Polymerization and multilayers of DBBA chains on Bi(111) surface

• 1、School of Physical Science and Technology, Southwest University, Chongqing 400715

Abstract：The debromination and polymerization of dibromo-bianthryl (DBBA), a precursor of graphene nanoribbons, on the surface of semi-metal Bi(111) surface was studied by low temperature scanning tunneling microscopy (LT-STM). It is found that DBBA molecules can be debrominated at a substrate temperature of 120 K, thus forming a one-dimensional polyanthracene covalent chains. This is the lowest debromination temperature of DBBA molecules on metal surfaces found so far. With the increase of molecular coverage, two-layer thick and three-layer thick polyanthracene chain arrays appeared on Bi(111) surface. However, there is large inter-chain gaps in the second and third polyanthracene layers. Interestingly, the inter-chain gap of the latter is almost twice as large as the former. After further deposition of DBBA onto the third polyanthracene layer, it was found that the undebrominated DBBA molecules appeared in the large gap of polyanthracene chains and formed self-assembled single and double chains by van der Waals interaction. As the number of DBBA increases, the wide grooves between the polyanthracene chains hinder the surface diffusion of DBBA, so that the upright DBBA molecules cannot form the ordered self-assembly structure. These results provide the essential information for understanding of the interaction between DBBA molecule and Bi(111) surface, the debromination and polymerization process of DBBA, and the interplay between the polymerizationand self-assembly of DBBA molecules on semi-metal surface.

Keywords： DBBA Bi(111) debromination polyanthracene chains STM