Scanning probe measurements of electron transport in molecules

Abstract

The ability to control the placement of molecules is essential for the patterning and fabrication of nanoscale electronic devices. We apply selective chemistry and self-assembly to reach higher resolution, greater precision, and chemical versatility in the nanostructures that we create. These methods demonstrate the possibilities of patterning films by exploiting the intrinsic properties and interactions of the molecules. We employ self-assembled monolayers as a means to isolate molecules with various electronic properties to determine the fundamental transport mechanisms, and the relationships between molecular structure, environment, connection, coupling, and function. Using self-assembly techniques in combination with scanning tunneling microscopy (STM), we are able to study candidate molecular switches individually and in small bundles. Alkanethiolate self-assembled mono-layers on gold are used as a host two-dimensional matrix to isolate and to insulate electrically the molecular switches. We then individually address and electronically probe each molecule using STM. The conjugated molecules exhibit reversible conductance switching, manifested as a change in apparent topographic height in STM images. The origins of switching and the relevant aspects of the molecular structure and environment required are discussed below. © 2007 Springer Science+Business Media, LLC.