C-13 NMR AND FTIR STUDY OF THERMAL ANNEALING OF AMORPHOUS HYDROGENATED CARBON

Amorphous hydrogenated carbon deposited from acetylene in a dc glow discharge has been studied using solid-state C-13 NMR and FTIR spectroscopies. The fraction of sp2 carbon and the fraction of sp2 carbons that bear a proton increase from 0.39 and 0.33, respectively, for the as-deposited material to approximately 1.0 and 0.44, respectively, after annealing at 500-degrees-C. The loss of aliphatic carbon with increasing temperature arises not from aromatization but from outgassing of hydrocarbons or evolution of CO and CO2 formed by reactions between oxygen and the film. Infrared spectra are presented which show absorption features not previously seen for this material. The changing structure with heat treatment and the role of oxygen in the formation and modification of the material are discussed.