2013 Volume 58 Issue 8 Pages 596-602
Structural and mechanical properties of diamond-like carbon (DLC) films were evaluated by Raman spectroscopy. Also, we showed that Raman spectroscopy can be used as a predicting tool of hardness of DLC films deposited on three-dimensional target. DLC films were prepared by bipolar plasma based ion implantation and deposition, and the positive and negative pulse voltages were varied from 1 to 3 kV and from −1 to −15 kV, respectively. With an increase in the pulse voltages, the Raman G-peak position and I(D)/I(G) ratio increased, and the G-peak full width at half maximum〔FWHM(G)〕decreased, indicating graphitization of the DLC films. In the low-wavenumber regime, the FWHM(G) increases when the G-peak shifts to higher wavenumbers, reaching a maximum value at around 1540 cm-1, and then decreases. This behavior was due to the structural changes occurring in the DLC films with an increase in the wavenumber. DLC to polymer-like carbon (PLC) transition occurred in the low-wavenumber regime, and DLC to graphite-like carbon (GLC) transition occurred in the high-wavenumber regime. Further, two different trends were observed in the relationship between the mechanical properties of the DLC films and the FWHM(G), originating from the structural change from DLC to GLC and PLC. The hardness of DLC films coated on a steel rod was successfully predicted by a Raman parameter of FWHM(G).
