Title: Single Molecule Conductance and Junction Breakdown of Strained Cyclic Disilanes
Description: A long-standing research interest of the Leighton group has been the utilization of strained silanes in the rapid and efficient synthesis of polyketides. Recently, we have been interested in how the effects of strain might manifest itself in the conductance and functionality of silicon-based molecular junctions. As electronic components continue to miniaturize to the point where transistor size and structure begin to resemble small molecules, understanding the principles that guide charge transport in single molecule junctions will be crucial. Herein, we describe our studies on a series of single molecule junctions formed by strained silicon wires. We demonstrate that high conductance pathways are accessed for the cis diastereomers of conformationally locked 1,2-disilaacenaphthenes via a bipodal binding motif which provides a stable electrical contact between the Si—Si bond and the gold electrodes. We then elucidate the mechanism of voltage-induced breakdown in silicon-based single molecule junctions.

We show that the naphthalene bridge provides a parallel conductance pathway to the silicon backbone, altering bond rupture behavior of the Si—Si bond. We further investigate the bond rupture mechanism through DFT and molecular dynamics calculations and conclude that breakdown occurs by the excitation of vibrational modes in the molecular junction by tunneling electrons, leading to homolytic Si—Si bond rupture.