First-Principles Predictions and in SituExperimental Validation of Alumina Atomic Layer Deposition on Metal Surfaces.

The atomic layer deposition (ALD)of metal oxides on metal surfacesis of great importance in applications such as microelectronics, corrosionresistance, and catalysis. In this work, Al2O3ALD using trimethylaluminum (TMA) and water was investigated onPd, Pt, Ir, and Cu surfaces by combining in situquartzcrystal microbalance (QCM), quadrupole mass spectroscopy (QMS), andscanning tunneling microscopy (STM) measurements with density functionaltheory (DFT) calculations. These studies revealed that TMA undergoesdissociative chemisorption to form monomethyl aluminum (AlCH3*, the asterisk designates a surface species) on both Pd and Pt,which transform into Al(OH)3* during the subsequent waterexposure. Furthermore, the AlCH3* can further dissociateinto Al* and CH3* on stepped Pt(211). Additional DFT calculationspredicted that Al2O3ALD should proceed on Irfollowing a similar mechanism but not on Cu due to the endothermicityfor TMA dissociation. These predictions were confirmed by in situQCM, QMS, and STM measurements. Our combined theoreticaland experimental study also found that the preferential decorationof low-coordination metal sites, especially after high temperaturetreatment, correlates with the differences in free energy betweenAl2O3ALD on the (111) and stepped (211) surfaces.These insights into Al2O3growth on metal surfacescan guide the future design of advanced metal/metal oxide catalystswith greater durability by protecting the metal against sinteringand dissolution and enhanced selectivity by blocking low-coordinationmetal sites while leaving (111) facets available for catalysis. [ABSTRACT FROM AUTHOR]