Correlations between deposition parameters, mechanical properties, and microstructure for diamond-like carbon films synthesized by RF-PECVD

Abstract

Diamond-like carbon (DLC) films were synthesized on silicon substrates by radio frequency plasma enhanced chemical vapor deposition (RF-PECVD). The reactant gas was pure acetylene and the working pressure, working power, and deposition time were, respectively, varied to comprehensively investigate their influence on the microstructure and mechanical properties of DLC films. A digital phase-shifting Twyman–Green interferometer was utilized to measure the residual stress resulting from the deposition process. Raman spectrometer and nanoindentation system were, respectively, utilized to clarify the constituent microstructure, hardness, and elastic modulus of DLC films. The results reveal that the hardness and elastic modulus are both closely correlated to the sp 3 content (I D/I G ratio), which is greatly dependent on working power but much less on working pressure and deposition time. Furthermore, the self-bias voltage is more dependent on working power than on working pressure and deposition time, a tendency contrary to that of the thickness investigation. Finally, it was found that the residual stress may be influenced by the ion energy and film temperature as well as the sp 3 content.