Sizable Band Gap in Epitaxial Bilayer Graphene Induced by Silicene Intercalation

Absence of a band gap in monolayer graphene is a big obstacle to its utilization in silicon electronics. With one more graphene layer added, however, bilayer graphene (BLG) provides a non-zero band gap by breaking the inversion symmetry. Opening a sizable band gap in BLG is of significance for potential applications in graphene-based electronic and photonic devices. Here, we report the generation of a sizable band gap in BLG by intercalating silicene between BLG and Ru substrate. We first grow high-quality Bernal-stacked BLG on Ru(0001) and then intercalate silicene to the interface between the BLG and Ru, which is confirmed by low-energy electron diffraction and scanning tunneling microscopy. Raman spectroscopy shows that the G and 2D peaks of the intercalated BLG are restored to the freestanding-BLG features. Angle-resolved photoelectron spectroscopy measurements show that a band gap of about 0.2 eV opens in the BLG. Density functional theory calculations indicate that the large-gap opening results from a cooperative contribution of the doping and rippling/strain in the BLG. This work provides insightful understanding on the mechanism of band-gap opening in BLG and enhances the potential of graphene-based device development.