Atomic Layer Deposition Nucleation on Isolated Self-Assembled Monolayer Functional Groups: A Combined DFT and Experimental Study

Abstract

We computationally design and experimentally corroborate the atomic layer deposition (ALD) of metal oxides with tailorable nucleation on selected self-assembled monolayers (SAMs) decorated with terminal functional groups. The low-temperature ALD processes for Al2O3, MnO, and especially ZnO are inhibited on nonpolar alkyl-terminated SAMs with high efficacy, in agreement with the thermodynamics calculated for reactivity with the alkyl-terminated SAMs as well as for potentially physisorbed precursors. Functional-SAM surfaces are also considered for the uniform nucleation of ALD oxides, while mixed alkyl-/functional-group-terminated SAMs are considered for the site-directed synthesis of metal oxide clusters. Long alkyl-chain SAMs with functional group termination including OH, COOH, and SH are predicted to react exergonically over a variable energy barrier which depends strongly on ALD precursor chemistry as well as functional group density. Experiments confirm that more efficient nucleation may be catalyzed via a single ALD precursor cycle of a more reactive precursor (e.g., trimethylaluminum) followed by growth of targeted metal oxides (ZnOx and MnOx). The computational strategy and experimental approach may be applicable to the selective deposition of technologically important hybrid organic–inorganic barrier films as well as catalytically relevant metal oxide and mixed-metal oxide precision few-atom clusters.