First principles study of band gap of Cu doped ZnO single-wall nanotube modulated by impurity concentration and concentration gradient

In this contribution, an effective method has been proposed to modulate the band gap of ZnO single-wall nanotube (SWNT). By adjusting the doping Cu concentration and the concentration gradient, the band gap can vary from 4.5 eV of the perfect ZnO SWNT to 1.95 eV. When the Cu concentration is fixed, the band gap decreases as concentration gradient decreases. Similarly, with the fixed concentration gradient, the band gap decreases as the concentration decreases. Thus, the band gap can be modulated through constructing appropriate impurity concentration and concentration gradient.