AVS 50th International Symposium
    Advanced Surface Engineering Monday Sessions
       Session SE-MoA

Paper SE-MoA5
Using NMR to Probe the Bonding in Amorphous Carbon Nitride Thin Films

Monday, November 3, 2003, 3:20 pm, Room 323

Session: Hard Coatings: Preparation, Properties, Wear, and Nanotribology
Presenter: B.C. Holloway, College of William & Mary
Authors: W.J. Gammon, College of William & Mary
O. Kraft, Inst. fur Materialforschung II, Germany
G.L. Hoatson, College of William & Mary
A.C. Reilly, College of William & Mary
B.C. Holloway, College of William & Mary
Correspondent: Click to Email
In this study the chemical bonding in hard and elastic amorphous carbon nitride (a-CNx) films is investigated with 15N, 13C, and 1H nuclear magnetic resonance (NMR) spectroscopy. Nanoindentation yields an elastic recovery of 80%, a hardness of 5 GPa, and an elastic modulus of 47 GPa. Our 13C NMR study demonstrates the lack of sp3 bonded carbon in this material. Furthermore, the 13C and 15N NMR data imply a film-bonding model that has an aromatic carbon structure with sp2 hybridized nitrogen incorporated in heterocyclic rings and in pentagons; a suggestion that is supported by our preliminary total energy calculations of graphite defect structures. Results from 15N and 13C cross polarization (CP) and 1H magic angle spinning (MAS) NMR experiments also suggest that the nitrogen bonding sites are susceptible to protonation. The most likely source of protons is from water absorbed during sample preparation for the NMR experiments. The sensitivity of the surface of a-CNx to water absorption may impact tribological applications for this material.