Single-molecule conductance of three sulphur-functionalized organometallic wires with two ruthenium(II) centres spaced by 1,3-butadiyne was firstly investigated using an electrochemically assisted-mechanically controllable break junction (EC-MCBJ) approach. It is demonstrated that single-molecular conductance of these diruthenium(II) incorporated systems is significantly higher than oligo(phenylene-ethynylene) (OPE) having comparable lengths and exhibits weaker length dependence. The conductance improvement in these diruthenium(II) molecules is ascribable to the better energy match of the Fermi level of gold electrodes with the HOMO that is mainly resident on the Ru-C^C-C^C-Ru backbone.Furthermore, modulation of molecular conductance is achieved by changing the length and pconjugated system of the chelating 2,2 0 :6 0 ,2 00 -terpyridyl ligand.

This work presents a study of Au conductance quantization based on a combined electrochemical deposition and mechanically controllable break junction (MCBJ) method. We describe the microfabrication process and discuss improved features of our microchip structure compared to the previous one. The improved structure prolongs the available life of the microchip and also increases the success rate of the MCBJ experiment. Stepwise changes in the current were observed at the last stage of atomic point contact breakdown and conductance histograms were constructed. The evolution of 1G0 peak height in conductance histograms was used to investigate the probability of formation of an atomic point contact. It has been shown that the success rate in forming an atomic point contact can be improved by decreasing the stretching speed and the degree that the two electrodes are brought into contact. The repeated breakdown and formation over thousands of cycles led to a distinctive increase of 1G0 peak height in the conductance histograms, and this increased probability of forming a single atomic point contact is discussed.

This work describes jump-to-contact STM-break junction experiments leading to novel statistical distribution of last-step length associated with conductance of a single atom contact. Last-step length histograms are observed with up to five for Fe and three for Cu peaks at integral multiples close to 0.075 nm, a subatomic distance. A model is proposed in terms of gliding from a fcc hollow-site to a hcp hollow-site of adjacent atomic planes at 1/3 regular layer spacing along with tip stretching to account for the multiple subatomic step-length behavior.