Synthesis of GaN Nanostructures at Low Temperatures by Chemical Vapor Deposition
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1080-O08-01
Synthesis of GaN Nanostructures at Low Temperatures by Chemical Vapor Deposition Christopher Y. Chow1,2, Balaji Raghothamachar1, Joan J. Carvajal3, Hui Chen1, and Michael Dudley1 1 Materials Science & Engineering, Stony Brook University, Stony Brook, NY, 11794 2 Chemistry, Stony Brook University, Stony Brook, NY, 11794 3 Physics and Crystallography of Materials, Universitat Rovira i Virgili, Tarragona, CAT, 43007, Spain ABSTRACT In this study, we report on the synthesis of gallium nitride (GaN) nanopowders on boron nitride (BN) substrates both with and without the use of metal catalyst by chemical vapor deposition (CVD). The synthesis process is based on the reaction between gallium (Ga) atoms from the decomposition of gallium acetylacetonate and ammonia (NH3) gas molecules. Using this process, gallium nitride (GaN) nanopowders have been synthesized at temperatures as low as 400oC, lower than previously reported. The grown nanopowders were characterized by SEM, EDX and TEM. Analysis reveals that higher yields were obtained by treating the BN substrates with Ni catalyst. Experiments to study the effect of growth conditions on the morphology of the nanopowders and analyze the growth mechanism are ongoing. INTRODUCTION Gallium nitride (GaN) is a wide band-gap semiconductor with important applications for the development of UV/blue emitters and detectors, high-frequency field-effect transistors (FETs), and high-power, high-temperature electronics1,2. Although much effort has recently been directed toward the synthesis of GaN one-dimensional nanostructures, such as wires, rods, belts, and tubes, as they reveal intriguing physical properties due to their size and dimensionality3,4, crystal growth processes for GaN bulk growth demand the availability of high purity, singlephase GaN powders. When these powders have sizes in the nanometer scale, they can also be used for study of electronic, thermal, and optical properties5 at the nanoscale. GaN powders are typically synthesized by chemical vapor deposition (CVD) through the direct reaction between Ga2O3 with ammonia (NH3) gas at temperatures around 1000 ºC, resulting in a product with an undesirably high concentration of residual oxygen. Other methods for the production of GaN powders are based on flowing NH3 over molten gallium at temperatures of 900-1000ºC6 or injecting NH3 into molten Ga under atmospheric pressure in the temperature range of 900-980 ºC7. Metallic catalysts, such as Ni, Au or Bi have also been used to increase the yields of GaN powders produced by these methods. The rapid and full stoichiometric conversion of molten Ga into high purity GaN powder reported by Wu et al., by mixing Ga with Bi and flowing NH3 over the mixture8 is one of the most efficient methods. However, the use of high temperatures in these procedures may present problems, such as the sublimation of GaN6, a tendency enhanced when decreasing the size of the powders to the nanometer range, or the decomposition of GaN above 850 ºC and 1000 ºC under high vacuum9 and atmospheric pr
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