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

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 (ZnO_x and MnO_x). 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.