▎ 摘　　要

We demonstrate charge and spin current transport in a graphene-based lateral spin valve using yttrium oxide (Y-O) as a tunneling barrier between graphene and a ferromagnetic electrode. A Y-O layer grown on graphene is flat, with a root-mean-square roughness of 0.17 nm, which is much lower than that of conventional barrier materials. This flatness allows the utilization of a very thin but well-defined tunneling barrier, leading to a large spin signal of similar to 20 Omega and a high spin injection efficiency of 15% with a low contact resistance of similar to 1 k Omega. These findings represent important progress toward the realization of graphene-based spintronics applications. (C) 2014 The Japan Society of Applied Physics