A first-principles study of a single C-chain doped AlN nanoribbons

Under the generalized gradient approximation (GGA), the structural and electronic properties are studied for both zigzag (ZAlNNRs) and armchair (AAlNNRs) AlN nanoribbons terminated with H atoms at both edges by using the first-principles projector-augmented wave (PAW) potential within the density function theory (DFT) framework. The results show that the Al-N, Al-C and Al-H bonds are ionic bonds while the C-C and C-H bonds are typical covalent bonds, and the N-C and N-H bonds have a degree covalent character. The systems of both perfect 7-ZAlNNR and perfect 7-AAlNNR with a single C-chain doped are still nonmagnetic semiconductors, and the C-chain reduces the band gap. The C-chain can change the band gap of 7-ZAlNNR from direct to indirect independent of the position of the C-chain, which is important in the practical application as light emitting devices. For N_Z-ZAlNNR-C(n) with N_Z = 3, 5, 6, 10, the band gap decrease successively for C-chain position n from 2 to 3, 5, 6, 7 and 10, respectively. For N_A-AAlNNR-C(n) of arbitrary width N_A, except N_A-AAlNNR-C(1) and N_A-AAlNNR-C(n = N_A) have a larger band gap, the band gap of the rest of the N_A-AAlNNR-C(n) are about 2.0 eV. Furthermore, the maximum band gap gradually decrease with the increase of the width N_A. The C-chain substituting Al-N chain process is endothermic for both 7-ZAlNNR and 7-AAlNNR.