Influence of deposition parameters on RF sputtered DLC thin films

Diamond like carbon (DLC) can be an ideal candidate as coating material for optical components owing to its high hardness value, chemical inertness and high transparency in the infrared spectral region. DLC thin films have been deposited by RF magnetron sputtering from a graphite target in argon atmosphere without hydrogen on glass and silicon substrates in order to study the influence of some parameters on the mechanical and optical properties. Increasing the power input values, from 100W to 400W, the DLC films compactness increases too as it can be deduced from the raise in this range of power of both hardness and refractive index values, calculated by microindentations size and reflectance and transmittance spectrophotometer measurements respectively. Moreover, a set of samples was deposited at different substrate temperatures and at the highest used value a lower value of hardness and refractive index as well are obtained. The possibility to correlate the films compactness to their absorption humidity has been investigated by means of the infrared transmittance spectra analysis. Densifying effect of RF sputtered DLC thin films examined in this work seems to be related, in conclusion, to the power input increasing rather than to the substrate temperature.