The electronic properties of ultra-narrow armchair MoS2 nanoribbons

Single-layer ultra-narrow MoS
2
armchair nano-ribbons (AMoS
2
NRs) are studied by density functional theory (DFT) in this paper. The width of AMoS
2
NRs is classified by the number of dimer lines (N) across the ribbons. Ultra-narrow bare AMoS
2
NRs with N=4, 5, 6 and 7 are indirect band gap semiconductors, different from cases where AMoS
2
NRs with N>7 and N=3. The reason is ascribed to the different ratio of states provided by d-orbitals of Mo atoms to states by p-orbitals of S atoms for AMoS
2
NRs with different widths. After passivation of edge atoms by hydrogen, most AMoS
2
NRs become direct band gap semiconductors except for AMoS
2
NR with N=4.