Effects of edge hydrogenation on structural stability, electronic, and magnetic properties of WS2 nanoribbons

Using density functional theory based first-principles, we have investigated the structural stability, electronic, and magnetic properties of tungsten disulfide nanoribbons (WS(2)NRs). When the edges are bare, Zigzag-edge WS2 nanoribbons (ZWS(2)NRs) and Armchair-edge WS2 nanoribbons (AWS(2)NRs) are ferromagnetic metal and nonmagnetic semiconductor, respectively. After edge hydrogenation, WS(2)NRs exhibit different structural stabilities and electronic structures according the patterns of edge hydrogenation. Hydrogenated ZWS(2)NRs keep ferromagnetic and metallic while AWS(2)NRs convert from nonmagnetic to magnetic when at least one edge is partially hydrogenated. The transition of AWS(2)NRs is contributed to the unpaired valence electrons. With the change of nanoribbon width n, magnetic moment of edge fully hydrogenated ZWS(2)NRs shows nearly periodical variation, the band gap of bare AWS(2)NRs oscillates like three distinct families and owing to the ever-present edge effect it converges to 0.5 eV as n increases. Compared with bare AWS(2)NRs, edge fully hydrogenated AWS(2)NRs have the same scaling rule of band-gap variation when n <= 12, while the band gap oscillates up and down when n > 12 because of the more obvious edge asymmetric effect than quantum confinement effect. These findings are essential for applications of WS(2)NRs in nanoelectronics and spintronics. (C) 2013 AIP Publishing LLC.