Chiral transfers and chiral switching in bilayer of vanadyl phthalocyanine

Abstract

Chiral transfer and chiral switch in the bilayer of achiral vanadyl phthalocyanine (VOPc) on Cd(0001) have been investigated with low temperature scanning tunneling microscopy (STM). In the monolayer regime, the VOPc molecules form a self-assembled layer consisting of periodic chiral voids. Further deposition of VOPc leads to the bilayer formation with an O-up top layer and an O-down bottom layer. High-resolution STM images demonstrate that not only single-molecule chirality but also organizational chirality is transferred from the underlying chiral voids to the top layer. The organizational chirality of the top layer manifests as chiral windmill protrusions, distinct from the chiral voids of the bottom layer. After annealing the bilayer to 310 K, strain is relaxed in the form of a mass density wave (MDW). In particular, the organizational chirality inside MDW domains is opposite to that outside the domains, indicating a chiral switch takes place after the strain relaxation.