Fabrication of nano-gap electrodes using ultrathin metal film

Organic molecules have attracted a great deal of attention because of their promising applications to electronics. Many researchers have recently studied electrical properties of ultrathin molecular films for the developments of molecular electronic devices (MEDs). Since electrical junctions between the metallic electrode and the molecular film are directly related to the carrier injection in the device, the nanoscale investigations of molecular structures and electrical properties at the metal/molecular film interface is indispensable. Scanning probe microscopy techniques are remarkably suitable methods for such investigations. However, it is often difficult to bring the probe tip in the close proximity of the electrode edge because of a large difference in height between the electrode and the ultrathin molecular film with the typical thickness of a few nm, which prevents us from the nanoscale investigations of the metal/molecular-film interface. In this study, for overcoming the difficulty we fabricated Pt nano-gap electrodes having a molecular-scale thickness and atomical flatness. We investigated the structures and the electrical properties of the molecular films at the electrode edge using atomic force microscopy (AFM) and Kelvin force microscopy.