NAN O E X P R E S S Open Access
Self-assembled growth of MnSi
~1.7
nanowires
with a single orientation and a large aspect ratio
on Si(110) surfaces
Zhi-Qiang Zou
1,2*
, Wei-Cong Li
1
, Xiao-Yong Liu
1,2
and Gao-Ming Shi
1,2
Abstract
MnSi
~1.7
nanowires (NWs) with a single orientation and a large aspect ratio have been formed on a Si(110) surface
with the molecular beam epitaxy method by a delicate control of growth parameters, such as temperature,
deposition rate, and deposition time. Scanning tunneling microscopy (STM) was employed to study the influence of
these parameters on the growth of NWs. The supply of free Si atoms per unit time during the silicide reaction plays
a critical role in the growth kinetics of the NWs. High growth temperature and low deposition rate are favorable for
the formation of NWs with a large aspect ratio. The orientation relationship between the NWs and the
reconstruction rows of the Si(110) surface suggests that the NWs grow along the 1
10½direction of the silicon
substrate. High-resolution STM and backscattered electron scanning electron microscopy images indicate that the
NWs are composed of MnSi
~1.7
.
Keywords: Self-assembled growth, Nanowires, Transition metal silicides, Scanning tunnel ing spectroscopy,
Silicon (110).
Background
Self-assembled nanowires (NWs) of metal silicides ha ve
received much attention recently for their potential applica-
tions as electrical interconnects on a s cale that cannot be
attained with conventional lithographic methods [1-4]. In
addition, such str uctures are expected to d isplay novel
physical properties related to the structural anisotropy and
quantum confinement effects and could be used as active
elements for the new generation of electronic, optoelectro-
nic, magnetic, and thermoelectric devices [5-7]. In the past
decade, it has been reported that NWs of rare-earth
silicides such as ScSi
2
[7], ErSi
2
[8,9], DySi
2
[2,10,11], GdSi
2
[12,13], and HoSi
2
[14,15] and 3d transition metal silicides
such as FeSi
2
[1], CoSi
2
[3], NiSi
2
[16], and TiSi
2
[17-19 ]
can be formed on silicon substrates by the molecular beam
epitaxy method. While the NW shape of rare-earth silicides
is thought to result from an anisotropic lattice mismatch
that is small (<1%) in length direction and large (>5%) in
width direction of the NW, the NW shape of FeSi
2
,
CoSi
2
,andNiSi
2
results from an ‘endotaxial’ growth
mechanism which involves the growth of silicide into
the Si substrate [1,3].
Very recently, we have reported that MnSi
~1.7
NWs can
also be grown on the Si substrates with reactive epitaxy
method at temperatures above approximately 500°C
[20-22]. The growth mechanism of the NWs was con-
sidered to be anisotropic lattice m ismatch between
the silicide and the Si substrates. The growth direction of
the NWs is confined along Si<110>, resulting in the NWs
orienting with the long axis along one direction (Si 1
10½),
two orthogonal directions (Si 01
1½and [011]), and three
directions (Si 01
1½,01
1½,and 1
10½) on the Si(110), (001),
and (111) surfaces, respectively. However, for scientific
investigation as well as device applications, it would be
highly expected to grow NWs with a single orientation
because the NWs grown in this mode would never cross
and have larger length. Parallel NW arrays can be used as
nanomechanical devices [23], and using parallel NWs, the
anisotropic electronic structure of silicide NWs can be
investigated by angle-resolved photoelectron spectroscopy
[11]. On the other hand, the Si(110) surface is currently
* Correspondence: zqzou@sjtu.edu.cn
1
Centre for Analysis and Testing, Shanghai Jiao Tong University, 800
Dongchuan Road, Shanghai 200240, China
2
Department of Physics, Shanghai Jiao Tong University, 800 Dongchuan
Road, Shanghai 200240, China
© 2013 Zou et al.; licensee Springer. This is an Open Access article distributed under the terms of the Creative Commons
Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction
in any medium, provided the original work is properly cited.
Zou et al. Nanoscale Research Letters 2013, 8:45
http://www.nanoscalereslett.com/content/8/1/45