Nanoscale structure and electronic transport in organic molecules

(Berrie and Timm)

One active area of research in the Berrie group is the investigation of the effect of nanoscale structure on conductivity of organic molecules. The idea of using organic molecules as electronic devices has received much attention recently, and there has been significant progress in this area. However, there is still not a solid understanding of the mechanism of charge transport in these systems. Dr. Berrie's group is interested in developing model organic thin film systems, such as those demonstrated schematically in Figure 2, in which the structure and packing in the films are well understood. The substituents on the phenyl rings as well as the size of the domains will be varied using AFM-based patterning methods such as nanografting. The conductivity of the molecules in these nanoscale domains will then be investigated using conductive-probe AFM and STM measurements as a function of chain length, substituents, and nanoscale domain size. All of the aspects required for this project (monolayer formation, patterning, conductive AFM) have been previously implemented successfully by undergraduates working in Dr. Berrie's laboratory.

Electron conduction through these molecules will also be investigated computationally using methods being developed by the Timm research group. The current-voltage characteristics of the molecules will be calculated in a master-equation approach, based on a tight-binding (extended Hückel) model for the molecule. One interesting aspect is the possibility of Coulomb drag, i.e., an electron tunneling through one of the molecules affects the motion of electrons in its neighbors. An undergraduate student could combine experimental work and computational modeling in one project.