Quantitative study of gas-phase reactions in ZnO thin-film coating process

A comprehensive investigation of the gas-phase reaction pathways of diethylzinc (DEZn) and tert -butanol ( t -BuOH) during metal-organic chemical vapor deposition (MOCVD) is conducted to improve the deposition quality of ZnO thin films from a micro-mechanistic perspective. This study employs quantum chemical calculations based on density functional theory (DFT) to analyze the reaction kinetics and thermodynamics of the DEZn and t -BuOH system, in order to identify the reaction mechanism and the most probable gas-phase reaction products at different temperatures under excess t -BuOH conditions. Results indicate that the gas-phase product distribution is governed by DEZn pyrolysis. At low temperatures ( T < 523.15 K ), the reaction is hindered by a complexation-dominated mechanism, inhibiting Zn(OH) ₂ formation and resulting in poor-quality, island-like film growth. A mechanistic shift occurs at 523.15 K due to partial pyrolysis of DEZn, transitioning the system to a bimolecular collision-dominated regime yielding primarily ( ZnOH ) 2 . Optimal film quality is achieved in the complete pyrolysis zone ( 583.15 – 673.15 K ), where ( ZnOH ) 2 and HZnOH synergistically promote ordered layered ZnO growth. These findings suggest that by utilizing temperature to modulate the supply ratio of monomers C 2 H 5 ZnH and dimers ( C 2 H 5 Zn ) 2 under excess t -BuOH condition, the structural properties of ZnO films can be precisely controlled.