Effect of Co–CoO Nanoparticles on the Charge Carriers Concentration in a Hybrid Structure Based on Single-Layer CVD Graphene

The effect of deposited aggregated Co–CoO nanoparticles with an average diameter of 160 nm on the concentration of charge carriers and mechanisms of their transport in Co–CoO/graphene/SiO₂ hybrid structures is studied. The structures are obtained by electrochemical deposition of cobalt nanoparticles on the surface of single-layer CVD graphene in the reversible galvanostatic mode from an electrolyte containing a mixture of CoSO₄∙6H₂O (1.25 g/L) and NaCl (0.064 g/L) at a cathode current density of 2.5 mA/cm² and an anodic current density of 1.25 mA/cm². It is shown that the deposition of Co–CoO nanoparticles leads to an almost twofold decrease in the conductivity of the structure. We attribute this effect to the exclusion of some of the intrinsic defects of graphene in the studied structure from the carrier transport process. The coexistence of quantum correction (QC) mechanisms to the Drude conductivity under weak localization conditions and conventional band (activation-like) conductivity was discovered. The QC dominance in conductivity both before and after deposition of Co–CoO particles, as well as a decrease in the value of the pre-exponential factor σ_a0 after deposition of the particles, included in the activation mechanism, from 2.8 × 10^–4 to 3.1 × 10^–5 S.