Simple synthesis of GaN nanoparticles from gallium nitrate and ammonia aqueous solution under a flow of ammonia gas

doi:10.1016/j.matlet.2005.07.075

Materials Letters

Volume 60, Issue 1, January 2006, Pages 73-76

https://doi.org/10.1016/j.matlet.2005.07.075 Get rights and content

Abstract

A simple method for the synthesis of nanosized gallium nitride (GaN) particles from a mixture of gallium nitrate (Ga(NO₃)₃) and aqueous ammonia solutions under a flow of ammonia gas in a temperature range of 700–900 °C is described. Nanosized GaN particles with an average diameter of approximately 20–50 nm were obtained. The resulting GaN nanoparticles showed an intense photoluminescence at 364 nm under UV excitation at 254 nm. The effects of the preparation conditions, such as temperature, length of heating time and ammonia concentration on the crystallinity and intensity of the photoluminescence of the particles were also investigated.

Introduction

Due to a unique combination of properties, gallium nitride (GaN) and related compounds has become a promising material for use in applications such as advanced light emitting devices [1] and high power electronic devices [2]. Moreover, nanoparticles and nanostructured materials comprised of metals and semiconductors that exhibit size-dependent optical, magnetic, electronic and catalytic properties have recently been heralded as the next generation of electronic devices in the design of advanced materials. Therefore, a method for the simple, scalable and low-cost production of well-dispersed nanosized GaN particles would be desirable, especially on an industrial scale.

The synthesis of GaN nanoparticles has been reported by many authors, using techniques such as metal organic chemical vapor deposition (MOCVD) [3], synthesis of GaN nanoparticles in a polymer or silica matrix [4], [5], pyrolysis at high temperatures [6], [7], and the formation of colloidal GaN quantum dots [8]. However, these methods entail a very high production cost together, are typically complicated and usually involve several steps thus making the overall process time consuming.

In the present work, we report on a simple method for the synthesis of nanosized GaN particles from a mixture of Ga(NO₃)₃ and ammonia solutions under a flow of ammonia gas. The use of an aqueous ammonia solution aids in the formation of well-dispersed GaN nanoparticles [9]. The proposed method has a number of advantages over previously used methods [3], [4], [5], [6], [7], [8] in that it is a straightforward process with a high production rate. In addition, the fast that it is a simple process suggests that it would be amenable to low-cost production. In a previous study, we used Ga₂O₃ nanoparticles produced by the pyrolysis of Ga(NO₃)₃, for the synthesis of GaN nanoparticles. In that report, the size of the resulting GaN nanoparticles was larger than that obtained using the present method.

Section snippets

Experimental

The precursors used in preparing GaN nanoparticles included gallium nitrate (Ga(NO₃)₃·nH₂O, Mitsuwa Chemicals Co., Ltd., Japan) as the gallium source, and ammonia solutions (28 wt.%, Kanto Kagaku, Japan). The number of n for Ga(NO₃)₃·nH₂O was determined to be 7.64 by ICP-AES analysis. Ga(NO₃)₃ was dissolved in ultra pure water and the total concentration of Ga was fixed at 0.5 mol/l. Ammonia solutions, ranging from 0 to 1.8 mol/l were mixed with the precursor solution at room temperature. The

Results and discussion

XRD patterns of GaN nanoparticles prepared at various temperatures showed diffraction lines that were consistent with those of hexagonal GaN (JCPDS No. 74-0243) (Fig. 1). The diffraction peaks became sharper with increasing preparation temperature, especially when a temperature of 900 °C was used, resulting in highly crystalline GaN nanoparticles. From the XRD results, no Ga₂O₃ diffraction patterns were observed even when the particles were prepared at lower temperatures (< 700 °C). This

Conclusion

In summary, a simple, scalable process using gallium nitrate and ammonia solutions as precursors was developed for the synthesis of nanosized GaN particles. The method permits nanosized GaN particles, approximately 20–50 nm in average diameter, to be produced. We also found that the GaN nanoparticles had an intense photoluminescence at 364 nm when UV excitation at 254 nm was used.

Acknowledgements

This work was partly supported by Grant-in-Aids and a fellowship sponsored by the Ministry of Education, Culture, Sports, Science and Technology of Japan and the Japan Society for the Promotion of Science (JSPS). A postdoctoral fellowship was also provided from JSPS for Ferry Iskandar. This work was also supported in part by the New Energy and Industrial Technology Development Organization (NEDO)'s “Nanotechnology Materials Program–Nanotechnology Particle Project” based on funds provided by the

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