Electronic spin transport in bilayer and single layer graphene

Graphene has drawn plenty of attention since its discovery in 2004. Due to its excellent properties, such as long spin relaxation length and gate-tunable spin transport, graphene is expected to be a potential candidate for spintronics applications. In this thesis, the systematic study of the spin relaxation mechanisms in bilayer and single layer graphene is presented. Graphene-based spin valve devices in four-terminal non-local geometry are fabricated for the investigation of the charge and spin transport properties. From the correlation between the charge carrier mobility and spin relaxation time, the major role of the D'yakonov-Perel' type of spin relaxation in bilayer graphene is discovered. And the Elliott-Yafet mechanism could dominate in single layer graphene. The first observation of long spin relaxation times of about 2 ns in bilayer graphene is presented in this thesis, which is longer than that in single layer and few layer graphene. Next the spin valve devices with CVD synthesized single layer and bilayer graphene are demonstrated. Both the charge and spin transport properties of CVD SLG and BLG show very comparable performances, including the carrier mobility, spin relaxation time, and spin relaxation length, to the exfoliated natural graphene. The results suggest that the CVD synthesized graphene could be promising for spintronics applications and possible to be integrated into wafer-scale semiconductor manufacturing