Experimental evidence of a mixed amorphous-crystalline graphene/SiC interface due to oxygen-intercalation

The introduction of atoms of different chemical species between epitaxial graphene and the SiC substrate by means of an intercalation process has been a reliable route to modify the interaction of this 2D material and its underlying substrate. Distinct atomic species have been intercalated so far and studies focusing on bond states of the electronically active layers were successful, retrieving the local chemical environment. However, the structure of interfacial layers is strongly affected whenever a more reactive atom is used in the intercalation process. In this work, we present experimental evidence based on X-ray crystal truncation rod scattering and photoelectron diffraction showing the coexistence of crystalline and amorphous regions in the oxidized interface. This interface between a bilayer graphene and the SiC substrate is generated by O-intercalation. Such fluctuations of the local structure are crucial to understand the abundant existence of silicon oxycarbides structures (SiOXCY) within the interfacial layer, which has been associated with the limited electronic properties of O- intercalated graphene bilayers. Consequently, this may be considered as a deterministic factor that affects device potentialities in these systems.