Bistable H2Pc Molecular Conductance Switch on Ag(100)

Abstract

Scanning tunneling microscopy (STM) and density functional theory (DFT) were used to study the tautomerization reaction of an H2Pc molecule adsorbed on a Ag(100) surface. The presence of two hydrogen atoms in the cavity of the H2Pc molecule enforces the existence of two molecular tautomers. It causes a reduction from 4- to 2-fold symmetry in STM images that can be recorded as two current states over the H2Pc molecule with a high-to-low current state ratio of ∼1.2. These findings are confirmed by the spatial distributions of the all-atom electron charge density calculated by using DFT and transmission maps together with tunneling current ratios (∼1.2) determined from the nonequilibrium Green's function transport calculations. Therefore, we demonstrate that an H2Pc molecule adsorbed on a Ag(100) surface is a good candidate for a bistable molecular conductance switch since neither the presence of the Ag(100) surface nor that of the STM tip alters the tautomerization.