Using density functional theory(DFT) of quantum chemistry

the gas reaction mechanism in TMG/NH3/H2 system is explored

especially the formation of amide DMGNH2 and its following nano-nucleation path. By calculating the changes of Gibbs free energy along different reaction path under different temperature

the most probable gas products of nucleation of nanoparticles are determined both thermodynamically and kinetically. It is found that DMGNH2 can be formed by elimination of CH4 from the adduct or by bimolecular collision when T < 622 K. DMGNH2 can be directly formed by the bimolecular collision reaction of TMG and NH3 when T > 622 K. When 662.5 K < T < 939 K

the reactions of dimer [DMGNH2]2 to [MMGNH]2 by successive elimination of CH4 are easy to occur. When 389 K < T < 734.7 K

the reactions of trimer [DMGNH3]3 to [MMGNH]3 by successive elimination of CH4 are easy to occur too. However

further elimination of CH4 from [MMGNH]2 and [MMGNH]3 to form [GaN]2 and [GaN]3 are both thermodynamically unfavorable

because the changes of Gibbs free energy of the reactions are greater than 0. Thus indicates that [MMGNH]2 and [MMGNH]3 are the two probable gas reaction products for the nucleation of oligomers in GaN-MOVPE growth.