Accurate Raman spectroscopy of diamond-like carbon films deposited by an anode layer source

Diamond-like carbon (DLC) films deposited by a new room-temperature deposition method were critically investigated by Raman spectroscopy. A gridless, linear anode layer Source was fed with acetylene at different flow rates at varying applied voltages producing highly adhesive and transparent DLC films. Raman spectra showed a correlation between the intensity ratio I-D/IG and the voltage applied to the ion source. When increasing the voltage from 1 to 3kV, the intensity ratio increased from 0.48 +/- 0.02 to 0.59 +/- 0.01 (measured at an excitation wavelength of 532nm and fitted with Gaussian functions). These observations were confirmed by stress measurements, where an increase of the voltage from 1 to 3kV resulted in a decrease of the compressive stress from - 2.34 +/- 0.17 to - 0.85 +/- 0.02GPa, indicating a decreased sp(3)- hybridised carbon fraction at elevated voltage. Under the described conditions we observed maximum substrate temperatures of 70 degrees C after deposition processes for several hours which clearly show the unique features of this relatively new deposition technique for hydrogenated tetrahedral DLC films. (C) 2008 Elsevier B.V. All rights reserved.