Keywords: molecular electronics, molecular wires, single-walled carbon nanotubes, DNA, scanning probe microscopy, electrostatic forces, electron transport, electrical properties, long molecules, nanotechnology, Spain, radial electromechanical properties, atomic force microscopy, AFM
Electrical properties of long molecules: single-walled carbon nanotubes and DNA
A fundamental requirement for a molecule to be considered a molecular wire (MW) is the ability to transport electrical charge with a reasonably low resistance. From this point of view, we performed experiments of electrical transport on carbon nanotubes and individual DNA molecules. By using a conductive atomic force microscopy (AFM) tip as a mobile electrode, we can experimentally determine the electron mean free path of carbon nanotubes with one end connected to a macroscopic gold electrode. We also investigated the radial electromechanical properties of carbon nanotubes by using AFM, showing that when a high strain is applied to the nanotube a gap in the electronic band structure of the tube is opened. Finally we show how the electrostatic force between the carbon nanotubes and the AFM tip can be used to investigate the conductance properties of carbon nanotubes. When similar experiments are performed on single DNA molecules, we do not find any traces of conductance.