Understanding the Stoichiometry of Two-Dimensional Metal Oxide Intercalation at Epitaxial Graphene/Silicon Carbide Interface by Octet rule and Formal Charge*

Metals intercalated into epitaxial graphene on silicon carbide (EG/SiC) are a basis for the formation of metal oxides in the same confined geometry. The interaction between intercalant and substrate changes the oxidation states in the two-dimensional metal oxide, as compared to 3D bulk geometries. This talk describes how fundamental chemical principles such as the octet rule and formal charge can be used to understand the metal oxides’ oxidation number, layer-by-layer stoichiometry, preferred thickness, and (if those principles are violated) the potential bonding and doping to the graphene.

These principles are demonstrated by an example of Indium Oxide intercalation in EG/SiC. Multi-layer elemental Indium was first intercalated. The controlled oxidation allows the formation of two layers of Oxygen and one layer of Indium, while the excess Indium is expelled. The stability of the experimental product with this layering configuration was explained. Our research underscores the critical role that simple chemical concepts play in unraveling the part-covalent part-ionic intercalant-substrate interaction. It also has practical significance for theorists in constructing structural candidates. This is because geometric relaxation has fixed number of particles, which makes the knowledge of likely stoichiometry prior to relaxation very important.