Insights into Crystalline Preorganization of Gas-Phase Precursors: Densification Mechanisms

Abstract

Using density functional theory calculations, we address the structural phase transition from the covalent metallic precursor molecules to their oxide layer structure during the gas-phase deposition process. We observe that the associated increase in the metal coordination number during the gas–solid transition, i.e., the redistribution mechanisms of oxygen atoms around the metal atoms, are identical and barrierless for Sn- or Hf-based precursors. These mechanisms, occurring in the grown oxide layers, are shown to be present at the early stage of gas phase agglomeration reactions, giving rise to unexpected species. The presence of OH hydroxyl groups on the surface/hydroxylated precursors are mainly responsible for this transition. Finally, we discuss the relevance of our calculations within the framework of the metal oxides growth by ALD process.