Determination of the molecular size of growth species in the AP-MOCVD of ZnO from DEZ and H2O

ZnO films were deposited by atmospheric pressure metal-organic chemical vapor deposition (AP-MOCVD) from diethylzinc (DEZ)-83% n-hexane and H2O. Analysis of the film growth rate on tubular quartz glass substrates revealed that the growth process is limited by the gas-phase diffusion of growth species in the temperature range of 400-600 °C. From the experimentally measured diffusivites and by correlating with the Chapman-Enskog equation, we obtained the effective molecular size of the growth species to be about 0.5 nm. The growth rate data at 650 °C indicates that the growth rate is limited by gas-phase reaction with a rate constant, kg of 60 s−1. At 700-750 °C, the film growth was gas-phase diffusion controlled. The molecular size was about 0.9 nm at 700 °C, and decreased to about 0.6 nm at 750 °C.