Electronic transport of unimolecular devices with a group coadsorbed on one electrode surface: a density functional...

The first-principles calculations based on the density functional theory are applied to investigate the effect of a chemical group coadsorbed on one electrode surface on the electronic transport of a molecular device. We find that the types of the coadsorbed groups and their sites on one electrode surface affect the electronic transport significantly, and the resulting shift of the molecular levels upon coadsorption depends jointly on various effects, such as the electrostatic interaction, shift of the Fermi level of the electrode, the chemical interaction, and so on. Among these factors, the chemical interaction-induced the charge transfer across metal-molecule interface is identified as a determining factor resulting in the variation of transport properties. Our findings suggest that the coadsorption may offer the novel possibility to modify the transport behaviors of a molecular device in a controlled way and can improve/add some particular functionalities or should be avoided in order to keep a stable transport for a molecular device.