Strategies to indium nitride and gallium nitride nanoparticles: Low-temperature, solution-phase and precursor routes.

摘要

I present new strategies to low-temperature solution-phase synthesis of indium and gallium nitride (InN and GaN) ceramic materials. The strategies include: direct conversion of precursor molecules to InN by pyrolysis, solution-phase synthesis of nanostructured InN fibers via molecular precursors and co-reactants, and synthesis of powders through reactions derived from molten-salt chemistry.; Indium nitride powders are prepared by pyrolysis of the precursors R ₂InN₃ (R = t-Bu (1), i-Amyl(2), Et(3), i-Pr( 4)). The precursors are synthesized via azide-alkoxide exchange of R₂InOMe with Me₃SiN₃. The precursors are coordination polymers containing five-coordinate indium centers. Pyrolysis of 1 and 2 under N₂ at 400°C yields powders consisting primarily of InN with average crystal sizes of 15–35 nm. 1 yields nanocrystalline InN with average particle sizes of 7 nm at 250°C. 3 and 4 yield primarily In metal from pyrolysis.; Refluxing 1 in diisopropylbenzene (203°C) in the presence of primary amines yields InN nanofibers 10–100 nm in length. InN nanofibers of up to 1 μm can be synthesized by treating 1 with 1,1-dimethylhydrazine (DMHy) The DMHy appears to control the fiber length by acting as a secondary source of active nitrogen in order to sustain fiber growth. The resulting fibers are attached to droplets of indium metal implying a solution-liquid-solid growth mechanism. Precursor 4 yields crystalline InN whiskers when reacted with DMHy. Reactions of 4 with reducing agents such as HSnBu₃, yield InN nanoparticles with an average crystallite size of 16 nm.; Gallium precursors R₂GaN₃ (R = t-Bu( 5), Me₃SiCH₂(6) and i-Pr( 7)), synthesized by azide-alkoxide exchange, are found to be inert toward solution decomposition and do not yield GaN. These compounds are molecular dimers and trimers unlike the indium analogs. Compound 6 displays a monomer-dimer equilibrium in benzene solution, but exists as a solid-state trimer.; InN powders are also synthesized by reactions of InCl₃ and LiNH₂ in a molten alkali-halide eutectic, KBr: Liar (60:40), at 400°C. The molten salt acts as an appropriate recrystallization medium for InN. Large InN platelets up to 500 nm could be synthesized. This is a significant step in finding mild reaction conditions that yield large InN crystals.