Abstract: This study utilized density functional theory (DFT) in quantum chemistry to investigate the gas-phase parasitic reaction mechanism between diethylzinc (DEZn) and tert-butanol (t-BuOH) during the metal-organic chemical vapor deposition (MOCVD) growth process of ZnO thin films. By calculating the Gibbs free energy changes along various reaction pathways at different temperatures, a comprehensive thermodynamic evaluation of key intermediates (HOZnOBu^t, H(ZnO)₂Bu^t, HZnOH), as well as the formation of dimers (Zn₂O₂H₄, Zn₂O₄H₄, Zn₄O₄H₄), and trimers (Zn₃O₆H₆) was performed. The main objective was to identify potential pathways and products that could lead to the formation of nanoparticles, which might impede ZnO thin film growth. Research has shown that under high-temperature deposition conditions (673.15 K<T<713.15 K), the intermediate product H(ZnO)₂Bu^t resulting from the thermal decomposition of DEZn readily reacts with H₂O to form (ZnOH)₂, supporting ZnO thin film growth. However, these intermediates can also undergo polymerization elimination reactions to generate dimers and trimers, serving as crucial precursors for nanoparticle formation. Notably, the most favorable pathway involved the formation of Zn₂O₄H₄ through the polymerization of (HOZnOBu^t)₂ followed by the elimination of C₄H₈. Therefore, the dimer Zn₂O₄H₄ emerged as a crucial precursor for nanoparticle formation.

Key words: ZnO, metal organic chemical vapor deposition, density functional theory, parasitic reaction, thin film, dimer