Indium nitride crystals with flower-like structure

Article abstract of DOI:10.1039/b211099g

Preparation of indium nitride at atmospheric pressure has been examined by means of halide chemical vapour deposition; from the SEM observations of the crystals deposited onto an Si(100) substrate it was found that they showed flower-like structure.

Full text of DOI:10.1039/b211099g

Indium nitride crystals with flower-like structure
Naoyuki Takahashi,* Arei Niwa, Haruka Sugiura and Takato Nakamura
Department of Materials Science and Technology, Faculty of Engineering, Shizuoka University, 3-5-1
Johoku, Hamamatsu 432-8561, Japan. E-mail: tntakah@ipc.shizuoka.ac.jp; Fax: +81-53-478-1197;
Tel: +81-53-478-1197
Received (in Cambridge, UK) 12th November 2002, Accepted 23rd December 2002
First published as an Advance Article on the web 14th January 2003
Preparation of indium nitride at atmospheric pressure has
been examined by means of halide chemical vapour deposi-
tion; from the SEM observations of the crystals deposited
onto an Si(100) substrate it was found that they showed
flower-like structure.
of 0.2 K. The substrate used was an n-type Si(100) wafer with
a resistance of 5 3 1024 W m. InCl3 in a source boat was
evaporated at a temperature of 523 K, and supplied to the
growth zone of the reactor by purified N2 carrier gas. NH3 was
also supplied to the growth zone of the reactor by purified N2
carrier gas. The partial pressures of InCl3 and NH3 were
adjusted independently by varying the flow rates of N2 carrier
gas. The partial pressure of NH3 was varied in the range 9.3 3
103–2.8 3 104 Pa at a constant partial pressure of InCl3 of 4.7
3 102 Pa. The purity of the N2 and NH3 gases (Air Liquide Co.
Ltd) are 99.9999% and 99.9995%, respectively. The purity of
InCl3 (Kojundo Chemical Lab. Co., Ltd) is 99.99%. The
Science and technology of three-dimensionally ordered materi-
als have led to great excitement during the last decade. Amongst
them, subjects dealing with very tiny objects are of immense
academic interest. There has already been much progress in the
synthesis, assembly and fabrication of three-dimensionally
ordered materials,1 and also potential applications of such
materials to a wide variety of technologies, such as glancing
angle deposition (GLAD)2 and template selectivity growth.3
Recently, we examined the preparation of InN utilising a
reaction of gaseous InCl3 and NH3 under atmospheric pressure
(AP-HCVD).4 It was found that when the substrate temperature
was in the range 723–823 K that indium nitride crystals with
unusual flower-like structures were formed. Here, we report the
results of the investigation on indium nitride with flower-like
structure grown on an Si(100) substrate by means of atmos-
pheric pressure halide chemical vapour deposition.
Table 1 Typical growth conditions
Substrate
Si(100)
4.7 3 102
2.8 3 104
N2
1.25 3 1025
823
InCl3 partial pressure/Pa
NH3 partial pressure/Pa
Carrier gas
Total flow rate/m3 s21
Growth temperature/K
A horizontal hot-wall quartz reactor was used for the
preparation of InN. The nitride was deposited onto an Si(100)
substrate under atmospheric pressure. The growth temperature
was measured just under the substrate stage with an error limit
Fig. 1 SEM image of the InN grown under condition of Table 1. (a)
magnification 3700, (b) magnification 34000.
Fig. 2 (a) TEM and (b) electron diffraction images of an InN crystal.
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CHEM. COMMUN., 2003, 318–319
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crystallographic structure of the deposited InN was examined
by a Rigaku Rint 2000 X-ray diffractometer. Their crystallinity
was evaluated by scanning electron microscopy (SEM), trans-
mission electron microscopy (TEM) and electron diffraction.
The crystal structure and orientation of the as-grown films
were examined by means of the X-ray diffractometry (XRD).
Only the diffraction peaks of InN and the Si substrate were
observed. The observed diffraction lines reveal that the
hexagonal structure is the only crystalline phase, exhibiting
sharp and symmetric reflections for basal (002) and (004)
planes, and broad and asymmetric reflections for the non-basal
(101), (103) and (110) planes.5 The lattice constant was
estimated to be 0.570 nm utilising the observed (002)
diffraction, which implies that the obtained lattice constant is
similar to the reported value of 0.57033 nm for the polycrystal-
line InN powder.5
Fig. 1(a) and (b) show SEM micrographs of the InN grown on
the Si(100) substrate under the conditions listed in Table 1. At
a glance of the SEM micrographs in Fig. 1(a), it is immediately
noticed that the deposited InN has an interesting geometry with
flower-like structure. The enlarged SEM micrograph of a
flower-like InN arrangement shows that it consists of six petal
crystals and a style crystal (Fig. 1(b)). One can see that there is
a sixfold axis along the style, and that the respective crystals
constituting the petals and a style are staggered hexagonal
bipyramids. The flower-like InN was formed only when the
substrate temperature was kept at 823 K. As for the partial
pressure of NH3, it was found that the geometry with flower-like
structure was hardly affected in the range of p(NH3) = 9.3 3
103–2.8 3 104 Pa at a constant partial pressure of InCl3 of 4.7
3 102 Pa examined in this study.
A representative TEM micrograph and an electron diffraction
pattern of the indium nitride crystals are shown in Fig. 2(a) and
(b), respectively, in which the top of the one of the staggered
hexagonal bipyramidal crystals was measured. In Fig. 2(a), it is
seen that there are a number of lines with a constant spacing of
0.2853 nm, which is assigned to the 002 spacing based on both
the JCPDS data5 and the XRD results mentioned above. Also,
an intense spot pattern appearing in the electron diffraction
image is a characteristic pattern of hexagonal structures (Fig.
2(b)). This means that the staggered hexagonal bipyramidal
crystals are single crystals of InN.
In summary, we have found that InN with flower-like
structure was deposited onto an Si(100) substrate by AP-HCVD
upon reaction of InCl3 and NH3. Each crystal constituting the
flower is a single crystal with staggered hexagonal bipyramidal
structure. The formation of such highly unusual crystals is
sensitive to the substrate temperature.
This work was supported by the Japan Society for the
Promotion of Science through a Grants-in-aid for Scientific
Research (A) No. 13305047.
Notes and references
1 P. V. Braun, 223rd ACS National Meeting Orlando, FL, USA, April,
2002, POLY-254(2002); P. H. Holloway and S. L. Jones, J. Surf. Anal.,
1998, 4, 226.
2
M Seto, K. Westra and M. Brett, J. Mater. Chem., 2002, 12, 2348.
3 B. Q. Wei, R. Vajtai, Y. Jung, J. Ward, R. Zhang, G. Ramanath and P. M.
Ajayan, Nature, 2002, 416, 495.
4 N. Takahashi, A. Niwa, T. Takahashi, T. Nakamura, M. Yoshioka and Y.
Momose, J. Mater. Chem., 2002, 12, 1573.
5 JCPDS File 1999, No. 50-1239.
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