Impurity screening in carbon nanotubes

Nanotube geometry determines electronic structure and thus impurity screening. A metallic carbon nanotube could effectively screen a charged impurity, while a semiconducting carbon nanotube could not. The ability to screen a long-range Coulomb field is mainly determined by whether there are: Free carriers in the subbands nearest the Fermi level. The detailed screening propel-ties are sensitive to the impurity position, and the tubular structure (such as radius and chiral angle). Strong, short-wavelength Friedel oscillations at long distances are found to exist only in metallic armchair nanotubes. They are relatively obvious for a smaller armchair nanotube, and could survive at room temperature.