The effect of quasi-free graphene layer on the electrical transport properties of sandwich-like graphene / Co nanoparticles / graphene structure

Abstract

The paper reports on the charge transport in the sandwich-like graphene / Co nanoparticles / graphene structure (G/CoNPs/G). It is fabricated by combining the electrochemical deposition of Co nanoparticles onto a single layer CVD graphene and their capping with another graphene layer. The isolated semi-spherical, surface oxidized Co NPs of 250 nm in diameter serve as a support for the top graphene layer and provide its suspended state confirmed by atomic force microscopy revealing periodic ripples on its surface. A high optical transparency of 92.4% is found for the G/CoNPs/G sandwich. The observed twofold reduction in the sheet resistance with a ~1.5 times increase in the positive magnetoresistive effect for G/CoNPs/G compared to the pristine graphene is attributed to the suppression of carrier scattering due to the substrate. From the Hall effect measurements, a predominant role of the top graphene layer in the charge transport in G/CoNPs/G is established, with a significantly increased carrier mobility µ~1800 cm2/(V·s). An elastic intervalley scattering length estimated from the magnetoresistance results is found to be three times increased in G/CoNPs/G, indicating that the top graphene layer is almost unaffected by the substrate. The proposed technology looks promising for possible optoelectronic and magneto-optical applications.