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 ID/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 sp3-hybridised carbon fraction at elevated voltage. Under the described conditions we observed maximum substrate temperatures of 70°C after deposition processes for several hours which clearly show the unique features of this relatively new deposition technique for hydrogenated tetrahedral DLC films.