A Study on the Growth Behavior and Stability of Molecular Layer Deposited Alucone Films Using Diethylene Glycol and Trimethyl Aluminum Precursors, and the Enhancement of Diffusion Barrier Properties by Atomic Layer Deposited Al₂O₃Capping

Abstract

As a route to the production of organic inorganic hybrid multilayers, the growth behavior of molecular layer deposited (MLD) alucone and atomic layer deposited (ALD) Al₂O₃ films on top, of each Other was examined. MLD alucone films were prepared using trimethyl aluminum and diethylene glycol precursors, the latter resulting in faster growth rates than ethylene glycol precursors. The sensitivity of individual alucone films with respect to ambient exposure was found to be related to moisture: permeation and hydration reactions, of which the mechanism is studied by density functional theory calculations. Deleterious effects such as thickness reduction over time could be suppressed by applying a protective Al₂O₃ layer on top of alucone: A preliminary nucleation period was required in the ALD process of Al₂O₃ films on alucone surfaces, prior to reaching a linear regime where the thickness increases linearly-with respect to the number of ALD cycles. The same behavior was observed for alucone growing on Al₂O₃. The protective Al₂O₃ films were found to effectively suppress moisture permeation, thus isolating the underlying alucone from the surrounding environment. The water vapor transmission rate was greatly reduced when an Al₂O₃/alucone/Al₂O₃ multilayer stack was formed, which suggests that proper combinations of organic/inorganic hybrid structures may provide chemically stable platforms, especially for mechanically flexible applications.