Tuning the Switching Probability of Azobenzene Derivatives on Graphite Surface through Chemical Functions

Molecules that can be triggered between different states, molecular switches, are considered as the building blocks for molecular electronics. The chemical nature of the molecular switches is decisive in controlling the mechanism/energy barrier of switching and the life time of different states. Here, we investigate the electronic structure, switching barrier, and electron/hole-induced switching of an adlayer of three different azobenzene (AB) derivatives on graphite surface. The adlayers of AB derivatives with carboxyl group form a hydrogen-bonded dimer-based assembly and the derivative with the thiocyanate group forms van der Waals-stabilized assembly. While all the molecules in the adlayer can be individually switched using electron/hole, the switching probability depends on their chemical nature. We use a combination of scanning tunneling microscopy and concomitant density functional theory calculations to demonstrate the switching probability of different AB derivatives. Molecules that are having strong inter-molecular interactions within the adlayer show low switching probability compared to the one having weak inter-molecular interaction. Additionally, we observe that the molecule–surface interaction also contributes to the switching.