Molecular orbital studies of the initial process of gallium oxide chemical vapor deposition: micro-hydrolysis of triethylgallium

Gallium-doped zinc oxide films prepared by atomic layer deposition have received much attention. When triethylgallium is hydrolyzed on the surface of zinc hydroxide, a multi-layered metal oxide film containing a specific amount of gallium at a controlled position is formed. In this study, to elucidate the micro-hydrolysis mechanism of triethylgallium, reaction mechanisms involving one or two water molecules were investigated by molecular orbital calculations. The complete hydrolysis of triethylgallium occurs in three steps with the first partial hydrolysis being the rate limiting step. The activation energy of hydrolysis by two molecules of water is ∼10 kcal mol−1 lower than that with one molecule of water for all steps. The addition of further water molecules significantly decreases the activation energy because the transition state is stabilized by hydrogen bonding between the water molecules. These results suggest the hydrolysis reaction proceeds spontaneously under mild conditions by controlling the concentration of water molecules.