Dual attenuation factor in nanographene molecular wires.

Designing molecular nanowires with high electrical conductance that facilitate efficient charge transport over long distances are highly desirable for future molecular-scale circuitry. However most of the molecular wires act as tunnel barriers and their electrical conductance is decaying exponentially with increasing the length. Just recently a few studies have shown increasing conductance with length. In this study, for the first time, we have identified new class of molecular wires that exhibit both increase and decrease of room temperature conductance with length (dual attenuation factor) depend on their connection points to electrodes. We show that this dual attenuation factor is an inherent property of these graphene-like nanowires and its demonstration depends on the constructive quantum interference pattern for different connectivities to electrode. This is significant because a given nanographene molecular wire can show both negative and positive attenuation factor. This enables a systematic design of connectivity dependent high/low-conductance molecular wires for future molecular-scale circuitry.