Conductance of Sidewall-Functionalized Carbon Nanotubes: Universal Dependence on Adsorption Sites
When a single molecule is chemisorbed on the sidewall of a metallic carbon nanotube (CNT) one of its two transmission channels close to the Fermi level is blocked (Channel 2 or b) while the other remains unaffected (Channel 1 or a). We have found that this behavior is quite universal in the sense that the depth and position of the transmission minimum depends only weakly on the molecular species. The same trend is common for all kind of metallic CNTs (armchair, zigzag and chiral CNTs).
Secondly, it is possible to adsorb an arbitrary number of molecules on the CNT sidewall and still conserve a fully open transport channel. To obtain this, all molecules must be adsorbed on the same sublattice and their relative positions should fulfill the displayed equation (blue solid line). On the other hand, if a single molecule is adsorbed outside this array of special sites, both channels are almost completely blocked and the conductance drops sharply (red dotted line). This property, which is not destroyed by finite temperature, could be used to create nanoswitches or memory devices or preferential chemisorption sites.