Session T26: Focus Session: Graphene XII: Synthesis and Growth

2:30 PM–5:30 PM, Wednesday, March 18, 2009
Room: 328

Sponsoring Unit: DMP
Chair: Taisuke Ohta, Sandia National Laboratories

Abstract ID: BAPS.2009.MAR.T26.15

Abstract: T26.00015 : Epitaxial graphene: Structure, growth and molecular interactions

5:18 PM–5:30 PM

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  Andrew Wee
    (National University of Singapore)

  Wei Chen
    (National University of Singapore)

  Siew Wai Poon
    (National University of Singapore)

  Han Huang
    (National University of Singapore)

  Shi Chen
    (National University of Singapore)

  Dongchen Qi
    (National University of Singapore)

  Eng Soon Tok
    (National University of Singapore)

  Kian Ping Loh
    (National University of Singapore)

The discovery of graphene has opened up a new paradigm in nanoelectronics that could offer better performance than conventional semiconductor devices. We used \textit{in situ} scanning tunnelling microscopy (STM), synchrotron synchrotron radiation techniques and density functional theory (DFT) calculations to investigate the structure of the various reconstructions of 6H-SiC(0001) prior to its thermal decomposition to form epitaxial graphene (EG). Using Co-decoration technique coupled with STM, the evolution of EG was found to preferentially begin at SiC step edges and occurs with the loss of Si and breakdown of the C-rich ($\surd $6$\times \surd $6)$R$30\r{ } template, which provides the C source for graphene growth. The C-rich phase that forms at the interface acts as a buffer layer for graphene from the underlying bulk SiC. We show that the transition from monolayer to trilayer EG adopts a bottom-up growth mechanism. With increasing annealing temperature, the fluorescence yield of Si $K$-edge NEXAFS indicates an increase in disorder of Si atoms in the SiC substrate beneath the surface due to out-diffusion of Si atoms to the surface forming increased Si vacancies. We also show that EG thermally grown on 6H-SiC(0001) can be p-type doped via a novel surface transfer doping scheme by modifying the surface with the electron acceptor, F4-TCNQ.

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