  Bilayer graphene (BLG) is semiconductor whose band gap and properties can be
tuned by various methods such as doping or applying gate voltage. Here, we show
how to tune electronic properties of BLG by intercalation of transition metal
(TM) atoms between two monolayer graphene (MLG) using a novel
dispersion-corrected first-principle density functional theory approach. We
intercalated V, Nb, and Ta atoms between two MLG. We found that the symmetry,
the spin, and the concentration of TM atoms in BLG-intercalated materials are
the important parameters to control and to obtain a Dirac Cone in their band
structures. Our study reveals that the BLG intercalated with one Vanadium (V)
atom, BLG-1V, has a Dirac Cone at the K-point. In all the cases, the present
DFT calculations show that the 2$p_z$ sub-shells of C atoms in graphene and the
3$d_{yz}$ sub-shells of the TM atoms provide the electron density near the
Fermi level E$\mathrm{_F}$ which controls the material properties. Thus, we
show that out-of-plane atoms can influence in-plane electronic densities in
BLG, and enumerate the conditions necessary to control the Dirac point. This
study presents a new strategy for controlling the material properties of BLG so
that they exhibit various behaviors, including: metal, semi-metal, and
semiconductor by varying the concentration and spin arrangement of the TM atoms
in BLG while offering insight into the physical properties of 2D
BLG-intercalated materials.
