  Very recently, ferroelectric polarization in staggered bilayer hexagonal
boron nitride (BBN) and its novel sliding inversion mechanism was reported
experimentally (Science 2021, 372, 1458; 2021, 372, 1462), which paves a new
way to realize van der Waals (vdW) ferroelectric devices with new
functionalities. Here, we develop vdW sliding ferroelectric tunnel junctions
(FTJs) using the sliding ferroelectric BBN unit as ultrathin barriers and
explore their transport properties with different ferroelectric states and
metal contacts via the first principles. It is found that the electrode/BBN
contact electric field quenches the ferroelectricity in the staggered BBN,
resulting a very small tunnelling electroresistance (TER). Inserting
high-mobility 2D materials between Au and BN can restore the BBN
ferroelectricity, reaching a giant TER of ~10,000% in sliding FTJs. We finally
investigate the metal-contact and thickness effect on the tunnelling property
of sliding FTJs. The giant TER and multiple non-volatile resistance states in
vdW sliding FTJs show the promising applications in voltage-controlled
nano-memories with ultrahigh storage density.
