Nanotubular structures of zinc oxide Y.J. Xing a,b , Z.H. Xi a , X.D. Zhang a , J.H. Song a , R.M. Wang b , J. Xu b , Z.Q. Xue a , D.P. Yu b, * a Department of Electronics, Peking University, Beijing 100871, People’s Republic of China b School of Physics, Electron Microscopy Laboratory, and State Key Laboratory for Mesoscopic Physics, Peking University, Beijing 100871, People’s Republic of China Received 10 July 2003; received in revised form 7 September 2003; accepted 10 November 2003 by Z.Z. Gan Abstract ZnO nanotubes with a regular polyhedral shape, hollow core, and wall thickness as small as 4 nm, have been prepared in large-area substrate by vapor phase growth. The nanotubes can be classified into two groups consisting of either polycrystalline or straight single crystal. The formation of the ZnO nanotubes was found closely related to the hexagonal structure of the ZnO crystal and the peculiar growth conditions used. q 2003 Elsevier Ltd. All rights reserved. PACS: 61.46. þ w; 81.16. 2 c; 81.07.De; 81.05.Hd Keywords: A. Nanostructures; A. Semiconductors; C. Scanning and transmission electron microscopy 1. Introduction Nano-sized tubular structures have stimulated intensive research interests [1–6], because these materials have enabled studies on fundamental physical properties [7,8], and served as building blocks to construct nanoscale devices [9,10]. However, nanotubular structures have only been grown for few materials, which have bulk lamellar structures, such as graphite or graphite-like structures (BN, BCN, WS 2 , MoS 2 ). Little is known for direct growth of nanotubular structures from 3-dimensional materials to date [11], though complex lithography was used to engineer Ge – Si thin films into nanotubes [12]. The nanophased ZnO compound was widely studied since this material exhibits a number of interesting fundamental properties and possible applications, including ZnO films [13], disordered nano- particles [14], nanobelts [15], and nanowires [16] in which very intense stimulated UV lasing action was observed at room temperature. Recently, the tubular structures of ZnO with the diameters of 30/350 nm were observed in the heterostructures of Zn core/ZnO sheath nanocables and in Zn(NH 3 ) 4 2þ precursor solutions [17,18]. However, these products have a low yield of the production and poor morphology and crystal quality. We demonstrate, in this communication, crystalline ZnO nanotubes with a regular polyhedral shape, hollow core, and wall thickness of 4– 20 nm, were prepared in large-area substrate by vapor phase growth. 2. Experimental The ZnO nanotubes were grown using thermal evapor- ation of Zn/ZnO powder mixture. Powders of zinc oxide (1.0 g) and zinc (0.3 g) were well mixed and put into the central zone of alumina tube in a tube furnace. The whole system was evacuated to about 300 Torr, and filled with Argon. The furnace was heated to about 1300 8C under flowing Ar atmosphere (40 sccm) for 1 h. Si substrates (5 £ 20 mm) were placed downstream inside the tube (temperature 700 8C) in sequence to collect the products. It is noted that proper amount of water was held in a glass vessel upstream the alumina tube to keep a wet oxidation 0038-1098/$ - see front matter q 2003 Elsevier Ltd. All rights reserved. doi:10.1016/j.ssc.2003.11.049 Solid State Communications 129 (2004) 671–675 www.elsevier.com/locate/ssc * Corresponding author. Tel./fax: þ 8610-62759474. E-mail address: [email protected] (D.P. Yu).
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aDepartment of Electronics, Peking University, Beijing 100871, People’s Republic of ChinabSchool of Physics, Electron Microscopy Laboratory, and State Key Laboratory for Mesoscopic Physics, Peking University, Beijing 100871,
People’s Republic of China
Received 10 July 2003; received in revised form 7 September 2003; accepted 10 November 2003 by Z.Z. Gan
Abstract
ZnO nanotubes with a regular polyhedral shape, hollow core, and wall thickness as small as 4 nm, have been prepared in
large-area substrate by vapor phase growth. The nanotubes can be classified into two groups consisting of either polycrystalline
or straight single crystal. The formation of the ZnO nanotubes was found closely related to the hexagonal structure of the ZnO
crystal and the peculiar growth conditions used.
q 2003 Elsevier Ltd. All rights reserved.
PACS: 61.46. þ w; 81.16. 2 c; 81.07.De; 81.05.Hd
Keywords: A. Nanostructures; A. Semiconductors; C. Scanning and transmission electron microscopy
1. Introduction
Nano-sized tubular structures have stimulated intensive
research interests [1–6], because these materials have
enabled studies on fundamental physical properties [7,8],
and served as building blocks to construct nanoscale devices
[9,10]. However, nanotubular structures have only been
grown for few materials, which have bulk lamellar
structures, such as graphite or graphite-like structures
(BN, BCN, WS2, MoS2). Little is known for direct growth
of nanotubular structures from 3-dimensional materials to
date [11], though complex lithography was used to engineer
Ge–Si thin films into nanotubes [12]. The nanophased ZnO
compound was widely studied since this material exhibits a
number of interesting fundamental properties and possible
applications, including ZnO films [13], disordered nano-
particles [14], nanobelts [15], and nanowires [16] in which
very intense stimulated UV lasing action was observed at
room temperature. Recently, the tubular structures of ZnO
with the diameters of 30/350 nm were observed in the
heterostructures of Zn core/ZnO sheath nanocables and in
Zn(NH3)42þprecursor solutions [17,18]. However, these
products have a low yield of the production and poor
morphology and crystal quality. We demonstrate, in this
communication, crystalline ZnO nanotubes with a regular
polyhedral shape, hollow core, and wall thickness of 4–
20 nm, were prepared in large-area substrate by vapor phase
growth.
2. Experimental
The ZnO nanotubes were grown using thermal evapor-
ation of Zn/ZnO powder mixture. Powders of zinc oxide
(1.0 g) and zinc (0.3 g) were well mixed and put into the
central zone of alumina tube in a tube furnace. The whole
system was evacuated to about 300 Torr, and filled with
Argon. The furnace was heated to about 1300 8C under
flowing Ar atmosphere (40 sccm) for 1 h. Si substrates
(5 £ 20 mm) were placed downstream inside the tube
(temperature 700 8C) in sequence to collect the products.
It is noted that proper amount of water was held in a glass
vessel upstream the alumina tube to keep a wet oxidation
0038-1098/$ - see front matter q 2003 Elsevier Ltd. All rights reserved.