题目：Periodically Rippled Epitaxial Graphene: An Electronically and Structurally Nanostructured Material

报告人：Prof. Rodolfo Miranda

时间：3月26日（周一）下午2：00-4：00
地点：力学楼434教室
主持人：杨槐教授

报告内容摘要：
    Graphene is an extraordinary material that allows for a low energy manifestation of Quantum ElectroDynamics at surfaces. Its charge carriers behave as massless Dirac fermions with a group velocity ≈1/300 of the speed of light and display ballistic transport of charge and spin and a half-integer Quantum Hall Effect at 300 K.
    Ultra perfect graphene monolayers can be epitaxially grown on many single crystal metal surfaces under Ultra High Vacuum conditions. These graphene layers are spontaneously nanostructured forming a periodic array of nanoripples caused by the difference in lattice parameter between graphene and the different substrates. In some cases, e.g. on Ru(0001), in-situ STM imaging of the graphene monolayers reveals that, in addition to the geometric corrugation, a much stronger electronic corrugation exists [1], while in some others, e.g. on Ir(111) the electronic component of the corrugation is very small. The periodicity of the ripples is 2-3 nm depending on the metal substrate.
    Local tunneling spectroscopy at 4 K shows that the rippled graphene layer consists in a periodic array of quantum dots containing electron and hole pockets. Electronic structure around the Fermi level, Image Potential States, Field Emission Resonances [2], doping and work function differences between “high” and “low” regions will be compared for epitaxial graphene on Ru(0001) and Ir(111). Experimentally determined plasmon and phonon dispersions of rippled graphene will be shown, as well as its effective Debye temperature. These corrugated potential landscapes of epitaxial graphene represent a periodic pattern that directs the self-assembly of different functional molecules [3] and the development of extended electronic states. Implications of these findings towards all-carbon electronic and plasmonic devices will be briefly discussed.

报告人简介：
    Prof. Miranda?s work on experimental physics has dealt with many problems blending physics and chemistry at surfaces under ultra high vacuum conditions, from the mechanisms of epitaxial growth, to the development of scanning tunnelling microscopy, molecular self-organization, the growth of grapheme or low dimensional magnetism. Prof. Rodolfo Miranda is the American Physics Society Fellow and has authored more than 200 scientific papers receiving more than 6000 citations by other authors, with an average of 29.17 citations per paper. The present h index of Prof. Miranda is 44.