Abstract
Graphene applications in electronics require experimental study of the formation of high-quality Ohmic contacts and deeper understanding of electron transport mechanisms at metal/grapheme contacts. We have studied carrier transport in twisted CVD graphene decorated with electrodeposited Co particles forming Ohmic contacts with graphene layers. We have compared layer resistivity as a function of temperature and magnetic field R�(T, B) for as-synthesized and decorated twisted graphene on silicon oxide substrates. Experiments have proven the existence of negative (induction < 1 Tl) and positive (induction > 1 Tl) contributions to magnetoresistance in both specimen types. The R�(T, B) functions have been analyzed based on the theory of 2D quantum interference corrections to Drude conductivity taking into account competition of hopping conductivity mechanism. We show that for the experimental temperature range (2–300 K) and magnetic field range (up to 8 Tl), carrier transport description in test graphene requires taking into account at least three interference contributions to conductivity, i.e., from weak localization, intervalley scattering and pseudospin chirality, as well as graphene buckling induced by thermal fluctuations.
Highlights
Graphenes have been intensely investigated in the last decade due to their specific physical properties such as high electrical and heat conductivities, well-developed surface, high mechanical strength, elasticity etc
We showed that the G/SiO2 and Co-G/SiO2 structures exhibit a competition between negative and positive magnetoresistance effects at low temperatures
Negative magnetoresistance effect is completely suppressed by weak magnetic fields (B ≤ 1 Tl), and Co particle deposition onto the graphene layer reduces the contribution of negative magnetoresistance effect
Summary
Graphenes have been intensely investigated in the last decade due to their specific physical properties such as high electrical and heat conductivities, well-developed surface, high mechanical strength, elasticity etc. In accordance with the graphene electronics development roadmap [1] the combination of these properties shows good promise. One of the most promising approaches to the synthesis of these composite structures is the deposition of particles of different magnetic and nonmagnetic metals on graphene layer surfaces [4,5,6]. The problem of fabricating high-quality electric contacts remains a problem of attention for fundamental and technical research intensifying the importance of understanding carrier transport mechanisms near and through metal/graphene contacts
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