Investigation on growth related aspects of catalyst-free InP nanowires grown by metal organic chemical vapor deposition

Article abstract of DOI:10.1016/j.jallcom.2009.01.073

Catalyst-free InP nanowires were grown on Si (1 0 0) substrates by metal organic chemical vapor deposition. In this method, in situ deposited In droplets are seeds of the InP nanowires growth. In order to control the growth of epitaxial InP nanowires, a d

Full text of DOI:10.1016/j.jallcom.2009.01.073

Journal of Alloys and Compounds 479 (2009) 832–834
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Journal of Alloys and Compounds
journal homepage: www.elsevier.com/locate/jallcom
Investigation on growth related aspects of catalyst-free InP nanowires grown by
metal organic chemical vapor deposition
Shuzhen Yua,b, Guoqing Miaoa,∗, Yixin Jina, Tiemin Zhanga,b, Hang Songa, Hong Jianga,
Zhiming Lia, Dabing Lia, Xiaojuan Suna
a Key Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, The Chinese Academy of Sciences, Changchun 130033, China
b Graduate School of the Chinese Academy of Sciences, Beijing 100049, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Catalyst-free InP nanowires were grown on Si (1 0 0) substrates by metal organic chemical vapor deposi-
tion. In this method, in situ deposited In droplets are seeds of the InP nanowires growth. In order to control
the growth of epitaxial InP nanowires, a detailed investigation on the growth related aspects such as the
In droplets deposition time, growth temperature, and V/III ratio has been made. The experimental results
indicate that the diameter, shape, and length of the nanowires can be controlled by growth conditions.
© 2009 Elsevier B.V. All rights reserved.
Received 18 September 2008
Received in revised form 16 January 2009
Accepted 21 January 2009
Available online 31 January 2009
Keywords:
Semiconductors
Nanostructures
Nanofabrications
Vapor deposition
1. Introduction
free growth of InP nanowires on InP (1 1 1) B substrates using in situ
deposited In droplets as seeds for nanowires growth.
Interest in one-dimensional systems such as nanowires and
nanorods has been sparked by a desire to offer a way to fabricate
devices with a bottom-up approach instead of conventional top-
down methods. Nanodevices based on semiconductor nanowires
have already been demonstrated [1–7]. Controlled growth of semi-
conductor nanowires is a key requirement for the development of
future nanoscale optoelectronic and nanoelectronic devices. Actu-
ally, growth conditions have great impact on controlling nanowires
growth. For example, many semiconductor nanowires are sen-
sitive to catalysts diameter, growth temperature, and reactants
pressure [8–17].Au nanoparticle is the most common catalyst to
grow nanowires by various methods such as metal organic chem-
ical vapor deposition (MOCVD) [12,13], pulsed laser deposition
(PLD) [18], molecular beam epitaxy (MBE) [19] and chemical beam
epitaxy (CBE) [20]. But Au catalyst can result in unintentional incor-
poration into nanowires or produce unwanted effect in nanowires
[21,22]. It has been demonstrated by Allen et al. [23] that Au catalyst
atoms are detected in Si nanowires by high-angle annular dark-
filed scanning transmission electron microscopy. In order to avoid
the contamination from Au atoms, a new growth method has been
proposed by Novotny and Yu [21]. They demonstrated the catalyst-
In this paper, we study the growth related aspects of InP
nanowires by varying the In droplets deposition time, growth tem-
perature, and V/III ratio to control the diameter, shape, and length
of the nanowires. Nanowires are characterized by scanning elec-
tron microscopy (SEM), transmission electron microscope (TEM)
and transmission electron diffraction (TED).
2. Experiments
The InP nanowires were grown on Si (1 0 0) substrate in a horizontal MOCVD
reactor with a constant system pressure of 76 Torr. Trimethylindium (TMI) and phos-
phine (PH3) were used as indium and phosphorus sources with hydrogen as the
carrier gas. The TMI flow was kept constant at 4.8 × 10−6 mol/min and the PH3 flow
varied with V/III ratios during the growth. Prior to the growth, Si (1 0 0) substrates
were cleaned with ultrasonic using organic reagent to remove organic residues
and particles. Native oxide was not removed from the substrates intendedly before
nanowires growth. After putting the substrates into the reactor, the substrates were
heated to growth temperature. Then the TMI was introduced into the reactor to
deposit the In droplets. The nanowires growth commenced by supplying the PH3
and TMI simultaneously after the In droplets deposition. The growth temperature
of the InP nanowires was the same as that of the In droplets.
3. Results and discussion
Fig. 1(a)–(d) shows SEM images of In droplets deposited at 330
and 370 ◦C, respectively, with different growth time. The Inset in
Fig. 1(b) shows an image of a hemispherical In droplet taken at a tilt
angle of 90◦. The average diameters of the In droplets in Fig. 1(a)–(c)
∗
Corresponding author. Tel.: +86 431 84627073; fax: +86 431 84627073.
E-mail address: miaogq@ciomp.ac.cn (G. Miao).
0925-8388/$ – see front matter © 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.jallcom.2009.01.073

S. Yu et al. / Journal of Alloys and Compounds 479 (2009) 832–834
833
Fig. 1. SEM images of In droplets grown at different temperature with varied growth time (a) 330 ◦C, 30 s; (b) 330 ◦C, 120 s; (c) 370 ◦C, 15 s; (d) 370 ◦C, 30 s. Inset in (b) shows
an image of single In droplet taken at a tilt angle of 90◦.
are about 50, 120, and 85 nm, respectively. The average diameters of
the In droplets in Fig. 1(b) and (d) are similar. Obviously, the diam-
eter of the In droplets can be varied by controlling the In droplets
deposition time or the growth temperature. Growth rate of the In
droplets increases rapidly when the growth temperature increases
from 330 to 370 ◦C (in Fig. 1(a) and (d)), resulting from the rapid
increase in TMI decomposition efficiency and diffusion length of In
atoms on the substrate surface with increasing temperature.
SEM images of InP nanowires grown at different V/III ratios and
temperatures are shown in Fig. 2(a)–(h). The growth times for all the
nanowires were 7 min. The nanowires in Fig. 2(a)–(d) were grown
at 330 ◦C with the V/III ratio of 15, 30, 50, and 100, respectively.
Their In droplets seeds were deposited for 120 s. The SEM images of
nanowires grown at 330, 350, 370, and 390 ◦C with the V/III ratio of
30 are shown in Fig. 2(e)–(h), respectively. Their In droplets seeds
were deposited for 30 s. From the images, it can be found that the
lengths of the wires are different from each other. Some of them
have lengths up to five micrometers. The angles between the wires
and the substrate are diverse.
Fig. 3 shows TEM image and corresponding TED pattern of the
InP nanowire. These reveal that the nanowires have a rotational
twin structure, which appears as alternate dark and bright contrasts
along the length of the nanowires. The rotational twin structure
is usually observed in III-V semiconductor nanowires such as InP
[9,24,25], GaAs [26], and InAs [27] nanowires. The TED pattern
shown in Fig. 3(b) confirms that the nanowires growth direction
is ꢀ1 1 1ꢁ. The two sets of spots originate from rotational twin zinc-
blende crystal structure.
from the vapor phase, then In atoms combine with P atoms to form
crystalline InP directly. Since the melting point of InP (1070 ◦C) is
much higher than that of the nanowire growth temperature, InP
precipitates at the liquid–solid interface, and the liquid droplet rises
from the Si substrate surface. Under this growth mechanism, we can
understand the tendency of the diameter, length, taper, and reverse
taper of the nanowires which are affected by In droplets deposition
time, growth temperature, and V/III ratio.
The diameters of the InP nanowires in Fig. 2(b), (e), and (g) are
consistent with those of the In droplets in Fig. 1(b), (a), and (d).
This means that the diameters of the nanowires can be controlled
by the diameters of the In droplets, in agreement with previous
reports [29]. As seen in Fig. 2(a)–(d), the kink, taper, and length
of the nanowires can be controlled by varying the V/III ratio and
growth temperature. High V/III ratios cause frequent wires, kink
and taper, whereas low V/III ratios cause problems associated with
low nanowires growth rate and reversely tapering nanowires. Uni-
form diameter of nanowires can be achieved by optimizing the
input V/III ratio. Obviously, the V/III ratio of 30 is suitable for InP
nanowires grown at 330 ◦C. Furthermore, in the temperature range
of 330–370 ◦C, different diameters of In droplets need the similar
optimal V/III ratio (Fig. 2(b) and (e)–(g)). While InP nanoparticles
deposition occurs at 390 ◦C, and the area density of the nanowires at
310 ◦C are too low. Another important observation from Fig. 2(e)–(g)
is that the InP nanowires growth rate increases with increasing
growth temperature, because the decomposition efficiency of PH3
and TMI are increased with increasing growth temperature. When
the In droplets deposition time, growth temperature, and V/III ratio
are constant, the length of the nanowires is determined by the
nanowires growth time.
The In droplet can be found at the top of each nanowire. The
melting point of bulk In is only 156.6 ◦C. Due to nanosize effect, the
melting temperature of nanoparticles is always lower than that of
bulk materials [28]. So the In droplets were indeed in molten state
during the growth. This means that the growth mechanism of the
wires is vapor–liquid–solid (V–L–S). When the PH3 and TMI were
supplied into the reactor, the In droplet absorbs In and P atoms
The TMI flow was kept constant and the flow of PH3 which pro-
vides P atoms for growing the nanowires varied with V/III ratios
during the growth. When the V/III ratio is high, quantities of P atoms
absorbed by the In droplet are much more than these of In atoms
absorbed by the In droplet. A large amount of In atoms which con-
Fig. 2. (a)–(d) SEM images of InP nanowires grown at 330 ◦C with varied V/III ratio (a) 15; (b) 30; (c) 50; (d) 100. (e)–(h) SEM images of InP nanowires grown at different
temperature (e) 330 ◦C; (f) 350 ◦C; (g) 370 ◦C; (h) 390 ◦C with the same V/III ratio of 30. The In droplets deposition time for (a)–(d) and (e)–(h) are 120 s and 30 s, respectively.

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S. Yu et al. / Journal of Alloys and Compounds 479 (2009) 832–834
Fig. 3. TEM image (a) and corresponding TED pattern (b) of single InP nanowire.
tain the absorbed In atoms and part of the In droplet are consumed
by these P atoms. The diameter of the In droplet becomes small. The
diameter of nanowire becomes smaller gradually. Then the tapering
nanowires are formed.
When the V/III ratio is 30, equal quantities of In and P atoms are
absorbed by the In droplet. No In atoms in the In droplet are con-
sumed by the absorbed P atoms. So the diameter of the In droplet at
the top of the nanowire is invariable, during the growth process. The
invariable diameter of the In droplet determines the uniformity of
the nanowires. That is why in the temperature range of 330–370 ◦C,
different diameters of the In droplets need the similar optimal V/III
ratio (Fig. 2(b) and (e)–(g)).
When the V/III ratio is lower than 30, quantities of P atoms
absorbed by the In droplet are fewer than these of In atoms
absorbed by the In droplet. So In atoms consumed by P atoms are
fewer than those absorbed by the In droplet. The absorbed In atoms
are surplus. So the diameter of the In droplet at the top of the
nanowire becomes larger and larger gradually and the reversely
tapering nanowires are formed. Also lacking P atoms decrease the
growth rate of nanowires. It can conclude that the shape of the
wires is affected by the relative quantities of In and P atoms which
are absorbed by the In droplet.
References
[1] K. Haraguchi, T. Katsuyama, K. Hiruma, K. Ogawa, Appl. Phys. Lett. 60 (1992)
745–747.
[2] X. Duan, Y. Huang, Y. Cui, J. Wang, C.M. Lieber, Nature 409 (2001) 66–69.
[3] X. Duan, Y. Huang, R. Agarwal, C.M. Lieber, Nature 421 (2003) 241–245.
[4] M.T. Bjork, B.J. Ohlsson, C. Thelander, A.I. Persson, K. Deppert, L.R. Wallenberg,
L. Samuelson, Appl. Phys. Lett. 81 (2002) 4458–4460.
[5] C. Thelander, T. Martensson, M.T. Bjork, B.J. Ohlsson, M.W. Larsson, L.R. Wallen-
berg, L. Samuelson, Appl. Phys. Lett. 83 (2003) 2052–2054.
[6] O. Hayden, R. Agarwal, W. Lu, Nanotoday 3 (2008) 12–22.
[7] Y. Hu, J. Xiang, G. Liang, H. Yan, C.M. Lieber, Nano Lett. 8 (2008) 925–930.
[8] K.A. Dick, K. Deppert, L. Samuelson, W. Seifert, J. Cryst. Growth 297 (2006)
326–333.
[9] S. Bhunia, T. Kawamura, S. Fujikawa, H. Nakashima, K. Furukawa, K. Torimitsu,
Y. Watanabe, Thin Solid Films 464–465 (2004) 244–247.
[10] P. Paiano, P. Prete, N. Lovergine, A.M. Mancini, J. Appl. Phys. 100 (2006)
094305–094308.
[11] M. Tchernycheva, J.C. Harmand, G. Patriarche, L. Travers, G.E. Cirlin, Nanotech-
nology 17 (2006) 4025–4030.
[12] K. Tateno, H. Hibino, H. Gotoh, H. Nakano, Appl. Phys. Lett. 89 (2006)
033114–033116.
[13] U. Kim, H.K. Seong, M.H. Kim, H.J. Choi, Mater. Lett. 63 (2009) 97–99.
[14] T. Stoica, R. Meijers, R. Calarco, T. Richter, H. Luth, J. Cryst. Growth 290 (2006)
241–247.
[15] M.S. Gudiksen, J. Wang, C.M. Lieber, J. Phys. Chem. B 105 (2001) 4062–4064.
[16] X.M. Cai, F. Ye, S.Y. Jing, D.P. Zhang, P. Fan, E.Q. Xie, J. Alloys Compd. 467 (2009)
472–476.
[17] K.A. Dick, K. Deppert, L. Samuelson, W. Seifert, J. Cryst. Growth 298 (2007)
631–634.
4. Conclusions
[18] E.P.A.M. Bakkers, M.A. Verheijen, J. Am. Chem. Soc. 125 (2003) 3440–3441.
[19] D.M. Cornet, V.G.M. Mazzetti, R.R. LaPierre, Appl. Phys. Lett. 90 (2007)
013116–013118.
Catalyst-free growth of InP nanowires with control over the
diameter, shape, and length of the nanowires has been investigated
in detail. The diameter of wires can be controlled by the diame-
ter of In droplets. The effect of V/III ratio on the shape of the InP
nanowires attributes to the relative quantities of In and P atoms
which are absorbed by In droplets. The growth rate of InP nanowires
increases with increasing growth temperature. The growth of InP
nanowires can be controlled, which leads to a reproducible pro-
cess, and can potentially offer high throughput for the fabrication
of nanodevices in large scale.
[20] P.J. Poole, J. Lefebvre, J. Fraser, Appl. Phys. Lett. 83 (2003) 2055–2057.
[21] C.J. Novotny, P.K.L. Yu, Appl. Phys. Lett. 87 (2005) 203111–203113.
[22] M. Mattila, T. Hakkarainen, H. Lipsanen, H. Jiang, E.I. Kauppinen, Appl. Phys.
Lett. 89 (2006) 063119–063121.
[23] J.E. Allen, E.R. Hemesath, D.E. Perea, J.L. Lensch-falk, Z.Y. Li, F. Yin, M.H. Gass,
P. Wang, A.L. Bleloch, R.E. Palmer, L.J. Lauhon, Nat. Nanotechnol. 3 (2008)
168–173.
[24] M. Mattila, T. Hakkarainen, H. Jiang, E.I. Kauppinen, H. Lipsanen, Nanotechnol-
ogy 18 (2007) 155301–155305.
[25] M. Moewe, L.C. Chuang, V.G. Dubrovskii, C.C. Hasnain, J. Appl. Phys. 104 (2008)
044313–044316.
[26] K. Hiruma, M. Yazawa, T. Katsuyama, K. Ogawa, K. Haraguchi, M. Koguchi, H.
Kakibayashi, J. Appl. Phys. 77 (1995) 447–462.
[27] X. Xu, W. Wei, X. Qiu, K. Yu, R. Yu, S. Si, G. Xu, W. Huang, B. Peng, Nanotechnology
17 (2006) 3416–3420.
[28] N. Wang, Y. Cai, R.Q. Zhang, Mater. Sci. Eng. R 60 (2008) 1–51.
[29] Y. Cui, L.J. Lauhon, M.S. Gudiksen, J. Wang, C.M. Lieber, Appl. Phys. Lett. 78 (2001)
2214–2216.
Acknowledgement
This work is supported by Projects of National Natural Science
Foundation of China under grant no. 50632060.