Structural and mechanical properties of DLC films prepared by bipolar PBII&D

In the present study, diamond-like carbon (DLC) films were prepared by bipolar plasma based ion implantation and deposition (PBII&D), and the structural and mechanical properties of the DLC films deposited on Si substrates were evaluated by Raman spectroscopy. In the PBII&D processing, 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 (hardness, elastic modulus, and internal stress) of the DLC films and the FWHM(G), originating from the structural change from DLC to GLC and PLC. (C) 2011 Elsevier B.V. All rights reserved.