Electron flow through molecular structures

In this chapter, a perspective is given on some aspects of electron flow through molecular bridges. The advent of molecular electronics, drive to understand charge transfer in biological systems, and functioning of devices such as organic lightemitting diodes and dye-sensitized solar cells all require deeper understanding of this topic. Application of SPM to such studies has opened the possibility of true single-molecule measurements, but has also introduced a number of artifacts and complications into the work, notably perturbations due to the force and local electric field applied by the tip. Additional chapters in this book provide specific studies of electron flow in thiolated hydrocarbons and of electrical and electromechanical measurements on biomolecules. Here, SPM measurements on two specific systems-electron flow through DNA, and STM measurements of isolated molecules on a semiconductor surface, are developed in detail. These studies are presented in the general context of electron flow measurements through single molecules, and are compared with parallel, non-SPM techniques. The strength of SPM to combine imaging with the electrical measurement is emphasized.