Molecular heterostructure by fusing graphene nanoribbons of different lengths through a pentagon ring junction

Graphene nanoribbons (GNRs) have attracted great research interest because of their widely tunable and unique electronic properties. The required atomic precision of GNRs can be realized via on-surface synthesis method. In this work, through a surface assisted reaction we have longitudinally fused the pyrene-based graphene nanoribbons (pGNR) of different lengths by a pentagon ring junction, and built a molecular junction structure on Au (111). The electronic properties of the structure are studied by scanning tunneling spectroscopy (STS) combined with tight binding (TB) calculations. The pentagon ring junction shows a weak electronic coupling effect on graphene nanoribbons, which makes the electronic properties of the two different graphene nanoribbons connected by a pentagon ring junction analogous to type I semiconductor heterojunctions.