A study of microstructure and nanomechanical properties of silicon incorporated DLC films deposited on silicon substrates

Silicon incorporation into DLC films prepared by plasma enhanced chemical v apour deposition (PECVD) was studied by a combination of surface analysis m ethods and nanomechanical measurements; namely XPS, Raman spectroscopy and nanoindentation. Addition of silicon into the films leads to an increase in the sp(3) contribution, as measured from XPS analysis, and a decrease in t he Raman band intensity ratio I-G/I-G. These changes are consistent with an evolving C-C bond network. The mechanical properties were first studied as a function of film thickness and indentation depth to assess the effect of substrate proximity. Silicon incorporation produces films with lower hardn ess and Young's modulus. It is suggested that, for such a PECVD process, th e weakening of the mechanical properties is caused by the increased hydroge n content in the doped films, as shown by the increased Raman background sl ope, These tendencies are attributable to the development of polymer-like c hains, which weakens the inter-molecular structure of the films. (C) 2001 E lsevier Science B.V. All rights reserved.