Oxidation behavior of diamond-like carbon films

Diamond-like carbon (DLC) films were synthesized by a combined PVD and PECVD process to produce a multilayered structure consisting of a Ti interlayer, a graded transition layer, and the carbon film. The oxidation behavior of DLC films was investigated using thermogravimetric (TGA) and differential thermal analyses (DTA). The phase identification and microstructural examinations were conducted by XRD, Raman and SEM/EDS. According to those results, DLC films disintegrated at 350 degrees C, showing typical graphitic transformation and oxidation behavior. The weight loss as a result of oxidation of carbon followed a linear reaction rate of -2.3 x 10(-4) g/min cm(2). At 450 degrees C, oxidation of the underlying TiN/TiCxNy interlayer occurred in addition to the oxidation of DLC. Weight gain caused by the formation of TiO2 was observed. The overall oxidation kinetics of DLC is close to a parabolic behavior with k(p)=5.48 x 10(-5) mg(2)/cm(4) h. Surface cracking of the film resulted from stress relief. The microhardness of DLC films decreased with increasing annealing temperature due to the graphitization and oxidation of DLC. The transition temperature was confirmed using the results from the Raman analysis. (C) 1999 Elsevier Science S.A. All rights reserved.