Reversible and irreversible reactions of trimethylaluminum with common organic functional groups as a model for molecular layer deposition and vapor phase infiltration

Abstract

Organic-inorganic hybrid materials are of great demand not at least for their enormous application potential in flexible devices. Atomic or molecular layer deposition (ALD or MLD) and vapor phase infiltration (VPI) offer novel pathways for the fabrication of such hybrids, but a clear understanding of the chemistry between the vaporized precursors and functional molecules is still lacking. In this work, the interactions between trimethylaluminum (TMA) and the organic functional groups -OH, -NH2, and -NO2 in the respective substituted phenyls, as well as their stability upon exposure to air are investigated. The experimental evidence agrees with theoretically predicted reaction pathways, showing that TMA initially binds to Lewis basic atoms of the investigated functional groups. Depending on the reaction energy barriers, the interaction between TMA and the investigated functional groups may result in either stable chemical bonding or intermediates that decompose upon exposure to humidity. This investigation contributes to the understanding of ALD/MLD and VPI processes at a molecular level and will support a better process optimization.