Degradation and stress evolution in a-C, a-C:H and Ti-C:H films

Presented in this contribution are some observations of the stress evolution and degradations of diamond-like a-C, a-C:H and Ti-C:H (10–20 at.% of Ti) films deposited by magnetron sputtering of the C or Ti target in the Ar or Ar+CH4 gas mixture. The compressive stresses increased during several days for all the Ti-C:H films regardless of their structure (amorphous or a-C:H with TiC nanocrystalline inclusions) and composition (10–20 at.% of Ti). This phenomenon was not observed for a-C and was slightly displayed for a-C:H films having high hydrogen content. The growth of stress was accompanied by a decrease of optical constants, n and k. Simultaneously, Raman spectra and composition of Ti-C:H films remained unchanged. The degradation in ambient air during several hours or days takes place mostly for the films prepared by reactive sputtering in the Ar+CH4 gas mixture, while a-C films, sputtered from the C target in argon, demonstrated stable behavior despite their high compressive stress level.