Influence of N-doping on dielectric properties of carbon-coated copper nanocomposites in the microwave and terahertz ranges

Carbon-coated Cu nanocomposites (Cu@C NCs) consisting of core-shell nanoparticles and nanorods were synthesized by arc discharge plasma under an atmosphere of He and H2 gas, and the N-doping of them was achieved by a post-treatment process using ureal as the precursor. The concentration of N in the N-doped samples varies in the range of 0.62%–2.31 % (in mole), with a transformation from pyrrolic N to graphitic N when increasing the relative content of ureal. Dielectric properties of the NCs without or with N-doping in the microwave and THz bands were investigated. The N-doped samples achieve the enhanced dielectric loss in both microwave and THz bands. In the microwave band, dielectric loss was dominated by interfacial polarization, dipolar polarization, and conduction loss, while in the THz band, plasma resonance, ionic polarization and conduction loss are responsible for the dielectric loss, with a strong absorption characteristic dominated by conductive effect.