Boron-doped ultrananocrystalline diamond/hydrogenated amorphous carbon composite (UNCD/ a-C:H) films were deposited by coaxial arc plasma deposition with a boron-blended graphite target at a base pressure of <103 Pa and at hydrogen pressures of 53.3 Pa. The hydrogenation effects on the electrical properties of the films were investigated in terms of chemical bonding. Hydrogen-scattering spectrometry showed that the maximum hydrogen content was 35 at. % for the film produced at 53.3-Pa hydrogen pressure. The Fourier-transform infrared spectra showed strong absorptions by sp3 C-H bonds, which were specific to the UNCD/a-C:H, and can be attributed to hydrogen atoms terminating the dangling bonds at ultrananocrystalline diamond grain boundaries. Temperature-dependence of the electrical conductivity showed that the films changed from semimetallic to semiconducting with increasing hydrogen pressure, i.e., with enhanced hydrogenation, probably due to hydrogenation suppressing the formation of graphitic bonds, which are a source of carriers. Carrier transport in semiconducting hydrogenated films can be explained by a variable-range hopping model. The rectifying action of heterojunctions comprising the hydrogenated films and n-type Si substrates implies carrier transport in tunneling.
|Journal||Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films|
|Publication status||Published - 2015|
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics
- Surfaces and Interfaces
- Surfaces, Coatings and Films