First Principles Model of Amorphous ALD Deposited Al₂O₃

Amorphous alumina (a-Al₂O₃) is widley used for applications such as Si passivation, dielectric layers in field effect transistors, and as a coating material at interfaces in Li-ion batteries. Through the use of ab initio molecular dynamics (AIMD) we develop a model for a-Al₂O₃ which is verified experimentally by both X-ray Absorption Spectroscopy (XAS) and solid-state Nuclear Magnetic Resonance (NMR). While crystalline models are often verified using X-ray diffraction, it is not the case that amorphous models can be verified in the same way. To create an XAS spectra of a-Al₂O₃ with density-functional theory (DFT), we calculated core-hole spectra for each Al environment in the model, and the resulting summed spectra matched the experimental XAS. Similarly, NMR from first principles was calculated as the sum of a set of snapshots from the AIMD. We constructed a model from first principles which matches both the electronic and structural properties of ALD deposited a-Al₂O₃ and therefore can be used to study this phase in conjunction with other materials.