Epitaxially Controllable h-BN on Graphene

The only insulation material in 2-D family, hexagonal boron nitride (h-BN), has been widely used as substrates in the field of 2-D electronic device. The atomically flat and inert surface provides a low scattering probability environment for electrical and quantum transport. In recent years, there are more and more studies of h-BN as main character involving quantum optics and twistronics. Here, we developed a layer-controlled growth method of h-BN on graphene/4H-SiC substrate by plasma-assisted molecular beam epitaxy (PA-MBE). The angle-resolved photoemission spectroscopy (ARPES) spectrum discovers the h-BN π band splitting at K point in experiment first time, revealing the stacking sequence of our h-BN is AB rather than AA' stacking. In addition, according to crystallographic point group theory, AB stacking is symmetry breaking, which results in the non-zero polarization in bilayer h-BN system. The piezoresponse force microscopy (PFM) measurement not only indicating the existence of polarization, but also demonstrating the capability of switching polarization up or down in bilayer h-BN system, i.e. ferroelectric. These fundamental investigations display an enormous potential for bilayer h-BN system as a candidate for ferroelectric non-volatile random-access memory (FRAM) in 2-D electronics.