Abstract
AbstractWe prepared three graphene devices with different levels of disorder in the graphene structure by 1. exfoliation from highly oriented pyrolytic graphite (HOPG), 2. chemical vapour deposition (CVD), using Cu foil as a catalyst, and by 3. CVD, using a Ni layer evaporated on a Si/SiO2 substrate as a catalyst. The gate voltage characteristics, quantum Hall effect (QHE) and temperature (T) dependences of the conductivity of these samples were studied. A comparison of the transport features indicates that, unlike the highly ordered crystal of exfoliated graphene, the graphene sample produced by the CVD method on the Ni substrate shows a significant degradation of the QHE signature with a resistivity value three orders of magnitude higher than that in a graphene crystal. In the exfoliated material phonon scattering dominates the electronic transport at high carrier density, thus reducing the conductivity at high T. Thermal assistance plays an important role in the electronic transport of our graphene grown on Ni with more disordered structure, which causes conductivity to increase with rising T. As to graphene grown on Cu foil, it displays many features similar to those of a perfect graphene crystal. This is good news for possible applications of CVD‐grown graphene. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
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