Abstract

Understanding the transport characteristics of molecules bonded between metal electrodes is of fundamental importance for molecular scale electronics. It is well known that these transport characteristics are influenced by the intrinsic properties of the molecules, including their length, conformation, the gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital and the alignment of this gap to the metal Fermi level. This talk will focus on the relation between intrinsic molecular properties and the conductance of single molecule junctions formed by breaking gold point-contacts in an environment of molecules with amine linkages [1] . The relation between molecular conductance and molecule conformation for the simple case of a biphenyl, two benzene rings linked together by a single C-C bond will be presented. Specifically, I will show that for a series of seven biphenyl derivatives, the molecular junction conductance decreases with increasing twist angle, following a cosine squared dependence [2] . I will also show that for substituted benzenes, the conductance varies inversely with the calculated ionization potential of the molecules [3] . This reveals that the occupied states are closest to the gold Fermi energy, indicating that the tunneling transport through these diamine molecules is analogous to hole tunneling through an insulating film.