Single-Molecule Wires Get a Lift

Lafferentz and co-researchers have developed an elegant approach that combines scanning tunneling microscopy (STM) imaging, nanomanipulation, and electrical measurement in order to controllably probe electrical conductance in a highly defined system. Reproducible electrical characterization of single or small groups of molecules can be done blindly, that is, without providing direct structural information, by various techniques. A relatively new approach to measuring single-molecule conductance is the SPM-based break junction. This method has opened up the possibility of electrically probing single molecules by tethering a conducting tip to molecules chemisorbed on an Au (111) surface by simply approaching the tip to the surface. Ultrahigh vacuum and low-temperature conditions are used to have a well-defined, clean, and mechanically stable system. Using this vertical manipulation procedure, controlled measurements of conductance versus length and current versus voltage at specific lengths could be performed.