Regulation of structural and terahertz properties of TiC nanoparticles by carbon-coating and nitrogen-doping

Carbon-coated titanium carbide nanocomposites (TiC@C NCs) were synthesized by arc discharge plasma under an atmosphere of Ar and CH4 gas, and nitrogen-doped carbon-coated titanium carbonitride nanocomposites (Ti(C,N)@NC NCs) were also obtained using a mixture gas of N2 and CH4. Terahertz (THz) optical and dielectric properties of these nanostructures were investigated using a THz time-domain spectrum system, and the extracted conductivity was analyzed to understand the transport mechanism. The dielectric response in these nanostructures is dominated by ionic polarization with a relaxation behavior, and absorption characteristic is free carrier absorption dependent on conductivity. Ti(C,N)@NC NCs achieve the enhanced dielectric response and high absorption loss due to nitrogen-doping increasing charge disorder and conductivity. AC conductivities of the samples were fitted to the universal power low function and indicated that the transport mechanism is electronic hopping.