Temperature dependence of the band gap of completely fluorinated/hydrogenated carbon nanotubes: the role of one-dimensional chains

The temperature dependence of the band gap $E_g(T)$ in zigzag single-walled carbon nanotubes at the maximum (50%) fluorination and hydrogenation has been theoretically investigated for three coating versions. It has been shown that the character of coating dramatically affects the dependence $E_g(T)$, which may vary over a wide range from very weak (typical of pure carbon nanotubes) to strong (typical of bulk semiconductors). The character of the temperature behavior $E_g(T)$ is directly related to the formation of one-dimensional alternating chains in nanotubes. The main factors determining this dependence are the diameter of carbon nanotube, impurity position, and impurity type.