established for the first time. The reaction was carried out in
an aqueous solution with NH4Cl as nitrogen source at
250 ꢀC. It was found that the bandgaps of IIIA nitrides and
their alloy nanocrystals can cover the region of 2.1–6.3 eV.
This work opens a new aqueous route to synthesize highly
covalent non-molecular solid nitride materials.
Acknowledgements
This work was supported by the Chinese National Natural
Science Foundation, Chinese Ministry of Education and
Chinese Academy of Sciences. The authors thank Prof.
Shuyuan Zhang for his technical assistance with the HRTEM
experiments.
References
1
(a) H. Morkoc and S. N. Mohammad, Science, 1995, 267, 51;
(b) H. Morkoc, S. Strite, G. B. Gao, M. E. Lin, B. Sverdlov
and M. Burns, J. Appl. Phys., 1994, 76, 1363; (c) T. Matsuoka,
T. Ohki, T. Ohno and Y. Kawaguchi, J. Cryst. Growth, 1994,
138, 727.
2
3
D. A. Neumayer and J. G. Ekerdt, Chem. Mater., 1996, 8, 9.
(a) S. Nakamura, in Blue Laser Light Emitting Diodes,
[Int. Symp.], eds. A. Yoshikawa, K. Kishino, M. Kobayashi
and T. Yasuda, IOS Press, Amsterdam, Netherlands, 1996,
pp. 119–124; (b) F. A. Ponce and D. P. Bour, Nature (London),
1997, 386, 351.
4
5
L. M. Sheppard, Ceram. Bull., 1990, 69, 1801.
M. Goano, E. Bellotti, E. Ghillino, C. Garetto, G. Ghione and
K. F. Brennan, J. Appl. Phys., 2000, 88, 6476.
Fig. 7 UV-vis spectra of as-prepared (A) InN, (B) GaN, (C) AlN,
(D) In0.8Ga0.2N and (E) In0.5Ga0.5N.
6
R. A. Fischer, A. Miehr, T. Metzger, E. Born, O. Ambacher,
H. Angerer and R. Dimitrov, Chem. Mater., 1996, 8, 1356.
M. Boækowski, Physica B, 1999, 265, 1.
T. Inushima, T. Shiraishi and V. Y. Davydov, Solid State
Commun., 1999, 110, 491.
7
8
obtained with a yield of ca. 5%. While adding I2 , the yield of
nitrides can be improved to 25%. The role of I2 in the reactions
can be described as follows:
9
O. Takai, K. Ikuta and Y. Inoue, Thin Solid Films, 1998,
318, 148.
10 H. Parala, A. Devi, F. Hipler, E. Maile, A. Birkner, H. W. Becker
and R. A. Fischer, J. Cryst. Growth, 2001, 231, 68.
11 I. Grzegory, J. Jun, M. Bockowski, S. Krukowski, M.
2M2ðNHÞ3 þ 3I2 ! 4MN þ N2 þ 6HI
ðVIIÞ
Thus, the above reactions (III), (IV), (V) and (VII) could be
possible steps in the overall reaction (II). It is a pity that
NH4SCN, NH:C(NH2)2 and M2(NH)3 are intermediates that
cannot be detected by us. Further work is desirable to identify
the mechanism of reaction (II).
´
Wroblewski, B. Lucznik and S. Porowski, J. Phys. Chem. Solids,
1995, 56, 639.
12 N. Takahashi, J. Ogasawara and A. Koukitu, J. Cryst. Growth,
1997, 172, 298.
13 (a) J. D. Houmes and H.-C. zur Loye, Chem. Mater., 1996, 8,
2551; (b) J. W. Hwang, J. P. Campbell, J. Kozubowski, S. A.
Hanson, J. F. Evans and W. L. Gladfelter, Chem. Mater., 1995,
7, 517.
14 R. W. Cumberland, R. G. Blair, C. H. Wallace, T. K. Reynolds
and R. B. Kaner, J. Phys. Chem. B, 2001, 105, 11 922.
15 H. Lu, W. J. Schaff, J. Hwang, H. Wu, G. Koley and L. F.
Eastman, Appl. Phys. Lett., 2001, 79, 1489.
16 (a) Y. Xie, Y. Qian, W. Wang, S. Zhang and Y. Zhang, Science,
1996, 272, 1926; (b) Y. J. Bai, Z. G. Liu, X. G. Xu, D. L. Cui,
X. P. Hao, X. Feng and Q. L. Wang, J. Cryst. Growth, 2002,
241, 189; (c) J. P. Xiao, Y. Xie, R. Tang and W. Luo, Inorg.
Chem., 2003, 42, 107.
It is noteworthy that the other reagents are also crucial to
the formation of nitrides. (1) NH4Cl not only provides the
nitrogen source, but also makes the reaction system weakly
acidic (before reaction pH ꢂ 6, after reaction pH ꢂ 3.5), expe-
diting M2S3 as the group IIIA metal source and preventing
group IIIA metal cations from hydrolyzing. Complementary
experiments showed that a basic environment is unsuitable
for these reactions. If using NH3 (pH ꢂ 9) as the nitrogen
source, oxides rather than nitrides were obtained. (2) Using
M2S3 as the group IIIA metal source not only retards the
hydrolysis of the group IIIA metal cations (compared with
indium halides), but also provides a group IIIA metal source
from a covalent compound, whose polarity is close to that of
group IIIA nitrides. With MX3 (X ¼ Cl, Br, I) or their corres-
ponding organometallic compounds as the group IIIA metal
source, no group IIIA nitrides can be obtained.
17 S. Gao, J. Lu, Y. Zhao, N. Chen and Y. Xie, Chem. Commun.,
2002, 3064.
18 C. D. Wanger, W. M. Riggs, L. E. Davis, J. F. Moulder and G. E.
Muilenberg, Handbook of X-Ray Photoelectron Spectroscopy,
Perkin-Elmer Corp., Eden Prairie, 1978.
19 K. Nakamoto, Infrared and Raman of Inorganic and Coordination
Compounds, 3rd edn., Wiley, New York, 1978.
20 (a) F. A. Cotton and G. Wilkinson, Advanced Inorganic Chemis-
try, John Wilkey & Sons, Inc., New York, 1972; (b) S. C. Chen,
C. Y. Tang and Z. D. Ding, Important Inorganic Reactions,
Shanghai Science and Technology Publisher, Shanghai, 1994 (in
Chinese); (c) R. K. Singh, B. P. Asthane and H. P. Bisl, Chem.
Phys. Lett., 1993, 209, 390.
Conclusions
In summary, the preparation of group IIIA nitride semi-
conductors in aqueous solution under mild conditions is
T h i s j o u r n a l i s Q T h e R o y a l S o c i e t y o f C h e m i s t r y a n d t h e
C e n t r e N a t i o n a l d e l a R e c h e r c h e S c i e n t i f i q u e 2 0 0 4
N e w . J . C h e m . , 2 0 0 4 , 2 8 , 2 1 4 – 2 1 7
217