Article

Monitoring dopants by Raman scattering in an electrochemically top-gated graphene transistor.

Department of Physics, Indian Institute of Science, Bangalore 560012, India.
Nature Nanotechnology (Impact Factor: 33.27). 04/2008; 3(4):210-5. DOI: 10.1038/nnano.2008.67
Source: PubMed

ABSTRACT The recent discovery of graphene has led to many advances in two-dimensional physics and devices. The graphene devices fabricated so far have relied on SiO(2) back gating. Electrochemical top gating is widely used for polymer transistors, and has also been successfully applied to carbon nanotubes. Here we demonstrate a top-gated graphene transistor that is able to reach doping levels of up to 5x1013 cm-2, which is much higher than those previously reported. Such high doping levels are possible because the nanometre-thick Debye layer in the solid polymer electrolyte gate provides a much higher gate capacitance than the commonly used SiO(2) back gate, which is usually about 300 nm thick. In situ Raman measurements monitor the doping. The G peak stiffens and sharpens for both electron and hole doping, but the 2D peak shows a different response to holes and electrons. The ratio of the intensities of the G and 2D peaks shows a strong dependence on doping, making it a sensitive parameter to monitor the doping.

0 Followers
 · 
315 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We report the comparative studies on structural, mechanical and corrosion properties of SiN, SiN/graphene and graphene/SiN hybrid systems deposited on titanium alloy surface. The deposited silicon nitride thin film and silicon nitride/graphene coatings systems were crack free, exhibited good adherence to the substrate and the surface morphology was homogeneous. The graphene/silicon nitride coatings system demonstrated a tendency to peeling off and had poor adhesion to the graphene monolayer deposited on the titanium alloy surface. Graphene transferred on titanium alloy surface and silicon nitride thin film surface was a single layer without defects. The hardness for silicon nitride thin film and SiN/graphene coatings was the same (22.4GPa). Graphene coating has no affect on surface hardness but it decreases electrochemical activity of the system. The best corrosion resistance has the Ti6Al4V sample coated with SiN/graphene coatings system. This sample retains the most stable mechanical and structural parameters during corrosion process. The SiN/graphene coatings system greatly improves the mechanical and corrosion properties of examined titanium alloy surface.
    Thin Solid Films 04/2015; DOI:10.1016/j.tsf.2015.04.005 · 1.87 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The effect of grain boundaries and wrinkles on the electrical properties of polycrystalline graphene is pronounced. Here we investigate the stitching between grains of polycrystalline graphene, specifically, overlapping of layers at the boundaries, grown by chemical vapor deposition (CVD) and subsequently doped by the oxidized Cu substrate. We analyze overlapped regions between 60 and 220 nm wide via Raman spectroscopy, and find that some of these overlapped boundaries contain AB-stacked bilayers. The Raman spectra from the overlapped grain boundaries are distinctly different from bilayer graphene and exhibit splitting of the G band peak. The degree of splitting, peak widths, as well as peak intensities depend on the width of the overlap. We attribute these features to inhomogeneous doping by charge carriers (holes) across the overlapped regions via the oxidized Cu substrate. As a result, the Fermi level at the overlapped grain boundaries lies between 0.3 and 0.4 eV below the charge neutrality point. Our results suggest an enhancement of electrical conductivity across overlapped grain boundaries, similar to previously observed measurements (Tsen et al., 2012). The dependence of charge distribution on the width of overlapping of grain boundaries may have strong implications for the growth of large-area graphene with enhanced conductivity.
    Carbon 12/2014; 80:513-522. DOI:10.1016/j.carbon.2014.08.091 · 6.16 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: For graphene films, the change of crystal structure induced by ion bombardment as well as the doping and strain generated in thermal annealing process is addressed in this work. Experimental results show that both the structure and number of defects for graphene depends strongly on the ion dose. Furthermore, it is found that the structure defects caused by ion bombardment in graphene can be healed and the graphene samples are all doped in subsequent thermal annealing. The frequency shift of G and 2D peaks in Raman spectra reveals that compressive strain in graphene results from the thermal annealing treatment and the occurrence of strain is influenced by the thermal annealing and defects in graphene. For graphene, since defects and thermal annealing are unavoidable for the fabrication of graphene-based devices, the systematical investigation on these two aspects in this work is, therefore, of great importance and significance.

Full-text (2 Sources)

Download
171 Downloads
Available from
May 23, 2014