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Abstract The density functional theory (DFT) of quantum chemistry was used to study the gasphase parasitic reactions in AlNMOCVD growth for UV optoeletronic devices. The reaction pathways of three oligomers of [DMAlNH2]2, [MMAlNH]2 and [MMAlNH]3 with NH3 were investigated, which were related with gaseous nanoparticle generation. By comparing the Gibbs free energy difference of ΔG and transition state barrier of ΔG*, the direction and probability of the related reactions were determined. The results show that there are two competition pathways for [DMAlNH2]2. When T is less than 749 K, the reaction path is dominated by bimolecular reaction with [Al(NH2)3]2 as the product. When T is more than 749 K, it is dominated by intramolecular reaction with [MMAlNH]2 as the product, since the reactions always take the path with lower energy barrier. The other two oligomers of [MMAlNH]2 and [MMAlNH]3 both tend to the bimolecular reaction with NH3 to form the more stable gas products of [AlNHNH2]2 and [AlNHNH2]3 with CH4 elimination. The [Al(NH2)3]2, [AlNHNH2]2 and [AlNHNH2]3 are probably the end gas precursors for surface reactions and for nanoparticle generation in AlNMOCVD process.
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