Tunable magnetism on Si (111 ) - (2×1 ) via chemisorption of graphene nanoribbons

We demonstrate from density-functional theory calculations that strong spin polarization can be achieved on a silicon surface via chemisorption of graphene nanoribbons (GNRs). The net electron spins are due to the unique silicon dangling-bond states induced by the chemisorption of GNRs and further localized by the well-aligned Si-C bonds between the silicon surface and the GNRs. The induced magnetic moment on the silicon surface depends on the width of GNRs and is thus tunable through controlling lateral separation among GNRs. We show that the silicon surface magnetization can even sustain large vertical compression to the GNRs and thus can be used as a functional switch upon high deformation of GNR. Similar magnetic behavior can be also achieved via chemisorption of certain organic molecules on the silicon surface. Our finding points to a viable nanofabrication approach to achieve intrinsic spin polarization on silicon nanostructure, thereby having implications in the emerging field of silicon-based spintronics. © 2010 The American Physical Society.