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  • Graphene Nanoribbons: Synthesis, Properties and Electronics
  • Release time:2011-05-17 clicks:1
  • Time: Sep 10th 10:00



    1.Graphene Nanoribbons: Synthesis, Properties and Electronics

    Xinran Wang

    Stanford University, USA

     Abstract´╝ÜGraphene nano-electronics has been very attractive due to

    high carrier mobility. The semi-metallic nature of bulk graphene

    requires width confinement down to ~sub-10nm in order to induce adequate

    bandgap for room temperature logic applications. In this talk, I will

    present our recent works on graphene (nanoribbon) electronics.

     First, we developed a unique chemical route to synthesize high

    quality, ultra-smooth graphene nanoribbons (GNRs) with width below 10nm.

    Transport measurements show that the bandgap scales inversely with GNR

    widths, indicating that bandgap opens in narrow GNRs due to quantum

    confinement. The first room temperature p-type graphene field-effect

    transistor (FET) is demonstrated with our chemically derived sub-10nm


     We next access the performance of chemically derived sub-10nm GNR

    FETs. At on state, the current density could be as high as ~2000uA/um,

    with on/off ratio ~ 106, subthreshold slope ~210mV/dec. The performance

    of sub-10nm GNR FETs is comparable to small diameter (d<1.2nm) carbon

    nanotube (CNT) FETs. The intrinsic carrier mobility and scattering mean

    free path is ~200cm2/Vs and ~10nm, respectively. We discuss the possible

    scattering mechanisms in the GNRs.

     Compared to CNTs, GNRs have open edges with high chemical reactivity.

    We can take advantage of this fact and chemically modify the GNR edges

    to change the electronic properties. We found that individual GNRs could

    be covalently functionalized by nitrogen species through high-power

    electrical joule heating in NH3 gas, leading to n-type electronic doping

    consistent with theory. The formation of C-N bond occurs mostly at the

    edges of graphene where chemical reactivity is high. We fabricated an n-

    type N-doped graphene field-effect transistor (FET) that operates at

    room temperature.

    2.Ripple texturing of suspended graphene atomic membranes

     Wenzhong Bao

     University of California, Riverside

     Abstract´╝Ü We investigate one-dimensional (1D) and 2D periodic ripples

    in suspended graphene sheets, using spontaneously and thermally induced

    longitudinal strains on patterned substrates. By in-situ SEM imaging, we

    provide the first measurement of graphene’s thermal expansion

    coefficient, which is anomalously large and negative, ~-7x10-6 K-1 at

    300K. Latest progress towards transport measurement in these devices

    will be discussed