Microstructures and visible-infrared optical properties of diamond-like carbon films deposited by magnetron sputtering

In this work, diamond-like carbon (DLC) films were deposited on monocrystalline silicon substrates by magnetron sputtering. The visible-infrared optical properties of the DLC films were firstly investigated under different sputtering powers and substrate temperatures, and then optimized for high transparence by spectral region through comprehensive experimental characterizations and simulation analysis. Finally, the optical properties of the DLC films were correlated with the microstructures and compositions dependent strongly on the deposition parameters. It was shown that, when the sputtering power was 100 W, the optimized DLC films deposited at the substrate temperatures of 200 degrees C and 400 degrees C, respectively, were found to possess the highest transparence in the visible and infrared regions. The high optical transparence of the DLC films should be primarily attributed to the large fraction of sp3 bonding. But, the presence of sp3 C-H bonding associated with substrate temperature, resulting from the decomposition of residual water vapor in the sputtering chamber during film deposition, could arise infrared adsorption and thus lower infrared transparence to some extent. This work provides a guideline for the fabrication and application of DLC films used as optical coatings in specified spectral regions.