grown materials with weak-yellow and
brown color on the di4erent zones of the substrates
were removedout from the furnace andmeasured
by XRD (XRD: Rigaku, D/MAX 2550 PC), SEM
(SEM: JEOL, JSM-5610LV), TEM (TEM: 160 kV,
JEM200CX) andRaman scattering spectroscopy
(Nicolet Almega), respectively, andthe chemical
composition was detected by energy-dispersive X-ray
spectroscopy (EDS) attachedto the SEM
3 Results and discussion
template, respectively It can be seen that the
di-ameter of those SiNWs is about 30 nm The insets
are the selectedarea electric di4raction (SAED)
im-ages, which show that the SiNWs were crystallized
well The top view of the SiNWs on the di4erent
The plenty of the SiNWs with the length of tens
of micrometers were observed The corresponding
EDS in the insets indicate that the SiNWs consists
of high-intensity Si andsmall quantity of oxygen
on the Al2O3 template, which displays high-intensity
peaks of the Si (1 1 1); (2 2 0); (3 1 1); (4 0 0)
and(3 3 1), indicating that the SiNWs were the well
crystalline structure [20] Some SiO2 and -Al2O3
substrate, respectively
Fig 1 TEM images of the SiNWs produced by thermal evaporation
of SiO on a silicon wafer (I, the upper right inset is the SAED image taken from the corresponding SiNWs), and on an Al 2 O 3
template (II, the upper right andlower right insets are the SAED images taken from the middle position (a) and end position (c)
of the SiNW).
Lee et al contributedthat silicon oxide playedan important role on the formation of SiNWs, so called oxygen-assistedmechanism [13,16] In our experi-ments, SiO powders were used as Si sources During
transportedby the gas to the lower-temperature region
reac-tion is as follows:
2SiO(↑) = Si + SiO2:
Trang 3J Niu et al / Physica E 23 (2004) 131–134 133
Fig 2 (a) SEM images of the SiNWs on a silicon wafer, and(b) on an Al 2 O 3 template The insets of (a) and(b) are the EDS taken from the corresponding SiNWs.
500
1000
1500
2000
2500
3000
Al2O3 Si
¦Ã -Al2O3
Al (220)
Si(331) Si(400) Si(311)
Si(220)
Si (111)
2 Theta (degree)
Fig 3 XRD spectrum of the SiNWs grown on an Al 2 O 3 template.
Therefore, in the XRD spectrum (Fig.3), SiO2could also be detected
When Si atoms precipitate, the atoms will easily centralize to form nuclei on low-energy places of sil-icon wafers such as defects With the increase of Si atoms, the nuclei will grow up to wires Andbecause
of oxide reaction and growth energy, some growth
di-rections of SiNWs will be limited; therefore, the 111 and 112 orientations of the SiNWs may be the main
directions, as reported in the previous work [10,14]
of the tip of the nanowires, indicating that is amor-phous The tip shouldbe the nuclear of the SiNW
Trang 4134 J Niu et al / Physica E 23 (2004) 131–134
0
500
1000
1500
2000
2500
3000
3500
4000
960cm -1 960cm -1
517.75cm -1 517.67cm -1
b
a
Raman Shift(cm -1 )
Fig 4 (a) Raman spectra of the SiNWs on a silicon wafer and
(b) on an Al 2 O 3 template.
Furthermore, the upside of the wire was crystalline,
as illustratedin the upper right inset of Fig.1(II) It
is considered that crystalline SiNWs grew from
amor-phous nuclei
template (b), which reveals that there are the same
can be seen from the spectra that the peaks with high
intensity are goodsymmetric andnarrow, which could
be due to the uniform diameter Usually, those peaks
are regarded to be the Jrst-order transverse optical
photon mode (TO) which is caused by the diameter
decrease of the SiNWs [21]
4 Conclusion
A large-scale crystalline SiNWs on silicon wafers
evaporation of silicon monoxide (SiO), respectively
The SiNWs were about ∼30 nm in diameter and tens
of micrometers in length It was also foundthat the
SiNWs crystallizedwell Finally, SiO is consideredto
be Si sources to produce SiNWs
Acknowledgements This work was supportedby the National Natu-ral Science Foundation of China (No.50272057 and 60225010) The authors wouldlike to thank Prof Youwen Wang andMr Z.C Chen, Zhejiang Univer-sity, for their great helps in measurements
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