Sub-nanometer oxides are at the core of many applications, ranging from catalysis and energy storage to the gate dielectrics used in semiconductor devices. The microstructure of these materials is crucial to their chemical and electronic properties, yet our understanding of how synthesis affects the microstructure of these materials is still incomplete.<br/><br/>In this work, we combine in-situ and ex-situ characterization techniques with molecular dynamics simulations to understand the evolution of the structure for a variety of oxide materials, including ZnO, MgO, In2O3, and HfO2. We have leveraged atomic layer deposition's unique ability to grow conformally on high surface area materials to characterize the evolution of the coordination environment and medium range order using EXAFS, XANES, and PDF. We have complemented these measurements with in-situ FTIR and quartz crystal microbalance to obtain a more complete picture of the growth process.<br/><br/>Through the combination of these experimental measurements and atomistic simulations, we have explored the evolution of microstructure during the early stages of growth, which is characterized by a progressive evolution of the coordination environment from isolated cations on the surface to a structure whose medium-range order resembles that of the bulk phases. Our results are consistent with local structural relaxation mechanisms having a key role in the evolution of the oxides structure at the temperatures characteristic of atomic layer deposition. The incorporation of this assumption into simple kinetic Monte Carlo simulations allows us to model the structure evolution in a way that is consistent with our experimental observations.

Structure of sub-nm oxides synthesized by atomic layer deposition: From isolated cations to bulk-like structure

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.