Cooperative Effects Enhance Electric-Field-Induced Conductance Switching in Molecular Monolayers

The anchoring of molecules with functional groups at surfaces permits information processing based on two stable molecular states that can be tuned externally by light irradiation and external fields. By using a molecular model that incorporates the essential characteristics of the problem, we show that the local interactions between adjacent molecules in a densely packed monolayer can stabilize domains with the same molecular state because of cooperative processes, enhancing significantly the switching properties between the molecular states. The case of electric-field-induced conductance switching is exploited in two possible applications: the design of a logic gates system and the operation of a sensing layer based on the modulation of the monolayer conductance by a ligand from an external solution. Extensions to other experimental systems (electrical and optical switches based on nanoparticles with ligand shells, molecular dipoles, and nanomagnets) where collective effects should be present can also be considered on the basis of the proposed concepts.