Conductance of molecular nanojunctions – Nikolai Zhitenev

Date: Mon. April 21st, 2003, 12:30 pm-1:30 pm
Location: Rockefeller 221

Using molecules as possible elements for electronic devices has an enormous appeal. In the size hierarchy of nature, molecules stand just above atoms making them ideal ultimate choice for ever-shrinking electronic devices. Synthetic chemistry offers vast diversity of molecular objects as well as certain degree of fine-tuning of electronic structure similar to the doping of semiconductors. However, wiring the molecules in a macroscopic circuit remains the challenging problem. Many different approaches to contact a small number of molecules have been developed the recent years. Some of the methods exploit the flexibility of tunable contacts to molecules afforded by scanning probes or break junctions. Other methods use a fixed contact arrangement. We employ new techniques that combine some advantages of both tunable and fixed contacts and experimentally compare these with other known approaches. The new methods are similar to the fabrication of single-electron transistors using the shadow angle evaporation. The device performance can be monitored during fabrication as with tunable contacts, but the contact geometry is fixed, providing good mechanical and thermal stability. Based on our ability to measure the conductance from the earlier stages of molecular junction formation and the scanning probes studies of monolayers of conjugated molecules I discuss the importance of the microscopic control of the molecule-metal interfaces, including the surface topography of the metal, formation of chemical bonds at the interfaces, surface diffusion, granularity, contamination and/or oxidation.