Design and Characterization of Novel Systems for Molecular Nanoscale Self-Assembly

Abstract

We describe a new molecular engineering approach based on self-assembled monolayers (SAM) that has the potential of fine structure tunability in molecular diodes from isolated molecular wires to two dimensional (2D) aggregates; this approach should be useful for studying dimensionality transition in molecular diodes. Using this technique, we have fabricated a variety of molecular diodes with structure tunability of two-component solid-state mixtures. These are molecular wires (1,4-methane-benzene-dithiol; Me-BDT) and molecular insulator spacers (1-pentanethiol; PT). SAM-based two-terminal devices were prepared at various concentration ratios (r) of wires/spacers, sandwiched between two gold electrodes. The transport properties of molecular diodes at low r values (r < 10-3) are dominated by the isolated molecular wires dispersed in the dielectric spacer matrix; we conclude that these are one-dimensional (1D)-type devices. At high r values (r > 10-3), aggregates of molecular wires are formed in the PT matrix that show additional in-plane order; we conjecture that these are 2D-type devices.