Theoretical investigation on different effects of nitrogen and boron substitutional impurities on the structures and field emission properties for carbon nanotubes

The first-principles density-functional theoretical calculations have been performed to investigate the effects of nitrogen and boron substitutional atom on the geometrical structures and field emission properties of capped (5, 5) carbon nanotubes (CNTs). The most favorable doping position of nitrogen atom is the fourth layer, and the work function of N-doped CNT is lower than that of pristine CNT. For B-doped CNT, boron atom is preferential to locate at the first layer, and the work function increases due to the doping. The results indicate that nitrogen doping can improve the field emission performance. On the contrary, boron doping will impede the field emission. These different effects of nitrogen and boron doping on the field emission properties of CNTs are explained.