Chapter 4 - The design, fabrication, and electronic properties of self-assembled molecular nanostructures

Abstract

This chapter summarizes the design, fabrication, and electronic properties of cluster-based molecular nanostructures. Details regarding the synthesis and characterization of both molecular wires and nanoscale metallic clusters have been discussed from a perspective that emphasizes the self-assembly of these nearly identical "building blocks" into interesting molecular nanostructures. A theory related to electronic conduction through individual molecular wires, attached at one end to a substrate and probed at the other end by an STM tip, has also been presented. This theory predicts the resistance of a molecular wire, and, more generally, the I (V)characteristics of any molecule. The importance of the coupling between the molecule and substrate was found to be crucial in this analysis. Well-characterized, "unit cell" molecular nanostructures have been fabricated from molecular wires and nanoscale clusters. The I (V) characteristics of a number of these selfassembled molecular nanostructures show compelling evidence of semiclassical Coulomb blockade and Coulomb staircase phenomena at room temperature. Finally, the self-assembly of these "unit cell" nanostructures into highly ordered twodimensional cluster networks has also been described. Each individual cluster in the network is electronically linked to its nearest neighbor by bridging molecular wires.