Electronic and structural properties of graphene-based metal-semiconducting heterostructures engineered by silicon intercalation

The initial decoupling of the (6√3 × 6√3)R30° buffer layer also called zero layer graphene (ZLG) on 6H-SiC(0 0 0 1) by Si intercalation has been investigated by means of high resolution photoemission spectroscopy (HRPES) and microscopy imaging techniques. A combination of complementary techniques has shown that the annealing above 700 °C of amorphous Si deposited on ZLG leads to the diffusion of the silicon over the surface. Two competing processes are then observed. Part of the silicon contributes to a progressive decoupling of the ZLG from the substrate (partial decoupling) while the rest agglomerates at the surface to form oriented silicon clusters. After sequences of Si deposition, followed by annealing at 750 °C, complete decoupling is observed into quasi-free standing monolayer (ML) graphene. Investigation of the evolution of the C1s and Si2p core levels during the intermediate states shows that the appearance of the graphene contribution coincides with the creation of an extra SiC bulk component, indicating their electronic decoupling. At partial decoupling of the ZLG, we have the coexistence of structurally linked metal-semiconducting materials presenting mutual electronic interactions and composed of nanometric metal-semiconducting heterojunctions.