Abstract: The optical properties (absorption, reflection, transmittance, transparency) and physical attributes (hardness, friction, durability, etc.) of metal oxides, nitrides, or films that combine these materials can be modified by adding fluorine to the deposition mixture. The extent of change in properties depends on the amount of fluorine incorporated. Contrary to previous information, the presence of fluorine does not prevent adhesion of overlayers such as hard carbon, hydrogenated carbon, or diamond-like carbon. Considering for example massive silicon oxynitride hardcoat layers which are part of wear resistant composite windows for visible spectral applications, preferably fluorine is incorporated in a relatively very thin surface-adjacent region or layer of the hardcoat on the side thereof on which a carbonaceous layer such as DLC is formed.