A DFT Study of the Al2O3 Atomic Layer Deposition on SAMs: Effect of SAM Termination

Abstract

The atomistic mechanism of the initial atomic layer deposition (ALD) reaction of trimethylaluminum [Al(CH3)3, TMA] on octadecyltrichlorosilane (OTS)-based self-assembled monolayers (SAMs) with different functional termination groups was investigated using density functional theory (DFT). The adsorption of TMA on −NH2-terminated OTS involves formation of a dative bond between the amine lone pair and the Al atom of TMA and is exothermic by 0.86 eV. Conversion of the dative bond to a covalent bond through a four-centered H transfer from the NH2 to the methyl group of TMA to form methane involves a barrier that is 1.22 eV above the adsorbed complex and is exothermic by 0.94 eV. Reaction between TMA and the −OH-terminated SAM results in an adsorption energy of 0.60 eV. Although the dative bond is weaker, the barrier to converting the dative bond to a covalent bond to form methane is only 0.65 eV relative to the complex structure and the overall reaction is exothermic by 1.44 eV. The reaction of TMA with the me...