Kinetic models for thermal decompositions of amorphous carbon and carbon nitride thinfilms

Abstract

Amorphous carbon (a-C) and carbon nitride(a-CNx)thin films prepared by sputter deposition on thin Corning glass substrates were studiedusing isothermal thermogravimetry and the differential method. Two typical reactionkinetics, the sigmoid and deceleratory reactions, were observed, which correspond to thefilms sputtered at higher (0.9–3 mTorr) and lower vacuums (7–16 mTorr), respectively. Thestructure bonding ratios and activation energies for thermal decompositions, whichincreased with the kinetic energy of the carbon species during deposition, were used tointerpret the observations of reactions. The free bonded and weakly bonded compositions,the amounts of which increased with sputtering pressure, could be active nucleus sites inearly reactions determining the reaction kinetics. The films with higher structurebonding ratios showed an induction period for generation of infrequently formednuclei and had typically sigmoid-type reaction kinetics, while those with largeamounts of free and weakly bonded compositions produced large amounts ofquickly formed nuclei in early reactions and showed deceleratory reaction kinetics.