Abstract
Thin films comprising nitrogen-doped ultrananocrystalline diamond/hydrogenated amorphous-carbon (UNCD/a-C:H) composite films were experimentally investigated. The prepared films were grown on Si substrates by the coaxial arc plasma deposition method. They were characterized by temperature-dependent capacitance-frequency measurements in the temperature and frequency ranges of 300-400 K and 50 kHz-2 MHz, respectively. The energy distribution of trap density of states in the films was extracted using a simple technique utilizing the measured capacitance-frequency characteristics. In the measured temperature range, the energy-distributed traps exhibited Gaussian-distributed states with peak values lie in the range: 2.84 x 10(16)-2.73 x 10(17) eV(-1)cm(-3) and centered at energies of 120-233 meV below the conduction band. These states are generated due to a large amount of sp(2)-C and pi-bond states, localized in GBs of the UNCD/a-C:H film. The attained defect parameters are accommodating to understand basic electrical properties of UNCD/a-C:H composite and can be adopted to suppress defects in the UNCD-based materials.