Size effect on doped single walled carbon nanotubes

Considering impurity doping in small sized carbon nanotubes of diameter around 0.4 nm, we have calculated the donor binding energy by increasing the dopant concentration through a screening function that includes the curvature effect. We could observe the sudden fall in donor binding energy and metallic behaviour of the smaller single walled carbon nanotubes around 10¹¹/cm² (0.0026%) of impurity concentration. This result is useful for nano electronic device application such as nano diodes and switches.