Ordered and reversible hydrogenation of silicene.

Collaborative Innovation Center of Quantum Matter, Beijing 100871, China(Received 9 October 2014; revised manuscript received 18 January 2015; published 23 March 2015)The hydrogenation of monatomic silicene sheet on Ag(111) was studied by scanning tunnelingmicroscopy and density functional theory calculations. It was observed that hydrogenation of siliceneat room temperature results in a perfectly ordered γ-ð3× 3Þ superstructure. A theoretical model, whichinvolves seven H atoms and rearranged buckling of Si atoms, was proposed and agrees with experimentsvery well. Moreover, by annealing to a moderate temperature, about 450 K, a dehydrogenation processoccurs and the clean silicene surface can be fully recovered. Such uniformly ordered and reversiblehydrogenation may be useful for tuning the properties of silicene as well as for controllable hydrogenstorage.