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Mar. 30, 2012
After the discovery of the convenient fabrication method by the exfoliation from graphite (A. Geim and K. S. Novoselov, 2010 Nobel Prize in physics), graphene has attracted world-wide attention as an innovative nanoelectronic material. In the spintronics field, graphene is expected to be an ideal spin-transport material due to the extremely long spin diffusion length and high carrier mobility. However, not only the non-uniformity in the carbon layer number and in the electronic states of exfoliated graphene are making it difficult to control the spin transport properties in graphene. It can be said that a new fabrication method which enables tailoring of graphene is indispensable for the development of spintronic applications.
From this view point, ultrahigh vacuum chemical vapor deposition (UHV-CVD) can be an alternative fabrication method, because single-layer graphene is known to be epitaxially grown on the catalytic metal crystal. In UHV-CVD, graphene grows by the catalytic reaction of hydrocarbon precursors on the metal surfaces.
In this study, we focused on a UHV-CVD growth of microstructure controlled graphene by using epitaxial metal thin films as a catalytic substrate and with in-situ spectroscopies (reflection high energy electron diffraction and Auger electron spectroscopy). It was successfully demonstrated that single-crystalline graphene with uniform number of carbon layer can be obtained by precise control of the exposure amount of precursors (e.g., benzene). In addition, it was found that the uniformity of the electronic states of UHV-CVD graphene can be remarkably high compared to exfoliated graphene by adjusting the exposure condition to complete the growth of the respective carbon layers.
Our findings would enable efficient controls of spin transport properties of graphene by the tailor-made synthesis, and would lead to developments in graphene-based spintronics and nanoelectronics.
This work has been published in the American Institute of Physics Journal Journal of Applied PhysicsEon March 15, 2012.
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