Mechanism for Si–Si Bond Rupture in Single Molecule Junctions

The stability of chemical bonds can be studied experimentally by rupturing single molecule junctions under applied voltage. Here, we compare voltage-induced bond rupture in two Si−Si backbones: one has no alternate conductive pathway whereas the other contains an additional naphthyl pathway in parallel to the Si−Si bond. We show that in contrast to the
first system, the second can conduct through the naphthyl group when the Si−Si bond is ruptured using an applied voltage. We investigate this voltage induced Si−Si bond rupture by ab initio density functional theory calculations and molecular dynamics simulations that ultimately demonstrate that the excitation of molecular vibrational modes by tunneling electrons leads to
homolytic Si−Si bond rupture.