▎ 摘　　要

Controlling a spin current by electrical means and eliminating the use of ferromagnetic contacts becomes a focus of research in spintronics, as compared with conventional magnetic control methods, electrical one could reduce the dimensions and energy consumption of integrated devices. Inspired by recent progress of controlling the hydrogenation on graphene [Xie et al., Appl. Phys. Lett. 98, 193113 (2011)], we investigate the electronic structure and spin-current transport of partially hydrogenated zigzag graphene nanoribbon (ZGNR) with various hydrogenation geometries, through first-principles calculations. It is found that for ZGNR in ferromagnetic edge-coupling state, near-edge hydrogenation would suppress the magnetization on the edge of ZGNR, and lower down the transmission around E-F to zero except two peaks, which reside discretely on both sides of E-F with opposite spins. Based on this feature, we propose and demonstrate a three-terminal device, where the spin polarization of the current can be modulated by gate voltage (V-g) to vary from (almost) 100% to -100%, which could serve as a perfect electrically-controlled "pure-carbon" dual-spin filter. Especially, the spin polarization varies gradually with V-g, so a current with any ratio of spin-up to spin-down electron numbers can be achieved. Moreover, the influences of ZGNR width and hydrogenation-region length on the system's performance are also discussed and a large range of ZGNR configurations are found to be suitable for the application of such a device. (C) 2013 AIP Publishing LLC.