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Träfflista för sökning "WFRF:(Kim Kyung Ho 1984) srt2:(2018)"

Sökning: WFRF:(Kim Kyung Ho 1984) > (2018)

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1.
  • He, Hans, et al. (författare)
  • Stable and Tunable Charge Carrier Control of Graphene for Quantum Resistance Metrology
  • 2018
  • Ingår i: 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018). - : IEEE. - 9781538609736 - 9781538609743
  • Konferensbidrag (refereegranskat)abstract
    • Here we demonstrate a stable and tunable method to alter the carrier concentration of epitaxial graphene grown on silicon carbide. This technique relies on chemical doping by an acceptor molecule. Through careful tuning one can produce chemically doped graphene quantum resistance devices which show long-term stability in ambient conditions and have performance comparable to that of GaAs quantum resistance standards. This development paves the way for controlled device fabrication of graphene quantum hall resistance standards, which can be reliably tailored to operate below 5 T and above 4 K out-of-the-box, without further adjustments from the end-user.
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2.
  • He, Hans, 1989, et al. (författare)
  • Uniform doping of graphene close to the Dirac point by polymer-assisted assembly of molecular dopants
  • 2018
  • Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723 .- 2041-1723. ; 9:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Tuning the charge carrier density of two-dimensional (2D) materials by incorporating dopants into the crystal lattice is a challenging task. An attractive alternative is the surface transfer doping by adsorption of molecules on 2D crystals, which can lead to ordered molecular arrays. However, such systems, demonstrated in ultra-high vacuum conditions (UHV), are often unstable in ambient conditions. Here we show that air-stable doping of epitaxial graphene on SiC—achieved by spin-coating deposition of 2,3,5,6-tetrafluoro-tetracyano-quino-dimethane (F4TCNQ) incorporated in poly(methyl-methacrylate)—proceeds via the spontaneous accumulation of dopants at the graphene-polymer interface and by the formation of a charge-transfer complex that yields low-disorder, charge-neutral, large-area graphene with carrier mobilities ~70 000 cm2V−1s−1at cryogenic temperatures. The assembly of dopants on 2D materials assisted by a polymer matrix, demonstrated by spin-coating wafer-scale substrates in ambient conditions, opens up a scalable technological route toward expanding the functionality of 2D materials.
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3.
  • Kim, Kyung Ho, 1984, et al. (författare)
  • Probing variable range hopping lengths by magneto conductance in carbonized polymer nanofibers
  • 2018
  • Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322 .- 2045-2322. ; 8:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Using magneto transport, we probe hopping length scales in the variable range hopping conduction of carbonized polyacetylene and polyaniline nanofibers. In contrast to pristine polyacetylene nanofibers that show vanishing magneto conductance at large electric fields, carbonized polymer nanofibers display a negative magneto conductance that decreases in magnitude but remains finite with respect to the electric field. We show that this behavior of magneto conductance is an indicator of the electric field and temperature dependence of hopping length in the gradual transition from the thermally activated to the activation-less electric field driven variable range hopping transport. This reveals magneto transport as a useful tool to probe hopping lengths in the non-linear hopping regime.
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