A Non-thermal Plasma Reactor for the Synthesis of Gallium Nitride Nanocrystals
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0892-FF11-05.1
A Non-thermal Plasma Reactor for the Synthesis of Gallium Nitride Nanocrystals R. Anthony, E. Thimsen, J. Johnson,1 S. Campbell1 and U. Kortshagen Department of Mechanical Engineering, High Temperature and Plasma Laboratory 1 Department of Electrical and Computer Engineering University of Minnesota, Minneapolis, MN 55455 ABSTRACT Gallium Nitride is of interest due to its direct bandgap, which allows for efficient emission in the near-UV range. Bulk GaN is already in use in solid-state devices that exploit its emissive properties, however, the promise of GaN nanocrystals as tunable emitters for use in lightemitting devices and lasers has led to the recent exploration of nanocrystalline GaN synthesis routes. Here we discuss the use of nonthermal plasmas for the synthesis of nanocrystalline powders of GaN. The particles were examined using transmission electron microscopy and x-ray photoelectron spectroscopy. INTRODUCTION Gallium Nitride (GaN) is an interesting material due to its direct bandgap, its high stability, and high tolerance to defects. The deposition of GaN films requires relatively complicated thin film techniques, while powders can often be produced with higher yields. There is also a belief that certain kinds of defects may be thermodynamically unstable in nanocrystals so that nanocrystals could potentially be less defect prone than thin films. In fact, efficient optical emission has been demonstrated from GaN powders [1]. Moreover, some efficient quantum dot materials, such as Cadmium Selenide (CdSe), present serious health hazards. However, GaN has low toxicity: thus, GaN nanoparticle synthesis and use in solid state devices is desirable for its safety with regard to health. The applicability of these highly efficient particles arises in their inclusion in high-brightness solid-state light emitting devices. Solid state light-emitting sources have shown energy efficiencies up to two times the current efficiency of fluorescent bulbs, though these sources are somewhat limited in the emission wavelengths available. Already, GaN nanocrystals can be used to produce ultraviolet and blue light in light-emitting devices [2], and new methods of using them in conjunction with organic semiconductors pose exciting and alternative routes to making inexpensive, highly efficient light emitting diodes (LED) [3]. Although GaN particles traditionally have not been employed in photovoltaic devices, there are methods surfacing that involve the use of layers of nanocrystals for solar cells [4] that emulate organic photovoltaics structures. Fabrication of GaN quantum dots has been attempted by several techniques, such as reactive laser ablation [2], metal-organic chemical vapor deposition (MOCVD) [5], grinding of largerparticle powders [6]. Here we describe a new route to production of GaN nanocrystalline powders using nonthermal plasma reactors, which have been shown to be an efficient high-yield synthesis route for producing nanocrystalline powders of Silicon [7,8].
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