  Strong Fermi level pinning (FLP) - often attributed to metal-induced gap
states at the interfacial contacts - severely reduces the tunability of the
Schottky barrier height of the junction and limits applications of the 2D
materials in electronics and optoelectronics. Here, we show that fluorinated
bilayer graphene (FBLG) can be used as a barrier to effectively prevent FLP at
metal/2D materials interfaces. FLBG can be produced via short exposure (1-3
min) to SF6 plasma that fluorinates only the top layer of a bilayer graphene
with covalent C-F bonding, while the bottom layer remains intrinsic, resulting
in a band gap opening of about 75 meV. Inserting FBLG between the metallic
contacts and a layer of MoS2 reduces the Schottky barrier height dramatically
for the low-work function metals (313 and 260 meV for Ti and Cr, respectively)
while it increases for the high-work function one ( 160 meV for Pd),
corresponding to an improved pinning factor. Our results provide a
straightforward method to generate atomically thin dielectrics with
applications not only for depinning the Fermi level at metal/transition metal
dichalcogenide (TMD) interfaces but also for solving many other problems in
electronics and optoelectronics
