Bonding structure in nitrogen doped ultrananocrystalline diamond

Abstract

The transport properties of diamond thin films are well known to be sensitive to the sp2/sp3-bonded carbon ratio, the presence of the grain boundaries and other defects, and to the presence of various impurities. In order to clarify the roles these factors play in the conduction mechanisms of nitrogen-doped ultrananocrystalline diamond (UNCD), Raman scattering, near edge x-ray absorption fine structure (NEXAFS), soft x-ray fluorescence (SXF), and secondary ion mass spectroscopy (SIMS) measurements were performed. Transmission electron microscopy analysis of nitrogen doped UNCD has previously indicated that the films are composed of crystalline diamond nano-grains with boundaries of amorphous carbon, and NEXAFS measurements reveal that the global amount of sp2-bonded carbon in these films increases slightly with nitrogen doping. The nitrogen content is quantified with high-resolution SIMS analysis, while NEXAFS and SXF indicates that the nitrogen exists primarily in tetrahedrally coordinated sites. These measurements indicate that the overall grain boundary volume of nitrogen-doped ultrananocrystalline diamond is increasing, while the grains themselves remain pure diamond. This supports our previously reported hypothesis that grain boundary conduction is the mechanism for the observed increase in conductivity in ultrananocrystalline diamond with nitrogen doping.

Are Diamonds a MEMS' Best Friend?

“…However, gaps between the film and the substrate are present, and the films are extremely rough [26]. Diamond films grown from CH 4 -Ar plasmas are able to form directly on SiO 2 substrates with appropriate diamond seeding processes (see nucleation section below) [14], [15], [23], [27]. It is therefore possible to use SiO 2 as a sacrificial substrate layer for multilayer UNCD devices.…”

“…Research at Argonne demonstrated that the electrical conductivity of UNCD films can be tailored from an insulator to practically a semimetal (∼ 260 −1 ·cm −1 ) depending on the amount of nitrogen incorporated in the UNCD films [23]. This unique electrical conduction phenomenon seems to depend on the combination of the particular grain boundary structure and bonding, including nitrogen incorporation into the grain boundaries [24].…”

Fabrication and characteristics of nitrogen-doped nanocrystalline diamond/p-type silicon heterojunction

“…The peak at 1333 cm -1 is assigned to the intrinsic zone-centre phonon band of diamond. The broad bands centered at about 1360 cm -1 and 1555 cm -1 are attributed to the disordered D band and graphitic G band especially related to nanocrystalline diamond (NCD), respectively [6,15,16]. The nitrogen presence in the lattices of N-NCD is demonstrated by the blue shift of 1360 cm -1 band from the D band (1340 cm -1 ) of undoped NCD [15].…”

Synthesis of diamond film and UNCD on BeCu substrate by hot filament CVD

“…22) In this study, these peaks were unclear. However, because the Raman spectra reported for UNCD were also unclear, 23) we can consider that the samples in this study were UNCD.…”