  Tunability of interfacial effects between two-dimensional (2D) crystals is
crucial not only for understanding the intrinsic properties of each system, but
also for designing electronic devices based on ultra-thin heterostructures. A
prerequisite of such heterostructure engineering is the availability of 2D
crystals with different degrees of interfacial interactions. In this work, we
report a controlled epitaxial growth of monolayer TaSe2 with different
structural phases, 1H and 1T, on a bilayer graphene (BLG) substrate using
molecular beam epitaxy, and its impact on the electronic properties of the
heterostructures using angle-resolved photoemission spectroscopy. 1H-TaSe2
exhibits significant charge transfer and band hybridization at the interface,
whereas 1T-TaSe2 shows weak interactions with the substrate. The distinct
interfacial interactions are attributed to the dual effects from the
differences of the work functions as well as the relative interlayer distance
between TaSe2 films and BLG substrate. The method demonstrated here provides a
viable route towards interface engineering in a variety of transition-metal
dichalcogenides that can be applied to future nano-devices with designed
electronic properties.
