Density Aluminium Oxide and Oxidation Simulation

density aluminium oxide

Aluminum oxide (Al2O3) is a stable metal phase that can be formed in two ways: by thermal oxidation at room temperature or by plasma oxidation. It can also be deposited by physical vapour deposition with an electron beam at low temperatures55 and by chemical vapor deposition. It consists of oxygen hexagonal close packed planes stacked in the c-direction with Al ions filling two-thirds of the octahedral interstitial positions, i.e., ABAB stacking.

In the crystalline form, aluminium oxide is typically called corundum, although other forms exist such as rubies and sapphires. It is one of the most important minerals in nature, used to make abrasives, ceramics and glass, as well as in many electronics.

A method for a detailed simulation of oxidation has been shown to be computationally feasible using molecular dynamics (MD). In MD, the system is first created in vacuum space and subsequently filled with a nominal density of oxygen atoms or molecules.

During the oxidation process, a series of events take place that change the stoichiometry and coordination number. These events are modelled individually in the MD model and their trends are elucidated.

In a typical simulation, the surface of an aluminium substrate is initially covered with oxygen atoms and a surface oxide layer evolves on the substrate over time as new oxygen atoms are deposited. In the metallisation stage, aluminium is added to the oxygen oxidised surface, which leads to the final tri-layer junction structure. The stoichiometric ratio between aluminium and oxygen is then calculated for each atomic position.

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