TOPICS

第6回 サイエンスカフェ講演会を開催いたします。

2010年07月21日

第6回サイエンスカフェ講演会を下記のとおり開催いたします。

教職員の皆様や研究室所属の学生さんの参加をお待ちしています。

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日時:7月29日(木)15:00~16:00頃
場所:T1-8F サイエンスカフェ

講演者:Prof. Dr. Roland Kawakami ( University of California, Riverside Department of Physics and Astronomy )

題目:Spin Transport in Graphene

概要:
 Plasmonics has been identified as the next generation technology for Graphene is an attractive material for spintronics due to the low intrinsic spin-orbit coupling, low hyperfine coupling, and high electronic mobility.These should lead to long spin lifetimes and long spin diffusion lengths. Experimentally, gate-tunable spin transport has been achieved at room emperature with spin diffusion lengths of ~2 microns. Recently, we have performed two important studies in graphene spintronics.
 First, we investigate the role of charged impurity scattering on the spin relaxation in single layer graphene (SLG). Because the experimentally measured spin lifetime of ~100 ps is orders of magnitude shorter than expected for an ideal graphene system, it is widely believed that extrinsic effects are limiting the spin lifetime in graphene. Because charged impurity scattering is the most important scattering mechanism for the mobility (i.e. momentum scattering), it is natural candidate for the spin scattering via the Elliot-Yafet mechanism. To investigate the role of charged impurity scattering on spin relaxation, we controllably deposit additional charged impurities (cryogenic gold atoms) onto graphene spin valves and measure their effect on spinlifetime.
 The second result is the achievement of tunneling spin injection into graphene.  We utilize Ti-assisted deposition of MgO tunnel barriers in order to reduce pinholes, which easily form for thin films on graphene.The use of tunnel barriers is found to enhance the spin injection efficiency by alleviating the conductivity mismatch between the ferromagnetic metal (Co) and the SLG. The non-local spin signal is found to be as high as 130 ohms at room temperature, which is significantly larger than in metallic and semiconducting lateral spin valves. We also investigate the gate dependence of the non-local spin signal, which differs greatly for tunneling and transparent contacts. The favorable characteristics of tunneling spin injection into graphene hold promise for future applications such as spin-based computing.

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