Nanoscale Ferroelectric Programming for Patterning High-Quality 2D Material Superlattices

Exposing two dimensional materials to an external electric field is one of the most effective ways to engineer their electrical properties. If the electrical potentials are applied as a superlattice pattern, phenomena including superconductivity, magnetism, Mott-like insulator states and exotic quasiparticle states can be induced. Here we show that a stack structure of van der Waals materials on thin ferroelectric films can be exposed to ultra-low voltage electron beam lithography (ULV-EBL) to nanopattern subsurface ferroelectric domains to create a surface charge superlattice potential which in turn regulates the electronic structure and transport properties. This direct-write approach can be applied over large areas with resolution limits below 20 nm under vacuum conditions with no chemical exposure. Observing a replica of Dirac cone from a 20 nm triangular superlattice pattern under graphene benchmarks this method. Moreover, we observe the Hofstadter spectrum under a high magnetic field which can not be seen with the original crystal lattice symmetry. Compared with other lithography or twisting methods, our method provides a clean resistless top-down way to imprint electrostatic potential to 2d materials with a degree of freedom to pattern any artificial layout, not only periodic, but also non-periodic. It offers a new pathway to help realizing analog quantum simulation in solid states and also to understand strongly correlated systems.