Adsorption of trimethylaluminum on period 4 and 5 transition metal surfaces

Abstract

It is known that atomic layer deposition (ALD) of Al₂O₃ using trimethylaluminum (TMA) on transition metal surfaces is dependent to the type of the metal element, so that only coinage metal surfaces show delayed nucleation. In this study, the molecular and dissociative adsorption of TMA on 20 transition metal surfaces were investigated using density functional theory (DFT) calculations. The adsorption energy of molecular TMA depends on the group numbers of the elements, so that late transition metals are expected to show weaker adsorption of TMA molecule compared to those on early transition metals. Dissociative adsorption of TMA is expected to spontaneously proceed on most transition metal surfaces. However, TMA is expected to have reversible molecular adsorption on the surfaces of Cu, Zn, Ag, and Cd. Together with low propensity toward oxidation, the nucleation delay of Al₂O₃ ALD on Cu and Ag can be explained.