Abdelrahman Zkria

Electrical characteristics of nitrogen-doped ultrananocrystalline diamond/hydrogenated amorphous carbon composite films prepared by coaxial arc plasma deposition

Nitrogen-incorporated ultrananocrystalline diamond/hydrogenated amorphous carbon composite (UNCD/a-C:H) films were synthesized in nitrogen and hydrogen mixed gas atmospheres by coaxial arc plasma deposition. The temperature dependence of electrical resistivity implies that carriers are transported in hopping conduction. Heterojunctions comprising 3 at. % nitrogen-doped films and p-Si substrates exhibited a typical rectifying action. The expansion of a depletion region into the film side was confirmed from the capacitance–voltage characteristics, and the built-in potential and carrier concentration were estimated to be 0.51 eV and 7.5 × 1016 cm−3, respectively. It was experimentally demonstrated that nitrogen-doped UNCD/a-C:H is applicable as an n-type semiconductor.

Chemical bonding structural analysis of nitrogen-doped ultrananocrystalline diamond/hydrogenated amorphous carbon composite films prepared by coaxial arc plasma deposition

Nitrogen-doped ultra-nanocrystalline diamond/hydrogenated amorphous carbon composite films prepared in hydrogen and nitrogen mixed-gas atmospheres by coaxial arc plasma deposition with graphite targets were studied electrically and chemical-bonding-structurally. The electrical conductivity was increased by nitrogen doping, accompanied by the production of n-type conduction. From X-ray photoemission, near-edge X-ray absorption fine-structure, hydrogen forward-scattering, and Fourier transform infrared spectral results, it is expected that hydrogen atoms that terminate diamond grain boundaries will be partially replaced by nitrogen atoms and, consequently, π C–N and C=N bonds that easily generate free electrons will be formed at grain boundaries.

Low-temperature carrier transport properties of n-type ultrananocrystalline diamond/p-type Si heterojunction diodes

PN heterojunctions comprised of n-type nitrogen-doped ultrananocrystalline diamond/hydrogenated amorphous carbon composite (UNCD/a-C:H) films deposited on p-type Si substrates were fabricated in nitrogen and hydrogen mixed gas atmospheres by coaxial arc plasma deposition. The heterojunction devices showed typical rectification properties similar to those observed for conventional abrupt pn heterojunctions. The possible conduction mechanisms that govern current transport in these devices were analyzed from dark current-voltage characteristics measured in temperature range of 300 down to 80 K. Electrical parameters of the diode such as ideality factor and barrier height were found to be strongly temperature dependent. At moderate forward bias voltages, the current follows a power-law dependence, which is generally attributed to a space-charge-limited-current conduction mechanism for single-carrier (electron) injection behavior. This junction behavior might be attributed to existence of large number of grain boundaries in the UNCD/a-C:H film that provides active centers for carrier recombination-tunneling processes at the junction interface.

Effects of nitrogen doping on the electrical conductivity and optical absorption of ultrananocrystalline diamond/hydrogenated amorphous carbon films prepared by coaxial arc plasma deposition

3 at. % nitrogen-doped ultrananocrystalline diamond/hydrogenated amorphous carbon composite (UNCD/a-C:H) films were synthesized by coaxial arc plasma deposition. Optically, the films possess large absorption coefficients of more than 105 cm−1 at photon energies from 3 to 5 eV. The optical band gap was estimated to be 1.28 eV. This value is smaller than that of undoped films, which might be attributable to increased sp2 fractions. The temperature dependence of the electrical conductivity implies that carrier transport follows a hopping conduction model. Heterojunctions with p-type Si substrates exhibited a typical rectifying action. From the capacitance–voltage characteristics that evidently indicated the expansion of a depletion region into the film side, the built-in potential and carrier concentration were estimated to be 0.51 eV and 7.5 × 1016 cm−3, respectively. It was experimentally demonstrated that nitrogen-doped UNCD/a-C:H films are applicable as an n-type semiconductor.