First-principles study of hydrogen interaction with carbon-doped GaN nanotube

We have performed the first-principles calculations onto the adsorption of hydrogen on the surface of the pristine or carbon-doped (8,0) zigzag gallium nitride nanotube (GaNNT). The results show that, for a hydrogen atom adsorbed on the top site of gallium (H-Ga), an acceptor energy level is present, while for a hydrogen atom on the top site of nitrogen (H-N), a donor energy level is present. There are the impurity bands inside the nanotube band gap for a carbon atom substitution for a gallium atom or a nitrogen atom (CGa or CN). The impurity bands disappear upon the adsorption of a hydrogen atom on the carbon-doped GaNNT. The adsorption of a hydrogen atom on the carbon atom of the carbon-doped GaNNT almost compensates the doping effect of carbon atom in carbon-doped GaNNT. Compared with pristine (8,0) GaNNT, carbon-doping enhances the binding energy of a hydrogen atom adsorbed on the similar site. The energetically and dynamically favorable site is top site of the carbon atom in carbon-doped GaNNT; this enhancement in hydrogen adsorption is more significant for the H-CN + GaNNT than it is for the H-CGa + GaNNT with a similar configuration.