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

Moleculesthat can be triggered between different states, molecularswitches, are considered as the building blocks for molecular electronics.The chemical nature of the molecular switches is decisive in controllingthe mechanism/energy barrier of switching and the life time of differentstates. Here, we investigate the electronic structure, switching barrier,and electron/hole-induced switching of an adlayer of three differentazobenzene (AB) derivatives on graphite surface. The adlayers of ABderivatives with carboxyl group form a hydrogen-bonded dimer-basedassembly and the derivative with the thiocyanate group forms van derWaals-stabilized assembly. While all the molecules in the adlayercan be individually switched using electron/hole, the switching probabilitydepends on their chemical nature. We use a combination of scanningtunneling microscopy and concomitant density functional theory calculationsto demonstrate the switching probability of different AB derivatives.Molecules that are having strong inter-molecular interactions withinthe adlayer show low switching probability compared to the one havingweak inter-molecular interaction. Additionally, we observe that themolecule-surface interaction also contributes to the switching.