Using a codoping model, where a cation and an anion are introduced simultaneously into the host to maintain charge neutrality, we probed the electron transport characteristics in a single molecular junction. We used the 1, 12-dicarba-closo-dodecaborane inorganic molecule as a precursor, replaced one of the vertex carbon atoms by a boron atom, and simultaneously decorated it with an endohedrally doped alkali atom (Li or Na) to look into the role of dopant atoms in the conductivity. The commonly used thiolate anchoring groups are used to attach the molecule between two gold electrodes, and a parameter-free, first-principles, single-particle Green’s function approach is used to calculate the current-voltage characteristics. When compared to the undoped system, a significant increase in current is observed for the system codoped with Na and B; about an order of magnitude increase in the observed current is found at an applied bias of $~$2 V. Charge transfer from the alkali atom to the host is found to have a profound effect on the electronic structure, causing a dramatic change in the conductivity. Since the single alkali atom controls the behavior of electron flow in this circuit, we call this device a “single-atom-controlled” device.

• Received 19 October 2010

DOI:https://doi.org/10.1103/PhysRevB.83.195420